The Arctic Intermediate Water (AIW) is a

water mass 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 ...

found between the top cold, relatively fresh polar water and the bottom deep water in the Arctic domain (bounded by the polar and

arctic front The Arctic front is the semipermanent, semi-continuous weather front between the cold arctic air mass and the warmer air of the polar cell. It can also be defined as the southern boundary of the Arctic air mass. Mesoscale cyclones known as pola ...

s).Swift, J. H . and Aagaard, K. (1981) Seasonal transitions and water mass formation in the Iceland and Greenland seas, ''Deep-Sea Research'', 28, 1107-1129 AIW is formed in small quantities compared to other water masses, and has limited influence outside of the Arctic domain.

Characteristics

Two types of AIW are found, which are lower AIW and upper AIW separately. Lower AIW is the

with temperature and

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

maximum found at 250~400m deep, right above the deep water, with temperature for lower AIW ranges from 0 to 3 °C and

greater than 34.9.Helland-Hansen B. and Nansen F. (1909) The Norwegian Sea. Its physical oceanography based upon the Norwegian researches 1900-1904, ''Report on Norwegian Fishery and Marine Investigations'', 2, 390 pp Upper AIW is defined to be a denser layer on top of the lower AIW, between surface cold water and the lower AIW, including

es with temperature maximum to minimum. It is characterized by temperatures less than 2 °C in the salinity ranges from 34.7 to 34.9.Blindheim, J. (1990) Arctic Intermediate Water in the Norwegian Sea, ''Deep-Sea Research'', 37, 1475-1489 The upper AIW is usually found at 75~150m, overlain by Arctic Surface Water (ASW). However, it could be found at the sea surface in winter. There are overlaps in density for upper and lower AIW according to their definitions. It is possible that

falling within the definition of upper AIW is below the defined lower AIW. For example, in

Norwegian Sea The Norwegian Sea ( no, Norskehavet; is, Noregshaf; fo, Norskahavið) is a marginal sea, grouped with either the Atlantic Ocean or the Arctic Ocean, northwest of Norway between the North Sea and the Greenland Sea, adjoining the Barents Sea to ...

, one intermediate layer of

slightly less than 34.9 was found below the

with temperature and

maximum.

Formation

It is generally accepted that AIW is formed and modified in the north part of Arctic domain. As AIW moves from north to south along the Greenland continental slope, its temperature and salinity, on the whole, decrease southwards due to mixing with surface cold water. The lower AIW is produced by the cooling and sinking of Atlantic Water (AW), which is traditionally defined with

greater than 35, and by the Polar Intermediate Water (PIW) that is colder than 0 °C with salinity in the range 34.4-34.7.

Seasonal variations

Amount of AIW varies with different seasons. For example, the upper AIW in Iceland sea increased from about 10% of the total volume in fall to over 21% in winter. In the same time, both ASW and lower AIW show significant summer-to-winter decreases, which might contribute to the new upper AIW. Similar process can also be found in Greenland sea, but with a smaller amount of formed upper AIW.

References

{{Reflist Hydrology