Quantifying the influence of volcanic forcing on water isotopes and
climate in polar and alpine regions using HadCM3
Abstract
The frequency of extreme weather events depends relatively more on
climate variability than on average changes. This makes variability a
crucial element to consider in future projections. Stable water isotopes
such as δ18O extracted from climate archives, including ice-cores, have
been used to reconstruct regional climate and evaluate climate
simulations. These archives have shown that variability in the Holocene
is much lower than that at the Last Glacial Maximum (LGM, 21 kyr ago).
However, state-of-the-art climate models still fail to simulate this
shift. Comparison is difficult, since paleoclimate equilibrium
simulations are typically run for few centuries and do not yet
incorporate water isotope tracers. Volcanic eruptions offer a unique
testbed to analyse the link between regional archives and global climate
since well reconstructed aerosol data from 800 CE onward allow the
investigation of small and large-scale effects in time and space on the
climate. Here, millenial simulations from the isotope-enabled version of
HadCM3 forced by solar and volcanic reconstructions in pre-industrial,
LGM and past-millenium scenarios were evaluated. We then analysed the
influence of volcanic eruptions on climate and δ18O values in polar and
alpine regions. This allowed us to test the dependency of isotope values
on regional shifts in climatology as well as global anomalies using
composite analysis of volcanic eruptions. We finally discuss the impact
of these results on the climatic representation of polar and alpine
ice-cores representing changes in global climate variability.