Download Section 02 - Forces Of Nature

OUR OCEAN PLANET
OUR OCEAN PLANET
SECTION 2 – FORCES OF NATURE
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2. FORCES OF NATURE
2. FORCES OF NATURE
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2.1 NATURAL FORCES
2.1 NATURAL FORCES
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2.1 NATURAL FORCES
2.1 NATURAL FORCES
Oceans are not static bodies of water but are highly dynamic and
are affected by many natural forces. These forces, acting on the
ocean, are responsible for the Earth’s weather and climate.
The following sections describe some of the most important forces
acting upon the oceans.
2.2.1 Sun
The Sun is the heat engine of our planet. Even having traveled
millions of kilometers, the Sun’s rays still release 130 trillion
horsepower per second on Earth. It causes evaporation in oceans
and lakes, and clouds to develop. It creates the winds as air heats
up, and drives both the clouds and ocean currents. It controls our
climate and, with the Moon, influences tides.
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2.1 NATURAL FORCES
2.1.2 Moon
The Moon is Earth’s only natural satellite and orbits the Earth
approximately every 28 days. The Earth and Moon also orbit the
Sun. The relative alignment of the Sun, Earth and the Moon gives
us different views of the Moon. There are 8 views (or “phases”) of
the moon, namely:
• New Moon
• Waxing Crescent Moon
• First Quarter Moon
• Waxing Gibbous Moon
• Full Moon
• Waning Gibbous Moon
• Last Quarter Moon
• Waning Crescent Moon
Note: “Waxing" means growing and refers to the size of the
illuminated part of the moon that is increasing.
The Moon has a powerful effect on tides. The Moon also has an
effect on the reproduction of many living creatures including sea
turtles, groupers and corals.
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2.1 NATURAL FORCES
2.1.3 Coriolis Effect
The Earth’s rotation also has an effect on winds and currents. The
Coriolis Effect describes the curving motion of wind caused by the
Earth's rotation. Instead of blowing directly north or south, air
deflects to the right in the northern hemisphere and to the left in the
southern hemisphere.
2.1.4 Volcanoes
Volcanoes form when magma reaches the Earth's surface, causing
eruptions of lava and ash. A volcanic eruption can seriously affect
global weather and climate patterns. For example, in Hawaii, when
lava flows reach the ocean, the ocean cools and solidifies it into new
land. Steam plumes rise into the atmosphere affecting rain patterns
globally.
2.1.5 Earthquakes & Seaquakes
Earthquakes are caused by the release of built-up pressure inside
the Earth's crust in the form of seismic waves. The effects of an
earthquake can be devastating – changed landscapes, destroyed
settlements and tremendous loss of life. An earthquake’s power is
measured on the Richter scale using an instrument called a
seismometer. When an earthquake occurs in the ocean, it is known
as a seaquake. Seaquakes can trigger huge ocean waves that can
swamp low lying areas.
Interesting!
“Magma” is hot molten rock that
forms below the surface of the
Earth. “Lava” is hot molten rock
found above the surface of the
Earth.
2.2 PHYSICAL OCEAN PROCESSES
2.2
PHYSICAL OCEAN
PROCESSES
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2.2 PHYSICAL OCEAN PROCESSES
2.2 PHYSICAL OCEAN PROCESSES
Natural forces, such as the sun and moon act on the ocean to form
Earth’s winds, waves, tides and currents, and to create special
weather patterns. Over a longer time scale, these natural forces can
also result in major changes in the Earth’s climate.
WEATHER
The term “ weather” describes whatever is happening outdoors in a
given place at a given time. Weather happens from minute to
minute and can change rapidly within a very short time. For
example, it may rain for an hour and then become sunny and clear.
The weather is also typically what we hear about in the daily news.
Daily weather reports include information about changes in
precipitation, barometric pressure, temperature, and wind conditions
at a given location.
CLIMATE
In contrast, the term “climate” describes the total of all weather
occurring over a period of years in a given place. This includes
average weather conditions, regular weather sequences (such as
winter, spring, summer, and fall), and special weather events (like
tornadoes and floods). Climate tells us what it's usually like in the
place where you live. For example, New Orleans has a humid
climate, Buffalo, New York a snowy climate, and Seattle a rainy
climate. The Cayman Islands have a tropical climate and are usually
warm.
Ocean Literacy Principle 3(a)
The ocean controls weather and
climate by dominating the Earth’s
energy, water and carbon systems.
Ocean Literacy Principle 3(b)
The ocean absorbs much of the
solar radiation reaching Earth. The
ocean loses heat by evaporation.
This heat loss drives atmospheric
circulation when, after it is released
into the atmosphere as water vapor,
it condenses and forms rain.
Condensation of water evaporated
from warm seas provides the
energy for hurricanes and cyclones.
2.2 PHYSICAL OCEAN PROCESSES
2.2.1 Rain
The ocean absorbs much of the solar radiation reaching Earth. The
ocean loses heat by evaporation. This heat loss drives atmospheric
circulation when, after it is released into the atmosphere as water
vapour, it condenses and forms rain. Condensation of water
evaporated from warm seas provides the energy for hurricanes and
cyclones.
2.2.2 Winds
The amount of the Sun’s heat energy penetrating the surface of the
Earth varies. The sun’s energy has a longer way to travel at the
poles and with less heat at the poles and more heat at the equator, a
major pressure gradient exists.
Winds are driven by these
differences or gradients. As the air heats up, it becomes less dense
and rises. To fill the gap produced underneath, air rushes in from
adjacent areas creating winds. In the tropics, these winds are
known as the “trade winds”. These winds do not just blow south in
the northern hemisphere and north in the southern hemisphere but
also blow slightly west due to the rotation of the Earth (Coriolis
Effect).
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2.2 PHYSICAL OCEAN PROCESSES
TROPICAL CYCLONES, HURRICANES & TYPHOONS
In tropical oceans, water evaporates and heat is transferred to the
atmosphere. As the air warms, it becomes less dense and rises in a
spiral, drawing yet more air upwards. This rising air has a heavy
load of moisture, which, as it reaches higher altitudes, cools and
condenses, releasing heat. The energy from this heat increases the
speed of the air, creating spiraling winds. In the center of the spiral
is a calm region of low pressure. This contrasts dramatically with the
high-pressure, fast-moving, cloud-filled air of the surrounding spiral.
While the developing hurricane is over the ocean, it is fed with
energy from the warm, moist, rising air, and its speed and ferocity
increases. Over land, however, a hurricane loses power as it is no
longer fed by the warm ocean and the increased friction over land
disrupts the spiral.
Tropical cyclones with a maximum wind speed of less than 60 km/hr
are called tropical depressions; when the maximum wind speed
ranges between 60 and 110 km/hr, they are tropical storms, and
when the maximum wind speed exceeds 110 km/hr, they are called
tropical cyclones. In the North Atlantic and eastern North Pacific
regions, tropical cyclones are called "hurricanes". In the western
North Pacific, they are called "typhoons" (which appropriately means
“big wind” in Chinese).
Interesting!
More energy is absorbed by the
oceans in the tropics than further
north or south because the Sun’s
rays strike the atmosphere at right
angles in the tropics.
This has two effects both ensuring
more heat is absorbed.
First, fewer rays are deflected off
the atmosphere so more pass
through.
Second, the distance the rays have
to travel through the atmosphere
before they hit the surface of the
Earth is shorter.
2.2 PHYSICAL OCEAN PROCESSES
HURRICANE NAMES
The naming of storms differs from place to place. In the Atlantic,
storms are named alphabetically by year and alternate between
male and female names. Six lists are used in rotation. Thus, the
2008 list will be used again in 2014. The only time that there is a
change in the list is if a storm is so deadly or costly that the future
use of its name on a different storm would be inappropriate for
reasons of sensitivity. If that occurs, the offending name is stricken
from the list and another name is selected to replace it.
REFERENCES & FURTHER READING
http://www.srh.noaa.gov/srh/jetstream/index.htm
http://www.nasa.gov/mission_pages/hurricanes/main/index.html
http://www.nhc.noaa.gov/aboutnames.shtml
http://www.nhc.noaa.gov/2004ivan.shtml
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2.2 PHYSICAL OCEAN PROCESSES
2.2.3 Waves
Waves are vibrations or oscillations moving through a medium (or
vacuum) transferring energy as they move. As a wave passes, each
bit of the medium vibrates in turn but stays where it is – it doesn’t
move with the wave. Think of a crowd wave at a football game. The
wave moves round the ground but each spectator stays in their seat
vibrating when it's their turn to stand up and sit down. Water and
sound waves need a solid, liquid or gas medium to move through
but electromagnetic waves (e.g. light, radio, microwave, infrared,
ultraviolet, etc.) can travel in a vacuum. There are two main types of
wave which vibrate differently:
(a) Transverse – the vibrations are at right angles to the direction of
the wave. Examples are electromagnetic waves (light, etc.), water
waves, and shear or shake seismic waves.
(b) Longitudinal – the vibrations are along the same direction as the
waves. Examples are sound waves, waves in a stretched spring,
and push or pressure seismic waves (which are generated during
earthquakes and faulting).
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2.2 PHYSICAL OCEAN PROCESSES
OCEAN WAVES
An ocean wave is a transverse wave. It has a:
 Crest or Peak – the highest point of the wave
 Trough – the lowest point of the wave
 Wavelength – the distance between two crests (or troughs)
 Amplitude – the maximum disturbance during a wave cycle
 Frequency – how quickly a wave moves forward
Most ocean waves are created by the wind blowing across the open
ocean and causing the surface water to ripple. If the wind continues
to blow, the ripples grow larger and turn into waves. The height of
waves depends on the strength and duration of the wind causing
them and how far they have been pushed across the ocean – this
distance is known as the “fetch”.
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2.2 PHYSICAL OCEAN PROCESSES
TSUNAMI (“SOO-NAH-ME”)
A “tsunami” is a very large and, potentially, destructive wave. It
forms when a disturbance such as a landslide, volcanic eruption or
undersea earthquake causes ripples in the ocean similar to a stone
thrown into a pond. A tsunami has very small amplitude offshore
and a very long wavelength (often hundreds of kilometers long). It
can pass almost unnoticed at sea forming only a slight swell (usually
only 30 cm (1 ft) above the normal sea level) but this still represents
a huge volume of rapidly-moving seawater. As it approaches land
and the ocean becomes very shallow, the water can inundate
coastal areas.
Interesting!
Tsunamis can travel thousands of
kilometers across the ocean and
still have enough energy to cause
massive damage when they make
landfall. One of the most
devastating tsunamis in recent
times travelled across two oceans
to strike Indonesia, Thailand and
Maldives in 2004.
REFERENCES & FURTHER READING
http://www.ypte.org.uk/docs/factsheets/env_facts/tsunami.html
http://www.bbc.co.uk/schools/gcsebitesize/physics/waves/whatarewavesrev1.shtml
http://news.nationalgeographic.com/news/2004/12/1228_041228_tsunami.html
2.2 PHYSICAL OCEAN PROCESSES
2.2.4 Tides
If you have ever watched the ocean washing onto a beach over an
extended period of time, you may have seen the water washing
higher up on the shore at one time and much lower down the shore
a few hours later. This rising and falling of the sea level is called the
“tide”. High tide is when the water is furthest up the beach while low
tide is when the water furthest away from shore.
Tides may be semidiurnal (two high waters and two low waters each
day), or diurnal (one tidal cycle per day). In most locations, tides are
semidiurnal.
Tides are caused by the gravitational pull of the Moon and the Sun
on the rotating Earth’s surface. As the Moon rotates around the
Earth, the water is pulled toward to Moon and forms the daily tides.
The Sun also has effects the tides because of its great mass, but it
is about half as much as that of the Moon because the Sun is much
further away from the Earth.
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2.2 PHYSICAL OCEAN PROCESSES
Spring tides are caused when the Full Moon (and again with the
New Moon) lines up in a straight path with the Sun and the Earth.
When the Moon and Sun are in line with the Earth, they work
together. Spring tides (which occur twice a month all year) rise
higher and fall lower than normal.
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2.2 PHYSICAL OCEAN PROCESSES
Neap tides are caused when the Sun, the Earth and the Moon (in
the first and third quarters) are at right angles to each other. These
tides are unusually low because the pull of the Moon and the pull of
the Sun somewhat cancel each other out as they engage in a tidal
tug of war. Neap tides have the smallest difference in water levels
between high and low tide.
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2.2 PHYSICAL OCEAN PROCESSES
BUILDING TOO CLOSE TO SEA LEVEL
People must be careful when they build homes, cities and
businesses near the shore. We must take into account high tides
and other factors such as hurricanes or storms that can temporarily
alter the sea level. Several famous cities, including Venice and New
Orleans, have been built so that they are dangerously close to sea
level (or actually below sea level). As a result, the inhabitants must
constantly remain vigilant and build special structures to keep the
ocean from flooding their cities. In Venice, tides can be so high that
St. Mark’s Square, at the centre of the city, can be under 0.5 m (1.5
ft) of water for several hours. Inhabitants put up temporary platforms
so that people can walk across the square. In New Orleans, high
waves caused by Hurricane Katrina in 2005 eventually broke the
dams (“levees”) that the people of New Orleans had constructed to
keep the ocean out. The city was flooded by overflowing lakes and
a huge amount of damage was done.
REFERENCES & FURTHER READING
http://en.wikipedia.org/wiki/Tide
http://www.weatherincayman.com/tideprediction.html
http://www.tide-forecast.com/
http://en.wikipedia.org/wiki/Hurricane_Katrina
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2.2 PHYSICAL OCEAN PROCESSES
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2.2.5 Currents
Ocean currents are masses of water that flow in a set direction for
thousands of kilometers. They are important because they affect the
climates of the continents especially those regions bordering on the
ocean.
Perhaps the most striking example is the Gulf Stream, which makes
northwest Europe much more temperate than any other region at the
same latitude. Another example is the Hawaiian Islands, where the
climate is somewhat cooler (sub-tropical) than the tropical latitudes
in which they are located because of the cold California Current.
There are several types of current:
1. Surface Currents
The best-known are wind-caused currents where the wind pushes the water along the surface. Surface
ocean currents develop typical clockwise spirals in the northern hemisphere and anti-clockwise rotation
in the southern hemisphere.
2.2 PHYSICAL OCEAN PROCESSES
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2. Deep Currents
There are also deep currents that flow vertically and horizontally beneath the surface. These are mainly
caused by differences in the density of adjacent waters and fall into two groups:
(a) Salinity Currents – Thermohaline Circulation
The thermohaline circulation (THC) is the global density-driven circulation of the oceans. The name
comes from “thermo” (heat) and “haline” (salt) which together determine the density of sea water. Winddriven surface currents (such as the Gulf Stream) cool as they move pole-wards from the equatorial
Atlantic Ocean and eventually sink at high latitudes. This dense water then flows into the ocean basins.
While the bulk of it upwells in the Southern Ocean, the oldest waters (with a transit time of around 1,600
years) upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins,
reducing differences between them and making the Earth's ocean a global system. The circulation
transports energy (heat) and matter (solids, dissolved substances and gases such as oxygen) around
the globe.
(b) Temperature Currents – Hydrothermal Circulation
Hydrothermal circulation is the circulation of hot water (“hydro” meaning water and “thermo” meaning
heat). Hydrothermal circulation occurs in the vicinity of sources of heat within the Earth's crust such as
the seafloor or near volcanic activity. For example, hydrothermal circulation in the oceans occurs
through mid-oceanic ridge systems. Cold dense seawater sinks into the basalt of the seafloor and is
heated at depth whereupon it rises back to the rock/ocean water interface due to its lesser density. The
heat source is the basalt or the underlying magma chamber. Hydrothermal vents are locations on the
seafloor where hydrothermal fluids mix into the overlying ocean. Perhaps the best known vent forms are
the chimneys referred to as “black smokers”.
2.2 PHYSICAL OCEAN PROCESSES
REFERENCES & FURTHER READING
http://en.wikipedia.org/wiki/Thermohaline_circulation
http://en.wikipedia.org/wiki/Hydrothermal_circulation
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2.2 PHYSICAL OCEAN PROCESSES
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2.2.6 El Niño and La Niña
The name “El Niño” (Spanish for the "Christ child" or “little boy”) was
originally coined in the late 1800s by fishermen along the coast of
Peru to refer to a seasonal invasion of warm, southward, ocean
current that displaced the north-flowing cold current in which they
normally fished; typically this would happen around Christmas.
Ocean Literacy Principle 3(c)
The El Niño Southern Oscillation
causes important changes in global
weather patterns because it
changes the way heat is released to
the atmosphere in the Pacific.
Today, the term no longer refers to the local seasonal current shift
but to part of a phenomenon known as El Niño-Southern Oscillation
(ENSO), a continual but irregular cycle of shifts in ocean and
atmospheric conditions that affect the globe. El Niño has come to
refer to the more pronounced weather effects associated with
anomalously warm sea surface temperatures interacting with the air
above it in the eastern and central Pacific Ocean. Its counterpart –
effects associated with colder-than-usual sea surface temperatures
in the region – was labeled "La Niña" (or "little girl").
Ocean Literacy Principle 3(d)
Most rain that falls on land originally
evaporated from the tropical ocean.
2.2 PHYSICAL OCEAN PROCESSES
El Niño is not totally predictable but occurs on average once every
four to seven years, and usually lasts for about 18 months after it
begins. El Niño events are accompanied by swings in the Southern
Oscillation (SO), an inter-annual see-saw in tropical sea level
pressure between the eastern and western hemispheres. During El
Niño, unusually high atmospheric sea level pressures develop in the
western tropical Pacific and Indian Ocean regions, and unusually
low sea level pressures develop in the southeastern tropical Pacific.
Southern Oscillation tendencies for unusually low pressures west of
the date line and high pressures east of the date line have also been
linked to periods of unusually cold equatorial Pacific sea surface
temperatures (SSTs) sometimes referred to as La Niña (or the "little
girl").
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2.2 PHYSICAL OCEAN PROCESSES
The effects of El Niño vary widely with geography. For people who
live in Indonesia, Australia, or southeastern Africa, El Niño can mean
severe droughts and deadly forest fires. Ecuadorians, Peruvians, or
Californians, on the other hand, associate it with lashing rainstorms
that can trigger devastating floods and mudslides. Severe El Niño
events have resulted in several thousand deaths worldwide, left
thousands of people homeless, and caused billions of dollars in
damage. Yet residents on the northeastern seaboard of the United
States can also credit El Niño with milder-than-normal winters (and
lower heating bills) and relatively benign hurricane seasons.
REFERENCES & FURTHER READING
http://www.pmel.noaa.gov/tao/elnino/nino-home.html
http://www.pmel.noaa.gov/tao/elnino/el-nino-story.html
http://www.pmel.noaa.gov/tao/elnino/la-nina-story.html
http://www7.nationalacademies.org/opus/elnino.html
http://www.epa.gov/climatechange/kids/climateweather.html
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2.3 CARBON
2.3 CARBON
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2.3 CARBON
2.3 CARBON
Carbon is critical to life on earth. In fact, carbon constitutes the very
definition of life, as its presence or absence helps define whether a
molecule is considered to be organic or inorganic. Every organism
on Earth needs carbon for structure, energy or, as in the case of
humans, both. Discounting water, you are about half carbon.
Additionally, carbon is found in forms as diverse as carbon dioxide
(CO2) gas and in solids such as limestone (CaCO3), wood, plastic,
diamonds, and graphite.
2.3.1 Carbon Cycle
The carbon cycle consists of a set of geological, physical, chemical
and biological processes that move carbon between the
atmosphere, oceans, geosphere and biosphere. The geological
processes operate on a time scale of millions of years while the
biological processes operate on a time scale of days to thousands of
years.
Ocean Literacy Principle 3(e)
The ocean dominates the Earth’s
carbon cycle. Half the primary
productivity on Earth takes place in
the sunlit layers of the ocean and
the ocean absorbs roughly half of all
carbon dioxide added to the
atmosphere.
Ocean Literacy Principle 3(f)
The ocean has had, and will
continue to have, a significant
influence on climate change by
absorbing, storing, and moving
heat, carbon and water.
2.3 CARBON
Geological processes have acted on the global carbon cycle since
the formation of the Earth. Over long periods of time, carbonic acid
(a weak acid formed by reactions between atmospheric carbon
dioxide (CO2) and water) slowly combines with minerals at the
earth’s surface.
These reactions form carbonates (carboncontaining compounds) through a process called weathering. Then,
through erosion, carbonates are washed into the ocean where they
settle to the bottom. The carbonates can be used by organisms to
build their skeletons or shells. For example, coral skeletons are
made of calcium carbonate (limestone).
Seafloor spreading pushes the seafloor under continental margins in
the process of subduction. As seafloor carbon is pushed deeper into
the Earth by tectonic forces, it heats up, eventually melts and can
rise back up to the surface, where it is released as CO2 and returned
to the atmosphere. This return can occur violently through volcanic
eruptions or more gradually in seeps, vents and CO2-rich hot
springs.
Weathering, subduction, and volcanism control
atmospheric CO2 concentrations over time periods of hundreds of
millions of years.
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2.3 CARBON
Biological processes play an important role in the movement of carbon between land, ocean, and
atmosphere through the processes of photosynthesis and respiration. Plants take in CO2 from the
atmosphere during photosynthesis and release CO2 into the atmosphere during respiration:
Energy (sunlight) + 6CO2 + H2O -> C6H12O6 (carbohydrates) + 6O2
Photosynthesis
C6H12O6 (carbohydrates) + 6O2 -> 6CO2 + 6 H2O + Energy
Respiration
Virtually all multi-cellular life on Earth depends on plants producing
carbohydrates (sugars) and oxygen from sunlight, CO2 and water
(photosynthesis) and the metabolic breakdown (respiration) of those
carbohydrates to produce the energy needed for movement, growth,
and reproduction.
The amount of carbon taken up by photosynthesis and released
back to the atmosphere by respiration each year is about 1,000
times greater than the amount of carbon that moves through the
geological cycle on an annual basis.
Interesting!
Plants use sunlight to convert
carbon dioxide and water into sugar
(food) and oxygen through a
process called photosynthesis.
Without sunlight, however, a green
plant is unable to make food and,
eventually, it will die.
2.3 CARBON
In the oceans, some organisms have calcium carbonate (CaCO3)
shells or skeletons. When these organisms die, the shells settle to
the bottom of the ocean and are buried in the sediments. The shells
of phytoplankton and skeletons of dead coral can become
compressed over time and are eventually transformed into
limestone. Additionally, under certain geological conditions, organic
matter can be buried and over time form deposits of the carboncontaining fuels coal and oil. It is the non-calcium containing organic
matter that is transformed into fossil fuel. Both limestone and fossil
fuel formation are biologically controlled processes and represent
long-term sinks for atmospheric CO2. When humans burn fossil
fuels, we release this CO2 in the atmosphere.
On land, the major exchange of carbon with the atmosphere results
from photosynthesis and respiration. During daytime in the growing
season, leaves absorb sunlight and take up CO2 from the
atmosphere. At the same time plants, animals, and soil microbes
consume the carbon in organic matter and return CO2 to the
atmosphere. Photosynthesis stops at night when the sun cannot
provide the driving energy for the reaction although respiration
continues.
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Interesting!
Most plants do not need roots to
live but all plants need a
photosynthetic area (such as
leaves) in order to photosynthesize
food. There are very few rooted
plants in the ocean because the
oceans are deep and plants cannot
root themselves to the sea floor and
still reach the sunlit areas of the
ocean. As a result, most oceanic
green plant life is planktonic (from
the Greek meaning “to wander”).
Those that are rooted are generally
found in relatively shallow areas
(e.g. sea grasses).
2.3 CARBON
REFERENCES & FURTHER READING
http://www.eo.ucar.edu/kids/green/cycles6.htm
http://www.visionlearning.org/library/module_viewer.php?c3=1&l=1&mid=95
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2.3 CARBON
2.3.2 Global Climate Change
The Earth has gone through many natural climatic changes through
geologic time. These climatic changes can result in major changes
in the ocean’s circulation which can, in turn, produce larger and even
more abrupt changes in climate.
Recently, however, the level of carbon dioxide in the atmosphere
has risen dramatically along with an increase in global average
temperature. How much of this is natural and how much is due to
human activity has been hotly debated. For example, during winter
in the northern hemisphere, photosynthesis ceases when many
plants lose their leaves but respiration continues, which leads to a
natural increase in atmospheric CO2 concentrations. With the onset
of spring, however, photosynthesis resumes and atmospheric CO2
concentrations are reduced. This cycle is reflected in the monthly
means of atmospheric CO2 concentrations shown by the oscillations
in the graph. Disturbingly, however, the long-term trend shows that
CO2 concentration is steadily rising. The graph is known as the
“Keeling curve” after the scientist who first recorded and plotted the
data.
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Ocean Literacy Principle 3(g)
Changes in the ocean’s circulation
have produced large, abrupt
changes in climate during the last
50,000 years.
2.3 CARBON
Since the onset of the industrial revolution about 150 years ago,
human activities such as the burning of fossil fuels and deforestation
have accelerated, and both have contributed to a long-term rise in
atmospheric CO2. Burning oil and coal releases carbon into the
atmosphere far more rapidly than it is being removed and this
imbalance causes atmospheric CO2 concentrations to increase. In
addition, by clearing forests, we reduce the ability of photosynthesis
to remove CO2 from the atmosphere also resulting in a net increase.
Studies that look at CO2 trapped in ice cores have provided
evidence that atmospheric CO2 concentrations are higher today than
they have been over the last half-million years or longer. These
highly increased levels have been directed attributed to human
activities,
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2.3 CARBON
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EFFECTS OF INCREASED CARBON DIOXIDE LEVELS – “WARMING”
Scientists believe the increase in CO2 is already causing important changes in the global climate.
Because CO2 increases the atmosphere’s ability to hold heat, it is called a “greenhouse gas”. Many
attribute the observed 0.6°C increase in global average temperature over the past century to increases
in atmospheric CO2. Without substantive changes in global patterns of fossil fuel consumption and
deforestation, warming trends are likely to continue. The best scientific estimate is that global mean
temperature will increase between 1.4°C and 5.8°C over the century as a result of increases in
atmospheric CO2 and other greenhouse gases. The increase in global temperature would cause
significant rise in average sea-level (0.09-0.88m) exposing low-lying coastal cities and low-lying islands
to increasingly frequent and severe floods. Glacial retreat and species range shifts are also likely to
result from global warming. Increased concentrations of CO2 could have an important impact on plant
growth patterns. Because some species of plants respond more favorably to increases in CO2 than
others, scientists believe we may see pronounced shifts in plant species, even without any change in
temperature. For example, under elevated CO2 conditions, shrubs may respond more favourably than
certain grasses due to their slightly different photosynthetic pathway. Because of this competitive
inequality, some scientists have hypothesized that grasslands will be invaded by CO2 -responsive grass
species or shrubby species as CO2 levels increases.
REFERENCES & FURTHER READING
http://www.bbc.co.uk/sn/climateexperiment/
http://www.ncdc.noaa.gov/oa/climate/globalwarming.html
2.4 ACTIVITIES
2.4 ACTIVITIES
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2.4 ACTIVITIES
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2.4.1 Winds
CORE ACTIVITY
Investigate winds and hurricanes, and their effects
(a) How do winds form?
(b) How do tropical cyclones form?
(c) What is a “hurricane”? What is a “typhoon”?
(d) Read the page on naming of tropical cyclones: http://www.nhc.noaa.gov/aboutnames.shtml. How are
storms named in the Atlantic? What are this year’s tropical cyclone names?
(e) Read the page on Hurricane Ivan: http://www.nhc.noaa.gov/2004ivan.shtml to get a sense of the
power of a hurricane. What were some effects of Hurricane Ivan on the Cayman Islands?
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ANSWERS
Investigate winds and hurricanes, and their effects
(a) How do winds form?
Winds are driven by heat from the sun. Most of this energy is absorbed in the tropics. As the air heats
up, it becomes less dense and rises. To fill the gap produced underneath, air rushes in from adjacent
areas creating winds. In the tropics, these winds are known as the “trade winds”.
(b) How do tropical cyclones form?
In tropical oceans, water evaporates and heat is transferred to the atmosphere. As the air warms, it
becomes less dense and rises in a spiral, drawing yet more air upwards. This rising air has a heavy load
of moisture, which, as it reaches higher altitudes, cools and condenses, releasing heat. The energy from
this heat increases the speed of the air, creating spiraling winds. In the center of the spiral is a calm
region of low pressure. This contrasts dramatically with the high-pressure, fast-moving, cloud-filled air of
the surrounding spiral. While the developing hurricane is over the ocean, it is fed with energy from the
warm, moist, rising air, and its speed and ferocity increases. Over land, however, a hurricane loses
power as it is no longer fed by the warm ocean and the increased friction over land disrupts the spiral.
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(c) What is a “hurricane”? What is a “typhoon”?
Tropical cyclones with a maximum wind speed of less than 60 km/hr are called tropical depressions;
when the maximum wind speed ranges between 60 and 110 km/hr, they are tropical storms, and when
the maximum wind speed exceeds 110 km/hr, they are called tropical cyclones. In the North Atlantic and
eastern North Pacific regions, tropical cyclones are called "hurricanes". In the western North Pacific,
they are called "typhoons".
(d) Read the page on naming of tropical cyclones: http://www.nhc.noaa.gov/aboutnames.shtml. How are
storms named in the Atlantic? What are this year’s tropical cyclone names?
The naming of storms differs from place to place. In the Atlantic, storms are named alphabetically by
year and alternate between male and female names. Six lists are used in rotation. Thus, the 2008 list
will be used again in 2014. The only time that there is a change in the list is if a storm is so deadly or
costly that the future use of its name on a different storm would be inappropriate for reasons of
sensitivity. If that occurs, the offending name is stricken from the list and another name is selected to
replace it. In 2008, they are Arthur, Bertha, Cristobal, Dolly, Edouard, Fay, Gustav, Hanna, Ike,
Josephine, Kyle, Laura, Marco, Nana, Omar, Paloma, Rene, Sally, Teddy, Vicky, and Wilfred.
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(e) Read the page on Hurricane Ivan: http://www.nhc.noaa.gov/2004ivan.shtml to get a sense of the
power of a hurricane. What were some effects of Hurricane Ivan on the Cayman Islands?
• Although Ivan was weakening while the center passed south of Grand Cayman on 12 September,
2004, the hurricane still brought sustained winds just below Category 5 strength to the island. This
resulted in widespread wind damage, and a storm surge that completely over swept the island except for
the extreme northeastern portion.
• Sustained winds of 130 knots (150 mph) and gusts of 149 knots (172 mph)
• Heavy rainfall caused extensive freshwater flooding and mud slides. Peak rainfall totals were 12.14
inches from Grand Cayman.
• Severe storm surge flooding of 8-10 ft with 20-30 ft waves caused more than 5-8 ft of water to cover
Grand Cayman Island at times. This resulted in the airport and numerous homes being completely
inundated by sea water.
• 2 deaths
• 95% of homes and other buildings damaged or destroyed.
• US$1.85 billion damage in the Cayman Islands.
2.4 ACTIVITIES
2.4.2 Waves
CORE ACTIVITY
Investigate waves and their effects
(a) Label the diagram with the following terms:
• Crest/Peak
• Trough
• Wavelength
• Amplitude
• Vibration/Oscillation Direction (up and down)
• Wave Direction (left to right)
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(b) What types of waves do not need solid-liquid-gas medium to travel through?
(c) Describe some of the characteristics of a tsunami
(d) How can we prepare for a possible tsunami?
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ANSWERS
Investigate waves and their effects
(a) Label the diagram with the following terms:
• Crest/Peak
• Trough
• Wavelength
• Amplitude
• Vibration/Oscillation Direction (up and down)
• Wave Direction (left to right)
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(b) What types of waves do not need solid-liquid-gas medium to travel through?
Electromagnetic waves (e.g. light, radio, microwaves, etc)
(c) Describe some of the characteristics of a tsunami
A “tsunami” (“soo-nah-me”) is a very large and, potentially, destructive wave. It is formed when a
disturbance such as a landslide, volcanic eruption, or undersea earthquake causes a ripple effect similar
to a stone thrown into a pond. A tsunami has very small amplitude (wave height) offshore and a very
long wavelength (often hundreds of kilometers long). It can pass almost unnoticed at sea forming only a
slight swell (usually only 30 cm (1 ft) above the normal sea surface) but this still represents a huge
volume of rapidly moving seawater. As it approaches land and the depth of the ocean becomes very
shallow, the water can inundate coastal areas. Tsunamis can travel thousands of kilometers across the
ocean and still have enough energy to cause massive damage when they make landfall.
(d) How can we prepare for a possible tsunami?
• Monitoring stations in the ocean and advanced notification
• Build settlements that are well above sea-level
• Use sea-walls in low-lying areas
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2.4.3 Tides
EXTENDED ACTIVITY
(a) The following data are typical tide data over 3 days. The date is given followed by the sunrise,
sunset, moonrise and moonset time. There are two high tides and two low tides per day. The times and
heights (in meters) for low and high tides are given relative to 0 where 0 is the average sea level. Thus,
a time of 0125 means 1:25 am while a tide value of 1.1 means the high tide level is 1.1 m above sea
level. Students should plot the data on a chart and join up the points.
Sunday May 04
Sunrise 0554,
Moonrise 0454
Sunset 1849
Moonset 1811
Low Tide:
0125
1.1
High Tide:
0512
1.3
Low Tide:
1253
-0.3
High Tide:
2106
1.7
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Monday May 05 – New Moon
Sunrise 0554,
Moonrise 0542
Sunset 1849
Moonset 1919
Low Tide:
0229
1.3
High Tide:
0516
1.3
Low Tide:
1341
-0.5
High Tide:
2213
1.8
Tuesday May 06
Sunrise 0553,
Moonrise 0637
Sunset 1849
Moonset 2029
Low Tide:
0338
1.4
High Tide:
0514
1.4
Low Tide:
1434
-0.6
High Tide:
2322
1.7
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(b) When was the highest tide? When was the lowest tide?
(c) What things affect the tide?
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ANSWERS
(a) The following data are typical tide data over 3 days. The date is given followed by the sunrise,
sunset, moonrise and moonset time. There are two high tides and two low tides per day. The times and
heights (in meters) for low and high tides are given relative to 0 where 0 is the average sea level. Thus,
a time of 0125 means 1:25 am while a tide value of 1.1 means the high tide level is 1.1 m above sea
level. Students should plot the data on a chart and join up the points.
Sunday May 04
Sunrise 0554,
Moonrise 0454
Sunset 1849
Moonset 1811
Low Tide:
0125
1.1
High Tide:
0512
1.3
Low Tide:
1253
-0.3
High Tide:
2106
1.7
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Monday May 05 – New Moon
Sunrise 0554,
Moonrise 0542
Sunset 1849
Moonset 1919
Low Tide:
0229
1.3
High Tide:
0516
1.3
Low Tide:
1341
-0.5
High Tide:
2213
1.8
Tuesday May 06
Sunrise 0553,
Moonrise 0637
Sunset 1849
Moonset 2029
Low Tide:
0338
1.4
High Tide:
0514
1.4
Low Tide:
1434
-0.6
High Tide:
2322
1.7
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(b) When was the highest tide? When was the lowest tide?
On May 05 at 2213, the high tide was 1.8 m above normal sea level
On May 06 at 1434, the high tide was -0.6 m below normal sea level
(c) What things affect the tide?
Tides are affected by the alignment of the Sun and Moon with the Earth and also wind and storms
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2.4.4 Tides (Mobile)
CORE ACTIVITY
(a) Make a tide mobile
Materials:
• One hanger
• Two wooden sticks
• String
• Magic markers or paint
• Glue
• Paper clips
Method:
On a piece of construction paper, draw your own stars, Sun, Earth,
and Moon. Color or paint the Sun yellow, the Moon purple, the
Earth blue and green, and the star white. Construct the mobile
according to the figure using the circles and star as a template.
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(b) What is the alignment of the Earth, Moon and Sun during Spring Tides?
(c) What is the alignment of the Earth, Moon and Sun during Neap Tides?
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ANSWERS
(a) Make a tide mobile
See previous instructions
(b) What is the alignment of the Earth, Moon and Sun during Spring
Tides?
Spring tides are caused when the Full Moon (and again with the
New Moon) lines up in a straight path with the Sun and the Earth.
When the Moon and Sun are in line with the Earth, they work
together. Spring tides (which occur twice a month all year) rise
higher and fall lower than normal.
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(c) What is the alignment of the Earth, Moon and Sun during Neap
Tides?
Neap tides are caused when the Sun, the Earth and the Moon (in
the first and third quarters) are at right angles to each other. These
tides are unusually low because the pull of the Moon and the pull of
the Sun somewhat cancel each other out. The Moon and the Sun
engage in a tidal tug of war. Neap tides have the smallest difference
in water levels between high and low tide.
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2.4.5 Currents (Salinity)
CORE ACTIVITY
(a) Salinity Currents
Materials:
• Two 1-pint milk bottles or two 250ml Erlenmeyer flasks with flat rims
• Several 3x5 cards
• Table salt
• Food coloring
• Paper towels or rags
• Plastic dishpan (or other container suitable for catching water)
Method:
1. Fill both bottles with water. Dissolve ½ teaspoon of salt in one bottle and add a drop of food coloring.
Place a 3x5 card on top of the salt water bottle and carefully invert it (the upward pressure of the air
should hold the card in place most of the time)
2. Place the salt water bottle on top of the fresh water container and have someone remove the card
(use the dish pan underneath as necessary). Observe results
3. Repeat Step 1 – place fresh water jar on top of salt water jar, remove card and observe
4. Repeat Step 1 – place both jars horizontally, remove card and observe
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(b) Is salt water heavier or lighter (higher or lower density) than fresh water? Explain your answer in
terms of the results you obtained from the experiment.
(c) What happens to river water when it flows into the ocean?
(d) A fisherman is fishing at a spot near the mouth of a river. At 2m (6 ft) down, he catches a fresh water
perch. At 10m (30 ft), he catches a salt water cod. The fisherman was really puzzled by this occurrence.
What would you tell him that would help him understand what happened?
REFERENCES & FURTHER READING
The Ocean Book: Aquarium & Seaside Activities & Ideas For All Ages, Centre for Marine Conservation,
Wiley Publishing Inc., (1989), ISBN 0-471-62078-5
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ANSWERS
(a) Salinity Currents
See previous instructions
(b) Is salt water heavier or lighter (higher or lower density) than fresh water? Explain your answer in
terms of the results you obtained from the experiment.
Salt water is heavier. The colored salty water sank into the clear fresh water (in step 2).
(c) What happens to river water when it flows into the ocean?
Since river water is fresh, it floats on top of the salt water until waves and currents cause the two to mix.
(d) A fisherman is fishing at a spot near the mouth of a river. At 2m (6 ft) down, he catches a fresh water
perch. At 10m (30 ft), he catches a salt water cod. The fisherman was really puzzled by this occurrence.
What would you tell him that would help him understand what happened?
The fisherman was fishing where the fresh water was standing in a layer above the sea water. Near the
surface, the water was the lighter river water. Near the bottom, the water was the denser sea water.
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2.4.6 Currents (Temperature)
CORE ACTIVITY
(a) Temperature Currents
Materials:
• Two 1-pint milk bottles or two 250ml Erlenmeyer flasks with flat rims
• Several 3x5 cards
• Table salt
• Food coloring
• Paper towels or rags
• Plastic dishpan (or other container suitable for catching water)
Method:
1. Fill one bottle with warm water the other with cool water. Add a drop of food coloring to the warm
water. Place a 3x5 card on top of the salt water bottle and carefully invert it (the upward pressure of the
air should hold the card in place most of the time)
2. Place the warm water bottle on top of the cool water container and have someone remove the card
(use the dish pan underneath as necessary). Observe results
3. Repeat Step 1 – place cool water jar on top of warm water jar, remove card and observe
4. Repeat Step 1 – place both jars horizontally, remove card and observe
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(b) Is warm water heavier or lighter (higher or lower density) than cool water? Explain your answer in
terms of the results you obtained from the experiment.
(c) Where does most heating of ocean water take place?
(d) Where does most dilution of sea water occur?
(e) Is it easier for a human to swim in salty or fresh water? Explain.
(f) Is it easier for a human to swim in cool water or warm water? Explain.
REFERENCES & FURTHER READING
The Ocean Book: Aquarium & Seaside Activities & Ideas For All Ages, Centre for Marine Conservation,
Wiley Publishing Inc., (1989), ISBN 0-471-62078-5
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ANSWERS
(a) Temperature Currents
See previous instructions
(b) Is warm water heavier or lighter (higher or lower density) than cool water? Explain your answer in
terms of the results you obtained from the experiment.
Warm water is lighter (lower density) than cool water. The warm, colored water remained in the upper
flask in experimental set up (a).
(c) Where does most heating of ocean water take place?
Most heating occurs at the surface
(d) Where does most dilution of sea water occur?
Most dilution of sea water occurs at the surface.
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(e) Is it easier for a human to swim in salty or fresh water? Explain.
It is easier for a human to swim in salt water. The salt water makes the person more buoyant. Salt
water is denser and the same volume displaced by the person will weigh more so the person floats more
easily.
(f) Is it easier for a human to swim in cool water or warm water? Explain.
It is easier for a human to swim in cool water. The person displaces the same volume but since the
water is cooler and denser it weighs more and the person floats more readily.
Teachers: a word of warning!
While a person will float more readily in cool water, the chance of excessive body heat loss also
increases. Cold water can lead to hypothermia. You may wish to discuss this so your students use
caution if they experiment on their own.
2.4 ACTIVITIES
2.4.7 El Niño
EXTENDED ACTIVITY
(a) What is an El Niño? About how often does it occur?
(b) Simulate the El Niño effect in the classroom
Materials:
• Clear hard plastic container (approx. 18" x 4" x 4" (or smaller) food containers are ideal)
• Water
• Mineral oil
• Blue food coloring
• Handheld battery-operated fan
• Paper sheet map showing the Pacific Ocean
• Red Oil-Based Paint (Optional)
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Method:
1. Fill the container with water to within 1" of the top
2. Add blue food coloring to the water (some food coloring will settle to the bottom which is fine because
this will show the upwelling.)
3. Pour some mineral oil in a bowl and mix in some red oil-based paint until the oil is evenly colored (it
does not affect the outcome if you don’t have red oil-based paint).
4. Gently pour the oil over the surface of the water (if it mixes wait for it to separate out again)
5. Place container on the paper and mark East (S. America) and West (Indonesia) at either end
The liquids in the plastic container represent a slice across the Pacific Ocean in the vicinity of the
equator. The oil represents the warm layer of surface water that has been heated by the sun. The blue
water represents the colder water below the surface warm layer. The fan represents the trade winds.
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(c) Have a student turn on the handheld battery-operated fan and direct the 'wind' across the surface of
the oil-topped water from the East to the West. Ask the class to describe what effect this has on the
"warm" and "cold" water.
(d) Have the student turn off the "trade winds" and ask the class to describe what happened when the
trade winds stop.
(e) What are some of the effects of El Niño on South America, North America (and the western United
States) and the Western Pacific?
REFERENCES & FURTHER READING
http://sealevel.jpl.nasa.gov/education/make-your-own-el-nino.html
http://www7.nationalacademies.org/opus/elnino.html
http://oceanworld.tamu.edu/resources/oceanography-book/oceansandclimate.htm
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ANSWERS
(a) What is an El Niño? About how often does it occur?
El Niño refers to the pronounced weather effects associated with anomalously warm sea surface
temperatures interacting with the air above it in the eastern and central Pacific Ocean. Its counterpart –
effects associated with colder-than-usual sea surface temperatures in the region – was labeled "La Niña"
(or "little girl"). El Niño occurs approximately once every four years.
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(b) Simulate the El Niño effect in the classroom
See previous instructions
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(c) Have a student turn on the handheld battery-operated fan and direct the 'wind' across the surface of
the oil-topped water from the East to the West. Ask the class to describe what effect this has on the
"warm" and "cold" water.
Note that the "warm" water piles up in the West as it is blown by the "trade winds" (fan). This is the
normal condition for the equatorial Pacific Ocean. You may notice that the sediment of the blue food dye
moves upwards towards the surface at the east end (this will only happen if there is sediment). This is
upwelling which, in the Pacific Ocean, brings nutrient-rich bottom waters to the surface. Plankton feed on
these nutrients. Fish, in turn, feed on plankton so these areas tend to be rich in fish and other sea life.
(d) Have the student turn off the "trade winds" and ask the class to describe what happened when the
trade winds stop.
You may need to do this several times to observe the motion. The "warm" water pulses across the
"ocean" from West to East – this pulse of water is the warm water that is the oceans part of the El Niño
condition. Note that the "upwelling" previously seen while the trade winds were blowing is no longer
present so no nutrient rich water surfaces to feed marine life. Now a thick layer of warm water (oil)
covers the surface in the East; this cuts off the nutrient-rich cold water from upwelling to the surface.
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(e) What are some of the effects of El Niño on South America, North America (and the western United
States) and the Western Pacific?
For people who live in Indonesia, Australia, or southeastern Africa, El Niño can mean severe droughts
and deadly forest fires. Ecuadorians, Peruvians, or Californians, on the other hand, associate it with
lashing rainstorms that can trigger devastating floods and mudslides. Severe El Niño events have
resulted in several thousand deaths worldwide, left thousands of people homeless, and caused billions of
dollars in damage.
2.4 ACTIVITIES
2.4.8 Carbon Cycle
CORE ACTIVITY
(a) Label the Carbon Cycle with the following terms:
• Photosynthesis
• Animal Respiration
• Plant Respiration
• Auto & Factory Emissions
• Ocean Uptake
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(b) What is photosynthesis? What organisms are able to photosynthesize food?
(c) What is respiration? What organisms respire?
(d) What are the main producers of carbon dioxide in the atmosphere?
(e) What is the main absorber of carbon dioxide from the atmosphere?
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ANSWERS
(a) Label the Carbon Cycle with the following terms:
• Photosynthesis
• Animal Respiration
• Plant Respiration
• Auto & Factory Emissions
• Ocean Uptake
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(b) What is photosynthesis? What organisms are able to photosynthesize food?
Photosynthesis is the process by which solar energy is used to turn atmospheric carbon dioxide into
carbohydrates (sugars). Green plants are the primary producers and are able to photosynthesize food
using sunlight – almost no animals are able to do this.
(c) What is respiration? What organisms respire?
Respiration is the process of inhalation and exhalation and is often called “breathing”. Within living cells,
however, the chemical energy of carbohydrates (sugars) is released in a series of steps where oxygen is
consumed and carbon dioxide and water are produced and released into the atmosphere. All animals
respire. However, green plants also respire carbon dioxide in the dark
(d) What are the main producers of carbon dioxide in the atmosphere?
• All animal life
• Green plants at night
• Humans burning fossil fuels in cars and factories
(e) What is the main absorber of carbon dioxide from the atmosphere?
The ocean dominates the Earth’s carbon cycle. Half the primary productivity on Earth takes place by
plants in the sunlit layers of the ocean and the ocean absorbs roughly half of all carbon dioxide added to
the atmosphere.
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2.4.9 Global Climate Change
EXTENDED ACTIVITY
Investigate Global Climate Change
(a) What should the Keeling Curve look like if there is no long term change to the carbon dioxide levels?
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(b) Name some factors that contribute to the rising carbon dioxide levels?
(c) Which countries produce the most carbon dioxide?
(d) If humans are NOT the cause of increased carbon dioxide levels, who/what else might be the cause?
(e) How might we reduce carbon dioxide emissions?
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ANSWERS
Investigate Global Climate Change
(a) What should the Keeling Curve look like if there is no long term change to the carbon dioxide levels?
The Keeling Curve should still oscillate but be flat or nearly flat. The fact that it is rising indicates
something is making the carbon dioxide levels climb, and scientists strongly believe this is primarily
caused by human activities.
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(b) Name some factors that contribute to the rising carbon dioxide levels?
• Factories burning fossil fuels
• Cars burning fossil fuels
(c) Which countries produce the most carbon dioxide?
• China
• United States
(d) If humans are NOT the cause of increased carbon dioxide levels, who/what else might be the cause?
Certain natural sources such as volcanoes, could potentially contribute to the increase in carbon dioxide
levels. However, the contribution would have to be continuous and accelerating (i.e. emitting more and
more carbon dioxide over time). Scientists are aware of this possibility but so far no natural candidate
has realistically been proposed that can explain this data. Scientists are now more than 90% certain that
humans are the cause of the rising carbon dioxide level.
(e) How might we reduce carbon dioxide emissions?
• Use public transport (e.g. buses, trains)
• Bicycle where possible
• Keep temperatures in houses a few degrees lower