Holocene Glacial–Paraglacial–Periglacial Transitions of a Sub‐Arctic Glacial Cirque, Fremri‐Grasárdalur, Northern Iceland

The aim of this work is to study a variety of glacial, periglacial and paraglacial features found in a small cirque, Fremri‐Grasárdalur, in Tröllaskagi (Northern Iceland). We implement a multidisciplinary approach combining high‐resolution geomorphological mapping, horizontal/vertical boulder displacement (from 1994 to 2019) and surface exposure dating of the abovementioned features by means of 36Cl cosmic‐ray exposure (CRE), Schmidt Hammer (SHD) and lichenometry. CRE and SHD dating indicate that the cirque deglaciation took place during the Early Holocene, c. 10.7–9.1 ± 1.1 ka. During the Late Holocene, the cirque was occupied by three distinct small glaciers, with asynchronous behaviour. Two of them, developed polygenic ice‐cored moraines over the course of at least three phases of glacial advances at 2.3–2.8 ± 0.4 ka, 1.8–1.4 ± 0.2 and 0.5 ± 0.1 ka, indicated by CRE and SHD dating of moraine boulders. While the third glacier in the cirque was also debris‐free, through the Late Holocene, it transitioned into a debris‐covered glacier. Following the Little Ice Age (LIA), all three glaciers exhibit retreat, with the recent decades exhibiting the most significant ice‐mass loss. The ongoing demise of the cirque glaciers has led to a detachment of the debris‐covered terrain from the remnant ice within the headwall—separated by a depression. The chronology inferred from the lichenometric data clearly shows the gradual retreat that formed this depression, between the late 19th century (~1890 ce) and the present day. One rock glacier was formed from the ice‐cored moraines and talus rock glaciers are present at the foot of the walls. Boulder displacement tracking data show that subsidence prevails in all debris mantle landforms, reflecting degradation of the inner ice core, while horizontal displacement is limited.