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Sample records for paleoclimatology

  1. Molecular proxies for paleoclimatology

    NASA Astrophysics Data System (ADS)

    Eglinton, Timothy I.; Eglinton, Geoffrey

    2008-10-01

    We summarize the applications of molecular proxies in paleoclimatology. Marine molecular records especially are proving to be of value but certain environmentally persistent compounds can also be measured in lake sediments, loess deposits and ice cores. The fundamentals of this approach are the molecular parameters, the compound abundances and carbon, hydrogen, nitrogen and oxygen isotopic contents which can be derived by the analysis of sediment extracts. These afford proxy measures which can be interpreted in terms of the conditions which control climate and also reflect its operation. We discuss two types of proxy; those of terrigenous and those of aquatic origin, and exemplify their application in the study of marine sediments through the medium of ten case studies based in the Atlantic, Mediterranean and Pacific Oceans, and in Antarctica. The studies are mainly for periods in the present, the Holocene and particularly the last glacial/interglacial, but they also include one study from the Cretaceous. The terrigenous proxies, which are measures of continental vegetation, are based on higher plant leaf wax compounds, i.e. long-chain (circa C 30) hydrocarbons, alcohols and acids. They register the relative contributions of C 3 vs. C 4 type plants to the vegetation in the source areas. The two marine proxies are measures of sea surface temperatures (SST). The longer established one, (U 37K') is based on the relative abundances of C 37 alkenones photosynthesized by unicellular algae, members of the Haptophyta. The newest proxy (TEX 86) is based on C 86 glycerol tetraethers (GDGTs) synthesized in the water column by some of the archaeal microbiota, the Crenarchaeota.

  2. Paleoclimatology

    SciTech Connect

    Not Available

    1991-01-01

    This book presents information that helps scientists to understand climate changes of the past. The book focuses on the results from observational modeling studies from the Quaternary and pre-Quaternary periods. The text includes sections on climate models and their structures, power, and limitations; the need for additional research, and the consequences of greenhouse warming. The book is 18th in the Oxford Monographs on Geology and Geophysics series.

  3. The Urbino Summer School in Paleoclimatology: Investing in the future of paleoclimatology

    NASA Astrophysics Data System (ADS)

    Schellenberg, S. A.; Galeotti, S.; Brinkhuis, H.; Leckie, R. M.

    2010-12-01

    Improving our understanding of global climate dynamics is increasingly critical as we continue to perturb the Earth system on geologically rapid time-scales. One approach is the modeling of climate dynamics; another is the exploitation of natural archives of climate history. To promote the synergistic integration of these approaches in the next generation of paleoclimatologists, a group of international teacher-scholars have developed the Urbino Summer School in Paleoclimatology (USSP), which has been offered since 2004 at the Università degli Studi di Urbino in Urbino, Italy. The USSP provides international graduate students with an intensive three-week experience in reconstructing the history and dynamics of climate through an integrated series of lectures, investigations, and field and laboratory analyses. Complementing these formal components, informal scientific discussions and collaborations are promoted among faculty and students through group meals, coffee breaks, socials, and evening presentations. The first week begins with a broad overview of climate history and dynamics, and then focuses on the principles and methods that transform geographically- and materially-diverse data into globally time-ordinated paleoclimatic information. Lectures largely serve as “connective tissue” for student-centered investigations that use ocean drilling data and student-collected field data from the spectacular exposures of the surrounding Umbre-Marche Basin. The second week provides sessions and investigations on various biotic and geochemical proxies, and marks the start of student “working groups,” each of whom focus on current understanding of, and outstanding questions regarding, a particular geologic time-interval. Parallel sessions also commence, wherein students self-select to attend one of three concurrently-offered more specialized topics. The third week is an intensive exploration of geochemical, climate, and ocean modeling that stresses the integration

  4. Energy Balance Models Applied To Global Paleoclimatology: The Merging Of Two Disciplines

    NASA Astrophysics Data System (ADS)

    North, G. R.

    2015-12-01

    EBMs have been around since the 1960s when they were introduced by Budyko and Sellers. Models with interactive ice caps exhibited multiple solutions, including a snowball planet. Seasonal models with geography arrived in the 1980s. Many interesting experiments were conducted in the 1970s -1990s, especially emphasizing the importance of land-sea distribution and seasonality for the inception of ice sheets. Crowley and North published a book Paleoclimatology in the 1990's whose aim was to introduce geologists to the power of climate models and to introduce (or spread the word) to climate modelers to the beauty of paleoclimatology. Paleoclimatology continues afford challenges and tests for today's climate models.

  5. Methods and future directions for paleoclimatology in the Maya Lowlands

    NASA Astrophysics Data System (ADS)

    Douglas, Peter M. J.; Brenner, Mark; Curtis, Jason H.

    2016-03-01

    A growing body of paleoclimate data indicates that periods of severe drought affected the Maya Lowlands of southeastern Mexico and northern Central America, especially during the Terminal Classic period (ca. 800-950 CE), raising the possibility that climate change contributed to the widespread collapse of many Maya polities at that time. A broad range of paleoclimate proxy methods have been applied in the Maya Lowlands and the data derived from these methods are sometimes challenging for archeologists and other non-specialists to interpret. This paper reviews the principal methods used for paleoclimate inference in the region and the rationale for climate proxy interpretation to help researchers working in the Maya Lowlands make sense of paleoclimate datasets. In particular, we focus on analyses of speleothems and lake sediment cores. These two paleoclimate archives have been most widely applied in the Maya Lowlands and have the greatest potential to provide insights into climate change impacts on the ancient Maya. We discuss the development of chronologies for these climate archives, the proxies for past climate change found within them, and how these proxy variables are interpreted. Finally, we present strategies for improving our understanding of proxy paleoclimate data from the Maya Lowlands, including multi-proxy analyses, assessment of spatial variability in past climate change, combined analysis of climate models and proxy data, and the integration of paleoclimatology and archeology.

  6. Isotopic Paleoclimatology

    NASA Astrophysics Data System (ADS)

    Bowen, R.

    Paleotemperature scales were calculated by H. C. Urey and others in the 1950s to assess past temperatures, and later work using the stable isotopes of oxygen, hydrogen, and carbon employed standards such as Peedee belemnite (PDB) and Standard Mean Ocean Water (SMOW). Subsequently, subjects as diverse as ice volume and paleotemperatures, oceanic ice and sediment cores, Pleistocene/Holocene climatic changes, and isotope chronostratigraphy extending back to the Precambrian were investigated.

  7. Geology, paleoclimatology and the evolution of the kidney: some explorations into the legacy of Homer Smith.

    PubMed

    Kooman, Jeroen P

    2012-01-01

    The aim of this review is to perform an overview of the relation between kidney development in different species and new developments in plate tectonics and paleoclimatology, which likely had a remarkable effect on evolution. The review follows the ideas of Homer Smith, but adds new data on the subjects which were unknown in Homer Smith's time. The structure and function of the kidney are a result of hundreds of millions of years of evolution, in which adaptations had to be made in response to environmental demands while maintaining the kidney's integrated function. The ideas of Homer Smith have greatly contributed to our understanding of this process, and continue to be of relevance both for researchers as well as physicians working in the field of kidney disease. PMID:22572704

  8. Marine tephra in the Japan Sea sediments as a tool for paleoceanography and paleoclimatology

    NASA Astrophysics Data System (ADS)

    Ikehara, Ken

    2015-12-01

    Tephra is a product of large and explosive volcanic events and can travel thousands of kilometers before deposition. Consequently, tephra deposits are common in terrestrial, lacustrine, marine, and glacial environments. Because tephra deposition is a geologically synchronous event, tephras constitute important isochrones in the Quaternary sequence, not only in Japan but also throughout the northwest Pacific and its marginal seas. As a result, establishing the chronostratigraphic order of tephra deposits is an effective tool for assessing local and regional stratigraphies and for correlating events among sites. For example, tephrostratigraphy can provide precise chronological constraints for other stratigraphic data, such as magneto- and biostratigraphic data. Spatiotemporal variability in the occurrence and geochemistry of tephras can also be used to trace the magmatic evolution of island arcs and their relationships to regional tectonics. In a paleoclimatic context, tephra deposits allow the correlation of past climate events among terrestrial, lacustrine, and marine environments. Tephrochronology is also a fundamental element used in reconstructing the marine reservoir effect, where the ages of tephra in marine and terrestrial settings are compared. Therefore, tephra is a valuable tool not only in stratigraphy, chronology, and volcanology but also in paleoceanography and paleoclimatology.

  9. Technical Note: The Linked Paleo Data framework - a common tongue for paleoclimatology

    NASA Astrophysics Data System (ADS)

    McKay, N. P.; Emile-Geay, J.

    2015-09-01

    Paleoclimatology is a highly collaborative scientific endeavor, increasingly reliant on online databases for data sharing. Yet, there is currently no universal way to describe, store and share paleoclimate data: in other words, no standard. Data standards are often regarded by scientists as mere technicalities, though they underlie much scientific and technological innovation, as well as facilitating collaborations between research groups. In this article, we propose a preliminary data standard for paleoclimate data, general enough to accommodate all the proxy and measurement types encountered in a large international collaboration (PAGES2K). We also introduce a vehicle for such structured data (Linked Paleo Data, or LiPD), leveraging recent advances in knowledge representations (Linked Open Data). The LiPD framework enables quick querying and extraction, and we expect that it will facilitate the writing of open-source, community codes to access, analyze, model and visualize paleoclimate observations. We welcome community feedback on this standard, and encourage paleoclimatologists to experiment with the format for their own purposes.

  10. Technical note: The Linked Paleo Data framework - a common tongue for paleoclimatology

    NASA Astrophysics Data System (ADS)

    McKay, Nicholas P.; Emile-Geay, Julien

    2016-04-01

    Paleoclimatology is a highly collaborative scientific endeavor, increasingly reliant on online databases for data sharing. Yet there is currently no universal way to describe, store and share paleoclimate data: in other words, no standard. Data standards are often regarded by scientists as mere technicalities, though they underlie much scientific and technological innovation, as well as facilitating collaborations between research groups. In this article, we propose a preliminary data standard for paleoclimate data, general enough to accommodate all the archive and measurement types encountered in a large international collaboration (PAGES 2k). We also introduce a vehicle for such structured data (Linked Paleo Data, or LiPD), leveraging recent advances in knowledge representation (Linked Open Data).The LiPD framework enables quick querying and extraction, and we expect that it will facilitate the writing of open-source community codes to access, analyze, model and visualize paleoclimate observations. We welcome community feedback on this standard, and encourage paleoclimatologists to experiment with the format for their own purposes.

  11. Paleoclimatological implications of Mid-Cretaceous paleosol sphaerosiderites from 70 degrees paleonorth, central Spitsbergen

    NASA Astrophysics Data System (ADS)

    White, T.

    2010-12-01

    Paleoclimatological reconstructions of Mid-Cretaceous greenhouse atmospheric hydrology have been accomplished using a model-data comparison approach based on a stable isotopic tracer version of the GENESIS GCM benchmarked using oxygen isotopic data obtained from paleosol sphaerosiderites. While ample data coverage exists for much of mid-latitude North America, the paleo Arctic realm has thus far been represented by data only from the North Slope, Alaska. The new data presented here provides an additional paleo Arctic data point from central Spitsbergen. Mid-Cretaceous paleosol sphaerosiderites were identified in cores that penetrated the uppermost portions of the Aptian-Cenomanian (?) Carolinefjellet Formation of the Adventdalen Group - the upper age limit of the Carolinefjellet Formation in central Spitsbergen remains undefined near the Albian-Cenomanian boundary. Notably, on the Barents Shelf to the south the coeval Kolmule Formation of the Adventdalen Group is known to range in age into the lower Cenomanian suggesting the possibility that the Carolinefjellet Formation may also contain the Albian-Cenomanian boundary. Seven distinct sphaerosiderite-bearing horizons were identified within a 2.5 meter interval of dominantly light to medium gray siltstone and fine sandstone overlain by dark gray siltstone and black carbonaceous shale. The samples were microdrilled for stable carbon and oxygen isotopic analysis. Sphaerosiderite oxygen isotope values range from -11.6 per mil to -7.9 per mil. A comparison of this data with an Albian-Cenomanian North American data set indicates that amplified paleoatmospheric hydrologic processes are not required to adequately model the Mid-Cretaceous greenhouse atmosphere. The data is further compared and contrasted to similar data for the Paleocene-Eocene boundary to substantiate this conclusion.

  12. Towards a semantic web of paleoclimatology

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Eshleman, J. A.

    2012-12-01

    The paleoclimate record is information-rich, yet signifiant technical barriers currently exist before it can be used to automatically answer scientific questions. Here we make the case for a universal format to structure paleoclimate data. A simple example demonstrates the scientific utility of such a self-contained way of organizing coral data and meta-data in the Matlab language. This example is generalized to a universal ontology that may form the backbone of an open-source, open-access and crowd-sourced paleoclimate database. Its key attributes are: 1. Parsability: the format is self-contained (hence machine-readable), and would therefore enable a semantic web of paleoclimate information. 2. Universality: the format is platform-independent (readable on all computer and operating systems), and language- independent (readable in major programming languages) 3. Extensibility: the format requires a minimum set of fields to appropriately define a paleoclimate record, but allows for the database to grow organically as more records are added, or - equally important - as more metadata are added to existing records. 4. Citability: The format enables the automatic citation of peer- reviewed articles as well as data citations whenever a data record is being used for analysis, making due recognition of scientific work an automatic part and foundational principle of paleoclimate data analysis. 5. Ergonomy: The format will be easy to use, update and manage. This structure is designed to enable semantic searches, and is expected to help accelerate discovery in all workflows where paleoclimate data are being used. Practical steps towards the implementation of such a system at the community level are then discussed.; Preliminary ontology describing relationships between the data and meta-data fields of the Nurhati et al. [2011] climate record. Several fields are viewed as instances of larger classes (ProxyClass,Site,Reference), which would allow computers to perform operations on all records within a specific class (e.g. if the measurement type is δ18O , or if the proxy class is 'Tree Ring Width', or if the resolution is less than 3 months, etc). All records in such a database would be bound to each other by similar links, allowing machines to automatically process any form of query involving existing information. Such a design would also allow growth, by adding records and/or additional information about each record.

  13. Paleoclimatology. (Latest citations from the NTIS bibliographic database). Published Search

    SciTech Connect

    1995-07-01

    The bibliography contains citations concerning studies of climate in the geologic past. Glacial deposits, fossils, and paleogeographical data are reviewed. Topics include geologic formations, sediments and ocean bottom sampling, geological age determination, climatic changes, and greenhouse effects. (Contains 50-250 citations and includes a subject term index and title list.)

  14. Paleoclimatology: Second clock supports orbital pacing of the ice ages

    SciTech Connect

    Kerr, R.A.

    1997-05-02

    For a while, it looked as if a water-filled crack in the Nevada desert might doom the accepted explanation of the ice ages. Twenty years ago, the so-called astronomical theory had carried the day. Oceanographers had found evidence implying that the march of ice ages over the last million years was paced by the cyclical stretching and squeezing of Earth`s orbit around the sun, which would have altered the way sunlight fell on the planet`s surface. But in 1988, researchers scuba diving in Nevada`s Devils Hole came up with a climate record--captured in carbonate deposits in the crack-that seemed to contradict this chronology. This article discusses the findings and the puzzles that still remain. The records of sea-level change in Barbados coral appear to be right and the astronomical theory is on solid ground using a new clock based on the radioactive decay of uranium-235 to protactinium-231. However, the Devils Hole record also seems to be correct.

  15. Late Miocene biogeography and paleoclimatology of the central North Atlantic

    USGS Publications Warehouse

    Poore, R.Z.

    1981-01-01

    Quantitative analyses of planktonic foraminiferal assemblages from Deep Sea Drilling Project (DSDP) Holes 334 and 410 demonstrate that subpolar and subtropical faunal provinces existed in the North Atlantic during the late Miocene. Climatic oscillations are clearly recorded in Hole 410 by variations in abundance of the Neogloboquadrina subpolar assemblage. These climatic oscillations have a period of about 1 m.y. Higher frequency oscillations with a periodicity of one to several hundred thousand years are evident from about 6.5 to 7.5 m.y. and are probably present throughout the entire late Miocene. A revised age of 7.0 m.y. is proposed for the first occurrence of the calcareous nannofossil Amaurolithus primus (the Amaurolithus datum). ?? 1981.

  16. Meteoric sphaerosiderite lines and their use for paleohydrology and paleoclimatology

    USGS Publications Warehouse

    Ludvigson, Greg A.; Gonzalez, Luis A.; Metzger, R.A.; Witzke, B.J.; Brenner, Richard L.; Murillo, A.P.; White, T.S.

    1998-01-01

    Sphaerosiderite, a morphologically distinct millimeter-scale spherulitic siderite (FeCO3), forms predominantly in wetland soils and sediments, and is common in the geologic record. Ancient sphaerosiderites are found in paleosol horizons within coal-bearing stratigraphic intervals and, like their modern counterparts, are interpreted as having formed in water-saturated environments. Here we report on sphaerosiderites from four different stratigraphic units, each of which has highly variable 13C and relatively stable 18O compositions. The unique isotopic trends are analogous to well-documented meteoric calcite lines, which we define here as meteoric sphaerosiderite lines. Meteoric sphaerosiderite lines provide a new means of constraining ground-water ??18O and thus allow evaluation of paleohydrology and paleoclimate in humid continental settings.

  17. [Paleoclimatology studies for Yucca Mountain site characterization]. Final report

    SciTech Connect

    1996-05-03

    This report consists of two separate papers: Fernley Basin studies; and Influence of sediment supply and climate change on late Quaternary eolian accumulation patterns in the Mojave Desert. The first study involved geologic mapping of late Quaternary sediments and lacustrine features combined with precise control of elevations and descriptions of sediments for each of the major sedimentary units. The second paper documents the response of a major eolian sediment transport system in the east-central Mojave Desert: that which feeds the Kelso Dune field. Information from geomorphic, stratigraphic, and sedimentologic studies of eolian deposits and landforms is combined with luminescence dating of these deposits to develop a chronology of periods of eolian deposition. Both studies are related to site characterization studies of Yucca Mountain and the forecasting of rainfall patterns possible for the high-level radioactive waste repository lifetime.

  18. The paleoclimatology of Lake Baikal: A diatom synthesis and prospectus

    NASA Astrophysics Data System (ADS)

    Mackay, Anson W.

    2007-06-01

    The paleoclimatic archive held in Lake Baikal sediments is of significant importance, given the lake's position in one of the world's most continental regions where there are few continuous, high quality records spanning the Quaternary. Here I review diatom and associated biogenic silica records from Lake Baikal sediments and provide a paleoclimatic synthesis of changes at various timescales over the Quaternary. I initially highlight major climatic and hydrological aspects of Lake Baikal, as understanding the contemporary system (both regionally and within the lake) are fundamental to understanding past change interpreted from the sedimentary archive. In this respect, special attention is given to factors that can affect the integrity of the diatom record, most notably dissolution processes. These mechanisms are likely to have had a relatively greater impact on the preservation of diatom valves during glacial periods because of overall lower diatom productivity. Lower diatom numbers and relative increased dissolution during cold periods explains the lack of diatoms and low biogenic silica concentrations found in the lake sediments during glacial periods. The biogenic record highlights the nature of the 100 ka cycle especially during the last 800 ka, although there is also a strong precessional component. Further work is needed to reassess biological responses in Lake Baikal with respect to different orbital forcing mechanisms, together with their impacts on evolution and speciation of diatoms. The biological record from Lake Baikal confirms that the last interglacial in central Asia lasted approximately 10.5 ka. Productivity in the lake (as inferred from diatom biovolume accumulation rates) exhibits millennial-scale variability with the occurrence of centennial-scale reductions in diatom biomass throughout the last interglacial period. The most severe reduction in diatom biomass (at c. 120 ka BP) is concurrent with millennial-scale cooling in the North Atlantic region. Links to changes in North Atlantic ocean thermohaline circulation via teleconnections are also evident in the nature of the abrupt ecological changes in the lake throughout the last 60 ka, linked to ice-rafting into the North Atlantic, otherwise known as Heinrich events. New robust radiocarbon chronologies for sediments deposited during the late glacial and Holocene in Lake Baikal allow detailed, multi-decadal records to be constructed for the last 14,000 years. Cooling events associated with millennial-scale cycles are also apparent in the Lake Baikal record, and both the diatom record and oxygen isotope record of the diatom silica highlight that biological responses to these abrupt events are almost simultaneous. Comparisons made between Lake Baikal records with others worldwide highlights that many of the Holocene cooling events are associated with melt-water outburst from the Laurentide ice sheet, and changes in solar insolation. During the last 1000 years, snow cover on Lake Baikal has been inferred from past diatom assemblages, and is closely linked to weakening of the North Atlantic Oscillation, allowing increasing intensity of the Siberian High to develop and during the 17th and 18th centuries. In the last 150 years, diatom species have been shown to be sensitive indicators of recent warming. However, impacts from future global warming will be complex, and are likely to impact not only on the balance between endemic and cosmopolitan diatoms throughout the lake, but on the balance between siliceous and non-siliceous algae, and sources of primary productivity.

  19. Paleoclimatological study using stalagmites from Java Island, Indonesia

    NASA Astrophysics Data System (ADS)

    Watanabe, Y.; Matsuoka, H.; Ohsawa, S.; Yamada, M.; Kitaoka, K.; Kiguchi, M.; Ueda, J.; Yoshimura, K.; Kurisaki, K.; Nakai, S.; Brahmantyo, B.; Maryunani, K. A.; Tagami, T.; Takemura, K.; Yoden, S.

    2006-12-01

    In the last decade, decoding geochemical records in stalagmites has been widely recognized as a powerful tool for the elucidation of paleoclimate/environment of the terrestrial areas. The previous data are mainly reported from areas that are located in middle latitude. However, this study aims at reconstructing past climate variations in the Asian equatorial regions by using oxygen isotopes and other geochemical proxies recorded in Indonesian stalagmites.. Especially, we focus on the detection of the precipitation anomaly that reflects the El Niño Southern Oscillation (ENSO). We performed geological surveys in Buniayu limestone caves, Sukabumi, West Java, and Karangbolong, Central Java, Indonesia and collected a series of stalagmites/stalactites and drip water samples. Detailed textures of stalagmite samples were observed using thin sections to identify "annual" bandings. Moreover, we also measured both (1) annual luminescent banding that can be viewed by ultraviolet-light stimulation and (2) uranium series disequilibrium ages using the MC-ICP-MS for each stalagmite to construct the age model. We also carried out 3H-3He dating and stable isotope measurements of drip water samples to understand hydrogeology in study areas. Based on these frameworks, oxygen isotopes and other geochemical proxies will be analyzed for annual or sub-annual time scales. The proxy data will then be compared with meteorological data set, such as local precipitation, in the past 50 years. Finally, we will reconstruct for longer timescales the past climate, particularly the precipitation anomaly, in the region to detect ancient ENSO.

  20. Paleoclimatological analysis of Late Eocene core, Manning Formation, Brazos County, Texas

    SciTech Connect

    Yancey, T.; Elsik, W.

    1994-09-01

    A core of the basal part of the Manning Formation was drilled to provide a baseline for paleoclimate analysis of the expanded section of siliciclastic sediments of late Eocene age in the outcrop belt. The interdeltaic Jackson Stage deposits of this area include 20+ cyclic units containing both lignite and shallow marine sediments. Depositional environments can be determined with precision and the repetitive nature of cycles allows comparisons of the same environment throughout, effectively removing depositional environment as a variable in interpretation of climate signal. Underlying Yegua strata contain similar cycles, providing 35+ equivalent environmental transacts within a 6 m.y. time interval of Jackson and Yegua section, when additional cores are taken. The core is from a cycle deposited during maximum flooding of the Jackson Stage, with deposits ranging from shoreface (carbonaceous) to midshelf, beyond the range of storm sand deposition. Sediments are leached of carbonate, but contain foram test linings, agglutinated forams, fish debris, and rich assemblages of terrestrial and marine palynomorphs. All samples examined contain marine dinoflagellates, which are most abundant in transgressive and maximum flood zones, along with agglutinated forams and fish debris. This same interval contains two separate pulses of reworked palynomorphs. The transgressive interval contains Glaphyrocysta intricata, normally present in Yegua sediments. Pollen indicates fluctuating subtropical to tropical paleoclimates, with three short cycles of cooler temperatures, indicated by abundance peaks of alder pollen (Alnus) in transgressive, maximum flood, and highstand deposits.

  1. Palynology, paleoclimatology and correlation of middle Miocene beds from Porcupine River (locality 90-1), Alaska

    USGS Publications Warehouse

    White, J.M.; Ager, T.A.

    1994-01-01

    Beds in the Upper Ramparts Canyon of the Porcupine River, Alaska (67?? 20' N, 141?? 20' W), yielded a flora rich in pollen of hardwood genera now found in the temperate climates of North America and Asia. The beds are overlain or enclosed by two basalt flows which were dated to 15.2 ?? 0.1 Ma by the 40Ar 39Ar method, fixing the period of the greatest abundance of warm-loving genera to the early part of the middle Miocene. The assemblage is the most northern middle Miocene flora known in Alaska. Organic bed 1 underlies the basalt and is older than 15.2 Ma, but is of early to middle Miocene age. The pollen assemblage from organic bed 1 is dominated by conifer pollen from the pine and redwood-cypress-yew families with rare occurrences of temperate hardwoods. Organic bed 2 is a forest floor containing redwood trees in life position, engulfed by the lowest basalt flow. A pine log has growth rings up to 1 cm thick. Organic beds 3 and 4 comprise lacustrine sediment and peat between the two basalt flows. Their palynoflora contain conifers and hardwood genera, of which about 40% have modern temperate climatic affinities. Hickory, katsura, walnut, sweet gum, wingnut, basswood and elm pollen are consistently present, and beech and oak alone make up about 20% of the pollen assemblage. A warm high latitude climate is indicated for all of the organic beds, but organic bed 3 was deposited under a time of peak warmth. Climate data derived by comparison with modern east Asian vegetation suggest that, at the time of deposition of organic bed 3, the Mean Annual Temperature (MAT) was ca. 9??C, the Warm Month Mean Temperature (WMMT) was ??? 20??C and the Cold Month Mean Temperature (CMMT) was ca. -2??C. In contrast, the modern MAT for the region is -8.6??C, WMMT is 12.6??C and CMMT is -28??C. Organic beds 3 and 4 correlate to rocks of the middle Miocene-late Seldovian Stage of Cook Inlet and also probably correlate to, and more precisely date, the lower third of the Suntrana Formation in the Alaska Range, beds at Unalaklect, part of the upper Mackenzie Bay sequence in the Beaufort-Mackenzie basin, and the Mary Sachs gravel of Banks Island. This suggests that forests with significant percentages of temperate deciduous angiosperms existed between latitudes 60?? and 72??N during the early middle Miocene. ?? 1994.

  2. Paleoclimatology indicators of the Salt Wash member of the Upper Jurassic Morrison Formation near Jensen, Utah

    SciTech Connect

    Medlyn, D.A. . Dept. of Geology); Bilbey, S.A. )

    1993-04-01

    The Upper Jurassic Morrison Formation has yielded one of the richest floras of the so-called transitional conifers'' of the Middle Mesozoic. Recently, a silicified axis of one of these conifers was collected from the Salt Wash member in essentially the same horizon as a previously reported partial Stegosaurus skeleton. In addition, two other axes of conifers were collected in the same immediate vicinity. Paleoecological considerations are extrapolated from the coniferous flora, vertebrate fauna and associated lithologies. Techniques of paleodendrology and relationships of extant/extinct environments are compared. The paleoclimatic conditions of the transitional conifers and associated dinosaurian fossils are postulated.

  3. A Miocene termite nest from southern Argentina and its paleoclimatological implications

    USGS Publications Warehouse

    Bown, T.M.; Laza, J.H.

    1990-01-01

    A Miocene termitarium attributable to the extant termite Syntermes (Isoptera: Termitidae, Nasutitermitinae) is the first fossil termite nest reported from South America and possibly the oldest record of the Isoptera from that continent. A new ichnogenus and ichnospecies, Syntermesichnus fontanae, is proposed for this distinctive trace fossil. It differs from nests constructed by other members of the Nasutitermitinae in its architectural organization and its large size. -from Authors

  4. Paleoecology and paleoclimatology of a late holocene peat deposit from Braendevinsskaer, Central West Greenland

    SciTech Connect

    Bennike, O. )

    1992-08-01

    The macroscopical plant and animal remains of a nearshore peat deposit in West Greenland are described and documented. The assemblages contain a mixture of limnic, terrestrial, and marine plants and animals. These are divided into four local macrofossil assemblage zones, of which zone 3, ca. A.D. 950 to ca. A.D. 1760, represents a wet phase which is correlated in part with the Little Ice Age.

  5. Speleothem Paleoclimatology and Modern Proxies: Calcite Farming In a Continuously Monitored Cave

    NASA Astrophysics Data System (ADS)

    Tremaine, D. M.; Froelich, P. N.; Kowalczk, A.; Kilgore, B.

    2009-12-01

    Continuous high-resolution (sub-hourly) time-series of local meteorology (solar irradiance, relative humidity, rainfall, wind speed and direction, barometric pressure, and temperature), cave air chemistry (t, rh, bp, radon-222, pCO2, air-flow velocity and direction), and cave-ceiling drips in Hollow Ridge Cave in North Florida reveal variations that must color interpretations of annually resolved speleothem records. The style and vigor of ventilation and mixing strongly influence diurnal and seasonal cave-air 222Rn, pCO2 and δ13CO2. Cave-air pCO2 controls CO2 degassing from drip waters, leading to oversaturation of calcite and dripstones. Periodic high-resolution spatial snapshots of 222Rn and δ13C gradients taken inside the cave reveal interior ventilation and mixing pathways that help us understand connections between 222Rn-modeled CO2 exchange and drip rates, drip chemistry, speleothem growth, and soilgas and dripwater contributions to dripstone δ13C. Drip waters and aquifer water are collected every two weeks. Isotopes (δ18O, D/H), major anions (Cl- and SO42-), cations (Na+, K+, Ca2+, Mg2+, Sr2+) and tracers (Ba, U, Si, Mn) in the drips are related to rainfall, evapotranspiration and soil weathering reactions in the epikarst. Drip composition is then compared to the chemistry of contemporaneous calcite. Sulfate and Mn2+ can be interpreted as qualitative proxies for soil redox (saturated epikarst). Chloride correlates negatively with drip rate, while sulfate correlates positively with drip rate. We are growing artificial speleothems (“calcite farming”) on quartz slides under drips atop active speleothems. Early winter calcite precipitation ranged from 0.034~0.161 mg/day. Late winter precipitation ranged from 0.031~0.306 mg/day. Summer yielded no calcite growth. Calcite does not precipitate during months when slow ventilation results in high cave-air pCO2. A larger number of slides are currently deployed to accumulate an analytical quantity of calcite. Isotopic (δ13C, δ18O) and elemental (Ca, Mg, Si, K, Sr, Ba, U, Mo, Si, Mn, Fe) analyses of the farmed calcite will serve as a modern calibration for interpretation of paleoclimate proxies. For example, δ13C of cave-air is controlled by mixing between outside air and soilgas (see Keeling Plot below). It is likely that annual δ13C incorporation into speleothems is a function of this ventilation and seasonal mixing, rather than C3/C4 of overlying vegetation.

  6. Beryllium-10 in the Taylor Dome ice core: Applications to Antarctic glaciology and paleoclimatology

    SciTech Connect

    Steig, E.J.

    1996-12-31

    An ice core was drilled at Taylor dome, East Antarctica, reaching to bedrock at 554 meters. Oxygen-isotope measurements reveal climatic fluctuations through the last interglacial period. To facilitate comparison of the Taylor Dome paleoclimate record with geologic data and results from other deep ice cores, several glaciological issues need to be addressed. In particular, accumulation data are necessary as input for numerical ice-flow-models, for determining the flux of chemical constituents from measured concentrations, and for calculation of the offset in age between ice and trapped air in the core. The analysis of cosmogenic beryllium-10 provides a geochemical method for constraining the accumulation-rate history at Taylor Dome. High-resolution measurements were made in shallow firn cores and snow pits to determine the relationship among beryllium-10 concentrations, wet and dry deposition mechanisms, and snow-accumulation rates. Comparison between theoretical and measured variations in deposition over the last 75 years constrains the relationship between beryllium-10 deposition and global average production rates. The results indicate that variations in geomagnetically-modulated production-rate do not strongly influence beryllium-10 deposition at Taylor Dome. Although solar modulation of production rate is important for time scales of years to centuries, snow-accumulation rate is the dominant control on ice-core beryllium-10 concentrations for longer periods. Results show that the Taylor Dome core can be used to provide new constraints on regional climate over the last 130,000 years, complementing the terrestrial and marine geological record from the Dry Valley, Transantarctic Mountains and western Ross Sea.

  7. The Upper Laacher See Tephra in Lake Geneva sediments: Paleoenvironmental and paleoclimatological implications

    USGS Publications Warehouse

    Moscariello, A.; Costa, F.

    1997-01-01

    Microstratigraphical analysis of Late glacial lacustrine sediments from Geneva Bay provided evidence of a tephra layer within the upper Aller??d biozone. The layer consists of alkali feldspar, quartz, plagioclase. amphibole, pyroxene, opaques, titanite and glass shards. Electron microprobe analyses and morphological study of glass shards allowed correlation with the upper part of the Laacher See Tephra of the Laacher See volcano (Eifel Mountains, Germany). Sedimentological features of enclosing lacustrine sediments suggest that a momentary decrease in precipitation occurred in the catchment area and consequent reduction in detrital supply in the lake, after the ash fall-out. This has been interpreted as the environmental response to a momentary cooling following the Laacher See Tephra aerosols emission. Comparison with Sedimentological features characterizing the Aller??d-Younger Dryas transition highlights the sensitivity of Lake Geneva system in recording both short and long-terms climate-induced environmental changes.

  8. Evolution of the Ishtmus of Panama: biological, paleoceanographic, and paleoclimatological implications

    NASA Astrophysics Data System (ADS)

    Jaramillo, Carlos

    2016-04-01

    The rise of the Isthmus of Panama has been the product of small-scale geological processes that, however, have had worldwide repercussions. Four major events have been linked to the rise of the Isthmus including 1) the onset of the Thermohaline circulation (TCH), 2) the onset of Northern Hemisphere Glaciation, 3) the birth of the Caribbean Sea, and 4) the Great American Biotic Interchange (GABI). The available evidence indicates that there is a strong link between the closure of Central American Seaway (CAS) and the onset of Atlantic Meridional Overturning Circulation (a precursor of THC), but at 10 Ma rather than at 3.5 Ma as it was assumed before. There are not evidences of a connection between the full emergence of the Isthmus at 3.5 Ma and the onset of the NHG. There are strong evidences that the full emergence of the Isthmus at 3.5 Ma changed the oceanography of the Caribbean Sea to its modern conditions, although the role of additional variables into Pleistocene Caribbean Sea conditions still need to be evaluated, including the changes in the climate of the Pleistocene and the cessation of the freshwater flow of several South American rivers into the Caribbean. GABI is more complex that often assumed and it seems that variables other than a continuous terrestrial Isthmus have controlled the direction, timing and speed of migrations. The building of Panamanian landscape can be summarized in four phases, 1) a late Eocene large island in central Panama and the Azuero Peninsula, 2) an early Miocene large scale generation of terrestrial landscapes in Central America that connected central Panama with North America, 3) a full closure of CAS at 10 Ma, interrupting the exchange of deep waters between Caribbean and Pacific, and generating most of the landscape across the Isthmus. Exchange of shallow waters continued until 3.5 Ma, albeit intermittently. 4) A continuous terrestrial landscape across the Isthmus over the past 3.5 Ma.

  9. New geochronological, paleoclimatological, and archaeological data from the Narmada Valley hominin locality, central India.

    PubMed

    Patnaik, Rajeev; Chauhan, Parth R; Rao, M R; Blackwell, B A B; Skinner, A R; Sahni, Ashok; Chauhan, M S; Khan, H S

    2009-02-01

    The oldest known fossil hominin in southern Asia was recovered from Hathnora in the Narmada Basin, central India in the early 1980's. Its age and taxonomic affinities, however, have remained uncertain. Current estimates place its maximum age at >236ka, but not likely older than the early middle Pleistocene. The calvaria, however, could be considerably younger. We report recent fieldwork at Hathnora and associated Quaternary type-sections that has provided new geological and archaeological insights. The portion of the exposed 'Boulder Conglomerate' within the Surajkund Formation, which forms a relict terrace and has yielded the hominin fossils, contains reworked and stylistically mixed lithic artifacts and temporally mixed fauna. Three mammalian teeth stratigraphically associated with the hominin calvaria were dated by standard electron spin resonance (ESR). Assuming an early uranium uptake (EU) model for the teeth, two samples collected from the reworked surface deposit averaged 49+/-1ka (83+/-2ka, assuming linear uptake [LU]; 196+/-7ka assuming recent uptake [RU]). Another sample recovered from freshly exposed, crossbedded gravels averaged 93+/-5ka (EU), 162+/-8ka (LU) or 407+/-21ka (RU). While linear uptake models usually provide the most accurate ages for this environment and time range, the EU ages represent the minimum possible age for fossils in the deposit. Regardless, the fossils are clearly reworked and temporally mixed. Therefore, the current data constrains the minimum possible age for the calvaria to 49+/-1ka, although it could have been reworked and deposited into the Hathnora deposit any time after 160ka (given the LU uptake ages) or earlier (given the RU ages). At Hathnora, carbonaceous clay, bivalve shells, and a bovid tooth recovered from layers belonging to the overlying Baneta Formation have yielded (14)C ages of 35.66+/-2.54cal ky BP, 24.28+/-0.39cal ky BP, and 13.15+/-0.34ky BP, respectively. Additional surveys yielded numerous lithics and fossils on the surface and within the stratigraphic sequence. At the foot of the Vindhyan Hills 2km from the river, we recovered a typologically Early Acheulean assemblage comprised of asymmetrical bifaces, large cleavers with minimal working, trihedral picks, and flake tools in fresh condition. These tools may be the oldest Acheulean in the Narmada Valley. Several lithics recovered from the Dhansi Formation may represent the first unequivocal evidence for an early Pleistocene hominin presence in India. In situ invertebrate and vertebrate fossils, pollen, and spores indicate a warm, humid climate during the late middle Pleistocene. High uranium concentrations in the mammalian teeth indicate exposure to saline water, suggesting highly evaporative conditions in the past. Late Pleistocene sediment dated between 24.28+/-0.39cal ky BP and 13.15+/-340ky BP has yielded pollen and spores indicating cool, dry climatic conditions corresponding to Oxygen Isotope Stage 2 (OIS 2). An early Holocene palynological assemblage from the type locality at Baneta shows evidence for relatively dry conditions and a deciduous forest within the region. The Dhansi Formation provisionally replaces the Pilikarar Formation as the oldest Quaternary formation within the central Narmada Basin. The Baneta Formation, previously dated at 70ka to 128ka, correlates with the late Pleistocene and early Holocene. Our results highlight the need for further Quaternary geological and paleoanthropological research within the Narmada Basin, especially because dam construction threatens these deposits.

  10. Late Pleistocene paleoclimatology of the central equatorial Pacific: Sea surface response to the southeast Trade Winds

    NASA Astrophysics Data System (ADS)

    Pisias, Nicklas G.; Rea, David K.

    1988-02-01

    Proxy indicators of sea surface temperature and equatorial divergence based on radiolarian assemblage data, and of trade wind intensity based on eolian grain size data show similar aspects of variability during the late Pleistocene: All indicators fluctuate at higher frequencies than the 100,000-year glacial-interglacial cycle, display reduced amplitude variations since 300,000 years ago, exhibit a change in the record character at about 300,000 years ago (the mid-Brunhes climatic event), and have higher amplitude variations in sediments 300,000-850,000 years old. Time series analyses were conducted to determine the spectral character of each record (δ18O of planktonic foraminifer, sea surface temperature values, equatorial divergence indicators, and wind intensity indicators) and to quantify interrecord coherence and phase relationships. The record was divided at the 300,000-year clear change in climatic variability (nonstationarity). The δ18O-based time scale is better lower in the core so our spectral analyses concentrated on the interval from 402,000-774,000 years. The δ18O spectra show 100,000- and 41,000-year power in the younger portion, 0-300,000 years, and 100,000-, 41,000- and 23,000-year power in the older interval, all highly coherent and in phase with the SPECMAP average stacked isotope record. Unlike the isotope record the dominant period in both the eolian grain size and equatorial divergence indicators is 31,000 years. This period is also important in the sea surface temperature signal where the dominant spectral peak is 100,000 years. The 31,000-year spectral component is coherent and in phase between the eolian and divergence records, confirming the link between atmospheric and ocean surface circulation for the first time in the paleoclimate record. Since the 31,000-year power appears in independent data sets within this core and also appears in other equatorial records [J. Imbrie personal communication, 1987], we assume it to be real and representative of both a nonlinear response to orbital forcing, possibly a combination of orbital tilt and eccentricity, and some resonance phenomenon required to amplify the response at this period so that it appears as a dominant frequency component. The mid-Brunhes climatic event is an important aspect of these records, but its cause remains unknown.

  11. The Paleoclimatological Power of Biodiversity: 500 yrs of New York City Watershed Drought

    NASA Astrophysics Data System (ADS)

    Pederson, N.; Cook, E.; Vranes, K.

    2010-12-01

    The frequency of water restriction has increased over the last decade for New York City (NYC) despite: 1) its location in perhumid climate and 2) a reduction in water consumption since 1979. Population growth and future climate change could trigger more frequent restrictions and litigation over supplies. We update drought history for the NYC water supply region from the mid-1970’s reconstruction to better understand why water restrictions have increased. Using nested reconstruction techniques, 31 tree-ring chronologies comprised of 12 species account for 59.1% of the average May-Aug Palmer Drought Severity Index from 1895-2006 in the Hudson River Valley. Verification statistics indicate a reasonably strong reconstruction from 1507-2006. The new reconstruction covers an extended season versus the prior reconstruction (May-Aug vs Jul) and yet captures more annual variation in drought (59.1% vs 54%), supporting research indicating that the use of multiple species, including non-traditional species such as Liriodendron tulipifera, Betula lenta and Carya spp., might improve reconstruction skill. While the mid-1960s drought is still the most intense drought, it is closely rivaled by multi-annual droughts centered on 1637 and 1687. The new reconstruction indicates that the current 38-year pluvial is rivaled only by the 1719-1766 and 1619 periods. Other notable multi-annual pluvials are centered on 1541, 1581 and 1831. Multi-taper method analysis of the new reconstruction indicates periodicity of drought similar to the prior reconstruction, with significant peaks at 12-13, 16-18 and 23-years. The years during recent water restrictions rank as a minor droughts when viewed over the past 500-years. In the context of decreasing water usage and the current pluvial, it appears that the NYC region is not be prepared for the next significant drought.

  12. Paleoceanographic and Paleoclimatologic Records of the Sea of Marmara during the Last 70 KA

    NASA Astrophysics Data System (ADS)

    Cagatay, M. N.

    2015-12-01

    The Sea of Marmara is located between the Mediterranean and the Black Sea to which it is connected with the İstanbul (Bosporus) and Çanakkale (Dardanelles) straits having sill depths of 35 and 65 m below the present sea level, respectively. It is presently characterized by a two-way flow system consisting of the upper Black Sea and lower Mediterranean waters separated with a permanent halocline at -25 m. A 28.88 m long RV Marion Dufresne core MD01-2430 from the western high provides a continuous stratigraphic record for the last ca 70 ka. This record shows only one lacustrine-marine transition at ~ 12.6 cal ka BP over this period, indicating that the Sea of Marmara was under lacustrine conditions disconnected from the Mediterranean Sea from the beginning of Marine Isotope Stage 4 (MIS-4) to the early MIS-1. Soon after the reconnection, the Marmara sapropel started depositing under dysoxic-suboxic conditions during 12.33-5.7 cal ka BP. The periods of high inorganic (carbonate) and organic carbon production and burial in the Sea of Marmara correlate very closely with the Greenland Intertadials (GI) recorded in the NGRIP oxygen isotope and Black Sea Ca data sets. The two partly overlapping Ca peaks in the Sea of Marmara record corresponding to ~12.6 cal ka BP and 14.5 cal ka BP represent the authigenic carbonate deposition that resulted from the mixing of lacustrine Marmara and saline Mediterranean waters during the latest marine reconnection and the Greenland Interstadial-1 (GI-1) high productivity period, respectively. Low δ18O (down to -9‰) and high δ13C (+2.4‰) values of bulk carbonate during the GIs strongly suggest high input of fresh waters from the Black Sea and high organic productivity in the lacustrine Marmara under warm and humid conditions. Low "carbonate-free" K concentrations during the GIs suggest low detrital input in the Marmara "Lake", which in turn indicates low erosion rates in the catchment with a high vegetation density. In contrast, the highest detrital input occurred during the Last Glacial Maximum (LGM) and deglaciation (22-15 ka BP) under cold-dry and low lake level conditions.

  13. Annually laminated sequences in the internal structure of some Belgian stalagmites -- Importance for paleoclimatology

    SciTech Connect

    Genty, D.; Quinif, Y.

    1996-01-01

    Fifteen stalagmites from four caves and one sealed tunnel in southern Belgium are composed of alternations of annually deposited white-porous and dark-compact laminae. This is demonstrated by comparing the number of laminae with the local history of the site for modern stalagmites and with radioisotopic ages for Late Glacial and Holocene stalagmites. Annual cyclicity in the internal structure of these speleothems is explained by the highly seasonal variations of the water excess, which influences underground water flow. Comparison between climatic data and modern stalagmites of a closed tunnel shows that growth laminae can record climatic variations: (1) there is a good correlation (R = 0.84) between lamina thickness in a stalagmite and water excess; (2) during years with a high water excess, dark-compact laminae are more developed, which makes the speleothem darker. Vertical successions of several laminae represent microsequences that may have recorded climatic variations with a time resolution of 1/2 year. In a Late Glacial stalagmite, successive laminae microsequences form very regular cycles of 11 years separated by a thick dark-compact lamina. It is supported that, as for modern stalagmites, the thick dark-compact lamina corresponds to a period of high water excess. Hence, this 11-year cycle may reflect a climatic cycle.

  14. Recrystallization-induced oxygen isotope changes in inclusion-hosted water of speleothems - paleoclimatological implications

    NASA Astrophysics Data System (ADS)

    Demény, Attila; Czuppon, György; Leél-Őssy, Szabolcs; Németh, Péter; Szabó, Máté; Tóth, Mária; Németh, Tibor

    2016-04-01

    Stable hydrogen and oxygen isotope data of water trapped in fluid inclusions were collected for recently forming stalagmites and flowstones in order to determine how dripwater compositions are reflected and preserved in the inclusion water compositions. The samples were collected from different cave sites (with temperatures around 10 ± 1 °C) from the central and north-eastern parts of Hungary. Hydrogen isotope compositions were found to reflect dripwater values, whereas the oxygen isotope data were increasingly shifted from the local dripwater compositions with the time elapsed after deposition. The δ18O data are correlated with X-Ray diffraction full width at half maximum values (related to crystal domain size and lattice strain), suggesting that the oxygen isotope shift is related to recrystallization of calcite. Transmission electron microscope analyses detected the presence of nanocrystalline (<50 nm) calcite, whose crystallization to coarser-grained calcite crystals (>200 nm) may have induced re-equilibration between the carbonate and the trapped inclusion water. Additional data indicated that amorphous calcium carbonate (ACC) may have formed as a precursor of nanocrystalline calcite. ACC-calcite transformation followed by Ostwald ripening process provides an explanation for unexpectedly low oxygen isotope compositions in the inclusion water, especially in cold caves where carbonate may form first as an amorphous phase. This research was supported by the National Office for Research and Technology of Hungary (GVOP-3.2.1-2004-04-0235/3.0), the Hungarian Scientific Research Fund (OTKA CK 80661 and OTKA NK 101664).

  15. High-resolution paleoclimatology of the coastal margin of northernmost California during the past 7,300 years

    NASA Astrophysics Data System (ADS)

    Barron, J. A.; Heusser, L. E.; Addison, J. A.; Burky, D.; Kusler, J. E.; Finney, B.

    2013-12-01

    Piston core TN062 0550, located 13 km offshore of Eureka, California (40.866 deg. N, 124.572 deg. W, 550 m water depth), contains a continuous high-resolution climate record of the past 7,300 yr. Deposition occurred at nearly constant sedimentation rates averaging 94 cm/kyr based on 14C AMS dating of planktonic foraminifers. Pollen and marine ecosystem proxies (diatoms, silicoflagellates, wt. percent biogenic silica) studied at 50-70 yr sample resolution show a stepwise development of the climate/ oceanographic system off northernmost California. The relative contributions of Sequoia sempervirens (coastal redwood) pollen, a proxy for coastal fog associated with offshore upwelling, and biogenic silica concentrations (a proxy for siliceous export productivity) increase (two fold and three fold, respectively) in successive steps at ~5,000 yr BP and from ~2,400 to 2,000 yr BP. These increases are interpreted to reflect a progressive intensification of spring upwelling based on modern observations of the California Current system. At 5,000 yr BP diatom assemblages change from an assorted mixture of warm, temperate, and cool-water taxa to a low diversity temperate-oceanic assemblage dominated by Thalassionema spp. At ~2,400 yr BP the diatom assemblage transitions to a mixture of nearshore upwelling taxa and taxa associated with the central North Pacific Gyre. Silicoflagellate assemblages undergo a similar increase in the representation of modern seasonal proxies at ~3,000 yr BP that may reflect intensified ENSO variability. A two-fold increase in the relative contributions of Quercus (oak) and riparian Alnus (alder) pollen between ~3,800 and 2,000 yr BP likely signals a period of enhanced fluvial runoff associated with increased winter precipitation. Given the present day association of the Eel River system with the northwestern half of the western US winter precipitation dipole, these pollen data suggest that the ~3,800 and 2,000 yr interval was dominated by protracted negative Pacific Decadal Oscillation-like (PDO) conditions. The widespread occurrence of drought in the southwestern US between ~3,800 and 2,200 yr BP supports this interpretation.

  16. Glacial and periglacial geomorphology and its paleoclimatological significance in three North Ethiopian Mountains, including a detailed geomorphological map

    NASA Astrophysics Data System (ADS)

    Hendrickx, Hanne; Jacob, Miro; Frankl, Amaury; Nyssen, Jan

    2015-10-01

    Geomorphological investigations and detailed mapping of past and present (peri)glacial landforms are required in order to understand the impact of climatic anomalies. The Ethiopian Highlands show a great variety in past and contemporary climate, and therefore, in the occurrence of glacial and periglacial landforms. However, only a few mountain areas have been studied, and detailed geomorphological understanding is lacking. In order to allow a fine reconstruction of the impact of the past glacial cycle on the geomorphology, vegetation complexes, and temperature anomalies, a detailed geomorphological map of three mountain areas (Mt. Ferrah Amba, 12°51‧N 39°29‧E; Mt. Lib Amba, 12°04‧N 39°22‧; and Mt. Abuna Yosef, 12°08‧N 39°11‧E) was produced. In all three study areas, inactive solifluction lobes, presumably from the Last Glacial Maximum (LGM), were found. In the highest study area of Abuna Yosef, three sites were discovered bearing morainic material from small late Pleistocene glaciers. These marginal glaciers occurred below the modeled snowline and existed because of local topo-climatic conditions. Evidence of such Pleistocene avalanche-fed glaciers in Ethiopia (and Africa) has not been produced earlier. Current frost action is limited to frost cracks and small-scale patterned ground phenomena. The depression of the altitudinal belts of periglacial and glacial processes during the last cold period was assessed through periglacial and glacial landform mapping and comparisons with data from other mountain areas taking latitude into account. The depression of glacial and periglacial belts of approximately 600 m implies a temperature drop around 6 °C in the last cold period. This cooling is in line with temperature depressions elsewhere in East Africa during the LGM. This study serves as a case study for all the intermediate mountains (3500-4200 m) of the North Ethiopian highlands.

  17. Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic

    NASA Astrophysics Data System (ADS)

    Hook, B. A.; Halfar, J.; Gedalof, Z.; Bollmann, J.; Schulze, D. J.

    2015-10-01

    The recent discovery of well-preserved mummified wood buried within a subarctic kimberlite diamond mine prompted a paleoclimatic study of the early Eocene "hothouse" (ca. 53.3 Ma). At the time of kimberlite eruption, the Subarctic was warm and humid producing a temperate rainforest biome well north of the Arctic Circle. Previous studies have estimated that mean annual temperatures in this region were 4-20 °C in the early Eocene, using a variety of proxies including leaf margin analysis and stable isotopes (δ13C and δ18O) of fossil cellulose. Here, we examine stable isotopes of tree-ring cellulose at subannual- to annual-scale resolution, using the oldest viable cellulose found to date. We use mechanistic models and transfer functions to estimate earliest Eocene temperatures using mummified cellulose, which was well preserved in the kimberlite. Multiple samples of Piceoxylon wood within the kimberlite were crossdated by tree-ring width. Multiple proxies are used in combination to tease apart likely environmental factors influencing the tree physiology and growth in the unique extinct ecosystem of the Polar rainforest. Calculations of interannual variation in temperature over a multidecadal time-slice in the early Eocene are presented, with a mean annual temperature (MAT) estimate of 11.4 °C (1 σ = 1.8 °C) based on δ18O, which is 16 °C warmer than the current MAT of the area (-4.6 °C). Early Eocene atmospheric δ13C (δ13Catm) estimates were -5.5 (±0.7) ‰. Isotopic discrimination (Δ) and leaf intercellular pCO2 ratio (ci/ca) were similar to modern values (Δ = 18.7 ± 0.8 ‰; ci/ca = 0.63 ± 0.03 %), but intrinsic water use efficiency (Early Eocene iWUE = 211 ± 20 μmol mol-1) was over twice the level found in modern high-latitude trees. Dual-isotope spectral analysis suggests that multidecadal climate cycles somewhat similar to the modern Pacific Decadal Oscillation likely drove temperature and cloudiness trends on 20-30-year timescales, influencing photosynthetic productivity and tree growth patterns.

  18. Stable isotope paleoclimatology of the earliest Eocene using kimberlite-hosted mummified wood from the Canadian Subarctic

    NASA Astrophysics Data System (ADS)

    Hook, B. A.; Halfar, J.; Gedalof, Z.; Bollmann, J.; Schulze, D.

    2014-11-01

    The recent discovery of well-preserved mummified wood buried within a subarctic kimberlite diamond mine prompted a paleoclimatic study of the early Eocene "hothouse" (ca. 53.3 Ma). At the time of kimberlite eruption, the Subarctic and Artic were warm and humid producing a temperate rainforest biome well north of the Arctic Circle. Previous studies have estimated mean annual temperatures in this region were 4-20 °C in the early Eocene, using a variety of proxies including leaf margin analysis, and stable isotopes (δ18O) of fossil cellulose. Here, we examine stable isotopes of tree-ring cellulose at subannual to annual scale resolution, using the oldest viable cellulose found to date. We use mechanistic models and transfer functions to estimate earliest Eocene temperatures using mummified cellulose, which was well preserved in the kimberlite. Multiple samples of Piceoxylon wood within the kimberlite were crossdated by tree-ring width. Multiple proxies are used in combination to tease apart likely environmental factors influencing the tree physiology and growth in the unique extinct ecosystem of the Polar rainforest. Calculations of interannual variation in temperature over a multidecadal time-slice in the early Eocene are presented, with a mean temperature estimate of 11.4 °C (1σ = 1.8 °C) based on δ18O. Dual-isotope spectral analysis suggests that multidecadal climate cycles similar to the modern Pacific Decadal Oscillation likely drove temperature and cloudiness trends on 20-30 year timescales.

  19. Uranium-series dating of travertine from Soda Dam, New Mexico: Constructing a history of deposition, with implications for landscape evolution, paleohydrology and paleoclimatology

    NASA Astrophysics Data System (ADS)

    Tafoya, A. J.; Crossey, L. J.; Karlstrom, K. E.; Kolomaznik, M.; Polyak, V. J.; Asmerom, Y.; Cox, C. J.

    2011-12-01

    We apply high precision uranium series geochronology to decipher rates of change in travertine growth at Soda Dam, New Mexico which preserve a paleohydrology record for parts of the last 500 ka. Travertine-depositing springs occur along the intersection of the Soda Dam fault, part of the Jemez fault zone, and the Jemez River. Modern travertine-depositing hot springs are part of the Valles geothermal system, which has been active throughout the Quaternary. Previous U-series dates (Goff et al., 1987) on the Soda Dam travertines were: Soda Dam = 4.8±0.2 ka; Deposit A (west side) = 215±40 ka and >350 ka; Deposit B (east side) = 98±7 ka near top and 58±3 ka in the core; Deposit C (southeast side) = 107±5 ka near base. New dates provide improved geochronologic and geologic context with respect to timing of movement in the western side of the Rio Grande Rift and the Pajarito fault, incision rates of the Jemez River, and timing of travertine accumulation. Large volumes of travertine preserved high in the landscape yield an age of 560.3 ± 324 ka. Inset into this deposit are Jemez River gravels that are 30 m above the modern river with travertine coating on cobbles giving an age of 200.6±2.1 ka and gravels cut by sparite sills of 109 ± 1.5 ka. These ages give river incision rates of 150 m/Ma over the last 200 ka. Deposit B is a mound accumulation on the east side of the river that developed on a banded central fissure ridge, much like the modern Soda Dam. The mound accumulation is 138.4 ± 1.1 ka near the base and 78.2 ± 1.6 ka at the top; the central fissure has a 20 cm thick vein system a portion of which yields a more restricted age range from 133.9±11 ka toward the walls to 95.8±1.0 ka toward the center. The combined data indicate the fissure/mound system was active from 138-78 ka, a 60,000 yr interval that spans the transition from glacial marine isotope stage 6 into interglacial marine isotope stage 5. Accumulation rates on the vein system of deposit B are 2.9 mm/ka from 134 to 117 ka and 2.0 mm/ka from 117 to 96 ka indicating a higher accumulation rate of travertine during the wetter glacial marine isotope stage 6 versus the interglacial marine isotope stage 5. Outcrop C, also on the east side, is 103.2 ± 0.5 ka at the base and 101.7 ± 0.5 ka at the top and gives a river incision rate of 160 m/Ma over the last 100 ka. Longer term average incision for the Jemez River are 195 m/Ma over the last 1.2 Ma and 230 m/Ma over the last 0.64 Ma. Our results produce incision rates that are generally consistent with previously reported incision rates and suggest semi-steady bedrock river incision, with perhaps a slight slowing over the last 200 ka. The dates also indicate persistent deposition along the Soda Dam fault system over at least 500 thousand years. Stable isotope values of the dated travertines range from δ180 = -19 to -6.5 per mil (PDB), reflecting variations in local spring chemistry and a potential paleoclimate record that will be investigated using closer spaced sampling and multiple proxies.

  20. Integrated biostratigraphy, stage boundaries and Paleoclimatology of the Upper Cretaceous-Lower Eocene successions in Kharga and Dakhala Oases, Western Desert, Egypt

    NASA Astrophysics Data System (ADS)

    Khalil, H.; Al Sawy, S.

    2014-08-01

    The Upper Cretaceous-Lower Eocene succession in the studied sections is divided into four rock units that arranged from base to top: the Dakhla, Tarawan, Esna and the Thebes formations. Detailed study of the foraminifera and calcareous nannofossils has led to the recognition of 58 and 82 species, respectively. Based on planktonic foraminifera and calcareous nannofossils 8 planktonic foraminiferal biozones (CF4, P2, P3, P4, E1, E2, E3 and E4) have been recognized as well as 8 calcareous nannofossil biozones (CC25b, NP3, NP4, NP5, NP6, NP7/8, NP9, and NP10). At Gabal Teir/Tarawan section, Kharga Oasis, the Paleocene can be divided into three stages; Danian, Selandian and Thanetian. The Danian/Selandian boundary is placed at P3a/P3b zonal boundary (LO of Igorina albeari) which corresponds to the level of LO of Lithoptychius ulii, Fasciculithus pileatus, Fasciculithus involutus and Lithoptychius janii (upper part of Zone NP4). The Selandian/Thanetian boundary, on the other hand, can be traced within the foraminiferal Zone P4 (Globanomalina pseudomenardii Zone) and between the nannofossil zones NP6 and NP7/8 (LO of Discoaster mohleri). At Gabal Ghanima section, the Paleocene/Eocene boundary is located within the lower part of the Esna Formation. It can be traced at the base of planktonic foraminiferal Zone E1 (LOs of Acarinina africana, A sibaiyaensis and Morozovella allinsoensis), and at the NP9a/NP9b subzonal boundary (LO of Rhomboaster spp). However, the lower Eocene succession seems to be condensed and punctuated by minor hiatus (absence of Subzone NP10a). The dominance of cool water nannofossil species in the late Maastrichtian and early Danian interval suggests a gradual decrease in the surface water paleotemperature. However, a slight warming condition prevailed around the Danian/Selandian transition as evidenced by the warm water nannofossil species. At the P/E boundary interval, the high abundance of warm-water taxa (e.g. Discoaster, Sphenolithus, Rhomboaster, Tribrachiatus and Pontosphaera species) indicates a warm-water paleotemperatures.

  1. Relation between D/H ratios and sup 18 O/ sup 16 O ratios in cellulose from linen and maize--Implications for paleoclimatology and for sindonology

    SciTech Connect

    DeNiro, M.J.; Sternberg, L.D.; Marino, B.D. ); Druzik, J.R. )

    1988-09-01

    The {sup 18}O/{sup 16}O ratios of cellulose and the D/H ratios of cellulose nitrate were determined for linen, a textile produced from the fibers of the flax plant Linum usitatissimum, and for maize (Zea mays) from a variety of geographic locations in Europe, the Middle East, and North and South America. The regression lines of {delta}D values on {delta}{sup 18}O values had slopes of 5.4 and 5.8 for the two species. Statistical analysis of results reported in the only other study in which samples of a single species that grew under a variety of climatic conditions were analyzed yielded slopes of {approximately}6 when {delta}D values of cellulose nitrate were regressed on {delta}{sup 18}O values of cellulose. The occurrence of this previously unrecognized relationship in three species suggests it may obtain in other plants as well. Determining the basis for this relationship, which is not possible given current understanding of fractionation of the isotopes of oxygen and hydrogen by plants, should lead to increased understanding of how D/H and {sup 18}O/{sup 16}O ratios in cellulose isolated from fossil plants are related to paleoclimates. The separation of most linen samples from Europe from those originating in the Middle East when {delta}D values are plotted against {delta}{sup 18}O values suggests it may be possible to use the isotope ratios of cellulose prepared from the Shroud of Turin to resolve the controversy concerning its geographic origin.

  2. Relation between D/H ratios and 18O /16O ratios in cellulose from linen and maize - Implications for paleoclimatology and for sindonology

    NASA Astrophysics Data System (ADS)

    DeNiro, Michael J.; Sternberg, Leonel D.; Marino, Bruno D.; Druzik, James R.

    1988-09-01

    The 18O /16O ratios of cellulose and the D/H ratios of cellulose nitrate were determined for linen, a textile produced from the fibers of the flax plant Linum usitatissimum, and for maize ( Zea mays) from a variety of geographic locations in Europe, the Middle East, and North and South America. The regression lines of δD values on δ 18O values had slopes of 5.4 and 5.8 for the two species. Statistical analysis of results reported in the only other study in which samples of a single species (the silver fir Abies pindrow) that grew under a variety of climatic conditions were analyzed yielded slopes of ~6 when δD values of cellulose nitrate were regressed on δ 18O values of cellulose. The occurrence of this previously unrecognized relationship in three species suggests it may obtain in other plants as well. Determining the basis for this relationship, which is not possible given current understanding of fractionation of the isotopes of oxygen and hydrogen by plants, should lead to increased understanding of how D/H and 18O /16O ratios in cellulose isolated from fossil plants are related to paleoclimates. The separation of most linen samples from Europe from those originating in the Middle East when δD values are plotted against δ 18O values suggests it may be possible to use the isotope ratios of cellulose prepared from the Shroud of Turin to resolve the controversy concerning its geographic origin.

  3. Lower Eocene alluvial paleosols (Willwood Formation, Northwest Wyoming, U.S.A.) and their significance for paleoecology, paleoclimatology, and basin analysis

    USGS Publications Warehouse

    Bown, T.M.; Kraus, M.J.

    1981-01-01

    The lower Eocene Willwood Formation of northwest Wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones, nearly all of which show paleopedogenic modifications. Pedogenesis of Willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation, early local cementation by calcium carbonate, and thin illuviation cutans on clastic grains. Pedogenesis in Willwood mudstones is indicated by plant bioturbation, insect and other invertebrate burrow casts and lebensspuren; free iron, aluminum, and manganese mobilization, including hydromorphic gleying; sesquioxide and calcareous glaebule formation in lower parts of the solum; presence of clay-rich and organic carbon-rich zones; and well differentiated epipedons and albic and spodic horizons. Probable A horizons are also locally well developed. Occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin, lenticular, and unconnected fluvial sandstones in the Willwood Formation of the central and southeast Bighorn Basin suggest that these soils formed during times of rapid sediment accumulation. The tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that Willwood floodplains were broad and essentially featureless. All Willwood paleosols were developed on alluvial parent materials and are complex in that B horizons of younger paleosols were commonly superimposed upon and mask properties of suspected A and B horizons of the next older paleosols. The soils appear to be wet varieties of the Spodosol and Entisol groups (aquods and ferrods, and aquents, respectively), though thick, superposed and less mottled red, purple, and yellow paleosols resemble some ultisols. Most Willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and (or) fluctuating water tables. The up-section decrease in frequency of gley mottles, increase in numerical proportion and thickness of red versus orange coloration, and increase in abundance of calcrete glaebules indicate better drained soils and probably drier climate in late Willwood time. This drying is believed to be related to creation of rain shadows and spacing of rainfall (but not necessarily decrease in absolute rainfall) due to progressive tectonic structural elevation of the mountainous margins of the Bighorn Basin. ?? 1981.

  4. Warm to cold polar climate transitions over the last 15,000 years: A paleoclimatology record from the raised beaches of northern Norway

    SciTech Connect

    Fletcher, C.H. ); Fairbridge, R.H. ); Moeller, J.K. ); Long, A.J. )

    1991-03-01

    Because of the strength of the cold, dry arctic high pressure vortex, and the absence of multiple air-mass sources, climate records from the polar region tend to display a cleaner signal than those from mid-latitude settings. The high arctic presents unique opportunities for the prediction of the natural background pattern of climate change prior to the disturbances generated by manmade atmospheric pollutants. The Varanger Peninsula of northernmost Norway was extensively depressed by an ice dome during the last glacial stage. Deglaciation was accompanied by isostatic recovery at a steady though exponentially decaying rate. Superimposed on the rising land is a discontinuous staircase of cobble beach ridges, deposited during the postglacial period by storms at the coast. The ridges are constructed during brief episodes of weather- and tide-related elevation of sea level and wave run-up. Storminess periods can only occur in the absence of sea ice associated with several decades of mild, relatively warm temperatures. A history of local relative sea level is constructed from over 70 radiocarbon dates of various water-level indicators. The sea-level history is used to construct a chronology of beach-ridge building that documents the cyclic, a periodic nature of arctic storminess conditions. The authors date a dynamic signal with multiple climate transitions from warm, stormy conditions to cool, calm conditions occurring roughly every 200 years between 15,000 years ago to 10,000 years ago. Throughout the Holocene the climate is more settled with longer periods separating the major warm to cool transitions.

  5. Variations in [sup 18]O/[sup 16]O ratios of kaolinites within a lateritic profile: Their significance for laterite genesis and isotope paleoclimatology

    SciTech Connect

    Giral, S.; Girard, J.P.; Savin, S.M. . Dept. of Geological Sciences); Nahon, D.B. )

    1992-01-01

    The authors have made an integrated study of the field occurrence, petrology, mineralogy and crystallography, and oxygen isotope geochemistry of an active lateritic profile from about 60 km north of Manaus (Amazonia, Brazil). The parent rock is an arkosic sandstone. The delta O-18 values of kaolinites from the profile are far from uniform. The total range is about 2.4 per mil (18.7 to 21.1 per mil). The calculated delta O-18 value of kaolinite in isotopic equilibrium with local average precipitation and mean annual temperature is 19.6 per mil, within the range of the measured values. Kaolinite of each of several textural occurrences also shows significant isotopic variation both vertically and within a given horizon. Different size fractions of kaolinite of a single textural occurrence within a single horizon also exhibit differences in delta O-18 values. At depths below a few meters, they expect the temperature and the delta O-18 values of the soil water profile to be relatively uniform at any time. If this is so, the variations in delta O-18 values of the kaolinites would suggest that the formation of different populations occurred at different times. They cannot yet distinguish between variations of conditions that were seasonal and variations that occurred on scales of many years. However, it is most important to resolve the causes of these variations before using the delta O-18 values of soil clays for purposes of paleoclimatic reconstruction.

  6. Paleontology, paleoclimatology and paleoecology of the late middle miocene Musselshell Creek flora, Clearwater County Idaho. A preliminary study of a new fossil flora

    SciTech Connect

    Baghai, N.L.; Jorstad, R.B.

    1995-10-01

    The Musselshell Creek flora (12.0-10.5 Ma) of northern Idaho is used to reconstruct paleoclimatic and paleoecologic parameters of the Pacific Northwest during the late Middle Miocene. Other megafossil and microfossil floral records spanning 12.0-6.4 Ma are unknown from this region. The Musselshell Creek fossil flora, previously undescribed, is preserved in lacustrine clays and sediments that accumulated in a narrow valley surrounded by rugged terrain. Dominant taxa include dicotyledons and conifers. Most of the leaves are preserved as impressions or compressions. Some fossil leaves retained their original pigmentation, cellular anatomy, and organic constituents. Other fossils include excellent remains of pollen and spores, dispersed leaf cuticle, pyritized wood, and disarticulated fish bones. A destructive statistical analysis of one block of sediment, approximately 30 cm x 45 cm (1.5 sq. ft) recovered 14 orders, 23 families, and 34 genera of spermatophyte plant fossils. These floral elements are compared with two other earlier Miocene floras which were similarly sampled. Common megafossil genera include Quercus, Zizy-phoides, Taxodium, Alnus, Castanea, Magnolia, Acer, Ex-bucklandia, Sequoia, Populus, and Betula. The rare occurrence of Ginkgo leaves is a first record of this taxon in the Idaho Miocene. Additional plant taxa, are represented by palynomorphs. Common pollen taxa are Pinus, Abies, Carya, Quercus, and Tilia. Most of the megafossil and microfossil flora assemblage is characteristic of a streambank to floodplain environment that existed in a warm to cool temperate climate similar to the modern Mid-Atlantic coast of the United States. 47 refs., 5 figs., 4 tabs.

  7. High-resolution paleoclimatology of the Santa Barbara Basin during the Medieval Climate Anomaly and early Little Ice Age based on diatom and silicoflagellate assemblages in Kasten core SPR0901-02KC

    USGS Publications Warehouse

    Barron, John A.; Bukry, David B.; Hendy, Ingrid L.

    2015-01-01

    Diatom and silicoflagellate assemblages documented in a high-resolution time series spanning 800 to 1600 AD in varved sediment recovered in Kasten core SPR0901-02KC (34°16.845’ N, 120°02.332’ W, water depth 588 m) from the Santa Barbara Basin (SBB) reveal that SBB surface water conditions during the Medieval Climate Anomaly (MCA) and the early part of the Little Ice Age (LIA) were not extreme by modern standards, mostly falling within one standard deviation of mean conditions during the pre anthropogenic interval of 1748 to 1900. No clear differences between the character of MCA and the early LIA conditions are apparent. During intervals of extreme droughts identified by terrigenous proxy scanning XRF analyses, diatom and silicoflagellate proxies for coastal upwelling typically exceed one standard deviation above mean values for 1748-1900, supporting the hypothesis that droughts in southern California are associated with cooler (or La Niña-like) sea surface temperatures (SSTs). Increased percentages of diatoms transported downslope generally coincide with intervals of increased siliciclastic flux to the SBB identified by scanning XRF analyses. Diatom assemblages suggest only two intervals of the MCA (at ~897 to 922 and ~1151 to 1167) when proxy SSTs exceeded one standard deviation above mean values for 1748 to 1900. Conversely, silicoflagellates imply extreme warm water events only at ~830 to 860 (early MCA) and ~1360 to 1370 (early LIA) that are not supported by the diatom data. Silicoflagellates appear to be more suitable for characterizing average climate during the 5 to 11 year-long sample intervals studied in the SPR0901-02KC core than diatoms, probably because diatom relative abundances may be dominated by seasonal blooms of a particular year.

  8. The Ice Core Data Gateway: The one stop gateway to ice core data held at the Antarctic Glaciological Data Center (AGDC), the World Data Center for Paleoclimatology, and the Arctic System Science's Data Coordination Center (ADCC).

    NASA Astrophysics Data System (ADS)

    Bauer, R.; Scambos, T.; Eakin, M.; Anderson, D.; McNeave, C.

    2002-12-01

    The Ice Core Data Gateway archives and distributes physical and geochemical data from ice cores collected in both the northern and southern hemispheres. Typical data sets include age-depth relationships, oxygen and hydrogen isotope concentrations, major element chemistry, accumulation rates and pollen. The data are in general presented as ASCII files with a short text metadata description. The archive is designed to provide access to ice core data sets over the long term, thereby making them available for comparison with future data: a critical component of change detection studies. By facilitating broad data access, the center promotes interdisciplinary scientific research. Investigators are encouraged to contribute data sets derived from ice cores to the Ice Core Data Gateway. Data center staff will work with you to compile data set documentation prior to making the data available to users. Contributing scientists are given prominent recognition in the documentation, and while the data center answers technical questions about format, citations for usage, etc., it can refer scientific questions to contributors if requested. Contributing your data to the Ice Core Data Gateway and associated data centers directly supports to NSF Office of Polar Programs Guidelines and Award Conditions for Scientific Data (http://www.nsf.gov/pubsys/ods/getpub.cfm?opp991). This effort is being coordinated with the West Antarctic Ice Sheet (WAIS) Initiative and U.S. component of the International Trans Antarctic Science Expedition (ITASE), and includes data from the Arctic System Science Program's Greenland Ice Sheet Project 2 (GISP2) ice core.

  9. Hidden histories and ancient mysteries of witches, plants and fungi

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Convergent findings from archaeobotany, molecular genetics, paleoclimatology and comparative linguistics mandate revisions to agricultural history. Recent research has demonstated that stripe rust (agent: Puccinia striiformis) and scald (species in Rhynchosporium) moved into western and northern Eu...

  10. Reconstructing Earth's Climate History: Inquiry-Based Exercises for Lab and Class

    NASA Astrophysics Data System (ADS)

    Wolfe, Brent

    2013-04-01

    For instructors in natural science undergraduate programs, there is a clear need to have students explore and understand the scientific evidence of past climate variability and learn what this tells us about the role of humans in shaping present-day climate. Indeed, research in the field of paleoclimatology has provided data that identifies one of the most pressing challenges facing society—global warming. Herein lay my motivation to fill an important gap in my university's undergraduate program in geography and environmental studies. To that end, about a year ago I began to develop a new fourth-year course in paleoclimatology.

  11. The Journey of Man: A Genetic Odyssey

    SciTech Connect

    Wells, Spencer

    2004-02-25

    Evidence from paleoanthropology and genetics has consistently shown that our species originated in Africa. Recent results from the Y-chromosome confirm this, but further posit that all modern humans were still living in Africa 60,000 years ago. The case for a recent 'African exodus' will be discussed, with supporting evidence drawn from DNA polymorphisms, paleoclimatology and archaeology.

  12. Physical geology

    SciTech Connect

    Skinner, B.; Porter, S.

    1987-01-01

    The book integrates current thinking on processes (plate techtonics, chemical cycles, changes throughout geologic time). It is an introduction to investigations into the way the earth works, how mountains are formed, how the atmosphere, hydrosphere, crust and mantle interact with each other. Treatments on climate, paleoclimatology and landscape evolution are included, as is a discussion on how human activity affects geological interactions.

  13. Soil microscopy and micromorphology

    SciTech Connect

    FitzPatrick, E.A.

    1993-12-31

    This book is a valuable resource to help geologists integrate knowledge of soil science into the endeavor of identifying paleosols. Attention is focused on the following: soil micromorphology, including sample preparation techniques; and physical and chemical properties. Various applications are presented of micromorphological soil study. Included is coverage on the disciplines of agriculture, archeology, engineering, geomorphology, paleoclimatology, paleopedology, and microbiology.

  14. In Memoriam; Recent Ph.D.s; Honors

    NASA Astrophysics Data System (ADS)

    2005-03-01

    In Memoriam. John C. Freeman, 84, 18 November 2004, Atmospheric Sciences, 1991. Thomas Gold, 84, 22 June 2004, Retired Life Member, AGU Fellow, Planetology, 1958. William H. Pickering, 93, 2004, Retired Life Member, AGU Fellow, Planetology, 1962. Geoff O. Seltzer, 45, 15 January 2005, Paleoceanography/Paleoclimatology, 1990.

  15. Climate and the collapse of civilization

    SciTech Connect

    Abate, T.

    1994-09-01

    This article looks at the archaeological debate over two important questions: whether abrupt climate changes caused or contributed to the collapse of ancient civilizations and, if the archaeological and paleoclimatological record yields evidence to that effect, what would it mean in a world that today debates whether industrial civilization is altering Earth's climate with uncertain consequences. Areas discussed include the following: climate hints from archaeological sites; hesitations about whether climate change caused civilizations to collapse; and the interdisciplinary checks on each side.

  16. Volcanic eruptions: Atmospheric effects. (Latest citations from the NTIS bibliographic database). Published Search

    SciTech Connect

    Not Available

    1994-02-01

    The bibliography contains citations concerning gaseous and particulate contributions to the Earth's atmosphere from volcanoes, and the effects these substances have on the climate and the environment. Citations cover case studies of specific volcanic eruptions, detection and measurement of volcanic gases and aerosols in the atmosphere, environmental effects on the biota, long and short term climatological effects, paleoclimatology and volcanoes, atmospheric and transport modeling, and solar radiation inhibition. (Contains a minimum of 214 citations and includes a subject term index and title list.)

  17. Volcanic eruptions: Atmospheric effects. May 1970-February 1990 (A Bibliography from the NTIS data base). Report for May 1970-February 1990

    SciTech Connect

    Not Available

    1990-03-01

    This bibliography contains citations concerning gaseous and particulate contributions to the Earth's atmosphere from volcanoes, and the effects these substances have on the climate and the environment. Case studies of specific volcanic eruptions; detection and measurement of volcanic gases, aerosols, and particulates in the atmosphere; environmental effects on the biota; long and short term climatological effects; paleoclimatology and volcanoes; atmospheric and transport modelling; and solar radiation inhibition are among the topics discussed. (Contains 157 citations fully indexed and including a title list.)

  18. Workshop on Early Mars: How Warm and How Wet?, part 1

    NASA Technical Reports Server (NTRS)

    Squyres, S. (Editor); Kasting, J. (Editor)

    1993-01-01

    This volume contains papers that have been accepted for presentation at the Workshop on Early Mars: How Warm and How Wet?, 26-28 Jul. 1993, in Breckenridge, CO. The following topics are covered: the Martian water cycle; Martian paleoclimatology; CO2/CH4 atmosphere on early Mars; Noachian hydrology; early Martian environment; Martian weathering; nitrogen isotope ratios; CO2 evolution on Mars; and climate change.

  19. Scientists and Reporters Just Want to Get to the Bottom of It All

    NASA Astrophysics Data System (ADS)

    Rosen, Julia

    2014-10-01

    After just a few short months, my desk at the Los Angeles Times had succumbed to the same peculiar malady as my desk at Oregon State University, where I did my Ph.D. in paleoclimatology: It seemed to have sprouted a thin coat of fluorescent sticky notes. Each tiny square bore a fact that merited remembering or a question that demanded answering, and, every day, they multiplied.

  20. Paleolimnology Web Portal: A Web Site Designed to Increase Paleolimnology Data Availability

    NASA Astrophysics Data System (ADS)

    Eakin, C. M.; Moy, C. M.; Habermann, T.; Gross, W. S.; Keltner, J. M.

    2001-12-01

    Despite widespread use of lacustrine records to interpret paleolimnologic and paleoclimatic change, there is a large gap between the data published in peer-reviewed journals and those submitted for archive and available to other researchers online. A primary goal of the World Data Center (WDC) for paleoclimatology and the International Geosphere-Biosphere Programme (IGBP) - Past Global Changes (PAGES) core programme is to have full and open sharing of all data sets needed for global change studies. To help improve the quantity and quality of data submitted to the WDC for Paleoclimatology, we are developing online data submission and advanced interactive browse and access tools. Our poster presents a new web-site designed to make paleolimnology data more accessible by incorporating web-based data submission forms, a multi-proxy relational database, and interactive mapping tools. The WDC for Paleoclimatology is currently designing intuitive and streamlined web-based submission forms, which will allow investigators to quickly submit their data and metadata on-line. We are also importing all existing data and metadata in our archives into a multiproxy relational database that will allow users to quickly query and retrieve paleolimnological data, as well as display the data in various formats. Furthermore, we are implementing two Paleolimnology mapping tools that will allow users to search, display, and query data in a geographical format. The first tool, WebMapper, uses a Java applet to draw maps and display metadata. This will be supplemented by a plotting tool that will provide basic plotting functions to allow users to examine data before downloading them. The second mapping tool, ArcIMS, allows users to overlay paleoclimatic data with various GIS data sets in addition to providing basic spatial analysis functions. We believe that these new web-based features will encourage more extensive data sharing and submission, making paleolimnological data more available and

  1. Pleistocene glaciation in the blue ridge province, southern appalachian mountains, north Carolina.

    PubMed

    Berkland, J O; Raymond, L A

    1973-08-17

    Glacial polish, grooves, and striations discovered at an elevation of 1370 meters in the headwaters of Boone Fork on Grandfather Mountain, North Carolina, indicate the former, existence of alpine glaciation at a latitude of 36 degrees 07'N. The Boone Fork glacier was located 890 kilometers south of the previously recognized southern limit of alpine glaciation in the Appalachian Mountains, and 350 kilometers southeast of the nearest point on the Laurentide ice sheet. This find has significant implications for studies of Pleistocene geomorphology, paleobiology, and paleoclimatology in the eastern United States.

  2. Hydrogeology of closed basins and deserts of South America, ERTS-1 interpretations

    NASA Technical Reports Server (NTRS)

    Stoertz, G. E.; Carter, W. D.

    1973-01-01

    Images from the Earth Resources Technology Satellite (ERTS-1) contain data useful in studies of hydrogeology, geomorphology, and paleoclimatology. Sixteen Return Beam Vidicon (RBV) images and 15 Multi-Spectral Scanner (MSS) images were studied. These covered deserts and semidesert areas in southwestern Bolivia, northwestern Argentina, northern Chile, and southeastern Peru from July 30 to November 17, 1972. During the first 3 months after launching, high-quality cloud-free imagery was obtained over approximately 90 percent of the region of interior drainage, or an area of 170,000 square miles.

  3. Greenhouse effect and the global climate. (Latest citations from the Aerospace database). Published Search

    SciTech Connect

    Not Available

    1993-09-01

    The bibliography contains citations concerning terrestrial climatic changes known as the greenhouse effect. The greenhouse effect is an accumulation of carbon dioxide and other gases that retain solar-induced heat, thereby increasing the average global temperature. Modeling studies, measurements of atmospheric gases, pollutants and temperatures, studies of climatic records for occurrence of similar changes (paleoclimatology), prediction of environmental changes due to the greenhouse effect, government energy policy as a result of possible climate change, and the contributions of manmade and natural pollutants to the greenhouse effect are among the topics discussed. (Contains a minimum of 52 citations and includes a subject term index and title list.)

  4. Volcanic eruptions: atmospheric effects. (Latest citations from the NTIS data base). Published Search

    SciTech Connect

    Not Available

    1992-04-01

    The bibliography contains citations concerning gaseous and particulate contributions to the Earth's atmosphere from volcanoes, and the effects these substances have on the climate and the environment. Case studies of specific volcanic eruptions; detection and measurement of volcanic gases, aerosols, and particulates in the atmosphere; environmental effects on the biota; long and short term climatological effects; paleoclimatology and volcanoes; atmospheric and transport modelling; and solar radiation inhibition are among the topics discussed. (Contains a minimum of 179 citations and includes a subject term index and title list.)

  5. Some topics on geochemistry of weathering: a review.

    PubMed

    Formoso, Milton L L

    2006-12-01

    Weathering is a complex process comprising physical disaggregation, chemical and biological decomposition of rocks and minerals transforming complex structure minerals in simpler ones. Hydrolysis of silicates is perhaps the most important process but associated certainly to biological weathering. It is discussed the role ofwaters: activities/concentrations of chemical species, pH, Eh, importance of complexes. Weathering is not only a destructive process. It can concentrate chemical species and form mineral deposits (kaolin, bauxite, Fe, Mn, P, Nb, Au). Weathering studies are important in pedology, engineering geology, hydrogeology, paleoclimatology and ecology. The use of stonemeal is based upon the study of rock weathering.

  6. Climate Warming and 21st-Century Drought in Southwestern North America

    NASA Astrophysics Data System (ADS)

    MacDonald, Glen M.; Stahle, David W.; Diaz, Jose Villanueva; Beer, Nicholas; Busby, Simon J.; Cerano-Paredes, Julian; Cole, Julie E.; Cook, Edward R.; Endfield, Georgina; Gutierrez-Garcia, Genaro; Hall, Beth; Magana, Victor; Meko, David M.; Méndez-Pérez, Matias; Sauchyn, David J.; Watson, Emma; Woodhouse, Connie A.

    2008-02-01

    Since 2000, southwestern North America has experienced widespread drought. Lakes Powell and Mead are now at less than 50% of their reservoir capacity, and drought or fire-related states of emergency were declared this past summer by governors in six western states. As with other prolonged droughts, such as the Dust Bowl during the 1930s, aridity has at times extended from northern Mexico to the southern Canadian prairies. A synthesis of climatological and paleoclimatological studies suggests that a transition to a more arid climate may be occurring due to global warming, with the prospect of sustained droughts being exacerbated by the potential reaction of the Pacific Ocean to warming.

  7. Studies of Cave Sediments: Physical and Chemical Records of Paleoclimate (Revised Edition)

    NASA Astrophysics Data System (ADS)

    Baker, Andy

    2007-10-01

    Caves have long fascinated humankind, from prehistory to present-day tourism. Caves are also a subject for a range of scientific investigations, including cave biology, archaeology, paleoclimatology, geology, hydrology, and geomorphology. One of the benefits caves provide is their role as a repository of material that might not otherwise survive on the Earth's surface, due to caves' interiors being protected from physical erosion by nature of their underground locations. Studies of Cave Sediments focuses on this role as a repository, in particular on Quaternary (historic to 1.8 million years old) paleoclimate information preserved in cave sediments.

  8. A phase-transition model for the rise and collapse of ancient civilizations: A pre-ceramic Andean case study

    NASA Astrophysics Data System (ADS)

    Flores, J. C.

    2015-12-01

    For ancient civilizations, the shift from disorder to organized urban settlements is viewed as a phase-transition simile. The number of monumental constructions, assumed to be a signature of civilization processes, corresponds to the order parameter, and effective connectivity becomes related to the control parameter. Based on parameter estimations from archaeological and paleo-climatological data, this study analyzes the rise and fall of the ancient Caral civilization on the South Pacific coast during a period of small ENSO fluctuations (approximately 4500 BP). Other examples considered include civilizations on Easter Island and the Maya Lowlands. This work considers a typical nonlinear third order evolution equation and numerical simulations.

  9. In Memoriam: Herbert E. Wright, Jr., 1917-2015

    NASA Astrophysics Data System (ADS)

    Whitlock, Cathy; Stein, Julie K.; Fritz, Sherilyn

    2016-01-01

    Professor Herbert E. Wright passed away on November 12, 2015 in his 98th year. His passing leaves many in Quaternary community reflecting on his enormous contributions to the discipline, as well as the many ways in which he touched our lives. Herb's legacy, writ large, is evidenced by decades of scholarly contributions to the fields of glacial geology, geomorphology, paleoecology, paleolimnology, paleoclimatology, and archaeology. During the course of his career, he authored and co-authored over 250 scientific publications and co-edited 16 influential volumes on the Quaternary.

  10. The climate of Lower Franconia since 1500

    NASA Astrophysics Data System (ADS)

    Glaser, R.; Hagedorn, H.

    1991-09-01

    The present article summarizes the essential methods and results of an investigation which was carried out by the paleoclimatological working group of the Geographical Institute of the University of Würzburg from 1983 1989. The aim of this investigation was a seasonal scale reconstruction of the historical climate of Lower Franconia (southern Germany) using instrumental data, narrative sources and harvest records for wine, grain and hay as well as dendrological data (proxy data). Both method and data discussed and regional climate patterns within Franconia are presented.

  11. Astrobiology: Interdisciplinary Research Providing a Vision for Planetary Exploration

    NASA Astrophysics Data System (ADS)

    Voytek, M. A.; New, M. H.; Billings, L.

    2009-12-01

    In 1960, NASA established an exobiology research program to fund research into the origin and evolution of life on Earth and the possibility of extraterrestrial life. Today, NASA's Astrobiology Program, which includes an element focusing on exobiology and evolutionary biology, funds transdisciplinary research into the origin, evolution, distribution, and future of life in the universe. This talk will address the the cross-cutting nature of astrobiology research, which encompasses work in mcirobial ecology, evolutionary studies, biogeosciences, earth sciences, planetary science, paleoclimatology, global environmental change; and the increasing focus of planetary exploration missions on astrobiological questions.

  12. Seasonal Streamflow Reconstructions of the Choctawhatchee River (AL-USA)

    NASA Astrophysics Data System (ADS)

    Tootle, G. A.; Therrell, M.; Moat, T.; Meko, M.

    2015-12-01

    Tree ring samples were collected from Bald Cypress (Taxodium distichum) species in watersheds adjacent to the Choctawhatchee River (Alabama and Florida - USA). These samples were collected to update an existing tree ring proxy that was developed in the late 1980's and early 1990's (Stahle and Cleaveland, 1992, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution # FL001, Choctawhatchee River. NOAA/NCDC Paleoclimatology Program, Boulder, Colorado, USA). The motivation for updating the tree ring proxy was to determine if recent droughts identified in historic unimpaired Choctawhatchee River streamflow records were reflected in Bald Cypress tree ring growth. Historic streamflow from 1934 to 2013 was obtained for the USGS station at Newton, Alabama and one, five and ten-year droughts were identified and ranked. Many of the most severe droughts were identified in recent (~2000 to present) records (see Figure). Combining the new tree ring proxy with other regional proxies, seasonal streamflow was reconstructed for the Choctawhatchee River Newton, Alabama gage. The reconstructed streamflow allows water managers and planners to observe past wet and dry periods that may exceed magnitude, duration and/or severity of wet and dry periods in observed records.

  13. Automated Analysis of Planktic Foraminifers Part III: Neural Network Classification

    NASA Astrophysics Data System (ADS)

    Schiebel, R.; Bollmann, J.; Quinn, P.; Vela, M.; Schmidt, D. N.; Thierstein, H. R.

    2003-04-01

    The abundance and assemblage composition of microplankton, together with the chemical and stable isotopic composition of their shells, are among the most successful methods in paleoceanography and paleoclimatology. However, the manual collection of statistically significant numbers of unbiased, reproducible data is time consuming. Consequently, automated microfossil analysis and species recognition has been a long-standing goal in micropaleontology. We have developed a Windows based software package COGNIS for the segmentation, preprocessing, and classification of automatically acquired microfossil images (see Part II, Bollmann et al., this volume), using operator designed neural network structures. With a five-layered convolutional neural network we obtain an average recognition rate of 75 % (max. 88 %) for 6 taxa (N. dutertrei, N. pachyderma dextral, N. pachyderma sinistral, G. inflata, G. menardii/tumida, O. universa), represented by 50 images each for 20 classes (separation of spiral and umbilical views, and of sinistral and dextral forms). Our investigation indicates that neural networks hold great potential for the automated classification of planktic foraminifers and offer new perspectives in micropaleontology, paleoceanography, and paleoclimatology (see Part I, Schmidt et al., this volume).

  14. Terrestrial biomarkers in the sediment of the East Sea (Japan Sea) since the MIS 11: implications for paleoproductivity and paleoclimatic changes

    NASA Astrophysics Data System (ADS)

    Hyun, S.; Suh, Y. J.; Woo, K. S.; Ikehara, M.

    2014-12-01

    Terrestrial biomarkers such as n-alkanes and cholesterol were analyzed to infer the variations of paleoproductivity and the corresponding paleoclimatologic information from the sediment of the Korean Plateau, East Sea (Japan Sea) since the Marine Isotope Stage (MIS) 11 (ca. 400 ka). Previous studies of SST variation have shown that glacial-interglacial scale changes were quite variable with the maximum range of 26oC in MIS 7, and the minimum range of 12oC during MIS 2 and 6. The distribution of terrestrial n-alkanes signatures is characterized by the occurrence of high odd number frequency with a minor contribution of specific compound (nC27 only). Average Chain Length (ACL) and Carbon Preferences Index (CPI), both of which are derived from n-alkane combination, show similar shifting between glacial and interglacial periods. This suggests that paleovegetation communities had been changed in responding to paleoclimatological variations, and the input amount of terrestrial compound was strongly linked with paleoclimatologic changes. In particular, depleted values of δ13Corg during MIS 2, 8 and 10 were coincident with lower nitrogen isotope values indicating local paleoceanographic effects such as paleoproductivity changes. Decoupling between δ13Corg and δ15Norg during MIS 1, 3, 5, 7 and coupling of the two during MIS 8 and 11 can be observed, which appear to be interpreted as local productivity changes. In particular, high abundance of cholesterol and C21 n-alkanes, which were derived from diatom, increased during interglacial periods. Therefore, alkenones, SST and n-alkanes signatures coincide with δ13Corg and δ15Norg variations during glacial-interglacial cycles and further strongly associated with cholesterol abundance suggesting that the paleoenvironmental conditions in East Sea during glacial-interglacial periods were sensitive not only to global climate changes but also to local paleceanographic variations. Surface water circulation around the Korea

  15. Comparative Analysis of Global Digital Elevation Models and Ultra-Prominent Mountain Peaks

    NASA Astrophysics Data System (ADS)

    Grohmann, Carlos H.

    2016-06-01

    Global Digital Elevation Models (GDEMs) are datasets of vital importance for regional-scale analysis in areas such as geomorphology, [paleo]climatology, oceanography and biodiversity. In this work I present a comparative assessment of the datasets ETOPO1 (1' resolution), GTOPO30, GLOBE, SRTM30 PLUS, GMTED2010 and ACE2 (30") against the altitude of the world's ultra prominent peaks. GDEMs' elevations show an expected tendency of underestimating the peak's altitude, but differences reach 3,500 m. None of the GDEMs captures the full range of elevation on Earth and they do not represent well the altitude of the most prominent peaks. Some of these problems could be addressed with the release of NASADEM, but the smoothing effect caused by moving-window resampling can only be tackled by using new techniques, such as scale-adaptative kernels and curvature-based terrain generalisation.

  16. Latitudinal species diversity gradient of marine zooplankton for the last three million years.

    PubMed

    Yasuhara, Moriaki; Hunt, Gene; Dowsett, Harry J; Robinson, Marci M; Stoll, Danielle K

    2012-10-01

    High tropical and low polar biodiversity is one of the most fundamental patterns characterising marine ecosystems, and the influence of temperature on such marine latitudinal diversity gradients is increasingly well documented. However, the temporal stability of quantitative relationships among diversity, latitude and temperature is largely unknown. Herein we document marine zooplankton species diversity patterns at four time slices [modern, Last Glacial Maximum (18,000 years ago), last interglacial (120,000 years ago), and Pliocene (~3.3-3.0 million years ago)] and show that, although the diversity-latitude relationship has been dynamic, diversity-temperature relationships are remarkably constant over the past three million years. These results suggest that species diversity is rapidly reorganised as species' ranges respond to temperature change on ecological time scales, and that the ecological impact of future human-induced temperature change may be partly predictable from fossil and paleoclimatological records. PMID:22738438

  17. AGU climate scientists visit Capitol Hill

    NASA Astrophysics Data System (ADS)

    Hankin, Erik

    2012-02-01

    On 1 February 2012, AGU teamed with 11 other scientific societies to bring 29 scientists researching various aspects of climate change to Washington, D. C., for the second annual Climate Science Day on Capitol Hill. The participants represented a wide range of expertise, from meteorology to agriculture, paleoclimatology to statistics, but all spoke to the reality of climate change as demonstrated in their scientific research. With Congress debating environmental regulations and energy policy amid tight fiscal pressures, it is critical that lawmakers have access to the best climate science to help guide policy decisions. The scientists met with legislators and their staff to discuss the importance of climate science for their districts and the nation and offered their expertise as an ongoing resource to the legislators.

  18. Paleobotanical Evidence for Near Present-Day Levels of Atmospheric CO2 During Part of the Tertiary

    NASA Astrophysics Data System (ADS)

    Royer, Dana L.; Wing, Scott L.; Beerling, David J.; Jolley, David W.; Koch, Paul L.; Hickey, Leo J.; Berner, Robert A.

    2001-06-01

    Understanding the link between the greenhouse gas carbon dioxide (CO2) and Earth's temperature underpins much of paleoclimatology and our predictions of future global warming. Here, we use the inverse relationship between leaf stomatal indices and the partial pressure of CO2 in modern Ginkgo biloba and Metasequoia glyptostroboides to develop a CO2 reconstruction based on fossil Ginkgo and Metasequoia cuticles for the middle Paleocene to early Eocene and middle Miocene. Our reconstruction indicates that CO2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the Paleocene/Eocene boundary. These results suggest that factors in addition to CO2 are required to explain these past intervals of global warmth.

  19. Molecular and isotopic composition of lipids in modern and fossil bivalve shells: Records of paleoenvironmental change?

    SciTech Connect

    CoBabe, E.A.

    1995-12-31

    Suites of lipids residing in situ in modern and fossil bivalve shells offer new possibilities for the study of paleoecology and paleoclimatology. Distributions of carbon isotopic compositions of modem shell lipids suggests that many of these compounds, including alkanes, sterols, fatty acids, ketones and phytadienes, are derived from the bivalves and not directly from the surrounding environment. The occurrence of fatty acids in modem and fossil shell material opens up the possibility that saturation levels of these compounds may be used as paleothermometers. To date, the utility of fatty acids in paleoclimate studies has been limited because of the swift breakdown of these compounds in sediment. However, initial results indicate that fatty acids in bivalve shells retain their original structure for at least several million years. Comparison of modem bivalve shell fatty acids from tropical, temperate and polar nearshore marine systems will be presented, along with analogous fossil data.

  20. Changes in the radiocarbon reservoir age in Lake Xingyun, Southwestern China during the Holocene.

    PubMed

    Zhou, Aifeng; He, Yuxin; Wu, Duo; Zhang, Xiaonan; Zhang, Can; Liu, Zhonghui; Yu, Junqing

    2015-01-01

    Chronology is a necessary component of paleoclimatology. Radiocarbon dating plays a central role in determining the ages of geological samples younger than ca. 50 ka BP. However, there are many limitations for its application, including radiocarbon reservoir effects, which may cause incorrect chronology in many lakes. Here we demonstrate temporal changes in the radiocarbon reservoir age of Lake Xingyun, Southwestern China, where radiocarbon ages based on bulk organic matter have been reported in previous studies. Our new radiocarbon ages, determined from terrestrial plant macrofossils suggest that the radiocarbon reservoir age changed from 960 to 2200 years during the last 8500 cal a BP years. These changes to the reservoir effect were associated with inputs from either pre-aged organic carbon or 14C-depleted hard water in Lake Xingyun caused by hydrological change in the lake system. The radiocarbon reservoir age may in return be a good indicator for the carbon source in lake ecosystems and depositional environment.

  1. Colombian late cretaceous tropical planktonic foraminifera: Redressing the imbalance

    SciTech Connect

    McCarthy, L.D.

    1993-02-01

    Recent work involving Late Cretaceous planktonic foraminifera has concentrated on European and other areas in the Northern Hemisphere. Many of the biostratigraphical and evolutionary models reflect this geographical restriction and ignore earlier studies from tropical areas. In 1955 Rolando Gandolfi described many new species and subspecies from Colombia and provided a different view of the evolutionary development of planktonic foraminifera. A re-examination of the Gandolfi type collection using Scanning Electron Micrography (Environmental Chamber technique) integrated with Colombian well samples from onshore Guajira area, Middle and Upper Magdalena Valley and Putumayo Basin has given a new view into the evolutionary development of Late Cretaceous planktonic foraminifera. This has enabled a modified globigerine Late Cretaceous biostratigraphy to be constructed for Colombia. This work redresses the imbalance between studies of tropical and northern high latitude Late Cretaceous planktonic foraminifera and provides an insight into the paleoenvironmental and paleoclimatological factors influencing the Colombian region at the time.

  2. Changes in the Radiocarbon Reservoir Age in Lake Xingyun, Southwestern China during the Holocene

    PubMed Central

    Zhou, Aifeng; He, Yuxin; Wu, Duo; Zhang, Xiaonan; Zhang, Can; Liu, Zhonghui; Yu, Junqing

    2015-01-01

    Chronology is a necessary component of paleoclimatology. Radiocarbon dating plays a central role in determining the ages of geological samples younger than ca. 50 ka BP. However, there are many limitations for its application, including radiocarbon reservoir effects, which may cause incorrect chronology in many lakes. Here we demonstrate temporal changes in the radiocarbon reservoir age of Lake Xingyun, Southwestern China, where radiocarbon ages based on bulk organic matter have been reported in previous studies. Our new radiocarbon ages, determined from terrestrial plant macrofossils suggest that the radiocarbon reservoir age changed from 960 to 2200 years during the last 8500 cal a BP years. These changes to the reservoir effect were associated with inputs from either pre-aged organic carbon or 14C-depleted hard water in Lake Xingyun caused by hydrological change in the lake system. The radiocarbon reservoir age may in return be a good indicator for the carbon source in lake ecosystems and depositional environment. PMID:25815508

  3. Stable hydrogen-isotope ratios in beetle chitin: preliminary European data and re-interpretation of North American data

    NASA Astrophysics Data System (ADS)

    Gröcke, Darren R.; Schimmelmann, Arndt; Elias, Scott; Miller, Randall F.

    2006-08-01

    Beetle exoskeletons contain chitin, a poly amino-sugar that is biosynthesized incorporating hydrogen isotopes from diet and water. As the stable isotope ratios D/H (or 2H/ 1H, expressed as δ D values) of precipitation and diet are jointly influenced by climate, the biochemically recorded hydrogen-isotope ratio in fossil beetle exoskeleton has the potential to be used for paleoclimatic reconstruction. New δ D data from modern beetles are presented as a preliminary database for Europe, with a re-evaluation of earlier North American data. We present correlated matrices of δ D values in modern beetle chitin and modern precipitation to demonstrate the concept. We review the pertinent literature to highlight the history, utility, and likely future research directions for the use of chitin's stable isotopes in entomological paleoclimatology.

  4. Ostracodology-Linking Bio- and Geosciences: Proceedings of the 15th International Symposium on Ostracoda, Berlin, 2005

    NASA Astrophysics Data System (ADS)

    Cronin, Thomas M.

    2008-04-01

    If you want to know about the ``paradox of sex'' or why a tiny crustacean prefers spinach over brussels sprouts, then read this book. Ostracodes are a class of small crustaceans of 33,000 known living and extinct species and many more yet to be described. They are notable for their application to paleoclimatology and paleoenvironmental reconstruction-as described by J. Holmes and A. Chivas in the 2002 AGU Geophysical Monograph Series volume 131. In addition, they can make the evolutionary claim to the oldest proven male animal, a 435-million-year-old Silurian fossil from England called Colymbosathon ecplecticos (D. J. Siveter et al., Science, 302, 1749-1751, 2003).

  5. Modeling glacial climates

    NASA Technical Reports Server (NTRS)

    North, G. R.; Crowley, T. J.

    1984-01-01

    Mathematical climate modelling has matured as a discipline to the point that it is useful in paleoclimatology. As an example a new two dimensional energy balance model is described and applied to several problems of current interest. The model includes the seasonal cycle and the detailed land-sea geographical distribution. By examining the changes in the seasonal cycle when external perturbations are forced upon the climate system it is possible to construct hypotheses about the origin of midlatitude ice sheets and polar ice caps. In particular the model predicts a rather sudden potential for glaciation over large areas when the Earth's orbital elements are only slightly altered. Similarly, the drift of continents or the change of atmospheric carbon dioxide over geological time induces radical changes in continental ice cover. With the advance of computer technology and improved understanding of the individual components of the climate system, these ideas will be tested in far more realistic models in the near future.

  6. Regional magnetic anomaly constraints on continental rifting

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Olivier, R.; Bentley, C. R.

    1985-01-01

    Radially polarized MAGSAT anomalies of North and South America, Europe, Africa, India, Australia and Antarctica demonstrate remarkably detailed correlation of regional magnetic lithospheric sources across rifted margins when plotted on a reconstruction of Pangea. These major magnetic features apparently preserve their integrity until a superimposed metamorphoric event alters the magnitude and pattern of the anomalies. The longevity of continental scale magnetic anomalies contrasts markedly with that of regional gravity anomalies which tend to reflect predominantly isostatic adjustments associated with neo-tectonism. First observed as a result of NASA's magnetic satellite programs, these anomalies provide new and fundamental constraints on the geologic evolution and dynamics of the continents and oceans. Accordingly, satellite magnetic observations provide a further tool for investigating continental drift to compliment other lines of evidence in paleoclimatology, paleontology, paleomagnetism, and studies of the radiometric ages and geometric fit of the continents.

  7. Sedimentary biomarker and isotopic indicators of the paleoclimatic history of the Walker Lake basin, western Nevada

    USGS Publications Warehouse

    Meyers, P.A.; Benson, L.V.

    1988-01-01

    Walker Lake, a terminal saline lake in western Nevada, has experienced major fluctuations in its water level due to changes in the regional climate during Quaternary times. As part of a paleo-climatological study of western Nevada, we have investigated organic matter ??13C and C/N values and lipid biomarker contents of sediments deposited at various periods over the past 150 thousand years of lake history. Surficial sediments from two cross-lake transects contain mostly lake-derived organic matter. Diagenetic losses of organic matter are evident in deeper sediments, and the proportion of aquatic and terrigenous organic materials changes in response to variations in preservational factors. Source identification of organic matter is complicated by the probability that Walker Lake has experienced desiccation at various times in its history which impacts the degree of preservation of organic substances. ?? 1988.

  8. Can Convergent Cross Mapping Untangle Idiosyncratic Speleothem Proxy Records to Reveal the Structure of Shared Climate Forcing?

    NASA Astrophysics Data System (ADS)

    Frappier, A. E.

    2015-12-01

    Rapid growth and development of speleothem paleoclimatology has generated diverse and important new terrestrial paleoenvironmental proxy records that increasingly illuminate both the enormous potential and great complexity of cave proxy systems and speleothem data. Speleothem records commonly exhibit complex covariation patterns between proxy variables (i.e. carbon and oxygen isotopes, various trace element concentrations and ratios, stratigraphic characteristics, growth rates, etc...). Such covariation patterns frequently change sign and magnitude over time, and often show periods without significant correlation that alternate with times with strongly coupled behavior. These patterns are evident when comparing records between sites and stalagmites, and even within a single stalagmite. Instability in covariation patterns and low long-term correlations both limit our confidence in applying speleothems proxy transfer functions over long time periods. Are these complex covariation patterns meaningful or merely mirages? When two speleothem records show the same result, replication is considered by the community to be evidence that both records are highly sensitive to a common climate signal and are thus reliable proxies for that climate signal. Signals derived from a single speleothem dataset could be noise, and thus of limited value until it is validated by the replication test. Are speleothems naturally idiosyncratic and noisy? Must all speleothem records be duplicated to establish reliability? I consider whether Convergent Cross Mapping (CCM) may offer a fruitful approach to these problems. CCM is a powerful statistical tool developed in George Sugihara's lab for complex dynamical systems that tests the direction of causality and strength of forcing among multiple time-series variables. I apply CCM to speleothem timeseries records to 1) reconstruct the underlying state climate variable of interest over time (in this case, precipitation), and 2) determine the

  9. SST and terrestrial n-alkanes records in sediment of the Korean Plateau, East Sea (Japan Sea) during the last 400 kyr: Paleoceanographic and paleoclimatic implications

    NASA Astrophysics Data System (ADS)

    Hyun, Sangmin; Suh, Yean Jee; Kim, Jin Kyung

    2014-05-01

    SST variation was reconstructed using alkenones and their variation was compared with terrestrial n-alkanes signature from the sediment of the Korean Plateau, East Sea (Japan Sea) during the last 400 ka. SST variation showed glacial-interglacial time scale variation with a maximum temperature of 26 oC in MIS 7, and a minimum of 12 oC at MIS 2 and 6. The distribution of terrestrial n-alkanes signatures is characterized by the occurrence of high odd number predominance in most samples, however minor dominance of a specific compound (nC27 only) was the additional characteristic.bAverage Chain Length (ACL) and Carbon Preferences Index (ICP), derived from n-alkane distributions, showed a similar shifting between glacial-interglacial time-scale. This suggests that paleovegetation communities changed in response to paleoclimatological variations, and the input of terrestrial compound is strongly linked with paleoclimatology. In the previous work, isotopic composition of δ13C and δ15N of organic matter showed extreme temporal variation since MIS 11 suggesting influx of a large amount of terrestrial organic matters from the neighboring continent during MIS 2, 8 and 10. In particular, depleted values of δ13C during MIS 2, 8 and 10 were coincident with lower nitrogen isotope values indicating local paleoceanographic effects such as paleoproductivity changes. Decoupling of δ13C and δ15N during MIS 1, 3, 5, and 7, and coupling of the two during MIS 8 and 11 is observed, which can be interpreted as local productivity changes. The alkenones SST and n-alkanes signature coincided with carbon and nitrogen isotope variation in terms of glacial-interglacial time scale suggesting that the paleoenvironments in the East Sea is sensitive to the global climate changes associated with not only orbital-scale glacial-interglacial variations but also local paleceanographic variations.

  10. Using Thecamoebians to Reconstruct 1300 Years of Limnological Change at Crystal Lake, Southern California

    NASA Astrophysics Data System (ADS)

    Silveira, E.; Palermo, J. A.; Kirby, M. E.

    2015-12-01

    Thecamoebians are microscopic unicellar organisms that live in freshwater lakes and produce tests—or shells—that are morphologically distinct to each species. The population distribution of thecamoebian species within a lake can reveal such lake dynamics as trophic status, temperature, and acidity. Crystal Lake is a small alpine lake located in the San Gabriel Mountains of the coastal southwest United States. This project's objective is to reconstruct a 1300 yr paleolimnological record for Crystal Lake using thecamoebian assemblages. The latter reconstruction will be examined in the context of paleoclimatological interpretations from the same core (Palermo et al., 2015) to determine to what extent - if any - changes in thecamoebian assemblages respond to, and record, paleoclimatological changes such as the Medieval Climate Anomaly and the Little Ice Age. Core CLPC14-1 was extracted from Crystal Lake's depocenter in May 2014. Grain size, magnetic susceptibility, and LOI 550°C and 950°C were measured at 1 cm contiguous intervals; additionally, C:N ratios and C and N isotopic analyses were measured every 2 cm (Palermo, 2015). Thecamoebian assemblages were analyzed in five modern surface samples, as well as throughout the core at 2 cm intervals (aligning with the other analyses performed). Statistical analysis was performed to determine significant patterns within the assemblages. Eleven AMS 14C dates of discrete organic matter (i.e. wood or charcoal) were used to generate an age model using Beacon v2.2; for the past 200 years, age control is based on correlation to Rothenberg et al. (2010) core ages (Palermo, 2015).

  11. Community-Supported Data Repositories in Paleobiology: A 'Middle Tail' Between the Geoscientific and Informatics Communities

    NASA Astrophysics Data System (ADS)

    Williams, J. W.; Ashworth, A. C.; Betancourt, J. L.; Bills, B.; Blois, J.; Booth, R.; Buckland, P.; Charles, D.; Curry, B. B.; Goring, S. J.; Davis, E.; Grimm, E. C.; Graham, R. W.; Smith, A. J.

    2015-12-01

    Community-supported data repositories (CSDRs) in paleoecology and paleoclimatology have a decades-long tradition and serve multiple critical scientific needs. CSDRs facilitate synthetic large-scale scientific research by providing open-access and curated data that employ community-supported metadata and data standards. CSDRs serve as a 'middle tail' or boundary organization between information scientists and the long-tail community of individual geoscientists collecting and analyzing paleoecological data. Over the past decades, a distributed network of CSDRs has emerged, each serving a particular suite of data and research communities, e.g. Neotoma Paleoecology Database, Paleobiology Database, International Tree Ring Database, NOAA NCEI for Paleoclimatology, Morphobank, iDigPaleo, and Integrated Earth Data Alliance. Recently, these groups have organized into a common Paleobiology Data Consortium dedicated to improving interoperability and sharing best practices and protocols. The Neotoma Paleoecology Database offers one example of an active and growing CSDR, designed to facilitate research into ecological and evolutionary dynamics during recent past global change. Neotoma combines a centralized database structure with distributed scientific governance via multiple virtual constituent data working groups. The Neotoma data model is flexible and can accommodate a variety of paleoecological proxies from many depositional contests. Data input into Neotoma is done by trained Data Stewards, drawn from their communities. Neotoma data can be searched, viewed, and returned to users through multiple interfaces, including the interactive Neotoma Explorer map interface, REST-ful Application Programming Interfaces (APIs), the neotoma R package, and the Tilia stratigraphic software. Neotoma is governed by geoscientists and provides community engagement through training workshops for data contributors, stewards, and users. Neotoma is engaged in the Paleobiological Data Consortium

  12. Defense of GAD during the 1950s and early 1960s

    NASA Astrophysics Data System (ADS)

    Frankel, H. R.

    2012-12-01

    Paleomagnetists favoring continental offered empirical and theoretical support for the GAD hypothesis. Initial support came from the discovery that the mean directions of rock units, regardless of polarity, laid down back through the Upper Tertiary centered on the rotational pole. Armed with Fisher's statistics, Hospers (1951, 1953) found that the mean direction of the NRM of Icelandic lava flows back through the Miocene better agreed with the GAD field than with the present field. Similarly, Campbell and Runcorn (1956), Creer (1956), and Irving and Green (1957) respectively found that the natural remanent magnetization of Late Tertiary Columbia River basalts, Quaternary basalts of Argentina, and Late Cenozoic New Volcanics of Victoria supported the hypothesis. If significant continental drift or "true" polar wander has occurred, paleomagnetic data alone cannot determine if the axial element of the GAD hypothesis holds earlier than Late Tertiary. Extending the GAD hypothesis back in time requires an approach involving a means independent of paleomagnetism for determining past latitudes. Irving was the first to realize that the paleoclimatology would work. If the GAD hypothesis holds, then paleolatitudes based on paleomagnetism and paleoclimatology should agree. Irving (1956) found that, except for the Squantum Tillite, the paleomagnetically and paleoclimatically determined paleolatitudes for Europe, North America, India, and Tasmania were in agreement. He concluded that the magnetic and rotational axes have coincided since the Paleozoic. Blackett (1961) also compared paleoclimatic and paleomagnetic data-sets. Irving and Briden (1962, 1964) further appealed to paleoclimatology to defend the hypothesis. Determining the paleolatitude spectra for several paleoclimatic indicators, they found the present latitude of fossil instances inconsistent with the latitude of modern instances while their paleomagnetically determined paleolatitudes, which assumed the GAD hypothesis

  13. Paleoproductivity vs. influx of terrestrial biomarker in sediment from the Korean Plateau, East Sea (Japan Sea) since the MIS 11

    NASA Astrophysics Data System (ADS)

    Hyun, Sangmin; Suh, Yean Jee; Ikehara, Miroru

    2015-04-01

    A piston core collected from the Korean Plateau, East Sea (Japan Sea) of Korea was conducted in terms of variations in paleoproductivity and influx of terrestrial biomarker. The distribution of terrestrial n-alkanes signatures is characterized by the occurrence of high odd number frequency with a minor contribution of specific compound (nC27 only). Average Chain Length (ACL) and Carbon Preferences Index (CPI), both of which are derived from n-alkane combination, show similar shifting between glacial and interglacial periods. Previous studies of SST variation have shown that glacial-interglacial scale changes were quite variable with the maximum range of 26oC in MIS 7, and the minimum range of 12oC during MIS 2 and 6. Therefore, paleovegetation communities had been changed in responding to paleoclimatological variations, and the input amount of terrestrial compound was strongly linked with paleoclimatologic changes. The isotopic composition of δ13C and δ15N of organic matter, which showed extreme temporal variation since MIS 11, indicates the influx of large amount of terrestrial organic matter from the neighboring terrestrial environments during MIS 2, 8 and 10. In particular, depleted values of δ13Corg during MIS 2, 8 and 10 were coincident with lower nitrogen isotope values indicating local paleoceanographic effects such as paleoproductivity changes. Decoupling between δ13Corg and δ15Norg during MIS 1, 3, 5, 7 and coupling of the two during MIS 8 and 11 can be observed, which appear to be interpreted as local productivity changes. In particular, high abundance of cholesterol and C21 n-alkanes, which were derived from diatom, increased during interglacial periods. Therefore, alkenones, SST and n-alkanes signatures coincide with δ13Corg and δ15Norg variations during glacial-interglacial cycles and further strongly associated with cholesterol abundance suggesting that the paleoenvironmental conditions in East Sea during glacial-interglacial periods were

  14. Glaciochemical investigations on the subterranean ice deposit of Vukušić Ice Cave, Velebit Mountain, Croatia

    NASA Astrophysics Data System (ADS)

    Kern, Z.; Fórizs, I.; Horvatinčić, N.; Széles, É.; Bočić, N.; Nagy, B.

    2010-09-01

    The 3H activity, 18O/16O and 2H/1H ratio and concentration of 33 metals and metalloids have been analysed on ice core samples from the perennial subterranean cave ice deposit of Vukušić Ice Cave, Velebit Mt. The tritium data suggested that the ice deposition at 2-2.4 m depth is build from precipitation fallen ~45 years before sampling and the uppermost ice layer could be estimated between early 1970s and early 1980s or between ~1954 and 1960. Both the fluctuation range of stable water isotopes and the derived isotopic waterline of the ice agree reasonably well with the corresponding data of the local precipitation. This fact predicts that the potential of Vukušić Ice Cave's ice deposit is superior for paleoclimatological studies to the nearby Ledena Pit. Principal component analysis helped to select three groups of elements. The Ca-Mg governed group (PC1) encompasses the bedrock related components; hence the fluctuation of these elements might reflect the past intensities of the dissolution process of the adjacent epikarst. The Zn governed group (PC2) preserves probably an atmospheric deposition signal and related to the emission of regional non-ferrous metallurgy. PC3 is governed by Al and Fe. This probably carries the distal, non-karstic crustal signal hence might be related to the past atmospheric circulation (i.e. wind direction and speed).

  15. Regional Scale High Resolution δ18O Prediction in Precipitation Using MODIS EVI

    PubMed Central

    Huang, Cho-Ying; Wang, Chung-Ho; Lin, Shou-De; Lo, Yi-Chen; Huang, Bo-Wen; Hatch, Kent A.; Shiu, Hau-Jie; You, Cheng-Feng; Chang, Yuan-Mou; Shen, Sheng-Feng

    2012-01-01

    The natural variation in stable water isotope ratio data, also known as water isoscape, is a spatiotemporal fingerprint and a powerful natural tracer that has been widely applied in disciplines as diverse as hydrology, paleoclimatology, ecology and forensic investigation. Although much effort has been devoted to developing a predictive water isoscape model, it remains a central challenge for scientists to generate high accuracy, fine scale spatiotemporal water isoscape prediction. Here we develop a novel approach of using the MODIS-EVI (the Moderate Resolution Imagining Spectroradiometer-Enhanced Vegetation Index), to predict δ18O in precipitation at the regional scale. Using a structural equation model, we show that the EVI and precipitated δ18O are highly correlated and thus the EVI is a good predictor of precipitated δ18O. We then test the predictability of our EVI-δ18O model and demonstrate that our approach can provide high accuracy with fine spatial (250×250 m) and temporal (16 days) scale δ18O predictions (annual and monthly predictabilities [r] are 0.96 and 0.80, respectively). We conclude the merging of the EVI and δ18O in precipitation can greatly extend the spatial and temporal data availability and thus enhance the applicability for both the EVI and water isoscape. PMID:23029053

  16. Ted Irving's early contributions to paleomagnetism

    NASA Astrophysics Data System (ADS)

    Frankel, H. R.

    2014-12-01

    Edward (Ted) Irving (1927 - 2014) was one of the most deeply and widely respected paleomagnetists, making significant contributions to the field throughout his career which spanned six decades. Restricting attention to the first decade of his career, the 1950s, he discovered from work on the Torridonian (1951-1953) that fine-grained red sandstones were generally suitable for paleomagnetic work (1951-1952). He rediscovered (1951) that paleomagnetism could be used to test continental drift, and initiated (1951) the first paleomagnetic test of whether India had drifted northward relative to Asia and argued (1954) that it had. He also made significant contributions to the first APW path for Great Britain (Creer, Irving, and Runcorn, 1954). He was the first to draw two APW paths to explain results from Great Britain and North America (1956) and to use paleomagnetism and paleoclimatology together to argue for continental drift (1954, 1956). With Ron Green, his first student, he first APW path for Australia (1958). He was the first to invoke axial rotations to explain away an apparent anomaly with an APW path (1959). His work on the Torridonian led to the first description of stratigraphically sequential reversals in sedimentary rocks. Moreover, his 1959 superb review of the paleomagnetic support for continental drift was instrumental in Hess's becoming a continental drifter before he came up with the idea of seafloor spreading.

  17. Paleoecological potential of mid-altitude peat deposits in the Tropical Andes: evidence from subfossil wood and palynology

    NASA Astrophysics Data System (ADS)

    Gonzalez Arango, Catalina; Andres Ayala Usma, David; Boom, Arnoud; Archila, Sonia; Montes, Camilo

    2016-04-01

    The understanding of past climatic and ecological phenomena at mid-altitudes in the tropical Andes is limited by the lack of ancient lakes and other well preserved paleoclimatological archives. During the opening of a main road a decade ago in the Central Cordillera of Colombia, some buried peat deposits became exposed within the Pereira Volcanodetritic Fan (~2000 m.a.s.l), revealing a rich resource of organic remains, including big fragments of subfossil trees and micro and macro plant remains ideal for multiproxy analysis. Radiocarbon dating and palynological analysis suggest that the deposit dates back to the last glacial period. We present the first δ13C results of a subfossil wood sample with visible tree rings, that was identified as a member of the genus Chrysochlamys (Clusiaceae) and that revealed a periodic signal that might be attributed to climatic variability. A clear seasonal pattern arises suggesting a different climatic configuration, most likely related to a broader migrational range of the ITCZ related to higher eccentricity. Pollen analysis reveals the prevalence of montane Andean forests and Paramo elements (today ca. 1200 meters higher) indicating much colder climates than today. These first findings indicate that mid-altitude Andean peats are highly sensitive to climatic variability and provide an excellent opportunity to study ancient environmental phenomena at extremely high resolution.

  18. Carboniferous coal swamp vegetation

    SciTech Connect

    Phillips, T.L.; Peppers, R.A.; DiMichele, W.A.

    1984-01-01

    The Carboniferous Period was one of considerable change on the Earth. The volume explores these changes by using plant morphology and paleoecology to develop the relationship between plant evolution and the derived coal sources. Both are interrelated by the regional and stratigraphic trends in paleoecology and paleoclimatology. The book is divided into three sections dealing with geology, plant morphology including palynology, and paleoecology. In Section I, the paleogeography, geologic settings of major coal basins, coal resources, coal-ball origins and occurrences, and the sources of paleobotanical information are presented with biostratigraphic correlations of Europe and the United States. Section II emphasizes plant morphology as form and structure provide the means of identifying plants and, in turn, establishing development, size, habit, reproductive biology, environmental parameters, and evolutionary change. Quantitative abundances and stratigraphic ranges of plants and spores are compared and summarized. Lastly, Section III integrates coal-ball peats and coal-spore floras as complementary sources for the quantitative analyses of coal-swamp vegetation in relation to climate and coal. The local and regional swamp studies are interfaced and basinal geology and depositional interpretations in a stratigraphic succession.

  19. Northwest Pacific typhoons documented by the Philippine Jesuits, 1566-1900

    NASA Astrophysics Data System (ADS)

    GarcíA-Herrera, Ricardo; Ribera, Pedro; HernáNdez, Emiliano; Gimeno, Luis

    2007-03-01

    In recent years, the population and the value of properties in areas prone to tropical cyclone (TC) have increased dramatically. This has caused more attention to be placed on the characterization of TC climatologies and the identification of the role that factors such as the main teleconnection patterns may play in TC variability. Due to the timescales involved, the instrumental records have proven too short to provide a complete picture. Thus, documentary and other paleoclimatological techniques have been used to reconstruct TC occurrence. This has been done mostly for the Atlantic basin, whereas in the Pacific basin, fewer attempts have been made. The aim of this paper is to provide a high-resolution chronology of typhoons and intense storms occurring in the Philippine Islands and their vicinity for the period 1566-1900. The chronology is based upon the writings of the Spanish Jesuit Miguel Selga, who produced the original work at the beginning of the 20th century. The sources, reliability, and completeness of the chronology are examined critically. A total of 652 events are included, 524 of which are reported as typhoons, the rest being considered as tropical storms. For each of these classes, the landfall location and the track (when sufficient information is available) have been drawn. This chronology is an indispensable step toward a final and complete typhoon record in the western Pacific basin.

  20. Recovering Paleo-Records from Antarctic Ice-Cores by Coupling a Continuous Melting Device and Fast Ion Chromatography.

    PubMed

    Severi, Mirko; Becagli, Silvia; Traversi, Rita; Udisti, Roberto

    2015-11-17

    Recently, the increasing interest in the understanding of global climatic changes and on natural processes related to climate yielded the development and improvement of new analytical methods for the analysis of environmental samples. The determination of trace chemical species is a useful tool in paleoclimatology, and the techniques for the analysis of ice cores have evolved during the past few years from laborious measurements on discrete samples to continuous techniques allowing higher temporal resolution, higher sensitivity and, above all, higher throughput. Two fast ion chromatographic (FIC) methods are presented. The first method was able to measure Cl(-), NO3(-) and SO4(2-) in a melter-based continuous flow system separating the three analytes in just 1 min. The second method (called Ultra-FIC) was able to perform a single chromatographic analysis in just 30 s and the resulting sampling resolution was 1.0 cm with a typical melting rate of 4.0 cm min(-1). Both methods combine the accuracy, precision, and low detection limits of ion chromatography with the enhanced speed and high depth resolution of continuous melting systems. Both methods have been tested and validated with the analysis of several hundred meters of different ice cores. In particular, the Ultra-FIC method was used to reconstruct the high-resolution SO4(2-) profile of the last 10,000 years for the EDML ice core, allowing the counting of the annual layers, which represents a key point in dating these kind of natural archives.

  1. Comparison and Significance of Two Different Organic Paleotemperature Reconstructions

    NASA Astrophysics Data System (ADS)

    Ma, X.; Zhang, H.; He, J.; Ruan, Y.; Dong, L.; Wang, H.; Li, L.

    2015-12-01

    Temperature is a basic parameter in the study of paleoclimatology and paleoceanography. In the present study, two organic geochemical proxies, UK'37 and TEX86 were used for the sea surface temperature reconstruction in the site MD123434 (18°49.84'N,116°18.89'E, water depth 2995m) in northern South China Sea. On the whole, the two reconstructed temperature correlated well with each other, reflecting low temperature in the last glacial and high in the Holocene. Nevertheless, detailed comparison illustrated relatively higher reconstructed temperature by the UK'37 method than that in TEX86 proxy, with a range of 23.0℃ to 27.8℃ and 18.9℃to 29.5℃ for UK'37 and TEX86 proxy respectively. The average temperature discrepancy (ΔT) between the two temperature proxies is ~3℃ during the last glacial and ~0℃ during the Holocene, which cannot be fully attributed to calculation errors. The offset between these two proxies may be caused by the different living water depths of the source organisms: haptophyte and Thaumarchaeota for the UK'37 and TEX86 respectively. The terrestrial GDGTs input and the different calibration equations on the TEX86 may possibly also contribute to the discrepancy. Meanwhile, growth seasonalities between the two source organisms cannot be ignored either.

  2. Last Glacial mammals in South America: a new scenario from the Tarija Basin (Bolivia).

    PubMed

    Coltorti, M; Abbazzi, L; Ferretti, M P; Iacumin, P; Rios, F Paredes; Pellegrini, M; Pieruccini, P; Rustioni, M; Tito, G; Rook, L

    2007-04-01

    The chronology, sedimentary history, and paleoecology of the Tarija Basin (Bolivia), one of the richest Pleistocene mammalian sites in South America, are revised here based on a multidisciplinary study, including stratigraphy, sedimentology, geomorphology, paleontology, isotope geochemistry, and (14)C geochronology. Previous studies have indicated a Middle Pleistocene age for this classic locality. We have been able to obtain a series of (14)C dates encompassing all the fossil-bearing sequences previously studied in the Tarija Basin. The dated layers range in age from about 44,000 to 21,000 radiocarbon years before present (BP), indicating that the Tarija fauna is much younger than previously thought. Glacial advances correlated to marine isotopic stages (MIS) 4 and 2 (ca. 62 and 20 ka BP, respectively) are also documented at the base and at the very top of the Tarija-Padcaya succession, respectively, indicating that the Bolivian Altiplano was not dry but sustained an ice cap during the Last Glacial Maximum. The results of this multidisciplinary study enable us to redefine the chronological limits of the Tarija sequence and of its faunal assemblage and to shift this paleontological, paleoclimatological, and paleoecological framework to the time interval from MIS 4 to MIS 2. PMID:17180614

  3. Testing coral-based tropical cyclone reconstructions: An example from Puerto Rico

    USGS Publications Warehouse

    Kilbourne, K. Halimeda; Moyer, Ryan P.; Quinn, Terrence M.; Grottoli, Andrea G.

    2011-01-01

    Complimenting modern records of tropical cyclone activity with longer historical and paleoclimatological records would increase our understanding of natural tropical cyclone variability on decadal to centennial time scales. Tropical cyclones produce large amounts of precipitation with significantly lower δ18O values than normal precipitation, and hence may be geochemically identifiable as negative δ18O anomalies in marine carbonate δ18O records. This study investigates the usefulness of coral skeletal δ18O as a means of reconstructing past tropical cyclone events. Isotopic modeling of rainfall mixing with seawater shows that detecting an isotopic signal from a tropical cyclone in a coral requires a salinity of ~ 33 psu at the time of coral growth, but this threshold is dependent on the isotopic composition of both fresh and saline end-members. A comparison between coral δ18O and historical records of tropical cyclone activity, river discharge, and precipitation from multiple sites in Puerto Rico shows that tropical cyclones are not distinguishable in the coral record from normal rainfall using this approach at these sites.

  4. STEPPE: Supporting collaborative research and education on Earth's deep-time sedimentary crust.

    NASA Astrophysics Data System (ADS)

    Smith, D. M.

    2014-12-01

    STEPPE—Sedimentary geology, Time, Environment, Paleontology, Paleoclimate, and Energy—is a National Science Foundation supported consortium whose mission is to promote multidisciplinary research and education on Earth's deep-time sedimentary crust. Deep-time sedimentary crust research includes many specialty areas—biology, geography, ecology, paleontology, sedimentary geology, stratigraphy, geochronology, paleoclimatology, sedimentary geochemistry, and more. In fact, the diversity of disciplines and size of the community (roughly one-third of Earth-science faculty in US universities) itself has been a barrier to the formation of collaborative, multidisciplinary teams in the past. STEPPE has been working to support new research synergies and the development of infrastructure that will encourage the community to think about the big problems that need to be solved and facilitate the formation of collaborative research teams to tackle these problems. Toward this end, STEPPE is providing opportunities for workshops, working groups and professional development training sessions, web-hosting and database services and an online collaboration platform that facilitates interaction among participants, the sharing of documentation and workflows and an ability to push news and reports to group participants and beyond using social media tools. As such, STEPPE is working to provide an interactive space that will serve as both a gathering place and clearinghouse for information, allowing for broader integration of research and education across all STEPPE-related sub disciplines.

  5. Multi-elemental mapping of a speleothem using laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Ma, Q. L.; Motto-Ros, V.; Lei, W. Q.; Boueri, M.; Zheng, L. J.; Zeng, H. P.; Bar-Matthews, M.; Ayalon, A.; Panczer, G.; Yu, J.

    2010-08-01

    Speleothems represent an important record of the paleoclimate, and more generally past environmental changes thanks to their laminar structure which is related to variations in rainfall and vegetation throughout the seasons and to their elemental as well as structural compositions which are sensitive to climatic and environmental conditions during their growth. Studies of their composition, especially those with spatial resolution, reveal rich information for paleoclimatology. In this paper, we demonstrate that laser-induced breakdown spectroscopy (LIBS) provides a suitable tool for elemental analysis and especially for 2-dimensional elemental mapping of speleothems. Main, minor, as well as trace elements can be analyzed with this technique. The temporal evolution of the induced plasma is first studied in order to determine a suitable detection window for emission spectrum recording following the impact of the laser pulse on the sample. The matrix effect is then evaluated with a scan on the sample surface by measuring the electron density and the temperature of the plasmas at different positions of the analyzed surface. Concentration mapping is performed for minor and trace elements such as Na, Mg, Al, Si, K, Fe and Sr, by measuring relative variations of line emission intensities from these elements. Finally, correlations in concentration among detected elements are determined. Groups of correlated elements can be attributed to different mineralogical phases.

  6. Lake sediment records of late Holocene monsoon variability in western Nepal (preliminary results)

    NASA Astrophysics Data System (ADS)

    Ghazoui, Zakaria; Bertrand, Sebastien; Sachse, Dirk; Nomade, Jerome; Prasad Gajurel, Ananta; van der Beek, Peter

    2015-04-01

    In Nepal, high altitude paleoclimatological and limnological studies face many logistical challenges due to remoteness, accessibility, and altitude of potential lake sampling sites. Therefore, paleolimnological investigations in the Nepalese Himalaya remain scarce, and most of our understanding of past Indian Summer Monsoon (ISM) variability relies on a low-density network of speleothems and ice cores. Here we report preliminary new data from three high-altitude lakes in the Nepal Himalaya. In order to improve our understanding of climate variability in western Nepal during the late Holocene three lakes were investigated and sampled in autumn 2014: Rara Lake, Mugu District; Phoksundo Lake, Dolpa District; Dhumba Lake, Mustang District. The sediment cores are being studied using a multi-proxy approach combining radiocarbon, 210Pb and 137Cs chronologies, physical properties (Geotek multi-sensor core logger), grain size (Malvern Mastersizer 3000) inorganic geochemistry (major and selected trace elements by ICP-AES and ITRAX XRF core scanning), bulk organic geochemistry (C, N concentrations and stable isotopes) and hydrogen isotopic composition of leaf wax long-chain n-alkanes (δDwax). These sediment records will provide important new insights into the late-Holocene variability of the Indian Summer Monsoon in Nepal, including the recent latitudinal shift of the rainbelt due to climate change in the 20th and 21st centuries.

  7. Normalizing paleoclimate variables in support of data-intensive science

    NASA Astrophysics Data System (ADS)

    Thrasher, B. L.; Wahl, E. R.; Morrill, C.

    2015-12-01

    Paleoclimate data are extremely heterogeneous - hundreds of different types of measurements and reconstructions are routinely made by scientists on an even larger number of kinds of physical samples. This heterogeneity is one of the biggest barriers to the development of accumulated data products and access capabilities, and to the use of paleo data beyond the community of paleoclimate specialists. We describe a new effort underway at the World Data Service for Paleoclimatology to create a set of standards for documenting variables (i.e., exactly what was measured or reconstructed). The nine-part variable description the WDS-Paleo uses currently is the starting point for this project, which will result in vocabularies that are complete, precise, standard, and extensible. This framework was designed to be general enough for use with all of the eighteen different proxy and reconstruction data types archived by the WDS-Paleo, thus allowing more uniformity to be applied to its holdings and allowing metadata to be stored and searched across proxy types in a single database structure. Ongoing work will extend this generalized variable framework, under the guidance of advisory panels consisting of subject matter experts, to generate proxy-specific and cross-proxy controlled vocabularies. This work will enable re-use of studies in larger compilations to enable scientific discovery that would not be possible from any one study alone, and will facilitate new, interdisciplinary uses for datasets.

  8. Replicated evolution of trophic specializations in an endemic cichlid fish lineage from Lake Tanganyika

    PubMed Central

    Rüber, Lukas; Verheyen, Erik; Meyer, Axel

    1999-01-01

    The current phylogenetic hypothesis for the endemic Lake Tanganyika cichlid fishes of the tribe Eretmodini is based solely on morphology and suggests that more complex trophic morphologies derived only once from a less specialized ancestral condition. A molecular phylogeny of eretmodine cichlids based on partial mitochondrial DNA cytochrome b and control-region sequences was used to reconstruct the evolutionary sequence of trophic adaptations and to test alternative models of morphological divergence. The six mitochondrial lineages found disagree with the current taxonomy and the morphology-based phylogeny. Mitochondrial lineages with similar trophic morphologies are not grouped monophyletically but are typically more closely related to lineages with different trophic phenotypes currently assigned to other genera. Our results indicate multiple independent origins of similar trophic specializations in these cichlids. A pattern of repeated divergent morphological evolution becomes apparent when the phylogeography of the mitochondrial haplotypes is analyzed in the context of the geological and paleoclimatological history of Lake Tanganyika. In more than one instance within Lake Tanganyika, similar morphological divergence of dentitional traits occurred in sympatric species pairs. Possibly, resource-based divergent selective regimes led to resource partitioning and brought about similar trophic morphologies independently and repeatedly. PMID:10468591

  9. Deep water provenance and dynamics of the (de)glacial Atlantic meridional overturning circulation

    NASA Astrophysics Data System (ADS)

    Lippold, Jörg; Gutjahr, Marcus; Blaser, Patrick; Christner, Emanuel; de Carvalho Ferreira, Maria Luiza; Mulitza, Stefan; Christl, Marcus; Wombacher, Frank; Böhm, Evelyn; Antz, Benny; Cartapanis, Olivier; Vogel, Hendrik; Jaccard, Samuel L.

    2016-07-01

    Reconstructing past modes of ocean circulation is an essential task in paleoclimatology and paleoceanography. To this end, we combine two sedimentary proxies, Nd isotopes (εNd) and the 231Pa/230Th ratio, both of which are not directly involved in the global carbon cycle, but allow the reconstruction of water mass provenance and provide information about the past strength of overturning circulation, respectively. In this study, combined 231Pa/230Th and εNd down-core profiles from six Atlantic Ocean sediment cores are presented. The data set is complemented by the two available combined data sets from the literature. From this we derive a comprehensive picture of spatial and temporal patterns and the dynamic changes of the Atlantic Meridional Overturning Circulation over the past ∼25 ka. Our results provide evidence for a consistent pattern of glacial/stadial advances of Southern Sourced Water along with a northward circulation mode for all cores in the deeper (>3000 m) Atlantic. Results from shallower core sites support an active overturning cell of shoaled Northern Sourced Water during the LGM and the subsequent deglaciation. Furthermore, we report evidence for a short-lived period of intensified AMOC in the early Holocene.

  10. The Development and Evaluation of the Climate Time Line Information Tool

    NASA Astrophysics Data System (ADS)

    McCaffrey, M. S.; Kowal, D.; Eakin, C. M.

    2002-12-01

    The Climate Time Line Information Tool or CTL (http://www.ngdc.noaa.gov/paleo/ctl) has been prototyped as a digital educational tool for conveying fundamental climatic processes and their human dimension for diverse audiences. Using a powers of ten approach to temporal scaling, the CTL website was developed through a CIRES Innovative Research Grant by Mark McCaffrey at the National Climatic Data Center's Paleoclimatology Program and Dan Kowal at the National Geophysical Data Center. CTL was specifcally designed as an interdisciplinary tool for conveying information about weather and climatic processes, such as the diurnal, annual and orbital cycles and ENSO. Moreover, the web site explores potential connections between climatic variability and human development over the past 100,000 years. Evaluation of the prototype examined issues of usability and navigation of the site as well as how its content and framework served the needs of undergraduate, middle and high school students, geoscience educators, and climate experts. The development and evaluation of the Climate Time Line provide a case study for other geoscience researchers and educators on: i) how objectives were set by developers; ii) how evaluators were involved in assessing the prototype; iii) the variety of evaluative methods available to test the viability of the product; and iv) how results from the evaluation can be used to finalize the prototype.

  11. Porosity and hydric behavior of typical calcite microfabrics in stalagmites

    NASA Astrophysics Data System (ADS)

    Muñoz-García, M. B.; López-Arce, P.; Fernández-Valle, M. E.; Martín-Chivelet, J.; Fort, R.

    2012-07-01

    Petrophysical techniques commonly used for material characterization are applied for the first time to speleothem samples to investigate the porosity and hydric behavior of calcite stalagmites used in paleoclimatology. These techniques allow the determination of the stalagmites' potential to undergo diagenetic transformations when substantial changes in drip waters occur in the cave environment. The petrophysical techniques include water absorption under vacuum and by capillarity, nuclear magnetic resonance, environmental scanning electron microscopy, and mercury intrusion porosimetry. The studied samples comprise five common calcite microfabrics, which have markedly different porosities and hydric behaviors and, as a consequence, different sensibilities to diagenetic processes related to the influx of water. The experiments show that stalagmites can behave as complex, small-scale hydrological systems and that the circulation of water through them by complex nets of interconnected pores might be common. As the circulation of water favors diagenetic transformations that involve geochemical and isotopic changes, the characterization of flow patterns is key for outlining areas that are susceptible to such modifications, which is critical to paleoclimatic studies that are based on speleothems because geochemical and stable isotopic data are used as paleoenvironmental proxies and absolute ages are obtained by using radioactive isotope ratios. These potential modifications also have obvious implications for studies based on fluid inclusions in speleothems. The integrated methodology, which uses primarily non-destructive techniques, shows a high potential for characterization of any type of speleothem and other continental carbonates such as tufas or sinters.

  12. A TEX86 surface sediment database and extended Bayesian calibration

    PubMed Central

    Tierney, Jessica E; Tingley, Martin P

    2015-01-01

    Quantitative estimates of past temperature changes are a cornerstone of paleoclimatology. For a number of marine sediment-based proxies, the accuracy and precision of past temperature reconstructions depends on a spatial calibration of modern surface sediment measurements to overlying water temperatures. Here, we present a database of 1095 surface sediment measurements of TEX86, a temperature proxy based on the relative cyclization of marine archaeal glycerol dialkyl glycerol tetraether (GDGT) lipids. The dataset is archived in a machine-readable format with geospatial information, fractional abundances of lipids (if available), and metadata. We use this new database to update surface and subsurface temperature calibration models for TEX86 and demonstrate the applicability of the TEX86 proxy to past temperature prediction. The TEX86 database confirms that surface sediment GDGT distribution has a strong relationship to temperature, which accounts for over 70% of the variance in the data. Future efforts, made possible by the data presented here, will seek to identify variables with secondary relationships to GDGT distributions, such as archaeal community composition. PMID:26110065

  13. Whither Dendroclimatology?

    NASA Astrophysics Data System (ADS)

    Bunn, A. G.; Lloyd, A. H.

    2007-12-01

    As in other fields of paleoclimatology, uniformitarianism is the key principle in dendroclimatology. The assumption that the processes that form tree rings now are the same as those in the past is what allows climate to be reconstructed from tree rings. Recent years have seen declining ring widths in the northern high latitudes coincident with increasing temperatures despite being an ostensibly temperature limited environment. There are several factors that could play into this phenomenon. It could be that that more nuanced statistical or process models are needed to fully understand the climate | growth relationship. Or, there could be exogenous forcings (e.g., global dimming) that contribute to the shift in the climate | growth relationship, and that understanding the nature of those forcings is needed. What can this "divergence problem" tell us about tree growth and climate and does the apparent loss of sensitivity indicate a violation of the uniformity principle? We will present an analysis of simulated and real tree-ring data that attempts to answer these questions and show that while there are basic gaps in our understanding, the careful modeling of climate | growth relations and the proper attribution of error are keys to the making progress on the "divergence opportunity."

  14. The role of fieldwork in rock decay research: Case studies from the fringe

    NASA Astrophysics Data System (ADS)

    Dorn, Ronald I.; Gordon, Steven J.; Allen, Casey D.; Cerveny, Niccole; Dixon, John C.; Groom, Kaelin M.; Hall, Kevin; Harrison, Emma; Mol, Lisa; Paradise, Thomas R.; Sumner, Paul; Thompson, Tyler; Turkington, Alice V.

    2013-10-01

    Researchers exploring rock decay hail from chemistry, engineering, geography, geology, paleoclimatology, soil science, and other disciplines and use laboratory, microscopic, theoretical, and field-based strategies. We illustrate here how the tradition of fieldwork forms the core knowledge of rock decay and continues to build on the classic research of Blackwelder, Bryan, Gilbert, Jutson, King, Linton, Twidale, and von Humboldt. While development of nonfield-based investigation has contributed substantially to our understanding of processes, the wide range of environments, stone types, and climatic variability encountered raises issues of temporal and spatial scales too complex to fit into attempts at universal modeling. Although nonfield methods are immensely useful for understanding overarching processes, they can miss subtle differences in factors that ultimately shape rock surfaces. We, therefore, illustrate here how the tradition of fieldwork continues today alongside laboratory and computer-based investigations and contributes to our understanding of rock decay processes. This includes the contribution of fieldwork to the learning process of undergraduates, the calculation of activation energies of plagioclase and olivine dissolution, the high Arctic, the discovery of a new global carbon sink, the influence of plant roots, an analysis of the need for protocols, tafoni development, stone monuments, and rock coatings. These compiled vignettes argue that, despite revolutionary advances in instrumentation, rock decay research must remain firmly footed in the field.

  15. Bibliography of the paleontology and paleoecology of the Devonian-Mississippian black-shale sequence in North America

    SciTech Connect

    Barron, L.S.; Ettensohn, F.R.

    1980-06-01

    The Devonian-Mississippian black-shale sequence is one of the most prominent and well-known stratigraphic horizons in the Paleozoic of the United States, yet the paleontology and its paleoecologic and paleoenvironmental implications are poorly known. This is in larger part related to the scarcity of fossils preserved in the shale - in terms of both diversity and abundance. Nonetheless, that biota which is preserved is well-known and much described, but there is little synthesis of this data. The first step in such a synthesis is the compilation of an inclusive bibliography such as this one. This bibliography contains 1193 entries covering all the major works dealing with Devonian-Mississippian black-shale paleontology and paleoecology in North America. Articles dealing with areas of peripheral interest, such as paleogeography, paleoclimatology, ocean circulation and chemistry, and modern analogues, are also cited. In the index, the various genera, taxonomic groups, and other general topics are cross-referenced to the cited articles. It is hoped that this compilation will aid in the synthesis of paleontologic and paleoecologic data toward a better understanding of these unique rocks and their role as a source of energy.

  16. Principles of demineralization: modern strategies for the isolation of organic frameworks. Part I. Common definitions and history.

    PubMed

    Ehrlich, Hermann; Koutsoukos, Petros G; Demadis, Konstantinos D; Pokrovsky, Oleg S

    2008-12-01

    In contrast to biomineralization phenomena, that are among the most widely studied topics in modern material and earth science and biomedicine, much less is systematized on modern view of demineralization. Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Demineralization is the process of removing the inorganic part, or the biominerals, that takes place in nature via either physiological or pathological pathways in organisms. In vitro demineralization processes, used to obtain mechanistic information, consist in the isolation of the mineral phase of the composite biomaterials from the organic matrix. Physiological and pathological demineralization include, for example, bone resorption mediated by osteoclasts. Bioerosion, a more general term for the process of deterioration of the composite biomaterials represents chemical deterioration of the organic and mineral phase followed by biological attack of the composite by microorganisms and enzymes. Bioerosional organisms are represented by endolithic cyanobacteria, fungi, algae, plants, sponges, phoronids and polychaetes, mollusks, fish and echinoids. In the history of demineralization studies, the driving force was based on problems of human health, mostly dental caries. In this paper we summarize and integrate a number of events, discoveries, milestone papers and books on different aspect of demineralization during the last 400 years. Overall, demineralization is a rapidly growing and challenging aspect of various scientific disciplines such as astrobiology, paleoclimatology, geomedicine, archaeology, geobiology, dentistry, histology, biotechnology, and others to mention just a few. PMID:18403210

  17. Growth of the European abalone ( Haliotis tuberculata L.) in situ: Seasonality and ageing using stable oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Roussel, Sabine; Huchette, Sylvain; Clavier, Jacques; Chauvaud, Laurent

    2011-02-01

    The ormer, Haliotis tuberculata is the only European abalone species commercially exploited. The determination of growth and age in the wild is an important tool for fisheries and aquaculture management. However, the ageing technique used in the past in the field is unreliable. The stable oxygen isotope composition ( 18O/ 16O) of the shell depends on the temperature and oxygen isotope composition of the ambient sea water. The stable oxygen isotope technique, developed to study paleoclimatological changes in shellfish, was applied to three H. tuberculata specimens collected in north-west Brittany. For the specimens collected, the oxygen isotope ratios of the shell reflected the seasonal cycle in the temperature. From winter-to-winter cycles, estimates of the age and the annual growth increment, ranging from 13 to 55 mm per year were obtained. This study shows that stable oxygen isotopes can be a reliable tool for ageing and growth studies of this abalone species in the wild, and for validating other estimates.

  18. Impacts of Population, Climate Variability and Change on the Management of the Colorado River

    NASA Astrophysics Data System (ADS)

    Udall, B. H.; Pulwarty, R.; Kenney, D.

    2005-12-01

    The Colorado River has been called the lifeline of the West. Draining portions of seven states and nearly 250,000 square miles, this river serves the needs of over 25 million people including all of the Southwest's major cities and several million acres of some of the most productive irrigated agriculture in the United States. Since a 1922 interstate compact first allocated the river, there have been numerous federal laws, Supreme Court decrees, and administrative decisions relating to the use of the system. The result is the most complex legal environment pertaining to water in the world. In addition, billions of dollars have been spent constructing huge reservoirs including Lake Mead and Lake Powell which in total store over four years of supply. Despite the enormous system capacity, new demands resulting from long-term population growth and from the completion of new water delivery projects, and an unprecedented five-year drought from 2000 to 2004 severely stressed both the water supply and the legal framework in the basin. The CU-NOAA Western Water Assessment, one of eight NOAA- OGP funded Regional Integrated Sciences and Assessments, conducts research, and provides decision support resources to water managers in the basin. Specifically, we provide paleoclimatology research and products, legal analysis, seasonal and sub-seasonal forecasting, climate change assessments, and system yield modeling. This presentation will feature a case study of the Western Water Assessment's activities in the basin including our involvement with several key stakeholders.

  19. The Tyrolean Iceman and excavated human remains as sources of information about the past, the present, and the future.

    PubMed

    Sjøvold, T

    1998-01-01

    The 5,200-year-old mummy of the so-called "Iceman" found in the Tyrolean Alps in September 1991 has not only provided unique information about the European Stone Age, but has also supported disciplines of glaciology and paleoclimatology, contributed to medical history, age-at-death determination, and plastic surgery. The Iceman is the oldest known case of medical tattooing. Since the body is unique, new noninvasive methods had to be developed to investigate it. Stereolithographic skull models were produced to study the skull. Age determination was partly based on computer tomography. These methods may even be used for present or future medical or forensic practice. Furthermore, a collection of identified skulls from a charnel house in Austria, dating from about 1780 AD to 1990 AD, has been used for testing and developing osteological methods, though the inclusion of the skulls in the charnel house is formally classified a second burial. These skulls have been studied by permission from the local Catholic church. Careful respect for the ancestors is crucial in both these and other cases. In return, access to the remains of ancestors provides information which may shed light upon the past, the present, and even help survival in the future.

  20. How does ice sheet loading affect ocean flow around Antarctica?

    NASA Astrophysics Data System (ADS)

    Dijkstra, H. A.; Rugenstein, M. A.; Stocchi, P.; von der Heydt, A. S.

    2012-12-01

    Interactions and dynamical feedbacks between ocean circulation, heat and atmospheric moisture transport, ice sheet evolution, and Glacial Isostatic Adjustment (GIA) are overlooked issues in paleoclimatology. Here we will present first results on how ocean flows were possibly affected by the glaciation of Antarctica across the Eocene-Oligocene Transition (~ 34 Ma) through GIA and bathymetry variations. GIA-induced gravitationally self-consistent bathymetry variations are determined by solving the Sea Level Equation (SLE), which describes the time dependent shape of (i) the solid Earth and (ii) the equipotential surface of gravity. Since the ocean circulation equations are defined relative to the equipotential surface of gravity, only bathymetry variations can influence ocean flows, although the sea surface slope will also change through time due to gravitational attraction. We use the Hallberg Isopycnal Model under late Eocene conditions to calculate equilibrium ocean flows in a domain in which the bathymetry evolves under ice loading according to the SLE. The bathymetric effects of the glaciation of Antarctica lead to substantial spatial changes in ocean flows, and close to the coast, the flow even reverses direction. Volume transports through the Drake Passage and Tasman Seaway adjust to the new bathymetry. The results indicate that GIA-induced ocean flow variations alone may have had an impact on sedimentation and erosion patterns, the repositioning of fronts, ocean heat transport and grounding line and ice sheet stability.

  1. A subdued topography among the high relief, tectonic-active island ---registered middle to late Pleistocene climatic changes in Taiwan

    NASA Astrophysics Data System (ADS)

    Liew, P.; Chen, B.

    2003-12-01

    The island of Taiwan is geographically in the frontal zone of the Asian monsoon region, and is geologically located in the collision boundary between the Philippine Sea plate and the Eurasian plate. A Holocene uplifting rate of up to 10mm/yr in the eastern coast has been documented in this high relief mountainous island, and active folds and thrusts are common. When tracing the rivers backward to the mountain, one often encounters a subdued topography, covered by primary lateritic soil, above the higher river terrace and below the rugged mountains, and is referred to as lateritic highland (LH) by a previous author. Studies in paleoclimatology and geomorphology enable us to refine the possible age and origin of this remarkable topography. The penultimate glacial-interglacial cycle and the last interglacial period should be the major interval for the development of lateritic highland. LH may be looked upon as a reference surface for studying the dynamic evolution of the tectonic landscape of Taiwan. It shows that the lower uplifting rate is the most important factor for the preservation of the LH topography in this island. Based on the morphology of LH, different deformation styles are recognized in north and south Chiayi (near tropic of cancer), in western Taiwan. To the north, platforms originating from piedmont LH are well developed, whereas to the south, platforms and piedmont LH are hardly visible. This contrast is probably due to a lithological variance between them.

  2. The Role of Internet Paleo Perspective Overviews in Making Data About Past Climate and Environmental Change More Accessible

    NASA Astrophysics Data System (ADS)

    Anderson, D. M.; Bauer, B. A.; Gille, E. P.; Gross, W. S.; Hartman, M. A.; Shah, A. M.; Woodhouse, C. A.

    2005-12-01

    The cornerstone of scientific discovery is the peer-reviewed journal article, yet for non-specialists these articles can be difficult to appreciate. Scientific writing and the sheer number of articles published each month compound the problem. At the World Data Center for Paleoclimatology, a primary goal is to make published scientific results more accessible to non-specialists. In partnership with scientists, we have created Paleo Perspectives, online essays that provide an introduction to the scientific literature on a topic, background needed to appreciate the results, figures with detailed captions, photographs, short movies and visualizations, summaries, glossaries, direct links to the data, and links to additional information. The power and flexibility of the Internet enables us to provide and update this rich array of material. We have produced three paleo perspectives (global warming, drought, abrupt climate change), with a fourth in review (arctic climate variability). Web statistics indicate these are some of the Data Center`s most often-used web pages (more so for hot topics such as global warming), and awards and accolades indicate that the content is appreciated and on-target. Review by scientists assures the accuracy of the presentations, and newly-contributed data provide material for updates.

  3. The Potential of Uranium-Series Disequilibrium in Marine and Lacustrine Diatom Frustules as a Tool for Geochronological and Paleoenvironmental Studies

    NASA Astrophysics Data System (ADS)

    Luo, S.; Tsai, Y.

    2008-12-01

    Accurate age dating of deep-sea sediment records from the polar region remains one of the major challenging issues in paleoceanographic and paleoclimatologic studies. As diatom is ubiquitous in aquatic systems, in particular in cold waters of the polar region, this study seeks to explore the utilities of uranium- series disequilibrium in diatom frustules as a chronometer for absolute age dating and/or as a proxy for paleo-environmental studies. In the uranium series, uranium-238, with a half-life of 4.468 billion year, decays to a stable nuclide lead-206 through a series of shorter-lived radionuclides. Uranium-238 and all of its daughter nuclides will achieve secular equilibrium on a time scale of about one million years in an igneous rock. Disequilibrium between the daughter and parent nuclides would occur in aquatic environments, such as in oceans and lakes, as a result of various naturally-occurring physical/chemical processes. This study shows that diatom acquires its uranium isotope composition from its ambient seawater, creating significant radioactive disequilibrium between uranium and its daughter nuclides in diatom frustules. This salient feature makes diatom frustules very useful for absolute age dating as well as for assessing the past changes of many geophysical and geochemical processes in the ocean and on the continents.

  4. Foraminiferal faunal estimates of paleotemperature: Circumventing the no-analog problem yields cool ice age tropics

    USGS Publications Warehouse

    Mix, A.C.; Morey, A.E.; Pisias, N.G.; Hostetler, S.W.

    1999-01-01

    The sensitivity of the tropics to climate change, particularly the amplitude of glacial-to-interglacial changes in sea surface temperature (SST), is one of the great controversies in paleoclimatology. Here we reassess faunal estimates of ice age SSTs, focusing on the problem of no-analog planktonic foraminiferal assemblages in the equatorial oceans that confounds both classical transfer function and modern analog methods. A new calibration strategy developed here, which uses past variability of species to define robust faunal assemblages, solves the no-analog problem and reveals ice age cooling of 5??to 6??C in the equatorial current systems of the Atlantic and eastern Pacific Oceans. Classical transfer functions underestimated temperature changes in some areas of the tropical oceans because core-top assemblages misrepresented the ice age faunal assemblages. Our finding is consistent with some geochemical estimates and model predictions of greater ice age cooling in the tropics than was inferred by Climate: Long-Range Investigation, Mapping, and Prediction (CLIMAP) [1981] and thus may help to resolve a long-standing controversy. Our new foraminiferal transfer function suggests that such cooling was limited to the equatorial current systems, however, and supports CLIMAP's inference of stability of the subtropical gyre centers.

  5. Investigating Climate Change Issues With Web-Based Geospatial Inquiry Activities

    NASA Astrophysics Data System (ADS)

    Dempsey, C.; Bodzin, A. M.; Sahagian, D. L.; Anastasio, D. J.; Peffer, T.; Cirucci, L.

    2011-12-01

    In the Environmental Literacy and Inquiry middle school Climate Change curriculum we focus on essential climate literacy principles with an emphasis on weather and climate, Earth system energy balance, greenhouse gases, paleoclimatology, and how human activities influence climate change (http://www.ei.lehigh.edu/eli/cc/). It incorporates a related set of a framework and design principles to provide guidance for the development of the geospatial technology-integrated Earth and environmental science curriculum materials. Students use virtual globes, Web-based tools including an interactive carbon calculator and geologic timeline, and inquiry-based lab activities to investigate climate change topics. The curriculum includes educative curriculum materials that are designed to promote and support teachers' learning of important climate change content and issues, geospatial pedagogical content knowledge, and geographic spatial thinking. The curriculum includes baseline instructional guidance for teachers and provides implementation and adaptation guidance for teaching with diverse learners including low-level readers, English language learners and students with disabilities. In the curriculum, students use geospatial technology tools including Google Earth with embedded spatial data to investigate global temperature changes, areas affected by climate change, evidence of climate change, and the effects of sea level rise on the existing landscape. We conducted a designed-based research implementation study with urban middle school students. Findings showed that the use of the Climate Change curriculum showed significant improvement in urban middle school students' understanding of climate change concepts.

  6. Obliquity Modulation of the Incoming Solar Radiation

    NASA Technical Reports Server (NTRS)

    Liu, Han-Shou; Smith, David E. (Technical Monitor)

    2001-01-01

    Based on a basic principle of orbital resonance, we have identified a huge deficit of solar radiation induced by the combined amplitude and frequency modulation of the Earth's obliquity as possibly the causal mechanism for ice age glaciation. Including this modulation effect on solar radiation, we have performed model simulations of climate change for the past 2 million years. Simulation results show that: (1) For the past 1 million years, temperature fluctuation cycles were dominated by a 100-Kyr period due to amplitude-frequency resonance effect of the obliquity; (2) From 2 to 1 million years ago, the amplitude-frequency interactions. of the obliquity were so weak that they were not able to stimulate a resonance effect on solar radiation; (3) Amplitude and frequency modulation analysis on solar radiation provides a series of resonance in the incoming solar radiation which may shift the glaciation cycles from 41-Kyr to 100-Kyr about 0.9 million years ago. These results are in good agreement with the marine and continental paleoclimate records. Thus, the proposed climate response to the combined amplitude and frequency modulation of the Earth's obliquity may be the key to understanding the glaciation puzzles in paleoclimatology.

  7. Classifying black and white spruce pollen using layered machine learning.

    PubMed

    Punyasena, Surangi W; Tcheng, David K; Wesseln, Cassandra; Mueller, Pietra G

    2012-11-01

    Pollen is among the most ubiquitous of terrestrial fossils, preserving an extended record of vegetation change. However, this temporal continuity comes with a taxonomic tradeoff. Analytical methods that improve the taxonomic precision of pollen identifications would expand the research questions that could be addressed by pollen, in fields such as paleoecology, paleoclimatology, biostratigraphy, melissopalynology, and forensics. We developed a supervised, layered, instance-based machine-learning classification system that uses leave-one-out bias optimization and discriminates among small variations in pollen shape, size, and texture. We tested our system on black and white spruce, two paleoclimatically significant taxa in the North American Quaternary. We achieved > 93% grain-to-grain classification accuracies in a series of experiments with both fossil and reference material. More significantly, when applied to Quaternary samples, the learning system was able to replicate the count proportions of a human expert (R(2) = 0.78, P = 0.007), with one key difference - the machine achieved these ratios by including larger numbers of grains with low-confidence identifications. Our results demonstrate the capability of machine-learning systems to solve the most challenging palynological classification problem, the discrimination of congeneric species, extending the capabilities of the pollen analyst and improving the taxonomic resolution of the palynological record.

  8. A comparison of high-resolution pollen-inferred climate data from central Minnesota, USA, to 19th century US military fort climate data and tree-ring inferred climate reconstructions

    NASA Astrophysics Data System (ADS)

    St Jacques, J.; Cumming, B. F.; Sauchyn, D.; Vanstone, J. R.; Dickenson, J.; Smol, J. P.

    2013-12-01

    A vital component of paleoclimatology is the validation of paleoclimatological reconstructions. Unfortunately, there is scant instrumental data prior to the 20th century available for this. Hence, typically, we can only do long-term validation using other proxy-inferred climate reconstructions. Minnesota, USA, with its long military fort climate records beginning in 1820 and early dense network of climate stations, offers a rare opportunity for proxy validation. We compare a high-resolution (4-year), millennium-scale, pollen-inferred paleoclimate record derived from varved Lake Mina in central Minnesota to early military fort records and dendroclimatological records. When inferring a paleoclimate record from a pollen record, we rely upon the pollen-climate relationship being constant in time. However, massive human impacts have significantly altered vegetation; and the relationship between modern instrumental climate data and the modern pollen rain becomes altered from what it was in the past. In the Midwest, selective logging, fire suppression, deforestation and agriculture have strongly influenced the modern pollen rain since Euro-American settlement in the mid-1800s. We assess the signal distortion introduced by using the conventional method of modern post-settlement pollen and climate calibration sets to infer climate at Lake Mina from pre-settlement pollen data. Our first February and May temperature reconstructions are based on a pollen dataset contemporaneous with early settlement to which corresponding climate data from the earliest instrumental records has been added to produce a 'pre-settlement' calibration set. The second February and May temperature reconstructions are based on a conventional 'modern' pollen-climate dataset from core-top pollen samples and modern climate normals. The temperature reconstructions are then compared to the earliest instrumental records from Fort Snelling, Minnesota, and it is shown that the reconstructions based on the pre

  9. A 3D Earth orbit model; visualization and analysis of Milankovitch cycles and insolation

    NASA Astrophysics Data System (ADS)

    Gilb, R. D.; Kostadinov, T. S.

    2012-12-01

    An astronomically precise and accurate Earth orbit graphical model, Earth orbit v2.0, is presented. The model offers 3D visualizations of Earth's orbital geometry, Milankovitch parameters and the ensuing insolation forcings. Prevalent paleoclimatic theories invoke Milankovitch cycles as a major forcing mechanism capable of shifting Earth's climate regimes on time scales of tens to hundreds of thousands of years. Variability of eccentricity (ellipticity of orbit), precession (longitude of perihelion) and obliquity (Earth's axial tilt) changes parameters such as amplitude of seasonal insolation, timing of seasons with respect to perihelion, and total annual insolation. Hays et al. (1976) demonstrated a strong link between Milankovitch cycles and paleoclimatological records, which has been confirmed and expanded many times since (e.g. Berger et al., 1994; Berger et al., 2010). The complex interplay of several orbital parameters on various time scales makes assessment and visualization of Earth's orbit and spatio-temporal insolation variability challenging. It is difficult to appreciate the pivotal importance of Kepler's laws of planetary motion in controlling the effects of Milankovitch cycles on insolation patterns on various spatio-temporal scales. These factors also make Milankovitch theory difficult to teach effectively. The model allows substantial user control in a robust, yet intuitive and user-friendly graphical user interface (GUI) developed in Matlab. We present the user with a choice between Berger et al. (1978) and Laskar et al. (2004) astronomical solutions for eccentricity, obliquity and precession. Berger solutions span from -1 Myr to +1 Myr, while Laskar provides solutions from -101 Myr to +21 Myr since J2000. Users can also choose a "demo" mode which allows the three Milankovitch parameters to be varied independently of each other, so the user can isolate the effects of each on orbital geometry and insolation. For example, extreme eccentricity can be

  10. Solar vs. Tidal Forcing of Centennial to Decadal Scale Variability in Marine Sedimentary Records from the Western Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Kirkwood, G.; Domack, E.; Brachfeld, S.

    2004-12-01

    and Whorf, 2000). We discuss these alternative forcing mechanisms with respect to: contrasts in regional processes of glacial marine sedimentation, the mechanism whereby the tidal or solar signal is transferred to the sediment column and possible cryptic stratigraphy of the Palmer Deep record (ie. missing time, Nederbragt and Thurow, 2002). Resolution of the correct forcing factor is critical to our ability to hind cast the last 100 years of paleoenvironmental data within these cores and hence to our attempts at recognizing an anthropogenic climate signal in the Antarctic Peninsula region. Howell, P. (2001), ARAND time series and spectral analysis package for the Macintosh, Brown University, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2001-044, NOAA/NGDC Paleoclimatology Program, Boulder, Colo. Keeling, Charles D., and Timothy P. Whorf (2000), The 1,800-year oceanic tidal cycle: A possible cause of rapid climate change, Proc. Natl. Acad. Sci., 97 (8), 3814-3819. Nederbragt, A. J., and Thurow, J. (2002) Sediment color variation and annual accumulation rates in laminated Holocene sediments, Site 1098, Palmer Deep. In Barker, P. F., Camerlenghi, A., Acton, G. D., and Ramsay, A.T.S. (eds), Proc. ODP Sci. Results, 178: College Station TX (Ocean Drilling Program). Warner, Nathaniel R., and E. Domack (2002), Millennial-to decadal-scale paleoenvironmental change during the Holocene in the Palmer Deep, Antarctica, as recorded by particle size analysis, Paleoceanography, 17 (3), 8004, doi:10.1029/2000PA000602.

  11. Evaluating Paleoecological Patterns Using Paleoenvironmental Proxies: The Promise and the Peril

    NASA Astrophysics Data System (ADS)

    Jackson, S. T.; Booth, R. K.

    2007-12-01

    Michigan and Wisconsin during an extended pluvial period (4000-3000 yr BP) that followed on a drought of extraordinary duration and severity (4200-4000 yr BP). Continued expansion of yellow birch, as well as hemlock and beech, after 3000 yr BP was mediated by edaphic mosaics and centennial-scale pluvial events. Our experience indicates that integrated paleoecological and paleoclimatological studies have payoffs for ecology, paleoecology, and paleoclimatology. Perils, though real, are no different from those encountered in other interdisciplinary enterprises in the historical sciences. We identify six key challenges for continued progress in this area: (1)identifying, refining, and applying paleoclimate proxies that are sensitive to the same climate variables and at the same timescales as the ecological systems of interest. (2) correlating events in time among records, particularly when paleoecological and paleoclimate data derive from different archives. (3) identifying and modeling lags in ecological response to climate forcings. (4) determining proximal mechanisms of past ecological responses to climate changes. (5) assessing indirect responses to climate forcing, and interactions between climate and other factors (e.g., pests, wildfires). (6) determining "when to quit" - when to conclude that climate forcing of an observed ecological event is insupportable (versus assuming that the proxies examined to date simply aren't sensitive to whatever the ecological system is responding to). Meeting these challenges will require engagement and collaboration among paleoecologists, paleoclimatologists, geochronologists, and ecologists.

  12. Four centuries of tropical Pacific sea-surface temperature from coral archives

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Guillot, D.; Cobb, K. M.; Cole, J. E.; Correge, T.; Tudhope, A. W.; Rajaratnam, B.

    2012-12-01

    during the instrumental and pre- instrumental period. In detail, SST patterns associated with individual drought episodes may deviate from the canonical La Nina (Cook et al., 2007). Finally, superposed epoch analysis confirms the results of Adams et al. (2003) that El Nino events tend to follow large tropical explosive eruptions. A formal analysis of uncertainties will put these findings into a probabilistic context. References Adams, J., M. Mann, and C. Ammann (2003), Proxy evidence for an El Nino-like response to volcanic forcing, Nature, 426, 274-278, doi:10.1038/nature02101. Cook, E. (2008), North american summer PDSI reconstructions, version 2a, NOAA/NGDC Paleoclimatology Program, Boulder CO, USA Data Contribution Series # 2008-046, IGBP PAGES/World Data Center for Paleoclimatology. Cook, E., R. Seager, M. Cane, and D. Stahle (2007), North American drought: Reconstructions, causes, and consequences, Earth Sc. Rev. Guillot, D., B. Rajaratnam, and J. Emile-Geay (in revision), A graphical model based approach to paleoclimate reconstruction, J. Amer. Statist. Assoc. McGregor, S., A. Timmermann, and O. Timm (2010), A unified proxy for ENSO and PDO variability since 1650, Climate of the Past, 6(1), 1-17, Newman, M., S.-I. Shin, and M. A. Alexander (2011), Natural variation in ENSO flavors, Geophys. Res. Lett., 38(14) Yeh, S.-W., J.-S. Kug, B. Dewitte, M.-H. Kwon, B. P. Kirtman, and F.-F. Jin (2009), El Nino in a changing climate, Nature, 461(7263), 511-514.

  13. Weathering and monsoonal evolution in the Eastern Himalayas since 13 Ma from detrital geochemistry, Kameng River Section, Arunachal Pradesh

    NASA Astrophysics Data System (ADS)

    Vögeli, Natalie; Van der Beek, Peter; Najman, Yani; Huyghe, Pascale

    2015-04-01

    The link between tectonics, erosion and climate has become an important subject to ongoing research in the last years (Clift et al. (2008), amongst others). The young Himalayan orogeny is the perfect laboratory for its study. The Neogene sedimentary foreland basin of the Himalaya contains a record of tectonics and paleoclimate since Miocene times, within the so called Siwalik Group. Therefore several sedimentary sections within the Himalayan foreland basin along strike in the Himalayan range have been dated and studied regarding exhumation rates, provenance and paleoclimatology (e.g. Quade and Cerling, 1995; Ghosh et al., 2004; Sanyal et al., 2004; van der Beek et al., 2006). Lateral variations have been observed and changes in exhumation rate as well as climate change in the past especially the strengthening of the Asian summer monsoon is still debated. Several paleoclimatological studies in the western Himalaya were conducted (Quade and Cerling, 1995; Najman et al., 2003; Huyghe et al., 2005), but the eastern part of the mountain range remains poorly studied. The Himalaya has a major influence on global and regional climate. The major force driving the evolution of this mountain belt is the India-Asia convergence, nevertheless it has been suggested that the monsoonal climate plays a major role for the erosion and relief pattern (Bookhagen and Burbank, 2006; Clift et al., 2008; Iaffaldano et al., 2011). Exhumation rates in the central Himalayas are more or less constant over last 13 Ma in the order of 1.8 km/myr, whereas exhumation rates in the eastern syntaxis increased post 3 Ma (Chirouze et al., 2013) to reach up to 10km/myr in the recent past. In this study we use a multidisciplinary approach in order to better understand the interplay of monsoon and weathering regime during the Mid Miocene to Pleistocene in the Himalaya. Therefore a sedimentary section in the eastern Himalaya was sampled. Pairs of fine and coarse grained sediment samples were taken in the

  14. Time averaging and stratigraphic disorder of molluscan assemblages in the Holocene sediments in the NE Adriatic (Piran)

    NASA Astrophysics Data System (ADS)

    Tomasovych, Adam; Gallmetzer, Ivo; Haselmair, Alexandra; Kaufman, Darrell S.; Zuschin, Martin

    2016-04-01

    Stratigraphic changes in temporal resolution of fossil assemblages and the degree of their stratigraphic mixing in the Holocene deposits are of high importance in paleoecology, conservation paleobiology and paleoclimatology. However, few studies quantified downcore changes in time averaging and in stratigraphic disorder on the basis of dating of multiple shells occurring in individual stratigraphic layers. Here, we investigate downcore changes in frequency distribution of postmortem ages of the infaunal bivalve Gouldia minima in two, ~150 cm-thick piston cores (separated by more than 1 km) in the northern Adriatic Sea, close to the Slovenian city Piran at a depth of 24 m. We use radiocarbon-calibrated amino acid racemization to obtain postmortem ages of 564 shells, and quantify age-frequency distributions in 4-5 cm-thick stratigraphic intervals (with 20-30 specimens sampled per interval). Inter-quartile range for individual 4-5 cm-thick layers varies between 850 and 1,700 years, and range encompassing 95% of age data varies between 2,000 and 5,000 years in both cores. The uppermost sediments (20 cm) are age-homogenized and show that median age of shells is ~700-800 years. The interval between 20 and 90 cm shows a gradual increase in median age from ~2,000 to ~5,000 years, with maximum age ranging to ~8,000 years. However, the lowermost parts of both cores show a significant disorder, with median age of 3,100-3,300 years. This temporal disorder implies that many shells were displaced vertically by ~1 m. Absolute and proportional abundance of the bivalve Gouldia minima strongly increases towards the top of the both cores. We hypothesize that such increase in abundance, when coupled with depth-declining reworking, can explain stratigraphic disorder because numerically abundant young shells from the top of the core were more likely buried to larger sediment depths than less frequent shells at intermediate sediment depths.

  15. Fast Vegetational Responses to Late-Glacial Climate Change

    NASA Astrophysics Data System (ADS)

    Williams, J. W.; Post, D. M.; Cwynar, L. C.; Lotter, A. F.; Levesque, A. J.

    2001-12-01

    How rapidly can natural ecosystems respond to rapid climate change? This question can be addressed by studying paired paleoecological and paleoclimatological records spanning the last deglaciation. Between 16 and 10 ka, abrupt climatic oscillations (e.g. Younger Dryas, Gerzensee/Killarney Oscillations) interrupted the general warming trend. Rates of climate change during these events were as fast or faster than projected rates of change for this century. We compiled a dozen high-resolution lacustrine records in North America and Europe with a pollen record and independent climatic proxy, a clear Younger Dryas signal, and good age control. Cross-correlation analysis suggests that vegetation responded rapidly to late-glacial climate change, with significant changes in vegetation composition occurring within the lifespan of individual trees. At all sites, vegetation lagged climate by less than 200 years, and at two-thirds of the sites, the initial vegetational response occurred within 100 years. The finding of rapid vegetational responses is consistent across sites and continents, and is similar to the 100-200 year response times predicted by gap-scale forest models. Likely mechanisms include 1) increased susceptibility of mature trees to disturbances such as fire, wind, and disease, thereby opening up gaps for colonization, 2) the proximity of these sites to late-glacial treeline, where climate may directly control plant population densities and range limits, 3) the presence of herbaceous taxa with short generation times in these plant communities, and 4) rapid migration due to rare long-distance seed dispersals. Our results are consistent with reports that plant ranges are already shifting in response to recent climate change, and suggest that these shifts will persist for the next several centuries. Widespread changes in plant distributions may affect surface-atmosphere interactions and will challenge attempts to manage ecosystems and conserve biodiversity.

  16. Glacial North Atlantic: Sea-surface conditions reconstructed by GLAMAP 2000

    NASA Astrophysics Data System (ADS)

    Pflaumann, U.; Sarnthein, M.; Chapman, M.; D'Abreu, L.; Funnell, B.; Huels, M.; Kiefer, T.; Maslin, M.; Schulz, H.; Swallow, J.; van Kreveld, S.; Vautravers, M.; Vogelsang, E.; Weinelt, M.

    2003-09-01

    The response of the tropical ocean to global climate change and the extent of sea ice in the glacial nordic seas belong to the great controversies in paleoclimatology. Our new reconstruction of peak glacial sea surface temperatures (SSTs) in the Atlantic is based on census counts of planktic foraminifera, using the Maximum Similarity Technique Version 28 (SIMMAX-28) modern analog technique with 947 modern analog samples and 119 well-dated sediment cores. Our study compares two slightly different scenarios of the Last Glacial Maximum (LGM), the Environmental Processes of the Ice Age: Land, Oceans, Glaciers (EPILOG), and Glacial Atlantic Ocean Mapping (GLAMAP 2000) time slices. The comparison shows that the maximum LGM cooling in the Southern Hemisphere slightly preceeded that in the north. In both time slices sea ice was restricted to the north western margin of the nordic seas during glacial northern summer, while the central and eastern parts were ice-free. During northern glacial winter, sea ice advanced to the south of Iceland and Faeroe. In the central northern North Atlantic an anticyclonic gyre formed between 45° and 60°N, with a cool water mass centered west of Ireland, where glacial cooling reached a maximum of >12°C. In the subtropical ocean gyres the new reconstruction supports the glacial-to-interglacial stability of SST as shown by () [1981]. The zonal belt of minimum SST seasonality between 2° and 6°N suggests that the LGM caloric equator occupied the same latitude as today. In contrast to the CLIMAP reconstruction, the glacial cooling of the tropical east Atlantic upwelling belt reached up to 6°-8°C during Northern Hemisphere summer. Differences between these SIMMAX-based and published U37k- and Mg/Ca-based equatorial SST records are ascribed to strong SST seasonalities and SST signals that were produced by different planktic species groups during different seasons.

  17. Dating the Laschamp Excursion: Why Speleothems are Valuable Tools for Constraining the Timing and Duration of Short-Lived Geomagnetic Events

    NASA Astrophysics Data System (ADS)

    Lascu, I.; Feinberg, J. M.; Dorale, J. A.; Cheng, H.; Edwards, R. L.

    2015-12-01

    Short-lived geomagnetic events are reflections of geodynamo behavior at small length scales. A rigorous documentation of the anatomy, timing, duration, and frequency of centennial-to-millennial scale geomagnetic events can be invaluable for theoretical and numerical geodynamo models, and for the understanding the finer dynamics of the Earth's core. A critical ingredient for characterizing such geomagnetic instabilities are tightly constrained age models that enable high-resolution magnetostratigraphies. Here we focus on a North American speleothem geomagnetic record of the Laschamp excursion, which was the first geomagnetic excursion recognized and described in the paleomagnetic record, and remains the most studied event of its kind. The geological significance of the Laschamp lies chiefly in the fact that it constitutes a global time-synchronous geochronological marker. The Laschamp excursion occurred around the time of the demise of Homo neanderthalensis, in conjunction with high-amplitude, rapid climatic oscillations leading into the Last Glacial Maximum, and precedes a major supervolcano eruption in the Mediterranean. Thus, the precise determination of the timing and duration of the Laschamp would help in elucidating major scientific questions situated at the intersection of geology, paleoclimatology, and anthropology. Here we present a geomagnetic record from a stalagmite collected in Crevice Cave, Missouri, which we have dated using a combination of high-precision 230Th ages and annual layer counting using confocal microscopy. We have found a maximum duration for the Laschamp that spans the interval 42,250-39,700 years BP, and an age of 41,100 ± 350 years BP for the height of the excursion. During this period relative paleointensity decreased by an order of magnitude and the virtual geomagnetic pole was located at southerly latitudes. Our chronology provides the first robust bracketing for the Laschamp excursion, and improves on previous age determinations

  18. An integrated chronostratigraphic data system for the twenty-first century

    USGS Publications Warehouse

    Sikora, P.J.; Ogg, J.G.; Gary, A.; Cervato, C.; Gradstein, F.; Huber, B.T.; Marshall, C.; Stein, J.A.; Wardlaw, B.

    2006-01-01

    Research in stratigraphy is increasingly multidisciplinary and conducted by diverse research teams whose members can be widely separated. This developing distributed-research process, facilitated by the availability of the Internet, promises tremendous future benefits to researchers. However, its full potential is hindered by the absence of a development strategy for the necessary infrastructure. At a National Science Foundation workshop convened in November 2001, thirty quantitative stratigraphers and database specialists from both academia and industry met to discuss how best to integrate their respective chronostratigraphic databases. The main goal was to develop a strategy that would allow efficient distribution and integration of existing data relevant to the study of geologic time. Discussions concentrated on three major themes: database standards and compatibility, strategies and tools for information retrieval and analysis of all types of global and regional stratigraphic data, and future directions for database integration and centralization of currently distributed depositories. The result was a recommendation to establish an integrated chronostratigraphic database, to be called Chronos, which would facilitate greater efficiency in stratigraphic studies (http://www.chronos.org/) . The Chronos system will both provide greater ease of data gathering and allow for multidisciplinary synergies, functions of fundamental importance in a variety of research, including time scale construction, paleoenvironmental analysis, paleoclimatology and paleoceanography. Beyond scientific research, Chronos will also provide educational and societal benefits by providing an accessible source of information of general interest (e.g., mass extinctions) and concern (e.g., climatic change). The National Science Foundation has currently funded a three-year program for implementing Chronos.. ?? 2006 Geological Society of America. All rights reserved.

  19. Synchronizing the Greenland ice core and radiocarbon timescales over the Holocene - Bayesian wiggle-matching of cosmogenic radionuclide records

    NASA Astrophysics Data System (ADS)

    Adolphi, F.; Muscheler, R.

    2016-01-01

    Investigations of past climate dynamics rely on accurate and precise chronologies of the employed climate reconstructions. The radiocarbon dating calibration curve (IntCal13) and the Greenland ice core chronology (GICC05) represent two of the most widely used chronological frameworks in paleoclimatology of the past ˜ 50 000 years. However, comparisons of climate records anchored on these chronologies are hampered by the precision and accuracy of both timescales. Here we use common variations in the production rates of 14C and 10Be recorded in tree-rings and ice cores, respectively, to assess the differences between both timescales during the Holocene. Compared to earlier work, we employ a novel statistical approach which leads to strongly reduced and yet, more robust, uncertainty estimates. Furthermore, we demonstrate that the inferred timescale differences are robust independent of (i) the applied ice core 10Be records, (ii) assumptions of the mode of 10Be deposition, as well as (iii) carbon cycle effects on 14C, and (iv) in agreement with independent estimates of the timescale differences. Our results imply that the GICC05 counting error is likely underestimated during the most recent 2000 years leading to a dating bias that propagates throughout large parts of the Holocene. Nevertheless, our analysis indicates that the GICC05 counting error is generally a robust uncertainty measurement but care has to be taken when treating it as a nearly Gaussian error distribution. The proposed IntCal13-GICC05 transfer function facilitates the comparison of ice core and radiocarbon dated paleoclimate records at high chronological precision.

  20. Drought as a Catalyst for Early Medieval European Subsistence Crises and Violence

    NASA Astrophysics Data System (ADS)

    Ludlow, Francis; Cook, Edward; Kostick, Conor; McCormick, Michael

    2016-04-01

    Tree-ring records provide one of most reliable means of reconstructing past climatic conditions, from longer-term multi-decadal fluctuations in temperature and precipitation to inter-annual variability, including years that experienced extreme weather. When combined with written records of past societal behaviour and the incidence of major societal stresses (e.g., famine, disease, and conflict), such records hold the potential to shed new light on historical interactions between climate and society. Recent years have seen the continued development of long dendroclimatic reconstructions, including, most recently the development of the Old World Drought Atlas (OWDA; Cook et al., 2015) which for the first time makes available a robust reconstruction of spring-summer hydroclimatic conditions and extremes for the greater European region, including the entirety of the Dark Ages. In this paper, we examine the association between hydroclimatic extremes identified in the OWDA and well-dated reports of severe drought in early medieval European annals and chronicles, and find a clear statistical correspondence, further confirming the accuracy of the OWDA and its importance as an independent record of hydroclimatic extremes, a resource that can now be drawn upon in both paleoclimatology and studies of climatic impacts on human society. We proceed to examine the association between hydroclimatic extremes identified in the OWDA and the incidence of a range of major societal stresses (scarcity and famine, epidemic disease, and mass human mortality) drawn from an exhaustive survey of early medieval European annals and chronicles. The outcome of this comparison firmly implicates drought as a significant driver of major societal stresses during early medieval times. Using a record of the violent killings of societal elites recorded on a continuous annual basis in medieval Irish monastic annals, we further examine the role of hydroclimatic extremes as triggers in medieval violence

  1. Raised bogs, a Climate Shift, Cultural Change, and Reduced Solar Activity in the Early First Millennium BC

    NASA Astrophysics Data System (ADS)

    van Geel, B.

    2006-12-01

    Matching of a high resolution sequence of uncalibrated 14C datings with the dendro-calibration curve not only offers improved dating precision, but can also reveal relationships between atmospheric 14C variations and short-term climatic fluctuations caused by variations in solar output. Holocene shifts to cool and wet climate types in the temperate zones often correspond to phases of sharply increasing values of atmospheric radiocarbon, pointing to a link between changing solar activity and climate change. In northwest Europe at ca. 850 BC a sharp climatic shift to cooler, wetter conditions occurred. The shift is reflected in the species composition and decomposition of raised bog deposits and is chronologically linked to cultural changes and migrations at the Bronze Age/Iron Age transition. The temporary sharp rise of the atmospheric 14C content around 800 BC was caused by a sudden decline of solar activity. The solar wind declined, permitting more cosmic rays to penetrate into the atmosphere, and therefore the production of the cosmogenic isotope 14C increased. The climate shift was also recorded in Central and Eastern Europe, with rapid and total flooding of the Upper Volga region and a highstand of the Caspian Sea. In the Mississippi River basin, flooding frequencies greatly increased and there was an abrupt gap in the cultural transition from `Late Archaic' to `Early Woodland'. Paleoclimatological teleconnections point to a considerable role of solar UV in climate forcing. In the Central African rain forest belt and western India there was also a strong climate shift around 850 cal BC, but it was a shift to dryness (weakening of the summer monsoon). A possible palaeoclimatological explanation for the dry-wet transition in the temperate zones, and the contemporaneous wet-dry transition in the tropics (climatic teleconnections) will be given.

  2. Effect Of Substrates On The Fractionation Of Hydrogen Isotopes During Lipid-Biosynthesis By Haloarcula marismortui

    NASA Astrophysics Data System (ADS)

    Dirghangi, S. S.; Pagani, M.

    2010-12-01

    Lipids form an important class of proxies for paleoclimatological research, and hydrogen isotope ratios of lipids are being increasingly used for understanding changes in the hydrological system. Proper understanding of hydrogen isotope fractionation during lipid biosynthesis is therefore important and attention has been directed toward understanding the magnitude of hydrogen isotope fractionation that occurs during lipid biosynthesis in various organisms. Hydrogen isotope ratios of lipids depend on the hydrogen isotopic composition of the ambient water, hydrogen isotopic composition of NADPH used during biosynthesis, growth conditions, pathways of lipid biosynthesis, and substrates in the case of heterotrophic organisms. Recently it has been observed that NADPH contributes a significant part of the hydrogen in fatty acids synthesized by bacteria during heterotrophic growth (Zhang et al, 2009). As NADPH is formed by reduction of NADP+ during metabolism of substrates, different metabolic pathways form NADPH with different D/H ratios, which in turn results in variation in D/H ratios of lipids (Zhang et al, 2009). Therefore, substrates play a significant role in hydrogen isotopic compositions of lipids. For this study, we are investigating the effects of substrates on hydrogen isotope fractionation during biosynthesis of isoprenoidal lipids by heterotrophically growing halophilic archaea. Haloarcula marismortui is a halophilic archaea which synthesizes Archaeol (a diether lipid) and other isoprenoidal lipids. We have grown Haloarcula marismortui in pure cultures on three different substrates and are in the process of evaluating isotopic variability of Archaeol and other lipids associated with substrate and the D/H composition of ambient water. Our results will be helpful for a better understanding of hydrogen isotope fractionations during lipid synthesis by archaea. Also, halophilic archaea are the only source of archaeol in hypersaline environments. Therefore, our

  3. Do Speleothem Stable Isotope Records Contain Hidden Tropical Cyclone Histories? Exploring C-O Isotope Correlation Patterns for Indicators of Tropical Cyclone Masking

    NASA Astrophysics Data System (ADS)

    Frappier, A. E.; Rossington, C.

    2013-12-01

    The newly-described tropical cyclone masking effect on stable isotope paleohydrological signals in speleothem records arises from the intermittent delivery of large pulses of isotopically distinct tropical cyclone rain. Recent work shows that 18-O depleted tropical cyclone stormwater depresses the δ18O value of speleothem calcite for months to years following a tropical cyclone event, masking the background stable isotope signal of persistent climate variability. Periods of high local storm activity can lead to speleothem calcite paleohydrological signals with significant wet biases on interannual to decadal timescales. Because speleothem carbon isotope ratios are independent of tropical cyclone rainfall, tropical speleothems are known to exhibit moderate C-O isotope covariation over time, periods when C-O isotope covariation breaks down and δ18O values are low may provide a marker for times when tropical cyclone masking is important. If so, existing speleothem stable isotope records from tropical cyclone-prone regions may contain signatures of tropical cyclone masking in the temporal evolution of C-O isotope covariation patterns. We present results from an exploratory analysis of several published speleothem records that are candidates for containing tropical cyclone masking signals. For each speleothem, overall C-O isotope covariation coefficients were calculated, and transient covariation patterns were analyzed using a sliding correlation index, the Covariation of Stable Isotopes (CoSI) index, and Local Correlation (LoCo). Local tropical cyclone historical and paleotempest records are compared and a method is presented to test for the presence of tropical cyclone masking intervals. The implications for speleothem paleoclimatology and paleotempestology are discussed.

  4. Stable isotope deltas: tiny, yet robust signatures in nature.

    PubMed

    Brand, Willi A; Coplen, Tyler B

    2012-09-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including (14)C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. (13)C, (2)H, and (18)O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as-25 per mil can be written as-25 mUr (or-2.5 cUr or-0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg 'units' are easily included (e.g. either+0.015 ‰ or+15 per meg

  5. Geochemistry of brachiopods: Oxygen and carbon isotopic records of Paleozoic oceans

    NASA Astrophysics Data System (ADS)

    Veizer, Ján; Fritz, Peter; Jones, Brian

    1986-08-01

    Combined trace element and isotope studies of 319 brachiopods, covering the Ordovician to Permian time span, show that δ 13C and δ 18O in well preserved specimens varied during the Paleozoic. The overall δ 13C secular trend is in accord with the previously published observations, but its details are obscured by vital isotopic fractionation effects at generic level. Nonetheless, the results suggest that the negative correlation between marine δ 13C carbonate and δ 34S sulphate deteriorates at time scales of ⩽ 10 6 years, due to the long residence time, and thus slow response, of SO 42- in the ocean. For oxygen isotopes, all Devonian and older specimens have δ 18O of ⩽ -4%, while the well preserved Permian samples have near-present day δ 18O of about -1% (PDB). This isotopic dichotomy is probably not due to post-depositional phenomena, salinity, or biogenic fractionation effects. This leaves open the perennial arguments for a change in 18O /16O of sea water versus warmer ancient oceans. The present data are difficult to explain solely by the temperature alternative. The coincidence of the proposed shift in δ 18O with the large Late Paleozoic changes in marine 87Sr /86Sr , 13C /12C , 34S /32S , and "sea level stands" argues for a tectonic cause and for a change in 18O /16O of sea water, although such explanation is difficult to reconcile with global balance considerations and with isotopic patterns observed in alteration products of ancient basalts and ophiolites. Whatever the precise cause, or combination of causes, the implications for tectonism and/or paleoclimatology are of first order significance.

  6. Post-depositional migration and preservation of methanesulfonic acid (MSA) in polar ice cores

    NASA Astrophysics Data System (ADS)

    Osman, M.; Marchal, O.; Guo, W.; Das, S. B.; Evans, M. J.

    2015-12-01

    Methanesulfonic acid (MSA; CH3SO3-) in ice cores is a unique, high-resolution proxy of regional sea ice behavior, marine primary productivity, and synoptic climatology. Significant uncertainties remain, however, in both our understanding of the production and transfer of MSA to the ice sheet, as well as its preservation over time, compromising the paleoclimatological utility of the proxy. Here we apply a numerical modeling approach to quantitatively investigate the post-depositional processes affecting MSA migration and preservation within the firn and ice column, building on recent observational and theoretical studies. Our model allows us to evaluate the timing and magnitude of the vertical movement of MSA in response to varying influences, including the competing effects of 1) concentration gradients of sea-salts typically deposited asynchronously to MSA, 2) snow accumulation and densification rates, and 3) in situ temperature gradients. We first test the model against a recently collected ice core from a high accumulation site in coastal West Antarctica, where monthly-resolved MSA records show an abrupt shift from a summer-to-winter maximum in MSA at ~23m depth (ρ ≈ 650 kg/m3), near the firn-ice transition. We find our model to be a robust predictor of the observed migrational features in this record, capturing both (i) the abrupt shift in summer-to-winter maximal concentrations of MSA (steady state ≈ 3.2 yrs), and (ii) the depression of the seasonal amplitude at depth. Further, our modeling results suggest post-depositional effects can lead to substantial interannual alteration of the MSA signal, contrary to previous assumptions that MSA migration is confined within annual layers at high accumulation sites. Using a broad range of polar MSA records and their associated, site-specific environmental conditions, we will evaluate the fidelity of subannual to interannual variability of MSA records and systematically determine the factors conducive to its

  7. Geomorphical and Geochronological Constrains of the Last Glacial Period in Southern Patagonia, Southern South America

    NASA Astrophysics Data System (ADS)

    García, J.; Hall, B. L.; Kaplan, M. R.; Vega, R. M.; Binnie, S. A.; Hein, A.; Gómez, G. N.; Ferrada, J. J.

    2013-12-01

    Despite the outer limits of the former Patagonian ice sheet (PIS, ~38-55S) having been extensively mapped, it remains unknown if the Patagonian glaciers fluctuated synchronously or asynchronously during the last glacial period. Previous work has revealed asynchronous spatiotemporal ice dynamics along the eastern and western ice-margins at the end of the last glaciation but it is not well understood if the northern and southern parts of the PIS reached concurrent maximum glaciation during the last glacial cycle. The Patagonian Andes is the only landmass involving the southern westerly wind belt latitudinal range, which is thought to have played a key role in past glacial and climate changes. Therefore, reconstructing southern Andes glacier history constitutes a key element for understanding the cause of glaciations in Patagonia and the role of the westerlies in climate change. Here, we discuss paleoglaciological and paleoclimatological implications of new 10Be and 14C data obtained from moraines and strategically selected mires in two contiguous glacially molded basins of south Patagonia (48-55S): Torres del Paine (51S) and Última Esperanza (52S). In this region, we focused our 10Be cosmogenic-dating efforts in the previously undated outer moraines deposited (supposedly) during the last glacial cycle. In order to crosscheck cosmogenic data we collected boulders embedded in moraines and cobbles from the main glaciofluvial plains grading from the outermost moraines. Geomorphic and cosmogenic dating affords evidence for glacial maximum conditions occurring between 40-50 ka (ka = thousand of years before present) in southern Patagonia, which is different from other chronologies within southern South America. We obtained 14C basal ages from sites located within moraine depressions and on former paleolake shorelines and thus these may provide key data on deglaciation and debated regional paleolake history.

  8. Fractionation Of Hydrogen Isotopes During Lipid-Biosynthesis By Tetrahymena thermophila, Dunaliella bardawil and Haloarcula marismortui

    NASA Astrophysics Data System (ADS)

    Dirghangi, S. S.; Pagani, M.

    2008-12-01

    Paleoclimatological research is mainly based on proxies that reflect different climatic variations. Organic compounds preserved in sediments form a very important group of proxies, of which lipids are an important class. Recently, attention has been directed toward understanding the magnitude of hydrogen isotope fractionation that occurs during lipid biosynthesis given its potential as a proxy for understanding changes in the hydrological system. Hydrogen isotope ratios of lipids depend on hydrogen isotopic composition of the ambient water, which in turn is dependent on hydrological conditions. Hydrogen isotope ratios of lipids also depend on the biosynthetic pathway, which causes differences between hydrogen isotope ratios of lipids synthesized by different organisms. The application of lipids derived from multiple source organisms (e.g. fatty acids) are less useful for reconstructing hydrogen isotopic compositions of ambient water, because of the lack of specificity regarding its source. On the other hand, lipids that are synthesized by specific kinds of organisms or lipids that in a specific environment are synthesized by specific kinds of organisms are more useful for reconstructing hydrogen isotopic compositions of the ambient water. For this study, we are investigating the hydrogen isotope fractionation between ambient water and lipids that are derived from specific organisms from hypersaline environments. Specifically, we have grown three organisms that are abundant in saline to hypersaline environments, including Tetrahymena thermophila (Protozoa), Dunaliella bardawil (Alga), and Haloarcula marismortui (Archaea) in pure cultures and are in the process of evaluating isotopic variability of specific lipids (i.e. Tetrahymanol in Tetrahymena, beta-carotene and Stigmasterol in Dunaliella, and archaeol in Haloarcula) and other non-specific fatty acids associated with the D/H composition of ambient water, growth temperature and salinity.

  9. Stable isotope deltas: Tiny, yet robust signatures in nature

    USGS Publications Warehouse

    Brand, Willi A.; Coplen, Tyler B.

    2012-01-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including 14C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. 13C, 2H, and 18O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as−25 per mil can be written as−25 mUr (or−2.5 cUr or−0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg ‘units’ are easily included (e.g. either+0.015 ‰ or+15 per meg

  10. Earth Orbit v2.1: a 3-D visualization and analysis model of Earth's orbit, Milankovitch cycles and insolation

    NASA Astrophysics Data System (ADS)

    Kostadinov, T. S.; Gilb, R.

    2014-06-01

    Milankovitch theory postulates that periodic variability of Earth's orbital elements is a major climate forcing mechanism, causing, for example, the contemporary glacial-interglacial cycles. There are three Milankovitch orbital parameters: orbital eccentricity, precession and obliquity. The interaction of the amplitudes, periods and phases of these parameters controls the spatio-temporal patterns of incoming solar radiation (insolation) and the timing and duration of the seasons. This complexity makes Earth-Sun geometry and Milankovitch theory difficult to teach effectively. Here, we present "Earth Orbit v2.1": an astronomically precise and accurate model that offers 3-D visualizations of Earth's orbital geometry, Milankovitch parameters and the ensuing insolation forcing. The model is developed in MATLAB® as a user-friendly graphical user interface. Users are presented with a choice between the Berger (1978a) and Laskar et al. (2004) astronomical solutions for eccentricity, obliquity and precession. A "demo" mode is also available, which allows the Milankovitch parameters to be varied independently of each other, so that users can isolate the effects of each parameter on orbital geometry, the seasons, and insolation. A 3-D orbital configuration plot, as well as various surface and line plots of insolation and insolation anomalies on various time and space scales are produced. Insolation computations use the model's own orbital geometry with no additional a priori input other than the Milankovitch parameter solutions. Insolation output and the underlying solar declination computation are successfully validated against the results of Laskar et al. (2004) and Meeus (1998), respectively. The model outputs some ancillary parameters as well, e.g., Earth's radius-vector length, solar declination and day length for the chosen date and latitude. Time-series plots of the Milankovitch parameters and several relevant paleoclimatological data sets can be produced. Both

  11. Stable isotope behavior during cave ice formation by water freezing in Scărişoara Ice Cave, Romania

    NASA Astrophysics Data System (ADS)

    PerşOiu, Aurel; Onac, Bogdan P.; Wynn, Jonathan G.; Bojar, Ana-Voica; Holmgren, Karin

    2011-01-01

    Recently, a series of studies have targeted the stable isotopic composition of cave ice as a possible source of paleoclimatic information, but none presented an explanation for the way in which the external climatic signal is transferred to cave ice. While the relation between the stable isotopic composition of precipitation and drip water can be relatively easily determined, a more complex problem arises, i.e., the possible alteration of the primary climatic signal recorded by the oxygen and hydrogen stable isotopes during the freezing of water to form cave ice. Here we report the results of the first detailed investigations of the oxygen and hydrogen stable isotope behavior during the formation of ice in Scărişoara Ice Cave. Samples of ice align on a straight line with a slope lower than 8 in a δ18O-δ2H plot, characteristic for ice formed by the freezing of water. A model is presented for the reconstruction of the initial isotopic composition of water, despite the complexity induced by kinetic effects during early stages of freezing. These results are consistent with ice that forms by the downward freezing of a stagnant pool of water, under kinetic conditions in the initial stages of the process, and isotopic equilibrium thereafter. As ice caves are described in many parts of the world, otherwise poorly represented in ice-based paleoclimatology, the results of this study could open a new direction in paleoclimatic research so that an array of significant paleoclimate data can be developed on the basis of their study.

  12. Climate research in the former Soviet Union. FASAC: Foreign Applied Sciences Assessment Center technical assessment report

    SciTech Connect

    Ellingson, R.G.; Baer, F.; Ellsaesser, H.W.; Harshvardhan; Hoffert, M.I.; Randall, D.A.

    1993-09-01

    This report assesses the state of the art in several areas of climate research in the former Soviet Union. This assessment was performed by a group of six internationally recognized US experts in related fields. The areas chosen for review are: large-scale circulation processes in the atmosphere and oceans; atmospheric radiative processes; cloud formation processes; climate effects of natural atmospheric disturbances; and the carbon cycle, paleoclimates, and general circulation model validation. The study found an active research community in each of the above areas. Overall, the quality of climate research in the former Soviet Union is mixed, although the best Soviet work is as good as the best corresponding work in the West. The best Soviet efforts have principally been in theoretical studies or data analysis. However, an apparent lack of access to modern computing facilities has severely hampered the Soviet research. Most of the issues considered in the Soviet literature are known, and have been discussed in the Western literature, although some extraordinary research in paleoclimatology was noted. Little unusual and exceptionally creative material was found in the other areas during the study period (1985 through 1992). Scientists in the former Soviet Union have closely followed the Western literature and technology. Given their strengths in theoretical and analytical methods, as well as their possession of simplified versions of detailed computer models being used in the West, researchers in the former Soviet Union have the potential to make significant contributions if supercomputers, workstations, and software become available. However, given the current state of the economy in the former Soviet Union, it is not clear that the computer gap will be bridged in the foreseeable future.

  13. IODP Expedition 359: Maldives Monsoon and Sea Level

    NASA Astrophysics Data System (ADS)

    Betzler, Christian; Eberli, Gregor; Zarikian, Carlos

    2016-04-01

    Drilling the carbonate platforms and drifts in the Maldives aimed to recover the marine tropical record of the Neogene sea-level changes and the onset of the monsoon related current system in the Indian Ocean. To reach this goal, eight sites were drilled along two transects in the Kardiva Channel in the Inner Sea of the Maldives during IODP Expedition 359. The recovered cores and log data retrieved the material to achieve all the objectives set for the expedition. The most arresting accomplishment is the documentation of how the sea level controlled the carbonate platform system that was thriving during the Miocene Climate Optimum abruptly transitioned into a current-dominated system in the late Middle Miocene. This transition is linked to the onset of an early intensification of the Indian monsoon and the coeval demise of some of the Maldivian platforms. Cores and downhole logs allowed producing a solid record and reconstructing the Neogene environmental changes in the central Indian Ocean. Preliminary shipboard analyses allow a precise dating of this major paleoclimatological and paleoceanographical changes, as it also applies for the extension of the Oxygen Minimum Zone (OMZ) into this part of the Indian Ocean. Coring produced a solid framework to foster the post-cruise research of these distinct topics. In addition, complete spliced sections and logging at key sites during Expedition 359 provide the potential to assemble a cycle-based astrochronology for the Neogene section in the Maldives. This high-resolution chronology will allow: 1) independent ages to be assigned to key biostratigraphic events in the Maldives for comparison with those from other tropical regions; 2) more precise ages for the major sequence boundaries and unconformities; and 3) evaluation of higher-resolution sedimentation rate variations.

  14. Evaluation of New Geological Reference Materials for U-Series Measurements

    NASA Astrophysics Data System (ADS)

    Denton, J. S.; Goldstein, S. J.; Nunn, A. J.; Ui Chearnaigh, K.; Amato, R.; Murrell, M. T.

    2012-12-01

    Uranium-series analytical measurements are widely used in geochemistry, geochronology, paleoclimatology, volcanology, environmental risk assessment and other fields. Recent advances in high-resolution, rapid, in situ microanalytical techniques e.g. LA-ICP-MS and SIMS present numerous opportunities for the geoanalytical community. As with other analytical techniques, the quality of the elemental concentration and isotopic data obtained through microanalytical techniques is dependent on the accurate characterization of suitable reference materials. Even for the case of fs-laser ablation applications, a range of well-characterized standards are required for high precision U-series work. Advances have been made in evaluating existing standard reference materials for U-series isotopic analysis, but this work is ongoing as more reference materials become available. In this study we present MC-TIMS and MC-ICP-MS results for uranium and thorium isotopic ratios and elemental concentrations measured in a suite of newly available Chinese Geological Standard Glasses (CGSG) designed for microanalysis. These glasses exhibit a range of chemical compositions including basalt, syenite, andesite and a soil. U concentrations for these glasses range from ≈2 to 14 μg/g and [Th]/[U] ratios range from ≈4 to 6. Uranium and thorium concentration and isotopic data will also be presented for rhyolitic obsidian from Macusani, SE Peru, which can be used as a rhyolitic reference material. These high-precision and high-accuracy ratios, from a suite of standards that exhibit a range of natural, non-basaltic compositions, will complement data from existing standards and expand the catalogue of reference materials that are appropriate for in situ U-series work. These results can be used to assess the performance of microanalytical techniques and will facilitate inter-laboratory comparison of data within the broader geoscience community.

  15. Partnering With Scientists To Increase the Visibility and Use of Published Global Climate Change Data

    NASA Astrophysics Data System (ADS)

    Schmidt, L. J.; Scott, M.; Geiger-Wooten, N.; McCaffrey, M. S.; Anderson, D. M.; Eakin, C. M.

    2003-12-01

    Scientific journal articles are notoriously difficult for non-scientists or scientists outside a specialty to comprehend. Yet in societally relevant fields such as global climate change, there is an urgent need to make the published results of scientific research more accessible and useable to a broad audience. NOAA's World Data for Paleoclimatology attempts to meet this need using the Internet to distribute raw data and information products from scientific publications. The Data Center creates "What's New" pages highlighting data from recent publications, along with descriptions and ancillary information such as photographs. The Data Center also authors a "Climate TimeLine", online slide sets and photo gallery, and "Paleo Perspectives" web pages that describe the broader significance of scientific research, and how the data are used to improve our understanding of global warming, drought, and climate change. With the goal to inform and engage, the Climate Time Line provides interactive activities, and information that can be integrated into the classroom. The approach benefits a diverse audience by demystifying climate science and making it more accessible, and benefits scientists by increasing the visibility and use of scientists' published data. The success of the approach can be seen in web site user statistics and comments, and numerous awards for providing valuable information via the Internet. To solve the challenge of simplifying complex scientific problems while maintaining the accuracy and integrity of the scientific information, the World Data Center works closely with scientists who contribute the data. Underlying the effort are the hundreds of scientists who have contributed their data to the World Data Center, and reviewed and edited the online extensions of their research.

  16. Scientific drilling and the evolution of the earth system: climate, biota, biogeochemistry and extreme systems

    NASA Astrophysics Data System (ADS)

    Soreghan, G. S.; Cohen, A. S.

    2013-11-01

    A US National Science Foundation-funded workshop occurred 17-19 May 2013 at the University of Oklahoma to stimulate research using continental scientific drilling to explore earth's sedimentary, paleobiological and biogeochemical record. Participants submitted 3-page "pre-proposals" to highlight projects that envisioned using drill-core studies to address scientific issues in paleobiology, paleoclimatology, stratigraphy and biogeochemistry, and to identify locations where key questions can best be addressed. The workshop was also intended to encourage US scientists to take advantage of the exceptional capacity of unweathered, continuous core records to answer important questions in the history of earth's sedimentary, biogeochemical and paleobiologic systems. Introductory talks on drilling and coring methods, plus best practices in core handling and curation, opened the workshop to enable all to understand the opportunities and challenges presented by scientific drilling. Participants worked in thematic breakout sessions to consider questions to be addressed using drill cores related to glacial-interglacial and icehouse-greenhouse transitions, records of evolutionary events and extinctions, records of major biogeochemical events in the oceans, reorganization of earth's atmosphere, Lagerstätte and exceptional fossil biota, records of vegetation-landscape change, and special sampling requirements, contamination, and coring tool concerns for paleobiology, geochemistry, geochronology, and stratigraphy-sedimentology studies. Closing discussions at the workshop focused on the role drilling can play in studying overarching science questions about the evolution of the earth system. The key theme, holding the most impact in terms of societal relevance, is understanding how climate transitions have driven biotic change, and the role of pristine, stratigraphically continuous cores in advancing our understanding of this linkage. Scientific drilling, and particularly drilling

  17. Ontology Design Patterns: Bridging the Gap Between Local Semantic Use Cases and Large-Scale, Long-Term Data Integration

    NASA Astrophysics Data System (ADS)

    Shepherd, Adam; Arko, Robert; Krisnadhi, Adila; Hitzler, Pascal; Janowicz, Krzysztof; Chandler, Cyndy; Narock, Tom; Cheatham, Michelle; Schildhauer, Mark; Jones, Matt; Raymond, Lisa; Mickle, Audrey; Finin, Tim; Fils, Doug; Carbotte, Suzanne; Lehnert, Kerstin

    2015-04-01

    Integrating datasets for new use cases is one of the common drivers for adopting semantic web technologies. Even though linked data principles enables this type of activity over time, the task of reconciling new ontological commitments for newer use cases can be daunting. This situation was faced by the Biological and Chemical Oceanography Data Management Office (BCO-DMO) as it sought to integrate its existing linked data with other data repositories to address newer scientific use cases as a partner in the GeoLink Project. To achieve a successful integration with other GeoLink partners, BCO-DMO's metadata would need to be described using the new ontologies developed by the GeoLink partners - a situation that could impact semantic inferencing, pre-existing software and external users of BCO-DMO's linked data. This presentation describes the process of how GeoLink is bridging the gap between local, pre-existing ontologies to achieve scientific metadata integration for all its partners through the use of ontology design patterns. GeoLink, an NSF EarthCube Building Block, brings together experts from the geosciences, computer science, and library science in an effort to improve discovery and reuse of data and knowledge. Its participating repositories include content from field expeditions, laboratory analyses, journal publications, conference presentations, theses/reports, and funding awards that span scientific studies from marine geology to marine ecology and biogeochemistry to paleoclimatology. GeoLink's outcomes include a set of reusable ontology design patterns (ODPs) that describe core geoscience concepts, a network of Linked Data published by participating repositories using those ODPs, and tools to facilitate discovery of related content in multiple repositories.

  18. Chronostratigraphy of Monte Vulture volcano (southern Italy): secondary mineral microtextures and 39Ar-40Ar systematics

    NASA Astrophysics Data System (ADS)

    Villa, Igor M.; Buettner, Annett

    2009-12-01

    The eruptive history of Monte Vulture has been the subject of several geochronological investigations during the past decades, which reliably dated only a small number of eruptions. Understanding the causes of sub-optimum data yield in the past requires an interdisciplinary approach. We re-analyzed samples from previous works and present new data on samples from the main volcano-stratigraphic units of Monte Vulture, so as to provide an improved, consistent chronostratigraphic database. Imaging of minerals by cathodoluminescence and backscattered electrons reveals that heterochemical, high-temperature deuteric reaction textures are ubiquitous. Such observations are common in metamorphic rocks but had not frequently been reported from volcanic rocks. In view of the mineralogical complexity, we base our chronological interpretation on isochemical steps, defined as steps for which the Cl/K and/or the Ca/K ratios are constant. Isochemical steps carry the isotopic signature of chemically homogeneous mineral phases and therefore allow a well-constrained age interpretation. Comparison of old and new 39Ar-40Ar data proves the reproducibility of age spectra and their shapes. This quantifies the analytical reliability of the irradiation and mass-spectrometric analyses. Anomalous age spectra are a reproducible property of some specific samples and correlate with mineralogical anomalies. The present data allow us to fine-tune the age of the volcanostratigraphic units of Monte Vulture during the known interval of main volcanic activity from ca. 740 to 610 ka. After a very long stasis, the volcanic activity in the Monte Vulture area resumed with diatremic eruptions, one of which (Lago Piccolo di Monticchio, the site of a palynological-paleoclimatological drilling) was dated at ca. 140 ka.

  19. High Arctic Forests During the Middle Eocene Supported by ~400 ppm Atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Maxbauer, D. P.; Royer, D. L.; LePage, B. A.

    2013-12-01

    Fossils from Paleogene High Arctic deposits provide some of the clearest evidence for greenhouse climates and offer the potential to improve our understanding of Earth system dynamics in a largely ice-free world. One of the most well-known and exquisitely-preserved middle Eocene (47.9-37.8 Myrs ago) polar forest sites, Napartulik, crops out on eastern Axel Heiberg Island (80 °N), Nunavut, Canada. An abundance of data from Napartulik suggest mean annual temperatures of up to 30 °C warmer than today and atmospheric water loads 2× above current levels. Despite this wealth of paleontological and paleoclimatological data, there are currently no direct constraints on atmospheric CO2 levels for Napartulik or any other polar forest site. Here we apply a new plant gas-exchange model to Metasequoia (dawn redwood) leaves to reconstruct atmospheric CO2 from six fossil forests at Napartulik. Individual reconstructions vary between 405-489 ppm with a site mean of 437 ppm (337-564 ppm at 95% confidence). These estimates represent the first direct constraints on CO2 for polar fossil forests and suggest that the temperate conditions present at Napartulik during the middle Eocene were maintained under CO2 concentrations ~1.6× above pre-industrial levels. Our results strongly support the case that long-term climate sensitivity to CO2 in the past was sometimes high, even during largely ice-free periods, highlighting the need to better understand the climate forcing and feedback mechanisms responsible for this amplification.

  20. Recovering Paleo-Records from Antarctic Ice-Cores by Coupling a Continuous Melting Device and Fast Ion Chromatography.

    PubMed

    Severi, Mirko; Becagli, Silvia; Traversi, Rita; Udisti, Roberto

    2015-11-17

    Recently, the increasing interest in the understanding of global climatic changes and on natural processes related to climate yielded the development and improvement of new analytical methods for the analysis of environmental samples. The determination of trace chemical species is a useful tool in paleoclimatology, and the techniques for the analysis of ice cores have evolved during the past few years from laborious measurements on discrete samples to continuous techniques allowing higher temporal resolution, higher sensitivity and, above all, higher throughput. Two fast ion chromatographic (FIC) methods are presented. The first method was able to measure Cl(-), NO3(-) and SO4(2-) in a melter-based continuous flow system separating the three analytes in just 1 min. The second method (called Ultra-FIC) was able to perform a single chromatographic analysis in just 30 s and the resulting sampling resolution was 1.0 cm with a typical melting rate of 4.0 cm min(-1). Both methods combine the accuracy, precision, and low detection limits of ion chromatography with the enhanced speed and high depth resolution of continuous melting systems. Both methods have been tested and validated with the analysis of several hundred meters of different ice cores. In particular, the Ultra-FIC method was used to reconstruct the high-resolution SO4(2-) profile of the last 10,000 years for the EDML ice core, allowing the counting of the annual layers, which represents a key point in dating these kind of natural archives. PMID:26494022

  1. EarthCube GeoLink: Semantics and Linked Data for the Geosciences

    NASA Astrophysics Data System (ADS)

    Arko, R. A.; Carbotte, S. M.; Chandler, C. L.; Cheatham, M.; Fils, D.; Hitzler, P.; Janowicz, K.; Ji, P.; Jones, M. B.; Krisnadhi, A.; Lehnert, K. A.; Mickle, A.; Narock, T.; O'Brien, M.; Raymond, L. M.; Schildhauer, M.; Shepherd, A.; Wiebe, P. H.

    2015-12-01

    The NSF EarthCube initiative is building next-generation cyberinfrastructure to aid geoscientists in collecting, accessing, analyzing, sharing, and visualizing their data and knowledge. The EarthCube GeoLink Building Block project focuses on a specific set of software protocols and vocabularies, often characterized as the Semantic Web and "Linked Data", to publish data online in a way that is easily discoverable, accessible, and interoperable. GeoLink brings together specialists from the computer science, geoscience, and library science domains, and includes data from a network of NSF-funded repositories that support scientific studies in marine geology, marine ecosystems, biogeochemistry, and paleoclimatology. We are working collaboratively with closely-related Building Block projects including EarthCollab and CINERGI, and solicit feedback from RCN projects including Cyberinfrastructure for Paleogeosciences (C4P) and iSamples. GeoLink has developed a modular ontology that describes essential geoscience research concepts; published data from seven collections (to date) on the Web as geospatially-enabled Linked Data using this ontology; matched and mapped data between collections using shared identifiers for investigators, repositories, datasets, funding awards, platforms, research cruises, physical specimens, and gazetteer features; and aggregated the results in a shared knowledgebase that can be queried via a standard SPARQL endpoint. Client applications have been built around the knowledgebase, including a Web/map-based data browser using the Leaflet JavaScript library and a simple query service using the OpenSearch format. Future development will include extending and refining the GeoLink ontology, adding content from additional repositories, developing semi-automated algorithms to enhance metadata, and further work on client applications.

  2. Modelling stable water isotopes during "high-precipitation" events at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Schlosser, Elisabeth; Masson-Delmotte, Valérie; Risi, Camille; Stenni, Barbara; Valt, Mauro; Powers, Jordan G.; Manning, Kevin W.; Duda, Michael G.; Cagnati, Anselmo

    2014-05-01

    For a correct paleoclimatologic interpretation of stable water isotopes from ice cores both pre- and post-depositional processes and their role for isotope fractionation have to be better understood. Our study focusses on "pre-depositional processes", namely the atmospheric processes that determine moisture transport and precipitation formation. At the deep ice core drilling site "Dome C", East Antarctica, fresh snow samples have been taken since 2006. These samples have been analysed crystallographically, which enables us to clearly distinguish between blowing snow, diamond dust, and "synoptic precipitation". Also the stable oxygen/hydrogen isotope ratios of the snow samples were measured, including measurements of 17-O. This is the first and only multi-year fresh-snow data series from an Antarctic deep drilling site. The Antarctic Mesoscale Prediction System (AMPS) employs Polar WRF for aviation weather forecasts in Antarctica. The data are archived and can be used for scientific purposes. The mesoscale atmospheric model was adapted especially for polar regions. The horizontal resolution for the domain that covers the Antarctic continent is 10 km. It was shown that precipitation at Dome C is temporally dominated by diamond dust. However, comparatively large amounts of precipitation are observed during several "high-precipitation" events per year, caused by synoptic activity in the circumpolar trough and related advection of relatively warm and moist air from lower latitudes to the interior of Antarctica. AMPS archive data are used to investigate the synoptic situations that lead to "high-precipitation" events at Dome C; in particular, possible moisture sources are determined using back-trajectories. With this meteorological information, the isotope ratios are calculated using two different isotope models, the Mixed Cloud Isotope Model, a simple Rayleigh-type model, and the LMDZ-iso (Laboratoire de Météorologie Dynamic Zoom), a General Circulation Model (GCM

  3. Distinguishing seawater from geologic brine in saline coastal groundwater using radium-226; an example from the Sabkha of the UAE

    USGS Publications Warehouse

    Kraemer, Thomas F.; Wood, Warren W.; Sanford, Ward E.

    2014-01-01

    Sabkhat (Salt flats) are common geographic features of low-lying marine coastal areas that develop under hyper-arid climatic conditions. They are characterized by the presence of highly concentrated saline solutions and evaporitic minerals, and have been cited in the geologic literature as present-day representations of hyper-arid regional paleohydrogeology, paleoclimatology, coastal processes, and sedimentation in the geologic record. It is therefore important that a correct understanding of the origin and development of these features be achieved. Knowledge of the source of solutes is an important first step in understanding these features. Historically, two theories have been advanced as to the main source of solutes in sabkha brines: an early concept entailing seawater as the obvious source, and a more recent and dynamic theory involving ascending geologic brine forced upward into the base of the sabkha by a regional hydraulic gradient in the underlying formations. Ra-226 could uniquely distinguish between these sources under certain circumstances, as it is typically present at elevated activity of hundreds to thousands of Bq/m3 (Becquerels per cubic meter) in subsurface formation brines; at exceedingly low activities in open ocean and coastal water; and not significantly supplied to water from recently formed marine sedimentary framework material. The coastal marine sabkha of the Emirate of Abu Dhabi was used to test this hypothesis. The distribution of Ra-226 in 70 samples of sabkha brine (mean: 700 Bq/m3), 7 samples of underlying deeper formation brine (mean: 3416 Bq/m3), the estimated value of seawater (< 16 Bq/m3) and an estimate of supply from sabkha sedimentary framework grains (<~6 Bq/m3) provide the first direct evidence that ascending geologic brine contributes significantly to the solutes of this sabkha system.

  4. Application of Laser Induced Breakdown Spectroscopy under Polar Conditions

    NASA Astrophysics Data System (ADS)

    Clausen, J. L.; Hark, R.; Bol'shakov, A.; Plumer, J.

    2015-12-01

    Over the past decade our research team has evaluated the use of commercial-off-the-shelf laser-induced breakdown spectroscopy (LIBS) for chemical analysis of snow and ice samples under polar conditions. One avenue of research explored LIBS suitability as a detector of paleo-climate proxy indicators (Ca, K, Mg, and Na) in ice as it relates to atmospheric circulation. LIBS results revealed detection of peaks for C and N, consistent with the presence of organic material, as well as major ions (Ca, K, Mg, and Na) and trace metals (Al, Cu, Fe, Mn, Ti). The detection of Ca, K, Mg, and Na confirmed that LIBS has sufficient sensitivity to be used as a tool for characterization of paleo-climate proxy indicators in ice-core samples. Techniques were developed for direct analysis of ice as well as indirect measurements of ice via melting and filtering. Pitfalls and issues of direct ice analysis using several cooling techniques to maintain ice integrity will be discussed. In addition, a new technique, laser ablation molecular isotopic spectroscopy (LAMIS) was applied to detection of hydrogen and oxygen isotopes in ice as isotopic analysis of ice is the main tool in paleoclimatology and glaciology studies. Our results demonstrated that spectra of hydroxyl isotopologues 16OH, 18OH, and 16OD can be recorded with a compact spectrograph to determine hydrogen and oxygen isotopes simultaneously. Quantitative isotopic calibration for ice analysis can be accomplished using multivariate chemometric regression as previously realized for water vapor. Analysis with LIBS and LAMIS required no special sample preparation and was about ten times faster than analysis using ICP-MS. Combination of the two techniques in one portable instrument for in-field analysis appears possible and would eliminate the logistical and cost issues associated with ice core management.

  5. Stable isotope deltas: tiny, yet robust signatures in nature.

    PubMed

    Brand, Willi A; Coplen, Tyler B

    2012-09-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including (14)C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. (13)C, (2)H, and (18)O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as-25 per mil can be written as-25 mUr (or-2.5 cUr or-0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg 'units' are easily included (e.g. either+0.015 ‰ or+15 per meg

  6. A varved lake sediment record from Finland: between the North Atlantic Oscillation and Siberian High Pressure Cell

    NASA Astrophysics Data System (ADS)

    Saarni, Saija; Saarinen, Timo

    2015-04-01

    Varved lake sediments are widely used for paleoclimatological and paleoenvironmental studies. The advantages of such records are precise time control, which enables high resolution studies of even seasonal scale, and the length of the records extending potentially beyond thousands of years. The clastic organic varved sediments from a small boreal Lake Kalliojärvi (area 0.15 km2, maximum depth 12 m) in Central Finland, record environmental change and snow accumulation history for more than two thousand years. The high quality sediments of the Lake Kalliojärvi are laminated until the present day and reflect the annual circulation of boreal zone. A single varve year consists of two laminae that are composed of i) minerogenic clasts and ii) amorphous organic matter and microfossils. Total varve thickness was measured, and the accumulation of minerogenic and organic matter were analyzed using digital image analysis. The major element composition of the lake sediments was also determined using micro X-ray fluorescence (µ-XRF). The clastic laminae are interpreted as a proxy for catchment erosion, reflecting spring floods triggered by snow melt. Qualitative comparison of minerogenic matter accumulation and reconstructed North Atlantic Oscillation (NAO) phases reveal correspondence between the two records. Positive NAO conditions occur simultaneously with increased minerogenic lamina thicknesses which suggest that the changes in snow accumulation are induced by NAO. However, there are indications that the strong Siberian High Pressure Cell (SHPC) prevailing on eastern Scandinavia may be important for Scandinavian climate via blocking the westerly winds. Strong SHCP potentially leads to colder winter temperatures in Finland and increased ice formation. Stronger and prolonged ice cover in lake environments cause prolonged water column stratification and increased oxygen deficiency which is related to an increased Fe/Mn ratio. This study discusses the importance of NAO and

  7. Effects of dating errors on nonparametric trend analyses of speleothem time series

    NASA Astrophysics Data System (ADS)

    Mudelsee, M.; Fohlmeister, J.; Scholz, D.

    2012-10-01

    A fundamental problem in paleoclimatology is to take fully into account the various error sources when examining proxy records with quantitative methods of statistical time series analysis. Records from dated climate archives such as speleothems add extra uncertainty from the age determination to the other sources that consist in measurement and proxy errors. This paper examines three stalagmite time series of oxygen isotopic composition (δ18O) from two caves in western Germany, the series AH-1 from the Atta Cave and the series Bu1 and Bu4 from the Bunker Cave. These records carry regional information about past changes in winter precipitation and temperature. U/Th and radiocarbon dating reveals that they cover the later part of the Holocene, the past 8.6 thousand years (ka). We analyse centennial- to millennial-scale climate trends by means of nonparametric Gasser-Müller kernel regression. Error bands around fitted trend curves are determined by combining (1) block bootstrap resampling to preserve noise properties (shape, autocorrelation) of the δ18O residuals and (2) timescale simulations (models StalAge and iscam). The timescale error influences on centennial- to millennial-scale trend estimation are not excessively large. We find a "mid-Holocene climate double-swing", from warm to cold to warm winter conditions (6.5 ka to 6.0 ka to 5.1 ka), with warm-cold amplitudes of around 0.5‰ δ18O; this finding is documented by all three records with high confidence. We also quantify the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the current warmth. Our analyses cannot unequivocally support the conclusion that current regional winter climate is warmer than that during the MWP.

  8. Effects of dating errors on nonparametric trend analyses of speleothem time series

    NASA Astrophysics Data System (ADS)

    Mudelsee, M.; Fohlmeister, J.; Scholz, D.

    2012-05-01

    A fundamental problem in paleoclimatology is to take fully into account the various error sources when examining proxy records with quantitative methods of statistical time series analysis. Records from dated climate archives such as speleothems add extra uncertainty from the age determination to the other sources that consist in measurement and proxy errors. This paper examines three stalagmite time series of oxygen isotopic composition (δ18O) from two caves in Western Germany, the series AH-1 from the Atta cave and the series Bu1 and Bu4 from the Bunker cave. These records carry regional information about past changes in winter precipitation and temperature. U/Th and radiocarbon dating reveals that they cover the later part of the Holocene, the past 8.6 thousand years (ka). We analyse centennial- to millennial-scale climate trends by means of nonparametric Gasser-Müller kernel regression. Error bands around fitted trend curves are determined by combining (1) block bootstrap resampling to preserve noise properties (shape, autocorrelation) of the δ18O residuals and (2) timescale simulations (models StalAge and iscam). The timescale error influences on centennial- to millennial-scale trend estimation are not excessively large. We find a "mid-Holocene climate double-swing", from warm to cold to warm winter conditions (6.5 ka to 6.0 ka to 5.1 ka), with warm-cold amplitudes of around 0.5‰ δ18O; this finding is documented by all three records with high confidence. We also quantify the Medieval Warm Period (MWP), the Little Ice Age (LIA) and the current warmth. Our analyses cannot unequivocally support the conclusion that current regional winter climate is warmer than that during the MWP.

  9. PaleoGeo: a Web based GIS database for paleoenvironmental studies

    NASA Astrophysics Data System (ADS)

    Song, Wonsuh; Kondo, Yasuhisa; Oguchi, Takashi

    2014-05-01

    Paleoenvironmental studies cover various fields such as paleohydrology, geomorphology, paleooceanology, paleobiology, paleoclimatology, and chronology. It is difficult for an individual researcher to collect and compile enormous data regarding these fields. We have been compiling portal data and presenting them using a web-based geographical information system (Web-GIS) called PaleoGeo for the multidisciplinary project 'Replacement of Neanderthals by Modern Humans'. The aim of the project is to reconstruct the distribution of Neanderthals and modern humans in time and space in relation to past climate change. We have been collecting information from almost three thousand articles of 13 journals regarding paleoenvironmental research (i.e., Boreas, Catena, Climatic Change, Earth Surface Processes and Landforms, Geomorphology, Journal of Quaternary Science, Palaeogeography, Palaeoclimatology, and Palaeoecology, Quaternary International, Quaternary Research, Quaternary Science Reviews, The Holocene, and The Journal of Geology). The topics of the articles were classified into six themes (paleohydrology, earth surface processes and materials, paleooceanology, paleobiology, palaeoclimatology, and chronology) and 19 subthemes (hydrology, flood, fluvial, glacier, fluvial/glacier, sedimentology, soil, slope process, periglacial, peat land, eolian, sea-level, biology, vegetation, zoology, vegetation/zoology, archaeology, climate, atmosphere, and chronology). The collected data consist of the journal name, information about each paper (authors, title, volume, year, and page numbers), site location (country name, longitude, and latitude), theme, subtheme, keywords, DOI (Digital Object Identifier), and period (era). Location data are indispensable for paleoenvironmental studies. The PaleoGeo shows information with a map, which is an advantage of this database system. However, the number of the paleoenvironmental studies is growing rapidly and we have to effectively cover them as

  10. Geochemical Approach to Archaeal Ecology: δ13C of GDGTs

    NASA Astrophysics Data System (ADS)

    Lichtin, S.; Warren, C.; Pearson, A.; Pagani, M.

    2015-12-01

    Over the last decade and a half, glycerol dialkyl glycerol tetraethers (GDGTs) have increasingly been used to reconstruct environmental temperatures; proxies like TEX86 that correlate the relative abundance of these archaeal cell membrane lipids to sea surface temperature are omnipresent in paleoclimatology literature. While it has become common to make claims about past temperatures using GDGTs, our present understanding of the organisms that synthesize the compounds is still quite limited. The generally accepted theory states that microorganisms like the Thaumarchaeota modify the structure of membrane lipids to increase intermolecular interactions, strengthening the membrane at higher temperatures. Yet to date, culture experiments have been largely restricted to a single species, Nitrosopumilus maritimes, and recent studies on oceanic archaeal rRNA have revealed that these biomarkers are produced in diverse, heterogeneous, and site-specific communities. This brings up questions as to whether different subclasses of GDGTs, and all subsequent proxies, represent adaptation within a single organismal group or a shift in community composition. To investigate whether GDGTs with different chain structures, from the simple isoprenoidal GDGT-0 to Crenarchaeol with its many cyclopentane groups, are sourced from archaea with similar or disparate metabolic pathways—and if that information is inherited in GDGTs trapped in marine sediments—this study examines the stable carbon isotope values (δ13C) of GDGTs extracted from the uppermost meters of sediment in the Orca Basin, Gulf of Mexico, using spooling-wire microcombustion isotope-ratio mass spectrometer (SWiM-IRMS), tackling a fundamental assumption of the TEX86 proxy that influences the way we perceive the veracity of existing temperature records.

  11. Precise determination of U isotopic compositions in low concentration carbonate samples by MC-ICP-MS.

    PubMed

    Wang, Ruo-Mei; You, Chen-Feng

    2013-03-30

    We developed a fast and simple analytical procedure for precise determination of U isotopic compositions in low concentration natural samples. The main advantage of the new method is that it requires only 12ng U and can obtain all U isotopic ratios without using spike. Five carbonate reference materials (JCp-1, RKM-4, RKM-5, GBW04412 and GBW04413) and 3 international standards with different matrices (IAPSO, IRMM-3184 and CRM-U010) were analyzed for ((234)U/(238)U) and (238)U/(235)U ratios by MC-ICPMS. Using our method, the results for these standards are in close agreement with the certified values, 1.144 ± 0.004, 0.966 ± 0.004 and 0.990 ± 0.003 for ((234)U/(238)U) and 137.72 ± 0.13, 137.64 ± 0.15 and 98.63 ± 0.04 for (238)U/(235)U, in IAPSO, IRMM-3184 and CRM-U010, respectively. The long-term reproducibility of ((234)U/(238)U) and (238)U/(235)U is 0.970 ± 0.002 and 137.56 ± 0.09; 1.144 ± 0.004 and 137.72 ± 0.13, respectively, for in-house U solution and IAPSO. The new ((234)U/(238)U) results for carbonates show much better precision than previous studies and also reflect their age variability. The obtained (238)U/(235)U ratios, representing the first measurements in these carbonate specimens, are rather constant. The method described here requires only 12 ng of U for analysis and can be completed in 5.2 min. The approach provides a fast method to measure ((234)U/(238)U) and (238)U/(235)U ratios in sample matrices commonly encountered in studies of chemical weathering, oceanography and paleoclimatology. PMID:23598194

  12. The faint young Sun problem

    NASA Astrophysics Data System (ADS)

    Feulner, Georg

    2012-05-01

    For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the “faint young Sun problem.” For the early Earth, models of stellar evolution predict a solar energy input to the climate system that is about 25% lower than today. This would result in a completely frozen world over the first 2 billion years in the history of our planet if all other parameters controlling Earth's climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane, or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved. Here I review research on the subject, including the latest suggestions for solutions of the faint young Sun problem and recent geochemical constraints on the composition of Earth's early atmosphere. Furthermore, I will outline the most promising directions for future research. In particular I would argue that both improved geochemical constraints on the state of the Archean climate system and numerical experiments with state-of-the-art climate models are required to finally assess what kept the oceans on the Archean Earth from freezing over completely.

  13. Climate Inferences from Geothermal Measurements in South America

    NASA Astrophysics Data System (ADS)

    Gurza Fausto, E.; Harris, R. N.; Montenegro, A.; Tassara, A.; Beltrami, H.

    2014-12-01

    Analysis of borehole temperature data have contributed significantly to estimating the last millennium surface temperature changes. Additionally, recent analysis have contributed to evaluate the Earth's energy balance by providing a quantitative value for the energy absorbed by the continents in the later part of the 20th century. Knowledge of the surface energy flux is important for understanding the solid Earth - atmosphere boundary condition, land cover changes, and their impact on regional and global climate models. We present data and analysis of 19 borehole temperature versus depth profiles from South America. The dataset includes 10 new borehole logs measured during 2012 at three sites in northern Chile (Vallenar, Sierra Gorda and Sierra Limon Verde). These new measurements complement six temperature logs measured during 1994 in the same region (sites near Michilla and Sierra Limon Verde; Springer et al., Tectonophysics, 1998) and four logs obtained from the NOAA Paleoclimatology Borehole Database located in Villa Staff, Toquepala and Talara in Peru. These data were analyzed for climate variability signals of the surface temperature and changes in the Earth's surface energy balance. The analysis suggests a cooling trend during the 19th century of approximately -0.5ºK. Furthermore, results show regionalized temperature changes in ground surface temperatures during the last 50 years with estimates of -0.4ºK in Vallenar, and approximately +1ºK in the Atacama Desert of Northern Chile. We place the results within the context of surface air temperature yearly means obtained from existing meteorological and proxy paleoclimatic data between Peru and Northern Chile. The use of geothermal measurements for climate variability studies provides a further understanding of the climatic and energy cycles of the Southern Hemisphere, where meteorological data can be scarce to non-existent.

  14. Treating pre-instrumental data as "missing" data: using a tree-ring-based paleoclimate record and imputations to reconstruct streamflow in the Missouri River Basin

    NASA Astrophysics Data System (ADS)

    Ho, M. W.; Lall, U.; Cook, E. R.

    2015-12-01

    Advances in paleoclimatology in the past few decades have provided opportunities to expand the temporal perspective of the hydrological and climatological variability across the world. The North American region is particularly fortunate in this respect where a relatively dense network of high resolution paleoclimate proxy records have been assembled. One such network is the annually-resolved Living Blended Drought Atlas (LBDA): a paleoclimate reconstruction of the Palmer Drought Severity Index (PDSI) that covers North America on a 0.5° × 0.5° grid based on tree-ring chronologies. However, the use of the LBDA to assess North American streamflow variability requires a model by which streamflow may be reconstructed. Paleoclimate reconstructions have typically used models that first seek to quantify the relationship between the paleoclimate variable and the environmental variable of interest before extrapolating the relationship back in time. In contrast, the pre-instrumental streamflow is here considered as "missing" data. A method of imputing the "missing" streamflow data, prior to the instrumental record, is applied through multiple imputation using chained equations for streamflow in the Missouri River Basin. In this method, the distribution of the instrumental streamflow and LBDA is used to estimate sets of plausible values for the "missing" streamflow data resulting in a ~600 year-long streamflow reconstruction. Past research into external climate forcings, oceanic-atmospheric variability and its teleconnections, and assessments of rare multi-centennial instrumental records demonstrate that large temporal oscillations in hydrological conditions are unlikely to be captured in most instrumental records. The reconstruction of multi-centennial records of streamflow will enable comprehensive assessments of current and future water resource infrastructure and operations under the existing scope of natural climate variability.

  15. European climate reconstructed for the past 500 years based on documentary and instrumental evidence

    NASA Astrophysics Data System (ADS)

    Wheeler, Dennis; Brazdil, Rudolf; Pfister, Christian

    2010-05-01

    European climate reconstructed for the past 500 years based on documentary and instrumental evidence Dennis Wheeler, Rudolf Brázdil, Christian Pfister and the Millennium project SG1 team The paper summarises the results of historical-climatological research conducted as part of the EU-funded 6th FP project MILLENNIUM the principal focus of which was the investigation of European climate during the past one thousand years (http://www.millenniumproject.net/). This project represents a major advance in bringing together, for the first time on such a scale, historical climatologists with other palaeoclimatological communities and climate modellers from many European countries. As part of MILLENNIUM, a sub-group (SG1) of historical climatologists from ten countries had the responsibility of collating and comprehensively analysing evidence from instrumental and documentary archives. This paper presents the main results of this undertaking but confines its attention to the study of the climate of the past 500 years and represents a summary of 10 themed papers submitted for a special issue of Climatic Change. They range across a variety of topics including newly-studied documentary data sources (e.g. early instrumental records, opening of the Stockholm harbour, ship log book data), temperature reconstructions for Central Europe, the Stockholm area and Mediterranean based on different types of documentary evidence, the application of standard paleoclimatological approaches to reconstructions based on index series derived from the documentary data, the influence of circulation dynamics on January-April climate , a comparison of reconstructions based on documentary data with the model runs (ECHO-G), a study of the quality of instrumental data in climate reconstructions, a 500-year flood chronology in Europe, and selected disastrous European windstorms and their reflection in documentary evidence and human memory. Finally, perspectives of historical-climatological research

  16. Can a paleodrought record be used to reconstruct streamflow?: A case study for the Missouri River Basin

    NASA Astrophysics Data System (ADS)

    Ho, Michelle; Lall, Upmanu; Cook, Edward R.

    2016-07-01

    Recent advances in paleoclimatology have revealed dramatic long-term hydroclimatic variations that provide a context for limited historical records. A notable data set derived from a relatively dense network of paleoclimate proxy records in North America is the Living Blended Drought Atlas (LBDA): a gridded tree-ring-based reconstruction of summer Palmer Drought Severity Index. This index has been used to assess North American drought frequency, persistence, and spatial extent over the past two millennia. Here, we explore whether the LBDA can be used to reconstruct annual streamflow. Relative to streamflow reconstructions that use tree rings within the river basin of interest, the use of a gridded proxy poses a novel challenge. The gridded series have high spatial correlation, since they rely on tree rings over a common radius of influence. A novel algorithm for reconstructing streamflow using regularized canonical regression and inputs of local and global covariates is developed and applied over the Missouri River Basin, as a test case. Effectiveness in reconstruction is demonstrated with reconstructions showing periods where streamflow deficits may have been more severe than during recent droughts (e.g., the Civil War, Dust Bowl, and 1950s droughts). The maximum persistence of droughts and floods over the past 500 years far exceeds those observed in the instrumental record and periods of multidecadal variability in the 1500s and 1600s are detected. Challenges for an extension to a national streamflow reconstruction or applications using other gridded paleoclimate data sets such as adequate spatial coverage of streamflow and applicability of annual reconstructions are discussed.

  17. Evidence for Global Biogeochemical Changes During the Toarcian Oceanic Anoxic Event

    NASA Astrophysics Data System (ADS)

    Them, T. R., II; Gill, B. C.; Gröcke, D. R.; Selby, D. S.; Martindale, R. C.; Caruthers, A. H.; Tulsky, E. T. T.

    2015-12-01

    The global versus regional nature of the Toarcian Oceanic Anoxic Event (T-OAE; ~183 million years ago) has been heavily debated over the course of the last decade. Several lines of geochemical evidence support a significant perturbation to the carbon cycle and redox-sensitive elemental cycles across this interval. It is thought that these represent feedbacks to the emplacement of the Karoo-Ferrar large igneous province. These include: elevated atmospheric pCO2, an enhanced greenhouse effect and hydrologic cycle leading to increased weathering rates, dissociation of biogenic methane clathrates, and widespread ocean anoxia. Despite evidence for these global phenomena, the overwhelming majority of stratigraphic successions studied are located in Europe. The global magnitude of these biogeochemical perturbations has been challenged, with some considering that this event was regional to Europe, and others suggesting that the carbon isotope excursion (CIE) itself is not a reliable stratigraphic marker. In order to test these competing hypotheses, we have generated a geochemical dataset to reconstruct paleoceanographic and paleoclimatological changes across the T-OAE from western North America. The Toarcian strata in western Alberta consist primarily of organic-rich calcareous siltstones and shales. These deposits represent ideal sedimentary facies to reconstruct environmental changes through the use of geochemical proxy data, especially those that use redox-sensitive transition metals. Ammonite biostratigraphy suggests a nearly continuous sequence from the late Pliensbachian to middle Toarcian. The organic carbon isotopes show the prominent negative CIE interpreted to relate to the release of isotopically depleted carbon at the onset of the T-OAE. Pyrite sulfur weight percentages increase across the CIE and remain elevated, and iron speciation data suggest the development of anoxic conditions. Initial osmium isotope compositions become more radiogenic during the CIE

  18. Trends and Correlation Estimation in Climate Sciences: Effects of Timescale Errors

    NASA Astrophysics Data System (ADS)

    Mudelsee, M.; Bermejo, M. A.; Bickert, T.; Chirila, D.; Fohlmeister, J.; Köhler, P.; Lohmann, G.; Olafsdottir, K.; Scholz, D.

    2012-12-01

    Trend describes time-dependence in the first moment of a stochastic process, and correlation measures the linear relation between two random variables. Accurately estimating the trend and correlation, including uncertainties, from climate time series data in the uni- and bivariate domain, respectively, allows first-order insights into the geophysical process that generated the data. Timescale errors, ubiquitious in paleoclimatology, where archives are sampled for proxy measurements and dated, poses a problem to the estimation. Statistical science and the various applied research fields, including geophysics, have almost completely ignored this problem due to its theoretical almost-intractability. However, computational adaptations or replacements of traditional error formulas have become technically feasible. This contribution gives a short overview of such an adaptation package, bootstrap resampling combined with parametric timescale simulation. We study linear regression, parametric change-point models and nonparametric smoothing for trend estimation. We introduce pairwise-moving block bootstrap resampling for correlation estimation. Both methods share robustness against autocorrelation and non-Gaussian distributional shape. We shortly touch computing-intensive calibration of bootstrap confidence intervals and consider options to parallelize the related computer code. Following examples serve not only to illustrate the methods but tell own climate stories: (1) the search for climate drivers of the Agulhas Current on recent timescales, (2) the comparison of three stalagmite-based proxy series of regional, western German climate over the later part of the Holocene, and (3) trends and transitions in benthic oxygen isotope time series from the Cenozoic. Financial support by Deutsche Forschungsgemeinschaft (FOR 668, FOR 1070, MU 1595/4-1) and the European Commission (MC ITN 238512, MC ITN 289447) is acknowledged.

  19. Reconstructing a mid-Cretaceous landscape from paleosols in western Canada

    USGS Publications Warehouse

    Ufnar, David F.; Gonzalez, Luis A.; Ludvigson, Greg A.; Brenner, Richard L.; Witzke, B.J.; Leckie, D.

    2005-01-01

    The Albian Stage of the mid-Cretaceous was a time of equable climate conditions with high sea levels and broad shallow epeiric seas that may have had a moderating affect on continental climates. A Late Albian landscape surface that developed during a regression and subsequent sea-level rise in the Western Canada Foreland Basin is reconstructed on the basis of correlation of paleosols penetrated by cores through the Paddy Member of the Peace River Formation. Reconstruction of this landscape refines chronostratigraphic relationships and will benefit future paleoclimatological studies milizing continental sphaerosiderite proxy records. The paleosols developed in estuarine sandstones and mudstones, and they exhibit evidence of a polygenetic history. Upon initial exposure and pedogenesis, the Paddy Member developed deeply weathered, well-drained cumulative soil profiles. Later stages of pedogenesis were characterized by hydromorphic soil conditions. The stages of soil development interpreted for the Paddy Member correlate with inferred stages of pedogenic development in time-equivalent formations located both basinward and downslope (upper Viking Formation), and landward and upslope (Boulder Creek Formation). On the basis of the genetic similarity among paleosols in these three correlative formations, the paleosols are interpreted as having formed along a single, continuous landscape surface. Results of this study indicate that the catena concept of pedogenesis along sloping landscapes is applicable to ancient successions. Sphaerosiderites in the Paddy Mem ber paleosols are used to provide proxy values for meteoric ??18O values at 52?? N paleolatitude in the Cretaceous Western Interior Basin. The meteoric ??18O values are used to refine existing interpretations about the mid-Cretaceous paleolatitudinal gradient in meteoric ?? 18O values, and the mid-Cretaceous hydrologic cycle. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).

  20. Probabilistic Generative Models for the Statistical Inference of Unobserved Paleoceanographic Events: Application to Stratigraphic Alignment for Inference of Ages

    NASA Astrophysics Data System (ADS)

    Lawrence, C.; Lin, L.; Lisiecki, L. E.; Khider, D.

    2014-12-01

    The broad goal of this presentation is to demonstrate the utility of probabilistic generative models to capture investigators' knowledge of geological processes and proxy data to draw statistical inferences about unobserved paleoclimatological events. We illustrate how this approach forces investigators to be explicit about their assumptions, and about how probability theory yields results that are a mathematical consequence of these assumptions and the data. We illustrate these ideas with the HMM-Match model that infers common times of sediment deposition in two records and the uncertainty in these inferences in the form of confidence bands. HMM-Match models the sedimentation processes that led to proxy data measured in marine sediment cores. This Bayesian model has three components: 1) a generative probabilistic model that proceeds from the underlying geophysical and geochemical events, specifically the sedimentation events to the generation the proxy data Sedimentation ---> Proxy Data ; 2) a recursive algorithm that reverses the logic of the model to yield inference about the unobserved sedimentation events and the associated alignment of the records based on proxy data Proxy Data ---> Sedimentation (Alignment) ; 3) an expectation maximization algorithm for estimating two unknown parameters. We applied HMM-Match to align 35 Late Pleistocene records to a global benthic d18Ostack and found that the mean width of 95% confidence intervals varies between 3-23 kyr depending on the resolution and noisiness of the core's d18O signal. Confidence bands within individual cores also vary greatly, ranging from ~0 to >40 kyr. Results from this algorithm will allow researchers to examine the robustness of their conclusions with respect to alignment uncertainty. Figure 1 shows the confidence bands for one low resolution record.

  1. Statistical algorithm to test the presence of correlation between time series with age/dating uncertainties.

    NASA Astrophysics Data System (ADS)

    Haam, E. K.; Huybers, P.

    2008-12-01

    To understand the Earth's climate, we must understand the inter-relations between its specific geographical areas which, in the case of paleoclimatology, can be profitably undertaken from an empirical perspective. However, assessment of the inter-relation between separate paleoclimate records is inevitably hindered by uncertainties in the absolute and relative age/dating of these climate records, because the correlation between two paleoclimate data with age uncertainty can change dramatically when variations of the age are allowed within the uncertainty limit. Through rigorous statistical analysis of the available proxy data, we can hope to gain better insight into the nature and scope of the mechanisms governing their variability. We propose a statistical algorithm to test for the presence of correlation between two paleoclimate time series with age/dating uncertainties. Previous works in this area have focused on searching for the maximum similarity out of all possible realizations of the series, either heuristically (visual wiggle matching) or through more quantitative methods (eg. cross-correlation maximizer, dynamic programming). In contrast, this algorithm seeks to determine the statistical significance of the maximum covariance. The probability of obtaining a certain maximum covariance from purely random events can provide us with an objective standard for real correlation and it is assessed using the theory of extreme order statistics, as a multivariate normal integral. Since there is no known closed form solution for a multivariate normal integral, a numerical method is used. We apply this algorithm to test for the correlation of the Dansgaard-Oeschger variability observed during MIS3 in the GISPII ice core and millennial variability recorded at cites including Botuvera Cave in Brazil, Hulu Cave in China, Eastern Indonesia, the Arabian Sea, Villa Cave in Europe, New Zealand and the Santa Barbara basin. Results of the analysis are presented as a map of the

  2. THE BIOGEOGRAPHIC ORIGIN OF ARCTIC ENDEMIC SEAWEEDS: A THERMOGEOGRAPHIC VIEW(1).

    PubMed

    Adey, Walter H; Lindstrom, Sandra C; Hommersand, Max H; Müller, Kirsten M

    2008-12-01

    The Arctic is geologically and biogeographically young, and the origin of its seaweed flora has been widely debated. The Arctic littoral biogeographic region dates from the latest Tertiary and Pleistocene. Following the opening of Bering Strait, about 3.5 mya, the "Great Trans-Arctic Biotic Interchange" populated the Arctic with a fauna strongly dominated by species of North Pacific origin. The Thermogeographic Model (TM) demonstrates why climate and geography continued to support this pattern in the Pleistocene. Thus, Arctic and Atlantic subarctic species of seaweeds are likely to be evolutionarily "based" in the North Pacific, subarctic species are likely to be widespread in the warmer Arctic, and species of Atlantic Boreal or warmer origin are unlikely in the Arctic and Subarctic. Although Arctic seaweeds have been thought to have a greater affinity with the North Atlantic, we have reanalyzed the Arctic endemic algal flora, using the Thermogeographic Model and evolutionary trees based on molecular data, to demonstrate otherwise. There are 35 congeneric species of the six, abundant Arctic Rhodophyta that we treat in this paper; 32 of these species (91%) occur in the North Pacific, two species (6%) occur in the Boreal or warmer Atlantic Ocean, and a single species is panoceanic, but restricted to the Subarctic. Laminaria solidungula J. Agardh, a kelp Arctic "endemic" species, has 18 sister species. While only eleven (61%) occur in the North Pacific, this rapidly dispersing and evolving genus is a terminal member of a diverse family and order (Laminariales) widely accepted to have evolved in the North Pacific. Thus, both the physical/time-based TM and the dominant biogeographic pattern of relatives of Arctic macrophytes suggest strong compliance with the evidence of zoology, geology, and paleoclimatology that the Arctic marine flora is largely of Pacific origin. PMID:27039853

  3. Pleistocene lake level changes in Western Mongolia

    NASA Astrophysics Data System (ADS)

    Borodavko, P. S.

    2009-04-01

    .Petersburg, Nauka, 304 p. 4. Tarasov, P.E., Harrison, S.P., Saarse, L., Pushenko, M.Ya., Andreev, A.A., Aleshinskaya, Z.V., Davydova, N.N., Dorofeyuk, N.I., Efremov, Yu.V., Khomutova, V.I., Sevastyanov, D.V., Tamosaitis, J., Dorofeyuk, N.I., Efremov, Yu.V., Khomutova, V.I., Sevastyanov, D.V., Tamosaitis, J.,Uspenskaya, O.N., Yakushko, O.F. and Tarasova, I.V., 1994. Lake status records from the Former Soviet Union and Mongolia: Data Base Documentation, World Data Center -A for Paleoclimatology NOAA Paleoclimatology Program, Paleoclimatology Publications Series Report No 2, Boulder, Colorado USA, 274 p. 5. Tserensodnom, Zh., 1971. Mongol orny Nuur. Ulaanbaatar, TUAH, 202 p. 6. Vipper, P., Dorofeyuk, N., Liiva, A., Meteltseva, E., and Sokolovskaya, V., 1981. Palaeogeography of the Central Mongolia during the upper Pleistocene and Holocene. Izv. Akad. Nauk ESSR, Ser. Biol., vol. 30, no. 1, pp. 74-82.

  4. Timing of maximum glacial extent and deglaciation from HualcaHualca volcano (southern Peru), obtained with cosmogenic 36Cl.

    NASA Astrophysics Data System (ADS)

    Alcalá, Jesus; Palacios, David; Vazquez, Lorenzo; Juan Zamorano, Jose

    2015-04-01

    Andean glacial deposits are key records of climate fluctuations in the southern hemisphere. During the last decades, in situ cosmogenic nuclides have provided fresh and significant dates to determine past glacier behavior in this region. But still there are many important discrepancies such as the impact of Last Glacial Maximum or the influence of Late Glacial climatic events on glacial mass balances. Furthermore, glacial chronologies from many sites are still missing, such as HualcaHualca (15° 43' S; 71° 52' W; 6,025 masl), a high volcano of the Peruvian Andes located 70 km northwest of Arequipa. The goal of this study is to establish the age of the Maximum Glacier Extent (MGE) and deglaciation at HualcaHualca volcano. To achieve this objetive, we focused in four valleys (Huayuray, Pujro Huayjo, Mollebaya and Mucurca) characterized by a well-preserved sequence of moraines and roches moutonnées. The method is based on geomorphological analysis supported by cosmogenic 36Cl surface exposure dating. 36Cl ages have been estimated with the CHLOE calculator and were compared with other central Andean glacial chronologies as well as paleoclimatological proxies. In Huayuray valley, exposure ages indicates that MGE occurred ~ 18 - 16 ka. Later, the ice mass gradually retreated but this process was interrupted by at least two readvances; the last one has been dated at ~ 12 ka. In the other hand, 36Cl result reflects a MGE age of ~ 13 ka in Mollebaya valley. Also, two samples obtained in Pujro-Huayjo and Mucurca valleys associated with MGE have an exposure age of 10-9 ka, but likely are moraine boulders affected by exhumation or erosion processes. Deglaciation in HualcaHualca volcano began abruptly ~ 11.5 ka ago according to a 36Cl age from a polished and striated bedrock in Pujro Huayjo valley, presumably as a result of reduced precipitation as well as a global increase of temperatures. The glacier evolution at HualcaHualca volcano presents a high correlation with

  5. Development and sustainability of NSF-funded climate change education efforts: lessons learned and strategies used to develop the Reconstructing Earth's Climate History (REaCH) curriculum (Invited)

    NASA Astrophysics Data System (ADS)

    St John, K. K.; Jones, M. H.; Leckie, R. M.; Pound, K. S.; Krissek, L. A.

    2013-12-01

    develop detailed instructor guides to accompany each module. After careful consideration of dissemination options, we choose to publish the full suite of exercise modules as a commercially-available book, Reconstructing Earth's Climate History, while also providing open online access to a subset of modules. Its current use in undergraduate paleoclimatology courses, and the availability of select modules for use in other courses demonstrate that creative, hybrid options can be found for lasting dissemination, and thus sustainability. In achieving our goal of making science accessible, we believe we have followed a curriculum development process and sustainability path that can be used by others to meet needs in earth, ocean, and atmospheric science education. Next steps for REaCH include exploration of its use in blended learning classrooms, and at minority serving institutions.

  6. Atlantic Meridional Overturning Circulation during Heinrich-Stadial 1 & 2 as seen by 231Pa/230Th

    NASA Astrophysics Data System (ADS)

    Antz, B.; Lippold, J. A.; Schulz, H.; Frank, N.; Mangini, A.

    2014-12-01

    Assessing the sensitivity of the Atlantic Meridional Overturning Circulation (AMOC) is a major challenge for paleoclimatology, because its strength and structure is a crucial element of the global heat- and carbon distribution towards the deep ocean. Here the focus is set on how excessive freshwater input through abrupt melting of continental ice sheets can affect its overturning vigour. Such forcing can be tested by investigating its behaviour during extreme iceberg discharge events into the open North Atlantic during the last glacial period, so called Heinrich-Events [Heinrich 1988; Hemming 2004]. The sedimentary activity ratio 231Pa/230Th has been increasingly used as a kinematic circulation proxy in the Atlantic Ocean over the past decade [Gherardi et al. 2009; McManus et al. 2004; Lippold et al. 2012]. Here we present 231Pa/230Th ratios from several Atlantic sediment cores across Heinrich Events 1 (~17 ka BP) and 2 (~24 ka BP). The comparison of the profiles demonstrates the potential pitfalls when interpreating a single 231Pa/230Th profile. E. g. core IODP 1313 (Mid Atlantic Ridge, 3412 m water depth) shows 231Pa/230Th between 0.04 and 0.06, which would indicate a vigorous circulation over the entire time period. On the other hand core GeoB 16202-2 (Brasilan coastal area, 2248 m water depth) has a profile similar to the well known data set of [McManus et al. 2004] (i.e. during Heinrich Stadials values close to the production ratio of ~0.093, lower values at Holocene and LGM). Such divergency can be explained by 231Pa/230Th dependence on water depth, latitude, water mass and water mass age [Luo et al. 2010; Lippold et al. 2011], but also on changes in bioproductivity especially the flux of biogenic opal [Anderson et al. 1983A; Bradtmiller et al. 2007; Chase et al. 2002]. To avoid misleading interpretations, the here shown data set is accompanied by measurements of biogenic opal contents to appraise possible influences on the proxies. We observe large

  7. Quantitative Investigation of Post-Burial H Isotope Exchanges in Organic Molecules

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Sessions, A. L.

    2010-12-01

    The development of compound-specific analyses has presented new challenges to our understanding of the mechanisms that underpin the 2H/1H distribution in ancient organic molecules. In general, the H-isotopic composition of organic compounds is successively determined by 1) biosynthetic fractionations and 2) post-burial fractionations. As burial temperatures increase, C-bound H is potentially exchangeable on timescales of 104-106 years [1]. However, the 2H/1H ratios at the exchange endpoint, i.e., equilibrium 2H/1H fractionation factors (αeq), are poorly known. This is because conventional isotope exchange experiments suffer from extremely slow exchange rates of alkyl H, while theoretical methods are limited by systematic uncertainties. To remedy this situation, we take advantage of keto-enol tautomerism that leads to fast equilibration of H adjacent to a carbonyl group (Hα). Values of αeq can then be obtained experimentally in a reasonable time, and used to calibrate theoretical calculations based on vibrational frequencies from ab initio quantum mechanical simulations. This yields calibration curves applicable to a wide variety of organic H positions, including those in alkanes, alkenes, ketones, carboxylic acids, esters, alcohols, ethers, and cyclic hydrocarbon molecules. The molecular equilibrium fractionation relative to water between 0 to 100°C are estimated to be -80 to -90‰ for n-alkyl lipids, -95 to -100‰ for acyclic isoprenoids, -80 to -95‰ for steroids, and -90 to -100‰ for hopanoids. Thus post-burial H exchange will remove the ~50-100‰ biosynthetic fractionations between isoprenoid and n-alkyl lipids, which is consistent with the observed δ2H changes in lipid molecules during thermal maturation [2]. The results can be used to evaluate the extent of H exchange in sedimentary organic matter and oils, which has significant implication on the use of H isotope records in paleoclimatology and petroleum chemistry. [1] Sessions et al. (2004) GCA

  8. Climate Literacy: STEM and Climate Change Education and Remote Sensing Applications

    NASA Astrophysics Data System (ADS)

    Reddy, S. R.

    2015-12-01

    NASA Innovations in Climate Education (NICE) is a competitive project to promote climate and Earth system science literacy and seeks to increase the access of underrepresented minority groups to science careers and educational opportunities. A three year funding was received from NASA to partnership with JSU and MSU under cooperative agreement "Strengthening Global Climate Change education through Remote Sensing Application in Coastal Environment using NASA Satellite Data and Models". The goal is to increase the number of highschool and undergraduate students at Jackson State University, a Historically Black University, who are prepared to pursue higher academic degrees and careers in STEM fields. A five Saturday course/workshop was held during March/April 2015 at JSU, focusing on historical and technical concepts of math, enginneering, technology and atmosphere and climate change and remote sensing technology and applications to weather and climate. Nine students from meteorology, biology, industrial technology and computer science/engineering of JSU and 19 high scool students from Jackson Public Schools participated in the course/workshop. The lecture topics include: introduction to remote sensing and GIS, introduction to atmospheric science, math and engineering, climate, introduction to NASA innovations in climate education, introduction to remote sensing technology for bio-geosphere, introduction to earth system science, principles of paleoclimatology and global change, daily weather briefing, satellite image interpretation and so on. In addition to lectures, lab sessions were held for hand-on experiences for remote sensing applications to atmosphere, biosphere, earth system science and climate change using ERDAS/ENVI GIS software and satellite tools. Field trip to Barnett reservoir and National weather Service (NWS) was part of the workshop. Basics of Earth System Science is a non-mathematical introductory course designed for high school seniors, high school

  9. Reconciling radiocarbon and ice core timescales over the Holocene - Cosmogenic radionuclides as synchronization tools

    NASA Astrophysics Data System (ADS)

    Muscheler, R.; Adolphi, F.; Mekhaldi, F.

    2015-12-01

    The atmospheric production rates of cosmogenic radionuclides, such as 14C and 10Be, vary globally due to external processes, namely the solar and geomagnetic modulation of the galactic cosmic ray flux as well as solar proton events. This signature is recorded in various archives such as ice cores (10Be) and tree-rings (14C). Hence, cosmogenic radionuclides offer a means to continuously assess timescale differences between two of the most widely used timescales in paleoclimatology - the radiocarbon and the ice core timescales. Short lived solar proton events additionally provide distinct marker horizons that allow synchronization of discrete horizons at annual precision. We will present a cosmogenic radionuclide based synchronization of the Greenland ice core timescale (GICC05, Svensson et al., 2008) and the radiocarbon timescale (IntCal13, Reimer et al., 2013) over the Holocene. This synchronization allows radiocarbon dated and ice core paleoclimate records to be compared on a common timescale at down to sub-decadal precision. We will compare these results to independent discrete isochrones obtained from tephrochronology and solar proton events. In addition, we will discuss implications for the accuracy and uncertainty estimates of GICC05 over the Holocene. Reimer, P. J., Bard, E., Bayliss, A., Beck, J. W., Blackwell, P. G., Bronk Ramsey, C., Buck, C. E., Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T. J., Hoffmann, D. L., Hogg, A. G., Hughen, K. A., Kaiser, K. F., Kromer, B., Manning, S. W., Niu, M., Reimer, R. W., Richards, D. A., Scott, E. M., Southon, J. R., Staff, R. A., Turney, C. S. M., and van der Plicht, J.: IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP, Radiocarbon, 55, 1869-1887, 10.2458/azu_js_rc.55.16947, 2013. Svensson, A., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Davies, S. M., Johnsen, S. J., Muscheler, R., Parrenin

  10. Oxygen isotope ratios of cellulose-derived phenylglucosazone: An improved paleoclimate indicator of environmental water and relative humidity

    NASA Astrophysics Data System (ADS)

    Sternberg, Leonel da S. L.; Pinzon, Maria C.; Vendramini, Patricia F.; Anderson, William T.; Jahren, A. Hope; Beuning, Kristina

    2007-05-01

    Oxygen atoms within fossil wood provide high-resolution records of climate change, particularly for the Quaternary. However, current analysis methods of fossil cellulose do not differentiate between different positions of the oxygen atoms. Here, we propose a refinement to tree-cellulose paleoclimatology modeling, using the cellulose-derived compound phenylglucosazone as the isotopic substrate. Stem samples from trees were collected at northern latitudes as low as 24°37'N and as high as 69°00'N. We extracted stem water and cellulose from each stem sample and analyzed them for their 18O content. In addition, we derived the cellulose to phenylglucosazone, a compound which lacks the oxygen attached to the second carbon of the cellulose-glucose moieties. Oxygen isotope analysis of phenylglucosazone allowed us to calculate the 18O content of the oxygen attached to the second carbon of the cellulose-glucose moieties. By way of these analyses, we tested two hypotheses: first, that the 18O content of the oxygen attached to second carbon will more closely reflect the 18O content of the stem water, and will not resemble the 18O content of either cellulose or its derivative phenylglucosazone. Second, tree-ring models that incorporate the variable oxygen isotope fractionation shown here and elsewhere are more accurate than those that do not. Our first hypothesis was rejected on the basis that the oxygen isotope ratios of the oxygen attached to the second carbon of the glucose moieties had a noisy isotopic signal with a large standard deviation and gave the poorest correlation with the oxygen isotope ratios of stem water. Related to this isotopic noise, we observed that the correlation between oxygen isotope ratios of phenylglucosazone with both stem water and relative humidity were higher than those observed for cellulose. Our hypothesis about tree-ring models which account for changes in the oxygen isotopic fractionation during cellulose synthesis was consistent only for the

  11. The Svalbard Barents Sea Ice Sheet deglaciation and its contribution to meltwater pulse 1a: Constraining ice sheet history with geomorphological mapping and 10Be exposure dating on Svalbard's southern cape

    NASA Astrophysics Data System (ADS)

    Nothaft, D. B.; Koffman, T.; Schaefer, J. M.; Young, N. E.; Hormes, A.; Briner, J. P.

    2014-12-01

    Pinpointing the sources of meltwater pulse (MWP) 1a—the most abrupt period of sea level rise during the last glacial termination—remains one of paleoclimatology's greatest challenges, with implications for the understanding of rapid climate change, isostatic rebound, and past ocean circulation. Here, we present an annotated geomorphological map of a southern region of Svalbard, Norway, that we will use in the interpretation of a soon-to-be published 10Be chronology of this study area where no cosmogenic nuclide exposure data has yet been produced. From this map, we infer historic ice sheet thickness, flow rate, and erosivity. Together, this data will enable us to constrain ice sheet volume change over time in southern Svalbard. The map identifies raised beaches at an altitude of 40 m, indicating an ice sheet thickness of 400-800 m during the Last Glacial Maximum (LGM) when compared to other shoreline data from the region and ice sheet models. We also observed an abundance of glacially smoothed features in valleys, despite an absence of such features at higher elevations. This could suggest a transition from warm-based, erosive ice to cold-based, non-destructive ice with increasing elevation. It is also possible that mountain peaks in this region were not glaciated at LGM. It is important to assess the historic erosivity of an ice sheet because cosmogenic nuclides may be inherited from prior interstadials when the bedrock was deglaciated, if not "reset" by erosion. This can result in erroneously old exposure dates. If this portion of the Svalbard Barents Sea Ice Sheet (SBSIS) did contribute largely to MWP-1a, then we would expect exposure dates from sites differing in elevation by 100 m or more to fall within a 500-year range, centered around 14 ka. Expeditions to collect samples for exposure dating at other field sites in southern Svalbard, scheduled for the coming field season, will help to further inform our understanding of the SBSIS deglaciation and the MWP

  12. Sedimentary dynamic processes of a contourite drift formation in the South China Sea: from long-term in situ observations to geological records

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Zhao, Y.; Zhang, Y.; Li, J.; Wen, K.; Li, X.; Tuo, S.; Zhong, G.

    2015-12-01

    Contourites are sediments deposited or substantially reworked by thermohaline-induced deepwater bottom currents. The study of contourites with growing interests is widely conducted in seismic stratigraphy, paleoceanography, paleoclimatology, and hydrocarbon exploration. However, the sedimentary dynamic process producing contourites in the deepwater environment is still poorly understood. This research presents an interdisciplinary approach from long-term in situ mooring and tripod observations, multi-beam seabed morphology, seismic stratigraphy, to IMAGES (Marion Dufresne) piston coring and ODP (JOIDES Resolution) drilling studies on the formation of a contourite drift on the lower slope of the northern South China Sea. The contourite drift with ~520 m thick is distributed in water depths ranging from 1650 m to 2500 m and has been accumulated since 1.5 Ma in early Pleistocene. The nowadays contour currents in the northern South China Sea were observed with velocities generally ranging in 0-2 cm/s with a dominant flow direction of ~250º (southwestward/along-slope). However, the relatively stable contour currents were disturbed by several bursts of increased velocities up to 8-11 cm/s, each lasting 2-3 weeks and followed by a direction reversal, which were caused by passing-through of deep-reaching mesoscale eddies. The along-slope sediment transport is induced by both mesoscale eddy and contour currents, and these suspended sediments are mainly derived from Taiwan according to provenance analysis of sediments traps equipped on moorings. Seismic stratigraphy and core sample analysis (oxygen isotope stratigraphy, clay mineralogy, and grain size) reveal a long sedimentary history with strong influence of deepwater currents that have carried the majority of Taiwan-sourced sediments moving westward since early Pleistocene. The glacial-cyclic terrigenous input from various surrounding drainage systems and their transport processes from fluvial source to deep-sea sink are

  13. Water-table decline in the south-central Great Basin during the Quaternary Period; implications for toxic-waste disposal

    USGS Publications Warehouse

    Winograd, I.J.; Szabo, B. J.

    1986-01-01

    The distribution of vein calcite, tufa, and other features indicative of paleo-groundwater discharge, indicates that during the early to middle Pleistocene, the water table at Ash Meadows, in the Amargosa Desert, Nevada, and at Furnace Creek Wash, in east-central Death Valley, California, was tens to hundreds of meters above the modern water table, and that groundwater discharge occurred up to 18 km up-the-hydraulic gradient from modern discharge areas. Uranium series dating of the calcitic veins permits calculation of rates of apparent water table decline; rates of 0.02 to 0.08 m/1000 yr are indicated for Ash meadows and 0.2 to 0.6 m/1000 yr for Furnace Creek Wash. The rates for Furnace Creek Wash closely match a published estimate of vertical crustal offset for this area, suggesting that tectonism is a major cause for the displacement observed. In general, displacements of the paleo-water table probably reflect a combination of: (a) tectonic uplift of vein calcite and tufa, unaccompanied by a change in water table altitude; (b) decline in water table altitude in response to tectonic depression of areas adjacent to dated veins and associated tufa; (c) decline in water table altitude in response to increasing aridity caused by major uplift of the Sierra Nevada and Transverse Ranges during the Quaternary; and (d) decline in water altitude in response to erosion triggered by increasing aridity and/or tectonism. A synthesis of geohydrologic, neotectonic, and paleoclimatologic information with the vein-calcite data permits the inference that the water table in the south-central Great Basin progressively lowered throughout the Quaternary. This inference is pertinent to an evaluation of the utility of thick (200-600 m) unsaturated zones of the region for isolating solidified radioactive wastes from the hydrosphere for hundreds of millenia. Wastes buried a few tens to perhaps 100 m above the modern water table--that is above possible water level rises due to future

  14. Fine-Scale Spatial Variability of Precipitation, Soil, and Plant Water Isotopes

    NASA Astrophysics Data System (ADS)

    Goldsmith, G. R.; Braun, S.; Romero, C.; Engbersen, N.; Gessler, A.; Siegwolf, R. T.; Schmid, L.

    2015-12-01

    Introduction: The measurement of stable isotope ratios of water has become fundamental in advancing our understanding of environmental patterns and processes, particularly with respect to understanding the movement of water within the soil-plant-atmosphere continuum. While considerable research has explored the temporal variation in stable isotope ratios of water in the environment, our understanding of the spatial variability of these isotopes remains poorly understood. Methods: We collected spatially explicit samples of throughfall and soil water (n=150 locations) from a 1 ha plot delineated in a mixed deciduous forest in the northern Alps of Switzerland. We complemented this with fully sunlit branch and leaf samples (n = 60 individuals) collected from Picea abies and Fagus sylvatica between 14:00 and 16:00 on the same day by means of a helicopter. Soil and plant waters were extracted using cryogenic vacuum distillation and all samples were analyzed for δ18O using an isotope ratio mass spectrometer. Results: The mean δ18O of throughfall (-3.3 ± 0.8‰) indicated some evaporative enrichment associated with passage through the canopy, but this did not significantly differ from the precipitation collected in nearby open sites (-4.05‰). However, soil was depleted (-7.0 ± 1.8‰) compared to throughfall and there was no significant relationship between the two, suggesting that the sampling for precipitation inputs did not capture all the sources (e.g. stream water, which was -11.5‰) contributing to soil water δ18O ratios. Evaporative enrichment of δ18O was higher in leaves of Fagus (14.8 ± 1.8‰) than in leaves of Picea (11.8 ± 1.7‰). Sampling within crowns of each species (n = 5 branches each from 5 individuals) indicated that variability in a single individual is similar to that among individuals. Discussion: Stable isotopes of water are frequently engaged for studies of ecohydrology, plant ecophysiology, and paleoclimatology. Our results help

  15. Dartmouth College Earth Sciences Mobile Field Program

    NASA Astrophysics Data System (ADS)

    Meyer, E. E.; Osterberg, E. C.; Dade, W. B.; Sonder, L. J.; Renshaw, C. E.; Kelly, M. A.; Hawley, R. L.; Chipman, J. W.; Mikucki, J.; Posmentier, E. S.; Moore, J. R.

    2011-12-01

    spend several weeks conducting traditional multiday mapping of complexly-deformed sedimentary, metamorphic and igneous rocks, and also collect and interpret geobiological, geochemical, geophysical, paleoclimatological, paleontological, and remote-sensing data outside the context of traditional mapping. During the Mono Lake segment, for example, students examine the interaction of ecology and chemistry in alkaline lakes. During the Canadian Rockies segment, students reconstruct Holocene paleoclimate using tree stumps and fossil wood detritus marking former positions of an alpine glacier. While a mobile, wide-ranging field program requires complicated logistics and potentially high per-student costs, the diversity of research topics, geological environments, and field techniques have made it a successful cornerstone of the Dartmouth Earth Sciences major. After the Stretch experience, significant fractions of our students become involved in ongoing faculty research, pursue senior theses, and go on to pursue Earth Sciences graduate degrees.

  16. Calcareous sinter from ancient aqueducts as a source of data in paleoclimate, tectonics and hydrology

    NASA Astrophysics Data System (ADS)

    Surmelihindi, G.; Passchier, C. W.

    2010-12-01

    During the lifetime the Roman Empire (300BC-400AD), about 1200 major aqueducts were built to supply cities in the Mediterranean with drinking water. The ruins of many of these channels contain sinter (calcium carbonate), which was deposited at a rate of 0.5-5 mm/year over the life of the aqueduct, usually 50-200 but up to 1000 years. Calcareous sinter inside the ancient aqueduct channels can give important insight into paleoclimatology in the form of temperature and rainfall, reflect palaeohydrology of water, water chemistry, flow rate, bacterial activity and source area of the water. This type of data is important to build climate models and to understand earthquake and flood patterns in the Mediterranean, and can be a new, additional source of information besides speleothems, travertine and tufa deposits. In our study we focus on Mediterranean climate patterns, and selected four aqueduct sites from Southern Turkey, Greece and Italy. The calcareous sinter deposits may reflect annual or subannual lamination characterized by alternating light, dense, coarse-grained and dark, porous, microcrystalline layers which are thought to represent winter and summer conditions respectively. Moreover, abrupt changes in the sequence of lamination can be a signal of natural hazards such as earthquakes or flood events. Deposits from the aqueduct of Patara (Southern Turkey) show 40-50 laminae couples, which may be annual layers. δ18O and δ 13C stable isotope data indicate high cyclicity within the sinter samples from Patara during the Roman period. Higher δ18O values correspond with dark, porous layers and lower values with light, dense layers. Major geochemical analyses show similar seasonal changes. Electron microprobe study shows that within dark laminae, detrital Fe, Mg, K, Al and Si are enriched whereas the light layers have high Ca content. Trace element analyses by LA-ICP-MS also indicate higher Mg/Ca and Sr/Ca values in the dark layers, which can be interpreted in terms

  17. A Demographic Analysis of American Geophysical Union Membership with Implications for Change

    NASA Astrophysics Data System (ADS)

    Rhodes, D. D.

    2006-12-01

    Demographers use population pyramids to characterize the age/gender structure of societal groups. Diagrams of the population of age cohorts for both sexes assume the shape of a pyramid in rapidly expanding groups, having many more young people than older adults. Stable populations have similar numbers of people in age cohorts from infants through middle-age adults. Shrinking populations have fewer children and relatively larger numbers of adults. Demographic analysis of the American Geophysical Union's (AGU) membership reveals significant differences among the numerous specialties and the membership as a whole. The population structure diagram of the total AGU membership is highly asymmetrical with 77.5% male and 22.5% female. Males outnumber females in every age cohort. This is most noticeable among members born prior to 1945. Males belonging to these cohorts make up 16.5% of the total membership, while female members of equivalent age include 0.8% of the total. The largest membership cohort (29% of the total) is comprised of males born between 1950 and 1964, a group that includes both the "baby boom" generation and post-war petroleum exploration expansion. In contrast, the female cohort with birth years from 1970 to 1979 is the largest grouping of women members (8.4% of AGU's membership). Furthermore, women comprise 36% of the members born since 1965, and only 14.5% of those born before 1965. Considered separately, the female membership's age structure is characteristic of a growing population, while the male side is in relative decline. The population structure of the entire membership is mirrored in some specialties, but there are remarkable differences in others. The largest specialty group (hydrology) includes 16.9% of the total AGU membership and has a population structure that differs little from that of the whole organization. Four specialties, Atmospheric Chemistry, Biogeosciences, and Paleoceanography and Paleoclimatology, and Marine Geochemistry differ

  18. Differential Responses of Neotropical Mountain Forests to Climate Change during the Last Millenium

    NASA Astrophysics Data System (ADS)

    Figueroa-Rangel, B. L.; Olvera Vargas, M.

    2013-05-01

    The long-term perspective in the conservation of mountain ecosystems using palaeoecological and paleoclimatological techniques are providing with crucial information for the understanding of the temporal range and variability of ecological pattern and processes. This perception is contributing with means to anticipate future conditions of these ecosystems, especially their response to climate change. Neotropical mountain forests, created by a particular geological and climatic history in the Americas, represent one of the most distinctive ecosystems in the tropics which are constantly subject to disturbances included climate change. Mexico due to its geographical location between the convergence of temperate and tropical elements, its diverse physiography and climatic heterogeneity, contains neotropical ecosystems with high biodiversity and endemicity whose structure and taxonomical composition have changed along centurial to millennial scales. Different neotropical forests expand along the mountain chains of Mexico with particular responses along spatial and temporal scales. Therefore in order to capture these scales at fine resolution, sedimentary sequences from forest hollows were retrieved from three forest at different altitudes within 10 km; Pine forest (PF), Transitional forest (TF) and Cloud forest (CF). Ordination techniques were used to relate changes in vegetation with the environment every ~60 years. The three forests experience the effect of the dry stage ~AD 800-1200 related to the Medieval Warm Period reported for several regions of the world. CF contracted, PF expanded while the TF evolved from CF to a community dominated by dry-resistant epiphytes. Dry periods in PF and TF overlapped with the increase in fire occurrences while a dissimilar pattern took place in CF. Maize, Asteraceae and Poaceae were higher during dry intervals while epiphytes decreased. A humid period ~1200-1450 AD was associated with an expansion and a high taxa turnover in CF

  19. Water Stable Isotopes: Atmospheric Composition and Applications in Polar Ice Core Studies

    NASA Astrophysics Data System (ADS)

    Jouzel, J.

    2003-12-01

    Natural waters formed of ˜99.7% of H216O are also constituted of other stable isotopic molecules, mainly H218O (˜2‰), H217O (˜0.5‰), and HD16O (˜0.3‰), where H and D (deuterium) correspond to 1H and 2H, respectively. Owing to slight differences in physical properties of these molecules, essentially their saturation vapor pressure, and their molecular diffusivity in air, fractionation processes occur at each phase change of the water except sublimation and melting of compact ice. As a result, the distribution of these water isotopes varies both spatially and temporally in the atmosphere, in the precipitation, and, in turn, in the various reservoirs of the hydrosphere and of the cryosphere. These isotopic variations have applications in such fields as climatology and cloud physics. More importantly, they are at the origin of two now well-established disciplines: isotope hydrology and isotope paleoclimatology. The various aspects dealing with isotope hydrology are reviewed by Kendall (see Chapter 5.11). In this chapter, we focus on this field known as "isotope paleoclimatology." As the behavior of H217O in the atmospheric water is very similar to that of H218O (more abundant and easier to precisely determine), isotope paleoclimatology is only based on the changes in concentrations of HDO and H218O. These concentrations are given with respect to a standard as δ=(Rsample-RSMOW)/RSMOW and expressed in per mil δ units (δD and δ18O, respectively). In this definition, Rsample and RSMOW are the isotopic ratios of the sample and of the Vienna Standard Mean Ocean Water (V-SMOW) with D/H and 18O/16O atomic ratios of 155.76×10-6 and 2005.2×10-6, respectively (Hageman et al., 1970; Baerstchi, 1976; Gonfiantini, 1978).The use of water stable isotopes in paleoclimatology is based on the fact that their present-day distribution in precipitation is strongly related to climatological parameters. Of primary interest is the linear relationship between annual values of

  20. Evolution of Glacier Snowline Since the End of the Last Ice Age in New Zealand

    NASA Astrophysics Data System (ADS)

    Kaplan, M. R.; Putnam, A. E.; Schaefer, J. M.; Denton, G. H.; Chinn, T. J.; Barrell, D.; Doughty, A. M.; Mackintosh, A. N.; Andersen, B. G.

    2012-12-01

    An important problem in paleoclimatology is how Southern Hemisphere climate changed since the end of the last ice age. The terrestrial glacier record reflects past snowline (=equilibrium line altitude) variability and is one of the few direct proxies available, in the middle latitudes, of former atmospheric properties. We reconstruct changes in snowline since ~15 ka on the South Island of New Zealand using geomorphologic mapping, 10Be surface-exposure dating, accumulation-area ratio (AAR) methods and numerical modeling. The snowline data are a proxy for the 0°C atmospheric isotherm, which occurs above 1500 m asl in the central Southern Alps, and trends in temperature since ~15 ka. Our findings show that snowline was depressed during the Antarctic Cold Reversal. Subsequently, snowline rose ~100 m during the Younger Dryas stadial in Europe. These late glacial changes appear coherent across the southern middle latitudes. In the early Holocene, snowline was depressed >200 m relative to modern in the Southern Alps. Between 11 ka and 600 years ago, short-term oscillations punctuated a multi-millennia trend of decreasing glacier extent as snowline rose ~100 m. Since ~600 yrs ago, net snowline has continued progressively to rise. The record implies long-term warming in New Zealand since the Late Glacial period. During the Holocene, the lowest snowlines and most extensive glaciers occurred in the early part of the epoch. Snowline reconstruction and numerical modeling allow us to estimate that temperature depression during the Late Glacial was ~2.1±0.4°C (relative to modern) and increased about 0.6 to 1°C between the early and late Holocene. Our terrestrial glacier and snowline records show coherence and also they are consistent with marine records in the Australian sector, documenting a regional climate pattern. However, the climate of the southwest Pacific region was fundamentally different from that observed in the Northern Hemisphere, where the most extensive

  1. NASA Partnership with JSU and MSU to Promote Remote Sensing Applications and Global Climate Change Education: 2013 Summer Course/Workshop

    NASA Astrophysics Data System (ADS)

    Reddy, S. R.

    2014-12-01

    NASA Innovations in Climate Education (NICE) is a competitive project to promote climate and Earth system science literacy and seeks to increase the access of underrepresented minority groups to science careers and educational opportunities. A three year funding was received from NASA to partnership with JSU and MSU under cooperative agreement "Strengthening Global Climate Change education through Remote Sensing Application in Coastal Environment using NASA Satellite Data and Models". The goal is to increase the number of undergraduate students at Jackson State University, a Historically Black University, who are prepared to pursue higher academic degrees and careers in the fields relevant to earth system science global climate change, marine and environmental sciences. A two week summer course/workshop was held during May 20-31, 2013 at JSU, focusing on historical and technical concepts of remote sensing technology and applications to climate and global climate change. Nine students from meteorology, biology, industrial technology and computer science/engineering of JSU participated in the course/workshop. The lecture topics include: introduction to remote sensing and GIS, introduction to atmospheric science and climate, introduction to NASA innovations in climate education, introduction to remote sensing technology for bio-geosphere, introduction to earth system science, principles of paleoclimatology and global change, daily weather briefing, satellite image interpretation and so on. In addition to lectures, lab sessions were held for hand-on experiences for remote sensing applications to atmosphere, biosphere, earth system science and climate change using ERDAS/ENVI GIS software and satellite tools. Field trip to Barnett reservoir and National weather Service (NWS) was part of the workshop. Some of the activities of the sessions will be presented. Basics of Earth System Science is a non-mathematical introductory course designed for high school seniors, high

  2. Tephrochronology of Lacustrine Ash Layers in Lake Petén Itzá Sediments drilled in the Frame of the International Continental Scientific Drilling Program (ICDP): Implications for Regional Volcanology and Central American Palaeoclimate

    NASA Astrophysics Data System (ADS)

    Kutterolf, S.; Schindlbeck, J. C.; Anselmetti, F.; Mueller, A.; Schwalb, A.; Eisele, S.; Hemming, S. R.; Wang, K. L.

    2015-12-01

    Climate records from lacustrine systems have been established in the last years to improve our understanding of the regional and temporal expression of climate change on the continents, and how it influenced the human evolution. Lake Petén Itzá, located in the center of the climatically sensitive Peninsula Yucatán, is a surficial closed-basin lake located in the lowlands of northern Guatemala drilled by ICDP. The region itself exhibits characteristic climate conditions, making it an ideal region for paleoclimatological and paleoecological studies. A key problem in obtaining a long-lasting climate record is to establish robust chronologies beyond 40 ka since they exceed the range of 14C dating, but tephra layers within these sediments may provide good age-constraints >40 ka. We here use large-magnitude, widespread, Pleistocene to Holocene silicic eruptions from caldera volcanoes in the Central American volcanic arc (CAVA), contributing to the drilled Petén Itzá lake sediments in the form of numerous lacustrine tephras providing time markers to develop a new, extended age model. We established robust and well-constrained correlations between the tephras in Lake Petén Itzá and the deposits at the CAVA source as well as their marine equivalents in the sediments of the Pacific Ocean based on major and trace element glass compositions. We document here 8 well-constraint time markers for the Petén Itza age models, which so far were only based on younger 14C dates and some preliminary, only major-element based, tephra correlations. Additionally ongoing Ar/Ar age dating of the Los Chocoyos eruption will provide a new pinning point froma an important regional marker horizon. In summary we have been able to modify the current age models, extend the paleoclimate and paleoecological record in this neotropical region to ~300 ka, and contribute greatly to the determination of the magnitude (eruptive volumes) and more precise eruption dates of CAVA eruptions.

  3. Climcor: Paleoclimatic Coring: High Resolution and Innovations.Cnrs Gathers the Present Coring Equipment , and Coordinates the Different Efforts Provided By the Concerned Communities (ocean, ice and continent)

    NASA Astrophysics Data System (ADS)

    Calzas, M.; Rousseau, D. D.

    2014-12-01

    Global climate changes have been evidenced in various ways since the start of paleoclimatology in the 70s. The access to past atmosphere conditions in the air bubbles trapped in ice-cores gave an important impulse as it made the green-house gases concentrations accessible a prerequisite for climate modelers. Indeed since the publication of CO2 and CH4 variations over the last climate cycle in Vostok ice-cores, our knowledge of the past climate conditions has improved tremendously. However, improvements in technical equipment and approaches indicate that more is still to come inducing expected new findings in terms of mechanisms. The IMAGES program yielded very good quality and long marine cores that permitted to compare marine and ice-core records with high confidence. Moreover they permitted to improve the knowledge of past oceans dynamics, especially those linked to the massive discharges of icebergs in the oceans, impacting the Atlantic meridional overturning circulation. On the continent, various environments are drilled and cored to provide also comparable and reliable records of past climate: lakes, peatbogs, speleothems and loess. These records are complementary yielding important dataset to feed the earth system models necessary for a better understanding of past climate dynamics. Technical limitation of the present equipments does not allow such important jump in the quality of the data, and therefore in the knowledge of i, past climate variations at extremely high resolution and ii, of the behavior of the different domains as studied in IPCC experiments while societal requirements are more and more expressed by policy makers. C2FN initiative at CNRS gathers the present coring equipments located in labs or at the technical division of INSU, and coordinates the different efforts provided by the concerned communities (ocean, ice and continent). Valorization of the results obtained are published in high ranked scientific journals and presented in scientific

  4. Studies of contemporary glacier basal ice cryostructures to identify buried basal ice in the permafrost: an example from the Matanuska Glacier, Alaska.

    NASA Astrophysics Data System (ADS)

    Stephani, E.; Fortier, D.; Kanevskiy, M.; Dillon, M.; Shur, Y.

    2007-12-01

    In the permafrost, massive ice bodies occur as buried glacier ice, aufeis ice, recrystalized snow, massive segregated ice, injection ice, ice wedges or ice formed in underground cavities ("pool ice", "thermokarst-cave ice"). The origin of massive ice bodies in the permafrost bears considerable implications for the reconstructions of paleoenvironments and paleoclimates. Our work aims to help the permafrost scientists working on massive icy sediments to distinguish buried basal glacier ice from other types of buried ice. To do so, the properties and structure of contemporary basal ice must be well known. Field investigations at the Matanuska Glacier (Chugach range, South-central Alaska), consisted in descriptions and sampling of natural basal ice exposures. We have used the basal ice facies classification of Lawson (1979) which is simple, easy to use in the field and provides a good framework for the description of basal ice exposures. Cores were extracted and brought back to the laboratory for water and grain-size analyses. The sediments forming the cryostructure were mostly polymodal, poorly sorted gravelly silt to gravelly fine sand, with mud contents generally over 50%. These data will be used to calibrate three-dimensional (3D) models produced from micro-tomographic scans of basal ice which will produce quantitative estimates of volumetric ice and sediments contents of basal ice cryostructures. Ultimately, visual qualitative and quantitative characterization of the basal ice components of 3D models together with field observations and laboratory analysis will allow for a new micro-facies and cryostructures classification of the basal ice. Our work will also have applications in glaciology, glacial geology, geomorphology, Quaternary and paleo-climatological studies based on inferences made from the structure of basal glacier ice. This paper presents the internal composition of the basal ice facies in terms of cryostructures assemblages (Fortier et al.: 2007) and

  5. Late Quaternary and future biome simulations for Alaska and Eastern Russia

    NASA Astrophysics Data System (ADS)

    Hendricks, Amy S.

    Arctic biomes across a region including Alaska and Eastern Russia were investigated using the BIOME4 biogeochemical and biogeography vegetation model. This study investigated past (the last 21,000 years), present, and future vegetation distributions in the study area, using climate forcing from five CMIP5 models (CCSM4, GISS-E2-R, MIROC-ESM, MPI-ESM, and MRI-CGCM3). The present-day BIOME4 simulations were generally consistent with current vegetation observations in the study region characterized by evergreen and deciduous taiga and shrub tundras. Paleoclimatological simulations were compared with pollen data samples collected in the study region. Pre-industrial biome simulations are generally similar to the modern reconstruction but differ by having more shrub tundra in both Russia and Alaska to the north, as well as less deciduous taiga in Alaska. Pre-industrial simulations were in good agreement with the pollen data. Mid-Holocene simulations place shrub tundras along the Arctic coast, and in some cases along the eastern coast of Russia. Simulations for the Mid-Holocene are in good agreement with pollen-based distributions of biomes. Simulations for the Last Glacial Maximum (LGM) show that the Bering Land Bridge was covered almost entirely by cushion forb, lichen and moss tundra, shrub tundra, and graminoid tundra. Three out of the five models' climate data produce evergreen and deciduous taiga in what is now southwestern Alaska, however the pollen data does not support this. The distributions of cushion forb, lichen, and moss tundra and graminoid tundra differ noticeably between models, while shrub tundra distributions are generally similar. Future simulations of BIOME4 based on the RCP8.5 climate scenario indicate a northward shift of the treeline and a significant areal decrease of shrub tundra and graminoid tundra regions in the 21st century. Intrusions of cool mixed, deciduous, and conifer forests above 60°N, especially in southwest Alaska, were notable

  6. Relations between rainfall–runoff-induced erosion and aeolian deposition at archaeological sites in a semi-arid dam-controlled river corridor

    USGS Publications Warehouse

    Collins, Brian; Bedford, David; Corbett, Skye; Fairley, Helen; Cronkite-Ratcliff, Collin

    2016-01-01

    Process dynamics in fluvial-based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam-building affect fluvial processes, the complexity in local response can be further increased by flood- and sediment-limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi-temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446-km-long semi-arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam-controlled fluvial sand bar deposition, aeolian sand transport, and rainfall-induced erosion. Empirical rainfall-erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration-excess overland flow and gullying govern large-scale (centimeter- to decimeter-scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic-driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four-minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short

  7. Paleoclimate of the Southern San Joaquin Valley, CA: Research Participation Opportunities for Improving Minority Participation and Achievement in the Geosciences

    NASA Astrophysics Data System (ADS)

    Baron, D.; Negrini, R.; Palacios-Fest, M. R.

    2004-12-01

    Numerous studies have shown that one of the best ways to draw students into geoscience programs is to expose them and their teachers to research projects designed to investigate issues relevant to their lives and communities. To be most effective, involvement in these projects should begin at the pre-college level and continue throughout their college career. Recognizing the importance of genuine research experiences, the Department of Geology at California State University, Bakersfield (CSUB), with support from the National Science Foundation's Opportunities for Enhancing Diversity in the Geosciences program, provides research participation opportunities for teachers and students from the Bakersfield City School District and the Kern High School District. Both districts have a high percentage of low-income and minority students that normally would not consider a degree or career in the geosciences. The project centers around a four-week summer research program and follow-up activities during the school year. The research investigates the climate history of the southern San Joaquin Valley as well as the frequency of flooding in the valley. Many teachers and students are familiar with periodic flooding from personal experience and are aware of the larger issue of climate change in the past and present from news reports. Thus, they can directly relate to the relevance of the research. The project draws on the faculty's expertise in paleoclimatology and geochemistry and takes advantage of CSUB's existing research facilities. Sediments in the dry lake basins of Buena Vista Lake and Kern Lake preserve a record of the regional climate history and flooding of the Kern River and its tributaries. In the first year of the project, 6 teachers and 10 high school students worked with CSUB faculty and students. Three cores from the lake basins were collected. The cores were analyzed using established geophysical, geochemical, lithological, and micropaleontological techniques

  8. The puzzling presence of calcite in skeletons of modern solitary corals from the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    Goffredo, Stefano; Caroselli, Erik; Mezzo, Francesco; Laiolo, Leonardo; Vergni, Patrizia; Pasquini, Luca; Levy, Oren; Zaccanti, Francesco; Tribollet, Aline; Dubinsky, Zvy; Falini, Giuseppe

    2012-05-01

    The skeleton of scleractinian corals is commonly believed to be composed entirely of aragonite due to the current Mg/Ca molar ratio of seawater, which thermodynamically favours the deposition of this polymorph of calcium carbonate (CaCO3). However, some studies have shown that other forms of CaCO3 such as calcite can be present in significant amount (1-20%) inside tropical coral skeletons, significantly impacting paleo-reconstructions of SST or other environmental parameters based on geochemical proxies. This study aims at investigating for the first time, (1) the skeletal composition of two Mediterranean solitary corals, the azooxanthellate Leptopsammia pruvoti and the zooxanthellate Balanophyllia europaea, across their life cycle, (2) the distribution of the different CaCO3 forms inside skeletons, and (3) their implications in paleoclimatology. The origin of the different forms of CaCO3 observed inside studied coral skeletons and their relationships with the species' habitat and ecological strategies are also discussed. CaCO3 composition of L. pruvoti and B. europaea was investigated at six sites located along the Italian coasts. Skeleton composition was studied by means of X-ray powder diffraction and Fourier transform infrared spectroscopy. A significant amount of calcite (1-23%) was found in more than 90% of the studied coral skeletons, in addition to aragonite. This calcite was preferentially located in the basal and intermediate areas than at the oral pole of coral skeletons. Calcite was also mainly located in the epitheca that covered the exposed parts of the coral in its aboral region. Interestingly in B. europaea, the calcite content was negatively correlated with skeleton size (age). The presence of calcite in scleractinian corals may result from different mechanisms: (1) corals may biologically precipitate calcite crystals at their early stages in order to insure their settlement on the substrate of fixation, especially in surgy environments; (2

  9. The PAGES 2k Global Multiproxy Database for Temperature Reconstructions of the Common Era

    NASA Astrophysics Data System (ADS)

    McKay, N.; Emile-Geay, J.

    2015-12-01

    In 2013 the PAGES 2k Consortium released a paleo-temperature database with more than 500 records from 7 continental-scale regions, along with continental-scale temperature reconstructions derived independent by expert groups for each region. A major motivation of this effort was to increase the amount of regional expertise involved in identifying and evaluating paleoclimate records for their use in temperature reconstructions. The project highlighted the value of engaging regionally-based expertise in paleoclimatology; however, the resulting database was somewhat disjoint, as each group assembled data independently with somewhat distinct goals and criteria, which hindered the use of the database to answer questions that span across multiple regions. Moreover, key data (e.g., native measurements, chronological uncertainties) and metadata (e.g., seasonality) were not included. Phase 2 of the PAGES 2k temperature database improves upon these shortcomings with a community-built flexible database that can be used to address major questions about the climate of the Common Era, and to refine the methodologies used to reconstruct it. As in phase 1, the database was built upon the expertise of dozens of paleclimatologists whose regional expertise spans the globe. Phase 2 of the temperature database includes about 800 temperature-sensitive timeseries, derived from ten archive types, including from the oceans. Here we present the characteristics and structure of the database, including a suite of diagnostics used to evaluate the fidelity of the temperature signal in the data. This includes their correlation with instrumental temperature data; however this assessment is not possible with all the records in the database, and we also recognize that such correlations are an imperfect metric of how strongly a timeseries reflects temperature throughout the Common Era. Consequently, we also explore other metrics, including how well each record corresponds with with nearby sites back

  10. A multiple-proxy approach to understanding rapid Holocene climate change in Southeast Greenland

    NASA Astrophysics Data System (ADS)

    Davin, S. H.; Bradley, R. S.; Balascio, N. L.; de Wet, G.

    2012-12-01

    The susceptibility of the Arctic to climate change has made it an excellent workshop for paleoclimatological research. Although there have been previous studies concerning climate variability carried out in the Arctic, there remains a critical dearth of knowledge due the limited number of high-resolution Holocene climate-proxy records available from this region. This gap skews our understanding of observed and predicted climate change, and fuels uncertainty both in the realms of science and policy. This study takes a comprehensive approach to tracking Holocene climate variability in the vicinity of Tasiilaq, Southeast Greenland using a ~5.6 m sediment core from Lower Sermilik Lake. An age-depth model for the core has been established using 8 radiocarbon dates, the oldest of which was taken at 4 m down core and has been been dated to approximately 6.2 kyr BP. The bottom meter of the core below the final radiocarbon date contains a transition from cobbles and coarse sand to organic-rich laminations, indicating the termination of direct glacial influence and therefore likely marking the end of the last glacial period in this region. The remainder of the core is similarly organic-rich, with light-to-dark brown laminations ranging from 0.5 -1 cm in thickness and riddled with turbidites. Using this core in tandem with findings from an on-site assessment of the geomorphic history of the locale we attempt to assess and infer the rapid climatic shifts associated with the Holocene on a sub-centennial scale. Such changes include the termination of the last glacial period, the Mid-Holocene Climatic Optimum, the Neoglacial Period, the Medieval Climatic Optimum, and the Little Ice Age. A multiple proxy approach including magnetic susceptibility, bulk organic geochemistry, elemental profiles acquired by XRF scanning, grain-size, and spectral data will be used to characterize the sediment and infer paleoclimate conditions. Additionally, percent biogenic silica by weight has been

  11. Long continental pollen record of the last ca. 500 ka in eastern Anatolia - First palynological results from Lake Van cores obtained in 2010

    NASA Astrophysics Data System (ADS)

    Pickarski, N.; Heumann, G.; Litt, T.

    2012-04-01

    Lake Van is located in a climatically sensitive semiarid and tectonically active region in Eastern Anatolia, Turkey. It is a key site to reconstruct terrestrial paleoecology and paleoclimate in the Near East during the Quaternary. Lake Van is the largest soda lake (surface area 3.570 km2) and the fourth largest terminal lake in the world (volume 607 km3). The maximum water depth is 460 m and the maximum length is 130 km WSW-ENE. The present lake level is at an elevation of 1,646 m above mean sea level. The northern and eastern part of Lake Van is mainly characterized by steppe vegetation related to the so-called Irano-Turanian plant geographical territory. In contrast, some remnants of deciduous oak forests can be observed mainly in the Bitlis Massive, SW of the lake. We present preliminary palynological results of a long continental sedimentary record obtained during a coring campaign supported by the International Continental Scientific Drilling Program (ICDP) in summer 2010. The composite profile from the Ahlat Ridge, the most important site for paleoclimatological studies (total length of ca. 218 m), yields a continuous paleoclimate archive encompassing ca. 500.000 years. The record is partly characterized by annually laminated sediments. By using pollen analysis, several glacial and interglacial/ interstadial periods can be observed. The warm stages can be identified based on higher amounts of pollen from thermophilous trees such as deciduous oak. In addition to the current interglacial stage (MIS 1), pronounced warm phases coincide with past interglacials probably correlative to MIS 5, 7, 9 and 11 or 13. Cold stages are characterized by pollen types related to steppe plants such as Artemisia, chenopods and grasses. The glacial-interglacial cycles as reflected in the palynological data are in broad agreement with those of stable oxygen isotope analyses based on autigenic carbonate of the lacustrine sediments (bulk). Caused by the state of the art, more

  12. Bulk composition of northern African dust and its source sediments — A compilation

    NASA Astrophysics Data System (ADS)

    Scheuvens, Dirk; Schütz, Lothar; Kandler, Konrad; Ebert, Martin; Weinbruch, Stephan

    2013-01-01

    incorporating the composition of source sediments (e.g., mineralogy) into global or regional dust transport models and can be compared with source analysis by remote sensing or back-trajectory analysis. However, source apportionment studies supported by our data set will not only be useful for actual dust samples, but will also be helpful for the understanding of paleo-wind directions and hence paleo-climatological conditions through the investigation of Quaternary eolian sediments deposited in and around northern Africa.

  13. Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity

    NASA Astrophysics Data System (ADS)

    Métivier, Laurent; Caron, Lambert; Greff-Lefftz, Marianne; Pajot-Métivier, Gwendoline; Fleitout, Luce; Rouby, Hélène

    2016-10-01

    The Earth's surface was depressed under the weight of ice during the last glaciations. Glacial Isostatic Adjustment (GIA) induces the slow recession of the trough that is left after deglaciation and is responsible for a contemporary uplift rate of more than 1 cm/yr around Hudson Bay. The present-day residual depression, an indicator of still-ongoing GIA, is difficult to identify in the observed topography, which is predominantly sensitive to crustal heterogeneities. According to the most widespread GIA models, which feature a viscosity of 2- 3 ×1021 Pa s on top of the lower mantle, the trough is approximately 100 m deep and cannot explain the observed gravity anomalies across North America. These large anomalies are therefore usually attributed to subcontinental density heterogeneities in the tectosphere or to slab downwelling in the deep mantle. Here, we use observed gravity gradients (GG) to show that the uncompensated GIA trough is four times larger than expected and that it is the main source of the North American static gravity signal. We search for the contribution to these GGs from mantle mass anomalies, which are deduced from seismic tomography and are mechanically coupled to the global mantle flow. This contribution is found to be small over Laurentia, and at least 82% of the GGs are caused by GIA. Such a contribution from GIA in these GG observations implies a viscosity that is greater than 1022 Pa s in the lower mantle. Our conclusions are a plea for GIA models with a highly viscous lower mantle, which confirm inferences from mantle dynamic models. Any change in GIA modelling has important paleoclimatological and environmental implications, encouraging scientists to re-evaluate the past ice history at a global scale. These implications, in turn, affect the contribution of bedrock uplift to the contemporaneous mass balance over Antarctica and Greenland and thus the present-day ice-melting rate as deduced from the GRACE space mission. Additionally

  14. SEARCH: Study of Environmental Arctic Change--A System-scale, Cross-disciplinary, Long-term Arctic Research Program

    NASA Astrophysics Data System (ADS)

    Wiggins, H. V.; Schlosser, P.; Loring, A. J.; Warnick, W. K.; Committee, S. S.

    2008-12-01

    The Study of Environmental Arctic Change (SEARCH) is a multi-agency effort to observe, understand, and guide responses to changes in the arctic system. Interrelated environmental changes in the Arctic are affecting ecosystems and living resources and are impacting local and global communities and economic activities. Under the SEARCH program, guided by the Science Steering Committee (SSC), the Interagency Program Management Committee (IPMC), and the Observing, Understanding, and Responding to Change panels, scientists with a variety of expertise--atmosphere, ocean and sea ice, hydrology and cryosphere, terrestrial ecosystems, human dimensions, and paleoclimatology--work together to achieve goals of the program. Over 150 projects and activities contribute to SEARCH implementation. The Observing Change component is underway through National Science Foundation's (NSF) Arctic Observing Network (AON), NOAA-sponsored atmospheric and sea ice observations, and other relevant national and international efforts, including the EU- sponsored Developing Arctic Modelling and Observing Capabilities for Long-term Environmental Studies (DAMOCLES) Program. The Understanding Change component of SEARCH consists of modeling and analysis efforts, with strong linkages to relevant programs such as NSF's Arctic System Synthesis (ARCSS) Program. The Responding to Change element is driven by stakeholder research and applications addressing social and economic concerns. As a national program under the International Study of Arctic Change (ISAC), SEARCH is also working to expand international connections in an effort to better understand the global arctic system. SEARCH is sponsored by eight (8) U.S. agencies, including: the National Science Foundation (NSF), the National Oceanic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA), the Department of Defense (DOD), the Department of Energy (DOE), the Department of the Interior (DOI), the Smithsonian

  15. The CREp program, a fully parameterizable program to compute exposure ages (3He, 10Be)

    NASA Astrophysics Data System (ADS)

    Martin, L.; Blard, P. H.; Lave, J.; Delunel, R.; Balco, G.

    2015-12-01

    Over the last decades, cosmogenic exposure dating permitted major advances in Earth surface sciences, and particularly in paleoclimatology. Yet, exposure age calculation is a dense procedure. It requires numerous choices of parameterization and the use of an appropriate production rate. Nowadays, Earth surface scientists may either calculate exposure ages on their own or use the available programs. However, these programs do not offer the possibility to include all the most recent advances in Cosmic Ray Exposure (CRE) dating. Notably, they do not propose the most recent production rate datasets and they only offer few possibilities to test the impact of the atmosphere model and the geomagnetic model on the computed ages. We present the CREp program, a Matlab © code that computes CRE ages for 3He and 10Be over the last 2 million years. The CREp program includes the scaling models of Lal-Stone in the "Lal modified" version (Balco et al., 2008; Lal, 1991; Stone, 2000) and the LSD model (Lifton et al., 2014). For any of these models, CREP allows choosing between the ERA-40 atmosphere model (Uppala et al., 2005) and the standard atmosphere (National Oceanic and Atmospheric Administration, 1976). Regarding the geomagnetic database, users can opt for one of the three proposed datasets: Muscheler et al. 2005, GLOPIS-75 (Laj et al. 2004) and the geomagnetic framework proposed in the LSD model (Lifton et al., 2014). They may also import their own geomagnetic database. Importantly, the reference production rate can be chosen among a large variety of possibilities. We made an effort to propose a wide and homogenous calibration database in order to promote the use of local calibration rates: CREp includes all the calibration data published until July 2015 and will be able to access an updated online database including all the newly published production rates. This is crucial for improving the ages accuracy. Users may also choose a global production rate or use their own data

  16. A New Method of Obtaining High-Resolution Paleoclimate Records from Speleothem Fluid Inclusions

    NASA Astrophysics Data System (ADS)

    Logan, A. J.; Horton, T. W.

    2010-12-01

    We present a new method for stable hydrogen and oxygen isotope analysis of ancient drip water trapped within cave speleothems. Our method improves on existing fluid inclusion isotopic analytical techniques in that it decreases the sample size by a factor of ten or more, dramatically improving the spatial and temporal precision of fluid inclusion-based paleoclimatology. Published thermal extraction methods require large samples (c. 150 mg) and temperatures high enough (c. 500-900°C) to cause calcite decomposition, which is also associated with isotopic fractionation of the trapped fluids. Extraction by crushing faces similar challenges, where the failure to extract all the trapped fluid can result in isotopic fractionation, and samples in excess of 500 mg are required. Our new method combines the strengths of these published thermal and crushing methods using continuous-flow isotope ratio analytical techniques. Our method combines relatively low-temperature (~250°C) thermal decrepitation with cryogenic trapping across a switching valve sample loop. In brief, ~20 mg carbonate samples are dried (75°C for >1 hour) and heated (250°C for >1 hour) in a quartz sample chamber under a continuously flowing stream of ultra-high purity helium. Heating of the sample chamber is achieved by use of a tube furnace. Fluids released during the heating step are trapped in a coiled stainless steel cold trap (~ -98°C) serving as the sample loop in a 6-way switching valve. Trapped fluids are subsequently injected into a high-temperature conversion elemental analyzer by switching the valve and rapidly thawing the trap. This approach yielded accurate and precise measurements of injected liquid water IAEA reference materials (GISP; SMOW2; SLAP2) for both hydrogen and oxygen isotopic compositions. Blanking tests performed on the extraction line demonstrate extremely low line-blank peak heights (<50mv). Our tests also demonstrate that complete recovery of liquid water is possible and that

  17. Coral Skeleton Density Banding: Biotic Response to Changes in Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Hill, C. A.; Sivaguru, M.; Fried, G. A.; Fouke, B. W.

    2010-12-01

    Density bands in the CaCO3 (aragonite) skeleton of scleractinian corals are commonly used as chronometers, where crystalline couplets of high and low density bands represent the span of one year. Isotopic analysis of these density bands provides a sensitive reconstructive tool for paleoclimatology and paleoecology. However, the detailed biotic mechanisms controlling coral skeleton aragonite nucleation and crystallization events and resulting skeletal growth rate remain uncertain. The coral tissue organic matrix, composed of macromolecules secreted by the calicoblastic ectoderm, is closely associated with skeletal precipitation and is itself incorporated into the skeleton. We postulate that density banding is primarily controlled by changes in the rate of aragonite crystal precipitation mediated by the coral holobiont response to changes in sea surface temperature (SST). To test this hypothesis, data were collected from coral skeleton-tissue biopsies (2.5 cm in diameter) extracted from four species of Montastraea growing on the fringing reef tract of Curacao, Netherlands Antilles. Annual mean variation in SST on Curacao range from 29o in mid-September to 26o C in late February. Samples were collected at strategic time periods spanning the 3o C annual variations in SST. Our nanometer-scale optical analyses of skeletal morphology have revealed consistent changes between high- and low-skeletal density bands, resulting in an 11% increase in the volume of aragonite precipitated in high-density skeletal bands. The re-localization and/or change in abundance of mucus, carbonic anhydrase (a molecule that catalyzes the hydration of carbon dioxide), calmodulin (a calcium-binding protein) and the change in density of gastrodermal symbiotic dinoflagellates has permitted estimates of seasonally-fluctuating carbon allocation by the coral holobiont in response to changing environmental conditions. This digital reconstruction of over 2000 images of one-micron-thick histological

  18. Geochemically tracking provenance changes in marine sediment from the South Pacific Gyre throughout the Cenozoic

    NASA Astrophysics Data System (ADS)

    Dunlea, A. G.; Murray, R. W.; Sauvage, J.; Spivack, A. J.; Harris, R. N.; D'Hondt, S. L.

    2012-12-01

    The South Pacific Gyre (SPG), characterized by extremely slow sedimentation rates, is the world's largest oceanic desert. The little eolian dust from continents in the Southern Hemisphere must traverse great distances to reach the SPG, and the ultra-oligotrophic waters minimize the biogenic flux of sediment to the seafloor. However sparse, the pelagic sediment that is ultimately found on the seafloor retains a chemical record that can be used to trace its origin. Using cores from Integrated Ocean Drilling Program Expedition 329, we trace downcore fluctuations in major, trace, and rare earth element (REE) composition and flux to yield clues to the geological, chemical, and biological evolution of the SPG throughout the Cenozoic. The shipboard scientific party generally described the completely oxic, brown pelagic clays recovered during Exp. 329 as zeolitic metalliferous clay. The homogenous, very fine-grained nature of these sediments speaks to the challenges we face in resolving eolian detrital material ("dust"), fine-grained ash (commonly altered), and authigenic aluminosilicates from one another. Based on ICP-ES and ICP-MS analyses followed by multivariate statistical treatments, we are developing chemical records from a number of sites located throughout the SPG. Building on earlier work at DSDP Site 596 (Zhou and Kyte, 1992, Paleocean., 7, 441-465), and based on backtrack paths from 100 Ma forward, we are working to construct a regionally and temporally continuous paleoclimatological history of the SPG. Preliminary La-Th-Sc concentrations from Sites U1367, U1368, and U1369 show a distinct authigenic influence, but several refractory elements retain their original provenance signature. Sediment ages are constrained using a constant-Co model, based on the geochemically similar work that Zhou and Kyte (1992) performed in the SPG. REE concentrations normalized to post-archean average shale (PAAS) reveal a negative Ce anomaly that becomes more pronounced closer to

  19. Did tropical rainforest vegetation exist during the Late Cretaceous? New data from the late Campanian to early Maastrichtian Olmos Formation, Coahuila, Mexico.

    NASA Astrophysics Data System (ADS)

    Upchurch, G. R.; Estrada-Ruiz, E.; Cevallos-Ferriz, S. S.

    2008-12-01

    A major problem in paleobotany and paleoclimatology is the origin of modern tropical and paratropical rainforests. Studies of leaf macrofossils, beginning with those of Wolfe and Upchurch, have suggested that tropical and paratropical (i.e., megathermal) rainforests with dominant angiosperms are of Cenozoic origin, and that comparable vegetation was either absent or greatly restricted during the Late Cretaceous. Earth System modeling studies, in contrast, predict the existence of megathermal rainforest vegetation during the mid- and Late Cretaceous, though with less areal extent than during the Late Cenozoic and Recent. Megathermal climate with year-round precipitation is simulated along the paleoequator and along the northern margin of the Tethys Ocean, and tends to occur in highly focused regions, in contrast to the more latitudinally zoned pattern of the Recent. Low-resolution climatic indicators, such as the distribution of coals and tree fern spores, are consistent with evidence from climate modeling for megathermal wet climates during the Late Cretaceous, and by extension megathermal rainforest vegetation. However, corroborative data from plant macrofossil assemblages is needed, because the physiognomy of leaves and woods directly reflects plant adaptation to the environment and can estimate climate independently of the generic and familial affinities of the paleoflora. Newly collected plant macrofossil assemblages from the late Campian to early Maastrichtian Olmos Formation of Coahuila, Mexico, provide evidence for megathermal rainforest vegetation on the northern margin of the Tethys Ocean at approximately 35 degrees paleolatitude. The newly collected leaf flora is 72 percent entire- margined and has abundant palms, features typical of modern megathermal rainforests. Thirty percent of the species have large leaves, and 50 percent of the species have drip tips, features indicative of wet conditions. Simple and multiple regression functions based on the

  20. Graduate training in Earth science across borders and disciplines: ArcTrain -"Processes and impacts of climate change in the North Atlantic Ocean and the Canadian Arctic"

    NASA Astrophysics Data System (ADS)

    Stein, Rüdiger; Kucera, Michal; Walter, Maren; de Vernal, Anne

    2015-04-01

    Due to a complex set of feedback processes collectively known as "polar amplification", the Arctic realm is expected to experience a greater-than-average response to global climate forcing. The cascades of feedback processes that connect the Arctic cryosphere, ocean and atmosphere remain incompletely constrained by observations and theory and are difficult to simulate in climate models. Our capacity to predict the future of the region and assess the impacts of Arctic change processes on global and regional environments hinges on the availability of interdisciplinary experts with strong international experience and understanding of the science/society interface. This is the basis of the International Research Training Group "Processes and impacts of climate change in the North Atlantic Ocean and the Canadian Arctic - ArcTrain", which was initiated in 2013. ArcTrain aims to educate PhD students in an interdisciplinary environment that combines paleoclimatology, physical oceanography, remote sensing and glaciology with comprehensive Earth system modelling, including sea-ice and ice-sheet components. The qualification program for the PhD students includes joint supervision, mandatory research residences at partner institutions, field courses on land and on sea (Floating University), annual meetings and training workshops and a challenging structured training in expert skills and transferrable skills. Its aim is to enhance the career prospects and employability of the graduates in a challenging international job market across academic and applied sectors. ArcTrain is a collaborative project at the University of Bremen and the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven. The German part of the project is designed to continue for nine years and educate three cohorts of twelve PhD students each. The Canadian partners comprise a consortium of eight universities led by the GEOTOP cluster at the Université du Québec à Montréal and including

  1. Reconciling late Quaternary transgressions in the Bohai Sea, China to the global sea level changes, and new linkage of sedimentary records to three astronomical rhythms

    NASA Astrophysics Data System (ADS)

    Yi, Liang

    2013-04-01

    The Bohai Sea in China was formed by subsidence during the Cenozoic. Some 2000-3000 m of fluvial, lacustrine and marine sediments has been deposited in the basin (IOCAS 1985), and these sediments have great potentials in high-/low-latitude interaction, environmental impacts on ancient human activities, and other important issues (Liu, 2009; Yi et al. 2012a), because it is influenced by the Siberian-Mongolian Highs and the ITCZ, and is close to the Nihewan basin and the Zhoukoudian site which are both world-renowned for the discovery of Homo erectus. Since the 1970s, hundreds of studies have been conducted around the Bohai Sea and the major results could be summarized as follows (Zhao et al., 1978; IOCAS, 1985; Liu, 2009, and references therein): (1) constrained by radiocarbon dating, TL/OSL or geomagnetic excursion, three transgressions (T1, T2, T3) developed during the Holocene, marine isotopic stage (MIS) 3 and MIS 5, respectively; and (2) regressions occurred at the beginning of glacial stages, i.e. MIS2 and MIS4. However, apparent inconsistency could be found between T2 and T3, and the question is that in the context that MIS 3 is an inter-stadial stage with a global sea level of 60~80 m lower than the present (Chappell et al. 1996), how did T2 occur in the Bohai Sea, and why did T2 have much larger influence than T3 which occurred at the beginning of MIS 5? To correlate regional environmental changes with global pattern and thus to detect the potential interaction between various driving factors on orbital timescales, three cores with a high recovery rate were drilled in the south Bohai Sea. This study was conducted following three perspectives: chronology (Yi et al. 2012b), sea-level change (Yi et al. 2012c) and paleoclimatology (Yi et al. 2012a), and the main results are as follows: 1. Chronology. Luminescence and radiocarbon dating methods were applied in dating these coastal/marine sediments: (1) For Holocene samples, most of the radiocarbon dates agree

  2. Salt Playas of the Bolivian Altiplano

    NASA Technical Reports Server (NTRS)

    2003-01-01

    In the high plateau of southwestern Bolivia, two large salt deserts, or playas, are located between the eastern and western Andes. The Salar de Uyuni is the largest and highest playa in the world, encompassing an area of more than 9000 square kilometers and situated more than 3600 meters above sea level. It is separated by a range of hills from its smaller neighbor to the north, the Salar de Coipasa. During the Pleistocene the climate of the region was wetter and the entire area was covered by a massive lake. As the waters slowly dried, abundant dissolved minerals were left behind to form the playas. The salt pans are now excellent indicators of rainfall fluctuations within the region and are also important sites for the study of paleoclimatology.

    These two image pairs from the Multi-angle Imaging SpectroRadiometer (MISR)depict the playas on January 16, 2002 and January 3, 2003. At this time of year the wet season has already begun, and the Salar de Coipaso is usually at least partially flooded. Data from these two dates were processed identically to preserve relative variations in brightness between them. Varying degrees of surface moisture around the two playas are illustrated by the different display techniques of the right and left-hand panels.

    At left are two false-color views acquired by MISR's nadir camera. Data from the near-infrared, green and blue bands are displayed as red, green and blue. This spectral display causes bright, wet surfaces to appear blue-green because water selectively absorbs longer wavelengths such as near-infrared. Significantly more standing water is present in the Salar de Coipaso in 2002 than in 2003. However, a stronger signal at the near-infrared band on the 2003 date, which causes the overall hue in the 2003 image to be redder than 2002, suggests an increase in photosynthetic activity (plant growth) at the 2003 date compared with one year earlier.

    The right-hand panels were created using only red band data, and are

  3. Reconstruction of sea surface water dynamics in the North Atlantic during the Mid-Pleistocene (~540-400 ka)

    NASA Astrophysics Data System (ADS)

    Martinez-Sanchez, Marta; Flores, José-Abel; Palumbo, Eliana; Alonso-García, Montserrat; Sierro, Francisco-Javier; Ornella Amore, Filomena

    2014-05-01

    . Sierro, José A. Flores, Arctic front shifts in the subpolar North Atlantic during the Mid-Pleistocene (800-400ka) and their implications for ocean circulation, Palaeogeography, Palaeoclimatology, Palaeoecology,Volume 311, Issues 3-4, 15 November 2011, Pages 268-280, http://dx.doi.org/10.1016/j.palaeo.2011.09.004. F.O. Amore, J.A. Flores, A.H.L. Voelker, S.M. Lebreiro, E. Palumbo, F.J. Sierro, A Middle Pleistocene Northeast Atlantic coccolithophore record: Paleoclimatology and paleoproductivity aspects, Marine Micropaleontology, Volumes 90-91, June 2012, Pages 44-59, , http://dx.doi.org/10.1016/j.marmicro.2012.03.006. E. Palumbo, J.A. Flores, C. Perugia, Z. Petrillo, A.H.L. Voelker, F.O. Amore, Millennial scale coccolithophore paleoproductivity and surface water changes between 445 and 360ka (Marine Isotope Stages 12/11) in the Northeast Atlantic, Palaeogeography, Palaeoclimatology, Palaeoecology, Volumes 383-384, August 2013, Pages 27-41, http://dx.doi.org/10.1016/j.palaeo.2013.04.024.

  4. Leaf wax n-alkane distributions in and across modern plants: Implications for paleoecology and chemotaxonomy

    NASA Astrophysics Data System (ADS)

    Bush, Rosemary T.; McInerney, Francesca A.

    2013-09-01

    Long chain (C21 to C37) n-alkanes are among the most long-lived and widely utilized terrestrial plant biomarkers. Dozens of studies have examined the range and variation of n-alkane chain-length abundances in modern plants from around the world, and n-alkane distributions have been used for a variety of purposes in paleoclimatology and paleoecology as well as chemotaxonomy. However, most of the paleoecological applications of n-alkane distributions have been based on a narrow set of modern data that cannot address intra- and inter-plant variability. Here, we present the results of a study using trees from near Chicago, IL, USA, as well as a meta-analysis of published data on modern plant n-alkane distributions. First, we test the conformity of n-alkane distributions in mature leaves across the canopy of 38 individual plants from 24 species as well as across a single growing season and find no significant differences for either canopy position or time of leaf collection. Second, we compile 2093 observations from 86 sources, including the new data here, to examine the generalities of n-alkane parameters such as carbon preference index (CPI), average chain length (ACL), and chain-length ratios for different plant groups. We show that angiosperms generally produce more n-alkanes than do gymnosperms, supporting previous observations, and furthermore that CPI values show such variation in modern plants that it is prudent to discard the use of CPI as a quantitative indicator of n-alkane degradation in sediments. We also test the hypotheses that certain n-alkane chain lengths predominate in and therefore can be representative of particular plant groups, namely, C23 and C25 in Sphagnum mosses, C27 and C29 in woody plants, and C31 in graminoids (grasses). We find that chain-length distributions are highly variable within plant groups, such that chemotaxonomic distinctions between grasses and woody plants are difficult to make based on n-alkane abundances. In contrast

  5. Major refit of R/V MARION DUFRESNE and giant sediment corer improvements

    NASA Astrophysics Data System (ADS)

    Leau, Hélène; Réaud, Yvan

    2015-04-01

    The french Research Vessel MARION DUFRESNE is equipped with a unique sediment coring facility, called CALYPSO, developed initially by Yvon BALUT at the French Polar Institute, Paul-Emile Victor (IPEV) that operates the vessel 217 days per year in all oceans. The CALYPSO sediment corer retrieves routinely 50 m long undisturbed sediment cores in any water depths, and presently holds the worldwide record of the longest core ever retrieved, that is 64.5 m. This vessel is then a fantastic opportunity for the paleoceanographic community to carry out expeditions at sea. Over the last 20 years, many international IMAGES coring expeditions were organized in all the ocean basins around the world on board the R/V MARION DUFRESNE. More than 1500 cores were retrieved, leading to major advances in the paleoceanography and paleoclimatology of the Late Quaternary. The vessel will celebrate her 20th anniversary in 2015 and will undergo a major refit on hull & machineries, public spaces, as well as scientific equipment. The coring capacity is currently being developed to further improve - The length of the retrievable core, with an objective of 75 m long core in routine - The quality of the sediment un-disturbance with a specially designed coring cable with controlled minimum elasticity - The safety of the operations at sea - The quality control of the operations with a suite of sensors and software allowing a detailed monitoring of the coring operation - The time requested for each operation - The environment data collection, in the same time as the coring operations The detailed description of the upgrades will be presented. They consist in a new suite of acoustic sensors that will be integrated on board the vessel during the 4 months ship yard stay from April to July 2015, amongst which a KONSBERG EM122 multibeam echo-sounder and a SBP 120-3 sub-bottom profiler, both mounted on a gondola fitted under the hull of the vessel. This equipment will allow the highest quality images of

  6. The Devil's Hole Is In The Details

    NASA Astrophysics Data System (ADS)

    Wallace, M. G.

    2012-12-01

    the Heliosphere: Effect of the Solar Journey on the Galactic Cosmic Ray Flux at Earth. Space Science Review DOI 10.1007/s11214-011-9766-x. Kohfeld, Karen E., and Andy Ridgewell, 2009, "Glacial-Interglacial Variability in Atmospheric CO2", Surface Ocean-Lower Atmosphere Processes Geophysical Research Series 187, pp. 251-286. Landwehr, J.M., Sharp, W.D., Coplen, T.B., Ludwig, K.R., and Winograd, I.J., 2011, "The chronology for the δ18O record from Devil's Hole, Nevada, extended into the mid-Holocene: U.S. Geological Survey Open-File Report 2011-1082, 5 p. NOAA Paleoclimatology Program - Paleocean Site Data. tr163-19_ssts-fwc.txt # SST data only # File Created: 19-Jan-2005. ftp://ftp.ncdc.noaa.gov/pub/data/paleo/paleocean/sediment_files/sst/tr163-19_ssts-fwc.txt. Patterson, DB, and Farley, KA (1998): Extraterrestrial 3He in seafloor sediments: Evidence for correlated 100 kyr periodicity in the accretion rate of interplanetary dust, orbital parameters, and Quaternary climate. Geochimica et Cosmochimica Acta, 62(23-24), 3669-3682. Shakun, Jeremy D. , Peter U. Clark, Feng He, Shaun A. Marcott, Alan C. Mix, Zhengyu Liu, Bette Otto-Bliesner, Andreas Schmittner & Edouard Bard, 2012, "Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation" Nature Vol 484. pp 49-55.

  7. Terrestrial cosmogenic 3He: where are we 30 years after its discovery?

    NASA Astrophysics Data System (ADS)

    Blard, Pierre-Henri; Pik, Raphaël; Farley, Kenneth A.; Lavé, Jérôme; Marrocchi, Yves

    2016-04-01

    It is now 30 years since cosmogenic 3He has been detected for the first time in a terrestrial sample (Kurz, 1986). 3He is now a widely used geochemical tool in many fields of Earth sciences: volcanology, tectonics, paleoclimatology. 3He has the advantage to have a high "production rate" to "detection limit" ratio, allowing surfaces as young as hundred of years to be dated. Although its nuclear stability implies several limitations, it moreover represents a useful alternative to 10Be in mafic environments. This contribution is a review of the progresses that have been accomplished since this discovery, and discuss strategies to improve both the accuracy and the precision of this geochronometer. 1) Measurement of cosmogenic 3He Correction of magmatic 3He. To estimate the non-cosmogenic magmatic 3He, Kurz (1986) invented a two steps method involving crushing of phenocrysts (to analyze the isotopic ratio of the magmatic component), followed by a subsequent melting of the sample, to extract the remaining components, including the cosmogenic 3He: 3Hec = 3Hemelt ‑4Hemelt x (3He/4He)magmatic (1) Several studies suggested that the preliminary crushing may induce a loss of cosmogenic 3He (Hilton et al., 1993; Yokochi et al., 2005; Blard et al., 2006), implying an underestimate of the cosmogenic 3He measurement. However, subsequent work did not replicate these observations (Blard et al., 2008; Goerhing et al., 2010), suggesting an influence of the used apparatus. An isochron method (by directly melting several phenocrysts aliquots) is an alternative to avoid the preliminary crushing step (Blard and Pik, 2008). Atmospheric contamination. Protin et al. (in press) provides robust evidences for a large and irreversible contamination of atmospheric helium on silicate surfaces. This unexpected behavior may reconcile the contrasted observations about the amplitude of crushing loss. This undesirable atmospheric contamination is negligible if grain fractions smaller than 150 mm are

  8. High Spatial Resolution Isotopic Abundance Measurements by Secondary Ion Mass Spectrometry: Status and Prospects

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.

    2007-12-01

    Secondary Ion Mass Spectrometry, SIMS or ion microprobe analysis, has become an important tool for geochemistry because of its ability study the distributions of elemental and isotopic abundances in situ on polished samples with high (typically a few microns to sub-micron) spatial resolution. In addition, SIMS exhibits high sensitivity for a wide range of elements (H to Pu) so that isotope analyses can sometimes be performed for elements that comprise only trace quantities of some mineral phase (e.g., Pb in zircon) or on major and/or minor elements in very small samples (e.g., presolar dust grains). Offsetting these positive attributes are analytical difficulties due to the complexity of the sputtering source of analyte ions: (1) relatively efficient production of molecular ion species (especially from a complex matrix such as most natural minerals) that cause interferences at the same nominal mass as atomic ions of interest, and (2) quantitation problems caused by variations in the ionization efficiencies of different elements and/or isotopes depending upon the chemical state of the sample surface during sputtering--the so-called "matrix effects". Despite the availability of high mass resolution instruments (e.g., SHRIMP II/RG, CAMECA 1270/1280/NanoSIMS), the molecular ion interferences effectively limit the region of the mass table that can be investigated in most samples to isotope systems at Ni or lighter or at Os or heavier. The matrix effects and the sensitivity of instrumental mass discrimination to the physical state of the sample surface can hamper reproducibility and have contributed to a view that SIMS analyses, especially for so- called stable isotopes, are most appropriate for extraterrestrial samples which are often small, rare, and can exhibit large magnitude isotopic effects. Recent improvements in instrumentation and technique have extended the scope of SIMS isotopic analyses and applications now range from geochronology to paleoclimatology to

  9. Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA

    USGS Publications Warehouse

    Dunagan, S.P.; Turner, C.E.

    2004-01-01

    During deposition of the Upper Jurassic Morrison Formation, water that originated as precipitation in uplands to the west of the Western Interior depositional basin infiltrated regional aquifers that underlay the basin. This regional groundwater system delivered water into the otherwise dry continental interior basin where it discharged to form two major wetland/lacustrine successions. A freshwater carbonate wetland/lacustrine succession formed in the distal reaches of the basin, where regional groundwater discharged into the Denver-Julesburg Basin, which was a smaller structural basin within the more extensive Western Interior depositional basin. An alkaline-saline wetland/lacustrine complex (Lake T'oo'dichi') formed farther upstream, where shallower aquifers discharged into the San Juan/Paradox Basin, which was another small structural basin in the Western Interior depositional basin. These were both wetlands in the sense that groundwater was the major source of water. Input from surface and meteoric water was limited. In both basins, lacustrine conditions developed during episodes of increased input of surface water. Inclusion of wetlands in our interpretation of what had previously been considered largely lacustrine systems has important implications for paleohydrology and paleoclimatology. The distal carbonate wetland/lacustrine deposits are well developed in the Morrison Formation of east-central Colorado, occupying a stratigraphic interval that is equivalent to the "lower" Morrison but extends into the "upper" Morrison Formation. Sedimentologic, paleontologic, and isotopic evidence indicate that regional groundwater discharge maintained shallow, hydrologically open, well oxygenated, perennial carbonate wetlands and lakes despite the semi-arid climate. Wetland deposits include charophyte-rich wackestone and green mudstone. Lacustrine episodes, in which surface water input was significant, were times of carbonate and siliciclastic deposition in scarce deltaic

  10. A 3D Visualization and Analysis Model of the Earth Orbit, Milankovitch Cycles and Insolation.

    NASA Astrophysics Data System (ADS)

    Kostadinov, Tihomir; Gilb, Roy

    2013-04-01

    , the seasons, and insolation. Users select a calendar date and the Earth is placed in its orbit using Kepler's laws; the calendar can be started on either vernal equinox (March 20) or perihelion (Jan. 3). Global insolation is computed as a function of latitude and day of year, using the chosen Milankovitch parameters. 3D surface plots of insolation and insolation anomalies (with respect to J2000) are then produced. Insolation computations use the model's own orbital geometry with no additional a-priori input other than the Milankovitch parameter solutions. Insolation computations are successfully validated against Laskar et al. (2004) values. The model outputs other relevant parameters as well, e.g. Earth's radius-vector length, solar declination and day length for the chosen date and latitude. Time-series plots of the Milankovitch parameters and EPICA ice core CO2 and temperature data can be produced. Envisioned future developments include computational efficiency improvements, more options for insolation plots on user-chosen spatio-temporal scales, and overlaying additional paleoclimatological proxy data.

  11. Digital relief 3D model of the Khibiny massive (Kola peninsula)

    NASA Astrophysics Data System (ADS)

    Chesalova, Elena; Asavin, Alex

    2015-04-01

    at the bottom and at the edge of the valley. Changing these parameters for different climatic seasons allows us to estimate the duration of the existence of gas in homogeneities in the aerial under soil and up soil layers. Complex ring structure site and manifestations of recent tectonic movements allow it to allocate more closed areas with different plant-land cover and different geomorphological features. In particular stand out - bogs, forest area on the slopes and riparian forest zone, the zone of mountain tundra and rocky plateau. Designated areas should be considered together with the full history of the evolution relief Khibin, processes of decrease glaciers and their occurrence. One of the results of the work performed is the allocation within the array of closed circuses, paleo-ice landforms drumlin and moraine ridges. These landforms represent the latest stage of the glacial history of glaciation on the Kola Peninsula and the Arctic coast. Estimated areal characteristics of different forms. In some cases it was possible to separate a sequence of glacial relief forms, which suggests staging a retreat of glaciers in the area. The project highlighted areas open mining apatite ores in Khibiny massif. Career located in the inner part of the massif form a closed area drain mine water pollution and wind. While the new career located on the border of the array and the forest zone characterized by a single watershed and accordingly included in the ecological life support cycle of residential villages and towns of Kirovsk and Apatity. This fact forces us to view mining activity as a powerful source of contamination. Designed GIS project thus can be used to solve a number of problems geomorphological orientation. In addition a number of application issues - the environment, paleoclimatology, geotectonic can be successfully addressed on the basis of the digital 3D model.

  12. Comparison of climate proxies from two 'Siamese twin

    NASA Astrophysics Data System (ADS)

    Belén Muñoz-García, María.; Rossi, Carlos; Jesús Turrero, María.; Martín-Chivelet, Javier

    2010-05-01

    of 281 samples drilled along the growth axes of both stalagmites. According to the proposed age model, the two stalagmites grew at very different rates, despite their proximity and their internal and external resemblance. The differences are very important in both magnitude and trends, suggesting that piping and dripping effects were strong enough to mask any paleoclimate information. On the contrary, the δ18O records of the Siamese sections of the two stalagmites are virtually identical, suggesting that this parameter is independent of stalagmite growth, being mostly controlled by external factors to the dripping system, probably climate variables (e.g., rainfall composition). Finally, important differences were found when comparing the δ13C time-series. These differences concern general patterns and trends, as well as the average values of each series. This could indicate that δ13C is much more influenced by piping effects than δ18O, and thus more difficult to interpret in terms of paleoclimate. In summary, similar δ18O records have been obtained in both stalagmites, but important differences were found in growth rates and δ13C values. A single record from only one of these stalagmites would have not been representative of the whole environmental system. These results suggest that the paleoclimate interpretations based on growth rates and δ13C records obtained in a single speleothem should be treated with caution. Contribution to project CGL2007-60618-BTE (MCI, Spain), research grants PR-2007-0111 and PR-2007-0197, and the Paleoclimatology and Global Change Research Group (UCM-CM-910198). L.R. Edwards and X. Wang are thanked for his advisory help and support during stays of JMC and MJT in the Univ. of Minnesota.

  13. An Orbital Beat in the Equatorial Atlantic (~18-27 Ma): Reliable Chronometer or Wishful Thinking?

    NASA Astrophysics Data System (ADS)

    Meyers, S. R.; Hinnov, L. A.

    2011-12-01

    Orbital-climate theory provides a vital framework for the fields of paleoclimatology and geochronology, having spawned advances in our understanding of climate system components, feedbacks, and thresholds, while also leading to a major revision of the geologic time scale. The numerous successes of Pleistocene cyclostratigraphy have motivated the search for orbital influence in strata spanning the Phanerozoic, culminating in the generation of both "anchored" (<50 Ma) and "floating" astrochronologies that can be used to evaluate environmental, biologic and biogeochemical change at very high resolution. Against this backdrop, a common challenge in the development of astrochronologies is the absence of sufficient independent time constraints (e.g., radioisotopic data) to directly calibrate spatial rhythms to temporal periods, and thus quantitatively test for orbital influence. As a consequence, many investigations attempt to test the orbital hypothesis using the "spectral frequency ratio" approach (e.g., the 5:2:1 ratio of short eccentricity, obliquity and precession), and/or by evaluating signal characteristics, such as amplitude modulations of the presumed precession cycle, prior to or following orbital-tuning. None of these approaches - as applied in common practice - explicitly tests the null hypothesis of no orbital influence, leading some to question the veracity of deep-time astrochronology. Here, we revisit proxy data from the equatorial Atlantic Ceara Rise (~18 to 27 Ma; Paelike et al., 2006), a site that has been instrumental in the development of astrochronologies for the Miocene and Oligocene time scale, and has also provided constraints on the theoretical astronomical solutions. Our cyclostratigraphic evaluation employs a method for astrochronologic testing applied to "un-tuned" proxy data, termed Average Spectral Misfit (Meyers and Sageman, 2007). This inverse method explicitly evaluates time scale uncertainty, and provides a formal statistical test of

  14. An Infrared Stimulated Luminescence (IRSL) Procedure for Estimating the Transport Rate of Potassium-Feldspar Grains in a Fluvial Setting

    NASA Astrophysics Data System (ADS)

    McGuire, C. P.; Rhodes, E. J.

    2013-12-01

    -Marquardt). The fitted bleaching parameters were used in addition to the single aliquot regenerative-dose (SAR) protocol growth curves to build a model of bleach and growth of IRSL during transport, deposition, and burial. While this model does not provide a unique solution for the sediment transport rate, it can be used to assess the likelihood of a range of transport rates. References: Buylaert, J.P., A.S. Murray, K.J. Johnson, and M. Jain. 'Testing the potential of an elevated temperature IRSL signal from K-feldspar.' Radiation Measurements. 44 (2009), 560-565. Critelli, Salvatore, Emilia le Pera and Raymond V. Ingersoll. 'The effects of source lithology, transport, deposition and sampling scale on the composition of southern California sand.' Sedimentology, 44 (1997), 653-671. Enzel, Y. and S.G. Wells. 'Extracting Holocene Paleohyrology and Paleoclimatology from modern extreme flood events: an example from Southern California.' Geomorphology. 19 (1997), 203-226

  15. Impact of volcanism on the evolution of Lake Van II: Temporal evolution of explosive volcanism of Nemrut Volcano (eastern Anatolia) during the past ca. 0.4 Ma

    NASA Astrophysics Data System (ADS)

    Sumita, Mari; Schmincke, Hans-Ulrich

    2013-03-01

    triggering increased partial melting or magma reservoir unloading following massive glacier melting. The ages of 5 dated ignimbrites span ca. 250 000 years suggesting that Nemrut Volcano went through a polycyclic evolution with multiple caldera collapses and major pyroclastic flow eruptions, the oldest dated so far as 265 ka. The widely held view of the impressive Nemrut Caldera now dated to have formed at ca. 30 ka, as the main paroxysmal event during the evolution of the volcano is no longer tenable. Distinct and coherent compositional characteristics, especially in trace element concentrations, characterize several groups of trachytic tephras. We speculate that the growth of Nemrut Volcano caused the isolation of the Lake Van basin. On account of their mineralogical (anorthoclase, hedenbergite, fayalite, aenigmatite) and alkalic chemical compositions and large volume, dated Nemrut fallout tephras are likely to represent excellent markers in lakes and other sites of paleoclimatological or archeological interest in neighboring countries to the northeast of Lake Van as far as the Caspian Sea in what may be called the East Anatolian Tephra Province.

  16. Late Quaternary and Future Biome Simulations for Alaska and Eastern Russia

    NASA Astrophysics Data System (ADS)

    Hendricks, Amy; Walsh, John; Saito, Kazuyuki; Bigelow, Nancy

    2015-04-01

    We simulated Arctic biomes across a region including Alaska and Eastern Russia using the BIOME4 biogeochemical and biogeography vegetation model. BIOME4, which produces an equilibrium vegetation distribution under a given climate condition, was forced by CMIP5/PMIP3 climate data. We are exploring vegetation and permafrost distributions during the last 21,000 years and future projections (2100 C.E.) to gain an understanding of the effects of climate shifts on this complex subsystem. When forced with the baseline modern climatology, compiled from the University of Delaware temperature and precipitation climatology and ERA-40 sunshine data, our biome simulations were generally consistent with current vegetation observations in the study region. Much of the study area was simulated to have evergreen and deciduous taiga and shrub tundras. Paleoclimatological simulations were compared with pollen data samples taken through the study region. Simulations for the Last Glacial Maximum show the Bering Land Bridge covered almost entirely by cushion forb, lichen, and moss tundra, shrub tundra, and graminoid tundra. Three out of the five models' climate data produce evergreen and deciduous taiga in what is now southwestern Alaska. The distributions of cushion forb, lichen, and moss tundra and graminoid tundra differ noticeably between models, however, shrub tundra distributions are generally in agreement. Simulations for the Mid-Holocene are in better agreement on pollen-based distributions of biomes. Shrub tundra is simulated along the Arctic coast, and in some cases along the eastern coast of Russia. All models show evergreen taiga along the southern coast of Russia as well as covering the southern half of present-day Alaska. Deciduous taiga is simulated in the interior regions of eastern Russia and Alaska, though the distributions in Alaska differ between models. Pre-Industrial biome simulations were very similar to Mid-Holocene simulations. Differences include more shrub

  17. Earth2Class Overview: An Innovative Program Linking Classroom Educators and Research Scientists

    NASA Astrophysics Data System (ADS)

    Passow, M.; Iturrino, G. J.; Baggio, F. D.; Assumpcao, C. M.

    2005-12-01

    The Earth2Class (E2C) workshops, held at the Lamont-Doherty Earth Observatory (LDEO), provide an effective model for improving knowledge, teaching, and technology skills of middle and high school science educators through ongoing interactions with research scientists and educational technology. With support from an NSF GeoEd grant, E2C has developed monthly workshops, web-based resources, and summer institutes in which classroom teachers and research scientists have produced exemplar curriculum materials about a wide variety of cutting-edge geoscience investigations suitable for dissemination to teachers and students. Some of the goals of this program are focused to address questions such as: (1) What aspects of the E2C format and educational technology most effectively connect research discoveries with classroom teachers and their students? (2) What benefits result through interactions among teachers from highly diverse districts and backgrounds with research scientists, and what benefits do the scientists gain from participation? (3) How can the E2C format serve as a model for other research institution-school district partnerships as a mechanism for broader dissemination of scientific discoveries? E2C workshops have linked LDEO scientists from diverse research specialties-seismology, marine geology, paleoclimatology, ocean drilling, dendrochronology, remote sensing, impact craters, and others-with teachers from schools in the New York metropolitan area. Through the workshops, we have trained teachers to enhance content knowledge in the Earth Sciences and develop skills to incorporate new technologies. We have made a special effort to increase the teaching competency of K-12 Earth Sciences educators serving in schools with high numbers of students from underrepresented groups, thereby providing greater role models to attract students into science and math careers. E2C sponsored Earth Science Teachers Conferences, bringing together educators from New York and New

  18. Middle-late Holocene climate variability in La Paz Basin, southern Gulf of California

    NASA Astrophysics Data System (ADS)

    Gómez-Lizárraga, L. E.; Perez-Cruz, L. L.; Fucugauchi, J. U.

    2013-12-01

    Sediments from DIPAL III-K47 core collected at 830 m depth in the western slope within the oxygen minimum zone of La Paz Basin, southern Gulf of California provide a detailed record of paleoceanography and paleoclimatology for the tropical Pacific on centennial time scales for the past 7300 years. The sedimentary sequence is compose of hemipelagic sediments and is laminated throughout its entire length (145 cm). According to the preliminary age model based on radiocarbon AMS dates, core covers the period from ca 7300 to 1000 cal yr BP. The estimated sedimentation rates are between 0.20 and 0.29 mm/yr. Radiolarian assemblages, geochemical (major and trace elements Al, Ba, Ca, K, Si Ti, Zr and Zr/Al and Ba/Al ratios) and magnetic susceptibility are used as proxies of variations of oceanic circulation patterns, paleoproductivity, aeolian activity and precipitation. Eighty-two intervals were sampled for radiolarians and the core was sampled at 1-cm intervals to produce records of major and trace elements. Factor Analysis of the radiolarian abundances counted in sediments samples identified three assemblages. The first one (Arachnocorallium calvata, Lithomelissa setosa, Lithomelissa thoracites and Peridium longispinum) suggests winter-spring like conditions (cold and dry), Gulf of California Water persistence and a relative increase in productivity that might become from the east-to-west upwelling gradient. The second radiolarian assemblage (Tetrapyle octacantha group and Phorticium pylonium group) was interpreted as stratification of the column water and the incursion of warm, oligotrophic Tropical Surface Water that remind summer-fall like conditions. The third assemblage (Clathrocircus stapedius, Phorticium pylonium group, Lithomelissa pentacantha, Phormacantha hystrix, Phormospyris stabilis scaphipes, Lithomelissa thoracites, Pseudocubus obeliscus, Druppatractus irregularis and Druppatractus variabilis), suggests a mix water column that favors the organic carbon

  19. Variations of the glacio-marine air mass front in West Greenland through water vapor isotopes

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2012-12-01

    While the isotopic distribution of precipitation has been widely used for research in hydrology, paleoclimatology, and ecology for decades, intensive isotopic studies of atmospheric water vapor has only recently been made possible by spectral-based technology. New instrumentation based on this technology opens up many opportunities to investigate short-term atmospheric dynamics involving the water cycle and moisture transport. We deployed a Los Gatos Water Vapor Isotope Analyzer (WVIA) at Kangerlussuaq, Greenland from July 21 to August 15, and measured the water vapor concentration and its isotopic ratios continuously at 10s intervals. A Danish Meteorological Institute site is located about 1 km from the site of the deployment, and meteorological data is collected at 30 min intervals. During the observation period, the vapor concentration of the ambient air ranges from 5608.4 to 11189.4 ppm; dD and d18O range from -254.5 to -177.7 ‰ and -34.2 to -23.2 ‰, respectively. The vapor content (dew point) and the isotopic ratios are both strongly controlled by the wind direction. The easterly winds are associated with dry, isotopically depleted air masses formed over the glacier, while westerly winds are associated with moist and isotopically enriched air masses from the marine/fjord surface. This region typically experiences katabatic winds off of the ice sheet to the east. However, during some afternoons, the wind shifts 180 degrees, blowing off the fjord to the west. This wind switch marks the onset of a sea breeze, and significant isotopic enrichment results. Enrichment in deuterium is up to 60 ‰ with a mean of 15‰, and oxygen-18 is enriched by 3‰ on average and up to 8 ‰. Other afternoons have no change in wind, and only small changes in humidity and vapor isotopic ratios. The humidity and isotopic variations suggest the local atmosphere circulation is dominated by relatively high-pressure systems above the cold glaciers and cool sea surface, and diurnal

  20. Post Rift Evolution of the Indian Margin of Southern Africa

    NASA Astrophysics Data System (ADS)

    Baby, Guillaume; Guillocheau, François; Robin, Cécile; Dall'asta, Massimo

    2016-04-01

    The objective of this study is to discuss the evolution of the South African Plateau along the Indian margin of Southern Africa. Since the classical works of A. du Toit and L.C. King and the improvement of thermochronological methods and numerical models, the question of the uplift of South African Plateau was highly debated with numerous scenarios: early Cretaceous at time of rifting (Van der Beek et al., J.Geophys.Res., 2002), late Cretaceous (Braun et al., Solid Earth, 2014), late Cenozoic (Burke & Gunnell, Geol.Soc.of America, 2008). Limited attention has been paid on the constraints provided by the offshore stratigraphic record of the surrounding margins. The objective of our study is to integrate onshore and offshore data (seismic profiles and industrial wells) to (1) analyse the infill of the whole margin (21°S to 31°S) from its hinterland to the distal deep water basin, (2) to constrain and quantify the vertical movements. We discuss the impact on accommodation and sediments partitioning, and their significance on South African Plateau uplift history. 1. Sedimentary basins of the Indian margin of Southern Africa are related to the break-up of Gondwana during late Jurassic, resulting in rifts and flexural basins. First marine incursions started during early Cretaceous times (oldest marine outcropping sediments are of Barremian age ~128 Ma). The region developed as a normal continental shelf at the Aptian-Albian transition (~113 Ma). 2. The Cretaceous geological history of the basins is characterized by differential uplift and subsidence of the basement, controlled by structures inherited from break up. As example, major early Cretaceous depocenters of the margin are located on the north of Save-Limpopo uplift (Forster, Paleogography, Paleoclimatology, Paleoecology, 1975) showing an eastward drainage pattern, maybe related to a proto Limpopo drainage. Those observations suggest that the escarpment bordering the Bushveld depression is an old relief inherited

  1. Buried glacier ice in permafrost, a window to the past: examples from Bylot Island, Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Fortier, D.; Coulombe, S.; Kanevskiy, M. Z.; Paquette, M.; Shur, Y.; Stephani, E.

    2011-12-01

    related to glacio-hydrologic supercooling, that we observed at the Matanuska Glacier in Alaska. Interestingly, the various types of ice contained in buried glacier ice permafrost date back to the englacial ice formation and its subsequent deformation by glacier flow and glacio-hydrological dynamics. It is thus older by several centuries to millennia than the permafrost aggradation itself (burial and active layer development) and we used the term antegenetic, in opposition to epigenetic or syngenetic, to characterize this type of permafrost. Buried glacier ice is a window to the past and a unique tool to reconstruct the paleogeography and paleoclimatology of Arctic regions. In a warming climate, as glaciers are receding, the burial of ice in the proglacial environment will offer opportunities to characterize antegenetic permafrost aggradation and its related cryofacies. In warming permafrost environments, as active layers on slope deepen and detachment slides are triggered, more buried Pleistocene glacier ice will likely be exposed.

  2. Precipitation rates and atmospheric heat transport during the Cenomanian greenhouse warming in North America: Estimates from a stable isotope mass-balance model

    USGS Publications Warehouse

    Ufnar, David F.; Ludvigson, Greg A.; Gonzalez, L.; Grocke, D.R.

    2008-01-01

    correlate with a mean annual average heat loss of 48??W/m2 at 10??N paleolatitude (present, 8??W/m2 at 15??N). The increased precipitation flux and moisture surplus in the mid-latitudes corresponds to a mean average annual heat gain of 180??W/m2 at 50??N paleolatitude (present, 17??W/m2 at 50??N). The Cenomanian low-latitude moisture deficit is similar to that of the Albian, however the mid-latitude (40-60??N) precipitation flux values and precipitation rates are significantly higher (Albian: 2200??mm/yr at 45??N; Cenomanian: 3600??mm/yr at 45??N). Furthermore, the heat transferred to the atmosphere via latent heat of condensation was approximately 10.6?? that of the present at 50??N. The intensified hydrologic cycle of the mid-Cretaceous greenhouse warming may have played a significant role in the poleward transfer of heat and more equable global conditions. Paleoclimatological reconstructions from multiple time periods during the mid-Cretaceous will aid in a better understanding of the dynamics of the hydrologic cycle and latent heat flux during greenhouse world conditions.

  3. Fidelity of Stable Oxygen Isotope Ratios as Environmental Recorders Using Multiple Coral Cores From Coastal Kenya

    NASA Astrophysics Data System (ADS)

    Naish, T.; Carter, B.; Abbott, S.; Field, B.; Zhu, H.; Wilson, G.; Alloway, B.; Edwards, S.; Pillans, B.; Barker, A.; Niessen, F.; Maslen, G.; Beu, A.; Fleitmann, D.; Dunbar, R. B.; Mucciarone, D. A.

    2004-12-01

    Climate variability in the western equatorial Indian Ocean reflects the combined influence of seasonally changing sea surface temperature (SST), ocean currents, and monsoon circulation, as well as inter-annual to -decadal variability associated with ENSO in the Pacific. However, the Indian Ocean also exhibits variability that appears unrelated to ENSO in the Pacific. The nature of interactions between air-sea variability in the Indian and Pacific oceans is not yet fully resolved, in part because of the lack of long-term, high-resolution SST records from key localities in the Indian Ocean. Such records are now being obtained using oxygen isotope profiles measured on corals from East Africa, Indonesia, Australia, and Indian Oceania (Maldives, Seychelles), with the longest coral-based time series from Malindi, Kenya, covering the last 300 years at near-monthly resolution. The value of these developing coral records depends on the fidelity with which they record regional climate variability. In order to assess the fidelity of oxygen isotope ratios (\\delta18O) in Indian Ocean corals as a proxy for sea surface temperature, we have generated stable isotopic time series from multiple Porites lutea coral heads collected along the coast of Kenya. Coral-based isotopic paleoclimatology is labor and time-intensive so detailed analyses using multiple coral heads from different sites within a region are extremely rare. Most published records are produced from a single coral head, yet questions have been raised about the accuracy of such records. To address such concerns, near-monthly resolution isotopic profiles, spanning 10 to 50 years prior to 1997, were measured on a total of 8 cores from five sites along a north-south transect between 2° and 4° S (Kiwayu: 2° 2'S, 41° 2'E, Malindi: 3° 14'S, 40° 8'E, Watamu: 3° 23'S, 39° 52'E, Mombasa: 3° 59'S, 39° 5'E, and Kisite: 4° 43'S, 39° 23'E. Correlations among individual \\delta18O time series (r values range from 0.65 to

  4. Continental-Scale Temperature Reconstructions from the PAGES 2k Network

    NASA Astrophysics Data System (ADS)

    Kaufman, D. S.

    2012-12-01

    We present a major new synthesis of seven regional temperature reconstructions to elucidate the global pattern of variations and their association with climate-forcing mechanisms over the past two millennia. To coordinate the integration of new and existing data of all proxy types, the Past Global Changes (PAGES) project developed the 2k Network. It comprises nine working groups representing eight continental-scale regions and the oceans. The PAGES 2k Consortium, authoring this paper, presently includes 79 representatives from 25 countries. For this synthesis, each of the PAGES 2k working groups identified the proxy climate records for reconstructing past temperature and associated uncertainty using the data and methodologies that they deemed most appropriate for their region. The datasets are from 973 sites where tree rings, pollen, corals, lake and marine sediment, glacier ice, speleothems, and historical documents record changes in biologically and physically mediated processes that are sensitive to temperature change, among other climatic factors. The proxy records used for this synthesis are available through the NOAA World Data Center for Paleoclimatology. On long time scales, the temperature reconstructions display similarities among regions, and a large part of this common behavior can be explained by known climate forcings. Reconstructed temperatures in all regions show an overall long-term cooling trend until around 1900 C.E., followed by strong warming during the 20th century. On the multi-decadal time scale, we assessed the variability among the temperature reconstructions using principal component (PC) analysis of the standardized decadal mean temperatures over the period of overlap among the reconstructions (1200 to 1980 C.E.). PC1 explains 35% of the total variability and is strongly correlated with temperature reconstructions from the four Northern Hemisphere regions, and with the sum of external forcings including solar, volcanic, and greenhouse

  5. Terrestrial cosmogenic 3He: where are we 30 years after its discovery?

    NASA Astrophysics Data System (ADS)

    Blard, Pierre-Henri; Pik, Raphaël; Farley, Kenneth A.; Lavé, Jérôme; Marrocchi, Yves

    2016-04-01

    It is now 30 years since cosmogenic 3He has been detected for the first time in a terrestrial sample (Kurz, 1986). 3He is now a widely used geochemical tool in many fields of Earth sciences: volcanology, tectonics, paleoclimatology. 3He has the advantage to have a high "production rate" to "detection limit" ratio, allowing surfaces as young as hundred of years to be dated. Although its nuclear stability implies several limitations, it moreover represents a useful alternative to 10Be in mafic environments. This contribution is a review of the progresses that have been accomplished since this discovery, and discuss strategies to improve both the accuracy and the precision of this geochronometer. 1) Measurement of cosmogenic 3He Correction of magmatic 3He. To estimate the non-cosmogenic magmatic 3He, Kurz (1986) invented a two steps method involving crushing of phenocrysts (to analyze the isotopic ratio of the magmatic component), followed by a subsequent melting of the sample, to extract the remaining components, including the cosmogenic 3He: 3Hec = 3Hemelt -4Hemelt x (3He/4He)magmatic (1) Several studies suggested that the preliminary crushing may induce a loss of cosmogenic 3He (Hilton et al., 1993; Yokochi et al., 2005; Blard et al., 2006), implying an underestimate of the cosmogenic 3He measurement. However, subsequent work did not replicate these observations (Blard et al., 2008; Goerhing et al., 2010), suggesting an influence of the used apparatus. An isochron method (by directly melting several phenocrysts aliquots) is an alternative to avoid the preliminary crushing step (Blard and Pik, 2008). Atmospheric contamination. Protin et al. (in press) provides robust evidences for a large and irreversible contamination of atmospheric helium on silicate surfaces. This unexpected behavior may reconcile the contrasted observations about the amplitude of crushing loss. This undesirable atmospheric contamination is negligible if grain fractions smaller than 150 mm are

  6. Tropical Atlantic SSTS at the Last Glacial Maximum derived from Sr/Ca ratios of fossil coral

    NASA Astrophysics Data System (ADS)

    Cohen, A. L.; Saenger, C. P.

    2006-12-01

    The sensitivity of the tropics to climate change is a particularly controversial issue in paleoclimatology. At the heart of this controversy are disagreements amongst different proxy datasets regarding the amplitude of glacial-interglacial changes in temperature, particularly at the sea surface. Data obtained from the aragonitic skeletons of massive reef corals have contributed in no small measure to the debate, yielding LGM and deglacial SSTs 5-6°C cooler than today (Guilderson et al., 1994; McCulloch et al., 1999; Correge et al., 2004), that imply a high sensitivity of Earth's climate to changes in boundary conditions (Crowley, 2000). We used SIMS ion microprobe to analyze Sr/Ca ratios of small pieces of Montastrea coral retrieved from a Barbados drillcore (Guilderson et al., 2001). U/Th dates place the samples between 22 and 24 kyr BP. Localized areas of dissolution and re-growth of secondary (diagenetic) aragonite crystals were identified at centers of septa. Sr/Ca ratios of these crystals were higher than Sr/Ca ratios of original coral crystals preserved in adjacent fasciculi and yielded relatively cooler derived SSTs. The original coral crystals, recognized by their size and orientation, were selectively targeted for analysis using a 20 micron-diameter sample spot. Our calibration study using modern corals from Bermuda, St Croix (USVI) and Barbados indicates that Montastrea Sr/Ca is strongly correlated with SST and with annual extension (growth) rate (Saenger et al., 2006). Growth rate of the fossil corals was determined from measurement of daily growth bands identified in petrographic thin-sections. Application of a growth-dependent Sr/Ca-T calibration yielded Barbados SSTs that were, on average, 2.5°C cooler than today during the LGM and ~1°C cooler than today during Heinrich Event 2. Our LGM SSTs are consistent with the original CLIMAP estimates (CLIMAP, 1976) and with more recent Mg/Ca-based SSTs derived from calcitic foraminifera in the Caribbean

  7. Assessing Climate Misconceptions of Middle School Learners and Teachers

    NASA Astrophysics Data System (ADS)

    Sahagian, D. L.; Anastasio, D. J.; Bodzin, A.; Cirucci, L.; Bressler, D.; Dempsey, C.; Peffer, T.

    2012-12-01

    ) environmental literacy and inquiry and (2) foster the development of geospatial thinking and reasoning using geospatial technologies as an essential component of the middle school science curriculum. The curriculum is designed to align instructional materials and assessments with learning goals. The following frameworks were used to provide guidelines for the climate change science content in addition to the science inquiry upon which schools must focus: Climate Literacy: The Essential Principles of Climate Sciences (U.S. Global Change Research Program, 2009) and the AAAS Project 2061 Communicating and Learning About Global Climate Change (AAAS, 2007). The curriculum is a coherent sequence of learning activities that include climate change investigations with Google Earth, Web-based interactivities that include an online carbon emissions calculator and a Web-based geologic time-line, and inquiry-based ("hands-on") laboratories. The climate change science topics include the atmosphere, Earth system energy balance, weather, greenhouse gases, paleoclimatology, and "humans and climate". It is hoped that with a solid foundation of climate science in the classroom, middle school learners will be in a position to evaluate new scientific discoveries, emerging data sets, and reasonably assess information and misinformation by which they are surrounded on a daily basis.

  8. Progress in applying lacustrine alkenones as a quantitative continental paleotemperature proxy

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Longo, W. M.; Theroux, S.; Toney, J. L.; Dillon, J.; Zhao, J.; D'Andrea, W. J.; Hou, J.; Tarozo, R.; Amaral-Zettler, L. A.

    2013-12-01

    approach to deconvolute alkenones produced by multiple haptophytes in saline lakes; 7) production of high resolution alkenone-based paleotemperature records from multiple sites (Greenland, Tibetan Plateau etc.). In addition to describing key progress in proxy development, we will show our latest results from studying a series of lakes from Northern Alaska (Toolik lake region), where alkenones are common and the haptophyte alkenone producers are closely related to those in a series of southwestern Greenland lakes. In situ temperature calibrations using water column samples have shown a virtually identical relationship to our previously published data from Greenland. Currently the only paleoclimate assessment for the region is based on pollen assemblages, which have been particularly difficult to translate into quantitative paleotemperature reconstructions. Our preliminary data demonstrate the great potential for obtaining the first quantitative paleotemperature reconstructions using alkenones from these lakes (some of the lake sediments extend to the last glacial maximum), which will fill an important gap in continental paleoclimatology.

  9. Reconciling late Quaternary transgressions in the Bohai Sea, China to the global sea level changes, and new linkage of sedimentary records to three astronomical rhythms

    NASA Astrophysics Data System (ADS)

    Yi, Liang

    2013-04-01

    The Bohai Sea in China was formed by subsidence during the Cenozoic. Some 2000-3000 m of fluvial, lacustrine and marine sediments has been deposited in the basin (IOCAS 1985), and these sediments have great potentials in high-/low-latitude interaction, environmental impacts on ancient human activities, and other important issues (Liu, 2009; Yi et al. 2012a), because it is influenced by the Siberian-Mongolian Highs and the ITCZ, and is close to the Nihewan basin and the Zhoukoudian site which are both world-renowned for the discovery of Homo erectus. Since the 1970s, hundreds of studies have been conducted around the Bohai Sea and the major results could be summarized as follows (Zhao et al., 1978; IOCAS, 1985; Liu, 2009, and references therein): (1) constrained by radiocarbon dating, TL/OSL or geomagnetic excursion, three transgressions (T1, T2, T3) developed during the Holocene, marine isotopic stage (MIS) 3 and MIS 5, respectively; and (2) regressions occurred at the beginning of glacial stages, i.e. MIS2 and MIS4. However, apparent inconsistency could be found between T2 and T3, and the question is that in the context that MIS 3 is an inter-stadial stage with a global sea level of 60~80 m lower than the present (Chappell et al. 1996), how did T2 occur in the Bohai Sea, and why did T2 have much larger influence than T3 which occurred at the beginning of MIS 5? To correlate regional environmental changes with global pattern and thus to detect the potential interaction between various driving factors on orbital timescales, three cores with a high recovery rate were drilled in the south Bohai Sea. This study was conducted following three perspectives: chronology (Yi et al. 2012b), sea-level change (Yi et al. 2012c) and paleoclimatology (Yi et al. 2012a), and the main results are as follows: 1. Chronology. Luminescence and radiocarbon dating methods were applied in dating these coastal/marine sediments: (1) For Holocene samples, most of the radiocarbon dates agree

  10. Center for accelerator mass spectrometry Lawrence Livermore National Laboratory

    SciTech Connect

    Roberts, M.L.; Southon, J.R.; Proctor, I.D.

    1997-09-01

    The Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Laboratory (LLNL) is a multi-disciplinary research organization that conducts both technological and applications research. CAMS operates both an HVEC FN tandem and a NEC Model 5SDH-2 tandem accelerator. Using highly sensitive accelerator-based element and isotope detection methods, staff at CAMS collaborate with a broad scope of external and internal researchers to solve problems for LLNL, the University of California, the U.S. Department of Energy, and other academic, government, and industrial laboratories. The HVEC FN tandem is used by the LLNL Accelerator Mass Spectrometry (AMS) group. AMS is a technique that uses isotope ratio mass spectrometry at MeV energies to quantify long lived radioisotopes. For AMS, the FN tandem is operated under a distributed computer control system that makes possible rapid and precise switching between experimental configurations on a daily basis. The accelerator and beam lines are unshielded with radiation protection provided by a computer supervised radiation monitoring system and proximity shielding. With AMS, we routinely measure the isotopes {sup 3} H, {sup 7} Be, {sup 10} Be, {sup 14} C, {sup 26} Al, {sup 36} Cl, {sup 41} Ca, {sup 59} Ni, and {sup 129} I at abundances as low as 1 part in 10{sup 15} . Research programs are as diverse as archaeology, dosimetry of carcinogens and mutagens, oceanic and atmospheric chemistry, paleoclimatology, and detection of signatures of nuclear fuel reprocessing for non-proliferation purposes. During the past year our AMS group has run approximately 20,000 research samples. The NEC Model 5SDH-2 tandem accelerator is used by the Ion Micro Analysis Group (IMAG), a joint collaboration between LLNL and Sandia National Laboratories/California in biological and materials science research. The 1.7 MV accelerator and an Oxford Microbeams Quadrupole Triplet Lens System are used to create a 3 MeV micron scale focused ion

  11. Organic-geochemical characterization of sedimentary organic matter deposited during the Valanginian carbon isotope excursion (Vocontian Basin, SE France)

    NASA Astrophysics Data System (ADS)

    Kujau, Ariane; Heimhofer, Ulrich; Ostertag-Henning, Christian; Mutterlose, Jörg; Gréselle, Benjamin

    2010-05-01

    typical for this time interval, including a prominent positive CIE. The high-resolution delta13Ccarb record allows for detailed correlation and comparison with existing chemostratigraphic records across this event. TOC values fluctuate between 0.20 and 4.05%, Rock-Eval pyrolysis results depict HI values of 134 to 383 mgHC/g TOC and OI values of 19 to 160 mg CO2/g TOC indicating the predominance of marine OM with only minor terrestrial inputs in all investigated samples. The aliphatic fraction of the OM extractable by organic solvents is dominated by n-alkanes, isoprenoids, and a variety of hopanes and steranes. No distinct changes during the CIE in the abundances of biomarkers specific for Dinoflagellates and methanotrophic bacteria are observed, pointing to no significant response of the marine biota in this basin to the carbon cycle perturbation. There is no indication for an anoxic water column during the CIE. Steranes show slightly enhanced values for the plateau phase of the excursion, and increasing values during the decline of the delta13C shift (e.g. dinosterane) what may just as well be due to the cooling episode or a change in sea-level (Melinte and Mutterlose, 2001). At this stage, the detailed analysis of the sedimentary OM does not provide evidence for the existence of an OAE or enhanced accumulation/preservation of OM associated with the Valanginian CIE. These findings point to paleoenvironmental changes on continents rather than in marine settings as causes for the isotope shift. References: Erba E. et al. (2004). Geology 32, 149-152. Gréselle B. (2007). PhD thesis, University Lyon1, Lyon. Gröcke D. et al. (2005). EPSL 240, 495-509. Lini A. et al. (1992). Terra Nova 4, 374-384. Melinte M. and Mutterlose J. (2001). Marine Micropaleontology 43, 1-25. Ogg J.G. et al. (2004). In: Gradstein FM, Ogg JG, Smith AG (eds.). A Geological Timescale 2004. Cambridge University Press, 63-86. Weissert H. et al. (1998). Paleogeography, Paleoclimatology, Palaeoecology 137

  12. Comparing Apples to Apples: Paleoclimate Model-Data comparison via Proxy System Modeling

    NASA Astrophysics Data System (ADS)

    Dee, Sylvia; Emile-Geay, Julien; Evans, Michael; Noone, David

    2014-05-01

    variability over the past millennium. part i: Methodology and validation. Journal of Climate 26 (7), 2302-2328. URL http://search.proquest.com/docview/1350277733?accountid=14749 Evans, M., Tolwinski-Ward, S. E., Thompson, D. M., Anchukaitis, K. J., 2013. Applications of proxy system modeling in high resolution paleoclimatology. Quaternary Science Reviews. URL http://adsabs.harvard.edu/abs/2012QuInt.279U.134E Landrum, L., Otto-Bliesner, B. L., Wahl, E. R., Capotondi, A., Lawrence, P. J., Teng, H., 2012. Last Millennium Climate and Its Variability in CCSM4. Journal of Climate (submitted) Molteni, F., 2003. Atmospheric simulations using a GCM with simplified physical parametrizations. I model climatology and variability in multi-decadal experiments. Climate Dynamics, 175-191

  13. Changements climatiques et variations du champ magnetique terrestre dans le sud de la Patagonie (Argentine) depuis 51 200 ans reconstitues a partir des proprietes magnetiques des sediments du lac Laguna Potrok Aike

    NASA Astrophysics Data System (ADS)

    Lise-Pronovost, Agathe

    and climatic evidence. The runoff events are generally associated with mass movement deposits during time of enhanced lake productivity in Laguna Potrok Aike and are also coeval within the limit of the chronology to warm atmospheric conditions recorded in Antarctica. In addition, we show that the authigenic formation of iron sulfide such as greigite is strictly associated to reworked sands and tephra layers providing the required suboxic conditions and dissolved sulfate. As a whole, rock magnetism of the sediment from Laguna Potrok Aike provides a high quality full-vector paleomagnetic record as well as rock-magnetic proxies of past climate changes in southeastern Patagonia that are also associated with climate changes in Antarctica. Keywords: [Paleomagnetism, sediment magnetism, paleoclimatology, Laguna Potrok Aike, Patagonia, Southern Hemisphere, millennial- to centennial-scale variability, last Glacial period, Holocene, wind intensity].