Download Ice Age North Polar Coverage

Climate through Earth history
Cenozoic cooling
Ice Age North Polar Coverage
Q.: How do we know the details of
temperature changes during the ice ages?
Oxygen isotopes and paleoclimate
•
As climate cools, marine
carbonates record an increase
in d18O.
• Warming yields a decrease in
d18O of marine carbonates.
JOIDES Resolution
Scientists examining core
from the ocean floor.
It is possible to reconstruct an
approximate chronology of the
ice ages by measuring the
oxygen isotopes in ocean
sediment cores. As marine
organisms perish, their skeletons
are deposited on the bottom of
the sea floor. The layers of
deposited skeletons provide
information about climate.
Q.: Are there any patterns in the data?
Spectral analysis shows these periodicities
throughout record
Milankovitch forcing
Milankovitch forcing
Milankovitch forcing
High-latitude
warming
beginning
~19,000 BP
Put the insolation signal all together,
compare it to the temperature data
Fits pretty well, but if we look at it closely, it’s not enough
We also see an
association
between CO2
and ice volume
from marine
sediments
And an association between Antarctic temperature and CO2
Temperature rises precede CO2 rises
The biological pump removes carbon from the atmosphere
Q.: Was the biological pump stronger
during the cold periods? How would we
know?
During glacial times, if there were more photosynthesis, then there would be a
greater difference between surface water and deep water d13C values
These data
suggest a stronger
carbon pump
during times
when CO2 was
low
This relationship
continues back as far
as 1 Ma BP