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Re: HYCOM
« Reply #100 on: August 06, 2020, 07:52:13 PM »
The university of Hamburg appears to be a sea ice concentration product. Unlike Masie 1km and 4km area products.

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Re: HYCOM
« Reply #101 on: August 07, 2020, 03:09:44 AM »
Thanks, interstitial. I am familiar with MASIE but just didn't understand that was what you were referring to. MASIE is less used on the forum because it is not recommended for comparison between years (being based on a manual algorithm), however it is perfectly suitable for making predictions for the current melting season. Note however that MASIE is only about extent, not area, as far as I am aware.

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Re: HYCOM
« Reply #102 on: August 07, 2020, 06:09:20 AM »
It helped me understand what data was out there. Generally I assume you know about this stuff. Masie does not distinguish between area and extent. If their is ice they count it if not the don't (an approximation of their words not mine). To me that sounds like a description of area though their philosophy on the subject is rather nebulous to me.

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Re: HYCOM
« Reply #103 on: August 13, 2020, 05:50:18 PM »
To my eyes Hycom is predicting significant losses in Greenland, Beufort and Chukchi seas. As always full screen is best to see the details.

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Re: HYCOM
« Reply #104 on: August 13, 2020, 06:03:03 PM »
Once again on thickness charts the forecast will always show at least white until it has completely melted out on nowcast.
Concentration charts clear up when it goes to zero. All of the blue and some of the blue green is below the 15% concentration threshold of most products.

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Re: HYCOM
« Reply #105 on: August 13, 2020, 06:06:10 PM »
The CAA seems to be more resilient than I expected but could flush out.

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Re: HYCOM
« Reply #106 on: August 17, 2020, 03:11:02 AM »
Looking at piomas model I see ice thinning by 1 m between 4/15 and 7/15. In less central locations the ice thins 1.25 m while in more central locations the ice thins by 0.75m. That is a melt rate of 8mm to 14mm per day. I also looked at Hycom on the same dates and came up with similar numbers. 7/15 includes about 4 weeks after the solstice. We are now almost three weeks beyond that. We are getting close to the time when the CAB normally starts to refreeze. The Beaufort will probably melt to the end.
Thanks for your interesting post interstitial. A few notes:
* The CAB continues to accumulate volume until May 5th-10th, at least according to PIOMAS.
* Peak volume loss rate is between mid-June and end-July. Using Wipneus regional numbers, an area of ~4M km2 loses ~4000 km3, so about 1m over 6 weeks, roughly 2.5 cm/day. Of course this mixes up top melt, bottom melt and export/import.

According to this interesting article referenced by A-Team on the Mosaic thread:

Quote
On our transects – regular walks across the floe ... We recorded a gradual decrease in the average ice thickness: a drop of approximately one metre over the course of July.

Quote
...ablation stakes allow us to distinguish between the melting below and melting above. ... We measured an average of ~85cm of ice thinning across our stakes sites from 26 June to 30 July. Surface ablation accounted for seventy-five percent of that thinning, while bottom melting made up the remaining twenty-five percent.

Quote
The remotely operated underwater vehicle (ROV) “Beast” surveys the ice from below ... Comparing the maps produced over several dives showed that not all the ice melted at the same speed. Especially the deep keels that extended more than 8 metres into the comparably “warm” ocean were eroding quickly. In some parts of the ridged ice, keel depth decreased by up to 2 metres in just the first 14 days.

This was in the very southern CAB so fits more or less with the average PIOMAS loss calculated above for the whole CAB.

vox_mundi

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Re: HYCOM
« Reply #107 on: November 15, 2020, 03:48:32 PM »
It seems the Navy Lab has discontinued ice concentration updates of HYCOM since the middle of October-Nov 1. Any story to this? Or has the administration ordered an end to all this science stuff?
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Re: HYCOM
« Reply #108 on: November 15, 2020, 07:25:04 PM »
It seems the Navy Lab has discontinued ice concentration updates of HYCOM

 I see what you mean re the archive, but the "nowcast" still seems to be updating:
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Re: HYCOM
« Reply #109 on: November 15, 2020, 09:29:30 PM »
Do you have a link to that, because here is what I'm using (I'm looking for ice thickness, sorry) and it stops at Nov 2, 2020

https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

Kinda coincidence that it stopped on election day.
« Last Edit: November 15, 2020, 09:40:08 PM by vox_mundi »
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Re: HYCOM
« Reply #110 on: November 15, 2020, 10:26:30 PM »
Do you have a link to that, because here is what I'm using (I'm looking for ice thickness, sorry) and it stops at Nov 2, 2020

https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticictn_nowcast_anim30d.gif

Kinda coincidence that it stopped on election day.
Try https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/navo/arcticice_nowcast_anim30d.gif

which is a link from the box at the bottom of https://www7320.nrlssc.navy.mil/GLBhycomcice1-12/arctic.html

WHOOPS - but the ice thickness animation does stop at 2nd November. damn
« Last Edit: November 15, 2020, 10:34:24 PM by gerontocrat »
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Re: HYCOM
« Reply #111 on: November 15, 2020, 11:15:08 PM »
Spooky; huh?  ???
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Re: HYCOM
« Reply #112 on: November 19, 2020, 02:52:07 AM »
And now it works!
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Re: HYCOM
« Reply #113 on: November 19, 2020, 11:23:34 AM »
And now it works!
Conspiracy theory

- the US navy won't update the thickness maps until they've processed the latest thickness data from the sonar records of the subs playing cat and mouse with the Russian subs under the Arctic.
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Re: HYCOM
« Reply #114 on: March 16, 2021, 08:28:41 PM »
Thanks , Uniquorn , great visuals revealing a much changed Arctic . It looks like this year there could be serious threat to the minimum ice volume record , while area and extent records may stand . b.c. .   

   ps  I'm happy for it to stay but could you stop the autoload so that revisits to the thread are possible .. as it is I would love to follow the mosaic thread but cannot as so many vids and gifs autoplay .. and I'd much rather be seeing them than not .
« Last Edit: March 16, 2021, 08:56:05 PM by be cause »
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Re: HYCOM
« Reply #115 on: March 29, 2021, 12:35:04 PM »
Jim just posted a video that shows Russian submarines surfacing around FJL, and I took this screenshot. Would you agree that this ice looks like it's around 1.25m thick? On HYCOM the ice around FJL is said to be around 1.25m also. So that confirms it for me again that HYCOM's ice thickness model is quite good.

In the article they said that the ice was around 1.5m.
« Last Edit: March 29, 2021, 12:40:57 PM by Freegrass »
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Re: HYCOM
« Reply #116 on: March 30, 2021, 03:44:28 PM »
This is basically within the range of the thicknesses of all volume models there, I think.

I’d be interested what are the “true” values in areas, where PIOMAS and CS2SMOS predict different values, i.e. the Beaufort at 130W where HYCOM predicts 3m and more over large areas (CS2SMOS is rather around 2m there) or inside the CAA where HYCOM predicts far lower thickness than CS2SMOS.

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Re: HYCOM
« Reply #117 on: May 13, 2021, 11:59:04 AM »
HYCOM is modelling 4m ice in the chukchi which could be a good verification test. Likely that it's these large floes in the centre of the image with shear cracks around them.

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Re: HYCOM
« Reply #118 on: May 13, 2021, 02:34:46 PM »
These are probably the same as the isolated MYI patch shown in the NSIDC ice age map.

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Re: HYCOM
« Reply #119 on: May 13, 2021, 06:35:30 PM »
I'll put this ascat/hycom comparison back up for a day (10MB) ascat is quite good for tracking.
mar2020-mar2021

edit: added latest available ice age map
These are probably the same as the isolated MYI patch shown in the NSIDC ice age map.

yep, give or take a couple of hundred km
« Last Edit: May 13, 2021, 09:42:04 PM by uniquorn »

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Re: HYCOM
« Reply #120 on: May 13, 2021, 10:39:40 PM »
That comparison video is pretty awesome Uniquorn. Thanks for that! It does show that HYCOM is doing a pretty good job on the ice movement. The only question that remains is if they're right about ice thickness. The difference between HYCOM and the satellite measurements is huge. But somehow I still trust HYCOM more than the measurements, which is probably not reasonable... I guess we'll just have to run out the season to see if HYCOM had it right...

EDIT: I think you could also interpret HYCOM thick ice as being older, and thus stronger ice? What do you think? Could that be a thing?

EDIT2: Is it possible that satellite measurements get screwed up because of older ice with a different density, and thus a different reflectability?
« Last Edit: May 13, 2021, 11:44:49 PM by Freegrass »
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uniquorn

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Re: HYCOM
« Reply #121 on: May 14, 2021, 12:41:25 AM »
That comparison video is pretty awesome Uniquorn. Thanks for that! It does show that HYCOM is doing a pretty good job on the ice movement. The only question that remains is if they're right about ice thickness. The difference between HYCOM and the satellite measurements is huge. But somehow I still trust HYCOM more than the measurements, which is probably not reasonable... I guess we'll just have to run out the season to see if HYCOM had it right...

EDIT: I think you could also interpret HYCOM thick ice as being older, and thus stronger ice? What do you think? Could that be a thing?

EDIT2: Is it possible that satellite measurements get screwed up because of older ice with a different density, and thus a different reflectability?

The only question? I think not ;)
For me the models are an aid to knowing what is happening rather than being 'right' about anything.

Older ice: Specificly I have a doubt about HYCOM thickness in the area between the pole and FJL in March which familiarity with ASCAT tells me is second year ice. I don't use ASCAT for estimating thickness, just for knowing roughly where ice came from but I think we have just seen some thicker ice come through the Fram which probably came from pole/FJL area. I haven't thoroughly tracked it so no strong opinion on that.

Satellites: That data requires interpretation too, that's why it's great that Lars Kaleschke posted asking for feedback on the forum for his next AMSR2 product. So yes, many things need to be checked in the lab and on the ice with local measurements but these are often few and very far between.
Even when we have buoys actually in the ice measuring thickness the data still needs interpretation and possibly debate. Very little interest in that...

Some Chukchi and Beaufort melt should be coming up soon. More opportunity to see if any model or satellite is near to 'right' .  In my view no satellite or model knows how thick most of the ice is. That's partly why it is so interesting.

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Re: HYCOM
« Reply #122 on: May 14, 2021, 01:28:15 AM »
Just for fun, I've had a look at comparing the above Hycom modelled image (11th May?) the sea ice webcam at Utqigvik (9th May last one I can find) and latest sentinel image (12th May).

Over those 3 dates, I believe the fundamental positioning of the ice has not changed a whole lot - so maybe considered a fair comparison.

On the sentinel image I have arrowed in magenta the location and direction of the sea ice webcam. You can also make out point barrow and some of the coastline.

Hycom indicates the 4m ice stretches out to the NW of Point Barrow. Sentinel tells us there are some breaks in the ice immediately north and west of the fast ice.

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Re: HYCOM
« Reply #123 on: May 14, 2021, 04:27:26 AM »
HYCOM is modelling 4m ice in the chukchi which could be a good verification test. Likely that it's these large floes in the centre of the image with shear cracks around them.
What I can see today on Worldview is this tear shaped piece that looks rather thick. And if you look closely at the rest of the ice along the coast, it does look rather thick. So HYCOM isn't all that wrong so far IMHO..

But you are right, still so many questions...  :)

The reason I trust HYCOM more than the satellites is because HYCOM uses submarine measurements to measure the ice. I'm pretty sure that they use those measurements to check and correct their model.
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Richard Rathbone

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Re: HYCOM
« Reply #124 on: May 14, 2021, 11:48:41 AM »

The reason I trust HYCOM more than the satellites is because HYCOM uses submarine measurements to measure the ice. I'm pretty sure that they use those measurements to check and correct their model.

I'm pretty sure this is wrong, and that no thickness data is assimilated. Its possible to assimilate thickness data, e.g. the PIOMAS forecast entries for SIPN assimilate the previous winter's cryosat data but I haven't seen anything about a HYCOM/CICE model doing this. The natural data to assimilate for HYCOM/CICE models is sea surface temperature and ice concentration, but they go haywire if they don't throw in something else to stabilise their predictions and I'm not sure what this model does. All the volume models used historic data from submarines in their development, but I don't think any are assimilating it.

This thread could have done with some links in the first post, does anyone know where to find the technical details on the current state of this model?

uniquorn

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Re: HYCOM
« Reply #125 on: May 14, 2021, 12:03:39 PM »
Just for fun, I've had a look at comparing the above Hycom modelled image (11th May?) the sea ice webcam at Utqigvik (9th May last one I can find) and latest sentinel image (12th May).

Thanks Niall, good idea to use the webcam, maybe revisit in a week?

HYCOM is modelling 4m ice in the chukchi which could be a good verification test. Likely that it's these large floes in the centre of the image with shear cracks around them.
What I can see today on Worldview is this tear shaped piece that looks rather thick. And if you look closely at the rest of the ice along the coast, it does look rather thick. So HYCOM isn't all that wrong so far IMHO..

There's a big difference between 'trust' and 'isn't all that wrong'. I will remain more cautious.
For me, it's better to include all the HYCOM 4m Chukchi sea ice in the analysis and see how it develops. It's drifting pretty quickly at the moment so should be fun to watch. 


The reason I trust HYCOM more than the satellites is because HYCOM uses submarine measurements to measure the ice. I'm pretty sure that they use those measurements to check and correct their model.

I'm pretty sure this is wrong, and that no thickness data is assimilated. Its possible to assimilate thickness data, e.g. the PIOMAS forecast entries for SIPN assimilate the previous winter's cryosat data but I haven't seen anything about a HYCOM/CICE model doing this. The natural data to assimilate for HYCOM/CICE models is sea surface temperature and ice concentration, but they go haywire if they don't throw in something else to stabilise their predictions and I'm not sure what this model does. All the volume models used historic data from submarines in their development, but I don't think any are assimilating it.

This thread could have done with some links in the first post, does anyone know where to find the technical details on the current state of this model?

While looking for tech data I found this
Analyzing the impact of CryoSat-2 ice thickness initialization on seasonal Arctic Sea Ice prediction
Quote
Abstract
Twin 5-month seasonal forecast experiments are performed to predict the September 2018 mean and minimum ice extent using the fully coupled Navy Earth System Prediction Capability (ESPC). In the control run, ensemble forecasts are initialized from the operational US Navy Global Ocean Forecasting System (GOFS) 3.1 but do not assimilate ice thickness data. Another set of forecasts are initialized from the same GOFS 3.1 fields but with sea ice thickness derived from CryoSat-2 (CS2). The Navy ESPC ensemble mean September 2018 minimum sea ice extent initialized with GOFS 3.1 ice thickness was over-predicted by 0.68 M km ² (5.27 M km ² ) vs the ensemble forecasts initialized with CS2 ice thickness that had an error of 0.40 M km ² (4.99 M km ² ), a 43% reduction in error. The September mean integrated ice edge error shows a 18% improvement for the Pan-Arctic with the CS2 data vs the control forecasts. Comparison against upward looking sonar ice thickness in the Beaufort Sea reveals a lower bias and RMSE with the CS2 forecasts at all three moorings. Ice concentration at these locations is also improved, but neither set of forecasts show ice free conditions as observed at moorings A and D.

Which looks interesting, though above my paygrade

edit: Accepted that there is a big difference in resolution but HYCOM appears to be completely missing the break up around Utqigvik(Barrow) noted above by Niall Dollard. Maybe they need to 'dial up' the warm Pacific water a bit ;)
« Last Edit: May 14, 2021, 12:55:16 PM by uniquorn »

Freegrass

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Re: HYCOM
« Reply #126 on: May 14, 2021, 01:12:11 PM »
Twin 5-month seasonal forecast experiments are performed to predict the September 2018 mean and minimum ice extent using the fully coupled Navy Earth System Prediction Capability (ESPC). In the control run, ensemble forecasts are initialized from the operational US Navy Global Ocean Forecasting System (GOFS) 3.1 but do not assimilate ice thickness data. Another set of forecasts are initialized from the same GOFS 3.1 fields but with sea ice thickness derived from CryoSat-2 (CS2). The Navy ESPC ensemble mean September 2018 minimum sea ice extent initialized with GOFS 3.1 ice thickness was over-predicted by 0.68 M km ² (5.27 M km ² ) vs the ensemble forecasts initialized with CS2 ice thickness that had an error of 0.40 M km ² (4.99 M km ² ), a 43% reduction in error. The September mean integrated ice edge error shows a 18% improvement for the Pan-Arctic with the CS2 data vs the control forecasts. Comparison against upward looking sonar ice thickness in the Beaufort Sea reveals a lower bias and RMSE with the CS2 forecasts at all three moorings. Ice concentration at these locations is also improved, but neither set of forecasts show ice free conditions as observed at moorings A and D.
Do I understand it correctly that what hey say here is basically what I said? That they use submarine measurements to error check their model? I'm pretty sure the submarine measurements are insufficient to integrate them into their model, but it does give them a tool to point check their model.

Above my paygrade as well...  :-\
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uniquorn

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Re: HYCOM
« Reply #127 on: May 14, 2021, 01:59:54 PM »
Twin 5-month seasonal forecast experiments are performed to predict the September 2018 mean and minimum ice extent using the fully coupled Navy Earth System Prediction Capability (ESPC). In the control run, ensemble forecasts are initialized from the operational US Navy Global Ocean Forecasting System (GOFS) 3.1 but do not assimilate ice thickness data. Another set of forecasts are initialized from the same GOFS 3.1 fields but with sea ice thickness derived from CryoSat-2 (CS2). The Navy ESPC ensemble mean September 2018 minimum sea ice extent initialized with GOFS 3.1 ice thickness was over-predicted by 0.68 M km ² (5.27 M km ² ) vs the ensemble forecasts initialized with CS2 ice thickness that had an error of 0.40 M km ² (4.99 M km ² ), a 43% reduction in error. The September mean integrated ice edge error shows a 18% improvement for the Pan-Arctic with the CS2 data vs the control forecasts. Comparison against upward looking sonar ice thickness in the Beaufort Sea reveals a lower bias and RMSE with the CS2 forecasts at all three moorings. Ice concentration at these locations is also improved, but neither set of forecasts show ice free conditions as observed at moorings A and D.
Do I understand it correctly that what hey say here is basically what I said? That they use submarine measurements to error check their model? I'm pretty sure the submarine measurements are insufficient to integrate them into their model, but it does give them a tool to point check their model.

Above my paygrade as well...  :-\

No. Unless, when using the word submarine, you mean these fixed buoy locations :)

My understanding is that this study looks at improving GOFS forecasting by assimilating thickness data from CryoSat-2 and verifying their efforts using the buoy data. Implying that GOFS does not currently assimilate it.
You could 'robustly defend' HYCOM by providing some more information to back up your claims.

Quote
In the control run, ensemble forecasts are initialized from the operational US Navy Global Ocean Forecasting System (GOFS) 3.1 but do not assimilate ice thickness data. Another set of forecasts are initialized from the same GOFS 3.1 fields but with sea ice thickness derived from CryoSat-2 (CS2).
« Last Edit: May 14, 2021, 02:43:51 PM by uniquorn »

Freegrass

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Re: HYCOM
« Reply #128 on: May 14, 2021, 03:09:09 PM »
In the control run, ensemble forecasts are initialized from the operational US Navy Global Ocean Forecasting System (GOFS) 3.1 but do not assimilate ice thickness data.
Operational Navy should be the submarines, no?
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oren

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Re: HYCOM
« Reply #129 on: May 14, 2021, 03:31:39 PM »
"operational US Navy Global Ocean Forecasting System (GOFS) 3.1" is not submarines.

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Re: HYCOM
« Reply #131 on: May 14, 2021, 05:25:16 PM »
Thanks Gero.

Quote
The existing global prediction capability (GOFS 3.0) was declared operational in September 2013 and is based upon global HYCOM with a horizontal resolution of 1/12.5° (~9 km at the equator, ~7 km at mid-latitudes) and 32 hybrid vertical layers. GOFS 3.0 includes a relatively simple embedded thermodynamic ice model. NCODA assimilates surface observations from satellites, such as altimeter sea surface height (SSH) anomalies and sea surface temperature (SST), plus in situ SST observations from ships and buoys as well as temperature and salinity profile data from expendable bathythermographs, conductivity-temperature-depth sensors, gliders and Argo floats. The ocean model uses atmospheric forcing from the operational Navy Global Environmental Model that is run daily at Fleet Numerical Meteorology and Oceanography Center.

Shame that they only provide surface maps. 34m would be nice to compare with Mercator.

Some work in progress
Quote
3D and 4D variational systems were tested and/or transitioned to improving Navy capabilities of forecasting Ocean environments. The work on coupling the assimilation systems between the ocean, waves, atmosphere, and acoustics made progress to further improve the forecast skill of the ocean environment.
Research Objectives

To advance analysis and prediction capabilities of Navy environmental modeling and forecasting systems by improvement of assimilation software. Three assimilation systems were primarily used in this project: RELO NCOM (3D-VAR), adjointless 4D-VAR, and 4D-VAR-NCOM.
Methodology

The advancement of 4D-VAR assimilation systems was supported by the following: 6.4 4D-VAR-NCOM RTP tested robustness. 6.2 Coupled Ocean-Atmosphere Variational Assimilation and Prediction System merged four-dimensional variational (4D-VAR) capabilities of the atmospheric and oceanic components COAMPS. 6.2 Coupled Ocean-Acoustic Assimilative Model for acoustic propagation forecast, 6.2 Extending Predictability in Coastal Environments project, 6.2 Calibration of Ocean Forcing with satellite Flux Estimates project, 6.1 Propagation and Dissipation of Internal Tides on Coastal Shelves used the 4DVAR- NCOM system, 6.1 Adjointless 4D-VAR for operational Navy ocean models.
Results

Even though the 4D-VAR-NCOM system has already been transitioned to NAVO, much effort was performed this fiscal year to improve its capabilities. Advancements were also made in understanding modeling and prediction of internal tides, heat fluxes, and error covariances. Good results were obtained from adjointless modelling, showing promise for continued exploring.

This is possibly newer work in progress
https://www7320.nrlssc.navy.mil/dynamic/posters/AGU18-max.pdf

similar work to the article up thread.

I’M IN LOVE WITH A RAGER

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Re: HYCOM
« Reply #132 on: May 17, 2021, 04:38:49 PM »
Anyone have further hypotheses regarding that hole of thin ice in the Siberian quadrant of HYCOM products? It’s even showing up in the SST data now. I wonder if it will fully melt out early

uniquorn

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Re: HYCOM
« Reply #133 on: May 17, 2021, 07:59:08 PM »
Anyone have further hypotheses regarding that hole of thin ice in the Siberian quadrant of HYCOM products? It’s even showing up in the SST data now. I wonder if it will fully melt out early
Tracking it here. No sign of it on the surface up to now so possibly an anomaly in the model.

OffTheGrid

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Re: HYCOM
« Reply #134 on: May 19, 2021, 10:20:17 PM »
Anyone have further hypotheses regarding that hole of thin ice in the Siberian quadrant of HYCOM products? It’s even showing up in the SST data now. I wonder if it will fully melt out early

The hydrothermal plume activity from volcanic activity has been clearly visible for several years in low level atmospheric gases.

The large supervolcano eruption thought to have happened with in the last Million years that created the large hole  80x50km where the Gakkel- meets the continental shelf of the Laptev is not far from here. Large explosive volcanic centres are spaced right across the Gakkel- from the Intensely and continuous Western Volcanic zone near Greenland. And the plumes on the Russian end are most likely the cause of this surface weakspot in the ice.

oren

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Re: HYCOM
« Reply #135 on: May 19, 2021, 10:24:09 PM »
With 3 km of ocean above the Gakkel ridge, there is simply no way for some bottom vents to cause a weak spot in the ice in a specific location.

FishOutofWater

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Re: HYCOM
« Reply #136 on: May 19, 2021, 10:42:51 PM »
Yes, Oren, claims that ice loss were related to volcanic activity not climate change have been repeatedly debunked by experts. Anyone who wishes to can google up the debunking. Needless to say, geothermal heat taken up in the deep ocean stays in the deep ocean because of ocean stratification and the high heat capacity of water.

interstitial

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Re: HYCOM
« Reply #137 on: May 21, 2021, 01:22:51 AM »
A few years ago there was a persistent warm spot in the Fram strait the ended up being a volcanic eruption, not a thermal vent. Early speculation was a model glitch. Am I missing something or remembering wrong?

WildFit

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Re: HYCOM
« Reply #138 on: May 21, 2021, 01:34:09 AM »
A few years ago there was a persistent warm spot in the Fram strait the ended up being a volcanic eruption, not a thermal vent. Early speculation was a model glitch. Am I missing something or remembering wrong?


You're totally correct and of course any persistent and large enough source of heat will sooner or later have an effect while the exact location where it will show depends on several factors like currents etc.

oren

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Re: HYCOM
« Reply #139 on: May 25, 2021, 03:26:35 PM »
Looking at this animation posted by Freegrass in the melting season thread and focusing on the coastal Laptev, I am wondering if it is true that Hycom does not recognize or model the existence of fast ice? Because it certainly seems that way, the (currently) fast ice is moving freely with the wind/currents, while I don't expect it to move at all. This lack would be a serious downside for any Arctic sea ice model.

Freegrass

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Re: HYCOM
« Reply #140 on: May 25, 2021, 06:07:30 PM »
Looking at this animation posted by Freegrass in the melting season thread and focusing on the coastal Laptev, I am wondering if it is true that Hycom does not recognize or model the existence of fast ice? Because it certainly seems that way, the (currently) fast ice is moving freely with the wind/currents, while I don't expect it to move at all. This lack would be a serious downside for any Arctic sea ice model.
I saw that too, and was also wondering about that... It does seem to be a flaw in the model.
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uniquorn

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Re: HYCOM
« Reply #141 on: June 10, 2021, 12:49:49 PM »
re fast ice and HYCOM. Since we are looking at thickness here rather than drift it's possible that the ice is thinning that quickly in the ESS rather than drifting though it seems too rapid for that. Not sure how to account for thickening in these weather conditions unless they are modelling submerged ridging. It's definitely not moving at 73N 150E yet.
edit: In the end, after a little while watching, I think they are ignoring fast ice.

And the low thickness blob that's moved to 90E. I've given up trying to verify that. There are countless polarview images that show nothing unusual.

edit2: The way the Beaufort changes thickness suggests that they are modelling ridging, or is that just dispersion and compression changing the average thickness in a cell?
« Last Edit: June 10, 2021, 01:30:53 PM by uniquorn »

johnm33

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Re: HYCOM
« Reply #142 on: June 10, 2021, 02:41:06 PM »
'low thickness blob' I did have a thought about this, it's a bit of a stretch since I'm not 100% convinced about enhanced turnover of Atl.Arc. waters this year but if there is sufficient incoming instead of holding fast to the Barents slope and creating vertical vortices as it passes which stop ingress onto the shelf, a huge slow circulation has formed overturning clockwise +/- parallel to the slope moving slowly towards Laptev, creating a subduction zone by St.Anna , and the heat from that portion of Atl. incoming surfaces where a counter rotating induced overturning current nears the surface. If this was the case bottom melt would occur thinning the 'signature' of the ice and rapid repair of cracks may become visible.
ani. 18M-16June

Freegrass

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Re: HYCOM
« Reply #143 on: June 10, 2021, 03:04:26 PM »
re fast ice and HYCOM. Since we are looking at thickness here rather than drift it's possible that the ice is thinning that quickly in the ESS rather than drifting though it seems too rapid for that. Not sure how to account for thickening in these weather conditions unless they are modelling submerged ridging. It's definitely not moving at 73N 150E yet.
edit: In the end, after a little while watching, I think they are ignoring fast ice.

And the low thickness blob that's moved to 90E. I've given up trying to verify that. There are countless polarview images that show nothing unusual.

edit2: The way the Beaufort changes thickness suggests that they are modelling ridging, or is that just dispersion and compression changing the average thickness in a cell?
Is it possible HYCOM doesn't care much about coastal fast ice, because their ships and subs never go there? Russia wouldn't be very happy with an American submarine that close to their coastline...

The fast thinning is definitely dispersion, as can be clearly seen on the Atlantic side...
90% of the world is religious, but somehow "love thy neighbour" became "fuck thy neighbours", if they don't agree with your point of view.

WTF happened?

uniquorn

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Re: HYCOM
« Reply #144 on: June 10, 2021, 03:27:11 PM »
'low thickness blob' I did have a thought about this, it's a bit of a stretch since I'm not 100% convinced about enhanced turnover of Atl.Arc. waters this year but if there is sufficient incoming instead of holding fast to the Barents slope and creating vertical vortices as it passes which stop ingress onto the shelf, a huge slow circulation has formed overturning clockwise +/- parallel to the slope moving slowly towards Laptev, creating a subduction zone by St.Anna , and the heat from that portion of Atl. incoming surfaces where a counter rotating induced overturning current nears the surface. If this was the case bottom melt would occur thinning the 'signature' of the ice and rapid repair of cracks may become visible.
ani. 18M-16June

That kind of scenario was what interested me. But there is zero evidence of it. Many areas are weaker than the blob location. Looking further back on the yearly ani, blob started at the beginning of May, probably too far away from St Anna. I think it's a model anomaly, a big one, but I'd be happy if someone provided evidence to the contrary.

uniquorn

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Re: HYCOM
« Reply #145 on: June 10, 2021, 03:31:50 PM »
re fast ice and HYCOM. Since we are looking at thickness here rather than drift it's possible that the ice is thinning that quickly in the ESS rather than drifting though it seems too rapid for that. Not sure how to account for thickening in these weather conditions unless they are modelling submerged ridging. It's definitely not moving at 73N 150E yet.
edit: In the end, after a little while watching, I think they are ignoring fast ice.

And the low thickness blob that's moved to 90E. I've given up trying to verify that. There are countless polarview images that show nothing unusual.

edit2: The way the Beaufort changes thickness suggests that they are modelling ridging, or is that just dispersion and compression changing the average thickness in a cell?
Is it possible HYCOM doesn't care much about coastal fast ice, because their ships and subs never go there? Russia wouldn't be very happy with an American submarine that close to their coastline...

The fast thinning is definitely dispersion, as can be clearly seen on the Atlantic side...

Agree about the Atlantic side but fast thinning under fast ice can't be due to dispersion

and thickening in the Beaufort?

As for the question, that would be one for a robust defender to answer ;)  with documentation

oren

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Re: HYCOM
« Reply #146 on: June 10, 2021, 03:33:33 PM »
The weird blob certainly looks like a model anomaly. With all the winds and ice transport going on in that area, it should have been mixed already, IMHO.

interstitial

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Re: HYCOM
« Reply #147 on: June 10, 2021, 05:00:17 PM »
As for the question, that would be one for a robust defender to answer ;)  with documentation
if you are referring to me I have no clue about the blob. I don't have a reason for it. The only relevant thing I can say is what appeared to be a warm spot on Null school ended up being a volcanic eruption. After a while the consensus seemed to point to model anomaly. I do not think that is what this. I am just making the point it might be something. At this point I think it may be a model anomoly as well. I just do not know.

As far as coastal fast ice I don't know that either. It would seem to be a large oversight if true. There is much information about this model available online but not all the details. It does run on a supercomputer so the notion that a full description would be anything less than hundreds perhaps thousands of pages seems unlikely. Frankly I was interested for a while but have lost interest since then.

uniquorn

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Re: HYCOM
« Reply #148 on: June 10, 2021, 05:32:18 PM »
As for the question, that would be one for a robust defender to answer ;)  with documentation
if you are referring to me I have no clue about the blob. I don't have a reason for it. The only relevant thing I can say is what appeared to be a warm spot on Null school ended up being a volcanic eruption. After a while the consensus seemed to point to model anomaly. I do not think that is what this. I am just making the point it might be something. At this point I think it may be a model anomoly as well. I just do not know.

As far as coastal fast ice I don't know that either. It would seem to be a large oversight if true. There is much information about this model available online but not all the details. It does run on a supercomputer so the notion that a full description would be anything less than hundreds perhaps thousands of pages seems unlikely. Frankly I was interested for a while but have lost interest since then.

Sorry interstitial, not you and I misquoted
Where is the evidence that the nullschool warm spot was related to a volcano. I must have missed it.
edit: : ( Hey wait, sorry to be picky, but you're angry on the chatter thread and lost interest on the HYCOM thread that you started? Oh well...
edit2: I get it, perhaps just focus on the ice.

I'll be a furious defender of HYCOM this season. It's up to others to poke holes in it so we can all figure out WTH is going on...

« Last Edit: June 10, 2021, 10:16:52 PM by uniquorn »

uniquorn

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Re: HYCOM
« Reply #149 on: June 13, 2021, 01:52:58 PM »
Just for fun, I've had a look at comparing the above Hycom modelled image (11th May?) the sea ice webcam at Utqigvik (9th May last one I can find) and latest sentinel image (12th May).

Over those 3 dates, I believe the fundamental positioning of the ice has not changed a whole lot - so maybe considered a fair comparison.

On the sentinel image I have arrowed in magenta the location and direction of the sea ice webcam. You can also make out point barrow and some of the coastline.

Hycom indicates the 4m ice stretches out to the NW of Point Barrow. Sentinel tells us there are some breaks in the ice immediately north and west of the fast ice.

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