Table 13 provides a summary of the version history of this product. 

Version 3 Update Notice

01 March 2018

The climatology presents a summary of the long-term record of satellite-derived sea ice concentrations calculated using the NASA Team (NT) and Bootstrap (BT) algorithms. Prior to this update, the climatology included NT and BT data from 1978 through 2015. Because no changes were made to the NT data that were used in the previous version of this product, only small differences due to averaging data from an additional year are expected.

Findings

Because the ice persistence and monthly climatology fields are based on the NT data set, there are only small differences. A few grid cells have small changes, but overall there are minimal changes in the ice persistence and monthly climatology fields in both hemispheres for all months.

The NT-derived fields of regional ice extent and areas similarly consist of just the additional year of data; the values through the end of 2015 are unchanged.

The BT-derived fields do show widespread changes because the underlying Bootstrap data have been updated to a new version. While monthly hemisphere-wide areas show average area increases of less than 2%, some smaller regions—for which even small changes in ice area can be a large percentage of the region’s total—can show much larger percentage changes.

While monthly hemisphere-wide areas show average area increases of less than 2%, some smaller regions–for which even small changes in ice area can be a large percentage of the region’s total–can show much larger percentage changes.

Recommendations

The updated Sea Ice Trends and Climatologies data are consistent in format and value with the previous version and can be used for the same purposes. Because the Bootstrap data have been updated for the entire time series, users of the Bootstrap data should update those applications with the entire Bootstrap data set. 

Version 2 Update Notice

01 January 2017

In the Northern Hemisphere, very small differences in sea ice extent were found: less than 0.2 percent for the NASA Team algorithm and less than 0.05 percent for the Bootstrap algorithm.

Differences in Northern Hemisphere sea ice area were also small. Most years had less than 0.05 percent. Differences in the Bootstrap sea ice area were generally less than 0.01 percent.

For both the Bootstrap and NASA Team algorithms, the differences in the Southern Hemisphere were negligible.

These small differences are found in the persistence and monthly climatology data also. The Northern Hemisphere monthly fields showed no difference in 95-98 percent of the sea ice values, and fewer than 0.02 percent of pixels had differences in ice concentration of greater than 2 percent.

Version 1 Update Notice

28 July 2014

Data are now available through 31 December 2013 for all Sea Ice Trends and Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS data sets.

Version 1 Update Notice

04 September 2013

Reprocessing is complete and updated data are now available through 31 December 2012 for all Sea Ice Trends and Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS data sets. With this update, the following changes have been implemented:

Total Ice-Covered Area and Extent

The cutoff value which defines a region as ice-covered or not ice-covered has been adjusted from 14.8 percent to 15 percent to more closely match the methodology used to calculate other sea ice extent and area products at NSIDC.

Ice Persistence and Monthly Climatology of Sea Ice Concentration (Monthly Means)

• Includes the new 15 percent cutoff value described above.
• To prevent inconsistencies between different algorithms, these parameters are now calculated exclusively using the NASA Team algorithm.

Monthly Ocean Masks and Maximum Extent Masks

The ocean mask files and maximum extent mask files were removed as they are not the masks used in the production of these data sets.

This most recent reprocessing also rectifies two previous releases of these data sets that contained erroneous data. In January/February of 2012, and May of 2013, the products were to have contained data from 2007 to 2010 and from 2010 to 2011, respectively. However, the climatology products contained data only through 2007. We recommend replacing previously downloaded 2010 and 2011 climatology data files with the climatology files that now extend through 2012. The Total Ice-Covered Area and Extent data set did contain post-2007 data, but reprocessed data utilizing the new methodology are available in the 2012 release.