L12 - Cycles and Tipping points

Question 1

What are the important oscillations?

Answer 1

ENSO, North Atlantic Oscillation, Southern Annular Mode

Question 2

El Niño

Answer 2

• warmer than normal Pacific temps
• trade winds weaken or reverse
• thermocline rises
• drought in Australia and flooding in SA

Question 3

La Niña

Answer 3

• cooler than normal Pacific temps
• trade winds strengthen
• cool upwelling at SA
• drought in SA and flooding in Australia

Question 4

Why is the thermocline high at the South American coast?

Answer 4

Because the ocean is relatively cool here. Any heating will also heat deeper ocean

Question 5

What is the Bjerknes feedback?

Answer 5

This is a positive feedback arising from El Nino. Easterly winds increase difference in SST between east and west, which further increases wind stress

Question 6

What are some current tipping elements?

Answer 6

1. Dieback of amazon rainforest
2. Dieback of boreal forest in Canada
3. West Antarctic ice sheet (stage 3?)
4. Sahara greening
5. Permafrost loss

Question 7

What is the salt advection feedback?

Answer 7

Describes the positive feedback which occurs when an increase in thermo-salinity difference increases ocean circulation, which further increases thermo-saline difference

Question 8

What would be the consequences of AMOC collapse?

Answer 8

Cooling of northern hemisphere, and warming and drying of Sahel and Amazon region