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Gerald H. Haug in der Vorlage fälschlich als Gerald Haugh bezeichnet, Francois Fripiat als Francois Fripat.
Abstract:
The long 100,000-year glacial-interglacial cycles are key features of climate evolution since the Mid-Pleistocene Transition, and changes in the Southern Ocean are proposed to have played an important role in the generation of these cycles. Data from the Indian and Pacific sectors of the Antarctic Zone over the last 150 ka show that during the glacial intervals, export production decreased, and surface nitrate concentration, as reflected by δ15N of organic matter bound in diatom frustules (δ15Ndb), decreased. Together these findings suggest that upwelling was weaker in the Antarctic Zone during the ice ages. While the most recent 150 kyr has been studied most intensively, previous cycles of glaciation and deglaciation are distinct in aspects of their orbital forcing and ice volume changes. Reconstructing similarities and differences among different glacial-interglacial cycles may thus clarify the mechanisms behind glacial-interglacial changes in the Southern Ocean. We report ~2-kyr resolution δ15Ndb measurements from the Pacific sector of the Antarctic Zone over the past 460 ka, with chronology supported by TEX86L-paleotemperature proxy correlation with the Antarctic ice cores. The results show continuously increasing Antarctic Zone δ15Ndb during peak glacial periods, which suggests progressive declines in surface nitrate concentration and thus in upwelling and/or vertical mixing intensity as land ice sheets grew, even though Antarctic ice core temperature and atmospheric CO2 appear to have stabilized at their minima earlier in each ice age. We will discuss the possible origins of the apparent (inverse) coupling of Antarctic Zone upwelling with global ice volume and its decoupling from atmospheric CO2 in the late (i.e. peak) glacials.
