Organic Carbon Burial Rates in Muddy Temperate Shelf Sea Sediments

Abstract Muddy continental shelf sediments act as important sinks for atmospheric CO 2 by accumulating organic matter, a small fraction of which is buried and stored as organic carbon (OC) over long timescales. Quantifying long‐term OC burial in shelf sediments is critical for understanding their role in climate regulation; however, this remains difficult due to limited age‐resolved data and the challenges of determining sediment accumulation rates and temporal changes in OC content. To address this, we quantified age‐resolved OC storage over the past two centuries in the upper 50 cm of the Western Irish Sea Mud Belt (WISMB) by measuring depth‐resolved OC content and sediment accumulation rates. The OC content (0.15%–1.62%), OC storage (1.30–15.15 gC cm −3 ), and sediment accumulation rates (0.26–0.37 cm yr −1 ) vary both spatially and temporally, with the highest OC accumulation and burial occurring in muddier, deeper‐water sediments. Between 53% and 91% of the OC accumulated in the surface 2 cm over the past 8 years (17.09–39.47 gC m −2 yr −1 ), and 60%–68% of the OC accumulated in the upper 10 cm over the past 38 years (21.90–51.13 gC m −2 yr −1 ), remains buried for more than 100 years (14.03–33.50 gC m −2 yr −1 ). These rates are comparable to those reported for other muddy continental shelf regions, including mud patches, coastal fjords, and glacial troughs.