GM7.3

The Upper Garonne Basin constituted the longest glacier of the Pyrenean ice field during the Late Pleistocene. From the peaks of the axial Pyrenees that exceed 2,800-3,000 m, the Garonne palaeoglacier flowed along ~80 km northwards during the major glacial advances reaching only 420-440 m. This palaeoglacier reached the Pyrenean foreland, at the Loures-Barouse-Barbazan basin (LBBB) where it formed a terminal moraine complex that is examined in this work. We have constrained the timing of the maximum glacial extent as well as the onset of the deglaciation from the end of the Last Glacial Cycle (LGC) based on the geomorphological observations and a 12-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. There are two moraine systems at the LBBB, where the first is composed of weathered ridges at the outermost part of the basin and the second encompasses well-preserved ridges stretching across the innermost part of the basin. Chronological data shows that the external moraines were abandoned by the ice at the end of the Penultimate Glacial Cycle (PGC) and the onset of the Eemian Interglacial, at ~129 ka. The few existing reliable boulders to date in the internal moraine showed inconsistent ages as they were probably affected by post-glacial processes and therefore, this work adds no evidence of subsequent glacial advances or standstills during the LGC in the LBBB. However, the terminal basin was already deglaciated during the global Last Glacial Maximum (GLGM) at 24-21 ka, as revealed by exposure ages from polished surfaces at the confluence of the Garonne-la Pique valleys, 13 km south of the entrance of the LBBB. This study introduces the first solid CRE database in the Pyrenees for the glacial advance that occurred during the PGC and provides also new evidence from the GLGM when the Garonne palaeoglacier had already significantly shrunk.

How to cite: Fernandes, M., Oliva, M., Vieira, G., Palacios, D., Fernández-Fernández, J. M., Delmas, M., García-Oteyza, J., Schimmelpfennig, I., Ventura, J., and Team, A.: Maximum glacier extent of the Penultimate Glacial Cycle in the Upper Garonne Basin (Pyrenees): new chronological evidence, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1698, https://doi.org/10.5194/egusphere-egu22-1698, 2022.

Recent studies have shown that during the last glacial cycle the extent, timing and style of glaciation was not uniform across the European Alps but influenced by local topographic or climatic factors. In the south-eastern part of the mountain range, for example, glaciers not only developed in the inner-Alpine sectors but also along the pre-Alpine chains, probably fuelled by high orographic precipitation in these regions. Despite their high climatic sensitivity, the evolution of these glaciers throughout the last glacial cycle is still not fully understood and more field data are needed to enable comparisons among different sites. To address this issue, we present new results from the Monte Cavallo Group (Venetian Prealps, NE-Italy), based on detailed geomorphological mapping, glacier reconstructions and Equilibrium Line Altitude (ELA) modelling; then we compare our findings to other paleoglaciers that existed along the fringe of the southern Alps.

The oldest sediments in the Monte Cavallo Group are deposits of a small lake basin, rich in organic macrofossils such as branches and bark remains. These sediments likely date back to at least the earliest part of MIS 3, or potentially even previous interglacial periods. As climate deteriorated towards the Last Glacial Maximum (LGM), glacier tongues advanced from the peak regions into the main valleys. While towards the west, some small tributaries merged with the large Piave glacier, most of the glacial system of the Monte Cavallo remained independent. Its maximum extent is marked by prominent lateral and frontal moraine ridges that allowed reconstructing the geometry and ELA of the glaciers during the LGM. Besides the valley glaciers, also mid-altitude plateaus were at least temporarily covered by ice, however these plateau glaciers probably quickly vanished after the LGM acme, due to their restricted elevation range. Glacial retreat in the valleys, on the other hand, was intermitted by phases of stagnancy or readvance, as indicated by smaller moraine ridges up-valley. Comparing these Late Glacial moraines with other regional records may reveal important patterns regarding the early stages of post-LGM deglaciation in the south-eastern Alps.

How to cite: Rettig, L., Hajdas, I., Monegato, G., Mozzi, P., and Spagnolo, M.: New insights into the last glacial cycle in the south-eastern European Alps from the glacial geomorphological record of the Monte Cavallo (NE Italy), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7499, https://doi.org/10.5194/egusphere-egu22-7499, 2022.

The Gröbminger Mitterberg, an isolated flat hill located within the Enns Valley, consists of fluvial, deltaic and lake bottom sediments on top of bedrock, which are covered by subglacial till. In comparison, the sedimentary succession in the Sölk Valleys, which drain into the Enns Valley, is more divers. The highest peaks reaching 2680 m a.s.l. and cirques are dominated by talus, relict rock glaciers and two groups of moraine ridges. Latero-frontal moraine ridges located higher than 1900 m a.s.l. are remarkable. Frequently, two or three ridges are located close to each other and have a morphologically fresh shape. Further downvalley, single laterao-frontal moraine ridges occur, which are often flattened and less prominent. They appear in different altitudes according to their catchment area. However, they do not reach the main valley floor. The slopes of the main valleys and secondary valleys are often covered by subglacial till and reworked slope deposit,s which are dominated by a silty-sandy matrix and angular to subrounded clasts. Additionally, many slopes have been affected by mass movements. At the valley mouth of secondary valleys, ice marginal sediments occur consisting of very rounded pebbles in a sandy matrix and in some areas, cross bedding can be observed. Slightly above the valley floor of the main valleys, gently sloping terrace bodies interfingering with truncated alluvial fans and slope sediments described above occur. These deposits are diamicts, which consist of sandy or silty matrix with rounded and angular clasts.

An interpretation of these findings suggests the following landscape evolution:

The sedimentological record of Gröbminger Mitterberg suggests aggradation of the Enns Valley floor to at least 850 m a.s.l. (200 m higher than today) prior to the Last Glacial Maximum (LGM). During the LGM, the area was covered by the Enns Glacier with tributary glaciers from the Sölk Valleys. The ice surface reached 1800 m a.s.l. in the northernmost part (in the Enns Valley), roughly 2100 m a.s.l. in the southernmost part at a transfluence pass (Sölkpass) and even higher altitudes in cirques. During that time, large areas were covered by basal till. With the breakdown of the ice mass and ice surface lowering at the onset of the phase of ice-decay, trunk glaciers and cirque glaciers got separated resulting in the formation of ice-marginal lakes. On the already ice-free slopes, reworking of the previously deposited sediment and mixing with talus started. Further, climate warming proceeded and ice retreat resulted in mass movements and rock falls. As soon as the valley floor was ice-free, aggradation started by large river systems accumulating sediment in the valley floor. This was followed by two separate cold stages, the Gschnitz Stadial (Heinrich Event 1, ~16-17 ka) and the Egesen Stadial (Younger Dryas, ~12-13 ka), where cirque glaciers developed in equilibrium with climate oscillations (up to three stabilisation phases recognised during Egesen Stadial). In the Holocene, climate warming led to river incision in the main valleys and resulted in today´s landscape.

How to cite: Griesmeier, G. E. U., Reitner, J. M., and Le Heron, D. P.: Landscape evolution of the Sölk Valleys and adjacent regions from the last Interglacial to today (Niedere Tauern range, Austria), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7124, https://doi.org/10.5194/egusphere-egu22-7124, 2022.

Glaciers provide an excellent natural laboratory for reconstructing the climate of the past as they respond sensitively to climate oscillations with advance or retreat. Therefore, we study glacier systems and their behavior during the transition from colder to warmer climate episodes in glaciated valleys of the Silvretta Massif in the Austrian Alps.  

Using a combination of geomorphological mapping and beryllium-10 surface exposure dating, we reconstruct ice extents of the past and find that glaciers stabilized during the Pre-Bølling to Bølling transition (14.4 ± 1.0 ka, n=3), during the Younger Dryas (ca. 12.9-11.7 ka; n=7), and during the earliest Holocene (ca. 12-10 ka; n=2). The first, (pre)-Bølling age group indicates a stable ice margin that postdates the Gschnitz stadial (ca. 17-16 ka) and predates the Younger Dryas. It shows that local inner-alpine glaciers prevailed until the onset of the Bølling warm phase (ca. 14.6 ka) or possibly even into the Bølling. The second Younger Dryas age group captures the spatial and temporal fine structure of glacier retreat during the Egesen stadial prior to Holocene warming. It evidences ice surface lowering of several tens of meters throughout the Younger Dryas, which is indicative of milder climate conditions at the end of the stadial compared to its beginning. The third age group falls into a period of substantial warming, the Younger Dryas-Holocene transition. The deposition of moraines during a period of abrupt warming implies centennial-scale cold snaps that were probably caused by feedback in the climate system. An explanation proposed in the Younger Dryas-Holocene context is the deglaciation of ice sheets in the Northern hemisphere and resulting freshwater input into the Atlantic ocean, which in turn slowed down ocean circulations and thus reduced heat transport toward (Northern) Europe.

The new geochronologies synthesized with pre-existing moraine records from the Silvretta Massif show that the transition from glacial to interglacial climate conditions occurred within a few centuries and illustrate the sensitive response of Silvretta glaciers to abrupt warming events in the past. Our ice-margin reconstructions provide an example of the response of glaciers and the climate system in a warming world.

How to cite: Braumann, S. M., Schaefer, J. M., Neuhuber, S., and Fiebig, M.: Climate transitions during the Late Glacial and the Early Holocene reconstructed from moraine records in the Austrian Alps, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9602, https://doi.org/10.5194/egusphere-egu22-9602, 2022.

The origin of the Southern sub-Alpine lakes was intensively discussed in the past century. Morphological observations, combined with seismic reflection acquisitions provided the fluvio-glacial origin of them. However, the formation and the post-Messinian evolution of the smaller lakes between the two branches of the Como Lake, Southern Alps, Italy, was only marginally investigated so far. This area is regionally named Triangolo Lariano, and several authors hypothesised the post-Messinian evolution of Segrino Lake area connecting its formation with the initial Messinian incision followed by the morainic block during the Last Glacial Maximum (LGM). The proposed study re-evaluates the origin of Segrino Lake as well as the lower Triangolo Lariano area, using morphological observation, orthophoto interpretation, detailed Terrain analysis on high-resolution DEM and finally, the interpretation and correlation of borehole stratigraphy. The results highlight a complex morphological evolution of the area up to the pre-Messinian times. In fact, considering the morphology and the geological characteristics of the bedrock as well as the morphometry of the area, fluvial and glacial phases were observed. Deep incised valleys linked with the Messinian Sea level change, and a complex drainage system are clearly detectable on the field and from detailed Terrain analysis. Finally, to reconstruct the paleogeography and order the chronology of the geological events that have occurred in the area, a set of borehole data were interpreted. These analyses allowed to observe an alternation of strata characterized by heterogeneous and interstratified deposits, that reflected a sequence of lacustrine, fluvial, glacial, lacustrine, and fluvial deposits. In fact, the careful evaluation of the stratigraphy highlights the presence of a pre-Messinian lacustrine phase in the area North of Segrino Lake. In addition, fluvial deposits, suspended valleys and paleo-meanders suggest a strong erosive phase dating back to the Messinian age. During this period, the Lambro River deeply incised into the bedrock forming the actual Segrino Valley. Subsequently, the glaciation phase remodelled the area, depositing erratic boulders and morainic material that caused changes in the drainage settings. In particular, the morainic barrier South of Segrino Lake is responsible for the formation of a new lake in the Segrino-Canzo area as well as in the lower part of the study area were the Pusiano and Alserio Lakes are located nowadays. In the following period the deglaciation and the new hydrological asset of the area led to a shrinking of Segrino-Canzo Lake, and finally a drainage inversion of Segrino Lake, with the outflow directed towards North, and the formation of an alluvial fan which isolated the actual Segrino Lake. Finally, the hypothesis already formulated in the past by some other authors, regarding the presence of a lake that he would fill the study area after the LGM, is therefore supported. New evidence due to the available borehole stratigraphy allowed us to recognize a new and more complex and highly heterogeneous evolution of the study area from Messinian time onwards.

How to cite: Simoncelli, L., Bosino, A., Vilímek, V., Kropáček, J., and Maerker, M.: Paleogeographic reconstruction of Segrino Lake area: Southern Alps, Northern Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4623, https://doi.org/10.5194/egusphere-egu22-4623, 2022.

The investigation of Holocene glacier chronologies has been recognised as a key element of research on mountain glaciations in the light of current global change. They can be utilised as high-resolution palaeoclimatic archives for the immediate and more distant geological past. During the past few decades considerable progress has been achieved, in particular due to substantial improvements of the ability to accurately date glacial landforms such as terminal moraines essential for reconstructing past glacier margins and subsequent analysis of glacier advance/retreat periods. The Southern Alps of New Zealand are among the few suitable regions for the investigation of Holocene glacier chronologies in the mid-latitudinal Southern Hemisphere.

Since early studies of Holocene glacier chronologies in the mid-20^th century, mapping of the investigated glacier forelands has been an integrated part of almost all scientific approaches regardless of the individual dating methods applied. These mapping attempts serve the identification and positioning of certain glacial or glaciofluvial landforms and allow the reconstruction of former glacier margins. They frequently also provide information on the location of sample sites selected for subsequent dating. If detailed geomorphological mapping schemes are in use, such maps additionally support the interpretation of any chronological data by identifying the genetic origin of any landform investigated. This enables the latter to be causally related to different dynamic stages of the glacier. Additionally, such maps may highlight potential uncertainties such as postdepositional disturbance or unclear morphodynamic connections between landforms and the glacier.

Reviewing recent publications it seems, however, that some appraisal of such detailed geomorphological mapping is often traded-off against the impressive progress with up-to-date dating techniques and high-resolution digital elevation models or satellite/aerial imagery. Unfortunately, the latter do neither qualify as geomorphological maps per se nor fully serve the abovementioned purpose. The widespread applied common GIS software has, furthermore, limitations with respect to its graphic capabilities and unintentionally entails negligence of established and well-suited signatures or geomorphological mapping schemes.

A detailed geomorphological map of the glacier foreland of Mueller Glacier, Southern Alps/New Zealand will be presented. It follows an established geomorphological mapping scheme ("GMK 25") that has been adequately modified to fit both purpose and selected scale. Despite several glacier chronological studies have been conducted on this glacier foreland and the site is considered a regional 'key site', this map constitutes the first of its kind. The detailed geomorphological map is utilised to assess discrepancies among existing chronologies by reviewing the morphometric properties and genetic origin of those landforms that have been dated. It reveals that potential postdepositional modification of some landforms investigated had not been appropriately considered with certain previous studies. As a result, the evidence for some glacier advances needs to be classified as 'weak'.  

Summarising, detailed geomorphological mapping is still essential for the study of Holocene glacier chronologies and should not lose its prominent position - or even disappear.

How to cite: Winkler, S.: Potential of detailed geomorphological mapping for the study of Holocene glacier chronologies: Mueller Glacier, Southern Alps/New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1502, https://doi.org/10.5194/egusphere-egu22-1502, 2022.

Geochronological dating of glacial landforms, such as terminal and lateral moraines, are useful for determining the extent and timing of past glaciation and for reconstructing the magnitude and rate of past climate changes. Here we report the first dataset of Late Quaternary glacial maximum extent and its deglaciation from the Ahuriri River valley, Southern Alps, New Zealand (44°23'54''S, 169°39'48''E) based on 66 beryllium-10 (¹⁰Be) surface-exposure ages from terminal-lateral moraine systems and glaciated bedrock surfaces situated at different sites of the valley. Our results show that the former Ahuriri Glacier reached its maximum extent 19.8±0.3 ka, which coincides with the global Last Glacial Maximum. By 16.7±0.3 ka, the glacier had retreat ~18 km up-valley and this deglaciation was accompanied by the formation of a shallow proglacial lake. Our surface-exposure chronology from the moraines situated upper right tributary of the Ahuriri River valley also indicates that other subsequent advance of the palaeo glacier culminated at 14.5±0.3 ka ago, while the next re-advance or still stand phases occurred at 13.6±0.3 ka. About 1000 yr later (12.6±0.2 ka), the former glacier built another prominent terminal-lateral moraine ridge in the lower section of the upper right tributary valley. In overall, our result supports the hypothesis that climate was ~5°C colder (ELA depression ~880 m) than present at 19.8±0.3 ka, while it was ~4.4°C colder (ELA depression ~770 m) at 16.7±0.3 ka. Furthermore, local air temperature was lower by 3.6°C (ELA depression ~630 m) during the 14.5-13.6 ka and by 2.0°C (ELA depression ~360 m) at 12.6 ka respectively relative to present. Our results clearly demonstrate the structure of last glacial termination in New Zealand such as strong glacier recession during this time-period in accordance of at least five glacier re advances or still stand phases. This new ¹⁰Be surface exposure dataset will help us in better understanding of past glacier-climate interactions in the Southern Alps and in the Southern Hemisphere in general.

How to cite: Tielidze, L., Eaves, S., Norton, K., Mackintosh, A., and Hidy, A.: Late Quaternary glacier-based climate reconstruction from the Southern Alps, New Zealand, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3235, https://doi.org/10.5194/egusphere-egu22-3235, 2022.

Precipitation, snow and ice melt from Andean river basins provide a crucial water source to mountain and downstream communities equally. Precipitation and temperature changes due to global climate change are likely to affect agriculture, hydropower generation and hazard risks, but are poorly constrained, especially in future projections.

Here we focus on two heavily glacierised regions of the Peruvian Andes, the Cordillera Blanca, and the Cordillera Vilcanota-Urubamba, to assess projected changes in extreme meteorological events and droughts. Previous work suggests increasing temperatures in both regions in the 21^st century, with contrasting projections of precipitation trends. There has been little focus, however, on how extremes in precipitation and temperature might vary in the future. Having created a bias-corrected regional climate model from 1980-2018, we use empirical quantile mapping to statistically downscale 30 CMIP5 models. This ensemble is analysed to determine future changes in climate extremes.  

Both minimum and maximum daily temperatures are projected to increase in the from 2018 to 2100. This leads to a large reduction in the number of frost days in both regions, and suggests that under a high-emissions scenario, almost every day in the late 21^st century will be in the 90^th percentile of temperatures experienced during 1980-2018. The number of wet and dry days is not projected to change, but precipitation falling on very wet days (in the 95^th percentile of the 1980-2018 period) is projected to increase significantly.

Lastly, we consider changes in future meteorological droughts using the standardised precipitation evapotranspiration index (SPEI) which considers potential evapotranspiration, as well as precipitation. We estimate potential evapotranspiration from temperature projections, using the Hargreaves method. Despite projected precipitation increases, temperature increases leading to an increase in evaporation may be large enough to increase meteorological droughts in the future, with the total number of drought months projected to almost double under high emission scenarios by the end of the 21^st century. In a region that already experiences water stress and hazards, these changes to both extreme rainfall and drought could have a significant impact for communities in the Peruvian Andes, and for the downstream urban areas and industry that rely on mountain river flow.

How to cite: Potter, E., Fyffe, C., Orr, A., Quincey, D., Ross, A. N., Rangecroft, S., Medina, K., Burns, H., Llacza, A., Jacome, G., Hellström, R., Castro, J., Hosking, J. S., Cochachin, A., Klein, C., Loarte, E., and Pellicciotti, F.: Projected increases in climate extremes and temperature-induced drought over the Peruvian Andes, 1980-2100, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9576, https://doi.org/10.5194/egusphere-egu22-9576, 2022.

Cordillera Blanca glaciers represent the greatest glacial freshwater reserve in tropical South America and have been shrinking substantially over recent decades, posing a threat to future water resources in the Peruvian Ancash region. A crucial step to better understand the evolution of these glaciers under changing conditions is to establish robust reconstructions of their past response to climate fluctuations. Such reconstructions are limited in the tropical Andes, which inhibits our understanding of the climatic drivers of tropical glacier length and surface mass balance changes. The relative importance of temperature versus precipitation rate changes on glacier length changes is therefore still debated in the region. Here, we present 42 cosmogenic ¹⁰Be exposure ages from moraine boulder samples, establishing for the first time a comprehensive chronology for Late-glacial, Holocene and Neoglacial advances of four distinct Cordillera Blanca mountain glaciers. We use this chronology to constrain a series of moraine-matching numerical model-run simulations conducted for each dated glacier advance using a spatially-distributed ice-flow model coupled with a positive degree-day surface mass balance parameterisation. These simulations aim at modelling and estimating former three-dimensional glacier geometries, equilibrium line altitudes, surface mass balance properties and their evolution through time. This analysis also enables us to use glacier surface mass balance as a proxy for past atmospheric temperature and precipitation variations at the time of the reconstructed glacier advances. This new, multi-method glacier reconstruction enables, for the Cordillera Blanca: 1) novel glacio-geomorphological interpretations, 2) an improved understanding of glacier extent, surface mass balance and volume change during the Late-glacial, Holocene and Neoglacial phases of advance, and 3) new estimations of paleoclimate conditions required for the reconstructed glacier events to occur.   

How to cite: Leger, T., Hein, A., Goldberg, D., and Fabel, D.: Late-glacial to Neoglacial evolution of glacier extent and surface mass balance in the Cordillera Blanca, Peruvian Andes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4999, https://doi.org/10.5194/egusphere-egu22-4999, 2022.

Proglacial lake sediments are widely recognised as accurate and high-resolution archives of climate and glacier variability. Sediments deposited in proglacial lakes are frequently varved, which offers the possibility to generate precisely-dated records, and their basal ages are often used to constrain deglaciation histories. It is often assumed that lake sedimentation starts immediately after deglaciation. With this in mind, we studied the onset of lake sedimentation in a recently deglaciated lake (Calluqueo Lake, Chilean Patagonia) to investigate the possible delay between proglacial lake formation and establishment of a continuous sediment record. Calluqueo Lake is a 3.5 km long lake composed of a large 220 m deep proximal basin, separated from a smaller 50 m deep distal basin by a 40 m deep sill. The lake is bordered by steep lateral moraines that contain large boulders. Aerial images and historical data show that Calluqueo Glacier entirely covered the lake basin until 1941. Since then, it rapidly receded until it became land-based in 1985. Side Scan sonar images and grab sampling shows that the sediment cover is limited to the small distal basin, which was entirely deglaciated by 1978. By comparison, no sediment was found in the deepest proximal basin although it has been ice free for at least three decades. Varve counting of sediments deposited in the distal basin shows that the stratigraphic record starts in 1996 ± 4 CE, i.e., that the first 20 – 50 years of the glacier’s retreat are not represented in the sediments of Calluqueo Lake. We hypothesize that the fine-grained sediments that are discharged into the lake immediately after its formation first start accumulating between the large boulders that compose the ablation moraine on the lake floor. The continuous stratigraphic record only starts forming after the coarse moraine deposits are buried under fine-grained particles. Our results have important implications for the use of proglacial lake sediments in paleoclimate and paleoenvironmental research. They suggest that proglacial lake sediment records lack the first 20 – 50 years of sedimentation. Although this delay may be negligible for reconstructions of deglaciation histories based on basal radiocarbon ages, it becomes significant for the use of lake sediment records from recently deglaciated environments.

How to cite: Piret, L., bertrand, S., and Torrejón, F.: Multidecadal Delay Between Deglaciation and Formation of a Proglacial Lake Sediment Record, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2237, https://doi.org/10.5194/egusphere-egu22-2237, 2022.

Glacial geomorphological and geochronological studies suggest that the Patagonian Ice Sheet (PIS) stretched from 38°S to 55°S during the Marine Isotope Stages (MIS) 2-3. While its western margin reached the Pacific Ocean, the easternmost sectors of the PIS were characterized by terrestrial lobes that fed large paleo glacial lakes after its maximum extension towards the end of the MIS 3. An ice-marginal stabilization occurred throughout the global Last Glacial Maximum followed by a rapid deglaciation after 18,000 yr before present.

Here we present an ensemble of transient numerical simulations of the PIS that have been carried out to provide information on its thickness and extents through the MIS 3 and MIS 2. Our aim here is to determine the range of climate conditions that matches the field-derived ice sheet geometries and the timing of local deglaciation, while bracketing the spread in possible ice volumes and sea level contributions originating from uncertainties in the internal parameters and external forcings. The model ensemble makes use of the new higher-order version of the ice sheet model SICOPOLIS forced by combination of present-day atmospheric conditions from the ERA5 reanalysis and outputs from the Paleoclimate Modeling Intercomparison Project (PMIP) and new Community Earth System Model (CESM) experiments. Our results indicate that the regional climate conditions required to reproduce a realistic growth and demise of the PIS through the Late Quaternary are not captured by coarse-resolution global climate models, implying the necessity of high spatial-resolution regional modeling. Our results also suggest that in order to realistically simulate the evolution of the PIS in agreement with geological archives, the MIS3 should have witnessed colder regional temperatures in and around Patagonia than those shown by global climate models for the MIS 2.

How to cite: Castillo, A., Prange, M., Bernales, J., Retamal-Ramírez, F., Schulz, M., and Rogozhina, I.: Numerical reconstructions of the Patagonian Ice Sheet: Growth and demise through the Late Quaternary, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9793, https://doi.org/10.5194/egusphere-egu22-9793, 2022.

Proglacial lakes provide valuable records of paleoclimate, volcanism, and glaciation. We present results from spatially extensive coring of Lago Argentino, a 1500 km² proglacial lake on the eastern margin of the Southern Patagonian Icefield (SPI). We recovered forty-seven sediment cores from water depths up to 600 m. Detailed analysis of this sediment reveals annual laminations – known as varves – which we use to build a high-resolution age-depth model for each core.

In this presentation, we discuss the insight gained into varve formation mechanisms, paleoclimate, and glacier change in the Lago Argentino basin of the Southern Patagonian Icefield. Firstly, we show that varves form by three distinct mechanisms across Lago Argentino (~west to east): a seasonal cycle in glacial sediment influx, a seasonal cycle in lake mixing, and a seasonal cycle in fluvial sediment influx. Second, we examine the evidence for recent glacier fluctuations across Lago Argentino. We find evidence that glaciers were locally larger early in the last millennium than during the Little Ice Age. Finally, we examine the periodicity of sediment mass accumulation rate and find dominant decadal to centennial periodicities (35, 80, 150 and 200 years). We relate periodicities in sediment accumulation to periodicities in known climatic drivers, specifically the Southern Annular Mode. These results provide new insight into multiannual glacial change and sedimentation dynamics in a complex glacio-lacustrine system and highlight the value of proglacial lake records for understanding present-day glacier change.

How to cite: Van Wyk de Vries, M., Ito, E., Shapley, M., Brignone, G., Romero, M., and Wickert, A. D.: Insight into glacier evolution, proglacial lake dynamics, and paleoclimate from Lago Argentino, Patagonia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6505, https://doi.org/10.5194/egusphere-egu22-6505, 2022.

The glacial history of Patagonia has been built from paleoclimate records found at the margin of the former Patagonian Ice-sheet. However, current deglaciation models of Patagonia still have spatio-temporal gaps to be filled. In this direction, the study of the submerged paleo-climate records at the Patagonian Fjord system and pro-glacial lakes could fill these gaps and enhance our knowledge on deglaciation in Patagonia. However, the exploration of such remote areas is hindered by logistic challenges and rough weather conditions.

In November of 2018 we collected the first high-resolution swath multibeam echosounder (MBES) bathymetry of Senos Icy and Glacier, the southern section of Canal Gajardo and Estero Portaluppi, which are fjords located at the flanks of Gran Campo Nevado. In this work, we present this new bathymetry and its first geomorphological interpretation. The analysis revealed a heterogeneous seafloor with geomorphological features related to glacial dynamics. The data interpretation is supplemented by shallow sub-bottom profiles that have been also acquired during that survey. We think that such information is the baseline for future exploration of these fjords focused on the already identified submerged glacial bedforms and their chronology.  

How to cite: Veloso-Alarcón, M., Iason-Zois, G., Geiger, A., Sebastien, B., and Rodrigo, C.: Advances on submarine geomorphology at the Fjord system of Gran Campo Nevado (~52°S), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-13508, https://doi.org/10.5194/egusphere-egu22-13508, 2022.