Simultaneously, the strong halocline coincides with the pycnocline, which limits the vertical range of wind mixing and convection (Matthäus and Franck, 1992, Matthäus and Lass, 1995, Lehmann et al., 2004 and Feistel et al., 2006, Reissmann et al. 2007). The halocline depth varies from about 50 m in the Bornholm Deep to 60 m in the Gdańsk Deep, becoming shallower after the passage of inflow water bringing saline waters from the North Sea. The southern Selleck Roscovitine Baltic is of particular importance for the whole Baltic Sea, being a transition area for highly saline waters entering from the
North Sea (Beszczyńska-Möller 2004). Deep water flow follows the bottom topography. The Słupsk Furrow, with a maximum depth of 92 m and width of 40 km, represents a gateway through which inflowing waters move into the eastern Baltic. The highly saline waters of North Sea origin pass through SF and then split into north-easterly (NE) and south-easterly (SE) branches. The selleck chemical SE branch enters GD, while the NE branch continues
through the Hoburg Channel towards the Gotland Basin. Inflows from the Danish Straits cause an increase of salinity and oxygen content in the Baltic Proper, whereas the accompanying change in temperature depends on the season in which the inflow occurs. Major inflows, as defined by Matthäus & Franck (1992), are less common and appear approximately every 10 years. The most recent such inflows occurred in 1993 and 2003 and are the subject of numerous detailed studies (Jakobsen, 1995, Matthäus and Lass, 1995, Feistel et al., 2003 and Piechura and Beszczyńska-Möller, 2004). The increased frequency of medium-sized and small baroclinic inflows was reported by Meier et al. (2006), resulting in the higher temperature of intermediate and near-bottom layers (Feistel et al., 2006 and Mohrholz et al., 2006). This study focuses on the seasonal
to long-term variability of temperature and salinity in three basins of the southern Baltic: the Bornholm Deep, the Słupsk Furrow and the Gdańsk Deep. According to the latest results, the salinity, stratification and volume of inflows into the Baltic Sea, are expected to change in the present century (Meier 2006). Further changes in water properties and dynamics may be expected in the context of on-going climate change. The paper is structured as follows: data and methods to are presented in section 2; the annual cycle of temperature in the upper layers is described in section 3, which also covers the long-term and seasonal changes in salinity and temperature-averaged properties in the basins. The results are discussed in section 4. The data analysed in this paper were collected during regular cruises of r/v ‘Oceania’ in the southern Baltic between 1998 and 2010 (Figure 1). The high-resolution hydrographic sections were performed using a profiling CTD (Conductivity, Temperature, Depth) probe towed behind the vessel.