Misplaced Pages

#72927

100-644: Originating from the eastward directed flow occurring east of the island of Honshu, Japan, the North Pacific Current extends over 40° of longitude. According to the Great Soviet Encyclopedia, the NPC may be considered to be a part or an extension of the Kuroshio current. The current covers a large area and brings warmer water from the subtropics to the sub-polar latitudes. Average sea surface temperature along

200-654: A continental shelf are often warmer. Onshore winds can cause a considerable warm-up even in areas where upwelling is fairly constant, such as the northwest coast of South America . Its values are important within numerical weather prediction as the sea surface temperature influences the atmosphere above, such as in the formation of sea breezes and sea fog . It is very likely that global mean sea surface temperature increased by 0.88°C between 1850–1900 and 2011–2020 due to global warming , with most of that warming (0.60°C) occurring between 1980 and 2020. The temperatures over land are rising faster than ocean temperatures . This

300-410: A halocline . If a zone undergoes a strong, vertical chemistry gradient with depth, it contains a chemocline . Temperature and salinity control ocean water density. Colder and saltier water is denser, and this density plays a crucial role in regulating the global water circulation within the ocean. The halocline often coincides with the thermocline, and the combination produces a pronounced pycnocline ,

400-489: A mid-ocean ridge , which creates a long mountain range beneath the ocean. Together they form the global mid-oceanic ridge system that features the longest mountain range in the world. The longest continuous mountain range is 65,000 km (40,000 mi). This underwater mountain range is several times longer than the longest continental mountain range – the Andes . Oceanographers state that less than 20% of

500-422: A depth of a few hundred meters or less. Human activity often has negative impacts on marine life within the continental shelf. Ocean temperatures depend on the amount of solar radiation reaching the ocean surface. In the tropics, surface temperatures can rise to over 30 °C (86 °F). Near the poles where sea ice forms, the temperature in equilibrium is about −2 °C (28 °F). In all parts of

600-530: A fraction of a millimetre thick) in the infrared or the top centimetre or so in the microwave are also used, but must be adjusted to be compatible with the bulk temperature." The temperature further below that is called ocean temperature or deeper ocean temperature . Ocean temperatures (more than 20 metres below the surface) also vary by region and time, and they contribute to variations in ocean heat content and ocean stratification . The increase of both ocean surface temperature and deeper ocean temperature

700-579: A gentle breeze on a pond causes ripples to form. A stronger gust blowing over the ocean causes larger waves as the moving air pushes against the raised ridges of water. The waves reach their maximum height when the rate at which they are travelling nearly matches the speed of the wind. In open water, when the wind blows continuously as happens in the Southern Hemisphere in the Roaring Forties , long, organized masses of water called swell roll across

800-405: A higher altitude (e.g., at the 500  hPa level, or 5.9 km) can lead to tropical cyclogenesis at lower water temperatures, as a certain lapse rate is required to force the atmosphere to be unstable enough for convection. In a moist atmosphere, this lapse rate is 6.5 °C/km, while in an atmosphere with less than 100% relative humidity , the required lapse rate is 9.8 °C/km. At

900-628: A lesser degree due to its greater thermal inertia . On calm days, the temperature can vary by 6 °C (10 °F). The temperature of the ocean at depth lags the Earth's atmosphere temperature by 15 days per 10 metres (33 ft), which means for locations like the Aral Sea , temperatures near its bottom reach a maximum in December and a minimum in May and June. Near the coastline, some offshore and longshore winds move

1000-461: A one-day lag. NOAA's GOES (Geostationary Orbiting Earth Satellites) satellites are geo-stationary above the Western Hemisphere which enables them to deliver SST data on an hourly basis with only a few hours of lag time. There are several difficulties with satellite-based absolute SST measurements. First, in infrared remote sensing methodology the radiation emanates from the top "skin" of

1100-496: A shallow area and this, coupled with a low pressure system, can raise the surface of the ocean dramatically above a typical high tide. The average depth of the oceans is about 4 km. More precisely the average depth is 3,688 meters (12,100 ft). Nearly half of the world's marine waters are over 3,000 meters (9,800 ft) deep. "Deep ocean," which is anything below 200 meters (660 ft), covers about 66% of Earth's surface. This figure does not include seas not connected to

SECTION 10

#1732837994073

1200-403: A wave-cut platform develops at the foot of the cliff and this has a protective effect, reducing further wave-erosion. Material worn from the margins of the land eventually ends up in the sea. Here it is subject to attrition as currents flowing parallel to the coast scour out channels and transport sand and pebbles away from their place of origin. Sediment carried to the sea by rivers settles on

1300-406: A zone undergoes dramatic changes in temperature with depth, it contains a thermocline , a distinct boundary between warmer surface water and colder deep water. In tropical regions, the thermocline is typically deeper compared to higher latitudes. Unlike polar waters , where solar energy input is limited, temperature stratification is less pronounced, and a distinct thermocline is often absent. This

1400-486: Is 5 years. When this warming or cooling occurs for only seven to nine months, it is classified as El Niño/La Niña "conditions"; when it occurs for more than that period, it is classified as El Niño/La Niña "episodes". The sign of an El Niño in the sea surface temperature pattern is when warm water spreads from the west Pacific and the Indian Ocean to the east Pacific. It takes the rain with it, causing extensive drought in

1500-439: Is a bay , a small bay with a narrow inlet is a cove and a large bay may be referred to as a gulf . Coastlines are influenced by several factors including the strength of the waves arriving on the shore, the gradient of the land margin, the composition and hardness of the coastal rock, the inclination of the off-shore slope and the changes of the level of the land due to local uplift or submergence. Normally, waves roll towards

1600-411: Is an important effect of climate change on oceans . The extent of the ocean surface down into the ocean is influenced by the amount of mixing that takes place between the surface water and the deeper water. This depends on the temperature: in the tropics the warm surface layer of about 100 m is quite stable and does not mix much with deeper water, while near the poles winter cooling and storms makes

1700-492: Is an important driver of North Atlantic SST and Northern Hemisphere climate, but the mechanisms controlling AMO variability remain poorly understood. Atmospheric internal variability, changes in ocean circulation, or anthropogenic drivers may control the multidecadal temperature variability associated with AMO. These changes in North Atlantic SST may influence winds in the subtropical North Pacific and produce warmer SSTs in

1800-444: Is an important reference point for oceanography and geography, particularly as mean sea level . The ocean surface has globally little, but measurable topography , depending on the ocean's volumes. The ocean surface is a crucial interface for oceanic and atmospheric processes. Allowing interchange of particles, enriching the air and water, as well as grounds by some particles becoming sediments . This interchange has fertilized life in

1900-408: Is because the ocean absorbs about 90% of excess heat generated by climate change . Sea surface temperature (SST), or ocean surface temperature, is the water temperature close to the ocean 's surface. The exact meaning of surface varies according to the measurement method used, but it is between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. For comparison,

2000-411: Is customarily divided into five principal oceans – listed below in descending order of area and volume: The ocean fills Earth's oceanic basins . Earth's oceanic basins cover different geologic provinces of Earth's oceanic crust as well as continental crust . As such it covers mainly Earth's structural basins , but also continental shelfs . In mid-ocean, magma is constantly being thrust through

2100-399: Is due to the fact that surface waters in polar latitudes are nearly as cold as deeper waters. Below the thermocline, water everywhere in the ocean is very cold, ranging from −1 °C to 3 °C. Because this deep and cold layer contains the bulk of ocean water, the average temperature of the world ocean is 3.9 °C. If a zone undergoes dramatic changes in salinity with depth, it contains

SECTION 20

#1732837994073

2200-452: Is irregular, unevenly dominating the Earth's surface . This leads to the distinction of the Earth's surface into a water and land hemisphere , as well as the division of the ocean into different oceans. Seawater covers about 361,000,000 km (139,000,000 sq mi) and the ocean's furthest pole of inaccessibility , known as " Point Nemo ", in a region known as spacecraft cemetery of

2300-656: Is made by sensing the ocean radiation in two or more wavelengths within the infrared part of the electromagnetic spectrum or other parts of the spectrum which can then be empirically related to SST. These wavelengths are chosen because they are: The satellite-measured SST provides both a synoptic view of the ocean and a high frequency of repeat views, allowing the examination of basin-wide upper ocean dynamics not possible with ships or buoys. NASA's (National Aeronautic and Space Administration) Moderate Resolution Imaging Spectroradiometer (MODIS) SST satellites have been providing global SST data since 2000, available with

2400-797: Is maintained by the National Data Buoy Center (NDBC). Between 1985 and 1994, an extensive array of moored and drifting buoys was deployed across the equatorial Pacific Ocean designed to help monitor and predict the El Niño phenomenon. Weather satellites have been available to determine sea surface temperature information since 1967, with the first global composites created during 1970. Since 1982, satellites have been increasingly utilized to measure SST and have allowed its spatial and temporal variation to be viewed more fully. Satellite measurements of SST are in reasonable agreement with in situ temperature measurements. The satellite measurement

2500-407: Is medium confidence that the tropical Pacific will transition to a mean pattern resembling that of El Niño on centennial time scale, but there is still high uncertainty in tropical Pacific SST projections because it is difficult to capture El Niño variability in climate models. Overall, scientists project that all regions of the oceans will warm by 2050, but models disagree for SST changes expected in

2600-454: Is produced and magma is forced up creating underwater mountains, some of which may form chains of volcanic islands near to deep trenches. Near some of the boundaries between the land and sea, the slightly denser oceanic plates slide beneath the continental plates and more subduction trenches are formed. As they grate together, the continental plates are deformed and buckle causing mountain building and seismic activity. Every ocean basin has

2700-407: Is pushed across the surface of the ocean by the wind, but this represents a transfer of energy and not horizontal movement of water. As waves approach land and move into shallow water , they change their behavior. If approaching at an angle, waves may bend ( refraction ) or wrap around rocks and headlands ( diffraction ). When the wave reaches a point where its deepest oscillations of the water contact

2800-423: Is reflected back out of the water. Red light is most easily absorbed and thus does not reach great depths, usually to less than 50 meters (164 ft). Blue light, in comparison, can penetrate up to 200 meters (656 ft). Second, water molecules and very tiny particles in ocean water preferentially scatter blue light more than light of other colors. Blue light scattering by water and tiny particles happens even in

2900-467: Is sometimes referred to as the World Ocean, global ocean or the great ocean . The concept of a continuous body of water with relatively unrestricted exchange between its components is critical in oceanography . The word ocean comes from the figure in classical antiquity , Oceanus ( / oʊ ˈ s iː ə n ə s / ; Ancient Greek : Ὠκεανός Ōkeanós , pronounced [ɔːkeanós] ),

3000-670: The North Sea or the Red Sea . There is no sharp distinction between seas and oceans, though generally seas are smaller, and are often partly (as marginal seas ) or wholly (as inland seas ) bordered by land. The contemporary concept of the World Ocean was coined in the early 20th century by the Russian oceanographer Yuly Shokalsky to refer to the continuous ocean that covers and encircles most of Earth. The global, interconnected body of salt water

3100-472: The South Pacific Ocean , at 48°52.6′S 123°23.6′W  /  48.8767°S 123.3933°W  / -48.8767; -123.3933  ( Point Nemo ) . This point is roughly 2,688 km (1,670 mi) from the nearest land. There are different customs to subdivide the ocean and are adjourned by smaller bodies of water such as, seas , gulfs , bays , bights , and straits . The ocean

North Pacific Current - Misplaced Pages Continue

3200-578: The Thames Barrier is designed to protect London from a storm surge, while the failure of the dykes and levees around New Orleans during Hurricane Katrina created a humanitarian crisis in the United States. Most of the ocean is blue in color, but in some places the ocean is blue-green, green, or even yellow to brown. Blue ocean color is a result of several factors. First, water preferentially absorbs red light, which means that blue light remains and

3300-410: The carbon cycle , and the water cycle by acting as a huge heat reservoir . Ocean scientists split the ocean into vertical and horizontal zones based on physical and biological conditions. The pelagic zone is the open ocean's water column from the surface to the ocean floor. The water column is further divided into zones based on depth and the amount of light present. The photic zone starts at

3400-406: The coastline and structure of the world ocean. A global ocean has existed in one form or another on Earth for eons. Since its formation the ocean has taken many conditions and shapes with many past ocean divisions and potentially at times covering the whole globe. During colder climatic periods, more ice caps and glaciers form, and enough of the global water supply accumulates as ice to lessen

3500-591: The ocean floor , they begin to slow down. This pulls the crests closer together and increases the waves' height , which is called wave shoaling . When the ratio of the wave's height to the water depth increases above a certain limit, it " breaks ", toppling over in a mass of foaming water. This rushes in a sheet up the beach before retreating into the ocean under the influence of gravity. Earthquakes , volcanic eruptions or other major geological disturbances can set off waves that can lead to tsunamis in coastal areas which can be very dangerous. The ocean's surface

3600-444: The sea surface skin temperature relates to the top 20 or so microns of the ocean's surface. The definition proposed by IPCC for sea surface temperature does not specify the number of metres but focuses more on measurement techniques: Sea surface temperature is "the subsurface bulk temperature in the top few metres of the ocean, measured by ships, buoys and drifters. [...] Satellite measurements of skin temperature (uppermost layer;

3700-572: The warm core that fuels tropical systems. This value is well above 16.1 °C (60.9 °F), the long term global average surface temperature of the oceans. However, this requirement can be considered only a general baseline because it assumes that the ambient atmospheric environment surrounding an area of disturbed weather presents average conditions. Tropical cyclones have intensified when SSTs were slightly below this standard temperature. Tropical cyclones are known to form even when normal conditions are not met. For example, cooler air temperatures at

3800-411: The 500 hPa level, the air temperature averages −7 °C (18 °F) within the tropics, but air in the tropics is normally dry at this height, giving the air room to wet-bulb , or cool as it moistens, to a more favorable temperature that can then support convection. A wet-bulb temperature at 500 hPa in a tropical atmosphere of −13.2 °C (8.2 °F) is required to initiate convection if

3900-442: The Earth's biosphere . Oceanic evaporation , as a phase of the water cycle, is the source of most rainfall (about 90%), causing a global cloud cover of 67% and a consistent oceanic cloud cover of 72%. Ocean temperatures affect climate and wind patterns that affect life on land. One of the most dramatic forms of weather occurs over the oceans: tropical cyclones (also called "typhoons" and "hurricanes" depending upon where

4000-452: The Moon are 20x stronger than the Moon's tidal forces on the Earth.) The primary effect of lunar tidal forces is to bulge Earth matter towards the near and far sides of the Earth, relative to the moon. The "perpendicular" sides, from which the Moon appears in line with the local horizon, experience "tidal troughs". Since it takes nearly 25 hours for the Earth to rotate under the Moon (accounting for

4100-403: The Moon's 28 day orbit around Earth), tides thus cycle over a course of 12.5 hours. However, the rocky continents pose obstacles for the tidal bulges, so the timing of tidal maxima may not actually align with the Moon in most localities on Earth, as the oceans are forced to "dodge" the continents. Timing and magnitude of tides vary widely across the Earth as a result of the continents. Thus, knowing

North Pacific Current - Misplaced Pages Continue

4200-468: The Moon's gravity, oceanic tides are also substantially modulated by the Sun's tidal forces, by the rotation of the Earth, and by the shape of the rocky continents blocking oceanic water flow. (Tidal forces vary more with distance than the "base" force of gravity: the Moon's tidal forces on Earth are more than double the Sun's, despite the latter's much stronger gravitational force on Earth. Earth's tidal forces upon

4300-400: The Moon's position does not allow a local to predict tide timings, instead requiring precomputed tide tables which account for the continents and the Sun, among others. During each tidal cycle, at any given place the tidal waters rise to maximum height, high tide, before ebbing away again to the minimum level, low tide. As the water recedes, it gradually reveals the foreshore , also known as

4400-444: The NPC can range in the winter from 45 to 61 °F (7.2-16.1 °C) and in the summer months 64 °F-74 °F (17.8-23.3 °C). As it flows from west to east, the latitudinal extent of the NPC increases so much that it spans some 20 degrees of latitude east of the dateline. This is associated with a decrease in the speed of current; eastward directed speeds at the surface are typically less than 0.05 m/s (5 cm/s) in

4500-643: The Okeanos is represented with a dragon-tail on some early Greek vases. Scientists believe that a sizable quantity of water would have been in the material that formed Earth. Water molecules would have escaped Earth's gravity more easily when it was less massive during its formation. This is called atmospheric escape . During planetary formation , Earth possibly had magma oceans . Subsequently, outgassing , volcanic activity and meteorite impacts , produced an early atmosphere of carbon dioxide , nitrogen and water vapor , according to current theories. The gases and

4600-706: The World Ocean, such as the Caspian Sea . The deepest region of the ocean is at the Mariana Trench , located in the Pacific Ocean near the Northern Mariana Islands . The maximum depth has been estimated to be 10,971 meters (35,994 ft). The British naval vessel Challenger II surveyed the trench in 1951 and named the deepest part of the trench the " Challenger Deep ". In 1960, the Trieste successfully reached

4700-421: The amounts in other parts of the water cycle. The reverse is true during warm periods. During the last ice age, glaciers covered almost one-third of Earth's land mass with the result being that the oceans were about 122 m (400 ft) lower than today. During the last global "warm spell," about 125,000 years ago, the seas were about 5.5 m (18 ft) higher than they are now. About three million years ago

4800-479: The atmosphere are thought to have accumulated over millions of years. After Earth's surface had significantly cooled, the water vapor over time would have condensed, forming Earth's first oceans. The early oceans might have been significantly hotter than today and appeared green due to high iron content. Geological evidence helps constrain the time frame for liquid water existing on Earth. A sample of pillow basalt (a type of rock formed during an underwater eruption)

4900-690: The behavior of the Earth's atmosphere above, so their initialization into atmospheric models is important. While sea surface temperature is important for tropical cyclogenesis , it is also important in determining the formation of sea fog and sea breezes. Heat from underlying warmer waters can significantly modify an air mass over distances as short as 35 kilometres (22 mi) to 40 kilometres (25 mi). For example, southwest of Northern Hemisphere extratropical cyclones , curved cyclonic flow bringing cold air across relatively warm water bodies can lead to narrow lake-effect snow (or sea effect) bands. Those bands bring strong localized precipitation , often in

5000-407: The bottom of the trench, manned by a crew of two men. Oceanographers classify the ocean into vertical and horizontal zones based on physical and biological conditions. The pelagic zone consists of the water column of the open ocean, and can be divided into further regions categorized by light abundance and by depth. The ocean zones can be grouped by light penetration into (from top to bottom):

5100-498: The central Pacific. As the NPC approaches the west coast of North America, it divides into two broad currents: the northward flowing Alaska Current and the southward flowing California Current. The splitting of flow is referred to as the bifurcation of the NPC. The Gulf of Alaska and the California Current receive different volumes and flows of warm water from the North Pacific Current. The Gulf of Alaska receives about 60% of

SECTION 50

#1732837994073

5200-501: The elder of the Titans in classical Greek mythology . Oceanus was believed by the ancient Greeks and Romans to be the divine personification of an enormous river encircling the world. The concept of Ōkeanós has an Indo-European connection. Greek Ōkeanós has been compared to the Vedic epithet ā-śáyāna-, predicated of the dragon Vṛtra-, who captured the cows/rivers. Related to this notion,

5300-583: The flow of the NPC while the California Current receives the remaining 40%. These values may fluctuate, resulting in changes in the volume and the speed of the NPC water entering into the Alaska and California Currents. The NPC forms the northward portion of the North Pacific Subtropical Gyre . As the eastward flow of the Kuroshio, the flow of the NPC can lead to the transport of material from

5400-453: The form of snow , since large water bodies such as lakes efficiently store heat that results in significant temperature differences—larger than 13 °C (23 °F)—between the water surface and the air above. Because of this temperature difference, warmth and moisture are transported upward, condensing into vertically oriented clouds which produce snow showers. The temperature decrease with height and cloud depth are directly affected by both

5500-412: The formation of unusually high rogue waves . Most waves are less than 3 m (10 ft) high and it is not unusual for strong storms to double or triple that height. Rogue waves, however, have been documented at heights above 25 meters (82 ft). The top of a wave is known as the crest, the lowest point between waves is the trough and the distance between the crests is the wavelength. The wave

5600-571: The greatest rates of warming in the tropical Indian Ocean, western Pacific Ocean, and western boundary currents of the subtropical gyres . However, the eastern Pacific Ocean, subtropical North Atlantic Ocean, and Southern Ocean have warmed more slowly than the global average or have experienced cooling since the 1950s. Ocean currents , such as the Atlantic Multidecadal Oscillation , can affect sea surface temperatures over several decades. The Atlantic Multidecadal Oscillation (AMO)

5700-497: The immediate sea surface, general temperature measurements are accompanied by a reference to the specific depth of measurement. This is because of significant differences encountered between measurements made at different depths, especially during the daytime when low wind speed and high sunshine conditions may lead to the formation of a warm layer at the ocean's surface and strong vertical temperature gradients (a diurnal thermocline ). Sea surface temperature measurements are confined to

5800-421: The interface between water and air is called swell – a term used in sailing , surfing and navigation . These motions profoundly affect ships on the surface of the ocean and the well-being of people on those ships who might suffer from sea sickness . Wind blowing over the surface of a body of water forms waves that are perpendicular to the direction of the wind. The friction between air and water caused by

5900-482: The intertidal zone. The difference in height between the high tide and low tide is known as the tidal range or tidal amplitude. When the sun and moon are aligned (full moon or new moon), the combined effect results in the higher "spring tides", while the sun and moon misaligning (half moons) result in lesser tidal ranges. In the open ocean tidal ranges are less than 1 meter, but in coastal areas these tidal ranges increase to more than 10 meters in some areas. Some of

6000-661: The largest tidal ranges in the world occur in the Bay of Fundy and Ungava Bay in Canada, reaching up to 16 meters. Other locations with record high tidal ranges include the Bristol Channel between England and Wales, Cook Inlet in Alaska, and the Río Gallegos in Argentina. Tides are not to be confused with storm surges , which can occur when high winds pile water up against the coast in

6100-404: The last 130 years due to the way they were taken. In the nineteenth century, measurements were taken in a bucket off a ship. However, there was a slight variation in temperature because of the differences in buckets. Samples were collected in either a wood or an uninsulated canvas bucket, but the canvas bucket cooled quicker than the wood bucket. The sudden change in temperature between 1940 and 1941

SECTION 60

#1732837994073

6200-466: The majority of Earth's surface. It includes the Pacific , Atlantic , Indian , Southern/Antarctic , and Arctic oceans. As a general term, "the ocean" and "the sea" are often interchangeable. Strictly speaking, a "sea" is a body of water (generally a division of the world ocean) partly or fully enclosed by land. The word "sea" can also be used for many specific, much smaller bodies of seawater, such as

6300-432: The mid-levels of the troposphere , roughly at the 500 hPa level, is normally a requirement for development. However, when dry air is found at the same height, temperatures at 500 hPa need to be even colder as dry atmospheres require a greater lapse rate for instability than moist atmospheres. At heights near the tropopause , the 30-year average temperature (as measured in the period encompassing 1961 through 1990)

6400-440: The ocean , approximately the top 0.01 mm or less, which may not represent the bulk temperature of the upper meter of ocean due primarily to effects of solar surface heating during the daytime, reflected radiation, as well as sensible heat loss and surface evaporation. All these factors make it somewhat difficult to compare satellite data to measurements from buoys or shipboard methods, complicating ground truth efforts. Secondly,

6500-408: The ocean faces many environmental threats, such as marine pollution , overfishing , and the effects of climate change . Those effects include ocean warming , ocean acidification and sea level rise . The continental shelf and coastal waters are most affected by human activity. The terms "the ocean" or "the sea" used without specification refer to the interconnected body of salt water covering

6600-688: The ocean, deep ocean temperatures range between −2 °C (28 °F) and 5 °C (41 °F). Constant circulation of water in the ocean creates ocean currents . Those currents are caused by forces operating on the water, such as temperature and salinity differences, atmospheric circulation (wind), and the Coriolis effect . Tides create tidal currents, while wind and waves cause surface currents. The Gulf Stream , Kuroshio Current , Agulhas Current and Antarctic Circumpolar Current are all major ocean currents. Such currents transport massive amounts of water, gases, pollutants and heat to different parts of

6700-508: The ocean, on land and air. All these processes and components together make up ocean surface ecosystems . Tides are the regular rise and fall in water level experienced by oceans, primarily driven by the Moon 's gravitational tidal forces upon the Earth. Tidal forces affect all matter on Earth, but only fluids like the ocean demonstrate the effects on human timescales. (For example, tidal forces acting on rock may produce tidal locking between two planetary bodies.) Though primarily driven by

6800-469: The ocean. If the wind dies down, the wave formation is reduced, but already-formed waves continue to travel in their original direction until they meet land. The size of the waves depends on the fetch , the distance that the wind has blown over the water and the strength and duration of that wind. When waves meet others coming from different directions, interference between the two can produce broken, irregular seas. Constructive interference can lead to

6900-419: The oceans absorb CO 2 from the atmosphere , a higher concentration leads to ocean acidification (a drop in pH value ). The ocean provides many benefits to humans such as ecosystem services , access to seafood and other marine resources , and a means of transport . The ocean is known to be the habitat of over 230,000 species , but may hold considerably more – perhaps over two million species. Yet,

7000-425: The oceans could have been up to 50 m (165 ft) higher. The entire ocean, containing 97% of Earth's water, spans 70.8% of Earth 's surface, making it Earth's global ocean or world ocean . This makes Earth, along with its vibrant hydrosphere a "water world" or " ocean world ", particularly in Earth's early history when the ocean is thought to have possibly covered Earth completely. The ocean's shape

7100-434: The oceans have been mapped. The zone where land meets sea is known as the coast , and the part between the lowest spring tides and the upper limit reached by splashing waves is the shore . A beach is the accumulation of sand or shingle on the shore. A headland is a point of land jutting out into the sea and a larger promontory is known as a cape . The indentation of a coastline, especially between two headlands,

7200-533: The oceans may have always been on the Earth since the beginning of the planet's formation. In this model, atmospheric greenhouse gases kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity . The origin of Earth's oceans is unknown. Oceans are thought to have formed in the Hadean eon and may have been the cause for the emergence of life . Plate tectonics , post-glacial rebound , and sea level rise continually change

7300-451: The photic zone, the mesopelagic zone and the aphotic deep ocean zone: The pelagic part of the aphotic zone can be further divided into vertical regions according to depth and temperature: Distinct boundaries between ocean surface waters and deep waters can be drawn based on the properties of the water. These boundaries are called thermoclines (temperature), haloclines (salinity), chemoclines (chemistry), and pycnoclines (density). If

7400-418: The power of a storm wave impacting on the foot of a cliff has a shattering effect as air in cracks and crevices is compressed and then expands rapidly with release of pressure. At the same time, sand and pebbles have an erosive effect as they are thrown against the rocks. This tends to undercut the cliff, and normal weathering processes such as the action of frost follows, causing further destruction. Gradually,

7500-420: The satellite cannot look through clouds, creating a cool bias in satellite-derived SSTs within cloudy areas. However, passive microwave techniques can accurately measure SST and penetrate cloud cover. Within atmospheric sounder channels on weather satellites , which peak just above the ocean's surface, knowledge of the sea surface temperature is important to their calibration. Sea surface temperature affects

7600-455: The seabed between adjoining plates to form mid-oceanic ridges and here convection currents within the mantle tend to drive the two plates apart. Parallel to these ridges and nearer the coasts, one oceanic plate may slide beneath another oceanic plate in a process known as subduction . Deep trenches are formed here and the process is accompanied by friction as the plates grind together. The movement proceeds in jerks which cause earthquakes, heat

7700-407: The seabed causing deltas to form in estuaries. All these materials move back and forth under the influence of waves, tides and currents. Dredging removes material and deepens channels but may have unexpected effects elsewhere on the coastline. Governments make efforts to prevent flooding of the land by the building of breakwaters , seawalls , dykes and levees and other sea defences. For instance,

7800-401: The shore at the rate of six to eight per minute and these are known as constructive waves as they tend to move material up the beach and have little erosive effect. Storm waves arrive on shore in rapid succession and are known as destructive waves as the swash moves beach material seawards. Under their influence, the sand and shingle on the beach is ground together and abraded. Around high tide,

7900-399: The source of the food supply which sustains most of the ocean ecosystem . Ocean photosynthesis also produces half of the oxygen in the Earth's atmosphere. Light can only penetrate a few hundred more meters; the rest of the deeper ocean is cold and dark (these zones are called mesopelagic and aphotic zones). The continental shelf is where the ocean meets dry land. It is more shallow, with

8000-511: The subpolar North Atlantic, the equatorial Pacific, and the Southern Ocean. The future global mean SST increase for the period 1995-2014 to 2081-2100 is 0.86°C under the most modest greenhouse gas emissions scenarios, and up to 2.89°C under the most severe emissions scenarios. There are a variety of techniques for measuring this parameter that can potentially yield different results because different things are actually being measured. Away from

8100-412: The surface and is defined to be "the depth at which light intensity is only 1% of the surface value" (approximately 200 m in the open ocean). This is the zone where photosynthesis can occur. In this process plants and microscopic algae (free floating phytoplankton ) use light, water, carbon dioxide, and nutrients to produce organic matter. As a result, the photic zone is the most biodiverse and

8200-424: The surface layer denser and it mixes to great depth and then stratifies again in summer. This is why there is no simple single depth for ocean surface . The photic depth of the ocean is typically about 100 m and is related to this heated surface layer. It can be up to around 200 m deep in the open ocean . The sea surface temperature (SST) has a diurnal range , just like the Earth's atmosphere above, though to

8300-681: The surface temperature signature due to tropical cyclones . In general, an SST cooling is observed after the passing of a hurricane, primarily as the result of mixed layer deepening and surface heat losses. In the wake of several day long Saharan dust outbreaks across the adjacent northern Atlantic Ocean, sea surface temperatures are reduced 0.2 C to 0.4 C (0.3 to 0.7 F). Other sources of short-term SST fluctuation include extratropical cyclones , rapid influxes of glacial fresh water and concentrated phytoplankton blooms due to seasonal cycles or agricultural run-off. The tropical ocean has been warming faster than other regions since 1950, with

8400-410: The surface. The exact meaning of surface varies in the literature and in practice. It is usually between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface. Sea surface temperatures greatly modify air masses in the Earth's atmosphere within a short distance of the shore. The thermohaline circulation has a major impact on average sea surface temperature throughout most of

8500-456: The system forms). As the world's ocean is the principal component of Earth's hydrosphere , it is integral to life on Earth, forms part of the carbon cycle and water cycle , and – as a huge heat reservoir – influences climate and weather patterns. The motions of the ocean surface, known as undulations or wind waves , are the partial and alternate rising and falling of the ocean surface. The series of mechanical waves that propagate along

8600-451: The term ocean also refers to any of the large bodies of water into which the world ocean is conventionally divided. The following names describe five different areas of the ocean: Pacific , Atlantic , Indian , Antarctic/Southern , and Arctic . The ocean contains 97% of Earth's water and is the primary component of Earth's hydrosphere and is thereby essential to life on Earth. The ocean influences climate and weather patterns,

8700-523: The top portion of the ocean, known as the near-surface layer. The sea surface temperature was one of the first oceanographic variables to be measured. Benjamin Franklin suspended a mercury thermometer from a ship while travelling between the United States and Europe in his survey of the Gulf Stream in the late eighteenth century. SST was later measured by dipping a thermometer into a bucket of water that

8800-434: The very clearest ocean water, and is similar to blue light scattering in the sky . Ocean water represents the largest body of water within the global water cycle (oceans contain 97% of Earth's water ). Evaporation from the ocean moves water into the atmosphere to later rain back down onto land and the ocean. Oceans have a significant effect on the biosphere . The ocean as a whole is thought to cover approximately 90% of

8900-498: The warm waters near the surface offshore, and replace them with cooler water from below in the process known as Ekman transport . This pattern generally increases nutrients for marine life in the region, and can have a profound effect in some regions where the bottom waters are particularly nutrient-rich. Offshore of river deltas , freshwater flows over the top of the denser seawater, which allows it to heat faster due to limited vertical mixing. Remotely sensed SST can be used to detect

9000-416: The water temperature and the large-scale environment. The stronger the temperature decrease with height, the taller the clouds get, and the greater the precipitation rate becomes. Ocean temperature of at least 26.5 °C (79.7 °F ) spanning through at minimum a 50- metre depth is one of the precursors needed to maintain a tropical cyclone (a type of mesocyclone ). These warm waters are needed to maintain

9100-405: The water temperature is 26.5 °C (79.7 °F), and this temperature requirement increases or decreases proportionally by 1 °C in the sea surface temperature for each 1 °C change at 500 hpa. Inside a cold cyclone , 500 hPa temperatures can fall as low as −30 °C (−22 °F), which can initiate convection even in the driest atmospheres. This also explains why moisture in

9200-420: The western Pacific Ocean. El Niño is defined by prolonged differences in Pacific Ocean surface temperatures when compared with the average value. The accepted definition is a warming or cooling of at least 0.5 °C (0.9 °F) averaged over the east-central tropical Pacific Ocean. Typically, this anomaly happens at irregular intervals of 2–7 years and lasts nine months to two years. The average period length

9300-707: The western Pacific and rainfall in the normally dry eastern Pacific. El Niño's warm rush of nutrient-poor tropical water, heated by its eastward passage in the Equatorial Current, replaces the cold, nutrient-rich surface water of the Humboldt Current . When El Niño conditions last for many months, extensive ocean warming and the reduction in Easterly Trade winds limits upwelling of cold nutrient-rich deep water and its economic impact to local fishing for an international market can be serious. Among scientists, there

9400-538: The western Pacific to the coast of North America. For example, some of the marine debris from the Japanese earthquake and tsunami of 2011 was transported by the NPC across the Pacific, leading to deposition of tsunami debris along the shores of Alaska, British Columbia, Washington and Oregon. Sea surface temperature Sea surface temperature (or ocean surface temperature ) is the temperature of ocean water close to

9500-592: The world's oceans. Warm sea surface temperatures can develop and strengthen cyclones over the ocean . Tropical cyclones can also cause a cool wake. This is due to turbulent mixing of the upper 30 metres (100 ft) of the ocean. Sea surface temperature changes during the day. This is like the air above it, but to a lesser degree. There is less variation in sea surface temperature on breezy days than on calm days. Coastal sea surface temperatures can cause offshore winds to generate upwelling , which can significantly cool or warm nearby landmasses, but shallower waters over

9600-476: The world, and from the surface into the deep ocean. All this has impacts on the global climate system . Ocean water contains dissolved gases, including oxygen , carbon dioxide and nitrogen . An exchange of these gases occurs at the ocean's surface. The solubility of these gases depends on the temperature and salinity of the water. The carbon dioxide concentration in the atmosphere is rising due to CO 2 emissions , mainly from fossil fuel combustion. As

9700-459: Was manually drawn from the sea surface. The first automated technique for determining SST was accomplished by measuring the temperature of water in the intake port of large ships, which was underway by 1963. These observations have a warm bias of around 0.6 °C (1 °F) due to the heat of the engine room. Fixed weather buoys measure the water temperature at a depth of 3 metres (9.8 ft). Measurements of SST have had inconsistencies over

9800-750: Was recovered from the Isua Greenstone Belt and provides evidence that water existed on Earth 3.8 billion years ago. In the Nuvvuagittuq Greenstone Belt , Quebec , Canada, rocks dated at 3.8 billion years old by one study and 4.28 billion years old by another show evidence of the presence of water at these ages. If oceans existed earlier than this, any geological evidence either has yet to be discovered, or has since been destroyed by geological processes like crustal recycling . However, in August 2020, researchers reported that sufficient water to fill

9900-475: Was the result of an undocumented change in procedure. The samples were taken near the engine intake because it was too dangerous to use lights to take measurements over the side of the ship at night. Many different drifting buoys exist around the world that vary in design, and the location of reliable temperature sensors varies. These measurements are beamed to satellites for automated and immediate data distribution. A large network of coastal buoys in U.S. waters

10000-504: Was −77 °C (−132 °F). One example of a tropical cyclone maintaining itself over cooler waters was Epsilon late in the 2005 Atlantic hurricane season . [REDACTED]  This article incorporates public domain material from websites or documents of the National Oceanic and Atmospheric Administration . Ocean The ocean is the body of salt water that covers approximately 70.8% of Earth . In English ,

#72927