AN EQUATORIAL EXCURSION OF THE ITCZ DURING TERMINATION II IN THE CEP

The Intertropical Convergence Zone (ITCZ) is a critical element of modern hydroclimate, and a main control on Monsoon location and intensity; it is a zone of increased atmospheric convection and precipitation found at the convergence of the northern and southern trade winds. There is wide agreement that the mean annual position of the ITCZ migrates on millennial timescales, but different proxies and model estimates disagree on the magnitude of the migration. Reconstructing the magnitude of the deglacial shifts in ITCZ position is of critical importance to understanding the reactivity of the ITCZ to climate events, as well as the lead-lag relationship between atmospheric circulation and Southern Ocean ventilation.

Previous work has constrained the ITCZ changes between the Holocene and the LGM in the CEP confirming that it is possible to use radiogenic isotopes of Pb and Nd to adequately distinguish between potential sources of dust to the central Pacific Ocean, to trace the extend of Asian loess dust into the CEP, and to examine the changes of the ITCZ during ice age climate transitions.

Here we address changes in dust provenance, and the response of the paleo-ITCZ to glacial-interglacial transitions around the penultimate termination (150 to 110 ka), with the necessary spatial and temporal resolution to see dust provenance changes during TII. A 3-ε_Nd-unit shift in Nd isotope ratios in core 17PC (at 0.48° N) suggests a southern transgression of the ITCZ across the equator during TII. Following the termination, early in Marine Oxygen Isotope Stage (MIS) 5, there is an increase in southern-hemisphere-sourced dust, which suggests a northward migration of the ITCZ towards about 7° N. This work allows us to compare the behavior of the ITCZ between the LGM/Holocene and penultimate terminations.