Transcript Archives of global climate change contained in ocean sediments

Archives of global climate change
contained in ocean sediments
Ocean sediments as continuous
climate archives
• Sediments consist of terrigenous material
+ organic rain + rain of calcite/silicate
shells
• Sedimentary rain not derived from rocks is
produced primarily by marine organisms
(shells and excrement)
• Sedimentation rates range from almost nil
to 10-20 cm/kyr
Microscope view of
rinsed seafloor sediment
Archer D.E., 1996
Marine paleothermometers
• Foraminiferal abundance
• Sediment chemistry (Alkenones)
• Coral chemistry
– δ18O, Sr/Ca
• Chemistry of foraminifera
– δ18O, Mg/Ca
Oxygen Isotopes
• For every 500 water molecules in the sea, one
bears the heavy isotope 18O
• In a variety of earth substances, the ratio of
heavy oxygen atoms (18O) to light oxygen atoms
(16O) varies from this 1/500 ratio by several
percent
• For example, marine CaCO3 has ~4% more
heavy oxygen than seawater, while Antarctic
snow has ~4% less heavy oxygen than seawater
From “The Glacial World According to Wally”, 2002
Bemis et al.,
1998
Data from Lea et
al., (2000)
presented in
Wally