Long term records and impacts of glacially-fed river systems in Patagonia

This research focuses on the long-term changes in fluvial geomorphology and sediment dynamics at the Rio Chubut (Argentina). The aim is to develop a geomorphological history and test the environmental drivers responsible for the temporal changes in geomorphic development.
Quaternary scientists study the past behaviour of the Patagonian ice sheet to aid understanding and projections of the environmental impact of contemporary climate change (Darvill et al, 2017; Boex et al, 2013; Glasser et al, 2008). Expansion and recession of the ice sheet and its glaciers cause geomorphic change in the environmental systems that it is coupled to. This includes proglacial lakes which have been studied for their high resolution varve records (Bendle et al, 2017). However, the extensive network of river systems that drain the ice sheet melt water depending on the extent of the ice, are understudied in the region despite being highly sensitive to ice dynamics and environmental change.
Research methods for this study begin with the mapping of geomorphology using remotely sensed data e.g. aerial imagery of the Rio Chubut to identify geomorphic units that indicate past environmental conditions. Small scale metric data such as channel width and meander wavelength has been collected from abandoned river channels to infer historic water supply and energy levels in the system. Fieldwork has been completed in Oct/Nov 2019 where geophysical survey, sediment description and sampling for luminescence dating was carried out to collect more data on channel characteristic, sediment supply and to constrain a chronology of change respectively. The data collected in the field will ultimately inform a luminescence-based landform chronology (to be completed in year 2) and hydrogeomorphological modelling (to be completed in year 3) which can test hypotheses on the magnitude, frequency and time scale of fluvial change.
Fluvial change in this region has wider significance given the deglacial decoupling from ice masses and the interaction with the Southern Westerlies, and other hydroclimate parameters e.g. El Nñio Southern Oscillation (ENSO), the loss of glacial waters from fluvial systems is a growing concern in Patagonia forming a key water supply sources. Characterising the dynamics and long term evolution of past fluvial systems through glacial, deglacial and postglacial times forms a valuable analogue for understanding future changes,
In summary, this project will develop insight into the way rivers formerly fed by glacial outwash have responded to climate shifts during and after the major glacial episodes of the late Quaternary.

References
Bendle, J.M., Palmer, A.P., Thorndycraft, V.R. and Matthews, I.P., 2017. High-resolution chronology for deglaciation of the Patagonian Ice Sheet at Lago Buenos Aires (46.5 S) revealed through varve chronology and Bayesian age modelling. Quaternary Science Reviews, 177, pp.314-339.

Boex, J., Fogwill, C., Harrison, S., Glasser, N.F., Hein, A., Schnabel, C. and Xu, S., 2013. Rapid thinning of the late Pleistocene Patagonian Ice Sheet followed migration of the Southern Westerlies. Scientific reports, 3, p.2118.

Darvill, C.M., Stokes, C.R., Bentley, M.J., Evans, D.J. and Lovell, H., 2017. Dynamics of former ice lobes of the southernmost Patagonian Ice Sheet based on a glacial landsystems approach. Journal of Quaternary Science, 32(6), pp.857-876.

Glasser, N.F., Jansson, K.N., Harrison, S. and Kleman, J., 2008. The glacial geomorphology and Pleistocene history of South America between 38 S and 56 S. Quaternary Science Reviews, 27(3-4), pp.365-390.