Thesis--Wisconsin. / Includes bibliographical references (leaves 105-110).

Glaciation/deglaciation is one of the most extreme and fundamental climatic events in Earth's history. The origin of the glacial-interglacial cycles has been explored for more than a century and the astronomical theory is now well established. However, the mechanism that links the astronomical forcing to the geological record in the Earth's climate system is poorly understood. In this thesis, aspects of the last glacial termination and the last glacial inception, are studied. First, the response of ocean's thermohaline circulation to changes in orbital geometry and atmospheric CO2 concentration in the last glacial termination is investigated using a coupled climate (atmosphere-ocean-sea ice) model. It is shown that the thermohaline circulation is affected by both orbital and CO2 forcing and the details of the mechanisms involved are explored. The climatic impact of changes in the thermohaline circulation is then investigated. It is revealed that the influence of changes in the thermohaline circulation on surface air temperature is concentrated in the North Atlantic and adjacent continents. It is also shown that this influence has its peak in winter rather than in summer. A dynamic ice sheet model is then globally and asynchronously coupled to the climate model. The relative importance of orbital and CO2 forcing in the mass balance of ice sheets is investigated using the coupled climate-ice sheet model. It is shown that CO2 forcing is of secondary importance to orbital forcing as the warming in eastern North America and Scandinavia due to CO2 forcing has its peak in winter, whereas that due to orbital forcing has its peak in summer. It is, nevertheless, concluded that the last glacial termination was initiated through increasing summer insolation and accelerated by a subsequent increase in atmospheric CO2 concentration. Second, the importance of subgrid topography in simulating the last glacial inception is investigated using the coupled climate model. The effects of subgrid elevation and subgrid ice-flow are incorporated in the model. Despite the use of high subgrid resolution, the coupled climate model fails to capture the last glacial inception. An atmospheric general circulation model is then used to explore the reasons for the failure, as well as the importance of changes in sea surface conditions and vegetation in simulating the last glacial inception. A realistic, geographic distribution of perennial snow cover and global net accumulation rate are successfully simulated when colder sea surface conditions than those of the present-day are specified. It is also shown that the effect of the vegetation feedback is large. It is revealed that changes in ocean circulation and vegetation are at least partly responsible for the complicated link between astronomical forcing and climate states during the glacial-interglacial cycles. As these two components play important roles, it is suggested that both components as well as ice sheet dynamics should be included in realistic paleoclimate simulations. / Graduate

No description available.

Thesis (M.S. - Geosciences)--University of Arizona, 1989. / Accompanied by folded map in pocket. Includes bibliographical references (leaves 36-41).

The Black Sea becomes periodically isolated from the global ocean during each glacial period. This occurs when the elevation of the global ocean is lower than the Bosporus sill, putting a stop to inflow of salt water to the Black Sea. This phenomenon allows the Black Sea to evolve from a marine environment to a freshwater one. It is also evident that the depth of the Bosporus sill does not remain at the same elevation, and instead is dynamic. The sill becomes filled with sediments during periods of its sub-aerial exposure but is subsequently eroded to its bedrock during periods of outflow from the Black Sea-Lake to the global ocean. This interpretation comes from the observations that during the last glacial period, the Black Sea-Lake was in a positive hydrological balance, fresh, and predominantly outflowing to the global ocean over a deep Bosporus sill, at approximately 80 meters below sea level (mbsl). It is highly likely that there were brief periods when the lake froze and the outflow suspended, such as during the extreme stadial conditions associated with the North Atlantic iceberg-discharge Heinrich Event 2 (HE 2) at ~24 kyr before present, when there is also no evident carbonate accumulation in stalagmites that receive water from evaporated Black Sea surface water. Upon the onset of deglaciation, large floods originating from the Fennoscandinavian Ice Sheet and the Alps, delivered meltwater so as to fully ventilate the Black Sea-Lake and even potentially replace all of the water in the basin. These floods occurred near the time of the deglacial iceberg-discharge Heinrich Event 1 (HE 1 at ~17 kyr before present), and left pulses of red-colored sediment everywhere on the western half of the Black Sea basin.

Thesis (M.S.)--University of Toledo, 2006. / Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science degree in Geology." Bibliography: leaves 57-65.

Thesis (Ph. D.)--Columbia University, 1939. / Vita. "Reprint of Colby monographs, no. 7, 1938." Bibliography: p. 62-64.

Thesis (Ph. D.)--University of Michigan, 1931. / Cover title. "From American Journal of Science, vol. XXXIV, August, 1937." Bibliography: p. 123-124.

Thesis (Ph. D.)--University of Chicago, 1895.

Thesis (Ph. D.)--Columbia University, 1939. / Vita. "Reprint of Colby monographs, no. 7, 1938." Bibliography: p. 62-64.