Browsing by Author "Nussbaumer, Samuel U."
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- Item10Be chronology of the Last Glacial Maximum and Termination in the Andes of central Chile: The record of the Universidad Glacier (34° S)(Elsevier Ltd., 2024) Fernández Navarro, Hans Andrés; García B., Juan Luis; Nussbaumer, Samuel U.; Tikhomirov, Dmitry; Pérez Mora, Francia Débora; Gartner Roer, Isabelle; Christl, Marcus; Egli, MarkusReconstructing mid-latitude glacier variations is a prerequisite for unveiling the interhemispheric climate linkages and atmospheric-ocean forcings that triggered those changes during the last glacial cycle. Nonetheless, the timing, magnitude, and structure of glacier fluctuations in the southern mid-latitudes remain incomplete. Here, we present a new Be-10 chronology of the Universidad Glacier in the Andes of central Chile (34 degrees S, 70 degrees W; similar to 2500 m a.s.l.) based on 21 cosmogenic-exposure ages of boulders on discrete moraine ridges defining former ice margins. Our findings include the mapping and dating of three moraines, UNI I, UNI II, and UNI III, located similar to 20 km, 15 km, and 10 km down-valley from the present-day glacier front, respectively. The Be-10 exposure ages of the UNI I moraine range from 135.9 +/- 7.1 to 51.4 +/- 2.7 ka (n = 3). The UNI II moraine gave a mean age of 18.0 +/- 0.9 (n = 15) and the UNI III moraine yielded a mean age of 13.9 +/- 0.8 ka (n = 3). The UNI I moraine implies the largest ice extent during a pre-Last Glacial Maximum (pre-LGM) period, including the penultimate glaciation. The UNI II is a moraine complex that represents cold and humid conditions in central Chile at the end of the LGM, which we attribute to the northward-shift of the Southern Westerly Winds (SWW). The UNI III moraine represents a return to glacial conditions interrupting the Termination, evidencing both a double-step deglacial trend observed through the southern middle and high latitudes at the end of the last ice age. The Andes at this subtropical latitude record a global signal of glacial and climate change.
- ItemDe-icing landsystem model for the Universidad Glacier (34° S) in the Central Andes of Chile during the past ∼660 years(2022) Fernandez, Hans; Garcia, Juan-Luis; Nussbaumer, Samuel U.; Janine Geiger, Alessa; Gartner-Roer, Isabelle; Perez, Francia; Tikhomirov, Dmitry; Christl, Marcus; Egli, MarkusReconstructing latest Holocene (< 1000 years) glacial landscape development in the Central Andes of Chile (30-35 degrees S) is key for understanding the response of the cryosphere during periods of negative glacier mass balance, such as the current one. The excellently preserved glacial landscape produced during the latest ice advance and retreat cycle is of particular interest for examining the detailed response of glaciers to deglaciation. To establish a conceptual model of glacier behavior under warm and dry climatic conditions, we reconstructed and dated the recent glacial history of the Universidad Glacier (34 degrees S) through detailed geomorphological mapping and Be-10 cosmogenic surface exposure dating. Our mapping describes a landsystem that spans from the current ice front to similar to 3 km down-valley, where a mosaic of glacial landforms includes mounded relief; sinkholes; debris -filled stripes; moraine belts; flutings; and a prominent basal till plain. Our Be-10 ages suggest that the Universidad Glacier has fluctuated in its forefield since the 13th - 15th centuries CE. We propose that the glacier evolved from a clean glacier to a debris-covered glacier, to an ice-cored moraine, and finally, to a massive dead-ice topography. This deglacial evolution intermittent and potentially reset by multiple standstills and/or re-advances during the overall retreat. The implication is that phases of active ice were followed by stagnation associated with progressive melting of dead ice under the supraglacial debris layer. Similar geomorphic features and processes are recorded in the present-day Universidad Glacier ablation zone, denoting a recurrent reconditioning over time analogous to the glacier's evolution during the latest Holocene.(C) 2022 Elsevier B.V. All rights reserved.
- ItemFluctuations of the Universidad Glacier in the Andes of central Chile (34? S) during the latest Holocene derived from a 10Be moraine chronology(2023) Fernandez-Navarro, Hans; Garcia, Juan-Luis; Nussbaumer, Samuel U.; Tikhomirov, Dmitry; Perez, Francia; Gartner-Roer, Isabelle; Christl, Marcus; Egli, MarkusThe reconstruction of glacier fluctuations during the latest Holocene (<1000 years) is necessary for understanding the climate context preceding the warmer conditions of the 20th and 21st centuries. The glacier records in the Andes of central Chile are suitably located to track former latitudinal changes of the Southern Westerly Winds (SSW), which are mostly unknown at this middle latitude region. Here, we present a reconstruction of the glacial fluctuations using Terrestrial Cosmogenic Nuclides (10Be) dating of boulders resting on moraines and other glacial landforms that make up the moraine complex in the forefield of the Universidad Glacier (34 degrees S). This massive and chaotic-looking moraine was built during the latest Holocene ice advances and subsequent decay of the Universidad Glacier to its present position. Geomorphological mapping and 10Be surface exposure ages (n = 20) show that the Universidad Glacier advanced at least twice to nearly the same maximum extent, first by the 13th to 16th centuries and then by the early to the mid-19th century. Since then, eight moraine ridges denote a rather active and gradual ice demise. We interpret the glacier advances as a response to an equatorward shift of the SWW linked to a long-term negative phase of the Southern Annular Mode (SAM), which embraced net humid and cold atmospheric conditions in central Chile between the 13th century and the mid-19th century. Our glacier chronology is comparable to others from Patagonia and New Zealand, altogether exposing the culmination of the latest Holocene glacial maximum by the mid-19th century, before overall ice decay in a global warming world, with accelerated ice loss since the mid-20th century. (c) 2022 Elsevier Ltd. All rights reserved.
- ItemGlacial to periglacial transition at the end of the last ice age in the subtropical semiarid Andes(Elsevier B.V., 2024) García B., Juan Luis; Carraha Molina, Javiera Paz; Fernández Navarro, Hans Andrés; Nussbaumer, Samuel U.; Pérez Mora, Francia Débora; Hidy, Alan J.; Gärtner-Roer, Isabelle; Haeberli, WilfriedAtmospheric warming and circulation reorganization at the end of the last ice age represent the most important climate change of the last 100,000 years and provide an opportunity to uncover how the southern subtropics cryosphere responded to strong changes in the global climate system. Extensive mapping and chronologic records on cryogenic landforms to better understand the association and interactions between glaciers and viscous creep of ice-rich permafrost landforms (rock glaciers) are widely missing in the region. In this paper, we reconstruct the geomorphic imprint of the Last Glacial Maximum (LGM) and the Termination I in the high Andes of the Río Limarí Basin (30–31°S) in the subtropical semiarid Andes of Chile. 74 new 10Be surface exposure dating ages constrain the timing of glaciation, deglaciation, and glacial to periglacial transition. Glacial advances occurred first by 41.2 ± 0.6 – 35.0 ± 0.5 ka during Marine Isotope Stage 3, but probably earlier also; then, a second advance occurred during the global LGM between 24.2 ± 0.4 and 18.6 ± 0.2 ka. Deglaciation by 17.6 ± 0.2 ka left extensive hummocky moraines on the main valleys. Characteristic patterns of furrows and ridges typical of rock glaciers and solifluction superimposed on the LGM hummocky moraine indicate ice-rich permafrost in glacial deposits likely between 15.5 ± 0.3 and 13.6 ± 0.3 ka. We propose that moraines deposited by LGM debris-covered glaciers served as a niche for strong seasonal frost and permafrost creep, which substantially modified the original landforms. Our results contribute to a better understanding of major transformations in an ice-rich high mountain area of the southern hemisphere where the interplay of temperature and precipitation changes drove glacial to periglacial transitions.
- ItemGlacier inventory and recent glacier variations in the Andes of Chile, South America(2017) Barcaza, Gonzalo; Nussbaumer, Samuel U.; Tapia, Guillermo; Valdes, Javier; García B., Juan Luis; Videla, Yohan; Albornoz, Amapola; Arias, Victor
- ItemLate Pleistocene to Holocene glacial, periglacial, and paraglacial geomorphology of the upper Río Limarí basin (30-31° S) in the Andes of central Chile(Taylor & Francis Group, 2024) Carraha Molina, Javiera Paz; García B., Juan Luis; Nussbaumer, Samuel U.; Fernández Navarro, Hans Andrés; Gartner-Roer, IsabelleWe present a field-based reconstruction of the geomorphology in the Subtropical Andean mountains of the Limari basin, semiarid central Chile (30-31 degrees S). Fieldwork campaigns and remote-sensing analysis served for detailed geomorphological mapping at four formerly glaciated valleys in the heads of the Combarbala and Rio Hurtado sub-basins. We identify a mosaic of glacial, periglacial, and paraglacial landforms. Glacial landforms include a massive dead-ice moraine complex, with thermokarst and debris-filled fractures suggesting former ice-cored moraine degradation. This landform is superimposed by transversal and arcuate ridges suggesting active-ice processes. Periglacial landforms such as rock glaciers, gelifluction, and protalus lobes occur in cirques and U-shaped valleys, but also on moraine deposits. Paraglacial processes are indicated by talus accumulation in those formerly glaciated slopes. The geomorphological imprint is evidence for the interaction and succession between glacial, periglacial, and paraglacial dynamics from the Late Pleistocene to the present.