[A-CG52] Science in the Arctic Region

[ACG52-04] A Numerical Study associated with Soya Warm Current Impact to Sea-Ice Distribution in Soth Part of Okhotsk Sea

*Ryu Saiki¹, Humio Mitsudera², Takuya Nakanowatari¹, Hiroshi Kuroda¹, Tomoshige Inoue³, Hiroaki Ueda³, Katsushi Iwamoto⁴ (1.Japan Fisheries Research and Education Agency, Kushiro, 2.Institute of Low Temperature Science, Hokkaido University, 3.Faculty of Life and Environmental Sciences, University of Tsukuba, 4.Monbetsu City Hall)

Keywords:physical oceanography, ice-ocean coupled regional model, composite analysis, sea-surface temperature anomaly, sea-ice distribution, Soya Warm Current

It is known that the Okhotsk Sea is a marginal sea beside the west-side of North Pacific Ocean as the southern limit of sea-ice spread in the Northern Hemisphere. It is significant for understanding the sea-ice distribution variability to predict of the marin lower ecosystems formation because the sea ice include dissolved iron and an essential trace metal for phytoplankton. The factors of the sea-ice distribution valiabily in the whole of Okhotsk Sea have been suggested by the cooling of the sea surface from autumn to winter and the impact of the East Sakhalin Current with low-temperature and low-salinity which flows southword from the north side of the Okhotsk Sea along the east coast of Sakhalin. However, it is usufficient to understand the factors with respect to the light-ice year and the heavy-ice year in the south part of Okhotsk Sea. In this study, we conducted a historical experiment using a ice-ocean coupled regional model to focus on the relationship between the interannual variability of sea-ice distribution in the south part of Okhotsk Sea and the variability of the Soya Warm Current with high-temperature and high-salinity from the Japan sea to the Okhotsk Sea. As the result of the composite analysis which based on the categorized light-ice years and heavy-ice years from 1994 to 2017, we found that the light-ice year temperature and salinity along the Soya Warm Current pass-way tend to be higher than the normal-ice year in December before the freezing. Further, An investigation of flow rate in the Soya Strait revealed that the little-ice years mean flow rate is larger than the heavy-ice years mean flow rate from November to December. Therefore, we may suggest that the amount of sea ice in the south part of Okhotsk Sea is affected by the Soya Warm Current variability in autumn. In this presentation, we will evaluate the impact of the Soya Warm Current with respect to the sea-ice distribution in the south part of Okhotsk Sea through sensitivity experiments on heat transport of the Soya Warm Current, and discuss the mechanism of its variability.