Nordic Seas

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Figure 1: Map of the Nordic Seas Map of the Nordic Seas.jpg
Figure 1: Map of the Nordic Seas

The Nordic Seas are located north of Iceland and south of Svalbard. They have also been defined as the region located north of the Greenland-Scotland Ridge and south of the Fram Strait-Spitsbergen-Norway intersection. [1] Known to connect the North Pacific and the North Atlantic waters, this region is also known as having some of the densest waters, creating the densest region found in the North Atlantic Deep Water. [2] The deepest waters of the Arctic Ocean are connected to the worlds other oceans through Nordic Seas and Fram Strait. There are three seas within the Nordic Sea: Greenland Sea, Norwegian Sea, and Iceland Sea. [1] The Nordic Seas only make up about 0.75% of the World's Oceans. [2] This region is known as having diverse features in such a small topographic area, such as the mid oceanic ridge systems. Some locations have shallow shelves, while others have deep slopes and basins. This region, because of the atmosphere-ocean transfer of energy and gases, has varying seasonal climate. During the winter, sea ice is formed in the western and northern regions of the Nordic Seas, whereas during the summer months, the majority of the region remains free of ice.

Contents

Several water masses are found interacting in the Nordic Sea. These water masses are present due to subduction, deep convective mixing, surface/frontal mixing, and entrainment of water from low and high latitudes. Interaction from multiple water sources can lead to varying conditions. New primary production is higher in this region, usually exceeding regenerated primary production. New production is higher in regions where water interacts with Atlantic Water, which has nutrient-rich waters. When looking at carbon flux from the atmosphere to the ocean, this region is considered one of the highest in the world's oceans. This region is also known as being one of the few bodies of water that take up large quantities of carbon dioxide yearly, ranging from 20 to 85 g C m−2y−1, [2] which is considered high in comparison the carbon dioxide flux in the world's oceans.

The Nordic Seas include the Greenland Sea, the Norwegian Sea, and the Iceland Sea. The Greenland and the Norwegian Sea are separately distinguished by Mohn's Ridge. [3] The Greenland and Iceland Sea are separated by the Jan Mayen fracture zone, and the Norwegian and Iceland Seas have the Aegir Ridge between them. [1] The Nordic Seas have varying and diverse features as a result of each sea having separate water mass structures and circulation patterns. The Greenland Sea produces dense waters because of its high salinity and cooler temperatures from winter cooling. Higher salinity is present as a result of the Greenland Sea's close proximity to the salinity inflow that occurs from the Atlantic Ocean. Another dense water source comes from the Arctic waters that also flow into the Greenland Sea. These water source mixtures are important because they play a role in the overflows that occur in the North Atlantic. The water that overflows from the Greenland ridge becomes the North Atlantic Deep Water [4] dense water, even though this body of water does not make up the deep waters of the Nordic Sea. [1]

Circulation

The circulation of the Nordic Seas is cyclonic. [5]

The Nordic Seas exchange water with the North Atlantic in the upper ocean. Warm water from the North Atlantic enters the Nordic Seas from the east, specifically in the Norwegian Atlantic Current (part of the North Atlantic Current). The western boundary of the Nordic Seas is the southward-flowing East Greenland Current. This current enters through the Fram Straight from the Arctic. This current is considered one of the main ways for Arctic sea ice to be exported. The East Greenland Current splits into the Jan Mayen Current on the eastern boundary of the Nordic Seas due to bathymetry. [1] The Jan Mayen Current plays an important role in the dense water formation that occurs in the Greenland Sea. [6] Continuing northward, the Norwegian Atlantic Current flows along the coast of Norway to the Arctic, eventually separating into the Barents Sea and the Spitsbergen Current. There are several gyre circulations that occur in the Nordic Seas. The subsurface waters leave the Nordic Seas through the south from overflows between Greenland and Scotland. The intermediate water leaves through the Denmark Straight and the Iceland Ridge. The densest overflow waters leave through the Faroe-Bank Channel. [1]

Water masses

The water masses that encompass the Nordic Seas are always changing in response to the local variations that occur between atmosphere-ocean fluxes and convection of intermediate to deep water. The Nordic Seas are found between the North Atlantic and the Arctic Ocean, both having variable surface water conditions. The Nordic Seas are complex in the variety of water masses it contains: two surface waters, three intermediate waters, and three deep waters. [1] Figure 3 shows the water mass circulations that occur in the Nordic Seas, displaying the surface waters, the intermediate waters, and the deep waters.

The two surface waters are the Atlantic Water and the Polar Surface Water. The Atlantic water is warm and has a higher salinity than the cooler, fresh Polar Surface Water. The difference in temperature and salinity between the two water masses plays a role in the climate of Scandinavia. The Atlantic Water enters the system with temperatures of 7 to 9 °C and a salinity of 35.2 psu. As the Atlantic water moves in the Norwegian Atlantic Current, the temperature cools to 1 to 3 °C with a salinity of 35.0 psu. [1] The warmth provided by this current plays a role in giving Scandinavia the warmer temperatures. The Polar Surface Water has a temperature around 1.5 °C and a salinity of approximately 34 psu. Depths are around 150 meters. This water increases in temperature as it reaches the Greenland Sea, but causes colder upper waters in the Greenland Sea. [1]

The first intermediate water is a remnant of the Atlantic Water from the East Greenland Current. This water has been cooled and covered by the Polar Surface Water. The temperature is around 2 °C with a salinity of 35 psu. The second intermediate water is the Arctic Intermediate Water. This water is cooler and fresher. The temperature is around -1.5 to 3 °C and has a salinity of approximately 34.88 psu. [4] Depths are around 800 meters. This intermediate water is a salinity minimum layer in the Nordic Seas, which is unique in that is lies below a salinity maximum layer, the Atlantic Water. The third intermediate layer is called the upper Polar Deep Water. This water mass comes through the Fram Strait and is found in the East Greenland Current. This intermediate water has a temperature of -0.5 °C and a salinity of 34.85-34.9 psu. [1]

The three deep waters consist of the Greenland Sea Deep Water, Norwegian Sea Deep Water, and the Arctic Ocean Deep Water. The Greenland Sea Deep Water has a temperature of approximately -1.8 °C and a salinity of 34.895 psu. [7] This water mass is formed by deep convection that occurs intermittently in the Greenland gyre. The Arctic Ocean Deep Water is approximately 34.92 psu. [1] This water mass has a higher salinity due to brine rejection in the Arctic Seas. The depth is around 1500 and 2000 meters. The Norwegian Sea Deep Water is a combination of the Arctic Ocean Deep Water and the Greenland Sea Deep Water. This water mass is found below 2000 meters. [8] Because of the warmer temperatures from the North Atlantic Current, this water mass is ice-free during the year. [1]

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The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about 106,460,000 km2 (41,100,000 sq mi). 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 and Asia from the "New World" of the Americas in the European perception of the World.

Norwegian Sea Marginal sea in the Arctic Ocean, northwest of Norway

The Norwegian Sea is a marginal sea in the Atlantic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a submarine ridge running between Iceland and the Faroe Islands. To the north, the Jan Mayen Ridge separates it from the Greenland Sea.

North Atlantic Deep Water Deep water mass formed in the North Atlantic Ocean

North Atlantic Deep Water (NADW) is a deep water mass formed in the North Atlantic Ocean. Thermohaline circulation of the world's oceans involves the flow of warm surface waters from the southern hemisphere into the North Atlantic. Water flowing northward becomes modified through evaporation and mixing with other water masses, leading to increased salinity. When this water reaches the North Atlantic it cools and sinks through convection, due to its decreased temperature and increased salinity resulting in increased density. NADW is the outflow of this thick deep layer, which can be detected by its high salinity, high oxygen content, nutrient minima, high 14C/12C, and chlorofluorocarbons (CFCs).

Ocean current Directional mass flow of oceanic water generated by external or internal forces

An ocean current is a continuous, directed movement of sea water 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.

Thermohaline circulation 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.

Water mass Body of water with common formation history

An oceanographic water mass is an identifiable body of water with a common formation history which has physical properties distinct from surrounding water. Properties include temperature, salinity, chemical - isotopic ratios, and other physical quantities which are conservative flow tracers. Water mass is also identified by its non-conservative flow tracers such as silicate, nitrate, oxygen, and phosphate.

East Greenland Current 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.

Greenland Sea Body of water

The Greenland Sea is a body of water that borders Greenland to the west, the Svalbard archipelago to the east, Fram Strait and the Arctic Ocean to the north, and the Norwegian Sea and Iceland to the south. The Greenland Sea is often defined as part of the Arctic Ocean, sometimes as part of the Atlantic Ocean. However, definitions of the Arctic Ocean and its seas tend to be imprecise or arbitrary. In general usage the term "Arctic Ocean" would exclude the Greenland Sea. In oceanographic studies the Greenland Sea is considered part of the Nordic Seas, along with the Norwegian Sea. The Nordic Seas are the main connection between the Arctic and Atlantic oceans and, as such, could be of great significance in a possible shutdown of thermohaline circulation. In oceanography the Arctic Ocean and Nordic Seas are often referred to collectively as the "Arctic Mediterranean Sea", a marginal sea of the Atlantic.

Norwegian Current A current that flows northeasterly along the Atlantic coast of Norway into the Barents Sea

The Norwegian 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 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.

Lincoln Sea Body of water in the Arctic Ocean

Lincoln Sea is a body of water in the Arctic Ocean, stretching from Cape Columbia, Canada, in the west to Cape Morris Jesup, Greenland, in the east. The northern limit is defined as the great circle line between those two headlands. It is covered with sea ice throughout the year, the thickest sea ice in the Arctic Ocean, which can be up to 15 m (49 ft) thick. Water depths range from 100 m (330 ft) to 300 m (980 ft). Water and ice from Lincoln Sea empty into Robeson Channel, the northernmost part of Nares Strait, most of the time.

Atlantic meridional overturning circulation System of currents in the Atlantic Ocean

The Atlantic meridional overturning circulation (AMOC) is the zonally integrated component of surface and deep currents in the Atlantic Ocean. It is characterized by a northward flow of warm, salty water in the upper layers of the Atlantic, and a southward flow of colder, deep waters that are part of the thermohaline circulation. These "limbs" are linked by regions of overturning in the Nordic and Labrador Seas and the Southern Ocean, although the extent of overturning in the Labrador Sea is disputed. The AMOC is an important component of the Earth's climate system, and is a result of both atmospheric and thermohaline drivers. Model projections suggest that the strength of the AMOC is “very likely” to decrease over the course of the 21st century due to climate change, which is likely to have an impact on weather patterns and sea level. Paleoclimate reconstructions and some models also raise the possibility of an AMOC collapse, which would likely affect the weather and climate system. This makes the AMOC an important climate indicator to monitor. Modern measurements of the AMOC are supported by the RAPID array, which is able to directly measure the strength of AMOC overturning directly as well as water characteristics such as temperature and salinity.

Arctic Ocean 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 the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea. It has been described approximately as an estuary of the Atlantic Ocean. It is also seen as the northernmost part of the all-encompassing World Ocean.

Fram Strait Passage between Greenland and Svalbard

The Fram Strait is the passage between Greenland and Svalbard, located roughly between 77°N and 81°N latitudes and centered on the prime meridian. The Greenland and Norwegian Seas lie south of Fram Strait, while the Nansen Basin of the Arctic Ocean lies to the north. Fram Strait is noted for being the only deep connection between the Arctic Ocean and the World Oceans. The dominant oceanographic features of the region are the West Spitsbergen Current on the east side of the strait and the East Greenland Current on the west.

Antarctic Intermediate Water (AAIW) is a cold, relatively low salinity water mass found mostly at intermediate depths in the Southern Ocean. The AAIW is formed at the ocean surface in the Antarctic Convergence zone or more commonly called the Antarctic Polar Front zone. This convergence zone is normally located between 50°S and 60°S, hence this is where almost all of the AAIW is formed.

West Spitsbergen Current 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.

The East Iceland Current (EIC) is a cold water ocean current that forms east of Greenland at 72°N, 11°W as a branch of the East Greenland Current that merges with the Irminger Current flowing southward until it meets the northeast part of Iceland. It quickly rotates in a counterclockwise direction and flows eastward along the Iceland-Faeroe Ridge before turning north and flowing into the Norwegian Sea. The EIC flows at an average rate of 6 centimeters per second, with a maximum velocity of 10 centimeters per second occurring as the current turns eastward.

The Arctic Intermediate Water (AIW) is a water mass found between the top cold, relatively fresh polar water and the bottom deep water in the Arctic domain. AIW is formed in small quantities compared to other water masses, and has limited influence outside of the Arctic domain.

Atlantification of the Arctic

Atlantification is the increasing influence of Atlantic water in the Arctic. Warmer and saltier Atlantic water is extending its reach northward into the Arctic Ocean. The Arctic Ocean is becoming warmer and saltier and sea-ice is disappearing as a result. The process can be seen on the figure on the far right, where the sea surface temperature change in the past 50 years is shown, which is up to 5 degrees in some places. This change in the Arctic climate is most prominent in the Barents Sea, a shallow shelf sea north of Scandinavia, where sea-ice is disappearing faster than in any other Arctic region, impacting the local and global ecosystem.

Faroe-Bank Channel overflow Overflow current from Nordic Seas towards North Atlantic Ocean

Cold and dense water from the Nordic Seas is transported southwards as Faroe-Bank Channel overflow. This water flows from the Arctic Ocean into the North Atlantic through the Faroe-Bank Channel between the Faroe Islands and Scotland. The overflow transport is estimated to contribute to one-third of the total overflow over the Greenland-Scotland Ridge. The remaining two-third of overflow water passes through Denmark Strait, the Wyville Thomson Ridge (0.3 Sv), and the Iceland-Faroe Ridge (1.1 Sv).

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Talley, Lynne; Pickard, George; Emery, William; Swift, James (2011). Descriptive Physical Oceanography. London, UK: Elsevier Inc. pp. 401–410. ISBN   978-0-7506-4552-2.
  2. 1 2 3 Drange, H; Dokken, T; Furevik, T; Gerdes, R; Berger, W (2005). The Nordic Seas: An Integrated Perspective (PDF). Washington, DC: American Geophysical Union. pp. 1–10.
  3. ↑ Dauteuil, O.; Brun, J.-P. (1996-08-01). "Deformation partitioning in a slow spreading ridge undergoing oblique extension: Mohns Ridge, Norwegian Sea". Tectonics. 15 (4): 870–884. doi:10.1029/95TC03682. ISSN   1944-9194.
  4. 1 2 Chen, C. "Ocean Water Masses- Intermediate, Deep, and Bottom Waters" (PDF). School for Marine Sciences and Technology UMass-Dartmouth. Retrieved April 2, 2017.
  5. ↑ Voet, G.; Quadfasel, D.; Mork, K. A.; Søiland, H. (2010). "The mid-depth circulation of the Nordic Seas derived from profiling float observations". Tellus A. 62 (4): 516–529. doi:10.1111/j.1600-0870.2010.00444.x. hdl: 11250/108390 . Retrieved 2017-04-27.
  6. ↑ Bourke, Robert H.; Paquette, Robert G.; Blythe, Robert F. (1992-05-15). "The Jan Mayen Current of the Greenland Sea". Journal of Geophysical Research: Oceans. 97 (C5): 7241–7250. doi:10.1029/92JC00150. ISSN   2156-2202.
  7. ↑ "The deep Greenland Sea is warming faster than the world ocean". www.sciencedaily.com. Retrieved 29 April 2017.
  8. ↑ Swift, James H.; Koltermann, Klaus Peter (1988-04-15). "The origin of Norwegian Sea Deep Water". Journal of Geophysical Research: Oceans. 93 (C4): 3563–3569. doi:10.1029/JC093iC04p03563. ISSN   2156-2202.
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