EAE 03 Oceans (7)

Question 1

How much CO₂ does the ocean absorb?

Answer 1

Every year the ocean absorbs approx ⅓ of human CO₂ emissions.

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Question 2

Why is temperature important?

Answer 2

• Temperature is important because it reflects the amount of heat held and transported by the ocean.
• It plays important role in circulation via density

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Question 3

Definition

Adiabatically

Answer 3

Occurring without gain or loss of heat.

I.e. no heat is transferred to or from the fluid.

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Question 4

How are pressure differences created?

Answer 4

Horizontal differences in height of the water

Density differences between water columns

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Question 5

What impact does ‘La Nina’ have?

Answer 5

Tropical cyclones more likely to form near Australia

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Question 6

What is the ‘age’ of water?

Answer 6

The “age” of water is commonly defined as the time since it was last at the surface.

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Question 7

What are the key ingredients for Tropical cyclone formation?

Answer 7

• Warm water, SST > 26.5
• A latitude at least 5° away from the equator
• Various other criteria not directly ocean conditions that can vary in all locations.

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Question 8

What influences surface salinity?

Answer 8

Surface salinity is set by

• Rainfall
• Evaporation
• Rivers
• Ice

etc.

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Question 9

How is pressure created underwater?

Answer 9

Pressure = the weight of water sitting above you

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Question 10

What influences interior salinity?

Answer 10

Interior salinity is set by currents that take water from the surface to interior regions

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Question 11

What is the Potential Temperature (θ)?

Answer 11

The temperature a water parcel would have at the surface, if it were raised to the surface adiabatically.

• From gas laws, T is proportional to P
• Thus, as pressure increases, (volume decreases) and temp increases.

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Question 12

What are the characteristics of water sinking in the Southern Ocean?

Answer 12

• Polynya’s (Holes in the sea ice) expose the relatively warm ocean (2°C) to the very cold atmosphere (-20°C), which leads to intense cooling
• Sea ice formation in these Polynya’s also leads to “brine rejection”, whereby the salt is expelled from the water freezing, which makes the remaining water saltier and denser.

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Question 13

What is SST?

Answer 13

Sea Surface Temperature

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Question 14

What impact does the ocean have on temperature?

Answer 14

Ocean effective stabilizes the earth’s temperature.

The ocean can absorb large amounts of heat without a large increase in temperature.

>90% of earths energy imbalance is stored in the ocean.

Thus, the ocean can effectively store large amounts of energy, while releasing this additional energy over long periods of time allows the ocean to play a central role in stabilizing Earth’s climate system.

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Question 15

What is ‘psu’?

Answer 15

Practical Salinity Units

Equivalent to parts per thousand (ppt)

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Question 16

How much of the earth’s surface is covered by water?

Answer 16

Water covers approx 71% of world surface

• Pacific Ocean 46%
• Atlantic Ocean 23%
• Indian Ocean 20%
• Others 11%

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Question 17

What cuases sinking in the North Atlantic?

Answer 17

• Water flowing northward becomes modified through evaporation and mixing with other water masses, leading to increased salinity.
• Upon reaching the North Atlantic, this water cools, and due to its cool temperatures and high salinity it becomes a very dense water mass.
• It is denser than the underlying water, which leads to sinking (oceanic convection).

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Question 18

How deep are ocean trenches?

Answer 18

Depths can reack 11km.

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Question 19

What is the average width of continental shelf?

Answer 19

Average width is approximately 65km.

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Question 20

What is Thermohaline circulation?

Answer 20

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

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Question 21

What does the sinking water in the North Atlantic become?

Answer 21

North Atlantic Deep Water (NADW)

The sinking water in the North Atlantic can reach depths of 2000m, becomes North Atlantic Deep Water (NADW).

NADW has:

* Temperature of 2-4°C
* Salinity of 34.9-35.0 psu
* Typically resides at depths of 1.5 to 4 km.

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Question 22

What are the flows in the Deep Ocean?

Answer 22

• Flow in the deep ocean is very slow, on the order of cm/s
• Models estimates that this can be more than 1000 years, like those of the North Pacific, which houses the oldest waters in the world.

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Question 23

What is the temperature range of the ocean?

Answer 23

The temperature range in the ocean varies from -2°C at the poles to >28°C at the equator.

The temperature of the ocean is primarily influenced by the heating at the air-sea interface.

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Question 24

What is the range of density?

Answer 24

• Density depends on salinity, temperature and pressure.
• Seawater density ranges from 1020~1030 kg/m³
• The average density is 1025 kg/m³

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Question 25

What increases the density of sea-water?

Answer 25

Density of water increases if it is

* Colder
* Saltier

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Question 26

Where are Polynyas found?

Answer 26

• Coastal Polynyas are fairly common around Antarctica, due to the persistent katabatic winds that blow the ice away from the coastline.
• Those in the middle of the open ocean are rare, and need specific conditions. (e.g. the last Weddell Polynya occurred in 1976).

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Question 27

What is ocean salinity?

Answer 27

Total dissolved solids (mainly sodium chloride or “table salt”)

About 3.5% by weight (i.e. 35 kg of salt in 1,000 kg of pure water on average or 35 psu)

Plays an important part in ocean circulation through its influence on density.

Varies geographically according to

    * Evaporation
    * Precipitation
    * River outflow
    * Ice formation
    * Ice melt.

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Question 28

What is the average depth of the ocean?

Answer 28

The average depth 3,800m of the ocean?

This compares with the earth’s radius of 6400km

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Question 29

What impact does sea surface temperature have on cyclones?

Answer 29

Tropical cyclone intensity can increase with increasing SST.

Hurricane wind speeds doubled as temperatures increased significantly.

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Question 30

What is the water around the Antartica called?

Answer 30

Antarctic Bottom Water (AABW).

These are the densest water in the world, hence the reference to “Bottom”

They have:

* Temperatures ranging from -0.8oC to 2oC.
* Salinities that range from 34.6 to 34.7 psu.

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Question 31

What impact does ‘La Nino’ have?

Answer 31

Tropical cyclones are less likely to form near Australia

The formation shifts in to central Pacific.

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