Sea Ice

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Simply put, sea ice is any form of ice that is found at sea and has originated from the freezing of sea water. The formation and movement of sea ice is controlled by various atmospheric and oceanographic parameters including air temperature, winds, ocean currents and bathymetry.

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The timing and amount of maritime activity in the eastern and northern waters of Canada is largely controlled by sea ice. By knowing the general nature of the ice cover at its maximum and minimum limits and the way the changes occur, it is possible to determine the possible access of commercial vessels to ports in eastern and northern Canada at any given time. Information on sea ice is also essential in estimating transportation costs and deciding on an appropriate vessel type. Constraints imposed by sea ice not only affect navigation but also the economy including winter employment in maritime regions. Monitoring of sea ice conditions is provided by ships, reconnaissance aircraft and satellites.

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Canadian Ice Service Ice Reconnaissance aircraft C-GCFR equipped with a Side Looking Airborne Radar (SLAR) for both visual and remote sensing observations

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Radarsat Canadian satellite. The main sensor for ice observation is the Synthetic Aperture Radar (SAR).

In the winter, sea ice is usually present in coastal waters of Canada except for those of British Columbia where warm ocean currents from the south prevent the formation of sea ice. Near the shore, the sea ice can remain uniform and stationary and is referred to as "landfast ice". Offshore, the sea ice is mobile and consists of a mix of ice and open water. In the summer, sea ice in Canadian waters is limited to the northern regions.

The map (below) shows the minimal (mid-September) and maximal (March) extent of the sea ice cover in Canadian waters. Beyond the minimal extent ice remains all year round. The progression from the annual minimal to maximal extent of the sea ice cover in Canadian waters is depicted in the following animation.

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The ice extents described above represent normal or average conditions but there are variations from one year to the next due to changing atmospheric and oceanographic factors. This is shown in the bar graph below depicting the minimal extent each year (on September 10) of the ice cover in square kilometres for the period 1969 to 1998. Large variations are observed ranging from over 1.1 million square kilometres in 1978 to 500 thousand square kilometres in 1998. The following animation illustrates the variability of the minimal extent of the ice cover for the same period.

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In recent years, concern about global climate change has drawn attention to the role of sea ice as a potential indicator as to whether or not the phenomenon is actually taking place, and if so, how rapidly. There is evidence of decreasing sea ice cover in the recent years but it is still too early to conclude whether the decrease is due to global warming or long term climate variability.