Maximising asif skills using near real time data

[cjp]

The SIMB3 is a great product indeed. Finally, sea ice buoys that one can easily understand and provide actual snow and ice thickness. The thermistor method of the Tbuoys has been highly confusing to derive thicknesses from, despite heroic efforts by uniquorn and Simon.

Cameron - thanks for joining and posting.

Is there also a measurement of the air temperature above the snow, and of the temperature profile inside the snow layer? This would help in the comparisons to Tbuoy data and to ice thickening formulas.

I'm very glad to hear this!

This is indeed the entire essence of the SIMB3 project. We wanted to build a device that could collect reliable measurements of snow/ice thickness time-series (mass balance) that are both easy to interpret and accurate in all seasons (i.e., summer). Other buoys have done this in the past, but have been extremely expensive. Our strategy with SIMB3 was to carefully blend off-the-shelf and custom parts to keep the cost as low as possible and the performance high. By doing this, we enable our clients to deploy 2 or 3 SIMB3s for what it used to cost to deploy 1.

Of course, having a less-expensive buoy also lessens the blow when the environment decides that it's not going to let you do science anymore (re: https://www.cryosphereinnovation.com/simb3/446170). 

[oren]

A question regarding the unknown height of the buoy during freeze-in: I understand it can affect the matching between the temp measurements and the snow/ice thickness measurements. But does it also affect the absolute thickness measurements themselves?
I mean, if the sounder is higher or lower above the snow, does the measured value depend on that? Or can the sounder find the thickness regardless of unknown initial conditions?

[uniquorn]

Of course, having a less-expensive buoy also lessens the blow when the environment decides that it's not going to let you do science anymore (re: https://www.cryosphereinnovation.com/simb3/446170).

dtc showing signs of difficulty ~5 days after deployment. Sounders seem fine up until data stops on mar31.

[uniquorn]

Since the thread is about mosaic data I took a look at mosaic simb4 (382860). ~40km winds on dec3 2019. From the temps it looks like a ridging event that may not have taken out the lower sounder until later in dec. I'd appreciate other interpretations.

Mosaic still not provided initial thickness. We can find out in 2023

[cjp]

A question regarding the unknown height of the buoy during freeze-in: I understand it can affect the matching between the temp measurements and the snow/ice thickness measurements. But does it also affect the absolute thickness measurements themselves?
I mean, if the sounder is higher or lower above the snow, does the measured value depend on that? Or can the sounder find the thickness regardless of unknown initial conditions?

Great question. The short answer is yes, but whether that matters depends on what you're looking to do.

When plotting SIMB3 data, I typically use a datum set at the snow/ice interface. The position of this datum relative to the SIMB3 depends on the floatation height of the buoy on installation which is primarily determined by the density of the water. The floatation height can vary quite a bit depending on where the buoy is deployed (i.e, salt vs. fresh water).

Once frozen-in, the vertical position of the SIMB3 relative to the ice is fixed and snow accumulation/melt and bottom growth/melt are reflected by increases and decreases in the surface and bottom sounder values. Through the season, we typically interpret increases in surface sounder values as snowmelt until the value reaches the initial (deployment) sounder value + the deployment snow height. Increases beyond this we interpret at surface ice melt.

The reason I say it depends is due to your "absolute thickness measurement" question. The SIMB3 rangefinders always measure the total snow+ice thickness between them. They will do this whether the buoy is floating or fixed. However, in order to demarcate surface vs. bottom melt or surface ice melt vs. snowmelt, the buoy must be frozen in.

I have a figure from my dissertation that explains this well. I'll see if I can dig it up!

[cjp]

Since the thread is about mosaic data I took a look at mosaic simb4 (382860). ~40km winds on dec3 2019. From the temps it looks like a ridging event that may not have taken out the lower sounder until later in dec. I'd appreciate other interpretations.

Mosaic still not provided initial thickness. We can find out in 2023

This buoy... While we'll never really know, I actually think the bottom sounder issue was a manufacturer defect. If you look at the ocean temp plot, you'll see it reporting drastically unphysical values. This thermister is inside the bottom sounder (and read over the same serial channel), so it makes me think something went wrong internally. I've never seen this kind of failure before in 40+ buoys.

[cjp]

Of course, having a less-expensive buoy also lessens the blow when the environment decides that it's not going to let you do science anymore (re: https://www.cryosphereinnovation.com/simb3/446170).

dtc showing signs of difficulty ~5 days after deployment. Sounders seem fine up until data stops on mar31.

Yeah, this buoy was an unfortunate loss. It's possible the SIDEX folks will be able to revisit it, but at this point, it's unclear if it died due to an environmental event or an electrical issue. I've left the modem turned on in case it transmits again.

I put a massive amount of work into this buoy. It had three Apogee pyranometers and a completely separate battery integrated into the ballast for powering their heaters. Seeing the sun slowly increase above the horizon in the Apogee data was super cool.

[SimonF92]

Regarding snow depth im still thinking that if there ever is an issue with the typical snow depth calculation via accoustic one could use our old method where we take the standard deviation of temperature for each thermistor across a 15 day period and threshold snow vs air on that. With the rationale that snow covered thermistors do not vary as much due to the insulative properties of snow.

Now, this technique wont work in the spring, but Cameron said that the typical technique tends to resolve in the spring, so we could use the alternate suggestion as a winter-time back up

I have drawn a reference line of where i see the snowline using this method.

(not going to open python because I will lose hours of working time in the black-hole)


PS really enjoying this 'insider info', Cameron

[cjp]

Yes! You can absolutely do that in winter. I often do this and compare the two. The surface sounder really shines in spring/summer when things thaw and the lovely monotonic temperature profile goes away 

And @Simon, it's fun sharing this info with people! I absolutely love that you all are using our data.

[oren]

Once frozen-in, the vertical position of the SIMB3 relative to the ice is fixed and snow accumulation/melt and bottom growth/melt are reflected by increases and decreases in the surface and bottom sounder values. Through the season, we typically interpret increases in surface sounder values as snowmelt until the value reaches the initial (deployment) sounder value + the deployment snow height. Increases beyond this we interpret at surface ice melt.

The reason I say it depends is due to your "absolute thickness measurement" question. The SIMB3 rangefinders always measure the total snow+ice thickness between them. They will do this whether the buoy is floating or fixed. However, in order to demarcate surface vs. bottom melt or surface ice melt vs. snowmelt, the buoy must be frozen in.

I have a figure from my dissertation that explains this well. I'll see if I can dig it up!

Thanks for the clear answer. To sum up my understanding, the rangefinder on its own can measure the total snow+ice, but cannot measure the location of the snow/ice interface, the "zero line". This needs to be figured out using deployment conditions, and as long as there is still snow can also be broadly deduced from temperature measurements.
Once the hole melts around the buoy and it is back to bobbing, the "zero line" data is no longer available but the total thickness still is.

[cjp]

Once frozen-in, the vertical position of the SIMB3 relative to the ice is fixed and snow accumulation/melt and bottom growth/melt are reflected by increases and decreases in the surface and bottom sounder values. Through the season, we typically interpret increases in surface sounder values as snowmelt until the value reaches the initial (deployment) sounder value + the deployment snow height. Increases beyond this we interpret at surface ice melt.

The reason I say it depends is due to your "absolute thickness measurement" question. The SIMB3 rangefinders always measure the total snow+ice thickness between them. They will do this whether the buoy is floating or fixed. However, in order to demarcate surface vs. bottom melt or surface ice melt vs. snowmelt, the buoy must be frozen in.

I have a figure from my dissertation that explains this well. I'll see if I can dig it up!

Thanks for the clear answer. To sum up my understanding, the rangefinder on its own can measure the total snow+ice, but cannot measure the location of the snow/ice interface, the "zero line". This needs to be figured out using deployment conditions, and as long as there is still snow can also be broadly deduced from temperature measurements.
Once the hole melts around the buoy and it is back to bobbing, the "zero line" data is no longer available but the total thickness still is.

Yes, your understanding is correct!

[uniquorn]

Since the thread is about mosaic data I took a look at mosaic simb4 (382860). ~40km winds on dec3 2019. From the temps it looks like a ridging event that may not have taken out the lower sounder until later in dec. I'd appreciate other interpretations.

Mosaic still not provided initial thickness. We can find out in 2023

This buoy... While we'll never really know, I actually think the bottom sounder issue was a manufacturer defect. If you look at the ocean temp plot, you'll see it reporting drastically unphysical values. This thermister is inside the bottom sounder (and read over the same serial channel), so it makes me think something went wrong internally. I've never seen this kind of failure before in 40+ buoys.

Thanks for the additional information. Looking at the last few rows of data the 'water temp' agrees quite well with the lowest dtc values. I think it's been frozen into the ice. Strangely it is closest to the 160dtc values. I'm not sure how that can be explained but it doesn't appear to have failed. Bent but still working?

Those jubilee clips might be a handy weak point, allowing the sensor bracket to break away and fold upwards as far as the cables will reach. Complete guess.

[cjp]

Huh, that's actually really interesting. I guess I never looked at it that closely.

This buoy was located at the central observatory near Polarstern during MOSAiC. I'll reach out to one of my contacts to see if they have any imagery of it.

[uniquorn]

Here looking at 387850 Mosaic SIMB3#3 which has deployment data

Deployment
MOSAiC L Site #2
Ice thickness: 77-83 cm
Snow thickness: 7 cm
Freeboard: 5 cm

Forgot about the freeboard here and it's tricky to cover all temps as it survives into summer. Ice cooling clearly takes longer than warming in this case. Serious melting when they reached the Fram Strait

[uniquorn]

Thinking about the balance between insolation and albedo, I looked at one of the SIMB buoys in the Beaufort. They have an air temperature sensor and a digital temperature chain along the length of the buoy which is deployed vertically and is white.

Here are the temperatures of air, the average of the top 11 sensors on the digital chain and the difference. Could this be used as a proxy for insolation? Including cloud cover?
Added just the difference temps. Feb10 it was at 73.5N -149. The difference gets more positive as the sun gets higher.

https://www.cryosphereinnovation.com/simb3/441910

Notice how the difference temperature changes, perhaps due to the sun angle on vertical buoy. Clouds and ambient temperature will also make a difference.

added the SIMB3 SIDEx #3 data, deployed in march

[uniquorn]

forgot about that idea, updated 441910 proxy insolation chart. Should probably multiply with a sun angle coeff to convert from vertical to flat.

[uniquorn]

update for simb3 441910 and 052460 temp maps and proxy insolation temp diffs
moving back to dev as I get different results for the snow/melt level to cryoinno when matching temps. A bigger difference between day and night temps at the top of the buoys recently. 441910 bottom melt eased off though ice warming and possible melt pond deepening continues.

@kassy  please can you remove Mosaic from the thread name at your leisure

[kassy]

Edited thread name as requested.

[uniquorn]

Thanks kassy.

Moved from the HYCOM thread

If only someone was interested enough to publish these buoy thicknesses regularly. All you need is a spreadsheet, available free from libreoffice, download the csv file from https://www.cryosphereinnovation.com/simb3/859790 or any other active buoy.

Add a new column called thickness and use this calculation

4.05 - surface_distance - bottom_distance

The sounders are 4.05m apart.

Then there is rate of thinning.....

I hate routine so it's not for me

[uniquorn]

Attempting to extend Cameron's excellent SIMB3 colourmaps to the Mosaic Tbuoys with a lot of help from SimonF92. Still have to get date conversion working, playng around with colours. The two horizontal lines are deployment thickness, surface is a guess based on temps

meereisportal deployment info and standard images for 2019T58

[SimonF92]

Been waiting to see these. They look good, im going to start working on this too from a different angle. Its time to revisit drawing the ice thickness i think.

Also i have a 'unix timestamp' to 'pandas day/month/year' conversion as part of the simb tutorial im working on. It might be helpful;

https://github.com/SimonF92/Arctic/blob/master/SIMB3%20Final%20Tutorial%20(Jupyter%20Notebook).ipynb

[uniquorn]

yep. I wanted to keep the thickness estimates in but needed to start simple so remmed a lot of code out.

Code changes made below should be self explanatory. I cut and paste the Tvalues into your example csv

#playing with colours
ctcolors = ['indigo','darkmagenta','magenta','pink', 'mediumorchid','darkslategrey','forestgreen','green','lightblue', 'blue', 'goldenrod','yellow','orangered','r','darkred']
#select therms 1 to 144 (I hope) to reduce ~static ocean temps
temps = time_thickness[time_thickness.columns[6:150]].T
#set temp limits and adjust surface using best guess from temps
plt.imshow(temps, cmap=cmap, vmin=-40, vmax=3, extent=[0, len(time_thickness), -len(temps)/50, 0.65], aspect='auto', zorder=0)
#adjust plot to depth
plt.ylim([-3, 0.8])
#manually add deploy th
plt.axhline(y=-1.59,color="black",linewidth=0.5)

I was hoping to use Cameron's timestamp code so need to convert from YY/MM/DDTHH:MM:SS to timestamp but there might be a more elegant method. Just using line numbers for now.

Could do with some new buoys

[SimonF92]

Thanks for this.

I have a few peeves with the mosaic data portal;

1) why did they remove the old buoys? Just because the data isnt current doesnt mean it isnt useful

2) they changed the data format for the one remaining active buoy, this is just a kick in the teeth for anyone connecting to the api

[uniquorn]

Housekeeping. They just moved the old data to old
https://data.meereisportal.de/download/buoys/old/

and now link to the processed data. The 'inactive' processed data is still available there in the processed format.

Took a look at T58 Heat 30sec, temperature increase map limited from 0.5C to 1.5C provides  a little more detail. Kept the same surface height guess which looks too low on this image.

Those near surface events at buoy day 120
2020-12-24T10:01:54   86.27287   7.74034
and ~135
2021-01-07T10:03:35   86.08634   3.15072
2021-01-08T10:01:52   86.69532   -3.7314
2021-01-09T10:01:47   86.81123   -8.40337
need an explanation.
Could be weather related, green dot location for day120 is just visible right of centre

added day135 weather

[uniquorn]

T58 rough alignment. Heat data stops 13 days before temp data. Those titles should read to 3C.

Looking at the heat30s data the ice is in a different state at deployment on aug27 to the end of data on may4

Need to find a buoy with a longer timespan to see that change happen

[uniquorn]

Mosaic 2019T63 Heat 30sec temperature map. Aligning ice surface at zero with ~10cm snow doesn't quite match the map data very well with 1.06m ice thickness at deployment.

correction to the code changes, offset varies with the buoy

offset=0.6
plt.imshow(temps, cmap=cmap, vmin=0.5, vmax=1.5, extent=[0, len(time_thickness), -len(temps)/48+offset, offset], aspect='auto', zorder=0)

Chose this because it had similar green to T58 at deployment and melt with the same temp settings

Might be some calibration issues with this thermistor string, yep, thinking about it those lines are at 1m intervals

[SimonF92]

T58 rough alignment. Heat data stops 13 days before temp data. Those titles should read to 3C.

Looking at the heat30s data the ice is in a different state at deployment on aug27 to the end of data on may4

Need to find a buoy with a longer timespan to see that change happen

Its interesting how relatively transient warm spells can penetrate >1m of ice and manifest effects over longer periods at the ocean interface. I had not realised the heat could convect so well until i saw this

[uniquorn]

still playing with colours. Wanted to show ocean temps for Bruce Steele so just a line for ice bottom. Needed another light colour to show slight diff in ocean temps

The horizontals are prob calibration issue, the verticals are more interesting

[Bruce Steele]

Uniquorn, Thanks. I am looking at the surface fresh water from 3 down to about 35 meters. Every year we see the colors on the ITP warm from ~ - 1.8 to ~ -1.2 from 8 meters, the top of the profiler run, down to the Pacific warm water where it is even warmer.  The simb3 temp profile shows when  the melt ponds form you can see heating not only of the ice but also the surface fresh water warms. And it warms all the way to the summer warm water layer at about 35-130 meters. I don’t know how much heat .2 to .4 C of heat represents over 30 meters of water. I expected more variability right at the
ice / seawater interface ~ 3 meters. I thought storms and wind would cause more variability due to extra mixing of warmer water from below but the surface seawater temperature seems to rise steadily if slowly once the meltponds form. I thought water temperatures at 3 meters would increase with extra mixing but I just don’t see it. If the two cyclones were indicative the surface water from 8 meters to the bottom of the ice gets colder when mixed . I suspect the heat from 8-35 meters mixes back up to the bottom of the ice between storms rather than during them.
 

 

[uniquorn]

Thanks for these ideas Bruce, yep, beginning to think that 30m layer makes a real difference. Planning to compare with the Mosaic buoys that didn't have that layer.

Was also wondering about fresher pond water refreezing adding heat at the bottom. I don't think that 4 hourly is enough to show mixing though and the dtc doesn't have enough resolution at 0.125C

-1.5   -1.5   -1.625   -1.5   -1.5   -1.625   -1.625   -1.5   -1.5   -1.5   -1.5   -1.5
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.5   -1.625   -1.5   -1.5   -1.5   -1.625
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.5   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625
-1.5   -1.625   -1.75   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625
-1.5   -1.625   -1.75   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.625   -1.625
-1.5   -1.625   -1.75   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.5   -1.625
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.625   -1.5   -1.625
-1.5   -1.625   -1.75   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.75   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625
-1.5   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.5   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.625   -1.625
-1.5   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.625   -1.5   -1.5   -1.5   -1.625
-1.5   -1.625   -1.75   -1.5   -1.625   -1.625   -1.625   -1.625   -1.5   -1.625   -1.625   -1.625

I'll look at itp120 7m-30m first though. Maybe 40m because theoretically it's the salinity that prevents mixing and that layer seems pretty stable. So convection then. Some signs at 30-35m. Cold saline has to cross over somehow, supposedly in blobs that we wouldn't see with this data. Generally though it looks like heat from above, starting from when the ice warms up.
meanwhile, updated itp121 to 40m. I'll stay on this thread as there may be some repetition.
itp121 at 75.3715° N, 141.1061° W still cloud covered today.

[uniquorn]

update on itp120 8m-40m, may30-jul27
paired with 443190 water temp 3m

I'm not sure what happens on jul7, no special weather events. A warm spot.

[uniquorn]

Mosaic2020T63
heat30 0.5C to 1.5C title needs fixing

[uniquorn]

052460 with air temps overlaid. Probably too much info at once.

Looked at difference between water temp and lowest dtc

[kassy]

Can there be such a thing? 

Quite like it.

[uniquorn]

runs from jul1 to show more detail. adjusted the surface line up 2cm

[uniquorn]

052460 update

[uniquorn]

052460 thickness, top and bottom distances. Snow maybe.

[uniquorn]

052460 temps, snow on refreezing melt pond.
More difficult to say what is happening at ice bottom.
Note the shorter time scale.

[uniquorn]

Experimenting with showing snow depth at end of season. The white horizontal lines show the original snow/ice thickness at deployment.

[uniquorn]

squeezing something out of aqua, terra, suomi/npp and noaa20 at the pole
very heavy contrast

[oren]

Superb animation, thanks.

[be cause]

thanks Uniquorn , but is there a reason to make the post temporary ?

[uniquorn]

mp4's load automatically on this forum and very few visitors are interested in buoy data. Regulars that know my posting style will download within 2 days. I'm often on a slow metered connection and clogging up my own threads would be counterproductive. It's already our of date

[kassy]

I could split out the post to a separate thread which you then just never visit. It should have a warning in the title ofc.

Made it into it´s own topic:
https://forum.arctic-sea-ice.net/index.php/topic,3663.0.html

[uniquorn]

A first look at itp121, 7m-24m temps limited from -1.55C to -1.0C to highlight near surface temps. Drift path overlaps a few times.

sep22 2020 - oct5 2021

better start looking at salinity