Distribution and Drivers of Organic Carbon Sedimentation Along the Continental Margins

AGU Advances, Journal Year: 2024, Volume and Issue: 5(4)

Published: Aug. 1, 2024

Abstract Organic carbon (OC) sedimentation in marine sediments is the largest long‐term sink of atmospheric CO 2 after silicate weathering. Understanding mechanistic and quantitative aspects OC delivery preservation critical for predicting role oceans modulating global climate. Yet, estimates marginal settings span an order magnitude, primary controls remain highly debated. Here, we provide first bottom‐up estimate along margins using a synthesis literature data. We quantify both terrestrial‐ marine‐sourced fluxes perform statistical analysis to discern key factors influencing their magnitude. find that host 23.2 ± 3.5 Tmol annually, with approximately 84% origin. Accordingly, calculate only 2%–3% exported from euphotic zone escapes remineralization before sedimentation. Surprisingly, over half all occurs below bottom waters oxygen concentrations greater than 180 μM, while less 4% <50 μM oxygen. This challenges prevailing paradigm bottom‐water (BWO) control on preservation. Instead, our reveals water depth most significant predictor sedimentation, surpassing other investigated, including BWO levels sea‐surface chlorophyll concentrations. finding suggests not production, but ability resist during transit through column settling seafloor.

Language: Английский

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The effects of bathymetry on the long-term carbon cycle and CCD

Proceedings of the National Academy of Sciences, Journal Year: 2024, Volume and Issue: 121(21)

Published: May 15, 2024

The shape of the ocean floor (bathymetry) and overlaying sediments provide largest carbon sink throughout Earth’s history, supporting ~one to two orders magnitude more storage than oceans atmosphere combined. While accumulation erosion these are bathymetry dependent (e.g., due pressure, temperature, salinity, ion concentration, available productivity), no systemic study has quantified how global basin scale bathymetry, controlled by evolution tectonics mantle convection, affects long-term cycle. We reconstruct spanning last 80 Myr describe steady-state changes in chemistry within Earth system model LOSCAR. find that both reconstructions representative synthetic tests show alkalinity, calcite saturation state, carbonate compensation depth (CCD) strongly on shallow (ocean ≤600 m) distribution deep marine regions (>1,000 m). Limiting Cenozoic alone leads predicted CCD variations 500 m, 33 50% total observed paleoproxy records. Our results suggest neglecting bathymetric significant misattribution uncertain cycle parameters atmospheric CO 2 water column temperature) processes biological pump efficiency silicate-carbonate riverine flux). To illustrate this point, we use our updated for an Early Paleogene C case study. obtain flux estimates a reversal weathering trend with respect present-day, contrasting previous studies, but consistent proxy records tectonic reconstructions.

Language: Английский

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Glacial troughs as centres of organic carbon accumulation on the Norwegian continental margin

Communications Earth & Environment, Journal Year: 2024, Volume and Issue: 5(1)

Published: June 15, 2024

Abstract The role of continental margin sediments in the carbon cycle and associated management potential for climate mitigation are currently poorly understood. Previous work has indicated that store significant amounts organic carbon, but few studies have quantified rates at which is accumulated. Here, we use machine learning to make spatial predictions stocks accumulation on Norwegian margin. We show surface (upper 10 cm) 814 Tg accumulate 6 yr −1 carbon. Shelf-incised glacial troughs account 39% 48% accumulation, with main hotspot located Skagerrak. Continental scales much larger than vegetated coastal ecosystems Norway because their extent. Future should explore what extent interventions could increase rates, e.g., by minimising anthropogenic disturbance seafloor sediments.

Language: Английский

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Ultrahigh-Resolution Mass Spectrometry Advances for Biogeochemical Analysis: From Seafloor Sediments to Petroleum and Marine Oil Spills

Journal of the American Society for Mass Spectrometry, Journal Year: 2024, Volume and Issue: unknown

Published: Dec. 9, 2024

This Perspective explores the transformative impact of ultrahigh-resolution mass spectrometry (UHR-MS), particularly Fourier transform ion cyclotron resonance (FT-ICR-MS), in characterization complex environmental and petroleum samples. UHR-MS has significantly advanced our ability to identify molecular formulas mixtures, revolutionizing study biogeochemical processes organic matter evolution on wide time scales. We start by briefly reviewing main technological advances context applications, highlighting some challenges technology such as quantitation structural identification. then showcase a selection impactful applications published last 20+ years. In field lipidomics, high-resolution analysis lipids sediments enables multiproxy studies provides novel insights into past conditions. also facilitated kerogen, complex, poorly soluble mixture formed from sedimented over geological scales, identification polar compounds within its fractions. (geo)chemistry, enabled biomarkers petroporphyrins, asphaltenes, high-molecular-weight naphthenic acids, shedding light complexity crude oil. The application oil spill science revealed significant transformations during weathering processes, photo-oxidation, which are crucial for assessing spills improving preparedness future spills. These advancements underscore role this maturing analytical deepening understanding geochemical cycles, potential research directions geochemistry.

Language: Английский

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