A pair of satellite images from 50 years apart reveals striking changes to the glaciers and ice caps in Northwest Greenland.
The image pair spans the era of the Landsat mission so far, revealing changes across a peninsula north of Thule Air Base. The Multispectral Scanner System (MSS) on Landsat 1 took the image on September 3, 1973. The second image was acquired on August 20, 2022, by the Operational Land Imager (OLI) on Landsat 8, shows the same area 49 years later.
The 1973 image resembles natural color, but it is actually in false color. This becomes apparent along some of the ice-free areas where vegetation is in red. But with very little vegetation in the northwest of Greenland, the false-color Landsat 1 image appears similar in color to the natural-color Landsat 8 image. Bare land is brown and ice and snow are white.
The similarity in color makes it easy to see where the glacial ice has narrowed, retreated and in one case surged. One can notice the clear retreat of the large glaciers flowing into the water of Wolstenholme Fjord. Smaller glaciers and isolated ice caps throughout the image all generally shrink, and in some places disconnect from each other. In contrast, the large glacier flowing west from Nunatarssuaq Ice Cap appears to lengthen. This surging behavior might be caused by ice at higher elevations of the ice cap draining into the glacier.
In 2022, the edges of the ice caps and glaciers generally appear much grayer than in 1973. A warm summer in 2022 melted away more of the bright-white snow cover exposing dirtier, darker ice. Fresh snowfall may also be present in the 1973 image, although September is early in the accumulation season, which largely runs from September until May.
The study showed that peripheral glaciers, which are relatively small and disconnected from the main ice sheet, account for a small proportion of Greenland’s ice-covered area (about 4 percent). However, peripheral glaciers account for 11 percent of the island’s ice loss, which makes them outsized contributors to current sea level rise.
Peripheral glaciers in northwest Greenland have been losing approximately 3.5 to 7 gigatons of ice per year in recent decades. That is more than the peripheral glaciers in southeast and southwest Greenland are losing, but less than in north Greenland, where peripheral glaciers have been losing up to 26 gigatons per year since the early 2000s.
https://earthobservatory.nasa.gov/images/150267/a-half-century-of-loss-in-northwest-greenland