One of the key developments in palaeoclimatology has been the discovery of recurrent and rapid climate changes in the past, illustrating that natural climate variability may also occur on the submillennial time-scales of relevance to humanity. Rapid climate events are widely believed to have involved, if not have been largely derived from changes in the oceans' large-scale circulation and have been associated by several workers with fundamental shifts in the Atlantic meridional overturning circulation.
The central aim of this proposal is to study how and why rapid climate variability has evolved as orbital and glacial boundary conditions have changed during the Pleistocene. This project attempts to clarify if there are interactions between orbital and suborbital components, and if the general conditions established by long-term processes exert control on the short-term processes of climate change. In order to address these issues, RACLIVAGO proposes to undertake a detailed study of North Atlantic millennial scale variability in surface and deep-water properties during the Mid-Pleistocene transition. The target area is Site U1313, recently drilled on the western flank of the Mid-Atlantic Ridge during Integrated Ocean Drilling Program Expedition 306. The time interval is centred at ~1Ma, when the frequency of the glacial-interglacial cycles changed from a dominant 41 kyr periodicity to a dominant late Pleistocene 100 kyr periodicity with bigger climatic oscillations.
A multiproxy strategy, involving geochemical and sedimentological indicators, will be adopted in order to determine the sequence of changes in water mass properties, sea surface and bottom water temperature and nutrients. Special emphasis will be on assessing the phasing of changes in the different oceanographic variables through episodes of rapid climate change: the results will provide the experimental data on the magnitude of the key parameters and their rate of changes needed for climate models.
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