[A-OS19] Coastal physical processes associated with mixing, eddies, internal waves

[AOS19-02] A new look at the Sea of Okhotsk water properties and their long-term variability using an advance mapping technique.

*Vigan Mensah¹, Kay I. Ohshima¹ (1.Institute of Low Temperature Science)

Keywords:Sea of Okhotsk, Dense Shelf Water, Soya Warm Current, Intermediate water

The Sea of Okhotsk is a marginal sea which plays an essential role in the supply of iron and dissolved oxygen to the North Pacific, and thus greatly contributes to the biological productivity of this ocean. The Sea of Okhotsk has been undergoing long-term (~ 50 years) changes, which include warming and a drop of its dissolved oxygen content. These changes are partly attributed to a decrease in the supply of Dense Shelf Water (DSW), a water mass generated in winter due to sea ice formation on the northwestern shelf of the sea. However, detailed quantification of the changes in DSW content in the Sea of Okhotsk have yet to be conducted. Here, advanced mapping techniques allow us to create a gridded data set with a topographic constraint scheme in the southern Sea of Okhotsk. These high-resolution (5-km) climatologies of water properties (temperature, salinity, dissolved oxygen, layer thickness) are generated for periods before and after 1990. These new climatologies allow us to clearly distinguish the inflow of DSW and Soya Current Water (SCW) in the Kuril Basin or/and on the Sakhalin and Hokkaido shelves. The warming and loss of DO content of the Okhotsk Sea Intermediate Water (OSIW) exceed 0.3°C and 0.7 ml/l, respectively. The climatologies reveal that the amount of waters with a high (>50%) DSW content has decreased by more than half between before and after 1990. Besides, unlike the previous studies, our new dataset suggests that SCW does not contribute to the formation of OSIW. OSIW would be composed of only DSW and western subarctic waters.