Sea Ice Station Umeä, Winter 2005 
33 
Fig. 4. Ice sample, Umeä Marine Sciences Centre 31 March 2005. 
Downwelling PAR (mikromoles/(s m2)) 
31 Mar -1 Apr 
■ 0cm down 
[Micromol] 
■10cm down 
[Micromol] 
■15cm down 
[Micromol] 
Fig. 5. Downwelling PAR irradiance in the ice sheet Umea Marine Sciences Centre. 
Modelling ice flow through Quark 
The Northern Quark forms a narrow and shallow strait between the Bay and Sea of Bothnia. 
There is a wide archipelago in both sides of the strait, which make the drift ice channel still 
much more narrow than the strait itself. It is know that in mild winters of ice flows through the 
Northern Quark but in cold winters a fast ice bridge forms across between Finland and Sweden. 
This fast ice bridge was used in severe winters for on-ice traffic before 1970 when the northern 
part of the Gulf of Bothnia was closed for shipping. In principle the phenomenon known as 
arching could occur in the strait but such has not been reported in literature.