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This study examines the role of processes transporting tracers across the Polar Front (PF) in the depth interval between the surface and major topographic sills, which this study refers to as the “PF core.” A preindustrial control simulation of an eddying climate model coupled to a biogeochemical model [GFDL Climate Model, version 2.6 (CM2.6)– simplified version of the Biogeochemistry with Light Iron Nutrients and Gas (miniBLING) 0.1° ocean model] is used to investigate the transport of heat, carbon, oxygen, and phosphate across the PF core, with a particular focus on the role of mesoscale eddies. The authors find that the total transport across the PF core results from a ubiquitous Ekman transport that drives the upwelled tracers to the north and a localized opposing eddy transport that induces tracer leakages to the south at major topographic obstacles. In the Ekman layer, the southward eddy transport only partially compensates the northward Ekman transport, while below the Ekman layer, the southward eddy transport dominates the total transport but remains much smaller in magnitude than the near-surface northward transport. Most of the southward branch of the total transport is achieved below the PF core, mainly through geostrophic currents. This study finds that the eddy-diffusive transport reinforces the southward eddy-advective transport for carbon and heat, and opposes it for oxygen and phosphate. Eddy-advective transport is likely to be the leading-order component of eddy-induced transport for all four tracers. However, eddy-diffusive transport may provide a significant contribution to the southward eddy heat transport due to strong along-isopycnal temperature gradients.

We have calculated normal modes with period between 8 and 80 h for a domain consisting of the Arctic, Atlantic, Indian and Pacific oceans. In this period range the numerical model has 56 modes, of which 13 are topographic vorticity waves all slower than 30 h. The trapping sites for these modes are the Siberian Shelf, the Icelandic Plateau, the Grand Banks, the Falkland Plateau and Patagonian Shelf, the Kerguelen Plateau, the New Zealand and Fiji Plateaus, and the Hawaiian Ridge. Predominantly planetary vorticity waves do not appear in the model at periods less than 80 h. The 41 modes found between 30 and 8 h include basin modes in the North Atlantic, Indian and equatorial Pacific; quarter-wave resonances in the Arabian Sea, Bay of Bengal and Gulf of Guinea; and Kelvin waves on the Antarctic coast, the Pacific North American coast and the New Zealand coast. Several vorticity and gravity modes exhibit an eastward circumglobal flow of energy that is confined to equatorial latitudes except where defl...