Solid Earth response of the Patagonia Andes to post-Little Ice Age glacial retreat

The goal of this proposal is to provide first-order observational constraints on glacial isostatic adjustment (GIA) around the rapidly shrinking Southern Patagonian Icefield (SPI), where the fastest uplift rates on the planet have been measured. This region offers a unique opportunity to understand how complex tectonics including a volcanic arc and "slab window" may strongly influence GIA. In this study, we propose a five-pronged approach to constrain the ice sheet and erosional/depositional history as well as the solid Earth response, and to integrate the results through ice sheet and geodynamic modeling. We propose to: 1) deploy an array of 28 broadband seismographs around the SPI to image mantle structure and provide independent constraints on the 3D viscosity structure and lithospheric thickness required for GIA modeling; 2) collect 480 km of high resolution marine seismic reflection data on the largest glacial lake in the region (Lago Argentino), where eight outlet glaciers drain, to determine submerged former ice frontal positions, and rates and patterns of erosion/deposition; 3) collect ~20 10m-long piston cores from the lake and glacial valleys to provide an annually resolved sediment record that will help constrain the interpretation of marine seismic data; 4) establish the terrestrial chronology of deglaciation through mapping and dating; and 5) build models of erosion, deposition, ice dynamics, and GIA, that together will simulate the geophysical state and glacial history of the SPI and its environs.