Projected Changes in the upper ocean in the North Pacific Ocean

The IPCC fifth assessment report provides up-to-date scientific knowledge and socio-economic aspects of the climate change, based on observational data and CMIP5 global models. This study aims to evaluate the performance of North Pacific upper-ocean simulation of CMIP5 global climate models by comparing their historical simulation results with observed climatology and to analyze their future climate change projection. Statistical analyses show that the spatial patterns of the Pacific Decadal Oscillation (PDO) simulated by CMIP5 models were improved compared with those by CMIP3 models, mainly due to better representations of teleconnection between the tropics and mid-latitudes. This PDO improvement can be attributed not only to a decrease in number of models showing poor performance, but also to better simulation of PDO spatial patterns. Sea surface temperature and mixed layer depth (MLD) in the North Pacific Ocean, however, still appear to have significant biases in CMIP5 historical runs. These biases might influence on the CMIP5 models’ future projections that show considerable changes in MLD in the North Pacific.