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Post by duwayne on Jun 27, 2024 18:56:32 GMT
polarportal.dk/en/greenland/surface-conditions/Above is graph of Greenland Surface Mass Balance. Curiously, if you look at coastal temperatures all around Greenland, they are all below freezing. I do not see how you can have a substantial negative mass balance if everywhere is below freezing. I am obviously missing something, or the data is telling porkies. Are you looking at average coastal temperatures or daily high temperatures? |
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Post by douglavers on Jun 28, 2024 0:31:01 GMT
The temperatures were all negative [degC].
Assume they were "average" temperatures. Even if the temp briefly spiked above freezing during the day, little melting would occur. The snow/ice base would rapidly refreeze any melt.
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Post by nonentropic on Jun 28, 2024 18:46:49 GMT
the sun can melt the surface.
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Post by duwayne on Jun 28, 2024 22:44:45 GMT
The temperatures were all negative [degC]. Assume they were "average" temperatures. Even if the temp briefly spiked above freezing during the day, little melting would occur. The snow/ice base would rapidly refreeze any melt. Possible reasons for ice mass decrease when average temperature is below freezing but highs are above freezing?
Water melts and then evaporates before it refreezes? This phenomenon would seem to be aided by the fact that water readily absorbs sunlight (heat) while ice reflects sunlight. This heat would drive evaporation.
Some water runs into the ocean before it refreezes?
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Summer 24
Jun 29, 2024 0:20:55 GMT
via mobile
Post by Sigurdur on Jun 29, 2024 0:20:55 GMT
The temperatures were all negative [degC]. Assume they were "average" temperatures. Even if the temp briefly spiked above freezing during the day, little melting would occur. The snow/ice base would rapidly refreeze any melt. Possible reasons for ice mass decrease when average temperature is below freezing but highs are above freezing?
Water melts and then evaporates before it refreezes? This phenomenon would seem to be aided by the fact that water readily absorbs sunlight (heat) while ice reflects sunlight. This heat would drive evaporation.
Some water runs into the ocean before it refreezes?
Sublimation. |
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Post by ratty on Jun 29, 2024 2:05:54 GMT
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Post by Sigurdur on Jun 29, 2024 3:29:51 GMT
Excellent find Ratty!! A lot of folks don't understand that ice melts at 20F or colder. Living in ND I have observed ice disappear even tho it remains below 0F, -18C. |
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Post by douglavers on Jun 29, 2024 11:01:26 GMT
The polar portal is saying that Greenland is loosing about 2 gigatons of water per day.
I will accept that quite a bit of ice is subliming [ sorry Sigurdur - the process is direct solid to vapour if temperature below freezing ].
However, I would be astonished if a vapour pressure of water over ice of only a few mm of Hg is enough to account for two cubic kms of water per day.
And yes - the temperature around Greenland is still below freezing.
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Post by duwayne on Jun 29, 2024 16:33:49 GMT
The polar portal is saying that Greenland is loosing about 2 gigatons of water per day. I will accept that quite a bit of ice is subliming [ sorry Sigurdur - the process is direct solid to vapour if temperature below freezing ]. However, I would be astonished if a vapour pressure of water over ice of only a few mm of Hg is enough to account for two cubic kms of water per day. And yes - the temperature around Greenland is still below freezing.
Sublimation plays a it's role. But in addition, the air temperature during the warm part of the day when temperatures are above freezing must cause thin surface melting broadly across the ice field. Then, water's very high absorption rate of sunlight would help supply heat for evaporation which occurs at the very top of the surface.
When I look at the current daily highs in some of the Greenland cities, they are well above freezing.
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Post by missouriboy on Jun 29, 2024 21:36:39 GMT
On a clear sunny day in Flagstaff AZ (7,000 ft) after a heavy snowfall, you could see sublimation at work. The top of the drifts just slowly evaporated. There was also melting.
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Post by flearider on Jun 29, 2024 21:38:08 GMT
The polar portal is saying that Greenland is loosing about 2 gigatons of water per day. I will accept that quite a bit of ice is subliming [ sorry Sigurdur - the process is direct solid to vapour if temperature below freezing ]. However, I would be astonished if a vapour pressure of water over ice of only a few mm of Hg is enough to account for two cubic kms of water per day. And yes - the temperature around Greenland is still below freezing.
Sublimation plays a it's role. But in addition, the air temperature during the warm part of the day when temperatures are above freezing must cause thin surface melting broadly across the ice field. Then, water's very high absorption rate of sunlight would help supply heat for evaporation which occurs at the very top of the surface.
When I look at the current daily highs in some of the Greenland cities, they are well above freezing.
well you do learn something every day .. didn't think Greenland had that many people on it thx  |
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Post by duwayne on Jun 29, 2024 22:25:18 GMT
Sublimation plays a it's role. But in addition, the air temperature during the warm part of the day when temperatures are above freezing must cause thin surface melting broadly across the ice field. Then, water's very high absorption rate of sunlight would help supply heat for evaporation which occurs at the very top of the surface.
When I look at the current daily highs in some of the Greenland cities, they are well above freezing.
well you do learn something every day .. didn't think Greenland had that many people on it thx "Cities" was a bad choice of words. I should have said locations. |
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Post by flearider on Jun 30, 2024 6:01:19 GMT
well you do learn something every day .. didn't think Greenland had that many people on it thx "Cities" was a bad choice of words. I should have said locations. 56k people live in Greenland .. and by the looks of it comfortable that is a hard lifestyle |
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Post by nonentropic on Jun 30, 2024 20:16:22 GMT
On a ski-field a shower of rain can dry out over night leaving dry snow. Sublimation. Thank god!
Most snow is lost at the bottom of the Greenland ice cake. The flux of energy from the hot earth, normal, into the extremely pressurized column of ice produces a flow of water at the base of the glacial stack. The generally accepted thermal gradient as you go down into the earth is 2.7C/100M it varies a bit.
What happens on top is the balance between precipitation, evaporation and rarely melting which is part of the hysterical cabals picture gallery.
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Post by ratty on Jul 2, 2024 8:20:41 GMT
USA highest recorded July temperatures with years ...  |
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