L18: Oceans

Question 1

Oceans cover ______ of the earths surface

Answer 1

71%

Question 2

What is the oceans maximum depth? What is this area called?

Answer 2

11 km, Marianas Trench

Question 3

What is salinity

Answer 3

which measures the proportion of dissolved ions in ocean water – is ~3.5% or 35‰ (‘per mil’ or parts per thousand)

Question 4

What are the primary constituents of an oceans salinity?

Answer 4

Chloride, Sodium, Sulfate, Magnesium, Calcium, Potassium, Bicarbonate

Question 5

Define sources

Answer 5

Ions enter into the oceans primarily from the dissolved load delivered from land from rivers, and from submarine volcanic activity, primarily at mid ocean ridges

Question 6

Define sinks

Answer 6

Ions are removed from seawater by the precipitation of minerals (sodium, chloride, sulfate), sequestration by living organisms to produce shells (primarily calcium, bicarbonate), sorption to clay minerals (potassium and sodium), being removed in sea spray, and in reactions with basaltic seafloor rocks (alteration)

Question 7

Where is salinity high and where is it low?

Answer 7

Salinity is high in regions of high evaporation, and low where river water enters into the ocean

Question 8

Changes in composition over time on earth?

Answer 8

The bulk composition of seawater likely stays fairly constant over time, but salinity was probably lower early in Earth history. Iron concentrations (as Fe2+) were higher in Proterozoic seawater, and thick banded iron formations were deposited as atmospheric oxygen increased and iron oxidized

Question 9

Where are temperatures highest? Where do they decrease?

Answer 9

Temperatures are highest in tropical Pacific and Indian Oceans, decrease poleward

Question 10

Temperature decreases with _________. Cold water is denser, therefore it _________.

Answer 10

• Depth

- Sinks

Question 11

Thermocline

Answer 11

the zone of rapid temperature change

Question 12

Salinity increases with _________. Why?

Answer 12

• Depth

- because saline water is denser and sinks

Question 13

Halocline

Answer 13

the region of rapid salinity change

Question 14

Seawater density increases with _________. Why?

Answer 14

• Depth

- both due to decreasing temperature and/or increasing salinity

Question 15

Pycnocline

Answer 15

the zone of rapid density change

Question 16

What cause ocean currents?

Answer 16

• Air currents (wind) interacting with the surface of the oceans
• The sinking of denser (colder or saline) water
• Effects resulting from rotation of the Earth

Question 17

Dense, cold, high salinity water __________ at the poles to drive deep ocean ____________

Answer 17

• Descends

- circulation

Question 18

Define thermohaline circulation

Answer 18

• the result of density- driven movement of water in the oceans.
• This deep circulation network plays a critical role in controlling global climate

Question 19

The sun heats the planet __________, which results in . . .

Answer 19

• Unevenly

- resulting in energy differences which lead to prevailing wind directions

Question 20

How are surface currents created?

Answer 20

The friction caused by winds resulting in energy differences which lead to prevailing wind directions passing over ocean water

Question 21

Surface circulation is dominated by _______ driven by the Coriolis Effect.

Answer 21

Gyres

Question 22

The coriolis effect leads to major westward drift at the equator, and sustains the 5 major gyres on the planet. Name these gyres.

Answer 22

N. and S. Atlantic, N. and S. Pacific, and the Indian Ocean

Question 23

Surface of solid Earth is rotating about its vertical axis to some degree, everywhere except at equator. Name the directions these travel in.

Answer 23

• Counterclockwise (CCW) in northern hemisphere

- Clockwise (CW) in southern hemisphere

Question 24

Objects moving in a straight line appear to curve relative to solid Earth beneath them. What directions do these travel in?

Answer 24

• Right in N. hemisphere

- Left in S. hemisphere

Question 25

What does the Coriolis effect cause?

Answer 25

wind-driven currents in the northern hemisphere to be notably clockwise (CW) of the actual wind direction

Question 26

Why are deeper currents progressively rotated CW?

Answer 26

because of slower water velocity. The overall average water movement is 90°CW of wind (in Northern hemisphere)

Question 27

What does Ekman Transport cause?

Answer 27

upwelling of deep, nutrient-rich ocean water to the surface where the transport direction is offshore

Question 28

Where do areas of downwelling occur?

Answer 28

Occur where Ekman transport is onshore. (Note diagram below is for CW Coriolis deflection in the N. hemisphere)

Question 29

What is the normal situation off of the South American coast?

Answer 29

The normal situation off of coast of South America is one where Ekman transport drives the upwelling of nutrient- rich water to the surface

Question 30

What is El Niño?

Answer 30

In certain years a change starts in approximately December, wherein upwelling declines, reducing fish and bird populations. The trade winds reverse in the west Pacific, ultimately having a worldwide effect on weather patterns.

Question 31

What occurs in a normal year?

Answer 31

In a normal year, surface currents off of South America move northward, and Ekman transport (counterclockwise in southern hemisphere) causes upwelling and movement of water offshore.

Question 32

What occurs during an El Niño year?

Answer 32

In an El Niño year, the atmospheric pressure difference between the west Pacific (low pressure) and east Pacific (high pressure) weakens, causing the trade winds to slow or reverse. Without trade winds to move upwelling water, upwelling stops, which can be disastrous for the fishing industry

Question 33

What is the frequency of El Niño years?

Answer 33

El Niño events occur approximately every 4 years, vary greatly in their severity, and are not easily predicted.

Question 34

What is an El Niña event?

Answer 34

The opposite end of the southern oscillation, when cold water dominates the equatorial Pacific

Question 35

What are ocean gyres?

Answer 35

Large system of circular ocean currents formed by global wind patterns and forces created by earths rotation