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Miesner F, Overduin PP, Grosse G, Strauss J, Langer M, Westermann S, Schneider von Deimling T, Brovkin V, Arndt S. Subsea permafrost organic carbon stocks are large and of dominantly low reactivity. Sci Rep 2023; 13:9425. [PMID: 37296305 PMCID: PMC10256719 DOI: 10.1038/s41598-023-36471-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 06/04/2023] [Indexed: 06/12/2023] Open
Abstract
Subsea permafrost carbon pools below the Arctic shelf seas are a major unknown in the global carbon cycle. We combine a numerical model of sedimentation and permafrost evolution with simplified carbon turnover to estimate accumulation and microbial decomposition of organic matter on the pan-Arctic shelf over the past four glacial cycles. We find that Arctic shelf permafrost is a globally important long-term carbon sink storing 2822 (1518-4982) Pg OC, double the amount stored in lowland permafrost. Although currently thawing, prior microbial decomposition and organic matter aging limit decomposition rates to less than 48 Tg OC/yr (25-85) constraining emissions due to thaw and suggesting that the large permafrost shelf carbon pool is largely insensitive to thaw. We identify an urgent need to reduce uncertainty in rates of microbial decomposition of organic matter in cold and saline subaquatic environments. Large emissions of methane more likely derive from older and deeper sources than from organic matter in thawing permafrost.
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Affiliation(s)
- F Miesner
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany.
| | - P P Overduin
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - G Grosse
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
- Institute of Geosciences, University of Potsdam, Potsdam, Germany
| | - J Strauss
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
| | - M Langer
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
- Department of Earth Sciences, Faculty of Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - S Westermann
- Department of Geosciences, University of Oslo, Oslo, Norway
- Center for Biogeochemistry in the Anthropocene, University of Oslo, Oslo, Norway
| | | | - V Brovkin
- Max Planck Institute for Meteorology, Hamburg, Germany
- CEN, University of Hamburg, Hamburg, Germany
| | - S Arndt
- BGeoSys, Department of Geosciences, Environment and Society, Université libre de Bruxelles, Brussels, Belgium
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Organic matter composition and greenhouse gas production of thawing subsea permafrost in the Laptev Sea. Nat Commun 2022; 13:5057. [PMID: 36030269 PMCID: PMC9420143 DOI: 10.1038/s41467-022-32696-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 08/10/2022] [Indexed: 11/29/2022] Open
Abstract
Subsea permafrost represents a large carbon pool that might be or become a significant greenhouse gas source. Scarcity of observational data causes large uncertainties. We here use five 21-56 m long subsea permafrost cores from the Laptev Sea to constrain organic carbon (OC) storage and sources, degradation state and potential greenhouse gas production upon thaw. Grain sizes, optically-stimulated luminescence and biomarkers suggest deposition of aeolian silt and fluvial sand over 160 000 years, with dominant fluvial/alluvial deposition of forest- and tundra-derived organic matter. We estimate an annual thaw rate of 1.3 ± 0.6 kg OC m−2 in subsea permafrost in the area, nine-fold exceeding organic carbon thaw rates for terrestrial permafrost. During 20-month incubations, CH4 and CO2 production averaged 1.7 nmol and 2.4 µmol g−1 OC d−1, providing a baseline to assess the contribution of subsea permafrost to the high CH4 fluxes and strong ocean acidification observed in the region. Subsea permafrost underneath the Arctic Ocean is one of the least understood compartments of the global carbon cycle. Here, Wild et al. shed light on its carbon sources, degradation history and potential greenhouse gas release after thaw.
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Authigenic Gypsum Precipitation in the ARAON Mounds, East Siberian Sea. MINERALS 2022. [DOI: 10.3390/min12080983] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Authigenic gypsum has been observed in marine methane hydrate-bearing sediments throughout the last decade. However, changes in mineral composition and gypsum precipitation in methane emission environments have not yet been reported in the Arctic. Expeditions aboard R/V ARAON revealed several mound structures described as active seeps, which were given the name ARAON Mounds (AMs). Core sediments from the AMs provide an excellent opportunity to research authigenic mineral production in the Arctic methane environment. We identified sedimentary units and investigated the mineral composition of gravity cores from the AMs and a background site. The background core ARA09C-St13, obtained between the mound structures, contains five sedimentary units that extend from the Chukchi Rise to Chukchi Basin, and core sediments from the AMs contain three sedimentary units in the same order. The fundamental difference between AMs and the background site is the lack of dolomite and abundance of gypsum in AMs. This gypsum precipitated authigenically in situ based on its morphological features. Precipitation was more closely associated with the absence of dolomite than the location of the sulfate–methane transition according to the vertical distribution of gypsum in the sediment. Chemical weathering and gypsum overgrowth were confirmed on dolomite surfaces recovered from the AMs, suggesting that dolomite dissolution is the primary source of Ca for gypsum precipitation. Dissolution of biological carbonates and ion exclusion may provide Ca for gypsum precipitation, but this mechanism appears to be secondary, as gypsum is present only in sedimentary units containing dolomite. The main sources of sulfate were inferred to be oxidation of H2S and disproportionation of sulfide, as no sulfide other than gypsum was observed. Our findings reveal that gypsum precipitation linked to methane emission in the Arctic Ocean occurs mainly in dolomite-rich sediments, suggesting that gypsum is a suitable proxy for identifying methane hydrate zones in the Arctic Ocean.
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Ship-Borne Observations of Atmospheric CH4 and δ13C Isotope Signature in Methane over Arctic Seas in Summer and Autumn 2021. ATMOSPHERE 2022. [DOI: 10.3390/atmos13030458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Determining the sources of methane emissions in the Arctic remains a complex problem, due to their heterogeneity and diversity. Information on the amount of emissions has significant uncertainties and may differ by an order of magnitude in various literature sources. Measurements made in the immediate vicinity of emission sources help to clarify emissions and reduce these uncertainties. This paper analyzes the data of three expeditions, carried out in the western Arctic seas during Arctic spring, summer, and early autumn in 2021, which obtained continuous data on the concentration of methane and its isotope signature δ13C. CH4 concentrations and δ13C displayed temporal and spatial variations ranging from 1.952 to 2.694 ppm and from −54.7‰ to −40.9‰, respectively. A clear correlation was revealed between the surface methane concentration and the direction of air flow during the measurement period. At the same time, even with advection from areas with a significant anthropogenic burden or from locations of natural gas mining and transportation, we cannot identify particular source of emissions; there is a dilution or mixing of gas from different sources. Our results indicate footprints of methane sources from wetlands, freshwater sources, shelf sediments, and even hydrates.
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Model Study of the Effects of Climate Change on the Methane Emissions on the Arctic Shelves. ATMOSPHERE 2022. [DOI: 10.3390/atmos13020274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Based on a regional ice-ocean model, we simulated the state of the water masses of the Arctic Ocean to analyze the transport of dissolved methane on the Arctic shelves. From 1970 to 2019, we obtained estimates of methane emissions at the Arctic seas due to the degradation of submarine permafrost and gas release at the ocean–bottom interface. The calculated annual methane flux from the Arctic shelf seas into the atmosphere did not exceed 2 Tg CH4 year−1. We have shown that the East Siberian shelf seas make the main contribution to the total methane emissions of the region. The spatial variability of the methane fluxes into the atmosphere is primarily due to the peculiarities of the water circulation and ice conditions. Only 7% of the dissolved methane originating from sediment enters the atmosphere within the study area. Most of it appears to be transported below the surface and oxidized by microbial activity. We found that increasing periods and areas of ice-free water and decreasing ice concentration have contributed to a steady increase in methane emissions since the middle of the first decade of the current century.
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Rees AP, Bange HW, Arévalo-Martínez DL, Artioli Y, Ashby DM, Brown I, Campen HI, Clark DR, Kitidis V, Lessin G, Tarran GA, Turley C. Nitrous oxide and methane in a changing Arctic Ocean. AMBIO 2022; 51:398-410. [PMID: 34628596 PMCID: PMC8692636 DOI: 10.1007/s13280-021-01633-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 08/13/2021] [Accepted: 09/15/2021] [Indexed: 05/25/2023]
Abstract
Human activities are changing the Arctic environment at an unprecedented rate resulting in rapid warming, freshening, sea ice retreat and ocean acidification of the Arctic Ocean. Trace gases such as nitrous oxide (N2O) and methane (CH4) play important roles in both the atmospheric reactivity and radiative budget of the Arctic and thus have a high potential to influence the region's climate. However, little is known about how these rapid physical and chemical changes will impact the emissions of major climate-relevant trace gases from the Arctic Ocean. The combined consequences of these stressors present a complex combination of environmental changes which might impact on trace gas production and their subsequent release to the Arctic atmosphere. Here we present our current understanding of nitrous oxide and methane cycling in the Arctic Ocean and its relevance for regional and global atmosphere and climate and offer our thoughts on how this might change over coming decades.
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Affiliation(s)
- Andrew P. Rees
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Hermann W. Bange
- GEOMAR Helmholtz-Zentrum Für Ozeanforschung Kiel, Chemische Ozeanographie, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Damian L. Arévalo-Martínez
- GEOMAR Helmholtz-Zentrum Für Ozeanforschung Kiel, Chemische Ozeanographie, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Yuri Artioli
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Dawn M. Ashby
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Ian Brown
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Hanna I. Campen
- GEOMAR Helmholtz-Zentrum Für Ozeanforschung Kiel, Chemische Ozeanographie, Düsternbrooker Weg 20, 24105 Kiel, Germany
| | - Darren R. Clark
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Vassilis Kitidis
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Gennadi Lessin
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Glen A. Tarran
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
| | - Carol Turley
- Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth, PL1 3DH UK
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Mann PJ, Strauss J, Palmtag J, Dowdy K, Ogneva O, Fuchs M, Bedington M, Torres R, Polimene L, Overduin P, Mollenhauer G, Grosse G, Rachold V, Sobczak WV, Spencer RGM, Juhls B. Degrading permafrost river catchments and their impact on Arctic Ocean nearshore processes. AMBIO 2022; 51:439-455. [PMID: 34850356 PMCID: PMC8692538 DOI: 10.1007/s13280-021-01666-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2021] [Revised: 10/15/2021] [Accepted: 11/01/2021] [Indexed: 05/25/2023]
Abstract
Arctic warming is causing ancient perennially frozen ground (permafrost) to thaw, resulting in ground collapse, and reshaping of landscapes. This threatens Arctic peoples' infrastructure, cultural sites, and land-based natural resources. Terrestrial permafrost thaw and ongoing intensification of hydrological cycles also enhance the amount and alter the type of organic carbon (OC) delivered from land to Arctic nearshore environments. These changes may affect coastal processes, food web dynamics and marine resources on which many traditional ways of life rely. Here, we examine how future projected increases in runoff and permafrost thaw from two permafrost-dominated Siberian watersheds-the Kolyma and Lena, may alter carbon turnover rates and OC distributions through river networks. We demonstrate that the unique composition of terrestrial permafrost-derived OC can cause significant increases to aquatic carbon degradation rates (20 to 60% faster rates with 1% permafrost OC). We compile results on aquatic OC degradation and examine how strengthening Arctic hydrological cycles may increase the connectivity between terrestrial landscapes and receiving nearshore ecosystems, with potential ramifications for coastal carbon budgets and ecosystem structure. To address the future challenges Arctic coastal communities will face, we argue that it will become essential to consider how nearshore ecosystems will respond to changing coastal inputs and identify how these may affect the resiliency and availability of essential food resources.
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Affiliation(s)
- Paul J. Mann
- Dept of Geography & Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST UK
| | - Jens Strauss
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
| | - Juri Palmtag
- Dept of Geography & Environmental Sciences, Northumbria University, Newcastle upon Tyne, NE1 8ST UK
| | - Kelsey Dowdy
- University of California, Santa Barbara, UCEN Rd, Goleta, CA 93117 USA
| | - Olga Ogneva
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Matthias Fuchs
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
| | | | - Ricardo Torres
- Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH UK
| | - Luca Polimene
- Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH UK
| | - Paul Overduin
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
| | - Gesine Mollenhauer
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Guido Grosse
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
- Institute of Geosciences, University of Potsdam, Potsdam, Germany
| | - Volker Rachold
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
| | - William V. Sobczak
- Department of Biology, College of the Holy Cross, 1 College St, Worcester, MA 01610 USA
| | | | - Bennet Juhls
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
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8
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Distinct methane-dependent biogeochemical states in Arctic seafloor gas hydrate mounds. Nat Commun 2021; 12:6296. [PMID: 34728618 PMCID: PMC8563959 DOI: 10.1038/s41467-021-26549-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 09/27/2021] [Indexed: 01/04/2023] Open
Abstract
Archaea mediating anaerobic methane oxidation are key in preventing methane produced in marine sediments from reaching the hydrosphere; however, a complete understanding of how microbial communities in natural settings respond to changes in the flux of methane remains largely uncharacterized. We investigate microbial communities in gas hydrate-bearing seafloor mounds at Storfjordrenna, offshore Svalbard in the high Arctic, where we identify distinct methane concentration profiles that include steady-state, recently-increasing subsurface diffusive flux, and active gas seepage. Populations of anaerobic methanotrophs and sulfate-reducing bacteria were highest at the seep site, while decreased community diversity was associated with a recent increase in methane influx. Despite high methane fluxes and methanotroph doubling times estimated at 5-9 months, microbial community responses were largely synchronous with the advancement of methane into shallower sediment horizons. Together, these provide a framework for interpreting subseafloor microbial responses to methane escape in a warming Arctic Ocean.
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9
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Source apportionment of methane escaping the subsea permafrost system in the outer Eurasian Arctic Shelf. Proc Natl Acad Sci U S A 2021; 118:2019672118. [PMID: 33649226 PMCID: PMC7958249 DOI: 10.1073/pnas.2019672118] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Extensive release of methane from sediments of the world’s largest continental shelf, the East Siberian Arctic Ocean (ESAO), is one of the few Earth system processes that can cause a net transfer of carbon from land/ocean to the atmosphere and thus amplify global warming on the timescale of this century. An important gap in our current knowledge concerns the contributions of different subsea pools to the observed methane releases. This knowledge is a prerequisite to robust predictions on how these releases will develop in the future. Triple-isotope–based fingerprinting of the origin of the highly elevated ESAO methane levels points to a limited contribution from shallow microbial sources and instead a dominating contribution from a deep thermogenic pool. The East Siberian Arctic Shelf holds large amounts of inundated carbon and methane (CH4). Holocene warming by overlying seawater, recently fortified by anthropogenic warming, has caused thawing of the underlying subsea permafrost. Despite extensive observations of elevated seawater CH4 in the past decades, relative contributions from different subsea compartments such as early diagenesis, subsea permafrost, methane hydrates, and underlying thermogenic/ free gas to these methane releases remain elusive. Dissolved methane concentrations observed in the Laptev Sea ranged from 3 to 1,500 nM (median 151 nM; oversaturation by ∼3,800%). Methane stable isotopic composition showed strong vertical and horizontal gradients with source signatures for two seepage areas of δ13C-CH4 = (−42.6 ± 0.5)/(−55.0 ± 0.5) ‰ and δD-CH4 = (−136.8 ± 8.0)/(−158.1 ± 5.5) ‰, suggesting a thermogenic/natural gas source. Increasingly enriched δ13C-CH4 and δD-CH4 at distance from the seeps indicated methane oxidation. The Δ14C-CH4 signal was strongly depleted (i.e., old) near the seeps (−993 ± 19/−1050 ± 89‰). Hence, all three isotope systems are consistent with methane release from an old, deep, and likely thermogenic pool to the outer Laptev Sea. This knowledge of what subsea sources are contributing to the observed methane release is a prerequisite to predictions on how these emissions will increase over coming decades and centuries.
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Chen M, Kim JH, Lee YK, Lee DH, Jin YK, Hur J. Subsea permafrost as a potential major source of dissolved organic matter to the East Siberian Arctic Shelf. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 777:146100. [PMID: 33684745 DOI: 10.1016/j.scitotenv.2021.146100] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 02/20/2021] [Accepted: 02/21/2021] [Indexed: 06/12/2023]
Abstract
Arctic subsea permafrost contains more organic carbon than the terrestrial counterpart (~1400 Pg C vs. ~1000 Pg C) and is undergoing fast degradation (at rates of ~10 to 30 cm yr-1 over the past 3 decades) in response to climate warming. Yet the flux of organic carbon sequestered in the sediments of subsea permafrost to overlying water column, which can trigger enormous positive carbon-climate feedbacks, remain unclear. In this study, we examined the dissolved organic matter (DOM) diffusion to bottom seawaters from East Siberian Sea (ESS) sediments, which was estimated at about 943-2240 g C m-2 yr-1 and 10-55 g C m-2 yr-1 at the continuous-discontinuous transition zone of subsea permafrost and the remainder shelf and slope sites, respectively. The released DOM is characterized by prevailing dominance (≥ 98%) of low molecular weight (Mn < 350 Da) fractions. A red-shifted (emission wavelength >500 nm) fluorescence fingerprint, a typical feature of sediment/soil DOM, accounts for 4-6% and 7-8% in the fluorescence distributions of seawaters and pore waters, respectively, on ESS shelf. Statistical analysis revealed that seawaters and pore waters possessed similar DOM composition. The estimated total benthic efflux of dissolved organic carbon (DOC) was ~0.7-1.0 Pg C yr-1 when the estimate was scaled up to the entire Arctic shelf underlain with subsea permafrost assuming the width of continuous-discontinuous transition zone is 1 to 10 m. This estimation is consistent with the established ~10-30 cm yr-1 degradation rates of subsea permafrost by estimating its thaw-out time. Compiled observation data suggested that subsea permafrost might be a major DOM source to the Arctic Ocean, which could release tremendous carbon upon remineralization via its degradation to CO2 and CH4 in the water column.
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Affiliation(s)
- Meilian Chen
- Environmental Program, Guangdong Technion - Israel Institute of Technology, Shantou 515063, China.
| | - Ji-Hoon Kim
- Petroleum and Marine Research Division, Korea Institute of Geoscience and Mineral Resources, 124 Gwahak-ro, Yuseong-gu, Daejeon 34132, South Korea
| | - Yun Kyung Lee
- Department of Environment & Energy, Sejong University, Seoul 05006, South Korea
| | - Dong-Hun Lee
- Hanyang University ERICA Campus, 15588 Ansan, South Korea; Marine Environment Research Division, National Institute of Fisheries Science, 216, Gijanghaean-ro, Gijang-eup, Busan 46083, South Korea
| | - Young Keun Jin
- Korea Polar Research Institute (KOPRI), Incheon 21990, South Korea
| | - Jin Hur
- Department of Environment & Energy, Sejong University, Seoul 05006, South Korea.
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11
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Ocean-Bottom Seismographs Based on Broadband MET Sensors: Architecture and Deployment Case Study in the Arctic. SENSORS 2021; 21:s21123979. [PMID: 34207695 PMCID: PMC8228194 DOI: 10.3390/s21123979] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 06/02/2021] [Accepted: 06/02/2021] [Indexed: 11/21/2022]
Abstract
The Arctic seas are now of particular interest due to their prospects in terms of hydrocarbon extraction, development of marine transport routes, etc. Thus, various geohazards, including those related to seismicity, require detailed studies, especially by instrumental methods. This paper is devoted to the ocean-bottom seismographs (OBS) based on broadband molecular–electronic transfer (MET) sensors and a deployment case study in the Laptev Sea. The purpose of the study is to introduce the architecture of several modifications of OBS and to demonstrate their applicability in solving different tasks in the framework of seismic hazard assessment for the Arctic seas. To do this, we used the first results of several pilot deployments of the OBS developed by Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) and IP Ilyinskiy A.D. in the Laptev Sea that took place in 2018–2020. We highlighted various seismological applications of OBS based on broadband MET sensors CME-4311 (60 s) and CME-4111 (120 s), including the analysis of ambient seismic noise, registering the signals of large remote earthquakes and weak local microearthquakes, and the instrumental approach of the site response assessment. The main characteristics of the broadband MET sensors and OBS architectures turned out to be suitable for obtaining high-quality OBS records under the Arctic conditions to solve seismological problems. In addition, the obtained case study results showed the prospects in a broader context, such as the possible influence of the seismotectonic factor on the bottom-up thawing of subsea permafrost and massive methane release, probably from decaying hydrates and deep geological sources. The described OBS will be actively used in further Arctic expeditions.
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12
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Cramm MA, Neves BDM, Manning CCM, Oldenburg TBP, Archambault P, Chakraborty A, Cyr-Parent A, Edinger EN, Jaggi A, Mort A, Tortell P, Hubert CRJ. Characterization of marine microbial communities around an Arctic seabed hydrocarbon seep at Scott Inlet, Baffin Bay. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 762:143961. [PMID: 33373752 DOI: 10.1016/j.scitotenv.2020.143961] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Revised: 11/13/2020] [Accepted: 11/15/2020] [Indexed: 06/12/2023]
Abstract
Seabed hydrocarbon seeps present natural laboratories for investigating responses of marine ecosystems to petroleum input. A hydrocarbon seep near Scott Inlet, Baffin Bay, was visited for in situ observations and sampling in the summer of 2018. Video evidence of an active hydrocarbon seep was confirmed by methane and hydrocarbon analysis of the overlying water column, which is 260 m at this site. Elevated methane concentrations in bottom water above and down current from the seep decreased to background seawater levels in the mid-water column >150 m above the seafloor. Seafloor microbial mats morphologically resembling sulfide-oxidizing bacteria surrounded areas of bubble ebullition. Calcareous tube worms, brittle stars, shrimp, sponges, sea stars, sea anemones, sea urchins, small fish and soft corals were observed near the seep, with soft corals showing evidence for hydrocarbon incorporation. Sediment microbial communities included putative methane-oxidizing Methyloprofundus, sulfate-reducing Desulfobulbaceae and sulfide-oxidizing Sulfurovum. A metabolic gene diagnostic for aerobic methanotrophs (pmoA) was detected in the sediment and bottom water above the seep epicentre and up to 5 km away. Both 16S rRNA gene and pmoA amplicon sequencing revealed that pelagic microbial communities oriented along the geologic basement rise associated with methane seepage (running SW to NE) differed from communities in off-axis water up to 5 km away. Relative abundances of aerobic methanotrophs and putative hydrocarbon-degrading bacteria were elevated in the bottom water down current from the seep. Detection of bacterial clades typically associated with hydrocarbon and methane oxidation highlights the importance of Arctic marine microbial communities in mitigating hydrocarbon emissions from natural geologic sources.
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Affiliation(s)
- Margaret A Cramm
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada.
| | - Bárbara de Moura Neves
- Fisheries and Oceans Canada, Ecological Sciences Section, 80 East White Hills Road, P.O. Box 5667, St. John's, Newfoundland A1C 5X1, Canada
| | - Cara C M Manning
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Thomas B P Oldenburg
- Department of Geoscience, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada
| | - Philippe Archambault
- ArcticNet, Québec Océan, Takuvik Département de Biologie, Université Laval, Québec G1V 0A6, Canada
| | - Anirban Chakraborty
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada
| | - Annie Cyr-Parent
- Department of Economic Development and Transportation, Government of Nunavut, Building 1104A, Inuksugait Plaza, PO Box 1000, Station 1500, Iqaluit, NU X0A 0H0, Canada
| | - Evan N Edinger
- Memorial University of Newfoundland, 230 Elizabeth Avenue, St. John's, Newfoundland A1C 5S7, Canada
| | - Aprami Jaggi
- Department of Geoscience, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada
| | - Andrew Mort
- Natural Resources Canada, 3303 33 Street NW, Calgary, Alberta T2L 2A7, Canada
| | - Philippe Tortell
- Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Casey R J Hubert
- Geomicrobiology Group, Department of Biological Sciences, University of Calgary, 2500 University Dr NW, Calgary, Alberta T2N 1N4, Canada
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Argentino C, Waghorn KA, Vadakkepuliyambatta S, Polteau S, Bünz S, Panieri G. Dynamic and history of methane seepage in the SW Barents Sea: new insights from Leirdjupet Fault Complex. Sci Rep 2021; 11:4373. [PMID: 33623088 PMCID: PMC7902819 DOI: 10.1038/s41598-021-83542-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 02/03/2021] [Indexed: 01/31/2023] Open
Abstract
Methane emissions from Arctic continental margins are increasing due to the negative effect of global warming on ice sheet and permafrost stability, but dynamics and timescales of seafloor seepage still remain poorly constrained. Here, we examine sediment cores collected from an active seepage area located between 295 and 353 m water depth in the SW Barents Sea, at Leirdjupet Fault Complex. The geochemical composition of hydrocarbon gas in the sediment indicates a mixture of microbial and thermogenic gas, the latter being sourced from underlying Mesozoic formations. Sediment and carbonate geochemistry reveal a long history of methane emissions that started during Late Weichselian deglaciation after 14.5 cal ka BP. Methane-derived authigenic carbonates precipitated due to local gas hydrate destabilization, in turn triggered by an increasing influx of warm Atlantic water and isostatic rebound linked to the retreat of the Barents Sea Ice Sheet. This study has implications for a better understanding of the dynamic and future evolution of methane seeps in modern analogue systems in Western Antarctica, where the retreat of marine-based ice sheet induced by global warming may cause the release of large amounts of methane from hydrocarbon reservoirs and gas hydrates.
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Affiliation(s)
- Claudio Argentino
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway.
| | - Kate Alyse Waghorn
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
| | - Sunil Vadakkepuliyambatta
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
| | - Stéphane Polteau
- Oslo Innovation Center, VBPR - Volcanic Basin Petroleum Research, 0349, Oslo, Norway
- Institute for Energy Technology, 2007, Kjeller, Norway
- SurfExGeo, 0776, Oslo, Norway
| | - Stefan Bünz
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
| | - Giuliana Panieri
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
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14
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New Catastrophic Gas Blowout and Giant Crater on the Yamal Peninsula in 2020: Results of the Expedition and Data Processing. GEOSCIENCES 2021. [DOI: 10.3390/geosciences11020071] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This article describes the results of an Arctic expedition studying the new giant gas blowout crater in the north of Western Siberia, in the central part of the Yamal Peninsula in 2020. It was named C17 in the geoinformation system “Arctic and the World Ocean” created by the Oil and Gas Research Institute of the Russian Academy of Sciences (OGRI RAS). On the basis of remote sensing, it can be seen that the formation of the crater C17 was preceded by a long-term growth of the perennial heaving mound (PHM) on the surface of the third marine terrace. Based on the interpretation of satellite images, it was substantiated that the crater C17 was formed in the period 15 May–9 June 2020. For the first time, as a result of aerial photography from inside the crater with a UAV, a 3D model of the crater and a giant cavity in the ground ice, formed during its thawing from below, was built. The accumulation of gas, the pressure rise and the development of gas-dynamic processes in the cavity led to the growth of the PHM, and the explosion and formation of the crater.
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15
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Crustal fingering facilitates free-gas methane migration through the hydrate stability zone. Proc Natl Acad Sci U S A 2020; 117:31660-31664. [PMID: 33257583 DOI: 10.1073/pnas.2011064117] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Widespread seafloor methane venting has been reported in many regions of the world oceans in the past decade. Identifying and quantifying where and how much methane is being released into the ocean remains a major challenge and a critical gap in assessing the global carbon budget and predicting future climate [C. Ruppel, J. D. Kessler. Rev. Geophys. 55, 126-168 (2017)]. Methane hydrate ([Formula: see text]) is an ice-like solid that forms from methane-water mixture under elevated-pressure and low-temperature conditions typical of the deep marine settings (>600-m depth), often referred to as the hydrate stability zone (HSZ). Wide-ranging field evidence indicates that methane seepage often coexists with hydrate-bearing sediments within the HSZ, suggesting that hydrate formation may play an important role during the gas-migration process. At a depth that is too shallow for hydrate formation, existing theories suggest that gas migration occurs via capillary invasion and/or initiation and propagation of fractures (Fig. 1). Within the HSZ, however, a theoretical mechanism that addresses the way in which hydrate formation participates in the gas-percolation process is missing. Here, we study, experimentally and computationally, the mechanics of gas percolation under hydrate-forming conditions. We uncover a phenomenon-crustal fingering-and demonstrate how it may control methane-gas migration in ocean sediments within the HSZ.
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16
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Park H, Watanabe E, Kim Y, Polyakov I, Oshima K, Zhang X, Kimball JS, Yang D. Increasing riverine heat influx triggers Arctic sea ice decline and oceanic and atmospheric warming. SCIENCE ADVANCES 2020; 6:6/45/eabc4699. [PMID: 33158866 PMCID: PMC7673719 DOI: 10.1126/sciadv.abc4699] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2020] [Accepted: 09/15/2020] [Indexed: 06/11/2023]
Abstract
Arctic river discharge increased over the last several decades, conveying heat and freshwater into the Arctic Ocean and likely affecting regional sea ice and the ocean heat budget. However, until now, there have been only limited assessments of riverine heat impacts. Here, we adopted a synthesis of a pan-Arctic sea ice-ocean model and a land surface model to quantify impacts of river heat on the Arctic sea ice and ocean heat budget. We show that river heat contributed up to 10% of the regional sea ice reduction over the Arctic shelves from 1980 to 2015. Particularly notable, this effect occurs as earlier sea ice breakup in late spring and early summer. The increasing ice-free area in the shelf seas results in a warmer ocean in summer, enhancing ocean-atmosphere energy exchange and atmospheric warming. Our findings suggest that a positive river heat-sea ice feedback nearly doubles the river heat effect.
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Affiliation(s)
- Hotaek Park
- Institute of Arctic Climate and Environmental Research, JAMSTEC, Yokosuka, Japan.
- Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan
| | - Eiji Watanabe
- Institute of Arctic Climate and Environmental Research, JAMSTEC, Yokosuka, Japan
| | - Youngwook Kim
- Numerical Terradynamic Simulation Group, WA Franke College of Forestry and Conservation, The University of Montana, Missoula, MT 59812, USA
- Department of Biology, College of Science United Arab Emirates University P.O. Box 15551, Al Ain, United Arab Emirates
| | - Igor Polyakov
- International Arctic Research Center and College of Natural Science and Mathematics, University of Alaska Fairbanks, 930 Koyukuk Drive, Fairbanks, AK, 99775, USA
- Finnish Meteorological Institute, Erik Palménin aukio 1, Helsinki, Finland
| | - Kazuhiro Oshima
- Faculty of Software and Information Technology, Aomori University, Aomori, Japan
| | - Xiangdong Zhang
- International Arctic Research Center and Department of Atmospheric Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
| | - John S Kimball
- Numerical Terradynamic Simulation Group, WA Franke College of Forestry and Conservation, The University of Montana, Missoula, MT 59812, USA
| | - Daqing Yang
- Environment and Climate Change Canada, Victoria, Canada
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17
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The Formation of Authigenic Carbonates at a Methane Seep Site in the Northern Part of the Laptev Sea. MINERALS 2020. [DOI: 10.3390/min10110948] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Authigenic carbonates from cold seeps are unique archives for studying environmental conditions, including biogeochemical processes associated with methane-rich fluid migration through the sediment column. The aim of this research was to study major oxide, mineralogical, and stable isotopic compositions of cold-seep authigenic carbonates collected in the northern part of the Laptev Sea. These carbonates are represented by Mg-calcite with an Mg content of 2% to 8%. The δ13C values range from −27.5‰ to −28.2‰ Vienna Peedee belemnite (VPDB) and indicate that carbonates formed due to anaerobic oxidation of methane, most likely thermogenic in origin. The authigenic pyrite in Mg-calcite is evidence of sulfate reduction during carbonate precipitation. The δ18O values of carbonates vary from 3.5‰ to 3.8‰ VPDB. The calculated δ18Ofluid values show that pore water temperature for precipitated Mg-calcite was comparable to bottom seawater temperature. The presence of authigenic carbonate in the upper horizons of sediments suggests that the sulfate–methane transition zone is shallowly below the sediment–water interface.
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18
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Abstract
The active emission of gas (mainly methane) from terrestrial and subsea permafrost in the Russian Arctic has been confirmed by ample evidence. In this paper, a generalization and some systematization of gas manifestations recorded in the Russian Arctic is carried out. The published data on most typical gas emission cases have been summarized in a table and illustrated by a map. The tabulated data include location, signatures, and possible sources of each gas show, with respective references. All events of onshore and shelf gas release are divided into natural and man-caused. and the natural ones are further classified as venting from lakes or explosive emissions in dryland conditions that produce craters on the surface. Among natural gas shows on land, special attention is paid to the emission of natural gas from Arctic lakes, as well as gas emissions with craters formation. In addition, a description of the observed man-caused gas manifestations associated with the drilling of geotechnical and production wells in the Arctic region is given. The reported evidence demonstrates the effect of permafrost degradation on gas release, especially in oil and gas fields.
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19
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Sigurðardóttir A, Barnard J, Bullamore D, McCormick A, Cartwright J, Cardoso S. Radial spreading of turbulent bubble plumes. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2020; 378:20190513. [PMID: 32762428 PMCID: PMC7422869 DOI: 10.1098/rsta.2019.0513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/11/2020] [Indexed: 06/11/2023]
Abstract
Weak bubble plumes carry liquid from the environment upwards and release it at multiple intermediate levels in the form of radial intrusive currents. In this study, laboratory experiments are performed to explore the spreading of turbulent axisymmetric bubble plumes in a liquid with linear density stratification. The thickness, volumetric flowrate and spreading rates of multiple radial intrusions of plume fluid were measured by tracking the movement of dye injected at the source of bubbles. The experimental results are compared with scaling predictions. Our findings suggest that the presence of multiple intrusions reduces their spreading rate, compared to that of a single intrusion. This work is of relevance to the spreading of methane plumes issuing from the seabed in the Arctic Ocean, above methane-hydrate deposits. The slower, multiple spreading favours the presence of methane-rich seawater close to the plume, which may reduce the dissolution of methane in the bubbles, and thus promote the direct transport of methane to the atmosphere. This article is part of the theme issue 'Stokes at 200 (part 2)'.
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Affiliation(s)
- Arna Sigurðardóttir
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
| | - Jonathan Barnard
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
| | - Danielle Bullamore
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
| | - Amy McCormick
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
| | - Julyan Cartwright
- Instituto Andaluz de Ciencias de la Tierra, CSIC–Universidad de Granada, 18100 Armilla, Granada, Spain
- Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, 18071 Granada, Spain
| | - Silvana Cardoso
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, UK
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20
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Alvarez J, Yumashev D, Whiteman G. A framework for assessing the economic impacts of Arctic change. AMBIO 2020; 49:407-418. [PMID: 31236784 PMCID: PMC6965338 DOI: 10.1007/s13280-019-01211-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 05/20/2019] [Accepted: 06/03/2019] [Indexed: 05/29/2023]
Abstract
The scientific literature on physical changes in the Arctic region driven by climate change is extensive. In addition, the emerging understanding of physical feedbacks and teleconnections between the Arctic and the rest of the world suggests that the warming in the Arctic region is likely to cause impacts that extend well beyond the region itself. However, there is only limited research on how Arctic change may affect economies and individual industry sectors around the world. We argue that there is a pressing need for more research on this topic and present a conceptual framework to guide future research for assessing the regional and global economic impacts of Arctic change, including both possible benefits and costs. We stress on the importance of a transdisciplinary approach, which includes an integration of the natural sciences, economics and social sciences, as well as engagement with a wide range of stakeholders to better understand and manage the implications of Arctic change.
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Affiliation(s)
- Jimena Alvarez
- Pentland Centre for Sustainability in Business, Lancaster University, Lancaster, LA1 4YX UK
- Salguero 3055, 1425, Ciudad Autónoma de Buenos Aires, Buenos Aires, Argentina
| | - Dmitry Yumashev
- Pentland Centre for Sustainability in Business, Lancaster University, Lancaster, LA1 4YX UK
| | - Gail Whiteman
- Pentland Centre for Sustainability in Business, Lancaster University, Lancaster, LA1 4YX UK
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21
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Thornton BF, Prytherch J, Andersson K, Brooks IM, Salisbury D, Tjernström M, Crill PM. Shipborne eddy covariance observations of methane fluxes constrain Arctic sea emissions. SCIENCE ADVANCES 2020; 6:eaay7934. [PMID: 32064354 PMCID: PMC6989137 DOI: 10.1126/sciadv.aay7934] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Accepted: 11/22/2019] [Indexed: 05/20/2023]
Abstract
We demonstrate direct eddy covariance (EC) observations of methane (CH4) fluxes between the sea and atmosphere from an icebreaker in the eastern Arctic Ocean. EC-derived CH4 emissions averaged 4.58, 1.74, and 0.14 mg m-2 day-1 in the Laptev, East Siberian, and Chukchi seas, respectively, corresponding to annual sea-wide fluxes of 0.83, 0.62, and 0.03 Tg year-1. These EC results answer concerns that previous diffusive emission estimates, which excluded bubbling, may underestimate total emissions. We assert that bubbling dominates sea-air CH4 fluxes in only small constrained areas: A ~100-m2 area of the East Siberian Sea showed sea-air CH4 fluxes exceeding 600 mg m-2 day-1; in a similarly sized area of the Laptev Sea, peak CH4 fluxes were ~170 mg m-2 day-1. Calculating additional emissions below the noise level of our EC system suggests total ESAS CH4 emissions of 3.02 Tg year-1, closely matching an earlier diffusive emission estimate of 2.9 Tg year-1.
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Affiliation(s)
- Brett F. Thornton
- Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden
- Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
| | - John Prytherch
- Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
- Department of Meteorology, Stockholm University, 106 91 Stockholm, Sweden
| | - Kristian Andersson
- Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden
| | - Ian M. Brooks
- School of Earth and Environment, University of Leeds, Leeds, UK
| | | | - Michael Tjernström
- Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
- Department of Meteorology, Stockholm University, 106 91 Stockholm, Sweden
| | - Patrick M. Crill
- Department of Geological Sciences, Stockholm University, 106 91 Stockholm, Sweden
- Bolin Centre for Climate Research, Stockholm University, 106 91 Stockholm, Sweden
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22
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Weber T, Wiseman NA, Kock A. Global ocean methane emissions dominated by shallow coastal waters. Nat Commun 2019; 10:4584. [PMID: 31594924 PMCID: PMC6783430 DOI: 10.1038/s41467-019-12541-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Accepted: 09/17/2019] [Indexed: 11/23/2022] Open
Abstract
Oceanic emissions represent a highly uncertain term in the natural atmospheric methane (CH4) budget, due to the sparse sampling of dissolved CH4 in the marine environment. Here we overcome this limitation by training machine-learning models to map the surface distribution of methane disequilibrium (∆CH4). Our approach yields a global diffusive CH4 flux of 2–6TgCH4yr−1 from the ocean to the atmosphere, after propagating uncertainties in ∆CH4 and gas transfer velocity. Combined with constraints on bubble-driven ebullitive fluxes, we place total oceanic CH4 emissions between 6–12TgCH4yr−1, narrowing the range adopted by recent atmospheric budgets (5–25TgCH4yr−1) by a factor of three. The global flux is dominated by shallow near-shore environments, where CH4 released from the seafloor can escape to the atmosphere before oxidation. In the open ocean, our models reveal a significant relationship between ∆CH4 and primary production that is consistent with hypothesized pathways of in situ methane production during organic matter cycling. The ocean emits the greenhouse gas methane, but its vastness renders estimations challenging. Here the authors use machine learning to map global ocean methane fluxes, finding a disproportionate contribution from shallow coastal waters, and a link between primary production and methane cycling.
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Affiliation(s)
- Thomas Weber
- Department of Earth and Environmental Science, University of Rochester, Rochester, NY, 14627, USA.
| | - Nicola A Wiseman
- Department of Earth and Environmental Science, University of Rochester, Rochester, NY, 14627, USA.,Department of Earth System Science, University of California, Irvine, CA, 92697, USA
| | - Annette Kock
- GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105, Kiel, Germany
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23
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Role of Warming in Destabilization of Intrapermafrost Gas Hydrates in the Arctic Shelf: Experimental Modeling. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9100407] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Destabilization of intrapermafrost gas hydrates is one of the possible mechanisms responsible for methane emission in the Arctic shelf. Intrapermafrost gas hydrates may be coeval to permafrost: they originated during regression and subsequent cooling and freezing of sediments, which created favorable conditions for hydrate stability. Local pressure increase in freezing gas-saturated sediments maintained gas hydrate stability from depths of 200–250 meters or shallower. The gas hydrates that formed within shallow permafrost have survived till present in the metastable (relict) state. The metastable gas hydrates located above the present stability zone may dissociate in the case of permafrost degradation as it becomes warmer and more saline. The effect of temperature increase on frozen sand and silt containing metastable pore methane hydrate is studied experimentally to reconstruct the conditions for intrapermafrost gas hydrate dissociation. The experiments show that the dissociation process in hydrate-bearing frozen sediments exposed to warming begins and ends before the onset of pore ice melting. The critical temperature sufficient for gas hydrate dissociation varies from −3.0 to −0.3 °C and depends on lithology (particle size) and salinity of the host frozen sediments. Taking into account an almost gradientless temperature distribution during degradation of subsea permafrost, even minor temperature increases can be expected to trigger large-scale dissociation of intrapermafrost hydrates. The ensuing active methane emission from the Arctic shelf sediments poses risks of geohazard and negative environmental impacts.
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24
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Comment on “Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf”. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9090384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The recent paper in Geosciences, “Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf” by Shakhova, Semiletov, and Chuvilin, (henceforth “S2019”), contains a number of false statements about our 2016 paper, “Methane fluxes from the sea to the atmosphere across the Siberian shelf seas”, (henceforth “T2016”). S2019 use three paragraphs of section 5 of their paper to claim methodological errors and issues in T2016. Notably they claim that in T2016, we systematically removed data outliers including data with high methane concentrations; this claim is false. While we appreciate that flawed methodologies can be a problem in any area of science, in this case, the claims made in S2019 are simply false. In this comment, we detail the incorrect claims made in S2019 regarding T2016, and then discuss some additional problematic aspects of S2019.
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25
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Understanding the Permafrost–Hydrate System and Associated Methane Releases in the East Siberian Arctic Shelf. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9060251] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This paper summarizes current understanding of the processes that determine the dynamics of the subsea permafrost–hydrate system existing in the largest, shallowest shelf in the Arctic Ocean; the East Siberian Arctic Shelf (ESAS). We review key environmental factors and mechanisms that determine formation, current dynamics, and thermal state of subsea permafrost, mechanisms of its destabilization, and rates of its thawing; a full section of this paper is devoted to this topic. Another important question regards the possible existence of permafrost-related hydrates at shallow ground depth and in the shallow shelf environment. We review the history of and earlier insights about the topic followed by an extensive review of experimental work to establish the physics of shallow Arctic hydrates. We also provide a principal (simplified) scheme explaining the normal and altered dynamics of the permafrost–hydrate system as glacial–interglacial climate epochs alternate. We also review specific features of methane releases determined by the current state of the subsea-permafrost system and possible future dynamics. This review presents methane results obtained in the ESAS during two periods: 1994–2000 and 2003–2017. A final section is devoted to discussing future work that is required to achieve an improved understanding of the subject.
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26
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Role of Salt Migration in Destabilization of Intra Permafrost Hydrates in the Arctic Shelf: Experimental Modeling. GEOSCIENCES 2019. [DOI: 10.3390/geosciences9040188] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Destabilization of intrapermafrost gas hydrate is one possible reason for methane emission on the Arctic shelf. The formation of these intrapermafrost gas hydrates could occur almost simultaneously with the permafrost sediments due to the occurrence of a hydrate stability zone after sea regression and the subsequent deep cooling and freezing of sediments. The top of the gas hydrate stability zone could exist not only at depths of 200–250 m, but also higher due to local pressure increase in gas-saturated horizons during freezing. Formed at a shallow depth, intrapermafrost gas hydrates could later be preserved and transform into a metastable (relict) state. Under the conditions of submarine permafrost degradation, exactly relict hydrates located above the modern gas hydrate stability zone will, first of all, be involved in the decomposition process caused by negative temperature rising, permafrost thawing, and sediment salinity increasing. That’s why special experiments were conducted on the interaction of frozen sandy sediments containing relict methane hydrates with salt solutions of different concentrations at negative temperatures to assess the conditions of intrapermafrost gas hydrates dissociation. Experiments showed that the migration of salts into frozen hydrate-containing sediments activates the decomposition of pore gas hydrates and increase the methane emission. These results allowed for an understanding of the mechanism of massive methane release from bottom sediments of the East Siberian Arctic shelf.
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27
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Angelopoulos M, Westermann S, Overduin P, Faguet A, Olenchenko V, Grosse G, Grigoriev MN. Heat and Salt Flow in Subsea Permafrost Modeled with CryoGRID2. JOURNAL OF GEOPHYSICAL RESEARCH. EARTH SURFACE 2019; 124:920-937. [PMID: 31423408 PMCID: PMC6686719 DOI: 10.1029/2018jf004823] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 11/15/2018] [Accepted: 01/28/2019] [Indexed: 05/14/2023]
Abstract
Thawing of subsea permafrost can impact offshore infrastructure, affect coastal erosion, and release permafrost organic matter. Thawing is usually modeled as the result of heat transfer, although salt diffusion may play an important role in marine settings. To better quantify nearshore subsea permafrost thawing, we applied the CryoGRID2 heat diffusion model and coupled it to a salt diffusion model. We simulated coastline retreat and subsea permafrost evolution as it develops through successive stages of a thawing sequence at the Bykovsky Peninsula, Siberia. Sensitivity analyses for seawater salinity were performed to compare the results for the Bykovsky Peninsula with those of typical Arctic seawater. For the Bykovsky Peninsula, the modeled ice-bearing permafrost table (IBPT) for ice-rich sand and an erosion rate of 0.25 m/year was 16.7 m below the seabed 350 m offshore. The model outputs were compared to the IBPT depth estimated from coastline retreat and electrical resistivity surveys perpendicular to and crossing the shoreline of the Bykovsky Peninsula. The interpreted geoelectric data suggest that the IBPT dipped to 15-20 m below the seabed at 350 m offshore. Both results suggest that cold saline water forms beneath grounded ice and floating sea ice in shallow water, causing cryotic benthic temperatures. The freezing point depression produced by salt diffusion can delay or prevent ice formation in the sediment and enhance the IBPT degradation rate. Therefore, salt diffusion may facilitate the release of greenhouse gasses to the atmosphere and considerably affect the design of offshore and coastal infrastructure in subsea permafrost areas.
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Affiliation(s)
- Michael Angelopoulos
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchPotsdamGermany
- Institute of GeosciencesUniversity of PotsdamPotsdamGermany
| | | | - Paul Overduin
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchPotsdamGermany
| | - Alexey Faguet
- Institute of Petroleum Geology and GeophysicsRussian Academy of SciencesNovosibirskRussia
- Department of GeophysicsNovosibirsk State UniversityNovosibirskRussia
| | - Vladimir Olenchenko
- Institute of Petroleum Geology and GeophysicsRussian Academy of SciencesNovosibirskRussia
- Department of GeophysicsNovosibirsk State UniversityNovosibirskRussia
| | - Guido Grosse
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine ResearchPotsdamGermany
- Institute of GeosciencesUniversity of PotsdamPotsdamGermany
| | - Mikhail N. Grigoriev
- Melnikov Permafrost InstituteSiberian Branch, Russian Academy of SciencesYakutskRussia
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28
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Abstract
The gas shows in the permafrost zone represent a hazard for exploration, form the surface features, and are improperly estimated in the global methane budget. They contain methane of either surficial or deep-Earth origin accumulated earlier in the form of gas or gas hydrates in lithological traps in permafrost. From these traps, it rises through conduits, which have tectonic origin or are associated with permafrost degradation. We report methane fluxes from 20-m to 30-m deep boreholes, which are the artificial conduits for gas from permafrost in Siberia. The dynamics of degassing the traps was studied using static chambers, and compared to the concentration of methane in permafrost as analyzed by the headspace method and gas chromatography. More than 53 g of CH4 could be released to the atmosphere at rates exceeding 9 g of CH4 m−2 s−1 from a trap in epigenetic permafrost disconnected from traditional geological sources over a period from a few hours to several days. The amount of methane released from a borehole exceeded the amount of the gas that was enclosed in large volumes of permafrost within a diameter up to 5 meters around the borehole. Such gas shows could be by mistake assumed as permanent gas seeps, which leads to the overestimation of the role of permafrost in global warming.
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29
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Abstract
Permafrost degradation of coastal and marine sediments of the Arctic Seas can result in large amounts of methane emitted to the atmosphere. The quantitative assessment of such emissions requires data on variability of methane content in various types of permafrost strata. To evaluate the methane concentrations in sediments and ground ice of the Kara Sea coast, samples were collected at a series of coastal exposures. Methane concentrations were determined for more than 400 samples taken from frozen sediments, ground ice and active layer. In frozen sediments, methane concentrations were lowest in sands and highest in marine clays. In ground ice, the highest concentrations above 500 ppmV and higher were found in massive tabular ground ice, with much lower methane concentrations in ground ice wedges. The mean isotopic composition of methane is −68.6‰ in permafrost and −63.6‰ in the active layer indicative of microbial genesis. The isotopic compositions of the active layer is enriched relative to permafrost due to microbial oxidation and become more depleted with depth. Ice-rich sediments of Kara Sea coasts, especially those with massive tabular ground ice, hold large amounts of methane making them potential sources of methane emissions under projected warming temperatures and increasing rates of coastal erosion.
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30
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Portnov A, Mienert J, Winsborrow M, Andreassen K, Vadakkepuliyambatta S, Semenov P, Gataullin V. Shallow carbon storage in ancient buried thermokarst in the South Kara Sea. Sci Rep 2018; 8:14342. [PMID: 30254290 PMCID: PMC6156565 DOI: 10.1038/s41598-018-32826-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 09/14/2018] [Indexed: 11/09/2022] Open
Abstract
Geophysical data from the South Kara Sea reveal U-shaped erosional structures buried beneath the 50–250 m deep seafloor of the continental shelf across an area of ~32 000 km2. These structures are interpreted as thermokarst, formed in ancient yedoma terrains during Quaternary interglacial periods. Based on comparison to modern yedoma terrains, we suggest that these thermokarst features could have stored approximately 0.5 to 8 Gt carbon during past climate warmings. In the deeper parts of the South Kara Sea (>220 m water depth) the paleo thermokarst structures lie within the present day gas hydrate stability zone, with low bottom water temperatures −1.8 oC) keeping the gas hydrate system in equilibrium. These thermokarst structures and their carbon reservoirs remain stable beneath a Quaternary sediment blanket, yet are potentially sensitive to future Arctic climate changes.
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Affiliation(s)
- Alexey Portnov
- School of Earth Sciences, The Ohio State University, Columbus, Ohio, USA. .,CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway.
| | - Jürgen Mienert
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
| | - Monica Winsborrow
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
| | - Karin Andreassen
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
| | - Sunil Vadakkepuliyambatta
- CAGE - Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway, 9037, Tromsø, Norway
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31
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Distributed natural gas venting offshore along the Cascadia margin. Nat Commun 2018; 9:3264. [PMID: 30111802 PMCID: PMC6093902 DOI: 10.1038/s41467-018-05736-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2017] [Accepted: 07/20/2018] [Indexed: 11/17/2022] Open
Abstract
Widespread gas venting along the Cascadia margin is investigated from acoustic water column data and reveals a nonuniform regional distribution of over 1100 mapped acoustic flares. The highest number of flares occurs on the shelf, and the highest flare density is seen around the nutrition-rich outflow of the Juan de Fuca Strait. We determine ∼430 flow-rates at ∼340 individual flare locations along the margin with instantaneous in situ values ranging from ∼6 mL min−1 to ∼18 L min−1. Applying a tidal-modulation model, a depth-dependent methane density, and extrapolating these results across the margin using two normalization techniques yields a combined average in situ flow-rate of ∼88 × 106 kg y−1. The average methane flux-rate for the Cascadia margin is thus estimated to ∼0.9 g y−1m−2. Combined uncertainties result in a range of these values between 4.5 and 1800% of the estimated mean values. Methane venting is a widespread phenomenon at the Cascadia margin, however a comprehensive database of methane vents at this margin is lacking. Here the authors show that the margin-wide average methane flow-rate ranges from ~4 × 106 to ~1590 × 106 kg y−1 and is on average around 88 ± 6 × 106 kg y−1.
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32
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Savvichev AS, Rusanov II, Kadnikov VV, Beletskii AV, Ravin NV, Pimenov NV. Microbial Community Composition and Rates of the Methane Cycle Microbial Processes in the Upper Sediments of the Yamal Sector of the Southwestern Kara Sea. Microbiology (Reading) 2018. [DOI: 10.1134/s0026261718020121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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33
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Winkel M, Mitzscherling J, Overduin PP, Horn F, Winterfeld M, Rijkers R, Grigoriev MN, Knoblauch C, Mangelsdorf K, Wagner D, Liebner S. Anaerobic methanotrophic communities thrive in deep submarine permafrost. Sci Rep 2018; 8:1291. [PMID: 29358665 PMCID: PMC5778128 DOI: 10.1038/s41598-018-19505-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 12/22/2017] [Indexed: 11/09/2022] Open
Abstract
Thawing submarine permafrost is a source of methane to the subsurface biosphere. Methane oxidation in submarine permafrost sediments has been proposed, but the responsible microorganisms remain uncharacterized. We analyzed archaeal communities and identified distinct anaerobic methanotrophic assemblages of marine and terrestrial origin (ANME-2a/b, ANME-2d) both in frozen and completely thawed submarine permafrost sediments. Besides archaea potentially involved in anaerobic oxidation of methane (AOM) we found a large diversity of archaea mainly belonging to Bathyarchaeota, Thaumarchaeota, and Euryarchaeota. Methane concentrations and δ13C-methane signatures distinguish horizons of potential AOM coupled either to sulfate reduction in a sulfate-methane transition zone (SMTZ) or to the reduction of other electron acceptors, such as iron, manganese or nitrate. Analysis of functional marker genes (mcrA) and fluorescence in situ hybridization (FISH) corroborate potential activity of AOM communities in submarine permafrost sediments at low temperatures. Modeled potential AOM consumes 72-100% of submarine permafrost methane and up to 1.2 Tg of carbon per year for the total expected area of submarine permafrost. This is comparable with AOM habitats such as cold seeps. We thus propose that AOM is active where submarine permafrost thaws, which should be included in global methane budgets.
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Affiliation(s)
- Matthias Winkel
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, 14473, Potsdam, Germany.
| | - Julia Mitzscherling
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, 14473, Potsdam, Germany
| | - Pier P Overduin
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Periglacial Research, 14473, Potsdam, Germany
| | - Fabian Horn
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, 14473, Potsdam, Germany
| | - Maria Winterfeld
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Marine Geochemistry, 27570, Bremerhaven, Germany
| | - Ruud Rijkers
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, 14473, Potsdam, Germany
| | | | | | - Kai Mangelsdorf
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 3.2 Organic Geochemistry, 14473, Potsdam, Germany
| | - Dirk Wagner
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, 14473, Potsdam, Germany
| | - Susanne Liebner
- GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Section 5.3 Geomicrobiology, 14473, Potsdam, Germany
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34
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Andreassen K, Hubbard A, Winsborrow M, Patton H, Vadakkepuliyambatta S, Plaza-Faverola A, Gudlaugsson E, Serov P, Deryabin A, Mattingsdal R, Mienert J, Bünz S. Massive blow-out craters formed by hydrate-controlled methane expulsion from the Arctic seafloor. Science 2018; 356:948-953. [PMID: 28572390 DOI: 10.1126/science.aal4500] [Citation(s) in RCA: 134] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 05/11/2017] [Indexed: 11/02/2022]
Abstract
Widespread methane release from thawing Arctic gas hydrates is a major concern, yet the processes, sources, and fluxes involved remain unconstrained. We present geophysical data documenting a cluster of kilometer-wide craters and mounds from the Barents Sea floor associated with large-scale methane expulsion. Combined with ice sheet/gas hydrate modeling, our results indicate that during glaciation, natural gas migrated from underlying hydrocarbon reservoirs and was sequestered extensively as subglacial gas hydrates. Upon ice sheet retreat, methane from this hydrate reservoir concentrated in massive mounds before being abruptly released to form craters. We propose that these processes were likely widespread across past glaciated petroleum provinces and that they also provide an analog for the potential future destabilization of subglacial gas hydrate reservoirs beneath contemporary ice sheets.
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Affiliation(s)
- K Andreassen
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway.
| | - A Hubbard
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - M Winsborrow
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - H Patton
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - S Vadakkepuliyambatta
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - A Plaza-Faverola
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - E Gudlaugsson
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - P Serov
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - A Deryabin
- Norwegian Petroleum Directorate, Harstad, Norway
| | | | - J Mienert
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
| | - S Bünz
- Centre for Arctic Gas Hydrate, Environment and Climate (CAGE), Department of Geosciences, UiT The Arctic University of Norway, N-9037 Tromsø, Norway
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35
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Kohnert K, Serafimovich A, Metzger S, Hartmann J, Sachs T. Strong geologic methane emissions from discontinuous terrestrial permafrost in the Mackenzie Delta, Canada. Sci Rep 2017; 7:5828. [PMID: 28725016 PMCID: PMC5517603 DOI: 10.1038/s41598-017-05783-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 06/05/2017] [Indexed: 11/09/2022] Open
Abstract
Arctic permafrost caps vast amounts of old, geologic methane (CH4) in subsurface reservoirs. Thawing permafrost opens pathways for this CH4 to migrate to the surface. However, the occurrence of geologic emissions and their contribution to the CH4 budget in addition to recent, biogenic CH4 is uncertain. Here we present a high-resolution (100 m × 100 m) regional (10,000 km²) CH4 flux map of the Mackenzie Delta, Canada, based on airborne CH4 flux data from July 2012 and 2013. We identify strong, likely geologic emissions solely where the permafrost is discontinuous. These peaks are 13 times larger than typical biogenic emissions. Whereas microbial CH4 production largely depends on recent air and soil temperature, geologic CH4 was produced over millions of years and can be released year-round provided open pathways exist. Therefore, even though they only occur on about 1% of the area, geologic hotspots contribute 17% to the annual CH4 emission estimate of our study area. We suggest that this share may increase if ongoing permafrost thaw opens new pathways. We conclude that, due to permafrost thaw, hydrocarbon-rich areas, prevalent in the Arctic, may see increased emission of geologic CH4 in the future, in addition to enhanced microbial CH4 production.
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Affiliation(s)
- Katrin Kohnert
- GFZ German Research Centre for Geosciences, Telegrafenberg, 14473, Potsdam, Germany.
| | - Andrei Serafimovich
- GFZ German Research Centre for Geosciences, Telegrafenberg, 14473, Potsdam, Germany
| | - Stefan Metzger
- National Ecological Observatory Network, Battelle, 1685 38th Street, Boulder, CO, 80301, USA.,University of Wisconsin-Madison, Dept. of Atmospheric and Oceanic Sciences, 1225 West Dayton Street, Madison, WI, 53706, USA
| | - Jörg Hartmann
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI), Am Handelshafen 12, 27570, Bremerhaven, Germany
| | - Torsten Sachs
- GFZ German Research Centre for Geosciences, Telegrafenberg, 14473, Potsdam, Germany
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36
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Bock M, Schmitt J, Beck J, Seth B, Chappellaz J, Fischer H. Glacial/interglacial wetland, biomass burning, and geologic methane emissions constrained by dual stable isotopic CH 4 ice core records. Proc Natl Acad Sci U S A 2017; 114:E5778-E5786. [PMID: 28673973 PMCID: PMC5530640 DOI: 10.1073/pnas.1613883114] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Atmospheric methane (CH4) records reconstructed from polar ice cores represent an integrated view on processes predominantly taking place in the terrestrial biogeosphere. Here, we present dual stable isotopic methane records [δ13CH4 and δD(CH4)] from four Antarctic ice cores, which provide improved constraints on past changes in natural methane sources. Our isotope data show that tropical wetlands and seasonally inundated floodplains are most likely the controlling sources of atmospheric methane variations for the current and two older interglacials and their preceding glacial maxima. The changes in these sources are steered by variations in temperature, precipitation, and the water table as modulated by insolation, (local) sea level, and monsoon intensity. Based on our δD(CH4) constraint, it seems that geologic emissions of methane may play a steady but only minor role in atmospheric CH4 changes and that the glacial budget is not dominated by these sources. Superimposed on the glacial/interglacial variations is a marked difference in both isotope records, with systematically higher values during the last 25,000 y compared with older time periods. This shift cannot be explained by climatic changes. Rather, our isotopic methane budget points to a marked increase in fire activity, possibly caused by biome changes and accumulation of fuel related to the late Pleistocene megafauna extinction, which took place in the course of the last glacial.
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Affiliation(s)
- Michael Bock
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland;
- Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
| | - Jochen Schmitt
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
| | - Jonas Beck
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
| | - Barbara Seth
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland
- Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
| | - Jérôme Chappellaz
- CNRS, IGE (Institut des Géosciences de l'Environnement), F-38000 Grenoble, France
- University of Grenoble Alpes, IGE, F-38000 Grenoble, France
- IRD (Institut de Recherche pour le Développement), IGE, F-38000 Grenoble, France
- Grenoble INP (Institut National Polytechnique), IGE, F-38000 Grenoble, France
| | - Hubertus Fischer
- Climate and Environmental Physics, Physics Institute, University of Bern, 3012 Bern, Switzerland;
- Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
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37
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Shakhova N, Semiletov I, Gustafsson O, Sergienko V, Lobkovsky L, Dudarev O, Tumskoy V, Grigoriev M, Mazurov A, Salyuk A, Ananiev R, Koshurnikov A, Kosmach D, Charkin A, Dmitrevsky N, Karnaukh V, Gunar A, Meluzov A, Chernykh D. Current rates and mechanisms of subsea permafrost degradation in the East Siberian Arctic Shelf. Nat Commun 2017. [PMID: 28639616 PMCID: PMC5489687 DOI: 10.1038/ncomms15872] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The rates of subsea permafrost degradation and occurrence of gas-migration pathways are key factors controlling the East Siberian Arctic Shelf (ESAS) methane (CH4) emissions, yet these factors still require assessment. It is thought that after inundation, permafrost-degradation rates would decrease over time and submerged thaw-lake taliks would freeze; therefore, no CH4 release would occur for millennia. Here we present results of the first comprehensive scientific re-drilling to show that subsea permafrost in the near-shore zone of the ESAS has a downward movement of the ice-bonded permafrost table of ∼14 cm year−1 over the past 31–32 years. Our data reveal polygonal thermokarst patterns on the seafloor and gas-migration associated with submerged taliks, ice scouring and pockmarks. Knowing the rate and mechanisms of subsea permafrost degradation is a prerequisite to meaningful predictions of near-future CH4 release in the Arctic. The rate of subsea permafrost degradation is a key factor controlling marine methane emissions in the Arctic. Here, using re-drilled boreholes, the authors show that the ice-bonded permafrost table in the near-shore East Siberian Arctic Shelf has deepened by ∼14 cm per year over the past 31–32 years.
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Affiliation(s)
- Natalia Shakhova
- National Tomsk Research Polytechnic University, 30 Prospect Lenina, Tomsk, Alaska 634050, Russia.,International Arctic Research Center, University of Alaska Fairbanks, Akasofu Building, Fairbanks, Alaska 99775-7320, USA
| | - Igor Semiletov
- National Tomsk Research Polytechnic University, 30 Prospect Lenina, Tomsk, Alaska 634050, Russia.,International Arctic Research Center, University of Alaska Fairbanks, Akasofu Building, Fairbanks, Alaska 99775-7320, USA.,Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Orjan Gustafsson
- Department of Environmental Science and Analytical Chemistry, and the Bolin Centre for Climate Research, Stockholm University, Stockholm 10691, Sweden
| | - Valentin Sergienko
- Institute of Chemistry, Russian Academy of Sciences, 100-Letiya Vladivostoka, Vladivostok 690022, Russia
| | - Leopold Lobkovsky
- P.P. Shirshov Oceanological Institute, Russian Academy of Sciences, 36 Nahimovski Prospect, Moscow 117997, Russia
| | - Oleg Dudarev
- National Tomsk Research Polytechnic University, 30 Prospect Lenina, Tomsk, Alaska 634050, Russia.,Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Vladimir Tumskoy
- Moscow State University, 1-12 Leninskie Gory, Moscow 119991, Russia.,Institute of Geography, Russian Academy of Sciences, 29 Staromonetniy Pereulok, Moscow 119017, Russia.,University of Tyumen, 6 Volodarskogo Street, Tyumen 625003, Russia
| | - Michael Grigoriev
- Melnikov Permafrost Institute, Russian Academy of Sciences, 36 Merzlotnaya Street, Yakutsk 677010, Russia
| | - Alexey Mazurov
- National Tomsk Research Polytechnic University, 30 Prospect Lenina, Tomsk, Alaska 634050, Russia
| | - Anatoly Salyuk
- Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Roman Ananiev
- P.P. Shirshov Oceanological Institute, Russian Academy of Sciences, 36 Nahimovski Prospect, Moscow 117997, Russia
| | | | - Denis Kosmach
- Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Alexander Charkin
- National Tomsk Research Polytechnic University, 30 Prospect Lenina, Tomsk, Alaska 634050, Russia.,Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Nicolay Dmitrevsky
- P.P. Shirshov Oceanological Institute, Russian Academy of Sciences, 36 Nahimovski Prospect, Moscow 117997, Russia
| | - Victor Karnaukh
- Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Alexey Gunar
- Moscow State University, 1-12 Leninskie Gory, Moscow 119991, Russia
| | - Alexander Meluzov
- P.P. Shirshov Oceanological Institute, Russian Academy of Sciences, 36 Nahimovski Prospect, Moscow 117997, Russia
| | - Denis Chernykh
- Pacific Oceanological Institute, Russian Academy of Sciences, 43 Baltiiskaya Street, Vladivostok 690041, Russia
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38
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Cryogenic Displacement and Accumulation of Biogenic Methane in Frozen Soils. ATMOSPHERE 2017. [DOI: 10.3390/atmos8060105] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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39
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Enhanced CO 2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane. Proc Natl Acad Sci U S A 2017; 114:5355-5360. [PMID: 28484018 DOI: 10.1073/pnas.1618926114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Continued warming of the Arctic Ocean in coming decades is projected to trigger the release of teragrams (1 Tg = 106 tons) of methane from thawing subsea permafrost on shallow continental shelves and dissociation of methane hydrate on upper continental slopes. On the shallow shelves (<100 m water depth), methane released from the seafloor may reach the atmosphere and potentially amplify global warming. On the other hand, biological uptake of carbon dioxide (CO2) has the potential to offset the positive warming potential of emitted methane, a process that has not received detailed consideration for these settings. Continuous sea-air gas flux data collected over a shallow ebullitive methane seep field on the Svalbard margin reveal atmospheric CO2 uptake rates (-33,300 ± 7,900 μmol m-2⋅d-1) twice that of surrounding waters and ∼1,900 times greater than the diffusive sea-air methane efflux (17.3 ± 4.8 μmol m-2⋅d-1). The negative radiative forcing expected from this CO2 uptake is up to 231 times greater than the positive radiative forcing from the methane emissions. Surface water characteristics (e.g., high dissolved oxygen, high pH, and enrichment of 13C in CO2) indicate that upwelling of cold, nutrient-rich water from near the seafloor accompanies methane emissions and stimulates CO2 consumption by photosynthesizing phytoplankton. These findings challenge the widely held perception that areas characterized by shallow-water methane seeps and/or strongly elevated sea-air methane flux always increase the global atmospheric greenhouse gas burden.
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40
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Structure and energetic characteristics of methane hydrates. From single cage to triple cage: A DFT-D study. J Mol Struct 2017. [DOI: 10.1016/j.molstruc.2016.10.093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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41
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Pisso I, Myhre CL, Platt SM, Eckhardt S, Hermansen O, Schmidbauer N, Mienert J, Vadakkepuliyambatta S, Bauguitte S, Pitt J, Allen G, Bower KN, O'Shea S, Gallagher MW, Percival CJ, Pyle J, Cain M, Stohl A. Constraints on oceanic methane emissions west of Svalbard from atmospheric in situ measurements and Lagrangian transport modeling. JOURNAL OF GEOPHYSICAL RESEARCH. ATMOSPHERES : JGR 2016; 121:14188-14200. [PMID: 28261536 PMCID: PMC5310218 DOI: 10.1002/2016jd025590] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 11/08/2016] [Accepted: 11/13/2016] [Indexed: 06/06/2023]
Abstract
Methane stored in seabed reservoirs such as methane hydrates can reach the atmosphere in the form of bubbles or dissolved in water. Hydrates could destabilize with rising temperature further increasing greenhouse gas emissions in a warming climate. To assess the impact of oceanic emissions from the area west of Svalbard, where methane hydrates are abundant, we used measurements collected with a research aircraft (Facility for Airborne Atmospheric Measurements) and a ship (Helmer Hansen) during the Summer 2014 and for Zeppelin Observatory for the full year. We present a model-supported analysis of the atmospheric CH4 mixing ratios measured by the different platforms. To address uncertainty about where CH4 emissions actually occur, we explored three scenarios: areas with known seeps, a hydrate stability model, and an ocean depth criterion. We then used a budget analysis and a Lagrangian particle dispersion model to compare measurements taken upwind and downwind of the potential CH4 emission areas. We found small differences between the CH4 mixing ratios measured upwind and downwind of the potential emission areas during the campaign. By taking into account measurement and sampling uncertainties and by determining the sensitivity of the measured mixing ratios to potential oceanic emissions, we provide upper limits for the CH4 fluxes. The CH4 flux during the campaign was small, with an upper limit of 2.5 nmol m-2 s-1 in the stability model scenario. The Zeppelin Observatory data for 2014 suggest CH4 fluxes from the Svalbard continental platform below 0.2 Tg yr-1. All estimates are in the lower range of values previously reported.
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Affiliation(s)
- I. Pisso
- NILU‐Norwegian Institute for Air ResearchKjellerNorway
| | - C. Lund Myhre
- NILU‐Norwegian Institute for Air ResearchKjellerNorway
| | - S. M. Platt
- NILU‐Norwegian Institute for Air ResearchKjellerNorway
| | - S. Eckhardt
- NILU‐Norwegian Institute for Air ResearchKjellerNorway
| | - O. Hermansen
- NILU‐Norwegian Institute for Air ResearchKjellerNorway
| | | | - J. Mienert
- Centre for Arctic Gas Hydrate, Environment and Climate, Department of GeologyUiT‐The Arctic University of NorwayTromsøNorway
| | - S. Vadakkepuliyambatta
- Centre for Arctic Gas Hydrate, Environment and Climate, Department of GeologyUiT‐The Arctic University of NorwayTromsøNorway
| | - S. Bauguitte
- FAAMNatural Environment Research CouncilCranfieldUK
| | - J. Pitt
- School of Earth, Atmospheric and Environmental SciencesUniversity of ManchesterManchesterUK
| | - G. Allen
- School of Earth, Atmospheric and Environmental SciencesUniversity of ManchesterManchesterUK
| | - K. N. Bower
- School of Earth, Atmospheric and Environmental SciencesUniversity of ManchesterManchesterUK
| | - S. O'Shea
- School of Earth, Atmospheric and Environmental SciencesUniversity of ManchesterManchesterUK
| | - M. W. Gallagher
- School of Earth, Atmospheric and Environmental SciencesUniversity of ManchesterManchesterUK
- National Centre for Atmospheric ScienceUK
| | - C. J. Percival
- School of Earth, Atmospheric and Environmental SciencesUniversity of ManchesterManchesterUK
| | - J. Pyle
- National Centre for Atmospheric ScienceUK
- Department of ChemistryUniversity of CambridgeCambridgeUK
| | - M. Cain
- National Centre for Atmospheric ScienceUK
- Department of ChemistryUniversity of CambridgeCambridgeUK
| | - A. Stohl
- NILU‐Norwegian Institute for Air ResearchKjellerNorway
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42
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Charette MA, Lam PJ, Lohan MC, Kwon EY, Hatje V, Jeandel C, Shiller AM, Cutter GA, Thomas A, Boyd PW, Homoky WB, Milne A, Thomas H, Andersson PS, Porcelli D, Tanaka T, Geibert W, Dehairs F, Garcia-Orellana J. Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:20160076. [PMID: 29035267 PMCID: PMC5069537 DOI: 10.1098/rsta.2016.0076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 06/30/2016] [Indexed: 05/06/2023]
Abstract
Continental shelves and shelf seas play a central role in the global carbon cycle. However, their importance with respect to trace element and isotope (TEI) inputs to ocean basins is less well understood. Here, we present major findings on shelf TEI biogeochemistry from the GEOTRACES programme as well as a proof of concept for a new method to estimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEI cycling in the Arctic, transformations within a major river estuary (Amazon), shelf sediment micronutrient fluxes and basin-scale estimates of submarine groundwater discharge. The proposed shelf flux tracer is 228-radium (T1/2 = 5.75 yr), which is continuously supplied to the shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf 228Ra fluxes are combined with TEI/ 228Ra ratios to quantify ocean TEI fluxes from the western North Atlantic margin. The results from this new approach agree well with previous estimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmospheric deposition by factors of approximately 3-23. Lastly, recommendations are made for additional GEOTRACES process studies and coastal margin-focused section cruises that will help refine the model and provide better insight on the mechanisms driving shelf-derived TEI fluxes to the ocean.This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
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Affiliation(s)
- Matthew A Charette
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Phoebe J Lam
- Department of Ocean Sciences, University of California-Santa Cruz, Santa Cruz, CA 95064, USA
| | - Maeve C Lohan
- Ocean and Earth Science, National Oceanography Centre, University of Southampton, Southampton SO14 3ZH, UK
| | - Eun Young Kwon
- Research Institute of Oceanography, Seoul National University, Seoul 151-742, Korea
| | - Vanessa Hatje
- Centro Interdisciplinar de Energia e Ambiente, Inst. de Química, Universidade Federal da Bahia, Salvador 40170-115, Brazil
| | - Catherine Jeandel
- University of Toulouse/CNRS/UPS/IRD/CNES, Observatoire Midi-Pyrénées, Toulouse 31400, France
| | - Alan M Shiller
- Department of Marine Science, University of Southern Mississippi, Stennis Space Center, MS 39529, USA
| | - Gregory A Cutter
- Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529, USA
| | - Alex Thomas
- School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK
| | - Philip W Boyd
- Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, Tasmania 7005, Australia
| | - William B Homoky
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
| | - Angela Milne
- School of Geography, Earth and Environmental Sciences, Plymouth University, Plymouth PL4 8AA, UK
| | - Helmuth Thomas
- Department of Oceanography, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2
| | - Per S Andersson
- Department of Geosciences, Swedish Museum of Natural History, Stockholm 104 05, Sweden
| | - Don Porcelli
- Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, UK
| | - Takahiro Tanaka
- Atmosphere and Ocean Research Institute, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa Chiba 277-8564, Japan
| | - Walter Geibert
- Marine Geochemistry Department, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Frank Dehairs
- Earth System Sciences and Analytical, Environmental and Geo-Chemistry, Vrije Universiteit Brussel, Brussels 1050, Belgium
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43
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Miller SM, Miller CE, Commane R, Chang RYW, Dinardo SJ, Henderson JM, Karion A, Lindaas J, Melton JR, Miller JB, Sweeney C, Wofsy SC, Michalak AM. A multi-year estimate of methane fluxes in Alaska from CARVE atmospheric observations. GLOBAL BIOGEOCHEMICAL CYCLES 2016; 30:1441-1453. [PMID: 28066129 PMCID: PMC5207046 DOI: 10.1002/2016gb005419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Methane (CH4) fluxes from Alaska and other arctic regions may be sensitive to thawing permafrost and future climate change, but estimates of both current and future fluxes from the region are uncertain. This study estimates CH4 fluxes across Alaska for 2012-2014 using aircraft observations from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and a geostatistical inverse model (GIM). We find that a simple flux model based on a daily soil temperature map and a static map of wetland extent reproduces the atmospheric CH4 observations at the state-wide, multi-year scale more effectively than global-scale, state-of-the-art process-based models. This result points to a simple and effective way of representing CH4 flux patterns across Alaska. It further suggests that contemporary process-based models can improve their representation of key processes that control fluxes at regional scales, and that more complex processes included in these models cannot be evaluated given the information content of available atmospheric CH4 observations. In addition, we find that CH4 emissions from the North Slope of Alaska account for 24% of the total statewide flux of 1.74 ± 0.44 Tg CH4 (for May-Oct.). Contemporary global-scale process models only attribute an average of 3% of the total flux to this region. This mismatch occurs for two reasons: process models likely underestimate wetland area in regions without visible surface water, and these models prematurely shut down CH4 fluxes at soil temperatures near 0°C. As a consequence, wetlands covered by vegetation and wetlands with persistently cold soils could be larger contributors to natural CH4 fluxes than in process estimates. Lastly, we find that the seasonality of CH4 fluxes varied during 2012-2014, but that total emissions did not differ significantly among years, despite substantial differences in soil temperature and precipitation; year-to-year variability in these environmental conditions did not affect obvious changes in total CH4 fluxes from the state.
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Affiliation(s)
- Scot M. Miller
- Department of Global Ecology, Carnegie Institution for Science, Stanford, California, USA
| | - Charles E. Miller
- Science Division, NASA Jet Propulsion Laboratory, Pasadena, California, USA
| | - Roisin Commane
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Rachel Y.-W. Chang
- Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Steven J. Dinardo
- Science Division, NASA Jet Propulsion Laboratory, Pasadena, California, USA
| | | | - Anna Karion
- National Institute of Standards and Technology, Gaithersburg, Maryland, USA
| | - Jakob Lindaas
- Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado, USA
| | - Joe R. Melton
- Climate Research Division, Environment and Climate Change Canada, Victoria, Canada
| | | | - Colm Sweeney
- Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA
| | - Steven C. Wofsy
- School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Anna M. Michalak
- Department of Global Ecology, Carnegie Institution for Science, Stanford, California, USA
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44
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Tinivella U, Giustiniani M. Gas hydrate stability zone in shallow Arctic Ocean in presence of sub-sea permafrost. RENDICONTI LINCEI 2016. [DOI: 10.1007/s12210-016-0520-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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45
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Kosmach DA, Sergienko VI, Dudarev OV, Kurilenko AV, Gustafsson O, Semiletov IP, Shakhova NE. Methane in the surface waters of Northern Eurasian marginal seas. DOKLADY CHEMISTRY 2016. [DOI: 10.1134/s0012500815120022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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46
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Shakhova N, Semiletov I, Sergienko V, Lobkovsky L, Yusupov V, Salyuk A, Salomatin A, Chernykh D, Kosmach D, Panteleev G, Nicolsky D, Samarkin V, Joye S, Charkin A, Dudarev O, Meluzov A, Gustafsson O. The East Siberian Arctic Shelf: towards further assessment of permafrost-related methane fluxes and role of sea ice. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2015; 373:rsta.2014.0451. [PMID: 26347539 PMCID: PMC4607703 DOI: 10.1098/rsta.2014.0451] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Sustained release of methane (CH(4)) to the atmosphere from thawing Arctic permafrost may be a positive and significant feedback to climate warming. Atmospheric venting of CH(4) from the East Siberian Arctic Shelf (ESAS) was recently reported to be on par with flux from the Arctic tundra; however, the future scale of these releases remains unclear. Here, based on results of our latest observations, we show that CH(4) emissions from this shelf are likely to be determined by the state of subsea permafrost degradation. We observed CH(4) emissions from two previously understudied areas of the ESAS: the outer shelf, where subsea permafrost is predicted to be discontinuous or mostly degraded due to long submergence by seawater, and the near shore area, where deep/open taliks presumably form due to combined heating effects of seawater, river run-off, geothermal flux and pre-existing thermokarst. CH(4) emissions from these areas emerge from largely thawed sediments via strong flare-like ebullition, producing fluxes that are orders of magnitude greater than fluxes observed in background areas underlain by largely frozen sediments. We suggest that progression of subsea permafrost thawing and decrease in ice extent could result in a significant increase in CH(4) emissions from the ESAS.
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Affiliation(s)
- Natalia Shakhova
- International Arctic Research Center, University of Alaska Fairbanks, Akasofu Building, Fairbanks, AK 99775-7320, USA Tomsk Polytechnic University, Institute of Natural Resources, Geology and Mineral Exploration, 30 Prospect Lenina, Tomsk, Russia
| | - Igor Semiletov
- International Arctic Research Center, University of Alaska Fairbanks, Akasofu Building, Fairbanks, AK 99775-7320, USA Tomsk Polytechnic University, Institute of Natural Resources, Geology and Mineral Exploration, 30 Prospect Lenina, Tomsk, Russia Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Valentin Sergienko
- Russian Academy of Sciences, Institute of Chemistry, 159, 100-Let Vladivostok Prospect, Vladivostok 690022, Russia
| | - Leopold Lobkovsky
- Russian Academy of Sciences, P.P. Shirshov Oceanological Institute, 36 Nahimovski Prospect, Moscow 117997, Russia
| | - Vladimir Yusupov
- Russian Academy of Sciences, Institute on Laser and Information Technologies, 2 Pionerskaya Street, Troitsk 142092, Russia
| | - Anatoly Salyuk
- Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Alexander Salomatin
- Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Denis Chernykh
- Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Denis Kosmach
- Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Gleb Panteleev
- International Arctic Research Center, University of Alaska Fairbanks, Akasofu Building, Fairbanks, AK 99775-7320, USA
| | - Dmitry Nicolsky
- University of Alaska Fairbanks, Geophysical Institute, Snow, Ice and Permafrost, PO Box 757320, Fairbanks, AK 99775-7320, USA
| | - Vladimir Samarkin
- Department of Marine Science, University of Georgia Atlanta, 3475 Lenox Road, NE Suite 300, Atlanta, GA 30326-3228, USA
| | - Samantha Joye
- Department of Marine Science, University of Georgia Atlanta, 3475 Lenox Road, NE Suite 300, Atlanta, GA 30326-3228, USA
| | - Alexander Charkin
- Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Oleg Dudarev
- Russian Academy of Sciences, Pacific Oceanological Institute, 43 Baltiiskaya Street, Vladivostok 690041, Russia
| | - Alexander Meluzov
- Russian Academy of Sciences, P.P. Shirshov Oceanological Institute, 36 Nahimovski Prospect, Moscow 117997, Russia
| | - Orjan Gustafsson
- Department of Applied Environmental Science and Bolin Centre for Climate Research, Stockholm University, Stockholm 10691, Sweden
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47
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Methane transport from the active layer to lakes in the Arctic using Toolik Lake, Alaska, as a case study. Proc Natl Acad Sci U S A 2015; 112:3636-40. [PMID: 25775530 DOI: 10.1073/pnas.1417392112] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Methane emissions in the Arctic are important, and may be contributing to global warming. While methane emission rates from Arctic lakes are well documented, methods are needed to quantify the relative contribution of active layer groundwater to the overall lake methane budget. Here we report measurements of natural tracers of soil/groundwater, radon, and radium, along with methane concentration in Toolik Lake, Alaska, to evaluate the role active layer water plays as an exogenous source for lake methane. Average concentrations of methane, radium, and radon were all elevated in the active layer compared with lake water (1.6 × 10(4) nM, 61.6 dpm⋅m(-3), and 4.5 × 10(5) dpm⋅m(-3) compared with 1.3 × 10(2) nM, 5.7 dpm⋅m(-3), and 4.4 × 10(3) dpm⋅m(-3), respectively). Methane transport from the active layer to Toolik Lake based on the geochemical tracer radon (up to 2.9 g⋅m(-2)⋅y(-1)) can account for a large fraction of methane emissions from this lake. Strong but spatially and temporally variable correlations between radon activity and methane concentrations (r(2) > 0.69) in lake water suggest that the parameters that control methane discharge from the active layer also vary. Warming in the Arctic may expand the active layer and increase the discharge, thereby increasing the methane flux to lakes and from lakes to the atmosphere, exacerbating global warming. More work is needed to quantify and elucidate the processes that control methane fluxes from the active layer to predict how this flux might change in the future and to evaluate the regional and global contribution of active layer water associated methane inputs.
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48
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Erickson III DJ, Sulzberger B, Zepp RG, Austin AT. Effects of stratospheric ozone depletion, solar UV radiation, and climate change on biogeochemical cycling: interactions and feedbacks. Photochem Photobiol Sci 2015; 14:127-48. [DOI: 10.1039/c4pp90036g] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Solar UV radiation and climate change interact to influence and determine the environmental conditions for humans on planet Earth.
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Affiliation(s)
- David J. Erickson III
- Computational Earth Sciences Group Computer Science and Mathematics Division
- Oak Ridge National Laboratory
- MS 6016 Oak Ridge TN 37831-6016
- USA
| | - Barbara Sulzberger
- Eawag: Swiss Federal Institute of Aquatic Science and Technology
- CH-8600 Duebendorf
- Switzerland
| | - Richard G. Zepp
- United States Environmental Protection Agency
- Georgia 30605-2700
- USA
| | - Amy T. Austin
- Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA) and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
- Universidad de Buenos Aires
- Buenos Aires
- Argentina
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49
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Abstract
We determined methane (CH4) emissions from Alaska using airborne measurements from the Carbon Arctic Reservoirs Vulnerability Experiment (CARVE). Atmospheric sampling was conducted between May and September 2012 and analyzed using a customized version of the polar weather research and forecast model linked to a Lagrangian particle dispersion model (stochastic time-inverted Lagrangian transport model). We estimated growing season CH4 fluxes of 8 ± 2 mg CH4⋅m(-2)⋅d(-1) averaged over all of Alaska, corresponding to fluxes from wetlands of 56(-13)(+22) mg CH4⋅m(-2)⋅d(-1) if we assumed that wetlands are the only source from the land surface (all uncertainties are 95% confidence intervals from a bootstrapping analysis). Fluxes roughly doubled from May to July, then decreased gradually in August and September. Integrated emissions totaled 2.1 ± 0.5 Tg CH4 for Alaska from May to September 2012, close to the average (2.3; a range of 0.7 to 6 Tg CH4) predicted by various land surface models and inversion analyses for the growing season. Methane emissions from boreal Alaska were larger than from the North Slope; the monthly regional flux estimates showed no evidence of enhanced emissions during early spring or late fall, although these bursts may be more localized in time and space than can be detected by our analysis. These results provide an important baseline to which future studies can be compared.
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50
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Tulk CA, Machida S, Klug DD, Lu H, Guthrie M, Molaison JJ. The structure of CO₂ hydrate between 0.7 and 1.0 GPa. J Chem Phys 2014; 141:174503. [PMID: 25381527 DOI: 10.1063/1.4899265] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A deuterated sample of CO2 structure I (sI) clathrate hydrate (CO2·8.3 D2O) has been formed and neutron diffraction experiments up to 1.0 GPa at 240 K were performed. The sI CO2 hydrate transformed at 0.7 GPa into the high pressure phase that had been observed previously by Hirai et al. [J. Phys. Chem. 133, 124511 (2010)] and Bollengier et al. [Geochim. Cosmochim. Acta 119, 322 (2013)], but which had not been structurally identified. The current neutron diffraction data were successfully fitted to a filled ice structure with CO2 molecules filling the water channels. This CO2+water system has also been investigated using classical molecular dynamics and density functional ab initio methods to provide additional characterization of the high pressure structure. Both models indicate the water network adapts a MH-III "like" filled ice structure with considerable disorder of the orientations of the CO2 molecule. Furthermore, the disorder appears to be a direct result of the level of proton disorder in the water network. In contrast to the conclusions of Bollengier et al., our neutron diffraction data show that the filled ice phase can be recovered to ambient pressure (0.1 MPa) at 96 K, and recrystallization to sI hydrate occurs upon subsequent heating to 150 K, possibly by first forming low density amorphous ice. Unlike other clathrate hydrate systems, which transform from the sI or sII structure to the hexagonal structure (sH) then to the filled ice structure, CO2 hydrate transforms directly from the sI form to the filled ice structure.
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Affiliation(s)
- C A Tulk
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - S Machida
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - D D Klug
- National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - H Lu
- National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada
| | - M Guthrie
- Geophysical Laboratory, Carnegie Institution of Washington, Washington, District of Columbia 20015, USA
| | - J J Molaison
- Neutron Scattering Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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