Lecture 3- Ocean basin circulation

Question 1

What types of currents are there?

Answer 1

-warm and cold

Question 2

What is the direction of winds in southern and northern hemisphere?

Answer 2

-anticlockwise= southern hemisphere -clockwise= northern hemisphere

Question 3

Which currents do we have to remember?

Answer 3

-Gulf stream -Peru stream -California stream -East Australian stream -Kuroshio stream

Question 4

How do winds contribute to the creation of ocean currents?

Answer 4

-the currents exist because of the wind, so the currents are dictated by the direction of the wind -wind is always faster than the ocean, thus it is exerting force on the ocean -rotation of high is opposite in the hemispheres -pattern of currents is similar to the patterns of winds

Question 5

Are the currents geographically influenced?

Answer 5

-yes -oceans are surrounded by land so currents are geographically determined as well -peru current= from the south, travels along the coast of South America thanks to the geogrpahy of the continent -north atlantic= gulf current= warm= iceland has mild winter thanks to that

Question 6

How does the intensity of light change with latitude?

Answer 6

-when the Sun hits the Earth head on than the light is the most intense, this occurs when the Sun is overhead, the regions where the Sun is high in the sky for longer therefor receive more intense light= more heat, these are primarily the equatorial regions -polar regions on the other hand receive dispersed light that is less intense, thus the poles are less heated

Question 7

How is the heat imbalance on the surface of the Earth dealt with?

Answer 7

-the equators is warmer and the pole cooler, the energy is transferred via the oceans and atmosphere, the heat imbalance creates winds as the warm air tends to rise and cool air tends to fall

Question 8

What would happen with the heat imbalance if the Earth didn’t rotate?

Answer 8

-poles would be cooler -equator would be warmer -these differences are smoothed over by the atmosphere and the oceans -the Sun warms up the equatorial region, the hot air rises up and moves towards the poles, it cools on its journey and then descends. The cold air from the poles then travels back to the equator. If the Earth didn’t rotate there would be only two of these systems, one in the northern hemisphere and one in the southern hemisphere

Question 9

What is the Coriolis effect?

Answer 9

-a deflection of moving objects when they are viewed in a rotating reference frame

Question 10

What is the Coriolis effect in terms of the Earth surface?

Answer 10

-the Earth rotates, the speed of the surface differs with latitude,it is the fastest at the equator and it is equal to 0 on the poles. -we have a parcel X, it is at a latitude 40S and the speed is about 1181km/h, it travels closer to the equator, if it goes in a straight line due to the faster rotation at the equator it is deflected, as it is in the southern hemisphere it is deflected anticlockwise and goes left, that is why currents in the southern hemisphere always go anticlockwise -it is the opposite in the northern hemisphere, there it is deflected in the clockwise direction thus the currents goes to the right

Question 11

In what direction is the deflection of winds in the southern hemisphere?

Answer 11

-left, anti-clockwise

Question 12

In what direction is the deflection of winds in the northern hemisphere?

Answer 12

-right, clockwise

Question 13

What happens when the Earth rotates?

Answer 13

-the continents plus the 24 hour rotation and the size of the planet mean that there isn’t just one system of the “cooling” mechanism but three in each hemisphere -this is due to fact that as the Earth rotates it takes longer for the winds to reach places so they cool faster

Question 14

What are the names of the belts?

Answer 14

-Hadley cell=closest to equator Ferrel cell= the middle Polar cell= closest to the pole

Question 15

What does the number of belts depend on?

Answer 15

-rotation rate and the size of the planet

Question 16

Which currents are colder and warmer, the ones on the western or easter side of the basins?

Answer 16

• warm= tend to be on the western side fo basins - cold= on easterly side of the basins

Question 17

What is the effect of the California current on the southwestern USA coast?

Answer 17

-cold current= less likely to rain as cold air doesnt’t rise as much= clouds don’t form

Question 18

Which currents are generally stronger, the ones on the western or eastern side of the basins?

Answer 18

-western are usually stronger (also warm)

Question 19

What is the current strength measured in?

Answer 19

-Sverdrups =1 million cubic meters per second -currents are much stronger than rivers, Gulf stream= 50 Sv, the Amazon= 0.2 Sv

Question 20

Do the current temperature and strength change throughout the year?

Answer 20

-yes, seasonal changes due to solar variation seasonally -this change causes maximum heating location to move north and south of the equator -the belts move with it, thus causing the patterns of winds to shift north and south also

Question 21

What are the effects of currents on sea surface temperature?

Answer 21

-large, you can see the influence of currents on a thermogenic map -eg, can see how the Peru current influences the water and there is an area of cold water being pushed up close to the equator

Question 22

Where are the currents we have to remember?

Answer 22

-

Question 23

What is the effect of the Gulf Stream?

Answer 23

-western boundary warm current -warms up northwestern parts of Europe eg. the Scilly islands( they can grow mediterranean plants in high latitudes), - can see on the photo that the stream is not completely uniform (due to geological structures and other currents’ interference) -important to know where it is for sea voyages and fishing

Question 24

What is the Kuroshio current?

Answer 24

-western boundary warm current, similar behaviour to the gulf stream -travels eastwards across the pacific -means black current in Japanese -it is warm and unproductive -interacts with cold current Oyashio, which has high biological activity -boundary between the two is at about 40 N, important to know for fisheries and travel

Question 25

What is the Peru current?

Answer 25

-very strong cold current off west coast of South America -caused by movement of water from west to east in mid-latitudes then striking S. America -current lowers sea surface temp. several degrees, within 100km of the coast, upwelling also lowers it by another 2-4 degrees -el nino= when upwelling is stopped or slower= so less fish and really warm

Question 26

What is the relationship of El Nino and the Galapagos?

Answer 26

-the islands are very exposed to this change in temperature but the local fauna an flora has adapted to it

Question 27

What is the East Australian Current?

Answer 27

-western boundary current -weak, only 15Sv -separates from the Australian coast near 34S and heads towards New Zealand -lot of current eddies

Question 28

What are the current eddies?

Answer 28

-In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid flows past an obstacle. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object. -in oceans it is similar but it is due to the turbulence of warm and cold water and their differing densities

Question 29

What are the effects of currents on life and on ocean climate?

Answer 29

-presence of currents can have a profound effect on ocean climate and life -ocean productivity is influenced by ocean current patterns -productivity measured on the basis of chlorophyll content -regions with low productivity= downwelling -warm currents= not much life