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A-Team

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Re: MOSAiC news
« Reply #1150 on: September 13, 2020, 06:20:49 PM »
The bow radar has resumed! It seems that acquisition never stopped but perhaps transmission of files to shore has only now been possible.

This goes out 5km in all directions except towards off-ship experimental sites so is a bit hard to register with the recent drone overhead of Sept 6th which showed almost entirely experimental sites! They do not even have a phone cam strapped to the radar mast to time-lapse for a visible correlation. (This does not even require an app, they come capable.)

The first image below registers the drone with bow radar. FOMO does not share compass direction on the drone shot nor its time of day (often given ambiguously as 'ship time' rather than the UTC of the bow radar). The drone photo only goes out 3.3 multiples of ship length (~400m) and so has far greater resolution than the bow radar which goes out 5000 m but with only ~500 pixels for it.

At any rate, some incredible ice advection can be seen in the 6-hour frame rate of the mp4 below, as well as the usual opening/closing of leads. As the ice freezes, the bow radar shows more brittle fracture than the mushy scenes of quasi-independent floes from the Fram.

FOMO has not made clear whether power lines and fiber optic data lines are being run out to remote sensors (which are only 4-5 ship lengths away this time). Consequently it is hard to determine whether trails and lines have been disrupted by lead openings and floe shifts.

Fascinating though local ice motion may be visually, it is not at all clear how to describe it scientifically or compare year on year (ie is it fracturing more). After N-ICE2015, its (very different) bow radar was written up in highly obscure technical terms. The real goal is to correlate it with wind stress and mechanical strength of the ice so the latter tensor can be deduced over the whole pack (without a ship being there) since the wind and drag are known fairly well from reanalysis.

https://data.meereisportal.de/maps/animations/Iceradar/?C=M;O=A
« Last Edit: September 14, 2020, 12:57:50 AM by A-Team »

uniquorn

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Re: MOSAiC news
« Reply #1151 on: September 13, 2020, 10:54:08 PM »
Sub -12 C now:

  88.7  105.8 20-09-10 22:00      -12.4 
  88.7  106.0 20-09-10 21:00      -12.1 
  88.7  106.1 20-09-10 20:00      -12.6 
 

And then back to above 0C with freezing rain and 'diamond dust'

Niall Dollard

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Re: MOSAiC news
« Reply #1152 on: September 14, 2020, 01:05:54 AM »
Yes the colder air at surface has been replaced and the upper air is warm too over Polarstern. But not diamond dust. That's usually seen in almost near clear air with temperatures below -12 C. As the milder air moved in Polarstern was reporting snow grains at first but as temperatures rose near zero the grains were replaced with freezing rain.

Models are forecasting it to turn cooler again by Wednesday. But no doubt there will be many mild incursions too this autumn.   

A-Team

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Re: MOSAiC news
« Reply #1153 on: September 14, 2020, 02:07:09 AM »
In terms of correcting the full-time DWD meteorologist on board the Polarstern who entered that call on the hourly awiMet report going to ECMWF, not going to do that from where I sit in smokey Arizona.

The FOMO today seems to show an icebow flanking an air temperature inversion giving rise to a pronounced refracted solar mirage of a type commonly seen in the Arctic. The optics are discussed in the attached pdf.

Wayne, a member here who has lived many years in far north Nunavut, has written very extensively about these inversions and what they mean for conditions of the ice but on Neven's blog, not the forums.

But as you say, it's all going to change.
« Last Edit: September 14, 2020, 02:14:55 AM by A-Team »

Niall Dollard

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Re: MOSAiC news
« Reply #1154 on: September 14, 2020, 08:12:28 AM »
No. Not correcting the meteorologist on board PS but our esteemed forum member who mentioned diamond dust.The ww code reported by PS was 77, which is snow grains. (Diamond dust is code 76). Next reports then were freezing rain.

uniquorn

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Re: MOSAiC news
« Reply #1155 on: September 14, 2020, 11:33:22 AM »
Sorry about that. I mixed up the ww and the WW
I should have said snow or mixed rain and snow moving to with less significant rain
Quote
W1 -- Most significant weather in past 6 hours
W2 -- Less significant weather in past 6 hours

    0 -- cloud covering less than half of sky
    1 -- cloud covering more than half of sky during part of period and more than half during part of period
    2 -- cloud covering more than half of sky
    3 -- sandstorm, duststorm or blowing snow
    4 -- fog, or thick haze
    5 -- drizzle
    6 -- rain
    7 -- snow or mixed rain and snow
    8 -- showers
    9 -- thunderstorms
Quote
76 -- diamond dust

Recent weather is hovering around 0C with continuous light drizzle.
« Last Edit: September 14, 2020, 12:49:10 PM by uniquorn »

A-Team

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Re: MOSAiC news
« Reply #1156 on: September 14, 2020, 01:45:12 PM »
Somewhere up-forum, all the weather commentaries for the entire expedition was extracted into a flatfile database and a MS Word-type glossary system proposed to stub in the code lookups to eliminate tedious and error-prone code lookups. No one picked up that baton.

Meanwhile, the last three bow radar frames for the 13th show a very large lead opening immediately in front of the Polarstern's bow if not right under the ship. We have no better time resolution for the cycle of closed, open, closed than 12 hours but it may have been much shorter. The lead is 68m wide on average; 6 km of length is visible to the outer edge of the image. It is a rocker event, so more a pivot than a shear.

This may or may not have done any damage to gangways, ice anchors, cables and experimental set-ups. It's possible field work was ongoing despite the miserable weather and staff separated by open water from the ship. Radar coverage of the experimental area has been blocked out the entire trip whereas N-ICE2015 had full 360º coverage.

All we know for certain at this time is that 'Follow Mosaic' will downplay -- or not even mention -- the incident no matter how much damage it caused. Indeed the 13th on FOMO is all smiles on a nitrate survey on yet another idyllic day.

The ship is in a surprisingly active area of ice motion due to a small cyclone enveloping it so this event will not be the end of it.
« Last Edit: September 14, 2020, 04:24:56 PM by A-Team »

FishOutofWater

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Re: MOSAiC news
« Reply #1157 on: September 14, 2020, 02:57:08 PM »
As the light goes away and the inversions over the ice intensify the ice edge becomes like a stationary front between air masses because the water still has heat. The pole is shockingly close to the ice edge this September so storms will be intensified by the boundary and can be expected to cause the Mosaic team many challenges.

The large scale synoptic pattern has chains of storms tracking from the north Atlantic into the subpolar seas and into the Arctic ocean proper. The record high heat content of the north Atlantic and possibly the Atlantic side of the Arctic ocean is contributing to the storminess. We won't hear about the impacts of these storms from the PR person, but expect more of them. The effects of the loss of sea ice on the Atlantic side of the Arctic ocean are affecting CFS model forecasts of the location of the polar vortex this fall, causing it to move towards the north Atlantic in the model. If this verifies, storminess will be intensified in the Barents and Kara seas as winter sets in.

I would guess that graupel was falling before it turned to freezing rain. Graupel is icy snow, a tiny ice ball with a core of snow.

uniquorn

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Re: MOSAiC news
« Reply #1158 on: September 14, 2020, 03:46:39 PM »
Quote
Somewhere up-forum, all the weather commentaries for the entire expedition was extracted into a flatfile database and a MS Word-type glossary system proposed to stub in the code lookups to eliminate tedious and error-prone code lookups. No one picked up that baton.

63 downloads, quite popular. Though no further analysis from them.
Looking at some thread stats is valid as we near the end of the mosaic project. Gauging popularity of areas of analysis can be useful to determine viewer interest and whether sizing an animation to fit the forum's tight limits is worth the effort

Thanks, I hadn't  heard of diamond dust or graupel before.

A-Team

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Re: MOSAiC news
« Reply #1159 on: September 14, 2020, 05:10:17 PM »
Quote
FooW: consider the big picture
This is helpful. We are taken up documenting day to day noise but it is all happening for underlying climate change reasons.

The composite below looks at the position of the Polarstern relative to the North Pole, the AMSR2 pole hole of no data, the wind power density, the distance to the ice edge, and a cyclonic storm barreling up from the North Atlantic that has brought measurable precipitation (2nd image, 3hr accumulation).

The ship has been drifting rapidly and may reach the pole yet though the ice we wanted them to look at will have drifted away. They are currently 454 km away from the ice edge based on the pixel ratio for the pole to Morris Jesup. Note a strong wind is bearing down on a vulnerable region of ice north of SevZem which could still dramatically lower its concentration.

Both images benefit from a click. You are wasting your time on this forum if not looking beyond thumbnails. We cannot accurately downscale indexed color.
« Last Edit: September 14, 2020, 05:35:29 PM by A-Team »

A-Team

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Re: MOSAiC news
« Reply #1160 on: September 15, 2020, 03:57:16 PM »
The worst ice movement of the whole year-long expedition is happening. It is probably not a risk to the ship itself (though the rudder got rammed by a floe earlier) but puts experimental equipment out on the ice in jeopardy.

'Follow Mosaic' has not said if they can keep field work going safely under these conditions; in the past, great effort went into just keeping power lines out and sensors upright and running. Today's post is all about chlorophyll, fading light and zooplankton. The photo could be a week old for all we know.

It's hard to see the scientific value of sampling a hole or two over winter in an immense ocean; how long will biological data stay relevant in the fast-changing Arctic. Does AWI believe the coming BOE will bring a fisheries and fossil fuel bonanza?

https://www.meereisportal.de/en/mosaic/sea-ice-ticker/ #53  diatom Melosira arctica
https://www.tandfonline.com/doi/abs/10.1080/0269249X.2013.877085
« Last Edit: September 16, 2020, 02:13:59 PM by A-Team »

uniquorn

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Re: MOSAiC news
« Reply #1161 on: September 15, 2020, 07:54:21 PM »
drift speed increased during sep13-14. click for motion

uniquorn

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Re: MOSAiC news
« Reply #1162 on: September 15, 2020, 09:32:47 PM »
That 25km2 of bow radar might overlay nicely onto buoy drift now that it is relatively static. A shame it's not hourly.
This is a wider view of the previous animation here with the tight cluster at the centre.

intermittent light snow


  Lat  Long  YY-MM-DD  UTC     Wind       T(C)  N  h  VV  wwWW  ICE  Pnn(hPa)
  89.1  108.3 20-09-15 20:00    4  230     -4.6  /  /  //  //// ///// 1005.2
  89.1  108.1 20-09-15 19:00    5  210     -4.9  /  /  //  //// ///// 1005.2
  89.1  107.9 20-09-15 18:00    5  200     -4.7  /  /  //  //// ///// 1004.9
  89.1  107.6 20-09-15 17:00    4  220     -4.7  /  /  //  //// ///// 1004.8
  89.1  107.3 20-09-15 16:00    4  230     -4.9  /  /  //  //// ///// 1004.8
  89.1  107.1 20-09-15 15:00    4  200     -4.9  8  2  98  7082 49/9/ 1004.7
« Last Edit: September 16, 2020, 11:26:40 AM by uniquorn »

A-Team

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Re: MOSAiC news
« Reply #1163 on: September 16, 2020, 02:55:26 PM »
The frenetic motion of floes continued for another day on Sept 15th. The bouncing floe within the open lead is 170x170m; the scale is 10m per pixel. Impacts on Mosaic operations remain undisclosed.

The Polarstern is represented by the gray ball; it is moored with its starboard bow against the ice (not shown as blocked from radar), so the bow is pointing east in the time series and ice motion below the ship is black (not visualized). The frames are 0.1 sec apart vs 6 hours apart on board so the motion is sped up 6*60*60*10 = 216,000 times, a lot but less than commonly done for Jakobshavn or Petermann glaciers.

The last frame is midnight on Sept 15th. The floe is at 89.1º latitude with air temperatures -4º, low enough to put a much-fractured ice skim on opening/closing leads. They do have kayaks on board but helicopter, fog permitting, is the main way to reach stranded equipment if indeed their specific floe is affected.

The winds at the ship have died down considerably from their peak of 16m/s but wind stress nearby can still propagate ice motion to their site.

The avi's frame of reference, while basically co-moving (lagrangian), has never been explained. The radar antenna rotates in a full circle, taking less than a minute to capture its scene. Of the 360 scenes taken per six hours, only one is retained for the shared video. The rest are shown on the bridge and also on meeting room monitors.

The bridge also has an instrument that measures ship heading, the angle between the mid-ship half-axial line and a line to north pole. (The magnetic pole cannot be used in the high Arctic.) This heading is shared to the radar display along with other parameters that have all been cropped out, with truncated 2dp lat lon and timestamp restored.

In production, each frame is rotated as specified by ship heading so north is always straight up the white scale bar. The ship is rigidly attached on its starboard side its floe by six sea anchors except when it breaks loose; anchors are checked and re-sunk daily as necessary.

The floe commonly rotates during the six hour gap between frames. This causes the 83º black-out area to rotate after correction to the fixed north pole heading. Recent months have seen a red ball added to each image to indicate the ship, rather than a more logical icon that shows bow and stern.

The center of the radar image (which verifies as a true circle) lies near the bottom of this red ball, NOT on its center. This is the location of the bridge mast on which the rotating radar is mounted several dozen meters above the water.

We do not know if the black-out area is symmetric with respect to the ship's long axis (perhaps because of intervening metal masts or smokestack); it may not extend to the experimental area to avoid rfi. If so, ice immediately port side is shown. The comparable radar on N-ICE2015 showed 360º.

The clumsy north icon obscuring the data is a recent add-on that serves no known purpose. It walks east and west without holding its lat lon, its position seemingly in accordance with blackout zone rotation.

Because the ship is so close to the pole, latitude lines converge rapidly. Only the white bar center goes straight up. Other latitude lines are straight but angled appropriately. The longitude lines are convex up and likely the expected arcs of circles.

The floe is mostly drifting along with the regional ice pack (which is known compact, ie at 100% sea ice concentration at 3x3 km resolution) but sometimes cohesive motion breaks down and floes in the scene have quasi-independent motions compatible with each other's constraints.

Motion of the Polarstern can be marked up within the video by tracking a lat lon intersection between frames. This gives jointed line segments and segmental mean velocities at six hour intervals. However GPS on ship and adjacent buoys are half-hourly or less with 4 dp precision, meaning a spreadsheet with a haversine column shows ship rotations and translations much better. as seen in uniq's many buoy products.

The speeds are rather high relative to those seen during the past year, over 1.2 km/hr for extended stretches. The Polarstern was subjected to a CCW gale force wind (small cyclone) during the affected period, likely responsible for the stress leading to the dramatic ice break-up motions.

The red bars on the buoy speed graphs show that six-hour sampling is not close enough to capture ups and downs in floe speeds whereas the half-hour buoy iridium call are satisfactory.

The buoy data is at the meereis gallery; the excel-ready haversine formula needs lat lon data in the first two columns; the csv speed file is attached.

=ACOS(COS(RADIANS(90-A2)) * COS(RADIANS(90-A3)) + SIN(RADIANS(90-A2)) *SIN(RADIANS(90-A3)) *COS(RADIANS(B2-B3))) *6356.752

https://tinyurl.com/yx9yle3o

uniquorn

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Re: MOSAiC news
« Reply #1164 on: September 16, 2020, 09:36:21 PM »
Probably best with VR headset but you can use the mouse (or finger) to look around. Look up first to  lose the auditorium.


uniquorn

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Re: MOSAiC news
« Reply #1165 on: September 16, 2020, 10:05:08 PM »
A lot of good videos on https://twitter.com/seaice_de

Quote
The Polarstern is represented by the gray ball; it is moored with its starboard bow against the ice
Quote
Lars Kaleschke@seaice_de
12 Sep  Too much tension? Be careful with the anchor line. A very dangerous environment. @MOSAiCArctic  - April 28



A-Team

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Re: MOSAiC news
« Reply #1166 on: September 18, 2020, 11:37:28 AM »
Floe motion is as crazy as ever around the Polarstern's position of 89.1  107.4 despite mild winds of 4m/s and cold temperatures of -9.4ºC. Despite two weeks of increasing ice chaos documented on bow radar, there has been no mention to date of its effects on scientific equipment deployment on Follow  :) :) :) Mosaic.

Instead, various science for science sake studies on snow flakes and algae are described that seem like escapism. Thee could just as well have been done in the Baltic. It might have been better to have just concentrated on studies relevant to climate change. There's been almost no mention of that over the last year.

The six hour time series raises questions about whether distinct floes exist at this near-pole site. What's seen are blocks of ice joining up with other blocks of ice, then leaving for another. When that repeats, the block boundaries are often different with new fractures and leads as boundaries. Spatial constraints limit the options though so despite many breaks and rejoins the picture can eventual return to resemble to the start.

The notion of solid SYI ice blocks welded together into a matrix with weak intervening FYI freezes doesn't seem applicable. Without having the whole history of formation, how are floe boundaries defined if most are ever-changing composites?
« Last Edit: September 18, 2020, 12:00:32 PM by A-Team »

OffTheGrid

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Re: MOSAiC news
« Reply #1167 on: September 18, 2020, 08:37:02 PM »
Watch out Mosaic!

There's been 14 second swells of 0.2 m coming out on the ESAS, AFTER passing all the way from Fram, under them <reader beware, this is nonsense>. May be having the effect you point out on the floe motion ATeam.
Also outburst flushing from Greenland, which looks to be going through exponential runaway geothermal blowout <reader beware, nonsense>, has been launching submarine landslides that are shedding violent fresh upwellings, and possibly mini tsunami surges, which could look like standard tidal effects, since the subglacial outbursts occur primarily at high tides. <nonsense>
Their "pretty frost flowers" are sadly a symptom of large energy injection from water vapour condensing. Driving bottom melt.
Gotta click the stupid gif to see the 11m long period waves heading for them in a few days.

<Warnings added. Posts must be fact-based. O>
« Last Edit: September 19, 2020, 06:39:14 PM by oren »

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Re: MOSAiC news
« Reply #1168 on: September 19, 2020, 05:34:05 AM »
Also outburst flushing from Greenland, which looks to be going through exponential runaway geothermal blowout, has been launching submarine landslides that are shedding violent fresh upwellings ... and possibly mini tsunami surges, which could look like standard tidal effects, since the subglacial outbursts occur primarily at high tides.

What are you smoking?
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Re: MOSAiC news
« Reply #1169 on: September 19, 2020, 12:00:28 PM »
Makes mostly sense to me,  a different style of writing, but then.. I am a smoker :)
I have been thinking about submarine landslides. Also to try to understand the north-east Greenland strangeness.
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A-Team

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Re: MOSAiC news
« Reply #1170 on: September 19, 2020, 01:57:09 PM »
The Mosaic expedition seems to be winding down/falling apart despite being scheduled to continue until Oct 12th. That's not unusual, the horse begins to gallop when it smells the barn.

It hasn't been made clear whether the 12th is the date when field equipment is borught in and the engines fired up or the date of arrival at the dock in Tromsø. The ice has been thickening but not to point where the return passage of a week would be hindered.

The ship's position is currently 89.1  110.7, quite close to the pole but some 2274km from port at 69.6 18.9 which would require about 100 hours of travel time in calm seas.

Ice movement yesterday continued to be extreme, or rather no one seemed to have suspected prior to the expedition what the new normal would be. The long lead re-opened again; it extends off the edge of the radar so 5km or more. The pack also has a bulk rotational component and that 179m broken-off floe pounding on the port side of the ship. This is surprising since the winds at their position have been brisk but not exceptional, below 10m/s.

uniquorn

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Re: MOSAiC news
« Reply #1171 on: September 19, 2020, 03:35:13 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
« Last Edit: September 19, 2020, 03:52:43 PM by uniquorn »

gandul

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Re: MOSAiC news
« Reply #1172 on: September 19, 2020, 04:01:39 PM »
Interesting gifs, now I understand offthegrid a bit better.

binntho

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Re: MOSAiC news
« Reply #1173 on: September 19, 2020, 04:09:06 PM »
Makes mostly sense to me,  a different style of writing, but then.. I am a smoker :)
I have been thinking about submarine landslides. Also to try to understand the north-east Greenland strangeness.

So "exponential runaway geothermal blowout" makes sense to you? OTG entire line of reasoning is from never-never land and does not apply to planet Earth. EDIT: In fact it's so totally off the grid that I suspect OTG is a nom-de-plume of someone making fun of us by threading pseudoscientific waffles on his hook and seeing how many bites he gets.
« Last Edit: September 19, 2020, 04:38:21 PM by binntho »
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binntho

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Re: MOSAiC news
« Reply #1174 on: September 19, 2020, 04:14:32 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
Absolutely (grrmble grrmble) and the gif is fantastic, almost like a Micky Mouse picture. But as usual I miss scale from your gifs, and it is tedious to have to freeze two frames, read the coordinates and then calculate the distance to see that your gif is appr. 10 x 5 km square.

EDIT: The speed of drift swings between 10% and 20% of normal walking speed. And the tidal swings are only a few hundred meters each way. The circular movement I guess has more to do with changing wind direction than anything else.
« Last Edit: September 19, 2020, 04:23:40 PM by binntho »
because a thing is eloquently expressed it should not be taken to be as necessarily true
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uniquorn

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Re: MOSAiC news
« Reply #1175 on: September 19, 2020, 04:22:04 PM »
The default scale is utm km which may be reasonably accurate this close to the pole, though confusing to some, so I normally remove it. Recent location of most of the nearest buoys to PS

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Re: MOSAiC news
« Reply #1176 on: September 19, 2020, 05:53:55 PM »

EDIT: The speed of drift swings between 10% and 20% of normal walking speed. And the tidal swings are only a few hundred meters each way. The circular movement I guess has more to do with changing wind direction than anything else.

Great. As you guessed that one hopefully you will run the numbers to prove it. Hourly wind direction from PS is here   P169 is near if you need buoy data.
I suspect it is the combination of both since wind drift appears to be of the same order of magnitude as 'tidal drift' and it's a more likely explanation than continuous tight wind vortexes at multiples of walking speed. 

Here attempting to overlay the tight group of buoys onto bow radar. Maybe they are either side of a fault line or along a ridge. click for animation.
« Last Edit: September 19, 2020, 08:57:07 PM by uniquorn »

oren

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Re: MOSAiC news
« Reply #1177 on: September 19, 2020, 06:40:19 PM »
OTG, I will delete further fantasy nonsense posts, be warned.

A-Team

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Re: MOSAiC news
« Reply #1178 on: September 19, 2020, 09:56:46 PM »
FOMO today: the last of the off-ship experimental equipment is being brought on board for a Sept 20th departure. The original plan called for Oct 15th but that was later changed to Oct 12th. They first set up on Oct 4th of 2019. They arrived at the North Pole on Aug 20th 2020and to their present floe shortly thereafter, so a month moored and a bare minimum of the freezing season sampled.

It may take them a while to reach the ice edge from where they are with helicopter fog, ice pressure and thickness hindering progress but open leads and intermediate concentration favoring it. The Polarstern can do some work while underway, notably surface water chemistry, disposable CTD casts and ice thickness measurements.

It's possible the ship will pause underway or near the ice edge to study the ice for a while. The return port is Bremerhaven as there are no more trip legs and no reason to meet up in Norway.

A truly massive logistical effort under trying conditions that they accomplished safely. It's too soon to say what scientific advances will come out of all the data collected (which launched buoys will continue for years). It seems like the primary focus was atmospheric boundary layer processes though of course they looked at everything imaginable.

As a guess: incremental improvement in many areas of our understanding of the Arctic but no real game-changers in terms of radical improvements to satellite interpretation or seasonal ice prediction from improved models.
« Last Edit: September 20, 2020, 04:41:48 AM by A-Team »

A-Team

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Re: MOSAiC news
« Reply #1179 on: September 20, 2020, 04:49:17 AM »
I went through the last 45 days of preprints at The Cryosphere journal looking for new Mosaic articles. There was a third one there, another N-ICE2015 piece now five years out, and quite a few others of interest to this and other Arctic forums, select ones below.

Most of the articles have quite readable sections, better than the abstracts. It's seldom a good idea to get too far from the mainstream in forum posts so these provide a good baseline for those wanting anchors to reality.
.
Never forget that extraordinary claims require extraordinary evidence. The burden of proof is always on the proposer; there is no burden of disproof on the non-believer.

Estimating statistical errors in retrievals of ice velocity and deformation parameters from satellite images and buoy arrays
https://tc.copernicus.org/articles/14/2999/2020/

Sea ice drifts under the influence of wind and ocean currents. Spatial gradients in the sea ice motion lead to distortion of the sea ice cover, termed deformation. The retrieval of sea ice drift vectors and deformation parameters from pairs or sequences of satellite synthetic aperture radar (SAR) images has gained increased attention during recent years because of the growing availability of suitable data.. Sea ice kinematics is also studied based on data from arrays of buoys or GPS receivers   which in addition can serve as reference in comparisons to motion vectors obtained from SAR images. The knowledge of spatially detailed motion and deformation fields is potentially useful in ice navigation to locate divergent or compressive ice areas, as complementary information for operational sea ice mapping, for validation of models for forecasting of ice conditions, and for assimilation into ice models.

Seasonal transition dates can reveal biases in Arctic sea ice simulations
https://tc.copernicus.org/articles/14/2977/2020/

Arctic sea ice experiences a dramatic annual cycle, and seasonal ice loss and growth can be characterized by various metrics: melt onset, breakup, opening, freeze onset, freeze-up, and closing. By evaluating a range of seasonal sea ice metrics, CMIP6 sea ice simulations can be evaluated in more detail than by using traditional metrics alone, such as sea ice area. We show that models capture the observed asymmetry in seasonal sea ice transitions, with spring ice loss taking about 1–2 months longer than fall ice growth. The largest impacts of internal variability are seen in the inflow regions for melt and freeze onset dates, but all metrics show pan-Arctic model spreads exceeding the internal variability range, indicating the contribution of model differences. Through climate model evaluation in the context of both observations and internal variability, we show that biases in seasonal transition dates can compensate for other unrealistic aspects of simulated sea ice. In some models, this leads to September sea ice areas in agreement with observations for the wrong reasons.

New insights into radiative transfer in sea ice derived from autonomous ice internal measurements
https://tc.copernicus.org/preprints/tc-2020-184/

The radiative transfer of short-wave solar radiation through the sea ice cover of the polar oceans is a crucial aspect of energy partitioning at the atmosphere-ice-ocean interface. A detailed understanding of how sunlight is reflected and transmitted by the sea ice cover is needed for an accurate representation of critical processes in climate and ecosystem models, such as the ice-albedo feedback. Due to the challenges associated with ice internal measurements, most information about radiative transfer in sea ice has been gained by optical measurements above and below the sea ice. To improve our understanding of radiative transfer processes within the ice itself, we developed a new kind of instrument equipped with a number of multispectral light sensors that can be frozen into the ice. A first prototype consisting of a 2.3 m long chain of 48 sideward planar irradiance sensors with a vertical spacing of 0.05 m was deployed at the geographic North Pole in late August 2018, providing autonomous, vertically resolved light measurements within the ice cover during the autumn season. Here we present the first results of this instrument, discuss the advantages and application of the prototype and provide first new insights into the spatiotemporal aspect of radiative transfer within the sea ice itself. In particular, we investigate how measured attenuation coefficients relate to the optical properties of the ice pack, and show that sideward planar irradiance measurements are equivalent to measurements of total scalar irradiance.

Implications of surface flooding on airborne thickness measurements of snow on sea ice
https://tc.copernicus.org/preprints/tc-2020-168/

Snow thickness observations from airborne snow radars, such as the NASA’s Operation IceBridge (OIB) mission, have recently been used in altimeter-derived sea ice thickness estimates, as well as for model parameterization. A number of validation studies comparing airborne and in situ snow thickness measurements have been conducted in the western Arctic Ocean, demonstrating the utility of the airborne data. However, there have been no validation studies in the Atlantic sector of the Arctic. Recent observations in this region suggest a significant and predominant shift towards a snow-ice regime, caused by deep snow on thin sea ice. During the Norwegian young sea ICE expedition (N-ICE2015) in the area north of Svalbard, a validation study was conducted on March 19, 2015, during which ground truth data were collected during an OIB overflight. Snow and ice thickness measurements were obtained across a two dimensional (2-D) 400 m × 60 m grid. Additional snow and ice thickness measurements collected in situ from adjacent ice floes helped to place the measurements obtained at the gridded survey field site into a more regional context. Widespread negative freeboards and flooding of the snow pack were observed during the N-ICE2015 expedition, due to the general situation of thick snow on relatively thin sea ice. These conditions caused brine wicking and saturation into the basal snow layers, causing more diffuse scattering and influenced the airborne radar signal to detect the radar main scattering horizon well above the snow/sea ice interface

Trends and spatial variation in rain-on-snow events over the Arctic Ocean during the early melt season
https://tc.copernicus.org/preprints/tc-2020-214/

 Rain-on-snow (ROS) events can accelerate the surface ablation of sea ice, thus greatly influencing the ice-albedo feedback. However, the variability of ROS events over the Arctic Ocean is poorly understood due to limited historical station data in this region. In this study early melt season ROS events were investigated based on four widely-used reanalysis products (ERA-Interim, JRA-55, MERRA2 and ERA5) in conjunction with available observations at Arctic coastal stations. The performance of the reanalysis products in representing the timing of ROS events and the phase change of precipitation was assessed. Our results show that ERA-Interim better represents the onset date of ROS events in spring and ERA5 better represents the phase change of precipitation associated with ROS events. All reanalyses indicate that ROS event timing has shifted to earlier dates in recent decades (with maximum trends up to −4 to −6 days/decade in some regions in ERA-Interim), and that sea ice melt onset in the Pacific sector and most of the Eurasian marginal seas is correlated with this shift. There has been a clear transition from solid to liquid precipitation, leading to more ROS events in spring, although large discrepancies were found between different reanalysis products. In ERA5, the shift from solid to liquid precipitation phase during the early melt season has directly contributed to a reduction in spring snow depth on sea ice by more than −0.5 cm/decade averaged over the Arctic Ocean since 1980, with the largest contribution (about −2.0 cm/decade) in the Kara-Barents Seas and Canadian Arctic Archipelago.

Methane cycling within sea ice; results from drifting ice during late spring, north of Svalbard
https://tc.copernicus.org/preprints/tc-2020-208/tc-2020-208.pdf

Sea ice is an important component of the Arctic system playing a significant role for gas exchange between ocean and atmosphere. However, global warming has led to a sharp retreat of sea ice coverage in the Arctic Ocean during the last decades. During 2019 sea ice covered 4.15 million km2 in summer representing a decrease of 33 % compared to the 1981-2010 average (Perovich et al., 2019). The negative downward trend in Arctic summer sea ice coverage has been observed for more than 30 years. This tendency is expected to continue  over the next decades   including a cascade of possible associated effects. In particular, sea ice retreat may quickly induce enhanced methane (CH4) emissions into the atmosphere due to the loss of its barrier function
for sea-air gas exchange. Because the Arctic holds large natural sources of this highly potent
greenhouse gas, this effect has to be considered as positive feedback of global warming. Moreover, the resulting decreased temporal flux retention of methane under the ice reduces oxidation intensity to the less potent CO2

Seasonal changes in sea ice kinematics and deformation in the Pacific Sector of the Arctic Ocean in 2018/19
https://tc.copernicus.org/preprints/tc-2020-211/

Arctic sea ice kinematics and deformation play significant roles in heat and momentum exchange between atmosphere and ocean. However, mechanisms regulating their changes at seasonal scales remain poorly understood. Using position data of 32 buoys in the Pacific sector of the Arctic Ocean (PAO), we characterized spatiotemporal variations in ice kinematics and deformation for autumn–winter 2018/19. In autumn, sea ice drift response to wind forcing and inertia were stronger in the southern and western than in the northern and eastern parts of the PAO. These spatial heterogeneities decreased gradually from autumn to winter, in line with the seasonal evolution of ice concentration and thickness. Areal localization index decreased by about 50 % from autumn to winter, suggesting the enhanced localization of intense ice deformation as the increased ice mechanical strength. In winter 2018/19, a highly positive Arctic Dipole and a weakened high pressure system over the Beaufort Sea led to a distinct change in ice drift direction and an temporary increase in ice deformation. During the freezing season, ice deformation rate in the northern part of the PAO was about 2.5 times that in the western part due to the higher spatial heterogeneity of oceanic and atmospheric forcing in the north. North–south and east–west gradients in sea ice kinematics and deformation of the PAO observed in autumn 2018 are likely to become more pronounced in the future as sea ice losses at higher rates in the western and southern than in the northern and western parts.

Clouds damp the radiative impacts of polar sea ice loss
https://tc.copernicus.org/articles/14/2673/2020/

Clouds play an important role in the climate system: (1) cooling Earth by reflecting incoming sunlight to space and (2) warming Earth by reducing thermal energy loss to space. Cloud radiative effects are especially important in polar regions and have the potential to significantly alter the impact of sea ice decline on the surface radiation budget. Using CERES (Clouds and the Earth's Radiant Energy System) data and 32 CMIP5 (Coupled Model Intercomparison Project) climate models, we quantify the influence of polar clouds on the radiative impact of polar sea ice variability. Our results show that the cloud short-wave cooling effect strongly influences the impact of sea ice variability on the surface radiation budget and does so in a counter-intuitive manner over the polar seas: years with less sea ice and a larger net surface radiative flux show a more negative cloud radiative effect. Our results indicate that 66±2% of this change in the net cloud radiative effect is due to the reduction in surface albedo and that the remaining 34±1 % is due to an increase in cloud cover and optical thickness. The overall cloud radiative damping effect is 56±2 % over the Antarctic and 47±3 % over the Arctic. Thus, present-day cloud properties significantly reduce the net radiative impact of sea ice loss on the Arctic and Antarctic surface radiation budgets. As a result, climate models must accurately represent present-day polar cloud properties in order to capture the surface radiation budget impact of polar sea ice loss and thus the surface albedo feedback.

A linear model to derive melt pond depth on Arctic sea ice from hyperspectral data
https://tc.copernicus.org/articles/14/2567/2020/

Melt ponds are key elements in the energy balance of Arctic sea ice. Observing their temporal evolution is crucial for understanding melt processes and predicting sea ice evolution. Remote sensing is the only technique that enables large-scale observations of Arctic sea ice. However, monitoring melt pond deepening in this way is challenging because most of the optical signal reflected by a pond is defined by the scattering characteristics of the underlying ice. Without knowing the influence of meltwater on the reflected signal, the water depth cannot be determined. To solve the problem, we simulated the way meltwater changes the reflected spectra of bare ice. We developed a model based on the slope of the log-scaled remote sensing reflectance at 710 nm as a function of depth that is widely independent from the bottom albedo and accounts for the influence of varying solar zenith angles. We validated the model using 49 in situ melt pond spectra and corresponding depths from shallow ponds on dark and bright ice Our results indicate that our model enables the accurate retrieval of pond depth on Arctic sea ice from optical data under clear sky conditions without having to consider pond bottom albedo. This technique is potentially transferrable to hyperspectral remote sensors on unmanned aerial vehicles, aircraft and satellites.

Surface-Based Ku- and Ka-band Polarimetric Radar for Sea Ice Studies
https://tc.copernicus.org/preprints/tc-2020-151/ Mosaic

To improve our understanding of how snow properties influence sea ice thickness retrievals from presently operational and upcoming satellite radar altimeter missions, as well as investigating the potential for combining dual frequencies to simultaneously map snow depth and sea ice thickness, a new, surface-based, fully-polarimetric Ku- and Ka-band radar (KuKa radar) was built and deployed during the 2019–2020 year-long MOSAiC International Arctic drift expedition. This instrument, built to operate both as an altimeter (stare mode) and a scatterometer (scanning mode), provided the first in situ Ku- and Ka-band dual frequency radar observations from autumn freeze-up through mid-winter, and covering newly formed ice in leads, first-year and second-year ice floes. Data gathered in the altimeter mode, will be used to investigate the potential for estimating snow depth as the difference between dominant radar scattering horizons in the Ka- and Ku-band data. In the scatterometer mode, the Ku- and Ka-band radars operated under a wide range of azimuth and incidence angle ranges, continuously assessing changes in the polarimetric radar backscatter and derived polarimetric parameters, as snow properties varied under varying atmospheric conditions. These observations allow for characterizing radar backscatter responses to changes in atmospheric and surface geophysical conditions. In this paper, we describe the KuKa radar and illustrate examples of these data and demonstrate their potential for these investigations.

Simulated Ka- and Ku-band radar altimeter scattering horizon on snow-covered Arctic sea ice
https://tc.copernicus.org/preprints/tc-2020-196/Surface-Based Ku- and Ka-band Polarimetric Radar for Sea Ice Studies

Owing to differing and complex snow geophysical properties, radar waves of different wavelengths undergo variable penetration through snow-covered sea ice. However, the mechanisms influencing radar altimeter backscatter from snow-covered sea ice, especially at Ka- and Ku-band frequencies, and its impact on the Ka- and Ku-band radar scattering horizon or the "track point" (i.e. the scattering layer depth detected by the radar re-tracker), are not well understood. In this study, we evaluate the Ka- and Ku-band radar scattering horizon with respect to radar penetration and ice floe buoyancy using a first-order scattering model and Archimedes’ principle. Our simulations demonstrate that the Ka- and Ku-band track point difference is a function of snow depth, however, the simulated track point difference is much smaller than what is reported in the literature from the CryoSat-2 Ku-band and SARAL/AltiKa Ka-band satellite radar altimeter observations. We argue that this discrepancy in the Ka- and Ku-band track point differences are sensitive to ice type and snow depth and its associated geophysical properties. Snow salinity is first increasing the Ka- and Ku-band track-point difference when the snow is thin and then decreasing the difference when the snow is thick (> 10 cm). A relationship between the Ku-band radar scattering horizon and snow depth is found. This relationship has implications for 1) the use of snow climatology in the conversion of radar freeboard into sea ice thickness and 2) the impact of variability in measured snow depth on the derived ice thickness.
« Last Edit: September 20, 2020, 05:06:54 AM by A-Team »

binntho

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Re: MOSAiC news
« Reply #1180 on: September 20, 2020, 06:49:20 AM »

EDIT: The speed of drift swings between 10% and 20% of normal walking speed. And the tidal swings are only a few hundred meters each way. The circular movement I guess has more to do with changing wind direction than anything else.

Great. As you guessed that one hopefully you will run the numbers to prove it. Hourly wind direction from PS is here   P169 is near if you need buoy data.
I suspect it is the combination of both since wind drift appears to be of the same order of magnitude as 'tidal drift' and it's a more likely explanation than continuous tight wind vortexes at multiples of walking speed. 
A guess does not need proof. Circular motion needs explanation, and I'm at a loss to see what else it could be. Some sort of ocean current turbulence is of course also a possibility, but less likely to my mind.

The drift speed is not at "multiples of walking speed" in normal parlance. Slow strolling is 1m/s, while brisk walking is nearer to 1.5 m/s. The buyos drift speed swings around 0.1 m/s. I'm not sure what you mean by "tidal drift", I don't think such a thing exists. But the sideways pulsation of water every 6 hours sems to be in the region of a few hundred meters each way every 6 hours, translating into a slow pendulum swing at 0.02 m/s.

Uniqorn's animation (repeated below) does not indicate any wind vortexes at any speed. The twoo loops at the center of the image can be seen as a result of slow drift closely aligned to the direcion of the tidal pulse. If we were to remove the tidal factor, the buoy movement would paint a circle with a radius of 1 or 2 km over a three day period. Changes in wind direction seems the most likely explanation, but it is of course the surrounding ice that is moving and the forces causing the changes in movement could just as well be found hundreds of kms distant.

because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

oren

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Re: MOSAiC news
« Reply #1181 on: September 20, 2020, 09:01:19 AM »
I went through the last 45 days of preprints at The Cryosphere journal looking for new Mosaic articles. There was a third one there, another N-ICE2015 piece now five years out, and quite a few others of interest to this and other Arctic forums, select ones below.
Thanks for this. It certainly makes an overworked half-brained layman like myself wish for more available study time. I have marked all articles and will attempt to read them, these seem highly relevant to the melting and/or freezing seasons and to long term forum debates.

u300673

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Re: MOSAiC news
« Reply #1182 on: September 20, 2020, 10:15:47 AM »

EDIT: The speed of drift swings between 10% and 20% of normal walking speed. And the tidal swings are only a few hundred meters each way. The circular movement I guess has more to do with changing wind direction than anything else.

Great. As you guessed that one hopefully you will run the numbers to prove it. Hourly wind direction from PS is here   P169 is near if you need buoy data.
I suspect it is the combination of both since wind drift appears to be of the same order of magnitude as 'tidal drift' and it's a more likely explanation than continuous tight wind vortexes at multiples of walking speed. 
A guess does not need proof. Circular motion needs explanation, and I'm at a loss to see what else it could be. Some sort of ocean current turbulence is of course also a possibility, but less likely to my mind.

The drift speed is not at "multiples of walking speed" in normal parlance. Slow strolling is 1m/s, while brisk walking is nearer to 1.5 m/s. The buyos drift speed swings around 0.1 m/s. I'm not sure what you mean by "tidal drift", I don't think such a thing exists. But the sideways pulsation of water every 6 hours sems to be in the region of a few hundred meters each way every 6 hours, translating into a slow pendulum swing at 0.02 m/s.

Uniqorn's animation (repeated below) does not indicate any wind vortexes at any speed. The twoo loops at the center of the image can be seen as a result of slow drift closely aligned to the direcion of the tidal pulse. If we were to remove the tidal factor, the buoy movement would paint a circle with a radius of 1 or 2 km over a three day period. Changes in wind direction seems the most likely explanation, but it is of course the surrounding ice that is moving and the forces causing the changes in movement could just as well be found hundreds of kms distant.


Have you considered inertial oscillations (e.g. https://tc.copernicus.org/articles/6/1187/2012/tc-6-1187-2012.pdf) ?

A-Team

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Re: MOSAiC news
« Reply #1183 on: September 20, 2020, 11:48:08 AM »
Quote
Have you considered near-inertial oscillations?
No they haven't. I've suggested it multiple times though and provided the semi-diurnal frequency using excel's spline fit to the discretized half hour buoy data in the Yermak Plateau area. Uniq provides fresh data links in #1176 but no one followed through. Project SHEBA went to some lengths to observe this effect; for a serious fluid dynamical treatment, the R Pinkel papers cover it.

From the recommended link above (Sea ice inertial oscillations in the Arctic Basin by F. Gimbert et al 2012):

"The effect of the Coriolis force on geophysical fluid dynamics has been studied for more than a century. Interestingly, the first studies of oceanic inertial oscillations (Ekman, 1905) were prompted by the observations of Nansen, made during the Fram’s journey along the Transpolar drift, that sea ice was moving with a 20–40º angle to the right of the wind direction (Nansen, 1902).

"Indeed, as the Coriolis force acts perpendicularly to the particle velocity, it induces a deviation of the trajectory to the right in the Northern Hemisphere. This deviation generates inertial
oscillations, characterized by a frequency of f = 2 sin(latitude in radians) cycles per day, close to a semi-diurnal frequency cycles per day in the Arctic."

The sine function takes on the value 1 at 90º giving two 12 hour cycles per day. After than it falls off slowly to zero at the equator. At Arctic latitudes, the frequency falls off quite slowly but remains quite distinguishable from tidal frequencies (not a big consideration at the Polarstern's location).

Lat   Sine(lat)   Sub-diurnal
90   1.0000   12.000
89   0.9998   12.002
88   0.9994   12.007
87   0.9986   12.016
86   0.9976   12.029
85   0.9962   12.046
84   0.9945   12.066
83   0.9925   12.090
82   0.9903   12.118
81   0.9877   12.150
80   0.9848   12.185
79   0.9816   12.225
78   0.9781   12.268
77   0.9744   12.316
76   0.9703   12.367
75   0.9659   12.423
74   0.9613   12.484
73   0.9563   12.548
72   0.9511   12.618
71   0.9455   12.691
70   0.9397   12.770

A free online scan of Nansen 1902 is at the links below; amazon sells a hard copy of the book for only $545.95. Despite text search, I have not been able to locate Nansen actually saying anything about ice drift angle with respect to wind direction. That seems to have been discussed only in volume III of Nansen's report (which is exhausively detailed) and only available for $35.

https://www.amazon.com/Norwegian-expedition-1893-1896-scientific-results/dp/1130729486

Ekman 1905 is an out of print book available on Johns Hopkins microfilm which can be read at the second link below.

Nansen, F.: Oceanography of the North Polar basin: the Norwegian
North Polar Expedition 1893–96, Scientific Results, 3, 1902.

https://www.biodiversitylibrary.org/item/57263#page/14/mode/1up
https://archive.org/details/norwegiannorthpo02framrich/page/n233/mode/2up?

Ekman, W.: On the influence of the earth’s rotation on ocean currents., Ark. Mat. Astron. Fys., 2, 1–52, 1905.

https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/33989/31151027498728.pdf?sequence=80&isAllowed=y
« Last Edit: September 20, 2020, 11:15:01 PM by A-Team »

uniquorn

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Re: MOSAiC news
« Reply #1184 on: September 20, 2020, 03:08:40 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
Absolutely (grrmble grrmble) and the gif is fantastic, almost like a Micky Mouse picture.<snippage>
No update from meereisportal buoys today.
Now, how to identify an inertial oscillation ice drift component, a tidal ice drift component and a wind driven ice drift component?
Note that the more northerly mickey mouse is flatter than the others.

binntho

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Re: MOSAiC news
« Reply #1185 on: September 20, 2020, 04:16:41 PM »
Amazing! I must admit that I have never heard of this inertial oscillation phenomenon. So no, I had not considered it ...

From the paper u300673 linked to above, and from A-Team's excellent post (as how could it not be) it seems that tidal oscillation and inertial oscillation have the same frequency and can easily be confused with each other.

Quote from: Sea ice inertial oscillations in the Arctic Basin
As the Arctic Basin lies between 70◦ and 90◦ of latitude, the inertial oscillation frequency varies from −1.88 to −2 cycles day−1 at these latitudes and is thus merged with the semi-diurnal tidal oscillation frequency. The differentiation of these two types of oscillations can be done by looking at the amplitude of the Fourier spectrum with respect to signed frequencies ...

So having considered inertial oscillation I find it easy to dismiss - it cannot explain the cyclical path of the buoy and so we are back to my first guess of changes in wind direction.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

SteveMDFP

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Re: MOSAiC news
« Reply #1186 on: September 20, 2020, 05:14:39 PM »
Amazing! I must admit that I have never heard of this inertial oscillation phenomenon. So no, I had not considered it ...

From the paper u300673 linked to above, and from A-Team's excellent post (as how could it not be) it seems that tidal oscillation and inertial oscillation have the same frequency and can easily be confused with each other.

Quote from: Sea ice inertial oscillations in the Arctic Basin
As the Arctic Basin lies between 70◦ and 90◦ of latitude, the inertial oscillation frequency varies from −1.88 to −2 cycles day−1 at these latitudes and is thus merged with the semi-diurnal tidal oscillation frequency. The differentiation of these two types of oscillations can be done by looking at the amplitude of the Fourier spectrum with respect to signed frequencies ...

So having considered inertial oscillation I find it easy to dismiss - it cannot explain the cyclical path of the buoy and so we are back to my first guess of changes in wind direction.

The inertial oscillation phenomenon is new to me, too.  But I suspect the quasi-circular motion of the buoys may depend on a confluence of factors--tides, inertial oscillation, wind, and also ocean turbulence with vortex formation.  The last might be the dominant factor here, just my guess.  In a region where vast flows are moving both north and south, vortex formation is inevitable.  And vortices are circular in motion.

gandul

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Re: MOSAiC news
« Reply #1187 on: September 20, 2020, 05:48:13 PM »
Amazing! I must admit that I have never heard of this inertial oscillation phenomenon. So no, I had not considered it ...

From the paper u300673 linked to above, and from A-Team's excellent post (as how could it not be) it seems that tidal oscillation and inertial oscillation have the same frequency and can easily be confused with each other.

Quote from: Sea ice inertial oscillations in the Arctic Basin
As the Arctic Basin lies between 70◦ and 90◦ of latitude, the inertial oscillation frequency varies from −1.88 to −2 cycles day−1 at these latitudes and is thus merged with the semi-diurnal tidal oscillation frequency. The differentiation of these two types of oscillations can be done by looking at the amplitude of the Fourier spectrum with respect to signed frequencies ...

So having considered inertial oscillation I find it easy to dismiss - it cannot explain the cyclical path of the buoy and so we are back to my first guess of changes in wind direction.

The inertial oscillation phenomenon is new to me, too.  But I suspect the quasi-circular motion of the buoys may depend on a confluence of factors--tides, inertial oscillation, wind, and also ocean turbulence with vortex formation.  The last might be the dominant factor here, just my guess.  In a region where vast flows are moving both north and south, vortex formation is inevitable.  And vortices are circular in motion.
Vortex effect: it either engulfs all the buoys in which case we would observe all buoys also rotating around a common center, or many vortices would be affecting the different buoys in which case the movement synchronicity would be lost.
So this factor must be really small
« Last Edit: September 20, 2020, 06:07:50 PM by gandul »

gandul

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Re: MOSAiC news
« Reply #1188 on: September 20, 2020, 06:06:07 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
Absolutely (grrmble grrmble) and the gif is fantastic, almost like a Micky Mouse picture.<snippage>
No update from meereisportal buoys today.
Now, how to identify an inertial oscillation ice drift component, a tidal ice drift component and a wind driven ice drift component?
Note that the more northerly mickey mouse is flatter than the others.
For each buoy, You could use a plane x,y (coordinates in your plot for instance) instead of lat lon to avoid arctifacts for being so close to the pole, then FFT the x and y components, get amplitude and phase for different frequencies and isolate translation and different modes of oscillation (x and y in phase or 180) or rotation (x and y in +/- 90 deg phase) in the 2D plane.
The wind drift won’t have a frequency in resonance with Earth rotation frequency (day)

SteveMDFP

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Re: MOSAiC news
« Reply #1189 on: September 20, 2020, 06:30:18 PM »

Vortex effect: it either engulfs all the buoys in which case we would observe all buoys also rotating around a common center, or many vortices would be affecting the different buoys in which case the movement synchronicity would be lost.
So this factor must be really small

Yes, you're right here.  My thinking hadn't fully developed on the possibility.  I'm sure there are lots of vortices in the region, but you're right that this idea does not explain the observed motion. 

A-Team

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Re: MOSAiC news
« Reply #1190 on: September 20, 2020, 07:01:02 PM »
Today will be the last day of bow radar. Note how the motion of the little floe is constrained by the walls of the lead around it, literally a boundary condition. This will also be the case at larger scales for the floe(s) bearing the buoys.

The little floe broke off 6 days ago and has been bouncing around ever since. What specifically accounts for its motions relative to the enveloping pack? Well, that would bring in some mix of all of the above.

FOMO screwed up royally again today, confusing Ctenophore with Cnidaria. These are different phyla that diverged in the late pre-Cambrian. 'Comb jellies' are very different beasts from 'jellyfish', they're only superficially related. Scientists have been working on the early evolution of Metazoa for centuries --  so inappropriate to ignore all that previous work and stub in ignorance on a public outreach site.

The ctenophore genomes of Mnemiopsis leidyi and Pleurobrachia bachei are much studied to understand the origin of vision and the nervous system, not to mention G-coupled protein receptors (the target of 50% of all human pharmaceuticals).

https://faculty.washington.edu/cemills/Ctenophores.html
https://academic.oup.com/gbe/article/12/2/3906/5729996
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3570280/
https://www.nature.com/articles/nature13400.pdf?origin=ppub
« Last Edit: September 20, 2020, 09:16:33 PM by A-Team »

uniquorn

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Re: MOSAiC news
« Reply #1191 on: September 20, 2020, 07:28:34 PM »
PS heading south, sailwx
updated
« Last Edit: September 20, 2020, 08:41:38 PM by uniquorn »

uniquorn

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Re: MOSAiC news
« Reply #1192 on: September 20, 2020, 09:11:14 PM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
Absolutely (grrmble grrmble) and the gif is fantastic, almost like a Micky Mouse picture.<snippage>
No update from meereisportal buoys today.
Now, how to identify an inertial oscillation ice drift component, a tidal ice drift component and a wind driven ice drift component?
Note that the more northerly mickey mouse is flatter than the others.
For each buoy, You could use a plane x,y (coordinates in your plot for instance) instead of lat lon to avoid arctifacts for being so close to the pole, then FFT the x and y components, get amplitude and phase for different frequencies and isolate translation and different modes of oscillation (x and y in phase or 180) or rotation (x and y in +/- 90 deg phase) in the 2D plane.
The wind drift won’t have a frequency in resonance with Earth rotation frequency (day)
ok. You seem to know how to do it. Here is gif of latest movement with data as txt. x and y are lon.utm and lat.utm. Let me know if you need anything else.

gandul

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Re: MOSAiC news
« Reply #1193 on: September 21, 2020, 12:42:38 AM »
drift update from P176.
2 submarine landslides a day seems unlikely. I think I'll stick with tides.
Absolutely (grrmble grrmble) and the gif is fantastic, almost like a Micky Mouse picture.<snippage>
No update from meereisportal buoys today.
Now, how to identify an inertial oscillation ice drift component, a tidal ice drift component and a wind driven ice drift component?
Note that the more northerly mickey mouse is flatter than the others.
For each buoy, You could use a plane x,y (coordinates in your plot for instance) instead of lat lon to avoid arctifacts for being so close to the pole, then FFT the x and y components, get amplitude and phase for different frequencies and isolate translation and different modes of oscillation (x and y in phase or 180) or rotation (x and y in +/- 90 deg phase) in the 2D plane.
The wind drift won’t have a frequency in resonance with Earth rotation frequency (day)
ok. You seem to know how to do it. Here is gif of latest movement with data as txt. x and y are lon.utm and lat.utm. Let me know if you need anything else.
No, thank you. I do for a living those sorts of things. I don’t have spare time, maybe once old and kids gone. I leave this to you, you kinda a genius, you do good.

oren

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Re: MOSAiC news
« Reply #1194 on: September 21, 2020, 08:47:42 AM »
It's time to thank you again uniquorn, for your immense analytic and graphical contribution on this thread and in many other threads. I am sure your time doesn't come free either. The output is much appreciated by me and by many other posters both silent and vocal, as well as by many lurkers I am sure.

A-Team

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Re: MOSAiC news
« Reply #1195 on: September 21, 2020, 11:34:49 AM »
Quote
great uniquorn contributions to forums
Looks like uniquorn was given some kind of big award for buoy work!

binntho

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Re: MOSAiC news
« Reply #1196 on: September 21, 2020, 11:45:57 AM »
It's time to thank you again uniquorn, for your immense analytic and graphical contribution on this thread and in many other threads. I am sure your time doesn't come free either. The output is much appreciated by me and by many other posters both silent and vocal, as well as by many lurkers I am sure.
Absolutely!
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

binntho

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Re: MOSAiC news
« Reply #1197 on: September 21, 2020, 12:19:07 PM »
The silly discussion above on what could be the cause of the circular movement of the buyo, i.e. the path shown in green below, has lead to a major discovery for me, and to a serious conundrum:

Are all of the "tidal movements" that uniqorn has been showing us in fact only "inertial oscillations"? Or only some of them? Which ones? How can we tell?

As A-Team has so boldly stated, tidal movement is negligible in the Arctic (or more precisely: Around Mosaic). Personally I have been of the same opinion regarding tides, but uniqorn did seem to have proved the opposite with his fantastic animations.

So what are we in fact looking at in all the wirls and curves around the green path line? Is it only the ice doing it's inertial oscillations on top of the ocean surface, is it the ocean itself inertially oscillating, is it the tidal pulse shifting waters back and forth or what?

I've made a very lukewarm search of tidal movements of Argo floats which would be incredibly interesting for comparison. Can tidal movement be seen at all in the drift of a typical Argo float in the North Atlantic (one of the strongest tidal areas) let alone in a near-todally-dead tidal zone such as the Mediterranean or the Arctic? What would the tidal signal look like in a buyo floating free of the ice pack?

All questions way above my pay grade.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

gandul

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Re: MOSAiC news
« Reply #1198 on: September 21, 2020, 02:36:36 PM »
I’d say there’s only one rotational mvmt of significance superposed to the green line, the red looks to me like a cycloid wrapped around. Is that the secondary oscillation that appears as the floe moves due to inertia-coriolis imbalance with 1/2 day period?


binntho

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Re: MOSAiC news
« Reply #1199 on: September 21, 2020, 03:42:26 PM »
I’d say there’s only one rotational mvmt of significance superposed to the green line,

Absolutely.

Quote
the red looks to me like a cycloid wrapped around. Is that the secondary oscillation that appears as the floe moves due to inertia-coriolis imbalance with 1/2 day period?
AKA inertial oscillation. This is exactly the question in my mind too - has uniqorn been showing us animations of tidal oscillation or inertial oscillation? And does that mean that there is no (or at the very most negligible) tidal movement in the Arctic?
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6