The submerged footprint of Perito Moreno glacier

Emanuele Lodolo,Jorge Lozano,Luca Baradello,Donaldo M Bran,Alejandro Tassone,Federica Donda,Roberto Romeo

doi:10.1038/s41598-020-73410-8

Abstract

Perito Moreno is the most famous calving glacier of the South Patagonia Icefield, the largest temperate glacier system of the Southern Hemisphere. Unlike most of the glaciers in the region that have strongly retreated in recent decades, the position of Perito Moreno glacier front remained relatively unchanged in the last century. However, earliest photographic documents show that, at the end of the nineteenth century, the front was ca. 800 m behind the current position. There is no reliable information about the positions of the Perito Moreno front in earlier times. Here we show evidence of two subaqueous moraine systems both in the Canal de Los Témpanos and in the Brazo Rico, the two arms of Lago Argentino along which Perito Moreno glacier has flowed over time. These moraines, identified for the first time in the Canal de Los Témpanos from bathymetric and high-resolution seismic profiles, mark the position of the largest glacier advance, tentatively correlated with the moraines of the “Herminita advance” identified and dated onland. We interpret these bedforms as the evidence of the most pronounced advance of Perito Moreno glacier during the mid-Holocene cooling event that characterized this sector of the Southern Hemisphere. This study highlights the importance of subaqueous glacial bedforms, representing decisive records of the glacial history and palaeoclimate, which could help unveiling the origin of the different behavior of glaciers like Perito Moreno that in a warming climate are relatively stable.

Highlights

In Patagonia there is considerable evidence, provided by studies on moraine systems, landforms and stratigraphic records, that glaciers and icefields have expanded and contracted in the past in response to variations in climate systems[1,2,3]
Among the several subaqueous moraine ridges identified on the lake-floor along both Brazo Rico and Canal de Los Témpanos, the closest glaciogenic bedforms to the present-day Perito Moreno front are represented by two moraine systems which border two almost flat lake-floor depressions, ca. 170 m deep (Fig. 1C)
Exposure ages range from 5.2 ± 0.4 to 4.6 ± 0.4 kyr on the outer Pearson moraines near Lago Argentino, and from 5.7 ± 0.5 to 4.5 ± 0.4 kyr on the Herminita Península[5]

Summary

Introduction

In Patagonia there is considerable evidence, provided by studies on moraine systems, landforms and stratigraphic records, that glaciers and icefields have expanded and contracted in the past in response to variations in climate systems[1,2,3] In this region, the icefields are nourished by mid-latitude weather systems characterized by abundant precipitation, causing high ablation rates, steep mass-balance gradients and high ice v elocities[3]. The glacier advances between June and December, and retreats between December and April, with a seasonal variation in its position of ± 65 m21 possibly due to frontal ablation (subaqueous melting), which is correlated with seasonal lake water temperature v ariations[12] This leads to recurrent cycles of advance, closure, damming, flood, failure and subsequent retreat of the glacier front. It has registered numerous front advances at irregular intervals since the end of the nineteenth century, whereas over the past decade, it has shown short-term advances and r etreats[21]

Methods

Results

Conclusion