HYCOM

[OffTheGrid]

<Vulcanism spam removed. O>

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I suppose if it melts this quickly none of it really matters...

At the end of 2020 melt season HYCOM shows no ice thicker than 2.4 meters. While I am not certain on the exact numbers ice can not thicken much beyond about 2 meters in a single season. The 2 m ice does not thicken to 4 m in a single season more like 2.5 m. Again I don't know the exact numbers. Ice thicker than that is formed by pressure ridging. When HYCOM shows 4 m ice I imagine it is either ridges or chunks of ice pushed together. When the melt season relieves that pressure I picture most of the thickness of those pressure ridges collapsing and some of the stacked rubble as well. As HYCOM is primarily a navigational aid and not a climate tool when it shows 4 m ice in an area it is most likely indicating that there is ridging up to 4 m in an area and not that the ice is 4 m thick throughout. I think this is a probable explanation for your longstanding concern that HYCOM shows thick ice melting too quickly. If I am right in this scenario some nearby open ocean and a shift in wind would tend to reduce maximum ice thickness rather quickly.

[uniquorn]

Thanks, so possibly max thickness per grid, not average thickness. That could explain the apparent rapid melt and requires more careful interpretation. It might also mean they are modelling thin ice as even thinner, though maybe thin ice has less ridging so avg would be closer to max.

Background info regarding thickening over 2m, this buoy in the Beaufort thickened ice and snow from 2.1m to 2.46m (36cm) but looking at just the bottom sounder shows an increase of only 13cm with bottom melt continuing well into January.

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Yes it is a navigation guide so it indicates thickest ice. But some Individual thicker floes have been identified by buoys and in person measurement. I speculate it is as an 95% confidence limit of a distribution. As in 95% of the thicknesses are below this level. It may be simpler than that it may just be the maximum thickness the model predicts I do not know.


I do not think it is appropriate to include the model forecast with the model reanalysis. Reliability wise the forecast has all the problems of any weather forecast added to it. My estimation is that as a predictive product it is not all that great. In my antidotal experience it tends to show ice melting out much faster than the reanalysis product shows. Last year I made some assertions about melting based on the product. It seemed like every time melting took longer than it predicted.

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Background info regarding thickening over 2m, this buoy in the Beaufort thickened ice and snow from 2.1m to 2.46m (36cm) but looking at just the bottom sounder shows an increase of only 13cm with bottom melt continuing well into January.

I have looked at data from the buoy threads from time to time but it is not something I have spent much time on. Are you saying the bottom sounder is more reliable and it only increases 13 cm? Or are you implying something else?

[oren]

Yes it is a navigation guide so it indicates thickest ice. But some Individual thicker floes have been identified by buoys and in person measurement. I speculate it is as an 95% confidence limit of a distribution. As in 95% of the thicknesses are below this level. It may be simpler than that it may just be the maximum thickness the model predicts I do not know.

What little I've read on the Hycom website does not support this speculation. It is my humble opinion that Hycom provides the average thickness, and any other claim requires some support from Hycom.
Also regarding the theory that Hycom is used by the navy, the website clearly says "Disclaimer: This 1/12° Global HYCOM+CICE system and web page are a demonstration and are not an operational product."
Finally, I have tried to look for Hycom model validation regarding sea ice thickness and failed. I've found validation of various other aspects of the model, which as far as I understand is primarily an ocean model, not a sea ice model, thus its validation focus may be elsewhere.

If anyone can find more information on the Hycom website, in the documentation or in research articles, it will be very welcome and much appreciated.

[wdmn]

Yes it is a navigation guide so it indicates thickest ice. But some Individual thicker floes have been identified by buoys and in person measurement. I speculate it is as an 95% confidence limit of a distribution. As in 95% of the thicknesses are below this level. It may be simpler than that it may just be the maximum thickness the model predicts I do not know.

What little I've read on the Hycom website does not support this speculation. It is my humble opinion that Hycom provides the average thickness, and any other claim requires some support from Hycom.
Also regarding the theory that Hycom is used by the navy, the website clearly says "Disclaimer: This 1/12° Global HYCOM+CICE system and web page are a demonstration and are not an operational product."
Finally, I have tried to look for Hycom model validation regarding sea ice thickness and failed. I've found validation of various other aspects of the model, which as far as I understand is primarily an ocean model, not a sea ice model, thus its validation focus may be elsewhere.

If anyone can find more information on the Hycom website, in the documentation or in research articles, it will be very welcome and much appreciated.

Article published in Oceanography, Volume 22, Number 2, a quarterly journal of
The Oceanography Society, 2009.

https://tos.org/oceanography/assets/docs/22-2_chassignet.pdf

[uniquorn]

Background info regarding thickening over 2m, this buoy in the Beaufort thickened ice and snow from 2.1m to 2.46m (36cm) but looking at just the bottom sounder shows an increase of only 13cm with bottom melt continuing well into January.

I have looked at data from the buoy threads from time to time but it is not something I have spent much time on. Are you saying the bottom sounder is more reliable and it only increases 13 cm? Or are you implying something else?

All the measurements should be reliable, some of the data may require more careful interpretation. In particular on 441910 the top sounder measurement may be affected by snow drifts or possibly icicles to account for the sudden large changes, so isolating bottom sounder data seemed relevant. I'm not trying to use buoys to discredit HYCOM, which is a useful model, just providing some real background data for comparison. The effort you've put in to documenting and attempting to verify the HYCOM model on this thread is very much appreciated.
To bring you up to date, the latest discussion of SIMB3 buoys is here with some more data on the buoy thread
Any interest in buoys is welcome. Buoy data is usually the kiss of death to a thread

[oren]

Thanks wdmn.
I also found this article from 2015, "High Resolution Sea-Ice Modelling and Validation of the Arctic
with Focus on South Greenland Waters, 2004–2013", that has this bit about thickness:

https://gfzpublic.gfz-potsdam.de/rest/items/item_1504406/component/file_1577914/content

RESULTS
General evaluation
The modelled sea-ice thickness and sea-surface temperatures (SST) averaged for September 2009 are shown in Figure 1. For this month, the observed and modelled sea ice extents are similar, with small deviations in the western Arctic and the Canadian Archipelago. The SST general patterns indicate that the large-scale ocean currents are captured by the model, with the warm North Atlantic Current up along the European coast, the generally cold sea surface of Baffin Bay and the cold East Greenland Current. This current is responsible for the export of sea ice southwards along the coast of Greenland and down to Cape Farewell in winter and early spring.
The sea-ice thickness distribution in the Arctic is also reasonable with thick ice located near the Canadian Archipelago and the northern coast of Greenland. There are no continuous measurements of the distribution of the thick ice, however, remote sensing results by CryoSat-2 as well as point measurements from the IceBridge-campaign support the modelled ice-thickness distribution and total volume (farreLL et al. 2009, farreLL et al. 2012, tiLLing et al. 2015).

The thickness validation appears to be qualitative and very limited.
Note I found this paper from the DMI page of the Hycom+CICE model, which I am not sure if it's the same model as shown on the navy website, or another version of it.

http://ocean.dmi.dk/models/hycom.uk.php

The 3D ocean model HYCOM and the sea-ice model CICE is developed at the University of Miami and Los Alamos National Laboratory. The models are fully coupled at each time step. Output are the surface variables sea level and ice conditions (concentration, thickness, velocity, convergense, strength, etc.) and 3-dimensional maps of current, temperature and salinity at sigma levels.

Model set-up
The DMI HYCOM-CICE set-up covers the Atlantic, north of about 20°S and the Arctic Ocean, with a horizontal resolution of about 10 km. Model forcing is ECMWF weather forecasts. A 144 hour forecast is produces twice daily, at 00 and 12 UTC.

[johnm33]

The 'blob' seems to be emerging nearer Fram, coincident with a surge of lower salinity from the Canadian side towards Nares/Fram. from 24:05->22:06

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Some days I can think and other days I struggle to remember things I know.


https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/prologue_hycomcice.html
“The data assimilation is performed once a day using the Navy Coupled Ocean Data Assimilation (NCODA) (Cummings, 2005) system with a model forecast as the first guess. NCODA assimilates available satellite altimeter observations (along track obtained via the NAVOCEANO Altimeter Data Fusion Center), satellite sea ice concentration, satellite and in situ SST as well as available in situ vertical temperature and salinity profiles from XBTs, Argo floats and moored buoys using a 3-Dimensional VARiational analysis (3DVAR) scheme.”
I know the altimeter works on the sea surface but I think they are using it on the ice as well. Hycom is primarily an ocean model but they use CICE sea ice model (see what they did there) to model the ice.
Oren: The forecasts use measured data to validate the model but a hind cast uses data to make the hind cast more accurate. Once again any data available is used to improve the hind cast.


HYCOM does give a forecast for sea ice. My personal but not methodical assessment is it shows excessive melting. I stopped paying attention to the HYCOM sea ice forecast after a month or two. The HYCOM sea ice hind cast is in my opinion what is worth looking at.

[oren]

Thanks for this.
Everything I've seen points at the altimeter used for SSH only, but the documentation is lacking, especially of the CICE integration.

[Sepp]

Any interest in buoys is welcome. Buoy data is usually the kiss of death to a thread

Well it trumps most models, predictions and other arguments... 

[Richard Rathbone]

Note I found this paper from the DMI page of the Hycom+CICE model, which I am not sure if it's the same model as shown on the navy website, or another version of it.

Its a different model.

[johnm33]

'Blob' "But there is zero evidence of it."
Further thought that I'm trying out; Instead of an increased flow through Fram, the 'incoming' is being inhibited by the 'outgoing' that is the flow from the general direction of Makarov has taken on a life of it's own gathering near surface waters from a broad swathe Chukchi-NSI, which now established keeps flowing. This drives the outflow, hard against N Greenland, which accelerates as it reaches the deep 'narrows' of Fram, the inertia of this flow causes a deficit in sea level height[which moves wave-like east across Amundsen/Nansen] during the tidally forced 'suction' period in the Nordic seas. This deficiit is replenished by a periodic acceleration of waters flowing off the Barents shelf [now the longest waterfall on Earth?]. These waters are denser than the basin waters they're falling into so cascade down the slope creating an overturning circulation across half the basin. Here again the flow passes the point of equilibrium forcing a counter current of surface waters onto the shelf bringing the ice with it.
So the waters falling off the shelf drive the overturning circulation, inhibiting the flow of incoming along the shelf slope preventing the usual vortice formation, thus allowing ice to move onto the shelf with the returning surface flow. There remains some inertia [east] in the water cascading off the shelf which continues to push towards Laptev/ESS. Once past Lomonosov the flow feeds into the general push towards Makarov.
 Nansen  has developed an opposite overturning circulation of it's own, forced by the Barents side, and now established this is beginning to gain momentum in it's flow towards Greenland causing the blob to emerge further west.
I was thinking what would falsify all this? and the lack of an oscilation in the flow on Barents would have, then serendipitously you posted the bouy animation on the main thread.
Should the flow from above Makarov continue or even gain momentum it may facilitate the Beaufort freshwater lens' departure through Nares, if it opens, or Fram.
some bonus gifs all 27:05-25:06 Looking at the sss gif [last] it's curious that the vortice/circular features indicating lower salinity/melt are preceded by, in some instances, higher salinity, warm deeper waters?
Just for reference I've deleted the SST gif and replaced it with uniquorns bouy gif

[oren]

I think this is a complex and speculative explanation for the weird blob, and a more reasonable explanation would simply be that it's a model artifact. Remember the model barely has any measurements drom the central Arctic.
What would falsify it? Not sure. What would prove it? Lots of data that is missing.

[kassy]

Persistence in time over the season would do it so it is a simple case of waiting until we have more data.

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Oren you make many unsubstantiated declarative statements about the HYCOM model without evidence to support them. I make many unsubstantiated declarative statements about the HYCOM model without evidence to support them. Many of my statements are speculative into the nature of how the model works and at times I try to convey that in my language when I talk about it. What I can say with confidence HYCOM is one of the most sophisticated ocean circulation models in the world. The HYCOM ocean circulation model has gone through extensive validation. The HYCOM ocean circulation model is updated daily by all the publicly available scientifically reliable data sets. What I can't say with that level of confidence is that it probably benefits from unlisted sources from sensors on various ships and submarines. This speculation is supported by the fact that the model is run in a navy facility. The output of the global circulation model is distributed in real time to navel vessels. The output is made publicly available after a short delay (I think 12 hours but might be 24). Plenty is available about how the global circulation model works. The website lists a long list of fundemental equations about how things mix and how they validated them. What I can't find much information about isn't the global circulation model it is the sea ice model. I keep calling this a model which is not entirely accurate. In truth much of the nowcast data is actual observation. They list a number of sources for that observational data then add that if some other data source becomes available they will use that as well as long as it is deemed reliable. The number of direct observational sources for sea ice thickness is short. Satellite sources are of questionable value at times of melting or overcast conditions. Work is being conducted to improve those sources but that is not yet complete. For now the only truly definitive observation for sea ice thickness is direct observation. This is followed by some on ice devices and satellites under certain conditions. The point I am trying to make is that many of the issues we discuss about the sea ice thickness product are specific to that product.


I do not know if that blob is real. You have no more evidence that it is not real than I do that it is real. So far looking at the ice I can see no evidence that it is there. The HYCOM nowcast product does have much more data about underwater conditions than sea ice thickness.

[oren]

I agree with most of your post, including the part describing my level of substantiation. Indeed HYCOM appears to be a great and well-validated ocean circulation model, with the part about the ice somewhat less developed. I do doubt the part about the submarines as input, as I believe the model takes inputs that are fed daily rather than sporadic. But even this belief is speculative too.
The weird blob just seems to me too weird to actually be there, but admittedly it could still be there despite this.

[Rod]

I have tried and tried to find that spot on Worldview. It is usually cloudy over that area, but if there was a real anomaly I would think it would show up in the satellite images at some point.

There is a lot of broken up ruble on the Atlantic side, but I just can’t find that spot.

I deal with models every day, and I have learned that when observational data does not support the model, it is time to give up on the model and try to figure out what went wrong.

I will be interested to follow this thread for a while longer to see what happens. Maybe the satellite data will verify the “blob” if we have some clear skies. But, I’m not seeing it now.

[johnm33]

Hycom seems to be suggesting a near reversal of the usual rotation of the ice pack. Previously, with exceptions, whenever the ice moved to and fro onto the CAA there was a general drift south circulating into Beaufort, that's only happening south of McLure, then to approx. 90W there's little N/S movement but further north the flow is towards Fram/Barents. This means very little recirculation of old ice is occuring, and suggests a change to the circulation current of near surface waters. The Idea is backed up by the salinity gif, where one would normally see an increase of salinity moving from the Atlantic down the coast of CAA now we see the reverse, in fact a recent surge for the exits Nares/Fram.
Time for a rethink?
The Beaufort gif is 4mb and doesn't add much so only temp. the others 1.6 and 1.3.

[Freegrass]

HYCOM is showing around 0.5m loss of ice thickness in the ESS and Chukchi seas. Can that be right? Did we lose that much already? Seems a lot to me in such a short time...

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The HYCOM forecast ice product is different than the nowcast ice product. When I have checked back in the past the forecast ice thickness product predicts too much melting. Personally I ignore it altogether. Try only making animations with out the forecast and it makes more sense IMO.

[johnm33]

SSS and thickness from Hycom. As the Arctic wakes up and becomes an appendage of the Atlantic I suspect we will see a slow replacement of the waters presently occupying the basins. Overcoming the inertia of these waters takes time and energy, and the diversion or extension of Atlantic currents into the Arctic has to be a factor in the slowdown of amoc. Here what I think I'm observing is the power of incoming Atl. currents forcing the reversal of the 'usual' rotation of Arc. waters. The flow from the Canadian basin gathers pace, slowly, and now begins to drive some of the forced low saline current east beyond Svalbard to be remixed and recirculated. For that to happen I would expect that water  itself to originate or be energetically attuned to below 80⁰N otherwise since there are now no impediments it would flow south as part of the east Greenland current hard against the contours according to it's density. That suggest it has come from the direction of the Pacific perhaps somewhere in the Canadian basin, and IF that is the case is another sign of the Arctic awakening.
Looking at the sss there are numerous signs of vortices at work, and this is to be expected if 'settled' water begins to move, or water moves N/S through the parallels. Being so close to the axis of rotation the only movement that does not generate +/-angular momentum is that 'parallel' to the pole. It's difficult to guess but perhaps with the opening of Nares, before the 10^th we'll see another acceleration of the near surface waters towards both it and Fram, but it depends on how compactable the ice is, what the wind does  either adding or reducing the force applied. So either we'll see an excess of ice piling up against Ellesmere and a 'logjam' preventing circulation developing or an acceleration of ice towards and out of Fram, maybe 5 weeks will give us the answer?   
both gifs run from 10:06-09:07

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Months ago Hycom indicated where the thick ice would be and where it would melt out quickly. So far this season has proceeded as predicted based on Hycom thickness. The other thickness products continue to fall short. I could do a more detailed analysis but I am tired of pointing out information gleaned from looking at the model only to have others declare I am wrong with little to no evidence. Piomas showed thin ice on 6/15 that would have melted in the Beufort by now. the degree of melting is more consistent with hycom.

[Freegrass]

Months ago Hycom indicated where the thick ice would be and where it would melt out quickly. So far this season has proceeded as predicted based on Hycom thickness. The other thickness products continue to fall short. I could do a more detailed analysis but I am tired of pointing out information gleaned from looking at the model only to have others declare I am wrong with little to no evidence. Piomas showed thin ice on 6/15 that would have melted in the Beufort by now. the degree of melting is more consistent with hycom.

I completely agree with you. HYCOM has proven itself worthy this season. I just hope they fix the problem they have with the fast ice, and then HYCOM could turn out to be our best tool in figuring out the ice.

[johnm33]

"I could do a more detailed analysis" I'm always interested in what you have to say, maybe frame it as an opinion to help reduce 'noise'.

[Freegrass]

It looks like HYCOM ice thickness is spot on... Just 1m left...

SideX 2021 #2 is showing .21 meters( 8.25 inches )  of ice melted in the last four days. One meter to go. Buoy is skirting along the edge of the Chukchi Plateau.   
https://www.cryosphereinnovation.com/simb3/859790
 SideX 2021 #3 is further south and also showing melt.
 Dartmouth 2020 #2  is ~ 76 north . It has lost .07 meters of ice in the last week. But ITP121 PAR has increased the last couple days so I expect melt to increase soon. 
 Dartmouth 2020 #1 still has a half meter of snow and is showing the least melt. It is tracking close to the ITP 120.

[Bruce Steele]

Freegrass, The SideX#2 is located over the Edge of the Chukchi plateau at the edge of the Beaufort gyre or there about. I think the people who set these buoys look for thick ice to place them . With only four SIMB3 buoys to look at we only get isolated views into the state of the ice in general but the thickest ice in the four buoys we have to look at is less than 2 meters thick. Hycom is too thick in the Beaufort if we use the buoys as a reference.
 I am happy to scroll through the four buoys as they give me new numbers every four hours. I don’t have a reference for how fast melt should proceed because I wasn’t watching the SIMB3 buoys in years past. Its detail is great after watching the ITP buoys for the last decade. It seems to me .1 meters is a fast decline for the four day period I referenced. If that rate continues we will see meltout for that buoy in less than three weeks.
 I wrote down ice thickness for the four buoys on June 30 so I could watch the July melt proceed.
     SideX #2.    1.22 meters
     SideX #3.    1.63
 Dartmouth #1  1.7 (snow is .5 of the 1.7 on this buoy)
 Dartmouth #2. 1.98 

[uniquorn]

If only ...
moved to a more appropriate thread

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Freegrass, The SideX#2 is located over the Edge of the Chukchi plateau at the edge of the Beaufort gyre or there about. I think the people who set these buoys look for thick ice to place them . With only four SIMB3 buoys to look at we only get isolated views into the state of the ice in general but the thickest ice in the four buoys we have to look at is less than 2 meters thick. Hycom is too thick in the Beaufort if we use the buoys as a reference.
 I am happy to scroll through the four buoys as they give me new numbers every four hours. I don’t have a reference for how fast melt should proceed because I wasn’t watching the SIMB3 buoys in years past. Its detail is great after watching the ITP buoys for the last decade. It seems to me .1 meters is a fast decline for the four day period I referenced. If that rate continues we will see meltout for that buoy in less than three weeks.
 I wrote down ice thickness for the four buoys on June 30 so I could watch the July melt proceed.
     SideX #2.    1.22 meters
     SideX #3.    1.63
 Dartmouth #1  1.7 (snow is .5 of the 1.7 on this buoy)
 Dartmouth #2. 1.98 

I looked at the location of Dartmouth #1 and it shows about 1.7m thickness on hycom if you look at the actual location. In general I think you should understand that the reason the hycom nowcast is not considered comparable from year to year is because they use all the publicly available data sets they can find to improve the accuracy. Since these buoys are deployed and retrieved semi regularly it makes the inputs inconsistent for data comparison purposes but more accurate overall. This is most of the reason hycom is better for showing the condition of the ice today. It does use things like these buoys to update its maps. It is stated on the website that they do this but they do not provide an updated list of sources used. Hycom may not fill in the spaces between these sounders correctly but the sounders themselves should be accurate. I am not sure how the half meter of snow was determined but if accurate Hycom does incorrectly consider that thickness to be ice. If true that could provide a possible explanation for why some of the really thick ice in Hycom can melt fast because it is really just snow. I would also note that the thickness scale in Hycom is not linear and emphasizes some thickness transitions very well and hides others. The color difference between 1.6 m and 2.4 m is very gradual while the color transition between 1.3 m and 1.5 m is very sharp. More than one person has commented about a dramatic change during the second transition while ignoring the same amount of change in the first.
Back to the original topic because it needs repeating since some seem to reject all logic concerning the hycom nowcast product. The hycom nowcast product uses all the measurement information they can find to update their product to current conditions. I have speculated about them having access to some unique real time data but their is some disagreement about that. But they certainly use buoy and sounder data when available. 

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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

It is likely already included in the Hycom thickness product so why bother?

[Rod]

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

It is likely already included in the Hycom thickness product so why bother?

My thoughts exactly! Our sea ice models are perfect . . . Why would anyone try to improve them? 

[interstitial]

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

It is likely already included in the Hycom thickness product so why bother?

My thoughts exactly! Our sea ice models are perfect . . . Why would anyone try to improve them? 

The Hycom model probably used that data to make the nowcast already.

[oren]

Since these buoys are deployed and retrieved semi regularly it makes the inputs inconsistent for data comparison purposes but more accurate overall. This is most of the reason hycom is better for showing the condition of the ice today. It does use things like these buoys to update its maps. It is stated on the website that they do this but they do not provide an updated list of sources used. Hycom may not fill in the spaces between these sounders correctly but the sounders themselves should be accurate

Back to the original topic because it needs repeating since some seem to reject all logic concerning the hycom nowcast product. The hycom nowcast product uses all the measurement information they can find to update their product to current conditions. I have speculated about them having access to some unique real time data but their is some disagreement about that. But they certainly use buoy and sounder data when available.

I strongly doubt Hycom uses point data from buoys in its daily data assimilation to update its local ice thickness, not because I hate Hycom or reject all logic regarding the product, but because nothing I've read about it seems to indicate that they do. Buoy data is sporadic and very specific to a single ice floe, and each type of buoy gives a different data set, often hard to interpret concerning ice thickness, as uniquorn can attest after making many insightful posts on the buoy 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

It is likely already included in the Hycom thickness product so why bother?

This statement is extremely optimistic about the product's capabilities, and perhaps not appreciative enough of the effort it takes to decode and understand what goes on with all the various buoys, an effort which I find very important to the ASIF.

[oren]

Just to add, even if Hycom did incorporate all buoy data into its nowcast product, at the end of the day Hycom's sea ice thickness output is a colorful map. If one wishes to chart the data, one cannot download numerical gridded files and provide a chart of a specific grid cell thickness, the way one can when using buoy data, neither is there a chart of the overall volume represented by Hycom for certain regions or the whole hemisphere. So, another reason to bother with other sources of data.

[interstitial]

No Oren you are wrong they do indicate they use buoy data. You consistently say all the time that nothing you have read about hycom indicates X. Well read some more because they do in fact use buoy data. You are currently conditioned to jump in and refute whenever I post about Hycom but you should take some time and reassess your position.


In addition I have on occasion checked and have found the data to be consistent. You do have to identify the specific location and grid color at a location to see what it should be. It is a pain to properly identify a location and color precisely but eyeballing it is where people get it wrong. Moving over some often changes thickness by a half meter or more.

[interstitial]

I agree that there is value in plotting buoy data and perhaps if more of it was done people could see that hycom does use it. However the challenge was set on they Hycom thread presumably to show that Hycom is wrong but the nowcast is corrected for direct measurements when they are available in near real time.

[oren]

No Oren you are wrong they do indicate they use buoy data. You consistently say all the time that nothing you have read about hycom indicates X. Well read some more because they do in fact use buoy data. You are currently conditioned to jump in and refute whenever I post about Hycom but you should take some time and reassess your position.

Do they use buoy data for ice thickness? I would highly appreciate any link or text supporting this.
Note I am merely trying to assess the truth about Hycom, from what I perceive as sparse documentation.

[Bruce Steele]

Interstitial, I spent my life as a fisherman and buoys are a big part about how I know what is coming at me. We didn’t used to have them and we looked at the clouds and the harbormaster flew flags for the weather forecasts.
 I watch ITP buoys and I try to imagine the ocean salinity and temperature layers in my head. I am glad Uniquorn posts graphics. Having real time snow and ice thickness buoys associated with two of the  ITP buoys helps me get a better picture of what I have been watching for the last decade as the Beaufort Buoys have documented a large buildup of heat from the Pacific Summer Water. All those buoys help me to understand surface melt dynamics and how that is separate from processes responsible for heat at depth.
 So if I think Hycom looks like it is showing more ice than I see on a few buoys it is just my opinion .
I will continue to watch the buoys and I hope they have a long life so we get as much information as possible .  I post numbers when I think they are interesting.   

[interstitial]

Again the buoys are valuable that is where the information comes from.


Oren I do not understand your lack of documentation comment. I have just spent several more hours going through even more documentation. The problem I have is after hours and hours of reading i know more about it but it is practically a full time job sorting through the layers of information. I came across a table listing buoys used as inputs for temperature and salinity but not for ice thickness but that section was not on ice thickness so that does not mean anything. It stated the typical buoy added 32000 data points per day.


Another source states
"[size=78%]The current version of the global HYCOM forecast system includes a built-in energy loan, thermodynamic ice model. In this non-rheological system, ice grows or melts as a function of SST and heat fluxes." [/size]
[/size][size=78%]But this is clearly just the first [/size][size=78%][/size]approximation[size=78%][/size][size=78%] because the hycom model is coupled with the CICE model which is rheological using information about the different forcings to generate layers of snow and ice and stresses and all of that. Most of the CICE information is general to how that model works and is not specific to the hycom cice coupled model. [/size][size=78%]
[/size]One thing is clearly evident they are using something to correct the nowcast ice thickness product because the forecast shows far more melting than the eventual nowcast. I have made several attempts to explain how they are correcting the nowcast as the forecast always seems to quickly diverge from the nowcast. Explain to me what data they are using to correct the nowcast. You have rejected every reasonable data source to do that without evidence. It has to be something. I think rejecting it because it would take some effort to interpret buoy data is ridicules. [size=78%]

[/size]My problem is you keep insisting that no data is used to make the nowcast. (technically you just reject all of my suggestions as to what is used) Can you at least understand why I reject this notion? Please explain this Oren.[size=78%]

[oren]

Indeed what I have understood so far is that ice thickness is modeled as a function of other parameters such as temperature and salinity. What they do assimilate is ice concentration, readily available over the whole NH from satellites. I read somewhere that they only correct the model's ice concentration where it diverges too much (10%?) from the satellite data, to avoid introducing noise and create contradictions, or something like that. But assimilation of ice concentration was stated clearly, though I wish I would have saved the reference. Assimilation of ice thickness data I have not seen anywhere, at least yet.
The ocean model assimilates data about temperature and salinity from buoy arrays, but that is a different thing.

Correcting ice concentration data is what makes sure the model (nowcast) is up to date with the behavior of the ice, but does not guarantee correct ice thickness which in essence cannot be verified as it requires many actual measurements averaged over a grid cell.

I have looked for documentation of CICE as it is implemented in Hycom, would appreciate any pointers.

[HapHazard]

Links to sources. Full stop.

[johnm33]

The first suggests the ice is eminently compressable/compactable.
The second, both through the spread of vortices NE and the supression of the 'usual' Atl. salinity ingress, suggests flow into the basin beneath via Chukchi and flow out to the NE.
The third suggests a pressure gradient forcing ice into the channels of the CAA, and preventing, for now, the flow of thicker ice into the gyre.
Time will tell but if nothing circulates into Beaufort it has to melt out, this year or next. I think this is another indication of increased flow out through Fram, at depth, acting as a 'flywheel' to maintain flow and accelerate the overall atlantification of the Arctic with every new forcing.

[interstitial]

concentration is a 2 d measurement and thickness is a different dimension. That sounds like a very bad way to generate thickness numbers. Essentially that would be similar to how piomas generates their numbers from the model only. Piomas started from initial conditions generated a long time ago. I am pretty sure they correct for extent.
Hycom uses the past three days to generate a hindcast and starts the model from there every day model out up to I think ten days. One of the initial conditions is current ice thickness. Hycom used to have a phrase on their website something like we also use every other piece of data we can find to correct initial conditions. They moved or changed that because I can no longer find that. They absolutely have to start with an initial thickness numbers before they can adjust for thermodynamics or rheology or concentration or whatever else you are imagining. The three day hindcast just can't start at 0 thickness. There are not that many floats out there if you started from scratch every day it would take significant time to look over all of them and individually determine thickness and enter the data separately that would take a lot of work. Doing it that way would be insane because you could easily automate the task to where you just had to briefly look at the data and approve alter or reject the data once it was set up. They do specifically talk about using limited data sets when they are available to improve the hindcasts and it is up to the operator to determine what is considered reliable or usable. That is why they discourage long term comparisons.


Since you asked I suggest looking on github for the cice model and how it works. They do not go into specifics about the hycom gofs cice specifically but reading it makes it clear that among other things they start with an initial thickness. The way you talk about it sound like the starting thickness is calculated internally from other inputs. The descriptions of the model make it clear that the ice thickness of any grid just starts from whatever initial conditions are fed into it. Beyond that reading the reference materials occasionally provides insights. Part of the problem is most of the documentation was made when the ocean model was regional and the ice part of the model interacted differently. I think they pulled the original ice documentation because it was no longer relevant and just never got around to replacing it. How many people even look for or care about it? Probably not very many.

[WildFit]

......technically you just reject all of my suggestions as to what is used

It's mostly not about Hycom vs. PIOMAS but about the person(s) who represent (speak out for) them.

I'm not saying it's intentional, I'd bet it's not, it's kind of a widely spread pattern to tend to defend and/or favor things represented by a nice, knowledgable and respected individual over things that are represented by less renown people or know as institutions only.

Would take a lot of text to explain hence this is meant to trigger some thoughts where objectivity is a declared goal and perhaps re-consider a few views.

[interstitial]

I reread this thread and am reminded of something Neven said. I am paraphrasing what he said but the gist is that trying to convince someone just makes them more entrenched in their position. Earlier posts by Oren and myself showed more willingness to consider the others position.
I was also reminded of some information that I read early on that was removed. I think I am done trying to convince others.

[oren]

I am really not sure what is going on. Am honestly trying to learn about Hycom, and am honestly wishing it to be the best model ever. We sorely need good volume models. However just taking it on faith is too much for me. It was claimed thickness was assimilated from submarines, but no documentation of this is found. The same was claimed about thickness from buoys, also no documentation of this is found. All I manage to find is sea ice concentration is assimilated from satellites, and thickness is calculated from thermodynamic and rheological considerations, very similar to PIOMAS though different model of course. Somehow you have decided I will not listen and am entrenched, however I would be thrilled to find more and better information about the model. Give me links, give me papers, I will read them willingly.

[Tor Bejnar]

I appreciate Oren's request for documentation.  Once in a while a whole bunch of us on this forum [not just this thread] head down a dead end, only to get turned around by someone who sought 'published evidence,' not just 'internet search returns' which is what started us off on the wrong foot.  Oftentimes, for sure, the 'internet' provides good information, even if hard to verify, etc.

[I remember reading a 'scientific' magazine article that said the printed image created from satellite bands was "exactly like what an astronaut would see from space"; the image showed part of the US Eastern Seaboard and looked like a giant aerial photograph, except that it had the inter-state boundaries in white.  I've seen white survey markings on the ground - giant "X"s and the like made by laying down sheets of white plastic held down with rocks or pegs (for 'truthing' aerial photographs or satellite images) - and was wondering why they had done this for all the state boundaries, and how did they keep the white plastic in the middle of rivers in place.  (OK, I didn't wonder that, but wondered who proofread the article.)]

[J Cartmill]

Oren here are some links.

There is a HYCOM forum that seems pretty active. Alan Wallcraft would probably have the best handle on the nuts and bolts.
https://groups.google.com/a/hycom.org/g/forum

https://apps.dtic.mil/sti/pdfs/AD1034517.pdf Probably the best one

https://www.hycom.org/attachments/225_Dimitri_lom.pdf

https://www.onr.navy.mil/reports/FY13/agposey.pdf

https://www.frontiersin.org/articles/10.3389/fmars.2019.00429/full

https://agupubs.onlinelibrary.wiley.com/doi/10.1002/2015JC011283