September Sea Ice Outlook: July Report

Release Date: 
28 July 2010

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Pan-Arctic Summary

The July Outlook for arctic sea ice extent in September 2010 shows some notable adjustments from the June Outlook, with both downward and upward revisions from last month.

Downward revisions reflect in part rapid ice loss observed during June together with the presence of the Arctic Dipole Anomaly (DA), which promotes clear skies, warm air temperatures, and winds that push ice away from coastal areas and encourages melt. Upward revisions reflect the slowdown of ice loss during the first two weeks of July and a change in atmospheric conditions to cooler, cloudier weather.

The July 2010 Sea Ice Outlook Report is based on a synthesis of 17 individual pan-Arctic estimates using a wide range of methods: statistical, numerical models, comparison with observations and rates of ice loss, composites of several approaches. Two contributors to the outlook represent "public" contributions.

Including all contributors, the individual Outlook values for September 2010 range from 1.0 to 5.6 million square kilometers, with a mean of 4.6 +/- 1.10 million square kilometers. Excluding the outlier of 1.0 million square kilometers by one of the public contributors gives a range of 4.0 to 5.7 million square kilometers, with a mean of 4.8 +/- 0.62 million square kilometers. This is below the 2009 minimum of 5.4 million square kilometers and just slightly above the 2008 minimum of 4.7 million square kilometers. Only three of the Outlook contributions give a value equal to or above the long-term linear trend line (5.6 and 5.7 million square kilometers, respectively). All of the estimates remain significantly below the 1979-2007 average of 6.7 million square kilometers, and six estimates indicate a new record minimum.

The spread of Outlook contributions suggests about a 29% chance of reaching a new September sea ice minimum in 2010 and only an 18% chance of an extent greater than the 2009 minimum (or a return to the long-term trend for summer sea ice loss). 53% of the Outlook contributions suggest the September minimum will remain below 5 million square kilometers, representing a continued trend of declining sea ice extent.

Figure 1. Distribution of individual Pan-Arctic Outlook (July Report) valuesFigure 1. Distribution of individual Pan-Arctic Outlook (July Report) values for September 2010 sea ice extent. Click to enlarge. Download High Resolution Version of Figure 1.