2019_programme: DIVERSE ACOUSTIC MANIFESTATIONS OF SHALLOW GAS IN THE GDAŃSK BAY (SOUTHERN BALTIC SEA)

• Session: 03. Acoustic Monitoring of Ocean Environments and Processes: Biology, Ecology, Geophysics and Man-made activities
  Organiser(s): Ratilal Purnima, Miksis-Olds Jennifer
• Lecture: DIVERSE ACOUSTIC MANIFESTATIONS OF SHALLOW GAS IN THE GDAŃSK BAY (SOUTHERN BALTIC SEA)
  Paper ID: 928
  Author(s): Jaśniewicz Damian, Idczak Jakub, Klusek Zygmunt, Brodecka-Goluch Aleksandra, Gorska Natalia, Bolałek Jerzy, Pezacki Patryk
  Presenter: Jaśniewicz Damian
  Presentation type: oral
  Abstract: Continental shelves and sub-bottom layers of shallow seas are considered as an areas of the most importance when it comes to global emission of methane from the marine environment. Due to relatively low solubility in water, methane can be often accumulated in shallow sediments as a gas. Presence of methane in shallow sediments is dependent on factors such as oxic conditions, organic matter and biogeochemical cycles, which are affected by recent intensification of climate changes. Non-invasive acoustic methods enable us to reveal various features of gaseous methane presence and its distribution through distinct acoustic gas manifestations.\n This study is focused on assessing the extent of sediments saturated by gaseous methane in the Gdańsk Bay as well as identifying and analyzing the spatial variability of their acoustic manifestations. Our approach was based on the combination of synthesis and digitization of various historical data obtained from literature sources, and analysis of new data from multi device acoustic measurements (single and split-beam echosounders, multi-beam echosounder and side-scan sonar). Acoustic backscattering data from sub-bottom layers, sediment surface and water column were analyzed. In addition, verification of methane presence based on geochemical analyses of upper layers of sediments taken by core sampler were performed.\n The obtained results revealed that the total area of the Gdańsk Bay sea bottom sediments saturated by gaseous methane constitutes of about 380 km2. Within the area of interest, at least three subareas of the distinct gas presence features can be specified based only on acoustic data. Moreover, results indicate strong spatial variation of gaseous methane sediments as well as gas emission from seafloor characterized by distinct acoustic recordings.
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• Corresponding author: Mr Jaśniewicz Damian
  Affiliation: Institute of Oceanology PAS
  Country: Poland
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