Repositorio Digital Marítimo, Fluvial y Costero

Farias, L. and Troncoso, M. and Sanzana, K. and Verdugo, J. and Masotti, I.. (2021). Spatial Distribution of Dissolved Methane Over Extreme Oceanographic Gradients in the Subtropical Eastern South Pacific (17° to 37°S). Journal of Geophysical Research: Oceans, 126 (5). pp. 1-27. doi https://doi.org/10.1029/2020JC016925 (Unpublished)

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Abstract

Methane (CH4) is one of the most powerful greenhouse gases with the capacity to influence the Earth's radiative budget as well as contribute to atmospheric chemistry. Natural oceanic production makes up to ∼4% of the overall global CH4 emissions, however, there is uncertainty around the accuracy of this value due to a lack of accurate measurements. Such is the case in the Subtropical Eastern South Pacific Ocean (SESP), a region with pronounced chlorophyll-a and oxygen gradients, which in turn affect the microbial CH4 cycling. This study was conducted during spring-summer (2014–2016) in the SESP. The region (∼17°–37°S/71°–110°W) is separated into (i) eutrophic, (ii) mesotrophic, and (iii) oligotrophic areas, according to oceanographic and biogeochemical criteria. The SESP presents high CH4 zonal variability with levels ranging from 0.63 to 33.4 nmol L−1, corresponding to 29% and 1,423% saturation, respectively. High CH4 concentrations (>1,000% saturation) are observed in the narrow eutrophic area subjected to coastal upwelling. These conditions clearly differ to those observed in the extended oligotrophic subtropical gyre (∼100% saturation). Furthermore, CH4 also tends to accumulate in the mesotrophic area (with upto 1,423% saturation), where oceanographic conditions as stratification, mesoscale eddies and the island mass effect could trigger the presence of a microbial biomass that may be able to induce CH4 regeneration. The CH4 efflux is estimated to be between 0.13 and 19.1 μmol m−2 d−1 (mean ± SD = 4.72 ± 4.67) and the SESP has an emission rate of ∼87.9 Gg CH4 yr−1.

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Item Type:	Article
Uncontrolled Keywords:	Sissolved methane. Subtropical eastern South Pacific. CH4 exchange acros air-sea interface. Mesoscale processes. Spatial CH4 distribution
Geographical coverage :	Chile. Valparaíso. Cabo de Hornos. Isla Rapa Nui. Costa de Caldera. Islas Desventuradas. Archipiélago de Juan Fernández
Depositing User:	Dirección General Marítima
ISSN:	2169-9275
Official URL:	https://agupubs.onlinelibrary.wiley.com/doi/10.102...
Identification Number:	https://doi.org/10.1029/2020JC016925

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