The Sea Ice Gridded Climatology (SIGC) Coverage and Extent Statistics- The SIGC data set is a statistical computation describing extent and coverage of sea ice in specified area of the Arctic and Antarctic Oceans. "Ice extent" is defined as "all the grid cells covered by any ice"; and "coverage" is defined as "all the grid cells with ice multiplied by concentration" (i.e. 0.1 are 1/10^th) (Coverage and Extent Statistics Data File Description). These data (53 files) were compiled from 23 years (1972-1994) of weekly National Ice Center (NIC) Arctic and Antarctic sea ice analyses. The weekly analyses produced during this period of record are in hardcopy format and are comprised of four primary data types. 1) Shore station reports 2) Ship reports 3) Aerial Reconnaissance, and 4) Satellite imagery and data. These charts were manually digitized and translated into the World Meteorological Organization (WMO) digital archive and transfer standard of Sea Ice in GRIDed (SIGRID) format. All weekly files in the SIGRID compacted raster format have a grid cell resolution of 25 km.

The directories are divided into the East (sea ice covered seas located (clockwise) between the longitudes of 95E and 95W in the Northern Hemisphere), West (sea ice covered seas located (clockwise) between the longitudes of 95W and 95E in the Northern Hemisphere) and Antarctic Coverage and Extent. The naming convention corresponds to the East, West, and Antarctic regions found on the NIC homepage. The cornerpoints for each sea are contained in the submap.info file.

Coverage and Extent Statistics Data File Description

The total extent of ice coverage is the summation of areas of all grid cells having any concentration of ice. The total ice coverage category is the summation of the area in each grid cell multiplied by the concentration in that cell. Total coverage is a measure of an equivalent area of 100% concentration of ice. The first line in each file is a 66-character header record containing the data set name, basin or sub-basin, and period of record for the charts:  

Each data record contains the basin or sub-basin identifier, chart date, week number, coverage, and extent (in square kilometers):   

E-mail comments regarding Products and Services to: National Ice Center Liaison
For problems with the website (broken links, etc.), please email comments to: Webmaster

Updated on: August 6, 2008

Previous | Home