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ktonine

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Re: What the Buoys are telling
« Reply #150 on: July 23, 2013, 05:59:13 AM »
...the underside of the ice is not flat...perhaps that explains differences from estimated thickness averages and single location measurements.

That could explain any difference in bottom readings - but the main difference is at the top surface.

Through winter until as recently as June 13 the two methods were in agreement. The top surface difference has become steadily more pronounced as the melt season has progressed. 


Jim Hunt

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Re: What the Buoys are telling
« Reply #151 on: July 23, 2013, 09:24:56 AM »
Buoy of the day is 2012L, AKA O-Buoy #7. According to the apparently fully functional sounders its thickness decreased by 11 cm in 24 hours, to 2.48 m.

According to the thermistors underneath the floe the water temperature is bobbing around the -1 degree mark. It looks to me like thermistor 11 is near the "top", and thermistor 35 is near the "bottom". What do you suppose 12-15 represent?
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helorime

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Re: What the Buoys are telling
« Reply #152 on: July 23, 2013, 09:34:16 AM »
The ice at  buoy 8 is melting and opening up incredibly quickly.
Any sufficiently advanced technology is indistinguishable from magic.

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Re: What the Buoys are telling
« Reply #153 on: July 23, 2013, 09:55:19 AM »
...What do you suppose 12-15 represent?
A melt pond?

Espen

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Re: What the Buoys are telling
« Reply #154 on: July 23, 2013, 09:59:43 AM »
Why are we trying to guess the thickness?  We have data from the colocated buoy, and it's 192cm thick [1].  All the guesses are useful for is proving just how bad the unaided human eye is at guesstimating distances from a small picture with no reference markers in frame.
http://imb.crrel.usace.army.mil/2012H.htm

[1] OK, the buoy appears to show the surface melt has stopped, and is thus possibly reading from the top of a melt pond.  Going by the melt rate before it hit the plateau (22 cm in about 10 days), we could maybe knock off another 20cm or so, for an actual thickness of ~170cm.

As always quick with the gun 8), it was not a guess Peter, but a just reflection. Can you live with that?
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Jmo

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Re: What the Buoys are telling
« Reply #155 on: July 23, 2013, 10:06:23 AM »
According to the thermistors underneath the floe the water temperature is bobbing around the -1 degree mark. It looks to me like thermistor 11 is near the "top", and thermistor 35 is near the "bottom". What do you suppose 12-15 represent?

Melt pond?  Same temp for approx 30cm just above 0C, so makes sense.
Thanks for the buoy data updates Jim.  :)
Jeff

Jim Hunt

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Re: What the Buoys are telling
« Reply #156 on: July 23, 2013, 10:57:13 AM »
The ice at  buoy 8 is melting and opening up incredibly quickly.

I can't see your .TIFF without clicking  :(

I'm not sure how fast the ice is melting, but it certainly looks like the wind is increasing.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

ktonine

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Re: What the Buoys are telling
« Reply #157 on: July 24, 2013, 02:21:33 AM »
Has anyone been watching the water accumulate on NP Webcam 2?  Over the past week the water has risen approximately 20cm.  Impossible to tell how much is precipitation and how much is due to melting snow/ice.  I don't think I've ever seen the levels rise that much before - floe must be shaped like a bowl.

DaddyBFree

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Re: What the Buoys are telling
« Reply #158 on: July 24, 2013, 03:32:04 AM »
Has anyone been watching the water accumulate on NP Webcam 2?  Over the past week the water has risen approximately 20cm.  Impossible to tell how much is precipitation and how much is due to melting snow/ice.  I don't think I've ever seen the levels rise that much before - floe must be shaped like a bowl.
Hi ktonine,
I have been watching Webcam 2 with much curiosity.  I was wondering if, in fact, that was actual ocean water flowing over the floe. I have little scientific perspective on the issue; however, I was considering making it into a personal betting game as to which of the markers will tip over next. ;)  We are down to nine of them left, and I am thinking the center-right marker is looking pretty tipsy.
B

Vergent

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Re: What the Buoys are telling
« Reply #159 on: July 24, 2013, 05:31:40 AM »


It's listing to starboard. there is a clear image of the foreground gauge. The top melt stopped in spite of a temp of 0.8 C. What this means is that the bottom is in contact with high salinity water and the bottom melt is refrigerating the ice. I think that "top melt" + "bottom melt" = a constant in this situation, the underlying salinity decides which happens.

Paradoxically, When the melt pond drains, the top melt will resume due to the fresh water underneath, in spite of the reduced albedo.

Vergent

Jim Hunt

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Re: What the Buoys are telling
« Reply #160 on: July 24, 2013, 12:20:59 PM »
I think that "top melt" + "bottom melt" = a constant in this situation, the underlying salinity decides which happens.

It's going to be a bit tricky to keep tabs on all that from now on, because the water seems to have got into the works of 2013E. Most of the thermistors are now reporting nothing at all, or gibberish. The bottom sounder failed in the middle of June. In all the circumstances do you believe what the top sounder is saying?

Meanwhile in other news, the top sounder of 2012H ( AKA OBuoy 8 ) has burst back into life and reports 10 cm of surface melt overnight, and OBuoy 7 looks to have received a dusting of snow from the so far unnamed Arctic cyclone:
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Phil.

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Re: What the Buoys are telling
« Reply #161 on: July 24, 2013, 01:56:42 PM »


It's listing to starboard. there is a clear image of the foreground gauge. The top melt stopped in spite of a temp of 0.8 C. What this means is that the bottom is in contact with high salinity water and the bottom melt is refrigerating the ice. I think that "top melt" + "bottom melt" = a constant in this situation, the underlying salinity decides which happens.

Paradoxically, When the melt pond drains, the top melt will resume due to the fresh water underneath, in spite of the reduced albedo.

Vergent

I'm not sure that the top melt has stopped, the stake in the foreground is now showing the 8th segment which it wasn't yesterday.

Vergent

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Re: What the Buoys are telling
« Reply #162 on: July 24, 2013, 03:29:01 PM »


Well, it's slowed down considerably, and we lost the gauge that was listing on the right. Clear and calm should get the melt going strong.

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MOwens

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Re: What the Buoys are telling
« Reply #163 on: July 25, 2013, 06:29:37 AM »

Well, it's slowed down considerably,

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I think you spoke too soon! :

MOwens

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Re: What the Buoys are telling
« Reply #164 on: July 25, 2013, 06:42:02 AM »
so there is a thin ice film around the camera and the buoy. ..could there be a bias for more ice retention around these buoys because of wind effects?

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Re: What the Buoys are telling
« Reply #165 on: July 25, 2013, 06:43:15 AM »
It's R2 D2 in a life raft.

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AartBluestoke

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Re: What the Buoys are telling
« Reply #166 on: July 25, 2013, 08:09:38 AM »
between the last 2 posts, it looks like the water level has risen. (water at the level of the cable connecting to the depth sensor vs water almost at transducer level)

Where is the water coming from for that?

Also, i wouldn't expect this situation to persist, eventually the ice would have to crack somewhere and drain as the forces involved in keeping 1m of ice submerged would be "significant" over a large area.

Seawater is about 1025kg/m3, sea ice (1st year) is about 900.  the density difference would result in around 9kN of force/m2 from submerging 1m thick ice. This means that the buoyancy forces alone could be around 20% of the fracture strength of the ice.

(The fracture toughness of ice is in the range of 50–150 kPa m1/2, with larger pieces having lower strength due to being more liekly to include a weakness -  from   http://link.springer.com/article/10.1023%2FA%3A1021134128038#page-2 )

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Re: What the Buoys are telling
« Reply #167 on: July 25, 2013, 09:11:19 AM »
Probably the last chart this season, looks like fresh ideas are needed to record melting (beneath ponds) properly...


Jim Hunt

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Re: What the Buoys are telling
« Reply #168 on: July 25, 2013, 12:41:00 PM »
Buoy of the day this morning is 2013C, located near Alert. Yesterday the air temperature rose considerably, as did the wind.  The net result (if the sensors are to be believed!) was 10 cm of surface melt in 20 hours:
« Last Edit: July 25, 2013, 08:44:53 PM by Jim Hunt »
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Peter Ellis

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Re: What the Buoys are telling
« Reply #169 on: July 25, 2013, 01:13:24 PM »
Pretty sure the top of the ice is where it drops below zero (i.e. around thermistor 19). The few readings above that likely represent a melt pond which is isothermal at zero degrees, followed by a jump at the air/water boundary.  So that trace shows the melt pond draining by ~20cm. 

There may also have been a few cm of melt at the base of the pond, but it's hard to be sure where the boundary is since thermistor 18 is plainly over-reading slightly relative to its neighbours and has been for several months.
« Last Edit: July 25, 2013, 01:18:47 PM by Peter Ellis »

Jim Hunt

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Re: What the Buoys are telling
« Reply #170 on: July 25, 2013, 01:37:10 PM »
Pretty sure the top of the ice is where it drops below zero (i.e. around thermistor 19).

2012C is one of the few buoys where the notes give you helpful hints such as:

Quote
Thermistor #7 at air-snow interface (7 cm above ice-snow interface)

The top sounder reckons there has been 42 cm of surface melt, which by my reckoning puts the current surface at (dodgy?) thermistor 18, which ties in quite nicely with your analysis!

[Edit - I fear my initial mental arithmetic was in error. 42 + 7 cm = 49! The current surface should be at thermistor 12]
« Last Edit: July 26, 2013, 08:56:41 AM by Jim Hunt »
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MOwens

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Re: What the Buoys are telling
« Reply #171 on: July 25, 2013, 09:19:21 PM »
...i wouldn't expect this situation to persist

..melt ponds can be "deep" according to the literature. Although, considering the thinness of the ice, I agree... unless the pond is already flush with sea level.

and btw, what is that popping out of the water back left? Nothing was there previous image...

Anne

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Re: What the Buoys are telling
« Reply #172 on: July 25, 2013, 10:48:40 PM »
and btw, what is that popping out of the water back left? Nothing was there previous image...
I think it's one of the old depth markers lodged in submerged ice. The ice is now shifting. I'm wondering how the buoy in the centre of the picture is going to come out of all these competing forces.

Richard Rathbone

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Re: What the Buoys are telling
« Reply #173 on: July 25, 2013, 11:23:08 PM »
and btw, what is that popping out of the water back left? Nothing was there previous image...
I think it's one of the old depth markers lodged in submerged ice. The ice is now shifting. I'm wondering how the buoy in the centre of the picture is going to come out of all these competing forces.
It looks like the sharks are circling the doomed boy. Just looking at the picture I can hear the music. ;D

helorime

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Re: What the Buoys are telling
« Reply #174 on: July 25, 2013, 11:39:16 PM »
Looks like the markers are completely under water... just a wavy view through the water of the front one 
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Re: What the Buoys are telling
« Reply #175 on: July 25, 2013, 11:46:03 PM »
It looks like the Buoy will be submerged by its own anchor wire?
Where is all that water coming from? A water pipe leakage?
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Phil.

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Re: What the Buoys are telling
« Reply #176 on: July 26, 2013, 12:46:46 AM »
It looks like the Buoy will be submerged by its own anchor wire?
Where is all that water coming from? A water pipe leakage?

The only way I can see it being explained is that there is a depression in the ice which formed the melt 'lake'.  That 'lake' has now joined with the ocean and filled up, hence the recent rapid rise in the water level wrt the stakes and buoy.  It will be interesting to see what happens next, the buoyancy forces on the submerged ice should have an effect soon.

ghoti

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Re: What the Buoys are telling
« Reply #177 on: July 26, 2013, 12:53:29 AM »
Yeah compare the current water level to the level of the snow surface around the buoy on July 16. How could the surface have been below sea level 10 days ago without the ice breaking up from the pressure?

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Re: What the Buoys are telling
« Reply #178 on: July 26, 2013, 01:07:56 AM »
I think the buoy is simply sinking into the ice it's sitting on.  There's surely a bore-hole underneath it, and meltwater has probably been trickling down and through. 
In other words, the buoy is the plug in the bathtub drain, and the bathtub is melting ice,

Espen

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Re: What the Buoys are telling
« Reply #179 on: July 26, 2013, 01:10:34 AM »
Nice to have some plumbers around ;)
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ghoti

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Re: What the Buoys are telling
« Reply #180 on: July 26, 2013, 01:45:04 AM »
Could be sinking but if it is the webcam buoy is sinking at exactly the same rate because the relative position of the buoy to the camera hasn't changed.

jdallen

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Re: What the Buoys are telling
« Reply #181 on: July 26, 2013, 02:13:00 AM »
The only way I can think of for that floe to be stable is if that is fresh water we're looking at. The buoyancy of the ice under that water would break the floe if it were below sea level.
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SteveMDFP

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Re: What the Buoys are telling
« Reply #182 on: July 26, 2013, 04:51:49 AM »
The only way I can think of for that floe to be stable is if that is fresh water we're looking at. The buoyancy of the ice under that water would break the floe if it were below sea level.

A good buoy goes with the floe.

Vergent

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Re: What the Buoys are telling
« Reply #183 on: July 26, 2013, 05:08:13 AM »
it reminds me of jugglers, he can not keep it up much longer. Look for a draining tomorrow.

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ktonine

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Re: What the Buoys are telling
« Reply #184 on: July 26, 2013, 05:49:51 AM »
it reminds me of jugglers, he can not keep it up much longer. Look for a draining tomorrow.

Vergent

That's what I thought two days ago when most of the white base of the buoy was still visible. 

A lot of water has been added since then.

Something has to give soon.

Has anyone been watching the water accumulate on NP Webcam 2?  Over the past week the water has risen approximately 20cm.  Impossible to tell how much is precipitation and how much is due to melting snow/ice.  I don't think I've ever seen the levels rise that much before - floe must be shaped like a bowl.


kevjohnno

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Re: What the Buoys are telling
« Reply #185 on: July 26, 2013, 08:21:35 AM »
The drift map on the PSC site has now been updated to show the two webcams as bing co-located with PAWs buoy 819920 .

I had sent them an email asking them to confirm which buoys the cams were with as the information on the web sites seemed inconclusive. Roger Andersen fom PSC quickly replied

"Kevin-

Hold on.

The checks I was immediately able to make confirmed the ID of the Barneo PAWS buoy as 975420, but it turns out that was a mistake, stemming from an original misunderstanding of the time order of deployment.  It should have registered that the Barneo PAWS was reporting from the upstream position, but I simply did not catch it.  So I now have to reverse myself.  Both Webcams #1 and #2 are co-located with PAWS Buoy 819920. 

Thank you very much for catching this, and calling it to my attention.

--Roger"


 I hope it's right now and I am grateful they replied to me so quickly.

Espen

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Re: What the Buoys are telling
« Reply #186 on: July 26, 2013, 08:35:39 AM »
The drift map on the PSC site has now been updated to show the two webcams as bing co-located with PAWs buoy 819920 .

I had sent them an email asking them to confirm which buoys the cams were with as the information on the web sites seemed inconclusive. Roger Andersen fom PSC quickly replied

"Kevin-

Hold on.

The checks I was immediately able to make confirmed the ID of the Barneo PAWS buoy as 975420, but it turns out that was a mistake, stemming from an original misunderstanding of the time order of deployment.  It should have registered that the Barneo PAWS was reporting from the upstream position, but I simply did not catch it.  So I now have to reverse myself.  Both Webcams #1 and #2 are co-located with PAWS Buoy 819920. 

Thank you very much for catching this, and calling it to my attention.

--Roger"


 I hope it's right now and I am grateful they replied to me so quickly.

I don't understand about the update of the drift map, it is still from July 17?
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kevjohnno

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Re: What the Buoys are telling
« Reply #187 on: July 26, 2013, 08:44:05 AM »
Espen they haven't updated the tracks on the drift map so they are still only up till 17/7 but they have updated the key info for the green track and remarked on  the change as note just above Svalbard on the map.

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Re: What the Buoys are telling
« Reply #188 on: July 26, 2013, 09:39:33 AM »
Hard to credit they're colocated with the same buoy when they look so different. Webcam 1 barely has any ponding and snow still lying: webcam 2 is one massive lake. How can that be?

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Re: What the Buoys are telling
« Reply #189 on: July 26, 2013, 09:58:17 AM »
Peter,

That is true, sometimes the weather is completely different too?
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Re: What the Buoys are telling
« Reply #190 on: July 26, 2013, 10:14:00 AM »
Peter,

That is true, sometimes the weather is completely different too?

"Collocated" could be quite relative.  We are *assuming* the bouys are looking at on another.  Are we certain?  They might actually be several KM apart.
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Jim Hunt

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Re: What the Buoys are telling
« Reply #191 on: July 26, 2013, 11:44:32 AM »
The drift map on the PSC site has now been updated to show the two webcams as being co-located with PAWs buoy 819920.

All of which casts even more doubt about which webcam is showing which buoys. According to NPEO, webcam 2 is "monitoring UPMC's Atmospheric Buoy", but if you check what that actually looks like webcam 1 seems to match that description much better.

Whilst both cameras may have started out near Barneo back in April, it seems certain the floes they're on have now drifted much further apart.

For what it's worth, the GPS for PAWS 819920 seems to match IMB 2013E quite well. Likewise for PAWS 974250 and 2013B.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

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Re: What the Buoys are telling
« Reply #192 on: July 26, 2013, 12:20:59 PM »


Did you ever try to hold a beach ball under water? The collective buoyancy of the ice under this lake must be about: 100kg/m^2 X 10,000 X (however many (100m)^2 the lake pond is)(assuming 1m thickness)

The forces must be balanced perfectly, otherwise the ice would shatter. The only explanation is that the ice has a very uniform thickness. A thin spot would sink, a thick spot would rise. Somewhere, it would crack.

V
« Last Edit: July 26, 2013, 04:19:35 PM by Vergent »

kevjohnno

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Re: What the Buoys are telling
« Reply #193 on: July 26, 2013, 01:07:30 PM »
Roger Andersen said in an earlier email to me that the cams were installed about 100 metres apart and about 100 metre from the PAWS buoy. James Morison, the principal investigator for the North Pole Environmental Observatory said much the same in this article about the melt at cam 2  http://www.theatlantic.com/technology/archive/2013/07/the-pond-at-the-north-pole/278093/

Roger also said that a number of buoys were positioned nearby (a buoy farm) as this gave redundancy of position location. He also said that he doubted the cams were still located on the same floe as the PAWS buoy but they would surely be still close.

It was because of the apparent discrepancy between the NPEO site info and the IMB site re the camera that I emailed the PSC. 

Vergent

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Re: What the Buoys are telling
« Reply #194 on: July 26, 2013, 02:35:58 PM »
thanks for that link!

They should put "objects may be nearer than they appear" across the bottom of the pictures. I am amending the above math to reflect this reality.

V

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Re: What the Buoys are telling
« Reply #195 on: July 26, 2013, 03:07:49 PM »
I think the buoy is simply sinking into the ice it's sitting on.  There's surely a bore-hole underneath it, and meltwater has probably been trickling down and through. 
In other words, the buoy is the plug in the bathtub drain, and the bathtub is melting ice,

But all the stakes have been sinking too if that's the case.

Jim Hunt

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Re: What the Buoys are telling
« Reply #196 on: July 26, 2013, 08:49:53 PM »
IMB 2013C is newsworthy again today, because it's on the move!

Currently it's just to the north of the open water opening up off Alert. Perhaps it will sail off down the Nares Strait shortly?
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

ghoti

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Re: What the Buoys are telling
« Reply #197 on: July 26, 2013, 11:15:14 PM »
Good catch Jim! I was just asking where that buoy was over on the Greenland section.

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Re: What the Buoys are telling
« Reply #198 on: July 27, 2013, 12:08:17 AM »
Those are huge melt ponds... Might as well be open water...
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Re: What the Buoys are telling
« Reply #199 on: July 27, 2013, 12:41:28 AM »
Those are huge melt ponds... Might as well be open water...

The dark areas are shadows of clouds.

V