Class 28: Oceanography. Class updates: Reading: Section 15.1-15.3, 16.1-16.2, 16.5 Today’s...

Class 28: Oceanography

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http://www.geo.utep.edu/

Class updates: Reading: Section 15.1-15.3,

16.1-16.2, 16.5

Today’s topics: Ocean water Ocean currents El Nino/La Nina

Class 28: Oceanography

Continents: green/tan

avg. height 840m Oceans: blue

avg. depth 3800m,

cover 66% planet

The Oceans



Mostly Chlorine (Cl), Sodium (Na)

Minor amounts: SO4, Mg, Ca, K

Dissolved salts ~4 %

Ocean Water Composition

Dissolved ions come from: Chemical weathering:

Rivers dump 2.5 billion

tons/yr of dissolved salts

Volcanic activity:

-outgassing: sulphur, bromine

-hydrothermal circulation:

hot water dissolving rocks

Salty Origin



Ocean is not getting saltier, so where? Shells/hard parts:

Chemical sediments:

clays, oozes

Where do ions go?





Ocean salt balanced by: Balancing Water (red)

• Rain

• Stream input

• Evaporation Balancing Salt (purple)

• River/volcanic input

• Reduction by sediments

and hard body parts

Salt Balance

Salinity = amount of salt

in the water

• Factors for balance

change over Earth

Salinity of Ocean Surface





• Shallow surface mixed zone (< 450 m)• Transition zone (< 1500 m thick) • Deep zone

Changes with depth



• Shallow surface mixed zone–mixed by wind and currents–Uniformly warm–Generally higher salinity (surface evaporation)

Top: Mixed Zone



•Transition zone (< 1500 m thick) –Temperature decreases rapidly - thermocline–Salinity decreases rapidly - halocline

Middle: Transition Zone



• Bottom water–Very cold, near freezing < 4˚C–Relatively low salinity

Bottom: Deep Zone



• Thermocline narrow at poles• Thermocline-top deep @ ~ 30, thicker @ equator

From North to South

Ocean conveyor belt• Warm @ surface • Cold @ bottom

Water is moving



http://www.geo.utep.edu/pub/jasper/geol_1312/movies/15a.html

• Warm water cools in North Atlantic• Cold water sinks: cold = densest

The Water Pump



• Cold water sinks and flows south along bottom:

Atlantic Deep Water

• Conveyor Belt = simplified• Actual surface flow in currents

Surface Currents

http://www.geo.utep.edu/pub/jasper/geol_1312/movies/14.html

• Map flow with oceanographic instruments• Current flow is more complex: turbulence

Adding complication




• Persistent winds push water

• Subtropics: Trades (from E)

• Mid latitudes: Westerlies

Currents and Winds



Currents and Winds



• Why do winds and currents go East or West?


Coriolis Effect• Anything moving from equator (look along arrow) bends to the right



http://daphne.palomar.edu/pdeen/Animations/34_Coriolis.swf

El Nino-Step 1• NORMAL CONDITION: • Trades (E to W) push water to W Pacific• W Pacific water = warm, E Pacific = upwelling cold• Air over warm water rises• Air over cold sinks



El Nino-Step 2• EL NINO CONDITION: • Trades (E to W) push less• Thermocline flattens: less upwelling cold water• Rain moves E:– Australia/Indonesia dry– Peru/Central Am wet



El Nino-Step 3• LA NINA CONDITION: • Trades (E to W) push extra hard• E Pacific = more upwelling cold• Air over warm water rises• Air over cold sinks



Southern Oscillation• El Nino and La Nina are the extreme hot and cold parts of the Southern Oscillation cycle







Class 28: Oceanography. Class updates: Reading: Section 15.1-15.3, 16.1-16.2, 16.5 Today’s...

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Transcript of Class 28: Oceanography. Class updates: Reading: Section 15.1-15.3, 16.1-16.2, 16.5 Today’s...