Scientists say “only a few millimetres sea level rise” if Antarctic ice shelf collapses

Collapse of Larsen C would add up to 2.5 mm to sea level by 2100

From the EUROPEAN GEOSCIENCES UNION

New study puts a figure on sea-level rise following Antarctic ice shelves’ collapse

Rift propagation along the Larsen C Ice Shelf. This rift, which led to the calving of an iceberg twice the size of Luxembourg last year, raised questions about the future stability of Larsen C Ice Shelf in a warming world. CREDIT
British Antarctic Survey

An international team of scientists has shown how much sea level would rise if Larsen C and George VI, two Antarctic ice shelves at risk of collapse, were to break up. While Larsen C has received much attention due to the break-away of a trillion-tonne iceberg from it last summer, its collapse would contribute only a few millimetres to sea-level rise. The break-up of the smaller George VI Ice Shelf would have a much larger impact. The research is published today in the European Geosciences Union journal The Cryosphere.

Recent, rapid warming in the Antarctic Peninsula is a threat to ice shelves in the region, with Larsen C and George VI considered to have the highest risk of collapse. Because these large ice platforms hold back inland glaciers, the ice carried by these glaciers can flow faster into the sea when the ice shelves collapse, which contributes to sea-level rise. The new study shows that a collapse of Larsen C would result in inland ice discharging about 4 mm to sea level, while the response of glaciers to George VI collapse could contribute over five times more to global sea levels, around 22 mm.

“These numbers, while not enormous in themselves, are only one part of a larger sea-level budget including loss from other glaciers around the world and from the Greenland, East and West Antarctic ice sheets. Taken together with these other sources, the impacts could be significant to island nations and coastal populations,” explains study-author Nicholas Barrand, a glaciologist at the University of Birmingham in the UK. He adds: “The Antarctic Peninsula may be seen as a bellwether for changes in the much larger East and West Antarctic ice sheets as climate warming extends south.”

Warming in the Antarctic Peninsula led, in 2002, to the dramatic collapse of Larsen B, an ice shelf just north of Larsen C. Unprecedented in its size, almost the entire ice shelf broke up in just over two weeks after being stable for the last 10,000 years.

“Larsen C is the most northerly remaining large ice shelf, therefore subject to the warmest temperatures, and the likeliest candidate for future collapse. George VI is further west and south, in a slightly cooler climate, but is still vulnerable to a warming atmosphere and ocean,” says lead-author Clemens Schannwell, who conducted the work while at the University of Birmingham and the British Antarctic Survey.

Last summer, an iceberg twice the size of Luxembourg broke away from Larsen C. But despite the recent attention on this ice shelf, the team found its future collapse would have a modest effect on global sea level. By using computer models to simulate the interactions between the Antarctic Peninsula ice sheet and the ice shelves, the team found that the glacier response to collapse of Larsen C would add up to 2.5 mm to sea level by 2100 and 4.2 mm by 2300.

 

“The vulnerability to change at George VI Ice Shelf and the possible sea level implications from these changes, are far greater,” says Schannwell. Sandwiched between the Antarctic Peninsula and Alexander Island, George VI Ice Shelf is, at 24,000 square kilometres, around half the size of Larsen C. But it would contribute far more to sea-level rise because it is fed by larger glaciers and is very effective at holding back the ice that drains into it from these glaciers. According to the simulations presented in the new The Cryosphere study, adjustment of the glaciers flowing into it following a collapse could contribute up to 8 mm to global sea levels by 2100 and 22 mm by 2300.

“Prior to our work, we didn’t know what would happen to the upstream ice in the Antarctic Peninsula if these shelves were to be lost. This could have important implications for the local environment and for global sea levels, information that is essential for climate-change mitigation planning and policy,” says Schannwell, who is now at the University of Tübingen in Germany.

“In light of the increasing temperatures projected for the coming century, the Antarctic Peninsula provides an ideal laboratory to research changes in the integrity of floating ice shelves. This region can tell us about ice shelf processes and allow us to observe the response of inland ice to ice-shelf changes. We should view these dramatic changes in the Antarctic Peninsula as a warning signal for the much larger ice sheet-ice shelf systems elsewhere in Antarctica with even greater potential for global sea-level rise.” concludes Barrand.

###

The publication in The Cryosphere: https://www.the-cryosphere.net/12/2307/2018/)

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98 thoughts on “Scientists say “only a few millimetres sea level rise” if Antarctic ice shelf collapses

  1. I think the interesting question is how all that ice will cool the oceans. The antarctic is circled by currents that isolate it from the world’s oceans. If huge chunks of ice break off and float into warmer water, they should have a measurable effect on the heat and salinity of the surface layer, and thereby the global climate. yes/no?

    • They have always been calving and melting. Though not very fast, given how cold the Southern Ocean is.

      Google “Iceberg B-9”. It calved in 1987 and is still very much around. Indeed it was B-9 that caused so much trouble for “the Ship of Fools” a few years ago.

    • Ice is less dense than water. Cold water is more dense than warm water. Floating ice displaces its mass in water. The average level doesn’t change, and there isn’t enough ice above to lower the actual level (semi-reasonable assumption). Floating ice melts and increases in density. The melting also cools surrounding water and increases its density. More density, less volume, sea levels drop. Everyone worried about sea level rise should be out melting icebergs. Or at least towing them to California and Capetown. With sailboats.

      • Good comment about temperature and density David. Better tow the icebergs to Kalifornia quickly though because all of that 900 deg basalt flowing into the ocean in Hawaii is causing thermal expansion of the water and off-setting your density increase. Of course the basalt is filling up the ocean and raising sea-level, but wait a minute sedimentation rates are higher in inter-glacial times, and…. I think this is a complex issue!

      • David, you neglect the fact that freshwater is less dense than sea water. It changes the relationship between the volume of ice and the volume it occupies when it melts. “Because of differences in the density and temperature of ice and sea water, the net effect is to increase sea level by 2.6% of this volume, equivalent to 49 microns per year spread across the global oceans.” It’s a tiny amount, but it contradicts your thesis.

        https://www.sciencedaily.com/releases/2010/04/100428142258.htm

  2. Why doesn’t some enterprising company reduce the size of the glaciers by mining them for water [ice], which is badly needed in certain parts of the world? Such a project would employ hundreds or thousands of workers and alleviate the danger of breakup of the glaciers. (Of course, making the kinds of motion and noise the procedure would involve might actually stimulate the glacier to break up. Oh, well . . .)

    • It would be a lot simpler to take an iceberg which has already broken off, and towing it to wherever the water is wanted.

      • Right……
        That concept has been proposed by numerous individuals who it seems have attained their engineering knowledge from reading Popular Mechanics.

        Its akin to towing a blimp with a model airplane, while the blimp is continually attempting to disintegrate.

    • The basic problem is the lack of market for ice burgs.
      Or one could deliver an ice burg somewhere, but then what.
      So one should focus on making a market for ice burgs, be a buyer for ice burgs.
      One could think of ice burg as temporary real estate, or if there continued to be delivered, to location permanent and adjustable real estate.

      Then once deliverable ice burg are a commodity, one set up the infrastructure to use them in terms of their use as a water resource.

    • reduce the size of the glaciers by mining them for water

      … or chop the ice into bricks and build an Italian ice cafe in the Antarctic.

    • But think of the CO2 generated by burning fuel to move the berg!! Unless they use a nuclear powered ocean going tug, it’s going to go through a huge amount of fuel to move it. I believe CO2 is a beneficial trace gas on which all life depends, but the cost of the fuel is non-trivial in the extreme.

      It would be less costly and more realistic to run nuclear powered desalination plants close to where the water is needed.

      • Actually, powering desalination plants with “green” (non-dispatchable/non-industrial grade) energy would be ideal. Wind and solar to power the desalination plants and run the pumps to highland reservoirs. About the only benefit that wind/solar can offer (still at a huge price)

      • …Unless they use a nuclear powered ocean going tug,….

        Actually JB there was an enterprise in the ’80s called Icebergs International proposing to tow icebergs to Saudi Arabia using French Nuclear tugs.. I suspect the first iceberg will arrive when Fusion technology is commercially viable.. then there’ll be enough cheap energy available to make the icebergs in Ras Tanura saving all those shipping and handling costs…
        cheers!

    • All of the detractions mentioned in the previous comments are what make these concepts the wildly successful endeavors they are.

  3. Fun and games with flow-models neglecting flotation equilibrium (Archimedes Principle) beyond the grounding line of the outlet glaciers, i.e. the model-naughts assume that the outlet glaciers only calve their mass and no shelf rebuilding (glacier ice in flotation equilibrium makes no contribution to sea level change [rise or fall]).

  4. Eco-loons running around in circles, crying “the ice-shelves are melting, they’re melting, melting…… Oh what a wicked world. How could a little CO2 molecule destroy our beautiful ice-shelves…..”

  5. Of course collapse of shelf-ice areas have minimal effect on sea level as they are already floating. Apparently Climate Science has now progressed to a point where it has discovered Archimedes’ Principle.

    And the “braking” effect of shelf-ice areas on feeder glaciers is to put things mildly, not as large and well-proven as is usually claimed.

    A study 18 years after the break-up of Larsen A (the only shelf for which there is data over a reasonable time-interval) showed that for the 5 glaciers where both pre-1995 and recent data are available, ice flow had increased for 3 glaciers, was unchanged for one and had decreased for one. Also for all three glacier where the flux had increased it is still decreasing after the initial rise, so it is unknown what the new equlibrum flow will be.

    When it comes to glacier area (which is much easier to measure), out of a total of 14 glaciers, 8 had shrunk, 5 showed no measurable change, and one had grown slightly. The average decrease counted over all 14 was 3.4%

    https://www.the-cryosphere.net/9/957/2015/tc-9-957-2015.pdf

    • Even if the breaking off of the shelf did destabilize the glaciers behind them, wouldn’t that only continue until the moving ice formed a new ice shelf?

      • Good question, Mark. However, this ‘stabilizing’ is very much a hypothesis, for which as far as I know no observational evidence has been found or even proposed. How would you verify whether the mechanism actually exists and works as proposed, or whether it is just a pie-in-the-sky, or here ice-in-the-water, idea?

      • Mark – Sure, and that would make sea level rise. Like adding ice cubes to a drink.

    • “And the “braking” effect”

      When the ice breaks off, which way does it move?…..if it was “braking” it would push back
      …it’s the pulling that makes it break off and float away

  6. To be clear, TOTAL disintegration of BOTH ice shelves, by 2300 would raise sea levels, 220 years in the future, by 1.02 inches.

    Idiotic to couch this as scary or alarming….it is actually re-assuring.

    • “Idiotic to couch this as scary or alarming”
      So who did that?

      People have pointed to collapse of the shelves as a symptom of warming. But who said that they would, on their own, raise sea levels by a scary amount?

      • Except that the Antarctic isn’t warming.

        The gigantic East Antarctic Ice Sheet, repository of most of the world’s fresh water, is growing.

        To the extent that the tiny West Antarctic Ice Sheet might be losing mass, it’s only because of subglacial volcanoes.

        All during the time that Arctic sea ice was declining, ie 1979-2012, Antarctic sea ice grew dramatically. Hence, CO2 can’t possibly explain Arctic sea ice decline during that period. Especially since it has been growing since 2012, despite continued CO2 increases.

        QED.

  7. Excerpted from published article:

    Recent, rapid warming in the Antarctic Peninsula is a threat to ice shelves in the region, with Larsen C and George VI considered to have the highest risk of collapse.

    And just what the ell does “rapid warming” in the Antarctic Peninsula have to do with the “collapse” of the Larsen C and/or George VI ice shelf?

    “DUH”, those two ice shelves are far, far too massive for any “rapid warming” of the near-surface air temperatures to cause a “thermal (expansion) shock” resulting in a “fracturing” or collapse of said ice shelves.

    “DUH”, …… gravity is the sole culprit responsible for the “fracturing” or “collapse” of ice shelves, …… be they glacier in origin or not.

    • Well obviously, ice shelves collapse due to the stress and exhaustion from fighting climate change. Duh.

    • Samuel, how would gravity be a factor when the shelves are floating?

      It’s not just the near-surface air temperatures, but ocean temps that are weakening the shelves. But surface temps make a difference, too. Pools of water form (yes, even in Antarctica) and filter down into cracks in the ice, then freeze and expand.

      • Kristi Silber ….. saidith:

        Samuel, how would gravity be a factor when the shelves are floating?

        Kristi, if the per say “shelves” are floating then they are called “icebergs”, ……. not ice shelves.

        It’s not just the near-surface air temperatures, but ocean temps that are weakening the shelves.

        Kristi, why don’tja place a big block of ice on the hot pavement of a parking lot in bright Sunlight to prove to yourself that it will fracture and/or collapse because of the “hot” air temperatures and “hot” pavement. Ps: take a cold 6-pack with you because you will need it during your “waiting”.

        and filter down into cracks in the ice, then freeze and expand.

        Shur nuff, Kristi, ……. the warm air temps caused the cracks, ….. and the cracks caused the fracks, ….. and then the fracks caused the collapse. ……. and then the iceberg floated away toward Australia.

          • Kristi, ……. so much for your “quick facts” that are actually NOT facts.

            Ice shelves are permanent floating sheets of ice that connect to a landmass.

            “DUH”, iffen they are permanent floating then they can NOT be connected to the glacial ice situate on the landmass.

            Glacier connected ice shelves are NOT boats, ……. they do not float.

      • There are several reasons that ice-shelves break up.

        One is actually gravity, since it is gravity that drives the continual small-scale calving of the ice-front (glacier ice becomes mechanically unstable when more than 50 meters tall)

        Another is tidal fracturing

        A third is bottom melting (though in some areas shelf ice actually thickens over tim by snow accumulation or ice accreting to the underside of the shelf or both)

        A fourth is refreezing of meltwater in fractures (usually due to tides). This only applies to the shelf areas around the Antarctic Peninsula, since there is very limited melting on the other more southerly shelves.

        • tty,
          “One is actually gravity, since it is gravity that drives the continual small-scale calving of the ice-front (glacier ice becomes mechanically unstable when more than 50 meters tall)”

          That makes sense. But would that be called an ice shelf “collapse”? And am I wrong that ice shelves float?

          • Ice shelves float, but have a grounding line, where the glaciers feeding them are still attached to rock.

          • Good grief.

            Sam C Cogar nonsensically wrote, “Kristi, if the per say “shelves” are floating then they are called “icebergs”, ……. not ice shelves.”

            No, ice shelves and icebergs are both examples of floating ice.

            Ice shelves are attached to the shoreline, but they’re still floating ice. The shoreline does not support their weight, the water does.

            Ice bergs are freely floating (i.e., not attached to the shoreline), often formed from broken-off pieces of ice shelves.

            Kristi correctly retorted, “Samuel, do you habitually redefine common terms?” and helpfully linked to a correct definition of “ice shelves” (though some of the other “quick facts” on that page are misleading).

            Sam then doubled down on his error, writing, “iffen they are permanent floating then they can NOT be connected to the glacial ice situate on the landmass. Glacier connected ice shelves are NOT boats, ……. they do not float.”

            Chimp also helpfully explained it to Sam, to no avail.

            Sam then tripled down on his error, writing, ” ice shelves extend out into or onto coastal waters but that doesn’t mean they are “floating” on the water. Docks and wharfs extend out into or onto coastal waters …… but no one has ever accused them of being “floating”.”

            Docks can either be floating or supported by pilings driven into the bottom. Ice shelves float on the water, while remaining attached to the land, just like floating docks.

            These folks would like to sell you a floating dock; click for some more pictures:
            https://thedockdoctors.com/floating-docks.html
            https://sealevel.info/floating_dock.png

          • A “Good grief” response from — Dave Burton

            Ice shelves are attached to the shoreline, but they’re still floating ice.

            Dave B, ……… to wit:

            float·ing – adjective

            1. buoyant or suspended in water or air. “a massive floating platform”

            synonyms: buoyant, on the surface, afloat, drifting, hovering, levitating, suspended, hanging, defying gravity

            2. not settled in a definite place; fluctuating or variable.

            The shoreline does not support their weight, the water does.

            Dave B, …… the tides come in (to shore) thus increasing the height of the sea surface and the tides go out (from shore) thus decreasing the height of the sea surface …… but the ice shelves do not “float” up n’ down with the rise n’ fall of the water depth.

            And large wind driven waves come in (onto the shore) thus increasing the height of the sea surface and large wind driven waves go back out (away from the shore) thus decreasing the height of the sea surface …… but the ice shelves do not “float” up n’ down with the rise n’ fall of the water depth.

            But your “floating docks” as pictured above DO …. “float” up n’ down with the rise n’ fall of the water depth.

    • Disinterest? NASA employees stuck looking at their smartphones during working hrs? A sit-in because of the current administration? Gavin Schmidt lost his mojo?

    • Perhaps the challenges of measuring sea level from Colorado have finally manifested. /sarc

      • yes, but they wanted to be sure they wouldn’t be inundated. Wouldn’t want to lose all the data in a tsunami, donchano. Also the skiing is way better in Boulder than on the coast.

        (removing tongue from cheek and returning to your regularly scheduled programming)

      • “Well, the Greenland icecap grew last year, and seems extremely likely to grow again this year”

        Yes, high snowfall led to the Greenland icecap growing. Why is it extremely likely to grow again?

        Re Joe Bastardi –

        “He is a private sector meteorologist. His clients can judge whether or not he is good at forecasting the weather (he probably does a credible job). However, when it comes to science and climate change, his public statements on the subject imply to me that he does not understand the very basics of the science. His statement regarding carbon dioxide and the first law of thermodynamics is a particular whopper. His only academic credential is a B.S. in Meteorology from Penn State in 1978. Fox News needs to find a more credible spokesperson.”

        – Judith Curry

        (The claim about the first law of theromodynamics may refer to this: AGW ““contradicts what we call the 1st law of thermodynamics. Energy can be neither created nor destroyed. So to look for input of energy into the atmosphere, you have to come from a foreign source.”)

        • Apparently you’re unaware that Judy Curry has not only changed her opinion about Joe, but switched to his side, ie the side with all the science.

          • If Curry truly has changed her opinion about him, my esteem for her has dropped a notch. I expect better from her. The science is on his side??? AGW contradicts the 1st law of thermodynamics? Sorry, Chimp, but your comment reflects poorly on your knowledge of the science.

          • Neither she nor I agree with him about the 1st Law, but do concur that human effect on global temperatures is negligible, and that more CO2 has been beneficial. We do have a local and possibly even regional effect on climate, due to urbanization, air conditioning, irrigation, dams, etc.

            But because of real pollution, ie particulates, SO2, etc, we can’t even say for sure what is the sign of any net human effect on global temperature, ie cooling or warming, but in any case, it’s insignificant.

            I guarantee you that I know more about science than you do.

        • “Why is it extremely likely to grow again?”

          Look at the diagram Kristi. More than half the melting season is past and there has only been minimal melting (about 25 GT).

          • My guess is that it’ll net out to about zero ice mass change this year, compared to an average ice mass loss of 200 Gt/year, and a small ice mass gain last year. It’s a lead-pipe cinch that this will at least be another year of above average ice mass trend (i.e., less than 200 Gt of ice loss).

            I wonder whether NASA JPL’s “Vital Signs” Earth Science Communications Team Climate Propaganda Ministry will continue to stall updates of their “ice sheets” page, to preserve the illusion that Greenland is continuing to lose ice? To maintain that fiction, they:

            1. stopped their graph over a year ago, and

            2. cherry-picked one data source, to exaggerate the trend (reporting “286.0” Gt/year instead of DMI’s reported “200 Gt/year”).

            My guess is that they were waiting for this year’s numbers to come in, in the expectation that last year’s gain was a transient “blip,” and this year would show at least 200 Gt loss. It’s now obvious that hope will be disappointed. So, will they continue to stall?

            https://sealevel.info/NASA_VitalSigns_LandIceGreenland_2018-07-24_annot1.png

  8. Because these large ice platforms hold back inland glaciers, the ice carried by these glaciers can flow faster into the sea when the ice shelves collapse

    Are we really sure that it’s the large ice platforms hold back inland glaciers” and not the contrary?
    That the inland glaciers, through friction with the ground holds back sea ice that is pull away by the waves?

    • “and is very effective at holding back the ice that drains into it from these glaciers.”

      They can’t be holding back the glaciers……they crack from pulling…not pushing

      • Mariano Marini

        That the inland glaciers, through friction with the ground holds back sea ice that is pull(ed) away by the waves?

        Latitude

        They can’t be holding back the glaciers……they crack from pulling…not pushing

        Sorry bout that, ya’ll, ….. but waves (water) don’t have any “pulling” or “sucking” power. But the waves and the tides do exert upward “lifting pressure” on the ice shelves. And of course, when the waves recede and/or the tide goes out …… then gravity exerts downward pressure …… and thus both the aforenoted “up/down” pressures causes stress resulting in “fatigue failure” in/of the ice. To wit:

        Giant Waves Breaking Up Antarctica’s Sea Ice
        https://www.livescience.com/45928-giant-waves-breaking-up-antarctica-ice.html

        • That story is about sea ice. No waves are ever going to budge shelf ice which is about 200 meters thick.

          The tides do however, as first noted by Amundsen back in 1912.

          Unless you have actually been there it is hard to comprehend just how big antarctig icebergs and shelf-ice are.

  9. “… adjustment of the glaciers flowing into it following a collapse could contribute up to 8 mm to global sea levels by 2100 and 22 mm by 2300.”

    “We should view these dramatic changes in the Antarctic Peninsula as a warning signal for the much larger ice sheet-ice shelf systems elsewhere in Antarctica with even greater potential for global sea-level rise.” concludes Barrand.”
    _____________________________________________________

    ” could contribute up to 8 mm to global sea levels”, “these dramatic changes” “with even greater potential for global sea-level rise”.

    could, dramatic changes, even greater potential –

    didn’t happen shortly.

    Even when: ice shelfs will gain new mass in the wake of such potential Happenings.

  10. “In light of the increasing temperatures projected for the coming century, the Antarctic Peninsula provides an ideal laboratory to research changes in the integrity of floating ice shelves. This region can tell us about ice shelf processes and allow us to observe the response of inland ice to ice-shelf changes. We should view these dramatic changes in the Antarctic Peninsula as a warning signal for the much larger ice sheet-ice shelf systems elsewhere in Antarctica with even greater potential for global sea-level rise.”

    All readers of this and policy makers too need to understand that the ice shelves are in fact more stable than the ‘increasing temperature projection for the coming century.’ You don’t have to go to Antarctica when the policy risk and science uncertainty is closer at hand.

  11. “Warming in the Antarctic Peninsula led, in 2002, to the dramatic collapse . . ”
    Wait a minute – has not the Antarctic Peninsula experienced approx 2 decades of a cooling trend amounting to cooling of just over 1 C?

  12. “The Antarctic Peninsula

    – may be seen as a bellwether for changes in the much larger East and West Antarctic ice sheets

    – as climate warming extends south.”

    — says it all.

    • Particularly since climate in the Peninsula has been cooling since the turn of the century:

      https://www.sciencedirect.com/science/article/pii/S0048969716327152

      Highlights

      We examine climate variability since the 1950s in the Antarctic Peninsula region.


      This region is often cited among those with the fastest warming rates on Earth.


      A re-assessment of climate data shows a cooling trend initiated around 1998/1999.


      This recent cooling has already impacted the cryosphere in the northern AP.


      Observed changes on glacial mass balances, snow cover and permafrost state

  13. What increasing temperatures? How long are we gonna let these climate scientists continue their lies?

    • IF you have a bath and IF you move around and slosh the water everywhere, creating a giant tsunami in said bathroom, THEN you will see the effects of SLR…(ummmm, just blame it on the other one occupying the tub at the same time)… D’OH ! ( No, those funny bubbles don’t count ! )

    • Think of the snails though. The snails aren’t going to notice the S-L-O-W rate of SLR, and when they finally do, it’ll be too late, especially for the crippled and bedridden ones. They will surely drown. Do you really want that on your conscience?

  14. Well, I can still read and there is no evidence I can see that major parts of the Antarctic ice will collapse. East Antarctica is still the most stable an cold part of our world. That’s where most of the land based ice on this planet is…

  15. Didn’t antarctic sea ice suddenly reduce a couple of years ago? If it happened, it seems to have been forgotten.

  16. Have you ever noticed that the catastrophic climate change crowd have a calamity-du-jour for a year or two, then, when Joe Public gets tired of it, they start banging away with a new calamity. A few years ago it was ocean acidification: we’re all gonna die because the oceans are turning acid and all life in them will be destroyed. Nowadays you hardly hear of it at all. Today it’s all sea level rise, our coastal cities will be inundated, we’re all gonna drown …

    Wait until next year or possibly the year after. Anyone want to hazard a guess at what the next calamity-du-jour will be? Rapidly mutating viruses? Giant killer bees? CO2-fueled volcanic eruptions? Say what you want about the CAGW crowd, they are not lacking in imagination.

  17. How could a collapse extend to 2100?
    In that case i would call it melting and not a collapse.

  18. So if the shelf beyond the rift was somehow “holding back the glacier” miles from the grounding point then it had to have been in compression. If that piece was in compression then how did a rift form in the first place let alone allow the piece to float away?

    It makes no mechanical sense. What would make sense is a very low frequency tremor both flexing the shelf and causing the glacier to briefly speed up. Favorable wind and or ocean current would then create rift(s) where the shelf cracked and eventually move the now disconnected piece(s) to float away.

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