03 Jul 2024
 | 03 Jul 2024
Status: this preprint is open for discussion.

Massive and localized export of selected marine snow types at eddy edges in the South Atlantic Ocean

Alexandre Accardo, Rémi Laxenaire, Alberto Baudena, Sabrina Speich, Rainer Kiko, and Lars Stemmann

Abstract. The open ocean plays a critical role in mitigating climate change by sequestering carbon dioxide (CO2) from the atmosphere for long periods of time. This carbon storage occurs over decades to millennia and relies on the physical pump that transports cold, dense, and DIC-rich waters to the deep ocean, as part of the ocean’s overturning circulation, and the biological carbon pump (BCP). The BCP encompasses a wide range of processes, from the fixation of atmospheric CO2 by phytoplankton activity to carbon sequestration in the deep ocean. Atmospheric CO2 concentrations would be about 200 ppm higher than in a world without biology, and the global climate would be much warmer by default. This study highlights the idea that BCP efficiency is enhanced by the ocean dynamics at mesoscale and submesoscale. In fact, our results suggest that frontal regions, such as those between mesoscale eddies, could lead to an important accumulation and transport of particulate organic matter (POM) from the mixed layer depth (MLD) down to depths of about 600 meters.  To reach these conclusions, a multifaceted approach was applied. It included in-situ measurements and marine snow images from a BGC Argo float equipped with an Underwater Vision Profiler (UVP6), satellite altimetry data, and Lagrangian physics diagnostics. We focused our study on three intense features in marine snow distribution observed during the 17-month long float mission in the Cape Basin, southwest of Africa. These features were located in the frontal region between mesoscale eddies. Our study suggests that a particle injection pump induced by a frontogenesis-driven mechanism has the potential to enhance the effectiveness of the biological pump by increasing the depth at which carbon is injected into the water column. This work also emphasizes the importance of establishing repeated sampling campaigns targeting the interface zones between eddies. This could improve our understanding of the mechanisms involved in the deep accumulation of marine snow observed at eddy interfaces. 

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Alexandre Accardo, Rémi Laxenaire, Alberto Baudena, Sabrina Speich, Rainer Kiko, and Lars Stemmann

Status: open (until 14 Aug 2024)

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  • RC1: 'Comment on egusphere-2024-1558', Anonymous Referee #1, 17 Jul 2024 reply
  • RC2: 'Comment on egusphere-2024-1558', Anonymous Referee #2, 24 Jul 2024 reply
Alexandre Accardo, Rémi Laxenaire, Alberto Baudena, Sabrina Speich, Rainer Kiko, and Lars Stemmann
Alexandre Accardo, Rémi Laxenaire, Alberto Baudena, Sabrina Speich, Rainer Kiko, and Lars Stemmann


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Short summary
The open ocean helps mitigate climate change by storing CO2 through the biological carbon pump (BCP). The BCP involves processes like phytoplankton capturing CO2 and sequestering it in the deep ocean via marine snow production. We found significant marine snow accumulation from the surface to 600 meters deep in frontal regions between eddies. We suggest that the coupling of hydrodynamics at eddy edges and biological activity (via planktonic organisms) may enhanced this process.