FN Archimer Export Format PT J TI The seasonal cycle of pCO(2) and CO2 fluxes in the Southern Ocean: diagnosing anomalies in CMIP5 Earth system models BT AF MONGWE, N. Precious VICHI, Marcello MONTEIRO, Pedro M. S. AS 1:1,2;2:2,3;3:1,2; FF 1:;2:;3:; C1 CSIR, SOCCO, Cape Town, South Africa. Univ Cape Town, Dept Oceanog, Cape Town, South Africa. Univ Cape Town, Marine Res Inst, Cape Town, South Africa. C2 CSIR, SOUTH AFRICA UNIV CAPE TOWN, SOUTH AFRICA UNIV CAPE TOWN, SOUTH AFRICA IN DOAJ IF 3.951 TC 45 UR https://archimer.ifremer.fr/doc/00673/78489/80818.pdf https://archimer.ifremer.fr/doc/00673/78489/80819.pdf https://archimer.ifremer.fr/doc/00673/78489/80820.pdf https://archimer.ifremer.fr/doc/00673/78489/80821.pdf LA English DT Article CR OISO - OCÉAN INDIEN SERVICE D'OBSERVATION AB The Southern Ocean forms an important component of the Earth system as a major sink of CO2 and heat. Recent studies based on the Coupled Model Intercomparison Project version 5 (CMIP5) Earth system models (ESMs) show that CMIP5 models disagree on the phasing of the seasonal cycle of the CO2 flux (FCO2) and compare poorly with available observation products for the Southern Ocean. Because the seasonal cycle is the dominant mode of CO2 variability in the Southern Ocean, its simulation is a rigorous test for models and their long-term projections. Here we examine the competing roles of temperature and dissolved inorganic carbon (DIC) as drivers of the seasonal cycle of pCO(2) in the Southern Ocean to explain the mechanistic basis for the seasonal biases in CMIP5 models. We find that despite significant differences in the spatial characteristics of the mean annual fluxes, the intra-model homogeneity in the seasonal cycle of FCO2 is greater than observational products. FCO2 biases in CMIP5 models can be grouped into two main categories, i.e., group-SST and group-DIC. Group-SST models show an exaggeration of the seasonal rates of change of sea surface temperature (SST) in autumn and spring during the cooling and warming peaks. These higher-than-observed rates of change of SST tip the control of the seasonal cycle of pCO(2) and FCO2 towards SST and result in a divergence between the observed and modeled seasonal cycles, particularly in the Sub-Antarctic Zone. While almost all analyzed models (9 out of 10) show these SST-driven biases, 3 out of 10 (namely NorESM1-ME, HadGEM-ES and MPI-ESM, collectively the group-DIC models) compensate for the solubility bias because of their overly exaggerated primary production, such that biologically driven DIC changes mainly regulate the seasonal cycle of FCO2. PY 2018 PD MAY SO Biogeosciences SN 1726-4170 PU Copernicus Gesellschaft Mbh VL 15 IS 9 UT 000432206000001 BP 2851 EP 2872 DI 10.5194/bg-15-2851-2018 ID 78489 ER EF