Why does Antarctica have no trees
Climate change : Trees in Antarctica
One of the great unknowns of climate change is how the ice sheets in the polar regions react to rising levels of carbon dioxide in the atmosphere. If the ice sheet over the Antarctic alone contains enough water to raise the sea level by 61 meters, it should melt completely. That would not only endanger distant island states, it would even partially flood cities like Berlin and Cologne. However, so far, climate researchers have hardly been able to estimate how great the risk for the Antarctic Ice Sheet actually is.
But there has already been a similar development: 21 to 13 million years ago the climatic conditions on earth fluctuated several times between the conditions as they existed before the industrial revolution and those that the Intergovernmental Panel on Climate Change predicted for the next 50 to 100 years. At that time, the ice sheets retreated so far and then pushed forward again so far that the sea level rose and fell by 30 to 36 meters, write researchers led by Richard Levy from the state geological research institute GNS in Lower Hutt in New Zealand and Edward Gasson from the University of Massachusetts in Amherst in the journal "PNAS".
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Climate change in the Miocene
The team had erected a derrick on the eight and a half meter thick ice 30 kilometers off the coast of the McMurdo Sound in East Antarctica. 380 meters below sea level, the device bored a further 1,137.84 meters into the subsurface. The lower 925 meters of the drill core had been deposited layer by layer 20.2 to 14.4 million years ago (in the Miocene era). The researchers analyzed the isotopes of various elements, remains of microorganisms and volcanic eruptions, and other properties.
According to this, the climate during this time resembled four times, for a few hundred thousand years each, the conditions before the beginning of industrialization in the 19th century: 280 carbon dioxide molecules mixed with one million particles in the air (280 parts per million, or 280 ppm for short) - and the ice masses grew far out into the Southern Ocean.
Tundra on the Antarctic coast
In addition, there were five long periods in which the temperatures were three to four degrees above today's values and the carbon dioxide content reached at least 500 ppm - as the IPCC expects in 50 to 100 years. The ice retreated far into the interior of the Antarctic. A tundra landscape stretched over an 80 kilometer wide strip on the coast of the Southern Ocean, in summer the temperature reached an average of plus ten degrees. The researchers discovered a lot of pollen in these layers, including from trees such as southern beeches.
Edward Gasson and his colleagues compared this data with a new computer model that calculates different scenarios for the development of the ice sheet over Antarctica. For the warm episodes, it showed that only small remnants were left of the ice masses over West Antarctica. In East Antarctica, the ice in the models had also retreated far inland - as confirmed by the drill core. In those times the sea level was 30 to 36 meters higher than it is today. Apparently the ice of the Antarctic reacted relatively sensitively at the time to the increase of the carbon dioxide content in the air, the authors conclude.
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