Late Heat Wave Causes Massive Melt in Greenland

Sep. 9 () –

Vast areas on the Greenland ice sheet are melting this September, an unprecedented widespread phenomenon with potential implications for the ice sheet next year.

Greenland’s melting season typically runs from May through early September. The 2022 season got off to a slow start, as below-average air temperatures in May and June culminated in the least amount of spring melt in a decade. Melting continued at a moderate rate throughout the summer, peaking in mid-July. At its peak on July 18, the surface melt encompassed 688,000 square kilometers of the ice sheet.

A late-season heat wave has triggered a major melt event from September 1-6. At its peak on September 3, the melt spanned 592,000 square kilometers of the ice sheet, the second-largest melt peak of the 2022 season and the largest of any September since record-keeping began in 1979. Melt events of this magnitude are unlikely in September because seasonal temperatures tend to drop as hours of sunlight decrease.

But unlikely does not mean impossible, According to the NASA Earth Observatory. The September 2022 melt was the result of a weather system that brought warm, moist air over the ice sheet. The map at the top of this page shows how air temperatures from August 30 through September 5, 2022, compare to temperatures for the same period in 2020, when melting was more typical. Temperatures in some places soared 15°C higher than in 2020. At the NSF (National Science Foundation) Summit Station, temperatures were reported to be above freezing (0°C).

The map was derived from the Goddard Earth Observing System (GEOS) model and represents the air temperature at 2 meters (about 6-7 feet) above the ground. The modeled data, which uses mathematical equations that represent real-world physical processes, provides a broad, estimated view of a region where ground-based weather stations are few and far between.

About 1.7 million square kilometers of Greenland is covered in ice, the largest ice sheet on the planet outside of Antarctica. Ice gains mass through snow accumulation and loses it through surface melting and runoff, calving of icebergs, and melting at the bottom of tidewater glaciers. As air and water temperatures have risen in recent decades, ice losses have outstripped gains, which contributes to sea level rise.

According to Lauren Andrews, a glaciologist with NASA’s Office of Global Modeling and Assimilation, melt events like the one in early September 2022 can affect current and future ice losses.

“When the melt season extends beyond its typical length, the total amount of mass lost during the melt season obviously increases,” said Andrews. “But what is not so obvious is that a longer melt season also delays the accumulation of snow on the surface. This, in turn, may affect the initial intensity of the subsequent melt season.”

Less snowpack in winter means snow can melt more quickly in spring, exposing large swaths of comparatively dark bare ice. Compared to bright new snow, these darker surfaces absorb more solar energy, which amplifies the melting during the long sunny days of the Arctic.