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Stephan

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Re: What's new in Greenland?
« Reply #500 on: February 29, 2020, 11:10:47 AM »
Just at the moment on the radio:
"Greenland in the focus of the super powers"
https://www.deutschlandfunk.de/begehrte-insel-groenland-im-fokus-der-grossmaechte.922.de.html?dram:article_id=466426
(in German)
It is too late just to be concerned about Climate Change

Juan C. García

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Re: What's new in Greenland?
« Reply #501 on: March 18, 2020, 06:43:01 PM »
Quote
Greenland lost a near-record 600 billion tons of ice last summer, raising sea levels

Greenland’s unusually mild summer in 2019 caused the world’s largest island to lose 600 billion tons of ice in just two months, rivaling the summer of 2012 for the most ice mass lost in a single melt season, according to NASA data released Wednesday.

The mass loss from Greenland alone was enough to raise global sea levels by 2.2 millimeters, the study found.
https://www.washingtonpost.com/weather/2020/03/18/greenland-lost-near-record-600-billion-tons-ice-last-summer-raising-sea-levels/?itid=hp_hp-more-top-stories_greenland-115pm%3Ahomepage%2Fstory-ans

Quote
Continuity of ice sheet mass loss in Greenland and Antarctica from the GRACE and GRACE Follow‐On missions

Abstract

We examine data continuity between the GRACE and GRACE‐FO missions over Greenland and Antarctica using independent data from the mass budget method (MBM) which calculates the difference between ice sheet surface mass balance and ice discharge at the periphery. For both ice sheets, we find consistent GRACE/GRACE‐FO time series across the data gap, at the continental and regional scales, and the data gap is confidently filled with MBM data. In Greenland, the GRACE‐FO data reveal an exceptional summer loss of 600 Gigatonnes in 2019 following two cold summers. In Antarctica, ongoing high mass losses in the Amundsen Sea Embayment of West Antarctica, the Antarctic Peninsula, and Wilkes Land in East Antarctica cumulate to 2130, 560, and 370 Gigatonnes, respectively, since 2002. A cumulative mass gain of 980 Gigatonnes in Queen Maud Land since 2009, however, led to a pause in the acceleration in mass loss from Antarctica after 2016.
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL087291
« Last Edit: March 18, 2020, 09:17:35 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

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

blumenkraft

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Re: What's new in Greenland?
« Reply #502 on: April 10, 2020, 11:12:40 AM »

Phoenix

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Re: What's new in Greenland?
« Reply #503 on: April 23, 2020, 01:31:26 AM »
Video of a small expedition to Humboldt Glacier last summer headed by cryo-scientist Eric Rignot.


Tor Bejnar

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Re: What's new in Greenland?
« Reply #504 on: April 24, 2020, 07:40:41 PM »
Wonderful video, Phoenix.  Yea, Humboldt!  I'll reiterate that the expedition was in 2019, just last year.
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vox_mundi

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Re: What's new in Greenland?
« Reply #505 on: April 30, 2020, 08:57:15 PM »
Catastrophic Outburst Floods Carved Greenland's 'Grand Canyon'
https://phys.org/news/2020-04-catastrophic-outburst-greenland-grand-canyon.html

Buried a mile beneath Greenland's thick ice sheet is a network of canyons so deep and long that the largest of these has been called Greenland's "Grand Canyon." This megacanyon's shape suggests it was carved by running water prior to widespread glaciation, but exactly when and how the island's grandest canyon formed are topics of intense debate.

Now scientists from the U.S. and Denmark are proposing a surprising new hypothesis for the megacanyon's formation: catastrophic "outburst" floods that suddenly and repeatedly drained large meltwater-filled lakes. The findings, published this week in the journal Geology, also suggest that Greenland's subglacial canyon network has influenced the island's ice sheet since its inception.

Although repeated outburst floods have been suggested as the mechanism by which the Columbia River and other North America canyon networks formed, they had not previously been considered as the source of the remarkable landscape hidden beneath the Greenland Ice Sheet

"If the floods we propose occurred, they could have influenced ocean circulation, causing abrupt climate changes with regional and perhaps global significance," says Keisling, now a postdoctoral fellow at Lamont-Doherty Earth Observatory. "The megacanyon beneath northern Greenland also influences how ice and water flow in the subglacial environment today, which affects present-day ice-sheet stability," he says.


Modeled outburst flood during ice-sheet retreat, routed to the outlet of Petermann Glacier. The animation covers 22,000 simulated years, and pauses to highlight a large ice-dammed proglacial lake during the deglaciation.

The researchers used coupled ice-sheet and climate models to simulate the Greenland Ice Sheet's evolution over multiple glacial-interglacial cycles during the global cooling from the Pliocene into the Pleistocene, 2.58 million years ago. They found that following long periods with stable temperatures, an exceptionally warm period could cause the ice sheet to retreat rapidly. This melting led to the development of large, ice-dammed lakes in areas where the bedrock was still depressed due to the former ice sheet's weight.

The simulations eventually show the ice dams give way, leading to large outburst floods. "Over time," says Keisling, "it appears that the filling and draining of these lakes as the ice repeatedly retreated and advanced carved Greenland's megacanyons." Similar floods have been documented at the edge of other retreating ice sheets, he says

https://scx2.b-cdn.net/gfx/news/2020/1-catastrophic.gif
Modelled outburst flood during a deglaciation scenario routed to the outlets of the northeast Greenland ice stream (NEGIS). The animation covers 25,000 simulated years, and pauses to highlight a large ice-dammed proglacial lake during the deglaciation

Based on comparisons with modern outburst floods, the researchers estimate that it took tens to hundreds of these events to carve Greenland's largest canyon. According to Keisling, widespread sediment deposition in the water-filled basins may have also impacted the ice sheet's behavior each time it grew back.

Benjamin A. Keisling et al, Pliocene–Pleistocene megafloods as a mechanism for Greenlandic megacanyon formation, Geology (2020).
https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G47253.1/584570/Pliocene-Pleistocene-megafloods-as-a-mechanism-for
« Last Edit: April 30, 2020, 10:10:20 PM by vox_mundi »
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Stumbi

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Re: What's new in Greenland?
« Reply #506 on: May 07, 2020, 12:10:02 AM »
I was just looking how far north there is already open water in the greenland fjords. Then i found this interesting spot with even open water in february. Rhoss fjord 72,50N27W east coast greenland west of traill island
Anybody know the background?
....somehow not able to attach a jpg or gif....work in progress.....
« Last Edit: May 07, 2020, 12:27:02 AM by Stumbi »
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gerontocrat

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Re: What's new in Greenland?
« Reply #507 on: May 25, 2020, 01:03:53 PM »
There isn't a thread for Greenland's "79 North Glacier", so I'm posting here. I expect AbruptSLR picked it up and posted it on the SL thread as the process described here is replicated in Antarctica?

https://www.awi.de/en/about-us/service/press/press-release/how-the-ocean-is-gnawing-away-at-glaciers.html
How the ocean is gnawing away at glaciers
[03. February 2020]
The Greenland Ice Sheet is melting faster today than it did only a few years ago. The reason: it’s not just melting on the surface – but underwater, too. AWI researchers have now found an explanation for the intensive melting on the glacier’s underside, and published their findings in the journal Nature Geoscience.


The glaciers are melting rapidly: Greenland’s ice is now melting seven times faster than in the 1990s – an alarming discovery, since climate change will likely intensify this melting in the future, causing the sea level to rise more rapidly. Accordingly, researchers are now working to better understand the underlying mechanisms of this melting. Ice melts on the surface because it is exposed to the sun and rising temperatures. But it has now also begun melting from below – including in northeast Greenland, which is home to several ‘glacier tongues’. Each tongue is a strip of ice that has slid down into the ocean and floats on the water – without breaking off from the land ice. The longest ice tongue, part of the ‘79° North Glacier’, is an enormous 80 km long. Over the past 20 years, it has experienced a dramatic loss of mass and thickness, because it’s been melting not just on the surface, but also and especially from below.

Too much heat from the ocean
A team led by oceanographer Janin Schaffer from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) in Bremerhaven has now identified the source of this intense underwater melting. The conclusions of their study, which the experts have just released in the journal Nature Geoscience, are particularly unsettling because the melting phenomenon they discovered isn’t unique to the 79° North Glacier, which means it could produce similar effects elsewhere.

For the purposes of the study, the researchers conducted the first extensive ship-based survey of the ocean floor near the glacier, which revealed the presence of a two-kilometre-wide trough, from the bottom of which comparatively warm water from the Atlantic is channelled directly toward the glacier. But that’s not all: in the course of a detailed analysis of the trough, Janin Schaffer spotted a bathymetric sill, a barrier that the water flowing over the seafloor has to overcome. Once over the hump, the water rushes down the back of the sill – and under the ice tongue. Thanks to this acceleration of the warm water mass, large amounts of heat from the ocean flow past the tongue every second, melting it from beneath. To make matters worse, the layer of warm water that flows toward the glacier has grown larger: measured from the seafloor, it now extends 15 metres higher than it did just a few years ago. “The reason for the intensified melting is now clear,” Schaffer says. “Because the warm water current is larger, substantially more warmth now makes its way under the ice tongue, second for second.”

To make matters worse, the layer of warm water that flows toward the glacier has grown larger: measured from the seafloor, it now extends 15 metres higher than it did just a few years ago. “The reason for the intensified melting is now clear,” Schaffer says. “Because the warm water current is larger, substantially more warmth now makes its way under the ice tongue, second for second.”

Other regions are also affected
In order to determine whether the phenomenon only manifests at the 79° North Glacier or also at other sites, the team investigated a neighbouring region on Greenland’s eastern coast, where another glacier, the Zachariæ Isstrøm, juts out into the sea, and where a large ice tongue had recently broken off from the mainland. Working from the surface of an ice floe, the experts measured water temperatures near the ocean floor. According to Schaffer: “The readings indicate that here, too, a bathymetric sill near the seafloor accelerates warm water toward the glacier. Apparently, the intensive melting on the underside of the ice at several sites throughout Greenland is largely produced by the form of the seafloor.” These findings will ultimately help her more accurately gauge the total amount of meltwater that the Greenland Ice Sheet loses every year.

Original publication
Janin Schaffer, Torsten Kanzow, Wilken-Jon von Appen, Luisa von Albedyll, Jan Erik Arndt and David H. Roberts: "Bathymetry constrains ocean heat supply to Greenland’s largest glacier tongue", Nature Geoscience, 3 February 2020,
DOI: 10.1038/s41561-019-0529-x - paywalled.
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sidd

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Re: What's new in Greenland?
« Reply #508 on: May 26, 2020, 01:13:03 AM »
Re: isn't a thread for Greenland's "79 North Glacier"

https://forum.arctic-sea-ice.net/index.php/topic,400.0.html

79N is also called Nioghalvfjerdsfjorden

sidd

Tealight

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Re: What's new in Greenland?
« Reply #509 on: June 02, 2020, 09:11:54 PM »
After being empty for over a year I finally had an idea what to put on my IceSheet main page.

Maps of the bedrock or surface elevation show exactly where it is high/low, but it's still hard to estimate how much area overall is at a particular elevation level. So I created a Histogram for Greenland Ice thickness, surface elevation and bedrock elevation.

https://cryospherecomputing.tk/IceSheets

Data abstraced from:
NSIDC BedMachine v3 Greenland


 


Tor Bejnar

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Re: What's new in Greenland?
« Reply #510 on: June 03, 2020, 06:48:18 AM »
That's great, Tealight!
The bedrock elevation histogram reminds me of the actual (human) birth date - due date histogram which shows a normal distribution around the due date except that there is a one-day dip right at birth date = due date.  In Greenland's case, it's where bedrock elevation = sea level.  I don't think the cause is the same.  :o
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VeliAlbertKallio

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Re: What's new in Greenland?
« Reply #511 on: July 08, 2020, 07:14:19 AM »
Colourful speck appeared 7.7. on Greenland Ice Sheet, does anyone has larger image of the area? Fournier triangulation has contorted its colours. (I hope this is not volcanic eruption in the making, shouldn't be as Greenland is supposedly volcanically extinct, if it were would be bad omen for its ice).
https://worldview.earthdata.nasa.gov/?v=71669.71520490224,-2646993.662074549,250535.7290737917,-2543027.7915132567&p=arctic&t=2020-07-07-T04%3A37%3A12Z&e=true
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blumenkraft

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Re: What's new in Greenland?
« Reply #512 on: July 08, 2020, 09:35:18 AM »
I don't see that via Sentinel 2. This might just be a wrong pixel rendering.

VeliAlbertKallio

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Re: What's new in Greenland?
« Reply #513 on: July 09, 2020, 02:57:56 AM »
Looks like a technical artefact as it has disappeared from today's image in South East Greenland, but re-appeared in Melville Bay. It seems ice sheet is in normal order barring the major melting underway.

The latest eruption near Melville Bay section of GIS is here: https://worldview.earthdata.nasa.gov/?v=-478804.7144347975,-1432374.8578587899,-389371.7075003524,-1380391.9225781437&p=arctic&t=2020-07-08-T04%3A37%3A12Z&e=true  So, bye bye to hot springs, geysers or GIS subglacial volcano.  ???

I don't see that via Sentinel 2. This might just be a wrong pixel rendering.
"Setting off atomic bombs is considered socially pungent as the years are made of fleeting ice that are painted by the piling up of the rays of the sun."

Reginald

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Re: What's new in Greenland?
« Reply #514 on: August 01, 2020, 03:37:25 AM »
There's a (paywalled) July 29 paper in Nature Climate Change: https://www.nature.com/articles/s41558-020-0860-7 that might be of interest:

Past perspectives on the present era of abrupt Arctic climate change

Abstract

Abrupt climate change is a striking feature of many climate records, particularly the warming events in Greenland ice cores. These abrupt and high-amplitude events were tightly coupled to rapid sea-ice retreat in the North Atlantic and Nordic Seas, and observational evidence shows they had global repercussions. In the present-day Arctic, sea-ice loss is also key to ongoing warming. This Perspective uses observations and climate models to place contemporary Arctic change into the context of past abrupt Greenland warmings. We find that warming rates similar to or higher than modern trends have only occurred during past abrupt glacial episodes. We argue that the Arctic is currently experiencing an abrupt climate change event, and that climate models underestimate this ongoing warming.

D-Penguin

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Re: What's new in Greenland?
« Reply #515 on: August 01, 2020, 04:52:48 PM »
There's a (paywalled) July 29 paper in Nature Climate Change: https://www.nature.com/articles/s41558-020-0860-7 that might be of interest:

Past perspectives on the present era of abrupt Arctic climate change

Abstract

Abrupt climate change is a striking feature of many climate records, particularly the warming events in Greenland ice cores. These abrupt and high-amplitude events were tightly coupled to rapid sea-ice retreat in the North Atlantic and Nordic Seas, and observational evidence shows they had global repercussions. In the present-day Arctic, sea-ice loss is also key to ongoing warming. This Perspective uses observations and climate models to place contemporary Arctic change into the context of past abrupt Greenland warmings. We find that warming rates similar to or higher than modern trends have only occurred during past abrupt glacial episodes. We argue that the Arctic is currently experiencing an abrupt climate change event, and that climate models underestimate this ongoing warming.

So, the question must be WHY do the climate models underestimate this ongoing warming? This failure of the science is significant and critical because the models inform the 'decision makers' regarding strategic decision making and policy formulation. Policy makers WAKE UP!!! IPCC WAKE UP!!! Although the IPCC is probably a lost cause. Scientists, start shouting (loudly).

+1 for bringing this publication to our attention but it is WRONG that it is behind a 'pay wall', it should be being quoted on prime-time newscasts. This is an example of 'science' NOT playing its part IMHO.
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kassy

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Re: What's new in Greenland?
« Reply #516 on: August 01, 2020, 07:13:38 PM »
Let me quote the most relevant line from the abstract:

Quote
We find that warming rates similar to or higher than modern trends have only occurred during past abrupt glacial episodes.

So this basically means we have activated the Greenland ice sheet which means we can add this to the list of points of danger to avoid which we did not avoid because GPD is important too.
See https://forum.arctic-sea-ice.net/index.php/topic,2994.100.html last bit of #129.
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Tom_Mazanec

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Re: What's new in Greenland?
« Reply #517 on: August 02, 2020, 12:35:00 AM »
What is GPD kassy?
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

oren

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Re: What's new in Greenland?
« Reply #518 on: August 02, 2020, 12:37:35 AM »
I assume GDP was meant.

vox_mundi

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Re: What's new in Greenland?
« Reply #519 on: August 14, 2020, 01:00:51 PM »
Warming Greenland Ice Sheet Passes Point of No Return
https://phys.org/news/2020-08-greenland-ice-sheet.html

Nearly 40 years of satellite data from Greenland shows that glaciers on the island have shrunk so much that even if global warming were to stop today, the ice sheet would continue shrinking.

The finding, published today, Aug. 13, in the journal Nature Communications Earth and Environment, means that Greenland's glaciers have passed a tipping point of sorts, where the snowfall that replenishes the ice sheet each year cannot keep up with the ice that is flowing into the ocean from glaciers.

... The researchers found that, throughout the 1980s and 90s, snow gained through accumulation and ice melted or calved from glaciers were mostly in balance, keeping the ice sheet intact. Through those decades, the researchers found, the ice sheets generally lost about 450 gigatons (about 450 billion tons) of ice each year from flowing outlet glaciers, which was replaced with snowfall.

"We are measuring the pulse of the ice sheet—how much ice glaciers drain at the edges of the ice sheet—which increases in the summer. And what we see is that it was relatively steady until a big increase in ice discharging to the ocean during a short five- to six-year period," King said.

The researchers' analysis found that the baseline of that pulse—the amount of ice being lost each year—started increasing steadily around 2000, so that the glaciers were losing about 500 gigatons each year. Snowfall did not increase at the same time, and over the last decade, the rate of ice loss from glaciers has stayed about the same—meaning the ice sheet has been losing ice more rapidly than it's being replenished.

"Glacier retreat has knocked the dynamics of the whole ice sheet into a constant state of loss," said Ian Howat, a co-author on the paper, professor of earth sciences and distinguished university scholar at Ohio State. "Even if the climate were to stay the same or even get a little colder, the ice sheet would still be losing mass."



Michalea D. King et al. Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat, Nature Communications Earth & Environment (2020)
https://www.nature.com/articles/s43247-020-0001-2
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kassy

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Re: What's new in Greenland?
« Reply #520 on: August 15, 2020, 09:37:15 PM »
This is interesting.

I was collecting climate failures vs our risk assessment here: https://forum.arctic-sea-ice.net/index.php/topic,2994.0.html

So i will add this one.

I know it is 2020 but this sort of thing should really alarm people.
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glennbuck

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Re: What's new in Greenland?
« Reply #521 on: August 16, 2020, 12:54:17 PM »
Nearly 40 years of satellite data from Greenland shows that glaciers on the island have shrunk so much that even if global warming were to stop today, the ice sheet would continue shrinking.

The finding, published today, Aug. 13, in the journal Nature Communications Earth and Environment, means that Greenland's glaciers have passed a tipping point of sorts, where the snowfall that replenishes the ice sheet each year cannot keep up with the ice that is flowing into the ocean from glaciers.

https://phys.org/news/2020-08-greenland-ice-sheet.html
« Last Edit: August 16, 2020, 01:18:42 PM by glennbuck »

vox_mundi

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“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

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kassy

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Re: What's new in Greenland?
« Reply #523 on: August 17, 2020, 03:58:27 PM »
Reading the last couple of posts to see if something has been posted is a common courtesy. New links can be added if they add info.
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kassy

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Re: What's new in Greenland?
« Reply #524 on: August 22, 2020, 10:44:48 AM »
During the Last Ice Age, Erratic Temperatures in Greenland Triggered Changes All Over the World

During the Last Glacial Period some 11,500 years ago, Greenland went through massive changes called interstadial events. Then, it quickly oscillated between lower and higher temperatures, which melted and then refroze (and then melted again) massive ice sheets in the region. Geological records appear to show that around the same time that this was happening in Greenland, Earth’s lower latitudes were experiencing similarly swift and dramatic climate changes, but it’s been hard for scientists to determine exactly when all of these abrupt shifts occurred. New research offers some clues as to what happened.

The new study, published in Science on Thursday, is based on scientists’ examination of stalagmite records from all over the world. The research was possible because stalagmites form in layers, and each layer preserves records of what environmental conditions were like when it formed.

The authors’ observations suggest that these changes in Greenland were connected to abrupt climate changes in faraway places – including even as far away as the tropics.

Records of Greenland’s ice cores show that the region experienced 25 major rapid temperature fluctuations during the Last Glacial Period. Those shifts, known as Dansgaard-Oeschger events, have been associated with sharp increases in air temperature over Greenland of up to a stunning 60 degrees Fahrenheit (16 degrees Celsius) in just a few decades, which rapidly melted ice. Though the warming periods were very quick, the hot conditions they created persisted for hundreds of years before giving way to a more gradual cooling period.

Based on that knowledge, the researchers examined 63 ancient climate records in stalagmites from caves around the world, across Europe, Asia, and South America. They found that changes seen there lined up with the changes in Greenland. Europe saw swift temperature increases and alterations in rainfall that lined up with when Dansgaard-Oeschger events were happening, as did Asia and South America’s monsoon regions.

...

https://www.gizmodo.co.uk/2020/08/during-the-last-ice-age-erratic-temperatures-in-greenland-triggered-changes-all-over-the-world/


Synchronous timing of abrupt climate changes during the last glacial period

Abstract
Abrupt climate changes during the last glacial period have been detected in a global array of palaeoclimate records, but our understanding of their absolute timing and regional synchrony is incomplete. Our compilation of 63 published, independently dated speleothem records shows that abrupt warmings in Greenland were associated with synchronous climate changes across the Asian Monsoon, South American Monsoon, and European-Mediterranean regions that occurred within decades. Together with the demonstration of bipolar synchrony in atmospheric response, this provides independent evidence of synchronous high-latitude–to-tropical coupling of climate changes during these abrupt warmings. Our results provide a globally coherent framework with which to validate model simulations of abrupt climate change and to constrain ice-core chronologies.

https://science.sciencemag.org/content/369/6506/963
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sidd

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Re: What's new in Greenland?
« Reply #525 on: August 23, 2020, 12:27:54 AM »
The paper by Corrick et al. cited above on combined NGRIP and speleothem dating is very nice. Alas, not open access, but do check out the Supplementary material, especially fig S4

It should show up on researchdate or scihub soon.

sidd

RoxTheGeologist

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Re: What's new in Greenland?
« Reply #526 on: August 26, 2020, 01:28:35 AM »
Is this calving unusual? It seems to have been around for a while!


oren

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Re: What's new in Greenland?
« Reply #527 on: August 26, 2020, 02:20:58 AM »
It is unusual, a result of a very slow process. It was discussed in the "Zachariae Isstrøm / Nioghalvfjerdsfjorden / NE Greenland" thread, first noticed on July 1st and covered in detail by Espen who has been tracking Spaltegletscher over the years.

https://forum.arctic-sea-ice.net/index.php/topic,400.msg271321.html#msg271321

RoxTheGeologist

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Re: What's new in Greenland?
« Reply #528 on: August 26, 2020, 05:46:08 AM »

Thanks Oren!

vox_mundi

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Re: What's new in Greenland?
« Reply #529 on: September 24, 2020, 06:45:36 PM »
Island-building in Southeast Asia Created Earth's Northern Ice Sheets
https://phys.org/news/2020-09-island-building-southeast-asia-earth-northern.html

The Greenland ice sheet owes its existence to the growth of an arc of islands in Southeast Asia—stretching from Sumatra to New Guinea—over the last 15 million years, a new study claims.

According to an analysis by researchers at the University of California, Berkeley, UC Santa Barbara and a research institute in Toulouse, France, as the Australian continent pushed these volcanic islands out of the ocean, the rocks were exposed to rain mixed with carbon dioxide, which is acidic. Minerals within the rocks dissolved and washed with the carbon into the ocean, consuming enough carbon dioxide to cool the planet and allow for large ice sheets to form over North America and Northern Europe.

"You have the continental crust of Australia bulldozing into these volcanic islands, giving you really high mountains just south of the equator," said Nicholas Swanson-Hysell, associate professor of earth and planetary science at UC Berkeley and senior author of the study. "So, you have this big increase of land area that is quite steep, in a region where it's warm and wet and a lot of rock types that have the ability to naturally sequester carbon."

Starting about 15 million years ago, this tropical mountain-building drew down carbon dioxide in the atmosphere, decreasing the strength of the greenhouse effect and cooling the planet. By about 3 million years ago, Earth's temperature was cool enough to allow snow and ice to remain through the summer and grow into huge ice sheets over the Northern Hemisphere, like that covering Greenland today.

Once Northern Hemisphere ice sheets grew, other climate dynamics led to a cycle of glacial maxima and minima every 40,000 to 100,000 years. At the most recent glacial maximum, about 15,000 years ago, massive ice sheets covered most of Canada, the northern portions of the U.S., as well as Scandinavia and much of the British Isles.

"If it wasn't for the carbon sequestration that's happening in the Southeast Asian islands, we wouldn't have ended up with the climate that includes a Greenland ice sheet and these glacial and interglacial cycles," ... "We wouldn't have crossed this atmospheric CO2 threshold to initiate Northern Hemisphere ice sheets."



Based on their model, chemical weathering in the Southeast Asian islands alone diminished CO2 levels from more than 500 parts per million (ppm) 15 million years ago to approximately 400 ppm 5 million years ago and, finally, to pre-industrial levels of 280 ppm. Fossil fuel-burning has now raised the level of carbon dioxide in the atmosphere to 411 ppm—"A process that took millions of years we have reversed in 100 years."

... While the threshold for Arctic glaciation is estimated to be about 280 ppm of carbon dioxide, the threshold for ice sheet formation at the South Pole is much higher: about 750 ppm. That's why the Antarctic ice sheets began forming much earlier, about 34 million years ago, than those in the Arctic. ...

Yuem Park el al., "Emergence of the Southeast Asian islands as a driver for Neogene cooling," PNAS (2020)
https://www.pnas.org/content/early/2020/09/23/2011033117
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Re: What's new in Greenland?
« Reply #530 on: September 24, 2020, 09:05:17 PM »
Finally, an explanation of what triggered the Quaternary Ice Age that makes sense to me!
Arctic ice is healthy for children and other living things.

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Re: What's new in Greenland?
« Reply #531 on: September 24, 2020, 09:37:34 PM »
The emergence of Indonesia for the draw down of atmospheric CO2 is an interesting hypothesis, but doesn't seem to match the paleo-CO2 records. I tried to get a copy of the paper but it is paywalled so wasn't really able to look at their arguments. Apparently a model shows that weathering there was sufficient to drive CO2 down enough to start Northern hemisphere glaciations.

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Re: What's new in Greenland?
« Reply #532 on: September 30, 2020, 06:39:53 PM »
Greenland Is On Track to Lose Ice Faster Than In Any Century Over 12,000 Years: Study
https://phys.org/news/2020-09-greenland-track-ice-faster-century.html



Greenland's rate of ice loss this century is likely to greatly outpace that of any century over the past 12,000 years, a new study concludes.

The research will be published on Sept. 30 in the journal Nature. The study employs ice sheet modeling to understand the past, present and future of the Greenland Ice Sheet. Scientists used new, detailed reconstructions of ancient climate to drive the model, and validated the model against real-world measurements of the ice sheet's contemporary and ancient size.

The findings place the ice sheet's modern decline in historical context, highlighting just how extreme and unusual projected losses for the 21st century could be, researchers say.

... "If the world goes on a massive energy diet, in line with a scenario that the Intergovernmental Panel on Climate Change calls RCP2.6, our model predicts that the Greenland Ice Sheet's rate of mass loss this century will be only slightly higher than anything experienced in the past 12,000 years," Briner adds. "But, more worrisome, is that under a high-emissions RCP8.5 scenario—the one the Greenland Ice Sheet is now following—the rate of mass loss could be about four times the highest values experienced under natural climate variability over the past 12,000 years."

Jason P. Briner, et.al, Rate of mass loss from the Greenland Ice Sheet will exceed Holocene values this century, Nature (2020)
https://www.nature.com/articles/s41586-020-2742-6
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vox_mundi

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Re: What's new in Greenland?
« Reply #533 on: November 10, 2020, 06:58:10 PM »
Scientists Discover Ancient Lake Bed Deep Beneath Greenland Ice
https://phys.org/news/2020-11-scientists-ancient-lake-bed-deep.html

Scientists have detected what they say are the sediments of a huge ancient lake bed sealed more than a mile under the ice of northwest Greenland—the first-ever discovery of such a sub-glacial feature anywhere in the world. Apparently formed at a time when the area was ice-free but now completely frozen in, the lake bed may be hundreds of thousands or millions of years old, and contain unique fossil and chemical traces of past climates and life. Scientists consider such data vital to understanding what the Greenland ice sheet may do in coming years as climate warms, and thus the site makes a tantalizing target for drilling. A paper describing the discovery is in press at the journal Earth and Planetary Science Letters.

The team says the basin once hosted a lake covering about 7,100 square kilometers (2,700 square miles), about the size of the U.S. states of Delaware and Rhode Island combined. Sediments in the basin, shaped vaguely like a meat cleaver, appear to range as much as 1.2 kilometers (three quarters of a mile) thick. The geophysical images show a network of at least 18 apparent onetime stream beds carved into the adjoining bedrock in a sloping escarpment to the north that must have fed the lake. The images also show at least one apparent outlet stream to the south. The researchers calculate that the water depth in the onetime lake ranged from about 50 meters to 250 meters (a maximum of about 800 feet).


Using geophysical instruments, scientists have mapped a huge ancient lake basin (outlined here in red) below the Greenland ice, covering about 2,700 square miles). Redder colors signify higher elevations, green ones lower. A stream system incised into the bedrock that once fed the lake is shown in blue. Credit: Paxman et al., EPSL, 2020

... "If we could get at those sediments, they could tell us when the ice was present or absent,"

What the sediments might contain is a mystery. Material washed out from the edges of the ice sheet have been found to contain the remains of pollen and other materials, suggesting that Greenland may have undergone warm periods during the last million years, allowing plants and maybe even forests to take hold. But the evidence is not conclusive, in part because it is hard to date such loose materials. The newly discovered lake bed, in contrast, could provide an intact archive of fossils and chemical signals dating to a so-far unknown distant past.

... The basin "may therefore be an important site for future sub-ice drilling and the recovery of sediment records that may yield valuable insights into the glacial, climatological environmental history" of the region, the researchers write. With the top of the sediments lying 1.8 kilometers below the current ice surface (1.1 miles), such drilling would be daunting, but not impossible.

Guy J.G. Paxman et al. A fault-bounded palaeo-lake basin preserved beneath the Greenland Ice Sheet, Earth and Planetary Science Letters (2020)
https://www.sciencedirect.com/science/article/pii/S0012821X20305914
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Stephan

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Re: What's new in Greenland?
« Reply #534 on: November 11, 2020, 06:58:32 PM »
How could these streams shown in blue NE of the ridge of the ancient lake have fed the lake? Their flow direction (downhill) goes away from that lake...
It is too late just to be concerned about Climate Change

oren

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Re: What's new in Greenland?
« Reply #535 on: November 11, 2020, 10:15:28 PM »
I was too embarrassed to ask why the streams seemed visually to be flowing away from the lake.

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Re: What's new in Greenland?
« Reply #536 on: November 11, 2020, 11:44:12 PM »
I agree with your observations, but the paper has a number of figures that make it a little clearer. This view might make more sense.Appearently, this basin is very close to the impact crater they discovered a couple of years ago.



When I have some more time I'll post some more ...
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Re: What's new in Greenland?
« Reply #537 on: November 12, 2020, 06:22:35 AM »
In reality the note on the image is poorly written, in fact are in blue not only the rivers feeding the lake, but also the rivers of the basin further north and flowing north, which intrigued everyone.
The images in the article are much clearer :

Click to enlarge

vox_mundi

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Re: What's new in Greenland?
« Reply #538 on: November 12, 2020, 04:19:28 PM »
Possible Thousand-Kilometer-Long River Running Deep Below Greenland's Ice Sheet
https://phys.org/news/2020-11-thousand-kilometer-long-river-deep-greenland-ice.html



Computational models suggest that melting water originating in the deep interior of Greenland could flow the entire length of a subglacial valley and exit at Petermann Fjord, along the northern coast of the island. Updating ice sheet models with this open valley could provide additional insight for future climate change predictions.

Radar surveys have previously mapped Greenland's bedrock buried beneath two to three thousand meters of ice. Mathematical models were used to fill in the gaps in survey data and infer bedrock depths. The surveys revealed the long valley, but suggested it was segmented, preventing water from flowing freely through it. However, the peaks breaking the valley into segments only show up in areas where the mathematical modeling was used to fill in missing data, so could not be real.

Researchers at Hokkaido University's Institute of Low Temperature Science, collaborating with researchers at the University of Oslo, ran numerous simulations to compare water dynamics in northern Greenland with and without valley segmentation.

The results, recently published in Cryosphere, show a dramatic change in how water melting at the base of the ice sheet would flow, if the valley is indeed open. A distinct subglacial watercourse runs all the way from the melting site to Petermann Fjord, which is located more than 1,000 kilometers away on the northern coast of Greenland. The watercourse only appears when valley segmentation is removed; there are no other major changes to the landscape or water dynamics.

If water is flowing, the model suggests it could traverse the whole length of the valley because the valley is relatively flat, similar to a riverbed. This suggests no parts of the ice sheet form a physical blockade. The simulations also suggested that there was more water flow towards the fjord with a level valley base set at 500 meters below sea level than when set at 100 meters below. In addition, when melting is increased only in the deep interior at a known region of basal melting, the simulated discharge is increased down the entire length of the valley only when the valley is unblocked. This suggests that a quite finely tuned relationship between the valley form and overlying ice can allow a very long down-valley water pathway to develop.

"Additional radar surveys are needed to confirm the simulations are accurate," says Greve, who has been developing the model used in the study, called Simulation Code for Polythermal Ice Sheets (SICOPOLIS). "This could introduce a fundamentally different hydrological system for the Greenland ice sheet. The correct simulation of such a long subglacial hydrological system could be important for accurate future ice sheet simulations under a changing climate."



Christopher Chambers et al. Possible impacts of a 1000 km long hypothetical subglacial river valley towards Petermann Glacier in northern Greenland, The Cryosphere (2020).
https://tc.copernicus.org/articles/14/3747/2020/

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Stephan

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Re: What's new in Greenland?
« Reply #539 on: November 12, 2020, 07:19:44 PM »
I agree with your observations, but the paper has a number of figures that make it a little clearer. This view might make more sense.Appearently, this basin is very close to the impact crater they discovered a couple of years ago.
Thank you for this clarification. So it is only the short creeks that fed the lake.
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vox_mundi

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Re: What's new in Greenland?
« Reply #540 on: November 17, 2020, 06:35:52 PM »
Greenland's Largest Glaciers Likely to Melt Faster Than Feared: Study
https://phys.org/news/2020-11-greenland-largest-glaciers-faster.html


a Frontal positions from 1875 to 2018 for Jakobshavn Isbræ. b Frontal positions from 1880 to 2018 for Kangerlussuaq Glacier. c Frontal positions from 1880 to 2018 for Helheim Glacier.

The three largest glaciers in Greenland—which hold enough frozen water to lift global sea levels some 1.3 metres—could melt faster than even the worst-case warming predictions, research published Tuesday showed.

A team of researchers based in Denmark and Britain used historical images and a host of other data to estimate how much ice had been lost from Greenland's Jakobshavn Isbrae, Kangerlussuaq Glacier and Helheim Glaciers in the 20th century.

They found that Jakobshavn Isbrae lost more than 1.5 trillion tonnes of ice between 1880-2012, while Kangerlussuaq and Helheim lost 1.4 trillion and 31 billion tonnes from 1900–2012, respectively.

Shfaqat Abbas Khan, a researcher at the Technical University of Denmark, said using photographs taken before the satellite era was another tool to help recreate the last century's ice loss.

"Historical measurements over the 19th and 20th century may hide important information that can significantly improve our future projections," he told AFP.



Prior models ran under RCP8.5 for the three glaciers featured in Tuesday's study predict a sea-level rise of 9.1–14.9mm by 2100.

The paper, published in Nature Communications, pointed out that the high-emissions pathway temperature increase was more than four times larger than during the 20th Century, when the three glaciers already added 8mm to seas.

"The worst-case scenario is underestimated. Ice loss may be anywhere from three or four times larger than previous predicted for the thee glaciers considered in this study," said Khan.



Centennial response of Greenland's three largest outlet glaciers, Nature Communications (2020)
https://www.nature.com/articles/s41467-020-19580-5

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

Moulins In Greenland Ice Sheet Larger Than Previously Thought: Study
https://phys.org/news/2020-11-holes-greenland-ice-sheet-larger.html

Holes that carry surface meltwater to the base of the Greenland ice sheet, called moulins, are much larger than previously thought, according to a new study based on observation and first-hand exploration by a team including a geologist from the University of Arkansas.

The extra volume could influence the stability of the Greenland ice sheet and how quickly it slides toward the sea.

M. D. Covington et al. Moulin Volumes Regulate Subglacial Water Pressure on the Greenland Ice Sheet, Geophysical Research Letters (2020)
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL088901

Abstract

Meltwater inputs to moulins regulate Greenland Ice Sheet sliding speeds by controlling water pressure in the most connected regions of the subglacial drainage system. While moulin storage capacities are a critical control on subglacial water pressure, few observations exist to constrain storage.

Using direct observations inside moulins, we show that moulin cross‐sectional areas can be at least 500 m2, far greater than is observed at the surface or assumed in models. Moulin water level measurements and numerical modeling reveal that diurnal variability in moulin water pressure is highly attenuated in moulins with large storage volumes (∼3% ice pressure), relative to moulins with smaller storage volumes (∼25% ice pressure).

Because large variability in moulin water pressure is linked to processes that ultimately reduce ice sliding speeds, ice sliding speeds in areas drained by large moulins may be more sensitive to long‐term increases in meltwater than areas drained by small moulins.
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oren

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Re: What's new in Greenland?
« Reply #541 on: November 17, 2020, 11:04:02 PM »
Quote
They found that Jakobshavn Isbrae lost more than 1.5 trillion tonnes of ice between 1880-2012, while Kangerlussuaq and Helheim lost 1.4 trillion and 31 billion tonnes from 1900–2012, respectively.
I find weird that these are the three largest glaciers in Greenland. Petermann? Zachariae? Humboldt? What criteria?
Also the numbers are weird. Did Helheim lose 50 times less than JH and Kangerlussuaq?
But I need to read the whole thing.

Espen

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Re: What's new in Greenland?
« Reply #542 on: November 18, 2020, 08:41:04 AM »
Quote
They found that Jakobshavn Isbrae lost more than 1.5 trillion tonnes of ice between 1880-2012, while Kangerlussuaq and Helheim lost 1.4 trillion and 31 billion tonnes from 1900–2012, respectively.
I find weird that these are the three largest glaciers in Greenland. Petermann? Zachariae? Humboldt? What criteria?
Also the numbers are weird. Did Helheim lose 50 times less than JH and Kangerlussuaq?
But I need to read the whole thing.

You are right! It is just because there is an airport next to those 3 glaciers? The 3 glaciers you mention is off limit to most on ground research, that is my guess? And in order to make the head lines you need to make it big?
Have a ice day!