Pacific Summer Water

 Arctic sea ice has declined significantly in recent decades. For example, the area of sea ice on September 15 averaged 7.3 million square kilometers in the 1980s, but decreased by more than half to 3.6 million square kilometers by 2020. This decline in sea ice has occurred mainly in the Pacific sector of the Arctic Ocean, and one of its causes is an increase in northward heat transport by Pacific Summer Water. The relatively warm Pacific Summer Water is transported from the Bering Sea, which is the marginal sea of the Pacific Ocean, to the Chukchi Sea, which is the marginal sea of the Arctic Ocean, through the Bering Strait from spring to autumn. Then, it is further transported to the subsurface of the Canada Basin in the Arctic Ocean. It was pointed out that this affects the surface water temperature of the Canada Basin in the Arctic Ocean, contributing to the decline in sea ice in the Pacific sector of the Arctic Ocean (for example, Shimada et al., 2006).

Schematic diagram of the flow of the Pacific sector of the Arctic Ocean. Modified figure from Tsukada, Ueno et al. Polar Science (2018).