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Messages - Andreas T

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1
Arctic sea ice / Re: What the Buoys are telling
« on: October 04, 2017, 07:36:47 PM »
This recent image serves as a reminder that snow is drifting quite a lot on the ice which must make it quite difficult to quantify what effect snowfall has. Thicker than average drifts alternating with thin patches.
The sentinel image from the 28th shows that floes are still moving and rotating, I would expect wind direction to have been quite uniform when those drifts were formed. Snow blowing onto the sea surface could have helped starting ice cover to form.

2
Arctic sea ice / Re: Fram Export
« on: September 25, 2017, 09:02:42 PM »
as a heads up about some interesting research in this area, here is a link to a press release by the AWI
https://www.awi.de/nc/en/about-us/service/press/press-release/arktisches-meereis-erneut-stark-abgeschmolzen.html
......
During the past weeks, sea-ice thickness measurements were the main topic of the TIFAX (Thick Ice Feeding Arctic Export) campaign, which involved research aircraft using laser scanners and a towed electromagnetic probe. In the area surveyed, which lies to the north of the Fram Strait between Greenland and Svalbard, the sea-ice thickness was ca. 1.7 metres, roughly 50 centimetres more than was recorded in 2016. This is most likely due in part to a higher percentage of several-year-old ice in the area. Nevertheless, the measured thickness is ca. 30 per cent lower than between 2001 and 2004. As Marcel Nicolaus summarises, “Despite the warm winter, the sea ice wasn’t unusually thin. Our explanation is that the small and thin ice coverage from the previous summer – the second-smallest area ever recorded – grew faster and thicker than in other years, since thin ice grows faster than thick ice.”

3
Arctic sea ice / Re: What the Buoys are telling
« on: September 24, 2017, 09:20:32 PM »
As the periods of sufficient sunlight to power the buoy bare getting shorter, we will soon have to say goodbye to OBuoy14 for 6 months. At the moment frost blooms are forming on the ice, which shows that the gaps between ice floes have frozen over. Air temperatures are only -5C which probably means that larger expanses of open water are not freezing yet.
Lets hope the frost starting to form on the camera is not covering up the lens too soon.
The sentinel shot is from the 22nd but probably gives a fair impression of the amount of ice surrounding the buoy location at pressent.

4
The melt pond discussed by Andreas T has mostly gone.
on the 1. Sept it looked completely gone, drained and frozen till the next season I thought but on the 10. there is more water which seems to have floated the ice cover on the southern lake.

5
Arctic sea ice / Re: Northwest Passage thread
« on: September 10, 2017, 02:14:32 PM »
a clear view on the 9th shows ice between Victoria strait and Bellot strait fairly spread out, possibly passable for non icebreakers taking a chance? Is there a equally recent chart from canadian ice service? I can't find one.
Ice drifting south towards other narrow part of the passage though, not sure what the name is.

6
Arctic sea ice / Re: What the Buoys are telling
« on: August 29, 2017, 11:09:53 PM »
There have been some low air temperatures, but the small pieces of ice are still the result of melting, enlarging brine channels are disintegrating icefloes, something which is usually seen in these late stages of bottom melt.

7
Arctic sea ice / Re: Arctic Image of the Day
« on: August 27, 2017, 03:35:26 PM »
to keep (another) nice image here is a downloaded shot form (local) yesterday evening
105west means UTC-7

8
Arctic sea ice / Re: What the Buoys are telling
« on: August 15, 2017, 01:10:52 AM »
Worldview shows that the kind of fragmentation we now see in the camera images is widespread in the area. Increased water movement is likely to promote further melting.
As woodstea says winddirection is forecast to change which will stop the flow of ice from the Beaufort into the western end of Parry channel. If that continues the chances of an open Northwest passage at the end of August look reasonable.

9
Arctic sea ice / Re: What the Buoys are telling
« on: August 14, 2017, 12:57:50 AM »
At Obuoy14 the narrow bit of ice which separated the water on the near right from the area in the middistance has finally melted through. What this makes more obvious is that the lack of movement of the various areas of ice surface are not moving relative to each other, i.e. it makes it very likely that they are still connected below the waterline. The thin strip of ice would most probably have broken off earlier had it been the only connection holding these parts of the floe together.
In the light of images from last autumn I expected the area on the near left to be thinner, younger ice but so far it has lasted as much as those bits which are remnants of last years melt season. Lets hope the reduction of lightlevels which are now lengthening the periods of insufficient power from the PV panels will allow us to see what happens over the next couple of weeks

10
Arctic sea ice / Re: Arctic Image of the Day
« on: August 12, 2017, 09:32:04 PM »
It is also worth checking the false  colour images using near infrared channels such as 3,6,7 bands https://go.nasa.gov/2vZiF7I which show up clouds against ice (ice red, clouds white)

11
Thanks, Wipneus, seeing those previous years shows how much variation there is around this spot. I also find it instructive how little trace these earlier, smaller meltpools have left on the present day glacier. I still think that changes in contours and drainage determines size of the pools and that this year's pool looks deeper to me. Further developments (over a year or two will tell more).

I have looked a bit more at ice berg movements at the exits of Jokelbught. I coloured in some of them at what looks to me like the larges gap in the islands south east of Schnauder oer.  The images of July 2016 and 2017 show that these have not taken the exit despite being very close to it when the sea ice broke up and allowed movement last year. There is mevement, i.e. no signs of grounding, there just seems to be little water movement across that gap, maybe it was different in other years.

12
Arctic sea ice / Re: What the Buoys are telling
« on: August 12, 2017, 05:54:16 PM »
I see the buoy track ok, could it be that Obuoy14 has somehow been deselected (there is a list on the right hand side menu which pops up when you click on the + sign)

13
Arctic sea ice / Re: The 2017 melting season
« on: August 12, 2017, 01:57:55 PM »
Jesus. This is north of Sib. Islands, today. The concentration charts don't make justice to the degradation of the pack here.
or have a look here:
ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/3.125km/Arc_20170811_res3.125.png

14
Arctic sea ice / Re: What the Buoys are telling
« on: August 12, 2017, 01:36:14 PM »
Undercutting of the ice edge is a feature of meltponds which can be seen in all buoy footage I have seen, especially later in the season, possibly linked to salinity of the water when mixing with ocean water below is occurring. I don't think ice growing out or lifting is involved, the small waves on the water surface will splash against the ice and melt it a little above the water surface.
Together with the warmer temperatures we have seen recently relative humidity has also been high. This shows that the air has not warmed locally (which would drop humidity) but has moved in from warmer areas and cooled to its dew point. If this has brought some condensation to the ice surface that would of course strengthen surface melt.

Relevant to the discussions of temperature and salinity profiles, there is a report by Polarstern on their site, which describes an eddy and its effect on those profiles. It is in the Fram strait at the moment.
https://www.awi.de/nc/en/expedition/ships/polarstern/weekly-reports-rv-polarstern/single-view/presse/woche-2-wie-man-einen-wirbel-findet.html
Jim has already linked to this as I was typing :o
It also reminded me of reading in Peter Wadham's "a farewell to ice" about a very persistent eddy he investigated in the Odden Ice tongue (when there still was one)

15
Arctic Background / Re: Research Icebreaker Polarstern
« on: August 12, 2017, 12:58:37 PM »
An interesting new report by polarstern on some opportunistic measurements of small scale features in the ocean.
https://www.awi.de/nc/en/expedition/ships/polarstern/weekly-reports-rv-polarstern/single-view/presse/woche-2-wie-man-einen-wirbel-findet.html it is in english despite the title in the link. One glitch in the translation: Bug is the german word for bow (as in front end of the ship), probably clear from the context.

16
looking around on Sentinel I have been intrigued by this meltlake not far from the calving front. As has been commented on elsewhere, these features are located on the glacier surface relative to features of the ground below it. I.e.. as the glacier ice moves along the meltlake stays in a surface depression which probably sits upstream of a bump in the rock surface below the glacier.
I have picked cloud free images from Aug 16 and 17 and the earliest available Mar 17 for an indication of surface contours in low sun angle illumination.
This meltlake does not seem to be very old, I could not see it in the MODIS images before 2014. Therefore it gives an opportunity to follow its development as its effect on the ice moves downstream (of the glacier). Possibly the meltlake has appeared in this location due to thinning of the glacier as the calving front has retreated towards it.
The March image shows a narower part of the lake which seems to have frozen over in the previous winter and I think can be seen again as a darker, deeper area this August. I am looking forward to finding out what happens as this moves towards the rise which stops the lake from draining down towards the sea.
Probably not a profoundly important feature but fun to watch.

17
the bergs near the calving front seem to have moved without a calving, but I would want to see a clear Sentinel image to be certain. The sea ice in the bay between the Zachariae glacier and the islands, (Jokelbught I guess?) is mobile but not getting away very far, the exits between the islands are narrow and in the south blocked by remnants of the ice shelf which broke up in 2002 (thats a bit bof a guess, I have not traced them back to that year) image attached
http://apps.sentinel-hub.com/sentinel-playground/?lat=78.09716267271118&lng=-19.786376953125&zoom=9&preset=1_NATURAL_COL0R&layers=B8A,B03,B02&maxcc=99&gain=0.3&gamma=0.7&time=2015-01-01|2017-08-07&cloudCorrection=none&atmFilter=&showDates=false
The largest and clearest exit does not have much transport through it because drift is slow and mostly north along side it it seems from looking at movement in 2016 and 2013.

18
Arctic sea ice / Re: Northwest Passage thread
« on: August 07, 2017, 03:19:59 PM »
I was thinking of fuel consumption and therefore carbon footprint etc. It might be more economical to burn a lot of fuel to go quicker along a longer route if cost of the ship and crew is factored in, but it may also be  burning less fuel on a longer route if propulsion through ice is less efficient. I don't know but have read about large efficiency gains possible with novel icebreaker designs which suggest that running through ice increases fuel consumption significantly.
Just making some guesses on motivation for the more circuitous route.

19
Arctic sea ice / Re: Ice Concentration Images and Animations
« on: August 06, 2017, 11:29:05 PM »
Peter is right, the effect can lead to the Bremen concentration chart showing open water where worldview shows ice which lasts for weeks longer. The strongest example I remember is of landfast ice in the Laptev sea which often is water covered when the snow melts, but there also was ice near Wrangel island last year which kept "coming back from the dead" repeatedly.
example of melt on landfast ice see here:
A reasonably good view of the fast ice between the New Siberian Islands and the Lena delta today. That Uni Bremen SIC map really fooled me  :):

20
Arctic sea ice / Re: Northwest Passage thread
« on: August 06, 2017, 10:55:44 PM »
all the same overlaying the ship track map over the 3,6,7band MODIS of the 5.AUG shows the ship chose a path of least resistance, it possibly makes for more economical (and ecological) use of the ships fuel?
https://go.nasa.gov/2vEPt5u
https://canadac3.ca/en/expedition/expedition-map/
I changed the colour of the track to green for contrast

21
Arctic Background / Re: Research Icebreaker Polarstern
« on: August 04, 2017, 10:35:48 PM »
the weekly reports describing the activities north of Spitsbergen are here: https://www.awi.de/nc/en/expedition/ships/polarstern/weekly-reports-rv-polarstern.html
noteworthy is the absence of meltponds in the northern part of the track, in contrast with the area nearer the island where meltponds were in advanced stages.

Polarstern is now in Framstrait working on long term observations.

22
Arctic sea ice / Re: Northwest Passage thread
« on: August 04, 2017, 03:29:14 PM »
Further west the first year ice in Victoria sound is gone but what remains between there and Bellot strait had a scatterering of old ice mixed in at the end of last season and will be a bit more resilient. It could of course be replenished from the North.

23
Arctic sea ice / Re: Northwest Passage thread
« on: August 04, 2017, 03:12:20 PM »
On 3,6,7 bands Terra https://go.nasa.gov/2wruFuO it looks like this:

24
Arctic sea ice / Re: What the Buoys are telling
« on: August 04, 2017, 03:01:21 PM »
A while ago someone gave a link to a paper on water flow through the CAA, but I can't find it again.
The attached bathymetry http://onlinelibrary.wiley.com/doi/10.1029/2011JC007261/full supports what I remember from that paper. The shallow depth where those islands lie across Parry channel directs part of the flow around Prince of Wales Island oddly south along its western side but north along the eastern side. This would mean the buoy is still heading for Lancaster sound. (The ice may well not last the trip though)
Victoria sound is ice free in the 3. Aug TERRA image btw.

25
Arctic sea ice / Re: IJIS
« on: August 04, 2017, 02:50:00 PM »
.....

the possibility that the big drops will occure later in the season is higher than earlier in the season IMO because higher temps extent more easily into fall now and the higher humidity somehow protects the ice during summer more often in the future, especially during peak-insolation periods in june and july.

the state in which the remaining ice currently is would allow for a huge drop in september given the right winds etc.
....
a reasonable comment about the ice (and not talking about yourself for a change, weiter so!) I very much agree. (please don't reply, I promise to stop commenting on your comments)
The low volume makes it possible that ice covered areas which survived the meltseason in previous years just won't last that long because the thickness is not enough to survive the bottom melt between now and mid September.
In area and extent 75cm of ice counts as much as 1m but with a melt rate of 3cm/day (just as an example) one makes it to the end of the month, the other does not. Time will tell.

26
Arctic sea ice / Re: What the Buoys are telling
« on: August 04, 2017, 02:25:13 PM »
I agree with Jim, the visible part of the thicker stem of the buoy exposed has become longer, at maximum snow depth it was almost completely covered. The other indication is the buoy with the conical top to its left. Initially we see its lower part partly covered in snow, then more snow cover. After the snow has melted away it is sitting on the ice and as the ice melts the distance from its top to the top of the IMB gets larger. I was skeptical about the rapidity of that top melt and noticed that bottom melt almost stalls during the steepest decline at the start of July, hence my suggestion the buoy might have slipped upward, thereby increasing the apparent top melt and making the bottom melt (which I would expect to be more steady) appear slower at the same time. The height of the buoy top above the horizon has increased since its deployment which supports that theory, but could also be explained by lowering of the camera by that top melt while the IMB remains fixed in the ice.
Thanks JIM for this excellent find, these images tell us so much more. I don't understand how you get the dates of the images though, does it relate to the file names, numbered from 00129 to 00453 for example?
Another thing I noticed: there is some movement of the distant buoys relative to the ablation stakes between image 00129 and image 00240. some shift along a crack between those it seems. Later the conical top buoy moves close to the IMB. If there are bits from that break floating about under the ice it would explain the intermittent readings from the bottom sounder.
More overthinking I guess, the ice is so thin now it could go quickly.

27
Arctic sea ice / Re: What the Buoys are telling
« on: August 01, 2017, 02:41:00 AM »
What is odd about the plot of 2017A is that the surface now would have been below the waterline back in March!
The floe was just under 1m thick in March, so sea level would have been no lower than -0.1 (8/9 of the floe below water) We have of course seen before that the buoy slips relative to the ice when ice melts preferentially around the buoy stem (Jim has shown pictures). Often that results in a sudden jump in distances from top and bottom sounder.  Maybe this has happened more gradually here. Another explanation could be that the part of the floe on which the bouy sits has been lifted since March or tilted (through ridging)
This may be a bit too technical for many here, so what is the point of pointing it out? Apart from liking to understand what is going on whatever the result (i.e. science) I guess it is a warning to be on the look out for misinterpretations based on taking what the buoy sensors see as representative of all the ice in that vicinity.
Namely that means here: I don't think we find that much top melt averaged over a large ice area there. Beyond that it just leaves me with the feeling that arctic sea ice is incredibly slippery  ;D I always want to have more information. If only we could have had a colocated Obuoy.

28
Arctic sea ice / Re: Northwest Passage thread
« on: July 31, 2017, 08:49:26 PM »
according to that site the MV Polar Prince should be in have been recently in Iqualuit, maybe Numerobis has some information?

29
this reply to a comment in the Nares thread belongs here I think.
This is from the 24th to me it suggests a surge of warm water coming out of the arctic at depth, into Petermann fjord, and there being forced to the surface melting and forcing out the seasonal fast ice.
...
Take a closer look
To put it into the terms of physics, what we are seeing with the help of information provided by Dr Muenchow and his colleagues, is that warmer intermediate water  entering the fjord is rising at the glacier front. This is driven by buoyancy as this water mixes with salt free meltwater from below the glacier tongue and surface melt which has entered the glacier through moulins and cracks. This low density water source drives the surface flow out of the fjord while a flow of denser water is drawn in below it. It is a classic imbalance of water columns of different density profiles.

30
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: July 31, 2017, 07:41:44 PM »
edit: moved my reply to John to the Petermann thread.

31
Arctic sea ice / Re: The 2017 melting season
« on: July 30, 2017, 05:18:02 PM »
It was clear on the Pacific front yesterday, and the ice in the Western Beaufort looks even worse than on the Hamburg concentration map. The image shows an area from 148-152W which is almost open water already. It's interesting that the areas of highest concentration are at the edge. I've been wondering if, at the periphery, in this era of mush, area is measuring something different from in the past, where bottom melt reaching far into the pack spreads the melting ice over all the area, and floes are too small to see te open water between them from the satellites
Healy is a little west of there 73.1N 151.4W and shows ice on the aloftcam since yesterday http://icefloe.net/Aloftcon_Photos/index.php?album=2017

32
Arctic sea ice / Re: The 2017 melting season
« on: July 20, 2017, 04:22:18 PM »
nullschool predicted strong winds from Baffin into Frobisher Bay on the 18th, if I remember correctly. Did that happen and cause problems?

33
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: July 20, 2017, 04:14:57 PM »
Ice in about all possible NW passages turns mobile.
I also note Beaufort ice being driven south back across astonishingly warm water.  That won't be good for it.
the attached image https://go.nasa.gov/2vns6Kn
shows band31 IR overlaid over visible. The purple swirls of colder meltwater coming from the area of ice nearer the coast (ignore the cloud bands even nearer the coast) shows what happens to the ice , on the advancing ice edge of the beaufort gyre no such meltwater plumes show, presumably moving under the ice? This seems to me confirms what JD says, little protection from the sun warmed water for the ice moving south.
I compare consecutive days to help me distinguish slowly moving water plumes from fast moving atmospheric effects.

34
Arctic sea ice / Re: What the Buoys are telling
« on: July 20, 2017, 10:33:47 AM »
it doesn't surprise me that you like that idea, but it at least 3000m water depth it isn't probable, or plausible. What happened to your earlier idea of pacific water shooting up to the Greenland coast?
The methane idea also does not explain why the lower contours are undisturbed and upwelling should also show up in the salinity contours.

35
Arctic sea ice / Re: The 2017 melting season
« on: July 19, 2017, 01:59:34 PM »
...

This shows that the ice has collapsed almost overnight, fracturing at both the western and eastern end of this channel.

As this is my first year watching a melt season via satellite, I have no experience of whether this is normal or not.

What mechanism could account for this? Is it bottom melt which has thinned the ice to a critical point?
This can be seen on worldview clicking back through the years back to 2009. 2010 is interesting when after an early (May!) start to the breakup from the east to Stefanson island, a line held across Parry channel for a month.
The mechanism behind this is that the ice is not uniformly thick and has some cracks from movement during the winter. As it weakens from thinning and softening (due to warming, enlarging of brine channels) it will initially be supported along the coasts of several islands. When one of these supports (the ice along the coast) gives way the stresses in the remaining ice become stronger so that it is most likely that everything becomes mobile in a very short time.


36
Arctic sea ice / Re: What the Buoys are telling
« on: July 18, 2017, 09:00:19 PM »
I guess this link will take you to a different image tomorrow but I can't remember quickly where to find the archive, the excellent high resolution 17. 7.  AMSR2 image from UH shows cracks opening to the north and partjy filling in the opened area in Parry channel. ftp://ftp-projects.cen.uni-hamburg.de/seaice/AMSR2/Arc_latest_yesterday_AMSR2_3.125km.png

37
Arctic sea ice / Re: What the Buoys are telling
« on: July 18, 2017, 01:58:46 PM »
2017A and B have updated. 2017A seems to be "bobing in the sea" with top and bottom sounder showing some modal oscillation (hope I'm using the correct term here)
water temperature dropped down after its warm spell, maybe increased mixing? If salty water mixes with ice temperature should drop to a lower equilibrium with ongoing melting, than if melting leads to a freshened meltwater layer under the ice.

38
Arctic sea ice / Re: Latest PIOMAS update (mid July update)
« on: July 18, 2017, 09:32:30 AM »
I have been watching this area and the discrepancy there is striking. PIOMAS has been piling ice against Svalbard for months. That movement towards the islands was visible on the tracking I did in AMSR images but later when it relaxed and slightly reversed in July water opened north of Spitsbergen but ice has still compacted against Nordaustlandet. What the satellite images don't tell us is how thick the floes are, but the dispersion should show as thinning on PIOMAS.
It seems possible to me that PIOMAS has underestimated the thinning which took place from bottom melt in that area (the strip of shelf on the north coast of Spitsbergen), it may also have got some of the movement wrong (more against Nordaustlandet than Spitsbergen)

39
Arctic sea ice / Re: What the Buoys are telling
« on: July 18, 2017, 01:16:13 AM »
The fact that up profiles are so different from down profiles makes me suspect something is wrong with those DO data. I don't know anything about how these are taken, but other ITP profiles don't have that issue.

40
Arctic sea ice / Re: What the Buoys are telling
« on: July 16, 2017, 04:21:30 PM »
another glimpse of Obuoy14's vicinity in todays AQUA 10:15 image
https://lance-modis.eosdis.nasa.gov/cgi-bin/imagery/realtime.cgi

The opening along Stefanson island is quite large now and east of the large crack ice is moving away.
The GPS data of the buoy shows an icrease of velocity but no other signs of movement

Edit: I have just seen a later MODIS image which shows the channel to the south (MClintock? ) breaking up.  I expect Obuoy14 to be back on the move tomorrow. I admit saying not in the next 4 weeks back on 6. June was playing it safe, giving it another week on 11. July a bit too generous.

The next thing to guess at is whether its going south or east

Bruce, those contours are certainly surprising in the location where the buoy is. I can't explain it. Noticeable is the salinity and temperature contours don't coincide exactly but it does suggest somehow water mixing up to the surface. The profiles show a maximum of -0.5 near the surface which should have quite a melting effect on the ice, my interpretation of the drift track is that it is still among the pack.

41
If it is possible to wait longer for the charging, of course almost any electrical socket becomes part of the charging infrastructure. In that sense there are more charging points than petrol stations. I know this isn't what you need when you want to cover distances the way we're used to with fuel burning cars.  I have no experience of driving or owning an electric car, but find reading some of the owners stories inspiring: https://www.tesla.com/de_AT/customer-stories/ireland-to-morocco-with-our-model-s

42
reading back through the thread I was reminded of the microcat sensors of itm5 which were placed at 79N last August. What I don't understand is the change in pressure, they all seem to be at lower pressure, 10 dbar less than a year ago. This might be that somehow they are sitting less deep in the water or does anyone have a better explanation? Temperatures have risen at all 4 sensors which isn't explained by a change in depth (if that is what happened) because temperature is higher at greater depth.
http://www.whoi.edu/page.do?pid=154416

43
Arctic Background / Re: Research Icebreaker Polarstern
« on: July 15, 2017, 01:02:32 PM »
A previous weekly report explains why the ship track shows repeated north- south movement around the 2. July, measurements were taken over the edge of the shelf where water depth drops into the arctic basin.

https://www.awi.de/nc/en/about-us/service/press/press-release/week-6-from-east-svalbard-towards-the-deep-arctic-ocean.html

polarstern is now on the way home it seems or at least to a change of personel in port.

44
I know this has been done before but I find this so impressive I think it is worth repeating. Images are largely self explanatory I hope, icebergs tip over when they are taller than wide. These bergs are 300m tall!  Quite a splash even with ice that is already afloat (not grounded).
In physics terms the work done to move a lot of bergs a few hundred meters sideways is not easily quantified as energy required (from lowering center of mass of the berg). I expect the upwelling of meltwater below the glacier front will add to the push on the floating bergs towards the sea ice which still covers the bay.

45
Arctic Background / Re: Interpretation of satellite images
« on: July 14, 2017, 07:37:39 PM »
I have been looking for areas of interest which can be investigated more closely with the high resolution Sentinel 2 images. One place which I have looked at earlier is north of Svalbard where ice has been compacting against the island for much of the last 4 months. A recent cloudfree image, worldview at max resolution of the 2. July shows some cracks with the typical hexagon pattern which  has been  pointed out as a sign of strong ice in the central arctic.
https://go.nasa.gov/2uhTnAs
looking at this with Sentinel I found that some of that ice has moved into that triangle of compacter ice quite recently (after 25. June).  I have marked a group of floes which remained recognizable over those dates.
http://apps.sentinel-hub.com/sentinel-playground/?lat=80.51918613079921&lng=18.090362548828125&zoom=9&preset=1_NATURAL_COL0R&layers=B04,B03,B02&maxcc=96&gain=0.5&gamma=1.1&time=2015-01-01|2017-06-25&cloudCorrection=none&atmFilter=&showDates=false&evalscript=
This demonstrates what the level of detail in Sentinel 2 can add. This area also has frequent Sentinel1 images


46
Arctic sea ice / Re: Glossary ... for newbies and others
« on: July 14, 2017, 10:48:03 AM »
garlic press is another casual term which refers to the Canadian Arctic Archipelago (CAA) and the fact that when ice in its passages has become mobile in August there is movement of ice which has compacted against the islands into those passages and from those passages into the Parry channel with its connection out into Baffin bay.
The narrowness of the passages into Parry channel (red arrows) compared to those from the open arctic ocean into the CAA shows how obstructed this flow is. Because of that the flow happens in stages. Ice which moves into the larger passages in late August freezes in in early October. In the following year it will partly melt, partly make its way into the Parry channel. If it survives there until freeze up, it may make it much reduced by melt into Baffin bay in the following year.
What matters of course is not how much ice arrives in Baffin bay but how much ice moves out of the Central Arctic Basin by this route.
I have not seen any attempt to quantify this but is claimed at times (including quite early in the melt season) by various people (I just picked the first I found)

The image is from 30. Aug 2015 https://go.nasa.gov/2ugn3xC just to give an example of a clear view

I think the opening of the CAA may be more important than it initially appears to be. It's kind of like opening a pressure relief valve of sorts. It seems to me, with my limited experience, to change the dynamics within the CAB.
                                                                                                                             
pauldry600
The Canadian Arpegio (or however you spell it) is notoriously difficult to break down so it may not all go but this will surely test it to the limit
It don't have to all go, as in melt. If enough gets weakened and broken up, the rest will eventually just flush out. Remember that at the end of last melt season, smaller floes were moving through until the end and got frozen together. I don't suspect the bonds between these to be any stronger than elsewhere. Also, wave activity has been infiltrating some of the channels, despite the dampening effect of the ice.

47
Arctic sea ice / Re: What the Buoys are telling
« on: July 14, 2017, 08:44:29 AM »
Maybe this should be in the NWP thread but since I think we will see signs of this at Obuoy14 soon.
In the 14 13. 7. Terra image a glimpse through the clouds shows a crack (red arrow) opening roughly 30km west of the Buoy position. While the earlier openings (blue arrow)were spreading slowly because of pinning by islands the ice which remains undisturbed at the moment will be less stable especially if there are openings spreading along the islands (green arrow)
This will put the break up in this vicinity on par with last year, earlier than I expected.
EDIT added a link to Wipneus' AMSR2 animation on another thread
Animated Canadian Archipelago. Some ice in the main channel (Barrow Strait) has "mobilized".

48
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: July 13, 2017, 08:00:38 PM »
the wind was blowing from the southern end of the strait until recently, strongly at times. See nullschool or these on the spot measurements from Hans island https://dataservices.sams.ac.uk/aws/

49
Antarctica / Re: Rift in Larsen C
« on: July 12, 2017, 12:49:44 PM »
yes the AQUA nighttime band31 https://go.nasa.gov/2u8atAA is pretty definite. Lighter colour shows warmer (than ice  surface) seawater in the crack which given the low resolution of the thermal IR band is fairly wide (or does the low resolution make it appear wider?)

50
Science / Re: "climate porn" vs. "not alarmed enough"
« on: July 12, 2017, 10:09:10 AM »
What Darvince has pointed out quite well is that this isn't a "strong" article if it is full of poorly chosen statements which are easily brushed aside because they are demonstrably not supporting what they are supposed to. The seed vault story is just a silly distortion of the facts.
To people who are disinclined (understatement) to listen to the message that strong action is needed to avoid the worst of climate change, giving them excuses to dismiss that message is just what they are looking for.
The "hope police" (what feeble whinging) doesn't shut down the debate, but people who value their reputation (like Michael Mann) are entitled to distance themselves from such poor spread and point out where there are discrepancies to what they know.
Scientists have to be more critical of themselves than most people are used to. That is how they come up with stuff that stands up to the more severe "test of time".
People are free to have opinions and voice them, if you don't like to look bad later check you have sound arguments which don't fall apart when corroboration is required.
I always considered it a sign of the weakness of the "denier's" arguments that they generally accept any statement uncritically as long as it supports their view. The strength of the view that anthropogenic climate change is alarming is that you can brush away the hype and there still is a strong argument in favour of action.


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