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September Sea Ice Outlook: July Report

Release Date: 
12 July 2013

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We appreciate the continuing contributions to the July Outlook (using June data). We received 21 Pan-Arctic responses for the September 2013 Arctic mean sea ice extent with a median value of 4.0 million square kilometers and the quartile values are 3.8 and 4.6 million square kilometers (Figure 1). The range of estimates was 3.2 to 5.9 million square kilometers. For comparison, the June 2013 median was 4.1 million square kilometers and the July median from 2012 was 4.6 million square kilometers. Thus the data from 2012 and recent estimates of thinning sea ice appear to have an impact in lowering Outlook estimates.

Figure 1. Distribution of individual Pan-Arctic Outlook values (July Report)Figure 1. Distribution of individual Pan-Arctic Outlook values (July Report) for September 2013 mean sea ice extent (values are rounded to the tenths).

Download High Resolution Version of Figure 1.

Individual responses continue to be based on a range of methods: statistical, numerical models, comparison with previous rates of sea ice loss, estimates based on various non-sea ice datasets and trends, and subjective information (i.e., the "heuristic" category). See Figure 2 for a comparison of different methods between June and July.

Credit: National Snow and Ice Data Center (NSIDC).Figure 2. Distribution of 2013 Sea Ice Outlook predictions by method and month. Box plots show median and approximate interquartile range (middle 50%) of each group. The overall July median, 4.0 million km2, is marked by a horizontal line. The modeling and statistical predictions appear fairly stable from June to July, with the statistical predictions generally more pessimistic. Heuristic predictions shifted more substantially, reflecting a changing pool of contributors. (Courtesy of Larry Hamilton, U. of New Hampshire)

As in 2012, sea ice thinning and not just anomalous weather should contribute to September 2013 sea ice loss.

In addition to the 21 pan-arctic Outlooks, we have 5 regional Outlooks that provide more detail for the Northwest Passage, Arctic Bridge (Hudson Bay / Hudson Strait), Laptev-Kara-Barents-Greenland Seas, Canadian Arctic Archipelago and Nares Strait.

The Pan-Arctic report was developed by Jim Overland, NOAA, Hajo Eicken, UAF, and Helen Wiggins, ARCUS. The Regional report was developed by Adrienne Tivy, National Research Council Canada, with assistance from Kristina Creek, ARCUS.