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Flow Dynamics Of The Ne Greenland Ice Stream With Hydrological Insights From Englacial Exploration Of Larsbreen Svalbard
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Book Synopsis Flow Dynamics of the NE Greenland Ice Stream with Hydrological Insights from Englacial Exploration of Larsbreen, Svalbard by : Kiya Riverman
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.
Book Synopsis The Influence of Meltwater on the Thermal Structure and Flow of the Greenland Ice Sheet by : Kristin Poinar
Download or read book The Influence of Meltwater on the Thermal Structure and Flow of the Greenland Ice Sheet written by Kristin Poinar and published by . This book was released on 2015 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the climate has warmed over the past decades, the amount of melt on the Greenland Ice Sheet has increased, and areas higher on the ice sheet have begun to melt regularly. This increase in melt has been hypothesized to enhance ice flow in myriad ways, including through basal lubrication and englacial refreezing. By developing and interpreting thermal ice-sheet models and analyzing remote sensing data, I evaluate the effect of these processes on ice flow and sea-level rise from the Greenland Ice Sheet. I first develop a thermal ice sheet model that is applicable to western Greenland. Key components of this model are its treatment of multiple phases (solid ice and liquid water) and its viscosity-dependent velocity field. I apply the model to Jakobshavn Isbræ, a fast-flowing outlet glacier. This is an important benchmark for my model, which I next apply to the topics outlined above. I use the thermal model to calculate the effect of englacial latent-heat transfer (meltwater refreezing within englacial features such as firn and crevasses) on ice dynamics in western Greenland. I find that in slow-moving areas, this can significantly warm the ice, but that englacial latent heat transfer has only a minimal effect on ice motion (10%). By contrast, in fast-flowing regions, which contribute most (60%) of the ice flux into the ocean, evidence of deep englacial warming is virtually absent. Thus, the effects of englacial latent heat transfer on ice motion are likely limited to slow-moving regions, which limits its importance to ice-sheet mass balance. Next, I couple a model for ice fracture to a modified version of my thermal model to calculate the depth and shape evolution of water-filled crevasses that form in crevasse fields. At most elevations and for typical water input volumes, crevasses penetrate to the top ~200–300 meters depth, warm the ice there by ~10°C, and may persist englacially, in a liquid state, for multiple decades. The surface hydrological network limits the amount of water that can reach most crevasses. We find that the depth and longevity of such crevasses is relatively robust to realistic increases in melt volumes over the coming century, so that we should not expect large changes in the englacial hydrological system under near-future climate regimes. These inferences put important constraints on the timescales of the Greenland supraglacial-to-subglacial water cycle. Finally, I assess the likelihood that higher-elevation surface melt could deliver water to regions where the bed is currently frozen. This hypothetical process is important because it could potentially greatly accelerate the seaward motion of the ice sheet. By analyzing surface strain rates and comparing them to my modeled basal temperature field, I find that this scenario is unlikely to occur: the conditions necessary to form surface-to-bed conduits are rarely found at higher elevations (~1600 meters) that may overlie frozen beds.
Book Synopsis Hydrologic Dynamics of the Greenland Ice Sheet from Remote Sensing and Field Measurements by : Vena Chu
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.
Book Synopsis Ice-stream Dynamics by : Teresa Marie Kyrke-Smith
Download or read book Ice-stream Dynamics written by Teresa Marie Kyrke-Smith and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Ice Stream Dynamics by : Coen Matthijs Hofstede
Download or read book Ice Stream Dynamics written by Coen Matthijs Hofstede and published by . This book was released on 2008 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Melt Water Retention Processes in Snow and Firn on Ice Sheets and Glaciers: Observations and Modeling by : W. Tad Pfeffer
Download or read book Melt Water Retention Processes in Snow and Firn on Ice Sheets and Glaciers: Observations and Modeling written by W. Tad Pfeffer and published by Frontiers Media SA. This book was released on 2018-11-08 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Melt takes place where the surface of glaciers or ice sheets interacts with the atmosphere. While the processes governing surface melt are fairly well understood, the pathways of the meltwater, from its origin to the moment it leaves a glacier system, remain enigmatic. It is not even guaranteed that meltwater leaves a glacier or ice sheet. On Greenland, for example, only slightly more than 50% of the meltwater runs off. The remainder mostly refreezes within the so-called firn cover of the ice sheet. This eBook contains 11 studies which tackle the challenge of understanding meltwater retention in snow and firn from various angles. The studies focus both on mountain glaciers and on the Greenland ice sheet and address challenges such as measuring firn properties, quantifying their influence on meltwater retention, modelling firn processes and meltwater refreezing as well as unravelling the mechanisms within the recently discovered Greenland firn aquifers.
Book Synopsis Deciphering Past and Present Ice Flow Patterns from Radar Reflections by : Steven Franke
Download or read book Deciphering Past and Present Ice Flow Patterns from Radar Reflections written by Steven Franke and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The large ice sheets on Earth respond to changes in the global climate. Ice mass loss increases with rising global mean temperature and thus is a major contributor to sea-level rise. In order to reduce the uncertainty to predict the contributions to sea-level rise of ice sheets, it is crucial to study how the ice sheets' fast-flowing drainage pathways (so-called ice streams) have evolved over the last thousand to millions of years. In this thesis, a contribution to the understanding of the flow characteristics of large ice streams in Greenland and Antarctica is performed by an analysis of (ice-penetrating) radar reflections within the ice column and at the ice base. My focus lies on the question how these data can be used to obtain information about present and paleo ice flow regimes. I concentrate on radar data acquired in Northeast Greenland in the upstream regions of the North East Greenland Ice Stream (NEGIS) and in the upstream catchment of the Nioghalvfjerdsbrae (79°N Glacier) as well as on data recorded at the onset of the Jutulstraumen Glacier in Antarctica. In my studies, I show that the NEGIS in its present form is a relatively young feature and that its geometry and flow characteristics are intertwined with the subglacial topography. I also found indications for a re-organization of ice stream activity in the NEGIS catchment during the Holocene. This suggests that ice streams are probably are less persistent than previously thought and adapt in their entire length to the changing geometry of the ice sheet on short time scales. In Antarctica, I investigate past ice flow patterns over a period of millions of years, as in the example of the Jutulstraumen Glacier basin in Antarctica. Many of the glacial and fluvial landscapes, which developed since the glaciation of Antarctica, have been mostly preserved under the contemporary thick ice sheet, and some even serve as basins for active subglacial lakes today.
Book Synopsis Greenland Ice Sheet Hydrology and Dynamics by : Adam Igneczi
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:
Book Synopsis Understanding Ice-sheet Dynamics Using Geophysical Observations and Numerical Ice-flow Models by : Laura Kehrl
Download or read book Understanding Ice-sheet Dynamics Using Geophysical Observations and Numerical Ice-flow Models written by Laura Kehrl and published by . This book was released on 2018 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mass loss from the world’s ice sheets is one of the largest sources of uncertainty in sea-level rise projections for the 21st century. One way to improve sea-level rise projections is to better understand the processes driving past ice-sheet mass loss. This dissertation investigates past changes in ice flow for two regions: (1) Helheim and Kangerlussuaq Glaciers, two fast-flowing tidewater glaciers in Southeast Greenland, and (2) the Allan Hills Blue Ice Area, a slow-flowing blue ice area in East Antarctica. For both regions, I constrain changes in ice-sheet dynamics using geophysical observations and interpret those changes using numerical ice-flow models. At Helheim and Kangerlussuaq, I examine seasonal and interannual variations in surface velocity, elevation, and terminus position from 2001 to 2016. I show that glacier dynamics depend on the extent of floating ice near the terminus. Helheim’s grounded terminus calved small, nontabular icebergs, while Kangerlussuaq’s floating ice tongue calved large, tabular icebergs. Furthermore, terminus-driven, seasonal speedups and dynamic thinning were generally larger at Helheim than at Kangerlussuaq, likely due to its grounded rather than floating ice tongue. To interpret the observed changes at Helheim and Kangerlussuaq, I use inverse methods to investigate changes in basal conditions under the two glaciers. The basal shear stress under Helheim and Kangerlussuaq decreased or remained relatively constant during terminus-driven speedup events, suggesting that changes in the stress balance were generally supported outside of the region of fast flow. Finally, I use the inferred basal shear stresses to help constrain the form of the basal sliding law. At the Allan Hills Blue Ice Area, I combine ice-penetrating radar data, an ice-flow model, and age constraints to determine a potential site to drill a million-year-old ice core. I also show that thickness anomalies in the englacial stratigraphy suggest that glacier velocity was 30% of present-day values during the last glaciation. While the dynamics of the Allan Hills Blue Ice Area are likely unimportant for sea-level rise projections, an ice core from the region could provide insight into the past stability of the Ross Sea Sector and West Antarctic Ice Sheet.
Book Synopsis Fundamentals of Glacier Dynamics by : C.J.van der Veen
Download or read book Fundamentals of Glacier Dynamics written by C.J.van der Veen and published by CRC Press. This book was released on 1999-01-01 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Glacier Dynamics presents an introduction to modelling the flow and dynamics of glaciers. The emphasis is more on developing and outlining procedures than on providing a complete overview of all aspects of glacier dynamics. Derivations leading to frequently-used equations are presented step-by-step to allow the reader to grasp the mathematical details and approximations involved and gain the understanding needed to apply similar concepts to different applications. The first four chapters discuss the background and theory needed for glacier modelling. The central part of the book discusses simple analytical solutions and time-evolving numerical models that are used to study general aspects of glacier dynamics and important feedback mechanisms. The final three chapters discuss applications specific to smaller mountain glaciers, the Greenland Ice Sheet, and the Antarctic Ice Sheet, respectively. This book will be suitable for graduate courses in geophysics and will also serve as a reference volume for scientists active in all aspects of glaciology and related research. Standard undergraduate mathematics and physics are sufficient background for studying the text.
Book Synopsis A New Model to Construct Ice Stream Surface Elevation Profiles and Calculate Contributions to Sea-Level Rise by : Yosuke Adachi
Download or read book A New Model to Construct Ice Stream Surface Elevation Profiles and Calculate Contributions to Sea-Level Rise written by Yosuke Adachi and published by . This book was released on 2012 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sea-level rise is a problem that affects regions worldwide - from the marshlands of the San Francisco Bay Area to the farmlands in coastal Bangladesh. Three-dimensional ice sheet models are the principle tools to evaluate mass loss from ice sheets that contribute to sea-level rise. We recognize that given the current limitations in representing the full extent of dynamical processes that affect ice sheet mass loss in 3-D ice sheet models, we cannot make reliable forecasts of sea-level rise from melting polar land ice. Thus, we take a completely different approach to gaining insight about the potential effects of climate change-induced perturbations on ice sheets. We build a flowline model that resolves the fast-flowing portions of ice sheets (i.e., ice streams). We express the dynamics along the flowline with (a) vertical shear deformation, (b) horizontal shear deformation, and (c) basal slip. Knowledge accumulated from prior force balance analyses performed on some polar ice streams allows us to form relations between (a) and (c), and between (a) and (c) combined and (b). Based on these relationships, we numerically construct surface elevation profiles along flowlines centered on ten select ice streams in Greenland and Antarctica, by prescribing three climate change-induced perturbations: grounding line retreat, ice stream widening, and surface mass balance increase. Comparing these constructed profiles to the current observed ones allows us to quantify the effect of these perturbations on the various characteristics that these ten ice streams possess. Pine Island Glacier, which flows over a long overdeepening, will lose more than half of its stored ice volume that is contributable to sea-level rise before it reaches a possible steady state. Recovery Ice Stream, with its slippery base, long stretch of streaming-flow, and longest flowline among those we examined, loses the most mass (812 km3/km width). Jutulstraumen, which has little room to widen and a short stretch of streaming-flow, experiences more mass gain due to surface mass balance increase than mass loss due to grounding line retreat and widening. The broad range of ice streams and their diverse responses to prescribed perturbations is a convincing message that an accurate assessment of the contribution of ice sheets to future sea-level rise can only be obtained by raising the resolution of models to resolve the fast-flowing features and looking at their mass changes individually over time.
Book Synopsis Influence of Meltwater on Greenland Ice Sheet Dynamics by : Laura A. Stevens
Download or read book Influence of Meltwater on Greenland Ice Sheet Dynamics written by Laura A. Stevens and published by . This book was released on 2017 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Seasonal fluxes of meltwater control ice-flow processes across the Greenland Ice Sheet ablation zone and subglacial discharge at marine-terminating outlet glaciers. With the increase in annual ice sheet meltwater production observed over recent decades and predicted into future decades, understanding mechanisms driving the hourly to decadal impact of meltwater on ice flow is critical for predicting Greenland Ice Sheet dynamic mass loss. This thesis investigates a wide range of meltwater-driven processes using empirical and theoretical methods for a region of the western margin of the Greenland Ice Sheet. I begin with an examination of the seasonal and annual ice flow record for the region using in situ observations of ice flow from a network of Global Positioning System (GPS) stations. Annual velocities decrease over the seven-year time-series at a rate consistent with the negative trend in annual velocities observed in neighboring regions. Using observations from the same GPS network, I next determine the trigger mechanism for rapid drainage of a supraglacial lake. In three consecutive years, I find precursory basal slip and uplift in the lake basin generates tensile stresses that promote hydrofracture beneath the lake. As these precursors are likely associated with the introduction of meltwater to the bed through neighboring moulin systems, our results imply that lakes may be less able to drain in the less crevassed, interior regions of the ice sheet. Expanding spatial scales to the full ablation zone, I then use a numerical model of subglacial hydrology to test whether model-derived effective pressures exhibit the theorized inverse relationship with melt-season ice sheet surface velocities. Finally, I pair near-ice fjord hydrographic observations with modeled and observed subglacial discharge for the Saqqardliup sermia–Sarqardleq Fjord system. I find evidence of two types of glacially modified waters whose distinct properties and locations in the fjord align with subglacial discharge from two prominent subcatchments beneath Saqqardliup sermia. Continued observational and theoretical work reaching across discipline boundaries is required to further narrow our gap in understanding the forcing mechanisms and magnitude of Greenland Ice Sheet dynamic mass loss.
Book Synopsis Understanding Antarctic Ice-stream Flow Using Ice-flow Models and Geophysical Observations by : David A. Lilien
Download or read book Understanding Antarctic Ice-stream Flow Using Ice-flow Models and Geophysical Observations written by David A. Lilien and published by . This book was released on 2019 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ice streams are the primary pathway by which Antarctic ice is evacuated to the ocean. Because the Antarctic ice sheets lose mass primarily through oceanic melt and calving, ice-stream dynamics exert a primary control on the mass balance of the ice sheets. Thus, changes in melt rates at the ice-sheet margins, or in accumulation in the ice-sheet interiors, affect ice-sheet mass balance on timescales modulated by the response time of the ice streams. Even abrupt changes in melt at the margins can cause ice-stream speedup and resultant thinning lasting millennia, so understanding the upstream propagation of marginally forced changes across timescales is key for understanding the ice sheets’ ongoing contribution to sea-level rise. This dissertation is comprised of three studies that use observations and models to understand changes to Antarctic ice-stream dynamics on timescales from decades to millennia. The first chapter synthesizes remotely sensed observations of Smith, Pope, and Kohler glaciers in West Antarctica to investigate the causes and extent of their retreat. These glaciers have displayed some of the largest measured grounding-line retreat, most rapid thinning, and largest speedup amongst Antarctic ice streams. This retreat has drawn interest in their stability both in its own right and as a harbinger of future changes to larger neighboring ice streams. In this study, recent melt rates were determined using flux divergence estimates derived from observations of ice thickness and surface velocity. Out-of-balance melt at the beginning of the study period indicates that the imbalance of this system predates the beginning of satellite velocity observations in 1996. Throughout much of 1996-2010, there was both greater melt over the ice shelves than flux across the grounding line, implying loss of floating ice and elevated melt forcing, and greater grounding-line flux than accumulation, implying adjustment of the grounded ice in response to the ongoing imbalance. The grounding line position of Kohler glacier, and a large melt channel that is unlikely to be a steady-state feature, suggest that the perturbation to this system began on Kohler glacier sometime around the 1970s. Viscosity of the ice shelves, inferred using a numerical model, indicates that weakening of the Crosson ice shelf was necessary to allow the observed speedup, though it is unable to determine whether the weakening was a cause or effect of the ongoing retreat. The second chapter uses a suite of numerical model simulations to determine the dominant drivers of the recent retreat of Smith, Pope, and Kohler glaciers, and extends those simulations that best match observations to evaluate likely future retreat. Similar to the findings of previous studies, the distribution of sub-shelf melt is found to be the primary control on the rate of grounding-line retreat, while the shelf-averaged melt rate exerts a secondary control. The model simulations indicate that, despite ongoing imbalance, the grounding-line position in 1996 was not inherently unstable, but rather elevated melt at the grounding line was required to cause the observed retreat. A weakening of the ice-shelf margins was found to hasten the onset of grounding-line retreat and led to greater speedup. However, without increases in melt beyond 1996 levels, marginal weakening was insufficient to initiate grounding-line retreat. All simulations that capture the observed retreat continue to lose mass until at least 2100, suggesting that ice in this basin may contribute over 8 mm to global mean sea level by 2100. The magnitude of thinning deep in the catchment suggests that the retreat of Kohler and Smith glacier may hasten the destabilization of the neighboring Thwaites glacier catchment. The third chapter uses the timescale of the recently drilled South Pole Ice Core (SPICEcore) and nearby geophysical observations to infer the history of ice flow near the South Pole during the last 10,000 years. The South Pole is located 180 km from the nearest ice divide and drains from the East Antarctic plateau through Academy glacier/Foundation ice stream. As a result, ice flow near the South Pole is potentially affected by the dynamics of these ice streams, and so the history of ice flow in this region has the potential to inform understanding of how marginally forced changes affect the ice-sheet interior. Because the South Pole is far from an ice divide, the accumulation record in SPICEcore incorporates both spatial variations in accumulation upstream and temporal variations in regional accumulation. Comparison between the SPICEcore accumulation record, derived by correcting measured layer thicknesses for thinning, with an accumulation record derived from new GPS and radar measurements upstream, yields insight into past ice flow and accumulation. When ice speeds are modeled as increasing by 15% since 10 ka, the upstream accumulation explains 77% of the variance in the SPICEcore-derived accumulation (vs. 22% without speedup). This correlation is only expected if the ice-flow direction and spatial pattern of accumulation were stable throughout the Holocene. The 15% speedup in turn suggests a slight (3-4%) steepening or thickening of the ice-sheet interior and provides a new constraint on the evolution of the East Antarctic Ice Sheet following the glacial termination.
Download or read book Dynamics of Upernavik Isstrøm written by and published by . This book was released on 2017 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Flow dynamics and till genesis associated with a marine-based Antarctic palaeo-ice stream by : C. O COFAIGH
Download or read book Flow dynamics and till genesis associated with a marine-based Antarctic palaeo-ice stream written by C. O COFAIGH and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Evolution and Dynamic Behaviour of the Northern Uummannaq Ice Stream System, West Greenland by : Timothy Patrick Lane
Download or read book The Evolution and Dynamic Behaviour of the Northern Uummannaq Ice Stream System, West Greenland written by Timothy Patrick Lane and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis considers the evolution and dynamic behaviour of the northern Uummannaq Ice Stream System (UISS), a large ice stream which extended to the Greenland shelf edge during the Last Glacial Maximum (LGM). The Uummannaq region has been shown to be dominated by areas of selective linear erosion (SLE) and areal scour. Over multiple glacial cycles, enhanced by favourable geology and uplift, SLE controlled the formation of a confluent fjord system which triggered the onset and development of the UISS. At the LGM, northern UISS ice thicknesses reached 1400-1968 m a.s.l., comparable to data from the southern UISS. However, in the north, thicknesses were not sufficient to overtop fjord confines, with ice flow remaining topographically controlled. The presence of thick, fast ice flowing ice in the onset zone suggests that subglacial conditions within the study area were characterised by intense basal sliding. The evolution of bedforms (roches moutonnées and whalebacks) was influenced by basal ice dynamics, but bedrock type, joints and bedding were also critical controls on bedform morphometry. Deglaciation following the LGM began on the outer shelf by 14.9 kyr, with increased air temperature, rising relative sea-level and bathymetric over-deepening driving the UISS to the outer edge of coastal fjords by 11.4-11.0 kyr. Geochronological data demonstrate that the retreat rate of the northern and southern UISS became highly asynchronous during the early-Holocene. In the south, topographic constrictions stabilised the ice from 11.0-9.3 kyr, before it retreated beyond its present ice margin at 8.7 kyr. Ice in the north became pinned at the mouth of Rink-Karrat Isfjord between 11.6-6.9 kyr, remaining stable through the Holocene Thermal Maximum, demonstrating the ability of topography to override climate and sea-level drivers. Geomorphological and sedimentological evidence has demonstrated that the Svartenhuk Peninsula in the northern Uummannaq region, previously cited as an LGM ice-free enclave, was overrun by ice during the LGM. Ice was sourced from the Svartenhuk interior, and expanded radially to the present coastline. This is contrary to existing work, and suggests there may be a need to reassess the evidence for interstadial, high sea-level conditions throughout Greenland.
Book Synopsis Hydrological Controls on Greenland Ice Sheet Motion by : Andrew Jachnik Tedstone
Download or read book Hydrological Controls on Greenland Ice Sheet Motion written by Andrew Jachnik Tedstone and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
