| Summary: | The biological pump, which removes carbon from the surface ocean and regulates atmospheric carbon dioxide, comprises multiple processes that include but extend beyond gravitational settling of organic particles. Contributions to the biological pump that arise from the physical circulation are broadly referred to as physical particle injection pumps; a synthetic view of how these physical pumps interact with each other and other components of the biological pump does not yet exist. In this study, observations from a quasi-Lagrangian float and ocean glider, deployed in the Southern Ocean’s subantarctic zone for one month during the spring bloom, offer insight into daily-to-monthly fluctuations in the mixed layer pump and the eddy subduction pump. Estimated independently, each mechanism contributes intermittent export fluxes on the order of several hundreds milligrams of particulate organic carbon (POC) per day. The float and the glider produce similar estimates of the mixed layer pump, with sustained weekly periods of export fluxes with a magnitude of 400 mg-POC-m-2-day-1. Export fluxes from the eddy subduction pump, based on a mixed layer instability scaling, occasionally exceed 500 mg-POC-m-2day-1, with some periods having strong inferred vertical velocities and others having enhanced isopycnal slopes. Regimes occur when a summation of the two pump estimates may misrepresent the total physical carbon flux. Disentangling contributions from different physical pump mechanisms from sparse data will remain challenging. Insight into how mesoscale stirring and submesocale velocities set the vertical structure of POC concentrations is identified as a key target to reduce uncertainty in global carbon export fluxes.
|
|---|