Physics

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003b
Physics
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Seawater Physics

• Temperature
• Light
• Sound
• Buoyancy
• Dissolved gasses
• Waves
• Tides

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Temperature
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Isotherms
polar
60o
temperate
30o
0o
tropic
30o
temperate
60o
polar
Lines of equal temperature
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Sea Surface Temperature
Oct. 2010
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Sea Surface Temperature
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Sea Surface Temperature
10-24-10 to 10-27-2010
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Temperature Salinity Density Low
High Low High Low High
surface
0 m 200 m 1000 m
thermocline
pycnocline
halocline
Thermocline Halocline Pycnocline
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Properties of Light in the Ocean
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The Electromagnetic Radiation Spectrum
Only green and blue wavelengths pass through
water a great distance.
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Light Absorption in the Ocean

• Light Intensity
• decreases with depth
• 0-200 m (photic zone)
• 200-1000m (dysphotic zone)
• gt1000 (aphotic zone)

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Light Penetration in the Ocean
Wavelength (nm)
400
700
600
500
0 m
Photic Zone
Photosynthesis
200m
No Photosynthesis
Dysphotic Zone
1000m
Aphotic Zone
65 of visible light is absorbed in the 1st m
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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

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Sound in Water
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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.
source of noise
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Speed of Sound (m/sec)
1,475
1,500
0 1000 2000 3000 4000
high speed
sofar layer
min speed
Depth (m)
high speed
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SOFAR Channel
Distance
0 500 1000 1500 2000
sound rays
Depth (m)
SOFAR channel
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Sofar Layer
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
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Organisms adaptation to buoyancy in water

• Blubber
• Swim bladder
• Pneumatophore

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Organisms adaptation to buoyancy in water

• Air chambers
• Large liver heterocercal tail
• Buoyancy Compensator Device (BCD)

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Dissolved Gasses in Seawater
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Solubility of Gases in Seawater as a Function of
Temperature (salinity _at_ 33o/oo)
Solubility (ml/l at atmospheric
pressure) Temperature N2 O2 CO2 (oC)

. 0 14.47 8.14 8,700
10 11.59 6.42 8,030 20
9.65 5.26 7,350 30 8.26 4.41 6,660
Zebra Tidepool Blenny
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Relationship between water depth, pressure, and
volume
Air weighs 14 lbs/in2 (psi)
Absolute pressure is the combined pressure of
water and air
Depth 0 ft 33 ft 66 ft 99 ft
Absolute Pressure 1 atm 14.7 psi 2 atm
29.4 psi 3 atm 44.1 psi 4 atm 58.8 psi
Volume x1 x 1/2 x 1/3 x 1/4
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Boyles Law
For any gas at a constant temperature, the volume
will vary inversely with absolute pressure while
the density will vary with absolute pressure.
I.e., volume ? with ? pressure ? pressure ?
density
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Henrys Law
When a mixture of gas is in contact w/a liquid,
each gas will dissolve in the liquid in
proportion to its partial pressure.
Gasses can go in and out of solution e.g., open
soda, get CO2 bubbles (CO2 is under pressure)
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Dissolved gasses in seawater Seawater Air N2 4
8 78 O2 36 21 CO2 15 0.04 Gasses
dissolve most readily in cold water
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Decompression sickness
It is caused when N2 enters the blood circulation
and the tissues. When extra N2 leaves the
tissues, large bubbles form. N2 bubbles can
travel throughout the system and into the lungs
and blood routes. Treatment hyperbaric chamber
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O2 Minimum Zone (OMZ)
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O2 Content (ml/L)
Water depth (m)
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What causes the O2 minimum layer?
Marine snow
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Why are there high levels of O2 at depth?
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O2 Dead Zones
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Surface currents are wind driven currents
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Ekman Transport
Water flow in the Northern hemisphere- 90o to the
right of the wind direction Depth is important
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Upwelling and downwelling

• Vertical movement of water (?)
• Upwelling movement of deep water to surface
• Hoists cold, nutrient-rich water to surface
• Produces high productivities and abundant marine
  life
• Downwelling movement of surface water down
• Moves warm, nutrient-depleted surface water down
• Not associated with high productivities or
  abundant marine life

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upwelling
downwelling
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Langmuir Circulation
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Tides are generated by

1. Gravitational pull of the moon and sun
2. Centripetal force of the rotating Earth

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Tides are generated by

• the gravitational pull of the moon and sun
• - moon has 2x greater gravitational pull than
  the
• sun
• - sun is 10 million x more massive than the
• moon and is 390 times farther away

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Centripetal force
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GRAVITATIONAL FORCE
CENTRIPETAL
GRAVITATIONAL CENTRIPETAL
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Tidal Cycles

• Diurnal Tide 24 hr 50 min cycle
• Semi Diurnal Tide 12 hr 25 min cycle
• Mixed Tide 12 hr 25 min cycle

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Description of tides

• High water a water level maximum ("high tide")
• Low water a water level minimum ("low tide")
• Tidal range the difference between high and low
  tide
• Spring Tide full moon and new moon (14.77 days)
• Neap Tide 1st quarter and 3rd quarter (14.77
  days)

Intertidal zone
High tide
Low tide
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The monthly tidal cycle(29½ days)

• About every 7 days, Earth alternates between
• Spring tide
• Alignment of Earth-Moon-Sun system
• Lunar and solar bulges constructively interfere
• Large tidal range
• Neap tide
• Earth-Moon-Sun system at right angles
• Lunar and solar bulges destructively interfere
• Small tidal range

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Earth-Moon-Sun positions and the monthly tidal
cycle
Spring Tide Highest high tide and lowest low tide
Neap Tide Moderate tidal range
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Tidal Range
56 ft
6 ft
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The Bay of Fundy Site of the worlds largest
tidal range

• Tidal energy is focused by shape and shallowness
  of bay
• Maximum spring tidal range in Minas Basin 17
  meters (56 feet)

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Alma at High Tide
Alma at Low Tide
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Tidal Information
http//life.bio.sunysb.edu/marinebio/mbweb.html
HAWAIIAN ISLANDS Mean Spring Mean Tide
       Station Latitude Longitude Range
Range Level Predictions SAND ISLAND, MIDWAY
ISLANDS 28 12.7' 177 21.6' 0.8 1.2 0.6
Predictions Laysan Island 25 46' 171 45' 0.7
1.0 0.4 Predictions East Island, French Frigate
Shoals 23 47' 166 13' 0.9 1.4 0.6 Predictions
Nonopapa, Niihau Island 21 52' 160 14' 1.0
1.6 0.7 Predictions Kauai Island Waimea Bay 21
57' 159 40' 1.0 1.6 0.7 Predictions Port
Allen, Hanapepe Bay 21 54' 159 35' 1.1 1.7 0.7
Predictions NAWILIWILI 21 57.4' 159 21.6'
Predictions Hanamaulu Bay 22 00' 159 20' 0.0
1.2 1.8 Predictions Hanalei Bay 22 13' 159
30' 1.3 1.8 0.8 Predictions Oahu Island
Haleiwa, Waialua Bay 21 36' 158 07' - - 1.6
0.7 Predictions Waianae 21 27' 158 12' 1.2
1.8 0.8 Predictions HONOLULU 21 18' 157 52'
1.3 2.0 0.8 Predictions Hanauma Bay 21 17'
157 42' 1.3 1.9 0.8 Predictions Waimanalo 21
20' 157 42' 1.1 1.8 0.8 Predictions MOKUOLOE
21 26.2' 157 47.6' 1.2 2.0 1.0 Predictions
Waikane, Kaneohe Bay 21 30' 157 51' 1.4 2.2
1.1 Predictions
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Ocean Zones
photic
100m
dysphotic
aphotic
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Inquiry

1. 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. Its high tide at 9am with a diurnal tidal cycle.
   When is the next high tide?
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?