Paleoclimate Lida Teneva, Tristan Lindot

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PaleoclimateLida Teneva, Tristan Lindot

• The proxies corals, ice cores, tree rings, ocean
  and lake sediments, cave stalagmites, sedimentary
  rocks, etc.
• Information temperature, atmospheric
  composition, sea level, vegetation change,
  precipitation patterns, ocean currents, etc.

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Corals

• Can be up to 300 years old
• Mostly used for last millennium climate studies
• Sr/Ca ratios and d18O geochemical temperature
  proxies
• Sr/Ca partly controlled by algal symbionts
• d18O partly controlled by local hydrography and
  biofractionation

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Ice cores

• Take us to 650,000 yrs BP (soon to 800,000)
• Isotopic composition (O H) in ice related to
  temperature
• Air bubbles trapped in ice reflect atmospheric
  composition
• Issues
• Imprecise dating of layers
• Air bubbles younger than surrounding ice

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Tree rings

• Bristlecone pine of the Great Basin region of
  western North America are the oldest known living
  trees, up to 5,000 years old.
• Tree growth is generally controlled by climate
  conditions during the year prior to and including
  the growing season.

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Tree rings and uncertainties

• The reconstruction models explain 60-75 of the
  variance in the gage records.
• Inevitable decline in tree sample size back in
  time.

The Blue River at Dillon Reservoir reconstruction
model (green) and the gaged record (blue) over
their common time period (1916-2002).
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Foraminifera

• Present in all the oceans,
• Many in the sediments,
• Very sensible to their environment,
• Can give information until
• 100,000 years ago.

• Limitations due to uncertainties on the tested
  sample.

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Sedimentary rocks

• Loess are sediments carried by winds,
• Their compositions change with changes in
  atmospheric circulation,
• Until 600,000 before present but geographically
  limited.

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Take-home points

• Many different proxies use depends on time-scale
  and climatic factors of interest
• Precision of dating decreases with age
• Need to understand all the variables that affect
  the proxies climate variability and biological
  variations

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