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Scientists are studying thousands of "forgotten" glaciers in Greenland, and it's easy to guess the outcome

Scientists are studying thousands of “forgotten” glaciers in Greenland, and it’s easy to guess the outcome

Thanks to old aerial photographs, researchers have obtained a good picture of the evolution of so-called peripheral glaciers. And it probably won’t surprise you that the speed at which these glaciers are retreating has doubled in the past 20 years.

Glaciers act as a sensitive measure of climate change – one that can be easily observed. But what is worrying is that we have known for some time that glaciers have been shrinking rapidly since the mid-20th century. Things move quickly, especially in Greenland. At least, with the glaciers we know. However, Greenland also has a lot of “forgotten” glaciers, which we never actually had a clear picture of. So far.

Oceanic glaciers
Although there has been extensive research on the impact of climate change on Greenland, most scientists’ focus is primarily on the Greenland ice shelf, which covers about 80 percent of the land. However, little seems to be known about so-called “oceanic glaciers”. These are glaciers that are located on the edges or outside of an ice sheet or ice shelf. In the case of Greenland, oceanic glaciers are smaller ice masses scattered along the island’s coast. These glaciers are separate from the central ice shelf and often have direct contact with the surrounding ocean. They contribute to sea level rise when they melt and release ice into the ocean. And we don’t actually have a detailed picture of these specific glaciers yet. This deficiency is partly due to a lack of monitoring data.

It changes
in Recent study A team of scientists examined how thousands of these ocean glaciers will change between 1890 and 2022. They used satellite images and a special archive of old aerial photographs (more on that later) to create the most detailed overview to date. Thanks to this unique data, researchers have documented changes in the length of more than a thousand glaciers over the past 130 years. The results may already be clear. The team discovered that the retreat of glaciers has accelerated dramatically in the 21st century. In fact, in the past 20 years, the rate of retreat of these glaciers in Greenland has doubled. Glaciers in southern Greenland have lost an average of eighteen percent of their length, while glaciers in other regions have shrunk by between five and ten percent over the past twenty years.

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This map shows the change in position of a glacier in southern Greenland. Photo: Laura Larocca

In sum, although Greenland’s glaciers have already lost a lot of ice over the past century, the pace of this retreat has accelerated dramatically in the past two decades. Remarkably, these results are consistent across Greenland’s diverse climates and geography, even among the world’s northernmost glaciers. The results thus highlight the region’s vulnerability to rising temperatures due to human-induced climate change. “Our research puts the recent retreat of terminal glaciers in different climate zones in Greenland into historical perspective,” says study first author Laura LaRocca. “It suggests that the rate of retreat of these glaciers in the 21st century is largely unprecedented compared to previous centuries. The only exception is the glaciers of northeastern Greenland, where recent increases in snowfall may slow the retreat.”

Old pictures
The fact that we now have a better picture of these “forgotten” glaciers is due, as mentioned, to analysis of satellite images and thousands of historical aerial photographs. “Some of these images were taken during early mapping expeditions in Greenland, which were conducted from open planes,” says researcher Yarrow Oxford. “These ancient images take the dataset back to the era before satellite observations, when detailed observations of the cryosphere were rare. It is remarkable that we now have long-term data for hundreds of glaciers. This allows us to document more than a century of changes in the response of glaciers.” In Greenland Climate Change.

Over Greenland in an open plane. Image: Danish Agency for Data Supply and Infrastructure

Lack of data
Before the launch of Earth observation satellites in the 1970s, researchers lacked a full understanding of how temperature changes affected Greenland’s glaciers. There simply was no large-scale, detailed observational data available, or so the researchers thought. A major breakthrough came about fifteen years ago when long-forgotten aerial photographs of the Greenland coast were rediscovered in a castle outside Copenhagen. These images, now stored in the Danish National Archives, have allowed researchers to reconstruct the history of the glaciers. “Beginning in the 1930s, Danish pilots wearing polar bear skins conducted aerial mapping expeditions in Greenland, collecting more than 200,000 photographs of the island’s coast,” Larocca says. “In doing so, they also inadvertently recorded the condition of the peripheral glaciers.”

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Climate change
The research concludes that climate change explains the accelerating retreat of glaciers. This means that glaciers across Greenland respond quickly to changing temperatures. This highlights the critical importance of slowing global warming. “What we do in the coming decades will have a huge impact on the glaciers,” Larocca asserts. “Every increase in temperature really matters.”

As global temperatures rise, it is more important than ever to better understand how the melting of peripheral glaciers will affect rising sea levels and reliable freshwater sources. “Although peripheral glaciers represent only about four percent of Greenland’s total ice-covered area, they contribute up to fourteen percent of the island’s current ice loss, a disproportionate share,” Larocca explains. “If we look globally at all glaciers, with the exception of the Greenland and Antarctic ice shelves, they have contributed about 21 percent of the observed sea level rise over the past two decades. Therefore, these small ice masses are an important part of the problem.” Sea level rise. Millions of people around the world also depend on glaciers for fresh water, agriculture and hydroelectric power, so it is deeply concerning that we allow this to continue. The choices we make in the coming years will have a major impact on how much ice we eventually lose The end.