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Author : Thomas Chudley
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (123 download)
Download or read book UAV-based Investigations Into the Hydrology and Dynamics of the Greenland Ice Sheet written by Thomas Chudley and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book GPS-based Investigations of Greenland Ice Sheet Dynamics written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book UAV Investigation Into Surface and Tidewater Mass Loss Processes of the Greenland Ice Sheet written by and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Kate Hannah Briggs
Publisher :
ISBN 13 :
Total Pages : 174 pages
Book Rating : 4.:/5 (827 download)
Download or read book Satellite Investigations of Ice Dynamics and Supraglacial Lake Development in Greenland written by Kate Hannah Briggs and published by . This book was released on 2012 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis aims to improve the current understanding of the processes which control the flow variability of Greenland Ice Sheet (GrIS) outlet glaciers. The most recent Intergovernmental Governmental Panel on Climate Change (IPCC) report (Meehl et al., 2007) identifies that a critical limitation to forecasts of sea-level rise are uncertainties in modelling the ice dynamics of the GrIS. Using Synthetic Aperture Radar (SAR) feature tracking, seasonal velocities of land- and marine- terminating glaciers in a region in the northeast of Greenland are measured. Records of air temperature in conjunction with seasonal observations of supraglacial lake development, sea ice conditions and ice front positions, derived from SAR imagery, are used to investigate the controls on the observed variations in ice velocity. A clear link between ice velocities and glacier hydrology is found. These findings are consistent with observations from other glaciers in Greenland and are suggestive of a universal hydrological forcing of ice velocity for the whole of the GrIS ablation zone. Lake drainage events have been identified as a key factor in linking atmospheric changes, glacier hydrology and ice velocities in Greenland. For modelling purposes, a means of parameterising the distribution and evolution of supraglacial lakes is therefore needed. Assuming that water will pond in surface depressions, this thesis assesses the ability of using Digital Elevation Models (DEMs) for this purpose. High resolution DEMs are created using Interferometric SAR (InSAR) for two, separate regions of the GrIS. The positions and areal extent of surface depressions are compared with those of lakes observed in optical satellite imagery. The level of correspondence between the two datasets is found to be poor as a result of the resolution of the DEMs and the physical differences between surface depressions and lakes (e.g. lakes may not fill the capacity of the depression). An alternative method for parameterising the seasonal distribution of supra-glacial lakes, by extrapolating trends observed in current lake distributions, is investigated. The locations and evolution of lakes in the west of Greenland during the summer of 2003 are mapped using 47 Moderate Resolution Imaging Spectroradiometer (MODIS) images. Clear trends are identified in the distributions of lakes with elevation and are linked to the seasonal melt-cycle and to changes in ice thickness and its influence on surface depressions, tensile stresses and hydrofracturing. It may be possible to extrapolate these trends to other regions and higher elevations on the ice sheet, thereby enabling the distribution of lakes to be parameterised in ice sheet models. The findings of this thesis help to contribute to the understanding of the interaction between climate and ice dynamics in the context of the GrIS.
Author : Samuel Huckerby Doyle
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book GPS-based Investigations of Greenland Ice Sheet Dynamics written by Samuel Huckerby Doyle and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Vena Chu
Publisher :
ISBN 13 :
Total Pages : 221 pages
Book Rating : 4.:/5 (926 download)
Download or read book Hydrologic Dynamics of the Greenland Ice Sheet from Remote Sensing and Field Measurements written by Vena Chu and published by . This book was released on 2015 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current need for forecasting Greenland Ice Sheet contributions to global sea level rise is complicated by the lack of understanding of ice sheet hydrology. The proportion of meltwater contributing to sea level rise, as well as the pathways transporting meltwater on, through, and out of the ice sheet, are not well understood. Remote sensing of hydrologic dynamics in combination with small-scale fieldwork allows examination of broad spatial and temporal trends in the Greenland hydrologic system responding to a changing climate. This dissertation reviews the current state of knowledge on Greenland Ice Sheet hydrology, and examines three components of the Greenland hydrologic system: (1) fjord sediment plumes as an indicator of meltwater output, (2) supraglacial streamflow as an indicator of meltwater input to the ice sheet, and (3) moulin distribution and formation as a mechanism diverting meltwater from the surface of the ice sheet to the bed. Buoyant sediment plumes that develop in fjords downstream of outlet glaciers are controlled by numerous factors, including meltwater runoff. MODIS retrievals of sediment plume concentration show a strong regional and seasonal response to meltwater production on the ice sheet surface, despite limitations in fjords with rapidly calving glaciers, providing a tool for tracking meltwater release to the ocean. Summertime field observations and high-resolution satellite imagery reveal extensive supraglacial river networks across the southwestern ablation zone transporting large volumes of meltwater to moulins, yet these features remain poorly mapped and their discharges unquantified. A GIS modeling framework is developed to spatially adapt Manning's equation for use with high-resolution WorldView-2 imagery to map supraglacial river discharge. Moulins represent connections between surface meltwater on the Greenland ice sheet and subglacial drainage networks, where increased meltwater can enhance ice sliding dynamics. A new high-resolution moulin dataset in western Greenland created from WorldView-1/2 imagery in the 2012 record melt year is used to assess moulin distribution and formation. Moulin locations show a significantly different distribution compared to geospatial variables in the entire study area, with moulins forming in areas of thinner ice, higher velocity and extensional strain rate, as well as lower surface elevation and slope, and higher bed elevation and slope.
Author : Kiya Riverman
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (992 download)
Download or read book Flow Dynamics of the NE Greenland Ice Stream with Hydrological Insights from Englacial Exploration of Larsbreen, Svalbard written by Kiya Riverman and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Glaciers and ice sheets are large reservoirs of freshwater. In order to project how these icy reservoirs will respond to future climate, predictive models must incorporate all relevant ice flow processes and dynamics. Here, I present observations of glaciers in Greenland and Svalbard that advance our understanding of the role of meltwater in rapid ice flow. Chapters 1-4 concern the North East Greenland Ice Stream (NEGIS), a large flow feature of the Greenland Ice Sheet that drains a catchment spanning ~11% of the ice sheet area. I investigate the controls on ice stream location using geophyscial and remote sensing techniques. I find water flow at the base of the ice is, in part, controlled by enhanced firn densification and surface elevation changes in areas of high stress. The basal conditions across the ice stream are very heterogeneous, with variable water content and till thickness (Chapters 2, 3). Under both shear margins, I find shear-marginal moraines, as well as mega-scale glacial lineations within the central trunk of the ice stream (Chapter 4). Chapters 5 and 6 concern the hydrology of cold glacier on Svalbard. I use glaciospeleology (ice caving) to map the englacial and subglacial channels on Larsbreen, Spitsbergen across 3 years. Waterfalls within the glacier migrate rapidly and dominate change within the englacial system each year. I suggest that formation and migration of the final waterfall to the bed of the glacier is a potentially large source of erosion.
Author : Jonathan Ryan
Publisher :
ISBN 13 :
Total Pages : 250 pages
Book Rating : 4.:/5 (111 download)
Download or read book UAV Investigation Into Surface and Tidewater Mass Loss Processes of the Greenland Ice Sheet written by Jonathan Ryan and published by . This book was released on 2018 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Adam Igneczi
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (19 download)
Download or read book Greenland Ice Sheet Hydrology and Dynamics written by Adam Igneczi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Peter Jansson
Publisher :
ISBN 13 :
Total Pages : 59 pages
Book Rating : 4.:/5 (72 download)
Download or read book Ice Sheet Hydrology from Observations written by Peter Jansson and published by . This book was released on 2010 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This report summarizes our understanding of ice sheet hydrology as reported on observations from Antarctica and Greenland. Much of our general understanding of ice sheet hydrological processes are based on work performed on valley glaciers. Since processes do not differ in function but perhaps in magnitude, the understanding gained from smaller glaciers work applies to ice sheets. Hence, this report does not deal with such basic processes. Glacier hydrological investigations on ice sheets have been few but are perhaps accelerating in numbers with the increased focus on both Greenland and Antarctica from the scientific community in the light of effects from climate change. The process oriented studies carried out over the past 50 years or so have not generally been much applied to ice sheets and observations on the morphology of ice sheet and valley glacier hydrological systems have not been connected although most glacier hydrologists would not consider such parallels a stretch of their imagination. Much of the new studies on ice sheet hydrology, thus far, fits in two categories. One concerns verification of well-documented processes but on an ice sheet scale; the other concerns ice sheet specific features. These categories constitute the basis for this report"--Pref.
Author : Conrad Pawel Koziol
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book Modelling the Impact of Surface Melt on the Hydrology and Dynamics of the Greenland Ice Sheet written by Conrad Pawel Koziol and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jonathan Ryan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book UAV Investigation of Surface and Tidewater Mass Loss Processes Across the Greenland Ice Sheet written by Jonathan Ryan and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Lei Yang
Publisher :
ISBN 13 :
Total Pages : 160 pages
Book Rating : 4.:/5 (637 download)
Download or read book Greenland Ice Sheet Change: Surface Climate Variability and Glacier Dynamics written by Lei Yang and published by . This book was released on 2007 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: The co-variability of glacier ice discharges and climate variability is also examined by using Polar MM5 V1 modeled summer temperature and April-September Positive Degree Day (PDD) anomalies. Ice discharges from south Greenland glaciers are found to be sensitive to temperature change. Based on sensitivities of ice discharge to melt index anomalies, time series of total ice discharge from 28 major glaciers since 1958 are modeled. The global sea level rise contribution from Greenland ice sheet during past 50 years is estimated be ∼0.6 mm yr-1 in average.
Author : Celia Trunz
Publisher :
ISBN 13 :
Total Pages : 344 pages
Book Rating : 4.:/5 (13 download)
Download or read book Modeling and Measuring Water Level Fluctuations in the Greenland Ice Sheet written by Celia Trunz and published by . This book was released on 2021 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the ablation zone of land terminating sectors of the Greenland Ice Sheet (GrIS), water pressures at the bed control ice motion variability on diurnal and seasonal timescales. During the melt season, large volumes of surface meltwater access the ice-bed interface through moulins.Moulins are large vertical shafts that connect the supraglacial and subglacial drainage systems. Moulins form when a crevasse intersects a surface meltwater source that can drive hydrofracture to the bed of the ice sheet. Upon reaching the bed, meltwater can establish and sustain an efficient, channelized drainage system. Due to the technical impossibility of physically exploring underwater passages beneath the GrIS, the subglacial drainage system must be studied through geophysical methods. To date, measurements of water level variability within moulins and boreholes have proved to be critical for constraining models. However, direct hydrologic measurements from the GrIS are sparse, due to the remoteness and harsh conditions of the ice sheet. The work presented in this dissertation combines simple physically based mathematical models with direct measurements from the ablation portion of Sermeq Avannarleq, in west Greenland to advance our understanding of the influence of moulin geometry and life span on glacier dynamics. In Chapter 2, I investigate the moulin life cycle within several neighboring surface catchments within the GrIS ablation zone. A combination of remote sensing and ground observations of moulin locations over two to three years reveals an annual pattern of systematic formation and abandonment of moulins after they are advected down-glacier.In Chapter 3, I use a modified single conduit model to explore the role of moulin shape and size on hydraulic head variability within moulins. This model shows that only the englacial storage capacity within the range of water level fluctuations affects the oscillation range of moulin hydraulic head, which controls subglacial channel water pressure dynamics. Further, the model shows that depth-varying changes in englacial water storage control the temporal shape of the head oscillations. Finally, in Chapter 4, I simulate the moulin water level variability in a moulin we instrumented in 2017-2018 using the recently developed Moulin Shape (MouSh) model. The MouSh model requires additional subglacial baseflow to simulate an accurate diurnal range of head oscillation. We hypothesize that this additional baseflow is the result of strong network connectivity with other moulins through a channelized subglacial drainage system, potentially supplemented by basal or non-local, upstream inputs. Additional work is necessary to accurately characterize moulin positions and life cycles, and to determine whether the observed annual formation and abandonment is widespread. Such characterization would improve the simulation of moulin inputs in models. In addition, further knowledge of the shape of moulins around the equilibrium head elevation would improve englacial storage parameterization in subglacial hydrological models and aid predictions of coupling between meltwater and ice motion under future melt scenarios. Finally, this work suggests that the connectivity of the subglacial network needs further study, to improve our understanding on how local and non-local drivers influence subglacial water pressures and ice sliding.
Author : Matthew Cooper
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.:/5 (119 download)
Download or read book Bare Ice Hydrologic Processes on the Greenland Ice Sheet Ablation Zone written by Matthew Cooper and published by . This book was released on 2020 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Greenland Ice Sheet is a major contributor to global sea level rise, with recent mass loss dominated by meltwater runoff from the ablation zone, i.e. areas of the ice sheet where annual mass losses exceed gains. In this zone, the winter snowpack melts entirely each summer exposing bare glacier ice. Observations of Greenland's ablation zone suggest the exposed bare ice surface is comprised of low-density ice termed "weathering crust" that may store meltwater, potentially reducing meltwater runoff export to surrounding oceans. Climate models are the primary tools used to forecast future Greenland mass loss, but these models treat the ablation zone as impermeable high-density ice with no meltwater retention capacity. Recent evidence suggests that climate models overpredict meltwater runoff from the ablation zone, which may be linked to weathering crust presence, but diagnosing climate model predictions is difficult because observations of meltwater runoff on the ice sheet surface are extremely rare and weathering crust presence is undocumented. This dissertation presents the results of four investigations that address this problem by pairing field observations of hydrologic and radiative properties of bare ice collected in Greenland's ablation zone with numerical modeling and analysis of climate model output. The results of these investigations reveal the presence of low-density weathering crust on Greenland's bare ice ablation zone surface and the potential for non-trivial meltwater runoff retention within weathering crust on Greenland's bare ice ablation zone surface. New estimates of spectral radiation attenuation coefficients are quantified and directly applied to a numerical model of spectral and thermodynamic heat transfer in bare ice. This model successfully simulates meltwater runoff from a supraglacial catchment on Greenland's southwest ablation zone surface. Model results suggest that nocturnal refreezing of meltwater stored within weathering crust occurs in Greenland's ablation zone, potentially reducing runoff up to 32% on annual timescales. These findings imply a reinterpretation of refreezing on bare ice as an important control on Greenland's ablation zone surface mass balance and the need to represent this process in climate model predictions of future Greenland mass loss.
Author : Claire M. Landowski
Publisher :
ISBN 13 : 9781267422538
Total Pages : 87 pages
Book Rating : 4.4/5 (225 download)
Download or read book Geochemistry and Subglacial Hydrology of the West Greenland Ice Sheet written by Claire M. Landowski and published by . This book was released on 2012 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: Meltwaters reaching the ice-bedrock interface of the Greenland Ice Sheet acquire a geochemical signature that is based on their starting composition, residence time in the basal hydrologic system, bedrock lithology, and the nature of the weathering processes at work. Working at Isunguata Sermia, a land-terminating outlet glacier of the West Greenland Ice Sheet, we measured the chemical composition of subglacial waters that are both in situ and that issue from the terminus, as a means of investigating drainage organization and the nature of water-rock interaction. Utilizing both major and minor elements, we find that concentration increases as discharge increases and that hydrologic organization is dynamic over daily cycles. We experiment using short-lived isotopes of radon and radium to age-date water, and while time-series results are inconclusive, we find that water residence time is much less than 20 days.
Author : Roderik van de Wal
Publisher :
ISBN 13 : 9789039303740
Total Pages : 144 pages
Book Rating : 4.3/5 (37 download)
Download or read book Ijs en Klimaat written by Roderik van de Wal and published by . This book was released on 1992 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt:
