Fig. 2: Variations in global water currents driven by bathymetric changes in the Central American Seaway (CAS) and restrictions between the Arctic Ocean (ArO) and the Global Ocean (GO).

A Simulated ocean current patterns under open marine connections between the ArO and the GO; B Simulated ocean currents with restricted ArO–GO connection. Enhanced exchange between the Atlantic and Pacific oceans occurs under conditions of a deep CAS (1), whereas a shallow CAS (2) results in reduced inter-ocean exchange. The scale represents water current speed in meters per second (m/s).