Antarctica Slope Front bifurcation eddy: A stationary feature influencing CO2 dynamics in the northern Antarctic Peninsula. (March 2023)

• Record Type: Journal Article
• Authors: Yuri Damini, Brendon; Rodrigo Costa, Raul; Dotto, Tiago S.; Rafael Borges Mendes, Carlos; Camilo Torres-Lasso, Juan; Azaneu, Marina do V.C.; Mata, Mauricio M.; Kerr, Rodrigo
• Is Part Of: Progress in oceanography. Volume 212(2023)
• Publication Date: 2023-03
• Subjects: Southern Ocean -- Eddies -- Carbonate chemistry -- CO2 fluxes -- Phytoplankton; Oceanography -- Periodicals; 551.4605
• DOI: 10.1016/j.pocean.2023.102985
• Languages: English
• ISSNs: 0079-6611

Abstract

Graphical abstract: Submitted to Progress in Oceanography. Highlights: Summer study of surface carbonate chemistry and phytoplankton groups at the Antarctica Slope Front bifurcation (ASFb) eddy . ASFb eddy acts as a CO2 outgassing structure due to enhanced dissolved inorganic carbon (DIC). DIC is modulated by the upwelling of intermediate waters and respiration processes. Cryptophyte abundance in the ASFb eddy's core is triggered by lateral advection. Abstract: The Southern Ocean is a key region for analyzing environmental drivers that regulate sea-air CO2 exchanges. These CO2 fluxes are influenced by several mesoscale structures, such as meanders, eddies and other mechanisms responsible for energy dissipation. Aiming to better understand sea-air CO2 dynamics in the northern Antarctica Peninsula, we investigated an anticyclonic stationary eddy located south of Clarence Island, in the eastern basin of Bransfield Strait – named the Antarctica Slope Front bifurcation (ASFb) eddy. Physical, chemical and biological data were sampled, and remote sensing measurements taken, in the region during late summer conditions in February 2020. The eddy's core consisted of cold (0.31 °C), salty (34.38) and carbon-rich (2247 μmol kg −1 ) waters with dissolved oxygen depletion (337 μmol kg −1 ). The core retains a mixture of local surface waters with waters derived from Circumpolar Deep Water (i.e., Warm Deep Water from the Weddell Sea and modified Circumpolar Deep Water from the Bransfield Strait) and Dense Shelf Water. The ASFb eddy acts as a CO2 outgassing structure that reaches a CO2 emission to the atmosphere of ∼1.5 mmol m −2 d –1 in the eddy's core, mostly due to enhanced dissolved inorganic carbon (DIC). The results suggest that surface variation in DIC in the eddy's core is modulated by (i) the entrainment of CO2 -rich intermediate waters at ∼500 m, (ii) low primary productivity, associated with small phytoplankton cells such as cryptophytes and green flagellates, and (iii) respiration processes caused by heterotrophic organisms (i.e., zooplankton community). By providing a comprehensive view of these physical and biogeochemical properties of this stationary eddy, our results are key to adding new insights to a better understanding of the behavior of mesoscale features influencing sea-air CO2 exchanges in polar environments.