Antarctic ice sheet is melting, but rising bedrock below could slow it down
An international team, led by DTU Space at the Technical University of Denmark with Colorado State University, has found that the bedrock below the remote West Antarctic Ice Sheet is rising much more rapidly than previously thought, in response to ongoing ice melt.
The study, “Observed rapid bedrock uplift in the Amundsen Sea Embayment promotes ice-sheet stability,” reveals new insights on the geology of the region and its interaction with the ice sheet and is published in the journal Science. The authors noted that the findings have important implications in understanding and predicting the stability of the ice sheet and Earth’s rising sea levels.
“We studied a surprising and important mechanism, glacial isostatic adjustment, that may slow the demise of the massive West Antarctic Ice Sheet by lifting up the bedrock and sediments beneath the ice sheet,” explained CSU Professor Rick Aster, a co-author of the study and head of the Department of Geosciences at the university.
Scientists have been concerned that this ice sheet is particularly precarious in the face of a warming climate and ocean currents, because it is grounded hundreds to thousands of feet below sea level — unlike the ice sheets of East Antarctica or Greenland — and its base slopes inland. This bowl-like topography makes it susceptible to runaway destabilization and even complete collapse over centuries to thousands of years.
CREDIT
VR. Barletta, DTU Space at the Technical University of Denmark/Google Earth/Terry Wilson, The Ohio State University
The entirety of West Antarctica contains enough ice that, if it were to melt, would contribute more than 10 feet of average global sea level rise. In addition, the ice sheet is so massive that it gravitationally attracts an ocean bulge that, if released, would lead to an additional increase of three feet or more to sea level in parts of the northern hemisphere.
The West Antarctic Ice Sheet is currently contributing approximately 25 percent of global melting land-based ice each year, and recent satellite-based studies have shown that this amount has increased in recent decades. This figure is equivalent to about 37 cubic miles or a cube of over three miles on each side.
Co-authors of the study based at The Ohio State University led the installation of sensitive GPS stations on rock outcrops around the remote region to measure the regional uplift of the Earth in response to the thinning ice sheet. Measurements showed that the bedrock uplift rates near the coast of West Antarctica were as high as 1.6 inches per year, one of the fastest rates ever recorded in glacial areas.
“This very rapid uplift may slow the runaway wasting and eventual collapse of the ice sheet,” said Aster. “The uplift tends to stabilize the critical grounding line where the ice sheet loses contact with underlying bedrock or sediment and goes afloat,” he explained. This grounding line then counteracts the process of the ice sheet collapsing.
Researchers also found that the uplift is accelerating and predicted that it will continue to do so into the next century.
“Our research indicates that recent and ongoing ice loss in the region has been underestimated by approximately 10 percent in past studies, because this bedrock uplift was inadequately accounted for in satellite measurements,” said Aster.
Lead author Valentina Barletta, a postdoctoral researcher at DTU Space, Technical University of Denmark, said that this uplift is occurring very rapidly, when compared with other regions of the Earth where glaciers are melting.
“Normally we would see this type of uplift happening slowly, over thousands of years after an ice age,” said Barletta. “What we found tells us that Earth’s underlying viscous mantle is relatively fluid and flows relatively quickly when the weight of the ice is taken off,” she added.
Terry Wilson, professor emeritus of Earth Sciences at The Ohio State University, said the rapid rise of the bedrock in this part of Antarctica suggests that the geological conditions beneath the ice are very different from what scientists had previously believed.
“The rate of uplift we found is unusual and very surprising,” he said. “It’s a game changer.”
Aster, Barletta and the study co-authors have also deployed a large network of sensitive seismographs across Antarctica to produce seismic tomographic images — analogous to a gigantic CAT scan — of the deep Earth below Antarctica.
This work assisted in the interpretation and modeling of the GPS uplift data by providing detailed mapping of a vast region of Earth’s mantle up to 400 miles below West Antarctica.
Previous and related studies conducted by the research team have also revealed that some hotter features below Antarctica extend still deeper, over 600 miles, into the Earth.
“These warmer mantle features drive the previously enigmatic volcanic activity in West Antarctica, including Mount Erebus on Ross Island,” said Aster. “This geothermal heat at the base of the ice sheet helps to sustain subglacial lakes in some regions and lubricates the ice sheet as it slips towards the ocean,” he added.
Aster said that while the research does provide room for a positive outcome, if future global warming is extreme, the entire West Antarctic Ice Sheet will still melt.
“To keep global sea levels from rising more than a few feet during this century and beyond, we must still limit greenhouse gas concentrations in the atmosphere, which can only occur through international cooperation and innovation,” he said.
###
“the geological conditions beneath the ice are very different from what scientists had previously believed.”
LOL..yeah right
Maybe it’s not uplifting…..maybe it’s volcanoes adding mass
My initial thoughts exactly. Hmmm…newly discovered active volcanoes. Potential reason for magma bulge???
It woz CO2 wot dunnit
This is certainly due to Brexit. There is an undeniable link between the start of Brexit and the hysteria about the melting of the Antarctic. I have heard from “Experts” that, if we can stop Brexit, the whole of Antarctica will refreeze and we will not all die.
Absolutely caused by Brexit. The weight of 17.4 million votes in the UK caused a tilt that is lifting Antarctica out of the ocean 🙂
” In addition, the ice sheet is so massive that it gravitationally attracts an ocean bulge that, if released, would lead to an additional increase of three feet or more to sea level in parts of the northern hemisphere.”
Now they are assuming it will all melt instantly to create a “Gravitational Bulge ” ??
ROTFLMAO !
Marcus, you may not be familiar with the concept of gravitational bulge, but what it means is this: the mass of ice in the icecap alters the gravitational field in its vicinity. It “pulls” ocean water towards itself, so that sea levels around Antarctica are higher than they would be if there was just the land there without the 3,000 metres of ice on top of it. If the ice melted, its gravitational pull would disappear and the ocean water would “relax” back to its normal and there would be a rise in sea level.
There’s a well documented gravitational bulge around Cyprus, caused by the Troodos Massif, a large mountain area made up of ultramafic rock with higher specific gravity than most rocks
It’s not clear if they quantified it or just made a guess, or whether they refer just to West Antarctic or the whole continent. The way they say “an additional increase of three feet or more to sea level in parts of the northern hemisphere” doesn’t inspire me with confidence though. If water from melting or release from a gravitational bulge enters the oceans, the sea level rise would be the same all over the globe.
But it’s not going to melt, a an additional 3 feet on top of the 10 feet should not be a cause for alarm.
“This geothermal heat at the base of the ice sheet helps to sustain subglacial lakes in some regions and lubricates the ice sheet as it slips towards the ocean,” but they claim it is warming climate and currents that are melting the ice. Talk about selective use of facts! If there is liquid water at the underside of the ice, it is melting from the bottom. Warming climate melts the other side (top) of the ice where I would expect to see pools of melt water. I don’t recall seeing any pictures of streams of water running over the surface of the ice.
..What !! Are you expecting them to use logic ?? Don’t hold your breath !! (we need that extra CO2) LOL
“This geothermal heat at the base of the ice sheet helps to sustain subglacial lakes in some regions and lubricates the ice sheet as it slips towards the ocean,” he added.
Aster said that while the research does provide room for a positive outcome, if future global warming is extreme, the entire West Antarctic Ice Sheet will still melt.
Peter, you are exactly correct. Geothermal heat at the base of the ice sheet is the elephant driving the melting, and global warming is the pimple on the elephant’s butt. Yet somehow, these climate ‘scientists’ focus on the pimple, and not the elephant.
Again, just not looking at the quantities. There is enough heat flux that, accumulating over thousands of years, it can form a subglacial water layer, with hundreds of metres of ice above to insulate. There is not nearly enough heat flux to deplete the ice sheet by melting on a decadal time scale.
Average Earth heat flow is less than 0.1 watt/m^2. Recent heat flow measurements in West Antarctica are only a few times higher than that. Such heat flow will melt very little ice above it. Perhaps enough to increase lubrication, but not enough to cause mass loss of ice.
Not melting, but lubricating the glacial flow.
I am afraid I am not as clever as you Nick. Perhaps you would be so kind as to explain the heat flux at the surface and how this is depleting the ice sheet.
Peter, it’s not melting enough ice for the melting itself to be an issue; it’s the lubrication effect, as explained in the article, and as noted just above by donb and Paul, which you must have glossed over. Why this matters is that that lubrication helps the ice to flow downhill and into the ocean faster. The idea is that the ice loss is supposed to be from increased calving of icebergs, which melt as they drift into warmer seas, not from increased melting in situ. Nick did not spell this out – probably assuming that readers knew enough basic glaciology to work it out for themselves
There seems to be a widespread assumption that heat flow has increased just recently and is causing “more” melting. Well, geothermal heat flows don’t change on decadal or even millenial scales. No evidence has been presented that the heat flow has increased recently. There’s no reason (IMHO) to assume that West Antarctic is not in a more or less steady state.
A steady state would be interrupted if there was an actual volcano under the ice. That could cause a lot of melting and cause a great deal of ice to move rapidly down to the ocean. Not sure if that’s happening or not, but it’s the most likely effect that could cause more ice loss now than a few decades ago. Global warming of a degree or so would have minimal effect where the temperature is effectively always below freezing and gets down to -90°C in the winter at the centre of the continent.
It’s about damn time, don’t you think?
The latest ‘Ship Of Fools’ to the Arctic ocean was launched with ‘major support’ by the NSF….
https://wattsupwiththat.com/2018/06/21/student-propaganda-cruise-to-the-arctic-to-be-carried-by-webcast/
“There is a disturbance in the Farce, young Luke Warmer!”
I usually welcome new glimpses of possible greater understanding but when it comes to the Western Antarctic ice sheets I fail to see the point of these nuances like isostatic rebound. I have a simple question. Answer it and then we can move on and start studying the rest. How many undersea volcanoes are active in the region? If we cannot find volcanoes then it is hubris to being searching for the fleas on their slopes.
The point was….it’s melting faster than we thought…we just can’t measure it because the bottom is coming up
And the bottom is coming up faster than we thought… and accelerating!
‘because the bottom is coming up’ This too like all happening in the world revolves around Stormy Daniels.
“Scientists discover 91 volcanoes below Antarctic ice sheet
This is in addition to 47 already known about”
D’OH !
What is missing from the equation is whether the volcanic ring of fire that underlies Western Australia has subduction that is lifting the overthrust.
Nope!
No measurements, all psychic intuition delving the secrets deep under the ice and under the ground.
Nor have they offered definitive measurements of the rising land surface, instead it is assumed based on the ice.
Antarctica steadily cooling is actually gloom.
Just as Antarctica led the planet into the Holocene interglacial, it will likewise lead us back out of it. And there is nowhere on earth where CO2 is less relevant than Antarctica.
And yet that is precisely where the effect of more CO2 in the air, if any, should be felt most powerfully, given the low level of atmospheric H2O.
Felix,
On the other hand, CO₂ effect is reduced by lower surface temperature.
The 15 µm absorption band emits at ~15 km height, the temperature is there ~220 K. When the surface has that temperature, the spectrum of outgoing radiation does not show an absorption band at 15 µm.
Please correct me if wrong, but did the WAIS not survive the Pliocene?
http://joidesresolution.org/wp-content/uploads/2017/12/bb.png
That profile is a work of art. Notice that it isn’t straight. That is because it has to be crooked if it is to follow both the axis of the West Antarctic Rift Valley and the axis of the Wilkes Subglacial Basin. And that in turn is the only way you can draw a profile right across Antarctica where bedrock is mostly below sea level.
“did the WAIS not survive the Pliocene?”
Nobody knows for sure. The Ross sea area was periodically ice-free during the Pliocene, but the highland areas in West Antarctica have apparently been ice-covered continuously since the Miocene like East Antarctica:
https://www.researchgate.net/publication/316450140_The_million-year_evolution_of_the_glacial_trimline_in_the_southernmost_Ellsworth_Mountains_Antarctica
https://www.researchgate.net/publication/292953288_Evidence_for_the_stability_of_the_West_Antarctic_Ice_Sheet_divide_for_14_million_years
Whether the marine-based parts of the WAIS collapsed during the Pliocene is really unknown. The claim that they did is based on very shaky sea-level data.
Thanks. Much as I expected.
They are mad, this Dans!
https://goo.gl/images/DHizi6
This article raises a lot more questions than it answers. Here are a few:
“This bowl-like topography makes it susceptible to runaway destabilization and even complete collapse over centuries to thousands of years.” How does bowl-like bedrock topography make an ice sheet susceptible to runaway destabilization and complete collapse over centuries to thousands of years? Wouldn’t the bowl-like topography help contain the ice and prevent it from sliding into the ocean?
“In addition, the ice sheet is so massive that it gravitationally attracts an ocean bulge that, if released, would lead to an additional increase of three feet or more to sea level in parts of the northern hemisphere.” Why only in parts of the “northern” hemisphere? Wouldn’t water released to the oceans contribute to sea level rise worldwide?
“Co-authors of the study based at The Ohio State University led the installation of sensitive GPS stations on rock outcrops around the remote region to measure the regional uplift of the Earth in response to the thinning ice sheet. Measurements showed that the bedrock uplift rates near the coast of West Antarctica were as high as 1.6 inches per year, one of the fastest rates ever recorded in glacial areas.” “Researchers also found that the uplift is accelerating and predicted that it will continue to do so into the next century.”
Weren’t these GPS stations installed relatively recently? If so, how did researchers also find that the uplift is accelerating? And how can they predict that it will continue to do so into the next century?
1000 year collapse? Seems collapse has lost its urgency. Over 1000 years I’d call that a prolonged decline. Hardly a collapse.
From the article: ” if future global warming is extreme”
The key word being “if”. Noone knows.
No one knows anything till it happens, but it is prudent to look at all possibilities and weigh up the probabilities.
If 6000ppm didn’t provide much heating, 500ppm won’t either.
The probability that the climate sensitivity of CO2 is in the 0.2C to 0.3C range.
That’s what the latest science is showing.
“That’s what the latest science is showing.”
Really, please provide a reference for that.
Markw supplies no reference and I get two down votes. Sheesh
who cares about downvoting?
What, are you in grade school? You can rest feeling vindicated that MarkW didn’t provide you a reference. Does it matter? I highly doubt you would accept anything other than the ministry of climate’s false data anyway.
Quantify “extreme.” The article doesn’t, nor does it speculate on the cause of this “extreme” warming.
Essentially this indicates that the volcanic areas of West Antarctica are similar to Iceland where the complete Isostatic adjustment only took 1000-2000 years, compared to >15,000 years for the Precambrian Shield areas of Scandinavia and Canada where it is still ongoing. Not really surprising given the geology.
https://www.researchgate.net/publication/230027982_Rapid_isostatic_rebound_in_southwestern_Iceland_at_the_end_of_the_last_glaciation
https://hal-insu.archives-ouvertes.fr/insu-00286999/document
Incidentally this also makes nonsense of the GIA models that are used to estimate melting rates, as far as West Antarctica is concerned.
It helps not having a president who PROMOTES doom and gloom.
Mmm, I’d agree it helps the cause of the uninformed to having an uninformed president.
Very true. And those of us who are not hopelessly delusional and MSM brainwashed figured that out between January 2009 and January 2017.
You really shouldn’t be so hard on Obama, after all he cares.
I know because he told us every day, even as he was destroying everything he touched.
Trump DUHHH. “Climate change invented by the Chinese” is the extent of his knowledge. And the sheeple follow him.
….yes, and thank God that’s over
MAGA
Just a bit of perspective on the climate of the Antarctica peninsula from Wikipedia (so it must be right!) –
“Because the Antarctic Peninsula, which reaches north of the Antarctic Circle, is the most northerly part of Antarctica, it has the mildest climates within this continent. Its temperatures are warmest in January, averaging 1 to 2 °C (34 to 36 °F), and coldest in June, averages from −15 to −20 °C (5 to −4 °F). Its west coast from the tip of the Antarctic Peninsula south to 68°S, which has a maritime Antarctic climate, is the mildest part of the Antarctic Peninsula. Within this part of the Antarctic Peninsula, temperatures exceed 0 °C (32 °F) for 3 or 4 months during the summer, and rarely fall below −10 °C (14 °F) during the winter. Farther south along the west coast and the northeast coast of the peninsula, mean monthly temperatures exceed 0 °C (32 °F) for only 1 or 2 months of summer and average around −15 °C (5 °F) in winter. The east coast of the Antarctic Peninsula south of 63°S is generally much colder, with mean temperatures exceeding 0 °C (32 °F) for only 0 or 1 month of summer, and winter mean temperatures ranging from −5 to −25 °C (23 to −13 °F). The colder temperatures of the southeast, Weddell Sea side, of the Antarctic Peninsula are reflected in the persistence of ice shelves that cling to the eastern side.”
So you see, there are several months of just above freezing temperatures around part of the peninsula, so the ice is bound to melt in a catastrophic fashion.
Having been there I can assure you that even that favoured corner of Antarctica is very heavily glaciated with very limited ice-free areas, it has no land animals, a single species of landbird (snowy sheathbill) and two species of vascular plants.
Hey look, their measurements of the surface heights are not matching their published “melt rates”, so they’re CYA by saying that the bedrock is rising! Let’s just call it “dark melting”, why should astronomers be the only ones to hide their lack of knowledge with “dark” things that go bump in the science?
‘is rising more rapidly than previously thought’? By whom? The Prince of Wales, perhaps?
Generally, Altitude error is specified to be 1.5 x Horizontal error specification. This means that the user of standard consumer GPS receivers should consider +/-23meters (75ft) with a DOP of 1 for 95% confidence. Altitude error is always considerably worse than the horizontal (position error).
GPS altitude accuracy – GPSInformation.net
gpsinformation.net/main/altitude.htm
I’m surprised that more is not being made of this. Is any GPS receiver capable of sub-meter resolution, much less at the inch or cm scales?
Of far greater concern to me is the health of the two massive ice sheets (Ross and Filchner-Ronne). IF I am right and increased sea ice production increases the THC which cools the world then these two ice sheets are critical. The loss of them would massively increase antarctic annual sea ice production facilitating the establishment of a viable sustainable ice build in the northern pacific and atlantic oceans and thus the end of the modern interglacial.
?w=776
https://news.nationalgeographic.com/2018/02/ross-ice-shelf-bore-antarctica-freezing/
‘This suggested that the entire Ross Ice Shelf, and much of the ice behind it, had collapsed.’
https://www.awi.de/en/about-us/service/press/archive/irreversible-ocean-warming-threatens-the-filchner-ronne-ice-shelf.html
I hope I’m wrong about the THC, or that the ice sheets prove stable this interglacial. I have two lovely grandchildren!
BTW, The period when the poles receive more insolation is ending– see
The polar regions will turn blue soon.
The Ross shelf did not disappear during the previous interglacial as shown by the ANDRILL-1B core, whatever National Geographic might phantasize.
Loading of the much bigger East Antarctica ice sheet which is gaining ice is tilting West Antarctica upwards more than any much smaller isostatic rebound. This is why its rising much faster “than we thought”. The whole science is overloaded with linear thinkers. Every time I hear “worse than we thought”, which is daily from this crowd, I read it that they are admitting they dont really know anything about it. Hudsons Bay has rebounded over 100m. This is causing downwarping along the NE coast of USA and upwarping further south (Carolinas, N Florida). So, W. Antarctica is rising much more rapidly than YOU thought!
I am pleased you mentioned the uncommon high geothermal flux in the region, although you couldnt think of a reason why. Some of your trolls on another thread took me to task for suggesting geothermal heating was a significant factor in melting. Some 90 volcanoes were noted in a recent study and some of your seismic activity is subglacial eruptions going 9n as we speak.
https://source.wustl.edu/2013/11/volcano-discovered-smoldering-under-a-kilometer-of-ice-in-west-antarctica/
But the science is still settled …
Blessed be the IPCC forever
‘“To keep global sea levels from rising more than a few feet during this century and beyond, we must still limit greenhouse gas concentrations in the atmosphere, which can only occur through international cooperation and innovation,” he said.’
So we’re still doomed. Good. For a few minutes there, I had doubts.
Maybe they’re getting ready to hedge their bets.
Sometimes these people remind me of the telephone companies. They sell you telephone services, then sell your number to telephone marketers, then they sell you caller-ID facilities, and then sell the marketers ways to get round caller ID… They are shameless.
Why the assumption that the ice melt is causing the uplift and not the other way around?
Melting ice in Antarctica increases only during El Niño.
I suspect this is a pre excuse for why it is not melting down in the near future as claimed.
“Data shows there is no CO2 doom for Antarctica”
“Oh that’s only because of uplift, AGW is still valid”.
Excuse studies are already starting to appear to explain the non doom that is becoming evident. “we were still right, it’s just that natural events are hiding the signal of CO2 doom for a bit longer”