Overview

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.

Parameter(s):

ICE EXTENTICE GROWTH/MELTSEA ICE CONCENTRATION

Platform(s):

DMSP, DMSP 5D-3/F17, Nimbus-7

Sensor(s):

SMMR, SSM/I, SSMIS

Data Format(s):

PNG, ASCII, Shapefile

Temporal Coverage:

26 October 1978 to 5 July 2016

Temporal Resolution:

1 day

Spatial Resolution:

25 km

25 km

Spatial Coverage:

30.98

180

-180

-39.23

-90

180

-180

Blue outlined yellow areas on the map below indicate the spatial coverage for this data set.

View Metadata Record

Data Access & Tools

This data set has been retired. There is a more recent version of these data.

Help Articles

General Questions & FAQs

Are the same regions used in the Sea Ice Index and MASIE-NH?

The regions differ slightly between the Sea Ice Index and the Multisensor Analyzed Sea Ice Extent - Northern Hemisphere (MASIE-NH). The two data sets are a source for sea ice extent, but they use different methods and data to estimate this parameter and their intended uses are also different.

Descriptions of and differences between the NASA Team and Bootstrap algorithms

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.

I just want to see a picture of sea ice extent or concentration, or a plot of ice trends by month. Where should I look?

The Sea Ice Index and the Arctic Sea Ice News Analysis (ASINA) Web pages provide images derived from passive microwave satellite data that depict the most recent daily sea ice conditions.

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.

How to Articles

Guide to the NSIDC Data Map Services API

The NSIDC Data Map Services Application Programming Interface (API) provides HTTP URLs for requesting geo-registered map images from NSIDC's geospatial database. A WMS request defines the geographic layer(s) and area of interest to be processed.

How to access and download NOAA@NSIDC data

NOAA@NSIDC data recently transitioned to HTTPS. The directory structure has NOT changed, but the beginning of the URL has changed from: ftp://sidads.colorado.edu/pub/DATASETS/ to: