Development of a Greenhouse Gas Ocean-Atmosphere Flux Sensor with MEMS-based Photoacoustic Technology

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Accurate measurements of the atmosphere?ocean fluxes of trace gases are important to an improved understanding of the cycling of climatically relevant gases. The direct eddy correlation (EC) method, which is considered to be the benchmark for accurate determination of air?sea fluxes of trace gases, relies on high? frequency measurements of the fluctuations of vertical wind velocity and gas concentration, and requires fast response sensors in combination with high sensitivity. These twin requirements have precluded oceanographic use of the EC technique for many species of interest, and direct measurements have been limited mainly to carbon dioxide at relatively high flux levels. The PI?s request funding to develop a fast, highly sensitive, gas concentration sensor, and to integrate it with a sonic anemometer, motion sensing, and data acquisition into an EC flux package suitable for operation from buoys and other platforms, such as ships. Our gas sensor is based on infrared (IR) absorption, but utilizes a novel, highly sensitive, photoacoustic detector. The PI?s expect that this combination will result in an improvement in sensitivity of several orders of magnitude over the IR absorption sensors that are currently in oceanographic use. This proposal was submitted under the US?Ireland R&D Partnership Program by E. Terray (PI-US), WHOI; B. Ward (Partner-IE), National University of Ireland, Galway, Ireland; and N. Mitchell (Partner-NI), Queens University Belfast, Northern Ireland (NI).