Direct measurement of volume flux in the Faroe-Shetland Channel and over the Iceland-Faroe Ridge

Determining the exchange of water across the Iceland-Faroe-Scotland ridge is of fundamental interest because it measures the rate of transformation of North Atlantic water into dense water and thus the strength of the meridional overturning circulation (MOC). Here we study this exchange by monitoring all water flowing through the area east of Iceland to near the bottom or ∼600 m depth using a 75 kHz acoustic Doppler current profiler (ADCP) mounted on the high-seas ferry M/F Norröna. Starting in March 2008, currents have been measured in the Faroe-Shetland Channel (FSC) and along the Iceland-Faroe Ridge (IFR) on the ferry's weekly round-trips between Iceland and Denmark. The detided average transports (to the north) across the two sections are 4.1 ± 0.1Sv (10⁶ m²s^-1) through the FSC and 4.4 ± 0.25 Sv across the IFR (this excludes ∼1.6 Sv circulating around the Faroes). The Norrna program is ongoing.