Figure 1.
Map of the Nordic Seas with surface salinity in shading (Zweng et al., 2013) . The black contour is the 700 m depth contour. Indicated are the Fram Strait, Barents Sea opening (BSO), the Svinøy section, and parts of the Greenland–Scotland Ridge. In red are also indicated rough pathways of the NwAFC and the Norwegian Atlantic Slope Current (NwASC) and its fractionation at the BSO.
Figure 2.
(a) Monthly mean and (b) deseasonalised monthly mean ADT [m] interpolated to the 700 m depth contour along NwASC. Note that the y-axis, which is linear in latitude, is not necessarily linear in distance.
Figure 3.
Lagged cross-correlation of points along the 700 m depth contour (along NwASC) with the base point near 63N 4E. The ADT has been deseasonlised prior to calculating the correlation. Following a straight line along the elevated correlation at increasing time lag gives an estimate of a propagation speed of about 2 cm s. This can be compared to a mean current speed of 15 cm s.
Figure 4.
The spatially varying ADT anomaly along the 700 m isobath in the NwASC; see Equations (3a,b). The anomaly is computed by subtracting the spatial mean from each individual month of the deseasonalised anomalies along the NwASC (Fig. 2b). This simple procedure highlights propagating anomalies and, as side effect, removes most of the linear trend present in Fig. 2b. The white lines represent a 2 cm s propagation speed. Note that the anomaly shown here has been slightly smoothed with a 4-month running mean filter.
Figure 5.
(a) Illustration of the leaky pipe model. The narrow current (the ‘leaky pipe’) has width , temperature and uniform flow u. The reservoir has width , temperature and no flow. The two regions interact through a mixing described by an eddy velocity . (b) The Green’s function [Equation (13)], where is the time lag, with parameter values representative for the NwASC (Section 4.2). The Green’s function gives an estimate of the tracer–tracer correlation function [Equation (17)], which means that the Green’s function can be compared to the lagged correlation in Fig. 3.