The variability of surface pCO2 and nutrients in the North Atlantic Ocean
This PhD thesis was part of the EU-funded project CAVASSOO (Carbon Variability Studies by Ships of Opportunity). The installation of a autonomously working pCO2 unit onboard the carcarrier M/V Falstaff was completed in January, 2002. Measurements started a month later with the first transatlantic crossing. The data of one year showed that the correlatin between pCO2 and nitrate was promising in this context and it could also be shown that nitrate correlated well with the mixed layer depth. Parameters such as temperature and chlorophyll on the other hand did not reveal a unique correlation with the pCO2. Within this thesis it was also shown that the seawater pCO2 in the eastern basin (10°W-35°W) showed smaller seasonal changes than in the western basin (36°W-70°W) in the North Atlantic. This was explained by the fact that in the eastern basin the temperature effect on the seawater pCO2 was counteracted by the biological effect yielding a damped seasonal pCO2 cycle. In the western basin, however, temperature was the major force on the pCO2 which was not reduced by a counteracting biology effect thus yielding a pronounced seasonal pCO2 cycle. The CO2 flux calculation showed that this region of the North Atlantic was a sink for atmospheric CO2 in 2002. When comparing the CO2 flux to a well-cited pCO2 climatology the difference was small (4%). The seasonal cycles of nutrients within different watermasses showed distinct patterns. The C:N ratio of the seasonal new production were similar to the Redfield ratio for all watermasses excecpt for the Gulfstream watermass. In the latter a carbon overconsumption with respect to Redfield could be shown which pointed at N2 fixation.