It may be only June, but predictions are already in for Arctic sea ice conditions in September, the month of maximum melt and minimum coverage.
A collection of 32 scientific forecasts, released on Thursday, yields a median prediction of about 1.93 million square miles of sea ice extent in September, slightly less than levels reached last September.
The September Sea Ice Forecast comes from the Sea Ice Prediction Network, part of the Arctic Research Consortium of the United States. The collected forecasts use a variety of methods -- statistical analysis, modeling and educated estimates -- in various combinations.
Last year, when maximum seasonal melt was reached on Sept. 17, Arctic sea ice extent was down to 1.94 million square miles, according to the National Snow and Ice Data Center in Colorado. It was the sixth-lowest sea ice minimum since satellite records began in 1979, but well above the all-time low of 1.32 million square miles reached on Sept. 16, 2012.
Sea-ice extent is defined by the center as the area with at least 15 percent ice coverage. The definition does not take into account the varying levels of concentration, movement or age, but the NSIDC and other organizatios do track those finer-scale factors, many of which are considered in the forecasts for September extent. The CryoSat program, run by the European Space Agency, tracks ice thickness, for example, though not in the summer months when surface melt ponds make measurements difficult.
Sea-ice extent reached a record-low maximum in February, considerably earlier than the usual March date, and it has been running relatively low since then. But only three of the 32 forecasts submitted to the Sea Ice Prediction Network anticipated a new record minimum this coming September.
Some patterns emerged from the different forecasts. In general, an especially early melt is expected in the East Siberian Sea and Kara Sea, both off Russia, and relative late ice-free conditions are expected in the Beaufort Sea and East Greenland Sea, the report said.
The new Sea Ice Outlook, which predicts ice extent averaged over the month of September rather than the annual minimum, will be followed up with refined outlooks issued in July and August.
Forecasting sea ice extent from year to year is a challenging task for climate scientists. A study published last year found that predictions tend to be fairly reliable when annual ice conditions closely track long-term trends. A new analysis by some of the same authors found that predictive models that incorporate an accelerating rate of melt rather than a linear rate tend to be slightly more accurate.