26 
4 Conclusions 
The estimated volume transports agree well with those calculated by the authors cited above. Accor 
ding to Tu rre 11 [1992b] the FIC west of Orkney is predominantly wind-driven in summer and winter. 
However, the inflow of AW east of Shetland has an additional significant non-wind-driven component 
during the summer months. Variations in wind stress magnitude and direction cause interannual variability 
of these inflows. For the FIC within the North Sea, Turrell [1992b] estimated a maximum southerly 
transport of 2.5xl0 5 m 3 /s in late August, while the NORA data yield 2.6xl0 5 m 3 /s between mid July and late 
August. 
The unexpected northwestward “residual flow” at the MOYENS mooring M7 and especially the great 
directional variability at M9 show that short records can be biased by mesoscale instabilities between the 
AW inflow at the western and the NCC at the eastern edge of the Norwegian Trench. According to I k e d a 
et al. [1989], these instabilities have a typical wavelength of 50-100 km and northward propagation speeds 
of 10-20 cm/s, i.e. they would pass a mooring in between 3 to 12 days. This agrees fairly with the observed 
period of current rotations at M9 which amounts to about 10 days (see Fig. 4a). 
The tidal streams at the MOYENS moorings are negligible although the tidal elevations are relatively 
strong. Further south, at the NORA section, distinct tidal streams and elevations are both observed with in 
creasing magnitude from east to west. The amplitudes of some tidal constituents reach considerable magni 
tudes. For the main diurnal and semi-diurnal constituents (N 2 , S 2 , O], and K,, see Table 6), we calculate a 
relative amplitude H r , i. e. the ratio between the amplitude of the tidal constituent and the respective M 2 - 
amplidtude, expressed in percent (see Table 8). In the NORA section (N1-N5) no significant change is ob 
served in the relative amplitudes; only the relative S 2 amplitude increases from west to east. At the M8 and 
M9 moorings the S 2 amplitudes amount to 55 and 64% respectively of the M 2 amplitude. The other consti 
tuents at the MOYENS positions are also greater than the corresponding NORA values except for the N2 
constituent at M9. 
Table 8 
Amplitudes H and relative amplitudes H T of the main diurnal and semi-diurnal tidal constituents of 
the NORA- and MOVENS section, calculated from tide gauge time series 
Consti 
tuent 
N1 
H 
H, 
N2 
H 
H, 
N3 
H 
H, 
N4 
H 
H, 
N5 
H 
H, 
M8 
H 
H, 
M9 
H 
H, 
cm 
% 
cm 
% 
cm 
% 
cm 
% 
cm 
% 
cm 
% 
cm 
% 
M, 
79.4 
100 
64.2 
100 
51.3 
100 
42.4 
100 
34.9 
100 
57.9 
100 
50.9 
100 
0, 
10.0 
13 
7.9 
12 
6.0 
12 
5.5 
13 
4.6 
13 
11.1 
19 
8,9 
17 
K, 
10.6 
13 
8.8 
14 
7,0 
14 
5.7 
13 
4,6 
13 
7.6 
13 
13.1 
26 
N, 
14.1 
18 
11.3 
18 
9.7 
19 
8.1 
19 
7.0 
20 
14.5 
25 
4.2 
8 
S, 
28.0 
35 
23.0 
36 
19,7 
38 
16.9 
40 
14.2 
41 
31.9 
55 
32.6 
64 
h, = №)/mj) x loo 
Our results will next be incorporated as northern boundary values in a numerical circulation model of 
the North Sea/Baltic Sea. The model results can then be compared with the model’s present performance 
and compared with field observations in the model area. 
Acknowledgements 
The authors would like to thank the officers and crews of RV Gauss and RV Valdivia for their help at 
sea; thanks are also due to Holger May for his excellent drawings.