Projection of ocean uptake of anthropogenic CO2 using an ocean carbon cycle model: Preliminary resul

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Projection of ocean uptake of anthropogenic CO2
using an ocean carbon cycle model Preliminary
results from the oceanic component of the
integrated earth system model at FRSGC

• Michio KAWAMIYA
• Chisato YOSHIKAWA
• Maki NOGUCHI
• Taroh MATSUNO
• Frontier Research System for Global Change,
• Yokohama, Japan

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Introduction

• Earlier estimates of future uptake of
  anthropogenic CO2 by the ocean

IPCC TAR
OCMIP type models simple representation of the
biological pump
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Model outline
OGCM Code COCO3.4 (Hasumi, 2000)
based on primitive equations Resolution 1 deg. X
1. deg. 54 vertical levels
(20 levels for the upper 100m)
Biological model Nitrogen based, 4-compartment
model by Oschlies Garcon (1998) modified
by Oschlies (2001)
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Comparative study between model-derived and
reanalysis forcing fields

• Forcing fields (SST, P-E, wind stress, solar
  radiation) from
• OMIP data (ECMWF reanalysis)
• CCSR/NIES coupled model output
• Initial conditions
• T, S results from an OMIP experiment
• Nitrate World Ocean Atlas 94
• TCO2, Alkalinity results from an OCMIP
  experiment
• Other biological variables constant (0.1
  mmol/m3)
• Spin-up 20 years

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Results
Surf. Chl.
Nitrate
Obs.
Reanalysis
Model-derived
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Nutrient trap along the coast of Peru--
Reanalysis data are less realistic? --
Wind stress
Surf. Nitrate
W along the 15S
Reanalysis
Model-derived
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Nutrient trap (2)
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Nitrate distribution in the Southern Ocean (1)
Nitrate Reanalysis
Nitrate Model-derived
Ekman W Reanalysis
Ekman W Model-derived
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Nitrate distribution in the Southern Ocean (2)
Mixed layer depth
Nitrate
WOA
Reanalysis
Model-derived
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Nutrient distribution in the Southern Ocean (3)
P-E
SSS
WOA
Reanalysis
Model-derived
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Air-sea exchange of CO2
Takahashi Et al. (1999)
Reanalysis
Model-derived
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Summary of the difference

• Nutrient trapping off Peru due to strong coastal
  upwelling under the OMIP forcing
• Low surface nitrate in the Southern Ocean under
  the model-derived forcing due to shallow mixed
  layer
• The above difference is not reflected in the
  air-sea CO2 exchange field because of differences
  in the processes governing the surface
  concentrations of nitrate and fCO2

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Forcing for the global warming experiment
SST, wind stress, P-E, solar radiation outputs
from a global warming
experiement
with a coupled model
based on the
IS92a scenario
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Surface chl. fields
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Air-sea exchange of CO2
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Air-sea exchange of CO2
Takahashi Et al. (1999)
Reanalysis
Model-derived
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Current ocean models underestimate the ocean
response to climate variations?Suggestion from
inversion studies
Forward model (LeQuere et al. 2000)
Inversion results
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Intrusion of anthropogenic CO2
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Another group at FRSGC is working on a model with
multiple size classes of plankton.
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Some results from the model with multiple size
classes
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Summary

• The experiments forced by reanalysis and
  model-derived data provide similar results
  regarding air-sea CO2 exchange.
• The current and future ocean uptakes of CO2
  estimate by the model are consistent with earlier
  results from models with simpler representation
  of the pelagic ecosystem.
• Apparently, no bug. Go for it!
• First results from a coupled carbon cycle model
  are expected early next year.