Journal articles on the topic 'Glacial reconstruction'
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1
Temovski, Marjan, Balázs Madarász, Zoltán Kern, Ivica Milevski, and Zsófia Ruszkiczay-Rüdiger. "Glacial Geomorphology and Preliminary Glacier Reconstruction in the Jablanica Mountain, Macedonia, Central Balkan Peninsula." Geosciences 8, no. 7 (July 23, 2018): 270. http://dx.doi.org/10.3390/geosciences8070270.
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Although glacial landforms on the Balkan Peninsula have been studied since the 19th century, only scarce data are available about the extent of the former glaciations in the Central Balkan Peninsula, the transition zone between the Mediterranean and Central Europe. Glacial features of the Jablanica Mt. were mapped, described and classified into morphostratigraphic units. A revised glacio-geomorphological map was produced and glacial landforms were assigned to six morphostratigraphic units. Ten primary and two secondary cirques were identified in the upper parts of the studied valleys, while downstream the valleys were steep and glacially shaped with several glacial steps and thresholds. Cirque and valley morphology indicate that subglacial deepening was limited within the cirques and was more intensive in the valley sections during more extensive glacial phases. The largest reconstructed glaciers were 4.6–7 km long, while the last cirque glaciers were only a few hundred meters long. Using morphostratigraphic data, a glacier reconstruction was carried out for the largest mapped glacial extent. On the basis of glacial geomorphology, a former equilibrium-line altitude (ELA) of ~1800 m and glacier cover of 22.6 km2 were estimated during this stage. The local ELA values were compared to the regional ELA record and enabled to tentatively attribute a MIS 6 age for the reconstructed maximum ice extent in the study area.
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Hall, Kevin, Ian Meiklejohn, and Adam Bumby. "Marion Island volcanism and glaciation." Antarctic Science 23, no. 2 (November 22, 2010): 155–63. http://dx.doi.org/10.1017/s0954102010000878.
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AbstractSub-Antarctic Marion Island was the site of extensive volcanism as well as glaciation during both the Quaternary and the Holocene. Initial reconstructions suggested a link between deglaciation and the initiation of faulting which, in turn, facilitated lava eruptions during the interglacials. However, our reassessment of the faulting, volcanic rock, and palaeoglacier distribution indicate that these original interpretations were erroneous. Features thought to be due to faulting are shown to be erosional scarps and this significantly changes interpretations of former glacier distribution. Further, the loss of the former ice cap has revealed new information on former glaciers and their flow directions, thereby allowing reconstruction of palaeoglaciers. Our new reconstruction fits with information from invertebrate genetic mapping that suggest some lava outcrops were nunataks and, therefore, refuges during the Last Glacial period. The new findings of glacial landforms in areas previously covered by snow suggest there was a significant ice advance during the Little Ice Age. Although Holocene volcanic rocks overlie and mask much of the glacial evidence, it has been possible to develop a proposed new reconstruction for glaciation, which is presented together with some of the implications.
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Glasser, Neil F., and Matthew R. Bennett. "Glacial erosional landforms: origins and significance for palaeoglaciology." Progress in Physical Geography: Earth and Environment 28, no. 1 (March 2004): 43–75. http://dx.doi.org/10.1191/0309133304pp401ra.
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Glacial inversion modelling of continental-scale palaeo-ice sheets is now recognized as an important tool in palaeoglaciology. Existing palaeoglaciological reconstructions of the dimensions, geometry and dynamics of former ice sheets are based mainly on glacial depositional, as opposed to glacial erosional, landforms. Part of the reason for this is a lack of detailed understanding of the origin and significance of glacial erosional landforms. Here we review recent developments in our understanding of the processes and landforms of glacial erosion and consider their value in palaeoglaciology. Glacial erosion involves the removal and transport of bedrock and/or sediment by glacial quarrying, glacial abrasion and glacial meltwater. These processes combine to create a suite of landforms that are frequently observed in areas formerly occupied by ice sheets and glaciers, and which can be used in palaeoglaciological reconstructions. For example, all landforms of glacial erosion provide evidence for the release of subglacial meltwater and the existence of warm-based ice. Landforms of glacial quarrying such as roches moutonnées, rock basins and zones of areal scouring are created when cavities form between an ice sheet and its bed and therefore are indicative of low effective basal pressures (0.1-1 MPa) and high sliding velocities that are necessary for ice-bed separation. Fluctuations in basal water pressure also play an important role in the formation of glacially quarried landforms. Landforms of glacial abrasion include streamlined bedrock features (‘whalebacks’), some ‘p-forms’, striae, grooves, micro-crag and tails, bedrock gouges and cracks. Abrasion can be achieved by bodies of subglacial sediment sliding over bedrock or by individual clasts contained within ice. Although abrasion models depend critically on whether clasts are treated as dependent or independent of subglacial water pressure, it appears that abrasion is favoured in situations where effective basal pressures are greater than 1 MPa and where there are low sliding velocities. Consequently, landforms dominated by glacial abrasion are created when there is no ice-bed separation. Landforms of glacial meltwater erosion include both subglacial and ice-marginal meltwater channels. Investigations of the relationship between glacial meltwater channels and other aspects of the subglacial drainage system, such as areas of ice-bed contact, areas of ice-bed separation and precipitate-filled depressions, enable inferences to be made concerning former subglacial water pressure-drainage relationships, effective pressures and glacier velocities. Meltwater palaeovelocity and palaeodischarge can also be calculated from measurements of channel shape, channel width and the size of material transported within former glacial meltwater channels. We surmize that glacial erosional landforms offer insight into former glacio-logical conditions at both the landform- and landscape-scale within palaeoglaciology. Exposure-age dating techniques, including cosmogenic isotope dating of bedrock surfaces, will be important in increasing our understanding of the age and chronological significance of landforms of glacial erosion. We conclude that landforms of glacial erosion are of great value in ice mass reconstruction and speculate that these landforms will achieve greater recognition within palaeoglaciology in line with improvements in exposure-age dating techniques.
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Gribenski, Natacha, Pierre G. Valla, Frank Preusser, Thibault Roattino, Christian Crouzet, and Jean-François Buoncristiani. "Out-of-phase Late Pleistocene glacial maxima in the Western Alps reflect past changes in North Atlantic atmospheric circulation." Geology 49, no. 9 (June 3, 2021): 1096–101. http://dx.doi.org/10.1130/g48688.1.
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Abstract Paleoglacier reconstructions in the northern and southern forelands of the European Alps indicate a synchronous Late Pleistocene glacial maximum during Marine Isotope Stage (MIS) 2, in phase with global ice volume records. However, strong controversy remains for the western foreland, where scarce and indirect dating as well as modeling studies suggest glacial maxima out of phase with the rest of the Alps. New luminescence dating brings the first direct Late Pleistocene glacial chronology for the western Alpine foreland and reveals two major glacier advances of similar maximum extent, at ca. 75–60 and ca. 40–30 ka, coinciding with MIS 4 and late MIS 3. We propose that asynchrony in glacial maxima between the western and the northern and southern Alpine forelands results from a progressive spatial reorganization of the atmospheric circulation over the North Atlantic in response to Northern Hemisphere ice-sheet fluctuations. While such a feedback mechanism has emerged from general circulation models, our Late Pleistocene paleoglacial reconstruction permits tracking of the spatiotemporal evolution of moisture advection patterns over Western Europe.
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Cleator, Sean F., Sandy P. Harrison, Nancy K. Nichols, I. Colin Prentice, and Ian Roulstone. "A new multivariable benchmark for Last Glacial Maximum climate simulations." Climate of the Past 16, no. 2 (April 6, 2020): 699–712. http://dx.doi.org/10.5194/cp-16-699-2020.
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Abstract. We present a new global reconstruction of seasonal climates at the Last Glacial Maximum (LGM, 21 000 years BP) made using 3-D variational data assimilation with pollen-based site reconstructions of six climate variables and the ensemble average of the PMIP3—CMIP5 simulations as a prior (initial estimate of LGM climate). We assume that the correlation matrix of the uncertainties in the prior is both spatially and temporally Gaussian, in order to produce a climate reconstruction that is smoothed both from month to month and from grid cell to grid cell. The pollen-based reconstructions include mean annual temperature (MAT), mean temperature of the coldest month (MTCO), mean temperature of the warmest month (MTWA), growing season warmth as measured by growing degree days above a baseline of 5 ∘C (GDD5), mean annual precipitation (MAP), and a moisture index (MI), which is the ratio of MAP to mean annual potential evapotranspiration. Different variables are reconstructed at different sites, but our approach both preserves seasonal relationships and allows a more complete set of seasonal climate variables to be derived at each location. We further account for the ecophysiological effects of low atmospheric carbon dioxide concentration on vegetation in making reconstructions of MAP and MI. This adjustment results in the reconstruction of wetter climates than might otherwise be inferred from the vegetation composition. Finally, by comparing the uncertainty contribution to the final reconstruction, we provide confidence intervals on these reconstructions and delimit geographical regions for which the palaeodata provide no information to constrain the climate reconstructions. The new reconstructions will provide a benchmark created using clear and defined mathematical procedures that can be used for evaluation of the PMIP4–CMIP6 entry-card LGM simulations and are available at https://doi.org/10.17864/1947.244 (Cleator et al., 2020b).
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Andrews, John T. "Postface." Géographie physique et Quaternaire 41, no. 2 (January 15, 2008): 315–18. http://dx.doi.org/10.7202/032686ar.
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ABSTRACT Although major progress has been made in several research topics on the Laurentide Ice Sheet, there are still substantial problems that require investigation over the next decade. Of particular importance will be the active participation between modelers and those who provide the "ground truth". Although individual reconstructions of the ice sheet, based on glacial isostasy, glaciology, climatology, and glacial geology, will continue to be developed and refined the next important step should be the development of an integrated climate/glaciology/isostatic ice sheet reconstruction that will serve to provide a holistic series of predictions about glacial, glacial marine, and periglacial landforms, sediments, and chronologies. These predictions can then serve as the basis for guiding field programs to examine bedforms and sediments associated with this ice sheet. This program of model reconstruction and verification will require a more complete understanding of glacial depositional processes than is currently available and, in addition, will be heavily dependant on a detailed dating program to improve our knowledge of the chronology of events.
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XU, XIANGKE, BAOLIN PAN, GUOCHENG DONG, CHAOLU YI, and NEIL F. GLASSER. "Last Glacial climate reconstruction by exploring glacier sensitivity to climate on the southeastern slope of the western Nyaiqentanglha Shan, Tibetan Plateau." Journal of Glaciology 63, no. 238 (January 23, 2017): 361–71. http://dx.doi.org/10.1017/jog.2016.147.
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ABSTRACTImprovements in understanding glacial extents and chronologies for the southeastern slope of the western Nyaiqentanglha Shan on the Tibetan Plateau are required to understand regional climate changes during the Last Glacial cycle. A two-dimensional numerical model of mass balance, based on snow–ice melting factors, and of ice flow for mountain glaciers is used to assess the glacier sensitivity to climatic change in a catchment of the region. The model can reproduce valley glaciers, wide-tongued glaciers and a coalescing glacier within step temperature lowering and precipitation increasing experiments. The model sensitivity experiments also indicate that the dependence of glacier growth on temperature and/or precipitation is nonlinear. The model results suggest that the valley glaciers respond more sensitively to an imposed climate change than wide-tongued and coalescing glaciers. Guided by field geological evidence of former glacier extent and other independent paleoclimate reconstructions, the model is also used to constrain the most realistic multi-year mean temperatures to be 2.9–4.6°C and 1.8–2.5°C lower than present in the glacial stages of the Last Glacial Maximum and middle marine oxygen isotope stage 3, respectively.
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Milivojevic, Milovan, and Jelena Kovacevic-Majkic. "Glacial lakes Buni and Jezerce: Albania." Glasnik Srpskog geografskog drustva 85, no. 1 (2005): 11–18. http://dx.doi.org/10.2298/gsgd0501011m.
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The paper presents glacial lakes and glacial relief forms at the foothill of the peak Maja Jezerce in Mt. Prokletije in Albania, near the border with Montenegro. The group of lakes Buni and Jezerce, which consists of six lakes and which genetically belongs to glacial-erosional lakes, is analyzed. Lakes are situated at the cirque bottom, between the moraines and limestone ridges. Except presented morphometric characteristics of lake basins, data about cirque are given, as well as the reconstruction of the glacier which was formed here. Recent erosion processes are intensive in this area and have considerably changed post-Pleistocene morphology of the lake, as well as the cirque bottom.
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Tóth, Mónika, Enikő K. Magyari, Stephen J. Brooks, Mihály Braun, Krisztina Buczkó, Miklós Bálint, and Oliver Heiri. "A chironomid-based reconstruction of late glacial summer temperatures in the southern Carpathians (Romania)." Quaternary Research 77, no. 1 (January 2012): 122–31. http://dx.doi.org/10.1016/j.yqres.2011.09.005.
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Late glacial and early Holocene summer temperatures were reconstructed based on fossil chironomid assemblages at Lake Brazi (Retezat Mountains) with a joint Norwegian"Swiss transfer function, providing an important addition to the late glacial quantitative climate reconstructions from Europe. The pattern of the late glacial temperature changes in Lake Brazi show both similarities and some differences from the NGRIP δ18O record and other European chironomid-based reconstructions. Our reconstruction indicates that at Lake Brazi (1740 m a.s.l.) summer air temperature increased by ~ 2.8ºC at the Oldest Dryas/Bølling transition (GS-2/GI-1) and reached 8.1–8.7ºC during the late glacial interstade. The onset of the Younger Dryas (GS-1) was characterized by a weak (< 1ºC) decrease in chironomid-inferred temperatures. Similarly, at the GS-1/Holocene transition no major changes in summer temperature were recorded. In the early Holocene, summer temperature increased in two steps and reached ~ 12.0–13.3ºC during the Preboreal. Two short-term cold events were detected during the early Holocene between 11,480–11,390 and 10,350–10,190 cal yr BP. The first cooling coincides with the Preboreal oscillation and shows a weak (0.7ºC) temperature decrease, while the second is characterized by 1ºC cooling. Both cold events coincide with cooling events in the Greenland ice core records and other European temperature reconstructions.
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Whitehead, J. M., P. G. Quilty, B. C. Mckelvey, and P. E. O’Brien. "A review of the Cenozoic stratigraphy and glacial history of the Lambert Graben—Prydz Bay region, East Antarctica." Antarctic Science 18, no. 1 (March 2006): 83–99. http://dx.doi.org/10.1017/s0954102006000083.
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The Cenozoic glacial history of East Antarctica is recorded in part by the stratigraphy of the Prydz Bay—Lambert Graben region. The glacigene strata and associated erosion surfaces record at least 10 intervals of glacial advance (with accompanying erosion and sediment compaction), and more than 17 intervals of glacial retreat (enabling open marine deposition in Prydz Bay and the Lambert Graben). The number of glacial advances and retreats is considerably less than would be expected from Milankovitch frequencies due to the incomplete stratigraphic record. Large advances of the Lambert Glacier caused progradation of the continental shelf edge. At times of extreme glacial retreat, marine conditions reached > 450 km inland from the modern ice shelf edge. This review presents a partial reconstruction of Cenozoic glacial extent within Prydz Bay and the Lambert Graben that can be compared to eustatic sea-level records from the southern Australian continental margin.
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Abe-Ouchi, A., F. Saito, M. Kageyama, P. Braconnot, S. P. Harrison, K. Lambeck, B. L. Otto-Bliesner, et al. "Ice-sheet configuration in the CMIP5/PMIP3 Last Glacial Maximum experiments." Geoscientific Model Development 8, no. 11 (November 6, 2015): 3621–37. http://dx.doi.org/10.5194/gmd-8-3621-2015.
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Abstract. We describe the creation of a data set describing changes related to the presence of ice sheets, including ice-sheet extent and height, ice-shelf extent, and the distribution and elevation of ice-free land at the Last Glacial Maximum (LGM), which were used in LGM experiments conducted as part of the fifth phase of the Coupled Modelling Intercomparison Project (CMIP5) and the third phase of the Palaeoclimate Modelling Intercomparison Project (PMIP3). The CMIP5/PMIP3 data sets were created from reconstructions made by three different groups, which were all obtained using a model-inversion approach but differ in the assumptions used in the modelling and in the type of data used as constraints. The ice-sheet extent in the Northern Hemisphere (NH) does not vary substantially between the three individual data sources. The difference in the topography of the NH ice sheets is also moderate, and smaller than the differences between these reconstructions (and the resultant composite reconstruction) and ice-sheet reconstructions used in previous generations of PMIP. Only two of the individual reconstructions provide information for Antarctica. The discrepancy between these two reconstructions is larger than the difference for the NH ice sheets, although still less than the difference between the composite reconstruction and previous PMIP ice-sheet reconstructions. Although largely confined to the ice-covered regions, differences between the climate response to the individual LGM reconstructions extend over the North Atlantic Ocean and Northern Hemisphere continents, partly through atmospheric stationary waves. Differences between the climate response to the CMIP5/PMIP3 composite and any individual ice-sheet reconstruction are smaller than those between the CMIP5/PMIP3 composite and the ice sheet used in the last phase of PMIP (PMIP2).
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Fouinat, Laurent, Pierre Sabatier, Jérôme Poulenard, David Etienne, Christian Crouzet, Anne-Lise Develle, Elise Doyen, et al. "One thousand seven hundred years of interaction between glacial activity and flood frequency in proglacial Lake Muzelle (western French Alps)." Quaternary Research 87, no. 3 (May 2017): 407–22. http://dx.doi.org/10.1017/qua.2017.18.
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AbstractLocal glacial fluctuations and flood occurrences were investigated in the sediment sequence of proglacial Lake Muzelle. Based on geochemical analysis and organic matter content established using loss on ignition and reflectance spectroscopy, we identified six periods of increased glacial activity over the last 1700 yr. Each is in accordance with records from reference glaciers in the Alps. A total of 255 graded layers were identified and interpreted as flood deposits. Most of these occurred during glacial advances such as the Little Ice Age period and exhibit thicker deposits characterized by an increase in the fine grain-size fraction. Fine sediment produced by glacial activity is transported to the proglacial lake during heavy rainfall events. The excess of glacial flour during these periods seems to increase the watershed’s tendency to produce flood deposits in the lake sediment, suggesting a strong influence of the glacier on flood reconstruction records. Thus, both flood frequency and intensity, which is estimated based on layer thickness as a proxy, cannot be used in reconstruction of past extreme events because of their variability. There is a need to take into account changes in sediment supply in proglacial areas that could preclude satisfactory interpretation of floods in terms of past climate variability.
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Piermattei, L., L. Carturan, F. de Blasi, P. Tarolli, G. Dalla Fontana, A. Vettore, and N. Pfeifer. "Analysis of glacial and periglacial processes using structure from motion." Earth Surface Dynamics Discussions 3, no. 4 (November 30, 2015): 1345–98. http://dx.doi.org/10.5194/esurfd-3-1345-2015.
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Abstract. Close-range photo-based surface reconstruction from the ground is rapidly emerging as an alternative to lidar (light detection and ranging), which today represents the main survey technique in many fields of geoscience. The recent evolution of photogrammetry, incorporating computer vision algorithms such as Structure from Motion (SfM) and dense image matching such as Multi-View Stereo (MVS), allows the reconstruction of dense 3-D point clouds for the photographed object from a sequence of overlapping images taken with a digital consumer camera. The objective of our work was to test the accuracy of the ground-based SfM-MVS approach in calculating the geodetic mass balance of a 2.1 km2 glacier in the Ortles-Cevedale Group, Eastern Italian Alps. In addition, we investigated the feasibility of using the image-based approach for the detection of the surface displacement rate of a neighbouring active rock glacier. Airborne laser scanning (ALS) data were used as benchmarks to estimate the accuracy of the photogrammetric DTMs and the reliability of the method in this specific application. The glacial and periglacial analyses were performed using both range and image-based surveying techniques, and the results were then compared. The results were encouraging because the SfM-MVS approach enables the reconstruction of high-quality DTMs which provided estimates of glacial and periglacial processes similar to those achievable by ALS. Different resolutions and accuracies were obtained for the glacier and the rock glacier, given the different survey geometries, surface characteristics and areal extents. The analysis of the SfM-MVS DTM quality allowed us to highlight the limitations of the adopted expeditious method in the studied alpine terrain and the potential of this method in the multitemporal study of glacial and periglacial areas.
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Combourieu-Nebout, Nathalie, Severine Fauquette, and Pierre Quezel. "What was the late Pliocene Mediterranean climate like; a preliminary quantification from vegetation." Bulletin de la Société Géologique de France 171, no. 2 (March 1, 2000): 271–77. http://dx.doi.org/10.2113/171.2.271.
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Abstract Reconstruction of the composition and organisation of the late Pliocene vegetation in central Mediterranean and quantification of the climatic requirements of its main representatives allow temperature and precipitation estimates during the late Pliocene glacial/interglacial cycles, at ca 2.4 Ma. The late Pliocene climatic glacial and interglacial conditions are illustrated on a bioclimagram which correlates the mean annual temperature and precipitation criteria. Comparison between modern and late Pliocene vegetation indicates that late Pliocene interglacial climate was approximately 4 degrees C warmer, with more higher amount of precipitation than today, and that conditions similar to modern ones prevailed during late Pliocene glacials.
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Bhat, Waseem Ahmmad, Irshad Ahmad Bhat, Mifta ul Shafiq, and Pervez Ahmed. "Glacio-Geomorphological Investigation and Deglaciation pattern of Nehnar valley, North Western Himalayas." Disaster Advances 15, no. 11 (October 25, 2022): 35–49. http://dx.doi.org/10.25303/1511da035049.
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Glacial landforms are pieces of evidence to comprehend the glaciological past and paleoclimatic conditions in the region. In paleo-glacial reconstructions, a critical geomorphological context is provided for determining glacial chronologies. The study provides a detailed geomorphological mapping and investigation of the Nehnar valley, NW Himalayas, Jammu and Kashmir, India. To map the glaciogeomorphological features, the study uses LISS-IV (5.8 m resolution) and Google Earth Pro (1 m resolution) images as well as morphological sketches and GPS data collected during field visits. The Advanced Spaceborne Thermal Emission and Reflection Radiometer Digital Elevation Model (ASTER-DEM, 30m resolution) has also been used to enhance the morphological and elevation characterization of glacial features. A host of glacial features like lateral and terminal moraines, serrate, debris cones, moulins and outwash plains are among several others mapped in the study region. Using dating techniques, the spatial data on glacial landform features in the area can be used to guide the reconstruction of paleo-glaciological setups. This fills in some of the gaps in our knowledge about glaciation in the Kashmir Himalaya during the Pleistocene.
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Abe-Ouchi, A., F. Saito, M. Kageyama, P. Braconnot, S. P. Harrison, K. Lambeck, B. L. Otto-Bliesner, et al. "Ice-sheet configuration in the CMIP5/PMIP3 Last Glacial Maximum experiments." Geoscientific Model Development Discussions 8, no. 6 (June 3, 2015): 4293–336. http://dx.doi.org/10.5194/gmdd-8-4293-2015.
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Abstract. We describe the creation of boundary conditions related to the presence of ice sheets, including ice sheet extent and height, ice shelf extent, and the distribution and altitude of ice-free land, at the Last Glacial Maximum (LGM) for use in LGM experiments conducted as part of the fifth phase of the Coupled Modelling Intercomparison Project (CMIP5) and the third phase of the Palaeoclimate Modelling Intercomparison Project (PMIP3). The CMIP5/PMIP3 data sets were created from reconstructions made by three different groups, which were all obtained using a model-inversion approach but differ in the assumptions used in the modelling and in the type of data used as constraints. The ice sheet extent, and thus the albedo mask, for the Northern Hemisphere (NH) does not vary substantially between the three individual data sources. The difference in the topography of the NH ice sheets is also moderate, and smaller than the differences between these reconstructions (and the resultant composite reconstruction) and ice-sheet reconstructions used in previous generations of PMIP. Only two of the individual reconstructions provide information for Antarctica. The discrepancy between these two reconstructions is larger than the difference for the NH ice sheets although still less than the difference between the composite reconstruction and previous PMIP ice-sheet reconstructions. Differences in the climate response to the individual LGM reconstructions, and between these reconstructions and the CMIP5/PMIP3 composite, are largely confined to the ice-covered regions, but also extend over North Atlantic Ocean and Northern Hemisphere continents through atmospheric stationary waves. There are much larger differences in the climate response to the latest reconstructions (or the derived composite) and ice-sheet reconstructions used in previous phases of PMIP.
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Blard, Pierre-Henri, Jérôme Lave, Kenneth A. Farley, Victor Ramirez, Nestor Jimenez, Léo C. P. Martin, Julien Charreau, Bouchaïb Tibari, and Michel Fornari. "Progressive glacial retreat in the Southern Altiplano (Uturuncu volcano, 22°S) between 65 and 14 ka constrained by cosmogenic 3He dating." Quaternary Research 82, no. 1 (July 2014): 209–21. http://dx.doi.org/10.1016/j.yqres.2014.02.002.
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AbstractThis work presents the first reconstruction of late Pleistocene glacier fluctuations on Uturuncu volcano, in the Southern Tropical Andes. Cosmogenic 3He dating of glacial landforms provides constraints on ancient glacier position between 65 and 14 ka. Despite important scatter in the exposure ages on the oldest moraines, probably resulting from pre-exposure, these 3He data constrain the timing of the moraine deposits and subsequent glacier recessions: the Uturuncu glacier may have reached its maximum extent much before the global LGM, maybe as early as 65 ka, with an equilibrium line altitude (ELA) at 5280 m. Then, the glacier remained close to its maximum position, with a main stillstand identified around 40 ka, and another one between 35 and 17 ka, followed by a limited recession at 17 ka. Then, another glacial stillstand is identified upstream during the late glacial period, probably between 16 and 14 ka, with an ELA standing at 5350 m. This stillstand is synchronous with the paleolake Tauca highstand. This result indicates that this regionally wet and cold episode, during the Heinrich 1 event, also impacted the Southern Altiplano. The ELA rose above 5450 m after 14 ka, synchronously with the Bolling–Allerod.
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Stutz, Jamey, Andrew Mackintosh, Kevin Norton, Ross Whitmore, Carlo Baroni, Stewart S. R. Jamieson, Richard S. Jones, et al. "Mid-Holocene thinning of David Glacier, Antarctica: chronology and controls." Cryosphere 15, no. 12 (December 7, 2021): 5447–71. http://dx.doi.org/10.5194/tc-15-5447-2021.
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Abstract. Quantitative satellite observations only provide an assessment of ice sheet mass loss over the last four decades. To assess long-term drivers of ice sheet change, geological records are needed. Here we present the first millennial-scale reconstruction of David Glacier, the largest East Antarctic outlet glacier in Victoria Land. To reconstruct changes in ice thickness, we use surface exposure ages of glacial erratics deposited on nunataks adjacent to fast-flowing sections of David Glacier. We then use numerical modelling experiments to determine the drivers of glacial thinning. Thinning profiles derived from 45 10Be and 3He surface exposure ages show David Glacier experienced rapid thinning of up to 2 m/yr during the mid-Holocene (∼ 6.5 ka). Thinning slowed at 6 ka, suggesting the initial formation of the Drygalski Ice Tongue at this time. Our work, along with ice thinning records from adjacent glaciers, shows simultaneous glacier thinning in this sector of the Transantarctic Mountains occurred 4–7 kyr after the peak period of ice thinning indicated in a suite of published ice sheet models. The timing and rapidity of the reconstructed thinning at David Glacier is similar to reconstructions in the Amundsen and Weddell embayments. To identify the drivers of glacier thinning along the David Glacier, we use a glacier flowline model designed for calving glaciers and compare modelled results against our geological data. We show that glacier thinning and marine-based grounding-line retreat are controlled by either enhanced sub-ice-shelf melting, reduced lateral buttressing or a combination of the two, leading to marine ice sheet instability. Such rapid glacier thinning events during the mid-Holocene are not fully captured in continental- or catchment-scale numerical modelling reconstructions. Together, our chronology and modelling identify and constrain the drivers of a ∼ 2000-year period of dynamic glacier thinning in the recent geological past.
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Sun, Yong, Xiangke Xu, Lianqing Zhang, Jinhua Liu, Xiaolong Zhang, Jiule Li, and Baolin Pan. "Numerical Reconstruction of Three Holocene Glacial Events in Qiangyong Valley, Southern Tibetan Plateau and Their Implication for Holocene Climate Changes." Water 12, no. 11 (November 16, 2020): 3205. http://dx.doi.org/10.3390/w12113205.
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The dating of well-preserved Holocene moraines in the Qiangyong Valley, southern Tibetan Plateau (TP), offers great potential for reconstructing Holocene glacier extents and examining climate changes in the region. Guided by Holocene moraine features, this study used Geographic Information System (GIS) model tools to reconstruct paleo-glacier surfaces and glacier equilibrium line altitude (ELA) depressions for three Holocene glacial stages in the valley. The GIS-based models showed that the Qiangyong Valley contained ice volumes of 8.1 × 108, 6.2 × 108, and 4.6 × 108 m3 during the early Holocene, Neoglacial, and Little Ice Age (LIA) glacial stages, and that the ELA was decreased by ~230 ± 25, ~210 ± 25, and ~165 ± 25 m, respectively, compared to modern conditions. Furthermore, the summer temperatures were estimated to be 1.56–1.79, 1.37–1.64, and 1.29–1.32 °C cooler than present to support the three Holocene glacier extents, based on the evidence that the respective precipitation increased by 20–98, 13–109, and 0.9–11 mm relative to the present, which were derived from the lacustrine pollen data for the southern TP. By comparison, this study found that the amplitudes of the ELA-based summer temperature depressions were much larger than the pollen-based counterparts for the three glacial stages, although the two proxies both showed increasing trends in the reconstructed summer temperatures.
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Foisy, Marc, and Gilbert Prichonnet. "A reconstruction of glacial events in southeastern New Brunswick." Canadian Journal of Earth Sciences 28, no. 10 (October 1, 1991): 1594–612. http://dx.doi.org/10.1139/e91-143.
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Sedimentological and petrographical data obtained from five sections located north and south of the Caledonian Highlands in southeastern New Brunswick demonstrate the existence of three main till units and one glaciofluvial unit, which have been grouped in four distinct lithostratigraphic units. The lower till was deposited by a glacier that overrode the Caledonian Highlands from northwest to southeast and advanced as far as Nova Scotia during Middle(?) to Late Wisconsinan times. The overlying middle till from the north provides evidence that ice continued to advance across the Highlands from northwest toward southeast and then was partially overwhelmed by another glacier that was advancing southwest along the southern border of the Highlands: this glacier deposited a coeval middle till. During Late Wisconsinan deglaciation, ice separated into two masses: a residual ice cap with radial outflow from the Highlands; and a lobe in the Chignecto Bay, retreating toward the northeast. The existence of a plateau ice cap is demonstrated by the presence of till and glaciofluvial deposits in the upper part of all surveyed sections, and is supported by the sequence of ice flow patterns recorded by striae and the centrifugal distribution of meltwater flow indicators. The weak development of soils, the fresh appearance of till and morainic landforms, and the lack of periglacial features throughout the area, especially on the Highlands, all favour the interpretation that the Caledonian Highlands were not a nunatak during the glacial maximum of the Late Wisconsinan Substage.
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Gschwentner, Philipp, Hanns Kerschner, and Christoph Spötl. "Late Glacial ice advance in the Kellerjoch region near Schwaz (Tyrol, Eastern Alps)." Austrian Journal of Earth Sciences 113, no. 1-2 (June 1, 2020): 211–27. http://dx.doi.org/10.17738/ajes.2020.0013.
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Abstract The Kellerjoch forms a small isolated massif at the northernmost rim of the central Eastern Alps of Tyrol and shows a number of geomorphological features of glacial and periglacial origin. Mapping yields evidence of two local glaciations postdating the Last Glacial Maximum. Using a simple glaciological approach the palaeoglaciers related to these events were reconstructed. The older glaciation yields an equilibrium line altitude (ELA) ranging from 1660 m for the maximum extent to 1800 m a.s.l. for the innermost moraine. For the younger glaciation, ELAs were reconstructed at 1905 m and 1980 m (depending on the reconstruction) for the Kellerjoch palaeoglacier 2, as well as 1870 m and 2060 m a.s.l. for the Proxen palaeoglacier and the Gart palaeoglacier, respectively. A comparison with published data from the Eastern Alps shows that the older glaciation in the Kellerjoch region likely corresponds to the Gschnitz stadial. Low basal shear stresses of the glacier tongues point towards a cold and dry climate, similar to the reconstruction for the Gschnitz type locality at Trins. The younger glaciation cannot unambiguously be assigned to a specific Late Glacial ice advance, but a Younger Dryas age is a distinct possibility.
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Shukla, Tanuj, Manish Mehta, DP Dobhal, Archna Bohra, Bhanu Pratap, and Anil Kumar. "Late-Holocene climate response and glacial fluctuations revealed by the sediment record of the monsoon-dominated Chorabari Lake, Central Himalaya." Holocene 30, no. 7 (March 10, 2020): 953–65. http://dx.doi.org/10.1177/0959683620908654.
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We studied a periglacial lake situated in the monsoon-dominated Central Himalaya where an interplay of monsoonal precipitation and glacial fluctuations during the late Holocene is well preserved. A major catastrophe occurred on 16–17 June 2013, with heavy rains causing rupturing of the moraine-dammed Chorabari Lake located in the Mandakini basin, Central Himalaya, and exposed 8-m-thick section of the lacustrine strata. We reconstructed the late-Holocene climatic variability in the region using multi-parametric approach including magnetic, mineralogical and chemical (XRF) properties of sediments, paired with grain size and optically simulated luminescence (OSL) dating. The OSL chronology suggests that the lake was formed by a lateral moraine during the deglaciation phase of Chorabari Glacier between 4.2 and 3.9 ka and thereafter the lake deposited about 8-m-thick sediment sequence in the past 2.3 ka. The climatic reconstruction of the lake broadly represents the late-Holocene glacial chronology of the Central Himalaya coupled with many short-term climatic perturbations recorded at a peri-glacial lake setting. The major climatic phases inferred from the study suggests (1) a cold period between 260 BCE and 270 CE, (2) warmer conditions between 900 and 1260 CE for glacial recession and (3) glacial conditions between ~1370 and 1720 CE when the glacier gained volume probably during the ‘Little Ice Age’ (LIA). We suggest a high glacial sensitivity to climatic variability in the monsoon-dominated region of the Himalaya.
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Steiger, Nathan J., Gregory J. Hakim, Eric J. Steig, David S. Battisti, and Gerard H. Roe. "Assimilation of Time-Averaged Pseudoproxies for Climate Reconstruction." Journal of Climate 27, no. 1 (January 1, 2014): 426–41. http://dx.doi.org/10.1175/jcli-d-12-00693.1.
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Abstract The efficacy of a novel ensemble data assimilation (DA) technique is examined in the climate field reconstruction (CFR) of surface temperature. A minimalistic, computationally inexpensive DA technique is employed that requires only a static ensemble of climatologically plausible states. Pseudoproxy experiments are performed with both general circulation model (GCM) and Twentieth Century Reanalysis (20CR) data by reconstructing surface temperature fields from a sparse network of noisy pseudoproxies. The DA approach is compared to a conventional CFR approach based on principal component analysis (PCA) for experiments on global domains. DA outperforms PCA in reconstructing global-mean temperature in all experiments and is more consistent across experiments, with a range of time series correlations of 0.69–0.94 compared to 0.19–0.87 for the PCA method. DA improvements are even more evident in spatial reconstruction skill, especially in sparsely sampled pseudoproxy regions and for 20CR experiments. It is hypothesized that DA improves spatial reconstructions because it relies on coherent, spatially local temperature patterns, which remain robust even when glacial states are used to reconstruct nonglacial states and vice versa. These local relationships, as utilized by DA, appear to be more robust than the orthogonal patterns of variability utilized by PCA. Comparing results for GCM and 20CR data indicates that pseudoproxy experiments that rely solely on GCM data may give a false impression of reconstruction skill.
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LALETINA, S. O., and V. V. LEMESHKOVA. "RECONSTRUCTION OF LAKE-GLACIER EVENTS IN THE ANABAR-PUTORANA REGION." Meteorologiya i Gidrologiya, no. 9 (September 2022): 125–28. http://dx.doi.org/10.52002/0130-2906-2022-9-125-128.
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The topic of reconstruction of ancient glacial lakes is currently of particular interest in connection with global climate change. The glaciers of the Arctic, Greenland, Eurasia are melting due to rising temperatures, and their melt waters form a completely new terrain. The study and reconstruction of the processes of development of ancient lacustrine-glacial events make it possible to predict the mechanism of similar geophysical processes in the future.
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Oliva, Marc, Dermot Antoniades, Enrique Serrano, Santiago Giralt, Emma J. Liu, Ignacio Granados, Sergi Pla-Rabes, Manuel Toro, Soon Gyu Hong, and Gonçalo Vieira. "The deglaciation of Barton Peninsula (King George Island, South Shetland Islands, Antarctica) based on geomorphological evidence and lacustrine records." Polar Record 55, no. 3 (May 2019): 177–88. http://dx.doi.org/10.1017/s0032247419000469.
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AbstractBarton Peninsula is an ice-free area located in the southwest corner of King George Island (South Shetland Islands, Antarctica). Following the Last Glacial Maximum, several geomorphological features developed in newly exposed ice-free terrain and their distribution provide insights about past environmental evolution of the area. Three moraine systems are indicative of three main glacial phases within the long-term glacial retreat, which also favoured the development of numerous lakes. Five of these lakes were cored to understand in greater detail the pattern of deglaciation through the study of lacustrine records. Radiocarbon dates from basal lacustrine sediments enabled the reconstruction of the chronology of Holocene glacial retreat. Tephra layers present in lake sediments provided additional independent age constraints on environmental changes based on geochemical and geochronological correlation with Deception Island-derived tephra. Shrinking of the Collins Glacier exposed the southern coastal fringe of Barton Peninsula at 8 cal ky BP. After a period of relative stability during the mid-Holocene, the ice cap started retreating northwards after 3.7 cal ky BP, confining some glaciers within valleys as shown by moraine systems. Lake sediments confirm a period of relative glacial stability during the last 2.4 cal ky BP.
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Leonard, Eric M. "Use of Lacustrine Sedimentary Sequences as Indicators of Holocene Glacial History, Banff National Park, Alberta, Canada." Quaternary Research 26, no. 2 (September 1986): 218–31. http://dx.doi.org/10.1016/0033-5894(86)90106-7.
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Bottom sediments from three lakes in the Canadian Rocky Mountains were examined with the aim of evaluating the usefulness of downvalley sediment studies in reconstruction of Holocene glacial histories. Analyses of organic carbon and carbonate contents of core sediments provide information on changing sedimentation rate and changing relative importance of glacial and non-glacial sediment sources. Sedimentary histories of the three lakes are similar, suggesting that they record regional glacial/climatic forcing, rather than localized events, and thus that they may be useful in reconstructing Holocene glacial history. Lacustrine sediments indicate a period of high sedimentation rates and relatively large glacial sediment contribution prior to 7500-7000 yr B.P., with much reduced rates and decreased glacial sediment contribution between about 6000 and 4000 yr B.P., possibly interrupted by a brief period of increased glacial sediment output shortly after 5000 yr B.P. Sometime after 4000 yr B.P., sedimentation rates and glacial sediment output began to rise again, reaching approximately present levels by 2750-2650 yr B.P., and have not since returned to low mid-Holocene levels. In detail over the last 3000 yr there is some indication of a slight decrease in sedimentation rate for more than 1000 yr after about 2200 yr B.P. Sedimentation rates and glacial sediment input into all three lakes rose between about 900 and 750 yr B.P. and have remained very high since. If the lake sediments are interpreted as a proxy record of upvalley glacial activity, they allow the development of a glacial chronology which is at once generally consistent with, and more complete and easily datable than, the surficial glacial record.
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Monnier, S., C. Camerlynck, F. Rejiba, C. Kinnard, and P. Y. Galibert. "Glacier ice in rock glaciers: a case study in the Vanoise Massif, Northern French Alps." Cryosphere Discussions 5, no. 6 (December 21, 2011): 3597–626. http://dx.doi.org/10.5194/tcd-5-3597-2011.
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Abstract. We investigated the Sachette rock glacier, Vanoise Massif, Northern French Alps, using former equilibrium line altitude reconstruction from glacial deposits, aerial photograph analysis, and ground-penetrating radar (GPR). The rock glacier is a young (probably <6000 yr) and active landform. The GPR survey consisted of two CMP measurements and four constant-offset profiles. From CMP measurements, the radar wave velocity in exposed shallow massive ice is 0.165–0.17 m ns−1. The constant-offset GPR data was processed and analysed in order to reconstruct the stratigraphy and model the radar wave velocity in two dimensions. The integration of the morphology, the velocity models, and the stratigraphy emphasized, in the upper half of the rock glacier, the good correspondence between high radar wave velocities (>0.15–0.16 m ns−1) and reflectors having a dipping-syncline structure, typical of true glaciers. Consequently, the rock glacier structure is described as being constituted of a glacial massive ice core embedded into diamictons. Our study of the Sachette rock glacier highlights possible significance of rock glaciers and interactions between glacier and permafrost in alpine environments.
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Schmidt, P., B. Lund, J.-O. Näslund, and J. Fastook. "Comparing a thermo-mechanical Weichselian Ice Sheet reconstruction to reconstructions based on the sea level equation: aspects of ice configurations and glacial isostatic adjustment." Solid Earth 5, no. 1 (May 26, 2014): 371–88. http://dx.doi.org/10.5194/se-5-371-2014.
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Abstract. In this study we compare a recent reconstruction of the Weichselian Ice Sheet as simulated by the University of Maine ice sheet model (UMISM) to two reconstructions commonly used in glacial isostatic adjustment (GIA) modelling: ICE-5G and ANU (Australian National University, also known as RSES). The UMISM reconstruction is carried out on a regional scale based on thermo-mechanical modelling, whereas ANU and ICE-5G are global models based on the sea level equation. The three models of the Weichselian Ice Sheet are compared directly in terms of ice volume, extent and thickness, as well as in terms of predicted glacial isostatic adjustment in Fennoscandia. The three reconstructions display significant differences. Whereas UMISM and ANU includes phases of pronounced advance and retreat prior to the last glacial maximum (LGM), the thickness and areal extent of the ICE-5G ice sheet is more or less constant up until the LGM. During the post-LGM deglaciation phase ANU and ICE-5G melt relatively uniformly over the entire ice sheet in contrast to UMISM, which melts preferentially from the edges, thus reflecting the fundamental difference in the reconstruction scheme. We find that all three reconstructions fit the present-day uplift rates over Fennoscandia equally well, albeit with different optimal earth model parameters. Given identical earth models, ICE-5G predicts the fastest present-day uplift rates, and ANU the slowest. Moreover, only for ANU can a unique best-fit model be determined. For UMISM and ICE-5G there is a range of earth models that can reproduce the present-day uplift rates equally well. This is understood from the higher present-day uplift rates predicted by ICE-5G and UMISM, which result in bifurcations in the best-fit upper- and lower-mantle viscosities. We study the areal distributions of present-day residual surface velocities in Fennoscandia and show that all three reconstructions generally over-predict velocities in southwestern Fennoscandia and that there are large differences in the fit to the observational data in Finland and northernmost Sweden and Norway. These difference may provide input to further enhancements of the ice sheet reconstructions.
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Dowsett, Harry, Aisling Dolan, David Rowley, Robert Moucha, Alessandro M. Forte, Jerry X. Mitrovica, Matthew Pound, et al. "The PRISM4 (mid-Piacenzian) paleoenvironmental reconstruction." Climate of the Past 12, no. 7 (July 13, 2016): 1519–38. http://dx.doi.org/10.5194/cp-12-1519-2016.
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Abstract. The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian ( ∼ 3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.
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Milivojevic, Milovan. "Glacial morphology of Komovi." Glasnik Srpskog geografskog drustva 84, no. 2 (2004): 45–60. http://dx.doi.org/10.2298/gsgd0402045m.
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The paper presents the glacial relief on Mt. Komovi in Montenegro. The most common are the macro-glacial forms, which are the best preserved - cirques and moraines. By the analysis of topographic maps and survey in the field the situation, orientation and morphometric data on these forms are given. The analysis of impact of exposures on the cirque bottom elevation is given. Furthermore, the level of preservation of glacial relief forms, depending on geological settings, is analyzed. Finally, there is the reconstruction of Pleistocene snow line elevation and spread of glaciations.
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Sternai, Pietro. "Reconstruction of the pre-glacial Alpine topography to address the glacially-induced modifications." Quaternary International 279-280 (November 2012): 466. http://dx.doi.org/10.1016/j.quaint.2012.08.1559.
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Booth, Derek B. "Glacier Physics of the Puget Lobe, Southwest Cordilleran Ice Sheet." Géographie physique et Quaternaire 45, no. 3 (December 13, 2007): 301–15. http://dx.doi.org/10.7202/032877ar.
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ABSTRACT The Puget lobe, the southwest-most extension of the Cordilleran ice sheet, provides an excellent opportunity to examine the connection between glacier physics and the resulting products of glaciation. The action of water, at and within the sediments of the glacier bed, is particularly significant for the geologic record of this ice sheet. Physical data and inferred mass balance relationships constrain lobe reconstruction and predict sliding velocities in excess of 500 m/a and water discharges of nearly 1 * 10" m3/a. This sub-glacial water produced a dendritic channel pattern well predicted by static analysis of sub-glacial hydrology. Near to the eastern ice margin, a much larger single channel drained subglacially and episodically, with tributary ice-dammed lakes releasing their water as jokulhlaups. Basal meltwater generated near-hydrostatic water pressures and very low till strengths at the base of the ice sheet. Water pressure dropped only close to the ice margin, allowing normal stresses to rise to significant fractions of the total ice overburden. Thus marginal and interior zones impose contrasting bed conditions. Although observation of sub-glacial deposits will reflect the late-stage passage of the marginal zone, conditions within the ice-sheet interior, far more significant to glacier history and behavior, may be substantially different.
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Orvis, Kenneth H., and Sally P. Horn. "Quaternary Glaciers and Climate on Cerro Chirripó, Costa Rica." Quaternary Research 54, no. 1 (July 2000): 24–37. http://dx.doi.org/10.1006/qres.2000.2142.
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Glacial lake sediments and glacial geomorphology in Valle de las Morrenas, a glacial trough on the north face of Cerro Chirripó, Costa Rica, provide evidence on high-altitude Pleistocene conditions in Central America. The most recent glacier in the valley (Chirripó stage I) receded very rapidly near the end of the Younger Dryas chronozone. Radiocarbon dates on basal organic sediments from lakes beneath upper, middle, and lower limits of that glacier fall close together, and two-sigma calibrated ages overlap for the period 9700–9600 cal yr B.P. Earliest datable transition sediments from the central lake date to 12,360–11,230 cal yr B.P. Larger, older moraines, and associated trimlines, allowed reconstruction of three paleoglaciers (Chirripó stages II, III, and IV). Computer analysis of hypsometry using published tropical-glacier vertical mass balance profiles yields ELAs of 3506–3523, 3515–3537, and 3418–3509 m, respectively; Chirripó II ELA-estimate positions applied to Chirripó I yield an ELA of 3538–3546 m. We infer minimal temperature depressions of 7.4–8.0°C for the Chirripó I–IV stages. Modeling the behavior of modern tropical glaciers yields basinwide net accumulation estimates of 440–620, 550–830, and 960–1760 mm yr−1 for the Chirripó II, III, and IV stages.
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Zech, R., Ch Kull, P. W. Kubik, and H. Veit. "LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from <sup>10</sup>Be surface exposure dating." Climate of the Past 3, no. 4 (October 26, 2007): 623–35. http://dx.doi.org/10.5194/cp-3-623-2007.
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Abstract. Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.
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Zech, R., Ch Kull, P. W. Kubik, and H. Veit. "LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from <sup>10</sup>Be surface exposure dating." Climate of the Past Discussions 3, no. 3 (June 27, 2007): 839–69. http://dx.doi.org/10.5194/cpd-3-839-2007.
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Abstract. Surface exposure dating (SED) is an innovative tool being already widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been substantially overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions further west and south.
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Williams, Stephen, Lonnie Parker, and Ayanna Howard. "Terrain Reconstruction of Glacial Surfaces : Robotic Surveying Techniques." IEEE Robotics & Automation Magazine 19, no. 4 (December 2012): 59–71. http://dx.doi.org/10.1109/mra.2011.2181769.
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Kenzler, Michael, and Heiko Hüneke. "Sea cliff at Glowe: stratigraphy and absolute age chronology of the Jasmund Pleistocene sedimentary record." DEUQUA Special Publications 2 (August 15, 2019): 43–50. http://dx.doi.org/10.5194/deuquasp-2-43-2019.
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Abstract. Four remarkable Pleistocene cliff outcrops scattered across the peninsula of Jasmund exhibit the dynamics of the Scandinavian Ice Sheet during the Weichselian glaciation in this area. The investigated sites display up to 30 m thick sequences of glacial tills with intercalated (glaci)fluvial to (glaci)lacustrine sediments. Based on detailed lithofacies analyses and a physical age chronology, we trace the reconstruction of the depositional sequences and their corresponding stratigraphic position within the Weichselian record.
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Seguinot, J., I. Rogozhina, A. P. Stroeven, M. Margold, and J. Kleman. "Numerical simulations of the Cordilleran ice sheet through the last glacial cycle." Cryosphere Discussions 9, no. 4 (August 7, 2015): 4147–203. http://dx.doi.org/10.5194/tcd-9-4147-2015.
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Abstract. Despite more than a century of geological observations, the Cordilleran ice sheet of North America remains poorly understood in terms of its former extent, volume and dynamics. Although geomorphological evidence is abundant, its complexity is such that whole ice-sheet reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (61.9–56.5 ka) and 2 (23.2–16.8 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.6–6.2 ka).
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Yokoyama, Yusuke, Anthony Purcell, Kurt Lambeck, and Paul Johnston. "Shore-line reconstruction around Australia during the Last Glacial Maximum and Late Glacial Stage." Quaternary International 83-85 (September 2001): 9–18. http://dx.doi.org/10.1016/s1040-6182(01)00028-3.
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Marshall, Shawn J., Lev Tarasov, Garry K. C. Clarke, and W. Richard Peltier. "Glaciological reconstruction of the Laurentide Ice Sheet: physical processes and modelling challenges." Canadian Journal of Earth Sciences 37, no. 5 (May 1, 2000): 769–93. http://dx.doi.org/10.1139/e99-113.
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Current understanding of Pleistocene ice-sheet history is based on collective inferences from three separate avenues of study: (1) the geologic and paleoceanographic records, (2) the isostatic record, and (3) the behaviour of contemporary glaciers and ice sheets. The geologic record provides good constraint on the areal extent of former ice sheets, while isostatic deflection patterns provide important information about late-glacial ice-sheet thickness. The picture emerging from geologic and isostatic deductions is suggestive of a thin and mobile Laurentide Ice Sheet relative to present-day Greenland and Antarctica. We model Laurentide Ice Sheet evolution through a glacial cycle to explore the glaciological mechanisms that are required to replicate the geologic and isostatic evidence. A number of glaciological processes important to the ice-sheet evolution are not fully understood, including marine-based ice dynamics, iceberg calving, rheologic properties of ice, and basal flow dynamics. We present a spectrum of glacial cycle simulations with different treatments of poorly constrained physical processes. We conclude that glaciological model reconstructions can only be reconciled with the late-glacial geologic record of a thin, low-sloping Laurentide Ice Sheet by invoking (1) extremely deformable ice, (2) widespread basal flow, or (3) paleoclimate-ice-sheet fluctuations which give last glacial maximum ice sheets that are far from equilibrium.
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Wickert, Andrew D. "Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum." Earth Surface Dynamics 4, no. 4 (November 8, 2016): 831–69. http://dx.doi.org/10.5194/esurf-4-831-2016.
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Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins – the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.
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Burge, Philip I., and James Shulmeister. "Re-envisioning the structure of last glacial vegetation in New Zealand using beetle fossils." Quaternary Research 68, no. 1 (July 2007): 121–32. http://dx.doi.org/10.1016/j.yqres.2007.03.009.
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AbstractA series of 18 fossil beetle assemblages are used to reconstruct the paleoenvironment of the northwest West Coast, New Zealand, over the period of the last interstadial–stadial transition (ca. 37,000–21,300 cal yr BP). The samples were recovered from an in-filled hollow within a dune field ca. 9 km south west of Westport (41°47′S, 171°30′E). This fossil beetle reconstruction is compared to an existing palynological reconstruction from the same site. The beetle assemblages indicate an environment of marshy shrubland interspersed with closed canopy coastal vegetation prior to glacial onset, and a mosaic of closed canopy patches and open tussock grassland during full glacial conditions. These interpretations, contrast with the palynologically based interpretation which indicates subalpine shrubland prior to glacial onset and widespread grassland with little woody vegetation during the period of maximum glacial cooling. This study is consistent with other non-pollen studies in New Zealand and indicates that the palynological interpretation of the paleoenvironment of the Westport region downplays the importance of closed canopy vegetation in the area during the transition from interstadial to full glacial (stadial) conditions. It challenges the interpretation of open vegetation at low elevations during glacial periods from pollen studies.
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Scapozza, Cristian, Chantal Del Siro, Christophe Lambiel, and Christian Ambrosi. "Schmidt hammer exposure-age dating of periglacial and glacial landforms in the Southern Swiss Alps based on <i>R</i>-value calibration using historical data." Geographica Helvetica 76, no. 4 (November 15, 2021): 401–23. http://dx.doi.org/10.5194/gh-76-401-2021.
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Abstract. As a contribution to the palaeoenvironmental history reconstruction of the Alpine periglacial domain, this study focuses on the Schmidt hammer exposure-age dating (SHD) of (peri-)glacial landforms using rebound-value (R-value) calibrations for 10 stations in the Scaradra glacier forefield (north-eastern part of the Ticino Canton, Lepontine Alps) and for 13 stations in the Splügenpass region (located between Switzerland and Italy, Rhaetian Alps). Linear calibration based on the known age of several moraines of the Scaradra glacier assessed by historical cartography allowed the reconstruction of the glacier fluctuations around the end of the Little Ice Age. Timing of deglaciation and of rock glacier development was defined in the Splügenpass region using the calibration of exposure ages based on two mule tracks built in 300 CE and 1250 CE, respectively. Discussion on R-value analysis and calibration improves the knowledge on the potential use of SHD for numerical-age dating in Alpine geomorphological studies.
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Murray, Donald R., and William W. Locke. "Dynamics of the Late Pleistocene Big Timber Glacier, Crazy Mountains, Montana, U.S.A." Journal of Glaciology 35, no. 120 (1989): 183–90. http://dx.doi.org/10.3189/s0022143000004470.
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Abstract The late Pleistocene Big Timber glacier of west-central Montana was used as the test case for a model which calculates the mass balance of a paleoglacier using glacial flow theory. Application of Glen’s flow law to a detailed reconstruction of the glacier provided an estimate of the component of mass flux due to internal deformation. Assuming basal slip to be zero where mass flux due to deformation was a maximum, the mass flux at the equilibrium-line altitude (ELA) an ablation gradient of 3.0 ± 0.6 mm/m, and an accumulation gradient of 1.0 ± 0.2 mm/m were determined. Application of the continuity model above and below the ELA generated a second estimate of mass flux at discrete points along the glacier. The difference between deformation flux and continuity flux yields a first approximation of slip, which is highly variable along the glacier. Since the mass-balance gradients are climatically controlled, this model provides information on the paleoclimatic setting of the glacier. The low gradients indicate that, during the last glacial maximum, the east side of the central Rocky Mountains experienced a cold, dry environment much like that of modern-day glaciers in the Brooks Range of Alaska.
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Coppola, A., G. Leonelli, M. C. Salvatore, M. Pelfini, and C. Baroni. "Tree-ring–based summer mean temperature variations in the Adamello–Presanella Group (Italian Central Alps), 1610–2008 AD." Climate of the Past 9, no. 1 (January 28, 2013): 211–21. http://dx.doi.org/10.5194/cp-9-211-2013.
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Abstract. Climate records from remote mountain sites and for century-long periods are usually lacking for most continents and also for the European Alps. However, detailed reconstructions of climate parameters for pre-instrumental periods in mountain areas, suffering of glacial retreat caused by recent global warming, are needed in the view of a better comprehension of the environmental dynamics. We present here the first annually-resolved reconstruction of summer (JJA) mean temperature for the Adamello–Presanella Group (Central European Alps), one of the most glaciated mountain groups of the Italian Central Alps. The reconstruction has been based on four larch tree-ring width chronologies derived from living trees sampled in four valleys surrounding the Group. The reconstruction spans from 1610 to 2008 and the statistical verification of the reconstruction demonstrates the positive skill of the tree-ring dataset in tracking summer temperature variability also in the recent period.
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Paul, André, Stefan Mulitza, Rüdiger Stein, and Martin Werner. "A global climatology of the ocean surface during the Last Glacial Maximum mapped on a regular grid (GLOMAP)." Climate of the Past 17, no. 2 (April 8, 2021): 805–24. http://dx.doi.org/10.5194/cp-17-805-2021.
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Abstract. We present a climatology of the near-sea-surface temperature (NSST) anomaly and the sea-ice extent during the Last Glacial Maximum (LGM, 23 000–19 000 years before present) mapped on a global regular 1∘×1∘ grid. It is an extension of the Glacial Atlantic Ocean Mapping (GLAMAP) reconstruction of the Atlantic NSST based on the faunal and floral assemblage data of the Multiproxy Approach for the Reconstruction of the Glacial Ocean Surface (MARGO) project and several recent estimates of the LGM sea-ice extent. Such a gridded climatology is highly useful for the visualization of the LGM climate, calculation of global and regional NSST averages, and estimation of the equilibrium climate sensitivity, as well as a boundary condition for atmospheric general circulation models. The gridding of the sparse NSST reconstruction was done in an optimal way using the Data-Interpolating Variational Analysis (DIVA) software, which takes into account the uncertainty in the reconstruction and includes the calculation of an error field. The resulting Glacial Ocean Map (GLOMAP) confirms the previous findings by the MARGO project regarding longitudinal and meridional NSST differences that were greater than today in all oceans. Taken at face value, the estimated global and tropical cooling would imply an equilibrium climate sensitivity at the lower end of the currently accepted range. However, because of anticipated changes in the seasonality and thermal structure of the upper ocean during the LGM as well as uneven spatial sampling, the estimated cooling and implied climate sensitivity are likely to be biased towards lower values.
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Seguinot, Julien, Irina Rogozhina, Arjen P. Stroeven, Martin Margold, and Johan Kleman. "Numerical simulations of the Cordilleran ice sheet through the last glacial cycle." Cryosphere 10, no. 2 (March 16, 2016): 639–64. http://dx.doi.org/10.5194/tc-10-639-2016.
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Abstract. After more than a century of geological research, the Cordilleran ice sheet of North America remains among the least understood in terms of its former extent, volume, and dynamics. Because of the mountainous topography on which the ice sheet formed, geological studies have often had only local or regional relevance and shown such a complexity that ice-sheet-wide spatial reconstructions of advance and retreat patterns are lacking. Here we use a numerical ice sheet model calibrated against field-based evidence to attempt a quantitative reconstruction of the Cordilleran ice sheet history through the last glacial cycle. A series of simulations is driven by time-dependent temperature offsets from six proxy records located around the globe. Although this approach reveals large variations in model response to evolving climate forcing, all simulations produce two major glaciations during marine oxygen isotope stages 4 (62.2–56.9 ka) and 2 (23.2–16.9 ka). The timing of glaciation is better reproduced using temperature reconstructions from Greenland and Antarctic ice cores than from regional oceanic sediment cores. During most of the last glacial cycle, the modelled ice cover is discontinuous and restricted to high mountain areas. However, widespread precipitation over the Skeena Mountains favours the persistence of a central ice dome throughout the glacial cycle. It acts as a nucleation centre before the Last Glacial Maximum and hosts the last remains of Cordilleran ice until the middle Holocene (6.7 ka).
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Bezusko, L., S. Mosyakin, and A. Bezusko. "Paleoclimatic reconstruction for the late pleistocene period of the plain part of Ukraine." Visnyk of the Lviv University. Series Geography, no. 38 (December 15, 2010): 3–11. http://dx.doi.org/10.30970/vgg.2010.38.2205.
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The article summarizes the results of quantitative paleoclimatic reconstructions conducted using different methods based on the palinological records of the Upper Pleistocene deposits of the plain part of Ukraine. Quantitative climatic characteristics for the Riss-Wurm interglacial period, Dubno interstadial and the Last Glacial Maximum are provided. It is concluded that primary refugia of thermophilic and hydrophilic trees on the plain areas did not exist during the Last Glacial Maximum. Key words: paleoclimatic reconstructions, Late Pleistocene, Riss-Wurm interglacial period, Dubno interstadial.
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Kellogg, Thomas B., Terry Hughes, and Davida E. Kellogg. "Late Pleistocene interactions of East and West Antarctic Ice-flow Regimes: evidence from the McMurdo Ice Shelf." Journal of Glaciology 42, no. 142 (1996): 486–500. http://dx.doi.org/10.3189/s0022143000003476.
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AbstractWe present new interpretations of deglaciation in McMurdo Sound and the western Ross Sea, with observationally based reconstructions of interactions between East and West Antarctic ice at the last glacial maximum (LGM), 16000, 12000, 8000 and 4000 BP. At the LGM, East Antarctic ice from Mulock Glacier split; one branch turned westward south of Ross Island but the other branch rounded Ross Island before flowing southwest into McMurdo Sound. This flow regime, constrained by an ice saddle north of Ross Island, is consistent with the reconstruction of Stuiver and others (1981a). After the LGM, grounding-line retreat was most rapid in areas with greatest water depth, especially along the Victoria Land coast. By 12000 BP, the ice-now regime in McMurdo Sound changed to through-flowing Mulock Glacier ice, with lesser contributions from Koettlitz, Blue and Ferrar Glaciers, because the former ice saddle north of Ross Island was replaced by a dome. The modern flew regime was established ∼4000 BP. Ice derived from high elevations on the Polar Plateau but now stranded on the McMurdo Ice Shelf, and the pattern of the Transantarctic Mountains erratics support our reconstructions of Mulock Glacier ice rounding Minna Bluff but with all ice from Skelton Glacier ablating south of the bluff. They are inconsistent with Drewry’s (1979) LGM reconstruction that includes Skelton Glacier ice in the McMurdo-Sound through-flow. Drewry’s (1979) model closely approximates our results for 12000-4000 BP. Ice-sheet modeling holds promise for determining whether deglaciation proceeded by grounding-line retreat of an ice sheet that was largely stagnant, because it never approached equilibrium flowline profiles after the Ross Ice Shelf grounded, or of a dynamic ice sheet with flowline profiles kept low by active ice streams that extended northward from present-day outlet glaciers after the Ross Ice Shelf grounded.
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Kellogg, Thomas B., Terry Hughes, and Davida E. Kellogg. "Late Pleistocene interactions of East and West Antarctic Ice-flow Regimes: evidence from the McMurdo Ice Shelf." Journal of Glaciology 42, no. 142 (1996): 486–500. http://dx.doi.org/10.1017/s0022143000003476.
Full textAbstract:
AbstractWe present new interpretations of deglaciation in McMurdo Sound and the western Ross Sea, with observationally based reconstructions of interactions between East and West Antarctic ice at the last glacial maximum (LGM), 16000, 12000, 8000 and 4000 BP. At the LGM, East Antarctic ice from Mulock Glacier split; one branch turned westward south of Ross Island but the other branch rounded Ross Island before flowing southwest into McMurdo Sound. This flow regime, constrained by an ice saddle north of Ross Island, is consistent with the reconstruction of Stuiver and others (1981a). After the LGM, grounding-line retreat was most rapid in areas with greatest water depth, especially along the Victoria Land coast. By 12000 BP, the ice-now regime in McMurdo Sound changed to through-flowing Mulock Glacier ice, with lesser contributions from Koettlitz, Blue and Ferrar Glaciers, because the former ice saddle north of Ross Island was replaced by a dome. The modern flew regime was established ∼4000 BP. Ice derived from high elevations on the Polar Plateau but now stranded on the McMurdo Ice Shelf, and the pattern of the Transantarctic Mountains erratics support our reconstructions of Mulock Glacier ice rounding Minna Bluff but with all ice from Skelton Glacier ablating south of the bluff. They are inconsistent with Drewry’s (1979) LGM reconstruction that includes Skelton Glacier ice in the McMurdo-Sound through-flow. Drewry’s (1979) model closely approximates our results for 12000-4000 BP. Ice-sheet modeling holds promise for determining whether deglaciation proceeded by grounding-line retreat of an ice sheet that was largely stagnant, because it never approached equilibrium flowline profiles after the Ross Ice Shelf grounded, or of a dynamic ice sheet with flowline profiles kept low by active ice streams that extended northward from present-day outlet glaciers after the Ross Ice Shelf grounded.