Sea Ice Index Updated with a New Arctic Pole Hole and Ice Masks

The NOAA at NSIDC program is pleased to announce that the Sea Ice Index data set has been updated with a reduced Arctic pole hole and improved Northern Hemisphere masks for removing spurious ice caused by residual weather effects.

Beginning 01 January 2008, the data will include a pole hole that covers 0.029 million sq km rather than the previous pole hole of 1.19 million square kilometers. In addition, an error in the pole hole used for data from 01 July 1987 to 31 December 2007 was corrected. These data now uses a pole hole of 0.31 million sq km rather than 1.19 million sq km. The varying pole hole sizes correspond to the orbit inclination of the satellite used to collect the input data.

The new masks are derived from the National Ice Center ice chart monthly climatologies which define more realistic boundaries for ice presence based on recent trends. These new masks have been applied to all historical data. Lastly, the extent values in the daily extent .csv file have been rounded to three decimal places instead of six because anything further than three digits is outside the precision of these data. More information can be found on the Sea Ice Index documentation Web page.

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