Abstract:
South Asian monsoon is an important part of global climate, affecting large areas of the Indian subcontinent. Monsoon is life and death to the people of South Asia as good monsoon is a boon to the farmers whereas an unusual monsoon can bring misery to the people through widespread floods and droughts. Strong differential heating of the Indian landmass and the latent heat released from precipitation mainly drive the present day summer monsoon circulation. During the northeast (winter) monsoon season, winds are dry and biological productivity in the northern Indian Ocean is low providing little food to the deep-sea. In opposition, the intense, wet, monsoonal winds of the southwest (summer) monsoon cause widespread upwelling and high surface productivity, thus a high supply of organic particles to the sea floor. During high surface productivity distinct fauna and flora flourish in the surface water column in various parts of the northern Indian Ocean. Study of these monsoon proxies accumulating in layers of sediment over hundreds to millions of years help understand the history of monsoons over various time scales. Recent study suggests a mechanistic link between the North Atlantic Ocean and the southwest monsoon at century-millennial time scales during the Holocene, suggesting importance of tropics and high latitude teleconnection. On short time scales monsoon variability has also been related to the Indian Ocean Sea Surface Temperature (SST), Himalayan-Eurasian snow as well as El Nino-Southern Oscillation (ENSO). This study reviews different aspects of past monsoon variability and its future implications.