Hudson Bay

Long ago, a giant sheet of ice sat on this land. Its weight pushed the ground down.

The ice melted, and now the land is slowly rising up again.

During the last ice age, the Laurentide Ice Sheet covered most of what is now Canada. It was centered on Hudson Bay, and its great weight pressed the land down. Since the ice began retreating about 20,000 years ago, the land has been bouncing back.

NASA says the ground around southern Hudson Bay still rises about 10 millimeters a year, or about 1 meter every century. Along James Bay, rows of beach ridges have formed, with new ones appearing at the water's edge as the land rises. Elsewhere around the bay are landforms carved by glaciers, called drumlins and eskers.

During the Pleistocene the Laurentide Ice Sheet covered most of present-day Canada and was centered on Hudson Bay, where its weight depressed the crust. Since the Last Glacial Maximum, about 20,000 years ago, the ice has retreated and the land has rebounded. NASA's Earth Observatory (2026) says glacial isostatic adjustment is relatively rapid around southern Hudson Bay, where the surface still rises about 10 mm a year, or 1 m per century.

On the shores of James Bay, closely spaced beach ridges formed as tides reworked sand and silt, with newer ridges forming at the water's edge as the land rises and relative sea level falls. Drumlins and eskers carved by the ice mark the landscape elsewhere around the bay.

In winter, ice covers the bay. In summer, most of it melts.

In 2024, wind blew the ice away early on one side of the bay.

Hudson Bay freezes over in winter and thaws in summer. In 2024, the ice behaved oddly. In early May, strong winds cleared the ice from the eastern part of the bay, while a wide band of ice stayed packed in the west for much of the summer.

By early June 2024, the bay's ice covered just 205,000 square kilometers, a record low in satellite records going back to 1979, according to the US National Snow and Ice Data Center.

NASA's Earth Observatory (July 2024) reports that exceptionally strong and persistent winds cleared sea ice from eastern Hudson Bay in early May 2024, while an unusually large band of ice stayed packed in the western half for much of the summer. The National Snow and Ice Data Center found that ice covered just 205,000 km² in early June, a record low in the satellite record that dates to 1979, and continued to report record-low levels in early July.

Around James Bay, NASA notes, sea ice that has clung to the shore for months typically begins to break up in mid- to late May, with melting complete by the end of July.

Polar bears hunt seals out on the ice.

When the ice melts, they come ashore and wait for it to freeze again.

NASA says roughly 1,700 polar bears live around Hudson Bay and rely on its ice. When the bay is frozen, they walk out onto it to hunt ringed seals and other prey. When the ice melts in summer, they come ashore and go without food, or eat whatever they can find, until the ice returns.

On the bay's coast, Wapusk National Park stretches from boreal forest to arctic tundra. Parks Canada says at least 38 kinds of mammals and over 200 kinds of birds have been found there, and calls it one of the world's largest polar bear denning areas. Around the bay, the Hudson Bay Lowlands hold huge peat bogs.

NASA's Earth Observatory (2024) puts the polar bears living around Hudson Bay at roughly 1,700. They hunt ringed seals and other prey on the ice; when it melts, they retreat to shore and fast or eat what they can find until it returns, burning about 1 kg of body mass a day on land. University of Alberta scientist Andrew Derocher has followed tagged bears tracked by satellite.

Wapusk National Park (11,475 km²) spans boreal forest to arctic tundra; Parks Canada records at least 38 mammal species and over 200 bird species, including the Cape Churchill caribou herd, and calls Wapusk one of the world's largest polar bear maternity denning areas. Beluga whales and four kinds of seal live near the park. The Hudson Bay Lowlands, NASA notes, are the world's second-largest peatland complex and store significant soil carbon.

Polar bears live near the shore. Never walk there alone.

Stay with a grown-up and a trained guide.

Parks Canada says the land around Wapusk National Park is polar bear country for much of the year, and that walking along the coast does not keep you away from bears. Visitors there should follow the rules and instructions of the tour operator they travel with.

The area is remote, the weather can be extreme, and the tides can rise and fall one to four meters, with tidal flats that can leave people stranded. PlayOwl's advice: only explore with a trained guide, and watch bears from a safe vehicle or viewpoint.

Parks Canada warns that the Wapusk area's remoteness and limited rescue capabilities raise the risk from natural hazards: extreme weather, unpredictable terrain and travel in polar bear country, where bear territory overlaps human territory for much of the year. Traveling the coastline does not avoid polar bears; tides range from one to four meters, and tidal flats along the eastern coast can stretch more than 10 km and strand people as the tide goes out. Visitors are told to obey the rules and instructions of their commercial operator and to be prepared for medical, wildlife and weather emergencies.

PlayOwl's own advice: never approach a polar bear, and treat the shore itself as bear habitat.