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 …

---

Modeling The Pleistocene History Of The Greenland Ice Sheet, Benjamin Andrew Keisling

Doctoral Dissertations

---

One of the most profound and immediate consequences of anthropogenic climate change is sea level rise, which in large part is driven by the melting of polar ice sheets. The Greenland Ice Sheet (GrIS) contains enough ice to raise global sea level by ~7 meters. Fluctuations of the GrIS in response to past climate change provide an opportunity to better understanding the stability of the ice sheet during periods of climatic change. In this thesis, we use numerical ice-sheet models to understand the causes and consequences of past fluctuations of the Greenland ice sheet. In Chapters 3 and 4, we …

---

Middle To Late Pleistocene Paleoenvironmental Reconstructions From Lake El'gygytgyn, Arctic Russia, Mary Helen Habicht

Doctoral Dissertations

---

Climate change is a major issue challenging the world today. Our global society faces rising temperatures, variable weather patterns, and rising sea level among other associated issues. Our action (or inaction) to address current changes will have serious ramifications for life on our planet in the coming centuries and millennia. In order to provide context for these present and future changes, we can utilize the paleo record to understand the natural variability of Earth’s climate system. One region of the world is changing more rapidly than the global average. Over recent decades, the Arctic has experienced warmer temperatures, reduced sea …

---

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 …

---

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

ARCTIC AND NORTH ATLANTIC PALEO-ENVIRONMENTAL RECONSTRUCTIONS FROM LAKE SEDIMENTS MAY 2017 GREGORY A. DE WET, B.Sc., BATES COLLEGE M.Sc., UNIVERSITY OF MASSSCHUSETTS, AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS, AMHERST Directed by: Drs. Raymond S. Bradley and Isla S. Castañeda There are few fields in the discipline of Earth Science that hold more relevancy in 2017 than studies of earth’s climate. Called the “perfect problem” considering its complexity and magnitude, climate change will continue to be one of the greatest challenges humanity will face in the 21^st century. And while numerical models provide valuable information on conditions in the future, …

---