The project goal is to study the biogeochemical response of gas hydrates to environmental change at the Svalbard Continental Margin.
Oregon State University, Corvallis, OR 97339-1086
Research is needed to better understand the role gas hydrates play in the global carbon cycle and their potential as a future energy resource. This includes determining
The upper edge of gas hydrate stability defines one of the most climate-sensitive boundaries and represents a potential “window” to fluid and gas migration from below the seaward-deepening bottom simulating reflector. Hydrate transformations can be documented through analyses of geochemical data, modeling efforts to quantify each process and its associated rate, and obtaining ground truth data of these geochemically-derived inferences through analyses of microbial communities. Characterizing carbon cycling in the critical zone on the upper continental slope will increase our knowledge of the processes that generate, transport, and consume methane in the sediment and water column.
German and Norwegian colleagues have ongoing programs focusing on characterizing gas hydrate abundance, distribution, and the effect of environmental changes on gas hydrate stability and associated methane budgets at the western Spitsbergen continental margin. In cooperation with those programs, Oregon State University researchers are exploring the role of biogeochemical processes in the region via pore water and sediment geochemical analyses, microbiological analyses, and numerical transport-reaction models. The roles of microbial methane generation and oxidation at and below the sulfate-methane transition zone will enable researchers to quantify the amount of methane as it moves, is consumed, or escapes at the seafloor. These fundamental data are needed in order to constrain models for assessing the residence time of carbon in various methane-rich reservoirs as well as the dynamic response of these systems to environmental change and the resulting effect in the overlying water column. The proposed research has the potential to increase our understanding of the response and impact of gas hydrates to changing environmental conditions.
This project has been completed and project results are documented in a final report, which can be accessed from the additional information section below.
Geochemical and microbiological samples from the past expeditions are being analyzed. The researchers have demonstrated the ability to extract DNA using two Svalbard cores from the past October expedition (GC-09 and GC-12) from depths ranging from 0 to 220 cm below seafloor, as well as amplification of the 16S rRNA. The research team established collaboration with Fengping Wang (State Key Laboratory of Microbial Metabolism at Shanghai Jiao Tong University in Shanghai, China) and funding for Scott Klassec (via a National Science Foundation summer fellowship) to use samples collected from the most recent Svalbard expedition for incubation experiments at high pressures to elucidate microbial response to changes in methane content. Building on the experience from the visit to Shanghai, Klassec has implemented sediment incubations for time-series experiments at situ temperatures and pressures under different methane concentrations. Methane consumption, sulfate reduction, and sulfide and dissolved inorganic carbon production will be measured. In addition to microbial community analysis, the team plans to quantify cell abundances and functional genes and transcripts associated with anaerobic methane oxidation and sulfate reduction. This work is partially supported by a Deep Carbon Observatory Deep Life Cultivation Internship grant to enrich or cultivate carbon-cycling microbes from subsurface environments. Preliminary results from these studies were presented at the AGU Fall Meeting in San Francisco, CA (Dec 2015), and at the Gordon Research Conference on Gas Hydrates in Galveston, TX (Feb-March 2016, Feb-March 2018), and the Ocean Sciences Meeting in Portland, OR (Feb. 2018). Long-term high pressure incubations of marine sediment samples are completed. A stainless steel pressure vessel was constructed with the help of the College of Earth, Ocean, and Atmospheric Sciences machine and technical development facility to increase throughput of high-pressure incubations. Thirty-day incubations were sampled in March, while 4- and 8-month incubations will end in mid-June. Upon depressurization, sampling consists of preserving and measuring headspace methane. Media samples are stored for measurement of sulfide, sulfate, dissolved inorganic carbon, and nutrients. Sediment is frozen for nucleic acid analysis and fixed for fluorescent microscopy. Consumption of methane and production of sulfide was noted over the first three months of the 8-month incubation, when media was replaced and new methane was added. Additional chemical measurements and conversions to rates are forthcoming. Extracted microbial community DNA from incubations and molecular analyses are underway. A manuscript is planned for fall 2018. Samples from two cores collected in Vestensa Ridge seep are being analyzed for biomarkers that can further illuminate the role of microbial communities in carbon cycling at seep sites. A manuscript is planned for early 2019.
Geochemical characterization of samples recovered from the various expeditions has been used in support of three publications in Nature Communications, Scientific Reports, and Marine Geology, as well as featured in two articles in the Fire in the Ice newsletter (2015 and 2017). Gas hydrate dynamics and associated geochemical response at newly discovered gas hydrate mounds off the shore of Svalbard were complemented with modelling of the non-steady-state porewater profiles and the observations of distinct layers of methane-derived authigenic carbonate nodules in the sediments, to document centurial to millennial methane emissions in the region. Results of temperature modelling suggest limited impact of short-term warming on gas hydrates deeper than a few metres in the sediments. The researchers conclude that the ongoing and past methane emission episodes at the investigated sites are likely due to the episodic ventilation of deep reservoirs rather than warming-induced gas hydrate dissociation in this shallow water seep site. This manuscript was recently published in the Journal Nature Geoscience. Results were also presented at the Gordon Research Conference on Gas Hydrates in Galveston, TX (Feb-March 2016). Ongoing studies focus on the geochemical signals to elucidate fluid sources feeding these gas hydrate mounds. Preliminary interpretations were presented at the Gas in marine sediment conference in Tromso, Norway (September 2016), and a manuscript has been recently accepted for publication in Geophysical Research Letters.
Samples for the water column component document a much broader seepage area than previously reported, extending from 74° to 79°, where more than a thousand gas discharge sites were imaged as acoustic flares. The gas discharge occurs in water depths at and shallower than the upper edge of the gas hydrate stability zone and generates a dissolved methane plume that is hundreds of kilometer in length. Data collected in the summer of 2015 revealed that 0.02-7.7% of the dissolved methane was aerobically oxidized by microbes and a minor fraction (0.07%) was transferred to the atmosphere during periods of low wind speeds. Most flares were detected in the vicinity of the Hornsund Fracture Zone, leading us to postulate that the gas ascends along this fracture zone. The methane discharges on bathymetric highs characterized by sonic hard grounds, whereas glaciomarine and Holocene sediments in the troughs apparently limit seepage. The large scale seepage reported here is not caused by anthropogenic warming. Preliminary results were presented at the 2016 Gordon Research Conference on Natural Gas Hydrate in Galveston, TX (March 2016), and at the International Conference on Gas Hydrates in Denver, CO, (June 2017). A manuscript has been published in the journal Scientific Reports, which is part of the Nature consortium with an impact factor of ~5.
Another collaborative effort with scientists from Norway, which include results from expeditions to the Svalbard margin in the context of this grant resulted in another paper, now published in the journal Marine Geology. The manuscript integrates available information to date and reports on the first detailed seafloor imaging and camera-guided multicore sampling at two of the most active pockmarks along Vestnesa Ridge, named Lomvi and Lunde. The researchers correlate seafloor images with seismically defined subseafloor structures, providing a geological and ecological context to better understand pockmark formation and water column observations. Subbottom and seismic surveys, water column imaging, geochemical data, and seafloor observations indicate ongoing fluid flow at these pockmarks. Visual inspection and sampling using a high-resolution deep-sea camera and multicorer system show exposed gas hydrate and authigenic carbonate in association with biota within two of these pockmarks. Distributed methane venting at both Lomvi and Lunde supports extensive chemosynthetic communities that include filamentous sulphide-oxidizing bacteria and Siboglinid tubeworms, all of which utilize chemical energy provided by the seeping fluids. Focused venting forms shallow gas hydrate, and sustains localized gas discharge from 50 m wide pits within the pockmarks. Cycles of carbonate precipitation and/or exhumation of carbonate deposits are indicated by scattered blocks of various size, pavements, and massive carbonate blocks up to 5 m in diameter. Consistent with other observations along continental margin settings, the research team shows that the extensive authigenic carbonate deposits in the Vestnesa pockmarks represent an important and prolonged methane sink that prevents much of the upwardly flowing methane from reaching the overlying ocean.
Samples obtained with the MeBo seafloor drill from the University of Bremen provide access to deeper sediment sequences not previously available using conventional coring approaches. Results from these efforts, which were led by a team of scientists from MARUM and GEOMAR, are now published in Nature Communications. Explained briefly, sediment recovered from drill-cores off Prins Karls Foreland during the MSM057 expedition contains no evidence of gas hydrate occurrence at this location. Rather, the fluid freshening observed in sediment cores reflect gas hydrate dissociation around 8 ka BP, when isostatic uplift outpaced eustatic sea-level rise, and the resulting decrease in hydrostatic pressure led to gas hydrate dissociation. Consistent with previous findings during this project, gas hydrate dissociation in this high-latitude setting is not the result of anthropogenic warming, but was likely triggered by tectonic and glacio-eustatic forcings. Additional samples collected off Vestnesa Ridge during the MSM057 expedition are under analyses, with two additional manuscripts in preparation.
Results from this research have been presented at the: International Conference on Gas Hydrates, Denver, CO, (two abstracts) June 2017; GeoBremen17 meeting, University of Bremen, (three abstracts) September 2017; Bubbles17, Norway, (two presentations) June 2017; Goldschmidt Conference, Paris, (two abstracts) August 2017; Ocean Sciences Meeting, Portland, OR, (one abstract) February 2018; Gordon Research Conference, TX, (four presentations) 2016-2018; the EGU General Assembly, Viena, (two presentations) April 2018.
Peszynska, M., Medina, F.P., Hong, W.-L., and Torres, M.E. 2015. “Reduced Numerical Model for Methane Hydrate Formation under Conditions of Variable Salinity. Time-Stepping Variants and Sensitivity.” Computation, 4(1), p.1.
Peszynska, M., Hong, W.-L. Torres, M.E., and Kim, J.-H. 2015. “Methane Hydrate Formation in Ulleung Basin Under Conditions of Variable Salinity: Reduced Model and Experiments.” Transport Porous Media, DOI 10.1007/s11242-016-0706-y.
Panieri, G., Fornari, D.J.. Serov, P., Åström, E.K.L., Plaza-Faverola, A., Mienert, J., Torres, M.E., and the CAGE scientific team. 2015. “Gas Hydrate, Carbonate Crusts, and Chemosynthetic Organisms on a Vestnesa Ridge Pockmark—Preliminary Findings.” Fire in the Ice, Vol 15(2):14-17.
Mau, S., Römer, M., Torres, M.E., Bussmann, I., Pape, T., Damm, E., Geprägs, P., Wintersteller, P., Hsu, C.W., Loher, M. and Bohrmann, G. 2017. “Widespread methane seepage along the continental margin off Svalbard-from Bjørnøya to Kongsfjorden.” Scientific Reports, 7:42997, DOI: 10.1038/srep42997.
Mau, S., Torres, M., Römer, M., Pape, T., and Bohrmann, G. 2017. “Methane Release Along Continental Margins: Natural Process or Anthropogenically Driven?” Fire in the Ice, Vol 17(2):5-8.
Hong, W.-L, Torres, M.E., Carroll, J.-L., Crémière, A., Panieri, G., Yao, H. and Serov, P. 2017. “Seepage from an arctic shallow marine gas hydrate reservoir is insensitive to momentary ocean warming.” Nature Communications, 8:15745 | DOI: 10.1038/ncomms15745.
Panieri, G., Bünz, S., Fornari, D. J., Escartin, J., Serov, P., Johnson, J. J, Jansson, P., Hong, W.-L., Sauer, S., Torres, M. E., Garcia, R., Gracias, N. 2017. “An integrated view of the methane system in the pockmarks at Vestnesa Ridge, 79°N.” Marine Geology, 390: 282-300.
Wallmann, K., Riedel, M., Hong, W.-L., Patton, H., Hubbard, A., Pape, T., Hsu, C.W., Schmidt, C., Johnson, J.E., Torres, M.E., and Andreassen, K. 2018. “Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming.” Nature Communications, 9(1):83.
Hong, W.-L., Torres, M. E., Portnov, A., Waage, M., Haley, B., and Lepland, A. 2018. “Variations in gas and water pulses at an Arctic seep: fluid sources and methane transport.” Geophysical Research Letters by W.-L, In press.