New applications of continuous atmospheric O2 measurements : meridional transects across the Atlantic Ocean, and improved quantification of fossil fuel-derived CO2

• Main Author: Pickers, Penelope
• Published: University of East Anglia 2016
• Subjects: 551.46
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.702094

High precision, continuous measurements of atmospheric O2 and CO2 are a valuable tool for gaining insight into carbon cycle processes, and for separating land biospheric, oceanic and fossil fuel fluxes of CO2. This thesis presents a new atmospheric O2 and CO2 measurement system that has been deployed on board a commercial container ship, travelling continuously between Germany (~55°N) and Argentina (~35°S). These data are the first ongoing atmospheric O2 measurements across the Atlantic Ocean, closing a gap in the global atmospheric O2 network. The Atlantic meridional transects of atmospheric O2 and CO2 display latitudinally‐varying seasonality. The annual mean latitudinal gradient in APO (Atmospheric Potential Oxygen; a tracer derived from O2 and CO2 measurements) does not show a pronounced bulge at the equator, in contrast to observations across the Pacific Ocean. Atmospheric O2 and CO2 measurements from Norfolk, UK are used to demonstrate a novel method for quantifying fossil fuel derived CO2 (ffCO2), using APO data. This APO ffCO2 quantification method is more precise than the frequently‐used CO tracer method, owing to a smaller range of APO:CO2 fossil fuel emission ratios compared to the CO:CO2 range. A sensitivity analysis of the fossil fuel emission ratios also indicates that the APO method is very likely more accurate than the CO method, and can therefore be used independently of 14CO2 measurements (unlike the CO method), which are costly and highly unreliable in many UK regions, owing to nuclear power plant influences. These new applications of atmospheric O2 measurements have significant future potential. The shipboard data can be used to test and improve global climate model estimates of meridional oceanic heat and carbon transport in the Atlantic. Using APO to quantify ffCO2 has significant policy relevance, with the potential to provide more accurate and more precise top‐down verification of fossil fuel emissions.