Time-variable flux of sinking aggregates to the deep ocean: Hybrid Eulerian-Lagrangian model

The descending flux of organic particles, formed in the euphotic layer of the ocean, is a key mechanism for delivering carbon and nutrients into the deep ocean layers. Our study aimed to enhance the model and numerical Eulerian-Lagrangian algorithm developed by Maderich et al. (2025) so that it can consider the time-dependent dynamics of aggregate flux and account for ballast minerals (silicate and calcium carbonate) in aggregate sinking. In the algorithm, the Euler equations were solved for spectral concentrations of aggregate components with different sizes, while the Lagrangian equations were solved for depth and sizes of individual aggregates. Novel analytical unsteady solutions of the system of one-dimensional equations in the Eulerian framework for the particulate organic matter (POM) concentration and the Lagrangian framework for the particle mass and depth for constant and age-dependent degradation were compared with numerical solutions. The impact of a bloom event on POM profile variability was simulated using the developed numerical algorithm. Vladimir Maderich, Igor Brovchenko, Kateryna Kovalets, Seongbong Seo, and Kyeong Ok Kim (2025). Simple Eulerian–Lagrangian approach to solving equations for sinking particulate organic matter in the ocean. Geosci. Model Dev., 18, 7373–7387