Oceans and Ocean Movements

Cool Facts 71% of all water on Earth is in our oceans. Average depth of the oceans is 2.65 miles deep! Deepest point in the ocean is about 7 miles deep! Pressure increases as you go down in the ocean. Until 2000, there were only 4 oceans.

Oceanography The study of Earth’s oceans Did not begin to study until 1800’s with the Challenger Challenger: first research ship Investigated ocean currents, temperature, and chemical composition of the ocean

Advanced Technology SONAR: SOund NAvigation and Ranging Submarines to investigate deep ocean trenches

Scientists use SONAR to map seafloor and NOW can use it to understand aquatic life! http://www.youtube.com/watch?v=-fAAxEIFeLU

Origin of Oceans Earth’s water may have originated from Comets or through volcanism. Comets: carried water, collided with Earth, then released the water Volcanoes: during eruptions, water vapor and carbon dioxide released, condensed, and formed Earth’s early atmosphere

The Major Oceans (5) Pacific Atlantic Indian Southern Arctic

Pacific Largest Contains deepest point on earth! (7 miles deep-Marianas Trench) Covers ~35% of the Earth Between Asia and NA/SA

Atlantic Next to NC! Deepest Point: Puerto Rico Trench Second largest Covers ~21% of Earth

Indian Deepest Point: Java Trench Near India-Africa on East and Asia on North Covers ~15% of Earth

Southern Ocean established in year 2000! Newest ocean Surrounds Antarctica Covers the South Pole

Arctic Smallest ocean Deepest Point: Arctic Basin Covers North Pole Often completely frozen during the winter

Sea Level Level of the oceans’ surfaces Can change in response to the melting of ice during warm periods and/or expanding of glaciers during ice ages Average sea level is rising at a rate of 1 to 2 millimeters per year  because glaciers are melting (indicates a warm period)

Composition of Ocean Water 96.5% pure water and 3.5% salts Salinity: total amount of solid material (salts) dissolved in water Salinity measured in parts per thousand (ppt).

Where does the salt come from? Salt = NaCl = the salt you put on food! Comes from erosion Salinity can decrease by precipitation, runoff from land, melting of ice (all adding more freshwater) Salinity can be increased by evaporation (only the water evaporates, not the salt) and by sea water freezing (only the water freezes, not the salt)

Why are our oceans salty? Salinity affects density! We need changes in density so we can have ocean currents (we will study this in a few days) So what makes our water MORE dense? Less salt or More salt?

Profile of an Ocean Ocean water is warmer at the surface because of the sun. Temperature decreases with depth. Thermocline: zone in ocean where there is rapid temperature change.

Density and how it relates to temperature. Colder water is more dense…means it will be below warm water. Because of this, there are 3 zones: Surface zone: at top Transition zone: in middle (includes thermocline) Deep zone: at bottom. Sunlight never reaches this section. 80% of ocean water found here.

Surface Zone Transition Zone Deep Zone

Ocean Movements Ocean water moves in 3 ways: Waves Currents Tides

Waves The movement that carries energy through the water Most waves are caused by wind moving over the water’s surface.

Anatomy of a Wave Crest: top of the wave Trough: bottom of the wave Wave height: vertical distance between the trough and the crest Wave length: horizontal distance between two crests or troughs.

Ocean Currents Masses of ocean water that flow from one place to another

2 types of currents Density currents: vertical currents that result from different densities of water. Denser water sinks. Surface currents: movements of water that flow horizontally in the upper part of the oceans surface-usually because of wind.

What ultimately fuels the currents? THE SUN Warms waters on surface-makes them less dense Causes evaporation-makes water more salty and therefore more dense

Tides Periodic rise and fall of sea level Caused by gravitational attraction between the earth and moon. Side of the earth facing the moon and opposite the moon experience tides. Usually 2 high and 2 low tides a day

Spring Tide When the earth, moon, and sun are all lined up. This creates higher, high tides and lower, low tides. Occurs at full and new moons.

Neap Tide During a first or third quarter moon, when the moon is at a right angle to the earth. Results in lower, high tides and higher, low tides.

Tidal range Difference in height between successive high and low tides. If high tide is 4 meters and low tide is 1 meter, what is the tidal range?

Tidal Patterns Diurnal tides: a single high tide and a single low tide each day Semidiurnal tides: two high tides and two low tides each day Mixed tides: two high and two low a day but the the heights are different between the two high and two low