Airborne radar can detect groundwater beneath glaciers

Scientists have used airborne ice-penetrating radar to detect the groundwater running beneath the Hiawatha Glacier in Greenland.

Even though melting glaciers and polar ice sheets are among the dominant sources of sea-level rise, the water beneath them has remained hidden from airborne radar prior to this study. 

The research, led by Stanford University, opens up the possibility that water can be detected under other glaciers at a continental scale to help improve sea-level rise projections. 

Measurements of water beneath ice sheets is a critical component that is currently missing from glacial melt scenarios. Groundwater estimates are urgently needed, as this meltwater could greatly impact the rate of global sea level rise. 

For example, groundwater fluctuations could cause large chunks of ice to calve from glaciers. Without taking this into account, models assume that these glaciers will stay intact and melt slowly. 

“If we could potentially map water underneath the ice of other glaciers using radar from the air, that’s a game-changer,” said senior study author Professor Dustin Schroeder.

The data was collected in 2016 as part of NASA’s Operation IceBridge. While the experts suspected groundwater existed beneath the Hiawatha Glacier, they were still surprised to see their theory confirmed in the analyses. “When you see these anomalies, most of the time they don’t pan out,” said study lead author Jonathan Bessette.

Based on the airborne radar signal, the researchers constructed two possible models to describe Hiawatha Glacier’s geology. They determined it was either frozen land with thawed ice below it, or porous rock that enables drainage. Each of these scenarios has a different implication for how Hiawatha Glacier will respond to global warming.

According to Schroeder, groundwater systems play a more significant role than what scientists currently model in ice sheets for sea-level-rise projections. The researchers hope their findings will prompt further investigation of the possibility for additional groundwater detection using airborne radar.

“What society wants from us are predictions of sea level – not only now, but in futures with different greenhouse gas emission scenarios and different warming scenarios – and it is not practical to survey an entire continent with small ground crews,” said Schroeder. 

“Groundwater is an important player, and we need to survey at the continental scale so that we can make continental-scale projections.”

The study is published in the journal Geophysical Research Letters.

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By Chrissy Sexton, Earth.com Staff Writer