Antarctic ice and sea level rise: unanswered questions

Antarctic ice and sea level rise: unanswered questions

How much sea levels will rise as a result of global warming? There is no clear answer to this question is no. Most often cited the IPCC assessment, but it is inaccurate, since the experts decided on the most conservative figures — just because of the huge number of unknowns.

One of the many "x's" — Antarctica, to predict the state of which is incredibly difficult. A recent review of the research in the journal Nature Geoscience perfectly sums up the state of our knowledge of the West Antarctic ice sheet.

Antarctica is divided in two parts of the Transantarctic Mountains. For several reasons, the ice cover to the west of the mountains are usually considered separately from the east. While East Antarctica larger than most of the studies devoted to the west, as it is more melting.

West Antarctic ice sheet is unstable because the continent under it forms a large pool, the bottom of which is considerably below the level of the sea. If the ice has melted so much that laid bare the outer ring of the pool, it is likely that the entire board will turn into an iceberg. Well, floating ice, known to be especially fragile.

Something similar has happened in the past, but the dating of these events is very vague. Without knowing the terms, we can not say how long it takes melting. It seems that it took several centuries. This means that at this age is enough? Maybe yes, maybe not: say, the current global warming — the fastest in recent geologic time.

Satellite data show that the West Antarctic ice sheet is losing 100 to 200 Gt per year, which should raise the sea level by 0,28-0,56 mm. This compares with a rate of melting of Greenland. However, the climate models do not take into account the Antarctic, because they can not adequately simulate the small-scale processes that affect weight loss. This is one of the reasons that the IPCC report of 2007 did not mention the upper limits predictions of sea level rise.

The most severe mass loss of the West Antarctic ice sheet occur where the ice meets the Southern Ocean — either due to the formation of icebergs, or due to melting of ice shelves. Knowledge of physics for researchers is very important, as floating ice shelves act as a support, which slows the movement of the glacier to the sea.

Climate change is melting indirectly — through the circumpolar deep water. The water is warm enough to heat the bottom of the ice shelves, and since pre-industrial times she warmed by another 0,2? C. To also change the wind rose drives her to the ice of the Amundsen Sea. With further warming, the picture may change, but for now it is the main cause of melting.

Atmospheric warming is particularly strong impact on the Antarctic Peninsula, where ice formed on the surface of pools of melt water, which leads to fractures. The water in the cracks has such pressure that the fault may last a kilometer.

Researchers have come to the conclusion that we are unlikely to see the collapse of the West Antarctic ice sheet in this century, but the uncertainty of events can not calm down. Recall: the collapse will lead to an increase in sea level by three meters.

Dmitry Tselikov
For those interested in this issue there is an enormous amount of material, including both documentary and feature films, which can always be viewed at, and, unlike most similar resources, the video is of excellent quality.

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