Oceanography - Final Exam

What is the chemical formula for water?

H₂O - 2 Hydrogen, 1 Oxygen

Structure of a water molecule

• Polar molecule with a bent shape (105 degree angle)

• O: has a partial negative charge

• H: has a partial positive charge

• Covalent bonds hold atoms together within molecules

• H bonds connect separate water molecules

Cohesion

water molecules stick to each other, creating surface tension

ex. insects can walk on water due to surface tension

Adhesion

water molecules stick to other substances

• contributes to water movement in plants against gravity

Capillary action

the process of a liquid flowing in a narrow space without the assistance of external forces like gravity (ex: water climbing up the roots of a tree)

Thermal properties of water

• High heat capacity

• Thermal inertia

• Helps to moderate Earth’s temperatures (day/night cycles, seasonal changes)

Heat capacity

the ability of a substance to absorb or release large amounts of heat with no change in temperature

Thermal inertia

the tendency of a substance to resist change in temperature

How does the ocean moderate Earth’s temperatures?

ocean currents act much like a conveyor belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics

Freezing properties of water

• Water expands when frozen

• Ice floats on liquid water

• Allows aquatic life to survive under frozen water bodies

How are the ocean layers organized?

Density stratification

• Denser layers of ocean water sink to the bottom

• Less dense layers of ocean water rise above

Surface zone/mixed layer

• Warm, less dense water

• Affected by wind, waves, and surface heating

• Varies seasonally and by location

Pycnocline

• Transition zone where density changes rapidly with depth

• Contains the thermocline (rapid temperature change) and halocline (rapid salinity change)

Deep zone

• Cold, denser water

• Relatively stable conditions

What factors affect seawater density?

• Temperature

• Salinity

• Water mass

How does temperature affect the density of seawater?

• Colder water is generally denser than warmer water

• Maximum density of pure water at 4 degrees Celsius

• Seawater continues to become denser as it cools to freezing

How does salinity affect the density of seawater?

• Higher salinity increases density

• Affects freezing point (more salt = lower freezing point)

• Affects evaporation (more salt = slower evaporation)

How does water mass affect seawater density?

• The ocean is a body of water with characteristic temperature and salinity

• Limited vertical movement between water masses of different density

• The heavier the mass, the lower the water layer

Photic zone

• Sunlit portion of the ocean

• Only a thin film of surface water receives sunlight

• Blue light penetrates deepest

Aphotic zone

• No sunlight reaches this zone

• Most of the ocean is in permanent darkness

Scattering

Light bounces between molecules

Absorption

Water molecules absorb light energy

How is sound transmissed through water?

• Sound travels much farther than light in water

• Speed of sound varies with:

  • Temperature

  • Salinity

  • Pressure (depth)

Shadow zone

area where little sound energy penetrates

What are sonar systems used for?

Used for navigation, mapping, and detecting objects

Active sonar

a type of sonar system that sends “pings” and listens for echoes

Passive sonar

a type of sonar system that listens without emitting any of its own signals

What makes water an excellent solvent?

it dissolves more substances than any other natural liquid

Ion

molecule with unbalanced electrical charge. moves through water via diffusion

Salinity

the quality or degree of being saline

Components of salinity

• Primarily sodium and chlorine ions

• Sources: weathering of surface rocks and outgassing from Earth’s interior

Forchhammer’s Principle

The ratio of dissolved ions is constant worldwide, it is the addition of more freshwater to an area that determines how salty the water there is compared to other places.

Nitrogen

most abundant dissolved gas, major dissolved gas

Oxygen

critical molecule for marine life, major dissolved gas

Carbon dioxide

highly soluble in water, major dissolved gas. moves quickly from atmosphere to ocean, slowly from ocean to atmosphere

Temperature

solubility factor. cold water holds more gas than warm water

pH scale

the measurement of concentration of hydrogen ions

• average seawater pH = ~8.0 (slightly basic)

Buffering capacity

• Seawater resists pH changes due to carbonate chemistry

  • If seawater is too basic, Carbonic acid yields Bicarbonate and Hydrogen ion (H⁺) and the pH drops

  • If seawater is too acidic, the reverse takes places; Bicarbonate and Hydrogen ion (H⁺) yields Carbonic acid and the pH rises

Ocean acidification

a reduction in the pH of the ocean over an extended period of time, caused primarily by uptake of carbon dioxide (CO₂) from the atmosphere

Surface tension

the property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules

Latent heat

the heat required to convert a solid into a liquid or vapor, or a liquid into a vapor, without change of temperature

Thermocline

a steep temperature gradient in a body of water, marked by a layer above and below which the water is at different temperatures (the gradual drop in temperature in water)

Halocline

a layer within a body of water (water column) where there is a sharp change in salinity (salt concentration) with depth

How does water get to the leaves in the tops of the trees against the force of gravity?

• Cohesion-tension theory

• Water molecules stick together, leaving no room for air

• A force propels them upwards

• Combination of capillary action and transpiration

Why does ice float on water? Why is this property important for aquatic life?

• Ice is less dense than water

• Provides habitats for arctic animals

Describe how heat and temperature are not the same thing.

Temperature: an object’s response to the input/removal of heat (the measurement)

Heat: the energy produced by the vibration of molecules

What is the relationship between the density of water and salinity?

Increasing salinity increases density

How is the ocean stratified by density? What names are given to the ocean’s density zones?

Warmer and less salty water sits above cooler, saltier water

• Surface zone/mixed layer

• Pycnocline

• Deep zone

How does the pH of water change with depth and why?

• Near the surface of water, pH is higher because light is available for algae to photosynthesize

• pH is lower in larger depths because of the low photosynthesization rate: less oxygen is produced

What might be some of the consequences of ocean acidification?

• Marine food chains could be altered and less available to humans

• Reefs and tourism opportunities have decreased storm protection

• Disruption of marine ecosystem

• Coral and marine organisms who rely on their shells will not be able to produce as much

How is heat transported from tropical regions to polar regions?

Atmospheric and ocean currents carry heat across the world.

Why is the ocean considered a “carbon sink”? Why is this important?

The ocean absorbs excess heat and energy released from rising greenhouse gas emissions trapped in the Earth's system. This is so it regulates the gases in our atmosphere

How might global warming affect the ocean’s density structure?

Because water becomes less dense and expands as it heats up, it occupies more space and causes sea levels to creep up

Density stratification

the formation in a body of water of relatively distinct and stable layers by density. less dense waters are on top; more dense waters are at the bottom

What are Earth’s ocean and atmosphere unevenly heated by?

The sun—the atmosphere circulates in response to this difference in heating

More solar energy is absorbed near the _______ than the poles

Equator

Coriolis Effect

a fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. air moves clockwise in the Northern Hemisphere while air moves counterclockwise in the Southern Hemisphere

How many circuits are there in the atmosphere?

Six (three in each hemisphere)

What two air masses can a storm form between?

Frontal storms

Frontal storm

this forms when a cold air mass forces a warm, moist air mass above it

What air mass can a storm form inside?

Tropical cyclones

Tropical cyclone

a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls

Atmosphere

gases that envelop Earth

Wind

mass movement of air

Weather

state of the atmosphere at a particular time and place

Climate

long-term statistical sum of weather in a given area

How much water vapour occupies the volume of air?

4%

What influences air density?

temperature and water content

What holds more water vapour; cold air or warm air?

warm air

What holds less water vapour; cold air or warm air?

cold air

How does precipitation occur?

when water vapor condenses into bigger and bigger droplets of water—results from air rising and cooling

Doldrums

an equatorial region of the Atlantic Ocean with calms, sudden storms, and light unpredictable wind

• ITCZ (Intertropical Convergence Zone)

Horse latitudes

a belt of calm air and sea occurring in both the northern and southern hemispheres between the trade winds and the westerlies

Trade winds

winds that reliably blow east to west just north and south of the equator—15^oN and S

Westerlies

prevailing winds that blow from the west at midlatitude—45^oN and S

Circulation cells

three cells (Hadley cell, Ferrel cell and Polar cell) in which air circulates through the entire depth of the troposphere

Where does cell circulation center?

on the meterogical equator

• thermal equator

  • changes position throughout the year

Storms

an extreme weather condition with very strong wind, heavy rain, and often thunder and lightning: a regional disturbance

Air mass

uniform temperature, humidity, and density

Front

boundary between air masses

Extratropical cyclones

form at polar front

What causes the weather?

uneven flow within circulation cells

Does the ocean affect weather at the centers of continents?

Yes. In a sense, all large-scale weather on Earth is oceanically controlled. The ocean acts as a solar collector and heat sink, storing and releasing heat.

Most great storms (tropical and extratropical cyclones alike) form over the ocean and then sweep over land.

Has anything similar to Earth’s weather patterns been seen on other planets?

• A few storms on Jupiter are large enough to be seen with small telescopes

• Tracks of tornadoes have been identified on Mars

  • Huge cyclonic storm photographed in 1999

• Venus’s huge cloud banks suggest polar fronts and extratropical cyclones

• Coriolis effect and uneven solar heating is present on all planets

Distinguish between a cyclone and an anti-cyclone.

• Cyclone: area of low pressure. air masses meet and rise

• Anticyclone: area of high pressure. air masses separate and sink

In a birds-eye view of a cyclone, how would you identify where the cyclone is located?

• Directionality of the cyclones allows researchers to identify where the cyclone may be located.

• Northern hemisphere: cyclones turn counterclockwise

• Southern hemisphere: cyclones turn clockwise

What are the four things a hurricane needs to form?

1. Disturbances over tropical waters

2. Low winds outside of hurricane area

3. High moisture level in the atmosphere

4. Coriolis effect (directionality)

When is hurricane season?

June 1st to November 30th

What happens to hurricanes once they reach land?

They die down and eventually dissipate due to the colder atmosphere on land.

Where do hurricanes start?

Over the ocean, typically (tropical waters)

State 5 benefits of having hurricanes

1. Rainfall is given to necessary areas

2. Breaks up bacteria

3. Balances global heat

4. Replenishes barrier islands

5. Replenishes inland plant life

Name 4 things that should be in a hurricane disaster supply kit

1. At least 2 litres of water (per person) to last for 3-5 days

2. Toiletries

3. First Aid Kit

4. List of contacts and phone numbers

What are the three stages of development of a hurricane? How long can hurricanes live?

1. Depression

2. Tropical storm

3. Hurricane

2-3 weeks

What is the calm center of circulation in a hurricane called?

The eye of the storm

What is the area with the fastest most violent winds in a hurricane called?

The eye wall

What is ocean circulation driven by?

it is driven by winds and by differences in water density

What two forces of nature distribute tropical heat worldwide?

winds and ocean currents

• Surface currents are wind-driven movements of water at or near the ocean’s surface

• Thermohaline currents are the slow, deep currents that affect the vast bulk of seawater beneath the pycnocline

Gyre

any large system of ocean surface currents moving in a circular fashion driven by wind movements around the peripheries of major ocean basins

El Niño

climate patterns in the Pacific Ocean that can affect weather worldwide. during this climate pattern, trade winds weaken. warm water is pushed back east, toward the west coast of the Americas

La Niña

climate patterns in the Pacific Ocean that can affect weather worldwide. during this climate pattern, trade winds are even stronger than usual, pushing more warm water toward Asia. Off the west coast of the Americas, upwelling increases, bringing cold, nutrient-rich water to the surface