Spatial Distribution of Dissolved Methane Over Extreme Oceanographic Gradients in the Subtropical Eastern South Pacific (17° to 37°S)

Troncoso, Macarena; Sanzana, K.; Verdugo, Josefa; Masotti, Ítalo

doi:10.1029/2020jc016925

Cited by 6 publications

(2 citation statements)

References 117 publications

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“…Farías et al. (2021) reported a CH 4 flux of 0.4 μmol/m 2 /d in the oligotrophic subtropical eastern South Pacific, which is comparable to our result in subtropical WNP (0.37 ± 0.36 μmol/m 2 /d). While in the South Pacific, Yoshida et al.…”

Section: Discussionsupporting

confidence: 91%

Methane Distribution, Production, and Emission in the Western North Pacific

Wang,

Du,

et al. 2024

JGR Oceans

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The ocean is a source of atmospheric methane (CH4), but there are still large uncertainties in the estimations of global oceanic CH4 emission due to sparse data coverage. In this study, we investigated the spatial distribution and influencing factors of CH4 in the Western North Pacific (WNP) during May–June 2021. High‐resolution continuous underway measurements showed that surface CH4 concentrations indicated an obvious spatial gradient with an increase from the south to the north due to the influence of water mixing between Kuroshio Extension (KE) and Oyashio. Surface water was generally oversaturated with respect to the atmospheric CH4, and high CH4 fluxes occurred in the Kuroshio‐Oyashio transition region due to high productivity and intensive air‐sea interaction, emphasizing the importance of the Kuroshio‐Oyashio transition region in global oceanic CH4 emission. Vertically, subsurface CH4 maximums were observed around 50–300 m due to in situ production through multiple pathways, and their distributions in the water column were affected by subduction of North Pacific Intermediate Water (NPIW) and advective transport. Methylphosphonate (MPn) enrichment experiment and 16S rRNA gene sequencing showed that in subtropical region and Kuroshio‐Oyashio transition region, Vibrio spp. might produce CH4 by degrading MPn. Although this process was inhibited by inorganic phosphorus and regulated by iron stress, it might be a potential source of CH4 in the oxygenated water in the WNP. Our results contribute to better constrain the global oceanic CH4 emission, and help understanding the role of biological and physical processes in regulating CH4 emission in the WNP.

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Section: Discussionsupporting

confidence: 91%

Methane Distribution, Production, and Emission in the Western North Pacific

Wang,

Du,

et al. 2024

JGR Oceans

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“…However, the effect of mesoscale eddies on dissolved gases, including CO 2 , methane, and NMHCs in marine waters remain poorly understood. In order to accurately assess global oceanic carbon emission fluxes, it is necessary to consider the effect of eddies on the climate-relevant gas emission fluxes (Yoshikawa et al, 2014;Li et al, 2019;Farias et al, 2021). As such, we conducted in situ measurements within an anticyclonic eddy in the North Pacific to constrain its influence on CO 2 , methane, and NMHCs dynamic in the KOE.…”

Section: Introductionmentioning

confidence: 99%

The distribution and emission of CO2, CH4 and light hydrocarbons in an anticyclonic eddy of the Kuroshio extension

Wang

Qiao

et al. 2023

Front. Mar. Sci.

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Mesoscale eddies are energetic and swirling circulations that frequently occur in the open ocean. The effects of mesoscale eddies on the biogeochemical cycling of climate-relevant gases remain poorly constrained. We investigated the distribution and air-sea fluxes of CO2, methane, and five non–methane hydrocarbons (NMHCs) in an anticyclone eddy of Kuroshio Extension during September 2019. Within eddy core, intense stratification hindered the replenishment of nutrients and favored the growth of small-size phytoplankton, such as Prochlorococcus. Seawater pCO2 decreased from 406.1 μatm at the eddy outside to 377.5 μatm at the eddy core, accompanied by a decrease in surface seawater temperature from 26.7 °C to 25.2 °C. The vertical distribution of methane (0.3-9.9 nmol L-1) was influenced by the eddy process, with a maximum at 80 m in the eddy core, which might be attributed to the degradation of phosphonates sustained by Prochlorococcus. The concentrations of five NMHCs (ethane, ethylene, propane, propylene, and isoprene) ranged from 17.2-126.2, 36.7-168.1, 7.5-29.2, 22.6-64.1, 54.5-172.1, 3.5-27.9 pmol L-1, respectively. Isoprene correlated well with Chl-a concentrations at the eddy core, while no significant correlation was observed at the eddy outside. Air-sea fluxes of CO2 and isoprene associated with the eddy core were higher than those of the eddy outside, while the maximum ventilation of methane and other NMHCs (ethane, ethylene, propane, and propylene) was found at the eddy outside. Collectively, physical processes such as eddies impact the production and distribution of light hydrocarbons in seawater and further influence their regional emissions to the atmosphere.

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Biogeochemistry of greenhouse gases in coastal upwelling systems: Processes and sensitivity to global change

Lachkar,

Cornejo-D'Ottone,

Singh

et al. 2024

Elem Sci Anth

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Major coastal upwelling systems are among the most productive marine ecosystems in the world. They contribute disproportionately to the cycling of carbon and nutrients in the ocean and influence marine biogeochemistry beyond their productive regions. Characterized by intense microbial respiration (both aerobic and anaerobic), major coastal upwelling systems are also hotspots for the production and outgassing of potent greenhouse gases (GHG) such as CO2, N2O, and CH4. Quantifying and understanding these roles in the context of a changing climate is therefore a subject of great interest. Here we provide a short synthesis of the current knowledge of the contributions of major coastal upwelling systems to the cycling of GHG. Despite variations within and among different systems, low-latitude coastal upwelling systems typically act as a net carbon source to the atmosphere, while those at higher latitudes function as weak sinks or remain neutral regarding atmospheric CO2. These systems also significantly contribute to oceanic N2O and CH4 emissions, although the extent of their contribution to the latter remains poorly constrained. We also overview recent and future changes to upwelling systems in the context of a warmer climate and discuss uncertainties and implications for GHG production. Although rapid coastal warming is anticipated in all major coastal upwelling systems, the future changes in upwelling-favorable winds and their implications within the context of increased stratification are uncertain. Finally, we examine the major challenges that impede our ability to accurately predict how major coastal upwelling systems will respond to future climate change, and present recommendations for future research to better capture ongoing changes and disentangle natural and forced variability.

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Spatial Distribution of Dissolved Methane Over Extreme Oceanographic Gradients in the Subtropical Eastern South Pacific (17° to 37°S)

Cited by 6 publications

References 117 publications

Methane Distribution, Production, and Emission in the Western North Pacific

Methane Distribution, Production, and Emission in the Western North Pacific

The distribution and emission of CO2, CH4 and light hydrocarbons in an anticyclonic eddy of the Kuroshio extension

Biogeochemistry of greenhouse gases in coastal upwelling systems: Processes and sensitivity to global change

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