Melting permafrost across Arctic regions has already caused highways to buckle and homes to sink. A new study conducted in the north of Alaska helps explain why rising temperatures are hitting roads, airports and other infrastructure particularly hard.

Researchers who monitored temperatures and melting near Prudhoe Bay on Alaska’s North Slope documented how the thawing of frozen ground beneath a highway tended to spread laterally to the side of the road, with the melting process accelerated by snow accumulations and puddling. Those interactions led to more rapid thawing than in areas of undisturbed permafrost. 

Researchers also found that melting in their test area, alongside a highway that runs atop permafrost, followed a two-phase process — a gradual initial thaw, followed by an accelerated process once warming exceeded a critical point. 

The upshot is that in Alaska and other areas of permafrost thaw, current models may “strongly underestimate the timing of future Arctic infrastructure failure,” the researchers wrote in a study recently published in The Cryosphere, a journal of the European Geosciences Union. That will likely lead to high replacement costs for infrastructure by the middle of the century, they wrote, adding that the timing of any structural failure and the “risk of disasters caused by damage to sensitive infrastructure” including pipelines and fuel storage remains to be studied. 

Arctic temperatures are rising at more than twice the rate of the global average, a dynamic that has reverberated in the form of extreme weather in distant places like Texas. Across the Arctic, the warming has led to melting in ground layers that previously remained frozen year-round, spurring housing crises from Alaska and Canada to Russia. A few years ago, Russia placed the cost of Arctic warming at $2.3 billion a year. About 18% of rural Alaskan communities are at high risk due to permafrost degradation, according to one 2019 study.

Read More: Melting Permafrost and the Housing Crisis in the Arctic

Scientists have registered ice degradation in permafrost as far back as 1949. Still, engineers of much of the infrastructure built before the 1990s — including roads, pipelines, airports, shipping facilities and other buildings constructed on permafrost — failed to take climate change into account and assumed that permafrost beneath structures would be a constant, said Vladimir Romanovsky, a professor at the Geophysical Institute of the University of Alaska Fairbanks, one of the study’s 13 authors. To model melting dynamics, the researchers, led by Thomas Schneider von Deimling of Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Potsdam, monitored temperatures at several points along the Dalton Highway, about 10 miles south of the Prudhoe Bay oil fields, the largest oil producer in U.S. history. 

Because the ice content of permafrost varies, so does the potential impact of thawing. At the upper end, some areas around Fairbanks contain 80% to 90% ice, Romanovsky said — which means rising temperatures could deplete most of the surface below structures.

Changes to permafrost haven’t been linear over the years, making degradation challenging to forecast, Romanovsky said. Permafrost around Fairbanks warmed from the late 1970s to the 1990s, but colder air temperatures and increased snow in the 2000s slowed the destabilization. Since the mid 2010s, he said, a stronger warming wave has accelerated the process. 

“By now, pretty much all engineers agree that they have to include climate change and related changes to permafrost in their calculations,” Romanovksy said. As for existing structures, he says there’s time to adapt but that solutions will be expensive — and therefore likely to be applied unevenly. “Engineers can go and solve problems of permafrost degradation if the infrastructure is critical and there’s money to do it,” he said. “But many local communities don’t have money to fight these changes.”