Sea off Antarctica warmed up to the bottom

Sea off Antarctica warmed up to the bottom

During the expedition for seven months, scientists have studied the changes in the Southern Ocean. The main conclusion drawn by the oceanographers — poslenie for 26 years in the Weddell Sea deep water warmed even, not just superficial.

May 20 scientific research vessel "Polarstern" Institute for Polar Marine Research Alfred Wegener returned to the port of Bremerhaven (Germany) from an expedition to the Weddell Sea (it is in the Southern Ocean off the coast of West Antarctica). The expedition lasted for seven months, and in the studies involved 200 scientists from 15 countries. Members of the expedition studied the changes in temperature and salinity throughout the water column of the Weddell Sea. Special attention is paid scientists of life to take place in the Southern Ocean changes.

Sea warmed

 

Weddell Sea attracts oceanographers no accident. The fact that it belongs to the Atlantic sector of the Southern Ocean, and this site is important for the climate of the globe, as there are exchanged by the Atlantic currents and currents of the Southern Ocean. A similar area is in the North Atlantic.

"The conclusion that can be drawn at this stage of the research — the temperature of the entire water column of the Weddell Sea (sea depth reaches 6820 meters) continues to grow. Over the past 26 years, it has increased on average by 0.06 degrees, "- said the head of the project Oceanographic Dr. Eberhard Farben. According to him, at first glance it may seem that this figure is not so significant. In fact it is not. "Due to the fact that changes occur in the superficial, intermediate and deep waters, it is a huge amount of heat. It has always been that the heating of the atmosphere leads to a warming of the upper ocean. For example, the report said, and IPCC (Intergovernmental Panel on Climate Change). What we are now able to prove that the ocean, at least in some areas may warm up the entire thickness "- explains Farben.

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In Antarctica is getting warmer.

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.

Climate scientists have long believed that Antarctica, as opposed to the whole world, not warmer, and freeze for at least a large part of it — the East Antarctic Ice schit.Odnako latest studies show that over the past 50 years, the continent was heated at the same rate as the whole Earth. Moreover, West Antarctica is warming faster than the East cooled. This means that the continent as a whole has become warmer, commented Eric Steigen, professor of geology and astronomy at the University of Washington, Director, Research Center for the Study of the Quaternary period.

"West Antarctica is very different from the East. Moreover, they share a physical barrier — the Transantarctic Mountains, "explains Steigen, lead author of the scientific report on global warming, recently published in the journal Nature.

For many years, scientists believed that a relatively small area, known as the Antarctic Peninsula, heated, while the rest of the continent, including West Antarctica, where the ice sheet most susceptible to the potential collapse — cooled. Steigen noted that the West Antarctic ice sheet, an average height of about 2 km above sea level, well below the East Antarctic (3 km above sea level). The whole continent is mainly resembles the desert while the western part is exposed to relatively warm, moist winds and large amounts of snowfall.

Studies show that for half a century warming in West Antarctica is an average of more than 0.1 degrees per decade. To fix the new trends in temperature, the researchers introduced a statistical method that uses satellite data and Antarctic weather stations. "Before resorting to interpolation, we do not use the satellite data that can provide important information about the spatial structure of climate change."

Satellites calculate the surface temperature by measuring the intensity of infrared light emitted by the snow, and can cover the entire continent. However, they are involved only in the past 25 years. Of course, there is also the Antarctic weather stations, which operate in 1957 (IGY), but almost all of them are a short distance from the coast and do not give direct information on the state of the interior of the continent.

Scientists have found that the results of temperature measurements at meteorological stations are almost identical to those obtained by satellite, for the same period of time. This discovery has enabled meteorologists use satellite data to determine the temperature in parts of the continent, where there are no weather stations. "The climate of Antarctica is much more complicated than it seems at first sight," says Steigen. "There is an opinion that the South Polar continent freezes. In fact, the opposite is true. Although it is not so simple. Antarctica is heated all at different rates. Despite the fact that some areas are cooled, the continent as a whole — is heated. "

Main reason to assume that a large part of Antarctica cooled — is formed in the polar region during the spring months in the protective ozone layer hole. Steigen also noted that the ozone hole has certainly played a role in cooling of East Antarctica. "But for some reason, decided that this influence extended to the entire continent, although it has no prerequisites. In any case, efforts to restore the ozone layer once begin to have an effect, and the hole can be reduced back to the middle of the century. This means that the entire Antarctic start to warm up on a par with the rest of the world. "

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.

Modern Antarctica

Map of the intensity of warming in West Antarctica (early news) for the past 50 years. The dark red area — the area most warming. NASA. (Click image to enlarge)

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.

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