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Author Topic: Greenland 2017 melt season  (Read 23690 times)

Shared Humanity

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Re: Greenland 2017 melt season
« Reply #150 on: November 02, 2017, 03:04:33 PM »
A warmer, wetter Greenland should be expected with climate change IMHO.
But does that mean net ice mass gain or loss?
Haven't a clue.
As we are seeing now, 'wetter' takes advantage over 'warmer', leading to an accumulation of mass in the ice sheet (probably as fluid water at the freezing point, inside pores and other open spaces inside the ice, otherwise as ice/snow).
At some point, the melting caused by 'warmer' will overtake, melting the extra accumulated mass away.

Yes, 2016 had a net SMB gain but given the decade long trend of SMB loss, it is a little premature to say that wetter will outweigh warmer, even in the short term.

Andre Koelewijn

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Re: Greenland 2017 melt season
« Reply #151 on: November 02, 2017, 03:15:33 PM »
In the very short term (recent past) it did, that does not mean at all it will stay like that for even a few years. This seems to be a rather unstable transition.

Shared Humanity

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Re: Greenland 2017 melt season
« Reply #152 on: November 02, 2017, 04:37:23 PM »
In the very short term (recent past) it did, that does not mean at all it will stay like that for even a few years. This seems to be a rather unstable transition.

That bottom trend chart hardly suggests an unstable transition.

Satellite observations over the past decade show that Greenland is losing mass at about 250bn tonnes per year.

You can see what this means for the total ice mass balance on Greenland on the graph posted above. The red dots are monthly changes in ice mass, representing the ups and downs of the seasonal cycle in each individual year. The overall trend shows a continued year-on-year decline. The sharp drop you see in 2012 was due to an unprecedented melt season but mass loss has continued since with the exception of this past year.

gerontocrat

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Re: Greenland 2017 melt season
« Reply #153 on: November 04, 2017, 01:55:25 PM »
A warmer, wetter Greenland should be expected with climate change IMHO.
But does that mean net ice mass gain or loss?
Haven't a clue.
As we are seeing now, 'wetter' takes advantage over 'warmer', leading to an accumulation of mass in the ice sheet (probably as fluid water at the freezing point, inside pores and other open spaces inside the ice, otherwise as ice/snow).
At some point, the melting caused by 'warmer' will overtake, melting the extra accumulated mass away.

Yes, 2016 had a net SMB gain but given the decade long trend of SMB loss, it is a little premature to say that wetter will outweigh warmer, even in the short term.

With trepidation I suggest that this SMB thing needs some clarification.

There are three factors to take account of for calculating changes in the TOTAL Greenland Mass Budget, surface precipitation, surface melting, calving.

Two are dealt with by "http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/", namely:
- Surface precipitation,
- Surface melting.
Precipitation exceeds melt, so on average surface mass increases by nearly 400 gt per annum.

The third factor is calving. I do not believe there is any direct measure of this. But NASA's GRACE project produced data on the total changes to the mass of Greenland, indicating net mass loss of 200+ Gt per annum.
Therefore one could assume mass loss from calving on average of circa 600 gt per annum.

2016 had a surface mass gain (from factors one and two) of about 200 gt greater than average. We do not know whether calving was above, below, or about average. The GRACE project data stops at January 2017, so we do not know whether the Greenland Ice Sheet gained or loss mass.

Losing GRACE is a bummer. With luck new satellites up there next March, and after calibrating etc new data by mid-year?
_________________________________________
Quote from http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/ --
"Over the year, it snows more than it melts, but calving of icebergs also adds to the total mass budget of the ice sheet. Satellite observations over the last decade show that the ice sheet is not in balance. The calving loss is greater than the gain from surface mass balance, and Greenland is losing mass at about 200 Gt/yr."
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Daniel B.

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Re: Greenland 2017 melt season
« Reply #154 on: November 05, 2017, 03:10:58 AM »
A warmer, wetter Greenland should be expected with climate change IMHO.
But does that mean net ice mass gain or loss?
Haven't a clue.
As we are seeing now, 'wetter' takes advantage over 'warmer', leading to an accumulation of mass in the ice sheet (probably as fluid water at the freezing point, inside pores and other open spaces inside the ice, otherwise as ice/snow).
At some point, the melting caused by 'warmer' will overtake, melting the extra accumulated mass away.

Yes, 2016 had a net SMB gain but given the decade long trend of SMB loss, it is a little premature to say that wetter will outweigh warmer, even in the short term.

With trepidation I suggest that this SMB thing needs some clarification.

There are three factors to take account of for calculating changes in the TOTAL Greenland Mass Budget, surface precipitation, surface melting, calving.

Two are dealt with by "http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/", namely:
- Surface precipitation,
- Surface melting.
Precipitation exceeds melt, so on average surface mass increases by nearly 400 gt per annum.

The third factor is calving. I do not believe there is any direct measure of this. But NASA's GRACE project produced data on the total changes to the mass of Greenland, indicating net mass loss of 200+ Gt per annum.
Therefore one could assume mass loss from calving on average of circa 600 gt per annum.

2016 had a surface mass gain (from factors one and two) of about 200 gt greater than average. We do not know whether calving was above, below, or about average. The GRACE project data stops at January 2017, so we do not know whether the Greenland Ice Sheet gained or loss mass.

Losing GRACE is a bummer. With luck new satellites up there next March, and after calibrating etc new data by mid-year?
_________________________________________
Quote from http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/ --
"Over the year, it snows more than it melts, but calving of icebergs also adds to the total mass budget of the ice sheet. Satellite observations over the last decade show that the ice sheet is not in balance. The calving loss is greater than the gain from surface mass balance, and Greenland is losing mass at about 200 Gt/yr."

We could assume that since the next loss has been averaging 200 Gt/yr, and this past season gain was 200 Gt above average, that the net balance was near zero.  However, without GRACE data, we do not know for sure. 

Adam Ash

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Re: Greenland 2017 melt season
« Reply #155 on: November 05, 2017, 12:54:43 PM »
Is it not likely that much if the mass gain is liquid water held near freezing within the ice sheet. The thermal input from this water will reduce ice strength making portions of the ice sheet much more susceptible to rapid collapse as slush when side support is lost, or with an earthquake providing energy to liquify the mass?

Shared Humanity

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Re: Greenland 2017 melt season
« Reply #156 on: November 05, 2017, 04:41:21 PM »
Is it not likely that much if the mass gain is liquid water held near freezing within the ice sheet. The thermal input from this water will reduce ice strength making portions of the ice sheet much more susceptible to rapid collapse as slush when side support is lost, or with an earthquake providing energy to liquify the mass?

I am fairly certain I have read research here suggesting this is happening, a lot. Not all melt water slices through the sheet to bedrock and then flows to the sea but once it travels below the surface of the sheet, it can and often does stay as water as it is no longer exposed to bitter cold temperatures. Yes, this captured melt water warms the ice but this isn't going to cause the sheet to turn to slush.

Could someone here direct me to research that has already been posted here?

sidd

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Re: Greenland 2017 melt season
« Reply #157 on: November 05, 2017, 09:29:26 PM »
Firn aquifer:


doi: 10.1038/NGEO2043

Extensive liquid meltwater storage in firn within the Greenland ice sheet, Forster eta al., Nature Geoscience 2013

doi: 10.3389/feart.2017.00005

Drainage of Southeast Greenland Firn Aquifer Water through Crevasses to the Bed. Poinar et al., Frontiers in Earth Science, 2017

sidd

nukefix

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Re: Greenland 2017 melt season
« Reply #158 on: November 06, 2017, 12:10:12 AM »
We could assume that since the next loss has been averaging 200 Gt/yr, and this past season gain was 200 Gt above average, that the net balance was near zero.  However, without GRACE data, we do not know for sure.
GRACE is not the only game in town, satellite altimetry and the input-output methods still work.

gerontocrat

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Re: Greenland 2017 melt season
« Reply #159 on: November 06, 2017, 09:10:27 AM »
GRACE is not the only game in town, satellite altimetry and the input-output methods still work.
Do you know where can we find data re 2017 total mass balance?
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Daniel B.

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Re: Greenland 2017 melt season
« Reply #160 on: November 06, 2017, 01:41:14 PM »
GRACE is not the only game in town, satellite altimetry and the input-output methods still work.
Do you know where can we find data re 2017 total mass balance?

Nothing definitive yet, but this link may yield some insight.

https://www.carbonbrief.org/guest-post-greenland-ice-sheet-2017

gerontocrat

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Re: Greenland 2017 melt season
« Reply #161 on: November 06, 2017, 01:57:56 PM »
GRACE is not the only game in town, satellite altimetry and the input-output methods still work.
Do you know where can we find data re 2017 total mass balance?

Nothing definitive yet, but this link may yield some insight.

https://www.carbonbrief.org/guest-post-greenland-ice-sheet-2017
And the this rather nice article by the DMI uses the GRACE data to derive mass loss from calving. I wonder what / when we will see data from other resources.
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gerontocrat

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Re: Greenland 2017 melt season
« Reply #162 on: November 14, 2017, 02:50:12 PM »
Data from http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

Precipitation over the last few days has been moderate. looking at cci-renalyzer suggests no major activity for the next few days at least. This is in contrast to September and October. Is there any likelihood that the development of La Nina conditions is not a coincidence? If there is a correlation, perhaps this winter and spring will be much dryer than last year?

Note also that mass gain is concentrated on the coastal SE quarter.
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gerontocrat

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Re: Greenland 2017 melt season
« Reply #163 on: November 20, 2017, 04:02:20 PM »
from http://www.dmi.dk/en/groenland/maalinger/greenland-ice-sheet-surface-mass-budget/

Pretty dry weather on Greenland, and cci-reanalyzer says dryness will persist.
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gerontocrat

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Re: Greenland 2017 melt season
« Reply #164 on: November 24, 2017, 03:47:39 PM »
Still very dry on Greenland. Some modest ? precipitation expected in the far south over the next few days
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Sigmetnow

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Re: Greenland 2017 melt season
« Reply #166 on: November 30, 2017, 04:30:49 AM »
OMG: Heat wave scorches Greenland up to 54°F warmer than normal
https://twitter.com/climateprogress/status/935950788966387712

Monster heat wave reaches Greenland, bringing rain and melting its ice sheet
https://thinkprogress.org/omg-heat-wave-scorches-greenland-up-to-54f-warmer-than-normal-9981de9c6a92/amp/
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Coffee Drinker

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Re: Greenland 2017 melt season
« Reply #167 on: December 02, 2017, 08:18:28 AM »
Monster heatwave melting its ice sheet. sure. Sensationalism at its best.

There is hardly any above freezing temps even along the coast.

http://www.wetterzentrale.de/maps/GFSOPEU00_21_5.png

Daniel B.

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Re: Greenland 2017 melt season
« Reply #168 on: December 02, 2017, 03:12:26 PM »
And yet, recent snowfalls continue to push accumulation above average.  Colder temperatures are forecast for this week, which may further push the ice balance higher.

gerontocrat

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Re: Greenland 2017 melt season
« Reply #169 on: December 02, 2017, 04:10:41 PM »
The temperature spike certainly happened, but the effect on the Greenland Surface Mass Balance was minimal - two days saw just 1% of Greenland melting.

November was a slow month for mass increase compared with Sept and Oct and last year. I thought colder was often associated with dryer, milder with wetter. We will see.
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Tor Bejnar

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Re: Greenland 2017 melt season
« Reply #170 on: December 02, 2017, 07:20:52 PM »
As warm air can hold more moisture than cold air, Greenland temperatures that are much warmer than normal (but still below freezing) might lead to more precipitation (snow). 
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Daniel B.

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Re: Greenland 2017 melt season
« Reply #171 on: December 02, 2017, 09:02:53 PM »
As warm air can hold more moisture than cold air, Greenland temperatures that are much warmer than normal (but still below freezing) might lead to more precipitation (snow).

In theory, that is correct.  Warmer temperatures have not always had that anticipated effect though.

Tor Bejnar

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Re: Greenland 2017 melt season
« Reply #172 on: December 02, 2017, 10:43:09 PM »
That's why I didn't say it will cause more snowfall.
 :)
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gerontocrat

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Re: Greenland 2017 melt season
« Reply #173 on: December 07, 2017, 04:17:38 PM »
Greenla
nd precipitation still on the low side, though cci-reanalyzer predicts a dump in Southern Greenland over the next few days.

So I am sticking with "my theory that belongs to me", i.e. that the decline in precipitation that started in November coincides with the onset of La Nina conditions and this is not a coincidence.
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