A soil climate monitoring network, consisting of seven automated weather stations, was established between 1999 and 2003 in the McMurdo Sound region of Antarctica. Soil temperature, soil water content, air temperature, relative humidity, solar radiation, and wind speed and direction are recorded hourly and downloaded annually. Two 30 m deep permafrost temperature monitoring boreholes were established adjacent to the soil climate stations in the Wright Valley and at Marble Point in January 2007. Sixteen thermistors (accurate to ±0.1°C) were installed in each borehole measuring temperature once every hour and recording the mean every six hours. One year of permafrost temperatures were available (January 2007 to January 2008). The overall aim of this thesis was to make use of the soil climate monitoring database from 1999 to 2007 to investigate Antarctic soil climate. Active layer depth (depth of thawing) varied inter-annually, with no significant trend between 1999 and 2007. The active layer increased with decreasing latitude (R2 = 0.94), and decreased with increasing altitude (R2 = 0.95). A multiple regression model was produced whereby active layer depth was predicted as a function of mean summer air temperature, mean winter air temperature, total summer solar radiation and mean summer wind speed (R2 = 0.73). Annual temperature cycles were observed at all depths in the boreholes. At Marble Point, an annual temperature range of lt;1°C occurred at 15.2 m, lt;0.5°C at 18.4 m and lt;0.1°C at 26.4 m and at Wright Valley, an annual temperature range of lt;1°C occurred at 14.0 m, lt;0.5°C at 17.2 m and lt;0.1°C at 25.2 m. Given that the depth of Zero Annual Amplitude determined depends on the sensitivity of the measurement method, it is suggested that instead of referring to a depth of Zero Annual Amplitude , the depth at which the annual temperature range is less than a given value is a more useful concept. Mean annual and mean seasonal air and soil temperatures varied inter-annually and there was no significant trend of warming or cooling over the 1999 - 2007 period. Mean annual air temperatures were primarily influenced by winter air temperatures. Mean annual and mean summer soil temperatures were warmer than air temperatures due to heating by solar radiation. Mean summer air temperatures correlated well with the Southern Annular Mode Index (SAMI) at all sites (0.61 lt; R2 lt; 0.73) except Victoria Valley; however there was no correlation between mean annual or mean winter temperatures and the SAMI. Air temperature was linearly correlated with near-surface soil temperature (1.3 - 7.5 cm) (R2 gt; 0.79). Near-surface soil temperature was strongly correlated with incoming solar radiation at Victoria Valley (0.14 lt; R2 lt; 0.76) and Granite Harbour (0.49 lt; R2 lt; 0.82), but was not significantly correlated at other sites (0 lt; R2 lt; 0.57). There was no significant correlation between air temperature and wind speed, air temperature and solar radiation and near-surface soil temperature and wind speed, despite occasions of strong correlation on the diurnal time scale. Diurnal summer cycles in air and soil temperatures were driven by solar radiation. Multiple regressions combining the effects of air temperature, solar radiation and wind speed approximated near-surface soil temperatures well at every site during both summer and winter (0.88 lt; R2 lt; 0.98).

No description available.

The recent quantification of the reservoir of carbon held in permafrost soils has rekindled the concern that the terrestrial biosphere will transition from a carbon sink to a carbon source during the 21st century. This dissertation is a compilation of four modelling studies that investigate the permafrost carbon feedback, its consequences for the projected future behaviour of the carbon cycle, and the origins of the proportionally between cumulative CO$_2$ emissions and near surface temperature change. The dissertation is centred around five questions: 1) what is the strength and timing of the permafrost carbon feedback to climate change? 2) If anthropogenic CO2 emissions cease, will atmospheric CO2 concentration continue to increase? 3) Can climate warming be reversed using artificial atmospheric carbon-dioxide removal? 4) What are the underlying physical mechanisms that explain the existence in Earth system models of the proportionality between cumulative CO2 emissions and mean global near surface temperature change? And 5) can strong terrestrial carbon cycle feedbacks, such as the permafrost carbon feedback, disrupt this proportionality? By investigating the these questions using the University of Victoria Earth System Climate Model (UVic ESCM) and analytical mathematics the following conclusions are drawn: 1) The permafrost carbon feedback to climate change is simulated to have a strength of 0.25 C (0.1 to 0.75)C by the year 2100 CE independent of emission pathway followed in the 21st century. This range is contingent on the size of the permafrost carbon pool and the simulated model climate sensitivity. 2) If CO2 emissions were to suddenly cease, the UVic ESCM suggests that whether or not CO2 would continue to build up in the atmosphere is contingent on climate sensitivity and the concentration of non-CO2 greenhouse gasses in the atmosphere. For a given model climate sensitivity there is a threshold value of radiative forcing from non-CO2 greenhouse gasses above which CO2 will continue to build up in the atmosphere for centuries after cessation of anthropogenic CO2 emissions. For a UVic ESCM the threshold value for the Representative Concentration Pathway (RCP) derived emission scenarios is approximately 0.6 Wm^-2 of non-CO2 greenhouse gas radiative forcing. The consequences of being above this threshold value are mild, with the model projecting a further 11-22 ppmv rise in atmosphere CO2 concentration after emissions cease. 3) If technologies were developed and deployed to remove carbon from the atmosphere simulations with the UVic ESCM suggest that a Holocene-like climate could be restored by the end of the present millennium (except under a high climate sensitivity and high emission scenario). However, more carbon must be removed from the atmosphere than was originally emitted to it. 4) The proportionality between cumulative CO2 emissions and global mean temperature change seen in most Earth system model simulations appears to arises from two factors: I) the stability of the airborne fraction of emitted carbon provided by the ocean uptake of carbon begin nearly a function of CO2 emission rate; and II) the diminishing heat uptake by the oceans compensating for the reduced radiative forcing per unit mass CO2 at high atmospheric CO2 concentrations. 5) Strong terrestrial carbon cycle feedbacks can disrupt the proportionality between cumulative CO2 emissions and global mean temperature change. However, within the range of emission rates project for the RCPs the permafrost carbon feedback is not strong enough to disrupt the relationship. Overall, the addition of the permafrost carbon pool to the UVic ESCM alters model behaviour in ways that if representative of the natural world will make stabilizing climate or reversing climate change more difficult than has previously been foreseen. / Graduate / 0768 / 0373 / andrewhughmacdougall@gmail.com

No description available.

Glacial geomorphology contains information about former climate which is required for modelling global climate change. Most peaks over 5500 m in the Cordillera Occidental show signs of former glaciation although few at present support perennial ice. Cirque headwalls, large sub-parallel lateral moraines, terminal moraines and minor re-advance moraines were measured at six representative study sites, as were active and inactive rock glaciers. The largest sets of lateral moraines are assumed to have formed when glaciers were in equilibrium at the peak of the last glaciation, and a succession of minor re-advance moraines was probably deposited during retreat of the ice. The radiometric age determinations corroborate existing opinion that this retreat began in the central Andes around 14 000-11 500 years BP. Reconstructed former equilibrium lines on fourteen selected palaeo-glaciers range in altitude from 4625 m at 16°S to 4775 m at 22°S. Five methods of former ELA reconstruction were tested based on geomorphological evidence collected in the field. The results imply lowering of the ELA caused by lower temperatures and increased precipitation compared to the present. The maximum extent of glaciation in the Cordillera Occidental appears to have been reached late in the last glacier cycle because of a shortage of available moisture which inhibited glacier growth when temperatures were colder. Active rock glaciers appear to respond to the thermal rather than the hydric regime and terminate close to the 0°C isotherm which was 300 m lower during deglaciation than at present.

The reconstruction of past environmental conditions is a fascinating research area that attracts the interest of many individuals in various geological disciplines. Paleoenvironmental reconstruction studies can shed light on the understanding of past climates and are a key to the prediction of future climate changes and their consequences. These studies take on special significance when focused on areas sensitive to climate change. The Arctic region, which is experiencing dramatic changes today in its peatlands and in its ocean, is prime example. The entire region plays a major role in global climate changes and has recently received considerable interest because of the potential feedbacks to climate change and its importance in the global carbon cycle. For a better understanding of the role of Arctic peatlands and the Arctic Ocean to global climate changes, more records of past conditions and changes in the region are needed. This work applies different geochemical proxies, with special emphasis on lipid biomarkers, to the study of a permafrost peat deposit collected from the Eastern European Russian Arctic and a marine core retrieved from the Lomonosov Ridge in the central Arctic Ocean. The results reported of this study show that molecular stratigraphy obtained from the analysis of lipid biomarkers in both peat and marine profiles, combined with other environmental proxies, can contribute significantly to the study of Arctic ecosystems of the past. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript. Paper 4: Manuscript.</p>

Snow and glaciers are considered the most important sources of the estimated 32-60% of global water resources which are provided by mountains. Consequently, snow and glaciers have regularly been the focus of climate change studies in mountain regions. Rock glaciers are a type of ice-debris landform characterized by creeping ice-rich permafrost. Recognition of the hydrological significance of rock glaciers is increasing and is of particular relevance to the Arid Andes, where rock glaciers cover greater area than glaciers by an order of magnitude. Little research exists on the hydrological significance of rock glaciers beyond potential water storage capacities and their runoff pathways. Additional knowledge and research approaches pertaining to the seasonal hydrological contributions and climatic sensitivities of rock glaciers are necessary for improved water resource planning in many regions around the world. This work explored the feasibility of utilizing the energy and water balance model GEOtop to quantify the thermal and hydrological dynamics of rock glaciers under several climate scenarios. Weather data was generated with the intermediate-stochastic weather generator AWE-GEN for a site in the Southeast Swiss Alps, which marked a novel approach in studies of rock glaciers. Weather data for a reference (REF) scenario was generated which approximates conditions during the observation period (1985 to 2012). AWE-GEN produced time series of weather data for the REF scenario with statistical properties of precipitation in close agreement with observations. Air temperature had substantial inaccuracies with mean annual air temperature (MAAT) cooler by 1.82 C due to negative temperature biases in summer months which are attributed to difficulties in estimating parameters of the weather generator model caused by local climatic factors. The influence of climate change was also examined. Data for 8 climate change scenarios were generated by specifying change factors for mean monthly air temperature. MAAT in the climate change scenarios was within +/-0.12 C of the speci ed change factor from MAAT in the REF scenario. The thermal and hydrological evolution of rock glacier soils were simulated for 50 years under the climatic forcing of the REF scenario followed by 50 years under each climate change scenario. Mean annual ground surface temperature (MAGST), active layer depth (Dal), permafrost total ice content (IWEtot), and the potential summer runoff contribution (MELTsum) were quanti ed and compared before and after the onset of the climate change conditions. Air temperature increases in the climate change scenarios were amplified in MAGST. Stable rock glacier points were resistant to changes in Dal and IWEtot under any annual, summer, and winter mean air temperature increase of 1 C, and summer and winter mean air temperature increases of 3 C despite notable changes in MAGST and MELTsum. Under warming scenarios, the greatest increase in MELTsum occurred for high elevation rock glacier points with the mean possible runoff contribution increasing 88% under 3 C of warming, which corroborates with increased runoff from high elevation permafrost in the Colorado Rockies in recent decades.

Subarctic and alpine areas are sensitive to climatic change when they lie at the margin of permafrost occurrence. Patterned ground in such areas is generated from an interplay among different mechanisms such as temperature, hydrology, soil texture, snow cower and vegetation. The aim of this study is to describe the connection between patterned ground characteristics and altitude and to evaluate the impact different variables have on the appearance of patterned ground. To understand these interactions is a discussion of self-organization processes, threshold effects and feedback mechanisms essential.  In this investigation, characteristics of patterned ground are examined along an elevation gradient in the Abisko area in Northern Sweden. The study is limited to formations that are categorized into non-sorted circles on flat ground. To detect significant correlations between the characteristics of patterned ground and altitude nine places between 400 and 1400 m above sea level with at least 100 m difference in altitudes were investigated. These sites were categorized into six ridges and three sinks to evaluate the importance of topography. Non-sorted circles have less dwarf shrub, more moss-lichen cover and more cryptogam crust than surrounding ground. Outside the formations the amount of dwarf shrub decreases and the moss-lichen cover increases above 1000 m above sea level. At the highest altitude also a cryptogam crust is occurring around non sorted circles. Significant correlations exist between declining ground temperature and altitude, declining distance between non-sorted circles and altitude, and less dwarf shrub vegetation on non-sorted circles and altitude. These relationships are expected and can be connected to cryoturbation and abiotic stress. Shorter distance between formations can be linked to increased abiotic stress and less coverage soil stabilizing dwarf shrub vegetation. Formations are larger in sinks than ridges and surrounded by less dwarf shrub and more moss-lichen vegetation. This difference can be explained by longer snow duration, humid soil conditions and prolonged freezing processes in ground. Non-sorted circles on an east aspect slope ridge at about 900 meters altitude is characterized by low soil temperatures, high soil moisture, low height and low coverage plants. Around these formations is a well-developed ground cover consisting primarily of dwarf shrub vegetation. These observations are a sign of positive interaction resulting in strong self-generating soil movements that have exceeded a threshold when breaking through vegetation cover. Low soil temperature and high moisture at the time of measurement might be explained by existing ice-front and free water convection. These patterned ground characteristics can be linked to permafrost, the inflow of water from higher leeward slopes and thin snow cower.

The recent quantification of the reservoir of carbon held in permafrost soils has rekindled the concern that the terrestrial biosphere will transition from a carbon sink to a carbon source during the 21st century. This dissertation is a compilation of four modelling studies that investigate the permafrost carbon feedback, its consequences for the projected future behaviour of the carbon cycle, and the origins of the proportionally between cumulative CO$_2$ emissions and near surface temperature change. The dissertation is centred around five questions: 1) what is the strength and timing of the permafrost carbon feedback to climate change? 2) If anthropogenic CO2 emissions cease, will atmospheric CO2 concentration continue to increase? 3) Can climate warming be reversed using artificial atmospheric carbon-dioxide removal? 4) What are the underlying physical mechanisms that explain the existence in Earth system models of the proportionality between cumulative CO2 emissions and mean global near surface temperature change? And 5) can strong terrestrial carbon cycle feedbacks, such as the permafrost carbon feedback, disrupt this proportionality? By investigating the these questions using the University of Victoria Earth System Climate Model (UVic ESCM) and analytical mathematics the following conclusions are drawn: 1) The permafrost carbon feedback to climate change is simulated to have a strength of 0.25 C (0.1 to 0.75)C by the year 2100 CE independent of emission pathway followed in the 21st century. This range is contingent on the size of the permafrost carbon pool and the simulated model climate sensitivity. 2) If CO2 emissions were to suddenly cease, the UVic ESCM suggests that whether or not CO2 would continue to build up in the atmosphere is contingent on climate sensitivity and the concentration of non-CO2 greenhouse gasses in the atmosphere. For a given model climate sensitivity there is a threshold value of radiative forcing from non-CO2 greenhouse gasses above which CO2 will continue to build up in the atmosphere for centuries after cessation of anthropogenic CO2 emissions. For a UVic ESCM the threshold value for the Representative Concentration Pathway (RCP) derived emission scenarios is approximately 0.6 Wm^-2 of non-CO2 greenhouse gas radiative forcing. The consequences of being above this threshold value are mild, with the model projecting a further 11-22 ppmv rise in atmosphere CO2 concentration after emissions cease. 3) If technologies were developed and deployed to remove carbon from the atmosphere simulations with the UVic ESCM suggest that a Holocene-like climate could be restored by the end of the present millennium (except under a high climate sensitivity and high emission scenario). However, more carbon must be removed from the atmosphere than was originally emitted to it. 4) The proportionality between cumulative CO2 emissions and global mean temperature change seen in most Earth system model simulations appears to arises from two factors: I) the stability of the airborne fraction of emitted carbon provided by the ocean uptake of carbon begin nearly a function of CO2 emission rate; and II) the diminishing heat uptake by the oceans compensating for the reduced radiative forcing per unit mass CO2 at high atmospheric CO2 concentrations. 5) Strong terrestrial carbon cycle feedbacks can disrupt the proportionality between cumulative CO2 emissions and global mean temperature change. However, within the range of emission rates project for the RCPs the permafrost carbon feedback is not strong enough to disrupt the relationship. Overall, the addition of the permafrost carbon pool to the UVic ESCM alters model behaviour in ways that if representative of the natural world will make stabilizing climate or reversing climate change more difficult than has previously been foreseen. / Graduate / 2015-05-01 / 0768 / 0373 / andrewhughmacdougall@gmail.com

To assess the affects of permafrost degradation on key components of the aquatic food web, an in situ manipulative mesocosm experiment was performed in an upland, unslumped Arctic lake located near Inuvik, Northwest Territories. In total, twelve replicate mesocosms were established, 3 control and 3 replicates of 3 treatment levels each dosed with differing amounts of sediments sourced from a nearby thermokarst slumped lake. Findings from the experiment showed that pelagic autotrophic processes had the greatest potential to contribute to higher trophic levels regardless of treatment. Even in the high sediment treatment level, which showed the least pelagic autotrophic production, pelagic autotrophic production was two orders of magnitude greater than pelagic heterotrophic production and 5 times greater than benthic autotrophic or heterotrophic production. Sediment treatment had no significant effect on benthic primary productivity; however, a 500% increase in benthic heterotrophic production was observed. This raises the possibility that increased activity in benthic heterotrophic production is the first step in thermokarst-affected lake ecosystem succession leading to the proliferation of benthic primary production observed in many slumped lakes in the western Canadian Arctic. Water column phosphorus concentrations increased with increasing sediment treatment while pelagic primary production decreased and zooplankton biomass increased. These results suggest that the initial effect of thermokarst disturbance is an enrichment of the system and that top-down predation from zooplankton regulate the abundance of phytoplankton in these systems. If incidences of thermokarst disturbance continue to increase as predicted by current climate models/scenarios, results from this study suggest that the structure and function of Arctic aquatic ecosystems will be significantly impacted. This study highlights the need for further research to obtain a better mechanistic and predictive understanding of the potential effects of thermokarst disturbance on the geochemistry and ecology of Arctic lakes at relevant spatial and temporal scales. / Graduate