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Would you believe that a cyclone -on June, July or August- could break the Arctic Sea Ice and contribute to have an ice-free Arctic before 2025?

Yes, I believe that a cyclone could contribute to have less than 1 million km2 of sea ice area, on a daily basis, before 2025.
39 (72.2%)
No, I believe that a cyclone could have that consequence, but I don´t believe that it will happen before 2025.
9 (16.7%)
No, I don´t believe that I cyclone will affect the Arctic Sea Ice in that way.
6 (11.1%)

Total Members Voted: 52

Voting closed: June 27, 2015, 12:18:16 AM

Author Topic: Cyclones and ice-free Arctic  (Read 28528 times)

Juan C. García

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Cyclones and ice-free Arctic
« on: June 07, 2015, 12:18:16 AM »
We define ice-free Arctic as a day in which there is less than 1 million km2 of Arctic sea ice area, measure by Cryosphere Today
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #1 on: June 07, 2015, 04:14:52 AM »
I think this is the year....The albedo feedback, land and ice, shatters any preexisting record. Then there is Cole's Correlation. There will be more cyclones in the coming months.

Verg

Gray-Wolf

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Re: Cyclones and ice-free Arctic
« Reply #2 on: June 07, 2015, 11:16:48 AM »
Though we have had a recent lesson in what to expect with relatively slack L.P.'s lodged over the pole a fierce cyclone positioned on one coast or another will bring differing effects ( significant WAA, export and choppy waters both tossing ice and mixing the water column).
KOYAANISQATSI

ko.yaa.nis.katsi (from the Hopi language), n. 1. crazy life. 2. life in turmoil. 3. life disintegrating. 4. life out of balance. 5. a state of life that calls for another way of living.
 
VIRESCIT VULNERE VIRTUS

Nick_Naylor

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Re: Cyclones and ice-free Arctic
« Reply #3 on: June 07, 2015, 04:04:05 PM »
I think this is the year....The albedo feedback, land and ice, shatters any preexisting record.

It sure looks that way subjectively to me on Worldview. Is there an objective measure of albedo?

Juan C. García

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Re: Cyclones and ice-free Arctic
« Reply #4 on: June 08, 2015, 06:25:34 AM »
Thank you Vergent, Gray-Wolf and Nick_Naylor for your comments.

Just to follow the answer of Vergent to Nick_Naylor question:



The arctic albedo is at least 20% below 2012. The area is the same. That corresponds to 100 watts in full sunlight. Discounting it to 50 watts for cloud cover, that will still melt 0.8 meters of ice over 60 days. Over 9 M km^2, that corresponds to 8 kkm^3. Eyeballing PIOMAS, that would put us in negative numbers. The poll didn't have negative numbers, so I picked the bottom bucket.

Verg
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

ChrisReynolds

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Re: Cyclones and ice-free Arctic
« Reply #5 on: June 08, 2015, 07:02:18 PM »
I've voted yes, but think that while feasible, it is rather unlikely.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #6 on: June 08, 2015, 09:25:58 PM »
I think this is the year....The albedo feedback, land and ice, shatters any preexisting record.

It sure looks that way subjectively to me on Worldview. Is there an objective measure of albedo?

2015:


2014: (unfortunately this database does not go back to 2012, we have to use a snow-cover proxy.)


Quote
Cold snow: Before melt onset the snow albedo is0.85.

Melting snow: Starting with the onset of snow melt,there is a linear decrease to 0.6 in 7 days

Pond formation: For the next 7 days, decrease from 0.6 to 0.32.

Pond drainage: For next 7 days, increase from 0.32 to 0.54.

Pond evolution: Decreases by 0.0083 d1 until albedo reaches 0.2.

Then the ice is assumed to rapidly melt and albedo drops in a single day to 0.07.

Open water: Albedo of 0.07

http://onlinelibrary.wiley.com/doi/10.1029/2012GL051432/pdf



7 + 7 + 7 + (.34  / .0083 = 41 ) + 1 =  63 days

The onset of snow melt was universal by June 1 (JD 152)

June 1(J.D. 152) + 63 days = August 3, (JD 215)

That leaves 42 days of melting to take care of the ice that was tardy because it was thick. But it will be attacked and scattered by wind and wave from the storms that will surely blow.

Vergent :(

Melt ponds 2015:


Meltponds 2014:


Snow cover 2014: http://i.imgur.com/ADba4yz.png

Snow cover 2012: http://i.imgur.com/9xkwmX2.png

Snow cover 2015: http://i.imgur.com/UtHfZsM.png

It look to me that the arctic ocean will be "ice free" in August.

Vergent


Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #7 on: June 09, 2015, 12:15:31 AM »
That's not an objective measure, it's a mathematical model.

Nick_Naylor

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Re: Cyclones and ice-free Arctic
« Reply #8 on: June 09, 2015, 01:28:50 AM »
Thanks Vergent and Juan. That's good stuff - I'll have to learn how to access that database.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #9 on: June 09, 2015, 01:57:23 AM »
That's not an objective measure, it's a mathematical model.

Peter,

Quote
The operational TOPAZ4 Arctic Ocean system uses the HYCOM model and a 100-member EnKF assimilation scheme. It is run daily to provide 10 days of forecast (one single member) of the 3D physical ocean, including sea ice; data assimilation is performed weekly to provide 7 days of analysis (ensemble average).

Like all forecasts it involves some modeling. The now-cast is based on satellite observations and the hind-cast is subjected to reanalysis.

Verg

edit: move quote
« Last Edit: June 09, 2015, 02:11:24 AM by Vergent »

jdallen

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Re: Cyclones and ice-free Arctic
« Reply #10 on: June 09, 2015, 03:30:56 AM »
The definition of insanity is when you have an unprecedented starting point, but expect a normal result. - Vergent
I find myself agreeing with Vergent here; current conditions do not appear to have any sort of precedent.
This space for Rent.

ChrisReynolds

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Re: Cyclones and ice-free Arctic
« Reply #11 on: June 09, 2015, 07:51:42 AM »
That's not an objective measure, it's a mathematical model.

Peter,

Quote
The operational TOPAZ4 Arctic Ocean system uses the HYCOM model and a 100-member EnKF assimilation scheme. It is run daily to provide 10 days of forecast (one single member) of the 3D physical ocean, including sea ice; data assimilation is performed weekly to provide 7 days of analysis (ensemble average).

Like all forecasts it involves some modeling. The now-cast is based on satellite observations and the hind-cast is subjected to reanalysis.

Verg

edit: move quote

What is the hindcast skill?

jdallen

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Re: Cyclones and ice-free Arctic
« Reply #12 on: June 09, 2015, 08:12:46 AM »
That's not an objective measure, it's a mathematical model.

Peter,

Quote
The operational TOPAZ4 Arctic Ocean system uses the HYCOM model and a 100-member EnKF assimilation scheme. It is run daily to provide 10 days of forecast (one single member) of the 3D physical ocean, including sea ice; data assimilation is performed weekly to provide 7 days of analysis (ensemble average).

Like all forecasts it involves some modeling. The now-cast is based on satellite observations and the hind-cast is subjected to reanalysis.

Verg

edit: move quote

What is the hindcast skill?

Actually, a really good question...
This space for Rent.

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #13 on: June 09, 2015, 09:48:37 AM »
I know it assimilates data, but the data it assimilates is not albedo data.  It assimilates concentration, sea surface temperature, cryosat thickness and a bunch of other stuff.  The albedo is still purely a model.

Nick asked, "Is there an objective measure of albedo?" and the answer is no.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #14 on: June 09, 2015, 11:28:52 AM »
I know it assimilates data, but the data it assimilates is not albedo data.  It assimilates concentration, sea surface temperature, cryosat thickness and a bunch of other stuff.  The albedo is still purely a model.

Nick asked, "Is there an objective measure of albedo?" and the answer is no.

Peter,

Could you please give a link to a paper that suports your statements? Or are you just making it up?

Verg

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #15 on: June 09, 2015, 11:48:01 AM »
The user manual for the website you're using.
http://marine.copernicus.eu/documents/PUM/CMEMS-ARC-PUM-002-ALL.pdf

The MyOcean "Arctic Ocean Physics Analysis and Forecast" site uses the Topaz4 model.

On page 16 of the TOPAZ documentation you find the following:

"Observations that are assimilated by TOPAZ4 include along-track Sea Level Anomalies (SLA) from
satellite altimeters, Sea Surface Temperature (SST) from NOAA and then the Operational Sea Surface
Temperature and Sea Ice Analysis (OSTIA), in situ temperature and salinity from hydrographic
cruises and moorings, ice concentrations (ICEC) from OSI-SAF."

Pages 17-18 go into more details about exactly which sources are used.

So, it assimilates (modelled) temperature from NOAA, (direct) measurements of sea level height from CryoSat and other similar satellites, (direct) temperature and salinity data from the few buoys etc. that are out there, plus (semi-direct) ice concentration data from microwave measurements.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #16 on: June 09, 2015, 12:26:37 PM »
Peter,

Quote
The development of a sea ice albedo parametrization algorithm based on optical satellite sensors has been done and a software package has been implemented (Melt Pond Detection – MDP).
This software package generates operational products showing sea ice albedo and meltpond
fraction in the period from spring to autumn.

 http://sidarus.nersc.no/sites/sidarus.nersc.no/files/Publishable%20Summary%20year%202.pdf

Verg







Vergent

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Re: Cyclones and ice-free Arctic
« Reply #17 on: June 09, 2015, 12:54:33 PM »
Quote
•Data-assimilation in the multi-category ice model:
Many more prognostic variables:
(fice, hice, temp_profile)*nb_ice_layer + albedo, qbrine

https://hycom.org/attachments/087_Counillon_LOM_2009.pdf

Quote
Current surface albedo algorithms are based on optical
data.

http://www.researchgate.net/profile/Fanny_Girard-Ardhuin/publication/265301464_Remote_sensing_of_sea_ice/links/54084e870cf2bba34c266dcc.pdf

Verg

sofouuk

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Re: Cyclones and ice-free Arctic
« Reply #18 on: June 09, 2015, 02:54:17 PM »
We define ice-free Arctic as a day in which there is less than 1 million km2 of Arctic sea ice area, measure by Cryosphere Today

+ Vergent's 'I think this is the year' - if that turns out to be true I'll eat my hat (and shorts, and any other item of clothing you care to name) ... and cheerfully, too, as it will mean haven't been completely wasting my time for the past four years  ::) to anyone who disagrees, see you in september

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #19 on: June 09, 2015, 04:47:30 PM »
We define ice-free Arctic as a day in which there is less than 1 million km2 of Arctic sea ice area, measure by Cryosphere Today

+ Vergent's 'I think this is the year' - if that turns out to be true I'll eat my hat (and shorts, and any other item of clothing you care to name) ... and cheerfully, too, as it will mean haven't been completely wasting my time for the past four years  ::) to anyone who disagrees, see you in september

September Arctic sea-ice minimum predicted by spring melt-pond fraction

http://www.micheltsamados.co.uk/september/





Bon appetit.

Verg  ::)

edit: emoticon

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #20 on: June 09, 2015, 05:20:04 PM »
Quote
The development of a sea ice albedo parametrization algorithm based on optical satellite sensors has been done and a software package has been implemented (Melt Pond Detection – MDP).
http://sidarus.nersc.no/sites/sidarus.nersc.no/files/Publishable%20Summary%20year%202.pdf

Great, so this Norwegian group have come up with an algorithm to directly measure albedo.  We know it's not being assimilated into the TOPAZ4 model, because the manual for TOPAZ4 tells you what they assimilate, and this isn't listed.  If the Norwegian group publishes real-time images anywhere, it would be fascinating to compare the TOPAZ4 modelled data with something closer to reality.

Quote
•Data-assimilation in the multi-category ice model:
Many more prognostic variables:
(fice, hice, temp_profile)*nb_ice_layer + albedo, qbrine
https://hycom.org/attachments/087_Counillon_LOM_2009.pdf

Thanks for this link.  It lists albedo as a prognostic variable, i.e. one that is predicted by the model rather than directly input/assimilated.
http://en.wikipedia.org/wiki/Prognostic_variable

Quote
Current surface albedo algorithms are based on optical
data.

http://www.researchgate.net/profile/Fanny_Girard-Ardhuin/publication/265301464_Remote_sensing_of_sea_ice/links/54084e870cf2bba34c266dcc.pdf

This looks to be a fundamental misunderstanding.  That paper is saying that the current methods used to measure albedo (which are in any case not assimilated into TOPAZ4) are not very good, because they are based on optical parameters only (i.e. visible wavelengths), and only usable at certain times of the year, and cetrain types of ice. 

The paper's main conclusion in regard to albedo is that they need to find better ways of measuring it, e.g. by also looking at radar and microwave measurements.

September Arctic sea-ice minimum predicted by spring melt-pond fraction

http://www.micheltsamados.co.uk/september/


It's not appropriate for you to add that "You are here" star onto Dr Tsamados' graph unless you are using the same method of melt pond estimation as he did - otherwise you're comparing apples and oranges.  How did you estimate the melt pond fraction when you added that star to the graph?

Buddy

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Recipe: Ice Free Cocktail
« Reply #21 on: June 09, 2015, 05:29:51 PM »
Add:  Continued pulses of warm Pacific Water into the Arctic through the next 15 months
Add:  Early snow melt in Russia, Canada, and the US....this year (already) and next year
Add:  Warm air temperatures throughout the Arctic
Add:  One El Nino
Add:  Some vicious wild fires in Russia, Alaska, and Canada
Shake:  With some healthy cyclones this summer and next summer....

Voila.....you have an "almost" ice free Arctic cocktail**

**except for a stubborn stretch along Canadian Archipelago
FOX (RT) News....."The Trump Channel.....where truth and journalism are dead."

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #22 on: June 09, 2015, 05:33:05 PM »
Great, so this Norwegian group have come up with an algorithm to directly measure albedo.  We know it's not being assimilated into the TOPAZ4 model, because the manual for TOPAZ4 tells you what they assimilate, and this isn't listed.  If the Norwegian group publishes real-time images anywhere, it would be fascinating to compare the TOPAZ4 modelled data with something closer to reality.

Looking at their site a bit harder, I find the following:

Quote
The current deliverable addresses the analysis of the sea ice albedo and pond fraction products on various scales,
from regional to global, from daily to trends over 10 years. This study has been performed with an updated
version of the MPD retrieval after additional analysis done with in situ data (see Part II). The cloud screening has
been improved as well.
The products have been analyzed for consistency by comparing with the ground based and airborne data, via
comparison with another remote sensing retrieval of melt pond fraction from MODIS data (by Roesel et al., 2011).
Weekly averages for June of two years – 2007 and 2011 – have been analyzed. Spatial trends of melt pond fraction
and sea ice albedo have been produced for June of each year of the whole MERIS dataset.
Currently, three summers of MERIS data (May to September 2009-2011) are processed and stored as daily
averages. In addition, June of every year of the MERIS dataset (2002-2011) is processed and available as daily
averages.

So, they don't have a real-time product, they have an experimental product which looks at a particular time window.  You can get daily data for June of every year from 2002-2011, and full-season May-September data for 2009 through 2011. 

Like I said, not an operational product, and TOPAZ4 does not assimilate albedo data.  I don't know of anywhere you can get real-time albedo measurements, which is the point of this little argument.

ChrisReynolds

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Re: Cyclones and ice-free Arctic
« Reply #23 on: June 09, 2015, 06:31:00 PM »
...see you in september

That is indeed the most economical attitude to take.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #24 on: June 09, 2015, 06:49:39 PM »
How are you calculating that melt pond fraction?

Peter,
 I was responding in good nature to a good natured post. Hint; "I'll eat my hat","you are here", and "Bon apetit".

Quote
MyOcean is a consortium of 60 partners in 28 countries (the 22 states of the EU-27 that have a sea coastline, plus Norway, Russia, Ukraine, Morocco, Israel and Canada).

So, your assertion that Norway can acquire observation based albedo, but MyOcean can't is full of it. MyOcean is the data portal for the whole group. So now, let us look at the observation tied forecast for albedo. Why do we know that it is observation tied? Because of the detail and texture. Why isn't in the catalog? Because it has not been published yet. We had the same argument in 2013 regarding acquired thickness, which was subsequently published.*

http://i.imgur.com/JGsbEKp.png
http://i.imgur.com/dSWJgDU.png

Open the images in two tabs and click back and forth. Have you ever seen that rapid a change in the arctic? This is melt pond formation, because melt pond formation is what drops the albedo below 0.6. Even if it is modeled albedo, the weather forecast is telling the albedo model that the arctic is about to get scorched.

Verg

edit: *They were using an ensemble of seven satellite altimeters. They seem to have reverted to modeled thickness.

Vergent

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Re: Cyclones and ice-free Arctic
« Reply #25 on: June 09, 2015, 07:11:37 PM »
Peter,

p.s. They only recently added albedo to the menu, yet the reanalyses goes back to 2013. Do you really think they are just making that stuff up?

ChrisReynolds

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Re: Cyclones and ice-free Arctic
« Reply #26 on: June 09, 2015, 07:21:42 PM »
So, your assertion that Norway can acquire observation based albedo, but MyOcean can't is full of it.

Vergent,

It is not unheard of for scientists to produce a paper detailing a new set of data, but not continue it because they have no funding. I have asked scientists before if they have data going beyond what was shown in a paper only to be told that they had no ongoing funding and hadn't kept up the processing of data. That's happened to me many times.

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #27 on: June 09, 2015, 08:57:13 PM »
Open the images in two tabs and click back and forth. Have you ever seen that rapid a change in the arctic? This is melt pond formation, because melt pond formation is what drops the albedo below 0.6. Even if it is modeled albedo, the weather forecast is telling the albedo model that the arctic is about to get scorched.

I don't disagree with any of the above, I'm simply pointing out that it is modelled albedo rather than actual, unless you disbelieve their own user manual for the product you're using.

I dug through the Norwegian group's site to find out what albedo observations they'd generated, and posted it.  They don't have real time data, and thus (per Nick's original question) there is as yet no way to verify the model predictions in real time.

ktonine

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Re: Cyclones and ice-free Arctic
« Reply #28 on: June 09, 2015, 11:37:53 PM »
I'm simply pointing out that it is modelled albedo rather than actual

Peter, every instrumental measurement is modeled data.  The objection to modeled data is nonsense.  Objections to unproven or non-validated models are scientific.  Objections simply because 'it's a model' belong over at WUWT.


Nick_Naylor

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Re: Cyclones and ice-free Arctic
« Reply #29 on: June 10, 2015, 01:07:39 AM »
I'm simply pointing out that it is modelled albedo rather than actual

Peter, every instrumental measurement is modeled data.  The objection to modeled data is nonsense.  Objections to unproven or non-validated models are scientific.  Objections simply because 'it's a model' belong over at WUWT.

I have found this conversation to be interesting. It seems (to me at least) that there is still some uncertainty about the nature of the albedo data being presented. Whether its derived from direct observation of some kind vs. modeled based on local weather conditions, it no doubt has value - but knowing its nature would make it that much more valuable.

LRC1962

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Re: Cyclones and ice-free Arctic
« Reply #30 on: June 10, 2015, 02:08:42 AM »
I'm simply pointing out that it is modelled albedo rather than actual

Peter, every instrumental measurement is modeled data.  The objection to modeled data is nonsense.  Objections to unproven or non-validated models are scientific.
Maybe I am just showing my total ignorance and stupidity, but I would think that determining albedo would be far simpler then determining volume which we agree to via PIOMAS. If I understand things correctly in simple terms, albedo is determined by the reflectivity of the surface. That should be a very simple problem using satellite imagery.  The brighter the surface the higher the albedo, darker the surface, the lower the albedo. Put it into a grid like you do for extent or area, build a mathematical formula that gives you the average brightness over a given area, then you come up with the albedo for that area.
Unless I am missing something very important, how hard can it be to get that number.
Edit: Remember, clouds also effect albedo. Now if you want to know what exactly is causing the lower albedo, that is a whole different far more difficult matter.
« Last Edit: June 10, 2015, 02:15:35 AM by LRC1962 »
"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: Cyclones and ice-free Arctic
« Reply #31 on: June 10, 2015, 02:24:06 AM »
So, your assertion that Norway can acquire observation based albedo, but MyOcean can't is full of it.

Vergent,

It is not unheard of for scientists to produce a paper detailing a new set of data, but not continue it because they have no funding. I have asked scientists before if they have data going beyond what was shown in a paper only to be told that they had no ongoing funding and hadn't kept up the processing of data. That's happened to me many times.

Another situation I could see. What PhD scientist wants to work on the same numbers for a whole life? Follow the biographies of the greatest scientist and none of them did that. They all worked on a variety of subjects sometimes at the same time, and some of those subjects were only further developed by others. If that does not occur, then no new data will be worked on.
"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

Nick_Naylor

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Re: Cyclones and ice-free Arctic
« Reply #32 on: June 10, 2015, 03:07:06 AM »
I'm simply pointing out that it is modelled albedo rather than actual

Peter, every instrumental measurement is modeled data.  The objection to modeled data is nonsense.  Objections to unproven or non-validated models are scientific.
Remember, clouds also effect albedo. Now if you want to know what exactly is causing the lower albedo, that is a whole different far more difficult matter.
Yes, they do, but I think we're implicitly looking for a hypothetical "clear-sky albedo", which is obviously not so easy to measure when clouds are in the way. At least that's how I interpret the intent of the myocean reports.

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #33 on: June 10, 2015, 10:33:22 AM »
There are two issues: (1) it's difficult to measure albedo at low sun angles, which means you can't get good data even for much of the melt season.  (2) albedo at what wavelength?  Albedo in the visible and infrared bands will be quite different - and also differentially affected by confounders such as cloud - and there may not be appropriate sensors up there to get the needed data.

Sensor availability is a major issue.  From the page Vergent linked describing the Norwegian group's work:
Quote
"The development of a sea ice albedo parametrization algorithm based on optical satellite sensors
has been done and a software package has been implemented (Melt Pond Detection – MDP).
This software package generates operational products showing sea ice albedo and meltpond
fraction in the period from spring to autumn. The software package involves processing of
MERIS data from the initial data (level 1b, full orbits) till the resulting maps which contain melt
pond fraction and spectral albedo for each pixel of the scene. The loss of ENVISAT in April
2012 implied that new MERIS data were not available after this date. The work is therefore
concentrated on analysis of archived MERIS data, which is most important for climate users who
need longer time series.
"

Juan C. García

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Re: Cyclones and ice-free Arctic
« Reply #34 on: June 12, 2015, 05:25:54 AM »
Now we have an Arctic Storm (I can´t say that it is a 67 km/hr "tropical" storm ;) ) at Barents Sea. How do you believe it is going to affect the melt season?

Thanks for your answers.

http://earth.nullschool.net/#current/wind/surface/level/orthographic=-59.41,92.76,1295

Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Juan C. García

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Re: Cyclones and ice-free Arctic
« Reply #35 on: June 12, 2015, 05:40:53 AM »
I am just guessing, but I think that it is moving ice from Kara Sea and the Arctic Basin to Barents Sea. This sea ice movement will make open water on Kara Sea and the sea ice will melt on Barents Sea on a couple of weeks (maybe 3 weeks).
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Michael Hauber

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Re: Cyclones and ice-free Arctic
« Reply #36 on: June 12, 2015, 11:30:11 AM »
One point I've noticed about 2012 is that as the season progressed rents appear in the ice in a wide area and expand throughout the season until the pack is preconditioned in such a away that the GAC can rip apart a large amount of the pack all at once, an area that I suspect may have largely melted anyway even without the cyclone.    I've had a look through EOSDIS on a day by day basis to try and track where these rents first appear, and they seem to get their start immediately following a brief cyclone on the 21 June.  This is then followed by significant amounts of clear weather during the next month and these rents gradually expand.  Around July 20 another pair of cyclones move over the area, and after this the ice state over a large area becomes noticeably ripped and torn and well on the way to the poor state that set the stage for GAC 2012.  I'm thinking maybe the GAC got too much credit as it was such an impressive beast of a system.  Perhaps the earlier and unremarked cyclones had a bigger role in setting the stage by weakening the ice pack.  And unlike in 2013 and 2014 the first of these was followed up by significant sunshine to be soaked up by all the small pieces of water in between the broken bits of ice.

Could we be about to see something similar?  The area just on the Chukchi side of the pole looks a little like the rent just after the initial storm on June 21 2012.  It is already showing a little bit of red shading on MODIS suggesting some surface melt.  Forecasts look like the area could be warmer and sunny for much of the next week, although a weak low pressure system (i.e. clouds, but not a lot of wind) may impact the area late in the 7 day run.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

epiphyte

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Re: Cyclones and ice-free Arctic
« Reply #37 on: June 13, 2015, 02:53:44 AM »
One point I've noticed about 2012 is that as the season progressed rents appear in the ice in a wide area and expand throughout the season until the pack is preconditioned in such a away that the GAC can rip apart a large amount of the pack all at once, an area that I suspect may have largely melted anyway even without the cyclone.    I've had a look through EOSDIS on a day by day basis to try and track where these rents first appear, and they seem to get their start immediately following a brief cyclone on the 21 June.  This is then followed by significant amounts of clear weather during the next month and these rents gradually expand.  Around July 20 another pair of cyclones move over the area, and after this the ice state over a large area becomes noticeably ripped and torn and well on the way to the poor state that set the stage for GAC 2012.  I'm thinking maybe the GAC got too much credit as it was such an impressive beast of a system.  Perhaps the earlier and unremarked cyclones had a bigger role in setting the stage by weakening the ice pack.  And unlike in 2013 and 2014 the first of these was followed up by significant sunshine to be soaked up by all the small pieces of water in between the broken bits of ice.

Could we be about to see something similar?  The area just on the Chukchi side of the pole looks a little like the rent just after the initial storm on June 21 2012.  It is already showing a little bit of red shading on MODIS suggesting some surface melt.  Forecasts look like the area could be warmer and sunny for much of the next week, although a weak low pressure system (i.e. clouds, but not a lot of wind) may impact the area late in the 7 day run.

By comparing with EOSDIS I've been slowly starting to make sense of the Sentinel 1 imagery over the past few days - and to me it seems very much the case that there's been widespread pre-conditioning of the ice, such that in it's current state it might put up little resistance to melting conditions and/or/stormy weather.

One thing I've noticed on this front is that there are indeed many leads opening up in unlikely places, such as along the mesh-patterned lines which I had previously assumed were likely thicker ridges. I'd speculate that maybe the whole pack has become so mobile that floes which come into contact with each other are not only of similar thickness, but also usually moving in the same direction, so there is no force between them to create the kind of ridges that used to occur, leaving instead just weak fault-lines where there was recently open water which never properly re-froze.

The SAR images are hard to interpret at first - but I think that especially over time they will provide a much clearer picture of what's really going on than we have had in the past. For the moment I'm not sure if I'm looking at them right, but if I am, then pretty much everywhere is looking decidedly threadbare...




Vergent

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Re: Cyclones and ice-free Arctic
« Reply #38 on: June 13, 2015, 10:05:13 AM »
There are two issues: (1) it's difficult to measure albedo at low sun angles, which means you can't get good data even for much of the melt season.

Peter,

Do you even know what a Lambertian reflector is or how it acts? I mean before you start giving lectures on optics, read a book, or take a course. While snow is not a perfect lambertian reflector, it is close.



With a Lambertian reflector, the  luminance, or diffuse reflection, in any direction is independent of the direction of illumination. In optics 101 your proclamation would score as an "absent". Please stop making things up.

Verg

 

Andreas T

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Re: Cyclones and ice-free Arctic
« Reply #39 on: June 13, 2015, 11:44:48 AM »
...... I would think that determining albedo would be far simpler then determining volume which we agree to via PIOMAS. If I understand things correctly in simple terms, albedo is determined by the reflectivity of the surface. That should be a very simple problem using satellite imagery.  The brighter the surface the higher the albedo, darker the surface, the lower the albedo. Put it into a grid like you do for extent or area, build a mathematical formula that gives you the average brightness over a given area, then you come up with the albedo for that area.
Unless I am missing something very important, how hard can it be to get that number.
Edit: Remember, clouds also effect albedo. Now if you want to know what exactly is causing the lower albedo, that is a whole different far more difficult matter.
The problem with that is that the satellite looks down, i.e. from a single direction. With the ideal scattering reflector Vergent shows in the previous comment, that gives a pretty good impression of how much light is absorbed. Some  surfaces we are interested here, firn, ice, water behave differently to various degrees. They reflect light not up at the satellite, but at roughly the incident angle away from the sun. In the buoy camera photos this shows clearly when meltponds look very dark with the sun behind the camera but reflect a strong glare into the lens from the opposite direction, making the water surface brighter than the snow. This reflection is stronger at low angles. The difficulty is to know how much that reflected light is as a proportion of the total incoming KW/m2
The other issue is  that snow absorbs more of the near IR part of the sun's radiation than the visible and nearly all longwave IR from clouds or atmosphere (but also emits strongly in long IR)

Andreas T

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Re: Cyclones and ice-free Arctic
« Reply #40 on: June 13, 2015, 12:50:43 PM »
an illustration of other effects on albedo: algae, or sediment in coastal water, darkening the ice.

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #41 on: June 13, 2015, 01:22:20 PM »
There are two issues: (1) it's difficult to measure albedo at low sun angles, which means you can't get good data even for much of the melt season.
Do you even know what a Lambertian reflector is or how it acts? I mean before you start giving lectures on optics, read a book, or take a course.

*shrug*  I'm giving a precis of the paper you linked.
http://www.researchgate.net/publication/265301464_Remote_sensing_of_sea_ice

Quote
... there  is  need  for more  observations  on  the  snow/ice  albedo  feedback. Current surface albedo algorithms are based on optical data.  Modelling  experiments  suggest  that  the  optical albedo  products  have  a  potential  applicability  in  the study  of  the  snow  and  sea  ice  mass  balance. However, the long periods of low sun elevation in the polar areas limit the possibility to estimate the surface albedo  using  optical  data.  Therefore  a  possibility to estimate  the  surface  albedo  using  microwave  data would be valuable. For sea ice it has been shown that SAR  data  can  be  used  for  surface  albedo  retrieval, because the aging of the snow and ice shows up both in  the  albedo  and  the  backscatter.

That says that (1) they want better albedo observations, (2) current albedo measurements are based on optical data, (3) that low sun elevations make it hard to measure optical albedo, and therefore (4) they want to use SAR data (active microwave radar) products to aid in albedo measurement.

The Norwegian team that did the historical reanalysis of albedo focused primarily on June (highest Sun elevation) with more limited data from other months with low Sun elevations. Since these are the scientists that are actually generating data, I tend to assume they know more than me - an attitude which is often lacking on these forums.

ChrisReynolds

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Re: Cyclones and ice-free Arctic
« Reply #42 on: June 13, 2015, 03:05:12 PM »
There are two issues: (1) it's difficult to measure albedo at low sun angles, which means you can't get good data even for much of the melt season.

Peter,

Do you even know what a Lambertian reflector is or how it acts? I mean before you start giving lectures on optics, read a book, or take a course. While snow is not a perfect lambertian reflector, it is close.



With a Lambertian reflector, the  luminance, or diffuse reflection, in any direction is independent of the direction of illumination. In optics 101 your proclamation would score as an "absent". Please stop making things up.

Verg

 

Wet snow?

Ice?

Wet ice?

Melt ponds?

Leads/polnyas?

I don't think Peter is being deliberately difficult here, I just think that the situation is more complex than you seem to grasp.

LRC1962

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Re: Cyclones and ice-free Arctic
« Reply #43 on: June 13, 2015, 07:29:01 PM »
I may be still confused, but I did not think measuring albedo cared greatly what was causing the absorption.
Do you disagree with the fact that we can measure quite accurately the energy imbalance between what is coming from the sun and what is being sent back to space? If you do disagree then you can declare we can not accurately measure albedo. If on the other hand you state that we can accurately make energy imbalance measurements then you must also agree that we can make accurate measurements of the albedo because they are directly related one with other. High albedo=cold, low albedo= hot, relative to total energy received.
Now Jason Box is very interested in what is causing lower albedo in Greenland and whether it is short or long term, he is not measuring directly what the albedo is.
As I stated before measuring albedo should not be a big problem, what is causing the exact albedo is a whole different story. Those two issues should be kept separate because they are very separate questions. In actual fact what satellites are determining when what they are seeing as to whether they are looking at FYI, MYI, snow, fractures, meltwater, algae .... is reflection which is what albedo is. How much light is getting reflected is never a point for those satellites directly as a sole point of interest, what they are trying to determine is why it is being reflected or absorbed. In that case because so many things can give off very similar signals that is what causes the problems of determining what you are looking at.
"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

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #44 on: June 13, 2015, 07:50:56 PM »
I refer you to Chris' example.  Say you point your satellite at a patch of ground and get a high signal.

Is that coming from (high albedo) snow, reflecting 90% of incident energy in all directions?

Or is it coming from a (low albedo) melt pond, reflecting only 40% of the incoming energy, but at just the right angle to reflect it at the satellite?

http://ipab.apl.washington.edu/WEB_CAM/camera1/usiabp_camera1_20150609064552.jpg

Looking at the ground in this picture, the brightest part is the water just by the pole for the buoy - but that is actually much lower albedo than the adjacent snow.  Trying to get accurate albedo is not easy.  The amount of light returned to the satellite will depend critically on the relative amounts of snow, wet snow, ice, wet ice, melt ponds, open (smooth) ocean, open (rough) ocean, and so forth - none of which you have direct measurements for and can synchronise with your observations, and many of which will be present in a single pixel of a satellite image. It also depends on how each of these different components interacts with the angle of the sun,  the amount and type of cloud (is the sunlight coming straight from the Sun, or is it lit from all sides by scattered radiation), and the wavelength of light you're investigating.

Andreas T

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Re: Cyclones and ice-free Arctic
« Reply #45 on: June 13, 2015, 11:25:03 PM »
from http://ceres.larc.nasa.gov/products.php?product=EBAF-TOA
my emphasis
Quote
SSF1deg: The LW fluxes in each hour box between CERES observations are determined by
linear interpolation of LW fluxes over ocean, while daytime and nighttime observations over land and desert are interpolated by fitting a half sine curve to the observations to account for the much stronger diurnal cycle over land and desert (Young et al. 1998). The SW radiative fluxes between CERES observation times are determined from the observed fluxes by using scene dependent diurnal albedo models, which describe how TOA albedo (and therefore flux) changes with solar zenith angle for each local time, assuming the scene properties remain invariant throughout the day. The sun angle dependent diurnal albedo models are based upon the CERES ADMs developed for the Tropical Rainfall Measuring Mission (TRMM) satellite (Loeb et al. 2003).
SW and LW radiative fluxes between CERES observation times are determined by supplementing the CERES observations with 3-hourly TOA fluxes derived from five geostationary satellites. Doelling et al. (2013) provides a detailed description of how broadband TOA fluxes are derived from geostationary data

measurment of albedo is clearly not simple and straightforward


Vergent

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Re: Cyclones and ice-free Arctic
« Reply #46 on: June 14, 2015, 01:30:38 AM »
I refer you to Chris' example.  Say you point your satellite at a patch of ground and get a high signal.

Is that coming from (high albedo) snow, reflecting 90% of incident energy in all directions?

Or is it coming from a (low albedo) melt pond, reflecting only 40% of the incoming energy, but at just the right angle to reflect it at the satellite?

This is a fake problem. Specular reflection is simply avoided by scanning the surface at a higher angle than the sun. Out of the thousands of high res images on Lance Modis show me one where there is a reflection from the sun. These images are scanned with the camera pointing down. The sun is always at a lower angle in the arctic. This is never a problem.

Verg

Andreas T

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Re: Cyclones and ice-free Arctic
« Reply #47 on: June 14, 2015, 11:20:48 AM »
The problem is that for reflecting surfaces you must take refection into account to know albedo! The reflected light is not absorbed but not seen by the satellite looking down. What is done for measurements like CERES is that it doesn't just look down but also at the horizon, i.e. at shallow angles to the earth surface AFAIK. Combining these measurements with measurements taken at different times to arrive at the value for a particular spot of surface makes this complicated as discussed in the link I gave previously. That doesn't mean it can't be done.

Peter Ellis

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Re: Cyclones and ice-free Arctic
« Reply #48 on: June 14, 2015, 11:35:03 AM »
I'm out of this discussion. Vergent, I look forward to your imminent production of a real-time albedo data series. After all, the optical pictures from MODIS are freely available, and the analysis is apparently much simpler than I thought. Do let us know which journal it's in.

oren

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Re: Cyclones and ice-free Arctic
« Reply #49 on: June 14, 2015, 01:11:48 PM »
And if the discussion is set to continue, why not start an appropriate albedo thread? It's kind of confusing in this one.