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.

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.

Download or read book Paleoclimate Investigation and Interpretation of Lacustrine Sediment from Lake Telmen and Lake Ugiy Mongolia written by Paul Joseph McDonald and published by . This book was released on 2008 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Mongolia, located in Central Asia, experiences the most continental climate on Earth. Although detailed paleoclimate data are abundant for selected areas throughout Asia, datasets from within Mongolia are relatively scarce and demonstrate significant spatial and temporal variability. In older paleoclimatic reconstructions Mongolian climate was thought to be controlled by the East Asian monsoon system in a similar manner to China to the south. However in recent decades, additional paleoclimate records throughout central Asia have indicated a climate asynchronous with China, dominated by the Westerlies rather than the East Asian monsoon. The objective of this thesis study is to supplement existing paleoclimate proxy records in order to better understand Holocene climate variability in Mongolia and to assess the role of the Westerlies in producing that variability. This study produces new bulk-carbonate isotopic and mineralogic records for north-central Mongolia from a 7,110 year Lake Telmen and a 5,100 year Lake Ugiy sediment core. Lake Telmen is a saline (4 g/l), closed-basin lake, ideal for amplifying hydrologic variability into large sedimentological responses and is thus well-suited for paleoclimate study. The relatively heavy [delta]18O carbonate stable isotopes (averaging -0.5 [zero/zero zero]) and abundant ankerite, quartz and phillipsite minerals suggest an arid climate dominated prior to approximately 4,500 yr B.P. Since 4,500 yr B.P., the Lake Telmen sediment data suggests an increase in humidity evidenced by lighter [delta]18O values (averaging -1.2 [zero/zero zero]) with a corresponding mineralogical shift to abundant monohydrocalcite and calcite. These new records are in agreement with previous Lake Telmen paleoclimate interpretations based upon pollen, diatoms and lithology, suggesting the East Asian monsoon does not control the Holocene climate in the Telmen region. The Lake Ugiy sediment core mineralogy supports this interpretation, revealing abundant terrigenous minerals, a shallow lake, and more arid conditions prior to approximately 4,000 yr. B.P.A more humid climate since 4,000 yr B.P. is based on lacustrine mud with calcite and Mg calcite inferred to represent deeper water conditions. Brief arid intervals occur during the otherwise humid late Holocene as inferred from heavy isotope values and ankerite, quartz and phillipsite abundance in Lake Telmen, and abundant Mg calcite in Lake Ugiy at about 1,300-1,600, 2,000-2,200 and 2,800-3,100 yr B.P. The records from this thesis study support published interpretations that suggest central Asian Holocene climate is dominated by the Westerlies and is asynchronous with Chinese climate dominated by the East Asian monsoon. A North Atlantic high pressure system associated with cold sea surface temperature (SST) redirected the Westerly track causing the movement of dry air into Mongolia during the early Holocene. However, during the early Holocene increased boreal summer insolation produced a stronger East Asian summer monsoon system and increased moisture in China. By the late Holocene the disappearance of the Laurentide ice sheet allowed for increased North Atlantic SST and the development of a low pressure system. The more zonal Westerlies now carried warm moist air across Europe and into Mongolia thereby increasing the moisture balance in the late Holocene. During the late Holocene, North Atlantic SST periodically cooled due to ice rafting. The cold North Atlantic and altered atmospheric pressure gradient may have diverted the path of the Westerlies so that cold dry air flowed into Mongolia. These cold episodes are known as Bond cycles and included events dated at 1,400 and 2,800 yr B.P. These Bond cycles are similar in age to brief arid events within Mongolia and suggest hemispheric teleconnnection and a possible role for North Atlantic SST to influence Mongolian climate."--Abstract.

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 525 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.

Download or read book Diatom Records of Holocene Climatic and Hydrological Changes in the Western Hudson Bay Region Canada written by Charlotte Ellen Friel and published by . This book was released on 2011 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapidly changing climates in northern Canada make the western Hudson Bay region an area of high importance for paleoenvironmental studies. Long-term changes in assemblages of diatoms (microscopic algae) were analyzed from lake sediment cores from Baker Lake, Nunavut, and Lake AT01, northern Ontario, to track responses to past environmental changes. Diatom assemblages dating to 6700 years ago in AT01 were initially characterized by cold-tolerant Fragilarioid assemblages, but shifted to an assemblage dominated by large benthic species and Cymbella diluviana consistent with the timing of the Holocene Thermal Maximum after 6300 years BP. A possible drainage event in Lake AT01 may have added significant hydrologic control on the diatom assemblages. The post-industrial period is marked by the largest compositional shifts in both records. Assemblages during the 20th century are indicative of reduced ice cover and enhanced thermal stratification linked to a climate regime shift noted in Hudson Bay since the mid-1990's.

Download or read book Diatoms in Castor Lake North Central Washington USA written by Kelly Dianne Hollingshead and published by . This book was released on 2012 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research provides a high temporal resolution (1 sample / 2-3 years) record of hydrologic variation for the last 2,000 years using a lake sediment record from Castor Lake, a closed-basin system in Washington, USA. The core was dated using 137Cs, 14C, and tephrochronology. Approximately 600 diatoms were identified and enumerated in 198 samples from a Castor Lake freeze core and Livingstone-piston core. A diatominference model for salinity was applied to reconstruct fossil diatom salinity. Diatominferred salinity for the last century tracked Palmer Drought Severity Index, indicating diatom community composition tracks effective moisture and can be used to infer past hydrologic change. The 2000-year record of salinity from Castor Lake shows that during the Medieval Climate Anomaly (800-1300 AD) Castor Lake experienced cooler, wetter conditions than during the Little Ice Age (1400-1850 AD), which is opposite to what has been reported for the US southwest. These findings are consistent with a wet Pacific Northwest and a dry southwest recorded during La Niña and cool Pacific Decadal Oscillation (PDO) phases. Although these suggest a link to sea surface temperatures, diatom-inferred salinity was only related to proxy records of the PDO for the period between 1000 and 1500 AD. This indicates that other forcing mechanisms could also be important to controlling effective moisture at Castor Lake.

Download or read book Quantitative Paleoclimate Reconstructions from the Melville Peninsula Nunavut Canada written by Jennifer Karen Adams and published by . This book was released on 2009 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: A transitional climate and the presence of Thule sites make the Melville Peninsula an area of high importance for paleoenvironmental studies. Lake sediment cores and surface samples from Melville Peninsula were analyzed for diatom assemblages. Fragilarioid diatom species dominate assemblages from the interior of the peninsula since the middle Holocene. The greatest changes in diatom communities occurred during the transition from the Holocene Thermal Maximum to the Neoglacial, and in the post-Little Ice Age period. Species richness reached maximum values in the most recent period, reaching 50.8 species in surface sediments. Diatom-inferred pH reconstruction from two lakes did not indicate substantial change throughout the Holocene despite assemblage changes, showing the complexity of interpreting paleoclimate records dominated by Fragilarioids. Analysis of modern assemblages from the interior and East coast of Melville Peninsula confirm the importance of site size and water chemistry, as determined by bedrock geology, in determining diatom species distributions.

Download or read book Quantitative Paleoclimate Reconstructions from the Melville Peninsula Nunavut Canada written by Jennifer Adams and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Paleoecological and Isotopic Records of Climate Change and Variability from Lakes and Speleothems Bear River Range Southeastern Idaho written by Zachary J. Lundeen and published by . This book was released on 2012 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tracking Environmental Change Using Lake Sediments written by John P. Smol and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: This third volume in the Developments in Paleoenvironmental Research series deals with the major terrestrial, algal, and siliceous indicators used in paleolimnology. Other volumes deal with the acquisition and archiving of lake sediment cores, chronological techniques, and large-scale basin analysis methods (Volume 1), physical and geochemical parameters and methods (Volume 2), zoological techniques (Volume 4), and statistical and data handling methods (Volume 5). These monographs will provide sufficient detail and breadth to be useful handbooks for both seasoned practitioners as well as newcomers to the area of paleolimnology. Although the chapters in these volumes target mainly lacustrine settings, many of the techniques described can also be readily applied to fluvial, glacial, marine, estuarine, and peatland environments.

Download or read book Lake Diatoms as a Proxy for Holocene Environmental Change West Greenland written by Louise Alice Best and published by . This book was released on 2013 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract:There is great interest over the Greenland Ice Sheet in terms of future climate change, though there is a lack of understanding of climate change during the Holocene. Lakes can provide continuous and detailed records of paleoclimate; the distinct taxonomy and preservation potential of diatoms makes them a particularly useful proxy within paleoenvironmental reconstructions. Contemporary diatom assemblages and the environmental conditions of 25 lakes from a localized area in the Godthåbsfjord region, southwest Greenland, as well as a fossil core from one of the lakes, are studied. Multivariate analysis is undertaken to establish the relationships between the contemporary diatoms and environmental conditions, and the addition of another dataset from Søndre Strømfjord, west Greenland, provided an insight into lake and diatom variability. Transfer functions are then developed for several environmental variables, including pH, temperature and lake depth, and applied to the fossil diatom assemblages from the lake core. The fossil diatom assemblages and quantitative reconstructions indicate an acidification of the lake through the Holocene, and the quantitative reconstructions, along with additional proxy data of pollen, provide a record of several warming and cooling phases through the Holocene, including the Little Ice Age. There are however several issues, including multiple forcing variables acting on the contemporary diatoms, the provision of modern analogues for the fossil assemblages, as well as preservation problems, that raise several questions over the reliability of lake diatoms as a proxy for Holocene environmental change in southwest Greenland.

Download or read book Arctic and North Atlantic Paleo environmental Reconstructions from Lake Sediments written by Gregory A. de Wet and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT ARCTIC AND NORTH ATLANTIC PALEO-ENVIRONMENTAL RECONSTRUCTIONS FROM LAKE SEDIMENTS MAY 2017 GREGORY A. DE WET, B.Sc., BATES COLLEGE M.Sc., UNIVERSITY OF MASSSCHUSETTS, AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS, AMHERST Directed by: Drs. Raymond S. Bradley and Isla S. Castañeda There are few fields in the discipline of Earth Science that hold more relevancy in 2017 than studies of earth's climate. Called the "perfect problem" considering its complexity and magnitude, climate change will continue to be one of the greatest challenges humanity will face in the 21st century. And while numerical models provide valuable information on conditions in the future, the results from these simulations must be contextualized by the past. Climate reconstructions from paleo-environmental archives, even from periods colder or different from what we are experiencing today, provide that context. Every piece of information gleaned from these studies informs our collective knowledge of the climate system. In some cases, environmental reconstructions may include proxies for anthropogenic as well as climatological information, directly addressing one of the most important questions in climate science: how does changing climate affect humans? The following chapters of this dissertation are exercises in trying to understand climate change in one of the most climatically sensitive regions on earth - the high northern latitudes. While my doctoral studies cover a wide range of timescales, it is broadly unified by the focus on the Arctic. In some cases, my research spans multiple glacial/interglacial cycles, in others the concentration is on the past few thousand years. In all cases, however, the goal is to utilize lacustrine sedimentary archives to inform our knowledge of climatic change in this important region. One of the most rewarding aspects of this Ph.D. has been the creativity I have been afforded in working towards that goal. Chapter One of this dissertation involves the analysis of organic molecules, specifically bacterial membrane lipids called branched glycerol dialkyl glycerol tetraethers (brGDGTs), to sediments from Lake El'gygytgyn. These biomarkers allow for a quantitative reconstruction of temperature from multiple interglacial periods over a million years ago. Our data suggests that "super interglacial" Marine Isotope Stage 31 may have in fact lasted much longer than previously thought in the Arctic, with implications for Antarctic ice sheet extent and CO2 concentrations highly relevant to our future. Though the extraction and analysis of these biomarkers is expensive and time-consuming, the data is highly valuable and informative. Conversely in some cases more "quick and dirty" techniques are sufficient to reconstruct important processes or factors back through time (e.g. the presence of a glacier within a lake catchment) at relatively low cost, and therefore are highly useful. The chapters dealing with Lake Gjøavatnet in Svalbard (Chapter Two) or the application of Fourier Transform Infrared (FTIR) spectroscopy to lake sediments (Chapter Five) exhibit how such techniques can also be highly informative. In Chapter Two, using a combination of core-scanning data and relatively simple destructive analyses (%loss-on-ignition, bulk carbon isotopes), we reconstructed past fluctuations in glacier extent over the Holocene, as well as identified intervals that may have been related to freshwater pulses in Fram Strait. Chapter Five is focused mainly on expanding and confirming the use of FTIR spectroscopy to Arctic lake sediments to reconstruct biogenic silica and organic matter concentrations through time. Though potentially a less direct climate proxy than paleotemperature from brGDGTs, this new technique allows for more rapid analyses using less sediment than previous methods, a valuable advance. Chapters Three and Four are in many ways the confluence of these earlier stages of my Ph.D., where we apply a wide range of proxies to answer questions related to climate and human population dynamics. The use of biomarkers is expanded in these projects, where a broad suite of organic molecules are used to reconstruct both climate and other paleo-environmental conditions, including vegetation changes, variations in pH, and potentially anthropogenic influences. Coupled with some of the more "basic" techniques described above, we characterize an environmental disturbance in the Faroe Islands ~2200 years ago that may be evidence for the first appearance of humans in the archipelago (Chapter Three). In Chapter Four, we explore the application of brGDGTs (among other proxies) to reconstruct temperature change in southwest Greenland during the period of Norse settlement and subsequent abandonment. This work is part of an ongoing investigation into the efficacy and calibration of this promising proxy in a locale where climate change likely had a dramatic impact on the fragile communities living there. In summary, I have not attempted to unify these chapters into a single climatological context (though some of my work, such as in the Faroes and Greenland, is highly related). Instead I present them as they are, individual projects that each have their own goals and merits within the broad framework of paleoclimatology. As I mentioned above, one of my favorite things about this field is the creativity we are afforded in our attempts to answer questions about the past. This Ph.D. has been an exercise in that creativity, focused in the high northern latitudes, and centered around the archive of lake sediments.

Download or read book Tracking Environmental Change Using Lake Sediments written by John P. Smol and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: Paleolimnology is a rapidly developing science that is now being used to study a suite of environmental and ecological problems. This volume is the fourth handbook in the Developments in Paleoenvironmental Research book series. The first volume (Last & Smol, 2001a) examined the acquisition and archiving of sediment cores, chronological techniques, and large-scale basin analysis methods. Volume 2 (Last & Smol, 2001b) focused on physical and chemical methods. Volume 3 (Smol et al. , 2001), along with this book, summarize the many biological methods and techniques that are available to study long-term environmental changeusing information preserved in sedimentary profiles. A subsequent volume (Birks et al. , in preparation) will deal with statistical and data handling procedures. It is our intent that these books will provide sufficient detail and breadth to be useful handbooks for both seasoned practitioners as well as newcomers to the area of paleolimnology. These books will also hopefully be useful to non-paleolimnologists (e. g. , limnologists, archeologists, palynologists, geographers, geologists, etc. ) who continue to hear and read about pal- limnology, but have little chance to explore the vast and sometimes difficult to access journal-based reference material for this rapidly expanding field. Although the chapters in these volumes target mainly lacustrine settings, many of the techniques described can also be readily applied to fluvial, glacial, marine, estuarine, and peatland environments. This current volume focuses on zoological indicators preserved in lake sediments, whilst Volume 3 focused on terrestrial, algal, and siliceous indicators.

Download or read book Early Pliocene Ross Sea Paleoclimate and a New Application of the Diatom Oxygen Isotope Proxy written by Hal W. Hackett and published by . This book was released on 2016 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxygen isotope measurements ([delta]18O) provide valuable insight into climate conditions. These data are advantageous as paleoclimate proxies, but records are sparse in high latitude waters, where calcareous microfossils are poorly preserved in marine sediments. Over glacial timescales, high latitude regions likely have the widest variability in terms of the [delta]18O values of marine waters; therefore, the paucity of data in these regions greatly hinders our ability to reconstruct global climatic and environmental change. This research is motivated to investigate Southern Ocean diatoms as a way to begin filling the gap in our knowledge. Diatoms are a cosmopolitan group of siliceous phytoplankton with characteristic ecological affinities. Diatom silica is increasingly being analyzed as a [delta]18O archive, and has the potential to provide comparable data to [delta]18O variations recorded by benthic foraminifera, but to date, studies have focused on Holocene sediments. This thesis presents oxygen isotope values from Early Pliocene Ross Sea diatoms, assessment of purification procedures, and implications for paleoclimate and the history of the West Antarctic Ice Sheet. ANDRILL AND-1B is a 13 Ma record from the Antarctic Geologic Drilling Project in the Ross Sea, which provides Lower to Mid Pliocene diatomite units. The context provided by age models and paleoenvironmental studies, along with more geologically recent Southern Ocean diatom [delta]18O measurements, make AND-1B an ideal dataset for further exploring the use of diatom [delta]18O values as a record of changes in salinity and temperature in high latitude seawater. Samples were purified; geochemically and mineralogically assessed using x-ray diffraction (e.g. identification of amorphous opal-A vs. mineral contamination) and x-ray fluorescence (e.g. elemental quantification of clay contamination); then analyzed for [delta]18O values using a step-wise fluorination (SWF) -- CO2 laser heating technique and a Thermo MAT 253 isotope ratio mass spectrometer. Correction methods based on different assumptions place constraints on true diatom [delta]18O values, with margins of error dependent on final sample purity. The results are intermediate between Holocene Antarctic diatom [delta]18O studies, indicating that diatom [delta]18O values can remain largely or entirely unaltered for at least 4.5 Ma. Interpreting these values through the current paleotemperature model, with the contingent paleoenvironmental constraints afforded by AND-1B, suggests water [delta]18O values offset about -10% relative to today's ocean. Stacked benthic foraminifera [delta]18O values for the Pliocene suggest an ocean average less than 1% different than the present; therefore, this points to a strong component of glacial water in a warmer, fresher Pliocene Ross Sea.

Download or read book Proceedings of the Great Lakes Paleo Levels Workshop written by and published by . This book was released on 1999 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Lake Status Records from the Former Soviet Union and Mongolia written by and published by . This book was released on 1996 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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.