Assessment of sea ice simulations in the CMIP5 Models
Abstract. The historical simulations of sea ice during 1979 to 2005 by the Coupled Model Intercomparison Project Phase 5 (CMIP5) are compared with satellite observations and Global Ice–Ocean Modeling and Assimilation System (GIOMAS) data in this study. Forty-nine models, almost all of the CMIP5 climate models and Earth System Models, are used. For the Antarctic, multi-model ensemble mean (MME) results can give good climatology of sea ice extent (SIE), but the linear trend is incorrect. The linear trend of satellite-observed Antarctic SIE is 1.56 × 105 km2 decade−1; only 1/7 CMIP5 models show increasing trends, and the linear trend of CMIP5 MME is negative (−3.36 × 105 km2 decade−1). For the Arctic, both climatology and linear trend are better reproduced. Sea ice volume (SIV) is also evaluated in this study, and this is a first attempt to evaluate the SIV in all CMIP5 models. Compared with the GIOMAS data, the SIV values in both Antarctic and Arctic are too small, especially in spring and winter. The GIOMAS SIV in September is 16.7 × 103 km3, while the corresponding Antarctic SIV of CMIP5 MME is 13.0 × 103 km3, almost 22% less. The Arctic SIV of CMIP5 in April is 26.8 × 103 km3, which is also less than the GIOMAS SIV (29.3 × 103 km3). This means that the sea ice thickness simulated in CMIP5 is too thin although the SIE is fairly well simulated.