Far-reaching effects of sea ice extent in the Sea of Okhotsk on sea-surface turbulent heat flux and their possible influence

Tomohiro Nakamura, Hokkaido University, Institute of Low Temperature Science, PORC, Sapporo, Japan, Yusuke Takahashi, Hokkaido University, Graduate School of Environmental Science, Sapporo, Japan and Takuya Nakanowatari, Japan Fisheries Research and Education Agency, Hokkaido National Fisheries Research Institute, Kushiro, Japan
Abstract:
Large interannual variations in sea-ice extent (SIE) in the Sea of Okhotsk affect the large-scale atmospheric circulation by generating Rossby waves. However, their effects on sea surface heat flux are still not well clarified. Here, we investigated effects of the variations in SIE, focusing on atmosphere and ocean near the sea surface. This was conducted by composite analysis for years of large and small SIE (hereafter, heavy- and light-ice years, respectively), using atmosphere and ocean reanalyses.

The difference of heavy- and light-ice year composites shows that sea surface turbulent heat flux varies significantly in an unexpectedly large area in the western North Pacific. This is because a cold and dry air from Siberia spreads farther in heavy ice years, owing to much less sensible and latent heat fluxes over sea ice compared with open water. Correlated with the difference in heat flux, storm track shifts southward and ocean mixed layer becomes deeper in the western subarctic in heavy ice years. These findings suggest possibilities of a feedback via SIE to the atmospheric circulation and effects on ocean ecosystem.

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