Skip to content

Sub-annual moraine formation at an active temperate Icelandic glacier

Research output: Contribution to journalArticle

This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterised by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognise two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low‐relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub‐annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub‐annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt‐driven squeeze events and (ii) larger push moraines formed during winter re‐advances. We suggest the development of this process‐form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed, and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice‐marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process‐form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin.
Original languageEnglish
JournalEarth Surface Processes and Landforms
Early online date7 Feb 2020
DOIs
Publication statusEarly online - 7 Feb 2020

Documents

  • Chandler_et_al-2020-Earth_Surface_Processes_and_Landforms

    Rights statement: This is the peer reviewed version of the following article: Chandler, B. M. P., Chandler, S. J. P., Evans, D. J. A., Ewertowski, M. W., Lovell, H., Roberts, D. H., Schaefer, M., and Tomczyk, A. M. ( 2020) Sub‐annual moraine formation at an active temperate Icelandic glacier. Earth Surf. Process. Landforms, which has been published in final form at https://doi.org/10.1002/esp.4835. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

    Accepted author manuscript (Post-print), 3.98 MB, PDF document

    Due to publisher’s copyright restrictions, this document is not freely available to download from this website until: 7/02/21

Related information

Relations Get citation (various referencing formats)

ID: 18804253