As best we can tell, Antarctica has been at or near the South Pole for about the past 100 million years, yet it appears that significant ice caps only occupied this polar continent beginning around 35 million years ago. This is surprising because research suggests that the amount of solar energy reaching Earth has not varied significantly during the Mesozoic and Cenozoic eras.

As a result of this conundrum, numerous hypotheses have been proposed to explain the onset of this glaciation of Antarctica during the transition between the Eocene and Oligocene epochs, including: (a) an increase in global volcanism, (b) the high-velocity impact of one or more meteoroids or asteroids into Earth, (c) a decrease in the concentration of carbon dioxide in Earth’s atmosphere, and (d) fundamental changes to the pattern of Earth’s global oceanic circulation.

In the cases of the first two hypotheses, an increase in the amount of particulate matter entrained in the atmosphere would inhibit addition of solar energy to the oceans and continents, thereby cooling the surface of Earth and favoring the growth of ice sheets in its polar regions. A significant decrease in the concentration of atmospheric carbon dioxide (a “greenhouse gas”) would allow more solar energy to escape Earth’s atmosphere, similarly causing global and/or regional climate cooling. Because of water’s exceptionally large heat capacity, fundamental changes in global ocean circulation can have dramatic impacts upon regional and global climates – for example, the sequestration of warm water away from polar continents has been suggested as one means of instigating regional cooling that would allow the development of large ice caps on polar landmasses.