Rapid changes in ocean circulation and climate have been observed in marine-sediment and ice cores over the last glacial period and deglaciation, highlighting the non-linear character of the climate system and underlining the possibility of rapid climate shifts in response to anthropogenic greenhouse gas forcing. To date, these rapid changes in climate and ocean circulation are still not fully explained. One obstacle hindering progress in our understanding of the interactions between past ocean circulation and climate changes is the difficulty of accurately dating marine cores. Here, we present a set of 92 marine sediment cores from the Atlantic Ocean for which we have established age-depth models that are consistent with the Greenland GICC05 ice core chronology, and computed the associated dating uncertainties, using a new deposition modeling technique. This is the first set of consistently dated marine sediment cores enabling paleoclimate scientists to evaluate leads/lags between circulation and climate changes over vast regions of the Atlantic Ocean. Moreover, this data set is of direct use in paleoclimate modeling studies.
International audienceWe studied a marine sedimentary section deposited at a high sedimentation rate in the Gulf of Aden (core MD92-1002) to document environmental and hydrological changes since the end of the last glacial periodand better understand the onset and decay of the Holocene Humid Period (HHP). Pollen analysis reveals that the period from the LGM to 13.5 ka was hyper arid with sparse vegetation cover characterized by xerophitic taxa from the Saharo-Sindian phyto-geographical region. Humidity increased since 14.9 ka to reach a maximumbetween ~ 9 and 7.5 ka, as revealed by peak abundances of the tropical mangrove Rhizophora and high values of a pollen-based humidity index.The HHP ended up gradually, starting to decline as soon as 7.5 ka and collapsing definitively at 4ka. This decline is characterized by the appearance of Mediterranean taxa and the return of arid conditions, comparable to that of today. Comparison of our pollen record with three speleothem records from the Arabian Peninsula makes it possible to reconstruct a northward and westward shift of the Inter-Tropical Convergence Zone at the onset of the HHP
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