Atmospheric forcing fields: NCEP/NCAR reanalysis dataset for 1958-2007. We use Version 2 of the Coordinated Ocean-ice Reference Experiments (CORE) datasets available from the GFDL website http://data1.gfdl.noaa.gov/nomads/forms/mom4/COREv2.html. The 50-year long (1948-2007) COREv2.0 data combines NCEP Reanalysis with satellite data, with the details of the combination motivated by certain limitations of reanalysis (Large, W.G. and S.G. Yeager, 2009: The global climatology of an interannually varying air-sea flux data set. Climate Dynamics, 33, 341-364, doi:10.1007/s00382-008-0441-3). The COREv2 dataset consists of 8 variables used for interannual forcing: -6-hourly wind velocity components at 10m above the surface -6-hourly potential temperature at 2m above the surface -6-hourly specific humidity at 2m above the surface -daily solar and infra-red downwelling radiation at the surface -monthly total precipitation and snow falling rates. NCEP/DOE reanalysis dataset for 2011. We use NCEP/DOE Reanalysis 2 dataset available from the website of the NOAA/OAR/ESRL PSD at http://www.esrl.noaa.gov/psd/. NCEP/DOE Reanalysis 2 is an improved version of the NCEP Reanalysis I model that fixed errors and updated paramterizations of of physical processes (Kanamitsu, M., W. Ebisuzaki, J. Woollen, S. K. Yang, J. J. Hnilo, M. Fiorino, and G. L. Potter, 2002: NCEP-DOE AMIP-II Reanalysis (R-2). Bull. Amer. Meteor. Soc., 83, 1631-1643). We use 7 variables in NCEP/DOE Reanalysis 2 dataset for interannual forcing as in the case of the COREv2 dataset. For the monthly diagnostic surface snow rate rate we use NOAA NCEP-NCAR CDAS-1 (Climate Data Assimilation System I) dataset available from the website http://iridl.ldeo.columbia.edu/SOURCES/.NOAA/.NCEP-NCAR/.CDAS-1/ (Kalnay, E., M. Kanamitsu, R. Kistler, W. Collins, D. Deaven, L. Gandin, M. Iredell, S. Saha, G. White, J. Woollen, Y. Zhu, A. Leetmaa, B. Reynolds, M. Chelliah, W. Ebisuzaki, W. Higgins, J. Janowiak, K. C. Mo, C. Ropelewski, J. Wang, R. Jenne, and D. Joseph, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77, 437-472). Model Spinup: One pass through the 1958-2007 forcing with the COREv2 dataset will be used as a spinup for the simulations beginning at 01Jan1958. In this "spin-up" run, the ocean is initially at rest with temperature and salinity set to January climatorogical values of Levitus (1982). In the Arctic and Southern Oceans, initial mean sea ice thickness of 3.5 m is imposed in regions with a sea surface temperature below 0 C. An initial ice concentration of 0.95 are also assumed (Vancoppenolle, et al, 2009a). Initial biogeochemical parameters are also set following Aumont and Bopp (2006). From this initial state, the ORCA2_LIM2_PISCES configuration of NEMO is integrated for 50 years with Newtonian restoring terms for sea surface salinity only. For the ocean surface forcing, the CORE bulk formula is used with the 50-year COREv2 dataset. 1958-2007 run: For the initial conditions at 01Jan1958 in the 50-year 1958-2007 experiment, the restart conditions at the end of 2007 in the spinup run were used that include restart conditions of biogeochemical parameters and the model was forced with the 50-year COREv2 dataset. The model results for the 40-year period 1968-2007 of this experiment are used to produce the figures. 2011 run: The ORCA2_LIM2_PISCES configuration of NEMO is integrated for 11 years (2001-2011) forced with the NCEP Reanalysis 2 dataset starting from the model conditions at the end of 2000 in the above 50-year 1958-2007 experiment. The model results for 2011 are analysed. ------------------------------------------------------------------------------------------ http://www.metoffice.gov.uk/hadobs/hadisst/ Hadley_Sea_Ice.pdf http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.reanalysis2.gaussian.html NOAA_sea_ice.pdf