<P> Hudson Bay has a lower average salinity level than that of ocean water . The main causes are the low rate of evaporation (the bay is ice - covered for much of the year), the large volume of terrestrial runoff entering the bay (about 700 km (170 cu mi) annually, the Hudson Bay watershed covering much of Canada, many rivers and streams discharging into the bay), and the limited connection with the Atlantic Ocean and its higher salinity . Sea ice is about three times the annual river flow into the bay, and its annual freezing and thawing significantly alters the salinity of the surface layer . </P> <P> One consequence of the lower salinity of the bay is that the freezing point of the water is higher than in the rest of the world's oceans, thus decreasing the time that the bay remains ice - free . </P> <P> The western shores of the bay are a lowland known as the Hudson Bay Lowlands which covers 324,000 km (125,000 sq mi). The area is drained by a large number of rivers and has formed a characteristic vegetation known as muskeg . Much of the landform has been shaped by the actions of glaciers and the shrinkage of the bay over long periods of time . Signs of numerous former beachfronts can be seen far inland from the current shore . A large portion of the lowlands in the province of Ontario is part of the Polar Bear Provincial Park, and a similar portion of the lowlands in Manitoba is contained in Wapusk National Park, the latter location being a significant polar bear maternity denning area . </P> <P> In contrast, most of the eastern shores (the Quebec portion) form the western edge of the Canadian Shield in Quebec . The area is rocky and hilly . Its vegetation is typically boreal forest, and to the north, tundra . </P>

Village in northern quebec on shore of hudson bay