Submitted as: model evaluation paper
31 Jan 2022
Submitted as: model evaluation paper | 31 Jan 2022
Status: this preprint is currently under review for the journal GMD.

The tidal effects in the Finite-volumE Sea ice–Ocean Model (FESOM2.1): a comparison between parameterised tidal mixing and explicit tidal forcing

Pengyang Song1, Dmitry Sidorenko1, Patrick Scholz1, Maik Thomas2,3, and Gerrit Lohmann1,4 Pengyang Song et al.
  • 1Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI), Bremerhaven, Germany
  • 2Helmholtz Centre Potsdam–GFZ German Research Centre for Geosciences, Potsdam, Germany
  • 3Institute of Meteorology, Freie Universität Berlin, Berlin, Germany
  • 4MARUM–Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Abstract. Tides are proved to have a significant effect on the ocean and climate. Previous modelling research either adds a tidal mixing parameterisation or an explicit tidal forcing to the ocean models. However, no research compares the two approaches in the same framework. Here we implement both schemes into a general ocean circulation model and assess both methods by comparing the results. The aspects for comparison involve hydrography, sea ice, mixed layer depth, Meridional Overturning Circulation (MOC), vertical diffusivity, barotropic streamfunction and energy diagnostics. We conclude that although the mesh resolution is poor in resolving internal tides in most mid-latitude and shelf-break areas, explicit tidal forcing still shows stronger tidal mixing at the Kuril–Aleutian Ridge and the Indonesian Archipelago than the tidal mixing parameterisation. Beyond that, the explicit tidal forcing method leads to a stronger upper cell of the Atlantic MOC by enhancing the Pacific MOC and the Indonesian Throughflow. Meanwhile, the tidal mixing parameterisation leads to a stronger lower cell of the Atlantic MOC due to the tidal mixing in deep oceans. Both methods maintain the Antarctic Circumpolar Current at a higher level than the control run by increasing the meridional density gradient but with different mechanisms. We also show several phenomena that are not considered in the tidal mixing parameterisation, for example, the changing of energy budgets in the ocean system, the bottom drag induced mixing on the continental shelves, and the sea ice transport by tidal motions. Due to the limit of computational capacity, an internal-tide-resolving simulation is not feasible for climate studies. However, a high-resolution short-term tidal simulation is still required to improve parameters and parameterisation schemes in climate studies.

Pengyang Song et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2022-25', Jonas Nycander, 01 Mar 2022
  • CEC1: 'Comment on gmd-2022-25', Juan Antonio Añel, 01 Mar 2022
    • AC1: 'Reply on CEC1', Pengyang Song, 10 Mar 2022
  • RC2: 'Comment on gmd-2022-25', Anonymous Referee #2, 07 Mar 2022

Pengyang Song et al.

Data sets

The tidal effects in the Finite-volumE Sea ice--Ocean Model (FESOM2.1): a comparison between parameterized tidal mixing and explicit tidal forcing Song, Pengyang; Sidorenko, Dmitry; Scholz, Patrick; Thomas, Maik; Lohmann, Gerrit

Pengyang Song et al.


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Short summary
Tides have essential effects on the ocean and climate. Most previous research applies parameterised tidal mixing to discuss their effects in models. By comparing a tidal mixing parameterisation and a tidal forcing on affecting the ocean state, we assess the advantages and disadvantages of the two methods. Our results show that tidal mixing in the North Pacific Ocean strongly affects the global Thermohaline Circulation. We also list some effects that are not considered in the parameterisation.