surface ocean currents

Question 1

ocean current

Answer 1

flow of ocean water caused by global winds, coriolis effect, land, gravitational pull from moon, density differences

Question 2

what causes seasons?

Answer 2

earths axis causes some places to be hit by the sun more directly than others

Question 3

coriolis effect

Answer 3

rotation of the earth causes winds in northern hemisphere to veer right, winds in southern hemisphere to veer left
it is nonexistent at the equator and gets stronger at higher latitudes

Question 4

three celled model

Answer 4

a model of the global wind currents in three cells of convection currents
polar cell (90-60), ferrel cell (60-30), hadley cell (30-0)
also forms polar easterlies, prevailing westerlies, ne trade winds, se trade winds, prevailing westerlies, and polar westerlies from coriolis effect
it is most accurate at the equator but less so at mid latitudes, it doesn’t account for seasons or continents

Question 5

what are gyres and how are they formed?

Answer 5

gyres are circular flows of water formed by interactions with the wind, the coriolis effect, ekman transport
there are five major gyres

Question 6

ekman transport

Answer 6

the coriolis effect also effects water, so water will also go and veer to the right/left
therefore, water goes right/left 45º compared to the wind on the surface
as you go down, the coriolis effect continues and creates a spiral as the water turns more and more but also reduces in speed
the net water transport would be 90º to the direction of wind in ideal conditions

Question 7

what are hills and geostrophic flow in gyres?

Answer 7

ekman transport pushes surface water towards the center of the gyre since the wind moves outwards, creating a sort of hill of water
the surface water is pulled downhill outwards by gravity but pulled inwards by the coriolis effect, balancing to create circular geostrophic flow that gives gyres their circular shape instead of an inwards spiral that would be expected due to ekman transport

Question 8

what are western boundary currents and how are they caused?

Answer 8

the spinning of earth and weakness of the coriolis effect at lower latitudes moves the hills of gyres towards the west
this makes the currents on the west side of gyres (western boundary currents) stronger than the ones on the east (eastern boundary currents)
additionally, the current before the western boundary current is at a lower latitude, meaning it is less effected by the coriolis effect causing to to travel more straight
this causes it to turn suddenly after slamming into the west side of the ocean basin, forming faster western boundary currents

Question 9

eddies

Answer 9

flow of water can meander and form eddies similar to oxbow lakes
they are circular rings of flowing water that flow in the opposite direction of the main current next to them due to the way they pinch off

Question 10

cold-core rings

Answer 10

cold-core rings flow counter(north) or clock(south) and keep cold water inside them
due to the coriolis effect, their net water transport is outwards so it pushes warm surface water away and allows cooler deep water to rise
since it spirals outwards and sucks water up, this is called up welling

Question 11

warm-core rings

Answer 11

warm-core rings flow clock(north) or counter(south) and keep warm water inside them
due to the coriolis effect, their net water transport is inwards so it keeps warm surface water inside it
since it spirals inwards it pushes water down, this is called down welling

Question 12

how is the three celled model formed?

Answer 12

warm air from the equator rises and spreads before sinking near 30º latitude
this air then goes back to the equator (forming the hadley cell) but some also continues further towards 60º latitude
around the poles (90º) the cold air sinks and spreads towards 60º latitude
this air then converges with the air originally from earlier, causing both the air masses to rise and form the polar and ferrel cells

Question 13

what are the three latitude ranges?

Answer 13

low (0-30)
mid (30-60)
high (60-90)

Question 14

what are the main wind formations and where do they occur?

Answer 14

the ne trade winds in the low north latitudes
the se trade winds in the low south latitudes
the prevailing westerlies in the mid latitudes both north and south
the polar easterlies in the high latitudes both north and south
the equatorial doldrums or intertropical convergence zone located slightly north of the equator (little to no wind)

Question 15

how many major currents are there in a gyre

Answer 15

four major currents: north south east and west
fastest warmest narrowest and deepest at west, weakest and coldest at the east

Question 16

what occurs at the equator, downwelling or upwelling?

Answer 16

downwelling due to the diverging currents

Question 17

what is the north equatorial countercurrent and how is it formed?

Answer 17

the north equatorial countercurrent is a current slightly north of the equator on the ocean surface that flows eastwards, counter to the surrounding currents
there is one located in the pacific, atlantic, and indian ocean basins
one reason it forms is because when the surrounding currents hit against the western side of the ocean basin, some of the water is deflected towards the equator, forming the necc
another reason it forms is because of the pressure gradient from west to east formed by the western hill shape of gyres

Question 18

what are equatorial undercurrents and how do they form?

Answer 18

equatorial undercurrents are located at the equator below the surface of the water in the thermocline
they flow eastwards, counter to surrounding currents
the equatorial undercurrent is also a result from the west-east pressure gradient, as the necc only balances the pressure gradient north of the equator
however it can’t flow at the surface due to the se trade winds which forms the west flowing south equatorial current, so it flows underneath the surface in the thermocline where it is not affected
the euc is a fast and narrow current since it flows at the equator where it is not affected by the coriolis effect.
additionally any water parcels that are diverted north or south of the equator are veered back to the euc due to the coriolis effect which becomes significant away from the equator

Question 19

what is a pressure gradient?

Answer 19

an imbalance in pressure and the subsequent movement from high to low pressure

Question 20

how does ekman transport near coasts affect marine life?

Answer 20

depending on how wind blows relative to the shoreline, it can cause surface water to move towards or away from the shore
if it moves towards the shore, it downwells and prevents deeper nutrient rich water from rising
if it moves away from the shore, it allows deeper nutrient rich water to rise through upwelling