Topographic controls on moraine morphology and density at two neighbouring plateau icefield outlet glaciers.

Topography is a key control on how glaciers and ice caps respond to changes in climate, modulating or amplifying the effects of climate change. Topographic controls, such as glacier hypsometry, debris supply, valley width, basin topography, topographic pinning points, bed gradient, and slope can exert a demonstrable impact on glacier dynamics and therefore moraine formation. However, there has been limited research exploring how topographic boundary conditions (such as the local angle of slope and changes in bed topography) can influence patterns of moraine formation across forelands, both in time and space. Given that it is frequently assumed that ice-marginal moraine patterns can be directly correlated with climate and thus used as proxies for glacier-climate interactions, it is important to improve understanding of topographic controls on ice-marginal processes.

Here we present a case study of topographic controls on ice-marginal moraine morphology and density at Midtdalsbreen and Blåisen, outlet glaciers of the plateau icefield Hardangerjøkulen, Norway. We combine geomorphological mapping of moraines with a statistical approach to quantify moraine density and its relationship to topography, with the aims of (a) establishing the distribution of ice-marginal landforms at Midtdalsbreen and Blåisen, and (b) investigating the influence of topography on the patterns of landform deposition and morphology. This approach shows that topography, in addition to a range of climatic and glaciological controls, influences ice-marginal moraine morphology and density at both local and foreland-wide scale. This highlights the need to consider the ways in which topography acts as a control on the patterns of moraine formation before using moraines as proxies to infer changes in glacier dynamics.