Permafrost thawing faster than expected due to extreme summer rainfall

Using a motor pump and sprinklers, researchers of the Plant Ecology & Nature Management group simulated the effect of extreme summer rains on the Siberian tundra ecosystem. Credit: Rúna Magnússon

In the past 50 years, the Arctic region has been warming three times faster than the average rate of global warming. This warming thaws the permafrost, the permanently frozen Arctic soil. New research published in Nature Communications has revealed that extreme summer rainfall is accelerating this process. As extreme rainfall events become more frequent thanks to a warmer climate, the permafrost may thaw even faster than under the influence of rising temperatures alone.

Permafrost forms the foundation of Arctic ecosystems and the settlements of humans who live on it. When the permafrost thaws, the soil loses its load-bearing capacity. In addition, the organic carbon stored in the frozen soil decomposes more easily into greenhouse gases, such as CO2 and methane, which contribute to global warming. The release of through permafrost thaw causes what is known as a positive feedback loop, a self-reinforcing process.

But in addition to the temperature, the precipitation in the Arctic region is also increasing. In winter, this has a negative impact on the permafrost. A thicker layer of snow in winter has an insulating effect and protects the permafrost from extremely cold air, so it does not cool as much. But little was known about the effect of precipitation in summer.

Rain experiment

Researchers from Wageningen University (WUR)’s Plant Ecology & Nature Management chair group carried out an irrigation experiment on the Northeast Siberian tundra to study the effects of extreme summer precipitation on permafrost. Ph.D. candidate Rúna Magnússon selected 20 monitoring sites and used sprinklers to give half the sites extra water. The experiment simulated the effects of a single, extremely wet summer. The sites were monitored for several years for permafrost thaw depth and other soil and vegetation characteristics.

A crumbling permafrost bank on the shores of a lake reveals man-sized ice structures hidden in the frozen ground. The dark color of the soil is due to the presence of organic material such as decomposed plant remains. Credit: Rúna Magnússon

On average, the permafrost thawed 35% faster in the irrigated sites, leaving a larger amount of soil susceptible to the decomposition of soil into greenhouse gas. An important finding was that the effect of an extremely wet summer lasted for several years; even two years after the sprinkler test, the permafrost under the irrigated sites was still thawing faster. An additional model analysis in cooperation with researchers from Stockholm University revealed that permafrost thaws particularly rapidly during periods of combined high and high air temperatures. “We were not surprised that the permafrost thawed to a greater depth during wet summers, but that the effect would be so extreme and last for several years was really unexpected,” says Magnusson.

Risk of underestimating climate change

As rainfall is expected to increase and precipitation extremes will become more frequent in warming Arctic regions, these results are bad news for the permafrost. “If we only take warmer temperatures into account, we will underestimate how much permafrost is thawing as a result of climate change, and how much extra CO2 and is being released,” explains Magnusson. “But it is difficult to realistically represent the effect of such precipitation extremes on permafrost thaw and in . This could lead us to underestimate future greenhouse gas emissions caused by permafrost thaw, and therefore our emissions targets to stay within the one-and-a-half or two degrees of global warming may turn out to be too optimistic.”

Future research will hopefully reveal the extent to which the sensitivity of permafrost to rain varies regionally, so that more reliable estimates of future can be made.



More information:
Rúna Í. Magnússon et al, Extremely wet summer events enhance permafrost thaw for multiple years in Siberian tundra, Nature Communications (2022). DOI: 10.1038/s41467-022-29248-x

Citation:
Permafrost thawing faster than expected due to extreme summer rainfall (2022, March 23)
retrieved 23 March 2022
from https://phys.org/news/2022-03-permafrost-faster-due-extreme-summer.html

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part may be reproduced without the written permission. The content is provided for information purposes only.

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Hexbyte Glen Cove Thawing permafrost could expose Arctic populations to cancer-causing radon

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Credit: Pixabay/CC0 Public Domain

According to a new study, thawing of permafrost due to climate change could expose the Arctic population to much greater concentrations of the invisible, lung cancer-causing gas radon.

Professor Paul Glover from the University of Leeds and his co-author suggest that has historically acted as a protective barrier, blocking radon from traveling to the surface and entering buildings there.

Radon is an invisible, odorless, naturally occurring radioactive gas. It causes approximately one in 10 lung cancer deaths and affects smokers much more than non-smokers. It causes higher death rates in sub-Arctic communities due to the prevalence of smoking.

Their study, published today in the AGU journal Earth’s Future, modeled radon production, its flow through soil, permafrost and model buildings—including those with sub-surface and surface basements and those built, more traditionally, on piles.

They show that in buildings with basements, the presence of radon gas can increase to more than 100 times its initial value for up to seven years, depending on the depth of the permafrost and how fast the permafrost thaws.

This demonstrates the importance of not only keeping the permafrost layer intact by limiting global warming, but also has significant implications for health provision, codes and ventilation advice.

The presence of a permafrost layer was found to act as a radon barrier, reducing surface radiation to a tenth of the background level, but increasing radon concentration behind the barrier by to up to 12 times. This was the case for a wide range of depths to the permafrost layer.

Professor Glover, from the School of Earth and Environment at Leeds, said, “Radon is known to be the second most important cause of lung cancer after smoking. Smoking also exacerbates radon-acquired lung cancer rates by about 26 times, and smoking is up to 4.4 times more prevalent in Arctic communities.

“Consequently, an unexpected plume of radon could represent a dangerous health hazard if it is not planned for. Fortunately, simply-installed ventilation is all that is often required if the problem is recognized.

“If the permafrost were stable, there would be no cause to be concerned. However, it is now widely recognized that is leading to significant thawing of permafrost, with a 42% expected loss of permafrost in the Arctic Circumpolar Permafrost Region (ACPR) by 2050.

“The radon can then pass through the permafrost and lead to a plume of radioactive gas within buildings that take[s] several years to peak and many more to dissipate.”

The Earth’s Future publication suggests that thawing of the permafrost barrier produces no increase in radon compared to the background level for traditionally-constructed buildings in the Arctic community, which are built on piles.

For buildings with basements, permafrost thaw can result in the radon concentration remaining greater than the 200 becquerel per cubic meter (Bq/m3) value that many nations use as an action threshold, for up to seven years depending on the depth of the permafrost and the thaw rate.

Professor Glover added, “Our results show clearly that the pent-up reservoir of radon can be released into the basements of buildings over a long period and will remain above radiation action levels for four to seven years.

“Since there has been no perceived historical radon problem in these communities and the gas itself is undetectable without specialist devices, we regard this as an important and totally avoidable threat to the health of the northern communities.”

Professor Glover stresses that these are initial results that have had to include many assumptions, not least because there is a significant lack of data about petrophysical properties of Arctic soil and permafrost.

It is possible that will find efficient pathways to the surface through both advection and diffusion and along zones of preferential thawing while the bulk of the more slowly.

Professor Glover is part of the Institute of Applied Geoscience and Petrophysics and Geomechanics group. Their work includes the theory, modeling, measurement and applications of Earth materials and processes. He was the founder and first president of the Energy, Resources and the Environment division of the European Geophysical Union.



More information:
P. W. J. Glover et al, Increased Radon Exposure From Thawing of Permafrost Due To Climate Change, Earth’s Future (2022). DOI: 10.1029/2021EF002598

Citation:

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Hexbyte Glen Cove Permafrost carbon feedbacks threaten global climate goals thumbnail

Hexbyte Glen Cove Permafrost carbon feedbacks threaten global climate goals

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Credit: CC0 Public Domain

Since it was first signed more than five years ago, the Paris Agreement has set the bar for the global effort to reduce greenhouse gas emissions, with more than 70 countries taking on ambitious nationally determined contributions that exceed initial commitments laid out in the agreement. However, a new paper released today in Proceedings of the National Academy of Sciences argues that the carbon budget these commitments are based on does not take into account the latest science on Arctic feedback loops, and calls for global leaders to rethink emissions goals.

“Arctic warming poses one of the greatests risks to our climate, yet it has not been adequately incorporated into existing climate projections and policies,” said Dr. Sue Natali, lead author and director of Woodwell Climate’s Arctic Program. “To build effective policy to address the climate crisis, it is essential that we recognize the full scope of the problem.”

Over the past decade, rapid Arctic warming has resulted in record-breaking Siberian heatwaves, extreme northern wildfires that release massive amounts of carbon into the atmosphere, the loss of Arctic sea ice, and an acceleration of permafrost thaw. Arctic permafrost, which has been accumulating and storing carbon for thousands of years, contains approximately twice the amount of carbon that is currently in the Earth’s atmosphere, and is releasing that carbon into the atmosphere as it thaws. Those emissions exacerbate warming, which triggers more thaw, potentially leading to an exponential increase in emissions and warming in the coming years. This new paper shows current carbon budgets fail to account for these from permafrost and the dangerous climate feedback loops they will set off.

“Based on what we already know about abrupt thaw and wildfire, these feedback loops are likely to substantially exacerbate the permafrost thaw feedback and resulting carbon emissions,” said Woodwell researcher and paper co-author Dr. Rachael Treharne. “Unless our models account for these anticipated effects, we’ll be missing a major piece of the carbon puzzle.”

In order to keep the Earth’s temperature below 1.5° or 2°C, the paper recommends incorporate the latest science on Arctic carbon emissions into and carbon budgets used to inform policy, and update risk assessments to determine how quickly we need to reduce emissions to meet climate goals.

“The science alone is not enough,” said Dr. Philip Duffy, president and executive director of the Woodwell Climate Research Center and commentary co-author. “We urgently need communication between scientific and policy communities to make sure our climate policies are effective in addressing the scale and scope of the climate crisis.”



More information:
Susan M. Natali el al., Permafrost carbon feedbacks threaten global climate goals, PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2100163118

Provided by
Woodwell Climate Research Center

Citation:
Permafrost carbon feedbacks threaten global climate goals (2021, May 17)
retrieved 18 May 2021
from https://phys.org/news/2021-05-permafrost-carbon-feedbacks-threa

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Hexbyte Glen Cove Coastal permafrost more susceptible to climate change than previously thought thumbnail

Hexbyte Glen Cove Coastal permafrost more susceptible to climate change than previously thought

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Micaela Pedrazas (left) and Cansu Demir, both graduate students at The University of Texas at Austin Jackson School of Geosciences, examining an exposed side of an ice wedge polygon, which was uncovered by erosion and melting. An ice lens is visible to the right of Demir. Credit: Bayani Cardenas

If you flew from the sea towards the land in the north slope of Alaska, you would cross from the water, over a narrow beach, and then to the tundra. From the air, that tundra would look like a landscape of room-sized polygonal shapes. Those shapes are the surface manifestations of the ice in the frozen ground below, a solidified earth known as permafrost.

Scientists long believed the solid permafrost extended offshore: from the , below that narrow beach and below the seafloor declining at a gentle slope. They viewed that permafrost like solid brick, locking the subsurface—and the vast amounts of carbon it holds—in place.

But new research led by Micaela Pedrazas, who earned her masters at The University of Texas at Austin Jackson School of Geosciences working with Professor Bayani Cardenas, has upended that paradigm. They found permafrost to be mostly absent throughout the shallow seafloor along a coastal field site in northeastern Alaska. That means carbon can be released from coastline sources much more easily than previously thought.

The study was published in Science Advances on Oct. 23 with coauthors from the Jackson School and UT’s Marine Science Institute.

Using a geophysical technique called imaging, the researchers mapped the subsurface beneath Kaktovik Lagoon along the northeastern coast of Alaska over the course of three years.

An aerial image of ice wedge polygons next to Kaktovik Lagoon. The polygons are signs of ice in the frozen ground below, a solidified earth known as permafrost. Credit: Nathan Sonderman

The results were unexpected. The beach and seafloor were entirely ice-free down to at least 65 feet. On the tundra itself, ice-rich permafrost was detected in the top 16 feet, but below that, the subsurface their imaging mapped was also ice-free.

“This leads to a new conceptual model,” Pedrazas said.

Permafrost is found in that remain frozen during the course of the year. Scientists have been tracking the impact of a warming climate on permafrost because as it melts, permafrost releases its stores of frozen carbon into the atmosphere as methane and , contributing to climate change.

Permafrost studies have almost exclusively focused on the region beneath the tundra. Because it’s not easy to work in such remote locations and under harsh weather conditions, the transition from sea to shore has been largely ignored.

“This study tells us that the coastline is much more complicated than we thought,” said co-author Jim McClelland from UT’s Marine Science Institute. “It opens up the possibility for routes of water exchange that we weren’t thinking about.”

Ph.D. student Cansu Demir and Professor Bayani Cardenas, both from The University of Texas Jackson School of Geosciences, installing a mini-groundwater well in the bed of Kaktovik Lagoon. Credit: Micaela Pedrazas

Besides global considerations, the work has local impacts. The communities along the coast, most of whom are Inupiat, live on the permafrost. As the permafrost thaws, it accelerates , which carves away at the land on which homes and infrastructure stand. In the Kaktovik region, erosion can be as great as 13 feet per year.

“Their cultural heritage and their welfare is integrated and intricately linked to their environment,” Cardenas said. “There’s an immediate need to understand what’s happening in these lagoons.”

The new paradigm requires reimagining the coastal Arctic ecosystem as well. Liquid groundwater means that carbon and nutrients can move between the tundra and the lagoon. It also means that saltwater can move beneath the tundra, potentially affecting freshwater sources.

Paul Overduin, who wasn’t involved in the research, but who studies permafrost at Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, said that this work is the first step in understanding ‘s transition from sea to shore.

“As is often the case, when we start looking at something people don’t know much about, you open up a whole bunch of questions that needed to be looked at,” he said. “That’s what’s really exciting here.”



More information:
“Absence of ice-bonded permafrost beneath an Arctic lagoon revealed by electrical geophysics” Science Advances (2020). advances.sciencemag.org/lookup … .1126/sciadv.abb5083

Citation:
Coastal permafrost more susceptible to climate change than previously thought (2020, October 23)
retrieved 26 October 2020
from https://phys.org/news/2020-10-coastal-permafrost-susceptible-climate-previously.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.