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Oceanography > Deep ocean currents - 7 > Flashcards

Deep ocean currents - 7 Flashcards

1
Q

What is thermohaline circulation?

A

A density driven flow of water generated by differences in water temperature and salinity

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2
Q

Water at the surface is expose to more rapid changes in…

A
  • Salinity: evaporation and precipitation

- Temperature: cooling and heating

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3
Q

Based on depth below the surface, water masses can be broadly classified as …

A
  • Central waters: 0-1 km
  • Intermediate waters: 1-2 km
  • Deep and bottom waters: >2 km
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4
Q

Where does deep and bottom water originate?

A

At the surface where it is cooled and/or density increases until it sinks

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5
Q

Where is deep water the youngest?

A

North Atlantic (200 years)

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6
Q

Where is deep water the oldest?

A

North Pacific (1200 years)

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7
Q

Where is water >10ºC confined?

A

Between 45ºN and 45ºS

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8
Q

‘Climate change affects thermohaline circulation’, true or false?

A

True … increased freshwater influx to the North Atlantic would prevent NADW from downwelling, thereby chasing weather patterns in Europe and North America

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9
Q

Which ocean has the most complex stratification?

A

The Atlantic ocean

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10
Q

What water masses are found in the Atlantic ocean?

A
  • Antarctic bottom water (ABW)
  • Antarctic deep water (ADW)
  • North Atlantic deep water (NADW)
  • Arctic Intermediate water (AIW)
  • Mediterranean Intermediate water (MIW)
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11
Q

Where does Antarctic bottom water form? where does it flow?

A

The Weddel Sea … Northward into the Atlantic

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12
Q

What is the densest water mass in the ocean?

A

ABW

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13
Q

What is Antarctic deep water?

A

A less saline, slightly warmer mass formed off the coast of Antartica

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14
Q

How does the ADW flow?

A

Flows along the surface to the Antarctic convergence where it sinks and becomes sandwiched between ABW and NADW

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15
Q

What is North Atlantic Deep Water?

A

A cold, salty water mass formed off the coast of Greenland. It flows southward along the bottom until it encounters the ABW and rides over this

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16
Q

What is Arctic Intermediate Water?

A

A water mass formed in subarctic regions and flows southward between surface water of the Sargasso Sea and NADW

17
Q

What is Mediterranean Intermediate Water?

A

A water war, highly saline water mass that flows out of the Mediterranean Sea

18
Q

To what depth does MIDW sink?

A

1 km … spreads westward across the Atlantic

19
Q

What is Common Water?

A

The Pacific Oceans main water mass, formed by a blending of ABW and NADW in the Antarctic Circumpolar Current.

20
Q

How does Common Water flow?

A

Injected into the Pacific basin and flows northward to 10ºS where it encounters Pacific Subarctic Water

21
Q

Which waters dominate the Pacific ocean above 2000 metres?

A

North Pacific Intermediate Water and Antarctic Intermediate Water

22
Q

Which ocean has the simplest stratification?

A

The Indian Ocean

23
Q

Which water mass dominates the Indian ocean?

A

Common Water

24
Q

What 3 water masses are found in the Indian ocean?

A
  • Common Water
  • Antarctic Intermediate Water
  • Red Sea Intermediate water
25
Q

What is the Red Sea Intermediate Water?

A

A warm, highly saline (40ppm) water mass formed in the Red Sea that sinks to 3000m in the Indian Ocean basin

26
Q

Where does Atlantic water flow into the Mediterranean basin?

A

Across the Straits of Gibraltar at the surface

27
Q

As water flows eastward in the Mediterranean basin …

A
  • salinity increases due to increase evaporation

- the sea surface slopes eastward creating a pressure gradient

28
Q

How is Mediterranean water formed?

A

Sinking, warm but highly saline (38ppm) water sinks in the east of the basin and flows along the bottom until it enters the Atlantic ocean

29
Q

What temperature is MIW and at what depth does it flow?

A

13ºC and flows at 1km depth

30
Q

What are surface water conditions in the Black Sea?

A

Surface waters are brackish (excess precipitation and river inflow from the Danube)

31
Q

What prevents mixing in the Black Sea?

A

A strong halocline and thermocline

32
Q

What is water like below the pycnocline in the Black Sea?

A
  • Anoxic

- Rich in dissolved hydrogen sulphide gas

33
Q

What is the turnover time of the Black Sea?

A

Approx 3000 years

34
Q

What % of the ocean has a temperature of 0-5ºC?

A

75%

Oceanography (13 decks)

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