Preprints
https://doi.org/10.5194/os-2021-9
https://doi.org/10.5194/os-2021-9

  02 Feb 2021

02 Feb 2021

Review status: this preprint is currently under review for the journal OS.

Global contributions of mesoscale dynamics to meridional heat transport

Andrew Delman and Tong Lee Andrew Delman and Tong Lee
  • Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA

Abstract. Mesoscale ocean processes are prevalent in many parts of the global oceans, and may contribute substantially to the meridional movement of heat. Yet earlier global surveys of meridional heat transport (MHT) have not formally distinguished between mesoscale and large-scale contributions, or have defined eddy contributions based on temporal rather than spatial characteristics. This work uses spatial filtering methods to separate large-scale (gyre and planetary wave) contributions from mesoscale (eddy, recirculation, and tropical instability wave) contributions to MHT by extending beyond a previous effort for the North Atlantic Ocean. Overall, mesoscale temperature fluxes produce a net poleward MHT at mid-latitudes and equatorward MHT in the tropics, thereby resulting in a net divergence of heat from the subtropics. Mesoscale temperature fluxes are often concentrated near the energetic currents at western boundaries, and the temperature difference between the boundary current and its recirculation determines the direction of the mesoscale temperature flux. The mesoscale contribution to MHT yields substantially different results from temporally-based eddy contributions to MHT, with the latter contributed substantially by gyre and planetary wave motions at low latitudes. Mesoscale temperature fluxes contribute the most to interannual and decadal variability of MHT in the Southern Ocean, the tropical Indo-Pacific, and the North Atlantic. Surface eddy kinetic energy (EKE) is not a good proxy for mesoscale temperature flux variability in regions with the highest time-mean EKE, though it does explain much of the temperature flux variability in regions of modest time-mean EKE. This approach to quantifying mesoscale fluxes can be used to improve parameterizations of mesoscale effects in coarse-resolution models, and assess regional impacts of mesoscale eddies and recirculations on tracer fluxes.

Andrew Delman and Tong Lee

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on os-2021-9', Anonymous Referee #1, 01 Mar 2021
  • RC2: 'Comment on os-2021-9', Anonymous Referee #2, 14 Mar 2021
  • RC3: 'Comment on os-2021-9', Anonymous Referee #3, 18 Mar 2021

Andrew Delman and Tong Lee

Andrew Delman and Tong Lee

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Short summary
This study quantifies the influence of ocean eddies and other mesoscale phenomena (spanning 50–1000 km) on heat movement. One finding is that mesoscale processes spread heat outwards from the subtropical latitudes towards both the equator and the poles. The effect of major ocean currents on heat movement in the ocean depends on the currents' mesoscale structure. Mesoscale processes also impact year-to-year changes in heat movement, especially at middle latitudes and in the tropical Pacific.