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.
Antarctica is covered with carnivorous cereal
April 9, 2011. Pickerel turfy covering summer coast of the Antarctic Peninsula and the islands off the coast of Antarctica, acquires nitrogen special way. According to scientists, that he would take a pike in the near future leading position in the region.
Scientists from the British Antarctic Survey, and several universities, led by Dr. Paul Hill (Paul W.Hill) from Bangor University have found a unique way by which vascular plants (Antarctic hair grass, it — turfy) on an island off the coast of Antarctica absorb nitrogen. Pickerel does not wait for the microorganisms to convert organic minerals (this process occurs in these latitudes, very slowly). She immediately absorb protein — small peptides. It has always been that it is able to do only mushrooms and animals, and in the plant world — mosses.
The unique ability to allow the jack to take a dominant position on the island of Signy (one of the South Orkney Islands), where scientists conducted their research, and virtually push mosses.
"Many people think that Antarctica is always completely covered with snow and ice. But in the summer on the Antarctic Peninsula and the islands surrounding the continent itself, the snow melts, and there appear plants — mosses and two species of vascular plants — Colobanthus quitensis (pearlwort Quito) and Deschampsia Antarctica (Antarctic hair grass), "- says Paul Hill.
According to the researchers, for the past 50 years, the climate on the coast of Antarctica is warming faster than anywhere else on Earth. Summer temperatures there have risen by about one degree Celsius, and the summer was longer. It is natural that these changes immediately responded plants.
Usually in coastal ecosystems dominated by mosses Signy Island. But in recent years, scientists have observed another trend: the driving position is exited cereals. Although mosses Sanionia uncinata still quite common and, as a rule, they are the first to colonize new territory. As they die, forming a small layer of soil. And already there are free to grow other settlers. However, in this case there is a problem — the competition for resources: nutrients and light needed for photosynthesis.
Competition to win the Antarctic hair grass. Its sharp leaves penetrate the moss, so it easy to get the right amount of light. With nutrients, however, is more complicated.
A new way of nitrogen assimilation
Plants need nitrogen to live. But they are only able to absorb its inorganic compounds, such as ammonium salts and nitric acid. And organic nitrogen can transform into mineral compounds only soil microorganisms. Some plants for this form with them a symbiotic relationship. However, according to Hill, Antarctica plants do not. Vascular plants but somehow cope with this problem. To understand how, Dr. Hill and his colleagues conducted the following experiment: they have introduced a special soil labeled form of organic nitrogen and observed how plants absorb them.
"The ability of plants to absorb nitrogen in the earliest stages of mineralization — the key to success. In our studies we have shown that in Antarctica Antarctic hairgrass absorb nitrogen through their roots in the form of short peptides. This is the initial stage of the transformation of proteins in the soil. In this way, the plants absorb nitrogen three times faster than the uptake of amino acids occurs, nitrate or ammonium salts. And 160 times faster than do mosses with which this grass competes "- the study authors write. In their view, if the temperature in the Antarctic will increase even more, and then the organic will decompose faster. This will give additional benefits pickerel and it seems that this grass will continue its expansion on the coast.
"Finding us a quick way of nitrogen assimilation is important not only for ecosystems of Antarctica. If it turns out that plants in temperate and tropical latitudes can act in the same way, it can be used to create new technologies in agriculture ", — said one of the study authors Nyusem Kevin (Kevin Newsham), of the British Antarctic Survey.
For details on how to compete with cereals in the Antarctic mosses and absorb nitrogen, can be found in the article «Vasclular plant success in a warming Antarctic may be due to efficient nitrogen acquisition», published in the journal Nature Climate Change.