Canada races to build icebreakers amid melting ice and geopolitical tensions

For millennia, a mass of sea ice in the high Arctic has changed with the seasons, casting off its outer layer in summer and expanding in winter as it spins between Russia, Canada and Alaska. Known as the Beaufort Gyre, this fluke of geography and oceanography was once a proving ground for ice to "mature" into thick sheets. But no more. A rapidly changing climate has reshaped the region, reducing perennial sea ice. As ocean currents spin what is left of the gyre, chunks of ice now clog many of the channels separating the northern islands. Canada's coast guard has…