Snow Melt Onset Over Arctic Sea Ice from SMMR and SSM/I-SSMIS Brightness Temperatures, Version 5
Data set id:
This is the most recent version of these data.
Version Summary
Changes to this version include:

Extended the data record through 2022; and reprocessed the entire data set using a newer version of the sea ice extent masks within the snow melt onset algorithm.
The Advanced Horizontal Range Algorithm (AHRA) has been updated to have a variable start date. The algorithm start date is now defined as the first day following the day of the annual maximum sea ice extent (SIE), making the first possible melt onset date as the day after the sea ice reaches its maximum extent. To derive the sea ice mask and identify maximum annual SIE, the cdr_seaice_conc variable was used as daily sea ice concentrations.


This data set includes yearly snow melt onset dates over Arctic sea ice derived from Scanning Multichannel Microwave Radiometer (SMMR), Special Sensor Microwave/Imager (SSM/I), and the Special Sensor Microwave Imager/Sounder (SSMIS) brightness temperature measurements. The data are gridded to the 25 km Northern Hemisphere Polar Stereographic projection and available from 1979 through 2022. One browse image is available for each year. This data set also contains value-added statistics for each grid cell, including: mean melt onset date, latest (maximum) melt onset date, earliest (minimum) melt onset date, range of melt onset dates (the difference between maximum and minimum onset dates), and the standard deviation of melt onset dates. One browse image is also provided for each statistical field.
DMSP, DMSP 5D-2/F11, DMSP 5D-2/F13, DMSP 5D-2/F8, DMSP 5D-3/F17, Nimbus-7
Data Format(s):
Temporal Coverage:
1 January 1979 to 31 December 2022
Temporal Resolution:
  • 1 year
Spatial Resolution:
  • 25 km
  • 25 km
Spatial Reference System(s):
NSIDC Sea Ice Polar Stereographic North
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 of annual snow melt onset dates on Arctic sea ice since 1979. The 43-year record is useful for monitoring climate trends and inter-annual variability (Bliss & Anderson, 2014; Box et al., 2019; Markus et al., 2009).
  • Weather filtering implemented in the AHRA algorithm reduces effects of short-term weather interference in melt onset detection (Drobot & Anderson, 2001).
  • The melt onset dates are fully reprocessed with the most up to date source data. Source data from different sensors are fully inter-calibrated for a consistent time series (Bliss, forthcoming).
  • Newly implemented algorithm start date methodology improves melt onset date detection on the ice periphery, better reflecting variability in the annual sea ice growth cycle (Bliss et al., 2017; Bliss, forthcoming).


  • Only one melt onset date is archived per year at each sea ice grid cell, thus, any freeze/thaw conditions that occur following the melt onset date are not captured.
  • Passive microwave-based melt onset date data products have higher uncertainties in regions of thin ice or low sea ice concentration where open water may be mistaken for melt (Bliss et al., 2017).
  • Low spatial resolution of the gridded data (nominally 25 km) make it difficult to ground truth melt onset dates with in situ observations or cross-compare with other data sources (Bliss & Anderson, 2018).

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