G013-05
Solid Earth response of the Patagonian Andes to post-Little Ice Age glacial retreat: a multi-pronged approach

Monday, 14 December 2020: 05:46
Virtual
Maria Beatrice Magnani1, Emi Ito2, Douglas Wiens3, Andrew D Wickert4, Erik Roman Ivins5, Anastasia Fedotova1, Maximillian S. Van Wyk de Vries6, Hannah F Mark3, Shanti Bhattacharya Penprase7 and GUANACO Team, (1)Southern Methodist University, Dallas, TX, United States, (2)University of Minnesota Department of Earth & Environmental Sciences and Limnological Research Center, Minneapolis, MN, United States, (3)Washington University in St Louis, St. Louis, MO, United States, (4)University of Minnesota, Department of Earth & Environmental Sciences and Saint Anthony Falls Laboratory, Minneapolis, MN, United States, (5)JPL/Caltech, Pasadena, CA, United States, (6)University of Minnesota, Department of Earth and Environmental Sciences and Limnological Research Center, Minneapolis, MN, United States, (7)University of Minnesota Twin Cities, Minneapolis, MN, United States
Recorded Presentation
Abstract:
The Southern Patagonia Icefield (SPI), part of the largest southern hemisphere temperate ice complex on Earth, is uniquely positioned above a slab window and northward migrating triple junction, and characterized by rapid thinning over the past 50 years and by long-term high-amplitude ice fluctuations, which left behind significant and datable moraines. Aggressive retreat, following the Little Ice Age (LIA), ~300 yrs BP, is well documented in moraine systems preserved in the glacial valleys of proglacial lakes, where Patagonian glaciers have receded during the Holocene. Today the region experiences extremely high (~40 mm/yr) GPS uplift rates centered around the icefields, suggesting an isostatic relationship between the cryospheric mass imbalance and the solid Earth response.

A new multidisciplinary study, the GUANACO project, targets changes in SPI extent, erosional/depositional history, and solid Earth response to variations in surface loads. The project comprises acquisition and analysis of first-order observational constraints, and integration of these diverse new data through ice sheet and geodynamic modeling.

The project hinges on a five-pronged approach to: 1) illuminate the mantle structure as constraints on viscosity and lithospheric thickness; 2) image the glaciolacustrine sediment of glacial valleys and Lago Argentino, the largest proglacial lake draining the SPI; 3) core the imaged sediment; 4) reconstruct the glacial and erosional load; and 5) model the GIA response.

To date, project members deployed and recorded two years of data from 28 passive seismic stations across the Northern and Southern Patagonia Icefields, acquired ~350km of high-resolution seismic reflection multichannel and coincident CHIRP data in Lago Argentino and adjacent valleys, extracted 45 gravity and piston cores from the bottom of lake and glacial valleys, deployed three weather and three ablation monitoring stations on Glacier Perito Moreno, and collected extensive moraine samples for cosmogenic dating.

The broadband seismic data image the extent of the slab window in the upper mantle and resolve changes in lithosphere thickness across the region, while seismic reflection data and cores provide images and dating for the glaciolacustrine facies deposited following ice loss since the Last Glacial Maximum.

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