Chapter 8 and 9 - Atmosphere Circulation and Currents

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

What are the three main ocean layers?

1. Surface zone/mixed layer

2. Pycnocline

3. Deep zone

How does temperature change with depth in the thermocline?

The deeper into the ocean you go, the more drastic the temperature drop is

How does temperature change below the thermocline?

Below the thermocline, temperatures experience a steep drop

Ocean current

regular movement of large amounts of water along defined paths

Thermohaline circulation

Ocean circulation driven by differences in density caused by temperature and salinity variations

Why are currents so important?

• Influence world climate and weather

• Ocean navigation and transportation

• Support marine life (transport mechanism, food source)

• Transport of materials (both helpful and harmful) and energy to different regions and depths of the ocean

Wind

The primary driving force of ocean currents

Where do surface currents flow?

around the periphery of ocean basins

Why can’t water flow uphill?

• Hills in the mid-oceans

• Maintained by wind energy (waves are pushed forward and down, cannot be pulled upwards)

Geostrophic gyres

The horizontal movement of surface water arising from a balance between the pressure gradient force and the Coriolis force

What are the five major gyres?

• North Atlantic Gyre

• South Atlantic Gyre

• North Pacific Gyre

• South Pacific Gyre

• Indian Ocean Gyre

Boundary current

ocean currents with dynamics determined by the presence of a coastline, and fall into two distinct categories: western boundary currents and eastern boundary currents

Western boundary currents

• Narrow, deep, fast currents

• Western boundaries of ocean basins

Eastern boundary currents

• Cold, shallow, broad currents

• Boundaries not well defined

Countercurrents

a current running in an opposite direction to another current

Undercurrents

a current of water below the surface and moving in a different direction from any surface current

What is the role of warm water?

to transfer heat to higher latitudes

What is the role of cold water?

to cool down lower latitudes

Upwelling

wind-induced vertical circulation. rising movement of a fluid parcel and its properties (e.g., salinity, temperature, pH)

Langmuir circulation

long sets of counter-rotating gyres at the ocean surface

Southern Oscillation

changes in winds across the tropical Pacific

“Global conveyor belt”

a constantly moving system of deep ocean circulation driven by temperature and salinity. regulates temperatures and salinities throughout the world

What drives ocean currents?

• Density gradients (differences) drive deep ocean currents

• Upwelling brings cold, nutrient-rich water from the depths up to the surface

• Wind is one of the primary drivers of surface currents

Water masses

• Surface water (to 200 meters)

• Central water (to bottom of main thermocline)

• Intermediate water (to 1500 meters)

• Deep water (below intermediate water to 4000 meters)

• Bottom water (in contact with seafloor)

How is Thermohaline and Surface Flow connected?

• Polar regions – formation of bottom water

  • Downwelling

• Water masses move slowly across ocean bottom, rise slowly

• Convergence zones

• Contour currents – bottom currents

How does ocean water circulate?

in currents which move all around the world

What percentage of the uppermost ocean do surface currents affect?

10%

Surface currents

currents that are driven by global wind systems that are fueled by energy from the sun. flows horizontally and transfers heat from the equator to the poles

Where does El Niño originate and how?

the Western Pacific. trade winds weaken and push warm water eastward, which reduces upwelling of cold water

How would El Niño affect PEI?

our shorelines and cliffs would erode and coastal flooding would occur

Marine Biogeography

the study of marine species, the geographic distribution of their habitats, and the relationships between living organisms and the environment

Why is marine biogeography important?

• Detecting unusual or concerning patterns/behaviours in marine life

• Mapping changes in the seafloor and habitats

• Researching ways to help the environment

Sea level change varies around the globe. Can you find a reason for this?

• Melting glaciers

• Thermal expansion of seawater as it warms

Why is the rate of local sea level rise greater than the global average in some coastal areas?

• Ground settling

• Upstream control

• Erosion

• Regional ocean currents

• Glacier melting

What risks do rising sea levels pose?

• Infrastructure near coastal areas are threatened

• Hurricanes and storms push farther inland

• More frequent high-tide flooding

• Saltwater contaminates freshwater

  • This would damage ecosystems

Ekman spiral

an arrangement of ocean currents: the directions of horizontal current appear to twist as the depth changes

Westward intensification

the tendency of currents along the western margins of all oceans to be particularly strong, swift, and narrow, flowing northwards in the northern hemisphere and southwards in the southern hemisphere

SCIDB

Surface water, central water, intermediate water, deep water, bottom water

Deep currents

• Driving factor: Density differences

• Slow, deep currents

• Entirely below the effect of wind

Surface currents

• At surface, up to a depth of about 400 m

• Driving factor: Wind

How long does it take for ocean water to circulate around the world?

1000 years

Downwelling

wind induced vertical circulation. downward movement of a fluid parcel and its properties (e.g., salinity, temperature, pH)