Major sea level rise likely as Antarctic ice melts?

So says the Beeb. And they have a cute picture of whales next to icebergs to prove it. It would be natural to think this was occaisioned by That East Antarctic mass loss, in full (i.e. the new GRACE results) but apparently not, it is just a coincidence: Sea levels are likely to rise by about 1.4m (4ft 6in) globally by 2100 as polar ice melts, according to a major review of climate change in Antarctica. Conducted by the Scientific Committee on Antarctic Research (SCAR), it says that warming seas are accelerating melting in the west of the continent. . Before I continue onwards let me quote Two years ago, the Intergovernmental Panel on Climate Change (IPCC) projected that the global average sea level would probably rise by 28-43 cm (11-16in) by the end of the century. But it acknowledged this figure was almost certainly too low, because it was impossible to model “ice dynamics” – the acceleration in ice melting projected to occur as air and water temperatures rise. Launching the SCAR report in London, lead editor John Turner from the British Antarctic Survey (BAS) suggested that observations on the ground had changed that picture, especially in parts of the West Antarctic ice sheet. “Warmer water is getting under the edges of the West Antarctic ice sheet and accelerating the flow of ice into the ocean,” he said. I do this merely to ask if you know a Top Fact about John Turner? He is very fond of donkeys. Now, back to the schedule.

So, the SCAR release is Antarctic Climate Change and the Environment and that is supported by the BAS press release (read it now folks – they have an irritating habit of moving them around every five minutes). On the off chance that you don’t want to read a 20 Mb pdf download, they helpfully provide a top 10 points list in BIG SHOUTY CAPITALS for the hard of understanding. I’ll leave you to read most of that for yourself (NN will like the bit about sea ice). They reckon that The predicted warming [to 2100] of around 3º C is not enough to cause melting across most of the ice sheet but that Loss of ice from the West Antarctic ice sheet is likely to contribute some tens of centimetres to global sea level by 2100… This is expected to contribute to a projected total sea level rise of up to 1.4 metres by 2100.

At this point we go back to the title of the Beeb’s story and say Aha! Yes: you’ve phrased that really very carefully. “Major sea level rise likely as Antarctic ice melts”. Not *because* but *as*. In that case, they ar relying on ~1.2m of SLR from misc sources to 2100, plus some more from Antarctica, and that is within the bounds of the reasonble.

Incidentally, have you noticed how exciting things have got recently? I’m sure only half a year ago I was bemoaning the lack of cliamte stuff, and now busloads are coming along all at once. It must be Copenhagen (argh! Oh no! I’ve said the word and I said I wouldn’t).

33 thoughts on “Major sea level rise likely as Antarctic ice melts?”

  1. And they have a cute picture of whales next to icebergs to prove it.

    So which is it? As the sea rises, the icebergs will be deeper in the water, or is it that the water will be so deep the whales will no longer be able to swim?

    Or was it just a cheap stock photo from a royalty-free CD 🙂


  2. And your point is?

    [In this case, my interest was in understanding the headline. I do now, having written it up. If you wanted a motto, though, it could be how different views are on this question: this study draws rather different conclusions to the GRACE work -W]


  3. W,

    You are just baiting me aren’t you? “Almost certainly too low.” What is your reference for that from AR4? I think they said it was impossible to predict. Just a bit different. And in any event they added something like .1 or .2 M as an extra margin.


  4. Please explain for us dummies how Antarctic ice can melt at so very many dozen or two or three or four degrees above the melting point of ice.

    And of course I am not speaking of the Peninsula around which people bath in volcanic splendor which has been the focus of so very many studies about CO2’s effect on the weather.

    I AGW is true, obviously lots of water will evaporate faster and then condense in eternally cold Antarctica as snowfall, so if Antarctica is loosing ice it means there is no warming in other places, right?


  5. William, any thoughts on Phil Jones stepping down and the university investigations into both Jones and Mike Mann? I need some talking points to combat the deniers, this really has me depressed.

    [“This too will pass” I suspect is the correct answer. Certainly, do nothing hasty 🙂 -W]


  6. This is not a new assessment of sea level rise. They are relying on Rahmstorf 2007 for the 1.4 meter figure. I can’t even begin to say how happy that makes me.

    [It is an interesting question. For myself, I’m going over to the idea that the semi-empirical approach may well be better than the GCM one, but don’t quote me -W]

    Concern that the IPCC sea-level projections may be biased on the low side has been reinforced by the increase in the rate of rise of sea level since the early 1990s. The rate of 3.1 mm/yr noted in the IPCC (2007) report is faster than the central range of the IPCC projections and at the very upper end of the IPCC projections (Rahmstorf et al, 2007). This suggests that one or more of the model contributions to sea-level rise is underestimated (see inset diagram in Fig 5.19). Given these observations, Rahmstorf et al. (2007) projected a likely maximum sea-level rise of 1.4 m by 2100. sea-level rise in the Southern Ocean and a maximum in the Arctic Ocean.


  7. “William, any thoughts on Phil Jones stepping down and the university investigations into both Jones and Mike Mann? I need some talking points to combat the deniers, this really has me depressed.”

    I wouldn’t be too depressed. An investigation is going to be the only way to overcome the tonnes of crap Jones and Mann are going to face from the deniers. As we know there’s not much there, independent investigations are going to be the only way to clear their names.


  8. W,

    Nothing wrong with a semi empirical approach in principle. But the Rahmstorf paper fails the key tests for a linear regression models. This was clear from published comments at the time, as well as some further analysis. I discuss that here.

    [Yes, I saw that but never had time to look at the details. I want to, because this is an intersting question. Any number of skeptic commentators here claim to be statistical experts, so it would be nice if they would do the analysis -W]


  9. Paul,

    Martin’s point was that the two coefficients were within error limits so that you couldn’t say that the original result was necessarily wrong. However, you can see from his comment that extrapolating from the result of the regression is problematic, which is what a forecast for 2100 would be.

    In the post I linked to from here I went on to look at other tests other than an out of sample test. The failure of those tests in addition to the out of sample test result, show that the model is not well specified.

    It may be that a different empirical model could be built. But it would almost certainly have to take into account that expansion from warming sea temperatures, and rise caused by increasing mass are separate processes, that almost certainly operate on completely different time scales.


  10. NikFromNYC [Sorry, I deleted his posts as noise]

    Apologies to WMC for this OT post, but whatever happened to the quality of trolls on Stoat? 😦

    [You just can’t get the staff nowadays -W]


  11. “zuiderzee” is one of the truly great geographical names.

    Lamb points out in “Climate History and the Modern WOrld” that indundations occur in catastrophic events (IIRC he was discussing 1287). A small rise in sea level combined with a storm and king tides can lead to large swathes of land returning to Neptune’s kingdom. It doesn’t tend to happen incrementally.


  12. So what’s happening to the Ross ice shelf?

    “… the Ross Ice Shelf is separating quickly from Ross Island where Scott Base and McMurdo are.

    “We are seeing the biggest ever break out of the Ross Ice Shelf in 15 years, our supply lines to the airfield are getting affected.”

    Scott Base manager Troy Beaumont told Stuff this afternoon that the sea was opening up and access to the iceshelf was becoming difficult.

    “The ice is breaking up,” he said.

    He said it was likely the Globemasters would be able to land at this point, but it would take staff longer to get onto the ice….”

    This is an earlier image: (don’t know how old that image is)

    [At a guess, not as exciting (at least climatologically) as it sounds. I happened to be talking to someone from BAS earlier today and they didn’t mention it. Icebergs break off every now and again -W]


  13. Coincidental? Or is the ice shelf susceptible to storm damage?

    “” we were stuck in the most intense storm I have ever encountered in 19 years in the navy,” skipper Lieutenant Commander Simon Griffith told Stuff yesterday from inside the Antarctic Circle, enroute for Dunedin and a Thursday docking.

    Hurricane force winds up to 182km/h “exploded off the Ross Ice Shelf” and sharp swells of 8m slammed into HMNZS Wellington.”


  14. Some older info:
    Journal of the Royal Society of New Zealand Dec 1981
    “In the east there is a predictable, though variable, pattern of sea ice breakout from October through January, while on the west there are few documented breakouts by February. In the east water is predominately derived from the open Ross Sea, whereas in the west the water originates from under the Ross Ice shelf.”

    But that’s 30 year old info. Anything newer?

    Scott/McMurdo/Ross Island are on the west side, as I read the maps:


  15. In related (albeit undated — old? new?) news:
    which points for images and videos to
    (a site apparently unavailable right now)

    “… The discovery of a substantial gap between the base of the ice and the bed is quite surprising. No such gaps have been previously detected or inferred under the ice streams. Antarctic subglacial lakes (like Lake Vostok) involve a substantial ice-bed gap, of course, but it is on a dimensional scale hundreds to thousands of times greater than that involved here; also, no such lakes have been found in association with ice streams. Theoretical calculations that interpreted earlier (pre-probe) ice-stream observations have assumed the existence of a gap, but the calculationsbased on the rate at which water exits from boreholes and enters a basal conduit systemimplied only a narrow gap, about a tenth of an inch wide. Some lines of reasoning suggest that such a gap is not present in the natural system at all but is opened up in the drilling process when borehole water under a high overpressure is injected into the ice/bed contact and opens up a gap along it. It seems quite unlikely, however, that a gap 1.5 m (59 inches) wide could be formed in this way during the short time (approximately two minutes) during which the high pressure is applied.

    Alternatively, such gaps are a known feature of glaciers that move by sliding of the ice over the bed. The basal sliding can cause cavities to open up between the ice and the bed, generally in the lee of protuberances in the bed. The process is called ice-bed separation or basal cavitation. The size of the cavities is controlled by the basal sliding speed, the amplitude of the basal roughness, and the basal water pressure. At high water pressure, slightly below the ice overburden pressure, the cavities are generally thin in the vertical dimension compared to their horizontal dimensions, and when penetrated by the hot-water drill they should appear as a gap between the base of the ice and the bed. This appears to be the situation encountered by the probe in boreholes no. 2 and 3.

    The significance of the probes observations of a basal gap is thus that in the neighborhood of boreholes no. 2 and 3 the ice stream moves by basal sliding. This is contrary to a widely held view that the motion is by shear deformation of soft sediment underlying the base of the ice. The mechanical decoupling of the ice from the bed, which is a necessary consequence of the gap, should contribute to rapid ice-stream motion, and it will introduce a significant complication into the ongoing efforts to analyze and model the rapid-flow mechanism.

    Another point of significance is the gaps role in the basal water-conduit system. In down-looking video at the bottom of borehole no. 2 the probe observed plumes of turbid water exiting from the bottom of the borehole via the basal gap, proving that the gap was part of the basal water system. (The water was leaving the borehole in response to clean water being pumped into the hole near the top.) In borehole no. 3 the situation was probably similar, producing the observed turbulent motions of water in the gap. The existence of the wide gap shows that the basal water system includes large cavities that can store and release large volumes of water. This must be important in the functioning of the water system and its influence on the basal water pressure, which is probably a key parameter in the ice-stream mechanism.

    In addition to observing the basal gaps in boreholes no. 2 and 3, in all three boreholes the probe observed a basal layer of ice loaded with rock debris, which has not been previously recognized in studies of the ice streams. The debris-laden layer was 15.8 m (52 ft) thick in borehole no. 1, 25 m (82 ft) in no. 2, and 11.6 m (38 ft) in no. 3. From their appearance in the video, various types of debris-laden ice could be identified, depending on their content of coarse rock fragments and fine clay particles (see image #5). Except for a relatively rock-poor layer at the base of the ice in borehole no. 3 (see image #2), and except for complex interbedding of the different debris-laden ice types (image #5), the rock and clay contents generally increase downward toward the bed, and may reach 60% rock by volume. This would qualify them as possible products of basal freeze-on, in which water-saturated subglacial rock debris gets frozen on to the base of the ice. Detection of basal freeze-on would be an indication that the ice mass is tending towards becoming frozen to the bed, which could be responsible for the great slowdown of Ice Stream C that occurred 150 years ago. Basal freeze-on operating for 150 years could add about 1.5 m (5 ft) to the thickness of the basal debris-laden ice layer, which is much less than the observed 12-25 m (38-82 ft). Other mechanisms are needed for emplacing rock debris so high above the bed and for distinctions among the various types of debris-laden ice, whose role in ice-stream mechanism is not known.”


  16. Ah, that was from 2001 — it’s been cited four times:

    Subglacial conditions during and after stoppage of an Antarctic Ice Stream: Is reactivation imminent?
    [PDF] from
    SW Vogel, S Tulaczyk, B Kamb… – Geophysical …, 2005 –
    Abstract Borehole observations from the base of the West-Antarctic Ice Sheet (WAIS) reveal
    the presence of a 10 to 15 m thick accretionary basal ice layer in the upstream area of Kamb Ice Stream (KIS). This ice layer has formed over a time of several thousand years by …


    “Borehole videos from the base of Kamb Ice Stream reveal a 10-14 m thick layer of sediment-laden basal ice and a 1.6 m deep water-filled cavity.

    Representing a several thousand-year record of basal freezing, its presence suggests that the shutdown of Kamb Ice Stream was associated with
    basal freeze-on and limited availability of basal water. The build-up of basal water over the last several decades suggests that the mechanism for shutdown has disappeared. Re-lubrication of the ice base may reactivate Kamb Ice Stream leading to a significant increase in the contribution of West-Antarctica to the global sea level.”

    His results dismiss the volcanos-under-ice:

    “Active or recently active subglacial volcanism may play an important role …. Petrological and geochemical characterization of subglacial sediment and sediment derived from basal-ice (basal sediment) however indicates that mafic volcanics, if responsible for these anomalies, are considerably older than Late Cenozoic (Mesozoic or Paleozoic), reducing the likelihood of considerable contribution to the geothermal flux significantly ….”


  17. More interesting ideas from the British (2009)
    Basal glacier ice and massive ground ice: different scientists, same science?

    “… in order to promote future collaboration certain obstacles need to be overcome. The contrasting ice-classification schemes employed by glaciologists and permafrost scientists, for example, need to be unified in order to allow detailed comparisons of ice-rich sequences in both environments. This could, in turn, enable exciting research advances, most notably by facilitating the identification of preserved remnants of Pleistocene ice sheets within permafrost regions that provide a potentially invaluable and currently largely untapped source of palaeoglaciological information.”

    There’s a chore for someone — rectification of names.


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