Preprints
https://doi.org/10.5194/egusphere-2025-571
https://doi.org/10.5194/egusphere-2025-571
17 Feb 2025
 | 17 Feb 2025

An Atlantic wide assessment of marine heatwaves beyond the surface in an eddy-rich ocean model

Tobias Schulzki, Franziska U. Schwarzkopf, and Arne Biastoch

Abstract. Periods of prolonged anomalously high temperatures in the ocean, known as marine heatwaves (MHWs), can have devastating effects on ecosystems. While MHWs are extensively studied in the near-surface ocean, little is known about MHWs at depth. As continuous observations in space and time are very sparse away from the surface, basin wide studies on MHWs at depth have to rely on models. This introduces additional challenges due to the long adjustment timescale of the deep ocean, resulting in a long-term drift following the model’s initialisation. This unrealistic model drift dominates the MHW statistics below approximately 100 m when a fixed baseline is used. As a result, MHW studies at depth require a long model spin-up, or have to apply a linear baseline removing temperature trends. Based on a comparison of two model configurations with eddy-permitting and eddy-rich horizontal resolution, we show that the representation of mesoscale dynamics leads to pronounced differences in the characteristics of MHWs, in particular along the boundaries and along pathways of highly variable currents. Our results highlight the importance of horizontal and vertical heat transport within the ocean on sub-surface, but also on near-surface, MHWs. By investigating the vertical coherence of MHWs in an example region, here the Cape Verde archipelago, we show that MHWs are coherent over layers of a few 100 to 1000 m thickness, independent of the baseline used. These ranges are closely related to the vertical structure of the temperature field.

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Journal article(s) based on this preprint

17 Oct 2025
An Atlantic-wide assessment of marine heatwaves beyond the surface in an eddy-rich ocean model
Tobias Schulzki, Franziska U. Schwarzkopf, and Arne Biastoch
Ocean Sci., 21, 2481–2504, https://doi.org/10.5194/os-21-2481-2025,https://doi.org/10.5194/os-21-2481-2025, 2025
Short summary
Tobias Schulzki, Franziska U. Schwarzkopf, and Arne Biastoch

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC2: 'Comment on egusphere-2025-571', Lorenzo Berra, 04 Apr 2025
    • AC3: 'Reply on CC2', Tobias Schulzki, 03 Jun 2025
  • RC1: 'Comment on egusphere-2025-571', Neil Malan, 22 Apr 2025
    • AC1: 'Reply on RC1', Tobias Schulzki, 03 Jun 2025
  • RC2: 'Comment on egusphere-2025-571', Anonymous Referee #2, 07 May 2025
    • AC2: 'Reply on RC2', Tobias Schulzki, 03 Jun 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC2: 'Comment on egusphere-2025-571', Lorenzo Berra, 04 Apr 2025
    • AC3: 'Reply on CC2', Tobias Schulzki, 03 Jun 2025
  • RC1: 'Comment on egusphere-2025-571', Neil Malan, 22 Apr 2025
    • AC1: 'Reply on RC1', Tobias Schulzki, 03 Jun 2025
  • RC2: 'Comment on egusphere-2025-571', Anonymous Referee #2, 07 May 2025
    • AC2: 'Reply on RC2', Tobias Schulzki, 03 Jun 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Tobias Schulzki on behalf of the Authors (03 Jun 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (23 Jun 2025) by Aida Alvera-Azcárate
RR by Anonymous Referee #1 (11 Jul 2025)
RR by Anonymous Referee #2 (16 Jul 2025)
ED: Publish subject to minor revisions (review by editor) (16 Jul 2025) by Aida Alvera-Azcárate
AR by Tobias Schulzki on behalf of the Authors (24 Jul 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (28 Jul 2025) by Aida Alvera-Azcárate
AR by Tobias Schulzki on behalf of the Authors (05 Aug 2025)

Journal article(s) based on this preprint

17 Oct 2025
An Atlantic-wide assessment of marine heatwaves beyond the surface in an eddy-rich ocean model
Tobias Schulzki, Franziska U. Schwarzkopf, and Arne Biastoch
Ocean Sci., 21, 2481–2504, https://doi.org/10.5194/os-21-2481-2025,https://doi.org/10.5194/os-21-2481-2025, 2025
Short summary
Tobias Schulzki, Franziska U. Schwarzkopf, and Arne Biastoch
Tobias Schulzki, Franziska U. Schwarzkopf, and Arne Biastoch

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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.

Short summary
Exceptionally high ocean temperatures can cause long-lasting damage to marine ecosystems. Most existing knowledge about such temperature extremes is focused on near-surface waters, yet ecosystems also thrive at greater depths. In this study, we present a comprehensive analysis of temperature extremes across the entire Atlantic Ocean, from the surface to the seafloor. Our findings underscore the importance of the ocean circulation in driving extreme temperature events.
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