Underwater Glacial Melting Is “Happening Far Faster Than Previously Forecast”, Study Finds
In a new study, a team of American scientists led by oceanographer Professor Dave Sutherland developed a new method to measure the submarine melt rate of a tidewater glacier.
They then used this technique to study the underwater melting of the LeConte Glacier, which flows into LeConte Bay south of Juneau in Alaska.
Alarmingly, they found that current methods may be dramatically underestimating glacial melt rates.
While previous models have been made on ice shelves in Antarctica by boring through to the ice-ocean interface beneath, the techniques aren't available for vertical-facing glaciers.
"We don't have that platform to be able to access the ice in this way," said Prof Sutherland of the University of Oregon, explaining it is too dangerous to get too close to them.
As such, most previous research on the underwater melting of glaciers relied on theoretical modeling, measuring conditions near the glaciers and then applying theory to predict melt rates, he added that that theory has never been directly tested.
"This theory is widely used in our field," said study co-author Dr Rebecca Jackson, an oceanographer at Rutgers University.
"It's used in glacier models to study questions like: how will the glacier respond if the ocean warms by one or two degrees?"
In order to test the models in the field, the research team deployed a multi-beam sonar to scan the glacier's ocean-ice interface from a fishing vessel six times in August 2016 and five times in May 2017, which allowed the team to image and profile large swathes of underwater ice.
They then looked for changes in melt patterns that occurred between the August and May measurements.
"We measured both the ocean properties in front of the glacier and the melt rates, and we found that they are not related in the way we expected. These two sets of measurements show that melt rates are significantly, sometimes up to a factor of 100, higher than existing theory would predict."
For those not in the know (ie. the majority of us), there are two main categories of glacial melt: discharge-driven and ambient melt, with most previous studies focusing on the below.
This is when large volumes of meltwater and released below the glacier and rises up quickly against the glacial face. The ambient melt is often disregarded as insignificant as it is so much less, however Prof Sutherland says its important to study both to improve projections of global sea level rise.
Global warming is real people!
Featured Image Credit: PA