An Autonomous Drifting Buoy to Measure Air-Sea CO2 Fluxes

We designed a new autonomous, drifting buoy with a floating chamber to measure air-sea CO₂ fluxes and gas transfer velocities (k) with high temporal and spatial resolution. The buoy is equipped with a sensor to measure aqueous and atmospheric pCO₂, and to monitor the increase or loss of CO₂ inside the chamber. A complete cycle lasts 40 minutes, and after flushing the chamber a new cycle is initiated. The buoy can be deployed for more than 12 hours, and at wind speeds of up to 10 m s^-1. Floating chambers are known to overestimate fluxes due to the creation of additional turbulence at the water surface. We correct fluxes by measuring turbulence with two Acoustic Doppler Velocimeter, one directly underneath the center of the floating chamber and the other one positioned sideways to measure turbulence outside the perimeter of the buoy.

The preliminary results of the first deployments in the Baltic Sea during summer 2015 demonstrate that the new drifting buoy is a powerful tool to improve our understanding of gas transfer velocity with in situ measurements.