Western Atlantic Intertropical Convergence Zone variability over the last full glacial cycle

Abstract

Pptn. changes in the western tropical Atlantic over the past 180,000 years are reconstructed using the stable carbon and deuterium isotopic compns. of higher plant leaf waxes preserved in Cariaco Basin sediments. Results indicate that less (more) pptn. fell over northern South America during stadial (interstadial) periods relative to today. Moreover, this trend is highly modulated by precessionally driven oscillations in Nov. insolation, such that dry events concurrent with periods of increased solar heating were less arid than those occurring when that heating was diminished (and visa versa). Together, these findings suggest that the duration of the seasonal displacement of the Intertropical Convergence Zone (ITCZ) was modified in response to changes in both the high latitude North Atlantic (presumably due to variations in the rate of meridional overturning circulation) and tropical insolation during the last glacial cycle, thus establishing an important link between seasonality and abrupt climate change.