Late-Holocene evolution of a small Sub-Arctic glacier, Gljúfurárjökull (Tröllaskagi, northern Iceland)

Abstract

Gljúfurárjökull, located on the Tröllaskagi Peninsula in northern Iceland, is a small glacier approximately 3.8 km in length. This study analyses the glacier's evolution through a combination of methods including: (i) geomorphological mapping, (ii) Cosmic-Ray Exposure (CRE) dating, (iii) lichenometry and (iv) palaeoglacier reconstruction (volume, extent and Equilibrium Line Altitude (ELA)) for each identified ice-marginal position. The mean CRE ages obtained are as follows: Glacial Phase 1: no samples available for CRE dating; Glacial Phase 2: 2.6±0.5 ka (n = 2); Glacial Phase 3: 3.2±1.1 ka (n = 7); Glacial Phase 4: 2.5±0.2 ka (n = 2); Glacial Phase 5: between 2.1 ka and a few hundred years. Lichenometry results for surfaces older than 130 years show inconsistencies both internally and in comparison with CRE ages. However, for the most recent glacier margins, lichenometric dates are coherent and align with historical photographic evidence. Accordingly, the ages proposed for glacier marginal positions 6 and 7 are 1899/1904 CE and 1912/1917 CE, respectively, slightly predating position 8, which is documented in aerial photographs from 1946 CE. The millennial- to centennial-scale evolution of Gljúfurárjökull outlined in this study is consistent with the patterns observed in debris-free glaciers across Tröllaskagi, as well as in many Icelandic and Arctic glaciers. Notably, the Little Ice Age (LIA) advance at Gljúfurárjökull was less extensive than earlier Neoglacial advances, a trend common in the Sub-Arctic and Arctic regions. Since the end of the LIA, the glacier has experienced a general retreat, interrupted only by a brief advance during the 1980s–1990s—again mirroring broader Arctic glacial behaviour. Overall, this study underscores the high sensitivity of Gljúfurárjökull to climatic fluctuations during the Late Holocene. The application of CRE dating reveals that the glacier's evolution aligns closely with patterns observed in other Icelandic and Arctic glaciers.