Unraveling the link between sediment acoustics and organic carbon

The top meter of marine sediments is estimated to store a total of 2322 Pg of carbon [Atwood et al., 2020. Front. Mar. Sci., vol. 7 p.165], which is twice that of terrestrial soils. Physical disturbance and remineralization of these carbon stocks could further accelerate climate change. Rapid and accurate quantification of sediment carbon stocks can (1) better inform carbon budgets and management of human activities in the ocean to minimize carbon remineralization and (2) monitor changes in sediment carbon stocks due to anthropogenic and natural disturbances. Sediment acoustics, which have been linked with sediment total organic carbon/content in mud banks, seagrass beds, and estuarine environments, can be measured in situ and offer a scalable solution toward rapid estimation of carbon stocks. However, before this modality can be applied broadly, a fundamental understanding between sediment acoustic properties and sediment organic/inorganic constituents must be realized. Here, direct ex situ measurements of sediment acoustic properties, sediment organic carbon, and grain size distribution will be compiled and compared across a variety of sediment types and locations from our own measurements and from published datasets. The development of a non-site-specific constitutive-based relationship will be discussed. [Work supported in part by ONR.]