Annual and interannual variation of the Atlantic inflow in the Faroe-Shetland Channel from 1993 to 2014

The Faroe-Shetland Channel (FSC) is one of three regions where exchange between the Atlantic Ocean and Norwegian Seas occurs across the Greenland-Scotland Ridge (GSR). This region therefore is a key location for the transfer of warm and saline Atlantic Water towards the Nordic Seas and Arctic Ocean, and for cold, dense overflow waters to return southwards into the Atlantic Ocean. The variability of heat and salt supplied by the Atlantic inflow is significant for the regional climate of Scotland and it is an important component of the larger scale Atlantic circulation.

This study presents the analysis of quasi-synoptic hydrographic observations collected along several standard sections (in particular, the Fair Isle-Munken section; FIM) in the FSC. Seasonal anomalies were calculated for volume, relative heat and salt transport. These show the seasonal cycle and inter-annual variability of these key quantities of the Atlantic inflow between 1993 and 2014.

The analysis of these quantities shows a periodically occurring oscillation with a period of approx. 3-5 years. Moreover, recorded increases in temperature and salinity of the Atlantic inflow are not reflected in volume, heat and salt transports. The time series of temperature and salinity, recorded on depth levels, show a strong seasonality, with maximum values in winter months and minimum in summer. Seasonality of volume, heat and salt transport above the 5°C isotherm have a similar phase. This presentation will further explore whether long-term variability in heat and salt transport of the Atlantic inflow are dominated by the heat/salt content or the volume transport component.