Author: Sean T. RooneyPublisher:
ISBN:
Category :
Languages : en
Pages : 165
Book Description
Subglacial geology of ice stream B, West Antarctica
Author: Sean T. RooneyThe Basal Regime of the West-Antarctic Ice Sheet Interaction of Subglacial Geology with Ice Dynamics
Author: Stefan Willi VogelPublisher:
ISBN:
Category : Glaciers
Languages : en
Pages : 310
Book Description
Antarctic Subglacial Aquatic Environments
Author: Martin J. SiegertPublisher: John Wiley & Sons
ISBN: 1118671481
Category : Science
Languages : en
Pages : 642
Book Description
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 192. Antarctic Subglacial Aquatic Environments is the first volume on this important and fascinating subject. With its underlying theme of bridging existing knowledge to future research, it is a benchmark in the history of subglacial lake exploration and study, containing up-to-date discussions about the history and background of subglacial aquatic environments and future exploration. The main topics addressed are identification, location, physiography, and hydrology of 387 subglacial lakes; protocols for environmental stewardship and protection of subglacial lake environments; details of three programs aiming to explore Vostok Subglacial Lake, Ellsworth Subglacial Lake, and Whillans Subglacial Lake over the next 3–5 years; assessment of technological requirements for exploration programs based on best practices for environmental stewardship and scientific success; and knowledge of subglacial lakes as habitats for microbial life and as recorders of past climate and ice sheet change. Its uniqueness, breadth, and inclusiveness will appeal to microbiologists and those interested in life in extreme environments, paleoclimatologists and those interested in sedimentary records of past changes, glaciologists striving to understand how water beneath glaciers affects their flow, and those engaged in developing technology to undertake direct measurement and sampling of extreme environments on Earth and in the solar system.
Subglacial Geology of Ice Stream B, West Antarctica
Author: Sean T. RooneyPublisher:
ISBN:
Category : Glaciology
Languages : en
Pages : 384
Book Description
Influence of subglacial geology on the onset of a West Antarctic ice stream from aerogeophysical observations
Author: R.E. BELLInfluence of subglacial geology on the position of a West Antarctic ice stream from seismic observations
Author: S. ANANDAKRISHNANInferring West Antarctic Subglacial Basin History and Ice Stream Processes Using Siliceous Microfossils
Author: Jason James CoenenPublisher:
ISBN: 9781369139457
Category : Ice sheets
Languages : en
Pages : 211
Book Description
In January of 2013 and 2015 the WISSARD (Whillans Ice Stream Subglacial Access Research Drilling) science team collected sediment cores from Subglacial Lake Whillans (SLW), and the Whillans Grounding Zone (WGZ) which are both part of the Whillans Ice Stream (WIS) in West Antarctica. These sediment cores along with sediment samples from the California Institute of Technology (Caltech) Glaciology group, which include sediments from Kamb Ice Stream (KIS) and Bindschadler Ice Stream (BIS) are compared with published micropaleontological data from the WIS Upstream B camp (UpB), the Crary Ice Rise (CIR) and the Ross Ice Shelf Project (RISP), using observations on preservation of microfossils in these deposits. Diatoms and other microfossils provide biostratigraphic and paleoenvironmental constraints on past marine deposition in West Antarctica interior basins, as well as inferences regarding ice stream erosion, particulate provenance and glacial mixing. Most subglacial samples contain a mixture of eroded diatoms that reflect initial deposition throughout the Cenozoic. Pleistocene diatoms are widespread but never abundant, reflecting erosion of marine sediments deposited in the West Antarctic marine basin during Quaternary ice sheet retreat events. Geologic drilling near Ross Island (the ANDRILL McMurdo Ice Shelf Project) provided abundant evidence for Pliocene and early Pleistocene retreat of the West Antarctic Ice Sheet, yet Pliocene diatoms are rare in sediments recovered from beneath grounded ice, which suggests erosion of Pliocene deposits in the Ross Embayment. Miocene age diatoms are dominant in subglacial and sub-ice shelf deposits, reflecting extensive Miocene deposition in the basin prior to entering a dominantly glacial phase. Additionally, Paleogene fossils, both marine and non-marine, occur widely, reflecting deeper erosion and providing insights into earlier basin history. SLW contains Upper Miocene fossils with a mix of younger and older taxa. These ages and taxa are consistent with previously published results from samples recovered ~200 km upstream from the UpB sites, suggesting a connection between the sites with little evidence of new subglacial erosion of material. Diatom abundance is on average lower than UpB in samples, suggesting sediments at SLW have experienced additional cumulative shearing and transport. WGZ cores exhibit stratigraphic variation in microfossil abundance as well as a transition in age dominance of taxa. Four lithostratigraphic units were observed in grounding zone cores, but a fifth unit is recognized based on microfossil data. Unit I is thought to be rain out from the base of the debris rich ice, which has a dominant Upper Miocene assemblage. Unit II is described as subglacial and is dominated by long ranging taxa, with a mix of younger material. Unit III is thought to be sub-ice shelf, which is consistent with diatomite microclasts (silt-sized aggregates) and a radiolarian that has a Late Pleistocene diatom assemblage. Unit IV is described as subglacial, based on the lithostratigraphy, however, microfossils are well-preserved, allowing definition of subunits, Unit IV-B and Unit IV-A. The stratigraphic variability at the grounding zone indicates changes in sediment provenance, indicating a variable glaciological regime, which suggesting a dynamic grounding line. Higher overall diatom abundance at WGZ indicates less cumulative glacial shear strain within the sediments than in SLW and UpB tills. KIS is one of the ice streams on the Siple Coast that has been shut down for the last 150 years. Most KIS sediments contain Upper Miocene fossils that are relatively unmixed and well-preserved, containing an order to two orders of magnitude higher diatom abundance than for all WIS samples. An exception is one sample from the KIS sticky spot (SS) that has low abundance and poor preservation indicating high cumulative shear strain. The unmixed Upper Miocene assemblage and preservation of the rest of these samples suggests close proximity to Miocene source rocks at this site. BIS is the northern-most active ice stream from this study in the Siple Coast area. These deposits contain no microfossils younger than Oligocene, suggesting tectonic processes, subglacial processes or change in source for this area. The age transition is also observed in other microfossil groups, which likely indicates a different source of sediments for BIS. Paleogene microfossils at this site are well preserved and relatively abundant. Biostratigraphic characterization of the Ross Embayment using age-specific diatoms help constrain basin scale productivity events that are linked to warm interglacial periods. Assessing when these events happened and diatom fragmentation patterns from different subglacial environments adds new insights into sediment-ice interactions and modern subglacial processes.
Exploration of Subsurface Antarctica
Author: M.J. SiegertPublisher: Geological Society of London
ISBN: 1786203227
Category : Science
Languages : en
Pages : 252
Book Description
Our appreciation of glaciological processes in Antarctica suffers from a lack of observations in regions where numerical models indicate the ice sheet to be susceptible to ocean and/or atmospheric warming. The solution lies in the use and development of glacier geophysics. In this volume we present a series of papers that demonstrate how geophysics can be deployed in Antarctica to comprehend: (1) boundary conditions that influence ice flow such as subglacial topography, the distribution of basal water and ice-sheet rheology; (2) phenomena that might affect ice-flow processes, such as complex internal ice-sheet structures and the proposition of large stores of hitherto unappreciated groundwater; and (3) how glacigenic sediments and formerly glaciated terrain on, and surrounding, the continent can inform us about past ice-sheet dynamics. The volume also takes a historical view on developments leading to current knowledge, examines active ice-sheet processes, and points the way forward on how geophysics can advance quantitative understanding of Antarctic ice-sheet behaviour.
The West Antarctic Ice Sheet
Author: Publisher: American Geophysical Union
ISBN:
Category : Geology
Languages : en
Pages : 297
Book Description
The Influence of Subglacial Hydrology on the Flow of West Antarctic Ice Streams
Author: Narelle Paula Marie BakerPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Subglacial hydrology is known to influence the flow of ice. However, difficulty in accessing the base of large ice sheets has made determining the interaction between ice streams, basal sediment and water difficult to discern. The aim of this thesis is to determine the influence of subglacial hydrology on the flow of the West Antarctic ice streams. This is achieved through development of a numerical flowline model, the Hydrology, Ice and Till (HIT) model. Ice thermodynamics are coupled to a till layer of Coulomb plastic rheology. The porosity of the till changes with basal melt and freeze and can be augmented by water transported through a subglacial conduit system. Water availability strongly affects ice flow, as till porosity influences the till failure strength and thereby the basal resistance of the ice. The model was developed in four stages and a number of sensitivity tests were performed. It was then applied to Kamb Ice Stream (Ice Stream C) and Whillians Ice Stream (Ice Stream B), West Antarctica. Results confirm that ice streams are capable of oscillating between fast and slow velocity states. Cycles are generated at the grounding line of an ice stream and the speed of the transition from slow to fast flow is governed by water availability. The period of oscillation of the cycles for the West Antarctic ice streams was found to be several hundred years, which is in line with observations of stagnation and reactivation of these ice streams. This shows that subglacial hydrology has a role in modulating the flow variability of ice streams and that rather large changes in the flow of the West Antarctic ice streams are likely to occur this century.