1 / 3Photo: Mark Ralston/AP/TT
Record high temperatures, warmer sea water, shrinking sea ice, growing danger of ocean currents being affected. This year, climate change seems to have reached the white continent, Antarctica, in earnest. Now the concern is growing that the changes will be permanent.
On the ice cap of the Antarctic High Plateau, the coldest place on Earth, the highest temperature ever recorded at the beginning of the year was in March – minus 12.2 degrees Celsius. Normally, the temperature at that time of year is around minus 50 degrees.
It is also clear that the sea water around the continent has been warmer than normal this year. In early July, sea ice reached an extent of about 12 million square kilometers, which may sound like a lot, but is 20 percent (3 million square kilometers) less than the average for the same period during 1981–2010, when it normally covered an area of 15 million square kilometers.
A loss of 3 million square kilometers is extreme. That corresponds to an area the size of India.
Unforeseeable consequences
The question is how serious this is. If the huge Antarctic ice sheet, which holds 75 percent of the Earth’s fresh water, were to start melting at a faster rate, there is an obvious risk that ocean currents will be affected.
A study suggests that more freshwater in the ocean could mean that the currents, which transport heat and nutrients northward, lose 40 percent of their power – with incalculable consequences for life in the sea and on land.
– It is a bit difficult to say how worried you should be. Until recently, Antarctica has remained on the mat, while the situation up in the Arctic has gotten increasingly worse, but now it is clear that the regrowth of ice during the winter is bad down there, says Michael Tjernström, professor of meteorology at Stockholm University.
He points out that the picture in the two polar regions differs. In the Arctic, the ice is disappearing because the air has become warmer. In Antarctica, it is mainly the sea water that has become warmer.
– The most worrying thing in Antarctica is that the ice shelves around the continent have become weaker, says Tjernström.
The ice breaks up
Ice shelves are parts of the ice sheet that have been pushed out into the sea over the continental shelf and float on top of the ocean water. The two large marginal seas on the Antarctic continent, the Weddell Sea and the Ross Sea, are covered by enormous ice shelves that each spread over approximately 450,000 square kilometers, an area equivalent to the size of Sweden.
– In some places, they have started to break up, a process that can go faster if the water gets warmer. In that case, the ice on land could be negatively affected, says Tjernström.
Many have been concerned that the wildlife in Antarctica, especially the penguins, will take a beating from this development. So far, however, most species seem to be doing decently well. Two of the species, the chinstrap penguin and the macaroni penguin, have clearly declined in numbers in recent years, while the Adelie penguin has increased. Other species in the Antarctic waters seem to be fairly stable – for now.
FACTS Antarctica
Antarctica covers an area of nearly 14 million square kilometers, making it the fifth largest continent in size, larger than both Europe and Australia. About 98 percent is covered by ice sheets.
Around the continent, the sea freezes during the winter. The sea ice covers about 19 million square kilometers in September-October before it begins to melt during the Southern Hemisphere summer.
The glaciation of Antarctica began on a smaller scale about 50 million years ago, during the Eocene period, but only gained momentum about 34 million years ago, at the beginning of the Oligocene. The reason was probably that the sea opened up between southern South America and Antarctica, which changed the ocean currents that then began to circulate around Antarctica and isolated the continent from other land masses. The result was a sharp cooling and growth of the ice.
Source: NASA, NE
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