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Patricia L Ciccioli - One of the best experts on this subject based on the ideXlab platform.
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glacial paradoxes during the late paleozoic ice age evaluating the Equilibrium Line altitude as a control on glaciation
Gondwana Research, 2012Co-Authors: John L Isbell, Lindsey C Henry, Erik L Gulbranson, Carlos O Limarino, Margaret L Fraiser, Zelenda J Koch, Patricia L CiccioliAbstract:Abstract The late Paleozoic ice age (LPIA) consists of multiple glaciations that waxed and waned across Gondwana during the Carboniferous and Permian. Three key intervals are evaluated using the concept of the Equilibrium-Line altitude (ELA) as a control on glaciation to provide insight into two intervals of paradoxical ice distribution during and following glaciation. The LPIA began in the mid-latitudes during the Visean in western Argentina with the growth of glaciers in the Protoprecordillera. Glaciation was initiated by uplift of the range above the ELA. In the Bashkirian, deglaciation occurred there while glaciation was beginning at the same latitude in uplands associated with the Parana Basin in Brazil. Analysis suggests that deglaciation of the Protoprecordillera occurred due to extensional collapse of the range below the ELA during a westward shift in the location of plate subduction. During Late Pennsylvanian–Early Permian peak glaciation for the LPIA, extensive glacimarine deposits indicate that glaciers reached sea level, which corresponds to a major lowering of the ELA due to global cooling. Finally, during the Early to early Late transition out of the LPIA, polar Gondwana was unglaciated. However, three glacial intervals occurred at mid- to high-latitudes in eastern Australia from the Sakmarian to the Capitanian/earliest Wuchiapingian. The magnitude of global cooling during these events is debatable as evidence indicates ice-free conditions and an elevated ELA at the South Pole in Antarctica. This suggests that severe global cooling was not the cause of the final three Australian glaciations, but rather that ELA-related conditions specific to eastern Australia drove these late-phase events. Possible causes for the Australian glaciations include: 1) anomalous cold conditions produced by coastal upwelling, 2) the presence of uplands allowing nucleation of glaciers, 3) fluctuations in pCO2 levels, and 4) increased precipitation due to the location of the area in the subpolar low pressure belt.
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glacial paradoxes during the late paleozoic ice age evaluating the Equilibrium Line altitude as a control on glaciation
Gondwana Research, 2012Co-Authors: John L Isbell, Lindsey C Henry, Erik L Gulbranson, Carlos O Limarino, Margaret L Fraiser, Zelenda J Koch, Patricia L CiccioliAbstract:Abstract The late Paleozoic ice age (LPIA) consists of multiple glaciations that waxed and waned across Gondwana during the Carboniferous and Permian. Three key intervals are evaluated using the concept of the Equilibrium-Line altitude (ELA) as a control on glaciation to provide insight into two intervals of paradoxical ice distribution during and following glaciation. The LPIA began in the mid-latitudes during the Visean in western Argentina with the growth of glaciers in the Protoprecordillera. Glaciation was initiated by uplift of the range above the ELA. In the Bashkirian, deglaciation occurred there while glaciation was beginning at the same latitude in uplands associated with the Parana Basin in Brazil. Analysis suggests that deglaciation of the Protoprecordillera occurred due to extensional collapse of the range below the ELA during a westward shift in the location of plate subduction. During Late Pennsylvanian–Early Permian peak glaciation for the LPIA, extensive glacimarine deposits indicate that glaciers reached sea level, which corresponds to a major lowering of the ELA due to global cooling. Finally, during the Early to early Late transition out of the LPIA, polar Gondwana was unglaciated. However, three glacial intervals occurred at mid- to high-latitudes in eastern Australia from the Sakmarian to the Capitanian/earliest Wuchiapingian. The magnitude of global cooling during these events is debatable as evidence indicates ice-free conditions and an elevated ELA at the South Pole in Antarctica. This suggests that severe global cooling was not the cause of the final three Australian glaciations, but rather that ELA-related conditions specific to eastern Australia drove these late-phase events. Possible causes for the Australian glaciations include: 1) anomalous cold conditions produced by coastal upwelling, 2) the presence of uplands allowing nucleation of glaciers, 3) fluctuations in pCO2 levels, and 4) increased precipitation due to the location of the area in the subpolar low pressure belt.
Atle Nesje - One of the best experts on this subject based on the ideXlab platform.
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glacier fluctuations Equilibrium Line altitudes and palaeoclimate in lyngen northern norway during the lateglacial and holocene
The Holocene, 2005Co-Authors: Jostein Bakke, Svein Olaf Dahl, Oyvind Paasche, Reidar Lovlie, Atle NesjeAbstract:Based on lacustrine and morpho-stratigraphical evidence from Lyngen in Troms, northern Norway, 13 marginal moraines have been mapped in front of Lenangsbreene in Strupskardet. Moraines M1-M13 are inferred to represent glacier halts or advance/readvance taking place during the Lateglacial and Holocene. The presence of collapse depressions suggests that some of them were ice cored (M1-M3). A chronological framework, taking into account a combination of former shoreLines and related glacier-meltwater channels, lichenometry and AMS radiocarbon-dated lacustrine sediments spanning the last 20 000 cal. yr BP, has been established. The distal glacier-fed lake Aspvatnet was isolated from the sea c 10 300 cal. yr BP, and the lacustrine sediments have been investigated by use of loss-on-ignition (LOI) magnetic susceptibility, water content, wet and dry bulk density (DBD), and the magnetic parameters anhysteretic remanent magnetization (ARM) and saturation remanent magnetization (SIRM). There is, in general, good agr...
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lateglacial and early holocene palaeoclimatic reconstruction based on glacier fluctuations and Equilibrium Line altitudes at northern folgefonna hardanger western norway
Journal of Quaternary Science, 2005Co-Authors: Atle Nesje, Jostein Bakke, Svein Olaf DahlAbstract:Northern Folgefonna (c. 23 km 2 ), is a nearly circular maritime ice cap located on the Folgefonna Peninsula in Hardanger, western Norway. By combining the position of marginal mor- aines with AMS radiocarbon dated glacier-meltwater induced sediments in proglacial lakes draining northern Folgefonna, a continuous high-resolution record of variations in glacier size and equili- brium-Line altitudes (ELAs) during the Lateglacial and early Holocene has been obtained. After the termination of the Younger Dryas (c. 11 500 cal. yr BP), a short-lived (100-150 years) climatically induced glacier readvance termed the 'Jondal Event 1' occurred within the 'Preboreal Oscillation' (PBO) c. 11 100 cal. yr BP. Bracketed to 10 550-10 450 cal. yr BP, a second glacier readvance is named the 'Jondal Event 2'. A third readvance occurred about 10 000 cal. yr BP and corresponds with the 'Erdalen Event 1' recorded at Jostedalsbreen. An exponential relationship between mean solid winter precipitation and ablation-season temperature at the ELA of Norwegian glaciers is used to reconstruct former variations in winter precipitation based on the corresponding ELA and an indepen- dent proxy for summer temperature. Compared to the present, the Younger Dryas was much colder and drier, the 'Jondal Event 1'/PBO was colder and somewhat drier, and the 'Jondal Event 2' was much wetter. The 'Erdalen Event 1' started as rather dry and terminated as somewhat wetter. Varia- tions in glacier magnitude/ELAs and corresponding palaeoclimatic reconstructions at northern Folge- fonna suggest that low-altitude cirque glaciers (lowest altitude of marginal moraines 290 m) in the area existed for the last time during the Younger Dryas. These low-altitude cirque glaciers of sug- gested Younger Dryas age do not fit into the previous reconstructions of the Younger Dryas ice sheet in Hardanger. Copyright 2005 John Wiley & Sons, Ltd.
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a theoretical approach to glacier Equilibrium Line altitudes using meteorological data and glacier mass balance records from southern norway
The Holocene, 2003Co-Authors: Oyvind Lie, Svein Olaf Dahl, Atle NesjeAbstract:Based on a close exponential relationship between mean ablation-season temperature and winter precipitation at the Equilibrium-Line altitude (ELA) of 10 Norwegian glaciers, three equations are derived. The e rst equation enables calculation of the minimum altitude of areas climatically suited for glacier formation, and is termed the altitude of instantaneous glacierization (AIG). Equation (2) is derived based on the ' principle of terrain adaptation' , enabling quantie cation of the glacial buildup sensitivity (GBS) in presently non-glaciated areas. The theoretical climatic temperature-precipitation ELA ( C TP-ELA) in presently non-glaciated areas is calculated in equation three by combining GBS with terrain altitude. Mass-balance records from four modern glaciers (A lfotbreen, Nigardsbreen, Storbreen and Gra subreen) situated in maritime to continental climate regimes in southern Norway are used to test these equations. Correlation between AIG and net balance measure- ments (bn) yielded correlation coefe cients of r = -0.80 to r = - 0.84. Calculated AIGs correspond well with observed ELAs on A lfotbreen, Nigardsbreen and Gra subreen, while it deviates from the observed ELA on Storbreen; the latter is probably due to leeward accumulation of wind-blown snow on this cirque glacier. Based on this approach, regional representative climatic ELAs can be calculated for non-glaciated areas with instrumental records of ablation-season temperature and winter precipitation.
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reconstruction of former glacier Equilibrium Line altitudes based on proglacial sites an evaluation of approaches and selection of sites
Quaternary Science Reviews, 2003Co-Authors: Svein Olaf Dahl, Jostein Bakke, Oyvind Lie, Atle NesjeAbstract:Abstract Various approaches are used to record variations in glacier activity and Equilibrium-Line altitudes (ELAs) based on proglacial sites (lacustrine and terrestrial). These approaches are based on a conceptual model of glacier-meltwater induced sedimentation in which the minerogenic (nonorganic) component of the sediments is related to the occurrence of a glacier in the catchment. The principal coupling to former glacier activity and ELAs is common for these approaches. However, different methods and techniques may complement each other, and both possibilities and limitations are demonstrated. Site selection for reconstructing variations in glacier activity/ELAs is evaluated and critical factors are discussed. Rerouting of glacier meltwater streams across local watersheds in combination with proglacial sites gives a distinct on/off signal for former glacier activity/ELAs. Together with representative lateral moraines of known age, local watersheds are important for calibrating reconstructed glacier activity/ELAs based on a chain of proglacial lakes. Based on the ‘modern analogue principle’, various proxies can record whenever glaciers existed in a catchment. In a chain of proglacial lakes with different sensitivity to record variations in glacier activity/ELAs, these proxies can be calibrated against independent records. For one-site approaches, however, variations in glacier activity/ELAs depend on the interpretation and sensitivity of the proxies used.
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timing Equilibrium Line altitudes and climatic implications of two early holocene glacier readvances during the erdalen event at jostedalsbreen western norway
The Holocene, 2002Co-Authors: Svein Olaf Dahl, Atle Nesje, Oyvind Lie, Kristine Fjordheim, John A MatthewsAbstract:Following the Younger Dryas, the e rst evidence of glacial activity in southern Norway in response to climatic change occurred during the early Holocene, when terminal moraines from the Erdalen Event formed beyond the position of later 'Little Ice Age' moraines. In front of present outlet glaciers on both sides of the Jostedalsbreen ice cap, sets of pre-'Little Ice Age' marginal moraines have been morphostratigraphicallycorre- lated with the Erdalen Event. The lithostratigraphyin a peat bog at Hellemyrane in Jostedalen, western Norway, provides e rm evidence for a two-phase Erdalen Event associated with two glacier readvances of Nigardsbreen at the Preboreal/Boreal transition. Radiocarbon dates from the peat bog give age estimates for the two phases: the e rst Erdalen Event readvance took place between 10 100 and 10 050 cal. BP, while the second occurred close to 9700 cal. BP. The lowering of the Equilibrium-Linealtitude (ELA) during these readvances is estimated using the 'Little Ice Age' ratio (LR) approach to be about 230 m and 215 m, respectively. The e rst readvance is attributed to an increase in winter precipitation, while the second readvance may have been primarily caused by a marked drop in summer temperature which reactivated already existing ice masses.
Paola Gallo - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics simulations of freezing point depression of tip4p 2005 water in solution with nacl
Journal of Molecular Liquids, 2018Co-Authors: M M Conde, Mauro Rovere, Paola GalloAbstract:Abstract Molecular dynamics simulations have been performed on an aqueous solution of TIP4P/2005 water and NaCl using the direct coexistence technique to determine the Equilibrium Line ice/NaCl solution and the freezing point depression of water in presence of NaCl at different salt concentrations below the eutectic point. We used large samples in order to avoid finite size effects and to minimize the error on the determination of the freezing temperature. Our results are in excellent agreement with the experimental freezing point depression showing that the set of parameters used in this work for the water and NaCl is a very good choice to reproduce the thermodynamic properties of the water/NaCl system with molecular dynamics simulations.
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Molecular dynamics simulations of freezing-point depression of TIP4P/2005 water in solution with NaCl
Journal of Molecular Liquids, 2018Co-Authors: M M Conde, Mauro Rovere, Paola GalloAbstract:Abstract Molecular dynamics simulations have been performed on an aqueous solution of TIP4P/2005 water and NaCl using the direct coexistence technique to determine the Equilibrium Line ice/NaCl solution and the freezing point depression of water in presence of NaCl at different salt concentrations below the eutectic point. We used large samples in order to avoid finite size effects and to minimize the error on the determination of the freezing temperature. Our results are in excellent agreement with the experimental freezing point depression showing that the set of parameters used in this work for the water and NaCl is a very good choice to reproduce the thermodynamic properties of the water/NaCl system with molecular dynamics simulations.
Brice R Rea - One of the best experts on this subject based on the ideXlab platform.
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testing the area altitude balance ratio aabr and accumulation area ratio aar methods of calculating glacier Equilibrium Line altitudes
Journal of Glaciology, 2021Co-Authors: Rachel P Oien, Brice R Rea, Matteo Spagnolo, Iestyn D Barr, R BinghamAbstract:In this study, we compare Equilibrium-Line altitudes (ELAs) calculated using the area–altitude balance ratio (AABR) and the accumulation–area ratio (AAR) methods, with measured ELAs derived from direct field observations. We utilise a GIS toolbox to calculate the ELA for 64 extant glaciers by applying the AABR and AAR methods to DEMs and polygons of their geometry. The calculated ELAs (c-ELAs) are then compared to measured zero-net balance ELAs (znb-ELAs) obtained from mass-balance time series held by the WGMS for the same glaciers. The correlation between znb-ELAs and AABR (1.56)/AAR (0.58) c-ELAs is very strong, with an r 2 = 0.99. The smallest median difference between znb-ELAs and c-ELAs (i.e. 65.5 m) is obtained when a globally representative AABR of 1.56 is used. When applied to palaeoglacier-climate applications, this difference translates to ~0.42°C, well within the uncertainty of palaeotemperature proxies used to determine mean summer temperature at the ELA. The more widely used mean AABR of 1.75 is shown to be statistically invalid due to the skewness of the dataset. On this basis, when calculating glacier ELAs, we recommend the use of a global AABR value of 1.56.
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climatic controls on the Equilibrium Line altitudes of scandinavian cirque glaciers
Geomorphology, 2020Co-Authors: R P Oien, Brice R Rea, Matteo Spagnolo, Iestyn D Barr, R BinghamAbstract:Abstract The Equilibrium-Line altitudes (ELAs) of reconstructed palaeoglaciers have been widely used to assess palaeoclimatic conditions, yet this concept has rarely been tested using modern glaciers. To address this shortcoming, correlations between the ELAs of 513 modern cirque glaciers and present-day climatic and topographic variables across Scandinavia, as well as regional trends in ELA and climate, are analysed. ELAs are calculated using the Area-Altitude-Balance-Ratio method, with a ratio of 1.5 ± 0.4. Results indicate that glacier ELAs are strongly correlated with distance from the coast. This reflects the present-day precipitation pattern of the region (characterised by high precipitation near the sea) and demonstrates a climate dominated by a maritime-continental transition. Temperature explains differences in glacier ELA regional trends as well as ELA changes with latitude. Following standard meteorological convention, Scandinavia is divided into two macro-climate regions and analyses are run within the macro-regions as well as the complete dataset. The strength of correlations between ELA and precipitation increases when the study is divided into northern and southern macro-regions. These results test long held assumptions about relationships between climate and cirque glacier ELA, which is of particular relevance to palaeoclimatic studies based on the reconstruction of former cirque glaciers.
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a gis tool for automatic calculation of glacier Equilibrium Line altitudes
Computers & Geosciences, 2015Co-Authors: Ramon Pellitero, Brice R Rea, Matteo Spagnolo, Jostein Bakke, Philip Hughes, Susan Ivyochs, Sven Lukas, Adriano RiboliniAbstract:A toolbox for the automated calculation of glacier Equilibrium-Line altitudes (ELAs) using the Accumulation Area Ratio, Area-Altitude Balance Ratio, Area-Altitude and Kurowski methods is presented. These are the most commonly-used methods of ELA calculation in palaeo-glacier reconstructions. The toolbox has been coded in Python and runs in ArcGIS requiring only the reconstructed surface of the palaeo-glacier (a DEM) as input. Through fast and automatic calculation this toolbox simplifies the process of ELA determination and can successfully work both for a single glacier and for large datasets of multiple glaciers. We describe Equilibrium Line Altitude calculation methods for palaeoglaciers.We examine suitability of each method for different glacier types.We present a toolbox for automatic ELA calculation on AAR and AABR methods.Toolbox is coded in Python and runs in ArcGIS.Toolbox use and operation are described.
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quantifying climate and glacier mass balance in north norway during the younger dryas
Palaeogeography Palaeoclimatology Palaeoecology, 2007Co-Authors: Brice R Rea, David J A EvansAbstract:Abstract Oksfjordjokelen is located at ∼ 70° N on the Troms–Finnmark border in North Norway. During the Younger Dryas, it was decoupled from and sat just beyond the margin of the Scandinavian Ice Sheet. At this time the major fjords in Troms and Finnmark were ice-free with outlet glaciers from the icefield filling a number of smaller side valleys. Only one outlet from the icefield, Sorfjorddalen, is temporally well-constrained by 14 C dating and association with the Main ShoreLine (associated with a period of minimal crustal rebound dated to the Younger Dryas). Sorfjorddalen is reconstructed using a valley centre-Line iterative model and assuming a no-slip basal boundary condition. This assumption of cold-based ice is supported by the geomorphological evidence of angular bouldery fronto-lateral moraines formed during the Younger Dryas. The Equilibrium Line altitude for the Sorfjorddalen is calculated using both the Balance Ratio and Accumulation Area Ratio methods, and this is used to constrain the snout positions (generally to mapped moraines) of the other outlets. This approach assumes similarity of mass balance gradients and geometries of the outlet glaciers which is supported by present-day symmetry of the icefield. This method is extremely useful in such environments where dateable material is often difficult, if not impossible, to find. Some margins terminated in deep water where bathymetry was lacking, making calving quantification problematic with subsequent impacts on Equilibrium Line altitudes poorly constrained. These deep-water terminating snouts were discounted from subsequent palaeo-climate reconstructions. An empirical Equilibrium Line altitude temperature-precipitation relationship was used to define limits of climate change required to sustain the reconstructed icefield. Palaeo-precipitation estimates were refined using a palaeo-temperature estimate for the Younger Dryas from Andoya. Calculations of ice flux through the Equilibrium Line altitude were used to further constrain the mass balance characteristics of the reconstructed icefield and these suggest similarities with ice masses found in the northern (Nordaustlandet) regions of Svalbard.
Carlos O Limarino - One of the best experts on this subject based on the ideXlab platform.
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glacial paradoxes during the late paleozoic ice age evaluating the Equilibrium Line altitude as a control on glaciation
Gondwana Research, 2012Co-Authors: John L Isbell, Lindsey C Henry, Erik L Gulbranson, Carlos O Limarino, Margaret L Fraiser, Zelenda J Koch, Patricia L CiccioliAbstract:Abstract The late Paleozoic ice age (LPIA) consists of multiple glaciations that waxed and waned across Gondwana during the Carboniferous and Permian. Three key intervals are evaluated using the concept of the Equilibrium-Line altitude (ELA) as a control on glaciation to provide insight into two intervals of paradoxical ice distribution during and following glaciation. The LPIA began in the mid-latitudes during the Visean in western Argentina with the growth of glaciers in the Protoprecordillera. Glaciation was initiated by uplift of the range above the ELA. In the Bashkirian, deglaciation occurred there while glaciation was beginning at the same latitude in uplands associated with the Parana Basin in Brazil. Analysis suggests that deglaciation of the Protoprecordillera occurred due to extensional collapse of the range below the ELA during a westward shift in the location of plate subduction. During Late Pennsylvanian–Early Permian peak glaciation for the LPIA, extensive glacimarine deposits indicate that glaciers reached sea level, which corresponds to a major lowering of the ELA due to global cooling. Finally, during the Early to early Late transition out of the LPIA, polar Gondwana was unglaciated. However, three glacial intervals occurred at mid- to high-latitudes in eastern Australia from the Sakmarian to the Capitanian/earliest Wuchiapingian. The magnitude of global cooling during these events is debatable as evidence indicates ice-free conditions and an elevated ELA at the South Pole in Antarctica. This suggests that severe global cooling was not the cause of the final three Australian glaciations, but rather that ELA-related conditions specific to eastern Australia drove these late-phase events. Possible causes for the Australian glaciations include: 1) anomalous cold conditions produced by coastal upwelling, 2) the presence of uplands allowing nucleation of glaciers, 3) fluctuations in pCO2 levels, and 4) increased precipitation due to the location of the area in the subpolar low pressure belt.
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glacial paradoxes during the late paleozoic ice age evaluating the Equilibrium Line altitude as a control on glaciation
Gondwana Research, 2012Co-Authors: John L Isbell, Lindsey C Henry, Erik L Gulbranson, Carlos O Limarino, Margaret L Fraiser, Zelenda J Koch, Patricia L CiccioliAbstract:Abstract The late Paleozoic ice age (LPIA) consists of multiple glaciations that waxed and waned across Gondwana during the Carboniferous and Permian. Three key intervals are evaluated using the concept of the Equilibrium-Line altitude (ELA) as a control on glaciation to provide insight into two intervals of paradoxical ice distribution during and following glaciation. The LPIA began in the mid-latitudes during the Visean in western Argentina with the growth of glaciers in the Protoprecordillera. Glaciation was initiated by uplift of the range above the ELA. In the Bashkirian, deglaciation occurred there while glaciation was beginning at the same latitude in uplands associated with the Parana Basin in Brazil. Analysis suggests that deglaciation of the Protoprecordillera occurred due to extensional collapse of the range below the ELA during a westward shift in the location of plate subduction. During Late Pennsylvanian–Early Permian peak glaciation for the LPIA, extensive glacimarine deposits indicate that glaciers reached sea level, which corresponds to a major lowering of the ELA due to global cooling. Finally, during the Early to early Late transition out of the LPIA, polar Gondwana was unglaciated. However, three glacial intervals occurred at mid- to high-latitudes in eastern Australia from the Sakmarian to the Capitanian/earliest Wuchiapingian. The magnitude of global cooling during these events is debatable as evidence indicates ice-free conditions and an elevated ELA at the South Pole in Antarctica. This suggests that severe global cooling was not the cause of the final three Australian glaciations, but rather that ELA-related conditions specific to eastern Australia drove these late-phase events. Possible causes for the Australian glaciations include: 1) anomalous cold conditions produced by coastal upwelling, 2) the presence of uplands allowing nucleation of glaciers, 3) fluctuations in pCO2 levels, and 4) increased precipitation due to the location of the area in the subpolar low pressure belt.