Thesis advisor: Noah P. Snyder / Multi-temporal elevation (MTE) analysis is used to study topographic changes at specific intervals. Barrier-island complexes are often studied using this MTE analysis to quantify changes to the environment after hurricanes to understand how dynamic landscapes respond to different forcings. The Sandy Pond spit (SPS) is a north-south trending barrier island on the eastern shore of Lake Ontario, New York, which responds dynamically to fluctuations in water levels, ice cover, and storms. Prior research reconstructed the geomorphic history of the SPS from 1878-2013, determining that the most significant factor affecting decadal change is the lake-water elevation. In the summers of 2017 and 2019, anomalously high precipitation and lake levels resulted in increased erosion along the SPS, and flooding in neighboring communities. In this study I used shoreline position, foredune crest position and elevation and volume of deposition and erosion to determine the dominant force of geometric change on the SPS before, during and after the high water events in 2017 and 2019, using the study period 2001-2020. Lidar data and small uncrewed aerial system images are used to generate digital elevation models (DEMs) and DEMs of difference (DoDs) from surveys conducted in May 2001, July 2007, June 2011, October 2015, May 2018, September 2018, July 2020 and August 2020. Results indicated water level was the most significant factor altering the topography of the SPS. Large storm events although erosive, were not as destructive to the shore environment as the long duration elevated summer water levels. From 2001-2015 the shoreline advanced an average of 0.25 m/year. From 2015-2018 and 2018-2020 the shoreline retreated 0.62 m/year, and 3.27 m/year respectively. The foredune position and elevation altered due to erosion of the dune toe caused by wave action and shoreline retreat from 2015-2020 compared to 2001-2015. To study volumetric changes, the SPS was split into seven ecogeomorphic zones that characterize the barrier-spit system at large. From 2007-2015 net deposition was recorded at five of the seven zones when applying a 95% confidence interval. The zones recording erosion were characterized by high dune complexes with sparse vegetation to anchor sand. From 2015-2018 net erosion was recorded in all seven zones, indicating water level had a statistically significant effect on the rate and volume of geomorphic change to this ecosystem. / Thesis (MS) — Boston College, 2022. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Indiana University-Purdue University Indianapolis (IUPUI) / Paleoclimate records from North and South America were used to develop a holistic understanding of global paleo-hydroclimatic drivers across a range of boundary conditions. Here, geophysical analysis of lacustrine sediment stratigraphy at Lago de Tota, Boyaca, Colombia provided evidence for significant lake-level fluctuations through the late Quaternary and produced a record that potentially spans the last 60 ka. Seismic data revealed a series of off-lap and on-lap sequences in the upper ~20 m of sediments that indicated large amplitude changes in lake-level, driven by variability in the mean latitude of the Intertropical Convergence Zone as controlled by insolation- and ocean circulation-driven hemispheric temperature gradients during glacial/stadial and interglacial/interstadial events. In North America, late Holocene flood recurrence in the Midwest and Holocene changes in the mean latitude of the polar front jet stream were investigated through multi-proxy examinations of sediment cores collected from swale lakes in northern Kentucky and southern Indiana, and a glacially formed kettle lake in northern Indiana. These results showed that the midlatitude jet stream was displaced to the south during the late Holocene, which increased the amount of Midwestern precipitation sourced from the northern Pacific and Arctic, especially during prolonged cool conditions. During these cool periods, when atmospheric flow was meridional and a greater amount of precipitation was delivered from the northerly sources, Ohio River flooding increased. During warm conditions, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Midwest, flooding on the Ohio River decreased. At present, streamflow in the Midwest is demonstrated here to be generally increasing, despite atmospheric conditions typically associated with reduced streamflow in the paleo-record, due in part to increasing precipitation and modern land-use dynamics. Together, these studies demonstrate the sensitivity and vulnerability of local-scale hydrological processes to synoptic climate change.

The Henry Mountains from the standpoint of plant geography are among the most interesting in the Rocky Mountain Region for they are entirely surrounded by desert and their unique location results in an intermingling of southern , eastern , and northern forms in the flora of this vicinity . In spite of these facts very little collecting or floral study has been done here and the Henry Mountains are still almost unknown floristically . This is unfortunate for much of the original vegetation has changed due to overgrazing by sheep . This preliminary study was undertaken with the view of obtaining a knowledge of the floristics of this region before still greater changes take place. This report is based upon a visit made to this region extending from June 15th to August 15th of 1930 and from April 31st to May 4th of 1931 . Most of the collecting and observations were confined to Mount Ellen, the northern-most peak of the range .

Landsystem analysis is a commonly applied methodology which focuses on process-form relationships when applied in glacial environments. It can be used to understand and recreate the geomorphological evolution of glacial deposits from modern and ancient sediments. The purpose of this study is to examine the forefields of three closely located outlet glaciers of the Vatnajökull Ice Cap in southeast Iceland to determine the factors affecting the landsystems of these glaciers. A combination of digital based methods and field work focusing on geomorphology and sedimentology were used to define the landsystems. A classification code and associated symbology was used in this study to create consistency of landsystem analysis and can be used in future similar studies of glacial environments. The three glaciers, Morsárjökull, Skaftafellsjökull and Svínafellsjökull were chosen due to their shared source and close proximity, lying within adjacent valleys. The historical changes of the three glaciers have been well documented with aerial photographs, historical maps and glacier margin measurements. LiDAR were used to interpolate 2 m digital elevation models (DEM) of the three glacier forefields. These glaciers have varying topography, bedrock type and ice distribution (hypsometry, equilibrium line altitude (ELA)) which impacts the deposition at the glacier margin. The forefields of Morsárjökull and Skaftafellsjökull exhibit many similarities in the distribution and scale of landforms similar to the characteristics of the established active temperate landsystem commonly found in Iceland. However, the forefield of Svínafellsjökull has many differences compared to Skaftafellsjökull and Morsárjökull in the scale, type and distribution of landforms and sediments. Bedrock type, hypsometry and glacial debris content are major factors that influence differences in these landsystems. These three forefields may be used as analogues to enhance understanding of paleoenvironmental conditions that existed along the southern margin of Pleistocene glaciers that covered much of northern North America and Europe in the past. / Thesis / Master of Science (MSc)

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