Missing factors in climate models suggest Antarctic melt may not be so bad after all

From MCGILL UNIVERSITY

Geophysics could slow Antarctic ice retreat

Gravitational effects, variations in Earth structure could damp rise in global sea levels

The anticipated melting of the massive West Antarctic Ice Sheet could be slowed by two big factors that are largely overlooked in current computer models, according to a new study.

The findings, published online in Nature Communications, suggest that the impact on global sea levels from the retreating ice sheet could be less drastic – or at least more gradual — than recent computer simulations have indicated.

Over the past year, numerous studies have warned that parts of the West Antarctic Ice Sheet are on the verge of a runaway retreat. Just last week a high-profile research paper forecast that this could lead eventually to a rise in global sea levels of as much as three metres.

The authors of the new Nature Communications paper, however, focus on two geophysical elements that they say aren’t adequately reflected in computer simulations for this region: the surprisingly powerful gravitational pull of the immense ice sheet on surrounding water, and the unusually fluid nature of the mantle beneath the bedrock that the ice sits on.

“The fate of the polar ice sheets in a warming world is a major concern for policy makers — and attention is rightly focused on the importance of restraining CO2 emissions and preparing for rising sea levels,” says lead author Natalya Gomez, an assistant professor of Earth and Planetary Sciences at McGill University in Montreal. “But our study shows that for Antarctica, in particular, computer models also need to take into account how gravitational effects and variations in Earth structure could affect the pace of future ice-sheet loss.”

The gravity effect

Most people think of gravity as the force that keeps our feet on the ground. But any large body – such as a massive expanse of ice — exerts a gravitational pull on other bodies, including water.

As the West Antarctic Ice Sheet melts, the researchers project, the reduction in its mass would reduce the gravitational pull to such an extent that it would lower sharply the sea level near the ice. This, in turn, would slow the projected pace of retreat of the ice sheet.

The elasticity effect

Gomez and co-authors David Pollard of Pennsylvania State University and David Holland of New York University also factor another important variable into their simulations. When an ice sheet retreats, the solid Earth beneath it, freed from the load of the ice, rebounds upward. This rebound occurs in two parts: an elastic component that happens right away, and a viscous component that happens over hundreds to thousands of years. (The Earth’s interior – or mantle – flows like a fluid but very slowly because it is very viscous).

The West Antarctic sits atop a region where the mantle flows more easily than in other parts of the Earth. So the land there will pop up faster than scientists – and their computer models — would expect based on the average viscosity of the Earth’s mantle.

“Our simulations show that when we assume a structure for the Earth’s interior that resembles the structure underneath the West Antarctic, the Earth’s surface rebounds higher and more quickly near the edge of the retreating ice sheet,” says co-author Holland of NYU. “This makes the water along that edge shallower, which slows the retreat of the ice sheet.”

CO2 emissions a crucial factor

The researchers’ simulations also confirm that the levels of future CO2 emissions will be a crucial factor in the pace of retreat for the region’s ice. “The lower the levels of CO2 in the atmosphere, the more the geophysical factors will be able to help stem the ice’s retreat,” Gomez says. “The greater the emissions, the more the geophysical forces risk being overwhelmed by the strength of warming.”

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“Sea-level feedback lowers projections of future Antarctic Ice-Sheet mass loss”, Natalya Gomez et al, Nature Communications, Nov. 10, 2015. DOI: 10.1038/ncomms9798

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63 thoughts on “Missing factors in climate models suggest Antarctic melt may not be so bad after all

  1. Am I being a tad cynical in wondering why there is a plethora of papers being published around now, some full of doom & gloom, some not so?

    • No of course not. There was always going to be a major propaganda push for COP21 with a gullible and weak legacy media only too willing to use it to fill the pages while not applying any journalistic investigation of the claims.

    • It seems to me that a number of people are posting panic for the build-up to Paris, and a number of others are posting rebuttals against what they seem to feel are bad science.

  2. Always need the “CO2 still threatens our future” money quote at the end to support the meme and continue the funding.

    • Indeed. Isn’t it interesting how experts in geophysics are able to casually intone that CO2 is a problem, without needing to run those expensive climate simulations?

      • Yes, indeed Ben. Simple necessity of getting published, which is needed to get promoted – must push the CAGW meme.

  3. A warmer planet that isn’t stuck in an Ice Age is evil according to the new faith whereas a frozen planet is fine with these vandals. I said years ago, the plan is to tell everyone that the Little Ice Age was the ideal climate for us.

  4. “The researchers’ simulations also confirm that the levels of future CO2 emissions will be a crucial factor . . . ”
    Hmm. It’s interesting how a study on tectonic elasticity, somehow, confirmed the CO2 Forcing hypothesis. Hmm. I wonder if there is anything in there that would bring some resolution on the continuing debate about good and bad cholesterol. Hmm.

    • CO2 emissions, cholesterol; throw in something about caffeine is good/bad and you have the grant writing Trifecta, James. (Come to think of it, it probably wouldn’t hurt if they added a line or two about whether or not Lee Harvey Oswald acted alone in Dallas.)
      These computer simulations are truly amazing!

    • CO2 is the only control knob, so of course it is a “crucial factor” (do I need a sarc tag for that?)

  5. “The lower the levels of CO2 in the atmosphere, the more the geophysical factors will be able to help stem the ice’s retreat,” Gomez says. “The greater the emissions, the more the geophysical forces risk being overwhelmed by the strength of warming.”
    Yet more drivel from people who should know better!

  6. Thanks, Anthony, but I find little new in this missing gravitational factors that are well-known to affect satellite sea-level measurements.
    And, of course, blaming CO2 for everything bad is not new either.

  7. A decent three-step sandwich feedback!

    The fate of the polar ice sheets in a warming world is a major concern for policy makers — and attention is rightly focused on the importance of restraining CO2 emissions and preparing for rising sea levels

    “I am in faith. Don’t stone me and keep funding coming.”

    This makes the water along that edge shallower, which slows the retreat of the ice sheet

    “We found a negative feedback.”

    The greater the emissions, the more the geophysical forces risk being overwhelmed by the strength of warming.

    “I am in faith. Don’t stone me and keep funding coming.”

    • Always need the “CO2 still threatens our future” money quote at the end to support the meme and continue the funding.

      Yes, Tucker!

      • The one faith I have in this world is that when I get to the end of a climate paper, my eyes will be met with the typical ‘CO2 is the monster under the bed’ dogma without ANY shred of evidence/data/graphs to support it. How such statements can pass the editorial review process is beyond my tiny brain to fathom.

      • Tucker writes: “How such statements can pass the editorial review process is beyond my tiny brain to fathom.”
        I don’t intend to preach to the choir Tucker, but on the off chance this was true frustration rather than intentional sarcasm I’ll toss in my $0.02.
        It gets through because even the editors fear challenging consensus. I made a short but sweet career of being a scientific iconoclast as (first) a peer reviewer and later an editor of a major scientific journal and I have no qualms about saying your career in the upper regions of scientific journalism can be painfully brief if you depart from common wisdom without bulletproof evidence. I was one of those lucky enough to have bulletproof evidence and my career survived, but that isn’t typical. An editor, faced with publishing something contrary to popular opinion would be advised to have a scapegoat; in this example the author(s). The editor need take no heat as long as the author(s) have done obeisance to the cult of AGW. It’s often called plausible deniability.

  8. If this is true that would mean a certain amount of sea level rise can be attributed to sea floor glacial rebound that is still occurring from the last glacial retreat.

    • Wrong way. That would cause a decrease in sea level as the ice went from sitting on top of the land to the water. We are definitely seeing the effect on land. See talk of “isotactic rebound”, which is causing northern regions like Canada and Scotland to rise 3-4 mm per year or more due to the loss of glacier weight, causing localized sea level drops.

    • If the sea floor rises because of glacial rebound, sea levels must rise, imagine a bulge forming in the bottom of your swimming pool. The great lakes get shallower every year because of glacial retention, which means they hold less water, where do you think that water goes?

      • Its the continents (and their margins) which rebound from the loss of ice, not the sea floor. The rise of the continents in many areas outpace the rate of sea level rise and to this day still show a net decrease in sea level on a relative basis.

    • By the way I am talking about areas where the glaciers have melted thousands of years ago and sea level has already risen, but the retention occurs for many millennia afterwards but at an ever slower rate.

  9. wasn’t ther a nasa study that said the global antarctic continent was in it’s whole still gaining ice? so how can antarctica’s melt make the sea levels to rise as it’s total balance is still growing?
    oh yes WAIS is not the entire continent…..however the more trumpets are blown for that part the more the impression is given that it is for the whole continent…..

    • Exactly. Take an extreme condition, a worst case scenario, and scare people with it.
      I first experienced that lying in about 1970, with claims about the pollution in Lake Erie. I’ve seen it several times since then, but nothing nearly as Goebbels-like as CAGW, though. Goebbels, as in what is often paraphrased as, “The bigger the lie, the more it will be believed.”
      What he actually said was, “The principle & which is quite true in itself and that in the big lie there is always a certain force of credibility; because the broad masses of a nation are always more easily corrupted in the deeper strata of their emotional nature than consciously or voluntarily.”
      It’s all propaganda…
      One nasty thing about it is that we are approaching the time when some of the purveyors are reaching retirement age, and have made entire careers out of it.

  10. Their Church of CAGW dogma forced them to pollute a serious technical study of Ice sheet local gravity and crust-mantle loading effects with the ridiculuous, “The researchers’ simulations also confirm that the levels of future CO2 emissions will be a crucial factor in the pace of retreat for the region’s ice. “The lower the levels of CO2 in the atmosphere, the more the geophysical factors will be able to help stem the ice’s retreat,” Gomez says. ”
    They must have feared that without that homage to church dogma, the grant handlers would not look kindly on their study that shows WAIS melt may not be the SLR boogeyman preached about by the high priests of Climate Change.

  11. As the West Antarctic Ice Sheet melts, the researchers project, the reduction in its mass would reduce the gravitational pull to such an extent that it would lower sharply the sea level near the ice. This, in turn, would slow the projected pace of retreat of the ice sheet.
    ====
    and the “unexpected” increase in snow fall..increases their mass and makes them move faster
    fun times!

  12. A recent post on WUWT showed that the Antarctic ice is actually growing. If we reduce CO2 and slow the loss of ice even more will that not reduce sea level? Our harbors will be dry and shipping will collapse ruining the world economy! CAGC (Catastrophic Anthropocentric Global Cooling)./sarc

    • Aha! But that is exactly what they are shooting for. For them humans are evil. Everything humans do is evil. Especially anything to do with industry is evil. Only innocent wild animals and GMO-less plants deserve to inherit the Earth. Bambi and Thumper – everything else is evil.

  13. Our simulations show that when some stuff, which isn’t going to happen, happens, then some other stuff which is only weakly understood may or may not happen which may lead to further events either happening or not happening. etc (sarc.)
    Wouldn’t these people be better off spending their time playing Minecraft.
    At least that way they’d be less of a burden on the tax payer.
    And they might learn something.

    • If only you had added a few more maybes and coulds and mights in your statement, your hypothesis may have gotten a govt grant …

    • indefatigablefrog, You should lay off the Minecraft and get yourself a climate science academic post. You obviously have the structure of climate science papers down to a tee. I would give you a grant if I were on a grant committee.

  14. When will the models include the active volcanism under the WAIS, observed by apostate UT Austin scientists?
    http://www.pnas.org/content/111/25/9070.abstract
    Significance
    Thwaites Glacier is one of the West Antarctica’s most prominent, rapidly evolving, and potentially unstable contributors to global sea level rise. Uncertainty in the amount and spatial pattern of geothermal flux and melting beneath this glacier is a major limitation in predicting its future behavior and sea level contribution. In this paper, a combination of radar sounding and subglacial water routing is used to show that large areas at the base of Thwaites Glacier are actively melting in response to geothermal flux consistent with rift-associated magma migration and volcanism. This supports the hypothesis that heterogeneous geothermal flux and local magmatic processes could be critical factors in determining the future behavior of the West Antarctic Ice Sheet.

  15. Camel’s Nose Under Tent ALERT
    In the Department of Foregone Conclusions and other such mendacities, the problem with this ‘article’ is that the foregone conclusion is … that the Antarctic Ice Shelves are going to melt, and that is just a matter of when, and how fast. The upside is, that only the camel’s nose is peeking under the tent: “the good news is, it won’t be so fast”. Well… that’s a relief.
    But there’s still a much larger camel outside. And if we get used to the smiling face peeking in, soon it’ll be a head. Then a neck. Then the whole darn camel. And it will claim, “why are you asking whether I belong here? You’ve not objected much all this time. Its proven you don’t care. No… I’m staying.”
    GoatGuy

  16. The anticipated melting of the massive West Antarctic Ice Sheet could be slowed

    Right there I quit reading. I am sooo tired of “could bes” and “may bes” that I refuse to read them anymore.

    • They want another Ice Age. Seriously. This is why they constantly harp about how this is hotter than in 1650 AD.

    • As someone once taught, “maybe” means “maybe yes” and “maybe not”, so when one comes across a sentence that reads “maybe” one needs to insert ALSO “maybe not” to see what the sentence reads.
      I read large portions of maybe 5-15 journal papers a week, on another subject, which touches geology, astronomy, ice cores, and ice sheets, and it is amazing how much speculation is allowed by journal editors. So many “maybes”, “we believe that”, “suggests that”, and such waffle phrases – they have no business in scientific papers. If the paper is based on maybes, the paper shouldn’t have been written in the first place.
      It is saddening to see such drivel, such lack of empiricism, and so much one-sided, hope-it-is-true interpretation of vague results from minimal experimenting. Over-stepping the evidence is rife. Jumping to conclusions seems to be the norm.
      It ain’t science. When did maybe become science? Some moment in my lifetime, but I don’t know when.

  17. Anthony
    An interesting graph on the DMI Ocean and Ice Services Arctic Sea Ice Extent The Northern Hemisphere Sea Ice coverage that you used to use is still available through Arctic Sea Ice Blog showing the
    “Current Sea Ice extent Total sea ice extent on the northern hemisphere since 2005. The ice extent values are calculated from the ice type data from the Ocean and Sea Ice, Satellite Application Facility (OSISAF), where areas with ice concentration higher than 30% are classified as ice.”
    I mention this as it is currently the highest ever recorded since 2005 and does not show up on the 15% DMI graph you are using in your Sea Ice Page.
    The only way to access it is to click on the map in the Arctic Sea Ice Services of Neven’s and then click on the small “go to” heading at the foot of the 15% graph.
    Worth a look even if it only lasts a small time.

  18. This rebound occurs in two parts: an elastic component that happens right away, and a viscous component that happens over hundreds to thousands of years. (The Earth’s interior – or mantle – flows like a fluid but very slowly because it is very viscous).
    =
    Notwithstanding that the rebound on a sphere would also affect far away regions at different time as the elastic rebound bulge propagates. See the pioneering paper by Clark, Farrell & Peltier 1978 in Quaternary Research.

  19. “Over the past year, numerous studies have warned that parts of the West Antarctic Ice Sheet are on the verge of a runaway retreat.”
    And how much has the West Antarctic Ice Sheet actually retreated, so far?

  20. What happens on the Western Antarctica Peninsula has absolutely no capacity to directly affect the great mass of ice that is the continental ice sheet. All the ice on the WAP could melt and it wouldn’t do JACK to sea levels. And with the rest of Antarctica actually colder than it’s been, that piddling peninsula isn’t going to affect anything whatsoever.

  21. Seriously, I looked into the fracking-earthquake claims and found that there is nothing to it. See my blog post at https://feet2thefire.wordpress.com/2015/08/07/a-look-at-fracking-earthquake-claims/
    And there is a paper out about the fracking-water claims, and the paper found specific evidence that the polluting of the well water comes from surface leaks, not from the fracking far below. See my blog post at https://feet2thefire.wordpress.com/2015/10/15/wow-fracking-may-not-be-the-source-of-gases-in-well-water/ That paper “Elevated levels of diesel range organic compounds in groundwater near Marcellus gas operations are derived from surface activities” is at http://www.pnas.org/content/early/2015/10/07/1511474112

  22. blah blah blah. The scare factory never ceases while the climate models are proving to be wrong. What a scam and we will all pay twice. Cap and trade of carbon will empty the coffers and the Govt’s will have nothing left when the next natural disaster occurs.. and they always will regardless of climate whatever. Cold or warm we will continue to have more and more expensive disaster relief due to population growth not due to more occurring extreme weather events (which by the way are occurring less along with all the other doom and gloom misinformation being spouted)

    • The real problem occurs when a society decides disaster relief is a profession. This is in fact what has happened.
      Disaster relief is charity. Those of us unable to provide physical aid send money to honest volunteer coordinators, the rest of us grab our 24 hour packs and head for the nearest airlift. Some of us take our trained SAR dogs, medical skills and tools. Those are the only legitimate forms of disaster relief. The rest are people making money off the pain and suffering of fellow humans. Dante would have an opinion on which circle those people should spend eternity in.

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