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nanning

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Re: Permafrost general science thread
« Reply #100 on: June 13, 2020, 05:24:06 PM »
Good post jens imo.

In a global all-lifeforms context:
N₂O is a powerful GHG, then there's also the high-impact threat of large marine methane bursts and in general the likely increasing permafrost emissions in all areas that will be warmed up in an accelerating, step-wise manner because of AGW (BAU).

These permafrost emissions are out of our control!
These emissions will go on. Even when we stop with our anthropogenic emissions. And they are accelerating.

Long term (?) consequences:
A hothouse Earth is coming for certain I think, taking the above in consideration together with all other tipping points. A hyperthermal is likely imo. But that is off-topic here. Sorry, just connecting dots. There are many more dots but I realised that I drifted from the thread topic. Cheers.
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kassy

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Re: Permafrost general science thread
« Reply #101 on: June 17, 2020, 06:45:43 AM »
Article about the research in #96:

https://e360.yale.edu/digest/climate-models-underestimate-co2-emissions-from-permafrost-by-14-percent-study-finds

Scientists estimate there are about 1,500 billion metric tons of carbon locked away in Arctic permafrost, and that 5 to 15 percent of this carbon could be emitted as carbon dioxide by 2100 — enough to increase global temperatures 0.3 to 0.4 degrees Celsius. But these estimates do not include the CO2 that forms when permafrost carbon escapes into Arctic lakes and rivers and is oxidized by ultraviolet and visible light, a process known as photomineralization.

Researchers at the University of Michigan studied organic carbon from six different Arctic locations and found that substantial carbon dioxide emissions could be released through photomineralization — enough to raise permafrost-related CO2 emissions by 14 percent.
...
“Only recently have global climate models included greenhouse gases from thawing permafrost soils. But none of them contain this feedback pathway,”

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vox_mundi

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Re: Permafrost general science thread
« Reply #102 on: July 01, 2020, 03:09:45 AM »
Beavers Gnawing Away at the Arctic Permafrost
https://phys.org/news/2020-06-beavers-gnawing-arctic-permafrost.html

Alaska's beavers are profiting from climate change, and spreading rapidly. In just a few years' time, they have not only expanded into many tundra regions where they'd never been seen before; they're also building more and more dams in their new homes, creating a host of new water bodies. This could accelerate the thawing of the permafrost soils, and therefore intensify climate change, as an International American-German research team reports in the journal Environmental Research Letters.


The upper two images are photos taken within the study area in 2016 showing the tundra region setting. The bottom two images are taken from similar tundra across Hotham Inlet in 2015 (lower left) and 2011 (lower right) showing beaver dams in a drained lake basin outlet and along a beaded stream course, respectively.

... Back in 2018, Ingmar Nitze and Guido Grosse from the AWI, together with colleagues from the U.S., determined that the beavers living in an 18,000-square-kilometer section of northwest Alaska had created 56 new lakes in just five years. For their new study, the team from the AWI, the University of Alaska in Fairbanks, and the University of Minnesota in Minneapolis have now taken a closer look at this trend. Using detailed satellite data and extended time series, the experts tracked the beavers' activities in two other regions in Alaska—and were surprised by what they found.

"Of course, we knew that the beavers there had spread substantially over the last few decades," says Nitze. This is partly due to climate change; thanks to rising temperatures, now more and more habitats offer the shrubs that the animals need for food and building material. Furthermore, the lakes, which used to freeze solid, now offer beaver-friendlier conditions, thanks to their thinner seasonal winter ice cover. Lastly, the rodents aren't hunted as intensively as in the past. As a result, it's a good time to be a beaver in the Arctic.

"But we never would have dreamed they would seize the opportunity so intensively," says Nitze. The high-resolution satellite images of the roughly 100-square-kilometer study area near the town of Kotzebue reveal the scale of the animals' activities there. From just two dams in 2002, the number had risen to 98 by 2019—a 5,000-percent increase, with more than 5 new dams being constructed per year. And the larger area surveyed, which covers the entire northern Baldwin Peninsula, also experienced a beaver dam boom. According to Nitze, "We're seeing exponential growth there. The number of these structures doubles roughly every four years."

This has already affected the water balance. Apparently, the rodents intentionally do their work in those parts of the landscape that they can most easily flood. To do so, sometimes they dam up small streams, and sometimes the outlets of existing lakes, which expand as a result. "But they especially prefer drained lake basins," Benjamin Jones, lead author of the study, and Nitze report. In many cases, the bottoms of these former lakes are prime locations for beaver activity. "The animals have intuitively found that damming the outlet drainage channels at the sites of former lakes is an efficient way to create habitat. So a new lake is formed which degrades ice-rich permafrost in the basin, adding to the effect of increasing the depth of the engineered waterbody," added Jones. These actions have their consequences: in the course of the 17-year timeframe studied, the overall water area in the Kotzebue region grew by 8.3 percent. And roughly two-thirds of that growth was due to the beavers.

The researchers suspect that there have been similar construction booms in other regions of the Arctic; accordingly, they now want to expand their 'beaver manhunt' across the Arctic. "The growth in Canada, for example, is most likely even more extreme," says Nitze. And each additional lake thaws the permafrost below it and on its banks. Granted, the frozen soil could theoretically bounce back after a few years, when the beaver dams break; but whether or not the conditions will be sufficiently cold for that to happen is anyone's guess.


Mapping beaver dams in high-resolution satellite imagery available for the northern Baldwin Peninsula, Alaska. The location of individual dams indicated with red arrow and the flow direction with a light blue arrow. (a) A series of four dams at the outlet of a lake, (b) a ~60 m long dam built in a drained lake basin, (c) a series of dams at the outlet of a lake near a confluence with a beaded stream, (d) a series of dams in a channel running through the middle of a drained lake basin, (e) five dams progressing down the outlet channel of a thermokarst lake, and (f) a series of dams in a beaded stream gulch. Examples shown here taken from 2019 images; note differences in scale across image frames. All dams were constructed after 2002.

Benjamin M. Jones et al, Increase in beaver dams controls surface water and thermokarst dynamics in an Arctic tundra region, Baldwin Peninsula, northwestern Alaska, Environmental Research Letters (2020).
https://iopscience.iop.org/article/10.1088/1748-9326/ab80f1
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vox_mundi

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Re: Permafrost general science thread
« Reply #103 on: July 20, 2020, 10:20:19 PM »
40 More Gt of CO2 Baked In: Plant Roots Increase Carbon Emission from Permafrost Soils
https://phys.org/news/2020-07-roots-carbon-emission-permafrost-soils.html

Plant roots in soil stimulate microbial decomposition, a mechanism called the priming effect. An international research team co-lead by Frida Keuper from INRAE and Umeå University and Birgit Wild from Stockholm University shows that the priming effect alone can cause emission of 40 billion tons carbon from permafrost by 2100. The study was published today in Nature Geoscience.

Scientists have previously anticipated that rapidly rising temperatures will drive the emission of 50-100 billion ton permafrost carbon by 2100. On top of that, plant roots feed sugar to the microorganisms in the soil, which the microbes can use to break down more soil organic matter—the priming effect—resulting in even higher greenhouse gas emissions.

The researchers combined maps of plant activity and data on soil carbon content from the Northern Circumpolar Soil Carbon Database with an extensive literature survey on priming and plant root properties, to estimate the priming effect in permafrost ecosystems and its influence on greenhouse gas emissions.

They show that the priming effect increases soil microbial respiration by 12 percent, which causes the additional loss of 40 billion tons of carbon by 2100 compared to current predictions for permafrost. This equals almost a quarter of the remaining "carbon budget" for human activities to limit global warming to max 1.5°C.

Carbon loss from northern circumpolar permafrost soils amplified by rhizosphere priming, Nature Geoscience (2020).
https://www.nature.com/articles/s41561-020-0607-0
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vox_mundi

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Re: Permafrost general science thread
« Reply #104 on: July 25, 2020, 02:53:37 AM »
Alaska Is Getting Wetter. That's Bad News for Permafrost and the Climate
https://phys.org/news/2020-07-alaska-wetter-bad-news-permafrost.html

Alaska is getting wetter. A new study spells out what that means for the permafrost that underlies about 85% of the state, and the consequences for Earth's global climate.

The study, published today in Nature Publishing Group journal Climate and Atmospheric Science, is the first to compare how rainfall is affecting permafrost thaw across time, space, and a variety of ecosystems. It shows that increased summer rainfall is degrading permafrost across the state.

As Siberia remains in the headlines for record-setting heat waves and wildfires, Alaska is experiencing the rainiest five years in its century-long meteorological record. Extreme weather on both ends of the spectrum—hot and dry versus cool and wet—are driven by an aspect of climate change called Arctic amplification.
"In our research area the winter has lost almost three weeks to summer," says study lead author and Fairbanks resident Thomas A. Douglas, who is a scientist with the U.S. Army Cold Regions Research and Engineering Laboratory. "This, along with more rainstorms, means far more wet precipitation is falling every summer."

Over the course of five years, the research team took 2750 measurements of how far below the land's surface permafrost had thawed by the end of summer across a wide range of environments near Fairbanks, Alaska. The five-year period included two summers with average precipitation, one that was a little drier than usual, and the top and third wettest summers on record. Differences in annual rainfall were clearly imprinted in the amount of permafrost thaw.

More rainfall led to deeper thaw across all sites. After the wettest summer in 2014, permafrost didn't freeze back to previous levels even after subsequent summers were drier. Wetlands and disturbed sites, like trail crossings and clearings, showed the most thaw. Tussock tundra, with its deep soils and covering of tufted grasses, has been found to provide the most ecosystem protection of permafrost. While permafrost was frozen closest to the surface in tussock tundra, it experienced the greatest relative increase in the depth of thaw in response to rainfall, possibly because water could pool on the flat surface. Forests, especially spruce forests with thick sphagnum moss layers, were the most resistant to permafrost thaw. Charlie Koven, an Earth system modeler with the Lawrence Berkeley National Laboratory, used the field measurements to build a heat balance model that allowed the team to better understand how rain was driving heat down into the permafrost ground.


Relationships between active layer depth and summer precipitation.

Thomas A. Douglas et al, Increased rainfall stimulates permafrost thaw across a variety of Interior Alaskan boreal ecosystems, npj Climate and Atmospheric Science (2020)
https://www.nature.com/articles/s41612-020-0130-4
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kassy

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Re: Permafrost general science thread
« Reply #105 on: July 25, 2020, 07:46:42 AM »
Experiments Reveal How Permafrost Carbon Becomes Carbon Dioxide

Field samples from Alaska show how sunlight and iron convert permafrost carbon to carbon dioxide. Climate models ignore this process.

...

Researchers have now experimentally studied how sunlight triggers carbon dioxide production from permafrost carbon that’s been flushed to lakes and rivers, a process long ignored in climate models.

Current estimates of global warming from permafrost carbon feedback are biased low, the team concluded.

...

Microbes and Sunlight
One way in which permafrost carbon gets converted to carbon dioxide is via microbes—some microscopic life-forms chow down on carbon and respire carbon dioxide.

Although this microbial process is generally taken into account in climate models, comparably little is known about the permafrost carbon that’s flushed to lakes and rivers, where it’s exposed to sunlight. “We’ve known for a while that sunlight converts organic carbon to carbon dioxide, but the governing control of this process has escaped us,” said Ward.

It’s been hypothesized that this photomineralization might be controlled by the presence of iron, which is abundant in Arctic fresh waters. “There have been lots of lab-based studies suggesting that iron is a key player, but this is the first to let nature tell us what controls this process,” said Ward.

In 2018, Ward and his colleagues collected five samples of permafrost from northern Alaska. Back in the laboratory, they thawed the permafrost, filtered out the microbes, and isolated the dissolved organic carbon and other constituents, including iron. They then exposed the samples to different wavelengths of ultraviolet and visible light.

Visible Light Wins
In nature, the highest rates of photomineralization occur in the presence of visible light, Ward and his colleagues calculated. Two factors contribute to this finding. First, Earth’s surface receives significantly more visible light than ultraviolet light. Second, iron kick-starts reactions at longer wavelengths, the team showed. (Visible light is characterized by longer wavelengths than ultraviolet light.)

Photomineralization’s wavelength dependence has important implications, said Ward. It means that permafrost carbon in deep lakes or rivers is still apt to be converted to carbon dioxide. “As you move deeper into the water column, there’s less ultraviolet light available and more visible light,” said Ward.

Older and More Effective
The researchers also determined that the older carbon found in permafrost—several thousand years old—was roughly twice as effective at producing carbon dioxide as modern carbon. Modern carbon has more sunlight-absorbing compounds, said team member Jenny Bowen, a biogeochemist at the University of Michigan, but permafrost carbon is better at reaping the reaction-promoting benefits of iron.

This unaccounted-for contribution from old carbon has the potential to fundamentally change the carbon cycle, said Ted Schuur, an ecosystem ecologist at Northern Arizona University in Flagstaff not involved in the research. “Stuff that wasn’t part of the atmosphere is suddenly ending up in the atmosphere.”
Since photomineralization of permafrost carbon isn’t presently included in climate models, estimates of future global warming are biased low, the researchers concluded. “Sunlight increases the amount of carbon dioxide coming from thawing permafrost by 14%,” said Bowen. “The planet will warm even more than expected.”

These results were published last month in Geophysical Research Letters.

...

https://eos.org/articles/experiments-reveal-how-permafrost-carbon-becomes-carbon-dioxide



Arctic Amplification of Global Warming Strengthened by Sunlight Oxidation of Permafrost Carbon to CO2

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL087085

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Re: Permafrost general science thread
« Reply #106 on: August 11, 2020, 03:02:10 PM »
Anthrax Outbreak In Russia Thought To Be Result Of Thawing Permafrost

Quote
Russia is fighting a mysterious anthrax outbreak in a remote corner of Siberia. Dozens of people have been hospitalized; one child has died. The government airlifted some families out because more than 2,000 reindeer have been infected.

Link >> https://www.npr.org/sections/goatsandsoda/2016/08/03/488400947/anthrax-outbreak-in-russia-thought-to-be-result-of-thawing-permafrost

kassy

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Re: Permafrost general science thread
« Reply #107 on: August 12, 2020, 12:26:45 PM »
Climate change: Warming world will be 'devastating' for frozen peatlands

The world's peatlands will become a large source of greenhouse gases as temperatures rise this century, say scientists.

Right now, huge amounts of carbon are stored in boggy, often frozen regions stretching across northern parts of the world.

But much of the permanently frozen land will thaw this century, say experts.

This will release warming gases at a rate that could be 30-50% greater than previous estimates.

Using data compiled from more than 7,000 field observations, the authors of this new study were able to generate the most accurate maps to date of the peatlands, their depth and the amount of warming gases they contain.

They show that the boggy terrain covers 3.7 million sq kilometres (1.42 million sq miles).

...

"But my best estimate is that this shift will occur in the second half of this century."

....

If this new peatland estimate is included with all the estimates for permafrost melting, it is projected to equal the annual emissions of the EU and UK by 2100.

"The only way to limit the permafrost carbon feedback is to reduce global warming," said Dr Hugelius.

https://www.bbc.com/news/science-environment-53726487

So this is both permafrost and non permafrost peatlands combined. That of course does not matter for the planet.

Large stocks of peatland carbon and nitrogen are
vulnerable to permafrost thaw
https://www.pnas.org/content/pnas/early/2020/08/04/1916387117.full.pdf
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morganism

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Re: Permafrost general science thread
« Reply #108 on: August 22, 2020, 07:13:48 PM »
Electric mud’ teems with new, mysterious bacteria

"The bacteria also alter the mud’s chemistry, making layers closer to the surface more alkaline and deeper layers more acidic, Malkin has found. Such pH gradients can affect “numerous geochemical cycles,” she says, including those involving arsenic, manganese, and iron, creating opportunities for other microbes.

With vast swaths of the planet covered by mud, cable and nanowire bacteria are likely having an influence on global climate, researchers say. Nanowire bacteria, for example, can strip electrons from organic materials, such as dead diatoms, then shuttle them to other bacteria that produce methane—a potent greenhouse gas. Under different circumstances, cable bacteria can reduce methane production.

https://www.sciencemag.org/news/2020/08/electric-mud-teems-new-mysterious-bacteria


BornFromTheVoid

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Re: Permafrost general science thread
« Reply #109 on: August 27, 2020, 11:45:35 AM »
New paper is available now, feel free to ask any question about it.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087917

Abstract
High overall rates of permafrost cliff retreat, coupled with spatial variability, have been accompanied by increased uncertainty over future landscape dynamics. We map long‐term (>80 years) retreat of the shoreline and photogrammetrically analyze historic aerial imagery to quantify the processes at a permafrost coast site with massive ground ice. Retreat rates have been relatively constant but topographic changes show that subsidence is a potentially critical but often ignored component of coastal sensitivity, exceeding landward recession by over 3 times during the last 24 years. We calibrate novel passive seismic surveys along clear and variable exposures of massive ground ice and then spatially map key sub‐surface layers. Combining decadal patterns of volumetric change with new ground ice variation maps enables past trends to be interpreted, future volumetric geomorphic behavior to be better constrained, and improves the assessment of permafrost coast sensitivity and the release of carbon‐bearing material.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Tor Bejnar

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Re: Permafrost general science thread
« Reply #110 on: August 27, 2020, 05:39:26 PM »
I wasn't familiar with the term "ground ice", so I looked it up on the inter-tubey thing:
From Glossary of Permafrost and Related Ground-Ice Terms (a PDF)
Quote
ice, ground (see also ice, buried; ice, epigenetic; ice, intrusive; ice,
syngenetic)
[glace de sol]
A general term referring to all types of ice formed in freezing and frozen
ground(see Figure 10).
COMMENT: Ground ice occurs in pores, cavities, voids or other
openings in soil or rock and includes massiveice, but generally excludes
buriedice. Ground ice may be epigenetic or syngenetic,
contemporaneous or relict, aggrading or degrading, perennial or
seasonal. It may occur as lenses, wedges, veins, sheets, seams, irregular
masses, or as individual crystals or coatings on mineral or organic
particles. Perennial ground ice can only occur within permafrost bodies.
REFERENCES: Mackay, 1972b; Pollard and French, 1980.

So (from reading the plain language offering), when climate warms, permafrost melts.  A couple things happen:
  • what was once hard (frozen hard) is now soft and erodible
  • what was once frozen H2O in the ground is now liquid and it flows away, causing the surface to 'slump' (locally or widespread)
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longwalks1

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Re: Permafrost general science thread
« Reply #111 on: August 27, 2020, 06:38:08 PM »
A short quote from BFV #109 post for  https://doi.org/10.1029/2020GL087917        Massive Ice Control on Permafrost Coast Erosion and Sensitivity

Quote
2.Regional Setting and Methods The Tuktoyaktuk Coastlands, northwest Canada,arelocated within the southern Beaufort Sea area  and aredominated  by  ice-rich permafrost landscapes(Rampton,  1988).  Thisgenerally flat, deltaiclandscape is punctuated by ice cored plateaus and domes acrossthe tundra. Here, we focus on Peninsula Point(Figure 1a), 6 km southwest of Tuktoyaktukandwithin the Pingo Canadian Landmark (a national historic site managed by Parks Canada), itis a representative type-site  for  intrasedimental  massive  ice (Gilbert  et  al.,  2016;  Mackay  &  Dallimore,  1992; Murton,  2009). Compoundingthe dynamic  erosion  processesin  the  area (Murton,  2005), reduced sea-ice (Overeem et al., 2011)and frozen ground seasons (Laberge & Payette, 1995; Liljedahl et al., 2016), increasing storm intensity (Vermaire et al., 2013)and a relative 2.5 mm a-1sea-level rise (Hill et al., 1993)have intensified the degradation of permafrost coasts in the region

Passive seismic surveys, nicer to the larger fauna, the caribou need all the TLC that they can get.   

Quote
3.2Mapping subsurface structure of massive iceThis work demonstrates that passive seismic surveys can determine the presence and depth of massive ice within challenging permafrost coast ground conditions.

Just a stellar usage of old data and new right sized technology. 

Just west of Tuktoyatuk.  About 30 - 35 km east of the McKenzie.  Quick background of the scene at
https://en.wikipedia.org/wiki/Pingo_National_Landmark

BornFromTheVoid

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Re: Permafrost general science thread
« Reply #112 on: August 27, 2020, 08:40:14 PM »
I wasn't familiar with the term "ground ice", so I looked it up on the inter-tubey thing:
From Glossary of Permafrost and Related Ground-Ice Terms (a PDF)
Quote
ice, ground (see also ice, buried; ice, epigenetic; ice, intrusive; ice,
syngenetic)
[glace de sol]
A general term referring to all types of ice formed in freezing and frozen
ground(see Figure 10).
COMMENT: Ground ice occurs in pores, cavities, voids or other
openings in soil or rock and includes massiveice, but generally excludes
buriedice. Ground ice may be epigenetic or syngenetic,
contemporaneous or relict, aggrading or degrading, perennial or
seasonal. It may occur as lenses, wedges, veins, sheets, seams, irregular
masses, or as individual crystals or coatings on mineral or organic
particles. Perennial ground ice can only occur within permafrost bodies.
REFERENCES: Mackay, 1972b; Pollard and French, 1980.

So (from reading the plain language offering), when climate warms, permafrost melts.  A couple things happen:
  • what was once hard (frozen hard) is now soft and erodible
  • what was once frozen H2O in the ground is now liquid and it flows away, causing the surface to 'slump' (locally or widespread)

We were dealing with a site that was specifically know for its massive ice bodies. These are thick  layers, up to 10s of meters, covered by permafrost and usually with permafrost below them too.

Here's an example from the field site, with the SfM models we used too.


We examined the erosion process called retrogressive thaw slumps. Where cliffs form over these massive ice bodies and spread inland really quickly. They can cause so much material to flow towards the shoreline that it results in large mud lobes causing transient progradation, like the lobe in the pic above. This means you get mass loss through vertical changes in the landscape several times faster than from shoreline retreat
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

BornFromTheVoid

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Re: Permafrost general science thread
« Reply #113 on: August 27, 2020, 08:44:21 PM »
A short quote from BFV #109 post for  https://doi.org/10.1029/2020GL087917        Massive Ice Control on Permafrost Coast Erosion and Sensitivity

Quote
2.Regional Setting and Methods The Tuktoyaktuk Coastlands, northwest Canada,arelocated within the southern Beaufort Sea area  and aredominated  by  ice-rich permafrost landscapes(Rampton,  1988).  Thisgenerally flat, deltaiclandscape is punctuated by ice cored plateaus and domes acrossthe tundra. Here, we focus on Peninsula Point(Figure 1a), 6 km southwest of Tuktoyaktukandwithin the Pingo Canadian Landmark (a national historic site managed by Parks Canada), itis a representative type-site  for  intrasedimental  massive  ice (Gilbert  et  al.,  2016;  Mackay  &  Dallimore,  1992; Murton,  2009). Compoundingthe dynamic  erosion  processesin  the  area (Murton,  2005), reduced sea-ice (Overeem et al., 2011)and frozen ground seasons (Laberge & Payette, 1995; Liljedahl et al., 2016), increasing storm intensity (Vermaire et al., 2013)and a relative 2.5 mm a-1sea-level rise (Hill et al., 1993)have intensified the degradation of permafrost coasts in the region

Passive seismic surveys, nicer to the larger fauna, the caribou need all the TLC that they can get.   

Quote
3.2Mapping subsurface structure of massive iceThis work demonstrates that passive seismic surveys can determine the presence and depth of massive ice within challenging permafrost coast ground conditions.

Just a stellar usage of old data and new right sized technology. 

Just west of Tuktoyatuk.  About 30 - 35 km east of the McKenzie.  Quick background of the scene at
https://en.wikipedia.org/wiki/Pingo_National_Landmark

Cheers!
The combination of the passive seismics with the cm scale surface models generated from drone imagery meant we could create 3D models of sections of the site too. That way we can figure out how much of the ground is soil vs ice. This matters for how fast it will erode, the mechanism by which it will erode, and knowing the constituents (ice vs soil) we can better constrain the volume of carbon that will be released too.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Tor Bejnar

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Re: Permafrost general science thread
« Reply #114 on: August 27, 2020, 08:46:49 PM »
cleaned up quotes (without actual access to paper):
Quote
    2. Regional Setting and Methods.  The Tuktoyaktuk Coastlands, northwest Canada, are located within the southern Beaufort Sea area and are dominated by ice-rich permafrost landscapes (Rampton, 1988).  This generally flat, deltaic landscape is punctuated by ice cored plateaus and domes across the tundra.  Here, we focus on Peninsula Point (Figure 1a), 6 km southwest of Tuktoyaktuk and within the Pingo Canadian Landmark (a national historic site managed by Parks Canada), it is a representative type-site  for  intrasedimental massive ice (Gilbert et al., 2016; Mackay & Dallimore, 1992; Murton, 2009). Compounding the dynamic erosion processes in  the area (Murton, 2005), reduced sea-ice (Overeem et al., 2011) and frozen ground seasons (Laberge & Payette, 1995; Liljedahl et al., 2016), increasing storm intensity (Vermaire et al., 2013) and a relative 2.5 mm a-1 sea-level rise (Hill et al., 1993) have intensified the degradation of permafrost coasts in the region.




    3.2 Mapping subsurface structure of massive ice.  This work demonstrates that passive seismic surveys can determine the presence and depth of massive ice within challenging permafrost coast ground conditions.
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Tor Bejnar

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Re: Permafrost general science thread
« Reply #115 on: August 27, 2020, 09:24:13 PM »
I've read a tiny bit about "retrogressive thaw slumps"  and was aware of how fast a multi-meter thick area (volume) of recent permafrost can mobilize, flowing into streams or the sea ("mud flows," we used to call them). 

I wasn't aware of how thick 'pure' ice could be within the permafrost.  At first (just now) I wondered how 'lenses' grew so thick, but then imagined a (10s-to-100s-of-centuries long) series of freeze/thaw [just above the ice] cycles could built up the ice layer to basically any thickness.  (I don't presume to understand the actual physics ... and my imagination is just my imagination.) 

Wow!  'Wouldn't want to be walking around that area on the wrong day!

A neighbor in New Hampshire, one Summer, paved his long-used mostly dirt driveway, and the next Spring (Mud Season) his pickup truck (well, one wheel) fell through the pavement up to its axle.  Solid ground really can become "quicksand". 
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BornFromTheVoid

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Re: Permafrost general science thread
« Reply #116 on: August 27, 2020, 10:27:58 PM »
I've read a tiny bit about "retrogressive thaw slumps"  and was aware of how fast a multi-meter thick area (volume) of recent permafrost can mobilize, flowing into streams or the sea ("mud flows," we used to call them). 

I wasn't aware of how thick 'pure' ice could be within the permafrost.  At first (just now) I wondered how 'lenses' grew so thick, but then imagined a (10s-to-100s-of-centuries long) series of freeze/thaw [just above the ice] cycles could built up the ice layer to basically any thickness.  (I don't presume to understand the actual physics ... and my imagination is just my imagination.) 

Wow!  'Wouldn't want to be walking around that area on the wrong day!

A neighbor in New Hampshire, one Summer, paved his long-used mostly dirt driveway, and the next Spring (Mud Season) his pickup truck (well, one wheel) fell through the pavement up to its axle.  Solid ground really can become "quicksand".

The one on Peninsula Point formed as the Laurentide ice sheet was retreating, so the ground was freezing but there was loads of subsurface meltwater flowing and freezing too. it may have been up to 20 m thick at one stage.

The number and growth of thaw slumps are crazy. This study from the nearby Banks Island, showing a 60 fold increase in their numbers since the mid 80s

https://www.nature.com/articles/s41467-019-09314-7

I have some cool pics and animation of the slumps too. I'll post them up tomorrow if I get the time. You can literally watch them developing just standing there.
I recently joined the twitter thing, where I post more analysis, pics and animations: @Icy_Samuel

Sebastian Jones

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Re: Permafrost general science thread
« Reply #117 on: August 28, 2020, 12:22:59 AM »
I've read a tiny bit about "retrogressive thaw slumps"  and was aware of how fast a multi-meter thick area (volume) of recent permafrost can mobilize, flowing into streams or the sea ("mud flows," we used to call them). 
........................


The one on Peninsula Point formed as the Laurentide ice sheet was retreating, so the ground was freezing but there was loads of subsurface meltwater flowing and freezing too. it may have been up to 20 m thick at one stage.

The number and growth of thaw slumps are crazy. This study from the nearby Banks Island, showing a 60 fold increase in their numbers since the mid 80s

https://www.nature.com/articles/s41467-019-09314-7

I have some cool pics and animation of the slumps too. I'll post them up tomorrow if I get the time. You can literally watch them developing just standing there.

We have a community science thaw slump monitoring project on the Dempster Highway- the road that leads (most of the way) to BFTV's study area.
I'd love to read the entire paper, is there a way to get it out from behind the paywall? SciHub does not have it yet.