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Steve C
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Seke Rob Black bodies more readily absorb AND radiate heat than white bodies. This is part of why the "blackbird" spy plane is painted black--to radiate heat from air friction at Mach 3. The role of heat radiation from dark vs. white Greenland ice is wholly speculative on my part. Probably a very tiny factor in the scheme of things. At everyday temperatures, heat radiation from objects is hard even to detect.
Toggle Commented Jul 1, 2012 on The dark side of Greenland at Arctic Sea Ice
Terry, I meant to convey that rainfall should wash away the dark material, tending to restore low albedo. But "abundant rainfall" and "Greenland" should never normally appear in the same sentence. Another thought about all that dark material. In summer, it causes the ice sheet to absorb more solar heat. In the winter, not only is it covered by snow, but I'd imagine it may tend to insulate the underlying ice. Over time, I'd expect the deep ice, say 100 meters below the surface, to warm up year round. I have no idea whether anyone monitors temps deep down in the Greenland Ice sheet. But if those gigatons of ice have been warming over time, the amount of summer melt for a given amount of heat absorption should also increase -- yet another positive feedback mechanism for ice melt in the Arctic.
Toggle Commented Jul 1, 2012 on The dark side of Greenland at Arctic Sea Ice
A point of physics may be worth pointing out here. It's obviously appreciated already that black surfaces absorb radiation energy better than light-colored surfaces. What's often forgotten is that black surfaces also EMIT radiation (infrared, microwave, etc) better than white surfaces. See "black body radiation" in a google search. At first blush, you might think that this would help the Greenland ice sheet to cool back down during the winter. But it's likely that all this dark material will be covered over by late september with fresh snow. I would guess the only dynamic that will work to reduce the albedo of the Greenland ice sheet will be abundant rainfall -- which will surely happen eventually as the arctic warms, but that, I imagine, won't happen until the globe is very tropical indeed. Steve C
Toggle Commented Jul 1, 2012 on The dark side of Greenland at Arctic Sea Ice
My first post here, for this novice cryophile... The current ferocious pace of melting all over the arctic this year seems obvious. One might expect that some of the thicker ice between Greenland and the Pole might survive... Except that this ice seems to be making a bee-line for the Fram Strait: http://iabp.apl.washington.edu/DAILYMAPS/dailyiceconc_60daytrack.jpg So I'm inclined to predict that virtually all the arctic ice that doesn't melt in situ this summer is likely to slip out the Fram Strait (if I'm interpreting the buoy drift correctly). The long-term implications would be sobering, indeed. SteveMDFP
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Jun 30, 2012