Abstract:

Based on conductivity–temperature–depth (CTD) data obtained by the Chinese National Arctic Research Expeditions (2008, 2010, 2012, and 2014), in combination with shared historical data, the water mass, upper-ocean heat content, net heat flux change, wind field, and sea level pressure were analyzed to investigate the interannual variability of the hydrologic structural characteristics of the Bering Sea. It was found that the waters of the Bering Sea could be divided into four masses: Bering Upper Water (BUW), Bering Middle Water (BIW), Bering Deep Water (BDW), and Bering Shelf Water (BSW). Variations of temperature and salinity were concentrated mainly in the upper water. In July 2012, the sea surface temperature (SST) was below normal, whereas in July 2014, strong positive SST anomalies developed. These abnormal phenomena resulted because of lower or higher heat content. We investigated the reasons for the SST anomaly in July 2014 and found that the mechanism was completely different from basin to shelf. The higher SST of shelf waters was mainly caused by higher cumulative net heat flux, whereas in the basin, it was due to unusually strong and persistent high pressure. This meant that the sea surface wind stress curl was enhanced, which caused continuous warm advection, and strong Ekman pumping, function that led to warming of the upper water.

Key words: Bering Sea, water mass, temperature, salinity, net heat flux, wind stress curl, sea level pressure