New chemical signatures and 39Ar dating from Weißseespitze ice cores (Eastern Alps): Tracing anthropogenic pollution from the Late Medieval to Early Modern Period

High-altitude glaciers in the western European Alps have preserved long-term records of anthropogenic air pollution, as shown by numerous ice core studies over the past three decades. These records reveal a significant increase in pollutants over the last two centuries, closely linked to industrialization, with pollutants transported from nearby regions. In contrast, long-term studies in the eastern Alps remain limited, as these glaciers were considered unsuitable for undisturbed ice core preservation due to their lower elevations and temperate basal conditions. However, recent findings suggest that, under specific circumstances, cold ice frozen to bedrock can exist below 4000 m, as demonstrated by the Weißseespitze (WSS) summit ice cap in the Eastern Alps (3499 m a.s.l.), which preserves a 6000-year-old record within ~10 m of depth, despite ongoing surface mass loss.

Building on earlier work, this study provides further insights into the WSS glacier through expanded chemical analyses of an 8.5 m deep ice core drilled in 2019, complementing previously reported data on major ions and levoglucosan. The extended dataset includes detailed profiles of 22 trace elements (Ag, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, In, Li, Mn, Ni, Pb, Rb, Se, Sr, Tl, U, V, Zn), carboxylic and dicarboxylic acids, obtained from discrete samples collected alongside the 2022 melting campaign performed at Ca’ Foscari University.

A Positive Matrix Factorization (PMF) analysis of the recorded impurities revealed significant anthropogenic contributions to the trace element profiles. This was supported by a Lagrangian particle dispersion model, showing that ~50% of the air masses over the WSS glacier originated in Central Europe, with a notable contribution from the Po Valley, emphasizing its historical role in pollution transport.

To refine the glacier's age-depth relationship and contextualize these findings, age constraints were obtained from micro-¹⁴C dating and ³⁹Ar dating using atom trap trace analysis (ATTA) from a parallel ice core and additional shallow cores, integrated with the chemical dataset. This analysis determined that the glacier surface formed approximately 356 +19 -23  years prior to 2019. Additionally, the dating established a precise timeline for a significant levoglucosan and chemical peak at a depth of 6.4 meters, placing it roughly 779 +53 -63  years before 2019. The  radiometric age data were combined with an age model using the Raymond model, suitable for ice cap conditions like WSS.

Building on these insights, the regional significance of the prominent horizon at 6.4 m depth in the 2019 Weißseespitze ice core was explored by comparing the levoglucosan record with micro-charcoal data from the Schwarzboden mire in the Maneid valley, a few kilometers southeast of the glacier. This comparison revealed a striking correspondence, offering new insights into the region’s environmental history.

This study highlights the WSS glacier’s exceptional value as a long-term archive of pre-industrial pollution. However, with the industrial period already erased by ice mass loss, this archive is critically endangered. Projections suggest that 30% of the Ötztal glaciers could vanish by 2030, emphasizing the untapped potential of Eastern Alpine glaciers in reconstructing past environmental changes before they disappear.