Oceans

OceansOceans

What do you know about What do you know about the oceans?the oceans?

Fig. 16.1, p.400

Arctic Ocean

Baltic Sea

Bay of Fundy

Persian Gulf

Atlantic Ocean

Pacific Ocean

Indian Ocean

Antarctic Ocean

Oceans cover 2/3 of the Earth’s surface.

15CO, p.374

Topography more varied with larger elevation changes than on the Earth’s surface.

• Mid-oceanic ridgesMid-oceanic ridges

• TrenchesTrenches

• Island arcsIsland arcs

• Hot spotsHot spots

Fig. 15.3, p.377

Highest mountain Mt. Everest 8848 meters

Average elevation of continents 840 meters

Sea levelAverage depth of oceans – 3800 meters

Floor of central oceans about – 5000 meters

Deepest ocean trench Mariana trench – 11,000 meters

Millions of square kilometers

Percent of Area

How is the bathymetry How is the bathymetry determined?determined?

Sonar: measuring the Sonar: measuring the time sound waves time sound waves take to return to shiptake to return to ship

Known facts: •travel time to bottom and back•Speed of sound in sea water

The distance is determined by plugging these values into a simple formula

Satellite altimetry Satellite altimetry • Dips and bumps are due Dips and bumps are due

to variations in to variations in gravitational forcegravitational force

• Sea surface copies the Sea surface copies the ocean floor surfaceocean floor surface

• Differences are Differences are measured using the time measured using the time radar signals take to radar signals take to travel through the travel through the atmosphere, hit the atmosphere, hit the ocean’s surface, bounce ocean’s surface, bounce back, and travel back to back, and travel back to the satellitethe satellite

Geosat satelliteGeosat satellite

• Launched in 1985Launched in 1985

• Orbits the Earth in Orbits the Earth in about 14 hoursabout 14 hours

• The Earth rotatesThe Earth rotates

• Satellite map of the Satellite map of the Earth’s Earth’s topography, 1.5 topography, 1.5 yearsyears For every increase of 1000

meters on the seafloor, there is 1 meter increase in height of water.

Geosat image of the ocean Geosat image of the ocean floorfloor

Continental margins: where Continental margins: where land meets the sealand meets the sea

Atlantic Ocean: plate boundary is in the center of the ocean basin, away from the continental margin

Passive marginPassive margin: without a : without a plate boundaryplate boundary

Active marginActive margin: contains a : contains a plate boundaryplate boundary

Variations in temperature:Variations in temperature:

From north to south due to the Sun’s radiation

Changes in the Sun’s angle Changes in the Sun’s angle cause variations in the cause variations in the amount of solar energy amount of solar energy reaching Earth’s surface.reaching Earth’s surface.

Variations in Sun’s rays with Variations in Sun’s rays with latitudelatitude

Layers of the Ocean: what Layers of the Ocean: what determines the ocean’s determines the ocean’s layers?layers?

Temperature: warmer at Temperature: warmer at equator cooler near the equator cooler near the polespoles

Surface temperature variations

Ocean basins

Temperature variations within Temperature variations within ocean basins: sketch and ocean basins: sketch and describe describe

Salinity of SeawaterSalinity of Seawater

• Water is bipolarWater is bipolar• The cation sodium The cation sodium

attaches to the attaches to the negative sidenegative side

• The anion chlorine The anion chlorine attaches to the attaches to the positive sidepositive side

• The figure The figure illustrates illustrates dissolved saltdissolved salt

The amount of solid The amount of solid material dissolved in watermaterial dissolved in water

Source of salts?Source of salts?Chemical weathering of Chemical weathering of rocks (dissolved load)rocks (dissolved load)

Volcanic activity: Volcanic activity: outgassingoutgassing

Do you think salinity Do you think salinity varies within ocean basins varies within ocean basins

or is the same?or is the same?

On the surface?On the surface?

Within the basin?Within the basin?

WHAT FACTORS MAY WHAT FACTORS MAY CHANGE THE SALINITY?CHANGE THE SALINITY?

Precipitation

Fig. 16.4, p.402

SalinitySalinity

Precipitation and Precipitation and EvaporationEvaporation

Red-precipitation

Blue-evaporation

Density: how heavy Density: how heavy something is relative to its something is relative to its sizesize• What factors change the density of What factors change the density of

sea water?sea water?

Temperature: increase, decreases densitySalinity: increase, increases density

Density determines the Density determines the vertical positionvertical position

Photic zone: where light Photic zone: where light penetrates; upper 600 ft or penetrates; upper 600 ft or 200 m200 m

PlanktonPlankton: : microscopic animals microscopic animals and plantsand plants

Copepod-1mm

Diatom-phytoplankton

Dinoflagellate- 250 microm.

Zooplankton

• bottom of the food chain•Use basic nutrients from sea water to produce skeletons and soft tissue• phytoplankton produce greater than 50%

Coriolis effect: earth’s Coriolis effect: earth’s rotation causes gyresrotation causes gyres

GyresGyres or circular patterns or circular patterns in the oceans create in the oceans create currentscurrents

Fig. 16.13, p.407

The Gulf StreamThe Gulf StreamBenjamin Franklin described Benjamin Franklin described in 1770in 1770 Much more complexMuch more complex

Fig. 16.12, p.406

On the surface

Air Temperature is influenced Air Temperature is influenced by ocean currents.by ocean currents.

Ocean currents influence Ocean currents influence climateclimate

UpwellingUpwelling

Orange and yellow are areas of high chlorophyll concentrations

Phytoplankton?

UpwellingUpwelling

• Wind drivenWind driven

• Wind blows water Wind blows water away from shoreaway from shore

• Cold nutrient-rich Cold nutrient-rich water is “pulled” to water is “pulled” to the surfacethe surface

• Nutrients are Nutrients are produced by produced by bacterial decay of bacterial decay of materialmaterial

• Phosphates, Phosphates, nitrates, carbonatesnitrates, carbonates

• Provide nutrients Provide nutrients for plankton (base for plankton (base of the food chain)of the food chain)

Upwelling: bottom waters Upwelling: bottom waters are nutrient richare nutrient rich

Upwelling: whereUpwelling: where

Upwelling: Upwelling: significancesignificance

• Supplies basic Supplies basic nutrients for single-nutrients for single-celled organisms celled organisms

• Diatoms (plants)Diatoms (plants)

• Offshore IrelandOffshore Ireland

Red: highest concentration

• Gravitational force of the moon Gravitational force of the moon causes the oceans to bulgecauses the oceans to bulge

• Periodic rise and fall of large bodies Periodic rise and fall of large bodies of waterof water

• The Earth turns on its axis, taking the The Earth turns on its axis, taking the moon about 25 hours to make one moon about 25 hours to make one obit in our skyobit in our sky

• Two tidal peaks and troughsTwo tidal peaks and troughs

TidesTides

Fluctuations due to the interaction of the Fluctuations due to the interaction of the sun, moon and Earthsun, moon and Earth

Centrifugal force of the Earth helps cause Centrifugal force of the Earth helps cause tidestides

Nova Scotia’s Bay of Funday

Spring TidesSpring Tides

• Full or new moonFull or new moon

• Sun and moon are alignedSun and moon are aligned

• StrongestStrongest

Neap Neap TidesTides

• Occur during quarter moonsOccur during quarter moons• The position of the sun and moon are The position of the sun and moon are

at right anglesat right angles• Gravitational pull cancelsGravitational pull cancels• Small increase or decrease of water Small increase or decrease of water

levellevel

Why is the ocean blue?Why is the ocean blue?

• Intensity of water Intensity of water at different depthsat different depths

• Absorptions is Absorptions is greater for longer greater for longer wave lengths-redwave lengths-red

• Ocean is blueOcean is blue• Most of the light is Most of the light is

absorbed in the absorbed in the few meters of few meters of waterwater

Did life begin in the oceans?Did life begin in the oceans?