These satellite-derived images depict current sea ice conditions and trends. Long-term changes in Arctic sea ice are an index of climate change. Southern Hemisphere sea ice images are also available. For more information about current conditions and their significance, see Arctic Sea Ice News and Analysis.
If you have questions about the Sea Ice Index images that are not answered here, please see Frequently Asked Questions about Arctic Sea Ice and the full Sea Ice Index documentation.
The daily extent images show the extent of ocean covered by ice at any concentration greater than 15 percent. This snapshot of current ice conditions may be missing data (gray dots or areas). The location of the ice edge is not accurate enough for operational purposes. The median line shows the typical ice extent for that day, based on data from 1979 to 2000. We assume the area around the North Pole that the satellite does not image is covered by ice. These images are not archived.
An alternative daily sea ice extent product, the 4km Multisensor Analyzed Sea Ice Extent (MASIE) product, may be more suitable for your needs. The MASIE site includes an FAQ page that explains the differences between it and the Sea Ice Index daily product.
The daily extent graphs provide a snapshot of changes in ice extent for the last four months for both the Northern and Southern hemispheres. The solid blue line is a time series of extent for the last four months. The solid gray line is the 1979 to 2000 average over a 5-month period that is included as a comparison to the blue extent line. The light gray area around the 1979 to 2000 average line shows the two standard deviation range of the data, which serves as an estimate of the expected range of natural variability.
Each graph also includes comparisons for previous periods described as follows:
Northern Hemisphere
Along with current and median total extent, the daily extent graph also includes the extent during 2007, the year of the record low minimum extent (dashed green line). Note that during the transition across the calendar year, data from 2006 or 2008 is included for continuity of the plot with the 2007 record year. This comparison shows the substantial recent change observed in Northern Hemisphere sea ice. For more data on trends in extent, select Monthly from the View/Browse Sea Ice Images menu on the Sea Ice Index home page.
Southern Hemisphere
The daily extent graph for the Southern Hemisphere shows the previous year as a comparison (dashed blue line). Note that during the transition across the calendar, data from the year before or the year after the comparison year is included. For more data on trends in extent, select Monthly from the View/Browse Sea Ice Images menu on the Sea Ice Index home page.
Shows the percentage of ice cover for each 25 km square data cell that is more than 15 percent covered by ice. This snapshot of current ice conditions may be missing data (gray dots or areas). The circular area around the pole is not covered by the satellite. These images are not archived.
The total area covered by ice at greater than 15 percent monthly mean concentration is shown. The median line shows the typical ice extent for that month, based on data from 1979 to 2000. We assume the area around the North Pole that the satellite does not image is covered by ice. Monthly extent is a better measure of conditions from year to year than is daily ice extent. You can compare archived monthly images using the Browse Image Spreadsheet Tool (BIST).
This graph plots ice extent anomalies (the difference in the extent for the month minus the mean extent for that month over 1979-2000) for the most recent complete month. The trend, in percent change per decade, is obtained using least squares regression, and a 95 percent confidence interval for the resulting slope is given.
Shows that month’s average percentage of ice cover for each 25 km square data cell that is more than 15 percent covered by ice. The area around the North Pole that is not imaged by the satellite is left out.
The given month’s concentration is subtracted from concentration for the mean for the month in question from the 1979 - 2000 portion of the data set. Note that an area may have a positive anomaly for a given month while at the same time showing a negative trend in concentration over time.
Least squares regression is used to calculate the trend in ice concentration for that month at each roughly 25 km data cell. If no trend is detectable at a 95 percent confidence level, the data cell is white.
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