Evolution of glaciers in the Northern Greater Caucasus (Elbrus region, Russia) during the Little Ice Age and older Holocene periods based on historical documents, tree-rings and cosmogenic dating

Located on the border of Europe and Asia, in between the Black and the Caspian seas, the Greater Caucasus is one of the world’s highest mountain systems, containing a glaciated total area of ~1200 km2. Yet, its glacier long-term chronology is still poorly constrained in comparison with other glaciated regions of the Northern Hemisphere and therefore the response of its glaciers to global low- and high-frequency climate forcings. In the Northern Greater Caucasus (Elbrus region, Russia), a number of informative data addressing Neoglacial glacier evolution have already been undertaken using methods such as historical data, remote sensing, tree-rings, lichenometry and radiocarbon dating of paleosols. The size and timing of major advances of the glaciers in this region is relatively well known after the 1880s thanks to first maps, while earlier advances were identified by tree-rings and lichenometry. However, little is known about glacier fluctuations older than the 19th century. In particular it remains puzzling if the Little Ice Age (LIA) glaciers extent in this region corresponds to the maximum glacier extent of the Holocene as generally assumed in the northern mid-latitudes in consistency with the Late Holocene decreasing trend of summer insolation. In order to complement this comprehensive existing corpus of data, we investigated seven glaciers’ forefields for cosmic-ray exposure (CRE) dating during field campaigns (2000s-2021). We present the first 10Be and 36Cl glacier chronologies from moraine boulders samples collected in glacier valleys of Greater Azau, Terskol, Kashkatash, Bashkhara, Schkhelda, Donguz-Orun and Irik. Results are spanning from ~3000 to ~300 yrs ago, which provide new insights on Neoglacial glacier variations. The oldest glacier culmination is identified by CRE dating at ~3000 yrs ago in the Greater Azau valley, which contrasts with the previously assigned minimum tree-ring dates of moraines with the oldest tree dated back from the 16th century (Solomina et al., 2022). Similar results were evidenced at the base of Bashkhara ~3200 yrs ago. Subsequent glacier advances were observed at ~2500 yrs at Terskol and at ~1600-1800 yrs ago in the Irik valley. Here, we notice that the pre-LIA glacier extents were not too far away from the subsequent LIA glacier advances as these moraines are spatially close to the LIA. The successive glacier advances occurred during the LIA that locally begun at ~600-800 yrs ago, as reported by CRE moraine dating in Donguz-Orun, Kashkatash and Terskol glaciers’ forefields. Other LIA glacier culminations are documented in Kashkatash valley at ~250 and ~150 yrs ago and in Schkhelda valley at ~160 yrs ago. More locally, it corroborates results from the Southern Caucasus (Tielidze et al., 2020) and the local Karakel lake sediment records (Teberda valley; Alexandrin et al., 2023). Our observations evidenced for the first time early Neoglacial glacier advances, which reveals that the LIA was not the largest Holocene extent in this region confirming recent observations in the Alps or in Greenland. This suggest the influence of additional climate forcings, superimposed on summer insolation with comparable effects on glacier size in Northern Caucasus that need to be further explored.