Upwelling water - 16

Question 1

What are the three main settings where upwelling occurs?

Answer 1

• Polar upwelling
• Equitorial upwelling
• Coastal upwelling

Question 2

Where and why does polar upwelling occur?

Answer 2

Occurs in the Southern Ocean due to the interaction of density driven thermohaline currents and wind driven surface currents south of the Antarctic Convergence (50ºS)

Question 3

Why does equatorial upwelling occur?

Answer 3

Ekman transport driven divergence in surface currents

Question 4

Why does coastal upwelling occur?

Answer 4

Interaction of coastal surface wind circulation with Ekman transport

Question 5

What is the Antarctic Circumpolar Current?

Answer 5

The largest ocean current, sometimes called the West Wind Drift, that flows clockwise around Antarctica. It is circumpolar due to lack of landmasses which keeps warm water away from the Antarctic continent

Question 6

When is Antarctic sea ice at its maximum and minimum?

Answer 6

Minimum in February-March and Maximum August-September

Question 7

What blooms are associated with Antarctic sea ice retreat?

Answer 7

• Ice algae dominates first phase
• Strong diatom bloom follows
• Phytoplankton bloom occurs near the Antarctic convergence

Question 8

What dominates phytoplankton blooms in the open ocean compared to closer to the continent?

Answer 8

Dominated by diatoms and grazed by copepods in open ocean … grazed by krill closer to the continent

Question 9

What is the average rate of upwelling?

Answer 9

5-10 metres a day (changed due to strength and distance of wind however)

Question 10

What nutrients are deep waters rich in?

Answer 10

Nitrate, Phosphate and Silicic acid

Question 11

What % of global marine productivity do phytoplankton contribute?

Answer 11

50%

Question 12

What is the ocean food?

Answer 12

Phytoplankton … Zooplankton … Predatory zooplankton … filter feeders … predatory fish … marine birds and mammals

Question 13

What are the 5 main coastal currents associated with upwelling?

Answer 13

• Canary current (NW Africa)
• Benguela current (S Africa)
• California current (California and Oregon)
• Humboldt current (Peru and Chile)
• Somali current (Somalia and Oman)

Question 14

How much higher are sea surface temperatures (SST) in the western pacific dural normal conditions?

Answer 14

8ºC warmer

Question 15

How much greater is the average sea level in the western pacific during normal conditions?

Answer 15

50cm

Question 16

What effect does piling up of warm water in the western pacific have on ocean layers?

Answer 16

Creates a 150 metre deep warm layer in the west that pushes the thermocline down while it rises in the east to around only 30 metres deep

Question 17

What is air pressure like during a positive ENSO phase?

Answer 17

Air pressure at Darwin, Australia is greater than air pressure at Tahiti

Question 18

Why is upwelling decreased during El Niño?

Answer 18

Water piles up off South America, pushing the thermocline deeper and preventing upwelling

Question 19

What are sea surface temperatures like during a positive ENSO phase?

Answer 19

Waters in the eastern pacific are warmer than normal, creating a shift in prevailing rainfall

Question 20

What are conditions like during the cool phase of El Niño?

Answer 20

Lower than normal sea surface temperatures in the eastern pacific, causing increased upwelling and a shift farther to the west of prevailing rain patterns

Question 21

How much do sea surface temperatures change during ENSO?

Answer 21

Plus or minus 3ºC

Question 22

How much greater is sea level during La Niña?

Answer 22

60cm higher when winds are at full strength

Question 23

What happens to thermocline during La Niña?

Answer 23

Thermocline tilts are nearly reaches the surface in the eastern pacific

Question 24

Where is the ITCZ best established?

Answer 24

5º North

Question 25

Why is the southern ITCZ weaker?

Answer 25

Widespread low sea surface temperature off South America due to the Humboldt current