The deep circulation of the Faroe-Shetland channel: opposing flows and topographic eddies

New insights into the deep circulation of the Faroe-Shetland channel are gained from a high- resolution regional ocean model. The simulation shows a more complex structure of the deep flow field than previously thought: a flow reversal of the deep and intermediate waters to the northeast on the Faro- ese flank of the channel and persistent topographic eddies that force the deep currents into a gyre-like structure. This flow reversal opposes the previously accepted understanding of a purely southwestward deep flow but is in agreement with velocity measurements. The southwestward transport of the overflow waters is found to be facilitated almost exclusively by a strong and narrow current on the Shetland side of the channel. Float release experiments show that up to 38% of the overflow water takes longer than a purely southwestward flow regime suggests and up to 13% takes twice as long. From the release of tracers, a substantial amount of lateral mixing is evident within the channel, predominantly facilitated by the topo- graphic eddies