Mg/Ca-derived sea surface temperature records from the Indian Ocean

Abstract

The Indian monsoon is important for more than one third population of the world. Understanding its past behavior is critical for forecasting its future behavior. To understand the changes in monsoon system of Indian subcontinent for the past 20 ka, Mg/Ca-based sea surface temperature records of different marine sediment cores from the Indian Ocean including the Arabian sea and Bay of Bengal is reviewed. From 17 Ka to 15 Ka (Heinrich Event), SSTs were warmer in general. During 14.7 Ka to 12.8 Ka (Bolling-Allerod), lower SSTs were observed, and Indian monsoon was stronger. While from 12.8 Ka to 11.5 Ka (Younger Dryas), there is an observed rise in sea surface temperature inferring that the Indian monsoon was weaker again. During the Holocene, the SSTs were inconsistently variable in general while the Indian monsoon was altogether stronger than the Deglaciation period. SST time series spectral analysis was also carried out to understand the periodicities and possible forcing factors of the monsoon. The observed periodicities mostly matched with solar insolation cycles and thermohaline circulation, which were also documented in previous studies, inferring that there is a tight relationship between the solar insolation, North Atlantic deep water system and associated ITCZ shifts, and the varying strengths of Indian monsoon during different time periods at various timescales.