Determination of the rate of oceanic storage of anthropogenic CO2 from measurements in the ocean interior: the South Atlantic Ocean

PhD ceremony: Mr. S.M.A.C. van Heuven, 12.45 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Determination of the rate of oceanic storage of anthropogenic CO₂ from measurements in the ocean interior: the South Atlantic Ocean

Promotor(s): prof. H.J.W. de Baar, prof. H.A.J. Meijer

Faculty: Mathematics and Natural Sciences

Carbon dioxide, CO₂, is exchanged between – and within – the oceans, the land and the atmosphere. By the burning of oil, coal and gas, humanity is adding additional CO₂ (‘anthropogenic’ CO₂, CO₂ ^ant) to the natural carbon cycle. In order to better constrain the changing carbon cycle, a better understanding is required of the rate of uptake of CO₂ ^ant by the oceans, which was the aim of the thesis research of Steven van Heuven.
The research consisted of (i) collecting new CO₂-related measurements from the ocean interior, (ii) compiling a data base of the new and historic measurements and (iii) using the resulting data base to assess the rate of increase of CO₂ ^ant in the South Atlantic Ocean. This ocean region is considered to be of great importance for the uptake of CO₂ ^ant from the atmosphere and its subsequent transport into the ocean interior.
During several seagoing expeditions, many thousands of ocean samples have been successfully analyzed. The subsequent research illustrates that it is very well possible to combine ~40 years of oceanographic data into a high-quality data base. Additionally, it is shown that it is possible to convincingly assess the increasing amounts of CO₂ ^ant in the ocean interior – particularly in an ocean that exhibits strong biological and hydrographical variability and for which not many data are available. The results strengthen the evidence for the idea that the South Atlantic Ocean is responsible for the storage of circa 400 million tonnes of CO₂ ^ant per year, or ~20% of the total oceanic uptake from the atmosphere.