Abstract:
by Anders Svensson, Jiamei Lin and many others
Precise synchronization of climate records is essential for deducing the mechanisms of the climate system. Ice cores from the Greenland and Antarctic ice sheets have been synchronized by the use of cosmogenic isotopes, gas concentrations, and traces of large volcanic eruptions. Here, we apply ice-core volcanic proxies and annual layer counting to identify large volcanic eruptions that have left a signature in both Greenland and Antarctica. Generally, no tephra is associated with those eruptions in the ice cores, so in most cases the source of the eruptions cannot be identified. Instead, we identify and match sequences of volcanic eruptions with bipolar distribution of sulfate, i.e. unique patterns of volcanic events separated by the same number of years at the two poles. The annual layers are thinning with depth making the layer counting and thus the synchronization very challenging in the early last glacial period. The precise bipolar synchronization allows to determine the exact inter-hemispheric phasing of abrupt climate change during the last glacial, and to investigate a possible relation between abrupt climate change and volcanism. Furthermore, the sulfate depositions on the ice caps allows to establish the frequency and magnitude of large volcanic eruptions in the last glacial period.