Ice Cores
•Very important paleoclimatic archives.
•Records of past atmospheric conditions.
–Temperature
–Humidity
–Snow accumulation
–Atmospheric composition
–Volcanic activity
–Tropospheric turbidity
–Wind speed, wind direction
–Atmospheric circulation
Ice Core drilling
Stable Isotopes-Concepts
•NameSymbolDefinition
•Atomic numberZ# protons (p+)
•Neutron numberN# neutrons (n)
•Mass numberA# p++ n
Abundance of stable isotopes of water
|
Isotope |
Z |
A |
Abundance (%) |
Atomic wt. (amu) |
|
H |
1 |
1 |
99.985 |
1.007825 |
|
D |
1 |
2 |
0.015 |
2.014102 |
|
16O |
8 |
16 |
99.762 |
15.994915 |
|
18O |
8 |
18 |
0.200 |
17.999160 |
|
17O* |
8 |
17 |
0.038 |
16.999131 |
Physical properties of water
|
H216O |
H218O |
|
|
Density (g/cm3at 20°C ) |
0.997 |
1.1106 |
|
Melting point (°C at 760torr) |
0.00 |
0.28 |
|
Boiling point (°C at 760torr) |
100.00 |
100.14 |
|
Vapor pressure (torrat 100°C) |
760.00 |
758.07 |
|
Viscosity (centipoiseat 20.2°C) |
1.002 |
1.056 |
Isotope effect and fractionation
•Isotopes undergo the same chemical and physical reactions.
•The rateof these reactions, however, could be different (isotope effect), resulting in the partitioning of isotopes (fractionation).
Terminology
δ=1000(Rsample/Rstandard–1)
where R=heavy isotope/lighter isotope
δ18O= 1000(18Rsample/18Rstandard–1)
where 18R=18O/16O
δD= 1000(2Rsample/2Rstandard–1)
where 2R=D/H
Standard is V-SMOW(Vienna-Standard Meteoric
Ocean Water).
δ18OV-SMOW = δDV-SMOW= 0‰
Temperature
Altitude
Distance from the source
Latitude
IAEA (2001).GNIP Maps and Animations.
IAEA (2001).GNIP Maps and Animations
IAEA (2001).GNIP Maps and Animations
Fricke and O’Neil, 1999
Edwards et al., 2004
d-excess
Dating Ice Cores
•Radio-isotopes
•Ice layers
•Ice flow models
•Reference horizons
Volcanic markers
provide additional
time control
Antarctic Ice Cores
Vostok Ice Core
Epica Group, 2004
Epica Group, 2004
MIS-5
MIS-3
MIS-1
MIS-4
Blunier and Brook, 2001, Science
