Warming has more impact than cooling on Greenland's ‘firn’

In this study, researchers found warming temperatures are rapidly changing how efficiently firn can store meltwater, and cooling temperatures may not help it fully recover as much as scientists might have hoped.

"The warming depletes what we call the 'firn air content' or the 'sponginess," Thompson-Munson said. "So you lose more of the sponginess due to warming than can be regained due to cooling. And it's important because this porous firn can buffer the ice sheet's sea level rise contribution."

To understand how firn responds to both warming and cooling temperatures, the team used a physics-based computer model called SNOWPACK, and honed in on one variable: temperature. The study is the first of its kind in two ways. First, researchers looked at the impacts of both warming and cooling temperatures on Greenland firn. Second, the scope of the research covered the entire ice sheet, while previous studies focused on smaller geographical areas.

"The Greenland ice sheet loses mass faster under warming than it gains mass under cooling," Kay said. "The key advance of this study is that Greenland's firn contributes to this greater warming-than-cooling asymmetric response."

Thompson-Munson said the study brings up an important question regarding geoengineering and the ability to reverse our Earth's warming. Any geoengineering concepts designed to decrease temperatures in the Arctic might not preserve ice and snow as efficiently as imagined; the degree of cooling will have to exceed the degree of warming to help firn and glaciers return to normal.

"To get back to initial conditions, we'd have to cool a lot more or start changing other variables as well," Thompson-Munson said. "It's hard to reverse what we've already done."