Structural evolution during cyclic glacier surges 1: Structural glaciology of Trapridge Glacier, Yukon, Canada

Interpreting the relationships among the internal processes of glaciers and their mesoscale structural products has been a longstanding challenge for glaciologists. Trapridge Glacier is a small polythermal surge‐type valley glacier that has been studied for 40 years. It offers an opportunity to investigate the structural evolution of a glacier through a series of surges, and to apply novel modeling approaches to gain physical insight as to how different structures are formed. Following the glacier's most recent slow surge, the structural attributes were documented, with emphasis on their three‐dimensional geometry and sequential development: ice stratification (S0), longitudinal foliation (S1) and associated medial moraine, folding of stratification (F1), transverse foliation (S2), thrusts (S3) and recumbent folds (F3), fractures (surface crevassing and crevasse traces) (S4). Efforts to represent these structures using models of glacier flow dynamics remain at an early stage but provide informative tests of model skill and of current understanding of the processes that control structure generation. Using field interpretations as a guide to the relevant processes of formation, structures on Trapridge Glacier are compared with computer‐simulated structures for the same glacier. Modeling achieved the greatest success in simulating moraine patterns, ice stratification, longitudinal foliation, and the downglacier decrease in the density of surface crevasse traces. The least successful effort was to simulate the orientation of crevasse traces.