At the turn of the century, Kanab Creek incised 30-meters into its alluvium, leaving behind fluvial terraces and thick basin fill sediments exposed along arroyo walls. Research objectives were to determine the timing and causes of past valley-filling and arroyo-cutting episodes along a 20 km-long reach of Kanab Creek in southern Utah. Fluvial deposits were mapped at the 1:12,000 scale and sediments were described and dated using Optically Stimulated Luminescence (OSL) and radiocarbon dating. The Kanab Creek valley can be divided into a narrow, upper terraced reach and a broad lower basin fill reach near Kanab, Utah. The most prominent terrace in the upper reach is Quaternary alluvial terrace 4 (Qat4), followed by Qat3, Qat2/3, and Qat2 map units. These are composed of tabular-bedded, fine-grained sand, silt, and clay layers. The Qat2/3 map unit is a both a fill and fill-cut terrace underlain by Qa4, Qa3, and Qa2 alluvium and is used when the Qat3 fill-cut (fill-strath) terrace can not be differentiated from the Qat2 fill terrace due to their similar geomorphic position. The Qat3 fill-cut terrace upstream correlates to ~8 meters of aggradation downstream. The youngest terrace, Qat1, is a minor terrace, composed of coarse-grained channel facies. More recent channel and floodplain deposits were deposited over the last century following arroyo cutting. OSL and radiocarbon results suggest at least four cycles of fluvial cutting and filling: >6-3.5ka (Qa4), ~3->1ka (Qa3), 0.7-0.12ka (Qa2), and post-1880 AD (Qa1). Correlation to regional climate records suggests major periods of aggradation correlate to regionally cooler and wetter climatic intervals. Periods of arroyo cutting occurred at >6ka, ~3ka, 1-0.7ka, and during historic arroyo cutting (1882-1914 AD), and correlate to regionally warmer, drier intervals. These periods of aggradation and incision are roughly contemporaneous with regional drainages, except for the large aggradation seen in Kanab Creek 6-3.5ka (Qa4). Analysis of terrace longitudinal profiles indicates Qat4 has the lowest concavity suggesting that Qat4 aggraded during a period of greater sediment supply and/or reduced flood regime. Although OSL samples exhibited some degree of incomplete zeroing, calculated ages using a minimum age model are consistent with radiocarbon results.

Extreme winter weather events in North America have become more frequent and increasingly destructive. This phenomenon was linked to a jet stream pattern that generates abnormally warm conditions in the west and cold conditions in the east, referred to as the North American Winter Dipole. Studies have shown that the Dipole may have amplified and this amplification could be linked to global warming. By analyzing the atmospheric and oceanic data worldwide, the wintertime circulation in the Northern Hemisphere shows signs of a persistent change after the 1980s. In the first part of this study, we examine how the ocean has changed in correspondence to the Dipole and the evolution of the pattern change. In the second part of this study, we use multiple global reanalysis datasets to construct the Dipole index. The result validates the reported Dipole variation during the modern period. We also use the Dipole variance to investigate the Dipole’s behavior in the paleoclimate and future warming conditions. Overall, we sought to better understand how the Dipole pattern evolves and how it may link to the different forcing, as a way to anticipate future change in North America’s winter.

This thesis presents a multi-proxy paleoenvironmental reconstruction from the sedimentary archives of Lilandsvatnet, a small arctic lake on Vestvågøy, in the Lofoten Islands, Norway. Lofoten has a rich history of human settlements existing throughout the Holocene. The catchment of Lilandsvatnet was the location of a prominent Viking chieftain farm that existed throughout the Iron Age, and the sedimentary archive contains a strong signal of prehistoric and historic human settlements and land-use practices. Paleoenvironmental reconstructions in this thesis show evidence for Holocene environmental variability in response to both natural and anthropogenic forcing. Cryptotephra deposits from Icelandic eruptions further contrain sediment chronology in the study, allowing reconstructions of subtle changes in the landscape with excellent chronological control during the late Holocene period of settlement. Additionally, I attempt to improve existing methods for crypto-tephrochronology through the development of new techniques.

Two lakes were studied in detail for rock magnetic properties: Lake El'gygytgyn, a crater lake formed 3.6Ma in the Far Eastern Russian Arctic, and Heimerdalsvatnet, a Holocene coastal lake located in the Lofotens off the coast of northern Norway. These two lakes have vastly different environmental histories, the former a terrestrial lake formed from a meteor impact and never covered by continental ice sheets whereas the latter went from a coastal marine setting to a completely lacustrine environment due to isostatic rebound and sea level fluctuations. Their differences are considerable, however they provide the opportunity to compare Arctic lake systems to discern similarities and differences in their magnetic properties for application to future climatic investigations. Paleomagnetic measurements and down-core magnetic susceptibility were performed at the GFZ German Research Centre for Geosciences in Potsdam for Lake El'gygytgyn and at the Laboratoire de paleomagnétisme sédimentaire at ISMER for Heimerdalsvatnet. Rock magnetic properties were measured at the University of Massachusetts Amherst, Institute of Rock Magnetism, and/or Trinity College. These measurements included: magnetic susceptibility, hysteresis parameters, Curie temperatures, and low-temperature magnetic behavior. Imaging of magnetite grains was also performed. Magnetic susceptibility measurements in Lake El'gygytgyn suggested a correlation between glacials (interglacials) and low (high) susceptibility. The large range in susceptibility indicated there could be magnetite dissolution. The first study supported this hypothesis with evidence at low temperatures (10-35K) of minerals such as siderite, rhodochrosite, and/or vivianite which could form from iron released during dissolution. Marine Isotope Stage 31 was investigated for rock magnetic properties that could continue to support or oppose findings from the first study. It was determined the presence of siderite only occurred in interglacial periods whereas its absence (and probably presence of vivianite) related to glacial periods, indicating more reduced environments during glacials versus interglacials. Heimerdalsvatnet paleomagnetic data from the marine environment (lower part of the core) revealed scattered directions whereas data from the upper part of the core (lacustrine environment) showed better consistency. Rock magnetic measurements showed some variation downcore, however the measurements are not dependable since the amount of paramagnetic material was overwhelming compared to any ferromagnetic mineral present.

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Hourly winter weather conditions of the Last Glacial Maximum (LGM) are simulated using the Community Climate Model version 3 (CCM3) on a globally resolved T170 (~75 km) grid. This simulation has been run in-tandem with a lower temporally resolved six-year climatological run. The purpose of the study is to determine: (1) whether examination of higher-resolution simulations, on both spatial and temporal scales, can enhance paleometeorological inferences based previously on monthly statistics of model output and (2) whether certain synoptic-scale events, which may have only a modest impact on seasonal statistics, might exert a disproportionate impact on geological climate records. Analysis is focused on changes in wind flow, no analogue climate “states”, synoptic scale events including Northern Hemisphere cyclogenesis, and gust events over glacial dust source regions. Results show a decrease in North Atlantic and increase in North Pacific cyclogenesis during the LGM. Storm trajectories react to the mechanical forcing of the Laurentide Ice Sheet, with Pacific storms tracking over middle Alaska and northern Canada and terminate in the Labrador Sea. The latter result supports observations and other model runs showing a significant reduction in Greenland winter precipitation. The modified Pacific track results in increased precipitation and the delivery of warmer air along the west coast of North America. This could explain “early” glacial warming inferred in this region from proxy climate records, potentially representing instead a natural regional response to ice age boundary conditions. Results also indicate a low variability, “no analogue” region just south of the Laurentide Ice Sheet margin which has appropriate conditions to harbour temperature-sensitive trees west of the Appalachian Mountains. Combined with pollen data, this lends valuable insight into the known disagreement between modern seed dispersal experiments and calculated migration rates. Finally, hourly-scale gust events over dust source regions during the LGM are two to five times greater than the modern, providing a mechanism to help explain the increased glacial dust load seen in the ice cores. Backwards air-parcel trajectories from Antarctic ice core locations show air sources over Patagonia and the Altiplano with some inputs from South Africa agreeing with recent isotopic tracer analyses. Results demonstrate that high temporal and spatial resolution simulations can provide valuable insight to add to the cornucopia of information already available from lower-resolution runs. They can also enhance our interpretation of geological records, which have been previously assumed to record longer time-scale climatological mean-states and thus ignoring any extreme synoptic events which may actually have had a disproportionate impact on their preservation.

At present, the East Asian Monsoon (EAM) influences water availability for nearly one third of the global population. The intensity and position of the EAM has varied considerably since its onset, but disagreement still exists related to the precise latitudinal and intensity shifts of the Westerly Jet and associated storm fronts, which mark the northern extent of the monsoon. Paleoclimate research can assist in improved assessment and prediction of EAM intensity, radiative forcing, and biogeochemical cycles in the Japan Sea and North Pacific, especially under the currently changing climate. My research primarily focuses on using major-, trace- and rare earth elements in sediments from International Ocean Drilling Program Expedition 346 in the Japan (Ulleung Basin) and East China Seas (Okinawa Trough) to track variability in the EAM on millennial time scales. Using geochemical and multivariate statistical techniques (Q-Mode Factor analysis and Constrained Least Squares multiple linear regressions), I differentiated compositionally similar terrigenous aluminosilicate materials (continental crust components, eolian dusts, volcanic ash) from these sediment archives. I successfully constructed a robust record of aluminosilicate provenance, which enables more precise determinations of EAM position and intensity than previously possible. Most of my research focused on the interpretation of aluminosilicate records over several different timescales from three sites from Expedition 346. In tandem with this research, I also refined values of the well-known, and widely used, Standard Reference Material (SRM) Hawaiian Volcano Observatory Basalt (BHVO-2). In the Okinawa trough (Sites U1428/U1429), I identified and tracked the increase in flux of five continental crust materials, loesses, and volcanic ashes during glacial cycles, continental shelf exposure, and the migration of paleo-rivers in the last 400 kyr. Additionally, I constructed a 12 Myr record, which identified and quantified the dust fluxes to Ulleung Basin (Site U1430), and emphasized the importance of the Taklimakan and Gobi Deserts as main sources of dust to the Japan Sea and Pacific through the Cenozoic. Collectively, these aluminosilicate flux reconstructions are first to identify multiple specific Asian source regions through the Cenozoic, and highlight the complexity of accurately reconstructing monsoons and other aspects of paleoclimate from sediment in dynamic environments.

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