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.