Study: Sea ice trends in Canada

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1968 to 2010

During the past four decades, the average area covered by sea ice during summer has declined in all nine sea ice regions in Canada's North. It also declined in two of three northern shipping route regions. These northern routes are not normally navigable because of ice cover.

The largest declines occurred in five southern and eastern sea ice regions: Northern Labrador Sea, where sea ice decreased at a rate of 1,536 square kilometres, or 17%, per decade, followed by Hudson Strait (down 4,947 square kilometres, or 16%, per decade), Davis Strait (down 6,581 square kilometres, or 14%, per decade), Hudson Bay (down 16,605 square kilometres, or 11%, per decade) and Baffin Bay (down 18,658 square kilometres, or 10%, per decade).

The two shipping route regions that recorded declines were the Arctic Bridge route (Canadian portion), over which ice cover fell at a rate of 14,147 square kilometres (-15%) per decade, and the southern route of the Northwest Passage, over which it fell by 6,986 square kilometres (-6%) per decade.

The Northwest Passage links the Atlantic and Pacific oceans and the Arctic Bridge extends across the top of Hudson Bay into Hudson Strait and links North American markets to European and Asian markets.

The Northwest Passage shipping routes are usually blocked by sea ice during all seasons, significantly limiting any navigation. However, they could cut the distance for shipping voyages and all were navigable for a short period of time in late summer and early fall 2007.

This study also examines multi-year ice cover, which is the area covered by older ice that has survived at least one summer's melt.

Of the seven regions reporting multi-year sea ice, only the Baffin Bay region showed a statistically significant trend, which was downward. Historically, multi-year ice only ever covers a very small part of this region.

Note: This article is the fourth in an ongoing series in EnviroStats showcasing data related to Canada's climate and the impacts of climate change. These articles are short statistical analyses of climate-related data, such as temperature and snow cover. The third article in the series, released in September 2011, examined precipitation trends across Canada.

This study examines data consisting of the average area covered by total (all) and multi-year sea ice during the summer in Canada. Data were analysed for nine sea ice regions and three shipping route regions for total ice cover and five sea ice regions and two shipping route regions for multi-year ice cover between 1968 and 2010.

Time series data used for this article were derived from weekly sea ice charts produced by the Canadian Ice Service. The sea ice charts were produced using a combination of aerial surveys, surface observations, airborne and ship reports, and remotely sensed (satellite) data. The charts were compiled into a time series by the Climate Research Division at Environment Canada.

Environment Canada, Natural Resources Canada and Statistics Canada are collaborating on a project to prepare a series of CANSIM tables. They will be available early in 2012.

The article "Sea ice trends in Canada" is now available in the winter 2011 issue of EnviroStats, Vol. 5, no. 4 (16-002-X, free), from the Key resource module of our website under Publications.

The articles "Consumption-related greenhouse gas emissions in Canada, the United States and China" and "Use and disposal of compact fluorescent lights by Canadian households" are also available in this issue of EnviroStats.

For more information, or to enquire about the concepts, methods or data quality of this release, contact the information officer (613-951-0297;, Environment Accounts and Statistics Division.