03, 7.21 and 7.58°C for BD, SF and GD respectively. The average salinity
of these waters is 7.41, 7.3 and 7.26 PSU respectively (Figure 5). The transition layer is the area between the upper and lower layers. The depth of the transition layer changes seasonally with the thermocline and depends on the factors that force the mixing of the upper layers. The lower limit of the transition layer reaches to the depth of the halocline, which is the same as the depth of the pycnocline. The depth of the transition layer is therefore locked between 30 and 60 m. The hydrography of the near-bottom layer (demersal) depends strongly on inflows click here from the Danish Straits. Mixing between the layers is limited because of the strong stratification. Temperature fluctuations in the near-bottom layer are small and become weaker with distance from the Danish Straits. The average temperature in BD is 7.35 ± 2.32°C and 7.7 ± 1.44°C in SF just after the furrow. The salinity of Baltic Sea waters does not vary greatly from season to season (Figure 5). Selleck Alectinib In the layer exposed to atmospheric forcing, the average salinity varies within 7.32 ± 0.22 and decreases along the main axis from the Kattegat to the Gulf of Bothnia (Majewski
& Lauer (eds.) 1994). The average salinity and standard deviation of the near-bottom layer is 16.78 ± 0.95 in BD and 11.91 ± 0.66 in GD. These changes are caused by inflows of water from the Danish Straits that modify the hydrographical properties of the ambient click here waters by mixing and cause the pathways to separate. The seasonal variability in the surface water temperature is caused mainly by seasonal changes in the supply of solar energy to the sea surface
and the changes in the conditions of the exchange of energy between the sea and atmosphere. In BD and SF the maximum temperature of the surface layer occurs on day 249 of the year (7 September) (Appendix – Table 2). In GD the maximum occurs on day 254 (Table 4) of the year (9 September), whereas in BD the temperature maximum at the thermocline depth (20–30 m) occurs with a phase shift of 24 days from the surface layer (Figure 6). In SF the shift is > 12 days (Figure 7), in GD it is > 7 days (Figure 8). The amplitude of the annual temperature cycle in the 20 m surface layer lies between 14.8 and 16.4°C, decreasing with depth, reaching 10°C below 20 m in BD and 11.8°C in SF (Table 3) and GD. In the 30–40 m layer of SF and GD the temperature amplitude decreases to 8°C. Below 30–40 m depth there are no visible seasonal changes in temperature. At these depths advection is the most important forcing factor. In winter, the isothermal layer (Figure 9) with an average temperature of 3–4.5°C extends to a depth of 40–50 m. Despite the warming of the surface layer in April, a ‘winter water’ layer remains at 50 m depth, where it is likely to remain until the next cold season.