Significantly more ice in Greenland’s glaciers may be exposed to warming ocean waters than previously thought, new research suggests. Indeed, more than half the ice sheet may be subject to the melting influence of the sea.
These are the latest conclusions of a detailed mapping project exploring the topography of the seafloor and bedrock around and beneath Greenland’s glaciers.
Published in their final form last week in the journal Geophysical Research Letters, the maps draw on a variety of data sources, including satellite radar and aerial imagery, as well as special sonar data collected on ship expeditions to the front of the ice sheet. (An earlier, although nearly identical, version of the paper was published online in September.)
Included in the new paper are some of the most detailed data yet on the depths of the canyons and fjords scarring the Greenland coast, which carry water in from the sea to lap against the ice. The results suggest that the western and northern regions of Greenland are most exposed to the influence of ocean water. Out of 139 ocean-touching glaciers the team identified, they also found that 67 rest in waters 200 meters (about 650 feet) or more below sea level, where warm water is typically found—at least twice as many as previously thought.
And, worryingly, the research suggests that as these glaciers melt and retreat backward, the shape of the seabed will continue to expose many of them to warm ocean water for hundreds of miles as the ice moves inland.
The study also finds that the Greenland ice sheet may contain more ice, with a greater potential to raise global sea levels, than previous research has suggested—about 2.75 inches more, to be exact. Altogether, the new study suggests that the ice sheet has the potential to raise global sea levels by about 24.3 feet, should it melt entirely.
(a) BedMachine v3 bed topography (m), color coded between −1500 m and +1500 m with respect to mean sea level, with areas below sea level in blue and (b) regions below sea level (light pink) that are connected to the ocean and maintain a depth below 200 m (dark pink) and that are continuously deeper than 300 m below sea level (dark red). The thin white line shows the current ice sheet extent.
