Chromophoric dissolved organic matter dynamics revealed through the optimization of an optical-biogeochemical model in the NW Mediterranean Sea

Type Article
Date 2023
Language English
Author(s) Álvarez EvaORCID1, Cossarini Gianpiero1, Teruzzi AnnaORCID1, Bruggeman Jorn2, 3, Bolding Karsten2, 4, Ciavatta StefanoORCID5, Vellucci VincenzoORCID6, D’ortenzio Fabrizio7, Antoine David7, 8, Lazzari PaoloORCID1
Affiliation(s) 1 : National Institute of Oceanography and Applied Geophysics - OGS, Trieste, 34010, Italy
2 : Bolding & Bruggeman ApS, Asperup, 5466, Denmark
3 : Plymouth Marine Laboratory, Plymouth, PL1 3DH, UK
4 : Aarhus University, Department of Ecoscience, Silkeborg, 8600, Denmark
5 : Mercator Ocean International, 31400 Toulouse, France
6 : Sorbonne Université, CNRS, Institut de la Mer de Villefranche, IMEV, Villefranche-sur-Mer, F-06230, France
7 : Sorbonne Université, CNRS, Laboratoire d’Océanographie de Villefranche, LOV, Villefranche-sur-Mer, F-06230, France
8 : Remote Sensing and Satellite Research Group, School of Earth & Planetary Science, Curtin University, Perth, WA 6102, Australia
Source Biogeosciences (1726-4189) (Copernicus GmbH), 2023 , Vol. 20 , N. 22 , P. 4591-4624
DOI 10.5194/bg-20-4591-2023

Chromophoric dissolved organic matter (CDOM) significantly contributes to the non-water absorption budget in the Mediterranean Sea. The absorption coefficient of CDOM, αCDOM(λ), is measurable in situ and remotely from different platforms and can be used as an indicator of the concentration of other relevant biogeochemical variables, e.g., dissolved organic carbon. However, our ability to model the biogeochemical processes that determine CDOM concentrations is still limited. Here we propose a novel parametrisation of the CDOM cycle that accounts for the interplay between the light- and nutrient-dependent dynamics of local CDOM production and degradation, as well as its vertical transport. The parameterization is included in a one-dimensional (1D) configuration of the Biogeochemical Flux Model (BFM), which is here coupled to the General Ocean Turbulence Model (GOTM) through the Framework for Aquatic Biogeochemical Models (FABM). Here BFM is augmented with a bio-optical component that revolves spectrally the underwater light transmission. We did run this new GOTM-FABM-BFM configuration to simulate the seasonal αCDOM(λ) cycle at the deep-water site of the BOUSSOLE project in the North-Western Mediterranean Sea. Our results show that accounting for both nutrient and light dependence of CDOM production improves the simulation of the seasonal and vertical dynamics of αCDOM(λ), including a subsurface maximum that forms in spring and progressively intensifies in summer. Furthermore, the model consistently reproduces the higher-than-average concentrations of CDOM per unit chlorophyll concentration observed at BOUSSOLE. The configuration, outputs and sensitivity analyses from this 1D model application will be instrumental for future applications of BFM to the entire Mediterranean Sea in a 3D configuration.

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Álvarez Eva, Cossarini Gianpiero, Teruzzi Anna, Bruggeman Jorn, Bolding Karsten, Ciavatta Stefano, Vellucci Vincenzo, D’ortenzio Fabrizio, Antoine David, Lazzari Paolo (2023). Chromophoric dissolved organic matter dynamics revealed through the optimization of an optical-biogeochemical model in the NW Mediterranean Sea. Biogeosciences, 20(22), 4591-4624. Publisher's official version : , Open Access version :