archives of global climate change contained in ocean sediments
TRANSCRIPT
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
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