September Sea Ice Outlook: August Report

Release Date: 
1 September 2010

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Pan-Arctic Summary

For the August Outlook, a total of 18 contributions were received—16 from the scientific community and 2 from the general public. The mean prediction for the September minimum, excluding the two contributions from the general public, is 4.9 +/- 0.51 million square kilometers. This is a slight increase from the July Outlook of 4.8 +/- 0.62 million square kilometers and reflects in part the slowdown of ice loss observed in July. To put this estimate in context, this is below the 2009 minimum of 5.4 million square kilometers and represents a continuation of the long-term loss of summer arctic sea ice.

In July, the Arctic Dipole Anomaly (DA) pattern that was dominant in June (which promotes clear skies, warm air temperatures, and winds that push ice away from coastal areas and encourages melt) was replaced by low sea level pressure (SLP) over the Arctic Ocean, leading to ice divergence (ice extent "spreading out") and cooler temperatures. As a result, ice extent loss slowed. The July ice extent, however, still ended up as the second lowest recorded during the satellite (1979–2010) data record at 8.39 million square kilometers, 260,000 square kilometers above the average for July 2007.

August saw a return of high pressure over the Beaufort Sea coupled with low pressure over Siberia. This pattern helped to accelerate ice loss in the Beaufort and Chukchi Seas, where ice loss rates doubled in August. August also saw nearly ice-free conditions in the Northwest Passage (NWP) and the Northern Sea Route (NSR). Interestingly, two expedition teams, one from Norway and one from Russia, are attempting to circumnavigate the Arctic this season (

The estimates from the scientific community range from 4.0 to 5.6 million square kilometers, with 8 of the contributors suggesting a September minimum below 5.0 million square kilometers, 3 contributors suggesting a minimum of 5.0 million square kilometers, and 5 contributors suggesting a September minimum above 5.0 million square kilometers. Two contributors forecast a September minimum below that of 2007 at 4.0 million square kilometers and 3 contributors suggest a return to the long term downward linear trend for September sea ice loss (5.5 to 5.6 million square kilometers). None of the contributors indicate a return to the climatological sea ice extent of 6.7 million square kilometers.

Including all 18 contributions gives a September ice extent minimum of 4.8 +/- 0.77 million square kilometers, with a range of 2.5 to 5.6 million square kilometers.

Individual responses were based on a range of methods: statistical, numerical models, comparison with previous observations and rates of ice loss, or composites of several approaches.

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