HR: 1330h
AN: PP42A-0852    [PDF]
TI: Assessing the Rapid Temperature Changes of D/O Events 9 to 12 From Air Isotope Measurements on North GRIP Ice Using a New On-line Technique
AU: * Christof, H
EM: huber@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, Bern, 3012 Switzerland
AU: Markus, L
EM: leuenberger@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, Bern, 3012 Switzerland
AB: Rapid temperature variations fractionate gas isotopes in the firn column of polar ice sheets due to thermal diffusion and gravitation. Hence, gas isotope measurements allow the determination of past surface temperature variations during rapid climate changes like Dansgaard-Oeschger (D/O) events. We have developed a new on-line extraction and measuring technique for bubble air trapped in ice cores. An ice sample is continuously melted and the air is subsequently separated from the meltwater and analyzed in an isotope ratio mass spectrometer. It allows fast and high resolution measurements of the isotopic ratios of nitrogen ($\delta^{15}$N), oxygen ($\delta^{18}$O, $\delta^{17}$O) and argon ($\delta^{36}$Ar), as well as the corresponding elemental ratios. We will present high resolution measurements of four consecutive D/O events 9 to 12 on North GRIP ice (around 40'000 to 48'000 years BP). With the use of a combined firn densification, temperature, and gas diffusion model, based on oxygen isotope measurements of the ice, $\delta ^{18}$O$_{ice}$-temperature coefficients in the range between 0.3 and 0.4 $\permil$/K are found. This corresponds to temperature shifts of about 8 to $16\deg$C, which is in line with already determined temperature shifts for rapid climate change events. A first comparison of these isotope measurements with methane and nitrous oxide will be shown, to investigate leads and lags.
DE: 1620 Climate dynamics (3309)
DE: 1694 Instruments and techniques
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3344 Paleoclimatology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting