d 17 o proxy for atmospheric chemistry: towards model interpretation of the ice core record
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D 17 O proxy for atmospheric chemistry: Towards model interpretation of the ice core record. Becky Alexander NOAA Postdoctoral Fellow Harvard University. March 25, 2005. Outline. - PowerPoint PPT PresentationTRANSCRIPT
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)