Bi-hemispheric forcing for Indo-Asian monsoon during glacial terminations

Abstract

The drivers of the Indo-Asian monsoon dynamics during terminations have recently emerged as a controversial issue. Cheng et al. (2009. Ice Age Terminations. Science 326, 248–252), using East-Asian speleothem records, proposed a strict northern hemisphere insolation control at the orbital timescale with weak monsoon intervals occurring at terminations. On the contrary, An et al. (2011. Glacial–Interglacial Indian Summer Monsoon Dynamics. Science 333, 719–723), using a record from the Hequing paleolake basin, highlight the importance of the southern hemisphere climate forcings on Indian summer monsoon dynamics at glacial–interglacial timescale. The purpose of this note is to propose an explanation of the weak monsoon intervals at terminations, using a deep sea sediment stack monsoon record. The mechanism involved is linked to interhemispheric interactions, as proposed by An et al. (2011), superimposed to the role of orbital forcing (precession and obliquity parameters). This explanation clarifies the combination of complex drivers acting on the Indo-Asian monsoon dynamic at terminations.