Recent cooling trend in the Yellow and East China Seas and the associated North Pacific climate regime shift

Abstract

The Yellow and East China Seas (YECS) are widely believed to have experienced a robust, large-scale warming during the last few decades. After the warming reached its peak in the late 1990s, sea surface temperature (SST) reveals a basin-scale cooling trend in the YECS. To understand a mechanism of decadal transition in SST from a warming to a cooling trend, this study investigates its relationship with the large-scale climate changes around the YECS by using a cyclostationary basin mode from the satellite-based optimum interpolation SST for 1982&#8722 2014. The time series of the leading principal component varies coherently with the Pacific decadal oscillation index during the warming period before the late 1990s, however, its correlations decrease dramatically to an insignificant level after the late 1990s. This result indicates that a potential regime shift occurred in dynamical linkage between the YECS and North Pacific. During the cooling period after the late 1990s, the winter SST in the YECS is more closely associated with the variation of Siberian High (SH) along with an intensification of SH, suggesting that the intensified SH pressure system in recent decades plays an increasing role in determining states of the YECS compared to North Pacific oceanic processes. These observations highlight that the decadal variability in the YECS should be understood as a selective response from the oceanic processes in thele cooling trend in the YECS. To understand a mechanism of decadal transition in SST from a warming to a cooling trend, this study investigates its relationship with the large-scale climate changes around the YECS by using a cyclostationary basin mode from the satellite-based optimum interpolation SST for 1982&#8722 2014. The time series of the leading principal component varies coherently with the Pacific decadal oscillation index during the warming period before the late 1990s, however, its correlations decrease dramatically to an insignificant level after the late 1990s. This result indicates that a potential regime shift occurred in dynamical linkage between the YECS and North Pacific. During the cooling period after the late 1990s, the winter SST in the YECS is more closely associated with the variation of Siberian High (SH) along with an intensification of SH, suggesting that the intensified SH pressure system in recent decades plays an increasing role in determining states of the YECS compared to North Pacific oceanic processes. These observations highlight that the decadal variability in the YECS should be understood as a selective response from the oceanic processes in the