Questioning
estimates of CO2
uptake by the ocean
Vivian Scott
Supervisors: Chris Merchant, Helen Kettle
‘Missing’ carbon sink
Atmospheric CO2 increase less than can be
accounted for
Ref: www.whrc.org
Solubility and biological pump
Source: www.whrc.org
wind speed and
wave type
sea surface
temperature
CO2 transfer = solubility x
gas transfer velocity
x [pCO2 sea – pCO2 air]
CO2 concentration
salinity, sea surface
pressure and
temperature,
humidity
biological activity
Mean annual net air-sea CO2 flux
for year 1995
Takahashi et al. 2002
CASIX
• NERC Centre of Air-Sea Interactions
and fluXes• Reduce errors in direct ocean flux
estimates
• My role in CASIX: use sensitivity and
uncertainty analysis techniques to
study model behaviour
Sensitivity analysis
output
parameter uncertainty range
pCO2 sea
• Algae fix ~ 100 Pg C annually
• No shortage of CO2: nutrients,
light and temperature limit growth
• Models developed to study
phytoplankton growth dynamics
and carbon uptake
Biological pump
Phytoplankton modelling
• Equations developed by Richard Geider
(Essex) and model by Helen Kettle
• Extensive parameterisation requiredvalues of key parameters not well
defined
• Using GEM-SA (Gaussian Emulation
Machine for Sensitivity Analysis) to
explore sensitivity and interaction of
model parameters
Phytoplankton modelling
CO2
light
sea water
temperature
dissolved CO2
nutrient
chlorophyll
growth
carbon fixed
Future plans
Apply same methods to combined General Ocean
Turbulence Model (GOTM) and Hadley Centre Ocean
Carbon Cycle model (HadOCC) – understand model
sensitivity to help CASIX ten year hindcast