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Watershed And Aquatic Ecosystem Evolution During The Late Glacial And Early Holocene Inferred From High Resolution Diatom And Geochemical Records In The Yellowstone Region
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Book Synopsis Watershed and Aquatic Ecosystem Evolution During the Late-glacial and Early-Holocene Inferred from High-resolution Diatom and Geochemical Records in the Yellowstone Region by : Yanbin Lu
Download or read book Watershed and Aquatic Ecosystem Evolution During the Late-glacial and Early-Holocene Inferred from High-resolution Diatom and Geochemical Records in the Yellowstone Region written by Yanbin Lu and published by . This book was released on 2014 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: Four lake sediment cores collected from the Yellowstone region were examined with high-resolution geochemical analysis to investigate trends in watershed and lake evolution during the late-glacial and early-Holocene. During the early stage of lake development, clastic input was high, and lake productivity was low, and they decreased and increased, respectively, as vegetation gradually developed in the catchment. The decrease of clastic input was asynchronous among regional lakes, and occurred time transgressively from south to north. The long-term pattern of change in calcite precipitation was controlled primarily by lake-level change in small and shallow lakes and by lake productivity in large and deep lakes.
Book Synopsis Major Climatic Influences on Yellowstone Region Lake Ecosystems Suggested by Synchronous Transitions in Late Glacial and Early Holocene Diatom Assemblages by : Yanbin Lü
Download or read book Major Climatic Influences on Yellowstone Region Lake Ecosystems Suggested by Synchronous Transitions in Late Glacial and Early Holocene Diatom Assemblages written by Yanbin Lü and published by . This book was released on 2017 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diatom assemblages in sediment cores from three small lakes in the Greater Yellowstone Ecosystem that span the late-Glacial through early Holocene periods and are located in areas of varied surficial geology and precipitation seasonally were analyzed to evaluate the importance of large-scale climatic change relative to localized catchment process on aquatic ecosystem evolution. All assemblages underwent synchronous shifts in community structure in the intervals of 13.9-13.8, 13.2-13.1, 11.3-11.0 and 8.8-8.7 cal ka. The shift at 11.3-11.0 cal ka also is evident in other proxy records from these sites, such as pollen and charcoal, suggesting large-scale climatic influences on both aquatic and terrestrial ecosystems. Because the shifts in diatom assemblages are synchronous in lakes with variable geological settings and local precipitation patterns, we infer that large-scale climatic change was the more important driver of aquatic ecosystem evolution in this region during the late-Glacial and early Holocene periods.
Book Synopsis Climate and Vegetation Change During the Late-glacial/early-Holocene Transition Inferred from Multiple Proxy Records from Blacktail Pond, Yellowstone National Park, USA by : Teresa R. Krause
Download or read book Climate and Vegetation Change During the Late-glacial/early-Holocene Transition Inferred from Multiple Proxy Records from Blacktail Pond, Yellowstone National Park, USA written by Teresa R. Krause and published by . This book was released on 2013 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: A series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500 cal yr BP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500 cal yr BP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280 cal yr BP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280 cal yr BP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.
Book Synopsis Patterns of Terrestrial and Limnologic Development in the Northern Greater Yellowstone Ecosystem (USA) During the Late-glacial/early-Holocene Transition by : Teresa R. Krause
Download or read book Patterns of Terrestrial and Limnologic Development in the Northern Greater Yellowstone Ecosystem (USA) During the Late-glacial/early-Holocene Transition written by Teresa R. Krause and published by . This book was released on 2015 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: A high-resolution record of pollen, charcoal, diatom, and lithologic data from Dailey Lake in southwestern Montana describes postglacial terrestrial and limnologic development from ice retreat ca. 16,000 cal yr BP through the early Holocene. Following deglaciation, the landscape surrounding Dailey Lake was sparsely vegetated, and erosional input into the lake was high. As summer insolation increased and ice recessional processes subsided, Picea parkland developed and diatoms established in the lake at 13,300 cal yr BP. Closed subalpine forests of Picea, Abies, and Pinus established at 12,300 cal yr BP followed by the development of open Pinus and Pseudotsuga forests at 10,200 cal yr BP. Increased planktic diatom abundance indicates a step-like warming at 13,100 cal yr BP, and alternations between planktic and tychoplankic taxa suggest changes in lake thermal structure between 12,400 and 11,400 cal yr BP. An increasingly open forest, in combination with increased benthic diatoms, indicates warm dry summers during the early Holocene after 11,400 cal yr BP, in contrast to nearby records in northern Yellowstone that register prolonged summer-wet conditions until ca. 8000 cal yr BP. Because of its low elevation, Dailey Lake was apparently sensitive to the direct effects of increased summer insolation on temperature and effective moisture, registering dry summers. In contrast, higher elevations in northern Yellowstone responded to the indirect effects of an amplified seasonal insolation cycle on atmospheric circulation, including elevated winter snowpack and/or increased summer convective storms as a result of enhanced monsoonal circulation.
Book Synopsis Holocene Seasonal Variability Inferred from Multiple Proxy Records from Crevice Lake, Yellowstone National Park, USA by : Cathy Whitlock
Download or read book Holocene Seasonal Variability Inferred from Multiple Proxy Records from Crevice Lake, Yellowstone National Park, USA written by Cathy Whitlock and published by . This book was released on 2012 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 9400-yr-old record from Crevice Lake, a semi-closed alkaline lake in northern Yellowstone National Park, was analyzed for pollen, charcoal, geochemistry, mineralogy, diatoms, and stable isotopes to develop a nuanced understanding of Holocene environmental history in a region of northern Rocky Mountains that receives both summer and winter precipitation. The limited surface area, conical bathymetry, and deep water (> 31 m) of Crevice Lake create oxygen-deficient conditions in the hypolimnion and preserve annually laminated sediment (varves) for much of the record. Pollen data indicate that the watershed supported a closed Pinus-dominated forest and low fire frequency prior to 8200 cal yr BP, followed by open parkland until 2600 cal yr BP, and open mixed-conifer forest thereafter. Fire activity shifted from infrequent stand-replacing fires initially to frequent surface fires in the middle Holocene and stand-replacing events in recent centuries. Low values of ó18O suggest high winter precipitation in the early Holocene, followed by steadily drier conditions after 8500 cal yr BP. Carbonate-rich sediments before 5000 cal yr BP imply warmer summer conditions than after 5000 cal yr BP. High values of molybdenum (Mo), uranium (U), and sulfur (S) indicate anoxic bottom-waters before 8000 cal yr BP, between 4400 and 3900 cal yr BP, and after 2400 cal yr BP. The diatom record indicates extensive water-column mixing in spring and early summer through much of the Holocene, but a period between 2200 and 800 cal yr BP had strong summer stratification, phosphate limitation, and oxygen-deficient bottom waters. Together, the proxy data suggest wet winters, protracted springs, and warm effectively wet summers in the early Holocene and less snowpack, cool springs, warm dry summers in the middle Holocene. In the late Holocene, the region and lake experienced extreme changes in winter, spring, and summer conditions, with particularly short springs and dry summers and winters during the Roman Warm Period (~ 2000 cal yr BP) and Medieval Climate Anomaly (1200?800 cal yr BP). Long springs and mild summers occurred during the Little Ice Age, and these conditions persist to the present. Although the proxy data indicate effectively wet summer conditions in the early Holocene and drier conditions in the middle and late Holocene, none point specifically to changes in summer precipitation as the cause. Instead, summer conditions were governed by multi-seasonal controls on effective moisture that operated over multiple time scales.
Book Synopsis Limnogeology: Progress, Challenges and Opportunities by : Michael R. Rosen
Download or read book Limnogeology: Progress, Challenges and Opportunities written by Michael R. Rosen and published by Springer Nature. This book was released on 2021-04-24 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book honors the career of Professor Elizabeth Gierlowski-Kordesch who was a pioneer and leader in the field of limnogeology since the 1980s. Her work was instrumental in guiding students and professionals in the field until her untimely death in 2016. This collection of chapters was written by her colleagues and students and recognize the important role that Professor Gierlowski-Kordesch had in advancing the field of limnogeology. The chapters show the breadth of her reach as these have been contributed from virtually every continent. This book will be a primary reference for scientists, professionals and graduate students who are interested in the latest advances in limnogeologic processes and basin descriptions in North and South America, Europe, Africa, and China. *Free supplementary material available online for chapters 3,11,12 and 13. Access by searching for the book on link.springer.com
Book Synopsis Ecosystem Responses to Holocene Climate Variability Through the Analysis of High-resolution Lake Sediment Cores from Southwestern Québec, Canada by : Karen Neil
Download or read book Ecosystem Responses to Holocene Climate Variability Through the Analysis of High-resolution Lake Sediment Cores from Southwestern Québec, Canada written by Karen Neil and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Lake biotic responses to natural climate variability, fire disturbances, and human impacts over the Holocene were studied at two proximate sites in southwestern Québec. Sediments from Lac Noir and Lac Brûlé had annually deposited laminations (varves), enabling for the precise dating of continuous time-series and high-resolution analysis of subfossil diatom assemblages. The Lac Noir (45°46'31"N, 75°8'23"W, 176 m a.s.l.) record spanned ~11000 years of the Holocene. Stratigraphic changes in diatom assemblages of the lake could be divided into early, mid-, and late periods, broadly paralleling Milankovitch-scale climate intervals and vegetation changes inferred from regional palynological records. The early Holocene (11.1-8.0 ka) climate was cooler and dry, vegetation in the region was comprised of Picea-dominated woodlands, and the lake diatom flora included primarily benthic taxa. Warming in the mid-Holocene (8.0-3.6 ka) allowed for stabilization of soils and forests in the catchment, stronger thermal stratification in the lake, and resultant increases in oligo-mesotrophic diatom taxa such as Discostella stelligera. During the late Holocene (3.6 ka to present), an increase in the abundance of deciduous trees (e.g. Betula and Alnus) in response to cooling led to nutrient-enrichment and higher overall lake productivity. The record from Lac Brûlé (45°43'09"N, 75°26'32"W, 270 m a.s.l.) encompassed the last ~1200 years of the late Holocene. Generalized additive models (GAM) revealed a tight coupling between diatoms and catchment-mediated processes (e.g. vegetation and disturbances), which were closely aligned with climate variations. During the Medieval Warm Period (800-1300 CE), pollen-based inferences of warmer summer temperatures were associated with high abundances of Cyclotella bodanica var. intermedia and Cyclotella rossii; this signalled oligotrophic lake conditions and prolonged thermal stratification. The onset of the Little Ice Age (1450-1850 CE) marked a cooling in the region, and a decline in Tabellaria flocculosa str. IIIp indicated increased nutrient loading from the catchment area. Situated less than 300m from Lac Brûlé are remnants of the Wallingford-Back Mine, which ran from 1924-1972 CE; activities at the mine resulted in local changes to nutrient availability and primary productivity at this site. In previous studies of both Lac Noir and Lac Brûlé, pollen records had indicated overall similarities in the vegetation histories in response to climate variability during the late Holocene. Diatom assemblages were influenced by individual lake conditions and were thus unique to each site; nevertheless, they were closely linked with local and regional patterns of vegetation composition. A main point of difference in the paleo-records from both lakes was attributed to a local fire in the Lac Brûlé catchment at 1345 CE, which caused an early decline in hemlock (Tsuga). The decrease in hemlock was seen at Lac Noir only centuries later, and diatoms in each lake responded according to vegetation changes within their own respective catchments. This research shows that high-resolution sampling of lake sediments is able to detect diatom responses to both long-term and abrupt changes in the environment. Individual sites show similarly timed responses of other proxy-indicators, such as pollen and cladocera, to climate and land-use changes. However, distinct differences in the aquatic biota of well-dated proximate sites can be used to identify influences of regional climate variations, which are sometimes masked by localized, non-climatic processes.
Book Synopsis Late Glacial to Holocene Climate and Vegetation Changes on the Tibetan Plateau Inferred from Fossil Pollen Records in Lacustrine Sediments by : Yongbo Wang
Download or read book Late Glacial to Holocene Climate and Vegetation Changes on the Tibetan Plateau Inferred from Fossil Pollen Records in Lacustrine Sediments written by Yongbo Wang and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The past climate in central Asia, and especially on the Tibetan Plateau (TP), is of great importance for an understanding of global climate processes and for predicting the future climate. As a major influence on the climate in this region, the Asian Summer Monsoon (ASM) and its evolutionary history are of vital importance for accurate predictions. However, neither the evolutionary pattern of the summer monsoon nor the driving mechanisms behind it are yet clearly understood. For this research, I first synthesized previously published Late Glacial to Holocene climatic records from monsoonal central Asia in order to extract the general climate signals and the associated summer monsoon intensities. New climate and vegetation sequences were then established using improved quantitative methods, focusing on fossil pollen records recovered from Tibetan lakes and also incorporating new modern datasets. The pollen-vegetation and vegetation-climate relationships on the TP were also evaluated in order to achieve a better understanding of fossil pollen records. The synthesis of previously published moisture-related palaeoclimate records in monsoonal central Asia revealed generally different temporal patterns for the two monsoonal subsystems, i.e. the Indian Summer Monsoon (ISM) and East Asian Summer Monsoon (EASM). The ISM appears to have experienced maximum wet conditions during the early Holocene, while many records from the area affected by the EASM indicate relatively dry conditions at that time, particularly in north-central China where the maximum moisture levels occurred during the middle Holocene. A detailed consideration of possible driving factors affecting the summer monsoon, including summer solar insolation and sea surface temperatures, revealed that the ISM was primarily driven by variations in northern hemisphere solar insolation, and that the EASM may have been constrained by the ISM resulting in asynchronous patterns of evolution for these two subsystems. This hypothesis is further supported by modern monsoon indices estimated using the NCEP/NCAR Reanalysis data from the last 50 years, which indicate a significant negative correlation between the two summer monsoon subsystems. By analogy with the early Holocene, intensification of the ISM during coming decades could lead to increased aridification elsewhere as a result of the asynchronous nature of the monsoon subsystems, as can already be observed in the meteorological data from the last 15 years. A quantitative climate reconstruction using fossil pollen records was achieved through analysis of sediment core recovered from Lake Donggi Cona (in the north-eastern part of the TP) which has been dated back to the Last Glacial Maximum (LGM). A new data-set of modern pollen collected from large lakes in arid to semi-arid regions of central Asia is also presented herein. The concept of "pollen source area" was introduced to modern climate calibration based on pollen from large lakes, and was applied to the fossil pollen sequence from Lake Donggi Cona. Extremely dry conditions were found to have dominated the LGM, and a subsequent gradually increasing trend in moisture during the Late Glacial period was terminated by an abrupt reversion to a dry phase that lasted for about 1000 years and coincided with the first Heinrich Event of the northern Atlantic region. Subsequent periods corresponding to the warm Bølling-Allerød period and the Younger Dryas cold event were followed by moist conditions during the early Holocene, with annual precipitation of up to about 400 mm. A slightly drier trend after 9 cal ka BP was then followed by a second wet phase during the middle Holocene that lasted until 4.5 cal ka BP. Relatively steady conditions with only slight fluctuations then dominated the late Holocene, resulting in the present climatic conditions. In order to investigate the relationship between vegetation and climate, temporal variations in the possible driving factors for vegetation change on the northern TP were examined using a high resolution late Holocene pollen record from Lake Kusai. Moving-window Redundancy Analyses (RDAs) were used to evaluate the correlations between pollen assemblages and individual sedimentary proxies. These analyses have revealed frequent fluctuations in the relative abundances of alpine steppe and alpine desert components, and in particular a decrease in the total vegetation cover at around 1500 cal a BP. The climate was found to have had an important influence on vegetation changes when conditions were relatively wet and stable. However, after the 1500 cal a BP threshold in vegetation cover was crossed the vegetation appears to have been affected more by extreme events such as dust storms or fluvial erosion than by the general climatic trends. In addition, pollen spectra over the last 600 years have been revealed by Procrustes analysis to be significantly different from those recovered from older samples, which is attributed to an increased human impact that resulted in unprecedented changes to the composition of the vegetation. Theoretical models that have been developed and widely applied to the European area (i.e. the Extended R-Value (ERV) model and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model) have been applied to the high alpine TP ecosystems in order to investigate the pollen-vegetation relationships, as well as for quantitative reconstructions of vegetation abundance. The modern pollen-vegetation relationships for four common pollen species on the TP have been investigated using Poaceae as the reference taxa. The ERV Submodel 2 yielded relatively high PPEs for the steppe and desert taxa (Artemisia Chenopodiaceae), and low PPEs for the Cyperaceae that are characteristic of the alpine Kobresia meadows. The plant abundances on the central and north-eastern TP were quantified by applying these PPEs to four post-Late Glacial fossil pollen sequences. The reconstructed vegetation assemblages for the four pollen sequences always yielded smaller compositional species turnovers than suggested by the pollen spectra, indicating that the strength of the previously-reported vegetation changes may therefore have been overestimated. In summary, the key findings of this thesis are that (a) the two ASM subsystems show asynchronous patterns during both the Holocene and modern time periods, (b) fossil pollen records from large lakes reflect regional signals for which the pollen source areas need to be taken into account, (c) climate is not always the main driver for vegetation change, and (d) previously reported vegetation changes on the TP may have been overestimated because they ignored inter-species variations in pollen productivity
Book Synopsis A 2650-year-long Record of Environmental Change from Northern Yellowstone National Park Based on a Comparison of Multiple Proxy Data by : Cathy Whitlock
Download or read book A 2650-year-long Record of Environmental Change from Northern Yellowstone National Park Based on a Comparison of Multiple Proxy Data written by Cathy Whitlock and published by . This book was released on 2007 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Geochemical, stable-isotope, pollen, charcoal, and diatom records were analyzed at high-resolution in cores obtained from Crevice Lake, a varved-sediment lake in northern Yellowstone National Park. The objective was to reconstruct the ecohydrologic, vegetation, and fire history of the watershed for the last 2650 years to better understand past climate variations at the forest-steppe transition. The data suggest a period of limited bottom-water anoxia, relatively wet winters, and cool springs and summers from 2650 to 2100 cal yr BP (700?150 BC). Dry warm conditions occurred between 2100 and 850?800 cal yr BP (150 BC and AD 1100?1150), when the lake was anoxic, winter precipitation was low, and summer stratification was protracted. The data are consistent with overall warmer/drier conditions during the Medieval Climate Anomaly, although they suggest a shift towards wetter winters within that period. The period from 850 to 800 cal yr BP (AD 1100?1150) to 250 cal yr BP (AD 1700) was characterized by greater water-column mixing and cooler spring/summer conditions than before. In addition, fire activity shifted towards infrequent large events and pollen production was low. From 250 to 150 cal yr BP (AD 1700?1800), winter precipitation was moderate compared to previous conditions, and the lake was again stratified, suggesting warm summers. Between 150 and 42 cal yr BP (AD 1800?1908), winter precipitation increased and spring and summer conditions became moderate. Metal pollution, probably from regional mining operations, is evident in the 1870s. Large fires occurred between ca. 1800?1880, but in general the forests were more closed than before. The Crevice Lake record suggests that the last 150 years of Yellowstone?s environmental history were characterized by intermediate conditions when compared with the previous 2500 years.
Book Synopsis Holocene Environmental Variability Inferred from Lake Sediments, Southwest Yukon Territory, Canada by : Joan Bunbury
Download or read book Holocene Environmental Variability Inferred from Lake Sediments, Southwest Yukon Territory, Canada written by Joan Bunbury and published by . This book was released on 2009 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Diatom-inferred Records of Paleolimnological Variability and Continental Hydrothermal Activity in Yellowstone National Park, USA by : Sabrina Brown
Download or read book Diatom-inferred Records of Paleolimnological Variability and Continental Hydrothermal Activity in Yellowstone National Park, USA written by Sabrina Brown and published by . This book was released on 2019 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Paleolimnology written by Andrew S. Cohen and published by Oxford University Press. This book was released on 2003-05-29 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text, written by a leading researcher in the field, describes the origin and formation of lakes in order to give context to the question of how lacustrine deposits form. It explains the process of sedimentation in lakes and the chemistry of those deposits and describes how the age of lake deposits are determined. Additionally, this book shows how different groups of fossils are used in interpreting the paleontological record of lakes. In order to illustrate the more synthetic approaches to interpreting the history of lakes, the author also discusses such special topics as lake-level history, lake evolution, and the impact of environmental change on lakes.
Book Synopsis Knowing Yellowstone by : Jerry Johnson
Download or read book Knowing Yellowstone written by Jerry Johnson and published by Rowman & Littlefield. This book was released on 2010-06-16 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Visitors to Yellowstone National Park are drawn to the spectacular scenery, unique thermal features, and the large numbers of wild animals easily observed in their natural habitat. The thoughtful visitor to the park cannot help but be captivated by the unparalleled breadth of scientific knowledge needed to understand the intricate interrelationships that make up the yellowstone landscape. Knowing Yellowstone explores how scientists discover what they know about America's first national park and the surrounding lands. The chapter authors are scientists who represent the best of their fields of study. The science they describe is leading the way to our understanding of complex ecosystems worldwide.
Book Synopsis Late Holocene Diatom and Geochemical Evidence of Freshwater Flow Variation in Northern San Francisco Bay, California by : Scott William Starratt
Download or read book Late Holocene Diatom and Geochemical Evidence of Freshwater Flow Variation in Northern San Francisco Bay, California written by Scott William Starratt and published by . This book was released on 2004 with total page 1060 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Holocene Climate and Environmental Change in the Great Basin of the Western United States by : Scott Alan Reinemann
Download or read book Holocene Climate and Environmental Change in the Great Basin of the Western United States written by Scott Alan Reinemann and published by . This book was released on 2013 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: In this dissertation, I have completed a research project that focused on reconstructing past climate and environmental conditions in the Great Basin of the western United States. This research project incorporates four discrete but interrelated studies. (1) The geochemistry of lake sediments was used to identify anthropogenic factors influencing aquatic ecosystems of sub-alpine lakes in the western United States during the past century. Sediment cores were recovered from six high elevation lakes in the central Great Basin of the United States. Mercury (Hg) flux varied among lakes but all exhibited increasing fluxes during the mid-20th century and declining fluxes during the late 20th century. Peak Spheroidal Carbonaceous Particles (SCP) flux for all lakes occurred at approximately 1970, after which SCP flux was greatly reduced. Atmospheric deposition is the primary source of Hg and anthropogenically produced SCPs to these pristine high elevation lakes during the late 20th century. (2) Chironomids are used to develop centennial length temperature reconstructions for six sub-alpine and alpine lakes in the central Great Basin of the United States. Chironomid-inferred temperature estimates indicate that four of the six lakes were characterized by above average air temperatures during the post-AD 1980 interval and below average temperatures during the early 20th century. This study adds to the growing body of evidence that sub-alpine and alpine lakes in the western United States have been, and are increasingly being affected by anthropogenic climate change in the early 21st century. (3) A sediment core representing the past two millennia was recovered from Stella Lake in the Snake Range of the central Great Basin in Nevada. The core was analyzed for sub-fossil chironomids and sediment organic content. The chironomid-based mean July air temperature (MJAT) reconstruction suggests that the Medieval Climate Anomaly (MCA), was characterized by MJAT elevated 1.0°C above the subsequent Little Ice Age (LIA), but likely not as warm as recent conditions. The Stella Lake record provides evidence that elevated summer temperature contributed to the increased aridity that characterized the western United States during the MCA. (4) Lake sediment cores spanning roughly the last 7,000 years were recovered from four small sub-alpine and alpine lakes located in central Great Basin of the United States. Reconstructions of MJAT were developed for each of the study sites using a chironomid-based inference model for MJAT (two-component Weighted Averaging-Partial Least Squares (WA-PLS)). The elevated temperature that characterizes the mid-Holocene at Stella Lake is surpassed only during the Medieval Climate Anomaly and in the post-AD 1800 interval. The reconstructions for the sites located in the northern portion of the study transect are characterized by greater variability, likely reflecting the influence of both radiative forcing and catchment-specific conditions.
Book Synopsis Aquatic Ecosystem Response to Late Pleistocene and Holocene Climate Variations by : Sarah Hembrow
Download or read book Aquatic Ecosystem Response to Late Pleistocene and Holocene Climate Variations written by Sarah Hembrow and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: High resolution palaeoecological data is a valuable tool to determine past climate variability and ecological responses. This thesis examined the aquatic community response of three lakes on Fraser Island using biological and geochemical records for the last 18,000 years. The lake records demonstrate a trend of decreasing precipitation throughout the late Holocene, with increased climatic variability represented by episodic events. From these records, a more detailed knowledge of climate change in eastern Australia during the Holocene has been identified.
Book Synopsis A High-resolution Record of Holocene Drought Variability and the Diatom Stratigraphy of Foy Lake, Montana by : Jeffery Robert Stone
Download or read book A High-resolution Record of Holocene Drought Variability and the Diatom Stratigraphy of Foy Lake, Montana written by Jeffery Robert Stone and published by . This book was released on 2005 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt:
