>Magister Scientiae - MSc / Water is a fundamental resource and key in the provision of energy, food and health. However, water resources are currently under severe pressure as a consequence of climate change and variability, population growth and economic development. Two driving factors that affect the availability of water resources are land use land cover (LULC) change and climate variability. Increasing population influences both LULC change and climate variability by inducing changes in key hydrological parameters such as interception rates, evapotranspiration (ET), run-off, surface infiltration, soil moisture, water quality and groundwater availability thereby affecting the watershed hydrology. The effects of LULC change and climate variability on hydrologic parameters have been extensively studied.

In dieser Arbeit wird die Hypothese getestet, ob ein Teil der atmosphärischen Komponente interdekadischer Klimavariabilität durch die Anregung interner, atmosphärischer Moden, speziell von singulären Moden eines linearen, stationären Atmosphärenmodell, begründet werden kann. Die Analysen basieren auf einem linearen, baroklinen quasigeostrophischen Modell, wobei der Grundzustand aus Daten einer Langzeitintegration des ECHAMl/LSG abgeleitet wird. Sie beziehen sich auf eine detektierte Oszillationsmode mit einer Periode von 18 Jahren in dieser GCM Integration. Es zeigt sich, daß der führende rechte singuläre Vektor des linearen baroklinen Modells signifikant mit der interdekadischen Anomalie der atmosphärischen Zirkulation über der Nordhemisphäre korreliert. Damit kann ein Anteil von über 40% der räumlichen Varianz dieser interdekadischen Mode erklärt werden. / In the present paper we examine the hypothesis that a part of the atmospheric component of interdecadal variability is manifested in the exitation of internal, atmospheric modes, in particular in singular modes of a linearized, steady-state atmospheric model. This hypothesis is tested by using a baroclinic quasigeostrophic model, for which data from the dimate model ECHAMl/LSG are utilized to define the long-term mean basic state. The analysis refers to the interdecadal oscillation with a period of 18 years in this GCM-integration. A significant projection is found of the first singular vector and the interdecadal mode of atmospheric circulation. This singular vector is able to explain about 40% of the spatial variance of the interdecadal anomaly over the Northern Hemisphere.

This project summarizes the findings of research organized in two parts. The first involved the characterization of changes in the variability of climate that lead to extreme events. The second focused on the predictability of extreme climate on time-scales ranging from short forecast lead-times to long-lead climate predictions exceeding a year. Initial studies focused on three interrelated, yet regionally unique extreme climate phenomena. First, the relationship between increasing greenhouse gas (GHG) emissions and particulate matter (PM) concentration in basin terrain was investigated. Next, we evaluated changes in large-scale atmospheric circulation associated with two climate phenomena at either extreme side of the water cycle--droughts and floods. In the final analysis, an attempt was made to understand the mechanisms that link two North Pacific ENSO precursor patterns to the ENSO cycle.

Great Basin bristlecone pine (GBBP) (Pinus longaevaBailey) is one of the longest-lived organisms on Earth, and is one of the most highly fragmented high elevation conifer species. Throughout the Great Basin of the Intermountain West, GBBP are being impacted by changing disturbance regimes, invasive species, and climate change. To better understand the effects of climate variability and ecological disturbances in GBBP systems, three studies were designed and implemented. The first characterized the distribution of forest fuel in stands of GBBP and predicted how fuels may change under future climate scenarios. Using the Forest Inventory Analysis (FIA) plot variables of tree species, height, diameter at breast height (DBH), canopy base height (CBH), coarse (CWD) and fine (FWD) woody debris across elevational gradients, this study examined the effects of changes to fuel loading on predicted changes in fire behavior and severity. All classes of FWD decreased with elevation, and only 1000-hr fuels remained constant across elevational transects. This, combined with lower CBH and foliar moisture and increasing temperatures due to climate change, suggested increased fire potential at the GBBP treeline. The second study examined the role of volatile organic compounds (VOCs) and tree chemistry and their response to the environment. VOCs and within needle chemistry were collected and analyzed along elevational gradients near the northern and southern limits of GBBP. Random Forest analysis distinguished elevation using VOCs, with 83% accuracy, and identified the compounds most important for classification. Ordination revealed that temperature, heat load index, and relative humidity were each significantly correlated with VOCs. Within-needle chemistry provided less predictive value in classifying elevation (68% accuracy) and was correlated only with heat load index. These findings suggest that GBBP VOCs are highly sensitive to the environment. The final study explored the role of VOCs in host selection of mountain pine beetle (MPB). Mountain pine beetles oriented toward VOCs from host limber pine (Pinus flexilis James) and away from VOCs of non-host GBBP using a Y-tube olfactometer. When presented with VOCs of both trees, females overwhelmingly chose limber pine over GBBP. While there were only a few notable differences in VOCs collected from co-occurring GBBP and limber pine, 3-carene and D-limonene were produced in greater amounts by limber pine. There was no evidence that 3-carene is important for beetles when selecting trees, however, addition of D-limonene to GBBP VOCs disrupted the ability of beetles to distinguish between tree species. Climate change will impact how forests are managed and this research could provide insight into the mechanisms underlying the incredible longevity of this iconic tree species.

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Student Number : 0413447J - MSc research report - School of Geography and Environmental Studies - Faculty of Science / This research analyses the vulnerability and adaptation of communities living along the River Kaduna floodplain at Shiroro Local Government in Niger State to flood occurrences. These communities are one of the most flood-prone areas in Niger State, with fertile alluvial deposits for agricultural production. The analysis of rainfall and flood flow into the Kaduna River System shows that there is an increasing flood frequency and flood magnitude along the River Kaduna for the past two decades because of slight increase in rainfall amount. Although there is a slight increase in rainfall amounts, the flooding of the Kaduna River could be regarded as normal. This is because there is no major change in rainfall amounts. Therefore, any slight increase in rainfall may cause flooding. The 1990s with slight increase in rainfall coincides with the period of abundant flood flow in the Kaduna River System and very significant runoff into the Kaduna reservoir. Floods have impacted negatively on the life of the people living on the floodplain resulting into food insecurity, poverty and vulnerability to malnutrition and other health problems among the communities in Shiroro Local Government Area. There are three vulnerable groups identified within the communities (the very poor, those residing on the floodplain and those that depend only on agriculture). These three groups identified lack accesses to good shelters and social amenities like electricity, good water, roads, health facilities and schools. Moreover, this research shows that the adaptive capacity of these communities is being severely compromised by factors such as poverty, poor infrastructure, weakening social networks and environmental degradation.

Ice core records from Greenland have shown times of rapid warming during the most recent glacial period, called Dansgaard-Oeschger (D-O) events. D-O events are important to our understanding of both past climate systems and modern climate volatility. In this paper, we present new approaches for statistically evaluating the existence of cyclicity in D-O events and the possible lagged correlation between the Greenland and Antarctica temperature records. Specifically, we consider permutation testing and bootstrapping methodologies for assessing the cyclicity of D-O events and the correlation between the Greenland and Antarctica records. We find that there is not enough evidence to conclude that D-O events are cyclical; however, the Antarctica record leads the Greenland record by 545 years with a statistically significant correlation of 0.455.

Throughout earths history, the climate have always naturally varied due to both external forcings and internal mechanisms. With the outlook on future climate change, it is important to understand the climate system and this includes its natural variability. Depending on the driving mechanisms, the variability happens over different timescales. Among these is centennial variability, which still have unanswered questions. Studying centennial variability requires climate timeseries that are both long enough to encompass several cycles and detailed enough to resolve the variability signals. New data from long transient Holocene model simulations and recent efforts to compile large proxy databases now presents an opportunity to study centennial variability with better data foundation than earlier. To do so, this master thesis studies centennial variability in transient Holocene simulations from 9 models and 122 proxy records with a spectral analysis with the aim of finding the general signals related to cycle length, geographic dependencies and discuss the implications for the ongoing scientific discussion on the potential driver(s). The spectral analysis of the proxy records finds centennial variability significant from red noise in the majority of the records, with the highest concentration of cycle lengths around 120- 130 years, an average at 240-300 years, depending on the number of cycles included in the calculation, and no clear indication of it being dependent on which climate variable, although air temperature is the biggest group and influence the results the most. The analysis of the model global mean temperature (GMT) also finds centennial variability in all simulations with the highest concentration of cycle lengths around 120-150 years and an average just slightly above that. A good agreement between model and proxy data is thereby indicated, although the spread is slightly larger for the proxy data, but this is also a more diverse collection of data than the models. There is also a good agreement in the lack of latitudinal dependencies, where centennial variability is found at all latitudes of the model data (6 bands with a combined global coverage is analysed) and no clear differentiation is found between the proxy records at different latitudes. However, all the model data have most spectral density distributed over the 90N to 60N latitude band, which indicates either a particular variability sensitivity or potential driving mechanisms in this region. Four of the models also have differentiated/single forcings simulations and the spectral analysis of the GMT in all of these also reveals significant centennial variability with cycle lengths between 100-200 years. The simulations where only orbital forcing also show this and so the different forcings seem to induce some variability to the system, but none can be said to be the main driver based on the spectral analysis. This also includes solar irradiance, which long have been hypothesised to drive centennial variability, as all the simulations without this forcing, which includes some of the full forcing simulations as well, all have significant centennial variability. The results instead indicate that centennial variability is internally driven and that the Arctic is a region of interest for this aspect. The conclusions is not without uncertainties, as both proxies and model simulations have uncertainties, but when analysing with a largely uniform approach on a large data collection, there is good evidence of centennial variability with cycle lengths around 100-200 years across the entire range of available Holocene paleoclimate data

Forest plantations have been long-employed to reverse land degradation and support biodiversity, and are now recognized to both take in atmospheric carbon dioxide, reducing the intensity of the greenhouse effect, and moderate local weather. It is important to consider the impact forest aging and management will have on provisioning of these services under climate change and extreme weather events, such as drought. This study encompasses a chronosequence of three Eastern White Pine stands planted in 1939, 1974 and 2002, situated in Turkey Point, Ontario, Canada. The oldest forest received two selective thinning treatments, removing 30% of trees, in 1983 and 2012. Forest water use efficiency (WUE), which represents the amount of gross ecosystem productivity (GEP) per unit of water released through evapotranspiration (E), was compared among the three sites over 2008-2013. The youngest forest’s annual WUE increased over the study period, surpassing that of the older sites by 2013. When bulk surface conductance (Gs), representing gas exchange, was compared across the sites for the same years, the youngest site had the lowest Gs, particularly during drought. Gs at the oldest forest was highest and the most variable. Statistical analysis showed that across all the sites, E was more responsive to air temperature than atmospheric demand, soil moisture, and incident radiation. This study indicated that younger plantations may be more water-conservative during drought, and that air temperature is important to consider in projections of temperate coniferous forests’ carbon and water exchange. To assess the impact of the 2012 selective thinning on tree-level and ecosystem-level water use at the oldest forest, sapflow velocity (Js), transpiration (Et) and E were compared between the two stands planted in 1939 and 1974, from 2011 to 2013. A relatively severe drought over the 2012 growing season led to a decline in Et at the unthinned site for that year, however the Et decline was more pronounced at the older, thinned site. From 2011 to 2012, Js increased at the thinned site, converse to the unthinned site – wherein Js was low as expected during drought. Hydraulic redistribution and lag time from sapflow at 1.3 m height to canopy evapotranspiration were seemingly unaffected by the thinning, indicating that low-level selective harvesting was not detrimental to the hydrological functionality of the stand, and may have been beneficial in allowing more soil moisture access per tree. As such, the stand may be better positioned to withstand recurrent dry spells resulting from precipitation variability, as predicted with climate change. / Thesis / Master of Science (MSc)

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