Changes in ocean heat transport have long been thought of as a logical way to explain the large, high-latitude warmth of past time periods such as the Eocene and Miocene, and changes in the continental configuration of the Earth—as depicted here—is the popular way of explaining increases in ocean heat transport during Earth's history. The opening and closing of different ocean gateways such as that connecting the Indian and Atlantic Oceans during the Miocene has been hypothesized to deliver more warm water to the high latitudes, which could help melt polar ice.

Although such ideas have been put forth for over three decades, recent comprehensive modelling has shown that changes to ocean gateways or ocean heat transport do not bring about the expected warming. The above rendering is of the topography and bathymetry of the Miocene period, approximately 15 million years ago and is based on a reconstruction that Nick Herold, Matthew Huber and co-authors published in order for research groups to better represent this time period in their climate models.
Image courtesy of Matthew Huber, UNH-EOS.