Mechanisms that control the collapse of the Greenland ice sheet discovered

Mechanisms that control the collapse of the Greenland ice sheet discovered

New radar technology allowed geoscientists to observe Greenland's dynamic ice-ocean interface that drives sea level rise.

The almost 1.4 million km. Greenland squares are largely covered with ice and glaciers, causing up to a third of the sea level rise in Florida. That is why the new discovery by a team of geoscientists at the University of South Florida of one of the mechanisms that allows Greenland's glaciers to collapse into the sea has a special meaning for the Sunshine State.

In research published in Nature Communications, a group of scientists led by distinguished USF professor Tim Dixon, PhD, discovered a process that can control glacier "breaking", when large chunks of glacial ice collapse into the sea. , forming icebergs like the one that sank the Titanic. The discovery by the team that included Surui Xie, a USF doctoral student; David Holland, PhD, and Irena Vaková, PhD, at New York University (NYU) and NYU-Abu Dhabi Research Institute; and Denis Voytenko, PhD, formerly at NYU and now at Nielson Communications, will help the scientific community better model future ice loss in Greenland and rising sea levels.

Glacier breaking is one of the most dramatic aspects of climate change. Depending on the height of the glacier, the block can be similar to an ice structure the size of a tall skyscraper falling into the sea. Dixon's team caught one of those breaks on video.

"Iceberg breaking has been difficult to understand," Dixon said. "One of the big unknowns in future sea level rise is how quickly Greenland is collapsing, and iceberg breaking is one of the least understood mechanisms."

The team ventured to Greenland in the summer of 2016 to install a new radar system to better understand the process. In particular, they wanted to monitor the formations known as pro-glacial “mélange” (French word for mixture), a combination of sea ice and icebergs facing the glacier. Mixing can be tight in the long, narrow fjords that border many of Greenland's glaciers that meet the sea.

Scientists have long known that mixing can stop glaciers as they move out to sea, but they haven't had the data to fully understand the phenomenon.

Dixon's team developed a new radar-based approach to accurately measure the elevations of the mix off the Jakobshavn Glacier, a major outlet glacier on the west side of Greenland. Using analytical techniques developed by Xie, the scientists measured the height of the mixture. They found a thick wedge of mix against the glacier in late spring and early summer.

During this period, no icebergs were broken, the scientists observed. Once the wedge thinned and melted in midsummer, the break started in earnest.

"On the surface, this mix is ​​a subtle thing, it seems almost flat, but underwater, there are big variations," said Dixon. “It is really the underwater part that holds the glacier and prevents breakage from occurring. By accurately measuring the surface elevations, we were able to control the much larger subsurface variations, which define the thickness of the mix. "

Earlier this spring, NASA scientists reported that the Jakobshavn Glacier, which has been Greenland's fastest growing glacier for the past 20 years, was slowing its movement into the ocean in what appears to be a cyclical pattern of heating and cooling. But because Jakobshavn still delivers more ice than it accumulates each year, its large size makes it a major factor in rising sea levels, NASA scientists argue.

"Our study helps understand the bankruptcy process," said Dixon. “We are the first to discover that the mix is ​​not just a random pile of icebergs in front of the glacier. A wedge of the mixture can occasionally 'hold the door' and prevent the glacier from cracking. "

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Materials provided by the University of South Florida (USF Innovation). Note: Content can be edited for style and length.

Magazine reference: Surui Xie, Timothy H. Dixon, David M. Holland, Denis Voytenko, Irena Vaňkov & # 2013265921;. Rapid calving on the iceberg after removal of the pro-glacial glacial mix. Nature Communications, 2019; 10 (1) DOI: 10.1038 / s41467-019-10908-4

Video: Large Iceberg Breaking near Ilulissat (October 2020).