Monthly Extent and Concentration Images

Only monthly image files are available in the archive. Daily images are not archived.

To access the monthly images, go to the FTP directory.

Choose the month directory (indicated by a 3-character month abbreviation) for the data that you are interested in. Within the month directory, search for the year and type of monthly image files that are named according to the following convention:

H_yyyymm_type.png

Where H stands for the hemisphere: N (north) or S (south), yyyy is the 4-digit year, mm is the 2-digit month, and type is the type of image in the file: extn (extent), conc (concentration), anom (concentration anomalies), and trnd (concentration trends).

For example, the file N_200303_anom.png contains concentration anomalies for the Northern Hemisphere for March 2003.

GIS Compatible Files (shapefiles)

Monthly sea ice extent shapefiles, November 1978 to present. Shapefiles are available for Northern and Southern hemispheres, both polygons and polylines.

Monthly median shapefiles. Each month's shapefile indicates that month's median extent for the period 1979 to 2000. Shapefiles are available for Northern and Southern hemispheres, polylines only.

To access the files, go to the FTP shapefiles directory.

Choose a month directory (indicated by a 3-character month abbreviation). Shapefiles are organized in monthly directories, by extent for that month and year or by median extent for that month. Files are zipped. For example, extent_N_199806_polyline.zip contains the polyline extent shapefile for the Northern Hemisphere for June 1998.

Monthly Sea Ice Extent and Area Data Files

The ASCII data files tabulate extent and area (in millions of square kilometers) by year for a given month.

To access the files, go to the FTP directory.

Choose the month directory (indicated by a 3-character month abbreviation) for the data that you are interested in. Within the month directory, search for data files that are named according to the following convention:

H_mm_area.txt

Where H stands for the hemisphere: N (north) or S (south), and mm is the 2-digit month.

For example, the file N_04_area.txt contains data from the Northern Hemisphere for the month of April.

Daily Sea Ice Extent Data

These files provide the total extent for each day for the entire time period. There are two data files for each hemisphere: a final and a near-real time. The final file uses data processed at NASA Goddard that goes through manual quality control as input values. However, these data are not available on a near-real-time basis, so a near-real-time file is provided that provides data up to the present. The data in the near-real-time file are the data that are in the Daily Total Sea Ice Extent Time Series Graphs. The data files are in comma delimited ASCII text format (.csv). For more information on how these are processed, see the Daily Total Extent Data Files section of the Sea Ice Index documentation.

Access files:

• Northern Hemisphere Files
• Southern Hemisphere Files

Climatology Data File

These files contain the data for the solid grey line and the light grey standard deviation swath in the Daily Total Sea Ice Extent Time Series Graph. The data files are in comma delimited ASCII text format (.csv). For more information on how these are processed, see the Climatology Data Files section of the Sea Ice Index documentation.

Access files:

• Northern Hemisphere Files
• Southern Hemisphere Files

Passive Microwave Sea Ice Concentrations (Sea Ice Index Source Data)

These data are not part of the Sea Ice Index archive. They are the source data that the Sea Ice Index is derived from. To access these data and learn more about them, see the following links:

• Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data
• Near-Real-Time SSM/I Polar Gridded Sea Ice Concentrations (NRTSI).