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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. 

Many floating ice shelves in Antarctica buttress the ice streams feeding them, thereby reducing the discharge of icebergs into the ocean. The rate at which ice shelves calve icebergs and how fast they flow determine whether they advance, retreat, or remain stable, exerting a first-order control on ice discharge. To parameterize calving within ice sheet models, several empirical and physical calving “laws” have been proposed in the past few decades. Such laws emphasize dissimilar features, including along- and across-flow strain rates (the eigencalving law), a fracture yield criterion (the von Mises law), longitudinal stretching (the crevasse depth law), and a simple ice thickness threshold (the minimum thickness law), among others. Despite the multitude of established calving laws, these laws remain largely unvalidated for the Antarctic Ice Sheet, rendering it difficult to assess the broad applicability of any given law in Antarctica. We address this shortcoming through a set of numerical experiments that evaluate existing calving laws for 10 ice shelves around the Antarctic Ice Sheet. We utilize the Ice-sheet and Sea-level System Model (ISSM) and implement four calving laws under constant external forcing, calibrating the free parameter of each of these calving laws for each ice shelf by assuming that the current position of the ice front is in steady state and finding the set of parameters that best achieves this position over a simulation of 200 years. We find that, in general, the eigencalving and von Mises laws best reproduce observed calving front positions under the steady-state position assumption. These results will streamline future modeling efforts of Antarctic ice shelves by better informing the relevant physics of Antarctic-style calving on a shelf-by-shelf basis.