Australia: The Land Where Time Began

A biography of the Australian continent 

Oligocene Climate

Throughout the Eocene the temperatures had been dropping steadily until at about 34 Ma, at the start of the Oligocene, there was a sudden drop of the temperatures, the Oi-1, that was a transition in the climate of the Earth. By this time the temperature of the deep ocean water had dropped from 12° C during the PETM at the start of the Eocene to less than 3° C, and the beginning of the formation of large sheets of ice in Antarctica, associated with a sea level drop of 55 m as water was locked up in the glaciers. The area covered by tropical broadleaved forests shrank and the northern forests were replaced by tundra and steppe. A number of explanations have been proposed for the formation of the Antarctic ice sheets at this time. An hypothesis that is widely accepted is the separation of South America and Australia from Antarctica. As a result, the final separation of these continents allowed the formation of the cold Antarctic Circum Polar Current once the Southern Ocean was continuous around the margins of Antarctica with no barriers to impede or redirect its flow, effectively isolating Antarctica from the warmer waters from lower latitudes. This is suggested to have led to the first accumulation of sea ice on a large scale, and eventually to progressive buildup of the ice sheets on the Antarctic continent.

Sources & Further reading

1. McGuire, Prof. Bill, 2012, Waking the Giant: How a changing climate triggers earthquakes, tsunamis, and volcanoes, Oxford University Press.