Now Antarctica — one of the places on Earth where warming is occurring most rapidly. Before that, for 37 million years, Antarctica cooled. During this period, the temperature there is not increased even once, and only the last 50 years, scientists have observed the reverse process, when the coldest continent was warming up.
This conclusion is a team led by Dr. John Anderson (John B. Anderson) Rice University (Rice University) (Houston, USA) based on palynological studies, ice drilling and seismic measurements in the Antarctic Peninsula — the northern tip of Antarctica.
The history of the continent — the slow freezing
As Anderson says, early in its history, Antarctica continent was warm enough — the temperature never drops below 10 degrees. Only completely separated from Gondwana, it began to cool. Why is this happening, so not completely clear. On this account, there are only hypotheses, around which are waging a fierce controversy. Most scientists attribute the cooling of Antarctica with a simultaneous decrease in the level of carbon dioxide in the atmosphere and its isolation from the supercontinent.
The first ice appeared in the mountains of Antarctica about 37-34 million years ago. At the same time, according to Anderson, has been overtaken by the concentration of carbon dioxide in the atmosphere — then it reached the present values (390 ppm). And if the first Antarctica has a mild climate, lush vegetation is dominant, then at that time the majority of angiosperms disappeared. The next few years, tens of millions on the continent dominated forest with birch and pine and stretched Tundra. Cooling continued, gradually forests have disappeared, and their place was taken by Tundra. Around 12 million years ago, Antarctica is covered with shrubs, mosses and lichens.
Further fall in the concentration of carbon dioxide in the atmosphere, the formation of the Drake Passage, Antarctica, finally separate from South America, and the formation of the Antarctic Circumpolar cold flow led to the fact that the continent is completely pinned down the ice. "Later, there was only ice in the north of the Antarctic Peninsula — about 3.5 million years ago. The Antarctic Peninsula was under the ice in the last turn. When the ice has covered the entire continent, there remained a piece of tundra "- says Anderson.
Now in Antarctica is getting warmer. For example, over the last 50 years, the average winter temperature in the Antarctic Peninsula has increased by 6 degrees — is five times more than the global average. If before the ice around the peninsula maintained all year round, but now in the summer it melts. Further evidence of the warming — in the summer Antarctic Peninsula free of ice, covered with grass and moss, and it is difficult to believe that this is Antarctica.
Article Antersona doctor and his colleagues that looked like Antarctica for the past 37 million years, published in the journal PNAS.