Late Wisconsinan Ice-Wedge Polygons near Kitchener, Ontario, Canada

1972 ◽  
Vol 9 (6) ◽  
pp. 607-617 ◽  
Author(s):  
Alan V. Morgan
Keyword(s):  
Aerial Photographs ◽  
Air Temperatures ◽  
Ice Wedge ◽  
Late Wisconsinan ◽  
Sand And Gravel

Reconnaissance from a light aircraft has revealed areas of polygonal ground east of Kitchener, Ontario. Examination of aerial photographs of the same region has shown additional polygons all developed upon Port Stanley II Till. Trenching of a polygon has exposed wedge-shaped sand and gravel infilled structures interpreted as ice-wedge casts. The wedges are believed to have been active prior to 13 000 years B.P., probably under tundra conditions, with mean annual air temperatures some 25 °F (13–14 °C) cooler than present.

Ice-wedge casts in Late Wisconsinan glaciofluvial deposits, southern Ontario, Canada

2005 ◽  
Vol 42 (12) ◽  
pp. 2117-2126 ◽  
Author(s):  
Cunhai Gao
Keyword(s):  
Window Of Opportunity ◽  
Southern Ontario ◽  
Braided Rivers ◽  
Drifting Snow ◽  
Close Proximity ◽  
Glaciofluvial Deposits ◽  
Ice Wedge ◽  
Late Wisconsinan ◽  
Sand And Gravel ◽  
Contraction And Expansion

Ice-wedge casts in Late Wisconsinan glaciofluvial sand and gravel deposits in southern Ontario taper downwards to form a V- or funnel-shaped morphology, ranging from 1 to over 3 m deep and from 1.0 to 2.5 m wide at the top. Pressure-derived primary structures, caused by repeated thermal contraction and expansion, include upturned strata, realigned stones, and small folds in the enclosing sediments. Although paleotemperature is difficult to estimate, the presence of ice-wedge casts testifies to the former presence of permafrost under prevailing periglacial conditions over this area. The regional till stratigraphy constrains the timing of ice-wedge growth to ca. 15 000 to ca. 13 000 BP. At this time, newly exposed terrains would have occurred in an interlobate area where severe climate created favourable conditions for permafrost to develop due to the close proximity to the receding ice. Inactive areas in braided rivers such as raised topographic surfaces and sand-filled channels with limited vegetation cover and minimal capability to trap drifting snow would have greatly enhanced ice-wedge growth. Rapid climatic amelioration and vegetation colonization across this area beginning ca. 13 000 BP probably slowed or stopped the growth of ice wedges. This limited window of opportunity, both geographically and in time, probably accounts for the limited occurrence of ice-wedge casts in southern Ontario.

Late Wisconsinan glacitectonic structures and evidence of postglacial permafrost in north-central Newfoundland

1977 ◽  
Vol 14 (12) ◽  
pp. 2797-2806 ◽  
Author(s):  
N. Eyles
Keyword(s):  
High Rate ◽  
The West ◽  
North Central ◽  
Deformation Structures ◽  
Pollen Zone ◽  
Air Temperatures ◽  
Ground Collapse ◽  
Glacier Ice ◽  
Ice Wedge ◽  
Late Wisconsinan

Rhythmically-bedded glaciofluvial sediments deposited subaqueously and now exposed on an emerged coastal foreland in north-central Newfoundland, exhibit postdepositional deformation structures such as synclinal folds and faulted zones of ground collapse, the result of melting of underlying buried glacier ice. A high rate of glaciofluvial deposition is indicated. The development of fault systems in those sediments overlying decaying glacier ice can be compared with laboratory simulations of vertical foundering in sedimentary rocks. Ice-wedge casts transecting folded and faulted sections in the area are indisputable evidence of subsequent permafrost conditions, i.e. a period when mean annual air temperatures lay below −6 °C. A rise of at least 10.4 °C in mean annual air temperature is indicated since that time. A severe periglacial climate is considered to have existed in the area from 12 000 to 10 000 years BP and ice wedges developed with a minimum growth rate of 1.25 mm/year. Comparison with reports of ice-wedge casts in Nova Scotia and the west coast of Newfoundland indicate that the period which they formed in north-central Newfoundland may be correlated with the tundra pollen zone L-3 of Livingstone and Livingstone, the Greatlakian substage of the Lake Wisconsinan in Midcontinental North America.

scholarly journals Microtopographic control on the ground thermal regime in ice wedge polygons

2018 ◽  
Vol 12 (6) ◽  
pp. 1957-1968 ◽  
Author(s):  
Charles J. Abolt ◽  
Michael H. Young ◽  
Adam L. Atchley ◽  
Dylan R. Harp
Keyword(s):  
Thermal Conditions ◽  
Ground Temperature ◽  
The Arctic ◽  
Near Surface ◽  
Hydrologic Processes ◽  
Ground Temperatures ◽  
Air Temperatures ◽  
Winter Temperatures ◽  
Ice Wedge ◽  
Prudhoe Bay

Abstract. The goal of this research is to constrain the influence of ice wedge polygon microtopography on near-surface ground temperatures. Ice wedge polygon microtopography is prone to rapid deformation in a changing climate, and cracking in the ice wedge depends on thermal conditions at the top of the permafrost; therefore, feedbacks between microtopography and ground temperature can shed light on the potential for future ice wedge cracking in the Arctic. We first report on a year of sub-daily ground temperature observations at 5 depths and 9 locations throughout a cluster of low-centered polygons near Prudhoe Bay, Alaska, and demonstrate that the rims become the coldest zone of the polygon during winter, due to thinner snowpack. We then calibrate a polygon-scale numerical model of coupled thermal and hydrologic processes against this dataset, achieving an RMSE of less than 1.1 ∘C between observed and simulated ground temperature. Finally, we conduct a sensitivity analysis of the model by systematically manipulating the height of the rims and the depth of the troughs and tracking the effects on ice wedge temperature. The results indicate that winter temperatures in the ice wedge are sensitive to both rim height and trough depth, but more sensitive to rim height. Rims act as preferential outlets of subsurface heat; increasing rim size decreases winter temperatures in the ice wedge. Deeper troughs lead to increased snow entrapment, promoting insulation of the ice wedge. The potential for ice wedge cracking is therefore reduced if rims are destroyed or if troughs subside, due to warmer conditions in the ice wedge. These findings can help explain the origins of secondary ice wedges in modern and ancient polygons. The findings also imply that the potential for re-establishing rims in modern thermokarst-affected terrain will be limited by reduced cracking activity in the ice wedges, even if regional air temperatures stabilize.

Periglacial Features Indicative of Permafrost: Ice and Soil Wedges

1976 ◽  
Vol 6 (1) ◽  
pp. 3-26 ◽  
Author(s):  
Robert F. Black
Keyword(s):  
The United States ◽  
Pressure Effects ◽  
Freezing And Thawing ◽  
Wetting And Drying ◽  
Ice Wedge ◽  
Surface Patterns ◽  
Late Wisconsinan ◽  
Collapse Structures ◽  
Similar Soil ◽  
Permafrost Regions

Ice wedges are wedge-shaped masses of ice, oriented vertically with their apices downward, a few millimeters to many meters wide at the top, and generally less than 10 m vertically. Ice wedges grow in and are confined to humid permafrost regions. Snow, hoar frost, or freezing water partly fill winter contraction cracks outlining polygons, commonly 5–20 m in diameter, on the surface of the ground. Moisture comes from the atmosphere. Increments of ice, generally 0.1–2.0 mm, are added annually to wedges which squeeze enclosing permafrost aside and to the surface to produce striking surface patterns. Soil wedges are not confined to permafrost. One type, sand wedges, now grows in arid permafrost regions. Sand wedges are similar in dimensions, patterns, and growth rates to ice wedges. Drifting sand enters winter contraction cracks instead of ice. Fossil ice and sand wedges are the most diagnostic and widespread indicators of former permafrost, but identification is difficult. Any single wedge is untrustworthy. Evidence of fossil ice wedges includes: wedge forms with collapse structures from replacement of ice; polygonal patterns with dimensions comparable to active forms having similar coefficients of thermal expansion; fabrics in the host showing pressure effects; secondary deposits and fabric indicative of a permafrost table; and other evidence of former permafrost. Sand wedges lack open-wedge, collapse structures, but have complex, nearly vertical, crisscrossing narrow dikelets and fabric. Similar soil wedges are produced by wetting and drying, freezing and thawing, solution, faulting, and other mechanisms. Many forms are multigenetic. Many socalled ice-wedge casts are misidentified, and hence, permafrost along the late-Wisconsinan border in the United States was less extensive than has been proposed.

The Sisters Creek Formation: Pleistocene sediments representing a nonglacial interval in southwestern British Columbia at about 18 ka

1995 ◽  
Vol 32 (6) ◽  
pp. 758-767 ◽  
Author(s):  
Stephen R. Hicock ◽  
Olav B. Lian
Keyword(s):  
British Columbia ◽  
Glacial Maximum ◽  
Time Space ◽  
Late Wisconsinan ◽  
Sand And Gravel ◽  
New Time

Sisters Creek Formation is formally defined, stratotypes are established for it, and the time–space chart is updated for the Fraser Lowland, southwestern British Columbia. The Sisters Creek is a Pleistocene formation comprising in situ and reworked organic-rich sediments, and nonorganic silt, sand, and gravel. The formation was deposited during the Port Moody interstade (within the Late Wisconsinan Fraser Glaciation; δ18O stage 2) between the Coquitlam stade (early Fraser Glaciation) and the main Vashon stadial maximum that occurred about 14.5 ka. The Sisters Creek Formation represents a glacial recession in southwestern British Columbia that generally coincided with the timing of the last global glacial maximum. The new time–space chart implies that, in Fraser Lowland, the Fraser Glaciation represents the rapid advances and retreats of glacial lobes issuing from surrounding mountains, which remained ice-covered during interstades.

Pseudo-Ice-Wedge Casts of Connecticut, Northeastern United States

1983 ◽  
Vol 20 (1) ◽  
pp. 74-89 ◽  
Author(s):  
Robert F. Black
Keyword(s):  
United States ◽  
Water Table ◽  
Physical Environment ◽  
Northeastern United States ◽  
Complex Fracture ◽  
Ice Wedge ◽  
Sand And Gravel ◽  
Coated Sand ◽  
Horizontal Layers

AbstractSince 1965, ice-wedge casts have been reported in deposits of sand and gravel in Connecticut. These are wedge forms up to 1.1 m wide and many meters high. Most are single forms, not in polygonal array. They are found in adjoining states as well. Their distribution, dimensions, structure, and fabric and an assessment of the former physical environment preclude their origin as permafrost features. They appear to be tension fractures produced by the loading of coarse clastics on fine clastics near and below the water table where sediments creep toward a stream or depression. Locally movement started with kettle formation during deglaciation. However, some wedges cut horizontal layers of iron-coated sand and gravel and must be younger than those distinctly postglacial phenomena. Moreover, modern B horizons of the overlying soil have moved down into some wedges more than 2 m, indicating that fracturing is still active today. Complex fracture fillings in bedrock also have been attributed to a permafrost origin, but this too seems unlikely.

scholarly journals Spatial variability of CO<sub>2</sub> uptake in polygonal tundra: assessing low-frequency disturbances in eddy covariance flux estimates

2017 ◽  
Vol 14 (12) ◽  
pp. 3157-3169 ◽  
Author(s):  
Norbert Pirk ◽  
Jakob Sievers ◽  
Jordan Mertes ◽  
Frans-Jan W. Parmentier ◽  
Mikhail Mastepanov ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Eddy Covariance ◽  
Low Frequency ◽  
Optimization Method ◽  
Co2 Exchange ◽  
Aerial Photographs ◽  
Strong Increase ◽  
Vulnerability To Climate Change ◽  
Flux Measurements ◽  
Ice Wedge

Abstract. The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of −46 gC m−2 to the annual CO2 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (−82 gC m−2). Due to differences in light-use efficiency, wetter areas with low-centered polygons sequestered 47 % more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2 K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra.

Laurentide glaciation in west-central Alberta: a single (Late Wisconsinan) event

1989 ◽  
Vol 26 (2) ◽  
pp. 266-274 ◽  
Author(s):  
David G. E. Liverman ◽  
N. R. Catto ◽  
N. W. Rutter
Keyword(s):  
Canadian Shield ◽  
Similar Sequence ◽  
Sedimentary Sequences ◽  
Base Level ◽  
The North ◽  
West Central ◽  
Braided Stream ◽  
Stream System ◽  
Late Wisconsinan ◽  
Sand And Gravel

The Grande Prairie region in west-central Alberta shows evidence of Late Wisconsinan Laurentide glaciation in the form of a widespread till, containing abundant erratic clasts derived from the Canadian Shield. Two sections, located on the Smoky River at Watino and on the Simonette River 80 km to the southwest, expose sediment lying stratigraphically below the till. A similar sequence is exposed in both localities: 5–10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt. The gravel contains no Laurentide erratics and is thus preglacial. The contact between the basal gravel and the overlying sand and silt is sharp and conformable. 14C dates from the base of the Simonette section and throughout the Watino section suggest a Middle Wisconsinan age. Thus, the sediment exposed is interpreted as a conformable Middle Wisconsinan sequence. The sedimentary sequences were deposited in a moderate- to low-energy braided stream system flowing towards the north. The general fining-up trend in the sections was produced as a result of channel abandonment, rather than by a change in regional base level. The sand and gravel units contain no material derived from the Canadian Shield. Consequently, the surface till is Late Wisconsinan, and represents the only Laurentide glaciation in this area of Alberta.

The Drift des Demoiselles on the Magdalen Islands (Québec, Canada): sedimentological and micromorphological evidence of a Late Wisconsinan glacial diamict

2013 ◽  
Vol 50 (5) ◽  
pp. 545-563 ◽  
Author(s):  
Audrey M. Rémillard ◽  
Bernard Hétu ◽  
Pascal Bernatchez ◽  
Pascal Bertran
Keyword(s):  
Sea Level ◽  
Ice Flow ◽  
Glacial Deposit ◽  
Marine Transgression ◽  
Deformation Structures ◽  
Ice Cap ◽  
Ice Wedge ◽  
Late Wisconsinan ◽  
Different Origin ◽  
Magdalen Islands

The deposits identified as being the Drift des Demoiselles, which is the upper unit of the southern Magdalen Islands (Québec, Canada), belong to two units of different origin, glacial and glaciomarine. At Anse à la Cabane, the glacial deposit comprises two subunits: a glacitectonite at the base and a subglacial traction till at the top. Numerous glaciotectonic deformation structures suggest ice flow towards the southeast. The till is above an organic horizon dated to ∼47–50 ka BP. New data presented here show that the southern part of the Magdalen archipelago was glaciated during the Late Wisconsinan. We relate this ice flow to the Escuminac ice cap, whose centre of dispersion was located in the Gulf of St. Lawrence, northwest of the islands. At Anse au Plâtre, the top of the Drift des Demoiselles is a glaciomarine deposit. At Anse à la Cabane, the till is covered by a stratified subtidal unit located at ∼20 m above sea level. Both were deposited during the marine transgression that followed deglaciation. At Anse à la Cabane, three ice-wedge casts truncate the till and the subtidal unit, providing evidence that periglacial conditions occurred on the archipelago after deglaciation.

scholarly journals Accelerated wastage of the Monte Perdido Glacier in the Spanish Pyrenees during recent stationary climatic conditions

2015 ◽  
Vol 9 (5) ◽  
pp. 5021-5051 ◽  
Author(s):  
J. I. López-Moreno ◽  
J. Revuelto ◽  
I. Rico ◽  
J. Chueca-Cía ◽  
A. Julián ◽  
...  
Keyword(s):  
Air Temperature ◽  
Laser Scanning ◽  
Climatic Conditions ◽  
Snow Accumulation ◽  
Airborne Lidar ◽  
Ice Age ◽  
Aerial Photographs ◽  
Ice Volume ◽  
Accelerated Degradation ◽  
Air Temperatures

Abstract. This paper analyzes the evolution of the Monte Perdido Glacier, the third largest glacier of the Pyrenees, from 1981 to the present. We assessed the evolution of the glacier's surface area by use of aerial photographs from 1981, 1999, and 2006, and changes in ice volume by geodetic methods with digital elevation models (DEMs) generated from topographic maps (1981 and 1999), airborne LIDAR (2010) and terrestrial laser scanning (TLS, 2011, 2012, 2013, and 2014). We interpreted the changes in the glacier based on climate data from a nearby meteorological station. The results indicate an accelerated degradation of this glacier after 2000, with a rate of ice surface loss that was almost three-times greater from 2000 to 2006 than for earlier periods, and a doubling of the rate of ice volume loss from 1999 to 2010 (the ice depth decreased 8.98 ± 1.8 m, −0.72 ± 0.14 m w.e. yr−1) compared to 1981 to 1999 (the ice depth decreased 8.35 ± 2.12 m, −0.39 ± 0.1 m w.e. yr−1). This loss of glacial ice has continued from 2011 to 2014 (the ice depth decreased 2.1 ± 0.4 m, −0.64 ± 0.36 m w.e. yr−1). Local climatic changes during the study period cannot explain the acceleration in wastage rate of this glacier, because local precipitation and snow accumulation increased slightly, and local air temperature during the ablation period did not significantly increase. The accelerated degradation of this glacier in recent years can be explained by the lack of equilibrium between the glacier and the current climatic conditions. In particular, the average air temperature increased by at least 0.9 °C in this region since the end of the Little Ice Age (LIA) in the mid-1800s. Thus, this glacier shrinks dramatically during years with low accumulation or high air temperatures during the ablation season, but cannot recover during years with high accumulation or low air temperatures during the ablation season. The most recent TLS data support this interpretation. These data indicated that two consecutive markedly anomalous wet winters and cool summers (2012–13 and 2013–14) led to near zero mass balance conditions, with significant losses of ice in some areas. These anomalous periods could not counteract the dramatic shrinkage that occurred during the dry and warm period of 2011–2012.

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