Dominating Roles of Ice Sheets and Insolation in Variation of Tropical Cyclone Genesis Potential Over the North Atlantic During the Last 21,000 Years

Abstract

AbstractTo advance our knowledge on tropical cyclone (TC)'s sensitivity to various external forcings, we investigate evolution of TC genesis potential over the North Atlantic during the last 21,000 years that experienced more varied forcings than present‐day using transient simulations. Abrupt large amplitude of fluctuations in genesis potential during the studied period was dominated by meltwater discharge, whereas insolation controlled the long‐term trend. Increased (decreased) meltwater discharge from Northern Hemisphere ice sheets leads to detrimental (conducive) conditions for genesis via altering the Atlantic Meridional Overturning Circulation and hence three‐dimensional temperature structure and Hadley circulation. This effect is larger than the orographic effect of retreated ice sheets that favors TC formation. Decreasing (increasing) insolation broadly results in more (less) favorable conditions for genesis arising from larger (smaller) local vertical temperature contrast and stronger (weaker) meridional circulation. Our study highlights potential changes of ice sheets and insolation in affecting future long‐term TC activity.