The National Snow and Ice Data Center (NSIDC) has released Version 6 of the NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration data set and Version 4 of the Near-Real-Time NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration data set. These new versions provide daily and monthly sea ice concentration data for the north and south polar regions from 25 October 1978 to the present, on a 25 km × 25 km polar stereographic grid.
The main changes in these new versions include the following:
- Added AMSR2 as the input brightness temperature source beginning 1 January 2025.
- Removed the AMSR2 prototype sea ice concentration (prototype_am2 group) that was included in CDR Version 5.
- Fixed a bug that allowed sea ice concentration values less than 10% to be considered during land spillover corrections.
- Updated Python code to use current versions of core libraries, including NumPy and Xarray.
For detailed information about these changes, a comprehensive overview of CDR Version 6, and comparisons with Version 5, please refer to NSIDC Special Report 29:
https://nsidc.org/sites/default/files/documents/other/nsidc-special-report-29.pdf
Note that the older versions of these two data sets (CDR Version 5 and Near-Real-Time CDR Version 3) are also being retired. As of 15 January 2026, they will no longer be updated. However, the data will remain available until June 2026.
Data set DOIs
CDR Version 6: https://doi.org/10.7265/b18j-z797
Near-Real-Time CDR Version 4: https://doi.org/10.7265/tm2n-1m33