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Earth And Space Science NCEA Scholarship > Y13 Oceans > Flashcards

Y13 Oceans Flashcards

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1
Q

Reasons why oceans are important

A

Produces 70% atm oxygen (phytoplankton carrying out photosynthesis)

Absorbs CO2 from atm

Regulate earth temp
Distribute heat from equator to poles

Influences climate and weather
85% water added to the atmosphere comes from ocean evaporation, regulating temp

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2
Q

Formation of the ocean

A

Earth formed from dust and ice

GPE of dust and ice converted to KE, friction, hence molten surface to earth

Steam released into atm
Surface cooled, clouds formed, rain —> oceans

Comets and meteors entering earths atm add the other half of water

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3
Q

Properties of water

A

Absorb a lot of heat (high specific heat capacity)

Universal solvent - dissolves a lot of substances

Polar, so it forms a lattice when it freezes
So ice less dense than water

Strong intermolecular attraction - hydrogen bonding
Created surface tension

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4
Q

What is hydrogen bonding?

A

Strong intermolecular attraction between hydrogen and oxygen on another molecule

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5
Q

Define latent heat

A

The energy needed to change states

Latent heat of fusion - energy needed to change from solid to liquid

Latent head of vaporisation
Energy needed to change from liquid to gas

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6
Q

Define specific heat capacity

A

Amount of energy needed to raise the temperature of 1kg of water by 1C

Water has high heat capacity
So the ocean is slow to warm
Transports a huge amount of heat with only a small temperature change

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7
Q

Three main layers of the ocean

A

Mixed layer: surface
EUPHOTIC ZONE
Warmed by sunlight
Wind, waves, tides, convection currents mix this layer
Depth varies with seasons

Transition layer:
DISPHOTIC ZONE
Temp; salinity and density rapidly change

Deep layer:
APHOTIC ZONE
Fairly constant in temp and salinity

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8
Q

Parts of the transition layer

A

200m-1000m
Based on physical properties:

Thermocline - rapid temperature changes

Halocline - rapid salinity changes

Pycnocline - rapid density changes occur

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9
Q

Layers of the ocean in terms of light

A

Light is absorbed, reflected and scattered by the ocean

6% reflected at surface
65% absorbed in the first meter

Top 200m = euphotic or Protic zone = sunlight zone

200m-1000m = disphotic = twilight zone

Below 1000m = aphotic = midnight zone

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10
Q

Euphotic zone

A

Depth 50-200m, depending on turbulence and water clarity

The depth at which light drops to 1%

90% of all marine life lives here

Photosynthesis zone

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11
Q

Describe the temperature at different layers of the ocean

A

Mixed layer distributes heat, consistent

Transition layer
Thermocline, where heat energy is conducted slowly downwards, creating a temperature gradient
Temperature decreases rapidly

Deep layer: stays cold

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12
Q

How does the thermocline vary depending on latitude?

A

Upper seasonal thermocline and lower permanent thermocline

Seasonal thermocline depends on latitude

High latitude
No thermocline - low solar heating of surface layer

Mid latitudes - winter no thermocline
Summer strong thermocline. Direct sunlight and low winds so less mixing

Low latitudes - strong thermocline due to direct heating and low winds

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13
Q

Define salinity

A

The amount of dissolved salts in the ocean

Average salinity is 35ppt (parts per thousand)

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14
Q

How does salinity vary with layers of the ocean?

A

Mixed layer: similar due to mixing

Transition layer: the HALOCLINE

Deep: similar due to limited mixing

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15
Q

How is salinity reduced and increased

A

Reduced by rainfall (tropics and mid latitudes) and river runoff

Increased by evaporation (tropics) and ice formation (polar regions)
Seawater freezes, salt left behind, forming dense water which sinks

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16
Q

How does salinity vary with latitude

A

Poles: high rainfall, runoff and melting reducing salinity

Equator:
High evaporation, with rainfall reducing the effect

Tropics: Mid latitudes
Low rainfall with high evaporation, so high surface salinity

Low to high: poles, equator, tropics

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17
Q

What does density of the ocean depend on?

A

Temperature
Colder = denser

Salinity
Saltier = denser

Pressure
Deeper = denser

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18
Q

How does density vary with depth

A

Mixed layer: similar density due to mixing
Low density due to high temp
Varied with latitude due to temp and salinity

Transition: PYCNOCLINE
density increases rapidly with depth due to temp drop or salinity increase

Deep: density increases due to pressure
Cold dense water sinks

19
Q

Four factors affecting ocean currents

A

Solar radiation

Gravity

Winds and wind friction

Coriolis

20
Q

How does solar radiation cause ocean currents?

A

Uneven distribution of solar energy across globe results in uneven heating of ocean

Heating also causes evaporation and ppt, altering salinity and hence density

21
Q

How does gravity affect current?

A

Heating of water at equator causes expansion - equatorial bulge

Gravity and slope of earth - water flows toward poles

22
Q

Describe Ekman transport

A

Ocean surface waters influenced by friction force due to wind
Due to coriolis effect, ocean water moves at a 90 degree angle to the wind direction

Southern Hemisphere: 90 degrees to the LEFT

Northern Hemisphere: 90 degrees to the RIGHT

Coastal upwelling: Surface waters flow away from coast, replaced with UPWELLING of cold, nutrient rich water from below

23
Q

How does coriolis effect affect currents

A

As water moves away from equator, subject to coriolis force, deflected

This currents tend to move in curves

24
Q

What are surface currents and why are they important?

A

Top 10% of the ocean
Like rivers in the ocean, water flowing horizontally in the upper 400m

Transfer water and heat from tropical to polar regions
Influence weather and climate
Distribute nutrients, scatter organisms

25
Q

Describe Western boundary currents, how they are formed and where they flow

A

Narrow, fast moving currents on western boundaries of ocean basins
Eg. Gulf Stream, eastern Australia current

Trade winds move water across ocean basin from the east, causing ‘build up’ on western boundary
Water flows towards poles due to gravity

26
Q

Describe eastern boundary currents, how they work and where they go

A

Found on eastern boundaries of ocean basins

Broader and slower than western

Return the flow from western boundary currents, hence flow back toward equator

Powered by westerly winds

27
Q

Name the Transverse currents, and the direction of flow

A

North and South Equatorial currents
flow from EAST to WEST
driven by easterly trade winds

Arctic circumpolar current WEST to EAST
driven by strong westerly winds
carry the largest volume of water of any current (because strong winds, no land masses to slow it down)

28
Q

Counter currents

A

between North and South Equatorial currents, flowing in the opposite direction (west to east)

separates gyres

29
Q

What are gyres caused by and where are they located

A

large rotating masses of water caused by wind action and Coriolis effect

Sides of gyres are land masses
top and bottom are transverse currents

30
Q

Formation of the South Pacific Gyre

A

trade winds move water across the Pacific to the Western boundary, builds up.
Flows toward South Pole due to gravity.
Due to Coriolis, moves away from boundary. Carried by Westerlies to the East boundary.
Flows back toward equator, curving away from boundary due to Coriolis.

31
Q

what is thermohaline circulation and how does it work

A

A convection current, ‘vertical’ in the ocean

thermo = heat, haline = salt

Cold, salty water = denser, sinks. from poles to equator.
replaced by warm surface water. from equator to poles.

32
Q

three factors driving thermohaline circulation

A

temperature - cold winds cause surface temp to drop.

salinity - ocean ice formation causes increased salt concentration in the water.

evaporation - remaining water is saltier

33
Q

what two regions drive the global ocean conveyor belt?

A

North Atlantic up to Arctic

Southern Ocean

(thermohaline circulation)

34
Q

how tides work

A

bulge on two sides of earth, earth turns inside the bulge.

bulge due to sun and moon’s gravitational pull.
water is more responsive to this pull than earth, bulges

35
Q

describe the process of upwelling

A

wind blows across ocean surface, pushes it away from an area. water rises up to replace the diverging surface water.

36
Q

El Nino process

A

Normally - cell of circulation in Pacific, trade winds push warm surface water toward western boundary (Asia, Australia)
cold water replaces it at the Eastern boundary (Americas) - upwelling.
Temperature difference! warm in West (heats air, rising, unsettled weather), cool in East (descending air).
Sets up atmospheric circulation, reinforces Easterlies. Cycle.

El Nino: Weakened trade winds - less pushing and upwelling.
cancels normal temp difference, warm ocean spot moves east. `
changes rainfall and wind pattern over equatorial pacific.

Tropics - increase in floods/droughts

37
Q

Role of ocean currents

A

Redistribute massive amounts of Solar heat energy from one part of the earth to another

38
Q

waves vs tides vs currents

A

waves are usually created by wind, transport energy, NOT matter
measurable crest / trough

tides are a result of the interaction between the rotation of the earth and the gravitational pull of the moon

currents are large masses of water moving from one location to another
transports energy AND MATTER

39
Q

how do wind waves form

A

the transfer of energy from the wind to the water

friction of wind on surface

40
Q

three factors affecting the growth of wind waves

A

Wind strength: wind must move FASTER than wave crests to transfer energy to it

wind duration

Fetch: the uninterrupted distance over which the wind blows

a strong wind must blow in one direction for almost 3 days for the largest waves to develop
eg. in the Southern Ocean

41
Q

Why and how do tides occur

A

grav pull from sun / moon stronger on one side of the earth

the longest of all waves – wavelength = half the circumference of earth

42
Q

spring tides

A

New / Full moon (earth, moon and sun aligned).
Either the highest high or lowest low tides

43
Q

neap tides

A

first-quarter and third-quarter moons

the highest low tide and the lowest high tide
lunar and solar tides partially cancel

unusually small tidal range

44
Q

describe the ocean acidification process

A

CO2 reacts w/ H2O to form carbonic acid, H2CO3
dissociates to form bicarbonate ions,
HCO3-, and H+
some reacts to form CO3^2-, more H+

Earth And Space Science NCEA Scholarship (10 decks)

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