In 2011, the Arctic sea ice was the second lowest ever at 4.33 million square km (1.67 million square miles), compared with the low of 4.14 reached in 2007. The reduction of ice is having noticeable environmental consequences, including the opening of the northwest passage and the staking of territory by nations for future exploitation of oil and minerals.
Arctic Sea Ice
The minimum in 2011 (see Figure) was 2.43 million square km smaller than the 30 year mean from 1979-2009. Since 1979, sea ice area has declined at 12% per decade.
Effects on Arctic Wildlife
Wildlife in the Arctic have been significantly affected by these changes, both positively and negatively. With less summer ice in 2011, bowhead whales have been taking the Northwest Passage, uniting the Greenland and Alaskan populations.
The polar bear population has grown to about 25,000, but the polar bear has now been declared to be a threatened species, since it relies on the ice pack to hunt seals. If the projected disappearance of sea ice continues, then the polar bear may become extinct.
Arctic Ice Thickness
While effort has focused on the area of the summer ice, it is clear that the thickness of the sea ice is also declining. The thickness is important, especially in winter, as it can take many years to lay down thick ice which is more resistant to summer melting. Measurements in 2009 found that over a 4 year period, Arctic sea ice has been thinning at about 17 cm per year (5% per year). The older (more than 1 year old), thicker ice, declined by 42% in the same 4 years.
Antarctic Ice Changes
Simultaneously, NASA scientists are continuing to monitor Antarctic ice. In the past, the Antarctic ice sheet has changed relatively little, and has even shown a slight increase. The likelihood is that this is related to the Antarctic ozone hole.
Although ozone change is not generally related to climate change, ozone in the lower stratosphere warms the surface slightly. With a very large reduction in the ozone hole, close to 100% of the ozone over a narrow altitude range 15-20 km, since 1980 the Antarctic surface would have likely cooled due to ozone loss. This is sufficient to have counteracted the effect of greenhouse gas increases. It follows that, as ozone recovers over the next 50 years, temperatures over Antarctica may start to warm faster than over the Arctic.
Antarctic Ice Compared with Arctic Ice
There is an important difference between the Arctic and Antarctic, in that summer Antarctic sea ice melt is almost complete every year. Ice on the continent remains every year so that the positive feedback effect on the climate cannot occur. Nonetheless, there is an overall concern for sea level rise which might occur from any trend in melting over Antarctica.
Arctic Climate
A special report on Arctic issues, in the scientific journal Nature published 12 October 2011, points out that record high winter temperatures were experienced in January 2011, with temperatures above freezing for the first time ever in some places. The likelihood is that greenhouse gas increases are a major contribution to the warming of the Arctic.
Climate change in the Arctic is a positive feedback process. Hence, as the ice melts, so more sea is exposed, causing even more melting. However, climate models have underestimated sea ice melting. The sea ice thickness has been declining at about 4 times the rate predicted by climate models.
Rampal et al. suggest that this is due to the poor simulation of the movement of sea ice. Models generally assume no change in the ice drift rate, but as real ice becomes more fragmented due to summer melt, the connections between the fragments decrease. This accelerates the southward drift of the ice.
Hydrocarbons in the Arctic
The high price of oil is driving exploration to higher latitudes, as conditions allow. With its thick layers of sedimentary rocks, the Arctic offers previously untapped resources. Gautier et al. estimated that this could supply up to 30% of the world's undiscovered gas and 13% of the world's undiscovered oil. Currently a pristine environment, it would be a pity to open the region to potential new sources of pollution.
References
Gautier, D. L. et al. (2009), Assessment of undiscovered oil and gas in the Arctic, Science, 324, 1175-1179.
Gillett, N.P. and D.W.J. Thomson, (2003), Simulation of Recent Southern Hemisphere Climate Change, Science, 302, 273-275, DOI: 10.1126/science.1087440.
Heide-Jørgensen, M.P., et al., The Northwest Passage opens for bowhead whales, Biology Letters, 21 Sept 2011
Rampal, P. et al. (2011), IPCC climate models do not capture Arctic sea ice drift acceleration: Consequences in terms of projected sea ice thinning and decline, Journal of Geophysical Research,116, DOI: 10.1029/2011JC007110.
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