A Study of the Efficacy of Conceptual Models for Air-Sea Gas Transfer

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Air-sea exchange is a critical process in climate, as the oceans are a both a source and a sink for CO2, CH4, and trace species important in atmospheric chemistry and radiative transfer. This project aims to enhance our understanding of small-scale physics relevant for air-sea gas exchange, and to develop an effective method for using infrared imagery to estimate air-sea gas fluxes.The objective of the research is to:1. Determine if surface divergence models for water-side rate-controlled air-water transfer processes provide an accurate physical description of gas exchange.2. Determine if infrared images of the water surface can provide distributions of the temporal and depth scales required to use surface divergence models for predicting air-water gas fluxes.This research will use laboratory gas transfer data collected in a synthetic jet array tank (SJAT) to test a surface divergence model for air-water transfer of gas and heat. In particular, it will investigate the ability of the model to predict the measured air-water transfer velocities and their dependence on molecular diffusivity under conditions where the exchange process is forced by either mechanically generated turbulence or wind stress. Near-surface concentration fluctuations of carbon dioxide (CO2) will be measured using a laser-induced fluorescence technique and bulk gas fluxes will be measured for helium, sulfur hexafluoride, methane, and CO2. Infrared imagery will be used to characterize near-surface temperature fluctuations. Broader ImpactsThe project will promote teaching, training, and learning through such things as mentoring a post-doctoral research associate, participation of a summer undergraduate research intern, hands-on demonstrations on air-water gas transfer at venues such as the Earth Observations from Space Weekend at the Pacific Science Center, participation of the researchers in various outreach activities ranging from seminars on global climate change to laboratory tours and recruitment of summer research interns from underrepresented groups.