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Leibniz-Institut fuer Meereswissenschaften an der Universitaet Kiel

The prime interest of the IFM-GEOMAR ocean and climate modelling groups collaborating in GATEWAYS is to understand the role of regional processes around South Africa determining the Agulhas leakage and its impact on the Atlantic meridional overturning circulation (MOC). A particular focus is on the oceanic mesoscale that has been shown to have far-reaching consequences for the large-scale circulation and that is typically not sufficiently represented in today's paleo and climate models. The variability of the Agulhas leakage and its impact on the MOC on interannual to decadal timescales are explored for the current climate (last 50 years). Experiments under paleo conditions are performed to compare with current conditions and to explore and test potential scenarios on disrupted and increased Agulhas leakage arising from the paleo reconstructions. Particular interest is given on the signal propagation of Agulhas leakage changes into the North Atlantic, where fast wave propagation mechanisms are compared with advective processes acting on longer, decadal timescales. It is of particular importance how fast and at what magnitude changes in Agulhas leakage reach the subarctic deepwater formation areas.

The modelling framework consists of ocean-only models based on the NEMO code in a regional high-resolution model nested in a global coarse resolution ocean/sea-ice model. This configuration is forced by current-climate hindcasts (last 50 years) and sensitivity experiments which are motivated by paleo-reconstructions. In those forcing fields could be artificially changed (e.g., pole- and equatorward shifted winds). To consider the feedback within the atmosphere on decadal and centennial time scales the coupled ocean/atmosphere/sea-ice model KCM is integrated under current-climate and paleo boundary conditions (greenhouse gases, earth orbital parameters). If technique permits the high-resolution model is nested and integrated within the coupled model.

Output from the various model experiments is made available to all partner teams for comparison with available observations and output from other models. In addition, conceptual input is needed from the paleo observations to test scenarios of past states of Agulhas leakage in the high-resolution model.

 

Partner Profile

The Leibniz Institute of Marine Sciences (IFM-GEOMAR) at the University of Kiel is one of the leading institutes in marine research in Germany. The major goal of the institute is research and development in all parts of marine sciences. Apart from basic research, applied projects between science and economy are also supported. IFM-GEOMAR is a foundation by public law, jointly funded by the federal and provincial government. The institute is a member of the Leibniz Association (WGL) and the German Marine Research Consortium (KDM).

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