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earth surface science > Oceans > Flashcards

Oceans Flashcards

1
Q

How much of earths surface is covered by ocean

A

71%

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2
Q

How much of earths water does oceans holds

A

97%

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3
Q

What controls the climate and weather on earths surface?

A

The interactions between the oceans and atmosphere

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4
Q

What are oceans responsible for?

A

Oceans are responsible for keeping conditions on the earth steady

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5
Q

Name all 5 major oceans

A
  • Pacific
  • Atlantic
  • Arctic
  • India
  • Southern ocean
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6
Q

How can the effect of oceans on climate be measured

A

The effect of oceans on regional climates can be measured by comparing annual air temp at different latitudes

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7
Q

What are the most important bathymetric features of the sea floor?

A
  • Continental shelf - thinning continental crust
  • Slope and rise - transition between crust types
  • Abyssal plains
  • Oceanic ridges
  • Oceanic trenches
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8
Q

How old is the ocean?

A
  • Relatively young due to subduction of oceanic crust

- Oldest areas are ones furthest away from ridges

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9
Q

What is the geology of the ocean crust?

A
  • Formed at sea floor spreading ridges from magma
  • 10% of the mantle rock melts producing magic magma
  • 50% silica (forms pillow basalts, breccia and flows
  • Beneath is gabbros - formed through the cooling of magma under the crust
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10
Q

Describe oceanic sediment

A
  • Thickness increases away from oceanic ridges
  • Various sediment sources depending on the proximity to continent, water depth, currents, bio activity and climate
  • Terrigenous - material eroded from land
  • Pelagic - living organism shells - carbonate and silica
  • Volcanic ash
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11
Q

Where is oceanic sediment distributed?

A
  • Terrigenous - close to continents - from deltas
  • Red clay - located near shore environments
  • Silica - southern polar regions and equator in pacific
  • Carbonate - cannot be lower than 4000 as it will dissolve
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12
Q

Why do humans retrieve deep sea sediment cores?

A
  • Gives us information about the climate in the past

- Retrieved using drilling, majority of oceans have been drilled

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13
Q

Why is sea salty?

A

The dissolved ions have been concentrated in sea water as a result of chemical weathering and the degassing of the mantle volcanic activity

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14
Q

Why does salinity vary in the ocean?

A

surface waters evaporate, rain and stream water is added and ice forms and thaws

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15
Q

What are the different depths of the ocean divided into?

A

Divided into areas based on temp and density

- all zones based on horizontal distance from continental plate

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16
Q

How far does the sun penetrate into the ocean

A

only penetrates 200m of ocean water

17
Q

What is the photic zone?

A
  • The top 200m of the ocean

- Important for marine wildlife

18
Q

What is the aphasic zone?

A
  • Not enough light for photosynthesis

- Makes up majority of ocean water

19
Q

What are the 4 primary factors that control ocean circulation?

A
  • Water salinity
  • Water temp
  • Surface winds
  • Coriolis effect
20
Q

What is ocean circulation a major component of?

A

The climate system through the distribution of thermal energy

21
Q

What is surface ocean circulation primarily influenced by?

A
  • Winds - controlled by atmospheric circulation

- Earths rotation

22
Q

What is thermohaline circulation (THC)

A

The movement of sea water in a pattern of flow dependent on variations in temperature, which give rise to changes in salt content and hence in density

23
Q

What is deep sea circulation primarily influenced by?

A
  • Density (temp and salinity)

- Position of land masses

24
Q

What is the oceanic circulation system?

A
  • Global conveyer
  • Driven by changes in water temp and density
  • surface flow of North Atlantic dominated by Gulf Stream
  • Warm salty water driven northwards by prevailing winds
  • Water cools and density increases and sinks near South Greenland
  • This feeds the North Atlantic Deep Water (NADW)
  • Current flows southwards to compensate for North flowing Gulf Stream
  • Tother them comprise the Atlantic Meridional Overtiming Circulation (AMOC)
25
Q

Outline AMOC

A
  • Water evaporates near tropics
  • E-W trade winds precipitate it init pacific
  • Salinity increases in Atlantic and decreases in pacific
  • Causes warm, salty Gulf Stream
26
Q

Outline NADW

A
  • Surface water cools (denser)
  • Forms sea ice - becomes saltier (denser)
  • Sinks
27
Q

What are the stages of Broeckers (1990) Salt Oscillator Hypothesis?

A
  • Injection of fresh water into N Atlantic reduces surface water density
  • sinking no longer takes place
  • AMOC slows down/shuts down
  • reduces northward heat transfer via Gulf Stream
  • Northern hemisphere ice sheets grow
  • salt content gradually increases (evaporation) as salty water is not removed from from the Atlantic
  • As salt accumulates, it gradually increases density until AMOC is able to start again
  • Positive feedback mechanisms
28
Q

What happens during times of NADW formation?

A
  • Ice melting dilutes salinity of North Atlantic

- Eventually slowing or stopping NADW formation

29
Q

What happens when NADW does not form?

A
  • Less salt removed and little heat transported north
  • Ice sheets stop melting
  • North Atlantic gets salty and NADW starts to form again

earth surface science (17 decks)

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