Alkenone-sea surface temperatures in the Japan Sea over the past 36 kyr: warm temperatures at the last glacial maximum

The Japan Sea experienced bottom water anoxia at the last glacial maximum ( LGM) since it is surrounded by four shallow straits, the sill depths of whi ch are close to, or shallower than, the drop in sea level (similar to 120 m ) that occurred then. A distinctive negative delta O-18 excursion of plankt onic foraminifera also took place during the LGM. This excursion has been i nterpreted from foraminiferal data as recording a drop in the paleosalinity of surface waters on the assumption of a constant low sea surface temperat ures between 34 and Il ka. We present here a profile of alkenone-based sea surface temperatures (alkenone-SSTs) over the past 36 kyr. Our results sugg est that SSTs during the LGM were much higher than those previously assumed . After considering the factors that might affect estimation of alkenone-SS Ts and comparisons of core-top alkenone-SSTs values with values for modern seawater we conclude that the higher alkenone-SSTs during the LGM are relia ble and reasonable. These warm SSTs were probably caused by radiative equil ibrium associated with the development of stable water stratification in th e Japan Sea during the LGM. (C) 2001 Elsevier Science Ltd. All rights reser ved.