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Author Topic: Latest PIOMAS update (November)  (Read 816950 times)

miki

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Re: Latest PIOMAS update (January update)
« Reply #2250 on: January 06, 2018, 06:50:14 AM »
I've posted the latest PIOMAS update on the ASIB, including stuff about CryoSat and the situation wrt temps and snow cover: PIOMAS January 2018.

Thanks so much, Neven. Excellent summary, as usual.

A-Team

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Re: Latest PIOMAS update (January update)
« Reply #2251 on: January 09, 2018, 05:09:18 PM »
Quote
wip: thickness animation for the last month. It seems you need to click, even with size less than 700x700, for the animation to start.
I tested sizes on a tiny 3-frame animation over at DevCorner. It seems 601 width and above will not animate properly any more. 600 animates irregularly. 599 and below animate as before.

Note these slightly larger animation still load fully and take up exactly the same amount of server storage space, they just need a click-tab to get going. They do not record visitor view counts otherwise.

There was an admin setting shown once upon a time where the 700x700 was displayed as the choice. Maybe Neven changed that? Or it got defaulted down to 600x600 in the course of other admin changes?

https://forum.arctic-sea-ice.net/index.php/topic,1259.msg138340.html#msg138340

Neven

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Re: Latest PIOMAS update (January update)
« Reply #2252 on: January 09, 2018, 11:34:08 PM »
There was an admin setting shown once upon a time where the 700x700 was displayed as the choice. Maybe Neven changed that?

Maybe he did. Just to be sure he changed it back to 700x700.
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jdallen

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Re: Latest PIOMAS update (January update)
« Reply #2253 on: January 16, 2018, 05:44:23 AM »
Having a mad thought (tm) about ice thickness calculations/estimation, as I ponder ways to track heat transfer through the arctic..  It ties back to a few questions.  Bear with me, this may be redundant.

(1) Is snow depth on ice something which can be easily derived?  Are there gridded data sets which are able to provide that based on some sort of reasonably reliable sensor?

(2) Can we reasonably derive the ice/snow surface temperature either through estimated 2M temperatures?

(3) Alternatively, how good is the gridded temperature as derived from observed upwelling IR?

(4) Under the ice, can we reasonably assume the ice-water interface temp to be -1.8C?

It follows by this that we may be able to proxy ice thickness by comparing the heat flow as indicated by the observed temperature of the snow surface and subtracting out estimated flow through the snow using an average thermal transfer value, and then plugging that into an inverted equation for heat flow through ice, solving instead for thickness.

Anyone aware of research/modelling utilizing something like this strategy?  I'd rather not re-invent the wheel here.

I may want to start a separate thread for this, but I wanted to plant a seed here first.
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Neven

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Re: Latest PIOMAS update (January update)
« Reply #2254 on: January 16, 2018, 10:13:59 AM »
Quote
(1) Is snow depth on ice something which can be easily derived?  Are there gridded data sets which are able to provide that based on some sort of reasonably reliable sensor?

If only!  :(
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Michael

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Re: Latest PIOMAS update (January update)
« Reply #2255 on: January 16, 2018, 10:45:44 AM »
(1) Is snow depth on ice something which can be easily derived?  Are there gridded data sets which are able to provide that based on some sort of reasonably reliable sensor?
The the usual approach is to use climatology based on Warren 1999, modified to to allow for the increase in FYI.
http://journals.ametsoc.org/doi/abs/10.1175/1520-0442%281999%29012%3C1814%3ASDOASI%3E2.0.CO%3B2

Lord M Vader

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Re: Latest PIOMAS update (January update)
« Reply #2256 on: January 31, 2018, 08:46:34 AM »
Seems like the mid-January update was cancelled. Anyone who know why? Looking forward to the February update soon! :)

Wipneus

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Re: Latest PIOMAS update (February update)
« Reply #2257 on: February 03, 2018, 01:58:20 PM »
Gridded PIOMAS model data has been updated. The "official" volume data and graphs not yet, as far as I can tell.

Estimated from the thickness data, the latest value is from 31st of January: 17.57 [1000 km3], which is the second lowest value for that day, 2017 is lowest by a rather large margin at 16.16   [1000 km3].

Attached the animation for January.

Wipneus

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Re: Latest PIOMAS update (February update)
« Reply #2258 on: February 03, 2018, 02:19:48 PM »
Thickness map on 31st Jan 2018, compared with previous years.

Wipneus

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Re: Latest PIOMAS update (February update)
« Reply #2259 on: February 03, 2018, 04:44:45 PM »
2018 versions of volume and volume-anomaly graphs.

Wipneus

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Re: Latest PIOMAS update (February update)
« Reply #2260 on: February 03, 2018, 05:53:31 PM »
Fram export graph updated.

Wipneus

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oren

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Re: Latest PIOMAS update (February update)
« Reply #2262 on: February 03, 2018, 07:12:17 PM »
Thanks Wipneus. It seems 2018 is already headed into trouble.

A-Team

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Re: Latest PIOMAS update (February update)
« Reply #2263 on: February 03, 2018, 08:20:17 PM »
Export volume (area under the curve relative to 4 million possible) gives 0.8 million cu km exported for Oct, Nov, Dec, Jan.

The last 8 years of Fram export for these months are shown in the simulcast below:

Pavel

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Re: Latest PIOMAS update (February update)
« Reply #2264 on: February 04, 2018, 12:04:47 PM »
Thanks for the update. This year we have the stronger ice along the Siberian coast than last year. But we remember the 2017 snowy June and late melt ponds formation in the Laptev sea fast ice. I'm curious to see what we'll have this year

Richard Rathbone

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Re: Latest PIOMAS update (February update)
« Reply #2265 on: February 04, 2018, 02:11:39 PM »
Looks like the biggest pile up against Siberia for over a decade. If that persists through the maximum some of that ice might make it through the summer, but there will be big holes on the other side.

Jim Hunt

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Re: Latest PIOMAS update (February update)
« Reply #2266 on: February 04, 2018, 06:15:39 PM »
Looks like the biggest pile up against Siberia for over a decade.

CryoSat-2's version of events. 2014 looks to have been the worst in their records, but that's later in the season. I'll check my records to see if I have something more directly comparable.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Blizzard92

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Re: Latest PIOMAS update (February update)
« Reply #2267 on: February 06, 2018, 09:57:59 PM »
UC Irvine - Earth System Science Ph.D. Candidate
Cornell University - Atmospheric Sciences B.Sc.

Twitter: @ZLabe
Website: http://sites.uci.edu/zlabe/

A-Team

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Re: Latest PIOMAS update (February update)
« Reply #2268 on: February 07, 2018, 10:47:14 PM »
Quote
CryoSat-2's version of events
Ascat's version of events, for the 124 days between 30 Sep 17 to 31 Jan 18. Here four of wipneus' monthly summary animations are butted end to end, then side by side with the same days of Ascat ice backscatter of C-band radar (roughly sea ice age, very roughly thickness). An awful lot of structural details are missing from Piomas.

The static png compares Jan 31st for the three sources. Cryosat has been rotated 45º ccw to match the Greenland down orientation of the other two. Blizzard92's has been rotated 45º cw. The Topaz product shown @seaice_de is so not readily re-oriented.

However here's a very nice animation comparing SMOS and Piomas in January from 2011-18.

http://www.seaice.de/PIOMAS_SMOS_Jan_2018.gif

« Last Edit: February 08, 2018, 08:47:13 PM by A-Team »

Neven

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Re: Latest PIOMAS update (February update)
« Reply #2269 on: February 07, 2018, 11:05:17 PM »
PIOMAS February 2018 is up on the ASIB.
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gerontocrat

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Re: Latest PIOMAS update (February update)
« Reply #2270 on: February 07, 2018, 11:32:53 PM »
PIOMAS February 2018 is up on the ASIB.
Thanks Neven, for the monthly fix. With no mid-month update I was having violent PIOMAS withdrawal symptoms.

ps: On the Northern Hemisphere Snow thread you have started, I posted graphs from Environment Canada -Snow Water Equivalent well up (though extent not so much).
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oren

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Re: Latest PIOMAS update (February update)
« Reply #2271 on: February 08, 2018, 01:53:50 AM »
Thanks Neven. An interesting read as usual.

jdallen

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Re: Latest PIOMAS update (February update)
« Reply #2272 on: February 08, 2018, 07:22:13 AM »
PIOMAS February 2018 is up on the ASIB.
Succinct as usual.

Regarding snow cover - it won't help much on the Atlantic side if the huge areas in the Barentsz and around FJL remain open through the rest of the refreeze and begin immediately taking up insulation weeks early which previously got bounced back out of the atmosphere.

If the storms continue, that snow and thinner ice will be more vulnerable to rainfall events. That buffer provided by snow cover could vanish in hours.

We are once again hoping we don't get a bad dice roll.
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A-Team

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Re: Latest PIOMAS update (February update)
« Reply #2273 on: February 08, 2018, 09:17:52 PM »
SMOS ice thinness classes of >0.3m, >0.6m, >1.0m compare rather well to Piomas monthly averages for January for the last nine years, downsized to the forum from https://twitter.com/seaice_de and presented there at a much larger scale:

http://www.seaice.de/PIOMAS_SMOS_Jan_2018.gif

However differencing the Jan 2018's tells a somewhat different story. Here the scale is too small for the Arctic Ocean proper (the rest melts out so who cares), especially since the interest is on the ice pack periphery. SMOS of course is available in netCDF but I've not seen Piomas in standard format. Panoply could do the quantitative subtractive display if both were there.

The key really is percent difference. If ice 0.5 m thick is off by 0.1 m, that is already 20%. How do we follow subtle trends in ice volume year-ion-year in this environment? And what does average thickness even mean when the ice can be moving by at 45 km a day, across a couple of grid cells: what ice are we talking about after a month of this? In the Beaufort, we have a 1000 km stringer of sparse 3 m floes sprinkled in amongst late FYI. What should be monitored in this situation?

Most eyes will be on the Beaufort this coming melt season. It looks especially weak in SMOS with the difference with Piomas seeming significant. The Chukchi is a lost cause, the Kara will melt out as it always does, and the Barents Edge will retreat early as its periphery is largely extruded immature ice from the Kara.

Technical note: Radial coordinates can be unwrapped but the AO is so lopsided with respect to latitude that the little gained by discarding unused interior to better compare peripheries would be offset by the confusion engendered.
« Last Edit: February 09, 2018, 12:43:05 AM by A-Team »

Neven

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Re: Latest PIOMAS update (February update)
« Reply #2274 on: March 05, 2018, 11:29:57 PM »
PIOMAS has been updated. Last February 3rd lowest increase since 2005 (only 2014 and 2016 grew less volume in February). Change in differences with previous years:
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Blizzard92

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Re: Latest PIOMAS update (February update)
« Reply #2275 on: March 06, 2018, 12:39:00 AM »
My PIOMAS sea ice thickness and volume figures have been updated at http://sites.uci.edu/zlabe/arctic-sea-ice-figures/ and http://sites.uci.edu/zlabe/arctic-sea-ice-volumethickness/.
UC Irvine - Earth System Science Ph.D. Candidate
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Wipneus

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Re: Latest PIOMAS update (March update)
« Reply #2276 on: March 06, 2018, 09:14:18 AM »
Yes, 2018 is now in solid second lowest place (behind 2017).
Attache is my anomaly graph.

Wipneus

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Re: Latest PIOMAS update (March update)
« Reply #2277 on: March 06, 2018, 09:17:50 AM »
The February animation.

oren

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Re: Latest PIOMAS update (March update)
« Reply #2278 on: March 06, 2018, 09:34:12 AM »
Thank you Wipneus. I get the feeling that the resolution of the PIOMAS model is not nearly enough to deal with recent phenomena we've observed in the Bering and north of Greenland. It shows reductions of volume in both locations but it's averaged aggressively.
I also note that the animation shows an area of very thick ice north of the New Siberian islands. I wonder if it's really there, and if so what effect will it have on the melting season. Maybe it's the result of wind compaction events from both the Pacific and the Atlantic sides.

Wipneus

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Re: Latest PIOMAS update (March update)
« Reply #2279 on: March 06, 2018, 09:42:48 AM »
The latest thickness map, with comparisons with recent years.

Wipneus

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Re: Latest PIOMAS update (March update)
« Reply #2280 on: March 06, 2018, 10:10:39 AM »
Oren, maybe we sometimes try to read too much from the distribution of the ice. Historically  PIOMAS data was only volume data, volume calculated from a model that obeyed principally the first law of thermodynamics. Ice too thick in one place may be compensated by ice too thin elsewhere and volume is affected less.

The gridded thickness data was provided later and I see it as an opportunity to look into the inner workings of the model and perhaps squeeze some more information out of it. The scientists behind PIOMAS can probably point to many shortcomings, but which do influence the outcome (the total volume)?

Thank you Wipneus. I get the feeling that the resolution of the PIOMAS model is not nearly enough to deal with recent phenomena we've observed in the Bering and north of Greenland.

Resolution is one obvious problem, perhaps the parameterization of the physics in ice transport is lacking.

oren

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Re: Latest PIOMAS update (March update)
« Reply #2281 on: March 06, 2018, 10:12:57 AM »
Oren, maybe we sometimes try to read too much from the distribution of the ice. Historically  PIOMAS data was only volume data, volume calculated from a model that obeyed principally the first law of thermodynamics. Ice too thick in one place may be compensated by ice too thin elsewhere and volume is affected less.

The gridded thickness data was provided later and I see it as an opportunity to look into the inner workings of the model and perhaps squeeze some more information out of it. The scientists behind PIOMAS can probably point to many shortcomings, but which do influence the outcome (the total volume)?

Thank you Wipneus. I get the feeling that the resolution of the PIOMAS model is not nearly enough to deal with recent phenomena we've observed in the Bering and north of Greenland.

Resolution is one obvious problem, perhaps the parameterization of the physics in ice transport is lacking.
Thanks for the explanation.

Wipneus

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Re: Latest PIOMAS update (March update)
« Reply #2282 on: March 06, 2018, 11:50:14 AM »
Maybe it is a good idea to show the PIOMAS grid again. Because it has its "pole" in North Greenland, the highest resolution is maximal over the ice around Greenland. That would be good for Fram and Nares transport modeling. But I do not expect the movement of ice in two cell wide Nares Str. will be accurately modeled. 

Wipneus

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Re: Latest PIOMAS update (March update)
« Reply #2283 on: March 06, 2018, 01:26:19 PM »
Here is the Fram export estimated from PIOMAS thickness and velocity. Not much (net) export in February!

Neven

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Re: Latest PIOMAS update (March update)
« Reply #2284 on: March 06, 2018, 01:43:00 PM »
That last dip (in red) was probably due to the storm, I guess.
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gerontocrat

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Re: Latest PIOMAS update (March update)
« Reply #2285 on: March 06, 2018, 01:50:53 PM »
Maybe it is a good idea to show the PIOMAS grid again. Because it has its "pole" in North Greenland, the highest resolution is maximal over the ice around Greenland. That would be good for Fram and Nares transport modeling. But I do not expect the movement of ice in two cell wide Nares Str. will be accurately modeled.

Any new satellites going up that will improve resolution?
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oren

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Re: Latest PIOMAS update (March update)
« Reply #2286 on: March 06, 2018, 08:32:24 PM »
Maybe it is a good idea to show the PIOMAS grid again. Because it has its "pole" in North Greenland, the highest resolution is maximal over the ice around Greenland. That would be good for Fram and Nares transport modeling. But I do not expect the movement of ice in two cell wide Nares Str. will be accurately modeled.

Any new satellites going up that will improve resolution?
It's not a question of new satellites. PIOMAS is a model, and as such uses a grid resolution that its developers chose. I know they are feeding/constraining the model with sea ice concentration data from NSIDC, which impacts the resolution choice. Should they choose to use data from AMSR instead (10km or even 3.125km resolution), and upgrade the model's grid resolution, the model might give better results, but I imagine that would be a tremendous undertaking, the result will still be a model with built-in uncertainties and limitations, and AMSR data is not available for all past years, negating the ability to make useful volume comparisons.

Neven

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Re: Latest PIOMAS update (March update)
« Reply #2287 on: March 07, 2018, 12:54:51 AM »
Compare, compare, compare

oren

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Re: Latest PIOMAS update (March update)
« Reply #2288 on: March 07, 2018, 02:04:59 AM »
Thank you Neven for your (as usual) spot on summary and analysis, and for the link to the Scribbler piece.

gerontocrat

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Re: Latest PIOMAS update (March update)
« Reply #2289 on: March 07, 2018, 02:33:52 PM »
February Volume 38% below the maximum in 1979  - Polar Science Center

February sea ice extent declining at 3.1% per decade - NSIDC.

i.e. - February Volume declines at over three times faster than February extent.
      - Both volume and extent continue to decline very much according to a linear regression.

No tipping point yet.



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meddoc

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Re: Latest PIOMAS update (March update)
« Reply #2290 on: March 07, 2018, 04:10:39 PM »
So, PIOMAS March 01. ca: 19.000 km3
You can easily extract 30% off that, according to a recent Study.
Not much Volume to be melted in Full Sunlight.

gerontocrat

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Re: Latest PIOMAS update (March update)
« Reply #2291 on: March 07, 2018, 04:15:37 PM »
So, PIOMAS March 01. ca: 19.000 km3
You can easily extract 30% off that, according to a recent Study.
Not much Volume to be melted in Full Sunlight.

Easy? Not sure if 5,700 cubic kilometres of ice can easily be extracted.

Lots of studies, no definitive universally accepted answer. So I stay with PIOMAS until proved otherwise. It may be wrong but it is a consistent long-term series.
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A-Team

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Re: Latest PIOMAS update (March update)
« Reply #2292 on: March 08, 2018, 06:09:04 PM »
Quote
stay with PIOMAS
With such poor grid resolution in the Arctic Ocean proper and mediocre agreement with amended CryoSat, SMOS, Ascat roughness age, snow contributions, ice provenance, icepack motion and commonsense, how is it able to determine these subtle daily and monthly variations to such incredible nominal precision? The trick lies in not posting a netCDF which discourages quantitative comparison, using a virtual averaging volume which is not subject to observational calibration or validation, and getting a free reset on the periphery when the ice is all melted out at the September minimum.

Quote
That last dip (in red) was probably due to the storm, I guess.
Right. This was a very unusual event completely attributable to strong persistent winds blowing up the Fram. Despite some nonsense on twitter, it had nothing whatsoever to do with melting ice, föhn winds coming down off Greenland, bizarre warmth at KMJ, upwelling (Kaffeeklub and beyond are far too shallow), or a stable new polynya (it froze over almost immediately as shown by WorldView VIIRS cracking).

There's also been serious confusion about "dynamic" ice thickening of Arctic Ocean ice. Rheological deformation of ice is real enough in thousand-meter thick Greenland and Antarctic ice sheets (eg previous discussions of deviatoric stress tensor invariants as supported by ice-penetrating radargrams) but it's only a useful metaphor for the ice pack in continuum mechanics-based modeling (eg CICE elasto-viscous-plastic deformation intended for fully coupled global climate models).

If you are standing out there on the ice, you won't experience any dynamic thickening. Instead, at the scale of large floes or along the all-important marginal ice zone, solid mechanics fracturing is at work:

Formation of an aggregate scale in Arctic sea ice.
MA Hopkins, S Frankenstein, AS Thorndike
J. Geophys. Res. 109, C01032 (2004).
http://onlinelibrary.wiley.com/doi/10.1002/2015JC010909/full

In this event, the southerly component of North Atlantic deformation was, unsurprisingly, taken up by the Kara tongue intrusion where it was sliced earlier passing around Ushakov Island. Contrary to climate-site tweeters, rifting and ridging flares are easily seen on Ascat despite its resolution -- it may have only 85,000 pixels for the Arctic Ocean proper but they're all grid cells. (Mostly we see heavily interpolated sparse grids; turning interpolation off is a Panoply option.)

Here the issue is a perceptual misunderstanding: a ragged line of contrasting values is reliably recognized (bottom 70º azsimuthal Ascat  bump map contextual animation) even if only one pixel wide for one day of a time series whereas the same number scattered over the image would be seen, if at all, as noise. (Sentinel-1AB confirms this.)

The new ice is currently being compressively squashed against the coast, moving westward along the coast and heading out the door to the south under persistent northern winds associated with this week's meandering weak high. The East Greenland Current works as a rachet: ice leaves with the surface current and doesn't come back.

Here the current was temporarily overwhelmed by an opposing wind as far as drifting surface ice was concerned. However import of previously exported ice from the Fram has proven transitory in the past, under weather patterns of the satellite era.

Where exactly does the East Greenland Current begin to kick in? Ascat and VIIRS time series showed during this event that it's quite a ways farther north than the latitude line connecting Nord Station with Svalbard. On the bottom animation (which pushes very hard on Ascat using transient 32-bit grayscale to mitigate lumping), the dividing line on the newly formed ice shows up clearly: some is going west, the rest is going south.

Fram floe trajectories are very similar to kayaking down a river. At low gradients you have to paddle, be that with or against the wind, because the river pools up and resembles a lake. As the gradient steepens above the head of a rapid, your boat gets caught up in the current and downriver you go, regardless of wind. Except here the wind was strong enough long enough to blow your boat back upriver.
« Last Edit: March 08, 2018, 07:11:08 PM by A-Team »

Wipneus

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2293 on: March 20, 2018, 02:47:44 PM »
PIOMAS has updated its gridded thickness data. Latest date is 15th March.
Calculated volume is 20.97 [1000km3], second lowest for the day behind 2017.

Attached is the Fram Strait export graph. Other graphs are being processed.

Wipneus

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2294 on: March 20, 2018, 02:51:46 PM »
The volume and volume-anomaly graphs with 1-15 March estimated from the thickness data.

Neven

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2295 on: March 20, 2018, 03:01:58 PM »
I would expect PIOMAS volume to go up a lot, given the low temps and open skies of the past two weeks. Did 2018 creep towards the pack and away from 2017?
Compare, compare, compare

Wipneus

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2296 on: March 20, 2018, 03:05:23 PM »
The animated first 15 days of March.

Pavel

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2297 on: March 20, 2018, 05:34:28 PM »
The Siberian side looks pretty thick, but snow and/or cold anomalies needed to protect this ice in summer. The Chukchi sea is in trouble, and The strong cyclone in several days can boost huge opening up just in the start of the melting season

oren

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2298 on: March 20, 2018, 05:47:59 PM »
I would expect PIOMAS volume to go up a lot, given the low temps and open skies of the past two weeks. Did 2018 creep towards the pack and away from 2017?
Yes it did, rhough not by a whole lot.

A-Team

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Re: Latest PIOMAS update (March mid monthly update)
« Reply #2299 on: March 21, 2018, 03:22:45 PM »
Here is a simultaneous comparison of Piomas to Ascat, SMOS thin ice, and CICE thick ice for 28 Feb to 15 Mar 2018. It will need a new tab to animate. Piomas is doing better in some areas but still is not fully consistent at good resolution to what we know from ice provenance and other thickness tools.

Again it's hard to understand, once the peripheral ice is gone, how Piomas volume could be doing better than 15-20% absolute accuracy in any given year for the Arctic Ocean proper and how inter-year volume comparison would fare any better (as gaussian error goes as the quadrature(, with consequences to trend line nuancing.

The png at bottom shows daily ice motion over the first 80 days of 2018. The late February wind storm leading to negative Fram export stands out quite clearly. Individual days are shown more clearly at OSI SAF; these are shown animated over at Page One of the 2018 melt season.

http://osisaf.met.no/p/osisaf_hlprod_qlook.php?year=2018&month=03&day=20&action=Today&prod=LR-Drift&area=NH&size=100%25
« Last Edit: March 22, 2018, 01:41:39 PM by A-Team »