Preprints
https://doi.org/10.5194/egusphere-2024-1489
https://doi.org/10.5194/egusphere-2024-1489
28 May 2024
 | 28 May 2024

The Alongshore Tilt of Mean Dynamic Topography and its Implications for Model Validation and Ocean Monitoring

Christoph Renkl, Eric C. J. Oliver, and Keith R. Thompson

Abstract. Mean dynamic topography (MDT) plays an important role in the dynamics of shelf circulation. Coastal tide gauge observations in combination with the latest generation of geoid models are providing estimates of the alongshore tilt of MDT with unprecedented accuracy. Additionally, high-resolution ocean models are providing better representations of nearshore circulation and the associated tilt of MDT along their coastal boundaries. It has been shown that the newly available geodetic estimates can be used to validate model predictions of coastal MDT variability on global and basin scales. On smaller scales, however, there are significant variations in alongshore MDT that are on the same order of magnitude as the accuracy of the geoid models.

In this study, we use a regional ocean model of the Gulf of Maine and Scotian Shelf (GoMSS) to demonstrate that the new observations of geodetically referenced coastal sea level can provide valuable information also for the validation of such high-resolution models. The predicted coastal MDT is in good agreement with coastal tide gauge observations referenced to the Canadian Gravimetric Geoid model (CGG2013a) including a significant tilt of alongshore MDT along the coast of Nova Scotia. Using the validated GoMSS model and several idealized models, we show that this alongshore tilt of MDT can be interpreted in two complementary, and dynamically consistent, ways: In the coastal view, the tilt of MDT along the coast can provide a direct estimate of the average alongshore current. In the regional view, the tilt can be used to approximate upwelling averaged over an offshore area. This highlights the value of using geodetic MDT estimates for model validation and ocean monitoring.

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Journal article(s) based on this preprint

27 Jan 2025
| Highlight paper
The alongshore tilt of mean dynamic topography and its implications for model validation and ocean monitoring
Christoph Renkl, Eric C. J. Oliver, and Keith R. Thompson
Ocean Sci., 21, 181–198, https://doi.org/10.5194/os-21-181-2025,https://doi.org/10.5194/os-21-181-2025, 2025
Short summary Co-editor-in-chief
Christoph Renkl, Eric C. J. Oliver, and Keith R. Thompson

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-1489', Chris Hughes, 27 Jun 2024
    • AC1: 'Reply on RC1', Christoph Renkl, 01 Sep 2024
  • RC2: 'Comment on egusphere-2024-1489', Anonymous Referee #2, 12 Jul 2024
    • AC2: 'Reply on RC2', Christoph Renkl, 01 Sep 2024

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-1489', Chris Hughes, 27 Jun 2024
    • AC1: 'Reply on RC1', Christoph Renkl, 01 Sep 2024
  • RC2: 'Comment on egusphere-2024-1489', Anonymous Referee #2, 12 Jul 2024
    • AC2: 'Reply on RC2', Christoph Renkl, 01 Sep 2024

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Christoph Renkl on behalf of the Authors (01 Sep 2024)  Author's response   Author's tracked changes 
EF by Natascha Töpfer (03 Sep 2024)  Manuscript 
ED: Referee Nomination & Report Request started (10 Sep 2024) by John M. Huthnance
RR by Chris Hughes (30 Sep 2024)
RR by Anonymous Referee #2 (04 Oct 2024)
ED: Reconsider after major revisions (08 Oct 2024) by John M. Huthnance
AR by Christoph Renkl on behalf of the Authors (13 Nov 2024)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (18 Nov 2024) by John M. Huthnance
AR by Christoph Renkl on behalf of the Authors (19 Nov 2024)  Manuscript 

Journal article(s) based on this preprint

27 Jan 2025
| Highlight paper
The alongshore tilt of mean dynamic topography and its implications for model validation and ocean monitoring
Christoph Renkl, Eric C. J. Oliver, and Keith R. Thompson
Ocean Sci., 21, 181–198, https://doi.org/10.5194/os-21-181-2025,https://doi.org/10.5194/os-21-181-2025, 2025
Short summary Co-editor-in-chief
Christoph Renkl, Eric C. J. Oliver, and Keith R. Thompson
Christoph Renkl, Eric C. J. Oliver, and Keith R. Thompson

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

It is shown that newly available geodesy combined with suitably located coastal tide gauges is accurate enough for validating model predictions of coastal mean dynamic topography (MDT). Moreover, alongshore differences of MDT can provide estimates of (1) average alongshore current and (2) area-integrated nearshore circulation. Thereby estimates of MDT from geodesy and tide-gauges have value for ocean monitoring.
Short summary
Mean dynamic topography (MDT), describes variations in the mean sea surface height above a reference surface called geoid. We show that MDT predicted by a regional ocean model, including a significant tilt along the coast of Nova Scotia, is in good agreement with estimates based on sea level observations. We demonstrate that this alongshore tilt of MDT can provide a direct estimate of the average alongshore current, and can also be used to approximate upwelling averaged over an offshore area.