Preliminary and novel estimates of CO2 gas transfer using a satellite scatterometer during the 2001GasEx experiment

Abstract

The ocean takes up approximately 30% of the annual anthropogenic emissions of CO2. However, the air–sea exchange of carbon dioxide varies by a factor of 2 depending on the formulation of the exchange process. This considerable uncertainty is due in part to the difficulty in parameterizing the gas transfer velocity, k 660, usually given as a function of wind speed. Recent field data showed that parametrization using the mean square slope of small scale surface waves provides a more robust strategy to estimate gas transfer (Frew et al.2004). Here we present a preliminary estimation of the gas transfer velocity as a function of upwind Normalized Radar Cross-Section (NRCS) as measured by the scatterometer QuikSCAT. The gas transfer velocity calculated from upwind NRCS exhibits a quadratic-like dependence at low and intermediate wind speeds (≃6 ms–1 ). This approach represents a promising new tool to obtain global quasi-synoptic estimates of oceanic uptake of CO2.