Intermediate water from the Greenland Sea in the Faroe Bank Channel: spreading of released sulphur hexafluoride

The Faroe Bank Channel is the deepest passage for dense water leaving the Nordic Seas into the North Atlantic. The contribution to this part of the Greenland-Scotland Overflow by intermediate water from the Greenland Sea is investigated by the tracer sulphur hexafluoride (SF6) that was released into the central Greenland Sea in summer 1996. Continuous monitoring has since traced it around the Nordic Seas and into the connecting areas. It was observed for the first time close to the Faroe Islands in early 1999, indicating a transport time from the Greenland Sea of around 2.5 years. This study estimates that approximately 16 kg of SF6 had passed the Faroe Bank Channel by the end of 2002, that is 5% of the total amount released. Both the arrival time and the amount of exported SF6 deduced from the observations are consistent with the results from a numerical ocean model simulating the tracer release and spreading.