Transcript Sediment Cores from the Ocean Floor

ADDITIONAL PROXY DATA FOR
STUDYING CLIMATE CHANGE
Copyright 2008
Sediment Cores from the Ocean
Floor
Photo credit: Ocean Drilling Program, Texas A&M University
Copyright 2008
Scientists can learn about past
climates from microscopic fossils
in the ocean cores
• Foraminifera (“forams”)
• Single-celled marine animals
• Some planktonic, some
benthic
• Widely distributed in the
oceans
• Very good preservation as
18O of seawater
d
decreases
fossils in ocean sediments
d18And
O record
of
increases
during
during
warming
• Shells made of CaCO3
ocean water
cooler
periods
periods
Photo credit: M. Manighetti & L. Northcote, Water & Atmosphere Online, New Zealand
Institute of Water & Atmospheric Research
Copyright 2008
Speleothems
Photo © Paul Williams, New Zealand National Institute of Water & Atmospheric Research
Photo: Dave Bunnell
Because speleothems (cave formations)
such as stalactites grow in annual layers or
“rings”, d18O ratios in their CaCO3 can be
used to study past climate.
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Studies of Modern and Fossil Plants
• Leaf shapes & surfaces from
fossil leaves can be used as
palaeoclimate indicators – as
with modern leaves, certain
shapes are associated with
warm or cold climates.
• Density of leaf stomata (pores)
can indicate ancient
atmospheric CO2 levels.
Because plants take in CO2
through the stomata, more
stomata are needed if CO2
levels are low, and fewer
if the levels are high.
• Tree ring width can indicate
ancient climate, and annual
tree rings can be used to
determine the time in the past.
Photo credit: Woudloper
Photo credit: Dartmouth Electron
Microscope Facility
Photo credit; Hannes Grobe
Photo credit: Patricia Miller
Photo credit: Menchi
Copyright 2008
Illustration from
Prof. Alan J.
Thorpe, 2005, on
behalf of the
Institute of Physics.
Using computer models for “hindcasting” of
recorded climate observations
Illustration © Institute of Physics and IOP Publishing Limited (“IOPP”) 2006
Copyright 2008
Illustration from
Prof. Alan J.
Thorpe, 2005, on
behalf of the
Institute of Physics.
Natural variations alone do not explain observed
trends & a model incorporating both natural and
anthropogenic factors yields the best fit
Illustration © Institute of Physics and IOP Publishing Limited (“IOPP”) 2006
Copyright 2008
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Foraminifera photo & δO-18 plot adapted from B. Manighetti & L. Northcote, Water & Atmosphere Online,
Copyright 2008
-30°C
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DATA SHEET 67
Graphs of temperature and calcium from the GISP2 (Greenland Ice Sheet Project) ice
core. Temperature values were determined from d18O analyses of ice core layers.
Calcium concentrations are equivalent to the concentration of calcium dust particles
trapped in the ice core. Dust particles can be transported into the atmosphere by
wind and can travel great distances, but they eventually settle out back to Earth.
Calcium is a major component of limestone rock, which is formed in the oceans and
which is deposited as limestone mud on the world’s continental shelves.
Illustration courtesy of Teachers’ Domain. Source: Zach Smith, Wright Center for Education, Tufts University
Copyright 2008