The Dynamics of Arctic Ocean Mesoscale Eddies and their Role in the Beaufort Gyre Circulation Syste

The Arctic has been an important focus of global climate change with its decreasing sea-ice cover in recent decades. The Arctic Ocean is central to the system, with ocean eddies transporting heat and other anomalous water properties and modifying the large-scale ocean dynamics. Extreme conditions, the existence of ice cover and other logistical challenges of working in remote regions has limited observation of eddies in the Arctic Ocean. Recent observational systems that can autonomously profile the water column have provided extensive temperature, salinity and velocity measurements across the Arctic Ocean since 2004, with sufficiently high temporal and spatial resolution to sample mesoscale eddies of order 10 km in diameter. This thesis takes advantage of this collection of high resolution measurements to provide the first Arctic-wide assessment of the eddy field.;Eddies are found to be ubiquitous features within the Arctic halocline. The majority of eddies are anticyclones with anomalously cold cores. It is shown how the horizontal and vertical scales of eddies are related to their ambient stratification conditions. The magnitudes and spatial pattern of the baroclinic Rossby deformation radius is computed from stratification across the Arctic Ocean and horizontal scales of eddies are found to be comparable to the local deformation radius. Eddy vertical scales are shown to be consistent with the adjustment of a particular water-column stratification to an initial potential vorticity anomaly. Taller eddies are observed in more weakly-stratified deeper depths of the water column. The theoretical analysis provides a physical explanation for the fouuation of a previously un-observed eddy type having two separate, vertically-aligned cores.;The distribution of eddies across the Arctic Ocean is shown to be non-uniform, with eddies concentrated in regions of major circulation systems. One of the main circulation systems in the Arctic, the Beaufort Gyre, is a region of prominent eddy activity. The eddy field in the Beaufort Gyre region is shown to be growing more active in the recent decade, consistent with an intensifying Beaufort Gyre over this time and increased baroclinic instability (i.e., eddies regulate the strength of the gyre by releasing available potential energy). Most of the kinetic energy in the Beaufort Gyre water column is in the form of mesoscale eddies. The partitioning of eddy kinetic energy into barotropic and baroclinic modes reveals that energy is predominantly in the first two baroclinic modes. It is shown here how this is a result of strong halocline stratification, which limits the efficiency of kinetic energy transfer to the barotropic mode.;The combined results of this thesis contribute to our understanding of how the Arctic Ocean's eddy field relates to the dynamics of the changing system.