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EOSC 372 > 3A Basic Physical Oceanography > Flashcards

3A Basic Physical Oceanography Flashcards

1
Q

What is pressure?

A

force pressing against an object

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2
Q

what happens when pressure is not uniform?

A

not force goes from the high pressure side to the low pressure side

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3
Q

what makes pressure not as strong in the ocean

A

liquid is almost incompressible, pressing down on it causes it to push out laterally

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4
Q

which direction does pressure come from in the ocean

A

all directions

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5
Q

what is hydrostatic balance

A

pressure below a water parcel is slightly higher to balance pressure and gravity coming from above

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6
Q

what are the two forces in the ocean at rest

A

gravity
pressure gradient

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7
Q

what is the equation representing the balance of forces in the ocean at rest

A

Fgravity = - Fpressure
-pg = deritive of p/z

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8
Q

what direction to pressure and gravity work in

A

vertical

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9
Q

equation for mass

A

density x volume

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10
Q

equation for weight

A

mass x g

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11
Q

what is the weight per unit area

A

integral of density gravity area per vertical depth

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12
Q

what is hydrostatic pressure

A

weight of the water above per unit area

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13
Q

how does density vary with depth

A

heavier as we got deeper

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14
Q

what is happening horizontally in terms of pressure gradients

A

spatial changes in density cause very small gradients
compared to the vertical

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15
Q

what can cause pressure to vary horizontally at a given depth

A

surface height variation
horizontal density variations

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16
Q

what happens to light availability as we go deeper into the ocean

A

decreases exponentially

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17
Q

what is the two layer ocean model

A

a layer where photosynthesis is significant and one underneath that is not significant
2 weakly stratified layers

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18
Q

does the layer boundary in the two layer model change?

A

yes, depending on processes we’re considering

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19
Q

what is one way to choose an interface depth in a two layer approximation from a sigma t and depth graph?

A

choose spot where density is changing rapidly with depth

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20
Q

benefits of the two layer model

A

simplify conceptually

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21
Q

what causes the pressure to increase in a two layer model

A

raising the ocean surface
raising the interface surface

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22
Q

what is the equation for pressure

A

P = pgh

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23
Q

what is different about the pressure change at from change of height at the surface vs the interface

A

need to consider the lost/gained amount of pressure from the other layer when the interface height changes

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24
Q

what does a change in density below you cause in water

A

nothing, density is allows weight of water above you

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25
Q

what causes mixing to work faster?

A

turbulence

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26
Q

what does moleculatr mixing depend on?

A

transport of heat due to diffusion
Fd

27
Q

how fast is molecular mixing

A

slow, works best over sharp gradients

28
Q

what does turbulent mixing depend on

A

transport of heat due to diffusion
transport of heat by turbulent flow
Fd + Fadvective

29
Q

how fast is turbulent mixing

A

much faster than molecular mixing

30
Q

how is turbulence enhancing molecular diffusion

A

stretching fluid
increase SA
wide range of scales
highly intermittent in the ocean

31
Q

what is the main thing that causes mixing in the ocean

A

turbulent eddies

32
Q

what direction can eddies mix?

A

both horizontal and vertical

33
Q

what are the two ways to generate turbulence?

A

shear
convection

34
Q

what is shear?

A

spatial gradient in flow velocity
(fast moving water beside/above/below slow moving water

35
Q

what are examples of turbulence caused by shear

A

tides/ internal waves
wind-driven mixing

36
Q

what is convection?

A

movement caused by less dense fluid rising and more dense fluid sinking because of gravity
unstable densities cause vertical turbulence

37
Q

examples of turbulence caused by convection

A

winter cooling at surface
freezing/evaporation causing high salinity at surface
double diffusion process

38
Q

what do tides cause

A

strong mixing near the bottom
internal waves on rough bottoms

39
Q

what are internal waves

A

wave that are 5-10 meters down
moving water faster over another neighbour layer
break causes mixing

40
Q

what are the causes of internal waves

A

winds
tides

41
Q

wind driven mixing

A

wind moving the surface layer faster than below layers
surface wave and top layer wave breaking causes mixing

42
Q

what is type one of convection driven mixing?

A

classic convection

43
Q

what is classic convection

A

convection due to ‘classic’ convection instability
dense water going under lighter water

44
Q

what are examples of classic convection

A

winter cooling at surface
freezing/evaporation causing high salinity at surface

45
Q

what is type two of convection driven mixing?

A

double diffusion

46
Q

what is double diffusion

A

convection driven by two different density gradients with different rates of diffusion

47
Q

what are the two types of double diffusion

A

diffusive instability
fingering instability

48
Q

diffusive instability

A

cold, fresh (light) water above warm salty (dense) water

49
Q

fingering instability

A

warm salty (light) water above cold fresh water (dense)

50
Q

what is the basic steps of finger instability

A

perturbation causes tongues to enter each layer from each layer
water diffuses 100 faster than salt, so water changes temperature and becomes lighter/denser
becomes heavier/lighter than other water until salt has also diffused

51
Q

what kind of eddies cause stronger/faster mixing

A

faster
bigger

52
Q

why does more mixing happen horizontally vs vertically

A

much more energy to move water across density surfaces (up/down) than acroess density surfaces (sides)

53
Q

what can cause more mixing to occur in the vertical

A

when water is less stratified and vice versa

54
Q

what two processes are happening at the surface mixing layer

A

wind is mixing surface, less stratified
sun is warming surface, more stratified

55
Q

what kind of energy does wind change? how?

A

increase kinetic energy of mixing
indirectly increase potential energy of stratification
by making density difference smaller between surface and depth; moves center of mass up

56
Q

what kind of energy does cooling/evaporation change? how?

A

increase potential energy of stratification
by making density difference smaller between surface and depth; moves center of mass up

57
Q

what kind of energy does solar warming change

A

decrease potential energy of stratification
by making density differences larger

58
Q

what kind of energy does rain/runoff change

A

decrease potential energy of stratification
by making density differences larger

59
Q

mixing layer

A

region of the upper ocean that is actively mixing
not necessarily mixed yet
processes that change mixing energy affect depth

60
Q

surface mixed layer

A

region of upper ocean that is homogeneous
not necessarily mixing now

61
Q

why does the mixed layer deepen in the fall

A

cooling
strong winds

62
Q

when is maximum depth of mixed layer usually

A

early spring

63
Q

why does the mixed layer shallow in the spring

A

warming
weak winds

EOSC 372 (5 decks)

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