Alkenone sea surface temperature in the Okhotsk Sea for the last 15 kyr.

Abstract

A sediment core collected from the Sea of Okhotsk, a marginal sea of the western North Pacific, has been analyzed for alkenones to reconstruct changes in the sea surface temperatures (SST) over the last 15 kyrs. A comparison of the core-top U 37′ value with the modern surface temperatures indicates that alkenones are produced at present in summer-fall season, a production seasonality probably identical to the one prevailing in the past, as suggested by evidences of enhanced sea ice cover and subsequent limitation of the phytoplankton growth period to summer‐fall at the glacial/deglacial transition. The alkenone downcore profile indicated that summer SST at the early deglaciation period (15 kyrs BP) were around 5 °C lower than today (ca. 11°C). A rapid SST increase (more than 3°C) was found to occur from 13.7 to 11.6 kyrs BP, following the melting water pulse event (MWP-1A). This warming was assumed to be the consequence of a radical change in the atmospheric/oceanic circulations which induced an enhanced heat transport from the sub-tropical to the northern North Pacific. A significant surface water cooling was evidenced from 11 to 8 kyrs BP, possibly caused by the supply of cold Siberian permafrost melt-water to the Okhotsk Sea through the Amur River.