scholarly journals Pingo Growth and collapse, Tuktoyaktuk Peninsula Area, Western Arctic Coast, Canada: a long-term field study

2002 ◽  
Vol 52 (3) ◽  
pp. 271-323 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Freezing Point ◽  
Growth Data ◽  
Long Term Study ◽  
Western Arctic ◽  
Mound Growth ◽  
Arctic Coast ◽  
Spring Flow ◽  
Potential Use ◽  
Term Field

Abstract Growth data from precise surveys have been obtained for 11 pingos for periods ranging from 20 to 26 years. Most of the 1350 pingos, perhaps one quarter of the world's total, have grown up in the bottoms of drained lakes underlain by sands. Permafrost aggradation on the drained lake bottoms has resulted in pore water expulsion, solute rejection below the freezing front, a freezing point depression, and groundwater flow at below 0° C to one or more residual ponds, the sites of pingo growth. Sub-pingo water lenses underlie many growing pingos.The pure ice which grows by downward freezing in a sub-pingo water lens may be composed of seasonal growth bands which, like tree rings, are of potential use in the study of past climates. Growing pingos underlain by sub-pingo water lenses can often be identified by features such as peripheral pingo rupture, spring flow, frost mound growth, normal faulting, and oscillations in pingo height. Such features, and others, are associated with hydrofracturing and water loss from a sub-pingo water lens. Some of the data derived from the long-term study of pingo growth are relevant to the identification of collapse features, interpreted as paleo pingos, in areas now without permafrost.

A long-term field study (1951-2003) of ventifacts formed by katabatic winds at Paulatuk, western Arctic coast, Canada

2005 ◽  
Vol 42 (9) ◽  
pp. 1615-1635 ◽  
Author(s):  
J Ross Mackay ◽  
C R Burn
Keyword(s):  
Field Measurements ◽  
Katabatic Winds ◽  
Abrasion Rate ◽  
Western Arctic ◽  
Arctic Coast ◽  
Optical Examination ◽  
East West ◽  
Coastal Settlement ◽  
Term Field

Field measurements have been made since 1951 on hundreds of ventifacts abraded by strong, southerly, katabatic winds that blow in winter and summer past Paulatuk, a small western Arctic coastal settlement. Sand is commonly entrained by the strongest winds in winter. The ventifacts, all glacial erratics deposited prior to 12 ka BP, have been gradually rotated by the southerly winds until the long axes of most ventifacts now trend approximately east–west, normal to the katabatic winds. In contrast, pebbles have a slightly preferred north–south orientation, parallel to the katabatic winds. The facets on sandstone and diabase ventifacts are almost planar, but are rounded on granites and hackled on limestones, reflecting the influence of both solution and abrasion. Abrasion is evident on the built structures in Paulatuk, but despite the over 50 years of observation, abrasion of the ventifacts has been virtually undetectable. The extremely slow abrasion rate has been estimated from: observations on two ventifacts from 1951 to 2003; photographic comparisons and observations of 60 ventifacts from 1968 to 2003; optical examination of 14 granite slabs, polished and unpolished, exposed to abrasion from 1967 to 1976; and comparisons of the windward and leeward sides of six large rock caches built with ventifacts probably long before 1900. If the present rates of abrasion are representative of Holocene conditions, ventifact formation has probably taken much of postglacial time. The increase in vegetation cover around many rocks between 1968 and 2003 suggests that the climate has changed in the last three decades.

scholarly journals Thermally induced movements in ice-wedge polygons, western arctic coast: a long-term study

2002 ◽  
Vol 54 (1) ◽  
pp. 41-68 ◽  
Author(s):  
J. Ross MacKay
Keyword(s):  
Active Layer ◽  
Term Study ◽  
Thermally Induced ◽  
Seasonal Movements ◽  
Long Term Study ◽  
Ice Wedge ◽  
Western Arctic ◽  
Arctic Coast

AbstractThermally induced seasonal movements of the active layer and subjacent permafrost have been measured in numerous ice-wedge polygons that have varied in age, type, crack frequency, and topographic location. The field observations show that, in winter, thermal contraction, which is inward, is constrained or vanishes at the polygon centres but, in summer, thermal expansion, which is outward, is unconstrained at the ice-wedge troughs. Therefore, there tends to be a small net summer transport of the active layer, to varying depths, into the ice-wedge troughs. The movement has been observed in all polygons studied. The slow net transport of material into the ice-wedge troughs has implications for: permafrost aggradation and the growth of syngenetic wedges in some troughs; the palaeoclimatic reconstruction of some ice- wedge casts; and the interpretation of polygon stratigraphy based upon the assumption that the polygon material has accumulatedin situ.

Long-term field study of a deep-corrugated metal box type culvert

1994 ◽  
Vol 31 (2) ◽  
pp. 175-180 ◽  
Author(s):  
Shad M. Sargand ◽  
Glenn A. Hazen ◽  
Teruhisa Masada ◽  
John O. Hurd
Keyword(s):  
Field Performance ◽  
Reference Points ◽  
Load Test ◽  
Static Load Test ◽  
Static Loads ◽  
Long Term Study ◽  
Corrugated Metal ◽  
Over Time ◽  
Term Field

A deep-corrugated metal box culvert structure was instrumented with strain gages and tape extensometer reference points in the field. Performance was monitored during backfilling and, paving and under static loads shortly after completion of installation. Beyond the initial study, deflection readings were taken periodically for 3 years. Also, the static load test was conducted during the second and third years to examine changes in structural responses over time. The results of the study showed that the culvert deflection stabilized within the 3 year period. The overall deflection recorded during the construction phases was about 2 cm, and the additional deflection of about 0.8 cm took place during the long-term study period. The deflection, moment, and thrust responses of the culvert under static loads improved over time. This was considered to be because of backfill soil densification under repeated traffic loads. Key words : long-term field performance, culvert, box type, deep corrugation, deflection, live loads.

Some mechanical aspects of pingo growth and failure, western Arctic coast, Canada

1987 ◽  
Vol 24 (6) ◽  
pp. 1108-1119 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Elastic Plate ◽  
Plate Theory ◽  
Early Growth ◽  
Thin Elastic Plate ◽  
Normal Faulting ◽  
Overburden Thickness ◽  
Changing Roles ◽  
Western Arctic ◽  
Arctic Coast ◽  
Spring Flow

Many closed-system pingos are underlain by sub-pingo water lenses, and the same is probably true of numerous open-system pingos. In the early growth stage the bending of the frozen overburden of a pingo by a sub-pingo water lens can be compared to the bending of a thin elastic plate. Although the assumptions of elastic plate theory do not apply fully to a growing pingo, because time-dependent plastic and creep deformation are involved, the application of elastic plate theory nevertheless helps to explain the peripheral normal faulting and spring flow of pingos, summit failure, the ease with which elongated pingos appear to collapse, and the changing roles played by the radius and overburden thickness of pingos from early growth to the cessation of growth.

A full-scale field experiment (1978–1995) on the growth of permafrost by means of lake drainage, western Arctic coast: a discussion of the method and some results

1997 ◽  
Vol 34 (1) ◽  
pp. 17-33 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Heat Transfer ◽  
Groundwater Flow ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Freezing Point ◽  
Three Dimensional ◽  
Negative Temperature ◽  
Lake Bottom ◽  
Western Arctic ◽  
Arctic Coast

On 13 August 1978, a lake on the western Arctic coast was artificially drained, in a multidisciplinary experiment on the growth of permafrost on the unfrozen bottom of the drained lake. A bowl-shaped talik (unfrozen basin) with a maximum depth of about 32 m underlay the lake bottom prior to drainage. In the first winter after drainage, downward freezing started on the exposed lake bottom and upward freezing from permafrost beneath the talik. After drainage, the soft lake-bottom sediments hardened from water loss and freeze–thaw consolidation. Gradual thinning of the active layer at many sites was accompanied by ground uplift and the growth of aggradational ice. Downward and upward freezing has resulted in solute rejection, freezing-point depressions, pore-water expulsion from the freezing of the saturated lake-bottom sands, and convective heat transfer from groundwater flow in an open hydrologie system. The increasingly saline intrapermafrost groundwater, flowing at an increasingly negative temperature because of a freezing-point depression, has accelerated the rate of permafrost growth in the interpermafrost zone in the direction of flow. The experiment has demonstrated that the growth of permafrost at the drained lake site, and at other sites with groundwater flow, requires a three-dimensional conductive–convective heat transfer approach.

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