Ch. 15 Sec. 1 The Oceans

Oceanography Scientific study of the earths oceans Scientific study of the earths oceans Challenger: British research ship Challenger: British research ship –First to use sophisticated measuring devices –Investigated currents, temp, chem. Composition

Meteor: German research ship Meteor: German research ship –First to use sonar to map the sea floor –Sound Navigation Ranging

Submersibles use a side-scan sonar to investigate deep ocean trenches Submersibles use a side-scan sonar to investigate deep ocean trenches

Oceanography Topex/Poseidon: advance satellite Topex/Poseidon: advance satellite –Monitor ocean surface temps, currents, and wave conditions

Origin of Oceans – 2 sources Comets  Meteorite when hits surface Comets  Meteorite when hits surface –Collide with earth releasing water –Meteorites contain.5% water –Earth is 4.6 bil yrs old

Origin of Oceans Volcanism: Volcanism: –Violent eruptions period over hundreds of millions yrs. –Release CO 2 and water vapor into air (early Atmosphere) –Earths crust cooled and condensed into oceans –Water molecules released and destroyed by UV rays keep a balance

Earths Water 97% Salt Water 97% Salt Water 3% Fresh Water: Ice caps 3% Fresh Water: Ice caps Global sea level rises and falls through time Global sea level rises and falls through time Rise: Rise: –Melting of ice caps during warming periods –Rising of the earths crust Falls: Falls: –Freezing and expansion of glaciers during ice ages –Lowering of the earths crust Now: Rising about 1-2 mm a year Now: Rising about 1-2 mm a year

Water Blue Planet Blue Planet –One large ocean – 61 % covered in N. Hemisphere –81 % covered in S. Hemisphere

Water Major Oceans: Major Oceans: –Pacific, Atlantic, Indian, Artic and Antartic Seas: Seas: –Smaller b/c they are land locked

15 – 2 Sea water

Chemical Properties of Sea Water Sea water is 96.5% water, 3.5% salts Sea water is 96.5% water, 3.5% salts Salinity: Salinity: –Measures the amount of dissolved salts in sea water –Expressed in ppt (parts per thousand) –35 ppt = 3.5% –Most abundant salt in the ocean is sodium chloride (NaCl) –Others include magnesium sulfate (MgSO 4 ) and Calcium Chloride (CaCl 2 )

Salinity Variations Actual salinities vary from place to place Actual salinities vary from place to place Regions of high evaporation have greater salinity Regions of high evaporation have greater salinity –37-38 ppt Regions of low evaporation have lower salinity Regions of low evaporation have lower salinity –32-33 ppt

Salinity Sources Salinity not much different then years ago Salinity not much different then years ago Evaporation leaves salt behind Evaporation leaves salt behind Calcium shells of marine organisms dissolve Calcium shells of marine organisms dissolve Weathering of rocks produces salinity Weathering of rocks produces salinity

Removal of Salts Small salty spray droplets from breaking waves are picked up by wind and deposited on land Small salty spray droplets from breaking waves are picked up by wind and deposited on land Marine organisms remove the ions to make their shells Marine organisms remove the ions to make their shells

Physical Properties of Sea Water Denser than fresh water Denser than fresh water –Salt ions heavier than water molecules Freezing point is lower Freezing point is lower –Salt lowers Freezing point (about -2 o C)

Physical Properties Water Absorbs light: Water Absorbs light: –Water is clear but gets dark going down Which color travels furthest? Which color travels furthest? –Light only penetrates water in first 100 m down Photosynthesis only good at top Photosynthesis only good at top

Ocean Layering Surface Temps. -2 o C – 30 o C Surface Temps. -2 o C – 30 o C Layers due to density difference Layers due to density difference Temps decrease with depths Temps decrease with depths –Surface (0-100 m ) relatively warm –Thermocline: rapid decrease in Temp. –Bottom Cold Temps near freezing (4 o C)

Ch. 15 Sec. 3 Ocean Movements

Wave Characteristics Wave – rhythmic motion that carries energy through space and matter Wave – rhythmic motion that carries energy through space and matter Generated by wind Generated by wind Water moves up and down in a circular pattern Water moves up and down in a circular pattern –Energy moves forward slightly

Wave Characteristics Crest – highest point Crest – highest point Trough - lowest point Trough - lowest point Wave speed increases w/ wavelength Wave speed increases w/ wavelength

Wave Characteristics Wave Height Wave Height –Wind speed, wind duration, and fetch (expanse of water) Breaking waves Breaking waves –Waves get smaller towards shoreline ( ↓ wavelength) –Lose energy by hitting the bottom –Collapsing waves called Breakers Breakers

Tides Periodic rise and fall of the sea level Periodic rise and fall of the sea level –High Tide: water level rising –Low Tide: water level lowering –Varies from place to place Caused by the gravitational pulls of the Moon Caused by the gravitational pulls of the Moon – (to a lesser extent) Sun, and the rotation of the Earth. –Tides Tides

Tides Suns Influence Suns Influence –Suns great mass causes Solar Tides Moons Influence Moons Influence –Earth/Moon orbit around a center gravitational pull –Uneven tidal bulges on opposite sides of the earth –Smaller but closer: Lunar tides are much higher

Tides Spring Tides Spring Tides –Occur when moon is full or new –Earth, Sun, Moon are aligned

Tides Neap Tides Neap Tides –Occur when moon is 1 st or 3 rd Quarter –Sun, Moon, Earth at a right angle

Ocean Currents Density Current Density Current –Caused by difference in salinity and temperature –Move slowly in deep ocean waters Surface Currents Surface Currents –Upper few 100 meters of the ocean –Move as fast as 100 km/day –Driven by global wind systems and the Coriolis effect

Ocean Currents Gyres: Gyres: –Continents deflect the ocean currents into circular patterns –North Pacific, North Atlantic, South Pacific, South Atlantic, Indian Ocean –Gyres hit land and warm air is deflected towards poles –Cool down and flow back

Gyres

Upwelling Upward motion of ocean water Upward motion of ocean water Cold from the bottom of the ocean Cold from the bottom of the ocean Mostly off the western coasts from the trade wind belts Mostly off the western coasts from the trade wind belts Rich in nutrients which support marine life Rich in nutrients which support marine life