A moderately intense melt season for the Greenland Ice Sheet has continued in July, with an extended period of high temperatures and coastal melting in mid-July. Temperatures at Summit closely approached the freezing mark on July 13, but no obvious surface melting occurred there despite warm conditions on successive days recorded by National Oceanic and Atmospheric Administration (NOAA) instruments. Data gaps from the Special Sensor Microwave Imager/Sounder (SSMIS) satellite data delivery continue, requiring more interpolation for daily melt extents. We are attempting to transition to another microwave satellite sensor.
Overview of conditions
A prolonged period of extensive ice sheet melting from roughly July 7 to July 20 tipped the 2025 melt season to above the 1981 to 2010 average for total melt-day extent (Figure 1a). Through July 20, the 2025 cumulative melt extent—the sum of the daily melt areas for all days—ranks sixteenth in the 47-year satellite record.
On several days during the mid-July melt surge, melt reached the southern portion of the ice sheet, but the total number of days for that region continues to lag the region’s long-term average (Figure 1b). The west-central ice sheet coast continues to have above average melting, as does the east-central coast. In the north, the number of melt days is high near Pituffik Space Force Base (formerly Thule Air Force Base), but below average along the northwestern coast and far northeastern areas. So far this summer, the peak daily melt extent was on July 19, at 752,000 square kilometers (290,000 square miles) or about 45 percent of the ice sheet area.
A note on our method of determining melt days and the chart of daily melt extent shown here and on the webpage: For the graphic shown in the analysis reports, the team only reports melt extents in total square kilometers for days when the ice sheet is completely covered by midday satellite data overpasses. By contrast, the daily updates on the Ice Sheets Today webpage report the mapped extents using an interpolation across partial gaps in satellite data coverage.
Conditions in context
Temperatures over the Greenland Ice Sheet from July 7 to 20 were mostly near-average, although a large swath of the central and eastern areas were between 1 to 2 degrees Celsius (2 to 4 degrees Fahrenheit) above average. Below average atmospheric pressure occurred to the west of the Canadian Archipelago, and above average pressure developed over Iceland. This pattern drove air over the ice sheet from the southwest, creating the extended period of melting (Figure 2a). So far this season, (April 1 to July 18, not shown), above average conditions of 0.4 to 1.4 degrees Celsius (0.7 to 2.5 degrees Fahrenheit) have been the rule over the entire island except the far northeastern corner where temperatures are near average. Cool conditions have been prevalent over Baffin Island and northernmost Quebec. The above-average atmospheric pressure near Iceland has been a feature of the past several months as well, on average.
Net snow accumulation—total snow and rain, minus evaporation and melt runoff—has been mostly above average through spring but is now near-average as runoff near the coastal parts of the ice sheet are only slightly above the long-term average (Figure 2b).
Perfect Snowball Weather
Summit Station, at the top of the ice sheet, at 3,210 meters elevation (10,530 feet) experienced a string of days with peak temperatures just below the freezing mark. Air temperatures at mid-day were above -3 degrees Celsius (27 degrees Fahrenheit) on July 13, July 14, July 15, and July 18, which is not show in Figure 3. As is usually the case during warm events, the highest temperatures are associated with high air pressure. Melt events had been extremely rare prior to 2012 but have occurred several times since then as climate on the island has warmed.
Rapid drop in reflection
The mid-summer warmth over the Greenland Ice Sheet led to a sudden drop in the reflectivity, or albedo, of the snow surface. The average albedo for the entire ice sheet plummeted in mid-July (Figure 4). Albedo went from near-record high values—indicating a bright, white surface—for the date (2017 to 2024 reference period) to near-record low levels—a dark surface—in the data set. The ice sheet became darkest during the high-melt year of 2019. Reflectivity of the surface can change dramatically in both directions, with fresh snowfall suddenly brightening the surface at any point in the year, or strong melting that exposes dark ice and older snow, or initiating biological activity, all of which lower reflection off the surface.
