Organic carbon burial rates in muddy temperate shelf sea sediments

Abstract

Continental shelves are globally significant sinks for atmospheric CO2, thereby mitigating climate change. Evaluating their contribution to climate regulation requires quantification of long-term organic carbon burial rates into the seabed. However, this understanding is hindered by a scarcity of age-resolved sedimentary organic carbon data resulting from methodological challenges, primarily in obtaining sedimentation rates and quantifying organic carbon degradation. Here, we estimate sedimentation rates for the Western Irish Sea Mud Belt (WISMB) by dating sediments using natural and anthropogenic radionuclides from authorised radionuclide discharges from the Sellafield nuclear facility. In combination with empirical high-resolution organic carbon depth profiles, the average long-term (>100 years) organic carbon burial rate for the WISMB is estimated as 23 gC m⁻² yr⁻¹, with an organic carbon burial efficiency of 74% compared to an average short-term (<30 years) organic carbon accumulation rate of 31 gC m⁻² yr⁻¹. These results highlight the significant organic carbon burial rates in the WISMB, comparable with other global depositional zones, including coastal fjords and glacial troughs. This study shows that empirical age-resolved sediment depths and organic carbon degradation profiles can improve assessments of long-term organic carbon burial in depositional shelf seas, helping to resolve the significant role of shelf seas in climate regulation.

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Identifiers

ORCID for David G. Reading: orcid.org/0000-0002-6697-8525

ORCID for Phillip E. Warwick: orcid.org/0000-0001-8774-5125

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