Geoscience Reference
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Fig. 8.12 Hovercraft used by
the Finnish soldiers in World
War II, Lake Ladoga in April
1942. SA-kuva (The Finnish
Wartime Photograph Archive).
Photograph by lieutenant T.
R ä is ä nen
Fig. 8.13 Winter shipping in
Lake Saimaa, Finland. The
main route goes from the
Eastern Lake District of
Finland to the Baltic Sea via
Saimaa canal. Due to ice
problems in the canal, the
winter shipping is stopped in
normal years for the mid-
winter. Photograph by Mr.
Seppo Piironen, printed by
permission
winter shipping is to keep the same all-year transportation system for the industry, even
though expenses can become high in the ice season.
Winter navigation in lakes has dif
culties not present in marine conditions. When a
ship channel is opened, local heat loss becomes large, and more ice is generated. Channels
grow thicker and more dif
cult to get through. In shallow lakes, ship routes are in places
narrow and it is not possible to start a new channel near the old one. Especially this is a
problem in canals between lakes and between lakes and the sea. The more there is ice
breaking the more ice is generated, and in canals it is not possible to push ice away.
Example, Saimaa Canal from the Eastern Lake District of Finland to the Baltic Sea needs
to be closed down for 2
3 months every winter. On the other hand, ice pressure, which is
a major problem in sea ice
-
fields, does not become a major issue in lakes where fetches are
limited.
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