The School of Earth and Atmospheric Sciences Presents Dr. Arne Biastoch, GEOMAR

Regional Imprints of Changes in the Atlantic Meridional Overturning Circulation in the Eddy-rich Ocean Model VIKING20XA hierarchy of global 1/4° and 1/20° nested ocean/sea-ice models of the Atlantic Ocean is described. It is shown that the eddy-rich configurations performed in hindcasts of the past 50-60 years under CORE and JRA55-do atmospheric forcings realistically simulate the large-scale horizontal circulation, the distribution of the mesoscale, overflow and convective processes, and the representation of regional current systems in the North and South Atlantic.  The representation, and in particular the temporal evolution, of the Atlantic Meridional Overturning Circulation (AMOC) strongly depend on numerical choices for the application of freshwater fluxes. The interannual variability instead is highly correlated, also with observations, including the 2010 minimum observed by RAPID at 26.5°N. Regional observations in western boundary current systems at 53°N, 26.5°N and 11°S are explored in respect to their ability to represent the AMOC and to monitor the temporal evolution of the AMOC. It is shown that in particular the outflow of North Atlantic Deepwater at 53°N is a good indicator of the subpolar AMOC trend during the recent decades if provided in density coordinates.