Space agencies such as National Aeronautics and Space Administration (NASA) and the European Space Agency(ESA) began keeping photographic records of arctic sea ice coverage in the 1970's. Until recently, ice blocked navigation through the Northwest Passage. Based on satellite images, the ESA reported in 2007 that ice loss had opened up the passage, rendering it navigable. The first commercial ship sailed through the Northwest Passage in September 2008, transporting aid and cargo from Montreal to several communities on the western edge of the passage.

As shown in the picture above, Arctic sea ice minima have steadily retreated towards the pole since the 1970s due to warming oceans and melting ice. Reduced sea ice in the passage is hindering the ability of some carnivorous species (such as polar bears and seals) to maintain their traditional feeding territories. It has also allowed Pacific species such as the gray whale and a plankton species to migrate across to the North Atlantic Ocean.

The deep waters of the Canadian Arctic offer a shorter trade route that the relatively shallow Panama Canal and treacherous Strait of Magellan cannot match, as well as new territory for fossil fuel exploration. Canadian politicians believe that the passage lies in Canadian waters; other nations hold it as an international strait where foreign vessels should have right of passage without being subject to regulation or law. This international dispute has persisted for decades, with no hint of slowing down. It illustrates the wide-reaching social, economic and political effects of climate change and the oceans.

Congratulations! You have now completed Lesson 8. Continue on to Lesson 9 to learn about responses to climate change.