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uniquorn

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2022 melt season buoy data and discussion
« on: June 24, 2022, 03:23:11 PM »
It's time to come out of the dev section after over 2 years of studying buoy data.

As always, best efforts to get the analysis here correct but most of it will be done 'quickly' in near real time using raw data and it's highly likely that no one else is checking it.

551610 snow melted out completely after another day of positive temps. Probable melt pond of 20cm near the buoy. No further bottom melt yet.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #1 on: June 24, 2022, 05:56:09 PM »
The ocean beneath TOP4 (and 551610) warming up a little from lows of -1.61C in april to a high of -1.49C on jun16. Could be due to the proximity of the shelf break or the surprising amount of open water just visible under cloud (or both).
<>
https://go.nasa.gov/3OacvGf

551610, WHOI TOP4 and WHOI ITP122 are co-located.
Quote
itp122
Last position on 2022/6/24 63015 UTC : 78.3453° N, 130.7655° W
551610
Longitude: -130.8 Deg, Latitude: 78.34 Deg
   -130.76596      78.344784
top4
Last position on 2022/6/24 23014 UTC : 78.3444° N, 130.766° W

2m water temps under the ice beneath WHOI TOP4 rose a little more to a peak of -1.47C.
Down to 20m though.

Cloudy, but between 0.56C and 1.9C air temps over the last 24hrs
https://go.nasa.gov/3OJfxBb
« Last Edit: June 24, 2022, 08:00:22 PM by uniquorn »

binntho

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Re: 2022 melt season buoy data and discussion
« Reply #2 on: June 25, 2022, 07:31:06 AM »
... snow melted out completely after another day of positive temps. Probable melt pond of 20cm near the buoy. No further bottom melt yet.
I've just started looking at the SIMB3 data and most of it looks fairly straight-forward. But how do you see snow and melt ponds? I'm guessing it's from the dtc values. What should I be looking for?
because a thing is eloquently expressed it should not be taken to be as necessarily true
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oren

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Re: 2022 melt season buoy data and discussion
« Reply #3 on: June 25, 2022, 10:10:00 AM »
I think the methods of divulging the information from the data have been discussed in detail in the Developers section.
Regarding the buoy above, I am somewhat surprised by both of these observations. The location, north of the CAA, is not where I'd expect to see a complete snow melt-out around the solstice. And the water down to 20m to warm up like this is also not what I would expect so soon.
I assume the water is fresher in that region (the fresh water "lens" of the Beaufort "Gyre"?), as otherwise -1.5C should be impossible.
But in any case, it could very well be that my expectations are simply wrong.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #4 on: June 25, 2022, 12:53:24 PM »
... snow melted out completely after another day of positive temps. Probable melt pond of 20cm near the buoy. No further bottom melt yet.
I've just started looking at the SIMB3 data and most of it looks fairly straight-forward. But how do you see snow and melt ponds? I'm guessing it's from the dtc values. What should I be looking for?

Look for temperatures above zero in the ice layer.
To avoid too much technical discussion in this thread, perhaps the best method would be to post what you have done so far in the dev section and work from there.

Jim Hunt

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Re: 2022 melt season buoy data and discussion
« Reply #5 on: June 25, 2022, 01:04:14 PM »
But how do you see snow and melt ponds?

Snow depth comes via the "surface_distance" column in the spreadsheets. However you also need to know the initial distance of the ice surface from the top sounder, which isn't included in the CSV files! That can be worked out from the "Ice and Snow Growth/Melt" charts on the individual SIMB2 pages.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #6 on: June 25, 2022, 01:10:00 PM »
<>
Regarding the buoy above, I am somewhat surprised by both of these observations. The location, north of the CAA, is not where I'd expect to see a complete snow melt-out around the solstice. And the water down to 20m to warm up like this is also not what I would expect so soon.
I assume the water is fresher in that region (the fresh water "lens" of the Beaufort "Gyre"?), as otherwise -1.5C should be impossible.
But in any case, it could very well be that my expectations are simply wrong.

Yes, it is well documented that some areas in the Beaufort have lower salinity so ocean temperatures can be higher, though I would avoid calling it fresh. TOP4 is reporting odd salinity values. Will take a look at itp122 for ref.
Re the temp rise, we are fortunate to have data to 4 decimal places. A rise of 0.02C beneath ice is interesting but probably won't make any news headlines.


oren

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Re: 2022 melt season buoy data and discussion
« Reply #7 on: June 25, 2022, 02:05:48 PM »
Thanks, uniquorn. The chart shows a rise of ~0.05C over ~10 days, unless I a misreading it?
This seemed like a fast change.
In any case I will continue reading and try to build better expectations/intuition. (Thanks for the thread btw).

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #8 on: June 25, 2022, 02:43:06 PM »
Yep. Might be related to proximity to the shelf break. Too cloudy for worldview yesterday, no polarview.
Latest profile rose to -1.4511C 191.0551 salinity at 2m

itp122 confirms though it is only up to 4m depth

If it meets up with the 50m layer then it may be due to turbulent mixing near the shelf.
speculation alert

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #9 on: June 25, 2022, 03:06:24 PM »
hmm. 551610 had another warm 'day' and a significant deepening of the melt pond. A bit cooler now though.

edit: looked at the cryoinno temp profile to check this. Their palette could be better but the 'hover over' shows each temperature. Darker blue is warmer temp. The selected point shows as aqua.
It's a good start for a beta product
« Last Edit: June 25, 2022, 05:02:35 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #10 on: June 25, 2022, 07:38:08 PM »
whoi itp122 near surface salinity is going down which suggests melt rather than mixing from below. So probably some warmer meltwater.
Maybe the higher salinity on May15-19 is brine drainage. It coincides with 2 warmer days.

The whoi graphics algorithm struggling with the temporary lack of data.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #11 on: June 26, 2022, 10:55:08 AM »
Cloudy over 551610 yesterday. Melt pond refreezing from below.
Air temps from -0.8125 to 1.375

https://go.nasa.gov/3A6SYlM for rough location
medium contrast
« Last Edit: June 26, 2022, 11:42:42 AM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #12 on: June 26, 2022, 02:09:02 PM »
Location of the 3 SIMB3 buoys on Worldview
https://go.nasa.gov/3OK7kfM
From top down: 052460, 569620 and 551610

Large animation of drift since jun2  (22.4MB)

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #13 on: June 26, 2022, 03:05:02 PM »
569620 is having a better time than 551610. imho it still has ~10cm of snow sitting on 10cm of slush at surface. Only one tick up of bottom melt or ablation since warmer weather arrived.

air temps hit a peak of 3.8125C on jun25. This is shown on the black line linked to the right hand scale.

569620 is co-located with whoi TOP2 and ITP127
Quote
569620
-140.1 Deg, Latitude: 81.50 Deg
top2
Last position on 2022/6/26 70014 UTC : 81.4846° N, 140.1704° W
itp127
Last position on 2022/6/26 63015 UTC : 81.4842° N, 140.179° W

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #14 on: June 26, 2022, 06:07:32 PM »

Thanks, uniquorn. The chart shows a rise of ~0.05C over ~10 days, unless I a misreading it?
This seemed like a fast change.
In any case I will continue reading and try to build better expectations/intuition. (Thanks for the thread btw).

Latest TOP4 profile shows 2m temp beneath the ice continuing to rise to almost -1.42C and salinity continuing to drop to 190.82

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #15 on: June 27, 2022, 11:58:13 AM »
551610 showing 5cm of surface melt and another 2cm bottom melt after warmer air temps between 0.9C and 1.9C yesterday
Additionally, the melt pond near the buoy appears to be roughly 45cm deep.
« Last Edit: June 27, 2022, 12:56:17 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #16 on: June 27, 2022, 12:35:59 PM »
For those unfamiliar with the temperature contour chart, a quick run through.

The SIMB3 is roughly 4m long and has two sounders at top and bottom that measure distance to the ice at the bottom and the snow, ice or melt pond at the top.
They also have a strip of temperature sensors along the length of the buoy which can measure temps from roughly a metre above the ice, throughout it's thickness down to the ocean below.
Also included is a separate air temperature and pressure sensor and water temperature sensor.

The small animation shows how we build up the images to present all that data in a, hopefully, understandable format.

1. Show the distance measurements from the sounders. Air, snow, ice and ocean are shown as blocks of colour. Snow depth, which is usually not provided, can be estimated from temperature data. Height and depth are indicated on the left axis. Some of the ocean data is not shown as the sensors don't have the resolution to show small changes in temperature.
Dates are along the bottom (y axis)
2. Show the temperature data by making the air, snow, ice and ocean semi transparent. This step only added to help understand the data.
3. Just use lines to indicate the snow, ice surface and ice bottom so the colours match the colour bar on the right. Note that the colour bar temperatures are limited from -3.5C to +2C. This highlights temperature changes in the snow and ice at this time of year. Upper buoy temperatures may be much warmer, as shown down thread. 
4. It would be nice to see how the buoy temperatures relate to the air temps. To do this we add another scale to the right axis and adjust it so that the air temperature line in black doesn't obscure the most interesting buoy data. Hopefully ;)

More about that process here
« Last Edit: June 27, 2022, 04:34:19 PM by uniquorn »

oren

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Re: 2022 melt season buoy data and discussion
« Reply #17 on: June 27, 2022, 01:59:47 PM »
A great explanation, especially the animation. Although in principle I already knew everything, it helped to clarify and cement the knowledge that was swimming around my mind.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #18 on: June 27, 2022, 04:26:38 PM »
Thanks.
Despite being white, the top of 551610 above the ice surface still gets up to 8C warmer than the air temperature, presumably due to insolation. We can cautiously use this to estimate how sunny it has been.

Below is a chart comparing air temp and top of buoy average temp (the top 10 sensors) linked to the left hand scale.
A second scale has been added on the right to show surface distance.

From this chart we could cautiously propose that snow melt on a flat surface is more likely to begin during consistently above zero temps than during sunny but below zero days.

Discussion is very welcome.

Deployment photo of top4, 551610, fluxbuoy48 and itp122
« Last Edit: June 27, 2022, 04:36:12 PM by uniquorn »

oren

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Re: 2022 melt season buoy data and discussion
« Reply #19 on: June 27, 2022, 07:16:02 PM »
A very interesting addition to the data set, as the buoy top temp seems indeed to be a proxy for sunlight. But I think the missing piece in the snowmelt puzzle is the core temp of the ice floe (seen upthread). On June 19th the floe lost its last -3C vestiges and the snow started melting, even though both sunlight and above 0 temps were available several days before that. I think the heat flux into the ice helps keep the snow cool, at least during marginal melt conditions, until thr ice warms above a certain threshold.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #20 on: June 27, 2022, 09:44:00 PM »
Could be that. Thinking on it more, maybe enough snow very near the buoy melts on jun9 to explain the warm temps but isn't widespread enough to be detected by the sounder till jun18. It looks like there was some fresh snow on jun16.

Some more food for thought. A full range temp contour from -4C to +10C, which maybe I should have started with, and a 2cm temp difference contour. Sensor1-sensor2 etc.
The dashed line is temperature just above the snow layer at sensor42 which decreases suspiciously evenly. Maybe a measure of decreasing reflection from the darkening snow layer, or maybe not. edit: Could be due to increasing distance from the snow/pond as it melts.

I think the buoy is affecting the data, behaving like a very thin ridge.
« Last Edit: June 28, 2022, 02:16:47 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #21 on: June 28, 2022, 01:51:04 PM »
551610 quick update:
air temps hovering around 1C. Melt pond maybe deepened a little. Probably not very sunny

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #22 on: June 28, 2022, 02:10:22 PM »
569620 quick update.
A tick up of 2cm bottom melt on jun26. Snow depth reduced to roughly 5cm maybe sitting on 15cm of slush. (inuit might have a better word for it) Air temp peaked at 2C

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #23 on: June 28, 2022, 10:46:19 PM »
551610 quick update:
air temps hovering around 1C. Melt pond maybe deepened a little. Probably not very sunny

whoi top4 is co-located, ocean temps at 2m peaked at close to -1.4C

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #24 on: June 29, 2022, 12:31:26 PM »
551610 update

10cm of ice melt since snow melted out on  jun24/25
6cm of bottom melt since jun10
melt pond is 50cm deep near the buoy
ice + melt pond thickness is 1.67m

Now we are all experts I've added dtc42 to the contour chart as a rough sunnydayometer ;)
« Last Edit: June 29, 2022, 02:36:11 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #25 on: June 29, 2022, 01:59:47 PM »
itp122 co-located with 551610.
salinity contours for ref

tempting to propose that the higher salinity jun15-19 oops, may15-19 is brine drainage
« Last Edit: June 30, 2022, 12:08:12 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #26 on: June 29, 2022, 11:21:13 PM »
<>
Latest profile rose to -1.4511C 191.0551 salinity at 2m
<>
<>
Latest TOP4 profile shows 2m temp beneath the ice continuing to rise to almost -1.42C and salinity continuing to drop to 190.82

Apologies for posting these salinity numbers, they are way off the scale. TOP4 has had a problem with the ctd since deployment. While the relative values may still indicate something, co-located itp122 should be used for salinity

edit:
out of interest here is a comparison of itp122 profile1190 and top4 prof4648 salinity (latest available at this time) The TOP4 scale on the right has been inverted. Maybe an onboard processor has failed and some meaningful data can still be retrieved.
« Last Edit: June 30, 2022, 08:05:52 PM by uniquorn »

oren

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Re: 2022 melt season buoy data and discussion
« Reply #27 on: June 30, 2022, 12:40:28 AM »
itp122 co-located with 551610.
salinity contours for ref

tempting to propose that the higher salinity jun15-19 is brine drainage
Did you mean melt pond drainage? Such that warmer and fresher water gets mixed with the ocean surface water.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #28 on: June 30, 2022, 05:29:16 PM »
Sorry about that, should have been may15-19

Timely though as we do see signs of melt pond drainage in yesterday's 551610 ice bottom temps. Also some temporary disturbance in bottom distance.
A cooler cloudy day so little surface change.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #29 on: July 01, 2022, 11:14:57 AM »
A sunnier day for 569620. Melt pond depth increasing to 30cm near the buoy. Air temps 0C to 1.4C.
Maybe 4cm of snow left.

551610 quick update here

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #30 on: July 01, 2022, 11:54:24 AM »
Some background on the SIMB3

The evolution of the seasonal ice mass balance buoy
Cameron J. Planck a,⁎, James Whitlock a , Chris Polashenski a,b , Donald Perovich a
https://par.nsf.gov/servlets/purl/10112635


Design stage to SIMB1 to SIMB3

there's room for a much bigger battery in there ;)

oren

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Re: 2022 melt season buoy data and discussion
« Reply #31 on: July 01, 2022, 01:04:33 PM »
A sunnier day for 569620. Melt pond depth increasing to 30cm near the buoy. Air temps 0C to 1.4C.
Maybe 4cm of snow left.

551610 quick update here
Interesting that the snow started melting while the ice core was still quite cold.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #32 on: July 01, 2022, 03:07:58 PM »
Best efforts with 052460. dtc data is very patchy but the last 2 strips suggest slush or melt pond down to 30cm. Nothing to verify core temp at onset of snow melt. There are some profiles of older buoys in previous threads.

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Re: 2022 melt season buoy data and discussion
« Reply #33 on: July 01, 2022, 11:20:19 PM »
Following on from here we take a look at freezing point departure for itp122. We calculate the freezing point using the formula below then subtract it from the measured temperature.

Quote
in this equation tf is the freezing point in °C, S the salinity in PSS-78 and p the pressure in decibars. The equation is valid in the practical salinity range of 4 to 40 at atmospheric pressure. Measurements at elevated pressures showed no significant dependence of the pressure coefficient on salinity in the range of 27 to 35 (Fujino et al. 1974). The estimated error to pressure of 500 decibars is 0.003°C .

1. freezing point contour
2. fp departure contour

« Last Edit: July 01, 2022, 11:26:55 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #34 on: July 02, 2022, 01:22:46 PM »
Argo float 3902111 surfaced after hiding under ice for 3 months.
https://fleetmonitoring.euro-argo.eu/float/3902111

Quote
Last station date
30/06/2022 08:18:30
Cycle 106
Last Surface Data
3 dbar -1.599℃ 33.584 PSU
Position: 82.124N 43.272E

Looks like ~10m layer low salinity

Location https://go.nasa.gov/3nzDu2e light contrast
Must have found some open water somewhere under all that cloud

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #35 on: July 02, 2022, 02:53:39 PM »
551610 quick update
more meltwater at ice bottom, some of it refrozen. dtc perhaps starting to fail yesterday. All the white areas were -0.125C. I changed them to NA to avoid confusion(mine)

Nearly all the remaining ice is warmer than ocean temperature now. The bottom of the melt pond may have refrozen a few cm

tech note:
no nice interpolation any more as it extends the data gaps


Cloudy for 2 days. Rough location on jun30, exact loc jul2, heavy contrast
https://go.nasa.gov/3R4eRIm
« Last Edit: July 02, 2022, 03:13:14 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #36 on: July 02, 2022, 05:04:34 PM »
569620 update
snow almost melted out but looks like it snowed again with cooler 'overnight' conditions. Despite that another 2cm tick up of bottom melt.
under cloud now  https://go.nasa.gov/3nwTH8i

note: cryoinno have the snow layer a 5cm thicker than my estimate. Initial snow depth would make this a lot easier

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Re: 2022 melt season buoy data and discussion
« Reply #37 on: July 03, 2022, 01:14:23 AM »
Re 551610, I hope this is the situation just around the buoy itself. Otherwise if this is  representative of the whole floe, that's really bad so early in the season, in a region supposed to be relatively protective of the ice

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #38 on: July 03, 2022, 10:50:43 AM »
551610 update.
Unfortunately the digital temperature chain data is failing, similar to 052460 up thread. The sounder data still looks good showing a small drop at the top and more refreeze at the bottom. It's not all bad news.

@Oren There are a few images of buoys near the middle of melt ponds. South facing ridges may develop melt ponds in a similar way, but buoys don't melt so the analogy is limited.

old buoy in a melt pond

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Re: 2022 melt season buoy data and discussion
« Reply #39 on: July 03, 2022, 11:57:54 AM »
Thanks, uniquorn. That's what I hope happened for 551610.

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Re: 2022 melt season buoy data and discussion
« Reply #40 on: July 06, 2022, 02:24:56 PM »
551610 is 12 hours late reporting, assumed missing in action. Maybe a ridging event since I've never seen that much bottom thickening before at this time of year. Sudden dtc problems and reduction in bottom distance, maybe it was bent or tilted before failure.

last position: 78.408032   -130.270664
https://go.nasa.gov/3P4Ijwa  heavy contrast

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #41 on: July 06, 2022, 02:41:52 PM »
Co-located whoi top4 tells some of the story. A warmer layer has appeared at 1m depth with temps rising to a peak of -0.4412C. Note that 551610 last thickness report was 177cm, ignoring later data would give a minimum thickness of around 160cm.
Ice maybe thinner in top4 location a few metres away. These are temps averaged from rawer data though. That might include anything between 1m-2m. Should take a look at them.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #42 on: July 06, 2022, 03:51:14 PM »
Remarkable. top4 raw data lowest dbar is 1.62, giving us a rough confirmation of ice thickness.

Temp rises rapidly from 1.97m to 1.72m on the latest profile.
« Last Edit: July 06, 2022, 03:57:11 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #43 on: July 06, 2022, 06:23:36 PM »
Hopefully 569620 dtc will last out until new buoys are deployed. A similar profile to 551610 may be developing. Sudden deepening of melt pond on a sunny day with refreeze from bottom.

3 of the new buoys belong to AWI, may be on the Polarstern?
edit: They won't have temperature strips but will have a MicroCTD
https://www.cryosphereinnovation.com/simb3/300434064564590/
« Last Edit: July 06, 2022, 06:38:08 PM by uniquorn »

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #44 on: July 06, 2022, 11:14:32 PM »
Latest from 551610
Quote
Reports of my demise have been greatly exaggerated

latest incoming has dtc data largely complete. Maybe that bottom refreeze is real near this buoy... -0.4C down to -1.4c over 20cm might do it. top4 salinity data is bad so no freezing point data.

air temp 1.81C, top of buoy ~4C
surface melt of ~30cm, melt pond ~40cm
recent bottom refreeze ~22cm

Michael Hauber

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Re: 2022 melt season buoy data and discussion
« Reply #45 on: July 07, 2022, 05:13:57 AM »
What possible explanation for bottom refreeze is there other than instrument error?  Surface temps are just above freezing so cannot cool down the ice to cause freezing.  If water below ice was cool enough to cause freezing it would already be frozen, barring unusual conditions of super cooled liquid with a absence of nucleation impurities which shouldn't be possible in open ocean water?

Or is increasing thickness being caused somehow by ridging with thin floes of ice being forced underneath the floe with the buoy?

Also third chart looks upside down with  show a gradual loss of thickness over most of the winter, then a turnaround to slow thickening just about the start of June when the melting season would typically start?
Climate change:  Prepare for the worst, hope for the best, expect the middle.

oren

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Re: 2022 melt season buoy data and discussion
« Reply #46 on: July 07, 2022, 07:46:07 AM »
I'm guessing it's possible that fresh water from the melt pond drains and freezes when it reaches the colder ocean water.
But maybe some of the results are an artifact of the buoy bobbing in its melted hole in the middle of the floe.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #47 on: July 07, 2022, 12:29:17 PM »
Low salinity water is known to refreeze when it drains to ice bottom. This buoy's data is very patchy so it's difficult to establish if that is happening in this case.

Tracer studies of pathways and rates of meltwater transport through Arctic summer sea ice
H. Eicken, H. R. Krouse, D. Kadko, D. K. Perovich
First published: 18 October 2002
https://doi.org/10.1029/2000JC000583

Quote
Abstract

[1] At the Surface Heat Budget of the Arctic Ocean (SHEBA) program's field site in the northern Chukchi Sea, snow and ice meltwater flow was found to have a strong impact on the heat and mass balance of sea ice during the summer of 1998. Pathways and rates of meltwater transport were derived from tracer studies (H218O, 7Be, and release of fluorescent dyes), complemented by in situ sea-ice permeability measurements. It was shown that the balance between meltwater supply at the surface (averaging between 3.5 and 10.5 mm d−1) and ice permeability (between <10−11 and >10−9 m2) determines the retention and pooling of meltwater, which in turn controls ice albedo. We found that the seasonal evolution of first-year and multiyear ice permeability and surface morphology determine four distinct stages of melt. At the start of the ablation season (stage 1), ponding is widespread and lateral melt flow dominates. Several tens of cubic meters of meltwater per day were found to drain hundreds to thousands of square meters of ice through flaws and permeable zones. Significant formation of underwater ice, composed between <30 and >50% of meteoric water, formed at these drainage sites. Complete removal of snow cover, increase in ice permeability, and reductions in hydraulic gradients driving fluid flow mark stage 2, concurrent with a reduction in pond coverage and albedo. During stage 3, maximum permeabilities were measured, with surface meltwater penetrating to 1 m depth in the ice and convective overturning and desalination found to dominate the lower layers of first-year and thin multiyear ice. Enhanced fluid flow into flaws and permeable zones was observed to promote ice floe breakup and disintegration, concurrent with increases in pond salinities and 7Be. Advective heat flows of several tens of watts per square meter were derived, promoting widening of ponds and increases in pond coverage. Stage 4 corresponds to freeze-up. Roughly 40% of the total surface melt was retained by the ice cover within the ice matrix as well as in surface and under-ice ponds (with a total net retention of 15%). Based on this work, areas of improvement for fully prognostic simulations of ice albedo are identified, calling for parameterizations of sea-ice permeability and the integration of ice topography and refined ablation schemes into atmosphere-ice-ocean models.
my emphasis


Ice formation in the Arctic during summer: false-bottoms
Advisor: Alain Pham Ngoc Dinh
Student: Phan Thanh Nam
https://nam.u-cergy.fr/MSThesis.pdf
and
https://hal.archives-ouvertes.fr/hal-00297325v2/document

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #48 on: July 07, 2022, 10:38:24 PM »
Quote
third chart looks upside down
The chart is for bottom distance from the sounder. Ice gets nearer to the sounder as it gets thicker.

551610 update
Most of the recent dtc values are 0. I've set them to NA which shows as white. Missing transmissions are all NA except for the date which has been set at 4hr intervals.

It's a mess but it still may tell us something.

Quote
Or is increasing thickness being caused somehow by ridging with thin floes of ice being forced underneath the floe with the buoy?
Could be.

uniquorn

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Re: 2022 melt season buoy data and discussion
« Reply #49 on: July 07, 2022, 10:59:21 PM »
569620 melt pond looks stable. 551610 took 7days to deepen. We can see how they compare.