L18_Paleoclimate-Recent-Time

Waterisotopesorg gabe bowen purdue university 10 0

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Unformatted text preview: chemical behavior, but because they have different masses, they par=cipate in reac=ons at different rates. Isotope “delta” ( δ ) values: A measure of the amount of rare isotope (e.g., 18O) rela=ve to an interna=onal reference standard. - 20 ‰ 0 ‰ +20 ‰ δ18O (SMOW) 20 parts per thousand more 18O than the interna=onal reference water, SMOW (standard mean ocean water) Isotope “delta” ( δ ) values: A measure of the amount of rare isotope (e.g., 18O) rela=ve to an interna=onal reference standard. - 20 ‰ 0 ‰ +20 ‰ δ18O (SMOW) δ18O = [(Rsa / Rst) – 1]*1000 Where Rsa = 18O/16O ra=o of sample Rst = 18O/16O ra=o of standard 20 parts per thousand more 18O than the interna=onal reference water, SMOW (standard mean ocean water) Isotope Map (“Isoscape”) of Global Precipita=on Low δ18O High δ18O - 30 - 20 www.waterisotopes.org (Gabe Bowen, Purdue University) - 10 0 Isotopes in rain and snow 0 δ18O (‰ vs. SMOW) Temperature Effect General Rule: δ18O, δD values decrease with decreasing temperature Rela=ons: δ18O = 0.695*T –...
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