ITCZ rather than ENSO signature for abrupt climate changes across the tropical Pacific?

Latitudinal movements of the Intertropical Convergence Zone (ITCZ), analogous to its present-day seasonal shifts, and El Nino Southern Oscillation (ENSO)-type variability both potentially impacted rainfall changes at the millennial timescale during the last glacial period. In this study we compare tropical Pacific sedimentary records of paleoprecipitation to decipher which climate mechanism was responsible for the past rainfall changes. We find that latitudinal movements of the ITCZ are consistent with the observed rainfall patterns, challenging the ENSO hypothesis for explaining the rapid rainfall changes at low latitudes. The ITCZ-related mechanism appears to reflect large-scale atmospheric rearrangements over the tropical belt, with a pronounced Heinrich-Dansgaard/Oeschger signature. This observation is coherent with the Simulated tropical rainfall anomalies induced by a weakening of the Atlantic thermohaline circulation in modeling experiments. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved.