Norwegian Current

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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 passes the Opening into the Barents Sea, a large outcrop of the Arctic Ocean. Compared to its partial source the North Atlantic Current (which otherwise loops into the East Greenland Current) it is colder and less salty; the other sources are the less saline North and Baltic seas and the Norwegian fjords and rivers. It is considerably warmer and saltier than the Arctic Ocean, which is freshened by precipitation and ice in and around it. Winter temperatures in the flow are typically between 2 and 5 °C the co-parent North Atlantic flow, a heat remnant of its Gulf Stream chief contributor, exceeds 6 °C.

Contents

Norwegian coastal waters are dominated by two main water masses, the Norwegian Coastal Current and the North Atlantic Drift Water (Atlantic Water). As the Norwegian Coastal Current moves northward, North Atlantic Drift Water is mixed in, raising the salinity (see Salinity below).

The current is both wind-driven, “piling up” of water along the Norwegian coast by southwesterly winds (creating elevation and thus pressure differences), and also driven by its salinity distribution which in turn creates density gradients. [1]

North Atlantic Current (red) and Norwegian Current (orange) North Atlantic currents.svg
North Atlantic Current (red) and Norwegian Current (orange)

Sources

It is composed primarily of outflow from the Baltic Sea (50% of its freshwater input) through the Skagerrak into the North Sea (10% of its freshwater input) circulation, joining with a fraction of the North Atlantic Drift (the western turn of the northward Gulf Stream). [1] The current is seasonally affected but on average has inputs of fjords and rivers of Norway being 40% of its freshwater input. [1] [2] North-west of the Skagerrak (Baltic's access) the current has about 2100 m3/s of freshwater, 75% of which is Baltic outflow, 15% North Sea outflow and 10% runoff from Norway and Sweden [1] It is thus seen from a saline osmotic pressure viewpoint as a continuation of the Baltic Current [2] and means relatively less salty ocean water than would intuitively be expected counterbalances the naturally non-saline precipitation and ice melt topping up the Arctic (and outcrop Barents) Seas. The current uses the Norwegian Trench picking up fresh and brackish water. It is a surface current it flows along the top 50100 metres. [3] [4] [5]

As the current moves North north-east, saltier North Atlantic Drift Water joins (see Salinity below).

Properties

Salinity

The Norwegian Coastal Current is a wedge-shaped current that has varying salinity and temperature characteristics, and thus densities. The volume of freshwater inputs is greatest in the summer months and smaller during the winter months, contributing to the variability in salinity. On average, it has a salinity of about 34.5 psu (ppt); the near coastal waters have a slightly lower salinity (32-31 psu), the current's boundary to the North Atlantic Drift is marked by a slightly higher salinity, 35 ppt. [2]

Temperature

The average winter temperature of the Norwegian Coastal Current is about 3.5 °C [3] [6] and ranges from 2 to 5 °C, while in summer the temperature of the current is warmer as the tributary sources (Baltic sea, Norwegian fjords, rivers) are warmed up.

Velocity

Although there is much variability in the current's velocities, ranging from as little as 20 cm/s to 100 cm/s at its maximum [1] it is characterized by a velocity of 30 cm/s. [7]

Effects on climate

A mechanism of exchange of energy between the atmosphere and the surface waters of the Atlantic Ocean, Norwegian Coastal Current, is very important to the climate of Norway.

In the winter time, there is a release of heat from the ocean to the overlying air masses. These air masses generally flow in the direction of north-east, thereby warming the adjacent land masses (Norway); especially the coastal regions.

In the summer, the effect is actually reversed. Warm air masses (heated by the Sun on long days) above the Atlantic Ocean will transfer heat to the underlying cooler ocean. This results in cooler air masses reaching the Scandinavian Peninsula, thereby cooling it down in the summer months, especially the coastal regions.

Hence, the Atlantic Ocean and the nearby coastal waters have a moderating effect on the extremes of temperature in Norway, making (especially the coastal regions) warmer in the winter and cooler in the summer. The same effect is very pronounced at Iceland.

To a slight extent, the Norwegian Coastal Current is conveying warmer water into the Barents Sea, decreasing the amount of ice that will form there. [3] In this perspective, the effect of the North Atlantic Drift is much larger.

Fisheries effects

The current brings nutrient rich water along the coast of Norway, and with it rich fisheries of cod, herring, and capelin. Wind driven upwelling along the Strait of Skagerrak brings abundant nutrients to the surface which are then carried along the coastline. Norway has one of the biggest fishing industries in the world, harvesting an average of 3 million metric tons of fish each year. The Norwegian coast is also an important spawning ground for many of the commercial fishes. [1]

Global climate change

The 1990s was an exceptional decade for interannual climate variations in Norway.

The temperatures were, on average, warmer, producing wet, warm winters and hot summers in Norway.[ citation needed ] This has led to increased precipitation extremes, and changes in fish stocks.[ citation needed ]

Increased atmospheric temperatures due to global climate change cause strong south westerly winds to pile water up along the Norwegian coast. The pressure difference creates storm surges that have increased coastal flooding in recent years. [1]

Temperatures have also been rising in the deep layers of Norwegian coastal waters.

Increasing temperatures cause a decrease in sea ice that is supplying the Norwegian Sea with greater amounts of freshwater and lowering the salinities overall.[ further explanation needed ]

This decrease in salinity could cause changes in the rate at which (Arctic) bottom water form (through the process of sea ice formation and the sinking of the highly saline by-product excluded when sea ice forms). If the rate of the formation of (Arctic) bottom water is slowed, then the entire inward flow of the North Atlantic Drift to the Arctic Ocean may be slowed down. [1]

Additionally, increased warming of the North Atlantic Drift is a much larger contributor to the inhibition of formation of sea ice in the Arctic, than the contribution from the Norwegian Coastal Current. Hence, the impact of the Norwegian Coastal Current on climate change is relatively small.

See also

Related Research Articles

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<span class="mw-page-title-main">North Atlantic Deep Water</span> Deep water mass formed in the North Atlantic Ocean

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<span class="mw-page-title-main">Barents Sea</span> Marginal sea of the Arctic Ocean, off the northern coasts of Norway and Russia

The Barents Sea is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territorial waters. It was known earlier among Russians as the Northern Sea, Pomorsky Sea or Murman Sea ; the current name of the sea is after the historical Dutch navigator Willem Barentsz.

<span class="mw-page-title-main">White Sea</span> Southern inlet of the Barents Sea in northwest Russia

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<span class="mw-page-title-main">Ocean current</span> Directional mass flow of oceanic water generated by external or internal forces

An ocean current is a continuous, directed movement of seawater generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, shoreline configurations, and interactions with other currents influence a current's direction and strength. Ocean currents are primarily horizontal water movements.

<span class="mw-page-title-main">Thermohaline circulation</span> Part of large-scale ocean 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 temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes. This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters 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. The water in these circuits transport both energy and mass around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

<span class="mw-page-title-main">East Greenland Current</span> Current from Fram Strait to Cape Farewell off the eastern coat of Greenland

The East Greenland Current (EGC) is a cold, low-salinity current that extends from Fram Strait (~80N) to Cape Farewell (~60N). The current is located off the eastern coast of Greenland along the Greenland continental margin. The current cuts through the Nordic Seas and through the Denmark Strait. The current is of major importance because it directly connects the Arctic to the Northern Atlantic, it is a major contributor to sea ice export out of the Arctic, and it is a major freshwater sink for the Arctic.

<span class="mw-page-title-main">Greenland Sea</span> Body of water

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Bottom water is the lowermost water mass in a water body, by its bottom, with distinct characteristics, in terms of physics, chemistry, and ecology.

<span class="mw-page-title-main">Pechora Sea</span> A marginal sea at the north-west of Russia, the south-eastern part of the Barents Sea

The Pechora Sea is an Arctic sea to the north-west of European Russia, forming the south-eastern portion of the Barents Sea. It is bordered to the west by Kolguyev Island; to the east by Vaygach Island's western coasts and the Yugorsky Peninsula; and to the north by the southern end of Novaya Zemlya.

<span class="mw-page-title-main">Climate of the Arctic</span>

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<span class="mw-page-title-main">Arctic Ocean</span> Ocean in the north polar region

The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately 14,060,000 km2 (5,430,000 sq mi) and is known as one of the coldest of oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea. It has also been described as an estuary of the Atlantic Ocean. It is also seen as the northernmost part of the all-encompassing World Ocean.

<span class="mw-page-title-main">Fram Strait</span> Passage between Greenland and Svalbard

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<span class="mw-page-title-main">Gulf Stream</span> Warm Atlantic Ocean current

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<span class="mw-page-title-main">Beaufort Gyre</span> Wind-driven ocean current in the Arctic Ocean polar region

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<span class="mw-page-title-main">West Spitsbergen Current</span> Warm, salty current that runs poleward just west of Spitsbergen

The West Spitsbergen Current (WSC) is a warm, salty current that runs poleward just west of Spitsbergen,, in the Arctic Ocean. The WSC branches off the Norwegian Atlantic Current in the Norwegian Sea. The WSC is of importance because it drives warm and salty Atlantic Water into the interior Arctic. The warm and salty WSC flows north through the eastern side of Fram Strait, while the East Greenland Current (EGC) flows south through the western side of Fram Strait. The EGC is characterized by being very cold and low in salinity, but above all else it is a major exporter of Arctic sea ice. Thus, the EGC combined with the warm WSC makes the Fram Strait the northernmost ocean area having ice-free conditions throughout the year in all of the global ocean.

The Great Salinity Anomaly (GSA) originally referred to an event in the late 1960s to early 1970s where a large influx of freshwater from the Arctic Ocean led to a salinity anomaly in the northern North Atlantic Ocean, which affected the Atlantic meridional overturning circulation. Since then, the term "Great Salinity Anomaly" has been applied to successive occurrences of the same phenomenon, including the Great Salinity Anomaly of the 1980s and the Great Salinity Anomaly of the 1990s. The Great Salinity Anomalies were advective events, propagating to different sea basins and areas of the North Atlantic, and is on the decadal-scale for the anomalies in the 1970s, 1980s, and 1990s.

<span class="mw-page-title-main">Nordic Seas</span>

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<span class="mw-page-title-main">Atlantification of the Arctic</span>

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Oceanic freshwater fluxes are defined as the transport of non saline water between the oceans and the other components of the Earth's system. These fluxes have an impact on the local ocean properties, as well as on the large scale circulation patterns.

References

  1. 1 2 3 4 5 6 7 8 Saetre, Roald, ed. 2007. The Norwegian Coastal Current—Oceanography and Climate. Tapir Academic Press; Trondheim. ISBN   82-519-2184-8
  2. 1 2 3 Mork, M. (1981). "Circulation Phenomena and Frontal Dynamics of the Norwegian Coastal Current". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences. 302 (1472): 635. Bibcode:1981RSPTA.302..635M. doi:10.1098/rsta.1981.0188.
  3. 1 2 3 Gyory, Joanna , Arthur J. Mariano, Edward H. Ryan. 2001–2008. "The Norwegian & North Cape Currents." Ocean Surface Currents. (Accessed 2009)
  4. Helland-Hansen, B., and F. Nansen, 1909: The Norwegian Archived 2010-04-19 at the Wayback Machine Report on Norwegian Fishery and Marine-Investigations, 2, 1–359.
  5. Ikeda, M.; Johannessen, J.A.; Lygre, K.; Sandven, S. (1989). "A Process Study of Mesoscale Meanders and Eddies in the Norwegian Coastal Current". Journal of Physical Oceanography. 19: 20. Bibcode:1989JPO....19...20I. doi: 10.1175/1520-0485(1989)019<0020:APSOMM>2.0.CO;2 . ISSN   1520-0485.
  6. Saetre, R., and R. Ljoen, 1972: The Norwegian Coastal Current. Proceedings of the First International Conference on Port and Ocean Engineering, vol.1, pp.514–535.
  7. Haugan, Peter M.; Evensen, Geir; Johannessen, Johnny A.; Johannessen, Ola M.; Pettersson, Lasse H. (1991). "Modeled and Observed Mesoscale Circulation and Wave-Current Refraction During the 1988 Norwegian Continental Shelf Experiment". Journal of Geophysical Research. 96: 10487. Bibcode:1991JGR....9610487H. doi:10.1029/91JC00299.

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