Transcript psci183_oceansI - Cal State LA

Oceans
The Last Frontier
Ocean Facts
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About 71% of Earth’s surface is covered by water
Average depth of the Pacific Ocean = 4,638 m
Average depth of the Atlantic Ocean = 3,872 m
Average temperature = 3.9°C (39.0°F)
Age of oceans = 4 billion years
Salinity in Oceans
• Salinity
– Total amount of dissolved solids
expressed in grams in 1 kg of
water
• Average salinity in oceans = 35 ‰
– 35 parts per thousand (ppt)
– 35 g/kg
• Salinity variations
– Due to differences in local rates
of evaporation and precipitation
(water budget)
Constituents of Sea Water
• Most abundant seawater elements are sodium (Na+) + chloride (Cl-)
• Major constituents: SO42-, Mg2+, Ca2+, K+, and HCO3• Minor and trace elements also present
Salts in the Ocean
Why is the ocean salty?
• Salts come from:
– River discharge
– Volcanic eruptions
• Why is the ocean not getting
saltier?
– Salts going in = salts going out
Salts Going Out
• Sea Sra
• Sea Spray
• Evaporites
• Biological
– Fecal pellets
– Shell formation
• Adsorption
• Mid-ocean ridge magma
Factors Affecting Salinity
• Precipitation
• Evaporation
• River runoff
• Freezing
Principle of Constant Proportions
– The amount of salt varies, but the relative
proportions of ions are constant
– Because of this principle, it is necessary
to test for 1 salt ion (usually Cl) to
determine total amount of salt present
Determining Salinity
1. Calculating Salinity
– Salinity=1.8065 x chlorinity (‰)
2. Salinometers
– Salinity determined by the
electrical conductivity produced
by dissolved salts
Oceans II
Surface Currents
Heat Variations
Latitude
• Depends on angle sunlight hits surface
– Sunlight at polar latitudes covers wider area; therefore, less heat
– At equator, sunlight covers less area; more heat
Heat Transfer
• Heat is transferred from equator to poles
– Air Circulation
– Ocean currents
Origin of Currents
• Ocean surface currents are wind driven
• Air movement due to less dense air rising and more dense
air sinking
• Horizontal air flow along Earth’s surface is wind
• Air circulating in this manner is convection currents
Wind Movement
Non-rotating Earth
• Simple wind pattern
– Warm air rises at equator, flows toward poles
– Air cools at poles, sinks, and flows toward equator
• Winds named by direction from which they blow
– North-blowing winds = southerly winds
– South-blowing winds = northerly winds
Wind Movement
Rotating Earth
• At equator, warm air rises
– Zone of low pressure
– Clouds and precipitation
– Reaches troposphere and
moves poleward
– As it spreads, it cools
• 30° N&S, cool air sinks
– Area of high pressure
– Dry conditions
– Location of world deserts
• 60° N&S, air masses meet
– Form Polar Front
– Air masses rise, diverge and
sink @ 90° and 30° N&S
Wind Movement
• At equator, warm air rises, condenses and precipitates
• At 30° and 90°, cool air sinks
• Air that sinks does not flow back in a straight north-south path –
it curves (Coriolis Effect)
Rotation on a Globe
• Buffalo and Quito located on same line of longitude (79ºW)
• Both cities circles the globe in one day (360º/24 hours = 15º/1 hour)
• Quito has larger circumference; thus, travels farther
• Quito needs to travel faster than Buffalo
Apparent Deflection
• Hypothetical war game
• If a cannonball is shot north
from Quito
• It will travel a straight path
• But, because Earth is
rotating east to west
• The cannonball appears to
veer to the right in Northern
Hemisphere
• This is the Coriolis Effect
Wind Movement
Coriolis Effect
• Deflected winds due to
movement over spinning
object
– Produce wind bands
• In Northern Hemisphere:
– Winds are deflected to the right
– Travel clockwise around high P
• In Southern Hemisphere:
– Winds are deflected to the left
– Travel counter-clockwise around
high P
Assume water-covered Earth
Surface Current Circulation