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August 12th Across Three Decades - University Of Illinois Cryosphere Imaging

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hatrack Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 03:07 PM
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August 12th Across Three Decades - University Of Illinois Cryosphere Imaging
1979 (My apologies for lack of a true 30-year anniversary, but their whole-year records only go back to 1979)



1987



1997



2007



http://arctic.atmos.uiuc.edu/cryosphere/
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 03:09 PM
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1. Love a duck. The phrase "nonlinear process" comes to mind.
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hatrack Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 03:15 PM
Response to Reply #1
3. One of these things is not like the other, one of these things is not the same . . .
Looks like I picked the wrong week to stop sniffing glue!
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 03:16 PM
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4. You can kind of see the setup in 1997. Large areas at 60%.
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hatrack Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 03:20 PM
Response to Reply #4
5. Yeah, I noticed that - kind of like the beta version
But now we're getting the full Vista treatment!
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 03:14 PM
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2. At a rough guess, that's an area about the size of Greenland, suddenly absorbing sunlight.
Along with all the other positive feedbacks we know and hate, I wonder if that is going to extend the normal melting season.
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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 05:18 PM
Response to Reply #2
6. Counting on my fingers....
the change in albedo makes for an extra 80W/m2 where the ice has melted. I'll leave you to work out the size of Greenland in m2, and how much extra heat energy it adds up to until the sun starts setting again. (Hint: remember, the SI prefix for quintillion is "exa-").

I don't see how it can't be affected. At some point, the winter ice is going to be smaller than the "normal" summer ice: I wonder if this will be the lucky year?

:(
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 05:50 PM
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7. Does that account for low angle of incidence?
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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 06:23 PM
Response to Reply #7
8. I assumed 14 degrees on average
Edited on Mon Aug-13-07 06:30 PM by Dead_Parrot
and 850W/m2 "square-on" ground-level irradiance, which makes for ~200W/m2 insolance at that angle: I took the albedo of ice at 50%, and water at 10%. So, very rule-of-thumb, but close enough.

I should have had another coffee before posting, since I didn't allow for cloud cover, although I just found this from NOAA:



Which suggests I'm actually shooting low. Go figure.
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 06:30 PM
Response to Reply #8
9. Ice is generally quoted at 90% albedo, although it must vary.
Well, those are interesting plots. Are those insolation plots for absorption, or just incidence?
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Dead_Parrot Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 06:39 PM
Response to Reply #9
10. Not sure
Still trying to figure that one out. :(

I was wondering about the ice albedo - while looking up the albedo for water, I stumbled across this which gives 52%. I assumed it was a full-spectrum figure or something and dropped it in. :shrug:

If you plumb in 90% ice albedo and 300W insolance, you get an extra 240W/m2.

Yikes.
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jeffreyi Donating Member (194 posts) Send PM | Profile | Ignore Mon Aug-13-07 08:58 PM
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11. Wow
great job. That series of images would make a spectacular poster.
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phantom power Donating Member (1000+ posts) Send PM | Profile | Ignore Mon Aug-13-07 09:58 PM
Response to Reply #11
12. Late September is likely to be the main event.
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