North Atlantic Current
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The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm
western boundary current Boundary currents are ocean currents with dynamics determined by the presence of a coastline, and fall into two distinct categories: western boundary currents and eastern boundary currents. Eastern boundary currents Eastern boundary currents are ...
within the
Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...
that extends the Gulf Stream northeastward. The NAC originates from where the Gulf Stream turns north at the Southeast Newfoundland Rise, a submarine ridge that stretches southeast from the
Grand Banks of Newfoundland The Grand Banks of Newfoundland are a series of underwater plateaus south-east of the island of Newfoundland on the North American continental shelf. The Grand Banks are one of the world's richest fishing grounds, supporting Atlantic cod, swordf ...
. The NAC flows northward east of the Grand Banks, from 40°N to 51°N, before turning sharply east to cross the Atlantic. It transports more warm tropical water to northern latitudes than any other boundary current; more than 40  Sv () in the south and 20 Sv () as it crosses the
Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North ...
. It reaches speeds of near the
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
n coast. Directed by topography, the NAC meanders heavily, but in contrast to the meanders of the Gulf Stream, the NAC meanders remain stable without breaking off into eddies. The colder parts of the Gulf Stream turn northward near the "tail" of the Grand Banks at 50°W where the
Azores Current The Azores Current is a generally eastward to southeastward-flowing ocean current in the North Atlantic Ocean. It originates near the Grand Banks of Newfoundland where the Gulf Stream splits into two branches, the northern branch becoming the N ...
branches off to flow south of the
Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...
. From there the NAC flows northeastward, east of the
Flemish Cap The Flemish Cap is an area of shallow waters in the north Atlantic Ocean centered roughly at 47° north, 45° west or about 563 km (350 miles) east of St. John's, Newfoundland and Labrador. The shallow water is caused by a wide underwater ...
(47°N, 45°W). Approaching the Mid-Atlantic Ridge, it then turns eastward and becomes much broader and more diffuse. It then splits into a colder northeastern branch and a warmer eastern branch. As the warmer branch turns southward, most of the subtropical component of the Gulf Stream is diverted southward, and as a consequence, the North Atlantic is mostly supplied by subpolar waters, including a contribution from the
Labrador Current The Labrador Current is a cold current in the North Atlantic Ocean which flows from the Arctic Ocean south along the coast of Labrador and passes around Newfoundland, continuing south along the east coast of Canada near Nova Scotia. Near Nova Scot ...
recirculated into the NAC at 45°N. West of Continental Europe, it splits into two major branches. One branch goes southeast, becoming the
Canary Current The Canary Current is a wind-driven surface current that is part of the North Atlantic Gyre. This eastern boundary current branches south from the North Atlantic Current and flows southwest about as far as Senegal where it turns west and later j ...
as it passes northwest
Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
and turns southwest. The other major branch continues north along the coast of
Northwestern Europe Northwestern Europe, or Northwest Europe, is a loosely defined subregion of Europe, overlapping Northern and Western Europe. The region can be defined both geographically and ethnographically. Geographic definitions Geographically, North ...
. Other branches include the
Irminger Current The Irminger Current is a north Atlantic ocean current setting westward off the southwest coast of Iceland. It is composed of relatively warm and saline waters from the eastern North Atlantic that are fed by the North Atlantic Drift. The Irminger ...
and the
Norwegian Current The Norwegian Current (also known as the Norway Coastal Current) is one of two dominant arctic inflows of water. It can be traced from near Shetland, north of Scotland, otherwise from the eastern North Sea at depths of up to 100 metres. It finally ...
. Driven by the global
thermohaline circulation Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective ''thermohaline'' derives from '' thermo-'' referring to temp ...
, the North Atlantic Current is part of the wind-driven Gulf Stream, which goes further east and north from the North American coast across the Atlantic and into the
Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...
. The North Atlantic Current, together with the Gulf Stream, have a long-lived reputation for having a considerable warming influence on European climate. However, the principal cause for differences in winter climate between North America and Europe seems to be winds rather than ocean currents (although the currents do exert influence at very high latitudes by preventing the formation of sea ice).


Climate change

Unlike the
AMOC The Atlantic meridional overturning circulation (AMOC) is part of a global thermohaline circulation in the oceans and is the zonally integrated component of surface and deep currents in the Atlantic Ocean. It is characterized by a northward f ...
, the observations of Labrador Sea outflow showed no negative trend from 1997 to 2009, and the Labrador Sea convection began to intensify in 2012, reaching a new high in 2016. As of 2022, the trend of strengthened Labrador Sea convection appears to hold, and is associated with observed increases in
marine primary production Marine primary production is the chemical synthesis in the ocean of organic compounds from atmospheric or dissolved carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it al ...
. Yet, a 150-year dataset suggests that even this recently strengthened convection is anomalously weak compared to its baseline state. Some
climate model Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the c ...
s indicate that the deep convection in
Labrador , nickname = "The Big Land" , etymology = , subdivision_type = Country , subdivision_name = Canada , subdivision_type1 = Province , subdivision_name1 ...
- Irminger Seas could collapse under certain
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
scenarios, which would then collapse the entire circulation in the North
subpolar gyre In oceanography, a gyre () is any large system of circulating ocean currents, particularly those involved with large wind movements. Gyres are caused by the Coriolis effect; planetary vorticity, horizontal friction and vertical friction determin ...
. It is considered unlikely to recover even if the temperature is returned to a lower level, making it an example of a climate tipping point. This would result in rapid cooling, with implications for economic sectors, agriculture industry, water resources and energy management in Western Europe and the East Coast of the United States. Frajka-Williams et al. 2017 pointed out that recent changes in cooling of the subpolar gyre, warm temperatures in the subtropics and cool anomalies over the tropics, increased the spatial distribution of meridional gradient in sea surface temperatures, which is not captured by the AMO Index. A 2021 study found that this collapse occurs in only four
CMIP6 In climatology, the Coupled Model Intercomparison Project (CMIP) is a collaborative framework designed to improve knowledge of climate change. It was organized in 1995 by the Working Group on Coupled Modelling (WGCM) of the World Climate Research ...
models out of 35 analyzed. However, only 11 models out of 35 can simulate North Atlantic Current with a high degree of accuracy, and this includes all four models which simulate collapse of the subpolar gyre. As the result, the study estimated the risk of an abrupt cooling event over Europe caused by the collapse of the current at 36.4%, which is lower than the 45.5% chance estimated by the previous generation of models In 2022, a paper suggested that previous disruption of subpolar gyre was connected to the Little Ice Age. A 2022
Science Magazine ''Science'', also widely referred to as ''Science Magazine'', is the peer-reviewed academic journal of the American Association for the Advancement of Science (AAAS) and one of the world's top academic journals. It was first published in 1880, ...
review study on climate tipping points noted that in the scenarios where this convection collapses, it is most likely to be triggered by 1.8 degrees of global warming. However, model differences mean that the required warming may be as low as 1.1 degrees or as high as 3.8 degrees. Once triggered, the collapse of the current would most likely take 10 years from start to end, with a range between 5 and 50 years. The loss of this convection is estimated to lower the global temperature by 0.5 degrees, while the average temperature in Europe decreases by around 3 degrees. There are also substantial impacts on regional
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
.


See also

*
North Atlantic Oscillation The North Atlantic Oscillation (NAO) is a weather phenomenon over the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High. Through fluctuations in the ...
* Ocean gyre * Physical oceanography


References

; Notes ; Sources * * *


External links


"The North Atlantic Current"
Elizabeth Rowe, Arthur J. Mariano, Edward H. Ryan,
Cooperative Institute for Marine and Atmospheric Studies The Cooperative Institute for Marine and Atmospheric Studies (CIMAS) is a research institute of the University of Miami located in its Rosenstiel School of Marine and Atmospheric Science (RSMAS) in Miami, Florida. CIMAS brings together the Univer ...
Currents of the Atlantic Ocean Barents Sea {{Marine-current-stub