Archives of global climate change

choppedspleenMechanics

Feb 22, 2014 (7 years and 10 months ago)

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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


δ
18
O, Sr/Ca


Chemistry of foraminifera


δ
18
O, Mg/Ca



Oxygen Isotopes


For every 500 water molecules in the sea, one
bears the heavy isotope
18
O


In a variety of earth substances, the ratio of
heavy oxygen atoms (
18
O) to light oxygen atoms
(
16
O) varies from this 1/500 ratio by several
percent


For example, marine CaCO
3

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