The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Broadband acoustic inversion for gas flux quantification - application to a methane plume at Scanner Pockmark, central North Sea

Broadband acoustic inversion for gas flux quantification - application to a methane plume at Scanner Pockmark, central North Sea
Broadband acoustic inversion for gas flux quantification - application to a methane plume at Scanner Pockmark, central North Sea

The release of greenhouse gases from both natural and man-made sites has been identified as a major cause of global climate change. Extensive work has addressed quantifying gas seeps in the terrestrial setting while little has been done to refine accurate methods for determining gas flux emerging through the seabed into the water column. This paper investigates large-scale methane seepage from the Scanner Pockmark in the North Sea with a new methodology that integrates data from both multibeam and single-beam acoustics, with single-beam data covering a bandwidth (3.5 to 200 kHz) far wider than that used in previous studies, to quantify the rate of gas release from the seabed into the water column. The multibeam data imaged a distinct fork-shaped methane plume in the water column, the upper arm of which was consistently visible in the single-beam data, while the lower arm was only intermittently visible. Using a novel acoustic inversion method, we determine the depth-dependent gas bubble size distribution and the gas flux for each plume arm. Our results show that the upper plume arm comprises bubbles with radii ranging from 1 to 15 mm, while the lower arm consists of smaller bubbles with radii ranging from 0.01 to 0.15 mm. We extrapolate from these estimates to calculate the gas flux from the Scanner Pockmark as between 1.6 and 2.7 × 10 6 kg/year (272 to 456 L/min). This range was calculated by considering uncertainties together with Monte Carlo simulation. Our improved methodology allows more accurate quantification of natural and anthropogenic gas plumes in the water column.

broadband, bubble, gas, methane, sonar, underwater acoustics
2169-9275
Li, Jianghui
9c589194-00fa-4d42-abaf-53a32789cc5e
Roche, Ben
2746ee9e-1b87-4d2f-b4e1-dcdc0ca7a719
Bull, Jonathan
974037fd-544b-458f-98cc-ce8eca89e3c8
White, Paul
2dd2477b-5aa9-42e2-9d19-0806d994eaba
Leighton, Timothy
3e5262ce-1d7d-42eb-b013-fcc5c286bbae
Provenzano, Giuseppe
076fb0cd-74db-4b62-bc0b-afffbe442cc4
Dewar, Marus
92a8672d-4cf9-4c6c-aaa8-071a70f59505
Henstock, Timothy
27c450a4-3e6b-41f8-97f9-4e0e181400bb
Li, Jianghui
9c589194-00fa-4d42-abaf-53a32789cc5e
Roche, Ben
2746ee9e-1b87-4d2f-b4e1-dcdc0ca7a719
Bull, Jonathan
974037fd-544b-458f-98cc-ce8eca89e3c8
White, Paul
2dd2477b-5aa9-42e2-9d19-0806d994eaba
Leighton, Timothy
3e5262ce-1d7d-42eb-b013-fcc5c286bbae
Provenzano, Giuseppe
076fb0cd-74db-4b62-bc0b-afffbe442cc4
Dewar, Marus
92a8672d-4cf9-4c6c-aaa8-071a70f59505
Henstock, Timothy
27c450a4-3e6b-41f8-97f9-4e0e181400bb

Li, Jianghui, Roche, Ben, Bull, Jonathan, White, Paul, Leighton, Timothy, Provenzano, Giuseppe, Dewar, Marus and Henstock, Timothy (2020) Broadband acoustic inversion for gas flux quantification - application to a methane plume at Scanner Pockmark, central North Sea. Journal of Geophysical Research: Oceans, 125 (9), [e2020JC016360]. (doi:10.1029/2020JC016360).

Record type: Article

Abstract

The release of greenhouse gases from both natural and man-made sites has been identified as a major cause of global climate change. Extensive work has addressed quantifying gas seeps in the terrestrial setting while little has been done to refine accurate methods for determining gas flux emerging through the seabed into the water column. This paper investigates large-scale methane seepage from the Scanner Pockmark in the North Sea with a new methodology that integrates data from both multibeam and single-beam acoustics, with single-beam data covering a bandwidth (3.5 to 200 kHz) far wider than that used in previous studies, to quantify the rate of gas release from the seabed into the water column. The multibeam data imaged a distinct fork-shaped methane plume in the water column, the upper arm of which was consistently visible in the single-beam data, while the lower arm was only intermittently visible. Using a novel acoustic inversion method, we determine the depth-dependent gas bubble size distribution and the gas flux for each plume arm. Our results show that the upper plume arm comprises bubbles with radii ranging from 1 to 15 mm, while the lower arm consists of smaller bubbles with radii ranging from 0.01 to 0.15 mm. We extrapolate from these estimates to calculate the gas flux from the Scanner Pockmark as between 1.6 and 2.7 × 10 6 kg/year (272 to 456 L/min). This range was calculated by considering uncertainties together with Monte Carlo simulation. Our improved methodology allows more accurate quantification of natural and anthropogenic gas plumes in the water column.

Text
2020JC016360R - Accepted Manuscript
Restricted to Repository staff only
Request a copy

More information

Accepted/In Press date: 29 July 2020
e-pub ahead of print date: 3 August 2020
Published date: September 2020
Keywords: broadband, bubble, gas, methane, sonar, underwater acoustics

Identifiers

Local EPrints ID: 443106
URI: http://eprints.soton.ac.uk/id/eprint/443106
ISSN: 2169-9275
PURE UUID: 4b69fdfa-027e-464b-ad04-f70d0fbd9eed
ORCID for Jianghui Li: ORCID iD orcid.org/0000-0002-2956-5940
ORCID for Paul White: ORCID iD orcid.org/0000-0002-4787-8713
ORCID for Timothy Leighton: ORCID iD orcid.org/0000-0002-1649-8750
ORCID for Timothy Henstock: ORCID iD orcid.org/0000-0002-2132-2514

Catalogue record

Date deposited: 11 Aug 2020 16:30
Last modified: 26 Nov 2021 03:11

Export record

Altmetrics

Contributors

Author: Jianghui Li ORCID iD
Author: Ben Roche
Author: Jonathan Bull
Author: Paul White ORCID iD
Author: Giuseppe Provenzano
Author: Marus Dewar

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×