Direct velocity observations of volume flux between Iceland and the Shetland Islands

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Atlantic Waters flowing northward into the Nordic Seas are important for their role as an early indicator of changes to deepwater formation. As such, this requires a fundamental understanding of the pathways and volume fluxes through the primary passageways from the Atlantic into the Nordic Seas. A mean annual volume transport of 6.1 ± 0.3 Sv was observed flowing in above the σt = 27.8 isopycnal (a proxy for the lower limit of Atlantic Water depth), through the Faroe Shetland Channel (FSC) and over the Iceland Faroes Ridge (IFR) from March 2008 to June 2012, using repeat velocity sections obtained from a vessel mounted Acoustic Doppler Current Profiler (ADCP). A new vessel route has expanded the spatial coverage of FSC observations and reveals a difference in average inflow transport, which most likely results from an interannual variation in the total transport through the FSC, which in turn is tied to a weakening of the southerly flow over the western slope of the channel. This interannual variability has increased the mean transport through the FSC from 0.9 Sv observed over the first 2 years of this program by Rossby and Flagg (2012) to a 4.5 year mean of 1.7 ± 0.2 Sv, which emphasizes the importance of knowing the flow along the Faroese shelf. Interannual fluctuations in transport observed over the IFR are related to the width of the inflow over the Faroese half of the ridge. Key Points Direct measurements show 4.6 Sv of inflow across the IFR toward the Nordic Seas Flows across the IFR and through the FSC are have high short-term variability

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Journal of Geophysical Research: Oceans