English
norskBlar i forfatter "Chand, Shyam"
Viser treff 1-17 av 17
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Bottom-simulating reflector dynamics at Arctic thermogenic gas provinces: An example from Vestnesa Ridge, offshore west Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06) -
Constraints on Gas Hydrate Distribution and Morphology in Vestnesa Ridge, Western Svalbard Margin, Using Multicomponent Ocean‐Bottom Seismic Data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-26)Gas hydrates occur within sediments on the western Svalbard continental margin and the Vestnesa Ridge, a large sediment drift that extends in a west‐north‐west direction from the margin towards the mid‐ocean ridge. We acquired multi‐component ocean‐bottom seismic (OBS) data at ten locations on the crest area of the eastern segment of the Vestnesa Ridge, an area with active gas seepage. P and S‐wave ... -
Detection of gas hydrates in faults using azimuthal seismic velocity analysis,Vestnesa Ridge, W-Svalbard Margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-24)Joint analysis of electrical resistivity and seismic velocity data is primarily used todetect the presence of gas hydrate-filled faultsand fractures. In this study, we present a novel approach to inferthe occurrence of structurally-controlled gas hydrateaccumulations using azimuthal seismic velocity analysis. We perform thisanalysis using ocean-bottom seismic (OBS) data at two sites on Vestnesa ... -
Detectionof gas hydrates infaults using azimuthal seismic velocity analysis,Vestnesa Ridge, W-Svalbard Margin
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-24)Joint analysis of electrical resistivity and seismic velocity data is primarily used to detect the presence of gas hydrate‐filled faults and fractures. In this study, we present a novel approach to infer the occurrence of structurally‐controlled gas hydrate accumulations using azimuthal seismic velocity analysis. We perform this analysis using ocean‐bottom seismic (OBS) data at two sites on Vestnesa ... -
Discharge of Meteoric Water in the Eastern Norwegian Sea since the Last Glacial Period
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-03)Submarine groundwater discharge could impact the transport of critical solutes to the ocean. However, its driver(s), significance over geological time scales, and geographical coverage are poorly understood. We characterize a submarine groundwater seep from the continental slope off northern Norway where substantial amount of meteoric water was detected. We reconstruct the seepage history from ... -
Gas hydrate and free gas detection using seismic quality factor estimates from high-resolution P-cable 3D seismic data
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-23)We have estimated the seismic attenuation in gas hydrate and free-gas-bearing sediments from high-resolution P-cable 3D seismic data from the Vestnesa Ridge on the Arctic continental margin of Svalbard. P-cable data have a broad bandwidth (20–300 Hz), which is extremely advantageous in estimating seismic attenuation in a medium. The seismic quality factor (Q), the inverse of seismic attenuation, ... -
Gas seeps in Norwegian waters – distribution and mechanisms
(Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-01)Gas seeps and fluid-flow related seabed features are found over the entire Norwegian exclusive economic zone (EEZ). Multibeam water-column data from c. 136 000 km2 has revealed more than 5 000 gas seeps. Most of the gas seeps seem to have biogenic, thermogenic or mixed origin; some may be of abiotic origin. The spatial distribution of the gas seeps appears to correlate with: 1 – structural highs ... -
The history and future trends of ocean warming-induced gas hydrate dissociation in the SW Barents Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-01-13)The Barents Sea is a major part of the Arctic where the Gulf Stream mixes with the cold Arctic waters. Late Cenozoic uplift and glacial erosion have resulted in hydrocarbon leakage from reservoirs, evolution of fluid flow systems, shallow gas accumulations, and hydrate formation throughout the Barents Sea. Here we integrate seismic data observations of gas hydrate accumulations along with gas hydrate ... -
Long-term fluid expulsion revealed by carbonate crusts and pockmarks connected to subsurface gas anomalies and palaeo-channels in the central North Sea
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-19)Gas seepage through the seafloor into the water column is inferred based on acoustic mapping, video observations and geochemical analyses at multiple locations in the Viking Graben and Utsira High areas of the central North Sea. Flares in the Viking Graben occur both inside and along the periphery of a submarine melt water channel where pockmarks (up to 500 m in diameter) and methane-derived carbonate ... -
Modelling persistent methane seepage offshore western Svalbard since early Pleistocene
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-31)Recent observations of extensive methane release into the oceans and atmosphere have raised concern as to whether rising temperatures across the Arctic could drive rapid destabilization of gas hydrate reservoirs. Here, we report modelling results from hydrate-modulated methane seepage from Vestnesa Ridge, offshore western Svalbard, suggesting that continuous leakage has occurred from the seafloor ... -
New cold seep sites on the continental slope southwest to Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-04-09)We discovered seafloor features such as bacterial mats and carbonate crusts typical for active methane seeps on the continental slope southwest of Svalbard. These features are associated with two main northwest-southeast trending morphological structures that are oriented parallel to the regional continental slope. Both structures occur at c. 800 m water depth, at the boundary between the Storfjorden ... -
Protracted post-glacial hydrocarbon seepage in the Barents Sea revealed by U–Th dating of seep carbonates
(Journal article; Tidsskriftartikkel; Peer reviewed, 2024-03-01)The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U–Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156–383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west ... -
Role of tectonic stress in seepage evolution along the gas hydrate-charged Vestnesa Ridge, Fram Strait
(Journal article; Tidsskriftartikkel, 2015-02-03) -
Role of tectonic stress in seepage evolution along the gas hydrate‐charged Vestnesa Ridge, Fram Strait
(Journal article; Tidsskriftartikkel; Peer reviewed, 2015-01-13)Methane expulsion from the world ocean floor is a broadly observed phenomenon known to be episodic. Yet the processes that modulate seepage remain elusive. In the Arctic offshore west Svalbard, for instance, seepage at 200–400 m water depth may be explained by ocean temperature‐controlled gas hydrate instabilities at the shelf break, but additional processes are required to explain seepage in ... -
Sources and turnover of organic carbon and methane in fjord and shelf sediments off Northern Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-10-22)To better understand the present and past carbon cycling and transformation processes in methane-influenced fjord and shelf areas of northern Norway, we compared two sediment cores from the Hola trough and from Ullsfjorden. We investigated (1) the organic matter composition and sedimentological characteristics to study the sources of organic carbon (C<sub>org</sub>) and the factors influencing ... -
Strategy for Detection and High-Resolution Characterization of Authigenic Carbonate Cold Seep Habitats Using Ships and Autonomous Underwater Vehicles on Glacially Influenced Terrain
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-26)Cold seep habitats with authigenic carbonates and associated chemosynthetic communities in glacially influenced terrains constitute an important part of the benthic ecosystems, but they are difficult to detect in large-scale seabed surveys. The areas they occupy are normally small, and survey platforms and sensors allowing high-resolution spatial characterization are necessary. We have developed a ... -
Timescales of methane seepage on the Norwegian margin following collapse of the Scandinavian Ice Sheet
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-05-11)Gas hydrates stored on continental shelves are susceptible to dissociation triggered by environmental changes. Knowledge of the timescales of gas hydrate dissociation and subsequent methane release are critical in understanding the impact of marine gas hydrates on the ocean–atmosphere system. Here we report a methane efflux chronology from five sites, at depths of 220–400 m, in the southwest Barents ...
