Ocean Properties
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Transcript of Ocean Properties
Ocean PropertiesOcean Properties
Ocean ConceptsOcean Concepts• Buoyancy• Temperature• Light• Density• Pressure• Depth• Sound
Buoyancy
Buoyancy & Isostasy
http://bcs.whfreeman.com/understandingearth/content/cat_110/ch18/earth4e_1817.html?v=category&i=18110.01&s=00110&n=18000&o=%7C00510%7C06000%7C14000%7C17000%7C20000%7C23000%7C22000%7C18000%7C
Archimedes Principle of Buoyancy
A floating object displaces a volume of fluid equal in mass to the floating object
empty loaded with fish
Displaced water
• Objects that are more dense than water will sink.• Objects that are less dense than water will float.• Objects that are the same density as water will neither
sink nor float.
float
Neutrally buoyant
sink
• Blubber
• Swim bladder
• Pneumatophore
Organisms adaptation to buoyancy in water
• Air chambers
• Large liver & heterocercal tail
• Buoyancy Compensator Device
(BCD)
Organisms adaptation to buoyancy in water
Temperature
IsothermsIsotherms
Lines of equal temperature
60o
30o
0o
30o
60o
polar
polar
temperate
tropic
temperate
Sea Surface TemperatureSea Surface Temperature
Oct. 2010
Sea Surface TemperatureSea Surface Temperature
Sea Surface TemperatureSea Surface Temperature
10-24-10 to 10-27-2010
Properties of Light in the Ocean
The Electromagnetic Radiation Spectrum
Only green and blue wavelengths pass through water a great distance.
Light Absorption in the Ocean
• Light Intensity–decreases with depth
–0-100 m (photic zone)
–100-1000m (dysphotic zone)
–>1000 (aphotic zone)
Coral Reef Communities
Hermatypic corals:• possess zooxanthellae• are reef builders
Light: Clear water Warm temperature: 18-32oCLow nutrientsLow productivity in water
Ahermatypic corals:• no zooxanthellae• rely on tentacular feeding• can live in aphotic zone
Cauliflower coral(Pocillopora meandrina)
6 m
0 m
25 m
13 m
Lobe coral(Porites lobata)
Finger coral(Porites compressa)
Plate coral(Porites rus)
High light levelsModerate wave energy
Moderate light levelsOccasional storm wave energy
Low light levelsLow wave energy
Very low light, Primarily downwelling No wave energy
Water color and life in the ocean
• Ocean color is influenced by:– The amount of turbidity from runoff– The amount of photosynthetic pigment, which
corresponds to the amount of productivity
• Yellow-green = highly productive water– Found in coastal and upwelling areas (eutrophic)
• Clear indigo blue = low productivity water– Found in the tropics and open ocean (oligotrophic)
Light Penetration in the Ocean
~65% of visible light is absorbed in the 1st m
Photic Zone
Aphotic Zone
No Photosynthesis
100m
0 m
Wavelength (nm)400 700600500
Photosynthesis
Dysphotic Zone
1000m
Light Absorption in the Ocean• Spectral Characteristics
– red wavelengths absorbed more readily by water than blue wavelengths
– blue light penetrates deepest in the oceans
Light effects organisms residing in the photic and aphotic zone.
• Phytoplankton productivity• Algae- green, brown, red• Predator/Prey relationships• Diurnal vertical migration• Bioluminescence- luminescent organs on
underside mimic downwelling light
Refraction- as light enters the water, it bends; this is due to light traveling through different densities
Light entering the ocean is weakened by scattering and absorption.
DensityDensity
Air0.08 lbs
1 ft
1 ftfw
62.4 lbs
1 ft
1 ftsw
64 lbs
1 ft
1 ft
Piston example:
Air is compressible Water is incompressible
64 lbs
64 lbs
Water doesn’t change density under pressure
Ocean Layers• Photic zone: 0-100m
- neustonic layer: 0-1m • Mesopelagic (dysphotic or twilight) zone:
100-1000m • Aphotic zone: bathypelagic zone 1000-
4000m• Abyssal and Hadal (trench) zones:
6000m
Describe biological and physical characteristics of each depth
Temperature Salinity DensityLow High Low High Low High
surface 0 m
100 m
1000 m
Thermocline + Halocline = Pycnocline
thermocline pycnoclinehalocline
Thermocline
• El Nino– Disruption of thermocline
• Upwelling areas– Cool, nutrient-rich deep water is brought to
the sunlit surface– Peru fisheries
Thermocline
Temperature profile
depth
Peru Anchovy Fishery
Peru Anchovy Fishery
• Upwelling zone off Peru
• Fishery began 1950
• Greatest fish catches for any single species
• Fish exported for domestic animal feed
• Fishery collapsed due to El Niño and overfishing
= El Niño19571965197219761982-83
Peru Anchovy Fishery
Peru Anchovy Fishery
Normal Year
El Niño Year
Sound in Water
Speed of sound- faster in ocean (higher density)
1500 m/sec, which is 4x faster than in air
Difficult to determine direction of sound
Can hear many things such as ships miles away, shrimp eating, helicopters overhead, and whales communicating.
Sound in Water
source of noise
Dep
th (
m)
0
1000
2000
3000
4000
Speed of Sound (m/sec)
1,475 1,500
sofar layermin speed
high speed
high speed
Dep
th (
m)
0
500
1000
1500
2000
SOFAR Channel
Distance
SOFAR channel
sound rays
The depth at which the speed of sound is minimum; Thus, loud noises can be heard for thousands of km
Sound generated by Navy test in Indian Ocean at sofar layer was heard as far away as the Oregon coast. May affect behavior and anatomy of marine organisms
Sofar LayerSofar Layer
Diurnal vertical migration
Organisms within the deep scattering layer undertake a daily migration to hide in deep, darker waters during daytime
Deep sea scattering layer:Deep sea scattering layer:Composite echogram of hydroacoustic data showing a distinct krill scattering layer.Black line represents surface tracking of a blue whale feeding
patchiness
Ocean Productivity
Regional productivity
• Photosynthetic productivity varies due to:
– Amount of sunlight – Availability of nutrients
• Thermocline (a layer of rapidly changing temperature) limits nutrient supply
• Examine three open ocean regions:1. Polar oceans (>60° latitude)2. Tropical oceans (<30° latitude)3. Temperate oceans (30-60° latitude)
Productivity in tropical, temperate, and polar oceans
Zooplankton
Productivity polar oceans
Productivity in tropical oceans
Productivity in temperate oceans
O2 Minimum Zone (OMZ)
O2 Content (ml/L)
Wat
er d
epth
(m
)
What causes the O2 minimum layer?
Marine snow
Why are there high levels of O2 at depth?
O2 Dead Zones
Inquiry1. What zone does photosynthesis occur?2. Why does light appear to bend when it enters
water?3. Which wavelength of light penetrates the
ocean the deepest?4. What is SOFAR?5. Describe the relationship between El Nino and
Peru Upwelling.6. What causes the OMZ?7. How do sharks maintain buoyancy?8. What areas in the ocean are the most
productive?9. Why is the open ocean considered a biological
desert?