Palaeoglacial and palaeoclimate inferences from cirque morphometry and spatial distribution across northern Patagonia (40o – 45o S)

Abstract

The evolution of the cryosphere and climate in northern Patagonia during the late Pleistocene are relatively well-known thanks to chronologies on ice-marginal features. However, this knowledge mainly represents the magnitude and duration of extreme cold intervals occurring during glacial maxima. Consequently, less is known about the state of the glaciers and climate during transitions between full glacial and interglacial stages. Given that morphometric attributes of glacial cirques are considered as robust indicators of palaeoglacial and palaeoclimate conditions during phases of minor glaciation, examining cirques will yield key insights to assess the typology of glaciers and associated climate conditions during those pivotal periods. In this study, we systematically analyzed the morphology and spatial distribution of 3081 cirques in northern Patagonia between ∼40o and ∼ 45o S. Our findings revealed that circular cirques, reflecting widespread long-lived small glaciers, dominate northern Patagonia. Eastward increase of cirque floor altitude from the coast to the continent along with prevailing east-to-south aspects indicate a key role of westerly-controlled climate and radiative balance in cirque development. Morphometry and spatial distribution of cirques along with statistical analyses indicate that annual total precipitation, minimum temperature, and incoming solar radiation altogether play a major role in cirque development in northern Patagonia, although the relative importance of these factors might vary spatially. Regional lithology exerts a secondary influence mostly in cirque geometry. We conclude that the most frequent state of the cryosphere within the Pleistocene glacial cycles in northern Patagonia is characterized by moderate glaciations similar to that existing during glacial terminations.