Salt Water

Salt Water

How Ocean Water Differs from Fresh Water

Ocean water’s salinity = 200X greater than fresh water Average salinity of oceans is 35 ppt (parts

per thousand) Oceans at equator (because of

evaporation) and poles (the creation of ice) have the highest salinity removing water increases salinity

Ocean locations near rivers have low salinity, due to addition of fresh water

from the World Ocean Atlas 2001

Oceans 70% of the Earth’s surface is covered by

oceans Oceans are the largest ecosystem on

Earth 97% of the water on Earth in oceans (too

salty to drink) All oceans are connected Light only goes down 100 meters, so

most of the oceans are pitch black Oceans undergo constant change

Composition of Salt Water Salt water is composed of minerals

dissolved during run-offs occurring over millions of years

Volcanic eruptions also release minerals from inside Earth

The Origin of Ocean Water

(c) McGraw Hill Ryerson 2007

Oceans have filled over hundreds of millions of years.

Scientists believe the oceans are more than 3 billion years old.

Water may have originally been released from volcanic eruptions, or arrived on Earth via icy comets.

Ocean Basins

(c) McGraw Hill Ryerson 2007

The surface of the ocean floor is as varied as the land. The five major oceans, from largest to smallest, are

the Pacific the Atlantic the Indian the Southern the Arctic

The low points in the oceans are called basins. Oceans are vital to life, as they control temperature,

create weather patterns and provide water for water cycles.

Ocean Basins

(c) McGraw Hill Ryerson 2007

The largest changes to the ocean basin occur through the movement of tectonic plates, although there is also erosion via storms, earthquakes and icebergs.

Mid-ocean ridges occur where new rock is forced up, and ocean floor spreads outward. The Mid-Atlantic Ridge is the largest example on

Earth The Juan de Fuca plate lies 200 km off Vancouver

Island A trench forms when the dense oceanic plates

run into, and slide under, the continental plates.

Ocean Basins (continued)

(c) McGraw Hill Ryerson 2007

Abyssal plains are the pieces of oceanic crust between a spreading mid-ocean ridge and the trench it disappears into. These make up 30% of the Atlantic sea floor, and 65% of

the Pacific seafloor. Abyssal plains can be

covered in 1 km of sediments Seamounts are old

volcanic mountains found on abyssal plains. The Hawaiian Islands are an example.

See page 407

Continental Margins

(c) McGraw Hill Ryerson 2007

Continental margins are part of continental plates.

Continental margins are made up of a continental shelf (averaging 80 km wide) and a continental slope down to the oceanic plate.

Continental shelves were above water during the last ice age.

Ocean Currents

(c) McGraw Hill Ryerson 2007

There are more than 20 major currents which move large amounts of water predictably around the oceans. Currents move large quantities of water, minerals, solar

energy, oxygen and carbon dioxide, plankton and fish. Currents are caused and driven by water

density and salt content, the wind, the spin of Earth, coastlines and the moon.

Largest current is the Antarctic Circumpolar Current in the Southern Ocean, at 24 000 km long

Ocean currents are either Surface currents (0 - 200 m) Deep water currents (200 m and deeper)

Ocean Waves and Their Effect on Shaping Land

(c) McGraw Hill Ryerson 2007

Most waves are created by wind. In open ocean, waves are called swells.

Swells “break” in shallow water, show characteristic curl.

The largest waves are tsunamis, caused by undersea earthquakes, landslides or volcanic eruptions.

Waves erode coastal areas based on the force of the waves, and the composition of the shoreline.

Tides

(c) McGraw Hill Ryerson 2007

Tides are caused by gravities of Earth and the Moon. High tides occur where the Moon is

closest to Earth (and opposite side) Low tides occur at 90º to the high tides.

Tidal range is the difference between high and low tide

The Sun’s gravity, when lined up properly, can produce extreme tides. These are called spring tides When the Sun, Moon and Earth are not lined up,

the tides are called neap tides.

Oceans and Climate

(c) McGraw Hill Ryerson 2007

Water has a high heat capacity Water heats up and cools down slowly, and can

absorb large amounts of thermal energy. Oceans can store and transport huge amounts of

energy Oceans influence weather through the water cycle

Weather tracked over many years = climate Climates vary greatly

around the world Climate measures temperature +

precipitation > 30 years

How Oceans Affect Weather

(c) McGraw Hill Ryerson 2007

Through convection, heat energy transfers from the ocean’s surface to the air, and this warm air rises The warm “bubble” of air is called a thermal The thermal rises until it loses its heat, and then drops back

down again. This process of heat transfer is called convection. El Niño is the warming ocean effect that occurs some

years in December off the Pacific coast of Ecuador. El Niño can change the weather around the world, including

warmer and wetter in BC, and droughts in Africa and Australia. Changing ocean temperatures also cause sea life to change

behaviours. La Niña is a cooling of similar waters, and produces almost the

opposite effects of El Niño.

The Moderating Effect of Oceans on Climate

Oceans can make cold, northern locations warmer Locations like BC, Norway and England benefit Because of water’s high heat capacity, heat

energy can be carried from south to north by currents like the Gulf Stream (in England and Norway) or the Pacific Drift (in BC). As the warm water evaporates, it carries energy

over the mainland of the province. Mountains block the warmth from reaching into

the interior. Edmonton and Manchester, England are the same

latitude

Edmonton, Alberta

January average temperature = 7 C

Manchester, England

January average temperature = +6 C