Chapter 8The Blue Planet

The Blue Planet

The Blue Planet

The Blue Planet

The Blue Planet

• The formation of the oceans transformed our world from a hot, barren wilderness into the only water-covered planet in the Solar System.

• The oceans still affect life on Earth, controlling weather patterns and impacting upon global environmental cycles.

Birth of the oceans• When Earth’s crust solidified

sufficiently to enable oceans to form, the water came from two sources:– Steam and other gases vented from

volcanic activity– Extraterrestrial

• 5-30 icy comets, up to 40 feet across, strike the atmosphere every day

• Satellite observations reveal space snowballs vaporizing over the Atlantic adding water to the oceans

Water and Light• Seawater with its high

concentrations of dissolved and suspended materials, absorbs light.

• When dissolved and suspended materials are at low concentration, such as in the Mediterranean, the clarity of the water is high so sunlight penetrates to a greater depth.

• Off the coast of SW Spain

Water and light• Different

wavelengths of light penetrate to different depths.

• Below about 660 ft (200m) no light penetrates at all in the open ocean.

• Note red absorbed first; blue remains the longest.

Water and Light

• The depth to which only 1% of sunlight penetrates is called the euphotic zone.

• The photic zone, the depth at which photosynthesis occurs, is limited by the penetration of light with wavelengths between 400-700 nm.

Ocean Zones

• The oceans occupy the depressions, or basins, in the surface of Earth that are created by the edges of surrounding continental masses.

• The margins of these basins are an extension of the adjacent landmass, known as the continental shelf, that is covered by relatively shallow seas.

Ocean Zones

• Pelagic- features and processes of the water column.

• Benthic- features and processes relating to the seafloor.

Ocean Zones• In the Pelagic environment, vertical

grades, including those of light, temperature, and salinity, determine the distribution of organisms.

• The greatest changes are seen at the boundary between the mixed surface waters and the deeper water masses.

• In some shallow-water areas, a thermocline, or boundary develops between the warmer surface and the cold water below. Temperatures may drop rapidly across such thermoclines.

Pelagic

• Divided into Neritic and Oceanic• Neritic- shallow area out from shore

above the continental shelf.• Oceanic- lies beyond the point of the

continental shelf

Neritic

• Neritic is divided into:– Littoral zone: shore between the tides– Supralittoral zone: above high water– Sublittoral zone: below low tide

Pelagic Layers

• Epipelagic- surface• Mesopelagic- where light from the

surface starts to disappear (200 m )• Bathypelagic- 1000 m, dark• Abyssopelagic- 4000 m, dark • Hadal- 6000 m the deepest trenches

Pelagic Zones

• Each of these zones contains a different community of species adapted to these different conditions of salinity, temperature and light intensity.

• The epipelagic zone contains the most abundant life which depends on the primary production of the plankton community.

Pelagic Zones• Passing down the

pelagic zones, the proportion of carnivores increases as the density of primary producers decreases.

• Eye size increases as light intensity decreases.

• Viper Fish

• Deep sea squid

Benthic

• Divided into Subneritic and Suboceanic

• Subneritic- before the continental shelf

• Suboceanic- Continental shelf out

The Ocean Zones

The abyss• The only light that is produced is through

bioluminescence- light signals produced by animals.

• The anglerfish uses the light to lure prey within reach.

• Lantern fish signal between members of the same species & use the light to find food.

• Some deep-sea animals rely on the presence of symbiotic bacteria to produce the flashes or continuous beams of light.

• Angler fish • Lantern fish

Bioluminescence

The World Ocean

• Four large basins: – Pacific– Atlantic– Indian– Arctic

The World Ocean• All the great oceans are

interconnected and exchange water, heat and organisms.

• Oceanographers often refer to the Earth’s seawater as the “world ocean.”

• From the South Pole, the Atlantic, Indian and Pacific appear as branches of the Southern Ocean.

The World Ocean

The World Ocean• The Arctic Ocean is almost landlocked and

much is covered with permanent ice.• The Southern Ocean was officially

recognized in 2000. It’s northern boundary is defined as the 60oS.

• The major oceans are subdivided into smaller seas, gulfs or bays, that are usually defined by obvious geographical boundaries such as the Mediterranean and Black seas.

The World Ocean

• The Sargasso Sea in the Atlantic Ocean is named for the mass of seaweed that accumulates.

Sargasso Sea

The World Oceans

• Boundaries between oceans usually are marked by the coastlines of the continental landmasses at their margins, or by major underwater features such as ocean ridges.

The World Ocean

• Not all seas are part of the World Ocean.

• The Caspian Sea and Salton Seas are salt lakes.

The Caspian Sea• The Caspian Sea • Oil Rig in the

Caspian Sea

The Salton Sea

The World Ocean

Pacific Ocean

• Asia

Pacific Ocean

• Size– World’s largest ocean– Has ½ of world’s seawater– Larger than all of the land masses

combined– covering 1/3 of the Earth’s surface– twice the size of the Atlantic

Pacific Ocean• Features

– The deepest – Marianas Trench at 36,201 ft.= 6.8 miles – Active plate margins. (The Earth’s highest

mountain from base to peak is Mauna Kea, Hawaii at 38,184 ft.)

– Size is decreasing 4 inches per year.– Currents can take 1000 years to make 1 circuit.

Pacific Ocean• The plate margins are extremely

active, decreasing the Pacific’s size by subduction while the Atlantic and Indian Oceans continue to grow.

• The immense distances between the more remote islands of the Pacific has meant that they have been isolated until relatively recent times. This isolation has brought about many unique biological communities.

Pacific Ocean

• Oceania

Pacific Resources• 1. good fishing• 2. gold• 3. iron deposits

off Japan• Some oil and gas

• Range of Pacific cod

Pacific Ocean: Resources• Two main commercial fishing sites:

– Shallow seas of North Pacific– Along the coast of South America

• In the colder northern waters there are fisheries for cod, sea bass and various flatfish species.

• In the upwelling zone, the fisheries are almost entirely anchovy, much of which is converted to fish meal to feed livestock.

• Shellfish, crabs, lobsters and shrimp are found in the Yellow and South China seas and around Australia.

Pacific Ocean: Resources• The famed

Alaskan King Crab is caught off Alaska and the Aleutian Islands.

• Gold has been mined from the beaches of Alaska for years.

Pacific Ocean• The Pacific has enormous fields of

manganese nodules, yet to be collected on a commercial scale.

• Iron deposits off of Japan are extracted.

• The recent discovery of oil and gas in the Malay archipelago has stimulated oil and gas prospecting around the rim of the Pacific.

Malay Archipelago

Pacific Ocean

Pacific Ocean

Atlantic Ocean: Size

• Second largest• 6.5 times the size of the U.S.

The Atlantic Ocean: Features

• Still widening 1 inch per year (spreading at mid-Atlantic ridge)

• Many great rivers drain into the Atlantic. Receives four times as much freshwater run-off than the Pacific

• Low salinity waters dominate• Flows 400X faster than the Amazon

Atlantic Ocean

• The margins of the Atlantic Ocean are far more stable than those of the Pacific.

• These stable continental shelves are the location of important fishing grounds.

Atlantic Ocean: Resources

• Mariculture widespread• Good fishing off continental shelves

of U. S., NW Europe and E. Canada• Some of the finest diamonds in the

world are found off the SW coast of Africa.

• Extract & dredge for sand & gravel• Oil & Gas

Fishing• The cod and herring fisheries of the North

Sea and Newfoundland cod fisheries were the first to develop trawlers to spend long periods at sea.

• Thus they could fish far from their ports. The 1990’s led to the collapse of this fish market from overfishing.

• The majority of fish now come from NW Europe, eastern Canada and the U. S.

Fishing• Lobster and shrimp

come from Maine, the Caribbean, northern Brazil and along the South African coast.

• Crabs are an important resource to the eastern U. S.

• Mariculture- a specialized branch of aquaculture involving the cultivation of marine organisms for food.

• Mariculture is widespread in the North Atlantic with salmon and trout being farmed in Canada, Scandinavia and western Scotland. Tuna are farmed in Nova Scotia. Mariculture of oysters, clams, and mussels have expanded in the U.S., but degradation of water quality may limit further growth.

Atlantic Ocean• The mineral wealth of the Atlantic has principally

been its reserves of oil and gas in its shelf seas.• After 30 years of production, reserves are nearing

complete exhaustion.• Oil exploration in the North Atlantic is now

looking to deep waters west of the Shetland Islands. In the South Atlantic, the Falkland Plateau is thought to contain significant reserves.

• The North Sea, Caribbean region and along the West African Coast continue to be sites of oil and gas.

Atlantic Ocean

• The value of sand and gravel is greater than that of all minerals combined (apart from oil & gas).

• Extraction and dredging primarily off the NW coast of Europe, in the North Sea and from the Great Bahamas Bank.

Atlantic Ocean

North Atlantic

Atlantic Ocean

• South Atlantic

Indian Ocean• Size

– The third largest of the world’s oceans.

Indian Ocean: Features

• Deep trench, Java Trench is 24,450 ft= 4.6 miles

• Currents change direction twice a year. So 1/5 the fish of the Atlantic.

• High salinity• Low oxygen content• ½ of the Indian reefs are endangered• Red Sea is spreading

Indian Ocean• Contains the largest deposit of river

sediments on Earth because two of the largest rivers in the world, the Indus and Ganges, flow into it on either side.

• The current systems of the Indian Ocean are unique in that they change direction twice a year. Currents in all other oceans flow the same direction year round. Currents change with the monsoon season.

Indian Ocean

• The most famous inhabitant of the Indian Ocean is the coelacanth fish which was thought to be extinct until it was caught in 1938.

Indian Ocean

• Coelacanth fish (see-la-canth)

Indian Ocean

• Even though the Indian Ocean is almost the same size as the Atlantic, it yields only about 1/5 of the quantity of fishes harvested annually.

• Reasons:– Lack of continental shelf seas– Seasonal reversal of wind patterns

Indian Ocean: Resources

• Oil and gas• Manganese nodules• Phosphates• Tourism• ¼ million seahorses exported for

traditional medicine uses, $350/lb

Indian Ocean: Resources

• Exploitation of the mineral wealth of the Indian Ocean has concentrated on the oil and gas fields of the Persian Gulf and more recently off western Australia.

• Extensive deposits of other minerals such as manganese nodules and phosphates have long been extracted along the east coast of South Africa.

Indian Ocean• Composition of

Manganese nodules– Manganese– Nickel– Copper– cobalt

Indian Ocean• Mass tourism is

the sole resource for many of the smaller island nations such as the Maldives and Seychelles.

• Their coral reefs and white-sand beaches form the main attraction.

Indian Ocean• Maldives

Indian Ocean

• Seychelles

Southern Ocean

• Size– Least charted– Not recognized until 2000

Southern Ocean• Formed in 2000 by the International

Hydrographic Organization for the purposes of navigation.

• The choice of 60oS as the northern boundary was not completely arbitrary.

• It approximates the southern edge of the Antarctic Circumpolar Current. This current flows clockwise around Antarctica.

Southern Ocean: Features

• 60o S is the northern boundary• Deepest point, South Sandwich

Trench, 23, 736 ft= 4.5 miles• Ferocious winds, high waves (roaring

40’s)• Inifinite fetch

Southern Ocean

• The waves can have an infinite fetch (the distance traveled with no obstruction), since they flow around the world without touching land.

Southern Ocean• Scientists and

tourists tend to converge on the west coast of the Ross Sea which is the most open area during the Antarctic summer.

Southern Ocean

• Ross Sea

Southern Ocean

• The Weddell Sea

Southern Ocean: Resources

• Living resources:– Blue whales, elephant seals, birds, krill,

squid– Danger of “overfishing”

• Penguins used to be taken for oil• No more whaling since 1982• Kelp forest in danger

Kelp Forest• Kelp provides food and shelter• Kelp prefers cold water• 1 ½o temperatue rise has increased the

sea urchin population which feeds on kelp

• Loss of kelp could be the biggest issue in this ocean.

• Introducing lobster which eat sea urchin to see if kelp can “bounce back

Arctic Ocean

• Size: Is the smallest• Features:

– Almost completely landlocked. The central part is permanently covered in 10 ft of ice.

– Shallowest – average depth of only 4690 ft.– wide continental shelf, taking up

approximately 50% of the total seafloor.

Arctic Ocean• Features

– The North Pole lies within the Arctic Ocean. Unlike the South Pole, the North Pole is not sited on a landmass, but a region of sea ice that can be 164 ft in winter to as little as 6 ½ ft in summer.

Arctic Ocean: Resources

• Alaskan oil– at very top northern edge of Alaska– (Ice Road Truckers)

• Marine life abounds– Hares, polar bears, seals, gulls,

gullemots (bird)

Arctic Ocean

Distribution of Water

• 97% Salt water; 3% Freshwater

Ocean AreaOcean Area, km2

Pacific Ocean 155,557,000

Atlantic Ocean 76,762,000

Indian Ocean 68,556,000

Southern Ocean 20,327,000

Arctic Ocean 14,056,000

Seawater and Salinity• The saltiness of seawater is referred to as

its salinity.• Measurements of salinity are of great

importance because salinity affects innumerable physical, chemical and biological processes.

• The presence of large amounts of dissolved salts in seawater affects its density, usually 1.03 times that of freshwater at the same temperature.

Seawater and Salinity• Average salinity of the oceans is 35,

varying between 33-37 parts per thousand.• This variance depends on the balance

between evaporation, which increases salinity, and the effect of diluting rainfall.

• Enclosed seas salinity ranges can be extreme– Red Sea 40 ppt– Baltic Sea 7 ppt

Seawater and Salinity• Red Sea• Site of sunbathing

and scuba

Seawater and Salinity• Dead Sea• Salinity 10 times

that of seawater• Impossible for a

human body to sink in it.

Seawater and Salinity• Baltic Sea

Seawater and Salinity• Sediment-laden

freshwater is held against the coast and does not mix with the much denser seawater, sometimes referred to as a salt plug.

• The lack of mixing produces a visible boundary between the two water masses.

• Bay of Bengal

Seawater and Bioaccumulation• Of the other 80 elements that occur in

seawater, a number are concentrated by marine organisms- a process known as bioaccumulation.

• For example, vanadium is found in seawater at less than one millionth that of sodium, yet some filter-feeders have been found to accumulate vanadium 100,000 times greater than the surrounding seawater.

Seawater and Bioaccumulation• Other

bioaccumulators include– Oysters absorb

zinc– Lobsters absorb

copper– Shellfish

concentrate mercury

Mimamata Bay

Bioaccumulation

• http://www.cfsan.fda.gov/~dms/admehg3.html What you need to know about mercury and fish

• See fish poster.

Assignment: The Poisoning of Minamata

• http://www.american.edu/TED/MINAMATA.HTM Minamata, Japan disaster

Discover Magazine

• “Our Preferred Poison”• http://discovermagazine.com/2005/

mar/our-preferred-poison

Changing Levels of the Sea

• Anyone who has lived near the sea or spent time on the seashore is aware of the daily rhythm of the tides.

• The tides can change the meeting point of the sea and land by as much as 50 ft vertically and by thousands of meters horizontally.

• The tides follow the lunar cycle.

Changing Levels of the Sea• Unusually high water levels may occur

when onshore winds occur at the same time as high tide.

• Some changes are more subtle and gradual.• There is an apparent rise in global sea level

1/16th of an inch per year.• Sea level in the western Pacific can be as

much as 6 inches lower during El Nino years.

Changing Levels of the Sea

• Global changes are affected by the volume of water in the ocean basins, thermal expansion of the surface layers of the ocean, and changes in the depth of the ocean basins.

• The volume of water locked into icecaps can change the level of water in the ocean basins.

Changing Level of the Sea• In the Mediterranean, tectonic movements

have resulted in the submergence of some Roman and Bronze Age ports and the uplift of others which are no longer at sea level.

• Some coasts are sinking or rising gradually.

• The Southern coast of England is slowly sinking, while that of Northern Scotland is rising.

Change in the Level of the Sea• Human induced changes such as

extraction of groundwater, oil and gas from coastal and near-shore areas cause a rising of sea level.

• Extraction of groundwater has caused lowering of land in Bangkok.

• Melting of land-locked ice by global warming may cause the rise in sea level up to 3.5 inches by 2100.

Changing Levels of the Sea• 1m Sea level rise

of Florida• 4 m rise

Solar and lunar tides

• Tides are generated by the interaction of the gravitational pulls of the Sun and Moon on Earth, causing the oceans to wash to and fro, as if they were in a giant bowl.

• Differences in water depth, the shape of the adjacent landmasses and the rotation of the Earth affect the tidal rhythm.

Solar and Lunar Tides

• For example, the Bay of Fundy, on the east coast of Canada, amplifies the tides so that the area has the greatest tidal range in the world at 56 ft.

• Spring tides have the greatest tidal range

• Neap tides have minimal tidal range

Spring Tides

• Occurs every new and full Moon when the gravitational pulls of the Sun and Moon are aligned and reinforce each other.

• Produces the greatest tidal range during these periods.

Neap Tides

• Occurs when the Moon is either in its first or last quarter when the gravitational pull on the oceans is at right-angles to that of the Sun.

• This reduces the high tides and the depth of the low tides.

Solar and Lunar Tides

Tides

Tidal Patterns

• Semidiurnal tide- twice daily tide as found in Cape Cod, Massachusetts

Tidal Patterns

• Diurnal Tide- a single tide per day as found in Mobile, Alabama

Tidal Patterns

• Mixed tide- two tides per day, but with a large difference in height of the tide between consecutive high water stages such as found in Los Angeles, California.

Surface Currents• Surface currents are divided into

open ocean currents and boundary currents.

• The three main oceanic basins have similar current patterns.

• In equatorial regions, the currents follow surface winds and normally flow westward coinciding with the Doldrums.

Surface Currents

Deep Water Currents• Surface currents affect only the uppermost

10% of the oceans.• Most water movements are much bigger,

deeper and slower.• Deep ocean currents, usually referred to as

the thermohaline circulation, are not affected by surface winds.

• They are driven by changes in the density of the water that are produced by water temperature and salinity.

Deep water currents

• The Great Ocean Conveyor is the name sometimes applied to the deep circulation that links the Pacific, Atlantic and Indian oceans.

• It is slow-moving water vital to life in the deep ocean because it carries oxygen down from the surface layers.

Deep water currents

The Gulf Stream• Is the biggest and best-known western

boundary current and originates in the Gulf of Mexico flowing northward along the eastern coast of N. America at 4 mph.

• The flow of water is 300 times that of the normal flow of the Amazon.

• As the Gulf stream moves into the Atlantic it becomes less defined and is called the North Atlantic Current or drift.

The Gulf Stream

• Turtles from the Caribbean and Gulf of Mexico are known to migrate out into the Atlantic carried by the Gulf Stream.

• The water of the Gulf Stream is warm, clear and blue because of its lack of nutrients.

The Gulf Stream

Gulf Stream

The Gulf Stream• http://www.cccturtle.org/contents.htm• Information on sea turtles and threats

to their survival

El Nino and La Nina

• This oceanographic and weather phenomenon is centered around the western coasts of Central and South America.

• It takes its name from the Spanish for Christ child, since it commences around Christmas every three to eight years.

El Nino and La Nina• In non-El Nino years, the trade winds drag

huge volumes of surface water westward, away from the coast.

• This allows the cold, nutrient-rich waters of the Peru Current to reach the surface near the coast.

• These waters support rich supplies of plankton that are vital to sustaining the local fisheries and vast numbers of seabirds.

El Nino and La Nina

• In an El Nino event, the trade winds slacken and warm water remains at the coast.

• This water blocks the upwelling of the Peru Current so that there is no significant plankton production.

• Fishes and birds either die of starvation or go elsewhere.

El Nino and La Nina• These events also cause changes in global

weather patterns.• 1997-1998 was a severe El Nino event.

There was an increase in the number of tornadoes in the American SW because of the extra warming of air masses by the coastal warm water.

• Droughts were severe in Papua New Guinea, Hawaii and SW Africa because the normal flow of moist, rain-producing air in the trade winds was blocked.

El Nino and La Nina

• El Nino seems to cause massive floods in some areas and catastrophic droughts in others.

El Nino and La Nina• The El Nino of 2003

brought starving sea lions inshore in search of food at Monterey Bay and along other parts of the California coast.

• Since June, 1997 about 6,000 sea mammals have perished

• http://www.cnn.com/EARTH/9802/15/nino.lions/

Wave generation

• Waves are generated by wind blowing over the surface of the sea.

• Despite appearances, a wave is not a ridge of water traveling on the surface of the sea.

• It is where the energy of the wind has been translated into circular movements of water molecules.

Wave generation• http://can-do.com/uci/lessons98/Oceanwav

es.html

Tsunamis• Tsunamis are sometimes incorrectly called

tidal waves. These waves are not related to tidal activity.

• Their name is derived from a Japanese term meaning “harbor wave.”

• On average, Japan experiences a tsunami every 6.7 years, the highest rate in the world.

• It is only when these waves reach shore that they cause havoc.

• Japanese artist, Hokusai Katsushita draws inspiration from the power and magnitude of tsunamis.

• Shown is The Great Wave.

Tsunamis• Tsunamis can be generated by earthquakes,

undersea landslides, volcanic eruptions and large icebergs breaking away from glaciers.

• The tsunami associated with the eruption of Krakatoa in 1883 killed more the 35,000 people.

• The Pacific warning system has been in place since 1948 and issues warnings whenever an earthquake greater than 6.75 is detected.

Tsunamis• Warnings and evacuation plans have

greatly reduced deaths, but the devastating power of tsunamis reamains.

• 1960- earthquake in Chile generated a tsunami that killed 61 people in Hawaii

• The Hawaiian islands are exposed on all directions by the Ring of Fire. These islands expect at least one tsunami every year and a serious tsunami every seven years. The worst lost of life in Hawaii was in 1946 when 159 lives were lost.

Tsunamis• Tsunamis generation

– A sudden displacement of a large volume of water

– Causes a wave usually less than 40 inches– As the tsunamis approaches the coast, a large

amount of the sea pulls back from the shoreline past the low water mark to join with the developing tsunami.

– This is followed by one more immense walls of water, up to 100 feet that rush up the shore and push inland with unstoppable force.

Tsunamis

Tsunami

• http://www.csc.noaa.gov/products/tsunamis/htm/cascadia/t_intro.htm

• Tsunami in Cascadia fault• http://serc.carleton.edu/NAGTWorks

hops/visualization/collections/tsunami.html

• Tsunami visualizations

Major Centers of Oceanography• The Australian Institute of Marine Science• The Alfred Wegener Institute• Woods Hole Oceanographic Institution• Harbor Branch Oceanographic Institution• Monterey Bay Aquarium Research Institute• Southampton Oceanography Centre• Japan Marine Science and Technology Center• University of Hawaii, School of Ocean and Earth

Science and Technology• International Hydrographic Bureau• Shirshov Institute of Oceanography