Preprints
https://doi.org/10.5194/gmd-2020-431
https://doi.org/10.5194/gmd-2020-431

Submitted as: model evaluation paper 04 Mar 2021

Submitted as: model evaluation paper | 04 Mar 2021

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

Sensitivity of asymmetric Oxygen Minimum Zones to remineralization rate and mixing intensity in the tropical Pacific using a basin-scale model (OGCM-DMEC V1.2)

Kai Wang1, Xiujun Wang1,2, Raghu Murtugudde2, Dongxiao Zhang3, and Rong-Hua Zhang4 Kai Wang et al.
  • 1College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China
  • 2Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20740, USA
  • 3JISAO, University of Washington and NOAA, Pacific Marine Environmental Laboratory, Seattle, Washington 98115, USA
  • 4Institute of Oceanology, Chinese Academy of Sciences, Qingdao, Shandong 266071, China

Abstract. The tropical Pacific Ocean holds the world’s two largest Oxygen Minimum Zones (OMZs), showing a prominent hemispheric asymmetry, with a much stronger and broader OMZ north of the equator. However, many models have difficulties in reproducing the observed asymmetric OMZs in the tropical Pacific. Here, we apply a fully coupled basin-scale model (OGCM-DMEC V1.2) to evaluate the impacts of remineralization rate and the intensity of vertical mixing on the dynamics of OMZs in the tropical Pacific. We first utilize observational data of dissolved oxygen (DO), dissolved organic nitrogen (DON) and oxygen consumption to calibrate and validate the basin-scale model. Our model experiments demonstrate that enhanced vertical mixing combined with reduced remineralization rate can significantly improve our model capability of reproducing the asymmetric OMZs. Our study shows that DO is more sensitive to biological processes over 200–400 m but to physical processes over 400–1000 m. Enhanced vertical mixing not only causes an increase in DO supply at mid-depth, but also results in lower rates of biological consumption in the OMZs, which is associated with redistribution of DON. Our analyses demonstrate that weaker physical supply in the ETNP is the dominant process responsible for the asymmetry of the lower OMZs whereas greater biological consumption to the north plays a larger role in regulating the upper OMZs. This study highlights the complex roles of physical supply and biological consumption in shaping the asymmetric OMZs in the tropical Pacific.

Kai Wang 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-2020-431', Anonymous Referee #1, 30 Mar 2021
  • RC2: 'Comment on gmd-2020-431', Anonymous Referee #2, 18 Apr 2021
  • RC3: 'Comment on gmd-2020-431', Anonymous Referee #3, 13 May 2021

Kai Wang et al.

Model code and software

Sensitivity of asymmetric Oxygen Minimum Zones to remineralization rate and mixing intensity in the tropical Pacific using a basin-scale model (OGCM-DMEC V1.2) Kai, Wang, Xiujun, Wang, Raghu, Murtugudde, Dongxiao, Zhang, and Rong-Hua, Zhang https://doi.org/10.5281/zenodo.4384131

Kai Wang et al.

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Short summary
We use observational data of dissolved oxygen (DO) and organic nitrogen to calibrate a basin-scale model (OGCM-DEMC V1.2), and then evaluate model capacity for simulating mid-depth DO in the tropical Pacific. Sensitivity studies show that enhanced vertical mixing combined with reduced biological consumption performs well in reproducing the asymmetric OMZs. We find that DO is more sensitive to biological processes in the upper OMZs but to physical processes in the lower OMZs.