Archive photos of the Norwegian archipelago’s glaciers enabled researchers to reconstruct past melting and project ice mass loss under future climate change
19 January 2022
Glaciers in Svalbard, a Norwegian archipelago in the Arctic circle, are expected to lose ice at roughly double the current rate by the end of the century, even if the world meets its climate targets.
The islands are home to one of the world’s northernmost permanent settlements, a “doomsday vault” for the planet’s seeds and a back-up of open source code for future generations.
The area is seen as a preview of what is in store for other regions under climate change, as it has warmed at a rate of 1.7°C per decade since 1991, which is seven times the global average for the same period.
But understanding how Svalbard’s glaciers will respond to future warming is hampered by a lack of observations before the modern satellite era. To fill in the historical gaps, a Nordic-US team mined archives to find 5500 aerial stereo photographs of the glaciers taken in 1936 and 1938, before the second world war interrupted further surveys.
To get around the paucity of data between the photos and the modern satellite record beginning in 2010, the researchers used the fact that Svalbard has a high number of glaciers – more than 1500. Because some of these experience different climate conditions, they could use the 1930s photographs from across Svalbard to understand how the archipelago’s glaciers respond to climate, a strategy they called a space-for-time approach. They then used the information in the photographs, in combination with historical temperature and precipitation data, to model rates of ice loss across Svalbard between the 1930s and 2010.
To see what this century holds for the glaciers, the researchers ran four scenarios of low to high global climate change by 2100. They found that the rate at which glaciers thinned between 1936 and 2010 will increase at least 1.9 times under modest warming, to 0.67 metres a year. If humanity’s emissions go unchecked, in the most extreme scenario, that jumps to 0.92 metres annually.
Emily Geyman at the California Institute of Technology, who led the research, says the impacts will be greatest for local people. But the findings have global ramifications. “Svalbard is often treated as a canary in the coal mine. Studying the behaviour of its glaciers gives you a glimpse into the future for other regions,” she says.
The good news, writes Twila Moon at the University of Colorado, Boulder, in an accompanying journal article discussing the findings, is that the anticipated future ice loss is smaller than some previous projections. But Svalbard’s vanishing glaciers will still contribute to rising seas: Geyman found that their melt had already contributed 1.4 per cent of global sea level rise since 1936.
Geyman and her colleagues say one caveat is that their future projections don’t account for feedbacks that could change how future melt speeds up or slows down. However, she is excited that her space-for-time approach opens up an innovative way to better understand other glaciers where historical information is limited.
“Using an entirely different approach, it confirms the veracity of the other approaches, and that is reassuring,” says Jonathan Bamber at the University of Bristol, UK.
Journal reference: Nature, DOI: 10.1038/s41586-021-04314-4
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