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johnm33

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Re: Importance of waves in the Arctic
« Reply #50 on: July 08, 2015, 08:50:14 PM »
This is a paper on internal waves in the arctic http://psc.apl.washington.edu/northpole/Mixing.html
 to get some idea of the possible scale of these

This shows that atoll https://en.wikipedia.org/wiki/Pratas_Islands in context, the image is from http://www.livescience.com/42459-huge-ocean-internal-waves-explained.html?li_source=pm&li_medium=most-popular&li_campaign=related_test " In the tank, the internal waves formed when tidal currents pushed cold, heavy bottom water over two seafloor ridges, setting up a disturbance called a standing wave" and there's a short vid.
More from the Andaman sea

from http://www.livescience.com/30098-indian-ocean-internal-waves.html which is fairly short.
Where might these be generated in the arctic? well, just guessing, but likely where tidal forces race adjacent to steep shelves or ridges.


worth looking how these match up, images from here http://www.esr.org/arctic_tides_index.html and here http://geology.com/world/arctic-ocean-bathymetry-map.shtml
Not that tides themselves are really sufficient but if you've got a significant fraction of 15,000 cubic kilometers on the move, or a high/ low pressure system moving, across those areas then I suspect that would do it.
There's a brief explanation of atmospheric effects on sea height here http://weather.mailasail.com/Franks-Weather/Pressure-And-Tides

johnm33

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Re: Importance of waves in the Arctic
« Reply #51 on: July 09, 2015, 11:26:14 AM »
Perhaps it's wishful thinking on my part but some of these leads show signs of being caused by internal wave action. Where the deeper dense layers are sloughing around in the Canadian Basin getting within a few meters of the surface and the surface waters moving independently pass over the crests picking up heat and inherent turbulence as they calm the storm beneath them.

Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #52 on: July 09, 2015, 05:31:02 PM »
This is a paper on internal waves in the Arctic.


Thanks for the heads up John. I've not read that before. My focus up to now has been on surface gravity waves, which at long periods can happily do quite a bit of vertical mixing. See my video for an anecdotal example!

Some more reading to be added to my ever growing to do list!
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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #53 on: July 18, 2015, 11:27:08 PM »
Harvey Goodwin works off the RV Lance, and reports via Twitter that:

When a light swell comes in the 5km sea ice floe we'd been working on broke into pieces not more than 30m in an hour!. Equipment rescue after sea ice breakup. Some cables cut but no equipment lost!


https://twitter.com/Harvey_Goodwin/status/622413054618279936



A bit of digging suggests the picture was taken on June 22nd or thereabouts.

https://twitter.com/OceanSeaIceNPI/status/612971542385946624



Now more fully documented at:

"R/V Lance Encounters Another Energetic Wave Event in the Arctic"

« Last Edit: July 19, 2015, 09:18:22 PM by Jim Hunt »
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Andreas T

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Re: Importance of waves in the Arctic
« Reply #54 on: July 21, 2015, 11:09:03 AM »
Obuoy9 which is now near the Greenland coast in the north east water polynya at about 81N 11.5W showed this image today. Does that show a swell Jim? Swells which are not attenuated by ice could reach that position from the atlantic, I guess.

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Re: Importance of waves in the Arctic
« Reply #55 on: July 21, 2015, 04:45:53 PM »
Does that show a swell Jim? Swells which are not attenuated by ice could reach that position from the atlantic, I guess.

It's a bit too fuzzy to be sure Andreas! When I have a spare second I'll check the WW3 forecast. It certainly looks as though some local wind is chopping up the surface a bit.
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Andreas T

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Re: Importance of waves in the Arctic
« Reply #56 on: July 21, 2015, 05:38:54 PM »
I am thinking of the darker shades in the sea surface which seem to form lines at about 120 deg to the floe edge. This could be caused by different angle toward the sky i.e. a long swell from southeast (camera is looking south in this image) or it could be just gusts of wind rippling the surface in different ways. It was visible in several images around that time in different place but similar direction I thought.
Can't see anything now in the 15:00 image so probably nothing. camera looking further towards west. Azimuth at 110 corresponds to 200deg from north by my observations of sun position.
« Last Edit: July 21, 2015, 05:47:04 PM by Andreas T »

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Re: Importance of waves in the Arctic
« Reply #57 on: July 27, 2015, 01:15:40 PM »
This popped up in my mail box today via Google Alerts, from Alaska Dispatch News:

Study: Beaufort, Chukchi and Bering waves are getting bigger

Waves grew bigger and spaced farther apart as ice cover diminished in the Arctic and sub-Arctic waters off Alaska and western Canada, new research shows.

Since the 1970s, the biggest waves in the Beaufort, Chukchi and Bering Seas have grown at a rate of 0.3 to 0.8 percent per year, according to a comprehensive study led by Environment Canada. The time it takes waves to cycle, a measurement known as period, has grown even more, by 3 to 4 percent per year, more than tripling since 1970, according to the study, published by the American Meteorological Society’s Journal of Climate.

The study tracks significant wave height, which is the height of the biggest third of the waves, and mean wave period, which is the average of time for wave crests and troughs to complete their cycles.

It uses a wide variety of weather and climate observations collected over the years, including recorded sea-surface temperatures, atmospheric conditions, wind speeds and other parameters, to calculate the wave patterns going back over the past decades.

While wind patterns have changed over the period of time covered in the study, wind changes are not responsible for most of the increase in wave action, the study found. Instead, swells -- the rolling mechanical waves that travel long distances over the ocean --  account for most of the wave changes researchers measured, said lead author Xiaolan Wang, a research scientist with Environment Canada.

The study does not conclude that the expanding open water caused the bigger waves. “It’s not my area of research,” Wang said.

Still, it points out the correlation, and includes maps showing the expansion of open-water area in the three seas over the decades.

“Waves cannot be generated in ice-covered conditions,” she said.

Read the rest here.

PS I'm moving this thread to the more appropriate Arctic Background category.
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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #58 on: July 27, 2015, 03:24:36 PM »
PS I'm moving this thread to the more appropriate Arctic Background category.

But I just had a long chat this morning with a certain Cambridge Professor about the recent work of Walter Munk with a bunch of Californian surfers  :o
« Last Edit: July 27, 2015, 03:43:38 PM by Jim Hunt »
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Neven

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Re: Importance of waves in the Arctic
« Reply #59 on: July 27, 2015, 06:27:21 PM »
Sorry, Jim, hadn't noticed this has more to do with the Arctic than AGW in general.
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Re: Importance of waves in the Arctic
« Reply #60 on: July 27, 2015, 08:12:41 PM »
Hadn't noticed this has more to do with the Arctic than AGW in general.

But surely it should really be in the Arctic foreground, or even in "Science"?  ;)
« Last Edit: July 27, 2015, 11:52:39 PM by Jim Hunt »
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TerryM

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Re: Importance of waves in the Arctic
« Reply #61 on: August 06, 2015, 04:05:59 AM »
The long fetch that's opened in the ESS is troubling.
Isn't this what Shakhova warned about WRT the possibility of vast methane deposits being released as wave action warms the frozen sea floor?
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Re: Importance of waves in the Arctic
« Reply #62 on: August 28, 2015, 02:06:23 PM »
The long fetch that's opened in the ESS is troubling.


There's a fair fetch in the Chukchi/Beaufort Seas at the moment also:

Barrow Battered By Big Waves

Flooding at Barrow, whilst water temperatures reported by IMB buoy 2014G north of the Chukchi Sea were at around -0.7 °C before the current cyclone arrived.

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Re: Importance of waves in the Arctic
« Reply #63 on: September 07, 2015, 02:48:17 AM »
Walter Munk is still hard at work at the age of 97

http://www.nytimes.com/2015/08/25/science/walter-munk-einstein-of-the-oceans-at-97.html

Nowadays, as he forges ahead on wind, waves and other projects, he occasionally forgets the times of meetings and gets around with a walker. But he remains a frequent presence in Scripps, walking the halls of a building that now bears his name. The secret to his longevity?

“I like my work and I like my life, and I enjoy doing it,” he said.

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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #64 on: September 15, 2015, 07:13:21 PM »
A video showing "ice waves" in the Bering Strait during the final trials of the University of Alaska's R/V Sikuliaq:

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johnm33

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Re: Importance of waves in the Arctic
« Reply #65 on: September 17, 2015, 01:40:10 PM »
Jim H. posted this elsewhere I'm just putting the link in this thread too for future reference.
https://scripps.ucsd.edu/news/oceanographers-find-clues-behind-arctics-fourth-lowest-sea-ice-minimum

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Re: Importance of waves in the Arctic
« Reply #66 on: September 23, 2015, 04:05:14 PM »
Linked by A-Team in the Sikuliaq thread this is a paper on the internal waves so of interest to anyone following this thread too. http://www-pord.ucsd.edu/~jen/research.html

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Re: Importance of waves in the Arctic
« Reply #67 on: September 27, 2015, 12:55:23 PM »
There's plenty of potential overlap with the R/V Sikuliaq thread for the next couple of months, but here's the plan for the US Office of Naval Research's "Sea State and Boundary Layer Physics of the Emerging Arctic Ocean" research cruise which starts from Nome, Alaska on October 1st:

ONR Sea State DRI Cruise Plan R/V Sikuliaq, Fall 2015

The associated web site can be viewed at:

http://www.apl.uw.edu/project/project.php?id=arctic_sea_state

The cruise will be organized into modules, each targeting specific processes and
conditions from the science objectives and each emphasizing a subset of observational
assets. Complimenting the modules will be event (storm) based sequences: transect
before, buoys during, transect after. Both shipboard (e.g., cameras, wave radars, CTD)
and autonomous measurements (e.g., AUVs, wave buoys) will be employed during the
cruise, often simultaneously.




« Last Edit: September 28, 2015, 01:15:39 PM by Jim Hunt »
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johnm33

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Re: Importance of waves in the Arctic
« Reply #68 on: September 29, 2015, 12:35:58 PM »
Linked to by Jim Hunt on the Sikuliaq thread, preliminary results from their deep sea mooring. https://scripps.ucsd.edu/projects/arcticmix/bringing-it-all-home/ Internal waves and mixing.
Curiously the first reports [BBC radio4] about shell pulling out of the arctic mentioned 'arctic mix' findings of extreme turbulence as the prime reason for pulling out, but by the third repeat the narrative had shifted to poor reserves.

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Re: Importance of waves in the Arctic
« Reply #69 on: November 17, 2015, 10:19:37 AM »
Here's the plan for the US Office of Naval Research's "Sea State and Boundary Layer Physics of the Emerging Arctic Ocean" research cruise which starts from Nome, Alaska on October 1st


Here's Jim Thomson's final report on the Sikuliaq's recent "Sea state cruise":

http://www.apl.uw.edu/project/projects/arctic_sea_state/pdfs/cruise_report.pdf

Our measurements suggest that waves play an important role in the fall freeze-up of the Beaufort
and Chukchi Seas, especially near the ice edge facing the prevailing easterly winds. Pancake ice
formation was common, and, in one particular event, extended for almost 100 nm. Our
measurements suggest that ocean heat also is important, and that mixing can delay or temporarily
reverse the formation of first-year ice. Eventually, strong heat loss to the atmosphere becomes
the dominant process, especially during off-ice wind events, and large expanses of the ocean
freeze rapidly. As intended, we observed a significant advance in ice cover, and we sampled
several wave/wind events.


According to the associated section of the Office of Naval Research web site:

By the numbers, we have collected:

  •     32 days (559 hours) of visual ice observations
  •     228423 ice camera images
  •     467 physical ice samples
  •     4292 casts of the underway CTD (Conductivity, Temperature, Depth)
  •     478 hours of flux measurements from the meteorological mast
  •     35 days of wave and ice measurements from the ship’s Rutter radar (2,325,000 images)
  •     153 weather balloon (radiosonde) launches
  •     12 ice stations
  •     7 wave experiments

Note also that:

The Sea State DRI team is funded by the Office of Naval Research for two more years to analyze
and synthesize the data collected during this effort. Results will be presented in a special issue of
an academic journal and at academic conferences. A preliminary list of paper topics was drafted
by the team onboard the ship. Results will be used to improve forecasts of ice and waves in the
Arctic region.


In a report from October 12th on the web site:

The storm we have been measuring has just peaked at 5-m waves and 35-kt winds. We deployed a total of 14 buoys spanning almost 200 km. As the storm built, the whole region was covered in pancake ice — an ice formation pattern that is common when waves are present. As we re-surveyed the line this morning, the pancakes are gone. Much of the region is open water now, suggesting that the wave energy exceeded a threshold for pancake ice and mixed the newly forming ice away instead. Even early in the storm, we can see this process in this short video clip:




Here's how the cruise panned out in practice:



« Last Edit: November 17, 2015, 10:37:39 AM by Jim Hunt »
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Neven

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Re: Importance of waves in the Arctic
« Reply #70 on: February 25, 2016, 10:23:59 AM »
A new paper was posted in The Cryosphere:

Wave climate in the Arctic 1992–2014: seasonality and trends

Justin E. Stopa, Fabrice Ardhuin, and Fanny Girard-Ardhuin Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Océanographie Physique et Spatiale (LOPS), IUEM, 29280, Brest, France

Abstract. Over the past decade, the diminishing Arctic sea ice has impacted the wave field which is principally dependent on the ice-free area and wind. This study characterizes the wave climate in the Arctic using detailed sea state information from a wave hindcast and merged altimeter dataset spanning 1992–2014. The wave model uses winds from the Climate Forecast System Reanalysis and ice concentrations derived from satellites as input. The ice concentrations have a grid spacing of 12.5 km, which is sufficiently able to resolve important features in the marginal ice zone. The model performs well, verified by the altimeters and is relatively consistent for climate studies. The wave seasonality and extremes are linked to the ice coverage, wind strength, and wind direction. This creates distinct features in the wind-seas and swells. The increase in wave heights is caused by the loss of sea ice and not the wind verified by the altimeters and model. However, trends are convoluted by inter-annual climate oscillations like the North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation. The Nordic-Greenland Sea is the only region with negative trends in wind speed and wave height and is related to the NAO. Swells are becoming more prevalent and wind-sea steepness is declining which make the impact on sea ice uncertain. It is inconclusive how important wave-ice processes are within the climate system, but selected events suggest the importance of waves within the marginal ice zone.

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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #71 on: February 25, 2016, 12:20:44 PM »
I've been too busy winding up the denizens over at Judy Curry's with waves, and you beat me to it  :(

For more from Ardhuin, Wadhams et al. see also:

"Ocean waves across the Arctic: attenuation due to dissipation dominates over scattering for periods longer than 19 s"

The attenuation of surface waves in sea ice is poorly understood but has been attributed to the combination of scattering and dissipation.  Scattering and dissipation have very different  effects  on  the  directional  and  temporal  distribution  of  wave  energy,  making  it  possible  to  better  understand their relative importance by analysis of swell spectral spreading  and  arrival  times.   Here  we  compare  wave  measurements from far inside the ice pack with a spectral wave model that has adjustable scattering and dissipation attenuation  formulations.   It  was  found  that  scattering  plays  a negligible role in the attenuation of long swells.
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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #72 on: March 11, 2016, 01:43:27 PM »
Intriguingly Sentinel 3A's synthetic aperture radar appears to already be measuring "significant wave height" in the Central Arctic Basin!

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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #73 on: April 30, 2016, 07:54:50 PM »
Somewhat earlier than originally anticipated this year, my first look at waves in the Beaufort Sea of 2016:

Wind Waves in the Beaufort Sea in April 2016

Sentinel 3A data isn't flowing freely yet, so I ponder using CryoSat-2 to measure Beaufort Sea wave height. The data may well be out there, but not in a form that I can readily decode.
« Last Edit: May 01, 2016, 03:23:59 PM by Jim Hunt »
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A-Team

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Re: Importance of waves in the Arctic
« Reply #74 on: May 01, 2016, 05:02:34 AM »
Looks very similar to what Navy Hycom was showing the other day ... apparently from WaveWatch III. Needs a 90º rotation but seems to be the very same area. Waves will prove a huge issue as the Arctic Ocean has more blue water, longer fetches, longer in the season.


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Re: Importance of waves in the Arctic
« Reply #75 on: May 01, 2016, 12:39:59 PM »
Waves will prove a huge issue as the Arctic Ocean has more blue water, longer fetches, longer in the season.

Quite so!

I don't suppose you know how to persuade PanoplyJ to display 1D lat/long/wave height in a georeferenced human readable format do you?
« Last Edit: May 01, 2016, 02:27:29 PM by Jim Hunt »
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Re: Importance of waves in the Arctic
« Reply #76 on: May 01, 2016, 04:24:27 PM »
how to persuade PanoplyJ to display 1D lat/long/wave height readably


Do you have the link to the netCDF handy? (Not that I have time today but sidd or wipneus might.) Normally it will display the numeric array. Panoply is a glass half full, the monkey at the keyboard approach will occasionally get something ok to display.

http://www.giss.nasa.gov/tools/panoply/

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Re: Importance of waves in the Arctic
« Reply #77 on: May 01, 2016, 04:25:43 PM »
Jim,

I want to thank you for creating this thread some time ago. I have always been fascinated by the mechanical forces at work on the Arctic Ocean as the ice weakens. Certainly waves, as you argued a couple years ago are one of the largest. When ice starts moving around rapidly it has an amazing ability to alter the properties of the ice around it. This is true for existing ice and ice that is forming.

As mentioned elsewhere on this blog, ice tends to form more rapidly in areas adjacent to the shores or existing ice. I am not sure if this is due to the calming effect that this ice has on the sea around it but this seems plausible. Where ice forms on open water that are buffeted with waves, ice can behave oddly indeed. I am wondering if newly formed ice might look like this in the open Arctic Ocean. Might it act similarly to seeding clouds, providing a surface for new ice to form. What would the mechanical strength of flows look like when they form like this. I would imagine it is far different than the leads that freeze in newly formed cracks in the ice.

https://www.youtube.com/results?search_query=video+of+ice+balls+on+lake+michigan


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Re: Importance of waves in the Arctic
« Reply #78 on: May 01, 2016, 04:39:41 PM »
Do you have the link to the netCDF handy?

My first thought was to try and make some sense out of this lot:

ftp://ftp.star.nesdis.noaa.gov/pub/sod/lsa/cs2igdr/c079/
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Re: Importance of waves in the Arctic
« Reply #79 on: May 01, 2016, 06:04:10 PM »
I was looking at 73/4 above and wondering if the waves here starting at 71deg/135deg and moving north and west are the same phenomenon.

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Re: Importance of waves in the Arctic
« Reply #80 on: May 01, 2016, 09:08:06 PM »
wondering if the waves here starting at 71deg/135deg and moving north and west are the same phenomenon.


jnm, i wondered about that lead area animation too. It seems to visually mix opening fractures with established fetches along the coast that are different from ice fractures.

Jim, I am wondering what it takes for waves to wash over floes (which would soon be the end of them). It seems for ice 1m thick, the freeboard is only the height of a cigarette; meanwhile we are seeing waves 1-2m along the coast, fairly high winds and presumably chop. C

an a really massive floe like Big Block just bob up and down like a cork with the top staying dry? They seem more like heavily loaded barges than corks. And if Beaufort floes are lifted up by passing waves, why aren't they broken into smaller pieces (as reported elsewhere)?

make some sense out of this ftp://ftp.star.nesdis.noaa.gov/pub/sod/lsa/cs2igdr/c079/


So far I've learned that my Panoply 4.05 is 14 versions back from the current release. This is really an admirable software effort but I haven't put enough effort in at my end. As with SNAP Toolbox, gdal and imagemagick.

http://www.giss.nasa.gov/tools/panoply/versions.html

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Re: Importance of waves in the Arctic
« Reply #81 on: May 02, 2016, 10:16:33 AM »
Jim,

I want to thank you for creating this thread some time ago.


You're very kind, but actually LRC created this thread. I had been banging on about the effect of waves on sea ice for quite some time before that though! For an insight into how sea ice forms in open ocean I suggest taking a look at this video instead, starting at around 3 minutes 25 seconds:

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Re: Importance of waves in the Arctic
« Reply #82 on: May 02, 2016, 10:30:12 AM »
wondering if the waves here starting at 71deg/135deg and moving north and west are the same phenomenon.


jnm, i wondered about that lead area animation too. It seems to visually mix opening fractures with established fetches along the coast that are different from ice fractures.


Using surfing terminology the winds have been "cross shore" for much of April, but are turning "offshore" at the start of May. Wouldn't that explain the change in direction of the forecast fractures?

Jim, I am wondering what it takes for waves to wash over floes (which would soon be the end of them). It seems for ice 1m thick, the freeboard is only the height of a cigarette; meanwhile we are seeing waves 1-2m along the coast, fairly high winds and presumably chop. Can a really massive floe like Big Block just bob up and down like a cork with the top staying dry? They seem more like heavily loaded barges than corks. And if Beaufort floes are lifted up by passing waves, why aren't they broken into smaller pieces (as reported elsewhere)?


As per above, the "chop" has been travelling parallel to the ice edge up to now. That is changing, but the "fetch" will be reduced as a consequence.

I fancy I can see wave washed ice in some of the recent images, but I could easily be imagining it!



So far I've learned that my Panoply 4.05 is 14 versions back from the current release. This is really an admirable software effort but I haven't put enough effort in at my end. As with SNAP Toolbox, gdal and imagemagick.


I've upgraded to Panoply 4.5, and read what I can find of TFM, but no joy so far :(
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Re: Importance of waves in the Arctic
« Reply #83 on: May 09, 2016, 11:00:07 AM »
It's just speculation but I wonder if the breaks stretching from NE-SW are the result of internal waves, caused by water rushing towards Banks Is./ Canadian shores and forming an interference pattern of broad waves over which the ice breaks.
 
even more pronounced on compressive strength.

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Re: Importance of waves in the Arctic
« Reply #84 on: May 09, 2016, 07:29:02 PM »
It's just speculation but I wonder if the breaks stretching from NE-SW are the result of internal waves, caused by water rushing towards Banks Is./ Canadian shores and forming an interference pattern of broad waves over which the ice breaks.
 
even more pronounced on compressive strength.



The interference pattern isn't waves, but a reaction of the ice to a distortion - any fault line propagates very fast (same physics as in seismic activity) and stretches through the pack until there is no more windstress/distortion acting along the fault line. Next to a fault line, you cannot have another fault line, because all the distortion/stress has been accounted for by the existing fault line. So you go into a pseudo-equal spacing of parallel faults. Different systems of fault lines can overlap, but the have to be at a significant angle to each other, and they only run through as long as there are no significant leads in between the ice-pack (otherwise a fault line ends at the lead). Similar issue by the way with the frequent glacier terminus having near-rectangular blocks.

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Re: Importance of waves in the Arctic
« Reply #85 on: May 20, 2016, 11:36:01 AM »
" The interference pattern isn't waves," Can we agree to disagree? I've reassessed my take on the prescence of internal waves and perhaps I'm just seeing what I want to see but I've grown more convinced and think they are manifest in all the basins, though I'll leave it to a proffessional to call it. They appear when the ice has built up a head of steam and are then accelerated by more powerful winds, or when powerful winds apply the brakes to an area already moving in concert. The most unambiguous signal of movement in the basins is in Beaufort where there's the most movement of ice. Looking at the central feature

and the underlying bathymetry

again 76/155 why the drop in salinity if it's not warm basal water melting the ice?

I also did another google seach for internal waves, images this link has an interesting interactive http://www.whoi.edu/oceanus/feature/the-waves-within-the-waves
This ones more technical http://psc.apl.washington.edu/northpole/Mixing.html  abstract
    "Recent findings demonstrate the sensitivity of Arctic Ocean circulation to background, deep-ocean mixing. Results with a large-scale coupled ice-ocean model [Zhang and Steele, 2007] suggest the appropriate model background mixing for the Arctic Ocean is an order of magnitude lower than for ice-free oceans. Background mixing in the deep ocean is related to internal wave energy, which in ice-covered seas has been observed to be lower than in ice-free oceans, and to change with time and bathymetric conditions [Levine et al., 1985 and 1987; Halle and Pinkel, 2003; Pinkel, 2005]. Present thinking is that internal wave energies and background mixing are reduced in ice-covered seas by, among other things, dissipation of internal wave energy in the surface boundary layer immediately below the ice. Consequently, if the ice cover is reduced due to global warming, we may see a climate feedback that has not been considered before. If the ice cover is reduced, we may see increased internal wave energy, mixing, and heat flux in the deep ocean because less internal wave energy would be lost in the under-ice boundary layer. This would tend to result in increased heat flux to the ice, a positive climate feedback that would melt more ice. The effect could arguably be greatest near the continental slopes and submarine ridges, which are the likely areas of greatest internal wave increase and the paths of warm Atlantic water through the Arctic Basin."
  As is this http://folk.uib.no/ngfif/Reprints/Guthrie_etal_JGR13.pdf
abstract "To determine whether deep background mixing has increased with the diminishment of
the Arctic sea ice, we compare recent internal wave energy and mixing observations with
historical measurements. Since 2007, the North Pole Environmental Observatory has
launched expendable current probes (XCPs) as a part of annual airborne hydrographic
surveys in the central Arctic Ocean. Mixing in the upper 500 m is estimated from XCP
shear variance and Conductivity-Temperature-Depth (CTD) derived Brunt-V

ais

al

a
frequency. Internal wave energy levels vary by an order of magnitude between surveys,
although all surveys are less energetic and show more vertical modes than typical
midlatitude Garrett-Munk (GM) model spectra. Survey-averaged mixing estimates also vary
by an order of magnitude among recent surveys. Comparisons between modern and
historical data, reanalyzed in identical fashion, reveal no trend evident over the 30 year
period in spite of drastic diminution of the sea ice. Turbulent heat fluxes are consistent with
recent double-diffusive estimates. Both mixing and internal wave energy in the Beaufort
Sea are lower when compared to both the central and eastern Arctic Ocean, and expanding
the analysis to mooring data from the Beaufort Sea reveals little change in that area
compared to historical results from Arctic Internal Wave Experiment. We hypothesize that
internal wave energy remains lowest in the Beaufort Sea in spite of dramatic declines in sea
ice there, because increased stratification amplifies the negative effect of boundary layer
dissipation on internal wave energy."
It's worth taking a look at http://www7320.nrlssc.navy.mil/hycomARC/navo/arc_list_beaufortopening.html from the 3rd and following the evolution of the movement on a frame by frame, unless your computer literate and can slow the animation down.


plinius

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Re: Importance of waves in the Arctic
« Reply #86 on: May 20, 2016, 04:19:49 PM »
It seems to me that the waves they are talking about are not equal to the waves you are hypothesizing about.  Just figure what your "wavelengths" are (it is actually a pseudowavelength for the lead opening) and why they get shorter the weaker the ice becomes. Or do you think that the deep ocean is suddenly producing short-wave tsunamis because the ice-cover gets weaker?

johnm33

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Re: Importance of waves in the Arctic
« Reply #87 on: May 20, 2016, 08:22:18 PM »
"It seems to me" No I'm definitely talking about internal waves, though I can't say the evidence for any particular lead being formed by them is unambiguous. But if you have say a 2k wavelength wave raising the ice surface slowly by 2-3m first theres the tendency of the ice to flow to the trough then with an opening the wind gains purchase, how do you call that? Sensors in the ocean has to be the answer.
2K wavelength

9 mile wavelength [byeyeball]


from http://maps.ngdc.noaa.gov/viewers/bathymetry/
http://go.nasa.gov/1TtB8w6 [EOSDIS]
« Last Edit: May 21, 2016, 12:48:46 PM by johnm33 »

Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #88 on: May 26, 2016, 12:14:36 PM »
Thanks to timallard for bringing to my attention this longer video about the October 12th 2015 storm in the Beaufort Sea:



A transcript is available on the APL web site:

http://www.apl.washington.edu/project/project.php?id=arctic_sea_state

The main portion of the Beaufort was still open water at that point. And a strong easterly wind event came through that built large waves — waves that got to almost five meters in height. And the winds were something like up to thirty knots. And these waves were coming into the newly forming ice and making pancake ice.

We saw this happening so we quickly made a plan. And we put out this long array of buoys. We put out a total of 16 different types of wave measurement buoys.

So what we thought we were going to do was put these buoys out and they would measure the waves for awhile until the ice slowly started to mature enough so that it damped the waves. And the pancakes would start to lock  together and then the waves wouldn’t be able to penetrate further into the ice pack and that would be the end of the event. But that’s not what happened. What happened is the ice went away. Almost all the ice melted - really unexpected by everyone on board the ship.

There was a very warm layer of water 20 meters down beneath the surface. And these waves coming in were  enough to drive additional mixing and bring that warm water up from the subsurface and that warm water melted the ice and changed that balance happening at the surface.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

johnm33

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Re: Importance of waves in the Arctic
« Reply #89 on: May 28, 2016, 04:14:27 PM »
I've convinced myself that a body of Pacific water is about to slam into Banks Is/Amundsen Gulf area from the direction of NSI, so we should see a positive anomoly show up on Nullschool, some evaporation and if it's as warm as I'm guessing then perhaps enough to create it's own weather locally. It'll then bounce back and should smash up and melt the nearest ice, after that it's up to the wind but an interesting week ahead.

anim. http://www7320.nrlssc.navy.mil/hycomARC/navo/beaufortopening_nowcast_anim30d.gif
from http://www7320.nrlssc.navy.mil/hycomARC/beaufort.html

LRC1962

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Re: Importance of waves in the Arctic
« Reply #90 on: June 03, 2016, 12:11:51 AM »
"It seems to me" No I'm definitely talking about internal waves, though I can't say the evidence for any particular lead being formed by them is unambiguous. But if you have say a 2k wavelength wave raising the ice surface slowly by 2-3m first theres the tendency of the ice to flow to the trough then with an opening the wind gains purchase, how do you call that? Sensors in the ocean has to be the answer.
https://www.insidescience.org/content/undersea-waves-may-melt-arctic-ice/3976 May help with the needed physicsof internal waves.
"All truth passes through three stages: First, it is ridiculed; Second,  it is violently opposed; and Third, it is accepted as self-evident."
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LRC1962

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Re: Importance of waves in the Arctic
« Reply #91 on: June 03, 2016, 12:24:39 AM »
@JimH: for the crazies of the world

https://vimeo.com/166930720
"All truth passes through three stages: First, it is ridiculed; Second,  it is violently opposed; and Third, it is accepted as self-evident."
       - Arthur Schopenhauer

johnm33

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Re: Importance of waves in the Arctic
« Reply #92 on: July 10, 2016, 10:35:42 PM »
I've stated above that I think the type of cracks on this [random] image, here stretching from north of bering towards the archipelago are signals of internal waves. Due no doubt to winds shifting the ice around, so how to distinquish between the simple effects of wind and the signs of internal waves? The best candidates, for internal waves are those which have low numbers of more or less parallel cracks, especially when they are followed by orthogonal cracks in fairly short order. You get very few of these appearing when the ice reaches the coastlines and becomes locked. What I think I'm observing now is a reduction due to the fragmentation  of the ice, such that no coherent crack exists for long enough to get picked up by the satelite. That doesn't mean they're not happening, but they're getting lost in the general wind driven movement, and the likely smaller surface waves.

if you want to expand the image http://www7320.nrlssc.navy.mil/hycomARC/navo/arcticictn/nowcast/ictn2016050918_2016051000_042_arcticictn.001.gif
[edit updated links]
« Last Edit: August 04, 2016, 10:13:05 AM by johnm33 »

johnm33

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Re: Importance of waves in the Arctic
« Reply #93 on: July 23, 2016, 11:07:45 PM »
I've been looking at this, http://marine.copernicus.eu/web/69-interactive-catalogue.php since Jim Hunt recently linked to it elsewhere. I found this interesting

it shows [imo] the waves and subsequent break-up of the ice this season quite well. Open the link, it's the first product, basket, view, +below the hand gives you arctic option, i like the pallette i've chosen but there's a selection,  bottom left is the animation icon, i run it from 06:01 at 2fps.
Not waves but this one gives some sense of the oceans daily movements.

johnm33

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Re: Importance of waves in the Arctic
« Reply #94 on: August 04, 2016, 10:45:33 AM »
Adding to 92 above, I've seen no signs of internal waves since the 16th july

The ice is now so smashed that the winds and surface gravity waves move the ice around disguising any signs of them. The other side of this coin is that now the ice is at the mercy of gravity waves, the peices will smash into each other dousing themselves in brine and breaking apart. Nullschool is showing powerful winds blowing into the Arctic from SE of NSI poleward. My opinion is that the ice here is largely lightweight layer cake and could disappear at a shocking rate. We'll see in the next few days.
https://earth.nullschool.net/#current/wind/surface/level/orthographic=-0.48,86.69,811/loc=155.151,79.500 Unfortunately waves north of about 77N are not being looked for.
https://earth.nullschool.net/#current/ocean/primary/waves/overlay=sea_surface_temp_anomaly/orthographic=-0.48,86.69,811/loc=155.151,79.500
« Last Edit: August 04, 2016, 10:51:00 AM by johnm33 »

Tor Bejnar

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Re: Importance of waves in the Arctic
« Reply #95 on: August 19, 2016, 09:16:44 PM »
I expect we are going to learn something of the importance of waves in the Arctic as soon as the current series of regenerating high-Arctic lows passes into history.  The Windyty wind forecast for next Tuesday suggests 3 meter seas fairly close to the ice. (Yes, I know 4 days out is 'just guessing'.)
Arctic ice is healthy for children and other living things.

Tor Bejnar

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Re: Importance of waves in the Arctic
« Reply #96 on: August 24, 2016, 02:43:35 AM »
So, how are the winds, now that Tuesday is here?  4m waves near the ice!
Image from today.
2nd image is a forecasts for Saturday (I know: 4 days is an eternity for arctic weather forecasting).
Arctic ice is healthy for children and other living things.

ghoti

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Re: Importance of waves in the Arctic
« Reply #97 on: August 24, 2016, 03:16:52 AM »
I haven't been able to find any near real time data from CCGS Louis St Laurent or IB Oden. They are in the thick of it and wave height info would be amazing to have.

Anyone know if there is a source that I just haven't found yet?

johnm33

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Re: Importance of waves in the Arctic
« Reply #98 on: September 08, 2016, 06:55:46 PM »

Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #99 on: October 02, 2016, 10:46:33 AM »
A new paper from Jim Thomson et al.

"Emerging trends in the sea state of the Beaufort and Chukchi seas"

The autumn storms that regularly occur in the Beaufort and Chukchi Seas are elevating the sea state now, and will continue so into the future, simply because it is increasingly likely that the storms will occur over larger open water areas that persist longer into autumn. It is yet to be determined if the higher sea states will in turn feed back to the large-scale evolution of the sea ice. The increasing sea state may affect not only the ice cover development, but also wave forcing in the coastal zone. Either way, the increasing sea states may alter air-sea fluxes and associated ecosystem processes. It is possible that the increasing sea state may play an important role in modulating the presumed changes in air-sea fluxes and upper ocean properties that are occurring, and in turn may modulate the response of sea ice to climate change. Finally, higher sea states are of operational importance to mariners and seabed drilling operators in the region, for whom higher sea states can increase the likelihood of dangerous icing conditions on ships and structures.


not to mention:

The process of wind-wave generation in partial ice cover is likely far more complex than present models suggest and is in acute need of improved understanding.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein