The nature and use of trimlines for analysing 3-dimensional glacier change in rugged terrain

Reconstructions of former ice sheets and glaciers provide important palaeoglaciological information about their behaviour in response to climate changes. It is also possible to use such reconstructions to test and refine numerical glacial models, improving understanding of both palaeo and modern ice masses. The geomorphological evidence base for palaeoglacial reconstructions is often fragmentary, requiring interpolation across spatial gaps and estimation of ice thickness. These elements of subjectivity limit the robustness and reproducibility of reconstructions and this is particularly so in the rugged terrain of mountainous regions, where ice margins interact strongly with topography. This thesis aims to improve understanding of the geomorphological signature of ice margins in rugged terrain, in order to increase accuracy and confidence in producing empirical palaeoglacial reconstructions. An empirically-based method for improving interpolation between ice marginal landforms was investigated using characteristics of modern glacier-topography relationships. Despite much early promise in a pilot study, collection of sufficient data to underpin the method became too cumbersome, due to excessive measurement sensitivity in GIS analysis, and was abandoned for the purpose of this thesis. It is suggested that this avenue could be usefully continued with machine learning approaches. Glacial trimlines were then investigated because they assist both ice margin interpolation and constraint of palaeo ice thickness but have been under-utilised. A literature review on trimline characteristics and analysis of glacial trimlines in Svalbard led to a new classification scheme for their identification and interpretation, insights into controls on their formation and preservation, and examples of best practice for their mapping from remotely sensed imagery. As a proof of concept, glacial trimlines were combined with modelling to produce 3-dimensional reconstructions of the Little Ice Age geometry and volume of 15 glaciers in central western Spitsbergen, Svalbard. Glacier reduction to their modern size was found to be highly varied and related to topographic controls. The findings and recommendations of this research should be built on, in order to expand the use of glacial trimlines in palaeoglacial reconstructions and in the study of the impact of topography on glacier fluctuations.