Ocean–atmosphere exchange of organic carbon and CO₂ surrounding the Antarctic Peninsula

Abstract. Exchangeable organic carbon (OC) dynamics and CO₂ fluxes in the Antarctic Peninsula during austral summer were highly variable, but the region appeared to be a net sink for OC and nearly in balance for CO₂. Surface exchangeable dissolved organic carbon (EDOC) measurements had a 43 ± 3 (standard error, hereafter SE) μmol C L⁻¹ overall mean and represented around 66% of surface non-purgeable dissolved organic carbon (DOC) in Antarctic waters, while the mean concentration of the gaseous fraction of organic carbon (GOC H^–1) was 46 ± 3 SE μmol C L⁻¹. There was a tendency towards low fugacity of dissolved CO₂ (fCO_2-w) in waters with high chlorophyll a (Chl a) content and high fCO_2-w in areas with high krill densities. However, such relationships were not found for EDOC. The depth profiles of EDOC were also quite variable and occasionally followed Chl a profiles. The diel cycles of EDOC showed two distinct peaks, in the middle of the day and the middle of the short austral dark period, concurrent with solar radiation maxima and krill night migration patterns. However, no evident diel pattern for GOC H^–1 or CO₂ was observed. The pool of exchangeable OC is an important and active compartment of the carbon budget surrounding the Antarctic Peninsula and adds to previous studies highlighting its importance in the redistribution of carbon in marine environments.