Birte-Marie Ehlers

• The Arctic region plays an important role in the configuration of the present day global climate. In particular the Fram Strait area, presently the only deep-water gateway between the Arctic Ocean and the world ocean, accounts for the Arctic region climate. It is still speculative how and when this deep-water connection opened due to its tectonic and geologic evolution, and how strong this influenced northern ocean circulations. It is assumed that the change of the northern ocean circulations correlate with long-term climate changes. This study provides a compilation of a geodynamic model of the northern North Atlantic, which is continued to the Arctic Ocean, and investigates the tectonic and bathymetric development. Due to the movements of the Eurasia, Greenland, and North American plates, as well as sediment accumulation changes, the width and seafloor depth of the Fram Strait was significantly modified since its initial break-up. Geophysical data in the northern North Atlantic and in the Arctic Ocean, gathered by the Alfred Wegener Institute during the last years, make this study possible. The results present an advanced age model of the oceanic crust. A palaeobathymetric reconstruction results in a timing of the Fram Strait opening of 25 Ma for a shallow-water exchange. From 17 Ma on, a deep-water exchange between the northern North Atlantic and the Arctic Ocean was possible. To link the results of the palaeobathymetric reconstruction to the global climate history, palaeoceanographic model scenarios are calculated for the present day bathymetric configuration and the palaeobathymetry of the Middle Miocene (15 Ma), the Early Miocene (20 Ma) and the Middle Eocene (45 Ma). The study shows the complex relationship between plate tectonics, the crustal development, sediment accumulations, bathymetric changes and changes in ocean circulation in the northern North Atlantic and in the Arctic Ocean and speculates on their link to global past long-term climate changes.