Cryospheric Climate Indicators: Sea Ice Index

"A linear increase in heat in the Arctic Ocean will result in a non-linear, and accelerating, loss of sea ice."
– Norbert Untersteiner, Professor Emeritus, University of Washington, July 2006

These images depict average sea ice conditions for last month. Graphs and images also provide snapshots of trends and anomalies, comparing last month's sea ice conditions with the mean for the month. Ice extent is derived from satellite passive microwave data. In the Northern Hemisphere, sea ice typically reaches its annual minimum extent in September, and its maximum extent in February or (usually) March.

Daily images are also available. Monthly averages are considered more accurate indicators of overall trends. Please read Image Derivation and Interpretation Resources to understand the uses and limitations of these figures.

Trends in Extent
Northern Hemisphere (Arctic)			Southern Hemisphere (Antarctic)
	Extent	Concentration	Concentration Anomalies	Concentration Trends

All anomalies and trends are calculated related to the monthly average, with a reference period of 1979-2000. Click an image thumbnail for a higher-resolution image and legend.

View Images, 1979 to Present

Quickly compare conditions in different months and years by displaying multiple images in tabular form, or animate images as a time series:

Animated Images	View Images Using Google Earth
Extent, Concentrations, and Anomalies	Extent and Concentration Trends

Sea Ice Index References

Meier, W., J. Stroeve, F. Fetterer, K. Knowles. 2005. Reductions in arctic sea ice cover no longer limited to summer. Eos: Transactions of the American Geophysical Society 86, 326.

Fetterer, F., and K. Knowles. 2004. Sea ice index monitors polar ice extent. Eos: Transactions of the American Geophysical Society 85, 163.

User Services

NSIDC strongly encourages you to register as a user of this data product. As a registered user, you will be notified of updates and corrections. When registering, please include the title of this data set, Sea Ice Index.

Acknowledgements

Florerence Fetterer, Kenneth Knowles, and NSIDC staff developed the Sea Ice Index with financial support from NOAA NESDIS and in cooperation with NOAA NGDC. This site is maintained with assistance from the NSIDC NASA DAAC.

Citations and Credits

You may download and use any images from the Sea Ice Index. Please credit NSIDC.

Please use this citation when referencing the Sea Ice Index:

Fetterer, F., K. Knowles, W. Meier, and M. Savoie. 2002, updated 2008. Sea Ice Index. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.

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