Read Books Online and Download eBooks, EPub, PDF, Mobi, Kindle, Text Full Free.
Synchronous Climatic Change Inferred From Diatom Records In Four Western Montana Lakes In The Us Rocky Mountains
Download Synchronous Climatic Change Inferred From Diatom Records In Four Western Montana Lakes In The Us Rocky Mountains full books in PDF, epub, and Kindle. Read online Synchronous Climatic Change Inferred From Diatom Records In Four Western Montana Lakes In The Us Rocky Mountains ebook anywhere anytime directly on your device. Fast Download speed and no annoying ads. We cannot guarantee that every ebooks is available!
Book Synopsis Synchronous Climatic Change Inferred from Diatom Records in Four Western Montana Lakes in the U.S. Rocky Mountains by : Brandi B. Bracht-Flyr
Download or read book Synchronous Climatic Change Inferred from Diatom Records in Four Western Montana Lakes in the U.S. Rocky Mountains written by Brandi B. Bracht-Flyr and published by . This book was released on 2012 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Late-Holocene environmental and climatic conditions were reconstructed from diatom assemblages in sediment cores from four western Montana lakes: Crevice Lake, Foy Lake, Morrison Lake, and Reservoir Lake. The lakes show synchroneity in timing of shifts in diatom community structure, but the nature of these changes differs among the lakes. Two of the sites provide highly resolved records of hydrologic balance, while the other two stratigraphic sequences primarily record temperature impact on lake thermal structure. All four lakes show significant change in five discrete intervals: 2200-2100, 1700-1600, 1350-1200, 800-600, and 250 cal yr BP. The similarities in the timing of change suggest overlying regional climatic influences on lake dynamics. The 800-600 cal yr BP shift is evident in other paleorecords throughout the Great Plains and western US, associated with the transition from the Medieval Climate Anomaly to the Little Ice Age. Large-scale climatic mechanisms that influence these lake environments may result from atmospheric circulation patterns that are driven by interactions between Pacific and Atlantic sea-surface temperatures, which are then locally modified by topography.
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 Diatom-inferred Records of Paleo-climate and Paleo-hydrogeology from Lakes in Regions of Different Climate by : Jay York Seabright Hodgson
Download or read book Diatom-inferred Records of Paleo-climate and Paleo-hydrogeology from Lakes in Regions of Different Climate written by Jay York Seabright Hodgson and published by . This book was released on 2009 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: I comparatively investigated mid-to-late Holocene paleo-climate and paleo-hydrogeology in three regions with different climates (Alaska, New Mexico, and Alabama) using diatom frustules as the primary proxy sampled from lake sediment cores. This cross-regional research differs from previous paleo-limnology syntheses because it was designed a priori to simultaneously decipher differential environmental conditions using uniform measurements of the same proxy types with equal environmental sensitivities across spatial scales. Data were analyzed with a combination of multivariate ordination and time series bandwidth analysis to identify significant bifurcation points between periods of changing environmental conditions. Each study region demonstrated different environmental changes through time. Diatom community dynamics in Alaska were significantly correlated with temperatures, indicating that diatom community structure is a validated temperature change surrogate. In New Mexico, diatom dynamics were significantly correlated with both precipitation and solar intensity, suggesting that diatoms are validated surrogates of solar-modulated drought. Additionally, the diatoms indicated that the study lake was susceptible to drought-induced acidification. In Alabama, the combination of diatoms and sedimentary organic matter elucidated oxbow lake evolution and fluctuations in coastal plain water tables. These changes were potentially caused by alterations in precipitation and eustatic sea levels following the last glaciation. Similar interpretations of mid-Holocene hydrogeology have been reported elsewhere in the coastal plain. This cross-regional research demonstrated differential proxy responses between each climate region. More importantly, it also suggested reasons why uniform methods elucidated varying responses across broad spatial scales. Global climate change has the potential to affect different regional climates very differently from each other. My intersite research indicated that each region did not capture a ubiquitous global climate pressure. Instead, each region experienced asynchronous climate changes through time. This research is an important first step and a valuable approach in discerning climate change responses among different regions that could, subsequently, be applied more broadly across other regions and lead to improved climate change analyses.
Book Synopsis Patterns and Processes of Lake Responses to Quaternary Climate Change in Rock Mountain Watersheds and Across North America by : David T. Liefert
Download or read book Patterns and Processes of Lake Responses to Quaternary Climate Change in Rock Mountain Watersheds and Across North America written by David T. Liefert and published by . This book was released on 2020 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: The sensitivity of water resources to climate change challenges water planning in the semi-arid western United States. Paleoclimate records illustrate the potential for hydrological change in response to warming, but questions remain regarding the sensitivity of Rocky Mountain snowpack to temperature change and how watershed processes interact with climate to affect the flux of water from headwater areas. I investigated these themes using the water budgets, sedimentology, and isotope compositions of lakes in the Snowy Range, Wyoming, and across North America. I found that snowmelt controls the volumes of small subalpine lakes and that drainage promotes seasonal water loss and lake-stream connectivity. The sediment histories of small lakes thus reflect snowpack changes and show that snowpack increased from the mid-Holocene to present as the region cooled by >1°C to reach the 20th-century mean. Snowfield reductions coincided with the desiccation of lakes, which further underscore the sensitivity of water supplies to warming. Lacustrine carbonate oxygen isotopes document severe drying from 4.2–4 ka and align with records from adjacent regions to show widespread aridity associated with the 4.2 ka climatic anomaly. Although the 4.2 ka drought may reflect stochastic variability, mapped lake-level trends reveal predictable multi-century to millennial hydrologic changes throughout North America in response to post-glacial atmospheric circulation and insolation dynamics of the late Quaternary. The results here show that the Rocky Mountains and other water-producing areas were commonly drier than today, and that 21st-century warming could reproduce the mid-Holocene declines in snowpack and late-season groundwater recharge critical to streamflow.
Book Synopsis Climatic Changes Inferred from Analyses of Lake-sediment Cores, Walker Lake, Nevada ; Prepared in Cooperation with the U.S. Department of Energy by : In Che Yang
Download or read book Climatic Changes Inferred from Analyses of Lake-sediment Cores, Walker Lake, Nevada ; Prepared in Cooperation with the U.S. Department of Energy written by In Che Yang and published by . This book was released on 1989 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 The Climatic Changes of Later Geological Times by : Josiah Dwight Whitney
Download or read book The Climatic Changes of Later Geological Times written by Josiah Dwight Whitney and published by . This book was released on 1882 with total page 450 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Water Chemistry of Rocky Mountain Front Range Aquatic Ecosystems by : Robert C. Musselman
Download or read book Water Chemistry of Rocky Mountain Front Range Aquatic Ecosystems written by Robert C. Musselman and published by . This book was released on 1996 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Long-Term Hydroclimatic Change in the U.S. Rocky Mountain Region: Implications for Ecosystems and Water Resources by : Gregory Thomas Pederson
Download or read book Long-Term Hydroclimatic Change in the U.S. Rocky Mountain Region: Implications for Ecosystems and Water Resources written by Gregory Thomas Pederson and published by . This book was released on 2010 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Both natural and anthropogenic climate change are driven by forcings that interact and result in hydroclimatic changes that alter ecosystems and natural resources at different temporal and spatial scales. Accordingly, changes within regions (i.e. individual points to large watersheds) may differ from patterns observed at sub-continental to global scales, thus necessitating the generation of point- to region-specific, cross-scale hydroclimatic data to elucidate important drivers of observed changes, and provide information at scales relevant to resource managers. Herein, we use the Northern U.S. Rocky Mountains as a study region to explore 1) the covariability between observed hydrologic and climatic changes, 2) the nature of changes occurring at the scale of days to decades, and 3) the ocean-atmosphere teleconnections operating at continental- to hemispheric-scales underlying the observed regional patterns of hydroclimatic variability. We then expand the scope of study to include the entire central North American Cordillera to investigate changes in winter precipitation (i.e. snowpack) spanning the last millennia+, with a focus on the spatial and temporal coherence of events from the medieval climatic anomaly to present. To accomplish this we utilize the full suite of hydroclimatic observational records in conjunction with proxy records of snowpack derived from a distributed network of tree-ring chronologies. Results from observational records in the Northern Rockies show important changes have occurred in the frequency and means of biophysically important temperature thresholds, and that recent changes appear greater in magnitude at the mid- to high-elevations. These changes, coupled with interannual- to interdecadal-scale moisture variability driven by ocean-atmosphere teleconnections, are shown to be strong controls on the timing and amount of regional snowpack and streamflow. Across the cordillera, tree-ring based records of snowpack show that before 1950, the region exhibited substantial inter-basin variability in snowpack, even during prolonged droughts and pluvials, marked by a predominant north-south dipole associated with Pacific variability. Snowpack was unusually low in the Northern Rocky Mountains for much of the 20th century and over the entire cordillera since the 1980s; heralding a new era of snowpack declines entrained across all major headwaters in western North America.
Book Synopsis Reconstructing Climate Variability on the Tibetan Plateau by : Juliane Wischnewski
Download or read book Reconstructing Climate Variability on the Tibetan Plateau written by Juliane Wischnewski and published by . This book was released on 2010 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spatial and temporal temperature and moisture patterns across the Tibetan Plateau are very complex. The onset and magnitude of the Holocene climate optimum in the Asian monsoon realm, in particular, is a subject of considerable debate as this time period is often used as an analogue for recent global warming. In the light of contradictory inferences regarding past climate and environmental change on the Tibetan Plateau, I have attempted to explain mismatches in the timing and magnitude of change. Therefore, I analysed the temporal variation of fossil pollen and diatom spectra and the geochemical record from palaeo-ecological records covering different time scales (late Quaternary and the last 200 years) from two core regions in the NE and SE Tibetan Plateau. For interpretation purposes I combined my data with other available palaeo-ecological data to set up corresponding aquatic and terrestrial proxy data sets of two lake pairs and two sets of sites. I focused on the direct comparison of proxies representing lacustrine response to climate signals (e.g., diatoms, ostracods, geochemical record) and proxies representing changes in the terrestrial environment (i.e., terrestrial pollen), in order to asses whether the lake and its catchments respond at similar times and magnitudes to environmental changes. Therefore, I introduced the established numerical technique procrustes rotation as a new approach in palaeoecology to quantitatively compare raw data of any two sedimentary records of interest in order to assess their degree of concordance. Focusing on the late Quaternary, sediment cores from two lakes (Kuhai Lake 35.3ʻN; 99.2ʻE; 4150 m asl; and Koucha Lake 34.0ʻN; 97.2ʻE; 4540 m asl) on the semi-arid northeastern Tibetan Plateau were analysed to identify post-glacial vegetation and environmental changes, and to investigate the responses of lake ecosystems to such changes. Based on the pollen record, five major vegetation and climate changes could be identified: (1) A shift from alpine desert to alpine steppe indicates a change from cold, dry conditions to warmer and more moist conditions at 14.8 cal. ka BP, (2) alpine steppe with tundra elements points to conditions of higher effective moisture and a stepwise warming climate at 13.6 cal. ka BP, (3) the appearance of high-alpine meadow vegetation indicates a further change towards increased moisture, but with colder temperatures, at 7.0 cal. ka BP, (4) the reoccurrence of alpine steppe with desert elements suggests a return to a significantly colder and drier phase at 6.3 cal. ka BP, and (5) the establishment of alpine steppe-meadow vegetation indicates a change back to relatively moist conditions at 2.2 cal. ka BP. To place the reconstructed climate inferences from the NE Tibetan Plateau into the context of Holocene moisture evolution across the Tibetan Plateau, I applied a five-scale moisture index and average link clustering to all available continuous pollen and non-pollen palaeoclimate records from the Tibetan Plateau, in an attempt to detect coherent regional and temporal patterns of moisture evolution on the Plateau. However, no common temporal or spatial pattern of moisture evolution during the Holocene could be detected, which can be assigned to the complex responses of different proxies to environmental changes in an already very heterogeneous mountain landscape, where minor differences in elevation can result in marked variations in microenvironments. Focusing on the past 200 years, I analysed the sedimentary records (LC6 Lake 29.5ʻN, 94.3ʻE, 4132 m asl; and Wuxu Lake 29.9ʻN, 101.1ʻE, 3705 m asl) from the southeastern Tibetan Plateau. I found that despite presumed significant temperature increases over that period, pollen and diatom records from the SE Tibetan Plateau reveal only very subtle changes throughout their profiles. The compositional species turnover investigated over the last 200 years appears relatively low in comparison to the species reorganisations during the Holocene. The results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem. Forest clearances and reforestation have not caused forest decline in our study area, but a conversion of natural forests to semi-natural secondary forests. The results from the numerical proxy comparison of the two sets of two pairs of Tibetan lakes indicate that the use of different proxies and the work with palaeo-ecological records from different lake types can cause deviant stories of inferred change. Irrespective of the timescale (Holocene or last 200 years) or region (SE or NE Tibetan Plateau) analysed, the agreement in terms of the direction, timing, and magnitude of change between the corresponding terrestrial data sets is generally better than the match between the corresponding lacustrine data sets, suggesting that lacustrine proxies may partly be influenced by in-lake or local catchment processes whereas the terrestrial proxy reflects a more regional climatic signal. The current disaccord on coherent temporal and spatial climate patterns on the Tibetan Plateau can partly be ascribed to the complexity of proxy response and lake systems on the Tibetan Plateau. Therefore, a multi-proxy, multi-site approach is important in order to gain a reliable climate interpretation for the complex mountain landscape of the Tibetan Plateau.
Book Synopsis A Diatom Record of Late-Holocene Climate Variability in the Northern Rocky Mountains by : Brandi Bobette Bracht
Download or read book A Diatom Record of Late-Holocene Climate Variability in the Northern Rocky Mountains written by Brandi Bobette Bracht and published by . This book was released on 2007 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Climatic Changes of Later Geological Times: A Discussion Based on Observations Made in the Cordilleras of North America by : J. D. Whitney
Download or read book The Climatic Changes of Later Geological Times: A Discussion Based on Observations Made in the Cordilleras of North America written by J. D. Whitney and published by BoD – Books on Demand. This book was released on 2024-05-23 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reprint of the original, first published in 1882.
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:
Book Synopsis Response of Diatoms to Climate Change in Mountain Lakes in the Northern Calcareous Alps with Indications for the Future Development of the Lake Biota by : Wolfgang Küfner
Download or read book Response of Diatoms to Climate Change in Mountain Lakes in the Northern Calcareous Alps with Indications for the Future Development of the Lake Biota written by Wolfgang Küfner and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Postglacial Record of Climate Change from East Crooked Lake and Tofte Lake, Minnesota by : Kelly Michael Wendt
Download or read book A Postglacial Record of Climate Change from East Crooked Lake and Tofte Lake, Minnesota written by Kelly Michael Wendt and published by . This book was released on 2010 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Impact of Basin Morphology on Diatom Response to Mid-Holocene Climate Change by : Kristina Louise Brady
Download or read book The Impact of Basin Morphology on Diatom Response to Mid-Holocene Climate Change written by Kristina Louise Brady and published by . This book was released on 2006 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Water Quality Reconstruction from Fossil Diatoms by : Steven A. Heiskary
Download or read book Water Quality Reconstruction from Fossil Diatoms written by Steven A. Heiskary and published by . This book was released on 2002 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt:
