EXPLORE CARDIFF UNIVERSITY
PhD Title -- Constraining marine carbon fluxes and their effect on atmospheric CO2
Supervisors -- Dr Stephen Barker (Cardiff University) and Prof. Andy Ridgwell (University of Bristol)
My research focuses on the transport of particulate organic carbon (POC) from the surface ocean to the deep ocean and how changes in this will influence atmospheric CO2 and climate. Modelling studies have shown that changes in the ratio of particulate inorganic carbon (PIC) to POC (the "rain-ratio") can potentially account for large changes in atmospheric CO2 such as observed in glacial/interglacial cycles. However, recent studies of global sediment trap data have observed a quantitative relationship between POC and minerals, particularly calcium carbonate(CaCO3), suggesting that the density of CaCO3 aids the sinking of POC (the ballast-ratio
hypothesis). If true, the rain ratio will vary less and account for less change in atmospheric CO2. With current and projected ocean acidification, the ballasting of POC fluxes could lead to a net positive feedback for atmospheric CO2 levels.
Currently the precise relationships between POC and ballast minerals are largely unknown. My research aims to improve our knowledge of carbon fluxes by initially analysing an up-to-date global database of sediment traps to elaborate on observed quantitative relationships. The outcomes of this analysis will then inform an approach using the Earth System model GENIE. Various paramaterisations of ballasting will be applied in GENIE to quantify their effect on atmospheric CO2 and climate. Ballasting in GENIE will then be applied to past analogues of ocean acidification and other
relevant events in the palaeo-record such as the Silicic Acid Leakage Hypothesis and glacial/interglacial cycles. The results will help clarify and quantify the mechanisms behind particulate carbon fluxes in the ocean and informing modelling and other related studies.