Arctic Sea Ice Extent & Volume at Record Lows for the Date

On 28 May, the extent of Arctic sea ice dropped to a record low for the date of 11,162,188 km2, surpassing the previous record low of 11,199,844 km2 set on 28 May 2006.  Since reaching a seasonal maximum of approximately 14,407,344 km2 on 31 March, the extent of sea ice has fallen a staggering 3,245,156 km2 or 2,016,446 square miles.  That is an area roughly half the size of the entire United States (including Alaska) and represents a decline of roughly 55,950 km2 per day (34,766 square miles per day). While the extent of Arctic sea ice normally declines during the "melt season" that typically begins in March and continues into September, the decline is unusually rapid for this time of year.

Meanwhile, the sea ice volume for the date is at a record low, falling 9-10,000 km3 below the average (1979-2009) values for the date.  That volume, greater than that of Lakes Michigan and Huron combined (8,260 km3 or 1,980 cu mi), is the largest negative anomaly on record (i.e. for all dates since 1979).

In addition to being a very large  volume in absolute terms, the volume also is large relative to the total volume of Arctic sea ice.  According to a model developed by the  University of Washington's Polar Science Laboratory (PSL), the average Arctic sea ice volume in late May averaged around 26,000 km3 during the 1979-2009 period. The current negative anomaly in ice volume therefore represents a loss of around one third of the average sea ice volume.

The first figure below is from the International Arctic Research Center (IARC) and Japan Aerospace Exploration Agency (JAXA) Information System (IJIS) (see Data of Sea Ice Extent).  It shows the extent of sea ice during each year since 2002, with 2010 indicated in red.  It illustrates that while sea ice extent during much of April 2010 was high relative to the other years, it has plummeted since then to a record low on 28 May.

Arctic Sea Ice Extent, 2002-2010


Arctic Sea Ice Volume Anomaly, 1979 though 24 May 2010

The second figure above shows the extent to which Arctic sea ice volume is below 1979-2009 levels at any given time.  The figure is from the Pan-Arctic Ice Ocean Modeling and Assimilation System (PIOMAS) developed by PSL (see Arctic Sea Ice Volume Anomaly).  The gray line shows daily anomalies in sea ice volume, while the blue line shows the trend since 1 January 1979.  The trend clearly shows a rapid increase since 1979 in the magnitude of the negative anomaly, i.e. the volume of Arctic sea ice is dropping lower and lower below average with each successive year.

So what does this tell us about the fate of Arctic sea ice extent as the melting season progresses towards the minimum (usually in September)? The remaining ice is relatively thin -- and therefore more likely to break up and to melt.  This year to date is the warmest on record, and the warmth has been especially pronounced in the Arctic.  Those conditions are likely to persist into the Fall.  The extent of remaining ice therefore is likely to decline rapidly during the rest of the melt season. We ultimately may see Arctic sea ice decline to record lows in 2010.

Sea ice is not just of central importance to ecosystems and communities in the Arctic.  It also plays a critical role in climate both in the Arctic and to the south.  The continued decline in Arctic sea ice therefore will have growing consequences that will be disruptive and that will increasingly spill beyond the Arctic.  See our report, Arctic Climate Feedbacks: Global Implications (2009) [PDF], for details.

Online Resources:

WWF Climate Change Blog > Arctic.  Recent postings include:

As Arctic sea ice shrinks faster than 2007, NSIDC director Serreze says, “I think it’s quite possible” we could “break another record this year.”  Climate Progress, 24 May 2010.

Polar Meltdown (subscription required).  Article by David Biello in Scientific American (June 2010).  The article is part of a feature series of articles on What the Future Holds.  The Polar Metldown is one of what the editors call 12 Events that Will Change Everything in the opening article of the series.

The central role of diminishing sea ice in recent Arctic temperature amplification.  Letter by James A. Screen & Ian Simmonds in Nature, 464, 1334-1337 (29 April 2010). 

Scientists See Rapid Ice Loss in the Arctic Ocean.  Canadian Broadcasting Corporation, Thu, May 20, 2010. 

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