Hudson Bay

Although considered an extension of the Atlantic Ocean, Hudson Bay, a shallow gulf covering 827,000 square kilometers in the northern part of east-central Canada, is often treated as a separate entity because of its isolation. The area remains a vast, essentially unspoiled wilderness and preserve for wildlife. The uplift of lands surrounding Hudson Bay has provided earth scientists with clues about processes associated with the retreat of ice sheets, especially crustal rebound.

Location and Discovery

Ranking twelfth in area among Earth’s seas and oceans, the horseshoe-shaped Hudson Bay is approximately 1,370 kilometers long and 1,050 kilometers wide. The southern end of Hudson Bay extends into a smaller bay of almost identical shape—a “bay within a bay”—called James Bay. The Hudson Bay is bounded by the Canadian provinces of Quebec to the east and south, Ontario to the south, Manitoba to the southwest, and Nunavut to the northwest (Nunavut was formed in 1999 by the partition of the Northwest Territory). The bay is linked to the Atlantic Ocean by Hudson Strait and to the Arctic Ocean by the Foxe Channel and Roes Welcome Sound. Hudson Bay and its islands are administered by the District of Keewatin, a region within Canada’s Nunavut Territory. Its largest islands are Southampton (41,214 square kilometers) and Mansel (3,181 square kilometers), both located in the north. Other large islands include Coats (5,499 square kilometers), located on the southeast side of Fisher Strait, and Akimiski (3,002 square kilometers) within James Bay. Island groups include the elongated Belcher Islands and smaller Nastapoka Islands positioned in the southeastern portion of the bay and the Ottawa Islands to the west of the Ungava Peninsula.

Early exploration of the bay was driven by the hope of locating a northwesterly shortcut to Asia. Systematic investigations of such a route began with John Cabot’s visit to Canada’s eastern shore in 1497. Hudson Bay was discovered by and named for English navigator Henry Hudson. During his first expedition in 1607, Hudson and the crew of his ship, the Hopewell, landed on the shores of Greenland and the Svalbard Islands, later turning north in an unsuccessful attempt to find a route to East Asia by way of the Arctic Ocean. He returned the following year to renew the search, passing the Novaya Zemlya Islands in the Barents Sea. Hudson began his last expedition in 1610, during which he reached Hudson Bay and spent three months investigating its eastern shores and islands. Pack ice prevented a departure from the bay, and after a winter of extreme deprivation, the crew of his ship mutinied. Placed in a boat and set adrift by the mutineers, Hudson and eight others were never seen again.

Further exploration of the bay was carried out by Sir Thomas Button, who reached the western shore of the bay near present-day Churchill, Manitoba, in 1612. The following summer, Button departed from the bay, passing Southampton Island on his way to Hudson Strait. Others who explored the bay included William Baffin in 1615 and Luke Fox and Thomas James in 1631. In 1662, Pierre Esprit Radisson and Médard Chouart de Groseillers became the first to reach Hudson Bay using an overland route. Since its first exploration, the bay has been a graveyard for many mariners. Numerous sunken vessels and the only stone military fortification in the Arctic are part of the bay’s historical legacy.

Geology

Hudson Bay is located within a depression of the vast Canadian Shield and is underlain with ancient Precambrian rocks more than 500 million years old. Covering 4.8 million square kilometers in Canada and the northern United States, the shield encompasses Labrador, Baffin Island, and portions of Quebec, Ontario, Manitoba, Saskatchewan, the Northwest Territory, Nunavut, Wisconsin, Minnesota, New York, and Michigan. The oldest region within the North American crustal plate, the shield is considered a craton, an area of the land surface that has been stable for many millions of years and perhaps even from the original formation of the continental masses. Radiometric dating of some Canadian Shield formations has yielded an age of 4.5 billion years, nearly as old as the planet is believed to be. Hudson Bay is bordered by Paleozoic limestone, sandstone, and dolomitic rocks. Rocks of sedimentary origin within the Canadian Shield contain the fossils of some of the Earth's earliest forms of life.

The bay is believed to have been formed by glacial activity during the Pleistocene epoch, which began about 2.4 million years ago. Centered over what is now Hudson Bay, the Laurentide ice sheet stripped away soil and deposited glacial drift as it moved across the landscape. The enormous weight of accumulated ice on the continent depressed that portion of the crust, causing it to sink into the underlying plastic layer of the mantle. As the ice sheet began to melt, numerous remnants were left in the form of till deposits and long, sinuous ridges of sand and gravel called eskers. The retreat of ice sheets of the Wisconsin glacial period began about 13,000 years ago, although large portions of glacial ice remained until about 7,000 years ago. As the ice melted, relatively warm seawater invaded Hudson Bay through the Hudson Strait, further shrinking the ice mass. Eventually, the ice sheet was split into the Labrador and Keewatin ice centers, disappearing completely between 6,500 and 5,000 years ago. As the ice melted, the depressed crust began to undergo isostatic rebound, slowly returning to its natural level as determined by the buoyancy of the continental mass on the mantle layer. Isostatic adjustment within the Hudson Bay region is incomplete, and the entire area surrounding the bay continues to rise at a rate of about 0.6 meters per century. The uplifting of the landscape is especially obvious along portions of the coast where lines representing former beaches run parallel to the shore. The rapid rate of rebound suggests that Hudson Bay will become much shallower and may disappear when isostatic equilibrium has eventually been reached.

The underwater physiography of Hudson Bay demonstrates broad contours that are generally concentric with its periphery. The bay averages 128 meters in depth, with the deepest known depth of 183 meters. Its floor is predominantly smooth but is incised with cuts and banks in some places. There are a few submarine troughs and ridges with trends controlled by the geologic structure. The basin forming Hudson Bay has a north-south elongation, which reflects its bedrock structure.

Marine currents are the most significant agents of sediment transport within the bay. Because Hudson Bay is covered by snow and ice during several months of the year, the normal movement of sedimentary discharge from streams is inhibited during those periods. In some cases, sediments, coarse gravel, and boulder-sized rocks are carried by moving ice away from shore in a process known as ice rafting. Although concentrated within 30 to 36 kilometers of the shoreline, materials carried by ice rafting are strewn over the entire floor of the bay. In most places within the bay, but particularly in the western half, postglacial sedimentation has become a less important factor than marine erosion in shaping underwater physiography.

Coastal Landscape and Water

Typical shoreline areas of the northern portion of the bay are low in elevation, rocky, and indented with numerous inlets and small islands. In other areas, the bay is surrounded by a broad, flat plain. A few higher areas (with elevation exceeding 305 meters) are located to the north and northeast on Southampton Island and Quebec’s Ungava Peninsula. Hudson Bay’s drainage basin is more than 3,800,000 square kilometers. Shoreline areas on the west and southwest coasts form an extensive region of drowned swampland. Deltas and estuaries are common; in some locations, tidal flats extend up to 9 kilometers inland. Tundra, which surrounds much of the bay, is, in essence, a cold desert in which moisture is scarce. Plant cover in the tundra includes grasses, lichens, and a scattering of low-growing shrubs. Muskeg or bogs with small black spruce trees are found in the south, especially around James Bay. Plants must complete their annual cycles during the brief summer in waterlogged environments, resulting from poor drainage tied to the underlying permafrost. The soil surrounding the bay includes infertile entisols, histosols, inceptisols, and spodosols. A discontinuous region of permafrost extends southward to 54 degrees north latitude on the western side of Hudson Bay and 61 degrees north latitude on the eastern side.

Arctic in nature, waters found within Hudson Bay demonstrate fairly uniform temperatures that average near freezing. Decreasing from the periphery of the bay to the center, temperatures are slightly warmer over underwater shoals and cooler over deeper areas, reflecting seasonal warming near the surface layer. The general pattern of water circulation is counterclockwise. River outflow maintains an influx of freshwater that inhibits saline Atlantic waters from entering Hudson Strait, resulting in the low salinity of Hudson Bay waters, especially in the spring and summer months. The difference between high and low tide ranges from just less than 1 meter to greater than 4 meters in the western portion of the bay. Pack ice blankets the water from October to June each year. Strong prevailing winds along most of the shoreline help to separate land from pack ice. The bay has historically been navigable for a short period, extending from early July to October. However, in recent years, this period has steadily lengthened, presumably due to the effects of global warming, and a fully closed ice pack has not formed.

Hudson Strait connects Hudson Bay with the Atlantic Ocean to the east. Unlike in the bay, water within the strait is predominantly deep, with recorded depths of up to 500 meters. Undersea cliffs and canyons are found near the strait’s shoreline. Water from the West Greenland Current mixes with water passing out of Hudson Bay within the strait, creating conditions that support plankton and a diversity of invertebrate and fish species.

Climate

Hudson Bay’s climate is influenced by cold, dry, and stable continental polar and Arctic air masses. The bay is normally covered with a bleak and inhospitable blanket of snow and ice during the year. A diagonal line from Chester Inlet in the northwest to the Belcher Islands in the southeast divides Hudson Bay into two climatic regions. To the northeast, the bay has a Köppen classification of ET (tundra), while the southwest is classified as Dfc (continental taiga climate). Average January temperatures for most of the land area surrounding Hudson Bay range from -30 to -20 degrees Celsius. In contrast, average July temperatures range from 10 to 20 degrees Celsius. The coldest land area adjacent to the bay is located on its northwest side, extending from Manitoba’s border with Nunavut to Southampton Island. Precipitation totals throughout the region surrounding Hudson Bay are highest in the summer. The influence of the bay’s continental climate can be illustrated in a comparison with Scotland, located at about the same latitude. In contrast to conditions around Hudson Bay, Scotland’s maritime climate, moderated by the Atlantic Ocean and, more specifically, the Gulf Stream, supports pastures for cattle and sheep.

Wildlife and Human Occupation

During the summer months, the fauna of Hudson Bay is dominated by birds and insects, especially mosquitoes and flies. The rocky coastline and islands, along with tidal flats and inland marshes, provide nesting sites for one of the world’s largest concentrations of migrating waterfowl and shorebirds. Along with almost one-half of the eastern Arctic’s population of lesser snow geese are Canada geese, Brant geese, old-squaws, loons, black guillemots, and common eiders. Also found within the area are gulls, Hudsonian godwits, whimbrels, snowy owls, horned larks, ptarmigan, and the world’s largest concentration of peregrine falcons. Caribou, arctic hare, and lemmings are also found on its shores. One of the highest densities of polar bear denning in Canada is found adjacent to Churchill, where numerous bears gather during the autumn to await the return of the ice and better feeding. This polar bear population, however, has experienced a drastic decline attributed to climate change. Over forty freshwater, Arctic, and subarctic marine fish species are found within the bay. Examples include capelin, Arctic cod, ogac, and Arctic char, as well as salmon, cod, halibut, and plaice. Seals, whales, dolphins, walruses, and beluga whales also inhabit the bay.

The earliest occupants of the area were the nomadic Inuit people, who lived in igloos and skin tents. In 1670, the Hudson’s Bay Company received a charter from the English crown for exclusive trading rights within the watershed of Hudson Bay. Soon after, trading posts were constructed at the mouths of the Moose and Albany Rivers. Between 1682 and 1713, the French attempted to force the British out of the bay. However, by the terms of the 1713 Treaty of Utrecht, the French handed over all posts in the area to the British. In 1929, the Hudson Bay Railway was completed to the town of Churchill, facilitating shipments of grain produced in Canada’s prairie provinces by boat to world markets. During World War II, the United States operated an air base near Churchill on the western side of the bay. The shoreline of Hudson Bay remains sparsely settled, with a few small trading villages located at the mouths of rivers entering the bay in Quebec, Manitoba, and Ontario. Pack ice filling the bay makes villages on its shores inaccessible for much of the year. The shoreline has a population density of fewer than three people per square mile.

Principal Terms

Canadian Shield: the geologic core of North America, extending over north-central Canada, that experienced glaciation during the Pleistocene epoch; characterized by an undulating surface of moderate relief and containing the oldest dated rock formations on the planet

craton: an area of the land surface that has been stable for millions of years

entisol: a weakly developed soil layer that does not exhibit distinct horizons or stratification layers

histosol: soil composed primarily of organic material

ice sheet: a broad, flat glacial mass with relatively gentle relief; ice sheets once covered extensive portions of North America

inceptisol: relatively recent soil deposits that exhibit the first signs of horizon differentiation

isostatic rebound: a process based on the opposing influences of buoyancy and gravity within Earth’s crust by which the surface adjusts itself vertically until these forces are balanced and isostatic equilibrium has been reached

Pleistocene epoch: the most recent ice age period, during which Earth experienced cycles of continental glaciation

spodosol: an acidic soil characterized by subsurface accumulations of humus complexed with aluminum and iron

Bibliography

Dickie, Gloria. “Canada's Hudson Bay Polar Bear Population Plummets as Climate Change Warms Arctic.” Reuters, 28 Dec. 2022, www.reuters.com/world/americas/canadas-hudson-bay-polar-bear-population-plummets-climate-change-warms-arctic-2022-12-23. Accessed 15 Apr. 2023.

Dickson, R. R., Jens Meincke, and Peter Rhines, editors. Arctic-Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate. Dordrecht: Springer, 2008.

French, Hugh, and Olav Slaymaker. Changing Cold Environments: A Canadian Perspective. Oxford: Wiley-Blackwell, 2012.

Gismond, Melissa. “The Untold Story of the Hudson's Bay Company.” Canadian Geographic, 2 May 2020, canadiangeographic.ca/articles/the-untold-story-of-the-hudsons-bay-company. Accessed 24 July 2024.

Hood, Peter J., editor. Earth Science Symposium on Hudson Bay. National Advisory Committee on Research Geological Survey of Canada Paper, 1968.

Levinton, Jeffery S., and John R. Waldman. The Hudson River Estuary. New York: Cambridge University Press, 2006.

Middleton, Gerard V., editor. Encyclopedia of Sediments and Sedimentary Rocks. Dordrecht: Springer, 2003.

Mills, Eric L. The Fluid Envelope of Our Planet: How the Study of Ocean Currents Became a Science. Toronto: Toronto University Press Inc., 2009.

Pienitz, Reinhard, Marianne S. V. Douglas, and John P. Smol. Long-Term Environmental Change in Arctic and Antarctic Lakes. Dordrecht: Springer, 2004.

Riley, John L. Flora of the Hudson Bay Lowland and Its Postglacial Origins. Ottawa: National Research Council (Canada) Research Press, 2003.

Ruddiman, W. F., and H. E. Wright. North America and Adjacent Oceans During the Last Deglaciation. Boulder, Colo.: Geological Society of America, 1987.

Stroeve, Julienne, et al. "Ice-free Period Too Long for Southern and Western Hudson Bay Polar Bear Populations If Global Warming Exceeds 1.6 to 2.6 °C." Communications Earth & Environment, vol. 5, no. 1, 2024, pp. 1-12, doi.org/10.1038/s43247-024-01430-7. Accessed 24 July 2024.