IMS Ice Extent Graphs
Total IMS Sea and Lake Ice extent coverage calculations are based on all water bodies that have the majority of the surface covered at 4 KM resolution. Total ice coverages are only calculated from March – September of each year to capture the maximum and minimum values for the season. Values represent the entire area of ice covered water bodies over the entire Northern Hemisphere and are calculated in Lambert Azimuthal Equal Area Projection with a WGS84 Datum. The daily total ice extents are calculated from a 3-day running mean to eliminate daily variability and provide a clear trend line.
IMS Sea Ice values are a subset of the IMS Sea and Lake Ice extent that is geographically bounded over the same extent as the NIC Arctic Daily Ice edge and NIC sea ice charts (see http://nsidc.org/data/docs/noaa/g02172_nic_charts_climo_grid/index.html#spatialcover for geographic extent documentation). The same 3 day running mean values, time intervals, and projection used for the Total IMS Sea and Lake Ice Extent are applied for calculations of the IMS Sea Ice Extent values.
For further information regarding the IMS analysis methodology and data sources, please reference publications on the IMS main webpage (http://www.natice.noaa.gov/ims/) and NSIDC documentation (http://nsidc.org/data/docs/noaa/g02156_ims_snow_ice_analysis/index.html).
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