Measurements of atmospheric O 2 in relation to the ocean carbon cycle Ralph Keeling Scripps...
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Measurements of atmospheric O 2 in relation to the ocean carbon cycle Ralph Keeling Scripps Institution of Oceanography
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Measurements of atmospheric O2 in relation to the ocean carbon cycle
Ralph KeelingScripps Institution of Oceanography
The carbon cycle
Mauna Loa (black)South Pole (red)
Northern and Southern CO2 records
Where is the signal of the oceans in these data?
CO2 variability• Land biosphere dominates CO2 variability on all time scales
except long term.
• Advances from using inverse models of atmospheric CO2 data (e.g. CarbonTracker) are mostly limited to short-term fluxes on land.
• Large uncertainties still surround long-term fluxes.
• Atmospheric CO2 data alone cannot yield much new insight into ocean biogeochemistry.
Ocean CO2 uptake: H2O + CO2 + CO3
= ↔ 2HCO3
-
B F
OZ
Z
ΔCO2 = F – O – BΔO2 = -1.4F + 1.1B +Z ΔO2 + 1.1ΔCO2 = -0.3F -1.1O + Z
Atmospheric CO2 & O2 budgets
ΔAPO = “AtmosphericPotentialOxygen”
Northern and Southern APO records
• Ocean dominates APO variability on all time scale except long term.
• Long-term trend in APO dominated by fossil-fuel and ocean CO2 uptake.
• Shorter-term variability mostly related to air-sea O2 exchanges.
Stations with atmospheric O2 observations
1990 1995 2000 2005 2010
per
me
g
-180
-160
-140
-120
-100
-80
-60
-40
N. Hem. Atmospheric trend Global Atmospheric APO trend Modeled trend (UVic model) Projection based on C* data
Fossil-fuel corrected APO trend
Cape Grim Trend
Any trend in amplitude is less than 1% per year.No evidence of large changes over the past 2 decades.
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Oxy
gen
Co
nce
ntr
atio
n (
per
meg
)
-500
-400
-300
-200
-100
0
Cape Grim Observatory, 41°S
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Oxy
gen
Co
nce
ntr
atio
n (
per
meg
)
-500
-400
-300
-200
-100
0
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012
Oxy
gen
Co
nce
ntr
atio
n (
per
meg
)
-100
0
100
Seasonal Cycles of Air-Sea O2 exchange
Seasonal air-sea O2 fluxes
JUNE DECEMBER
SouthernHemisphere
NorthernHemisphere
What are we headed in ocean biogeochemistry data assimilation?
•Joint ocean/atmosphere/land biosphere data assimilation
•Assimilations that optimize processes controlling fluxes rather than the fluxes themselves.
•Enhance ocean modeling component to assimilate changing ocean physics (e.g. Argo data, etc).
•Assimilation of CO2, O2, pCO2, ocean color
