Ephemerality of discrete methane vents in lake sediments

Geophysical Research Letters
By: , and 

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Abstract

Methane is a potent greenhouse gas whose emission from sediments in inland waters and shallow oceans may both contribute to global warming and be exacerbated by it. The fraction of methane emitted by sediments that bypasses dissolution in the water column and reaches the atmosphere as bubbles depends on the mode and spatiotemporal characteristics of venting from the sediments. Earlier studies have concluded that hot spots—persistent, high-flux vents—dominate the regional ebullitive flux from submerged sediments. Here the spatial structure, persistence, and variability in the intensity of methane venting are analyzed using a high-resolution multibeam sonar record acquired at the bottom of a lake during multiple deployments over a 9 month period. We confirm that ebullition is strongly episodic, with distinct regimes of high flux and low flux largely controlled by changes in hydrostatic pressure. Our analysis shows that the spatial pattern of ebullition becomes homogeneous at the sonar's resolution over time scales of hours (for high-flux periods) or days (for low-flux periods), demonstrating that vents are ephemeral rather than persistent, and suggesting that long-term, lake-wide ebullition dynamics may be modeled without resolving the fine-scale spatial structure of venting.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Ephemerality of discrete methane vents in lake sediments
Series title Geophysical Research Letters
DOI 10.1002/2016GL068668
Volume 43
Issue 9
Year Published 2016
Language English
Publisher AGU Publications
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 8 p.
First page 4374
Last page 4381
Online Only (Y/N) N
Additional Online Files (Y/N) N