The role of environmental factors in regional and local scale variability in permafrost thermal regime

Thesis (M.S.) University of Alaska Fairbanks, 2016Global climate change is a topic of great concern and research interest because there are still many components of the Earth System which we do not fully understand and cannot predict how they will respond to this change. One of these components is the permafrost that underlies approximately 24% of the Northern Hemisphere land surface. Permafrost is a thermal condition, found primarily at higher latitudes and elevations, in which subsurface material remains below 0 °C for at least two, but often up to thousands of years. As such, permafrost can accumulate large amounts of carbon in the form of organic material that remains frozen, unavailable for decomposition. However, as the climate warms, permafrost warms and thaws, slowly making this stored carbon available for decomposition into greenhouse gases, which have the potential to create a large positive feedback to climatic warming. A major challenge in permafrost research is that it is not possible to directly obtain spatial information about permafrost through remote sensing alone. This means that we must infer the presence or absence of permafrost and its thermal state based on other remotely sensible parameters such as vegetation, land surface temperature, and topography using a combination of modelling and remote sensing. To do this, we must understand the effects of different environmental factors, such as vegetation, hydrology, topography, and snow on the ground thermal regime and permafrost. In this thesis, the effects of these environmental factors are examined in relation to permafrost presence or absence and the ground thermal regime on a regional and local scale. The regional scale study focuses on the use of vegetation communities, ecotypes, as integrators of variation in environmental factors to influence the ground thermal regime. At the local scale, the microtopography created by ice-wedge polygons is examined as a cause of variations in environmental factors and the impact this has on the permafrost thermal regime of these features. We find that at both scales, remotely sensible parameters such as ecotypes and microtopography show great promise in the efforts to scale-up both field measurements and modelling results.Introduction -- Chapter 1 Scaling-up Permafrost Thermal Measurements in Western Alaska using an Ecotype approach -- Chapter 2 The Impact of Microtopography on Ground Thermal Regime in an Ice-Wedge Polygon Landscape -- Conclusion -- References -- Appendices

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An independent command : command and control of the 1st Australian Task Force in Vietnam

The commander of the 1st Australian Task Force in Vietnam held the key operational command in Australia's largest military commitment of the Cold War period. Although the Vietnam War has been written on at length, the brigade level of command, held in Vietnam by the commander of 1 ATF, has received comparatively little attention. This is the more remarkable given the Australian Army's recently renewed interest in a 'task force' structure and the modern trend away from large-scale conventional warfare. This monograph examines the problems and conditions faced by the seven Task Force commanders; their styles of command and the degree of independence they were allowed by Australian and US higher commanders; how much operational command they exercised and the types of operations carried out under each. It concludes that although the commanders were allowed a large degree of independence, apparent variations in Task Force methods were due less to the influence of personality than to differences in the types of operations required to counter a changing enemy situation

Partitioning of evapotranspiration and its relation to carbon dioxide exchange in a Chihuahuan Desert shrubland

Key to evaluating the consequences of woody plant encroachment on water and carbon cycling in semiarid ecosystems is a mechanistic understanding of how biological and non-biological processes influence water loss to the atmosphere. To better understand how precipitation is partitioned into the components of evapotranspiration (bare-soil evaporation and plant transpiration) and their relationship to plant uptake of carbon dioxide (CO2) as well as ecosystem respiratory efflux, we measured whole plant transpiration, evapotranspiration, and CO2 fluxes over the course of a growing season at a semiarid Chihuahuan Desert shrubland site in south-eastern Arizona. Whole plant transpiration was measured using the heat balance sap-flow method, while evapotranspiration and net ecosystem exchange (NEE) of CO2 were quantified using the Bowen ratio technique

In-situ measurements of sediment temperature under shallow water bodies in Arctic environments

The thermal regime under lakes, ponds, and shallow near shore zones in permafrost zones in the Arctic is predominantly determined by the temperature of the overlying water body throughout the year. Where the temperatures of the water are warmer than the air, unfrozen zones within the permafrost, called taliks, can form below the water bodies. However, the presence of bottom-fast ice can decrease the mean annual bed temperature in shallow water bodies and significantly slow down the thawing or even refreeze the lake or sea bed in winter. Small changes in water level have the potential to drastically alter the sub-bed thermal regime between permafrost-thawing and permafrost-forming. The temperature regime of lake sediments is a determining factor in the microbial activity that makes their taliks hot spots of methane gas emission. Measurements of the sediment temperature below shallow water bodies are scarce, and single temperature-chains in boreholes are not sufficient to map spatial variability. We present a new device to measure in-situ temperature-depth profiles in saturated soils or sediments, adapting the functionality of classic Lister-type heat flow probes to the special requirements of the Arctic. The measurement setup consists of 30 equally spaced (5cm) digital temperature sensors housed in a 1.5 m stainless steel lance. The lance is portable and can be pushed into the sediment by hand either from a wading position, a small boat or through a hole in the ice during the winter. Measurements are taken continuously and 15 minutes in the sediment are sufficient to acquire in-situ temperatures within the accuracy of the sensors (0.01K after calibration at 0°C). The spacing of the sensors yield a detailed temperature-depth-profile of the near-surface sediments, where small-scale changes in the bottom water changes dominate the temperature field of the sediment. The short time needed for a single measurement allows for fine-meshed surveys of the sediment in areas of interest, such as the transition zone from bottom-fast to free water. Test campaigns in the Canadian Arctic and on Svalbard have proven the device to be robust in a range of environments. We present data acquired during winter and summer, covering non-permafrost, thermokarst lake and offshore measurements

Data for the Desert Citrus Industry

This item is part of the Agricultural Experiment Station archive. It was digitized from a physical copy provided by the University Libraries at the University of Arizona. For more information, please email CALS Publications at [email protected]

Scaling-up permafrost thermal measurements in western Alaska using an ecotype approach

Permafrost temperatures are increasing in Alaska due to climate change and in some cases permafrost is thawing and degrading. In areas where degradation has already occurred the effects can be dramatic, resulting in changing ecosystems, carbon release, and damage to infrastructure. However, in many areas we lack baseline data, such as subsurface temperatures, needed to assess future changes and potential risk areas. Besides climate, the physical properties of the vegetation cover and subsurface material have a major influence on the thermal state of permafrost. These properties are often directly related to the type of ecosystem overlaying permafrost. In this paper we demonstrate that classifying the landscape into general ecotypes is an effective way to scale up permafrost thermal data collected from field monitoring sites. Additionally, we find that within some ecotypes the absence of a moss layer is indicative of the absence of near-surface permafrost. As a proof of concept, we used the ground temperature data collected from the field sites to recode an ecotype land cover map into a map of mean annual ground temperature ranges at 1 m depth based on analysis and clustering of observed thermal regimes. The map should be useful for decision making with respect to land use and understanding how the landscape might change under future climate scenarios

In-situ measurements of sediment temperature under shallow water bodies in Arctic environments

The thermal regime under lakes, ponds, and shallow near shore zones in permafrost zones in the Arctic is predominantly determined by the temperature of the overlying water body throughout the year. Where the temperatures of the water are warmer than the air, unfrozen zones within the permafrost, called taliks, can form below the water bodies. However, the presence of bottom-fast ice can decrease the mean annual bed temperature in shallow water bodies and significantly slow down the thawing or even refreeze the lake or sea bed in winter. Small changes in water level have the potential to drastically alter the sub-bed thermal regime between permafrost-thawing and permafrost-forming. The temperature regime of lake sediments is a determining factor in the microbial activity that makes their taliks hot spots of methane gas emission. Measurements of the sediment temperature below shallow water bodies are scarce, and single temperature-chains in boreholes are not sufficient to map spatial variability. We present a new device to measure in-situ temperature-depth profiles in saturated soils or sediments, adapting the functionality of classic Lister-type heat flow probes to the special requirements of the Arctic. The measurement setup consists of 30 equally spaced (5cm) digital temperature sensors housed in a 1.5 m stainless steel lance. The lance is portable and can be pushed into the sediment by hand either from a wading position, a small boat or through a hole in the ice during the winter. Measurements are taken continuously and 15 minutes in the sediment are sufficient to acquire in-situ temperatures within the accuracy of the sensors (0.01K after calibration at 0°C). The spacing of the sensors yield a detailed temperature-depth-profile of the near-surface sediments, where small-scale changes in the bottom water changes dominate the temperature field of the sediment. The short time needed for a single measurement allows for fine-meshed surveys of the sediment in areas of interest, such as the transition zone from bottom-fast to free water. Test campaigns in the Canadian Arctic and on Svalbard have proven the device to be robust in a range of environments. We present data acquired during winter and summer, covering non-permafrost, thermokarst lake and offshore measurements

The impact of streetlights on an aquatic invasive species: artificial light at night alters signal crayfish behaviour

Artificial light at night (ALAN) can significantly alter the behaviour, communication and orientation of animals, and will potentially interact with other stressors to affect biodiversity. Invasive, non-native species are one of the largest threats to freshwater biodiversity; however, the impact of ALAN on such species is unknown. This study assessed the effects of ALAN at ecologically relevant levels on the behaviour of a globally widespread invasive species, the signal crayfish (Pacifastacus leniusculus). In experimental aquaria, crayfish were exposed to periods of daylight, control (<0.1 lx) and street-lit nights to test two hypotheses: (1) signal crayfish under natural conditions are nocturnal animals, spending more time in shelter during the day, whilst active and interacting during the night, and (2) ALAN reduces crayfish activity and intraspecific interactions, whilst increasing their propensity to use shelter. Our results confirm that signal crayfish are largely nocturnal, showing peak activity and interaction levels during control nights, whilst taking refuge during daylight hours. When exposed to short-term simulated light pollution from a streetlight at night however, activity and interactions with conspecifics were significantly reduced compared to control nights, whilst time spent in shelters increased. By altering crayfish behaviour, ALAN may change the ecosystem impacts of invasive crayfish in the wild. This study is the first to show an impact of ALAN on the behaviour of an invasive, non-native species, and provides information for the management of invasive crayfish in areas where ALAN is prevalent