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

A sediment core collected from the Sea of Okhotsk, a marginal sea of the we stern 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(K') value with the modern surface temperatures indicat es that alkenones are produced at present in summer-fall season, a producti on seasonality probably identical to the one prevailing in the past, as sug gested by evidences of enhanced sea ice cover and subsequent limitation of the phytoplankton growth period to summer-fall at the glacial/deglacial tra nsition. The alkenone downcore profile indicated that summer SST at the ear ly deglaciation period (15 kyrs BP) were around 5 degrees C lower than toda y (ca. 11 degrees C). A rapid SST increase (more than 3 degrees C) was foun d to occur from 13.7 to 11.6 kyrs BP, following the melting water pulse eve nt (MWP-1A). This warming was assumed to be the consequence of a radical ch ange in the atmospheric/oceanic circulations which induced an enhanced heat transport from the sub-tropical to the northern North Pacific. A significa nt surface water cooling was evidenced from Ii to 8 kyrs BP, possibly cause d by the supply of cold Siberian permafrost melt-water to the Okhotsk Sea t hrough the Amur River.