The ocean’s Biological Carbon Pump (BCP) plays a pivotal role in the oceanic carbon cycle by transporting organic carbon from the surface to the deep ocean, thereby regulating atmospheric CO₂ levels and long-term climate. A critical, yet poorly constrained component of the BCP is the velocity at which marine snow particles sink in the ocean. Various observations, imaging, laboratory experiments, and modeling have revealed significant variability in marine snow sinking velocities, influenced by factors such as particle composition, size, density, ballast minerals, but also hydrodynamic conditions such as vertical currents. The oceanic vertical currents are extremely difficult to assess since very variable and up to several orders of magnitude smaller than their horizontal counterparts. Nonetheless vertical velocities about 1 mm/s (~100 m/day) can have strong influences on sinking velocities.
This session invites contributions, , based on models or observations, exploring the physical, chemical and biological controls on marine snow sinking velocities as well as their biogeochemical feedback and parameterization. We welcome studies assessing sinking velocities using novel methodologies and biogeochemical models investigating the role of particle composition on sinking rates, examining the impact of environmental drivers (e.g., temperature, currents, internal tides, turbulence) on particle sinking rates and studies integrating observational, experimental, and modeling approaches to improve parameterizations of sinking velocities in global biogeochemical models.
By bringing together interdisciplinary research, this session aims to advance our understanding of the BCP’s efficiency and its representation in Earth system models, ultimately contributing to more accurate projections of ocean long term carbon sequestration.