苏北浅滩及长江口海域春季海表面温度长期升温机制分析

Long-term warming trend of sea surface temperature in spring in the Subei Bank and the Changjiang Estuary

在1982—2016年,苏北浅滩及长江口海域春季海表面温度主要呈现出从南至北、从近岸至离岸升温趋势逐渐减小的特征,其中长江口附近海域升温速率最大。研究显示,苏北浅滩及长江口附近海域春季海表面温度的长期升温趋势主要与该海域经向热输送及长江平流热输送的增强有关。进一步的研究发现,春季经向风速的增强导致该海域经向热输送的增加,而春季经向风速的年际及年代际变率又受到太平洋年代际振荡、北极涛动的调控,其中,太平洋年代际振荡指数与经向风速呈负相关,北极涛动指数与经向风速呈正相关,北极涛动指数的年际增加以及太平洋年代际振荡指数的年际降低使得春季南风增强,进而南向的冷平流减弱,北向的热平流增强,使该海域春季海表面温度长期升温。在此过程中,净热通量对其升温过程起到抑制作用,而前冬海温主要是对春季海表面温度的年代际振荡产生重要影响,其主要体现为1982—1999年的升温及2000—2016年的降温过程。

During the spring of 1982 to 2016, the sea surface temperature (SST) in the Subei Bank and the Changjiang Estuary featured the following characteristics: the warming trend in the south was larger than that in the north, while the warming trend in the coastal sea was larger than that in the sea basin, with the Changjiang Estuary exhibiting the largest warming. The long-term warming trend in the Subei Bank and the Changjiang Estuary was closely associated with the strengthened meridional heat transport and the strengthened heat transport by the Changjiang River. Moreover, the inter-annual and inter-decadal variations of the southern wind speed was positively correlated with the Arctic oscillation (AO) index and negatively correlated with the Pacific decadal oscillation (PDO) index. The increase of AO index and the decrease of PDO index strengthened the south wind and then caused the increase of SST in the Subei Bank and the Changjiang Estuary. During this process, the net heat flux played an inhibitory role, and the temperature in the previous winter primarily influenced the inter-decadal oscillation of SST in spring, which primarily appeared as the increase of SST from 1982 to 1999 and the decrease from 2000 to 2016.