Southern Hemisphere and Deep-Sea Warming Led Deglacial Atmospheric CO 2 Rise and Tropical Warming

Abstract

Establishing what caused Earth's largest climatic changes in the past requires a precise knowledge of both the forcing and the regional responses. We determined the chronology of high- and low-latitude climate change at the last glacial termination by radiocarbon dating benthic and planktonic foraminiferal stable isotope and magnesium/calcium records from a marine core collected in the western tropical Pacific. Deep-sea temperatures warmed by ∼2°C between 19 and 17 thousand years before the present (ky B.P.), leading the rise in atmospheric CO 2 and tropical–surface-ocean warming by ∼1000 years. The cause of this deglacial deep-water warming does not lie within the tropics, nor can its early onset between 19 and 17 ky B.P. be attributed to CO 2 forcing. Increasing austral-spring insolation combined with sea-ice albedo feedbacks appear to be the key factors responsible for this warming.