Modeling Spatial Distributions Of Tidal Marsh Blue Carbon Using Morphometric Parameters From Lidar, Bonnie Turek

Masters Theses

Tidal marshes serve as important “blue carbon” ecosystems that accrete large amounts of carbon with limited area. While much attention has been paid to the spatial variability of sedimentation within salt marshes, less work has been done to characterize spatial variability in marsh carbon density. Driven by tidal inundation, surface topography, and sediment supply, soil properties in marshes vary spatially with several parameters, including marsh platform elevation and proximity to the marsh edge and tidal creek network. We used lidar to extract these morphometric parameters from tidal marshes to map soil organic carbon (SOC) at the meter scale. Fixed volume …

Geomorphology Of Tidal Wetlands: Impacts Of Extreme And Annual Flood Events To Salt Marsh And Mangrove Systems, Frances R. Griswold

Doctoral Dissertations

Tidal wetlands are vital for buffering coastal settings from the threats of accelerated sea level rise and storms. Understanding the factors that are most influential for the maintenance and recovery of tidal wetlands after extreme events compounded by future accelerated sea level rise is of the utmost importance, yet this knowledge is not well established. Two tidal wetland schemas investigated in this dissertation are mangrove systems in Vieques, Puerto Rico (including robust lagoonal-mangrove forest systems and fringing mangrove forests), and salt marshes in New England. While the climatic forcings, vegetation type, and locations are vastly different for these two tidal …

Identifying New Invasives In The Face Of Climate Change: A Focus On Sleeper Populations, Ayodelé C. O'Uhuru

Masters Theses

Sleeper populations are established populations of a non-native species whose population growth is limited by one or more abiotic or biotic conditions, such as climate change. While the northeastern US is predicted to be a hotspot for future invasions, identifying potential sleeper populations before they become invasive can inform proactive, climate-smart invasive species management. I focused on 169 introduced species that are established in one or more northeastern states. I used the Environmental Impact Classification for Alien Taxa (EICAT) framework to systematically identify and review the peer-reviewed literature for these candidate species to quantify their negative ecological and socioeconomic impacts. …

The Global Impact Of The Antarctic Ice Sheet In A Warming World: Using Numerical Modeling And Critical Physical Geography To Assess Climate Change, Sea Level Rise, And Climate Justice

Doctoral Dissertations

Anthropogenic climate change is causing disruptions in the Earth system with negative ramifications for life on our planet. Increasing atmospheric greenhouse gas concentrations lead to accumulated heat content and the cryosphere is one of the earliest places to show changes in response to rising temperatures. The melting of the Antarctic Ice Sheet will have myriad effects on global climate due to interconnections and feedbacks between the ice sheet, ocean, and atmosphere. In this dissertation I use numerical modeling and critical geography to assess future climate conditions that occur in response to changes in Antarctic Ice Sheet melt as well as …

Antarctic Ice Sheet Stability During Warm Periods: Integrating Numerical Modeling With Geologic Data, Anna Ruth W. Halberstadt

Doctoral Dissertations

Sea level rise is one of the major social and environmental challenges that threatens modern civilization, yet the response of polar ice sheets to future warming is deeply uncertain. Mass loss from the Antarctic Ice Sheet is projected to dominate global sea level rise in the near future, but how much, and when, remains a key unknown. The challenges associated with projecting Antarctica’s future sea level contribution are derived from a knowledge gap of physical ice sheet processes in a world warmer than today, and a lack of understanding of climatic thresholds that drive potentially irreversible retreat. Future and even …

X-Band Phased-Array Weather-Radar Polarimetry Testbed, William Heberling Iv

Doctoral Dissertations

Phased-array weather radar have potential to replace reflector dish radar in major weather radar networks such as NEXRAD, providing faster update times and greater scan flexibility. However, the use of electronic scanning introduces polarization errors on weather radar measurables, requiring polarimetric bias calibration. The sources of polarimetric bias have been described theoretically, but experimental verification is still limited. Additionally, no standard method of calibration for polarimetric bias exists for phased-arrays. Therefore, the University of Massachusetts Amherst (UMass) presents a fully operational X-Band phased-array weather radar polarimetric testbed. The testbed evaluates the calibration of a planar dual-polarization X-band phased-array radar through …

Coastal Groundwater Catchments Of The Gulf Of Alaska, Aeon Russo

Masters Theses

High latitude mountain environments are experiencing disproportionately adverse effects in a currently changing climate. The Gulf of Alaska (GoA) region is an exemplar of this. Dramatic shifts are occurring in the region’s freshwater reservoirs as glaciers retreat more with each passing year. Research in the region places much focus on observing and predicting climate driven shifts in glacier mass balance, surface discharge, and associated nutrient fluxes to the ocean. On the other hand, coastal groundwater discharge (CGD) is given very little attention. Global and near-global estimates of CGD indicate variable results spanning an order of magnitude. Focusing on regionally specific …

The Role Of Agulhas Leakage In Pliocene Climate Change, Neil Patel

Doctoral Dissertations

The late Pliocene (2.6-3.3 Myr) was an epoch of gradual cooling, with expanding Antarctic ice sheets and sea ice preceding a general Northern Hemisphere glaciation. A decline in the strength of the Atlantic Meridional Circulation (AMOC) in the late Pliocene may have decreased Southern Hemisphere oceanic heat transport into the Northern Hemisphere; pre-conditioning it for glaciation. A common explanation for a weakening of the AMOC in paleoclimate is freshwater forcing into the North Atlantic. In this thesis, I posit that a northward shift in the Southern Hemisphere westerlies in the late Pliocene, due to an expanded Antarctic ice sheet, weakens …

Numerical Climate Model Simulations Investigating The Role Of Arctic Sea Ice Export Events In Modulating Deglacial Climate, Anthony J. Joyce

Doctoral Dissertations

Periods of abrupt climate cooling during the last deglaciation (20,000-8,000 yrs ago) are often attributed to glacial outburst floods slowing the Atlantic meridional overturning circulation (AMOC). Yet, despite over 40 years of research, conclusive evidence that such events significantly impact climate remains elusive. This study uses a climate model to investigate an alternative freshwater forcing mechanism in which the episodic break-up and mobilization of thick perennial Arctic sea ice might have disrupted large-scale climate. The results presented here show the first evidence that (1) the Arctic Ocean stored enormous volumes of freshwater during colder periods as thick masses of sea …

Hydrologic Structure And Function Of Vernal Pools In South Deerfield, Massachusetts, Charlotte Axthelm

Masters Theses

Vernal pools are small, ephemeral wetlands lacking an inlet or outlet. These wetlands, also known as seasonal pools, are found in a wide range of biomes, and their characteristics vary based on location. While the vegetation of western U.S. pools, and amphibians of eastern U.S. pools have been extensively studied, many aspects of vernal pools have not been fully characterized. In particular, although the general seasonal wetting and drying cycle is understood qualitatively, few studies have attempted to quantify the hydrological regime of vernal pools in New England. As water level variation drives many, if not all, of the characteristics …

A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood

Doctoral Dissertations

Homogeneous sheared and stably stratified turbulence is considered as a fundamental flow relevant to the study of geophysical turbulence and, generally, anisotropic turbulence. Numerical experiments are performed via high resolution direct numerical simulation (DNS) in a geophysically-relevant parameter space previously inaccessible to simulation. Turbulent dynamics relevant to the modeling of geophysical hydrodynamics are investigated as a function of mean flow and fluid parameters. An active tuning scheme is implemented to induce temporally stationary turbulent kinetic energy in order to evaluate turbulence that is statistically independent of initial conditions and spatio-temporally homogeneous. Subject to this constraint, the parametric dependence of the …

Wildfires In The Northeastern United States: Evaluating Fire Occurrence And Risk In The Past, Present, And Future, Daniel R. Miller

Doctoral Dissertations

Climate change is one of the most complex and challenging issues facing the world today. A changing climate will affect humankind in many ways and alter our physical environment, presenting ethical challenges in how we respond. The impact of climate change will likely be exacerbated in heavily populated regions of the planet, such as the Northeastern United States (NEUS). The NEUS is comprised of complex, sprawling urban centers and rural regions, both of which are vital to the economic and cultural character of the region. Furthermore, both urban and rural areas in the NEUS contain communities that have been historically …

Mid-Pliocene To Early Pleistocene Sea Surface And Land Temperature History Of Nw Australia Based On Organic Geochemical Proxies From Site U1463, Rebecca Smith

Masters Theses

Ocean gateways facilitate water circulation between ocean basins, and therefore directly impact thermohaline circulation and global climate. In order to better predict the effects of future climate change, it is critical to constrain past changes in ocean gateway behavior, and corresponding changes in thermohaline circulation, particularly during analogue periods for modern climate change. The Indonesian Throughflow (ITF) is a primary ocean gateway and vital component of the global conveyor that transports water from the Pacific Ocean into the Indian Ocean, however due to a lack of long and continuous sedimentary records from locations under its influence, changes in ITF behavior …

Eccentricity Modulation Of Precessional Variation In The Earth’S Climate Response To Astronomical Forcing: A Solution To The 41-Kyr Mystery, Rajarshi Roychowdhury

Doctoral Dissertations

The 41,000-year variability of Earth’s glacial cycles during the late Pliocene-early Pleistocene is usually attributed to variations in Earth’s obliquity (axial tilt). However, a satisfactory explanation for the lack of precessional variation in marine d¹⁸O records, a proxy for ocean temperature and ice-volume, remains contested. Here, a physically based climate model is used to show that the climatic effect of precession is muted in global isotope records due to two different mechanisms, with each dominating as a function of eccentricity. At low eccentricities (e0.019), the time-integrated summer insolation and number of positive degree-days impacting ice sheets varies at …

Arctic And North Atlantic Paleo-Environmental Reconstructions From Lake Sediments, Gregory A. De Wet

Doctoral Dissertations

ABSTRACT

Juvenile River Herring In Freshwater Lakes: Sampling Approaches For Evaluating Growth And Survival, Matthew T. Devine

Masters Theses

River herring, collectively alewives (Alosa pseudoharengus) and blueback herring (A. aestivalis), have experienced substantial population declines over the past five decades due in large part to overfishing, combined with other sources of mortality, and disrupted access to critical freshwater spawning habitats. Anadromous river herring populations are currently assessed by counting adults in rivers during upstream spawning migrations, but no field-based assessment methods exist for estimating juvenile densities in freshwater nursery habitats. Counts of 4-year-old migrating adults are variable and prevent understanding about how mortality acts on different life stages prior to returning to spawn (e.g., juveniles …

Ecological Consequences Of Lost Anadromous Forage Fish In Freshwater Ecosystems, Steven R. Mattocks

Masters Theses

Beginning in the early 1600s, dam construction in New England obstructed anadromous fish access to spawning grounds during migration. As a result, anadromous forage fish populations have declined, which has impacted freshwater, marine, and terrestrial ecosystems. To determine the impacts of dams on anadromous forage fish and freshwater ecosystems, I used historical and current data to estimate population changes in alewives (Alosa pseudoharengus) from 1600-1900. A significant reduction in spawning habitat occurred in New England as a result of 1,642 dams constructed between 1600 and 1900, resulting in 14.8% and 16.6% lake and stream habitat remaining by 1900, …

Ocean Gateways And Glaciation: Planktic Foraminiferal Records From The Southern Ocean, Equatorial Pacific, And Caribbean, Andrew J. Fraass

Doctoral Dissertations

Ocean gateway changes, once the best mechanism for driving abrupt climatic change, have fallen from favor. They have been largely replaced within the literature by changes in CO₂ concentration and orbital forcing. This dissertation looks at three intervals of relative stability (Oligocene), prolonged change (Plio-Pleistocene), or transient events (Oligocene/Miocene boundary) in order to better understand the oceanographic circumstances which govern ‘events’ in the paleoceanographic record. Chapter 1 discusses the chronostratigraphy of Integrated Ocean Drilling Program (IODP) Site U1396 (Expedition 340) in the Caribbean Sea. A combination of paleomagnetostratigraphy, biostratigraphy, astrochronology, and correlation to Marine Isotope Stages (MIS) allows a …

A Paleobathymetric Model And Evolution Of The Brazilian Marginal Basins During The Late Maastrichtian To Eocene Based On Benthic Foraminiferal Biofacies, Renata Moura De Mello

Doctoral Dissertations

Benthic foraminiferal biofacies were delimited for the Maastichtian to upper Eocene of five Brazilian marginal basins (Sergipe-Alagoas, Mucuri, Campos, Santos and Pelotas) and two DSDP Sites 356 and 20C of the western South Altantic. Five biofacies, denoted with letters A to E, were defined using Q-mode cluster analysis and correspondence analysis for all of the 11 sites. The benthic foraminiferal biofacies were used to establish a paleobathymetric and paleoenvironmental model for the Brazilian marginal basins. The model tracks the evolution of the margin as it built seaward and transitioned from abyssal (2000-3000 m) to bathyal (m) and neritic (m) depositional …

Using Digital Elevation Models Derived From Airborne Lidar And Other Remote Sensing Data To Model Channel Networks And Estimate Fluvial Geomorphological Metrics, Noah Slovin

Masters Theses

Recent advances in remote-sensing technologies and analysis methods, specifically airborne-LiDAR elevation data and corresponding geographical information system (GIS) tools, present new opportunities for automated and rapid fluvial geomorphic (FGM) assessments that can cover entire watersheds. In this thesis, semi-automated GIS tools are used to extract channel centerlines and bankfull width values from digital elevation models (DEM) for five New England watersheds. For each study site, four centerlines are mapped. LiDAR and NED lines are delineated using ArcGIS spatial analyst tools with high-resolution (1-m to 2-m) LiDAR DEMs or USGS National Elevation Dataset (NED) DEMs, respectively. Resampled LiDAR decreases LiDAR DEM …

A High-Resolution Paleoenvironmental And Paleoclimatic History Of Extreme Events On The Laminated Sediment Record From Basin Pond, Fayette, Maine, U.S.A., Daniel R. Miller

Masters Theses

Future impacts from climate change can be better understood by placing modern climate trends into perspective through extension of the short instrumental records of climate variability. This is especially true for extreme climatic events, such as extreme precipitation and wildfires, as the period of instrumental records provides only a few examples and these have likely have been influenced by anthropogenic warming. Multi-parameter records showing the past range of climate variability can be obtained from lakes. Lakes are particularly good recorders of climate variability because sediment from the surrounding environment accumulates in lakes, making them sensitive recorders of climate variability and …

Analysis Of The Impact Of Technological Change On The Cost Of Achieving Climate Change Mitigation Targets, Robert W. Barron

Doctoral Dissertations

There is widespread consensus that low carbon energy technologies will play a key role in the future global energy system. Many of the low-carbon technologies under consideration are not yet commercially available, and their ultimate value depends on a host of deeply uncertain socioeconomic, environmental, and technological considerations. While it is clear that significant investment in the energy system is needed, the optimal allocation of these investments is unclear. This dissertation develops a methodology for (1) analyzing the impact of low carbon energy technologies on the cost of meeting emission reduction targets (policy cost) and (2) using this information to …

Sediment Records From Coastal Ponds: Temporal Archives Of Storm Inundation And Environmental Change, Christine M. Brandon

Doctoral Dissertations

Hurricanes are powerful storms that can cause billions of dollars in damage and kill many people when they strike populated coastal areas. Understanding how frequently coastal cities can expect storms of a certain magnitude would help inform more effective mitigation and adaptation strategies. Unfortunately, current estimates of hurricane frequency rely on numerical models based on weather observations that, on the east coast of the United States, only extend ~150 years into the past. While this is sufficient for estimating the characteristics (i.e. wind speed and storm surge height) of annual or decadal storms, the properties of larger, rarer, and more …

Dissolution, Ocean Acidification And Biotic Extinctions Prior To The Cretaceous/Paleogene (K/Pg) Boundary In The Tropical Pacific, Serena Dameron

Masters Theses

The several million years preceding the Cretaceous/Paleogene (K/Pg) boundary has been the focus of many studies. Changes in ocean circulation and sea level, extinctions, and major volcanic events have all been documented for this interval. Important research questions these changes raise include the climate dynamics during the warm, but not hot, time after the decay of the Late Cretaceous greenhouse interval and the stability of ecosystems prior to the mass extinctions at the end-Cretaceous.

I document several biotic perturbations as well as changes in ocean circulation during the Maastrichtian stage of the latest Cretaceous that question whether the biosphere was …

X-Band Dual Polarization Phased-Array Radar For Meteorological Applications, Krzysztof Orzel

Doctoral Dissertations

This dissertation details the development and operation of a novel dual-polarized Phase-Tilt Weather Radar (PTWR) designed for meteorological applications. The use of radar has a well-documented history in detection and classification of weather phenomena, but due to the limited mechanical scanning speed, its usage for severe weather observations remains far from ideal. The PTWR utilizes phased-array technology and provides unique capabilities such as smart scanning, fast scan update, and tracking. This technology is considered a candidate for a replacement and consolidation of the current US weather and surveillance radar networks. The dissertation can be divided into three parts. First, the …

Cultivating Communities Of Practice To Develop Local Preparedness For Climate Change, Konda Reddy Chavva

Doctoral Dissertations

The goal of this research was to study the effectiveness of field facilitators’ (FFs) community of practice in improving ways in which FFs and farmers communicate and work together to strengthen farmers’ climate change preparedness through identifying locally suitable adaptation strategies in drought-prone districts of Andhra Pradesh State in India. In development initiatives like the one studied, FFs are often the key liaison person with each community—farmers in this case. FFs interact regularly with farmers, with whom they establish and sustain critical relationships over time. Further, they take the lead in building farmers’ capacities by contextualizing technical information that professionals …

Sedimentological, Geochemical And Isotopic Evidence For The Establishment Of Modern Circulation Through The Bering Strait And Depositional Environment History Of The Bering And Chukchi Seas During The Last Deglaciation, Ben M. Pelto

Masters Theses

Sea level regression during the Last Glacial Maximum exposed the Bering Land Bridge, and cut off the connection between the North Pacific and Arctic Ocean, ending the exchange of North Pacific Water through the Bering Strait. Exchange of North Pacific Water comprises a major portion of fresh water input to the Arctic Ocean, and is of vital importance to North Atlantic Deep Water formation, a vital component of Atlantic Meridional Overturning Circulation. Bering Strait throughflow thus plays an integral role in global climate stability. A suite of four cores was selected, three in the Bering Sea and one in the …

Uncertainty In Climatic Change Impacts On Multiscale Watershed Systems, Olga V. Tsvetkova

Open Access Dissertations

Uncertainty in climate change plays a major role in watershed systems. The increase in variability and intensity in temperature and precipitation affects hydrologic cycle in spatial and temporal dimensions. Predicting uncertainty in climate change impacts on watershed systems can help to understand future climate-induced risk on watershed systems and is essential for designing policies for mitigation and adaptation. Modeling the temporal patterns of uncertainties is assessed in the New England region for temperature and precipitation patterns over a long term. The regional uncertainty is modeled using Python scripting and GIS to analyze spatial patterns of climate change uncertainties over space …