Basic OceanographyBasic Oceanography

• 4 main basins4 main basins

• ““Super Ocean” – interconnectedSuper Ocean” – interconnected

• physico-chem differences = different physico-chem differences = different envts = different communities of envts = different communities of organisms organisms

• Gulfs and seas – enclosed, strong Gulfs and seas – enclosed, strong terrestrial influence terrestrial influence

Bathymetry – Ocean floor Bathymetry – Ocean floor featuresfeatures

• ShelfShelf

• SlopeSlope

• RiseRise

• Abyssal plainAbyssal plain

• Mid-ocean ridgeMid-ocean ridge

• Seamount Seamount

• TrenchTrench

• Island arcIsland arcwww.noc.soton.ac.uk/obe/PROJECTS/pap/images/largemap1.jpg

stloe.most.go.th/.../LOcanada6/604/9_en.htm

Basin cross sectionBasin cross section

Continental marginsContinental margins

• Slope – cont. boundary, 1500-4000 m, 4° slope, Slope – cont. boundary, 1500-4000 m, 4° slope, sand to silt-clay, terrigenous and biogenicsand to silt-clay, terrigenous and biogenic

• Submarine canyons – Glacial or river cut @ lower Submarine canyons – Glacial or river cut @ lower sea levels, carry shelf sediments via turbidity sea levels, carry shelf sediments via turbidity flowsflows

• Rise – 4000-6000m, 0.1-1° slope, alluvial fans Rise – 4000-6000m, 0.1-1° slope, alluvial fans spread by deep currents spread by deep currents

• ShelfShelf• SlopeSlope• RiseRise• Submarine Submarine

canyonscanyons

http://www.neseabirds.com/graphics/figure1.jpg

•Shelf – to 250 m, 0.1° slope, 50-1000 km width, Shelf – to 250 m, 0.1° slope, 50-1000 km width, terrigenous or oolotic sediment, sand – silt, highly terrigenous or oolotic sediment, sand – silt, highly productiveproductive

Abyssal plain Abyssal plain

• 3.5-5.5 km, 3.5-5.5 km,

• <0.1<0.1° slope,° slope,

• ““marine snow”marine snow”

• biogenicbiogenic– CalcareousCalcareous– Siliceous Siliceous

• TerrigenousTerrigenous– Red clayRed clay

http://www.ga.gov.au/image_cache/GA1705.jpg

http://www.noc.soton.ac.uk/gg/BOSCORF/curatorial/pacific.html

• Red clay – Red clay – vol. dust, marine vol. dust, marine debris, zeolite, iron oxidesdebris, zeolite, iron oxides

• Calcareous Calcareous tropical-temperate, high prod., tropical-temperate, high prod.,

max. 4500-5000 mmax. 4500-5000 m

• Siliceous Siliceous - silica available, - silica available, moderate prod., low calcium moderate prod., low calcium carbonate; polar and deep carbonate; polar and deep tropical/subtropicaltropical/subtropical

• Mid-ocean ridgeMid-ocean ridge– Global networkGlobal network– Plate boundaryPlate boundary– Sea floor Sea floor

spreadingspreading– 2-3 km, emerge 2-3 km, emerge

Iceland, AzoresIceland, Azores

• TrenchesTrenches– SubductionSubduction– Equilibrium Equilibrium

w/spreadingw/spreading– 10 km melt zone10 km melt zone– Volcanic arcs Volcanic arcs – PR- 8400m deepPR- 8400m deep– Mariana – > 11 Mariana – > 11

kmkm

TemperatureTemperature

• Extremely important in regulating Extremely important in regulating distribution and abundance of distribution and abundance of organismsorganisms

• Latitude, depthLatitude, depth

• Seawater rangeSeawater range

-1.9 C -1.9 C 40 C 40 C

Surface TemperatureSurface Temperature• Homeotherms (endotherms) and Homeotherms (endotherms) and

Poilkiotherms (ectotherms) – metabolism Poilkiotherms (ectotherms) – metabolism increase 2x for each 10° increaseincrease 2x for each 10° increase

• Temperature based biogeographic zonesTemperature based biogeographic zones

ThermoclineThermocline

• Warm surface Warm surface water, tropics, water, tropics, summer summer

• Declines w/depthDeclines w/depth

• Rapid decline: Rapid decline: thermoclinethermocline

• Persistent in Persistent in tropics, summertropics, summer

• Deeper: isothermalDeeper: isothermal

Depth

Temperature

Thermocline

Density and Ocean Density and Ocean CirculationCirculation

• Temperature, salinity Temperature, salinity

• Themocline and pycnocline separate Themocline and pycnocline separate water masses water masses

• Upper or surface and deepUpper or surface and deep– surface T & S vary with latitude, seasonsurface T & S vary with latitude, season– deep constantdeep constant

Wind and Ocean CirculationWind and Ocean CirculationSurface water mass in constant motion Surface water mass in constant motion via waves and currentsvia waves and currents

• Waves – Waves – Energy transport, not Energy transport, not molecules – no horizontal transport molecules – no horizontal transport

•CurrentsCurrents transport huge volumes of transport huge volumes of water across vast distanceswater across vast distances

- result of from major wind - result of from major wind bands and Coriolis Forcebands and Coriolis Force

WavesWaves

• Movement of energy Movement of energy onlyonly

• Function of wind speed, fetch durationFunction of wind speed, fetch duration

• Propagate away from originPropagate away from origin

• Wave length – distance between crestsWave length – distance between crests

• Period – time for 2 crests to passPeriod – time for 2 crests to pass

• Wave passage generates motion to depth of ~ Wave passage generates motion to depth of ~ ½ WL (“wave base”)½ WL (“wave base”)

• Each 1/9 of WL, orbit diameters drop by ½, so Each 1/9 of WL, orbit diameters drop by ½, so by ½ depth motion imperceptibleby ½ depth motion imperceptible

WavesWaves

• Bottom slows energy passageBottom slows energy passage

• WL declines, height increasesWL declines, height increases

• At 1.3x wave height wave breaks, At 1.3x wave height wave breaks, releases energyreleases energy

Wind systems and currentsWind systems and currents• Temperature differences tropics to poles Temperature differences tropics to poles

generate windsgenerate winds

• Unequal heatingUnequal heating– Sun angle: oblique at polesSun angle: oblique at poles– Albedo (reflectiveness): high at polesAlbedo (reflectiveness): high at poles– Both reduce light absorption and heat build Both reduce light absorption and heat build

upup

• Atmosphere and ocean move heat from Atmosphere and ocean move heat from tropicstropics

Coreolis effectCoreolis effect

Coriolis ForceCoriolis Force• The effect of earth rotation on the The effect of earth rotation on the

direction of the wind. direction of the wind.

• two reasons, two reasons,

• 1- system of latitude and longitude 1- system of latitude and longitude fixed to a rotating earth, so our frame fixed to a rotating earth, so our frame of reference for a free-moving object of reference for a free-moving object above the Earth is constantly changing. above the Earth is constantly changing.

• 2 - the amount of turning about a 2 - the amount of turning about a vertical axis varies from a maximum at vertical axis varies from a maximum at the poles and minimum at the equator. the poles and minimum at the equator.

Deflection: a missile from the North Deflection: a missile from the North Pole to Equator; Earth, and the target, Pole to Equator; Earth, and the target, has rotated, so it appears that the has rotated, so it appears that the missile has changed direction.missile has changed direction.The deflection works the same way for The deflection works the same way for an east-west wind, the path will curve an east-west wind, the path will curve to the right as it moves across the to the right as it moves across the surface.surface.

Coreolis effect - windCoreolis effect - wind

• Speed of rotation – movement away Speed of rotation – movement away from poles decreases rotational from poles decreases rotational speedspeed

• Deflection due to earth’s rotation – Deflection due to earth’s rotation – northward moving deflects wind northward moving deflects wind eastwardeastward

• No Hemisphere – deflect to right, No Hemisphere – deflect to right, Southern, to leftSouthern, to left

Three-cell circulation model•considers effects of coriolis force due to the Earth’s rotation. •Northern and Southern Hemisphere are each divided into three cells of circulation, each spanning 30 degrees of latitude. •Equator, 30° North and South, and 60° North and South. •Hadley, Ferrel, polar cells•Heat transfer away form equator by atmosphere

Hadley CirculationHadley Circulation

• Tropical air rises, creates low Tropical air rises, creates low pressure system belowpressure system below

• Low level cool air moves in from Low level cool air moves in from higher latitudes to replace ithigher latitudes to replace it

• Warm air travels to poles, cools, Warm air travels to poles, cools, becomes more dense, sinksbecomes more dense, sinks

• Hadley cellHadley cell

Primary circulation cells and Primary circulation cells and prevailing wind belts of Earthprevailing wind belts of Earth

Surface currentsSurface currents• a large mass of continuously moving a large mass of continuously moving

oceanic wateroceanic water• ~40 named currents~40 named currents• Do not move in direction of windDo not move in direction of wind• Interaction of Coriolis effect, wind and land Interaction of Coriolis effect, wind and land

massesmasses– wind friction on water – uneven sea surface, wind friction on water – uneven sea surface,

starts water movingstarts water moving– Coriolis effect deflectionCoriolis effect deflection– contact with the continents deflect currents, contact with the continents deflect currents,

creating giant oceanic current circles or gyrescreating giant oceanic current circles or gyres. .

GyresGyres

– Direction – counterclockwise northern Direction – counterclockwise northern HemisphereHemisphere

– Indian Ocean exceptionIndian Ocean exception– West, east sides of gyres West, east sides of gyres – Temperature transfer N-S profound impactTemperature transfer N-S profound impact– Spiral gyres “pile up” water in centerSpiral gyres “pile up” water in center– Antarctic circumpolar current – westerlies Antarctic circumpolar current – westerlies

blow uninterruptedblow uninterrupted– Narrow weak counter currents separate Narrow weak counter currents separate

gyres - Equatorial countercurrentgyres - Equatorial countercurrent

Subsurface flowsSubsurface flows

• 90% of water mass movement90% of water mass movement

• Density drivenDensity driven

• Arctic and Antarctic modelArctic and Antarctic model– Deep and bottom water, ice meltDeep and bottom water, ice melt

Eckman Spiral Eckman Spiral

– – each sheet of each sheet of water drags on water drags on the one belowthe one below

– – netnet transport transport is 90is 90oo to right to right (northern (northern hemisphere) of hemisphere) of the wind the wind directiondirection