Early Holocene cold snaps and their expression in the moraine record of the Eastern European Alps

• Main Authors: Braumann, Sandra M., Schaefer, Joerg M., Neuhuber, Stephanie M., Lüthgens, Christopher, Hidy, Alan J., Fiebig, Markus
• Format: Text
• Language: English
• Published: 2021
• Subjects: geo; envir; Arctic; Climate change
• Online Access: https://doi.org/10.5194/cp-2021-54; https://cp.copernicus.org/preprints/cp-2021-54/

Glaciers preserve climate variations in their geological and geomorphological records, which makes them prime candidates for climate reconstructions. Investigating the glacier-climate system over the past millennia is particularly relevant because, first, the amplitude and frequency of natural climate variability during the Holocene provides the climatic context against which modern, human-induced climate change must be assessed. Second, the transition from the last glacial to the current interglacial promises important insights into the climate system during warming, which is of particular interest with respect to ongoing climate change. Evidence of stable ice margin positions that record cooling during the past 12 ka are preserved in two glaciated valleys of the Silvretta Massif in the Eastern European Alps, the Jamtal (JAM) and the Laraintal (LAR). We mapped and dated moraines in these catchments including historical ridges using Beryllium-10 Surface Exposure Dating (10Be SED) techniques, and correlate resulting moraine formation intervals with climate proxy records to evaluate the spatial and temporal scale of these cold phases. The new geochronologies indicate two moraine formation intervals (MFI) during the Early Holocene (EH): 10.8 ± 0.7 ka (n = 9) and 11.2 ± 0.8 ka (n = 12). Boulder ages along historical moraines (n = 6) imply at least two glacier advances during the Little Ice Age (LIA; c. 1250–1850 CE), around 1300 CE and in the second half of the 18th century. An earlier advance to the same position may have occurred around 500 CE. The Jamtal and Laraintal moraine chronologies provide evidence that millennial scale EH warming was superimposed by centennial scale cooling. The timing of EH moraine formation is contemporaneous with brief temperature drops identified in local and regional paleoproxy records, most prominently with the Preboreal Oscillation (PBO), and is consistent with moraine deposition in other catchments in the European Alps, and in the Arctic region. This consistency points to cooling ...