Spatial and temporal variability of free gas content in shallow sediments: Lake Kinneret as a case study

E. Uzhansky, B. Katsnelson, A. Lunkov, I. Ostrovsky

Research output: Contribution to journalArticlepeer-review

Abstract

Organic-rich aquatic sediments are a significant source of methane to the atmosphere. In situ remote quantifications of gas content in shallow sediment is a complex task due to its large spatiotemporal heterogeneity. The spatial and multiannual changes of free gas (methane) content (Θ) in shallow sediments were studied in deep subtropical Lake Kinneret. We implemented recently developed acoustic methodology that allows estimating Θ in sediment based on assessment of sound speed. This method is based on measurement of reflection coefficient of acoustic signal at low-to-mid frequencies from the water-sediment interface using geoacoustic inversion technique. The used approach provides an assessment of the mean gas content over certain bottom area near the sampling location. Analysis of acoustic measurements carried out in 2015–2018 shows distinct changes in Θ with bottom depth along the offshore transects. We found the inverse relationship between Θ and lake level. The observed patterns in sedimentary gas content are supported by previous observations showing (a) changes of acoustic sediment properties with depth and (b) inverse relationship between rate of gas ebullition from bottom and lake level. The obtained absolute values of Θ at different locations were the same order of magnitude as those estimated directly from frozen cores. The validity and reliability of the method and its further development are discussed.

Original languageEnglish
Pages (from-to)491-505
Number of pages15
JournalGeo-Marine Letters
Volume40
Issue number4
DOIs
StatePublished - 1 Aug 2020

Bibliographical note

Funding Information:
This work was supported by the Israel Science Foundation, grant 565/15.

Publisher Copyright:
© 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

ASJC Scopus subject areas

  • Oceanography
  • Environmental Science (miscellaneous)
  • Geotechnical Engineering and Engineering Geology
  • Earth and Planetary Sciences (miscellaneous)

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