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Enno Zinngrebe
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Here is a very nice NASA video on this green arctic soup sea ... (for me that seems to fit quite convincingly to Espen/Neven´s observation)
Toggle Commented Sep 19, 2012 on Minimum open thread at Arctic Sea Ice
Thank you bfraser. Just on cue to support you: "Giant algae blooms thriving under thinning Arctic sea ice" It actually makes sense if one thinks about it: not long ago on this blog was discussed how the solar energy input through thin first year ice was really measurably many times greater than through perennial ice. Should not come as a wonder if little things take their advantage! Still, I would never have thought of it.
Toggle Commented Sep 19, 2012 on Minimum open thread at Arctic Sea Ice
Hi, since I´m new to this, I don´t know what you mean with this shining star :) But I don´t think it is something like the sunglint in MODIS images of tropical seas where the sun shines from right behind the satellite. How are satellite, pole and sun configured around the 21st Sept? Again looking at it I find the Green to be locally variable, like NE of Frz. Jsf. Lands, or r03c04 as it´s called on this blog. That doesnt seem to be astronomical? Or would it? I´m also impressed how well the new Uni Bremen AMSR2 map and the MODIS image agree, once the clouds are gone.
Toggle Commented Sep 19, 2012 on Minimum open thread at Arctic Sea Ice
re: Espen, the Green Ocean. I don´t know - I guess something biological would have to be the first suspect? But it happens to be that in the same location there is something funny with the buoys? Yesterday´s discussion sent me clicking through the live buoy oceanographic data and the two in the Laptev Sea seem to show something strange: unfortunately I am not knowledgeable in interpreting such data. Are they even real or are they malfunctions? Maybe someone here can explain. It just strikes me that this is about in the same area where you & Neven noticed this greening.
Toggle Commented Sep 19, 2012 on Minimum open thread at Arctic Sea Ice
jim williams, you will like this site (from a random wild goose chase). "The observations additionally suggest that efficient lateral mixed layer restratification processes may be active in the Arctic, also impeding mixed layer deepening." that may be a hint that the change in the waters might come sideways, rather than by basin wide simultaneous "layer collapse". Might be nice to find the papers that must have come out of this work.
Toggle Commented Sep 18, 2012 on Minimum open thread at Arctic Sea Ice
beaufort sea anomalous anomaly: Beaufort Sea Buoy Map: there seems to be no buoy swimming right in the curious hotspot (of course). I have no idea how one gets these buoy´s presumably live data. Maybe someone knows? There seem to be no ships in the area tracked by ASI? But the above map shows many little black triangles - I guess weather stations - including on the coast right next to the Hot Spot. If that were truly 18 deg C ocean water that would have to show up in those stations. is maybe the data site for one of the nearest buoys, 90041. Nowhere near such high T (they give just above 0 C which I find interestingly warm) but note that the temperature plot has many funny spikes to that 20 C plot limit, maybe this is a technical issue?
Jim thank you. I quite agree. (And then shouldnt scientists try to litter the Arctic marginal seas with buoys, so that they could detect such a change?) Then if it goes as you say, one should expect that the *winter* sea ice extent would follow - and thereby mark - the gradual progress of the Atlantic surfacing into the Arctic Basin? Marking the line where that new water has become cooled enough to allow winter ice? So, that would mean that maybe areas like the Laptev or East Sib Seas lose thier winter ice cover before the Baffin Bay does? Interesting angle. Again thanks for the explanations. "freeze freshening" is a term I still have difficulties with. Making Ice means taking out the non-salt part out of the water so it should make saltier water, no? Whereas melting ice should make fresher water? That still confuses me.
Toggle Commented Sep 18, 2012 on Minimum open thread at Arctic Sea Ice
"As soon as there's no more ice to melt by mid summer the water will start getting saltier and the halocline will quickly break down, ending Winter refreezes. " I am not sure I can follow that. I agree that is is one crucial issue for estimating what really will be the consequence of all the newly summer ice free seas. But I am completely layman in oceanography, so I would have to ask, very basically, what keeps up the halocline in the first place? Can someone explain that? I have read statements to the effect that ice formation would act to *destratify* a top layer because it would form downwelling rejected brines and these would sink through & thereby mix the toplayer. So if there were suddenly high ice formation rates where there formerly were low ones because ice was perennial, that should tend to destratify. But if it were doing that to such an extent that it destroyed the upper layer stratification as a whole, then lower Atlantic warm water would come up and destroy the ice for good. So can someone explain this riddle? I thought that the top fresher layer was due largely to the riverine freshwater input and the prevention of mixing by the perennial ice. Is that right? If it is then shouldnt be the main danger for the top stratification that the summer-deiced seas could be much better mixed by wind and storm action? But the Sea of Okhotsk, or the Gulf of Lawrence, they all cant hardly be less well mixed that a seasonally ice free arctic might become. Yet they form ice every winter. Why can they do it while the Barents Sea can´t? sorry if these questions seem basic. I´m still quite struggling with all this.
Toggle Commented Sep 18, 2012 on Minimum open thread at Arctic Sea Ice
Hi .. i also want to give thanks to Neven for this fine post. I tend to think if a model isnt good enough the appropriate thing to do is to make a better model. No science bashing from me :) But I want to add a rather humorous paper that is very fitting to this thread. "The fully-coupled climate model HadGEM1 produces one of the most accurate simulations of the historical record of Arctic sea ice seen in the IPCC AR4 multi-model ensemble. In this study, we examine projections of sea ice decline out to 2030, produced by two ensembles of HadGEM1 with natural and anthropogenic forcings included. These ensembles project a significant slowing of the rate of ice loss to occur after 2010, with some integrations even simulating a small increase in ice area." This is just published in the journal for summer 2012. I tip my hat to these folks for having the guts to unabashedly publish their model´s call for an ice increase in the face of the biggest ice collapse we have seen yet. This paper is really quickly superseded by nature. But there, but for the Grace of God, ... in fact it is an interesting little read - mentioning a rare negative feedback: "A negative feedback effect by which rapid reductions in ice thickness north of Greenland reduce ice export is found to play a major role." Maybe this is a hint to where the odel goes wrong.
Hi Jim i found a book for you. you may like it for the introduction with the fine figures 1.1 and 1.3. And it has a summary (after four highly tech papers) that seems worth studying. "Adding the computed release of brines fromfreezing sea ice to the average winter density stratification and neglecting any horizontal advection of dense water, salt rejection would convectively erode the halocline down to a depth of 20 m. ... (this) can be considered as an upper bound estimate of the destratification potential, which further supports our hypothesis that even during strong polynya events ice production is not high enough to erode the halocline ... (This is) indirect evidence that the mechanisms responsible for vertical mixing in the (Laptev Sea) are predominantly wind- and tidally driven, rather than convective. This has far-reaching consequences for both the vertical and lateral distribution of nutrients, sediments, pollutants and heat." And in the outlook: "Understanding how the stratification of shallow shelf water and the ice production and salt rejection in polynyas might change in a warming climate is one of the major challenges of current polar research. On the one hand, it is likely, that the stability of the halocline will be strengthened by an increase in the Siberian river discharge (...). Rising Arctic surface temperatures (...) will probably weaken ice production and increase summer sea icemelt, further promoting the stability of the halocline. On the other hand, the observed positive trend in summer cyclonicity over the Eurasian Arctic (...) might destabilize the water column (change the water-column structure). Likewise, a decrease in ice production could be compensated by an increase in polynya activity during the freeze-up period and in early spring (...) caused by an increase in the frequency and strength of cyclones penetrating into the Eurasian Arctic (...)." These lines attach themselves in my mind to that current Cryosphere-discuss-net paper that someone linked to above, where it was noted that the summer sea ice extent (in the Laptev Sea) anticorrelates well with the annual wind driven ice export from the laptev in the preceding winter, and where it was noted (before this summer!) that the ice export out of the Laptev in the winter 11-12 has been off-the charts strong and the spring ice cover there has been extremely thin in consequence - citing 0.4 meters. That is exactly what that phd thesis book calculates as what polynya ice should reach. So, seeing as it seems that the larger marginal part of the Artic ocean turns into one giant annular polynya that makes ice all winter as it is being continually denuded by wind, this phd thesis seems to say that´s fine, even this much ice production could not be expected to destroy the upper layer stratification. (Is that right?) So, OK, I hope you see how this links to your question. At least I hope it does.
Toggle Commented Sep 14, 2012 on Minimum open thread at Arctic Sea Ice
On the question if not increased oceanic heat input from the Atlantic dooms the ice (Jim Williams, above). I have been trying to find things to read about this in recent weeks. There is a lot of good articles. I want to cite from one abstract, by Korhonen et al 2012 "While the warming of the Atlantic inflow was widespread in the Arctic Ocean during the 1990s, the warm and saline inflow events in the early 2000s appear to circulate mainly in the Nansen Basin. Nevertheless, even in the Nansen Basin the seasonal ice melt appears independent of the continuously increasing heat content in the Atlantic layer. As no other oceanic heat sources can be identified in the upper layers, it is likely that increased absorption of solar energy has been causing the ice melt prior to the observations." As (or if) I understand it, the people seem to say, that only the presence of the upper freshwater layer in the Arctic enables an arctic ice cap to exist at all: even without humans, heat content in the (mostly Atlantic) influx waters would be sufficient to keep the Arctic ice free even during the polar night (see p. 267). But, they seem to say, that warm water doesnt get near the ice and therefore it doesnt play a role in the ice melt (yet); even if it warms a bit - as it seems to do. But; should the arctic freshwater layer break down in large scale due to too little ice, these warm waters might come to the surface and ruin all option for ice. (E. g. this would be a quite distinct tipping point behaviour). Caveat: my understanding may not be right.
Toggle Commented Sep 12, 2012 on Minimum open thread at Arctic Sea Ice
r w Langford: Yes they have. Kawaguchi et al 2012, Polar Science 6:39: "Anomalous sea-ice reduction in the Eurasian Basin of the Arctic Ocean during summer 2010" It is behind a paywall but I can reproduce the abstract : ............... During the summer of 2010 ice concentration in the Eurasian Basin, Arctic Ocean was unusually low. This study examines the sea-ice reduction in the Eurasian Basin using ice-based autonomous buoy systems that collect temperature and salinity of seawater under the ice along the course of buoy drift. An array of GPS drifters was deployed with 10 miles radius around an ice-based profiler, enabling the quantitative discussion for mechanical ice divergence/convergence and its contribution to the sea-ice reduction. Oceanic heat fluxes to the ice estimated using buoy motion and mixed-layer (ML) temperature suggest significant spatial difference between fluxes under first-year and multi-year ice. In the former, the ML temperature reached 0.6 K above freezing temperature, providing >60–70 W m−2 of heat flux to the overlying ice, equivalent to about 1.5 m of ice melt over three months. In contrast, the multiyear ice region indicates nearly 40 W m−2 at most and cumulatively produced 0.8 m ice melt. The ice concentration was found to be reduced in association with an extensive low pressure system that persisted over the central Eurasian Basin. SSM/I indicates that ice concentration was reduced by 30–40% while the low pressure persisted. The low ice concentration persisted for 30 days even after the low dissipated. It appears that the wind-forced ice divergence led to enhanced absorption of incident solar energy in the expanded areas of open water and thus to increased ice melt. ............... (I should mention that I am just a know nothing amateur on all things here as would be any citizen; only reading this blog for a few years; and convincd that if people on a blog can think of something then the scientists for sure will have thought of it too, so all I can do is try to hunt their writings .. which often yields more than one can understand). for instance I dont quite get what they now mean, which is the ultimate heat source: heat from the deeper atlantic water? That would be in line with Polyakov et al Or do they mean the bottom melt heat comes actually from upside (incident solar energy)? That would be consistent with who state that "over the course of the summer season, sufficient energy enters the upper ocean through open water to wholly support the observed [bottom melt]." colour me confused.
I would like to nominate Rudels(2012): it seems to be developed from a price acceptance lecture - I think it would make excellent background reading for many people here?
Toggle Commented Sep 4, 2012 on Oceanic Patterns at Arctic Sea Ice
Hallo Jim Is this: something like what you are looking for? groeten E
In the same current issue can be found this: what does it mean? can someone explain it in layman terms? is it not relevant? For example: "Furthermore, it is possible that surface anticyclonic differences over the Arctic contribute to year-to-year variability of summer Arctic sea ice concentration along the Siberian coast." Or does that simply mean that sea ice melt depends on weather, which is a triviality?
Toggle Commented Mar 1, 2012 on 2012 minimum global sea ice area at Arctic Sea Ice
A) Janne - these AWI expedition weekly data do not seem to contain thickness data or I cant see them. Even though they said that was the focus of their effort. But I recall that the AWI post expedition press releases did talk about 1.3-1.7 m thick first year ice. Whereas the Cryosat map shows 2.x m for the same area. But somewhere in the Cryosat press conference video they say explicitly that their data was checked against an airborne measurement of the same area (Beaufort Sea) and that that airborne measurement was 2.7 m thus right agreeing with the satellite data. What the reason for the discrepancy is I have no clue but maybe what AWI talked about was first year ice only selected in an area and what Cryosat measured was all the ice on average in an area? Just a guess. B) Hidden in the video in Neven´s post is actually an interesting part that directly answers a discussion that several people had some days back on these pages - namely the relation between sea level rise from melting and counteracting isostasy. They explain that indeed, isostasy acts immediately, but that more importantly, a large mass of on-land ice attracts water to it, and that the melting of the ice sheet would mean that this gravitational attraction towards Greenland stops, letting the water flow away, lowering the local sea level. They show a map saying that in fact this gravitational release effect more than counterbalances melt-related SLR in the local Greenland area, leading to a net *sinking* of the sea level around Greenland due to its ice sheet melting! I thought this should be interesting to some people here ...
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