Eddies and algal stoichiometry: Physical and biological impacts on the organic carbon pump

Kooijman, S.A.L.M. [Promotor]Dijkstra, H.A. [Copromotor

Critical turbulance revisited: the impact of submesoscale vertical mixing on plankton patchiness.

By supplying nutrients to the ocean surface, submesoscale vertical motions can have a strong impact on phytoplankton growth and phytoplankton distributions. To study this impact, we model a phytoplankton population in a baroclinically unstable submesoscale eddy using a phytoplankton model coupled to a three-dimensional hydrodynamic model. In the eddy, strong vertical transports are generated as a consequence of baroclinic instability. The resulting plankton distributions turn out to depend strongly on the light intensity and local vertical transport. To analyze these distributions in detail, we use more idealized coupled hydrodynamic-biological models and we extend the critical turbulence concept to three dimensions

Influence of (sub)mesoscale eddies on the soft-tissue carbon pump

In an idealized situation of a baroclinically unstable single eddy, we study the impact of eddy-induced mixing on the soft-tissue carbon pump. The new element here is the coupling of a three-dimensional nonhydrostatic ocean model with a physiological plankton model that is able to represent a variable plankton C:N ratio. During the development and breakup of the eddy, a complicated vertical velocity field appears. The processes of transport and plankton growth, as well as the effect of the flow on the C:N ratio, are studied in detail. The physical processes associated with eddy breakup have a strong impact on the local environment in which the plankton grows. The changes in the local environment lead to a decrease of the C:N ratio (about 30% throughout the upper 150 m of the domain) and hence a weakening of the soft-tissue carbon pump. According to a sensitivity analysis, the decrease of the C:N ratio as a consequence of the flow field appears robust; it does not depend on specific parameter values in the model

Influence of (sub)mesoscale eddies on the soft-tissue carbon pump

In an idealized situation of a baroclinically unstable single eddy, we study the impact of eddy-induced mixing on the soft-tissue carbon pump. The new element here is the coupling of a three-dimensional nonhydrostatic ocean model with a physiological plankton model that is able to represent a variable plankton C:N ratio. During the development and breakup of the eddy, a complicated vertical velocity field appears. The processes of transport and plankton growth, as well as the effect of the flow on the C:N ratio, are studied in detail. The physical processes associated with eddy breakup have a strong impact on the local environment in which the plankton grows. The changes in the local environment lead to a decrease of the C:N ratio (about 30% throughout the upper 150 m of the domain) and hence a weakening of the soft-tissue carbon pump. According to a sensitivity analysis, the decrease of the C:N ratio as a consequence of the flow field appears robust; it does not depend on specific parameter values in the model