A Deeper View of the North-Pacific: Transport and Spreading Pathways at 1000 metres According to Argo

The basin wide dynamics of the North Pacific Ocean have been studied extensively at the surface, but less so at depth. This study analyzes the transport and spreading of float trajectories at 1000 metres depth to gain a deeper understanding of the differences and similarities between deep oceanic pathways and those at the surface. This analysis was conducted using data provided by the global Argo program, which has seeded the ocean with profiling floats for the last three decades. Here floats were used as Lagrangian tracers for ocean circulation, under the assumption that the location information relayed by floats at the ocean surface approximately every 10 days is representative of their location at the 1000 m parking depth. After ordering these location data into continuous trajectories, we explored averaged mean velocity and eddy-kinetic energy fields, as well as estimates for spreading via diffusivity (defined as the rate of change of dispersion of trajectories from a common source). Preliminary findings indicate that the Argo dataset at 1000m demonstrates retention of basin scale physical features, such as gyre circulation and the Kuroshio western boundary current, at depth. Other research questions addressed in this study include the Kuroshio's role as a transport barrier, as well as the existence of deep-penetrating mesoscale eddies and their role in the spreading of water parcels.