User:Jegg247/Circumpolar deep water

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Circumpolar Deep Water (CDW) is a designation given to the water mass in the Pacific and Indian oceans that essentially characterizes a mixing of other water masses in the region. A distinguishing characteristic is the water is not formed at the surface, but rather by a blending of other water masses, including the North Atlantic Deep Water (NADW), the Antarctic Bottom Water (AABW), and the Pacific Intermediate Water masses.

Physical Properties
CDW, the greatest volume water mass in the Southern Ocean, is a mixture of NADW, AABW, and Antarctic Intermediate Water (AAIW), as well as recirculated deep water from the Indian and Pacific Oceans.

CDW sits at a depth of around 500 meters which is near the sea floor of the continental shelf.

The are two types of CDW: Upper Circumpolar Deep Water (UCDW) and Lower Circumpolar Deep Water (LCDW). UCDW originates in the Indian and Pacific Oceans and has lower oxygen levels and higher nutrients than LCDW. LCDW comes from North Atlantic Deep Water and has a higher salinity.

In the Indian Ocean, CDW has a temperature of 1.0 to 2.0°C. In the Pacific Ocean, it is slightly colder with a temperature of 0.1 to 2.0 °C.

The salinity of CDW is 34.62 to 34.73 ‰.

Because the CDW is a mix of other water masses, its temperature-salinity (TS) profile is the point where the TS lines of the other water masses converge. TS diagrams refer to temperature and salinity profiles, which are one of the major ways water masses are distinguished from each other. The convergence of the TS lines thus proves the mixing of the other water masses. Circumpolar deep water is between 1–2 °C (34–36 °F) and has a salinity between 34.62 and 34.73 practical salinity units (PSU).

Influence on Antarctic ecosystems and ice shelves
The CDW plays an important role in the Antarctic Circumpolar Current (ACC) because it contributes to the melting of the base of ice shelves. It has been shown that galciers ending in CDW have melted considerably while glaciers in the northwest, with no CDW, have not.

CDW is salty and slightly above freezing temperature, which is warm compared to ice shelves. When CDW flows upward onto the continental shelf and carries with it warmer water, it contributes to ice shelf melting. Upwelling of the CDW onto the Antarctic continental shelves brings nutrients that support ecosystems along the west Antarctic Peninsula.

Gradients around Antarctica are formed between shelf water and CDW which are called the Antarctic Slope Front.