Glacier response to Holocene warmth inferred from in situ 10Be and 14C bedrock analyses in Steingletscher's forefield (central Swiss Alps)

Mid-latitude mountain glaciers are sensitive to local summer temperature changes. Chronologies of past glacier fluctuations based on the investigation of glacial land-forms therefore allow for a better understanding of natural climate variability at local scale, which is relevant for the assessment of the ongoing anthropogenic climate warming. In this study, we focus on the Holocene, the current interglacial of the last 11 700 years, which remains a matter of dispute regarding its temperature evolution and underlying driving mechanisms. In particular, the nature and significance of the transition from the early to mid-Holocene and of the Holocene Thermal Maximum (HTM) are still debated. Here, we apply an emerging approach by combining in situ cosmogenic Be-10 moraine and Be-10-C-14 bedrock dating from the same site, the forefield of Steingletscher (European Alps), and reconstruct the glacier's millennial recession and advance periods. The results suggest that, subsequent to the final deglaciation at similar to 10 ka, the glacier was similar to or smaller than its 2000 CE extent for similar to 7 kyr. At similar to 3 ka, Steingletscher advanced to an extent slightly outside the maximum Little Ice Age (LIA) position and until the 19th century experienced sizes that were mainly confined between the LIA and 2000 CE extents. These findings agree with existing Holocene glacier chronologies and proxy records of summer temperatures in the Alps, suggesting that glaciers throughout the region were similar to or even smaller than their 2000 CE extent for most of the early and mid-Holocene. Although glaciers in the Alps are currently far from equilibrium with the accelerating anthropogenic warming, thus hindering a simple comparison of summer temperatures associated with modern and paleo-glacier sizes, our findings imply that the summer temperatures during most of the Holocene, including the HTM, were similar to those at the end of the 20th century. Further investigations are necessary to refine the magnitude of warming and the potential HTM seasonality.

Automated summary

This study focuses on the fluctuations of mid-latitude mountain glaciers and their relationship with local summer temperature changes. The researchers reconstruct the millennial recession and advance periods of the Steingletscher glacier in the European Alps during the Holocene. The findings suggest that glaciers in the region were similar to or even smaller than their current extent for most of the early and mid-Holocene, indicating that the summer temperatures during that time were similar to those at the end of the 20th century. However, due to the accelerating anthropogenic warming, glaciers in the Alps are currently far from equilibrium, making a simple comparison between modern and paleo-glacier sizes challenging.