Response of the Intertropical Convergence Zone to the first appearance of permanent Antarctic ice sheet at the Eocene-Oligocene transition

Abstract

The position of the inter-tropical convergence zone (ITCZ), the tropical maximum rainfall belt where northeast and southeast trade winds converge, is sensitive to hemispheric temperature gradients between poles and equator. The ITCZ shifts into the warm hemisphere with weak atmospheric circulation; hence its paleo-positions provide valuable constraints on the evolution of hemispheric climate asymmetry. Our dust Nd isotope data from the IODP Exp. 320 U1334 site show that the ITCZ shifted deep into the Northern Hemisphere at the Eocene-Oligocene (E – O) transition in response to the first development of permanent Antarctic ice sheets through Cenozoic history. Our dust records exhibit change of dust provenance from Asia to Central/South America at the earlier stage of the E – O transition, suggesting that ice sheets in Antarctic had formed to a considerable mass enough to affect the atmospheric circulation at the earlier stage of E - O global cooling. The asymmetric response of sea ice to the present warming trend can potentially progress to a situation similar to early Oligocene characterized by extensive ice cover in Antarctic with ice-free Arctic. Our results may predict the response of the ITCZ, thus the tropical rainfall maximum zone, shifting northward progressively in the future.fts into the warm hemisphere with weak atmospheric circulation; hence its paleo-positions provide valuable constraints on the evolution of hemispheric climate asymmetry. Our dust Nd isotope data from the IODP Exp. 320 U1334 site show that the ITCZ shifted deep into the Northern Hemisphere at the Eocene-Oligocene (E – O) transition in response to the first development of permanent Antarctic ice sheets through Cenozoic history.Our dust records exhibit change of dust provenance from Asia to Central/South America at the earlier stage of the E – O transition, suggesting that ice sheets in Antarctic had formed to a considerable mass enough to affect the atmospheric