(1) The Antarctic Circumpolar Current (ACC) is a fast, cold, deep-ocean current that flows from west to east around Antarctica, thereby inhibiting the penetration of warm, pole-ward moving tropical currents from reaching high southern latitudes. The potential influence of the ACC on regional climate is best emphasized with a comparison to the North Atlantic Ocean, where a circumpolar current does not exist due to the presence of numerous landmasses that impede such ocean circulation. As a result, the pole-ward moving Gulf Stream is able to transport warm tropical waters far to the North, keeping western Europe especially temperate despite its moderately high latitudes. In the Southern Ocean, where landmasses are few, water is able to freely and quickly circulate around Antarctica, thermally isolating the polar continent from warm tropical waters.
(2) Drake Passage and the Scotia Sea currently form the gap between the Antarctic and South American continental lithospheric plates, yet such a tectonic configuration was not always the case. Similar geology in the southern Andes and on the Antarctic Peninsula have led scientists to believe that for much of the Mesozoic and early Cenozoic eras, Antarctica and southernmost South America were connected and part of a single supercontinent, which would have inhibited the development of a circumpolar current. The oldest oceanic crust known in the Scotia Sea is less than 30 million years old, suggesting that the separation of Antarctica from South America, as would be required to develop the ACC, may have coincided with the abovementioned initial Cenozoic glaciation of Antarctica (at about 35 Ma).
Although this conceptual model connecting plate tectonics with ocean circulation and climate change is elegant and intriguing, it is not clear that geologic data support it. Recent geophysical, paleoceanographic and climate-modeling studies indicate that the relationship between Antarctic glaciation and tectonic gateway development in the Scotia Sea is currently equivocal. Our research is applying rigorous tests to this hypothesis through the integration of several different types of geologic data.