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| North American continental shelf | |
|---|---|
| Name | North American continental shelf |
| Other name | Continental shelf of North America |
| Region | North America |
| Area km2 | approximately 10,000,000 |
| Coastline km | extensive |
| Countries | United States, Canada, Mexico, Greenland |
North American continental shelf is the submerged perimeter of North America extending from the shoreline to the continental slope and abyssal plains. It includes the shallow marine margins off the Atlantic Ocean, Pacific Ocean, Arctic Ocean, and adjacent seas such as the Gulf of Mexico and Bering Sea. The shelf is a primary interface for coastal nations such as the United States, Canada, Mexico, and Greenland for resources, navigation, and sovereignty.
The continental shelf encompasses major physiographic regions including the Grand Banks, Georges Bank, the Chesapeake Bay shelf, the Mid-Atlantic Bight, the Florida Platform, the Gulf of Mexico shelf, the Yucatán Shelf, the Pacific Coast Ridges off California, the Bering Shelf near Alaska, and the Arctic margins bordering Hudson Bay and the Beaufort Sea. Shelf width varies from narrow near the West Coast of the United States and Pacific Northwest to broad expanses such as the Grand Banks of Newfoundland and the East China Sea—(note: for comparison with another continental shelf). Key coastal cities and ports adjacent to the shelf include New York City, New Orleans, Los Angeles, Vancouver, Halifax, Tampa Bay, and Corpus Christi. Hydrographic features include submarine canyons like Hudson Canyon, banks like Georges Bank, and shelves contiguous with island systems such as the Aleutian Islands and Baja California.
Formation of the shelf reflects tectonic and sedimentary history tied to events like the breakup of Pangaea, the opening of the Atlantic Ocean, and the accretionary processes along the Pacific Ring of Fire. Passive margin shelves such as the Atlantic Seaboard developed by thermal subsidence and long-term sedimentation from river systems like the Mississippi River, Saint Lawrence River, and Mackenzie River. Active margin shelves adjacent to Cascadia Subduction Zone and the San Andreas Fault show truncated profiles shaped by uplift and erosion. Glacial-interglacial cycles influenced shelf exposure during Last Glacial Maximum, producing reworked deposits, drowned river valleys, and features studied at sites like Sable Island and Cape Hatteras. Sediment provenance is traced to sources including the Rocky Mountains, Appalachian Mountains, and Canadian Shield, while stratigraphic analysis employs cores from projects led by institutions such as the United States Geological Survey, the Geological Survey of Canada, and the Ocean Drilling Program.
Shelf hydrography is governed by major currents and water masses including the Gulf Stream, the Labrador Current, the California Current, the Alaskan Current, and seasonal flows in the Gulf of Mexico Loop Current. Temperature and salinity gradients create fronts and mixing zones on features like Georges Bank and the Shelf-Break Front, affecting stratification and nutrient fluxes. Tidal regimes vary from macrotidal embayments like the Bay of Fundy to microtidal stretches off Southern California. Wave climates and storm impacts are driven by systems such as Hurricane Katrina, nor'easters impacting New England, and extratropical storms affecting British Columbia. Physical processes include upwelling along the West Coast of North America, shelf-slope exchanges at the continental slope, internal waves, and shelf-wide circulation patterns analyzed in models developed at institutions like Scripps Institution of Oceanography and Woods Hole Oceanographic Institution.
The shelf supports rich biotic communities from benthic habitats to pelagic fisheries, including spawning and nursery grounds for species such as Atlantic cod near Grand Banks, Pacific salmon in Bering Sea margins, and reef communities on the Florida Keys. Habitats include seagrass meadows in Tampa Bay, kelp forests off California, cold-water coral assemblages on shelf-edge banks, and benthic mudflats in estuaries like the Delaware Bay. Key ecological interactions involve predation by marine mammals such as the North Atlantic right whale, gray whale migrations along the Pacific Coast, and seabird colonies at Pribilof Islands and Cape Cod. Biodiversity assessments are conducted by organizations including the National Oceanic and Atmospheric Administration, Fisheries and Oceans Canada, and the International Union for Conservation of Nature.
The shelf is a principal zone for extraction and harvesting: commercial fisheries targeting species like Atlantic herring, Pacific cod, blue crab, and shrimp; hydrocarbon production in basins such as the Gulf of Mexico oil fields, Hibernia oil field analogs on the east coast, and offshore plays off California and Alaska; mineral prospects including sand, gravel, and emerging interest in polymetallic deposits. Offshore wind developments are advancing at sites influenced by projects in Rhode Island and plans near Nova Scotia and California. Shipping lanes and ports such as Port of New York and New Jersey and Port of Los Angeles rely on shelf bathymetry and dredging managed by agencies like the U.S. Army Corps of Engineers.
Anthropogenic pressures include overfishing exemplified by historical collapses like the Cod fishery collapse, oil spills such as the Deepwater Horizon oil spill and legacy incidents at Exxon Valdez, coastal development impacts in regions like Florida Keys National Marine Sanctuary and Chesapeake Bay, and pollution from agricultural runoff in the Mississippi River watershed contributing to hypoxia in the Gulf of Mexico hypoxic zone. Climate-driven changes include warming waters, acidification linked to atmospheric Carbon dioxide rise, loss of sea ice in the Arctic Ocean with implications for polar bear habitat and subsistence communities like those in Nunavut. Conservation responses involve marine protected areas such as those designated by NOAA National Marine Fisheries Service, international science collaborations at PICES and ICES, and restoration programs like those under the National Estuary Program.
Sovereign rights and management of the shelf are framed by treaties and laws including baseline regimes under the United Nations Convention on the Law of the Sea (UNCLOS) concepts as applied by United States policy, continental shelf claims presented to the Commission on the Limits of the Continental Shelf, and national statutes such as the Outer Continental Shelf Lands Act in the United States and corresponding legislation in Canada and Mexico. Regional governance involves interagency coordination among bodies like NOAA, the U.S. Bureau of Ocean Energy Management, Fisheries and Oceans Canada, and cross-border arrangements through mechanisms including the Commission for Environmental Cooperation and bilateral agreements on fisheries and oil and gas development.
Category:Continental shelves