• FTP data access has been replaced by HTTPS. Note that FTP data access will still be available through 31 December 2023 but the link to it will no longer be available from this page.

NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration, Version 4
Data set id:
DOI: 10.7265/efmz-2t65
This is the most recent version of these data.
Version Summary
* CDR now begins 25 October 1978
* NSIDC-produced daily and monthly NASA Team (NT) and NASA Bootstrap (BT) variables are new included
* Four variables in the daily files and four variables in the monthly files have been renamed.
* Goddard-produced variables were removed
* Yearly aggregated files containing daily data and period-of-record aggregated files containing monthly data are available in addition to the daily and monthly NetCDF files.
* Gap filling implemented using spatial and temporal interpolation
* Arctic pole hole filled by spatial interpolation
* NSIDC’s BT algorithm has been updated to use Goddard’s BT version 3.1 algorithm
* Updated the NASA Team weather filter threshold for the Southern hemisphere instruments.
* In addition to the BT weather and land spillover filters, the NT filters are now also applied.
* Individual land masks have been merged into one composite land mask.


This data set provides a Climate Data Record (CDR) of sea ice concentration from passive microwave data. The CDR algorithm output is a rule-based combination of ice concentration estimates from two well-established algorithms: the NASA Team (NT) algorithm (Cavalieri et al. 1984) and NASA Bootstrap (BT) algorithm (Comiso 1986). The CDR is a consistent, daily and monthly time series of sea ice concentrations from 25 October 1978 through the most recent processing for both the north and south polar regions. All data are on a 25 km x 25 km grid. Note: A near-real-time version of this data set also exists to fill the gap between the time that this data set is updated through to the present. The data set is called the Near-Real-Time NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration (https://nsidc.org/data/g10016).
DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F8, DMSP 5D-3/F17, Nimbus-7
Data Format(s):
Temporal Coverage:
25 October 1978 to 31 December 2022
Temporal Resolution:
1 day
Spatial Resolution:
25 km
25 km
Spatial Reference System(s):
NSIDC Sea Ice Polar Stereographic North

NSIDC Sea Ice Polar Stereographic South
Spatial Coverage:
Blue outlined yellow areas on the map below indicate the spatial coverage for this data set.

Data Access & Tools

Help Articles

General Questions & FAQs

NSIDC currently archives passive microwave sea ice concentration products based on two algorithms: the NASA Team algorithm and the Bootstrap algorithm. Both algorithms were developed by researchers at the NASA Goddard Space Flight Center in the 1980s.

How to Articles

NOAA@NSIDC data recently transitioned to HTTPS. The directory structure has NOT changed, but the beginning of the URL has changed from: ftp://sidads.colorado.edu/pub/DATASETS/ to:
Currently three NOAA@NSIDC data sets are available in NOAA's PolarWatch Data Catalog. Please note that in the catalog the Climate Data Record (CDR) data sets are split up into Antarctic and Arctic data sets:
This external R tutorial guides you through an R script for the NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration data in PolarWatch: