English
norskBlar i forfatter "Jansson, Pär"
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Autonomous methane seep site monitoring offshore western Svalbard: hourly to seasonal variability and associated oceanographic parameters
(Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-18)Improved quantification techniques of natural sources are needed to explain variations in atmospheric methane. In polar regions, high uncertainties in current estimates of methane release from the seabed remain. We present unique 10- and 3-month time series of bottom water measurements of physical and chemical parameters from two autonomous ocean observatories deployed at separate intense seabed ... -
High-resolution underwater laser spectrometer sensing provides new insights into methane distribution at an Arctic seepage site
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-13)Methane (CH4) in marine sediments has the potential to contribute to changes in the ocean and climate system. Physical and biochemical processes that are difficult to quantify with current standard methods such as acoustic surveys and discrete sampling govern the distribution of dissolved CH4 in oceans and lakes. Detailed observations of aquatic CH4 concentrations are required for a better understanding ... -
An integrated view of the methane system in the pockmarks at Vestnesa Ridge, 79°N
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-08)The Vestnesa Ridge is a NW-SE trending, ~ 100 km-long, 1–2 km-thick contourite sediment section located in the Arctic Ocean, west of Svalbard, at 79°N. Pockmarks align along the ridge summit at water depths of ~ 1200 m; they are ~ 700 m in diameter and ~ 10 m deep relative to the surrounding seafloor. Observations of methane seepage in this area have been reported since 2008. Here we summarize and ... -
Methane at Svalbard and over the European Arctic Ocean
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-05)Methane (CH<sub>4</sub>) is a powerful greenhouse gas. Its atmospheric mixing ratios have been increasing since 2005. Therefore, quantification of CH<sub>4</sub> sources is essential for effective climate change mitigation. Here we report observations of the CH<sub>4</sub> mixing ratios measured at the Zeppelin Observatory (Svalbard) in the Arctic and aboard the research vessel (RV) Helmer Hanssen ... -
Methane bubbles in the Arctic Ocean. Quantification, variability analysis and modelling of free and dissolved methane from the seafloor to the atmosphere
(Doctoral thesis; Doktorgradsavhandling, 2018-11-09)Intensive but heterogeneous and transient seepage of methane (CH4) bubbles from the seafloor exist west of Prins Karls Forland (PKF), offshore western Svalbard. The powerful greenhouse gas CH4, has 32 times higher warming potential than carbon dioxide (CO2) and if seepage of CH4 from the seafloor reaches the atmosphere, it will contribute to the warming climate. Warming of the oceans may in turn, ... -
A new numerical model for understanding free and dissolved gasprogression toward the atmosphere in aquatic methane seepage systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-16)We present a marine two‐phase gas model in one dimension (M2PG1) resolving interaction between the free and dissolved gas phases and the gas propagation toward the atmosphere in aquatic environments. The motivation for the model development was to improve the understanding of benthic methane seepage impact on aquatic environments and its effect on atmospheric greenhouse gas composition. Rising, ... -
Physical controls of dynamics of methane venting from a shallow seep area west of Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-06)We investigate methane seepage on the shallow shelf west of Svalbard during three consecutive years, using discrete sampling of the water column, echosounder-based gas flux estimates, water mass properties, and numerical dispersion modelling. The results reveal three distinct hydrographic conditions in spring and summer, showing that the methane content in the water column is controlled by a combination ... -
Reduced methane seepage from Arctic sediments during cold bottom-water conditions
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-13)Large amounts of methane are trapped within gas hydrate in subseabed sediments in the Arctic Ocean, and bottom-water warming may induce the release of methane from the seafloor. Yet the effect of seasonal temperature variations on methane seepage activity remains unknown as surveys in Arctic seas are conducted mainly in summer. Here we compare the activity of cold seeps along the gas hydrate stability ... -
Variability of Acoustically Evidenced Methane Bubble Emissions Offshore Western Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-22)Large reservoirs of methane present in Arctic marine sediments are susceptible to rapid warming, promoting increasing methane emissions. Gas bubbles in the water column can be detected, and flow rates can be quantified using hydroacoustic survey methods, making it possible to monitor spatiotemporal variability. We present methane (CH<sub>4</sub>) bubble flow rates derived from hydroacoustic data ...
