Baltic Sea

this inow event was classied as 'moderate' by Matthäus (1993). Somewhat later, on
the base of an increased data density, Matthäus et al. (2008) reclassied this event as
MBI. It became evident that most of involved deep waters entered the southern Baltic Sea
via the Drogden Sill and not, as assumed before, through the Darss Sill. These authors also
described the next notable strong inow event. It entered the EGB (Fig. 1.2) in November
1997 and lasted until May 1998. This event was extraordinary in many respects and several
specics are highlighted in chapter 3. This inow can be considered to be the starting point
of an unusual series of so-called warm inow events, cf. Feistel et al. (2003a), Feistel
et al. (2003b), Feistel et al. (2006). The intermediate intrusions of these warm water
masses originate from near-surface layers of the Kattegat formed under summer environmental
conditions. In contrast to the barotropic inows occurring usually during the winter season, this
baroclinic warm water inow started in the late summer. However, this hydrographic situation
of positive temperature anomalies resulted in a number of unusual stratication properties in
the deep EGB that have so far received only little attention. Therefore, the main objective of
the chapter 3 focuses on changed stratication conditions due to upward mixing within the
enclosed deep basin. Realistic mixing parameters will be discussed, especially under the aspect
of double-diusive processes.
1.6 Deep boundary currents
Several studies about the mass/ volume uxes through the Stolpe Channel can be found in
the literature. These used numerical experiments by applying appropriate circulation models
as well as hydrographic data sets with a dierent station spacing. However, the most pioneering
study about such transports was a mix of both approaches and published by Krauss
and Brügge (1991). Their results suggest that the renewal of the deep water in the EGB
is a combination of wind-driven currents within the near-surface layers and density-driven,
geostrophically adjusted currents within near-bottom layers. Easterly winds produce sea level
gradients with low values in the east and high values in the west of the Baltic Proper. This,
however, forces down-slope gradient currents towards the east. Whereas the density-driven
ow is slow but persisting, strong easterly and northerly winds uctuate on the synoptic scale
and accelerate transports of dense deep water through the Stolpe Channel. For example,
Kouts and Omstedt (1993) investigated these conditions for two decades (1970 − 1990)
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