A microscopic simulation of particle flux in ocean waters: Application to radioactive pair disequilibrium

234Th‐Derived Particle Fluxes and Seasonal Variability: When Is the SS Assumption Reliable? Insights From a Novel Approach for Carbon Flux Simulation

“…The contrasted reaction of 234 Th deficits to changes in the carbon export during the prepeak and postpeak export phases is a consequence of the different mechanisms that govern the increase and decrease of 234 Th deficits (de Soto et al, ). The increase of 234 Th deficits is the result of the adsorption process and the export, both dictated by the particle dynamics.…”

“…The equations used to simulate particle dynamics and radionuclide scavenging are shown in the supporting information. A thorough description of the simulation can be found in De Soto et al (). We obtain (i) the depth profile of sinking carbon concentration throughout time ( n ( z , t )) as a result of the iterative application of steps 1, 2, and 4, and the depth profile of 234 Th concentration throughout time in (ii) the dissolved phase ( a D Th ( z , t )) and (iii) the particulate phase ( a P Th ( z , t )) as a result of the iterative application of step 3.…”

“…Our simulated scenario is therefore a simplification of a real complex ecosystem, however, provides the base to further implement more realistic situations that include more complex processes such as multiple particle size, temporally variable degradation and sinking rates, or physical non‐SS effects due to circulation (see de Soto et al, ), and it serves as a flexible test bed for analyzing the bias introduced when using SS or NSS approaches for Th‐POC fluxes evaluation. In actual bloom scenarios where physical effects due to water circulation might play a significant role, the accuracy of the SS/NSS approaches may only be expected to be reduced.…”

“…A smoothed Gaussian function of 45‐day width was used to reproduce the annual pattern of Chl a concentration of the PAP site in 2009 (Le Moigne, Villa‐Alfageme, et al, ; see also Data Set S1 in the supporting information). The effective adsorption/desorption rates for 234 Th are estimated in de Soto et al (). The details of how all these input parameters were determined are provided in the supporting information.…”

“…The novelty of this work is the use of a novel approach based on stochastic simulations to couple particle dynamics and radioisotope scavenging in ocean waters by using time‐dependent functions. Thereby, this method allows us to study transient regimes by means obtaining outputs over time for any time scale of interest (de Soto et al, ) and quantify the SS/NSS issue through comparing the SS and NSS export estimates with the actual carbon flux.…”