Showing papers on "Permafrost published in 1985"

Interpreting paleoclimate from l8O and 2H in plant cellulose: comparison with evidence from fossil insects and relict permafrost in southwestern Ontario

Abstract: The oxygen-isotope content of terrestrial plant cellulose is related to that of the source waters by a two-step process involving evapotranspirative leaf-water enrichment and equilibrium isotopic e...

Diurnal Thermal Regime in a Peat-Covered Palsa, Toolik Lake, Alaska

Abstract: Strong spatial and temporal variations in temperature and effective thermal diffusivity are apparent from short-term thermal records measured in the peat atop an ice-cored palsa in northern Alaska. Intersite differences in near-surface temperature regimes apparently result from topographic influences, vegetative cover, and site wetness. Values of effective thermal diffusivity indicate that ablation of the ice core is inhibited by advection of cold water near the ice-peat contact and by internal evaporation near the surface. These findings support the conclusions of earlier investigators, who emphasized the importance of peat for maintaining palsas near their equatorward limit. Key words: active layer, frost mound, palsa, peat, permafrost, soil temperature, thermal properties, Alaska

The influence of microtopographic heterogeneity on carbon dioxide efflux from a subarctic bog

Abstract: Soil carbon dioxide efflux was measured in hummock and hollow niicrohabitals of a subarctic peat bog near Fairbanks, Alaska, during the 1983 growing season. Regardless of the presence of permafrost, hummocks showed a late June or early July peak in soil respiration followed by a gradual decrease. Hollows and wet Carex Lawns showed a gradual increase in soil respiration with no mid-season peaks. Regression equations using soil temperature and soil moisture as independent variables explained 76% of the variance associated with soil carbon dioxide efflux. Sucrose (100 g m−2) applied to a field plot caused a significant increase in soil respiration but nitrogen (5 g m−2) did not. Sequential effects of nitrogen and phosphorus on peat respiration were demonstrated in a laboratory experiment.

Evidence of sustained regional permafrost during deposition of fossiliferous Late Pleistocene river sediments at Stanton Harcourt (Oxfordshire, England)

Abstract: A detailed analysis is presented of ice-wedge casts in well exposed fluvial sediments containing fossiliferous channel fills. An explanation of their origin is proposed by analogy with contemporary ice-wedge casting in Banks Island, Canada and Spitsbergen. It is demonstrated that (a) extensive casting of ice-wedges occurs within the modern continuous permafrost zone, due to lateral movements of river channels causing local permafrost degradation, and (b) these ice-wedge casts may later be reactivated by subsequent thermal contraction cracking at the same foci, leading ultimately to production of composite ice-wedge casts. The presence of ice-wedge casts truncated at several stratigraphical levels within a single sequence and associated composite ice-wedge casts is most simply explained by the casting of many of these intraformational wedges due to local permafrost degradation, caused by river channel movements within a regional permafrost environment. The recognition of such ice-wedge casting implies a regional permafrost environment throughout deposition of certain fossiliferous sedimentary units. The basal fossiliferous deposits may antedate development of permafrost. Plant macrofossils from these basal deposits gave a radiocarbon date of 34.7 ka BP. This conflicts with age estimates from thermoluminescence of 91 ± 8 and 93 ± 9 ka BP of silt from higher in the gravel succession. Fossiliferous deposits at higher levels having evidence of syndepositional permafrost contain molluscan faunas with very few species.

Unfrozen water content in saline soils: results using time-domain reflectometry

Abstract: The use of time-domain reflectometry (TDR) for determining the phase composition of saline permafrost from measurement of the apparent dielectric constant, Ka, is examinedCombined TDR–dilatometry

The effects of gas composition and geothermal properties on the thickness and depth of natural gas hydrate zones

Abstract: When natural gas and water are contacted at low temperature and high pressure, gas hydrates can form. In colder climates (such as Alaska, Northern Canada, and Russian Siberia) and beneath the earth's oceans, conditions are appropriate for gas hydrate formation. This paper gives the depths and potential thickness of such hydrate formations as a function of the geothermal gradient, the gas composition, and where appropriate, the permafrost thickness, the pressure gradient, and the ocean bottom temperature.

Large-scale karst features and open taliks at Vardeborgsletta, outer Isfjorden, Svalbard

Abstract: Ground temperature measurements show that open taliks occurring at Vardeborgsletta are probably caused by the heat of circulating water from great depths. The absence of permafrost has allowed the ground water to circulate, and large-scale karst features have developed in a limestone area. Karst processes are also active today, and dolines and ponds with sinking drainage occur.

Method for preventing thaw settlement along offshore artic pipelines

Abstract: A method for installing a pipeline for transporting a warm fluid, such as newly-produced oil, across arctic seafloor underlain by a permafrost zone without danger of rupture of the pipeline caused by thawing in the supporting permafrost zone comprises (1) drilling a series of boreholes along the seafloor through a thawed zone of subsea soil so as to penetrate a distance into a zone of permafrost lying thereunder, (2) circulating a warm fluid through each borehole so as to cause a zone of prethawing in the permafrost zone and thereby create a slump trough on the surface of the seafloor along a path marked by the series of boreholes; and (3) installing a warm fluid bearing pipeline along the bottom of the slump trough. Usually a temperature differential between the warm fluid and the bottom of the borehole of at least 2 degrees Fahrenheit is required to assure economical prethawing of the permafrost zone.

Weathering of quartz grains in the liquefied horizon of permafrost solonchaks in the arid steppe zone, Central Mongolia

Abstract: Morphoscopic investigations of quartz grains (0,6–0,8 mm) were carried out with the use of scanning electron microscope. The grains originated from the liquefied horizon of the strongly alkaline permafrost solonchaks of the arid steppe zone of Central Mongolia. The grain surface in this horizon is smoothed due to various processes of chemical corrosion and by deposition of silicate crusts of variable thickness. The record of the preceding abrasion resulting from transportation of weathered material to their deposition site was blurred by the above mentioned processes. The permanently hydrated cool environment favoured moreover the cryohydrothermal block- and granular disintegration as well as the cryothermal and cryomechanical fracture and chipping.

Geomorphologic Evidence for Ground Ice on Mars

Abstract: For ground ice to exist on Mars, two conditions have to be met. One is the presence of permafrost; the second is the availability of water. Because the mean temperature of Mars’surface is − 80 C., permafrost 1–3 km thick occurs over the entire planet. Remote-sensing measurements suggest that water presently exists in the atmosphere and in the polar caps; frost has been observed at the Viking landing sites. Landforms that support the contention that ground ice exists on Mars include lobate ejecta from craters, small valley networks, and numerous features that may be attributed to thermokarst. Chaotically collapsed terrain, chain craters, irregular depressions, and valleys tributary to canyons all appear to be related to loss of ground ice. Patterned ground has dimensions similar to that on Earth as well as dimensions of giant size. Masswasting features are common on scarps Even though individual features may be explained as results of other processes, the combined evidence indicates that a large reservoir of ground ice has existed on Mars.

Erosion of Northern Reservoir Shores: An Analysis and Application of Pertinent Literature,

Abstract: : This monograph describes the current state of knowledge of northern reservoir shore erosion, primarily by examining the results of erosional studies on lakes, coasts and rivers. The major erosional processes of reservoir beaches and bluffs and their mechanics are discussed in detail. Thermal and physical parameters affecting the erodibilty of shores, the environmental impacts of erosion, and the basic characteristics of the unique reservoir environment are reviewed. Current models of shore zone development are also presented. This literature analysis revealed that knowledge of erosion and recession in northern impoundments is severely limited. Quantitative analyses of the processes of erosion and their relative importance, parameters determining the nature, rate and timing of erosion, and models to predict the erodibility of a shore for use in minimizing shoreline recession remain in need of basic field research. Originator supplied keywords: Cold regions, Erosion models, Freeze-thaw, Ground water, Ice cover, Lakes, Overland flow, Permafrost, Rates, Recession, Reservoirs, Shores, Slope movement, Water level, Waves.

Turf-banked terraces in the olympic mountains, washington, u.s.a.

Abstract: Turf-banked terraces are either poorly developed or absent in most mountains of the Pacific Northwest. They are well developed, however, in the northeast section of the Olympic Mountains, Washington. Here rain shadow effects promote a continental climatic regime, seasonally frozen ground, and periglacial geomorphic activity. In addition, the northeastern Olympics consists of flattened and rounded ridges composed of sedimentary rocks. These upper surfaces were exposed as nunataks during Pleistocene glacial advances and prolonged weathering has produced fine material from which the turf-banked terraces are formed. Preferred sites are located above timberline at 1725 to 1950 m on northerly exposures with slope gradients of 12 to 24?. Three plant communities (Late-Snowbank, Tread, and Riser) were distinguished across the terraces. The features were generally completely vegetated with surface humus layers 5 to 20 cm thick, bound with extensive root systems. Soil textures, exclusive of rocks, averaged 62% sand, 2007o silt, and 18%7o clay. Some terraces have buried organic layers. In situ rock measurements indicate an average soil movement rate of 0.8 to 6.0 mm y-~ over an 8-yr period with an overall mean displacement of 2.8 mm. This is an order of magnitude less than measurements made in other active solifluction areas. It is suggested that the features are presently only marginally more active than in the past when more severe climatic conditions existed. There is good evidence for the former presence of permafrost which would have facilitated the origin and development of the features.

Strength-Deformation Properties of Arctic Silt

Abstract: Hydrocarbon exploration and production activities in the Beaufort Sea require construction of gravity structures capable of withstanding extremely large ice loads at sites where the subsea soil profile often consists of Arctic silts overlying relic permafrost. These conditions pose two unusual foundation design problems: lack of experience with structures where horizontal forces constitute the dominant design load; and the highly variable and unique nature of arctic silts compared to other offshore soil deposits. Classification and related properties of Arctic silts located in Harrison Bay, Alaska are summarized. The effect of temperature on results of consolidation tests is discussed. The main focus is on undrained stress-strain-strength anisotropy of normally consolidated Arctic silt.

The Engineering Geology Hazards of Rock Glaciers

Abstract: Rock glaciers are common, yet, because of the association with past periglacial and glacial activity, are often ignored as present day engineering hazards. As alpine development increases, rock glacier location and analysis becomes vital. Air and ground reconnaissance easily identifies rock glaciers using four characteristics: 1) slope angle somewhere between that of the adjoining rock face and the valley floor below; 2) surface of coarse rock fragments; 3) little or no surface vegetation; and 4) concave-upward slope profiles in the upper parts and strongly convex fronts. Active rock glaciers are best avoided because of rock glacier movement and ice melting and subsidence. Inactive rock glaciers may be built on or excavated depending on the presence of clear ice layers in the rock glacier and the amount of risk engineers are willing to assume. On inactive rock glaciers containing only interstitial ice, permafrost construction techniques may be effective.

Freezing and Thawing of Soil-Water Systems

Abstract: This book presents a state-of-the-practice review on freezing and thawing of soil-water systems through ten interrelated papers on this subject. The papers review the following topics: Thawing of frozen clays; modeling and applications of soil freezing and thawing; partial verification of a thaw settlement model; hydraulic properties of selected soils; a continuum approach to frost heave modeling; a model for dielectric constants of frozen soils; a numerical model of subsea permafrost; frost heave of full-depth asphalt concrete pavements; the origin of aggradational ice in permafrost; and experimental investigation of regelation flow with an ice sandwich permeater.

Hydrolithosphere and Problems of Subsurface Ice in the Equatorial Zone of Mars

Abstract: It is assumed that on Mars liquid water (lower hydrolithosphere) is confined under the icy upper lithosphere (upper hydro1ithosphere), which is indeed a rigid and practically impervious carapace. The mobility of the lithospheric water and probably also of a part of the stocking rocks under the permafrost probably originates by sapping some important surface features, for instance subcircular depressions of increasing sizes, with steep slopes, aligned along the main fractures. This process is probably primordial in the origin of the Valles Marineris system. If the oscillations of the cryo-marge (basis of the permafrost) are able to make thin enough the icy upperlithosphere until a break out point, the disruption of the aquifer to the surface is possible, generating high artesian pressure in the lowest regions of the planet (supposed process of the outflows according with the Carr’s model). It seems likely that more or less important ice caps existed in some places in the equatorial zone of Mars, with the same origin (subsurface water). Three possibilities are suggested to explain the variations of the cryomarge and the thinning of the permafrost: modifications of the geothermal gradient; climatic oscillations; progressive heating of the water during the filling of the aquifers.

Subsea permafrost: Probing, thermal regime and data analyses 1975-1981. Summary report (Final)

Abstract: This is the summary report of a program to study the distribution and properties of subsea permafrost in Alaskan waters. More specifically, the objectives have been-- to obtain reconnaissance level information on subsea permafrost conditions over a wide geographic area, to investigate conditions at the sea bed relevant to the evolution of the underlying permafrost regime, and to study the heat and salt transport processes in subsea permafrost with the eventual goal of predicting its response to natural or man-induced conditions. The field measurements have included soil type, temperature, electrical conductivity of the soil pore water, thermal and hydraulic conductivity, in-situ ice detection, and pore water pressure. In the last few years, subsea permafrost data have been obtained by the petroleum industry as part of geotechnical investigations for offshore pipelines and structures. Most of the information is proprietary, and the data obtained by the OCSEAP and USGS programs still comprise the bulk of what is in the public domain.

Temperature and Time Effects on the Closure of a Gravel Room in Permafrost

Abstract: Underground excavations in arctic and subarctic regions will increase in numbers as the northern regions are developed. Excavations in frozen ground are subject to significant creep deformation which is highly temperature and time dependent. The U.S. Army Cold Regions Research and Engineering Laboratory (USA CRREL) permafrost tunnel was monitored to investigate these dependencies. The creep behavior of the gravel room was described by a combined exponential and power relationship between closure rate, time factor, and ground temperature. For the long term stability of an underground opening in frozen ground, the time effect upon the closure rate is secondary to the influence of temperature. The strata separation in the gravel roof of the tunnel opening was also studied. The partings were observed only during periods of high temperature and closure. The results of the study suggest that after consideration of factors such as ground temperature and time dependency, underground chambers in permafrost can be designed and utilized for long term applications.

Some recent discoveries of ice-wedge cast networks in North-East Scotland—A comment

Abstract: SIRS—In their recent description of newly discovered occurrences of ice-wedge polygons in north-east Scotland, Gemmell and Ralston (1984) concluded that such permafrost features, except perhaps for those in ‘Moraineless Buchan’, were most probably formed during the cold period of the Loch Lomond Stadial. This conclusion appears to rest on an assumption that the earlier period of recession of the main Devensian ice was in general characterised by a 'rapid and substantial warming', thus precluding permafrost activity at that time.