Age of the Mt. Ortles ice cores, the Tyrolean Iceman and glaciation of the highest summit of South Tyrol since the Northern Hemisphere Climatic Optimum

Abstract

Abstract. In 2011 four ice cores were extracted from the summit of Alto dell'Ortles (3859 m), the highest glacier of South Tyrol in the Italian Alps. This drilling site is located only 37 km southwest from where the Tyrolean Iceman, ∼ 5.3 kyrs old, was discovered emerging from the ablating ice field of Tisenjoch (3210 m, near the Italian-Austrian border) in 1991. The excellent preservation of this mummy suggested that the Tyrolean Iceman was continuously embedded in prehistoric ice and that additional ancient ice was likely preserved elsewhere in South Tyrol. Dating of the ice cores from Alto dell'Ortles based on 210 Pb, tritium, beta activity and 14 C determinations, combined with an empirical model (COPRA), provides evidence for a chronologically ordered ice stratigraphy from the modern glacier surface down to the bottom ice layers with an age of ∼ 7 kyrs, which confirms the hypothesis. Our results indicate that the drilling site has continuously been glaciated on frozen bedrock since ∼ 7 kyrs BP. Absence of older ice on the highest glacier of South Tyrol is consistent with the removal of basal ice from bedrock during the Northern Hemisphere Climatic Optimum (6-9 kyrs BP), the warmest interval in the European Alps during the Holocene. Borehole inclinometric measurements of the current glacier flow combined with surface ground penetration radar (GPR) measurements indicate that, due to the sustained atmospheric warming since the 1980s, an acceleration of the glacier Alto dell'Ortles flow has just recently begun. Given the stratigraphic-chronological continuity of the Mt. Ortles cores over millennia, it can be argued that this behaviour has been unprecedented at this location since the Northern Hemisphere Climatic Optimum.

Lead and Antimony in Basal Ice From Col du Dome (French Alps) Dated With Radiocarbon: A Record of Pollution During Antiquity

“…PO 14 C measurements suggest that the CDK ice core extends to~5,000 ± 600 cal years BP (Figure 1). This is consistent with basal ice ages found at other Alpine sites, that is,~4,000 cal years BP (Hoffmann et al, 2018) and >10,000 cal years BP for two CG ice cores, and~7,000 cal years BP for Mount Ortles (3,905 m above sea level; Gabrielli et al, 2016). The CDK ice layer ages obtained from the PO 14 C measurements do not increase monotonically with depth as would be expected from well-behaved ice flow.…”

Understanding hydrological processes in glacierized catchments: Evidence and implications of highly variable isotopic and electrical conductivity data

“…The spatial variability of δ 2 H of glacier ice was remarkable and was not affected by elevation, as shown by the very depleted glacier ice sampled on 08/01/2014 ( Figure 2) and 08/31/2015 (Figure 3) in the lower part of the glacier. These very negative samples of glacier ice may have formed at high elevation during colder periods in the past, as suggested by recent ice core researches in the nearby Ortles glacier (Gabrielli et al, 2016), and the depleted glacier ice is now emerging in the lower ablation area of the glacier (Carturan, 2016).…”

Age ranges of the Tibetan ice cores with emphasis on the Chongce ice cores, western Kunlun Mountains

“…4), by applying a two-parameter flow model (2p model) (Bolzan, 1985 and in the Supplement). To avoid overfitting of the data and giving to much weight to individual data points, we prefer not to make assumptions about changes in accumulation, such as by applying a Monte Carlo approach Gabrielli et al, 2016). However, we understand that the 2p model is limited, though widely used for establishing the ice core chronology including the Dunde (Thompson et al, 1989) and the Puruogangri (Thompson et al, 2006) ice cores, and cannot account for the complex flow regimes close to the glacier bedrock.…”