17O proxy for atmospheric chemistry: Towards model

interpretation of the ice core record

Becky Alexander

NOAA Postdoctoral Fellow

Harvard University

March 25, 2005

OutlineOutline

• Atmospheric chemistry and the oxidation capacity of the atmosphere:

climate ↔ chemistry

• Sulfate 17O from the Vostok record

• GEOS-CHEM 17O simulations

• Future plans

Department of Atmospheric Sciences, University of Washington, Seattle

Secondary Species

CO2, H2SO4, O3, …

Oxidizing Power of the AtmosphereOxidizing Power of the Atmosphere

VolcanoesMarine Biogenics

Biomass burning

Continental Biogenics

Primary Species H2S, SO2, CH4, CO, DMS, CO2, NO, N2O,

particulates

Climate change

OHhH2O

Primary Emissions

DMS, SO2, CH4, …

O3

OH

Model Estimates of Past OH and OModel Estimates of Past OH and O33

-50

0

50

100

150

200

% c

han

geIndustrial

EraRelative to

preindustrial Holocene

LGMRelative to

preindustrial Holocene

-30

-20

-10

0

10

20

% c

han

ge

Karol et al., 1995

Thompson et al., 1993

Martinerie et al., 1995

Glacial/Interglacial CHGlacial/Interglacial CH44 variations variations

Kaplan, 2002

Wetland CH4 emissions

Present day

LGM

Wetland CH4 emissions 24% less in

LGM.

Not enough to explain glacial/interglacial change (~50%) in atmospheric CH4 concentrations.

0

50

100

150

200

250

300

350

0 20 40 60 80 100 120

Age (kyr)

SO4 (ppb)

-500

-490

-480-470

-460-450-440

-430

-420

-410

D (‰)

The Vostok Ice Core Record: The Vostok Ice Core Record: AerosolsAerosols

SO

42- (

pp

b)

[SO42-] tracks [MSA-] suggesting a predominant DMS

(oceanic biogenic) source (Legrand et al., 1991)

D (‰

)

D from Jouzel et al., 1987

[SO42-] from M. Legrand

Sulfur Cycle in the AtmosphereSulfur Cycle in the Atmosphere

Surface

DMSCS2

H2SSO2 SO4

2- OH

O3, H2O2

OH, NO3

MSA

OH

Radiative Forcing: Greenhouse Radiative Forcing: Greenhouse Gases and AerosolsGases and Aerosols

IPCC report, 2001

Effects of Aerosols on ClimateEffects of Aerosols on ClimateDirect Effect

Indirect Effect

Reflection

RefractionAbsorption

Ramanathan et al., 2001

Aerosol number density (cm-3)

Clo

ud

dro

ple

t n

um

be

r d

en

sity

(cm

-3)

Great Smoky Mountains

Visibility: 150 miles Visibility: 15 miles

New Particle FormationNew Particle Formation

SO2 + OH (+O2 + H2O) H2SO4(g) (+HO2)

CCN> ~ 0.1 m

H2O

NH3?

H2SO4(g)

Conden

satio

n

RCOOH

Activation

Water vaporWater vapor

Updraft velocityUpdraft velocity

Aerosol number densityAerosol number density

Size distributionSize distribution

Chemical compositionChemical composition

From Boucher and Lohmann, 1995

nssSO42- (mg m-3)

CD

NC

(m

-3)

HSO3- + H2O2/O3

SO42-

-60

-40

-20

0

20

40

60

-80 -60 -40 -20 0 20 40 60 80

SMOW

Air O2

Mass-Dependent FractionationMass-Dependent Fractionation

Mass-dependent fractionation line: 17O/18O 0.5

17O

18O

Basaltic and sedimentary rocks

Rain and cloud water

17O/18O 1

-80

-60

-40

-20

0

20

40

60

-100 -80 -60 -40 -20 0 20 40 60 8018O

17O

Product Ozone

Residual Oxygen

Starting Oxygen

Mass-dependent fractionation line: 17O/18O 0.5

O + O2 O3*

Thiemens and Heidenreich, 1983

Mass-Independent FractionationMass-Independent Fractionation

17O

17O

17O = 17O – 0.5*18O 0

Source ofSource of 1717OO SulfateSulfateSO2 in isotopic equilibrium with H2O :

17O of SO2 = 0 ‰

1) SO32- + O3 (17O=35‰) SO4

2- 17O = 8.8 ‰

17O of SO42- a function relative amounts of OH, H2O2, and O3 oxidation

Savarino et al., 2000

3) SO2 + OH (17O=0‰) SO42- 17O = 0 ‰

2) HSO3-+ H2O2 (17O=1.7‰) SO4

2- 17O = 0.9 ‰ Aqueous

Gas

Analytical ProcedureAnalytical Procedure

SO42-

Ag2SO4

Decontamination

Concentrate Ion Chromatograph Ionic separation

Ag2SO4 O2 + SO2

Removable quartz tube

1050°C

magnet

To vacuum

To vacuumGC

SO2 trap

He flow

Sample loop 5A mol.sieve

ventSO2 port

O2 port

Analytical ProcedureAnalytical Procedure

Isotope Ratio Mass Spectrometer

Vostok Ice Core Vostok Ice Core

1717O nssSOO nssSO442-2-

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140

Age (kyr)

17O

-6

-5

-4

-3

-2

-1

0

1

2

3

Ts

Ts data: Kuffey and Vimeux, 2001, Vimeux et al., 2002

Alexander et al., 2002

17O

(‰

)

Ts

Climate Variations in the Oxidation Climate Variations in the Oxidation Pathways of Sulfate FormationPathways of Sulfate Formation

OH (gas-phase) oxidation greater in glacial period compared to interglacial

Age (kyr)

% O

H

0

10

20

30

40

50

60

70

80

90

0 20 40 60 80 100 120 140

Age (kyr)

-6

-5

-4

-3

-2

-1

0

1

2

3

T

s

AntarcticaOcean

DMS

OH NO3

SO2

OH

H2SO4

O3

SO42-

Transport

Wet and dry deposition

Vostok sulfate explanationVostok sulfate explanation

CCN

Sulfate Formation Pathways in Sulfate Formation Pathways in GEOS-CHEMGEOS-CHEM

SO2H2SO4

OH

DMSOH NO3

H 2O 2

, O 3

SO42- pH = 4.5

Gas-phase

Aqueous-phase

Park et al., 2004

http://www-as.harvard.edu/chemistry/trop/geos/index.html

1.0E-15

1.0E-14

1.0E-13

1.0E-12

1.0E-11

1.0E-10

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

pH

Oxi

da

tio

n r

ate

(M/s

ec)

1.0E-15

1.0E-14

1.0E-13

1.0E-12

1.0E-11

1.0E-10

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

pH

Ox

ida

tio

n r

ate

(M

/se

c)

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

1

7O (‰

)

Lee et al., 2001

H2O2

O3

pH dependency of OpH dependency of O33 oxidation and its oxidation and its

effect on effect on 1717O of SOO of SO442-2-

GEOS-CHEM GEOS-CHEM 1717O Sulfate SimulationO Sulfate Simulation

SO2 + OH (gas-phase) 17O=0‰

S(IV) + H2O2 (in-cloud) 17O=0.9‰

S(IV) + O3 (in-cloud) 17O=8.8‰

Assume constant, global 17O value for oxidants

17O ‰ method reference

O3 35 Photochemical model

Lyons 2001

H2O2 1.3-2.2 (1.7)

Rainwater measurements

Savarino and Thiemens 1999

OH 0 Experimental Dubey et al., 1997

1717O sulfate: GEOS-CHEMO sulfate: GEOS-CHEM

January 2001

July 2001

0.0‰ 2.3‰ 4.6‰

0

2

4

6

8

0 1 2 3 4

17O

sul

fate

(‰

)

H2O2 (ppbv)

HSO3-,

H2O2, O3

1717O sulfate: GEOS-CHEM and measurementsO sulfate: GEOS-CHEM and measurements

January 2001 July 2001

0.0‰ 2.3‰ 4.6‰

Davis, CA fogwater

4.3 ‰

Whiteface Mtn, NY

fogwater 0.3 ‰

White Mtn, CA aerosol

1-1.7‰

La Jolla rainwater

1.1 ‰

La Jolla aerosol 0.2-1.4‰

South Pole aerosol

0.8-2‰

Site A, Greenland ice core 0.5-3‰

Vostok & Dome C ice

cores 1.3-4.8‰

Desert dust traps 0.3-3.5‰

INDOEX aerosol

0.5-3‰

Alert 1.0‰

Alkalinity in the Marine Boundary LayerAlkalinity in the Marine Boundary Layer

Na+, Cl-, HCO3

-/CO32-

pH=8

Acids:

H2SO4(g)

HNO3(g)

RCOOH(g)

SO2(g) SO42-

O3

CO2(g)

H+ + HCO3- H2O•CO2

DMS

SO2

Free troposphere

H2SO4(g)

OH

Cloud other aerosols

(acid or neutral)

O3

CO2(g)

H 2O

2

Emission

Marine Boundary Layer

Subsidence

OH NO3

Sea-salt aerosol

HCO3-/CO3

2-

Emission

RCOOH(g)

HNO3(g)

Subsidence

Deposition

NH3(g)

GEOS-CHEM Sea-salt AlkalinityGEOS-CHEM Sea-salt Alkalinityhttp://www-as.harvard.edu/chemistry/trop/geos/index.html

SO42-

March 1998

January 1997

Na+ [g m-3]31 119750 13

INDOEX Cruises INDOEX Cruises

High volume air sampler

GEOS-CHEM Sea-Salt

Pre-INDOEX Jan. 1997 INDOEX March 1998

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-15 -10 -5 0 5 10 15Latitude (degrees)

nss

SO

42-

17O

(‰

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-15 -10 -5 0 5 10 15Latitude (degrees)

ns

sSO

42-

17 O

(‰

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-15 -10 -5 0 5 10 15Latitude (degrees)

ns

sSO

42-

17 O

(‰

)

Pre-INDOEX CruisePre-INDOEX CruiseJanuary 1997

Alexander et al., 2005

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-15 -10 -5 0 5 10 15Latitude (degrees)

nss

SO

42-

17O

(‰

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-15 -10 -5 0 5 10 15Latitude (degrees)

ns

sSO

42-

17 O

(‰

)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

-15 -10 -5 0 5 10 15Latitude (degrees)

ns

sSO

42-

17 O

(‰

)

INDOEX Cruise INDOEX Cruise

March 1998

Alexander et al., 2005

GEOS-CHEM Alkalinity BudgetGEOS-CHEM Alkalinity Budget

fSO2

fHNO3

fexcess

0.1 0.3 0.5 0.7

[SO2] % decrease

[SO42-]

% increase

SO2 + OH % decrease

10 30 50 705

GEOS-CHEM Sulfur BudgetGEOS-CHEM Sulfur Budget

SO2 H2SO4OH New particle

formation

CCN

Light scattering

DMSOH NO3

Phytoplankton

H 2O 2

SO42-

H 2O 2

SO42-

O3

Sea-salt aerosol

O3

Sea-salt aerosol

Marine DMS and ClimateCharleson et al., 1987; Shaw 1985

0.0 1.6 3.2 4.7 6.3 ‰

January July

GEOS-CHEM: Seasonal GEOS-CHEM: Seasonal Variability in Variability in 1717O SulfateO Sulfate

South Pole aerosol

0.8-2‰

Alert aerosol 1‰

Arctic Haze FormationArctic Haze Formation

J M M J S N J

1

2

3

10

10

10

Sulfate

ng m-3

Picture from L. Barrie

Sirois et al., 1999

Arctic MeasurementsArctic Measurements

Alert (82°N, 85°W)

Measurements

GEOS-CHEM

Measurements: Justin McCabe, UCSD, personal communication

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1 2 3 4 5 6 7 8 9 10 11 12

Month

17 O

(‰

)

Arctic Night-time ChemistryArctic Night-time Chemistry

SIV + ½ O2 SVI

Mn2+, Fe3+

17O = 0‰

??

From Sirois and Barrie, 1999

xV (ng m-3)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1 2 3 4 5 6 7 8 9 10 11 12

Month

17 O

(‰

)

GEOS-CHEM

Measurements

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1 2 3 4 5 6 7 8 9 10 11 12

Month

17 O

(‰

)

GEOS-CHEM

[Fe(III)] = 0.5 mol/l [Mn(II)] = 0.05 m/l

Measurements

Alert: Metal Catalysis?Alert: Metal Catalysis?

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1 2 3 4 5 6 7 8 9 10 11 12

Month

17 O

(‰

)

GEOS-CHEM

[Fe(III)] = 0.5 mol/l [Mn(II)] = 0.05 m/l

[Fe(III)] = 5.0 mol/l [Mn(II)] = 0.5 m/l

Measurements

Metals: Greenland ice core recordMetals: Greenland ice core record

Hong et al., 1996Candelone et al., 1995

GRIPSummit

1773 1992

ConclusionsConclusions

“Minor” oxidants significant in polar regions during winter. Important for

interpreting ice core records.

Alkaline sea-salt aerosols impact sulfate formation and hence radiative properties

of sulfate aerosols.

Some Future DirectionsSome Future Directions

Fe, Si, …

CaCO3

CO2(g)

Acids:

H2SO4(g)

HNO3(g)

RCOOH(g)

SO2(g) SO42-

Dust (Fe)

From Meskhidze et al., 2005

Oceanic Phytoplankton

Some Future DirectionsSome Future Directions

NASA GISS general circulation model

(GCM)

GEOS-CHEM chemical transport model

(CTM)

Wetland CH4 emissions (BIOME4)

Present day

LGM

David Rind (Columbia/NASA)

Loretta Mickley Shiliang Wu

Jed Kaplan

AcknowledgementsAcknowledgements

Mark H. Thiemens

Charles C.W. Lee

Justin McCabe

Joël Savarino

Robert Delmas

Daniel Jacob

Rokjin Park

Loretta Mickley

Bob Yantosca

Daly Postdoctoral Fellowship (EPS)