Award: OCE-1948685

The oceans play a crucial role in the global carbon cycle, taking up approximatelya quarter of annual anthropogenic carbon emissions. A significant amount of this carbon is transportedby relatively large, fast sinking particles from the surface to the deep ocean where it can reside for centuries.We have a good understanding of the biological and physical processes thatcreate these large particles and these processes are included in oceanicbiogeochemical models. However, we have a poor understanding of the processesthat fragment particles and these are not included in biogeochemical models. This isimportant because many properties of these particles (e.g. their sinking speed, carboncontent) depend in part of the size of the particles. The aim of this proposal was touse experimental and field observations to examine the breakup of marine particles causedby fluid shear and to use simple computational models to help interpret these data. We were able to show that particles most often broke into two similar-sized particles. This isimportant for model development because it means that models of particle fragmentation don'thave to consider details of the size distribution of particles formed from fragmentation. Theresulting simplification will help when incorporating fragmentation into global biogeochemical models.We also found that the history of fluid shear experienced by a particle affects itsstrength, and hence determines whether or not it will break apart. Incorporating this effect intofuture models will be more challenging because it requires the model to keep track of wherethe particle has been and what fluid shears it experienced. With these results in hand we can start to develop realistic models of marine particlefragmentation to accompany existing models of particle formation. Doing this will helpimprove model predictions of oceanic carbon cycling and storage. Last Modified: 07/11/2023 Submitted by: Adrian B Burd