Arctic Apocalypse?

Published on Monday, 19 September 2011 13:31

	By Robin Whitlock Follow @RobinWhitlock66

According to Reuters, the summer melting of Arctic sea ice reached record levels this year, hastening the advance towards a future in which there is no summer ice in the Arctic at all.

The figures were obtained by two research institutes, one of them German, the other American, and they confirm that the five biggest melts in a 32 year history of satellite-obtained data focused on the region have occurred within the last five years.

The most likely cause is man-made (anthropogenic) global warming exacerbated by natural weather patterns. The likely result may be further disruptions in global weather patterns, some of which may have already occurred according to scientists pointing to colder winters in Europe and North America.

The idea that climate change can cause temperature to drop in certain regions may be hard to grasp and is often cited by climate change deniers as evidence that climate change isn’t happening at all, but closer examination of the meteorological dynamics leads scientists to suspect that warming Arctic oceans have diverted polar winds south, thereby chilling parts of Europe and North America. Recent cold winters should therefore be seen as evidence of climate change rather than evidence refuting it.

Researchers at Germany’s University of Bremen report that the extent of polar melt has this year has topped that of 2007 following a record retreat of the ice northwards on September 8^th. The US National Snow and Ice Data Centre (NSIDC) in Boulder, Colorado, has issued similar reports confirming that the melt season this year closely follows 2007 if not equalising it. Meanwhile Georg Heygster from Bremen University says that the years since 2007 have all seen larger summer melts than those before and that it is the rate or trend of melting that is more important.

In 2007, the summer Arctic ice shrank by nearly 40% compared to its 1979-2000 average extent. This however was merely the continuation of a process, largely fuelled by climate change that has been going on for some years.

For example, in 2000 the Ward Hunt Ice Shelf started to crack. This particular mass of ice had been in existence for some 3000 years previously, but in that year it began to fracture and over the next two years it split into two and started to break into pieces. Data from satellites estimate that the Arctic ice-cap is declining by a rate of 9% each decade.

Both Bremen and NSIDC use satellites to obtain their data. The satellites measure microwave radiation from the ice but there are subtle differences between the two: NSIDC’s images are sharper, but Bremen’s achieve a higher resolution of 6 kilometers compared to NSIDC’s 25 kilometers. Nevertheless, both institutions agree that the ice is melting faster than expected. Scientists tend to focus their measurements on the extent of sea ice rather than its thickness because it’s easier for satellites to measure extent. 

Both the minimum and maximum extent of sea ice is examined along with thickness, environmental conditions and observable changes in the melting season which lasts from March to September.

“An ice-free summer Arctic is rapidly on its way” says Kim Holmen, research director at the Norwegian Polar Institute. “Most data indicate that the models are underestimating the rate of ice-loss. That means we see more rapid change than the model scenarios have suggested. It also means that there are processes out there that influence ice that we have yet to understand.”

The Intergovernmental Panel on Climate Change (IPCC) predicted that an ice-free summer would be a reality in the Arctic by the end of the century. However, some estimates are now suggesting this could happen much earlier, with one model predicting an ice-free Arctic summer in 2013 while others are more optimistic pointing to somewhere between 2020 and 2050.

Wieslaw Maslowski of the California Naval Postgraduate School suggests it could happen around 2016 “plus or minus three years”.

Most experts agree that the thickness of the ice is also diminishing alongside the area it covers. Researchers at the University of Washington in Seattle calculated that the ice volume, combining area and thickness, reached record levels last year and would reach an all-time low again this year.

Sea ice is a key factor in the regulation of global climate, largely because of the albedo effect, the ability of bright colours to reflect solar radiation back into space. As the ice melts, so the dark surface of the ocean which replaces it tends to absorb heat thereby warming the oceans further.

This in turn hastens the rate of melting of the existing ice. Melting ice is therefore a positive feedback loop to climate change, in the sense that it tends to hasten the rate of warming. This is one reason why we should all be concerned about melting ice.

Another reason is that ice melt leaves a layer of fresh water at the ocean’s surface which can inhibit the global ocean currents (known as thermohaline circulation). Taken to an extreme, this was the central plot in the movie The Day After Tomorrow, which predicted a sudden ice age due to fresh water disrupting ocean circulation.

In reality, this disastrous effect would take hundreds of years to achieve, but it may have some more local short-term effects. Nevertheless, this particular aspect of the issue is still being investigated.

Earlier this year, the Catlin Arctic Survey sent researchers to the Arctic and also to Greenland to examine the likelihood of such a thing happening. Dr Simon Boxall of the National Oceanography Centre in Southampton commented that “If the ice continues to melt at its present rate, predictions made as recently as 2003 could happen 60 years earlier than expected”.

In April, New Scientist reported that melting ice and permafrost had created a pool of fresh water in the Arctic Ocean measuring 7500 cubic kilometres which could flush into the Atlantic Ocean and slow the Gulf Stream. 

The fresh water anomaly is currently being tracked by the Dutch Royal Netherlands Institute of Sea Research.

“Recent Arctic melting runs the risk of increasing the freshwater build-up, potentially making the consequences of the eventual breakout more extreme” says the Institute’s Laura de Steur. "In the worst case, these Arctic surges can significantly change the densities of marine surface waters in the far North Atlantic."  

Worryingly, Detlef Quadfasel of the climate centre at Hamburg University in Germany supports de Steur’s conclusions. “Some climate models do predict the circulation could weaken in coming decades” he says.

Monitoring of the effect of melting ice on the Gulf Stream or the Atlantic Conveyor as it is otherwise known is part of a larger 10-nation European programme called Project Clamer which is looking at the impact of climate change on European waters.

The melting ice also causes sea-levels to rise, thereby endangering coastal communities all over the world. The outlying islands north of Scotland, particularly the Hebrides, are already experiencing coastal storms which many believe to be a result of climate change.

According to a 2001 US Environmental Protection Agency study a 3 ft sea-level rise by 2100 would inundate some 22,400 square miles of land along the Alaskan and Gulf coasts of the United States especially Louisiana, Florida, Texas and North Carolina.

Cities all around the world, particularly those situated close to the coast such as London and New York, are directly threatened by melting polar ice and the resultant rise in sea levels. Yet there is at least one shred of good news to report in this respect – those cities are all too aware of this and are actively preparing for it.

Relevant Links

US National Snow and Ice Data Centre, September 15

Daily updated AMSR-E sea ice maps