Sea Ice Outlook: Post-Season Highlights

18 December 2015

The Sea Ice Outlook Post-Season Highlights were developed by ARCUS, based on the full report.

Highlights and Take-Home Points

The Sea Ice Outlook Post-Season Highlights are based on the full report.

The Sea Ice Outlook (SIO), a contribution to the Study of Environmental Arctic Change (SEARCH) provides an open forum for researchers and others to develop, share, and discuss seasonal Arctic sea ice predictions.

  • The September 2015 Arctic sea ice extent was the fourth lowest extent observed in the modern satellite record, which started in 1979, at 4.63 million square kilometers, according to National Snow and Ice Data Center (NSIDC) estimates.

  • This year the SIO had a total of 105 submissions from June through August: 102 pan-Arctic submissions and 3 regional submissions.

  • The median prediction of September extent from August Outlooks compared reasonable well relative to standard baseline metrics of persistence (i.e., use 2014 value to estimate 2015) and trend (extrapolate the 1979-2014 trend line to estimate 2015). The median of 4.8 million square kilometers was significantly lower than the persistence value of 5.28 million square kilometers, but was roughly the same as the extrapolated trend estimate of 4.76 million square kilometers.

  • This median August Outlook estimate of 4.8 million square kilometers, with a quartile range of 4.2 to 5.2 million square kilometers (Figure 5 in full report), was a small downward adjustment from June and July (5.0, quartile range: 4.4-5.2) and represents an improved estimate relative to the observed extent as the forecast period shortened and information from June and July could be incorporated. However, we note that many participants submit the same prediction in each month.

  • The median estimate of pan-Arctic extent from the distributions of statistical and dynamical modeling methods compared more favorably with observations than from the distributions of heuristic and mixed methods.

  • Following the relatively cool May and June, the Arctic experienced one of the warmest Julys on record, which led to rapid ice loss through the month.

  • The full report includes additional discussion on the various ways used to calculate the observed sea ice extent; the relative performance of different Outlook methods (e.g., statistical, modeling, heuristic); the summer conditions; regional and ice-free-date predictions; and lessons from 2015 and recommendations for the 2016 Outlook