Potential Role of Mid‐Latitude Seaway on Early Paleogene Atlantic Overturning Circulation.

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. Plain Language Summary: Recent geological evidence demonstrated that a mid‐latitude seaway connected the proto‐Paratethys sea and the North Sea during the early Eocene. Then, this connection was closed since the late Eocene‐early Oligocene. Here, using climate modeling, we investigated the effects of this mid‐latitude seaway evolution, particularly in modulating the Atlantic meridional overturning circulation (AMOC). Our simulations show that the open seaway prohibits the relatively fresh Arctic surface water from leaking into the Labrador Sea and thus favors the formation of AMOC. On the contrary, the closed seaway allows more relatively fresh Arctic surface water to influence the Labrador Sea, thus triggering the AMOC reduction. Our study pinpoints a controlling role of the mid‐latitude seaway in modulating global ocean circulation during the early Paleogene. Key Points: The evolution of the mid‐latitude seaway in the early Paleogene influences ocean circulationThe opening of the seaway favors the Atlantic meridional overturning circulation (AMOC), while its closing leads to AMOC shutdown [ABSTRACT FROM AUTHOR]