A thesis submitted to the Faculty of Science in fulfilment of the requirements for the degree of Doctor of Philosophy. 30 August 2016 in Johannesburg, South Africa. / The presence of Portulacaria afra affects the flow of ecosystem services from the thicket landscapes of the Eastern Cape. Degraded and intact thicket ecosystems deliver different bundles of ecosystem services, and within each bundle the services are linked non-linearly, so that land-use and management decisions which seek to increase a particular service affect the delivery of other services. One of the challenges of restoring the historically degraded thicket areas is understanding the trade-offs between various objectives, including re-establishing biodiversity and critical services such as carbon sequestration, climate regulation, water provision and forage supply. This thesis uses a variety of techniques to assess some of these trade-offs at several spatial and temporal scales. The amount, rate and nature of carbon assimilation by P. afra at a variety of spatial and temporal scales are also explored. Methods At a landscape scale stream flow data from transformed and intact catchments, near Jansenville and Bucklands respectively, are used to compare the freshwater ecosystem services provided by the presence of P. afra. Similarly, at a landscape scale, the new high resolution Multi-angle Imaging SpectroRadiometer (MISR-HR) products are used to explore the differences in the surface energy budget of intact thicket and degraded ecosystems. Two simple radiative transfer models are used to assess the radiative forcing (RF) trade-off between carbon uptake-related global cooling and albedo-related global warming. From samples and measurements taken from a field site 15 km south-west of the town of Kirkwood, radiocarbon and stable carbon isotope analysis, growth ring analysis, dendrometry, infrared thermometry, water use efficiency and eddy covariance data are used to quantify the rate of carbon assimilation by P. afra, and unpack the contribution of C3- and CAM-derived carbon to total carbon sequestration. Results Intact thicket cover results in a higher total yield of water as a fraction of rainfall, fewer extreme high flow events, and a higher volume of low-flow in comparison to landscapes thought to represent transformed former thickets. Intact thickets have a lower albedo than degraded thickets. Restoring to an intact state will result in a mean albedo decrease of 5% (absolute) which constitutes a direct radiative forcing of +0.019 pW m-2 at a global scale. This warming effect overwhelms the climate benefit derived from carbon sequestration related to P. afra growth by a factor of 1.6. The growth data suggests that P. afra produces two growth rings annually on average, with the average growth increment of 0.8mm in diameter. The multi-year and multi-source aboveground relative growth rate mean is 0.006 (±0.005 SD) g DM per g DM per year, which is mean average increment about 1.1% per year. The eddy covariance data highlighted the temporal variability in the system, measuring intact P. afra thicket vegetation as a net source of carbon to the atmosphere 0.018 gC m-2 hr-1, over the three short-duration campaigns. CAM is now understood to come in several variants. The sampled stems, averaged across all rings, had a δ13C signature of -15.8±1.0 ‰ indicative of “strong CAM” behaviour. P. afra plants in the Kirkwood locality over the past decades have derived 61% of their carbon through the CAM pathway and 39% through the C3 pathway, with substantial inter-stem variation. The soil isotope data suggests 51 - 63% C3 derived carbon, with values increasing with sampling depth. There are occasional large excursions, always in a single growth ring, towards more negative δ13C values (-19.0‰); in other words towards the C3 range. Although thought to be related to water stress, it was hard to determine a single trigger for the switching between C3 and CAM modes. This is consistent with findings for other strongly CAM plants. From the dendrometers and infrared thermometry, P. afra shows flexible stomatal behaviour on a range of timescales. For the majority of the study period the stomata were open both day and night. There is variation in stomatal closure over the year, which appears strongly seasonal, and suggests a link to the bimodal rainfall pattern experienced in the region. Using decision tree to classify the photosynthetic mode, this data suggest that the individual plants being measured are spending only 4% of the time in classical CAM mode, and the majority of the time in CAM-cycling. Conclusions Restoration of transformed thicket will improve freshwater ecosystem services associated with useful water yield, sustained supply, and flood control. It is important to include land-atmosphere feedbacks other than carbon assimilation when assessing the climate service delivered by restoration. The negative and positive radiative forcing will operate over different timelines. CAM metabolism plays an important but not exclusive role in carbon gain. Contrasting patterns between plant and soil C3 fraction may relate to allocation issues and the contribution by plants other than P. afra. The growth rates of thickets are not substantially greater than similar water-limited ecosystems. / LG2017

Peatlands contain a significant amount of the global soil carbon, but the climate feedback affecting carbon stability within these peatland systems is still relatively unknown. Organic matter composition of peatlands plays a major role in determining carbon storage, and while high latitude peatlands seem to be the most sensitive to climate change, a global picture of peat organic matter chemistry is required to gauge overall peatland stability and to improve models of greenhouse gas emissions fueled by soil carbon decomposition. The goal of this research is to test the hypothesis that carbohydrate content, an indicator of soil organic matter lability or reactivity, will be lower in carbon deposits near the equator and greater in high latitude peatlands. Conversely we hypothesize that peat aromatic content will be higher at low latitudes relative to higher latitudes. As a part of the Global Peatland Microbiome Project (GPMP), around 1400 samples of peat across a latitudinal gradient from 79N to 65S were measured with Fourier transform infrared spectroscopy (FTIR) to examine the organic matter functional groups of peat. Carbohydrate and aromatic content, as determined by FTIR, are useful proxies of decomposition potential and recalcitrance, respectively. A highly significant relationship was observed between carbohydrate and aromatic content, latitude, and elevation. Carbohydrate contents of high latitude sites were significantly greater than at sites near the equator, in contrast to aromatic content which showed the opposite trend. It was also clear that at locations with similar latitudes but different elevations, the carbohydrate content was higher and aromatic content was lower at higher elevations. Higher carbohydrate content at higher latitudes indicates a greater potential for lability and resultant mineralization to form the greenhouse gases, carbon dioxide and methane, whereas the composition of low latitude peatlands is consistent with their apparent stability in the face of greater temperatures. The combination of low carbohydrates and high aromatics at warmer locations near the equator could foreshadow the organic matter composition of high latitude peat transitioning to a more recalcitrant form with a warming climate accompanying the evolution of greenhouse gases. / A Thesis submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2018. / April 16, 2018. / Decomposition, FTIR, Latitude, Organic Matter, Peatlands, Stability / Includes bibliographical references. / Jeffrey Chanton, Professor Directing Thesis; Robert Spencer, Committee Member; Olivia Mason, Committee Member.

The cold blob refers to an observationally unprecedented, gyre-scale, record-breaking cold of mean surface temperature over the subpolar North Atlantic. Its anomalous cold feature goes against the rising trend of global mean surface temperature in the context of a warming climate. Observations show that the Atlantic cold blob emerged in early 2014 and can penetrate deeper into the ocean interior beyond 500m depths. A sudden drop in upper ocean heat content is associated with an accumulative increase in freshwater content. Prior works pointed out that intense surface forcing during two consecutive winters was a primary driver. We hypothesize that surface forcing alone is insufficient for the cold blob to persist. Our analysis shows, for the first time, that variations in the net surface heat fluxes cannot explain the decline in upper ocean heat content during 2014–2017. Therefore, surface forcing fails to explain the origin of the cold blob. To investigate alternative mechanisms, non-assimilative simulations based on a coupled ocean-sea ice model (GFDL MOM5/SIS1) with two different atmospheric forcings (MERRA2 and ERA-interim) are employed to examine the transports of mass, heat, and freshwater within the cold blob area. Initial diagnosis verified that both model runs can reproduce the cold blob characteristics at similar magnitudes to Argo observations. Model results show a decreasing trend of heat transport at the southern boundary, implying that reduced poleward ocean heat transport likely accounts for the formation and persistence of the cold blob. This cooling signal from the south is accompanied by a freshening signal. Changes in the residual heat fluxes suggest that reduced warming for the subsurface layer at 100–700 m depths apparently occurred since 2006 before turning into enhanced cooling during late 2013. Variations in the residual freshwater fluxes remain positive for the entire past decade and subsequently result in an accumulative surplus of freshwater content in this area. The model run with incorporated Greenland meltwater estimates sheds light on the relative contribution of meltwater advection. To a great extent, Greenland meltwater can amplify the freshening tendency in the subpolar North Atlantic by approximately up to 200% during the present decade. In the long run, upper ocean cooling and freshening would lead to increased stratification and reduced mixing with deeper waters, therefore enhancing the likelihood that the subsurface cold blob persists. / A Dissertation submitted to the Department of Earth, Ocean and Atmospheric Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2018. / November 5, 2018. / Air-Sea Interaction, Climate Change, Cold Blob, Greenland Meltwater, Polar-Lower Latitude Linkage, Subpolar North Atlantic / Includes bibliographical references. / Mark A. Bourassa, Professor Directing Dissertation; James B. Elsner, University Representative; Allan J. Clarke, Committee Member; William K. Dewar, Committee Member; Kevin G. Speer, Committee Member.

Southeast Florida is a region of the U.S. that is predicted to incur severe damage due to climate change (CC). As a result, one particular grassroots organization created a CC workshop to educate, advocate, and build resiliency locally. Social movement’s literature reveals processes of framing, resource mobilization, and organizational structure that have had successful outcomes locally while climate action literature argues that civil society has been ineffective at creating significant impacts on the global scale of climate policy. In order to expand this literature further, I conducted a research project to examine how different frames presented in CC education influence climate actions in the Southeast Florida region. Using qualitative research methods of participant observations and interviews, my analysis of the data collected suggests that organizers of the workshop used an environmental and climate justice narrative along with a collective action framework, relying on three master frames of place, justice, and power to educate members on CC. Amongst the prognoses presented to members during the education were climate action solutions primarily within the meso (community/civic engagement) level to create structural change within the region. I found that participants interpreted CC to be an issue of 2 places in Southeast Florida, one on the coast and one inland and, thus, depending on which region participants lived, their level of climate action was affected, whether at the individual or community/civic level. Therefore, some participants focused on individual behavioral and household consumer tactics, while other participants worked on community building and creating structural change. Given the unsuccessful nature of local organizations at impacting global climate negotiations and the goal of social movement processes to create change within societal structures, this case study contributes to the growing body of knowledge regarding the influence of climate education on climate actions. / Includes bibliography. / Thesis (M.A.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

This dissertation focuses on the economics of infrastructure development and public finance. The dissertation is composed of three papers: The first paper analyzes the optimal solutions for supplying electricity to national economies from both domestic as well as distant energy resources using transmission systems that can connect the huge renewable energy resources of Africa. The results point to options for achieving substantial increases in the sustainable energy supply and for improving access to energy across the continent. The second paper models a comparative local and national electricity distribution planning in Senegal by examining the trade-off between access and costs. The third paper uses exogenous variations in rainfall across municipalities in Mali to estimate the causal effect of household income shocks on municipal-level tax revenues. It also exploits a national tax collection incentive policy to measure the impacts of rainfall variation on intergovernmental transfers.

Using methods from dynamical systems theory in observations, low-order and general circulation models (GCMs), this dissertation explores (a) the response of midlatitude jet and eddy energy to climate change and variability, and (b) variability in predictability of the first kind of the El Niño/Southern Oscillation (ENSO) phenomenon. First, an analysis framework inspired by the Lorenz-1984 model is developed to study the relationship of the probability structure of the North Atlantic jet stream and storm track (location and strength) with (a) hemispheric surface temperature gradients (equator-to-pole gradient and ocean-land contrast), and (b) ENSO. Both the equator-to-pole gradient and the ocean-land contrast are projected to decrease in response to greenhouse gas forcing. The shifts in the probability structure of jet and eddy energy in relation to decreasing surface temperature gradients are in the opposite direction than the shifts for El Niño forcing. However, in climate change projections, the El Niño-like tropical pacific warming dominates the response of the jet/eddy energy probability, resulting in a strengthening and equatorward shift of the subtropical jet. The response of the subpolar jet is separate (poleward shift and strengthening), indicating that the combined effect of the tropical and extratropical SST changes under strong greenhouse gas forcing may set up conditions for a separation of the jet stream in the North Atlantic. Then, ENSO predictability of the first kind is examined in observations and in pre-industrial model simulations, using local lyapunov exponents. Multidecadal variations in ENSO predictability are shown in a 2000-yr long simulation from the Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 model. The GCM is found to be less predictable than nature and than an intermediate model of the tropical Pacific (Zebiak-Cane model). Finally, it is shown that increased predictability is associated with a deeper thermocline in the west Pacific up to five years prior to the peak of the event, along with an earlier deepening of the thermocline in the east Pacific in the months preceding the peak. This dissertation therefore illustrates that the analysis of key features of tropical and extratropical climate in a physically meaningful "reduced space" can provide a focused interpretation of GCM projections for climate change and variability.

This dissertation explores two aspects of interdecadal climate variability: the predictability of variability in the tropical Pacific region on longer-than-interannual timescales, and changes to subsurface heat content in the tropical Atlantic Ocean over a decade. Chapter 1 assesses the ability of a general circulation model (GCM) and an intermediate- complexity model (ICM) to simulate persistent cool states of the Tropical Pacific. These states, which are La Niña-like on average, last from seven to ten years and induce prolonged droughts in many parts of the world. We find that these models produce analogs to real-world examples of these states and that they are modestly predictable in the ICM. We also find some predictability of the interdecadal shifts in the mean state in this model. In Chapter 2, an attractor reconstruction technique is used to investigate the predictability of interdecadal variability in the ICM further. We find that the interdecadal regimes of the ICM emerge as a pair of distinct orbits in a three-dimensional state space, and that the observed system possesses some comparable characteristics. The ICM is found to spend over a third of the time in states from which the regime of the following fifteen years is predictable with high confidence. The implications for developing an interdecadal prediction scheme are discussed. Chapter 3 examines changes in the heat content of the tropical Atlantic below the thermocline during the recent global warming hiatus. We use simulated Lagrangian particles in an ocean reanalysis dataset to analyze the changes to the circulation of the upper tropical Atlantic Ocean that occurred between the hiatus decade and the decade prior to it; and develop a testable hypothesis for how variability in the tropical Pacific region may have influenced the subsurface heat content of the Atlantic.

Scleractinia (stony corals) are powerful tools in the field of paleoceanography, allowing researchers to reconstruct past ocean conditions based on variations in coral geochemistry. As corals regularly accrete their aragonite skeletons they preserve a history of climate on regional to global scales. Often able to provide centuries long continuous records of climate, an individual coral colony can provide insight into significant environmental perturbations. If preservation permits, fossil corals can be used to evaluate climate thousands of years in the past. Researchers use paleoclimate proxies, which are indirect geochemical fingerprints of environmental conditions, to create paleoclimate time series. Paleoclimate proxies are prevalent throught the literature and while many are well constrained by years to decades of use, individual conditions unique to study sites and timescale prevent the use of blanket assumptions regarding their interpretation. In this dissertation I illustrate the varied ways that the same or similar coral-based climate proxies can be used to reconstruct past ocean conditions. Part I (Ch. 2, 3) presents two studies based along of the Pacific Coast of Panamá to examine the influence of the seasonal migration of the Intertropical Convergence Zone (ITCZ). I analyzed a long-term coral δ18O time series from a living massive Porites colony to address low-frequency variation overprinted by the wet-dry seasonality. The coral record uncovered a clear decadal (~11 year) cycle in coral δ18O-inferred precipitation. I propose this mode is related to basin-wide processes, specifically a component of the Pacific Decadal Oscillation, which describes large-scale patterns in sea surface temperature (SST) and precipitation influencing marine ecosystems. In Chapter 2, I supplement the coral δ18O record with a coral Ba/Ca time series from a different coral colony. Coral Ba/Ca can be used as a proxy for river discharge (Q), although this practice is relatively new. Our coral record outlined seasonal variation in river Q and can also be used to identify past El Niño events and prolonged periods of drought. Uncovering a geochemical indicator of El Niño in this region is particularly powerful since conditions become warm and dry, which negate each other in coral δ18O rendering the proxy unable to consistently identify these climate events. This chapter furthers the community’s understanding of the many ways that trace metals can be used in paleoceanographic research, specifically to constrain local hydroclimate. In Part II (Ch. 4, 5) I present two studies in the Great Barrier Reef (GBR) based on coral δ18O and Sr/Ca records from modern and fossil Isopora, a coral species that is nearly completely absent from the paleoceanographic literature. Although this suite of climate proxies is similar to those used in Part I, in Part II the GBR corals provide a history of sea surface temperature rather than hydroclimate, which is due to prevailing local environmental conditions over a given timescale. In Chapter 4 I developed the first modern Sr/Ca- and δ18O-Sea Surface Temprature (SST) calibration using Isopora, which approaches those calculated for the commonly used Porites corals. Using Isopora in Pacific-based paleoceanographic research allows us to analyze coral records from reefs that might not be dominated by Porites. In Chapter 5 I applied the new Isopora Sr/Ca- and δ18O-SST calibrations to fossil corals recovered during Integrated Ocean Discovery Program (IODP) 25. The fossil corals date beyond the Last Glacial Maximum (LGM, ~20 kyr BP) to 25 kyr BP. In the Pacific SST change since the LGM is better constrained for more equatorial locations so our fossil samples from the GBR extend the geographic network of LGM-aged coral-based climate proxies. I measured ~5-7°C of cooling in the GBR at the LGM compared to today. The SST change through the LGM deglaciation provides valuable understanding of reef resilience and future risk of or adaptability to climate change. Each chapter in this dissertation uses similar strategies but provides a unique perspective on past climate change in the tropical Pacific. This dissertation identifies the many ways that coral proxies can be utilized with specific examples of the ways in which interpretation can vary. It is necessary to consider the environmental specifics of a given region before blindly interpreting paleo-proxy data. Furthermore, coral-based proxy records are supremely powerful tools in exploring and uncovering past climate histories of a given region. Coral-records can supplement and extend the limited instrumental record with centuries to millenia long information on SST and hydroclimate. These data can improve climate models, further our knowledge of coral reef growth, and deepen our understanding of regional hydroclimate, which are all vital to our understanding of global climate.

A high quality, historical surface air temperature data set is essential for the reliable investigation of climate change and variability. In this study, such a data set has been prepared for Australia by adjusting raw mean annual temperature data for inhomogeneities associated with station relocations, changes in exposure, and other problems. Temperature records from long-term stations were collaborated from the set of all raw data held by the Australian Bureau of Meteorology. These long-term records were extended by combining stations and manually entering previously unused archived temperature measurements. An objective procedure was developed to determine the necessary adjustments, in conjunction with complementary statistical methods and station history documentation. The objective procedure involved creating a reference time series for each long-term station, from the median values at surrounding, well-correlated stations. Time series of annual mean maximum and mean minimum temperatures have been produced for 224 stations, and the adjusted dataset has been made available to the research community. The adjusted data are likely to be more representative of real climatic variations than raw data due to the removal of discontinuities. The adjusted data set has been compared with previously used temperature data sets, and data sets of other parameters. The adjusted data set provides adequate spatial coverage of Australia back to 1910. Additional adjusted data are available prior to this date at many stations. Trends in annual mean maximum, minimum, the mean of the maximum and minimum, and the range between the maximum and minimum, have been calculated at each site. Maximum and minimum temperatures have increased since about 1950, with minimum temperatures increasing faster than maximum temperatures.

Thesis (Ph. D.)--Washington State University, December 2007. / Includes bibliographical references (p. 195-209).