You are shipwrecked on a desert island and write a distress note, stuff it into a bottle, and throw it into the ocean. Can you predict where the message might end up? Why or why not?

Ocean Currents Ocean currents are stream like movements of water in the larger ocean. They can be cold or warm water currents (warm=Gulf and North Atlantic Drift, cold= Labrador and California). Currents are affected by the wind, weather, earth’s rotation, and position of the continents.

Gulf Stream

California Current

World Currents

Surface vs River Currents Surface and river currents are similar because both are long moving bodies of water. However, rivers flow because of gravity toward the ocean and ocean currents are driven by wind and the rotation of the earth.

Types of Ocean Currents There are two types of currents: surface and deep currents. Surface currents are located on the surface of the water and controlled by global winds, Coriolis effect, and continental deflections. Deep currents are deep below the surface and are controlled by difference in density of the water.

Surface Currents 1- Global winds blow from east to west from the equator 0⁰ to 30⁰, west to east from 30⁰ to 60⁰ and east to west 60⁰ to 90⁰ poles. 2- Coriolis Effect is because of the earth’s rotation. Currents in Northern hemisphere rotate clockwise and in the Southern Hemisphere counterclockwise. 3- Continental deflection is the shape of continents above the water level that causes currents to alter their direction of flow.

Global Winds

Corolis Effect

Continental Deflection

Surface Currents Temperature and Salinity also affect surface currents. Warm water currents originate at the equator and cold water currents originate at the poles.

Deep Currents Deep currents are not affected by wind because of their depth. Deep currents are controlled by temperature and salinity (density). Decreasing temperature increases density. ↓ sinks Increasing salinity increases density.↓ sinks

Warm water Less dense versus cold water ? Very salty water is More dense than less salty water?

Warm water currents begin near the equator and flow north as surface currents. Cold water currents begin near the poles and flow south as deep water currents. The continual exchange of energy (hot to cold) makes a continuous cycle of heating and cooling ocean currents. The process takes 1000’s of years.

Deep vs Warm Currents

Surface Currents Because the air above a warm current is warm it can bring milder winters to places that would otherwise be significantly colder (Gulf Stream and Britain). Likewise with cold currents the air above is cold and it can bring cooler summers to place that would otherwise be significantly warmer (California Current and California).

Upwelling Is the process in which cold nutrient rich water from deep ocean rises to the surface replaces the warm surface water. Upwelling helps plankton to grow supporting the other forms of life in the ocean. Picture on page 127.

Upwelling

El Nino A weather condition that occurs on a year cycle. The South Pacific trade winds move less water to the Western Pacific and the surface temperature becomes warmer than normal. This leads to more evaporation into the atmosphere and causes higher amounts of precipitation.

Normal Year Weather

El Nino

NOAA National Oceanic and Atmospheric Administration collects info about El Nino by buoys that monitor air temp., surface temp., currents, and wind directions. Scientist hope to predict El Nino patterns more accurately by using this data.

La Nina Is the reverse of El Nino. The surface waters of the Pacific Ocean become unusually cold (cold water on top of warm water).

La Nina

Tsunamis Tsunamis are waves that form when a large volume of water is suddenly moved up or down. They are usually caused by earthquakes, landslides, volcanic eruptions, or impact by a meteor of comet. Seen more in the Pacific Ocean because of the large volcanic area around the Ring of Fire.

tsunami

Waves The parts of a wave are crest, trough, wavelength, wave height, amplitude, and period. Wave length is measured from trough to trough or crest to crest. Amplitude is the distance from the center of a wave to the crest or trough. Amplitude equals ½ the wave height.

waves

Waves The period is the time it takes for two crests or troughs to pass a fixed point. Waves transfer energy from one place to another. Energy passed from the wind to the ocean to the land.

Waves The wind forms most of the ocean’s waves. Wave length/wave period= wave speed. The deeper the water the less energy the wave has.

Waves What can cause ocean waves? 1.Wind 2.Earthquakes (tsunami) 3.Landslides 4.Meteor impact (tsunami)

Waves Deep water waves are waves that move in water deeper than one half their wavelength. Shallow water waves are waves that move in water shallower than one half their wavelength. When deep water waves become shallow water waves they build up in height reacting with the ocean floor until gravity pulls them over and they become breakers. The area between the breaker zone and the shoreline is called the surf.

Waves Long shore waves hit the shoreline at an angle. Shore current waves hit the shoreline head on and creates an undertow that pull objects out to sea. If strong enough it is called a rip tide. White caps are waves that form in deep water are foaming, bubbling waves with very steep crests are pulled over before they reach shallow water. Swells are long wavelength waves that can travel thousands of miles across the open ocean.

Long shore wave

Undertow Wave

White Cap

Swell

Waves Storm Surges cause a rise in local sea level due to strong winds from a hurricane or typhoon causing a wall of water to pile up as the storm comes ashore. Storm surges are more destructive than storm winds normally.

Storm Surge is caused by constant high winds pushing large volumes of water onto the land

Tides High and low tides are caused by the gravitational forces of the moon and sun. Since the sun is much further away than the moon it has less effect on the tides than the moon does. Remember F= M 1 x M 2 / D 2

Tides A Greek named Pytheas first put forth the theory that the moon affected the tides. This was not proven for nearly 2000 years until Newton and his Law of Gravity. The moon pulls on every object on earth but it is much more noticeable on liquids than it is on solids because liquid particles move so much more freely than solids do.

Tides High tide occurs when the moon is directly overhead and exerts the most gravitational pull. High tide also occurs on the other side of the earth at the same time. Low tide occurs exactly 90 degrees on either side of the high tide location. High tide and low tide are approximately 52 minutes later the next day because of the time it takes the moon to make one complete revolution around the earth.

Tides Mont. St. Michel in France experiences some of the most extreme tidal changes. During high tide it is an island and during low tide there is a walk way to the castle. Fundy Bay in Nova Scotia has the largest range of high versus low tides in the world about 55 feet difference.

St. Michel in France

Bay of Fundy

Spring Tide

Spring Tides

Neap Tides

Tides Sun↔Earth↔Moon= spring tide this alignment is full moon. Sun↔Moon↔Earth= spring tide this alignment is new moon. Sun↔Earth Neap tides occur ↕ when the sun,earth, Moon and moon are at 90° to each other ( 1 st and 3 rd quarters)

Tides There are four major types of tides 1.High 2.Low 3.Spring-Has the largest daily range of tides. 4.Neap-Has the smallest daily range of tides.