A stochastic model of Lagrangian marine particles for the ocean's biological carbon pump
Marine particles are invisible to the naked eye; nevertheless, they are central to the Earth's carbon cycle. The marine food web produces a myriad of microscopic biogenic waste products –from dead phytoplankton cells and animal carcasses, exudates, faeces, colonies of microbes– that sink into the ocean interior, forming a snowfall of particles. Sinking marine particles connect the productive surface ocean with the darker ocean interior and the seafloor sediments, carrying particulate organic carbon (POC) that sustains the metabolism of marine life and contributes to the oceanic storage of atmospheric carbon. This process is known as the ocean's biological carbon pump. In this talk, I will present a biogeochemical model of Lagrangian marine particles that mechanistically interact with each other and the planktonic food web as they gravitationally sink. A Lagrangian framework tracks particles throughout their life history and allows recording their fractal size, porosity, density, stickiness and sinking velocity, providing information on particle attributes alongside POC fluxes. I will show how I have calibrated the model to reproduce time-series observations of particle fluxes and particle number concentrations, two variables known to have spatiotemporal mismatches. This model has the potential to underpin the mechanisms that control the transfer efficiency of POC flux to the deep ocean.
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