Damping of climate-scale oceanic variability by mesoscale eddy turbulence

• Main Author: Sevellec, Florian
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: Antarctic; Southern Ocean; The Antarctic; Drake Passage; Antarc*
• Online Access: https://eprints.soton.ac.uk/445025/; https://eprints.soton.ac.uk/445025/1/Damping_of_climate_scale.pdf; https://eprints.soton.ac.uk/445025/2/manuscript.pdf

The impact of mesoscale eddy turbulence on long-term, climatic variability in the ocean’s buoyancy structure is investigated using observations from a mooring deployed in the Drake Passage, Southern Ocean. By applying the Temporal-Residual-Mean framework and characterizing the variance contributors and the buoyancy variance budget, we identify the main source and sink of long-term buoyancy variance. Long-term buoyancy variance amplitude is set by long-term vertical velocity fluctuations acting on the steady stratification. This baro-clinic buoyancy flux is also the main source of the variance, indicative of the effect of large-scale baroclinic instability. This source is balanced by a sink of long-term buoyancy variance associated with the vertical advection of the steady stratification by the eddy-induced circulation. We conclude that mesoscale eddy turbulence acts as a damping mechanism for long-term, climatic variability in the region of the observations, consistent with an ‘eddy saturated’ behaviour of the Antarctic Circumpolar Current.