Diagram: Arctic sea ice extent since 1972

Arctic sea ice extent (total area of at least 15% ice concentration) since 1972.

Diagram: Antarctic sea ice extent since 1972

Antarctic sea ice extent (total area of at least 15% ice concentration) since 1972.

Click on the image to enlarge. Annual Arctic sea ice extent (total area of at least 15% ice concentration) for selected years since 1979.		Click on the image to enlarge. Annual Antarctic sea ice extent (total area of at least 15% ice concentration) for selected years since 1979.
Click on the image to enlarge. Annual Arctic sea ice extent (total area of at least 15% ice concentration) for the last 6 years and the minimum year 2012.		Click on the image to enlarge. Annual Antarctic sea ice extent (total area of at least 15% ice concentration) for the last 7 years.

Time Series Of Sea Ice Extent

To adapt data from a newer source to the data from an older source, the newer data were linearly transformed such that both mean and standard deviation or the newer time series matched the mean and standard deviation of the older time series in the overlap period.

In addition, the data are smoothed by a 5-day running mean. Consequently, the current day and the day before are only averaged over three respectively four days and might still vary slightly for two (resp. one) days

Since July 3, 2012, AMSR2 data is displayed which is adapted with the same parameters as its predecessor AMSR-E. The fit parameters are not deduced by comparing it during an overlap period to another time series. Hence, the data ought to be treated with caution until confirmation by independent sources.

The diagrams show sea ice extent data since 1979. The complete time series is composed of observations from different sensors, using different sea ice concentration retrieval algorithms and adaptations to each other using certain overlap periods: (1): Merged ESMR, SMMR, and SSM/I-SSMIS Sea Ice Extent from NSIDC (2): See information on this data set at NSIDC
#	Period	Algorithm	Sensor, Frequencies, Source	Adapted to	Overlap period
1.	1972 - 2002	NASA Team	SMMR & SSM/I, 19 and 37 GHz from NSIDC(1)	#2.	1989 - 2002
2.	Oct 26, 1978 - Dec 2010	NASA Team	Sea ice concentrations from NIMBUS-7 SMMR and DMSP SSM/I-SSMIS passive microwave data, 19 and 37 GHz, from NSIDC(2)	reference only, but not part of the time series because of some gaps 1978 - 1988
3.	2003 - Oct 4, 2011	ASI	AMSR-E, 89 GHz	#2.	2002 - 2007
4.	Oct 5, 2011 -Jul 2, 2012	ASI	SSMIS F-17, 91 GHz	#3.	Sep 2010 – Sep 2011 (using SSMIS F-17 data)
5.	Jul 3, 2012 to date	ASI	AMSR2, 89 GHz	#3. (same fit parameters used)	Jul 3, 2012 to date

Time Series Data

Text files containing the total sea ice extent in the northern hemisphere until end of 2024 can be found here (extent_n_19720101-20241231_amsr2.txt) and for the southern hemisphere here (extent_s_19730101-20241231_amsr2.txt). The daily data of the current year 2025 are available here (extent_n_2025_amsr2_smooth.txt) for the North and here (extent_s_2025_amsr2_smooth.txt) for the South.

More data can be found in the Data Archive. To quickly browse datasets, please have a look at the Data Browser.

How to cite

Please help maintaining this service by properly citing and acknowledging if you use the data for publications:
Spreen, G., L. Kaleschke, and G.Heygster (2008), Sea ice remote sensing using AMSR-E 89 GHz channels J. Geophys. Res.,vol. 113, C02S03, doi:10.1029/2005JC003384.

The gridded data from years 2002-2018 are also available at the data publisher PANGAEA, one data set each for Arctic and Antarctic, AMS-E-based and AMSR2-based:

Melsheimer, Christian, Spreen, Gunnar (2020): AMSR-E ASI sea ice concentration data, Arctic, version 5.4 (NetCDF) (June 2002 - September 2011). PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.919777 (DOI registration in progress).

Melsheimer, Christian; Spreen, Gunnar (2020): AMSR-E ASI sea ice concentration data, Antarctic, version 5.4 (NetCDF) (June 2002 - September 2011). PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.919778 (DOI registration in progress).

Melsheimer, Christian; Spreen, Gunnar (2019): AMSR2 ASI sea ice concentration data, Arctic, version 5.4 (NetCDF) (July 2012 - December 2018). PANGAEA, https://doi.org/10.1594/PANGAEA.898399

Melsheimer, Christian; Spreen, Gunnar (2019): AMSR2 ASI sea ice concentration data, Antarctic, version 5.4 (NetCDF) (July 2012 - December 2018). PANGAEA, https://doi.org/10.1594/PANGAEA.898400

Contact

For questions regarding the data please contact Gunnar Spreen or Christian Melsheimer.

Institute of Environmental Physics, University of Bremen, Germany.