Helgi Björnsson,Institute of Earth Sciences, University of Iceland, Reykjavik, Iceland

Contribution of Icelandic ice caps to sea level rise:trends and variability since the Little Ice Age

4th TPE workshop, Dehradun, India, 1-4 April 2013

GRL 2013

2,15%

97,2%

0,001%

0,63%

0,01%

Contribution to studies of global

changes of glaciers in the hydrological cycle

Present rising rate

IPCC AR4 2007

Rate of rise 1993-2003

3.1 ± 0.7 mm year-1

Varmaútþensla

Thermal expansion

Glaciers outside north and south polar regions

Greenland

Antarctica ??

Sea level change

Contributions:Dh ~20-30 cm

Dh:20-50 cm

Future prognoses of rising sea level

0,8 – 1 m ?

West-Antarctica and Greenland reacting faster to global warming than models have been able to predict

Latest reports (2005-2010) of sea level rise: 3.3 ± 0.7 mm yr-1

Thermal expansion less than 50%

Antarctica 0.3 mm yr-1

Greenland0.6 mm yr-1

Other ice masses0.8 mm yr-1 Thermal expansion of oceans

1.6 mm yr-1

Glacier recession outside polar regions since 1970

Iceland

Estimated average annual mass balance, mw.e. a-1

Red: DDEMBlack: annual mass balance measurements

Glaciers cover 11% of Iceland, 11,000 km2, 3,600 km3

 

Iceland

at the boundary between polar and mid-latitude atmospheric circulation cells in the westerlies

and confluence of warm and cold sea currents

Sea surface temperature, oCInter-annual variability in mass balance

may be expected in the North Atlantic areaforced by fluctuations in atmospheric circulation and ocean currents

Air temperature

Precipitation

Mass balance ± 0.15 mw.e. a-1

Sea temperature

Near zero mass balance 1980-1995

1900

General mass loss reflects: Higher summer temperature Longer melting seasons Warm winters reducing proportion of precipitation falling as snow Earlier exposure of low albedo

glacier ice (radiation:3/4 of melt energy)

Higher sea temperatures

Fluctuations relate to:

Cold springs, late exposure of low albedo glacier ice

Snowfall during summers

Deposition of tephra aerosolsMaritime climate outlets decreasing faster than inland

Annual total mass loss of Iceland‘s glaciers 1995-2011

2.7 to 25.3 ± 1.5 Gt a-1

-0.2 to -2.2 ± 0.15 mw.e. a-1

Average 9.5 ± 1.5 Gt a-1 (0.03 mm a-1 SLE)

Annual total mass loss of Iceland‘s glaciers

Total ice melt 1995-2010:85% directly climate related13% (20 Gt) due to lowering of albedo by tephra aerosols< 3% melted by geothermal heat2% melted by volcanic eruptions

Modelled mass balance

Observed mass balance

Observed summer temperature and winter precipitation

Observed sea temperature

Firnline

Ablation area

Accumulation area

Ice flow

Runoff

through mass balance measurements

and meteorological observations

Coupled mass-balance-ice-flow model

Mass balance related to climate

Distributed snow accumulation and temperature-index melt (positive degree-day model, PDD)

Mass-balance evolution simulated with a coupled mass-balance-ice-flow model

forced by daily mean temperature records and accumulated precipitationfrom nearby meteorological stations and

calibrated with seasonal stake measurements of winter and summer mass balance

winter

summer

DDEM

Future0.2 °C/decade

3.4 mm/decade.

Climate change scenario (A1B) for Icelandic highland

Predicted glacier response

Sea surface temperature

Glaciers in a cold temperate climate

Iceland

oC

Interannual variations in mass balance may be expected in the North Atlantic area, forced by fluctuations in atmospheric circulation and ocean currents,

superimposed on the projected trend of increasingly negative glacier mass balance

Iceland 2200?

Note:Volumes and areas are normalized to present day valuesSpecific runoff is from the present day glacier covered area

Predicted response to the A1B climate change scenario

Model responses shown for three Icelandic ice caps:Vatnajökull, Langjökull and Hofsjökull

Mass balance model coupled with a ice-flow model (given geometry)

Year 2060: sea level rise 0,06 mm/a

Mass balance modelling Mass balance related to climate

Meteorological observations

Iceland 2200?

2005-2010

3.3 mm ár-1

3.3 +/- 0.4 frá 1993-2009

Varmaútþensla1.6 mm ár-1

Jöklar utan heimskauta0.8 mm ár-1

Grænlandsjökull0.6 mm ár-1

Suðurskautslandið 0.3 mm ár-1

Hlutur jökla orðinn meiri en útþensla hafs

?

1961-2003

1.8 +/- 0.5 mm ár-1

1.7 +/- 0.3 frá 1950-2009

Varmaútþensla0.42 +/- 0.12 mm ár-1

Jöklar utan heimskauta0.5 +/- 0.18 mm ár-1

Grænlandsjökull0.05 +/- 0.12 mm ár-1

Suðurskautslandið0.14 +/- 0.41 mm ár-1

?

1993-2003

3.1 +/- 0.7 mm ár-1

3.3 +/- 0.4 frá 1993-2009

Varmaútþensla1.6 +/- 0.5 mm ár-1

Jöklar utan heimskauta0.77 +/- 0.22 mm ár-1

Grænlandsjökull0.21 +/- 0.12 mm ár-1

Suðurskautslandið0.21+/-0.35 mm ár-1

??