Sea Ice Index, Version 1 (G02135)
Version 1 of the Sea Ice Index is no longer available and has been replaced with Version 2. Please see the Version 2 record to obtain that data. The Sea Ice Index provides a quick look at Arctic- and Antarctic-wide changes in sea ice. It is a source for consistent, up-to-date sea ice extent and concentration images, in PNG format, and data values, in ASCII text files, from November 1978 to the present. Sea Ice Index images also depict trends and anomalies in ice cover calculated using a 30-year reference period of 1981 through 2010. The images and data are produced in a consistent way that makes the Index time-series appropriate for use when looking at long-term trends in sea ice cover. Both monthly and daily products are available. However, monthly products are better to use for long-term trend analysis because errors in the daily product tend to be averaged out in the monthly product and because day-to-day variations are often the result of short-term weather. Monthly extent products are also available as geographic information systems (GIS) compatible shapefiles. Data are available via FTP.
ICE EXTENT ICE GROWTH/MELT SEA ICE CONCENTRATION
DMSP, DMSP 5D-3/F17, Nimbus-7, Nimbus-7
SMMR, SSM/I, SSMIS
PNG, ASCII, Shapefile
26 October 1978 to 5 July 2016
Data Access & Tools
The regions differ slightly between the Sea Ice Index and the Multisensor Analyzed Sea Ice Extent - Northern Hemisphere (MASIE-NH).
NSIDC currently archives passive microwave sea ice concentration products based on two algorithms: the NASA Team algorithm and the Bootstrap algorithm. Both algorithms were developed by researchers at the NASA Goddard Space Flight Center in the 1980s.
Why is the daily change in sea ice extent in the northern hemisphere larger at the beginning of each month?
If you plot the average daily change in sea ice extent in the northern hemisphere, based on the data from 'Sea_Ice_Index_Daily_Extent_G02135_v3.0.xlsx', you may notice that at the beginning of each month, particularly in the summer, the daily change is larger.