The potential of glacial cirques as a paleoclimatic proxy in northern Patagonia

Abstract:

In Patagonia, glacial landforms, especially moraines, have proved to be a valid source of paleoclimatic information, especially as tracers of the past position and intensity of the Southern Westerly winds and climate in general. However, the potential of cirques, both with and without current glaciers, as a regional paleoclimate proxy have remained practically unstudied. In order to fill this gap, here we explore the factors controlling the morphology and spatial distribution of ~1431 cirques in northern Patagonia (~40^o - ~44^o S). We used the ACME tool for ArcGIS 10.4 to extract cirques morphometric parameters from an ALOS PALSAR digital elevation model and MatLab for statistical analysis. Our preliminary findings show that cirque floor altitude increase by ~2100 m more or less linearly inland or eastward from the Pacific, suggesting a key role of westerly delivered moisture in altitudinal distribution of regional cirques. Additionally, the prevailing southeastern aspects likely reflect the influence of westerly circulation as well (e.g., in the lee), and shade in the afternoon. Other potential controlling factors such as dominant lithology and main fracture network seem to play a secondary role in cirque geometry and spatial distribution. Our results strongly indicate that the hypsometry (r² -0.66), cirque floor altitude (r² -0.71) and aspect of the northern Patagonian cirques are mostly controlled by climatic factors, specifically by precipitation patterns and temperature, and, therefore, they are suitable as indicators of regional past climate conditions.