Thaw Zone Research Articles

Hydrogeology of Reclaimed Floodplain in A Permafrost Area, Yakutsk, Russia

A study was performed to evaluate the current permafrost and groundwater conditions in the reclaimed floodplain of the Lena, one of the largest rivers in the permafrost zone. Data from ongoing hydrogeological monitoring were compared with earlier observations conducted during the reclamation process. The results demonstrate that the placement of dredged fill led to the development of suprapermafrost thaw zones (taliks). The anthropogenic taliks vary in thickness from 10 to 15 m in areas of buried bars to 20 m or more in the former locations of oxbow lakes. There is similarity in seasonal groundwater fluctuation patterns and response to river stage variations across the study area suggesting that a continuous aquifer connected to surface water. The connection with the river is most evident during the spring flood period. Two mechanisms of ground saturation are identified during this time. One is lateral seepage flow from the Lena River into the fill mass. The zone of its influence is limited to 150–170 m from the stream. The second is hydraulic pressure transmission from the river through the subchannel flow connected with the anthropogenic suprapermafrost aquifer. Its influence extends across the entire fill area. Continuous water movement at the base of the fill prevents permafrost aggradation from below. The study results should be taken into account when developing and implementing design and construction standards for engineering structures in the reclaimed floodplains of the permafrost zone.

Development of perennial thaw zones in boreal hillslopes enhances potential mobilization of permafrost carbon

Permafrost thaw alters subsurface flow in boreal regions that in turn influences the magnitude, seasonality, and chemical composition of streamflow. Prediction of these changes is challenged by incomplete knowledge of timing, flowpath depth, and amount of groundwater discharge to streams in response to thaw. One important phenomenon that may affect flow and transport through boreal hillslopes is development of lateral perennial thaw zones (PTZs), the existence of which is here supported by geophysical observations and cryohydrogeologic modeling. Model results link thaw to enhanced and seasonally-extended baseflow, which have implications for mobilization of soluble constituents. Results demonstrate the sensitivity of PTZ development to organic layer thickness and near-surface factors that mediate heat exchange at the atmosphere/ground-surface interface. Study findings suggest that PTZs serve as a detectable precursor to accelerated permafrost degradation. This study provides important contextual insight on a fundamental thermo-hydrologic process that can enhance terrestrial-to-aquatic transfer of permafrost carbon, nitrogen, and mercury previously sequestered in thawing watersheds.

Distribution, properties and origin of viscous-flow features in the McMurdo Dry Valleys, Antarctica

Satellite images and high resolution air photos, coupled with field examinations, were used to examine 24 rock glaciers/debris-covered glaciers and 25 gelifluction sheets, collectively referred to as viscous-flow features, in the McMurdo Dry Valleys, Antarctica. Debris-covered glaciers are the dominant form and are longer (mean length=2.5km), wider (mean width=0.8km), and less steep (mean slope=12°) than similar features reported in most arctic and alpine environments. The catchment areas tend to be large, averaging over 9km2. Most of the debris-covered glaciers are tongue-shaped, and where excavation was possible, the ice core was readily observable. Gelifluction sheets primarily occur at the base of valley sidewalls below talus on slopes ranging from 5 to 30° (average=13°) and contain a very thin active layer (normal range 20 to 40cm). Both viscous-flow forms occur on the north- and south-facing slopes of the east–west trending valleys and are concentrated in the inland mixed zone and stable upland microclimatic zone; these lobes were not found in the coastal thaw zone. Gelifluction sheets result from the melting of snow high on the valley walls, subsurface flow of meltwater on top of the permafrost, and slow movement downslope. They are readily observable from nonsorted polygons that are stretched into rectangles that are perpendicular to the slope and contain raised polygon rims upslope. The movement of gelifluction sheets can be detected from upturned stones containing carbonate coatings. Rates of horizontal surface flow of the viscous-flow features are comparable to those reported elsewhere in Antarctica and in the alpine and arctic regions of the world. Some of the viscous-flow features appear to be inactive, possibly reflecting the recession of alpine glaciers in high elevation cirques.

Temporal rainfall patterns with water partitioning impacts on maize yield in a freeze–thaw zone

Understanding all components of the water balance, especially temporal rainfall patterns, is essential to optimize water use in rain-fed agriculture area. The effect of temporal rainfall patterns on water balance, evapotranspiration (ET), and crop growth was evaluated by considering root water extraction of plants in a rain-fed maize field. Soil water contents at depths of 15, 30, 60, and 90 cm were measured daily in 2-year growth seasons. A soil water balance approach was applied to estimate changes in daily soil water storage. For the detailed water partitioning of the water balance and root water extraction, the soil–water-atmosphere-plant (SWAP) model with water and crop modules was applied. Results suggested that the main depths of root water uptake occurred in the top 60 cm soil layer. Crop transpiration (T) can reach a level above 40% of the total water consumption during all growth stages, and its reduction was mainly due to the dry condition of soil. The crop yield in 2010 was 1125 kg ha−1 higher than that in 2011, although the rainfall amount in that year was 132 mm less than the rainfall amount in 2011. The water use efficiency (WUE) was also higher in 2010. Therefore, the influence of temporal rainfall patterns was clearly more important than rainfall amounts (water partitioning into evaporation (E), T, and soil water content). Growing season T/ET can be a potential parameter for maize productivity. The field can be irrigated at pivotal growth stages under dry conditions to obtain the optimal effect in improving WUE and increasing grain yield. The SWAP model was a useful tool to analyze water partitioning in the freeze–thaw zone.

A review of geomorphic processes and landforms in the Dry Valleys of southern Victoria Land: implications for evaluating climate change and ice-sheet stability

Abstract The Dry Valleys are subdivided into three microclimate zones on the basis of summertime measurements of atmospheric temperature, soil moisture, relative humidity and wind-speed/ direction. Subtle variations in these climate parameters result in considerable differences in process geomorphology and in the development of unique landforms within each zone. The mapped zones include a coastal thaw zone, an inland mixed zone and a stable upland zone. Landforms within each zone are subdivided into macroscale features (e.g. valleys, slopes and gullies), mesoscale features (e.g. polygons and viscous-flow features) and microscale features (e.g. rock and near-surface soil features, including the effects of salt weathering, wind erosion and pitting). We present a review of landscape development in the Dry Valleys with implications for long-term climate change and ice-sheet stability. Chronological control is afforded by 40 Ar/ 39 Ar dating of volcanic ash-fall deposits and cosmogenic nuclide analyses of surface boulders. Collectively, the data call for persistent cold and dry conditions in the stable upland zone for approximately the last 14 Ma, although some level of climatic amelioration and landform modification may have occurred within low-lying regions and in the inland mixed zone.

Drainage subsidence associated with Arctic permafrost degradation

Arctic sources of greenhouse gas associated with permafrost degradation constitute a large uncertainty in existing climate models. Greenhouse gas release from the Arctic subsurface is mediated by numerous interconnected physical processes; one facet of these is the interplay between surface deformation and melting of subsurface ice. First, we construct analytic solutions describing fluid drainage and soil subsidence subsequent to thawing of a 1‐D permafrost column. These solutions lead to formulas giving the total amount of subsidence as well as the time over which subsidence occurs. We give an example application of the analytic model to peat plateau degradation in the Canadian Hudson Bay Lowland and show that the degree of subsidence predicted from our model is consistent with recorded subsidence of peat in western Norway that was drained for cultivation purposes. Second, we numerically model an initially frozen, fluid‐saturated, 2‐D soil matrix with a thaw zone advancing from the surface downward. With the surface temperature fixed at 5°C, a thaw front propagates to ∼10 m depth within 20 years, and due primarily to drainage of fluid from the pore space, a region of soil depressed by ∼3 m forms above an initially ice‐rich subsurface zone. Soil underlying this depressed zone may have its permeability reduced by between 1 and 2 orders of magnitude; this reduction in permeability can act as a negative feedback to thawing.

Eastern Beringia and beyond: Late Wisconsinan and Holocene landscape dynamics along the Yukon Coastal Plain, Canada

Terrestrial permafrost archives along the Yukon Coastal Plain (northwest Canada) have recorded landscape development and environmental change since the Late Wisconsinan at the interface of unglaciated Beringia (i.e. Komakuk Beach) and the northwestern limit of the Laurentide Ice Sheet (i.e. Herschel Island). The objective of this paper is to compare the late glacial and Holocene landscape development on both sides of the former ice margin based on permafrost sequences and ground ice. Analyses at these sites involved a multi-proxy approach including: sedimentology, cryostratigraphy, palaeoecology of ostracods, stable water isotopes in ground ice, hydrochemistry, and AMS radiocarbon and infrared stimulated luminescence (IRSL) dating. AMS and IRSL age determinations yielded full glacial ages at Komakuk Beach that is the northeastern limit of ice-free Beringia. Herschel Island to the east marks the Late Wisconsinan limit of the northwest Laurentide Ice Sheet and is composed of ice-thrust sediments containing plant detritus as young as 16.2calkaBP that might provide a maximum age on ice arrival. Late Wisconsinan ice wedges with sediment-rich fillings on Herschel Island are depleted in heavy oxygen isotopes (mean δ18O of −29.1‰); this, together with low d-excess values, indicates colder-than-modern winter temperatures and probably reduced snow depths. Grain-size distribution and fossil ostracod assemblages indicate that deglaciation of the Herschel Island ice-thrust moraine was accompanied by alluvial, proluvial, and eolian sedimentation on the adjacent unglaciated Yukon Coastal Plain until ~11calkaBP during a period of low glacio-eustatic sea level. The late glacial–Holocene transition was marked by higher-than-modern summer temperatures leading to permafrost degradation that began no later than 11.2calkaBP and caused a regional thaw unconformity. Cryostructures and ice wedges were truncated while organic matter was incorporated and soluble ions were leached in the thaw zone. Thermokarst activity led to the formation of ice-wedge casts and deposition of thermokarst lake sediments. These were subsequently covered by rapidly accumulating peat during the early Holocene Thermal Maximum. A rising permafrost table, reduced peat accumulation, and extensive ice-wedge growth resulted from climate cooling starting in the middle Holocene until the late 20th century. The reconstruction of palaeolandscape dynamics on the Yukon Coastal Plain and the eastern Beringian edge contributes to unraveling the linkages between ice sheet, ocean, and permafrost that have existed since the Late Wisconsinan.

Comparison of thermal and radar active layer measurement techniques in the Leaf Bay area, Nouveau-Québec

Continuous profiles of the frost table for a series of traverses in unconsolidated sediments in the Leaf Bay area, Ungava, were obtained using an all terrain vehicle borne impulse radar system. The results correlate extremely well with data obtained by the insertion of rigid temperature probes at frequent intervals along the traverses. Each of the two systems has its own particular advantages and disadvantages. The radar profiling system provides more continuous information and can be carried out more rapidly than the system using the temperature probes. However, it requires some local ground control as regards soil moisture profiles and values for soil texture and soil temperature. A definite advantage of the rigid temperature probe is that it produces a temperature curve as a by-product and this can be used to assess the effect of different terrain factors on heat flow in the soil. It is, furthermore, a much cheaper and less bulky apparatus than the radar equipment, requiring no auxiliary logistical support for field use. Neither method can be applied universally for thaw zone and active layer determination. The trials in the tidal flats were a failure, the earth materials being too stony for the temperature probe and the salt water in the soil not permitting proper signal propagation for the radar. Neither method is suitable for penetrating bedrock and, in such a case, reliance has to be placed on temperature measurements in drillholes.

Two chloride sources in soils of the McMurdo Dry Valleys, Antarctica

Sulfate, nitrate, and chloride are major water‐soluble anions in soils of the McMurdo Dry Valleys (MDV), Antarctica. We measured the chloride stable isotope composition of 40 soil samples from 16 different soil profiles. The soil profiles come from three different microclimate zones in the MDV: a coastal thaw zone, which fosters a seasonally saturated active layer; a stable upland zone, in which air and soil temperatures are too cold to foster active layers and/or significant snowmelt; and an intermediate, inland mixed zone. Results show that the total water‐soluble chloride content is low in both the coastal and the upland zones, but highly variable in the inland mixed zone (average 770 to 11520 ppm). Individual soil δ37Cl values range from −2.10‰ to +0.56‰, with profile average δ37Cl values broadly decreasing from the coast toward upland valleys. Vertically, the δ37Cl increases with depth in soil profiles developed on basal tills but decreases on sublimation tills. We propose that the spatial [Cl−] and δ37Cl patterns are the result of continuous influx and leaching of two major chloride sources, an airborne sea‐salt chloride (SSC) with a δ37Cl value ≥ ∼0.0‰ and a secondary atmospheric chloride (SAC) with a δ37Cl value ≤ −2.10‰. Our model suggests that sublimation tills have their Cl− input from two boundaries: a till‐atmosphere interface at the top and a buried‐ice‐till interface at the bottom, differing distinctively from basal tills where there is no salt contribution from the bottom. Our model also suggests a higher influx of SSC relative to SAC in the MDV in the past. Overall, characterizing the sources, budgets, and spatial/vertical patterns of chloride constitutes a first step toward unraveling climate, tectonic, and landscape changes archived in MDV soil profiles.

Antarctic dry valleys: Microclimate zonation, variable geomorphic processes, and implications for assessing climate change on Mars

The Antarctic Dry Valleys (ADV) are generally classified as a hyper-arid, cold-polar desert. The region has long been considered an important terrestrial analog for Mars because of its generally cold and dry climate and because it contains a suite of landforms at macro-, meso-, and microscales that closely resemble those occurring on the martian surface. The extreme hyperaridity of both Mars and the ADV has focused attention on the importance of salts and brines on soil development, phase transitions from liquid water to water ice, and ultimately, on process geomorphology and landscape evolution at a range of scales on both planets. The ADV can be subdivided into three microclimate zones: a coastal thaw zone, an inland mixed zone, and a stable upland zone; zones are defined on the basis of summertime measurements of atmospheric temperature, soil moisture, and relative humidity. Subtle variations in these climate parameters result in considerable differences in the distribution and morphology of: (1) macroscale features (e.g., slopes and gullies); (2) mesoscale features (e.g., polygons, including ice-wedge, sand-wedge, and sublimation-type polygons, as well as viscous-flow features, including solifluction lobes, gelifluction lobes, and debris-covered glaciers); and (3) microscale features (e.g., rock-weathering processes/features, including salt weathering, wind erosion, and surface pitting). Equilibrium landforms are those features that formed in balance with environmental conditions within fixed microclimate zones. Some equilibrium landforms, such as sublimation polygons, indicate the presence of extensive near-surface ice; identification of similar landforms on Mars may also provide a basis for detecting the location of shallow ice. Landforms that today appear in disequilibrium with local microclimate conditions in the ADV signify past and/or ongoing shifts in climate zonation; understanding these shifts is assisting in the documentation of the climate record for the ADV. A similar type of landform analysis can be applied to the surface of Mars where analogous microclimates and equilibrium landforms occur (1) in a variety of local environments, (2) in different latitudinal bands, and (3) in units of different ages. Documenting the nature and evolution of the ADV microclimate zones and their associated geomorphic processes is helping to provide a quantitative framework for assessing the evolution of climate on Mars.

Approximate calculation of thaw depth in permafrost beneath a building of complex configuration

The three-dimensional problem of the formation of a thaw zone of any planform configuration over time in permafrost is examined. An approximate method of its solution is set forth and illustrated by a computational example. The paper is compiled from results of studies supported by the Russian Fund for Fundamental Research (Project N 94-05-16195-a).

Determination of perimeter of thaw zone during test prethawing of the beds of buildings and structures

A procedure for determining the radius of the circular-cylindrical thaw bowl to obtain the compressibility characteristics of frozen soils by the method of test thawing, as well as the width of the prethaw zone of the beds of buildings and structures built on beds in accordance with principle II is presented and substantiated. Results of analysis of the relationships obtained and practical design recommendations are set forth.

Distribution of the phase front in the freezing of finely-dispersed soils

The process of the freezing of soils is examined with allowance for the migration of moisture in the freezing and thaw zones.

The origin of hummocks, western Arctic coast, Canada

Hummocks (nonsorted circles) are widely distributed in arctic and subarctic regions. The hummocks under discussion are composed of fine-grained frost-susceptible soils; the late summer frost table is bowl-shaped; and the hummocks grade from those which are completely vegetated (earth hummocks) to those with bare centres (mud hummocks). The mound form is usually attributed to an upward displacement of material resulting from cryostatic (freeze-back) pressure generated in a confined, wet, unfrozen pocket of the active layer. Theoretically, cryostatic pressure should not develop in a frost-susceptible hummock soil, because ice lensing at the top and (or) bottom of the active layer will desiccate the last unfrozen pocket so that the pore water is under tension, not pressure. Field observations carried out at Garry Island, Northwest Territories, for 1965–1979 and for 1967–1979 at Inuvik, Northwest Territories, involving: summer and winter excavations; the measurement of the deformation of tubes, soil pressure, soil temperature, soil heave, soil moisture migration; and observations on hummock stability provide no field evidence for the cryostatic theory. An alternative model of hummock growth, based upon field observations, is here proposed. The upward displacement of material is believed caused by freeze–thaw of ice lenses at the top and bottom of the active layer with a gravity-induced cell-like movement, because the top and bottom freeze–thaw zones have opposite curvatures. The cell circulation is evident from the grain-size distribution of hummock soils and from upward-moving tongues of saturated soil observable in late summer. The most active period is in late summer. Model experiments in the laboratory have been successful in producing mounds by freeze–thaw of a kaolin slurry in a bowl-shaped container in support of the proposed theory.

Casing Strain Resulting From Thawing of Prudhoe Bay Permafrost

A compact five-spot well pattern was completed through permafrost at Prudhoe Bay and circulated with hot fluid, creating thaw zones. Compaction Prudhoe Bay and circulated with hot fluid, creating thaw zones. Compaction and deformation of soil in these zones led to casing strain. Analysis determined that casing strains were caused by large differences in compactibility of soil types. Introduction The development of petroleum reserves in the arctic region of Alaska requires new petroleum engineering technology to deal with permafrost problems. A conventional well drilled through permafrost is subjected to the hazards of external freezeback pressures, internal freezeback pressures, and thaw consolidation (compaction). These three major concerns have been studied extensively by operators in the Alaskan arctic. Solutions to the problems associated with the freezeback of shut-in wells have been published in the past four years. Thawing of permafrost around a wellbore also can lead to casing damage. When ice melts, it is reduced approximately 9 percent in volume. Stresses carried through the ice phase of in-situ permafrost tend to transfer to the soil matrix as the ice melts and the pore pressure diminishes because of this reduction. The soil tends to compact when subjected to a higher stress level. The degree of compaction depends on the type of soil, the stress state in the frozen permafrost, the pore pressure after thaw, and the size of the thawed region. Although most compaction is accounted for by lateral movement of the surrounding frozen permafrost, some vertical consolidation or subsidence also can be expected. This vertical consolidation or movement can damage the casing strings throughout the permafrost section. The original field rules for Prudhoe Bay development required that a producing well be protected from subsidence damage by refrigeration, insulation, or other means. To understand thaw consolidation in the thick permafrost at Prudhoe Bay, BP Alaska Inc. conducted a permafrost at Prudhoe Bay, BP Alaska Inc. conducted a field test to thaw a limited region surrounding a well. The amount of thaw in this field test was equivalent to that created around a heavily insulated producing well. Both casing strain and formation movement were detected with a moderate degree of uncertainty in the field data. One solution to the internal freezeback problem is to replace water-base mud with a gelled, weighted oil-base fluid. The thermal-insulating properties of this fluid are quite good. However, a producing well insulated in this manner would develop a larger thaw radius during its operating life than was created in the BP Alaska field test. Petroleum engineers designing casing programs for field Petroleum engineers designing casing programs for field development were uncertain of the effect of this large thaw zone on casing integrity in a producing well. To assess the significance of the consolidation process for a gelled-oil-insulated completion, a major field test at Prudhoe Bay was conducted. The test site was located in Prudhoe Bay was conducted. The test site was located in Section 11, T10N, R15E, in the center of the Prudhoe Bay field and adjacent to a BP Alaska well where numerous cores were taken in the permafrost. Core analysis provided a complete lithology of the permafrost. The provided a complete lithology of the permafrost. The goal of the field test was to observe casing integrity and to measure the strain of a casing string surrounded by a thaw zone equivalent in size to a zone created by a well after 20 year's production. This paper describes the field test, operational aspects, and results. JPT P. 468

Portable Refraction Seismography Survey of Gold Placer Areas Near Nome, Alaska: ABSTRACT

A seismic refraction study of the beach and tundra gold placer areas near Nome, Alaska, was made using a small, light-weight, portable seismograph during the summer of 1967. Geophone configuration and type of energy source were determined during a preliminary experimental survey. Because the beach study was successful, a short experimental seismic line was completed inland to determine the usefulness of a portable refraction seismograph in permafrost areas near Nome. Basic problems in permafrost areas are the high seismic velocities in the overburden, caused by increase in elastic modules in frozen ground, and the acoustical absorption and variable thickness of the overlying tundra. The increase in sediment velocity reduces the possibility that there is a marked velocity contrast at the bedrock-overburden interface, and the organic material of the tundra absorbs returning seismic energy. These problems were reduced by detonating the explosive energy source on the permafrost surface and by placing the geophones in the thaw zone of silt beneath the spongelike ma ter of the tundra. The beach survey results indicated that internal stratigraphy of the overburden could be interpreted and seismic velocities assigned to the different units. A very low-velocity, dry to damp layer of Holocene sands covering most of the beach has seismic velocity values of 0.15-0.73 km/sec. In other low-velocity layers included in the overburden, and especially conspicuous near river mouths, velocity values range from 0.62 to 1.00 km/sec. A poorly consolidated nearshore or estuarine silt, clay, and sand layer of Sangamon age (late Pleistocene) with velocity values of 1.20-1.80 km/sec is below the very low-velocity layer. Beneath the estuarine material is a till of Illinoisan age (middle Pleistocene) that has a velocity of 2.80-4.00 km/sec. Bedrock was well defined in all seismograms and exhibited velocity values from 4.20 to 5.60 km/sec. A basement contour map of the beach was constructed from depth data obtained along the beach with the refraction seismograph, from offshore seismic-reflection data, and from onshore drillhole information. Several buried channels were identified which may be sites of possible gold placer deposits. Beneath the tundra a bedrock surface dips under Dry Creek from both sides, and a bedrock contour map was drawn from refraction-seismograph data and drillhole information. Results of the Nome tundra survey illustrate the feasibility of the portable seismograph as a placer prospecting tool for use in tundra-permafrost areas. End_of_Article - Last_Page 471------------