The effect of changing topological constraints on poleward ocean heat transport induced by plate tectonics over the last 600 million years

Abstract

The changing configurations of continents due to plate tectonics is thought to be responsible for some of the variation in climate over the last 600 Ma. Different topological constraints on the oceans may affect their ability to transport heat poleward and change the equilibrium pole-equator temperature of Earth. An ocean model was run for three simple continental geometries to determine the effect of land distribution on the heat transport capacity and pole-equator temperature gradient of the ocean. The first configuration, a circle of land centered over the south pole, meant to resemble Earth at 600 Ma, produces a haline mode of convection in which water sinks in the subtropics. The ocean in this mode has a high pole-equator temperature gradient and low levels of heat transport. The second configuration, a strip of land extending between the north and south poles, resembles the land of the Permian 250 Ma. This configuration with the same atmospheric forcing produces a thermal mode of circulation, similar to the modern North Atlantic, in which surface water sinks at the poles. The ocean in this mode has a lower pole-equator temperature gradient and higher levels of poleward ocean heat transport. A third configuration, similar to the second but with an equatorial ocean passageway, resembles the mid-Cretaceous. This configuration also produces a thermal mode and has slightly higher levels of heat transport than the second model. This research suggests that continental geometry could have played an important role in determining the pole-equator temperature gradient and the levels of ocean heat transport in the past.