Cross-linking laboratory and field measurements to quantify the role of bubbles in air-sea CO2 exchange

Abstract

The global oceans are a major sink of anthropogenic carbon dioxide (CO2), playing a critical role in mitigating climate change. The ocean CO2 uptake estimate contains significant uncertainties due to a lack of mechanistic understanding of the role of bubbles in air-sea CO2 exchange. Bubbles resulting from wave breaking may mediate about 40% of the global air-sea CO2 flux.  However, bubble-mediated transfer is poorly quantified and under-represented in CO2 flux estimates. In this study, we will present a synthesis analysis of the bubble-mediated gas transfer measurements in the last decade. We show contrasting evidence regarding the importance of bubbles in the air-sea CO2 exchange, particularly in the comparison between laboratory and field measurements. This suggests a lack of mechanistic understanding of the air-sea gas exchange processes. Through innovative cross-linking of comprehensive field and laboratory observations using multiple techniques, we aim to make a step change in understanding the mechanisms of bubble-mediated transfer and reconcile field and laboratory measurements.  We also aim to provide novel parameterisations of gas transfer velocity with explicit representation of bubbles, thereby reducing uncertainty in air-sea CO2 flux estimates.