Preprints
https://doi.org/10.5194/os-2021-36
https://doi.org/10.5194/os-2021-36

  04 May 2021

04 May 2021

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

Causes of uncertainties in the representation of the Arabian Sea oxygen minimum zone in CMIP5 models

Henrike Schmidt1,2, Julia Getzlaff1, Ulrike Löptien1,2, and Andreas Oschlies1,2 Henrike Schmidt et al.
  • 1GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
  • 2Kiel University, Christian-Albrechts-Platz 4, 24118 Kiel, Germany

Abstract. Open ocean oxygen minimum zones (OMZs) occur in regions with high biological productivity and weak ventilation. They restrict marine habitats and alter biogeochemical cycles. Global models show generally a large model-data misfit with regard to oxygen. Reliable statements about their future development and the quantification of their interaction with climate change are currently not possible. One of the most intense OMZs is located in the Arabian Sea (AS). We give an overview of the main model deficiencies with a detailed comparison of the historical state of ten climate models from the 5th coupled model intercomparison project (CMIP5) that present our present-day understanding of physical and biogeochemical processes. Considering a threshold of 60 μmol l−1, we find a general underestimation of the OMZ volume in the AS compared to observations, that is caused by a too shallow layer of oxygen-poor water in the models. The deviation of oxygen values in the deep AS is the result of subduction of higher oxygenated waters in the Southern Ocean in the models compared to observations. In addition, model deficiencies related to the coarse resolution of the abyssal ocean, are identified in the deep water mass transport from the Southern Ocean northward into the AS. Differences in simulated water mass properties and ventilation rates of Red Sea Water and Persian Gulf Water cause different mixing in the AS and thus influence the intensity of the OMZ. These differences also point towards variations in the parametrisations of the overflow from the marginal seas among the models. The results of this study are intended to foster future model improvements regarding the OMZ in the AS.

Henrike Schmidt 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 os-2021-36', Anonymous Referee #1, 19 May 2021
    • AC1: 'Reply on RC1', Henrike Schmidt, 02 Jul 2021
  • RC2: 'Comment on os-2021-36', Anonymous Referee #2, 21 May 2021
    • AC2: 'Reply on RC2', Henrike Schmidt, 05 Jul 2021
  • RC3: 'Comment on os-2021-36', Anonymous Referee #3, 02 Jun 2021
    • AC3: 'Reply on RC3', Henrike Schmidt, 05 Jul 2021

Henrike Schmidt et al.

Henrike Schmidt et al.

Viewed

Total article views: 504 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
425 62 17 504 23 1 1
  • HTML: 425
  • PDF: 62
  • XML: 17
  • Total: 504
  • Supplement: 23
  • BibTeX: 1
  • EndNote: 1
Views and downloads (calculated since 04 May 2021)
Cumulative views and downloads (calculated since 04 May 2021)

Viewed (geographical distribution)

Total article views: 482 (including HTML, PDF, and XML) Thereof 482 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 25 Jul 2021
Download
Short summary
Oxygen poor regions in the open ocean restrict marine habitats. Global climate simulations show large uncertainties regarding the prediction of these areas. We analyze the representation of the simulated oxygen minimum zones in the Arabian Sea using ten climate models. We give an overview of the main deficiencies that cause the model-data misfit in oxygen concentrations. This detailed process analysis shall foster future model improvements regarding the oxygen minimum zone in the Arabian Sea.