Thesis (M.S.)--Ohio University, November, 2009. / Title from PDF t.p. Includes bibliographical references.

This study presents results from stable isotope analyses of a modern stalagmite and three soda straw stalactites from Kapsia Cave, the Peloponnese, Greece. The resulting values from the stalagmite are put into context of local meteorological data, as well as previous research from Kapsia Cave. The potential for using soda straw stalactites as complementary climate archives on shorter time scales on the Peloponnese is also explored. The isotopic values in the stalagmite confirm a strong link to the amount effect on an annual scale. On a seasonal scale, variations in the isotopic signal can be detectedas a result of i.e. increased cave air temperature in summer. The stable isotope values in the soda straw stalactites largely correspond to previous isotopic measurements in Kapsia Cave. The trend of the isotopic carbon signal in two of the straws also strengthens earlier theories suggesting a link to CO2 concentrations in the external atmosphere. Soda straws are, thus, encouraged for use in future climate studies, although the sampling method should be further explored. The results of this study contribute to an increased understanding of Peloponnesian speleothems in relation to environmental processes and new insights are suggested into the use of soda straw stalactites as climate archives.

Icicles are a ubiquitous and picturesque feature of cold winter weather. Their familiar form emerges from a subtle interplay between the solidification dynamics of ice and the gravity-driven flow of the thin water film flowing over their evolving surface. The latent heat released by freezing is advected by the water film and ultimately carried away by the surrounding sub-zero air, which is also flowing. Like many processes far from equilibrium, icicle growth can exhibit nonlinear pattern formation. While scaling theory predicts that icicles converge to `platonic', self-similar shapes, natural icicles often exhibit regular ripple patterns about their circumference, which are due to a morphological instability. This thesis presents a comprehensive experimental study of icicles that sheds new light on the dynamics of their growth and the origin of their form. A table-top apparatus was designed and built for the controlled growth of icicles, under different conditions of temperature, water supply rate, ambient air motion, and water purity. Image analysis and Fourier methods were used to examine their morphology. Contrary to theoretical expectations, ripples do not appear on icicles made from pure water. Instead, ripples grow and travel on icicles made from salt solutions, even at very low concentrations. The addition of non-ionic surfactant or dissolved gases does not produce ripples, unless ionic impurities are also present. The ripple wavelength is independent of time and growth conditions. The ripple amplification rate and traveling velocity vary weakly with the ionic concentration, as do the tip and radial growth speeds of the icicle. While the tip and radial growth also depend on the ambient temperature and input mass flux, the ripple dynamics is not correlated with extrinsic conditions. If the ambient temperature or input mass flux is sufficiently low, the tip growth only advances for a short period of time before it ceases. After cessation, the shape of the icicle deviates increasingly from self-similarity. The most self-similar icicles are made from pure water with the surrounding air gently stirred, whereas icicles made from impure water in still air tend to grow multiple tips.

Icicles are a ubiquitous and picturesque feature of cold winter weather. Their familiar form emerges from a subtle interplay between the solidification dynamics of ice and the gravity-driven flow of the thin water film flowing over their evolving surface. The latent heat released by freezing is advected by the water film and ultimately carried away by the surrounding sub-zero air, which is also flowing. Like many processes far from equilibrium, icicle growth can exhibit nonlinear pattern formation. While scaling theory predicts that icicles converge to `platonic', self-similar shapes, natural icicles often exhibit regular ripple patterns about their circumference, which are due to a morphological instability. This thesis presents a comprehensive experimental study of icicles that sheds new light on the dynamics of their growth and the origin of their form. A table-top apparatus was designed and built for the controlled growth of icicles, under different conditions of temperature, water supply rate, ambient air motion, and water purity. Image analysis and Fourier methods were used to examine their morphology. Contrary to theoretical expectations, ripples do not appear on icicles made from pure water. Instead, ripples grow and travel on icicles made from salt solutions, even at very low concentrations. The addition of non-ionic surfactant or dissolved gases does not produce ripples, unless ionic impurities are also present. The ripple wavelength is independent of time and growth conditions. The ripple amplification rate and traveling velocity vary weakly with the ionic concentration, as do the tip and radial growth speeds of the icicle. While the tip and radial growth also depend on the ambient temperature and input mass flux, the ripple dynamics is not correlated with extrinsic conditions. If the ambient temperature or input mass flux is sufficiently low, the tip growth only advances for a short period of time before it ceases. After cessation, the shape of the icicle deviates increasingly from self-similarity. The most self-similar icicles are made from pure water with the surrounding air gently stirred, whereas icicles made from impure water in still air tend to grow multiple tips.

The West Pacific Warm Pool (WPWP) plays an important role in the global heat budget and global hydrologic cycle, so knowledge about its past variability would improve our understanding of global climate. Variations in WPWP precipitation are most notable during El Niño-Southern Oscillation events, when climate changes in the tropical Pacific impact rainfall not only in the WPWP, but around the globe. The stalagmite records presented in this dissertation provide centennial-to-millennial-scale constraints of WPWP precipitation during three distinct climatic periods: the Last Glacial Maximum (LGM), the last deglaciation, and the Holocene. In Chapter 2, the methodologies associated with the generation of U/Th-based absolute ages for the stalagmites are presented. In the final age models for the stalagmites, dates younger than 11,000 years have absolute errors of ±400 years or less, and dates older than 11,000 years have a relative error of ±2%. Stalagmite-specific 230Th/232Th ratios, calculated using isochrons, are used to correct for the presence of unsupported 230Th in a stalagmite at the time of formation. Hiatuses in the record are identified using a combination of optical properties, high 232Th concentrations, and extrapolation from adjacent U/Th dates. In Chapter 3, stalagmite oxygen isotopic composition (d18O) records from N. Borneo are presented which reveal millennial-scale rainfall changes that occurred in response to changes in global climate boundary conditions, radiative forcing, and abrupt climate changes. The stalagmite d18O records detect little change in inferred precipitation between the LGM and the present, although significant uncertainties are associated with the impact of the Sunda Shelf on rainfall d18O during the LGM. A millennial-scale drying in N. Borneo, inferred from an increase in stalagmite d18O, peaks at ~16.5ka coeval with timing of Heinrich event 1, possibly related to a southward movement of the Intertropical Convergence Zone (ITCZ). An inferred precipitation maximum (stalagmite d18O minimum) during the mid-Holocene in N. Borneo supports La Niña-like conditions and/or a southward migration of the ITCZ over the course of the Holocene as likely mechanisms for the observed millennial-scale trends. In Chapter 4, stalagmite Mg/Ca, Sr/Ca, and d13C records reflect hydrologic changes in the overlying karst system that are linked to a combination of rainfall variability and cave micro-environmental effects. Dripwater and stalagmite geochemistry suggest that prior calcite precipitation is a mechanism which alters dripwater geochemistry in slow, stalagmite-forming drips in N. Borneo. Stalagmite Mg/Ca ratios and d13C records suggest that the LGM climate in N. Borneo was drier and that ecosystem carbon cycling may have responded to the drier conditions. Large amplitude decadal- to centennial-scale variability in stalagmite Mg/Ca, Sr/Ca and d13C during the deglaciation may be linked to deglacial abrupt climate change events.

<p> Speleothems are calcium carbonate deposits, such as stalagmites, stalactites and flowstones, formed in a cave environment by loss of carbon dioxide from saturated groundwaters. Variations in the 18o/16o ratio of calcite are related to changes in depositional temperature provided that the speleothem formed in isotopic equilibrium with its seepage water (conditions characterised by slow coloss and no evaporation of seepage water). Variations in 18o/16o of the seepage water will also be reproduced in the calcite but allowance for this effect can be made if 18o/16o ratio of the source (ocean water) can be estimated (from deep sea sediment cores) and if the influence of temperature on 18o/16o ratio of precipitation at the site can be determined. Because cave temperatures closely approximate mean annual surface temperature, the axial 18o/16o record of a speleothem is therefore an indication of paleoclimate and of temperature change over the period of its growth. </p> <p> The frequency distribution of age measurements for several speleothems from an area may also be used as a paleoclimatic indicator because cold or glacial conditions above the cave will inhibit speleothem growth by freezing water at the surface and removing vegetation and soil cover, the main source of CO2 for the limestone dissolution-reprecipitation process. </p> <p> Pure, non-porous calcite speleothems from several limestone regions have been dated in this study by the 230Th/234U method, and in cases of uranium-rich speleothems, by the 231Pa/230Th method also. For ten such cases, examined, good agreement of ages determined by both dating methods was found. </p> <p> Relatively few deposits however, have shown deposition under isotopic equilibriwn conditions, due probably to the well-ventilated nature of the caves studied. </p> <p> The age distribution for speleothem from Cascade Cave on Vancouver Island, B.C., indicates growth during the mid-Wisconsin interstadial dated as 65 -30,000 yrs. B.P. Stable isotope profiles for two speleothems which grew over this period both show values of 18o/16o ratios of calcite which are significantly lower than calcite growing in the cave today. This is the first clearly-defined record of such an occurence (in previous work, 18o/16o of fossil speleothem was generally greater than modern). Using estimates of the change in 18o/16o of ocean water from a Pacific deep sea core, and the value determined by Dansgaard (1964) for the temperature dependence of 18o/16o of precipitation for oceanic sites, a realistic paleotemperature record is derived. The results indicate that temperatures at the Cascade Cave site were about 4.0°C , 64,000 yrs. ago· and gradually declined to 0°c by 35,000 yrs. ago. These data are consistent with the findings of Canadian workers from 14c and palynological studies of fossil organic matter in the area, and do not support the proposal by some American workers of a major glaciation occurring between 35 - 40,000 yrs. B.P. </p> <p> The age distribution for 140 analyses of 82 speleothems collected from caves in north-west England show abundant deposition during the periods 130 -90,000 yrs. B.P. and 13,000 yrs. B.P. to present, with limited growth over the periods > 350 -170,000 yrs. B.P. and 70 -35,000 yrs. B.P. No ages were found to lie within the periods 170 -140,000 yrs. B.P. and 35-15,000 yrs. B.P. These intervals are correlated to the Wolstonian and Devensian glaciations respectively. </p> <p> Only four speleothems were found to have grown in isotopic equilibrium with their seepage waters, and one of these showed periods of non-equilibrium deposition. In contrast to the Vancouver Island results, 18o/16o all ratios were found to be greater than or equal to modern, indicating that the apparent oceanic location of this site is not expressed in the on the value for temperature dependence of 18o/16o precipitation. </p> <p> An oxygen isotope profile for a flowstone dated between 126,000 and 109, 000 yrs. B.P. shows 18o/16o ratios commencing at values slightly lower than for modern calcite and shifting to still lower values at about 112, 000 yrs. B.P. This shift may indicate a cooling event perhaps carrelative with the isotope stage 5e-5d transition seen in the deep sea core record. A profile for a flowstone over the period 290 -190,000 yrs. B.P. shows excellent correlation to interglacial stages 9e and 7c seen in the deep sea core record, and a pronounced growth hiatus dated at about 250 210,000 yrs. B.P. correlates with glacial stage 8. These are the first speleothem results to show a climatic record beyond 200,000 yrs. B.P. </p> <p> The differences in 18o/16o behaviour for speleothems from the two locations (N .E. Pacific and ..E. Atlantic) are interpreted in terms of their relative proximity to the ocean, potential for exchange of water vapour and 'rainout' by airmasses moving towards the cave sites, and possibility of change in meteorological conditions (principally storm track) over the periods studied. </p> <p> In a subsidiary study, evidence for major sea level lowering during the Illinoian glaciation is recognised by age determinations on the calcite core of speleothems collected at 45m below present sea level from a 'blue hole' near Andros Island in the Bahamas. </p> <p> The possibility of applying the 234U/238U dating method to speleothem is also investigated in this work, by the analysis of modern calci tes and their seepage waters, using a new method for uranium extraction from groundwater. However the variations in 234U/238U ratios observed over short distances in the same cave demonstrate that estimation of initial fossil 234U/238U in the speleothem cannot simply be made by averaging modern ratios for the cave. </p> <p> Consideration is also given to the temperature dependent distribution of trace elements in calcite, particularly magnesium and strontium. Analyses of modern calcites and waters show that Mg incorporation is strongly temperature dependent whereas Sr is not. The possibility of using Mg variations in fossil speleothem as indication of temperature change is briefly examined but the results for one sample are found to be inconclusive. </p> / Thesis / Doctor of Philosophy (PhD)

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