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Articles 1 - 10 of 10
Full-Text Articles in Physical Sciences and Mathematics
A Bayesian Inversion For Emissions And Export Productivity Across The End-Cretaceous Boundary, Alexander A. Cox
A Bayesian Inversion For Emissions And Export Productivity Across The End-Cretaceous Boundary, Alexander A. Cox
Dartmouth College Master’s Theses
The end-Cretaceous mass extinction was marked by both the Chicxulub impact and the ongoing emplacement of the Deccan Traps flood basalt province. Both of these events perturbed the environment by the emission of climate-active volatiles, primarily CO2 and SO2. To understand the mechanism of extinction, we must disentangle the timing, duration, and intensity of volcanic and meteoritic environmental forcings. In this thesis, we used a parallel Markov chain Monte Carlo approach to invert for the aforementioned volatile emissions, export productivity, and remineralization from 67 to 65 million years ago using the LOSCAR (Long-term Ocean-atmosphere-Sediment CArbon cycle Reservoir) model. The parallel …
Parameterization Of Cryosat-2 Radar Waveforms Across The Greenland Ice Sheet, Alexander Clark Ronan
Parameterization Of Cryosat-2 Radar Waveforms Across The Greenland Ice Sheet, Alexander Clark Ronan
Dartmouth College Master’s Theses
Geodetic surface mass balance calculations regularly rely on satellite radar altimeters such as CryoSat-2 to understand elevation and volume changes of the Greenland Ice Sheet (GrIS). However, the impact of changing GrIS shallow subsurface stratigraphic conditions on CryoSat-2 elevation products is poorly understood. We seek to investigate the long-term impacts of changing surface and shallow subsurface conditions on CryoSat-2 Level 2 elevation products derived from the Offset Center of Gravity (OCOG), Ocean - Customer Furnished Item (CFI), and University College London (UCL) Land-Ice retracking algorithms through the analysis of radar waveform characteristics. We further investigate time series from 2010 to …
The Flow Of Power: Addressing Asymmetric Flood Risk In The Upper Valley, Eric Vr Hryniewicz
The Flow Of Power: Addressing Asymmetric Flood Risk In The Upper Valley, Eric Vr Hryniewicz
Geography Undergraduate Senior Theses
Floods are the most damaging natural disasters in America. Land use change in upland watersheds can increase the probability and severity of floods (Bronstert, Niehoff, & Burger, 2002). When watersheds are divided by political and private property boundaries it leads to a misalignment of incentives in which downstream users lack recourse for upstream land use decisions contributing to flood risk. In this thesis, researchers interrogate the attributes of town officials and towns that determine what motivates town governments to act on flooding and what motivates and enables town officials to collaborate on planning and how do they collaborate in practice. …
Downstream Gradients In Unit Stream Power Influence Log Jam Location And Process Domain, Eliza H. Malakoff
Downstream Gradients In Unit Stream Power Influence Log Jam Location And Process Domain, Eliza H. Malakoff
Dartmouth College Master’s Theses
Growing calls for the use of natural materials and processes to meet management goals have positioned artificial log jams as a compelling alternative to hard engineering instream and floodplain habitat. Deep uncertainties remain, however, about where and how wood should be placed to best mimic natural river processes. In this study, I test whether at-a-point or downstream gradients in unit stream power, an estimate of a river’s ability to do work, exert control over where and how log jams form. Using field observations of 360 log jams in New Hampshire and Vermont and an additional 320 previously published locations of …
Integrating Remote And In-Situ Techniques To Quantify Landscape Evolution, Matthew Maclay
Integrating Remote And In-Situ Techniques To Quantify Landscape Evolution, Matthew Maclay
Dartmouth College Master’s Theses
With the increasing availability and resolution of remote sensing techniques, the resulting data products are increasingly being applied to answer societally relevant questions regarding quantifying the effects of climate change, mitigating natural hazards, and understanding landscape changes over varying temporal and spatial scales. While the power and potential for such large-scale, efficient, and cost-effective surveys are undeniable, a thorough understanding of any environment requires that remotely sensed data are ground-truthed or put into context with in-situ observations. In this thesis, Chapter 1 presents a literature review of Martian analog sites and discusses the importance of integrating in-situ and remote sensing …
Wildfire Activity, Climate Response, And Ice Core Signal Preservation In The North Pacific Region, Margaret Lonergan
Wildfire Activity, Climate Response, And Ice Core Signal Preservation In The North Pacific Region, Margaret Lonergan
Dartmouth College Master’s Theses
Wildfires have become more destructive over recent decades with climate change, so understanding how fire regimes will change with further climate change is critical for effective fire management practices. Paleofire records provide insight into how fire regimes have responded to temperature and precipitation variability in the past. Ice cores, such as the Denali ice core from central Alaska, capture regional-scale fire proxies including black carbon at an annual resolution for centuries to millennia. This makes them ideally suited to construct high temporal resolution, regional paleofire records extending back into the Common Era. However, it is critical to understand the instrumental …
Timing And Source Of Water Supporting Early Lakes In The Xanthe Terra Region Of Mars, Noemi A. Ortega Dominguez
Timing And Source Of Water Supporting Early Lakes In The Xanthe Terra Region Of Mars, Noemi A. Ortega Dominguez
Dartmouth College Master’s Theses
Whether an ancient ocean existed on Mars remains controversial. Modeling of Mars’ early climate indicates a dry and cold environment; meanwhile geologic evidence supports a wet and warm environment that potentially hosted a globally connected aquifer with a northern ocean. One geomorphic line of evidence in support of persistent standing water and a northern ocean are inferred deltaic deposits along and near the Mars dichotomy boundary. However, not all these deltaic deposits appear to have consistent delta front elevations, and many are within craters, calling into question whether these deposits formed within the same body of water or even at …
Oh The Places Snow Blows: Observations And Impacts Of Snow Redistribution On Arctic Sea Ice, David Clemens-Sewall
Oh The Places Snow Blows: Observations And Impacts Of Snow Redistribution On Arctic Sea Ice, David Clemens-Sewall
Dartmouth College Ph.D Dissertations
Arctic sea ice has declined dramatically due to climate change. This decline impacts Arctic communities, ecosystems, international trade, and the world's climate. However, due to uncertain physical processes, climate models generally do not capture the severity of the observed decline---adding uncertainty to projections of future climate change. A major uncertainty in the Arctic sea ice component of climate models is how much heat passes through the snow on top of the ice in the winter. This heat flux controls how much ice grows each winter, impacting how much ice survives the summer melt. Snow is an excellent thermal insulator (about …
The Impact Of Contact Geometry On Sea Ice Stress And Fracture At The Scale Of Ice Floes, Michael J. May
The Impact Of Contact Geometry On Sea Ice Stress And Fracture At The Scale Of Ice Floes, Michael J. May
Dartmouth College Master’s Theses
Observations of stress and strain at the scale of ice floes are necessary to fill a gap in our understanding of sea ice mechanical behavior. Current climate and ice dynamics models represent ice mechanical properties using stress-strain relationships largely determined at laboratory-scale (<1m) or from regional-scale (10+km) deformation observations. The former scale does not include all mechanisms of deformation operating in the ice pack; the latter aggregates multiple modes of deformation into non-physical fluid analogies. The Sea Ice Dynamics Experiment (SIDEx) was run in Feb-Mar 2021 to fill this gap, observing stress and strain at the scale of sea ice failure processes. Here we present stress sensor observations. Stress gages (N=31) were deployed over a 4.5km2 area in the southern Beaufort Sea to observe in-situ stress. These data were analyzed in the context of deformation observations from satellite imagery and local laser and radar interferometers to explain the drivers of sea ice stress variations before and after fracture. Three case studies between 14 March and 24 March, during which fractures propagated through …
Geomorphic And Paleoclimatic Implications Of Glacial Extent Records In The Sierra Nevada Del Cocuy, Colombia During Termination 1, Jordan Nickerson Herbert
Geomorphic And Paleoclimatic Implications Of Glacial Extent Records In The Sierra Nevada Del Cocuy, Colombia During Termination 1, Jordan Nickerson Herbert
Dartmouth College Master’s Theses
Reconstructions of past glacial extents using geomorphic mapping and cosmogenic dating provide an opportunity to infer past climates. A record of the past extents of tropical mountain glaciers is particularly useful because there are few other means to reconstruct past temperatures in high-altitude, low-latitude locations. The tropics play an outsized role in mediating global climate, yet there is a lack of understanding of how the tropics may have influenced past climate changes such as the most recent deglaciation (Termination 1, ~18–11.7 ka). Improving reconstructions of tropical mountain glaciers will aid in understanding the role of the tropics in the global …