FACTORS GOVERNING THE SEASONAL VARIABILITY OF ATMOSPHERIC CARBONYL SULFIDE

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FACTORS GOVERNING THE SEASONAL VARIABILITY OF
ATMOSPHERIC CARBONYL SULFIDE
Parv Suntharalingam Harvard/Univ. of East
Anglia A.J. Kettle, S. Montzka, D. J. Jacob
GEOS-Chem Meeting April 12th, 2007
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Carbonyl Sulfide (COS) Uptake by Leaf During
Photosynthesis Can Carbonyl Sulfide help in
Constraining Estimates of Global Primary
Production ?
COS
CO2
COS
CO2
GPP Gross flux of CO2 converted to organic
matter during photosynthesis
COS and CO2 are taken up through leaf stomata
during photosynthesis
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SEASONAL CYCLES OF COS and CO2COS measurements
S. Montzka (NOAA-GMD)
COS
CO2
J F M A M J J A S O N D
J F M A M J J A S O N D
Seasonal cycles of COS and CO2 are correlated,
especially at forested sites. CAN COS
MEASUREMENTS CONSTRAIN BIOSPHERIC CO2 UPTAKE ?
Significant uncertainties remain on aspects of
COS budget
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SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE
COS
Mean atmospheric conc. 500 ppt
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SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE
COS
Oxidation
CS2
DMS
OCEAN
ANTHROPOGENIC
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SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE
Tropospheric Oxidation, Stratospheric Photolysis
COS
Oxidation
CS2
DMS
OCEAN
PLANTS
SOILS
ANTHROPOGENIC
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SOURCES AND SINKS OF ATMOSPHERIC CARBONYL SULFIDE
Tropospheric Oxidation, Stratospheric Photolysis
Uncertainty remains on source/sink fluxes
COS
Oxidation
CS2
??
DMS
??
??
??
OCEAN
PLANTS
Biomass Burning
SOILS
ANTHROPOGENIC
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ATMOSPHERIC COS BUDGETKettle et al. 2002
Gridded Fields
ANNUALLY BALANCED BUDGET Total sources/sinks
460 Gg S/year
-238
-130
-92
-180
280
Not included here Biomass Burning 35 Tg S (8)
Stratospheric Photolysis 16 Tg (3.5) Minor
sources lt 3
Also based on Chin and Davis, 1993 Watts, 2000
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• OUTLINE
• Model atmospheric COS with recent best estimates
  of seasonal sources and sinks Kettle et al.
  2002
• Evaluate against measurements from global
  observation network Montzka et al. 2006
• Which processes govern observed seasonal
  variability ? Can we improve estimates of prior
  COS fluxes?

AIM Improved constraints on factors governing
COS seasonal variability
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COS SURFACE OBSERVATION NETWORK NOAA-GMD Flask
measurements since 2000 Montzka et al. 2006
Barrow (BRW)

alt

brw

lef

mhd


hfm
nwr


kum mlo
Mauna Loa (MLO)

smo

cgo
South Pole (SPO)
spo
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GEOS-Chem COS SIMULATION

• INPUT FLUX DISTRIBUTIONS Kettle et al.
  2002
• SOURCES
• Ocean (Direct CS2 and DMS oxidation to COS)
• Anthropogenic (Direct and CS2 oxidation to COS)
• SINKS
• Terrestrial plant uptake
• Soil uptake
• COS oxidation by OH (tropospheric)
• To be Implemented
• Biomass burning
• Stratospheric photolysis

GEOS-Chem Version 7-03-06 Resolution 2x2.5 30
vertical levels Meteorology Year 2001
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COS SINK DISTRIBUTIONS Kettle et al. 2002
Soil Uptake (JAN)
Plant Uptake (JAN)
pmol/m2/sec
Soil Uptake (JUL)
Plant Uptake (JUL)
Soil uptake based on soil moisture and
temperature. (Only 1 soil type)
Plant fluxes derived from NPP and NDVI fields
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COS SOURCE DISTRIBUTIONS Kettle et al. 2002
Anthropogenic (JAN)
Ocean (JAN)
pmol/m2/sec
Anthropogenic (JUL)
Ocean (JUL)
Ocean fluxes based on ocean photochemical model
and DMS distributions
Anthropogenic COS fluxes distributed according to
SO2 emissions (GEIA 1985)
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SEASONAL VARIABLITY OF COS FLUXESFlux
Distributions Kettle et al 2002
Southern Hemisphere
Northern Hemisphere
OCEAN
ANTH.
OCEAN
Gg S per month
SOILS
PLANT
TOTAL SURFACE COS FLUX

• AGGREGATED FLUXES
• N Hemisphere variability driven by plant uptake
  and ocean fluxes
• S Hemisphere variability driven by ocean fluxes

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SEASONAL ANOMALIES AT MEASUREMENT SITESData S.
Montzka (NOAA-GMD)
Cape Grim, Tasmania
South Pole

• Seasonal cycle has similar phase at Southern
  Hemisphere and Northern Hemisphere sites
• Northern Hemisphere sites show larger seasonal
  amplitude

Barrow, Alaska
Park Falls, Wisconsin
Data for years 2001-2005
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SEASONAL CYCLE AT REMOTE/OCEAN SITESObservations
and Model Seasonal Anomalies
X Observations Model

• Good agreement at Southern Hemisphere
  remote/ocean sites

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SEASONAL CYCLE AT REMOTE/OCEAN SITESObservations
and Model Seasonal Anomalies
X Observations Model

• Good agreement at Southern Hemisphere
  remote/ocean sites
• Observed seasonality not well reproduced as move
  northwards

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SEASONAL CYCLE AT TERRESTRIAL STATIONS
Observations and Model Seasonal Anomalies
Observed seasonal cycle not well simulated at
Northern Hemisphere terrestrial sites
X Observations Model
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GLOBAL PLANT UPTAKE OF COS SUMMARY OF ESTIMATES
(Table 4 Sandoval-Soto et al. 2005)Units
Tg COS/year
Brown and Bell (1986) 2-5
Goldan et al. 1988 0.2-0.6
Kesselmeier and Merk (1993) 0.93 0.07
Chin and Davis (1993) 0.16-0.91
Watts (2000) 0.56 0.1
Xu et al. (2002) 2.3 0.5
Kettle et al. (2002) 0.39 0.5
Sandoval-Soto et al. (2005) 1.37-2.81
Kettle et al. 2002 NPP-based estimate is lower
than recent estimates
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SEASONAL CYCLE AT TERRESTRIAL SITES Increased
Model Plant COS Uptake (Factor of 3)
Increased COS uptake by plants better matches
observed seasonality
ORIG MODEL
X Observations Original Model
Model Increased plant uptake
INCREASED UPTAKE MODEL
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SEASONAL CYCLE AT TERRESTRIAL SITES Increased
Model Plant COS Uptake (Factor of 3)

• BUT
• Now need an additional source (for balanced
  annual budget)

X Observations Original Model
Increased plant uptake
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SEASONAL CYCLE AT TERRESTRIAL SITES Increased
Model Plant COS Uptake (Factor of 3)

• BUT
• Now need an additional source (for balanced
  annual budget)
• Phase problems remain

X Observations Original Model
Increased plant uptake
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SEASONAL CYCLE AT TERRESTRIAL SITES Increased
Model Plant COS Uptake (Factor of 3)

• BUT
• Now need an additional source (for balanced
  budget)
• Phase problems remain
• Missing source flux ?

X Observations Original Model
Increased plant uptake
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SUMMARY

• Primary influences on COS seasonal cycle Ocean
  fluxes in Southern Hemisphere Plant uptake and
  ocean fluxes in Northern Hemisphere.
• Increasing plant uptake of COS by a factor of 3
  (to 0.7 Tg S/year) improves model representation
  of seasonal cycle at terrestrial sites
• But, annual COS budget no longer in balance
  missing source ?

ONGOING/PLANNED WORK

• Add source and sink for biomass burning and
  stratospheric photolysis
• Update anthropogenic COS emissions based on
  latest SO2 inventories.
• Inverse model analysis of COS measurements to
  improve source/sink flux estimates