Regionally distinct drivers of the carbonate system dynamics in the Drake Passage and northern Antarctic Peninsula

Abstract

The Drake Passage (DP) and the adjacent northern Antarctic Peninsula (NAP) are highly dynamic regions within the Southern Ocean where physical and biogeochemical processes simultaneously influence the CO2 system. Ocean total alkalinity (AT) and total dissolved inorganic carbon (CT) serve as valuable early indicators of calcium carbonate undersaturation and help evaluate the buffering capacity of the ocean. However, significant uncertainty remains in predicting carbonate system dynamics in the DP and NAP due to a lack of seasonal representation and the spatial variability. To address this uncertainty, we identified factors affecting the carbonate system at a regional level using unprecedented surface data from two consecutive austral summer and early fall periods (February–April 2003 and 2004). The data revealed that the dynamics of AT and CT in the DP and NAP exhibited both conservative and non-conservative behaviors influenced by the position of the Polar Front (PF), and the proximity to land. In coastal regions, salinity and terrestrial influence were major determinants, while in oceanic regions, nutrients and phytoplankton productivity played a more prominent role. The position of the PF creates a latitudinal edge in nutrient ratios, establishing a new hierarchy of carbonate chemistry drivers where silicate gains prevalence toward the southern DP and NAP. The results highlight significant regional variability in the carbonate system, with increasing AT and CT from north to south, making NAP the most vulnerable region due to accelerated acidification and ice melt-growth. Susceptibility to ocean acidification and seasonal fluctuations in the carbonate system indicate a higher risk to calcareous structures in the southernmost region.