Disentangling topographic and climatic controls on glacier length: A case study in the tropical Colombian Andes

Reconstructing past climate from moraine records is complicated by the influence of non-climatic factors, particularly topography, on glacier extent. Such topographic controls have been widely identified in the literature, but a systematic quantitative assessment of their effects on glacier extent is lacking. Here, we investigate the relative influence of topographic and climatic factors on tropical glacier length variability in the Sierra Nevada del Cocuy, Colombia using a coupled ice-flow–energy-balance glacier model. Employing a parameter sweep over 450 topographic scenarios and 40 climatic scenarios for a total of 18,000 unique topo-climatic scenarios, we identify a critical transition in glacier length around 5 °C to 6 °C below modern temperature where variability in inter-valley glacier length shifts from headwall elevation-controlled to valley slope-controlled. We show through a relative weights analysis that, for this particular topo-climatic parameter space, climate accounts for 84% of the modeled variability in glacier length, while topography contributes 16%. Among climatic variables, temperature plays a more dominant role than precipitation, and headwall elevation influences glacier length most of any topographic variable. After accounting for all possible combinations of parameter subsets, we find that a sizable portion of topo-climatic scenarios (22%) yields glacier lengths dominated by topographic factors rather than climatic factors. These findings highlight the complex interplay between climate and topography, demonstrating that topography, though typically secondary to climate, has a notable impact on glacier length in this particular glacier regime. As such, this study provides a framework for quantifying the relative contributions of climate and topography to glacier evolution, critical for interpreting past glacier extents and predicting future changes.