Support the Arctic Sea Ice Forum and Blog

Author Topic: What's new in Greenland?  (Read 132993 times)

solartim27

  • ASIF Middle Class
  • Posts: 528
    • View Profile
  • Liked: 13
  • Likes Given: 15
« Last Edit: January 18, 2018, 11:01:42 PM by solartim27 »
FNORD

AbruptSLR

  • ASIF Emperor
  • Posts: 16479
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: What's new in Greenland?
« Reply #301 on: February 09, 2018, 06:29:17 PM »
The linked reference provides a nice review of outlet glaciers in northern Greenland:

Hill, E. A., Carr, J. R., Stokes, C. R., and Gudmundsson, G. H.: Dynamic changes in outlet glaciers in northern Greenland from 1948 to 2015, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-17, in review, 2018.

https://www.the-cryosphere-discuss.net/tc-2018-17/

Abstract. The Greenland Ice Sheet (GrIS) is losing mass in response to recent climatic and oceanic warming. Since the mid-1990s, marine-terminating outlet glaciers across the GrIS have retreated, accelerated and thinned, but recent changes in northern Greenland have been comparatively understudied. Consequently, the dynamic response (i.e. changes in surface elevation and velocity) of these outlet glaciers to changes at their termini, particularly calving from floating ice tongues, remains unknown. Here we use satellite imagery and historical maps to produce an unprecedented 68-year record of terminus change across 18 major outlet glaciers and combine this with previously published surface elevation and velocity datasets. Overall, recent (1995–2015) retreat rates were higher than at any time in the previous 47 years, but change-point analysis reveals three categories of frontal position change: (i) minimal change followed by steady and continuous retreat, (ii) minimal change followed by a switch to a period of short-lived rapid retreat, (iii) glaciers that underwent cycles of advance and retreat. Furthermore, these categories appear to be linked to the terminus type, with those in category (i) having grounded termini and those in category (ii) characterised by floating ice tongues. We interpret glaciers in category (iii) as surge-type. Glacier geometry (e.g. fjord width and basal topography) is also an important influence on the dynamic re-adjustment of glaciers to changes at their termini. Taken together, the loss of several ice tongues and the recent acceleration in the retreat of numerous marine-terminating glaciers suggests northern Greenland is undergoing rapid change and could soon impact on some large catchments that have capacity to contribute an important component to sea level rise.
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #302 on: February 20, 2018, 09:25:57 AM »
That Hill paper is brilliant. Check out figs 7,8,9. Open access.

sidd

Espen

  • ASIF Governor
  • Posts: 3116
    • View Profile
  • Liked: 24
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #303 on: February 20, 2018, 10:20:29 PM »
That Hill paper is brilliant. Check out figs 7,8,9. Open access.

sidd

Not so in my oppinion according to the paper Steensby Gletscher should be advancing, that is not true the glacier retreated more than 20 km over the last decade??
Have a ice day!

sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #304 on: February 21, 2018, 05:36:56 AM »
That figure is odd considering this statement on pg 8:

"Steensby Glacier underwent minimal change during the study period (1 m a -1 : 1948–2015), but
with a high rate of retreat from 1978 to 2015 (-366 m a -1 )."

Fig 4 shows Steensby at +104m/yr till 2010 or later, but then retreating at 3Km/yr

Perhaps you should post a comment there. the paper is still in discussion, i think.

sidd

P.S. : I think i figured it out fig3 is the average from 1948, and the rapid recent retreat has not swung the average yet.
« Last Edit: February 21, 2018, 08:48:45 AM by sidd »

sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #305 on: March 01, 2018, 12:30:00 AM »
Nice paper by Joughin, Smith and Howat with new velocity maps.

"It is unclear whether external forcing, internal dynamics, or some combination of both have contributed to the changes in terminus extent that have produced the recent slowdown. Temperature records from the nearby coastal station at Egedesminde 20 indicate that 2017 was the second coldest year, behind 2015, in the 21 st Century (GISS, 2018). Thus, one plausible hypothesis is that the recent colder temperatures may have contributed to the advance and slowdown, although if there were cooler water at the terminus it could have played a role as well. Whether this slowdown could reduce summer thinning and increase winter thickening sufficiently to stabilize the glacier over scales of years to decades is unclear."

...

"If the recent slowdown is not the beginning of a period of stabilization, then the terminus of Jakobshavn Isbrae likely will continue to retreat at least 60 km inland until it recedes from the trough’s deeper parts (Joughin et al., 2012)"

Open access. Read the whole thing.

doi: 10.5194/tc-2018-40

sidd


sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #306 on: March 03, 2018, 02:54:16 AM »
Bamber and the usual suspect have a paper out on Arctic freshwater flux:

doi: 10.1002/2017JC013605

"The cumulative freshwater flux anomaly exceeded 6300±316 km^3 by 2016. This is roughly twice the estimate of a previous analysis that did not include glaciers and ice caps outside of Greenland and which extended only to 2010. From 2010 onward, the total freshwater flux is about 1300 km 3 /yr, equivalent to 0.04 Sv, which is roughly 40% of the estimated total runoff to the Arctic for the same time period. Not all of this flux will reach areas of deep convection or Arctic and Sub-Arctic seas. We note, however, that the largest freshwater flux anomalies, grouped by ocean basin, are located in Baffin Bay and Davis Strait ... "

"The total cumulative FWF anomaly is close to reaching a value where it will be comparable to the interannual
variability in FWF driven by other processes in the climate system [Boning et al., 2016]."

I attach a figure

sidd

AbruptSLR

  • ASIF Emperor
  • Posts: 16479
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: What's new in Greenland?
« Reply #307 on: March 14, 2018, 11:02:48 PM »
If the findings of the linked reference are correct then "chain-reactions of fast draining lakes" could threaten the stability of key portions of Greenland's ice sheet over the coming 50 years:

Poul Christoffersen et al, Cascading lake drainage on the Greenland Ice Sheet triggered by tensile shock and fracture, Nature Communications (2018). DOI: 10.1038/s41467-018-03420-8

http://www.nature.com/articles/s41467-018-03420-8

Abstract: "Supraglacial lakes on the Greenland Ice Sheet are expanding inland, but the impact on ice flow is equivocal because interior surface conditions may preclude the transfer of surface water to the bed. Here we use a well-constrained 3D model to demonstrate that supraglacial lakes in Greenland drain when tensile-stress perturbations propagate fractures in areas where fractures are normally absent or closed. These melt-induced perturbations escalate when lakes as far as 80 km apart form expansive networks and drain in rapid succession. The result is a tensile shock that establishes new surface-to-bed hydraulic pathways in areas where crevasses transiently open. We show evidence for open crevasses 135 km inland from the ice margin, which is much farther inland than previously considered possible. We hypothesise that inland expansion of lakes will deliver water and heat to isolated regions of the ice sheet’s interior where the impact on ice flow is potentially large."

See also:

Title: "Chain reaction of fast-draining lakes poses new risk for Greenland ice sheet"

https://phys.org/news/2018-03-chain-reaction-fast-draining-lakes-poses.html

Extract: "A growing network of lakes on the Greenland ice sheet has been found to drain in a chain reaction that speeds up the flow of the ice sheet, threatening its stability."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

litesong

  • ASIF Citizen
  • Posts: 374
    • View Profile
  • Liked: 20
  • Likes Given: 14
Re: What's new in Greenland?
« Reply #308 on: March 16, 2018, 05:26:27 PM »
Yes, that is a lollapalooza! I just read about it from this Science Daily: https://www.sciencedaily.com/releases/2018/03/180314092305.htm
But I see I'm already late, here. ha ha ha
It almost sounds like the stress-tensor theory they expounded in our 1970's aeronautical structures classes.
« Last Edit: March 16, 2018, 06:01:41 PM by litesong »

gerontocrat

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: What's new in Greenland?
« Reply #309 on: March 20, 2018, 10:52:25 AM »
http://spacenews.com/iridium-raising-new-debt-to-cover-late-aireon-payments/

Iridium raising new debt to cover late Aireon payments
by Caleb Henry — February 26, 2018


You might be asking what on earth has Iridium's debts got to do with Greenland ?

Once upon a time there was the GRACE project (US & Germany) that gave us the data on ice mass loss in Greenland (and Antarctica and loads of other data used in more than 6000 scientific papers). It lasted much longer than its design life but NASA finally took it off life support in January 2017.

Do not despair - the new improved GRACE Follow-on project is due to happen this spring (and the specs look great). But the private sector are doing the launch with Iridium satellites also involved. Things have got messy - see below.

This project has major importance. The data will be (amongst other things) the definitive record of ice mass change of the ice-sheets, eliminating uncertainty, speculation and denial.

Quote

WASHINGTON — A company that fleet operator Iridium formed to help finance its second-generation satellite constellation is taking longer than expected to pay Iridium back for carrying its sensor network to orbit.

McLean, Virginia-based Iridium said Feb. 22 that to avoid counting on aircraft-tracking startup Aireon for liquidity, Iridium went back to its lenders to raise additional debt to finish the $3 billion Iridium Next constellation it’s in the midst of deploying.

Next SpaceX launch in late March

Iridium CEO Matt Desch said the successful Feb. 22 launch of a SpaceX Falcon 9 from Vandenberg Air Force Base cleared the way for greater schedule certainty with Iridium Next, which is launching entirely from the California facility. So far SpaceX has completed four Falcon 9 launches for Iridium, and has four more to go, though the original launch campaign was supposed to have been completed in 2017.

The fifth Iridium Next launch will likely occur March 29, he said. Subsequent missions should follow every five to six weeks until the constellation is complete, he said. Each launch carries 10 satellites at a time, with the exception of the sixth launch, which will carry five Iridium Next satellites and two U.S.-German science satellites called GRACE-FO.

The GRACE-FO, or Gravity Recovery and Climate Experiment Follow-On satellites, were originally supposed to launch on a Dnepr rocket through the Russian-Ukrainian joint venture Kosmotras, but the mission never happened. Iridium had two satellites slated to launch on Dnepr as well, but booked a shared Falcon 9 after Russian red tape left the launch, once forecast for 2015, on indefinite hold.

What a complicated world we live in. ("Oh! what a tangled web we weave" Sir Walter Scott 1808 - not the Bard).

PS Ice-Sat 2 - will look at ice thickness - launch in September 2018 (We hope). A definitive measurement of ice thickness would be a big plus?
http://environmentalresearchweb.org/cws/article/news/70881
« Last Edit: March 20, 2018, 10:59:18 AM by gerontocrat »
"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)

sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #310 on: March 29, 2018, 08:08:36 PM »
Paper by Graeter et al on increasing melt in Greenland over the last twenty years. They looked at cores from the percolation zone, and it is clear from the ice left behind by melt evetns that melt frequency has been increasing over the last two decades. I attach fig 1.

doi:10.1002/2017GL076641

sidd

gerontocrat

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: What's new in Greenland?
« Reply #311 on: April 11, 2018, 02:21:03 PM »
GRACE FOLLOW-ON LAUNCH AT LAST -

https://www.prnewswire.com/news-releases/nasa-invites-media-to-launch-of-grace-follow-on-spacecraft-300627660.html

Quote
GRACE-FO will launch as part of a commercial rideshare mission with five Iridium Communications Inc. satellites aboard a SpaceX Falcon 9 rocket. The Iridium-6/GRACE-FO launch is scheduled for no earlier than 1:03 p.m. PDT (4:03 p.m. EDT) May 19 from Vandenberg Air Force Base in California.

Read all about it on https://gracefo.jpl.nasa.gov/ from the jet propulsion lab. Also about ICE-SAT-2
"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

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: What's new in Greenland?
« Reply #312 on: April 18, 2018, 11:43:14 AM »
A paper on Glacier Calving in Greenland from October 2017. Certainly improved my understanding of the subject.
https://link.springer.com/content/pdf/10.1007%2Fs40641-017-0070-1.pdf

And an older one from 2012 also giving me a bit more insight.
http://www.pnas.org/content/109/49/19934
Mapping Greenland’s mass loss in space and time

See map below - how to find an up-to-date equivalent?


"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)

Juan C. García

  • ASIF Middle Class
  • Posts: 884
    • View Profile
  • Liked: 152
  • Likes Given: 220
Re: What's new in Greenland?
« Reply #313 on: July 03, 2018, 02:43:03 PM »
OMG, the water's warm! NASA study solves glacier puzzle
By Carol Rasmussen,
NASA's Earth Science News Team

Quote
Tracy and Heilprin were first observed by explorers in 1892 and have been measured sporadically ever since. Even though the adjoining glaciers experience the same weather and ocean conditions, Heilprin has retreated upstream less than 2.5 miles (4 kilometers) in 125 years, while Tracy has retreated more than 9.5 miles (15 kilometers). That means Tracy is losing ice almost four times faster than its next-door neighbor.

Quote
Using ocean data from NASA's Oceans Melting Greenland (OMG) campaign, the study documents a plume of warm water flowing up Tracy's underwater face, and a much colder plume in front of Heilprin.

https://climate.nasa.gov/news/2754/omg-the-waters-warm-nasa-study-solves-glacier-puzzle/
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.

solartim27

  • ASIF Middle Class
  • Posts: 528
    • View Profile
  • Liked: 13
  • Likes Given: 15
Re: What's new in Greenland?
« Reply #314 on: July 03, 2018, 05:51:34 PM »
Nice overview of what you can find on Cryoportal from this thread.
Ruth Mottram (@ruth_mottram) Tweeted:
The final meeting for phase 2 of the @esaclimate #CCI #Greenland #icesheet project showing the evolution of the #icevelocity data with improvements to coverage and algorithms from #Sentinel1

Data: https://t.co/Tu4tdFe3kq https://t.co/iLrq1wUElg https://twitter.com/ruth_mottram/status/1014089754839744513?s=17

http://cryoportal.enveo.at
FNORD

gerontocrat

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: What's new in Greenland?
« Reply #315 on: July 14, 2018, 11:02:50 AM »
A nice reminder that when Greenland's glaciers calve, big stuff falls off.
"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)

Shared Humanity

  • ASIF Governor
  • Posts: 3138
    • View Profile
  • Liked: 93
  • Likes Given: 14
Re: What's new in Greenland?
« Reply #316 on: July 14, 2018, 05:06:04 PM »
Great photo.

gerontocrat

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: What's new in Greenland?
« Reply #317 on: July 14, 2018, 08:03:12 PM »
More about that iceberg

https://www.bbc.co.uk/news/world-europe-44831663

Huge iceberg threatens Greenland village
Quote
A huge iceberg has drifted close to a village in western Greenland, prompting a partial evacuation in case it splits and the resulting wave swamps homes. The iceberg is looming over houses on a promontory in the Innaarsuit village but is grounded and did not move overnight, local media say.

Local officials say they have never seen such a big iceberg before.

Last summer, four people died after waves swamped houses in northwestern Greenland after an earthquake. Those of Inaarsuit's 169 residents living nearest the iceberg have been moved, Danish news agency Ritzau said. "There are cracks and holes that make us fear it can calve anytime," village council member Susanne Eliassen told the local newspaper Sermitsiaq. The village's power station and fuel tanks are close to the shore, she said. Some experts have warned that extreme iceberg events risk becoming more frequent because of climate change. This in turn increases the risk from tsunamis.

"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)

litesong

  • ASIF Citizen
  • Posts: 374
    • View Profile
  • Liked: 20
  • Likes Given: 14
Re: What's new in Greenland?
« Reply #318 on: July 20, 2018, 03:07:32 AM »
A nice reminder that when Greenland's glaciers calve, big stuff falls off.
Here's how such "big stuff" falls off.

oren

  • ASIF Governor
  • Posts: 2971
    • View Profile
  • Liked: 319
  • Likes Given: 591
Re: What's new in Greenland?
« Reply #319 on: July 20, 2018, 08:37:18 AM »
Thanks litesong. When ASLR posts about ice-cliff failure in the Antractica threads, this is what it looks like in real life. When the leading ice is calved, the remaining ice cliff loses its support and is too tall to stand unsupported.

VeliAlbertKallio

  • ASIF Citizen
  • Posts: 144
    • View Profile
    • Sea Research Society (SRS)
  • Liked: 13
  • Likes Given: 34
Re: What's new in Greenland?
« Reply #320 on: July 31, 2018, 11:02:08 PM »
Our Changing Climate in Action: the Risk of Global Warming and the Environmental Damage from the Rising Ocean Water Table | Sustainable Seas Enquiry | Written evidence submitted by Veli Albert Kallio, FRGS (SSI0121) | Ordered to be published 23 May 2018 by the House of Commons.

Abstract:

Recently NATURE published a discussion on construction of sills in attempt to prevent or slow melting glaciers that are discharging ice into the ice fjords. Several further papers promptly followed publication of this essentially erroneous article in a respected NATURE magazine. Here it is pointed out that there is a discrepancy of several magnitudes thus excluding a long-term viability to manage the edges of ice fjords or continental ice shelves/sheets due to a phenomenon known as the mega-erratics. These are blocks of hard rocks that are several kilometres in size that have been dislocated by a warmed and wet edges of glacier/ice sheet/ice shelf. This Parliament evidence points out the error that was not apparent to the peer-reviewers at the time and in subsequent papers that followed. The Parliament was shown evidence that large enough obstacles cannot be possibly made to prevent ice discharges due to a progression of melting, that softens and lubricates glaciers, ice caps and ice sheets. The forces unleashed by the ice front exceeds several magnitudes from the conceived objects that sills were proposed. The only, and very only effect is temporary and limited to prevention of warm water incursion where these methods will work for a while in a cold, dry, and relatively stable ice formations.

Long-term projections suggested to prevent warmed and water-infested glaciers from discharging ice into the ocean cannot be made as the forces of ice exceed many magnitudes of the sills and levies that can be made of concrete blocks, aggregates or other materials. Thus the prevention of sea level rise by this method for centuries or millennia is not functional one and thus the mitigation and prevention of rubbish gyros in ocean, the supply of housing, nuclear and food production security must be looked at as solution by the ocean littoral states. Several examples of various types of risk to the sustainability of oceans have been presented in addition to the above exposed misconception. This comes with much regret as it appears that one 'hoped-for-solution' to manage the future climate change impacts has largely foundered on the issue that the sills cannot be made strong enough to contain most important, warmed glaciers or edges of unstable ice shelves. However, for a short-term this may offer small-scale solutions provided that costs remain sufficiently small. Aggressively melting ice formations with darkened surfaces, wide spread melt water ponds, or water filled crevasses it does not offer much, if any, prolonged ice stability. (The document is best viewed as a .pdf file due to the lay-out of graph and legends.)

https://www.academia.edu/37157851/Our_Changing_Climate_in_Action_the_Risk_of_Global_Warming_and_the_Environmental_Damage_from_the_Rising_Ocean_Water_Table_Sustainable_Seas_Enquiry_Written_evidence_submitted_by_Veli_Albert_Kallio_FRGS_SSI0121_Ordered_to_be_published_23_May_2018_by_the_House_of_Commons

Stopping the Flood: Could We Use Targeted Geoengineering to Mitigate Sea Level Rise?
Michael J. Wolovick1 and John C. Moore2,3
1Atmosphere and Ocean Sciences Program, Department of Geosciences, Princeton University, GFDL, 201 Forrestal Road,
Princeton, NJ 08540, USA
2College of Global Change and Earth System Science, Beijing Normal University, Beijing, China
3Arctic Centre, University of Lapland, Finland
Correspondence: M.J. Wolovick (wolovick@princeton.edu)

Abstract. The Marine Ice Sheet Instability (MISI) is a dynamic feedback that can cause an ice sheet to enter a runaway collapse. Thwaites Glacier, West Antarctica, is the largest individual source of future sea level rise and may have already entered the MISI. Here, we use a suite of coupled ice–ocean flowband simulations to explore whether targeted geoengineering using an artificial sill or artificial ice rises could counter a collapse. Successful interventions occur when the floating ice shelf regrounds 5 on the pinning points, increasing buttressing and reducing ice flux across the grounding line. Regrounding is more likely with a continuous sill that is able to block warm water transport to the grounding line. The smallest design we consider is comparable in scale to existing civil engineering projects but has only a 30% success rate, while larger designs are more effective. There are multiple possible routes forward to improve upon the designs that we considered, and with decades or more to research designs it is plausible that the scientific community could come up with a plan that was both effective and achievable. While 10 reducing emissions remains the short-term priority for minimizing the effects of climate change, in the long run humanity may need to develop contingency plans to deal with an ice sheet collapse.

--

http://data.parliament.uk/writtenevidence/committeeevidence.svc/evidencedocument/environmental-audit-committee/sustainable-seas/written/83150.pdf

AbruptSLR

  • ASIF Emperor
  • Posts: 16479
    • View Profile
  • Liked: 178
  • Likes Given: 12
Re: What's new in Greenland?
« Reply #321 on: August 01, 2018, 09:23:44 PM »
From about 50 to 80 million years ago Greenland passed over a hotspot in the Earth's mantle, and consequently it has a band of relatively high geothermal heat flux extending from its northwest corner to its southeast coast.  This unexpected high geothermal heat flux implies that existing ice mass loss projections for Greenland are likely too low:

Title: "How Greenland scorched its underside"

https://www.bbc.com/news/science-environment-45031592

Extract: "From its northwest corner to its southeast coast, the world's biggest island has a band of relatively warm bedrock.

Scientists say this confirms Greenland ran over a hotspot of upwelling molten rock tens of millions of years ago as it shifted towards the Arctic."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

RoxTheGeologist

  • ASIF Citizen
  • Posts: 313
    • View Profile
  • Liked: 39
  • Likes Given: 1
Re: What's new in Greenland?
« Reply #322 on: August 01, 2018, 10:37:04 PM »

Interesting!

It sounds like a stretch to imply heat-flux from magnetism, but sadly I didn't pay enough attention in the geo-magnetism course.  If anyone can slip me a copy I'd like to read it....


bluesky

  • ASIF Citizen
  • Posts: 106
    • View Profile
  • Liked: 8
  • Likes Given: 6
Re: What's new in Greenland?
« Reply #323 on: August 03, 2018, 10:48:53 PM »

"Large ice loss variability at Nioghalvfjerdsfjorden Glacier, Northeast-Greenland"
(Christoph Mayer et al.) July 2018

https://www.nature.com/articles/s41467-018-05180-x.pdf

Abstract:
"Nioghalvfjerdsfjorden is a major outlet glacier in Northeast-Greenland. Although earlier studies showed that the floating part near the grounding line thinned by 30% between 1999 and 2014, the temporal ice loss evolution, its relation to external forcing and the implications for the grounded ice sheet remain largely unclear. By combining observations of surface features, ice thickness and bedrock data, we find that the ice shelf mass balance has been out of equilibrium since 2001, with large variations of the thinning rates on annual/multiannual time scales. Changes in ice flux and surface ablation are too small to produce this variability. An increased ocean heat flux is the most plausible cause of the observed thinning. For sustained environmental conditions, the ice shelf will lose large parts of its area within a few decades and ice modeling shows a significant, but locally restricted thinning upstream of the grounding line in response."

extract from discussion:
" the reason for the large interannual fluctuations of the thinning rates revealed by this study still need to be found. AW anomalies in Fram Strait take about 1.5 years and longer to reach the 79 North Glacier21, while fjord temperatures may vary greatly on shorter time scales. Also the transient adjustment of the cavity circulation further modulates the response of the glacier to ocean forcing30. Following the method of31 and using the hydrographic profiles to constrain the water mass transformation inside the ice shelf cavity (Supplementary Fig. 2b), it can be shown that the observed 40% increase in basal melting is associated with a 30% stronger cavity overturning circulation. Herein, the temperature difference between ingoing and outgoing waters (using the same definitions as ref.29) changes little between the different years, but the increased meltwater input at the ice base drives a more vigorous sub-ice shelf circulation that accomplishes the additional heat flux of 0.7±1.8×1011 W into the cavity. This results in a reduction of the cavity exchange time scale from about 120±26 days to about 90±35 days, which further increases the sensitivity of the ice shelf to ocean changes30. Thus, while our analysis suggests that the ocean is likely the main driver of the observed changes at 79 North Glacier, the regional dynamics that control the heat transport into the ice shelf cavity and other contributors, such as subglacial discharge induced by surface melt or geothermal heat flux will need further attention to fully understand the observed thickness evolution. Potential consequences for the future ice shelf stability: Despite the fact that 79 North Glacier has a more stable grounding line situation than Zachariæ Isstrøm (rising bedrock inland), the loss of the ice shelf might contribute to destabilize the entire, marinebased ice sheet sector. At the moment the ice shelf is well buttressed in the fjord and even the loss of the outer part would probably not change this. Without the buttressing effect of the floating ice tongue in the fjord, our simplified model approach demonstrates that the ice thickness strongly decreases and the grounding line retreats by about 10km. This is comparable to the results of a recent study32 and poses the question if the disintegration of the ice shelf and its related consequences on the grounded ice are likely to happen in the near future. The ice thickness reduced by about 30% during the period 1998 until 2014. Compared with balanced conditions, implying a mass balance of −12myear−1 in the region of Midgardsormen, the mean ice loss during the observation period results in an almost 1.5 times higher mass balance magnitude. The numerical simulations demonstrate that the thinning will lead to large areas of very thin ice, which are most likely unstable and large parts of the ice shelf will disappear during coming decades. Given that the environmental conditions already enabled ice thickness reductions up to 13m within one year that process could be considerably faster for enhanced oceanic energy fluxes into the ice shelf cavity. Even though the consequences are serious for the neighboring part of the ice sheet, where the ice thins by about 200m after the loss of the ice shelf, it seems that the increased fluxes will not reach far into the ice sheet during the next century, resulting in thickness losses in the order of 30m about 20km upstream. It needs to be considered, however, that our simple model setup is not appropriate to simulate the long-term feedback mechanisms. Therefore a more detailed investigation is required for investigating the long-term stability of the ice sheet in this sector of Greenland."



sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #324 on: August 04, 2018, 01:51:37 AM »
Thanx for the Mayer reference, very pretty paper. They used the migration of an ice ridge to deduce historical grounding lines, lateral stress and ice thickness. I can see i shall have to spend some hours on it.

sidd

johnm33

  • ASIF Upper Class
  • Posts: 1031
    • View Profile
  • Liked: 40
  • Likes Given: 8
Re: What's new in Greenland?
« Reply #325 on: August 04, 2018, 01:05:28 PM »
Very timely too the fast ice has just about cleared [29th] from the front of the ice shelf, and it's now more exposed to tides and Atl. waters. The shelf may only have to retreat a little to have dramatic effects on the overturning circulation.

oren

  • ASIF Governor
  • Posts: 2971
    • View Profile
  • Liked: 319
  • Likes Given: 591
Re: What's new in Greenland?
« Reply #326 on: August 04, 2018, 01:13:51 PM »
It would be best to cross-post these interesting posts to the Zachariae/Nioghalvfjerdsfjorden thread.
https://forum.arctic-sea-ice.net/index.php/topic,400.0.html

litesong

  • ASIF Citizen
  • Posts: 374
    • View Profile
  • Liked: 20
  • Likes Given: 14
Re: What's new in Greenland?
« Reply #327 on: August 09, 2018, 02:25:25 AM »

sidd

  • ASIF Governor
  • Posts: 3861
    • View Profile
  • Liked: 70
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #328 on: August 11, 2018, 11:09:53 PM »
Hard rain falling:

"The extended period of above-normal frequency and intensity of AR events affecting Greenland during 2000–2012 coincided with a well-documented uptick in GrIS mass loss, culminating with the extreme melt season of 2012 which also featured highly anomalous moisture transport by ARs to western and northern Greenland. Subsequent years have seen less extreme GrIS mass loss and a shift of the greatest melt anomalies to northern areas of the GrIS ..."

"Strong AR impacts cause increased melt in all areas of the GrIS and decreased SMB in the ablation zone during summer, and warm seasons with above-average GrIS melt extent are characterized by anomalously strong moisture transport by ARs over Greenland. ARs typically result in SMB gains in the GrIS ablation zone during non-summer seasons and in the accumulation zone during all seasons. However, the intense summer SMB losses in the ablation zone during years of enhanced moisture transport outweigh the positive AR contributions to SMB in other regions and seasons."

AR is Atmospheric river. SMB is surface mass balance.

I notice Fettweis is an author.

DOI: 10.1029/2018JD028714

sidd

litesong

  • ASIF Citizen
  • Posts: 374
    • View Profile
  • Liked: 20
  • Likes Given: 14
Re: What's new in Greenland?
« Reply #329 on: August 16, 2018, 01:33:31 AM »

Tor Bejnar

  • ASIF Upper Class
  • Posts: 2157
    • View Profile
  • Liked: 83
  • Likes Given: 24
Re: What's new in Greenland?
« Reply #330 on: August 31, 2018, 07:09:02 PM »
GeoTalk: To understand how ice sheets flow, look at the bedrock below

  An interview with Mathieu Morlighem, associate professor of Earth System Science at the University of California, Irvine who uses models to better understand ongoing changes in the Cryosphere.  GeoLog  ·  August 17, 2018
Quote
...
Subglacial bed topography is probably the most important input parameter in an ice sheet model and remains challenging to measure. The bed controls the flow of ice and its discharge into the ocean through a set of narrow valleys occupied by outlet glaciers. I am hoping that the new product that I developed, called BedMachine, will help reduce the uncertainty in numerical models, and help explain current trends.
...

[Edit: this is my post #1997 = the year I married my wife, the artist who created the avatar I use here.]
Arctic ice is healthy for children and other living things.

Mr.Far

  • ASIF Lurker
  • Posts: 19
    • View Profile
  • Liked: 0
  • Likes Given: 1
Re: What's new in Greenland?
« Reply #331 on: October 11, 2018, 09:01:06 AM »
The Arctic has slowly but surely gained visibility as an increasingly important part of the Danish/Greenlandic narrative (in which Greenland’s, in fact, Danish ‘colony’, role has miraculously evolved over time to that of an ‘equal partner’ in the Danish Realm). Denmark submitted the last (fifth) claim in 2014 (it lays claim to the North Pole). But, wait a minute! Its bid for 895,000 sq km of the Arctic Ocean sounds particularly audacious given that this is 20 times the size of Denmark!

They say that the obtaining rights to the North Pole has a symbolic meaning. But… isn’t it too much for the country, which lies on the same latitude as (for example) Britain – more than 2,000 miles from the North Pole?

Espen

  • ASIF Governor
  • Posts: 3116
    • View Profile
  • Liked: 24
  • Likes Given: 0
Re: What's new in Greenland?
« Reply #332 on: October 11, 2018, 09:58:33 PM »
Greenland is very important to Denmark and the danish political sense of self, without Greenland Denmark would have very little Geo political negotiating power with the US in particular and to some degree other major powers like Russia and China.
The problem now is, Denmark never invested in Greenland in real good faith, and the people of Greenland realized that, but it is an interesting development. The elephant in the room is China. 
Have a ice day!

bluesky

  • ASIF Citizen
  • Posts: 106
    • View Profile
  • Liked: 8
  • Likes Given: 6
Re: What's new in Greenland?
« Reply #333 on: October 21, 2018, 12:25:22 AM »

https://www.eurekalert.org/pub_releases/2018-10/uol-cmf101518.php

Atmospheric pressure above Greenland together with rapid warming are badly modelled, with consequences on forecasting regional impact of climate change in Europe, particularly the UK:

"Climatologists may be unable to accurately predict regional climate change over the North Atlantic because computer model simulations have failed to accurately include air pressure changes that have taken place in the Greenland region over the last three decades.
This deficiency may mean regional climate predictions for the UK and parts of Europe could be inaccurate, according to new research published today.
Researchers compared real data with simulation data over a 30 year period and found that the simulations on average showed slightly decreasing air pressure in the Greenland region, when in fact, the real data showed a significant increase in high air pressure - or so-called 'Greenland blocking' - during the summer months. These simulations are widely used by climate scientists worldwide as a basis for predicting future climate change.
The findings raise serious questions about the accuracy of regional climate projections in the UK and neighbouring parts of Europe because meteorological conditions in those regions are closely linked to air-pressure changes over Greenland…."

Tor Bejnar

  • ASIF Upper Class
  • Posts: 2157
    • View Profile
  • Liked: 83
  • Likes Given: 24
Re: What's new in Greenland?
« Reply #334 on: October 26, 2018, 08:32:46 PM »
Sermip Nunataa, Greenland No Longer a Nunatak
From a Glacier’s Perspective - October 23, 2018
Quote
Sermip Nunataa (Nunatak-Island within ice sheet glacier) was a nunatak of the southern Greenland Ice Sheet between Sermilik Brae and Sondre Qipisaqqu Brae.  Here we examine changes from 1993-2018 of the margin of the ice sheet in the area and the impact on this and neighboring nunataks.

In 1993 the Sermip Nunatak was 2.5 km inland from the ice sheet margin.  ...

A video of the area may show Sermip Nunataa at 19:28 (min:sec) as it was in 2007.

Quote
Published on Jul 16, 2012
7 juillet 2007
Rushes du film « Home » :Survol du glacier de Sermilik Brae au Groënlandcertains icebergs retournés de couleur bleutée. Images d'archive INA
Institut National de l'Audiovisuel
or, per Google Translate
Quote
Published on Jul 16, 2012
July 7, 2007
Rushes from the film "Home": a flyby of the Sermilik Brae Glacier at Greenland some icebergs returned in bluish colour. INA Archive Images
National Institute of Audiovisual
[map from the 'From a Glacier's Perspective' article]

Arctic ice is healthy for children and other living things.

Red

  • ASIF Citizen
  • Posts: 181
    • View Profile
  • Liked: 4
  • Likes Given: 4
Re: What's new in Greenland?
« Reply #335 on: November 04, 2018, 12:01:34 PM »
This I'm sure isn't new per say but some good satellite shots here. I wonder if it will become more common as glaciers retreat further exposing more dry valley bottoms.

https://www.syfy.com/syfywire/a-dust-storm-over-greenland?utm_source=samizdat&utm_medium=partner&utm_campaign=free

OK, so this I was not expecting: ESA’s Earth-observing Sentinel-2 satellite took an amazing image showing a dust storm blowing over a fairly unusual location on the planet… and by unusual, I mean Greenland. Yes, Greenland.

And by “dust”, I mean flour. Glacial flour.

Yeah. This whole thing is weird. But it makes sense, and bonus: The image of the storm is gasp-worthingly lovely.

gerontocrat

  • ASIF Governor
  • Posts: 3620
    • View Profile
  • Liked: 359
  • Likes Given: 7
Re: What's new in Greenland?
« Reply #336 on: November 04, 2018, 12:39:57 PM »
I first read about Greenland's dry valleys in "Miss Smilla's Feeling for Snow" by Peter Hoeg (1992).
It seems that due to the bare rock and surrounding hills temperatures can easily rise in to the 30's centigrade in dry spells in summer.
"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)

Thomas Barlow

  • ASIF Lurker
  • Posts: 8
    • View Profile
  • Liked: 1
  • Likes Given: 1
Re: What's new in Greenland?
« Reply #337 on: November 06, 2018, 03:51:11 AM »

Stephan

  • ASIF Citizen
  • Posts: 195
    • View Profile
  • Liked: 29
  • Likes Given: 24
Re: What's new in Greenland?
« Reply #338 on: November 06, 2018, 09:22:11 PM »
Thanks for the interesting video. :)

magnamentis

  • ASIF Upper Class
  • Posts: 1806
    • View Profile
    • Philosophy Ethics Numerology Mikrocirkulation Vaskular Therapie Gesundheit Blut Gesundheit Schmerzen Multiple Sklerose Diabetes Immunsystem Fibromyalgia Modular Mobile Computing iOS Software OSX Android Custom Rom Rooted
  • Liked: 66
  • Likes Given: 104
Re: What's new in Greenland?
« Reply #339 on: November 06, 2018, 10:06:08 PM »

thanks for this one, this is the kind of info that helps increase understanding and complexity.
http://magnamentis.com
Knowledge, Understanding & Insight Are Among The Best Sources For Personal Freedom & Vitality !

vox_mundi

  • ASIF Citizen
  • Posts: 171
    • View Profile
  • Liked: 23
  • Likes Given: 15
Re: What's new in Greenland?
« Reply #340 on: November 14, 2018, 09:28:53 PM »
May explain the disappearance of the Clovis people and North American megafauna ...

Massive Crater Under Greenland’s Ice Points to Climate-Altering Impact In the Time of Humans
https://www.sciencemag.org/news/2018/11/massive-crater-under-greenland-s-ice-points-climate-altering-impact-time-humans

Quote

https://gizmodo.com/a-massive-impact-crater-has-been-detected-beneath-green-1830437095/amp

Hidden beneath Hiawatha Glacier is a 31-kilometer-wide impact crater, big enough to swallow Washington, D.C., Kjær and 21 co-authors report today in a paper in Science Advances. The crater was left when an iron asteroid 1.5 kilometers across slammed into Earth, possibly within the past 100,000 years

The timing is still up for debate, but some researchers on the discovery team believe the asteroid struck at a crucial moment: roughly 13,000 years ago, just as the world was thawing from the last ice age. That would mean it crashed into Earth when mammoths and other megafauna were in decline and people were spreading across North America.

 The impact would have been a spectacle for anyone within 500 kilometers. A white fireball four times larger and three times brighter than the sun would have streaked across the sky. If the object struck an ice sheet, it would have tunneled through to the bedrock, vaporizing water and stone alike in a flash. The resulting explosion packed the energy of 700 1-megaton nuclear bombs, and even an observer hundreds of kilometers away would have experienced a buffeting shock wave, a monstrous thunder-clap, and hurricane-force winds. Later, rock debris might have rained down on North America and Europe, and the released steam, a greenhouse gas, could have locally warmed Greenland, melting even more ice.



Preliminary evidence suggests it happened relatively recently. The crater appears to be well-preserved—a surprising observation given that ice is a powerful erosive force. The crater is likely fairly young from a geological perspective.

Open Access: Kurt H. Kjær et.al., A large impact crater beneath Hiawatha Glacier in northwest Greenland, Science Advances  14 Nov 2018
« Last Edit: November 14, 2018, 09:40:26 PM by vox_mundi »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

vox_mundi

  • ASIF Citizen
  • Posts: 171
    • View Profile
  • Liked: 23
  • Likes Given: 15
Re: What's new in Greenland?
« Reply #341 on: November 14, 2018, 10:03:06 PM »
Earlier evidence that points to this impact.

Wendy S. Wolbach et al, Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago. 1. Ice Cores and Glaciers, The Journal of Geology (2018). DOI: 10.1086/695703

Wendy S. Wolbach et al. Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago. 2. Lake, Marine, and Terrestrial Sediments, The Journal of Geology (2018). DOI: 10.1086/695704 , www.journals.uchicago.edu/doi/full/10.1086/695704



Topper site in middle of comet controversy
https://m.phys.org/news/2012-09-topper-site-middle-comet-controversy.html

Exploding asteroid theory strengthened by new evidence located in Ohio, Indiana
https://m.phys.org/news/2008-07-asteroid-theory-evidence-ohio-indiana.html

Did a comet hit the Great Lakes region and fragment human populations 12,900 years ago?
https://m.phys.org/news/2007-05-comet-great-lakes-region-fragment.html

Discovery of widespread platinum may help solve Clovis people mystery.
https://m.phys.org/news/2017-03-discovery-widespread-platinum-clovis-people.html

The mammoth's lament: Study shows how cosmic impact sparked devastating climate change
https://m.phys.org/news/2013-05-mammoth-lament-cosmic-impact-devastating.html

Research suggests toward end of Ice Age, humans witnessed fires larger than dinosaur killer, thanks to a cosmic impact
https://m.phys.org/news/2018-02-ice-age-human-witnessed-larger.html
« Last Edit: November 14, 2018, 10:10:16 PM by vox_mundi »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

bligh8

  • ASIF Citizen
  • Posts: 191
    • View Profile
  • Liked: 2
  • Likes Given: 1
Re: What's new in Greenland?
« Reply #342 on: November 15, 2018, 05:48:56 PM »
Thanks Vox....Fascinating stuff

johnm33

  • ASIF Upper Class
  • Posts: 1031
    • View Profile
  • Liked: 40
  • Likes Given: 8
Re: What's new in Greenland?
« Reply #343 on: November 15, 2018, 08:24:07 PM »
Some details about local [to this] finds at link http://evols.library.manoa.hawaii.edu/handle/10524/35885

« Last Edit: November 15, 2018, 08:45:59 PM by johnm33 »

vox_mundi

  • ASIF Citizen
  • Posts: 171
    • View Profile
  • Liked: 23
  • Likes Given: 15
Re: What's new in Greenland?
« Reply #344 on: November 15, 2018, 09:49:16 PM »
thanks johnm33 and bligh8 (wave back)
https://media1.tenor.com/images/16fe97b70683870d3d4357a31c5a95a8/tenor.gif

Multiple lines of evidence for possible Human population decline/settlement reorganization during the early Younger Dryas
https://www.researchgate.net/figure/Clovis-and-immediate-post-Clovis-assemblages-at-eleven-quarry-locations-in-the_tbl1_229344558
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

bligh8

  • ASIF Citizen
  • Posts: 191
    • View Profile
  • Liked: 2
  • Likes Given: 1
Re: What's new in Greenland?
« Reply #345 on: November 16, 2018, 01:12:05 AM »
We've drifted off topic here abit so I'll just quote this

Citations
• ... The nature of the relationship between humans and climate is a core issue in geographical research and the increased availability of paleoclimatic, paleoecological, and archae- ological data have resulted in the proliferation of studies on this complex relationship (deMenocal, 2001;Wu and Liu, 2004;An et al., 2005;Kuper and Kröpelin, 2006;Barton et al., 2007;Munoz et al., 2010;Maher et al., 2011;McMichael, 2012;Rosen and Rivera-Collazo, 2012;Dong et al., 2013;Xie et al., 2013;Foerster et al., 2015;Büntgen et al., 2016;Hughes et al., 2017). Climate change is often argued to be a primary force influencing human activities ( Jin and Liu, 2002;Zhang et al., 2008;Hill et al. 2009;Anderson et al., 2011;Ziegler et al., 2013). The Western Loess Plateau (WLP) lies to the west of the Liupan Mountains in North China (Fig. 1B). ...

From <https://www.researchgate.net/figure/Clovis-and-immediate-post-Clovis-assemblages-at-eleven-quarry-locations-in-the_tbl1_229344558>

And move along…..Thanks

Martin Gisser

  • ASIF Middle Class
  • Posts: 954
  • alias Mars Joh. P. Florifulgurator
    • View Profile
  • Liked: 50
  • Likes Given: 92
Re: What's new in Greenland?
« Reply #346 on: November 16, 2018, 04:01:01 AM »
Armchair science question: So, when the crater is dated, then the Younger Dryas conundrum might finally be resolved?
"The universe is irrelevant for all practical purposes, so better forget about being thrown into it." --Florifulgurator

oren

  • ASIF Governor
  • Posts: 2971
    • View Profile
  • Liked: 319
  • Likes Given: 591
Re: What's new in Greenland?
« Reply #347 on: November 16, 2018, 12:14:14 PM »
I guess that depends on the dating. If it's dated to ~12,800 years BP,  it will be too much of a coincidence to assume no link with YD exists, although there will still be some science in explaining the actual mechanism. If it's dated otherwise, well then.
My bet is on the older dating/no linkage option.

Tor Bejnar

  • ASIF Upper Class
  • Posts: 2157
    • View Profile
  • Liked: 83
  • Likes Given: 24
Re: What's new in Greenland?
« Reply #348 on: November 16, 2018, 04:48:05 PM »
I've read only a little about the Younger Dryas (and not much recently), but I recall reports of iridium or other meteorite-associated detritus with soot across North America matching its start (ah, see here).  If this hypothesis is accurate, a meteorite somewhere would be the cause.  This one is 'good enough for me' for the time being.  I look forward to the timing of this event getting narrowed (from the current 10-100 ka).  ["ka" = "thousand years before present"; similarly "ma" million years … and "ga" billion (109) years ...]
Arctic ice is healthy for children and other living things.

vox_mundi

  • ASIF Citizen
  • Posts: 171
    • View Profile
  • Liked: 23
  • Likes Given: 15
Re: What's new in Greenland?
« Reply #349 on: November 16, 2018, 05:38:23 PM »
I wonder if an iron-rich impactor would show up as a magnetic anomaly beneath the crater.
http://www.impact-structures.com/geophysics-of-impact-structures-2/geomagnetic-surveys/



Large Platinum anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3740870/



... The Platinum (Pt) concentrations gradually rise by at least 100-fold over ∼14 y and drop back during the subsequent ∼7 y. The decay of the Pt signal is consistent with the ∼5-y lifetime of dust in the stratosphere. The observed gradual ingrowth of the Pt concentration in ice over ∼14 y may suggest multiple injections of Pt-rich dust into the stratosphere that are expected to result in a global Pt anomaly.

The Pt anomaly is accompanied by extremely high Pt/Ir (Iridium) and Pt/Al (Aluminum) ratios (Fig. 2), indicative of a highly unusual source of Pt in the ice.


(Note: semi-log y scale)

.. Circumstantial evidence such as very high, superchondritic Pt/Al ratios associated with the Pt anomaly and its timing, different from other major events recorded on the GISP2 ice core such as well-understood sulfate spikes caused by volcanic activity and the ammonium and nitrate spike due to the biomass destruction, hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis.

--------------------------------------

Very high-temperature impact melt products as evidence for cosmic airbursts and impacts 12,900 years ago
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3396500/

We examined sediment sequences from 18 dated Younger Dryas boundary (YDB) sites across three continents (North America, Europe, and Asia), spanning 12,000 km around nearly one-third of the planet. All sites display abundant microspherules in the YDB with none or few above and below. In addition, three sites (Abu Hureyra, Syria; Melrose, Pennsylvania; and Blackville, South Carolina) display vesicular, high-temperature, siliceous scoria-like objects, or SLOs, that match the spherules geochemically.

... Abundance peaks in SLOs were observed in the YDB layer at three dated sites at the onset of the YD cooling episode (12.9 ka). Two are in North America and one is in the Middle East, extending the existence of YDB proxies into Asia. SLO peaks are coincident with peaks in glassy and Fe-rich spherules and are coeval with YDB spherule peaks at 15 other sites across three continents. In addition, independent researchers working at one well-dated site in North America  and one in South America (10–12) have reported YDB melt glass that is similar to these SLOs. YDB objects have now been observed in a total of eight countries on four continents separated by up to 12,000 km with no known limit in extent. The following lines of evidence support a cosmic impact origin for these materials.
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late