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Monitoring the Helheim Glacier with Lidar

image of Monitoring the Helheim Glacier with Lidar

One of the outstanding presentations at the RIEGL Training Symposium in 2019 came from David Finnegan from the U.S. ACE CRREL lab in Hanover, NH. He has developed an impressive lidar data collection system for monitoring the massive Helheim Glacier in Greenland.

This is a portion of an article in Science.

As befits its mythical name, the domain of the Norse god of the dead, Helheim is truly an arbiter of Greenland’s fate. The glacier is one of the ice sheet’s primary drains, sliding into the sea at 8 kilometers per year and accounting for 4% of the ice sheet’s annual mass loss. Its towering front, as tall as the Statue of Liberty, measures 6 kilometers across. Sea ice shed from the glacier chokes the fjord for tens of kilometers. The glacier’s terminus has behaved erratically over the past 15 years, first retreating by 5 kilometers from 2002 to 2005 and then advancing and stabilizing for nearly 10 years. Then, in 2014, a more severe retreat began, sending the terminus 2 kilometers beyond its previous low. Meanwhile, the glacier has thinned by more than 100 meters, leaving a telltale “bathtub ring” high on the rock around the fjord.

Year after year Straneo returned to the fjord. Meanwhile, Hamilton’s frustration with the limited data from the GPS units grew. Then, he met David Finnegan, a remote sensing scientist at the U.S. Army’s Cold Regions Research and Engineering Laboratory (CRREL) in Hanover, New Hampshire, who uses reflected laser light to map terrain. What if they used such a laser for constantly monitoring Helheim’s front? Tying together such fracturing with the influx of Atlantic water could help them figure out what role, if any, the water plays in the loss of ice.

In 2012, Finnegan’s team perched a prototype autonomous laser scanner on one of the fjord’s walls, overlooking Helheim’s terminus. The scanner played a beam of infrared light across the glacier, its front, and the sea ice, tracking the calving process iceberg by iceberg. The data dropped jaws when Finnegan presented them at a meeting in 2013. This was big data come to glaciology, each reflected point tied to coordinates in space—as though the team suddenly had one million GPS units on the glacier at once.

Even with those two complementary lines of evidence, Helheim’s ice loss defied explanation. “Each year was kind of different,” Stearns says. Figure out a mechanism for 1 month, and a year later it was irrelevant. Too many variables, such as the flow of meltwater under the glacier and the temperatures beneath the sea ice, could not be tied down. Only a sustained monitoring system, targeting every element of the glacier and fjord, could show how the system delivered ice from the glacier to the ocean and how a warming climate might influence it.

That vision took a step toward reality just after Finnegan’s talk, when Cyndi Atherton approached him. Atherton, who had joined Heising-Simons to direct its scientific grants, wanted to fund research that could make a room gasp. “What would you do with a blank check?” she asked. Heising-Simons began to finance the development of the Atlas scanners, which could capture the entirety of Helheim’s crumbling tongue from perches on both walls of the fjord.

Three years into the work, tragedy struck: Hamilton died in 2016, at 50 years old, after his snowmobile fell 30 meters into an Antarctic crevasse. The researchers left behind hardened their desire to understand Helheim. Last year, Heising-Simons asked Straneo and Stearns to assemble a team that would tie down all Helheim’s variables at once. The project would be a proof of principle, Atherton said, “that will allow other governments to say this is valuable, and we’re going to extend from this site to other sites.”

The work began last summer.

For the full article on monitoring the glacier you must subscribe to Science magazine.

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