A comparison of the CMIP5 models on the historical simulation of the upper ocean heat content in the South China Sea

Abstract

Seventeen models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) activity are compared on their historical simulation of the South China Sea (SCS) ocean heat content (OHC) in the upper 300 m. Ishii’s temperature data, based on the World Ocean Database 2005 (WOD05) and World Ocean Atlas 2005 (WOA05), is used to assess the model performance by comparing the spatial patterns of seasonal OHC anomaly (OHCa) climatology, OHC climatology, monthly OHCa climatology, and interannual variability of OHCa. The spatial patterns in Ishii’s data set show that the seasonal SCS OHCa climatology, both in winter and summer, is strongly affected by the wind stress and the current circulations in the SCS and its neighboring areas. However, the CMIP5 models present rather different spatial patterns and only a few models properly capture the dominant features in Ishii’s pattern. Among them, GFDL-ESM2G is of the best performance. The SCS OHC climatology in the upper 300 m varies greatly in different models. Most of them are much greater than those calculated from Ishii’s data. However, the monthly OHCa climatology in each of the 17 CMIP5 models yields similar variation and magnitude as that in Ishii’s. As for the interannual variability, the standard deviations of the OHCa time series in most of the models are somewhat larger than those in Ishii’s. The correlation between the interannual time series of Ishii’s OHCa and that from each of the 17 models is not satisfactory. Among them, BCC-CSM1.1 has the highest correlation to Ishii’s, with a coefficient of about 0.6.