New Radiocarbon Constraints on the Global Cycling of Solid-Phase Extractable Dissolved Organic Carbon

Radiocarbon ( increment C-14) measurements suggest the deep ocean stores marine dissolved organic carbon (DOC) on millennial timescales. The mechanisms that mediate this residence time remain unconstrained. Solid-phase extraction (SPE) has emerged as a widely used technique to isolate DOC for subsequent analyses. We present SPE-DOC concentrations and increment C-14 values for three GO-SHIP Repeat Hydrography transects, spanning the Pacific, Southern and Indian Oceans. Comparisons of SPE-DOC with total DOC increment C-14 values are used with an isotopic mass-balance to estimate the size of the refractory DOC (RDOC) reservoir and changes in RDOC relative abundance in the global ocean. Estimated RDOC abundance is similar across the deep Pacific and Indian Oceans (average = 93 +/- 5%, 35 +/- 6 mu M), whereas RDOC in the surface ocean varies as a function of total DOC concentration. Our results fill in spatial SPE-DOC increment C-14 sampling gaps for the global ocean, and our mass-balance RDOC estimates are consistent with previous observations.

Automated summary

Radiocarbon measurements indicate that the deep ocean stores marine dissolved organic carbon (DOC) over millennial timescales, with solid-phase extraction (SPE) being a widely used technique to isolate DOC for analysis. Results show that the refractory DOC (RDOC) abundance is similar in the deep Pacific and Indian Oceans, while varying in the surface ocean based on total DOC concentration. This study fills in sampling gaps for SPE-DOC increment C-14 in the global ocean and provides consistent estimates of RDOC abundance compared to previous observations.