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Shared Humanity

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Re: Greenland 2019 Melt Season
« Reply #250 on: June 30, 2019, 02:50:09 PM »
Thanks...both of you.

Shared Humanity

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Re: Greenland 2019 Melt Season
« Reply #251 on: June 30, 2019, 02:53:43 PM »

Melt. Temperatures above freezing around most of the coast in the next week, with considerable warmth arriving into the far North. Perhaps melt above average to very much above average. The SST anomalies in Baffin Bay can only increase.

SMB mass change is a matter of which will prevail, precipitation and melt. But it still looks likely the SMB graph will show the 2019 line continuing to cross the 2012 red line in a day or two.
And what is the prognosis for calving given all this melt and runoff ? Not a lot of news about icebergs in Baffin Bay and iceberg alley to be found.


With such aggressive, widespread melt on southwest Greenland, shouldn't we be looking for basal and surface melt surges? I remember seeing a video from 2012 where roads and bridges were washed away by torrents of water.

Sebastian Jones

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Re: Greenland 2019 Melt Season
« Reply #252 on: June 30, 2019, 05:42:33 PM »
Thanks...both of you.
I want to take this opportunity to thank particularly the venerable ( meant respectfully) Gerontocrat and those that support his analyses- for not just keeping us informed on what is happening on Greenland almost in real time- but also for adding to our understanding of the processes involved. Thanks!

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b_lumenkraft

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Re: Greenland 2019 Melt Season
« Reply #254 on: June 30, 2019, 11:41:20 PM »
I guess we will see this in the numbers tomorrow, that the fat melt hasn't stopped yet.

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #255 on: July 01, 2019, 12:36:41 PM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 30 June 2019

Again almost a word for word repeat of yesterday's post because this event just will not stop.

Melt remains strong and even stronger yet again, the maximum again for the year. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see strong short-term spikes.

Precipitation, mainly in the South East, was not strong, and mass loss was aroundaverage.

Outlook - a tale of 2 halves, West and East.

GFS Precipitation outlook for the next 7 days now looking  like very dry to drought in the West coast and centre, some precipitation all the way down the East coast. Much is coming all the way from a warm/hot western Siberia passing over the Atlantic edge of the Arctic sea ice. A bit of rain may come from the south to affect the southern tip of Greenland. GFS says at least on the fringes (i.e. at low altitude) some precipitation is likely to fall as rain.

Melt. Temperatures above freezing around most of the coast in the next week, with considerable warmth arriving into the far North. Perhaps melt above average to very much above average. The SST anomalies in Baffin Bay can only increase.

SMB mass change is a matter of which will prevail, precipitation and melt. But it still looks likely the SMB graph will show the 2019 line continuing to cross the 2012 red line in a day or two.
And what is the prognosis for calving given all this melt and runoff ? Not a lot of news about icebergs in Baffin Bay and iceberg alley to be found.

It becomes clear that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation remains that in 2012 lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.
_____________________________________________________
Note from DMI

When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


Note from me (to any denier creeps out there):
From 2002 to 2017 Greenland lost over 3 thousand billion tons of mass, an average of nearly 300 billion tons per annum. This is about the same as the average annual mass loss of ice from the entire Arctic Seas.
https://climate.nasa.gov/vital-signs/ice-sheets/

This is simply because mass loss from glaciers calving exceeds mass gain on the surface from snowfall.

WOBBLY GIF ATTACHED - click to start
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b_lumenkraft

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Re: Greenland 2019 Melt Season
« Reply #256 on: July 01, 2019, 05:49:58 PM »
From the Nares Strait thread:

Huge melt event in Kane Basin.

Looks like this in Sentinel.  :o

oren

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Re: Greenland 2019 Melt Season
« Reply #257 on: July 01, 2019, 06:22:46 PM »
This is not a melt event involving sea ice in Kane Basin itself. Rather, it's meltwater on the ice sheet, in the lower reaches of Petermann and Humboldt glaciers behind their respective calving fronts. It happens most years that I could find, and in 2012 covered a wider area, but this year it's much bluer. I never did notice it before that Sentinel image though.
Note: some years removed due to clouds. Click to animate.

Rod

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Re: Greenland 2019 Melt Season
« Reply #258 on: July 02, 2019, 12:20:02 AM »
Interesting article from NSIDC on the big melting event last month:

A record melt event in mid-June

http://nsidc.org/greenland-today/2019/07/a-record-melt-event-in-mid-june/


wallen

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Re: Greenland 2019 Melt Season
« Reply #259 on: July 02, 2019, 02:52:40 AM »
A viewing of the West side of Greenland on Worldview with corrective reflectance (7-2-1) The sheer volume of melt and I would image runoff is staggering.

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #260 on: July 02, 2019, 01:11:52 PM »
Interesting article from NSIDC on the big melting event last month:

A record melt event in mid-June

http://nsidc.org/greenland-today/2019/07/a-record-melt-event-in-mid-june/
What is going on over the last 21 days is a lot more than a headline catching spike. The melt just will not stop.
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oren

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Re: Greenland 2019 Melt Season
« Reply #261 on: July 02, 2019, 01:16:49 PM »
Melt percent has been stubbornly staying at +2SD level for the last ~3 weeks. A very big event. I believe the persistence gives meltwater the chance to accumulate and flow, rather than refreeze in situ.

Tor Bejnar

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Re: Greenland 2019 Melt Season
« Reply #262 on: July 02, 2019, 08:38:46 PM »
Oren,
How did you determine that the grey zone that shows "all but the highest and lowest daily records of 1981-2010 data" (per Gerontocrat's June 29 post) is approximately 2SD? Is there a 'rule of thumb' involved here?  You said it was so on June 30.

There are 30 data points for each day, remove the largest and smallest; the resulting graph shows approximately how many standard deviations of the original set? 

To test this, I created a set of 30 random numbers between 20 and 40, which is approximately the range shown on the daily melt extent (%) chart at maximum melt in mid-July.  I then added a random number between -5.0 and +5.0 to each of the first set, so that I might have numbers larger an smaller than the 20 and 40.  With this new set of numbers, I identified 2SD, per Excel's formula [=2 * STDEV(set)].  Also obtained average, 2nd lowest [=SMALL(set,2)] and 2nd highest values.  I obtained multiple sets of data and averaged them.
Results: 
Average = 29.8
2SD = 13.5
Ave - 2SD = 16.3
Ave + 2SD = 43.3
2nd Lowest = 19.2
2nd Highest = 40.5

Interesting: not so terribly far off!  The range between +/- 2SD was 27 while the range between 2nd highest to 2nd lowest was only 21.3.
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anaphylaxia

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Re: Greenland 2019 Melt Season
« Reply #263 on: July 02, 2019, 09:36:37 PM »
Oren,
How did you determine that the grey zone that shows "all but the highest and lowest daily records of 1981-2010 data" (per Gerontocrat's June 29 post) is approximately 2SD? Is there a 'rule of thumb' involved here?  You said it was so on June 30.
...
I think the trick is with the mathematical properties of normal distribution, and the number of years available for observation. A 2-3 sigma event represents 4.2 % of all in a normal distribution, and there are ~40 years of data available, thus discarding one maxima and minima gets rid of the 5 % of the observations, corresponding to roughly the probability of them occuring.

Stephan

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Re: Greenland 2019 Melt Season
« Reply #264 on: July 02, 2019, 10:09:15 PM »
Gerontocrat,
is it possible to add to the melt percentage chart the melt percentage of 2012 with an extra line to see how good 2019 catches up with the record-breaking year?
Thanks in advance.
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oren

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Re: Greenland 2019 Melt Season
« Reply #265 on: July 02, 2019, 11:11:31 PM »
Oren,
How did you determine that the grey zone that shows "all but the highest and lowest daily records of 1981-2010 data" (per Gerontocrat's June 29 post) is approximately 2SD? Is there a 'rule of thumb' involved here?  You said it was so on June 30.
...
I think the trick is with the mathematical properties of normal distribution, and the number of years available for observation. A 2-3 sigma event represents 4.2 % of all in a normal distribution, and there are ~40 years of data available, thus discarding one maxima and minima gets rid of the 5 % of the observations, corresponding to roughly the probability of them occuring.
Indeed. The probability of random values to fall within a distance of +-2SD around the mean in a normal distribution is 95%. 28/30 of the ("random") observations for each day is ~94% of all the values. so the shaded area is approximately +-2SD.

lifeblack

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Re: Greenland 2019 Melt Season
« Reply #266 on: July 03, 2019, 12:29:05 AM »

There are 30 data points for each day, remove the largest and smallest; the resulting graph shows approximately how many standard deviations of the original set? 

To test this, I created a set of 30 random numbers between 20 and 40, [...]  With this new set of numbers, I identified 2SD, per Excel's formula [=2 * STDEV(set)]. 

Just to keep things mathematically clear, 'random' does not generally create a normal (gaussian) distribution (bell-curve), and the  68-95-99.7 magical property of standard deviation is only true for gaussian distributions.

Having said that though, it still sounds like a reasonable approximation

Tor Bejnar

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Re: Greenland 2019 Melt Season
« Reply #267 on: July 03, 2019, 01:10:44 AM »
Although I asked the question - and thanks for the several responses - I went out to discern if I could 'rationalize' Oren's 'rule of thumb' and feel I successfully supported it empirically.  Yes my data wasn't anything near normal, but I wonder how 'normal' Greenland's data is!

Thanks all!

I'll add a postscript.  My 1st year Physics university lecturer was from Ireland.  (The day after a helicopter was hijacked and used to help an IRA member in a British prison escape, we discussed the event in class.)  Anyway, this man had learned in secondary school, he said, all sorts of mathematical/arithmetic shortcuts, such as Pi2~=10.  He could do the arithmetic associated with an 'all the blanks filled' formula as fast in his head to 1 significant digit (but correct order of magnitude) as I could punch the numbers into my HP35 pocket calculator, only I sometimes made keyboard mistakes.  (The HP's reverse-Polish system made this type of calculations very easy.)  My sense is that a European science and math education in high school is often 'richer' than an American one.
« Last Edit: July 03, 2019, 01:23:57 AM by Tor Bejnar »
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oren

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Re: Greenland 2019 Melt Season
« Reply #268 on: July 03, 2019, 02:30:15 AM »
Just to keep things mathematically clear, 'random' does not generally create a normal (gaussian) distribution (bell-curve), and the  68-95-99.7 magical property of standard deviation is only true for gaussian distributions.

Having said that though, it still sounds like a reasonable approximation
You are correct lifeblack, I've used the "random" term flexibly.
To my defense, although my B.Sc was in both physics and math, I have always and forever identified as a (hobby) physicist, never as a mathematician.

Phil.

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Re: Greenland 2019 Melt Season
« Reply #269 on: July 03, 2019, 04:22:04 AM »
Although I asked the question - and thanks for the several responses - I went out to discern if I could 'rationalize' Oren's 'rule of thumb' and feel I successfully supported it empirically.  Yes my data wasn't anything near normal, but I wonder how 'normal' Greenland's data is!

Thanks all!

I'll add a postscript.  My 1st year Physics university lecturer was from Ireland.  (The day after a helicopter was hijacked and used to help an IRA member in a British prison escape, we discussed the event in class.)  Anyway, this man had learned in secondary school, he said, all sorts of mathematical/arithmetic shortcuts, such as Pi2~=10.  He could do the arithmetic associated with an 'all the blanks filled' formula as fast in his head to 1 significant digit (but correct order of magnitude) as I could punch the numbers into my HP35 pocket calculator, only I sometimes made keyboard mistakes.  (The HP's reverse-Polish system made this type of calculations very easy.)  My sense is that a European science and math education in high school is often 'richer' than an American one.
Yes, we learned all sorts of tricks back then in the absence of calculators out of necessity.  I still use the pi^2 trick, p1=22/7 etc.  One thing we learned was how to make approximations to speed up mental calculations, I still get remarks from students when I give my answer while they're still entering data.  :) Once while building some research equipment we needed to make an adjustment to the spacing to give a rotation of 30º.  I looked at it and told the tech that we'd need a 0.012" shim, they looked at me in astonishment and said there's no way you can know that!  They went and got the calculator and it turned out we needed 0.0115", they repeated the calculation a few times in disbelief.

Tor Bejnar

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Re: Greenland 2019 Melt Season
« Reply #270 on: July 03, 2019, 05:03:52 AM »
I like pi ~=113 into 355 or "113355" with a manual divide calculation structure put in the middle:

      __3.141592... (and then it goes off)
113/355


A couple years after I was in that Physics class, I was in my roommate's side of the room.  We were figuring out how much cash we needed to take to the post office, and we figured out we needed to mail 20 letters and postage was 13 cents then.  I ran over to my side of the room to get my calculator and he said "$2.60" and I said "How do you know?" as I knew he didn't own a calculator...  Some lessons we (I) don't learn quickly!
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sidd

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Re: Greenland 2019 Melt Season
« Reply #271 on: July 03, 2019, 06:50:45 AM »
sin(30 degrees) = 1/2 is one i use a lot

perhaps we need a thread called quick math trix

sidd

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #272 on: July 03, 2019, 10:56:05 AM »
Gerontocrat,
is it possible to add to the melt percentage chart the melt percentage of 2012 with an extra line to see how good 2019 catches up with the record-breaking year?
Thanks in advance.
Nope. No can do. The graph is straight from DMI's polar portal website. I don't download data on Greenland - a bridge too far for me.

NSIDC's Greenland Today (http://nsidc.org/greenland-today/) has an interactive chart thingy
https://nsidc.org/greenland-today/greenland-surface-melt-extent-interactive-chart/

Note that I am not posting data from there. Why? They do use the same definitions for melt and SMB changes. But they use a different model (I think) with coarser resolution. e.g. The DMI melt graph does not show the same huge spike on Jun 10 -11.

I don't want to mix apples and pears, and DMI does the daily SMB balance data. So it is DMI for me.
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gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #273 on: July 03, 2019, 11:09:15 AM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 30 June 2019

Again almost a word for word repeat of previous days' posts because this event just will not stop.

Melt remains strong and even stronger yet again, the maximum again for the year. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see strong short-term spikes.

Precipitation, mainly in the South East, was not strong, and mass loss was around average.

Outlook - a tale of the South-East and the rest.

GFS Precipitation outlook for the next 7 days now looking  like very dry to drought over most of Greenland apart from the SE. i.e. back to normal. GFS says at least on the fringes (i.e. at low altitude) any precipitation is likely to fall as rain.

Melt. Temperatures above freezing around most of the coast in the next week. The SST anomalies in Baffin Bay can only increase as final sea ice melt out is completed..

SMB mass change is a matter of which will prevail, precipitation and melt. But it still looks likely the SMB graph will show the 2019 line continuing to cross the 2012 red line in a day or two.
And what is the prognosis for calving given all this melt and runoff ? Not a lot of news about icebergs in Baffin Bay and iceberg alley to be found.

It becomes clear that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation remains that in 2012, even though melt was spectacularly high,  lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.
_____________________________________________________
Note from DMI

When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


Note from me to any denier creeps out there:
From 2002 to 2017 Greenland lost over 3 thousand billion tons of mass, an average of nearly 300 billion tons per annum. This is about the same as the average annual mass loss of ice from the entire Arctic Seas. https://climate.nasa.gov/vital-signs/ice-sheets/

This is simply because mass loss from glaciers calving exceeds mass gain on the surface from snowfall.
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BenB

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Re: Greenland 2019 Melt Season
« Reply #274 on: July 03, 2019, 11:35:53 AM »
Gerontocrat, I have a quick question. You've said in your recent posts that melt was strong, as confirmed by the graph, and that precipitation was not strong, resulting in around average mass loss. Presumably the precipitation, albeit not strong in absolute terms, was significantly above average, otherwise it wouldn't offset the strong melt. Or am I missing something?

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #275 on: July 03, 2019, 12:09:16 PM »
Gerontocrat, I have a quick question. You've said in your recent posts that melt was strong, as confirmed by the graph, and that precipitation was not strong, resulting in around average mass loss. Presumably the precipitation, albeit not strong in absolute terms, was significantly above average, otherwise it wouldn't offset the strong melt. Or am I missing something?
After having a look and a think I think you are right, and to add to that while melt looks to be right up there at perhaps +2SD, what looks like a small amount of precipitation can reduce the SMB loss to average.

Another piece of evidence to suggest that maybe variation in precipitation is more important than melt. Maybe one day I will try and extract the precipitation data if it is on the DMI portal., especially to see if 2012 was really dry.
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BenB

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Re: Greenland 2019 Melt Season
« Reply #276 on: July 03, 2019, 12:33:52 PM »
Thanks, Gerontocrat. I have a follow-up question to you and others:

Even if a relatively small amount of precipitation may offset above-average melting in the daily SMB, is this actually good for the ice in the medium/long term? Or does the fact that anomalous precipitation is also presumably falling as rain at lower altitudes contribute to destabilisation/lubrication of glaciers, potentially increasing rates of glacier flow and the amount of calving?

oren

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Re: Greenland 2019 Melt Season
« Reply #277 on: July 03, 2019, 12:42:01 PM »
A high melt rate, especially if sustained throughout the season, will certainly contribute to glacier speedup and increased calving. This is what happened in 2012 and afterwards, for example in Jakobshavn.

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Re: Greenland 2019 Melt Season
« Reply #278 on: July 03, 2019, 12:52:33 PM »
A high melt rate, especially if sustained throughout the season, will certainly contribute to glacier speedup and increased calving. This is what happened in 2012 and afterwards, for example in Jakobshavn.

I wonder what will be the extend of the Greenland cold blob come wnd of this season and how will next year's weather will be affected

BenB

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Re: Greenland 2019 Melt Season
« Reply #279 on: July 03, 2019, 12:53:42 PM »
I understand that, Oren, but I was wondering specifically whether there is a difference between a high melt rate combined with anomalously high precipitation (what we are seeing this year), and a year with high melt but without the precipitation, e.g. 2012, presumably, judging by the strongly negative net SMB. Or did 2012 also have relatively high precipitation at low altitude, but little/none falling as snow? That seems unlikely, on the face of it, but I don't entirely rule it out.

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #280 on: July 03, 2019, 02:26:21 PM »
Thanks, Gerontocrat. I have a follow-up question to you and others:

Even if a relatively small amount of precipitation may offset above-average melting in the daily SMB, is this actually good for the ice in the medium/long term? Or does the fact that anomalous precipitation is also presumably falling as rain at lower altitudes contribute to destabilisation/lubrication of glaciers, potentially increasing rates of glacier flow and the amount of calving?
The only thing I can add is that Greenland Mass loss (SMB minus calving)  in the 21st Century was quite a lot (3+ trillion tons 2002 to 2017).

Will be watching out for reports / new papers.

Attached is a graph from NASA / JPL Grace Data - no longer accessible as they've dumped access by ftp , and data access (also to GRACE-FO) now looks locked up for scientific user groups. Nothing for us who pay for the damn project.
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gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #281 on: July 03, 2019, 02:46:36 PM »
Thanks, Gerontocrat. I have a follow-up question to you and others:

Even if a relatively small amount of precipitation may offset above-average melting in the daily SMB, is this actually good for the ice in the medium/long term? Or does the fact that anomalous precipitation is also presumably falling as rain at lower altitudes contribute to destabilisation/lubrication of glaciers, potentially increasing rates of glacier flow and the amount of calving?
Will be watching out for reports / new papers***.

***And I forgot completely about this one even though I posted on AbruptSLR's thread as he had a similar one about the WAIS. Shoot me. Worth a read, I would say, as it was probably the reason I started obsessing about Greenland rain vs melt..

https://www.the-cryosphere.net/13/815/2019/
Increased Greenland melt triggered by large-scale, year-round cyclonic moisture intrusions
Marilena Oltmanns1, Fiammetta Straneo2, and Marco Tedesco3,4

4 Conclusions
By combining remote-sensing-based melt extent data and observations
from weather stations, we have shown that surface
melt is triggered by cyclonic weather events in summer and
winter. Through the advection of heat and moisture over large
portions of the ice sheet, these events lead to increases in
cloud cover, precipitation, an enhanced absorption of longwave
radiation and decreases in the albedo in the south and
near the coast. Previous studies have found that cyclonic rainfall
events in late summer have accelerated the glacial flow
(Doyle et al., 2015), suggesting that the identified melt events
can also trigger dynamic instabilities in the ice sheet. Since
the efficiency of the glacial flow was critically determined
by the seasonal condition of the subglacial drainage system
(Doyle et al., 2015), we mostly expect melt events in late
summer to have this effect
.
The strong, rapid and short-lived character of the temperature
increase, the high wind speeds, the precipitation
and their frequent occurrence, also excluding summer, distinguish
the investigated cyclonic weather events from the
anticyclones, centered over Greenland, that have previously
been recognized as the main driver of surface melting (Overland
et al., 2012; Fettweis et al., 2013; Hanna et al., 2013a,
2016). However, regarding the extended duration of melt
events in summer, we surmise that the identified melt triggers
can evolve into the previously described persistent high pressure
anomalies, which is supported by studies suggesting
that particularly intense and long-lasting atmospheric blocking
episodes in summer have been reinforced by cyclones
that preceded them (Neff et al., 2014; McLeod and Mote,
2015).




"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

BenB

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Re: Greenland 2019 Melt Season
« Reply #282 on: July 03, 2019, 05:16:51 PM »
Thanks again, Gerontocrat. I actually read the whole paper, which made very interesting reading. It seems that as well as the impacts on dynamic processes that you bolded, the enhanced surface melting caused by greater cloud cover, increased absorption of LW radiation and lower albedo means that in summer the net impact of these precipitation events is to increase mass loss, even at the level of surface mass balance. In winter, on the other hand, there is a net SMB gain. One reason for this:

While in winter, most of the melting and precipitation occurs within the first 3 days of the events, in summer, melting, runoff and refreezing are still significantly amplified after 6 days.


Another interesting point is that:

The runoff–refreezing ratio is delayed compared to the others, being highest in August and falling off in November. This strong seasonality shows that most of the runoff associated with summer events occurs later in the season,

This could partly explain why at this time of summer any enhanced melt caused by the precipitation we're currently seeing is not (significantly) outweighing the additional accumulation of snow at higher altitudes. Or it could just be noise. Finally, they observed:

a northward and upslope shift of the boundary between rain/melting and snowfall, hence changing the balance between Greenland's mass gain and mass loss within a single weather event.

Climate change in action, and it will only get worse.

RoxTheGeologist

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Re: Greenland 2019 Melt Season
« Reply #283 on: July 03, 2019, 07:06:12 PM »
sin(30 degrees) = 1/2 is one i use a lot

perhaps we need a thread called quick math trix

sidd

SOOO far off topic. Sorry.

Read Fenyman's autobiography; he had a math race with a guy with an abacus and he uses a number of tricks to win. I believe it's at a time before calculators existed!

My favorite impressive math trick is 1/7ths; 0.142857 recurring.  They are blindingly easy to remember and the reaction to quoting fractions to 10 decimal places in your head is entertaining. My grandpa was a bank manager, and could add up columns of numbers blindingly quickly, far faster than I could type them into a adding machine. He was my role model :)

0.142857... (2x7, 4x7, 8x7 +1)
0.285714...
0.428571...
0.571428...
0.714285...
0.851428...

Its the same sequence, starting from each of the numbers, and the sequence of numbers is trivial to remember.

Alexander555

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Re: Greenland 2019 Melt Season
« Reply #284 on: July 03, 2019, 08:41:35 PM »
What's the explanation for these 3 years with much bigger losses ?

b_lumenkraft

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Re: Greenland 2019 Melt Season
« Reply #285 on: July 03, 2019, 09:10:58 PM »
The melt just keeps going. Today it's south Greenland.

This is a GIF showing 3 frames from the RAMMB (a couple of hours) in M8 band.

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #286 on: July 03, 2019, 09:35:10 PM »
What's the explanation for these 3 years with much bigger losses ?
2012- amazing melt.
Other years - Don't know. Just depends on how much winter snowfall (mass gain) and how much summer melt + calving (mass loss). I do not have the data.

When if we ever see GRACE-FO data re 2017-18, we will likely see a mass GAIN as snowfall was far above average, melt was poor and perhaps calving less than usual.

Highly volatile - this year so far looks likely to be above average mass loss.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Phil.

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Re: Greenland 2019 Melt Season
« Reply #287 on: July 03, 2019, 10:40:09 PM »
Rox the last one should be 0.857142.. not 0.851428...   ;)

RoxTheGeologist

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Re: Greenland 2019 Melt Season
« Reply #288 on: July 03, 2019, 11:08:14 PM »
Oh yeah, typo lol. I didn't double check :)

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #289 on: July 04, 2019, 10:25:23 AM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 3 July 2019

Again almost a word for word repeat of previous days' posts because this event just will not stop.

Melt remains strong and even stronger yet again, the maximum again for the year. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see strong short-term spikes.

Precipitation, mainly in the South East, was not strong, and mass loss was around average.

Outlook - very dry?.

GFS Precipitation outlook for the next 5 days now looking  like very dry to drought over all Greenland.

Melt. Temperatures above freezing around most of the coast in the next week. The SST anomalies in Baffin Bay can only increase as final sea ice melt out is completed..

SMB mass change is a matter of which will prevail, precipitation and melt. It looks likely the SMB graph will above average SMB loss over the next few days.

And what is the prognosis for calving given all this melt and runoff ? Not a lot of news about icebergs in Baffin Bay and iceberg alley to be found.

It becomes clear that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation remains that in 2012, even though melt was spectacularly high,  lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.
_____________________________________________________
Note from DMI

When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


Note from me to any denier creeps out there:
From 2002 to 2017 Greenland lost over 3 thousand billion tons of mass, an average of nearly 300 billion tons per annum. This is about the same as the average annual mass loss of ice from the entire Arctic Seas. https://climate.nasa.gov/vital-signs/ice-sheets/

This is simply because mass loss from glaciers calving exceeds mass gain on the surface from snowfall.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #290 on: July 04, 2019, 10:56:03 AM »
And a couple of images from DMI to show why so many people are waiting for GRACE-FO to start producing data.

But GRACE-FO has started producing data, they've even got a scientists users group.
But "ftp" has been abandoned.
Nothing in a format useable by us "volk" what paid for it being published yet.
__________________________________________________________
A moan, about bloody scientists making sure peasants like me can only see what they let us see.

My guess is that one day it will be goodbye to anything other than YAML ASCII and NetCDF for holding data, i.e. goodbye to xls and .csv files from NSIDC and JAXA. At which time little ol' me will chuck the laptop in the bin..

See
https://earthdata.nasa.gov/esdis/eso/standards-and-references/yaml-encoding-ascii-format-for-grace-grace-fo-mission-data
and
https://podaac.jpl.nasa.gov/GRACE-FO
Quote
The GRACE-FO mission will continually generate the full records of Level 1-3 datasets which are listed in table below by three key partners​.  All GRACE-FO datasets are managed and distributed by PO.DAAC. To promote GRACE-FO data interoperability, all datasets are produced in either standard netCDF and/or ASCII YAML format, in compliance with PO.DAAC data best practices and NASA ESDIS metadata standards. Different from GRACE ASCII files, GRACE-FO ASCII files have been redesigned with its header constructed in the YAML format.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #291 on: July 05, 2019, 06:35:10 AM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 4 July 2019

Yet again almost a word for word repeat of previous days' posts because this event just will not stop.

Melt remains strong and even stronger yet again, the maximum again for the year. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see strong short-term spikes.

Precipitation, was very low, and mass loss was well above average.

GFS Precipitation outlook for the next 5 days now looking  like very dry to drought over all Greenland.

Melt. Temperatures above freezing around most of the coast in the next week. The SST anomalies in Baffin Bay can only increase as final sea ice melt out is completed..

SMB mass change is a matter of which will prevail, precipitation and melt. It looks likely the SMB graph will show above average SMB loss over the next few days.

And what is the prognosis for calving given all this melt and runoff ? Not a lot of news about icebergs in Baffin Bay and iceberg alley to be found.

It becomes clear that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation remains that in 2012, even though melt was spectacularly high,  lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.
_____________________________________________________
Note from DMI

When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


Note from me to any denier creeps out there:
From 2002 to 2017 Greenland lost over 3 thousand billion tons of mass, an average of nearly 300 billion tons per annum. This is about the same as the average annual mass loss of ice from the entire Arctic Seas. https://climate.nasa.gov/vital-signs/ice-sheets/

This is simply because mass loss from glaciers calving exceeds mass gain on the surface from snowfall.
[/quote]
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Stephan

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Re: Greenland 2019 Melt Season
« Reply #292 on: July 05, 2019, 06:24:53 PM »
It remains mild and dry close to the southern tip of Grønland:
It is too late just to be concerned about Climate Change

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #293 on: July 06, 2019, 10:27:21 AM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 5 July 2019

Yet again almost a word for word repeat of previous days' posts because this event just will not stop.

Melt remains strong and even stronger yet again, the maximum again for the year. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see strong short-term spikes.

Precipitation, was almost zero, and as a result mass loss was greatly above average.

GFS Precipitation outlook for the next 5 days now looking  like very dry to drought over all Greenland.

Melt. Temperatures above freezing around most of the coast in the next week. The SST anomalies in Baffin Bay can only increase as final sea ice melt out is completed..

SMB mass change is a matter of which will prevail, precipitation or melt. It looks likely the SMB graph will show above average SMB loss over the next few days.

Signs of more normal temperatures over Greenland after about a week. i.e. melt wiould continue, but at a more average rate. We will see.

It becomes clear that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation remains that in 2012, even though melt was spectacularly high,  lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.
_____________________________________________________
Note from DMI

When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


Note from me to any denier creeps out there:
From 2002 to 2017 Greenland lost over 3 thousand billion tons of mass, an average of nearly 300 billion tons per annum. This is about the same as the average annual mass loss of ice from the entire Arctic Seas. https://climate.nasa.gov/vital-signs/ice-sheets/

This is simply because mass loss from glaciers calving exceeds mass gain on the surface from snowfall.
[/quote]
[/quote]
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

Rod

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Re: Greenland 2019 Melt Season
« Reply #294 on: July 06, 2019, 05:43:37 PM »
8 million Olympic size swimming pools in 5 days ...

Rod

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Re: Greenland 2019 Melt Season
« Reply #295 on: July 07, 2019, 03:08:47 AM »
Incredible image posted by Zack today showing some of the Greenland melt ponds.

Tor Bejnar

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Re: Greenland 2019 Melt Season
« Reply #296 on: July 07, 2019, 05:57:24 AM »
Most of these melt ponds are partially covered by floating ice.  I've read that some melt ponds do not freeze solid during the winter (which surprised me), but it explains the phenomenon demonstrated here, floating ice on melt ponds on glacial ice.  As a melt pond gets deeper and wider with today's warm temperatures, the floating ice will sever its connection to the shore, and even if 'thick', won't reach the shore of the larger pond.  A possibility is for a melt pond to drain after the surface freezes in the winter, leaving a cave, so that when re-filled, the pond will lift the 'lid' as described just above.
Arctic ice is healthy for children and other living things.

gerontocrat

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Re: Greenland 2019 Melt Season
« Reply #297 on: July 07, 2019, 10:22:46 AM »
http://polarportal.dk/en/greenland/surface-conditions/ as at 6 July 2019

No, I am not being lazy. The words are the same because the story is the same because this event just will not stop.

Melt remains strong and even stronger yet again, the maximum again for the year. Again concentrated in the West and the South. I am sure the persistence of this strong melt is unusual, as normally we just see strong short-term spikes.

Precipitation, was almost zero, and as a result mass loss was greatly above average.

GFS Precipitation outlook for the next 5 days still looking  like very dry to drought over most Greenland.

Melt. Temperatures above freezing around most of the coast in the next week. The SST anomalies in Baffin Bay can only increase as final sea ice melt out is completed..

SMB mass change is a matter of which will prevail, precipitation or melt. It looks likely the SMB graph will show above average SMB loss over the next few days.

Signs of more normal temperatures over Greenland after about a week. i.e. melt would continue, but at a more average rate. We will see.

It becomes clear that precipitation, or the lack of it, may determine the overall SMB loss during the melting season at least as much as melt. My speculation remains that in 2012, even though melt was spectacularly high,  lack of precipitation was as or more important than melt in the unprecedented SMB loss that year.
_____________________________________________________
Note from DMI

When comparing melt with the surface mass balance under ”Daily change”, note that melting can occur without surface mass loss since the meltwater can refreeze in the underlying snow. Likewise, surface mass loss can occur without melting due to sublimation.

The map illustrates how the surface of the Greenland Ice Sheet gains and loses mass on a daily basis. This is known as the surface mass balance. It does not include the mass that is lost when glaciers calve off icebergs and melt as they come into contact with warm seawater.


Note from me to any denier creeps out there:
From 2002 to 2017 Greenland lost over 3 thousand billion tons of mass, an average of nearly 300 billion tons per annum. This is about the same as the average annual mass loss of ice from the entire Arctic Seas. https://climate.nasa.gov/vital-signs/ice-sheets/

This is simply because mass loss from glaciers calving exceeds mass gain on the surface from snowfall.
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

oren

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Re: Greenland 2019 Melt Season
« Reply #298 on: July 07, 2019, 10:27:49 AM »
This is simply relentless. 3-4 weeks of the same +2SD result. Much worse than a volatile high melt low melt situation. The meltwater has no chance to stabilize. This could cause some lake outburst and/or extra-strong calving around the Greenland perimeter.

Darvince

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Re: Greenland 2019 Melt Season
« Reply #299 on: July 07, 2019, 02:01:58 PM »
Today, tomorrow, and Tuesday look to be worse for the ice sheet before a slight cooldown afterwards. I'd expect the 7th, 8th, and 9th to all have highest mass loss for the year again (maybe approaching -10GT?) before it either stabilizes or declines afterwards.

... And, we still have five or so weeks left which could have another huge melt event like on 12th June. CFS (not very trustworthy) has weeks three thru five being well above average like the coming week.