Geol 225, ESC -225:  Study Guide for Test 2,  Oceanography.

 

Ch. 5, 6,7, 8 and first part of 9.

 

Ch.5.  The properties of seawater.

 

1. Compared to related hydrogen compounds such as H2S, H2Se, H2Te, why does water have: a) high melting point b) high boiling point, c) high heat capacity, d) high solvent power.

Know structure of H20, its bond type and dipolarity effects, the dihedral angle between  hydrogen ions in liquid water and ice.

 

2. Why does ice float on water?

 

3. Why must ice be heated to 3.98oC at 1 bar to acquire maximum density?

                 

4. What are the constituents of water?

                  a) Major constituents, o/oo (per mill) , obey the low of constant proportions,                  b) Nutrients (ppm)-  P,N, Si.  These are taken as oxides not as elements.

                  c) Gases (%), N2, O2, CO2, Ar, H2, Ne, He. O2 and CO2, photosynthesis, respiration

                  d) Trace elements (ppb).  Li, I, Mo, Zn, Fe, etc.  Could be toxic

                  e) Organic compounds: Lipids (fats), protein, carbohydrates, hormones, and vitamin.

                 

 

5. How is constancy of major constituents established?

                  Input  must balance output

                  weathering: H2O + CO2  = H2CO3  =  H+ + HCO3-.

 

6.  If rivers are the major source of input, how come the low concentrations yield the high concentrations in seawater?

                  1. Residence timeof dissolved ions,       2. Stirring by oceanic currents

                  3. Circulation though ocean crust ones in every 10 million years.

 

7.  What are the effects of salinity on properties of water?

                  a) Freezing point.  hydration reduces it, b) evaporation, hydration reduces it

                  c) density, salinity increases it.

 

8.Compare and contrast among the following

Thermocline, halocline, pycnocline, SOFAR Channel, Oxygen-minimum zone

 

9. How are the flow paths of currents traced?

 

 

10. Describe pH buffering and the role of carbonate species in water.

 H2O + CO2  =  H2CO3 =  H+ + HCO3-  =  2H+  +  CO3=.

 

Ca CO3    =   Ca ++    +   CO3=.

 

If acid is add to water forwrd reaction proceeds (calcite dissolves) and PH will be maintained.  The reverse is true if a base is added.

 

Photosynthesis ( Respiration is the reverse of photosynthesis.)

 

6CO2  + 6H2O + energy  ->  C6H12O6  + 6O2

                                                                        Glucose

 

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Ch  6. Ocean circulation: 

10%; surface circulation caused by wind drag

                   90%; thermohaline circulation caused by density contrast.

 

What factors affect Atmospheric pressure?

                  a) Temperature: b)Water vapor content, c) altitude                      

1. What is pressure gradient? 

                 

2. What is Coriolis deflection? 

                  The magnitude of the deflection is directly proportional to the flow rate.

 

3a.  Name the layers of the atmosphere?

 

3b. Solar heat budget.

                  differences of insolation at the tropics and polar regions.

 

4. Name the general wind circulation?

                  4-A  Assume that earth was stationary, and completely covered by water.

                 

4-B. Assume that Earth is completely surrounded by water, and it rotates from west to east, and that the rotation axis is not tilted.

,(i) Trade winds, (ii) Prevailing westerlies, and (iii) Polar easterlies

                  Note: winds are named from the direction that they come.

4-C. Real earth has continents, and tilted axis, and there is an atmosphere-ocean coupling. These complicate results of assumption 4-B.

4-C1.  Effects of continents.  Continents:  30 ¡ hi is overwhelmed  by lows .   winds deflect  by continents

4-C2      Effects of tilted rotation axis.  Tilting gives seasonality- Monsoon

 

5. How are Sea surface currents generated?

                  By interaction of (i) wind drag (ii) pressure gradients, and (iii) coriolis effect, ,(iv)Ekman transport resulting in a geostrophic current

                  Ekman transport causes zonal westerly currents from the Trade winds, and zonal easterly currents from the Westerly winds.  Interaction a of the zonal currents with continents explains the formation of the circulation gyres

 

6. Describe the types of vertical surface water flows?

 

Ekman spiral and transport: ,,Upwelling. down welling. at zones of Convergence divergence  of  circulation

 

Langmuir circulation.

 

7. What is geostrophic flow?

 

8. Why is there asymmetry around circulation gyres? warm- or col - core rings

 

9. What generates the equatorial undercurrent (EUC)?

 

10). What are the Characteristics of deep water (thermohaline) circulation?

Mediterranean- Why is it  a biological desert ?

Black sea.  Why is its salinity 2,2%, and does its bottom water contain H2S.

                 

11) How does the ocean affect global climate change?

a)        Chemical exchange: N2 and O2 and CO2 from the atmosphere are absorbed in the ocean, and H20 from the ocean is transferred to the atmosphere

b) Heat exchange. Note: latent heat of fusion is 80 cal, and latent heat vaporization is 540 cal.  Heat used for breaking bonds, (endothermic) or making bonds (exothermic) does not raise or lower temperature and is called latent heat.  Heat used to raise temperature is called sensible heat.

 

Vapor carries latent heat from the ocean to the atmosphere.  Thus both heat and freshwater are introduced in the atmosphere .  At higher latitude, the air occupies more volume (expands and loses heat) the water condenses and several condensates are clustered to form clouds (condensation is an endothermic reaction, taking away heat from the atmosphere and making it cold.  Also clouds reflect back sun's light).  Cold air diverges aloft toward areas of low pressure and en route gravity pulls down water particles (precipitation, when gravity exceeds the air drag)which fall on surface and flow ocean-ward as surface run off or in ground water to complete the hydrologic cycle.  Where air converges aloft, the air descends and compresses on the lower atmosphere and holds water vapor, so that deserts are formed about 30¡ latitude.

 

b)       Atmosphere and surface water circulation (heat transferred from topics to high latitudes on the western side of circulation gyres) transport heat pole ward.  Yet, because circulation gyres are less important in transferring heat in polar regions, the atmosphere does that transfer.  At high latitudes, cold dense water sink and advect to the equator as part of thermohaline circulation, which characterize deep water circulation. A global conveyor belt that releases heat from the ocean to the atmosphere is set up.  Warm  surface water is transported from northern Pacific and Indian oceans to the northern, Atlantic Ocean at which heat is dissipated to the atmosphere so that the water becomes cold and dense and sinks to the depth of the ocean from which it advects to northern Indian and Pacific oceans to complete the conveyor belt system.   The northern Atlantic serves as a heat pump, pulling warmer surface water, further northward as warm air is given off to the Atmosphere in the conveyor belt system.  Recent research suggests that global warming might melt the ice in Siberia and Greenland bringing freshwater to the North Atlantic and shutting off the Conveyor belt system within a century or so for fresh water will not sink.

 

(Basically change in water vapor content of the atmosphere, arising from perturbations in the oceans, causes global climate change.  Also fresh water convects  due to due to heat exchange. )

 

 

 

El Nino is another way by which heat is released by the ocean to the atmosphere.  Warm water piled up against Australian and Indonesian waters  spreads towards the Americas one in 3 to 7 years, and the warm pacific ocean (E Nino) may last about a year or two .  The piling up of warm water in the Australian waters of Pacific by strong Trade Winds results in upwelling of nutrition deep water s near Peru causing plankton bloom, and profusion grazers and predators up the food chain. At thei stime the thermocline is heavily declining toward Australia, with thicker warm water above it.  The distribution of warm and cold water across the Pacific causes gravitaional instabilty, the energy from which results in Kelvin waves (high amplitude, long wavelength internal waves) migrating from west to east in the thermocline.  When a kelvin wave  arrives at the east of the thermocline it depresses the thermocline.  By the time the second kelvin wave trough arrives in the east, the thermoclaine will have been well below the surface water, with warm surface water spreading to the east, and sloshing against Peru , and EL Nino is on.  Nutritious deep water does not well up to the surface, planktons, grazers and carnivores do not abound.

 

 

 

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Ch 7. Waves

 

1. Describe wave properties

crest

trough

Wavelength =  L

wave  period = P.  Unique for each wave

Frequency  = f, 

wave height- = H.

Wave amplitude=  1/2 height ; A = H/2

Wave front

wave orthogonal or; ray

wave base.  -= L/2 below equilibrium surface

Deep wave,  deeper  than L/2.

Intermediate wave  = water depth from L/2 to L/20.

Shallow wave.   Water depth < L/20.

Breaker zone = for H/L > 1/7

 

Celerity = C = wave speed and depends on water depth. 

For deep water wave , C = L/P=  1.25 L1/2, 1.56P

For shallow wave ;  C = 3,13 D1/2

 

B) names of waves in increasing period?

capillary:( P < 0.1 sec.) from puff of wind, resolved by surface tension, Convex upward, joined by v's

chop (P= 1-10 sec)

swell (P = 10-30 sec)

seiche (p= 10 min- 10hr)

tsunami-  (P 10-60 min)earthquake, or submarine slump, very fast 760 km/hr, shallow water wave

megatsunami-  large slide with A  = @  450 feet

 

tide -( P= 12.4 to  24.8 hr)- moon and sun,  shallow water wave

 

Internal wave-  travels in the pycnocline. A = @ 50 m. 

 

2.  What factors affect wave generation?

 

3. How do waves move across the sea?

 What happens in the fetch area? Wave interference,

 

What happens in the open ocean? Wave dispersal

 

What happens in the shallow part of the ocean where the waves arrive?

 (i) Wave are transformed (to intermediate and shallow waves) , (ii)collapse aat  shore as (spilling, surging , plunging) breakers and (iii)waves are refracted, and defracted.

 

4. What are tiny and giant waves?

Capillary waves,

Giant waves interference of oppositely moving currents (e.g., Agulhas vs Antarctica ) currents)

 

5.What are storm surges?  Hurricane related.

 

6. What are standing waves?  Seiches

For closed basin: P = 2l (gd)1/2 sec.  the longer the basin the longer the time for the seiche to oscillate.

For semi open basin (estuary)  P = 4l (gd)1/2 sec

 

Resonance, or reinforcement arises when the wind strikes at the natural period ( or cadence) of the basinand makes the seiche dangerous.

 

 

7. What are internal waves?

One example is the kelvin wave

d) in the Pacific Equator.  Downwelling warm water causes density instability currents, Kelvin waves, which propagate eastward on the thermocline  along the equator guided by Coriolis deflection.  These waves depress the thermocline near  Peru and  herald an El Nino season.

30 to 40 meters amplitude of internal wave  becomes 10 to 15 cm variation on surface water and can be detected by satellite altimetry, so that El Nino may be predicted.  Large kelvin waves correspond to El Nino.

 

8. What are Tsunamis?:

 

9. What is a Megatsunami?

 

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Ch 8. Tides

 

Tidal Patterns

- Diurnal,  ,- Semidiurnal, - Semidiurnal with mixed tides

 

Tidal levels: HWL- LWL

Semidurnal mixed tides have  HHWL LHWL, HLWL, LLWL

                  MTL- mean tide level is estimated by taking the average water level over many years.

In regions of mixed tides, the mean lower low tide level is used as the tidal datum or zeroth depth reference.  The tidal datum assures navigators that their ships won't touch bottom ground.

 

Define:  Minus tide, flood tide, ebb tide, slack water, Spring Tide, neap tide,tidal current: tidal range, tidal bulge,  rotary wave,  cotidal line, tidal day, tidal bore

 

 

2. How do Tides originate?

 

b) equilibrium model of tides:  Assume an earth which is covered by water of equal

 

c) Dynamic model tides:

 

3. How do tides operate in small and elongate basins? Gulf of St. Lawrence, Canada.

 

Bay of Fundy. Canada.

 

 

Tidal celerity  c= 3.13 d1/2 m/sec. in the average ocean , 4 km depth,  c= 198m/sec (or 444 miles /hour).

in a depth of 1 km    C= 99 m/sec (or 222 miles/sec)

 

Tidal rhythm based on the vedio display:

 

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CH. 9.  Marine ecology.

 

 Only the first part of the Chapter.

 

1.  The ocean habitat of organisms is divided benthic and  pelagic envoronments

 

Benthic environments is subdivided into what?

Pelagic environment is subdivided into what?.

 

Oceanographic classification of envirnment , Photic dysphotic (twlight),,aphotic  > 450

 

Hwy is the oceanic environment divided by life styles?

 

 Know the 5 kingdoms of organisms, and brief charcteristics of each.

 

 Why are bacteria called he link between the living and the non-living matter.

 

What equation shows how cynobacteria changed the composition of the atmosphere .