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vigilius

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Re: What the Buoys are telling
« Reply #1500 on: July 04, 2017, 04:10:45 PM »
Well, here we are again, expecting signs of greater movement any time...   ...I post this one because I initially had a hard time interpreting the dark areas in the near foreground which turned out to be the shadow of the buoy and its remaining mast, just harder to interpret when cast on the newly-varied terrain.

And I have a question, in fact maybe I should go to the stupid questions thread. The picture posted is at noon UTC which makes me think that since the shadow is straight ahead, the camera must be pointed approximately NNW. But when I look at the azimuth reading in the GPS tab, it seems to be saying we are pointed ESE. On the other hand, the azimuth graph does not actually seem to start at zero so maybe I am incapable of figuring it out.

OTOH maybe I should just go to the stupid questions thread and stay there for another year before saying anything else. (LOL)

ghoti

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Re: What the Buoys are telling
« Reply #1501 on: July 04, 2017, 04:37:08 PM »
The Obuoy14 camera azimuth is different from the azimuth designated for the buoy. I've attached a frame of the Obuoy movie which shows the sun azimuth at the top left as well as the time, buoy azimuth, and the shadow cast roughly 15 degrees off of center.

It is just a coincidence that the sun shadow is currently centered at UTC noon. The buoy's position would make local noon at about UTC - 6. The sun azimuth at UTC noon is now about 75 degrees. However the buoy's azimuth is south southeast.

This will all soon change of course when the buoy floats free.

vigilius

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Re: What the Buoys are telling
« Reply #1502 on: July 04, 2017, 04:48:16 PM »
Quote
The Obuoy14 camera azimuth is different from the azimuth designated for the buoy.

Well, I am sorta comforted by the thought that this confirms what I was so clumsily trying to say. OTOH it is sorta counterintuitive to think that the buoy's azimuth is different from that of the camera. I guess I anthropomorphize this poor buoy too much.

BTW I was trying to say NW, I said NNW, I must have been thinking of Cary Grant.

And thank you for your kind response, ghoti.
« Last Edit: July 04, 2017, 04:54:04 PM by vigilius »

woodstea

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Re: What the Buoys are telling
« Reply #1503 on: July 04, 2017, 08:07:45 PM »
The Obuoy14 camera azimuth is different from the azimuth designated for the buoy.
Here's one estimate I tried to make of that difference last year, when we were trying to figure out if we could see land and if so, what land in particular:

Here we have a shot of the moon. I used a sun/moon position calculator (http://www.satellite-calculations.com/Satellite/suncalc.htm) and for this lat/lon (estimated from graphs) and time it said the moon's azimuth should be 244 degrees. Given the azimuth reading from the graph I would say that the offset for the camera azimuth is probably more than 90 degrees, more like...110? I wish we had lat/lon coordinates in real time rather than just on the movies.

In any case I'd say we are looking WSW here, so that the closest point on Banks Island is out of view to the left.

Andreas T

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Re: What the Buoys are telling
« Reply #1504 on: July 04, 2017, 09:51:28 PM »
I noticed that discrepancy when looking at Obouy9 as it drifted along the coast of Greenland and it drove me nuts trying to figure out what part of the coast it was looking at.
So this is a feature of this type of buoy in general it seems.

Rob Dekker

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Re: What the Buoys are telling
« Reply #1505 on: July 05, 2017, 10:13:31 AM »
It is just a coincidence that the sun shadow is currently centered at UTC noon. The buoy's position would make local noon at about UTC - 6. The sun azimuth at UTC noon is now about 75 degrees. However the buoy's azimuth is south southeast.

This will all soon change of course when the buoy floats free.

This azimuth stuff is very confusing to me, and I never figured it out.
So thank you ghoti for explaining, but I still don't get it. Let me put my confusion into a few questions :

Is the "buoy's azimuth" a fixed angle w.r.t. the camera direction ? And if so, did we figure out what that angle is ? Or is the "buoy's azimuth" simply the direction in which the buoy is moving ?
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Rob Dekker

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Re: What the Buoys are telling
« Reply #1506 on: July 05, 2017, 10:26:50 AM »
this is a very optimistic ( ice friendly ) prediction IMO, almost looks like what we see today extent wise. i expect much less extent that in that image by the end of august ( i consider 22nd of august end of august )

I'm with the late Slater on this one.
I don't think 5.22 for Aug 22 is unrealistic. It's a bit more than 2015 and a bit less than 2010.

Slater et al's method works off ice concentration, and it just happens that ice concentration has been pretty high over the past month (few melting ponds). NSIDC also came in with pretty high June 'area' numbers.
And at risk of going off topic for this thread, albedo feedback has been very modest this summer, with a whopping 4 million km^2 land snow cover anomaly.

Besides, we have seen two periods of high pressure over the Beaufort (resulting in ice compaction) in June, so I don't think 'extent' is a good measure for the state of the ice.

So I'm optimistic this year.

[Edit 5/17: Removed quote after Jim's remarks about nested quotes below]
« Last Edit: July 06, 2017, 04:06:38 AM by Rob Dekker »
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woodstea

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Re: What the Buoys are telling
« Reply #1507 on: July 05, 2017, 10:38:12 AM »
Is the "buoy's azimuth" a fixed angle w.r.t. the camera direction ? And if so, did we figure out what that angle is ? Or is the "buoy's azimuth" simply the direction in which the buoy is moving ?

Yes, I'm pretty sure it is a fixed angle. My best guess last year was that it's somewhere around 110 degrees. The azimuth is currently about 160 degrees according to the graph on the GPS page, so that makes the camera direction roughly 270 degrees, or due west. Looking at the photo above I'd say it was more WSW, so maybe 110 degrees offset is too much. I eventually decided I didn't care too much about the exact number -- just figure about a quarter turn clockwise from the azimuth.

Peter Ellis

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Re: What the Buoys are telling
« Reply #1508 on: July 05, 2017, 02:13:00 PM »
Yeah, I suspect the "azimuth" measures changes relative to wherever due north was when the buoy was initially placed.  The webcams are usually fixed to point at something else nearby that the scientists want to monitor - e.g. calibrated markers to measure snow depth, or some other co-located buoy - and so the camera doesn't start off pointing due north.  That's why there's an offset.

magnamentis

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Re: What the Buoys are telling
« Reply #1509 on: July 05, 2017, 08:56:49 PM »
Those images from Obuoy 14 are quite dramatic.

It is clear that the melting ponds already drained, which means there are openings in the ice to the ocean. What is not clear is how much longer this ice can withstand the relentless insolation that came with the high pressure zone over the area.

At some point, this ice should disintegrate in-situ and start breaking up.
Even Slater's forecast is that Parry Channel will likely open up this year :


this is a very optimistic ( ice friendly ) prediction IMO, almost looks like what we see today extent wise. i expect much less extent that in that image by the end of august ( i consider 22nd of august end of august )

I'm with the late Slater on this one.
I don't think 5.22 for Aug 22 is unrealistic. It's a bit more than 2015 and a bit less than 2010.

Slater et al's method works off ice concentration, and it just happens that ice concentration has been pretty high over the past month (few melting ponds). NSIDC also came in with pretty high June 'area' numbers.
And at risk of going off topic for this thread, albedo feedback has been very modest this summer, with a whopping 4 million km^2 land snow cover anomaly.

Besides, we have seen two periods of high pressure over the Beaufort (resulting in ice compaction) in June, so I don't think 'extent' is a good measure for the state of the ice.

So I'm optimistic this year.

no problem, that makes things even more interesting, let's wait and see.

enjoy further

Jim Pettit

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Re: What the Buoys are telling
« Reply #1510 on: July 05, 2017, 10:29:57 PM »
no problem, that makes things even more interesting, let's wait and see.
enjoy further

Unless it's for some reason absolutely necessary, please include only the comment immediately preceding yours when replying. That'll make things much easier to read. Thanks!

FWIW, this can be cluttery and heard to read:


Quote from: Commenter Number One
That's what I thought. Thanks, folks!
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Almost to the end for real this time? I also added words of my own and quoted everyone else.
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I am the umpteenth person in this thread, and I'm quoting everyone who went before me
Quote from: Commenter Number Seven
I saw everything going on still, so had to add some more of my own.
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Arriving late--as usual--I added this.
Quote from: Commenter Number Five
Jumping into the fray yet again, I also added some words of my own.
Quote from: Commenter Number Four
I also added some stuff.
Quote from: Commenter Number Three
Then I came along again, quoted all the preceding comments, and added my own stuff.
Quote from: Commenter Number Two
I came along the second time to add some more
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That's what I thought. Thanks, folks!
Quote from: Commenter Number Nine
Almost to the end, I also added words of my own and quoted everyone else.
Quote from: Commenter Number Eight
I am the eighth person in this thread, and I'm quoting everyone who went before me
Quote from: Commenter Number Seven
I saw everything going on, so had to add my own.
Quote from: Commenter Number Six
Arriving late, I added this.
Quote from: Commenter Number Five
Jumping into the fray, I also added some words of my own.
Quote from: Commenter Number Four
I was fourth, and also added some stuff.
Quote from: Commenter Number Three
Then I came along, quoted the two preceding comments, and added my own stuff.
Quote from: Commenter Number Two
I came along next and quoted the first
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I started this thread

;-)

Neven

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Re: What the Buoys are telling
« Reply #1511 on: July 05, 2017, 11:04:08 PM »
What Jim said. And be grateful to him, as I was about to get my scissors.
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be cause

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Re: What the Buoys are telling
« Reply #1512 on: July 05, 2017, 11:44:30 PM »
LOL .. can I just add an LOL .. just to fill this LOL thread as I haven't (LOL) LOL'led here LOL for LOL hours ...
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 + 2 = 2021 + 1 =  ' if only we could have seen it coming ' ...

vigilius

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Re: What the Buoys are telling
« Reply #1513 on: July 06, 2017, 01:31:25 AM »
July 4 vs. July 5. Lumps continue to subside, some water has run off. (had to edit, I got the order of the pix wrong the first time)
« Last Edit: July 06, 2017, 01:52:55 AM by vigilius »

Rob Dekker

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Re: What the Buoys are telling
« Reply #1514 on: July 06, 2017, 04:37:35 AM »
July 4 vs. July 5. Lumps continue to subside, some water has run off.
Thanks vigilius !
I find it very interesting how the melting ponds are draining on the Obuoy 14 images.
From a large lake last week to puddles in the latest images, and they are still draining.

If it melted through the bottom of the ice, draining would be very rapid (level with sea-level in a matter of hours). Instead it progresses very slowly.

It is almost as if these ponds are draining over the 'edge' of the floe, or a crack that is not aligned with the bottom of the melting ponds, where the edge is slowly melting itself...
That would suggest that the ice is still pretty thick up there...

Does anyone any other ideas how to explain the slow draining process ?
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Dundee

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Re: What the Buoys are telling
« Reply #1515 on: July 06, 2017, 05:59:13 AM »
Reviewing the video from last year, water first showed up peeking through what looked like a thick snow layer in very late June. On July 16, a companion buoy drops (following relatively rapid draining) and by very late in the month it is free-floating. There is a refreeze and more snow the first week in August and the floe then disintegrates. Throughout, the appearance of the higher terrain is snowy.

The surface currently has a distinctly icy appearance - not really like saturated snow. A thick snow layer with an impermeable ice layer in the top half might do it - the melt sits on the ice layer.  When it fails rather than draining quickly to sea, the water drains into the permeable snow layer which, depending on the permeability of the snow, could be a much slower process.

I'm grasping at straws a bit - the buoy moved a lot and saw sharply different conditions, and was in fundamentally different ice between the two years. Trying to draw conclusions based on visual appearance between the two is probably iffy.

Tor Bejnar

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Re: What the Buoys are telling
« Reply #1516 on: July 06, 2017, 06:11:17 AM »
from here and elsewhere in these threads:
Quote
Arctic melt ponds form when meltwater clogs ice pores (I thought we already know this...)
Article about a new study that has been accepted for publication in the Journal of Geophysical Research: Oceans, a journal of the American Geophysical Union.
The ice is colder than the water, so water seeping down freezes, most of the time.  The ice forms a self-healing basin.
Arctic ice is healthy for children and other living things.

Hyperion

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Re: What the Buoys are telling
« Reply #1517 on: July 06, 2017, 08:38:36 AM »
I'm thinking that meltlake largely formed beneath a thick insulating snow blanket. Since its freshish the warmer water should sink to the bottom and burrow. But once the initial drain has happened the salinity should rise without snow left to freshen it and a self sealing mechanism should kick in until the pool salinity rises to that of the floe beneath and the core temp reaches melting point? And then it just goes to slush in a hurry?
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oren

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Re: What the Buoys are telling
« Reply #1518 on: July 06, 2017, 10:39:32 AM »
I think it's very thick snow over quite thick ice, undergoing a constant and serious torching in situ. I am sure the remaining thickness is much lower than initial conditions.
Indeed last year tended to refreeze a lot on the surface, and it finished more by breakup (and bottom melt?) than by top melt. This year you can actually see it melt from the top.

seaicesailor

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Re: What the Buoys are telling
« Reply #1519 on: July 06, 2017, 11:44:58 AM »
Update from our blind friend 2017A
The www reports 98 cm of thickness, with 9 cm of surface melt and 21 cm of bottom melt accumulated; melting has accelerated dramatically in the last week for obvious reasons.
Looking at the plot I would say there is more melt at both ends, but as others indicated before, drainage from the top, and direct heating from the sun may produce these results. Vertical displacement of the buoy might also have happened making the reference of the plots invalid.
The bottom water dramatically warms up to close to -1C, I suspect most probably to effect of drained water from the surface, since it seems to happen almost simultaneously along the whole column (however, on second look there seems to be a faster raise of temperature at the depth = 100 cm and around, which is just below the ice. Algae heating up? Fresher warmer water from the top just accumulating?)
« Last Edit: July 06, 2017, 12:12:08 PM by seaicesailor »

oren

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Re: What the Buoys are telling
« Reply #1520 on: July 06, 2017, 12:29:59 PM »
At these rates, I strongly doubt the floe survives the summer. And all of this is happening as the buoy is heading north, into the CAB heartland.

seaicesailor

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Re: What the Buoys are telling
« Reply #1521 on: July 06, 2017, 05:50:12 PM »
At these rates, I strongly doubt the floe survives the summer. And all of this is happening as the buoy is heading north, into the CAB heartland.
I am afraid that it will not last much, too. With the rough weather taking over we'll see what it shows next week.

magnamentis

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Re: What the Buoys are telling
« Reply #1522 on: July 06, 2017, 06:06:12 PM »
<snip, off-topic; this is a forum, not your living room; N.>
« Last Edit: July 06, 2017, 09:58:56 PM by Neven »

ghoti

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Re: What the Buoys are telling
« Reply #1523 on: July 06, 2017, 06:59:13 PM »
It is interesting that between 50 and 100cm depth 2017A seems to be freezing at -1C. This suggests that the ice there has a salinity of only 17 PSU. That's sea water diluted about half with fresh melt water. I can't wait for the next update :)

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Re: What the Buoys are telling
« Reply #1524 on: July 06, 2017, 10:31:18 PM »
Hey – the ice is back around #14  :)
I'm puzzled where it comes from, Temps have been positive throughout. Is it large scale convergence/compression?

magnamentis

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Re: What the Buoys are telling
« Reply #1525 on: July 06, 2017, 10:53:42 PM »
Hey – the ice is back around #14  :)
I'm puzzled where it comes from, Temps have been positive throughout. Is it large scale convergence/compression?

that's not new ice, how much you see of it depends on the water level of the melt "lakes" after they drained and/or in early morning when temps are around freezing it looks a bit more frozen than in the afternoon or before drainage. no substantial new ice came from anywhere.

oren

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Re: What the Buoys are telling
« Reply #1526 on: July 07, 2017, 12:05:19 AM »
It does look like there is some glazing of ice over the water, although I fail to see how this might be possible with temps above zero throughout the buoy's weather chart.

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Re: What the Buoys are telling
« Reply #1527 on: July 07, 2017, 01:29:28 AM »
Its a well know phenomena in world-view imagery that ice which turns blue, from melt ponding, will again turn white then gray before it melts completely. I believe that is what we are seeing here, grayish skeleton ice which will struggle to survive another couple of weeks in this weather.

vigilius

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Re: What the Buoys are telling
« Reply #1528 on: July 07, 2017, 01:31:02 AM »
Click to animate July 4, 5, 6.
Trying to get the images at around the same time of day.

DrTskoul

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Re: What the Buoys are telling
« Reply #1529 on: July 07, 2017, 01:32:34 AM »
Click to animate July 4, 5, 6.
Trying to get the images at around the same time of day.
Looks like runoff.

Looks like it.. drainage...

Hyperion

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Re: What the Buoys are telling
« Reply #1530 on: July 07, 2017, 02:00:49 AM »
It does look like there is some glazing of ice over the water, although I fail to see how this might be possible with temps above zero throughout the buoy's weather chart.

If its fresher water sitting on melting saltice then it could easily get chilled with the colder stuff  rising to the top as greasy ice crystals.
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DrTskoul

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Re: What the Buoys are telling
« Reply #1531 on: July 07, 2017, 02:05:22 AM »
After looking more carefully it is a combination... right at the front it looks like freezing

Hyperion

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Re: What the Buoys are telling
« Reply #1532 on: July 07, 2017, 02:06:18 AM »
It is interesting that between 50 and 100cm depth 2017A seems to be freezing at -1C. This suggests that the ice there has a salinity of only 17 PSU. That's sea water diluted about half with fresh melt water. I can't wait for the next update :)

Me too! thats a huge rise in the core temp over the last few days. Perhaps its that soggy and porous that the snow melt is soaking through and washing out the brine pockets. Of course there is a big steam hose blasting out of bering with 30 kg per sqm coming in at 100km per hr, to rain over that area. So it could be rain flushing out the brine and raising the temp. Nullschool says its over 2C in near surface in that area so its likely that large areas are about to go POOF!  :(
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Rob Dekker

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Re: What the Buoys are telling
« Reply #1533 on: July 07, 2017, 08:39:49 AM »
The slow draining of the melting ponds on Obuoy 14 images suggests that draining occurs through small cracks and not through the bottom. That means the ice there is still pretty thick.
About 2017A, please remember that ice at the top melts at 0 C and ice at the bottom melts at -1.8C.
« Last Edit: July 07, 2017, 08:45:25 AM by Rob Dekker »
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Andreas T

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Re: What the Buoys are telling
« Reply #1534 on: July 07, 2017, 11:57:19 AM »
Thank you Vigilius for those images taken at the same time of day, different direction and angle of sun makes such a difference to the appearance of the ice. Seeing earlier how a shallow covering of water can look much deeper over ice which is after all fairly transparent (at least translucent) when waterlogged, I think what we are seeing isn't ice forming on the water but becoming visible when water level falls.
Drainage is probably through enlarging brine channel which are gradually flushed out with meltwater, maybe blocking temporarily when low salinity surface water meets colder ice further down?

Andreas T

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Re: What the Buoys are telling
« Reply #1535 on: July 08, 2017, 08:49:53 AM »
obuoy14 is now rotating in its hole. The camera has panned to the left. Azimuth reading does not show a change apart from an improbable excursion earlier today, I hope this doesn't mean we lost that information for good.

air temperature has dropped slightly with clouds coming over. I still think we see falling water level but also melting ice surface which is looking rougher and more porous.

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Re: What the Buoys are telling
« Reply #1536 on: July 08, 2017, 12:14:44 PM »
If the camera view at any time of the day includes the sun, then you could confirm rotation with successive views of the sun at same time on different days and look at the angle left / right of the camera axis.

oren

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Re: What the Buoys are telling
« Reply #1537 on: July 08, 2017, 12:27:47 PM »
Isn't he rotation confirmed by the rectangular piece of ice shifting to the right side of the image?

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Re: What the Buoys are telling
« Reply #1538 on: July 08, 2017, 03:55:15 PM »
The azimuth data on the GPS tab shows about a 20 degree drop or rotation to the north. The appearance of surface  roughness seems more like a bit of snow fell on the area. There was at least one image returned that also had a blob of snow on the camera dome.

Andreas T

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Re: What the Buoys are telling
« Reply #1539 on: July 08, 2017, 06:49:57 PM »
since I posted this morning the azimuth data has dropped by 15deg (as I read it 155 down to 140) thats anticlockwise looking down on it, which means southward from its southwesterly direction and fits the shift in camera viewing angle onto the landscape we saw since March. When we get a view of the sun (a clearer sky than at present is needed for that) it will appear at 21:00 where it was in Vigilius' comment 1513 at 22:00UTC.
Maybe it was snowfall which produced that change of surface structure, hard to tell.

vigilius

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Re: What the Buoys are telling
« Reply #1540 on: July 09, 2017, 05:53:11 AM »
Well, FWIW here's July 6,7,&8, click to animate.
However, it was cloudy on the 7th, and I wasn't able to get them all at exactly the same time and then there's the little matter of the buoy actually, you know, taking that little anticlockwise turn-
so the progression is probably not as interesting or useful this time. (Just trying to think of something useful to do around here LOL)

oren

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Re: What the Buoys are telling
« Reply #1541 on: July 09, 2017, 09:03:20 AM »
Thx vigilius. For whatever it's worth, meltwater continued to drain on the 7th (when looking at the far left "river").

Jim Hunt

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Re: What the Buoys are telling
« Reply #1542 on: July 09, 2017, 01:12:05 PM »
It is interesting that between 50 and 100cm depth 2017A seems to be freezing at -1C. This suggests that the ice there has a salinity of only 17 PSU.

See the seminal work of G F N Cox on sea ice salinity. E.g.

https://www.cambridge.org/core/journals/journal-of-glaciology/article/salinity-variations-in-sea-ice/0976B42E5B21CAE25BE26A0DD811513F/core-reader
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

vigilius

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Re: What the Buoys are telling
« Reply #1543 on: July 10, 2017, 04:34:52 AM »
Daily gif featuring July 7, 8, 9. Click to animate. Sure did enjoy the sun while we had it. Between 8th and 9th looks like the water rose a bit (unless the ice is sinking on account of mass loss?). Sure looks slushy to me.

Bruce Steele

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Re: What the Buoys are telling
« Reply #1544 on: July 11, 2017, 01:12:00 AM »
ITP 97 is the only ice tethered buoy still working in the Beaufort this year. It is showing a lot of heat in the first ~ ten meters of surface water. It is still over deep water but if the current warm water holds we can expect a large hole  to form in the area west of McClure Sound.  The warning has gone on for several days already.

http://www.whoi.edu/page.do?pid=155136

Look at the T /S contours

vigilius

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Re: What the Buoys are telling
« Reply #1545 on: July 11, 2017, 04:46:08 AM »
Three day gif, July 8, 9, 10. Click to animate. Water level seemed up on the 9th, has dropped back now on the 10th. Still mostly cloudy.

oren

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Re: What the Buoys are telling
« Reply #1546 on: July 11, 2017, 07:40:46 AM »
Interestingly the pond in near right doesn't drain when the rest of them do.

vigilius

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Re: What the Buoys are telling
« Reply #1547 on: July 11, 2017, 10:06:29 AM »
Clouds have blown off, hope we get some good Worldview images of the Parry Channel to go along with this. But wow, just like oren was noting, the water in the middle of the picture has drained significantly but that pond in the near right hasn't budged.

seaicesailor

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Re: What the Buoys are telling
« Reply #1548 on: July 11, 2017, 11:31:42 AM »
Could we be looking at the ice freeboard now, meaning it is not draining because it is inundated?

Darvince

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Re: What the Buoys are telling
« Reply #1549 on: July 11, 2017, 01:19:16 PM »
I think that pond simply has no connection to the ocean below. Melt ponds are only able to form because the liquid water draining down through floes at first freezes in the deeper layers.