Assessment of forcing mechanisms on net community production and dissolved inorganic carbon dynamics in the Southern Ocean using glider data

• Main Author: Schütt, Julia
• Format: Other/Unknown Material
• Language: English
• Published: Lunds universitet/Institutionen för naturgeografi och ekosystemvetenskap 2017
• Subjects: net community production; geography; physical geography; dissolved inorganic carbon; Southern Ocean; Earth and Environmental Sciences
• Online Access: http://lup.lub.lu.se/student-papers/record/8905815

In the Subantarctic Zone of the Southern Ocean, a combination of physical forcings, chemical solubility and biological fixation is controlling the carbon uptake and thus the role the Southern Ocean is playing in the remediation of global climate change. Therefore, it is necessary to understand the mechanisms controlling oceanic carbon budgets and to quantify biological uptake rates to make reliable future climate predictions. In this study, the data of two ocean gliders simultaneously sampling the ocean interior and the CO2 exchange processes at the ocean surface were used to model the biological net community production (NCP) based on Chlorophyll a. A comparison was made to the seasonal development of surface water diurnal changes in dissolved inorganic carbon (DIC) concentration, as well as to the physical forcing mechanisms controlling both processes. The cross-seasonal net community production was found to range between -90 and 242 mg m-2 d-1 with 118 mg m-2 d-1 on average and the seasonal average daily change in dissolved inorganic carbon concentration was -235 mg m-2 d-1, leaving the two processes at overlapping and comparable ranges. It was shown that both time series were following similar seasonal trends of daily carbon drawdown and release when comparing the time series smoothed with a running mean filter, leading to the conclusion that the here modeled daily dissolved inorganic carbon fluxes are largely controlled by the biology. Although, the dissolved inorganic carbon data is fluctuating with a higher amplitude and holds higher daily variability. The net community production was largely controlled by the mixed layer depth and by light, the dissolved inorganic carbon flux did not show any correlation with any of the physical drivers. It was reasoned that contrary to biological processes, the DIC dynamics are subject to chemical and thermodynamical forcings that are evident during short-lived events and might be most prominently occurring during spring. In the beginning of the productive season, ...