Sea surface temperatures of the western Arabian Sea during the last deglaciation

Abstract

In this study we present a sea surface temperature (SST) record from the western Arabian Sea for the last 20,000 years. We produced centennial‐scale δ18O and Mg/Ca SST time series of core NIOP929 with focus on the glacial‐interglacial transition. The western Arabian Sea is influenced by the seasonal NE and SW monsoon wind systems. Lowest SSTs occur during the SW monsoon season because of upwelling of cold water, and highest SSTs can be found in the low‐productivity intermonsoon season. The Mg/Ca‐based temperature record reflects the integrated SST of the SW and NE monsoon seasons. The results show a glacial‐interglacial SST difference of ∼2°C, which is corroborated by findings from other Arabian Sea cores. At 19 ka B.P. a yet undescribed warm event of several hundred years duration is found, which is also reflected in the δ18O record. A second centennial‐scale high SST/low δ18O event is observed at 17 ka B.P. This event forms the onset of the stepwise yet persistent trend toward Holocene temperatures. Highest Mg/Ca‐derived SSTs in the NIOP929 record occurred between 13 and 10 ka B.P. Interglacial SST is ∼24°C, indicating influence of upwelling. The onset of Arabian Sea warming occurs when the North Atlantic is experiencing minimum temperatures. The rapid temperature variations at 19, 17, and 13 ka B.P. are difficult to explain with monsoon changes alone and are most likely also linked to regional hydrographic changes, such as trade wind induced variations in warm water advection.