SEA-SURFACE TEMPERATURES AND THE HISTORY OF MONSOON UPWELLING IN THE NORTHWEST ARABIAN SEA DURING THE LAST 500,000 YEARS

Arabian Sea sediments record changes in the upwelling system off Arabi a, which is driven by the monsoon circulation system over the NW India n Ocean. In accordance with climate models, and differing from other l arge upwelling areas of the tropical ocean, a 500,000-yr record of pro ductivity at ODP Site 723 shows consistently stronger upwelling during interglaciations than during glaciations. Sea-surface temperatures (S STs) reconstructed from the alkenone unsaturation index (U-37(K')) are high (up to 27 degrees C) during interglaciations and low (22-24 degr ees C) during glaciations, indicating a glacial-interglacial temperatu re change of >3 degrees C in spite of the dampening effect of enhanced or weakened upwelling. The increased productivity is attributed to st ronger monsoon winds during interglacial times relative to glacial tim es, whereas the difference in SSTs must be unrelated to upwelling and to the summer monsoon intensity. The winter (NE) monsoon was more effe ctive in cooling the Arabian Sea during glaciations then it is now. (C ) 1995 University of Washington.