The impact of ocean biogeochemistry on physics and its consequences for modelling shelf seas

Skákala, Jozef, Bruggeman, Jorn, Ford, David, Wakelin, Sarah, Akpınar, Anıl, Hull, Tom, Kaiser, Jan ORCID: https://orcid.org/0000-0002-1553-4043, Loveday, Benjamin R., O’Dea, Enda, Williams, Charlotte A. J. and Ciavatta, Stefano (2022) The impact of ocean biogeochemistry on physics and its consequences for modelling shelf seas. Ocean Modelling, 172. ISSN 1463-5003

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Abstract

We use modelling and assimilation tools to explore the impact of biogeochemistry on physics in the shelf sea environment, using North-West European Shelf (NWES) as a case study. We demonstrate that such impact is significant: the attenuation of light by biogeochemical substances heats up the upper 20 m of the ocean by up to 1 °C and by a similar margin cools down the ocean within the 20–200 m range of depths. We demonstrate that these changes to sea temperature influence mixing in the upper ocean and feed back into marine biology by influencing the timing of the phytoplankton bloom, as suggested by the critical turbulence hypothesis. We compare different light schemes representing the impact of biogeochemistry on physics, and show that the physics is sensitive to both the spectral resolution of radiances and the represented optically active constituents. We introduce a new development into the research version of the operational model for the NWES, in which we calculate the heat fluxes based on the spectrally resolved attenuation by the simulated biogeochemical tracers, establishing a two-way coupling between biogeochemistry and physics. We demonstrate that in the late spring-summer the two-way coupled model increases heating in the upper oceanic layer compared to the existing model and improves by 1–3 days the timing of the simulated phytoplankton bloom. This improvement is relatively small compared with the existing model bias in bloom timing, but is sufficient to have a visible impact on model skill in the free run. We also validate the skill of the two-way coupling in the context of the weakly coupled physical-biogeochemical assimilation currently used for operational forecasting of the NWES. We show that the change to the skill is negligible for analyses, but it remains to be seen how much it differs for the forecasts.

Item Type: Article
Additional Information: Funding Information: This work was supported by a Natural Environment Research Council (NERC) funded project of the Marine Integrated Autonomous Observing Systems (MIAOS) programme: Combining Autonomous observations and Models for Predicting and Understanding Shelf seas (CAMPUS). It also benefitted from another NERC funded project Alternative Framework to Assess Marine Ecosystem Functioning in Shelf Seas (AlterECO, http://projects.noc.ac.uk/altereco/), grant no. NE/P013899/1. The work also benefited from the Copernicus Marine Environment Monitoring Service (CMEMS) funded projects OPTIcal data Modelling and Assimilation (OPTIMA) and NOWMAPS. Furthermore, this work was also partially funded by the SEAMLESS project, which received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 101004032. We would like to thank Dawn Ashby for drawing the schematic Fig. 1. The ocean colour data were provided by the European Space Agency Climate Initiative 'Ocean Color' (https://esa-oceancolour-cci.org/). The glider data used in the study (http://dx.doi.org/10.5285/b57d215e-065f-7f81-e053-6c86abc01a82 and http://dx.doi.org/10.5285/b58e83f0-d8f3-4a83-e053-6c86abc0bbb5) are publicly available on https://www.bodc.ac.uk/data/published_data_library/catalogue/. We also used L4 time series for chlorophyll a concentrations provided by the Western Channel Observatory (https://www.westernchannelobservatory.org.uk/). The model was forced by the atmospheric ERA5 product of The European Centre for Medium-Range Weather Forecasts (ECMWF, https://www.ecmwf.int/). The river forcing data used by the model were prepared by Sonja van Leeuwen and Helen Powley as part of UK Shelf Seas Biogeochemistry programme (contract no. NE/K001876/1) of the NERC and the Department for Environment Food and Rural Affairs (DEFRA). We acknowledge use of the MONSooN system, a collaborative facility supplied under the Joint Weather and Climate Research Programme, a strategic partnership between the Met Office and the NERC. The different outputs for the free run simulations and reanalyses are stored on the MONSooN storage facility MASS and can be obtained upon request.
Uncontrolled Keywords: data assimilation,impact of biogeochemistry on physics,north-west european shelf (10e–10w, 40n–68n),ocean chlorophyll concentration,operational systems,phytoplankton spring bloom,sea surface temperature,two-way coupled physical–biogeochemical model,computer science (miscellaneous),geotechnical engineering and engineering geology,oceanography,atmospheric science,sdg 14 - life below water ,/dk/atira/pure/subjectarea/asjc/1700/1701
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 22 Feb 2022 10:30
Last Modified: 23 Oct 2022 03:34
URI: https://ueaeprints.uea.ac.uk/id/eprint/83633
DOI: 10.1016/j.ocemod.2022.101976

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