京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20912号 / 理博第4364号 / 新制||理||1626(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 井岡 邦仁, 教授 川合 光, 教授 田中 貴浩 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The following is a compilation of field data collected in 2011 and 2012 in Apalachicola, FL as part of a five year study assessing the ecological effects of sea level rise in the northern Gulf of Mexico. Many coastal communities, both natural and developed, will soon be working to mitigate the effects of sea level rise, if they are not already doing so. This thesis investigates the natural patterns of the Apalachicola estuarine system through the collection and analysis of in situ water, sediment, and biomass samples. Additionally, results of the field samples are presented and recommendations for additional sampling are given. The field methods and procedures developed in this study were designed to be repeated in other estuaries to build upon the work that has been conducted in Apalachicola. Water samples were tested for total suspended solids (TSS) and compared against hydrodynamic (tidal circulation and streamflow) and meteorological (wind and precipitation) characteristics. Streamflow was determined to influence a seasonal base level concentration of TSS. Wind strength and direction consistently influenced small TSS concentration fluctuations, an effect amplified by the shallow nature of the estuary. Tidal circulation appeared to have minor influences on TSS concentration fluctuations within the base level concentration range. Precipitation appeared to influence large TSS concentration fluctuations; however, due to limited data collection during storm events, more data is required to conclusively state this. Sediment cores throughout the lower Apalachicola River revealed that coarse particles settled out in upstream areas while fine particles tended to stay in suspension until low energy areas in the lower portions of the river or marsh system were reached. Finally, biomass samples were used to iv develop regression models utilizing remotely sensed data to predict biomass density in marsh areas with unprecedented accuracy. The documented patterns of this system are to be used as inputs and validation points to update an existing hydrodynamic model and to aid in the coupling and development of sediment transport and marsh equilibrium models. The field campaign developed and implemented here provides a foundation for this novel coupled modeling effort of estuarine systems. From the 2011 and 2012 sampling conducted, it is apparent that Apalachicola can be modeled as a closed system with river inflow and sediment influx as boundary conditions. Forcing local conditions should accurately represent the system. Ultimately, these models will be used to simulate future sea level rise scenarios and will provide useful decision making tools to coastal managers. Future work will include replicating water sampling in subsequent wet and dry seasons in Apalachicola, FL to confirm observed trends, in addition to implementing this sampling in Grand Bay, MS and Weeks Bay, AL. Additional biomass samples will be taken to validate the strong correlations found between remotely sensed data and in situ samples. In similar studies, it is recommended that water samples be taken to adequately represent influences from tidal cycles and riverine inflow. It is also recommended that spatially distributed biomass samples be taken to validate regression models.

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<p>We present a numerical study of gas accretion into galaxies using the SPH code, Gasoline. Numerical tests on shock treatment in Gasoline are run to evaluate how well cosmological-scale, high Mach number shocks are treated. We find that shock solutions are far too noisy, and in specific density and metallicity regimes, this seeds a phase separation instability of hot and cold gas. We propose this instability as the source of cold blobs seen in many numerical simulations. We find that improved shock behavior is primarily attained through increased viscosity parameters. Analysis is also performed on four cosmological simulations from the McMaster Unbiased Galaxy Simulations (MUGS) (Stinson et al. 2010). In agreement with recent literature, we find cold flows of gas seeded by dark matter filaments stretching far into the inner galaxy in all analyzed galaxies. Tracking of star and gas particles is performed, and we find that cold mode accretion makes up between 40% and 60% of total gas accretion. As well, we find that cold gas is in general very quickly formed into stars, and that between 40% and 70% of total star mass comes from cold gas accretion.</p> / Master of Science (MSc)

Disturbances impact abiotic and biotic components within forested ecosystems. This dissertation identifies the impacts of recreational crossing disturbances on water quality, uses dendrochronological techniques to estimate sediment deposition and identify impacts hydrology and climate on radial growth in riparian forested wetlands, and quantifies influences of biotic and abiotic factors on the occurrence of frost-induced cambial damage. In southwestern Virginia, modeled soil erosion rates for multiple-use (hiking, mountain biking, and horseback riding) recreational trail approaches to stream crossings were found to be 13 times greater than rates for undisturbed forests. Downstream changes in macroinvertebrate-based indices indicated water quality was negatively affected downstream from culvert and ford crossings. These findings illustrate recreational stream crossings have the potential to deliver sediment into adjacent streams, particularly where best management practices are not being rigorously implemented, and as a result can negatively impact water quality below stream crossings. Impacts of hydrologic regime were apparent on sediment deposition and on green ash (Fraxinus pennsylvanica Marsh.) and water tupelo (Nyssa aquatica L.) radial growth along the Tensaw River in southwest Alabama. Annual dendrogeomorphic sediment accretion rates were significantly greater for a recent time period (25 years) when compared to longer term rates (131 years) along a natural levee and backswamp. Radial growth in green ash along the natural levee and backswamp was found to be significantly correlated with days flooded and average daily stage level during April while water tupelo further in the backswamp appeared resistant to hydrologic and climatic fluctuations. Results illustrate the importance of riparian wetlands in trapping sediment from adjacent waterways and highlight the role hydrologic regime plays in bottomland succession and productivity. Across northern lower Michigan, late spring frost-induced cambial damage in jack pine (Pinus banksiana Lamb.) occurred more frequently in younger trees and in trees with smaller diameters. Biotic and abiotic factors were found to influence the occurrence of earlywood frost rings. Frequent occurrences of frost-rings can be used to identify frost-prone environments and geographical boundaries for plant species. This dissertation bridged gaps in knowledge of recreational, hydrogeomorphic, and climatic disturbances in forested ecosystems which can be used to develop management strategies. / Ph. D.

<p dir="ltr">Recent high-water levels in Lake Michigan caused extensive shoreline changes along the Indiana coastline. To evaluate recent shoreline changes of the Indiana coastline along Lake Michigan, topographic LiDAR surveys available for the years 2008, 2012, 2013, 2018, 2020, and 2022 were analyzed. This study included LiDAR data of over 400 cross-shore transects, generated at 100 m spacing. Beach profiles were generated to detect the shoreline position and quantify beach width and nearshore volume change. The analysis revealed accretion of both shoreline and beach width from 2008 to 2013 during a low water level period. The beach was rebuilt with a median increased value of 4 m. On the contrary, the shoreline eroded during increasing and high-water periods. Both shoreline and beach width receded with median values of 41 m and 32 m respectively during the period of water level increase from 2013 to 2020. Consequently, the beach profiles lost a median sand volume of 21.6 m³/m. Overall, the Indiana shoreline moved with a median of 18 m landward from 2008 to 2022. However, there was a large amount of spatial variability in the shoreline changes. The shoreline movement varied spatially between 63 m recession to 29 m accretion. Similarly, beach profiles showed a loss of median sand volume of 10 m³/m. The volume change ranged from 918 m³/m loss to 296 m³/m accumulation varying spatially along the shoreline. The largest sand loss was experienced at the downdrift of Michigan city harbor near Mt. Baldy. In addition to the spatial variation, the recession also varied slightly with shoreline type. The natural and hardened beaches were mostly recessional. The recession along the hardened shoreline was influenced by the timing of construction and its proximity to inland areas. Buffered beaches, characterized by a swath of vegetation or dunes, experienced the least erosion.</p>

Sediment accumulation and loss were measured in a water tupelo (Nyssa aquatica)- baldcypress (Taxodium distichum) forested wetlandin years 2, 7, 10 and 12 following harvesting disturbance. A 3 X 3 Latin Square design was replicated three times and compared to a psuedo-replicate reference stand (REF). Disturbance treatments were chainsaw fellind of trees with (1) helicopter removal of logs (HELI), (2) helicopter removal of logs followed by a simulated skidder removal (SKID), and helicopter removal of logs follwed by glyphosphate application (GLYPH). Measurements of sediment accretion show little difference between treatments and reference in the first two years following harvest. After two years the harvest treatments accumulate more sediment than the REF. Of the harvest treatments, the GLYPH plots accumulate the greatest quantities of sediment. The difference in sediment accretion between the harvest treatments begins to fade in the 12th year of recovery. Results show that skidder and helicopter removal of logs differ very little in the amount of sediment trapped, while glyphosphate application increased the wetland's ability to trap sediment beginning in the second year. In addition, sediment trappin is associated with herbaceous cover that slows flood waters and allows soil particles to precipitate from flood water. / Master of Science