What is happening to Ice and the North Pole and South Pole

We are close to the time of the year when Arctic sea ice extent is traditionally at its lowest. In the second or third week of September we can get news of whether the extent of summer sea ice in theArctichas reached a new low. In 2007 the extent of summer sea ice reached its lowest ever and it seems that we are on track to equal that record in the next week or two.

We are now at about 4.5 million square kilometres, which is about 2 million square kilometres less than at the same time of year in 2003, The maximum extent of Arctic sea ice this year (in March) was 1.3 million square kilometres less than the average maximum extent for the 32 years from1979 to 2000. It is not conclusive proof of global warning but it is a compelling piece of evidence that supports climate change.

At the other end of the world the Antarctic’s sea ice is marginally increasing, but not by as much as theArcticis decreasing. What we have lost on the swings we have only partially gained on the roundabout.

There is no doubt that as a whole the planet is warming and it is a paradox that as the planet is warming, the North Pole is losing sea ice but the South Pole is gaining it. In fact the Antarctic gains sea ice in the winter but loses virtually all of its sea ice in the summer, unlike the Arctic which still retains summer sea ice. The Arctic has no land ice, because it has no land.

This might support climate change, rather than global warming, but there is an explanation in terms of global warming.

As the atmosphere warms, the water cycle, in which water molecules change from ice to liquid to gas to liquid and back to ice and so forth, accelerates these changes. This creates more precipitation in the Southern Ocean surroundingAntarcticarelatively speaking. The increased in precipitation is mainly in the form of snow. The snow insulates the upper part of the ocean from the ocean heat below. This reduces the amount of melting occurring below the sea ice. Also snow reflects atmospheric heat away from the sea ice, which reduces melting from above.

Another reason is that ozone levels over the Southern Hemisphere are very low and this causes cooling in the stratosphere, which leads to colder winds which freeze the sea.

A third reason advanced is that the Southern Ocean is becoming less salty, due to precipitation and there is less mixing of the cold and warmer layers of the ocean  which stratify more as a result.

Sea Ice is an important measure of global warming in the Arctic, which has no land mass, The Antarctic does have a land mass and we can measure land ice there, although not as precisely as scientists would like. The current theory is that the Antarctic is losing land ice at between 100 giga tonnes to 300 giga tonnes a year. It is losing land ice and the rate of loss seems to be accelerating.

In northernGreenlandthe Petermann Glacier is 300km long and about1000m high. Last year (2010) a lump of ice comprising 77 200 sq km broke off the Petermann Glacier and more break offs are expected over the next few years. Many, not all, glaciers are melting, even ones inGreenland.

We may argue about the causes of climate change but anyone to claims that the climate is not changing might want to look at what it happening at the poles, and think again.

Filed under: climate change, global warming Tagged: land ice, sea ice, sea ice extent

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