[A-HW18] Material transportation and cycling at the land-sea interface: from headwaters to the ocean

[AHW18-18] Estimation of freshwater discharge from the Gulf of Alaska drainage basins

*Peng Xin¹, Humio Mitsudera¹, Muqing Shi¹, Takayuki Shiraiwa¹ (1.Hokkaido University)

Keywords: hydrological modeling, freshwater discharge, Gulf of Alaska

Overturning circulation originating in the Sea of Okhotsk is suggested to be important for the biogeochemical environment in the North Pacific Ocean and potentially the global climate, as it transports cold, oxygenated and nutrient-rich water from the surface into deeper layers of the ocean. The strength of this circulation is determined by the variability of sea surface salinity along the circulation pathway, which includes regions such as the Alaskan Stream, the Bering Sea, and the Sea of Okhotsk. Factors that influence the surface salinity in such regions therefore became a crucial subject for a better understanding of the circulation. One possible factor that we focused is the freshwater discharge from the Alaskan coastal basins, including the five major river basins and the line sources (a number of basins along the coast). Among the basins, a large part of area is covered by glaciers, which contributes to the freshwater discharge by snow and ice melting. We therefore applied a physically-based hydrological model to simulate the a series of hydrologic processes. Our results indicated that the freshwater discharge into the Gulf of Alaska (GOA) is one of the primary possibilities, and the results indicates discharge from line sources accounts for a larger part than that from five basins. We also discussed its annual and interannual variation as well as its closely connection to the overturning circulation.