One of the 200,000 photos collected by Danish pilots (from open-cockpit airplanes) of Greenland's coastline. Credit: Danish National Archives
Key points:
- Using satellite images and a unique archive of historical aerial photos, researchers compiled the most complete picture of Greenland’s outlying glaciers to date.
- They found glacier retreat accelerated dramatically in the 21st century.
- The study focused on peripheral glaciers, which represent only about 4% of Greenland’s total ice-covered area, but contribute 14% of the island’s current ice loss.
According to a multiyear collaborative effort between the United States and Denmark, the rate of glacial retreat during the 21st century is twice as fast as retreat during the 20th century. And, despite the range of climates and topographical characteristics across Greenland, the findings are ubiquitous, even among Earth’s northernmost glaciers.
The researchers say the findings underscore the region’s sensitivity to rising temperatures due to human-caused climate change.
To piece together the magnitude of glacier retreat, the research team combined satellite images with historical aerial photographs of Greenland’s coastline, which is dotted with thousands of glaciers that are separate from the island’s massive central ice sheet. With these one-of-a-kind data, the researchers documented changes in the lengths of more than 1,000 of the country’s glaciers over the past 130 years.
The study found that climate change explains the accelerated glacier retreat the researchers saw, and that glaciers across Greenland respond quickly to changing temperatures. This highlights the importance of slowing global warming.
“This work is based on vast analyses of satellite imagery and digitization of thousands of historical aerial photographs—some taken during early mapping expeditions of Greenland from open-cockpit airplanes,” said Northwestern’s Yarrow Axford, a senior author of the study. “Those old photos extend the dataset back prior to the satellite era, when widespread observations of the cryosphere are rare. It’s quite extraordinary that we can now provide long-term records for hundreds of glaciers, finally giving us an opportunity to document Greenland-wide glacier response to climate change over more than a century.”
While climate change’s effects on Greenland are well studied, most researchers focus on the Greenland Ice Sheet, which covers roughly 80% of the country. But fluctuations in Greenland’s peripheral glaciers— the smaller ice masses distinct from the ice sheet that dot the country’s coastline—are widely undocumented, in part due to a lack of observational data.
As global temperatures increase, it has become more imperative than ever to better understand how these melting glaciers will affect rising sea levels and reliable sources of fresh water.
“Peripheral glaciers only represent about 4% of Greenland’s total ice-covered area, but they contribute 14% of the island’s current ice loss—a disproportionately large portion,” said Laura Larocca, the study’s first author. “If you look globally at all glaciers that are distinct from the Greenland and Antarctic Ice Sheet, they have contributed roughly 21% of observed sea level rise over the last two decades. So, these smaller ice masses are an important part of the sea level problem.”