Changes in the Ice-Front Position and Surface Elevation of Glaciar Pío XI, an Advancing Calving Glacier in the Southern Patagonia Icefield, From 2000–2018

Abstract

Glaciar Pío XI has advanced and thickened over the past several decades in contrast to the generally retreating and thinning trends seen in other glaciers in the Southern Patagonia Icefield (SPI). To quantify recent changes in ice-front positions and glacier surface elevation over the ablation area of Glaciar Pío XI, we analyzed satellite data acquired from 2000 to 2018. Two major glacier termini, and most of the small outlet glaciers, showed advancing trends, including the largest advance (1,400 m), observed at the southern terminus during the study period. Surface elevation increased by 37.3 ± 0.4 m as a mean over the study area, and the rate of the increase accelerated by 135 ± 10% from Period 1 (2000–2007) to Period 2 (2007–2017/18). Elevation change during Period 1 was only slightly positive except for extraordinary thickening (∼20 m a−1) observed near the southern terminus and one of the outlet glacier fronts, whereas significant thickening (∼2.7 m a−1) occurred over the entire ablation area during Period 2. Satellite imagery showed an emergence of sedimentary mounds in front of the southern terminus, suggesting that reduction in frontal ablation and increasingly compressive flow regime are the main drivers of the recent rapid thickening and advance. Most likely, the influence of the sediment deposition on the southern terminus subsequently propagated to the northern terminus and upper reaches of the glacier. The rate of ice mass increase during the study period was 0.48 ± 0.03 Gt a−1, which corresponds to 4% of the total mass loss from the SPI from 2000 to 2015/16.

Increasing rate of 21st century volume loss of the Patagonian Icefields measured from proglacial river discharge

“…The scale of the sub-basins used in this study (Fig. 2) is therefore smaller than GRACE's spatial resolution and the increased rates of glacier volume loss we observe from hydrograph separation could be masked by reduced rates of glacier volume loss or even volume gain (Rivera and Casassa, 1999;Hata and Sugiyama, 2021) on the summit of the icefields or West-draining tidewater glaciers. We see no evidence of the 2008-2012 slowdown in the rate of mass loss which propose.…”

“…(2) Image-based measurements of glacier frontal ablation or areal change (Davies and Glasser, 2012;Sakakibara and Sugiyama, 2014;Hata and Sugiyama, 2021;. (3) Direct measurements of changes in ice-surface elevation or ice volume, through satellite altimetry or differencing of repeat digital elevation models Willis and others, 2012;Malz and others, 2018;Abdel Jaber and others, 2019;Hugonnet and others, 2021).…”

“…Upsala, Jorge Montt: Saito and others, 2013; Minowa and others, 2021), while others have remained stable or advanced (e.g. Perito Moreno, Pio XI: Skvarca and Naruse, 1997; Rivera and Casassa, 1999; Guerrido and others, 2014; Hata and Sugiyama, 2021).…”

Climatic and Morphometric Explanatory Variables of Glacier Changes in the Andes (8–55°S): New Insights From Machine Learning Approaches

“…Southward of 42 °S, the mean GAV estimated here (-24 ± 0.4% to -32 ± 1.3%) was higher than that observed by Meier et al (2018Meier et al ( ) (-9 ± 5%, 1986Meier et al ( -2016: this is likely related to differences in the study periods and also because we did not consider the large calving glaciers of the Patagonian ice-fields, where we found glacier outlines inconsistences, particularly in accumulation zones; these glaciers covering an area up to 13% of the total in South Patagonia and 20% in North Patagonia. Overall, we discarded the glacier growth due to methodological limitations, but this should have a limited impact because many studies have described a general glacier shrinking across the Andes (e.g., Malmros et al, 2016;Meier et al, 2018;Paul and Mölg, 2014;Rabatel et al, 2011;Rivera and Bown, 2013;Seehaus et al, 2019Seehaus et al, , 2020, with few exceptions that have been reported (Rivera and Casassa, 1999;Wilson et al, 2016;Hata and Sugiyama, 2021).…”

“…In the Dry Andes, an average GAV of -29% was estimated in the Desert Andes (Rabatel et al, 2011), similar to that observed by Malmros et al (2016) in the Central Andes (average of −30 ± 3%, . However, a sharp contrast was observed in the Wet Andes, where the Lakes District shows a GAV between -87% (1975-2007) and -20% (1961-2007) on different volcanoes (Rivera and Bown, 2013), in the North Patagonia this reduction was -25% (1985-2011, Paul and Mölg, 2014, and from the Northern Patagonian ice-field to Tierra del Fuego, Meier et al (2018) estimated an average GAV of -9 ± 5% including several exceptions of glacier advance, e.g., Glacier Pio XI in the Southern Patagonian ice-field (Hata and Sugiyama, 2021;Rivera and Casassa, 1999;Wilson et al, 2016).…”