3A Basic Physical Oceanography

Question 1

What is pressure?

Answer 1

force pressing against an object

Question 2

what happens when pressure is not uniform?

Answer 2

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

Question 3

what makes pressure not as strong in the ocean

Answer 3

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

Question 4

which direction does pressure come from in the ocean

Answer 4

all directions

Question 5

what is hydrostatic balance

Answer 5

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

Question 6

what are the two forces in the ocean at rest

Answer 6

gravity
pressure gradient

Question 7

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

Answer 7

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

Question 8

what direction to pressure and gravity work in

Answer 8

vertical

Question 9

equation for mass

Answer 9

density x volume

Question 10

equation for weight

Answer 10

mass x g

Question 11

what is the weight per unit area

Answer 11

integral of density gravity area per vertical depth

Question 12

what is hydrostatic pressure

Answer 12

weight of the water above per unit area

Question 13

how does density vary with depth

Answer 13

heavier as we got deeper

Question 14

what is happening horizontally in terms of pressure gradients

Answer 14

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

Question 15

what can cause pressure to vary horizontally at a given depth

Answer 15

surface height variation
horizontal density variations

Question 16

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

Answer 16

decreases exponentially

Question 17

what is the two layer ocean model

Answer 17

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

Question 18

does the layer boundary in the two layer model change?

Answer 18

yes, depending on processes we’re considering

Question 19

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

Answer 19

choose spot where density is changing rapidly with depth

Question 20

benefits of the two layer model

Answer 20

simplify conceptually

Question 21

what causes the pressure to increase in a two layer model

Answer 21

raising the ocean surface
raising the interface surface

Question 22

what is the equation for pressure

Answer 22

P = pgh

Question 23

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

Answer 23

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

Question 24

what does a change in density below you cause in water

Answer 24

nothing, density is allows weight of water above you

Question 25

what causes mixing to work faster?

Answer 25

turbulence

Question 26

what does moleculatr mixing depend on?

Answer 26

transport of heat due to diffusion Fd

Question 27

how fast is molecular mixing

Answer 27

slow, works best over sharp gradients

Question 28

what does turbulent mixing depend on

Answer 28

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

Question 29

how fast is turbulent mixing

Answer 29

much faster than molecular mixing

Question 30

how is turbulence enhancing molecular diffusion

Answer 30

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

Question 31

what is the main thing that causes mixing in the ocean

Answer 31

turbulent eddies

Question 32

what direction can eddies mix?

Answer 32

both horizontal and vertical

Question 33

what are the two ways to generate turbulence?

Answer 33

shear convection

Question 34

what is shear?

Answer 34

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

Question 35

what are examples of turbulence caused by shear

Answer 35

tides/ internal waves wind-driven mixing

Question 36

what is convection?

Answer 36

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

Question 37

examples of turbulence caused by convection

Answer 37

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

Question 38

what do tides cause

Answer 38

strong mixing near the bottom internal waves on rough bottoms

Question 39

what are internal waves

Answer 39

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

Question 40

what are the causes of internal waves

Answer 40

winds tides

Question 41

wind driven mixing

Answer 41

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

Question 42

what is type one of convection driven mixing?

Answer 42

classic convection

Question 43

what is classic convection

Answer 43

convection due to 'classic' convection instability dense water going under lighter water

Question 44

what are examples of classic convection

Answer 44

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

Question 45

what is type two of convection driven mixing?

Answer 45

double diffusion

Question 46

what is double diffusion

Answer 46

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

Question 47

what are the two types of double diffusion

Answer 47

diffusive instability fingering instability

Question 48

diffusive instability

Answer 48

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

Question 49

fingering instability

Answer 49

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

Question 50

what is the basic steps of finger instability

Answer 50

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

Question 51

what kind of eddies cause stronger/faster mixing

Answer 51

faster bigger

Question 52

why does more mixing happen horizontally vs vertically

Answer 52

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

Question 53

what can cause more mixing to occur in the vertical

Answer 53

when water is less stratified and vice versa

Question 54

what two processes are happening at the surface mixing layer

Answer 54

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

Question 55

what kind of energy does wind change? how?

Answer 55

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

Question 56

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

Answer 56

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

Question 57

what kind of energy does solar warming change

Answer 57

decrease potential energy of stratification by making density differences larger

Question 58

what kind of energy does rain/runoff change

Answer 58

decrease potential energy of stratification by making density differences larger

Question 59

mixing layer

Answer 59

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

Question 60

surface mixed layer

Answer 60

region of upper ocean that is homogeneous not necessarily mixing now

Question 61

why does the mixed layer deepen in the fall

Answer 61

cooling strong winds

Question 62

when is maximum depth of mixed layer usually

Answer 62

early spring

Question 63

why does the mixed layer shallow in the spring

Answer 63

warming weak winds