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Watkin M
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Isn't the simplest explanation for the increasingly dramatic pause in SIE simply that the jet stream has reverted to "normal" over the north Atlantic? For the first time since (I think) 2007 the NAO has been solidly positive through the autumn. Here in the UK that means its been gloriously warm (15C), wet and very windy. Just like the good old days. Seems to me that this atmospheric pattern should be pushing a lot of warm air and warm water into the Barentz Sea. It might also result in extreme compaction of older ice to the north which is still very "slushy". Northerly winds to the immediate east of Greenland will also cause increased export of ice through the Fram Strait, reducing ice cover in the CAB. A higher solar flux may be part of the reason the jet stream has normalised (I seem to recall that sunspot intensity is correlated with the NAO), but the fact that ice extent in the summer of 2013 increased significantly on prior years may also be relevant. After all, a number of people have proposed the counter argument - that reduced ice extent from 2007 onwards was the cause of the persistently negative NAO we saw between 2008 to 212 - and which produced cold winters in western Europe. One last depressing thought. A positive NAO in autumn / winter seems to inhibit ice formation - at least in the most vulnerable sectors - the Barentz, Kara Seas and Baffin Bay. If we do get a more normal winter season as far as the atmosphere is concerned, it may be about to reveal the extent of the damage done to the structure of the ice sheet over the past few years. Perhaps the next phase of Artic warming will not be about summer ice loss, but about a reduced refreeze in winter?
Toggle Commented Nov 12, 2013 on PIOMAS October 2013, take two at Arctic Sea Ice
Indeed. lol.
Toggle Commented Sep 17, 2013 on Pinpointing the minimum at Arctic Sea Ice
Maybe it was just a fleet of icebreakers?
Toggle Commented Sep 16, 2013 on Pinpointing the minimum at Arctic Sea Ice
Hi. Would also like to say thxs to Neven. Have learned such a lot this summer. I posted a while ago about the fracturing "event" which caused much of the ice to the north of Ellesmere Island and Greenland to break up in mid to late August. The sky was cloudier last year, so hard to compare exact dates, but there is no sign on MODIS of anything of the same magnitude occurring in 2012. Chris R has very helpfully posted a link to detailed PIOMASS thickness map for May, which shows (I think - the colours are tricky) that the ice in this area was very much thinner this year at the start of the melt season. This presumably explains why the ice broke up despite the weather being less favourable for melt. I am guessing the ice was thin in the spring because of record melting last year. MODIS is now showing a wide lead (up to 10km) running from the Beaufort Sea, interrupted only by patches of broken ice, all the way to the Fram Strait. Interesting this lead runs precisely through the area which PIOMASS shows with a maximum negative anomaly in May. Although its been developing for weeks, opening and closing and sometimes filling with "rubble", over the last few days it's opened considerably in several sections. You have to view MODIS over several days to see the entire length of the lead as the area is quite cloudy at the moment. You can see the effect quite clearly to the north of Greenland in the images from the 10th and 12th. It now appears, and this is the reason for my post, that the ice "cap", or what's left of it, is now structurally detached from the remaining fast ice. I am wondering if this might be significant - or unprecedented? Would appreciate it if anyone can point me towards pictures comparable to Worldview for years before 2012. Would also be interested to know if anyone has an explanation. Maybe I'm imagining things, but its almost as if a million+ sqm of ice has simply upped and moved north. I understand the principle of compaction, but its not obvious to me that wind has been blowing in the right direction - not over such a distance - and not strongly either. And surely the prevailing current is onshore?
Toggle Commented Sep 16, 2013 on Pinpointing the minimum at Arctic Sea Ice
LRC. "It APPEARED to retain integrity would probably be better". Hope I am understanding correctly, but you seem to be suggesting that there is a micro scale structure to the ice that isn't necessarily visible by satellite using either IR, MW or visual imaging? Eg apparently solid ice may actually be "rotten" in some way? Looking at 2012 MODIS again, it strikes me that that some of the ice I was assuming was continuous "multi-year" ice might actually have been a matrix with more or less scattered floes of older ice originating from the 2011 melt season embedded in first year ice from winter 2011/12. First year ice is presumably the weaker element of the matrix, effectively creating fault lines throughout the pack which fail when stressed beyond a critical threshold. If this is true (and just hypothesising here) in 2013 the underlying structural strength of the pack would reflect the record melt of 2012. This could explain how the ice could fracture to a greater extent across a much wider region during a cold summer which also lacked a major late season storm. Last question before I return to lurking, how solid are the ice depth and density assumptions used to calculate PIOMASS and other volumetric measures? If the multi-year pack is significantly comprised of thicker, denser blocks of old ice embedded in newer thinner ice, would the algorithms used to interpret satellite data actually pick this up in the average? Or could the changing state of the pack be causing over (or under) estimation of thickness and/or mass?
Toggle Commented Aug 28, 2013 on Hole at Arctic Sea Ice
Hi. Hope you don't mind me briefly unlurking, but I've also been fascinated over the past two weeks by the dramatic fragmentation of the multi-year ice lying between Greenland, Ellesmere Island and the pole. As far as I can see from MODIS, this did not happen to anything like the same extent last year, despite the fact that 2012 was significantly warmer in the area - illustrated by less snow on land, more ice melt in the north coast fjords, and more open water immediately adjacent to the coast. In 2012, MODIS does show multiple fractures in the region, but the resulting flows are more like 100km across - except near the coast. And in 2012 there were large melt ponds visible into September, which to me suggests the ice has largely retained its integrity. This year, especially to the north of Greenland, the ice has broken up into thousand of smaller flows, typically in the region of 1km to 10k across. No sign of melt ponds, but plenty of open water. Does anyone have any idea as to why this might have happened? PAC2012 didn't smash up the ice in this region last year - and this years collapse didn't seem to coincide with a storm. In fact the weather was clear for much of the period - presumably indicating light winds. I also have no idea if this matters? The big questions to me is will a larger number of smaller flows be ejected out of the Fram Strait more rapidly - or would large pieces of ice move at the same speed?
Toggle Commented Aug 27, 2013 on Hole at Arctic Sea Ice
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Aug 27, 2013