Antarctic role in northern hemisphere glaciation

Abstract

Earth's climate underwent a major transition from the warmth of the late Pliocene, when global surface temperatures were ∼2° to 3° C higher than today, to extensive Northern Hemisphere glaciation (NHG) ∼2.73 million years ago (Ma).We show that North Pacific deep waters were substantially colder (4° C) and probably fresher than the North Atlantic Deep Water before the intensification of NHG. At ∼2.73 Ma, the Atlantic-Pacific temperature gradient was reduced to <1° C, suggesting the initiation of stronger heat transfer from the North Atlantic to the deep Pacific.We posit that increased glaciation of Antarctica, deduced from the 21 ±10-meter sea-level fall from 3.15 to 2.75 Ma, and the development of a strong polar halocline fundamentally altered deep ocean circulation, which enhanced interhemispheric heat and salt transport, thereby contributing to NHG Copyright2014 by the American Association for the Advancement of Science; all rights reserved.