The role of high Rossby number processes on vertical pathways in the upper ocean

Ruth Musgrave

WOODS HOLE OCEANOGRAPHIC INSTITUTION

A study of vertical pathways in the upper ocean at scales from $\mathcal{O}$10 m - 1 km is proposed, where the high relative vorticities of surface flows lead to high Rossby numbers processes such as filaments and vortices. These processes are not quasigeostrophic and their vertical velocities cannot be determined using established quasigeostrophic methods (i.e. the omega-equation). They arise in the forward cascade of energy from low Rossby number features, and vertical velocities associated with them are expected to have larger magnitudes but shorter timescales than those governed by quasigeostrophic dynamics. This work will address outstanding questions relating to the role of high Rossby number processes and their associated vertical velocities on advective pathways in the upper ocean, using both observations and numerical models. ///// The observational component of the proposed work will employ ship-based bow chain surveys in the western Alboran Sea to make measurements of temperature, salinity, fluorescence and oxygen at extremely high horizontal resolution ($\sim$ 1 m) in the upper ocean at relatively high ship speeds (10 kn), reducing issues of space-time alias that have challenged prior studies using this technology. Concurrent work will examine high Rossby number processes in a series of nonhydrostatic idealized numerical models of a baroclinically unstable front, with parameters close to those observed in the western Alboran Sea. The simulations will both aid interpretation of the bow chain measurements and also quantify the influence of model resolution and nonhydrostatic processes on vertical pathways in frontal regions. Through collaboration with other DRI members, particle trajectories, Lagrangian pathways and barriers, and particle clustering and dispersion will be assessed in these simulations. The comparison of Lagrangian metrics at different resolution will enable an assessment of the accuracy of vertical pathways determined in lower resolution, regional numerical models.

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You can access the relevant Webpage for the CALYPSO 2019 experiment here.