The role of the mid-latitude seaway between the proto-Paratethys and the North Sea on the early Paleogene ocean circulation is examined with a state-of-art earth system model. The early Eocene simulations here demonstrate that the open mid-latitude seaway captures most relatively fresh surface water from the Arctic and Greenland-Norwegian Sea and prohibits them from leaking into the Labrador Sea, thus benefiting the Atlantic meridional overturning circulation (AMOC). However, the closure of the seaway triggers the AMOC reduction as more relatively fresh surface water enters the Labrador Sea, and the AMOC finally shuts down. Together with geological reconstructions, our results also provide insights into understanding the evolution of the Atlantic-Arctic oceanic gateways during the Paleogene.

Early Paleogene, Atlantic Overturing Circulation, paleogeographic evolution