Earth’s Oceans –
“The Water Planet”
Unit 6
Chapters 22 - 24
Why does the Earth look mostly
blue when viewed from space?
Oceanography
• Oceanography – is the study of the ocean
using chemistry, biology, physics, geology,
and other sciences.
Water Molecule
• Water molecule (H20) = 1 Oxygen, 2 Hydrogens
• Polarity – uneven distribution of charge between H & O
– Hydrogen is positive charge and Oxygen is negative charge =
Dipolar molecule
• H bonding - strong bond between a positively charged H
atom of one molecule with a negatively charged atom of
another molecule.
– Hydrogen bonds determine the structure of water in
solid form.
– Arrange in “frame” with large spaces
between molecules
(less dense, like ice)
O
+ H
H+
O
+ H
_
_
H+
Properties of Water
• Oceans cover >70% of
Earth’s surface
• Density –
– Salinity and Temperature
affect density of seawater
– Ice (solid form of water)
is less dense than the
liquid form because of
the structure
• Ice floats on water.
– Salt concentration –
the more salt the more
dense the water is.
• (Dead Sea – people
float on water
because salt water is
more dense).
http://www.trekearth.com/gallery/Middle_East/Israel/Southern/
Beer_Sheva/Dead_Sea/photo1019336.htm
Seawater
• Salinity – measure of dissolved
salts in water.
– Measure by evaporating water
and weighing amount of salt
left over.
– Average salinity = 35
practical salinity units (psu) or
35%.
– Based on amount of fresh
water entering sea. (so salinity
may be different at times –
also depends on climate)
• Seawater liquid between
-2ºC to 100.3ºC (normally water
is a liquid between 0ºC - 100ºC
– Throw salt on sidewalk/road to
melt ice. (seawater more
stable than pure water)
Freshwater freezes, leaves
salt behind in seawater.
http://tvl1.geo.uc.edu/ice/Image/pretty/467-4.html
Salinity in Seawater can change
• Depends on amount of freshwater coming into sea
– So area with lots of freshwater coming into sea may
be less than the average 35% salinity (because less
salt, more freshwater)
• Depends on climate
– So area with hot, dry climates will evaporate water
more quickly, so salinity is more than average (less
freshwater, leaves more salt)
– Area very cold forming ice, salt is left behind in water
and freshwater freezes, so salinity would be higher
here.
Composition of Seawater
• More than 70 elements
make up seawater
–
–
–
–
–
Piles of salt, Bolivia
Chloride ~55%
Sodium ~30.6%
Sulfate ~7.7%
Magnesium ~3.7%
All others ~3%
• Important elements in
seawater:
– Salt (Sodium Chloride=
NaCl) and magnesium
mined from seawater.
– Calcium for hard shells
(shellfish)
– Nitrogen and phosphorous
from photosynthesis.
http://en.wikipedia.org/wiki/File:Piles_of_Salt_Salar_de_Uyuni_Bolivia_
Luca_Galuzzi_2006_a.jpg
•Salts enter ocean via:
- Underwater volcanoes
- Erode from mineralrich rocks
- Decomposed marine
organisms.
Temperature Profile of Ocean
• 3 temperature zones:
– Surface zone/Mixed
Layer
(warmed by sunlight)
– Middle zone/
Thermocline (penetrated
by little light, temperatures
change rapidly)
– Deep zone
(very cold, without light)
http://files.myopera.com/nielsol/blog/Thermocline_2.jpg
Temperature Profile of Ocean
• Surface zone/Mixed Layer –
wind and waves mix heat
evenly, absorbs sun’s light,
home to millions of
photosynthetic organisms and
home to most marine life.
(between 50 – 300 meters
deep).
• Middle zone/Thermocline –
temperatures drop rapidly.
(down to 1000 meters deep).
• Deep water zone – cold at all
depths, cold water is denser so
sinks to bottom and moves
away from polar region.
http://alex.state.al.us/uploads/23942/thermocline.gif
Ocean Life
• Phytoplankton – singlecelled protists, near the
surface of the ocean
(photosynthesis organism),
base of ocean’s food chain.
– Diatom – (thin shell of silica)
http://www.astrographics.com/GalleryPrints/Display/GP2131.jpg
• Large population can
change color of water =
algal bloom.
• Zooplankton – microscopic
animals that drift in ocean
and eat phytoplankton.
http://drake.marin.k12.ca.us/stuwork/rockwater/PLANKTON/zoodrawings.gif
Ocean Life
• Coral – sea animal fastened
to rocky sea floor.
• Lives in water with
temperatures between 18ºC
to 21ºC and generally up to
90 meters in depth (where
sunlight reaches), ocean
currents bring their food.
• Nekton – free swimming
organisms (fish, reptiles,
whales, squid, & jellyfish)
http://www.chbr.noaa.gov/categories/raim/images/coral_01.jpg
http://biology.unm.edu/ccouncil/Biology_203/Images/Protostomes/squid.jpg
Deep Ocean Life
• Carbon dioxide accumulates in
deep because no organisms to
convert to oxygen (sunlight doesn’t
reach here).
• Ocean vents provide habitat for
deep water animals.
• ocean floor vents: (Cold ocean
water seeps through floor cracks,
then its heated by hot rocks in
crust)
– Cracks in ocean floor release
hot water (16ºC).
– Smokers - 380ºC hot water
from volcano-like chimney (hot
water reacts with seawater and
forms black iron sulfide clouds.
– Hydrogen sulfide gas provides
food for nearby bacteria.
Black smoker
http://whyfiles.org/coolimages/images/csi/nur04506.jpg
Bathymetry – Ch. 23
• Bathymetry – study of underwater depths
Ocean Floor
• Continental Shelf- shoreline out to continental slope (flat)
• Continental Slope – shelf edge to where water depth increases
rapidly (sediments build up temporarily, until they tumble down to
form continental rise).
• Continental Rise – lies on ocean crust (part of ocean basin, not
continent).
• Abyssal Plain – deep seafloor, flat
http://cgc.rncan.gc.ca/org/atlantic/unclos_e.php
Ocean Floor
http://www.earthscape.org/t2/meg01/meg01c.html#margin
Ch. 24 – Currents and Tides
Ocean Currents
Ocean Currents – any continuous flow of water
along a broad path in the ocean.
Types of Currents:
– Surface Currents – an ocean current that
generally flows in the upper 1,000 meters of
the ocean and primarily driven by the wind.
– Deep/Density Currents – is heavier and
denser than surrounding water, and sink from
the surface toward the bottom of the ocean
where they circulate in the deep ocean for
500 to 2,000 years before resurfacing.
Global Ocean Currents
Coriolis Effect and the Currents
Direction in which currents
flow depends is
influenced by the Coriolis
Effect.
• Ocean currents in
Northern Hemisphere
turn clockwise (to the
right)
• Ocean currents in the
Southern Hemisphere
turn counterclockwise (to
the left)
Warm and Cold Currents
• Warm Currents flow away from equatorial
region on the western side of ocean basin.
– (Example: Gulf Stream in North Atlantic, begins in
Caribbean Sea and follows east coast of US
northward around Cape Hatteras, NC, then veers
NE across Atlantic and is called North Atlantic Drift,
carries warm water to Iceland and British Isles, helps
give warmer climate there.)
• Cold Currents flow toward the equator on the
eastern side of ocean basins.
– (Example: Canary Current in North Atlantic or
Labrador Current flowing out of Baffin Bay past
Newfoundland – carries icebergs south, also meets
the Gulf stream and produces some of thickest fog in
world)
Winds and Ocean Currents
Two sets of prevailing winds tend to form most
ocean currents:
Trade winds and Westerly winds
• Trade winds – steady, blow from northeast in
the Northern Hemisphere and from the
southeast in Southern Hemisphere, in North
Atlantic push North Equatorial Current westward
• Westerlies – blow from southwest in Northern
Hemisphere and from northwest in Southern
Hemisphere, in North Atlantic push North
Atlantic Drift eastward.
(we live here in the westerlies)
Westerlies (where
we live) - push
North Atlantic
Drift Current
eastward
Trade Winds –
push North
Equatorial
Current
westward
Draw the cold and warm currents in on our
big ocean map
Density Currents
• heavier and denser than
surrounding water,
• sink from the surface
toward the bottom of the
ocean where they
circulate in the deep
ocean from 500-2,000
years before resurfacing,
• act as global conveyor
belt moving warm water
to colder areas and cold
water to warm areas,
• move oxygen important
for marine animals,
• drive the deep sea
currents.
Upwelling Currents
• vertical current,
• occurs when cold deep water
comes to surface,
• most common on the western
sides of continents where
prevailing winds blow along the
coastline toward the equator,
• cold water rises to replace the
surface water that has been
moved out to sea by Coriolis
Effect,
• contain large amounts of
nutrients that phytoplankton
need to grow,
• major commercial fishing areas.
Ocean Tides
• Tides – the periodic rise and fall of the
ocean surface due to the gravitational pull
of the moon and the sun.
– High tide = when water reaches the highest
point on the shore.
– Low tide – when water reaches the lowest
point on the shore.
High
Low
High
Low
Ocean Tides
• Spring Tide – when the sun, moon (at full or
new moon phase), and Earth are all aligned.
Get extreme high tides and extreme low tides.
• Neap Tide – when the sun and moon (at quarter
phases) are at 90 degrees from each other. High
tides not very high, low tides not very low (high
and low tides are very similar).
Tides and Storms and the
Land that Protects Us
• During storms the tides will increase.
• Barrier Islands protect the mainland and
help reduce the size of these waves from
smashing into the mainland and help
prevent damage to areas inland.
– Example: during a Hurricane tides will
increase and you may get a storm surge.
Barrier Islands act as a block and get hit the
hardest, so the mainland doesn’t.
Barrier Islands Add Protection for the
Mainland
Chesapeake Bay
Estuary
• Estuary – an area where fresh water and salt
water are mixing
– Example: Chesapeake Bay
• Fresh water from the rivers (Potomac, Rappahanock,
James, Susequehanna, etc) flow into the Bay while salt
waters from the Atlantic Ocean flow and mix into the
Bay.
Chesapeake Bay Issues
• Sedimentation –
sediments running into
the waters.
• Runoff - Increased
phosphorus and nitrogen
in the water (from use of
fertilizers).
• Overfishing, crabbing,
etc.
Troubled Waters
• Coral Reefs – provide food and shelter for about ¼ of all
ocean species, unfortunately many coral reefs are being
damaged.
– Fish that live there are caught for salt water aquariums
and coral is collected.
– Tourism – boats hit coral, their fuels poison them, etc.
– Pollution from soil and fertilizer runoff and increase algae
growth and algal blooms block out the sunlight that corals
need.
– Ocean temperatures change naturally and corals cannot
handle these temperature changes as a result the corals
release the algae that live within them and turn white and
die = coral bleaching
• Some places like in the US have areas that are
protected so people can not go into the area.
Coral Bleaching
Climates and the Oceans
• Climate is an area’s long term pattern of
weather.
– It looks mainly at temperature and precipitation
(but also includes winds, severe weather
occurrences)
– It is controlled by latitude, elevation, nearby bodies
of water, nearby ocean currents, topography,
prevailing winds, and vegetation.
• Example: London, England is 1100km closer to the North
Pole than Cleveland, Ohio, but London’s average
temperature is the same is Cleveland’s.
– This is because warm ocean currents are flowing in
toward London, which helps to warm the temperatures.
Climate Controls
Climate and the Oceans
Sea Breeze – vs- Land Breeze
– Sea Breeze – forms when land is heated
more than the nearby water (water takes
longer to heat).
• During the day, coastal land is warmer than the
water. Pressure decreases over the land, and
causes a cool sea breeze to blow inland. So warm
air rises over the land and moves out to sea, as it
cools it sinks to replace the cool air that is flowing
inland.
– Land Breeze – At night the air over the land
becomes colder than the air over the water,
so that causes the cool land breeze to blow
out to sea.
Climates and the Oceans - Climate
Changes
• Earth’s climate is constantly changing.
• Changes in Earth’s heat/energy budget trigger
changes in climate.
– Earth’s motion – Earth wobbles on its axis, the tilt
varies, and our orbit varies (this makes the seasons
vary).
– Plate Tectonics – continents shifting positions to
different latitudes means their climates will change
(movement of continents will change the wind directions
and how ocean currents flow).
– Sunspots – number of sunspots correlates to
climate (more sunspots, the higher temperatures are).
Climates and the Oceans - Climate
Changes
– Volcanoes – explosive volcanoes erupt and
put dust and gases into the atmosphere.
(makes acid rain, reflects more sunlight back into space
so temperatures get colder, some put more carbon in
the atmosphere which makes warmer temperatures).
– Humans – deforestation and burning of fossil fuels have
increased. (burning fossil fuels increases carbon and
therefore increases temperatures, cutting down trees
will prevent carbon from being removed from the
atmosphere, which makes temperatures warmer).
Climates and the Oceans Climate Changes
• How do we know what climates were in
the past??
– Look at seafloor sediments, glacier samples,
tree ring studies.
Temperatures from the Northern Hemisphere
from the last 1,000 Years
Which greenhouse gas effects
global climate the most?
Watch how the glaciers melt and the vegetation type changes
over time if temperatures are to rise 4-5 degrees each year
(until 2050)
Climates and the Oceans - El Nino Effect
El Nino with warm currents flowing into the
western coast of US – causing warm, dry in
the Northern US and cooler, moist air in the
Southern US.
Climates and the Oceans - El Nino Effect
• El Nino – ocean current that is warmer than usual,
alters the pattern of atmospheric circulation, and is
often linked to severe weather patterns.
– Southeast Asia and parts of Australia get droughts
and wildfires, in the southern US sometimes it
causes severe flood and crop damage, and warm
and dry across the northern part of the US.
– All because of a warming ocean current
• Scientists believe these warming currents may be
left over from major climate changes in the past
(and the deep, density driven currents travel around
the Earth for many years before making a loop), OR
maybe from increase in Carbon dioxide.