This study analyzed sea ice coverage in each Zone which was separated by Shipping Safety Control Zones and focused on two periods from 1980 to 2011 (Period I: 1980–1998, Period II 1999–2011). NWP1 recorded low sea ice coverage less than 30% between August and September in 2011. We assumed that the ships were able to navigate with little prevention through the NWP2 in the definition of this paper after 2005. The distribution of SLP made sea ice flows into the central Canadian Arctic Archipelago (CAA). Sea ice flowed from Arctic Ocean the CAA, and high sea ice coverage was recorded.
The Arctic Ocean has two main sea routes: the Northern Sea Route (NSR) and the Northwest Passage (NWP). NSR goes through along the Siberian coast and the NWP extends along the northern North American coast and through the middle of the Canadian Arctic Archipelago (CAA). If sea areas for the sea route in the Arctic Ocean open, the NSR would be just 60% of the length of the conventional route between the Far East and Europe [Kitagawa et al., 2000]. And the NWP links the Atlantic and Pacific oceans and provides a route between Europe and Asia that is 9,000 km shorter than the Panama Canal route and 17,000 km shorter than traveling around Cape Horn, South America. [e.g. Howell and Yackel, 2004]. The Arctic Ocean used to be covered by thick sea ice during summer. However Arctic sea ice has decreased drastically in recent years. This decrease was particularly extreme during summer 2007, when the area of sea ice plunged to its lowest level since satellite observations of sea ice began in the 1970s [Zhang et al., 2008]. Sea ice area within the CAA has exhibited decreases from 1979 to 2006 [Parkinson and Cavalieri, 2008].