The glacial landsystem of a tropical glacier: Charquini Sur, Bolivian Andes

The geomorphological signature of tropical glaciers has the potential to provide important information on the response of ice masses in high-mountain environments to climate warming. This study investigates the glacial geomorphology of Charquini Sur, Bolivia. Detailed geomorphological mapping was conducted both in the field and from satellite imagery in order to produce a 1:4,000 scale geomorphological map of the glacier foreland. Sedimentological analyses (description of physical characteristics, clast shape and roundness, particle-size distribution) provided additional insight into the landform-sediment assemblage. Glacial landforms are well preserved and include up to 11 moraine ridge suites, seven of which are cross-valley frontal moraine arcs. These can be linked to an existing lichenometric chronology from previous work and record glacier recession since the local Little Ice Age (LIA) maximum in the late-1600s. Lateral moraine ridges also record continuous thinning of the glacier over this time period. Smaller groups of parallel ridges are interpreted as annual moraines formed during recession. Intermorainic areas consist of flutings and a typically thin sediment cover of subglacial, supraglacial and glaciofluvial origin, with prominent ice-moulded bedrock protuberances in places. Analysis of the landform-sediment assemblage provides an insight into the main controls on landform genesis in the basin and implies there have been temporal changes in ice-marginal dynamics since the LIA. We present the first landsystem model for a tropical cirque glacier, documenting its behaviour since the LIA and providing an indication of glacier response in rapidly-warming high-mountain environments.