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Messages - bill kapra

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Arctic sea ice / Re: 2020 Sea ice area and extent data
« on: August 06, 2020, 05:48:24 AM »
Thank you Gerontocrat!
Longtime lurker very much appreciates your efforts. Glad to kick in a little bit to help. Here’s to all of the members of thus board and the strong community you’ve created. A plaesure and honor to be among you.

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Arctic sea ice / Re: The 2020 melting season
« on: August 03, 2020, 05:30:25 AM »
Does anyone have the CAB detaching from North America on their 2020 bingo card?

Time for a new thread “When will the Northwest Sea Route open”?

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Arctic sea ice / Re: The 2020 melting season
« on: July 29, 2020, 06:14:18 AM »
with respect, reversion to the mean isnt remarkable. And the selection of time slices is one of the most seductive analytical fallacies.

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Arctic sea ice / Re: The 2020 melting season
« on: July 24, 2020, 03:22:16 PM »

It certainly is not the reason. Clickon this animation of the last ten days of the furious pace of discharge from the central arctic sea into the Beaufort, both down the CAA coast, and also clearly visible the motion towards the Chukchi of the fragmented and low concentration central Beaufort.
The Irminger current historically used to turn south below Greenland and dip around Greenland before merging with the Labrador and heading south.
As pictured. Last ten years Its been turning south further north near Svalbard. Now last year, and even more this it has decided to go over the top of Greenland, and this year, not even satisfied by colonising the CAA, and Aided by the Beaufort clockwise gyre being closer to Mckenzie Bay,  it has stopped the Alaskan coastal current, heading east from Bering,  or at least pushed it under to flood the central Beaufort.
As you are seeing some is also going along the siberian coast.

Could this shift have an impact on the AMOC’s northern branch or is the current too relatively small to have a substantial effect?

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Arctic sea ice / Re: The 2020 melting season
« on: July 20, 2020, 06:49:02 PM »

     I'll go one step farther out on a limb and propose that there is a break point around 2 meters ice thickness.  That is about the amount that can freeze in one winter or melt out in a melt season.  I have to wonder if going below 2 meters thickness indicates a shift to less melt resistance.  It certainly reflects the shfit from MYI to FYI which we all agree has been one of the big story lines since 2007.  And speaking of 2007, I think that it, not 2012, is the epic year that should get more attention in terms of understanding the effects of melt season weather and the modern progession of ASI decline.  No disresect to 2012, but 2007 was a knock out punch that came out of nowhere.  The MYI ice loss that year set the stage for all that has happened since.

That seems reasonable... that we could assess annual melt midseason and compare to average thickness based on the nonlinearity you point out.

But, with local variability of ice thickness, how valuable would such a measure be? And, has it been built for 2020?

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Arctic sea ice / Re: The 2020 melting season
« on: July 18, 2020, 08:53:46 PM »
It's FRIV, not FRIZ. Please don't misspell him,

That wasn't a typo. It's a racial slur and was done on purpose.

I really doubt that - I haven't seen racism here in the ACIF at all, if I did I'd shout it out loud... I'm the ultimate lurker (here since the beginning) I read and learn so much but post rarely.

Please keep it polite - it's an incredible season and thanks to Oren and of course Neven for all of this - it is a pleasure to observe and learn.

Ditto, Mark. I’ve been lurking here for ever. Very rarely have anything useful to contribute but often learn new things and frequently bring them to my university students.

Thank you all for being such an amazing resource and a (mostly) civil group.

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Arctic sea ice / Re: Basic questions about melting physics
« on: August 21, 2019, 10:29:41 PM »
Thanks for the fix and the reference, Nanning. Fascinating materials problem here!

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Arctic sea ice / Re: When will the Northwest Passage "open" in 2019?
« on: August 21, 2019, 02:28:51 AM »
Was looking for the Parry ice chart on Canadian Ice Service website but it comes up as unavailable and dated Aug.1. Is that because they don’t post until near-navigable?

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Arctic sea ice / Re: Basic questions about melting physics
« on: August 21, 2019, 01:57:10 AM »
Hey folks,

Longtime lurker. Soft condensed matter guy. Just starting to look at sea ice and stumbled across this. FWIW:

Critical behavior of transport in sea ice

Author links open overlay panelK.M.Golden
Show more
https://doi.org/10.1016/j.physb.2003.08.007Get rights and content
Abstract
Geophysical materials such as sea ice, rocks, soils, snow, and glacial ice are composite media with complex, random microstructures. The effective fluid, gas, thermal, and electromagnetic transport properties of these materials play an important role in the large-scale dynamics and behavior of many geophysical systems. A striking feature of such media is that subtle changes in microstructural characteristics can induce changes over many orders of magnitude in the transport properties of the materials, which in turn can have significant large-scale geophysical effects. For example, sea ice, which mediates energy transfer between the ocean and atmosphere, plays a key role in global climate, and serves as an indicator of climatic change, is a porous composite of ice, brine and gases. Relevant length scales range from microns and millimeters for individual brine structures, to centimeters and meters for connected brine channels across floes, to hundreds of kilometers across an ice pack. Sea ice is distinguished from many other porous composites, such as sandstones or bone, in that its microstructure and bulk material properties can vary dramatically over a relatively small temperature range. The fluid permeability of sea ice ranges over six orders of magnitude for temperatures between 0°C and −25°C. Moreover, small changes in brine volume fraction around a threshold value of about 5%, corresponding to variations in temperature around a critical point of about −5°C, control an important transition between low and high fluid permeability regimes. Below this critical temperature, the sea ice is effectively impermeable, while for higher temperatures the brine phase becomes connected over macroscopic scales, allowing fluid transport through the ice. This transition has been observed to impact a wide range of phenomena such as surface flooding and snow–ice formation, enhancement of heat transfer due to fluid motion, mixing in the upper ocean, melt pool persistence, surface albedo (ratio of reflected to incident radiation) and other optical properties, growth and nutrient replenishment of algal and bacterial communities living in sea ice, and remote sensing of the sea ice pack from space. Recently, we have shown how continuum percolation theory can be used to understand the critical behavior of fluid transport in sea ice. Here we review this application of percolation theory to sea ice, and briefly discuss electromagnetic transport in sea ice, in particular how the geometry and connectivity of the brine microstructure determine its effective complex permittivity.

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Arctic sea ice / Re: The 2019 melting season
« on: August 19, 2019, 04:45:32 PM »
A fractal swirl of more concentrated ice north of the the ESS gets stirred over the past week-now it being pushed into the warm SSTs in the wetern Beaufort Sea

I think that the fractal nature of dispersing ice is a key factor that may bollix up our analyses.

While both area and extent seem like simple enough measures that they can ignore surface geometry, each struggles to capture the structural complexity of boundary and edges. (Compare, for example, a simple shape occupying 15% of a pixel vs a highly dispersed set of blobs — the latter has a far greater edge length exposed. A fractal increases that edge even more).

These fractal swirls could also have really interesting impact on metling/refreezing dynamics and on the subsequent makeup of myi.

Does anyone have citations of studies on these structures and their dynamics?

If I had to guess, I’d say that, to the extent we see structures like this, the ice is in worse shape than extent and area numbers suggest.

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Arctic sea ice / Re: 2019 sea ice area and extent data
« on: August 12, 2019, 01:05:55 AM »
Science isn’t liberal or conservative and I take refuge in this thread because it’s focused on the data (and analysis). Hope it stays that way.

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Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 04:13:42 PM »
Thx Uniquorn and Shared Humanity!

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Arctic sea ice / Re: The 2019 melting season
« on: July 07, 2019, 02:03:24 PM »
worldview aqua modis, mclure strait to lincoln sea, jul6 with noaa bathymetry. All the fractures are sheared. click to run. (3.5MB)
Very little compressive strength shown on hycom.
edit:Added bathymetry scale

Very interesting graphics!

This may be a dumb question but does it surprise you that the cracking is taking place uniformly along a line that also spans the inlets/channels? That strikes me as interesting because the topo indicates that these function as outflows (presumably due to snow melt). Does the fact that the ice is pulling away there imply that the ice in those passages is not being shifted forward by much and does this further imply that there’s really little residual terrestrial ice/snow on the islands to melt? Or is there enough flow below the surface that the ice does not get pushed outward by meltwater behind?

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Sorry, thought we were speculating....
figuring on reversion to the mean but one never knows!

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4M. The weather won’t be as extreme this year and so extent will remain close but not a minumum. But that will mask the underlying dynamic of slushy, thin ice throughout.

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Arctic sea ice / Re: The 2019 melting season
« on: July 02, 2019, 11:47:05 PM »
I am at times amazed at the low quality English used by some of the native speakers on the forum

As a university professor in an English-speaking country, I can regretfully confirm that written English is weakening.

On the other hand, in a polyglot community like this one, just getting one’s meaning across is probably enough.

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Arctic sea ice / Re: 2019 sea ice area and extent data
« on: July 01, 2019, 11:50:59 PM »
Just a quick thank you to Gerontocrat and the gang here. I’m a years-long lurker, teaching university courses on environment and am grateful to you all for the detailed and well-documented material.

To paraphrase the Washington Post’s masthead, science dies in darkness. You all keep shining the light and it is a great service to your peers.

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Arctic sea ice / Re: The 2016 melting season
« on: August 06, 2016, 12:57:09 AM »
Greetings all and thanks from a longtime lurker for such a great conversation.

I'm a physicist/dynamicist so just an amateur re. climatology, hence the lurking...

Am moved to post now because of the interesting SST anomaly surrounding the large, fractured section of Ice in the ESS. This "big blob" of cold seems to be finally encircled by warm water.

I'm wondering what you all know about the subsurface currents in the CAB and whether the northern edge of that encirclement can supply the heat necessary to maintain itself as the central pack solidifies.

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