Researchers in Canada say the average area covered by sea ice during summer has declined for four decades in all nine sea ice regions in the country\'s North. The largest declines occurred in the Northern Labrador Sea where sea ice decreased at a rate of almost 600 square miles or 17 percent per decade, a release from Statistics Canada said Thursday. Other areas with significant declines per decade were the Hudson Strait, down 16 percent per decade, Davis Strait down 14 percent, Hudson Bay down 11 percent and Baffin Bay down 10 percent, the release said. Sea ice area also reportedly declined in two of three northern shipping route regions not normally navigable because of ice cover: the Arctic Bridge route and the southern route of the Northwest Passage. 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.