During the year, some Canadian waters become more hazardous due to the presence of sea or lake ice, and/or icebergs. 

Environment Canada’s Canadian Ice Service (CIS), working in partnership with the Canadian Coast Guard and the US National Ice Center, provides mariners with up-to-date information and warnings about ice conditions. To help researchers and policy-makers, the CIS analyses the ice conditions year-round in the Arctic, as well as the ice conditions during the winter in the Great Lakes and on the East Coast. This information is what makes up Canada's ice climatology.

CIS ice analysts and forecasters use the information they gather to describe the ice distribution, as well as information about the stage of development of the ice (an indication of the thickness of the ice). Mariners can then use this information to take advantage of the safest and easiest path through the ice, or if possible, to avoid it altogether.

A good example of what the CIS does is the surveillance and tracking of icebergs. Icebergs that drift southward along the Labrador Coast and past Eastern Newfoundland can pose a significant threat to mariners and marine facilities. Regular aerial surveillance helps to keep track of the southern and eastern limit of the icebergs so that ships can be aware of where there is an increased risk to navigation. Iceberg information is provided by CIS in partnership with the American International Ice Patrol.