Perito Moreno glacier: a multidisciplinary study on its Late-glacial and Holocene dynamics

LOZANO, JORGE G.; CAFFAU, MAURO; VILAS, JUAN F.; DONDA, FEDERICA; GROSSI, MAURIZIO; TASSONE, ALEJANDRO; BRAN, DONALDO M.; BARADELLO, LUCA; LODOLO, E.

Trieste

Congreso; 90° CONGRESSO DELLA SOCIETÀ GEOLOGICA ITALIANA; 2021

Società Geologica Italiana

Perito Moreno glacier is one of the most studied glaciers in Patagonia, and probably the most well-known in the world. Currently, it has two calving fronts in Lago Argentino, one discharging within Brazo Rico/Brazo Sur to the east and the other within Canal de Los Témpanos to the north. Whereas most of the Lago Argentino outlet glaciers underwent considerable ice mass loss and retreated during the last 80?100 years, Perito Moreno glacier shows an apparent anomalous behavior and may be regarded as having been stable since 1920. Periodic advances of the Perito Moreno glacier?s front form a natural ice dam as it progresses across the rocky shore of the Magallanes Península. That event blocks the water flow from the Brazo Rico?Brazo Sur arms of Lago Argentino, raising their water level. Spectacular water outburst have occurred semi-periodically when the ice-dam collapsed, as the most recent episode of March 12, 2018.Between November 2017 and April 2019, OGS and CONICET-University of Buenos Aires performed three geophysical surveys in the lake arms hosting Perito Moreno glacier, i.e., Brazo Rico/Brazo Sur and Canal de Los Témpanos. These campaigns have been financed by the Italian Ministero degli Affari Esteri e della Cooperazione Internazionale (MAECI) and Ministerio de Ciencia y Tecnología (MinCyT) within a bi-lateral Italian-Argentinean scientific collaboration. High-resolution seismic profiles, complemented with bathymetric profiles, have allowed to map the whole lake floors of Brazo Rico/Brazo Sur and the southern part of Canal de Los Témpanos, and to identify the main seismostratigraphic units within the glacio-lacustrine cover (Lozano et al., 2020). In addition, several sediment cores have been recovered from a small inlet in the eastern sector of Brazo Sur. All these data represent an unprecedented geological and geophysical dataset which allowed us to: (i) propose an evolutionary scheme, albeit simplified, of the Late-glacial dynamics of the Perito Moreno, based on the sequence of moraines identified along the two arms of Lago Argentino (Lodolo et al., 2020a); (ii) constrain the latest major advance of Perito Moreno glacier, occurred at ca. 6000 kyrs BP (Lodolo et al., 2020b); (iii) provide evidence of a Little Ice Age ice-damming episode (324-266 cal yrs BP) as revealed by radiocarbon dating of a vegetal fragment found near the top of a recovered sediment core (Caffau et al., under review).The outcomes of our studies represent a further step to decipher the complex glacial dynamics of southern Patagonia, and highlights the key role played by both subaqueous glacial bedforms as signatures of the glacier imprints within lake floors and by glaciolacustrine deposits as archives of information for decoding past climatic conditions at high latitudes.