Characteristics of lateral-frontal moraine formed at Arctic and Alpine glaciers
Recent climatic amelioration during the 20th and 21st centuries has stimulated the recession of glaciers world-wide. Moraines developed by valley glaciers provide a sedimentary record of their past response to climatic forcing. Despite the use of moraines for understanding the character and behaviour of former glaciers, our understanding of moraine development is lacking largely due to limited opportunities to study active moraine formation. This thesis reports on internal structure and sedimentary composition of lateral-frontal moraine at two Arctic (Austre Lovénbreen, Svalbard and Isfallsglaciären, Sweden) glaciers and one Alpine (Schwarzberggletscher, Switzerland) glacier and aids understanding of their palaeo-environmental significance. The internal structure and sedimentary architecture of Arctic lateral-frontal moraine is documented using ground penetrating radar (GPR) and via shallow excavation. Lateral-frontal moraine at both Arctic sites are shown to contain buried ice within their lateral zones, but not within their frontal zones, although the volumetric content of the buried ice and potential origin varies between sites. Frontal zones are therefore likely to be better preserved in the geomorphological record following complete de-icing, whereas lateral zones, which may also be subject to de-icing and external censoring from slope processes, may be poorly preserved. As the internal structure is dissimilar across Arctic sites, it is argued that the processes involved in the development of landforms by Arctic polythermal glaciers vary between high-Arctic and continental Scandinavian settings. Arctic lateral-frontal moraine are also distinct from those found at Alpine sites which are organised into stacked diamicton units that dip away from the lateral margin of the glacier. The sedimentary signature of Arctic and Alpine lateral-frontal moraine are investigated and compared. All moraines investigated exhibit clast-form gradients which is interpreted to relate to the relative significance and spatial variation of ‘active’ and ‘passive’ debris transport mechanisms within Arctic and Alpine valley glacier landsystems. However, the climatic, glaciological, and topographic regimes in which the moraines form influence the resulting character of the landform. The evolution of a degrading ice-cored moraine at Austre Lovénbreen is investigated using repeat photogrammetric topographic surveys. Relict glacier ice is undergoing moderate rates of degradation, predominately via down-wastage and could potentially be preserved as an archive of former high-Arctic glacier characteristics. This thesis also contributes to the wider body of knowledge in relation to the use of unmanned aerial vehicles (UAVs) and ‘Structure-from-Motion’ (SfM) photogrammetry for geomorphological research. The multi-technique approach employed by this research has allowed for the glaciological significance of subsets of lateral-frontal moraine (‘Controlled’, ‘Østrem’ and ‘Alpine’ type) within in glaciated valley landsystem to be better understood. Conceptual models accounting for landform development are presented and aid Quaternary studies that seek to identify and use lateral-frontal moraine for dating past glacier activity and determining palaeo-glacier characteristics.
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