Sea Ice Index
The Sea Ice Index provides a quick look at sea ice changes in spatial and historical context, and gives a consistent, up-to-date source of sea ice extent and sea ice concentration values and images. The NSIDC Near-Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations and the Sea Ice Concentrations from Nimbus-7 SSMR and DMSP SSM/I Passive Microwave Data data sets are used to generate the monthly records of sea ice extent and sea ice concentration for the Arctic and Antarctica from satellite passive microwave data.
Data files tabulate monthly mean extent and area, in millions of square kilometers, by year for a given month. Plots of monthly sea ice extent anomalies with trend lines and significance intervals are available. Monthly images show sea ice extent (with an outline of the median extent for that month for comparison), sea ice concentration, trends in sea ice concentration, and anomalies in sea ice concentration. Anomalies and median extent are calculated using a reference period of 1979 through 2000.
Daily images of sea ice extent and concentration, along with a time series plot of extent for the most recent four months, can be viewed and downloaded on the data product site but are not archived. Some products are available as GIS compatible shapefiles and KML files. The Browse Image Spreadsheet Tool (BIST) can be used for animated images and for displaying archived images of extent and trends side by side, to make it easy to compare images from different years and months.
Data are stored in ASCII text, Portable Network Graphics (PNG), Keyhole Markup Language (KML), and Geospatial Vector Data format and are available from November 1978 to present via FTP or the Sea Ice Index Web site.
The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.
Fetterer, F., K. Knowles, W. Meier, and M. Savoie. 2002, updated 2009. Sea Ice Index. [indicate subset used]. Boulder, Colorado USA: National Snow and Ice Data Center. http://dx.doi.org/10.7265/N5QJ7F7W.