Abstract
AbstractThe physical mechanisms that remove energy from the Southern Ocean’s vigorous mesoscale eddy field are not well understood. One proposed mechanism is direct energy transfer to the internal wave field in the ocean interior, via eddy-induced straining and shearing of preexisting internal waves. The magnitude, vertical structure, and temporal variability of the rate of energy transfer between eddies and internal waves is quantified from a 14-month deployment of a mooring cluster in the Scotia Sea. Velocity and buoyancy observations are decomposed into wave and eddy components, and the energy transfer is estimated using the Reynolds-averaged energy equation. We find that eddies gain energy from the internal wave field at a rate of −2.2 ± 0.6 mW m−2, integrated from the bottom to 566 m below the surface. This result can be decomposed into a positive (eddy to wave) component, equal to 0.2 ± 0.1 mW m−2, driven by horizontal straining of internal waves, and a negative (wave to eddy) component, equal to −2.5 ± 0.6 mW m−2, driven by vertical shearing of the wave spectrum. Temporal variability of the transfer rate is much greater than the mean value. Close to topography, large energy transfers are associated with low-frequency buoyancy fluxes, the underpinning physics of which do not conform to linear wave dynamics and are thereby in need of further research. Our work suggests that eddy–internal wave interactions may play a significant role in the energy balance of the Southern Ocean mesoscale eddy and internal wave fields.
Highlights
The wind represents the largest energy source to the large-scale quasigeostrophic (QG) ocean circulation, providing 0.7–1 TW of work (Wunsch 1998; Scott and Xu 2009)
The observations presented in this paper stem primarily from a mooring array located upon a 3700-mdeep seamount in the Scotia Sea (Brearley et al 2013; Sévellec et al 2015), close to the climatological position of the Subantarctic Front (SAF) (Fig. 1a)
The dominant features of the mesoscale flow are the jets and eddies associated with the Antarctic Circumpolar Current (ACC)
Summary
The wind represents the largest energy source to the large-scale quasigeostrophic (QG) ocean circulation, providing 0.7–1 TW of work (Wunsch 1998; Scott and Xu 2009). More than 60% of this takes place in the Southern Ocean, where the time-mean wind work on the QG flow often exceeds 10 mW m22 locally (Hughes and Wilson 2008). In combination with atmospheric buoyancy forcing and dynamical instabilities, leads to the emergence of the Antarctic Circumpolar Current (ACC) and its vigorous mesoscale eddy field (Chelton et al 2011). Mesoscale eddies play an important role in the Southern Ocean limb of Denotes content that is immediately available upon publication as open access.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
