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Andrew Dodds
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Larsboelen - Newton's laws apply to everything.. but the ice sheet does not have much momentum. In that way it's a bit like continental drift - if you calculate the momentum you find that it's so small that, for instance, the human population of a continent could stop it by all pushing together. It's the continually-acting forces that give the *appearance* of a process with momentum. (This can be counter-intuitive..) Personally, I find the situation of the WAIS more worrying in terms of rapid sea level rise.. although I suspect that the southern GIS is already doomed as well. It really is a case of working out 'how quickly' more than 'if it melts'.
Fredt.. I just like the analogy.. it also works, interestingly, as an explanation for why the composition of basalt differs from that of the mantle generally, or why hydrothermal vein deposits tend to be full of rare and valuable minerals. There's interesting stuff going on when you suck a Popsicle. This year will be.. interesting as far as sea ice goes. As far as I can tell, we are one exceptional year away from essentially-zero ice.
Toggle Commented Mar 22, 2013 on Max reached (?) at Arctic Sea Ice
Wayne - There's a good experiment you can try.. with a popsicle, or other flavoured ice, just see what happens when you suck it. All of the impuirities/flavourings come out first, leaving a stick of near-pure ice on a stick. This will be what's happening inn the Arctic - multi year ice will get a bit of heat, and melt slightly. The vast majority of the salt will go straight into the small amount of melt, leaving pure ice behind. Hence the older sea ice is, the less salty.
Toggle Commented Mar 21, 2013 on Max reached (?) at Arctic Sea Ice
John: This sort of study: Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by –142 ± 49, +14 ± 43, –65 ± 26, and –20 ± 14 gigatonnes year. Simple addition gives Antartica as -71 Gt / year (not sure that you can add the uncertainty) And this is apparently accelerating. The reason seems to be not so much surface temperatures but oceanic heat transport melting the ice from underneath and so making ice drain faster.
Toggle Commented Feb 7, 2013 on CT SIA anomaly above zero at Arctic Sea Ice
Lennart - Gives a recent overview. Actually I think my 10m may have been slightly OTT, 3 is indeed closer. Although, of course, the rate of change of temperature/forcing never approached the levels we are seeing now.
Toggle Commented Oct 4, 2012 on PIOMAS October 2012 (minimum) at Arctic Sea Ice
Lennartvdl.. I come to this from the viewpoint of a geologist, with a fair bit of experience of computer modellng. Basically, from what we can see in the record, anything up to 10m/century, with spikes of 2m/decade are possible. However, this is within the context og the glacial/interglacial cycle - the current warming seems to be faster. Modelling ice loss - sea or land - is a very fraught problem. You have an in-situ forcing, changes in external heat transport, albedo changes, induced weather changes, and in the case of land ice, changes in the physical properties of the ice sheet. Thus far, where modelers have tried to simplify these features (because you have to to get anywhere at all..) it seems that this results in models that underestimate ice loss. This is reasonable, if there are parts of the system you can't model yet, you have to be conservative or your models can end up looking silly. Anyway.. from past evidence, I would not be particularly surprised to see 3m or more of sea level rise by 2100, at least no more surprised than rolling a 6 with a die..
Toggle Commented Oct 4, 2012 on PIOMAS October 2012 (minimum) at Arctic Sea Ice
Just from the numbers, it seems that if we have a big YOY decline, it reduces the final volume by about 2500km3 (2006-07, 2009-10). If that happened now, we'd be down to a few hundred km3 left.. and at 1m think, you need 1000 km3 to get 1 million km2 Area. So... given a big melt year, volume-wise, then we would be within touching distance of seasonally ice-free from next year onwards, unless there is a very large and surprising jump..
Toggle Commented Oct 3, 2012 on PIOMAS October 2012 (minimum) at Arctic Sea Ice
Idunno - I think that the average curve is slightly misleading for this, what you need to do is work out a baseline average before significant declines set in. For example, an eyeball of CT from 1979 to 1989 sees minima in the range 5.0-5.5 Mkm2. If we then take 5.25Mkm2 as the pre-AGW average, that means that 2.62Mkm2 is the 50%-missing number. It also means that in absolute terms, the anomaly is probably bigger than commonly reported.
Hi, Long time reader, first time poster.. Was just playing around with Cryosphere Today and came up with this comparison (Aug 6 2007 vs Aug 6 2012): It's genuinely disturbing, it illustrates just how much has changed. Even in the 'freak year' of 2007, much of the sea ice that remained was fairly contiguous pack (~100% cover); whereas today it looks like there's barely any solid ice areas left.
Toggle Commented Aug 9, 2012 on Arctic storm part 3: detachment at Arctic Sea Ice
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Aug 9, 2012