21 Sep 2023
 | 21 Sep 2023
Status: this preprint is currently under review for the journal BG.

Ocean models as shallow sea oxygen deficiency assessment tools: from research to practical application

Sarah Piehl, René Friedland, Thomas Neumann, and Gerald Schernewski

Abstract. Oxygen is a key indicator of ecosystem health and part of environmental assessments used as a tool to achieve a healthy ocean. Oxygen assessments are mostly based on monitoring data that are spatially and temporally limited, although monitoring efforts have increased. This leads to an incomplete understanding of the current state and ongoing trends of the oxygen situation in the oceans. Ocean models can be used to overcome spatial and temporal limitations and provide high-resolution 3D oxygen data but are rarely used for policy-relevant assessments. In the Baltic Sea where environmental assessments have a long history and which is known for the world’s largest permanent hypoxic areas, ocean models are not routinely used for oxygen assessments. Especially for the increasingly observed seasonal oxygen deficiency in its shallower parts, current approaches cannot adequately reflect the high spatio-temporal dynamics. To develop a suitable shallow water oxygen deficiency assessment method for the western Baltic Sea, we evaluated first the benefits of a refined model resolution. Secondly, we integrated model results and observations by a retrospective fitting of the model data to the measured data using several correction functions as well as a correction factor. Despite its capability to reduce the model error, none of the retrospective correction functions applied led to consistent improvements. One reason is probably the heterogeneity of the used measurement data, which are not consistent in their temporal and vertical resolution. Using the Arkona Basin as an example, we show a potential future approach where only high temporal and/or vertical resolution station data is integrated with model data to provide a reliable and ecologically relevant assessment of oxygen depletion with a high degree of confidence and transparency. By doing so we further aim to demonstrate strengths and limitations of ocean models and to assess their applicability for policy-relevant environmental assessments.

Sarah Piehl et al.

Status: open (until 14 Dec 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2023-152', Anonymous Referee #1, 27 Nov 2023 reply
  • RC2: 'Comment on bg-2023-152', Anonymous Referee #2, 06 Dec 2023 reply
  • RC3: 'Comment on bg-2023-152', Anonymous Referee #3, 07 Dec 2023 reply

Sarah Piehl et al.

Sarah Piehl et al.


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Short summary
We integrated observations essential for policy decisions with high-resolution 3D model results to improve the reliability of oxygen assessments. Based on our findings, we suggest merging only high temporal and/or vertical resolution station data with model data to increase confidence in oxygen assessments. While showing the strengths and limitations of our approach we show that model simulations are an useful tool for policy-relevant oxygen assessments.