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oren

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Re: Albedo-Warming Potential
« Reply #100 on: April 27, 2019, 07:45:24 PM »
Thanks a lot Tealight.

gerontocrat

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Re: Albedo-Warming Potential
« Reply #101 on: April 27, 2019, 08:04:46 PM »
Here are 2 area graphs,

The High Arctic 7 seas as defined by Tealight,

All 14 Arctic Seas per NSIDC.

As you can see, as far as the High Arctic is concerned, melting has not really started yet.
It also shows that the summer melt produced relatively steeper decline in these central seas.
« Last Edit: April 27, 2019, 08:14:05 PM by gerontocrat »
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kiwichick16

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Re: Albedo-Warming Potential
« Reply #102 on: April 28, 2019, 06:55:03 AM »
losing  a million  sq kms per decade @ at the annual minimum in September.......at that rate the Arctic will be ice free sometime in the 2030's  ....if not before

Stephan

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Re: Albedo-Warming Potential
« Reply #103 on: April 28, 2019, 01:02:03 PM »
Tealight - thanks a million for all the work you've done
Gerontocrat - thanks for the ice cover charts to support Tealight's evaluation.

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Tealight

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Re: Albedo-Warming Potential
« Reply #104 on: May 01, 2019, 01:05:08 AM »
Just in time before the May melt ponds start I created the regional anomaly charts. Just like last year almost all of the early accumulated AWP anomaly comes from the Bering Sea, but this year none of the regions is in the negative.

https://cryospherecomputing.tk/NRTawp

dosibl

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Re: Albedo-Warming Potential
« Reply #105 on: May 02, 2019, 04:54:43 PM »
No surprise that we're tracking to get a similar anomaly in the Bering as last year, iirc last years ~250 mj/m2 was basically double any prior year.

Tealight, my understanding of the 'potential' part of AWP is that the calculation doesn't account for weather, correct? A cloudy season and a sunny season with similar extent would produce similar AWP numbers but would experience different actual warming?

oren

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Re: Albedo-Warming Potential
« Reply #106 on: May 03, 2019, 12:52:15 AM »
No surprise that we're tracking to get a similar anomaly in the Bering as last year, iirc last years ~250 mj/m2 was basically double any prior year.

Tealight, my understanding of the 'potential' part of AWP is that the calculation doesn't account for weather, correct? A cloudy season and a sunny season with similar extent would produce similar AWP numbers but would experience different actual warming?
2019 is actually tracking somewhat higher, at 200 instead of 175.

My understanding of the 'P' is the same.

Tealight

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Re: Albedo-Warming Potential
« Reply #107 on: May 03, 2019, 02:21:56 AM »
No surprise that we're tracking to get a similar anomaly in the Bering as last year, iirc last years ~250 mj/m2 was basically double any prior year.

Tealight, my understanding of the 'potential' part of AWP is that the calculation doesn't account for weather, correct? A cloudy season and a sunny season with similar extent would produce similar AWP numbers but would experience different actual warming?

You are right that it doesn't account for weather and doesn't calculate actual warming. The data presented here is just a model to rank years against each other instead of a daily or monthly minimum number. It also quantifies the actual surface albedo change in the Arctic. However, the underlying physics are good enough for real applications. Maybe I can give more information tomorrow.

Darvince

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Re: Albedo-Warming Potential
« Reply #108 on: May 05, 2019, 07:11:02 PM »
I note that 2016 despite its very strong early start ended up with a lower AWP anomaly than 2012 in the high Arctic. I guess that's the power of cloudy weather for you.

Tealight

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Re: Albedo-Warming Potential
« Reply #109 on: May 05, 2019, 08:27:26 PM »
Very popular here are the sea ice minimum and maximum polls guessing the correct sea ice extent in millions of square kilometer. A more scientific oriented version of it is the Sea Ice Prediction Network: https://www.arcus.org/sipn
This year was the second time they made a trial run to forecast the Antarctic summer minimum and I participated (as Nico Sun) with a forecast model derived from this Albedo-Warming Potential model. The underlying physics are the same. The major difference is that instead of accumulating an energy value in a grid cell, this energy is used to calculate the sea ice thickness loss. Additionally I added an outgoing infrared radiation variable to get an actual energy balance.

With the post season report released I can proudly claim victory not only in overall area values, but also on a regional scale with the lowest error over the entire 3 month forecasting period. This is in part thanks to the real world usefulness of the AWP model and in part due to the submission deadline of 1st December. Some other team's can only run their models at the beginning of every month and had to use October data for their model initialization. I attached the two most relevant figures, but recommend to read the whole report.

Full 2018-2019 post season report
http://www.climate.be/users/fmasson/SIPN-South_2018-2019_postseason.pdf

General SIPN south website
http://acecrc.org.au/sipn-south/


Sea Ice Loss Formula of the forecast model:

Ed = MJ_inlat,day x (1 - SIC) - MJ_out
z = Ed / Efusion

Ed = Melt energy per day
MJ_in = incoming solar radiation per m2
MJ_out = outgoing infrared emmision per m2
SIC = sea ice concentration
z = thickness loss in m
Efusion = Enthalpy of fusion per m3
« Last Edit: May 05, 2019, 10:59:20 PM by Tealight »

magnamentis

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Re: Albedo-Warming Potential
« Reply #110 on: May 05, 2019, 08:34:10 PM »
I note that 2016 despite its very strong early start ended up with a lower AWP anomaly than 2012 in the high Arctic. I guess that's the power of cloudy weather for you.

i think that's because there was way more open water in the CAB in 2012 at the end of the melting seasons hence AWP is somehow logically higher under those conditions and will be again once such a state has been reached

oren

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Re: Albedo-Warming Potential
« Reply #111 on: May 05, 2019, 08:55:52 PM »
Well done Tealight/Nico!

gerontocrat

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Re: Albedo-Warming Potential
« Reply #112 on: May 05, 2019, 09:39:44 PM »
So Nico Sun gets the medal. Will Tealight get upset ?
Will they send rude letters to the science journals about each other?

And by the way, now the regional Arctic models are up and running, with the key separating out of the high Arctic seas, will he or him or they enter the lists on foreasting the Arctic sea ice minimum?

Tealight, you derive AWP using sea ice area and then use this as a basis to calculate the energy available to reduce sea ice thickness ? How do you translate reduced thickness into resulting sea ice area and extent? A sea might have remaining ice piled up in one area  or spread out giving a higher extent value due to varying winds and currents?

Ps: An impressive piece of work. What with the work on glaciers as well - stunning.
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bbr2314

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Re: Albedo-Warming Potential
« Reply #113 on: May 05, 2019, 10:11:24 PM »
So Nico Sun gets the medal. Will Tealight get upset ?
Will they send rude letters to the science journals about each other?

And by the way, now the regional Arctic models are up and running, with the key separating out of the high Arctic seas, will he or him or they enter the lists on foreasting the Arctic sea ice minimum?

Tealight, you derive AWP using sea ice area and then use this as a basis to calculate the energy available to reduce sea ice thickness ? How do you translate reduced thickness into resulting sea ice area and extent? A sea might have remaining ice piled up in one area  or spread out giving a higher extent value due to varying winds and currents?

Ps: An impressive piece of work. What with the work on glaciers as well - stunning.
Tealight and Nico Sun are the same person...

Tor Bejnar

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Re: Albedo-Warming Potential
« Reply #114 on: May 05, 2019, 11:17:48 PM »
Ever have an agrument all by yourself?
 ::) :-\
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Tealight

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Re: Albedo-Warming Potential
« Reply #115 on: May 05, 2019, 11:18:23 PM »
Thanks everyone. I can confirm it feels good to beat major international organisations like NASA, MetOffice and ecmwf.

Tealight, you derive AWP using sea ice area and then use this as a basis to calculate the energy available to reduce sea ice thickness ? How do you translate reduced thickness into resulting sea ice area and extent? A sea might have remaining ice piled up in one area  or spread out giving a higher extent value due to varying winds and currents?

Technically I keep track of two sea ice concentration values. One to calculate the melt (using SIC from previous years) and another calculated from thickness. The second one is the final model output. The additional thickness step makes the model more robust against flashes of low SIC like short term melt ponds.

For the Antarctic I used the following formula to get the best results:
SIC(%) = (Thickness(m)^1.3) / 0.0155

Thickness(m)   SIC value (%)
1.4   100
1.25   86
1   65
0.75   44
0.5   26
0.25   11
0   0

anything over 1.4m stays at 100% SIC.

PaulPassmore

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Re: Albedo-Warming Potential
« Reply #116 on: May 10, 2019, 04:17:20 PM »
Quote
No surprise that we're tracking to get a similar anomaly in the Bering as last year, iirc last years ~250 mj/m2 was basically double any prior year.

Tealight, my understanding of the 'potential' part of AWP is that the calculation doesn't account for weather, correct? Maybe this website https://edubirdie.com/math-problem-solver could do this calculation? A cloudy season and a sunny season with similar extent would produce similar AWP numbers but would experience different actual warming?

It's weird that calculations are so different every year. It seems like main rules are changing all the time.

b_lumenkraft

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Re: Albedo-Warming Potential
« Reply #117 on: May 11, 2019, 07:37:13 AM »
It's weird that calculations are so different every year. It seems like main rules are changing all the time.

Well, it's not that weird, this is a highly complex system after all.

Hello and welcome to the forum Paul.

gerontocrat

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Re: Albedo-Warming Potential
« Reply #118 on: May 11, 2019, 12:49:07 PM »
It's weird that calculations are so different every year. It seems like main rules are changing all the time.

Well, it's not that weird, this is a highly complex system after all.

Hello and welcome to the forum Paul.
The basic laws of physics underlying the calculations do not change. The rules for calculations only change if studies have proved better algorithms. When that happens, the new calculations are applied to all previous data to ensure the record is consistent.

What does change is the weather and behaviour of the oceans that can completely change the pattern of sea ice melt and freeze sea by sea.

Chaos Theory
Edward Lorenz was an early pioneer of the theory. His interest in chaos came about accidentally through his work on weather prediction in 1961.

Welcome to chaos, Paul.
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jai mitchell

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Re: Albedo-Warming Potential
« Reply #119 on: May 16, 2019, 08:36:15 PM »
any analysis of the current impact of albedo forcing due to seasonal sea ice loss during the satellite period should be compared with regional ice loss impacts not arctic basin impacts,  this is due to the variable seasonal solar radiation which maxes at the summer solstice and the retreat of sea ice from the periphery during this time.

The only good study I have found on this was looking at the Beaufort Sea by NASA

https://earthobservatory.nasa.gov/images/84930/the-arctic-is-absorbing-more-sunlight

Quote
When averaged over the entire Arctic Ocean, the increase in absorbed solar radiation is about 10 Watts per square meter. This is equivalent to an extra 10-watt light bulb shining continuously over every 10.76 square feet of Arctic Ocean for the entire summer. Regionally, the increase is even greater, Loeb noted. Areas such as the Beaufort Sea, which has experienced the some of the most pronounced decreases in sea-ice coverage, show a 50 watts per square meter increase.

This is necessary because future sea ice loss impacts during the summer will grow to over 5-fold of the current forcing (determined to be some percentage of 25% of total CO2 forcing around at 2014. 

This large regional forcing will produce rapid changes in the Arctic, especially as we move toward June 21 Summer sea ice loss.

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iceman

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Re: Albedo-Warming Potential
« Reply #120 on: May 18, 2019, 03:55:04 PM »
any analysis of the current impact of albedo forcing due to seasonal sea ice loss during the satellite period should be compared with regional ice loss impacts not arctic basin impacts,  this is due to the variable seasonal solar radiation which maxes at the summer solstice ....

At the Arctic circle (latitude of southern Chukchi), insolation reaches 90% of its peak value around this time of year. Open water, clear skies... not good.

We can expect some rotation of ice from Beaufort into Chukchi, which would confound the regional impact of albedo forcing on a time scale of a melting season.

gerontocrat

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Re: Albedo-Warming Potential
« Reply #121 on: May 18, 2019, 05:08:54 PM »
A fella called Tealight, with the help of his Avatar Nico Sun, has done the biz at https://cryospherecomputing.tk/NRTawp. It is updated daily and is wunderbar. Note he has analyses for the Arctic in total, individual seas, and "The High Arctic" (=the seven seas of the Arctic Ocean itself)

Using his AWP data combined with lots of other maths re sea ice SST's etc, he has already smashed the opposition on forecasting Antarctic Sea Ice. I am hoping to see if he is going attempt the same for the Arctic.

Examples of graphs and maps attached.
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Tealight

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Re: Albedo-Warming Potential
« Reply #122 on: June 08, 2019, 01:07:52 AM »
The recent warm temperatures over the central Arctic did not result in a significant albedo drop. I suspect the peak sunshine intensity this far north is just too low to force widespread meltponding. Without imported heat from the south it just stays an iceblock. It's like trying to melt some metal in a common household oven. You can heat it for a few days, but you never melt the surface unlike a few minutes in a furnace.

The absence of importet heat means 2016 won the battle for first place and in a few days begins the dominance of 2012 until the end of the melting season.

FishOutofWater

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Re: Albedo-Warming Potential
« Reply #123 on: June 08, 2019, 01:29:05 AM »
The largest thermal anomalies in May were in the Canadian side of the Arctic where it is normally so cold that the average temperature was below freezing for sea ice. This explains much of what happened to keep melt pond formation down.

However, sea ice transport towards the Fram and Nares straits has been exceptionally high compared to recent years. The melt season may have surprises ahead but we must remember than 2012 was exceptional.

Thanks Tealight for your valuable contribution.

dosibl

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Re: Albedo-Warming Potential
« Reply #124 on: June 10, 2019, 08:16:23 PM »
The Beaufort seems to have exceeded the Y axis on the daily anomaly graphs, not sure if that value can be easily changed or if this would be problematic for older graphs which have the current Y axis maximum.

Tealight

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Re: Albedo-Warming Potential
« Reply #125 on: June 15, 2019, 10:18:05 PM »
After a short drop 2019 is back to challenge 2016 for 1st place in accumulated AWP. All thanks to the recent melt pond surge. But the Beaufort Sea still leads all regions by a wide margin because open ocean is darker than melt ponds.

The Beaufort seems to have exceeded the Y axis on the daily anomaly graphs, not sure if that value can be easily changed or if this would be problematic for older graphs which have the current Y axis maximum.

It was an easy fix.

oren

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Re: Albedo-Warming Potential
« Reply #126 on: June 15, 2019, 10:41:49 PM »
Thanks for the update Tealight.
With most of the negative anomalies found in Hudson Bay and in the Kara-Barents-Fram complex, both regions prone to imminent melt, that gives the overall positive anomaly an added twist.

bbr2314

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Re: Albedo-Warming Potential
« Reply #127 on: June 16, 2019, 02:23:08 AM »
Thanks for the update Tealight.
With most of the negative anomalies found in Hudson Bay and in the Kara-Barents-Fram complex, both regions prone to imminent melt, that gives the overall positive anomaly an added twist.
I have been harping on this. The only "good" anomalies are in regions that will melt out in July-August anyways. We know Slater's graph has issues but even his graph shows 5.89M KM^2 extent remaining as of 8/4, WITH a major part of HB remaining that is unlikely to be there at that point (or will be gone shortly thereafter).



This should result in an easy cinching of the record for most of August, IMO, and probably September as well. If not the record, which I suspect it will be, this season will easily rank alongside 2012 + 2016.

Tealight

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Re: Albedo-Warming Potential
« Reply #128 on: June 16, 2019, 02:43:51 AM »
You are right. All negative anomaly isn't in regions that affect the central Arctic.

Despite currently eastern winds in the Beaufort Sea, the ocean current aka Beaufort gyre still pushes the warm water west/north-west. In July and August we should see strong bottom melt in the central Arctic north of Wrangel Island. I don't think it quite reaches the North Pole.

I predict the September minimum to match 2012/2016 if AWP continues this way or a mean 2010s area/extent if conditions go worse.
« Last Edit: June 16, 2019, 10:25:59 AM by Tealight »

Sterks

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Re: Albedo-Warming Potential
« Reply #129 on: June 16, 2019, 09:56:01 PM »
Very popular here are the sea ice minimum and maximum polls guessing the correct sea ice extent in millions of square kilometer. A more scientific oriented version of it is the Sea Ice Prediction Network: https://www.arcus.org/sipn
This year was the second time they made a trial run to forecast the Antarctic summer minimum and I participated (as Nico Sun) with a forecast model derived from this Albedo-Warming Potential model. The underlying physics are the same. The major difference is that instead of accumulating an energy value in a grid cell, this energy is used to calculate the sea ice thickness loss. Additionally I added an outgoing infrared radiation variable to get an actual energy balance.

With the post season report released I can proudly claim victory not only in overall area values, but also on a regional scale with the lowest error over the entire 3 month forecasting period. This is in part thanks to the real world usefulness of the AWP model and in part due to the submission deadline of 1st December. Some other team's can only run their models at the beginning of every month and had to use October data for their model initialization. I attached the two most relevant figures, but recommend to read the whole report.

Full 2018-2019 post season report
http://www.climate.be/users/fmasson/SIPN-South_2018-2019_postseason.pdf

General SIPN south website
http://acecrc.org.au/sipn-south/


Sea Ice Loss Formula of the forecast model:

Ed = MJ_inlat,day x (1 - SIC) - MJ_out
z = Ed / Efusion

Ed = Melt energy per day
MJ_in = incoming solar radiation per m2
MJ_out = outgoing infrared emmision per m2
SIC = sea ice concentration
z = thickness loss in m
Efusion = Enthalpy of fusion per m3
Did you submit to the SIPN? The site seems abandoned, no way to know the participants of course...

Tealight

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Re: Albedo-Warming Potential
« Reply #130 on: June 17, 2019, 06:26:31 PM »
Did you submit to the SIPN? The site seems abandoned, no way to know the participants of course...

I did submit my forecast. The June Report is scheduled to be released on the 21 June 2019. It seems like the whole ARCUS (Arctic Research Consortium of the United States) website was taken offline, not just SIPN.
« Last Edit: June 18, 2019, 12:54:23 PM by Tealight »

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Re: Albedo-Warming Potential
« Reply #131 on: June 17, 2019, 11:14:34 PM »
So I responded regarding these awesome graphs in the main thread wrt cloud cover and it got me thinking about cloud cover and satellites, surely someone must be getting a decent track record of how cloudy it is up in the arctic (or the whole planet for that matter), and i tracked down these links, I couldn't create an account, but if you're looking for a source of cloud cover info to relate back to the albedo stuff...

http://www.cloudsat.cira.colostate.edu/

http://www.cloudsat.cira.colostate.edu/community-products/arctic-observation-and-reanalysis-integrated-system


Phoenix

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Re: Albedo-Warming Potential
« Reply #132 on: July 07, 2020, 07:47:09 AM »
It's been a year since anyone posted in this thread so I'm not sure if you're monitoring Tealight.

First...thanks for the wonderful contribution. Love your site.

I'm wondering if you would considering some kind of tool to validate your model in terms of its ability to predict sea ice volumes.

Your model arrives at an accumulated regional AWP in terms of MJ/m2 for each Arctic region.

1. If you multiply that by total regional m2, you'll get the total regional AWP in MJ.

2. If your regions are the same as those used to calculate PIOMAS volume, you can divide the regional AWP by ice volume decline over a given period to determine MJ / km3 loss and see if the result is relatively consistent from year to year.

Where things vary is a clue that we need to further investigate cause and effect.

For example, PIOMAS showed a record CAB volume decline in the second half of June as reported by Oren in the PIOMAS thread. At the same time, CAB AWP anomaly at your site wasn't showing a positive anomaly until the last few days of the month and wasn't giving the signal to expect the PIOMAS outcome.

Trying to reconcile the two, I realize that your model isn't attempting to be perfect so the expectation isn't there that it will be. But it does occur to me that some attempt to reconcile might be valuable. Perhaps the lack of cloudiness in the last few days makes a huge difference? Alternatively, perhaps the reduction in aerosol emissions due to covid means that all of the fixed assumptions regarding insolation potential might need to be re-evaluated and potentially upgraded?

Food for thought....


Phoenix

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Re: The 2020 melting season
« Reply #133 on: July 08, 2020, 03:04:46 PM »
The potential in the Arctic at this time of year under ice free conditions is 450-500 W/m2 per day.

According to Nico Sun, the CAB runs at about 20% of potential solar input at this time of year, so in a typical early July day, it's receiving about 100 W / m2.

https://cryospherecomputing.tk/awp-region.html

Does heat matter? I think so. You indicate tens of W / m2. That would be less than insolation, but still material.
You are bluffing your way through this argument, and badly. You cannot quote Nico Sun without understanding what it is he is really calculating. I have now gone and refreshed my failing memory, and it turns out he is assuming an albedo of 80% for ice and snow, and 85% for ice and snow in the High Arctic. For open water he is assuming 0% albedo. This is why he is showing ~20%-25% of potential solar input for the CAB: 15% of the CAB sea ice area, plus 100% of the (total CAB surface minus CAB sea ice area). However we are currently in a situation where the CAB is made up of gray ice full of extensive melt ponds and hardly any snow, with an albedo which is probably 50%-60% and certainly not 85%. So in a typical July day it is probably receiving double your number at about 200 W/m2.
In addition, his assumption is that the weather (cloudy/sunny), which he ignores, averages out. However a stuck weather pattern generating clear skies over the CAB in early July does not necessarily average out and thus the generated anomaly is not necessarily comparable.
I would of course appreciate input from those who can estimate these numbers better, this is just a back of the envelope exercise.

If you click on the link to Nico's CAB chart, it shows the July 1 ice free AWP at ~ 26 MJ / m2 and the actual historical July 1 AWP at 5-6 MJ / m2. That's where the 20% comes from.

If you go to the bottom of the page in the right hand column, it shows historical full season CAB AWP ranging from 19-27% of potential since 1979.

https://cryospherecomputing.tk/awp-region.html

Nico's accumulated CAB AWP anomaly calculation for the 2020 season (comparing to last 20 year average) is extremely close to zero and was in negative territory on a daily basis every day from late May until late June before the current weather pattern hit.

https://cryospherecomputing.tk/NRTawp.html


Comradez

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Re: Albedo-Warming Potential
« Reply #134 on: July 08, 2020, 04:38:20 PM »
Keep in mind what "albedo warming potential" means, with emphasis on *potential.*

It means, assuming cloud-free skies. 

So, for example, if an earlier year might have had 27% CAB AWP, you'd need to still check what the actual cloud-cover was like for that year to see how much of that albedo warming potential translated into albedo warming actuality (AWA).  It could be the case that the CAB was almost totally cloud-covered during that time, in which case the AWP of 27% might translate into a AWA of near 0%. 

By contrast, let's say in 2020 the CAB AWP is 20%.  If cloud cover over the CAB is only on average, say, only 10% (because of a mega high pressure system), then the AWA would be more like 18%. 

I don't known what the actual numbers would be, but I hope this clears up some confusion about why people are so impressed by the mega high pressure system right now over the CAB, and why actual albedo warming (AWA) is likely to be much higher this year than past years even though past years might have had slightly higher AWP. 

Glen Koehler

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Re: Albedo-Warming Potential
« Reply #135 on: July 08, 2020, 08:07:41 PM »
Thanks Comradez, that provides a much better understanding of the AWP situation.  I was looking at the AWP graph as actual energy input.  Clear vs cloudy sky cover radically changes that interpretation.

igs

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Re: Albedo-Warming Potential
« Reply #136 on: July 08, 2020, 10:18:14 PM »
Keep in mind what "albedo warming potential" means, with emphasis on *potential.*

It means, assuming cloud-free skies. 

So, for example, if an earlier year might have had 27% CAB AWP, you'd need to still check what the actual cloud-cover was like for that year to see how much of that albedo warming potential translated into albedo warming actuality (AWA).  It could be the case that the CAB was almost totally cloud-covered during that time, in which case the AWP of 27% might translate into a AWA of near 0%. 

By contrast, let's say in 2020 the CAB AWP is 20%.  If cloud cover over the CAB is only on average, say, only 10% (because of a mega high pressure system), then the AWA would be more like 18%. 

I don't known what the actual numbers would be, but I hope this clears up some confusion about why people are so impressed by the mega high pressure system right now over the CAB, and why actual albedo warming (AWA) is likely to be much higher this year than past years even though past years might have had slightly higher AWP.


A great and spot on post, a pleasure to read.
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Tealight

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Re: Albedo-Warming Potential
« Reply #137 on: July 09, 2020, 01:44:36 AM »
Hi AWP interested people,

The Albedo Warming Potential was never intended to be used as a melting forecast indicator. It's purpose was first to rank years differently from the September minimum. Only later it turned out be be a good indifcator for the re-freeze season. Maybe I should include this on the website. It's been four years now since the original ungridded version and new people stumbling on it don't find my old posts.

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First...thanks for the wonderful contribution. Love your site.

Thank you :)

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I'm wondering if you would considering some kind of tool to validate your model in terms of its ability to predict sea ice volumes.

No. I have a sea ice forecast model which uses the same major albedo physics, but includes a few other "melt mechanisims". You could describe them as curve fitting variables. The albedo model on it's own is not good to predict actual sea ice loss.

Current extra factors in my 2020 model
Heat loss to space: otherwise it would never re-freeze
bottom melting: for stronger late august to early september melt than possible from albedo
fake cooling/heating layer: to replicate icedrift. Mostly Fram export, northern Beafort Sea and into Canadian Achipelago
CO2 levels: to correct heat loss to space over time. If I use a fixed value my model overpredicts iceloss in the 1980s and underpredicts ice loss in the 2010s. (This correction is 2-3 times as strong as the percentage increase in CO2 levels.)

https://www.arcus.org/sipn/sea-ice-outlook/2020/june

I investigated an Ice-Melt AWP model, which doesn't consider ice-free areas. It certainly gives interesting results and maps which look completly different, but I'm not sure it's any good as a melting indicator. I can share it in 1-2 days.


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However we are currently in a situation where the CAB is made up of gray ice full of extensive melt ponds and hardly any snow, with an albedo which is probably 50%-60% and certainly not 85%. So in a typical July day it is probably receiving double your number at about 200 W/m2.

Are these albedo values just guessed? If you actually measure gray ice in paint you get 200/255 RGB values or equivalent to 78% albedo. I have a program to calculate the albedo of an image and even the melt pond areas are in the 70% range. I feel in general people tend to overestimate albedo drop from snowfree areas and meltponds. See my attched images for measurements.


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he is assuming an albedo of 80% for ice and snow, and 85% for ice and snow in the High Arctic. For open water he is assuming 0% albedo

Close but not quite. My energy values already include water albedo. This is one reason why my high arctic energy values during summer solitice are below lower latitude ones. My early anamoly only model had an 80% value, but since I calculate absolute numbers (1-2 years ago) and not only anomaly values it changed.


0% SIC results in 100% absorption of my water albedo corrected energy values.
100% SIC results in 15% absorption of my water albedo corrected energy values.

Formula:
AWPdaily = ((1-SIC) * MJ) + 0.15 * MJ * SIC

Example:
MJ = 20
SIC = 75%
AWP = (1-0.75)*20 + 0.15 * 20* 0.75
AWP = 5 + 2.25
AWP = 7.75
« Last Edit: July 09, 2020, 11:00:23 AM by Tealight »

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Re: Albedo-Warming Potential
« Reply #138 on: July 09, 2020, 05:32:09 AM »
If you actually measure gray ice in paint you get 200/255 RGB values or equivalent to 78% albedo. I have a program to calculate the albedo of an image and even the melt pond areas are in the 70% range. I feel in general people tend to overestimate albedo drop from snowfree areas and meltponds. See my attched images for measurements.


Thank you so much for taking the time to point this out!

It makes a very big difference in outlook and interpretation of events when the range of opinion around solar input is so wide. Especially in the current moment.

I hope your prediction that you submitted to the SIPN comes true as well !!
« Last Edit: July 09, 2020, 05:44:02 AM by oren »

oren

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Re: Albedo-Warming Potential
« Reply #139 on: July 09, 2020, 05:42:42 AM »
Thank you Tealight for the detailed explanation. And thank you again for the Cryosphere Computing site with all its analytical resources, probably the most quoted "amateur" website here on the ASIF.

My albedo "estimate" was of course a wild guess. I was hoping others would help quantify it. I do "know" this year's ice has lower albedo than average. Here are also some data points from NSIDC:
https://nsidc.org/cryosphere/seaice/processes/albedo.html
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Sea ice has a much higher albedo compared to other Earth surfaces, such as the surrounding ocean. A typical ocean albedo is approximately 0.06, while bare sea ice varies from approximately 0.5 to 0.7. This means that the ocean reflects only 6 percent of the incoming solar radiation and absorbs the rest, while sea ice reflects 50 to 70 percent of the incoming energy. The sea ice absorbs less solar energy and keeps the surface cooler.

Snow has an even higher albedo than sea ice, and so thick sea ice covered with snow reflects as much as 90 percent of the incoming solar radiation. This serves to insulate the sea ice, maintaining cold temperatures and delaying ice melt in the summer. After the snow does begin to melt, and because shallow melt ponds have an albedo of approximately 0.4 to 0.5, the surface albedo drops to about 0.75. Albedo drops further as melt ponds grow and deepen.

uniquorn

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Re: Albedo-Warming Potential
« Reply #140 on: July 09, 2020, 08:51:58 PM »
Fascinating. A quick measurement (histogram) of two areas of the Kara sea yesterday. I think the areas are clear but light cloud is tricky to spot. https://go.nasa.gov/2BU2MUy

oren

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Re: Albedo-Warming Potential
« Reply #141 on: July 09, 2020, 09:00:03 PM »
If you actually measure gray ice in paint you get 200/255 RGB values or equivalent to 78% albedo. I have a program to calculate the albedo of an image and even the melt pond areas are in the 70% range.

Fascinating. A quick measurement (histogram) of two areas of the Kara sea yesterday.

Maybe this belongs in the stupid questions threads, but does this method measure albedo correctly with no bias?

interstitial

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Re: Albedo-Warming Potential
« Reply #142 on: July 10, 2020, 05:44:41 AM »
That would work for the visable spectrum but you would still have to correct for which frequencies some are far more important than others. Depending on how much work you want to do at the very least it could make a first approximation. Their might be an approximation that works well IDK.

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Re: Albedo-Warming Potential
« Reply #143 on: July 15, 2020, 11:53:55 PM »
Tealight, do you still not account for cloud cover due to its complexity or have you been able to work around the multiple types problem?
Btw great work, keep it up
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Re: Albedo-Warming Potential
« Reply #144 on: July 16, 2020, 12:41:48 AM »
Just skimming a few papers on ice albedo, it seems that an ice sheet with ponding will have an albedo closer to 50% than 70-80%. 

The charts on the left show the Beaufort near the Alaska coast, and the charts on the right show the CAB north of Greenland. Top is 2007, bottom is 2003-2011 average.


https://tc.copernicus.org/articles/14/165/2020/

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Re: Albedo-Warming Potential
« Reply #145 on: July 16, 2020, 01:53:44 AM »
Just skimming a few papers on ice albedo, it seems that an ice sheet with ponding will have an albedo closer to 50% than 70-80%. 


The way I read the NSIDC section that Oren quotes above is that when melt ponds are present, the surface albedo is a composite of the melt pond albedo and the ice albedo below.

We know that EMR penetrates water to a certain depth so its important what happens when EMR penetrates the pond water and reaches the surface of the ice below. Some of that EMR might be absorbed and some might be reflected back.

Here's the NSIDC line:

After the snow does begin to melt, and because shallow melt ponds have an albedo of approximately 0.4 to 0.5, the surface albedo drops to about 0.75. Albedo drops further as melt ponds grow and deepen.

My literal interpretation of that language is that ice covered with a fresh shallow melt pond has an aggregate albedo of 0.75. This is roughly the same number that Nico has provided above of 0.70.

oren

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Re: Albedo-Warming Potential
« Reply #146 on: July 16, 2020, 05:26:07 AM »
This literal interpretation is incorrect. Shallow melt ponds albedo is 0.4 to 0.5 per NSIDC. 0.75 is under the assumption of a low fraction of melt ponds, and the rest snow-covered ice. Bare ice has a lower albedo, and high melt pond fraction combined with deeper melt ponds results in extremely low albedo.

I followed one of the references from sedziobs' link above.
Polashenski, C. M.: Attributing change and understanding melt ponds on a seasonal ice cover, PhD thesis, 2011
Available in full PDF from http://libarchive.dartmouth.edu/cdm/compoundobject/collection/dcdis/id/327893/rec/6

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The variations in integrated shortwave albedo caused by shifts in pond coverage were quite significant. Spatially averaged albedo, calculated from measurements along the transect lines, is plotted in Figure 40c. Prior to pond formation, when the ice surface is snow covered, albedo is relatively stable. Albedo varies between ~0.7 and ~0.8 depending on the age and surface temperature of the snow. As snow melts, exposing bare ice and forming melt ponds, albedo drops significantly and begins to show greater variability. Albedo follows a trend inverse to that of pond coverage. Plotting albedo vs. pond coverage in Figure 40d illustrates the strength of this correlation and helps to confirm that pond coverage is the primary driver of albedo changes on melting ice.
Attached are four images from this source.

oren

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Re: Albedo-Warming Potential
« Reply #147 on: July 16, 2020, 05:32:41 AM »
From another source
https://www.pnas.org/content/111/9/3322
Observational determination of albedo decrease caused by vanishing Arctic sea ice
Kristina Pistone, Ian Eisenman, and V. Ramanathan, 2014

The mean seasonal cycle in sea ice surface albedo during 2000–2011 derived from the CERES data in the region 80–90°N (blue line) and from in situ surface albedo measurements from the Surface Heat Budget of the Arctic (SHEBA) project (18) of 1997–1998 (black line). Blue error bars indicate one SD of CERES 2000–2011 year-to-year variability, and gray shading indicates one SD of SHEBA spatial variability along a 200-m survey line.



oren

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Re: Albedo-Warming Potential
« Reply #148 on: July 16, 2020, 05:35:05 AM »
Note that this year melt ponds are more prevalent than usual, or at least were at the time the original issue was debated. Also note the data quoted above is from years that had much less melting than this decade. So a 50%-60% albedo for this year's July is probably quite optimistic.

sedziobs

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Re: Albedo-Warming Potential
« Reply #149 on: July 16, 2020, 05:52:01 AM »
Note that this year melt ponds are more prevalent than usual, or at least were at the time the original issue was debated. Also note the data quoted above is from years that had much less melting than this decade. So a 50%-60% albedo for this year's July is probably quite optimistic.
Nice finds Oren. I think the 2007 Beaufort figure I cited illustrates what may be happening in the CAB this year. Albedo drops sharply from 80% to 45% as melt pond fraction reaches 50%. As the ponds drain, albedo then rebounds to 60% over 10 days or so. From there albedo steadily drops to zero as the ice melts.

Normally in the CAB, albedo drops from 80% in June to 50-65% in July before rising again in August. In any case, albedo of 70% is uncommon from mid-June to mid-August.