In 1789, when North West Company explorer Alexander Mackenzie outfitted his birch bark canoe in preparation for his North West expedition, he included an oak mast and a canvas sail. He hoped to use the sail to speed his crossing of “Slave Lake,” the large body of water that appeared on a map drawn by his colleague, Peter Pond.

Why Was the Weather So Cold? All across the Northern Hemisphere from the 15th – early 19th centuries, temperatures plummeted, glaciers advanced, straits and rivers froze, and formerly fertile agricultural areas became unproductive. New World explorers such as Alexander Mackenzie, who battled ice in Great Slave Lake in the middle of June, were caught in the grip of the “Little Ice Age.” This period of colder-than-average weather may have begun as early as 1450, and lasted as late as 1850. It lowered worldwide average temperatures by 1 – 2 degrees. Some regions, such as North America and Northern Europe, experienced even harsher weather. The prolonged cold snap was fatal to residents of Iceland and Greenland, when sea ice isolated them from the rest of the world. Scientists have offered several explanations for the Little Ice Age, including drastically lowered sunspot activity and sun-blocking volcanic dust.

Mackenzie and his party of at least 12 men and women (including fellow Nor’Wester Laurent Leroux, 4 French Canadian voyageurs, 1 German trader, a Chipewyan known as “English Chief,” additional Chipewyan guides and wives of some of the men) set off from Fort Chipewyan, on Lake Athabasca, in early June. But by the time they had struggled through rapids, biting winds and sudden snowstorms to reach the mouth of the Slave River, rosy visions of a summertime sail on a balmy lake had already given way to a cruel realization: the weather was cold, and getting colder. The situation deteriorated even further when the party reached the south side of Great Slave Lake. They were met with a wall of ice floes, pushed to the shore by north winds.

Slowly, fearfully, Mackenzie and his crew followed a string of islands across the lake. The broken ice constantly threatened to tear the birch bark of their canoes, and the grease-soaked cloth that covered their supplies was no match for the rain and snow. When the group finally neared the north shore, it was all they could do to prevent the strong winds and currents from dashing their canoes against the rocky shores.

The harrowing crossing took 7 days. When they landed, a new problem arose: they couldn’t find the river that was supposed to take them west. For 2 weeks, the group wandered through the bays, inlets, beaver ponds, mud flats and sandbars of the lake’s western shore. When it became clear that their Dogrib guide, hired after their arrival on the north shore, could not find his way, a dangerous quarrel erupted between the Chipewyan English Chief and the local guide. Finally, on June 29, the outlet of the river was located, and Mackenzie’s prolonged ordeal on Great Slave Lake was over.