Understanding how the latitudinal distribution of methane sources changed between stadial and interstadial climate states during the last glacial period can provide important clues about how terrestrial hydroclimate and ecosystems evolved between these different states. The punctuation of the millennial-scale structure by Heinrich events is also of interest in this...
The South Pole ice core (SPC14), drilled in the field seasons of 2014/2015 and 2015/2016, is an intermediate length, 1,751-m ice core which preserves a 54,000-year record of past climate and atmospheric composition. The SPC14 ice core adds to the spatial grid of ice cores in Antarctica extending into the...
Nitrous oxide is an important greenhouse gas that has both natural and anthropogenic sources in the modern atmosphere (Ciais et al., 2013). This project expanded the knowledge of the history of atmospheric N2O in the geologic past by measuring N2O concentrations in air trapped in very old polar ice. A...
New ice cores retrieved from the Taylor Glacier (Antarctica) blue ice area contain ice and air spanning the Marine Isotope Stage (MIS) 5/4 transition, a period of global cooling and ice sheet expansion. Chronologies were determined for the ice and air bubbles in the new ice cores by visually matching...
Methane is a product of biogeochemical processes which respond to changes in climate. The history of atmospheric methane is recorded by ice cores providing insight into past changes in these biogeochemical processes. This dissertation is comprised of three studies which focus on centennial- and millenial-scale variability of methane from ice...
For many years, scientists worldwide have been using glacial ice to reconstruct and study Earth’s past climates. While the most continuous records we have are from sites near both poles, there is also mid-latitude perennial ice in the form of mountain glaciers and cave ice. Very little is known about...
The three studies that comprise this dissertation seek to answer significant
questions in paleoclimatology through unconventional applications of ice core
greenhouse gas data. These studies involve different gases and span the interval of time
between the Last Glacial Maximum and the Industrial Revolution, but are united by their
nontraditional use...
The exchange of carbon on earth is one of the fundamental processes that sustains life and regulates climate. Since the onset of the Industrial Revolution, the burning of fossil fuels and anthropogenic land conversion have altered the carbon cycle, increasing carbon dioxide in the atmosphere to levels that are unprecedented...
Ice cores are considered the gold standard for recording past climate and biogeochemical changes. However, gas records derived from ice core analysis have until now been largely limited to centennial and longer timescales because sufficient temporal resolution and analytical precision have been lacking, except during rare times when atmospheric concentrations...
This thesis focuses on the application of the cosmogenic nuclide Beryllium-10 (10Be) in an effort to better constrain the thickness history of the Fennoscandian Ice Sheet (FIS) at the Last Glacial Maximum (LGM) and into the Holocene, as well as begin to answer the long-standing question regarding the age
and...
This thesis focuses on the investigation of extraterrestrial tracers Ir, Pt and 3He in polar ice cores. These tracers may be used to identify characteristics of interplanetary dust particles, and to quantify the flux of extraterrestrial material during impact events, certain volcanic eruptions, and stable background periods. In the first...
Chemically defined liquid media were devised which supported
excellent growth of Taphrina cerasi and T. deformans. When grown
in fermentation culture vessels, T. cerasi and T. deformans released
cytokinins into the liquid media. The presence of these cell division
factors was demonstrated with the soybean tissue assay which is
specific...
The teliospore of Tilletia caries germinates to produce a promycelium
with a whorl of primary sporidia at its tip. The time between
emergence of the promycelium and the development of primary sporidia
averaged 2.3 h. Fusion between compatible sporidia occurred within
an additional 3.8 h. Primary sporidia appeared to be...