scholarly journals Subglacial water-sheet floods, drumlins and ice-sheet lobes

1999 ◽  
Vol 45 (150) ◽  
pp. 201-213 ◽  
Author(s):  
E.M. Shoemaker
Keyword(s):  
New York ◽  
Lake Michigan ◽  
New York State ◽  
Ice Sheet ◽  
Lake Ontario ◽  
High Water ◽  
Green Bay ◽  
Subglacial Lake ◽  
Western Lake ◽  
Subglacial Lakes

AbstractThe effect of subglacial lakes upon ice-sheet topography and the velocity patterns of subglacial water-sheet floods is investigated. A subglacial lake in the combined Michigan–Green Bay basin, Great Lakes, North America, leads to: (1) an ice-sheet lobe in the lee of Lake Michigan; (2) a change in orientations of flood velocities across the site of a supraglacial trough aligned closely with Green Bay, in agreement with drumlin orientations; (3) low water velocities in the lee of Lake Michigan where drumlins are absent; and (4) drumlinization occurring in regions of predicted high water velocities. The extraordinary divergence of drumlin orientations near Lake Ontario is explained by the presence of subglacial lakes in the Ontario and Erie basins, along with ice-sheet displacements of up to 30 km in eastern Lake Ontario. The megagrooves on the islands in western Lake Erie are likely to be the product of the late stage of a water-sheet flood when outflow from eastern Lake Ontario was dammed by displaced ice and instead flowed westward along the Erie basin. The Finger Lakes of northern New York state, northeastern U.S.A., occur in a region of likely ice-sheet grounding where water sheets became channelized. Green Bay and Grand Traverse Bay are probably the products of erosion along paths of strongly convergent water-sheet flow.

Subglacial water-sheet floods, drumlins and ice-sheet lobes

1999 ◽  
Vol 45 (150) ◽  
pp. 201-213 ◽  
Author(s):  
E.M. Shoemaker
Keyword(s):  
New York ◽  
Lake Michigan ◽  
New York State ◽  
Ice Sheet ◽  
Lake Ontario ◽  
High Water ◽  
Green Bay ◽  
Subglacial Lake ◽  
Western Lake ◽  
Subglacial Lakes

AbstractThe effect of subglacial lakes upon ice-sheet topography and the velocity patterns of subglacial water-sheet floods is investigated. A subglacial lake in the combined Michigan–Green Bay basin, Great Lakes, North America, leads to: (1) an ice-sheet lobe in the lee of Lake Michigan; (2) a change in orientations of flood velocities across the site of a supraglacial trough aligned closely with Green Bay, in agreement with drumlin orientations; (3) low water velocities in the lee of Lake Michigan where drumlins are absent; and (4) drumlinization occurring in regions of predicted high water velocities. The extraordinary divergence of drumlin orientations near Lake Ontario is explained by the presence of subglacial lakes in the Ontario and Erie basins, along with ice-sheet displacements of up to 30 km in eastern Lake Ontario. The megagrooves on the islands in western Lake Erie are likely to be the product of the late stage of a water-sheet flood when outflow from eastern Lake Ontario was dammed by displaced ice and instead flowed westward along the Erie basin. The Finger Lakes of northern New York state, northeastern U.S.A., occur in a region of likely ice-sheet grounding where water sheets became channelized. Green Bay and Grand Traverse Bay are probably the products of erosion along paths of strongly convergent water-sheet flow.

Linear zones, seismicity, and the possibility of a major earthquake in the intraplate western Lake Ontario area of eastern North America

1998 ◽  
Vol 35 (7) ◽  
pp. 762-786 ◽  
Author(s):  
J L Wallach ◽  
A A Mohajer ◽  
R L Thomas
Keyword(s):  
New York ◽  
Seismic Hazard ◽  
New York State ◽  
Spatial Relationship ◽  
Lake Ontario ◽  
Eastern Canada ◽  
Georgian Bay ◽  
Major Earthquake ◽  
Western Lake ◽  
Large Earthquakes

Seismic hazard assessments conducted in eastern Canada rely on seismological data, which are essential, but alone, inadequate. That is because the earthquake record is too short to provide a representative picture of where large earthquakes have occurred in the past. Consequently, seismic hazard may be underestimated in areas, such as that encompassing western Lake Ontario, that are devoid of documented large earthquakes. To attempt to ascertain the likelihood of a major earthquake occurring in that highly populated and industrialized area, three regionally extensive geophysically expressed lineaments were investigated and the results were combined with available seismological information. The most conspicuous is the Niagara-Pickering linear zone, within which there have been at least two, if not three, periods of brittle faulting, including displacements compatible with the current stress field. It also appears to represent the same major structure as the Akron magnetic boundary in eastern Ohio, the site of the mb = 4.9 Leroy earthquake. The second is the Georgian Bay linear zone, which extends from Georgian Bay to New York State. It displays evidence of recent outcrop-scale faulting, an alignment of earthquakes along its southwestern boundary, and a possible spatial relationship to other earthquakes, including two of M >= 5. Lastly, there is the Hamilton - Lake Erie lineament, which is parallel and proximal to a possible fault and coincides with a linear array of small to moderate earthquakes. All three converge on the western Lake Ontario area, which has a higher frequency of seismicity than the adjacent areas. Thus, the western Lake Ontario area might have a greater potential to experience a major earthquake than heretofore believed.

scholarly journals Improved Detection Using Negative Elevation Angles for Mountaintop WSR-88Ds. Part III: Simulations of Shallow Convective Activity over and around Lake Ontario

2007 ◽  
Vol 22 (4) ◽  
pp. 839-852 ◽  
Author(s):  
Rodger A. Brown ◽  
Thomas A. Niziol ◽  
Norman R. Donaldson ◽  
Paul I. Joe ◽  
Vincent T. Wood
Keyword(s):  
New York ◽  
Flow Direction ◽  
New York State ◽  
Lake Ontario ◽  
Heavy Snowfall ◽  
Land Area ◽  
Lake Effect ◽  
Northern Side ◽  
Low Altitude ◽  
The Difference

Abstract During the winter, lake-effect snowstorms that form over Lake Ontario represent a significant weather hazard for the populace around the lake. These storms, which typically are only 2 km deep, frequently can produce narrow swaths (20–50 km wide) of heavy snowfall (2–5 cm h−1 or more) that extend 50–75 km inland over populated areas. Subtle changes in the low-altitude flow direction can mean the difference between accumulations that last for 1–2 h and accumulations that last 24 h or more at a given location. Therefore, it is vital that radars surrounding the lake are able to detect the presence and strength of these shallow storms. Starting in 2002, the Canadian operational radars on the northern side of the lake at King City, Ontario, and Franktown, Ontario, began using elevation angles of as low as −0.1° and 0.0°, respectively, during the winter to more accurately estimate snowfall rates at the surface. Meanwhile, Weather Surveillance Radars-1988 Doppler in New York State on the southern and eastern sides of the lake—Buffalo (KBUF), Binghamton (KBGM), and Montague (KTYX)—all operate at 0.5° and above. KTYX is located on a plateau that overlooks the lake from the east at a height of 0.5 km. With its upward-pointing radar beams, KTYX’s detection of shallow lake-effect snowstorms is limited to the eastern quarter of the lake and surrounding terrain. The purpose of this paper is to show—through simulations—the dramatic increase in snowstorm coverage that would be possible if KTYX were able to scan downward toward the lake’s surface. Furthermore, if KBUF and KBGM were to scan as low as 0.2°, detection of at least the upper portions of lake-effect storms over Lake Ontario and all of the surrounding land area by the five radars would be complete. Overlake coverage in the lower half (0–1 km) of the typical lake-effect snowstorm would increase from about 40% to about 85%, resulting in better estimates of snowfall rates in landfalling snowbands over a much broader area.

scholarly journals A younger glacial Lake Iroquois in the Lake Ontario basin, Ontario and New York: re-examination of pollen stratigraphy and radiocarbon dating

2020 ◽  
Vol 57 (4) ◽  
pp. 453-463
Author(s):  
C.F.M. Lewis ◽  
T.W. Anderson
Keyword(s):  
New York ◽  
New York State ◽  
Lake Ontario ◽  
Late Glacial ◽  
Glacial Lake ◽  
Lake Basin ◽  
Long Distance ◽  
Small Lake ◽  
Pollen Stratigraphy ◽  
Lake Basins

Revision of palynochronologic and radiocarbon age estimates for the termination of glacial Lake Iroquois, mainly based on a currently accepted younger determination of the key Picea–Pinus pollen transition, shows agreement with recently established constraints for this late glacial event in the Lake Ontario basin at 13 000 cal years BP. The date of emergence or isolation of small lake basins reflects the termination of inundation by glacial lake waters. The increasing upward presence of plant detritus and the onset of organic sedimentation marks the isolation level in the sediments of a small lake basin. The upward relative decline and cessation of pollen from trees such as Pinus, Quercus, and other thermophilous hardwoods that were wind transported long distances from southern areas also mark the isolation of inundated small lake basins by the declining water level of Lake Iroquois as local vegetation grew and local pollen overwhelmed long-distance-transported pollen. Re-examination of data in small lake basins north of Lake Ontario using the above criteria shows that the age range for the termination of Lake Iroquois derived from these data overlaps other age constraints. These constraints are based on a varve-estimated duration of post-Iroquois phases before incursion of the Champlain Sea, a newly discovered late ice advance into northern New York State, and the age of a mastodon at Cohoes, New York. The new age (13 000 cal years BP) for Lake Iroquois termination is significantly younger than the previous estimate of 11 800 14C (13 600 cal) years BP.

Detecting active subglacial lakes beneath the Greenland Ice Sheet using ArcticDEM

2020 ◽  
Author(s):  
Jade Bowling ◽  
Amber Leeson ◽  
Malcolm McMillan ◽  
Stephen Livingstone ◽  
Andrew Sole
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Elevation ◽  
Surface Model ◽  
Ice Dynamics ◽  
Subglacial Lake ◽  
Flow Speeds ◽  
Elevation Data ◽  
Hydrological System ◽  
Subglacial Lakes

<p>A total of 63 subglacial lakes have been documented beneath the Greenland Ice Sheet using a combination of radio-echo sounding and surface elevation change measurements. Of these, only 7 lakes have shown evidence of hydrological activity over the period 2001-2018. Draining lakes have been observed to drive transient changes in local ice flow speeds in Antarctica. The sudden discharge of water during a subglacial lake outburst event causes the subglacial lake roof to subside, which propagates to the surface, resulting in the formation of collapse basins (typically ~50-70 m in depth). These surface features can be detected using remote sensing techniques.</p><p>Whilst over 100 active subglacial lakes have been identified in Antarctica, predominantly beneath ice streams, little is known about the extent, volume of water stored and residence times of active subglacial lakes in Greenland, together with any potential influence of drainage events on local ice dynamics and sediment evacuation rates. Here, we explore the potential of the high resolution ArcticDEM stereogrammetric digital surface model (DSM) open source dataset, generated from satellite optical imagery, to identify and monitor subglacial lake-derived collapse basins. The ArcticDEM provides 2 m time-stamped surface elevation data, covering ~160 million km<sup>2</sup>, offering an exciting opportunity to map elevation changes between 2009-2017. This study presents the first effort to utilise ArcticDEM data at an ice-sheet scale to identify and monitor active subglacial lakes beneath the Greenland Ice Sheet, which we hope will ultimately improve our understanding of its complex subglacial hydrological system.</p>

Diet of Burbot in Green Bay and Western Lake Michigan With Comparison to Other Waters

1997 ◽  
Vol 23 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Thomas W. Fratt ◽  
Daniel W. Coble ◽  
Fred Copes ◽  
Richard E. Bruesewitz
Keyword(s):  
Lake Michigan ◽  
Green Bay ◽  
Western Lake

scholarly journals Potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets

2013 ◽  
Vol 7 (6) ◽  
pp. 1721-1740 ◽  
Author(s):  
S. J. Livingstone ◽  
C. D. Clark ◽  
J. Woodward ◽  
J. Kingslake
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Simplified Approach ◽  
Subglacial Lake ◽  
Ice Stream ◽  
Geophysical Surveys ◽  
Subglacial Lakes ◽  
The Antarctic ◽  
Subglacial Drainage

Abstract. We use the Shreve hydraulic potential equation as a simplified approach to investigate potential subglacial lake locations and meltwater drainage pathways beneath the Antarctic and Greenland ice sheets. We validate the method by demonstrating its ability to recall the locations of >60% of the known subglacial lakes beneath the Antarctic Ice Sheet. This is despite uncertainty in the ice-sheet bed elevation and our simplified modelling approach. However, we predict many more lakes than are observed. Hence we suggest that thousands of subglacial lakes remain to be found. Applying our technique to the Greenland Ice Sheet, where very few subglacial lakes have so far been observed, recalls 1607 potential lake locations, covering 1.2% of the bed. Our results will therefore provide suitable targets for geophysical surveys aimed at identifying lakes beneath Greenland. We also apply the technique to modelled past ice-sheet configurations and find that during deglaciation both ice sheets likely had more subglacial lakes at their beds. These lakes, inherited from past ice-sheet configurations, would not form under current surface conditions, but are able to persist, suggesting a retreating ice-sheet will have many more subglacial lakes than advancing ones. We also investigate subglacial drainage pathways of the present-day and former Greenland and Antarctic ice sheets. Key sectors of the ice sheets, such as the Siple Coast (Antarctica) and NE Greenland Ice Stream system, are suggested to have been susceptible to subglacial drainage switching. We discuss how our results impact our understanding of meltwater drainage, basal lubrication and ice-stream formation.

scholarly journals Possible groundwater dominance in the subglacial hydrology of ice sheet interiors: example at Dome C, East Antarctica

2016 ◽  
Author(s):  
Brad T. Gooch ◽  
Sasha P. Carter ◽  
Omar Ghattas ◽  
Duncan A. Young ◽  
Donald D. Blankenship
Keyword(s):  
Groundwater Flow ◽  
Ice Sheet ◽  
Sheet Thickness ◽  
East Antarctica ◽  
Path Model ◽  
Cross Sectional ◽  
Subglacial Lake ◽  
Groundwater Flux ◽  
Groundwater Systems ◽  
Subglacial Lakes

Abstract. We hypothesize that groundwater systems may be the main water transport mechanism over (distributed, inefficient) water sheets at large scales in the interiors of ice sheets where melt rates are very low. We compare melt rate magnitudes to potential groundwater volume fluxes and also calculate the theoretical transmissivity ranges of subglacial water sheet and groundwater flow systems. Theoretical groundwater systems are on par with or are more transmissive than water sheets for the upper half of the permeability spectrum. In addition, we develop a 2D cross-sectional subglacial flow path model that connects subglacial lakes near Dome C, East Antarctica. This model integrates subglacial water sheet flux and hypothetical groundwater flow forcing, better bridging two historically disparate modeling frameworks – subglacial hydrology and ice sheet hydrogeology. Our model results suggest that the water sheet thickness can be highly dependent on groundwater flux and that the water sheet transmissivity is within the total range of the modeled groundwater system transmissivity. We infer from these results that subglacial lake stability and basal radar reflections underneath the interior of East Antarctica may possibly be affected by groundwater flow.

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