Direct measurement of the oceanic carbon monoxide flux by eddy correlation

This report presents results from a field trial of ship-based air-sea flux measurements of carbon monoxide (CO) by direct eddy correlation with an infrared-laser trace gas analyzer. The analyzer utilizes Off-Axis Integrated-Cavity-Output Spectroscopy (OA-ICOS) to achieve high selectivity for CO, rapid response (similar to 2 Hz) and low noise. Over a two-day sea trial, peak daytime seawater CO concentrations were similar to 1.5 nM and wind speeds were consistently 10-12 m s(-1). A clear diel cycle in CO flux with an early afternoon maximum was observed. An analysis of flux error suggests the effects of non-stationarity are important, and air-sea CO flux measurements are best performed in regions remote from continental pollution sources.