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Messages - Glen Koehler

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Arctic sea ice / Re: Latest PIOMAS update (January, mid-monthly update)
« on: January 20, 2021, 06:31:50 PM »
More analysis derived from the PIOMAS data from Wipneus

The January monthly average graph is attached, using actual data to 15 Jan and average volume gain from 10 to 31 Jan giving a monthly average of 15.6 thousand km3. This is 120 km3 less than the trend value - less than half a year ahead of trend. This would be 2nd lowest in the satellite record, 975km3 more than Jan 2017.

It should be noted that the Jan 2017 was 2,200 km3 or 8 years below the linear trend. One way looking at the 2021 Jan average is that over half that 2017 2,200km3 deviation has been clawed back by Jan 2021.

Also attached is a table and graph of the 365 day trailing average volume . It is still 891 km3 above the record low on 31 August 2017, but is currently declining at 2km3 per day, some 2 1/2 times the long-term average. It is certainly possible that a new record low could be reached in 2022, but in 2021? - highly unlikely.

Arctic sea ice / Re: Latest PIOMAS update (January, mid-monthly update)
« on: January 20, 2021, 12:41:09 PM »
Appreciated as always, Wipneus.

Here's my contribution

Arctic sea ice / Re: 2021 Sea ice area and extent data
« on: January 16, 2021, 08:22:12 PM »
from NSIDC Data

There is usually a record breaker somewhere. The St Lawrence is at record low sea ice for the time of year both in Area (4 days) and in Extent (2 days).

Given that this sea is very much the smallest sea with the max sea ice extent in March well below 200 k in recent years, it will probably not be that significant is the wider scheme of things.

This is one of the best non-technical pieces I've read on SSW, the PV and effects in the mid-latitudes.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: January 08, 2021, 01:15:57 AM »
As far as I know Hycom is not comparable across the years from 2016 to 2020 as the model was changed in the interim.

Arctic sea ice / Re: Latest PIOMAS update (January)
« on: January 06, 2021, 03:43:20 AM »
Finally, in its last gasp 2020 managed to break away from 2016, though this did not suffice to cross above 2012.
The main region to thank is the Siberian sector. Laptev and Kara have both left record low territory at last. In the Pacific sector one could have a hoped for a higher year-end result, considering the high volume throughout the summer. The CAB is still very low but not as bad as 2016.
Looking at daily record lows, 2020 had a respectable showing, but is still behind 2012, 2019, and 2017. 2010 has finally lost its only daily record and was kicked of of the chart.
Hopefully, early 2021 will see better volume growth than early 2017 had.

My next update will require the annual hell of adding a new line to all charts and fixing colors.
The usual thanks to Wipneus, without whom the regional data would not be available anywhere.

Arctic sea ice / Re: What the Buoys are telling
« on: December 30, 2020, 07:39:00 PM »
Definitely looks like it depends on the year (and where the buoys are)

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: December 30, 2020, 04:15:12 PM »
NSIDC Data Query

Not a lot of people know that the NSIDC sea ice extent total is greater than the sum of extents of the 14 seas.....

I wrote to NSIDC this...
Every day I download the 5-day Arctic Sea Ice trailing averages for the 14 regions from N_Sea_Ice_Index_Regional_Daily_Data_G02135_v3.0.xlsx and post an analysis on the Arctic Sea Ice Forum. That analysis includes adding up the total sea ice extent of the 14 seas.

But that total does not agree with the 5-day trailing average extent from
file Sea_Ice_Index_Daily_Extent_G02135_v3.0.xlsx

The value from this file is always about 100k km2 greater than the figure
from adding up the 14 individual Arctic regions. See table below

Is this just because its how the algorithms work?
Which figure for the total should I use ?

              Total of
              the 14 seas
              5-day extent      NSIDC 5 day extent   Difference
21-Dec     12.118                    12.216                   0.098
22-Dec     12.220                    12.326                   0.106
23-Dec     12.297                    12.401                   0.104
24-Dec     12.346                    12.451                   0.105
25-Dec     12.390                    12.494                   0.104

And got a reply from the man himself (Walter Meier)
"The total is the entire polar stereo grid. If one looks at the regions, there are areas of the grid outside of these regions. Most, if not all of such ice is false ice - i.e., either weather effects or land-spillover error. However, there can be some legitimate ice - mostly this would be in winter in places like the Bohai Sea off the coast of China or in the Chesapeake Bay (though this is brackish water, so one could argue if that is “true” sea ice). The area of such extraneous ice is, as noted in the data, quite small: ~100,000 sq km."

Arctic sea ice / Re: Arctic Image of the Day
« on: December 30, 2020, 12:28:27 AM »
I thought this one worthy of the forum

Arctic sea ice / Re: What the Buoys are telling
« on: December 29, 2020, 02:37:13 PM »
I filter data at

df = df[df['H_Velocity'] < 50]

So 50km per day (2.08km/h)

There is probably a lot you dont agree with in the methodology (which I completely accept), im going to provide the code to you- the thing is it will take a long long time to run (but you could just run a few years instead of all).

I just finshed adding the 2017-2020 dat files so the initial sweep is complete

Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 29, 2020, 01:27:33 PM »
Fall freeze up to date, emphasis on MYI.

Arctic sea ice / Re: What the Buoys are telling
« on: December 28, 2020, 09:29:11 PM »
1994 dir. Contains 92-95
check 11252

Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 25, 2020, 12:46:43 AM »
The mp4 below shows 84 days of the fall freeze season, from Oct 01 to Dec 23. Here SMOS was used at 132.24% enlargement to provide masks for land, open water and thin ice as Ascat alone has distracting artifacts there especially early in the season.

Note a white band of ice (an extended virtual buoy for tracking purposes) forms early on in the northern Laptev at the FYI/SYI edge (as it did last year) and will likely remain trackable until May. The overall pattern of ice movement here has been a squash towards Greenland and the CAA.

The physical explanation for the hundreds of km of white band remains elusive. Efficient scattering from low dielectric near-surface ice is typically seen in older ice that has lost its brine pockets. However Ascat's active microwave beam can also be reflected back from crumpled ice with right-sized debris particles. How and why this would form at the edge of SYI perhaps may require strong 'offshore' winds piling up newly formed ice. The area is inaccessible to ships and the feature may not be apparent at visible or infrared wavelengths anyway.

Other stably advecting Ascat features such the large dark elongated patch in the north Beaufort also lack interpretation. This area froze up very rapidly in patches per Smos-Smap and so may have incorporated extra near-surface salinity which would indeed make it appear darker.

Note too the unusual mid-December surge of ice west across the Chukchi to the shores of Chukotka; usually western Alaskan ice originating northeast of Banks Island turns north upon reaching the eastern Chukchi, perhaps riding Bering Strait inflows.

This can be attributed to the persistent anti-cyclone over the period 08-24 Dec 2020 that has brought clear skies and with it excellent Suomi band 15 views of heat loss from leads and their motion ( opens to a good palette set-up). As the large diameter anti-cyclone wandered across the Arctic Ocean towards the Kara side, winds often blew in the opposite direction of that needed for a return Gyre.

Export out the Fram has picked up but has the odd oblique meridional surge is from the central CAB rather than the usual zonal route between the pole and the SZ-FJL-Svalbard. This could have the effect of exporting older thicker ice but this year, as witnessed by the Polarstern, the ice between Greenland and the pole did not fit that description in September.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 23, 2020, 11:45:30 AM »
You can find ice charts going back to the 1800's here:

Arctic sea ice / Re: What's new in the Arctic ?
« on: December 23, 2020, 01:02:03 AM »
Mosaic On Steroids: Russia’s New Project 00903 Long-Endurance Arctic Research Vessel is Expected to Operate On Research Missions In the Arctic region, for Up to Two Years at a Time.

Russia has launched a new Arctic research vessel, named the North Pole. The Project 00903 ship is described as an “ice-resistant self-propelled platform” and is intended to drift through the waters of the frozen north, conducting geological, sonar, geophysical, and oceanographic surveys. It is also far from pretty.

The vessel’s distinctly egg-shaped hull, constructed from special high-durability steel, stems from its requirement to deal with light ice, being propelled along at a speed of around 10 knots. This ship is not an icebreaker, however, and its reinforced hull is designed to be better able to shrug off ice rather than plow through it. Instead, its overall design has been optimized for endurance and autonomy.

Measuring 276 feet long by 74 feet wide, and with a displacement of 10,225 tons, the North Pole is intended to be the first vessel of its kind to be permanently based in the high Arctic.

Previously, Russia, and before that the Soviet Union, made use of drifting ice stations for supporting Arctic research teams. These were built on naturally occurring ice packs or glacier fragments. Beginning in 1937, a total of 40 expeditions had been run, normally in the months of September to October. One of these ice stations provided the U.S. intelligence community with a rare windfall when, in May 1962, under Project Coldfeet, they investigated an abandoned Soviet research station high in the Arctic.

However, the effects of global climate change since the early 2000s means that these kinds of stations are no longer a practical proposition since solid ice is increasingly hard to find.

So, now Russia has turned to the “ice-resistant self-propelled platform,” or Project 00903, which will be able to venture into the Arctic region under its own power, or with the help of an icebreaker, before beginning its “autonomous” mission. In this case, the autonomy refers to being able to operate independently of resupply for extended periods of time, enabling researchers to study the Arctic region for up to two years at a time, without having to dock in port.

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 20, 2020, 11:30:30 PM »
I went looking back to what Oren used before but NSIDC regional data is extent only so that is not going to help.

Jan: -2 (for Extent) minus 13 (for Volume) = -15
    The Vol. estimate got 13 years earlier, but Extent est. became later not earlier, and thus farther away from the Vol estimate.  This is the opposite of convergence and NOT what the hypothesis predicts.

But it is consistent with melting stuff. Volume is hard to make and extent not so much. Extent chases area chases volume.

On another note there must be some thickness which leads to trouble. What is the average thickness to disappear in a year? At some point all kinds of processes that were not important are going to play a role. The summer ice will become ever more shattered and drift more.

Of the 4 measurements i would totally go with volume as the best predictor.

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 19, 2020, 09:39:17 PM »

thank you for your excellent reply and thoughts.
I have performed a second experiment on the data. I only used the first twenty (instead of thirty) years. One of the reasons is to omit the super melting year 2007 which, lying almost at the end of the 1979-2008 series, may have influenced the statistical analysis. And, the years 1997-1998 have been unspectacular, both extent- and volume-wise.

Please find the same evaluation, which has to be taken with a certain grain of salt as only 20 years were used. Especially the April value seems not to be very trustful, but I double-checked the data.
But the general trend is comparable. Please notice that the slopes (column stg) are again much smaller than the slopes 19291979-2008 have been. This results in a massive time shift of the "BOE numbers" compared to what they are calculated today. And who may know whether this tendency goes on like that in the next decade?

Spring months still develop apart. June is still undecided. Summer, autumn and winter values converge.

Please note that I used the NSIDC data for the whole Arctic including all peripheral seas.

One final note to the "undecided" September from the 1979-2008 evaluation: The slope has been higher than it should have been because Sep 2007 was so low. This resulted in a "BOE number" close to what it is estimated today.

See attached table.

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 17, 2020, 05:39:48 PM »
I just did a "quick and dirty" experiment with a set of reduced data (1979-2008) versus 1979-2020.
I calculated the "BOE numbers" for the time period 1979-2008 and compared it with the full period (1979-2020). I reduced the evaluation on extent and volume and just performed the linear evaluation. Finally I compared the differences (column Delta) for each month (extent versus volume). If the Delta in extent is larger than the Delta in volume, the "BOE numbers" converge. If it is the other way round, the values develop apart.

1. The slope of almost all months has grown steeper from 1979-2008 to 1979-2020.
2. This results in earlier "BOE numbers" for most, but not all of the months. The "BOE numbers" for extent increased in Jan, March and April!
3. There is a clear season for convergence: summer and autumn, marked in green. In winter and spring the values go even further apart, marked in pale magenta (column "Delta"). June and Sep are more or less undecided.

See attached table.

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: December 16, 2020, 11:16:26 AM »

I attach the December monthly average graph based on actual data to Dec 15th and assuming 10 year average sea ice extent gains to the end of the month.

The resulting extent of 11.11 million km2 would be 2nd lowest in the satellite record, 0.11 million km2 above the record low of Dec 16, and 0.31 million km2 less than Dec 19.

Arctic sea ice / Re: Arctic Ocean salinity, temperature and waves
« on: December 15, 2020, 10:30:15 PM »
Oceanographers Find Explanation for the Arctic's Puzzling Ocean Turbulence

Eddies are often seen as the weather of the ocean. Like large-scale circulations in the atmosphere, eddies swirl through the ocean as slow-moving sea cyclones, sweeping up nutrients and heat, and transporting them around the world.

In most oceans, eddies are observed at every depth and are stronger at the surface. But since the 1970s, researchers have observed a peculiar pattern in the Arctic: In the summer, Arctic eddies resemble their counterparts in other oceans, popping up throughout the water column. However, with the return of winter ice, Arctic waters go quiet, and eddies are nowhere to be found in the first 50 meters beneath the ice. Meanwhile, deeper layers continue to stir up eddies, unaffected by the abrupt change in shallower waters.

This seasonal turn in Arctic eddy activity has puzzled scientists for decades. Now an MIT team has an explanation. In a paper published today in the Journal of Physical Oceanography, the researchers show that the main ingredients for driving eddy behavior in the Arctic are ice friction and ocean stratification.

By modeling the physics of the ocean, they found that wintertime ice acts as a frictional brake, slowing surface waters and preventing them from speeding into turbulent eddies. This effect only goes so deep; between 50 and 300 meters deep, the researchers found, the ocean's salty, denser layers act to insulate water from frictional effects, allowing eddies to swirl year-round.

The results highlight a new connection between eddy activity, Arctic ice, and ocean stratification, that can now be factored into climate models to produce more accurate predictions of Arctic evolution with climate change.

"As the Arctic warms up, this dissipation mechanism for eddies, i.e. the presence of ice, will go away, because the ice won't be there in summer and will be more mobile in the winter," says John Marshall, professor of oceanography at MIT. "So what we expect to see moving into the future is an Arctic that is much more vigorously unstable, and that has implications for the large-scale dynamics of the Arctic system."

... Now that they have confirmed that ice friction and stratification have an effect on Arctic eddies, the researchers speculate that this relationship will have a large impact on shaping the Arctic in the next few decades. There have been other studies showing that summertime Arctic ice, already receding faster year by year, will completely disappear by the year 2050. With less ice, waters will be free to swirl up into eddies, at the surface and at depth. Increased eddy activity in the summer could bring in heat from other parts of the world, further warming the Arctic.

At the same time, the wintertime Arctic will be ice covered for the foreseeable future, notes Meneghello. Whether a warming Arctic will result in more ocean turbulence throughout the year or in a stronger variability over the seasons will depend on sea ice's strength.

Regardless, "if we move into a world where there is no ice at all in the summer and weaker ice during winter, the eddy activity will increase," Meneghello says. "That has important implications for things moving around in the water, like tracers and nutrients and heat, and feedback on the ice itself."

Genesis and decay of mesoscale baroclinic eddies in the seasonally ice-covered interior Arctic Ocean, Journal of Physical Oceanography, (2020)

Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 07, 2020, 10:05:51 AM »
Overall graph and regional differences with 2012 and 2016

Arctic sea ice / Re: Latest PIOMAS update (November mid-monthly update)
« on: December 07, 2020, 06:30:25 AM »
Thanks a lot Wipneus for your important work with PIOMAS data.
A few charts showing that 2020 is unfortunately still leading in the important places, though it lags the total behind 2016 mainly thanks to a 140k surplus in the Greenland Sea.
CAB and Pacific side rates of growth seems to be following in parallel to the slower years, such as 2016. In the Siberian side the rate of growth has been following the faster years, though on a very delayed curve. Hopefully by the next update 2020 will be firmly above 2016.

Click to enlarge.
Looking at the same charts again, 2020 is still in a bad place.
Although the CAB has finally inched above 2016 with a tiny 90 km3 lead, the total of the Inner Basin still sees 2020 as lowest on record by a similar gap. This is due to disappointingly slow growth on both the Siberian side, where trouble brewed all summer and volume is still lowest on record, but also on the Pacific side, which is quickly losing its hard-won advantage. The Beaufort + Chukchi actually managed to lose net volume in the past four months, while most years add a net of several hundred km3.
2016 is still leading thanks to a 190 km3 gap in the Greenland Sea, and a 250 km3 advantage in the Peripheral seas. This lead can go on for quite a while but does not promise a safe melting season in any way. I remind that after the abysmal 2016 winter, 2017 "dodged a cannonball" with very lucky weather. This is not guaranteed to happen again, so hopefully 2020 will pull away above 2016 at some point.

Click to enlarge.

Arctic sea ice / Re: Latest PIOMAS update (December)
« on: December 06, 2020, 07:47:00 PM »
PIOMAS  Volume as at 01 Dec 2020  9,861 KM3

- Volume gain from minimum on this date is 5,832 km3, 598 km3, (9%),  less than the 10 year average of 6,430 km3.

- Volume is at position #2 in the satellite record

- Volume is  374 km3 LESS than 2012
- Volume is  350 km3 MORE than 2016
- Volume is  596 km3 LESS than 2019


Average remaining freeze (of the last 10 years) would produce a maximum volume in April 2021 of 21,410 km3, 628 km3 above the 2017 record low maximum volume of 20,782 km3.
N.B. Click on image  for full-size

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: December 05, 2020, 03:40:51 PM »
Interestingly, I thought that if the Arctic was not ice free in the Holocene (at least so far) at least it probably was in the Eemian, so it would not be completely novel in "recent" Earth history.
Seems I was wrong:
So AFAIK the Arctic may be about to be ice free for the first time in a couple million years?

Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 05, 2020, 12:49:13 PM »
New November record high for Siberia:

Arctic sea ice / Re: The 2020/2021 freezing season
« on: December 04, 2020, 03:34:47 AM »
In the data thread, there is mention of high export via Greenland Sea and reduce freeze in Kara.

I cant remember where I read this (probably here) but isn't that one of the really bad signs that things are getting really, really bad?

And if my memory serves me well in this, are we about to experience a short burst of massive change?
(I am not a fan of linear changes in nature, it tends to do things in bursts rather than nice smooth downward trends.)

Is Arctic Warming Behind a Monster Saharan Dust Storm?

The June 2020 dust storm set records in terms of its geographic size and its aerosol optical depth—essentially a measure of its thickness determined by the ability of satellites to see through it. It reached an altitude of 6,000 meters (19,600 feet). In certain locations over the Atlantic Ocean, its thickness was double what had ever been recorded during the month of June during the history of the satellite record, which dates back to 1995.

The researchers analyzed what made it happen in a study appearing today in the journal Geophysical Research Letters

.Evan, lead author Diana Francis of Khalifa University of Science and Technology in the United Arab Emirates, and colleagues attributed the dust storm's magnitude to conditions set up by the development of a type of high-pressure system called a subtropical high off the coast of the Sahara. This increased the north-south pressure gradient over West Africa leading to record-strength, persistent northeasterly winds. The intensification of the northeasterly winds over the Sahara generated continuous dust emissions over several days in the second half of June 2020.

The researchers found that the subtropical high was embedded in a circumglobal wavetrain, a chain of wind patterns that extended around the planet, and was present in the Northern Hemisphere for most of June 2020. This wavetrain may have been caused by record-low Arctic sea ice extent observed in June 2020 as well. The warming of the Arctic region is believed to be altering the course of wind patterns in the mid-latitudes and subtropics and causing severe weather events, though there is controversy among scientists about this concept.

"The development of the subtropical high off the African coast had a deterministic role in both dust emissions and rapid westward transport of the airborne dust across the tropical Atlantic," said Francis. "The clockwise circulation associated with the high, intensified the African Easterly Jet, a jet stream present over the Sahara around five kilometers (3.2 miles) in altitude, which rapidly transported the dust towards the Caribbean and southern United States."

The study also touches on a controversial topic within the science community. Though not the main focus of study, the wavetrain pattern that set the Godzilla dust storm in motion looked very similar to one observed in 2010 when sea ice in the Arctic Ocean was substantially diminished, Francis' team noted.

"As the Arctic sea-ice cover was rather low in June 2020, around the lowest on record in the period of satellite observations, it may have contributed to the observed large-scale anomaly pattern," the study concludes. "Thus, if such patterns become more common in a warmer world, it is plausible that these extreme dust outbreaks will increase in frequency in the future."

Diana Francis et al. The Atmospheric Drivers of the Major Saharan Dust Storm in June 2020, Geophysical Research Letters (2020)

Arctic sea ice / Re: MOSAiC news
« on: December 01, 2020, 03:01:53 PM »
Lobelia has added flexible gif and mp4 time series generation downloads to the CMEMS ocean page linked to by a 'social media' icon next to 'add layers' that also allows iframe embedding (not supported here), tinyUrls and static pngs.

Uniq has already posted excellent examples on the main and test forums. Lobelia-CMEMS is a very important new resource for the Arctic Ocean but over the last six weeks only 2-3 of the 1795 site registrants have used it. As is said about the lottery, you can't win if you don't play.

Below, grayscale palette gif output from Lobelia has been run through ImageJ, Gimp and CloudConvert to add some graphic refinements, notably for freedom to change palette to an arbitrary LUT, move the date to a better place, recolor ocean blue, crop, rotate to Greenland down, overlay the Polarstern drift path and so on.

The mp4 shows 84 days of ice thickness as modeled by nextSim from Sept 15th out to a predicted Dec 7th. The scale has been set to range over 0-3m which has the effect of not displaying thinner ice optimally; that would require a scale setting of 0-0.5m which would not display the main ice pack at all.

It's not completely clear what the 'floes' and 'leads' actually represent down on the ice as these features are below the resolution of any of the satellite tools used by nextSim. Whatever, they do seem to allow an accurate depiction of ice movement, notably the pick-up in Fram export in mid-November.

The second mp4 shows the full range of 111 weeks contained in the archive. It is a little jumpy but the daily scale would make for quite a large file and the hourly would be way out of bounds.

The third mp4 shows ice thickness for the full year of the Mosaic expedition restricted to the Svalbard area to emphasize the vigorous TransPolar Drift and Fram export compared to the virtual lack so far this season. The file size is still quite small meaning 2x the dimensions would be about 8 MB.

These mp4 were initially made as gifs where resolution is better (because mp4 involves lossy compression). After loading and study of most effective frame rate in ImageJ, 'hourly' can easily be changed to 'six hourly' or daily' can  to 'every other day' etc. This avoids choice limitations in the Lobelia panel. However, ordering more frames slows down product delivery which is a lot slower now than Nasa's WorldView.

"The Arctic Sea Ice Analysis and Forecast system uses the neXtSIM stand-alone sea ice model running the Maxwell-Elasto-Brittle sea ice rheology on an adaptive triangular mesh of 10 km average cell length. The model is available back to 01 Nov 2018

neXtSIM uses surface atmosphere forcings from the ECMWF (European Centre for Medium-Range Weather Forecasts) and ocean forcings from TOPAZ4, the ARC MFC PHY NRT system (002_001a). neXtSIM runs daily, assimilating OSI-SAF sea ice concentrations (both SSMI and AMSR2) from the SI TAC and providing 7-day forecasts.

The output variables are the ice concentrations, ice thickness, ice drift velocity and snow depths, provided at hourly frequency. The adaptive Lagrangian mesh is interpolated for convenience on a 3 km resolution regular grid in a Polar Stereographic projection. The projection is identical to other ARC MFC products."

A Maxwell elasto-brittle rheology for sea ice modelling
V Dansereau et al 01 Jul 2016 free full text Maxwell 1867 key feature of viscoelastic model

A new rheological model is developed that builds on an elasto-brittle (EB) framework used for sea ice and rock mechanics, with the intent of representing both the small elastic deformations associated with fracturing processes and the larger deformations occurring along the faults/leads once the material is highly damaged and fragmented. A viscous-like relaxation term is added to the linear-elastic constitutive law together with an effective viscosity that evolves according to the local level of damage of the material, like its elastic modulus.

The coupling between the level of damage and both mechanical parameters is such that within an undamaged ice cover the viscosity is infinitely large and deformations are strictly elastic, while along highly damaged zones the elastic modulus vanishes and most of the stress is dissipated through permanent deformations. A healing mechanism is also introduced, counterbalancing the effects of damaging over large timescales.

In this new model, named Maxwell-EB after the Maxwell rheology, the irreversible and reversible deformations are solved for simultaneously; hence drift velocities are defined naturally. First idealized simulations without advection show that the model reproduces the main characteristics of sea ice mechanics and deformation: strain localization, anisotropy, intermittency and associated scaling laws.

The availability of ice buoy and satellite data has allowed three all-important characteristics of the deformation of sea ice to be revealed: its strong localization in space (heterogeneity), its localization in time (intermittency) and its anisotropy.

The anisotropic nature of sea ice deformation is made evident by the analysis of satellite-imagery derived ice motion products which shows that high strain rates concentrate along oriented, linear-like faults, or leads, often termed “linear kinematic features” (Kwok, 2001). The signature of the strong heterogeneity and intermittency of sea ice deformation is the emergence of spatial and temporal scalings in the deformation fields over a wide range of scales.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 27, 2020, 10:40:18 PM »
amsr2 awi v103 hudson, nov1-27(early) click for animation
noaa sea ice concentration, hudson nov27, 1981-2019 animation and compressed static (might be useful for the atmospheric connections thread) No data for 82 and 85.
The static image is compressed 1/10 width for easier visual comparison see more detail for other areas on the mosaic thread here
amap hudson bay currents.

Arctic sea ice / Re: MOSAiC news
« on: November 25, 2020, 03:38:17 PM »
The mp4 shows the Kara sea from Sep 15th to Dec 31st (108 days) for the years 2020-2010 (L to R, top to bottom, 2020 repeated with days 71-108 grayed as not arrived). It is quite interesting to see how the Kara Sea fills in, mainly from the land side (and by hundred of islands) but supplemented by growing the Arctic Ocean sea ice, with ice often forming just south of Severnaya Zemlya (a cold spot which had late relic ice this August).

Tracking open days of the NorthEast Passage shows it has been opening earlier and closing later over the last forty years.

SSTfnd 10m water column temperatures are just a degree or two above sea water freezing according to data from Nov 24th.

Water circulation patterns in the Kara Sea are complex. The Kara Sea tends to be sea ice covered between September and May,[7] and between May and August heavily influenced by freshwater run-off (roughly 1200 km3/yr from the Russian rivers (Ob, Yenisei, Pyasina, Pur, and Taz). The Kara Sea is also affected by the water inflow from the Barents Sea, which brings 0.6 Sv in August and 2.6 Sv in December. The advected water originates from the Atlantic, but it was cooled and mixed with freshwater in the Barents Sea before it reaches the Kara Sea. Simulations with the Hamburg shelf ocean model suggest that no typical water current pattern consists in the Kara Sea throughout the year. Depending on the freshwater run-off, the dominant wind patterns, and the sea ice formation, the water currents change.

Surface area   926,000 km2 (358,000 sq mi)
Average depth   131 m (430 ft)
Water volume   121,000 km3 (98×109 acre⋅ft)
Frozen   Practically all year round [[1999 wikipedia]]

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 20, 2020, 02:04:25 PM »
I still find 2018 the best analogue. We are cca 2 weeks behind:

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: November 20, 2020, 10:10:00 AM »
JAXA ARCTIC SEA ICE EXTENT:  8,867,280 KM2 as at 19-Nov-2020

- Extent gain on this day 38k, 13 k less than the average gain on this day (of the last 10 years) of 51k,
- Extent gain from minimum on this date is 5,312 k, which is 202 k, 4% more than the 10 year average of 5,110 k.

- Extent is at position #2 in the satellite record

- Extent is  483 k LESS than 2019,
- Extent is  565 k MORE than 2016,
- Extent is  538 k LESS than 2012
- Extent is  872 k LESS than 2007
- Extent is  598 k LESS than the 2010's Average
On average 51.8% of extent gains  from minimum to maximum done, and 112 days to maximum

Projections. (Table JAXA-Arc1)

Average remaining extent gain (of the last 10 years) would produce a maximum in March 2021 of 13.62 million km2, 0.26 million km2 below the March 2017 record low maximum of 13.88 million km2.
The 2016-17 freezing season ended with the current record low maximum sea ice extent.
However, from now on the remaining freeze for that year is very much the highest in the last 10 years and more, at 17% above the average. 2019-20 remaining freeze was just 7% above the 10 year average.

N.B. Click on image to enlarge

Arctic sea ice / Re: MOSAiC news
« on: November 19, 2020, 05:11:17 PM »
At the end of the 2019/20 winter the Laptev volume (black line) was at an all time low, long before the Siberian heat wave and the summer cyclone.
Right. Don't forget the 800kg oceanographic gorilla swimming in the Laptev below the meteorology! We have not seen much progress in getting people to actually read Polyakov 2020 despite it representing 15 years of in situ observational data describing the increasingly dominant atlantification influences at the top of the Laptev bathymetric bight.

It's free full text, the latest in a decades-long series rarely considered here, posted maybe a dozen times on various forums but to no effect. Atlantification pulses, being oceanography, have a certain inertial inevitability about them unlike wait-and-see seasonal variability of Siberian weather (that overlies the strong autumn Arctic Amplification warming trend).
Intensification of Near‐Surface Currents and Shear in the Eastern Arctic Ocean
IV Polyakov et al. Aug 2020

'Measurements of currents from a 15‐year mooring record in the eastern European Basin demonstrate that the previously identified weakening of stratification in the halocline (Polyakov 2017, 2018) has been accompanied by increased upper‐ocean current speeds and associated current shear. Most of this increased energy and shear is in the semidiurnal band which includes baroclinic tides and wind‐driven inertial oscillations, with little change of mean along‐slope water transport (Pnyushkov 2018).

Increased shear together with weakening stratification indicate a greater potential for shear‐driven turbulent mixing, consistent with the recent transition in sea ice and upper ocean state to conditions previously unique to the western Nansen Basin [[Sv-FJL-SZ line]].

This increased coupling between AW heat and the sea ice may lead to a positive feedback between reduced sea ice and higher mixing rates as the longer periods and increased areal extent of open water facilitate more energetic wind‐driven inertial oscillations and associated upper‐ocean shear coinciding with weakening halocline stratification. As sea ice declines, a new Arctic state is emerging which, due to the positive feedback mechanism outlined above, may be pushing the system toward a tipping point.'

This article was submitted back in the spring of 2020 before any of this unprecedented season unfolded. It's aging well so far!

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 17, 2020, 06:41:36 PM »
I think many have noticed this already, and maybe it has been said.
but just now i just realized that we now have as much ice volume at the annual March maximum as we had at the September annual minimum in the years 85-95

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 17, 2020, 05:29:33 PM »
As Glen showed in his post previously, the dip below the trendline started around 2005 and has continued to today.  Above, Simon showed the residually strongly skewed in recent decades.  All told, the sea ice minimum appears to be reverting to the long term trend after a short term accelerated loss.  Whether the long term trend will be maintained or a new trend associated with a state change dominates remains to be seen.  Stay tuned.

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 17, 2020, 04:22:48 PM »
Strongly autocorrelated data vs Arctic Extent, plotted as an ACF

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 17, 2020, 04:02:04 PM »

But mostly I take umbrage with the claim that the residuals of the trendline in the above graph are autocorrelated. Please explain what you mean by this, preferably with a concise argument underpinned by sound mathematics so the rest of us can understand what you mean.

Attached is what happens when you fit a straight line to a curve. Residual stays one side of 0 for consecutive data points and only changes sign a few times *twice with this simple curve). White noise would have it changing sign roughly 50% of time then roughly 25% of time is stays same sign twice before changing sign and so on.

What is being pointed out is that residual stay same side of 0 far too frequently and this is a sign that you are fitting a straight line to a curve.

Edit also added a straight line fit where as it happens residuals change sign 16 times for 32 data points. (should be 15.5 times but 16 is as close as you can get)

Arctic sea ice / Re: When will the Arctic Go Ice Free?
« on: November 17, 2020, 03:51:10 PM »

The only way to make those trendlines right is to break the chart into 2 parts: before 2007 and after 2007 and use two trendlines, because a state change obviously happened then.

The problem with this statement is that you can choose it arbitrarily
for example

The only way to make those trendlines right is to break the chart into 2 parts: before 1996 and after 1996 and use two trendlines, because a state change obviously happened then.

Un ou deux points isolés ne suffisent pas pour déterminer une tendance ou une cassure

Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: November 16, 2020, 11:10:51 AM »
JAXA data - a bit more

I attach the monthly average graph for November - 2020 data being actual daily extent to 15th November and assuming average extent gains from the 16th to the end of the month.

Despite the extreme extent gains from the 24th October to a few days ago (see 2nd graph attached), if extent gains are averge from now, the November 2020 average will be 2nd lowest and nearly 400k (or more than 6 years) below the linear trend value for 2020.

Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 13, 2020, 02:40:21 AM »
       FWIW, my own opinion about 2007 is to agree with you from a different basis.  It seems to me that the loss of multi-year ice in 2007 either reflected or helped initiate systemic changes in the ASI system.  Various posts in the forum have described how, even though 2012 gets most of the attention since it holds the records, that when looked at from different points of view, 2007 was the Big Year.  I have no hope of remembering in which thread, but (I think it was) Oren or BFTV who put up a post this summer listing losses from September to September which showed that when viewed from that time frame, 2007 outdistanced every other year for losses.  So that's a second (but also not statistically validated) observation to lend weight to your proposition. 
Indeed, here is an expanded version of that post which is found upthread. As my PIOMAS Excel is built around Wipneus data, the following only looks at daily data since 2000.
For each year, I look at the volume gain over the preceding autumn and winter, starting at day 266 of the previous year (~Sep 23rd) and ending at day 121 of that year (~May 1st). Then I look at the volume loss over that year's spring and summer, until day 266. The four worst years in each column are bolded. The results are quite interesting.
Indeed, 2007 is the winner for total net loss. However, its main claim to fame should be the low winter gain. Its summer loss was high for its time but nothing much compared to later years. Looking at the data in chart form clearly shows that something was different after 2007, much higher losses and much higher gains as a larger part of the Arctic participated in the seasonal cycle. In my next post I will look at the various regions, and attempt to find out where the missing 2007 winter volume was located.
In general, high net losses typically occur in years that had a low winter gain compared to their surrounding neighbors, marked in the chart. Also marked is 2017, the year the Arctic dodged a cannonball despite poor winter gain, by having the lowest summer loss since 2004.
In addition, most top years for high summer losses were also top years for high early summer losses.

Click to enlarge images.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 13, 2020, 12:41:24 AM »
Is it normal?                   Recently it seems that it is.
Does it affect surface?   It seems not much at the moment

Beaufort 50m temperatures from whoi itp buoys, 2006-oct2020

previously discussed here

Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 12, 2020, 03:44:24 PM »
Piomas 2006/7 every 5th day from the 40yr mp4 here.

added sep22, 1980-2020.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 12, 2020, 02:17:28 PM »
The freezing days anomaly has been following the record 2016 very closely so far.

Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 12, 2020, 01:59:08 PM »
       Tamino/Grant Foster is/was the king of change point analysis. 

And he did an anlysis in 2015, based on extent anomaly data. For sea ice minimum, he found one change point, in 1996 if I read the graph correctly.

Arctic sea ice / Re: Latest PIOMAS update (November)
« on: November 12, 2020, 12:40:47 PM »
To me it does suggest that in winter 2007-2008 something changed rather substantially.
As Oren wrote it would also be interesting to separate the arctic ocean proper from the peripheral seas and see what impact this has on the trendlines for Vgrowth. Anyone knows where i can find the data in Excel format?
Wipneus provides the data twice a month on this thread in two files. (You have to unzip the data as its in format .gz)

One file has monthly average volume by each sea going back to 1979. (attachment 1)
The other file has daily volume by each sea going back to 2000 (attachment2).
The daily total volume going back to 1979 is from (attachment 3)

I also attach the monthly data by each sea from 1979 with additional columns for the High Arctic (7 central seas) total and the 7 Peripheral Seas total (attachment 4)

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 12, 2020, 12:09:14 PM »
       +2.7C per decade is Monstrous. 

You ain't seen nothing yet. 10 C in 1-3 years IS monstrous and that did happen at the end of the last glacial and then again with beginning and end of the Younger Dryas:

"The high-resolution records from the NGRIP
ice core reveal that polar atmospheric circulation
can shift in 1 to 3 years,
resulting in decadal- to
centennial-scale changes from cold stadials to
warm interstadials/interglacials associated with
large Greenland temperature changes of 10 K

(6, 20). Neither the magnitude of such shifts nor
their abruptness is currently captured by state-ofthe-
art climate models.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 12, 2020, 10:51:30 AM »
       +2.7C per decade is Monstrous.
Going out on the limb of my ignorance, I'll hazard a guess that for the near term at least, the recent above-average increases in Extent and Area could lose some momentum.  If that DMI anomaly does not fall, it is easy to imagine a new record low maximum in spring 2021.
You and I have similar hobbies, but I think yours is further evolved and more detailed.

Oh, without question 2.7c is monstrous, and I'm very much of the opinion we are in the middle of a "tip over" into a new climate regime.

As to the recent century and multiple century extent and area increases - they neither surprised me nor reassured me.  Quite the contrary, they represent heat getting locked in, and the exchange of ocean heat with atmosphere slowing down.

They will without question slow down - as the areas of "hot" open water become farther removed from areas with persistent low temperatures. 
I attach a graph of daily extent change for the freezing season. I have used a 7 day trailing average to make the graph less noisy. Extent gains are quickly heading back down to something like average.

It makes it clear, at least to me, that the extreme extent gains were an almost inevitable consequence of previous very low extent gains from a very low minimum. On the 24th October extent gains from minimum were just over 1 million less than the 10 year average. By November 10th, 275k above average. It is also clear that compared with the other years of very low minimums (apart from 2016), sea ice extent recovery rebound happened later.

What happens next? My eyes are pretty much glued to the Atlantic Front, though with the ESS and the Beaufort now pretty much full-up ice, looking for resistance to freeze in the Chukchi is also a distraction.
ps: From Aluminimum's latest gif it looks like the last bit of the Laptev to freeze will be the hole centred on 80 North.

Arctic sea ice / Re: The 2020/2021 freezing season
« on: November 12, 2020, 08:18:51 AM »
       +2.7C per decade is Monstrous.
Going out on the limb of my ignorance, I'll hazard a guess that for the near term at least, the recent above-average increases in Extent and Area could lose some momentum.  If that DMI anomaly does not fall, it is easy to imagine a new record low maximum in spring 2021.
You and I have similar hobbies, but I think yours is further evolved and more detailed.

Oh, without question 2.7c is monstrous, and I'm very much of the opinion we are in the middle of a "tip over" into a new climate regime.

As to the recent century and multiple century extent and area increases - they neither surprised me nor reassured me.  Quite the contrary, they represent heat getting locked in, and the exchange of ocean heat with atmosphere slowing down.

They will without question slow down - as the areas of "hot" open water become farther removed from areas with persistent low temperatures.  By the end of the season, most of these will still freeze - the Chukchi, & Kara for example, and probably the Okhotsk - but the Bering and Barents will likely remain significantly ice free for the duration.

Mostly I think this will be driven primarily from the fact we will have little or no circulation which isolates the Arctic from inflows from lower latitude.  I think we are set up currently to it set up much like 2016, and the recent flows from tropical storms have persistently carried moisture and heat across the Barents into the Kara and then around into the Laptev and central basin.  (see my previous post with a capture from Climate Reanalyzer).

There are similar but less talked about intrusions of heat on the Pacific side, which are blowing across Kamchatka and into the Bering and Chukchi.  I don't see these patterns breaking down soon.

Arctic sea ice / Re: MOSAiC news
« on: November 12, 2020, 06:46:22 AM »
The Smos and Smos-Smap ice thinness retrievals show the advance of their cut-off (ice thicker than 0.5m, shown as tan color) over the freeze season. For a slow re-freeze like this year, some regions can lose quite a few weeks of ice growth leaving them poorly conditioned for the melt season next spring.

The first graphic below compares 2020 with 2010-2019 for Nov 9th. The red color shows >0.5m ice in an earlier year but not this year; blue indicates the opposite. There is an excess of red in each of the comparison years available -- overall 4x as many red pixels (191,886 to 53,412) -- even though the Beaufort has had a normal or even rapid re-freeze this year.

The second figure shows successive nesting of half meter ice at ten day intervals from Sept 15th to Nov 09th. The idea here was to establish ice classes based on how long ice growth has continued since newly attaining 0.5m. While there has not been enough ice movement yet to distort the nesting, neither 5- nor 10-day intervals proved long enough to provide clear categories.

It may be necessary to go to 21- or even 30-day intervals to establish clear classes; not enough time has elapsed so far this fall for this. The open water still seen on Nov 12th may not even freeze over at all until late December for the Chukchi and Svalbard-FJL areas, with more weeks needed to attain a half meter thickness.

It's also easy to track boundaries of thicker ice using CryoSat2 in combination with SMOS. The perimeter of >1.0m ice is shown at the bottom for 13 days ending Nov 9th. It's hardly advancing.

The Laptev-ESS are forming a measurable ice skin but an elevated SSTfnd in the underlying mixed layer water column could delay attainment of half meter or more thickness. Although ice can thicken rapidly at first given cold enough air temperatures above, when several weeks of freeze season are essentially lost, not enough time remains for brine exclusion maturation..

Three drifting buoys are still reporting hourly subsurface seawater temperatures from the shrinking open water pockets of the Laptev. Uniq attached that data as a txt file above; it opens readily in excel etc if .csv is appended giving fileName.txt.csv The third file shows the graph of buoy #761 up to day number 316 (Nov 11th).

A lot more analyses could be done on these three buoys and others set in the ice, for example comparison of observed SST and posted Ospo-GHRSST. Uniq has requested 'more hands on deck' several times but so far forum members have not stepped forward to help with charting.

Ironically this is one of the few areas where Mosaic data is openly available and well-organized at meereisportal. The Polarstern installed many dozen buoys in the ice and 74 of these are still actively reporting data that cannot be obtained from satellite. meereis buoy data portal additional international buoys in Arctic

[Technical note: The daily png ice thickness maps provided by Cryo2Smos are badly dithered, as is the scale bar. That is, each day uses many thousands of colors rather sticking to a palette of 256. This causes successive days to use similar but not identical colors for ice thickness. There is no upside to this, no visual benefit.

The downside is it is not possible to make a time series in gif format because the choice of 256 colors has to be fixed. Out of gamut colors then have to be brought to the 'nearest' element of the palette, causing major distortions and inconsistencies in data representation.

The fix: tile up the daily images in gimp, then change from RGB to indexed color. This forces a global choice of 256 best colors. Upon slicing, each of the frames uses the same palette so upon reassembly into layers, saving out as gif gives a satisfactory animation.

The netCDF file here is properly made so the png problem may have arisen from improper resizing somewhere along the production pipeline]

Arctic sea ice / Re: River ice and Discharge
« on: November 09, 2020, 10:30:43 AM »
A new study shows that increased heat from Arctic rivers is melting sea ice in the Arctic Ocean and warming the atmosphere.

According to the research, major Arctic rivers contribute significantly more heat to the Arctic Ocean than they did in 1980. River heat is responsible for up to 10% of the total sea ice loss that occurred from 1980 to 2015 over the shelf region of the Arctic Ocean. That melt is equivalent to about 120,000 square miles of 1-meter thick ice.

Rivers have the greatest impact during spring breakup. The warming water dumps into the ice-covered Arctic Ocean and spreads below the ice, decaying it. Once the sea ice melts, the warm water begins heating the atmosphere.

The research found that much more river heat energy enters the atmosphere than melts ice or heats the ocean. Since air is mobile, this means river heat can affect areas of the Arctic far from river deltas.

This diagram shows the relative amount of warming caused by Arctic rivers, with the sources of heat in orange and the heat sinks in turquoise. In spring, rivers flow into the Arctic Ocean, warming the water and melting sea ice, which in turn warms the atmosphere. A feedback occurs as the reflective ice disappears, allowing the dark ocean water to absorb more heat and melt more sea ice. Credit: Graphic adapted from Science Advances paper

The impacts were most pronounced in the Siberian Arctic, where several large rivers flow onto the relatively shallow shelf region extending nearly 1,000 miles offshore. Canada's Mackenzie River is the only river large enough to contribute substantially to sea ice melt near Alaska, but the state's smaller rivers are also a source of heat.

Increasing riverine heat influx triggers Arctic sea ice decline and oceanic and atmospheric warming, Science Advances (2020).

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