Baltic Sea

30
15
SFN/SFS (66−71) (cm/s)
20
10
0
−10
−20
Volume Transport (6671m) (km 3 /d)
10
5
0
5
10
−30
−100 −80 −60 −40 −20 0 20 40 60 80 100
SL ∆(VP−SA) (cm)
15
100 80 60 40 20 0 20 40 60 80 100
SL (VPSA) (cm)
A
Figure 4.31: Regression SL ∆ (Ventspils-Sassnitz) with measured depth averaged zonal velocity from
ADCPs (A). SL ∆ (Ventspils-Sassnitz) with volume transport (66 −71 m) (VoltrpSF ADCP 66−71 ) Stolpe
Channel (B). The two ne lines correspond to the 95% condence interval of the regression line (thick
line).
force is the prevailing inuence. At 71 m a drop in the correlation is visible on both sides of
the channel, implying that the bottom boundary layer reached up to this depth and therefore
has a thickness of about 4 m. This thick bottom boundary layer could support Paka et al.
(1998) theory of a bottom friction induced Ekman transport. From 59 m down to 70 m the
negative correlation of the u-component SFS with both the wind and the sea level continuously
increased. On the northern side of the channel the high negative correlation between the wind
and the eastward current as well as with the sea level rst decreased and only increased again
below the jump in 65 m. This jump also coincides with the salinity/ density gradient in
Fig. 4.8. Due to the strong negative correlation between the sea level and the two ADCPs
in depths greater than 66 m, the mean between the vertical averaged u-velocities (66 - 71 m)
of SFN and SFS was created to get an overall deep boundary current. This detrended deep
zonal current, now called SFN/SFS(66-71), is cross-correlated with the regional wind by
R=-0.63 and has no lag. How well the wind and the deep zonal current are counteracting is
displayed in the standardised series of 38 and SFN/SFS(66-71) in Fig. 4.30 B. On
one occasion the deep current went accordingly with the wind around 27 - 29 November, but
in general winds and currents counteracted.
The regression between SL ∆(VP-SA) and the vertical averaged eastward velocity between 66
and 71 m ( SFN/SFS, 66-71)) in Fig. 4.31 (after Hagen and Seifert (2009)) delivers
92
B