Misplaced Pages

#471528

173-460: The Atlantic meridional overturning circulation ( AMOC ) is the main ocean current system in the Atlantic Ocean . It is a component of Earth's ocean circulation system and plays an important role in the climate system . The AMOC includes Atlantic currents at the surface and at great depths that are driven by changes in weather, temperature and salinity . Those currents comprise half of

346-648: A central lagoon . Important human migrations occurred in the Pacific in prehistoric times. Modern humans first reached the western Pacific in the Paleolithic , at around 60,000 to 70,000 years ago. Originating from a southern coastal human migration out of Africa, they reached East Asia , Mainland Southeast Asia , the Philippines, New Guinea , and then Australia by making the sea crossing of at least 80 kilometres (50 mi) between Sundaland and Sahul . It

519-516: A collapse between 2025 and 2095. This study received a lot of attention and criticism because intermediate-complexity models are considered less reliable in general and may confuse a major slowing of the circulation with its complete collapse. The study relied on proxy temperature data from the Northern Subpolar Gyre region, which other scientists do not consider representative of the entire circulation, believing it may be subject to

692-399: A decisive role in influencing the climates of regions through which they flow. Ocean currents are important in the study of marine debris . Upwellings and cold ocean water currents flowing from polar and sub-polar regions bring in nutrients that support plankton growth, which are crucial prey items for several key species in marine ecosystems . Ocean currents are also important in

865-463: A long-term weakening of the AMOC, it remains difficult to detect when analyzing changes since 1980, including both direct – as that time frame presents both periods of weakening and strengthening – and the magnitude of either change is uncertain, ranging between 5% and 25%. The review concluded with a call for more-sensitive and longer-term research. Some reconstructions have attempted to compare

1038-569: A much colder northern Europe and greater sea-level rise along the U.S. East Coast." In addition to water surface temperatures, the wind systems are a crucial determinant of ocean currents. Wind wave systems influence oceanic heat exchange, the condition of the sea surface, and can alter ocean currents. In the North Atlantic, equatorial Pacific, and Southern Ocean, increased wind speeds as well as significant wave heights have been attributed to climate change and natural processes combined. In

1211-766: A multi-year upwelling cycle that occurs in synchronization with the El Niño /La Niña cycle. At the same time, the NADW moves southward and at the southern end of the Atlantic transect, around 80% of it upwells in the Southern Ocean, connecting it with the Southern Ocean overturning circulation (SOOC). After upwelling, the water is understood to take one of two pathways. Water surfacing close to Antarctica will likely be cooled by Antarctic sea ice and sink back into

1384-452: A recovery of the NAG. It is now known the NAG is largely separate from the rest of the AMOC and could collapse independently of it. By 2014, there was enough processed RAPID data up until the end of 2012; these data appeared to show a decline in circulation which was 10 times greater than that which was predicted by the most-advanced models of the time. Scientific debate about whether it indicated

1557-480: A response from the authors of 2021 study, who defended their findings. Some researchers have interpreted a range of recently observed climatic changes and trends as being connected to a decline in the AMOC; for instance, a large area of the North Atlantic Gyre near Greenland has cooled by 0.39 °C (0.70 °F) between 1900 and 2020, in contrast to substantial ocean warming elsewhere. This cooling

1730-453: A result, influence the biological composition of oceans. Due to the patchiness of the natural ecological world, dispersal is a species survival mechanism for various organisms. With strengthened boundary currents moving toward the poles, it is expected that some marine species will be redirected to the poles and greater depths. The strengthening or weakening of typical dispersal pathways by increased temperatures are expected to not only impact

1903-471: A separate tipping point. Some scientists have described this research as "worrisome" and noted it can provide a "valuable contribution" once better observational data is available but there was widespread agreement among experts the paper's proxy record was "insufficient". Some experts said the study used old observational data from five ship surveys that "has long been discredited" by the lack of major weakening seen in direct observations since 2004, "including in

SECTION 10

#1732765977472

2076-418: A significant role in influencing climate, and shifts in climate in turn impact ocean currents. Over the last century, reconstructed sea surface temperature data reveal that western boundary currents are heating at double the rate of the global average. These observations indicate that the western boundary currents are likely intensifying due to this change in temperature, and may continue to grow stronger in

2249-440: A similarly long delay. In 2022, a paleoceanographic reconstruction found a limited effect from massive freshwater forcing of the final Holocene deglaciation ~11,700–6,000 years ago, when the sea level rise was around 50 m (160 ft). It suggested most models overestimate the effects of freshwater forcing on the AMOC. If the AMOC is more dependent on wind strength – which changes relatively little with warming – than

2422-466: A single "conveyor belt" of continuous water exchange. Normally, relatively warm, less-saline water stays on the ocean's surface while deep layers are colder, denser and more-saline, in what is known as ocean stratification . Deep water eventually gains heat and/or loses salinity in an exchange with the mixed ocean layer, and becomes less dense and rises towards the surface. Differences in temperature and salinity exist between ocean layers and between parts of

2595-686: A slowdown of 0.46 sverdrups per decade since 1950. In the future, 2 °C temperature rise will weaken AMOC by 33% in comparison to a state without climate change, which could be reached over the coming decade. The result will be big changes in climate and ecosystems. Also it found that AMOC weakening rise temperature and salinity in the South Atlantic Ocean through the propagation of Kelvin and Rossby waves . Large review papers and reports are capable of evaluating model output, direct observations and historical reconstructions to make expert judgements beyond what models alone can show. Around 2001,

2768-470: A southward shift in the tropical rain belt, and large impacts on ecosystems and human activities." After this some researchers say new findings show collapse can come much faster while other disagree. The Atlantic meridional overturning circulation (AMOC) is the main current system in the Atlantic Ocean, and is also part of the global thermohaline circulation , which connects the world's oceans with

2941-464: A stable circulation. In November 2024, Nature Geoscience published a study which try to solve the problem. The scientists used "Earth system and eddy-permitting coupled ocean–sea-ice models". Then observations and models corresponded to each other much better. The study found a slowdown of 0.46 sverdrups per decade since 1950. Direct observations of the strength of the AMOC have been available since 2004 from RAPID , an in situ mooring array at 26°N in

3114-523: A strong impact of climate change or a large interdecadal variability of the circulation began. Data up until 2017 showed the decline in 2008 and 2009 was anomalously large but the circulation after 2008 was weaker than it was in 2004–2008. The AMOC is also measured by tracking changes in heat transport that would be correlated with overall current flows. In 2017 and 2019, estimates derived from heat observations made by NASA 's CERES satellites and international Argo floats suggested 15-20% less heat transport

3287-407: A strong state like the one throughout recorded history or effectively collapse to a much weaker state and not recover unless the increased warming and/or freshening that caused the collapse is reduced. The warming and /freshening could directly cause the collapse or weaken the circulation to a state in which its ordinary fluctuations (noise) could push it past the tipping point. The possibility the AMOC

3460-487: A wind-driven current which flows clockwise uninterrupted around Antarctica. The ACC connects all the ocean basins together, and also provides a link between the atmosphere and the deep ocean due to the way water upwells and downwells on either side of it. Ocean currents are patterns of water movement that influence climate zones and weather patterns around the world. They are primarily driven by winds and by seawater density, although many other factors influence them – including

3633-478: Is 4,280 m (14,040 ft; 2,340 fathoms), putting the total water volume at roughly 710,000,000 km (170,000,000 cu mi). Due to the effects of plate tectonics , the Pacific Ocean is currently shrinking by roughly 2.5 cm (1 in) per year on three sides, roughly averaging 0.52 km (0.20 sq mi) a year. By contrast, the Atlantic Ocean is increasing in size. Along

SECTION 20

#1732765977472

3806-467: Is a bistable system that is either "on" or "off" and could suddenly collapse has been a topic of scientific discussion ever since. In 2004, The Guardian published the findings of a report commissioned by Pentagon defense adviser Andrew Marshall that suggests the average annual temperature in Europe would drop by 6 °F (3.3 °C) between 2010 and 2020 as the result of an abrupt AMOC shutdown. Some of

3979-425: Is also known as the ocean's conveyor belt. Where significant vertical movement of ocean currents is observed, this is known as upwelling and downwelling . The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content , factors which together determine the density of seawater. The thermohaline circulation is a part of the large-scale ocean circulation that

4152-482: Is commonly understood, then it would be more resistant to collapse. According to some researchers, the less-studied Southern Ocean overturning circulation (SOOC) may be more vulnerable to collapse than the AMOC. High-quality Earth system models indicate a collapse is unlikely and would only become probable if high levels of warming (≥4 °C (7.2 °F)) are sustained long after 2100. Some paleoceanographic research seems to support this idea. Some researchers fear

4325-609: Is considered part of the Southern Ocean. While the total amount of carbon absorption by all carbon sinks is generally projected to increase throughout the 21st century, a continuing decline in the North Atlantic sink would have important implications. Other processes that were attributed in some studies to AMOC slowing include increasing salinity in the South Atlantic, rapid deoxygenation in the Gulf of St. Lawrence , and an approximately 10% decline in phytoplankton productivity across

4498-458: Is consistent with changes in the AMOC. The onset of the interstadial also caused a period of sea level rise from ice-sheet collapse that is designated Meltwater pulse 1A . The Bølling and Allerød stages of the interglacial were separated by two centuries of the opposite pattern – northern-hemisphere cooling, southern-hemisphere warming – which is known as the Older Dryas because

4671-407: Is debate over the relative contributions of different factors and it is unclear how much of this weakening is due to climate change or the circulation's natural variability over millennia. Climate models predict the AMOC will further weaken during the 21st century; this weakening would affect average air temperatures over Scandinavia , Great Britain and Ireland because these regions are warmed by

4844-474: Is driven by global density gradients created by surface heat and freshwater fluxes . Wind -driven surface currents (such as the Gulf Stream ) travel polewards from the equatorial Atlantic Ocean , cooling en route, and eventually sinking at high latitudes (forming North Atlantic Deep Water ). This dense water then flows into the ocean basins . While the bulk of it upwells in the Southern Ocean ,

5017-552: Is enough uncertainty to suggest it could be triggered at warming levels of between 1.4 °C (2.5 °F) and 8 °C (14 °F). The assessment estimates once AMOC collapse is triggered, it would occur between 15 and 300 years, and most likely at around 50 years. The assessment also treated the collapse of the Northern Subpolar Gyre as a separate tipping point that could tip at between 1.1 °C (2.0 °F) degrees and 3.8 °C (6.8 °F), although this

5190-500: Is generally considered incorrect. While one modeling study suggested collapse of the AMOC could result in Ice Age-like cooling, including sea-ice expansion and mass glacier formation, within a century, the accuracy of those results is questionable. There is a consensus the AMOC keeps northern and western Europe warmer than it would be otherwise be, with the difference of 4 °C (7.2 °F) and 10 °C (18 °F) depending on

5363-505: Is likely connected to the AMOC, it could indicate a "quiet" loss of stability that is not seen in most models. In February 2021, a major study in Nature Geoscience reported the preceding millennium saw an unprecedented weakening of the AMOC, an indication the change was caused by human actions. The study's co-author said the AMOC had already slowed by about 15% and effects now being seen; according to them: "In 20 to 30 years it

Atlantic meridional overturning circulation - Misplaced Pages Continue

5536-462: Is likely to weaken further, and that will inevitably influence our weather, so we would see an increase in storms and heatwaves in Europe, and sea level rises on the east coast of the US." In February 2022, Nature Geoscience published a "Matters Arising" commentary article co-authored by 17 scientists that disputed those findings and said the long-term AMOC trend remains uncertain. The journal also published

5709-610: Is normally seasonal; it is most-pronounced in February, when cooling reaches 0.9 °C (1.6 °F) at the area's epicenter but it still experiences warming relative to pre-industrial levels during warm months, particularly in August. Between 2014 and 2016, waters in the area stayed cool for 19 months before warming, and media described this phenomenon as the cold blob . The cold-blob pattern occurs because sufficiently fresh, cool water avoids sinking into deeper layers. This freshening

5882-491: Is not known with any certainty what level of maritime technology was used by these groups – the presumption is that they used large bamboo rafts which may have been equipped with some sort of sail. The reduction in favourable winds for a crossing to Sahul after 58,000 B.P. fits with the dating of the settlement of Australia, with no later migrations in the prehistoric period. The seafaring abilities of pre-Austronesian residents of Island South-east Asia are confirmed by

6055-560: Is not static but experiences small, cyclical changes and larger, long-term shifts in response to external forcings. Many of those shifts occurred during the Late Pleistocene (126,000 to 11,700 years ago), which was the final geological epoch before the current Holocene . It also includes the Last Glacial Period , which is colloquially known as the "last ice age". Twenty-five abrupt temperature oscillations between

6228-598: Is only simulated by a fraction of climate models. The most likely tipping point for the collapse of Northern Subpolar Gyre is 1.8 °C (3.2 °F) and once triggered, the collapse of the gyre would occur between 5 and 50 years, and most likely at 10 years. The loss of this convection is estimated to lower the global temperature by 0.5 °C (0.90 °F) while the average temperature in Europe would decrease by around 3 °C (5.4 °F). There would also be substantial effects on regional precipitation levels. In October 2024, 44 climate scientists published an open letter to

6401-561: Is strong evidence for past changes in the strength and structure of the AMOC during abrupt climate events, such as the Younger Dryas and many of the Heinrich events . In 2022, another millennial-scale reconstruction found the Atlantic multidecadal variability strongly displayed increasing "memory", meaning it is now less likely to return to the mean state and instead would proceed in the direction of past variation. Because this pattern

6574-697: The Americas , although evidence for this remains inconclusive. The first contact of European navigators with the western edge of the Pacific Ocean was made by the Portuguese expeditions of António de Abreu and Francisco Serrão , via the Lesser Sunda Islands , to the Maluku Islands , in 1512, and with Jorge Álvares 's expedition to southern China in 1513, both ordered by Afonso de Albuquerque from Malacca . The eastern side of

6747-424: The Americas , more than 25,000 islands, large and small, rise above the surface of the Pacific Ocean. Multiple islands were the shells of former active volcanoes that have lain dormant for thousands of years. Close to the equator, without vast areas of blue ocean, are a dot of atolls that have over intervals of time been formed by seamounts as a result of tiny coral islands strung in a ring within surroundings of

6920-576: The Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica ) in the south, and is bounded by the continents of Asia and Australia in the west and the Americas in the east. At 165,250,000 square kilometers (63,800,000 square miles) in area (as defined with a southern Antarctic border), this largest division of the World Ocean and the hydrosphere covers about 46% of Earth's water surface and about 32% of

7093-482: The Atlantic meridional overturning circulation (AMOC) is in danger of collapsing due to climate change, which would have extreme impacts on the climate of northern Europe and more widely, although this topic is controversial and remains an active area of research. The "State of the cryosphere" report, dedicates significant space to AMOC, saying it may be enroute to collapse because of ice melt and water warming. In

Atlantic meridional overturning circulation - Misplaced Pages Continue

7266-520: The Bering Sea in the Arctic to the northern extent of the circumpolar Southern Ocean at 60°S (older definitions extend it to Antarctica 's Ross Sea ), the Pacific reaches its greatest east–west width at about 5°N latitude , where it stretches approximately 19,800 km (12,300 mi) from Indonesia to the coast of Colombia  – halfway around the world, and more than five times

7439-506: The East Australian Current , global warming has also been accredited to increased wind stress curl , which intensifies these currents, and may even indirectly increase sea levels, due to the additional warming created by stronger currents. As ocean circulation changes due to climate, typical distribution patterns are also changing. The dispersal patterns of marine organisms depend on oceanographic conditions, which as

7612-645: The Gulf Stream , which, together with its extension the North Atlantic Drift , makes northwest Europe much more temperate for its high latitude than other areas at the same latitude. Another example is Lima, Peru , whose cooler subtropical climate contrasts with that of its surrounding tropical latitudes because of the Humboldt Current . The largest ocean current is the Antarctic Circumpolar Current (ACC),

7785-682: The IPCC Third Assessment Report projected high confidence the AMOC thermohaline circulation would weaken rather than stop and that warming effects would outweigh cooling, even over Europe. When the IPCC Fifth Assessment Report was published in 2014, a rapid transition of the AMOC was considered "very unlikely" and this assessment was offered at a high level of confidence. In 2021, the IPCC Sixth Assessment Report again said

7958-543: The North Atlantic Current . Weakening of the AMOC would also accelerate sea level rise around North America and reduce primary production in the North Atlantic. Severe weakening of the AMOC may lead to a collapse of the circulation, which would not be easily reversible and thus constitutes one of the tipping points in the climate system . A collapse would substantially lower the average temperature and amount of rain and snowfall in Europe. It may also raise

8131-521: The North Atlantic Gyre and has little connection with the rest of the AMOC. The NADW is not the deepest water layer in the Atlantic Ocean; the Antarctic bottom water (AABW) is always the densest, deepest ocean layer in any basin deeper than 4,000 metres (2.5 mi). As the upper reaches of the AABW flow upwells , it melds into and reinforces the NADW. The formation of the NADW is also the beginning of

8304-976: The North Pacific Ocean and the South Pacific Ocean (or more loosely the South Seas ). The Pacific Ocean can also be informally divided by the International Date Line into the East Pacific and the West Pacific , which allows it to be further divided into four quadrants, namely the Northeast Pacific off the coasts of North America , the Southeast Pacific off South America , Northwest Pacific off Far Eastern / Pacific Asia , and

8477-601: The Pacific War ; however, by the end of that war, Japan was defeated and the U.S. Pacific Fleet was the virtual master of the ocean. The Japanese-ruled Northern Mariana Islands came under the control of the United States. Since the end of World War II, many former colonies in the Pacific have become independent states . The Pacific separates Asia and Australia from the Americas. It may be further subdivided by

8650-738: The Sirena Deep , is also located in the Mariana Trench. The western Pacific has many major marginal seas , including the Philippine Sea , South China Sea , East China Sea , Sea of Japan , Sea of Okhotsk , Bering Sea , Gulf of Alaska , Gulf of California , Mar de Grau , Tasman Sea , and the Coral Sea . In the early 16th century , Spanish explorer Vasco Núñez de Balboa crossed the Isthmus of Panama in 1513 and sighted

8823-725: The Southern Hemisphere . The North Equatorial Current , driven westward along latitude 15°N by the trade winds , turns north near the Philippines to become the warm Japan or Kuroshio Current . Turning eastward at about 45°N , the Kuroshio forks and some water moves northward as the Aleutian Current , while the rest turns southward to rejoin the North Equatorial Current. The Aleutian Current branches as it approaches North America and forms

SECTION 50

#1732765977472

8996-418: The Southern Ocean also occurred during these events. This is consistent with the strengthened AMOC transporting more heat from one hemisphere to another. The warming of the northern hemisphere would have caused ice-sheet melting and many D-O events appear to have been ended by Heinrich events , in which massive streams of icebergs broke off from the then-present Laurentide ice sheet . As the icebergs melted in

9169-710: The Southwest Pacific around Oceania . The Pacific Ocean's mean depth is 4,000 meters (13,000 feet). Challenger Deep in the Mariana Trench , located in the northwestern Pacific, is the deepest known point in the world, reaching a depth of 10,928 meters (35,853 feet). The Pacific also contains the deepest point in the Southern Hemisphere , the Horizon Deep in the Tonga Trench , at 10,823 meters (35,509 feet). The third deepest point on Earth,

9342-685: The Strait of Magellan to the Philippines , the explorer indeed found the ocean peaceful; however, the Pacific is not always peaceful. Many tropical storms batter the islands of the Pacific. The lands around the Pacific Rim are full of volcanoes and often affected by earthquakes . Tsunamis , caused by underwater earthquakes, have devastated many islands and in some cases destroyed entire towns. The Martin Waldseemüller map of 1507

9515-1124: The Tibetan Plateau , the Rocky Mountains and the Andes prevent any equivalent moisture transport back to the Atlantic. Due to this process, Atlantic surface water becomes salty and therefore dense, eventually downwelling to form the North Atlantic Deep Water (NADW). NADW formation primarily occurs in the Nordic Seas and involves a complex interplay of regional water masses such as the Denmark Strait Overflow Water (DSOW), Iceland-Scotland Overflow Water (ISOW) and Nordic Seas Overflow Water. Labrador Sea Water may play an important role as well but increasing evidence suggests water in Labrador and Irminger Seas primarily recirculates through

9688-474: The U.S. East Coast ; at least one such event has been connected to a temporary slowing of the AMOC. This effect would be caused by increased warming and thermal expansion of coastal waters, which would transfer less of their heat toward Europe; it is one of the reasons sea level rise along the U.S. East Coast is estimated to be three-to-four times higher than the global average. Ocean current Ocean currents flow for great distances and together they create

9861-495: The Weddell Sea Bottom Water is losing volume, what can impact global ocean circulation and climate. UNESCO mentions that the report in the first time "notes a growing scientific consensus that melting Greenland and Antarctic ice sheets, among other factors, may be slowing important ocean currents at both poles, with potentially dire consequences for a much colder northern Europe and greater sea-level rise along

10034-818: The Western Hemisphere . The Southern Pacific Ocean harbors the Southeast Indian Ridge crossing from south of Australia turning into the Pacific-Antarctic Ridge (north of the South Pole ) and merges with another ridge (south of South America) to form the East Pacific Rise which also connects with another ridge (south of North America) which overlooks the Juan de Fuca Ridge . For most of Magellan's voyage from

10207-439: The World Ocean , and together they drive the thermohaline circulation. The Pacific Ocean is less saline than the other oceans because it receives large quantities of fresh rainfall. Its surface water is insufficiently saline to sink lower than several hundred meters, meaning deep ocean water must come from elsewhere. Ocean water in the North Atlantic is more saline than that in the Pacific, partly because extensive evaporation on

10380-583: The crab claw sail ) – it is likely that the progressive development of these technologies were related to the later steps of settlement into Near and Remote Oceania. Starting at around 2200 BCE, Austronesians sailed southwards to settle the Philippines . From, probably, the Bismarck Archipelago they crossed the western Pacific to reach the Marianas Islands by 1500 BCE, as well as Palau and Yap by 1000 BCE. They were

10553-401: The global conveyor belt , which plays a dominant role in determining the climate of many of Earth's regions. More specifically, ocean currents influence the temperature of the regions through which they travel. For example, warm currents traveling along more temperate coasts increase the temperature of the area by warming the sea breezes that blow over them. Perhaps the most striking example is

SECTION 60

#1732765977472

10726-552: The lower cell of the circulation. The downwelling that forms the NADW is balanced by an equal amount of upwelling. In the western Atlantic, Ekman transport , the increase in ocean-layer mixing caused by wind activity, results in strong upwelling in the Canary Current and the Benguela Current , which are located on the northwest and southwest coasts of Africa. As of 2014, upwelling is substantially stronger around

10899-533: The southern hemisphere . In addition, the areas of surface ocean currents move somewhat with the seasons ; this is most notable in equatorial currents. Deep ocean basins generally have a non-symmetric surface current, in that the eastern equator-ward flowing branch is broad and diffuse whereas the pole-ward flowing western boundary current is relatively narrow. Large scale currents are driven by gradients in water density , which in turn depend on variations in temperature and salinity. This thermohaline circulation

11072-488: The "gold standard" for simulating the entire climate but often have to simplify certain interactions. GCMs typically show the AMOC has a single equilibrium state and that it is difficult or impossible for it to collapse. Researchers have raised concerns this modeled resistance to collapse only occurs because GCM simulations tend to redirect large quantities of freshwater toward the North Pole, where it would no longer affect

11245-498: The AMOC between 1900 and 1980, and a single- sverdrup reduction in AMOC strength did not occur until 1980, a variation that remains within range of natural variability. According to a 2018 study, in the last 150 years, the AMOC has demonstrated exceptional weakness when compared to the previous 1,500 years and indicated a discrepancy in the modeled timing of AMOC decline after the Little Ice Age . A 2017 review concluded there

11418-512: The AMOC collapsed after 300 years when bias correction was applied to the model. One 2016 experiment combined projections from eight then-state-of-the-art CMIP5 climate models with the improved Greenland ice-sheet melt estimates. It found by 2090–2100, the AMOC would weaken by around 18% (3%–34%) under the intermediate Representative Concentration Pathway 4.5, and by 37% (15%–65%) under the very high Representative Concentration Pathway 8.5, in which greenhouse gas emissions increase continuously. When

11591-426: The AMOC has weakened by 15–20% in 200 years and that the circulation slowed during most of the 20th century. Between 1975 and 1995, the circulation was weaker than at any time over the past millennium. This analysis had also shown a limited recovery after 1990 but the authors cautioned another decline is likely to occur in the future. In 2018, another reconstruction suggested a weakening of around 15% has occurred since

11764-517: The AMOC is "very likely" to decline within the 21st century and that there was a "high confidence" changes to it would be reversible within centuries if warming was reversed. Unlike the Fifth Assessment Report, it had only "medium confidence" rather than "high confidence" in the AMOC avoiding a collapse before the end of the 21st century. This reduction in confidence was likely influenced by several review studies that draw attention to

11937-405: The AMOC is most-sensitive to change during periods of extensive ice sheets and low CO 2 , making the Last Glacial Period a "sweet spot" for such oscillations. It has been suggested the warming of the southern hemisphere would have initiated the pattern as warmer waters spread north through the overall thermohaline circulation. The paleoclimate evidence is not currently strong enough to say whether

12110-409: The AMOC. Another possible early indication of a slowing of the AMOC is the relative reduction in the North Atlantic's potential to act as a carbon sink. Between 2004 and 2014, the amount of carbon sequestered in the North Atlantic declined by 20% relative to 1994–2004, which the researchers considered evidence of AMOC slowing. This decline was offset by a comparable increase in the South Atlantic, which

12283-415: The AMOC. Thus, the AMOC carries up to 25% of the total heat toward the northern hemisphere, and plays an important role in the climate around northwest Europe. Because atmospheric patterns also play a large role in heat transfer, the idea the climate in northern Europe would be as cold as that in northern North America without heat transport via ocean currents (i.e. up to 15–20 °C (27–36 °F) colder)

12456-460: The Arctic flower Dryas octopetala became dominant where forests were able to grow during the interglacial. The interglacial ended with the onset of the Younger Dryas (YD) period (12,800–11,700 years ago), when northern-hemisphere temperatures returned to near-glacial levels, possibly within a decade. This happened due to an abrupt slowing of the AMOC, which, in a similar manner to Heinrich events ,

12629-852: The Atlantic, the Strait of Magellan was at times patrolled by fleets sent to prevent the entrance of non-Spanish ships. On the western side of the Pacific Ocean the Dutch threatened the Spanish Philippines . The 18th century marked the beginning of major exploration by the Russians in Alaska and the Aleutian Islands , such as the First Kamchatka expedition and the Great Northern Expedition , led by

12802-533: The Atlantic. The andesite line is the most significant regional distinction in the Pacific. A petrologic boundary, it separates the deeper, mafic igneous rock of the Central Pacific Basin from the partially submerged continental areas of felsic igneous rock on its margins. The andesite line follows the western edge of the islands off California and passes south of the Aleutian arc , along

12975-551: The Atlantic. Observational data needs to be collected for a prolonged period to be of use. Thus, some researchers have attempted to make predictions from smaller-scale observations; for instance, in May 2005, submarine-based research from Peter Wadhams indicated downwelling in the Greenland Sea  – a small part of the AMOC system – which was measured using giant water columns nicknamed chimneys, transferring water downwards

13148-672: The Canary Current than the Benguela Current, though an opposite pattern existed until the closure of the Central American Seaway during the late Pliocene . In the Eastern Atlantic, significant upwelling occurs only during certain months of the year because this region's deep thermocline means it is more dependent on the state of sea surface temperature than on wind activity. There is also

13321-735: The Chilean coast, the South Equatorial Current divides; one branch flows around Cape Horn and the other turns north to form the Peru or Humboldt Current . The climate patterns of the Northern and Southern Hemispheres generally mirror each other. The trade winds in the southern and eastern Pacific are remarkably steady while conditions in the North Pacific are far more varied with, for example, cold winter temperatures on

13494-532: The D-O events started with changes in the AMOC or whether the AMOC changed in response to another trigger. For instance, some research suggests changes in sea-ice cover initiated the D-O events because they would have affected water temperature and circulation through Ice–albedo feedback . D-O events are numbered in reverse order; the largest numbers are assigned to the oldest events. The penultimate event, Dansgaard–Oeschger event 1, occurred some 14,690 years ago and marks

13667-844: The Danish-born Russian navy officer Vitus Bering . Spain also sent expeditions to the Pacific Northwest , reaching Vancouver Island in southern Canada, and Alaska. The French explored and colonized Polynesia , and the British made three voyages with James Cook to the South Pacific and Australia, Hawaii , and the North American Pacific Northwest . In 1768, Pierre-Antoine Véron , a young astronomer accompanying Louis Antoine de Bougainville on his voyage of exploration, established

13840-679: The Moluccas, between 1525 and 1527, Portuguese expeditions encountered the Caroline Islands , the Aru Islands , and Papua New Guinea . In 1542–43 the Portuguese also reached Japan. In 1564, five Spanish ships carrying 379 soldiers crossed the ocean from Mexico led by Miguel López de Legazpi , and colonized the Philippines and Mariana Islands . For the remainder of the 16th century, Spain maintained military and mercantile control, with ships sailing from Mexico and Peru across

14013-571: The Nordic Council of Ministers, claiming that according to scientific studies in the past few years, the risk of AMOC collapse has been greatly underestimated, it can occur in the next few decades, while some changes are already happening. It would have devastating and irreversible impacts especially for Nordic countries, but also for other parts of the world. The letter says that tipping points like this one, can be passed already at 1.5-2 degrees of warming. They called on Nordic countries to ensure

14186-466: The North Atlantic over the past 200 years. Historically, CMIP models, the gold standard in climate science, show the AMOC is very stable; although it may weaken, it will always recover rather than permanently collapse – for example, in a 2014 idealized experiment in which CO 2 concentrations abruptly double from 1990 levels and do not change afterward, the circulation declines by around 25% but does not collapse, although it recovers by only 6% over

14359-443: The North Atlantic track. In 2020, research found a weakened AMOC would slow the decline in Arctic sea ice . and result in atmospheric trends similar to those that likely occurred during the Younger Dryas , such as a southward displacement of Intertropical Convergence Zone . Changes in precipitation under high-emissions scenarios would be far larger. A decline in the AMOC would be accompanied by an acceleration of sea level rise along

14532-468: The North Atlantic. Both of these causes would increase the difference between the surface and deep layers, thus making the upwelling and downwelling that drives the circulation more difficult. In the 1960s, Henry Stommel did much of the research into the AMOC with what later became known as the Stommel Box model, which introduced the idea of Stommel Bifurcation in which the AMOC could exist either in

14705-802: The Pacific Ocean to the Philippines via Guam , and establishing the Spanish East Indies . The Manila galleons operated for two and a half centuries, linking Manila and Acapulco , in one of the longest trade routes in history. Spanish expeditions also arrived at Tuvalu , the Marquesas , the Cook Islands , the Solomon Islands , Vanuatu , the Marshalls and the Admiralty Islands in the South Pacific. Later, in

14878-518: The Pacific Ocean's irregular western margins lie many seas, the largest of which are the Celebes Sea , Coral Sea , East China Sea (East Sea), Philippine Sea , Sea of Japan , South China Sea (South Sea), Sulu Sea , Tasman Sea , and Yellow Sea (West Sea of Korea). The Indonesian Seaway (including the Strait of Malacca and Torres Strait ) joins the Pacific and the Indian Ocean to

15051-512: The Pacific in recorded history. They were part of a Spanish expedition to the Spice Islands that would eventually result in the first world circumnavigation . Magellan called the ocean Pacífico (or "Pacific" meaning, "peaceful") because, after sailing through the stormy seas off Cape Horn , the expedition found calm waters. The ocean was often called the Sea of Magellan in his honor until

15224-653: The Philippines already in 7000 BCE. Additional earlier migrations into Insular Southeast Asia, associated with Austroasiatic-speakers from Mainland Southeast Asia, are estimated to have taken place already in 15000 BCE. At around 1300 to 1200 BCE, a branch of the Austronesian migrations known as the Lapita culture reached the Bismarck Archipelago , the Solomon Islands , Vanuatu , Fiji , and New Caledonia . From there, they settled Tonga and Samoa by 900 to 800 BCE. Some also back-migrated northwards in 200 BCE to settle

15397-479: The U.S. East Coast." As of 2024, there is no consensus on whether a consistent slowing of the AMOC circulation has occurred but there is little doubt it will occur in the event of continued climate change. According to the IPCC, the most-likely effects of future AMOC decline are reduced precipitation in mid-latitudes, changing patterns of strong precipitation in the tropics and Europe, and strengthening storms that follow

15570-654: The United States. Significant contributions to oceanographic knowledge were made by the voyages of HMS Beagle in the 1830s, with Charles Darwin aboard; HMS Challenger during the 1870s; the USS Tuscarora (1873–76); and the German Gazelle (1874–76). In Oceania, France obtained a leading position as imperial power after making Tahiti and New Caledonia protectorates in 1842 and 1853, respectively. After navy visits to Easter Island in 1875 and 1887, Chilean navy officer Policarpo Toro negotiated

15743-663: The Younger Dryas and long-term, post-glacial warming resumed after it ended. The AMOC has not always existed; for much of Earth's history, overturning circulation in the northern hemisphere occurred in the North Pacific. Paleoclimate evidence shows the shift of overturning circulation from the Pacific to the Atlantic occurred 34 million years ago at the Eocene-Oligocene transition , when the Arctic-Atlantic gateway had closed. This closure fundamentally changed

15916-481: The andesite line and include New Guinea, the islands of New Zealand, and the Philippines. Some of these islands are structurally associated with nearby continents. High islands are of volcanic origin, and many contain active volcanoes. Among these are Bougainville , Hawaii, and the Solomon Islands. The coral reefs of the South Pacific are low-lying structures that have built up on basaltic lava flows under

16089-408: The andesite line. Within the closed loop of the andesite line are most of the deep troughs, submerged volcanic mountains, and oceanic volcanic islands that characterize the Pacific basin. Here basaltic lavas gently flow out of rifts to build huge dome-shaped volcanic mountains whose eroded summits form island arcs, chains, and clusters. Outside the andesite line, volcanism is of the explosive type, and

16262-594: The arctic, icing from October to May can present a hazard for shipping while persistent fog occurs from June to December. A climatological low in the Gulf of Alaska keeps the southern coast wet and mild during the winter months. The Westerlies and associated jet stream within the Mid-Latitudes can be particularly strong, especially in the Southern Hemisphere, due to the temperature difference between

16435-532: The area. For instance, studies of the Florida Current suggest the Gulf Stream was around 10% weaker from around 1200 to 1850 due to increased surface salinity, and this likely contributed to the conditions known as Little Ice Age . The AMOC makes the Atlantic Ocean into a more-effective carbon sink in two major ways. Firstly, the upwelling that takes place supplies large quantities of nutrients to

16608-525: The base of a counter-clockwise circulation in the Bering Sea . Its southern arm becomes the chilled slow, south-flowing California Current . The South Equatorial Current , flowing west along the equator, swings southward east of New Guinea , turns east at about 50°S , and joins the main westerly circulation of the South Pacific, which includes the Earth-circling Antarctic Circumpolar Current . As it approaches

16781-459: The circulation has a large impact on the climate of the Earth. The thermohaline circulation is sometimes called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is imprecisely used to refer to the meridional overturning circulation , (MOC). Since the 2000s an international program called Argo has been mapping the temperature and salinity structure of

16954-469: The circulation stability bias within general circulation models , and simplified ocean-modelling studies suggesting the AMOC may be more vulnerable to abrupt change than larger-scale models suggest. In 2022, an extensive assessment of all potential climate tipping points identified 16 plausible climate tipping points, including a collapse of the AMOC. It said a collapse would most likely be triggered by 4 °C (7.2 °F) of global warming but that there

17127-404: The circulation toward an unrealistically constant flow of freshwater. In one study, the difference between constant and variable freshwater flux delayed collapse of the circulation in a typical Stommel's Bifurcation EMIC by over 1,000 years. The researchers said this simulation is more consistent with reconstructions of the AMOC's response to Meltwater pulse 1A 13,500-14,700 years ago and indicates

17300-541: The circulation, a movement that does not occur in nature. In 2024, three researchers performed a simulation with one of the Community Earth System Models (CIMP) in which a classic AMOC collapse had occurred, much like it does in intermediate-complexity models. Unlike some other simulations, they did not immediately subject the model to unrealistic meltwater levels but gradually increased the input. Their simulation had run for over 1,700 years before

17473-482: The coast of Africa and through the Indonesian archipelago . Once this water returns to the North Atlantic, it becomes cooler and denser, and sinks, feeding back into the NADW. Equatorial areas are the hottest part of the globe; due to thermodynamics , this heat moves towards the poles . Most of this heat is transported by atmospheric circulation but warm, surface ocean currents play an important role. Heat from

17646-422: The collapse occurred and they had also eventually reached meltwater levels equivalent to a sea level rise of 6 cm (2.4 in) per year, about 20 times larger than the 2.9 mm (0.11 in)/year sea level rise between 1993 and 2017, and well above any level considered plausible. According to the researchers, those unrealistic conditions were intended to counterbalance the model's unrealistic stability and

17819-478: The complex models are too stable and that lower-complexity projections pointing to an earlier collapse are more accurate. One of those projections suggests AMOC collapse could happen around 2057 but many scientists are skeptical of the projection. Some research also suggests the Southern Ocean overturning circulation may be more prone to collapse than the AMOC. In October 2024, 44 climate scientists published an open letter, claiming that according to scientific studies in

17992-554: The cost and emissions of shipping vessels. Ocean currents can also impact the fishing industry , examples of this include the Tsugaru , Oyashio and Kuroshio currents all of which influence the western North Pacific temperature, which has been shown to be a habitat predictor for the Skipjack tuna . It has also been shown that it is not just local currents that can affect a country's economy, but neighboring currents can influence

18165-401: The current state of the AMOC with that from a century or so earlier. For instance, a 2010 statistical analysis found a weakening of the AMOC has been continuing since the late 1930s with an abrupt shift of a North-Atlantic overturning cell around 1970. In 2015, a different statistical analysis interpreted a cold pattern in some years of temperature records as a sign of AMOC weakening. It concluded

18338-459: The diameter of the Moon. Its geographic center is in eastern Kiribati south of Kiritimati , just west from Starbuck Island at 4°58′S 158°45′W  /  4.97°S 158.75°W  / -4.97; -158.75 . The lowest known point on Earth – the Mariana Trench  – lies 10,911 m (35,797  ft ; 5,966 fathoms ) below sea level. Its average depth

18511-402: The difference between temperatures aloft and sea surface temperatures is the greatest; however, each particular basin has its own seasonal patterns. On a worldwide scale, May is the least active month, while September is the most active month. November is the only month in which all the tropical cyclone basins are active. The Pacific hosts the two most active tropical cyclone basins , which are

18684-570: The dispersal and distribution of many organisms, inclusing those with pelagic egg or larval stages. An example is the life-cycle of the European Eel . Terrestrial species, for example tortoises and lizards, can be carried on floating debris by currents to colonise new terrestrial areas and islands . The continued rise of atmospheric temperatures is anticipated to have various effects on the strength of surface ocean currents, wind-driven circulation and dispersal patterns. Ocean currents play

18857-493: The east and the islands of Kiribati in the southeast. Melanesia, to the southwest, includes New Guinea , the world's second largest island after Greenland and by far the largest of the Pacific islands. The other main Melanesian groups from north to south are the Bismarck Archipelago , the Solomon Islands , Santa Cruz , Vanuatu , Fiji and New Caledonia . The largest area, Polynesia , stretching from Hawaii in

19030-505: The east coast of Russia contrasting with the milder weather off British Columbia during the winter months due to the preferred flow of ocean currents . In the tropical and subtropical Pacific, the El Niño Southern Oscillation (ENSO) affects weather conditions. To determine the phase of ENSO, the most recent three-month sea surface temperature average for the area approximately 3,000 km (1,900 mi) to

19203-665: The eastern edge of the Kamchatka Peninsula , the Kuril Islands , Japan, the Mariana Islands , the Solomon Islands , and New Zealand's North Island . The dissimilarity continues northeastward along the western edge of the Andes Cordillera along South America to Mexico, returning then to the islands off California. Indonesia, the Philippines, Japan, New Guinea, and New Zealand lie outside

19376-512: The eighteenth century. Magellan stopped at one uninhabited Pacific island before stopping at Guam in March 1521. Although Magellan himself died in the Philippines in 1521, Spanish navigator Juan Sebastián Elcano led the remains of the expedition back to Spain across the Indian Ocean and round the Cape of Good Hope , completing the first world circumnavigation in 1522. Sailing around and east of

19549-539: The equator into northern (North Pacific) and southern (South Pacific) portions. It extends from the Antarctic region in the South to the Arctic in the north. The Pacific Ocean encompasses approximately one-third of the Earth's surface, having an area of 165,200,000 km (63,800,000 sq mi) – larger than Earth's entire landmass combined, 150,000,000 km (58,000,000 sq mi). Extending approximately 15,500 km (9,600 mi) from

19722-498: The equator moves either northward or southward; the Atlantic Ocean is the only ocean in which the heat flow is northward. Much of the heat transfer in the Atlantic occurs due to the Gulf Stream , a surface current that carries warm water northward from the Caribbean . While the Gulf Stream as a whole is driven by winds alone, its northern-most segment, the North Atlantic Current , obtains much of its heat from thermohaline exchange in

19895-601: The equator, which can have a salinity as low as 34 parts per thousand, is less salty than that found in the mid-latitudes because of abundant equatorial precipitation throughout the year. The lowest counts of less than 32 parts per thousand are found in the far north as less evaporation of seawater takes place in these frigid areas. The motion of Pacific waters is generally clockwise in the Northern Hemisphere (the North Pacific gyre ) and counter-clockwise in

20068-606: The first completely documented European landing in Australia (1606), in Cape York Peninsula , and Abel Janszoon Tasman circumnavigated and landed on parts of the Australian continental coast and arrived at Tasmania and New Zealand in 1642. In the 16th and 17th centuries, Spain considered the Pacific Ocean a mare clausum  – a sea closed to other naval powers. As the only known entrance from

20241-474: The first humans to reach Remote Oceania , and the first to cross vast distances of open water. They also continued spreading southwards and settling the rest of Maritime Southeast Asia , reaching Indonesia and Malaysia by 1500 BCE, and further west to Madagascar and the Comoros in the Indian Ocean by around 500 CE. More recently, it is suggested that Austronesians expanded already earlier, arriving in

20414-510: The frequency of extreme weather events and have other severe effects. The IPCC , summarized the scientific consensus for the year 2023 as follows: "The Atlantic Meridional Overturning Circulation is very likely to weaken over the 21st century for all considered scenarios (high confidence), however an abrupt collapse is not expected before 2100 (medium confidence). If such a low probability event were to occur, it would very likely cause abrupt shifts in regional weather patterns and water cycle, such as

20587-407: The global thermohaline circulation that includes the flow of major ocean currents, the other half being the Southern Ocean overturning circulation . The AMOC is composed of a northward flow of warm, more saline water in the Atlantic's upper layers and a southward, return flow of cold, salty, deep water. Warm water from the south is more saline ('halocline') because of the higher evaporation rate in

20760-533: The great "Southern Sea" which he named Mar del Sur (in Spanish). Afterwards, the ocean's current name was coined by Portuguese explorer Ferdinand Magellan during the Spanish circumnavigation of the world in 1521, as he encountered favorable winds on reaching the ocean. He called it Mar Pacífico , which in Portuguese means 'peaceful sea'. Top large seas: Across the continents of Asia, Australia and

20933-515: The hemispheres occurred during this period; these oscillations are known as Dansgaard–Oeschger events (D-O events) after Willi Dansgaard and Hans Oeschger , who discovered them by analyzing Greenland ice cores in the 1980s. D-O events are best known for the rapid warming of between 8 °C (15 °F) and 15 °C (27 °F) that occurred in Greenland over several decades. Warming also occurred over the entire North Atlantic region but equivalent cooling over

21106-477: The implementation of the Paris Agreement to prevent it. The "State of the cryosphere" report, dedicates significant space to AMOC, saying it may be enroute to collapse because of ice melt and water warming. Impacts will include cooling of Northern Europe faster than 3°C per decade, "with no realistic means of adaptation". In the same time, the Antarctic Circumpolar Current (ACC) is also slowing down and

21279-439: The incorporation of the island into Chile with native Rapanui in 1888. By occupying Easter Island, Chile joined the imperial nations. By 1900 nearly all Pacific islands were in control of Britain, France, United States, Germany, Japan, and Chile. Although the United States gained control of Guam and the Philippines from Spain in 1898, Japan controlled most of the western Pacific by 1914 and occupied many other islands during

21452-483: The islands in the world. There are about 25,000 islands in the Pacific Ocean. The islands entirely within the Pacific Ocean can be divided into three main groups known as Micronesia , Melanesia and Polynesia . Micronesia, which lies north of the equator and west of the International Date Line , includes the Mariana Islands in the northwest, the Caroline Islands in the center, the Marshall Islands to

21625-575: The islands of eastern Micronesia (including the Carolines , the Marshall Islands , and Kiribati ), mixing with earlier Austronesian migrations in the region. This remained the furthest extent of the Austronesian expansion into Polynesia until around 700 CE when there was another surge of island exploration. They reached the Cook Islands , Tahiti , and the Marquesas by 700 CE; Hawaiʻi by 900 CE; Rapa Nui by 1000 CE; and finally New Zealand by 1200 CE. Austronesians may have also reached as far as

21798-509: The large scale prevailing winds drive major persistent ocean currents, and seasonal or occasional winds drive currents of similar persistence to the winds that drive them, and the Coriolis effect plays a major role in their development. The Ekman spiral velocity distribution results in the currents flowing at an angle to the driving winds, and they develop typical clockwise spirals in the northern hemisphere and counter-clockwise rotation in

21971-857: The large-scale models. While models have improved over time, the sixth and as of 2020 current generation CMIP6, retains some inaccuracies. On average, those models simulate much greater AMOC weakening in response to greenhouse warming than the previous generation; when four CMIP6 models simulated the AMOC under the SSP3-7 scenario in which CO 2 levels more than double from 2015 values by 2100 from around 400 parts per million (ppm) to over 850 ppm, they found it declined by over 50% by 2100. The CMIP6 models are not yet capable of simulating North Atlantic Deep Water (NADW) without errors in its depth, area or both, reducing confidence in their projections. To address these problems, some scientists experimented with bias correction. In another idealized CO 2 doubling experiment,

22144-430: The lower cell of the circulation. Some of this water will rejoin the AABW but the rest of the lower-cell flow will eventually reach the depths of the Pacific and Indian oceans. Water that upwells at lower, ice-free latitudes moves further northward due to Ekman transport and is committed to the upper cell . The warm water in the upper cell is responsible for the return flow to the North Atlantic, which occurs mainly around

22317-508: The mid-twentieth century. A 2021 reconstruction used over a century of ocean-temperature-and-salinity data, which appeared to show significant changes in eight independent AMOC indices that could indicate "an almost complete loss of stability". This reconstruction was forced to omit all data from 35 years before 1900 and after 1980 to maintain consistent records of all eight indicators. These findings were challenged by 2022 research that used data recorded between 1900 and 2019, and found no change in

22490-436: The model's output should not be regarded as a prediction but rather as a high-resolution representation of the way currents would start changing before a collapse. Other scientists agreed this study's findings would mainly help with calibrating more-realistic studies, particularly once better observational data becomes available. Some research indicates classic EMIC projections are biased toward AMOC collapse because they subject

22663-461: The models developed after Stommel's work suggest the AMOC could have one or more intermediate stable states between full strength and full collapse. This is more-commonly seen in Earth Models of Intermediate Complexity (EMICs), which focus on certain parts of the climate system like AMOC and disregard others, rather than in the more-comprehensive general circulation models (GCMs) that represent

22836-470: The module, the AMOC was subjected to four-to-ten times more freshwater when compared to the standard run. It simulated for RCP 4.5 very similar results to those of the 2016 study while below RCP 8.5, the circulation declines by two-thirds soon after 2100 but does not collapse past that level. In 2023, a statistical analysis of output from multiple intermediate-complexity models suggested an AMOC collapse would most likely happen around 2057 with 95% confidence of

23009-445: The more-saturated surface waters and is prevented from releasing carbon back into the atmosphere when it is downwelled. While Southern Ocean is by far the strongest ocean carbon sink, The North Atlantic is the largest single carbon sink in the northern hemisphere. Because the Atlantic meriditional overturning circulation (AMOC) is dependent on a series of interactions between layers of ocean water of varying temperature and salinity, it

23182-462: The near future. There is evidence that surface warming due to anthropogenic climate change has accelerated upper ocean currents in 77% of the global ocean. Specifically, increased vertical stratification due to surface warming intensifies upper ocean currents, while changes in horizontal density gradients caused by differential warming across different ocean regions results in the acceleration of surface zonal currents . There are suggestions that

23355-428: The next 1,000 years. In 2020, research estimated if warming stabilizes at 1.5 °C (2.7 °F), 2 °C (3.6 °F) or 3 °C (5.4 °F) by 2100; in all three cases, the AMOC declines for an additional 5–10 years after the temperature rise ceases but does not approach collapse, and partially recovers after about 150 years. Many researchers have said collapse is only avoided due to biases that persist across

23528-601: The north to New Zealand in the south, also encompasses Tuvalu , Tokelau , Samoa , Tonga and the Kermadec Islands to the west, the Cook Islands , Society Islands and Austral Islands in the center, and the Marquesas Islands , Tuamotu , Mangareva Islands , and Easter Island to the east. Islands in the Pacific Ocean are of four basic types: continental islands, high islands, coral reefs and uplifted coral platforms. Continental islands lie outside

23701-619: The northern Philippines , but also earlier groups associated with Austroasiatic-speakers , resulting in the modern peoples of Island Southeast Asia and Oceania. A later seaborne migration is the Neolithic Austronesian expansion of the Austronesian peoples . Austronesians originated from the island of Taiwan c.  3000 –1500 BCE. They are associated with distinctive maritime sailing technologies (notably outrigger boats , catamarans , lashed-lug boats, and

23874-575: The northwestern Pacific and the eastern Pacific. Pacific hurricanes form south of Mexico, sometimes striking the western Mexican coast and occasionally the Southwestern United States between June and October, while typhoons forming in the northwestern Pacific moving into southeast and east Asia from May to December. Tropical cyclones also form in the South Pacific basin , where they occasionally impact island nations. In

24047-399: The ocean was encountered by Spanish explorer Vasco Núñez de Balboa in 1513 after his expedition crossed the Isthmus of Panama and reached a new ocean. He named it Mar del Sur ("Sea of the South" or "South Sea" ) because the ocean was to the south of the coast of the isthmus where he first observed the Pacific. In 1520, navigator Ferdinand Magellan and his crew were the first to cross

24220-515: The ocean with a fleet of automated platforms that float with the ocean currents. The information gathered will help explain the role the oceans play in the earth's climate. Ocean currents affect temperatures throughout the world. For example, the ocean current that brings warm water up the north Atlantic to northwest Europe also cumulatively and slowly blocks ice from forming along the seashores, which would also block ships from entering and exiting inland waterways and seaports, hence ocean currents play

24393-497: The ocean's ecosystems and its function as a carbon sink . Changes in the strength of the AMOC can affect multiple elements of the climate system. Climate change may weaken the AMOC through increases in ocean heat content and elevated flows of freshwater from melting ice sheets . Studies using oceanographic reconstructions suggest as of 2015, the AMOC is weaker than it was before the Industrial Revolution . There

24566-562: The ocean's surface. One of the most dramatic is the Great Barrier Reef off northeastern Australia with chains of reef patches. A second island type formed of coral is the uplifted coral platform, which is usually slightly larger than the low coral islands. Examples include Banaba (formerly Ocean Island) and Makatea in the Tuamotu group of French Polynesia . The volume of the Pacific Ocean, representing about 50.1 percent of

24739-489: The ocean, the ocean water would have become fresher, weakening the circulation and stopping the D-O warming. There is not yet a consensus explanation for why AMOC would have fluctuated so much, and only during this glacial period. Common hypotheses include cyclical patterns of salinity change in the North Atlantic or a wind-pattern cycle due to the growth and decline of the region's ice sheets, which are large enough to affect wind patterns. As of late 2010s, some research suggests

24912-656: The oceans. Ocean temperature and motion fields can be separated into three distinct layers: mixed (surface) layer, upper ocean (above the thermocline), and deep ocean. Ocean currents are measured in units of sverdrup (Sv) , where 1 Sv is equivalent to a volume flow rate of 1,000,000 m (35,000,000 cu ft) per second. There are two main types of currents, surface currents and deep water currents. Generally surface currents are driven by wind systems and deep water currents are driven by differences in water density due to variations in water temperature and salinity . Surface oceanic currents are driven by wind currents,

25085-408: The oldest waters (with a transit time of around 1000 years) upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. On their journey, the water masses transport both energy (in the form of heat) and matter (solids, dissolved substances and gases) around the globe. As such, the state of

25258-404: The past few years, the risk of AMOC collapse has been greatly underestimated, it can occur in the next few decades, with devastating impacts especially for Nordic countries. They called on Nordic countries to ensure the implementation of the Paris Agreement to prevent it. Until 2024 there was a disagreement between observations showing a slowdown of the circulation and climate models showing

25431-475: The planet's total surface area, larger than its entire land area (148,000,000 km (57,000,000 sq mi)). The centers of both the Water Hemisphere and the Western Hemisphere , as well as the oceanic pole of inaccessibility , are in the Pacific Ocean. Ocean circulation (caused by the Coriolis effect ) subdivides it into two largely independent volumes of water that meet at the equator ,

25604-581: The quest for Terra Australis ("the [great] Southern Land"), Spanish explorations in the 17th century, such as the expedition led by the Portuguese navigator Pedro Fernandes de Queirós , arrived at the Pitcairn and Vanuatu archipelagos, and sailed the Torres Strait between Australia and New Guinea, named after navigator Luís Vaz de Torres . Dutch explorers, sailing around southern Africa, also engaged in exploration and trade; Willem Janszoon , made

25777-400: The reference they cite for it". In November 2024, Nature Geoscience published a study which try to solve the problem of the differences between observation showing a slowdown of the circulation and the climate models which showing a stable circulation. The scientists used some new methods and models. Then, the observations and the models corresponded to each other much better. The study found

25950-518: The same latitude North America's weather was colder. A good example of this is the Agulhas Current (down along eastern Africa), which long prevented sailors from reaching India. In recent times, around-the-world sailing competitors make good use of surface currents to build and maintain speed. Ocean currents can also be used for marine power generation , with areas of Japan, Florida and Hawaii being considered for test projects. The utilization of currents today can still impact global trade, it can reduce

26123-450: The same time, the Antarctic Circumpolar Current (ACC) is also slowing down and is expected to lose 20% of it power by the year 2050, "with widespread impacts on ocean circulation and climate". UNESCO mentions that the report in the first time "notes a growing scientific consensus that melting Greenland and Antarctic ice sheets, among other factors, may be slowing important ocean currents at both poles, with potentially dire consequences for

26296-450: The settlement of Buka by 32,000 B.P. and Manus by 25,000 B.P. Journeys of 180 kilometres (110 mi) and 230 kilometres (140 mi) are involved, respectively. The descendants of these migrations today are the Negritos , Melanesians , and Indigenous Australians . Their populations in maritime Southeast Asia , coastal New Guinea , and Island Melanesia later intermarried with the incoming Austronesian settlers from Taiwan and

26469-424: The shape and configuration of the ocean basin they flow through. The two basic types of currents – surface and deep-water currents – help define the character and flow of ocean waters across the planet. Ocean currents are driven by the wind, by the gravitational pull of the moon in the form of tides , and by the effects of variations in water density. Ocean dynamics define and describe the motion of water within

26642-452: The southeast of Hawaii is computed, and if the region is more than 0.5 °C (0.9 °F) above or below normal for that period, then an El Niño or La Niña is considered in progress. In the tropical western Pacific, the monsoon and the related wet season during the summer months contrast with dry winds in the winter which blow over the ocean from the Asian landmass. Worldwide, tropical cyclone activity peaks in late summer, when

26815-438: The surface concentrates salt within the remaining water and partly because sea ice near the Arctic Circle expels salt as it freezes during winter. Even more importantly, evaporated moisture in the Atlantic is swiftly carried away by atmospheric circulation before it can fall back as rain. Trade winds move this moisture across Central America and to the eastern North Pacific, where it falls as rain. Major mountain ranges such as

26988-423: The surface waters, supporting the growth of phytoplankton and therefore increasing marine primary production and the overall amount of photosynthesis in the surface waters. Secondly, upwelled water has low concentrations of dissolved carbon because the water is typically 1,000 years old and has not been exposed to anthropogenic CO 2 increases in the atmosphere. This water absorbs larger quantities of carbon than

27161-413: The survival of native marine species due to inability to replenish their meta populations but also may increase the prevalence of invasive species . In Japanese corals and macroalgae, the unusual dispersal pattern of organisms toward the poles may destabilize native species. Knowledge of surface ocean currents is essential in reducing costs of shipping, since traveling with them reduces fuel costs. In

27334-490: The thermohaline circulation structure; some researchers have suggested climate change may eventually reverse this shift and re-establish the Pacific circulation after the AMOC shuts down. Climate change affects the AMOC by making surface water warmer as a consequence of Earth's energy imbalance and by making surface water less saline due to the addition of large quantities of fresh water from melting ice – mainly from Greenland – and through increasing precipitation over

27507-478: The transition from the Oldest Dryas period to the Bølling–Allerød Interstadial ( Danish: [ˈpøle̝ŋ ˈæləˌʁœðˀ] ), which lasted until 12,890 years Before Present . It was named after the two sites in Denmark with vegetation fossils that could only have survived during a comparatively warm period in the northern hemisphere. The major warming in the northern hemisphere was offset by southern-hemisphere cooling and little net change in global temperature, which

27680-485: The tropical zone. The warm saline water forms the upper layer of the ocean ('thermocline'), but when this layer cools down, the density of the salty water increases, making it sink into the deep. This is an important part of the motor of the AMOC system. The limbs are linked by regions of overturning in the Nordic Seas and the Southern Ocean . Overturning sites are associated with intense exchanges of heat, dissolved oxygen, carbon and other nutrients, and very important for

27853-624: The tropics and Antarctica, which records the coldest temperature readings on the planet. In the Southern hemisphere, because of the stormy and cloudy conditions associated with extratropical cyclones riding the jet stream, it is usual to refer to the Westerlies as the Roaring Forties, Furious Fifties and Shrieking Sixties according to the varying degrees of latitude. The ocean was first mapped by Abraham Ortelius ; he called it Maris Pacifici following Ferdinand Magellan 's description of it as "a pacific sea" during his circumnavigation from 1519 to 1522. To Magellan, it seemed much more calm (pacific) than

28026-404: The two scenarios were extended past 2100, the AMOC stabilized under RCP 4.5 but continued to decline under RCP 8.5, leading to an average decline of 74% by 2290–2300 and a 44% likelihood of a complete collapse. In 2020, another team of researchers simulated RCP 4.5 and RCP 8.5 between 2005 and 2250 in a Community Earth System Model that was integrated with an advanced ocean physics module. Due to

28199-423: The viability of local fishing industries. Currents of the Arctic Ocean Currents of the Atlantic Ocean Currents of the Indian Ocean Currents of the Pacific Ocean Currents of the Southern Ocean Oceanic gyres Pacific Ocean Main five oceans division: Further subdivision: The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions . It extends from

28372-400: The west, and Drake Passage and the Strait of Magellan link the Pacific with the Atlantic Ocean on the east. To the north, the Bering Strait connects the Pacific with the Arctic Ocean . As the Pacific straddles the 180th meridian , the West Pacific (or western Pacific , near Asia) is in the Eastern Hemisphere , while the East Pacific (or eastern Pacific , near the Americas) is in

28545-463: The width of the Pacific with precision for the first time in history. One of the earliest voyages of scientific exploration was organized by Spain in the Malaspina Expedition of 1789–1794. It sailed vast areas of the Pacific, from Cape Horn to Alaska, Guam and the Philippines, New Zealand, Australia, and the South Pacific. Growing imperialism during the 19th century resulted in the occupation of much of Oceania by European powers, and later Japan and

28718-474: The wind powered sailing-ship era, knowledge of wind patterns and ocean currents was even more essential. Using ocean currents to help their ships into harbor and using currents such as the gulf stream to get back home. The lack of understanding of ocean currents during that time period is hypothesized to be one of the contributing factors to exploration failure. The Gulf Stream and the Canary current keep western European countries warmer and less variable, while at

28891-434: The world's oceanic water, has been estimated at some 714 million cubic kilometers (171 million cubic miles). Surface water temperatures in the Pacific can vary from −1.4 °C (29.5 °F), the freezing point of seawater, in the poleward areas to about 30 °C (86 °F) near the equator. Salinity also varies latitudinally, reaching a maximum of 37 parts per thousand in the southeastern area. The water near

29064-454: Was at less than a quarter of its normal strength. In 2000, other researchers focused on trends in the North Atlantic Gyre (NAG), which is also known as the Northern Subpolar Gyre (SPG). Measurements taken in 2004 found a 30% decline in the NAG relative to the measurement in 1992; some interpreted this measurement as a sign of AMOC collapse. RAPID data have since shown this to be a statistical anomaly, and observations from 2007 and 2008 have shown

29237-483: Was caused by freshening due to ice loss from the Laurentide ice sheet. Unlike true Heinrich events, there was an enormous flow of meltwater through the Mackenzie River in what is now Canada rather than a mass iceberg loss. Major changes in the precipitation regime, such as the shift of the Intertropical Convergence Zone to the south, increased rainfall in North America, and the drying of South America and Europe, occurred. Global temperatures again barely changed during

29410-468: Was combined with reconstructed trends from data that were recorded 25 years before RAPID. This study showed no evidence of an overall decline in the AMOC over the past 30 years. A Science Advances study published in 2020 found no significant change in the AMOC circulation compared to that in the 1990s, although substantial changes have occurred across the North Atlantic in the same period. A March 2022 review article concluded while global warming may cause

29583-401: Was immediately described as evidence of a slowing of the AMOC slowdown. Later research found atmospheric changes, such as an increase in low cloud cover and a strengthening of the North Atlantic oscillation (NAO) have also played a major role in this local cooling. The overall importance of the NAO in the phenomenon is disputed but cold-blob trends alone cannot be used to analyze the strength of

29756-480: Was occurring than was implied by the RAPID, and indicated a fairly stable flow with a limited indication of decadal variability. The strength of Florida Current has been measured as stable over the last four decades after correction for changes in Earth's magnetic field . Climate reconstructions allow research to assemble hints about the past state of the AMOC, though these techniques are necessarily less reliable than direct observations. In February 2021, RAPID data

29929-469: Was the first to show the Americas separating two distinct oceans. Later, the Diogo Ribeiro map of 1529 was the first to show the Pacific at about its proper size. (Inhabited dependent territories are denoted by the asterisk (*), with names of the corresponding sovereign states in round brackets. Associated states in the Realm of New Zealand are denoted by the hash sign (#).) Territories with no permanent civilian population. The Pacific Ocean has most of

#471528