scholarly journals A subglacial hydrologic drainage hypothesis for silt sorting and deposition during retreat in Pine Island Bay

2019 ◽  
Vol 60 (80) ◽  
pp. 14-20
Author(s):  
Dustin M. Schroeder ◽  
Emma J. MacKie ◽  
Timothy T. Creyts ◽  
John B. Anderson
Keyword(s):  
Late Holocene ◽  
Water System ◽  
Small Scale ◽  
Alternative Mechanism ◽  
West Antarctica ◽  
Subglacial Lake ◽  
Sediment Deposits ◽  
Flow Speeds ◽  
Subglacial Meltwater ◽  
Continuous Deposition

AbstractLate Holocene sediment deposits in Pine Island Bay, West Antarctica, are hypothesized to be linked to intensive meltwater drainage during the retreat of the paleo-Pine Island Ice Stream after the Last Glacial Maximum. The uppermost sediment units show an abrupt transition from ice-proximal debris to a draped silt during the late Holocene, which is interpreted to coincide with rapid deglaciation. The small scale and fine sorting of the upper unit could be attributed to origins in subglacial meltwater; however the thickness and deposition rate for this unit imply punctuated- rather than continuous-deposition. This, combined with the deposit's location seaward of large, bedrock basins, has led to the interpretation of this unit as the result of subglacial lake outbursts in these basins. However, the fine-scale sorting of the silt unit is problematic for this energetic interpretation, which should mobilize and deposit a wider range of sediment sizes. To resolve this discrepancy, we present an alternative mechanism in which the silt was sorted by a distributed subglacial water system, stored in bedrock basins far inland of the grounding line, and subsequently eroded at higher flow speeds during retreat. We demonstrate that this mechanism is physically plausible given the subglacial conditions during the late Holocene. We hypothesize that similar silt units observed elsewhere in Antarctica downstream of bedrock basins could be the result of the same mechanism.

scholarly journals Subglacial hydrology and the formation of ice streams

2014 ◽  
Vol 470 (2161) ◽  
pp. 20130494 ◽  
Author(s):  
T. M Kyrke-Smith ◽  
R. F Katz ◽  
A. C Fowler
Keyword(s):  
Ice Sheet ◽  
Water System ◽  
Coupled Model ◽  
Water Film ◽  
Mass Conservation ◽  
Ice Streams ◽  
Base Level ◽  
Ice Sheet Dynamics ◽  
Ice Water ◽  
Subglacial Meltwater

Antarctic ice streams are associated with pressurized subglacial meltwater but the role this water plays in the dynamics of the streams is not known. To address this, we present a model of subglacial water flow below ice sheets, and particularly below ice streams. The base-level flow is fed by subglacial melting and is presumed to take the form of a rough-bedded film, in which the ice is supported by larger clasts, but there is a millimetric water film which submerges the smaller particles. A model for the film is given by two coupled partial differential equations, representing mass conservation of water and ice closure. We assume that there is no sediment transport and solve for water film depth and effective pressure. This is coupled to a vertically integrated, higher order model for ice-sheet dynamics. If there is a sufficiently small amount of meltwater produced (e.g. if ice flux is low), the distributed film and ice sheet are stable, whereas for larger amounts of melt the ice–water system can become unstable, and ice streams form spontaneously as a consequence. We show that this can be explained in terms of a multi-valued sliding law, which arises from a simplified, one-dimensional analysis of the coupled model.

scholarly journals Subglacial Lake CECs: Discovery and in situ survey of a privileged research site in West Antarctica

2015 ◽  
Vol 42 (10) ◽  
pp. 3944-3953 ◽  
Author(s):  
Andrés Rivera ◽  
José Uribe ◽  
Rodrigo Zamora ◽  
Jonathan Oberreuter
Keyword(s):  
West Antarctica ◽  
Subglacial Lake ◽  
Research Site

Charcoal signatures defined by multivariate analysis of charcoal records from 10 lakes in northwest Wisconsin (USA)

2011 ◽  
Vol 75 (1) ◽  
pp. 125-137 ◽  
Author(s):  
Elizabeth A. Lynch ◽  
Sara C. Hotchkiss ◽  
Randy Calcote
Keyword(s):  
Late Holocene ◽  
Climate Changes ◽  
Regional Climate ◽  
Fire Regimes ◽  
Small Scale ◽  
Regional Patterns ◽  
Crown Fires ◽  
Sand Plain ◽  
In Fire ◽  
Standard Techniques

AbstractWe show how sedimentary charcoal records from multiple sites within a single landscape can be used to compare fire histories and reveal small scale patterns in fire regimes. Our objective is to develop strategies for classifying and comparing late-Holocene charcoal records in Midwestern oak- and pine-dominated sand plain ecosystems where fire regimes include a mix of surface and crown fires. Using standard techniques for the analysis of charcoal from lake sediments, we compiled 1000- to 4000-yr-long records of charcoal accumulation and charcoal peak frequencies from 10 small lakes across a sand plain in northwestern Wisconsin. We used cluster analysis to identify six types of charcoal signatures that differ in their charcoal influx rates, amount of grass charcoal, and frequency and magnitude of charcoal peaks. The charcoal records demonstrate that while fire histories vary among sites, there are regional patterns in the occurrence of charcoal signature types that are consistent with expected differences in fire regimes based on regional climate and vegetation reconstructions. The fire histories also show periods of regional change in charcoal signatures occurring during times of regional climate changes at ~700, 1000, and 3500 cal yr BP.

scholarly journals An Interdisciplinary Approach to the Sustainability of a Gravity-Fed Water System in the Peruvian Andes

2019 ◽  
Vol 14 (3) ◽  
pp. 49-60
Author(s):  
Riley Orabona Wagner ◽  
Sydney Hsu ◽  
John Nicholas Kick ◽  
Sofia Bisogno ◽  
Camille Heubner ◽  
...  
Keyword(s):  
Water System ◽  
Interdisciplinary Approach ◽  
Design Parameters ◽  
Small Scale ◽  
Development Projects ◽  
Peruvian Andes ◽  
Princeton University ◽  
Future Success ◽  
Local Partnerships ◽  
Engineers Without Borders

This paper analyzes the methods utilized by the Princeton University Chapter of Engineers Without Borders to ensure the sustainability of a gravity-fed water system in rural northwestern Peru. While similar small scale development projects consider sustainability in their design process, some do not recognize the importance of an interdisciplinary approach to sustainability. This team, however, is inherently interdisciplinary in nature due to its unique subteam structure, which subsequently affects its approach to sustainability. By examining the technical, social, and financial considerations of the project conducted by the Princeton University Chapter of Engineers Without Borders, this paper argues for a three-pronged approach to sustainability. As can be seen through thoughtful design parameters, strong local partnerships, and strategic financial mechanisms, the project displays promise of future success with regards to sustainability. The main objective of the Princeton Chapter of Engineers Without Borders in this partnership is to ensure that the community has the knowledge, tools, and resources necessary to maintain the water system in a self-sufficient manner at the completion of the chapter’s involvement.

scholarly journals Mobile crowd participation to root small-scale piped water supply systems in India and Bangladesh

2019 ◽  
Vol 9 (1) ◽  
pp. 139-151 ◽  
Author(s):  
A. Mink ◽  
B. A. Hoque ◽  
S. Khanam ◽  
D. Van Halem
Keyword(s):  
Water Supply ◽  
Water System ◽  
Internet Access ◽  
Water Quality Monitoring ◽  
Small Scale ◽  
Water Supply Systems ◽  
Smartphone Applications ◽  
Piped Water ◽  
Supply Systems ◽  
Mobile Crowd

Abstract In the arsenic-contaminated Ganges-Brahmaputra-Meghna Delta in India and Bangladesh, small-scale piped water supply seems a promising way to provide safe drinking water to households in the region. The use of smartphone applications can support monitoring of the system and enhance local engagement and empowerment. In this paper the scope for mobile crowd participation as a research and monitoring tool for piped water supply systems in Bihar, India and in Khulna and Chittagong, Bangladesh is investigated. In these areas, the use of smartphones and internet access are growing rapidly and smartphone applications would enable real-time water quality monitoring, payment of water bills, awareness creation, and a dialogue between the end-user and the water supplier. To identify the relevance and acceptability of piped water supply and smartphone monitoring, four surveys with potential end-users were conducted. Based on these surveys we conclude that in the investigated areas there is a desire for piped water systems, that households already own smartphones with internet access, and that there is an interest in smartphone monitoring. The enabling environment to deploy mobile crowd participation for piped water system monitoring stimulates further research towards an investigation of potential functionalities and the actual development of such an application.

Late Holocene Vegetation Changes in Greenwater Valley, Mojave Desert, California

1985 ◽  
Vol 23 (2) ◽  
pp. 227-235 ◽  
Author(s):  
Kenneth L. Cole ◽  
Robert H. Webb
Keyword(s):  
Lower Limit ◽  
Principal Components ◽  
Mojave Desert ◽  
Late Holocene ◽  
Small Scale ◽  
Vegetation Changes ◽  
Factor Analyses ◽  
Downward Shift ◽  
A Site ◽  
Coleogyne Ramosissima

Small-scale late Holocene vegetation changes were determined from a series of 13 modern and fossil packrat middens collected from a site in the Greenwater Valley, northern Mojave Desert, California. Although the site is above the modern lower limit ofColeogyne ramosissima(black-brush), macrofossils of this shrub are only present in samples younger than 270 yr B.P. In order to measure changes more subtle than presence vs absence, macrofossil concentrations were quantified, and principal components and factor analyses were used to distinguish midden plant assemblages. Both the presence/absence data and the statistical analyses suggest a downward shift of 50 to 100 m forColeogyne(blackbrush) communities between 1435 and 1795 A.D.

scholarly journals Late-Holocene climate evolution at the WAIS Divide site, West Antarctica: bubble number-density estimates

2011 ◽  
Vol 57 (204) ◽  
pp. 629-638 ◽  
Author(s):  
J.M. Fegyveresi ◽  
R.B. Alley ◽  
M.K. Spencer ◽  
J.J. Fitzpatrick ◽  
E.J. Steig ◽  
...  
Keyword(s):  
Late Holocene ◽  
Accumulation Rate ◽  
Ice Core ◽  
Temperature History ◽  
Flow Density ◽  
Number Density ◽  
West Antarctica ◽  
Surface Cooling ◽  
Bubble Number ◽  
Bubble Number Density

AbstractA surface cooling of ∼1.7°C occurred over the ∼two millennia prior to ∼1700 CE at the West Antarctic ice sheet (WAIS) Divide site, based on trends in observed bubble number-density of samples from the WDC06A ice core, and on an independently constructed accumulation-rate history using annual-layer dating corrected for density variations and thinning from ice flow. Density increase and grain growth in polar firn are both controlled by temperature and accumulation rate, and the integrated effects are recorded in the number-density of bubbles as the firn changes to ice. Number-density is conserved in bubbly ice following pore close-off, allowing reconstruction of either paleotemperature or paleo-accumulation rate if the other is known. A quantitative late-Holocene paleoclimate reconstruction is presented for West Antarctica using data obtained from the WAIS Divide WDC06A ice core and a steady-state bubble number-density model. The resultant temperature history agrees closely with independent reconstructions based on stable-isotopic ratios of ice. The ∼1.7°C cooling trend observed is consistent with a decrease in Antarctic summer duration from changing orbital obliquity, although it remains possible that elevation change at the site contributed part of the signal. Accumulation rate and temperature dropped together, broadly consistent with control by saturation vapor pressure.

scholarly journals Subglacial Lake Ellsworth: A candidate forin situexploration in West Antarctica

2004 ◽  
Vol 31 (23) ◽  
Author(s):  
Martin J. Siegert ◽  
Richard Hindmarsh ◽  
Hugh Corr ◽  
Andy Smith ◽  
John Woodward ◽  
...  
Keyword(s):  
West Antarctica ◽  
Subglacial Lake
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