Download Physical Oceanography

OCEANOGRAPHY
Name______________________
Color all water LIGHT BLUE. Color all land LIGHT GREEN.
Label the 5 Oceans: Pacific, Atlantic, Indian, Arctic, Antarctic.
Label the 7 Continents: N.America, S.America, Europe, Asia, Africa, Australia, Antarctica.
Label North, South, East, and West.
Draw & Label the Equator (0° latitude), Prime Meridian (0° longitude), and the International Date Line (180° longitude).
Draw & Label the Mid-Atlantic Ocean Ridge and the Mariana Trench.
Label the Bering Strait, Red Sea, Baltic Sea, North Sea, Gulf of Mexico, and Mediterranean Sea.
The Ocean Floor
Section 14.1 – THE VAST WORLD OCEAN
ORIGIN OF THE OCEANS

How old is the Earth? 4.6 billion years old

Where did the water come from?
o Comets and Meteorites: carry lots of water, which transferred to Earth upon impact.
o Volcanism: volcanic gas has mostly water vapor and CO2
 The CO2 and other gases formed the Earth's atmosphere
 As the Earth cooled, the water vapor condensed, forming the oceans.
THE BLUE PLANET

Earth is known as the "Blue Planet" because ~71 % of it is covered by oceans.
o Average Depth of the Oceans: 3800 m (3.8 km)
o Where is most of the water - Northern or Southern Hemisphere? Southern
o All oceans are really one big body of water.
o 97 % of the water on earth is found in the oceans. Only 3 % is freshwater.
o OCEANOGRAPHY: study of Earth’s Oceans

Sea Level = level of the ocean’s surfaces
o Sea Level has risen and fallen by hundreds of meters due to the…

Ice Caps melting (H2O level rises) & Glaciers expanding (H2O level falls)
o Sea Level is also affected by tectonics.

TECTONICS = movement of Earth’s landmasses.

Tectonics can change the level of the seafloor, thus changing sea levels.
o Currently, sea level is rising 1-2mm/year due to melting glaciers
GEOGRAPHY OF THE OCEANS

There are 4 major OCEANS:
o Pacific, Atlantic, Indian, & Arctic
o Largest = Pacific, Smallest = Arctic

Sea Ice: Ice is ( more / less ) dense than water, so it floats.

SEAS = smaller than oceans, and partially or fully landlocked.
o All seas and oceans belong to one global ocean, whose waters are thoroughly mixed.
MAPPING THE OCEAN FLOOR

The topography of the ocean floor is as diverse as that of the continents.

Bathymetry = measurement of the ocean floor (bathos = depth, metry = measurement)

Began with the ship "Challenger" in the 1870's
o Although today’s technology is much more sophisticated!!

SONAR was first used in the 1920s to map the seafloor features of the S. Atlantic Ocean.

SONAR = SOund NAvigation and Ranging
o How does it work? Uses echoes of sound, return time, and velocity of sound in water to
measure depth.
o See page 398 in textbook.
o Velocity of sound in water: 1500 m/s
o Equation:
(Time for echo return) X (Velocity of sound in water)
2
o Problem: It takes 4 seconds for an echo to return.
How deep is the ocean?
o SIDE-SCAN SONAR = aim SONAR at angles
o It is used to map underwater hills, trenches, ridges, etc.

SATELLITES continually gather information about the ocean floor.
o Data has shown that the ocean surface is not totally flat…
o Why?? Gravity attracts water toward regions where massive ocean
floor features occur. Mountains/Ridges have elevated water. Trenches have depressions.

SUBMERSIBLES (small underwater crafts) give us much data.
o Manned crafts:

Trieste – Jacques Piccard (1960)

went to the Mariana Trench (10,912 m)

Alvin – 4000 m

Sea Cliff II – 6000 m
o Unmanned crafts: called AUVs (autonomous underwater vehicles)
Ocean Water and Ocean Life
Section 15.1 – THE COMPOSITION OF SEAWATER
SALINITY

Salinity: the total amount of solid material dissolved in water.

Seawater is about 96.5 % water and 3.5 % dissolved salts.

Expressed as grams of salt per kilograms of water (or parts per thousand – ppt )

Average salinity: 35 ppt (3.5 %)

Most abundant salt in seawater: sodium chloride (NaCl)

Seawater also has dissolved gases and nutrients

Sources of Sea Salts: chemical weathering of rocks and volcanism

Processes Affecting Salinity:

Adding water decreases salinity: precipitation, runoff, icebergs & sea ice melting

Losing water increases salinity: evaporation, formation of sea ice
o How does salinity increase when sea ice forms? When ice forms, salt is left behind in the
water.
OCEAN TEMPERATURE VARIATION

Surface Layer Temperatures: Varies with the amount of
solar radiation received, which is a function of latitude.
Middle latitudes (near the equator) have higher
temperatures, and vice versa.

Temperature Variation with Depth:
o Colder water is denser than warmer water, so cold water will sink. Deeper = Colder!
o Three temperature layers:

Surface layer: warmest

Thermocline: (300m-1000m) a rapid change of temperature with depth.


It creates a vertical barrier to many types of marine life.
Bottom layer: coldest
o In polar regions, the surface layer & thermocline don't exist because it’s too cold.
OCEAN DENSITY VARIATION

Density varies with depth due to both temperature and salinity.

Denser Water = ( colder or warmer ) and ( salty or fresh )  why floating is easier in the ocean!
The Dynamic Ocean
Sections 16.1 & 16.2 - OCEAN CIRCULATION & WAVES AND TIDES
4 Movements of the Ocean: Waves, Tides, Currents & Upwellings
WAVES = rhythmic movement that carries energy through space or matter (water)

Generated mainly by wind
o As a wave passes, water moves in a circle, returning to its original position.
o The water doesn't move forward, only the energy.
Draw diagram here – p.456

Wave Measurements:
o Highest point = crest. Lowest point = trough.
o Distance from Crest to Trough = wave height.
o Distance from Crest to Crest (or trough to trough) = wavelength.
o Wave speed increases with wavelength.

Breaking Waves: see page 457
o As waves reach the shallow water near a shoreline, energy is lost due to friction against the
seafloor. This slows the wave.
o Incoming wave crests catch up with slower crests, decreasing the wavelength.
o Waves get higher, steeper, and unstable, causing the crests to collapse.
o Collapsing wave crests = breakers.
Draw diagram here – p.457
TIDES = periodic rise and fall of sea level

High Tide = highest level

Low Tide = lowest level

Tidal Cycles (High Tide  Low Tide  High Tide) usually = 24 hrs 50 mins
o Diurnal: 1 high tide, 1 low tide every day
o Semidiurnal: 2 high tides, 2 low tides every day (this is what we have in NC)
o Mixed: 1 high, 1 low, 1 semi-high, 1 semi-low every day

Causes of Tides:
o Gravitational Pull of the Moon and the Sun
o Spring Tide = High tide is highest, low tide is lowest.
Draw diagram here – see p. 459 A
o Neap Tide = high tide lower than usual, low tide higher than usual.
Draw diagram here – see p. 459 B
o Which is bigger - Solar or Lunar Tides? Why? Moon is closer / stronger gravitational pull
OCEAN CURRENTS

CURRENT = movement of a section of water
o Density Current = controlled by density. Move very slowly.
o Surface Current = controlled by wind. Move very quickly.


Only affect the top few hundred meters of water
Continents deflect some currents so that they join other currents, causing a circular current, called
a gyre.
o 5 Major Gyres: North & South Pacific, North & South Atlantic, and Indian Ocean
o In the Northern Hemisphere, the gyres circulate in a clockwise direction.
o In the Southern Hemisphere, the gyres circulate counterclockwise.

Currents flow westward near the equator. When they hit land, they are deflected toward the poles.
This carries warm water to colder regions of the world.

When it gets to the polar regions, the water cools and is deflected back toward the equator on the
other side of the ocean.
UPWELLING

Water not only moves horizontally (currents) but it also moves vertically.

UPWELLING = upward motion of ocean water

Cold water flows upward to replace warm surface water blown out to sea by offshore winds.

They mainly occur on western coasts.

Rich in nutrients, thus supporting lots of marine life.
Currents & Gyres
Color all water LIGHT BLUE. Color all land LIGHT GREEN.
Label the following in color (red = warm current, blue = cold current): See Page 449
Gulf Stream, North Atlantic Current, Canary Current, North Equatorial Current, South Equatorial Current, Brazil Current, Benguela
Current, California Current, North Pacific Current, Kuroshio Current, East Australian Current, Peru Current, West Wind Drift,
W.Australian Current, Agulhas Current
Draw and Label the 5 Major Gyres.