These feats served as a prelude to the first solo circumnavigation via the Northwest Passage, which consumed four years two months and ended in 1990. On 14 July 1986, he departed from Newcastle to make his way across the North Atlantic up the west coast of Greenland to enter Lancaster Sound, eventually reaching Fort Ross at the east end of Bellot Strait. Due to heavy pack ice and the start of an early winter, "Mabel E. Holland" remained in the ice for two full years at this location. When Cowper returned the next summer, he found the boat waterlogged, and spent the short summer pulling her ashore and repairing her. In 1988, he managed to reach Alaska having left the boat at Inuvik, Northwest Territories on the Mackenzie River, before one of the coldest winters in recorded Arctic history.