Midterm 2 practice problems

In most cases a sentence or two is all that would be expected on an exam.

Plate Tectonics

1) As continents drift about they have occasionaly bunched near the poles. Why is this important for climate? (platform for ice sheet formation, etc)

2) Continents have occasionally bunched near the equator. Why is this significant for weathering?

3) Where and what happens at diverging and converging plate boundaries (Fig 7-21), especally with regard to the rock cycle (Fig 7-25)?

Carbon Cycle 

1) Roughly compare the sizes of carbon reservoirs of the atmosphere, marine and land biosphere, and sedimentary rocks.

2) Describe the biological pump. How does it affect the concentration of carbon and oxygen dissolved in sea water at the ocean surface? 

3) Describe the role of plate tectonics in the the carbonate - silicate cycle.

4) In what way does the carbonate-silicate cycle serve to stabilize the temperature of the climate system? 

5) Scientists estimate that burning the entire fossil fuel reservoir (4700 GtC) might increase atmospheric concentration from 760 GtC to about 4000 GtC. What other reservoirs are likely to increase in response? How?

6) Why is the ocean expected to acidify in the future and what does it mean for animals with calcium carbonate shells?

7) How does carbon "leak" out of the short-term organic carbon cycle? How is it re-introduced to the  biosphere?

8) Write down the formulas for the photosynthesis reaction and the respiration and decay reaction. Which one requires energy to proceed and which one releases energy? (You need not memorize the chemical reactions for any other cycles in the carbon cycle, except for this pair.)

Climate of the deep past

1) Why were there high levels of CO2 and CH4 in the early atmosphere? How do we know they were high?

2) Why did CH4 decline when O2 rose and how might this have caused the Huronian glaciation?

3) What happens in simple climate models when ice cover on Earth reaches about 30 deg while the planet is still in a cooling phase? How do the major feedback compete and which one wins out when the ice rapidly marches to the equator?

4) Be familiar with the snowball earth timeline.

5) Life somehow managed to survive the snowball earth episodes and appears to have diversified ("exploded") soon after. What are the leading theories about how this happened. The ideas about thin sea ice in the tropics are probably incorrect, so don't take the discussion in the text book on this matter too seriously.

6) More often than not in the last 500 million years it was warmer than at present. Higher temperatures are attributed to higher levels of CO2. Give three reasons why CO2 might have been higher?

7) What is the leading explanation for the reduction in CO2 during the cenozoic (past 65 million years)?


Ice age climate

1) How do oxygen isotopes record information about climate in (a) ocean sediments and (b) ice cores?

2) What are the major transitions in the pleistocene

3) How and why do CO2 and CH4 vary with temperature during the ice ages? Would their change reinforce the ice age climate? (see p 281-282, don't struggle too long with the shelf nutrient hyp. or coral reef hyp.)

4) Why are ice sheets sensitive to summertime temperature?

5) Milankovitch argued that ice volume should respond to summertime insolation. How do ice sheets work? In other words why is summertime insolation (or temperature) more important than accumulation.

Milankovitch Cycles

1) Why do scientists still debate whether Milankovitch was right? (See Fig 14-8. People insist on comparing ice volume to insolation. Instead they should compare ice melt rate to insolation -- as suggested in Fig 14-9. The fit is actually very good! I'll show this in class. )

2)  A brief summary of how the orbital parameters influence insolation/ice advance
  • eccentricity: High eccentricity would promote high seasonal variation.  A circlular orbit has zero eccentricity, so perihelion is irrelevant. Hence eccentricity modulates the precession signal.  High eccentricity also reduces yearly insolation, which in general can cause ice to advance.
  • precession: when SH summer solstice occurs at perihelion (eccentricity > 0), the SH experiences warmer summers and colder winters, and the NH experiences colder summers and warmer winters. Hence the NH is more likely to exeperience ice advance. (The reverse occurs when NH summer solstice is at perihelion). For the curious -  When equinox occurs at perihelion (spring or autumn), summer and winter are unaffected, but spring and autumn are warmed/cooled. There is little influence on  ice.
  • obliquity: low obliquity is better for ice advance because low obliquity implies cooler summers (and warmer winters).
3) Assuming ice sheets grow when summer insolation is low at a latitude of 65N, are the current conditions of the earth orbit (tilt of the axis, time of the calendar year when the earth passes closest to the sun, and the ellipticity of the orbit) relatively favorable or unfavorable to initiate an ice age? (Pay attention to sections on Friday for the answer, or try to figure it out on the web. The book doesn't say.)

4) Presently perihelion occurs in earily January. In 10,000 years it will occur in early July. If this is the only change in climate forcing compared to present, will orbital configurations be more or less favorable for initiating ice age?

Holocene Climate

1)  What is the Younger Dryas event?

2) What is the nature of the abrupt climate events? e.g., When did they occur? How many "interstadials"  were there in the last ice age? What is the interval between events and about how long did they last? What is the magnitude of the event? Have they occured in the holocene? Don't worry about the theory of stochastic resonance, few people believe in it.
 
3) How do volcanoes influence climate in the 1-5 year time scale?

4) How can you reconcile the excellent match between the sunspot cycle data and temperature shown in Fig 15-8 with the more widely held belief among scientists that the 20th century temperature trend is due increasing levels of greenhouse gases?