Spatially Complete Global Surface Albedos Derived from MODIS Data
The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don...
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Transcript of The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don...
![Page 1: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/1.jpg)
The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today
and Reflections on Tomorrow
Don Perovich1 and Tom Grenfell21Cold Regions Research and Engineering Laboratory, 2University of Washington
![Page 2: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/2.jpg)
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incident
reflectedAlbedo
Melting
+
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Lower albedoAbsorbedsunlight
![Page 3: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/3.jpg)
Ice-albedo feedback: seasonal evolution
July August 7 September
April May 17 June 10
Surface types: snow, bare ice, melt ponds, and leads
![Page 4: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/4.jpg)
Albedo evolution of surface types
Snow, leads, bare ice constant – ponds always changing
![Page 5: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/5.jpg)
Surface physical propertiesJune 17 August 7
Regenerating surface scattering layer Deepening ponds
![Page 6: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/6.jpg)
• Estimate as a composite of surface types• determine the albedos of types• determine the relative areas (A)• albedo () is linear combination
•S=snow, i=, p=pond and w=water.
wwppiiss AAAA
Large-scale albedo
Combine albedos with fractional areas
![Page 7: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/7.jpg)
Albedo evolution
5 phases – timing is critical
Snow warming
Pond evolution
Fall freezeup
Pon
d fo
rmat
ion
Sno
w m
elt
![Page 8: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/8.jpg)
General form
Know form of albedo evolution
![Page 9: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/9.jpg)
Modest changes
Adjust “wavelength” and “amplitude”
![Page 10: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/10.jpg)
What if …Multiyear
Not a minor adjustment – it’s a new regime
First year
big changes
![Page 11: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/11.jpg)
First year ice – albedo evolution
Decrease is rapid
![Page 12: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/12.jpg)
First year ice – albedo evolution
Decrease is rapid, sometimes is reversed
![Page 13: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/13.jpg)
First year ice – albedo evolution
Decrease is rapid, sometimes is reversed, sometimes oscillates
![Page 14: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/14.jpg)
First year ice – albedo evolution
24 June
15 June
18 June
• Tremendous variability• Multiple evolutionary paths
• Flooded• Drained• Superposed
• Need to understand physical properties• Role of melt, topography, and permeability
Big change in physical evolution – big change in albedo evolution
![Page 15: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/15.jpg)
Deformed first year ice
Who knows? Interconnections cause cascading changes
![Page 16: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/16.jpg)
Changes are happening now
Average bottom ablation from 100 thickness gauges
Bottom ablation measured at SHEBA - 1998
![Page 17: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/17.jpg)
Bottom ablation and solar heating
In the past source of heat was sunlight deposited in leads
SHEBA 1998Heat used in bottom ablation
![Page 18: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/18.jpg)
Solar heating
Transmittance through leads not sufficient
![Page 19: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/19.jpg)
Solar heating
Leads, melt ponds and bare ice all contribute
![Page 20: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/20.jpg)
1975 versus 1998
Ice is thinner, transmission to ocean is greater
• No change in bare ice albedo• Decrease in pond albedo• Increase in bare ice transmittance• Major increase in pond transmittance
• Simple optical model• “Standard” ice conditions
• 3.0 m vs. 1.5 m• 2.5 m vs. 1.0 m
![Page 21: The Sea Ice-Albedo Feedback in a Warming Climate: Albedos from Today and Reflections on Tomorrow Don Perovich 1 and Tom Grenfell 2 1 Cold Regions Research.](https://reader035.fdocuments.in/reader035/viewer/2022062807/5697c0221a28abf838cd377e/html5/thumbnails/21.jpg)
Summary
Integration and synthesis are key
Current state•Good understanding•Five distinct phases in albedo evolution•Summer is the interesting time•Melt ponds are major uncertainty
Modest changes•Fundamentals are the same•Can adapt present treatment•Change “wavelength / amplitude” of albedo cycle
Major changes•All bets are off•Can speculate, but not extrapolate•Probably accelerated feedback•Difficulty is that changes are interrelated