G012-0015
An Overview of Little Ice Age and Holocene Glacial Isostasy of the Patagonian Icefields

Monday, 14 December 2020
Poster
Erik Roman Ivins, JPL/Caltech, Pasadena, CA, United States, Maria Beatrice Magnani, Southern Methodist University, Dallas, TX, United States, Douglas Wiens, Washington University in St Louis, St. Louis, MO, United States, Emi Ito, University of Minnesota Department of Earth & Environmental Sciences and Limnological Research Center, Minneapolis, MN, United States, Andrew D Wickert, University of Minnesota, Department of Earth & Environmental Sciences and Saint Anthony Falls Laboratory, Minneapolis, MN, United States, Andreas Richter, TU Dresden, Dresden, Germany, Reinhard O R Dietrich, Dresden University of Technology, Dresden, Germany and GUANACO Team
Abstract:
This presentation will summarize past work on glacial isostatic adjustment (GIA) from both theoretical and observational points of view. We reflect on past progress and on the main scientific issues that remain unresolved, and which we think can be addressed with two new and very diverse data sets: (1) Data from high resolution seismic reflection and sedimentary coring in proglacial lakes of the Southern Patagonian Icefields: (2) New information about the deep solid Earth structure imaging. As GIA models are revisited with these new constraints in hand, we may expect to discover new insight into what role might be played by laterally varying rheology and the timing of Late Holocene glacial retreat. Inferences of steady-state creep strength from seismic imaging will help inform modelers of the sensitivity to the finer details of the glacial recession and unloading that causes rebound uplift rates measured with GNSS positioning to be so high: ~ 3-4 cm/yr. An environmentally important and enduring question regarding Little Ice Age (LIA) recession since the mid 19th century revolves around the character of loss in ice mass as a function of time. At least three quite different scenarios are possible: (i) The mass loss rate is high at the beginning of post-LIA maximum (pLIAmax), then decreases and later increases again, somewhat in sync with other mountain glacier systems in the late 20th Century. (ii) At the beginning of pLIAmax, rates are small and slowly grow to the values we determine in the early 1990’s. (iii) The starting pLIAmax rates are moderate and are subsequently characterized by small re-advances and larger retreats, ending in the retreat phase that has been well documented since the early 1990’s. Uncertainty (± 11 Gt/yr) in mass balance during the era of comprehensive space observations (beyond 2002) is also a factor in properly modelling the present-day viscoelastic uplift that is observed. Seismic reflections and lake coring data collected by the GUANACO field project will help distinguish between the differing glacial scenarios. Seismic imaging of the mantle by the broadband GUANACO seismic array will give the first definitive picture of the extent and structure of the regional slab window associated with the northward migrating oceanic ridge collision with the western margin of the continent (0–12 Ma).
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