Baltic Sea

5. Discussion and Conclusions
5.1 Deep water intrusions
The exceptional warm inow event of winter 1997/1998 was investigated with the help of a
unique data set combining time series observations from two moorings located at the basin's
rim and two high-resolution CTD surveys conducted just before and during the late-stage of
the inow.
The temperature and velocity records obtained at 170 m depth by the moorings NE and SW
suggest an inow period from end of November 1997 to start of May 1998 at mooring NE,
and from December 1997 to the end of May 1998 for mooring SW. Highest temperatures
were measured between mid and end of March. The inow occurred in several pulses of warm
water, associated with strongly enhanced current velocities. Correlations of temperature and
velocity data at the two stations suggest that signals detected between NE and SW travel
with a speed of approximately 0.03 m/s along isobaths. Amplitudes of both temperature
and velocity signals had signicantly decreased by the time the signal arrived at position SW.
During the pulses, velocities are roughly aligned with the local topography. However, it is
important to point out that the measurements were conducted about 50 m above the bottom,
i.e. possibly outside dense bottom gravity currents.
Notable dierences were observed between the strong inow in 1993, and the inow discussed
here. The 1993 inow analysed by Zhurbas and Paka (1997), Zhurbas and Paka
(1999) and Kuzmina et al. (2005) was a cold water inow with intrusions interleaving
in and below the halocline. Inowing water was found only above 180 m at the eastern
rim of the EGB, i.e. approximately 70 m above the deepest part of the basin. In contrast,
the warm inow of the winter 1997/1998 entirely replaced the deep water in the EGB. In
addition, the inow in form of warm-water intrusions dominated the hydrography in and
below the halocline at intermediate depths. The advective creation of temperature variance
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