Download or read book Ice Dynamics and Recent Geometric Changes of the Devon Island Ice Cap Nunavut Canada written by David Burgess and published by . This book was released on 2006 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamics and Mass Balance of Penny Ice Cap Baffin Island Nunavut In a Changing Climate written by Nicole Schaffer and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a detailed study of recent changes in the mass balance and dynamics of Penny Ice Cap (PIC), and projects its evolution under a warming climate. Mass losses from 2005-2014 were quantified from airborne altimetry elevation change measurements, and adjusted for vertical ice motion caused by firn compaction and/or ice dynamics. Mass loss from PIC increased four-fold between the mid-1990s (-1.3 ± 0.7 Gt a-1) and 2005-2013 (-5.4 ± 1.9 Gt a-1). The adjustment calculations indicate that mass loss may be overestimated by 19% if vertical motion is not properly accounted for. The velocity response to increased surface melt was quantified using satellite imagery and historical ground measurements from Highway Glacier, on the southern part of PIC. Over the period 1985-2011, the six largest outlet glaciers on the ice cap decelerated at an average rate of 21 m a-1 over the 26 year period (0.81 m a-1), or 12% decade-1. Highway Glacier decelerated by 71% between 1953 and 2009/11. The recent slowdown of outlet glaciers has coincided with increases in mass loss and an inferred reduction in basal sliding. The ice-cap-wide mass balance was modeled from 1958 to 2099 with an enhanced temperature index model. Since the mid-1990s mass balance rates over PIC have become increasingly negative. Peak mass loss is projected to occur in the late 2070s and PIC is expected to lose 16-20% of its 2014 ice volume by 2099 assuming a moderate climate warming scenario (RCP4.5). If a +2°C offset is applied to this scenario, the ice cap is expected to lose 30-40% of its initial ice volume by 2099. These results provide the first comprehensive evaluation of the impact of vertical ice motion on mass loss derived from geodetic measurements over a large Arctic ice cap. The ice velocity record provides insights into the relationship between surface melt rates and glacier motion over the past 30-60 years. This study projects the mass change of the largest ice cap in the southern Canadian Arctic to 2099, calibrated and validated with a wealth of spatially distributed data for the first time.
Download or read book Spatial and Temporal Variations in Ice Motion Belcher Glacier Devon Island Nunavut Canada written by Wesley Van Wychen and published by . This book was released on 2010 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Glaciers of North America written by Richard S. Williams and published by . This book was released on 2002 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2006 with total page 774 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reconstructing the Recent Accumulation History and Mass Balance Trends for High Elevation Regions of the Devon Island Ice Cap in the Canadian Arctic written by William Colgan and published by . This book was released on 2007 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Velocity Variability of Devon Ice Cap Tidewater Glaciers written by Bradley D. Danielson and published by . This book was released on 2014 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tidewater outlet glaciers drain approximately 47% of the ~105,000 km^2 covered by ice caps in the Queen Elizabeth Islands of Nunavut, Canada, suggesting that iceberg discharge may be an important process in the mass balance of these ice caps. Seasonal and inter-annual velocity changes of tidewater glaciers may result in the misestimation of annual or multi-year iceberg calving fluxes, if these are estimated on the basis of short-term ice velocity measurements derived from repeat satellite imagery. The aim of this study is to observe and quantify the variability of tidewater glacier velocity at a range of time scales, and to examine the processes driving these variations, with a focus on the impact of temporal and spatial variations in the delivery of surface meltwater to the glacier bed. High-frequency ice surface velocity measurements were made at four tidewater outlet glaciers of the Devon Ice Cap. Observations over three summers on Belcher Glacier revealed an annually consistent pattern of ice velocities higher than the annual mean during the 50-60 day long melt season. During this fast-flow period, surface meltwater entered the glacier via moulins and the rapid drainage of supra-glacial melt ponds and water filled crevasses. Rapid drainage events coincided with short-duration ice velocity fluctuations. Inter-annual variations in the magnitude of the enhanced velocity in summer and the velocity variability during the fast-flow period were linked to factors which affect the rate and timing of meltwater delivery to the subglacial drainage system, such as variations in spring snowpack thickness and the degree of variability in late summer meltwater production. The effective contribution to the annual displacement resulting from enhanced velocities during the summer melt season was only ~5-8% at the glacier terminus, due to the relatively short duration of the fast-flow period. On the lower 5-8 km of the Belcher Glacier and North Croker Glacier, multi-year changes in annual mean velocity were observed that were not clearly linked to inter-annual variations in the amplitude and/or timing of the seasonal velocity cycle. Because of their flow mechanics, these glaciers may be poised to respond extremely sensitively to even minor long-term changes in driving stress. For such glaciers, it may be extremely difficult to identify any obvious external forcing for relatively large, long-term changes in velocity and rates of iceberg discharge. Overall, the results provide a demonstration of the seasonal bias that may be expected in different zones of the Devon Ice Cap if annual mean glacier velocities are estimated from velocity measurements made over periods less than a full annual cycle.
Download or read book Recent Changes in Glacier Facies Zonation on Devon Ice Cap Nunavut Detected from SAR Imagery and Field Validation Methods written by Johannes Tyler de Jong and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Glacier facies represent distinct regions of a glacier surface characterized by near surface structure and density that develop as a function of spatial variations in surface melt and accumulation. In post freeze-up (autumn) synthetic aperture radar (SAR) satellite imagery, the glacier ice zone and dry snow zone have a relatively low backscatter due to the greater penetration of the radar signal into the surface. Conversely, the saturation and percolation zones are identifiable based on their high backscatter due to the presence of ice lenses and pipes acting as efficient scatterers. In this study, EnviSat ASAR imagery is used to monitor the progression of facies zones across Devon Ice Cap (DIC) from 2004 to 2011. This data is validated against in situ surface temperatures, mass balance data, and ground penetrating radar surveys from the northwest sector of DIC. Based on calibrated (sigma nought) EnviSat ASAR backscatter values, imagery from autumn 2004 to 2011 shows the disappearance of the 'pseudo' dry snow zone at high elevations, the migration of the glacier and superimposed ice zones to higher elevations, and reduction in area of the saturation/percolation zone. In 2011, the glacier and superimposed ice zone were at their largest extent, occupying 92% of the ice cap, leaving the saturation/percolation zone at 8% of the total area. This is indicative of anomalously high summer melt and strongly negative mass balance conditions on DIC, which results in the infilling of pore space in the exposed firn and consequent densification of the ice cap at higher elevations.
Download or read book Accumulation on the Devon Island Ice Cap Northwest Territories Canada written by Robert M. Koerner and published by . This book was released on with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Mass Balance Study written by Roy Martindale Koerner and published by . This book was released on 1966 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modelling Melt Refreezing and Runoff Across the Surfaces of High latitude Ice Masses written by Richard M. Morris and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The wet snow line responds in a linear way to change in air temperature, and the runoff line is sensitive to the specified depth within the firn of the impermeable layer. Over the next century, the model shows that the dry snow zone will disappear completely under moderate warming scenarios, and the percolation zone will also disappear under intense warming scenarios. Including a more complicated representation of vertical meltwater percolation through the snow and firn grid substantially alters modelled autumn density profiles, and produces more accurate values of meltwater percolation depth and ice fraction within the autumn snowpack. However, bulk snowpack properties are of similar accuracy to the un-modified model. Scaling up of the model, in both spatial and temporal terms, will make it useful for assistance in the interpretation of satellite radar altimetry data sets, as well as assessing future changes in the spatial variability of refreezing and runoff, reducing the uncertainty in long term surface mass balance predictions across large ice masses.
Download or read book Glacier climate Studies on the Devon Island Ice Cap N W T written by R. J. Braithwaite and published by . This book was released on 1970 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Devon Island Ice Cap written by Roy Martindale Koerner and published by . This book was released on 1977 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Study of distribution of melt layers in deep ice cores and correlation with climate in past few hundred years.
Download or read book Glacier climate Studies on the Devon Island Ice Cap N W T 1968 written by R. J. Braithwaite and published by . This book was released on 1969 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigating Mass Loss and Changing Ice Dynamics of Arctic Ice Caps Using Remote Sensing written by Whyjay Zheng and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Glacier thinning and retreat have accelerated globally in the last century and are the largest contributor to rising sea levels. For the Arctic region, observations and modeling results have shown that extensive warming is taking place. However, the recent glacier dynamics (mass balance and ice discharge) in many Arctic regions have not been well studied due to the remote nature of these glaciers.This thesis uses multiple types of satellite data to quantify the mass balance and ice discharge for three Arctic regions showing dramatic glacier change in recent decades possibly due to Arctic warming. The objective is to resolve the mass budget and velocity pattern on a per glacier basis and understand the mechanisms driving recent changes. To facilitate the entire workflow, our research team has developed the Cryosphere and Remote Sensing Toolkit (CARST) software, and I am the lead author. CARST provides useful python and bash scripts that use satellite imagery, particularly SAR and optical images, to monitor changes of glaciers and ice caps through time. The first study area is Franz Josef Land (FJL), Russia, which is currently subjected to a rapidly-warming climate in the Arctic. I combine surface elevation data derived from different sources and times, including the WorldView satellite series and the ArcticDEM data set (2011-2015), SPOT-5 (2007), CryoSat-2 (2011-2015), and a digitized cartographic map (1953). I calculate elevation change rate (dh/dt) in two different periods, and the results show a two-fold rate of ice loss over the past 60 years, from _2.18 ± 0.72 Gt/yr (1953-2011/2015 average) to _4.43 ± 0.78 Gt/yr (2011-2015). Despite being spatially variable, a trend of increased thinning from NE towards SW is discovered, suggesting a link to the local gradient in temperature and precipitation. Ice loss is mostly focused on marine-terminating glaciers probably due to the interaction between glaciers and warming ocean water. These retreating glaciers generated a new island in 2016 and more islands are likely to emerge in the foreseeable future as FJL's ice loss has reached an unprecedented rate. The research focus in the following chapter shifts to the neighboring archipelago called Severnaya Zemlya, Russia. A surge-like collapse initiated in 2013 in Vavilov Ice Cap, one of many ice caps in this region. By spring 2019, this ice cap had lost 9.5 Gt of ice. Using time series of surface elevation and glacier velocity derived from multiple satellite data sets such as WorldView (elevation), ArcticDEM (elevation), ASTER (elevation), Landsat 8 (velocity), Sentinel-1, (velocity), Sentinel-2 (velocity), Radarsat-2 (velocity), and ALOS-2 (velocity), I identify a shift of flow pattern starting in 2017 when shear margins formed within the grounded marine piedmont fan. Multiple summer speedups occurred after the new flow pattern formed, possibly with the aid of basal lubrication due to surface melt. With the analysis using multiple physical models, it is suggested that the collapsed ice cap has entered a new ice stream-like regime in which diffusion of surface thinning controls the glacier dynamics. This is the first documented case of an ice stream-like feature ever being formed, and this glacier now flows at a higher speed and drains the ice cap more efficiently. To publicize the findings and their scientific implications, I made two videos showing the temporal changes of the terminus position and speed pattern, which are available on Youtube. In the last chapter, I further develop a physical framework for the glacier perturbation model to understand how different glaciers respond to basal lubrication. The modified 1-D flowline model suggests two physical quantities, Péclet number (Pe) and a value dubbed J0, governing glacier vulnerability to basal lubrication. To test the model, I use the Ice Thickness Models Intercomparison eXperiment (ITMIX) data set and the NASA MEaSUREs ITS_LIVE data set. ITMIX contains velocity, elevation, and ice thickness data from Austfonna Ice Cap, Svalbard, where multiple glacier collapse events occurred within the past 10 years. I calculate Pe and |J0| using data from the ITMIX and compare them with the speed change revealed by the ITS_LIVE data set. The results show that a low Pe and a high |J0| correspond to the high magnitude of glacier speedup during 1995-2018, as suggested by the model prediction. My analysis implies that basal lubrication can lead to a prolonged or even permanent change of glacier dynamics for some glaciers. These "weak" glaciers might be able to waste ice more rapidly than we thought, posing a warning of an underestimated sea level rise projection.
Download or read book Arctic Ice Shelves and Ice Islands written by Luke Copland and published by Springer. This book was released on 2017-05-30 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides an overview of the current state of knowledge of Arctic ice shelves, ice islands and related features. Ice shelves are permanent areas of ice which float on the ocean surface while attached to the coast, and typically occur in very cold environments where perennial sea ice builds up to great thickness, and/or where glaciers flow off the land and are preserved on the ocean surface. These landscape features are relatively poorly studied in the Arctic, yet they are potentially highly sensitive indicators of climate change because they respond to changes in atmospheric, oceanic and glaciological conditions. Recent fracturing and breakup events of ice shelves in the Canadian High Arctic have attracted significant scientific and public attention, and produced large ice islands which may pose a risk to Arctic shipping and offshore infrastructure. Much has been published about Antarctic ice shelves, but to date there has not been a dedicated book about Arctic ice shelves or ice islands. This book fills that gap.
Download or read book Ice atmosphere Interactions on the Devon Ice Cap Canada written by Gabrielle Gascon and published by . This book was released on 2014 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: In order to better constrain the magnitude of projected sea-level rise from Canadian Arctic glaciers during the 21st century warming, it is critical to understand the environmental mechanisms that enhance surface warming and melt, and how the projected increase in surface melt will translate into increased runoff. Between 2004 and 2010, a 4 °C increase in mean air summer temperature, and a 6.1 day yr-1 increase in melt season duration were observed on the Devon Ice Cap, Nunavut. At the same time, a combination of strengthening of the 500 hPa ridge over the Arctic in June-July, and more frequent south-westerly low-pressure systems in August after 2005 created atmospheric conditions that contributed to an increase in the surface energy balance of the ice cap. At 1400m elevation, these changes led to a doubling of the available melt energy and surface melt between 2007 and 2010. Currently, refreezing of meltwater in firn buffers the relationship between increased surface melt and runoff. Between 2007 and 2012, increased meltwater percolation and infiltration ice formation associated with high surface melt rates modified the stratigraphy of firn in the ice cap's accumulation area very substantially. Growth of a 0.5-4.5 m thick ice layer that filled much of the pore volume of the upper part of the firn reduced vertical percolation of meltwater into deeper parts of the firn. This progressively limited the water storage potential of the firn reservoir, and likely caused a significant increase in surface runoff. An evaluation of the snowpack model Crocus against ground observations for the period 2004-2012 showed that, although the model simulated observed density/depth profiles relatively well at all sites, its representation of heterogeneous percolation as a homogeneous process created conditions that favoured excessive near-surface freezing. At the same time, Crocus's parameterization of the permeability of ice layers forced meltwater to percolate through them, preventing the buildup of thick impermeable ice layers. These results highlight the importance of treating meltwater percolation in firn as a heterogeneous process, and of accurately representing the impermeability of ice layers to meltwater flow, if the model is to accurately reproduce firn density profile evolution and surface runoff during periods of climate warming.
