Direct observation of #permafrost #degradation and rapid #soil #carbon loss in #tundra (Nat Geosci., abstract)

[Source: Nature Geoscience, full page: (LINK). Abstract, edited.]

Article | Published: 01 July 2019

Direct observation of permafrost degradation and rapid soil carbon loss in tundra

César Plaza, Elaine Pegoraro, Rosvel Bracho, Gerardo Celis, Kathryn G. Crummer, Jack A. Hutchings, Caitlin E. Hicks Pries, Marguerite Mauritz, Susan M. Natali, Verity G. Salmon, Christina Schädel, Elizabeth E. Webb & Edward A. G. Schuur

Nature Geoscience (2019)

 

Abstract

Evidence suggests that 5–15% of the vast pool of soil carbon stored in northern permafrost ecosystems could be emitted as greenhouse gases by 2100 under the current path of global warming. However, direct measurements of changes in soil carbon remain scarce, largely because ground subsidence that occurs as the permafrost soils begin to thaw confounds the traditional quantification of carbon pools based on fixed depths or soil horizons. This issue is overcome when carbon is quantified in relation to a fixed ash content, which uses the relatively stable mineral component of soil as a metric for pool comparisons through time. We applied this approach to directly measure soil carbon pool changes over five years in experimentally warmed and ambient tundra ecosystems at a site in Alaska where permafrost is degrading due to climate change. We show a loss of soil carbon of 5.4% per year (95% confidence interval: 1.0, 9.5) across the site. Our results point to lateral hydrological export as a potential pathway for these surprisingly large losses. This research highlights the potential to make repeat soil carbon pool measurements at sentinel sites across the permafrost region, as this feedback to climate change may be occurring faster than previously thought.

Keywords: Climate change; Global warming; Permafrost.

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#Rivers across the #Siberian #Arctic unearth the #patterns of #carbon #release from thawing #permafrost (Proc Natl Acad Sci USA, abstract)

[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost

Birgit Wild, August Andersson, Lisa Bröder, Jorien Vonk, Gustaf Hugelius, James W. McClelland, Wenjun Song, Peter A. Raymond, and Örjan Gustafsson

PNAS first published May 6, 2019 / DOI: https://doi.org/10.1073/pnas.1811797116

Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved March 26, 2019 (received for review July 9, 2018)

 

Significance

High-latitude permafrost and peat deposits contain a large reservoir of dormant carbon that, upon warming, may partly degrade to CO2 and CH4 at site and may partly enter rivers. Given the scale and heterogeneity of the Siberian Arctic, continent-wide patterns of thaw and remobilization have been challenging to constrain. This study combines a decade-long observational record of 14C in organic carbon of four large Siberian rivers with an extensive 14C source fingerprint database into a statistical model to provide a quantitative partitioning of the fraction of fluvially mobilized organic carbon that specifically stems from permafrost and peat deposits, and separately for dissolved and particulate vectors, across the Siberian Arctic, revealing distinct spatial and seasonal system patterns in carbon remobilization.

 

Abstract

Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO2 and CH4 to directly amplify global warming, another part will enter the fluvial network, potentially providing a window to observe large-scale PP-C remobilization patterns. Here, we employ a decade-long, high-temporal resolution record of 14C in dissolved and particulate organic carbon (DOC and POC, respectively) to deconvolute PP-C release in the large drainage basins of rivers across Siberia: Ob, Yenisey, Lena, and Kolyma. The 14C-constrained estimate of export specifically from PP-C corresponds to only 17 ± 8% of total fluvial organic carbon and serves as a benchmark for monitoring changes to fluvial PP-C remobilization in a warming Arctic. Whereas DOC was dominated by recent organic carbon and poorly traced PP-C (12 ± 8%), POC carried a much stronger signature of PP-C (63 ± 10%) and represents the best window to detect spatial and temporal dynamics of PP-C release. Distinct seasonal patterns suggest that while DOC primarily stems from gradual leaching of surface soils, POC reflects abrupt collapse of deeper deposits. Higher dissolved PP-C export by Ob and Yenisey aligns with discontinuous permafrost that facilitates leaching, whereas higher particulate PP-C export by Lena and Kolyma likely echoes the thermokarst-induced collapse of Pleistocene deposits. Quantitative 14C-based fingerprinting of fluvial organic carbon thus provides an opportunity to elucidate large-scale dynamics of PP-C remobilization in response to Arctic warming.

carbon cycle – climate change – radiocarbon – peat – leaching

Keywords: Climate change; Global Warming; Permafrost; Russia.

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#Rivers across the #Siberian #Arctic unearth the #patterns of #carbon #release from thawing #permafrost (Proc Natl Acad Sci USA, abstract)

[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

Rivers across the Siberian Arctic unearth the patterns of carbon release from thawing permafrost

Birgit Wild, August Andersson, Lisa Bröder, Jorien Vonk, Gustaf Hugelius, James W. McClelland, Wenjun Song, Peter A. Raymond, and Örjan Gustafsson

PNAS first published May 6, 2019 / DOI: https://doi.org/10.1073/pnas.1811797116

Edited by Mark H. Thiemens, University of California, San Diego, La Jolla, CA, and approved March 26, 2019 (received for review July 9, 2018)

 

Significance

High-latitude permafrost and peat deposits contain a large reservoir of dormant carbon that, upon warming, may partly degrade to CO2 and CH4 at site and may partly enter rivers. Given the scale and heterogeneity of the Siberian Arctic, continent-wide patterns of thaw and remobilization have been challenging to constrain. This study combines a decade-long observational record of 14C in organic carbon of four large Siberian rivers with an extensive 14C source fingerprint database into a statistical model to provide a quantitative partitioning of the fraction of fluvially mobilized organic carbon that specifically stems from permafrost and peat deposits, and separately for dissolved and particulate vectors, across the Siberian Arctic, revealing distinct spatial and seasonal system patterns in carbon remobilization.

 

Abstract

Climate warming is expected to mobilize northern permafrost and peat organic carbon (PP-C), yet magnitudes and system specifics of even current releases are poorly constrained. While part of the PP-C will degrade at point of thaw to CO2 and CH4 to directly amplify global warming, another part will enter the fluvial network, potentially providing a window to observe large-scale PP-C remobilization patterns. Here, we employ a decade-long, high-temporal resolution record of 14C in dissolved and particulate organic carbon (DOC and POC, respectively) to deconvolute PP-C release in the large drainage basins of rivers across Siberia: Ob, Yenisey, Lena, and Kolyma. The 14C-constrained estimate of export specifically from PP-C corresponds to only 17 ± 8% of total fluvial organic carbon and serves as a benchmark for monitoring changes to fluvial PP-C remobilization in a warming Arctic. Whereas DOC was dominated by recent organic carbon and poorly traced PP-C (12 ± 8%), POC carried a much stronger signature of PP-C (63 ± 10%) and represents the best window to detect spatial and temporal dynamics of PP-C release. Distinct seasonal patterns suggest that while DOC primarily stems from gradual leaching of surface soils, POC reflects abrupt collapse of deeper deposits. Higher dissolved PP-C export by Ob and Yenisey aligns with discontinuous permafrost that facilitates leaching, whereas higher particulate PP-C export by Lena and Kolyma likely echoes the thermokarst-induced collapse of Pleistocene deposits. Quantitative 14C-based fingerprinting of fluvial organic carbon thus provides an opportunity to elucidate large-scale dynamics of PP-C remobilization in response to Arctic warming.

carbon cycle – climate change – radiocarbon – peat – leaching

Keywords: Climate Change; Global Warming; Permafrost; Russia.

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Complex #membrane remodeling during #virion assembly of the 30,000 years-old #Mollivirus sibericum (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

Complex membrane remodeling during virion assembly of the 30,000 years-old Mollivirus sibericum

E. R. Quemin, S Corroyer-Dulmont, A Baskaran, E Penard, A. D. Gazi, E Christo-Foroux, P Walther, C Abergel, J Krijnse-Locker

DOI: 10.1128/JVI.00388-19

 

ABSTRACT

Cellular membranes ensure functional compartmentalization by dynamic fusion-fission remodeling and are often targeted by viruses during entry, replication, assembly and egress. Nucleocytoplasmic large DNA viruses (NCLDVs) can recruit host-derived open membrane precursors to form their inner viral membrane. Using complementary 3D-electron microscopy techniques including focused-ion beam scanning electron microscopy and electron tomography, we show that the giant Mollivirus sibericum utilizes the same strategy but also displays unique features. Indeed, assembly is specifically triggered by an open cisterna with a flat pole in its center and open curling ends that grow by recruitment of vesicles, never reported for NCLDVs. These vesicles, abundant in the viral factory (VF), are initially closed but open once in close proximity to the open curling ends of the growing viral membrane. The flat pole appears to play a central role during the entire virus assembly process. While additional capsid layers are assembled from it, it also shapes the growing cisterna into immature crescent-like virions and is located opposite to the membrane elongation and closure sites, thereby providing virions with a polarity. In the VF, DNA-associated filaments are abundant and DNA is packed within virions, prior to particle closure. Altogether, our results highlight the complexity of the interaction between giant viruses and their host. Mollivirus assembly relies on the general strategy of vesicle recruitment, opening and shaping by capsid layers similar to all NCLDVs studied until now. However, the specific features of its assembly suggests that the molecular mechanisms for cellular membrane remodeling and persistence are unique.

 

Importance

Since the first giant virus Mimivirus was identified, other giant representatives are isolated regularly around the World and appear to be unique in several aspects. They belong to at least four viral families and the ways they interact with their hosts remain poorly understood. We focused on Mollivirus sibericum, the sole representative of “Molliviridae” which was isolated from a 30,000 years-old permafrost sample, and exhibits spherical virions of complex composition. In particular, we show that (i) assembly is initiated by a unique structure containing a flat pole positioned at the center of an open cisterna; (ii) core packing involves another cisterna-like element seemingly pushing core proteins into particles being assembled; (iii) specific filamentous structures contain the viral genome before packaging. Altogether, our findings increase our understanding on how complex giant viruses interact with their host and provide the foundation for future studies to elucidate the molecular mechanisms of Mollivirus assembly.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Mimivirus; Molliviridae; Mollivirus sibericum.

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#Permafrost #carbon: #Catalyst for #deglaciation (Nat Geosc., abstract)

[Source: Nature Geoscience, full page: (LINK). Abstract, edited.]

NATURE GEOSCIENCE | NEWS AND VIEWS

Permafrost carbon: Catalyst for deglaciation

Andrew H. MacDougall

Nature Geoscience (2016) / doi:10.1038/ngeo2802 / Published online 22 August 2016

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The sources contributing to the deglacial rise in atmospheric CO2 concentrations are unclear. Climate model simulations suggest thawing permafrost soils were the initial source, highlighting the vulnerability of modern permafrost carbon stores.

(…)

Keywords: Research; Abstracts; Permafrost; Climate Change; Global Warming.

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#Permafrost: It’s a #gas (Nat Geosc., abstract)

[Source: Nature Geoscience, full page: (LINK). Abstract, edited.]

NATURE GEOSCIENCE | NEWS AND VIEWS

Permafrost: It’s a gas

Torben R. Christensen

Nature Geoscience (2016) / doi:10.1038/ngeo2803 / Published online 22 August 2016

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Climate change is causing widespread permafrost thaw in the Arctic. Measurements at 33 Arctic lakes show that old carbon from thawing permafrost is being emitted as methane, though emission rates have not changed during the past 60 years.

(…)

Keywords: Research; Abstracts; Permafrost; Climate Change; Global Warming.

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#USGS Projects Large #Loss of #Alaska #Permafrost by 2100 (USGS, Nov. 30 ‘15)

[Source: US Geological Survey (USGS), full page: (LINK).]

USGS Projects Large Loss of Alaska Permafrost by 2100 [  ENVR   ]

Released: 11/30/2015 1:35:24 PM

Contact Information: U.S. Department of the Interior, U.S. Geological Survey, Office of Communications and Publishing, 12201 Sunrise Valley Dr, MS 119, Reston, VA 20192 / Jon Campbell, Phone: 703-648-4180 / Bruce  Wylie, Phone: 605-594-6078

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Using statistically modeled maps drawn from satellite data and other sources, U.S. Geological Survey scientists have projected that the near-surface permafrost that presently underlies 38 percent of boreal and arctic Alaska would be reduced by 16 to 24 percent by the end of the 21st century under widely accepted climate scenarios. Permafrost declines are more likely in central Alaska than northern Alaska.

Northern latitude tundra and boreal forests are experiencing an accelerated warming trend that is greater than in other parts of the world.  This warming trend degrades permafrost, defined as ground that stays below freezing for at least two consecutive years. Some of the adverse impacts of melting permafrost are changing pathways of ground and surface water, interruptions of regional transportation, and the release to the atmosphere of previously stored carbon.

“A warming climate is affecting the Arctic in the most complex ways,” said Virginia Burkett, USGS Associate Director for Climate and Land Use Change.

“Understanding the current distribution of permafrost and estimating where it is likely to disappear are key factors in predicting the future responses of northern ecosystems to climate change.”

In addition to developing maps of near-surface permafrost distributions, the researchers developed maps of maximum thaw depth, or active-layer depth, and provided uncertainty estimates. 

Future permafrost distribution probabilities, based on future climate scenarios produced by the Intergovernmental Panel on Climate Change (IPCC), were also estimated by the USGS scientists.  Widely used IPCC climate scenarios anticipate varied levels of climate mitigation action by the global community.

These future projections of permafrost distribution, however, did not include other possible future disturbances in the future, such as wildland fires. In general, the results support concerns about permafrost carbon becoming available to decomposition and greenhouse gas emission.

The research has been published in Remote Sensing of Environment.  The current near-surface permafrost map is available via ScienceBase.

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Current probability of near-surface permafrost in Alaska. Future scenarios.

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Current probability of near-surface permafrost in Alaska. Future scenarios. (High resolution image)

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Keywords: Research; USA; USGS; Updates; Permafrost; Alaska; Climate Change; Global Warming.

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