Study bolsters theory of heat source under Antarctica

Study bolsters theory of heat source under Antarctica
Illustration of flowing water under the Antarctic ice sheet. Blue dots indicate lakes, lines show rivers. Marie Byrd Land is part of the bulging "elbow" leading to the Antarctic Peninsula, left center. Credit: NSF/Zina Deretsky

A new NASA study adds evidence that a geothermal heat source called a mantle plume lies deep below Antarctica's Marie Byrd Land, explaining some of the melting that creates lakes and rivers under the ice sheet. Although the heat source isn't a new or increasing threat to the West Antarctic ice sheet, it may help explain why the ice sheet collapsed rapidly in an earlier era of rapid climate change, and why it is so unstable today.

The stability of an ice is closely related to how much water lubricates it from below, allowing glaciers to slide more easily. Understanding the sources and future of the meltwater under West Antarctica is important for estimating the rate at which ice may be lost to the ocean in the future.

Antarctica's bedrock is laced with rivers and lakes, the largest of which is the size of Lake Erie. Many lakes fill and drain rapidly, forcing the ice surface thousands of feet above them to rise and fall by as much as 20 feet (6 meters). The motion allows scientists to estimate where and how much water must exist at the base.

Some 30 years ago, a scientist at the University of Colorado Denver suggested that heat from a plume under Marie Byrd Land might explain regional volcanic activity and a topographic dome feature. Very recent seismic imaging has supported this concept. When Hélène Seroussi of NASA's Jet Propulsion Laboratory in Pasadena, California, first heard the idea, however, "I thought it was crazy," she said. "I didn't see how we could have that amount of heat and still have ice on top of it."

With few direct measurements existing from under the ice, Seroussi and Erik Ivins of JPL concluded the best way to study the mantle plume idea was by numerical modeling. They used the Ice Sheet System Model (ISSM), a numerical depiction of the physics of ice sheets developed by scientists at JPL and the University of California, Irvine. Seroussi enhanced the ISSM to capture natural sources of heating and heat transport from freezing, melting and liquid water; friction; and other processes.

To assure the model was realistic, the scientists drew on observations of changes in the altitude of the ice sheet surface made by NASA's IceSat satellite and airborne Operation IceBridge campaign. "These place a powerful constraint on allowable melt rates—the very thing we wanted to predict," Ivins said. Since the location and size of the possible mantle plume were unknown, they tested a full range of what was physically possible for multiple parameters, producing dozens of different simulations.

They found that the flux of energy from the mantle plume must be no more than 150 milliwatts per square meter. For comparison, in U.S. regions with no volcanic activity, the heat flux from Earth's mantle is 40 to 60 milliwatts. Under Yellowstone National Park—a well-known geothermal hot spot—the heat from below is about 200 milliwatts per square meter averaged over the entire park, though individual geothermal features such as geysers are much hotter.

Seroussi and Ivins' simulations using a heat flow higher than 150 milliwatts per square meter showed too much melting to be compatible with the space-based data, except in one location: an area inland of the Ross Sea known for intense flows of water. This region required a heat flow of at least 150-180 milliwatts per square meter to agree with the observations. However, seismic imaging has shown that mantle in this region may reach the ice sheet through a rift, that is, a fracture in Earth's crust such as appears in Africa's Great Rift Valley.

Mantle plumes are thought to be narrow streams of hot rock rising through Earth's mantle and spreading out like a mushroom cap under the crust. The buoyancy of the material, some of it molten, causes the crust to bulge upward. The theory of was proposed in the 1970s to explain geothermal activity that occurs far from the boundary of a tectonic plate, such as Hawaii and Yellowstone.

The Marie Byrd Land mantle plume formed 50 to 110 million years ago, long before the West Antarctic ice sheet came into existence. At the end of the last ice age around 11,000 years ago, the ice sheet went through a period of rapid, sustained ice loss when changes in global weather patterns and rising sea levels pushed warm water closer to the ice sheet—just as is happening today. Seroussi and Ivins suggest the mantle plume could facilitate this kind of rapid loss.

Their paper, "Influence of a West Antarctic mantle on basal conditions," was published in the Journal of Geophysical Research: Solid Earth.


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More information: Helene Seroussi et al. Influence of a West Antarctic mantle plume on ice sheet basal conditions, Journal of Geophysical Research: Solid Earth (2017). DOI: 10.1002/2017JB014423
Citation: Study bolsters theory of heat source under Antarctica (2017, November 8) retrieved 23 September 2019 from https://phys.org/news/2017-11-bolsters-theory-source-antarctica.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Nov 08, 2017
It sucks that this is going to be bandied about as if it's victory for climate denialists when it's just another reason why human-caused global warming is such a concern.

Nov 09, 2017
Given Marie Byrd Land is a dome with established drainage and few (1 ?) sub-glacial lakes, is there still potential for a jökulhlaup (literally "glacial run") glacial outburst flood ??

Nov 09, 2017
This heat flux, alone, as is noted in the article, cannot account for all the melt water. Most of it is due to the immense pressure of the overlying ice sheet. The issue of its disposition is one merely of topography, as liquid water flows downhill and pools in basins.

This is very basic stuff.

The heat flux due vulcanism is a very minor factor, which has been understood for a long time. Of far greater concern are the steadily increasing sea and air temperatures, not only upon the WAIS, but the rest of the continent, as well.

So, in answer to the as yet unasked question: No, this does not refute human activity as the overwhelmingly prime driver of AGW, neither in Antarctica nor anywhere else.

Nov 10, 2017

"Unasked" seems to be worth repeating.


Perhaps, but it was intended to preempt the inevitable denierside troll intrusion.

Is that you, @gordonhervey1?


Nov 11, 2017
So basically the takeaway idea here is that the mantle plume makes the WAIS more vulnerable to AGW than it would be otherwise, but isn't in and of itself capable of producing the observed collapses.

Just so we're all clear on this point.

Nov 11, 2017
And then there's this

"SHOCK CLAIM: John Kerry 'visited Antarctica to examine secret Nazi UFO base'
US SECRETARY of State John Kerry visited Antarctica to examine the remains of a secret Nazi UFO base, it has extraordinarily been claimed."

Extraordinary claimings are the fruit of the internet.

But we could imagine the existence of large, water-carved, habitable voids under the ice which could be valuable real estate indeed.

Nov 11, 2017
We could even imagine excavating such voids under stable ice which would provide refuge from global disaster. These voids would be easier to construct than subterranean shelters as well as being easier to climatize.

Nov 11, 2017
when it's just another reason why human-caused global warming is such a concern.
I don't understand the logic of such post. If the global warming has geothermal origin, why we should consider human-caused global warming? The economically unsustainable switching to "renewables" just increases the https://data.worl...M.FO.ZS, being less effective energy source as a whole.


And I do not understand the logic of yours. The point was to pre-empt specifically the claim you do, that *anything* - even this observation if increased risk from AGW but that did not explain (A)GW - is to be a token support to argue that AGW is not happening and is a threat to us.

In US wind energy is now the cheapest energy production, so how can it be "economically unsustainable" or "less effective"? [ https://arstechni...r-drops/ ]

Nov 12, 2017
when it's just another reason why human-caused global warming is such a concern.
I don't understand the logic of such post. If the global warming has geothermal origin, why we should consider human-caused global warming? The economically unsustainable switching to "renewables" just increases the https://data.worl...M.FO.ZS, being less effective energy source as a whole.


Because global warming doesn't have a geothermal source. We have this geothermal heating on TOP of AGW, which is why it makes AGW even more of a concern.

Nov 12, 2017

"Unasked" seems to be worth repeating.


Perhaps, but it was intended to preempt the inevitable denierside troll intrusion.

Is that you, @gordonhervey1?


How flattering, are you his acquaintance? He sounded like he was used to an obsequious group of students and I'm a long time out of highschool is all. I have no wish to be mistaken for having opinions on climate science by the way, my points about earth science earlier in these comments are because there's a danger from the WAIS in it's own right.


Hahaha, gordonhervey1

And all well and good. But just a bit short of an answer, one way or another. Sufficiently vague so as not to warrant, outright, a label of snakeoiler, but yet not quite affirmative enough to rule out that warrant.

And a little later, you make another comment, that (deliberately, one supposes) fails to perform in a similar fashion, in response to DaSchneib:

Contd

Nov 12, 2017
So basically the takeaway idea here is that the mantle plume makes the WAIS more vulnerable to AGW than it would be otherwise, but isn't in and of itself capable of producing the observed collapses.

Just so we're all clear on this point.


Your reply, gordonhervey1:

"A new volcano formed under Marie Byrd Land in 2010/11, something to consider in the context of mantle conditions, that's rated as liable to destructively erupt within decades. Ban Ki-Moon visited Chilean bases in 2007 and discussed the possible short term "overnight" loss of the WAIS, different to collapse in terms of slow warming (whether climatic &/or geothermal)."

Which, to me, at least, doesn't seem to add anything. Just kinda floating around without any obvious purpose.

Would you please be so kind as to explain how you meant this observation to relate to, modify, or recontextualize, DaSchneib's comment?

Nov 14, 2017
Care to draw any conclusions from it, @gordon?

Nov 14, 2017
Yeah, what I figured, another denier geologist. Bye, denier geologist. Go suck some oil or stuff some coal where the sun don't shine. We don't need #liardeniergeologists here.

Nov 14, 2017
Would you please be so kind as to explain how you meant this observation to relate to, modify, or recontextualize, DaSchneib's comment?

Caliban, there's a link to the research in my first comment at the top.


I'm not interested in the link, gordonhervey1.

What I am interested in is how, in your own words, you would apply those findings to modify or recontextualize Da Schneib's comment.

I thought I was pretty clear with that request, but apparently was not, for which I apologize.

Can you please elaborate, as requested?

Nov 14, 2017
Get a life pal! This article isn't about AGW, take your 'worthy cause' and obfuscation somewhere else.


Ouch!

What's the matter, gordonhervey1 --did I inadvertently chafe a mangy spot on your trollhide?

By the way --that wouldn't be the trollhide of nonoUNme, aka Caliban's Troll, aka Noumenon, now, would it?

For future reference, troll-who-goes-by-gordonhervey1, you are making a big mistake in assuming that you can slip such mealy-mouthed, damn-by-faint-praise, fence sitting, shadow-casting denialism past the serious commenters here, undetected or unscathed.

For the record, if I've made a mistake in identifying you as a troll, all that need be done to set things aright is for you to make a civil and sincere reply to my request.


Nov 14, 2017
And suggestive of a mental health problem in it's absurdity Caliban.


Hahahahahahaha.

Still no answer to my question, gordonhervey1.

Why is that?

I would say that it is quite suggestive of trolldom, but I suppose we won't get a definitive answer this time around, since you refuse a reasonable request.

Nov 15, 2017
It's all whiny because it tried to be a sneaky @gordie and got caught.

Nov 16, 2017
You and Da Schneib have violated the terms of commenting here and have been reported.


Hey, gordo--

When did Porg institute a Term of Use prohibiting Troll Detection?

You could have saved yourself no end of trouble by just answering my quite reasonable question in the first place.

But your work is starting to pile up, because now you have two to answer!

Nov 16, 2017
What is it with deniers that they're always sneaking around?

Seriously, did you think no one would notice? C'mon, @sneakygordie, the people around you aren't as stupid as you are. You should be used to it by now.

And while we're on the subject, why is it that the #climatecranks are always libertardians and trumpet around about free speech, but try to censor anyone who disagrees with them?

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