Arctic sea ice follows and annual cycle of melting and freezing. In summer months, sea ice is shed to an annual minimum level of ice coverage, before the cooler temperatures and shorter days of autumn terminate the melting period and the ice again begins to grow.
Since 1979, satellites keeping close watch over the Arctic have recorded this annual oscillation of sea ice and transmitted this information to atmospheric scientists with NASA and the National Snow and Ice Data Center (NSIDC) at the University of Colorado at Boulder. If there’s one lesson these teams have learned over the past 33 years, it’s that the goal posts keep moving: the average minimum level of summer ice coverage across the Arctic is decreasing. According to both NASA and NSIDC, the minimum summer ice coverage has decreased approximately 13% since 1979, and average annual thickness of sea ice has also decreased over the same period. Arctic summer sea ice reached its lowest known coverage area of 1.61 million square miles on September 28, 2007 after an unusually warm summer.
At least, that was the record low level of Arctic sea ice coverage until two days ago. On August 26, 2012, the total area covered by Arctic sea ice dropped another 27,000 square miles to just 1.58 million square miles. This year’s melting season won’t end until cooler temperatures begin their return in late September. Thus, as NASA and NSIDC grimly noted in their press releases, this new record low could be supplanted by further decreases in ice levels over the next month. As Julia Whitty notes in Mother Jones, at current rates the Arctic could be losing as much as 29,000 square miles of sea ice daily (roughly equivalent to an area the size of South Carolina). But unlike 2007 when the previous record was set, 2012 does not appear to be an abnormally warm Arctic summer. This year may instead represent a new normal for sea ice levels in the far north.
Add this new record low to the growing number of signs that the Arctic is warming at a peculiar and notably faster rate than the rest of the planet. While scientists can generally attribute small annual variations in sea ice coverage to variations in weather patterns, it appears that the Arctic is on a general trend of decreasing summer ice coverage. As Julia Whitty notes also notes in her Mother Jones article, the six most recent years (from 2007 to 2012) were also the six years with the lowest levels of Arctic summer sea ice since the beginning of satellite data collection in 1979. According to Walt Meier, a scientist with NSIDC, “The Arctic used to be dominated by multiyear ice, or ice that stayed around for several years. Now it’s becoming more of a seasonal ice cover and large areas are now prone to melting out in summer.”
Will the Arctic Ocean stabilize into a new (albeit dramatically lower) area covered by summer sea ice? Or, will this trend accelerate until the Arctic is ice-free during the summer? As James Astill noted in his special report on the Arctic in The Economist, Arctic nations are betting on the latter scenario and investing heavily in exploration and extraction of natural resources in the Arctic. As Michael Lemonick with Climate Central notes, the consequences for this dramatic loss of sea ice could be severe: “Arctic ice, whether on land or on the sea, is a powerful reflector that bounces a lot of sunlight back into space rather than letting it warm the Earth. When that ice melts, it exposes the darker ground or water underneath, turning the region into an energy absorber rather than a reflector.” Thus, this trend for the Arctic could accelerate climate change globally.
Ultimately, only more data can settle what the new climactic norm will be for the Arctic region, and how this new norm will affect warming temperatures across the rest of the planet. NSIDC will release its full findings for this year’s already record-busting 2012 melting season in October, after the official end of this year’s melting season. Stay tuned.
- August 27, 2012. “Arctic sea ice breaks lowest extent on record.” National Snow and Ice Data Center. University of Colorado at Boulder.
- August 27, 2012. “Arctic Sea Ice Shrinks To New Low In Satellite Era.” NASA.
- Arctic Sea Ice News and Analysis page for the National Snow and Ice Data Center. University of Colorado at Boulder.
- Whitty J. August 27, 2012. “Arctic Ice Shatters Melt Record.” Mother Jones.
- Astill J. June 16, 2012. “The melting north.” The Economist.
- Lemonick MD. August 27, 2012. “Arctic Sea Ice Sets Record Low, and it’s Not Over Yet.” Climate Central.
- NASA Goddard Space Flight Center’s Scientific Visualization Studio (also available in the above press release from NASA).
- Polar bear and cub: Angela Plumb and The Telegraph.