Developing process-based models for the sediment and landform signature of glacilacustrine systems

Overview

Proglacial lakes, water bodies that form along the margins of ice sheets and outlet glaciers, are ubiquitous within previously glaciated regions and glaciated regions today. Quaternary lake records provide a wealth of palaeoenvironmental information (e.g. Benn, 1989; Palmer et al., 2019) that contribute to our understanding of ice-sheet and glacier response to changing climate. Today, as a response to current climate change, many temperate glaciers worldwide are retreating, resulting in the rapid increase in number and size of proglacial lakes (Carrivick and Tweed, 2013). Researching these rapidly developing and active proglacial lake systems provides important analogues to both enhance palaeoglaciological reconstructions as well as predict future changes associated with glacial retreat in deep water settings. Furthermore, this research has increasing societal relevance with respect to the significant impacts on ground conditions that palaeo-glacilacustrine sequences can have within the foundation zones of major infrastructure developments (e.g. windfarms) both onshore and offshore.

The formation of proglacial lakes results in the decoupling of the glacial margin from its outwash plain, or sandur, with the proglacial lake trapping much of the sediment that would otherwise be transported downstream (Bogen et al., 2015). Small proglacial lakes can be quickly infilled due to the vast amounts of meltwater-derived sediment, but larger lakes can persist in the landscape for longer, resulting in a complex sediment sequence preserved and interpreted in the Quaternary record (e.g, Benn, 1989; Palmer et al., 2019). Despite their importance, however, few recent studies have addressed process-form relationships within modern ice-contact lakes (cf. Gilbert, 1975; Gustavson, 1975) and relatively little is known about the dynamics of large scale systems associated with temperate ice-masses subject to contemporary rapid deglaciation (e.g. Ostrem et al. 2005). Instead, the majority of landsystems and ground models used in Quaternary science and engineering geology are derived from the sedimentary record. (e.g Benn, 1989; Bennett et al., 2000).

In Iceland, the outlet glaciers of the Vatnajökull ice cap have recently developed proglacial and supraglacial lakes at glacier termini as a response to rapid thinning and retreat (e.g., Fjallsjökull, Hoffellsjökull, Kviarjökull and Skeiðarárjökull). Changes of the glacier margin positions and lake extents are well documented (e.g. Thórarinsson, 1939; Schomacker, 2010, Evans et al. 2019; Guðmundsson et al., 2019) however, very little research has been conducted on the sedimentary processes within these active proglacial lakes (e.g. Churski, 1973). These recently formed proglacial lakes provide the ideal natural laboratory for a process-based study with known lake and ice-marginal histories, together with the opportunity to link climatic, lacustrine, and meltwater processes with sediment deposition and landform development.

Click on an image to expand

Image Captions

Oblique aerial photo taken in September 2019 of the snout of Skeiðarárjökull showing a number of proglacial lakes up to 4 km2 in area (Photo: Andy Russell).

Methodology

The sedimentary sequences captured in the recently formed proglacial lakes from SE Iceland will be derived from field data acquisition and the analysis of previously collected data.

Field expeditions will involve two seasons in SE Iceland in 2022 and 2023. A geophysical survey (swath bathymetry, acoustic sub-bottom profiling) will be undertaken on selected proglacial lakes. These data will be used to map the geomorphology of the lake floor, calculate the sediment volume and to visualise the acoustic stratigraphy of the buried lake sediments. Sediment cores will be collected to ground-truth the acoustic stratigraphy and allow laboratory-based lithofacies analysis. Lake temperature-depth profiles will be determined using strings of thermistors to identify meltwater input and thermal regime.

Sediment cores will be analysed in the laboratory. A number of methods will be used for lithofacies analysis. These include, core logging, X-radiographs, destructive physical property of the sediments and passive analysis using the GEOTek MSCL and XRF equipment.

Data analysis and visualisation: 3D seismic software (e.g. OpendTect and Kingdom Suite) will be used to visualise the data, and facies models of sedimentary architecture will be constructed from both the acoustic stratigraphy as well as the lithofacies analysis described above. From this, the student will produce a process-based depositional model of active proglacial lakes in rapidly deglaciating terrain.

Project Timeline

Year 1

Research design and development of detailed project methodology. Analysis of previously collected geophysical data. In-house training in geophysical data acquisition and processing will be provided. Field season 1.

Year 2

Analysis of field data and sediment cores, refinement of fieldwork methodology, analysis and visualisation of geophysical data. Field season 2

Year 3

Complete processing and analysis of field and remotely sensed data. Write draft publications; present work at conference; draft thesis.

Year 3.5

Complete and submit the thesis; finalise remaining publication manuscripts

Training
& Skills

The student will receive training in relevant GIS and geophysical techniques and specialist software packages. Training in field data collection techniques, such as seismic refraction surveys and sediment coring will be provided. The student will also receive bespoke lab-based training for lithofacies analysis. The student will partake in a RYHA Powerboat level II boat-handling course.

The student will be encouraged to write papers for publication throughout the duration of the project. The supervisory team will support the development in writing skills.

References & further reading

Benn D.I. 1989. Controls on sedimentation in a Late Devensian ice-dammed lake, Achnasheen, Scotland. Boreas, 18, 31-42.

Bennett, M.R. Huddart, D. and McCormick, T. 2000. An integrated approach to the study of glaciolacustrine landforms and sediments: a case study from Hagavatn, Iceland. Quaternary Sci. Rev., 19, 633-665.

Bogen, J., Xu, M. and Kennie, P. 2015. The impact of pro-glacial lakes on downstream sediment delivery in Norway. Earth Surf. Process. Landforms, 40, 942–952.

Carrivick, J.L., Tweed, F.S., 2013. Proglacial lakes: character, behaviour and geological importance. Quaternary Sci. Rev., 78, 34-52.

Churski, Z., 1973. Hydrographic features of the proglacial area of Skeiðarárjökull. Geographica Polonica 26, 209-254.

Evans, D.J.A., Ewertowski, M.W. & Orton, C. 2019. The glacial landsystem of Hoffellsjokull, SE Iceland: contrasting geomorphological signatures of active temperate glacier recession driven by ice lobe and bed morphology. Geografiska Annaler, 101A, 249-276 Guðmundsson, S., Björnsson, H., Pálsson, F., Magnússon, E., Sæmundsson, Þ., Jóhannesson, T., 2019. Terminus lakes on the south side of Vatnajökull ice cap, SE-Iceland. Jökull, 69, 1-34 Gilbert, R. 1975. Sedimentation in Lillooet Lake, British Columbia. Can. J. Earth Sci., 12, 697-1711.

Gustavson, T.C. 1975. Sedimentation and physical limnology in proglacial Malaspina Lake, southeastern Alaska. In: A.V. Jopling, B.C. McDonald (Eds.), Glaciofluvial and Glaciolacustrine Sedimentation, Society of Economic Paleontologists and Mineralogists Special Publication No. 23.

Østrem, G., Haakensen, N., Olsen, H.C., 2005. Sediment transport, delta growth and sedimentation in Lake Nigardsvatn, Norway. Geografiska Annaler 87A, 243e258 Palmer, A.P., Bendle, J.M., MacLeod, A. Rosea, J., Thorndycraft, V.R., 2019. The micromorphology of glaciolacustrine varve sediments and their use for reconstructing palaeoglaciological and palaeoenvironmental change. Quaternary Sci. Rev., 226, 105964.

Schomacker, A. 2010. Expansion of ice-marginal lakes at the Vatnajökull ice cap, Iceland, from 1999 to 2009. Geomorphology, 119 (3-4), 232-236

Thórarinsson, S. 1939. The ice dammed lakes of Iceland with particular reference to their value as indicators of glacier oscillations. Geografiska Annaler, 21A, 216–242.

Further Information

Dr Louise Callard (louise.callard@newcastle.ac.uk) Tel:+44 (0)191 2083806

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