Surface melting on the Greenland Ice Sheet is on a slightly above-average track for the 2025 melt season, with melt along the western coast leading the way. Overall, total melt-day extent as of June 20 is thirteenth highest in the 47-year satellite record. However, ongoing changes in the operation and data transfer from our main Special Sensor Microwave Imager/Sounder (SSMIS) satellite system for melt observations is leading to frequent gaps in coverage.
Overview of conditions
Melting so far this year on the Greenland Ice Sheet has been limited to coastal areas but extends to the lower-elevation perimeter of the island’s ice sheet. The number of melt days is 3 to 5 days above average in these near-coastal areas, but 1 to 4 days below average at higher elevations in the southern part of the ice sheet (Figure 1a). However, gaps in satellite data coverage are hindering our ability to track all daily melt extent totals.
An early melt surge in mid-May set a daily record for May 19 in the 47-year satellite coverage period, with melt occurring primarily along the southwestern side of the ice sheet. A more extensive melt event in mid-June led to a peak surface melt extent of around 30 percent of the ice sheet, and melt area exceeded 15 percent of the ice sheet area from June 15 to 25 (Figures 1b and 1c). This second melt event was strongest along the western boundary of the ice sheet, but over the length of the event it completely encircled the island. Higher elevations, greater than about 1,500 meters (4,900 feet), have so far had very little melting in 2025, although on June 18, the National Oceanic and Atmospheric Administration (NOAA) near-surface air temperatures at Summit briefly reached -1 degrees Celsius (30 degrees Fahrenheit).
Figure 1b. This map illustrates the cumulative melt days on the Greenland Ice Sheet from June 10 to June 25, 2025. — Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
Figure 1c. This map illustrates the difference from the 1981 to 2010 average melt days from June 10 to 25, 2025. — Credit: National Snow and Ice Data Center/T. Mote, University of Georgia
Conditions in context
The western side of the ice sheet has been slightly warmer than average in June, with temperatures at 0.4 to 0.8 degrees Celsius (0.7 to 1.4 degrees Fahrenheit) above average in the central western ice margin (Figure 2). Below average conditions existed in June along the eastern coast, especially near Scoresby Sund, where temperatures were 1.6 degrees Celsius (2.9 degrees Fahrenheit) below average. Below average air pressure over Iceland drew air down from the north, but average circulation along the western margin slightly favored winds from the south.
Modeled net snow accumulation—total snow and rain, minus evaporation and melt runoff—had been mostly above average through Greenland's spring, especially over the over the northern half of the island.
Darkness fell upon the land
Albedo, or reflectiveness, of the snow surface on the Greenland Ice Sheet drops as the melt season progresses because of several effects. Even with air temperatures below freezing, snow on the surface coarsens over time, which leads to more light absorption. As melting begins, meltwater wetting the snow lowers the reflectivity up to 20 percent. With more extensive melting, darker meltwater lakes appear, and meltwater runoff exposes coarse blue ice and dust-laden ancient ice at the edges of the ice sheet.
As of June 20, most of the Greenland Ice Sheet was darker than average for the date because of many exposed aging snow surfaces, with darker ice and a few lakes along the western margin (Figure 3). However, an unusually dark area in the south-central ice sheet area is likely caused by a problem with the data, such as cloud presence or processing issues. At the southern end of the ice sheet, fresh snowfall brightened the surface.
Hanging together, despite their differences
The NSIDC Greenland Today Ice Sheet surface melting report regularly refers to several sources of data. Our leading indicator of melting is based on passive microwave satellite data from a long series of satellites starting in late 1978. However, we look at and often cite several other related indicators of melt. Figure 4 shows how these different parameters agree overall with some important differences at times.
In Figure 4, NSIDC’s melt extent index (adapted from Mote et al., 1995) initially shows little melt in early spring, a time when the snowpack warms and the snow grains coarsen but do not melt. The Modèle Atmosphérique Régional (MAR) climate and ice sheet model (Fettweis et al., 2017; version 3.14) also calculates a melt extent index, and melt production volume, from a complex numerical approach that accounts for weather conditions, conditions within the snow, energy balance of the snow surface, amount of recent (seasonal) snowfall, and snow albedo or reflectivity. While this tracks the larger trends in the NSIDC satellite-derived melt extent, there are differences mainly because the model products are daily averages while the NSIDC index is sensitive to the presence of meltwater within the snowpack only at the time when the satellite passes over Greenland. Therefore, the satellite product could underestimate or overestimate the presence of meltwater if the satellite pass occurs early or late in the day rather than noon or early afternoon. Particularly for the mid-June widespread melt event, the satellite algorithm produced more extensive melting than the weather model.
Weather parameters themselves, such as 2-meter Temperature (interpreted for 6.5 feet above the surface), and the National Center for Environmental Prediction (NCEP) temperature at the 700 millibars pressure level (about 3,000 meters or 10,000 feet above the surface) all show broadly similar trends. A further indication of warm and melting conditions—and the likelihood that they will persist—is the Greenland Blocking Index (GBI) measured at the 500 millibars pressure level (about 5,500 meters or 18,000 feet). The GBI is a measure of atmospheric blocking, or persistent high pressure, over a regional area that includes Greenland.
Further reading
Fettweis, X., J. E. Box, C. Agosta, C. Amory, C. Kittel, C. Lang, D. Van As, D., H. Machguth, and H. Gallée. 2017. Reconstructions of the 1900–2015 Greenland ice sheet surface mass balance using the regional climate MAR model. The Cryosphere, 11(2), 1015-1033, doi:10.5194/tc-11-1015-2017.
Mote, T. L. and M. R. Anderson. 1995. Variations in snowpack melt on the Greenland ice sheet based on passive-microwave measurements. Journal of Glaciology, 41(137), 51-60, doi:10.3189/S0022143000017755.