Investigating coupled deviations of oxygen and carbon dioxide in the surface ocean

Abstract

Behaviour of oxygen (O2) and carbon dioxide (CO2) in the global ocean is often linked via physical and biogeochemical processes. Their deviations from atmospheric equilibrium determine whether the global ocean acts as a source or a sink for the two gases across various temporal and spatial scales, which eventually contributes to regulation of global climate and Earth’s life support system. Although these deviations are thought to be decoupled owing to the different restoration times of O2 and CO2, systematic comparisons of the two gases in the global surface ocean reveal unexpected coupled variations. The works presented in this thesis investigate O2 and CO2 dynamics in three heterogenous oceanic regions – the deep-water formation region of the Labrador Sea, the shallow coral-containing subtropical waters of the North Lagoon in Bermuda and the Southern Ocean. Surface O2 and CO2 deviations from atmospheric equilibrium in these three regions are found to be coupled. My study focuses on identifying possible drivers of these phenomena, the nature of their interactions and their impacts. The studies adopt the Carbon and Oxygen Relative to Saturation CORS method as the primary analytical technique in which deviations of dissolved O2 and CO2 concentrations are compared to one another using data from ships, mooring stations and floats as well as results from model simulations, in-situ monitoring and laboratory-generated measurements. The studies show that complex interactions of multiple processes drive the observed persistent O2 and CO2 excursions from atmospheric equilibrium. CORS results that were identified in earlier work as indicative of erroneous data are here shown instead to be real. This thesis introduces two novel analytical techniques: (1) a technique to quantify coral reef metabolism by using paired O2-CO2 measurements (“the O2-CO2 technique”), and (2) a technique to investigate CO2 data quality of floats by comparing against O2 data (“ the expected y-axis intercept method”). Finally, the works presented in this thesis provide new insights into the applications and implications of the CORS method as an insightful analytical tool in aquatic science.

More information

Identifiers

ORCID for Amavi Silva: orcid.org/0000-0002-3096-2599

ORCID for Toby Tyrrell: orcid.org/0000-0002-1002-1716

ORCID for Duncan Purdie: orcid.org/0000-0001-6672-1722

Catalogue record

Export record