West Antarctic ice sheet collapse even more catastrophic for U.S. coasts


The fate of FL and LA if we’re myopic and greedy enough to let the West Antarctic Ice Sheet (WAIS) collapse [click to see entire SE coast].

A new study in Science finds that sea level rise from a collapse of the WAIS would likely be 25% higher for North America than previously estimated:

The catastrophic increase in sea level, already projected to average between 16 and 17 feet around the world, would be almost 21 feet in such places as Washington, D.C., scientists say, putting it largely underwater. Many coastal areas would be devastated. Much of Southern Florida would disappear.

This article has already started to make news around the globe (Reuters story here). But, frankly, divining the difference between a rise of 16.5 feet (an incalculably devastating catastrophe) and 21 feet (an incalculably devastating catastrophe) is like trying to count the number of devils on a pin.

Nonetheless, WAIS collapse is all but inevitable given business-as-usual warming of 5-7°C. As I explained in my book:

Perhaps the most important, and worrisome, fact about the WAIS is that it is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level.

For a longer discussion of WAIS and its unique instability, see “Antarctica has warmed significantly over past 50 years.”

So what is new in the Science article, “The Sea-Level Fingerprint of West Antarctic Collapse” (subs. req’d)? Study coauthor and geophysicist Jerry X. Mitrovica, director of the Earth System Evolution Program at the Canadian Institute for Advanced Research, explains:

The typical estimate of the sea-level change is five metres, a value arrived at by taking the total volume of the West Antarctic Ice Sheet, converting it to water and spreading it evenly across the oceans. However, this estimate is far too simplified because it ignores three significant effects:

  • When an ice sheet melts, its gravitational pull on the ocean is reduced and water moves away from it. The net effect is that the sea level actually falls within 2,000 km of a melting ice sheet, and rises progressively further away from it. If the West Antarctic Ice Sheet collapses, sea level will fall close to the Antarctic and will rise much more than the expected estimate in the northern hemisphere because of this gravitational effect;
  • The depression in the Antarctic bedrock that currently sits under the weight of the ice sheet will become filled with water if the ice sheet collapses. However, the size of this hole will shrink as the region rebounds after the ice disappears, pushing some of the water out into the ocean, and this effect will further contribute to the sea-level rise;
  • The melting of the West Antarctic Ice Sheet will actually cause the Earth’s rotation axis to shift rather dramatically — approximately 500 metres from its present position if the entire ice sheet melts. This shift will move water from the southern Atlantic and Pacific oceans northward toward North America and into the southern Indian Ocean.

And this all means that if WAIS collapses, “the rise in sea levels around many coastal regions will be as much as 25 per cent more than expected, for a total of between six and seven metres if the whole ice sheet melts.”

A digital animation of various sea-level rise scenarios up to six metres is at

The time to act is now.

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30 Responses to West Antarctic ice sheet collapse even more catastrophic for U.S. coasts

  1. JCH says:

    Louisiana Tech has the oldest helmet logo in Division 1 football.

    For how much longer?

  2. Steve Bloom says:

    Unfortunately, we can’t be sure we haven’t already committed to WAIS melting.

    Also, the map is a little misleading in that by the time the WAIS was gone we’d also have major contributions from the small glaciers, portions of the Greenland and East Antarctic ice sheets, and thermal expansion. These could as much as double the amount of melt.

  3. paulm says:

    Steve they should try to talk about the total sea level rise where possible. So the 25% increase should have been adjusted to give the % of the total expected.

    Much more realistic.

  4. paulm says:

    James Hansen basically has said that we are committed to large WAIS melting and Greenland etc unless we preform miracles.

    Target Atmospheric CO2: Where Should Humanity Aim?
    CO2 will need to be reduced from its current 385 ppm to at most 350 ppm, but likely less than that.

  5. jorleh says:

    Is here somebody who believes that CO2 emissions don´t go up like the last decades until 2020? And for that, until 2030? And CH4? Florida and the other coastal areas are going to swim.

  6. DavidONE says:

    Here’s a Google Maps with interactive sea level rise:

  7. Bob Wright says:

    Future Pennsylvania: No more fall foliage, snow cover, cold water fish, apples, sweet corn, Jersey shore. 90 deg all summer, 24 days over 100, more droughts and severe storms, and lots and lots of climate refugees from the coasts, Mexico, and the dried up southwest. PA is third behind California and Texas in GHG emisions. What a legacy.

  8. Vernon says:

    Well, I have to admit that would be a worry if it were not a fact that it has been warmer in Antarctica than it is now and the Ross Iceshelf survived that.

    Hall et al (2006) Holocene elephant seal distribution implies
    warmer-than-present climate in the Ross Sea

    Our reconstruction implies that during parts of the middle and late Holocene, sea ice was less extensive, the warm season was likely longer, and the environment was more like the sub-Antarctic than at present in the Ross Embayment. Our data on seal distribution cannot inform us about the fate of the Ross Ice Shelf during these periods. However, the lack of coastal landforms, such as beaches south of the present calving front (unpublished observation), and the dates of marine organisms on the adjacent McMurdo Ice Shelf both suggest that the Ross Ice Shelf has been continuously present over the last 7,000 yr

    [JR: How much warmer, ’cause it’s gonna got a lot hotter soon.]

  9. jcwinnie says:

    Unfortunately, even if you explain over and over to the BAUAAAE (Business As Usual And Above All Else) crowd how lack of commitment to 350 ppm is a poor business decision, it seems unlikely that they will cease and desist from destruction of life on the planet as we know it. For them such argument is so much (yadda-yadda-yadda or the sound the adults made in the Peanuts television special). The scale is an unaccustomed time frame, the scope an unaccustomed size, and they own the government.

  10. Steve Bloom says:

    Vernon, it’s uncontroversial that the Milankovitch cycle-driven mid-Holocene warming raised high-latitude temps to something like current levels, and that this resulted in only a very modest amount of melting. As Joe notes, one difference is that we’re not slowing down. Another is the committed warming “in the pipeline,” about .6C.

    But most important, particularly for the polar regions, is that the present warming is very much global and is raising ocean temps. It is no coincidence that ocean current heat transport has been tagged as the principal cause of melting in both polar regions. This effect would not have been seen in the mid-Holocene for the simple reason that increased high-latitude warming means *decreased* lower latitude warming.

  11. Vernon says:

    JR; Well according to the authors:

    The presence of southern elephant seal colonies (which today exclusively occupy areas where the mean January temperature exceeds 0°C, usually by considerable margins), the disappearance of ice-obligate penguins, and the inferred significant reduction in sea ice, both in
    intensity and seasonal duration, suggest that the front of the Ross Ice Shelf could have been subject to January temperatures that surpassed the 1.5°C threshold during two long periods at 1,000–2,300 and 4,000–6,000 14C yr B.P.

    That would mean it was at least 4.5C warmer than now. If I read the IPCC AR4 correctly, means the most likely warming scenario will not get close to this for the Antarctic.

  12. Vernon says:

    Steve Bloom:

    Actually, the Artic warming has been linked to carbon black for 35 to 70 percent of the melting (depends on the year) by a UC Irving study a few years ago. Basically, the polution from Europe and Sibera get blown up over the Artic and deposts carbon black and other polution.

    And no it is not saying that the Antarctic was as warm as we currently are, it is saying that it was 4.5C warmer than we are now. It has been much warmer in the past.

  13. Mauri Pelto says:

    We cannot fall into the trap and be short sighted. Yes soot matters to snow albedo. However, thanks to clean air regulations etc in Europe and North America, it has been noted by many in ice corres that there is less pollution not more in the snowpack. Lonnie Thompson has noted this in ice cores from around the world and in this link it is noted for Greenland. So though it matters, it is hard to make a case soot is increasing.

  14. Vernon says:

    Still does not change the fact that the Antarctic has been a lot warmer that it currently is and the Ross Ice Shelf still did not break up.

    [JR: Again, please direct me to a link to a study that says how much “a lot warmer” it was and when.]

  15. Jim Eager says:

    Vernon, you mean all that carbon black that fell into the sea as the multi-year ice melted?

  16. David B. Benson says:

    Vernon — WAIS is rather more complex than you currently seem to understand. The Ross Ice Shelf is not the most vunerable part, IMO.

  17. The only good thing I can see about the map is that Guantanamo is underwater. Not to worry by this time we will all be without clean drinking water and life, if we manage to make that far, will be completely different. As an Optimist I hope for the better. However, putting Gen Wesley Clark in charge of biofuel lobby, the recusal of Secretary Chu to oversight nuclear weapons, cutting half of the renewable energy stimulus and yet kept 6 Billion for nuclear weapons we’re opting for dirty brown.
    CIA Leo Panetta won’t stay in that job long. The ringmasters already taking hope and castrating it. There is too much of the same and not enough change to make the difference. I am afraid that the bill going through is not going to the right things to allow us and every generation that can manage to survive after us a very bright future.
    good luck and good night

  18. Steve Bloom says:

    Vernon, where exactly does that paper say 4.5C warmer? In any case you’re stretching the results severely:

    “It may be that the environment, although warmer than present, did not reach the critical temperature over a sufficiently large portion of the ice shelf necessary to initiate rapid collapse, or that a steep climate gradient left much of the shelf in a stable zone. In addition, pinning points, such as Ross Island, may have contributed to its stability.”

    So the claim begins to look more limited, and as the paper discusses elsewhere isn’t all that different from some prior results:

    “Although our new reconstruction differs from some previous interpretations (13, 20, 21), it is consistent with late Holocene atmospheric circulation intensity records from Siple Dome (22) and with methanesulfonic acid data from nearby Newall Glacier that suggest expanded sea ice between 300 and 1,250 yr B.P (23). In addition, our ‘seal optimum’ is coeval with a significant accumulation rate increase at Taylor Dome, which may have resulted from sea-ice reduction and greater moisture availability (24).”

    Whether the Ross ice shelf in particular is vulnerable to the observed warming currents is very much a matter of current study, but as David Benson mentioned the Pine Island and Thwaites glaciers are the biggest concern.

    Re the soot, there is no basis for claiming that it (or anything other than warming currents) is the key factor driving the striking loss of Arctic summer sea ice in the last decade, nor does the paper you mention make such a claim.

  19. The sooner sea level rises, the sooner the doubters will change their minds. The bad news is that the other climate effects will cause civilization to fall or cause our extinction before then. Hope for a faster sea level rise because it could save us, like a severe pandemic or a nuclear war could save us.

  20. Vernon says:

    The carbon black was in ref to Arctic melting.

    The study says that the average temperature exceeded 1.5C during this time in January and during modern times the average January temp is -3C, so the difference is 4.5C. Hence it is 4.5C cooler now in January.

    Oh, and the carbon black gets replenished every year when the seasonal winds carry the pollution from Asia and Europe into the Arctic. Actually it makes it all the way to North America.

    If were going to play end of the world as we know it games, lets do about something that we know will pretty much wipe us out such as comet or asteroid strike, super volcano at Yellow Stone erupting, or Canary Island collapse.

    The warming trend in the Antarctic is .2C per century with average temp at -50C for most the Icecap. At this rate we have about 2000 years before melting is an issue. By then our most likely problem is that we will finally be headed back into 80-100k Ice Age.

    [JR: How many times have we been through this — the climate change we are seeing now is nonlinear. Also, the Antarctic is already losing ice mass a full century ahead of model projections. It is melting from underneath, which is particularly dangerous given about the West Antarctic ice sheet is grounded BELOW the water level.]

  21. JCH says:

    If carbon black can do it, then all Osama Bin laden has to do is dust Greenland and West Antarctica.

  22. Vernon says:

    JHC: sure, all he would need is the annual output of Europe and Asia to dust the Arctic. The point is that per the IPCC most of the climate drivers except GHGs our current level of understanding is LOW!

    The only evidence that temperatures are higher now than in the past are tree ring studies. There is mounting evidence that tree rings grown is not correlated with temperature increases. The actual growth curve has been shown to be an inverted U in other plant studies. This is also shown in the divergence between current temperatures and tree rings used for temperature proxies in the IPCC AR4.

    What this means is that there is evidence that our understanding of past temperatures are wrong and the current warming is not exceptional.

  23. Martin says:


    did you doctor the cut and paste job you have above in which this appears: “could have been subject to January temperatures that surpassed the 1.5°C threshold during two long periods at 1,000–2,300 and 4,000–6,000 14C yr B.P.”??? Because, in the text it says “could have been subject to January temperatures that surpassed the -1.5°C threshold during two long periods at ~1,000–2,300 and 4,000–6,000 14C yr B.P.” In addition the text says nothing about “average” January temperature, as you have. It only says “could have surpassed.” Thus, your whole claim of 4.5c warmer then disintegrates like every other claim you’ve made.

    Thanks for playing!



  24. Vernon says:


    It is wrong but it was not my error, it appears that when you copy it from the PDF into HTML it drops the – sign. Thanks for catching that. The correct difference between past temperatures is 3C not 4.5C.

    Did you type it in or cut and paste? I tried it with both IE and Chrome on two different machines and both times it dropped the minus sign when I cut and pasted the text.

    And about why it had to be 3C warmer than now from the paper.

    If you read the text it says that Elephant Seals only breed and molt in locations where the average temperature exceeds 0C, usually by a significant amount. Current average temperatures (Land) avg -3C currently. Therefore the average temperature in January was a minimum of 3C warmer during those periods.

    Thanks for the catch though. I will be more careful in the future when moving text.

  25. Bob Wright says:

    AOL just posted a good article about this on its “Welcome” page, complete with U AZ maps of a 1 meter rise. But if you scroll down to the comments, you will be shocked. It is truly “In” to be a denier in the blogosphere.

  26. Martin says:


    you’re still reading too much into the statement “which today exclusively occupy areas where the mean January temperature exceeds 0°C”. If the authors of the paper meant to imply that that the avg. Jan temp was over 0c, they could have said so. Instead, they only concluded that temps could have surpassed -1.5c.

    In addition, stating that the Jan temp was warmer in the past does not mean that mean annual temps were warmer or that water temps were warmer. As I said, you are reading way too much into this paper, especially if you want to use it to argue that there’s no danger of the Ross collapsing.


  27. Vernon says:


    I am reading what they said which was for the seals to be there the average temp would have to be 0C or above. From that they concluded that the Ross Ice Shelf was subjected to more that -1.5C temps for extended periods.

    For that level of warming in the Antarctic it had to much warmer globally, which means it was much warmer than it is now.

  28. llewelly says:

    Vernon Says:
    February 6th, 2009 at 1:15 pm:

    Hall et al (2006) Holocene elephant seal distribution implies
    warmer-than-present climate in the Ross Sea content/ 103/ 27/ 10213.full.pdf+html
    [long quote from referenced paper snipped]
    JR: How much warmer, ’cause it’s gonna got a lot hotter soon.

    The principal flaws in Vernon’s arguments are (a) global warming will not end in 2099, (b) AR4 projections do not include positive feedbacks in the carbon cycle, which (mostly post-AR4) have been shown to be much more likely than previously believed, (c) research more recent than AR4 shows the AR4 projections probably underestimate polar warming (see for example Arctic summer sea ice exents since 2005). Hall et. al. is clearly good news for the Ross Ice Shelf, but the risk of it melting remains significant.

    For global temperatures, (rather than the regional Antarctic temperaturs Vernon is on about.), see this
    Globalwarmingart graph by Robert Rhode. Scroll down for his sources in the peer-reviewed literature.

    There’s a lot of scatter in the estimates, but it’s likely 1998, 2004, 2005, and probably a few other recent warm years were warmer than the Holocene Climactic Optimum. (HCO for convenience) It won’t be long before global average annual temps are always solidly warmer than the HCO. ( Projections. ) . This implies a modest redistribution of heat currently in the atmosphere might bring January temperatures around the Ross Sea to the warmth reached during the HCO. Much of the argument in this thread depends on models which are known to reproduce past global temperatures with significantly greater skill than regional temperatures.

    Vernon Says:
    February 6th, 2009 at 3:01 pm

    That would mean it was at least 4.5C [Vernon later claimed 3C, Martin argued for 1.5C] warmer than now. If I read the IPCC AR4 correctly, means the most likely warming scenario will not get close to this for the Antarctic.

    I would like to know what part of AR4 you are relying on. When I look at pg 904 in Chapter 11 , I see about 2.5 C warming in annual temperature near the Ross ice shelf. When I look at pg 923, I see about 2.5 C warming in DJF temperature averaged over the whole of Antarctica. Heat won’t be evenly distributed throughout Antarctica as a whole, or throughout a season or a year. Since the same scenario results in global average temperatures significantly above the HCO peak, a modest redistribution of that heat could result in a Ross sea warmer than in the HCO. In other words – even if the big flaws in Vernon’s arguments are ignored – the AR4 projections can’t rule out an elephant seal friendly Ross Sea with much confidence. Further warmer (which would doubtless come with time) would expose the Ross ice shelf to temperatures substantially beyond what it has survived in the past.

  29. Vernon says:

    llewelly Says:

    The principal flaws in Vernon’s arguments are (a) global warming will not end in 2099, (b) AR4 projections do not include positive feedbacks in the carbon cycle, which (mostly post-AR4) have been shown to be much more likely than previously believed, (c) research more recent than AR4 shows the AR4 projections probably underestimate polar warming (see for example Arctic summer sea ice exents since 2005).

    The problems raised by llewelly’s only work if you makes the assumption that we fully understand all the climate drivers. That the GCMs actually calculate rather than use parameters to estimate climate drivers, which they do not. So based on that: (a) The problem with this argument is that there is no way till after the fact to know when or if global warming has ended. After all, it takes 30 years to qualify as climate, right? (b) AR4 does not include positive feedbacks because we lack the understanding of most climate drivers to know whether they are positive or negative feedback or in the case of water, both. (c) Please list published studies that show that AR4 underestimated warming.

    The truth is that recent studies shows that GCM’s consistently overestimate warming in the Antarctic due to the failure to understand how water acts in the intense cold (atmospheric).

    The facts are that the only ‘proof’ that we are warmer now than in the past is based on tree rings and once again I will say is that the science indicates that plants do not have linear growth curve with temperature. It is actually an inverted U with cold and hot being detrimental to plant growth. Other studies show that there was a MWP, LIA, and RWP. Then there is the ‘they were just regional’ argument however even ice cores from Antarctic show that they all existed.

    The article this is all in reference to is Antarctic melting. The Antarctic has been cooling for 30+ years (makes it climate) so worries about mythical worries about melting is currently based on nothing.

  30. james crabb says:

    Have many people discussed the effects of the isostatic rebound due to rapid collapse of the WAIS.