877 articles
Nootka Sound
Nootka Sound, a sound on the west coast of Vancouver Island, British Columbia, between Clayoquot and Kyuquot Sounds. Site of Cook's 1778 visit, the sea-otter fur trade, and the 1790 Nootka Convention between Spain and Britain.
Nord Stream 2 (Северный поток — 2)
Nord Stream 2 (Северный поток — 2) is a Gazprom-owned twin Baltic Sea gas pipeline from Russia to Germany, completed in 2021 at a cost of about $11 billion but never commissioned after Germany froze certification in 2022 and sabotage destroyed one string.
Norfolk Ridge
Norfolk Ridge, a submerged continental ridge of Zealandia linking New Caledonia to northern New Zealand, about 1,500 km long with 20–25 km thick continental crust, formed by Eocene–Oligocene uplift during Tonga-Kermadec subduction initiation.
North American Basin
North American Basin (US BGN ACUF: North America Basin), a large deep-sea basin in the western North Atlantic between Newfoundland Ridge and the Puerto Rico Trench, containing the Sohm and Hatteras abyssal plains and Blake Ridge.
North Aral Sea
North Aral Sea (Lesser Aral), the Kazakhstan portion of the former Aral Sea fed by the Syr Darya. Split from the South Aral by 1987; the 2005 Kokaral dam restored its level, area, salinity, and fisheries.
North Channel
The North Channel is a sheltered stretch of water along the north shore of Lake Huron in Ontario, Canada, cut off from the main lake by Manitoulin Island.
North Fiji Basin
North Fiji Basin (NFB): active back-arc basin in the Southwest Pacific behind the New Hebrides subduction zone; multiple spreading ridges, 50–80 mm/yr spreading, hot upper mantle, hydrothermal vents, Archaean analogue.
North Indian Ocean
The North Indian Ocean is the northern portion of the Indian Ocean, comprising the Arabian Sea and the Bay of Bengal, whose currents reverse seasonally with the monsoon winds.
North Pacific Gyre
The North Pacific Gyre (North Pacific Subtropical Gyre) is a clockwise system of rotating currents bounded by the Kuroshio, California, and North Equatorial Currents; its convergent center traps floating plastic, forming the Great Pacific Garbage Patch.
North Pacific Index
The North Pacific Index, or NP index, is a climate index measuring the strength of the winter Aleutian low, defined by Trenberth and Hurrell in 1994.
North Sea
The North Sea is a marginal sea between the British Isles and continental Europe, formerly the land bridge Doggerland, now central to European offshore wind: 300 GW targeted by 2050 under the North Seas Energy Cooperation.
North Sentinel Island
North Sentinel Island: forested, ~60 sq km island in the Bay of Bengal, Andaman and Nicobar Islands, India, home to the uncontacted Sentinelese; a tribal reserve with a 5 km exclusion zone under the 1956 PAT Regulation.
North Water Polynya
The North Water Polynya (Pikialasorsuaq, Sarvarjuaq) is the largest, most productive polynya in the Northern Hemisphere, an ~80,000 km² open-water area in northern Baffin Bay maintained by a Kane Basin ice arch, upwelling, and ice advection.
Northumberland Strait
The Northumberland Strait is an arm of the Gulf of St. Lawrence separating Prince Edward Island from New Brunswick and Nova Scotia, with Canada's warmest ocean waters.
Northwest Passage
The Northwest Passage is a sea route through Canada's Arctic archipelago linking the Atlantic and Pacific oceans, long sought by European explorers and first sailed by Roald Amundsen in 1903–1906.
Norton Sound
Norton Sound: shallow Bering Sea inlet on Alaska's west coast south of the Seward Peninsula, named by Captain Cook in 1778 for Sir Fletcher Norton; receives the Yukon River, home to Nome and subsistence salmon fisheries.
Norwegian Sea
The Norwegian Sea (Norskehavet) is a marginal sea of the Atlantic Ocean northwest of Norway, connecting the North Atlantic with the Arctic Ocean via the Nordic Seas.
Ocean
The ocean is the interconnected salt-water body covering about 70% of Earth's surface, holding 97% of its water, absorbing roughly 30% of CO2 emissions and 93% of excess heat, and governed largely under UNCLOS.
Ocean Beach, San Francisco
Ocean Beach is San Francisco's roughly five-mile Pacific shoreline south of the Cliff House, backed by the Great Highway and O'Shaughnessy seawall, an erosion hot spot studied by USGS, and fronted since 2025 by the car-free Sunset Dunes park.
Ocean temperature
Ocean temperature: seawater temperature from surface to depth, a key climate indicator. The ocean stores about 90% of excess heat; 2025 upper-2000 m ocean heat content set a record, up ~23 zettajoules over 2024.
Oceanic basin
Oceanic basin: the large crustal depressions holding the Pacific, Atlantic, Indian, Southern, and Arctic oceans; defined by ridges, trenches, abyssal plains, and only about 27-29% mapped.
Oceanic trench
Oceanic trench: long, narrow seafloor depressions at subduction zones, the deepest parts of the ocean. 38 known, 28 in the Pacific; deepest is Challenger Deep, Mariana Trench, about 10,924 m.
Olenyok Gulf
Olenyok Gulf (Оленёкский залив), a shallow gulf of the Laptev Sea in Yakutia, Russia, west of the Lena Delta; 65 km long, about 130 km wide, up to 15 m deep, ice-covered from mid-October to June.
Ontong Java Plateau
Ontong Java Plateau, largest oceanic plateau on Earth, western Pacific near Solomon Islands; formed ~120 Ma, area over 1.5 million km2, 30-35 km crust, submarine tholeiitic basalts, origin debated between thermochemical plume, spreading, and impact.
Opening of the Atlantic Ocean
The opening of the Atlantic Ocean began as Pangaea rifted apart about 201 million years ago, with Central Atlantic seafloor spreading starting around 190 Ma.
Operation Highjump
Operation Highjump (officially the U.S. Navy Antarctic Developments Program, 1946-47), Task Force 68 under Byrd and Cruzen: 4,700 men, 13 ships, aerial photomapping of Antarctica, Little America IV, early withdrawal from Ross Sea pack ice.
Øresund
Øresund (the Sound) is the 118 km strait between Denmark and Sweden linking the Baltic Sea and Kattegat, site of the Sound Toll (c. 1429–1857) and the 2000 Øresund Bridge between Copenhagen and Malmö.
Orléans Strait
Orléans Strait (Canal d'Orléans, Dallmannstraße) is a NE-SW Antarctic Peninsula strait separating Trinity and Tower islands from Davis Coast; named by d'Urville's 1837-40 French expedition, charted by Nordenskjöld.
OSPAR Convention
OSPAR Convention (Convention for the Protection of the Marine Environment of the North-East Atlantic), signed 1992, in force 1998; replaces Oslo 1972 and Paris 1974 conventions; 15 governments plus EU governed by the OSPAR Commission through binding Decisions and non-binding Recommendations.
Ostrov Oleniy
Ostrov Oleniy (Остров Олений, "Deer Island") is the name of several separate islands in Russia, the largest lying in the southern Kara Sea off Siberia's Gyda Peninsula.