The Experts below are selected from a list of 18363 Experts worldwide ranked by ideXlab platform
Geoffrey O Seltzer - One of the best experts on this subject based on the ideXlab platform.
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evaluation of recent glacier recession in the cordillera blanca peru ad 1962 1999 spatial distribution of mass loss and Climatic Forcing
Quaternary Science Reviews, 2005Co-Authors: Bryan G Mark, Geoffrey O SeltzerAbstract:We use a combination of aerial photogrammetry, satellite imagery, andd ifferential GPS mapping to quantify the volume of ice lost between AD 1962 and 1999 from three glaciers on Nevado Queshque in the Cordillera Blanca, Peru´ (� 101S). The largest averagedsurface lowering (thinning) occurredin the southwest aspect (22 m) andthe least in the eastern aspect (5 m). A heuristic sensitivity analysis indicates that 9.3 W m � 2 was requiredto melt the total observedice loss andthis can be explainedby sensible heat transfer relatedto a temperature rise of 1 1C, combinedwith a latent heat d ecrease relatedto a 0.14 g kg � 1 increase in specific humidity. A first-difference analysis of temperature records from 29 stations in the Cordillera Blanca shows an average rising trend of 0.261C per decade over the 37 year interval, more than adequate to supply the hypothesized sensible heat transfer. A simple transmittivity model within a digital elevation model indicates solar radiation related to altered cloudiness was not a predominant Climatic Forcing. The distribution of glacier area with altitude calculated with the digital terrain model explains the observed asymmetrical ice melt. r 2005 Elsevier Ltd. All rights reserved.
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evaluation of recent glacier recession in the cordillera blanca peru ad 1962 1999 spatial distribution of mass loss and Climatic Forcing
Quaternary Science Reviews, 2005Co-Authors: Bryan G Mark, Geoffrey O SeltzerAbstract:Original abstract: We use a combination of aerial photogrammetry, satellite imagery, andd ifferential GPS mapping to quantify the volume of ice lost between AD 1962 and 1999 from three glaciers on Nevado Queshque in the Cordillera Blanca, Peru´ ( 101S). The largest averagedsurface lowering (thinning) occurredin the southwest aspect (22 m) andthe least in the eastern aspect (5 m). A heuristic sensitivity analysis indicates that 9.3Wm 2 was requiredto melt the total observedice loss and this can be explainedby sensible heat transfer relatedto a temperature rise of 1 1C, combinedwith a latent heat decrease relatedto a 0.14 g kg 1 increase in specific humidity. A first-difference analysis of temperature records from 29 stations in the Cordillera Blanca shows an average rising trend of 0.26 1C per decade over the 37 year interval, more than adequate to supply the hypothesized sensible heat transfer. A simple transmittivity model within a digital elevation model indicates solar radiation related to altered cloudiness was not a predominant Climatic Forcing. The distribution of glacier area with altitude calculated with the digital terrain model explains the observed asymmetrical ice melt.
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glacier recession in the peruvian andes Climatic Forcing hydrologic impact and comparative rates over time
2005Co-Authors: Bryan G Mark, Geoffrey O SeltzerAbstract:Tropical glaciers are intriguing and apparently rapidly disappearing components of the cryosphere that literally crown a vast ecosystem of global significance. Half of the Earth’s surface area lies between the tropics of Capricorn and Cancer, wherein a staggering 75% of the global population resides (Thompson 2000). Tropical glaciers are highly sensitive to climate changes over different temporal and spatial scales, notably ENSO, and are important hydrological resources in tropical highlands (Francou et al. 1995; 2000; this volume; Wagnon et al. 2001; Kaser and Osmaston 2002). Moreover, resolving the complex dynamics and variability of the tropical climate over longer time periods presents important goals to the global modelling community. Compiling an accurate understanding of the timing and climate response of tropical glaciers in the past is a crucial source of palaeoClimatic information for the validation and comparison of climate models (e.g. Farrera et al. 1999; Hostetier and Clark 2000; Porter 2001; Harrison et al. 2002; Seltzer et al. 2002). Deciphering the relative strength of different Climatic Forcing mechanisms on tropical glacier behaviour and quantifying hydrological changes associated with glacier recession are therefore relevant to interpreting the past climate and predicting the impact of future climate changes. Much scientific, social and political attention now concerns future changes in climate, with temperature change predominant.
Bryan G Mark - One of the best experts on this subject based on the ideXlab platform.
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evaluation of recent glacier recession in the cordillera blanca peru ad 1962 1999 spatial distribution of mass loss and Climatic Forcing
Quaternary Science Reviews, 2005Co-Authors: Bryan G Mark, Geoffrey O SeltzerAbstract:We use a combination of aerial photogrammetry, satellite imagery, andd ifferential GPS mapping to quantify the volume of ice lost between AD 1962 and 1999 from three glaciers on Nevado Queshque in the Cordillera Blanca, Peru´ (� 101S). The largest averagedsurface lowering (thinning) occurredin the southwest aspect (22 m) andthe least in the eastern aspect (5 m). A heuristic sensitivity analysis indicates that 9.3 W m � 2 was requiredto melt the total observedice loss andthis can be explainedby sensible heat transfer relatedto a temperature rise of 1 1C, combinedwith a latent heat d ecrease relatedto a 0.14 g kg � 1 increase in specific humidity. A first-difference analysis of temperature records from 29 stations in the Cordillera Blanca shows an average rising trend of 0.261C per decade over the 37 year interval, more than adequate to supply the hypothesized sensible heat transfer. A simple transmittivity model within a digital elevation model indicates solar radiation related to altered cloudiness was not a predominant Climatic Forcing. The distribution of glacier area with altitude calculated with the digital terrain model explains the observed asymmetrical ice melt. r 2005 Elsevier Ltd. All rights reserved.
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evaluation of recent glacier recession in the cordillera blanca peru ad 1962 1999 spatial distribution of mass loss and Climatic Forcing
Quaternary Science Reviews, 2005Co-Authors: Bryan G Mark, Geoffrey O SeltzerAbstract:Original abstract: We use a combination of aerial photogrammetry, satellite imagery, andd ifferential GPS mapping to quantify the volume of ice lost between AD 1962 and 1999 from three glaciers on Nevado Queshque in the Cordillera Blanca, Peru´ ( 101S). The largest averagedsurface lowering (thinning) occurredin the southwest aspect (22 m) andthe least in the eastern aspect (5 m). A heuristic sensitivity analysis indicates that 9.3Wm 2 was requiredto melt the total observedice loss and this can be explainedby sensible heat transfer relatedto a temperature rise of 1 1C, combinedwith a latent heat decrease relatedto a 0.14 g kg 1 increase in specific humidity. A first-difference analysis of temperature records from 29 stations in the Cordillera Blanca shows an average rising trend of 0.26 1C per decade over the 37 year interval, more than adequate to supply the hypothesized sensible heat transfer. A simple transmittivity model within a digital elevation model indicates solar radiation related to altered cloudiness was not a predominant Climatic Forcing. The distribution of glacier area with altitude calculated with the digital terrain model explains the observed asymmetrical ice melt.
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glacier recession in the peruvian andes Climatic Forcing hydrologic impact and comparative rates over time
2005Co-Authors: Bryan G Mark, Geoffrey O SeltzerAbstract:Tropical glaciers are intriguing and apparently rapidly disappearing components of the cryosphere that literally crown a vast ecosystem of global significance. Half of the Earth’s surface area lies between the tropics of Capricorn and Cancer, wherein a staggering 75% of the global population resides (Thompson 2000). Tropical glaciers are highly sensitive to climate changes over different temporal and spatial scales, notably ENSO, and are important hydrological resources in tropical highlands (Francou et al. 1995; 2000; this volume; Wagnon et al. 2001; Kaser and Osmaston 2002). Moreover, resolving the complex dynamics and variability of the tropical climate over longer time periods presents important goals to the global modelling community. Compiling an accurate understanding of the timing and climate response of tropical glaciers in the past is a crucial source of palaeoClimatic information for the validation and comparison of climate models (e.g. Farrera et al. 1999; Hostetier and Clark 2000; Porter 2001; Harrison et al. 2002; Seltzer et al. 2002). Deciphering the relative strength of different Climatic Forcing mechanisms on tropical glacier behaviour and quantifying hydrological changes associated with glacier recession are therefore relevant to interpreting the past climate and predicting the impact of future climate changes. Much scientific, social and political attention now concerns future changes in climate, with temperature change predominant.
Anders Levermann - One of the best experts on this subject based on the ideXlab platform.
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glacial cycle simulations of the antarctic ice sheet with the parallel ice sheet model pism part 1 boundary conditions and Climatic Forcing
The Cryosphere, 2020Co-Authors: Torsten Albrecht, Ricarda Winkelmann, Anders LevermannAbstract:Abstract. Simulations of the glacial–interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also Climatic Forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level Forcing. Hence, this study serves as a “cookbook” for the growing community of PISM users and paleo-ice sheet modelers in general. For each of the different model uncertainties with regard to Climatic Forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.
Anantha Prasad - One of the best experts on this subject based on the ideXlab platform.
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predicting the potential future distribution of four tree species in ohio using current habitat availability and Climatic Forcing
Ecosystems, 2001Co-Authors: Mark W Schwartz, Louis R. Iverson, Anantha PrasadAbstract:We investigated the effect of habitat loss on the ability of trees to shift in distribution across a landscape dominated by agriculture. The potential distribution shifts of four tree species (Diospyros virginiana, Oxydendron arboreum, Pinus virginiana, Quercus falcata var. falcata) whose northern distribution limits fall in the southern third of Ohio were used to assess possible distribution shift scenarios as a result of global warming. Our predictions derive from the results of simulations using (a) forest inventory based estimates of current distribution and abundance of target species; (b) a satellite-based estimate of forest habitat availability; and (c) a tree migration model (SHIFT). The current distribution and abundance of trees was estimated using USDA Forest Service?s Forest Inventory Analysis data and distribution maps from the late 1960s; pre-European settlement forest?nonforest maps were used to represent the fully forested condition for calibration and comparison. Habitat-availability estimates in Ohio were estimated using classified Landsat Thematic Mapper (TM) data from 1994. Tree abundance, forest availability and migration were modeled using a 1-km2 pixel size. Forest availability was estimated as the proportion of forested TM pixels within each cell. The probability of a migrating species colonizing an unoccupied cell is modeled as a function of forest availability and distance to occupied cells.
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Predicting the Potential Future Distribution of Four Tree Species in Ohio Using Current Habitat Availability and Climatic Forcing
Ecosystems, 2001Co-Authors: Mark W Schwartz, Louis R. Iverson, Anantha PrasadAbstract:We investigated the effect of habitat loss on the ability of trees to shift in distribution across a landscape dominated by agriculture. The potential distribution shifts of four tree species (Diospyros virginiana, Oxydendron arboreum, Pinus virginiana, Quercus falcata var. falcata) whose northern distribution limits fall in the southern third of Ohio were used to assess possible distribution shift scenarios as a result of global warming. Our predictions derive from the results of simulations using (a) forest inventory based estimates of current distribution and abundance of target species; (b) a satellite-based estimate of forest habitat availability; and (c) a tree migration model (SHIFT). The current distribution and abundance of trees was estimated using USDA Forest Service’s Forest Inventory Analysis data and distribution maps from the late 1960s; pre-European settlement forest–nonforest maps were used to represent the fully forested condition for calibration and comparison. Habitat-availability estimates in Ohio were estimated using classified Landsat Thematic Mapper (TM) data from 1994. Tree abundance, forest availability and migration were modeled using a 1-km 2 pixel size. Forest
Junsheng Nie - One of the best experts on this subject based on the ideXlab platform.
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Distinguishing tectonic versus Climatic Forcing on landscape evolution: An example from SE Tibetan Plateau
Geological Society of America Bulletin, 2021Co-Authors: Fangbin Liu, Martin Danišík, Dewen Zheng, Kerry Gallagher, Junsheng NieAbstract:Distinguishing climate from tectonic Forcing in shaping the Earth’s surface has been a long-standing issue in the Earth sciences. Great debate exists regarding when and how the SE Tibetan Plateau achieved its current low-relief topography, and both lateral extrusion and lower crust flow have been proposed as the dominant mechanism. Reconstruction of the exhumation history of the SE Tibetan Plateau is key to understanding these formation processes and resolving the significance of different Forcing mechanisms. Here we report zircon and apatite (U-Th)/He ages from steep transects across the Lincang granite belt of the SE Tibetan Plateau. Our results reveal a two-stage exhumation history during the Cenozoic with rapid cooling phases in the late Eocene and the middle Miocene. In the late Eocene, the climate was generally dry and there is plenty of evidence for increased extrusion and upper crustal shortening. We suggest tectonic processes are responsible for the first inferred cooling. In contrast, the Asian summer monsoon precipitation increased during the middle Miocene, and we posit the middle Miocene cooling phase records a phase of rapid river incision triggered by the intensified precipitation and associated fault movements. The results are consistent with recent paleo-altimetry work in this region suggesting that the present-day topography of the SE Tibetan Plateau had been largely constructed by the late Eocene. Together, these data suggest that extrusion and/or upper crustal shortening setup the first order topography of the SE Tibetan Plateau, which was then modified by climate-triggered fluvial incision and feedbacks initiated in the middle Miocene.