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Marcel_g
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P-Maker, very interesting. Thanks for pointing me to that thread, although I almost hesitate to look at it because I'll never get any work done once I do! ;-) I was kind of wondering about whether Hansen et. al had more evidence for super storms than a couple of boulders and the ridges. And yes, I didn't include Totten or Cook in my numbers, or thermal expansion, or other land based glaciers. Add in the slowing of the AMOC, and the east coast of the US is in for some serious SLR in short order. As well, regarding PIG and Thwaites (the main part of the WAIS) the ice fall mechanism (if I understand what you mean by ice falls) won't come into play because their grounding lines have already passed the highest point of bedrock, so the grounding line will continue to go 'downhill' as it melts inland. cheers, Marcel
Toggle Commented Aug 28, 2015 on Jakobshavn record retreat at Arctic Sea Ice
P-maker, I think the work that Rignot and his colleagues did in the Pine Island Area wasn't about the WAIS lifting mechanically, it was that the changed ocean currents around the continent, combined with the surface layer of colder fresher water from increased ice melt, were causing the base of the glaciers' terminii to be exposed to much warmer sea water, thus increasing their discharge rates. As well, in the case of the Pine Island area, Rignot discovered that the glaciers there have had their grounding lines melt back behind a restraining ridge of bedrock, meaning that there is no longer anything to physically slow them down and the warmer sea water can go downhill as it eats away at the base.
Toggle Commented Aug 21, 2015 on Jakobshavn record retreat at Arctic Sea Ice
Thanks for the welcome P-maker. Unfortunately, I'm not a true glaciologist, rather I'm just an amateur observer who, like many others here, can't take my eyes away from this incredible spectacle of melting ice. Unfortunately I won't ever have time to actually read Hansen's paper, I'm just going by the summaries provided by various climate centred sites like climatecrocks.com. Before Hansen's paper came out, but after seeing the news about Rignot's work on the Pine Island Glacier and its neighbours in WAIS, and reading that some of the significant glaciers in Greenland and the Totten are in East Antarctica are similarly based well below sea level, I plotted out melt rates on a crude graph to see how the various contributors would add up. It was a fun exercise, but really only for my own purposes and all pretty speculative. I included the Pine Island area (1.2m over 150 yrs), the rest of WAIS (3m over 320 yrs), marine terminating Greenland (1.5m over 200yrs), and 4m from the rest of Greenland over 320 yrs (leaving 2m of Greenland ice intact). I made assumptions that the ice melt would continue to accelerate, and I used tanh curves to approximate my assumption that overall, the ice melt will start slowly, go the fastest in the middle, then slow down again as it approaches equilibrium or zero. This all added up to roughly 30cm by 2050 and 2m by 2100. These numbers didn't include other terrestial glaciers, the Totten glacier (1m+), thermal expansion of the oceans, or the slowing of the AMOC. I found that to be fairly alarming, because once the other contributors are factored in, sea level rise at this rate would be very disruptive and within 35 yrs. And then Hansen comes out with his paper that a really sudden pulse of SLR is plausible enough to put it up for peer review. cheers, marcel
Toggle Commented Aug 21, 2015 on Jakobshavn record retreat at Arctic Sea Ice
P-maker, Interesting comments about ice falls vs ice streams, do you know if that's included in Hansen's recent paper about abrupt sea level rise? Abrupt sea level rise is something I'm quite worried about. I originally thought that droughts, floods and fishery collapses would be the initial fronts of climate disruption and SLR would impact later, but after seeing what Dr. Rignot and his colleagues found in West Antarctica (unstoppable collapse already started due to warm water under cutting the ice sheet) and what Dr. Box has found about Greenland's melt factors (albedo, moulin drainage, ice softening), I don't think we can discount the possibility of sea level rise happening much more quickly. That being said, I don't think Greenland is going to contribute all 7m before the WAIS: once Greenland's marine terminating glaciers have retreated back to being above sea level, or too far from deeper warm sea water, they'll slow down, and WAIS is going to melt very fast. Rignot said at the current rate it will take the Pine Island area about 200 years, but that the rate is accelerating. If I remember correctly, that area has 1.2m of SLR in it. And there are other areas in WAIS and the Totten area in East Antarctica which are marine terminating and accelerating, so I think the WAIS is going to be contributing significantly at the same time as Greenland. Neven, as an avid lurker, thanks very much for the blog and the forum.
Toggle Commented Aug 20, 2015 on Jakobshavn record retreat at Arctic Sea Ice
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Aug 20, 2015