New study shows Antarctic ice shelf is thinning from above and below

Antarctica
Credit: Newcastle University

A decade-long scientific debate about what's causing the thinning of one of Antarctica's largest ice shelves is settled this week (Wednesday 13 May) with the publication of an international study in the journal The Cryosphere.

The Larsen C Ice Shelf—whose neighbours Larsen A and B, collapsed in 1995 and 2002—is thinning from both its surface and beneath. For years scientists were unable to determine whether it is warming air temperatures or warmer ocean currents that is causing the Antarctic Peninsula's floating to lose volume and become more vulnerable to collapse. This new study takes an important step forward in assessing Antarctica's likely contribution to future sea-level rise.

The research team combined satellite data and eight radar surveys captured during a 15-year period from 1998-2012. They found that Larsen C Ice Shelf lost an average of 4 metres of , and had lowered by an average of one metre at the surface.

Lead author, Dr Paul Holland from British Antarctic Survey (BAS), says:

"What's exciting about this study is we now know that two different processes are causing Larsen C to thin and become less stable. Air is being lost from the top layer of snow (called the firn), which is becoming more compacted—probably because of increased melting by a warmer atmosphere. We know also that Larsen C is losing ice, probably from warmer ocean currents or changing ice flow.

"If this vast ice shelf—which is over two and a half times the size of Wales and 10 times bigger than Larsen B - was to collapse, it would allow the tributary glaciers behind it to flow faster into the sea. This would then contribute to sea-level rise."

The Antarctic Peninsula is one of the fastest warming regions on Earth, with a temperature rise of 2.5°C over the last 50 years.

The team, who continue to monitor the ice shelf closely, predict that a collapse could occur within a century, although maybe sooner and with little warning. A crack is forming in the ice which could cause it to retreat back further than previously observed. The appears also to be detaching from a small island called Bawden Ice Rise at its northern edge.

Professor David Vaughan, glaciologist and Director of Science at BAS, says:

"When Larsen A and B were lost, the glaciers behind them accelerated and they are now contributing a significant fraction of the sea-level rise from the whole of Antarctica. Larsen C is bigger and if it were to be lost in the next few decades then it would actually add to the projections of sea-level rise by 2100.

"We expect that sea-level rise around the world will be something in excess of 50 cm higher by 2100 than it is at present and that will cause problems for coastal and low-lying cities. Understanding and counting up these small contributions from Larsen C and all the glaciers around the world is very important if we are to project, with confidence, the rate of into the future."

The study was carried out by scientists from British Antarctic Survey, the United States Geological Survey, University of Colorado, University of Kansas and Scripps Institution of Oceanography.

It was funded by the Natural Environment Research Council in the UK, National Science Foundation in the US and a range of international funding bodies around the world.


Explore further

Study shows above ice warming responsible for Larsen-B Ice Shelf collapse, not instability

More information: Oceanic and Atmospheric forcing of Larsen C Ice Shelf thinning by P.R Holland, A. Brisbourne, H.F.J Corr, D. McGrath, K. Purdon, J. Paden, H.A. Fricker, F.S Paolo, and A.H. Fleming is published in the European Geosciences Union journal The Cryosphere on 13 May 2015.
Journal information: The Cryosphere

Citation: New study shows Antarctic ice shelf is thinning from above and below (2015, May 12) retrieved 22 May 2019 from https://phys.org/news/2015-05-antarctic-ice-shelf-thinning.html
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May 12, 2015
New study shows Antarctic ice shelf is thinning from above and below


Antarctica Has So Much Sea Ice Scientists Have Trouble Getting There
http://dailycalle...g-there/

May 12, 2015
SEA ice. This article is not about sea ice. Antarctica's ice is melting at accelerating rates and overall levels of ice are at record lows. Sea ice is actually a very interesting phenomena if it's not cherry picked as evidence of something it's not.

May 12, 2015
It is curious when one article says:
"Scientists are still unsure why Antarctic sea ice levels are growing"
and then this article says: "Antarctic Peninsula is one of the fastest warming regions on Earth."
So which is it?.. Or is it both or none of the above?
Does anyone really understand anything or is this just computer modeling at its best?

May 12, 2015
It is curious when one article says:
"Scientists are still unsure why Antarctic sea ice levels are growing"
and then this article says: "Antarctic Peninsula is one of the fastest warming regions on Earth."
So which is it?.. Or is it both or none of the above?
Does anyone really understand anything or is this just computer modeling at its best?


Nothing curious about it, Sammy.

Sea ice is sea ice.

The majority of the WAIS is glacial(land) ice, that is piled up in the contact zone between land, continental shelf waters, and the sea proper, and doesn't vary dramatically on a seasonal basis.

You are perfectly well aware of this important distinction, and yet you continue to post this same bit of misleading chicanery, as if no one knows the answer except for climate scientists, who are purposefully confusing the two. which, of course, they aren't.

Which means you are a double fraud, which I don't find curious at all.

Now piss off.

May 13, 2015
It is curious when one article says:
"Scientists are still unsure why Antarctic sea ice levels are growing"
and then this article says: "Antarctic Peninsula is one of the fastest warming regions on Earth."
So which is it?.. Or is it both or none of the above?
Does anyone really understand anything or is this just computer modeling at its best?

It's both.

Consider sea-ice is frozen salt water.
Consider sea-ice is blown.
Consider winds are known to be increasing there (yes really).

Now, try and put the above together and come up with a scientific rationale.
Hint;
Warmer temps (sea and air) melt ice.
Ice has very little salt in it (yes really).
Fresh water is less dense than is salty.
It therefore is more likely to reamain ot the surface.... where sea-ice forms MORE EASILY..... which is blown further out by the stronger winds.

Geddit?

May 13, 2015
And so, the AGW Cult's CLIMATE FRAUD continues.
This ice shelf sits above known geothermal activity.
http://www.geoche...ca-1.jpg

May 13, 2015
antigoracle claims
And so, the AGW Cult's CLIMATE FRAUD continues.
This ice shelf sits above known geothermal activity
No. The FRAUD antigoracle, is you & other uneducated politically driven blind followers trying to find some way to push their fingers through 100+ years of Science & point the 'they did it' digit at someone they hate because the AGW deniers have failed so many times to understand Physics and come across as a redneck, uneducated lot who are fearful there is pressure on for change...

Antigoracle doesn't get basic physics, ie hypnotized to ignore & manipulated to view anything Science achieves from narrow combative political perspectives...

The fact all continents are above geothermal activity, is beyond antigoracle's consideration & its the comparative heat flow which is the issue, how MUCH there is...

antigoracle's link
http://www.geochembio.com/ecology/IMG/geothermal-antarctica-1.jpg
Shows large areas NOT with geothermal influence...

May 21, 2015

again there is no mention that this is the result of volcanic hotspot under the ice and has nothing to do with climate and nothing we can about this geothermal activity first reported in 2008 - this is the source of the warm water identified in the article
livescience.Com/46194-volcanoes-melt-antarctic-glaciers

see map of geothermal activity related to this ice sheet (along the peninsula is Larsen B in the Weddell Sea) ......... all the way to Ross Island
s23.postimg.Org/vkoeicgqj/Antarctic_Volcanoes.jpg

May 21, 2015
duplicate - sorry

May 21, 2015
No, the volcanoes are not the primary cause of ice loss in Antarctica. It's true that there are volcanoes there, but the heat from the volcanoes is much, much, much, much too small to account for the current loss, let alone the acceleration in ice melt. Some of the scientists involved in studying the Antarctic ice were interviewed in an article about this: https://news.vice...ice-caps . A relevant quote:
Rignot, also the lead author of a study out last month that documented widespread retreat of the West Antarctic Ice Sheet, said geothermal heating contributes to a few millimeters of melting annually, compared to rising sea temperatures which can trigger rates of up to 100 meters each year.

So they don't mention the volcanoes because ice loss due to volcanoes is insignificant compared to the loss due to global warming.

May 22, 2015
zz, thank you for this reference which I had not seen (I'll use it to try and find other related studies)- I have concerns remaining in the interpretation of the geothermal activity's impact because of the correlation of the increased melt in this area to the 3X heat gradient measured in addition to the lack of ocean warming since 2006 leads me to suspect that the source of the warm water contributing to this melt is the geothermal activity (a reference for the lack of ocean warming dynamic landscapesandcycles.Net/cooling-deep-oceans.html )

May 22, 2015
I acknowledge that a lack of actual long term data on ocean temps leave a large opportunity for conflicting concepts

May 22, 2015
in addition to the lack of ocean warming since 2006 leads me to suspect that the source of the warm water contributing to this melt is the geothermal activity (a reference for the lack of ocean warming dynamic landscapesandcycles.Net/cooling-deep-oceans.html )

This claim by landscapesandcycles is a bit of misinformation. The claim is based on the Wunsch and Heimbach (2014) paper that looks at the deep ocean. In particular, the paper shows that the water around Antarctica is warming. As for the ocean cooling, the paper only showed that the deep ocean was cooling, but that was small compared to the rest of the warming. The author, in response to a similar misinformation article, wrote:
Contrary to the implications of Lloyd's article, parts of the deep ocean are warming, parts are cooling, and although the global abyssal average is negative, the value is tiny in a global warming context.

So the paper did not find the ocean, as a whole, was cooling.

May 22, 2015
Something to keep in mind, the landscapesandcycles.net website is something of an anti-science site. It's fine to read it, if that's your thing, but just keep it in mind. If you have any more questions about the paper, you can look at http://www.skepti...ans.html . As for the Southern ocean, recent work (http://www-pcmdi....ming.pdf ) has found that the amount of heating in the upper part of the Southern ocean has been greatly underestimated. Which means the warming of the upper ocean around Antarctica is much greater than Wunsch and Heimbach (2014) thought.

May 22, 2015
zz, thank you for this reference which I had not seen...
@onlymho
If i may offer some advice:
do not take ANY site at its word unless it links studies and the study validates the findings

there is only one reliable source for data, and that is the scientific studies.
period.

there ARE sites that give articles explaining what is going on (Like zz5555's "skeptical Science" site), but unless it specifically references a study (Like skeptical science) and you can go to said study and validate the findings as legitimate, then it can be considered hearsay and thus unreliable
(a common tactic for certain politically motivated sites like the "watts" site)

plus, verify that there are no refuting studies
certain posters have been known to sow confusion with one study while there are several refuting studies saying the opposite

ALWAYS ask for/validate the studies

never go to sites that are NOT legit journals/science/edu
-like "Lord" moncton, et al

follow the evidence

May 23, 2015
onlymho claims
.. geothermal activity first reported in 2008 - this is the source of the warm water identified in the article
livescience.Com/46194-volcanoes-melt-antarctic-glaciers
Your link doesnt work but, this one does, its been updated, note, lower case & needs the .html at the end:-
http://www.livesc...ers.html
This shows mere milliwatts, which is VERY low compared to CO2's radiative forcing >1.5W/m^2 whilst the link shows 0.2W/m^2 ie ~ a tenth, there is no doubt it will add but, bearing in mind latent heat of fusion of water & immense ocean water all around its clear CO2 will have greater effect esp on coastline.

onlymho added
see map of geothermal activity related to this ice sheet ...
http://s23.postim...noes.jpg
Source of this image requires qualification & also re legend but, bear in mind its ice "loss" as +ve or the legend is wrong, ie Most loss around coastline

cont

May 23, 2015
@onlymho
Since you only recently joined on May 21, 2015

I hope you have seen, there are many who start off with passably scientific queries with appearance of sincerity but pursue a political agenda & thus shift stance which includes ignoring Science which is fundamentally based upon the Physics of heat & its movement through the various materials in & on Earth.

Whilst Sol's insolation reduces, temperatures of atmosphere & heat in oceans rise generally in relation to CO2's rise

So for the reasoned observer interested in convergence as part of dialectic, politics has no place, the Physics is settled, the Science of the permutations of that Physics, is not settled but, it is asymptotic

So far the main contributor of heat retention to the atmosphere is CO2 & unfortunate fact CO2 lifts water vapour ppm also which is a stronger greenhouse gas & does so by way of Psychrometry.

Its helpful for a good start in dialectic to know you are sincere & keen to converge etc ?

May 23, 2015
thank you all for your comments and guidance - I have joined 3 paper reference sites that require registration / membership and sometimes fees for access to the actual studies and so provided the public access articles that referenced them (so have now found many papers by Rignot but none yet that support the quote that the geothermal activity is insufficient to produce melting) I also found a study that purported to demonstrate recent increase in this heat source evidenced by the change in gravity due to rise in plumes. Another series of graphs from NOAA showing a decrease of ocean temps in the upper 700 m except for the Indian ocean. The conflicting data that I have reviewed leaves me unconvinced of reasons for reported increase in temperature (GW). The biggest concern is that the models have not been valuable (ie accurate) in predicting the results experienced and so I've tried to review the explanations put forward to account for those variances. .....

May 24, 2015
Onlymho:
Can you point to the NOAA graphs showing the heat content in the upper layers are decreasing except for in the Indian Ocean? Here's the latest global OHC from NOAA and it shows pretty dramatically increasing heat in the upper layers of the ocean, at least globally: https://www.nodc....dex.html (0-700 OHC is the first of the graphs). If only the Indian Ocean is increasing, the increase there must be huge so that the ocean as a whole is warming. Call me skeptical of your graphs.

I suspect you haven't seen any conflicting data as I'm not aware of any data that conflicts with the science. Can you point that out?

I'm also interested in your claim that the models haven't been valuable. They've been shown to do quite well for their intended purpose: long term climate projections. Some anti-science groups claim that failure to work over short term means they fail altogether, but that's nonsense. I'm skeptical of this claim, as well.

May 24, 2015
The conflicting data that I have reviewed leaves me unconvinced of reasons for reported increase in temperature (GW). The biggest concern is that the models have not been valuable (ie accurate) in predicting the results experienced and so I've tried to review the explanations put forward to account for those variances.

I should also note that models are unnecessary in showing why CO2 is the primary cause of the current warming. The models are pretty much unnecessary for most of climate science. So anyone claiming that any supposed failure of the models also shows the science is faulty is either ignorant of the science or outright lying. I assume that your claim is made out of ignorance.

May 24, 2015
Another series of graphs from NOAA showing a decrease of ocean temps in the upper 700 m except for the Indian ocean.

I've just looked at the actual heat content data for the separate oceans: https://www.nodc....ata.html . They clearly show the heat rising in all 3 basins and globally (they don't have separate ones for the Southern or Arctic Oceans). Look at the data yourself. If you've found graphs purportedly from NOAA that show temperature decreasing in the Atlantic and Pacific, you would rightly be suspicious. I can't think of a way to add heat and decrease the temperature.

May 28, 2015
Incidentally, key issue regarding positive feedback effect of CO2 raising H2O in the atmosphere is presented extremely well Eg
https://en.wikipe...ometrics

FACT is water, vapour, steam etc has been VERY well studied for >150years and its well proven both experimentally and theoretically via Physics/Maths that water vapour precipitates out VERY quickly within mere hours once its position on Psychrometric chart changes, this graphical predictive technique is used DAILY by Food & Environmental scientists to gauge propensity for water to dew in a very wide range of environments whether outside, indoors, inside fridges, food containers etc

It is the key issue just WHY CO2 is raising Water Vapour levels as the heat load is much higher than ANY other sources, something Water_Prophet just CANNOT grasp & thus lies to gain credence.

Water_Prophet has also claimed to have "4 technical degrees" but, cannot ever prove it !

Physics, not idle ignorance please !

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