
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
Stable Isotopes-Concepts • Name Symbol Definition • Atomic number Z # protons (p+) • Neutron number N # neutrons (n) • Mass number A # p+ + n
Isotope effect and fractionation • Isotopes undergo the same chemical and physical reactions. • The rate of these reactions, however, could be different (isotope effect), resulting in the partitioning of isotopes (fractionation).
Terminology d=1000(Rsample/Rstandard – 1) where R=heavy isotope/lighter isotope d18O= 1000(18Rsample/18Rstandard – 1) where 18R=18O/16O dD= 1000(2Rsample/2Rstandard – 1) where 2R=D/H Standard is V-SMOW (Vienna-Standard Meteoric Ocean Water). d18OV-SMOW = dDV-SMOW = 0‰
Temperature Altitude Distance from the source Latitude IAEA (2001). GNIP Maps and Animations.
d-excess • Meteoric Water Line: dD=8*d18O+10 d-excess under “normal” conditions d= dD-8*d18O Increased relative humidity or lower sea-surface temperature (reduced evaporation rates) produces lower d-excess values.
Dating Ice Cores • Radio-isotopes • Ice layers • Ice flow models • Reference horizons
Volcanic markers provide additional time control
Seasonal variations can be detected with microparticles and glacio-chemical data
MIS-4 MIS-1 MIS-3 MIS-5 Blunier and Brook, 2001, Science
Colder/Drier? Warmer/Wetter?