December 9, 2025 Dataset Open Access

Daily melt-pond fraction on Arctic sea ice from TERRA MODIS visible imagery

Sadikni, Remon; Kern, Stefan

Abstract: Reflectance measurements carried out at Terra MODIS bands 1, 3 and 4 are combined in a spectral un-mixing approach to estimate the melt-pond fraction on Arctic sea ice north of 60°N for months June through August for the years 2000 through 2024. The resulting data set has daily temporal sampling and is offered on a polar-stereographic grid (true latitude is 70°N) with 500 m x 500 m and 12.5 km x 12.5 km grid resolution. The data files contain, in addition to the melt-pond fraction, also the fraction of open water between the sea ice and the net sea-ice surface fraction, i.e. the fraction of sea ice without melt ponds. For information about the approach used and the validation of the data set offered here we refer to Rösel et al. (2012) and Sadikni and Kern (2025).

TableOfContents:

• 500 m x 500 m product: grid-cell fraction of melt ponds (on sea ice); grid-cell fraction of sea ice without melt ponds; grid-cell fraction of open water
• 12.5 km x 12.5 km product: grid-cell fraction of melt ponds (on sea ice); grid-cell fraction of sea ice without melt ponds; grid-cell fraction of open water; grid-cell_fraction_of_melt_ponds standard_deviation; grid-cell_fraction_of_sea_ice_without_melt_ponds standard_deviation; grid-cell_fraction_of_open_water standard_deviation; number of clear-sky 500 m grid cells; clear-sky mask

While the 12.5 km x 12.5 km comes with latitude and longitude values for each grid cell, those of the 500 m x 500 m product are provided in a separate netCDF file.

Note that the grid resolution of 12.5 km (and 500m) is only valid at the latitude at which the tangential plane of the polar stereographic projection touches the Earth's surface - here 70°N. North of this latitude the actual grid cell area is smaller, south of it it is larger (see also https://nsidc.org/data/user-resources/help-center/guide-nsidcs-polar-stereographic-projection#anchor-grid-distortion). In order to assist in the computation of the actual area (in km2) covered by melt ponds (or the other two surface types) we provide a netCDF file of the true area of each grid cell of the 12.5 km x 12.5 km product.

Technical Info:

• 500 m x 500 m product: dimensions: 13286 columns x 13293 rows; temporalExtent_startDate: 2000-06-01; temporalExtent_endDate: 2024-08-31; temporalResolution: daily; spatialResolution: 500; spatialResolutionUnit: meter; horizontalResolutionXdirection: 500; horizontalResolutionXdirectionUnit: meter; horizontalResolutionYdirection: 500; horizontalResolutionYdirectionUnit: meter; verticalResolution: none; verticalResolutionUnit: none; verticalStart: none; verticalEnd: none; instrumentName: Moderate Resolution Spectroradiometer (MODIS); instrumentType: 32-band imaging spectroradiometer; instrumentLocation: Earth Observation Satellite (EOS) Terra; instrumentProvider: NOAA/NASA
• 12.5 km x 12.5 km product: dimensions: 531 columns x 531 rows; temporalExtent_startDate: 2000-06-01; temporalExtent_endDate: 2024-08-31; temporalResolution: daily; spatialResolution: 12500; spatialResolutionUnit: meter; horizontalResolutionXdirection: 12500; horizontalResolutionXdirectionUnit: meter; horizontalResolutionYdirection: 12500; horizontalResolutionYdirectionUnit: meter; verticalResolution: none; verticalResolutionUnit: none; verticalStart: none; verticalEnd: none; instrumentName: Moderate Resolution Spectroradiometer (MODIS); instrumentType: 32-band imaging spectroradiometer; instrumentLocation: Earth Observation Satellite (EOS) Terra; instrumentProvider: NOAA/NASA

Missing data (either because the MOD09GA product has gaps or because the melt-pond fraction retrieval failed): 2000-08-06 to 2000-08-17; 2001-06-16 to 2001-07-02; 2002-06-15 to 2002-06-19; 2002-07-11; 2004-06-20 to 2004-06-22; 2005-07-21; 2008-08-06 to 2008-08-08; 2008-08-11; 2008-08-22; 2010-06-17; 2010-08-01; 2010-08-16; 2013-06-09; 2013-06-15; 2014-08-02; 2016-06-07; 2016-06-08; 2016-06-11; 2016-08-12; 2018-08-04; 2021-08-11; 2024-06-21; 2024-06-22; 2024-06-25.

Methods: For a description of the methods used see Sadikni and Kern, 2025.

Units:

• 500 m x 500 m product: 1, 1, 1
• 12500 m x 12500 m product: 1, 1, 1, 1, 1, 1, 1, 1

geoLocations: westBoundLongitude: -180.0 degrees East; eastBoundLongitude: 180.0 degrees East; southBoundLatitude: 60.0 degrees North; northBoundLatitude: 90.0 degrees North; geoLocationPlace: northern hemisphere

Size:

• 500 m x 500 m product: Single file: 2.1 GigaByte; zip-file or one month: 1.5 to 4.0 GigaByte (depends on gaps due to cloud cover); total volume (as unpacked netCDF): 4.87 TeraByte 
• 12.5 km x 12.5 km product: Single file: ~10 MegaByte; zip-file of one month: 60 to 100 MegaByte (depends on gaps due to cloud cover);  total volume (as unpacked netCDF): 22.8 GigaByte

Format: netCDF

DataSources: MODerate resolution Imaging Spectroradiometer MODIS aboard the Earth Observation Satellite (EOS) Terra collection 6.1 product MOD09A1 of the surface spectral reflectance: https://lpdaac.usgs.gov/products/mod09gav061/ (last access: Dec. 6, 2024).

Contact: remon.sadikni (at) uni-hamburg.de; stefan.kern (at) uni-hamburg.de

Web page: https://www.cen.uni-hamburg.de/en/icdc/data/cryosphere/arctic-meltponds.html