Regional scales
The regional approach is required when a high spatial resolution is needed in order to resolve smaller scales and processes. It allows us to predict more accurately regional climate changes, but it is also relevant for the understanding of distinctive systems as the Mediterranean or the Arctic basins, and to estimate how a more precise and detailed consideration of processes, such as those related to ice-sheets, coastal shelf areas or overflow regions could feed back to the larger scale.
The regions currently under research are marked on the figure below:
Arctic (ARC)
Strong warming due to antrophogenic climate change increases the moisture transport northward to high latitudes and thus the freshwater input into the Arctic Ocean. This change in the Artic Ocean freshwater budget leads to the following questions: Is the additional freshwater stored in the Arctic Ocean or is it exported into the North Atlantic? How is the meridional overturning circulation and therewith the global climate influenced by these changes in the Arctic hydrologic cycle?
To answer these questions, the global ocean model MPIOM is coupled with the regional atmospheric model REMO covering the full catchment area of the Arctic rivers. To close the hydrologic cycle of the Arctic, a Hydrological Discharge model (HD) providing lateral terrestrial waterflows is included in REMO.
Interactions between Northwest European Shelfs and the Atlantic (NWES)
The Atlantic Ocean and its marginal seas deeply affect the living conditions of broad areas of western Europe. They cause the relatively mild climate and provide transportation routes for numerous goods. But the oceans can also pose a threat to coastal regions.
Potential changes on the Northwest European shelfs and their exchange with the Atlantic current within the next decades will be estimated using a holistic model approach. The model configuration connects a global atmospheric GCM with a regional one (REMO/HD) covering a part of the North Atlantic. The resolution of the global ocean model (MPIOM) is strongly refined on the Northwest European Shelf and the Northeast Atlantic.
In addition a global ocean biogeochemistry model, which represents basic aspects of the cycling of P, N, C, Si, O and processes of marine sediments (HAMOCC), will be used. With this model system likely scenarios of anthropogenic impact will be investigated.
Mediterranean (MED)
We are modelling the Mediterranean Sea at times of climate extremes in order to understand its sensitivity to high- and low-latitude climate forcings and to estimate the response to expected global changes.
We particularly focus on understanding the series of changes in the conditions of the Mediterranean hydrography, which occurred during the early Holocene (9.5 - 6 ky B.P.). Those changes led to the formation of Sapropel S1, an organic rich sediment layer deposited under anoxic (low oxygen) conditions. We investigate plausible scenarios leading to the deposition of Sapropel S1 with the regional setup of the ocean model (MPIOM) for the Mediterranean, coupled to the biogeochemical model HAMOCC.
We also investigate the Mediterranean ocean climate of the Last Glacial Maximum and compare the model results with reconstructions from proxy data.
Mediterranean outflow spreading (GIB)
The Mediterranean Outflow Water (MOW) spreads as a basin-scale positive salinity anomaly at about 1000-1200 m depth through the North Atlantic. There are numerous modelling studies about MOW itself and its impact on the North Atlantic circulation. However, the basin-scale Mediterranean salinity tongue originates from a Mediterranean Water slope-bounded gravity plume in the Strait of Gibraltar and the Gulf of Cadiz. Therefore, small scale processes and local scale nonlinear interaction with tides and topography may have an impact on the MOW properties and its further spreading pattern in the North Atlantic.Those processes are not accounted for in most of the global/basin scale models, where Mediterranean Outflow is usually prescribed as a source term or as a boundary condition. We overcome these difficulties by taking advantage of the global MPIOM model capability for regional high resolution and its allowance for an explicit inclusion of tides.