Docstoc

schneider

Document Sample
schneider Powered By Docstoc
					Surface Ocean pCO2 and Air-Sea
CO2-exchange in Coupled Models

        Birgit Schneider1*, Laurent Bopp1, Patricia Cadule1,
        Thomas Frölicher2, Marion Gehlen1, Fortunat Joos2,
        Corinne Le Quéré3 and Joachim Segschneider4
        1Laboratoire  des Sciences du Climat et de L‘Environnement (LSCE), Gif-sur-
          Yvette, France
        2 Division of Climate- and Environmental Physics, University of Bern, Bern,

          Switzerland
        3 University of East Anglia, Norwich, UK
        4 Max-Planck-Institut für Meteorologie, Hamburg, Germany




        *birgit.schneider@lsce.ipsl.fr
                              Outline

1. How good are the models in simulating surface ocean pCO2 and
   Air-Sea CO2-exchange?
   -> climatological fields: compared to the new Takahashi 2007
      data base and OCMIP-2 model output
   -> interannual variability: compared to observations and output
      from a forced model
   -> temporal trends: compared to observations


2. How good are the models reproducing temporal variability of marine
   biological production?
   -> interannual variability: compared to observation-based
      estimates derived from satellite data
                     Models and Experiments


                      IPSL                 MPIM                              NCAR
ocean model        OPA 8                    MPIOM                            NCAR-CSM1.4
hor. resolution  ORCA 2° x 2°x cos lat   1.5° x 1.5°                      3.6° x 0.8°-1.8°
vert. resolution   31 levels                40 levels                        25 levels
mar. biogeochem.   PISCES                   HAMOCC5.1                        OCMIP-2 mod.


               CO2 emissions
       30
       25
                                          All models have been treated
       20                                 according to the C4MIP protocol.
                                          (Friedlingstein et al., 2006)
       15
       10     historical       A2
                                          Period investigated: 1985-2005
        5
        0
        1850 1900 1950 2000 2050 2100
                                   !!!

The models were forced by CO2-emissions only!*)
Consequently, they produce their own patterns of climate
variability and can not be compared to observations on a
year by year basis.

Model evaluation needs to be done statistically and by
comparison with climatological distributions.




*)NCAR also includes forcing by other GHGs, solar activity and volcanic
emissions.
Modeled and Observed ΔpCO2
Spatial and Temporal Correlations of ΔpCO2




                           Taka 2007
                           Taka 2007
                           Taka 2007
      Sea-Air CO2-flux Equatorial Pacific
                          (165°W-90°W, 5°N-10°S)

             observed                                   modeled




Feely et al., JGR, 2006                 LQ2007 data from Le Quéré et al., Science, 2007
Climate Impact on Marine Biological Production
                                      SI SSTano

                                     -0.2 -1.0       La Nina
                                     -0.1 -0.5
                                                               SI = stratification index
                                       0     0                   ρ200 – ρsurf (kg m-3)
                                      0.1   0.5
          R2=0.73          R2=0.85
                                      0.2   1.0
                                                     El Nino



                                       SI SST 2006
  SEAWIFS-data from Behrenfeld et al., Nature,ano                               SI SSTano

                                     -0.2 -1.0                                  -0.2 -1.0

                                     -0.1 -0.5                                  -0.1 -0.5

                                       0     0                                   0     0

                                      0.1   0.5                                 0.1   0.5

                                      0.2   1.0          R2=0.02   R2=0.05      0.2   1.0
             R2=0.70    R2=0.67
Climate Impact on Marine Biological Production
                             SI SSTano                                   SI SSTano

                             -0.2 -1.0                                   -0.2 -1.0    La Nina
                             -0.1 -0.5                                   -0.1 -0.5

                              0     0                                     0      0

                             0.1   0.5                                   0.1    0.5
   R2=0.73         R2=0.85
   slope=-876   slope=-151   0.2   1.0        R2=0.04          R2=0.03   0.2    1.0
                                                                                      El Nino



                             SI SSTano                                    SI SSTano

                             -0.2 -1.0                                   -0.2 -1.0

                             -0.1 -0.5                                   -0.1 -0.5

                              0     0                                      0     0

                             0.1   0.5                                    0.1   0.5
   R2=0.70        R2=0.67
   slope=-787   slope=-246   0.2   1.0        R2=0.02     R2=0.05         0.2   1.0


                                                        NCAR

                                         SI = stratification index = ρ200 – ρsurf (kg m-3)
                                         Schneider et al., Biogeosciences Discuss., 2007
      Temporal Trends 1985-2005
Anomalies of Surface Ocean pCO2 Increase (Ocean-Atmosphere), ppm




                                     pCO2 increase (ppm/per year):

                                            ATM          OCE
                                       IPSL 1.49         1.26
                                       MPIM 1.69         1.60
                                       NCAR 1.88         1.73
                            Conclusions

• All models compare considerably better to the new pCO2 climatology
  (Takahashi et al., 2007) than to the one before.

• The seasonal cycle of surface ocean pCO2 is well represented by two
  out of three coupled models yielding a better match with observations
  than annual mean fields. For all OCMIP-2 models it is the opposite.

• Coupled model have difficulties in capturing the amplitude and/or
  frequency of the interannual variability of Air-Sea CO2-exchange.

• In contrast to observations models show a slightly lower surface ocean
  pCO2 increase than the atmosphere, suggesting a still increasing
  oceanic sink for anthropogenic CO2. (-> ozone effect?)

• For a realistic representation of the interannual variability of marine
  productivity next to ocean circulation the iron cycle and nutrient co-
  limitations are of major importance.
               Anthropogenic Air-Sea CO2-fluxes

          3

         2.5

          2
GtC/yr




         1.5

          1

         0.5

          0
                IPSL   MPIM      NCAR   LeQuéré 2007   Mikaloff 2006   Takahashi 2007   IPCC 2007



                       Inventories of Anthropogenic CO2 (GtC):
                                     1995           2000
                              IPSL   103           115
                              MPIM    91           112
                              NCAR    87            98
                              Sabine 118           (Sabine et al., Science, 2004)
                        Regional Sea-Air CO2-fluxes

              > 44 S      44 S - 18 S          18 S - 18 N     18 N - 49 N   > 49 N
         1

     0.8

     0.6

     0.4

     0.2
GtC/yr




         0

   -0.2

   -0.4

   -0.6

   -0.8

         -1
                 IPSL       MPIM        NCAR        LeQuéré 2007      Gruber 2007
SST - CO2flux relationships
SST - CO2flux relationships (anomalies)
El Nino Variability
                     Background



1. Can we reduce the uncertainty in estimating the oceanic
   sink for anthropogenic CO2?

2. Is there a significant contribution of marine biological
   productivity to the air-sea CO2-exchange?

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:13
posted:10/17/2012
language:Unknown
pages:17