Summer monsoon belt displacement and precipitation sources in the Northern Arabian Sea: A multi-proxy palaeoenvironmental reconstruction for Late Holocene

The identification of precipitation sources and palaeoenvironmental changes in the Arabian Sea during the late Holocene could improve our knowledge of future variations in the summer monsoon. In this study, we compare and contrast foraminifera, stalagmite isotopes, clay mineralogy and palaeooceanographic data in order to shed new light on the interactions between atmospheric and oceanographic parameters on the summer monsoon belt displacement and precipitation sources during the late Holocene. We showed that during warm periods (e.g. the Roman and Medieval periods), the increased intensity of northern Levar winds led to a decrease in summer monsoon precipitation in the northern Arabian Sea. Increased wind stress from the north led to the transportation of warm and saline water from the Persian Gulf to the northeast of the Arabian Sea. These conditions were favorable to the regeneration of tropical storms originating in the Bay of Bengal, between 1900 and 1500 calyr BP (similar to Golab-Shaheen tropical cyclone). By contrast, maximum summer monsoon winds are observed during cooler periods when N Levar winds were weakest. A poleward movement of the summer monsoon belt that happened around 1400 calyr BP led to an increase in NW summer Shamal wind intensity, increased Persian Gulf outflow to the Gulf of Oman, cold-water upwelling events in the eastern part of the Oman Gulf and increases in water temperature in the center of the Arabian Sea. Consequently, the number of tropical storms originating in the Arabian Sea (e.g. similar to Gonu and Phet) increased during cooler periods. These data provide a template to understand the present and future evolution of the summer monsoon in the Arabian Sea, under climate change.