Direct Observations of Biological Carbon Export From Profiling Floats in the Subtropical North Atlantic

Abstract

The complex interplay of biological and physical mechanisms comprising the ocean's biological carbon pump has not been well characterized to date, due to the difficulty of observing these mechanisms in situ at adequate spatial and temporal resolution. An annual time series is presented of direct measurements of export production and particle properties collected using optical sediment trap-equipped profiling floats cycling every 1.5–2.5 days. The observations indicate strong variability in particle export and bio-optical properties, influenced by the spring bloom, mesoscale eddy activity, and the mixed layer pump. Temporal and vertical decoupling of fluxes at depths ranging from 150 to 1,000 m was also observed, and remineralization length scales were more variable than predicted by temperature- and oxygen-based models. Net primary production was computed from float observations using a modification of the Carbon-based Productivity Model and used to estimate export and export (e-) ratios, which were compared to predictions of literature export models. Mechanistic models explicitly incorporating ecosystem processes and their depth dependence may perform better at reproducing regional observations collected at high temporal resolution.