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Refreezing Water Causes Weird Warps in Greenland’s Ice

The flat, glistening, white expanse of the Greenland Ice Sheet, stretching out across hundreds of thousands of square miles, appears placid, unchanging … boring even. But this tranquil surface belies the turmoil taking place below, at the base of the ice sheet. There, scientists have discovered sections of ice up to a kilometer thick and tens of kilometers long where meltwater has refrozen to the base of the ice sheet, setting off a dynamic process that causes the layers of ice to build up over the eons and contort into sinuous folds.

Melting and refreezing at the bottom of ice sheets warps the layer-cake structure of the ice above, as seen in this radar image from Greenland.
Credit: Mike Wolovick

The refreezing and folding heats the surrounding ice, which impacts how it flows on its journey from the ice sheet’s interior out to the ocean. Several of those regions coincide with the place where one glacier dramatically speeds up. Understanding what controls the behavior and flow of ice sheets and the glaciers within them is a key part of improving climate models that project what effects global warming might have on the ice and how that might impact sea level rise.

“What this shows is we have to go past just watching the surface,” said Robin Bell, a climate researcher with Columbia University’s Lamont-Doherty Earth Observatory and leader of a new study describing the strange sections of ice in the journal Nature Geoscience.

Peering Inside an Ice Sheet

Sections of refrozen ice were known to exist at the base of the East Antarctic Ice Sheet, which is much thicker, larger and colder than the Greenland Ice Sheet, itself almost incomprehensibly large. Early radar measurements made by flights over Greenland hinted that something similar could be hiding under the surface there, but the data was too coarse and sparse to tell for sure. Some thought the radar signatures were the echoes of mountains trapped below the ice. But her experience in Antarctica had Bell “pretty convinced” that they were showing these “basal units” of refrozen meltwater.

She was able to confirm her suspicions when NASA’s Operation IceBridge — a series of scientific flights taken across Earth’s polar region, taking radar scans, measuring gravity and gathering other valuable data — were able to peer beneath the ice surface in greater detail and in side-by-side transects. Bell compared the difference between the early radar and the data from IceBridge to writing with a crayon and then with “a beautiful fine marker.”

The radar data showed that while the surface of the ice sheet may appear “boring” during the hours and hours spent in a research plane, “when you can actually look inside the ice sheet, it’s like, ‘Wow’,” she told Climate Central.

The flat topography of the Greenland Ice Sheet seen from a plane stands in sharp contrast to the jagged features found to be underlying much of the ice sheet.
Credit: Kirsty Tinto

“They did a commendable job of locating these features,” said glaciologist Joe MacGregor, of the University of Texas, who was not involved in the research.

‘Tortured Ice’

The basal units start with meltwater — a key influence on the flow of glaciers and ice sheets. Meltwater comes from two sources: It forms when the sun’s rays shine on the surface of the ice sheet in the summer, creating pools that can then go cascading down huge conduits in the ice sheet called moulins, eventually winding its way to the ice sheet’s base. It can also form at the base of the ice sheet as heat generated in Earth’s interior warms the ice or as friction from the movement of the ice against the bedrocks causes it to melt.

Once there, two processes can also cause the meltwater to refreeze to the bottom of the ice sheet: “One is it just kind of cools slowly,” Bell said. As if you took it and “just threw it in the freezer.”

The other is a little more complicated. The movement of the meltwater is under the control of the glacier, which can cause the water to flow upslope on the underlying bedrock. This causes the water to become supercooled and it freezes instantly.

When the meltwater refreezes, Bell and her colleagues think that something that sounds a bit paradoxical happens: The freezing water gives off heat, which softens the surrounding ice and causes the layers of ice to warp to create what Bell calls “tortured ice.”

An uplifted and deformed ice sheet in Greenland's fast flowing Petermann Glacier as seen in this radar image.
Credit: Mike Wolovick

The ice sheet is often described as a layer cake, made up of layers of ice that build over the eons as new snow is deposited at the top of the ice sheet, pushing down on older layers sitting underneath. The basal units throw this tidy arrangement into disarray, bending the layers and forcing older layers atop newer ones. These contortions can reach halfway up the thickness of the ice sheet.

“It’s a pretty ugly cake if that’s what it is,” MacGregor said.

Next Steps

Bell and her team think the softening and warping of the ice sheet in these areas affects the ice sheet’s flow there. The data Bell and her team examined shows that several of these units line up with the point where Greenland’s Petermann Glacier speeds its flow.

“It does actually seem to affect how one of these glaciers is flowing,” MacGregor said.

That match was a surprise to the team, but shows them that there are unanticipated processes controlling the flow of the ice, Bell and MacGregor both said, and the bottom of the ice sheet is more varied than previously thought.

It’s too early to tell how this refreezing and its effects might factor into calculations of sea level rise, MacGregor said, but it does give scientists more insight into the workings of the whole ice sheet system.

Now, scientists need to model the processes at play to figure out exactly how it works and see if they can predict “where and when this process happens,” Bell said. Whether the freezing is controlled by the meltwater, or the thickness of the ice overhead or perhaps by the cycling of the ice ages isn’t known. “I officially say, ‘We don’t quite know yet’,” Bell said.


By Ken Griffith (28056)
on July 26th, 2014

That climate change may be occurring is still an open question.  I do believe that the earth goes through natural cyclical changes, but not necessarily due to man made influences.

I also believe that global warming ascribed totally to man’s influences is a croc. It is politically advantageous to Democratic demagoguery. Any science professor who disagrees with the rest of the profession is virtually read out of his profession by other scientists.  Global warming actions by politicians have become a religion and the news media do not report the reasoning and contradictory views by scientists.

I think the EPA is too radical and needs to be legislatively reigned in.  I will never vote for a politician who advocates further actions that even hint that economic and social freedoms will will suffer.

Reply to this comment

By Tony Allred (San Diego)
on August 4th, 2014

Ken, Climate change is not an “open question”, it is happening.  Keep politics out of science (“Democratic Demagoguery” in your words).  Yes, the earth has gone through several natural climate changes over the eons, but this one correlates directly with the increase in human produced greenhouse gases.  Whether or not you “believe” in it or not is irrelevant.  The “smoking gun” has been revealed:  Carbon 14 concentrations in the CO2 prove without a doubt that it is comprised primarily of burning of fossil fuels, not vulcanism or any other sources.  The scientific method is greater than your beliefs.  Do the research yourself, don’t rely on Faux News.

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By Mary Hansen (Northbrook, IL 60062)
on July 26th, 2014

Senator Daniel Patrick Moynihan once said something to the effect that, “everyone is entitled to his own opinion, but not to his own facts.”  You might find that the information that you have been reading has been purposely distorted as they also occurred in debates about the relationship of cancer and cigarettes, the ozone layer and other areas that have called for governmental regulations. “Merchants of Doubt -How a handful of Scientists Obscured the Truth on Issues from Tobacco to Global Warming” by Naomi Oreskes and Eric M. Conway is likely in your local library and shares the documentation of what I am asserting.  Please check it out.

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By Colleen Glaser (38460)
on August 1st, 2014

Thank you Mary Hansen for the book title I am going to find and read it asap.

Reply to this comment

By Mari Ann 'Ross (Dallas, TX 75235)
on August 2nd, 2014


Could it be said, perhaps, earth’s natural cyclical changes “and” [with, emphasis added] man-made influences have created “global warming”?

In the alternative,

Could it be said, perhaps, the earth’s natural cyclical changes “and” [with, emphasis added] man-made influences have [in concert] have sped-up “global warming”?

Reply to this comment

By tony m (lincoln ne 68506)
on August 3rd, 2014          Ken/Mary/Colleen go to this link for actual sea ice information real time then decide for yourself. Tony

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By Robert Sweetman (Rogue River,OR)
on August 8th, 2014

It’s fair to say and understandably so that most of the comments I’ve read thus far represent just how poorly educated people are about the theoretical body of knowledge of how physics works, and in particular how it relates to the many factors that relate to what influences planetary climate behavior.

So I will leave them a gift here as links to video presentations by some of the world’s leading climate scientists across the spectrum to gain some real scientific knowledge and background on the subject, so they can at least have a working knowledge base in which to make their points based on science and not political ideology as a substitute for what they clearly lack in knowledge of the subject.

Happy Trails,


UCSD Scripps Institute,: Distinguished Professor Emeritus Richard Somerville, a world-renowned climate scientist
“Scientific Case for Urgent Action to Limit Climate Change”

Professor Stefan Rahmstorf: Potsdamn Institute for Climate Impact Research
“The Climate Crisis”,

Kevin Anderson, former Director of the Tyndall Centre (the UK’s top academic institute researching climate change)
Climate Change: Going beyond the dangerous

Professor Kevin Anderson: Real Clothes for the Emperor - Facing the Challenges of Climate change

Professor Steven Chu - Energy and Climate Change: Challenges and Opportunities

Professor Michael Mann—The Hockey Stick and the Climate Wars: Dispatches From The Front Lines

UCTV: Professor David Lea, Department of Earth Science at UC Santa Barbara: Presentation
Can Global Warming Be Held to 2°C ?

Comparing climate projections to observations up to 2011
Stefan Rahmstorf1, Grant Foster2 and Anny Cazenave3

Shepherd, Andrew et al. (2012). \A Reconciled Estimate of Ice-Sheet Mass Balance”. In: Science 338.6111, pp. 1183{1189. doi:
10.1126/science.1228102. eprint:


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By Some Dude (Sevierville, TN 37865)
on August 12th, 2014

All that and not a MENTION of all the volcanic activity under the ice SINCE 1993 and even before?

Polar ice caps melt not because the air there is warmer than 0 deg Celsius, but because they are overheated from underneath…

Lots of large active volcanoes under the Arctic for a long time now.

PS: What should happen to temperatures AFTER The Little Ice Age? Well… THAT ended in the 1800s… and waddaya know… temperatures increased. How scientifically staggering and unexplainable (/s).

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