When Laura Larocca visited Denmark in 2019, the climate scientist sifted through thousands of old aerial photographs of Greenland’s icy coastline, which were rediscovered in a castle outside Copenhagen about 15 years ago.
Now housed in the Danish National Archives, the historical images inspired her and other researchers to reconstruct the territory’s glacial history and how it has changed amid a rapidly warming climate.
After digitizing thousands of archived paper images dating back to the 1930s, Larocca’s team combined them with satellite images of Greenland today to measure how much its frozen landscape has changed.
The comparison found Greenland’s glaciers have experienced an alarming rate of retreat that has accelerated over the last two decades. The study, published this week in the journal Nature Climate Change, found that the rate of glacial retreat during the 21st century has been twice as fast as the retreat in the 20th century.
Natural History Museum of Denmark/Niels Jakup Korsgaard
The work was “very time consuming, and it took a lot of people, a lot of hours of manual labor,” said Larocca, the lead author of the study and an assistant professor at Arizona State University School of Ocean Futures. “The change is stunning — it really highlights the fast pace at which the Arctic is warming and changing.”
Over the past several decades, the Arctic has warmed four times faster than the rest of the world, a 2022 study showed. The fallout of that warming is mounting. For the first time on record, it rained at the summit of Greenland — roughly two miles above sea level during the summer of 2021. Earlier this week, scientists found that northern Greenland’s huge glaciers, which were long thought to be relatively stable, now pose potentially “dramatic” consequences for sea level rise.
The Danish Agency for Datasupply and Infrastructure/Hans Henrik Tholstrup/University of Copenhagen
Natural History Museum of Denmark/Niels Jakup Korsgaard
What struck Larocca the most was how the Danish pilots who took the original photos had no idea they would be a major contribution to climate science nearly a century later.
“It is quite interesting that a lot of these photos were taken because of military operations,” she said. “So, they have ties with a lot of international and US history, as well. But it’s kind of neat how over 100 years later, we’re using these photos for science to document how much these glaciers have changed over time.”
The Danish Agency for Datasupply and Infrastructure/Hans Henrik Tholstrup/University of Copenhagen
Larocca said she hopes this new visual-heavy study will draw attention to the rapidly melting territory and the threat it poses to the world’s coastlines as sea level rises.
“[The paper] really reinforces that our choices over the next few decades and how much we reduce our emissions really matter to these glaciers,” Larocca said. “Every incremental increase in temperature will have significant consequences for these glaciers, and that swift action to limit global temperature rise will really help to reduce their future loss and contribution to sea level.”