The Mackenzie is the Canadian river system ranked 13th by length that empties into the Beaufort Sea.
The Mackenzie’s main stem begins at Great Slave Lake in the Northwest Territories and flows northward through boreal forest and tundra. Including the Slave, Peace, and Finlay rivers, the complete Mackenzie system extends about 4,241 kilometres.
The river forms a huge delta before entering the Canadian part of the Beaufort Sea, an Arctic marginal sea. Its watershed covers roughly one-fifth of Canada and supports wetlands, migratory birds, fish, and communities across a sparsely populated region.
The Yukon is another major northern river, but it flows into the Bering Sea. The Fraser reaches the Strait of Georgia near Vancouver, while the Nelson drains into Hudson Bay. The Mackenzie’s Arctic destination is the key clue.