The Meridional Overturning Circulation (MOC) is a major component of the meridional heat transfer in the North Atlantic Ocean. We have been able to demonstrate the possibility of reconstructing past drops in MOC during the major melt water surges of the la st deglaciation, using a new paleoceanographic proxy, the sedimentary 231Pa/230Th ratio. These MOC drops were clearly associated with drastic coolings of the Northern Hemisphere high latitudes. Climate of the past few thousands years is significantly more stable. It is however characterized by a significant variability in the decadal to millennial time scale. However nothing is known on the variability of the MOC over this time scale.
The problem is important, as numerous climate models predict a reduction of the MOC with future global warming, associated with progressive high latitude salinity drop. The project is to test the applicability of the 231Pa/230Th methodology to reconstruct changes in THC over the Holocene, and compare it with existing paleoclimatic reconstructions for the period, and thus contribute to the understanding of the mechanisms which link meridional heat transfer, MOC and climate during periods of climatic changes.
This project will be conducted at the Bjerknes Centre for Climate Research, as the necessary instrumentation is available as well as access to very high sedimentation rate cores from the Northern Atlantic Ocean and Arctic seas. It will involve the application of the kinematic proxy for the MOC in relation to climate transition s on depth transects at various regions important for detecting overflow to be able to evaluate changes in the AMOC during selected rapid climate transitions; This project implements specifically some research axes defined in the FP6 work program, namely the detailed analysis of modes of natural variability of the climate and the evolution of its frequency over the last millennium.
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