Ch 3 Ocean Circulation

• The ocean never rests• Currents move and mix ocean waters and

transport heat, nutrients, pollutants, and organisms

• Ocean profoundly affects not only marine organisms and their habitats, but also the earth’s climate and therefore all habitats on land

Ocean Surface Circulation

• Driven by the wind• Strongest currents are on the surface• Driven by heat energy from the sun

The Coriolis Effect

• The tendency of objects moving large distances on the earth’s surface to bend to the right in the Northern Hemisphere and to the left in the Southern Hemisphere

• Due to the Earth being round and rotating• Anything that moves over its surface tends to

turn a little rather than moving in a straight line• Influences surface currents and wind

WHAT YOU NEED TO KNOW #1

• Coriolis effect results in winds deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, thus creating our trade winds. Global winds drag on the water’s surface, causing it to move and build up in the direction that the wind is blowing.

WHAT YOU NEED TO KNOW #2

• This also results in the deflection of major surface ocean currents to the right in the Northern Hemisphere (in a clockwise spiral) and to the left in the Southern Hemisphere (in a counter-clockwise spiral). These major spirals of ocean-circling currents are called “gyres” and occur north and south of the equator. They do not occur at the equator, where the Coriolis effect is not present. For years sailors have referred to this calm equilateral area as the doldroms.

• The Ekman spiral, named after Swedish scientist Vagn Walfrid Ekman who first theorized it in 1902, is a consequence of the Coriolis effect. When driven by wind, the topmost layer of surface water in the Northern Hemisphere flows at about 45 degrees to the right of the wind direction. Deeper layers of water respond to the friction of the layer above and also deflect to the right but at a slower speed.

• Each subsequent deeper layer slides horizontally over the one above it like a deck of cards creating a spiral effect, until the movement ceases at a depth of about 100 meters (330 feet). Because the deeper layers of water move more slowly than the shallower layers, they tend to “twist around” and flow opposite to the surface current.

• http://kdegar.weebly.com/coriolis-effect-and-winds.html

Coriolis Effect

• Video• http://www.youtube.com/watch?v=aeY9tY9vK

gs• 6:10• http://www.youtube.com/watch?v=mcPs_Od

QOYU• http://www.youtube.com/watch?v=i2mec3vg

eaI

What we’re doing

• http://www.youtube.com/watch?v=7DVL0ugj1O4

JOURNAL ASSIGNMENT

• 1. Do hurricanes turn clockwise or counter clockwise in the Northern hemisphere? WHY?

• 2. Fact or myth: The coriolis effect is responsible for the direction toilet water swirls. WHY OR WHY NOT.

JOURNAL ANSWER

• 1. counterclock wise in the northern hemisphere due to the Coriolis Effect. Counter clockwise in the southern hemisphere

JOURNAL ANSWER

• 2. So why doesn’t Coriolis hold true for a toilet? The rotation of the Earth is very small: only one rotation per day. The water in a toilet might make a several rotations a second so its rotation rate is many thousand times greater than that of the Earth. As a result Coriolis force is orders of magnitude smaller than any of the forces involved in a flushing toilet. The Coriolis force is so small, that it plays no role in determining the direction of rotation of a draining toilet.

• the Coriolis force on earth only works on• very large scales. It doesn’t affect such small• things as toilets and sinks. You may have heard• of people claiming that toilets and sinks swirl• counterclockwise in the Northern Hemisphere• and clockwise in the Southern Hemisphere due• to this force. As cool as that would be, it’s just• not true. It turns out that the way the water swirls has to do

with a number of conditions such as the• shape of the bowl and the way the water• enters the bowl.

• COLORING BOOK PAGE 1

Wind patterns

• Wind is driven by heat energy from the sun• Energy is transferred by wind• Prevailing winds- A wind that blows

predominantly from a single general direction. • The trade winds of the tropics, which blow

from the east throughout the year, are prevailing winds

What creates trade winds?

• More energy is absorbed around equator• Air at equator is less dense and rises• Air from adjacent areas gets sucked in to

replace rising equatorial air• This creates wind that is bent by the Coriolis

effect: “trade winds” . Steadiest winds on Earth. Between 30 degrees North and south latitude

Page 50 text

Trade winds

• Start at 8:21-9:45• http://www.youtube.com/watch?v=RT6WwN

mDfEQ

• The major wind patterns on earth are created by the rising of sum warmed air and the sinking of cold air

• Other winds are also driven by solar energy but are more variable than the trades

• The westerlies lie at middle latitudes and move in the opposite direction to the trade winds. 30-60 degrees latitude

• Polar easterlies are the most variable winds of all

Page 51

Surface currents

• Winds push sea surface creating currents• Currents move at a 45 degree angle from the

wind due to Coriolis effect• Top layer of water pushes the layer below

which will move slightly to the right and slightly slower

• Called Ekman Spiral• Figure 3.19 page 51 in text

• Ekman layer- upper part of the water column that is affected by the wind

• Ekman layer moves at 90 degrees from the wind direction- Ekman transport

• Page 50 “ the coriolis effect causes surface currents to move at 45 degrees from the wind that drives them. Lower water layers move at progressively greater angles from the wind in a pattern called an Ekman spiral. This produces Ekman transport, in which the upper part of the water column moves perpendicular to the wind direction, to the right in the Northern Hemisphere and the left in the Southern Hemisphere”

Ekman Transport

• If the ocean current is regarded as layered, then each deeper layer moves more slowly than the overlying layer

Ekman 8 min

• http://www.youtube.com/watch?v=InX6gw5yJc8

GYRES

• Gyres- A large, nearly circular system of wind driven surface currents that center around latitude 30 degrees in both hemispheres

• Rotate clockwise in Northern hemisphere and counter clockwise in Southern

• Gyres moderate climate by bringing warm water north and cold water south

• “large clockwise eddy” OR “”swirling vortex”

24 second Gyre animation

• http://www.youtube.com/watch?v=x0EqbdSMC8E

Major Gyres page 51

• North Atlantic• South Atlantic• North Pacific• South Pacific• Indian Ocean • Many other smaller ones too

Gyres Page 51

High heat capacity and gyres

• The warm currents on the western side of the gyres carry vast amounts of solar heat from the Equator to higher latitudes

• Cold currents flow in the opposite direction on the eastern sides

• Ocean currents act as a thermostat, warming the poles, cooling the tropics, and regulating the climate of our planet

What are gyres? 2:22

• http://www.youtube.com/watch?v=h6i16CrI8ss

Sean Chamberlin explains Gyres 7:33

• http://www.youtube.com/watch?v=t_w_jQHKXi4

Great Pacific Garbage Patch

• North Pacific gyre is one of the largest ocean gyres

• This area contain a lot of litter• It is estimated to cover an area roughly twice

the size of Texas and contain approximately 3 million tons of plastic litter

Garbage Patch 2:42

• http://www.youtube.com/watch?v=tnUjTHB1lvM

Help Nemo swim thru currents

• http://ocp.ldeo.columbia.edu/climatekidscorner/nemo_page.shtml

Currents activity

• http://www.bigelow.org/shipmates/deep_currents_standards.html

The Case of the Leaky Gyre

• http://www.youtube.com/watch?v=FxXaT7yO4TQ

• 5:19

Journal

• What is the gulf stream?

Journal answer

• The Gulf Stream is one of the most important wind driven currents. It transports very warm tropical water from the Caribbean Sea and the Gulf of Mexico across the North Atlantic to northern Europe. The warmth of the water heats the air above and the movement of this warm air is a very important way by which heat is transported northwards. As a result, northern Europe is very much warmer than corresponding latitudes in North American and countries around the Pacific Ocean.

• Page 1 in the Marine Biology coloring book• Currents activity

Thermohaline Circulation

• Densest water sinks• Therefore, the ocean is usually layered or

STRATIFIED with the densest water on the bottom and the least dense on the surface

• Deep water is cold and dense• Surface water is relatively warm and light

3 layers of the ocean

• Surface layer- usually 100-200 m deep• Mixed by wind, waves, and currents• “mixed layer”• Thermoclines-a zone in the water column that

shows a sudden change in temperature with depth. The main thermocline is the zone where the temp change marks the transition between the warm surface water and the cold deep water

thermoclines

Intermediate layer

• Below the surface layer• 1,000-1,500 m• The main thermocline is the zone where the

temp change marks the transition between the warm surface water and the cold deep water

• The main thermocline breaks down only occasionally. There are permanent and seasonal thermoclines

Deep and bottom layers

• Uniformly cold• less than 4 degrees C (39 degrees F)

Review video 9:42

• http://www.youtube.com/watch?v=IbY1_YYWLEA

• http://www.youtube.com/watch?v=1PWjOMrPkrI

• Hoyle: water masses and global circulation activity

Stability and Overturn

• Stable water column- warmer water floats on top of denser water below unless wind or wave energy stirs it

• Stability depends on density difference• Unstable water column- surface water sinks

causing downwelling and displaces and mixes with deeper water. Surface water becomes more dense than the water below. Creates OVERTURN.

Overturn

• Occurs over a small area • Downwelling water mixes with deeper water• Sinks according to density• Known as thermohaline circulation

Downwelling

• http://www.youtube.com/watch?v=SHTDzLlUU6M

Figure 3.22

• Page 54

• AND coloring book page 2

The great ocean conveyor

• Global, thermohaline circulation• Transports heat and salt• Mixes the oceans on a timescale of about

4,000years• Critical in regulating the earth’s climate and

brings dissolved oxygen to the deep sea• http://oceanservice.noaa.gov/facts/conveyor.

html

• To sink all the way to the bottom of the ocean, surface water must become very dense (cold and salty)

• This occurs at only a few locations intermittently

• 1. Atlantic ocean south of Greenland• 2. North of Antarctica

Page 55

NASA: The Great Ocean Conveyor Video

•http://www.youtube.com/watch?v=3niR_-Kv4SM

• http://www.youtube.com/watch?v=SdgUyLTUYkg

journal

• Read and summarize the national geographic news article, “ global warming may alter Atlantic currents”

El Nino Video 4:31

• http://www.youtube.com/watch?v=7FVZrw7bk1w

What is El Nino

• El Niño is a climate pattern that describes the unusual warming of surface waters along the tropical west coast of South America. El Nino has an impact on ocean temperatures, the speed and strength of ocean currents, the health of coastal fisheries, and local weather from Australia to South America.

When does it occur?

• El Niño events occur irregularly at two- to seven-year intervals.

• El Niño has long been recognized by fishers off the coast of Peru as the yearly appearance of unusually warm water in the Pacific Ocean. The name El Niño, meaning the "little boy" in Spanish, was used because the phenomenon often arrived around Christmas.

What is Southern Oscillation

• Led by the work of Sir Gilbert Walker in the 1930s, climatologists determined that El Niño occurs simultaneously with the Southern Oscillation. The Southern Oscillation is a change in atmospheric pressure over the tropical eastern and western Pacific Ocean. When coastal waters become warmer in the eastern tropical Pacific (El Niño), atmospheric pressure decreases in the eastern Pacific and increases in the western Pacific (Southern Oscillation). Climatologists define these linked phenomena as El Nino-Southern Oscillation (ENSO). Today, most scientists use the terms El Niño and ENSO interchangeably.

What are the “normal conditons”

• In order to understand the development of El Niño, its important to be familiar with non-El Niño conditions in the Pacific Ocean. Normally, strong trade winds blow west across the tropical Pacific, the region of the Pacific Ocean located between the Tropic of Cancer and the Tropic of Capricorn. These winds push warm surface water toward the west Pacific. The western Pacific Ocean borders Asia, the islands of Oceania, and Australia.

What is upwelling?

• Due to the warm trade winds, the sea surface is normally about .5 meter (1.5 feet) higher and 8 degrees Celsius (14 degrees Fahrenheit) warmer in Indonesia than Ecuador. The westward movement of warmer waters causes cooler waters to rise toward the surface along the coasts of Ecuador, Peru, and Chile. This process is known as upwelling. This cold upwelling elevates the thermocline, the level of ocean depth that separates warm surface water from the colder water below.

What is the benefit of upwelling?

• Upwelling elevates this cold water, rich in nutrients, to the euphotic zone, the upper layer of the ocean. Nutrients in the cold water include nitrates and phosphates. Tiny organisms called plankton use these nutrients for photosynthesis, the process that creates food from sunlight. Other organisms, such as clams, eat the plankton, while intermediate predators like fish or marine mammals prey on the clams

• Upwelling also influences global climate. The process increases rainfall over the western Pacific's warmer waters, such as the islands of Indonesia and New Guinea. The eastern Pacific, along the coast of South America, remains relatively dry.

What are the conditions during an El Nino event?

• During an El Niño event, westward-blowing trade winds weaken along the Equator. These changes in pressure and wind speed cause warm surface water to move eastward along the Equator, from the western Pacific to the coast of South America.

What happens when upwelling doesn’t occur?

• The warm water builds up, or thickens, along the coasts of Ecuador, Peru, and Chile. Pushing the thermocline down as much as 152 meters (500 feet), this thick layer of warm water does not allow for normal upwelling to occur. Without this upwelling of nutrient-rich cold water, the euphotic zone of the eastern Pacific can no longer support its normally productive ecosystem. Fish populations die or migrate. El Niño has a devastating impact on the Ecuadorian and Peruvian economies.

• El Niño also produces widespread and sometimes severe changes in climate. Rainfall increases drastically in Ecuador and northern Peru, which normally have fairly arid climates. Coastal flooding and erosion are common El Niño events. Rains and floods may destroy homes, schools, hospitals, and businesses. They also limit transportation and destroy crops.

• The eastward movement of oceanic and atmospheric heat sources causes unusually severe winter weather at the higher latitudes of North and South America. Heavy rain along Central America's Pacific coast is common in El Niño years. Regions as far north as the U.S. states of California and Washington may experience longer, colder winters because of El Niño.

• El Niño has diverse impacts on tropical storms in the Pacific and Atlantic. Most meteorologists think El Niño events contribute to more tropical storms in the eastern Pacific, while contributing to a reduced number of hurricanes in the Atlantic and Gulf of Mexico.

When were the worst El Nino Events?

• El Niño events of 1982-83 and 1997-98 were the most intense of the 20th century. During the 1982-83 event, sea-surface temperatures in the eastern tropical Pacific were many degrees above normal. These strong temperature increases caused severe climatic changes: Australia experienced harsh drought conditions; typhoons devastated Tahiti; and record rainfall and flooding hit central Chile. The west coast of North America was unusually stormy during the winter season, and fish catches were dramatically reduced from Chile to Alaska.

• The El Niño event of 1997-98 is regarded as the strongest of the 20th century. This was the first El Niño event to be scientifically monitored from beginning to end

How does El Nino cause disease?

• In addition to increased natural hazards and economic devastation, health crises are also associated with El Niño events. Diseases carried by mosquitoes and flies, such as dengue fever and malaria, increase as warmer, more humid weather expands mosquitoes habitat.

El Nino- Southern Oscillation REVIEW

• When normal patterns of winds, currents and upwelling change

• Currents along coasts of Peru and Chile change producing strong upwelling bringing nutrients to the surface

• Upwelling decreases around Christmas therefore named El Nino “The Child”

Southern Oscillation- REVIEW

• Refers to a long distance linkage in atmospheric pressure. When the pressure is high over the Pacific Ocean, it tends to be low over the Indian Ocean, and vice versa. Over a period of months or years, the air pressure swings back and forth like a giant seesaw that extends halfway around the world. The changes in atmospheric pressure bring dramatic changes in wind and rainfall, including the failure of the summer monsoon

Effects of El Nino REVIEW

• Floods in some areas• People killed• Crop and livestock destroyed• Drought in other areas• Disease outbreak from water contamination• Warmth increased mosquito borne diseases• Bubonic plague and hantavirus (respiratory

disease)

El Nino

• Coloring book page 2

The GLOBE 6:53

• http://www.pbs.org/newshour/thenews/theglobe/story.php?id=13179&package_id=632

• Answer the questions on the graphic organizer for the news segment “El Nino”

La Nina

• Page 359

BBC El Nino 48 min

• http://www.youtube.com/watch?v=MzcKBeW44ao

WAVES

Waves

• http://www.youtube.com/watch?v=0a5WyAjL1MM

• “Mr. Probz”

Where do waves “Come From”?

• The Sun!• When air heats up, it expands and as a result,

it rises. But when air rises, it doesn’t just leave a big hole behind with no air in it. Cooler air from the surroundings rushes in to replace it and that is what we call wind.

• As wind passes over the water's surface, friction forces it to ripple. The strength of the wind, the distance the wind blows (fetch) and the length of the gust (duration) determine how big the ripples will become.

The wave height is determined by three factors:– Wind Speed- measured in knots (equal to 1.15

mph)– Fetch- area of open water over which the wind

blows– Duration- how long the wind has blown in the

same direction

Waves page 55-56

• Define:– Crest– Trough– Height– Wavelength– Period– Fetch– Seas– Swells– surf

Page 57

• Water particles do not move along with a wave but instead move in circles. Under the crest they move up and forward with the wave, then they are pulled back down under the trough. As wave after wave passes, the water and anything floating in or on it moves in circles.

• In deep waters, only wavelength and wave period affect a waves speed. As the wave approaches shallow water, or water that is half the wavelength or less deep, the ocean floor begins to affect the wave's shape and speed. Wave height increases, and the crests become more peaked. As the steepness increases, the wave becomes unstable. The forward speed of the crest becomes faster than the speed of the wave, and the wave breaks.

NOAA explanation

• http://www.montereyinstitute.org/noaa/lesson09.html

Good, bad, ugly

• http://www.youtube.com/watch?v=oPNQVQgrwbo

How waves are made

• http://www.youtube.com/watch?v=5_HefhiwioE

Tallest wave ever recorded

• http://geology.com/records/biggest-tsunami.shtml

“Savageseas”

• http://www.pbs.org/wnet/savageseas/multimedia/wavemachine.html

How do waves affect marine life?

• 1. Distribution of nutrients-By pushing water onto the shore, waves make it possible for intertidal animals to live in areas of beaches and shorelines that would otherwise be too dry to sustain them

How do waves affect marine life cont…

• 2. habitat- Waves have a major impact on shorelines and their habitability for various species of marine animals. Waves erode sediment from some shorelines and deposit them on others, creating beaches of sand and gravel that are able to support vastly different species of aquatic life than that which can live along rocky seashores. Another way that waves affect shorelines, and the animals that live along them, is to transform beach slope. This in turn affects the areas that become exposed during low tide, which can either expand or reduce the habitable areas available for intertidal animals.

How do waves affect Marine Life cont….

• 3. Life Cycles- Waves play a substantial role in the natural life cycles of intertidal species. Storms and large waves can deposit kelp on beaches, where it provides nourishment for various plants and animals. Marine animals that attach to rocks, such as mussels, sometimes have entire colonies torn away by strong waves, making way for other species to inhabit that area.

Wave ENERGY• Wave energy is produced when electricity

generators are placed on the surface of the ocean. The energy provided is most often used in desalination plants, power plants and water pumps. Energy output is determined by wave height, wave speed, wavelength, and water density. To date there are only a handful of experimental wave generator plants in operation around the world.

Surfing Waves

• http://www.youtube.com/watch?v=7nS_aR8XX_U

• http://www.youtube.com/watch?v=usi5iMoS-l0

NOAA WAVES

• http://oceanexplorer.noaa.gov/edu/learning/player/lesson09.html

Ocean Waves

• Labeling worksheet• Ocean Waves lab 12

• Tides web site• http://

marinebio.org/oceans/currents-tides.asp

• Coloring book page 3

Bob Marley

• High and Low Tides

• http://www.youtube.com/watch?v=enfTlBjXgl8

• Tides are the periodic rising and falling of ocean waters caused by the gravitational forces of the sun and moon

WHY are there tides?

• The tides are caused by the gravitational pull off the moon and sun and by the rotations of the earth, moon and sun

• The moon and earth are held together by gravitational attraction

• The moon’s gravity is strongest on the side of the earth closest to the moon

• Here the moon’s gravity pulls the water in the ocean toward the moon, so that if the earth were covered entirely by water the ocean would bulge toward the moon

• On the opposite side of the earth, further away from the moon, the moon’s gravitational pull is weaker, so the water does not move toward the moon- bulges in the opposite direction

•This centrifugal force arises because the moon does not revolve around the earth

• On a water covered earth the water would form two bulges on opposite sides of the planet, one bulge toward the moon where the moon’s gravity predominates and the other bulge away from the moon where centrifugal force predominates

• The water would be relatively deep under the bulges and shallow away from the bulges

Tides page 57

• Read page 57 “why are there tides”• EXPECT THIS TO BE AN ESSAY QUESTION

How do the tides work? 2:01

• http://www.youtube.com/watch?v=CTQ6ciHENgI&feature=youtu.be

• http://www.youtube.com/watch?v=l37ofe9haMU

• Oceanographers say that tides rise and fall, while tidal currents EBB (during a falling tide) and FLOOD (during a rising tide)

High tide page 60

• Occurs when the point is under a bulge• Any point will have 2 high tides and 2 low tides per

day• 2 “buldges” one for moon’s gravitational pull and one

for centrifugal force (An apparent force that acts outward on a body moving around a center, arising from the body's inertia)

• Full tidal cycle takes 24 hours and 50 minutes• WHY???- figure 3.32• Because the moon moves while the earth is rotating

• Tidal range- difference in water level between successive high and low tides

• Spring tides-tides with a large tidal range. They occur around the times of full or new moon

• Neap tides- The tides with a small tidal range. They occur around the times when the moon is in quarter

• Semidiurnal tides- there are two high tides and two low tides a day

• Mixed semidiurnal tides- successive high tides of different height

• Diurnal- there is only one high and one low tide every day

Page 62

• Tides vary from place to place and time to time because of the effects of continents, islands, and bottom topography

• http://www.youtube.com/watch?v=kJOvxQElfLc

Bay of Fundy Time Lapse

• http://www.youtube.com/watch?v=5W2sM1Ma7YA

• http://www.youtube.com/watch?v=OP0cpXpw8yk

Hopewell Rocks Time Lapse

• http://www.youtube.com/watch?v=EnDJ6_XpGfo

REVIEW

• Moon exerts gravitational pull on Earth. Creates bulge of water. Creates high tide and low tide.

• Sun exerts gravitational force too. Depending on sun’s position to the Earth, it can enhance or diminish the tidal effect cause by the moon.

REVIEW

• When the sun and moon are aligned (full or new moon) their gravitational forces act in the same direction and produce more pronounced high and low tides- SPRING TIDES

REVIEW

• When the sun and the moon are at right angles relative to the Earth, the gravitational force of the sun partially cancels out the gravitational force of the moon. Result is less pronounced high and low tides- NEAP TIDES

“The Moon made me Do It”

• http://oceanservice.noaa.gov/education/tutorial_tides/welcome.html

• Computer lab 43 questions

Tides Charts for Graphing

• http://www.massmarineeducators.org/activities/tides.php

activities

• Graphing tides

• NOAA the Moon Made Me Do It- computer lab