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Andreas T

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Re: What the Buoys are telling
« Reply #1300 on: May 16, 2017, 03:57:20 PM »
...

So maybe it began with nearly 20 cm of snow but had lost several cm of that by the end?

(Safe) Prediction: that remaining snow isn't going to see out the month!

EDIT: but wait..

Thermal conductivity of ice = 0.005; of water = 0.0014.

So ice has about 3.5 times the thermal conductivity of water.

Conversely, the same depth of water will show about 3.5 times the vertical displacement between the thermistors as ice. There must be some densely packed snow - almost ice but with some trapped air - that shows similar. And maybe that's what we are seeing from 2017A in March? How do we know if it melts? It just gets a little more compact in turning into water, with a similar displacement between thermistors. Perhaps that's what has already happened here - an alternative explanation?

Now I'm uncertain what is going on in that plot, but my apologies for the stream-of-consciousness post!
I am guessing that "vertical displacement" means temperature difference between thermistors. As I said in my earlier comment that  means temperature gradient delta t / delta y (using y as my coordinate perpendicular to the ice surface). With a fixed thermal conductivity of the ice the heat transfer is proportional to that gradient (larger temperature difference between ice bottom and ice top means more heat transferred).
The thermal conductivity of water would only matter if water would remain completely still, which is impossible here because water is cooled at the ice/water interface and sinks. It is also becoming more saline because of the freezing which also increases density and generates convection. Water temperature changes are very small and you call tell which thermistors are in water because they are all showing a temperature very near the freezing point (1.65 from memory)
The discontinuity SIS is pointing out therefore indicates the point where snow above and ice below transfer equal heat fluxes from seawater to atmosphere but because of lower conductivity of snow (air inclusion) that can only happen at steeper temperature gradient.
Of course heat capacity of ice plays a part when ice changes temperature and then the temperature profile deviates from a straight line (constant gradient).

melting is not explicitly shown in that graph. We can  guess it when somewhere that shows the behavior of ice or snow starts to behave like air or water (i.e. shows the flat temperature profile of a convecting fluid.
This is complicated by snow being possibly carried away by wind (mechanically) or sublimating.

vigilius

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Re: What the Buoys are telling
« Reply #1301 on: May 16, 2017, 05:46:37 PM »
Okay, I am still pondering AndreasT's points, in the meantime posting a random image from #14 just for the sake of keeping this thread toward the top. I have high hopes for the heroic buoy in coming weeks. Ummm, does this mean I am not lurking anymore? (I gotta say, when I post stuff in this forum I get real answers which make me think about posts I just scanned on the first run-through, and it's going to make me more careful about reading more thoroughly before I post but I hope I can be forgiven for this one careless comment)

Andreas T

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Re: What the Buoys are telling
« Reply #1302 on: May 16, 2017, 09:09:46 PM »
Not a random image if you connect it with the temperature measurements. 24h sunshine now keeps the buoy powered up without interruptions but IR radiation balance under clear sky is dropping temperatures when the sun angle is lowest.
Nothing to forgive, Vigilius  :)  (in my opinion) I wish some others on the forum were as thoughtful as you!

I have looked at some other buoys (sadly without cameras) but some of the sensors seem to be malfunctioning.
http://data.meereisportal.de/gallery/index_new.php?active-tab1=method&buoytype=all&region=all&buoystate=active&submit3=display&lang=en_US&active-tab2=buoy

edit: replaced the temperature graph with a later one showing more of the 16 May, the thin cloud in vigilius' image contributed to higher temperature I think
« Last Edit: May 17, 2017, 07:56:05 AM by Andreas T »

Andreas T

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Re: What the Buoys are telling
« Reply #1303 on: May 17, 2017, 10:52:03 AM »
I missed the image for midnight but here is the one for 1 hour past local midnight. Again temperature not as low as 24 hours ago. Thin cloud providing some downwelling longwave radiation I think.

Eli81

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Re: What the Buoys are telling
« Reply #1304 on: May 17, 2017, 10:54:47 PM »
Some interesting spikes to ~5C(!) today... Thinking it's anomalous, but humidity spikes at the same time...  Thoughts? Did some 'tropical' air blow through?  ;D



Jim Hunt

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Re: What the Buoys are telling
« Reply #1305 on: May 18, 2017, 02:20:33 AM »
The latest update from IMB buoy 2017A:

http://GreatWhiteCon.info/2017/05/facts-about-the-arctic-in-may-2017/#May-17

Current Buoy Data (05/16/2017):

Pos: 74.33N, 157.57W
Air Temp: -6.4 C
Air Pres: 1006.9 mb
Snow depth : 11 cm
Ice thickness : 119 cm
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Andreas T

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Re: What the Buoys are telling
« Reply #1306 on: May 18, 2017, 09:15:32 PM »
Some interesting spikes to ~5C(!) today... Thinking it's anomalous, but humidity spikes at the same time...  Thoughts? Did some 'tropical' air blow through?  ;D
There have been similar spikes where air temperature jumps abruptly by as much as 10C and drops just as quickly with a second spike shortly after. These are nearly at the same time of day as previous ones.
I find that highly suspicious. The sensors on the obuoy are shaded and should not "catch" the sun as the thermistor strings do on the IMBs but maybe there is some odd reflection heating the sensor?
What surprises me is that the 17th was definitely not sunny and the camera was showing increasing fog before the spikes (I was looking to catch local noon) although the image I saved is taken later

edit:  the camera image now, 20:00 UTC / local 13:00 is looking just the same as yesterday and temperature is at maximum for the year to date, -3C. Once more its not clear sky and sun which brings high surface temperature on snow covered ice.
« Last Edit: May 18, 2017, 10:50:57 PM by Andreas T »

stonedwaldo

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Re: What the Buoys are telling
« Reply #1307 on: May 20, 2017, 05:13:31 AM »
It's great to see that we are about to hit 7 days of straight uptime on #14! It appears that the batteries started to really drop out about a month ago and are only providing slight power buffering from the solar panels, which are now benefiting from 24hr daylight.

Also, there have been quite a few blizzards or dense ice fogs over the last 2+ weeks. When we had some clear conditions a few days back, I feel like the drifts appeared a bit larger and more widespread.

Finally, some forecasts are calling for a more southerly flow and warmer conditions near #14 in a few days.

https://earth.nullschool.net/#2017/05/22/0300Z/wind/surface/level/overlay=temp/orthographic=-86.29,70.21,3000/loc=-106.572,74.151

Jim Hunt

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Re: What the Buoys are telling
« Reply #1308 on: May 23, 2017, 01:25:41 AM »
O-Buoy 14 currently reports temperatures above zero:

http://GreatWhiteCon.info/2017/05/facts-about-the-arctic-in-may-2017/#comment-221841

Unfortunately her webcam was still shrouded in mist when it last managed to upload an image :(
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woodstea

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Re: What the Buoys are telling
« Reply #1309 on: May 23, 2017, 05:05:30 PM »
It's great to see that we are about to hit 7 days of straight uptime on #14! It appears that the batteries started to really drop out about a month ago and are only providing slight power buffering from the solar panels, which are now benefiting from 24hr daylight.

Also, there have been quite a few blizzards or dense ice fogs over the last 2+ weeks. When we had some clear conditions a few days back, I feel like the drifts appeared a bit larger and more widespread.

When the view is obscured like this I am always wondering whether it's fog or whether something is obstructing the lens -- like a thin layer of frost. Fog seems like the right answer here considering that the humidity is high, and considering that we've had some back and forth between the foggy view and a clear view during the last month.

I understand that there's a difference between ice fog and freezing fog. This would be freezing fog, right? Supercooled droplets of water rather than ice crystals, since the temperature is near 0°C.

I am tremendously interested to see what the view looks like once it clears. Will we see evidence of melting? How long before we see melt pools like we did last year?
« Last Edit: May 23, 2017, 05:15:24 PM by woodstea »

magnamentis

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Re: What the Buoys are telling
« Reply #1310 on: May 23, 2017, 05:09:05 PM »
It's great to see that we are about to hit 7 days of straight uptime on #14! It appears that the batteries started to really drop out about a month ago and are only providing slight power buffering from the solar panels, which are now benefiting from 24hr daylight.

Also, there have been quite a few blizzards or dense ice fogs over the last 2+ weeks. When we had some clear conditions a few days back, I feel like the drifts appeared a bit larger and more widespread.

When the view is obscured like this I am always wondering whether it's fog or whether something is obstructing the lens -- like a thin layer of frost. Fog seems like the right answer here considering that the humidity is high, and considering that we've had some back and forth between the foggy view and a clear view during the last month.

I understand that there's a difference between ice fog and freezing fog. This would be freezing fog, right? Supercooled droplets of water rather than ice crystals, since the temperature is near 0°C.

I am tremendously interested to see what the view looks like once it clears. Will we see evidence of melting? How long before we see melt pools like we did last year?

while it can be both, this time it's fog because at times one can see the horizon which is not possible if the lense is layered with vapor, snow or anything of that kind. once the lense is covered one can see that very well. if you want to verify this just check several times a day until the light conditions allow to see the horizon, i think it's even there in one of the recently posted images but you'll see.
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magnamentis

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Re: What the Buoys are telling
« Reply #1311 on: May 23, 2017, 10:08:32 PM »
in this (current [see time stamp]) image you can clearly see the horizon as well as some features in the foreground which as i said clearly indicate that the lense is not obscured this time ( but it has been in the past while one can see the difference with a bit of experience )
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oren

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Re: What the Buoys are telling
« Reply #1312 on: May 24, 2017, 05:34:14 PM »
Finally a clear image

RoxTheGeologist

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Re: What the Buoys are telling
« Reply #1313 on: May 24, 2017, 06:12:13 PM »
Does the surface look slightly blue in places, or is it a trick of the light?

Andreas T

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Re: What the Buoys are telling
« Reply #1314 on: May 24, 2017, 06:36:19 PM »
scroll up to the image vigilius posted on the 16th, very similar lighting, very similar colours.
The first signs of melting I expect from watching these buoys for a few years is a slumping or sagging of the snow as it becomes coarser and denser (firn). There would be bluer tones in the shadows (because transparency increases) but the scenery in front of Obuoy14 is very flat this year. Its position in Canadian archipelago has meant there was (almost?) no movement around it over the winter, no ridges formed since September.
This has the advantage that we have a good idea what lies under the snow: the stuff we saw snow in in October. See these stills or watch the movie
 http://obuoy.datatransport.org/monitor#buoy14/movie

Jim Hunt

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Re: What the Buoys are telling
« Reply #1315 on: May 25, 2017, 01:07:39 AM »
The sun is now high in the sky. No melt ponds that I can see as yet however:
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

vigilius

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Re: What the Buoys are telling
« Reply #1316 on: May 25, 2017, 02:00:51 PM »
Colder and clear this AM,  our heroic buoy puts in an appearance via shadow.

Tor Bejnar

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Re: What the Buoys are telling
« Reply #1317 on: May 25, 2017, 04:33:54 PM »
I think we can see land in the distance.  Do we know which island(s)? (Map from Obuoy website, annotated) [edit: per the next post, I've uncovered the marker.]
« Last Edit: May 25, 2017, 06:22:24 PM by Tor Bejnar »
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Andreas T

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Re: What the Buoys are telling
« Reply #1318 on: May 25, 2017, 06:09:13 PM »
The map on the Obuoy monitor site oddly shows a track which ends short of the green position marker. If I read the position as 74.3N 103W out of the GPS display it fits the green marker position rather than the end of the red track which stops too far west. (I am using worldview https://go.nasa.gov/2r0VxCv to locate lat/ long position in relation to the surrounding islands.
This would put it about 70km from land in any direction. The direction the camera is pointing can be read from the picture vigilius posted: 11 UTC is 4 AM local time at at 105W, which give me a rough estimate of the camera direction as 240 deg clockwise from north (I don't know whether that is  azimuth or what) corrections welcome.
The images posted by Jim and vigilius also illustrate again that clear sky and sunshine brought lower temperature readings. Lower temperature does not necessarily equate to lower energy absorption, but with snow cover (still) intact, which shouldn't be surprising after a few hours of above zero temps, I don't expect much energy to go into the snow, ice and seawater below.
« Last Edit: May 25, 2017, 06:18:01 PM by Andreas T »

Tor Bejnar

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Re: What the Buoys are telling
« Reply #1319 on: May 25, 2017, 07:37:51 PM »
... which give me a rough estimate of the camera direction as 240 deg clockwise from north ...
So, WSW of the marker's pointer is Stefansson Island.

From Wikipedia:
Stefansson Island is an uninhabited island in the Canadian Arctic Archipelago in the Kitikmeot Region of Nunavut, Canada. It has a total area of 4,463 km2 (1,723 sq mi), making it the 128th largest island in the world, and Canada's 27th largest island. The island is located in Viscount Melville Sound, with M'Clintock Channel to the east. It lies just off Victoria Island's Storkerson Peninsula, separated by the Goldsmith Channel. Stefansson Island's highest mount is 267 m (876 ft).

The first European sighting of the island was in 1917 by Storker T. Storkerson who was travelling with Canadian explorer Vilhjalmur Stefansson (1879-1962), for whom the island was named.
(See interesting life of the explorer.)
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seaicesailor

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Re: What the Buoys are telling
« Reply #1320 on: May 26, 2017, 04:22:09 PM »
The latest 6 days or so available of the B 2017A temperature profiles. I am showing the non-filtered data (red dashed line) and the filtered data. The result of filtering is that some spatial wiggling is removed, but also that the profiles take a 24h-averaged temperature approximately.

I think this daily-averaged temperature, for the thermistors not covered by ice or snow, is skewed to higher values frequently and I don't find another explanation that they are heated by sun or by the buoy material being heated by sun...
« Last Edit: May 26, 2017, 04:57:13 PM by seaicesailor »

woodstea

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Re: What the Buoys are telling
« Reply #1321 on: May 26, 2017, 08:39:29 PM »
I think we can see land in the distance.  Do we know which island(s)? (Map from Obuoy website, annotated) [edit: per the next post, I've uncovered the marker.]

You may be right, but I do remember that as the buoy was working its way into the Parry Channel last year, I often thought I could make out land in certain photos, but then other photos with similar azimuth but different sun angle seemed to show no land. When this first started happening the buoy was just too far out for it to be possible. I suspect that's the case now, if it's true that the buoy is 70 km away from the nearest island and the highest point on that island is 267 meters.

The map on the Obuoy monitor site oddly shows a track which ends short of the green position marker. If I read the position as 74.3N 103W out of the GPS display it fits the green marker position rather than the end of the red track which stops too far west.

The end of the red track is the last position of the buoy when it went dark for the winter. After that it continued to move with the ice to its current position, which has barely changed since the buoy woke up again.

Tor Bejnar

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Re: What the Buoys are telling
« Reply #1322 on: May 26, 2017, 09:21:09 PM »
Thanks, woodstea.  That explains the gap and the red dot at the bottom of the marker.

This calculator suggests one can see a 200 m tall mountain 50 km away.  at 70 km, the mountain would need to be at least 400 m tall. (250 m - 56.5 km)

Then there are false images (actual reflections) where one can see objects that are below the horizon.
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Rattle

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Re: What the Buoys are telling
« Reply #1323 on: May 26, 2017, 09:44:33 PM »
Is it my imagination, or is that water at the horizon?


magnamentis

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Re: What the Buoys are telling
« Reply #1324 on: May 26, 2017, 10:11:59 PM »
Is it my imagination, or is that water at the horizon?

you can verify this with  sat images, there is open water not too far out but what we see is the dark surface "mirroring" in the cloud base, one can observe that often in barrows, open water quite far out, hence not directly visible, but the clouds are darker over open water and at times there is some increased humidity in the air, at times even visible fog over open waters and that's what we see.

again you can verify this be measuring the distance to open water and will easily see that it's too far away to be "seen" directly. this, provided nothing has changed during the last 2 days as far as open water is concerned, i'm not checking such details on a  daily basis, just about twice a week.
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woodstea

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Re: What the Buoys are telling
« Reply #1325 on: May 26, 2017, 11:03:28 PM »
Distant open water is also something I imagined I saw frequently last year during the freeze-up -- the mind sees what it wants (or expects) to see. I think it's an illusion in this case. I don't see open water anywhere near this buoy in Worldview or the uni-bremen ice concentration map. The buoy is closer to Stefansson Island I think than to open water.

magnamentis

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Re: What the Buoys are telling
« Reply #1326 on: Today at 12:08:43 AM »
kind of fata morgana LOL there is open water exactly i that direction at the entrance of the main passage. has been more 2 days ago, currently has been closing up a bit.
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Hyperion

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Re: What the Buoys are telling
« Reply #1327 on: Today at 12:17:24 AM »
The latest 6 days or so available of the B 2017A temperature profiles. I am showing the non-filtered data (red dashed line) and the filtered data. The result of filtering is that some spatial wiggling is removed, but also that the profiles take a 24h-averaged temperature approximately.

I think this daily-averaged temperature, for the thermistors not covered by ice or snow, is skewed to higher values frequently and I don't find another explanation that they are heated by sun or by the buoy material being heated by sun...

Is that slow slow rising at the ice water interface indicative of bottom melt?
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