Novel hypothesis goes underground to predict future of Greenland ice sheet

Novel hypothesis goes underground to predict future of Greenland ice sheet
Glaciers and lava flows, east Greenland. The layered rocks in the high peaks formed when the Iceland hot spot broke through after passing beneath Greenland. The main ice sheet is visible in the distance. Credit: Richard Alley, Penn State

The Greenland ice sheet melted a little more easily in the past than it does today because of geological changes, and most of Greenland's ice can be saved from melting if warming is controlled, says a team of Penn State researchers.

"There is that suggests the ice sheet was more sensitive to warming and in the past million years, and not so much in the more recent past," said David Pollard, research professor in the Earth and Environmental Systems Institute at Penn State.

Too much warming will cause Greenland to lose most or all of its ice over the coming centuries, but most research indicates that the threshold warmth for complete ice loss has not been reached yet.

Paleoclimatic records indicate that most of Greenland was ice-free within the last 1.1 million years even though temperatures then were not much warmer than conditions today. To explain this, the researchers point to there being more heat beneath the ice sheet in the past than today.

Data show that when the Iceland hot spot—the heat source that feeds volcanoes on Iceland—passed under north-central Greenland 80 to 35 million years ago, it left deep underground but did not break through the upper mantle and crust to form volcanoes as it had in the west and east. The Earth's climate then was too warm for Greenland to have an ice sheet, but once it cooled the ice sheet formed, growing and shrinking successive with ice ages.

"The idea is that the loading and unloading, flexing and unflexing from ice ages tapped into slightly melted rock that was left deep under Greenland by the Iceland hot spot and brought that melt up," said Richard Alley, Evan Pugh University Professor of Geosciences at Penn State.

Changes to the ice sheet allowed the molten rock to move closer to the Earth's surface, even to the base of the ice. The hotter bed melted more ice from below, lubricating the ice sheet so it was thinner and easier to melt from above.

The melted rock wants to come up, according to Alley. As the ice sheet grows and shrinks, it essentially shakes the melt, drawing it up in pulses.

"The first shakes usually do the most moving," Alley said.

The effect would have been largest when the first big ice sheet grew and then shrank, he added. More recent changes to the ice sheet also affect geothermal fluxes, but not as much as they had in the past.

"The hypothesis does not change the reality that if we make it hot, Greenland's ice melts, and no one will like that," Alley said. "It does not even really tell us whether geology just at this moment is making it harder or easier for the ice to melt. The ability of the ice to melt got easier in the past and is sort of bumpily getting harder, and we do not know where on the bumps we are."

Pollard tested the team's hypothesis using a numerical, three-dimensional ice-sheet model. The researchers report their results in the Journal of Geophysical Research in January.

"The Greenland ice sheet is very likely to melt a lot and retreat, and contribute to sea level in the next few centuries," Pollard said. "This study is part of the puzzle of figuring out how much it will melt and retreat. We are using past geologic data to validate the models that are being used for the future."

If Greenland's ice sheet were to completely melt today, global sea levels would rise nearly 23 feet and flood coastal areas. Parts of cities like New York would be underwater. The team says future studies should integrate geologic and geophysical data as well as glaciological, atmospheric, oceanic and paleoclimatic information to better project how much and how fast the will melt and its effect on sea-level rise.

"If you had a better idea of how much and how fast sea level rises from warming, you could make wiser decisions," Alley said. "This research is a piece of the effort to provide policymakers and planners with the background information that will allow them to make good decisions."


Explore further

Modest warming risks 'irreversible' ice sheet loss, study warns

More information: R. B. Alley et al, Possible Role for Tectonics in the Evolving Stability of the Greenland Ice Sheet, Journal of Geophysical Research: Earth Surface (2019). DOI: 10.1029/2018JF004714
Journal information: Journal of Geophysical Research

Citation: Novel hypothesis goes underground to predict future of Greenland ice sheet (2019, February 1) retrieved 18 June 2019 from https://phys.org/news/2019-02-hypothesis-underground-future-greenland-ice.html
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Feb 01, 2019
More propaganda. More wolf-crying.


Feb 02, 2019
@Bart_A You seem not to care about geology or the movement of magma or this interesting hypothesis of transitory ancient warming from below. Have you considered that perhaps you don't belong here?

Feb 02, 2019
waiting to find that placer gold.

Feb 02, 2019
Considering that if the Iceland hotspot is moving east, this isn't likely to traverse Greenland again, and this doesn't sound like "future." Another clickbait physorg title.

Feb 02, 2019
gee, an ice-free Greenland in exchange for some crappy welfare supported islands or creaky old N. American coastal cities? Sounds good.

Feb 02, 2019
@Bart_A You seem not to care about geology or the movement of magma or this interesting hypothesis of transitory ancient warming from below. Have you considered that perhaps you don't belong here?
Bart's not very bright. I wouldn't bother responding to one of the "Christian" psychotics. It will just encourage it to post here more.

Feb 02, 2019
Feel free to go live there, @ThoriumBoi. Maybe the coastal cesspool gangs who have more guns than you do won't catch you there.

I am totally over worrying about how many guns a bunch of idiots in low-population states have. Prepare for more people, angry about their cesspools overflowing when you deniers said they wouldn't, coming for you with more guns than you got and with ropes.

Feb 02, 2019
And after legitimate commenters here have not been protected from threats of violence from these supposed "Christians," who keep repeating they have more guns, I see there is no restraint, and I state that if "warmers" whose lawns have been inundated with sewage seek to get revenge upon the denier liars, I will not stand in their way and will in fact help them find denier liars if I can.

Feb 02, 2019
Are you ready to stop whining about how many guns you have, liar denier Trumpian psychotics?

This is what embracing Hitleresque tactics has earned you. You will find that every state will have larger populations than you will oppose you. You will be executed as traitors.

Feb 02, 2019
Trumpian psychotics


The fact that you mentioned Trump in a science article says you are the one that has the Trump derangement syndrome... Trump has made you mentally ill.

Feb 03, 2019
"...most of Greenland's ice can be saved from melting if warming is controlled, says a team of Penn State researchers."

Really? Good luck with controlling the temperature of an ice sheet that essentially covers the entire country. It seems to be the norm today that every paper has to make outrageous, over-the-top claims, all with extremely limited data.

Feb 03, 2019
Trumpian psychotics


The fact that you mentioned Trump in a science article says you are the one that has the Trump derangement syndrome... Trump has made you mentally ill.
says Old_C_Code

If the USA has a war with Russia - whose side do you think Da Schneebo aka Da Schitforbrains would be on? Most likely he would go running to those gun owners to protect him when the Russian Navy lands in New York City.

Feb 03, 2019
Better than ODS because the black dude got elected President twice, I guess.

In terms of actually doing the job, he seems to have presided over the elimination of wars. Most people don't get this, but most of what the President does domestically is controlled by Congress appropriations. It's in foreign policy that a President stands or fails.

Trump denigrates the US' foreign policy of decades. He's an idiot.

Feb 04, 2019
If Greenland's ice sheet were to completely melt today, global sea levels would rise nearly 23 feet

A little perspective: at the current rate, if the measurements are accurate (they aren't), it will take more than 10,000 years for the Greenland ice sheet to completely melt and contribute those 23 feet to sea level rise.

Greenland ice mass balance 2003-2011
http://polarporta...-change/

More recent weigh-ins suggest the ice sheet is not losing nearly as much as in the prior decade.
https://www.clima...ice-mass

Regardless of the relatively large uncertainties, 10,000 years should give us time to, you know, migrate further inland. Unless another Milankovitch-cycle induced glacial period begins and melting ice is no longer a "problem".


Feb 04, 2019
Of course no one bothered to check the actual paper or discuss much what it means. It is proposing (an interesting) hypothesis, no more. The consequences depends on if the hypothesis can be tested correct or not.

propaganda

A little perspective

It seems to be the norm today that every paper has to make outrageous, over-the-top claims, all with extremely limited data.


No.

The problem is that the sea level is increasing now, and this ice sheet is contributing now, and the amount of data - which is fair to middling and not "limited" in most sense - suffice to say that as well as (mostly) what we can and cannot do. Also, please provide peer reviewed references akin to how the research papers do. Claims without evidence can be rejected without evidence.

Feb 04, 2019
"The idea is that the loading and unloading, flexing and unflexing from ice ages tapped into slightly melted rock that was left deep under Greenland by the Iceland hot spot and brought that melt up," said Richard Alley, Evan Pugh University Professor of Geosciences at Penn State.
Changes to the ice sheet allowed the molten rock to move closer to the Earth's surface, even to the base of the ice. The hotter bed melted more ice from below, lubricating the ice sheet so it was thinner and easier to melt from above."

https://phys.org/...html#jCp

Feb 04, 2019
"Two giant plumes of hot rock deep within the earth are linked to the plate motions that shape the continents, researchers have found."

https://phys.org/...html#jCp

AND

"If our conclusions are correct, every piece of land that we are now sitting on got its start someplace like the Andes or Tibet, with very mountainous surfaces," said Tang, lead author of the study and a postdoctoral research associate in Rice's Department of Earth, Environmental and Planetary Sciences (EEPS). "Today, most places are flat because that is the stable stage of the continental crust. But what we found was that when the crust formed, it had to start out with mountain-building processes."

https://phys.org/...html#jCp

The Earth is very hot underneath the continental crust - often hot enough to warm glaciers to the point of melting. This is Fact.

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