Arctic Sea Ice
Sea ice in the Arctic is rapidly disappearing, and the decline has accelerated. In September of 2012, summer sea ice volume dropped to yet another new record low, shrinking to 20% of the 1979 summer volume (Polar Science Center, 2012). Global warming is a key driver of this trend, with warming in the Arctic increasing twice as fast as warming generally due to unique feedbacks in the Arctic climate system. The loss of summer sea ice has occurred far faster than predicted. In 2007, the International Panel on Climate Change estimated that the Arctic would see an ice-free summer somewhere near 2100. Now most experts predict ice-free summers may occur as soon as 2030, a condition that hasn’t existed for thousands of years. Some say it could happen this decade.
Arctic sea ice is often referred to as the ‘planet’s air conditioner’ for its ability to help regulate the earth’s temperature. The loss of Arctic sea ice poses serious risks for the United States, including new threats to national security as well as the potential for unusual weather patterns such as those that brought severe winter storms to the lower 48 over the last few months.
The extent of Arctic sea ice loss in 2012 shattered the previous all-time record low set in 2007 by about 18 percent, a total loss equivalent to approximately 43 percent of the size of the contiguous United States (Perovich, et. al 2012). As the area of Arctic sea ice has declined precipitously, we’ve also seen a simultaneous, equally sharp, decline in sea ice thickness. Together, these factors have contributed to a dramatic collapse in total sea ice volume, prompting some scientists and journalists to assert that Arctic sea ice is in a “death spiral” (Leahy 2010; Romm 2013).
Arctic sea ice has been retreating over the past 30 years, and the rate of retreat is accelerating at a pace that exceeds most models’ forecasts (Stroeve et al., 2007). As sea ice declines, it becomes younger and thinner, and therefore more vulnerable to further melting (Stroeve et al. 2011).
If heat-trapping pollution continues, summer sea ice will be lost entirely. Observations and climate model predictions have projected different time horizons for an ice-free Arctic (Overland and Wang, 2013). Many recent estimates based on climate models depict an ice-free
Arctic summer occurring in 20-30 years from now (Serreze, 2011; Stroeve et al. 2012, Overland and Wang, 2013), with models that have most accurately hindcast historical sea ice trends currently suggesting this will most probably happen in 22 years, and in eight years if the current trend continues (Stroeve et al. 2007; Wang and Overland 2009, 2012; Melillo et al. 2013). Direct extrapolation of observed sea ice volume paints an even grimmer picture, with complete loss occurring by 2016 (Vidal 2012; Maslowski et al. 2012; Overland and Wang, 2013).
Regardless of approach, all projections indicate an eventual sea ice free Arctic with continued emissions of greenhouses gasses, threatening the invaluable ecosystem service the Arctic sea ice provides while simultaneously exacerbating global warming.
As the earth’s natural air conditioner, sea ice moderates solar heating by increasing the reflectivity of Earth’s surface and decreasing the amount of heat that would otherwise by absorbed by ice-free Arctic seas. The loss of the air-conditioner effect creates a feedback loop that accelerates global warming (Melillo 2013). Other feedback loops exacerbated by melting sea ice, such as the release of greenhouse gases due to the thawing of permafrost and ocean bottom deposits of frozen methane, pose extremely high-stakes consequences for our climate if triggered.
The impacts and implications of rising temperatures and melting ice in the Arctic extend beyond just the Arctic itself. Changes in the Arctic led by sea ice loss are affecting weather patterns farther south in the lower United States. The loss of Arctic summer sea ice and the rapid warming of the area are altering the jet stream—and thus weather patterns—over North America, Europe and Russia, increasing the likelihood of extreme weather and driving winter storms south (Francis & Vavrus 2012; Melillo 2013).
An ice-free Arctic Ocean also increases national security concerns as a result of potential new international disputes and increased possibilities for military and commercial marine traffic between the Pacific and Atlantic Oceans (Markon et al. 2012; Melillo 2013).
- Research shows that before the 20th century’s influx of greenhouse gases, the Arctic was in a 2,000-year cooling trend (Kaufman et al. 2009), but that trend has reversed. In fact, due to interactions between global warming and feedback unique to the Arctic, the region has been warming at double the rate of the rest of the globe, and its ice is disappearing (Blunden et al. 2013).
- Ice thickness in the Arctic has declined 50 percent since 1980, and September minimum ice extent has plummeted as well, at a rate of 14 percent per decade relative to the 1981-2010 average (Perovich et al. 2013). In fact, the rate of ice retreat is accelerating at a pace that exceeds most models’ forecasts (Stroeve et al. 2007).
- In 2012, the ice extent reached an all-time record low, at 50 percent of the historic average. The area of missing ice was equivalent in size to 43 percent of the contiguous United States (Perovich et al. 2012). While sea ice recovered a bit in 2013 (leading to spurious claims of global cooling), NASA’s Walt Meier explains how this small recovery is normal and expected. “In our satellite data, the Arctic sea ice has never set record low minimums in consecutive years.” 2013’s Arctic sea ice extent was still the sixth lowest on record (Perovich et al. 2013).
- The average age of Arctic ice has been falling as well. In 1988, 26 percent of ice was four years old or older, compared to just 7 percent in 2013 (Perovich et al. 2013). And the Arctic melt season has lengthened at a rate of five days per decade from 1979 to 2013 (Stroeve et al. 2014).
- Ice melt has impaired many important functions the Arctic performs in our climate. Arctic sea ice serves as the planet’s air conditioner, moderating solar heating by increasing the reflectivity of Earth’s surface and decreasing the amount of heat that would otherwise be absorbed by ice-free Arctic seas. The loss of the air-conditioner effect, as sea ice disappears, creates a feedback loop that accelerates global warming (Bintanja and Linden 2012; NCA Chpt 22, p. 763).
- Changes in the Arctic, especially sea ice loss, may also be affecting weather patterns in the United States. The loss of Arctic summer sea ice and the rapid warming of the area alter the jet stream, which changes the movement of weather patterns over North America, Europe and Russia. These changes may increase the likelihood of extreme weather in mid-latitudes and drive winter storms south (Francis and Vavrus 2012; Lui et al. 2012).
- Through this jet stream alteration, Arctic sea ice melt was found to increase the likelihood of cold winter extremes in the northern hemisphere (Tang et al. 2013). It may also have influenced Superstorm Sandy’s path, keeping it where it could do the most damage.
- If heat-trapping pollution continues, summer sea ice will be lost entirely. The climate models that most accurately simulate past sea ice trends suggest this will probably happen within 22 years, possibly as soon as eight years (Kerr 2012; NCA Chpt 22, p. 762).
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