Baltic Sea

Mean Volume Transports Mean Volume Transports
Time Period ADCPs VoltrpSF ADCP (km 3 /d) Model VoltrpSF 9.5 (km 3 /d)
23/09/2006 - 19/12/2006 (87 days) 0.75 ± 2.32 0.81 ± 3.15
29/09/2006 - 02/10/2006 (75 hours) 1.91 ± 0.93
14/10/2006 - 17/10/2006 (54 hours) 1.52 ± 1.15
28/11/2006 - 01/12/2006 (73 hours) 1.78 ± 1.36
Table 4.1: Comparison of geostrophically balanced mean volume transport across the Stolpe Channel
for the whole measuring period between the ADCPs SFN/SFS and modelled transports for densities ≥
9.5 kg/m 3 . Examples of mean volume transport of three detailed events.
isopycnal identied in the CTD transects. This discrepancy is due to the fact that the salinity
gradient in the model is not as pronounced as in the measurements (see Fig. 4.8 C, D for
CTD transects, model transects not shown). Temperatures and salinities in the model are well
reproduced by the model, but it has diculties expressing sharp salinity gradients.
Average eastward transports are of around 5 km 3 /day and happen more frequently than westward
transports (Fig. 4.15). When transports turn westward, they are in general slightly higher
than eastward transports with about 7 km 3 /day. During the storm event on 4 November 2006
transports increased suddenly to over 15 km 3 /day. Modelled transports reect the estimated
transport values from measured data very well. Largest transports are well and precisely captured
by the model, but smaller transport values, especially at the beginning of the recording
period, are going in the opposite direction. The model slightly overestimates transports in
both eastward and westward directions. This is also visible in Table 4.1 where mean volume
transports over the whole recording period are listed. Estimated mean volume transports from
measured data are of 0.75 ± 2.32 km 3 /d, whereas the model produces mean transports of
0.81 ± 3.15 3 /d. On some occasions the model peaks early compared to the measured values.
Cross-correlations between measured and modelled volume transports have a correlation
coecient of 0.79 and no lag.
Table 4.1 not only compares measured and modelled mean volume transport for the 87 days
of deployment, but also lists measured transports of 2 − 4 days selected for three dierent
occasions. The pulse-like eastward currents led to the question how much water passes the
Stolpe Channel in one of these pulse-like events visible in Fig. 4.12, hence for three dierent
occasions the eastward volume transport was calculated from ADCP measurements. The
2 − 4 day long strong eastward currents were more prominent and also stronger in ADCP SFN
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