Baltic Sea

direction as the wind. The deep layer, however, acts in the opposite direction. Although,
during periods of, for example, low eastward winds (the wind was rotated by 180 ◦ to match
the currents), eastward currents were observed, where westward currents would be expected
instead to match the theory. Krauss and Brügge (1991) concluded that a wind blowing
constantly in a certain directions produces a counter current in the lower or bottom layer. By
switching the wind o in their model the strong directional transport broke down into eddies
and topographically controlled irregular motions. This, however could not be observed in the
ADCP data.
From the correlations below, the following ow mechanism can be derived: The regional
wind steers the sea level (correlation between the wind 38 and sea level dierence:
R= 0.89) and to a smaller extend inuences a counter ow of the deep currents between
66 - 71 m (correlation between 38 and SFN/SFS(66-71): R= -0.63). The deep current
is more inuenced by changes in the sea level (correlation between SL ∆(VP-SA) and
SFN/SFS(66-71): R= -0.68). Correlations of the sea level dierence with estimated
transports between 66 - 71 m and modelled transports below the 9.5 kg/m 3 isopycnal are all
slightly less correlated (R= -0.65) than the deep velocities. Separate correlations of each
ADCP with the regional wind and sea level dierence reveal a stronger inuence of the wind
in the upper layer on the norther side of the channel, while on the southern side the Ekman
transport induced by the Coriolis force is predominant.
Pulse-like currents in the Stolpe Channel are partly driven by the regional wind, i.e. up to
50 % and partly driven by sloping density gradients of dense water masses in the bottom of
the channel and therefore resulting geostrophic currents. The height of the eastward ow's
upper boundary at SFN (65 m depth) and SFS (52 m) was similar to the slope of the salinity/
density gradient observed in the hydrographic cross-sections. Resulting eects of a sloping
density gradient on bottom currents was studied by Paka et al. (1998) and conrm their
observations that the current uctuations are density driven, when wind velocities are low. The
frequency spectra of the along-slope current of SFN and SFS reveal that the 2 - 4 day long
current uctuations originate from changes in the regional wind. Each of these uctuations
transport a volume of around 1.78 ± 1.15 km 3 /d eastwards. These 2 - 4 day long uctuations
transport nearly the same amount in a single event as the 3-monthly mean of 0.75 ±
2.32 km 3 /d from estimated transports (0.81 ± 3.15 km 3 /d from modelled transports) and are
99