Atlantic Ocean

The Atlantic Ocean is the world's second-largest ocean, covering approximately 106,460,000 km² — about 20% of Earth's surface — and separating the American continents to the west from Europe and Africa to the east. Stretching from the Arctic Ocean in the north to the Southern Ocean in the south, the Atlantic spans more than 16,000 km from north to south and averages 3,332 m in depth, plunging to 8,376 m at the Puerto Rico Trench, its deepest point. No ocean has shaped human civilisation more directly: it was the highway of European exploration and colonisation from the 15th century onwards, the conduit of the transatlantic slave trade, the battlefield of two World Wars, and today carries the world's busiest ocean trade corridor between Europe and the Americas.

The Atlantic is bounded by North America and South America on the west, and by Europe and Africa on the east. Its northern gateway connects to the Arctic Ocean between Greenland and Iceland, and its southern opening merges with the Southern Ocean below approximately 60°S. The ocean's characteristic S-shaped outline — mirroring the contours of the continents it separates — reflects the geological history of the break-up of the supercontinent Pangaea, which began approximately 180 million years ago when what is now Africa and South America rifted apart. The central spine of this ongoing geological process is the Mid-Atlantic Ridge, the world's longest mountain range, running the full length of the ocean floor from Iceland in the north to near the tip of South America in the south.

For deck officers and maritime professionals, the Atlantic presents a formidable range of operational environments: the stormy, iceberg-prone North Atlantic; the hurricane belt of the tropical Atlantic and Caribbean; the trade-wind zones of the central ocean; the complex, current-swept approaches to the Strait of Gibraltar; and the vast, isolated expanses of the South Atlantic. Five NAVAREA zones cover its waters. The Gulf Stream — one of the world's most powerful ocean currents — exerts a dominant influence on North Atlantic routing. The Atlantic's thermohaline circulation system, the Atlantic Meridional Overturning Circulation (AMOC), is the ocean engine that keeps northwestern Europe warm and moderates global climate. Its current weakening is one of the most consequential oceanographic trends of the 21st century.

1. Geography

The Atlantic Ocean's most defining geological feature is the Mid-Atlantic Ridge, the world's longest mountain range at approximately 16,000 km in length, running almost the full north-south extent of the ocean. The Ridge marks the divergent boundary between the North American and Eurasian plates in the north, and between the South American and African plates in the south. New ocean floor is continuously created at this spreading centre at a rate of approximately 2.5 cm per year — meaning the Atlantic is widening by roughly 2–3 cm annually. The Ridge rises to within 2,000 m of the surface in many places; above sea level, it forms the volcanic island of Iceland (which sits directly on the Ridge), the Azores archipelago, Ascension Island, St Helena, and Tristan da Cunha.

The ocean's distinctive S-shape separates the North and South American coastlines from those of Europe and Africa, with the narrowest crossing — the transatlantic distance from Dakar (Senegal) to Recife (Brazil) — being only approximately 2,850 km. The widest point in the North Atlantic, between Florida and the coast of West Africa, measures approximately 7,600 km. This geometry has been fundamental to maritime history: the short southern crossing was exploited in the slave trade, while the longer North Atlantic route was the path of European settlement of North America, 20th-century commercial shipping, and transatlantic aviation.

The Atlantic contains several major semi-enclosed marginal seas that are oceanographically and commercially important. To the west, the Caribbean Sea (approximately 2,754,000 km²) is enclosed between the Lesser and Greater Antilles island chains to the north and east, and the South American and Central American coasts to the south and west. The Gulf of Mexico (approximately 1,550,000 km²) is bordered by the United States, Mexico, and Cuba and connects to the Caribbean and Atlantic via the Straits of Florida and the Yucatan Channel. Both are warm, tropical, and hurricane-prone. To the east, the Mediterranean Sea connects to the Atlantic through the 14 km-wide Strait of Gibraltar, where a two-layer exchange flow of surface Atlantic water entering and denser, saltier Mediterranean outflow beneath creates one of the ocean's most distinctive water mass features.

Further north, the North Sea connects to the Atlantic through the passages between Scotland and Norway, and the Baltic Sea links to the North Sea via the Danish Straits. The Sargasso Sea is a unique, boundary-less region of the North Atlantic subtropical gyre, defined by the encircling currents rather than any landmass, famous for its floating Sargassum algae and as the breeding ground of Atlantic eels. On the equatorial West African coast, the Gulf of Guinea is an economically important marginal embayment whose offshore fields produce a significant fraction of sub-Saharan Africa's oil. The continental margins of both the eastern and western Atlantic are broad in some sectors — the Grand Banks of Newfoundland, the Patagonian Shelf, and the North Sea continental shelf — and narrow in others, particularly along the West African coast and the northeast coast of South America.

The North Atlantic subtropical gyre circulates clockwise in the Northern Hemisphere, driven by the prevailing westerlies to the north and the trade winds to the south. The South Atlantic subtropical gyre circulates anticlockwise in the Southern Hemisphere. Together, these two gyres define the large-scale circulation patterns that mariners have exploited for centuries to plan efficient ocean passages, sailing with favourable currents and trade winds on the outbound leg and returning on the opposing gyre.

2. Oceanography

The Atlantic's most critically important oceanographic feature is the Atlantic Meridional Overturning Circulation (AMOC), sometimes called the thermohaline conveyor belt. AMOC transports warm, relatively saline surface water from the tropics and subtropics northward through the North Atlantic, releasing enormous quantities of heat to the atmosphere over the North Atlantic and northwestern Europe. This heat release cools and densifies the water, causing it to sink into the deep ocean in specific formation zones — particularly in the Labrador Sea and the Nordic Seas (Norwegian and Greenland Seas). The resulting North Atlantic Deep Water (NADW) then flows southward at depth through the entire Atlantic, driving the broader global thermohaline circulation. AMOC transports roughly 17 Sverdrup (17 million cubic metres per second) of water — and enormous quantities of heat — and is the primary reason that northwestern Europe is approximately 5–10°C warmer than equivalent latitudes on the North American coast.

The Gulf Stream is the Atlantic's most famous surface current and one of the world's strongest ocean currents, transporting approximately 30 million m³/s (30 Sverdrups) of water northward along the eastern coast of North America — a volume equivalent to roughly 150 times the combined flow of all the world's rivers. The Gulf Stream originates in the Gulf of Mexico, exits through the Straits of Florida, flows northeastward along the US East Coast at speeds of 2–4 knots (occasionally up to 5 knots), and separates from the coast near Cape Hatteras (North Carolina), after which it flows across the North Atlantic as the North Atlantic Current. Eastbound transatlantic vessels have exploited the Gulf Stream for centuries to reduce passage time and fuel consumption; westbound vessels routinely route south of the Stream to avoid its contrary current. The Gulf Stream also marks a significant thermal and density boundary, and its associated meanders and eddies create complex, rapidly changing conditions that must be accounted for in both routing and fishing operations.

Other significant Atlantic currents include the Labrador Current, which flows southward from the Arctic along the coast of Labrador and Newfoundland, carrying sub-zero waters and icebergs into the western North Atlantic shipping lanes. The collision of the cold Labrador Current and the warm Gulf Stream near the Grand Banks creates a zone of persistent fog, rapid weather changes, and the iceberg hazard that famously sank RMS Titanic in April 1912. The Benguela Current, flowing northward along the west coast of southern Africa, is a major upwelling current that brings cold, nutrient-rich deep water to the surface, sustaining one of the world's most productive fisheries off Namibia and South Africa.

The tropical Atlantic is the primary breeding ground for Atlantic hurricanes(tropical cyclones). The North Atlantic hurricane season officially runs from 1 June to 30 November, with peak activity in August through October. Hurricanes form from tropical disturbances over the warm waters of the tropical Atlantic and Caribbean (sea surface temperatures must generally exceed 26°C to sustain a tropical cyclone). They typically track westward under the influence of the trade winds before curving northward and then northeastward as they encounter the mid-latitude westerlies. The North Atlantic averages approximately 14 named storms per season, of which 7 become hurricanes and 3 become major hurricanes (Category 3 or above). The Gulf of Mexico, Caribbean, and US East Coast are most severely affected. Vessels in these waters during hurricane season must maintain continuous weather monitoring and have pre-planned hurricane avoidance routes.

The Atlantic's salinity is notably higher than the Pacific (33–37 ppt vs 34–35 ppt for the Pacific), partly because the Atlantic's relatively narrow width means that water evaporated from its surface can fall as rain on the American and European continents, while the more remote Pacific receives more precipitation directly back into the ocean. This higher salinity contributes to the deep-water formation processes that drive AMOC.

3. Marine Ecology

The Atlantic Ocean supports some of the world's most iconic and ecologically significant marine species. Blue whales (Balaenoptera musculus), the largest animals ever known to have lived, migrate through the North Atlantic, feeding on krill concentrations in summer feeding grounds before moving to tropical and subtropical breeding grounds in winter. Their North Atlantic population remains depleted from historic whaling and is slowly recovering. Humpback whales (Megaptera novaeangliae) are among the most studied and celebrated cetaceans in the Atlantic. Renowned for their complex, evolving songs produced by males during the breeding season — some lasting 20 minutes and audible over hundreds of kilometres — humpbacks undertake one of the longest migrations of any mammal, feeding in North Atlantic waters in summer and migrating to tropical Caribbean breeding grounds in winter. Their recovery from near-extinction following the 1986 IWC moratorium on commercial whaling is one of conservation's success stories.

The North Atlantic right whale (Eubalaena glacialis) is one of the most critically endangered large mammals on Earth, with a population estimated at approximately 360 individuals as of 2024. Named by whalers as the “right” whale to hunt — slow-moving, coastal, and floating when killed — it was hunted to near-extinction by the 17th century. Despite commercial whaling protection since 1935, the population is still declining, primarily due to entanglement in fishing gear (particularly lobster and snow crab pot rope along the US and Canadian East Coast) and vessel strikes by large ships. The US National Marine Fisheries Service (NMFS) has implemented mandatory vessel speed restrictions (10 knots maximum) in Seasonal Management Areas along the US East Coast during periods of right whale presence, a legal requirement for all vessels 65 feet (19.8 m) or longer. Mariners must be aware of these restrictions, which are enforced by the US Coast Guard.

Atlantic bluefin tuna (Thunnus thynnus) is the largest tuna species and one of the ocean's apex predators, capable of reaching 3 m in length and 680 kg in weight. Atlantic bluefin range across the entire North Atlantic and into the Mediterranean, where they spawn. Highly prized in the Japanese sushi and sashimi market — single fish have sold for over $3 million at the Toyosu market in Tokyo — Atlantic bluefin have been subjected to intense commercial fishing pressure. Management is shared between ICCAT (International Commission for the Conservation of Atlantic Tunas) and, for the Mediterranean spawning stock, the EU. The eastern Atlantic and Mediterranean stock has largely recovered under recent strengthened quota management; the western Atlantic stock remains at lower historical levels.

The Grand Banks cod fishery (Gadus morhua) was once the Atlantic's most commercially important single species, sustaining European and North American economies for five centuries after John Cabot's 1497 voyage reported waters so thick with cod that baskets could be lowered into the sea and raised full of fish. Industrial-scale trawling from the 1950s onwards collapsed the stock to approximately 1% of its historical biomass by 1992, triggering a Canadian moratorium that ended 30,000 livelihoods. The stock has not recovered to pre-collapse levels even after three decades of moratorium, demonstrating the potentially irreversible nature of ecosystem-scale fisheries collapse.

The Sargassum ecosystem of the Sargasso Sea is unique: vast rafts of golden-brown pelagic algae provide habitat for an endemic community of species found nowhere else, including sargassum fish (Histrio histrio), sargassum shrimp, and several species of nudibranchs. The Sargasso Sea is the exclusive spawning ground of both the European eel (Anguilla anguilla) and the American eel (Anguilla rostrata). Leatherback turtles(Dermochelys coriacea) undertake remarkable transatlantic migrations, nesting on West African and Caribbean beaches and feeding in the cold, jellyfish-rich waters of the North Atlantic as far north as Canada and the British Isles. Atlantic salmon (Salmo salar) feed in the North Atlantic before returning to their natal rivers in Europe and North America — with Greenland and the Faroe Islands as important feeding grounds — a lifecycle that makes them vulnerable to both freshwater habitat degradation and high-seas interception fishing.

4. Maritime Trade Routes

The Atlantic Ocean carries the world's busiest ocean trade corridor — the Europe–Americas shipping lane. Containerised goods, crude oil, LNG, bulk commodities, vehicles, and break-bulk cargo move continuously between the major port clusters of northern Europe (Rotterdam, Antwerp, Hamburg, Felixstowe) and the eastern seaboard of North America (New York/New Jersey, Savannah, Houston, Baltimore), as well as between European ports and the major South American hubs (Santos, Buenos Aires, Cartagena, Callao). This North Atlantic trade route is arguably the most economically significant ocean corridor on Earth, reflecting the combined GDP weight of North America and Europe.

Transatlantic container trade is one of the three major legs of the global container shipping network, alongside the Asia–Europe and Transpacific lanes. The largest container shipping alliances — MSC, Maersk, CMA CGM, Hapag-Lloyd — operate weekly services linking north European range ports with US East Coast and Gulf of Mexico ports, typically transiting the North Atlantic in 7–10 days at service speeds of 18–22 knots. The Panama Canal is critical to transatlantic trade, enabling direct connections between Atlantic and Pacific ports; the 2016 expansion of the Canal to accommodate Neo-Panamax vessels (up to 14,000 TEU) significantly increased its role in routing Atlantic container services.

Historically, the North Atlantic was also the world's premier passenger shipping route. The great ocean liners of the Cunard Line (Mauretania, Lusitania,Queen Mary, Queen Elizabeth) and the White Star Line (Olympic,Titanic) competed for the Blue Riband — the record for the fastest transatlantic crossing — and transported millions of European emigrants to North America between 1880 and 1960. Transatlantic aviation, following the establishment of regular commercial services in the late 1950s (BOAC and Pan Am operating Boeing 707s from 1958), ended the liner era within a decade.

The Gulf of Mexico energy corridor is a major component of Atlantic trade, with crude oil from the Gulf of Mexico, offshore West Africa, and Brazil moving to US Gulf refineries and onward to global markets. Houston (the world's largest petrochemical complex) and the ports of Corpus Christi and Beaumont-Port Arthur serve as the primary nodes for this trade. West Africa–Brazil trade exploits the short transatlantic distance at equatorial latitudes — the Dakar-to-Recife crossing is only approximately 2,850 km — and has grown significantly as Brazil and West Africa both expand deepwater oil production. The Cape of Good Hope route around the southern tip of Africa — used before the Suez Canal era and still used by vessels too large for the Canal or when the Canal is disrupted — connects the Atlantic to the Indian Ocean and represents an important alternative routing option for bulk carriers and VLCCs.

The Strait of Gibraltar is the Atlantic's principal eastern gateway, funnelling Mediterranean trade through a 14 km-wide channel where the Atlantic meets the Mediterranean. The Port of Algeciras (Spain) and the Port of Tanger Med (Morocco) on either side of the Strait are among the world's busiest container transhipment hubs, positioned to serve as relay points between Atlantic and Mediterranean container services. The Dover Strait connects the Atlantic via the English Channel to the North Sea and is the world's busiest shipping lane by vessel count, with approximately 500–600 vessels per day. The Drake Passage between Cape Horn and the South Shetland Islands connects the South Atlantic to the Pacific south of South America — notorious for the world's stormiest seas but still used by vessels unable to transit the Panama Canal due to size constraints. The Strait of Magellan provides a calmer but navigationally demanding alternative passage between the Atlantic and Pacific.

5. Key Ports

The Atlantic's coastline is home to several of the world's most significant port complexes, spanning multiple continents and spanning every category of cargo.

Rotterdam (NLRTM) — Europe's Gateway

The Port of Rotterdam, located at the mouth of the Rhine-Maas delta on the southern coast of the North Sea, is Europe's largest port by cargo tonnage, handling over 440 million tonnes annually. Its deep Maas approach channel, dredged to 24 metres, accommodates fully laden VLCCs. Rotterdam's Maasvlakte 2 container terminals (Rotterdam World Gateway, APM Terminals) handle some of the world's largest container vessels, while Europoort hosts Shell Pernis — Europe's largest refinery. The port is the western terminal of the Rhine barge network extending deep into continental Europe.

Hamburg (DEHAM) — Northern Europe's Trade Hub

Hamburg, approximately 100 km up the River Elbe from the North Sea, is Germany's largest container port and one of Europe's most important, handling approximately 8–9 million TEU annually. The tidal Elbe approach requires careful tidal window planning for large vessels. Hamburg's hinterland connectivity via rail and waterway makes it the primary gateway for central European trade with the Americas and Asia.

Antwerp (BEANR) — World Chemical Capital

Antwerp on the River Scheldt is Europe's second-largest port and the world's largest chemicals port, handling approximately 60 million tonnes of liquid chemicals annually. It is a critical Atlantic gateway for European pharmaceutical and industrial chemical supply chains, served by the pilotage-compulsory Western Scheldt channel from the North Sea entrance.

New York / New Jersey (USNYC) — East Coast Flagship

The Port of New York and New Jersey is the largest port on the US East Coast and the third-largest in the United States by total cargo volume, handling approximately 9 million TEU annually. The Port Authority of New York and New Jersey operates six marine terminals. The Bayonne Bridge raising completed in 2019 increased the vertical clearance to 66.5 metres, enabling the largest container vessels to access the port, triggering a significant shift of containerised cargo from US West Coast ports to East Coast alternatives via the Suez and Panama Canals.

Houston (USHOU) — Americas' Energy Hub

The Port of Houston, located 80 km inland on the Houston Ship Channel, is the largest US port by total cargo tonnage and the centre of the world's largest petrochemical complex. It handles crude oil, LNG, refined petroleum products, chemicals, and containerised cargo, serving as the primary Atlantic gateway for US Gulf oil and gas exports including the LNG export boom driven by the shale revolution. The Houston Ship Channel requires constant dredging maintenance and is subject to traffic management by the US Army Corps of Engineers.

Santos (BRSSZ) — South America's Largest Port

The Port of Santos, located near São Paulo on the Brazilian coast, is the largest port in South America and Latin America by cargo volume, handling approximately 130 million tonnes annually including significant volumes of soybeans, sugar, ethanol, coffee, and containerised goods. Santos is the primary export point for Brazil's vast agricultural hinterland and a major node on Atlantic trade routes connecting Brazil to Europe, the US East Coast, and Asia via the Cape of Good Hope.

Lagos (NGLOS) — West Africa's Commercial Capital

The Port of Lagos (Apapa Port), Nigeria, is the largest port in West Africa and a major node in Atlantic trade. It serves Nigeria — Africa's largest economy and oil producer — with crude oil export terminals at Bonny, Brass, and Escravos offshore. The Lekki Deep Sea Port, inaugurated in 2023, is capable of handling ultra-large container vessels and is transforming Nigeria's position in Atlantic container trade. Lagos Apapa remains challenging operationally, with significant congestion, anchorage management difficulties, and security concerns in the Gulf of Guinea.

Cape Town (ZACPT) — South Atlantic Gateway

The Port of Cape Town, at the southwestern tip of the African continent, serves as a critical waypoint on the Cape of Good Hope route between the Atlantic and Indian Oceans, used particularly by VLCCs and Capesize bulk carriers too large for the Suez Canal. Cape Town provides bunkering, provisions, crew changes, and ship repair services for vessels on the Europe–Asia and Americas–Asia Cape route. The Table Bay anchorage and the port's exposed western-facing approaches can be challenging in the frequent Cape south-westerly gales.

6. History

The first documented Atlantic crossing by Europeans was made by Norse seafarers around 1000 AD. Leif Eriksson, sailing from Greenland with a crew of 35, established the settlement of Vinland at L'Anse aux Meadows (in modern Newfoundland, Canada) — the only confirmed pre-Columbian European settlement in the Americas. The Norse reached Greenland from Iceland (itself colonised from Norway in the 9th century) using clinker-built longships and knarrs, navigating by sun-shadow board, stars, and the flight patterns of land birds. The Vinland colony was short-lived — likely abandoned within a few decades due to conflicts with indigenous Skraelings — but represents a remarkable feat of open-ocean navigation in an era without compass or chart.

Christopher Columbus's first voyage in 1492, sailing from Palos de la Frontera (Spain) with three ships — Santa María, Pinta, and Niña — under the patronage of the Spanish Crown, opened the Atlantic to systematic European exploitation. Columbus made landfall in the Bahamas on 12 October 1492, believing he had reached the East Indies. His achievement, though based on a fundamental geographical misunderstanding, triggered the era of European colonisation of the Americas and the transatlantic exchange of peoples, diseases, animals, plants, and ideas that permanently changed both hemispheres. Portuguese explorer Vasco da Gama's rounding of the Cape of Good Hope in 1497–1498 opened the Atlantic sea route to Asia, making Portugal the dominant maritime power of the early 16th century.

The transatlantic slave trade (approximately 1500–1867) was the largest forced migration in human history, transporting an estimated 12.5 million enslaved Africans across the Atlantic to the Americas, of whom approximately 10.7 million survived the crossing (the Middle Passage). The trade formed the third leg of the triangular trade: manufactured goods from Europe to West Africa, enslaved people from Africa to the Americas, and sugar, cotton, tobacco, and other plantation crops from the Americas back to Europe. The brutal conditions of the Middle Passage — extreme overcrowding, disease, inadequate food and water, and systematic violence — resulted in a mortality rate of approximately 15% during the crossing. The trade was abolished by Britain in 1807 and by the United States in 1808, with enforcement by the Royal Navy's West Africa Squadron from 1808 to 1860 — the largest peacetime naval commitment in British history.

The first transatlantic telegraph cable was successfully laid in 1866 by the SSGreat Eastern — the largest ship of her era — under the direction of Cyrus Field and the Atlantic Telegraph Company, after two failed attempts in 1857 and 1858. The cable ran from Valentia Island (Ireland) to Heart's Content (Newfoundland) — approximately 4,000 km — and reduced transatlantic communication time from the 10–12 days required for the fastest mail steamer to a matter of minutes. The cable transformed Atlantic commerce, diplomacy, and journalism, and represented the first truly global communications network.

RMS Titanic sank in the North Atlantic on 15 April 1912, approximately 600 km south of Newfoundland, after striking an iceberg at 23:40 on 14 April. Of the 2,224 passengers and crew, 1,517 died — one of the deadliest peacetime maritime disasters in history. The disaster exposed critical failures in passenger ship safety, particularly inadequate lifeboat provision (Titanic carried lifeboats for 1,178 persons — only 52% of capacity), the absence of mandatory lifeboat drills, and inadequate radio watch-keeping. It directly drove the 1914 SOLAS (Safety of Life at Sea) Convention and established the International Ice Patrol, which continues to monitor North Atlantic iceberg conditions for mariners today.

The Battle of the Atlantic (3 September 1939 – 8 May 1945) was the longest continuous military campaign of the Second World War, fought across the full breadth of the Atlantic between Allied convoys and German U-boat wolf packs. Germany's strategic aim was to sever Britain's maritime supply lines through unrestricted submarine warfare; the Allies' task was to maintain the flow of food, fuel, weapons, and troops necessary to sustain the British war effort and eventually mount the invasion of Europe. Over six years, German U-boats sank 3,500 merchant ships (14.5 million gross tonnes) and 175 Allied naval vessels, killing over 72,000 sailors and merchant mariners. The Allies ultimately prevailed through the combined effect of centimetric radar, breaking of the Enigma codes at Bletchley Park, introduction of escort carriers covering the mid-Atlantic “air gap,” and improved convoy escort tactics. The Battle of the Atlantic shaped Cold War naval doctrine, including the SOSUS (Sound Surveillance System) network of underwater acoustic hydrophones laid across the North Atlantic to detect Soviet submarines during the Cold War, and the NATO GIUK (Greenland-Iceland-UK) Gap strategy.

Transatlantic aviation came of age on 14–15 June 1919, when Alcock and Brown completed the first nonstop transatlantic flight, from Newfoundland to County Galway in 16 hours and 12 minutes. Lindbergh's solo New York–Paris crossing in the Spirit of St. Louis (33.5 hours, 20–21 May 1927) captured the world's imagination. Regular transatlantic commercial air services began in 1939 (Pan American Boeing 314 flying boats) but the jet age, inaugurated by BOAC and Pan Am Boeing 707 services from 1958, ended the ocean liner era within a decade and permanently shifted the passenger carrying role from sea to air.

7. Navigation Safety

The Atlantic Ocean is covered by five NAVAREA zones under the IMO/IHO World-Wide Navigational Warning Service (WWNWS). NAVAREA I (Northeast Atlantic including the North Sea and Norwegian Sea) is coordinated by the United Kingdom Hydrographic Office (UKHO). NAVAREA II (North Central Atlantic, covering the open ocean between approximately 35°W and the Americas to the east of the NAVAREA IV boundary) is also coordinated by the United Kingdom. NAVAREA III (Mediterranean Sea and the northeast Atlantic approaches south of about 48°N, east of 35°W) is coordinated by Spain. NAVAREA IV (Western North Atlantic including the US East Coast, Gulf of Mexico, and Caribbean) is coordinated by the United States (National Geospatial-Intelligence Agency, NGA). NAVAREA VI (South Atlantic) is coordinated by Brazil. Mariners transiting the Atlantic must ensure their GMDSS installation is correctly configured to receive SafetyNET broadcasts for all NAVAREA zones being transited, and must maintain NAVTEX watch in coastal areas within NAVTEX range (approximately 300–400 nm).

North Atlantic Tracks (NAT) are daily-published organised routes for transatlantic aviation managed under ICAO, adjusted to optimise jet stream utilisation. While NAT is an aviation construct, mariners crossing the North Atlantic should be aware that its corridors concentrate aircraft at defined altitudes — relevant context for coordinating air-sea search and rescue. Commercial weather routing services (StormGeo, Applied Weather Technology, Oceanroutes) provide ship operators with optimised routeing advice that takes advantage of the Gulf Stream on eastbound passages and avoids its contrary current westbound, adjusts to avoid North Atlantic gale centres, and optimises fuel consumption across the voyage.

Iceberg season in the North Atlantic runs approximately from February to July, with peak hazard in April and May. Icebergs calve from Greenland glaciers and are carried southward by the Labrador Current into the shipping lanes of the North Atlantic. The International Ice Patrol (IIP), established in 1914 following the Titanic disaster, monitors iceberg positions using aerial surveillance, satellite data, and drift modelling, broadcasting iceberg limit positions and individual berg warnings to mariners. COLREG Rule 6 (safe speed) and Rule 19 (restricted visibility) are particularly relevant in iceberg-threatened waters: vessels must reduce speed to a level at which they can stop within the distance of clear visibility.

Hurricane avoidance is critical for vessels navigating the tropical North Atlantic, Caribbean, and Gulf of Mexico from June to November. Mariners should monitor National Hurricane Center (NHC) advisories, track forecast cones carefully, and follow the established strategy of routing to maintain maximum distance from a hurricane's dangerous semicircle (the right-hand side of the track in the Northern Hemisphere, where wind speeds are highest and the sea state most confused). Vessels caught by a rapidly intensifying hurricane in the open Atlantic should attempt to navigate to the navigable semicircle (left of the track) and run with the storm if necessary to gain sea room.

GMDSS coverage in the Atlantic corresponds to the ocean's distance from coast. GMDSS Sea Area A1 (within range of VHF DSC coast stations, 20–30 nm offshore) covers port approaches and nearshore waters. Sea Area A2 (within MF DSC range, approximately 150–400 nm offshore) covers coastal ocean passages. Sea Area A3 (the vast majority of the Atlantic between 70°N and 70°S) is covered by Inmarsat-C geostationary satellite communications and SafetyNET. Vessels entering Sea Area A3 must have operational Inmarsat-C (or equivalent) equipment for distress alerting and receiving maritime safety information. The vast Southern Ocean reaches of the South Atlantic may fall into Sea Area A4 (polar), where Inmarsat coverage is limited and HF radio (MF/HF DSC) becomes the primary distress communication method.

8. Environment

The weakening of AMOC is among the most consequential climate change risks facing the Atlantic. Scientific analysis of deep-ocean sediment cores and observational data from the RAPID-AMOC monitoring array (a transatlantic array of ocean moorings at 26°N, operated since 2004) indicates that AMOC has weakened by approximately 15% since the mid-20th century and is at its weakest point in over 1,000 years. The mechanism is the freshening of North Atlantic surface water from accelerated Greenland ice sheet melt, which reduces the density contrast that drives deep-water formation. A significant further weakening or collapse of AMOC could cool northwestern European temperatures by several degrees Celsius (partially or wholly offsetting greenhouse warming in those regions while intensifying it elsewhere), shift tropical rainfall patterns, raise US East Coast sea levels, and alter Atlantic storm tracks. The implications for maritime operations, port infrastructure, and ocean routing would be profound and highly uncertain.

The Atlantic contains two major plastic pollution gyres. The North Atlantic Garbage Patch, centred in the North Atlantic subtropical gyre (the Sargasso Sea region), accumulates plastic debris carried by the encircling currents. The South Atlantic Garbage Patch similarly concentrates in the South Atlantic subtropical gyre. Unlike the Pacific Great Pacific Garbage Patch, the Atlantic gyres are less intensively studied but represent major concentrations of microplastic particles that have entered Atlantic food chains from zooplankton to fish to seabirds and marine mammals. MARPOL Annex V prohibits the discharge of all plastics from vessels anywhere in the ocean; its effective enforcement relies on port state control inspections and adequate port reception facilities.

Deep-sea mining is an emerging environmental concern in the Atlantic. While the Clarion-Clipperton Zone (CCZ) — the primary area of commercial interest for polymetallic nodule mining — is located in the Pacific, the mid-Atlantic Ridge system contains hydrothermal vent fields with polymetallic sulphide deposits that are of interest to mining companies. The International Seabed Authority (ISA), which regulates mineral extraction in the international seabed area (the “Area” beyond national jurisdiction), has issued exploration contracts for mid-Atlantic Ridge hydrothermal deposits. The environmental impact of mining these unique deep-sea vent ecosystems — which harbour extraordinary biodiversity found nowhere else and operate on geological timescales — is a subject of intense scientific debate.

Ocean acidification — the decrease in seawater pH caused by the absorption of atmospheric CO₂ — is proceeding at a rate unprecedented in at least 300 million years. Surface ocean pH has decreased by approximately 0.1 pH unit since the Industrial Revolution, representing a 26% increase in acidity. The North Atlantic is particularly affected because its cold waters absorb CO₂ more efficiently. Acidification threatens calcifying organisms — pteropods (sea butterflies), oysters, mussels, corals — at the base of Atlantic food chains, with cascading implications for fisheries and the marine ecosystems that sustain them. Deep-water corals along the Northeast Atlantic margins (Lophelia pertusa reefs off Norway, Scotland, and Ireland) are among the first ecosystems predicted to be affected by aragonite undersaturation.

Rising sea levels driven by thermal expansion of warming oceans and ice sheet melt pose a direct threat to the Atlantic's low-lying coastal infrastructure. US East Coast sea level rise is accelerated relative to the global average by the additional factor of AMOC weakening, which reduces the northward water transport that currently depresses sea levels along the northeastern US coast. Cities including Miami, New York, Boston, New Orleans, Lagos, Amsterdam, and London face increasing flood risk as sea levels rise, driving massive investments in coastal protection infrastructure. The fishing stock collapses described above — cod on the Grand Banks, herring in various Atlantic regions — demonstrate that the Atlantic's ecological systems are not resilient to sustained extraction at industrial scales and require enforced international management frameworks to recover.