Negligible atmospheric release of methane from decomposing hydrates in mid-latitude oceans

Joung, DongJoo; Ruppel, Carolyn D.; Southon, John; Weber, Thomas; Kessler, J. D.

doi:10.1038/s41561-022-01044-8

Cited by 17 publications

(8 citation statements)

References 53 publications

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“…However, our knowledge of recent trends on which future emission scenarios of N 2 O and CH 4 from the coastal ocean rely is still far from complete. In particular, hydrate dissolution due to ocean warming may enhance this flux at the seafloor, but only at the feather‐edge of the hydrate stability zone, which occurs in ∼400 m deep water in mid‐latitudes—which could be too deep for the methane to make it to the surface and escape to the atmosphere (Joung et al., 2022). Shallow hydrocarbon‐fed seep fields allow for more efficient methane release to the atmosphere (Hovland et al., 1993), but their impact appears to be highly localized (Joung et al., 2020), and the global‐scale contribution of geological CH 4 to marine emissions remains highly uncertain (Etiope et al., 2019).…”

Section: Discussionmentioning

confidence: 99%

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

Resplandy,

Hogikyan,

Müller

et al. 2024

Global Biogeochemical Cycles

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The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). In this second phase of the Regional Carbon Cycle Assessment and Processes (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap‐filled observation‐based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO2 in both observational products and models, but the magnitude of the median net global coastal uptake is ∼60% larger in models (−0.72 vs. −0.44 PgC year−1, 1998–2018, coastal ocean extending to 300 km offshore or 1,000 m isobath with area of 77 million km2). We attribute most of this model‐product difference to the seasonality in sea surface CO2 partial pressure at mid‐ and high‐latitudes, where models simulate stronger winter CO2 uptake. The coastal ocean CO2 sink has increased in the past decades but the available time‐resolving observation‐based products and models show large discrepancies in the magnitude of this increase. The global coastal ocean is a major source of N2O (+0.70 PgCO2‐e year−1 in observational product and +0.54 PgCO2‐e year−1 in model median) and CH4 (+0.21 PgCO2‐e year−1 in observational product), which offsets a substantial proportion of the coastal CO2 uptake in the net radiative balance (30%–60% in CO2‐equivalents), highlighting the importance of considering the three greenhouse gases when examining the influence of the coastal ocean on climate.

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Section: Discussionmentioning

confidence: 99%

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

Resplandy,

Hogikyan,

Müller

et al. 2024

Global Biogeochemical Cycles

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, our knowledge of recent trends on which future emission scenarios of N 2 O and CH 4 from the coastal ocean rely is still far from complete. In particular, hydrate dissolution due to ocean warming may enhance this flux at the seafloor, but only at the feather-edge of the hydrate stability zone, which occurs in ∼400 m deep water in mid-latitudes-which could be too deep for the methane to make it to the surface and escape to the atmosphere (Joung et al, 2022). Shallow hydrocarbon-fed seep fields allow for more efficient methane release to the atmosphere (Hovland et al, 1993), but their impact appears to be highly localized (Joung et al, 2020), and the global-scale contribution of geological CH 4 to marine emissions remains highly uncertain (Etiope et al, 2019).…”

Section: Coastal Ocean N 2 O and Chmentioning

confidence: 99%

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

Resplandy

Hogikyan

Bange

et al. 2023

Preprint

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The coastal ocean contributes to regulating atmospheric greenhouse gas concentrations by taking up carbon dioxide (CO2) and releasing nitrous oxide (N2O) and methane (CH4). Major advances have improved our understanding of the coastal air-sea exchanges of these three gasses since the first phase of the Regional Carbon Cycle Assessment and Processes (RECCAP in 2013), but a comprehensive view that integrates the three gasses at the global scale is still lacking. In this second phase (RECCAP2), we quantify global coastal ocean fluxes of CO2, N2O and CH4 using an ensemble of global gap-filled observation-based products and ocean biogeochemical models. The global coastal ocean is a net sink of CO2 in both observational products and models, but the magnitude of the median net global coastal uptake is ~60% larger in models (-0.72 vs. -0.44 PgC/yr, 1998-2018, coastal ocean area of 77 million km2). We attribute most of this model-product difference to the seasonality in sea surface CO2 partial pressure at mid- and high-latitudes, where models simulate stronger winter CO2 uptake. The global coastal ocean is a major source of N2O (+0.70 PgCO2-e /yr in observational product and +0.54 PgCO2-e /yr in model median) and of CH4 (+0.21 PgCO2-e /yr in observational product), which offsets a substantial proportion of the net radiative effect of coastal \co uptake (35-58% in CO2-equivalents). Data products and models need improvement to better resolve the spatio-temporal variability and long term trends in CO2, N2O and CH4 in the global coastal ocean.

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“…The role of gas hydrate away from the landward limit of its stability zone in amplifying climatic change is thought to be negligible in some studies, partly because the methane released from gas hydrates could be re‐trapped and consumed before entering the ocean (Joung et al., 2022; Li et al., 2017, 2023; Ruppel & Kessler, 2017). Our study demonstrates that methane can be vented from deeply buried sediments along different pathways and through GHSZ.…”

Section: Discussionmentioning

confidence: 99%

Submarine fluid flow system feeding methane emission in the northern South China Sea

Wang,

Li,

Wang

et al. 2024

Basin Research

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Submarine fluid flow system can transport methane into ocean. However, its evolution is not fully understood, particularly methane migration through the gas hydrate stability zone (GHSZ) in deep‐water settings. Here, we used 3D seismic and well‐logging data to show the currently active fluid flow system in the northern South China Sea. It was interpreted to have two parts and they together feed intermittent methane emission. Three gas clouds have been seismically imaged beneath the base of gas hydrate stability zone (BGHSZ) and a set of new faults can be identified within them. Twenty‐eight seismic pipes were found to penetrate three vertically stacked mass transport deposits (MTDs) above the gas clouds. Log‐seismic correlation shows that the seismic reflections in the pipe represent MTD sediment, bulk carbonate and gas hydrate‐ or free gas‐bearing sediments. We interpreted faults and pipes as the main migration conduits below and above the BGHSZ respectively. The MTD within the GHSZ could seal the underlying free gas transported by faults and thus overpressure built up at the base prior to the occurrences of the pipes and the fracturing through the overlying sedimentary succession. Subsequently, focused fluid flow entered the GHSZ, with the methane probably bypassing the GHSZ before pore clogging of gas hydrates occurred. Additionally, mapping of high‐amplitude reflections surrounding the upper portion of gas clouds reveals the relict free gas associated with three paleo‐GHSZ bases. Episodic emplacements of new MTDs repeatedly caused the upward shifts of the BGHSZ and the resultant gas hydrate dissociation, contributing to methane emission. We proposed that the occurrences of MTDs may facilitate methane emission by intermittently trapping methane and inducing gas hydrate dissociation in deep‐water settings.

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Negligible atmospheric release of methane from decomposing hydrates in mid-latitude oceans

Cited by 17 publications

References 53 publications

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

A Synthesis of Global Coastal Ocean Greenhouse Gas Fluxes

Submarine fluid flow system feeding methane emission in the northern South China Sea

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