Ice is the dominant feature of Arctic marine ecosystems. It continuously sculpts the coastal landscape and acts as a major limiting factor to all biological activity. Two distinct zones are distinguished in the Arctic region based on ice: the Arctic Basin marine region is characterized by the year-round presence of sea ice, while the other Arctic subregions have ice-free periods ranging from less than a month to up to four months. The Arctic coast (including islands) encompasses 68% of Canada's coastline, stretching 165 000 km from James Bay and Baffin Island to the Yukon. The region exhibits a wide range of coastal landforms and reliefs fashioned by the processes of volcanism, glaciation, faulting and folding. The tidal range is generally less than 0.5 m in the northern and western sectors but increases to 1.0-5.0 m in the east and south.