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Messages - uniquorn

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1
Developers Corner / Re: Test space
« on: Today at 11:23:52 PM »
Thanks Jim, up to now very few have tested my instructions. I missed a bit.

Quote
ImageJ recognizes Ascat gif as a false color RGB. Image —>  Type —>  8-bit to set it an authentic grayscale.
Then maybe 8 bit —>16 bit if doing multiple adjustments, to reduce round-off effects that posterize 8-bit.

My workaround has been this..
3a. From the Image menu select Type->RGB Color
Labels will work too

2
Ice melting in the WSC north east of Svalbard. Drift is, perhaps, a bit faster than melt at the moment.
rammb, mar7-8  https://col.st/cpTW8

3
Developers Corner / Re: Test space
« on: Today at 11:27:53 AM »
A-Team does a better job but here is my method:

1. Download, install and open Fiji (ImageJ with plug-ins)
2. Drag the ascat files into the Fiji console. (start with a small selection, say, 5 days)
3. From the Image menu select Stacks->Images to Stack
4. Click the rectangle or ellipse button, select area of interest then from the Image menu select Crop.
5. From the Image menu select Adjust->Brightness/Contrast. Scroll through the images to view their histograms.
6. In the B&C console I increase the minimum to 41, in winter this doesn't lose too much information. Apply to all slices.
7. From the Image menu select Stack->Label, click the Preview checkbox and play with the numbers.
8. From the Image menu select Stacks->Make Montage. Set Scale Factor to 1 and click OK
9. From the Process menu select Enhance Local Contrast (CLAHE). I use 127,256,5.3 (For me this is usually just below 'too blocky' but A-Team prefers lower. Play with the numbers.
10. From the Image menu select Stacks->Tools->Montage to Stack and click OK.
11. From the Image menu select Stacks->Animation->Animation Options and choose a speed.
12. From the File menu select Save As->Gif

ImageJ has very few 'undo' options and it's easy to lose a lot of changes. Image->Duplicate is your friend. :)

4
Brief lift off deep into the Mclure Strait and the Amundsen Gulf. 40km/hr easterlies during mar6-7

https://go.nasa.gov/3c914wF mar3-7

added a 250m close up on Mclure

5
Developers Corner / Re: Test space
« on: March 07, 2021, 04:35:10 PM »
cs2smos-piomas-ascat-jan-feb
best viewed full screen

6
Arctic sea ice / Re: PIOMAS vs CryoSat
« on: March 07, 2021, 02:41:52 PM »
Hopefully this is the right thread for this comparison of PIOMAS and CS2SMOS, jan-feb.
cs2smos_o_v203_01_l4 so some days are missing. Colours have been re-indexed to prevent dithering

7
Greenland and Arctic Circle / Re: The Nares Strait thread
« on: March 07, 2021, 01:14:57 PM »
Movement at the Lincoln Sea entrance to the strait. 
rammb JPSS band I5 Mar5-7

8
Arctic sea ice / Re: MOSAiC news
« on: March 06, 2021, 06:36:28 PM »
Update on the remaining Mosaic Pbuoys in the Arctic Ocean, jan1-mar6.
The animation struggling a little with the P115 data.
Static image for low volume users.

9
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 06, 2021, 01:03:00 PM »
update on ice north of Greenland, https://go.nasa.gov/3qvcLTH mar3 and 6.

amsr2-uhh, baffin, feb26-mar5. Some rapid changes in wind direction recently.

10
Arctic sea ice / Re: Home brew AMSR2 extent & area calculation
« on: March 05, 2021, 07:28:30 PM »
UH AMSR2 extent in the Okhotsk sea. Very similar to 2014 and 2017 so far, though from a higher high.

11
Arctic sea ice / Re: What the Buoys are telling
« on: March 05, 2021, 12:13:18 PM »
SIMB3 443910 is paired with whoi itp120 in the beaufort.
Ice+snow appear to have thickened during the freezing season by 72cm from 1.12m to 1.786m
Location: 2021   63.75089  -148.2591  74.9978

SIMB3 441910 is paired with whoi itp121 in the beaufort.
Ice+snow appear to have thickened by 67cm from 2.1m to 2.771m
Location: 2021   63.75089  -150.4194  73.3404

Both buoy locations are just visible on yesterday's iwsviewer image here
This doesn't work for me using firefox but does with chrome

Buoy location is roughly centre of image

added images enhanced from polarview jp2. Tempting to think the bright dot is the buoy.

12
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 04, 2021, 10:54:46 PM »
Had to get yermak first. Here is the area we were looking at. There aren't so many cloud free frames.
https://col.st/H6bhU  , mar3-4

13
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 04, 2021, 09:46:02 PM »
In case there's any doubt about cracks here's rammb, band I5, Fram funnel and Yermak, mar2-4
best viewed at half speed
https://col.st/mWRhW

14
Arctic sea ice / Re: Gulf Stream stall
« on: March 04, 2021, 08:30:54 PM »
Quote
In the Atlantic Ocean, Subtle Shifts Hint at Dramatic Dangers
The warming atmosphere is causing an arm of the powerful Gulf Stream to weaken, some scientists fear.

By MOISES VELASQUEZ-MANOFF
and JEREMY WHITE

https://www.nytimes.com/interactive/2021/03/02/climate/atlantic-ocean-climate-change.html

COLD BLOB alert ;)

Interesting article with a lot of moving images.

Concluding comments:
Quote
Dr. Broecker’s old schematics of the AMOC posit a neat warm current flowing north along the western edge of the Atlantic and an equally neat cold current flowing back south below it. In fact, says Dr. Lozier, that deeper current is not confined to the western edge of the Atlantic, but rather flows southward via a number of “rivers” that are filled with eddies. The network of deep ocean currents is much more complicated than once envisioned, in other words, and figuring out how buoyant meltwater from Greenland might affect the formation of cold deepwater has become more complicated as well.

This is the place scientists currently find themselves in. They suspect the AMOC can work like a climate switch. They’re watching it closely. Some argue that it’s already changing, others that it’s too soon to tell.

“There’s no consensus on whether it has slowed to date, or if it’s currently slowing,” said Dr. Lozier. “But there is a consensus that if we continue to warm the atmosphere, it will slow.”

15
Arctic sea ice / Re: MOSAiC news
« on: March 04, 2021, 06:01:20 PM »
An interesting question posed by Niall Dollard here required investigation of yesterday's polarview north of Greenland. On the same image is the mosaic floe2 identified using the mosaic 2020T85 location.

Quote
2021-03-03T12:30:15,86.144000,-28.754640
This can be located using the iwsviewer here (for a while)
This viewer doesn't work for me using Firefox but works fine using Chrome

Here is a close up from the jp2 image.

Floe2 could be the lighter blob, centre of the 3rd image.

16
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 04, 2021, 11:50:06 AM »
Quote
Ice north of Greenland perhaps missing the larger MYI component this year.
a closer view with a bit less cloud
Uniquorn, I wonder why the cracks are not visible on this DMI sentinel image taken the same day ?

Good idea, we could learn a lot from more comparisons of radar and brightness temperature images
Quote
Sentinel-1 is the first of the Copernicus Programme satellite constellation conducted by the European Space Agency.[4] This mission is composed of a constellation of two satellites, Sentinel-1A and Sentinel-1B, which share the same orbital plane. They carry a C-band synthetic-aperture radar instrument which provides a collection of data in all-weather, day or night. This instrument has a spatial resolution of down to 5 m and a swath of up to 400 km. The constellation is on a sun synchronous, near-polar (98.18°) orbit. The orbit has a 12-day repeat cycle and completes 175 orbits per cycle.

Quote
Brightness Temperature (Band I5, Night)
Temporal coverage: 17 September 2017 - Present

The VIIRS Brightness Temperature, Band I5 Night layer is the brightness temperature, measured in Kelvin (K), calculated from the top-of-the-atmosphere radiances. It does not provide an accurate temperature of either clouds nor the land surface, but it does show relative temperature differences which can be used to distinguish features both in clouds and over clear land. It can be used to distinguish land, sea ice, and open water over the polar regions during winter (in cloudless areas).

The VIIRS Brightness Temperature layer is calculated from VIIRS Calibrated Radiances (VNP02) and is available from the joint NASA/NOAA Suomi National Polar orbiting Partnership (Suomi NPP) satellite. The sensor resolution is 375m, the imagery resolution is 250m, and the temporal resolution is daily.

My layman interpretation is that Sentinel-1 is showing ice surface features picked up by reflected radar while VIIRS Brightness Temperature(Band 15) is showing temperature difference, in this case mostly that escaping from the ocean beneath the ice, for example, old leads in various thicknesses of refreeze.

A basic overlay is a useful start for further interpretation despite the huge difference in resolution. Large older floes are clearly identified amongst the younger refreeze by brightness temperature with radar showing their intricate surface features.
Brightness temperature scale ~200%, Sentinel-1 scale ~20%. Both images have been contrast adjusted to clarify the overlay. Different palettes might reveal more.

click for overlays

Thinking about it, it's possible that leads may be exaggerated somewhat by brightness temp detection from space. It is very good for showing ice dynamics during winter though. In summer the temperature diff is much less.

17
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 03, 2021, 11:40:47 PM »
Laptev, brightness temp and aqua modis, medium contrast. https://go.nasa.gov/3uUDP1I

18
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 03, 2021, 10:22:40 AM »
https://go.nasa.gov/2OfVdNV, mar2-3. Ice north of Greenland perhaps missing the larger MYI component this year.

a closer view with a bit less cloud

19
Arctic sea ice / Re: MOSAiC news
« on: March 02, 2021, 06:38:05 PM »
A rough comparison of mosaic T78 which was 1.52m at deployment in the CAB and simb3 442920 which was 2.1m at deployment in the Beaufort. Both are shown up thread. The simb3 profile has been shifted left to align the two ice surfaces.
edit:no temperatures are shown. This is just for comparing rate of change.
sep20-feb18

Thicker ice is said to insulate more and thicken more slowly but that doesn't really explain the slower cool down from surface. Perhaps it is older ice. But it also cools down faster later in the season. That could be due to colder air temperatures or perhaps that warm layer at 30m makes a difference. simb3 442920 is co-located with whoi itp121 providing us with the ocean temperatures directly below.(white is warmer than 1.8C) There aren't enough fully functional buoys to test that idea this year.

There is a mosaic CTD Obuoy, 2020O10 deployed near to T78 measuring temperatures from 10m to 100m depth. 100m is the warmest at around -1.3C.

20
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 02, 2021, 10:24:29 AM »
https://go.nasa.gov/3e0Pfek, atlantic side, heavy contrast
updated below

21
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: March 01, 2021, 11:25:05 AM »
Worldview aqua modis of Chukchi today, slight contrast adjustment
https://go.nasa.gov/2O8uJO7

Perhaps all caused by pressure difference across the bering strait, maybe a component from underlying ocean current.

Nearest buoy is air launched buoy AXIB 300234065495020 attempting a complete circuit of 'the gyre'. Temps very cold recently. No salinity data. Jan2018-feb2021, a sturdy buoy.

22
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 28, 2021, 10:44:19 PM »
Barents had a large drop.
That is so weird. Looking at your Gif, it seems like the ice expanded a lot along the Novaya Zemlya coast. Where did the loss come from?
it's a forecast to mar7

23
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 28, 2021, 07:25:14 PM »
Large increase in the Okhotsk sea over the last 2 days (wipneus data)

Barents had a large drop.
NERSC forecast, atlantic side, to mar7

24
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: February 28, 2021, 02:22:13 PM »
https://go.nasa.gov/2NDCZWH  brightness temp from suomi/npp and noaa20, feb28

25
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 28, 2021, 11:06:44 AM »
Wipneus UH_AMSR2_3.125km_Area_Extent-v0.0.txt is updated to feb25 at the moment

Okhotsk extent to feb25.
From the animation above I'd say it has increased more over the last couple of days.

Ice over the Yermak plateau (north of Svalbard) has taken a bit of a beating. Too cloudy to see much over the questionably thicker/thinner area closer to the pole.   https://go.nasa.gov/3e6uRJ9
Yermak is the striated circular area upper right on the second image.

26
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 28, 2021, 11:00:30 AM »
Some peripheral seas, amsr2-uhh, feb19-27.
okhotsk, bering, atlantic side and baffin(labrador).  All scaled to 50%
bering is smaller so runs automatically, the others need a click

27
The forum / Re: Forum Decorum
« on: February 27, 2021, 07:08:00 PM »
<>In reality I probably should have been more hands on<>
It's predictably unreal ;)

28
Arctic sea ice / Re: What the Buoys are telling
« on: February 27, 2021, 06:31:19 PM »
argo 3902108 approaching the NW corner of Svalbard, 3.3C at 3m depth on feb24

argo 6903547 a little further west in the Fram, 3.36C at 2.8m depth on feb26

29
Arctic sea ice / Re: What the Buoys are telling
« on: February 27, 2021, 02:47:14 PM »
An ARGO float in the WSC north of Svalbard, which last reported in October, has woken up again!
Float ID 7900550.
Just a scratch of a halocline, and a 2-300m layer of Atlantic water still at ~2.5C.
Really pretty similar to some of the profiles from October, sans the halocline. Or rather, with the halocline being absorbed into the Atlantic layer.

and again on 20th, must have been under ice for a while previously. Temp at 5m depth = -0.077C, atlantic water(mixed layer?) down to ~200m

30
Arctic sea ice / Re: MOSAiC news
« on: February 26, 2021, 10:12:41 PM »
Lastly, a comparison with the SIMB3 441910 deployed in the Beaufort in 2.1m ice. Here the ice surface at deployment is roughly at dtc50 so the ice bottom is at roughly dtc155. The gradient change is just about reaching dtc155 today.
digital temperature chain

31
Arctic sea ice / Re: MOSAiC news
« on: February 26, 2021, 06:28:36 PM »
The same treatment of T58 from the beginning of the mosaic expedition on oct9 2019. Ice is 1.57m thick at deployment, snow is 18cm. Highly likely that the 9 thermistor wide peak is snow and the ice surface is roughly at thermistor33, making ice bottom at thermistor111. We see some agreement between Heat and ice temps at ~thermistor74 around nov11 2019 but the ice temperature gradient change doesn't reach thermistor111 until mar13 2020.
'Phase change' during june/july2020 reaches down to ~thermistor83 before failure. Not sure how to interpret thermistors beyond 125 during that period.

32
Arctic sea ice / Re: MOSAiC news
« on: February 25, 2021, 11:08:00 AM »
Following on from T85 analysis here on dec4.
Quote
Here we have 4m thick ice (or thicker) where thermistors 1 to 10 are clearly above surface so all or nearly all of the remaining sensors are in ice.
It's possible that thermistors 210-240 are in the ocean but look at the temps. Flat line from thermistor 140 onwards. The thick ice is still cooling.

That cooling is still ongoing. There is an interesting small gradient change from mid january onwards between thermistors 150 and 210. Previously I would have identified that as thickening, now I think that is also phase change as the winter cold finally reaches the bottom of the ice.
Unfortunately T85 Heat is not working or turned off.

It's weird that all these buoys are in place but in essence there is no good reliable way to find out where the ice ends and the water starts. There must be a better way than just thermistors with ambiguous results. An interesting engineering challenge, which I have no clue how to solve.
Hopefully with all the equipment installed during the mosaic expedition someone is writing a paper on this. Otherwise we wait till 2023 for more detailed data....

T85 temps 1-239
T85 temps 130-239 close up.
Latest date static charts.

33
Arctic sea ice / Re: MOSAiC news
« on: February 24, 2021, 09:36:22 PM »
<>How does this fit with the Heat120 data? Not well at all. However, has the ice really thickened to 2.74cm? Looking at CS2SMOS from your post, it seems very plausible.<>

Based on the SIMB measured data showing thickening of only ~65cm and the T84 and T81 data above then 1.2m thickening for T78 is very likely an over optimistic interpretation but the data suggests that we should looking a little deeper than the temperature gradient change to flat line.
So what does a closer look tell us?

T78 Temperature almost flatlines at Thermistor122-126 over the last 4 days.
126-110=16 times 2cm is 32cm thickening

T78 Heat120 looks like it changes to water at Thermistor 139
139-110=29 times 2cm is 48cm thickening 

So the amended ice thickness estimate at T78 is 1.84-2.00m thick

None of these temperature/heat comparisons appear to agree with the 2 papers below.

Interfaces and Ocean Heat Flux derived from SIMBA_2015a and SIMBA_2015f data during N-ICE campaign in winter 2015.
https://www.seanoe.org/data/00485/59709/
Quote
The ice/ocean interface is estimated from temperature profiles alone since the winter sea-ice remains colder than the ocean. The ocean just below the ice is at or just above the freezing temperature (estimated from a near surface conductivity-temperature-depth (CTD) sensor see Koenig et al. [2016]). The method detects (1) the first sensor, downward of the snow/ice interface, with a temperature above the ocean freezing temperature and (2) the last sensor in the ice with a temperature below the mean ocean temperature by at least twice the ocean temperature standard deviation in that profile. The ice/ocean interface is then defined as half way between the last sensor in the ice and the first sensor in the ocean.
edit: added buoy data for this paper N-ICE2015 SIMBA quality controlled and derived data

Discrimination Algorithm and Procedure of Snow Depth and Sea Ice Thickness Determination Using Measurements of the Vertical Ice Temperature Profile by the Ice-Tethered Buoys
https://www.mdpi.com/1424-8220/18/12/4162
Quote
3.1.2. Interface between Ice and Ocean To identify the lower ice interface (ice-ocean interface), temperature profiles for the lower ice layer were obtained from some thermistors near the bottom of the sea ice. The seawater temperature was determined using the lower five thermistors, which generally had a negligible temperature gradient from the bottom of the sea ice.   The points where the temperature profile of the lower ice layer intersected the ocean temperature were regarded as the ice-ocean interface (Figure 3b). The ice-ocean interface determined by the method of seeking described above had a good accuracy in winter or sea ice growth period. This method became unreliable in summer, especially in ice melting period when the temperature gradient across the lower interface weakened. In summer, the temperature profile of sea ice became non linear with a C-shaped curve. Then the lower ice interface was determined from the obvious inflection point in the vertical C-shaped ice temperature profile (Figure 3d).  In winter,temperature profile of sea ice remained linear and temperature of the basal ice layer was colder than the upper ocean.  There will be a sharp inflection point occurring at the interface.  Thus, ice-ocean interface can be estimated from the vertical gradients of sea ice temperature profile.

34
Arctic sea ice / Re: The caa-greenland mega crack
« on: February 23, 2021, 10:55:32 PM »
A small lift off, not cutting so deep into the PGAS and Peary Channel. Brightness temperature showing the thinner ice from the Jan6 lift off. To the right, the Fram funnel wind shear line just visible by the cloud front on feb23



https://go.nasa.gov/3pNHOcS, feb20-23

35
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 23, 2021, 02:03:47 PM »
NERSC CMEMS ice concentration forecast, atlantic side, feb22-mar2

36
Arctic sea ice / Re: MOSAiC news
« on: February 23, 2021, 12:35:00 PM »
Mosaic 2020T81, deployed near T78 and T84 but this time in a 26cm melt pond above 1.14m thick ice. Thermistor data hasn't been updated since feb10 but TS data is still coming in. Maybe the processing is slower.

The melt pond appears to have slowed the phase change beneath it as it is still not complete by feb10.
2020R21 maybe waiting for daylight

37
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 23, 2021, 10:27:46 AM »
SIMB3 443910 is paired with whoi itp120 in the beaufort.
Ice+snow appear to have thickened during the freezing season by 64cm to 1.716m

SIMB3 344910 is paired with whoi itp121 in the beaufort.
Ice+snow appear to have thickened by 65cm to 2.753m



More details on the buoy thread


<>Meanwhile JAXA extent is flatlining<>
Just a touch of refreeze in Okhotsk so far. amsr2-uhh, feb1-22

edit: added Wipneus UH_AMSR2_3.125km extent, Okhotsk

38
Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: February 23, 2021, 01:10:47 AM »
arc feb22 for ref

39
Arctic sea ice / Re: What the Buoys are telling
« on: February 22, 2021, 10:27:00 PM »
SIMB3 344910 is paired with whoi itp121 in the beaufort.

Ice+snow appear to have thickened by 65cm to 2.753m

40
Arctic sea ice / Re: What the Buoys are telling
« on: February 22, 2021, 10:09:39 PM »
SIMB3 443910 is paired with whoi itp120 in the beaufort.
Quote
Instrument experienced a dynamic event on 09/29/2020 which caused a downward shift in the rangefinder values and failure of the temperature string.

Ice+snow appear to have thickened by 64cm to 1.716m

41
Arctic sea ice / Re: MOSAiC news
« on: February 22, 2021, 05:40:27 PM »
Drift path for T84 for february. The TS file now contains surface(ice) temp, barometric pressure, tilt and compass heading. (no cairo to keep file size down)

T84 thermistor1 was 54cm above ice at deployment

42
Arctic sea ice / Re: MOSAiC news
« on: February 22, 2021, 01:38:52 PM »
T84 also has additional deployment data but unfortunately a photo is not available. Thermistor 26 at surface, ice thickness 1.14m, Snow depth 0.03 m, so bottom of the ice at thermistor84. Similar analysis below with a closer look at temperatures near to -1.8C.

It's possible that drilling the deployment hole affects the results, allowing faster local melt that refreezes over time.

Similar story for T84 so I'm starting to be convinced by the rotten ice idea. A cautious estimate of ice bottom thermistor 90 gives us 90-84 times 2cm, only 12cm thickening, optimistic would be the barest trace of ice bottom of 115(red dot).

43
Larger version of t78 temp and heat120 overlay, no dots. Analysis here

44
Arctic sea ice / Re: MOSAiC news
« on: February 21, 2021, 10:58:36 PM »
Well we have another chance to develop our thickness estimate algorithm soon. Core ice temperature is dropping to levels where we thought we had some reasonable estimates last year. I have doubts though.
Looking at T78 data the deployment report (1) states the ice was 1.52m thick with 2cm of fresh snow on aug23. Thermistor buoy sensors are 2cm apart so we can't really detect snow at that point but we are also given the sensor id of the air/snow interface as 33. Great. So the bottom of the ice on that day was at sensor 110.
The temperature profile then was almost flat by winter standards but a more detailed look shows the ice thickness quite well. (2)
Thermistors 33 and 110 have been marked roughly at the beginning of the animation(3) and again on nov22 when the temperature profile shows them clearly (with a short pause both times). There is not much additional thickening since then.
So my doubt is this. Did the ice melt quickly during end of august/september or has it been 1.5m thick and possibly porous all the time but took 3 months to cool down again?

added T78 drift path(4)
It's nice to have the actual thermistor air-snow and ice-water numbers at deployment.
Looking at the animation, it appears like there was massive bottom melt, and then re-thickening.
This is what I would expect in general with the given temperature profile.
At first, ice top is warmer than at the bottom. This surely brings about bottom melt, as heat trickles from above and the salt water eats away from below, and I think would also depend on the rate of drag of the ice over the water.
The image from Aug 23 clearly shows ice-water interface at thermistor 110.
Next, the temp profile is flat. My understanding is that the bottom would still be melting, albeit at a much slower pace.
The image from Sep 13 seems to be the last day of top melt, as well as the ice having a cold core again (cold gradient from the middle to the bottom).
Eventually, the ice top is colder than the ice bottom, with a gradient appearing through the ice. From this point on the ice starts bottom freezing and it's easier to spot where the ice ends.
The image from Sep 21 in my opinion shows the ice-water interface at around thermistor 55.
The image from Oct 15 seems to show the ice-water interface at thermistor 70.
The end of the animation again shows the ice to exceed thermistor 110.

Admittedly these are just generalizations, since I can't put any quantitative expectations as to the rates of melting and freezing. The rates do depend on the steepness of the warm or cold gradient though. Therefore I would not expect a whole lot of bottom melting, also given the rather late date of deployment. However, eyeing the animation, it would appear as if the bottom melted all the way to thermistor 55. Some possible explanations:
* Bottom was higher than thermistor 110 to begin with, with 110 being some protruding edge. However, the animation data does support this initial placement for the ice-water interface.
* Melting did not actually reach thermistor 55, though I can't see any other explanation for the cold gradient ending where it ends on Sep 23, except that it was the ice-water edge.
* The ice was extremely mobile which enhanced bottom melt way beyond what the temp profile would suggest. This can be checked by looking at T78 drift.
* The ice has not cooled enough for the gradient to reach the ice-water interface.
* My intuition for rates of bottom melt is disconnected from reality (very probable).

All in all, a very interesting mystery, with wider implications. If indeed ice can bottom-melt so quickly at the end of the season, we are not so far away from blue ocean as the extent extrapolations seem to suggest.

Following up on Tbuoy thickness estimates. Here is an update of T78 temperature profiles, the blue line, with the Heat120 temperatures overlaid in black. A bit confusing in this format so some explanation:

Heat120 records the change in temperature after heating each thermistor for 120secs. The idea being that air, snow, ice and water will heat differing amounts, allowing us to see which is which. Some further interpretation is required.

Again thermistors 33 and 110 have been marked roughly at the beginning of the animation, marking the thickness of the ice the day after deployment date when the first heat120 cycle ran on aug24.

30 days later on sep22 the heat cycle shows a similar thickness but I think by now this is mostly rotten ice from bottom 'not quite' melt. Could perhaps be described as phase changing. This ice would probably be no match for an icebreaker or a heavy storm but just about maintains its integrity to the end of the season.

Skip to day 60 and we see a similar thickness but we can see the ice state changing from the surface downwards as the weather cools during October. Surface temperature on oct21 was about -20C.

By day 88, nov20 the ice is happy again, phase change back at depth almost complete and the heat cycle perhaps shows some signs of bottom thickening, also marked, optimistically, at thermistor160.

After that even a fertile imagination struggles to interpret small changes in temperature though I made a guess at day126, dec28 at thermistor170. Perhaps SimonF32's analysis will show more.
So 170-33 time 2cm is 2.74m, a possible increase of 1.2m.

I'd be interested in other interpretations.

Apologies for removing the 2 temperature scales. It was necessary for the overlay.

The warmer Heat cycle temps in the final frame are interesting....

Added t78 location, not far from the shear line
and amsr2 awi v103 for more detail.

45
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 21, 2021, 12:10:38 PM »
regarding the dmi80 graph .. it is tracking perfectly the (stratospheric) rise this time in 2018 that coincided  with the first great opening N. of Greenland . Deja vu ?
  Where has the worldview of the winter Arctic gone since I recommended it a couple of days ago ? Too scary for us mere mortals to see ? .. or have we lost a precious resource ?
   https://go.nasa.gov/2ONoaRl   b.c.
NOAA-20 viirs brightness temperature has come back but it's too cloudy today. https://go.nasa.gov/2OZ85Iw

46
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 21, 2021, 09:57:06 AM »
amsr2-uhh atlantic side, feb15-10. Too cloudy for brightness temp on worldview. Ice north east of Greenland is certainly mobile.

47
The forum / Re: Forum Decorum
« on: February 20, 2021, 07:24:15 PM »
If that is the same johnm33, welcome back.

48
Arctic sea ice / Re: "Smart" and "Stupid" Questions - Feel Free To Ask
« on: February 20, 2021, 07:11:43 PM »
So I ask the same question: what is the cause and what might be the effects, especially as 10 hpa temperatures have stayed down and 30 hpa temps have dropped as well?
http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/
No idea but here is a comparison of 10hPa and 30hPa Zonal temps. 1979-2021 sep-feb.
A lot of variation over the years.

49
Arctic sea ice / Re: The 2020/2021 freezing season
« on: February 20, 2021, 01:31:05 PM »

Satellite observations of thickness have severe deficiencies work is being done to improve their performance. At this point they are not very reliable at some observations.
Hycom is most interested in providing an accurate picture of current conditions and a short term forecast used for operating in the Arctic. The starting conditions are updated by any and all observations available. This includes the aforementioned satellites. As satellite thickness observations improve so will the daily starting point for Hycom model. The condition of ice at the north pole surprised researchers on the polar star but were consistent with the Hycom model.

CS2 and PIOMAS were chosen because their data is available to us for further analysis. There are many models that could be compared on this or perhaps another thread, Hycom, DMI and CMEMs among them. Regarding the current condition of pole to fram ice, mosaic floe2 is in that area with 4 thermistor buoys, an ocean CTD buoy and 5 snow buoys that no one is looking at. Local measurements that might help resolve the discussion.

Some discussion of the thermistor buoy data here

This image from below the ice perhaps highlights the difficulties encountered when measuring and modelling sea ice thickness.

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