Iceland-Faroe overflow revealed by in-situ observations

Overflow across the Iceland-Faroe Ridge is an important contributor to the deep limb of the Atlantic Meridional Overturning Circulation. Despite decades of observations, the strength, stability, and exact pathways of the overflow have remained uncertain. Here, we present results from several dedicated year-long current observations along the ~300 km long ridge crest. These observations reveal strong overflow at the central parts of the ridge with smaller contributions across both ends. The observations support the hypothesis that overflow is inhibited at both ends by upper-layer inflow of Atlantic water to the Norwegian Sea. In contrast, retroflection of Atlantic inflow over the central parts, allows the overflow to cross the ridge there, apparently as pulsating flow along two main pathways. The available data do not allow accurate estimates of volume transport, but they indicate that these pathways may well supply overflow in amounts consistent with previously published estimates.