Thesis (M.S.)--Boise State University, 2009. / Includes abstract. Includes bibliographical references (leaves 81-91).

Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 237-250). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Oregon, 2002. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 170-178). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves).

Thesis (M.S.)--Boise State University, 2009. / Title from t.p. of PDF file (viewed Mar. 29, 2010). Includes abstract. Includes bibliographical references (leaves 81-91).

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.

Scleractinia (stony corals) are powerful tools in the field of paleoceanography, allowing researchers to reconstruct past ocean conditions based on variations in coral geochemistry. As corals regularly accrete their aragonite skeletons they preserve a history of climate on regional to global scales. Often able to provide centuries long continuous records of climate, an individual coral colony can provide insight into significant environmental perturbations. If preservation permits, fossil corals can be used to evaluate climate thousands of years in the past. Researchers use paleoclimate proxies, which are indirect geochemical fingerprints of environmental conditions, to create paleoclimate time series. Paleoclimate proxies are prevalent throught the literature and while many are well constrained by years to decades of use, individual conditions unique to study sites and timescale prevent the use of blanket assumptions regarding their interpretation. In this dissertation I illustrate the varied ways that the same or similar coral-based climate proxies can be used to reconstruct past ocean conditions. Part I (Ch. 2, 3) presents two studies based along of the Pacific Coast of Panamá to examine the influence of the seasonal migration of the Intertropical Convergence Zone (ITCZ). I analyzed a long-term coral δ18O time series from a living massive Porites colony to address low-frequency variation overprinted by the wet-dry seasonality. The coral record uncovered a clear decadal (~11 year) cycle in coral δ18O-inferred precipitation. I propose this mode is related to basin-wide processes, specifically a component of the Pacific Decadal Oscillation, which describes large-scale patterns in sea surface temperature (SST) and precipitation influencing marine ecosystems. In Chapter 2, I supplement the coral δ18O record with a coral Ba/Ca time series from a different coral colony. Coral Ba/Ca can be used as a proxy for river discharge (Q), although this practice is relatively new. Our coral record outlined seasonal variation in river Q and can also be used to identify past El Niño events and prolonged periods of drought. Uncovering a geochemical indicator of El Niño in this region is particularly powerful since conditions become warm and dry, which negate each other in coral δ18O rendering the proxy unable to consistently identify these climate events. This chapter furthers the community’s understanding of the many ways that trace metals can be used in paleoceanographic research, specifically to constrain local hydroclimate. In Part II (Ch. 4, 5) I present two studies in the Great Barrier Reef (GBR) based on coral δ18O and Sr/Ca records from modern and fossil Isopora, a coral species that is nearly completely absent from the paleoceanographic literature. Although this suite of climate proxies is similar to those used in Part I, in Part II the GBR corals provide a history of sea surface temperature rather than hydroclimate, which is due to prevailing local environmental conditions over a given timescale. In Chapter 4 I developed the first modern Sr/Ca- and δ18O-Sea Surface Temprature (SST) calibration using Isopora, which approaches those calculated for the commonly used Porites corals. Using Isopora in Pacific-based paleoceanographic research allows us to analyze coral records from reefs that might not be dominated by Porites. In Chapter 5 I applied the new Isopora Sr/Ca- and δ18O-SST calibrations to fossil corals recovered during Integrated Ocean Discovery Program (IODP) 25. The fossil corals date beyond the Last Glacial Maximum (LGM, ~20 kyr BP) to 25 kyr BP. In the Pacific SST change since the LGM is better constrained for more equatorial locations so our fossil samples from the GBR extend the geographic network of LGM-aged coral-based climate proxies. I measured ~5-7°C of cooling in the GBR at the LGM compared to today. The SST change through the LGM deglaciation provides valuable understanding of reef resilience and future risk of or adaptability to climate change. Each chapter in this dissertation uses similar strategies but provides a unique perspective on past climate change in the tropical Pacific. This dissertation identifies the many ways that coral proxies can be utilized with specific examples of the ways in which interpretation can vary. It is necessary to consider the environmental specifics of a given region before blindly interpreting paleo-proxy data. Furthermore, coral-based proxy records are supremely powerful tools in exploring and uncovering past climate histories of a given region. Coral-records can supplement and extend the limited instrumental record with centuries to millenia long information on SST and hydroclimate. These data can improve climate models, further our knowledge of coral reef growth, and deepen our understanding of regional hydroclimate, which are all vital to our understanding of global climate.

Earth’s climate can exist in many stable states that are vastly different from the modern climate state. Understanding modern and future climate requires a thorough understanding of the full range of possible climate states and the processes that trigger transitions between states. Quantitative reconstructions of past climate variables provide constrains on the magnitude, mechanisms and feedbacks involved in producing stable climate states. As such, they provide insights into past climate states unobservable today. This thesis focuses on quantifying three metrics of past climate systems: (a) quantitative rainfall amount, which provides means for assessing how the spatial distribution of rainfall changed in the past, (b) the isotopic composition of past rainwater (δP ), which provides means for understand- ing how atmospheric circulation changed in the past, and (c) relative humidity, which provides estimates of evaporative processes and hydrospheric fluxes. The regions studied are in the two far reaches of the Asian continent. In eastern Asia, changes in rainfall amount and δP over the past 125 ka were studied using geomorphological evidence from a closed basin lake in Inner Mongolia, China and compound-specific δDwax and δ13Cwax from organic molecules in lake sediments. In western Asia, the research focused on processes that govern modern δP and modern δDwax and δ13Cwax in soils. In addition the hydrological regime of the Eastern Mediterranean and the Levant during the Last Glacial Maximum were studied using evidence from speleothem δ18Oc and foraminifera δ18O. These records provide empirical and quantitative information about rainfall amount, δP and relative humidity at singular locations, and as such provide the building blocks for producing coherent large-scale reconstruction of the migration of rain-belts in the past.

Bogs are sensitive palaeoclimate archives as they rely solely on atmospheric deposition for water and nutrients. A range of biological mire surface wetness proxies have been explored in previous studies, but linking geochemical elements to particular plant macrofossils and a quantitative water table depth reconstruction has not been attempted. The thesis aims to combine biological and geochemical data to evaluate the potential of these proxies when combined and to test the applicability of halogens as a palaeoclimate proxy. To do so, records of plant macrofossils, testate amoebae and geochemistry were reconstructed then ordinated from three bogs (Tyndrain, Wales; Raeburn Flow, Scotland; Annaholty, Ireland) along the western seaboard of the North Atlantic. Additionally, lead enrichment (Pb EF) and the pattern of lithogenic elements were measured to infer phases of anthropogenic activity. A testate amoebae based transfer function, used to identify water table changes, suggests regional climatic variability with only the ‘2650 BP wet shift' identifiable at all three sites. RBF and ANN show several shifts between wetter and drier conditions which appear to be in antiphase. In contrast, at TYN only drier phases were recorded during the Dark Ages and the Little Ice Age. No direct link between the halogens and mire surface wetness based on the testate amoebae was detectable. Factor analyses by principal components run on the halogens combined with Sphagnum mosses, monocots, unidentified organic matter, lithogenic elements and mire surface wetness to identify underlying factors driving their distribution, suggest inter-­‐site variability. It was not possible to identify a principal sink in terms of a specific moss species with any certainty, although a negative correlation with Sphagnum Section Acutifolia (dry indicator species) was found at ANN. Iodine appears to be more closely associated with the lithogenic elements, while bromine has similarities with both iodine and chlorine. iv The Pb EF results for Raeburn Flow and Annaholty are in agreement with patterns for historical global Pb production (i.e. Roman, Medieval and Industrial period enrichments are identifiable) and evidence for changes in land use. This limits the potential of lithogenic elements as palaeoclimatic indicators. Overall, the halogen pattern is inconclusive and requires further study, although for Annaholty a link between wetter conditions and an increase in halogens can be demonstrated.

The interplay between convective processes and the stabilizing effects of largescale systems remains debated, especially for warmer climates. We study sets of simulations of past and present climates in which carbon dioxide (CO2) concentrations vary over a wide range: from pre-industrial era levels of 280 ppm to an exceedingly high value of 8960 ppm. This allows us to assess the importance of convective processes relative to middle latitude thermal stratification and changes to the general circulation in progressively warmer climate states. As a tool to assess the stability of the atmosphere, we calculate a thermodynamic variable called saturation potential vorticity (P*), which has the property of being identically zero wherever lapse rates are neutral with respect to moist convection, and large where lapse rates are stable. Using P* allows us to examine convective motions arising from both gravitational accelerations as well as symmetric instabilities. We assess the ability of current models (of varying spectral resolutions) in resolving conditions unstable to slantwise convection. We show that the coarse resolution reanalysis data captures instances of observed slantwise convection. Our results show examples of vertically stable lapse rates, while being conditionally unstable along slanted angular momentum surfaces. This suggests the need for model parameterizations of convection to include instabilities arising from symmetric displacements. Tropical regions are neutral with respect to moist convection while higher latitudes most often have stable lapse rates, especially during the winter months. In the warmer climate simulations, the frequency of convectively neutral air masses increases in both middle latitude and polar regions, especially during the summer months. These simulations also show expansion of the Hadley cell and shifting of middle latitude storm tracks. Using Maximum Potential Intensity (MPI) as a tool to assess the upper bound of hurricane strength, we show sustainment of intense tropical cyclones in regions they cannot in our present climate.