News is just out that Arctic ice levels may now be at their lowest ever level, following the 2011 summer melt season, beating the 2007 record. NSIDC will be confirming this sometime in October 2011.
So, with this in mind, let’s take a look at how global warming is affecting the Earth’s coldest regions and ice sheets, collectively called the cryosphere, derived from a Greek word meaning frost or cold. It is used to describe the areas of the Earth’s surface where water is in a solid form, usually snow or ice. These areas include sea ice, freshwater ice, glaciers, permafrost and snow.
The Earth’s polar icecaps, found at the North and South poles, contain the largest concentrations of ice on Earth. The North pole is home to the Arctic, and the South pole the Antarctic. Also in the north is the massive Greenland ice sheet. Both the Antarctic and Greenland ice sheets sit on top of continents or landmasses, whereas the Arctic is a frozen ocean. Sea ice however is found in both the North and South polar regions, and in total it covers an area about twenty times the size of Canada.
WHAT IS SEA ICE ?
Well, it is simply frozen ocean water. It forms and melts in the ocean. Icebergs, glaciers, ice sheets/shelves, however, all originate on land, and are formed with fresh not saltwater. Sea ice grows in the winter months and melts during the summer. Some ice remains all year round, and about fifteen per cent of the world’s oceans are covered during part of the year.
WHY IS IT SO IMPORTANT ?
Ice has a bright reflective surface, so as sunlight strikes it most of it is reflected back into space. As such, areas covered by ice don’t absorb much of the sun’s energy, allowing temperatures in the polar regions to remain cool. If higher temperatures melt the ice over time, as is beginning to happen, then more of the sun’s energy can be absorbed by the ice-free sea or land, allowing temperatures to rise further.
The term ‘albedo’ is used to determine how well a surface reflects solar energy. A surface with an albedo of zero means that it is a perfect absorber of the sun’s energy, such as a black surface. An albedo of one means that the surface is a perfect reflector, such as a white surface. Sea ice will reflect about fifty to seventy per cent of the sun’s energy. Open sea reflects about six per cent, whereas snow-covered ice about ninety per cent, simply because it’s white and therefore has a higher reflective surface.
Just as the Amazon regulates climate by absorbing and storing huge amounts of CO2, the ice-covered regions of Earth act much in the same way, by regulating temperature and reflecting large amounts of solar energy back into space. If these regions melt, then not only will ocean levels rise but temperatures will also increase.
HOW IS THE ARCTIC RESPONDING TO GLOBAL WARMING ?
The North pole sits right in the middle of the Arctic Ocean, which is fenced in by eight different countries. During the winter the ice extends over the entire ocean and onto the fringes of the land. During the summer, the ice retreats back into the ocean. Air temperatures in the region have, on average, increased by about 5°C (9°F) over the last 100 years, which is higher than anywhere else on the planet. This has caused Arctic sea ice to decrease by about fourteen per cent since the 1970s.
The local Inuit population have started to notice the warmer summers, the earlier break-up of the ice in spring, and extensive areas of melting permafrost in places like Alaska and Siberia. This in turn is affecting their hunting season, foundations of properties and other infrastructure in the region. Arctic sea ice has been measured by the National Snow and Ice Data Centre (NSIDC) and NASA, using satellite data, and the findings are that massive reductions in sea ice are occurring at the end of the northern summer.
The sea ice extends to about 15,000,000 square kilometres (5,792,000 square miles) during winter, and down to an average 7,000,000 square kilometres (2,703,000 square miles) during the summer. It therefore loses just over fifty per cent of ice cover after the summer melt season. The annual average extent of Arctic sea ice has decreased by about three per cent per decade since about 1980, which is the equivalent of an area of about 750,000 square kilometres (289,575 square miles). The amount of ice left after the summer melt is also decreasing by about 7.7 per cent each decade.
NSIDC measures Arctic sea-ice extent, or the area of ocean that is covered by at least fifteen per cent ice, which typically reaches its minimum in September, at the end of the summer melt season.
In 2007, NSIDC data reveals that Arctic sea ice during the 2007 melt season plummeted to the lowest levels since satellite measurements began in 1979. The September sea-ice minimum went down to 4,130,000 square kilometres (1,594,000 square miles), the lowest September on record, shattering the previous record for the month, set in 2005, by twenty-three per cent. Computer models however have predicted the Arctic will be ice-free in the summer months from 2080 if the overall warming trend continues.
In March 2007, a fire onboard the British nuclear submarine HMS Tireless forced it to the surface. Two sailors died in the explosion. The Navy had been conducting tests under the Arctic and the data retrieved indicated that the summer Arctic sea ice may actually be gone by as soon as 2020. This however appears to be a worst-case scenario.
Arctic sea ice is about 2 to 3 metres (6.5 to 9.8 feet) thick on average, so a loss of 7,000,000 square kilometres (2,703,000 square miles) times 2.5 metres (8.2 feet) (thickness) is a considerable amount of water. Melting sea ice however does not necessarily add much to sea-level rise when it melts, much like melting ice cubes in a glass do not cause the glass to overflow. Melting glaciers and ice-covered continents however are a different matter and when they melt, sea levels will rise.
A new NASA-led study found a twenty-three per cent loss in the extent of the Arctic’s thick year-round sea ice cover during the past two winters. The scientists discovered less perennial sea ice in March 2007 than ever before. This drastic reduction is the primary cause of this summer’s fastest-ever sea-ice retreat on record and subsequent smallest-ever extent of total Arctic coverage.
Record summer melting has also meant that the usually frozen Northwest Passage waterway, which connects the Atlantic to the Pacific, has become fully navigable, a fact that may raise tensions between Canada, which maintains that the waterway lies in its territorial waters, and other countries in the region. The race is now on to exploit the Arctic’s natural resources as oil companies drill for oil there. A disaster along the lines of the Deepwater-Horizon spill, would be cataclysmic.
For a recent news article showing stark photographic differences over time between Himalayan glaciers, click here.
For more information, check out THE A-Z OF GLOBAL WARMING, the above article is taken from chapter N – No More Ice!
Alternatively for a fast paced eco-thriller, involving a race to prevent the Arctic from melting, try TIPPING POINT.