Variations in mineralogy of dust in an ice core obtained ...

Clim Past 17 1341ndash1362 2021httpsdoiorg105194cp-17-1341-2021copy Author(s) 2021 This work is distributed underthe Creative Commons Attribution 40 License

Variations in mineralogy of dust in an ice core obtained fromnorthwestern Greenland over the past 100 yearsNaoko Nagatsuka1 Kumiko Goto-Azuma12 Akane Tsushima3 Koji Fujita4 Sumito Matoba5 Yukihiko Onuma6Remi Dallmayr7 Moe Kadota58 Motohiro Hirabayashi1 Jun Ogata1 Yoshimi Ogawa-Tsukagawa1Kyotaro Kitamura1 Masahiro Minowa4 Yuki Komuro1 Hideaki Motoyama12 and Teruo Aoki12

1National Institute of Polar Research Tokyo 190-8518 Japan2Department of Polar Science The Graduate University for Advanced Studies SOKENDAI Tokyo 190-8518 Japan3Graduate School of Science Chiba University Chiba 277-0882 Japan4Graduate School of Environmental Studies Nagoya University Nagoya 464-8601 Japan5Institute of Low Temperature Science Hokkaido University Sapporo 060-0819 Japan6Institute of Industrial Science University of Tokyo Kashiwa 277-8574 Japan7Alfred Wegener Institute Am Alten Hafen 26 27568 Bremerhaven Germany8Graduate School of Environmental Science Hokkaido University Sapporo 060-0810 Japan

Correspondence Naoko Nagatsuka (nagatsukanaokonipracjp)

Received 16 November 2020 ndash Discussion started 3 December 2020Revised 25 March 2021 ndash Accepted 14 April 2021 ndash Published 21 June 2021

Abstract Our study is the first to demonstrate a high-temporal-resolution record of mineral composition in aGreenland ice core over the past 100 years To reconstructpast variations in the sources and transportation processesof mineral dust in northwestern Greenland we analysed themorphology and mineralogical composition of dust in theSIGMA-D ice core from 1915 to 2013 using scanning elec-tron microscopy (SEM) and energy-dispersive X-ray spec-troscopy (EDS) The results revealed that the ice core dustconsisted mainly of silicate minerals and that the composi-tion varied substantially on multi-decadal and inter-decadalscales suggesting that the ice core minerals originated fromdifferent geological sources in different periods during thepast 100 years The multi-decadal variation trend differedamong mineral types Kaolinite which generally formed inwarm and humid climatic zones was abundant in colder pe-riods (1950ndash2004) whereas mica chlorite feldspars maficminerals and quartz which formed in arid high-latitude andlocal areas were abundant in warmer periods (1915ndash1949and 2005ndash2013) Comparison to Greenland surface tempera-ture records indicates that multi-decadal variation in the rela-tive abundance of these minerals was likely affected by localtemperature changes in Greenland Trajectory analysis showsthat the minerals were transported mainly from the west-

ern coast of Greenland in the two warming periods whichwas likely due to an increase in dust sourced from local ice-free areas as a result of shorter snowice cover duration inthe Greenland coastal region during the melt season causedby recent warming Meanwhile ancient deposits in northernCanada which were formed in past warmer climates seem tobe the best candidate during the colder period (1950ndash2004)Our results suggest that SEMndashEDS analysis can detect vari-ations in ice core dust sources during recent periods of lowdust concentration

1 Introduction

Aeolian mineral dust in snow and ice on ice sheets pro-vides key information about global and local climate changePast ice core dust records have revealed substantial variationsin the concentration composition particle size and mor-phology of minerals on glacialndashinterglacial timescales (ca800 kyr BP eg Petit et al 1990 Lambert et al 2008) ge-ologic timescales (from the Eemian to the Holocene egMaggi 1997 Ram and Koenig 1997 Steffensen 1997Ruth et al 2003 Schuumlpbach et al 2018 Simonsen etal 2019) and seasonal scales (eg Bory et al 2003a Drabet al 2002) Ice core dust records show a close relation-

Published by Copernicus Publications on behalf of the European Geosciences Union

1342 N Nagatsuka et al Variation in Greenland ice core dust mineralogy over the past 100 years

ship with temperature changes and atmospheric circulationDust concentrations in Greenland ice cores during the lastglacial period were 10 to 100 times higher than those overthe Holocene and were strongly correlated with temperaturechanges (as indicated by δ18O records eg De Angelis etal 1997 Mayewski et al 1997 Fuhrer et al 1999 Ruthet al 2003 Schuumlpbach et al 2018) Steffensen (1997) alsoshowed a systematic connection between dust volume distri-bution total dust mass and δ18O in the Greenland Ice CoreProject (GRIP) ice core indicating that climate changes ap-pear to have modified the processes of formation transportand deposition of mineral dust in the same way over the last120 000 years Meanwhile there is a significant correlationbetween the dust flux of the European Project for Ice Cor-ing in Antarctica (EPICA) ice core with Antarctic tempera-ture during glacial periods but not during interglacial peri-ods suggesting that the conditions of source areas and thetransport of ice core dust change according to the glacialndashinterglacial cycle (Lambert et al 2008) The variability of icecore dust may be related to changes in atmospheric transportand dust source areas affected by climate change (Svenssonet al 2000) Thus it is important to reconstruct the varia-tions in the sources and transportation processes of mineraldust in ice cores

Geochemical analyses such as stable isotope ratios of SrNd and Pb have been used to identify possible sources ofGreenland ice core dust These isotopic ratios have strongregional variations that are controlled by their geological ori-gins and are hardly altered during transportation in the at-mosphere or after deposition (Capo et al 1998 Faure andMensing 2004) The isotope ratios of the GRIP and Green-land Ice Sheet Project 2 (GISP2) ice core dust obtained from44 to 12 kyr BP indicated that eastern Asian deserts appearedto be the most likely dust sources (Biscaye et al 1997Svensson et al 2000) and that centraleast central Europeanloess might also be a major source of dust in the last glacialice core (Uacutejvaacuteri et al 2015) Lupker et al (2010) analysedthe Sr and Nd isotopic ratios of mineral dust in an ice corefrom southern Greenland (Dye 3) in the age range of 1786ndash1793 CE and revealed that the Sahara might be an additionaldust source Han et al (2018) showed temporal variationsin the source areas of the NEEM ice core dust based on Srand Pb isotope analysis the primary dust source was east-ern Asian deserts from 31 to 23 kyr and the Sahara from23 to 12 kyr However these analyses have targeted mostlyice core dust from glacial periods characterized by a highdust concentration because Sr and Nd isotopic ratio analysesneed large numbers of samples Although some studies haveanalysed the Sr and Nd isotopes of ice core minerals duringthe Holocene a recent period of low dust concentration theyneeded to concentrate decades to thousands of years of icefor each sample (eg Bory et al 2003a Han et al 2018 Si-monsen et al 2019) Thus there is limited information aboutpossible sources of mineral dust in interglacial periods dur-ing which dust concentrations are low

Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) are useful tools for re-vealing the source areas of ice core dust samples with lowamounts of mineral dust SEM provides morphological in-formation and EDS provides the mineralogical compositionof individual particles allowing the evaluation of the con-tinental dust input and showing variations in ice core dustproperties Donarummo et al (2003) analysed the size distri-bution and mineral composition of GISP2 ice core dust dur-ing the 1930s by SEMndashEDS and suggested that the centralUnited States might have contributed a substantial amount ofminerals to the ice core when the source area was affectedby intense droughts The SEMndashEDS analysis of dust fromsnow pit samples from 1989 to 1991 at Summit in centralGreenland indicated that the possible sources were likely tobe Asian deserts and the source areas have not changed sea-sonally (Drab et al 2002) Therefore SEMndashEDS analysiscan demonstrate a high-temporal-resolution record of com-position and sources of ice core minerals during interglacialperiods However continuous variations in the dust proper-ties of Greenland ice cores during recent years are still notwell known

Possible source areas for the Greenland ice core dustmay have varied in recent years Most of the Earthrsquos sur-face has changed rapidly because of recent climate warm-ing and human activities which may result in changes in at-mospheric transport and sources of mineral dust to the icesheet For example dust outbreaks occurring in eastern Asiandeserts which are vast sources of aeolian mineral dust re-markably increased from 2000 to 2002 compared with the1990s (Kurosaki and Mikami 2003) The dust from Asiandeserts is transported to Greenland across the ocean Zhanget al (2020) revealed that there has been an abrupt shift to-ward a hotter and drier climate over east Asia over the past260 years according to tree-ring-based reconstructions ofheat waves and soil moisture Furthermore there may alsobe an increasing contribution of dust from local source ar-eas in Greenland (Amino et al 2021) The retreating iceand decreasing seasonal snow will expose more sediment inthe proglacial area delivering greater quantities of fine sed-iments to the floodplain than at present Bullard and Austin(2011) reported that exposure of the proglacial floodplain inKangerlussuaq western Greenland during ice retreat mayalso make more material available for aeolian transport

This paper aims to describe the temporal variations insources of minerals in a Greenland ice core covering a nearly100-year period (1915ndash2013) with a 5-year resolution dur-ing which the Arctic region was remarkably warming Themorphology and mineralogical composition of the ice coredust were analysed by SEM and EDS and variations are dis-cussed in terms of changes in the ice core dust sources

Clim Past 17 1341ndash1362 2021 httpsdoiorg105194cp-17-1341-2021

N Nagatsuka et al Variation in Greenland ice core dust mineralogy over the past 100 years 1343

2 Samples and analytical methods

21 SIGMA-D ice core

The ice core was drilled at 2100 m asl in an accumula-tion area of the northwestern Greenland Ice Sheet called theSIGMA-D site (77636 N 59120W) in May 2014 (Ma-toba et al 2015) The SIGMA-D site is located 250 km eastof the town of Qaanaaq and lies in the upstream section ofHeilprin Glacier the largest outlet glacier in this area (Fig 1)The ice core was recovered from the surface down to a depthof 22272 m (total core length)

22 Water isotope and ion concentration measurement

To determine the annual layers of the SIGMA-D ice corethe stable isotopes of water (δ18O) and the concentrationsof sodium and sulfate ions (Na+ and SO2minus

4 ) were measuredat the Institute of Low Temperature Science Hokkaido Uni-versity and the concentration of tritium was measured at theNational Institute of Polar Research (NIPR) Tokyo Japan

The ice core samples were cut into 5ndash10 cm pieces withcross sections of 30 cm2 and decontaminated by removingthe surface of each sample with a ceramic knife Then eachsample was placed in a clean polyethylene bag and meltedin a water bath before being transferred to pre-cleanedpolypropylene bottles in a tent for sample preparation at thefield camp (Matoba et al 2015) δ18O was measured using anear-infrared cavity ring-down spectrometer (IR-CRDS Pi-carro L2130-i USA) with a high-throughput Picarro-A0212vaporizer The precision of determination was plusmn008 permil forδ18O The concentrations of Na+ and SO2minus

4 were determinedby ion chromatography (ICS-2100 Thermo Fisher Scien-tific USA) Dionex AS-14A and CS-12A columns (ThermoFisher Scientific) were used for anion and cation analysesrespectively The limit of quantification was 5 ppb for bothions For SO2minus

4 we also calculated its non-sea-salt (nss) frac-tions as follows

[nssSO2minus4 ] = [SO2minus

4 ] minus (SO2minus4 Na+)seatimes[Na+] (1)

where (SO2minus4 Na+)sea is the mass ratio of SO2minus

4 to Na+ inthe seawater which is 0252 (Wilson 1975 Legrand andMayewski 1997) Tritium concentrations were measured us-ing a liquid scintillation counter (LSC-LB3 Aloka Co LtdJapan) The vertical resolution of the tritium measurementswas 05 m

23 Dust concentration

The concentration of dust in the SIGMA-D ice core was mea-sured using an Abakus laser particle sensor (Klotz GmbHGermany) connected to a continuous-flow analysis (CFA)system a slightly modified version of the one reported byDallmayr et al (2016) The size bins cover the range from 15to 150 microm and the depth resolution of the measurement was

2ndash3 cm CFA analysis has not been performed since 2003(above a depth of 635 m) due to poor core quality

24 SEMndashEDS analysis of mineral dust

To extract mineral particles from the ice core at 5-year in-tervals 4 cm2 cross sections were cut from the 50 cm longarchived core sections in the minus20 C cold room at NIPRThe possibly contaminated outer layers (sim 1 cm thick) wereremoved using a pre-cleaned ceramic knife Then severalmillimetres of the ice surface was scraped off by the ce-ramic knife and collected in a clean 100 mL polyethylenebottle for every 5-year interval The samples were freeze-dried at minus45 C using a freeze dryer (DRW240DA Advan-tec Japan) on a polycarbonate membrane filter (Advantec)with a diameter of 25 mm and pore size of 01 microm The mor-phological characteristics and chemical composition of in-dividual mineral particles on the membrane filter were ob-served by SEM (Quanta FEG 450 FEI) combined with EDS(X-Max 50 Oxford Instruments UK) at NIPR The filter tar-gets were mounted on aluminium stubs using double-facedadhesive carbon tape and coated with vaporized platinum forSEM observation In total 150 particles were randomly cho-sen from the filter and the equivalent circle diameter thetwo-dimensional area (A) and the perimeter (P ) were mea-sured on digital photographs with an image-processing ap-plication (ImageJ National Institutes of Health USA) Thenthe shape parameters of the particles were obtained namelycircularity (= (4πA)timesPminus2) The major elemental composi-tion (Na Mg Al Si Cl S Ca K Fe P and Ti) and relatedoxides (Na2O MgO Al2O3 SiO2 CaO K2O Fe2O3 P2O5and TiO2) were obtained from the EDS spectra The accel-eration voltage and working distance for SEM analysis were20 kV and 10 mm respectively and each EDS spectrum hadmore than 100 000 acquisition counts To be counted as amineral dust a particle had to contain at least one of the ele-ments Na Mg Si Al K Ca and Fe each with an atomic ra-tio () amount at least twice that of the error () We did notcount soluble particles such as CaSO4 Na2SO4 and NaClthat can be derived from volcanic and marine aerosols

25 Mineral identification

The mineralogical identification was performed using ele-mental composition and related oxides of individual min-eral particles Previous studies used protocols to semi-quantitatively identify the mineralogy of individual parti-cles in ice cores by SEMndashEDS analysis (eg Mudroch etal 1977 Maggi 1997 Donarummo et al 2003 Wu etal 2016) The identification of the SIGMA-D ice core dustfollowed three procedures (Wu et al 2016) First the spec-trum pattern of each particle was matched to those of stan-dard minerals (Severin 2004) Second we compared the ox-ide composition and morphology of the ice core dust withthose of the standard minerals Finally a sorting scheme used

httpsdoiorg105194cp-17-1341-2021 Clim Past 17 1341ndash1362 2021

Figure 1 Location map of the SIGMA-D site (77636 N 59120W 2100 m asl) Contour lines are drawn at a 500 m interval The blueframe in the inset map of Greenland (GrIS) denotes the domain of the main map The green shaded region in the inset map denotes theice-free coastal terrain (GrC) and HT NG GR RL SA and D3 denote Hans Tausen NGRIP GRIP Renland Site-A and Dye-3 ice coresites for the back-trajectory comparison respectively

to identify minerals in the GISP2 Greenland ice core dust bySEMndashEDS was applied to identify the mineral types fromthe peak intensity ratios (Donarummo et al 2003) Compar-ing the results of these procedures enables reliable mineralidentification (Maggi 1997 Wu et al 2016)

Based on the formation process (weathering types) forma-tion environment (temperature and humidity) and possiblesources of the SIGMA-D ice core dust most of the silicateswe analysed could be classified into the following five typesType A consists primarily of kaolinite which is a clay min-eral generally formed by chemical weathering in warm andhumid regions including Africa South America and South-east Asia (eg Mueller and Bocquier 1986 Velde 1995Bergaya et al 2006) We also found a mineral composedof Si and Al but with a higher proportion of Si and a lowerproportion of Al compared with kaolinite It is likely pyro-phyllite which is generally found with kaolinite and is thusalso classified as Type A Type B comprises mica chloriteand a mixture of the two which are clay minerals formed bymechanical weathering of igneous and metamorphic rocksin cold and dry regions (eg Cremaschi 1987 Pye 1987Velde 1995) Type C consists of feldspars (NaCa- and K-feldspars) which are also formed by mechanical weatheringin cold and dry regions (eg Nahon 1991) Type D consistsof mafic minerals containing abundant Mg and Fe such ashornblende and pyroxene which are less frequent in atmo-spheric dust and are formed by mechanical weathering (egDeer et al 1993) Type E consists of quartz which are the

most physically and chemically resistant minerals to weath-ering and their abundance in the atmosphere is related to thelarge desert source areas (Pye 1987 Yokoo et al 2004 Gen-thon and Armengaud 1995) According to previous studiessome minerals have localized distributions Ito and Wagai(2017) showed the global terrestrial distribution of clay sizemineral groups revealing that Type A minerals were pre-dominant in humid regions in low- or middle-latitude areaswhereas Type B minerals were abundant in arid andor high-latitude areas Furthermore kaolinite (Type A) can be used asan indicator of intensive weathering in palaeoclimatic condi-tions (Biscaye 1965 Griffin et al 1968) For example therelative abundance of kaolinite (Type A) to chlorite (Type B)is a mineral indicator that is most sensitive to latitude de-pendency The kaolinite chlorite ratio shows higher valuesfor minerals from low latitudes such as North Africa butshowed lower values for minerals from the Northern Hemi-sphere such as Asia and North America (eg Biscaye etal 1997 Maggi 1997 Svensson et al 2000 Donarummoet al 2003) This trend reflects a decrease in weathering in-tensity with latitude In addition to variations in kaolinite andchlorite Type C D and E minerals also reflect the geolog-ical and climatic conditions of their source areas as men-tioned above Thus compositional variations among the fivetypes of minerals can be used as an indicator of the sourceand transportation process of ice core dust in different peri-ods In this study we consider each type of mineral as pos-sibly being contributed from the following sources Type A

low- to mid-latitude areas (eg central Africa South Amer-ica and Southeast Asia) Types B and C high-latitude (egNorth America Russia north Europe and Greenland) andordesert areas (eg Asia and North Africa) Type D local areas(Greenland) and Type E desert areas (eg Asia and NorthAfrica)

26 Backward trajectory analysis

To investigate the possible source regions of the ice core dustthe air mass transport pathways were analysed using the Hy-brid Single-Particle Lagrangian Integrated Trajectory (HYS-PLIT) model which is distributed by the National Oceano-graphic and Atmospheric Administration (NOAA Stein etal 2015) Points at 50 500 1000 and 1500 m above groundlevel (agl) at the SIGMA-D site were set as the initialpoints of an air mass for the 7 d backward trajectories Theprobability distribution of the air mass at altitudes below1500 m agl was calculated at a 1 resolution We assumedwet and dry deposition processes for the preserved aerosoltracers (Iizuka et al 2018 Parvin et al 2019) For wet de-position the probability was weighted by the daily precip-itation when the air mass arrived at the ice core site Fordry deposition the probability was based on the counting ofnon-precipitation days when the air mass arrived We useddaily precipitation from the ERA-40 and ERA-Interim re-analysis datasets both of which were produced by the Eu-ropean Centre for Medium-Range Weather Forecasts (Deeet al 2011 Uppala et al 2005) The daily precipitationof ERA-40 (p40) was calibrated with that of ERA-Interim(pint) via linear regression obtained for the period 1979ndash2001(pint = 047p40 R2

= 0702 p lt 0001) to maintain consis-tency between the two precipitation datasets for the entire pe-riod (1958ndash2013) We also calculated the regional contribu-tion from the probability distribution for which land regionswere divided into the following five regions the GreenlandIce Sheet the Greenland coast Canada (including Alaska)northern Eurasia and mid-latitude arid regions (consistingof China Central Asia and the Middle East) (Fig 2a)

To compare the sources of mineral dust in the GreenlandIce Sheet the air mass transport pathways were analysed notonly from the SIGMA-D site but also from the other sixGreenland ice core sites for which Bory et al (2003b) re-vealed the dust sources based on Sr and Nd isotope ratios thefour interior sites (NGRIP GRIP Site-A and Dye-3) containmore dust from eastern Asian deserts compared with the twocoastal sites (Hans Tausen and Renland) We analysed the7 d back trajectories of the air masses for 1981ndash2010 with aninitial height of 500 and 1500 m agl at the ice core sites

27 Snow cover fraction

To examine the surface conditions of neighbouring sourceareas of mineral dust we analysed inter-annual changes insnow cover fraction derived from multiple numerical simu-

lations by a climate model Various international organiza-tions have used global climate models to conduct numericalsimulations that reproduce or predict climate change frompast to future The results have been published by CoupledModel Intercomparison Project Phase 6 (CMIP6 Eyring etal 2016) under the auspices of the World Climate ResearchProgramme In the present study snow cover fractions de-rived from historical simulations for the period 1850ndash2014(Onuma and Kim 2020a b c d) were used to examinemineral dust sources for SIGMA-D The dataset was pro-duced by MIROC6 a climate model developed by a Japanesemodelling community (Tatebe et al 2019) Four reanaly-sis datasets namely GSWP3 (Kim 2017) CRUJRA (Harris2019) Princeton (Sheffield et al 2006) and WFDEI (Wee-don et al 2014) provided the meteorological conditions forthe Land Surface Snow and Soil moisture Model Intercom-parison Project (LS3MIP van den Hurk et al 2016) whichis a sub-project of CMIP6 We obtained data on inter-annualchanges in snow cover fraction during summer on the north-west and southwest coasts of Greenland (boundary at 70 N)

3 Results

31 Dating of the SIGMA-D ice core

Dating of the SIGMA-D ice core was performed by an-nual layer counting of δ18O and Na+ that showed obviousseasonal variations (Fig A1) The observed seasonality ofchemical components and the water stable isotope ratio in thesnowpack and ice cores have previously been reported at var-ious sites on the Greenland Ice Sheet (Whitlow et al 1992Legrand and Mayewski 1997 Kuramoto et al 2011 Oy-abu et al 2016 Kurosaki et al 2020) The winter seasonof the SIGMA-D ice core was defined as the depth at whichδ18O was at its minimum value and Na+ was at its maxi-mum value and we counted winter season to winter seasonas 1 year

Other fixed dates were provided by the tritium profile andnssSO2minus

4 spikes A sharp tritium peak at 1156 m we cor-responds to the H-bomb test in 1963 (Koide et al 1982Clausen and Hammer 1988) indicating an accumulation rateof 023 m we yrminus1 from 1963 to 2013 The large nssSO2minus

4peak appearing at 5417 m we is assumed to correspondto the eruption of the Laki volcano in 1783 The nssSO2minus

4signal of the 1783 Laki eruption has also been found inother ice cores in Greenland Arctic Canada and Svalbard(Clausen and Hammer 1988 Grumet et al 1998 Matoba etal 2002) Similarly we assume other nssSO2minus

4 spikes to bethe signatures of unknown (1810) Tambora (1816) and Kat-mai (1912) volcanic eruptions at shallower depths of 47534603 and 2350 m we respectively Comparing the annuallayer counting and these reference horizons we estimate thatthe ice core dating includes a 1-year error

As a result of these analyses we estimate that the upper11287 m (8606 m we) of the ice core is equivalent to the

Figure 2 Map showing (a) the location of the SIGMA-D (Sigma-D) ice core site in Greenland and five regions for calculating regionalcontribution (GrIS Greenland Ice Sheet grey GrC Greenland coast green CND Canada and Alaska orange NEU northern Eurasia lightblue Arid arid regions including China Central Asia and the Middle East red) and (b) the probability distribution of an air mass at theSIGMA-D site from a 7 d three-dimensional back-trajectory analysis from 1958 to 2014

period from 1660 to 2013 In this study we used ice samplesto a depth of 3860 m (2275 m we) covering 1915 to 2013for the SEM and EDS analyses (Table 1)

32 Particle morphology

Figure 3 shows SEM images of the mineral dust in theSIGMA-D ice core The number size distribution of mineraldust in the SIGMA-D ice core showed that most particles hada diameter of lt 2 microm (Fig 4) which is consistent with otherGreenland ice core dust (eg Steffensen 1997 Biscaye etal 1997) The mean and maximum particle diameters cal-culated as 5-year averaged values ranged from 102 to 253and 494 to 2651 microm respectively with a single modal struc-ture at the peak ranging from 035 to 115 microm The size dis-tribution varied among the samples collected from differentperiods showing a narrower peak with finer mode (035ndash053 microm) for the samples from 1965 to 1979 and a broaderpeak with a coarser mode for the samples from 1920 to1924 and 1945 to 1949 (097ndash115 microm Fig A2) There werecoarser particles with diameters of gt 10 microm in the samplesfrom 1915 to 1959 and from 1990 to 2013 but no particleswith diameters of gt 10 microm were found in the samples from1960 to 1989 except for the sample from 1980 to 1984

33 Quantitative estimation of mineral dust

The elemental composition of individual mineral particlesobtained from the EDS analysis showed that the ice core dustwas composed mainly of silicate minerals in all the sam-ples (65 ndash95 Fig 6) Based on a peak intensity ratiosorting scheme (Donarummo et al 2003) and comparisonof oxide composition and morphological information with

those of standard minerals the silicates were categorized asquartz NaCa- and K-feldspars clays (kaolinite pyrophyl-lite smectite illite mica and chlorite as well as mixed lay-ers of illitendashsmectite and micandashchlorite) and mafic mineralsrich in magnesium and iron (Figs 3 and 7) These mineralswere also found in Greenland ice cores from glacial periods(eg Maggi 1997 Svensson et al 2000)

Semi-quantitative analysis of the EDS spectrum showedthat the proportion of kaolinite among 150 mineral parti-cles found in each sample was the highest (5 ndash66 ) andthat of smectite was the lowest (0 ndash2 ) in nearly everyperiod (Fig 7 and Table 2) The proportion of pyrophyllitemicandashchlorite mix quartz feldspars and illitendashsmectite mixwas the second highest varying from 5 ndash27 3 ndash25 3 ndash22 2 ndash21 and 2 ndash15 respectively The min-eralogy of the SIGMA-D ice core dust showed significantlyhigher kaolinite contents compared with those of the otherGreenland ice cores (GRIP 4 ndash16 Svensson et al 2000GISP2 0 ndash2 Donarummo et al 2003)

The silicate mineral composition showed large variationsamong the samples on two different timescales First thecompositions varied on a multi-decadal scale with higherkaolinite and pyrophyllite contents (30 ndash66 and 5 ndash27 ) and lower micandashchlorite mix contents in the 1950to 2004 samples (3 ndash15 respectively) especially in the1975 to 2004 samples The opposite trend was observed inthe 1915 to 1949 and 2005 to 2013 samples (kaolinite andpyrophyllite 5 ndash20 and 6 ndash16 respectively micandashchlorite mix 9 ndash25 ) The compositional variation alsoshowed higher feldspars mafic and quartz contents in the1915 to 1949 and 1990 to 2013 samples (feldspars 2 ndash21 mafic 0 ndash9 quartz 5 ndash22 ) than in the otherperiods (feldspars 3 ndash6 mafic 0 ndash4 quartz 3 ndash

Table 1 Description of the SIGMA-D ice core dust samples

Period Ice Dust (size)

Top Bottom Average Maximum Log-normal(m) (m) (microm) (microm) mode (microm)

1915ndash1919 3700 3860 197 1280 0731920ndash1924 3549 3700 251 1628 1151925ndash1929 3380 3549 222 2651 0461930ndash1934 3185 3380 157 1210 0581935ndash1939 3022 3185 227 2009 0591940ndash1944 2857 3022 176 1501 0591945ndash1949 2687 2857 253 2185 0971950ndash1954 2502 2687 149 1285 0551955ndash1959 2367 2502 201 1409 0751960ndash1964 2189 2367 125 667 0601965ndash1969 1995 2189 127 965 0531970ndash1974 1785 1995 103 494 0351975ndash1979 1630 1785 102 553 0431980ndash1984 1461 1630 191 1188 0581985ndash1989 1250 1461 122 554 0471990ndash1994 1003 1250 220 1591 0681995ndash1999 756 1003 208 1486 0772000ndash2004 462 756 145 872 0652005ndash2009 231 462 188 1129 0602010ndash2013 000 231 203 2595 051

Figure 3 SEM images of each mineral group in the SIGMA-D ice core

Figure 4 Particle size distribution and log-normal fitting results (mode mode diameter and R2 half peak width) of minerals in the ice coresamples from 1915 to 2013

Figure 5 (a) Circularity distribution of mineral particles from different period (b) Variation in proportion of circularity values of gt 08

Figure 6 Variations in the insoluble mineral records in the ice core in 5-year resolution

6 ) Second the compositions varied on shorter timescalesin inter-decadal cycles Variations in the compositions offeldspars mica chlorite and micandashchlorite mix were simi-lar but opposite to those of kaolinite and pyrophyllite

Non-silicate minerals were also found in the ice core sam-ples and were composed mainly of Ca- and Fe-dominantminerals identified as carbonates (calcite) and Fe-oxides(pyrite magnetite or hematite) respectively (Fig 6) Therelative abundance of both minerals ranging from 0 to15 has increased in the last 10 years The carbonate miner-als showed the highest abundance in the 1960ndash1964 sample

34 Source regions of SIGMA-D ice core dust

To identify the source regions of the ice core dust we appliedthe HYSPLIT back-trajectory model and calculated the prob-ability distributions of an air mass arriving at the SIGMA-Dsite from 1958 to 2014 (Figs 2b and 8) The results showthat the air mass at elevations above ground level from 0 to1500 m came mainly from the western coast of Greenlandincluding the Baffin Bay whereas a smaller part came fromnorthern Canada (Figs 2b and 8a) Excluding the ice sheetand ocean areas that could not be possible sources of mineraldust the air mass is considered to have come mainly from theGreenland coast (50 ndash60 ) and Canada (sim 40 ) with asmall contribution from northern Eurasia (sim 3 Fig 8b)Contributions from these three possible source regions showlittle seasonal and inter-annual variabilities (Fig 8b and c)The air mass contribution from the Greenland coast waslarger in dry deposition than wet deposition during summerwhich may have caused an increase in dust sourced fromlocal ice-free areas However there was no significant dif-ference in the overall trend between the two deposition pro-cesses

4 Discussion

41 Variation in silicate mineral composition

The SEMndashEDS analysis revealed that the SIGMA-D icecore dust samples collected from 1915 to 2013 containedmainly silicate minerals which is the most abundant fam-ily of crustal minerals (Deer et al 1993) Silicate mineralcomposition showed variations on a multi- and inter-decadalscale indicating that the ice core minerals originated fromdifferent geological sources in different periods during thepast 100 years

Variation trends in the silicate mineral composition of theSIGMA-D ice core samples substantially differed amongmineral types (Fig 9) indicating that the minerals in theice core were derived from multiple geological sources Thedominance of Type A minerals in the samples from 1950to 2004 indicated that the minerals might be derived mainlyfrom low- or middle-latitude areas in the periods In contrastthe abundance of Type B C D and E minerals in the samplesfrom 1915 to 1949 and from 2005 to 2013 indicated that theminerals were likely derived from arid deserts andor high-latitude areas including Greenland

The morphological characteristics of the ice core dustalso support the changes in the sources of silicate mineralsThe size distribution of the minerals showed lower meanmaximum and modal diameters from 1950 to 1989 com-pared with the other periods when the samples consistedmainly of Type A minerals (Table 1 Fig A2) The circular-ity also showed a similar trend containing smaller amountsof particles with circularity valuesgt 080 from 1950 to 1989(Fig 5) The particle size depended on the mineralogy of theice core dust The coarser fraction (gt 2 microm) of the ice coredust samples contained little clay especially for Type A min-erals (Fig 10) but contained an abundance of Type C D andE minerals This particle size dependence is consistent withother analyses of Greenland ice core dust (Biscaye 1965Svensson et al 2000) Thus the ice core dust was likely

Figure 7 Variations in the silicate mineral records in the ice core in 5-year resolution (a) Mineral composition and (b) proportion of eachmineral Mica and chlorite composed of mica micandashchlorite mix chlorite and feldspars composed of NaCa-feldspar and K-feldspar

derived from different geological sources in the late 1900scompared with the other periods

42 Possible causes of mineralogical variation

One of the possible causes of the temporal variations in thesilicate mineral composition is a surface temperature changein Greenland Reconstructions of temperature variability in

Greenland have revealed there were two intense warmingperiods (1920sndash1940s and since the 1990s) and a coolingperiod (1950sndash1980s) in the past 100 years (eg Box etal 2009 Kobashi et al 2011 Cappelen 2019) These trendswere strong in the western coastal region and were similar tothose of the silicate mineral compositions The proportion ofType A minerals was low in the samples from 1915 to 1949increased from 1950 to 2004 and decreased again after 2005

N Nagatsuka et al Variation in Greenland ice core dust mineralogy over the past 100 years 1351Ta

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

Figure 8 (a) Contribution of an air mass from possible source ar-eas from 1958 to 2013 for which precipitation at the SIGMA-Dsite is taken into account (b) Seasonal and (c) annual variations inthe regional contribution of air mass to the SIGMA-D site throughwet and dry depositions excluding the ice sheet and ocean areasGrC GrIS CND and NEU denote the ice-free Greenland coastalregion (Fig 1) Greenland Ice Sheet Canada and northern Eurasiarespectively (Fig 2a)

In contrast the proportion of Type B C D and E mineralsshowed the opposite trend Therefore Type A minerals wereabundant in the colder periods whereas Type B C D and Eminerals were abundant in the warmer periods (Fig 9) Theseresults suggest that the multi-decadal variation in SIGMA-D ice core silicates was likely affected by local temperaturechanges in Greenland

The North Atlantic Oscillation (NAO) is also thought tobe a possible cause of compositional variations in the sil-icate minerals The NAO is known to show inter-decadalvariations and is strongly related to the incidence and inten-sity of blocking high pressure over Greenland (Woollings etal 2010 Hanna et al 2014) Thus the NAO can change theatmospheric circulation patterns and transportation processesassociated with the ice core dust which could be relatedto inter-decadal variations in the silicates However there isno clear correlation between the NAO and silicate mineralrecords One of the reasons for this may be the low samplingresolution which makes it difficult to determine a correlationwith the NAO index

Figure 9 Comparison of historical changes in proportion of silicate minerals from the SIGMA-D ice core (a kaolinite group b smectitegroup c micandashchlorite group d feldspar group e mafic mineral f quartz) with those in (g) the North Atlantic Oscillation index (NAOHurrell and National Center for Atmospheric Research Staff 2020) and (h) surface temperature anomalies and (i) snow cover fractionanomalies in Greenland Surface temperature anomalies deviate from the 1948ndash2013 average in Thule The temperature record of Greenlandis from Berkeley Earth and Thule (Pituffik) and Upernavik in western Greenland located 100 km south and 650 km southeast of Qaanaaq arefrom Cappelen (2019) Snow cover fraction anomalies deviate from the 1915ndash2013 average in NW and SW Greenland

Figure 10 Historical changes in proportion of large particles (diametergt 2 microm) in (a) kaolinite (b) micandashchlorite (c) feldspars (d) maficminerals and (e) quartz

In addition to the NAO sulfate aerosols originating fromvolcanic eruptions have also been identified as another im-portant cause of the cooling in Greenland especially alongthe western ice sheet margins during the 1900s (Box etal 2009) such as the Mt Agung eruption in 1963 the MtSt Helens eruption in 1980 and the Mt Pinatubo eruption in1991 However the chemical compositions of ash from thesevolcanoes (Taylor and Lichte 1980 Pallister et al 1992Devi et al 2019) were different from the composition of theType A minerals that were abundant in the cooling periodThe SEM observations also did not identify ice core miner-als exhibiting morphological characteristics of volcanic ashThese results indicate that the effect of volcanic materials onthe variation in silicate mineralogy may be negligible in theSIGMA-D ice core

43 Possible sources for mineral dust in the SIGMA-Dice core

The trajectory analysis revealed that the majority of the airmass came from the western coast of Greenland and that

a smaller proportion came from northern Canada between1958 and 2014 The contribution from these two possiblesource regions showed little inter-annual variabilities (Fig 8band c) indicating that the transportation processes of the icecore dust have not substantially changed on an annual ba-sis over the last 5 decades Thus the variations in the ge-ological origins of the ice core dust were unlikely due tochanges in air mass transportation An alternative cause ofdust variability could be a change in the surface conditions ofthe source areas Retreats of the ice sheet and local glaciershave accelerated since 2000 in Greenland increasing the ex-posure of the ground surface in snowice-covered areas in thecoastal region (eg van den Broeke et al 2009 Bendixenet al 2017) Furthermore the modelled snow cover frac-tion anomaly during summer (June July and August) on thenorthwest and southwest coasts of Greenland is negativelyconsistent with the temperature anomalies (Fig 9h and i)The snow cover fractions are lower during the two warm-ing periods of 1920sndash1950s and 2000ndash2013 Given that thesnow cover fraction should directly relate to the snow coverduration this result suggests that the snow cover duration on

the west coast of Greenland was shortened in the warmingperiods and thus might also have contributed to the increasein local dust emissions Bullard and Mockford (2018) anal-ysed records of dust events in the western Greenland coastalregion and revealed that the annual severity of dust emis-sions was higher from 2000 to 2010 than during the pre-ceding decades This was likely due to increasing meltwa-ter runoff delivering sediments from the ice sheet to outwashplains with the increase in atmospheric temperature Highdust emissions on the western coast of Greenland occurred inspring and summer when the snow cover is rapidly decreas-ing (Bullard and Mockford 2018) Our trajectory analysisalso indicated that the air mass contribution from the Green-land coast was slightly larger in spring and summer than inautumn and winter (Fig 8b) Therefore the snowice coverduration in the Greenland coastal region was shortened by therecent warming during the melt season causing an increasein the local supply of dust to the SIGMA-D site Althoughno satellite observations are available for the first warmingperiod (1920sndash1940s) aerial photos maps and paintings in-dicated ice retreat in Greenland (Box and Herrington 2007)Thus the abundant Type B C D and E minerals found inthe two warming periods were likely due to an increase indust sourced from local ice-free areas

The ice core dust morphology and composition also in-dicated a contribution from local sediment in the warmingperiods Simonsen et al (2019) used particles with diam-eters of lt 2 and gt 8 microm as indicators of distant and localdust sources respectively for the Renland Ice Cap Project icecore in eastern Greenland The size distribution of SIGMA-D ice core dust showed that the samples from the cold pe-riod (1950ndash1999) contained fewer particles with diametersof gt 8 microm (0ndash4 particles) than those from the warm periods(1915ndash1949 and 2000ndash2013 1ndash9 particles) Furthermore thehigher proportions of Type C and E minerals in the SIGMA-D ice core samples in 1915ndash1949 and 2000ndash2013 correspondto higher concentrations of the two minerals in the surfacedust and soil on and around the Qaanaaq Glacier (Nagat-suka et al 2014) Since the Abakus laser particle sensorconnected to the CFA system detected particles with diam-eters of 15 and 15 microm and CFA analysis has not been per-formed since 2003 (above a depth of 635 m) due to poorcore quality we cannot compare the size distribution datawith that measured by the SEM However the Abakus dustprofiles (Fig A3) showed higher concentration for the parti-cles with diameters of gt 15 gt 5 and gt 8 microm in the warmperiod (1915 to the 1950s) compared with the cold period(1955ndash1999 except for a large peak in 1978) which sup-ports an increase in local dust contribution from 1915 to the1950s as shown by the SEMndashEDS results

Previous studies indicated dust transport from distantdeserts such as those in Asia and Africa which are anotherpossible source for three of the mineral types (B C and E)found at high-elevation sites on the Greenland Ice Sheet dur-ing the past century (Bory et al 2003a Drab et al 2002)

However our trajectory analysis showed little contributionfrom these regions in the 7 d back trajectory A similar anal-ysis of an ice core on the southeastern coast of Greenlandsuggested that air mass contribution from Asian and arid re-gions was negligible even for the 25 d back trajectory (Iizukaet al 2018) Schuumlpbach et al (2018) also reported littlecontribution of air mass from Asian arid regions and ad-dressed a limitation of the back-trajectory analysis namelythat it could not capture dust transport from Asia to Green-land which might be through the upper troposphere Bory etal (2003b) suggested that sources providing dust to an icecore site are dependent on distance from the ice sheet marginandor the altitude and that long-range transport from Asiandeserts likely accounts for most of the dust deposited at in-terior sites (NGRIP GRIP Site-A and Dye-3) whereas lo-cal sources represent an additional and primary contributor atcoastal sites in Greenland (Hans Tausen and Renland) Our7 d back-trajectory analysis shows the significantly low con-tribution of air masses from Asian and arid regions (less than01 ) whereas the air mass contribution from the Greenlandcoast is high (7 ndash14 ) especially for Renland and HansTausen followed by the Sigma-D site (Fig 11a and d) Themineralogical composition of SIGMA-D also showed a sub-stantially lower proportion of Type B (chlorite) and Type Eminerals and a higher proportion of Type A minerals (1 ndash11 3 ndash22 5 ndash66 ) compared with other Green-land ice core dust originating from Asian deserts (eg GRIP12 ndash27 28 ndash48 4 ndash16 Svensson et al 2000)Thus very little of the mineral dust in the ice core fromSIGMA-D which is located in a coastal area may have comefrom distant deserts whereas a large proportion likely camefrom the local areas in the warming periods

Possible sources of ice core dust in the colder period(1950ndash2004) are likely to be found in low to mid-latitudesbecause the Type A mineral that is typical of humid tropicalclimatic zones such as modern-day Africa South Americaand Southeast Asia was abundant in that period Althoughback-trajectory analysis cannot estimate contributions fromdistant sources as described above it is unlikely that largeamounts of ice core dust were transported from such tropicalregions However our back-trajectory analysis suggests thatnorthern Canada might also be a possible source of Type Aminerals and some studies support this argument (Fig 11b)For example Darby (1975) analysed the clay mineral com-position of marine sediments from deep-sea cores in the Arc-tic Ocean and revealed that there was abundant kaolinite(Type A minerals) apparently derived from shale and soilsof northern Alaska and northern Canada which were relictdeposits of warmer climates in the Tertiary This abundantkaolinite was deposited in a non-marine environment (Allenand Johns 1960) Clay mineralogy of North Sea basin sedi-ment cores also revealed that increased kaolinite concentra-tions were associated with the PaleocenendashEocene ThermalMaximum (Kemp et al 2016) The Type A minerals werelikely transported from such ancient soils formed by chemi-

Figure 11 Air mass contribution for the 7 d back trajectoryfrom (a) arid regions (China Central Asia and the Middle East)(b) North America (Canada and US) (c) Eurasia (EU and Russia)and (d) the Greenland coast at the seven ice core sites on Green-land Error bars indicate the standard deviation of contributionsfrom 1981 to 2010

cal weathering in high-latitude areas in past warming eventsThus we concluded that northern Canada is likely the bestcandidate for the SIGMA-D ice core dust source during thecold period

The SEMndashEDS results of the SIGMA-D ice core dust candemonstrate variations in the ice core dust sources over thepast 100 years The relatively higher proportion of Type Aminerals (more than 30 ) in almost all the periods indi-cates that the ice core dust was constantly supplied from adistant source (mainly northern Canada) to the SIGMA-Dsite and that the source areas have not changed over the past100 years However dust was additionally provided from lo-cal ice-free areas in the warm periods (1915ndash1949 and 2005ndash2013) because the snowice cover duration in the Greenlandcoastal region was shortened by the recent warming duringthe melt season

5 Conclusions

Analysis of the SEMndashEDS of individual dust morphologyand mineralogy in the SIGMA-D ice core revealed that theice core dust consisted mainly of silicate minerals includ-ing quartz feldspars and mafic minerals and clay miner-als including kaolinite illite smectite mica and chloriteMost of the particles had a diameter oflt 2 microm implying thatthe ice core contained mainly long-range-transported wind-blown mineral dust The silicate mineral composition variedsubstantially on multi-decadal and inter-decadal scales Themulti-decadal variation trend differed among mineral typesformed in different source areas which corresponded tosurface temperature changes in Greenland kaolinite which

is typical of humid tropic climatic zones was abundantin the colder period (1950ndash2004) whereas mica chloritefeldspars mafic minerals and quartz which are generallyformed in arid high-latitude andor local areas were abun-dant in the warmer periods (1915ndash1949 and 2005ndash2013)This indicates that the ice core minerals originated from dif-ferent geological sources in different periods during the past100 years The multi-decadal variation in the relative abun-dance of the minerals was likely affected by local temper-ature changes in Greenland The trajectory analysis showedthat the air mass arriving at the SIGMA-D site came mainlyfrom the western coast of Greenland and that a smaller pro-portion came from northern Canada during 1958ndash2013 Thecontributions from the two showed little inter-annual vari-ability indicating that an alternative cause of variability inthe geological origins of the ice core dust was likely to be achange in the surface conditions of source areas rather thanin air mass transportation The abundant mineral types in thetwo warmer periods might be explained as an increase indust sourced from local ice-free areas resulting from short-ened snowice cover duration in the Greenland coastal re-gion caused by the recent warming during the melt sea-son Meanwhile ancient deposits in northern Canada whichwere formed in past warmer climates seem to be the bestcandidate during the colder period (1950ndash2004) We con-cluded that ice core dust was constantly supplied from dis-tant sources (mainly northern Canada) to the SIGMA-D siteas well as local ice-free areas in the warm periods Althoughfurther analyses are needed to identify the cause of inter-decadal variations in ice core dust our study is the firstto demonstrate a high-temporal-resolution record of mineralcomposition in a Greenland ice core over the past 100 years

Appendix A

Figure A1 δ18O Na+ nssSO2minus4 and tritium records in the upper 11287 m (8606 m we) of the SIGMA-D ice core Major volcanic signals

we identified are shown in the nssSO2minus4 record The bottom plots show the enlarged record from 0 to 10 m we

Figure A2 (a) Comparison of particle size distribution and log-normal fitting results (mode mode diameter and R2 half peak width) of theice core minerals among the samples (b) Historical changes in the mode diameter and R2

Figure A3 (a) Annual average number concentration of the SIGMA-D ice core dust particles with diameters of gt 15 gt 5 and gt 8 micromfrom 1915 to 2002 as measured by the Abakus laser particle sensor and (b) the averaged concentrations from 1915 to 1954 and from 1955 to1999

Data availability Datasets used in this study are available at thefollowing DOIs

MIROC6 model output prepared for CMIP6 LS3MIP experi-ments is available at

httpsdoiorg1022033ESGFCMIP65622 (land-hist On-uma and Kim 2020a)

httpsdoiorg1022033ESGFCMIP65627 (land-hist-cruNcep Onuma and Kim 2020b)

httpsdoiorg1022033ESGFCMIP65628 (land-hist-princeton Onuma and Kim 2020c) and

httpsdoiorg1022033ESGFCMIP65629 (land-hist-wfdeiOnuma and Kim 2020d)

δ18O ion concentrations and mineral dust data are available athttpsdoiorg10175920012021052501 (Nagatsuka et al 2021)

Author contributions NN designed the study and carried out theice core dust analysis and wrote the manuscript with the help ofKGA and KF KF SM YO YK MM and HM drilled the ice coreAT SM MK and MH obtained ion concentration and water isotopedata NN AT KF SM and MK analysed the chronology of the icecore KF conducted the back-trajectory analysis YO conducted theCMIP6 model analysis RD MH JO YOT KK and KGA con-ducted the CFA analysis KGA and YOT analysed the dust data TAinitiated the project All authors discussed and commented on thepaper

Competing interests The authors declare they have no conflictsof interest

Acknowledgements We would like to thank Tetsuhide Ya-masaki for general fieldwork support We also thank the two re-viewers Anders Svensson and Laluraj C M and the editor ElizabethThomas for valuable suggestions which substantially improved thispaper

Financial support This research has been supported by theJapan Society for the Promotion of Science (JSPS) Fellow-ship (SIGMA project (grant nos 23221004 and 16H01772)and 15H01731 15K16120 16J08380 16H06291 18H0336318H04140 19K20443 20H04980) the Integrated Research Pro-gram for Advancing Climate Models from the Ministry of Educa-tion Culture Sports Science and Technology (MEXT Japan (grantno JPMXD0717935457)) the Arctic Challenge for Sustainability(ArCS (grant no JPMXD130000000)) the Arctic Challenge forSustainability II (ArCS II (grant no JPMXD1420318865)) the En-vironment Research and Technology Development Fund of the En-vironmental Restoration and Conservation Agency of Japan (grantnos JPMEERF20172003 and JPMEERF20202003) and the Na-tional Institute of Polar Research Japan through project researchno KP305

Review statement This paper was edited by Elizabeth Thomasand reviewed by Anders Svensson and Laluraj C M

References

Allen V T and Johns W D Clays and clay min-erals of New England and Eastern Canada GSABulletin 71 75ndash86 httpsdoiorg1011300016-7606(1960)71[75CACMON]20CO2 1960

Amino T Iizuka Y Matoba S Shimada R Oshima N SuzukiT Ando T Aoki T and Fujita K Increasing dust emissionfrom ice free terrain in southeastern Greenland since 2000 PolarSci 27 100599 httpsdoiorg101016jpolar20201005992021

Bendixen M Iversen L L Bjoslashrk A A Elberling BWestergaard-Nielsen A Overeem I Barnhart K R Khan SA Box J E and Abermann J Delta progradation in Green-land driven by increasing glacial mass loss Nature 550 101ndash104 httpsdoiorg101038nature23873 2017

Bergaya F Theng B K G and Legaly G (Eds) Handbook ofClay Science Development in Clay Science Elsevier Amster-dam 2006

Biscaye P E Mineralogy and sedimentation of recent deep-sea clay in the Atlantic Ocean and adjacent seas and oceansGSA Bulletin 76 803ndash832 httpsdoiorg1011300016-7606(1965)76[803MASORD]20CO2 1965

Biscaye P E Grousset F E Revel M Van der Gaast SZielinski G A Vaars A and Kukla G Asian provenance ofglacial dust (stage 2) in the Greenland Ice Sheet Project 2 icecore Summit Greenland J Geophys Res 102 26765ndash26781httpsdoiorg10102997JC01249 1997

Bory A J-M Biscaye P E and Grousset F E Two dis-tinct seasonal Asian source regions for mineral dust depositedin Greenland (NorthGRIP) Geophys Res Lett 30 1167httpsdoiorg1010292002GL016446 2003a

Bory A J-M Biscaye P E Piotrowski A M and SteffensenJ P Regional variability of ice core dust composition andprovenance in Greenland Geochem Geophy Geosy 4 1107httpsdoiorg1010292003GC000627 2003b

Box J E and Herrington A Was there a 1930rsquos meltdown ofGreenland glaciers American Geophysical Union Fall MeetingSan Francisco USA 10ndash14 December 2007 C11A-0077 2007

Box J E Yang L Bromwich D H and Bai L Greenland IceSheet Surface Air Temperature Variability 1840ndash2007 J Cli-mate 22 4029ndash4049 httpsdoiorg1011752009JCLI281612009

Bullard J E and Austin M J Dust generation on aproglacial floodplain West Greenland Aeolian Res 3 43ndash54httpsdoiorg101016jaeolia201101002 2011

Bullard J E and Mockford T Seasonal and decadal vari-ability of dust observations in the Kangerlussuaq areawest Greenland Arct Antarct Alp Res 50 S100011httpsdoiorg1010801523043020171415854 2018

Capo R C Stewart B W and Chadwick O A Strontiumisotopes as tracers of ecosystem processes theory and meth-ods Geoderma 82 197ndash225 httpsdoiorg101016S0016-7061(97)00102-X 1998

Cappelen J (Ed) Denmark ndash DMI Historical Climate Data Col-lection 1768ndash2018 DMI Report 19-02 DMI Copenhagen Den-mark 2019

Clausen H B and Hammer C U The Laki andTambora eruptions as revealed in Greenland icecores from 11 locations Ann Glaciol 10 16ndash22httpsdoiorg103189S0260305500004092 1988

Cremaschi M Paleosols and Ventusols in the Central Po Plain(Northern Italy) A Study in Quaternary Geology and Soil De-velopment Unicopli Milano Italy 1987

Dallmayr R Goto-Azuma K Kjaeligr H A Azuma N Takata MSchuumlpbach S and Hirabayashi M A High-Resolution Contin-uous Flow Analysis System for Polar Ice Cores Bull GlaciolRes 34 11ndash20 httpsdoiorg105331bgr16R03 2016

Darby D A Kaolinite and other clay minerals in Arc-tic Ocean sediments J Sediment Res 45 272ndash279 httpsdoiorg101306212F6D34-2B24-11D7-8648000102C1865D 1975

De Angelis M Steffensen J P Legrand M Clausen H andHammer C Primary aerosol (sea salt and soil dust) deposited inGreenland ice during the last climatic cycle Comparison withEast Antarctic records J Geophys Res 102 26681ndash26698httpsdoiorg10102997JC01298 1997

Dee D P Uppala S M Simmons A J Berrisford P Poli PKobayashi S and Vitart F The ERA-Interim reanalysis Con-figuration and performance of the data assimilation system Q JRoy Meteor Soc 137 553ndash597 httpsdoiorg101002qj8282011

Deer F R S Howie R A and Zussman J An Introduction tothe Rock-Forming Minerals Longman White Plains New YorkUSA 1993

Devi S Bijaksana S Fajar S J and Santoso N A Character-ization of Volcanic Ash From the 2017 Agung Eruption BaliIndonesia IOP Conf Ser Earth Environ Sci 318 012014httpsdoiorg1010881755-13153181012014 2019

Donarummo J Ram M and Stoermer E F Possible de-posit of soil dust from the 1930rsquos US dust bowl iden-tified in Greenland ice Geophys Res Lett 30 1269httpsdoiorg1010292002GL016641 2003

Drab E Gaudichet A and Jaffrezo J L Mineral particles con-tent in recent snow at Summit (Greenland) Atmos Environ36 5365ndash5367 httpsdoiorg101016S1352-2310(02)00470-3 2002

Eyring V Bony S Meehl G A Senior C A Stevens BStouffer R J and Taylor K E Overview of the CoupledModel Intercomparison Project Phase 6 (CMIP6) experimen-tal design and organization Geosci Model Dev 9 1937ndash1958httpsdoiorg105194gmd-9-1937-2016 2016

Faure G and Mensing T M Isotopes Principles and Applica-tions John Wiley amp Sons USA 2004

Fuhrer K Wolff E W and Johnsen S J Timescales for dustvariability in the Greenland Ice Core Project (GRIP) ice corein the last 100000 years J Geophys Res 104 31043ndash31052httpsdoiorg1010291999JD900929 1999

Genthon C and Armengaud A GCM simulations of atmospherictracers in the polar latitudes South Pole (Antarctica) and Sum-mit (Greenland) cases Sci Total Environ 160ndash161 101ndash116httpsdoiorg1010160048-9697(95)04348-5 1995

Griffin J J Windom H and Goldberg E D The distribution ofclay minerals in the world ocean Deep-Sea Res 15 433ndash459httpsdoiorg1010160011-7471(68)90051-X 1968

Grumet N S Wake C P Zielinski G Fisher D A Koerner RM and Jacobs J D Preservation of glaciochemical time-seriesin snow and ice from Penny Ice Cap Baffin Island GeophysRes Lett 25 357ndash360 httpsdoiorg10102997GL037871998

Han C Hur S D Han Y Lee K Hong S Erhardt T Fis-cher H Svensson A M Steffensen J P and VallelongaP High-resolution isotopic evidence for a potential Saharanprovenance of Greenland glacial dust Sci Rep 8 15582httpsdoiorg101038s41598-018-33859-0 2018

Hanna E Fettweis X Mernild S H Cappelen J RibergaardM H Shuman C A Steffen K Wood L and Mote T L At-mospheric and oceanic climate forcing of the exceptional Green-land ice sheet surface melt in summer 2012 Int J Climatol 341022ndash1037 httpsdoiorg101002joc3743 2014

Harris I C CRU JRA v20 A forcings dataset of gridded landsurface blend of Climatic Research Unit (CRU) and Japanesereanalysis (JRA) data Jan1901-Dec2018 Centre for Environ-mental Data Analysis available at httpscataloguecedaacukuuid7f785c0e80aa4df2b39d068ce7351bbb (last access 20 June2020) 2019

Hurrell J W NAO Index Data provided by the ClimateAnalysis Section NCAR Boulder USA 2003 avail-able at httpsclimatedataguideucareduclimate-datahurrell-north-atlantic-oscillation-nao-index-station-basedlast access 27 May 2021 (updated regularly)

Iizuka Y Uemura R Fujita K Hattori S Seki OMiyamoto C Suzuki T Yoshida N Motoyama Hand Matoba S A 60 year record of atmospheric aerosoldepositions preserved in a high-accumulation dome icecore Southeast Greenland J Geophys Res 123 574ndash589httpsdoiorg1010022017JD026733 2018

Ito A and Wagai R Global distribution of clay-size minerals onland surface for biogeochemical and climatological studies SciData 4 170103 httpsdoiorg101038sdata2017103 2017

Kemp S J Ellis M A Mounteney I and Kender S Palaeocli-matic implications of high-resolution clay mineral assemblagespreceding and across the onset of the PalaeocenendashEocene ther-mal maximum North Sea Basin Clay Miner 51 793ndash813httpsdoiorg101180claymin2016051508 2016

Kim H Global Soil Wetness Project Phase 3 Atmospheric Bound-ary Conditions (Experiment 1) Data Integration and AnalysisSystem (DIAS) [data set] httpsdoiorg1020783DIAS5012017

Kobashi T Kawamura K Severinghaus J P Barnola J-MNakaegawa T Vinther B M Johnsen S J and Box J EHigh variability of Greenland surface temperature over the past4000 years estimated from trapped air in an ice core GeophysRes Lett 38 L21501 httpsdoiorg1010292011GL0494442011

Koide M Michel R Goldberg E Herron M M and Lang-way C C Characterization of radioactive fallout from pre- andpost-moratorium tests to polar ice caps Nature 296 544ndash547httpsdoiorg101038296544a0 1982

Kuramoto T Goto-Azuma K Hirabayashi M Miyake T Mo-toyama H Dahl-Jensen D and Steffensen J P Seasonal vari-

ations of snow chemistry at NEEM Greenland Ann Glaciol52 193ndash200 httpsdoiorg1031891727564117972523652011

Kurosaki Y and Mikami M Recent frequent dust events and theirrelation to surface wind in East Asia Geophys Res Lett 301736 httpsdoiorg1010292003GL017261 2003

Kurosaki Y Matoba S Iizuka Y Niwano M Tanikawa TAndo T Hori A Miyamoto A Fujita S and Aoki T Re-construction of sea ice concentration in northern Baffin Bayusing deuterium excess in a coastal ice core from the north-western Greenland Ice Sheet J Geophys Res-Atmos 125e2019JD031668 httpsdoiorg1010292019JD031668 2020

Lambert F Delmonte B Petit J R Bigler M Kaufmann PR Hutterli M A Stocker T F Ruth U Steffensen J Pand Maggi V Dust-climate couplings over the past 800000years from the EPICA Dome C ice core Nature 452 616ndash619httpsdoiorg101038nature06763 2008

Legrand M and Mayewski P Glaciochemistry of po-lar ice cores A review Rev Geophys 35 219ndash243httpsdoiorg10102996RG03527 1997

Lupker M Aciego S M Bourdon B Schwander J andStocker T F Isotopic tracing (Sr Nd U and Hf) of continen-tal and marine aerosols in an 18th century section of the Dye-3 ice core (Greenland) Earth Planet Sc Lett 295 277ndash286httpsdoiorg101016jepsl201004010 2010

Maggi V Mineralogy of atmospheric microparticles depositedalong the Greenland Ice Core Project ice core J Geophys Res102 26725ndash26734 httpsdoiorg10102997JC00613 1997

Matoba S Narita H Motoyama H Kamiyama Kand Watanabe O Ice core chemistry of Vestfonna IceCap in Svalbard Norway J Geophys Res 107 4721httpsdoiorg1010292002JD002205 2002

Matoba S Motoyama H Fujita K Yamasaki T Minowa MOnuma Y Komuro Y Aoki T Yamaguchi S Sugiyama Sand Enomoto H Glaciological and meteorological observationsat the SIGMA-D site northwestern Greenland Ice Sheet BullGlaciol Res 33 7ndash14 httpsdoiorg105331bgr337 2015

Mayewski P A Meeker L D Twickler M S Whitlow S YangQ Lyons W B and Prentice M Major features and forcingof high-latitude northern hemisphere atmospheric circulation us-ing a 110000-year-long glaciochemical series J Geophys Res102 26345ndash26366 httpsdoiorg10102996JC03365 1997

Mudroch A Zeman A J and San R Identification ofmineral particles in fine grained lacustrine sedimentswith transmission electron microscope and x-ray en-ergy dispersive spectroscopy J Sediment Petrol 47244ndash250 httpsdoiorg101306212F713F-2B24-11D7-8648000102C1865D 1977

Mueller J P and Bocquier G Dissolution of kaolinites and ac-cumulation of iron oxides in lateritic-ferruginous nodules Min-eralogical and microstructural transformations Geoderma 37113ndash116 httpsdoiorg1010160016-7061(86)90025-X 1986

Nagatsuka N Takeuchi N Uetake J and Shimada RMineralogical composition of cryoconite on glaciers innorthwest Greenland Bull Glaciol Res 32 107ndash114httpsdoiorg105331bgr32107 2014

Nagatsuka N Matoba S Kadota M Fujita K Tsushima ADallmayr R Hirabayashi M Ogata J Ogawa-TsukagawaY and Goto-Azuma K Stable isotope ion concentrations

and mineral dust data from northwestern Greenland ice core(SIGMA-D) 100 Arctic Data archive System (ADS) [data set]Japan httpsdoiorg10175920012021052501 2021

Nahon D B Introduction to the Petrology of Soils and ChemicalWeathering John Wiley New York 1991

Onuma Y and Kim H MIROC6 model outputprepared for CMIP6 LS3MIP land-hist Version20200423 Earth System Grid Federation [data set]httpsdoiorg1022033ESGFCMIP65622 2020a

Onuma Y and Kim H MIROC6 model output pre-pared for CMIP6 LS3MIP land-hist-cruNcep Version20200918 Earth System Grid Federation [data set]httpsdoiorg1022033ESGFCMIP65627 2020b

Onuma Y and Kim H MIROC6 model output pre-pared for CMIP6 LS3MIP land-hist-princeton Version20200918 Earth System Grid Federation [data set]httpsdoiorg1022033ESGFCMIP65628 2020c

Onuma Y and Kim H MIROC6 model output pre-pared for CMIP6 LS3MIP land-hist-wfdei Version20200727 Earth System Grid Federation [data set]httpsdoiorg1022033ESGFCMIP65629 2020d

Oyabu I Matoba S Yamasaki T Kadota M and IizukaY Seasonal variations in the major chemical species of snowat the South East Dome in Greenland Polar Sci 10 36ndash42httpsdoiorg101016jpolar201601003 2016

Pallister J S Hoblitt R P and Reyes A G A basalt trigger forthe 1991 eruptions of Pinatubo volcano Nature 356 426ndash428httpsdoiorg101038356426a0 1992

Parvin F Seki O Fujita K Iizuka Y Matoba S and Ando TAssessment for paleoclimatic utility of biomass burning tracersin SE-Dome ice core Greenland Atmos Environ 196 86ndash94httpsdoiorg101016jatmosenv201810012 2019

Petit J R Mounier L Jouzel J Korotkevich Y S KotlyakovV I and Lorius C Palaeoclimatological and chronological im-plications of the Vostok core dust record Nature 343 56ndash58httpsdoiorg101038343056a0 1990

Pye K Aeolian Dust and Dust Deposits Academic San DiegoUSA 1987

Ram M and Koenig G Continuous dust concentration profile ofpre-Holocene ice from the Greenland Ice Sheet Project 2 icecore Dust stadials interstadials and the Eemian J GeophysRes 102 26641ndash26648 httpsdoiorg10102996JC035481997

Ruth U Wagenbach D Steffensen J P and Bigler MContinuous record of microparticle concentration and sizedistribution in the central Greenland NGRIP ice core dur-ing the last glacial period J Geophys Res 108 4098httpsdoiorg1010292002jd002376 2003

Schuumlpbach S Fischer H Bigler M Erhardt T Gfeller GLeuenberger D Mini O Mulvaney R Abram N J Fleet LFrey M M Thomas E Svensson A Dahl-Jensen D Ket-tner E Kjaer H Seierstad I Steffensen J P Rasmussen SO Vallelonga P Winstrup M Wegner A Twarloh B WolffK Schmidt K Goto-Azuma K Kuramoto T HirabayashiM Uetake J Zheng J Bourgeois J Fisher D ZhihengD Xiao C Legrand M Spolaor A Gabrieli J BarbanteC Kang J-H Hur S D Hong S B Hwang H J HongS Hansson M Iizuka Y Oyabu I Muscheler R Adol-phi F Maselli O McConnell J and Wolff E W Green-

land records of aerosol source and atmospheric lifetime changesfrom the Eemian to the Holocene Nat Commun 9 1476httpsdoiorg101038s41467-018-03924-3 2018

Severin K P Energy dispersive spectrometry of common rockforming minerals Kluwer Academic Publishers Dordrecht theNetherlands 2004

Sheffield J Goteti G and Wood E F Development of a 50-Year High-Resolution Global Dataset of Meteorological Forc-ings for Land Surface Modeling J Climate 19 3088ndash3111httpsdoiorg101175JCLI37901 2006

Simonsen M F Baccolo G Blunier T Borunda A DelmonteB Frei R Goldstein S Grinsted A Kjaeligr H A Sowers TSvensson A Vinther B Vladimirova D Winckler G Win-strup M and Vallelonga P East Greenland ice core dust recordreveals timing of Greenland ice sheet advance and retreat NatCommun 10 4494 httpsdoiorg101038s41467-019-12546-2 2019

Steffensen J The size distribution of microparticles from selectedsegments of the Greenland Ice Core Project ice core representingdifferent climatic periods J Geophys Res 102 26755ndash26763httpsdoiorg10102997JC01490 1997

Stein A F Draxler R R Rolph G D Stunder B J B Co-hen M D and Ngan F NOAArsquos HYSPLIT AtmosphericTransport and Dispersion Modeling System B Am Meteo-rol Soc 96 2059ndash2077 httpsdoiorg101175BAMS-D-14-001101 2015

Svensson A Biscaye P E and Grousset F E Character-ization of late glacial continental dust in the greenland icecore project ice core J Geophys Res 105 4637ndash4656httpsdoiorg1010291999JD901093 2000

Tatebe H Ogura T Nitta T Komuro Y Ogochi K TakemuraT Sudo K Sekiguchi M Abe M Saito F Chikira MWatanabe S Mori M Hirota N Kawatani Y MochizukiT Yoshimura K Takata K Orsquoishi R Yamazaki D SuzukiT Kurogi M Kataoka T Watanabe M and Kimoto MDescription and basic evaluation of simulated mean state in-ternal variability and climate sensitivity in MIROC6 GeosciModel Dev 12 2727ndash2765 httpsdoiorg105194gmd-12-2727-2019 2019

Taylor H E and Lichte F E Chemical composition of MountSt Helens volcanic ash Geophys Res Lett 7 949ndash952httpsdoiorg101029GL007i011p00949 1980

Uppala S M Kallberg P W Simmons A J Andrae U daCostaBechtold V Fiorino M Gibson J K Haseler J HernandezA Kelly G A Li X Onogi K Saarinen S Sokka N Al-lan R P Andersson E Arpe K Balmaseda M A BeljaarsA C M van de Berg L Bidlot J Bormann N Caires SChevallier F Dethof A Dragosavac M Fisher M FuentesM Hagemann S Holm E Hoskins B J Isaksen L JanssenP A E M Jenne R McNally A P Mahfouf J F MorcretteJ J Rayner N A Saunders R W Simon P Sterl A Tren-berth K E Untech A Vasiljevic D Viterbo P and WoollenJ The ERA-40 Reanalysis Q J Roy Meteor Soc 131 2961ndash3012 httpsdoiorg101256qj04176 2005

Uacutejvaacuteri G Stevens T Svensson A Kloumltzli U S Man-ning C Neacutemeth T Kovaigravecs J Sweeney M R GockeM Wiesenberg G L B Markovic S B and ZechM Two possible source regions for central Greenland

last glacial dust Geophys Res Lett 42 10399ndash10408httpsdoiorg1010022015GL066153 2015

van den Broeke M Bamber M J Ettema J Rignot E SchramaE van de Berg W J van Meijgaard E Velicogna I andWouters B Partitioning recent Greenland mass loss Science326 984ndash986 httpsdoiorg101126science1178176 2009

van den Hurk B Kim H Krinner G Seneviratne S I Derk-sen C Oki T Douville H Colin J Ducharne A CheruyF Viovy N Puma M J Wada Y Li W Jia B Alessan-dri A Lawrence D M Weedon G P Ellis R HagemannS Mao J Flanner M G Zampieri M Materia S Law RM and Sheffield J LS3MIP (v10) contribution to CMIP6 theLand Surface Snow and Soil moisture Model IntercomparisonProject ndash aims setup and expected outcome Geosci Model Dev9 2809ndash2832 httpsdoiorg105194gmd-9-2809-2016 2016

Velde B Origin and Mineralogy of Clays Clays and EnvironmentSpringer-Verlag New York 1995

Weedon G P Balsamo G Bellouin N Gomes S Best MJ and Viterbo P The WFDEI meteorological forcing dataset WATCH Forcing Data methodology applied to ERA In-terim reanalysis data Water Resour Res 50 7505ndash7514httpsdoiorg1010022014WR015638 2014

Whitlow S Mayewski P A and Dibb J E A comparison ofmajor chemical species seasonal concentration and accumula-tion at the South Pole and Summit Greenland Atmos Environ26A 2045ndash2054 httpsdoiorg1010160960-1686(92)90089-4 1992

Wilson T R S Salinity and the major elements of sea waterChap 6 in Chemical Oceanography 2nd edn edited by Ri-ley J P and Skirrow G Academic Press Orland 1 365ndash4131975

Woollings T Hannachi A Hoskins B and Turner A Aregime view of the North Atlantic Oscillation and its re-sponse to anthropogenic forcing J Climate 23 1291ndash1307httpsdoiorg1011752009JCLI30871 2010

Wu G Zhang X Zhang C and Xu T Mineralogicaland morphological properties of individual dust particles inice cores from the Tibetan Plateau J Glaciol 62 46ndash53httpsdoiorg101017jog20168 2016

Yokoo Y Nakano T Nishikawa M and Quan H Miner-alogical variation of SrmdashNd isotopic and elemental composi-tions in loess and desert sand from the central Loess Plateauin China as a provenance tracer of wet and dry deposi-tion in the northwestern Pacific Chem Geol 204 45ndash62httpsdoiorg101016jchemgeo200311004 2004

Zhang P Jeong J H Yoon J H Kim H Wang S YS Linderholm H W Fang K Wu X and Chen DAbrupt shift to hotter and drier climate over inner EastAsia beyond the tipping point Science 370 1095ndash1099httpsdoiorg101126scienceabb3368 2020

Abstract
Introduction
Samples and analytical methods
- SIGMA-D ice core
- Water isotope and ion concentration measurement
- Dust concentration
- SEMndashEDS analysis of mineral dust
- Mineral identification
- Backward trajectory analysis
- Snow cover fraction
- - Results
  - - Dating of the SIGMA-D ice core
    - Particle morphology
    - Quantitative estimation of mineral dust
    - Source regions of SIGMA-D ice core dust
    - - Discussion
      - Variation in silicate mineral composition
        
        Possible causes of mineralogical variation
        
        Possible sources for mineral dust in the SIGMA-D ice core
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        Author contributions
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 2: Variations in mineralogy of dust in an ice core obtained ...

ship with temperature changes and atmospheric circulationDust concentrations in Greenland ice cores during the lastglacial period were 10 to 100 times higher than those overthe Holocene and were strongly correlated with temperaturechanges (as indicated by δ18O records eg De Angelis etal 1997 Mayewski et al 1997 Fuhrer et al 1999 Ruthet al 2003 Schuumlpbach et al 2018) Steffensen (1997) alsoshowed a systematic connection between dust volume distri-bution total dust mass and δ18O in the Greenland Ice CoreProject (GRIP) ice core indicating that climate changes ap-pear to have modified the processes of formation transportand deposition of mineral dust in the same way over the last120 000 years Meanwhile there is a significant correlationbetween the dust flux of the European Project for Ice Cor-ing in Antarctica (EPICA) ice core with Antarctic tempera-ture during glacial periods but not during interglacial peri-ods suggesting that the conditions of source areas and thetransport of ice core dust change according to the glacialndashinterglacial cycle (Lambert et al 2008) The variability of icecore dust may be related to changes in atmospheric transportand dust source areas affected by climate change (Svenssonet al 2000) Thus it is important to reconstruct the varia-tions in the sources and transportation processes of mineraldust in ice cores

Geochemical analyses such as stable isotope ratios of SrNd and Pb have been used to identify possible sources ofGreenland ice core dust These isotopic ratios have strongregional variations that are controlled by their geological ori-gins and are hardly altered during transportation in the at-mosphere or after deposition (Capo et al 1998 Faure andMensing 2004) The isotope ratios of the GRIP and Green-land Ice Sheet Project 2 (GISP2) ice core dust obtained from44 to 12 kyr BP indicated that eastern Asian deserts appearedto be the most likely dust sources (Biscaye et al 1997Svensson et al 2000) and that centraleast central Europeanloess might also be a major source of dust in the last glacialice core (Uacutejvaacuteri et al 2015) Lupker et al (2010) analysedthe Sr and Nd isotopic ratios of mineral dust in an ice corefrom southern Greenland (Dye 3) in the age range of 1786ndash1793 CE and revealed that the Sahara might be an additionaldust source Han et al (2018) showed temporal variationsin the source areas of the NEEM ice core dust based on Srand Pb isotope analysis the primary dust source was east-ern Asian deserts from 31 to 23 kyr and the Sahara from23 to 12 kyr However these analyses have targeted mostlyice core dust from glacial periods characterized by a highdust concentration because Sr and Nd isotopic ratio analysesneed large numbers of samples Although some studies haveanalysed the Sr and Nd isotopes of ice core minerals duringthe Holocene a recent period of low dust concentration theyneeded to concentrate decades to thousands of years of icefor each sample (eg Bory et al 2003a Han et al 2018 Si-monsen et al 2019) Thus there is limited information aboutpossible sources of mineral dust in interglacial periods dur-ing which dust concentrations are low

Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) are useful tools for re-vealing the source areas of ice core dust samples with lowamounts of mineral dust SEM provides morphological in-formation and EDS provides the mineralogical compositionof individual particles allowing the evaluation of the con-tinental dust input and showing variations in ice core dustproperties Donarummo et al (2003) analysed the size distri-bution and mineral composition of GISP2 ice core dust dur-ing the 1930s by SEMndashEDS and suggested that the centralUnited States might have contributed a substantial amount ofminerals to the ice core when the source area was affectedby intense droughts The SEMndashEDS analysis of dust fromsnow pit samples from 1989 to 1991 at Summit in centralGreenland indicated that the possible sources were likely tobe Asian deserts and the source areas have not changed sea-sonally (Drab et al 2002) Therefore SEMndashEDS analysiscan demonstrate a high-temporal-resolution record of com-position and sources of ice core minerals during interglacialperiods However continuous variations in the dust proper-ties of Greenland ice cores during recent years are still notwell known

Possible source areas for the Greenland ice core dustmay have varied in recent years Most of the Earthrsquos sur-face has changed rapidly because of recent climate warm-ing and human activities which may result in changes in at-mospheric transport and sources of mineral dust to the icesheet For example dust outbreaks occurring in eastern Asiandeserts which are vast sources of aeolian mineral dust re-markably increased from 2000 to 2002 compared with the1990s (Kurosaki and Mikami 2003) The dust from Asiandeserts is transported to Greenland across the ocean Zhanget al (2020) revealed that there has been an abrupt shift to-ward a hotter and drier climate over east Asia over the past260 years according to tree-ring-based reconstructions ofheat waves and soil moisture Furthermore there may alsobe an increasing contribution of dust from local source ar-eas in Greenland (Amino et al 2021) The retreating iceand decreasing seasonal snow will expose more sediment inthe proglacial area delivering greater quantities of fine sed-iments to the floodplain than at present Bullard and Austin(2011) reported that exposure of the proglacial floodplain inKangerlussuaq western Greenland during ice retreat mayalso make more material available for aeolian transport

This paper aims to describe the temporal variations insources of minerals in a Greenland ice core covering a nearly100-year period (1915ndash2013) with a 5-year resolution dur-ing which the Arctic region was remarkably warming Themorphology and mineralogical composition of the ice coredust were analysed by SEM and EDS and variations are dis-cussed in terms of changes in the ice core dust sources

21 SIGMA-D ice core

3 Results

4 Discussion

ble

2R

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ive

abun

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e(

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ilica

tem

iner

algr

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n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 3: Variations in mineralogy of dust in an ice core obtained ...

21 SIGMA-D ice core

3 Results

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

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ach

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-fel

dspa

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Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 4: Variations in mineralogy of dust in an ice core obtained ...

3 Results

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

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ach

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Sam

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-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 5: Variations in mineralogy of dust in an ice core obtained ...

3 Results

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 6: Variations in mineralogy of dust in an ice core obtained ...

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 7: Variations in mineralogy of dust in an ice core obtained ...

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 8: Variations in mineralogy of dust in an ice core obtained ...

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 9: Variations in mineralogy of dust in an ice core obtained ...

4 Discussion

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 10: Variations in mineralogy of dust in an ice core obtained ...

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 11: Variations in mineralogy of dust in an ice core obtained ...

ble

2R

elat

ive

abun

danc

e(

)ofs

ilica

tem

iner

algr

oups

fore

ach

sam

ple

Sam

ple

peri

odK

aolin

itePy

roph

yllit

eSm

ectit

eIl

litendash

smec

tite

Illit

eM

ica

Mic

andashch

lori

teC

hlor

iteN

aC

a-fe

ldsp

arK

-fel

dspa

rM

afic

Qua

rtz

Unk

now

n

1915

ndash191

918

115

90

06

58

71

49

45

16

56

55

115

21

419

20ndash1

924

163

67

22

67

44

22

230

30

37

67

22

207

22

1925

ndash192

919

010

90

74

42

94

421

95

84

40

78

813

12

919

30ndash1

934

197

157

24

55

00

47

252

39

31

00

08

134

55

1935

ndash193

913

815

41

615

42

47

310

62

44

10

84

914

66

519

40ndash1

944

145

80

00

58

36

43

159

51

65

22

36

217

87

1945

ndash194

920

38

60

010

93

11

613

35

514

83

94

710

23

119

50ndash1

954

326

265

08

114

00

23

68

38

30

00

08

53

68

1955

ndash195

929

917

20

714

22

26

710

45

23

00

03

73

019

60ndash1

964

374

217

09

122

26

09

87

09

35

09

35

61

1965

ndash196

934

713

20

013

23

50

711

81

44

21

42

15

68

319

70ndash1

974

312

80

07

43

07

22

152

109

29

14

58

138

1975

ndash197

956

914

60

06

93

11

53

10

83

10

00

85

43

819

80ndash1

984

664

49

00

35

07

42

14

28

21

28

49

1985

ndash198

938

727

00

78

00

71

57

32

23

60

70

05

14

419

90ndash1

994

368

241

08

53

08

00

30

38

105

08

23

90

30

1995

ndash199

945

27

41

53

73

00

75

22

29

63

08

15

25

220

00ndash2

004

632

128

08

15

30

08

45

15

08

00

83

23

2005

ndash200

95

05

81

72

510

72

522

39

913

27

43

310

75

020

10ndash2

013

95

105

11

63

32

158

42

137

53

105

84

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 12: Variations in mineralogy of dust in an ice core obtained ...

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 13: Variations in mineralogy of dust in an ice core obtained ...

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 14: Variations in mineralogy of dust in an ice core obtained ...

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 15: Variations in mineralogy of dust in an ice core obtained ...

5 Conclusions

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 16: Variations in mineralogy of dust in an ice core obtained ...

Appendix A

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 17: Variations in mineralogy of dust in an ice core obtained ...

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 18: Variations in mineralogy of dust in an ice core obtained ...

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 19: Variations in mineralogy of dust in an ice core obtained ...

References

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 20: Variations in mineralogy of dust in an ice core obtained ...

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 21: Variations in mineralogy of dust in an ice core obtained ...

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

Page 22: Variations in mineralogy of dust in an ice core obtained ...

Abstract
Introduction
- SIGMA-D ice core
- - Results
    - - Discussion
        
        
        
        Conclusions
        
        Appendix A
        
        Data availability
        
        
        Competing interests
        
        Acknowledgements
        
        Financial support
        
        Review statement
        
        References

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Variations in mineralogy of dust in an ice core obtained ...

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