English
norskBlar i forfatter "Yao, Haoyi"
Viser treff 1-12 av 12
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Biomarker and isotopic composition of seep carbonates record environmental conditions in two Arctic methane seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-12)Present-day activity of cold-seeps in the ocean is evident from direct observations of methane emanating from the seafloor, the presence of chemosynthetic organisms, or the quantification of gas concentrations in the water column and pore water solutes. Verifying past cold seep activity and biogeochemical characteristics is more challenging but may be reconstructed from proxy records of authigenic ... -
Complementary biomarker-based methods for characterising Arctic sea ice conditions: A case study comparison between multivariate analysis and the PIP25 index
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-11-10)The discovery of IP25 as a qualitative biomarker proxy for Arctic sea ice and subsequent introduction of the so-called PIP25 index for semi-quantitative descriptions of sea ice conditions has significantly advanced our understanding of long-term paleo Arctic sea ice conditions over the past decade. We investigated the potential for classification tree1 (CT) models to provide a further approach ... -
Foraminiferal δ18O reveals gas hydrate dissociation in Arctic and North Atlantic ocean sediments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-07)Paleoceanographic investigations in the Arctic and north Atlantic are crucial to understanding past and current climate change, in particular considering amounts of pressure-temperature sensitive gas stored in marine sediments of the region. Many paleoceanographic studies are based on foraminiferal oxygen and carbon stable isotope compositions (δ<sup>18</sup>O, δ<sup>13</sup>C) from either planktonic ... -
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge
(Journal article; Peer reviewed, 2019-05-29)We report a rare observation of a mini-fracture in near-surface sediments (30 cm below the seafloor) visualized using a rotational scanning X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of Svalbard (1200 m water depth). Porewater geochemistry and lipid biomarker signatures revealed clear differences in the geochemical and biogeochemical regimes of this core compared with ... -
Implications of transient methane flux on associated biological communities in high-arctic seep habitats, Storbanken, Norwegian Barents sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-21)The continental margins of the Arctic Ocean basin contain methane seeps, where transient fluxes of seafloor methane are released due to the thermal dissociation of gas hydrates. An increase in shallow methane seeps identified over the past decade, potentially due to enhanced warming of the Arctic Ocean bottom water and associated destabilization of hydrate structure. Biological communities associated ... -
Interactions between deep formation fluid and gas hydrate dynamics inferred from pore fluid geochemistry at active pockmarks of the Vestnesa Ridge, west Svalbard margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-11)Seafloor seepage sites along the Vestnesa Ridge off west-Svalbard have been, for decades, a natural laboratory for the studies of fluid flow and gas hydrate dynamics at passive continental margins. The lack of ground truth evidence for fluid composition and gas hydrate abundance deep in the sediment sequence however prohibits us from further assessing the current model of pockmark evolution from the ... -
Manganese/iron‐supported sulfate‐dependent anaerobic oxidation of methane by archaea in lake sediments
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-04)Anaerobic oxidation of methane (AOM) by methanotrophic archaea is an important sink of this greenhouse gas in marine sediments. However, evidence for AOM in freshwater habitats is rare, and little is known about the pathways, electron acceptors, and microbes involved. Here, we show that AOM occurs in anoxic sediments of a sulfate‐rich lake in southern Switzerland (Lake Cadagno). Combined AOM‐rate ... -
Methane transport and sources in an Arctic deep-water cold seep offshore NW Svalbard (Vestnesa Ridge, 79°N)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-29)We investigate the uppermost 60 cm of sediment in active pockmarks of a deep-water methane seep site from Vestnesa Ridge offshore NW Svalbard. Using video guided core sampling with a remotely operated vehicle we collected push cores directly from bacterial mats within two active pockmarks, Lunde and Lomvi. Pore water analyses show very shallow sulphate methane transition zones and transport-reaction ... -
Multi-proxy approach to unravel methane emission history of an Arctic cold seep
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)Arctic Ocean sediments contain large amounts of methane in the form of free gas and gas hydrate. This highly dynamic methane reservoir is susceptible to be modified by bottom water warming. The warming may lead to gas hydrate destabilization releasing elevated methane fluxes to the seafloor and seawater. Reconstructing past methane dynamics can be achieved by using specific proxies left in the ... -
Origin and transformation of light hydrocarbons ascending at an active pockmark on Vestnesa Ridge, Arctic Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-10-25)We report on the geochemistry of hydrocarbons and pore waters down to 62.5 mbsf, collected by drilling with the MARUM‐MeBo70 and by gravity coring at the Lunde pockmark in the Vestnesa Ridge. Our data document the origin and transformations of volatiles feeding gas emissions previously documented in this region. Gas hydrates are present where a fracture network beneath the pockmark focusses migration ... -
Reconstruction of past and present methane emission in the Arctic cold seeps using biogeochemical proxies
(Doctoral thesis; Doktorgradsavhandling, 2020-03-26)Global warming is now highly concerned by society as extreme weather is more often than ever, and the Arctic is experiencing warming twice as fast as the global mean. A large amount of carbon is stored in the forms of methane and methane hydrate in the continental margins worldwide. Methane is the most predominant gaseous compound in natural gas hydrate, which is stable under low temperature and ... -
Seepage from an arctic shallow marine gas hydrate reservoir is insensitive to momentary ocean warming
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-07)Arctic gas hydrate reservoirs located in shallow water and proximal to the sediment-water interface are thought to be sensitive to bottom water warming that may trigger gas hydrate dissociation and the release of methane. Here, we evaluate bottom water temperature as a potential driver for hydrate dissociation and methane release from a recently discovered, gas-hydrate-bearing system south of ...
