Transfer efficiency of organic carbon in marine sediments

The burial of organic carbon in marine sediments regulates Earth's carbon cycle and climate. Here, authors present 'transfer efficiencies' as a new framework for quantifying the sedimentary portion of the marine organic carbon cycle. Quantifying the organic carbon (OC) sink in marine sediments is crucial for assessing how the marine carbon cycle regulates Earth's climate. However, burial efficiency (BE) - the commonly-used metric reporting the percentage of OC deposited on the seafloor that becomes buried (beyond an arbitrary and often unspecified reference depth) - is loosely defined, misleading, and inconsistent. Here, we use a global diagenetic model to highlight orders-of-magnitude differences in sediment ages at fixed sub-seafloor depths (and vice-versa), and vastly different BE's depending on sediment depth or age horizons used to calculate BE. We propose using transfer efficiencies (T-eff's) for quantifying sediment OC burial: T-eff is numerically equivalent to BE but requires precise specification of spatial or temporal references, and emphasizes that OC degradation continues beyond these horizons. Ultimately, quantifying OC burial with precise sediment-depth and sediment-age-resolved metrics will enable a more consistent and transferable assessment of OC fluxes through the Earth system.

Automated summary

The study introduces "transfer efficiencies" as a new framework for quantifying the sedimentary portion of the marine organic carbon cycle. The commonly-used burial efficiency metric is loosely defined and inconsistent, while transfer efficiencies provide a more accurate and precise measurement with an emphasis on the ongoing degradation of organic carbon.