Preprints
https://doi.org/10.5194/egusphere-2025-2526
https://doi.org/10.5194/egusphere-2025-2526
10 Jul 2025
 | 10 Jul 2025

Seasonal cycles of the carbon export flux in the ocean: Insights from the SISSOMA mechanistic model

Athanasios Kandylas and Andre William Visser

Abstract. This study aims to investigate the seasonal dynamics of carbon export flux in the ocean using the SISSOMA modeling framework. SISSOMA uses a 2-dimensional state space (size and excess density) to follow the fate of aggregates in the mixed layer which are transformed through three main processes, e.g., aggregation, fragmentation, and remineralization, until they eventually sink out of the surface ocean. The model tracks aggregate size, mass, and porosity which allows for a direct estimate of aggregate sinking speed through a Reynolds number modified Stokes' law. First, a simple seasonal cycle with a single peak of POM production is presented, which provides a solid basis to understand the model's dynamics and enables us to perform sensitivity analyses on important parameters. The effect of increased stratification on a reconstructed ecosystem in the north Atlantic is then presented and discussed. Overall, our results showcase the nonlinear relationship between the production of primary particles and the export of aggregates out of the mixed layer and unveil key mechanics of the three transformative processes. Moreover, it has been shown that remineralization rates, stickiness, and the size/ excess density characteristics of the primary particles all affect in various ways the intensity, seasonal cycle, and the resulted size spectrum of the aggregate community. Finally, our results indicate the crucial role that turbulence plays in both the timing and the magnitude of the carbon export flux which might affect not only the potential of the system to remove carbon out of the mixed layer but also have a direct impact on the organisms inhabiting the mesopelagic layer which rely on the sinking particles to cover their energetic needs.

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Athanasios Kandylas and Andre William Visser

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CEC1: 'Comment on egusphere-2025-2526', Juan Antonio Añel, 25 Jul 2025
    • AC1: 'Reply on CEC1', Athanasios Kandylas, 30 Jul 2025
      • CEC2: 'Reply on AC1', Juan Antonio Añel, 30 Jul 2025
  • RC1: 'Comment on egusphere-2025-2526', Anonymous Referee #1, 22 Aug 2025
  • RC2: 'Comment on egusphere-2025-2526', Anonymous Referee #2, 07 Sep 2025
Athanasios Kandylas and Andre William Visser
Athanasios Kandylas and Andre William Visser

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Short summary
The ocean plays an important role in regulating the Earth's climate by storing excess atmospheric carbon in its interior mainly through the sinking of small organic particles originating from planktonic organisms. Once produced these particles are constantly being transformed (sticking together, breaking into smaller pieces and being consumed by microbes). Here, we try to understand the dynamics of these processes by testing a variety of factors, such as stickiness and water column mixing.
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