Submitted as: development and technical paper 15 Jan 2021

Submitted as: development and technical paper | 15 Jan 2021

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

A discrete interaction numerical model for coagulation and fragmentation of marine detritic particulate matter

Gwenaëlle Gremion1, Louis-Philippe Nadeau1, Christiane Dufresne1, Irene R. Schloss2,3,4, Philippe Archambault5, and Dany Dumont1 Gwenaëlle Gremion et al.
  • 1Institut des sciences de la mer de Rimouski, UQAR, Québec-Océan, Rimouski (Quebec), Canada
  • 2Instituto Antártico Argentino, Buenos Aires, Argentina
  • 3Centro Austral de Investigaciones Científicas (CADIC-CONICET), Ushuaia, Argentina
  • 4Universidad Nacional de Tierra del Fuego, Ushuaia, Argentina
  • 5ArcticNet, Québec-Océan, Université Laval,(Quebec), Canada

Abstract. A simplified model, representing the dynamics of marine organic particles in a given size range experiencing coagulation and fragmentation reactions is developed. The framework is based on a discrete size spectrum on which reactions act to exchange properties between different particle sizes. The reactions are prescribed according to triplets interactions. Coagulation combines two particle sizes to yield a third one, while fragmentation breaks a given particle size into two (i.e. the inverse of the coagulation reaction). The complete set of reactions is given by all the permutations of two particle sizes associated with a third one. Since, by design, some reactions yield particle sizes that are outside the resolved size range of the spectrum, a closure is developed to take into account this unresolved range and satisfy global constraints such as mass conservation. In order to minimize the number of tracers required to apply this model to an Ocean General Circulation Model focus is placed on the robustness of the model to the particle size resolution. Thus, numerical experiments were designed to study the dependence of the results on i) the number of particle size bins used to discretize a given size range (i.e. the resolution) and ii) the type of discretization (i.e. linear vs nonlinear). The results demonstrate that in a linearly size discretized configuration, the model is independent of the resolution. However, important biases are observed in a nonlinear discretization. A first attempt to mitigate the effect of nonlinearity of the size spectrum is then presented and shows significant improvement in reducing the observed biases.

Gwenaëlle Gremion et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on gmd-2020-423', Astrid Kerkweg, 26 Feb 2021
    • AC1: 'Reply on CEC1', Gwenaelle Gremion, 26 Mar 2021
  • RC1: 'Comment on gmd-2020-423', Anonymous Referee #1, 26 Feb 2021
    • AC2: 'Reply on RC1', Gwenaelle Gremion, 26 Mar 2021
  • RC2: 'Comment on gmd-2020-423', Anonymous Referee #2, 08 Mar 2021
    • AC3: 'Reply on RC2', Gwenaelle Gremion, 26 Mar 2021

Gwenaëlle Gremion et al.

Model code and software

Source code and user manual of the Coagfrag Model (Version Version 1) Gremion, G. and Nadeau, L.-P.

Gwenaëlle Gremion et al.


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Short summary
An accurate description of the detritic organic particles is key to improve estimations of carbon export into the ocean abyss in ocean General Ocean Circulation Models. Yet, most parametrization are numerically impractical due to the required number of tracers needed to resolve the particle size spectrum. Here, a new parametrization that aims to minimize the tracers number while accurately describing the particles dynamics is developed and tested in a series of idealized numerical experiments.