A new report appears to add to the mounting evidence that global warming is changing the face of Canada's North.

Statistics Canada says the average area covered by sea ice during summer has declined in all nine of Canada's northern sea-ice regions over the past four decades.

The agency says summer sea ice has also declined in two of three northern shipping route regions, which 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 cent, per decade,
• Hudson Strait (down 4,947 square kilometres, or 16 per cent, per decade)
• Davis Strait (down 6,581 square kilometres, or 14 per cent, per decade)
• Hudson Bay (down 16,605 square kilometres, or 11 per cent, per decade)
• Baffin Bay (down 18,658 square kilometres, or 10 per cent, per decade).

The two shipping route regions that recorded declines were:

• The Canadian portion of the Arctic Bridge route, over which ice cover fell at a rate of 14,147 square kilometres, or 15 per cent, per decade
• The southern route of the Northwest Passage, over which it fell by 6,986 square kilometres, or six per cent, 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, linking 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 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.