Holocene glacier change in the Silvretta Massif (Austrian Alps) constrained by a new 10Be chronology, historical records and modern observations

Mountain glaciers are important water resources in Alpine regions and are sensitive to climate change. Reconstructing glacier oscillations improves our understanding of the amplitude and the frequency of climate variability and resolves time periods when the climate system was in transition – from glacial to interglacial conditions at the beginning of the Holocene, and from a naturally controlled system to an anthropogenically influenced system in the course of industrialization. With this study, we contribute a new Holocene mountain glacier chronology from the Eastern European Alps. The study area, the Ochsental in the Silvretta Massif, features pronounced Holocene moraine ridges and is an important catchment for hydropower production. We present 18 new 10Be exposure ages of bedrock outcrops (n = 2) and boulders (n = 16). We complement the 10Be glacier chronology with historical records and instrumental time series and correlate it with pre-existing climate proxy records for capturing ice margin positions at different times during the Holocene. The Ochsental chronology is compared to cosmogenic nuclide moraine records across the European Alps to provide an Alpine-wide perspective on the transition from the Younger Dryas (YD; c. 12.9 to 11.7 ka) to the Holocene (c. 11.7 ka to present). Results show that glaciers in the Ochsental stabilized at the position of a preserved Holocene moraine c. 9.9 ± 0.7 ka after retreating from their Late Glacial position. This Holocene moraine formation interval is concurrent with a cold spell detected in some climate proxy records in the Swiss and Austrian Alps, the Central European Cold Phase 1 (CE-1). Glaciers were presumably much smaller during the Mid-Holocene and readvanced to a position close to the preserved Early Holocene moraine during the Little Ice Age (LIA; c. 1250 to 1850 CE). LIA 10Be ages range from 390 ± 20 yrs to 135 ± 5 yrs and point to multiple advances within this time period with most robust evidence for a culmination during the 18th century. The 10Be record and the historical glacier records overlap and are remarkably consistent, which demonstrates that 10Be surface exposure dating produces reliable ages even for young glacial deposits. Within the last c. 170 years, Ochsentaler glacier has retreated c. 2.3 km, which highlights the impact of recent warming on Alpine mountain glaciers.