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oren

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Re: What the Buoys are telling
« Reply #800 on: August 18, 2015, 11:27:43 AM »
A heat wave has hit 2015D with temps over 1.2 C producing a burst of melt:

The one-day change is impressive.

Gonzo

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Re: What the Buoys are telling
« Reply #801 on: August 18, 2015, 08:10:11 PM »

Andreas T
Quote
Have a look around on the site where you copied that photo, there is an "overview" page with positions on a map
Thanks Andreas, I think I have it down now. Just the North Pole drifting station I can't figure out dates of where it was and when.

Andreas T

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Re: What the Buoys are telling
« Reply #802 on: August 19, 2015, 12:04:18 AM »

Andreas T
Quote
Have a look around on the site where you copied that photo, there is an "overview" page with positions on a map
Thanks Andreas, I think I have it down now. Just the North Pole drifting station I can't figure out dates of where it was and when.
only way I can think of would be to go to IMB2015D data file (bottom of page at http://imb.erdc.dren.mil/2015D.htm )
which will list lat / lon for every hour since it was set up in an excel file.
Jim Hunt at
edit: wrong link!   Jim has posted correct one below
 shows clickable positions  on map
« Last Edit: August 19, 2015, 02:51:15 PM by Andreas T »

Jim Hunt

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Re: What the Buoys are telling
« Reply #803 on: August 19, 2015, 12:18:39 PM »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Andreas T

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Re: What the Buoys are telling
« Reply #804 on: August 19, 2015, 02:52:11 PM »
Thanks Jim, I pasted the wrong link

DavidR

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Re: What the Buoys are telling
« Reply #805 on: August 19, 2015, 03:34:45 PM »
Jim Hunt shows clickable positions on map

I assume this is what you are thinking of?

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2015-imbs/#2015D-Map
Jim,
 I presume the melt figures given for surface and bottom melt are seasonal figures not daily  or monthly?
Toto, I've a feeling we're not in Kansas anymore

Jim Hunt

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Re: What the Buoys are telling
« Reply #806 on: August 19, 2015, 03:51:27 PM »
I presume the melt figures given for surface and bottom melt are seasonal figures not daily  or monthly?

Correct.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Gonzo

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Re: What the Buoys are telling
« Reply #807 on: August 19, 2015, 04:46:32 PM »
Jim Hunt
Quote
I assume this is what you are thinking of?
http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/summer-2015-imbs/#2015D-Map
Great thanks!

Andreas T

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Re: What the Buoys are telling
« Reply #808 on: August 21, 2015, 09:58:55 PM »
IMB2015E http://imb.erdc.dren.mil/2015E.htm  has been reporting incredibly low air temperatures for a while but now it has dropped below -40. A sad end to its short career.

Gonzo

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Re: What the Buoys are telling
« Reply #809 on: August 23, 2015, 04:41:30 PM »
IMB2015E http://imb.erdc.dren.mil/2015E.htm  has been reporting incredibly low air temperatures for a while but now it has dropped below -40. A sad end to its short career.
So it sank?

vigilius

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Re: What the Buoys are telling
« Reply #810 on: August 24, 2015, 01:07:55 AM »
Saw this earlier today from #9. Can someone please tell me what I'm looking at here?

Sonia

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Re: What the Buoys are telling
« Reply #811 on: August 24, 2015, 01:33:15 AM »
Saw this earlier today from #9. Can someone please tell me what I'm looking at here?
Ice, snow, water, fog.

The green color did catch my eye.  I though it might mean that piece of ice is rather thick.  I've been amazed that the views from O-buoy 9 have continued to be so interesting.

diablobanquisa

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Re: What the Buoys are telling
« Reply #812 on: August 24, 2015, 09:52:59 AM »
 :o


seaicesailor

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Re: What the Buoys are telling
« Reply #813 on: August 26, 2015, 11:13:57 PM »
2014I (colocated with obuoy#11) is ready to go, or floating around already:



I hope the new 2015F North of ESS survives. I really do! Otherwise next year we lose interesting info we hadn't this one. But bottom melt is accelerating very fast. And this one is 80 N but may get under the weather too.



This one really shows how the silent bottom melt keeps it going even when surface has badly re-frozen for days!

Thank you Jim Hunt for putting all the data together for us :--)

seaicesailor

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Re: What the Buoys are telling
« Reply #814 on: August 27, 2015, 12:01:07 AM »
2015 F is approximately located at the red dot Id say, great chances of survival, depending on bottom melt ceasing soon enough.

Rubikscube

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Re: What the Buoys are telling
« Reply #815 on: August 27, 2015, 01:59:07 AM »
Wow, nice catch diablo.

If those red dots where to melt by minimum, then there should be a really significant drop in SIA and SIE yet to come. But I agree that 2015F will very likely survive. Very interesting to see this much bottom melt far beyond the ice edge.

ghoti

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Re: What the Buoys are telling
« Reply #816 on: September 05, 2015, 07:46:50 PM »
Obuoy 8 is now in the ice and active.

http://obuoy.datatransport.org/monitor#buoy8/camera

It is around 83N 120E as of now.

seaicesailor

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Re: What the Buoys are telling
« Reply #817 on: September 07, 2015, 03:30:48 PM »
Update on our CAB (ESS-sector) buoy. Bottom melting steadily continues well inside the pack, at this location ~81N, although at a slow rate of 5 cm / week or so. No data from the broken ice in the Beaufort-Chukchi sector but one can only speculate . . .






Vergent

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Re: What the Buoys are telling
« Reply #818 on: September 12, 2015, 08:55:12 PM »
ITP-91 is now posting data.

http://www.whoi.edu/page.do?pid=146976

Verg

Anne

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Re: What the Buoys are telling
« Reply #819 on: September 13, 2015, 12:14:08 PM »
O Buoy 15 is now transmitting from the ice
http://obuoy.datatransport.org/monitor#buoy15/gps

helorime

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Re: What the Buoys are telling
« Reply #820 on: September 14, 2015, 12:28:47 AM »
Suddenly a completely different view from obuoy 10.  It had been rotating a bit and occasionally showing other instruments and a completely flat landscape of floes and narrow channels.  Now this.
Any sufficiently advanced technology is indistinguishable from magic.

ktonine

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Re: What the Buoys are telling
« Reply #821 on: December 30, 2015, 07:54:31 PM »
Cross posted from 2015/2016 freezing season:

Buoy 300234062785480 located at 85.45N rose 25C in 9 hours (and is now above freezing). It was -24.3C at 0600 hours (day 363.25) and +1.0C at 1500 hours (day 363.626).

Table of buoys.

Datafile for 300234062785480

Andreas T

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Re: What the Buoys are telling
« Reply #822 on: February 28, 2016, 04:24:13 PM »
Update on our CAB (ESS-sector) buoy. Bottom melting steadily continues well inside the pack, at this location ~81N, although at a slow rate of 5 cm / week or so. No data from the broken ice in the Beaufort-Chukchi sector but one can only speculate . . .



2015F is the only IMB posting current data http://imb.erdc.dren.mil/2015F.htmat the moment (SIsailor's graph is updating)
the different growth rates for this buoy and 2015J http://imb.erdc.dren.mil/2015J.htm over the winter are interesting. The 1.6m ice at 2015J grew clearly less than the 1.1 m ice at 2015F with similar air temperatures.
« Last Edit: February 28, 2016, 04:29:34 PM by Andreas T »

Jim Hunt

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Re: What the Buoys are telling
« Reply #823 on: February 28, 2016, 09:07:30 PM »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

seaicesailor

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Re: What the Buoys are telling
« Reply #824 on: February 29, 2016, 12:29:00 AM »
Update on our CAB (ESS-sector) buoy. Bottom melting steadily continues well inside the pack, at this location ~81N, although at a slow rate of 5 cm / week or so. No data from the broken ice in the Beaufort-Chukchi sector but one can only speculate . . .



2015F is the only IMB posting current data http://imb.erdc.dren.mil/2015F.htmat the moment (SIsailor's graph is updating)
the different growth rates for this buoy and 2015J http://imb.erdc.dren.mil/2015J.htm over the winter are interesting. The 1.6m ice at 2015J grew clearly less than the 1.1 m ice at 2015F with similar air temperatures.

Well, I guess the thicker the ice starts, the slower it grows given the similar thermal conductivity of ice, but this is pretty simplistic. 2015F is also at higher latitude, slightly colder bottom ocean temperature?
The 2015F has grown during the Winter similarly to past buoys listed at the webpage. It did not start serious bottom freezing until half November.

Andreas T

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Re: What the Buoys are telling
« Reply #825 on: March 15, 2016, 12:37:37 AM »
The key with sea ice is that it has a fixed temperature at the bottom:  melting point at sea water salinity. What you should calculate is heat flux through snow cover and icethickness to the sea water beneath. This is driven by the temperature gradient between top and bottom, i.e. the snow layer keeps the ice surface warmer than the snow surface most of the time. If temperatures rise quickly then that may be reversed for a while but since the ice is warmed from below as well as above in that case this situation won't last long.
The main significance of snow cover in winter is that it lessens ice growth by reducing conduction (diffusion) of heat at any given temperature difference between surface temperature and sea water temperature.

I gave some numbers about how ice surface temperature responds to atmospheric temperature change with 30 cm on top. Meaning that the ice problem stays identical and the heat flux (and hence bottom freezing rate) does not change much whether there is 30 cm of snow on top or zero. So if there are 10 C excess for months bottom freezing is going to reduce the same as it was no snow......
I'm trying to get a handle on this from the IMB data. I looked around for reasonably stable temperatures over a snow cover which extends over at least a couple of temperature sensors. This is 2014C from 24/03/2014 to 13/04/2014, the temperature gradient in the ice is conducting heat from the ice / water interface to the ice surface. x-axis is time , each line is the temp at 10cm spacing from the surface. The red line fluctuates with diurnal cycle of radiative balance but averages below the green and that in turn below the blue line. The difference between the temperature gradient over those 20cm is steeper than that over any 20cm deeper in the ice. Since ice temperature hardly changes, heat flux through the steep gradient and the shallow temp gradient is the same. The steep gradient is in snow, the shallow gradient is in ice (top sounder gives 20cm of snow)
So what is the effect of the snow? Of a roughly 16 degC average temperature difference between sea surface and atmosphere 5degC drop is over 20cm or so of snow. That means without snow the difference through the ice would be roughly 140% of what it is "now", and heat transfer, i.e. ice growth  would be 140%too.
Alternatively the same heat transfer would occur as "now" if no snow but top surface at only -11 degC below sea surface temp. That same top surface temp with snow cover would then reduce heat transfer to 71%.
These numbers are reduced if the thermal inertia of the ice is taken into account, but your calculation seems to be based on thermal inertia alone without taking the heat flux into account.

I hope that helps to make this clearer

I moved this over from the freezing season thread because it uses older data to illustrate a general point about snow cover.

Each line in the graph shows how the temperature varied over a roughly two week period at one of the string of temperature sensors on the 2014C IMB buoy http://imb.erdc.dren.mil/2014C.htm some background information at
http://greatwhitecon.info/resources/ice-mass-balance-buoys/
The coldest temperatures were measured at the uppermost sensor S1 out in the air above the snow surface. Each higher temperature curve comes from a sensor 10cm lower on the buoy. The temperature difference between neighboring sensors shows how heat is transfered towards the ocean below the ice.
« Last Edit: March 15, 2016, 05:47:27 PM by Andreas T »

Andreas T

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Re: What the Buoys are telling
« Reply #826 on: March 15, 2016, 09:06:00 AM »
Maybe another graph illustrates what I am hoping to show.
Obuoy14 shows how air temperature fluctuates between day and night just as it does in the IMB air temp data (we know there are some issues with sun shining on the sensors on the string but since I am actually interested what happens further down I'll ignore that)

In addition to this air temperature curve the IMB buoy has sensors spaced at 10cm vertical intervals all the way into the ocean below.
The additional lines in my graph show these temperature/time curves from the uppermost S1 down to S14 i.e. x-axis time (4hour intervals between data points) y-axis temperature in degC
« Last Edit: March 15, 2016, 09:13:16 AM by Andreas T »

Jim Hunt

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Re: What the Buoys are telling
« Reply #827 on: March 15, 2016, 10:15:49 AM »
Did somebody mention Ice Mass Balance buoys?

Here's the temperature profiles for 2015F up to March 1st. One of the thermistors seems to be a bit out of whack?

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/winter-2015-16-imbs/#2015F-Temp

Would it interest anyone to learn that many moons ago I added the "Heat Equation" to one of my IMB spreadsheets?


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seaicesailor

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Re: What the Buoys are telling
« Reply #828 on: March 15, 2016, 11:53:35 AM »
Did somebody mention Ice Mass Balance buoys?

Here's the temperature profiles for 2015F up to March 1st. One of the thermistors seems to be a bit out of whack?

http://GreatWhiteCon.info/resources/ice-mass-balance-buoys/winter-2015-16-imbs/#2015F-Temp

Would it interest anyone to learn that many moons ago I added the "Heat Equation" to one of my IMB spreadsheets?

Yes I would :- )

In the profiles above, you think is it snow from termistor 1 to 5 or nothing like that (given the discontinuity, well, the change of slope)

Jim Hunt

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Re: What the Buoys are telling
« Reply #829 on: March 15, 2016, 12:53:08 PM »
Yes I would :- )

Things are rather frantic here just at the moment, but I'll try and dig something out when time permits.

The discontinuity is masked by the sensor "glitch", but yes. At this time of year the change of slope reveals the ice/snow boundary, to the nearest +/- 5 cm at least.
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Andreas T

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Re: What the Buoys are telling
« Reply #830 on: March 15, 2016, 04:52:19 PM »
I agree that the slope (temperature gradient) shows thermal conductivity when temperature stays constant at both ends of the gradient. The problem is that temperature at the surface does change. Even in the darkness of midwinter, storms and cloud cover change air temperatures and radiative balance. At this time of the year the reappearance of the sun shows in the daily cycling of temperatures seen in temperature / time plots.
Jim's vertical profiles don't show that (I know he does pick comparable times for his profiles). The gradients through the snow vary with those temperature fluctuations.
At 2015F the sounder reports a snow depth of 17cm http://imb.erdc.dren.mil/newdata.htm which could only cover two sensors (spacing 10cm) but maybe there is a snow drift piled higher against the mast of the buoy. The sensors themselves are warmed by the sun and give readings which can be too high.
By looking at these changes over time (data recorded every 4 hours) I am trying to get a better picture.

jdallen

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Re: What the Buoys are telling
« Reply #831 on: March 15, 2016, 07:59:24 PM »
I agree that the slope (temperature gradient) shows thermal conductivity when temperature stays constant at both ends of the gradient. The problem is that temperature at the surface does change. Even in the darkness of midwinter, storms and cloud cover change air temperatures and radiative balance. At this time of the year the reappearance of the sun shows in the daily cycling of temperatures seen in temperature / time plots.
Jim's vertical profiles don't show that (I know he does pick comparable times for his profiles). The gradients through the snow vary with those temperature fluctuations.
At 2015F the sounder reports a snow depth of 17cm http://imb.erdc.dren.mil/newdata.htm which could only cover two sensors (spacing 10cm) but maybe there is a snow drift piled higher against the mast of the buoy. The sensors themselves are warmed by the sun and give readings which can be too high.
By looking at these changes over time (data recorded every 4 hours) I am trying to get a better picture.

Thermal lag - the time required for heat to move through the medium - and the heat content of the ice itself provides a buffer.  Once you get past the first 20CM or so, the gradient will reflect the difference between the *average* temperatures at either end.  This will be even more true if you have additional buffering in the form of snow on top of the ice.  Prompt changes in temperature will only affect readings to the extent they remain constant long enough to influence heat flow accordingly.
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vigilius

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Re: What the Buoys are telling
« Reply #832 on: April 08, 2016, 07:35:26 AM »
http://obuoy.datatransport.org/monitor#buoy13/camera

First pix of the season that I've seen from #13. This is what that high pressure system looks like topside? BTW I wonder what happened to #15, just placed last fall, I think. Any chance it could wake up?

Jim Hunt

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Re: What the Buoys are telling
« Reply #833 on: April 08, 2016, 11:37:44 AM »
BTW I wonder what happened to #15, just placed last fall, I think. Any chance it could wake up?

Maybe it got squashed, or maybe its batteries just went flat? IIRC O-Buoys can wake up on the arrival of sufficient solar power following a long, dark, cold winter.

For more #13 piccies see also: http://forum.arctic-sea-ice.net/index.php/topic,1493.msg73354.html#msg73354
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Andreas T

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Re: What the Buoys are telling
« Reply #834 on: April 08, 2016, 02:52:47 PM »
I am sorry this graph is badly labeled, I don't have enough time or suitable soft ware to make a better version. It is simply temperature on Y-axis time on x-axis. coloured lines are different sensors of IMB 2015F. As the ice cools more sensors drop below the freezing point. Thin black lines mark -5, -10 ... -30 deg C
I think it shows the effect of warm periods and prolonged cooling when surface temperatures rise from -30 to -20
more discussion later if anybody is interested

oren

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Re: What the Buoys are telling
« Reply #835 on: April 09, 2016, 01:23:47 AM »
I am sorry this graph is badly labeled, I don't have enough time or suitable soft ware to make a better version. It is simply temperature on Y-axis time on x-axis. coloured lines are different sensors of IMB 2015F. As the ice cools more sensors drop below the freezing point. Thin black lines mark -5, -10 ... -30 deg C
I think it shows the effect of warm periods and prolonged cooling when surface temperatures rise from -30 to -20
more discussion later if anybody is interested

Actually a great chart, once I figured out the top layers of the buoy are shown at the bottom and vice versa (should have been obvious in hindsight).
I can see around the beginning of January how cooling of the bottom layers and thickening stopped for a while because of the rise in surface temps.

Andreas T

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Re: What the Buoys are telling
« Reply #836 on: April 15, 2016, 06:17:39 PM »
Thanks oren, I enjoy reading information like this out of a chart. The slowdown you describe can also be seen in the bottom sounder graph for January. Pity this is only IMB reporting now.

Obuoy14 has seen temperature rise to 0deg C yesterday and the camera is starting to deice! I hope we won't be limited to discussing just three buoys for the rest of the season.


Jim Hunt

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Re: What the Buoys are telling
« Reply #837 on: April 17, 2016, 04:26:38 PM »
Obuoy14 has seen temperature rise to 0deg C yesterday and the camera is starting to deice!

It hasn't finished deicing itself yet, but does nonetheless reveal some sunbeams and a clear blue sky today:
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Andreas T

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Re: What the Buoys are telling
« Reply #838 on: April 17, 2016, 07:20:51 PM »
I guess I was too hasty: temperatures have been between -10 and -25 deg C http://obuoy.datatransport.org/monitor#buoy14/weather for two days now. This seems to show the limited effect of sunshine on snow (and frost)

plinius

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Re: What the Buoys are telling
« Reply #839 on: April 22, 2016, 02:35:40 PM »
Obuoy14 has seen temperature rise to 0deg C yesterday and the camera is starting to deice!

It hasn't finished deicing itself yet, but does nonetheless reveal some sunbeams and a clear blue sky today:

Obviously doesn't need 0C as much as a bit of sunlight to de-ice. Pretty done now:

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Re: What the Buoys are telling
« Reply #840 on: April 22, 2016, 07:06:01 PM »
Obviously doesn't need 0C as much as a bit of sunlight to de-ice. Pretty done now:
This is an example of the complicating factors around melting ice. The colour and reflectivity of the surface that ice is covering also is very important. If you have sunlight  that is hitting a dark surface that can easily turn sunlight into infrared that is partially covered by ice, that covering will act like a thermal blanket trapping the heat thereby melting the ice. You see that on asphalt all the time. Snow and ice melt on it at very low temperatures as long as sunlight has a chance to get to the asphalt surface. If the camera has a dark surface, once a hole got through to that surface that sunlight could get to, the rest of the ice would melt quite fast even at fairly low temps.
That is the problem the Dark Snow Project is working so that we can get a better handle on how much melt does occur at what temps.
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Andreas T

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Re: What the Buoys are telling
« Reply #841 on: April 26, 2016, 11:21:05 PM »
good point LRC, it could also be driving sublimation, I could not see any melt on the snow in front of the camera but it was getting less.

At Obuoy14 tracks have appeared but are they two legged or four legged tracks?

Jim has a shot from the 22. 4. on his site http://greatwhitecon.info/resources/arctic-sea-ice-images/winter-2015-16-images/ for comparison
« Last Edit: April 26, 2016, 11:29:31 PM by Andreas T »

Jim Hunt

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Re: What the Buoys are telling
« Reply #842 on: April 27, 2016, 10:43:42 AM »
Jim has a shot from the 22. 4

I even have shots from the 24th and 25th:
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Tor Bejnar

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Re: What the Buoys are telling
« Reply #843 on: April 27, 2016, 06:55:51 PM »
Well, we know the footprints were left between 20:01 UTC on April 24 and 16:01 on April 25.

I recall sunny days where if felt like it should be warm, but it was still cooold.  But ice certainly sublimates in such conditions.  Wet clothes on the clothesline would freeze-dry all the time.  A 4' tall snowman that got only morning sun, over the course of a cold January, got skinny and leaned over and nearly touched its head to the ground. (It had a few inches to go before it tumbled over).
Arctic ice is healthy for children and other living things.

Andreas T

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Re: What the Buoys are telling
« Reply #844 on: April 27, 2016, 09:48:46 PM »
Do you know what the other buoys in the picture are? The big yellow thing is a depth profiler as far as I know and in the bottom right seems to be a the top of a (defunct?) mass balance buoy.http://www.erdc.usace.army.mil/Media/FactSheets/FactSheetArticleView/tabid/9254/Article/553850/ice-mass-balance-imb-buoy-program.aspx If there are human visitors could we hope to get the IMB back on line? Only 2015F is reporting data at the moment.

Jim Hunt

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Re: What the Buoys are telling
« Reply #845 on: April 27, 2016, 10:19:09 PM »
The big yellow thing is Ice Tethered Profiler 89. Watch the O-Buoy 14 movie to discover what happened to the IMB buoy. The red dome belongs to Autonomous Ocean Flux Buoy 37
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

vigilius

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Re: What the Buoys are telling
« Reply #846 on: May 08, 2016, 02:05:47 AM »
Last image posted from O-buoy #13 is from April 29 and the instruments seem to have gone silent. Have we lost another one? (whimper, sigh)

Andreas T

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Re: What the Buoys are telling
« Reply #847 on: May 13, 2016, 12:25:48 AM »
obuoy14 shows air temperature climbing above 0degC for the first time this year. Intersting is also that this comes with a rise in relative humidity showing that it isn't air warmed locally but warm and moist air blowing in from the south. The camera was blurred for over a day not sue whether that was frosting or precipitation as temperatures were still cold initially. A little more snow is visible now but of course it's not clear whether that has fallen at the buoy or been drifted into place.

Andreas T

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Re: What the Buoys are telling
« Reply #848 on: May 16, 2016, 05:53:02 PM »
somebody has suggested a look at the ice temperatures measured by 2015F as warming is reaching into the arctic.
The location of this buoy has not seen the dramatic warming shown elsewhere but a look at ice temperatures might be informative. I have produced another temperature over time plot (x-axis shows days since 16th March data points are at 4h intervals
each line represents one of the sensors spaced at 10cm from above the ice and snow surface to the sensor just below the ice in seawater. since temperatures are still below the freezing point of seawater at that location the lowest sensor is the uppermost line (-1.65 degC).
 Most of the time air temperature is the lowest line dropping to -30 in March with daily oscillations due to changes in sun angle (and to some extent sun warming the pole  on the side on which the sensors are mounted).
At the beginning of the month when temperatures rose but were still below the temperature of the ice, ice temperature were rising because reduced cooling at the surface meant that the continuous warming by the ocean had a stronger effect.
Now temperatures at the surface sometimes are above the ice temperature and the ice is warmed from above and below, but these episodes have so far been brief, the chief effect has still been reduced cooling and more or less steeply rising temperature of the ice towards its equilibrium with the water temperature.
« Last Edit: May 16, 2016, 07:23:15 PM by Andreas T »

oren

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Re: What the Buoys are telling
« Reply #849 on: May 16, 2016, 07:21:07 PM »
Thank you again Andreas. Very interesting chart.