Marine Life

Early Oceans
The Early atmosphere was probably dominated at first by water vapor, which, as the temperature dropped, would rain out and form the oceans. This would have been a deluge of truly global proportions an resulted in further reduction of CO2. Then the atmosphere was dominated by nitrogen, but there was certainly no oxygen in the early atmosphere. The dominance of Banded-Iron Formations (BIFs; see picture) before 2.5Ga indicates that Fe occurred in its reduced state (Fe2+). Whereas reduced Fe is much more soluble than oxidized Fe (Fe3+), it rapidly oxidizes during transport. However, the dissolved O in early oceans reacted with Fe to form Fe-oxide in BIFs. As soon as sufficient O entered the atmosphere, Fe takes the oxidized state and is no longer soluble. The first occurrence of redbeds, a sediments that contains oxidized iron, marks this major transition in Earth’s atmosphere.

Atlantic Ocean (Fig. 3.1) extends northward from Antarctica and includes all of the Arctic Sea, the European Mediterranean, and the American Mediterranean (the Caribbean sea). The boundary between the Atlantic and Indian Oceans is the meridian of Cape Agulhas (20�E). The boundary between the Atlantic and Pacific Oceans is the line forming the shortest distance from Cape Horn to the South Shetland Islands. In the north, the Arctic Sea is part of the Atlantic Ocean, and the Bering Strait is the boundary between the Atlantic and Pacific.
The Atlantic Ocean is the second largest of the world's five oceans (after the Pacific Ocean, but larger than the Indian Ocean, Southern Ocean, and Arctic Ocean). The Kiel Canal (

Germany

), Oresund (Denmark-Sweden), Bosporus (

Turkey

), Strait of Gibraltar (Morocco-Spain), and the Saint Lawrence Seaway

Location:	body of water between Africa, Europe, the Southern Ocean, and the Western Hemisphere
Geographic coordinates:	0 00 N, 25 00 W
Map references:	Political Map of the World
Area:	total: 76.762 million sq km note: includes Baltic Sea, Black Sea, Caribbean Sea, Davis Strait, Denmark Strait, part of the Drake Passage, Gulf of Mexico, Labrador Sea, Mediterranean Sea, North Sea, Norwegian Sea, almost all of the Scotia Sea, and other tributary water bodies
Area - comparative:	slightly less than 6.5 times the size of the US
Coastline:	111,866 km
Climate:	tropical cyclones (hurricanes) develop off the coast of Africa near Cape Verde and move westward into the Caribbean Sea; hurricanes can occur from May to December, but are most frequent from August to November
Terrain:	surface usually covered with sea ice in Labrador Sea, Denmark Strait, and coastal portions of the Baltic Sea from October to June; clockwise warm-water gyre (broad, circular system of currents) in the northern Atlantic, counterclockwise warm-water gyre in the southern Atlantic; the ocean floor is dominated by the Mid-Atlantic Ridge, a rugged north-south centerline for the entire Atlantic basin
Elevation extremes:	lowest point: Milwaukee Deep in the Puerto Rico Trench -8,605 m highest point: sea level 0 m
Natural resources:	oil and gas fields, fish, marine mammals (seals and whales), sand and gravel aggregates, placer deposits, polymetallic nodules, precious stones
Natural hazards:	icebergs common in Davis Strait, Denmark Strait, and the northwestern Atlantic Ocean from February to August and have been spotted as far south as Bermuda and the Madeira Islands; ships subject to superstructure icing in extreme northern Atlantic from October to May; persistent fog can be a maritime hazard from May to September; hurricanes (May to December)
Environment - current issues:	endangered marine species include the manatee, seals, sea lions, turtles, and whales; drift net fishing is hastening the decline of fish stocks and contributing to international disputes; municipal sludge pollution off eastern US, southern Brazil, and eastern Argentina; oil pollution in Caribbean Sea, Gulf of Mexico, Lake Maracaibo, Mediterranean Sea, and North Sea; industrial waste and municipal sewage pollution in Baltic Sea, North Sea, and Mediterranean Sea
Geography - note:	major chokepoints include the Dardanelles, Strait of Gibraltar, access to the Panama and Suez Canals; strategic straits include the Strait of Dover, Straits of Florida, Mona Passage, The Sound (Oresund), and Windward Passage; the Equator divides the Atlantic Ocean into the North Atlantic Ocean and South Atlantic Ocean

Pacific Ocean extends northward from Antarctica to the Bering Strait. The boundary between the Pacific and Indian Oceans follows the line from the Malay Peninsula through Sumatra, Java, Timor,

Australia

at Cape Londonderry, and Tasmania. From Tasmania to Antarctica it is the meridian of South East Cape on Tasmania 147�E.

The Pacific Ocean is the largest of the world's five oceans (followed by the Atlantic Ocean, Indian Ocean, Southern Ocean, and Arctic Ocean). Strategically important access waterways include the La Perouse, Tsugaru, Tsushima,

Taiwan

Singapore

, and Torres Straits

Location:	body of water between the Southern Ocean, Asia, Australia, and the Western Hemisphere
Geographic coordinates:	0 00 N, 160 00 W
Map references:	Political Map of the World
Area:	total: 155.557 million sq km note: includes Bali Sea, Bering Sea, Bering Strait, Coral Sea, East China Sea, Gulf of Alaska, Gulf of Tonkin, Philippine Sea, Sea of Japan, Sea of Okhotsk, South China Sea, Tasman Sea, and other tributary water bodies
Area - comparative:	about 15 times the size of the US; covers about 28% of the global surface; larger than the total land area of the world
Coastline:	135,663 km
Climate:	planetary air pressure systems and resultant wind patterns exhibit remarkable uniformity in the south and east; trade winds and westerly winds are well-developed patterns, modified by seasonal fluctuations; tropical cyclones (hurricanes) may form south of Mexico from June to October and affect Mexico and Central America; continental influences cause climatic uniformity to be much less pronounced in the eastern and western regions at the same latitude in the North Pacific Ocean; the western Pacific is monsoonal - a rainy season occurs during the summer months, when moisture-laden winds blow from the ocean over the land, and a dry season during the winter months, when dry winds blow from the Asian landmass back to the ocean; tropical cyclones (typhoons) may strike southeast and east Asia from May to December
Terrain:	surface currents in the northern Pacific are dominated by a clockwise, warm-water gyre (broad circular system of currents) and in the southern Pacific by a counterclockwise, cool-water gyre; in the northern Pacific, sea ice forms in the Bering Sea and Sea of Okhotsk in winter; in the southern Pacific, sea ice from Antarctica reaches its northernmost extent in October; the ocean floor in the eastern Pacific is dominated by the East Pacific Rise, while the western Pacific is dissected by deep trenches, including the Mariana Trench, which is the world's deepest
Elevation extremes:	lowest point: Challenger Deep in the Mariana Trench -10,924 m highest point: sea level 0 m
Natural resources:	oil and gas fields, polymetallic nodules, sand and gravel aggregates, placer deposits, fish
Natural hazards:	surrounded by a zone of violent volcanic and earthquake activity sometimes referred to as the "Pacific Ring of Fire"; subject to tropical cyclones (typhoons) in southeast and east Asia from May to December (most frequent from July to October); tropical cyclones (hurricanes) may form south of Mexico and strike Central America and Mexico from June to October (most common in August and September); cyclical El Nino/La Nina phenomenon occurs in the equatorial Pacific, influencing weather in the Western Hemisphere and the western Pacific; ships subject to superstructure icing in extreme north from October to May; persistent fog in the northern Pacific can be a maritime hazard from June to December
Environment - current issues:	endangered marine species include the dugong, sea lion, sea otter, seals, turtles, and whales; oil pollution in Philippine Sea and South China Sea
Geography - note:	the major chokepoints are the Bering Strait, Panama Canal, Luzon Strait, and the Singapore Strait; the Equator divides the Pacific Ocean into the North Pacific Ocean and the South Pacific Ocean; dotted with low coral islands and rugged volcanic islands in the southwestern Pacific Ocean

Indian Ocean extends from Antarctica to the continent of Asia including the Red Sea and Persian Gulf. The Indian Ocean is the third largest of the world's five oceans (after the Pacific Ocean and Atlantic Ocean, but larger than the Southern Ocean and Arctic Ocean). Four critically important access waterways are the Suez Canal (Egypt), Bab el Mandeb (Djibouti-Yemen), Strait of Hormuz (Iran-Oman), and Strait of Malacca (Indonesia-Malaysia).

Location:	body of water between Africa, the Southern Ocean, Asia, and Australia
Geographic coordinates:	20 00 S, 80 00 E
Map references:	Political Map of the World
Area:	total: 68.556 million sq km note: includes Andaman Sea, Arabian Sea, Bay of Bengal, Flores Sea, Great Australian Bight, Gulf of Aden, Gulf of Oman, Java Sea, Mozambique Channel, Persian Gulf, Red Sea, Savu Sea, Strait of Malacca, Timor Sea, and other tributary water bodies
Area - comparative:	about 5.5 times the size of the US
Coastline:	66,526 km
Climate:	northeast monsoon (December to April), southwest monsoon (June to October); tropical cyclones occur during May/June and October/November in the northern Indian Ocean and January/February in the southern Indian Ocean
Terrain:	surface dominated by counterclockwise gyre (broad, circular system of currents) in the southern Indian Ocean; unique reversal of surface currents in the northern Indian Ocean; low atmospheric pressure over southwest Asia from hot, rising, summer air results in the southwest monsoon and southwest-to-northeast winds and currents, while high pressure over northern Asia from cold, falling, winter air results in the northeast monsoon and northeast-to-southwest winds and currents; ocean floor is dominated by the Mid-Indian Ocean Ridge and subdivided by the Southeast Indian Ocean Ridge, Southwest Indian Ocean Ridge, and Ninetyeast Ridge
Elevation extremes:	lowest point: Java Trench -7,258 m highest point: sea level 0 m
Natural resources:	oil and gas fields, fish, shrimp, sand and gravel aggregates, placer deposits, polymetallic nodules
Natural hazards:	occasional icebergs pose navigational hazard in southern reaches
Environment - current issues:	endangered marine species include the dugong, seals, turtles, and whales; oil pollution in the Arabian Sea, Persian Gulf, and Red Sea
Geography - note:	major chokepoints include Bab el Mandeb, Strait of Hormuz, Strait of Malacca, southern access to the Suez Canal, and the Lombok Strait

Southern Ocean
Some authors use the name Southern Ocean to describe the ocean surrounding Antarctica.
A decision by the International Hydrographic Organization in the spring of 2000 delimited a fifth world ocean - the Southern Ocean - from the southern portions of the Atlantic Ocean, Indian Ocean, and Pacific Ocean. The Southern Ocean extends from the coast of Antarctica north to 60 degrees south latitude, which coincides with the Antarctic Treaty Limit. The Southern Ocean is now the fourth largest of the world's five oceans (after the Pacific Ocean, Atlantic Ocean, and Indian Ocean, but larger than the Arctic Ocean).

Location:	body of water between 60 degrees south latitude and Antarctica
Geographic coordinates:	65 00 S, 0 00 E (nominally), but the Southern Ocean has the unique distinction of being a large circumpolar body of water totally encircling the continent of Antarctica; this ring of water lies between 60 degrees south latitude and the coast of Antarctica and encompasses 360 degrees of longitude
Map references:	Antarctic Region
Area:	total: 20.327 million sq km note: includes Amundsen Sea, Bellingshausen Sea, part of the Drake Passage, Ross Sea, a small part of the Scotia Sea, Weddell Sea, and other tributary water bodies
Area - comparative:	slightly more than twice the size of the US
Coastline:	17,968 km
Climate:	sea temperatures vary from about 10 degrees Celsius to -2 degrees Celsius; cyclonic storms travel eastward around the continent and frequently are intense because of the temperature contrast between ice and open ocean; the ocean area from about latitude 40 south to the Antarctic Circle has the strongest average winds found anywhere on Earth; in winter the ocean freezes outward to 65 degrees south latitude in the Pacific sector and 55 degrees south latitude in the Atlantic sector, lowering surface temperatures well below 0 degrees Celsius; at some coastal points intense persistent drainage winds from the interior keep the shoreline ice-free throughout the winter
Terrain:	the Southern Ocean is deep, 4,000 to 5,000 meters over most of its extent with only limited areas of shallow water; the Antarctic continental shelf is generally narrow and unusually deep, its edge lying at depths of 400 to 800 meters (the global mean is 133 meters); the Antarctic icepack grows from an average minimum of 2.6 million square kilometers in March to about 18.8 million square kilometers in September, better than a sixfold increase in area; the Antarctic Circumpolar Current (21,000 km in length) moves perpetually eastward; it is the world's largest ocean current, transporting 130 million cubic meters of water per second - 100 times the flow of all the world's rivers
Elevation extremes:	lowest point: -7,235 m at the southern end of the South Sandwich Trench highest point: sea level 0 m
Natural resources:	probable large and possible giant oil and gas fields on the continental margin, manganese nodules, possible placer deposits, sand and gravel, fresh water as icebergs; squid, whales, and seals - none exploited; krill, fishes
Natural hazards:	huge icebergs with drafts up to several hundred meters; smaller bergs and iceberg fragments; sea ice (generally 0.5 to 1 meter thick) with sometimes dynamic short-term variations and with large annual and interannual variations; deep continental shelf floored by glacial deposits varying widely over short distances; high winds and large waves much of the year; ship icing, especially May-October; most of region is remote from sources of search and rescue
Environment - current issues:	increased solar ultraviolet radiation resulting from the Antarctic ozone hole in recent years, reducing marine primary productivity (phytoplankton) by as much as 15% and damaging the DNA of some fish; illegal, unreported, and unregulated fishing in recent years, especially the landing of an estimated five to six times more Patagonian toothfish than the regulated fishery, which is likely to affect the sustainability of the stock; large amount of incidental mortality of seabirds resulting from long-line fishing for toothfish note: the now-protected fur seal population is making a strong comeback after severe overexploitation in the 18th and 19th centuries
Environment - international agreements:	the Southern Ocean is subject to all international agreements regarding the world's oceans; in addition, it is subject to these agreements specific to the Antarctic region: International Whaling Commission (prohibits commercial whaling south of 40 degrees south [south of 60 degrees south between 50 degrees and 130 degrees west]); Convention on the Conservation of Antarctic Seals (limits sealing); Convention on the Conservation of Antarctic Marine Living Resources (regulates fishing) note: many nations (including the US) prohibit mineral resource exploration and exploitation south of the fluctuating Polar Front (Antarctic Convergence) which is in the middle of the Antarctic Circumpolar Current and serves as the dividing line between the very cold polar surface waters to the south and the warmer waters to the north
Geography - note:	the major chokepoint is the Drake Passage between South America and Antarctica; the Polar Front (Antarctic Convergence) is the best natural definition of the northern extent of the Southern Ocean; it is a distinct region at the middle of the Antarctic Circumpolar Current that separates the very cold polar surface waters to the south from the warmer waters to the north; the Front and the Current extend entirely around Antarctica, reaching south of 60 degrees south near New Zealand and near 48 degrees south in the far South Atlantic coinciding with the path of the maximum westerly winds

The Arctic Ocean is the smallest of the world's five oceans (after the Pacific Ocean, Atlantic Ocean, Indian Ocean, and the recently delimited Southern Ocean). The Northwest Passage (US and

Canada

) and Northern Sea Route (

Norway

and

Russia

) are two important seasonal waterways. A sparse network of air, ocean, river, and land routes circumscribes the Arctic Ocean.

Location:	body of water between Europe, Asia, and North America, mostly north of the Arctic Circle
Geographic coordinates:	90 00 N, 0 00 E
Map references:	Arctic Region
Area:	total: 14.056 million sq km note: includes Baffin Bay, Barents Sea, Beaufort Sea, Chukchi Sea, East Siberian Sea, Greenland Sea, Hudson Bay, Hudson Strait, Kara Sea, Laptev Sea, Northwest Passage, and other tributary water bodies
Area - comparative:	slightly less than 1.5 times the size of the US
Coastline:	45,389 km
Climate:	polar climate characterized by persistent cold and relatively narrow annual temperature ranges; winters characterized by continuous darkness, cold and stable weather conditions, and clear skies; summers characterized by continuous daylight, damp and foggy weather, and weak cyclones with rain or snow
Terrain:	central surface covered by a perennial drifting polar icepack that averages about 3 meters in thickness, although pressure ridges may be three times that size; clockwise drift pattern in the Beaufort Gyral Stream, but nearly straight-line movement from the New Siberian Islands (Russia) to Denmark Strait (between Greenland and Iceland); the icepack is surrounded by open seas during the summer, but more than doubles in size during the winter and extends to the encircling landmasses; the ocean floor is about 50% continental shelf (highest percentage of any ocean) with the remainder a central basin interrupted by three submarine ridges (Alpha Cordillera, Nansen Cordillera, and Lomonosov Ridge)
Elevation extremes:	lowest point: Fram Basin -4,665 m highest point: sea level 0 m
Natural resources:	sand and gravel aggregates, placer deposits, polymetallic nodules, oil and gas fields, fish, marine mammals (seals and whales)
Natural hazards:	ice islands occasionally break away from northern Ellesmere Island; icebergs calved from glaciers in western Greenland and extreme northeastern Canada; permafrost in islands; virtually ice locked from October to June; ships subject to superstructure icing from October to May
Environment - current issues:	endangered marine species include walruses and whales; fragile ecosystem slow to change and slow to recover from disruptions or damage; thinning polar icepack
Geography - note:	major chokepoint is the southern Chukchi Sea (northern access to the Pacific Ocean via the Bering Strait); strategic location between North America and Russia; shortest marine link between the extremes of eastern and western Russia; floating research stations operated by the US and Russia; maximum snow cover in March or April about 20 to 50 centimeters over the frozen ocean; snow cover lasts about 10 mon

The oceans of Earth are unique in our Solar System. No other planet in our Solar System has liquid water (although recent finds on Mars indicate that Mars may have had some liquid water in the recent past). Life on Earth originated in the seas, and the oceans continue to be home to an incredibly diverse web of life.

Ocean Functions
The oceans of Earth serve many functions, especially affecting the weather and temperature. They moderate the Earth’s temperature by absorbing incoming solar radiation (stored as heat energy). The always-moving ocean currents distribute this heat energy around the globe. This heats the land and air during winter and cools it during summer.

The motions of the atmosphere, traced out by clouds, and the size of the oceans dominate the view of earth from space. So vast are the oceans, in fact, that they take up almost 71% of the entire surface of the globe (139 million square miles). The oceans have an average depth of 12,230 feet (3730 m) and reach the deepest point in the Mariana Trench of the northwester Pacific Ocean, at 36,204 feet (11,038m) below sea level. The ocean basins hold at vast quantity of water, over 285 million cubic miles of water (1185 million cu. km.). This vast quantity of water arose from the Earth’s interior as it cooled.

Marine Organisms
The oceans are the largest repositories of organisms on the planet, with representatives from all phyla. Life is extremely abundant in the sea, from the obvious large whales, fish, corals, shrimp, krill and seaweed, to the microscopic bacteria floating freely in the seas. The bacteria is so abundant that just one spoonful of ocean water contains from 100 - 1,000,000 bacteria cells per cubic centimetre!

Water surrounds all marine organisms, composes the greater bulk of their bodies, and is the medium by which various chemical reactions take place, both inside and outside of their bodies.

Marine organisms face a variety of challenges in their quest for life and reproduction. They must obtain food for growth and survival, avoid being food for other organisms, cope with the physical environment, and have an effective strategy for bringing forth reproducing offspring.

Ocean	Area (square miles)	Average Depth (ft)	Deepest depth (ft)
Pacific Ocean	64,186,000	15,215	Mariana Trench, 36,200 ft deep
Atlantic Ocean	33,420,000	12,881	Puerto Rico Trench, 28,231 ft deep
Indian Ocean	28,350,000	13,002	Java Trench, 25,344 ft deep
Southern Ocean	7,848,300 sq. miles (20.327 million sq km )	13,100 - 16,400 ft deep (4,000 to 5,000 meters)	the southern end of the South Sandwich Trench, 23,736 ft (7,235 m) deep
Arctic Ocean	5,106,000	3,953	Eurasia Basin, 17,881 ft deep