Air-sea gas exchange in shallow water environments
Date
2023
Authors
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Publisher
University of Delaware
Abstract
The exchange of gases across the air-sea interface influences the cycling of climatically important trace gases such as carbon dioxide (CO2). In the open ocean, considerable effort has been devoted to parameterizing the gas transfer velocity (k) in terms of wind speed (U), an easily and widely measured forcing function. Air-sea gas exchange parameterizations are also needed for coastal and shallow water environments. However, there are significant differences between shallow coastal ecosystems and the open ocean in terms of forcing factors on air-sea gas exchange. This study represents a time-series evaluation of air-sea CO2 exchange using the eddy covariance technique in Kane‘ohe Bay, Hawaii. Findings indicate the difficulty of measuring small CO2 fluxes in harsh environments and the significant influence of the Webb et al. (1980) correction on the raw CO2 flux. After pivoting to the evaluation of daily ΔpCO2 values, we can conclude the daily ΔpCO2 cycle is dependent primarily on the metabolic activity in the reef. We hypothesize that gas transfer velocity parameterizations considering surface turbulence will more accurately represent fluxes in this region, which will be confirmed with direct measurements of k from our University of Hawaii collaborators. Using dissipation to estimate k, Kane‘ohe Bay was found to be a source of CO2 to the atmosphere (3.521E-09 kg m-2 s-1 (0.08 umol m-2 s-1)).
Description
Keywords
Carbon dioxide, Wind speed, Air-sea gas exchange, Shallow water environments, Gas transfer velocity