Details:

Journal Title:
Continental Shelf Research
Personal Author:
Weidner, Elizabeth ; Weber, Thomas.C. ; Mayer, Larry ; Jakobsson, Martin ; Chernykh, Denis ; ... More +
Weidner, Elizabeth ; Weber, Thomas.C. ; Mayer, Larry ; Jakobsson, Martin ; Chernykh, Denis ; Semiletov, Igor Less -
NOAA Program & Office:
NOS (National Ocean Service)
Description:
The bubble-mediated transport and eventual fate of methane escaping from the seafloor is of great interest to researchers in many fields. Acoustic systems are frequently used to study gas seep sites, as they provide broad synoptic observations of processes in the water column. However, the visualization and characterization of individual gas bubbles needed for quantitative studies has routinely required the use of optical sensors which offer a limited field of view and require extended amounts of time for deployment and data collection. In this paper, we present an innovative method for studying individual bubbles and estimating gas flux using a calibrated wideband from the Bolin Centre for Climate Research database: http://bolin.su.se/data/.and split-beam echosounder. The extended bandwidth (16 – 26 kHz) affords vertical range resolution of approximately 7.5 cm, allowing for the differentiation of individual bubbles in acoustic data. Split-aperture processing provides phase-angle data used to compensate for transducer beam-pattern effects and to precisely locate bubbles in the transducer field of view. The target strength of individual bubbles is measured and compared to an analytical scattering model to estimate bubble radius, and bubbles are tracked through the water column to estimate rise velocity. The resulting range of bubble radii (0.68–8.40 mm in radius) agrees with those found in other investigations with optical measurements, and the rise velocities trends are consistent with published models. Together, the observations of bubble radius and rise velocity offer a measure of gas flux, requiring nothing more than vessel transit over a seep site, bypassing the need to deploy time-consuming and expensive optical systems.
Keywords:
[+]
Aquatic Science Geology Oceanography
Source:
Continental Shelf Research, 173, 104-115
DOI:
https://doi.org/10.1016/j.csr.2018.12.005
ISSN:
0278-4343
Format:
PDF
Publisher:
Elsevier BV
Document Type:
Journal Article
Funding:
Grant no. NA15NOS4000200
Rights Information:
Accepted Manuscript
Compliance:
Library
Main Document Checksum:
[+]
urn:sha256:590195863d6845069119dc2f55fde87984c53c85131052bf6bdd3cbe19aee7d9
Download URL:
https://repository.library.noaa.gov/view/noaa/57779/noaa_57779_DS1.pdf
File Type:

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