• On Wednesday, May 29 from 9:00 a.m. to 11:00 a.m. (US Mountain Time), the following data collections may not be available due to a planned system maintenance: ASO, AMSR Unified, AMSR-E, Aquarius, High Mountain Asia, IceBridge, ICESat/GLAS, ICESat-2, LVIS, MEaSUREs, MODIS, Nimbus, SMAP, SnowEx, SSM/I-SSMIS and VIIRS. Users of the SMAP near real-time products should use the Persistent HTTPS File System for data access. 

  • This data set will be retired and no longer available for download on 27 May 2024. We recommend using the newest version of Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS (NSIDC-0079) data set as an alternative.

Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS, Version 3
Data set id:
DOI: 10.5067/7Q8HCCWS4I0R
There is a more recent version of these data.
Version Summary
Changes to this version include:

  • Intercalbration techniques between SMMR and F08, as well as F08 and F11 were changed to match sea ice area rather than sea ice extent.

  • Ocean tie points now change each day (similar to the ice tie points) based on brightness temperatures for that day.

  • The threshold for the lower limit for ice was relaxed to allow retrieval of ice at 10 percent ice concentration.


    This sea ice concentration data set was derived using measurements from the Scanning Multichannel Microwave Radiometer (SMMR) on the Nimbus-7 satellite and from the Special Sensor Microwave/Imager (SSM/I) sensors on the Defense Meteorological Satellite Program's (DMSP) -F8, -F11, and -F13 satellites. Measurements from the Special Sensor Microwave Imager/Sounder (SSMIS) aboard DMSP-F17 are also included. The data set has been generated using the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) Bootstrap Algorithm with daily varying tie-points. Daily (every other day prior to July 1987) and monthly data are available for both the north and south polar regions. Data are gridded on the SSM/I polar stereographic grid (25 x 25 km) and provided in two-byte integer format.
    DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F8, DMSP 5D-3/F17, Nimbus-7
    Data Format(s):
    Binary, Binary
    Temporal Coverage:
    1 November 1978 to 31 December 2022
    Temporal Resolution:
    • 1 day
    • 1 month
    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.
    Strengths and Limitations


    • Long-term continuous record, with complete daily coverage of the Antarctic and the Arctic (excluding the “pole-hole”) since August 1987, preceded by every-other-day coverage since late October 1978. This makes it useful for tracking climate trends and variability and as a large-scale climate indicator (Comiso and Nishio, 2008)
    • Thorough inter-calibration between sensors for consistency throughout record (Comiso and Nishio, 2008)
    • Dynamic algorithm coefficients that adjust daily to account for changing surface characteristics (Comiso et al., 2017)
    • Manual corrections and spatial and temporal interpolation to remove errors and fill in data gaps (Comiso and Nishio, 2008)
    • Concentrations are generally reliable within the ice pack (away from the ice edge) during cold (non-melt) conditions (Comiso and Nishio, 2008)
    • Microwave observations provide surface snow and ice coverage during cloudy and night-time (including polar night) conditions (Comiso and Nishio, 2008)
    • Useful input/validation of climate model simulations (National Center for Atmospheric Research Staff, 2017)


    • Low spatial resolution (25 km gridded) limits detail on concentration and precision of ice edge; is unsuitable for detailed mapping of ice concentration (Comiso et al., 1997)
    • Underestimates sea ice concentration during melt season (Kern et al., 2020) and/or when the ice is thin (Ivanova et al., 2015)
    • Potential errors due to physical temperature variations, particularly for extreme cold temperatures (Comiso et al., 1997)
    • False coastal ice can occur due to mixed land and ocean within a sensor footprint (Comiso and Nishio, 2008)


    Data Access & Tools

    A free NASA Earthdata Login account is required to access these data. Learn More

    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

    Many NSIDC DAAC data sets can be accessed using the NSIDC DAAC's Data Access Tool. This tool provides the ability to search and filter data with spatial and temporal constraints using a map-based interface.Users have the option to
    The NSIDC provides Python scripts for reformatting specific NSIDC SMMR-SSM/I-SSMIS data products in polar stereographic projections from NetCDF to binary.
    Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system. We provide basic command line Wget and curl instructions for HTTPS file system downloads below.