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Author Topic: Greenland 2017 melt season  (Read 7191 times)

lurkalot

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Re: Greenland 2017 melt season
« Reply #50 on: July 20, 2017, 08:35:35 PM »
Ever heard of Sod's Law, Gerontocrat? A few minutes after your post, NSIDC revealed one of the biggest melt days on record.

BlackPhillip

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Re: Greenland 2017 melt season
« Reply #51 on: July 20, 2017, 08:50:52 PM »
Ever heard of Sod's Law, Gerontocrat? A few minutes after your post, NSIDC revealed one of the biggest melt days on record.


Is it raining or is it snowing?

DMI and NSIDC seem to disagree.

DMI has decent melting for 7/19, but any mass loss for that date is completely overwhelmed by significant snow on the interior of southern Greenland. On the whole it looks like Greenland very slightly gained mass on that date.



NSIDC shows a significant portion of southern Greenland (including interior) as melting, which has led to a very high (extraordinarily high if you consider how this season is going) melt %.



Does anyone know what is actually happening?

Juan C. García

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Re: Greenland 2017 melt season
« Reply #52 on: July 20, 2017, 10:16:58 PM »
« Last Edit: July 20, 2017, 10:26:49 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

oren

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Re: Greenland 2017 melt season
« Reply #53 on: July 20, 2017, 10:20:01 PM »
 Holy s**t!

Neven

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Re: Greenland 2017 melt season
« Reply #54 on: July 20, 2017, 10:26:49 PM »
Maybe the difference has to do with DMI being about surface mass, while NSIDC is about surface melt? Or maybe one interpreted precipitation as rain and the other as snow. I have no idea, I don't follow Greenland melt all that much. But there could be another spike, as the forecast is for warm, sunny weather over much of Greenland in days to come.
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gerontocrat

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Re: Greenland 2017 melt season
« Reply #55 on: July 21, 2017, 02:12:10 PM »
Maybe the difference has to do with DMI being about surface mass, while NSIDC is about surface melt? Or maybe one interpreted precipitation as rain and the other as snow.

DMI is about both melt (mass loss obviously mainly on the periphery) and mass gain - snow fall. You need the complete set of three images to get it all. DMI and NSIDC's analysis are in agreement, but DMI is adding back snowfall to get the surface mass budget.

It is of note (at least to me) that a high melt percentage (actually, not that high) can be offset totally by some snowfall. It is also getting late in the melting season. The end result for the surface mass balance is going to be unusual.
« Last Edit: July 21, 2017, 02:58:45 PM by gerontocrat »

Adam Ash

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Re: Greenland 2017 melt season
« Reply #56 on: July 21, 2017, 02:44:37 PM »
I guess the one thing the SMB may not account for is the melt of the underside of glaciers?  Presumably the lowering of the top ice surface to ballance the bottom melt is noted in the overall mass  ballance.

nukefix

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Re: Greenland 2017 melt season
« Reply #57 on: July 22, 2017, 12:04:58 PM »
The Greenland surface melt products are sensitive to the presence of small amounts of liquid water (wet snow) on the surface. The SMB can still be positive when surface melt (=wet snow) is detected on the ice sheet.

oren

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Re: Greenland 2017 melt season
« Reply #58 on: July 22, 2017, 01:24:00 PM »
I don't see a contradiction. Isn't rain included in the SMB as well? As long as it doesn't run off the ice sheet, and I'm sure a lot of it doesn't,  it adds to surface mass, and registers as surface melt as well.

gerontocrat

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Re: Greenland 2017 melt season
« Reply #59 on: July 22, 2017, 01:59:39 PM »
Ever heard of Sod's Law, Gerontocrat? A few minutes after your post, NSIDC revealed one of the biggest melt days on record.

OK, lurkalot, so the dog has managed a "whoof" or two. But a whoof, (first graph: melt-combine) does not change the story for the year (2nd graph : accumulated smb). The dog has to bark a lot louder and longer to change the story's plot.
Whereupon, looking at cci-reanalyzer, it seems the dog is raising its volume somehwat now and for the next few days

To me there is a serious question as to whether this year is a one-off or a climatic change, especially as elsewhere there has been much discussion about unusually high snowfall all around the Arctic Ocean (and maybe on the ocean) last fall, winter and spring.
« Last Edit: July 22, 2017, 02:10:53 PM by gerontocrat »

Coffee Drinker

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Re: Greenland 2017 melt season
« Reply #60 on: Today at 04:14:51 AM »
The average height of the ice sheet is something like 2000m. How often does it actually rain at that altitude during the Greenland summer?

My gut feeling tells me that the Greenland ice sheet is predominately driven by precipitation and not so much by actual temperature.