Hamburg 2009 – wissenschaftliches Programm

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SYMU: Marine Umweltphysik

SYMU 1: Marine Umweltphysik I

SYMU 1.3: Hauptvortrag

Mittwoch, 4. März 2009, 16:00–16:30, Physik H II

The northern AMOC: Overflows across the Greenland-Scotland Ridge — •Detlef Quadfasel — Institut für Meereskunde, University of Hamburg, Hamburg

The exchange of water, heat, and salt across the Greenland-Scotland Ridge is a two-way coupling between the Nordic Seas and the Atlantic Ocean that is essential for both the Atlantic Meridional Overturning Circulation (AMOC) and the conditions in the Nordic Seas and the Arctic. Climate models do not, however, give any clear indication, how this coupling will be affected by climate change (IPCC, 2007). In this region, systematic measurements have been carried out for more than a decade and time series of flow properties (temperature and salinity) and transports have been obtained for all the main exchange branches. A complementary set of time series is provided by ocean models, constrained by atmospheric input from reanalysis data sets. For some exchange branches, there are considerable differences between these simulated time series and the measurements, but for other branches, especially the Faroe Bank Channel overflow, the correspondence is remarkably good. By combining the measurements and model results, typical values for the exchange properties and magnitudes have been established with a fair degree of confidence and insight has been gained on the processes that maintain the flows and induce variations. In spite of variability, the main exchanges are more appropriately characterized by a high degree of stability from daily to decadal time scales.