Why Is the War Winter 1939/40 particularly interesting? (Details see 10 pages PDF)
The suddenness is what counts most. From one day to the other man befell the sea with unknown, widespread brutal force. Only four months into WWII, Northern Europe was back in a small ice age. Numerous meteorological extreme conditions reveal a strong relationship to the high level of naval warfare activities. For example:
__The regions most affected in Europe were those close to North Sea and Baltic. (Fig. 1, 3, 4, 5, 9, 11, 13)
__Highest sea ice extent in the North Sea (German Bight) in several decades.
__The first entire freezing of the Baltic Sea in the 20th Century.
__Record cold in Poland – Siedlce, -41,0°C, 11 January 1940 (Fig.13)
__Moscow lowest ever recorded −42.1 °C (−43.8 °F) in January 1940 (see Wikipedia).