Baltic Sea

for the southernmost zonal section that was not sampled due to severe weather conditions.
Available for our analysis were therefore 208 CTD stations from the M-7 survey and 195 CTD
stations from the M-8 survey (see Fig. 1.2). Both eld campaigns started in the northwest and
followed zonal transects towards the southern deep basin. In each case, the station spacing
was 2.5 nm (4.6 km). This was sucient to resolve eddy-like patterns of the mass eld larger
than about 9 km, smaller eddies cannot be resolved. The internal Rossby radius is therefore
marginally resolved but for even smaller features aliasing eects have to be expected. Note
that the two grid stations closest to the central station BMP271 were formally identied with
BMP271 to increase the temporal resolution in the centre of the basin (see Fig. 1.2).
Data acquisition and validation procedures are described in more detail by Hagen and Feistel
(2001). Potential temperature, θ, and potential density, σ θ , were computed according to
the thermodynamical relations suggested by Feistel and Hagen (1995) with the required
reference level placed at the sea surface. Finally, all vertical proles were low-pass ltered with
a 3 m running window in order to suppress high-frequency noise, and to avoid aliasing errors.
For the 2006/07 study within the RAGO (tiefe RAndströme im östlichen Gotlandbecken der
Ostsee, English: deep boundary currents in the Eastern Gotland Basin of the Baltic Sea)
project, two diagonal CTD transects with 13 CTD proles each were carried out. The rst
transect went from northeast to southwest on 26 − 27 September 2006 and the other transect
went from northwest to southeast on 27 − 28 September 2006. The stations were chosen from
the MESODYN project's grid and both transects had a spacing of around 3.5 nm, shown as
a dotted cross in Fig. 1.1. These transects provided a snapshot of the hydrographic situation
in the EGB and were then compared to data from the central monitoring station (BMP271),
the model data and also to the temperature data from the three moorings to complete the
general picture.
The two CTD transect across the Stolpe Channel carried out on the 22 and 29 September
2006 were also rst established and part of the MESODYN project described in detail by
Reissmann (1999), Reiÿmann (2002) and Reissmann (2006). From the transects with
its 11 CTD stations (marked as dotted line in Fig. 1.1) and a station spacing of 2.5 nm not only
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