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LRC1962

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Importance of waves in the Arctic
« on: April 08, 2015, 11:20:27 PM »
A few publications I have found regarding waves in the Arctic.
Wave heights in the 21st century Arctic Ocean simulated with a regional climate model
In conclusion, we conducted an analysis of possible changes to the wind-wave climate in the Arctic Ocean in
the 21st century. This was done by means of a third-generation wave model and climate modeling under an
anthropogenic-forcing scenario. The outcomes demonstrate overall growth in wave height in the Arctic.
Concurrent with mean wave growth, models predict more frequent extreme waves in different areas of
the Ocean.

Estimates of ocean wave heights and attenuation in sea ice using the SAR wave mode on Sentinel-1A
Abstract
Swell evolution from the open ocean into sea ice is poorly understood, in particular the amplitude attenuation expected from scattering and dissipation. New synthetic aperture radar (SAR) data from Sentinel-1A wave mode reveal intriguing patterns of bright oscillating lines shaped like instant noodles. We investigate cases in which the oscillations are in the azimuth direction, around a straight line in the range direction. This observation is interpreted as the distortion by the SAR processing of crests from a first swell, due to the presence of a second swell. Since deviations from a straight line should be proportional to the orbital velocity toward the satellite, swell height can be estimated, from 1.5 to 5 m in the present case. The evolution of this 13 s period swell across the ice pack is consistent with an exponential attenuation on a length scale of 200 km.
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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #1 on: April 22, 2015, 11:06:57 AM »
« Last Edit: April 22, 2015, 11:12:58 AM by Jim Hunt »
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Re: Importance of waves in the Arctic
« Reply #2 on: April 22, 2015, 11:40:58 AM »
Some additional references:

Sea ice floes dissipate the energy of steep ocean waves: http://arxiv.org/pdf/1502.06040

On the 2012 record low Arctic sea ice cover: Combined impact of preconditioning and an August storm 2013 - http://onlinelibrary.wiley.com/doi/10.1002/grl.50349/full

Storm-induced sea-ice breakup and the implications for ice extent: http://www.nature.com/articles/nature13262

In Situ Measurements of an Energetic Wave Event in the Arctic Marginal Ice Zone: http://onlinelibrary.wiley.com/doi/10.1002/2015GL063063/abstract

Swell and sea in the emerging Arctic Ocean - http://onlinelibrary.wiley.com/doi/10.1002/2014GL059983/epdf

Fracture of summer perennial sea ice by ocean swell as a result of Arctic storms: http://onlinelibrary.wiley.com/doi/10.1029/2011JC007221/abstract

Waves in-ice observations made during the SIPEX II voyage of the Aurora Australis: http://dx.doi.org/10.4225/15/53266BEC9607F
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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #3 on: June 22, 2015, 11:44:33 AM »
An enquiry copied from the 2015 melting season thread:

Pardon a newbie question. Will wave motion form if the ice is very broken and if so would that affect the meltdown?




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Re: Importance of waves in the Arctic
« Reply #4 on: June 22, 2015, 11:49:23 AM »
A picture of "a wave" in the Arctic, courtesy of ktonine and the following article:

Arctic Seas Surprisingly Alive in Winter

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Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #5 on: June 22, 2015, 01:11:46 PM »
It seems from a "debate" elsewhere that some people are labouring under the misapprehension that:

The only thing that happens in the basin is tides, which have a period(high to high) of about 12 hours.


and that:

You either have waves or you have ice.... you do not get both.


However, according to Asplin et al..

Laser data collected during the helicopter EMI survey at station MYI indicated a swell period of 13.5 s, and a wavelength ranging from 200–300 m. Laser data were collected while the helicopter hovered over a large MY ice floe. These data were augmented with three-dimensional dynamic ship positioning data, which revealed approximate ship heave amplitude of 0.4 m, also with a period of 13.5 s. The swell caused the vast MY ice floe nearest the Amundsen to ride up one side of the swell and fracture as it crested the wave peak, creating smaller ice floes of width approximately one half of the wavelength of the swell. In a matter of minutes from the initial onset of swell propagation, all large MY ice floes in the region were fractured in this manner, yielding a new distribution of smaller MY ice floes ranging from 100–150 m in diameter

On 09 September 2009, we conducted a longitudinal helicopter EMI survey at 72.5 N, and determined the limit of the swell penetration into the pack ice at 72.526 N 134.51 W, a penetration of 350 km. Furthermore, the rotted FY ice margin was heavily fractured, with small floe sizes ranging from 20–50 m in diameter.


Whatever theory may predict regarding the interactions of sea ice and "waves", empirical evidence suggests that long period swells can in actual fact penetrate 100s of km into "pack ice".
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Re: Importance of waves in the Arctic
« Reply #6 on: June 22, 2015, 05:07:20 PM »
A picture of "a wave" in the Arctic, courtesy of ktonine and the following article:

Arctic Seas Surprisingly Alive in Winter




You might want to double check the location for that picture.

http://arctic-winter-cruise.blogspot.com/2011/12/crashing-waves.html

SO, there are big waves in the Bering Sea in December?

Sorry to interject science into the discussion. Here is a table of the relationship between wind speed and wave period and wavelength:

https://en.wikipedia.org/wiki/Swell_(ocean)

[hide]Conditions Necessary for a Fully Developed Sea at Given Wind Speeds, and the Parameters of the Resulting Waves
Wind Conditions   Wave Size
Wind Speed in One Direction   Fetch   Wind Duration   Average Height   Average Wavelength   Average Period and Speed
19 km/h (12 mph)   19 km (12 mi)   2 h   0.27 m (0.89 ft)   8.5 m (28 ft)   3.0 s, 2.8 m/s (9.3 ft/s)
37 km/h (23 mph)   139 km (86 mi)   10 h   1.5 m (4.9 ft)   33.8 m (111 ft)   5.7 s, 5.9 m/s (19.5 ft/s)
56 km/h (35 mph)   518 km (322 mi)   23 h   4.1 m (13 ft)   76.5 m (251 ft)   8.6 s, 8.9 m/s (29.2 ft/s)
74 km/h (46 mph)   1,313 km (816 mi)   42 h   8.5 m (28 ft)   136 m (446 ft)   11.4 s, 11.9 m/s (39.1 ft/s)
92 km/h (57 mph)   2,627 km (1,632 mi)   69 h   14.8 m (49 ft)   212.2 m (696 ft)   14.3 s, 14.8 m/s (48.7 ft/s)

So, it takes 92 km/hr to make waves with a period greater than 13 seconds.



http://onlinelibrary.wiley.com/doi/10.1029/2009GL040676/full

Here we see the attenuation of waves by ice. Waves with periods of 13 seconds attenuate by a factor of  1/1,000,000 in fifty kilometers. That means a ten meter wave would be a 0.01mm( 100 000 angstroms ) ripple at that distance. Do you really want to call 0.01 mm a wave?

Verg



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Re: Importance of waves in the Arctic
« Reply #7 on: June 22, 2015, 05:34:41 PM »
Whatever theory may predict regarding the interactions of sea ice and "waves", empirical evidence suggests that long period swells can in actual fact penetrate 100s of km into "pack ice".


Urban Dictionary: straw man
www.urbandictionary.com/define.php?term=straw+man
Urban Dictionary
Top Definition. straw man. A logic fallacy involving the purposeful misrepresentation of an argument in order to strike it down. Beware of logic fallacies.


I make a statement about waves, you argue that my statements are false because I meant tides, swells and surges. No, I meant waves. And you have the audacity to use a picture misidentified as in the Arctic basin to bolster your argument. You also used observations in the sea of Okhotsk to refute a statement about the arctic basin. You use a singular event to refute an in general rule.

I ask you a direct question that would end a senseless semantic squabble, and you ignore it,

Jim Hunt,

Pardon a newbie question. Will wave motion form if the ice is very broken and if so would that affect the meltdown?


Welcome to ASIF

In general waves do not penetrate into the ice pack. Their effect is only on the periphery.

Verg :)


In what way does a remarkable observation of a surge in 2009 penetrating the arctic ice cap refute the assertion that "in general" this does not happen?

There are continuous reports of wave action 100's of km from the edge.


Does it support the assertion that there are "continuous reports" of such events? If you were grading a test, which of these statements would you grade as true, and which are false?

Verg


Please stop playing the troll.

Verg
« Last Edit: June 22, 2015, 05:57:17 PM by Vergent »

Jim Hunt

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Re: Importance of waves in the Arctic
« Reply #8 on: June 22, 2015, 05:40:21 PM »
Hi Vergent,

SO, there are big waves in the Bering Sea in December?


I refer you to the title of this thread. Is the Bering Sea in the Arctic?

Here we see the attenuation of waves by ice. Waves with periods of 13 seconds attenuate by a factor of  1/1,000,000 in fifty kilometers. That means a ten meter wave would be a 0.01mm( 100 000 angstroms ) ripple at that distance. Do you really want to call 0.01 mm a wave?


Are Asplin et al. telling porky pies, or alternatively is the model used by Squire et al. lacking in some way?
« Last Edit: June 22, 2015, 05:53:18 PM by Jim Hunt »
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Vergent

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Re: Importance of waves in the Arctic
« Reply #9 on: June 22, 2015, 06:58:06 PM »
Jim,

Are Asplin et al. telling porky pies, or alternatively is the model used by Squire et al. lacking in some way?


First let's look at 2009, and see if there are unusual conditions;



In 2009, while the CAB area loss was not that remarkable, but, the CAB area loss was all in one contiguous place. This expanse of exposed deep water creates the possibility for a long wavelength surge to develop within the CAB itself. What was needed was for a 92 km/h wind to blow for 69 hours. The coincidence of these two rare events created the exceedingly rare rare event recorded by Aspin et al. Edit; afterthought; the 2009 event could have been caused by a seiche type event in the ESS/Chukchi area.

However, with climate change, the rare may become commonplace.

Verg

BTW, the source you cited for that picture identified it as;

Verge - THINK!  Here's the Healy in late fall in the Beaufort/Chukchi
« Last Edit: June 22, 2015, 07:25:29 PM by Vergent »

Vergent

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Re: Importance of waves in the Arctic
« Reply #10 on: June 22, 2015, 07:16:33 PM »

http://www.sci-news.com/othersciences/geophysics/science-extreme-waves-arctic-ocean-02084.html

Here is another remarkable event. But the 5m waves would have a period of 9 - 10s.

Verg

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Re: Importance of waves in the Arctic
« Reply #11 on: June 22, 2015, 08:02:45 PM »
Please stop playing the troll.

Jim Hunt isn't a troll, nor does he play one here. Don't even suggest it and stop being so aggressive, please.
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Vergent

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Re: Importance of waves in the Arctic
« Reply #12 on: June 22, 2015, 09:42:26 PM »
Neven,

Sorry, I got frustrated because people kept telling me I was wrong, when I knew i was right. Here is proof:

A high-resolution hindcast of wind and waves for The North Sea,
The Norwegian Sea and The Barents Sea

arxiv.org/ftp/arxiv/papers/1111/1111.0770.pdf

Over an 11 year history(1991-2002), measured by quality controlled buoys, the maximum wave height was less than 13 meters(page 25). Only 2 surges with periods greater than 15 seconds were detected. They were 16 and 17 seconds(page 29). A 17 second period wave can penetrate the ice to 200 km, but it would be attenuated by a factor of 10,000 when it got there. A 12.5 meter high surge would be attenuated to 1.2 mm. We do not know if these surges even made it to the ice.



Conclusion; While it is theoretically possible for surges to enter the Arctic Ice Cap, it is an exceedingly rare event and is dwarfed by other factors like tides and surface winds. It has been a negligible issue. Waves interact in the marginal ice field. It may become a significant issue when the CAB is more significantly exposed.

What happened in 2009? I do not know.

Verg

 Edit; I found a copy of the article where you can copy the graphs:

 



Figure 12. Observed versus modeled ((top) WAM10 and (bottom) ERA-40) mean period, Tm (s), for the period 1991–2002. Only data from a subset of quality-controlled stations found in Figure 5 were used.
« Last Edit: June 22, 2015, 11:03:36 PM by Vergent »

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Re: Importance of waves in the Arctic
« Reply #13 on: June 22, 2015, 11:02:09 PM »
Here is another remarkable event. But the 5m waves would have a period of 9 - 10s.


I know. I've blogged about it. See above:

http://forum.arctic-sea-ice.net/index.php/topic,1222.msg50645.html#msg50645

FYI - This has happened for the second time now. A comment of yours was invisible to me when I posted one of mine.
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Re: Importance of waves in the Arctic
« Reply #14 on: June 22, 2015, 11:03:50 PM »
However, with climate change, the rare may become commonplace.

We can agree on something then!
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Re: Importance of waves in the Arctic
« Reply #15 on: June 22, 2015, 11:13:40 PM »
What happened in 2009? I do not know.


Here's what happened once again (always assuming you agree that Asplin et al. aren't telling porky pies):

A swell period of 13.5 s, and a wavelength ranging from 200–300 m. Approximate ship heave amplitude of 0.4 m, also with a period of 13.5 s.


Here's where it happened once again (at the point marked "MYI" on the map):

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Re: Importance of waves in the Arctic
« Reply #16 on: June 22, 2015, 11:22:12 PM »
You have the audacity to use a picture misidentified as in the Arctic basin to bolster your argument.

No I didn't. I posted an interesting picture of a wave in the Arctic (and an interesting link) in a topic about waves in the Arctic. Thanks for your interesting link.

I ask you a direct question that would end a senseless semantic squabble, and you ignore it,

You ignored a set of increasingly heavy hints to pursue "a senseless semantic squabble" somewhere else.

Please stop playing the troll.

I echo what Neven said.
« Last Edit: June 23, 2015, 01:05:19 AM by Jim Hunt »
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Re: Importance of waves in the Arctic
« Reply #17 on: June 23, 2015, 12:16:57 AM »
Neven,

Sorry, I got frustrated because people kept telling me I was wrong, when I knew i was right. Here is proof:

A high-resolution hindcast of wind and waves for The North Sea,
The Norwegian Sea and The Barents Sea

arxiv.org/ftp/arxiv/papers/1111/1111.0770.pdf

Over an 11 year history(1991-2002), measured by quality controlled buoys, the maximum wave height was less than 13 meters(page 25). Only 2 surges with periods greater than 15 seconds were detected. They were 16 and 17 seconds(page 29). A 17 second period wave can penetrate the ice to 200 km, but it would be attenuated by a factor of 10,000 when it got there. A 12.5 meter high surge would be attenuated to 1.2 mm. We do not know if these surges even made it to the ice.


It was not two surges, but two measurements of mean period (as the label on the diagram indicates) that were measured greater than 15 seconds.  I note from these tables that significant numbers of measurements of mean period > 10 seconds were made.  A distribution (see page 34) of periods shows that non-negligible numbers of waves have periods of 2.5 x the mean period.  So we have a small but significant number of times were the mean period is 10s, and each time this happens, a small percentage of waves will have periods as high as 25 s.  Looking at the attenuation diagrams you provided, such waves can penetrate for 1600 km, maintaining 10% of their original height.
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Re: Importance of waves in the Arctic
« Reply #18 on: June 23, 2015, 12:18:32 AM »

First let's look at 2009, and see if there are unusual conditions;



In 2009, while the CAB area loss was not that remarkable, but, the CAB area loss was all in one contiguous place.


As was the case in 2007, 2008, 2010, 2011, 2012, but not really in 2013 or 2014.
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Re: Importance of waves in the Arctic
« Reply #19 on: June 23, 2015, 02:49:09 AM »
Neven,

Sorry, I got frustrated because people kept telling me I was wrong, when I knew i was right. Here is proof:

A high-resolution hindcast of wind and waves for The North Sea,
The Norwegian Sea and The Barents Sea

arxiv.org/ftp/arxiv/papers/1111/1111.0770.pdf

Over an 11 year history(1991-2002), measured by quality controlled buoys, the maximum wave height was less than 13 meters(page 25). Only 2 surges with periods greater than 15 seconds were detected. They were 16 and 17 seconds(page 29). A 17 second period wave can penetrate the ice to 200 km, but it would be attenuated by a factor of 10,000 when it got there. A 12.5 meter high surge would be attenuated to 1.2 mm. We do not know if these surges even made it to the ice.


It was not two surges, but two measurements of mean period (as the label on the diagram indicates) that were measured greater than 15 seconds.  I note from these tables that significant numbers of measurements of mean period > 10 seconds were made.  A distribution (see page 34) of periods shows that non-negligible numbers of waves have periods of 2.5 x the mean period.  So we have a small but significant number of times were the mean period is 10s, and each time this happens, a small percentage of waves will have periods as high as 25 s.  Looking at the attenuation diagrams you provided, such waves can penetrate for 1600 km, maintaining 10% of their original height.


Michael,

Thank you for this. 25 second surges seem impossible in the shallow northern waters. This dataset includes Iceland, Ireland, and England. A narrower data set near the marginal ice zone is needed.

I found a surf report site for Svalbard:

http://www.surf-forecast.com/maps/Svalbard/significant-wave-height/150

Now they seem to peak out at 6 ft, which, is a mean and follows the relationship you suggest would indicate peak wave height of around 15 ft. Less than 5 meters. Too small to enter the basin.

There also is a global animation:

http://www.surf-forecast.com/weather_maps/Global-Pacific

It's scale is in wave energy. It appears that wave energy is attenuated by a factor of 5 as it passes through the window between England and Iceland. It also shows how deep wave intrusion under the antarctic ice is continuous.

Again thanks for putting me straight about that data.

Verg

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Re: Importance of waves in the Arctic
« Reply #20 on: June 23, 2015, 11:02:20 AM »
So we have a small but significant number of times were the mean period is 10s, and each time this happens, a small percentage of waves will have periods as high as 25 s.  Looking at the attenuation diagrams you provided, such waves can penetrate for 1600 km, maintaining 10% of their original height.

Quite so, but nevertheless Asplin et al. report a 0.4 meter 13.5 second swell 250 km from the ice edge on September 6th 2009, with the effects of said swell visible from a helicopter for a further 100 km.
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Re: Importance of waves in the Arctic
« Reply #21 on: June 23, 2015, 11:15:45 AM »
I found a surf report site for Svalbard


If you were a surfer you would look at the period forecast before the wave height. Here's one from my friendly local neighbourhood surf forecasting site:

http://magicseaweed.com/World-Surf-Chart/64/?chartType=PERPW

Here's one I prepared earlier for the Arctic basin on September 6th 2009:

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Re: Importance of waves in the Arctic
« Reply #22 on: June 23, 2015, 06:39:17 PM »
Quite so, but nevertheless Asplin et al. report a 0.4 meter 13.5 second swell 250 km from the ice edge on September 6th 2009, with the effects of said swell visible from a helicopter for a further 100 km.

That bears repeating.

This was an extraordinarily well-documented event -- by before and after video, by helicopter EMI, by laser altimetry, by ship's instrumentation of heave, pitch and roll, by ice coring, by ice salinity measurement, by floe size and thickness distributions, by ship's crew, by scientific staff who were about to disembark onto by the MYI just prior to its collapse, by further swells observed 3 days following, etc etc -- that was published in a major peer-reviewed geophysics journal.

There is nothing that special about the Siberian cyclonic lows with central pressures of 990 mb and 986 mb; the only thing special is a monitoring icebreaker happened to be out there in the ice in the condition it was in on Sept 2012.

The article remains utterly uncontroversial within the scientific community with 39 articles citing the 2012 paper. One of those is a follow-up article by the same authors (bad url at www.bio.gc.ca/ but available through ResearchGate).

The results of Radarsat-2 imagery analysis show that a flexural fracture event which occurred in the Beaufort Sea region on 06 September 2009 affected ~40,000 km2. Open water fractional area in the area affected initially decreased from 3.7% to 2.7%, but later increased to ~20% following wind-forced divergence of the ice pack.

Energy available for lateral melting was assessed by estimating the change in energy entrainment from longwave and shortwave radiation in the mixed-layer of the ocean following flexural fracture. 11.54 MJ · m-2 of additional energy for lateral melting of ice floes was identified in affected areas. The impact of this process in future Arctic sea ice melt seasons was assessed using estimations of earlier occurrences of fracture during the melt season, and is discussed in context with ocean heat fluxes, atmospheric mixing of the ocean mixed layer, and declining sea ice cover. We conclude that this process is an important positive feedback to Arctic sea ice loss


Another relevant citing article describes 4 m swell in pack ice SE of Svalbard/N of Hopen Island in early May 2010. The March 2015 paper is paywalled but Dr. Collins sent a pdf within 10 minutes. This has a very nice review of Arctic wave literature and wave physics of the witnessed event, another hair-raising story of researchers about to go off-ship. Here the main instrumentation was shipboard GPS with vertical position accuracy of 0.05 m. Recommended read.
These are the largest known waves recorded in the Arctic with substantial ice cover present, and we expect the measurement of large-wave events to occur more frequently in the future due to the fetch wave-ice fetch feedback loop.

http://scholarworks.uno.edu/cgi/viewcontent.cgi?article=1049&context=oceanwaves
http://onlinelibrary.wiley.com/doi/10.1002/2015GL063063/abstract

See also "Swell and sea in the emerging Arctic Ocean", a mooring study by J Thomson and WE Rogers Geophys Res Lett http://onlinelibrary.wiley.com/doi/10.1002/2014GL059983/pdf (free full):

Wave observations were collected using a 600 kHz Nortek Acoustic Wave and Current (AWAC) sensor deployed on a subsurface mooring at 75 ◦ N, 150 ◦ W as part of the Beaufort Gyre Exploration Project. The AWAC was mounted at the top (50 m below the surface) of the 3000 m mooring, looking up to the surface. The AWAC uses sonar pings to determine the distance from the instrument to the sea surface, and this dis- tance is recorded at 1 Hz for 1024 s at the beginning of each hour. These records are processed using a fast Fourier transform to determine the wave energy spectra, as well as the significant wave height (defined as 4 times the square root of the variance in sea surface elevation at frequencies 0.05–0.6 Hz), or the ice draft when ice is present.

We show that the increased open water of 2012 allowed waves to develop beyond pure wind seas and evolve into swells. The swells remain tied to the available fetch, however, because fetch is a proxy for the basin size in which the wave evolution occurs. Thus, both sea and swell depend on the open water fetch in the Arctic, because the swell is regionally driven. This suggests that further reductions in seasonal ice cover in the future will result in larger waves, which in turn provide a mechanism to break up sea ice and accelerate ice retreat.

In summary, I find it quite inappropriate, bordering on rudeness, to continuing challenging -- without any observational basis or consideration of readily available subsequent on-topic papers -- the original authors' summary of waves in ice being an unsuspected and trending feedback mechanism furthering loss of Arctic sea ice.

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Re: Importance of waves in the Arctic
« Reply #23 on: June 23, 2015, 07:36:16 PM »
Thanks for the ResearchGate tip A-Team. Whilst there I noticed that one of LRC's original ("behind paywall") articles is available:

Estimates of ocean wave heights and attenuation in sea ice using the SAR wave mode on Sentinel-1A

Over the last 30 years, the dramatic reduction in ice cover and thickness in the Arctic is opening larger ocean expanses for wave development. Understanding how the waves influence the breaking of ice in floes, and how sea ice attenuates surface gravity waves, are essential improvements for Earth system models at high latitudes. The representation of sea ice in commonly used numerical wave models is still fairly crude, often based on a partial blocking of wave energy. Wave transformation in sea ice combines a change in phase speed, scattering by ice floes and changes in ice thickness, and dissipation. Recent refinements taking into account both scattering by ice floes and friction below the ice have been introduced by Doble and Bidlot [2013]. However the functional form of parametrizations and the magnitude of the coefficients are still very uncertain due to the paucity of wave measurements in ice-covered waters.



 
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Re: Importance of waves in the Arctic
« Reply #24 on: June 25, 2015, 12:31:57 PM »
Everyone,

Please read this so we can be speaking the same language;

http://www.stormsurf.com/page2/tutorials/wavebasics.shtml

Verg

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Re: Importance of waves in the Arctic
« Reply #25 on: June 26, 2015, 11:16:40 AM »
Please read this so we can be speaking the same language;

Verg,

I'm afraid that once again I fail to comprehend the point you are endeavouring to make. I pointed interested readers (possibly even big wave surfers!) at that same page in my own article on the topic. Aren't you and I already speaking the same language?

Is there any possibility you could elucidate at greater length?
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Re: Importance of waves in the Arctic
« Reply #26 on: June 27, 2015, 05:18:45 AM »
Jim,

I grew up in a maritime community. I learned words regarding the sea before I can remember. But "wave" and "swell" were two distinct and different terms. I lived on Virginia beach and as a four year old played in the eye of hurricane Hazel. But, yesterday, my sister came back from sailing on the Santa Monica bay and remarked about the "swells" that were coming in. I realized that she shared my linguistics.

On the sea, there are very specific terms to describe the situation. "Aft" "Forward", "Port", "Starboard", these are not colloquialisms, these are terms that save the ship in distress. "Swell" and "Wave" are in the same category. They are not the same thing at all.

Verg

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Re: Importance of waves in the Arctic
« Reply #27 on: June 27, 2015, 05:28:46 AM »
Jim,

As a surfer, I thought you knew the distinction. That is why I thought you were "playing the troll". I have been hesitant to apologize because, well, the foundations of linguistics are in early childhood. No-one is guilty of that. We use words differently. We have to live with that. But on the bridge of an ocean going ship,....you better know the difference between a swell and a wave.

Verg

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Re: Importance of waves in the Arctic
« Reply #28 on: June 27, 2015, 11:59:46 AM »
Verg,

I am well aware of the difference between a wave and a swell, even though some authors of papers in scientific journals seem not to be. That's one reason why many moons ago I posted webcam pictures of some "waves" in the Arctic Basin:



and "a modest swell" in the Arctic Basin:



Do those images conform to your own "linguistics"?
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Vergent

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Re: Importance of waves in the Arctic
« Reply #29 on: June 28, 2015, 04:16:58 AM »
Jim,

even though some authors of papers in scientific journals seem not to be.

We have another point of agreement.

Verg

Michael Hauber

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Re: Importance of waves in the Arctic
« Reply #30 on: June 28, 2015, 08:53:57 AM »
Science has a specific definition for wave, which goes beyond just ocean waves to cover an extremely wide range of physical phenomena.    This definition can apply to surf, sound, light, gravity, traffic jams and plenty more.  According to this definition all swells are a wave.  After all we refer to the 'wavelength' of a swell, and not the 'swelllength'.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

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Re: Importance of waves in the Arctic
« Reply #31 on: June 28, 2015, 10:12:24 AM »




Actually, some scientists refer to the "period of total swell".

Verg

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Re: Importance of waves in the Arctic
« Reply #32 on: June 28, 2015, 11:00:43 AM »
This whole discussion is rather odd and puzzling to me. From the basic physics (and the quotes from observations above) it looks obvious to me what the issues are.
Short waves are dissipated quickly in sea ice where it breaks up floes and crushes them against each other. This of course is an energy input as well as increasing surface area of the ice and increasing mixing around them.
Every blog from an icebreaker I have read includes the observation that the ship is a lot calmer once it is among ice floes, the sea surface is moving about less (to avoid using a wrong word)
Swells of long wavelength are dissipated less but that also means they have less energy input, if they had they would become weaker as their energy is dissipated. They can on the other hand break larger floes further from the edge. The larger floe will experience large forces from change in surface height over a long distance (wavelength) which a smaller floe doesn't even notice.
Thus long swells reach further into the pack, have a selective impact on large floes but less impact on the smaller floes.
Could this be something everybody agrees on?

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Re: Importance of waves in the Arctic
« Reply #33 on: June 28, 2015, 04:28:41 PM »
This whole discussion is rather odd and puzzling to me. From the basic physics (and the quotes from observations above) it looks obvious to me what the issues are.
Short waves are dissipated quickly in sea ice where it breaks up floes and crushes them against each other. This of course is an energy input as well as increasing surface area of the ice and increasing mixing around them.
Every blog from an icebreaker I have read includes the observation that the ship is a lot calmer once it is among ice floes, the sea surface is moving about less (to avoid using a wrong word)
Swells of long wavelength are dissipated less but that also means they have less energy input, if they had they would become weaker as their energy is dissipated. They can on the other hand break larger floes further from the edge. The larger floe will experience large forces from change in surface height over a long distance (wavelength) which a smaller floe doesn't even notice.
Thus long swells reach further into the pack, have a selective impact on large floes but less impact on the smaller floes.
Could this be something everybody agrees on?

Yes.

Verg

Michael Hauber

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Re: Importance of waves in the Arctic
« Reply #34 on: June 28, 2015, 09:23:01 PM »
This whole discussion is rather odd and puzzling to me. From the basic physics (and the quotes from observations above) it looks obvious to me what the issues are.
Short waves are dissipated quickly in sea ice where it breaks up floes and crushes them against each other. This of course is an energy input as well as increasing surface area of the ice and increasing mixing around them.
Every blog from an icebreaker I have read includes the observation that the ship is a lot calmer once it is among ice floes, the sea surface is moving about less (to avoid using a wrong word)
Swells of long wavelength are dissipated less but that also means they have less energy input, if they had they would become weaker as their energy is dissipated. They can on the other hand break larger floes further from the edge. The larger floe will experience large forces from change in surface height over a long distance (wavelength) which a smaller floe doesn't even notice.
Thus long swells reach further into the pack, have a selective impact on large floes but less impact on the smaller floes.
Could this be something everybody agrees on?

Yes, but one more important fact is that waves with a longer period have more energy in total.  The circulation reaches deeper into the ocean and moves more water below the surface. 
Climate change:  Prepare for the worst, hope for the best, expect the middle.

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Re: Importance of waves in the Arctic
« Reply #35 on: June 30, 2015, 06:50:29 PM »
One more important fact is that waves with a longer period have more energy in total.

It's the hottest day of the year here. I don't know about you guys, but I'm off to the beach. 3 feet at 9 secs plus a newly arrived 1 foot at 17 secs. And an offshore breeze to boot  :)
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

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Re: Importance of waves in the Arctic
« Reply #36 on: July 01, 2015, 01:23:01 AM »
Good surfing Jim.

I stumbled on this, while searching for Canadian ice charts.:

A Review of Extreme Wave Conditions in the Beaufort Sea

http://www.dfo-mpo.gc.ca/Library/90666.pdf

I suggest you read section 3 & 4 first, some of the previous studies they describe are found to be flawed.

Verg




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Re: Importance of waves in the Arctic
« Reply #37 on: July 01, 2015, 04:13:10 AM »
Verg, that pdf is dated 1985, thirty years ago. What possible relevance could that have to modern reports, cited above, of swells interacting with pack ice that no one on this forum troubles themselves to read?

The two recent studies on the Beaufort event describe an event observed before, during, and after with a very heavily instrumented ship -- this is completely unprecedented. Maybe start with reading those. Full text.

I'm thinking we should delete this entire forum and start over with an active moderator. The open water reach has become much longer in August and September in the Arctic Ocean these days and the opportunities for breaking up pack ice much greater. This is an important new negative feedback on Arctic Ocean ice and one that deserves better.

Commentary on sea wave and swell so far has been not been at the level of the respective wikipedia articles. We are aiming a bit higher than that on these forums. At a bare minimum, people need to learn how to do Google Scholar searches to locate and read full text scientific articles on this topic from the last 2-3 years -- these will better explain current thinking and review all earlier work.

The great thing about this topic is Arctic open reach is so new that a half dozen papers about covers it. So folks, ok to ask questions but not ok to post personal musings until AFTER you have READ these few. (I'm getting about as exasperated as AbruptSLR on the methane forum!)
 
To learn what a swell really means in terms of a 3000 m moored buoy with upward looking sonar observing waves 50 m above in the Beaufort, here is a reader-friendly one -- and it's only FOUR PAGES (sampler below). 

There you can learn how scientists unwrap actual waves into their wave energy spectra by fourier transform and determine 'significant wave height' as 4 * square root in sea surface elevation variance at moderate frequency, etc. etc. etc.

Wave theory gets real complicated in a hurry. Spare me your thoughts on that, years ago I was teaching nonlinear dispersive partial differential equations -- cnoidal waves, solitons, KdV and all that, not in some 1834 English canal but rather non-abelian Yang-Mills vacua. Here we just want to touch on the most basic basics of wind waves in deep water.

Once a wave train hits an ice pack heterogenous in so many ways, forget it -- theory is worthless (for lack of specifiable boundary conditions). Fortunately we have a few outstanding observations of what actually happens next.

But best of all, thanks to Asplin 2014, we don't actually need a ship out there anymore because we know when and where major wind events are happening so with Radarsat/Sentinel we can maybe monitor the aftermath directly on floe size and predict enhanced lateral melt.

1. http://www7320.nrlssc.navy.mil/pubs/2014/rogers2-2014.pdf

2. 10.1002/2013JC009557 Implications of fractured Arctic perennial ice cover on thermodynamic and dynamic sea ice processes. MG Asplin et al

 

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Re: Importance of waves in the Arctic
« Reply #38 on: July 01, 2015, 11:36:08 AM »
A-Team,

What??? I shared a link. I made no conclusion about it. It was just a source of information, relevant to this thread. It documented several storms, and showed the expected frequency of them in the past. So, why the hostility?  "we should delete this entire forum" Why? Because I shared a link to a scientific paper?

Verg

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Re: Importance of waves in the Arctic
« Reply #39 on: July 01, 2015, 11:43:02 AM »
Good surfing Jim.

I stumbled on this, while searching for Canadian ice charts.:

A Review of Extreme Wave Conditions in the Beaufort Sea

http://www.dfo-mpo.gc.ca/Library/90666.pdf

I suggest you read section 3 & 4 first, some of the previous studies they describe are found to be flawed.

Verg


A-Team

Please Quote and highlight what you find so offensive.

Verg

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Re: Importance of waves in the Arctic
« Reply #40 on: July 01, 2015, 12:05:17 PM »
Good surfing Jim.

Thanks Verg.

It was a perfect evening, apart from the angle of the swell. I even got to illustrate a "clean up set" from the inside, a topic I discussed with a climate modeller from the Hadley Centre only recently. You will note that I was further out than the rest of the lineup, but unfortunately nowhere near far enough!

If you all promise not to laugh I can provide a video recording of the longest "hold down" of my career since I tried to take on triple overhead Soup Bowl and lost.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

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Re: Importance of waves in the Arctic
« Reply #41 on: July 01, 2015, 12:17:43 PM »
Please Quote and highlight what you find so offensive.

Verg,

Your overly concise "linguistics" are all too easily misunderstood, as are mine occasionally!
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

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Re: Importance of waves in the Arctic
« Reply #42 on: July 01, 2015, 12:35:12 PM »
Thanks Jim, for the surf report.

Verg

Edit: BTW, here is the "surf report" for the north pole;

The broadband signals are mostly dominated by the ice
swell, which has a peak period ranging from 20 to 30 s.
The ice swell manifests itself with equal amplitude on the
vertical and horizontal channels. Figure 2a shows 1 hour of
recording that only contains the ice-swell signal, which at
this time has a peak period of 27 s. Peak-to-peak amplitude
is ∼0.1 mm s−1, which corresponds to ∼0.5 mm of peak to-peak
vertical and horizontal displacement, as is typically
observed (e.g. Hunkins, 1962; LeSchack and Haubrich,
1964; Dugan and others, 1992).


http://oceans.taraexpeditions.org/wp-content/uploads/2015/01/Marsan_JG2011.pdf

http://onlinelibrary.wiley.com/doi/10.1029/JZ067i006p02477/full

« Last Edit: July 01, 2015, 11:21:12 PM by Vergent »

Michael Hauber

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Re: Importance of waves in the Arctic
« Reply #43 on: July 02, 2015, 12:59:05 AM »
Verg, that pdf is dated 1985, thirty years ago. What possible relevance could that have to modern reports, cited above, of swells interacting with pack ice that no one on this forum troubles themselves to read?


I read some of the stuff you posted, and agree with you that waves are a significant issue within the Arctic and reach deep within the pack.  I see Jim Hunt also responded to your previous post:

Thanks for the ResearchGate tip A-Team. Whilst there I noticed that one of LRC's original ("behind paywall") articles is available:

I do see that one member of this forum follows up your post full of useful scientific information with a post suggesting that everyone reads a basic introductory primer on wave/swell issues and then a link to what wave conditions were in the Arctic 30 years ago.  But that is just one person, and doesn't mean that no one is reading or understanding what you have said, or that the forum is a waste of time and should be deleted.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

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Re: Importance of waves in the Arctic
« Reply #44 on: July 02, 2015, 07:50:03 AM »
I'm thinking we should delete this entire forum and start over with an active moderator.


I disagree. I've been studying this stuff since long before Asplin et al. published anything. I hope you'll forgive me when I point out that I'm currently in the midst of a robust online "debate" with the likes of David Rose, Judy Curry and Michael Shellenberger?

Have you bothered to click any of my links, and if so did you comprehend the content? My own introduction to the subject, linked to above, was written for the benefit of the global surfing community in general and the long serving Great White Con Arctic Basin Big Wave Surfing team leader in particular:

https://twitter.com/andrew_cotton/status/616390191390003201

« Last Edit: July 02, 2015, 07:59:34 AM by Jim Hunt »
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Re: Importance of waves in the Arctic
« Reply #45 on: July 04, 2015, 08:47:09 PM »
I recommend watching both videos in my latest Arctic article from cover to cover:

Is Time Running Out for Arctic Sea Ice?

However if you're in a rush skip to 28:30 minutes into the second one, where Prof. Peter Wadhams points out that on his cruise around the Arctic this coming September:

We're looking at one particular thing, which may not be the most important thing, but the retreat of the sea ice in summer is going much faster than computer models predict, and we think that one factor there is the fact that as the sea ice retreats it opens up this huge area of open water in the Arctic Ocean which then becomes like an ocean with lots of waves and storms and swell, and the waves themselves break the remaining ice up and cause it to retreat faster so that there's a kind of collaborative effect there that the remaining ice is vanishing faster because of so much open water producing wave action.




« Last Edit: July 04, 2015, 09:35:21 PM by Jim Hunt »
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Re: Importance of waves in the Arctic
« Reply #46 on: July 05, 2015, 02:01:50 AM »
Some additional sources of numerous "waves-in-ice" papers:

The NERSC WIFAR project: http://msc.nersc.no/?q=node/69

P.Wadhams@ResearchGate: https://www.researchgate.net/profile/P_Wadhams
« Last Edit: July 07, 2015, 04:23:21 PM by Jim Hunt »
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Re: Importance of waves in the Arctic
« Reply #47 on: July 05, 2015, 11:00:22 AM »
Not exactly contemporary science, but it sprang to my mind on reading this thread. Back in the 18th century, they didn't know about the North polar ice cap.

In James Boswell's "THE JOURNAL OF A TOUR TO THE HEBRIDES WITH SAMUEL JOHNSON", which occurred in 1773, he writes:

"Talking of Phipps's voyage to the North Pole, Dr Johnson observed, that it 'was conjectured that our former navigators have kept too near land, and so have found the sea frozen far north, because the land hinders the free motion of the tide; but, in the wide ocean, where the waves tumble at their full convenience, it is imagined that the frost does not take effect'."

So you're in good company supposing that waves might have an effect!

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Re: Importance of waves in the Arctic
« Reply #48 on: July 06, 2015, 05:59:11 PM »
An extract from a personal communication from Peter Wadhams:

I'm going out in September in the "Sikuliaq" (University of Alaska) to do some more specific wave-ice interaction experiments, assuming there is any ice to experiment on.
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Re: Importance of waves in the Arctic
« Reply #49 on: July 07, 2015, 04:14:49 PM »
If you all promise not to laugh.....


I went to the beach this time last week to cool off a bit. This is what happened next:

Reality is merely an illusion, albeit a very persistent one - Albert Einstein