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6. Ice Conditions in the Szczecin Lagoon and Pomeranian Bay During the Winter 
1999/2000 
The ice winter of 1999/2000 is the third mild ice winter after 1997/98 and 1998/99. In the southern Bal 
tic, mild ice winters occur with a relative frequency of 36% (reference period 1961 - 1990). 
Meteorological conditions in the 1999/2000 winter period 
December 1999 
December 1999 was a month of vivid cyclonal activity, with a comparatively warm westerly air flow 
over Europe. There were only sporadic intrusions of Arctic air masses which followed several very 
active depressions tracking east and northeast across the Baltic Sea. Negative air temperatures oc 
curring at the Baltic Sea coasts were due to radiative cooling in transient high pressure areas of weak 
pressure gradients. 
Minimum air temperatures in the area of Szczecin Lagoon were recorded on 6 December (the night 
minimum fell to about -2°C), in the week preceding Christmas (between -0.5° and -4.3°C), and in 
the two nights before New Year’s Eve (-0.2° and -3.0°C in Szczecin). This was only weakly reflected 
in the water temperatures, which oscillated between 4.8°C at the beginning of the month and 0.5°C in 
the coolest spell between 20 and 23 December. 
January 2000 
In the first nine days of the month, intensive westerly air flow continued over Europe. However, com 
pared to December, the routes of the eastward moving cyclones shifted farther to the north, so that in 
the entire central belt of continental Europe including the southern coasts of the Baltic Sea, higher 
pressure and a weaker gradient prevailed. Air temperatures in the area of Szczecin Lagoon varied 
between 1° and 6°C. From 9 January, central Europe was covered by a high-pressure system whose 
centre oscillated between the Biscay and the Black Sea. The polar maritime air masses slowed down 
and stagnated, cooling to negative values which were not very low, however. In the area of Szczecin 
Lagoon, the minimum temperatures in the days from 12 to 16 January oscillated between -1.5° and 
-6.0°C. 
Between 16 and 23 January, the air flow over central Europe changed temporarily from southwest 
erly and southerly directions to the northwesterly and northeasterly due to an anticyclone which ap 
peared off the British Isles on 13 January and spread eastward. Along its eastern edge, several de 
pressions tracked southeast, accompanied by stormy winds over the Baltic Sea. Between 22 and 26 
January, the ridge of the anticyclone extended across Scandinavia and Central Europe. This pressure 
pattern initially led to an inflow of fresh polar maritime air into the Baltic Sea area. In the area of 
Szczecin Lagoon, a warmer spell between 17 and 19 January was again followed by negative air tem 
peratures. Daily mean values varied between about -1° and -6°C, and minima between about -1° 
and -14°C. The cold spell continued until 26 January. On 27 January, the westerly air flow returned 
and air temperatures again reached positive values. 
February 2000 
In February, westerly air flow prevailed. Only between 20 and 23 February did a ridge of high pres 
sure form over Central Europe. 
Mean air temperatures in the area of Szczecin Lagoon were positive, except the above-mentioned short 
spell of higher pressure and negative night minima, when the minimum air temperature in Szczecin one 
night dropped as low as -6.8°C (on 22 February). The water temperature fell only to 1.0°C. 
Table 6.1. Air and water temperatures in the Szczecin Lagoon and Pomeranian Bay in the winter of 
1999/2000