Abstract
Hydrographic data from the World Ocean Database 2013 and the Chinese National Arctic Research Expedition were used to investigate the summertime changes in the eastern Chukchi Sea from 1974 to 2017. Owing to the Pacific inflow and timing of the sea ice retreat, water masses and vertical thermohaline structures in the eastern Chukchi Sea have changed but with regional differences. The entire eastern Chukchi Sea warmed up with significant temperature increase in the central shelf; however, the surface and bottom salinity in the southern, central, and northern shelves exhibited different trends. The northward extension of the Pacific Summer Water after 1997 influenced the summer hydrography significantly. Moreover, the data reveal changes in the characteristics of various water masses. Both Bering Summer Water (BSW) and Pacific Winter Water in the deeper layer became saltier, whereas the Alaskan Coastal Water in the upper layer became fresher after 1997. The previous definition of the BSW should be modified to include the warming water mass in the southern Chukchi Sea in the more recent years. Furthermore, the vertical thermohaline structure over the Chukchi shelves experienced considerable changes in its characteristics due to the combined effects of the Pacific inflow and surface forcing.
Highlights
As one of the cold sources of the earth system, the Arctic plays a significant role in ocean circulation and the global climate
The water columns were roughly mixed with weak stratification, and the mixed responses in vertical thermohaline structures
We have addressed the general hydrographic characteristics of the Chukchi Sea during summer and the associated regional changes from 1972 through 2017 by using a large amount of hydrographic data from the World Ocean Database 2013 and the Chinese National Arctic Research
Summary
As one of the cold sources of the earth system, the Arctic plays a significant role in ocean circulation and the global climate. As a peripheral sea of the Arctic, the Chukchi Sea has several important features: it provides the pathway for the Pacific water to flow into the Arctic and becomes one of the most important regions to mix the Pacific and Arctic water; since it has a seasonal to perennial sea ice cover, the minimum ice extent and edge in this area have been widely used as indicators of global climate change [6,7]. Strait during summer [20], and the upper ocean in the Arctic has warmed to unprecedented levels, including the shallow Chukchi Sea [21]. We use available hydrographic data to investigate the oceanic changes in the eastern Chukchi Sea with a focus on the water mass characteristics and vertical thermohaline structures.
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