Dissertation Defense: Shayma Ali Alali

Title: Calibrating a Sea-State Dependent Gas Transfer Velocity using Ocean Circulation Models

Abstract: Air-sea gas exchange is the process by which gases are transported between the atmosphere and ocean boundary layer. The rate of gas exchange is important in calculating the global budgets of climate-active trace gases. The rate of gas exchange is influenced by multiple factors in the atmosphere and ocean boundary layers, such as wind speed, sea surface temperature, and ocean/atmospheric concentration. In most models, the transfer velocity (k w ) is parameterized as having a quadratic relationship to wind speed with a scaling parameter obtained from inversion of radiocarbon in a global ocean model (Wanninkhof, 2014). However, bubbles produced by breaking waves have been shown to be an important component of air-sea gas transfer of CO 2 (Reichl & Deike, 2020).

In this dissertation, the two parameterizations are compared using a global inverse circulation ocean model (OCIM2) to evaluate if the inclusion of bubble-mediated gas exchange will improve model performance. This study uses multiple tracers across a variety of solubilities (∆ 14 C, CFC-11, CFC-12, SF 6 ) and model outputs are compared with GLODAPv2 bottle
observations. Globally, the bubble-mediated parameterization does not improve model performance, although certain regions, such as the North Atlantic, do show improvements. This dissertation provides a better understanding of the mechanisms needed to develop a physically based and universal parameterization for accurately projecting the trajectories of climate-active gases.