Metrics for the Sea Ice Outlook

This website describes metrics of spatial forecasts included in the Sea Ice Outlook. We ask that if you do submit processed fields to 2019 SIO, you include information on the forecast grid (latitude, longitude, grid area), and identify land points with the _FillValue attribute on the variable in the NetCDF file. To arrange for a way to submit the data, please contact

  • Sea Ice Probability (SIP)

    SIP is defined as the fraction of ensemble members in an ensemble forecast with September ice concentration in excess of 15%.

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    Example of SIP forecasts (July 2018 SIP forecasts of September 2018).

  • Ice Free Date (IFD)

    Ice-free date (IFD) is the first date (quantified as day of year) in the melt season at which the ice concentration at a given location first drops below 15%. Below are the IFDs in observations since 2015 up to May 2019.

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  • Ice Advance Date (IAD)

    Ice advance date (IAD) is the first date (quantified as day of year) in the freeze up season at which ice concentration at a given date first increases over 15%. Below is an example of IAD for freeze up of 2016. The black contour indicates the sea-ice edge on September 15th (day of year 259)

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