Evolving glacier landsystems during Patagonian Ice Sheet recession influenced by a changing topographic setting

In mountain icefield settings, such as the southernmost Andes, topography has a strong influence on the pattern and magnitude of glacier retreat in response to palaeoclimate. We investigate the geomorphic signature of the Río Cisnes palaeo-outlet glacier in northeast Patagonia, which retreated over a reverse-bed slope following the local glacial maximum. Glaciation of this valley was associated with a range of erosional, ice-contact, subglacial, glaciofluvial, and glaciolacustrine landforms. Using process-form regimes from modern analogue environments, we interpret landforms within a glacial landsystems framework. We develop a conceptual model that demonstrates both temporary and permanent changes in glacial landsystems, also reflecting changes in the strength of glacier-climate coupling. Specifically, we identify three components of the mountain icefield landsystem that relate to spatiotemporal changes during deglaciation: 1) the active temperate outlet lobe landsystem, 2) the temperate glaciolacustrine-calving outlet glacier landsystem and, 3) the temperate cirque and valley glacier landsystem. The temperate glaciolacustrine-calving outlet glacier landsystem is characterised by two distinct developmental phases: i) Early stage — Drainage via Atlantic spillway and, ii) Late stage — Atlantic spillway abandonment. The spatial evolution of landsystems and phases therein were influenced by a complex regional topographic setting, which forced landsystem overprinting by the development of a large ice-dammed lake during glacier recession. These landsystems display patterns and characteristics that are likely to be repeated across other eastern outlet valleys of the Patagonian Andes, with implications for interpreting palaeo-glacier chronologies. • Conceptual landsystems model for Patagonian palaeo-outlet glacier reflects regional topography. • Spatiotemporal changes to landsystems were paced by the regional reverse-bed slope and topography. • Landsystems presented here are likely to be reflected across other Patagonian outlet valleys. • Detailed landsystems work should be conducted prior to generating chronological datasets.