Simulation of ocean temperature change due to the opening of Drake Passage

An ocean general circulation model (GCM) is used to test the hypothesis that the opening of Drake Passage in the Oligocene may have lead to cooling in southern high latitudes. Results of previous studies show that no ocean models using restoring boundary conditions for the surface heat flux could reveal substantial southern high latitude cooling without prescribing atmospheric cooling a priori. To compute the surface heat flux that would be free from the restoring constraints we use another method, which is derived from an atmospheric energy balance model with lateral heat transport. In experiments conducted with both idealized and realistic topography the energy balance method produces substantial cooling not only in high latitudes but in deep waters as well.