Transcript APES Lesson 76 (5th Ed) - The Oceansx - science-b

AP Environmental
Science
Mr. Grant
Lesson 76
The Oceans
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Mastery Check
What is causing ocean acidification? What
consequences do scientists expect ocean acidification
to bring about?
As ocean water soaks up CO2, it becomes more acidic. As ocean acidification
proceeds, many sea creatures have difficulty forming shells because the
chemicals they need are less available. This process is harming corals in
particular. Corals build reefs, which are hubs for marine biodiversity and
which provide billions of dollars’ worth of ecosystem services. Because coral
reefs are declining, scientists are warning that ocean acidification will be one
of the most damaging consequences of global climate change.
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Objectives:
• Define the terms photic zone, pelagic zone and benthic zone.
• Identify physical, geographical, chemical, and biological
aspects of the marine environment.
• Explain how the oceans influence, and are influenced by,
climate.
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Define the terms photic zone, pelagic
zone and benthic zone.
Photic Zone:
The surface layer of a body of water. In the photic zone,
enough light is present for organisms to photosynthesize.
In the ocean, around 90% of the life can be found in the
photic zone.
Pelagic Zone:
A term that refers to open area of a sea or large lake,
away from the bottom or out of sight of shore.
Benthic Zone:
The bottom of a sea or lake.
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Identify physical, geographical, chemical, and
biological aspects of the marine environment.
• Oceans cover 71% of Earth’s surface and contain over 97% of
its surface water.
• Seafloor topography can be complex.
• Ocean water contains 96.5% H2O by mass and various
dissolved salts.
• Colder, saltier water is denser and sinks. Water temperatures
vary with latitude, and temperature variation is greater than
surface layers.
• Surface currents move horizontally through the oceans, driven
by wind and other factors.
• Vertical water movement includes upwelling and down
welling, which affect the distribution of nutrients and life.
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Cod are groundfish
The U.S. and
Canada have
paid billions to
retrain
fishermen who
lost their jobs
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The Oceans
 Oceans are an important part of the Earth’s
interconnected aquatic systems
 Receive most inputs of water sediments, pollution
 Oceans influence climate, teem with biodiversity,
provide resources, and help transportation and
commerce
 Oceans cover 71% of Earth’s surface and contain
97.5% of its water
 They are a single vast body of water
 Oceans influence the atmosphere, lithosphere, and
biosphere
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Oceans cover most of the Earth’s surface
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Seafloor topography can be rugged
 The seafloor consists of underwater volcanoes, steep
canyons, mountain ranges, vast trenches, mounds of debris,
and some flat areas
 We can look at the ocean’s bathymetry (depths) and
topography (landforms)
 Continental shelves = areas of shallow, gently sloping
sea floor next to the continents
 Sea floor angles down from there at the self-slope break
 The continental slope then drops to the deep ocean
basin below
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A stylized bathymetric profile of the ocean
A stylized
map reflects
the ocean’s
bathymetry
(depths) and
topography
(landforms)
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Seafloor topography can be rugged
 Some island chains are formed by reefs on the
continental shelf (e.g., Florida Keys)
 Others are volcanic in origin (e.g., Aleutian Islands)
 Where underwater structures exist, life thrives
 Topographically complex areas serve as habitat and
make for productive fishing grounds
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Seafloor topography can be rugged
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Ocean water contains high concentrations of
dissolved salt
 Ocean water is 96.5% water by mass
 Remainder is mostly ions of dissolved salts
 Ocean water is over 33,000 parts per million salts,
fresh water is 500 ppm
 Salts enter oceans in runoff from the land
 Evaporation removes pure water, leaving salt behind
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Ocean water contains high concentrations of
dissolved salt
 Oceans contain low levels of nutrients (nitrogen and
phosphorus)
 Oxygen is added by plants, bacteria, and
atmospheric diffusion
 Carbon dioxide enters the oceans from the
atmosphere
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Ocean water
contains salt
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Solar energy structures ocean water from
surface to bottom
 Water temperature declines with depth
 Heavier (colder, saltier) water sinks; light (warmer,
less salty) water stays near the surface
 Surface zone
 Warmed by sunlight and stirred by wind
 Consistent water density down to about 150m
 Contains about 2% of the oceans water
 Pycnocline = zone below the surface
 Density increases rapidly with depth
 Contains about 18% of ocean water
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The ocean
has
several
layers
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Solar energy structures ocean water from
surface to bottom
 Deep zone = zone below the pycnocline; remaining 80%
 Dense, sluggish water
 Unaffected by winds, storms, sunlight, temperature
 Temperatures are more stable than land temperatures
 Water has high heat capacity = heat required to increase
temperature by a given amount
 It takes more energy to warm water than air
 Oceans regulate Earth’s climate
 They absorb and release heat
 The ocean’s surface circulation moves heat around
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Surface water flows horizontally in currents
 Currents = vast riverlike flows in the oceans
 Move horizontally in the upper 400 m of water
 Driven by density differences, heating and cooling,
gravity, and wind
 Some currents such as the Gulf Stream are rapid
and powerful
 The warm water moderates Europe’s climate
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Currents form patterns across the globe
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Surface water flows horizontally in currents
 Currents have helped carry people across the globe
 Also transport heat, nutrients, pollution, and the
larvae of many marine species
 Pacific Ocean currents transported debris from the
tsunami in Japan to the western U.S. coast
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Vertical movement of water affects marine
ecosystems
 Upwelling = the upward flow of cold, deep water
toward the surface
 Water is rich in nutrients
 Sites of high primary productivity and lucrative
fisheries
 Also occurs where strong winds blow away from, or
parallel to, coastlines
 Downwelling = process in which oxygen-rich water
sinks where surface currents come together
 “Buries” CO2 in the deep waters
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Vertical movement affects ecosystems
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Explain how he oceans influence, and are
influenced by, climate.
• The thermohaline circulation shapes regional climate,
or instance, keeping Europe warm. Global warming
could potentially shut down existing circulation
patterns.
• El Niño and La Niña events alter climate and affect
fisheries.
• The oceans sequester atmospheric carbon and have
slowed global climate change, but they could soon
become saturated.
• Absorption of excess carbon dioxide leads to ocean
acidification, which hinders corals in forming reefs.
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Ocean currents affect Earth’s climate
 Horizontal and vertical movement of oceans affects
global and regional climates
 Thermohaline circulation = a worldwide current system
 Warmer, fresher water moves along the surface
 Cooler, saltier, denser water moves deep beneath the
surface
 North Atlantic Deep Water (NADW) = one part of the
thermohaline conveyor belt
 Water in the Gulf Stream flows to Europe
 Released heat keeps Europe warmer than it would be
 Sinking cooler water creates a region of downwelling
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Ocean currents affect Earth’s climate
 Interrupting the thermohaline circulation of the
NADW could trigger rapid climate change
 Melting ice from Greenland will run into the North
Atlantic, making surface waters less salty, less dense
 Could stop NADW formation and shut down the
northward flow of warm water
 Europe would rapidly cool
 This circulation is already slowing
 But Greenland may not have enough runoff to stop it
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The North Atlantic Deep Water
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Ocean currents affect Earth’s climate
 El Niño–Southern Oscillation (ENSO) = a
systematic shift in atmospheric pressure, sea
surface temperature, and ocean circulation in the
tropical Pacific Ocean
 Normal winds blow east to west, from high to low
pressure
 This forms a large convective loop in the atmosphere
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Ocean currents affect Earth’s climate
 Winds push water west, causing it to “pile up”
 Nutrient-rich, cold water along Peru and Ecuador
rises from the deep
 Decreased pressure in the eastern Pacific triggers
El Niño
 Warm water flows eastward, suppressing upwellings
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ENSO, El Niño, and La Niña
Normal conditions
El Niño conditions
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Ocean currents affect Earth’s climate
 Coastal industries (e.g., Peru’s anchovy fisheries) are
devastated (no upwelling means low productivity)
 Worldwide, fishermen lost $8 billion in 1982–1983
 Global weather patterns change
 Rainstorms, floods, drought, fires
 La Niña = the opposite of El Niño
 Cold waters rise to the surface and extend westward
 ENSO cycles are periodic but irregular (every 2–8 years)
 Globally warming sea and air may be increasing the
strength and frequency of these cycles
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Climate change is altering ocean chemistry
 Global climate change will affect ocean chemistry and
biology
 Burning fossil fuels and removing vegetation increase
CO2, which warms the planet
 Oceans absorb carbon dioxide (CO2) from the air
 But oceans may not be able to absorb much more CO2
 Increased CO2 in the ocean makes it more acidic
 Ocean acidification makes chemicals less available for
sea creatures (e.g., corals) to form shells
 Fewer coral reefs means decreased biodiversity and
ecosystem services
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Climate change is altering the oceans
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