Browsing by Author "Gilhooly, William, III"
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Item A 4600-year record of lake level and hydroclimate variability from an eastern Andean lake in Colombia(2016-05) Rudloff, Owen M.; Bird, Broxton Williams; Gilhooly, William, III; Filippelli, Gabriel M.Hydroclimatic variability in the eastern Colombian Andes is examined using a decadally-resolved, multiproxy lake sediment record from Laguna de Ubaque, Colombia. Hydroclimate trends are examined and compared to existing local, regional, and trans-Andean records to enhance existing knowledge of Late Holocene Colombian precipitation and assess potential hydroclimatic forcing mechanisms in tropical South America. Sedimentological analyses, including percent lithics, grain size, C:N and magnetic susceptibility are sensitive to hydroclimate and lake level while charcoal size and concentrations reflect fire variability. Results show that deep lacustrine conditions characterized by laminated deposits were not established until approximately 3500 cal yr B.P., prior to which, terrestrial C:N values and unstructured sediments indicate that drier, marsh-like conditions prevailed. Between 3500 and 2000 cal yr B.P., interrupted only by a 300-year arid interval from 2800 to 2500 cal yr B.P., greatly increased overall clastic deposition indicates a broad precipitation maximum while decreased sand deposition and the preservation of finely laminated sediment indicate deep lake conditions. After 2000 cal yr B.P., decreased clastic deposition suggests reduced precipitation, but the continued accumulation of laminated sediments indicates that conditions were wet enough to fill the basin continuously until the present day. These observations address two of the driving questions of Andean paleoclimate: were the northern and southern Andes in vi phase during the Holocene, or out of phase, and what are the main drivers of Holocene Andean climate? We find that the early part of Ubaque’s record more closely resembles southern Andean precipitation records until 2000 cal yr B.P., at which point it abruptly switches to resemble northern precipitation records. We attribute this to a combination of the southward migration of the intertropical convergence zone (ITCZ), and an increase in eastern Pacific sea surface temperatures (SST). In addition, we find that Colombian hydroclimate records exhibit a bimodal precipitation pattern, which we attribute to their location either on the Andean slopes or in the high interior Andes.Item Investigating the Effects of Synoptic-Scale Climatic Processes on Local-Scale Hydrology by Combining Multi-Proxy Analyses of Lacustrine Sediments and Instrumental Records(2022-09) Gibson, Derek Keith; Bird, Broxton; Gilhooly, William, III; Jacinthe, Pierre-André; Licht, Kathy; Wang, XianzhongPaleoclimate records from North and South America were used to develop a holistic understanding of global paleo-hydroclimatic drivers across a range of boundary conditions. Here, geophysical analysis of lacustrine sediment stratigraphy at Lago de Tota, Boyaca, Colombia provided evidence for significant lake-level fluctuations through the late Quaternary and produced a record that potentially spans the last 60 ka. Seismic data revealed a series of off-lap and on-lap sequences in the upper ~20 m of sediments that indicated large amplitude changes in lake-level, driven by variability in the mean latitude of the Intertropical Convergence Zone as controlled by insolation- and ocean circulation-driven hemispheric temperature gradients during glacial/stadial and interglacial/interstadial events. In North America, late Holocene flood recurrence in the Midwest and Holocene changes in the mean latitude of the polar front jet stream were investigated through multi-proxy examinations of sediment cores collected from swale lakes in northern Kentucky and southern Indiana, and a glacially formed kettle lake in northern Indiana. These results showed that the midlatitude jet stream was displaced to the south during the late Holocene, which increased the amount of Midwestern precipitation sourced from the northern Pacific and Arctic, especially during prolonged cool conditions. During these cool periods, when atmospheric flow was meridional and a greater amount of precipitation was delivered from the northerly sources, Ohio River flooding increased. During warm conditions, when clockwise mean-state atmospheric circulation advected southerly moisture from the Gulf of Mexico into the Midwest, flooding on the Ohio River decreased. At present, streamflow in the Midwest is demonstrated here to be generally increasing, despite atmospheric conditions typically associated with reduced streamflow in the paleo-record, due in part to increasing precipitation and modern land-use dynamics. Together, these studies demonstrate the sensitivity and vulnerability of local-scale hydrological processes to synoptic climate change.Item A Laminated Carbonate Record of Late Holocene Precipitation from Martin Lake, LaGrange County, Indiana(2016-01) Stamps, Lucas G.; Bird, Broxton Williams; Gilhooly, William, III; Licht, Kathy J.Precipitation trends and their driving mechanisms are examined over a variety of spatial and temporal scales using a multi-proxy, decadally-resolved sediment record from Martin Lake that spans the last 2300 years. This unique archive from a northern Indiana kettle lake documents significant climate variability during the last 2 millennia and shows that the Midwest has experienced a wide range of precipitation regimes in the late Holocene. Three independent proxies (i.e., oxygen and carbon isotopes of authigenic carbonate and %lithics) record variations in synoptic, in-lake and watershed processes related to hydroclimate forcing, respectively. Together, these proxies reveal enhanced summer conditions, with a long period of water column stratification and enhanced summer rainfall from 450 to 1200 CE, a period of time that includes the so-called Medieval Climate Anomaly (950-1300 CE). During the Little Ice Age, from 1260 to 1800 CE, the three proxy records all indicate drought, with decreased summer rainfall and storm events along with decreased lake stratification. The Martin Lake multi-proxy record tracks other Midwest climate records that record water table levels and is out-of-phase with hydroclimate records of warm season precipitation from the High Plains and western United States. This reveals a potential warm season precipitation dipole between the Midwest and western United States that accounts for the spatial pattern of late Holocene drought variability (i.e., when the Midwest is dry, the High Plains and the western United States are wet, and vice versa). The spatiotemporal patterns of late Holocene North American droughts are consistent with hydroclimate anomalies associated with mean state changes in the Pacific North American teleconnection (PNA). Close associations between late Holocene North American hydroclimate and records of Northern Hemisphere temperatures and the Pacific Ocean-atmosphere system suggests a mechanistic linkage between these components of the global climate system that is in line with observational data and climate models. Based on our results, predominantly –PNA conditions and enhanced Midwestern summer precipitation events are likely to result from continued warming of the climate system. In the western United States, current drought conditions could represent the new mean hydroclimate state.Item Mediators of Fine-Scale Population Genetic Structure in the Black Blow Fly, Phormia regina (Meigen) (Diptera: Calliphoridae)(2019-08) Owings, Charity Grace; Picard, Christine J.; Walsh, Susan; Wang, Xianzhong; Holland, Jeffery D.; Gilhooly, William, IIIPopulation genetic structure is difficult to assess in blow flies (Diptera: Calliphoridae) due to high connectivity and genetic diversity of subpopulations. Previous studies revealed high relatedness among individuals within wild samples of blow fly populations, however broad geographic structure was absent. The aim of this research was to determine if blow fly genetic structure exists at a fine spatiotemporal resolution and, if so, to elucidate the influence of environmental factors and resource availability on fly genetics. Specifically, blow fly population genetic patterns were tested against a null hypothesis that flies adhere to a patchy population model with high genetic diversity (i.e. no structure) and high resource availability. Samples of the black blow fly, Phormia regina Meigen (Diptera: Calliphoridae), were collected at six urban parks in Indiana, USA (=urban) in 2016 and 2017 (N = 14 and 16 timepoints, respectively). Additional sampling in different ecoregions was performed to determine if trends observed at a high-resolution scale were also present at a broad geographic scale. Therefore, P. regina were also collected at four sites within two national parks (the Great Smoky Mountains and Yellowstone National Parks) over a three-day period. Randomly selected females (N = 10) from each sample underwent the following analyses: 1) gut DNA extraction, 2) molecular analysis at 6 microsatellite loci, 3) vertebrate-specific 12S and 16S rRNA sequencing, and, 4) vertebrate fecal metabolite screening. Flies from the national parks and a comparable subset of urban data also underwent stable isotope analysis (SIA) to determine larval food source. Overall, strong seasonal population genetic structure was observed over both years in the urban environment (2016 F’ST = 0.47, 2017 F’ST 0.34), however spatial structure was lacking, as seen in previous studies (2016 F’ST = 0.04, 2017 F’ST 0.03). Weather conditions prior to and on the day of blow fly collections, interspecific competition, and resource availability greatly impacted the genetic diversity and kinship of P. regina. A total of 17 and 19 vertebrate species were detected by flies in 2016 and 2017, respectively, and many flies tested positive for vertebrate feces, suggesting that many varied resources are important for maintaining high gene flow among geographic locations. Genetic diversity was non-existent in flies collected from the Smokies (F’ST = 0.00), while very slight spatial structure existed in the Yellowstone populations (F’ST = 0.07). Environmental factors such as temperature, humidity, and wind speed were all statistically relevant in maximizing fly collections with vertebrate resources. In 720 min of total sampling time in the national parks and a subset of urban data, 28 vertebrate species were identified, and fecal resources appeared to be the most abundant in Yellowstone. Stable isotope analysis revealed a majority of larval resources in the national parks were herbivores, with a more even distribution of carnivore and herbivore carcasses present in the urban environment, which likely explains the high genetic diversity of adult flies in these regions. Overall, the null hypothesis that P. regina adheres to a patchy population model could not be rejected for the Smokies populations. However, the urban and Yellowstone populations appear to adhere to a Levins metapopulation model in which variable availability in resources leads to random bottleneck events in the local populations. Overall, environmental conditions, competition, and resource availability are all important factors influencing P. regina population genetic structure in different environments.Item Midcontinental Hydroclimate Variability from a 1,500-yr Wisconsin Lake Sediment Record(2023-12) Nealy, Cameron Alexander; Bird, Braxton; Gilhooly, William, III; Licht, KathyLacustrine sediment archives preserve continuous records of changes in basin- to regional-scale processes that reflect broader variability in climatic conditions. Here, we present a 1,500-yr sediment record of inferred effective moisture (P/E) that spans the Current Warm Period (CWP; last 150 years), Medieval Climate Anomaly (MCA; ca. 950–1250 CE), and Little Ice Age (LIA; ca. 1300–1800 CE) from glacially-formed Pope Lake in central Wisconsin. A suite of sediment proxies constrained by 14C and 210Pb ages was developed at decadal resolution to investigate Common Era changes in Upper Midwest effective moisture in response to temperature and synoptic scale atmospheric variability, such as the Pacific North American (PNA) pattern. Lake water isotopes reconstructed with authigenic carbonate oxygen isotopes (d18Ocal) from Pope Lake compare favorably with other Midwestern closed-basin lakes, indicating that evaporation was a significant control on the isotopic composition of lake water. Relatively lower d18Ocal values during the MCA suggest that the moisture availability was greater during the MCA than LIA, despite increased air temperatures. This is supported by low carbon/nitrogen (C/N) ratios and low terrestrial lithic contributions that reflect increased lake levels during the MCA. Reversals of these trends during the cooler LIA were observed. Comparisons of the Pope Lake record to synoptic scale forcings suggest that shifts in regional P/E were consistent with high amplitude PNA variability that likely affected the source and seasonality of precipitation. The general warm/wet and cool/dry relationship noted during the MCA and LIA underscores how global temperature anomalies may alter the balance of effective moisture in the Upper Midwest in relatively short succession. The Pope Lake sediment record presented here is an important step in establishing hydroclimatic history that may inform expectations of future climate for a region sparsely populated with similar high resolution late Holocene records.