The tidal effects in the Finite-volumE Sea ice–Ocean Model (FESOM2.1): a comparison between parameterised tidal mixing and explicit tidal forcing
- 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
- 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)
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RC1: 'Comment on gmd-2022-25', Jonas Nycander, 01 Mar 2022
The comment was uploaded in the form of a supplement: https://gmd.copernicus.org/preprints/gmd-2022-25/gmd-2022-25-RC1-supplement.pdf
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AC2: 'Reply on RC1', Pengyang Song, 22 Mar 2022
The comment was uploaded in the form of a supplement: https://gmd.copernicus.org/preprints/gmd-2022-25/gmd-2022-25-AC2-supplement.pdf
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AC2: 'Reply on RC1', Pengyang Song, 22 Mar 2022
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CEC1: 'Comment on gmd-2022-25', Juan Antonio Añel, 01 Mar 2022
Dear authors,
After checking your manuscript, it has come to our attention that it does not comply with our Code and Data Policy.
https://www.geoscientific-model-development.net/policies/code_and_data_policy.html
You have archived your code in GitHub. However, GitHub is not a suitable repository. GitHub itself instructs authors to use other alternatives for long-term archival and publishing, such as Zenodo. Therefore, please, publish your code in one of the appropriate repositories.In this way, you must reply to this comment with the link to the repository used in your manuscript, with its DOI. Moreover, you must include in a potential reviewed version of your manuscript the modified 'Code and Data Availability' section, including the DOI of the code.
Please, reply as soon as possible to this comment with the link for it so that it is available for the peer-review process, as it should be.
Regards,
Juan A. Añel
Geosci. Model Dev. Exec. Editor-
AC1: 'Reply on CEC1', Pengyang Song, 10 Mar 2022
Thanks for informing. We have archived the model source code on zenodo. The new citation and DOI number is below.
Song, Pengyang, Sidorenko, Dmitry, Scholz, Patrick, Thomas, Maik, & Lohmann, Gerrit. (2021). The tidal effects in the Finite-volumE Sea ice--Ocean Model (FESOM2.1): a comparison between parameterized tidal mixing and explicit tidal forcing. https://doi.org/10.5281/zenodo.6342761
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AC1: 'Reply on CEC1', Pengyang Song, 10 Mar 2022
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RC2: 'Comment on gmd-2022-25', Anonymous Referee #2, 07 Mar 2022
This manuscript deals with a comparison of an coarse resolution ocean model with a very simplistic parameteriation of tidal mixing and a model version without that scheme but explicit tidal potential included.
There is a major physical flaw in this model setup. The authors seem to believe that having the long internal tidal waves in their model they have implemented "tidal mixing". This is not the case. The long tidal waves do not break, except mabye close to continental shelves. In contrast, it is the energy transfer by non-linear interaction from the long internal tides to the shorter background internal wave field, the "GM wave field", and the breaking of the shortest wave lengths in that GM wave field, which leads to the bulk of the "tidal mixing" in the interior ocean. This process is certainly not resolved in the current model. One would need very high resolution and non-hydrostatic dynamics to simulate that process. In the present manuscript, it is unclear how the long tidal waves would induce mixing, and the issue is not touched at all. However, it is clear that it would not correspond in any way to what happens in the ocean.
It is therefore of no use to compare the model experiments as done here, and this manuscript should be rejected.
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AC3: 'Reply on RC2', Pengyang Song, 22 Mar 2022
The comment was uploaded in the form of a supplement: https://gmd.copernicus.org/preprints/gmd-2022-25/gmd-2022-25-AC3-supplement.pdf
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AC3: 'Reply on RC2', Pengyang Song, 22 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 https://doi.org/10.5281/zenodo.5770344
Pengyang Song et al.
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