Support the Arctic Sea Ice Forum and Blog

Author Topic: Greenland 2023-24 SMB, melting and GRACE mass  (Read 2604 times)

gerontocrat

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Greenland 2023-24 SMB, melting and GRACE mass
« on: November 05, 2023, 10:36:33 AM »
Until the 2024 melt gets going around April 2024, this thread is about the Surface Mass Balance change (i.e. snowfall) from 1 Sept 2023 to 31 Aug 2024, plus DMI and JPL GIS Mass Loss data from GRACE /GRACE-FO data.

SMB gain as at 4 November is 163 GT, 23 GT (16%) above the 2017-2022 average, which is also well above the longterm average from DMI.

Wetter than average conditions are largely confined to the coast, especially in the SE.
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #1 on: November 11, 2023, 06:53:34 PM »
GFZ have updated the GIS Mass Loss monthly data to mid-June 2023. (Note that GFZ and JPL-NASA both go mid-month to mid-month)

The hiatus in GIS Mass Loss continues (see next post).
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #2 on: November 11, 2023, 07:30:00 PM »
There is a hiatus in GIS Mass Loss

GIS Mass Loss is
the sum of calving + basal melting of marine-terminating glaciers + melting at the boundary between the ice sheet and the ice sheet from friction and freshwater intrusion from above (e.g. via moulins)

minus SMB gain or plus SMB loss. We have SMB data from the DMI.

This year SMB gains were high (lots of snowfall), and melting did not really take off until after mid-June. This is shown on the attached graph.

When we get GIS Mass Loss data for mid-June to mid-August we may see big monthly losses as melt was high (see 2nd graph).
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #3 on: November 25, 2023, 07:09:17 PM »
Until the 2024 melt gets going around April 2024, this thread is about the Surface Mass Balance change (i.e. snowfall) from 1 Sept 2023 to 31 Aug 2024, plus DMI and JPL GIS Mass Loss data from GRACE /GRACE-FO data (whenever it is updated).

SMB gain as at 24 November is 206 GT, 18 GT (10%) above the 2017-2022 average, which is also above the longterm average from DMI.

Wetter than average conditions are largely confined to the coast, especially in the SE.

i.e. not a lot going on.
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #4 on: December 10, 2023, 02:33:17 PM »
Until the 2024 melt gets going around April 2024, this thread is about the Surface Mass Balance change (i.e. snowfall) from 1 Sept 2023 to 31 Aug 2024, plus DMI and JPL GIS Mass Loss data from GRACE /GRACE-FO data (whenever it is updated).

SMB gain as at 9 December is 235 GT, 9 GT (4%) above the 2017-2022 average, which is also above the longterm average from DMI, but well below the 2022-3 SMB gain by this date.

Wetter than average conditions are largely confined to the coast, especially in the SE.

i.e. not a lot going on.
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #5 on: December 10, 2023, 02:49:23 PM »
However JPL/NASA have added another 3 months of Greenland Ice Sheet Mass data - to mid-September 2023.

In those 3 months Greenland lost 350GT of mass. During those 3 months surface melt in Greenland was well above average, and overall SMB loss was 160GT for those 3 months.

Nevertheless, overall SMB gain for the 12 months to September 2023 was nearly 400GT, which is a very large brake on Greenland Ice Sheet Mass Loss.

Climate science suggests that a warmer wetter Greenalnd will increase snowfall but also increase rain on snow events and more above freezing days at low altitude. Initially this may increase annual SMB gains until warmth overpowers increases in snow. When? "aye, there's the rub".
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #6 on: January 09, 2024, 02:23:01 PM »
JPL/NASA have added another 3 months of Greenland Ice Sheet Mass data - to mid-October 2023.

There was a small mass gain of 15 GT in that month, made up of a 55GT mass gain in SMB and a 40GT mass loss of 40GT from marine-terminating laciers calving & melting.
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #7 on: January 27, 2024, 06:49:10 PM »
Until the 2024 melt gets going around April 2024, this thread is about the Surface Mass Balance change (i.e. snowfall) from 1 Sept 2023 to 31 Aug 2024, plus DMI and JPL GIS Mass Loss data from GRACE /GRACE-FO data (whenever it is updated).

SMB gain as at 26 Jan 2024 is 327 GT, 10 GT (3%) above the 2017-2022 average of 317 GT, which is a little below the longterm average from DMI.

Melt viirtually zero

i.e. not a lot going on.
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #8 on: February 09, 2024, 07:10:49 PM »
GFZ have at last produced another update of GIS Mass Loss, this time to October 2023.
The data includes mass loss by 8 drainage basins, which I have also grouped into 3 regions.

Some of the graphs attached have blank spaces where monthly data was not produced by the first GRACE satellites.

Total Mass Loss since early 2002 is 4,635 GT, about 220 GT a year.

Perhaps the most interesting feature is that Mass Loss in Drainage Basin 306 that fronts the southern half of Baffin Bay has basically stalled since late 2019. Until then Mass Loss was occurring at the highest rate of all the basins. We do not have SMB data from DMI by drainage basins, though they hope one day to be able to produce it. If we had it we would be able to get at least an idea if the stall in Mass Loss of that basin is due to increased SMB (i.e. snowfall) and / or reduced calving and melt of marine-terminating glaciers.

Meanwhile Mass Loss in basin 307 that fronts the Northern half of Baffin Bay and Basin 304 in SE Greenland continues unabated.

Overall, Mass Loss is higher in West Greenland.

ps: Processing GRACE-FO data is a complex business that chews up people and super-computer time. GFZ tells me that this year and next year they have funding to produce more frequent and more-up-to-date analyses. Let's also hope that DMI get the resources they need to develop their capabilities as well.
"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

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #9 on: February 18, 2024, 11:34:33 AM »
Until the 2024 melt gets going around April 2024, this thread is about the Surface Mass Balance change (i.e. snowfall) from 1 Sept 2023 to 31 Aug 2024, plus DMI and JPL GIS Mass Loss data from GRACE /GRACE-FO data (whenever it is updated).

SMB gain as at 17 Feb 2024 is 354 GT, 5 GT (1%) below the 2017-2022 average of 359 GT, which is below the longterm average from DMI.

Melt virtually zero

i.e. not a lot going on.
"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)

Renerpho

  • Grease ice
  • Posts: 540
    • View Profile
  • Liked: 234
  • Likes Given: 61
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #10 on: February 18, 2024, 05:59:05 PM »
Total Mass Loss since early 2002 is 4,635 GT, about 220 GT a year.

https://svs.gsfc.nasa.gov/31156/ gives a total loss of about 5,500 GT, and an average of 271 GT per year. I don't know anything about this data product, but I am confused by the difference. Do you know what's going on?
Before I came here I was confused about this subject. Having listened to your lecture I am still confused. But on a higher level.

gerontocrat

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #11 on: February 18, 2024, 07:11:40 PM »
Total Mass Loss since early 2002 is 4,635 GT, about 220 GT a year.

https://svs.gsfc.nasa.gov/31156/ gives a total loss of about 5,500 GT, and an average of 271 GT per year. I don't know anything about this data product, but I am confused by the difference. Do you know what's going on?
The calculation by JPL to Nov 23 is GIS mass loss of 5,525 GT while the calculation by German Research Centre for Geosciences (GFZ) is 4,635.

About a year or so ago I asked GFZ about the differences (much higher for the GIS than the AIS). GFZ said they both start from the same place - raw data from the GRACE satellites.

Then the data is processed by JPL using JPL's algorithm, and by GFZ using GFZ's algorithm, Glacial Isostatic Adjustment (GIA) being the major change.

GFZ basically said they had confidence in their model. You can read about it here: http://gravis.gfz-potsdam.de/corrections

But they did say recently that this year and next year they had funding to do development work on the GRACE-FO based systems they have ( see http://gravis.gfz-potsdam.de/gis)

I am using JPL's data for integration with SMB data from DMI.
But the JPL product does not have analyses by basins (despite a promise long ago), so I use GFZ data for the basin analyses

So no real explanation

"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)

Renerpho

  • Grease ice
  • Posts: 540
    • View Profile
  • Liked: 234
  • Likes Given: 61
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #12 on: February 18, 2024, 07:19:35 PM »
So no real explanation

Interesting, thank you! Maybe the additional funding will help not just improve the model (as well as the final data product), but also look at possible problems with it. This is something all complex models should be subjected to, but as you said previously, working on this data is hard and expensive. On the plus side, having two independent products from the same raw data that differ by ~20% gives an indication of what kind of uncertainty there probably is in each number. Greenland ice is decreasing by 200-300 GT per year.

P.S. Congratulations for making your 20,000th post.  :)
Before I came here I was confused about this subject. Having listened to your lecture I am still confused. But on a higher level.

gerontocrat

  • Multi-year ice
  • Posts: 20087
    • View Profile
  • Liked: 5257
  • Likes Given: 69
Re: Greenland 2023-24 SMB, melting and GRACE mass
« Reply #13 on: February 18, 2024, 07:44:12 PM »
P.S. Congratulations for making your 20,000th post.  :)
20,000? scary.
That wasn't the idea when I started to post on the ASIF
"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)