Spatio-temporal variations of stratification and its factors in the Chukchi Sea

Misaki Onuka1, Hiromichi Ueno2, Motoyo Itoh3, Takashi Kikuchi3, Shigeto Nishino3, Eiji Watanabe4, Toru Hirawake5, Michiyo Yamamoto-Kawai6 and Kohei Mizobata6, (1)Hokkaido University, Sapporo, Japan, (2)Hokkaido University, Faculty of Fisheries Sciences, Sapporo, Japan, (3)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan, (4)Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan, (5)Hokkaido University, Faculty of Fisheries Sciences, Hakodate, Japan, (6)Tokyo University of Marine Science and Technology, Tokyo, Japan
Abstract:
Temporal and spatial variation of stratification in the Chukchi Sea was investigated through analysis of temperature and salinity obtained on board T/S Oshoro-maru and R/V Mirai from 2007 to 2013. In this analysis, stratification index was used to quantify the magnitude of stratification. As the result, we found that the seasonal and interannual variation of stratification differed between the northern and southern parts of the Chukchi Sea. In the northern part (north of 69°N), stratification was almost the same from July to October, but its constituent varied: temperature contribution to the stratification decreased from July to October. In the southern part, on the other hand, stratification was strengthened from July to October due to surface freshening. Interannual variation of stratification was relatively strong in the southern part. We further used total alkalinity to investigate surface freshening in detail. In 2013, Meteoric Water (river runoff + precipitation) fraction increased from July to October, probably causing surface freshening. On the other hand, in 2012, sea ice melt water had a significant impact on surface freshening from July to October.
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