Analysis exposes faster disintegration of major Greenland glacier

Analysis exposes faster disintegration of major Greenland glacier
Radar depth-sounder data from before and after the breakup of the Zachariæ Isstrøm ice shelf. The green line reveals the ice bottom, and loss of ice between 1999-2014. The white line represents hydrostatic equilibrium estimates of the ice bottom. Credit: University of Kansas

A study appearing in Science magazine today shows a vast ice sheet in northeast Greenland has begun a phase of speeded-up ice loss, contributing to destabilization that will cause global sea-level rise for "decades to come."

A team of scientists, including a researcher from the University of Kansas-based Center for Remote Sensing of Ice Sheets (CReSIS), found that since 2012 warmer air and sea temperatures have caused the Zachariæ Isstrøm ice sheet to "retreat rapidly along a downward-sloping, marine-based bed."

By itself, the Zachariæ Isstrøm glacier holds enough water to trigger a half-meter rise in ocean levels around the world.

"The acceleration rate of its ice velocity tripled, melting of its residual ice shelf and thinning of its grounded portion doubled, and calving is occurring at its grounding line," the authors wrote.

"Ice loss is happening fast in glaciological terms, but slow in human terms—not all in one day or one year," said John Paden, associate scientist for CReSIS and courtesy associate professor of electrical engineering and computer science at KU, who helped analyze data about the thickness of the glacier's ice for the study.

Paden's collaborators include J. Mouginot, E. Rignot, B. Scheuchl, M. Morlighem and A. Buzzi from the University of California Irvine, along with I. Fenty and A. Khazendar of the California Institute of Technology.

Analysis exposes faster disintegration of major Greenland glacier
CReSIS researcher John Paden of the University of Kansas is shown with NASA P3 aircraft deployed to collect Greenland data for Operation IceBridge. Credit: University of Kansas

"Within a few generations, ice loss could make a substantial difference in sea levels," Paden said. "When you add up all the glaciers that are retreating, it will make a difference to a large number of people. Sea level has increased some over the last century, but only a small number of people have been affected compared to what is likely to come."

Paden crunched data acquired by CReSIS during NASA's Operation IceBridge and previous NASA flights over Greenland, including decades-old measurements of Zachariæ Isstrøm. The sensor development and data processing tools used to do this were funded through National Science Foundation and NASA grants, with the support of many CReSIS collaborators.

"There are several other sources of data, but one of them is the Landsat satellite imagery that goes back to 1975," Paden said. "With that, you can look at what the ice shelf is doing, how it's shrinking over time. Satellite optical and radar imagery were used to measure surface-velocity changes over time and to measure the position of the grounding line based on tidal changes."

Paden said the "grounding line," or the boundary between land and sea underneath a glacier, is a zone of special interest.

"The grounding line is where the starts to float and is where the ice flux was measured," Paden said. "The grounding line is a good place to determine thickness across the ice. The terminus of Zachariæ Isstrøm is now at the grounding line—the ocean is right up against the grounded part of the glacier."

While air temperatures have warmed, causing boosted surface runoff, Paden said from calving off the front of the glacier into the ocean accounts for most of the ice mass reduction from Zachariæ Isstrøm.

"Ice floating out into the ocean and melting is greater than the ice lost from surface melting," he said.

A neighboring glacier with an equal amount of ice, named Nioghalvfjersfjorden, is also melting fast but receding gradually along an uphill bed, according to the researchers. Because Zachariæ Isstrøm is on a downslope, it's disappearing faster.

"The downward slope combined with warming ocean temperatures is what seems to be causing the acceleration now and why we predict it will continue to accelerate over the next few decades," Paden said. "Until its grounding line is pinned on an upslope bed, then the dynamic effect is expected to decrease."

Together, the ice in Zachariæ Isstrøm and Nioghalvfjersfjorden represent a 1.1-meter rise in sea levels worldwide. According to the KU researcher, the team's work is intended to inform people in coastal areas who need to make choices about the future.

"From a societal standpoint, the reason why there's so much focus on sheets is because predicted rise will affect nearly every coastal country—the United States for sure, and low-lying countries with limited resources are likely to be the worst off. Mass displacements of potentially millions of people will affect countries that have no coastlines. We study this to have an understanding of how soon things are likely to happen and to help us use our limited resources mitigate the problem."


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More information: "Fast retreat of Zachariæ Isstrøm, northeast Greenland," by J. Mouginot et al. www.sciencemag.org/lookup/doi/ … 1126/science.aac7111
Journal information: Science

Citation: Analysis exposes faster disintegration of major Greenland glacier (2015, November 12) retrieved 19 July 2019 from https://phys.org/news/2015-11-analysis-exposes-faster-disintegration-major.html
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Nov 12, 2015
The fact that Greenland alone could cause a 1.1 metre rise in sea levels is pretty terrifying when we have an unstoppable collapse of the Antarctic ice sheet as well

Nov 13, 2015
So what can we do? Learn more about climate change and join the efforts to expose, confront, and replace U.S. Congressmen/women that continue to deny the reality. They put our future generations at risk and should be sent home!

Here's a good website.
Google search... AAAS Climate Change What We Know

ExhaustingHabitability

Nov 13, 2015
You're missing a few points that make that impractical Reducers.

1). Money in politics. We get to choose which face of the two-faced, one party system we elect. That's not a choice.
2). Feckless fools staring at the boob tube. Turn it off, you eliminate the influence of money in politics. Many wail and moan about it...but don't ask them to turn off the tele. Not even for 6 weeks before the local primary? How pitiful is that?
3). 40% of Americans "aren't particularly concerned about AGW". How many of the "concerned" don't want major economic or lifestyle disruption? You don't have a majority to hold them to account.
4). Without AGW we'd be in the middle of a mass extinction, caused by humans. Outrage in LA over someone watering their lawn. Where's the outrage at large families? Hell, Democrats want more paid time off for hobby breeding. But if they have good AGW cred, that's OK with you???
QED: your logic is seriously flawed.

Nov 13, 2015
no stopping a process that has gone on for billions of years, prepare for it, Quit futile attempts to prevent or reverse it. Climate Change is natural and has been happening since Earth beginning. Before man there was climate change. when man is long gone, there will still be climate change.

Denier meme #1
Man-made climate change is certainly not natural ... and as a result something can be done.
A "natural" change would be a tad tricky to stop as it wold involve altering the Earth's orbital track.
FFS

Nov 15, 2015
Article is a huge fear mongering exaggeration. Ocean levels may rise 1.1 metres from this activity, but as the researcher says - its on a geologic time scale - i.e. several thousand years. Just as the oceans were several metres lower a few thousand years ago, they will be higher a few thousand from now.

Since we rebuild all buildings on earth every hundred years or so, moving cities is free and automatic.

Rest assured that a meteorite of 20km class will blast into the earth and kill 99.9% of surface life in 24 hours. Its not in doubt by any scientific organization.

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