File:FBCO properties.png|thumb|350x350px| Temperature, salinity (both 2019 vessel cruise measurements) and current speed (2019 ADCP ensemble) profiles, and overflow transport (daily averages since 1996) for the part of the Faroe-Bank Channel where the overflow takes place. Data retrieved from ENVOFAR. The water flowing over the Greenland-Scotland Ridge through the Faroe-Bank Channel consists of a very well-mixed bottom layer, with a stratified water layer on top. The temperature of this stratified layer can get to 11 °C in the upper 100 m of the channel, with a salinity around 35.1 g/kg; between 100 and 400 m depth the temperature of the water in the stratified layer is around 8 °C, with a salinity of 35.2 g/kg. Therefore, it may be complicated to exactly define which water entering the FBC contributes to the actual overflow. Four definitions are possible, two of which depending on the overflow velocity, one depending on the overflow flux, and one depending on the overflow water properties. The simplest definition is in terms of velocities: water with a velocity in northwestern direction is then termed Faroe-Bank Channel overflow. A third definition is so-called
kinematic overflow: the water flux from the bottom of the channel up to the interface height, being the level where the velocity in northwestern direction measures one half of the maximum velocity in the profile. The overflow flux is then calculated throughQ_{k}(t) = \int_{x_{1}}^{x_{2}} v_{0}(x,t) \left(h_{0}(x,t) - h_{B}\right) \operatorname{d}\!x + \int_{x_{1}}^{x_{2}} q_{B}\left(x,t\right)\operatorname{d}\!xwhere v_{0} is the average profile
velocity, h_{0} is the interface height, h_{B} is the height of the layer below the lowest measurement station in the channel, and q_{B} is the
volume flux per unit width of the channel. This definition is most often used when estimating values for the magnitude of the FBCO.
Periodicity Temperature and salinity profiles as well as current speeds in the FBC vary strongly on a day-to-day basis. The dense water forms domes that move through the channel with a period of 2.5 to 6 days. At the ocean surface, this periodicity can be observed in the form of
topographic Rossby waves at the sea surface, which are caused by
mesoscale oscillations in the velocity field. The resulting eddies are the consequence of
baroclinic instabilities within the overflow water, which then induce the observed periodicity. On a greater timescale, atmospheric forcing also causes periodic changes in the FBCO. When the atmospheric circulation governing the Nordic Seas is in a
cyclonic (
anticyclonic) regime, the source of the deep water predominantly comes via a western (eastern) inflow path, and the FBCO will be weaker (stronger). The eastern inflow path is called the
Faroe-Strait Channel Jet. This transition from a cyclonic to an anticyclonic regime takes place on an interannual timescale, but the atmospheric forcing also shows a seasonal cycle. During summer the weakened cyclonic winds are associated with a higher FBCO transport. This indicates a fast barotropic response to the wind forcing. == Outflow ==