Measurements of the isotopic
composition of carbon dioxide were performed on EPICA Dome C ice on 76
different depth levels covering the last 40’000 years. The time resolution is
in the order of 500 years for the last 18’000 years. For each depth level at
least two determinations were obtained. The d13C signals show different
trends during the last 18000 years that are anti-parallel to the CO2
concentration evolution as measured on the same ice core. However millennial
scale deviations from these trends are observed for at least three time
periods. The robustness and significance of these deviations are investigated
by Monte Carlo simulations performed with
different subsets of the measurements. The decreases of carbon isotopes could
be connected with observed step-like increases of the CO2 concentration.
Furthermore, a similar evolution as for stable carbon isotopes is visible for
detrended radiocarbon. We will discuss potential mechanisms responsible for the
trends as well as for the millennial scale deviations in carbon-13, including
changes in the thermohaline circulation as well as potential influences of a
changing 17O-18O relationship.
Author: M. C. Leuenberger, M. Eyer, Serge Bogni, et al (leuenberger at climate dot unibe dot ch)
Filesize: 105.00 Kb