What is NADW and Aabw?

North Atlantic Deep water (NADW) is a water mass that is derived from the warm salty waters of the Gulf Stream. … In the modern ocean, fresher water masses from the southern ocean, Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW) lie below and above NADW, respectively.

How can you identify Antarctic Intermediate Water?

Antarctic Intermediate Water, ocean water mass found in all the southern oceans at depths of about 1,650 to 4,000 ft (500 to 1,200 m), characterized by temperatures of 37° to 45° F (3° to 7° C) and salinities of 33.8 to about 34.5 parts per thousand.

What and where is the Aabw?

The Antarctic bottom water (AABW) is a type of water mass in the Southern Ocean surrounding Antarctica with temperatures ranging from −0.8 to 2 °C (35 °F) and salinities from 34.6 to 34.7 psu.

Why are the NADW and the Aabw important for global ocean circulation?

They influence the density structure of the deep ocean and thereby lead to alterations in the strength of the ACC. Changing the wind stress south of 30°S influences the magnitude of the deep water production of both hemispheres.

How is Aaiw formed?

Formation. The formation of AAIW can be explained very simply through the Ekman transport process and the divergence and convergence of water masses. The winds over Antarctica are called the polar easterlies where winds blow from the east to the west.

Why is AABW so dense?

Antarctic Bottom Water is formed around the edge of Antarctica, especially in the Ross and Weddell seas, where the formation of ice during the winter season adds salt to the water below the ice, making very dense water.

What makes Aaiw low salinity?

The AAIW, characterized by a salinity minimum (S < 34.3), has contributions from the coldest and densest (σθ ~ 27.3 kg/m3) member of the Southern Hemisphere Subpolar Mode Water or Subantarctic Mode Water (SAMW), which originates from deep winter convection along the Subantarctic Zone, and AAIW derived from the …

Where is the Antarctic Intermediate Water formed?

the Southern Ocean The Antarctic Intermediate Water is formed in the Southern Ocean and is characterized by a salinity minimum below the thermocline. It is found north of the Subantarctic Front.

Where does the Mediterranean intermediate water form?

In the Atlantic, Mediterranean Intermediate Water (MIW) flows through the Straits of Gibraltar into the open ocean. This water is warm and salty from the warm temperatures and high evaporation characteristic of the Mediterranean Sea, so it is denser than the normal surface water and forms a layer about 1-1.5 km deep.

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What is the coldest water on Earth?

A “supercoolometer”, a device that sounds like it should be used to measure hipsters, has found the coldest seawater on Earth, under Antarctic sea ice. NIWA oceanographer Dr Craig Stevens and his team are researching why, in a warming world, sea ice is growing in the Antarctic even though it is receding in the Arctic.

How cold is the water in Antarctica in winter?

The Antarctic Ocean’s freezing temperatures of 28.8 degrees Fahrenheit (minus 1.8 degrees Celsius) are lower than the freezing point of fish blood, which is about 30.4 degrees F (minus 0.9 degrees C), which would seem to suggest that all those fish should be frozen in their tracks.

What is the coldest ocean in the world?

The Arctic Ocean The Arctic Ocean is the smallest, shallowest, and coldest part of the ocean.

Is Aabw saltier than NADW?

All varieties of AABW are very cold and relatively fresh in comparison to North Atlantic Deep Water (NADW). … While these overflow waters comprise the densest waters in some of the North Atlantic and thus sink to the seafloor near where they are formed, they are substantially warmer, saltier, and lighter than AABW.

How far south does the NADW travel?

NADW travels down the west side of the North Atlantic Ocean at a depth of 2000-4000m and through the west side of the South Atlantic. Much of NADW upwells in the Southern Ocean, but portions join the Antarctic Circumpolar Current and travel at depth into the Indian and Pacific Oceans.

Is the NADW well oxygenated?

These well-oxygenated bottom waters originate from down-welling/thermohaline circulation in polar regions. … Here North Atlantic Deep Water (NADW) is formed which feeds the upwelling in many other regions of the world ocean.

What is the average speed of the ACC?

The Antarctic Circumpolar Current’s eastward flow is driven by strong westerly winds. The average wind speed between 40°S and 60°S is 15 to 24 knots with strongest winds typically between 45°S and 55°S.

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How is North Atlantic deep water formed?

Formation and sources. The NADW is a complex of several water masses formed by deep convection and also by overflow of dense water across the Greenland-Iceland-Scotland Ridge.

Which water mass forms the deepest layer in the Atlantic Ocean?

North Atlantic Ocean Ocean; the other is the North Atlantic Deep Water, which has a temperature of 2.2 to 3.5 °C (4 to 6.3 °F) and a salinity between 34.90 and 34.97 ppt and which occupies the deepest layers of the ocean (generally below 1,000 metres [about 3,300 feet]).

Is the ocean well stirred?

The surface layer is the top layer of the water. This layer is also known as the mixed layer and is well stirred from the wind and other forces. This top ocean layer tends to be the warmest layer due to heating from the sun.

How deep is the water around Antarctica?

The deep ocean around Antarctica is a special place for several reasons. Because Antarctica is pushed down by the weight of its ice sheets, the submerged continental shelf around it is deeper than usual, around 500-600m deep at its edge rather than 100-200m deep.

What’s at the bottom of Antarctica?

Scientists have discovered two new lakes buried deep beneath the Antarctic Ice Sheet. These hidden gems of frigid water are part of a vast network of ever-changing lakes hidden beneath 1.2 to 2.5 miles (2 to 4 kilometers) of ice on the southernmost continent.

Which of these conditions describes the Antarctic Bottom Water?

Antarctic bottom water is an important water mass that forms on the Antarctic continental shelf as a cold, dense residual brine during the formation of sea ice. Its salinity of 34.62 parts per thousand and temperature of -1.9° C (28.6° F) result in a high…

How is North Pacific intermediate water formed?

The North Pacific Intermediate Water is a well-defined salinity minimum, located in the North Pacific subtropical gyre. … NPIW forms when low-salinity, high-oxygen subpolar water is overrun by warm, saline subtropical waters. The NPIW occurs where the cold, low-saline Oyashio and warm, saline Kuroshio currents meet.

When did the Antarctic circumpolar current form?

The timing of the opening of the Drake Passage, between South America and the Antarctic Peninsula, is more disputed; tectonic and sediment evidence show that it could have been open as early as pre-34 Ma, estimates of the opening of the Drake passage are between 20 and 40 Ma.

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Why might intermediate water forming in the Mediterranean Sea flow at the same depth as intermediate water formation in the Antarctic?

Mediterranean water is saltier than Atlantic water at the same depth so Med water sinks as it leaves the Med.

Which ocean current drives the thermohaline circulation?

The cold, salty waters that drive the thermohaline circulation form in the Arctic Ocean, the North Atlantic, and the Southern Ocean. The shallow ocean floor along the Bering Straight prevents deep currents from flowing out of the Arctic Ocean into the Pacific.

Where does deep water formation occur?

Deep water formation takes place in a few localised areas: the Greenland-Norwegian Sea, the Labrador Sea, the Mediteranean Sea, the Wedell Sea, the Ross Sea. Spreading of deep waters (e.g., North Atlantic Deep Water, NADW, and Antarctic Bottom Water, AABW), mainly as deep western boundary currents (DWBC).

How long does thermohaline circulation take?

Lecture notes from one of Columbia University’s 2007 The Climate System class suggests this process takes between 100-1000 years. This paper says Thermohaline Circulation overturns deep water every 600 years or so.

What are the five water masses?

We talk about “the global ocean circulation” because although the Earth officially has five oceans, they are not totally separate bodies of water. In fact, the Arctic, Atlantic, Indian, Pacific and Southern oceans are interconnected, with water circulating and moving between them.

What process causes the Mediterranean intermediate water to become more dense than water in the adjacent Atlantic ocean?

Mediterranean and Red Sea Intermediate Waters become more dense by significantly increasing salinity as surface water evaporates.

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