Dissolved methane in the sills region of the Gulf of California

Dissolved methane in the sills region of the Gulf of California

An unusual combination of features makes the Midriff Islands region of the northern Gulf of California (NGC) a strong atmospheric methane source. Oceanographic isolation by a series of sills and islands along with upward transport of nutrient-rich water enhanced by tidal currents, upwelling, and ove...

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Autores principales: Macías-Zamora, José Vinicio, Castro-Morales, Karel, Burke, Roger Allen, López-Mariscal, Manuel
Formato: info:eu-repo/semantics/article
Lenguaje:eng
Publicado: Iniversidad Autónoma de Baja California 2013
Acceso en línea:https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2232
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language eng
description An unusual combination of features makes the Midriff Islands region of the northern Gulf of California (NGC) a strong atmospheric methane source. Oceanographic isolation by a series of sills and islands along with upward transport of nutrient-rich water enhanced by tidal currents, upwelling, and overflows results in high productivity. The resulting high phytoplankton biomass likely stimulates biogeochemical cycling that, in turn, may stimulate biological methane production in the water column and sediments. Additionally, venting of abiogenic methane-rich hydrothermal fluids in this tectonically active area and seepage of biogenic or thermogenic methane gas from the sediments may also be important sources. We found elevated methane concentrations throughout our study area, the highest within the Ballenas Channel, which was supersaturated with respect to atmospheric methane at all depths. Our vertical methane profiles show that elevated dissolved methane concentrations in the NGC are mainly associated with Gulf of California Water (GCW). Data from 22 stations suggest southward advection of methane via the methane-rich GCW, and lower methane concentrations south of the sills area. Our observations of supersaturated methane concentrations at all stations and all depths in the Ballenas Channel suggest that it is a strong source of methane to the atmosphere and to other parts of the NGC. In particular, station 7 at 50, 20, and 0 m depths had methane (CH4) concentrations of 49.1, 48.3, and 43.5 nM, respectively, corresponding to saturation values of 2090%, 2050%, and 1850%, respectively. Our calculated NGC fluxes ranged from 3.4 to 103.4 µmol CH4 m–2 d–1. The average methane flux calculated for our entire study area was 21.1 µmol CH4 m–2 d–1. These values are higher than those measured at many other high productivity sites worldwide including upwelling sites, and suggest input of methane via hydrothermal fluids or seepage from the sediments. Key words: dissolved methane, gas chromatography, potential methane sources and origin. 
format info:eu-repo/semantics/article
author Macías-Zamora, José Vinicio
Castro-Morales, Karel
Burke, Roger Allen
López-Mariscal, Manuel
spellingShingle Macías-Zamora, José Vinicio
Castro-Morales, Karel
Burke, Roger Allen
López-Mariscal, Manuel
Dissolved methane in the sills region of the Gulf of California
author_facet Macías-Zamora, José Vinicio
Castro-Morales, Karel
Burke, Roger Allen
López-Mariscal, Manuel
author_sort Macías-Zamora, José Vinicio
title Dissolved methane in the sills region of the Gulf of California
title_short Dissolved methane in the sills region of the Gulf of California
title_full Dissolved methane in the sills region of the Gulf of California
title_fullStr Dissolved methane in the sills region of the Gulf of California
title_full_unstemmed Dissolved methane in the sills region of the Gulf of California
title_sort dissolved methane in the sills region of the gulf of california
publisher Iniversidad Autónoma de Baja California
publishDate 2013
url https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2232
_version_ 1792609598714150912
spelling repositorioinstitucional-20.500.12930-74552023-05-09T14:30:48Z Dissolved methane in the sills region of the Gulf of California Metano disuelto en la región de umbrales del golfo de California Macías-Zamora, José Vinicio Castro-Morales, Karel Burke, Roger Allen López-Mariscal, Manuel An unusual combination of features makes the Midriff Islands region of the northern Gulf of California (NGC) a strong atmospheric methane source. Oceanographic isolation by a series of sills and islands along with upward transport of nutrient-rich water enhanced by tidal currents, upwelling, and overflows results in high productivity. The resulting high phytoplankton biomass likely stimulates biogeochemical cycling that, in turn, may stimulate biological methane production in the water column and sediments. Additionally, venting of abiogenic methane-rich hydrothermal fluids in this tectonically active area and seepage of biogenic or thermogenic methane gas from the sediments may also be important sources. We found elevated methane concentrations throughout our study area, the highest within the Ballenas Channel, which was supersaturated with respect to atmospheric methane at all depths. Our vertical methane profiles show that elevated dissolved methane concentrations in the NGC are mainly associated with Gulf of California Water (GCW). Data from 22 stations suggest southward advection of methane via the methane-rich GCW, and lower methane concentrations south of the sills area. Our observations of supersaturated methane concentrations at all stations and all depths in the Ballenas Channel suggest that it is a strong source of methane to the atmosphere and to other parts of the NGC. In particular, station 7 at 50, 20, and 0 m depths had methane (CH4) concentrations of 49.1, 48.3, and 43.5 nM, respectively, corresponding to saturation values of 2090%, 2050%, and 1850%, respectively. Our calculated NGC fluxes ranged from 3.4 to 103.4 µmol CH4 m–2 d–1. The average methane flux calculated for our entire study area was 21.1 µmol CH4 m–2 d–1. These values are higher than those measured at many other high productivity sites worldwide including upwelling sites, and suggest input of methane via hydrothermal fluids or seepage from the sediments. Key words: dissolved methane, gas chromatography, potential methane sources and origin.  Una combinación inusual de rasgos oceanográficos hacen de la región de las grandes islas del norte del golfo de California (NGC) una importante fuente de metano hacia la atmósfera. El aislamiento oceanográfico por umbrales e islas y el transporte vertical de agua rica en nutrientes, aumentado por mareas, surgencias y desbordes, resultan en alta productividad. La alta biomasa fitoplanctónica probablemente estimula el reciclado biogeoquímico, que a su vez estimula la producción biológica de metano en el agua y sedimento. Adicionalmente, el venteo de fluidos hidrotermales ricos en metano en esta zona tectónicamente activa y las filtraciones de gas metano, termogénico o biogénico, del sedimento también pueden ser fuentes importantes. Se encontraron concentraciones elevadas de metano a lo largo del área de estudio, principalmente dentro del canal de Ballenas, con supersaturación respecto al metano atmosférico en todas las profundidades. Nuestros perfiles verticales de metano muestran que las elevadas concentraciones de metano en el NGC están asociadas al Agua del Golfo de California (AGC). Datos de 22 estaciones sugieren una advección de metano al sur vía AGC rica en metano, y concentraciones menores de metano al sur de los umbrales. La supersaturación en el canal de Ballenas sugiere que éste es una fuente importante de metano hacia la atmósfera y hacia otras partes del NGC. En particular, la estación 7 a 50, 20 y 0 m de profundidad presentó concentraciones de metano (CH4) de 49.1, 48.3 y 43.5 nM, respectivamente (saturaciones de 2090%, 2050% y 1850%, respectivamente). El flujo de gas hacia la atmósfera varió de 3.4 a 103.4 µmol CH4 m–2 d–1, con un promedio total para toda el área de 21.1 µmol CH4 m–2 d–1. Estos valores son más altos comparados con aquellos medidos en otros sitios de alta productividad a nivel mundial, incluyendo zonas de surgencias, y sugieren una entrada de metano vía procesos hidrotermales o filtraciones desde el sedimento. 2013-06-01 2021-06-03T03:55:22Z 2021-06-03T03:55:22Z info:eu-repo/semantics/article info:eu-repo/semantics/publishedVersion Peer-reviewed Article Artículo Arbitrado https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2232 10.7773/cm.v39i2.2232 https://hdl.handle.net/20.500.12930/7455 eng https://www.cienciasmarinas.com.mx/index.php/cmarinas/article/view/2232/1434 application/pdf Iniversidad Autónoma de Baja California Ciencias Marinas; Vol. 39 No. 2 (2013); 119-135 Ciencias Marinas; Vol. 39 Núm. 2 (2013); 119-135 2395-9053 0185-3880

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