Variation of monsoonal upwelling: A response to changing solar radiation

In the western Arabian Sea, the distribution of planktonic foraminifera is related to coastal upwelling and therefore to the low-level summer monsoon winds which force the upwelling. Records of faunal variation over the past 30 kyr reveal that the Indian Ocean summer monsoon has been both stronger (9 kyr) and weaker (18 kyr). These paleoceanographic reconstructions and analogies to general circulation model simulations suggest that changes in the distribution of seasonal solar radiation and surface albedo are responsible for the changes in monsoon intensity. This study illustrates that the Milankovitch Hypothesis of climate change, which changes the seasonal distribution of solar radiation as a function of orbital variations, applies to low-latitude as well as high-latitude climate changes.