geol midterm 2

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  1. on which time scales does climate vary?
    • year-to-year
    • century-to-century
  2. what is a monsoon?
    a seasonal climate oscillation, marked by a reversal of winds and rainfall patterns
  3. why are monsoons important to society?
    because some billions of people depend critically on monsoon rains for food
  4. wind patterns associated with asian summer monsoon
    from southwest to north east
  5. what is the ENSO?
    • atmospheric see-saw pattern between Northern Australia and Tahiti
    • an ocean warming along coast of S. america
  6. what is the recurrence time of ENSO events?
    2-7 years
  7. why is ENSO prediction valuable to society 1-2 yrs in advance?
    because it gives decision-makers some lead time to prepare for its impacts
  8. what is the ultimate cause of the seasonal cycle?
    tilt + revolution
  9. why are corals a preferred archive to gain insight into ENSO's past behavior?
    • they can live for centuries
    • can be accurately dated
    • their skeleton incorporates isotopic variations that are closely related to temperature/precipitation changes
  10. what is the North Atlantic Oscillation (NAO)?
    a pattern of atmospheric variability defined by the sea-level pressure difference between iceland and the Azores
  11. what creates climate variability?
    • internal climate feedbacks (Bjerknes feedback)
    • natural climate forcings (sun, volcanic eruptions)
    • anthropogenic forcings
  12. ice albedo feedback is an example of
    positive feedback
  13. what are 2 examples of negative feedbacks?
    • silicate weathering thermostat
    • stefan-boltzman law (radiative heat loss increasing with temperature)
  14. what are 3 examples of positive feedbacks?
    • water vapor feedback
    • ice albedo feedback
    • land vegetation-drought feedback
  15. Bjerknes feedback involves mutually reinforcing interactions between
    slackening of the trade winds, eastward movement of the pacific warm pool
  16. what controls the carbon cycle on geologic time scales (millions of years)?
    volcanic emissions and silicate weathering
  17. since 1950, CO2 has risen in the atmosphere at about ___ the rate of annual fossil fuel consumption
  18. why has CO2 risen in the atmosphere at about half the rate of annual fossil fuel consumption since 1950?
    the continental biosphere and the world's ocean offset fossil fuel burning (5.43 GtC/year) by soaking up 3GtC/year
  19. what types of proxy data do scientists use to reconstruct pre-historic climates?
    • ice cores
    • tree rings
    • speleothems
  20. what about deep sea sediment cores informs us about past glacial periods?
    d18O of deep-dwelling foraminifera shells records ice volume
  21. the cenozoic is the geologic eon corresponding to the past 65 million years. how do we know the timing of the events that punctuated such a period?
    • principle of superposition
    • radiometric dating with long-lived nuclides
  22. overall, what happens to the oxygen isotopic composition of the deep ocean over the cenozoic?
    • it gets more positive
    • it gets heavier
  23. why does the oxygen isotopic composition of the ocean change during the cenozoic?
    the lighter isotope 16O is preferentially evaporated from the ocean and stored on land in glaciers, causing the ocean to become isotopically heavier
  24. during which period was the antarctic continent ice-free?
    paleocene-eocene thermal maximum
  25. the paleocene-eocene thermal max happened approximately
  26. what are glaciers?
    accumulations of snow on land, turning into ice over time
  27. where can we find glaciers today?
    • mountains
    • valleys
    • poles
  28. what do ice cores record about climate?
    • temperature of snow formation
    • atmospheric composition
  29. what do antarctic ice cores teach us about climate and CO2?
    temperature and CO2 have gone hand-in-hand for the past ~800k yrs
  30. oscillations in global ice volume. pattern: a slow gradual, descent into cold conditions, and an abrupt return to warm conditions. what do we call such warming episodes?
    glacial terminations
  31. over the past million years or so, what was the average spacing between ice ages?
    ~100k yrs
  32. according to milankovitch theory, what is the pacemaker of the ice ages?
    the insolation received at 65N during summer
  33. what determines the average yearly insolation received by a point on earth?
    • precession
    • obliquity
    • eccentricity
  34. when did the last glacial max occur?
    20,000 yrs ago
  35. at the last glacial maximum, a large ice sheet covered much of north america, in particular the northern half of the USA and canada. what was it named?
    Laurentide ice sheet
  36. in his AGU lecture, Dr Richard Alley calls CO2 "the biggest control knob" because
    it seems to be explaining a large part of global temperature change
  37. did the last glaciation happen smoothly?
    no, it was marked by some abrupt cold reversal around 13kya
  38. what defines abrupt climate change?
    • faster than the responsible forcing
    • too fast for living systems to adapt
  39. 2 examples of abrupt climate change
    • Younger Dryas
    • Dansgaard-Oeschger events
  40. what processes matter for abrupt climate change?
    • destabilization of the methane clathrates
    • weakening of the thermohaline circulation by freshening
    • melting permafrost
  41. what physical notion can help explain the abrupt nature of certain climate events?
    tipping points
  42. climate reconstructions of the past millennium are
    quantitative proxy estimates based on a network of well-dated proxy records
  43. which of the following climate events happened in the last millennium?
    Little ice age
    younger dryas
    last glacial max
    little ice age
  44. what is the hockey stick controversy about?
    whether the current global warmth is unprecedented in the past millenium
  45. amongst the following civilization collapses, which was unlikely to be related to climate change?
  46. the anasazi indians lived in the US southwest, a region presently marginal for agriculture. archeological records indicate that their population peaked around 1100AD, but that their main center was abandoned around 1170AD. what is a likely explanation?
    the population peaked before the most severe megadrought of the millennium
  47. what lesson can we derive from the climate-induced collapse of past civilizations?
    even advanced societies can break down if climate change overcomes their resilience
  48. the anthropocene is the name given to
    the geological era marked by widespread human-caused environmental change
  49. major evolutionary change happened around 3.2mya in human's family tree. what notable environmental change may help explain this?
    aridification of east africa, resulting in a shift from woodland to grassland vegetation
Card Set:
geol midterm 2
2011-04-26 22:07:48

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