How the North Atlantic Multidecadal Oscillation may have influenced the Indian summer monsoon during the past two millennia

Abstract

Observations have indicated that the North Atlantic SST variations have persistent effects on the Indian summer monsoon rainfall at multidecadal and longer timescales. The question of how such influences may have been achieved is addressed in this study using both instrumentation data of the 20th century and proxy records of the last 2000 years. Major results show that the North Atlantic SST anomalies strongly affect the Tibetan Plateau surface temperature and heat sources. The latter cause changes in the meridional temperature gradient between Tibetan Plateau and the tropical Indian Ocean. Through the thermal wind effect, the meridional temperature gradient anomalies change the lower tropospheric zonal winds and the monsoon circulation and rainfall. Copyright 2008 by the American Geophysical Union.