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Sample records for schaden aller tiefen

  1. AllerML: markup language for allergens.

    PubMed

    Ivanciuc, Ovidiu; Gendel, Steven M; Power, Trevor D; Schein, Catherine H; Braun, Werner

    2011-06-01

    Many concerns have been raised about the potential allergenicity of novel, recombinant proteins into food crops. Guidelines, proposed by WHO/FAO and EFSA, include the use of bioinformatics screening to assess the risk of potential allergenicity or cross-reactivities of all proteins introduced, for example, to improve nutritional value or promote crop resistance. However, there are no universally accepted standards that can be used to encode data on the biology of allergens to facilitate using data from multiple databases in this screening. Therefore, we developed AllerML a markup language for allergens to assist in the automated exchange of information between databases and in the integration of the bioinformatics tools that are used to investigate allergenicity and cross-reactivity. As proof of concept, AllerML was implemented using the Structural Database of Allergenic Proteins (SDAP; http://fermi.utmb.edu/SDAP/) database. General implementation of AllerML will promote automatic flow of validated data that will aid in allergy research and regulatory analysis.

  2. AllerML: Markup Language for Allergens

    PubMed Central

    Ivanciuc, Ovidiu; Gendel, Steven M.; Power, Trevor D.; Schein, Catherine H.; Braun, Werner

    2011-01-01

    Many concerns have been raised about the potential allergenicity of novel, recombinant proteins into food crops. Guidelines, proposed by WHO/FAO and EFSA, include the use of bioinformatics screening to assess the risk of potential allergenicity or cross-reactivities of all proteins introduced, for example, to improve nutritional value or promote crop resistance. However, there are no universally accepted standards that can be used to encode data on the biology of allergens to facilitate using data from multiple databases in this screening. Therefore, we developed AllerML a markup language for allergens to assist in the automated exchange of information between databases and in the integration of the bioinformatics tools that are used to investigate allergenicity and cross-reactivity. As proof of concept, AllerML was implemented using the Structural Database of Allergenic Proteins (SDAP; http://fermi.utmb.edu/SDAP/) database. General implementation of AllerML will promote automatic flow of validated data that will aid in allergy research and regulatory analysis. PMID:21420460

  3. Obituary: Lawrence Hugh Aller, 1913-2003

    NASA Astrophysics Data System (ADS)

    Kaler, James B.

    2003-12-01

    The announcement still lies in my inbox: ``Lawrence Aller died last Sunday." On 16 March 2003, one of the world's fine astronomers passed away at the age of 89, leaving behind a legacy that will ripple as long as there are students of the celestial science, one that incorporated observation, theory, education, care, decency, and kindness. Lawrence was born in the humblest of conditions in Tacoma, Washington, on 24 September 1913. His mother, Lella (Belle) Allen, was a homemaker and his father Leslie Aller, was an occassional printer and gold prospector who thought that the use of the mind was a waste of time. With fierce persistence and dedication, Lawrence pulled off a feat that would probably not be possible now: getting into college without having finished high school, the result of being dragged to work in his father's primitive gold mining camp. His interest, sparked by leaflets from the Astronomical Society of the Pacific and by Russell, Dugan, and Stewart's venerable textbook, led him to a correspondence, and finally a meeting, with Donald Menzel of Harvard, who persuaded the admissions director of the University of California at Berkeley to admit him in 1932. From there, Lawrence went on to graduate school at Harvard and the Harvard Society of Fellows, where he studied with Menzel and developed his interest in stellar and nebular astronomy. After working in the War effort, he made his professorial debut at Indiana University, where he stayed until 1948 before leaving for the University of Michigan. Residing there for the next 14 years, he established his research reputation and helped develop the Michigan graduate program. In 1962, the opportunity arose to return to California, to UCLA, where he again was instrumental in founding a PhD program. There he stayed, through his retirement in 1984, doing research right up to the end. Eight other schools received him as visiting professor. Lawrence knew that to make inroads into astronomy, he needed to apply

  4. The R. M. Aller Astronomical Observatory Research on Double and Multiple Stars: Highlights and Projects

    NASA Astrophysics Data System (ADS)

    Docobo, J.-A.

    2012-12-01

    In this talk, I will speak about some relevant results that we have obtained in the Ramon Maria Aller Astronomical Observatory (OARMA) concerning binaries. More concretely, I will discuss our current research project and highlights of our work.

  5. Antioxidant properties of Aller-7, a novel polyherbal formulation for allergic rhinitis.

    PubMed

    D'Souza, P; Amit, A; Saxena, V S; Bagchi, D; Bagchi, M; Stohs, S J

    2004-01-01

    Allergic rhinitis, a frequently occurring immunological disorder affecting men, women and children worldwide, is a state of hypersensitivity that occurs when the body overreacts to a substance such as pollen, mold, mites or dust. Allergic rhinitis exerts inflammatory response and irritation of the nasal mucosal membranes leading to sneezing; stuffy/runny nose; nasal congestion; and itchy, watery and swollen eyes. A novel, safe polyherbal formulation (Aller-7/NR-A2) has been developed for the treatment of allergic rhinitis using a unique combination of extracts from seven medicinal plants including Phyllanthus emblica, Terminalia chebula, Terminalia bellerica, Albizia lebbeck, Piper nigrum, Zingiber officinale and Piper longum. In this study, the antioxidant efficacy of Aller-7 was investigated by various assays including hydroxyl radical scavenging assay, superoxide anion scavenging assay, 1,1-diphenyl-2-picryl hydrazyl (DPPH) and 2,2-azinobis-ethyl-benzothiozoline-sulphonic acid diammonium salt (ABTS) radical scavenging assays. The protective effect of Aller-7 on free radical-induced lysis of red blood cells and inhibition of nitric oxide release by Aller-7 in lipopolysaccharide-stimulated murine macrophages were determined. Aller-7 exhibited concentration-dependent scavenging activities toward biochemically generated hydroxyl radicals (IC50 741.73 microg/ml); superoxide anion (IC50 24.65 microg/ml by phenazine methosulfate-nicotinamide adenine dinucleotide [PMS-NADH] assay and IC50 4.27 microg/ml by riboflavin/nitroblue tetrazolium [NBT] light assay), nitric oxide (IC50 16.34 microg/ml); 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical (IC50 5.62 microg/ml); and 2,2-azinobis-ethyl-benzothiozoline-sulphonic acid diammonium salt (ABTS) radical (IC50 7.35 microg/ml). Aller-7 inhibited free radical-induced hemolysis in the concentration range of 20-80 microg/ml. Aller-7 also significantly inhibited nitric oxide release from lipopolysaccharide-stimulated murine

  6. Abrupt pre-Bølling-Allerød warming and circulation changes in the deep ocean.

    PubMed

    Thiagarajan, Nivedita; Subhas, Adam V; Southon, John R; Eiler, John M; Adkins, Jess F

    2014-07-03

    Several large and rapid changes in atmospheric temperature and the partial pressure of carbon dioxide in the atmosphere--probably linked to changes in deep ocean circulation--occurred during the last deglaciation. The abrupt temperature rise in the Northern Hemisphere and the restart of the Atlantic meridional overturning circulation at the start of the Bølling-Allerød interstadial, 14,700 years ago, are among the most dramatic deglacial events, but their underlying physical causes are not known. Here we show that the release of heat from warm waters in the deep North Atlantic Ocean probably triggered the Bølling-Allerød warming and reinvigoration of the Atlantic meridional overturning circulation. Our results are based on coupled radiocarbon and uranium-series dates, along with clumped isotope temperature estimates, from water column profiles of fossil deep-sea corals in a limited area of the western North Atlantic. We find that during Heinrich stadial 1 (the cool period immediately before the Bølling-Allerød interstadial), the deep ocean was about three degrees Celsius warmer than shallower waters above. This reversal of the ocean's usual thermal stratification pre-dates the Bølling-Allerød warming and must have been associated with increased salinity at depth to preserve the static stability of the water column. The depleted radiocarbon content of the warm and salty water mass implies a long-term disconnect from rapid surface exchanges, and, although uncertainties remain, is most consistent with a Southern Ocean source. The Heinrich stadial 1 ocean profile is distinct from the modern water column, that for the Last Glacial Maximum and that for the Younger Dryas, suggesting that the patterns we observe are a unique feature of the deglacial climate system. Our observations indicate that the deep ocean influenced dramatic Northern Hemisphere warming by storing heat at depth that preconditioned the system for a subsequent abrupt overturning event during the

  7. A search for shocked quartz grains in the Allerød-Younger Dryas boundary layer

    NASA Astrophysics Data System (ADS)

    Hoesel, Annelies; Hoek, Wim Z.; Pennock, Gillian M.; Kaiser, Knut; Plümper, Oliver; Jankowski, Michal; Hamers, Maartje F.; Schlaak, Norbert; Küster, Mathias; Andronikov, Alexander V.; Drury, Martyn R.

    2015-03-01

    The Younger Dryas impact hypothesis suggests that multiple airbursts or extraterrestrial impacts occurring at the end of the Allerød interstadial resulted in the Younger Dryas cold period. So far, no reproducible, diagnostic evidence has, however, been reported. Quartz grains containing planar deformation features (known as shocked quartz grains), are considered a reliable indicator for the occurrence of an extraterrestrial impact when found in a geological setting. Although alleged shocked quartz grains have been reported at a possible Allerød-Younger Dryas boundary layer in Venezuela, the identification of shocked quartz in this layer is ambiguous. To test whether shocked quartz is indeed present in the proposed impact layer, we investigated the quartz fraction of multiple Allerød-Younger Dryas boundary layers from Europe and North America, where proposed impact markers have been reported. Grains were analyzed using a combination of light and electron microscopy techniques. All samples contained a variable amount of quartz grains with (sub)planar microstructures, often tectonic deformation lamellae. A total of one quartz grain containing planar deformation features was found in our samples. This shocked quartz grain comes from the Usselo palaeosol at Geldrop Aalsterhut, the Netherlands. Scanning electron microscopy cathodoluminescence imaging and transmission electron microscopy imaging, however, show that the planar deformation features in this grain are healed and thus likely to be older than the Allerød-Younger Dryas boundary. We suggest that this grain was possibly eroded from an older crater or distal ejecta layer and later redeposited in the European sandbelt. The single shocked quartz grain at this moment thus cannot be used to support the Younger Dryas impact hypothesis.

  8. AllerTOP--a server for in silico prediction of allergens.

    PubMed

    Dimitrov, Ivan; Flower, Darren R; Doytchinova, Irini

    2013-01-01

    Allergy is a form of hypersensitivity to normally innocuous substances, such as dust, pollen, foods or drugs. Allergens are small antigens that commonly provoke an IgE antibody response. There are two types of bioinformatics-based allergen prediction. The first approach follows FAO/WHO Codex alimentarius guidelines and searches for sequence similarity. The second approach is based on identifying conserved allergenicity-related linear motifs. Both approaches assume that allergenicity is a linearly coded property. In the present study, we applied ACC pre-processing to sets of known allergens, developing alignment-independent models for allergen recognition based on the main chemical properties of amino acid sequences. A set of 684 food, 1,156 inhalant and 555 toxin allergens was collected from several databases. A set of non-allergens from the same species were selected to mirror the allergen set. The amino acids in the protein sequences were described by three z-descriptors (z1, z2 and z3) and by auto- and cross-covariance (ACC) transformation were converted into uniform vectors. Each protein was presented as a vector of 45 variables. Five machine learning methods for classification were applied in the study to derive models for allergen prediction. The methods were: discriminant analysis by partial least squares (DA-PLS), logistic regression (LR), decision tree (DT), naïve Bayes (NB) and k nearest neighbours (kNN). The best performing model was derived by kNN at k = 3. It was optimized, cross-validated and implemented in a server named AllerTOP, freely accessible at http://www.pharmfac.net/allertop. AllerTOP also predicts the most probable route of exposure. In comparison to other servers for allergen prediction, AllerTOP outperforms them with 94% sensitivity. AllerTOP is the first alignment-free server for in silico prediction of allergens based on the main physicochemical properties of proteins. Significantly, as well allergenicity AllerTOP is able to predict

  9. AllerTOP v.2--a server for in silico prediction of allergens.

    PubMed

    Dimitrov, Ivan; Bangov, Ivan; Flower, Darren R; Doytchinova, Irini

    2014-06-01

    Allergy is an overreaction by the immune system to a previously encountered, ordinarily harmless substance--typically proteins--resulting in skin rash, swelling of mucous membranes, sneezing or wheezing, or other abnormal conditions. The use of modified proteins is increasingly widespread: their presence in food, commercial products, such as washing powder, and medical therapeutics and diagnostics, makes predicting and identifying potential allergens a crucial societal issue. The prediction of allergens has been explored widely using bioinformatics, with many tools being developed in the last decade; many of these are freely available online. Here, we report a set of novel models for allergen prediction utilizing amino acid E-descriptors, auto- and cross-covariance transformation, and several machine learning methods for classification, including logistic regression (LR), decision tree (DT), naïve Bayes (NB), random forest (RF), multilayer perceptron (MLP) and k nearest neighbours (kNN). The best performing method was kNN with 85.3% accuracy at 5-fold cross-validation. The resulting model has been implemented in a revised version of the AllerTOP server (http://www.ddg-pharmfac.net/AllerTOP).

  10. Paleostress field analysis of the southeastern part of the Aller Lineament

    NASA Astrophysics Data System (ADS)

    Brandes, Christian; Schmidt, Carolin

    2013-04-01

    The Aller Lineament is more than 200 km long and one of the most important fault zones in the Central European Basin System. It was active during the Mesozoic and there is evidence for Late Quaternary tectonic movements (Veldkamp et al., 2002). The evolution of the central and southeastern part of this fault zone was analysed in detail with seismic surveys (Best, 1996; Lohr et al., 2007), but a comprehensive outcrop based paleostress field analysis stills lacks. We analysed faults and conjugate shear fractures in the upper Aller Valley to derive the deformation history and the paleostress field evolution at the southeastern end of the fault zone. Especially conjugate shear fractures serve as important fabric for the paleostress analysis. Hancock & Kadhi (1978) showed that in such a system σ1 bisects the smallest dihedral angle and σ2 is parallel to the intersection of the conjugate fractures. The great advantage of conjugate shear fractures is that the orientation of the three major stress directions can be accurately constrained. Different paleostress directions were identified in the data from the upper Aller Valley. Sets of NW-SE trending normal faults are developed in Upper Triassic sandstones, which indicate an NE-SW directed extensional phase. This was most likely the initial phase of faulting along the Aller Lineament. It took place in the Late Triassic and matches the results derived from seismic sections presented by Best (1996). Sets of NNE-SSW trending, conjugate fractures with a vertical acute angle in the fracture sets are developed. They indicate a vertical maximum principle normal paleostress, which could have resulted from the formation of relay zones between individual NW-SE trending fault planes. From a second set of conjugate shear fractures, a maximum horizontal compressive paleostress vector was reconstructed that is NNE-SSW to N-S oriented. This fits with the previous results from the Central European Basin System and reflects the NNE

  11. Working on binaries at the R. M. Aller Observatory. The last 30 years (and the near future)

    NASA Astrophysics Data System (ADS)

    Docobo, J. A.

    2011-07-01

    We performed exhaustive work during the past 30 years in the Astronomical Observatory of the University of Santiago de Compostela (called Ramón María Aller since 1981). In this communication, I explain all the necessary efforts made to obtain the current high level status of investigation (particularly on double and multiple stars), teaching, and scientific dissemination. The projects for the near future are also mentioned.

  12. Increasing insolation and greenhouse gas concentration trigger Bølling-Allerød warming

    NASA Astrophysics Data System (ADS)

    Obase, Takashi; Abe-Ouchi, Ayako

    2017-04-01

    During the last deglaciation, a major global warming was punctuated by several abrupt climate changes, likely related to Atlantic Meridional Overturning Curculation (AMOC) (Clark et al. 2012). Transient deglaciation experiments from the Last Glacial Maximum have been conducted by applying time-dependent insolation, greenhouse gas concentrations, and glacial meltwater forcing (Liu et al. 2009). They have showed that reduction in glacial meltwater discharge rate into North Atlantic induces abrupt recovery of AMOC, warming of Greenland and cooling of Antarctica (bipolar response) during the period of Bølling-Allerød (BA, 14.6 ka). We conduct a transient simulation from the Last Glacial Maximum to BA using an atmosphere-ocean coupled general circulation model (AOGCM) MIROC 4m (an IPCC-class Japanese community model). The model is initialized with the 21ka, and we change insolation, greenhouse gas concentrations and meltwater fluxes following the protocol of PMIP4 (Ivanovic et al. 2016). Glacial meltwater is derived from ice sheet reconstruction (ICE6g, Peltier et al. 2015). We assume the glacial meltwater due to ice sheet loss is uniformly applied to the area of 50-70N North Atlantic Ocean. We conduct additional experiments branched from 16 ka, where 50-80% of ICE6g meltwater fluxes are applied without reducing the meltwater fluxes before the BA. The model results show that abrupt resumption of AMOC and warming of Greenland occurred at around the period of BA even under hosing of 0.06 Sv. Transition from cold stadial mode to warm interstadial mode occurs in about 100 years, which is consistent with reconstructions (Buizert et al. 2014). The result implies that increasing summer insolation and greenhouse gas concentration trigger abrupt AMOC recovery and warming in the Northern Hemisphere, and large fluctuation of meltwater due to ice sheet melting may not be necessary.

  13. Dynamic controls on the subarctic North Pacific productivity peak during the Bølling-Allerød

    NASA Astrophysics Data System (ADS)

    Gong, Xun; Lembke-Jene, Lester; Tiedemann, Ralf; Lohmann, Gerrit

    2016-04-01

    Prominent maxima of biological productivity are recorded in both the Northwest and Northeast Pacific during the deglacial, interstadial Bølling-Allerød. These have been linked to a suite of differing causes and mechanisms, such as preservation effects, iron fertilization, riverine fluxes, upper ocean stratification and coastal upwelling. There is also widespread evidence for shifts in the subarctic Pacific ocean circulation during the deglaciation. However, while the dynamics of nutrient provision and limitation within the photic zone are certainly of high significance, the important role of physical circulation changes in the subsurface to deep ocean in replenishing nutrient supplies to the upper ocean, and of upper ocean temperature changes in fostering productivity peaks, remain largely unconstrained over the course of the last deglaciation. Here, using an Earth System Model COSMOS, we conducted a simulation representing the climate transition from the Last Glacial Maximum to the Bølling-Allerød. In association with marine proxy evidence, we will discuss the deglacial evolution of the surface to deep ocean circulation and mixing in the North Pacific, and examine their respective roles in determining the upwelling of nutrients from deeper layers, along with the formation of the North Pacific Intermediate water.

  14. Catastrophic meltwater discharge down the Hudson Valley: a potential trigger for the Intra-Allerød cold period

    USGS Publications Warehouse

    Donnelly, Jeffrey P.; Driscoll, Neal W.; Uchupi, Elazar; Keigwin, Loyd D.; Schwab, William C.; Thieler, E. Robert; Swift, Stephen A.

    2005-01-01

    Glacial freshwater discharge to the Atlantic Ocean during deglaciation may have inhibited oceanic thermohaline circulation, and is often postulated to have driven climatic fluctuations. Yet attributing meltwater-discharge events to particular climate oscillations is problematic, because the location, timing, and amount of meltwater discharge are often poorly constrained. We present evidence from the Hudson Valley and the northeastern U.S. continental margin that establishes the timing of the catastrophic draining of Glacial Lake Iroquois, which breached the moraine dam at the Narrows in New York City, eroded glacial lake sediments in the Hudson Valley, and deposited large sediment lobes on the New York and New Jersey continental shelf ca. 13,350 yr B.P. Excess 14C in Cariaco Basin sediments indicates a slowing in thermohaline circulation and heat transport to the North Atlantic at that time, and both marine and terrestrial paleoclimate proxy records around the North Atlantic show a short-lived (<400 yr) cold event (Intra-Aller??d cold period) that began ca. 13,350 yr B.P. The meltwater discharge out the Hudson Valley may have played an important role in triggering the Intra-Aller??d cold period by diminishing thermohaline circulation. ?? 2005 Geological Society of America.

  15. Intensification of the Northeast Pacific oxygen minimum zone during the Bölling-Alleröd warm period

    USGS Publications Warehouse

    Zheng, Yen; van Geen, Alexander; Anderson, Robert F.; Gardner, James V.; Dean, Walter E.

    2000-01-01

    Although climate records from several locations around the world show nearly synchronous and abrupt changes, the nature of the inferred teleconnection is still poorly understood. On the basis of preserved laminations and molybdenum enrichments in open margin sediments we demonstrate that the oxygen content of northeast Pacific waters at 800 m depth during the Bölling-Alleröd warm period (15–13 kyr) was greatly reduced. Existing oxygen isotopic records of benthic and planktonic foraminifera suggest that this was probably due to suppressed ventilation at higher latitudes of the North Pacific. Comparison with ventilation records for the North Atlantic indicates an antiphased pattern of convection relative to the North Pacific over the past 22 kyr, perhaps due to variations in water vapor transport across Central America.

  16. Differential proxy responses to late Allerød and early Younger Dryas climatic change recorded in varved sediments of the Trzechowskie palaeolake in Northern Poland

    NASA Astrophysics Data System (ADS)

    Słowiński, Michał; Zawiska, Izabela; Ott, Florian; Noryśkiewicz, Agnieszka M.; Plessen, Birgit; Apolinarska, Karina; Rzodkiewicz, Monika; Michczyńska, Danuta J.; Wulf, Sabine; Skubała, Piotr; Kordowski, Jarosław; Błaszkiewicz, Mirosław; Brauer, Achim

    2017-02-01

    High-resolution biological proxies (pollen, macrofossils, Cladocera and diatoms), geochemical data (μ-XRF element scans, TOC, C/N ratios, δ18Ocarb and δ13Corg values) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were applied to reconstruct lake system responses to rapid climatic and environmental changes of the Trzechowskie palaeolake (TRZ; Northern Poland) during the late Allerød - Younger Dryas (YD) transition. Palaeoecological and geochemical data at 5-15 years temporal resolution allowed tracing the dynamics of short-term shifts of the ecosystem triggered by abrupt climate change. The robust age control together with the high-resolution sampling allowed the detection of leads and lags between different proxies to the climate shift at the Allerød-Younger Dryas transition. Our results indicate (1) a water level decrease and an increase in wind activities during the late Allerød and the Allerød-YD transition, which caused intensified erosion in the catchment, (2) a two-decades delayed vegetation response in comparison to the lake depositional system. Comparison with the Lake Meerfelder Maar record revealed slightly different vegetation responses of the Trzechowskie palaeolake at the YD onset.

  17. Absence of geochemical evidence for an impact event at the Bølling–Allerød/Younger Dryas transition

    PubMed Central

    Paquay, François S.; Goderis, Steven; Ravizza, Greg; Vanhaeck, Frank; Boyd, Matthew; Surovell, Todd A.; Holliday, Vance T.; Haynes, C. Vance; Claeys, Philippe

    2009-01-01

    High concentrations of iridium have been reported in terrestrial sediments dated at 12.9 ka and are interpreted to support an extraterrestrial impact event as the cause of the observed extinction in the Rancholabrean fauna, changes in the Paleoindian cultures, and the onset of the Younger Dryas cooling [Firestone RB, et al. (2007) Proc Natl Acad Sci USA 104:16016–16021]. Here, we report platinum group element (PGE: Os, Ir, Ru, Rh, Pt, Pd), gold (Au) concentrations, and 187Os/188Os ratios in time-equivalent terrestrial, lacustrine, and marine sections to seek robust evidence of an extraterrestrial contribution. First, our results do not reproduce the previously reported elevated Ir concentrations. Second, 187Os/188Os isotopic ratios in the sediment layers investigated are similar to average crustal values, indicating the absence of a significant meteoritic Os contribution to these sediments. Third, no PGE anomalies distinct from crustal signatures are present in the marine record in either the Gulf of California (DSDP 480, Guaymas Basin) or the Cariaco Basin (ODP 1002C). Our data show no evidence of an extraterrestrial (ET)-PGE enrichment anomaly in any of the investigated depositional settings investigated across North America and in one section in Belgium. The lack of a clear ET-PGE signature in this sample suite is inconsistent with the impact of a large chondritic projectile at the Bølling–Allerød/Younger Dryas transition. PMID:20007789

  18. Nanodiamonds and wildfire evidence in the Usselo horizon postdate the Allerød-Younger Dryas boundary

    PubMed Central

    van Hoesel, Annelies; Hoek, Wim Z.; Braadbaart, Freek; van der Plicht, Johannes; Pennock, Gillian M.; Drury, Martyn R.

    2012-01-01

    The controversial Younger Dryas impact hypothesis suggests that at the onset of the Younger Dryas an extraterrestrial impact over North America caused a global catastrophe. The main evidence for this impact—after the other markers proved to be neither reproducible nor consistent with an impact—is the alleged occurrence of several nanodiamond polymorphs, including the proposed presence of lonsdaleite, a shock polymorph of diamond. We examined the Usselo soil horizon at Geldrop-Aalsterhut (The Netherlands), which formed during the Allerød/Early Younger Dryas and would have captured such impact material. Our accelerator mass spectrometry radiocarbon dates of 14 individual charcoal particles are internally consistent and show that wildfires occurred well after the proposed impact. In addition we present evidence for the occurrence of cubic diamond in glass-like carbon. No lonsdaleite was found. The relation of the cubic nanodiamonds to glass-like carbon, which is produced during wildfires, suggests that these nanodiamonds might have formed after, rather than at the onset of, the Younger Dryas. Our analysis thus provides no support for the Younger Dryas impact hypothesis. PMID:22547791

  19. The students' observatory 1935 - 43: when Aller measured radial velocities and Popper interpreted stellar spectra, with brief updates on the significance of DQ Her, SN 1937C, Alpha Cygni, RY Scuti, and the rotation of M33.

    NASA Astrophysics Data System (ADS)

    Trimble, V.

    This note presents reminiscences given at a symposium on "Stellar astronomers in California: past, present, and future", held at UCLA, September 1993, to mark the 80th birthdays of Daniel M. Popper and Lawrence H. Aller.

  20. No support from osmium isotopes for an impact event at the Bølling-Allerød/Younger Dryas transition

    NASA Astrophysics Data System (ADS)

    Paquay, F.; Ravizza, G. E.

    2009-12-01

    The hypothesis that an extraterrestrial (ET) impact as a triggering mechanism for the abrupt Bølling-Allerød/Younger Dryas climatic transition, the North American megafaunal extinction and the demise of the Clovis culture still remains controversial. Reports of elevated iridium concentrations (> several ng/g) measured in magnetic grains and bulk sediments are used in previous work to argue that a chondritic bolide vaporized upon impact, or fully exploded into the atmosphere. If such a scenario is correct, high Ir concentrations are expected to be accompanied by a systematic decrease in the 187Os/188Os ratios toward unradiogenic, chondrite-like values, reflecting an ET platinum group element (PGE) component. In our study, Os, Ir and Pt were pre-concentrated from 5-20g of powdered samples by NiS fire assay after spiking the samples with a tracer solution enriched in 190Os, 191Ir and 198Pt. Large sample weights were used in order to minimize the nugget effect. Analyses of seven of the same black mat layers investigated in the original reports (Firestone et al. 2007), failed to reproduce previously reported high Ir concentrations, and yielded high 187Os/188Os ratios (1.00-1.90) that are typical of a crustal signature rather than an extraterrestrial one. In addition, a high-resolution study of 187Os/188Os ratios and Os and Ir concentrations in bulk sediments from two ocean margin sites where the Younger Dryas (YD) onset is clearly established by multiple proxies (DSDP 480, Guaymas Basin; ODP 1002C, Cariaco Basin) failed to detect any ET-PGE enrichment anomaly or systematic 187Os/188Os excursion to low ratios at the onset of the YD. Rather measured 187Os/188Os ratios remained within a few percent of present-day seawater 187Os/188Os across the BA/YD transition at both of the marine sites. These results undermine previous claims of a chondritic projectile. Moreover they are difficult to reconcile with the impact of a body from any known meteorite class because

  1. From the Allerød to the mid-Holocene: palynological evidence from the south basin of the Caspian Sea

    NASA Astrophysics Data System (ADS)

    Leroy, Suzanne A. G.; Tudryn, Alina; Chalié, Françoise; López-Merino, Lourdes; Gasse, Françoise

    2013-10-01

    Pollen and dinoflagellate cysts have been analysed in a core from the south basin of the Caspian Sea, providing a picture of respectively past vegetation and water salinity for the Late Pleistocene to middle Holocene. A relatively sharp lithological change at 0.86 m depth reflects a shift from detrital silts to carbonates-rich fine silts. From this depth upwards, a Holocene chronology is built based on ten radiocarbon dates on ostracod shells and bulk carbonates. From the vegetation point of view, the Late Pleistocene deserts and steppes were partially replaced in the most sheltered areas by an open woodland with Pinus, Juniperus-Hippophae-Elaeagnus and even Alnus-Quercus-Pterocarya and Fraxinus, related to the Allerød palynozone. This was interrupted by the Younger Dryas palynozone when Artemisia reaches a maximum in a first instance followed by a very dry phase with only a slight return of Pinus and Quercus and the rare presence of Ulmus-Zelkova. From 11.5 to 8.4 cal. ka BP, an open landscape dominated by shrubs such as Ephedra and progressively increasing Quercus appeared. The final spread of diverse evergreen and deciduous trees is delayed and occurs after 8.4 cal. ka BP. It is suggested that this delay is caused by an arid climate in the Early Holocene linked to high insolation and perhaps to a lake effect. The dinocyst assemblages fluctuate between slightly brackish (Pyxidinopsis psilata and Spiniferites cruciformis, 7 psu and lower) and more brackish (Impagidinium caspienense, ˜13 psu). In the Lateglacial (Khvalynian highstand), the assemblages remained dominated by relative low salinity taxa. A late and brief increase of salinity occurred prior to 11.2 cal. ka BP associated with the Mangyshlak lowstand. It is suggested that it was caused by a brief drop in meltwater flow from both the north and the southeast (Uzboy) and a likely evaporation increase. This lowstand occurs quasi at the same time as the end of a longer lowstand in the Black Sea. The freshest

  2. Permafrost thawing as a possible source of abrupt carbon release at the onset of the Bølling/Allerød

    PubMed Central

    Köhler, Peter; Knorr, Gregor; Bard, Edouard

    2014-01-01

    One of the most abrupt and yet unexplained past rises in atmospheric CO2 (>10 p.p.m.v. in two centuries) occurred in quasi-synchrony with abrupt northern hemispheric warming into the Bølling/Allerød, ~14,600 years ago. Here we use a U/Th-dated record of atmospheric Δ14C from Tahiti corals to provide an independent and precise age control for this CO2 rise. We also use model simulations to show that the release of old (nearly 14C-free) carbon can explain these changes in CO2 and Δ14C. The Δ14C record provides an independent constraint on the amount of carbon released (~125 Pg C). We suggest, in line with observations of atmospheric CH4 and terrigenous biomarkers, that thawing permafrost in high northern latitudes could have been the source of carbon, possibly with contribution from flooding of the Siberian continental shelf during meltwater pulse 1A. Our findings highlight the potential of the permafrost carbon reservoir to modulate abrupt climate changes via greenhouse-gas feedbacks. PMID:25409739

  3. Lead and Lags of Lake System Responses to Late Allerød and Early Younger Dryas Climatic Fluctuation - an Example from Varved Lake Sediments from Northern Poland (Central Europe)

    NASA Astrophysics Data System (ADS)

    Slowinski, M. M.; Zawiska, I.; Ott, F.; Noryśkiewicz, A. M.; Plessen, B.; Apolinarska, K.; Lutyńska, M.; Michczynska, D. J.; Wulf, S.; Skubała, P.; Błaszkiewicz, M.; Brauer, A.

    2014-12-01

    The transition from the warmer Allerød to the cooler Younger Dryas period is well understood to represent sudden and extreme climate changes during the end of the last glaciation. Thus, lake sediment studies within paleoclimatic and paleoecological research on this transition are ideal to enhance the knowledge about "lead and lags" of lake system responses to abrupt climate changes through applying multi-proxy sediment analyses. In this study, we present the results of high-resolution studies on varved late glacial sediments from the Trzechowskie paleolake, located in the northern Poland (center Europe). High-resolution bio-proxies (pollen, macrofossils, Cladocera and diatoms), geochemical analyses (µ-XRF data, TOC, C/N ratios, δ18Ocarb and δ13Corg stable isotopes) and a robust chronology based on varve counting, AMS 14C dating and tephrochronology were used to reconstruct the lake system responses to rapid climatic and environmental changes of Trzechowskie paleolake during the late Allerød - Younger Dryas transition. Paleoecological and geochemical analyses, which were carried out in a 4 to 16 years temporal sample resolution, allowed to defining short-termed shifts of the ecosystem that were triggered by abrupt climate changes. The rapid and pronounced cooling at the beginning of the Younger Dryas had a major impact on the lake and its catchment as clearly reflected by not synchronous changes of both, biotic and geochemical proxies. The results of high-resolution analysis indicate (a) an increased precipitation during the Allerød-YD transition, which is responsible for an increase of soil erosion in the catchment during this period, (b) a delayed response of the vegetation compared to the lake depositional system at the YD onset of 20 years, and (c) a non-synchronicity of vegetation responses between Western (Lake Meerfelder Maar) and Eastern European sites (Trzechowskie palaeolake) at the YD onset. This study is a contribution to the Virtual Institute

  4. Biostratigraphic Evidence of the Allerød-Younger Dryas-Preboreal Oscillation in Northern Iceland

    NASA Astrophysics Data System (ADS)

    Rundgren, Mats

    1995-11-01

    Basal sediments of Lake Torfadalsvatn, northern Iceland, record changes in terrestrial and limnic environments in the period 11,300-9000 14C yr B.P. These changes were probably forced by climate and connected with displacements of the marine polar front and sea-ice margin. Pollen, spores, green algae ( Pediastrum), saturation isothermal remanent magnetization, and carbon content of the basal sediments provide the first detailed biostratigraphic record of the last glacial-interglacial transition in Iceland. During the first pioneer phase, beginning at ca. 11,300 14C yr B.P., grasses and fell-field herbs became established, and lake productivity was very low. At ca. 10,900 14C yr B.P., climatic and soil conditions became favorable for shrubs and dwarf shrubs. This change, together with increased limnic productivity, clearly indicates long seasons without ice-cover in the sea immediately north of Iceland. A return to a colder climate (Younger Dryas), probably in connection with a southward displacement of the marine polar front, occurred by 10,600 14C yr B.P. Shrub and dwarf-shrub vegetation disappeared, and limnic productivity diminished. A second pioneer vegetation phase, dominated by Oxyria/Rumex and grasses, was initiated by a change to longer seasons without sea ice at ca. 9900 14C yr B.P. This warming is also evident as a contemporaneous increase in lake productivity. After ca. 9400 14C yr B.P. the reestablishment of dwarf-shrub heaths and very high limnic productivity indicate further warming.

  5. Transient Simulation of Last Deglaciation with a New Mechanism for B lling-Aller d Warming

    SciTech Connect

    Erickson, David J

    2009-01-01

    We conducted the first synchronously coupled atmosphere-ocean general circulation model simulation from the Last Glacial Maximum to the Boelling-Alleroed (BA) warming. Our model reproduces several major features of the deglacial climate evolution, suggesting a good agreement in climate sensitivity between the model and observations. In particular, our model simulates the abrupt BA warming as a transient response of the Atlantic meridional overturning circulation (AMOC) to a sudden termination of freshwater discharge to the North Atlantic before the BA. In contrast to previous mechanisms that invoke AMOC multiple equilibrium and Southern Hemisphere climate forcing, we propose that the BA transition is caused by the superposition of climatic responses to the transient CO{sub 2} forcing, the AMOC recovery from Heinrich Event 1, and an AMOC overshoot.

  6. Limitierungen bei der Ermittlung der Grundwasserfließrichtung in tiefen Aquiferen am Beispiel des Malms im Süddeutschen Molassebecken

    NASA Astrophysics Data System (ADS)

    Savvatis, Alexandros; Steiner, Ulrich; Huber, Bernhard; Fritzer, Thomas; Schneider, Michael

    2015-12-01

    The groundwater flow direction in deep inclined aquifers is generally determined from contour maps based on the conversion of the reservoir pressure from deep wells to standardized groundwater levels. The standardizing is done with a representative water column of constant density in which an increasing depth of the aquifer has an increasing influence on the calculated groundwater levels. However, integration of new pressure data from recently drilled geothermal wells in the Malm of the South German Molasse Basin in the greater area of Munich led to a hydrogeologically unrealistic groundwater flow direction below the Alps. The present work demonstrates the applied method for standardization, performs an error analysis, and shows the limits of the applicability of this method. An alternative approach is introduced along with a concrete example where the local flow direction is determined by neighboring wells (cluster method). A sensitivity analysis with respect to the uncertainty in temperature shows that this approach provides realistic results from realistic input scenarios. The presented cluster method is therefore able to provide pilot points for calibration/verification of a basin-scale groundwater flow model.

  7. Physik gestern und heute Suprafluidität - Von den Schwierigkeiten einer Messung

    NASA Astrophysics Data System (ADS)

    Sichau, Christian

    2003-03-01

    Der Vater der Tieftemperaturphysik, Heike Kammerlingh Onnes, benötigte zu Beginn des 20. Jahrhunderts für die Verflüssigung von wenigen Litern Heliums noch mehrere Jahre, eine riesige Apparatur und viel Geld. Heute gelingt dies routinemäßig. Die Untersuchung der Materie bei tiefen Temperaturen, insbesondere zur Suprafluidität, bietet viele Überraschungen.

  8. Aktuelle Regelungen zur Leistungsbeurteilung und zu Zeugnissen an Deutschen Sekundarschulen. Eine Vergleichende Studie aller Bundeslander--Darstellung und Diskussion Wesentlicher Ergebnisse (Recent Regulations for the Assessment of Achievement and for Grading at German Secondary Schools. A Comparative Study among all Federal Laender--Presentation and Discussions of Important Results.

    ERIC Educational Resources Information Center

    Bohl, Thorsten

    2003-01-01

    Discusses a comparative study of regulations for assessment of achievement and grading in German secondary schools. Results reveal schools provide alternatives to traditional grading and take into account interdisciplinary or special learning achievements and social behavior. Summarizes major results. Discusses problems in the basic conception and…

  9. Comparative Analysis of Angiogenic Gene Expression in Normal and Impaired Wound Healing in Diabetic Mice: Effects of Extracorporeal Shock Wave Therapy

    DTIC Science & Technology

    2010-01-01

    difficult-to-heal wounds, ESWT has been used to treat severe angina pec- toris, ischemic heart disease and various musculoskeletal afflictions including...2010) Double-blind and placebo- controlled study of the effecti venes. and safety of extracorporeal cardiac shock wave therapy for severe angina ... pectoris . Circ I 74(3):589-591 34. Schaden W, Fischer A, Sailler A (2001) Extracorporeal shock wave therapy of nonunion or delayed osseous union. Clin

  10. Colour Them Happy

    ERIC Educational Resources Information Center

    Paskell, Anthony

    1969-01-01

    This article came about as the result of a chance meeting of the author, Anthony Paskell with Bob Aller, (a West Coast artist) and the remarkable experience that evolved. Mr. Aller held a series of art sessions on various Indian Reserves, all based on his unique approach to the teaching of Art (and art-related experiences)--a non-teaching…

  11. Colour Them Happy

    ERIC Educational Resources Information Center

    Paskell, Anthony

    1969-01-01

    This article came about as the result of a chance meeting of the author, Anthony Paskell with Bob Aller, (a West Coast artist) and the remarkable experience that evolved. Mr. Aller held a series of art sessions on various Indian Reserves, all based on his unique approach to the teaching of Art (and art-related experiences)--a non-teaching…

  12. Lamb shift of an atom in a dielectric medium

    SciTech Connect

    Milonni, P.W.; Schaden, M.; Spruch, L.

    1999-06-01

    Adapting an approach used by Feynman for the Lamb shift of an isolated atom, we obtain a nonperturbative expression for the Lamb shift of an atom in a dielectric medium, previously calculated perturbatively [P. W. Milonni, J. Mod. Opt. {bold 42}, 1191 (1995)]. The separation of the Lamb and Casimir components of the field energy is greatly simplified, and previous nonperturbative results for the Lamb shift [M. Schaden, L. Spruch, and F. Zhou, Phys. Rev. A {bold 57}, 1108 (1998)], based on the generalized argument theorem, are obtained much more easily and directly. {copyright} {ital 1999} {ital The American Physical Society}

  13. Kreuzungsassistenz

    NASA Astrophysics Data System (ADS)

    Mages, Mark; Hopstock, Matthias; Klanner, Felix

    Eine der Hauptunfallursachen insbesondere im innerstädtischen Straßenverkehr ist das Fehlverhalten von Verkehrsteilnehmern im Bereich von Kreuzungen und Einmündungen. So ereigneten sich im Jahr 2006 etwa 43 % aller Unfälle mit schwerem Sachschaden, 36 % aller Unfälle mit Personenschaden und 18 % aller Unfälle mit Todesfolge bei den kreuzungsrelevanten Unfalltypen Abbiegen (Unfalltyp 2 gemäß [12]) bzw. Einbiegen/Kreuzen (Unfalltyp 3) [20]. Daher steht die Kreuzung derzeit aus verkehrs- und sicherheitstechnischer Sicht im Fokus der Forschung.

  14. MYXINOIDA, Schleimaale, Inger

    NASA Astrophysics Data System (ADS)

    Rieger, Gunde; Maier, Wolfgang

    Schleimaale leben in Bodennähe bzw. im Schlamm eingegraben in allen Ozeanen bis in 2500 m Tiefe, bevorzugt in mehr als 30 m Tiefe in küstennahen Bereichen der gemäßigten Breiten. Geringere Salinität und vor allem Wassertemperaturen über 20°C sind limitierende Faktoren für ihr Vorkommen, das sich daher in wärmeren Zonen auf größere Tiefen beschränkt. Auch vom East Pacific Rise ist seit kurzem eine neue Art der Gattung Eptatretus bekannt (S. 198).

  15. Quantenwelt im Nanozylinder: Elektronische Eigenschaften von Kohlenstoff-Nanoröhrchen

    NASA Astrophysics Data System (ADS)

    Strunk, Christoph

    2005-07-01

    Kohlenstoff-Nanoröhren sind einzelne oder mehrfach ineinander gesteckte molekulare Hohlzylinder. In ihnen bilden Kohlenstoffatome ein Graphit ähnliches Kristallgitter. Diese Fullerene zeichnen sich durch eine außerordentlich hohe Elastizität und Zugfestigkeit aus. In ihren elektronischen Eigenschaften verhalten sie sich entweder wie Halbleiter oder wie metallische Leiter. Aus halbleitenden Nanoröhren konnten bereits winzige Feldeffekttransistoren hergestellt werden, ein erster Schritt hin zu einer molekularen Elektronik. Die Grundlagenforscher interessiert vor allem das Verhalten metallischer Nanoröhren bei tiefen Temperaturen. An ihren elektronischen Systemen lassen sich zum Beispiel Quanteninterferenzphänomene oder Elektron-Elektron-Wechselwirkungen untersuchen.

  16. Biomoleküle in Bewegung: Proteindynamik

    NASA Astrophysics Data System (ADS)

    Parak, Fritz G.

    2004-11-01

    Viele Proteinmoleküle sind kleine Maschinen. Im Stillstand ist ihr Aufbau wohlbekannt. Doch wie sie arbeiten, ist meistens unklar. Die Grundlagen dieser Proteindynamik werden am Beispiel des Sauerstoffspeicher-Proteins Myoglobin physikalisch untersucht. Dabei ist die Mößbauer-Spektroskopie am Hämeisen besonders hilfreich. Während sich das Myoglobin bei sehr tiefen Temperaturen in einem festkörperähnlichen Standby-Modus befindet, werden oberhalb einer charakteristischen Temperatur im Molekül proteinspezifische Bewegungsmoden aktiviert. Sie lassen sich als langsame, diffusionsartige Fluktuationen von Molekülsegmenten um die mittlere Struktur beschreiben. Diese Moden öffnen Kanäle in das Proteininnere, durch die Sauerstoffmoleküle zur Hämgruppe gelangen können. So ermöglichen sie Strukturänderungen, die für die biologische Funktion entscheidend sind.

  17. USE OF THE RIBONUCLEASE PROTECTION ASSAY FOR IDENTIFYING CHEMICALS WHICH ELLICIT HYPERSENSITIVITY RESPONSES

    EPA Science Inventory

    Use of the Ribonuclease Protection Assay (RPA) for Identifying Chemicals that Elicit Hypersensitivity Responses. L.M. Plitnick, 1, D.M. Sailstad, 2, and R.J. Smialowicz, 2 1UNC, Curriculum in Toxicology, Chapel Hill, NC and 2USEPA, NHEERL, RTP, NC.

    The incidence of aller...

  18. Research in Traveling Wave Charge Transport Technology

    DTIC Science & Technology

    1987-02-01

    structural and electronic quality of cir- cuit features. This is particularly useful in applications where Schottky barrier diode leakage degradation due to...pattern definition with photoresist layer unstripped. 1 jijure 151. Cleaved edge profile aller pattern definition with photoresist laser stripped... diode edge guarding, barrier metal type, and process temperature on leakage current behavior. Experimental Work A Schottky barrier diode array

  19. USE OF THE RIBONUCLEASE PROTECTION ASSAY FOR IDENTIFYING CHEMICALS WHICH ELLICIT HYPERSENSITIVITY RESPONSES

    EPA Science Inventory

    Use of the Ribonuclease Protection Assay (RPA) for Identifying Chemicals that Elicit Hypersensitivity Responses. L.M. Plitnick, 1, D.M. Sailstad, 2, and R.J. Smialowicz, 2 1UNC, Curriculum in Toxicology, Chapel Hill, NC and 2USEPA, NHEERL, RTP, NC.

    The incidence of aller...

  20. World Sheet Dynamics of Effective String Theory and the Gribov Ambiguity in QCD

    NASA Astrophysics Data System (ADS)

    Cooper, Patrick

    This PhD thesis consists of a collection of results pertaining to effective string theory and quantum chromodynamics. A bijection is proven between manifestly ISO(1, p) x SO(D - p - 1) actions whose gapless degrees of freedom consist of Goldstone fields realizing the coset ISO(1, D - 1)/ISO(1, p) x SO(D - p - 1) non-linearly, and effective actions describing p + 1 dimensional surfaces embedded in a D dimensional Minkowskian target space. Continuing with effective strings, an interesting UV complete, albeit acausal theory is analyzed whose low energy effective action has a 'wrong sign' leading irrelevant operator. The constraints integrability puts on branon scattering is also catalogued in various dimensions, and in the presence of goldstini non-linearly realizing target space supersymmetry. An interesting hidden supersymmetry is discovered, for Green-Schwarz-like actions with an arbitrary coefficient preceding the Wess-Zumino term. Lastly, with regards to QCD, techniques from the program initiated by Vladimir Gribov in 1978 to investigate the effects of a non-perturbative residual gauge ambiguity are refined and applied to the Gribov-Zwanziger confinement scenario, showing an enhanced ghost propagator and divergent color coulomb potential. I then provide a careful analysis of how to correctly implement periodic boundary conditions in the finite temperature theory, which naively would be contradictory with the Maggiore-Schaden shift which is crucial to using familiar BRST cohomology techniques to define the subset of physical states of the Hilbert space.

  1. Fibrin glue as a protective tool for microanastomoses in limb reconstructive surgery.

    PubMed

    Langer, Stefan; Schildhauer, Thomas A; Dudda, Marcel; Sauber, Jeannine; Spindler, Nick

    2015-01-01

    Einleitung: Fibrinkleber ist ein immer häufiger in der klinischen Routine eingesetztes Tool zur Stabilisierung von Mikroanastomosen und Nervenreparatur.Dieser Artikel fasst die technischen Eigenschaften und Vorteile im Gebrauch sowie die variable Anwendungsmöglichkeit von Fibrinkleber im mikrochirurgischen Kontext zusammen und illustriert dies an einem extremitätenrekonstruierenden Fallbeispiel.Patienten und Methoden: 131 Patienten, an welchen sowohl elektiv als auch in einer Notfallsituation eine mikrochirurgische Intervention durchgeführt wurde, hauptsächlich in der Extremitäten erhaltenden Chirurgie, wurden retrospektiv untersucht; ebenso die Patienten, welche eine freie Lappenplastik erhalten hatten.Ergebnisse: Die Verwendung von Fibrinkleber in der Mikrochirurgie erlaubt ein exaktes Positionieren der Anastomose von Gefäßen und Nerven. Ein Verdrehen oder Kinking des Pedickels konnte in keinem Fall festgestellt werden. Die Überlebensrate der Lappen betrug >94%. In 99% der Fälle konnte der Fibrinkleber belassen werden. In dem seltenen Fall der Revision konnte der Fibrinkleber leicht entfernt werden ohne Schaden an der Anastomose zu hinterlassen. Zusammenfassung: Fibrinkleber ist nicht geeignet Anastomoseninsuffizienzen oder leckende Anastomosen zu behandeln, allerdings schützt er die Anastomose vor schadendem Druck ausgelöst durch Gewebe oder Flüssigkeit. Er bewahrt den Gefäßstiel vor Verdrehung und hilft dem Operateur beim Wiederauffinden der Anastomose im Fall einer Revision.

  2. Working mechanism of extracorporeal shockwave therapy in non-urological disciplines

    NASA Astrophysics Data System (ADS)

    Schaden, Wolfgang

    2005-04-01

    For 32 years of extracorporeal shockwave lithotripsy (ESWL) only the mechanical strength of shockwaves were of clinical interest. For use in orthopaedics, the absence of dangerous long term effects (malignant degeneration, etc.) is the only important message. The mechanical model tries to explain the effect of shock waves by the provocation of microleasions in the tissue stimulating repairing processes. First doubts on this mechanical model came up when Schaden (2001) could show, that less energy is more efficient in the treatment of non-unions. Due to the basic research of the last years knowledge increased about the microbiological effects. Under the influence of shock waves the change of permeability of cell membranes and the liberation of free radicals was reported. Also the production of nitric oxide (NO) and different growth factors like vascular endothelial growth factor (VEGF), bone morphogenetic proteins (BMP), transforming growth factor-beta 1 (TGF-b1), insulin-like growth factor-I (IGF-I) etc. was observed. The biological model tries to explain the effect of shock waves by stimulating the ingrowth of blood vessels and liberation of growth factors. Under the influence of shock waves, biological tissues seem to be able to produce important substances to initiate healing processes.

  3. 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.

  4. Spectrophotometry near the atmospheric cutoff of the strongest Bowen resonance fluorescence lines of O III in two planetary nebulae

    NASA Technical Reports Server (NTRS)

    O'Dell, C. R.; Opal, Chet B.

    1989-01-01

    Spectrophotometric results are presented for the stronger, well-resolved Bowen O III resonance fluorescence emission lines in the planetary nebulae 7027 and NGC 7662 down to and including the intrinsically strong line at 3133 A. These data are combined with results from the IUE atlas of spectra and similar results for the longer wavelength lines by Likkel and Aller (1986) to give the first full coverage of the Bowen lines. Good agreement is found with fluorescence theory for the primary cascade lines, except for the Likkel and Aller results. The efficiency of conversion of the exciting He II Ly-alpha into O III lines is determined, and values comparable to other planetary nebulae are found.

  5. VDI-Richtlinien - mit Technischen Regeln Wirtschaftlichkeit erhöhen und Standards setzen

    NASA Astrophysics Data System (ADS)

    Mandelartz, Johannes

    Der Verein Deutscher Ingenieure e.V. (VDI) ist ein gemeinnütziger, wirtschaftlich und politisch unabhängiger, technisch-wissenschaftlicher Verein von Ingenieuren und Naturwissenschaftlern. Mit über 137 000 persönlich zugeordneten Mitgliedern ist er eine der größten Ingenieur-Vereinigungen Europas und gilt in Deutschland als führender Sprecher der Technik und der Ingenieure. 1856 gegründet, hat er viele für die Technik wesentliche Entwicklungen in Gang gesetzt, so im Bereich der technischen Überwachung, der technischen Regelsetzung und Normung, der Arbeitsstudien, im gewerblichen Rechtsschutz und im Patentwesen. Seit seiner Gründung sieht es der VDI als seine Aufgabe, "das Zusammenwirken aller geistiger Kräfte der Technik im Bewusstsein ethischer Verantwortung zu fördern“ und die Lebensmöglichkeiten aller Menschen durch Entwicklung und sinnvoller Anwendung technischer Mittel zu verbessern.

  6. Interaction of the MUC1 Tumor Antigen and the Adenomatous Polyposis Coli Tumor Suppressor in Human Breast Cancer

    DTIC Science & Technology

    2006-03-01

    Cancer Res 2005, 7(4):R422-435. 36. Troyano A, Sancho P, Fernandez C, de Blas E, Bernardi P, Aller P: The selection between apoptosis and necrosis...was made in-house by the Mayo Clinic Arizona Immunology Core (6). Antibodies to phosphotyrosine (BD Biosciences, San Jose , CA), ERK1/2 (Cell...MUC1 (Pharmingen, San Jose , CA). Flow cytometry - Staining for MUC1 surface localization was performed on cells that were trypsinized, but not

  7. 25 Jahre - Institut fuer Geodaesie, Teil 3: Aus dem Leben des Instituts (25 Years - Institute of Geodesy, Part 3: The Life of the Institute)

    DTIC Science & Technology

    2000-01-01

    wesentlich niedrigeren Preise, in kleinen Gaststdtten ein. Sehr beliebt war das >Tam-Tamo, wo es ftir wenig Geld zdhe Schnitzel und hervorragende Avocados und...ausreichend bemnessen; sie erlaubten insbesondere in der Phase der Erstausstattung eine grol3zUlgige Beschaffung aller ftir Lehre und Forschung...Fakultdt der Rheinischen Friedrich-Wilhelms-Universitat in Bonn auf. Ein besonderes Ereignis unter den damaligen Bedingungen stellte ftir mich ein

  8. Infrarot-Thermografie in der Instandhaltung der chemischen Industrie

    NASA Astrophysics Data System (ADS)

    Huber, Christian

    Als Folge der raschen technologischen Entwicklung preisgünstiger, leistungsfähiger Thermografiekameras rückte diese für viele Anwendungen nutzbringend einzusetzende Inspektionsmethode zunehmend ins Interesse der Instandhalter aller Branchen. Die Infrarot(IR)-Thermografie wird damit als Schadensfrüherkennungsmethode integriert in das Repertoire bereits langjährig angewendeter Methoden wie der Schwingungsmesstechnik, Schmierstoffanalyse, Fehlerdiagnose an elektrotechnischen Komponenten sowie die gesamte Fülle zerstörungsfreier Untersuchungen im Werkstoffbereich.

  9. Rahmen, Herausforderungen und Visionen für die Unternehmensorganisation

    NASA Astrophysics Data System (ADS)

    Westkämper, Engelbert; Seidel, Bernhard; Bruhn, Manfred; Bahke, Torsten; Klotz, Ulrich; Buck, Hartmut

    Die Produktion trägt entscheidend zur gesamten Wertschöpfung des Landes mit mehr als einem Drittel aller Beschäftigten bei. Die direkte Wertschöpfung ist dabei für ein rohstoff- und energiearmes Land allein durch Veredelung und technisches Know-how sowie durch die Herstellung von Produkten für den Binnen- und Weltmarkt möglich.

  10. Apprendre à apprendre

    PubMed Central

    Diamond, Adele

    2009-01-01

    Comment aider les enfants à réussir à l’école et, plus généralement, à développer leurs capacités intellectuelles ? Les résultats de travaux fondamentaux en psychologie et en neurosciences permettent de proposer des méthodes pédagogiques efficaces, bien qu’elles semblent parfois aller contre le bon sens. PMID:20936089

  11. Biogeochemical Consequences of Infaunal Activities

    DTIC Science & Technology

    2005-01-01

    altering physical transport regimes. During the 40 years since Bemer presented the idealized model for sedimentary early dia- genesis [Berner, 1964...surface area per unit volume of sediments, using the original model by Aller [1980] 5- 4 - 3- 02 0 0 1000 2000 3000 4000 5000 Water depth (m) Figure 1...also potentially capable of describing micro-scale; heterogeneous processes that occur in the immediate vicinity of 3000 2 00010 10000 00 a(x

  12. Analyzing information contained in the OARMA Binary Orbit Catalog

    NASA Astrophysics Data System (ADS)

    Docobo, J. A.; Ling, J. F.; Campo, P. P.

    2012-05-01

    This poster displays a statistical summary based on the information contained in the Double Star Orbit Catalog of the Ramon Maria Aller Astronomical Observatory (OARMA). Among other findings, the current aleatory period-eccentricity distribution is particularly interesting. We have correlated eccentricities, periods, spectral types, Hipparcos parallaxes and the orientations of the orbital planes. A list is included that contains all of the names of the authors of the orbits as well as the number of orbits calculated by the authors (February 2011).

  13. PubMed

    Diamond, Adele

    2009-02-01

    Comment aider les enfants à réussir à l'école et, plus généralement, à développer leurs capacités intellectuelles ? Les résultats de travaux fondamentaux en psychologie et en neurosciences permettent de proposer des méthodes pédagogiques efficaces, bien qu'elles semblent parfois aller contre le bon sens.

  14. Multiple oscillations during the Lateglacial as recorded in a multi-proxy, high-resolution record of the Moervaart palaeolake (NW Belgium)

    NASA Astrophysics Data System (ADS)

    Bos, Johanna A. A.; De Smedt, Philippe; Demiddele, Hendrik; Hoek, Wim Z.; Langohr, Roger; Marcelino, Vera; Van Asch, Nelleke; Van Damme, Dirk; Van der Meeren, Thijs; Verniers, Jacques; Boeckx, Pascal; Boudin, Mathieu; Court-Picon, Mona; Finke, Peter; Gelorini, Vanessa; Gobert, Stefan; Heiri, Oliver; Martens, Koen; Mostaert, Frank; Serbruyns, Lynn; Van Strydonck, Mark; Crombé, Philippe

    2017-04-01

    This paper presents the results of multi-disciplinary research carried out on the deposits of Moervaart depression, NW Belgium, one of the largest palaeolakes (∼25 km2) that existed during the Lateglacial interstadial in NW Europe. The multi-proxy study, including physical (organic matter and calcium carbonate, magnetic susceptibility, micromorphological), botanical (pollen, macrofossils, diatoms), zoological (ostracods, molluscs, chironomids) and chemical analyses (stable carbon and oxygen isotopes) has resulted in a detailed reconstruction of the Lateglacial landscape as well of the local conditions that prevailed in the lake itself. A chronology of the record was provided by radiocarbon dating and comparison with radiocarbon dates of the nearby Rieme site. These yielded a good match with the regional biostratigraphy. During the Lateglacial, vegetation and geomorphology of the landscape in general changed from a tundra landscape to a boreal forest. The vegetation development, however, was interrupted by a number of cold reversals. Three centennial-scale cold oscillations are present in the record: 1) the so-called Older Dryas corresponding to GI-1d in the Greenland ice-cores, 2) a short and pronounced cold event during the early Allerød, which could be correlated to GI-1c2 and 3) a cooling event during the late Allerød probably corresponding to the Intra Allerød Cold Period (IACP) or GI-1b. The latter most likely was responsible for the disappearance of the Moervaart palaeolake.

  15. Deglacial climate variability in central Florida, USA

    USGS Publications Warehouse

    Willard, D.A.; Bernhardt, C.E.; Brooks, G.R.; Cronin, T. M.; Edgar, T.; Larson, R.

    2007-01-01

    Pollen and ostracode evidence from lacustrine sediments underlying modern Tampa Bay, Florida, document frequent and abrupt climatic and hydrological events superimposed on deglacial warming in the subtropics. Radiocarbon chronology on well-preserved mollusk shells and pollen residue from core MD02-2579 documents continuous sedimentation in a variety of non-marine habitats in a karst-controlled basin from 20 ka to 11.5 ka. During the last glacial maximum (LGM), much drier and cooler-than-modern conditions are indicated by pollen assemblages enriched in Chenopodiaceae and Carya, with rare Pinus (Pinus pollen increased to 20–40% during the warming of the initial deglaciation (∼ 17.2 ka), reaching near modern abundance (60–80%) during warmer, moister climates of the Bølling/Allerød interval (14.7–12.9 ka). Within the Bølling/Allerød, centennial-scale dry events corresponding to the Older Dryas and Intra-Allerød Cold Period indicate rapid vegetation response (

  16. How Synchronous was the Transition into the Younger Dryas across the Euro-Atlantic Region?

    NASA Astrophysics Data System (ADS)

    Schenk, F.; Muschitiello, F.; Heikkilä, M. P.; Väliranta, M.; Tarasov, L.; Brandefelt, J.; Johansson, A. V.; Naslund, J. O.; Wohlfarth, B.

    2015-12-01

    Observations of a currently weakening subpolar gyre south of Greenland has again increased scientific attention regarding the role of the Atlantic Meridional Overturning Circulation (AMOC) for the regional to global climate. The rapid climate shift of the Younger Dryas (YD, GS-1) cold reversal during the last deglaciation is attributed to an abrupt slowdown or collapse of the AMOC due to a strong meltwater pulse and/or the rapid disintegration of the Laurentide Ice sheet. Although such a dramatic event is not expected for the future, the spatiotemporal climatic response to such a slowdown is an interesting test case. Two recently well dated proxy records around the North Sea region suggest a non-synchronous early cooling/onset of the YD compared to Greenland (NGRIP). Presentation #61803 discusses the hypothesis of a local cooling as a response to increased ice berg calving and/or meltwater from Fenno-Scandinavian Ice Sheet (FIS) during the late Alleröd warm phase (GI-1a). Here we study CCSM3 model output from the quasi-transient atmosphere-ocean simulation (TraCE) where no strong contribution from FIS is considered from the late Alleröd into the YD. We evaluate to which extent the spatiotemporal temperature response to the AMOC slowdown of the simulation is synchronous over the Euro-Atlantic region and how atmospheric teleconnections reorganize during the rapid shift into the YD. In addition, we run time-slice experiments at high spatial resolution of around 100 km with the Community Earth System Model CESM1.0.5 for the late Alleröd and YD to compare spatial climatic differences for both periods taking into account the regional influence from continental ice sheets in more detail.

  17. Einleitung

    NASA Astrophysics Data System (ADS)

    Walther-Klaus, Ellen

    Deutschland hat sich in den letzten Jahrzehnten den internationalen Ruf erworben, auf dem Gebiet der Technologie führend zu sein. Große, weitreichende Erfindungen sind in Deutschland gemacht worden. Viele Nobelpreise gehen nach Deutschland: Robert Bosch, Nikolaus Otto und Konrad Zuse gehören genauso zu den großen Erfindern, wie Melitta Bentz und Emmy Noether. 85 % aller Nobelpreise, die seit 1901 nach Deutschland gingen, sind in den Kategorien Chemie, Physik und Medizin vergeben worden. Allein im Jahr 2007 wurden in Deutschland fast 50.000 Patente angemeldet.

  18. Lithostratigraphy and microfacies analyses of the Lateglacial and early Holocene sediment record from Lake Haemelsee (Germany)

    NASA Astrophysics Data System (ADS)

    Haliuc, Aritina; Brauer, Achim; Dulski, Peter; Engels, Stefan; Lane, Christine

    2015-04-01

    sedimentary conditions to climatic changes during Allerød and Allerød/Younger Dryas transition. An increased detrital sediment flux characterizes lithozone 6 and, most probably reflects the Younger Dryas cold interval. This interpretation is supported by the late Allerød Laacher See Tephra, an important chronostratigraphic marker horizon to link the floating 625 varve year chronology for the Allerød interstadial to an absolute time scale. Also, the preliminary pollen data provided the biostratigraphical information for establishing the lateglacial boundaries. Poorly preserved organic laminas are characteristic for lithozone 7 (1445-1474 cm). Our preliminary results demonstrate that the lake system responded sensitively to rapid and short-term climatic changes and these responses are well-expressed in sedimentological and geochemical variability.

  19. Erfahrungen im Aufbau des IT Service Desks der Technischen Universität München

    NASA Astrophysics Data System (ADS)

    Vellguth, Karmela

    Durch das Projekt IntegraTUM und die darin eingebettete Einrichtung eines IT Service Desks mit 1st, 2nd und 3rd Level Support gelang eine an ITIL orientierte Neuausrichtung der internen IT-Dienstleistungen. Die vormals existierende Struktur mit einer Vielzahl an Ansprechpartnern bei auftretenden IT-Problemen wurde aufgelöst. Die Nutzer haben nun eine Anlaufstelle erhalten, die sich für die Beantwortung aller Incidents in kürzester Zeit und mit qualitativ hohem Niveau zuständig fühlt.

  20. Constraining Circulation Changes Through the Last Deglaciation with Deep-sea Coral Radiocarbon and Sedimentary Pa231/Th230

    DTIC Science & Technology

    2012-02-01

    ice core from Greenland [NGRIP, 2004] (red) and the EDML ice core from Antarctica [EPICA, 2006] (blue) over the last deglaciation. Records are...Stadial 1 (H1), the Bølling-Allerød (BA), and the Younger Dryas (YD). YD BA H1 Greenland NGRIP Antarctica EDML 0 5 10 15 20 25 O (‰ ) Age (ka) 8... Greenland ) can explain more than half of the ~800 ‰ decrease over the past 30 ky, it does not account for all of it, suggesting that there must have been a

  1. Reconstruction of Late Glacial summer temperatures from chironomid assemblages in Lac Lautrey (Jura, France)

    NASA Astrophysics Data System (ADS)

    Heiri, Oliver; Millet, Laurent

    2005-01-01

    A chironomid-July air temperature inference model based on chironomid assemblages in the surface sediments of 81 Swiss lakes was used to reconstruct Late Glacial July air temperatures at Lac Lautrey (Jura, Eastern France). The transfer-function was based on weighted averaging-partial least squares (WA-PLS) regression and featured a leave-one-out cross-validated coefficient of determination (r2) of 0.80, a root mean square error of prediction (RMSEP) of 1.53 ° C, and was applied to a chironomid record consisting of 154 samples covering the Late Glacial period back to the Oldest Dryas. The model reconstructed July air temperatures of 11-12 ° C during the Oldest Dryas, increasing temperatures between 14 and 16.5 ° C during the Bølling, temperatures around 16.5-17.0 ° C for most of the Allerød, temperatures of 14-15 ° C during the Younger Dryas and temperatures of ca. 16.5 ° C during the Preboreal. The Lac Lautrey record features a two-step July air temperature increase after the Oldest Dryas, with an abrupt temperature increase of ca. 3-3.5 ° C at the Oldest Dryas/Bølling transition followed by a more gradual warming between ca. 14 200 and 13 700 BP. The transfer-function reconstructs a less rapid cooling at the Allerød/Younger Dryas transition than other published records, possibly an artefact caused by the poor analogue situation during the earliest Younger Dryas, and an abrupt warming at the Younger Dryas/Holocene transition. During the Allerød, two centennial-scale 1.5-2.0 ° C coolings are apparent in the record. Although chronologically not well constrained, the first of these cold events may be synchronous with the beginning of the Gerzensee Oscillation. The second is inferred just before deposition of the Laachersee tephra at Lac Lautrey and is therefore coeval with the end of the Gerzensee Oscillation. In contrast to the Greenland oxygen isotope records, the Lac Lautrey palaeotemperature reconstruction lacks a clearly defined Greenland

  2. Hinderniserkennung und -verfolgung mit einer PMD-kamera im automobil

    NASA Astrophysics Data System (ADS)

    Schamm, Thomas; Vacek, Stefan; Natroshvilli, Koba; Marius Zöllner, J.; Dillmann, Rüdiger

    Die Detektion von Hindernissen vor dem Automobil ist eine Hauptanforderung an moderne Fahrerassistenzsysteme (FAS). In dieser Arbeit wird ein System vorgestellt, das mit Hilfe einer PMDKamera (Photomischdetektor) Hindernisse auf der Fahrspur erkennt und deren relevante Parameter bestimmt. Durch die PMD-Kamera werden zunächst 3D-Tiefenbilder der Fahrzeugumwelt generiert. Nach einem initialen Filterprozess werden im Tiefenbild mit Hilfe eines Bereichswachstumsverfahrens Hindernisse gesucht. Zur Stabilisierung des Verfahrens und zur Parameterberechnung wird ein Kaiman Filter eingesetzt. Das Ergebnis ist eine Liste aller Hindernisse im Fahrbereich des Automobils.

  3. Allerod--younger dryas lake temperatures from midge fossils in atlantic Canada.

    PubMed

    Walker, I R; Mott, R J; Smol, J P

    1991-08-30

    Remains of freshwater midges are abundant in lake sediments, and their species distributions are closely related to the surface-water temperature of lakes; their distributions thus provide a powerful tool for paleoclimatology. The distribution of species in a core from Splan Pond in Atlantic Canada indicates that there were abrupt transitions in late-glacial temperatures between warm and cold states. The transitions are correlative with the well-known warm Allerød and cold Younger Dryas events in Europe. These data thus confirm the inference from palynological data that these events affected regions on both sides of the Atlantic.

  4. Climate variability of Late Pleistocene deglaciation in the North American midcontinent derived from tree rings

    NASA Astrophysics Data System (ADS)

    Panyushkina, Irina P.; Livina, Valerie N.; Leavitt, Steve W.; Mode, William N.

    2016-04-01

    High-resolution climatic proxies, such as tree rings spanning millennia, have excellent potential to describe high- and low-frequency variability of climate. In practice, however, although the number of Holocene millennium-length tree-ring records is still rather limited, they are especially rare for the Late Pleistocene warming period following the Last Glacial Maximum. Furthermore, detection of climatic variability in tree-ring data is hindered due to intricate methodology of chronology development that transforms changes in tree geometry and a variety of environmental responses of tree growth to a climatic signal. Following meticulous derivation of a new tree-ring chronology, we propose a novel approach to analyze annual, decadal, multi-decadal and centennial climate-related variability of floating tree rings dated back near the end of the Pleistocene. We have developed a 1400-year tree-ring width chronology of spruce from the Green Bay area (Wisconsin) dated from 14.5 ka to 13.1ka cal BP. This new North American midcontinent record is composed of 10 overlapped site chronologies and has two short gaps filled with linear interpolation. The Green Bay chronology covers most of the warm and moist Bølling-Allerød interstadial (14.7 ka -12.7 ka BP). Within the Bølling-Allerød interstadial, there were several abrupt and brief cooling excursions such as the Older Dryas with full-glacial-like temperature conditions. We have applied tipping point analysis to detect the changes of climate-system states during these turbulent times and obtained early warning signals in the tree-ring variance. The analysis detected four short-term bifurcations dated ca. 14,450 cal BP, 14,000 cal BP, 13,750-13,600 cal BP and 13,180-13,100 cal BP. The bifurcation events of the tree-ring record correspond well to the abrupt and short cooling temperature excursions of the Bølling-Allerød interstadial documented in δ18O and Ca of GRIP ice-core records, and the Laurentide ice sheet dynamics

  5. Stratification effects and IUE spectra of high excitation planetaries

    NASA Technical Reports Server (NTRS)

    Feibelman, W.; Aller, L. H.

    1982-01-01

    Individual strips across IUE low resolution images of a number of high excitation planetaries with appreciable angular disks (including NGC 2452, 3242, 6818, and IC 1297) are analyzed to assess stratification effects. The familiar enhancement of high excitation lines toward the center is well exhibited, but some unexpected structural features are found in NGC 2452 where C IV shows a single central maximum, but C III, Ne IV, and He II seem to have a central dip. The new IUE data permit improved chemical composition estimates for several planetaries previously analyzed by Aller and Czyzak.

  6. Pioneer Nebular Theorists from Zanstra to Seaton: and Beyond

    NASA Astrophysics Data System (ADS)

    Osterbrock, D. E.

    2002-02-01

    A brief history of theoretical nebular astrophysics, particularly in USA, is presented. The importance of observational knowledge of objects that actually exist is emphasized as a prerequisite for most theories. Herman Zanstra and Ira Bowen were the two most important theorists in opening the field. Donald Menzel and his students, especially James Baker, Leo Goldberg, and Lawrence Aller, were quite important in the further development of it. Henry Norris Russell started nebular astrophysics rolling, and several other later theorists, including Bengt Strömgren, Lyman Spitzer, Iosif Shklovsky and Michael Seaton, also made important contributions to it.

  7. The Casamance Separatism: From Independence Claim to Resource Logic

    DTIC Science & Technology

    2006-06-01

    d’alimenter à Dakar une représentation du conflit dans laquelle ce scénario était censé profiter au MFDC: tout se passer en effet comme si la rébellion...Genevieve Gassere, Manger ou s’en aller": Le Conflit Ethnoregional Casamançais et l’Etat Sénégalais (Thesis presentation, Dept of Political Science...vulnérable par le conflit dans le tissu socio-économique de la région naturelle de Casamance. A son terme, ce programme aboutit à la disparition

  8. Qualitätsmanagement in der Lebensmittelindustrie

    NASA Astrophysics Data System (ADS)

    Thorn, Volker

    Die wesentlichen Kunden der Lebensmittelindustrie sind der Einzel- und Großhandel und die Verbraucher. Jedes Unternehmen kann mittel- und langfristig nur existieren, wenn seine Kunden zufrieden sind. Kunden sind zufrieden, wenn ihre Erwartungen, die sie an Produkt, Service und Preis stellen, erfüllt werden. Also die bestimmte erwartete Qualität (Leistung) sichergestellt wird. Trotz aller Bemühungen und Anstrengungen der Anbieter, Qualitätsprodukte auf den Markt zu bringen, kames in den letzten Jahren immer wieder zu Lebensmittelskandalen.

  9. Aspects of Benthic Biology in Support of HEBBLE (High Energy Benthic Boundary Layer Experiment).

    DTIC Science & Technology

    1985-01-08

    Banis in the Gulf of Mexico (Yingst and Rhoads, in press), and at the Deep station in 40 m of water in Long Island Sound (Aller and Yingst, 1980...community structure in the vicinity of the Texas Flower Gardens, Gulf of Mexico . Estuarine, Coastal, and Shelf 9cience. Young, R.N. and J.B. Southard...tubes of benthic agglutinated foraminifera . Physical properties The vane shear strength is very uniform at 0.4 kPa through the soft brown mud but

  10. The ionization structure of planetary nebulae 10: NGC 2392

    NASA Technical Reports Server (NTRS)

    Barker, Timothy

    1989-01-01

    Spectrophotometric observations of emission-line intensities over the spectral range 1400 to 7200 A were made in six positions in the planetary nebula NGC 2392. Standard equations used to correct for the existence of elements in other than the optically observable ionization stages give consistent results for the different positions that are in excellent agreement with abundances calculated using ultraviolet lines, and there is no evidence for any abundance gradient in the nebula. The logarithmic abundances agree well with determinations by Aller and Keyes.

  11. Too early and too northerly: evidence of temperate trees in northern Central Europe during the Younger Dryas.

    PubMed

    Robin, Vincent; Nadeau, Marie-Josée; Grootes, Pieter M; Bork, Hans-Rudolf; Nelle, Oliver

    2016-10-01

    This paper presents highly unexpected paleobotanical data. Eight (14) C-accelerator mass spectrometry (AMS) dates of soil macrocharcoal pieces, identified taxonomically, indicate the presence of oak and beech in the Younger Dryas, and pine in the Allerød, in the northernmost low mountain range of Central Europe, the Harz Mountains, in Germany. If the presence of pine at such latitude and periods is not surprising, the presence of temperate-adapted trees is highly improbable, because they are assumed to have reached the area from a southern location several thousand years later. Two hypotheses are postulated to explain this record. Both are related to the warm periods of the Bølling and Allerød: the classically 'short' duration of this warm period makes the migration of the temperate trees from the identified refuge areas in the southern location implausible, and so the presence of intermediary microrefugia at a medium latitude in Central Europe is postulated; recent data reveal that the warm period of the Late Glacial phase was much longer than considered in the classical view and, thus, would be long enough for a northward migration of temperate-adapted trees. Although our dataset does not permit disentanglement of these hypotheses, it provides significant innovative insights for the biogeography of Central Europe.

  12. Deglacial hydroclimate of midcontinental North America

    NASA Astrophysics Data System (ADS)

    Voelker, Steven L.; Stambaugh, Michael C.; Guyette, Richard P.; Feng, Xiahong; Grimley, David A.; Leavitt, Steven W.; Panyushkina, Irina; Grimm, Eric C.; Marsicek, Jeremiah P.; Shuman, Bryan; Brandon Curry, B.

    2015-03-01

    During the last deglaciation temperatures over midcontinental North America warmed dramatically through the Bølling-Allerød, underwent a cool period associated with the Younger-Dryas and then reverted to warmer, near modern temperatures during the early Holocene. However, paleo proxy records of the hydroclimate of this period have presented divergent evidence. We reconstruct summer relative humidity (RH) across the last deglacial period using a mechanistic model of cellulose and leaf water δ18O and δD combined with a pollen-based temperature proxy to interpret stable isotopes of sub-fossil wood. Midcontinental RH was similar to modern conditions during the Last Glacial Maximum, progressively increased during the Bølling-Allerød, peaked during the Younger-Dryas, and declined sharply during the early Holocene. This RH record suggests deglacial summers were cooler and characterized by greater advection of moisture-laden air-masses from the Gulf of Mexico and subsequent entrainment over the mid-continent by a high-pressure system over the Laurentide ice sheet. These patterns help explain the formation of dark-colored cumulic horizons in many Great Plains paleosol sequences and the development of no-analog vegetation types common to the Midwest during the last deglacial period. Likewise, reduced early Holocene RH and precipitation correspond with a diminished glacial high-pressure system during the latter stages of ice-sheet collapse.

  13. Bundled turbidite deposition in the central Pandora Trough (Gulf of Papua) since Last Glacial Maximum: Linking sediment nature and accumulation to sea level fluctuations at millennial timescale

    NASA Astrophysics Data System (ADS)

    Jorry, StéPhan J.; Droxler, André W.; Mallarino, Gianni; Dickens, Gerald R.; Bentley, Sam J.; Beaufort, Luc; Peterson, Larry C.; Opdyke, Bradley N.

    2008-03-01

    Since Last Glacial Maximum (23-19 ka), Earth climate warming and deglaciation occurred in two major steps (Bølling-Allerød and Preboreal), interrupted by a short cooling interval referred to as the Younger Dryas (12.5-11.5 ka B.P.). In this study, three cores (MV-33, MV-66, and MD-40) collected in the central part of Pandora Trough (Gulf of Papua) have been analyzed, and they reveal a detailed sedimentary pattern at millennial timescale. Siliciclastic turbidites disappeared during the Bølling-Allerød and Preboreal intervals to systematically reoccur during the Younger Dryas interval. Subsequent to the final disappearance of the siliciclastic turbidites a calciturbidite occurred during meltwater pulse 1B. The Holocene interval was characterized by a lack of siliciclastic turbidites, relatively high carbonate content, and fine bank-derived aragonitic sediment. The observed millennial timescale sedimentary variability can be explained by sea level fluctuations. During the Last Glacial Maximum, siliciclastic turbidites were numerous when the lowstand coastal system was located along the modern shelf edge. Although they did not occur during the intervals of maximum flooding of the shelf (during meltwater pulses 1A and 1B), siliciclastic turbidites reappear briefly during the Younger Dryas, an interval when sea level rise slowed, stopped, or perhaps even fell. The timing of the calciturbidite coincides with the first reflooding of Eastern Fields Reef, an atoll that remained exposed for most of the glacial stages.

  14. Carbon isotopes from fossil packrat pellets and elevational movements of Utah agave plants reveal the Younger Dryas cold period in Grand Canyon, Arizona

    USGS Publications Warehouse

    Cole, K.L.; Arundel, S.T.

    2005-01-01

    Carbon isotopes in rodent fecal pellets were measured on packrat (Neotoma spp.) middens from the Grand Canyon, Arizona. The pellet samples reflect the abundance of cold-intolerant C4 and Crassulacean acid metabolism (CAM) plant species relative to the predominant C3 vegetation in the packrat diet. The temporal sequence of isotopic results suggests a temperature decline followed by a sharp increase corresponding to the B??lling/Aller??d-Younger Dryas - early Holocene sequence. This pattern was then tested using the past distribution of Utah agave (Agave utahensis). Spatial analyses of the range of this temperature-sensitive CAM species demonstrate that its upper elevational limit is controlled by winter minimum temperature. Applying this paleotemperature proxy to the past elevational limits of Utah agave suggests that minimum winter temperatures were ???8??C below modern values during the Last Glacial Maximum, 4.5-6.5 ??C below modern during the B??lling/Aller??d, and 7.5-8.7 ??C below modern during the early Younger Dryas. As the Younger Dryas terminated, temperatures warmed ???4 ??C between ca. 11.8 ka and 11.5 ka. These extreme fluctuations in winter minimum temperature have not been generally accepted for terrestrial paleoecological records from the arid southwestern United States, likely because of large statistical uncertainties of older radiocarbon results and reliance on proxies for summer temperatures, which were less affected. ?? 2005 Geological Society of America.

  15. Carbon isotopes from fossil packrat pellets and elevational movements of Utah agave plants reveal the Younger Dryas cold period in Grand Canyon, Arizona

    NASA Astrophysics Data System (ADS)

    Cole, Kenneth L.; Arundel, Samantha T.

    2005-09-01

    Carbon isotopes in rodent fecal pellets were measured on packrat (Neotoma spp.) middens from the Grand Canyon, Arizona. The pellet samples reflect the abundance of cold-intolerant C4 and Crassulacean acid metabolism (CAM) plant species relative to the predominant C3 vegetation in the packrat diet. The temporal sequence of isotopic results suggests a temperature decline followed by a sharp increase corresponding to the Bølling/ Allerød Younger Dryas early Holocene sequence. This pattern was then tested using the past distribution of Utah agave (Agave utahensis). Spatial analyses of the range of this temperature-sensitive CAM species demonstrate that its upper elevational limit is controlled by winter minimum temperature. Applying this paleotemperature proxy to the past elevational limits of Utah agave suggests that minimum winter temperatures were ˜8 °C below modern values during the Last Glacial Maximum, 4.5 6.5 °C below modern during the Bølling/Allerød, and 7.5 8.7 °C below modern during the early Younger Dryas. As the Younger Dryas terminated, temperatures warmed ˜4 °C between ca. 11.8 ka and 11.5 ka. These extreme fluctuations in winter minimum temperature have not been generally accepted for terrestrial paleoecological records from the arid southwestern United States, likely because of large statistical uncertainties of older radiocarbon results and reliance on proxies for summer temperatures, which were less affected.

  16. Benefits and risks of benzodiazepines and Z-drugs: comparison of perceptions of GPs and community pharmacists in Germany.

    PubMed

    Hoffmann, Falk

    2013-01-01

    Hintergrund und Fragestellung: Die neueren Benzodiazepinrezeptor-Agonisten Zolpidem und Zopiclon (“Z-Drugs”) werden in letzter Zeit häufiger als Hypnotika vom Benzodiazepintyp verschrieben, obwohl keine Belege für Unterschiede bezüglich des Nutzens und Schaden existieren. Ziel dieser Studie war es zu vergleichen, wie Hausärzte und Apotheker erwünschte und unerwünschte Wirkungen dieser Mittel einschätzen.Methoden: Ein schriftlicher Fragebogen wurde 2012 an eine Zufallsauswahl von 1.350 Hausärzten und 600 Apothekenleitern versendet. Die gleichen Items wurden auf einer 5-Punkte-Likert-Skala sowohl für Benzodiazepine wie Z-Drugs abgefragt. Zum Vergleich zwischen Hausärzten und Apothekern wurden Wilcoxon Signed Rank Tests durchgeführt. Aufgrund der zahlreichen Tests wurden nur p-Werte ≤0,01 als statistisch signifikant angesehen.Ergebnisse: Insgesamt antworteten 458 Hausärzte und 202 Apotheker (Rücklauf 33,9% und 33,7%). Hausärzte waren durchschnittlich 53,3 Jahre (40,6% weiblich) und Apotheker 48,8 Jahre alt (59,2% weiblich). Keine Unterschiede in der Einschätzung des Nutzens von Benzodiazepinen (bzw. Z-Drugs) fanden sich bei 3 (bzw. 2) von 5 Items. Keine Unterschiede zeigten sich auch bei 3 von 5 Items zu unerwünschten Wirkungen von Benzodiazepinen. Hingegen schätzten Apotheker, dass 4 der 5 untersuchten unerwünschten Wirkungen von Z-Drugs häufiger vorkamen als Hausärzte (p=0,003 oder kleiner). Beispielsweise antworteten 45,2% der Apotheker, dass Entzugserscheinungen häufig bzw. sehr häufig/immer unter Z-Drugs auftreten, hingegen nur 28,3% der Hausärzte.Schlussfolgerungen: Obwohl es insgesamt schwierig ist, eindeutige Schlussfolgerungen aus diesen Befunden zu ziehen, scheinen Apotheker einen kritischeren Blick auf Z-Drugs und deren unerwünschte Wirkungen zu haben.

  17. Paleoceanographic changes on the Farallon Escarpment off central California during the last 16,000 years

    USGS Publications Warehouse

    McGann, M.

    2011-01-01

    New benthic and planktic foraminiferal assemblage census data and Benthic Foraminiferal Oxygen Index (BFOI) values, previously published marine climate proxy data (stable isotopes and Ca/Cd), and unpublished results of total carbon, organic carbon, and calcium carbonate analyses of sediments recovered off central California on the Farallon Escarpment (1605m water depth; 37??13.4???N, 123??14.6???W; core F-8-90-G21) document paleoceanographic changes during the latest Quaternary which reflect the intensity and source of North Pacific Intermediate Water (NPIW) and surface productivity. Accelerator mass spectrometry radiocarbon dates of both benthic and planktic species provide an excellent age-depth model for the last 16,000 years, covering the latest glacial, B??lling-Aller??d, Younger Dryas, and early, middle, and late Holocene intervals. A Q-mode cluster analysis separated the benthic fauna into three clusters, one Pleistocene and two Holocene, whereas the planktic fauna was divided only into Pleistocene and Holocene clusters. Stable oxygen isotope values show an increase in water temperature of ~1??C from the late glacial to late Holocene and a change in faunal composition of the planktic assemblage implies surface waters warmed as well. A general trend of decreasing dissolved oxygen concentration from the Pleistocene (high oxic; 3.0-6.0+ ml/l O2) to the Holocene (low oxic; 1.5-3.0ml/l O2) suggested by the BFOI and Cd/Ca data reflect decreased ventilation as the source of the NPIW shifted from the Sea of Okhotsk to the tropical east Pacific at ~11,000 cal BP. The middle Holocene cooling reported in other central and northern California margin studies is not apparent in F-8-90-G21, which compares more favorably with studies from southern California and British Columbia. Total carbon and organic carbon values are highest in the B??lling-Aller??d, early Holocene, and late Holocene. Similarly, calcium carbonate values are high in the B??lling-Aller??d and peak in the

  18. Rapid Climatic Variability in the Western Mediterranean during the Last 25,000 Years from the High Resolution Pollen Record ODP Site 976

    NASA Astrophysics Data System (ADS)

    Combourieu Nebout, N.; Desprat, S.; Peyron, O.; Dormoy, I.; Beaudoin, C.; Kotthoff, U.; Marret, F.

    2009-12-01

    The high-temporal resolution pollen record from the Alboran Sea ODP Site 976, and associated pollen-based quantitative climate reconstruction and biomisation show that Mediterranean vegetation changes have been clearly modulated by short and long term variability during the last 25,000 years. The reliability of the quantitative climate reconstruction from marine pollen spectra using the Modern Analogue Technique (MAT) has been tested on 22 marine core-top samples from the Mediterranean. Although the MAT seems to slightly underestimate the winter temperatures and overestimate the winter precipitation, the present-day observed and MAT estimations show an adequate consistency, in particular for summer temperatures and annual and summer precipitation. According to these results, the MAT appears as a valuable approach to quantify the past climatic changes on land from marine Mediterranean pollen records. The ODP Site 976 pollen record and associated climatic reconstruction confirm that Mediterranean environments have a rapid response to the abrupt climatic changes of the last Termination such as Heinrich event 1, Bölling/Allerød and Younger Dryas and even the centennial cold event, Older Dryas, within the Bölling/Allerød period. The western Mediterranean vegetation and North Atlantic changes appear nearly synchronous. In contrast to the general warming climatic trend shown in Greenland and north European records (Rasmussen et al., 2006, 2007; Lowe et al., 2008; von Grafenstein et al., 1999), the ODP Site 976 pollen record shows a cooling trend during the Bölling/Allerød period. During the Holocene, recurrent declines of the forest cover over the Alboran Sea borderlands (southern Spain and northern Morocco) indicate abrupt climatic changes that correlate well with several events of increased Mediterranean aridity previously observed on land (Jalut et al. 2002) and with Mediterranean Sea cooling episodes detected by alkenone and foraminifer -based sea surface

  19. Deep soil compaction as a method of ground improvement and to stabilization of wastes and slopes with danger of liquefaction, determining the modulus of deformation and shear strength parameters of loose rock.

    PubMed

    Lersow, M

    2001-01-01

    For the stabilization of dumps with the construction of hidden dams and for building ground improvement, for instance for traffic lines over dumps, nearly all applied compaction methods have the aim to reduce the pore volume in the loose rock. With these methods, a homogenization of the compacted loose rock will be obtained too. The compaction methods of weight compaction by falling weight, compaction by vibration and compaction by blasting have been introduced, and their applications and efficiencies have been shown. For the estimation of the effective depth of the compaction and for a safe planning of the bearing layer, respectively, the necessary material parameters have to be determined for each deep compaction method. Proposals for the determination of these parameters have been made within this paper. In connection with the stabilization of flow-slide-prone dump slopes, as well as for the improvement of dump areas for the use as building ground, it is necessary to assess the deformation behavior and the bearing capacity. To assess the resulting building ground improvement, deformation indexes (assessment of the flow-prone layer) and strength indexes (assessment of the bearing capacity) have to be determined with soil mechanical tests. Förster and Lersow, [Patentschrift DE 197 17 988. Verfahren, auf der Grundlage last- und/oder weggesteuerter Plattendruckversuche auf der Bohrlochsohle, zur Ermittlung des Spannungs-Verformungs-Verhaltens und/oder von Deformationsmoduln und/oder von Festigkeitseigenschaften in verschiedenen Tiefen insbesondere von Lockergesteinen und von Deponiekörpern in situ; Förster W, Lersow M. Plattendruckversuch auf der Bohrlochsohle, Ermittlung des Spannungs-Verformungs-Verhaltens von Lockergestein und Deponiematerial Braunkohle--Surface Mining, 1998;50(4): 369-77; Lersow M. Verfahren zur Ermittlung von Scherfestigkeitsparametern von Lockergestein und Deponiematerial aus Plattendruckversuchen auf der Bohrlochsohle. Braunkohle

  20. Timing and nature of AMOC recovery across Termination 2 and magnitude of deglacial CO2 change

    NASA Astrophysics Data System (ADS)

    Deaney, Emily L.; Barker, Stephen; van de Flierdt, Tina

    2017-02-01

    Large amplitude variations in atmospheric CO2 were associated with glacial terminations of the Late Pleistocene. Here we provide multiple lines of evidence suggesting that the ~20 p.p.m.v. overshoot in CO2 at the end of Termination 2 (T2) ~129 ka was associated with an abrupt (<=400 year) deepening of Atlantic Meridional Overturning Circulation (AMOC). In contrast to Termination 1 (T1), which was interrupted by the Bølling-Allerød (B-A), AMOC recovery did not occur until the very end of T2, and was characterized by pronounced formation of deep waters in the NW Atlantic. Considering the variable influences of ocean circulation change on atmospheric CO2, we suggest that the net change in CO2 across the last 2 terminations was approximately equal if the transient effects of deglacial oscillations in ocean circulation are taken into account.

  1. Response of Peatland Carbon Accumulation to Postglacial Climate Changes on the Seward Peninsula, Western Alaska

    NASA Astrophysics Data System (ADS)

    Hunt, S. J.; Yu, Z.

    2011-12-01

    Understanding how carbon-rich peatland ecosystems have responded to past warm climates in terms of carbon (C) dynamics and community composition is crucial for projecting possible future changes. Warm climates in the recent past, such as the Bølling-Allerød interstadial (14.7-12.7 cal ka) and Holocene Thermal Maximum (HTM; 11-9 ka), provide unique opportunities to study peatland C dynamics and ecosystem change. Here we present preliminary data from a 272-cm peat core (core NL10-2) collected from the edge of Niukluk Lake on Seward Peninsula, Alaska (64° 49.645' N, 163° 27.235' W; elevation = 16 m asl). Niukluk Lake is a thermokarst lake located in the discontinuous permafrost zone near the forest-tundra ecotone and experiences a maritime climate, which is controlled by the Bering Sea and sea surface conditions (especially sea-ice extent). The chronology is based on 12 AMS dates from Sphagnum and other terrestrial plant macrofossils over the last 13.5 ka. Organic matter content (OM) shows a long-term increasing trend throughout the core since 13.5 ka, ranging from <20% at the bottom to >90% at the top of the core. Peat began accumulating at this site by 13.5 ka and was initially characterized by a very high carbon accumulation rate (67 g C m-2 yr-1 from 13.5 to 12.8 ka), potentially due to early deglacial warming during the Bølling-Allerød period. Dominance of well-preserved brown moss, aquatic species and high C accumulation rates during the majority of the Bølling-Allerød indicate a wet peatland surface and possibly a wet and warm climate. Preliminary pollen analysis during the Bølling-Allerød indicates a Betula and Salix dominated upland with a regional presence of Picea and Larix, along with the presence of aquatic species. Also, abundant charcoals are present at this interval, suggesting that wildfires might play a major role in modulating regional flora and permafrost dynamics. This highly productive period was followed by a hiatus from 12.8 ka to 9

  2. Late Vistulian and Holocene changes in the Ner river valley in light of geological and palaeoecological data from the Ner-Zawada peatland

    NASA Astrophysics Data System (ADS)

    Forysiak, Jacek; Obremska, Milena; Pawłowski, Dominik; Kittel, Piotr

    2010-12-01

    The Ner-Zawada peatland is located in the valley of the Ner River in Central Poland. It is a small fen peatland that was formed in the Alleröd Period. In the Younger Dryas, it was transformed into a lake and became a peatland again in the Holocene. Within the peatland and around it, geological and archaeological research was carried out. A sediment core collected in the central part of the peatland was subjected to the analysis of pollen, fossil Cladocera, and absolute dating. This study allows a reconstruction of palaeoecological changes in the peatland and drawing conclusions about the palaeogeography of the middle section of the Ner River valley during the past 13 000 years.

  3. Timing and nature of AMOC recovery across Termination 2 and magnitude of deglacial CO2 change

    PubMed Central

    Deaney, Emily L.; Barker, Stephen; van de Flierdt, Tina

    2017-01-01

    Large amplitude variations in atmospheric CO2 were associated with glacial terminations of the Late Pleistocene. Here we provide multiple lines of evidence suggesting that the ∼20 p.p.m.v. overshoot in CO2 at the end of Termination 2 (T2) ∼129 ka was associated with an abrupt (≤400 year) deepening of Atlantic Meridional Overturning Circulation (AMOC). In contrast to Termination 1 (T1), which was interrupted by the Bølling-Allerød (B-A), AMOC recovery did not occur until the very end of T2, and was characterized by pronounced formation of deep waters in the NW Atlantic. Considering the variable influences of ocean circulation change on atmospheric CO2, we suggest that the net change in CO2 across the last 2 terminations was approximately equal if the transient effects of deglacial oscillations in ocean circulation are taken into account. PMID:28239149

  4. Timing and nature of AMOC recovery across Termination 2 and magnitude of deglacial CO2 change.

    PubMed

    Deaney, Emily L; Barker, Stephen; van de Flierdt, Tina

    2017-02-27

    Large amplitude variations in atmospheric CO2 were associated with glacial terminations of the Late Pleistocene. Here we provide multiple lines of evidence suggesting that the ∼20 p.p.m.v. overshoot in CO2 at the end of Termination 2 (T2) ∼129 ka was associated with an abrupt (≤400 year) deepening of Atlantic Meridional Overturning Circulation (AMOC). In contrast to Termination 1 (T1), which was interrupted by the Bølling-Allerød (B-A), AMOC recovery did not occur until the very end of T2, and was characterized by pronounced formation of deep waters in the NW Atlantic. Considering the variable influences of ocean circulation change on atmospheric CO2, we suggest that the net change in CO2 across the last 2 terminations was approximately equal if the transient effects of deglacial oscillations in ocean circulation are taken into account.

  5. Pleistocene megafaunal collapse, novel plant communities, and enhanced fire regimes in North America.

    PubMed

    Gill, Jacquelyn L; Williams, John W; Jackson, Stephen T; Lininger, Katherine B; Robinson, Guy S

    2009-11-20

    Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the Bølling-Allerød warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago.

  6. Early warming of tropical South America at the last glacial-interglacial transition.

    PubMed

    Seltzer, G O; Rodbell, D T; Baker, P A; Fritz, S C; Tapia, P M; Rowe, H D; Dunbar, R B

    2002-05-31

    Glaciation in the humid tropical Andes is a sensitive indicator of mean annual temperature. Here, we present sedimentological data from lakes beyond the glacial limit in the tropical Andes indicating that deglaciation from the Last Glacial Maximum led substantial warming at high northern latitudes. Deglaciation from glacial maximum positions at Lake Titicaca, Peru/Bolivia (16 degrees S), and Lake Junin, Peru (11 degrees S), occurred 22,000 to 19,500 calendar years before the present, several thousand years before the Bølling-Allerød warming of the Northern Hemisphere and deglaciation of the Sierra Nevada, United States (36.5 degrees to 38 degrees N). The tropical Andes deglaciated while climatic conditions remained regionally wet, which reflects the dominant control of mean annual temperature on tropical glaciation.

  7. Abrupt climate change in southeast tropical Africa influenced by Indian monsoon variability and ITCZ migration

    NASA Astrophysics Data System (ADS)

    Tierney, Jessica E.; Russell, James M.

    2007-08-01

    The timing and magnitude of abrupt climate change in tropical Africa during the last glacial termination remains poorly understood. High-resolution paleolimnological data from Lake Tanganyika, Southeast Africa show that wind-driven seasonal mixing in the lake was reduced during the Younger Dryas, Inter-Allerød Cool Period, Older Dryas, and Heinrich Event 1, suggesting a weakened southwest Indian monsoon and a more southerly position of the Inter-Tropical Convergence Zone over Africa during these intervals. These events in Lake Tanganyika, coeval with millennial and centennial-scale climate shifts in the high latitudes, suggest that changes in ITCZ location and Indian monsoon strength are important components of abrupt global climate change and that their effects are felt south of the equator in Africa. However, we observe additional events in Lake Tanganyika of equal magnitude that are not correlated with high-latitude changes, indicating the potential for abrupt climate change to originate from within tropical systems.

  8. Late quaternary oceanographic conditions in the Western Bering Sea

    NASA Astrophysics Data System (ADS)

    Ovsepyan, E. A.; Ivanova, E. V.; Max, L.; Riethdorf, J.-R.; Nürnberg, D.; Tiedemann, R.

    2013-03-01

    The benthic and planktonic foraminiferal assemblages and the distribution of coarse grain-size factions were studied in the upper 4.5 m of the Core SO201-2-85KL (57°30.30' N, 170°24.79' E, water depth 968 m) retrieved from the Shirshov Ridge. This part of the core covers 7.5 to 50 kyr BP. The glacial period is established to be characterized by low surface water productivity, the wide distribution of sea ice and/or icebergs in this area, and a high oxygen concentration in the bottom layer. Enhanced productivity is inferred from the maximum abundance of planktonic foraminifers at the very beginning of the deglaciation. The late Bølling-Allerød interstadial and the early Holocene were marked by the further two-phase increase in the surface productivity and the weakened ventilation of the bottom water.

  9. MediMax Elektronik-Marktkette

    NASA Astrophysics Data System (ADS)

    Die Elektronikkette MediMax setzt auf Server Based Computing mit Windows Server 2003® und Thin Clients. Mit über 100 Filialen ist MediMax die erfolgreiche Fachmarktlinie der ElectronicPartner-Verbundgruppe in Deutschland. Die Zugehörigkeit zum Mutterverbund garantiert den Franchisenehmern der Elektronikkette eine schnelle Warenversorgung und günstige Einkaufskonditionen. Über 50.000 Artikel zahlreicher namhafter Markenhersteller und unterschiedlicher Preisklassen sind ständig abrufbar. Darüber hinaus profitieren die Filialen von einer zentralen Organisation und Betreuung ihrer IT. Von Düsseldorf aus administriert ein internes Supportteam die Arbeitsplätze aller Standorte und stellt außerdem die Warenwirtschaftslösung zur Verfügung. Dank der Umstellung auf eine moderne Server Based Computing-Umgebung sind Wartung und Support künftig so effizient wie nie zuvor.

  10. Radiocarbon ages of terrestrial gastropods extend duration of ice-free conditions at the Two Creeks forest bed, Wisconsin, USA

    USGS Publications Warehouse

    Rech, Jason A.; Nekola, Jeffrey C.; Pigati, Jeffrey S.

    2012-01-01

    Analysis of terrestrial gastropods that underlie the late Pleistocene Two Creeks forest bed (~ 13,800–13,500 cal yr BP) in eastern Wisconsin, USA provides evidence for a mixed tundra-taiga environment prior to formation of the taiga forest bed. Ten new AMS 14C analyses on terrestrial gastropod shells indicate the mixed tundra-taiga environment persisted from ~ 14,500 to 13,900 cal yr BP. The Twocreekan climatic substage, representing ice-free conditions on the shore of Lake Michigan, therefore began near the onset of peak warming conditions during the Bølling–Allerød interstadial and lasted ~ 1000 yr, nearly 600 yr longer than previously thought. These results provide important data for understanding the response of continental ice sheets to global climate forcing and demonstrate the potential of using terrestrial gastropod fossils for both environmental reconstruction and age control in late Quaternary sediments.

  11. A 16 ka lacustrine 18O record from High Himalaya reflecting the Indian Monsoon variability

    NASA Astrophysics Data System (ADS)

    Zech, M.; Tuthorn, M.; Zech, R.; Schlütz, F.; Zech, W.; Glaser, B.

    2012-04-01

    Establishing 18O records using organic matter of lake sediments is so far complicated due to analytical challenges. Based on the results obtained by a novel analytical method, the so-called compound-specific delta18O-analysis of hemicellulose monosaccharides (Zech, M. and Glaser, B., 2009. Rapid Communications in Mass Spectrometry 23, 3522-3532), we here present a first well-dated continuous late glacial lacustrine 18O record from High Himalayan lake sediments. Our 18O record, which reflects a coupled hydrological and thermal control, reveals the late glacial Indian Summer Monsoon variability depicting the Bölling/Alleröd and the Younger Dryas. Thus, it closely resembles the 18O records of South Asian speleothems and Greenland ice cores. We hence conclude that our novel 18O method enables regional paleoclimate reconstructions and that our 18O record highlights the previously suggested teleconnections between the Indian and the East Asian Monsoon and Greenland temperatures.

  12. Methodik und Qualität statistischer Erhebungen

    NASA Astrophysics Data System (ADS)

    Krug, Walter; Schmidt, Jürgen; Wiegert, Rolf

    Kapitel 8 wirft einen Blick hinter die Kulissen statistischer Arbeit und ihrer Methoden, insbesondere auch hinter die der amtlichen Statistik: Wie kommen die Myriaden von Zahlen zustande, die heute aus statistischen Quellenwerken aller Art und aus Datenbanken abgerufen werden können? Dabei wird deutlich, welche Schwierigkeiten bei Erhebungen, insbesondere bei Stichprobenerhebungen, zu überwinden sind, wie man Antwortverweigerer kooperativer stimmt, wie sich auch aus kleinen Stichproben auf intelligente Weise verlässliche Ergebnisse erzielen lassen und wie Großstichproben auf europäischer Ebene harmonisiert werden. Am Beispiel des Zensus 2011 wird gezeigt, wie sich eine Kombination von Stichproben und Registerauswertungen als Ersatz für eine Volkszählung nutzen lässt. Mitglieder der Deutschen Statistischen Gesellschaft waren daran kooperativ beteiligt.

  13. Relative timing of deglacial climate events in Antarctica and Greenland.

    PubMed

    Morgan, Vin; Delmotte, Marc; van Ommen, Tas; Jouzel, Jean; Chappellaz, Jérôme; Woon, Suenor; Masson-Delmotte, Valérie; Raynaud, Dominique

    2002-09-13

    The last deglaciation was marked by large, hemispheric, millennial-scale climate variations: the Bølling-Allerød and Younger Dryas periods in the north, and the Antarctic Cold Reversal in the south. A chronology from the high-accumulation Law Dome East Antarctic ice core constrains the relative timing of these two events and provides strong evidence that the cooling at the start of the Antarctic Cold Reversal did not follow the abrupt warming during the northern Bølling transition around 14,500 years ago. This result suggests that southern changes are not a direct response to abrupt changes in North Atlantic thermohaline circulation, as is assumed in the conventional picture of a hemispheric temperature seesaw.

  14. Investigating the Influence of Climate Changes on Rodent Communities at a Regional-Scale (MIS 1-3, Southwestern France).

    PubMed

    Royer, Aurélien; Montuire, Sophie; Legendre, Serge; Discamps, Emmanuel; Jeannet, Marcel; Lécuyer, Christophe

    2016-01-01

    Terrestrial ecosystems have continuously evolved throughout the Late Pleistocene and the Holocene, deeply affected by both progressive environmental and climatic modifications, as well as by abrupt and large climatic changes such as the Heinrich or Dansgaard-Oeschger events. Yet, the impacts of these different events on terrestrial mammalian communities are poorly known, as is the role played by potential refugia on geographical species distributions. This study examines community changes in rodents of southwestern France between 50 and 10 ky BP by integrating 94 dated faunal assemblages coming from 37 archaeological sites. This work reveals that faunal distributions were modified in response to abrupt and brief climatic events, such as Heinrich events, without actually modifying the rodent community on a regional scale. However, the succession of events which operated between the Late Pleistocene and the Holocene gradually led to establishing a new rodent community at the regional scale, with intermediate communities occurring between the Bølling and the Allerød.

  15. Survey of tea for the presence of gluten.

    PubMed

    Garber, Eric A E; Panda, Rakhi; Shireen, Kaniz F

    2015-06-01

    In 2013, the U.S. Food and Drug Administration conducted a survey of green and white teas marketed in the northeastern United States for the presence of undeclared wheat. Based on the requirement for concurrence between the RIDASCREEN gliadin (R5) enzyme-linked immunosorbent assay (ELISA) and the Morinaga Institutes of Biological Science (MIoBS) wheat protein ELISA, none of the 20 products included in the survey tested positive for wheat, rye, barley, or gluten. However, eight of the teas generated responses indicative of the presence of gluten with the RIDASCREEN gliadin (R5), AgraQuant gluten G12, and Aller-Tek (Skerritt) sandwich ELISAs. Five of the eight teas generated responses indicative of >20 ppm of gluten using the RIDASCREEN and AgraQuant ELISA test kits, and all eight had ≥ 20 ppm based on the Aller-Tek ELISA. Extracts prepared using the RIDASCREEN validated protocol and the MIoBS validated sodium dodecyl sulfate plus β-mercaptoethanol (overnight) protocol were analyzed using both test kits. The extracts prepared using the RIDASCREEN protocol tested positive for gluten with both test kits. Western blot analyses of the two sets of extracts using the R5 and MIoBS antibodies to visualize the bands revealed the presence of antigenic proteins in both sets of extracts, although the profiles and band intensities were different and inconsistent with the ELISA results. These results raise questions regarding the screening procedures used to detect gluten and how the observation of a homologous antigenic element is defined.

  16. Abrupt climate changes of the last deglaciation detected in a western Mediterranean forest record

    NASA Astrophysics Data System (ADS)

    Fletcher, W. J.; Sanchez Goñi, M. F.; Peyron, O.; Dormoy, I.

    2009-01-01

    Evidence for abrupt changes in western Mediterranean climate between 20 and 6 cal ka BP is examined in marine core MD95-2043 (Alborán Sea), using pollen data for temperate Mediterranean forest development and pollen-based climate reconstructions using the modern analogue technique (MAT) for annual precipitation (Pann) and mean temperatures of the coldest and warmest months (MTCO and MTWA). Major climatic shifts with parallel temperature and precipitation changes occurred at the onsets of Heinrich Event 1 (equivalent to the Oldest Dryas), the Bölling-Allerød (BA), and the Younger Dryas (YD). Multi-centennial-scale oscillations in forest development related to regional precipitation (Pann) variability occurred throughout the BA, YD, and early Holocene, with drier atmospheric conditions in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas), GI-1b (Intra-Allerød Cold Period) and GS-1 (YD), and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting (events at 11.4, 10.1, 9.3, 8.2 and 7.4 cal ka BP). The forest record also indicates multi-centennial variability within the YD interval and multiple Preboreal climate oscillations. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to western-central Europe relates to the dynamics of the jet stream and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alborán Sea by ~200 years (surface water age ~600 years) during the Lateglacial.

  17. Carbon isotope (δ13C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic

    NASA Astrophysics Data System (ADS)

    Consolaro, C.; Rasmussen, T. L.; Panieri, G.; Mienert, J.; Bünz, S.; Sztybor, K.

    2015-04-01

    We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (~ 80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dates reveal a detailed chronology for the last 14 ka BP. The δ 13C record measured on the benthonic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values termed carbon isotope excursion (CIE I and CIE II, respectively). The values were as low as -4.37‰ in CIE I, correlating with the Bølling-Allerød interstadials, and as low as -3.41‰ in CIE II, correlating with the early Holocene. In the Bølling-Allerød interstadials, the planktonic foraminifera also show negative values, probably indicating secondary methane-derived authigenic precipitation affecting the foraminiferal shells. After a cleaning procedure designed to remove authigenic carbonate coatings on benthonic foraminiferal tests from this event, the 13C values are still negative (as low as -2.75‰). The CIE I and CIE II occurred during periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic, suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

  18. Asynchronous east-west climate changes over the southwestern United States driven by competing moisture sources during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Shanahan, T. M.; Wicks, T.; Jimmie, J. A.

    2013-12-01

    During the last deglaciation, the climate of the southwestern US changed dramatically, reflecting large-scale shifts in atmospheric circulation that were driven largely by changing temperature and ice cover in the high latitudes of the Northern Hemisphere. While a great deal has been learned about the nature of these changes in the desert southwest from speleothem, lake sediment and other proxy climate records, much less is known about deglacial changes in atmospheric circulation to the east, where continuous high-resolution proxy records are rare. Here we present a new record of changing vegetation and atmospheric moisture in central Texas from the δ13C of bulk organic matter and the δD of plant waxes preserved in the sediments of Hall's Cave. The record shows that Northern Hemisphere cold intervals were characterized by dry conditions, with a decreased proportion of winter grasses, trees and shrubs, whereas during warm intervals conditions were wetter and the proportion of C3 plants increased. These changes are opposite of those recorded elsewhere in the arid southwest, and particularly at sites in Arizona and New Mexico where the glacial was wet and the Bølling-Allerød was exceptionally dry. δDwax variations suggest that these east-west differences in deglacial climate change reflect differences in the relative importance of westerly storm tracks and the low level jet (LLJ) for delivering moisture to these areas. Terminal Pleistocene drought during the Bølling-Allerød appears to have been restricted to the desert southwest, while sites in Texas and the Great Plains became wetter. The asynchronous nature of these changes is seemingly at odds with a climatic origin for the late Pleistocene extinction of North American land mammals.

  19. Synchoronous inter-hemispheric alpine glacier advances during the Late Glacial?

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Paasche, Øyvind

    2016-04-01

    The termination of the last glaciation in both hemispheres was a period of rapid climate swings superimposed on the overall warming trend, resulting from large-scale reorganizations of the atmospheric and oceanic circulation patterns in both hemispheres. Environmental changes during the deglaciation have been inferred from proxy records, as well as by model simulations. Several oscillations took place both in northern and southern hemispheres caused by melt water releases such as during the Younger Dryas in north and the Antarctic Cold Reversal in south. However, a consensus on the hemispheric linkages through ocean and atmosphere are yet to be reached. Here we present a new multi-proxy reconstruction from a sub-annually resolved lake sediment record from Lake Lusvatnet in Arctic Norway compared with a new reconstruction from the same time interval at South Georgia, Southern Ocean, suggesting inter-hemispheric climate linkages during the Bølling/Allerød time period. Our reconstruction of the alpine glacier in the lake Lusvatnet catchment show a synchronous glacier advance with the Birch-hill moraine complex in the Southern Alps, New Zealand during the Intra Allerød Cooling period. We propose these inter hemispheric climate swings to be forced by the northward migration of the southern Subtropical Front during the Antarctic Cold Reversal. Such a northward migration of the Subtropical Front is shown in model simulation and in palaeorecords to reduce the Agulhas leakage impacting the strength of the Atlantic meridional overturning circulation. We simply ask if this can be the carrier of rapid climate swings from one hemisphere to another? Our high-resolution reconstructions provide the basis for an enhanced understanding of the tiny balance between migration of the Subtropical Front in the Southern Ocean and the teleconnection to northern hemisphere.

  20. The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of a Wide, Low-Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?

    NASA Astrophysics Data System (ADS)

    Close, Laird M.; Zuckerman, B.; Song, Inseok; Barman, Travis; Marois, Christian; Rice, Emily L.; Siegler, Nick; Macintosh, Bruce; Becklin, E. E.; Campbell, Randy; Lyke, James E.; Conrad, Al; Le Mignant, David

    2007-05-01

    We imaged five objects near the star-forming clouds of Ophiuchus with the Keck Laser Guide Star AO system. We resolved sources 11 (Oph 16222-2405) and 16 (Oph 16233-2402) from Allers and coworkers into binary systems. Source 11 is resolved into a 243 AU binary, the widest known for a very low mass (VLM) binary. The binary nature of source 11 was discovered first by Allers and independently here, during which we obtained the first spatially resolved R~2000 near-infrared (J and K) spectra, mid-IR photometry, and orbital motion estimates. We estimate for 11A and 11B gravities (logg>3.75), ages (5+/-2 Myr), luminosities [log(L/Lsolar)=-2.77+/-0.10 and -2.96+/-0.10], and temperatures (Teff=2375+/-175 K and 2175+/-175 K). We find self-consistent DUSTY evolutionary model (Chabrier and coworkers) masses of 17+4-5 MJ and 14+6-5 MJ, for 11A and 11B, respectively. Our masses are higher than those previously reported (13-15 MJ and 7-8 MJ) by Jayawardhana & Ivanov. Hence, we find that the system is unlikely a ``planetary mass binary,'' as do Luhman and coworkers, but it has the second lowest mass and lowest binding energy of any known binary. Oph 11 and Oph 16 belong to a newly recognized population of wide (>~100 AU), young (<10 Myr), roughly equal mass, VLM stellar and brown dwarf binaries. We deduce that ~6%+/-3% of young (<10 Myr) VLM objects are in such wide systems. However, only 0.3%+/-0.1% of old field VLM objects are found in such wide systems. Thus, young, wide, VLM binary populations may be evaporating, due to stellar encounters in their natal clusters, leading to a field population depleted in wide VLM systems. Based on observations made with the Keck and Gemini North telescopes.

  1. A High-Resolution Survey of the Very Youngest Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Allers, Katelyn

    2012-10-01

    We propose to image the youngest { 0.5 Myr} brown dwarfs in the nearby Ophiuchus star-forming region {d=125 pc}. These observations will complete our high resolution imaging survey of a well-defined sample of young brown dwarfs and very low mass stars spanning the age range of 0.5-100 Myr {Allers et al. 2009, Allers et al. 2010, Biller et al. 2011}. Our proposed survey will be the culmination of the most extensive high resolution search for companions to young substellar objects conducted to date. We have established a novel, reddening-insensitive approach, which uses imaging in three WFC3 UVIS and IR filters to discern candidate companions from contaminant background stars. Our proposed survey is sensitive enough to discover planetary-mass companions. As only two planetary-mass companions to brown dwarfs are known {Chauvin et al. 2005, Todorov et al. 2010}, such discoveries will provide valuable new benchmark objects for testing atmospheric and evolutionary models of planetary-mass objects. Our survey will put the strongest constraints to date on the primordial binary fraction for brown dwarfs. By comparing results in Ophiuchus with our completed survey of the Upper Sco region {Biller et al. 2011}, we can directly measure how the binary characteristics change with age {i.e. as a cluster dynamically evolves}, providing key inputs for refining models of brown dwarf formation. The proposed observations are only possible with HST WFC3. Because of the high extinction of the Ophiuchus cloud, suitable tip-tilt stars are not available to allow for ground-based LGS AO imaging of our sample.

  2. Variations in sea surface hydrology in the southern Makassar Strait over the past 26 kyr

    NASA Astrophysics Data System (ADS)

    Schröder, Jan F.; Holbourn, Ann; Kuhnt, Wolfgang; Küssner, Kevin

    2016-12-01

    We present centennial-scale records of sea surface temperature and oxygen isotopes in a sediment core from Mandar Bay, offshore Sulawesi in the southern Makassar Strait, which provide new insights into the variability of Indonesian climate over the past 26 kyr. The age model for the core is constrained by 17 AMS radiocarbon ages, with a surface ocean reservoir age correction based on paired wood and foraminiferal samples. Small Holocene reservoir ages of 105 ± 180 years point to intense surface ocean-atmosphere interchange linked to increased monsoonal precipitation, whereas Last Glacial Maximum and deglacial reservoir ages are significantly higher. Mg/Ca derived sea surface temperature reconstructions based on Globigerinoides ruber (s. s., white) exhibit an extended plateau during the Antarctic Cold Reversal, suggesting an atmospheric connection to high-latitude Southern Hemisphere climate and a seasonal bias on G. ruber. This is in agreement with southern hemisphere sites along the track of the Indonesian Throughflow and in contrast to Northern Hemisphere records from the South China Sea, Sulu Sea and Western Pacific (off Mindanao), which exhibit warming during the Bølling-Allerød. Ice-volume corrected δ18O seawater (δ18Osw) increased during Heinrich Stadial 1 and the Younger Dryas, whereas the Bølling-Allerød is characterized by low δ18Osw. We attribute δ18Osw variability in the southern Makassar Strait during the Last Glacial Maximum and glacial termination to changes in provenance and seasonality of precipitation rather than to variability in the amount of local precipitation and runoff.

  3. Deglacial Timing and Dynamics of Paleoclimate Variations in the Bering Sea and Subarctic Pacific

    NASA Astrophysics Data System (ADS)

    Lembke-Jene, Lester; Kuehn, Hartmut; Gersonde, Rainer; Esper, Oliver; Arz, Helge; Lohmann, Gerrit; Tiedemann, Ralf

    2016-04-01

    One characteristic of the last glacial termination is the widespread decrease of mid-depth oxygen concentrations in the world ocean in intermediate water depth (i.e. above c. 2000 m). The resulting expansion of oxygen minimum zones is connected with the deposition of high-resolution, laminated sediments throughout the subarctic North Pacific, providing the potential to study marine archives with a high temporal resolution, combined with the possibility to establish relatively precise chronostratigraphic frameworks. From a comprehensive collection of sediment cores retrieved during R/V Sonne cruise SO202 INOPEX, we investigated sites in the Bering Sea that featured laminated deglacial facies. Sedimentary layer countings of laminated sections, AMS 14C measurements of foraminifera and correlation to the NGRIP Greenland oxygen isotope ice core record, aided by high-resolution micro-XRF data, X-ray images and supplementary geochemical data gave detailed information about the processes that led to laminae formation and provided the basis for establishing paleoceanographic reconstructions with exceptional temporal resolution, possibly on sub-decadal timescales. We selected one partly laminated, mid-depth key site from 1100 m water depth on the northeastern Bering Shelf slope to further investigate the timing, and surface - intermediate water development during the Termination I. A correlation between the NGRIP oxygen isotope reference record and our layer countings revealed that the laminations represent annual layered sediments (varves) and the presence of these laminations is tightly coupled to submillennial, short-term warm phases, especially during the Bølling-Allerød. The latter point strongly argues for a close atmospheric teleconnection between the North Atlantic and the North Pacific. As a result of our correlation approach we created an age model that is partly independent from radiocarbon dates in the varved time intervals. We used our resulting

  4. Provenance of Greenland Ice Sheet icebergs constrained by Ar-Ar radioisotope data from late glacial-early Holocene records

    NASA Astrophysics Data System (ADS)

    Knutz, P. C.; Storey, M.; Kuijpers, A.

    2009-12-01

    Radiogenic Ar-Ar dating of hornblende has been used to constrain the sources of ice-rafted detritus on the southwest Greenland margin and central Davis Strait. Single hornblende grains (total of 248) were picked from sand-size fractions of two marine cores, DA04-31P and TTR462G, covering the early Holocene to late glacial interval including Heinrich events (HE) 1-3. Paleoceanographic analyses of DA04-31P have indicated that the last deglaciation of the southern Greenland Ice Sheet occurred in multiple steps during the early deglacial/HE1, Allerød and early Holocene intervals (Knutz et al., in review). Each of these collapse stages were preceded by upper ocean warming related to enhanced Irminger Current activity. Pre-HE1, Allerød and Holocene hornblende samples show a bimodal signature of late Archean (2.5-3.0 Ga) and early Proterozoic (1.6-2.2 Ga) ages consistent with southern Greenland bedrock sources. In contrast hornblende grains from detrital carbonate HE layers and within the Younger Dryas interval show a dominant early Proterozoic spectrum that is similar to results obtained from the central North Atlantic IRD belt. The early Proterozoic age of Younger Dryas samples from the Davis Strait site and the high amounts of basalt in this core, presumably derived from the Disko-Nussuaq province, suggests that icebergs carrying Archean material from southern Greenland did not enter the Baffin Bay or at least not for this specific time interval. The conclusion of our study is that the Greenland Ice Sheet appears to have been a much larger contributor to non-Heinrich IRD in the North Atlantic than thought previously. P. C. Knutz, H. Ebbesen, S. Christiansen, M.-A. Sicre and A. Kuijpers. Multiple deglaciation steps of the southern Greenland Ice Sheet driven by vigorous Irminger Current: Significance for the Younger Dryas cooling. Submitted to Quaternary Science Reviews.

  5. Two-dimensional distribution of living benthic foraminifera in anoxic sediment layers of an estuarine mudflat (Loire estuary, France)

    NASA Astrophysics Data System (ADS)

    Thibault de Chanvalon, A.; Metzger, E.; Mouret, A.; Cesbron, F.; Knoery, J.; Rozuel, E.; Launeau, P.; Nardelli, M. P.; Jorissen, F. J.; Geslin, E.

    2015-10-01

    We present a new rapid and accurate protocol to simultaneously sample benthic living foraminifera in two dimensions in a centimetre-scale vertical grid and dissolved iron and phosphorus in two dimensions at high resolution (200 μm). Such an approach appears crucial for the study of foraminiferal ecology in highly dynamic and heterogeneous sedimentary systems, where dissolved iron shows a strong variability at the centimetre scale. On the studied intertidal mudflat of the Loire estuary, foraminiferal faunas are dominated by Ammonia tepida, which accounts for 92 % of the living (CellTracker Green(CTG)-labelled) assemblage. The vertical distribution shows a maximum density in the oxygenated 0-0.4 cm surface layer. A sharp decrease is observed in the next 2 cm, followed by a second, well-defined maximum in the suboxic sediment layer (3-8 cm depth). The presented method yields new information concerning the 2-D distribution of living A. tepida in suboxic layers. First, the identification of recent burrows by visual observation of the sediment cross section and the burrowing activity as deduced from the dissolved iron spatial distribution show no direct relation to the distribution of A. tepida at the centimetre scale. This lack of relation appears contradictory to previous studies (Aller and Aller, 1986; Berkeley et al., 2007). Next, the heterogeneity of A. tepida in the 3-8 cm depth layer was quantified by means of Moran's index to identify the scale of parameters controlling the A. tepida distribution. The results reveal horizontal patches with a characteristic length of 1-2 cm. These patches correspond to areas enriched in dissolved iron likely generated by anaerobic degradation of labile organic matter. These results suggest that the routine application of our new sampling strategy could yield important new insights about foraminiferal life strategies, improving our understanding of the role of these organisms in coastal marine ecosystems.

  6. Paradigms and proboscideans in the southern Great Lakes region, USA

    USGS Publications Warehouse

    Saunders, J.J.; Grimm, E.C.; Widga, C.C.; Campbell, G.D.; Curry, B. Brandon; Grimley, D.A.; Hanson, P.R.; McCullum, J.P.; Oliver, J.S.; Treworgy, J.D.

    2010-01-01

    Thirteen new chronometric dates for Illinois proboscideans are considered in relation to well-dated pollen records from northeastern and central Illinois. These dates span an interval from 21,228 to 12,944 cal BP. When compared to pollen spectra, it is evident that Mammut americanum inhabited spruce (Picea) and black ash (Fraxinus nigra) forest during the B??lling-Aller??d (14,700-12,900 cal BP) and early Younger Dryas (12,900-11,650 cal BP) chronozones. Both Mammuthus jeffersonii and Mammuthus primigenius inhabited spruce dominated open-woodland during the Oldest Dryas chronozone, while M.??primigenius persisted in a forest of predominantly black ash during the Aller??d chronozone. A newly discovered specimen from Lincoln, IL, clarifies the taxonomic distinction between M. primigenius and M.??jeffersonii. Hitherto, a paradigm of proboscidean succession during the full- to late-glacial periods was based on the vegetation succession of steppe tundra-like vegetation to spruce forest to spruce-deciduous forest. The presumed proboscidean succession was that of cold, dry steppe-adapted M. primigenius succeeded by more mesic-tolerant M. jeffersonii that in turn was succeeded by the wet forest-adapted M.??americanum. Reported data do not support this view and indicate a need for re-evaluation of assumptions of proboscidean ecology and history, e.g., the environmental tolerances and habits of M.??primigenius in regions south of 55??N, and its dynamic relationship with other proboscidean taxa. ?? 2009 Elsevier Ltd and INQUA.

  7. Search for Extraterrestrial Osmium at the Allerod - Younger Dryas Boundary

    NASA Astrophysics Data System (ADS)

    Beets, C.; Sharma, M.; Kasse, K.; Bohncke, S.

    2008-12-01

    Ir and Os are excellent markers of extraterrestrial impact events, due to their high abundance in ET objects (Alvarez et al., 1980 Science; Turekian, 1982 Geol. Bull. Am. Spec. Pap.). Os has the advantage over Ir, in that the 187Os/188Os ratio also greatly differs between meteorites and upper continental crust (UCC). The combination of [Os] and 187Os/188Os analyses would be superior in detecting any ET contribution. Firestone et al (2007 PNAS) attributed a widespread 12.9 ka Ir containing black carbon layer to a potential extraterrestrial impact at the Allerød-Younger Dryas (A-YD) boundary. In order to test this inference, we measured [Os] and 187Os/188Os on a radiocarbon dated A-YD record (13.210 to 12.788 cal years BP) from the Netherlands. This location is close to Lommel, a Belgian site studied by Firestone et al.(2007). The organic-rich sequence was sampled continuously over a 12 cm interval at 2 cm resolution (~70 years). About 10 g samples were freeze-dried, ground and homogenized in a zirconia ball-mill. The samples mixed with 190Os tracer solutions were dissolved in carius tubes and Os extracted in liquid bromine. Os was further purified using micro-distillation. Os isotopes were measured using N-TIMS on Dartmouth Triton. The procedural blank was 7 fg/g Os with an isotopic composition of 0.41±0.01 The Allerød samples have an order of magnitude higher abundance than UCC (200 vs. 30 pg/g), but similar 187Os/188Os ratios, >1.1. The sample at the base of the YD (12.893±75 cal years BP) contains a similar amount of Os, but has a distinctly lower isotopic signature, 0.53±0.002. The high [Os] in the A-YD section possibly reflects enrichment by preferential partitioning into organic matter. The Os isotope composition of 0.53, sandwiched between values >1.1, implies contribution of a significant amount of non-radiogenic Os. Since the pollen spectra show no reworking, the non-radiogenic Os could only have been delivered as a discrete pulse at 12.893 cal yr BP

  8. Ice Sheet Oscillations During the Last Deglaciation in Western Norway

    NASA Astrophysics Data System (ADS)

    Lohne, O. S.; Mangerud, J.; Svendsen, J.; Gyllencreutz, R.

    2009-12-01

    About 25-26ka cal BP, the Scandinavian Ice Sheet merged with the British Ice Sheet on the continental shelf in the northern part of the North Sea (Sejrup et al., 2009). The Norwegian Channel, that hosted a major ice stream, became finally deglaciated at around 18.5ka cal BP. The deglaciation of western Norway started first in the south and not later than 17-16 ka cal BP, the Jæren region was partly ice-free (Knudsen, 2006). The early deglaciation history in the Hardangerfjord-Bergen area was characterized by some rapid ice-margin oscillations. The extent and timing of the ice front variations are not well constrained, but probably they occurred sometime between 16-14.5ka cal BP. A main difficulty with the exact timing is the radiocarbon plateau around 12.3 ka 14C BP. Subsequently, during the Allerød, the ice sheet withdrew more than 50 km from the coastline, until it again started to re-advance. The recorded sea-level response of this re-advance indicates that the re-growth of the ice sheet started in the mid-Allerød, approximately at 13.6ka cal BP (Lohne et al., 2007), and it seems clear that the resulting ice sheet advance continued until the very end of the Younger Dryas when the prominent Herdla-Halsnøy Moraine was formed. In the 500-800 m deep Hardangerfjord the re-advance stopped at a bedrock threshold where the Halsnøy Moraine subsequently formed. As appear from the sediment stratigraphy in a lake basin on Halsnøy the advancing ice-margin reached the island slightly before the Vedde Ash fall (c. 12.1ka cal BP). The ice-front then halted on the bedrock sill, but stratigraphic evidence indicates that the fjord-glacier continued to grow in thickness. Marginal moraines from Halsnøy can be traced up to a level of about 1000 m a.s.l., 40 km further inland, reflecting a massive buildup of the ice sheet. The advancing ice-sheet reached its maximum position, both in the Bergen and Hardangerfjorden area, late in the YD. A more precise dating by radiocarbon is

  9. Diatoms as paleoecological indicators of environmental change in the Lake Czechowskie catchments ecosystem (Northern Tuchola Pinewoods, Poland)

    NASA Astrophysics Data System (ADS)

    Rzodkiewicz, Monika; Zawiska, Izabela; Noryśkiewicz, Agnieszka Maria; Obremska, Milena; Ott, Florian; Kramkowski, Mateusz; Słowiński, Michał; Błaszkiewicz, Mirosław; Brauer, Achim

    2016-04-01

    In this study we investigated four cores of biogenic sediments from the lakes located in close vicinity. Three cores are situated along a transect in the Lake Czechowskie basin from its deepest point towards a former lake bay. The fourth sediment core was retrieved from the nearby Trzechowskie paleolake. Lake Czechowskie is located in the northern part of the Tuchola Pinewoods District (Northern Poland) in a young glacial landscape. At present, the majority of the area is forested or used for agriculture. The main focus was of the study was Late Glacial and early Holocene period. We performed diatom, Cladocera and pollen analyses, the chronology was established by varve counting, confirmed by AMS 14C dating and Laacher See Tephra (Wulf et. all 2013). In this study we focused on the results of diatom analyses. Diatom assemblages are integrated indicators of environmental change because their distributions are closely linked to water quality parameters including such as nutrient availability. At the beginning of Allerød there are more eutrophic diatom taxa such as Staurosira construens, Pseudostaurosira brevistriata, Staurosira pinnata. These species are widely distributed in the littoral mainly freshwater, many of which are species of epiphytic, preferring water rich in nutrients. At the end of the Allerød we observe significant changes within diatom assemblages. The increase of planktonic Cyclotella comensis together with the decrease of benthic Stauroseria construens indicate the shortening of time with ice cove on the lake and longer time with summer stratification. In the Younger Dryas cooling we can see the increase of the abundance of diatom Staurosira construens which indicate cold spring and late ice-out (Bradbury et al., 2002). At the early Holocene planktonic diatoms increase in particular Cyclotella comensis, Punciculata radiosa and Cyclotella praetermissa. Some of Aulacoseira species at the end of Younger Dryas. The Holocene sediments showed no

  10. A ~25 ka Indian Ocean monsoon variability record from the Andaman Sea

    USGS Publications Warehouse

    Rashid, H.; Flower, B.P.; Poore, R.Z.; Quinn, T.M.

    2007-01-01

    Recent paleoclimatic work on terrestrial and marine deposits from Asia and the Indian Ocean has indicated abrupt changes in the strength of the Asian monsoon during the last deglaciation. Comparison of marine paleoclimate records that track salinity changes from Asian rivers can help evaluate the coherence of the Indian Ocean monsoon (IOM) with the larger Asian monsoon. Here we present paired Mg/Ca and δ18O data on the planktic foraminifer Globigerinoides ruber (white) from Andaman Sea core RC12-344 that provide records of sea-surface temperature (SST) and δ18O of seawater (δ18Osw) over the past 25,000 years (ka) before present (BP). Age control is based on nine accelerator mass spectrometry (AMS) dates on mixed planktic foraminifera. Mg/Ca-SST data indicate that SST was ∼3 °C cooler during the last glacial maximum (LGM) than the late Holocene. Andaman Sea δ18Osw exhibited higher than present values during the Lateglacial interval ca 19–15 ka BP and briefly during the Younger Dryas ca 12 ka BP. Lower than present δ18Osw values during the BØlling/AllerØd ca 14.5–12.6 ka BP and during the early Holocene ca 10.8–5.5 ka BP are interpreted to indicate lower salinity, reflect some combination of decreased evaporation–precipitation (E–P) over the Andaman Sea and increased Irrawaddy River outflow. Our results are consistent with the suggestion that IOM intensity was stronger than present during the BØlling/AllerØd and early Holocene, and weaker during the late glaciation, Younger Dryas, and the late Holocene. These findings support the hypothesis that rapid climate change during the last deglaciation and Holocene included substantial hydrologic changes in the IOM system that were coherent with the larger Asian monsoon.

  11. Sedimentary record of postglacial variability in near-bottom currents, sediment supply and ice rafting on the continental shelf off SW Spitsbergen

    NASA Astrophysics Data System (ADS)

    Sternal, B.; Szczuciński, W.; Forwick, M.; ZajÄ czkowski, M.; Lorenc, S.; Vorren, T. O.

    2012-04-01

    The continental shelf off the west coast of southern Spitsbergen is influenced by the northward-flowing water masses (warmer and more saline Atlantic Water carried by the West Spitsbergen Current and colder, fresher Arctic Water carried by the East Spitsbergen Current), as well as ice rafting. The present study was conducted to identify the influence of these factors on the sedimentary environment and to decipher temporal variations in the intensity of bottom currents, ice rafting off and glacial activity on southwestern Spitsbergen during the past 14,000 years. The study is based on a multiproxy analyses of one gravity core from the outer continental shelf (148 m water depth) in decadal to centennial resolution. Age control was obtained on a basis of ten AMS 14C dates along with 210Pb and 137Cs datings. To infer the style of sedimentation and the sediment supply the core was measured for magnetic susceptibility, X-rayed, analysed for grain-size distribution of bulk sediment and for coarse sand fraction components. The assessment of ice rafting intensity was based on coarse sand fraction counting (IRD), whereas to assume the type of ice rafting, whether by icebergs or sea ice, the analysis of quartz grains roundness was performed. Moreover, relative velocity of bottom currents was estimated by grain-size analysis of sortable silt fraction. We distinguish seven intervals: c. 14,000 - 12,600 cal yr BP - Bølling/Allerød (unit 1); 12,600 - 11,500 cal yr BP - Younger Dryas (unit 2) and 11,500 cal yr BP to present - Holocene (units 3 - 7). The smallest mean sortable silt values, reflecting relatively low bottom current velocity, occurred from the Bølling/Allerød to the early Younger Dryas and after ~0.5 cal ka BP. Increased velocities were inferred for the early Holocene as well as period between 8.8 - 7.8 cal yr BP. The IRD was present throughout the entire record indicating continuous supply of a material delivered from ice rafting, with variable dominance of

  12. Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA

    USGS Publications Warehouse

    Mason, J.A.; Miao, X.; Hanson, P.R.; Johnson, W.C.; Jacobs, P.M.; Goble, R.J.

    2008-01-01

    Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the B??lling-Aller??d episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial

  13. An INTIMATE Example: Into and out of the Younger Dryas at Lake Hämelsee, NW-Germany

    NASA Astrophysics Data System (ADS)

    de Bruijn, Renée; Engels, Stefan; Hoek, Wim Z.; Lane, Christine S.; Sachse, Dirk; Wagner-Cremer, Friederike

    2014-05-01

    Lake Hämelsee is a classical site with an excellent high-resolution record of Pleniglacial to Holocene climate and environment, contained in 18m of lacustrine sediments. At the centre of the lake, the Late Glacial interval consists of 2.7m of sapropelic and silty muds, that are mostly laminated (Merkt and Müller, QI 1999). In the framework of a summer school - 'An INTIMATE Example' - the lake was cored again, with the purpose of applying the latest techniques in palaeoclimatology and -ecology. Twenty international students and Early Stage Researchers (ESR's) from a wide range of backgrounds participated in lectures and field work and gained hands-on-experience with several proxies and techniques. Ongoing research by participants of the training school is focused on the timing and nature of the Allerød - Younger Dryas (YD) and YD - Preboreal transitions. Five short-term international exchange visits have provided opportunities for participants to learn and apply new techniques to the Hämelsee record, supervised by members of the INTIMATE network. A new age model will be constructed for the Late Glacial core section based on a combination of 14C-dates on macro-remains, varve chronology and tephrochronology. Tephrostratigraphic correlations will allow direct correlation of the record to both marine and ice core records from the North Atlantic region, as well as other European archives. Palaeoclimatic and -ecological research will include pollen-, chironomid-, LOI-, XRF-, lipid biomarker, stable isotope and GDGT-analysis. Temperature reconstructions will be made based on several of these proxies, providing a unique opportunity to compare independent reconstructions using material from a single record. Not only did the training school and subsequent research provide an excellent opportunity for ESR's to learn and work with international experts in the field - the collected data will also provide a high-resolution multi-proxy record of palaeoclimatology, -ecology and

  14. Paleo-iron supply to the Western Subarctic Pacific since the last glaciation

    NASA Astrophysics Data System (ADS)

    Lam, P. J.; Robinson, L. F.; Blusztajn, J.; McManus, J. F.; Cook, M. S.; Keigwin, L. D.

    2011-12-01

    A strong and pervasive productivity peak has been observed in cores around the North Pacific during the Bølling-Allerød warm period of the last deglaciation. Recently, it has been hypothesized that this peak may have been caused by an influx of iron from the continental shelves as they were flooded during the deglaciation (1). Here, we examine this hypothesis by reconstructing the flux and sources of detrital material to a sediment core from the Detroit seamount (Vinogradov 19/4 GGC-37, 50.4°N, 167.7°E, 3300m) in the Western Subarctic Pacific since the last glacial maximum (LGM), and compare to several proxies of paleo-productivity. We use 230Th-normalization to reconstruct the flux of biogenic and detrital material, and the neodymium and strontium isotopic compositions to distinguish between volcanic margin and continental loess sources of detrital material. We find that total detrital flux is highest during the last glacial maximum and early deglacial periods, a time of relatively low productivity, with approximately equal contributions from the volcanic margin and from continental loess. Total detrital flux starts to decline around 16kya, but increases again to 80% of the glacial maximum flux around the time of the Bølling-Allerød productivity peak. The local deglacial maximum in detrital flux coincides with a maximum in authigenic uranium, and immediately precedes maxima in opal flux, carbonate flux, benthic foraminifera abundance, and excess 231Pa/230Th. While the local deglacial maximum in detrital flux is consistent with iron stimulation of productivity, we conclude that iron supply alone is not sufficient to explain the deglacial productivity peak, since glacial times exhibited low productivity despite high detrital flux. Further, the relative and absolute contributions of detrital material of volcanic origin is lower during the deglaciation than during the LGM, suggesting that loess may have contributed more iron during the deglacial productivity

  15. Response of the Selle River to climatic modifications during the Lateglacial and Early Holocene (Somme Basin-Northern France)

    NASA Astrophysics Data System (ADS)

    Antoine, Pierre; Munaut, André-Valentin; Limondin-Lozouet, Nicole; Ponel, Philippe; Dupéron, Jean; Dupéron, Monique

    2003-10-01

    Research on Lateglacial sequences from the Selle valley leads to an overview of its evolution in relation to climatic variations between the end of the Weichselian Upper Pleniglacial and the beginning of the Holocene. The first major modification of the fluvial morphology is dated at the Upper Pleniglacial/Lateglacial transition (13,000 14C-yr BP). At that time, the response to climatic improvement and environmental modifications is marked by downcutting and evolution from a braided river to a transitional river pattern (Bølling infilling in the newly created channels). After a short cold phase recorded in a thin calcareous bed at the top of the Bølling peat attributed to the Older Dryas (Dr. II), the Allerød is characterized by the deposition of organic overbank silts within a large single channel meandering system. In lower slope environments, this period is also marked by slow rates of colluvial accumulation and by the development of upbuilding soils (Allerød soil). On the other hand, the end of the Lateglacial, is characterised by the infilling of the whole valley by fine calcareous overbank silts during the Younger Dryas cold phase (overflow of a large single channel and lateral input of chalk mud). A second major downcutting phase occurs at the beginning of the Holocene at around 10,000 BP, in parallel with another rapid climatic improvement and the renewed spread of vegetation. From a general point of view, the evolution of fluvial environments in the Selle valley is comparable with many other river valleys in NW Europe, showing that fluvial systems react very quickly to climatic variations of short duration (1000 to 100 years). Finally, in the Upper Selle River, incision events occur clearly before the main modifications of the vegetal cover. They are most likely linked to a rapid shift in the balance between water discharge and sediment supply, caused by climate modifications (shift to more temperate and oceanic conditions), and the resulting

  16. G-protein coupled receptor auto-antibodies in thromboangiitis obliterans (Buerger's disease) and their removal by immunoadsorption.

    PubMed

    Klein-Weigel, Peter F; Bimmler, Marion; Hempel, Petra; Schöpp, Sebastian; Dreusicke, Siegrid; Valerius, Jana; Bohlen, Anne; Boehnlein, Joana M; Bestler, Daniel; Funk, Stephanie; Elitok, Saban

    2014-09-01

    Hintergrund: Histopathologische und serologische Befunde sprechen für eine Immunpathogenese der Thromboangiitis obliterans (TAO, Buerger’sche Erkrankung). Autoantikörper scheinen eine wichtige Rolle im Krankheitsgeschehen zu spielen. Es wurden wiederholt positive therapeutische Effekte durch eine Immunadsorption (IA) gezeigt. Wir analysierten agonistische Autoantikörper (agAAK), die gegen G-Protein gekoppelte Rezeptoren (GPCR) gerichtet sind und analysierten, ob diese durch eine IA effektiv beseitigt werden können. Patienten und Methoden: Zwischen Dezember 2012 und Mai 2014 wurden 11 Patienten mittels IA über 5 konsekutive Tage behandelt. Die agAAK wurden unter Verwendung spezifischer ELISA-Techniken bestimmt. Ergebnisse: AgAAK wurden bei 9 von 11 Patienten (81.8 %) gefunden. Multiple agAAK waren bei 7 Patienten (63.6 %) nachweisbar. Darüber hinaus wurde ein agAAK-Cluster entdeckt, das sich gegen Loop1 des adrenergen α1-Rezeptors und Loop1 des Endothelin A (ETA)-Rezeptors richtet, und sich bei 72.7 % respektive 54.5 % der TAO-Patienten nachweisen ließ. AgAAK gegen Epitop 1 oder 2 des Angiotensin-1-Rezeptors wurden bei 3 Patienten, agAAK gegen Loop1/2 des Proteinase-aktivierten Rezeptor (PAR) wurden bei 2 Patienten nachgewiesen. AgAAK gegen den ETA-Rezeptor traten niemals ohne gleichzeitigen Nachweis von agAAK gegen den α1-adrenergen Rezeptor auf und waren immer gegen Loop1 gerichtet. Unmittelbar nach Beendigung der IA ließen sich bei 81.8 % aller Patienten und bei 77.8 % aller Fälle mit positiven agAAK vor der IA keine agAAK mehr nachgewiesen. Schlussfolgerungen: Wir konnten bei Patienten mit aktiver TAO agAAK gegen GPCR und darüber hinaus ein Antikörper-Cluster nachweisen, das sich bevorzugt gegen Loop1 des α-1-adrenergen Rezeptors und Loop1 des ETA-Rezeptors richtet. Die agAAK wurden mehrheitlich erfolgreich durch die IA eliminiert. Wir sind der Auffassung, dass gegen GPCR-gerichtete agAAK eine wichtige Rolle in der Pathogenese der TAO spielen und

  17. Lateglacial tree-line dynamics in Jura mountains (north eastern France) and palaeoclimatic implications

    NASA Astrophysics Data System (ADS)

    Bégeot, C.

    2003-04-01

    Mountain regions are ideally suited for studies on long-term environmental change because minor climatic shifts can be expected to generate large changes in biotic communities. In particular the distribution of vegetation along an altitudinal gradient and tree line position are very dependant of climatic parameters. To assess the impact and magnitude of climatic change over the Lateglacial period, high resolution pollen and plant macrofossils analyses have been carried out on cores from the Jura massif. It is a medium sized mountain culminating at 1723 m asl at north eastern France along the Swiss-French border. Four sites distributed along an altitudinal transect from 700 m to about 1500 m asl have been investigated. The combination of plant macrofossils and pollen analyses from different altitudes sites led us to reconstruct the treeline fluctuations. During the Bølling (12700-12100 BP), Betula woodland was established up to 800 m a.s.l. whereas Juniperus communities were reached 1000-1100 m asl. The Older Dryas (12100-11900 BP) was characterized by a decline of shrubby vegetation to lower altitudes. Pine forests were migrated progressively into the massif up to 1200 m a.s.l. during the Allerød (11900-11000 BP). Subsequently, the treeline retreated abruptly in response to the Younger Dryas deterioration (11000-10000 BP). Thus, open landscape with scattered trees was extended over a big part of the massif (at least above 800 m a.s.l.). The widespread expansion of mixed Pinus-Betula forests on highest altitudes occurred at the beginning of the Holocene. In addition to treeline variations, the high resolution pollen records show a great irregularity of pollen curves. Those of heliophilous shrubs show a decline in the middle part of the Bølling, around 12400 BP. This event can be correlated with the "Intra Bølling Cold Phase" recognised from ice and marine cores. During the Allerød, the predominance of Pinus is repeatedly interrupted by rises in Betula and

  18. Loess record of the Pleistocene Holocene transition on the northern and central Great Plains, USA

    NASA Astrophysics Data System (ADS)

    Mason, Joseph A.; Miao, Xiaodong; Hanson, Paul R.; Johnson, William C.; Jacobs, Peter M.; Goble, Ronald J.

    2008-09-01

    Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the Bølling-Allerød episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial

  19. Millennial- and sub-millennial-scale shifts in moisture availability for western Mediterranean forest development during the Deglaciation and Holocene

    NASA Astrophysics Data System (ADS)

    Fletcher, W. J.; Sanchez Goñi, M. F.; Peyron, O.; Dormoy, I.

    2009-04-01

    Pollen data for temperate Mediterranean forest development from marine core MD95-2043 (Alborán Sea, western Mediterranean) and pollen-based climate reconstructions using the modern analogue technique (MAT) for annual precipitation (PANN) and mean temperatures of the coldest and warmest months (MTCO and MTWA) provide evidence for abrupt changes in western Mediterranean climate between 20 and 1 cal ka BP. During the Deglaciation period (20 -6 cal ka BP), major climatic shifts with parallel precipitation and temperature changes occurred at the onsets of Heinrich Event 1 (equivalent to the Oldest Dryas), the Bölling-Allerød (BA), and the Younger Dryas (YD). Multi-centennial-scale oscillations in forest development related to regional precipitation (PANN) variability occurred throughout the BA, YD, and early Holocene, with drier atmospheric conditions in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas), GI-1b (Intra-Allerød Cold Period) and GS-1 (YD), and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting (events at 11.4, 10.1, 9.3, 8.2 and 7.4 cal ka BP). The forest record also indicates multi-centennial variability within the YD interval with an intra-YD episode of forest recovery. A possible climatic mechanism for the recurrence of sub-millennial-scale dry intervals and an opposed regional precipitation pattern with respect to western-central Europe relates to the dynamics of the jet stream and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alborán Sea by approx. 200 years (surface water age approx. 600 years) during the Lateglacial. During the (mid- to late-) Holocene, a significant millennial-scale oscillation in forest development is detected, centred at around 1750 yrs, which may reflect low frequency

  20. Abrupt climate changes of the last deglaciation detected in a Western Mediterranean forest record

    NASA Astrophysics Data System (ADS)

    Fletcher, W. J.; Sanchez Goñi, M. F.; Peyron, O.; Dormoy, I.

    2010-04-01

    Abrupt changes in Western Mediterranean climate during the last deglaciation (20 to 6 cal ka BP) are detected in marine core MD95-2043 (Alboran Sea) through the investigation of high-resolution pollen data and pollen-based climate reconstructions by the modern analogue technique (MAT) for annual precipitation (Pann) and mean temperatures of the coldest and warmest months (MTCO and MTWA). Changes in temperate Mediterranean forest development and composition and MAT reconstructions indicate major climatic shifts with parallel temperature and precipitation changes at the onsets of Heinrich stadial 1 (equivalent to the Oldest Dryas), the Bölling-Allerød (BA), and the Younger Dryas (YD). Multi-centennial-scale oscillations in forest development occurred throughout the BA, YD, and early Holocene. Shifts in vegetation composition and (Pann reconstructions indicate that forest declines occurred during dry, and generally cool, episodes centred at 14.0, 13.3, 12.9, 11.8, 10.7, 10.1, 9.2, 8.3 and 7.4 cal ka BP. The forest record also suggests multiple, low-amplitude Preboreal (PB) climate oscillations, and a marked increase in moisture availability for forest development at the end of the PB at 10.6 cal ka BP. Dry atmospheric conditions in the Western Mediterranean occurred in phase with Lateglacial events of high-latitude cooling including GI-1d (Older Dryas), GI-1b (Intra-Allerød Cold Period) and GS-1 (YD), and during Holocene events associated with high-latitude cooling, meltwater pulses and N. Atlantic ice-rafting. A possible climatic mechanism for the recurrence of dry intervals and an opposed regional precipitation pattern with respect to Western-central Europe relates to the dynamics of the westerlies and the prevalence of atmospheric blocking highs. Comparison of radiocarbon and ice-core ages for well-defined climatic transitions in the forest record suggests possible enhancement of marine reservoir ages in the Alboran Sea by 200 years (surface water age 600 years

  1. Persistence of the North American Monsoon over the last 50,000 years in Arizona, USA

    NASA Astrophysics Data System (ADS)

    Cole, K. L.; Ironside, K. E.; Cobb, N. S.

    2012-12-01

    Reconstruction of monsoon rainfall in the American southwest over the last 50,000 years has been complicated by past massive shifts in temperature and winter precipitation, as well as the rarity of proxy sources. Paleogeographical analysis of plant species distributions from plant macrofossils contained within packrat middens and sediment cores portray substantial shifts that are most easily attributed to these larger changes in temperature and winter precipitation. But some species can be more reliably associated with summer precipitation through spatial analyses of their climate space within their contemporary habitat. For example, warm-season C4 grasses and summer annuals were infrequent in southern Arizona throughout the late Wisconsinan, likely because of much lower temperatures and much higher levels of winter rainfall. But other species, today typical of summer precipitation regions further north, were especially abundant during selected intervals. Macrofossils of Arizona single-leaf pinyon (Pinus edulis var. fallax) and one seed juniper (Juniperus monosperma) are abundant in middens from northern Arizona and southern Utah ranging from 30,400 to > 50,000 C14 yr BP, suggesting at least 200% of the current summer precipitation. The abundance of Arizona single-leaf pinyon throughout Arizona during the Allerød Interval (~13.9 ka to ~12.9 ka) suggests that summer precipitation was at least 120% of modern. The rapid expansion and dominance of the southwestern interior race of Ponderosa pine (Pinus ponderosa), as well as increases in Rocky Mountain Juniper (Juniperus scopulorum), during the earliest Holocene (~11.7 ka to ~10.2 Ka) portray summer precipitation somewhat greater than that of today. These paleobotanical conclusions are supported by a recent analysis of Deuterium isotopes from 120 middens in 5 regional series. These isotopic values should reflect the relative frequency of precipitation originating from Pacific winter cyclonic storms versus sub

  2. Lateglacial and early-Holocene climate variability reconstructed from multi-proxy records on Andøya, northern Norway

    NASA Astrophysics Data System (ADS)

    Birks, Hilary H.; Aarnes, Ingelinn; Bjune, Anne E.; Brooks, Stephen J.; Bakke, Jostein; Kühl, Norbert; Birks, H. John B.

    2014-04-01

    We reconstruct mean July temperature (Tjul) from three sites on the island of Andøya, northern Norway for the period 15 000-9000 cal yr BP using three biotic proxies. A probabilistic indicator species approach (pdf method) was used for plant macrofossil data from all sites (M-Tjul). Reconstructions based on pollen (P-Tjul) (2 sites) and chironomids C-Tjul) (1 site) were done using weighted averaging and weighted-averaging partial least-squares, respectively. A sediment proxy for catchment glacier development was measured at the main site, Lusvatnet. The July temperature reconstructions from all the sites show a similar development through the deglaciation. An initial July temperature of 4 °C increased to a maximum of 7-8 °C during the Allerød at c.13 200 cal yr BP. There was no marked cooling at the start of the Younger Dryas (YD) chronozone, at Lusvatnet, C-Tjul decreased after 12 700 cal yr BP to a low of 6 °C at about 12 550 cal yr BP before increasing markedly around 12 400 cal yr BP. Conversely, P-Tjul rose slowly through the early YD. Both proxies exceeded the Allerød temperatures for around 300 years before decreasing towards a minimum of 6 °C at c. 12 000 cal yr BP. M-Tjul maintained a mean of c. 8 °C throughout the YD. Different sensitivities of proxies are discussed. Their different responses during the YD at the three sites, along with the glacial evidence, highlight the role of aridity. At c. 11 500 cal yr BP, July temperatures increased rapidly over Andøya to about 10 °C, and then rose gradually to maximum values of 12 °C at c. 9700 cal yr BP. The temperature reconstructions are consistent with the flow of Atlantic water into the Nordic Seas except during the YD, when variability in sea ice may have been more important. During the early Holocene there are some differences between sites, resulting from local site factors such as altitude and exposure, soil development, and catchment instability.

  3. Vegetation and Climate Change during the Last Deglaciation in the Great Khingan Mountain, Northeastern China.

    PubMed

    Wu, Jing; Liu, Qiang; Wang, Luo; Chu, Guo-qiang; Liu, Jia-qi

    2016-01-01

    The Great Khingan Mountain range, Northeast China, is located on the northern limit of modern East Asian Summer Monsoon (EASM) and thus highly sensitive to the extension of the EASM from glacial to interglacial modes. Here, we present a high-resolution pollen record covering the last glacial maximum and the early Holocene from a closed crater Lake Moon to reconstruct vegetation history during the glacial-interglacial transition and thus register the evolution of the EASM during the last deglaciation. The vegetation history has gone through distinct changes from subalpine meadow in the last glacial maximum to dry steppe dominated by Artemisia from 20.3 to 17.4 ka BP, subalpine meadow dominated by Cyperaceae and Artemisia between 17.4 and 14.4 ka BP, and forest steppe dominated by Betula and Artemisia after 14.4 ka BP. The pollen-based temperature index demonstrates a gradual warming trend started at around 20.3 ka BP with interruptions of several brief events. Two cold conditions occurred around at 17.2-16.6 ka BP and 12.8-11.8 ka BP, temporally correlating to the Henrich 1 and the Younger Dryas events respectively, 1and abrupt warming events occurred around at 14.4 ka BP and 11.8 ka BP, probably relevant to the beginning of the Bølling-Allerød stages and the Holocene. The pollen-based moisture proxy shows distinct drought condition during the last glacial maximum (20.3-18.0 ka BP) and the Younger Dryas. The climate history based on pollen record of Lake Moon suggests that the regional temperature variability was coherent with the classical climate in the North Atlantic, implying the dominance of the high latitude processes on the EASM evolution from the Last Glacial Maximum (LGM) to early Holocene. The local humidity variability was influenced by the EASM limitedly before the Bølling-Allerød warming, which is mainly controlled by the summer rainfall due to the EASM front covering the Northeast China after that.

  4. Evidence of a 700-year Lake Agassiz megaflood in the slackwater deposits of Mississippi River tributaries

    NASA Astrophysics Data System (ADS)

    Wang, H.; Stumpf, A.; Berg, R. C.; McKay, E. D., III

    2010-12-01

    One prominent event associated with retreat of the Laurentide Ice Sheet was the release of an exceptionally large volume of meltwater from Lake Agassiz. This discharge led to a sea-level rise of 20 meters in about 500 years and caused disruption to the global thermohaline circulation that led to an overall cooling during the Younger Dryas stadial (YDS). Recent studies suggest that the eastern and northern outlets of glacial Lake Agassiz remained closed until the early YDS, but new findings by the authors indicate that catastrophic floods drained through a southern outlet along the Mississippi River at this time. Here we present a detailed description of a dune-paleosol/peat succession from the middle Illinois River valley containing a slackwater deposit (peat) associated with these floods that has been dated using 14C and OSL methods to the Bølling-Allerød interstadial. At this site, Heinrich stadial 1 (HS1) and YDS dunes are separated by a well-developed Bølling-equivalent paleosol overlain by an Allerød-equivalent slackwater peat unit. The paleosol developed under warm/humid conditions, fundamentally different from the cold and dry conditions that prevailed during dune formation. Our age model indicates that the Bølling-equivalent paleosol developed for 1200 years followed by the meltwater megaflood. Preliminary measurements indicate the flood raised the Mississippi River level at its juncture with the Illinois River 18 m higher than the 500-year flood recorded in 1993. The megaflood blocked the Illinois River forming a large slackwater swamp, which lasted for 700 years. The release of cold meltwater through the Mississippi River basin inevitably lowered the sea surface temperature (SST) in the Gulf of Mexico, shortening the northern overturning circulation and shifting the Intertropical Convergence Zone (ITCZ) southward. As a consequence, the southerlies became weakened and retreated southward allowing the dry westerlies and northwesterlies to carry Pacific

  5. Century-scale climate-driven vegetation and environmental dynamics in southern Siberia during the last 47 kyr

    NASA Astrophysics Data System (ADS)

    Tarasov, Pavel; Bezrukova, Elena; Solovieva, Nadia; Riedel, Frank

    2010-05-01

    Radiocarbon-dated pollen and diatom records from Lake Kotokel in southern Siberia are used to reconstruct the environmental history of the area since ~47 kyr BP. Pollen data and reconstructed biome scores suggest predominance of a tundra-steppe vegetation and variable woody cover (5-20%) between ~47-30 kyr BP, indicating generally a harsh and unstable climate during this interval, conventionally regarded as the MIS3 interstadial. The short-term climate amelioration episodes in the glacial part of the records are marked by the peaks in taiga and corresponding minima in steppe biome scores and appear synchronously with the hemispheric temperature and precipitation changes recorded in the Greenland ice cores and Chinese stalagmites. The interval ~30-24 kyr BP was probably the driest and coldest of the whole record, as indicated by highest scores for steppe biome, woody coverage <5%, absence of diatoms and reduced size of the lake. A slight amelioration of the regional climate ~24-22 kyr BP was followed by a shorter than the previous and less pronounced deterioration phase. After 14.7 kyr BP the climate became warmer and wetter than ever during ~47-14.7 kyr BP, resulting in the deepening of the lake and increase in the woody coverage to 20-30% ~14.5-14 kyr and ~13.3-12.8 kyr BP. These two intervals correspond to the Meiendorf and Allerød interstadials, which until now were interpreted as part of the undifferentiated Bølling/Allerød interstadial complex in the Lake Baikal region. The increase in tundra biome scores and pronounced change in the diatom composition allow (for the first time) the unambiguous identification of the Younger Dryas (YD) in the region ~12.7-11.65 kyr BP, suggesting the synchronous onset of the YD and the Holocene interglacial across Eurasia. The maximal spread of the taiga communities in the region is associated with a warmer and wetter climate than the present prior to ~7 kyr BP. This was followed by a wide spread of Scots pine, indicating

  6. Quantitative interpretation of atmospheric carbon records over the last glacial termination

    NASA Astrophysics Data System (ADS)

    KöHler, Peter; Fischer, Hubertus; Munhoven, Guy; Zeebe, Richard E.

    2005-12-01

    The glacial/interglacial rise in atmospheric pCO2 is one of the best known changes in paleoclimate research, yet the cause for it is still unknown. Forcing the coupled ocean-atmosphere-biosphere box model of the global carbon cycle BICYCLE with proxy data over the last glacial termination, we are able to quantitatively reproduce transient variations in pCO2 and its isotopic signatures (δ13C, Δ14C) observed in natural climate archives. The sensitivity of the Box model of the Isotopic Carbon cYCLE (BICYCLE) to high or low latitudinal changes is comparable to other multibox models or more complex ocean carbon cycle models, respectively. The processes considered here ranked by their contribution to the glacial/interglacial rise in pCO2 in decreasing order are: the rise in Southern Ocean vertical mixing rates (>30 ppmv), decreases in alkalinity and carbon inventories (>30 ppmv), the reduction of the biological pump (˜20 ppmv), the rise in ocean temperatures (15-20 ppmv), the resumption of ocean circulation (15-20 ppmv), and coral reef growth (<5 ppmv). The regrowth of the terrestrial biosphere, sea level rise and the increase in gas exchange through reduced sea ice cover operate in the opposite direction, decreasing pCO2 during Termination I by ˜30 ppmv. According to our model the sequence of events during Termination I might have been the following: a reduction of aeolian iron fertilization in the Southern Ocean together with a breakdown in Southern Ocean stratification, the latter caused by rapid sea ice retreat, trigger the onset of the pCO2 increase. After these events the reduced North Atlantic Deep Water (NADW) formation during the Heinrich 1 event and the subsequent resumption of ocean circulation at the beginning of the Bølling-Allerød warm interval are the main processes determining the atmospheric carbon records in the subsequent time period of Termination I. We further deduce that a complete shutdown of the NADW formation during the Younger Dryas was

  7. Vulnerability and risk evaluation of agricultural nitrogen pollution for Hungary's main aquifer using DRASTIC and GLEAMS models.

    PubMed

    Leone, A; Ripa, M N; Uricchio, V; Deák, J; Vargay, Z

    2009-07-01

    In recent years, the significant improvement in point source depuration technologies has highlighted problems regarding, in particular, phosphorus and nitrogen pollution of surface and groundwater caused by agricultural non-point (diffuse) sources (NPS). Therefore, there is an urgent need to determine the relationship between agriculture and chemical and ecological water quality. This is a worldwide problem, but it is particularly relevant in countries, such as Hungary, that have recently become members of the European Community. The Italian Foreign Ministry has financed the PECO (Eastern Europe Countries Project) projects, amongst which is the project that led to the present paper, aimed at agricultural sustainability in Hungary, from the point of view of NPS. Specifically, the aim of the present work has been to study nitrates in Hungary's main aquifer. This study compares a model showing aquifer intrinsic vulnerability to pollution (using the DRASTIC parameter method; Aller et al. [Aller, L., Truman, B., Leher, J.H., Petty, R.J., 1986. DRASTIC: A Standardized System for Evaluating Ground Water Pollution Potential Using Hydrogeologic Settings. US NTIS, Springfield, VA.]) with a field-scale model (GLEAMS; Knisel [Knisel, W.G. (Ed.), 1993. GLEAMS--Groudwater Leaching Effects of Agricultural Management Systems, Version 3.10. University of Georgia, Coastal Plain Experimental Station, Tifton, GA.]) developed to evaluate the effects of agricultural management systems within and through the plant root zone. Specifically, GLEAMS calculates nitrate nitrogen lost by runoff, sediment and leachate. Groundwater monitoring probes were constructed for the project to measure: (i) nitrate content in monitored wells; (ii) tritium (3H) hydrogen radioisotope, as a tool to estimate the recharge conditions of the shallow groundwater; (iii) nitrogen isotope ratio delta15N, since nitrogen of organic and inorganic origin can easily be distinguished. The results obtained are satisfactory

  8. Vegetation and Climate Change during the Last Deglaciation in the Great Khingan Mountain, Northeastern China

    PubMed Central

    Wu, Jing; Liu, Qiang; Wang, Luo; Chu, Guo-qiang; Liu, Jia-qi

    2016-01-01

    The Great Khingan Mountain range, Northeast China, is located on the northern limit of modern East Asian Summer Monsoon (EASM) and thus highly sensitive to the extension of the EASM from glacial to interglacial modes. Here, we present a high-resolution pollen record covering the last glacial maximum and the early Holocene from a closed crater Lake Moon to reconstruct vegetation history during the glacial-interglacial transition and thus register the evolution of the EASM during the last deglaciation. The vegetation history has gone through distinct changes from subalpine meadow in the last glacial maximum to dry steppe dominated by Artemisia from 20.3 to 17.4 ka BP, subalpine meadow dominated by Cyperaceae and Artemisia between 17.4 and 14.4 ka BP, and forest steppe dominated by Betula and Artemisia after 14.4 ka BP. The pollen-based temperature index demonstrates a gradual warming trend started at around 20.3 ka BP with interruptions of several brief events. Two cold conditions occurred around at 17.2–16.6 ka BP and 12.8–11.8 ka BP, temporally correlating to the Henrich 1 and the Younger Dryas events respectively, 1and abrupt warming events occurred around at 14.4 ka BP and 11.8 ka BP, probably relevant to the beginning of the Bølling-Allerød stages and the Holocene. The pollen-based moisture proxy shows distinct drought condition during the last glacial maximum (20.3–18.0 ka BP) and the Younger Dryas. The climate history based on pollen record of Lake Moon suggests that the regional temperature variability was coherent with the classical climate in the North Atlantic, implying the dominance of the high latitude processes on the EASM evolution from the Last Glacial Maximum (LGM) to early Holocene. The local humidity variability was influenced by the EASM limitedly before the Bølling-Allerød warming, which is mainly controlled by the summer rainfall due to the EASM front covering the Northeast China after that. PMID:26730966

  9. Penultimate and last glacial cycles in the western Bering Sea: evidence from micropaleontological and sedimentary records

    NASA Astrophysics Data System (ADS)

    Ovsepyan, Ekaterina; Ivanova, Elena; Murdmaa, Ivar

    2014-05-01

    The short- and long-term variability of sea-surface bioproductivity, intermediate-water oxygenation, sea ice conditions and bottom current velocities are inferred from the high-resolution multi-proxy study based on benthic (BF) and planktonic (PF) foraminiferal assemblages and sedimentary record of the 18m-long Core SO201-2-85KL (western Bering Sea). Early MIS 6 is characterized by a very low seasonal bioproductivity, moderate bottom-water oxygenation, and expanded seasonal sea ice conditions, as documented by the abundant phytodetritus species Alabaminella weddelensis, Islandiella norcrossi and Epistominella arctica, suboxic group of BF, and high accumulation rates of gravel grains, respectively. Middle MIS 6 is represented by intercalation of green diatomaceous ooze and grey clayey silt layers with sharp peaks of BF abundance in green interbeds. These spikes might result either from short-term events of enhanced sea surface bioproductivity or from lateral BF transport by intensified bottom currents, as it is demonstrated by high-amplitude variations of the clay/silt ratio. Rather high seasonal productivity and northward migration of the sea ice margin are reconstructed for the late MIS 6 that is also characterized by a slight increase in the Northern Hemisphere summer insolation. Strong dissolution of calcareous microfossils is revealed for MIS 5.5-5.1 when the Bering Strait was open. Dissolution might be caused by an excess of carbon dioxide in the bottom-water due to an abundant organic matter decay and/or to an influence of the old CO2-rich deep water. MIS 4 - early Termination I is characterized by a dominance of glacial benthic foraminiferal assemblages that implies low bioproductivity conditions. A prevalence of suboxic BF group suggests moderate bottom-water oxygenation. Sea ice rafting occurred in the western Bering Sea during MIS 4 - early Termination I but the drifted ice was not so dense as during MIS 6. The well-known productivity spikes at Bølling/Aller

  10. Theory and practice in medical education--expectations and development of skills experienced by students of human medicine compared with students in other disciplines.

    PubMed

    Piedmont, Silke; Robra, Bernt-Peter

    2015-01-01

    Zielsetzung: Der vorliegende Artikel vergleicht Studierende der Humanmedizin (HM) mit Studierenden der Fächergruppen MINT, Geistes- und Sozialwissenschaften sowie Rechts- und Wirtschaftswissenschaften hinsichtlich ihrer Erwartungen an Studium und Beruf und der Kompetenzbereiche, in denen sie sich im Studium gefördert fühlen. Dadurch werden Spezifika der angehenden Humanmediziner/innen herausgearbeitet, die unter dem Fokus „Wissenschafts- und Praxisorientierung des Studiums“ diskutiert werden.Methodik: Datenbasis ist der Public Use File des „11. Studierendensurveys“, eine schriftliche Befragung von zufällig ausgewählten Studierenden an 25 deutschen Hochschulen im Wintersemester 2009/2010, die durch die Arbeitsgruppe Hochschulforschung der Universität Konstanz zur Verfügung gestellt wurde. Angaben von 7536 Studierenden werden einbezogen, darunter 488 (6,5%) angehende Humanmediziner/innen.Ergebnisse: Humanmedizinerinnen und Humanmediziner haben ein klares Berufsziel und möchten zügig studieren. Sie weisen ein weit überdurchschnittliches Interesse an der Arbeit mit und für Menschen auf. Rund jede/r zweite von ihnen ist an einer wissenschaftlichen oder forschenden Tätigkeit interessiert (je 53% - nahe am Durchschnitt aller Fächer). Verglichen mit den anderen Fächergruppen sprechen HM ihrem Studium am häufigsten einen Praxis- sowie Forschungsbezug zu und fühlen sich am häufigsten auch auf ihren Beruf vorbereitet. Jedoch sieht sich über die Hälfte aller Studierenden (Ø 53,3%; HM 54,5%) eher nicht in ihrer Forschungskompetenz gefördert. Vor allem MINT-Studierende können ihre Kompetenzen stärker durch selbständiges Erproben erweitern, während Praxis und Wissenschaft in der regulären Lehre der Humanmedizin eher theoretisch vermittelt werden. Entsprechend fühlen sich die HM in einigen Kompetenzbereichen, die für ihre spätere Arbeit nötig sind, weniger gefördert als Studierende anderer Fächergruppen, beispielsweise in ihrer Selbst

  11. Are single-well "push-pull" tests suitable tracer methods for aquifer characterization?

    NASA Astrophysics Data System (ADS)

    Hebig, Klaus; Zeilfelder, Sarah; Ito, Narimitsu; Machida, Isao; Scheytt, Traugott; Marui, Atsunao

    2013-04-01

    borehole and gravel pack? How does density difference between the original groundwater and the test solution influence the tracer breakthrough curves? To solve these questions, seven push-pull tests were performed under controlled boundary conditions in the same well DD-2 (100 m depth). Only single parameters, as e.g. flow rate or salinization of the test solution, were varied during the experiments. By conducting these different test setups, conclusions could be drawn about the application of the push-pull method under different settings. References: Hebig, K.H., Ito, N., Scheytt, T.J. & Marui, A. (2011). Hydraulic and hydrochemical characterization of deep coastal sedimentary basins by single-well Push-Pull tests. GSA Annual Meeting, 9-12 October 2011, Minneapolis, USA. Zeilfelder, S., Ito, N., Marui, A., Hebig, K. & Scheytt, T. (2012). Push-Pull-Test und Tracer-Test in ei-nem tiefen Grundwasserleiter in Kameoka, Japan. Kurzfassung in: Liedl, R., Burghardt, D., Simon, E., Reimann, T. & Kaufmann-Knoke (Hg.). Grundwasserschutz und Grundwassernutzung. Tagung der Fachsektion Hydrogeologie in der DGG (FH-DGG). 16. - 20. Mai 2012, Dresden. Kurfassungen der Vorträge und Poster. Schriftenreihe der DGG, Heft 78, S. 192.

  12. The anomaly in a breakthrough curve of a single well "push-pull" tracer test: A density driven effect?

    NASA Astrophysics Data System (ADS)

    Zeilfelder, Sarah; Hebig, Klaus; Ito, Narimitsu; Machida, Isao; Scheytt, Traugott; Marui, Atsunao

    2013-04-01

    aspects as a source. In this version of the PP test higher salinized test solution was injected into the aquifer. There are several hypotheses that could explain the behavior of the breakthrough curves of the tracer in this test design. Of all the possibilities (like sorption processes, unexpected tracer reactions, inhomogeneities in the aquifer, influence of the well design), we assume that ion exchange processes and density driven flow are the main reasons for the repeatedly observed anomaly. References: Hebig, K.H., Ito, N., Scheytt, T.J. & Marui, A. (2011). Hydraulic and hydrochemical characterization of deep coastal sedimentary basins by single-well Push-Pull tests. GSA Annual Meeting, 9-12 October 2011, Minneapolis, USA. Zeilfelder, S., Ito, N., Marui, A., Hebig, K. & Scheytt, T. (2012). Push-Pull-Test und Tracer-Test in einem tiefen Grundwasserleiter in Kameoka, Japan. Kurzfassung in: Liedl, R., Burghardt, D., Simon, E., Reimann, T. & Kaufmann-Knoke (Hg.). Grundwasserschutz und Grundwassernutzung. Tagung der Fachsektion Hydrogeologie in der DGG (FH-DGG). 16. - 20. Mai 2012, Dresden. Kurfassungen der Vorträge und Poster. Schriftenreihe der DGG, Heft 78, S. 192.

  13. Microbial diversity and biogeochemistry in glacier forefields: assessment of ecological stability in high alpine environments

    NASA Astrophysics Data System (ADS)

    Meola, M.; Lazzaro, A.; Zeyer, J.

    2012-04-01

    Microbial communities inhabiting recently deglaciated, unvegetated, high alpine soils (e.g. glacier forefields) need to be adapted to fluctuating environmental conditions, such as strong daily and seasonal humidity and temperature variations. Soil-related characteristics (e.g. oligotrophy, pH, water holding capacity, nutrient concentration) may in addition determine the presence of locally adapted microbial communities. Currently little is known on the ecological stability (resistance and resilience) of such an environment. In this project, we aim at understanding ecological stability of microbial communities of alpine glacier forefields through a reciprocal soil transplantation experiment. The study consists in i) determining bacterial phylotypes that may respond to environmental changes and ii) relating biological, chemical and physical data to observed microbial responses. We selected two different glacier forefields located in the Swiss Alps (approximately at 2500 m.a.s.l.) The Griessen forefield (Canton Obwalden) is characterized by a calcareous bedrock, while the Tiefen forefield (Canton Uri) is of siliceous composition. The sites are well characterized in terms of their geography (e.g. exposure, slope) and climatic fluctuations (Lazzaro et al. 2009, Lazzaro et al. 2011). At each site, we incubated stainless steel pots with four different soil treatments (autochthonous untreated, autochthonous sterilized, allochthonous untreated and allochthonous sterilized). The setup was repeated in quadruplicate. Soil temperature and soil moisture at 10 cm depth were measured every hour by Decagon EM 50 sensors (Decagon Devices Inc.). In July (D0), August (D1) and September (D2) 2011, soil aliquots were sampled from the pots for analysis. We plan to further extend the sampling for at least three snow-free seasons (2011-2013). Chemical analysis of the soil encompassed soluble ions, pH and DOC. Bacterial community analysis included microbial biomass (DAPI cell counts), basal

  14. Quantification of atmospheric methane oxidation in glacier forefields: Initial survey results

    NASA Astrophysics Data System (ADS)

    Nauer, Philipp A.; Schroth, Martin H.; Pinto, Eric A.; Zeyer, Josef

    2010-05-01

    The oxidation of CH4 by methanotrophic bacteria is the only known terrestrial sink for atmospheric CH4. Aerobic methanotrophs are active in soils and sediments under various environmental conditions. However, little is known about the activity and abundance of methanotrophs in pioneering ecosystems and their role in succession. In alpine environments, receding glaciers pose a unique opportunity to investigate soil development and ecosystem succession. In an initial survey during summer and autumn 2009 we probed several locations in the forefields of four glaciers in the Swiss Alps to quantify the turnover of atmospheric methane in recently exposed soils. Three glacier forefields (the Stein, Steinlimi and Tiefen) are situated on siliceous bedrock, while one (the Griessen) is situated on calcareous bedrock. We sampled soil air from different depths to generate CH4 concentration profiles for qualitative analysis. At selected locations we applied surface Gas Push-Pull Tests (GPPT) to estimate first-order rate coefficients of CH4 oxidation. The test consists of a controlled injection of the reactants CH4 and O2 and the tracer Ar into and out of the soil at the same location. A top-closed steel cylinder previously emplaced in the soil encloses the injected gas mixture to ensure sufficient reaction times. Rate coefficients can be derived from differences of reactant and tracer breakthrough curves. In one GPPT we employed 13C-CH4 and measured the evolution of δ13C of extracted CO2. To confirm rate coefficients obtained by GPPTs we estimated effective soil diffusivity from soil core samples and fitted a diffusion-consumption model to our profile data. A qualitative analysis of the concentration profiles showed little activity in the forefields on siliceous bedrock, with only one out of fifteen locations exhibiting substantially lower CH4 concentrations in the soil compared to the atmosphere. The surface GPPTs with conventional CH4 at the active location were not sensitive

  15. Leicht konfigurierbare Hardware-Abstraktionsschicht für flexible Automatisierung

    NASA Astrophysics Data System (ADS)

    Schmidtmann, Uwe; Kreutz, Gerhard; Barkhoff, Matthias; Virkus, Kristian; Stöckmann, Tobias; Jovic, Marcel

    Energie- und Materialverbrauch, Qualität sowie Durchsatz werden heutzutage als die Parameter angesehen, die die Wirtschaftlichkeit einer Produktion wesentlich bestimmen. Sie zu optimieren ist daher eine zentrale Aufgabe der Entwicklung zukünftiger Fertigungsanlagen. Dieses Ziel lässt sich erreichen, indem der gesamte Fertigungsprozess über alle Schichten der Automatisierungspyramide (ERP, MES, Feld) flexibel und rekonfigurierbar gestaltet wird. Mit Hilfe des aktuellen Forschungsprojektes LK3S wird eine Agentenplattform entwickelt, die diese Optimierung und Flexibilität ermöglichen soll. Dieser Beitrag diskutiert das Design und die Entwicklung einer Hardware-Abstraktionsschicht der Feldebene, die alle von der Agentenplattform benötigten Dienste bereitstellt und die die Verbindung zwischen Arbeitsaufträgen und Automatisierungsprimitiven herstellt, z. B. die Montage eines Reifens durch einen Roboter. Automatisierungsprimitiven bestehen aus einer Folge von elementaren Operationen, womit sie auf unterster Ebene unter Einhaltung aller Echtzeitvorgaben parallelisiert werden können. Sie haben eine ähnliche Bedeutung wie Mikrocode für CPUs. Selbst zur Laufzeit können neue Automatisierungsprimitiven in der Feldebene definiert, übertragen, aktiviert und entfernt werden.

  16. Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH4.

    PubMed

    Reyes, Alberto V; Cooke, Colin A

    2011-03-22

    Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (14C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality 14C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal 14C dates from Alaska as a case study, we show that nearly half the 14C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated 14C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated 14C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH4 concentration at the start of the Bølling-Allerød interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH4. Our results demonstrate that subtle methodological changes in the synthesis of basal 14C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle.

  17. A linear and nonlinear study of Mira

    SciTech Connect

    Cox, A.N.; Ostlie, D.A.

    1991-12-31

    Both linear and nonlinear calculations of the 331 day, long period variable star Mira have been undertaken to see what radial pulsation mode is naturally selected. Models are similar to those considered in the linear nonadiabatic stellar pulsation study of Ostlie and Cox. Models are considered with masses near one solar mass, luminosities between 4000 and 5000 solar luminosities, and effective temperatures of approximately 3000 K. These models have fundamental mode periods that closely match the pulsation period of Mira. The equation of state for the stellar material is given by Stellingwerf procedure, and the opacity is obtained from a fit by Cahn that matches the low temperature molecular absorption data for the Population I Ross-Aller 1 mixture calculated from the Los Alamos Astrophysical Opacity Library. For the linear study, the Cox, Brownlee, and Eilers approximation is used for the linear theory variation of the convection luminosity. For the nonlinear work, the method described by Ostlie and Cox is followed. Results showing internal details of the radial fundamental and first overtone modes behavior in linear theory are presented. Preliminary radial fundamental mode nonlinear calculations are discussed. The very tentative conclusion is that neither the fundamental or first overtone mode is excluded from being the actual observed one.

  18. Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas

    PubMed Central

    Petaev, Michail I.; Huang, Shichun; Jacobsen, Stein B.; Zindler, Alan

    2013-01-01

    One explanation of the abrupt cooling episode known as the Younger Dryas (YD) is a cosmic impact or airburst at the YD boundary (YDB) that triggered cooling and resulted in other calamities, including the disappearance of the Clovis culture and the extinction of many large mammal species. We tested the YDB impact hypothesis by analyzing ice samples from the Greenland Ice Sheet Project 2 (GISP2) ice core across the Bølling-Allerød/YD boundary for major and trace elements. We found a large Pt anomaly at the YDB, not accompanied by a prominent Ir anomaly, with the Pt/Ir ratios at the Pt peak exceeding those in known terrestrial and extraterrestrial materials. Whereas the highly fractionated Pt/Ir ratio rules out mantle or chondritic sources of the Pt anomaly, it does not allow positive identification of the source. Circumstantial evidence such as very high, superchondritic Pt/Al ratios associated with the Pt anomaly and its timing, different from other major events recorded on the GISP2 ice core such as well-understood sulfate spikes caused by volcanic activity and the ammonium and nitrate spike due to the biomass destruction, hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis. PMID:23878232

  19. Crimson Tide: The Harvard Books on Astronomy

    NASA Astrophysics Data System (ADS)

    Lindner, R. P.

    2001-12-01

    The Harvard Books on Astronomy, a series of crimson clad, fully illustrated volumes, cornered, for more than a generation, the market of readers interested in astronomy. A large number of astronomers owe their first serious initiation to the literature of astronomy to these books. Their style, presentation, design, and tone marked a clear departure from the inherited traditions in the field. Each summed up a field, awarded points for merit, and staked out paths for future study. No doubt each of the more mature readers of this abstract has his or her favorite volume, and even his or her own favorite edition of a particular volume. How the volumes evolved and what happened to the series with Harlow Shapley's retirement are not only questions in the history of the book but also form a commentary on the standards of scientific writing for the educated public. For this the major evidence comes from the volumes by Shapley himself, Leo Goldberg and Lawrence Aller, and the Boks. This paper discusses the origins of the series, the purpose of the works, the varying successes of the volumes, and the impact they had on the future astronomical community. In part, this is a contribution to the impact of Harlow Shapley upon the wider field and the role of Harvard in the American astronomical community. It is also a meditation upon the ways of recruitment into the field and forming ways of looking at research problems.

  20. Timing and new geomorphologic evidence of the last deglaciation stages in Sierra Nevada (southern Spain)

    NASA Astrophysics Data System (ADS)

    Palacios, David; Gómez-Ortiz, Antonio; Andrés, Nuria; Salvador, Ferrán; Oliva, Marc

    2016-10-01

    The main objective of this research is to improve knowledge of the deglaciation stages in Sierra Nevada (southern Spain) by applying 36Cl cosmogenic exposure dating to 28 samples from moraine and fossil rock glacier boulders and glacial polished surfaces, in 5 glaciated valleys around Veleta Peak (3396 m asl; 37°03‧02″N 3°20‧54″W). The results show that shortly before the Last Glacial Maximum (LGM) and during the LGM, the heads of the glacial valleys were occupied by ice tongues, with possible glacial transfluence between the valleys. After 19 ka, a major glacial regression started, but glaciers during the Oldest Dryas (OD) expanded again and refilled the valley bottoms. The glacial advances of the pre-LGM, LGM and OD formed polygenic moraine systems. During the Bølling-Allerød the glaciers receded and probably disappeared. Thereafter, the valley bottoms remained ice-free. During the Younger Dryas (YD) small glaciers developed again, but only in cirques shaped on east-facing slopes. Subsequently, these glaciers started retreating towards their valley heads and finally disappeared completely. With the onset of the Holocene, rock glaciers developed inside the deglaciated cirques on the eastern slopes of some valleys, but only under the most active and protected headwalls did large complex rock glaciers develop and remained active until the mid-Holocene.

  1. Evaluation of feed and feeding regime on growth performance, flesh quality and fecal viscosity of Atlantic salmon ( Salmo salar L.) in recirculating aquaculture systems

    NASA Astrophysics Data System (ADS)

    Sun, Guoxiang; Liu, Ying; Li, Yong; Li, Xian; Wang, Shunkui

    2015-10-01

    The effects of different feeds and feeding regimes on growth performance, flesh quality and fecal viscosity of Atlantic salmon ( Salmo salar L.) in recirculating aquaculture systems (RAS) were investigated. Fish (initial body weight of 1677 g ± 157 g) were fed with four commercial feeds (Nosan salmon-NS, Aller gold-AG, Skretting salmon-SS and Han ye-HY) in two feeding regimes (80% and 100% satiation) for 78 d. The results showed that salmon specific growth ratio (SGR) and weight gain ratio (WGR) were significantly affected by feed type and feeding regime ( P < 0.05). Feed conversion ratio (FCR) varied between 0.93 and 3.40, which was significantly affected by feed type ( P < 0.05), and slightly improved with increased satiation degree. The activities of digestive enzymes including protease, lipase and amylase were also significantly affected by feed type and feeding regime ( P < 0.05), increasing with satiation degree. Flesh qualities for vitamin E, hydroxyproline (HYP), liquid loss and muscle pH among all groups showed significant differences ( P < 0.05), ranging from 26.67 to 29.67, while no obvious difference was found in flesh color. Fecal viscosity for different treatments showed no significant difference, though improvement was found in 100% satiation group. From present experiment, it was concluded that both feed type and feeding regime can affect the important quality attributes of Atlantic salmon.

  2. Increased Drake Passage through-flow triggered abrupt re-invigoration of Atlantic Overturning Circulation during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Roberts, J.; McCave, I. N. N.; McClymont, E.; Kender, S.; Hillenbrand, C. D.; Matano, R. P.; Hodell, D. A.; Peck, V. L.

    2016-12-01

    The position of Antarctic Circumpolar Current (ACC) fronts in the Drake Passage is important for the supply of low-density intermediate water into the Atlantic, and is thus key to the stability of Atlantic Meridional Overturning Circulation (AMOC). We examined changes in the position of ACC fronts by reconstructing flow speed and temperature in the Drake Passage over the last 25,000 years. A dramatic convergence of flow speeds and temperatures at the entrance and exit of Drake Passage 14,700 years ago indicates a significant southward shift of the sub-Antarctic Front from a position north of Drake Passage. The timing of this southward shift coincides with an abrupt re-invigoration of AMOC at the onset of the Bølling-Allerød. We argue that 14,700 years ago, a southward shift in the position of the ACC fronts relative to Drake Passage enabled low-density intermediate water to enter the Atlantic; this accentuated the meridional density gradient in the Atlantic causing an abrupt re-invigoration of AMOC.

  3. [Asthma and cyclic neutropenia].

    PubMed

    Salazar Cabrera, A N; Berrón Pérez, R; Ortega Martell, J A; Onuma Takane, E

    1996-01-01

    We report a male with history of recurrent infections (recurrent oral aphtous disease [ROAD], middle ear infections and pharyngo amigdalitis) every 3 weeks since he was 7 months old. At the age of 3 years cyclic neutropenia was diagnosed with cyclic fall in the total neutrophil count in blood smear every 21 days and prophylactic antimicrobial therapy was indicated. Episodic events every 3 weeks of acute asthma and allergic rhinitis were detected at the age of 6 years old and specific immunotherapy to Bermuda grass was given during 3 years with markedly improvement in his allergic condition but not in the ROAD. He came back until the age of 16 with episodic acute asthma and ROAD. The total neutrophil count failed to 0 every 21 days and surprisingly the total eosinophil count increased up to 2,000 at the same time, with elevation of serum IgE (412 Ul/mL). Specific immunotherapy to D.pt. and Aller.a. and therapy with timomodulin was indicated. After 3 months we observed clinical improvement in the asthmatic condition and the ROAD disappeared, but the total neutrophil count did not improve. We present this case as a rare association between 2 diseases with probably no etiological relationship but may be physiopatological that could help to understand more the pathogenesis of asthma.

  4. Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas.

    PubMed

    Petaev, Michail I; Huang, Shichun; Jacobsen, Stein B; Zindler, Alan

    2013-08-06

    One explanation of the abrupt cooling episode known as the Younger Dryas (YD) is a cosmic impact or airburst at the YD boundary (YDB) that triggered cooling and resulted in other calamities, including the disappearance of the Clovis culture and the extinction of many large mammal species. We tested the YDB impact hypothesis by analyzing ice samples from the Greenland Ice Sheet Project 2 (GISP2) ice core across the Bølling-Allerød/YD boundary for major and trace elements. We found a large Pt anomaly at the YDB, not accompanied by a prominent Ir anomaly, with the Pt/Ir ratios at the Pt peak exceeding those in known terrestrial and extraterrestrial materials. Whereas the highly fractionated Pt/Ir ratio rules out mantle or chondritic sources of the Pt anomaly, it does not allow positive identification of the source. Circumstantial evidence such as very high, superchondritic Pt/Al ratios associated with the Pt anomaly and its timing, different from other major events recorded on the GISP2 ice core such as well-understood sulfate spikes caused by volcanic activity and the ammonium and nitrate spike due to the biomass destruction, hints for an extraterrestrial source of Pt. Such a source could have been a highly differentiated object like an Ir-poor iron meteorite that is unlikely to result in an airburst or trigger wide wildfires proposed by the YDB impact hypothesis.

  5. The spatial extent and dynamics of the Antarctic Cold Reversal

    NASA Astrophysics Data System (ADS)

    Pedro, Joel B.; Bostock, Helen C.; Bitz, Cecilia M.; He, Feng; Vandergoes, Marcus J.; Steig, Eric J.; Chase, Brian M.; Krause, Claire E.; Rasmussen, Sune O.; Markle, Bradley R.; Cortese, Giuseppe

    2016-01-01

    Antarctic ice cores show that a millennial-scale cooling event, the Antarctic Cold Reversal (14,700 to 13,000 years ago), interrupted the last deglaciation. The Antarctic Cold Reversal coincides with the Bølling-Allerød warm stage in the North Atlantic, providing an example of the inter-hemispheric coupling of abrupt climate change generally referred to as the bipolar seesaw. However, the ocean-atmosphere dynamics governing this coupling are debated. Here we examine the extent and expression of the Antarctic Cold Reversal in the Southern Hemisphere using a synthesis of 84 palaeoclimate records. We find that the cooling is strongest in the South Atlantic and all regions south of 40° S. At the same time, the terrestrial tropics and subtropics show abrupt hydrologic variations that are significantly correlated with North Atlantic climate changes. Our transient global climate model simulations indicate that the observed extent of Antarctic Cold Reversal cooling can be explained by enhanced northward ocean heat transport from the South to North Atlantic, amplified by the expansion and thickening of sea ice in the Southern Ocean. The hydrologic variations at lower latitudes result from an opposing enhancement of southward heat transport in the atmosphere mediated by the Hadley circulation. Our findings reconcile previous arguments about the relative dominance of ocean and atmospheric heat transports in inter-hemispheric coupling, demonstrating that the spatial pattern of past millennial-scale climate change reflects the superposition of both.

  6. Eastern tropical Pacific vegetation response to rapid climate change and sea level rise: A new pollen record from the Gulf of Tehuantepec, southern Mexico

    NASA Astrophysics Data System (ADS)

    Hendy, I. L.; Minckley, T. A.; Whitlock, C.

    2016-08-01

    A 30,000-year-long pollen record from the Gulf of Tehuantepec, southern Mexico shows the varying influence of air temperature, precipitation and eustatic sea-level rise on changes in coastal and upland vegetation patterns. During the late-glacial period, pine-juniper forests grew in the Sierra Madre del Sur along the Pacific Slope with broadleaf forests present at low elevations. Coastal wetland and riparian vegetation were limited in distribution. Significant cooling associated with Heinrich 1 (17,000-15,000 cal yr BP) resulted in an expansion of pine-juniper woodland. By the time of Bølling-Allerød warming (14,700-13,000 cal yr BP), extensive mangrove forest development was assisted by sea-level rise and reduced precipitation associated with a more southerly position of the Intertropical Convergence Zone (ITCZ) than at present. Concurrently, the expansion of oak into pine woodlands was promoted by warmer conditions than before. Increased summer precipitation in the early Holocene and stabilizing sea levels limited mangrove forests along the coast and allowed mixed conifer and hardwood forest to become more widespread inland. The onset of a more seasonal climate, driven by a weakening of the Mexican monsoon and a southerly shift in ITCZ position led to the establishment of modern open forests of pine and oak after 4300 cal yr BP.

  7. Abrupt climate change and collapse of deep-sea ecosystems

    USGS Publications Warehouse

    Yasuhara, Moriaki; Cronin, T. M.; Demenocal, P.B.; Okahashi, H.; Linsley, B.K.

    2008-01-01

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Aller??d Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until ???8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less. ?? 2008 by The National Academy of Sciences of the USA.

  8. Late Glacial vegetation reconstruction based on leaf waxes from the Gemündener Maar, Germany

    NASA Astrophysics Data System (ADS)

    Wüthrich, Lorenz; Lutz, Selina; Zech, Michael; Hepp, Johannes; Sirocko, Frank; Zech, Roland

    2015-04-01

    Lake sediments are valuable archives for the reconstruction of past changes in climate and vegetation. In the present study, we analyse samples from the Gemündener Maar, a lake situated in the western Eiffel, Germany, for their leaf wax composition: In the bottom part of the core, corresponding to the Oldest Dryas (i.e. older than ~15 ka), n-alkanes have a high average chain length (ACL), which points to a vegetation dominated by grass. During the Bölling/Alleröd, a decrease of the ACL can be interpreted as signal of more deciduous trees. During the Younger Dryas (~12.8 to 11.5 ka), the ACL increases again. Trees probably became again less abundant, before finally, the ACL records the return of deciduous trees during the early Holocene. In general, the total concentrations of both, n-alkanes and sugar biomarkers are high enough to measure compound-specific isotopes on n-alkanes (deuterium) and sugars (18-O). Combined, these two isotopes might help to obtain more information about the relative humidity and mean air temperature during the late glacial.

  9. Berlin in Motion: Interprofessional teaching and learning for students in the fields of medicine, occupational therapy, physiotherapy and nursing (INTER-M-E-P-P).

    PubMed

    Bohrer, Annerose; Heinze, Cornelia; Höppner, Heidi; Behrend, Ronja; Czakert, Judith; Hitzblech, Tanja; Kaufmann, Ina; Maaz, Asja; Räbiger, Jutta; Peters, Harm

    2016-01-01

    Zielsetzung: Das Berliner Projekt „Interprofessionelles Lehren und Lernen in Medizin, Ergotherapie, Physiotherapie und Pflege“ (INTER-M-E-P-P) verfolgt das Ziel, interprofessionelle Lehrveranstaltungen modellhaft zu entwickeln, zu erproben und in die Curricula der Studiengänge zu implementieren. Methodik: Unter der Leitung einer institutions-, professions- und statusübergreifenden Lenkungsgruppe werden interprofessionelle Lehrveranstaltungen konzipiert, durchgeführt und evaluiert. Spezifisch sind die studentische Partizipation in der Lenkungsgruppe und die Begleitung durch externe Supervision. Die Evaluation integriert die Perspektiven aller am Projekt Beteiligten und kombiniert qualitative und quantitative Methoden. Ergebnisse: INTER-M-E-P-P hat Strukturen zur Kooperation der beteiligten Hochschulen und Studiengänge aufgebaut. Drei Lehrveranstaltungen wurden interprofessionell konzipiert, durchgeführt und evaluiert. Die unterschiedliche curriculare, strukturelle und räumliche Verortung der Studiengänge führt zu einem hohen, ressourcenintensiven Planungs- und Umsetzungsaufwand. Stereotype und Rollenbilder der Planenden können den Prozess erschweren; unter externer Supervision jedoch die professionsspezifischen Blickwinkel erweitern und bereichern.Schlussfolgerung: Eine nachhaltige Implementierung von IPL in die Curricula der Gesundheitsstudiengänge ist derzeit durch Barrieren wie die räumliche Trennung und verschiedene Studien- und Prüfungsordnungen erschwert. Sie benötigt dauerhafte Unterstützungsstrukturen auf hochschulischer und politischer Ebene.

  10. Abrupt climate change and collapse of deep-sea ecosystems.

    PubMed

    Yasuhara, Moriaki; Cronin, Thomas M; Demenocal, Peter B; Okahashi, Hisayo; Linsley, Braddock K

    2008-02-05

    We investigated the deep-sea fossil record of benthic ostracodes during periods of rapid climate and oceanographic change over the past 20,000 years in a core from intermediate depth in the northwestern Atlantic. Results show that deep-sea benthic community "collapses" occur with faunal turnover of up to 50% during major climatically driven oceanographic changes. Species diversity as measured by the Shannon-Wiener index falls from 3 to as low as 1.6 during these events. Major disruptions in the benthic communities commenced with Heinrich Event 1, the Inter-Allerød Cold Period (IACP: 13.1 ka), the Younger Dryas (YD: 12.9-11.5 ka), and several Holocene Bond events when changes in deep-water circulation occurred. The largest collapse is associated with the YD/IACP and is characterized by an abrupt two-step decrease in both the upper North Atlantic Deep Water assemblage and species diversity at 13.1 ka and at 12.2 ka. The ostracode fauna at this site did not fully recover until approximately 8 ka, with the establishment of Labrador Sea Water ventilation. Ecologically opportunistic slope species prospered during this community collapse. Other abrupt community collapses during the past 20 ka generally correspond to millennial climate events. These results indicate that deep-sea ecosystems are not immune to the effects of rapid climate changes occurring over centuries or less.

  11. Hunted gazelles evidence cooling, but not drying, during the Younger Dryas in the southern Levant.

    PubMed

    Hartman, Gideon; Bar-Yosef, Ofer; Brittingham, Alex; Grosman, Leore; Munro, Natalie D

    2016-04-12

    The climatic downturn known globally as the Younger Dryas (YD; ∼12,900-11,500 BP) has frequently been cited as a prime mover of agricultural origins and has thus inspired enthusiastic debate over its local impact. This study presents seasonal climatic data from the southern Levant obtained from the sequential sampling of gazelle tooth carbonates from the Early and Late Natufian archaeological sites of Hayonim and Hilazon Tachtit Caves (western Galilee, Israel). Our results challenge the entrenched model that assumes that warm temperatures and high precipitation are synonymous with climatic amelioration and cold and wet conditions are combined in climatic downturns. Enamel carbon isotope values from teeth of human-hunted gazelle dating before and during the YD provide a proxy measure for water availability during plant growth. They reveal that although the YD was cooler, it was not drier than the preceding Bølling-Allerød. In addition, the magnitude of the seasonal curve constructed from oxygen isotopes is significantly dampened during the YD, indicating that cooling was most pronounced in the growing season. Cool temperatures likely affected the productivity of staple wild cereal resources. We hypothesize that human groups responded by shifting settlement strategies-increasing population mobility and perhaps moving to the warmer Jordan Valley where wild cereals were more productive and stable.

  12. Hunted gazelles evidence cooling, but not drying, during the Younger Dryas in the southern Levant

    PubMed Central

    Hartman, Gideon; Bar-Yosef, Ofer; Brittingham, Alex; Grosman, Leore; Munro, Natalie D.

    2016-01-01

    The climatic downturn known globally as the Younger Dryas (YD; ∼12,900–11,500 BP) has frequently been cited as a prime mover of agricultural origins and has thus inspired enthusiastic debate over its local impact. This study presents seasonal climatic data from the southern Levant obtained from the sequential sampling of gazelle tooth carbonates from the Early and Late Natufian archaeological sites of Hayonim and Hilazon Tachtit Caves (western Galilee, Israel). Our results challenge the entrenched model that assumes that warm temperatures and high precipitation are synonymous with climatic amelioration and cold and wet conditions are combined in climatic downturns. Enamel carbon isotope values from teeth of human-hunted gazelle dating before and during the YD provide a proxy measure for water availability during plant growth. They reveal that although the YD was cooler, it was not drier than the preceding Bølling–Allerød. In addition, the magnitude of the seasonal curve constructed from oxygen isotopes is significantly dampened during the YD, indicating that cooling was most pronounced in the growing season. Cool temperatures likely affected the productivity of staple wild cereal resources. We hypothesize that human groups responded by shifting settlement strategies—increasing population mobility and perhaps moving to the warmer Jordan Valley where wild cereals were more productive and stable. PMID:27035951

  13. Climate-induced fluvial dynamics in tropical Africa around the last glacial maximum?

    NASA Astrophysics Data System (ADS)

    Sangen, Mark; Neumann, Katharina; Eisenberg, Joachim

    2011-11-01

    The alluvia of the Ntem, Nyong and Sanaga fluvial systems in southern Cameroon recorded repeated fluvial activity fluctuations during the Late Pleistocene, including the last glacial maximum (LGM), the beginning of the African Humid Period and the northern hemispheric Bølling-Allerød. We applied a multi-proxy approach on alluvial stratigraphies dated between 22.4 and 13.0 cal ka BP, including remote sensing, sedimentological and morphogenetic methods, phytoliths, sponge spicules, 14C and δ 13C data. A distinct NE-SW gradient of landscape and fluvial dynamics around the LGM can be drawn, with evidence for the persistence of extended fluvial rainforest refuges only in the Ntem catchment. The Sanaga and Nyong catchment areas were characterized by frequent channel migrations, floodplain reorganization and unstable vegetation subject to fire, including grasslands, woodlands, and gallery forests with bamboo thickets. In spite of increasing rainfall after 16.4 cal ka BP, persisting landscape instability played the major role for fluvial system dynamics, floodplain transformations and vegetation development until 13.0 cal ka BP, before a general landscape stabilization and rainforest expansion set in at the beginning of the Holocene.

  14. Environmental transformations and cultural changes: A multidisciplinary case study for the Late Glacial and Final Palaeolithic from Northern Germany

    NASA Astrophysics Data System (ADS)

    Turner, F.; Tolksdorf, J. F.; Viehberg, F.; Schwarz, A.; von Bramann, U.; Bittmann, F.; Kaiser, K.; Schwalb, A.; Staesche, U.; Breest, K.; Pott, R.; Veil, S.

    2012-04-01

    In contrast to younger periods, studies integrating archaeological and environmental records for the Palaeolithic are still rare. Especially our knowledge about interactions between the drastic climatic/environmental changes and cultural developments during the Late Glacial is very limited. This multidisciplinary case study from river Jeetzel, a western Elbe tributary in Northern Germany, combines high resolution palaeoenvironmental investigations with fine-scaled archaeological research on stratified and surface sites. Various dating methods (palynostratigraphy, radiocarbon- and OSL-dating) and analyses of environmental and climatological proxies (pollen and plant macro-remains, ostracods, diatoms and green algae) on river palaeochannel sediments allow detailed reconstruction of interactions between Late Glacial climate, vegetation and fluvial developments. Biostratigraphical analyses on stratified archaeological sites and dating of charcoal / bone fragments from artefact scatters place the Late Palaeolithic occupation of Early Federmesser groups in an environmental context. Thus the former production of hitherto unknown amber art (amongst others a figurine representing a moose) can be ascribed to the Older Dryas and Early Allerød, which are the periods of main Late Glacial afforestation. Therewith our investigations suggest that Final Palaeolithic cultural changes may have been triggered by climatic and environmental transformations.

  15. Microfossils, a Key to Unravel Cold-Water Carbonate Mound Evolution through Time: Evidence from the Eastern Alboran Sea

    PubMed Central

    Stalder, Claudio; Vertino, Agostina; Rosso, Antonietta; Rüggeberg, Andres; Pirkenseer, Claudius; Spangenberg, Jorge E.; Spezzaferri, Silvia; Camozzi, Osvaldo; Rappo, Sacha; Hajdas, Irka

    2015-01-01

    Cold-water coral (CWC) ecosystems occur worldwide and play a major role in the ocean's carbonate budget and atmospheric CO2 balance since the Danian (~65 m.y. ago). However their temporal and spatial evolution against climatic and oceanographic variability is still unclear. For the first time, we combine the main macrofaunal components of a sediment core from a CWC mound of the Melilla Mounds Field in the Eastern Alboran Sea with the associated microfauna and we highlight the importance of foraminifera and ostracods as indicators of CWC mound evolution in the paleorecord. Abundances of macrofauna along the core reveal alternating periods dominated by distinct CWC taxa (mostly Lophelia pertusa, Madrepora oculata) that correspond to major shifts in foraminiferal and ostracod assemblages. The period dominated by M. oculata coincides with a period characterized by increased export of refractory organic matter to the seafloor and rather unstable oceanographic conditions at the benthic boundary layer with periodically decreased water energy and oxygenation, variable bottom water temperature/density and increased sediment flow. The microfaunal and geochemical data strongly suggest that M. oculata and in particular Dendrophylliidae show a higher tolerance to environmental changes than L. pertusa. Finally, we show evidence for sustained CWC growth during the Alleröd-Younger-Dryas in the Eastern Alboran Sea and that this period corresponds to stable benthic conditions with cold/dense and well oxygenated bottom waters, high fluxes of labile organic matter and relatively strong bottom currents PMID:26447699

  16. Evidence for a biological pump driver of atmospheric CO2 rise during Heinrich Stadial 1

    NASA Astrophysics Data System (ADS)

    Hertzberg, Jennifer E.; Lund, David C.; Schmittner, Andreas; Skrivanek, Alexandra L.

    2016-12-01

    The initial trigger of the atmospheric CO2 rise during Heinrich Stadial 1 (HS1: 14.5-17.5 kyr B.P.) remains elusive. We present a compilation of four paired surface and intermediate-depth foraminiferal δ13C records to test whether reduced biological pump efficiency led to the initial CO2 rise during the last deglaciation. Surface ocean δ13C decreased across HS1 while intermediate-depth δ13C increased, leading to a reduction in the upper ocean δ13C gradient. Our compilation also suggests the δ13C gradient increased during the Bølling-Allerød (12.9-14.5 kyr B.P.) and decreased during the Younger Dryas (YD: 11.7-12.9 kyr B.P.). The HS1 and YD data are consistent with reduced biological export of isotopically light carbon from the surface ocean and its remineralization at depth. Our results support the idea that a weaker Atlantic Meridional Overturning Circulation decreased biological pump efficiency by increasing the overall fraction of preformed nutrients in the global ocean, leading to an increase in atmospheric CO2.

  17. Investigating the Influence of Climate Changes on Rodent Communities at a Regional-Scale (MIS 1-3, Southwestern France)

    PubMed Central

    Royer, Aurélien; Montuire, Sophie; Legendre, Serge; Discamps, Emmanuel; Jeannet, Marcel; Lécuyer, Christophe

    2016-01-01

    Terrestrial ecosystems have continuously evolved throughout the Late Pleistocene and the Holocene, deeply affected by both progressive environmental and climatic modifications, as well as by abrupt and large climatic changes such as the Heinrich or Dansgaard-Oeschger events. Yet, the impacts of these different events on terrestrial mammalian communities are poorly known, as is the role played by potential refugia on geographical species distributions. This study examines community changes in rodents of southwestern France between 50 and 10 ky BP by integrating 94 dated faunal assemblages coming from 37 archaeological sites. This work reveals that faunal distributions were modified in response to abrupt and brief climatic events, such as Heinrich events, without actually modifying the rodent community on a regional scale. However, the succession of events which operated between the Late Pleistocene and the Holocene gradually led to establishing a new rodent community at the regional scale, with intermediate communities occurring between the Bølling and the Allerød. PMID:26789523

  18. High-resolution multi-proxy evidence for millennial- and centennial-scale climate oscillations during the last deglaciation in Jeju Island, South Korea

    NASA Astrophysics Data System (ADS)

    Park, Jungjae; Lim, Hyoun Soo; Lim, Jaesoo; Park, Yong-Hee

    2014-12-01

    Millennial- and centennial-scale climate and vegetation changes during the last deglaciation from Hanon Maar paleolake on Jeju Island, South Korea were reconstructed by high-resolution multi-proxy data (pollen, Anhysteretic Remanent Magnetization [ARM], Total Organic Carbon [TOC], Total Nitrogen [TN], Carbon/Nitrogen [C/N] ratio, carbon and nitrogen isotope compositions (δ15N and δ13C), major element geochemistry, and sediment grain size). The resolution of our multi-proxy data was sufficiently high to enable the detection of millennial- and even centennial-scale climate change in the study area during the last deglacial transition. We found centennial-scale cold reversals between 14,650 and 12,900 cal yr BP, possibly corresponding to the Bølling-Allerød [BA] oscillations. Hanon pollen data implied that climate amelioration around 11,900 cal yr BP terminated the Younger Dryas [YD] in the study area and that a cold event around 11,300 cal yr BP probably correlated with the Pre-Boreal Oscillation [PBO] cooling event. Our results indicate that rising summer insolation and northward expanding low-latitudinal warm currents exerted a strong influence on climatological teleconnection via westerlies between the North Atlantic and the East Asian region during the last deglaciation, presumably causing a decoupling between temperature and East Asian Summer Monsoon [EASM] precipitation during the last deglaciation.

  19. Von neuen Geschäftsideen zur gelebten Digitalisierung in Utility 4.0 - das Integrierte Geschäftsmodell

    NASA Astrophysics Data System (ADS)

    Doleski, Oliver D.

    Die Energiewirtschaft benötigt neue, digitale Geschäftsmodelle. Gegenwärtig folgt auf Liberalisierung und Energiewende die nächste Stufe einer weitreichenden Bereinigung des Versorgungsmarktes. Digitalisierung und Dezentralisierung sind heute in aller Munde und verlangen nach neuen Produkten und Dienstleistungen. Dabei wirken die immensen Herausforderungen einer digitalen Energiewelt wie Beschleuniger für die Transformation im Versorgungssektor und tragen damit zur breiten Etablierung von Utilities 4.0 bei. Dieser Entwicklungsprozess vollzieht sich mithilfe unterschiedlicher Methoden zur Realisierung neuer Geschäftsideen. Allerdings greifen die gängigen Konzepte zur Entwicklung von Geschäftsmodellen gerade im Hinblick auf die Berücksichtigung komplexer, unbeständiger Rahmenbedingungen und spezifischer Anforderungen der digitalen Energiewelt mitunter zu kurz. Vor diesem Hintergrund wird das auf dem ganzheitlichen St. Galler Management-Konzept beruhende Integrierte Geschäftsmodell iOcTen als geeignetes Instrumentarium zur Geschäftsmodellentwicklung vorgestellt. Neben der Modellbeschreibung unterstützt ein intuitiv verständlicher Leitfaden den Praktiker bei der Transformation vom klassischen Versorgungsunternehmen zum digitalen Energiedienstleistungsunternehmen.

  20. Changing amounts and sources of moisture in the U.S. southwest since the Last Glacial Maximum in response to global climate change

    USGS Publications Warehouse

    Feng, Weimin; Hardt, Benjamin F.; Banner, Jay L.; Meyer, Kevin J.; James, Eric W.; Musgrove, MaryLynn; Edwards, R. Lawrence; Cheng, Hai; Min, Angela

    2014-01-01

    The U.S. southwest has a limited water supply and is predicted to become drier in the 21st century. An improved understanding of factors controlling moisture sources and availability is aided by reconstruction of past responses to global climate change. New stable isotope and growth-rate records for a central Texas speleothem indicate a strong influence of Gulf of Mexico (GoM) moisture and increased precipitation from 15.5 to 13.5 ka, which includes the majority of the Bølling–Allerød warming (BA: 14.7–12.9 ka). Coeval speleothem records from 900 and 1200 km to the west allow reconstruction of regional moisture sources and atmospheric circulation. The combined isotope and growth-rate time series indicates 1) increased GoM moisture input during the majority of the BA, producing greater precipitation in Texas and New Mexico; and 2) a retreat of GoM moisture during Younger Dryas cooling (12.9–11.5 ka), reducing precipitation. These results portray how late-Pleistocene atmospheric circulation and moisture distribution in this region responded to global changes, providing information to improve models of future climate.

  1. Postglacial response of Arctic Ocean gas hydrates to climatic amelioration

    NASA Astrophysics Data System (ADS)

    Serov, Pavel; Vadakkepuliyambatta, Sunil; Mienert, Jürgen; Patton, Henry; Portnov, Alexey; Silyakova, Anna; Panieri, Giuliana; Carroll, Michael L.; Carroll, JoLynn; Andreassen, Karin; Hubbard, Alun

    2017-06-01

    Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate change, the processes and rates of subsurface/atmospheric natural gas exchange remain uncertain. Here we investigate the dynamics between gas hydrate stability and environmental changes from the height of the last glaciation through to the present day. Using geophysical observations from offshore Svalbard to constrain a coupled ice sheet/gas hydrate model, we identify distinct phases of subglacial methane sequestration and subsequent release on ice sheet retreat that led to the formation of a suite of seafloor domes. Reconstructing the evolution of this dome field, we find that incursions of warm Atlantic bottom water forced rapid gas hydrate dissociation and enhanced methane emissions during the penultimate Heinrich event, the Bølling and Allerød interstadials, and the Holocene optimum. Our results highlight the complex interplay between the cryosphere, geosphere, and atmosphere over the last 30,000 y that led to extensive changes in subseafloor carbon storage that forced distinct episodes of methane release due to natural climate variability well before recent anthropogenic warming.

  2. Paleomagnetic correlations between scandinavian ice-sheet fluctuations and greenland dansgaard-oeschger events, 45,000-25,000 yr B.P.

    NASA Astrophysics Data System (ADS)

    Mangerud, Jan; Løvlie, Reidar; Gulliksen, Steinar; Hufthammer, Anne-Karin; Larsen, Eiliv; Valen, Vidar

    2003-03-01

    Two paleomagnetic excursions, the Skjong correlated with the Laschamp (about 41,000 GISP2 yr B.P.) and the Valderhaug correlated with the Mono Lake (about 34,000 GISP2 yr B.P.), have been identified in stratigraphic superposition in laminated clay deposited in ice-dammed lakes in three large caves in western Norway. During both periods the margin of the Scandinavian Ice Sheet advanced and reached the continental shelf beyond the outermost coastline. The mild, 4000-yr-long Ålesund interstade, when the coast and probably much of the hinterland were ice-free, separated the two glacial advances. The two paleomagnetic excursions have also been indirectly identified as increased fluxes of 36Cl and 10Be in the GRIP ice core, Greenland. This article presents a correlation between ice-margin fluctuations of the Scandinavian Ice Sheet and the stratigraphy of GRIP/GISP cores, using the paleomagnetic excursions and the 36Cl and 10Be peaks and thus circumventing the application of different dates or time scales. Some of the fluctuations of the Scandinavian Ice Sheet were of the "Allerød/Younger Dryas type" in the sense that its margin retreated during mild interstades on Greenland and readvanced during cold stades. However, some fluctuations were apparently not in phase with the Greenland climate.

  3. Deglacial subsurface injections of Atlantic water into the Nordic Seas and its effect on interglacial climate development

    NASA Astrophysics Data System (ADS)

    Bauch, H. A.

    2012-04-01

    Using multi-proxy sediment records from two distant sites in the North Atlantic and the Nordic Seas, surface and bottom water changes were investigated over the past 135 ka with special emphasis on the last and present interglacial (Eemian and Holocene). The two interglacials exhibit a very similar developing structure during each preceding deglaciation (TI and TII) in the Nordic Seas by showing a pronounced cold-warm-cold variability. Like TI, also TII experienced a Younger-Dryas-like cold reversal (YDII), a preceding Bølling/Allerød-like (B/AII) and a H-event (H11). But unlike TI, the cold events during TII were associated with intermittent invasions of an Atlantic faunal component (Beella megastoma) which underscores a northward penetration of mid-latitude waters at the subsurface leaving a vertical water mass structure in the North which differed from that of TI. Very likely, this difference also affected the subsequent oceanic development because the main interglacials that followed not only reveal a regional antiphase, intra-interglacial behavior of peak ocean warmth between each other, they also verify strong contrasts in surface ocean hydrography. Moreover, colder Eemian than Holocene temperatures are noted in the Nordic Seas, and vice versa in the North Atlantic. A reduced intensity of Atlantic ocean heat transfer to the Arctic is therefore inferred for the Eemian, thus arguing for a reassessment of current Arctic paleoclimate models and a better reconciliation with empirical field data.

  4. Benthic foraminiferal stable isotope record of organic carbon fluxes during deposition of Mediterranean sapropel S1

    NASA Astrophysics Data System (ADS)

    Theodor, Marc; Schmiedl, Gerhard; Mackensen, Andreas

    2016-04-01

    We integrated Late Glacial to Holocene stable isotope records for different epi- and endobenthic foraminifera from the Mediterranean Sea in order to document the sequence of environmental changes across formation of the most recent sapropel S1. The stable carbon isotope record of epibenthic taxa corroborates results from model experiments indicating a Late Glacial onset of deep-water stagnation with short-term reventilation events during cold intervals of the Heinrich event 1, the Younger Dryas, and the 8.2 event. The stable carbon isotope difference between epi- and shallow endobenthic foraminifera exhibits marked temporal fluctuations linked to microhabitat shifts and changes in organic matter fluxes. We generated a transfer function for organic carbon fluxes based on a correlation between the stable carbon isotope signature of modern benthic foraminifera and observed organic carbon flux rates from different Mediterranean basins. Application of this transfer function to the down-core data reveals generally elevated organic matter fluxes during the Last Glacial Maximum and the Younger Dryas, while values drop significantly during the Bølling-Allerød interstadial and with onset of the Holocene. Our results support a scenario where average organic matter fluxes in the eastern Mediterranean Sea were not significantly enhanced during formation of sapropel S1. Instead, our data corroborate earlier results from benthic foraminiferal faunal successions and model experiments suggesting that sufficient amounts of organic matter are buried under oligotrophic conditions in an intermittently hypoxic water column.

  5. [Analysis of public quality reports for home care and long-term care with respect to their usefulness for the customer].

    PubMed

    Sünderkamp, Susanne; Weiß, Christian; Rothgang, Heinz

    2014-10-01

    Hintergrund: Seit dem Pflege-Weiterentwicklungsgesetz von 2008 und der Entwicklung der Pflegetransparenzvereinbarungen sollen Verbraucher die Möglichkeit erhalten, auf Basis einer flächendeckenden Qualitätsbeurteilung von ambulanten Pflegediensten und stationären Pflegeeinrichtungen eine informierte Wahl ihres Pflegeanbieters vorzunehmen. Ziel: Diese Studie prüft die Pflegenoten auf Basis einer empirischen Analyse der veröffentlichten MDK-Qualitätsberichte von 11 884 ambulanten Pflegediensten und 10 310 Pflegeheimen, was einer erstmaligen Vollerhebung aller bundesdeutschen Pflegeanbieter gleichkommt. Methoden: Auswertungen der deskriptiven Statistik und Diskussion der Ergebnisse in Hinblick auf die Nützlichkeit der Noten für den Verbraucher. Ergebnisse: Die Auswertungen zeigen eine begrenzte Aussagekraft der Pflegenoten für den Verbraucher. Ursächlich dafür sind insbesondere die durchschnittlich sehr guten Noten bei geringer Streuung und die großen Lücken in der Bewertung der einzelnen Kriterien, vor allem im ambulanten Bereich. Sie verstärken den Einfluss pflegeferner Kriterien auf die Gesamtnote und begünstigen den Ausgleich von Pflegemängeln durch guten Service. Dies kommt aber sehr selten vor. Eine stärkere Bewertung von Risikokriterien würde die Aussagekraft derzeit kaum erhöhen. Schlussfolgerungen: Die Konzeption der Pflegenoten bedarf einer gründlichen Optimierung, um die Nützlichkeit für den Verbraucher zu erhöhen.

  6. > Einleitung

    NASA Astrophysics Data System (ADS)

    Spath, Dieter; Pischetsrieder, Bernd

    Rund 40 Prozent aller Fahrzeuge fahren elektrisch. Ein Zustand, der aus heutiger Sicht noch in weiter Ferne liegt, war vor über 100 Jahren bereits Realität. Um 1900, einige Jahre nach der Erfindung des Automobils, wurden Fahrzeuge durch unterschiedliche Antriebskonzepte angetrieben. Die drei wichtigsten waren Dampfantrieb, Elektroantrieb und der Benzinmotor. Durch die überlegene Energiedichte und eine kostengünstige sowie scheinbar unendliche Verfügbarkeit des Energieträgers Öl entwickelte sich der Verbrennungsmotor zum dominanten Antriebskonzept. Der Einsatz von Elektrofahrzeugen beschränkte sich im Verlauf des 20. Jahrhunderts auf wenige Nischenanwendungen. Der verbrennungsmotorbasierte Antriebsstrang ist dem Elektroantrieb auch heute noch technisch und ökonomisch überlegen. Die Randbedingungen ändern sich jedoch. Die Verknappung des fossilen Brennstoffs Öl und die stetige Verschärfung der CO2-Emissionsziele in Verbindung mit einer starken Zunahme individueller Mobilität im asiatischen Raum und vielen weiteren Regionen der Welt stellen den Verbrennungsmotors als die dominante Antriebstechnologie in Frage. Trotz des Optimierungspotentials, welches auch nach über 120-jähriger Entwicklung noch im Verbrennungsmotor liegt, ist diese Technologie immer mit lokalen Schadstoff- und Lärmemissionen verbunden. Die Notwendigkeit der Reduktion von Treibhausgasen verbunden mit einem steigenden Urbanisierungsgrad wird in Zukunft einen Technologiewechsel vom Verbrennungsmotor zum elektrischen Antrieb attraktiv machen. Dieser Technologiewechsel bedeutet jedoch weit mehr als das Austauschen des Antriebsstranges, Elektromobilität ist ein komplexes Themengebiet mit unterschiedlichen Dimensionen.

  7. Depth to water in the western Snake River Plain and surrounding tributary valleys, southwestern Idaho and eastern Oregon, calculated using water levels from 1980 to 1988

    USGS Publications Warehouse

    Maupin, Molly A.

    1991-01-01

    The vulnerability of ground water to contamination in Idaho is being assessed by the ISHW/DEQ (Idaho Department of Health and Welfare, Division of Environmental Quality), using a modified version of the Environmental Protection Agency DRASTIC methods (Allers and others, 1985). The project was designed as a technique to: (1) Assign priorities for development of ground-water management and monitoring programs; (2) build support for, and public awareness of, vulnerability of ground water to contamination; (3) assist in the development of regulatory programs; and (4) provide access to technical data through the use of a GIS (geographic information system) (C. Grantham, Idaho Department of Health and Welfare, written commun., 1989). Digital representation of first-encountered water below land surface is an important element in evaluating vulnerability of ground water to contamination. Depth-to-water values were developed using existing data and computer software to construct a GIS data set to be combined with a soils data set developed by the SCS (Soul Conservation Service) and the IDHW/WQB (Idaho Department of Health and Welfare/Water Quality Bureau), and a recharge data set developed by the IDWR/RSF (idaho Department of Water Resources/Remote Sensing Facility). The USGS (U.S. Geological Survey) has developed digital depth-to-water values for eleven 1:100,00-scale quadrangles on the eastern Snake River Plain and surrounding tributary valleys.

  8. Depth to water in the eastern Snake River Plain and surrounding tributary valleys, southwestern Idaho and eastern Oregon, calculated using water levels from 1980 to 1988

    USGS Publications Warehouse

    Maupin, Molly A.

    1992-01-01

    The vulnerability of ground water to contamination in Idaho is being assessed by the IDHW/DEQ (Idaho Department of Health and Welfare, Division of Environmental Quality), using a modified version of the Environmental Orotection Agency DRASTIC methods (Allers and others, 1985). The project was designed as a technique to: (1) Assign priorities for development of ground-water management and monitoring programs; (2) build support for, and public awareness of, vulnerability or ground water to contamination; (3) assist in the development of regulatory programs; and (4) provide access to technical data through the use of a GIS (geographic information system) (C. Grantha,, Idaho Department of Health and Welfare, written commun., 1989). A digital representation of first-encountered water below land surface is an important element in evaluating vulnerability of ground water to contamination. Depth-to-water values were developed using existing data and computer software to construct a GIS data set to be combined with a sols data set developed by the SCS (Soil Conservation Service) and IDHW/WQB (Idaho Department of Health and Welfare/Water Quality Bureau), and a recharge data set developed by the IDWR/RSF (Idaho Department of Water Resources/Remote Sensing Facility). The USGS (U.S. Geological Survey) developed digital depth-to-water values for eleven 1:100,000-scale quadrangles on the eastern Snake River Plain and surrounding tributary valleys.

  9. Comprehension through cooperation: Medical students and physiotherapy apprentices learn in teams - Introducing interprofessional learning at the University Medical Centre Mannheim, Germany.

    PubMed

    Mette, Mira; Dölken, Mechthild; Hinrichs, Jutta; Narciß, Elisabeth; Schüttpelz-Brauns, Katrin; Weihrauch, Ute; Fritz, Harald M

    2016-01-01

    Zielsetzung: Um zukünftige Fachkräfte in der Patientenversorgung besser auf die interprofessionelle Zusammenarbeit vorzubereiten, wurden an der Universitätsmedizin Mannheim interprofessionelle Lerneinheiten für Medizinstudierende und Physiotherapieschüler entwickelt. Die Erfahrungen aus der Konzeption, Implementierung und Evaluation dieser Lerneinheiten werden dargestellt und diskutiert.Methoden: An 5 interprofessionellen Lerneinheiten nahmen 265 Medizinstudierende und 43 Physiotherapieschüler teil. Von diesen beantworteten 87-100% im Rahmen der Lehrveranstaltungsevaluation geschlossene und offene Fragen eines selbstentwickelten Fragebogens (24 Items). Die Antworten zu selbstberichtetem Lernzuwachs, Nutzen, Motivation und Zufriedenheit mit der Lerneinheit wurden nach Profession getrennt ausgewertet.Ergebnisse: Die Lerneinheiten wurden von beiden Teilnehmergruppen gut angenommen. Mehr als 75% aller Teilnehmer waren der Meinung, dass sie sich die neuen Lerninhalte nicht anderweitig besser hätten aneignen können. Signifikante Unterschiede zwischen Medizinstudierenden und Physiotherapieschülern gab es vorrangig beim empfundenen Lernzuwachs, den die Physiotherapieschüler als geringer angaben.In den offenen Fragen wurden am häufigsten interprofessionelle Aspekte positiv hervorgehoben. Kritisiert wurden am häufigsten organisatorische Punkte und der als gering empfundene Lernzuwachs.Schlussfolgerung: Die Einführung von interprofessionellem Lernen ist durch organisatorische Herausforderungen sehr aufwändig. Es ist aber lohnenswert, da die interprofessionellen Aspekte der Lerneinheiten von den Teilnehmern als wertvoll angesehen wurden. Anzustreben ist deshalb eine curriculare Verstetigung und Erweiterung interprofessionellen Lernens zu einem longitudinalen Strang.

  10. Diagenetic alteration of benthic foraminifera from a methane seep site on Vestnesa Ridge (NW Svalbard)

    NASA Astrophysics Data System (ADS)

    Schneider, Andrea; Crémière, Antoine; Panieri, Giuliana; Lepland, Aivo; Knies, Jochen

    2017-05-01

    Anomalously low δ13C values in foraminiferal calcite tests are due to diagenetic alteration in methane seep sites. Our study applies diagenetically altered fossil benthic foraminiferal tests as geochemical tracers in reconstructing natural past methane seepage episodes at Vestnesa Ridge offshore NW Svalbard. We combine examinations of the test wall microstructure, mineralogical and stable carbon isotope composition of foraminifera and co-occurring authigenic carbonate nodules. We present a classification of visual and mineralogical characteristics of the exterior and interior test wall microstructure of the benthic foraminiferal species Cassidulina neoteretis having experienced different degrees of diagenetic alteration during methane seepage. Carbonate nodules comprising high-Mg calcite cement with 13-15 mol% MgCO3 have δ13C values as low as -32.3‰, which is consistent with a methane-derived origin. The visual, mineralogical and stable isotope investigations of C. neoteretis indicate a variable degree of diagenetic alteration and show δ13C values between -0.6 and -16.9‰. The negative δ13C values in benthic foraminifera are largely caused by precipitation of isotopically light methane-derived authigenic carbonate as high-Mg-calcite coatings, whose relative contribution to the bulk foraminiferal carbonate is estimated to be up to 58 wt%. Another key finding is the identification of the first seepage episode concurrent with Heinrich Event 1 (HE 1), and a second seepage episode at the onset of the Bølling-Allerød Interstadial.

  11. Dating the onset of LGM ice surface lowering in the High Alps

    NASA Astrophysics Data System (ADS)

    Wirsig, Christian; Zasadni, Jerzy; Christl, Marcus; Akçar, Naki; Ivy-Ochs, Susan

    2016-07-01

    The general chronological outline of the Last Glacial Maximum (LGM) in the Alps is well known after more than two centuries of ice age research in Europe. Current studies focus on resolving the details of the deglaciation process after the LGM. Particularly few data in this context are available from the High Alps. Here we report chronological constraints on the onset of deglaciation in two different study areas from the Western and Eastern Alps: the Mont Blanc (Italy) and Zillertal Alps (Austria). We sampled 32 bedrock and boulder surfaces from high elevation ridges beneath the glacial trimline. The oldest 10Be exposure ages of ∼18.5 ka correspond to the initiation of lowering of the LGM ice surface. Identical ages from both study areas suggest synchronous decay of the LGM glaciers in the accumulation zones of the Western and Eastern Alps. Thus, the High Alpine ice surface lowered roughly synchronously to the downwasting of the glacier tongues in the forelands that was completed 19-18 ka. In both study areas, ages of numerous samples that are consistently 2-3 ka younger than 18.5 ka suggest the persistance of remnant ice patches at high elevations in the Lateglacial accumulation zones approximately until the Bølling-Allerød interstadial.

  12. New Algorithm for Peat Carbon Accumulation Estimation Reveals and Quantifies the Global Importance of Northern Peatlands to the Late Glacial and Early Holocene Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Nichols, J. E.; Peteet, D. M.

    2016-12-01

    Northern peatlands are vital to the global carbon cycle. Previous estimates of global peatland carbon accumulation rates were limited to data from peatlands with robust radiocarbon age models spanning the entire Holocene and Late Glacial periods. This stringent data policy eliminated large amounts of otherwise legitimate radiocarbon measurements. We introduce the AccumC algorithm for calculating carbon accumulation rate. This method has been used previously at single sites, but its flexibility allows it to be used to calculate carbon accumulation in multiple sites simultaneously. Using the AccumC algorithm, we are now able to include radiocarbon measurements from any peat, regardless of how many measurements were made from the same site. Our full dataset includes radiocarbon measurements from Loisel et al., 2014 (L-14), the Neotoma Paleoecology Database, the Canadian Archaeological Radiocarbon Database (CARD), and other published sources. With our expanded dataset, we have extended our record of northern peatland accumulation rates back to 22 ka, including the important deglacial period. We also now have sufficient data to divide carbon accumulation geographically into several peat-forming regions. The Holocene portion of the global record reinforces previous estimates, but the increased temporal resolution has uncovered new details, such as a previously unreported increase from 7 to 5 ka. We have also identified high rates of carbon accumulation during the Allerød warm interval and even a relative increase during the mystery interval (17.5 - 14.5 ka).

  13. Climate variation and terrigenous input in the Tagus prodelta reconstructed through the use of N-alkanes and Uk'37

    NASA Astrophysics Data System (ADS)

    Rodrigues, T.; Grimalt, J.; Flores, J.; Lebreiro, S.; Abrantes, F.

    2003-04-01

    Sea surface temperatures and river input have been reconstructed for the last 13,5kyr based on long chain alkenones and n-alkanes respectively, using a sedimentary sequence recovered from the Tagus prodelta (Portuguese Margin, 38ºN, 9ºW; PO287-26-1B; D13902; D13882). A preliminary age model has been constructed using five 14C AMS dating and correlation to core SU8118. In the upper part of this sequence temperatures ranged between 15ºC and 19ºC, exhibiting the lowest values during the Little Ice Age. This low temperature interval is marked by a general increase in organic carbon and total C37 alkenones pointing to increasing productivity. Minima sea surface temperature occur during the Younger Dryas event centred at about 12cal.kyr B.P. and the Allerød-Bølling interstadial occurs at the end of the sequence. The SST minima are concurrent with increases in tetra unsaturated alkenone (%C37:4), possibly reflecting the influence of less saline waters originated from iceberg melting. N-alkanes and n-alcohols exhibit the same trend indicating very good preservation of organic matter throughout the sequence. In addition, the strong agreement between these two proxies and C37 alkenones suggest river input as the main source of nutrients for the increased coccolith production in the area which in terms of coccolith assemblages were dominated by G. oceanica and other small gephyrocapsid.

  14. Influence of the intertropical convergence zone on the East Asian monsoon

    NASA Astrophysics Data System (ADS)

    Yancheva, Gergana; Nowaczyk, Norbert R.; Mingram, Jens; Dulski, Peter; Schettler, Georg; Negendank, Jörg F. W.; Liu, Jiaqi; Sigman, Daniel M.; Peterson, Larry C.; Haug, Gerald H.

    2007-01-01

    The Asian-Australian monsoon is an important component of the Earth's climate system that influences the societal and economic activity of roughly half the world's population. The past strength of the rain-bearing East Asian summer monsoon can be reconstructed with archives such as cave deposits, but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct. Here we present high-resolution records of the magnetic properties and the titanium content of the sediments of Lake Huguang Maar in coastal southeast China over the past 16,000years, which we use as proxies for the strength of the winter monsoon winds. We find evidence for stronger winter monsoon winds before the Bølling-Allerød warming, during the Younger Dryas episode and during the middle and late Holocene, when cave stalagmites suggest weaker summer monsoons. We conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone. Similar migrations of the intertropical convergence zone have been observed in Central America for the period AD 700 to 900 (refs 4-6), suggesting global climatic changes at that time. From the coincidence in timing, we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the Tang dynasty in China and the Classic Maya in Central America.

  15. MIS 3 to MIS 1 temporal and LGM spatial variability in Arctic Ocean sea ice cover: Reconstruction from biomarkers

    NASA Astrophysics Data System (ADS)

    Xiao, Xiaotong; Stein, Ruediger; Fahl, Kirsten

    2015-07-01

    Using the sea ice proxy IP25 and phytoplankton-derived biomarkers (brassicasterol and dinosterol), Arctic sea ice conditions were reconstructed for Marine Isotope Stage (MIS) 3 to 1—with special emphasis on the Last Glacial Maximum (LGM)—in sediment cores from the northern Barents Sea continental margin across the central Arctic Ocean to the southern Mendeleev Ridge. Our results suggest more extensive sea ice cover than present day during the latter part of MIS 3, increasing sea ice growth during MIS 2 and decreased sea ice cover during the last deglacial. The summer ice edge remained north of the Barents Sea even during extremely cold (i.e., Last Glacial Maximum (LGM)) as well as warm periods (i.e., Bølling-Allerød). During the LGM, the western Svalbard margin and the northern Barents Sea margin areas were characterized by high concentrations of both IP25 and phytoplankton biomarkers, interpreted as a productive ice edge situation caused by the inflow of warm Atlantic water. In contrast, the LGM central Arctic Ocean (north of 84°N) was covered by thick permanent sea ice throughout the year with rare breakup, indicated by zero or near-zero biomarker concentrations. The spring/summer sea ice margin significantly extended southward to the Laptev Sea shelf (southern Lomonosov Ridge) and southern Mendeleev Ridge during the LGM. Our proxy reconstructions are very consistent with published model results based on the North Atlantic/Arctic Ocean Sea Ice Model.

  16. Climatic variability in the northern sector of the American tropics since the latest MIS 3

    NASA Astrophysics Data System (ADS)

    Lozano-García, Socorro; Ortega, Beatriz; Roy, Priyadarsi D.; Beramendi-Orosco, Laura; Caballero, Margarita

    2015-09-01

    We inferred millennial-scale climate variations and paleohydrological conditions in the northern sector of the American tropics for 30.3-5.5 cal ka BP using geochemical characteristics of sediments from Lake Chalco in central Mexico. The sediment sequence is chronologically constrained with three tephra and nine radiocarbon dates. Temporal variations in titanium, total inorganic carbon, total organic carbon/titanium ratio, carbon/nitrogen ratio, and silica/titanium ratio indicate changes in runoff, salinity, productivity, and sources. Higher concentrations of Ti indicate more runoff during latest Marine Isotope Stage (MIS) 3 (30.3-28.6 cal ka BP). Runoff was lower during the last glacial maximum (LGM; 23-19 cal ka BP) than during the Heinrich 2 event (26-24 cal ka BP). The interval of reduced runoff continued up to 17.5 cal ka BP but increased during the Bølling/Allerød. Trends of decreasing runoff and increasing salinity are observed throughout MIS 1. Lake Chalco received less runoff during the LGM compared to deglaciation, opposite the trend of other North American tropical records. Different amounts of rainfall at different sites are possibly due to shifts in the position of the Intertropical Convergence Zone, changes in the size of the Altlantic warm pool, and varying sea-surface temperatures of the Atlantic and Pacific oceans.

  17. Younger Dryas “black mats” and the Rancholabrean termination in North America

    PubMed Central

    Haynes, C. Vance

    2008-01-01

    Of the 97 geoarchaeological sites of this study that bridge the Pleistocene-Holocene transition (last deglaciation), approximately two thirds have a black organic-rich layer or “black mat” in the form of mollic paleosols, aquolls, diatomites, or algal mats with radiocarbon ages suggesting they are stratigraphic manifestations of the Younger Dryas cooling episode 10,900 B.P. to 9,800 B.P. (radiocarbon years). This layer or mat covers the Clovis-age landscape or surface on which the last remnants of the terminal Pleistocene megafauna are recorded. Stratigraphically and chronologically the extinction appears to have been catastrophic, seemingly too sudden and extensive for either human predation or climate change to have been the primary cause. This sudden Rancholabrean termination at 10,900 ± 50 B.P. appears to have coincided with the sudden climatic switch from Allerød warming to Younger Dryas cooling. Recent evidence for extraterrestrial impact, although not yet compelling, needs further testing because a remarkable major perturbation occurred at 10,900 B.P. that needs to be explained. PMID:18436643

  18. Evolution in the sabre-tooth cat, Smilodon fatalis, in response to Pleistocene climate change.

    PubMed

    Meachen, J A; O'Keefe, F R; Sadleir, R W

    2014-04-01

    The late Pleistocene was a time of environmental change, culminating in an extinction event. Few fossil localities record a temporal series of carnivore fossil populations from this interesting interval as well as Rancho La Brea (RLB). We analysed mandibles of Smilodon fatalis from RLB using 2-D geometric morphometrics to examine whether, and how, mandibular shape changes through time. Smilodon fatalis shows mandibular evolution with oscillations between a small, ancestral-type morph in pits 77 (≈37 Kybp) and 2051 (≈26 Kybp), a larger, more derived morph in pits 91 (≈28 Kybp) and 61-67 (≈13.6 Kybp), and an intermediate morph from pit 13 (≈17.7 Kybp). These oscillations end in pit 61-67, with greatest body size, and are estimated to have its widest gape and lowest bite force. Additionally, variation is lowest in pit 61-67, which was deposited concurrent with the Bølling–Allerød warming event, which may have important implications for the timing or conditions during the extinction event. Contra to a temporal Bergmann's rule, such rapid warming events appear to be correlated with larger, derived, morphologies whereas static, cooler, climates correlate with gracile, ancestral morphologies.

  19. The role of sea ice in abrupt climate changes following the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Nisancioglu, Kerim; Dokken, Trond

    2017-04-01

    Climate changes following the last glacial maximum ( 21-10ka BP) are considered some of the most dramatic and wide reaching abrupt events of the geological past. On Greenland the transition from the last glacial maximum to the Bølling-Allerød (BA) warm period was extremely abrupt, as is the transitions in and out of the Younger Dryas (YD) cold period. In terms of ocean changes, there are indications from proxy records that the large scale Atlantic Meridional Overturning Circulation (AMOC) was significantly reduced a few thousand years before the BA and again at the start of the YD. However, the link between changes in AMOC and climate in the Northern Hemisphere and in particular on Greenland is unclear. Here, we study changes to climate and circulation in the North Atlantic across these key climate transitions based on a sediment core from the Nordic Seas as well as sensitivity studies with a global climate model. Preliminary results suggest that changes in sea ice and stratification of the Nordic Seas played a key role in the observed climate changes during and preceding the deglaciation of the large land based ice sheets. In particular the cold period following Heinrich Event 1 (H1) and ending at the BA as well as the cold YD are associated with expansions of Arctic sea ice into the Nordic Seas region.

  20. Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions

    NASA Astrophysics Data System (ADS)

    Steinthorsdottir, Margret; Wohlfarth, Barbara; Kylander, Malin E.; Blaauw, Maarten; Reimer, Paula J.

    2013-05-01

    A new stomatal proxy-based record of CO2 concentrations ([CO2]), based on Betula nana (dwarf birch) leaves from the Hässeldala Port sedimentary sequence in south-eastern Sweden, is presented. The record is of high chronological resolution and spans most of Greenland Interstadial 1 (GI-1a to 1c, Allerød pollen zone), Greenland Stadial 1 (GS-1, Younger Dryas pollen zone) and the very beginning of the Holocene (Preboreal pollen zone). The record clearly demonstrates that i) [CO2] were significantly higher than usually reported for the Last Termination and ii) the overall pattern of CO2 evolution through the studied time period is fairly dynamic, with significant abrupt fluctuations in [CO2] when the climate moved from interstadial to stadial state and vice versa. A new loss-on-ignition chemical record (used here as a proxy for temperature) lends independent support to the Hässeldala Port [CO2] record. The large-amplitude fluctuations around the climate change transitions may indicate unstable climates and that “tipping-point” situations were involved in Last Termination climate evolution. The scenario presented here is in contrast to [CO2] records reconstructed from air bubbles trapped in ice, which indicate lower concentrations and a gradual, linear increase of [CO2] through time. The prevalent explanation for the main climate forcer during the Last Termination being ocean circulation patterns needs to re-examined, and a larger role for atmospheric [CO2] considered.

  1. Deglacial Evolution of Atlantic Mid-Depth and Intermediate-Depth Water Variability

    NASA Astrophysics Data System (ADS)

    Oppo, D.; Gebbie, G.; Huang, K. F.; Guo, W.; Schmittner, A.; Liu, Z.; Curry, W. B.

    2014-12-01

    Deglacial variations in the Atlantic Meridional Overturning Circulation (AMOC) feature prominently in hypotheses of deglacial climate variability and atmospheric CO2rise. However, there is lingering uncertainty in the glacial deepwater mass configuration (e.g. Gebbie, 2014) and deglacial AMOC variability is even more poorly understood. For example, the deglacial evolution of the contribution of northern and southern source waters to the middle and intermediate depths of the Atlantic is still vigorously debated. Here, we evaluate the evolution of subsurface Atlantic ventilation, emphasizing middle and intermediate depths, by comparing new and published records of water mass variability to output from transient model simulations designed to provide insight into the climatic and oceanographic effects of a dramatic reduction in the AMOC, such as apparently occurred during Heinrich Stadial 1 (Liu et al., 2009; Schmittner and Lund, 2014). Gebbie, G. (2014), How much did Glacial North Atlantic Water shoal? Paleoceanography, 29, 190-209, doi: 10.1002/2013PA002557. Liu, Z., B. Otto-Bliesner, F. He, E. Brady, R. Thomas, P. U. Clark, A. E. Carlson, J. Lynch-Stieglitz, W. Curry, E. Brook, D. Erickson, R. Jacob, J. Kutzbach, J., and J. Chen (2009), Transient climate simulation of last deglaciation with a new mechanism for Bølling-Allerød warming, Science, 325, 310-314. Schmittner, A., and Lund, D. C. (submitted), Carbon Isotopes Support Atlantic Meridional Overturning Circulation Decline as a Trigger for Early Deglacial CO2 rise Climate of the Past Discussions.

  2. Climate variability during the deglaciation and Holocene in a high-altitude alpine lake deduced from the sedimentary record from Laguna Seca, Sierra Nevada, southern Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Camuera, Jon; Jiménez-Moreno, Gonzalo; José Ramos-Román, María; García-Alix, Antonio; Jiménez-Espejo, Francisco; Anderson, R. Scott

    2017-04-01

    High-resolution X-ray fluorescence (XRF), magnetic susceptibility (MS), color and lithological analyses have been carried out on a 3.6 m-long sediment core from Laguna Seca, a high-elevation dry lake from Sierra Nevada mountain range, southern Spain. This is the longest sedimentary record retrieved from an alpine lake in southern Iberian Peninsula. Besides, alpine lakes are very sensitive environments to climate changes and previous studies showed that Laguna Seca could provide an excellent record to identify millennial-scale climate variations during deglaciation and the whole Holocene. XRF analyses, in particular high calcium and low K/Ca ratios, show aridity phases, very well represented during Last Glacial Maximum (LGM) and the Younger Dryas (YD). Arid events are also shown at ca. 8.1 ka BP, ca. 4.4 ka BP and the latest Holocene. On the other hand, negative values in calcium and positive values in K/Ca appear in the Bølling-Allerød (BA) and during the early Holocene until ca. 6 ka BP, indicating more humidity and higher run-off. A progressive aridification trend is also observed in the Holocene, changing from more humid conditions during the early Holocene to more aridity during the late Holocene.

  3. On the history of plasma treatment and comparison of microbiostatic efficacy of a historical high-frequency plasma device with two modern devices.

    PubMed

    Napp, Judith; Daeschlein, Georg; Napp, Matthias; von Podewils, Sebastian; Gümbel, Denis; Spitzmueller, Romy; Fornaciari, Paolo; Hinz, Peter; Jünger, Michael

    2015-01-01

    Hintergrund: Kaltes Atmosphärendruckplasma (CAP) hat durch seine mannigfaltigen bioaktiven Eigenschaften ein neues medizinisches Feld definiert: die Plasmamedizin. Allerdings wurde vor etwa 100 Jahren CAP in verwandter Form in der Hochfrequenztherapie genutzt. Zielsetzung dieser Studie war eine Übersicht über die historischen Plasmabehandlungen zu gewinnen und Daten bezüglich der antimikrobiellen Wirkung eines historischen Hochfrequenzapparats zu gewinnen.Methode: Erstens wurde historische Literatur bezüglich CAP-Behandlungen ausgewertet, da aus dem heutigen Schrifttum keine Angaben gewonnen werden konnten. Zweitens wurde die Empfindlichkeit von fünf verschiedenen bakteriellen Wundisolaten auf Agar gegenüber einer historischen Plasmaquelle (violet wand [VW]) und zwei modernen Geräten (atmospheric pressure plasma jet [APPJ] und Dielectric Barrier Discharge [DBD]) ermittelt. Die erzielten Hemmhöfe wurde verglichen. Ergebnisse: Die seinerzeit populärsten elektromedizinischen Anwendungen erzeugten durch Glaselektroden sogenannte Effluvien, die mit modernem CAP verwandt sind. Alle drei untersuchten Plasmaquellen zeigten eine vollständige Eradikation aller behandelter Isolate im plasmabehandelten Bereich. Die historische Plasmaquelle (VW) war dabei ähnlich wirksam wie die modernen Plasmaquellen. Schlussfolgerung: In begrenztem Umfang kann retrograd ein Wirksamkeitsnachweis der historischen Plasmabehandlungen abgeleitet werden, insbesondere bei der Behandlung infektiöser Erkrankungen. Die zugrunde liegende Technologie könnte für die Entwicklung moderner Nachfolgegeräte genutzt werden.

  4. The WAIS Divide deep ice core WD2014 chronology - Part 2: Annual-layer counting (0-31 ka BP)

    NASA Astrophysics Data System (ADS)

    Sigl, M.; Fudge, T. J.; Winstrup, M.; Cole-Dai, J.; Ferris, D.; McConnell, J. R.; Taylor, K. C.; Welten, K. C.; Woodruff, T. E.; Adolphi, F.; Bisiaux, M.; Brook, E. J.; Buizert, C.; Caffee, M. W.; Dunbar, N. W.; Edwards, R.; Geng, L.; Iverson, N.; Koffman, B.; Layman, L.; Maselli, O. J.; McGwire, K.; Muscheler, R.; Nishiizumi, K.; Pasteris, D. R.; Rhodes, R. H.; Sowers, T. A.

    2015-07-01

    We present the WD2014 chronology for the upper part (0-2850 m, 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide ice core. The chronology is based on counting of annual layers observed in the chemical, dust and electrical conductivity records. These layers are caused by seasonal changes in the source, transport, and deposition of aerosols. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing to two high-accuracy, absolutely dated chronologies. For the Holocene, the cosmogenic isotope records of 10Be from WAIS Divide and 14C for Intcal13 demonstrated WD2014 was consistently accurate to better than 0.5 % of the age. For the glacial period, comparisons to the Hulu Cave chronology demonstrated WD2014 had an accuracy of better than 1 % of the age at three abrupt climate change events between 27 and 31 ka. WD2014 has consistently younger ages than Greenland ice-core chronologies during most of the Holocene. For the Younger Dryas-Preboreal transition (11 546 ka BP, 24 years younger) and the Bølling-Allerød Warming (14 576 ka, 7 years younger) WD2014 ages are within the combined uncertainties of the timescales. Given its high accuracy, WD2014 can become a reference chronology for the Southern Hemisphere, with synchronization to other chronologies feasible using high quality proxies of volcanism, solar activity, atmospheric mineral dust, and atmospheric methane concentrations.

  5. The WAIS Divide deep ice core WD2014 chronology - Part 2: Annual-layer counting (0-31 ka BP)

    NASA Astrophysics Data System (ADS)

    Sigl, Michael; Fudge, Tyler J.; Winstrup, Mai; Cole-Dai, Jihong; Ferris, David; McConnell, Joseph R.; Taylor, Ken C.; Welten, Kees C.; Woodruff, Thomas E.; Adolphi, Florian; Bisiaux, Marion; Brook, Edward J.; Buizert, Christo; Caffee, Marc W.; Dunbar, Nelia W.; Edwards, Ross; Geng, Lei; Iverson, Nels; Koffman, Bess; Layman, Lawrence; Maselli, Olivia J.; McGwire, Kenneth; Muscheler, Raimund; Nishiizumi, Kunihiko; Pasteris, Daniel R.; Rhodes, Rachael H.; Sowers, Todd A.

    2016-03-01

    We present the WD2014 chronology for the upper part (0-2850 m; 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS) Divide (WD) ice core. The chronology is based on counting of annual layers observed in the chemical, dust and electrical conductivity records. These layers are caused by seasonal changes in the source, transport, and deposition of aerosols. The measurements were interpreted manually and with the aid of two automated methods. We validated the chronology by comparing to two high-accuracy, absolutely dated chronologies. For the Holocene, the cosmogenic isotope records of 10Be from WAIS Divide and 14C for IntCal13 demonstrated that WD2014 was consistently accurate to better than 0.5 % of the age. For the glacial period, comparisons to the Hulu Cave chronology demonstrated that WD2014 had an accuracy of better than 1 % of the age at three abrupt climate change events between 27 and 31 ka. WD2014 has consistently younger ages than Greenland ice core chronologies during most of the Holocene. For the Younger Dryas-Preboreal transition (11.595 ka; 24 years younger) and the Bølling-Allerød Warming (14.621 ka; 7 years younger), WD2014 ages are within the combined uncertainties of the timescales. Given its high accuracy, WD2014 can become a reference chronology for the Southern Hemisphere, with synchronization to other chronologies feasible using high-quality proxies of volcanism, solar activity, atmospheric mineral dust, and atmospheric methane concentrations.

  6. High-resolution IP25-based reconstruction of sea-ice variability in the western North Pacific and Bering Sea during the past 18,000 years

    NASA Astrophysics Data System (ADS)

    Méheust, Marie; Stein, Ruediger; Fahl, Kirsten; Max, Lars; Riethdorf, Jan-Rainer

    2016-04-01

    Due to its strong influence on heat and moisture exchange between the ocean and the atmosphere, sea ice is an essential component of the global climate system. In the context of its alarming decrease in terms of concentration, thickness and duration, understanding the processes controlling sea-ice variability and reconstructing paleo-sea-ice extent in polar regions have become of great interest for the scientific community. In this study, for the first time, IP25, a recently developed biomarker sea-ice proxy, was used for a high-resolution reconstruction of the sea-ice extent and its variability in the western North Pacific and western Bering Sea during the past 18,000 years. To identify mechanisms controlling the sea-ice variability, IP25 data were associated with published sea-surface temperature as well as diatom and biogenic opal data. The results indicate that a seasonal sea-ice cover existed during cold periods (Heinrich Stadial 1 and Younger Dryas), whereas during warmer intervals (Bølling-Allerød and Holocene) reduced sea ice or ice-free conditions prevailed in the study area. The variability in sea-ice extent seems to be linked to climate anomalies and sea-level changes controlling the oceanographic circulation between the subarctic Pacific and the Bering Sea, especially the Alaskan Stream injection though the Aleutian passes.

  7. Musk ox (Ovibos moschatus) of the mammoth steppe: tracing palaeodietary and palaeoenvironmental changes over the last 50,000 years using carbon and nitrogen isotopic analysis

    NASA Astrophysics Data System (ADS)

    Raghavan, Maanasa; Espregueira Themudo, Gonçalo; Smith, Colin I.; Zazula, Grant; Campos, Paula F.

    2014-10-01

    Stable carbon and nitrogen isotope ratios have been used as markers for palaeoclimatic and palaeoecological reconstructions across various geographical and temporal ranges. Such studies are essential for understanding how a particular species responded to changing environmental conditions in the past, especially changing vegetation, which might have even generated conditions stressful enough to threaten the very survival of the species. We present in this study a dataset of stable carbon and nitrogen isotope measurements (δ13C and δ15N) generated from 160 Pleistocene and Holocene musk ox (Ovibos moschatus) specimens. We used the dataset to evaluate the usefulness of these dietary indicators in tracing vegetation and climatic fluctuations in the holarctic region during the Pleistocene and Holocene. Our data show that musk ox stable isotopes largely followed changes in precipitation and that these variations were closely associated with events such as the cold and arid Last Glacial Maximum (LGM), Bølling-Allerød interstadial, Younger Dryas stadial and the warmer and humid Holocene. Regional differences in the isotopic composition of the musk ox populations are also noticeable, altogether providing insights into how an adaptable, generalist diet in the face of climate change might have helped this species survive the Holocene megafaunal extinctions.

  8. Younger Dryas "black mats" and the Rancholabrean termination in North America.

    PubMed

    Haynes, C Vance

    2008-05-06

    Of the 97 geoarchaeological sites of this study that bridge the Pleistocene-Holocene transition (last deglaciation), approximately two thirds have a black organic-rich layer or "black mat" in the form of mollic paleosols, aquolls, diatomites, or algal mats with radiocarbon ages suggesting they are stratigraphic manifestations of the Younger Dryas cooling episode 10,900 B.P. to 9,800 B.P. (radiocarbon years). This layer or mat covers the Clovis-age landscape or surface on which the last remnants of the terminal Pleistocene megafauna are recorded. Stratigraphically and chronologically the extinction appears to have been catastrophic, seemingly too sudden and extensive for either human predation or climate change to have been the primary cause. This sudden Rancholabrean termination at 10,900 +/- 50 B.P. appears to have coincided with the sudden climatic switch from Allerød warming to Younger Dryas cooling. Recent evidence for extraterrestrial impact, although not yet compelling, needs further testing because a remarkable major perturbation occurred at 10,900 B.P. that needs to be explained.

  9. Contrasting ocean changes between the subpolar and polar North Atlantic during the past 135 ka

    NASA Astrophysics Data System (ADS)

    Bauch, Henning A.; Kandiano, Evguenia S.; Helmke, Jan P.

    2012-06-01

    Variations in the poleward-directed Atlantic heat transfer was investigated over the past 135 ka with special emphasis on the last and present interglacial climate development (Eemian and Holocene). Both interglacials exhibited very similar climatic oscillations during each preceding glacial terminations (deglacial TI and TII). Like TI, also TII has pronounced cold-warm-cold changes akin to events such as H1, Bølling/Allerød, and the Younger Dryas. But unlike TI, the cold events in TII were associated with intermittent southerly invasions of an Atlantic faunal component which underscores quite a different water mass evolution in the Nordic Seas. Within the Eemian interglaciation proper, peak warming intervals were antiphased between the Nordic Seas and North Atlantic. Moreover, inferred temperatures for the Nordic Seas were generally colder in the Eemian than in the Holocene, and vice versa for the North Atlantic. A reduced intensity of Atlantic Ocean heat transfer to the Arctic therefore characterized the Eemian, requiring a reassessment of the actual role of the ocean-atmosphere system behind interglacial, but also, glacial climate changes.

  10. Einfluss des Internets auf das Informations-, Einkaufs- und Verkehrsverhalten

    NASA Astrophysics Data System (ADS)

    Nerlich, Mark R.; Schiffner, Felix; Vogt, Walter

    Mit Daten aus eigenen Erhebungen können das einkaufsbezogene Informations- und Einkaufsverhalten im Zusammenhang mit den verkehrlichen Aspekten (Distanzen, Verkehrsmittel, Wegekopplungen) dargestellt werden. Die Differenzierung in die drei Produktkategorien des täglichen, mittelfristigen und des langfristigen Bedarfs berücksichtigt in erster Linie die Wertigkeit eines Gutes, die seine Erwerbshäufigkeit unmittelbar bestimmt. Der Einsatz moderner IKT wie das Internet eröffnet dem Endverbraucher neue Möglichkeiten bei Information und Einkauf. Die verkehrliche Relevanz von Online-Shopping wird deutlich, wenn man berücksichtigt, dass im Mittel rund 17% aller Online-Einkäufe, die die Probanden durchgeführt haben, Einkäufe in Ladengeschäften ersetzen. Dies gilt in verstärktem Maße für Online-Informationen: etwa die Hälfte hätte alternativ im stationären Einzelhandel stattgefunden. Da der Erwerb von Gütern des täglichen Bedarfs häufig nahräumlich und in relevantem Anteil nicht-motorisiert erfolgen kann, sind in diesem Segment - im Gegensatz zum mittel- und langfristigen Bedarf - nur geringe Substitutionseffekte zu beobachten.

  11. The Quaternary coversands of southwest France

    NASA Astrophysics Data System (ADS)

    Sitzia, Luca; Bertran, Pascal; Bahain, Jean-Jacques; Bateman, Mark D.; Hernandez, Marion; Garon, Henri; de Lafontaine, Guillaume; Mercier, Norbert; Leroyer, Chantal; Queffelec, Alain; Voinchet, Pierre

    2015-09-01

    Detailed stratigraphic analysis and numerical dating (OSL, IRSL, ESR, 14C) of Pleistocene coversands in southwest France enable the construction of a renewed chronostratigraphic framework for sand deposition. The chronological data obtained from sandsheet units testify to the development of transgressive dunefields since at least the Middle Pleistocene (MIS 10). Three main phases of accumulation occurred during the Last Glacial. The oldest one (64-42 ka) is associated with wet sandsheet facies, histic horizons and zibar-type dune fields, which reflect deposition in a context strongly influenced by the groundwater table. The Late Pleniglacial (24-14 ka) corresponds to the main phase of coversand extension in a drier context. Silty gley horizons suggest, however, local interruptions of sand drifting during GS 2.1. Lateglacial stabilization of the coversands may not have occurred before GI-1c (Allerød), which was typified by the development of cumulic arenosols. These were covered by parabolic dunes during the Younger Dryas. The variations in extent of the emerged continental shelf during the glacial-interglacial cycles may explain the uneven geographical distribution of sand deposition through time. Because of coastline retreat up to 100 km north of 45°N during the LGM lowstand, the coversands were unable to reach the northern part of the basin. Comparison with other European regions highlights stronger affinities of the French record with Portugal than with the Netherlands and Great Britain, probably because of reduced influence of permafrost.

  12. Interrelationship of age and diet in Romania's oldest human burial

    NASA Astrophysics Data System (ADS)

    Bonsall, Clive; Boroneanţ, Adina; Soficaru, Andrei; McSweeney, Kathleen; Higham, Tom; Miriţoiu, Nicolae; Pickard, Catriona; Cook, Gordon

    2012-04-01

    In 1968, excavations in the Climente II cave in the Iron Gates gorge of the River Danube in southwest Romania unearthed the skeleton of an adult male. The burial was assumed to be of Late Pleistocene age because of the presence of Late Upper Palaeolithic (LUP) artefacts in the cave. However, there was no strong supporting stratigraphic evidence, and the body position is reminiscent of Early Neolithic burial practice in the region. Here, we report the results of radiocarbon and stable isotope analyses of the Climente II skeleton, which show that the skeleton dates to the Bølling-Allerød Interstadial ~14,500 cal BP. This is several millennia older than any previously dated human remains from the Iron Gates region and confirms its status as the oldest known burial from Romania. The stable isotope results indicate a diet with an emphasis on aquatic resources, contrary to the commonly held view that the LUP inhabitants of the Iron Gates subsisted mainly by hunting large land mammals.

  13. The expansion of hazel ( Corylus avellana L.) in the southern Alps: a key for understanding its early Holocene history in Europe?

    NASA Astrophysics Data System (ADS)

    Finsinger, Walter; Tinner, Willy; van der Knaap, W. O.; Ammann, Brigitta

    2006-03-01

    In Northwestern and Central Europe the Holocene expansion of Corylus occurred before or at the same time as that of other thermophilous trees (e.g. Quercus). This sequence of expansion has been explained by migrational lag, competition, climatic changes, human assistance, or disturbance by fire. In the southern Alps, however, hazel expanded around 10,500 cal yr BP, more than two millennia after oak had become important. This delayed expansion is in contrast with the rapid expansion often assumed for hazel in central Northern Europe. We use two well-dated pollen and charcoal records from the southern forelands of the Alps: Lago Piccolo di Avigliana and Lago di Origlio. We conclude that distance of refugia, speed of seed dispersal, and competition cannot sufficiently explain the absence of the hazel expansion prior to the establishment of mixed oak forests in the southern Alps. Instead our records indicate that higher moisture availability and low temperatures inhibited hazel and favoured the establishment of pine and mixed oak forests during the Allerød. The expansion of hazel ˜11,000-10,500 cal yr BP was favoured by a combination of high seasonality, summer drought and frequent fires, which helped hazel to out-compete oak in the south as well as north of the Alps.

  14. Millennial meridional dynamics of Indo-Pacific Warm Pool during the last termination

    NASA Astrophysics Data System (ADS)

    Lo, L.; Shen, C.-C.; Wei, K.-Y.; Burr, G. S.; Mii, H.-S.; Chen, M.-T.; Lee, S.-Y.; Tsai, M.-C.

    2014-08-01

    To develop an in-depth understanding of the natural dynamics of the Indo-Pacific Warm Pool (IPWP) during the last deglaciation, stacked North- (N-) and South-IPWP (S-IPWP) thermal and hydrological records over the past 23-10.5 thousand years (ka) were built using planktonic foraminiferal geochemical data from a new core, MD05-2925 (9.3° S, 151.5° E, water depth 1661 m) in the Solomon Sea and eleven previous sites. Ice-volume corrected seawater δ18O (δ18OSW-IVC) stacks show that S-IPWP δ18OSW-IVC values are indistinguishable from their northern counterpart through glacial time. The N-IPWP SST stacked record features an increasing trend of 0.5 °C ka-1 since 18 ka. Its S-IPWP counterpart shows an earlier onset of temperature increase at 19 ka and a strong teleconnection to high-latitude climate in the Southern Hemisphere. Meridional SST gradients between N- and S-IPWP were 1.5 °C during the Bølling/Allerød period and < 0.5 °C during both Heinrich event 1 and the Younger Dryas due to a warmer S-IPWP. A warm S-IPWP during the cold events snapshots may possibly weaken the southern hemispheric convection branch of the Hadley Cell and reduce precipitation in the Asian Monsoon region.

  15. Millennial meridional dynamics of the Indo-Pacific Warm Pool during the last termination

    NASA Astrophysics Data System (ADS)

    Lo, L.; Shen, C.-C.; Wei, K.-Y.; Burr, G. S.; Mii, H.-S.; Chen, M.-T.; Lee, S.-Y.; Tsai, M.-C.

    2014-12-01

    To develop an in-depth understanding of the natural dynamics of the Indo-Pacific Warm Pool (IPWP) during the last deglaciation, stacked north- (N-) and south-IPWP (S-IPWP) thermal and hydrological records over the past 23-10.5 ka were built using planktonic foraminiferal geochemistry data from a new core, MD05-2925 (9.3° S, 151.5° E water depth 1661 m) in the Solomon Sea and eleven previous sites. Ice-volume-corrected seawater δ18O (δ18OSW-IVC) stacks show that S-IPWP δ18OSW-IVC values are indistinguishable from their northern counterparts through glacial time. The N-IPWP SST (sea surface temperature) stacked record features an increasing trend of 0.5 °C ka-1 since 18 ka. Its S-IPWP counterpart shows an earlier onset of temperature increase at 19 ka and a strong teleconnection to high-latitude climate in the Southern Hemisphere. Meridional SST gradients between the N- and S-IPWP were 1-1.5 °C during the Bølling/Allerød period and 1 °C during both Heinrich event 1 and the Younger Dryas, due to a warmer S-IPWP. A warm S-IPWP during the cold events could weaken the southern hemispheric branch of the Hadley cell and reduce precipitation in the Asian monsoon region.

  16. Climate impact on the Trzechowskie paleolake ecosystem during the Late Glacial and early Holocene in the light of multiproxy analysis

    NASA Astrophysics Data System (ADS)

    Słowiński, M.; Zawiska, I.; Noryśkiewicz, A. M.; Apolinarska, K.; Lutyńska, M.; Skubała, P.; Ott, F.; Wulf, S.; Brauer, A.

    2012-04-01

    The aim of the research was to reconstruct climate fluctuations during LG and early Holocene and their influence on the development of Trzechowskie paleolake. The paleolake is located in the eastern part of the Pomeranian Lakeland northern Poland (Tuchola Pinewoods). Its genesis is associated with the melting of a buried ice block. Trzechowskie paleolake is about 1.5 km long and the average width is 450 m (area ~ 28 ha). In our research we focused on the bottom sediments and multiproxy high resolution analysis were carryied out. We were able to reconstract local environment changes (plant and animal macrofossils, Cladocera, Diatom, Oribatidae mite, δ13C stable isotope, LOI, carbonate content - CaCO3), and the regional changes (pollen analysis and δ18O stable isotope). The chronology was based on palynological analysis, but also on the age-depth model, developed from five radiocarbon dates AMS14C. It clearly shows that the biogenic accumulation in the Trzechowskie paleolake started during Bølling-Allerød warmer period. The preliminary results of all analysis indicate that climate was the main factor responsible for Trzechowskie paleolake development during LG and early Holocane period. The environmental changes influenced sediment formation process and are marked in the lithology and chemistry but also had a strong effect on water plants, fito and zooplankton.

  17. Estimation of instantaneous peak flow from simulated maximum daily flow using the HBV model

    NASA Astrophysics Data System (ADS)

    Ding, Jie; Haberlandt, Uwe

    2014-05-01

    Instantaneous peak flow (IPF) data are the foundation of the design of hydraulic structures and flood frequency analysis. However, the long discharge records published by hydrological agencies contain usually only average daily flows which are of little value for design in small catchments. In former research, statistical analysis using observed peak and daily flow data was carried out to explore the link between instantaneous peak flow (IPF) and maximum daily flow (MDF) where the multiple regression model is proved to have the best performance. The objective of this study is to further investigate the acceptability of the multiple regression model for post-processing simulated daily flows from hydrological modeling. The model based flood frequency analysis allows to consider change in the condition of the catchments and in climate for design. Here, the HBV model is calibrated on peak flow distributions and flow duration curves using two approaches. In a two -step approach the simulated MDF are corrected with a priory established regressions. In a one-step procedure the regression coefficients are calibrated together with the parameters of the model. For the analysis data from 18 mesoscale catchments in the Aller-Leine river basin in Northern Germany are used. The results show that: (1) the multiple regression model is capable to predict the peak flows with the simulated MDF data; (2) the calibrated hydrological model reproduces well the magnitude and frequency distribution of peak flows; (3) the one-step procedure outperforms the two-step procedure regarding the estimation of peak flows.

  18. Postglacial response of Arctic Ocean gas hydrates to climatic amelioration.

    PubMed

    Serov, Pavel; Vadakkepuliyambatta, Sunil; Mienert, Jürgen; Patton, Henry; Portnov, Alexey; Silyakova, Anna; Panieri, Giuliana; Carroll, Michael L; Carroll, JoLynn; Andreassen, Karin; Hubbard, Alun

    2017-06-13

    Seafloor methane release due to the thermal dissociation of gas hydrates is pervasive across the continental margins of the Arctic Ocean. Furthermore, there is increasing awareness that shallow hydrate-related methane seeps have appeared due to enhanced warming of Arctic Ocean bottom water during the last century. Although it has been argued that a gas hydrate gun could trigger abrupt climate change, the processes and rates of subsurface/atmospheric natural gas exchange remain uncertain. Here we investigate the dynamics between gas hydrate stability and environmental changes from the height of the last glaciation through to the present day. Using geophysical observations from offshore Svalbard to constrain a coupled ice sheet/gas hydrate model, we identify distinct phases of subglacial methane sequestration and subsequent release on ice sheet retreat that led to the formation of a suite of seafloor domes. Reconstructing the evolution of this dome field, we find that incursions of warm Atlantic bottom water forced rapid gas hydrate dissociation and enhanced methane emissions during the penultimate Heinrich event, the Bølling and Allerød interstadials, and the Holocene optimum. Our results highlight the complex interplay between the cryosphere, geosphere, and atmosphere over the last 30,000 y that led to extensive changes in subseafloor carbon storage that forced distinct episodes of methane release due to natural climate variability well before recent anthropogenic warming.

  19. 10Be cosmic-ray exposure dating of moraines and rock avalanches in the Upper Romanche valley (French Alps): Evidence of two glacial advances during the Late Glacial/Holocene transition

    NASA Astrophysics Data System (ADS)

    Chenet, Marie; Brunstein, Daniel; Jomelli, Vincent; Roussel, Erwan; Rinterknecht, Vincent; Mokadem, Fatima; Biette, Melody; Robert, Vincent; Léanni, Laëtitia

    2016-09-01

    Cosmic-ray exposure (CRE) dating of moraines allow glacier fluctuations and past climate change reconstructions. In the French Alps, there is a lack of moraine dating for the Late Glacial/Holocene transition period. Here we present a chronology of glacier advances in the Upper Romanche valley (French Alps - Massif des Ecrins) based on 10Be CRE dating. CRE ages of moraines of 13.0 ± 1.1 ka and 12.4 ± 1.5 ka provide evidence for two stages of glacial advance or standstill at the end of the Late Glacial. The CRE dating of a rock avalanche deposit at 12.2 ± 1.5 ka is attributed to post-glacial debuttressing and reveals rapid deglaciation at the end of the Late Glacial. A CRE age of 7.1 ± 0.7 ka of a second mass-wasting, whose triggering factor is unidentified so far, indicates that up to an altitude of 2300 m a.s.l., the valley was ice-free as of ∼7 kyr at the latest. The re-evaluation of 21 moraine 10Be CRE ages from nine glacial valleys across the Alps shows multiple glacial advances occurring at the Late Glacial/Holocene transition. These results lead to a re-evaluation of the importance of cooling events during the Allerød and the Younger Dryas in the Alps.

  20. Stratigraphy and chronology of offshore to nearshore deposits associated with the Provo shoreline, Pleistocene Lake Bonneville, Utah

    USGS Publications Warehouse

    Godsey, Holly S.; Oviatt, Charles G.; Miller, David M.; Chan, Marjorie A.

    2011-01-01

    Stratigraphic descriptions and radiocarbon data from eleven field locations are presented in this paper to establish a chronostratigraphic framework for offshore to nearshore deposits of Lake Bonneville. Based on key marker beds and geomorphic position, the deposits are interpreted to have accumulated during the period from the late transgressive phase, through the overflowing phase, into the regressive phase of the lake. Radiocarbon ages of sediments associated with the Provo shoreline indicate that Lake Bonneville dropped rapidly from the Provo shoreline at about 12,600 14C yr BP (15,000 cal yr B.P.). The presence of one or more sand beds in the upper part of the Provo-aged marl indicates rapid lowering of lake level or storm events at the end of the Provo episode. An accurate understanding of the timing and nature of Lake Bonneville's climate-driven regression from the Provo shoreline is critical to correlations with records of regional and hemispheric climate change. The rapid descent of the lake from the Provo shoreline correlates with the decline of Lakes Lahontan and Estancia, and with the onset of the BØlling–AllerØd warming event.

  1. Last glacial-interglacial environments in the southern Rocky Mountains, USA and implications for Younger Dryas-age human occupation

    NASA Astrophysics Data System (ADS)

    Briles, Christy E.; Whitlock, Cathy; Meltzer, David J.

    2012-01-01

    The last glacial-interglacial transition (LGIT; 19-9 ka) was characterized by rapid climate changes and significant ecosystem reorganizations worldwide. In western Colorado, one of the coldest locations in the continental US today, mountain environments during the late-glacial period are poorly known. Yet, archaeological evidence from the Mountaineer site (2625 m elev.) indicates that Folsom-age Paleoindians were over-wintering in the Gunnison Basin during the Younger Dryas Chronozone (YDC; 12.9-11.7 ka). To determine the vegetation and fire history during the LGIT, and possible explanations for occupation during a period thought to be harsher than today, a 17-ka-old sediment core from Lily Pond (3208 m elev.) was analyzed for pollen and charcoal and compared with other high-resolution records from the southern Rocky Mountains. Widespread tundra and Picea parkland and low fire activity in the cold wet late-glacial period transitioned to open subalpine forest and increased fire activity in the Bølling-Allerød period as conditions became warmer and drier. During the YDC, greater winter snowpack than today and prolonged wet springs likely expanded subalpine forest to lower elevations than today, providing construction material and fuel for the early inhabitants. In the early to middle Holocene, arid conditions resulted in xerophytic vegetation and frequent fire.

  2. Abdichtungen mit Bitumenbahnen

    NASA Astrophysics Data System (ADS)

    Rahn, Axel C.; Unger, Wolfram

    Das Werk Bauwerksabdichtung von Karl Lufsky, im allgemeinen Sprachgebrauch auch Der Lufsky genannt, war immer das Standardwerk für Flächenabdichtungen mit Bitumenwerkstoffen. Karl Lufsky war erst Mitarbeiter des Geschäftsführers Otto Latendorf der 1924 in Berlin gegründeten Firma ARIDO Abdichtungs-GmbH und später ihr Geschäftsführer [8.1]. Eine Baustelle war seit 1950 der Keller der neuen Sowjetischen Botschaft Unter den Linden. Eines Tages sprach dort einer der russischen Ingenieur-Offiziere Otto Latendorf an und fragte ihn, ob er wohl eine schriftliche Zusammenfassung aller technischen Probleme der bituminösen Bauwerksabdichtung für ihn verfassen könnte. Mit dieser Schrift würde er sich dann zu seinem Abschlussexamen in Moskau melden. Vergüten wollte er den Arbeitsaufwand mit Lebensmittellieferungen. Otto Latendorf willigte ein und machte sich gemeinsam mit Karl Lufsky an die Arbeit. Dies war offensichtlich der Impuls für Karl Lufsky, einige Zeit später im Leipziger Teubner Verlag die erste Auflage des Buchs "Bauwerksabdichtungen“ herauszugeben, womit der Grundstein gelegt wurde, aus einer "Moskauer Examensarbeit“ in den letzten 50 Jahren ein bedeutendes Fachbuch zu machen.

  3. Traitement chirurgical des lésions sacro-iliaques dans les fractures instables de l’anneau pelvien par vissage sacro-iliaque percutané

    PubMed Central

    Karabila, Mohamed Amine; Hmouri, Ismail; Madani, Tarik; Mhamdi, Younes; Azouz, Mohamed; Kharmaz, Mohamed; Ouadaghiri, Mohamed; Lamrani, Moulay Omar; Lahlou, Abdou; Bardouni, Ahmed; Mahfoud, Mustapha; Berrada, Mohamed Saleh; Vasile, Christian

    2016-01-01

    Les fractures du bassin, le plus souvent multiples, sont fréquemment instables et surviennent le plus souvent dans des contextes traumatiques violents. Le traitement orthopédique de ces lésions est souvent pénible pour le patient et pour le personnel médical nécessitant une décharge au lit ou parfois des tractions qui peuvent aller jusqu'à 45 jours et peut compromettre la statique et la marche, le traitement chirurgical à ciel ouvert est un geste difficile, grevé d'une morbidité non négligeable avec un risque vasculaire (plexus veineux), nerveux (racines sacrées) ou septique notamment à prendre en compte, elle est donc généralement réservée aux formes neurologiques et fortement déplacées. La fixation percutanée sous radioscopie dans les fractures instables du bassin type B et C permet la synthèse des lésions postérieures source d’instabilité en fixant l’os coxal avec le corps de S1 ou S2 et la reprise rapide de la rééducation et de la marche. PMID:27795765

  4. Retrospective analysis of a VACM (vacuum-assisted closure and mesh-mediated fascial traction) treatment manual for temporary abdominal wall closure - results of 58 consecutive patients.

    PubMed

    Beltzer, Christian; Eisenächer, Alexander; Badendieck, Steffen; Doll, Dietrich; Küper, Markus; Lenz, Stefan; Krapohl, Björn Dirk

    2016-01-01

    Einleitung: Das optimale Behandlungskonzept eines temporären Bauchdeckenverschlusses (temporary abdominal closure, TAC) bei kritisch kranken viszeralchirurgischen Patienten mit offenem Abdomen („open abdomen“, OA) ist weiterhin unklar. Durch eine VACM-Therapie (vacuum-assisted closure and mesh-mediated fascial traction) scheinen sich gegenüber anderen Verfahren des TAC höhere Faszienverschlussraten (delayed primary fascial closure rate, FCR) realisieren zu lassen. Material und Methoden: Patienten unserer Klinik (n=58), welche in den Jahren 2005 bis 2008 mittels eines VAC/VACM-Behandlungsmanuals behandelt wurden, wurden retrospektiv analysiert. Ergebnisse: Die FCR aller Patienten betrug insgesamt 48,3% (95%-Konfidenzintervall: 34,95–61,78). Bei Patienten, bei denen im Verlauf ein Vicryl-Netz auf Faszienebene implantiert wurde (VACM-Therapie), konnte eine FCR von 61,3% realisiert werden. Die Letalität der mittels VACM therapierten Patienten betrug 45,2% (95%-KI: 27,32–63,97).Schlussfolgerung: Die Ergebnisse der eigenen Untersuchung bestätigen bisherige Studienergebnisse, die eine akzeptable FCR bei non-trauma-Patienten durch Anwendung der VACM-Therapie zeigen konnten. Die VACM-Therapie scheint aktuell Therapiekonzept der ersten Wahl bei Patienten mit OA und Indikation zum TAC zu sein.

  5. Interrelationship of age and diet in Romania's oldest human burial.

    PubMed

    Bonsall, Clive; Boroneanţ, Adina; Soficaru, Andrei; McSweeney, Kathleen; Higham, Tom; Miriţoiu, Nicolae; Pickard, Catriona; Cook, Gordon

    2012-04-01

    In 1968, excavations in the Climente II cave in the Iron Gates gorge of the River Danube in southwest Romania unearthed the skeleton of an adult male. The burial was assumed to be of Late Pleistocene age because of the presence of Late Upper Palaeolithic (LUP) artefacts in the cave. However, there was no strong supporting stratigraphic evidence, and the body position is reminiscent of Early Neolithic burial practice in the region. Here, we report the results of radiocarbon and stable isotope analyses of the Climente II skeleton, which show that the skeleton dates to the Bølling-Allerød Interstadial ~14,500 cal BP. This is several millennia older than any previously dated human remains from the Iron Gates region and confirms its status as the oldest known burial from Romania. The stable isotope results indicate a diet with an emphasis on aquatic resources, contrary to the commonly held view that the LUP inhabitants of the Iron Gates subsisted mainly by hunting large land mammals.

  6. Changing amounts and sources of moisture in the U.S. southwest since the Last Glacial Maximum in response to global climate change

    NASA Astrophysics Data System (ADS)

    Feng, Weimin; Hardt, Benjamin F.; Banner, Jay L.; Meyer, Kevin J.; James, Eric W.; Musgrove, MaryLynn; Edwards, R. Lawrence; Cheng, Hai; Min, Angela

    2014-09-01

    The U.S. southwest has a limited water supply and is predicted to become drier in the 21st century. An improved understanding of factors controlling moisture sources and availability is aided by reconstruction of past responses to global climate change. New stable isotope and growth-rate records for a central Texas speleothem indicate a strong influence of Gulf of Mexico (GoM) moisture and increased precipitation from 15.5 to 13.5 ka, which includes the majority of the Bølling-Allerød warming (BA: 14.7-12.9 ka). Coeval speleothem records from 900 and 1200 km to the west allow reconstruction of regional moisture sources and atmospheric circulation. The combined isotope and growth-rate time series indicates 1) increased GoM moisture input during the majority of the BA, producing greater precipitation in Texas and New Mexico; and 2) a retreat of GoM moisture during Younger Dryas cooling (12.9-11.5 ka), reducing precipitation. These results portray how late-Pleistocene atmospheric circulation and moisture distribution in this region responded to global changes, providing information to improve models of future climate.

  7. The disappearance of glaciers in the Tien Shan Mountains in Central Asia at the end of Pleistocene

    NASA Astrophysics Data System (ADS)

    Takeuchi, Nozomu; Fujita, Koji; Aizen, Vladimir B.; Narama, Chiyuki; Yokoyama, Yusuke; Okamoto, Sachiko; Naoki, Kazuhiro; Kubota, Jumpei

    2014-11-01

    Glaciers in Central Asia are among the largest ice masses in the Eurasian continent and have supplied vital water to local inhabitants for thousands of years. The glaciers in this region are generally believed to be remnants of the last deglaciation, however, glacier variability in the central Asian mountains since the Last Glacial Maximum (LGM) has not been well documented. Here, we report an 86.87 m-deep ice core record drilled on an ice cap in the Tien Shan Mountains of Central Asia. Radiocarbon dating of organic soil from the bottom of the ice-core borehole showed that the age of the soil was 12,656 - 12,434 cal years before present, coincident with the beginning of the Younger Dryas cold period (YD). This result indicates that the ice cap did not exist in the Bølling-Allerød period (BA), which was the warm period before the YD, and that the BA climate was significantly warmer than at present. It also indicates that the ice cap has never entirely disappeared in any warm periods throughout the Holocene. We estimated that during the BA its extent was 43% or less of the present glacier coverage in the mountains. Our results suggest that this region at the end of Pleistocene was considerably warmer than at present, and that most of the present glaciers in this region are not relics of the Last Glacial period, but are composed of ice formed during the YD and Holocene.

  8. Lifestyle and nickel allergy in a Swedish adolescent population: effects of piercing, tattooing and orthodontic appliances.

    PubMed

    Fors, Ronny; Persson, Maurits; Bergström, Erik; Stenlund, Hans; Stymne, Birgitta; Stenberg, Berndt

    2012-11-01

    The aim of this study was to estimate the prevalence of life-style practices in adolescents and their association with nickel allergy. Upper secondary school pupils (n = 4,376; 15-23 years) were patch-tested for nickel aller-gy, follow-ing completion of a questionnaire (answered by 6,095). Almost 86% girls and 21% of boys reported piercing. More girls (6%) than boys (3%) had a tattoo. Twenty-six percent of the girls and 18% of the boys were regular smokers. Vegetarian/vegan diets were reported by 20% of girls and by 6% of boys. Piercing, female gender, and vocational programme increased the risk of nickel allergy, whereas orthodontic appliance treat-ment prior to piercing reduced the risk of nickel allergy. Pupils in vocational programmes had the highest prevalence of nickel allergy. Lifestyle behaviours are interconnected and cluster in subgroups of adolescents. Female sex, piercing and choice of educational programme are prominent lifestyle markers. A trend shift is observed, where more girls than boys report tattooing.

  9. Late Pleistocene paleohydrology near the boundary of the Sonoran and Chihuahuan Deserts, southeastern Arizona, USA

    USGS Publications Warehouse

    Pigati, Jeffery S.; Bright, Jordon E.; Shanahan, Timothy M.; Mahan, Shannon

    2009-01-01

    Ground-water discharge (GWD) deposits form in arid environments as water tables rise and approach or breach the ground surface during periods of enhanced effective precipitation. Where preserved, these deposits contain information on the timing and elevation of past ground-water fluctuations. Here we report on the investigation of a series of GWD deposits that are exposed in discontinuous outcrops along a ???150-km stretch of the San Pedro Valley in southeastern Arizona, near the boundary of the Sonoran and Chihuahuan Deserts. Chronologic, isotopic, geochemical, faunal assemblage (ostracodes and gastropods), and sedimentological evidence collectively suggest that the elevation of the regional water table in the valley rose in response to a change in climate ???50 ka ago and remained relatively high for the next ???35 ka before falling during the B??lling-Aller??d warm period, rebounding briefly during the Younger Dryas cold event, and falling again at the onset of the Holocene. The timing of these hydrologic changes coincides closely with variations in ??18O values of calcite from a nearby speleothem to the west and changes in lake levels at pluvial Lake Cochise to the east. Thus, in southeastern Arizona, the assumption that changes in climate are reflected in all aspects of the hydrologic cycle of a region simultaneously is validated. The timing of these changes also broadly coincides with variations in the GISP2 ??18O record, which supports the hypothesis that atmospheric teleconnections existed between the North Atlantic and the deserts of the American Southwest during the late Pleistocene.

  10. Confirmation and Characterization of Young Disk-Bearing Brown Dwarfs and sub-Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    Gully-Santiago, M. A.; Allers, K. N.; Jaffe, D. T.

    2011-12-01

    The lowest mass objects in nearby star forming regions now accessible to spectroscopy are in the sub-brown dwarf regime, with estimated masses comparable to the masses of extrasolar planets and bordering the threshold of opacity limited fragmentation. We confirm and characterize, using R˜ 1500 near-infrared spectroscopy, 17 candidate young substellar objects in the Ophiuchus, Lupus I, and Chamaeleon II star forming regions from the Allers et al. (2006) sample. The spectral types range from M2-L2.5, with extinctions of 0 < AV < 10. We assign youth based on the presence of mid-IR excess and gravity sensitive spectral indices, like the triangular H-band continuum shape and the Na I equivalent width. All but one source from the photometrically selected sample of 19 are confirmed as bona fide young late type objects, an exceptional confirmation rate for this type of study. Two of the sources are known wide-separation binaries. We explore the advantage of increased resolution over existing low resolution spectroscopy for six objects. The objects' derived luminosities are in the range -3.3< log L/L⊙<-0.6, placing the lowest luminosity candidates comfortably in the substellar or even sub brown-dwarf mass regime.

  11. Einstellung und Wissen von Lehramtsstudierenden zur Evolution - ein Vergleich zwischen Deutschland und der Türkei

    NASA Astrophysics Data System (ADS)

    Graf, Dittmar; Soran, Haluk

    Es wird eine Untersuchung vorgestellt, in der Wissen und Überzeugungen von Lehramtsstudierenden aller Fächer zum Thema Evolution an zwei Universitäten in Deutschland und der Türkei erhoben worden sind. Die Befragung wurde in Dortmund und in Ankara durchgeführt. Es stellte sich heraus, dass ausgeprägte Defizite im Verständnis der Evolutionsmechanismen herrschen. Viele Studierende, insbesondere aus der Türkei, sind nicht von der Faktizität der Evolution überzeugt. Dies gilt sowohl für Studierende mit Fach Biologie als auch für Studierende mit anderen Fächern. Näher untersucht worden sind die Faktoren, die die Überzeugungen zur Evolution beeinflussen können, was ja in Anbetracht der hohen Ablehnungsrate der Evolution von besonderem Interesse ist. Das Vertrauen in die Wissenschaft spielt hierbei eine besondere Rolle: Wer der Wissenschaft vertraut, ist auch eher von der Evolution überzeugt, als diejenigen, die skeptisch gegenüber der Wissenschaft sind.

  12. Influence of the intertropical convergence zone on the East Asian monsoon.

    PubMed

    Yancheva, Gergana; Nowaczyk, Norbert R; Mingram, Jens; Dulski, Peter; Schettler, Georg; Negendank, Jörg F W; Liu, Jiaqi; Sigman, Daniel M; Peterson, Larry C; Haug, Gerald H

    2007-01-04

    The Asian-Australian monsoon is an important component of the Earth's climate system that influences the societal and economic activity of roughly half the world's population. The past strength of the rain-bearing East Asian summer monsoon can be reconstructed with archives such as cave deposits, but the winter monsoon has no such signature in the hydrological cycle and has thus proved difficult to reconstruct. Here we present high-resolution records of the magnetic properties and the titanium content of the sediments of Lake Huguang Maar in coastal southeast China over the past 16,000 years, which we use as proxies for the strength of the winter monsoon winds. We find evidence for stronger winter monsoon winds before the Bølling-Allerød warming, during the Younger Dryas episode and during the middle and late Holocene, when cave stalagmites suggest weaker summer monsoons. We conclude that this anticorrelation is best explained by migrations in the intertropical convergence zone. Similar migrations of the intertropical convergence zone have been observed in Central America for the period ad 700 to 900 (refs 4-6), suggesting global climatic changes at that time. From the coincidence in timing, we suggest that these migrations in the tropical rain belt could have contributed to the declines of both the Tang dynasty in China and the Classic Maya in Central America.

  13. Hunted gazelles evidence cooling, but not drying, during the Younger Dryas in the southern Levant

    NASA Astrophysics Data System (ADS)

    Hartman, Gideon; Bar-Yosef, Ofer; Brittingham, Alex; Grosman, Leore; Munro, Natalie D.

    2016-04-01

    The climatic downturn known globally as the Younger Dryas (YD; ∼12,900-11,500 BP) has frequently been cited as a prime mover of agricultural origins and has thus inspired enthusiastic debate over its local impact. This study presents seasonal climatic data from the southern Levant obtained from the sequential sampling of gazelle tooth carbonates from the Early and Late Natufian archaeological sites of Hayonim and Hilazon Tachtit Caves (western Galilee, Israel). Our results challenge the entrenched model that assumes that warm temperatures and high precipitation are synonymous with climatic amelioration and cold and wet conditions are combined in climatic downturns. Enamel carbon isotope values from teeth of human-hunted gazelle dating before and during the YD provide a proxy measure for water availability during plant growth. They reveal that although the YD was cooler, it was not drier than the preceding Bølling-Allerød. In addition, the magnitude of the seasonal curve constructed from oxygen isotopes is significantly dampened during the YD, indicating that cooling was most pronounced in the growing season. Cool temperatures likely affected the productivity of staple wild cereal resources. We hypothesize that human groups responded by shifting settlement strategies-increasing population mobility and perhaps moving to the warmer Jordan Valley where wild cereals were more productive and stable.

  14. Early warning of climate tipping points from critical slowing down: comparing methods to improve robustness

    PubMed Central

    Lenton, T. M.; Livina, V. N.; Dakos, V.; Van Nes, E. H.; Scheffer, M.

    2012-01-01

    We address whether robust early warning signals can, in principle, be provided before a climate tipping point is reached, focusing on methods that seek to detect critical slowing down as a precursor of bifurcation. As a test bed, six previously analysed datasets are reconsidered, three palaeoclimate records approaching abrupt transitions at the end of the last ice age and three models of varying complexity forced through a collapse of the Atlantic thermohaline circulation. Approaches based on examining the lag-1 autocorrelation function or on detrended fluctuation analysis are applied together and compared. The effects of aggregating the data, detrending method, sliding window length and filtering bandwidth are examined. Robust indicators of critical slowing down are found prior to the abrupt warming event at the end of the Younger Dryas, but the indicators are less clear prior to the Bølling-Allerød warming, or glacial termination in Antarctica. Early warnings of thermohaline circulation collapse can be masked by inter-annual variability driven by atmospheric dynamics. However, rapidly decaying modes can be successfully filtered out by using a long bandwidth or by aggregating data. The two methods have complementary strengths and weaknesses and we recommend applying them together to improve the robustness of early warnings. PMID:22291229

  15. Transient stratification as the cause of the North Pacific productivity spike during deglaciation

    NASA Astrophysics Data System (ADS)

    Lam, Phoebe J.; Robinson, Laura F.; Blusztajn, Jerzy; Li, Camille; Cook, Mea S.; McManus, Jerry F.; Keigwin, Lloyd D.

    2013-08-01

    During the Bølling-Allerød warm period of the last deglaciation, about 14kyr ago, there was a strong and pervasive spike in primary productivity in the North Pacific Ocean. It has been suggested that this productivity event was caused by an influx of the micronutrient iron from surrounding continental shelves as they were flooded by sea-level rise. Here we test this hypothesis by comparing numerous proxies of productivity with iron flux and provenance measured from a core from the subarctic Pacific Ocean. We find no evidence for an abrupt deglacial pulse of iron from any source at the time of peak productivity. Instead, we argue that the deglacial productivity peak was caused by two stepwise events. First, deep convection during early deglaciation increased nutrient supply to the surface but also increased the depth of the mixed layer, which pushed surface production deeper in the water column and induced light limitation. A subsequent input of meltwater from northern American ice sheets then stratified the water column, which relieved light limitation while leaving the surface waters enriched in nutrients. We conclude that iron plays, at most, a secondary role in controlling productivity during the glacial and deglacial periods in the subarctic Pacific Ocean.

  16. Rapid Climate Shifts during last Deglaciation over Central to Northern Europe

    NASA Astrophysics Data System (ADS)

    Schenk, F.; Muschitiello, F.; Brandefelt, J.; Wohlfarth, B.; Tarasov, L.; Naslund, J. O.; Johansson, A. V.

    2014-12-01

    Abrupt climate shifts during the last deglaciation provide test cases for analyzing the transient response of our climate system to changes in external forcings and internal feedbacks. The regional imprints of rapid climate shifts, their timing and hence connection to local vs. large-scale mechanisms are however still poorly understood owing to a limited number of records with usually large age uncertainties and low sampling rates. In this study we examine the spatiotemporal evolution of rapid climate shifts over central Europe and Scandinavia during Bølling-Allerød (14.7-12.7kyr BP) and Younger Dryas (~12kyr BP) by means of pollen data and climate simulations. For a better understanding of physical mechanisms behind regional imprints of climate shifts, time slice experiments with the Community Earth System Model (CCSM1.0.5) are set up at high resolution (1°x1°) using different topographies and ice sheets (ICE-5G and a new version of GLAC). Matching these time slice experiments with the spatial temperature pattern derived from pollen records, we estimate the extent to which environmental conditions (pollen) represent the direct large-scale influence of climate over the Euro-Atlantic sector vs. regional-scale climate effects e.g. caused by shrinking ice sheets and coastal transgression due to sea-level rise.

  17. Paleoenvironmental and paleoclimatic context during the Upper Palaeolithic (late Upper Pleistocene) in the Italian Peninsula. The small mammal record from Grotta Paglicci (Rignano Garganico, Foggia, Southern Italy)

    NASA Astrophysics Data System (ADS)

    Berto, Claudio; Boscato, Paolo; Boschin, Francesco; Luzi, Elisa; Ronchitelli, Annamaria

    2017-07-01

    Changes in large mammal population and biotic regionalism of the Italian Peninsula during Upper Pleistocene have been well documented over the last twenty years. On the other hand, only few studies have focused on the changes in small mammal fossil assemblages. Grotta Paglicci is a key archaeological site for Italian prehistory. It is well dated and it shows an uninterrupted chronological sequence of Upper Palaeolithic lithic industries, ranging from the Aurignacian to the Late Epigravettian. Small mammal remains from the Upper Palaeolithic layers of this cave have been identified and the assemblage has been analysed through the application of Simpson diversity index, Habitat Weighting and Bioclimatic model methods. The results show remarkable differences through the record: major climatic changes (GS2 is particularly well defined) are visible and a clear turning point is observable at the Bølling-Allerød interstadial transition. This is in line with environmental and climatic oscillations already detected in the Italian Peninsula. These data also suggest that a strong regionalism characterized the south-eastern Italian Peninsula during the Late Pleistocene.

  18. Absolute oscillator strengths for lines of neutral cobalt between 2276 A and 9357 A and a redetermination of the solar cobalt abundance

    SciTech Connect

    Cardon, B.L.; Smith, P.L.; Scalo, J.M.; Testerman, L.; Whaling, W.

    1982-09-01

    Absolute oscillator strengths of neutral cobalt have been determined from hook measurements for 159 transitions and emission intensity measurements for 314 transitions between 2276 A and 9357 A. Ninety-five of these transitions were subjected to the procedure developed by Cardon, Smith, and Whaling which fits combined absorption and emission data to a set of consistent, optimum, relative oscillator strengths and upper level lifetimes. These relative values were normalized to the radiative lifetimes of Figger et al. and of Marek and Vogt obtained by pulsed laser fluorescence. Absolute oscillator strengths for 362 transitions and 36 lifetimes were determined. Typical uncertainties in the reported absolute oscillator strengths are +- 15-25% (2/3 confidence level). Equivalent widths were obtained for nineteen solar cobalt lines with the McMath solar telescope at Kitt Peak National Observatory. These widths were used to redetermine the solar cobalt abundance, assuming the photospheric model of Holweger and a microturbulence velocity of 1.0 km s/sup -1/. The adopted solar cobalt abundance is the mean value log +12 = 4.92 +- 0.08 ( +- 19%), from the 19 cobalt transitions. This value is in excellent agreement with the solar values of Ross and Aller, of Biemont, and of Holweger and that of Cameron for carbonaceous chondrites.

  19. Absolute oscillator strengths for lines of neutral cobalt between 2276 A and 9357 A and a redetermination of the solar cobalt abundance

    NASA Astrophysics Data System (ADS)

    Cardon, B. L.; Smith, P. L.; Scalo, J. M.; Testerman, L.; Whaling, W.

    1982-09-01

    Absolute oscillator strengths of neutral cobalt have been determined from hook measurements for 159 transitions and emission intensity measurements for 314 transitions between 2276 Å and 9357 Å. Ninety-five of these transitions were subjected to the procedure developed by Cardon, Smith, and Whaling which fits combined absorption and emission data to a set of consistent, optimum, relative oscillator strengths and upper level lifetimes. These relative values were normalized to the radiative lifetimes of Figger et al. and of Marek and Vogt obtained by pulsed laser fluorescence. Absolute oscillator strengths for 362 transitions and 36 lifetimes were determined. Typical uncertainties in the reported absolute oscillator strengths are ±15-25% (2/3 confidence level). Equivalent widths were obtained for nineteen solar cobalt lines with the McMath solar telescope at Kitt Peak National Observatory. These widths were used to redetermine the solar cobalt abundance, assuming the photospheric model of Holweger and a microturbulence velocity of 1.0 km s-1. The adopted solar cobalt abundance is the mean value log Co/NH> + 12 = 4.92 ± 0.08 (±19%), from the 19 cobalt transitions. This value is in excellent agreement with the solar values of Ross and Aller, of Biemont, and of Holweger and that of Cameron for carbonaceous chondrites.

  20. Late-glacial environmental oscillations as recorded in the soil archives of Gasserplatz (Vorarlberg, Austria).

    NASA Astrophysics Data System (ADS)

    van Mourik, Jan; Slotboom, Ruud; van der Plicht, Hans; Streurman, Harm Jan; Kuijper, Wim; Hoek, Wim; de Graaff, Leo

    2013-04-01

    Gasserplatz is a shallow basin in the rather flat, glacially eroded confluence area of the former Rhine glacier and the Ill glacier. It became ice-free during the Feldkirch stadium ( ≈ 15.500 calBP) and transferred in a tiny lake. During the Late-glacial lacustrine carbonate (calcareous gyttja) was deposited, in the Holocene peat accumulated. Gasserplatz deposits are valuable soil archives for palaeo-environmental research. The Late-glacial environmental fluctuations have been recorded in the gyttja deposits. The combined results of pollen, macro-remains and stable isotope analyses that have been put into an independent time frame demonstrate that these fluctuations are associated with large scale temperature oscillations as registered in Greenland ice cores. The results show also a slight delay in environmental response on temperature change. The isotope stratigraphy points to higher temperatures during the whole Bølling while Betula trees arrived in Gasserplatz area later. During the Allerød there are frequent short-lived oscillations in temperature, but the palynological expression of these changes resulted in not more than three Betula peaks. Comparison with the research results of similar Alpine lake deposits makes clear that the fluctuations in the Betula curve are not a local but a regional phenomenon.

  1. Early warning of climate tipping points from critical slowing down: comparing methods to improve robustness.

    PubMed

    Lenton, T M; Livina, V N; Dakos, V; van Nes, E H; Scheffer, M

    2012-03-13

    We address whether robust early warning signals can, in principle, be provided before a climate tipping point is reached, focusing on methods that seek to detect critical slowing down as a precursor of bifurcation. As a test bed, six previously analysed datasets are reconsidered, three palaeoclimate records approaching abrupt transitions at the end of the last ice age and three models of varying complexity forced through a collapse of the Atlantic thermohaline circulation. Approaches based on examining the lag-1 autocorrelation function or on detrended fluctuation analysis are applied together and compared. The effects of aggregating the data, detrending method, sliding window length and filtering bandwidth are examined. Robust indicators of critical slowing down are found prior to the abrupt warming event at the end of the Younger Dryas, but the indicators are less clear prior to the Bølling-Allerød warming, or glacial termination in Antarctica. Early warnings of thermohaline circulation collapse can be masked by inter-annual variability driven by atmospheric dynamics. However, rapidly decaying modes can be successfully filtered out by using a long bandwidth or by aggregating data. The two methods have complementary strengths and weaknesses and we recommend applying them together to improve the robustness of early warnings.

  2. Links between salinity variation in the Caribbean and North Atlantic thermohaline circulation.

    PubMed

    Schmidt, Matthew W; Spero, Howard J; Lea, David W

    2004-03-11

    Variations in the strength of the North Atlantic Ocean thermohaline circulation have been linked to rapid climate changes during the last glacial cycle through oscillations in North Atlantic Deep Water formation and northward oceanic heat flux. The strength of the thermohaline circulation depends on the supply of warm, salty water to the North Atlantic, which, after losing heat to the atmosphere, produces the dense water masses that sink to great depths and circulate back south. Here we analyse two Caribbean Sea sediment cores, combining Mg/Ca palaeothermometry with measurements of oxygen isotopes in foraminiferal calcite in order to reconstruct tropical Atlantic surface salinity during the last glacial cycle. We find that Caribbean salinity oscillated between saltier conditions during the cold oxygen isotope stages 2, 4 and 6, and lower salinities during the warm stages 3 and 5, covarying with the strength of North Atlantic Deep Water formation. At the initiation of the Bølling/Allerød warm interval, Caribbean surface salinity decreased abruptly, suggesting that the advection of salty tropical waters into the North Atlantic amplified thermohaline circulation and contributed to high-latitude warming.

  3. A 15,400-year record of climate variation from a subalpine lacustrine sedimentary sequence in the western Nanling Mountains in South China

    NASA Astrophysics Data System (ADS)

    Zhong, Wei; Cao, Jiayuan; Xue, Jibin; Ouyang, Jun

    2015-09-01

    Multi-proxy records of a subalpine lacustrine sequence in Daping Swamp in the western Nanling Mountains provide evidence for exploring climate variability in the past 15,400 yr. Two dry and cool (15,400-14,500 and 13,000-11,000 cal yr BP) and one humid and warm interval (14,500-13,200 cal yr BP), which we correlate to Heinrich Event 1, the Younger Dryas and the Bølling-Allerød event respectively, are revealed. The early Holocene climate (11,000-8000 cal yr BP) was characterized by less humid and warm conditions, suggesting a weaker Asian summer monsoon (ASM) intensity. Our findings indicate that the Holocene optimum occurred between 8000 and 4500 cal yr BP, and the most intensified ASM appears from 8000 to 7000 cal yr BP. After 4500 cal yr BP, climate shifted to relatively cool and dry conditions. We speculate that five short dry and cool events centered at ~ 11,000, 9000, 8400, 6000, and 3500 cal yr BP were linked to the Holocene ice-rafting events detected in the North Atlantic. Migration of the ITCZ, and the oceanic-atmospheric circulations, particularly SST changes in the tropical Pacific may play a pivotal role in climate variation of the study region.

  4. Stratigraphy and chronology of offshore to nearshore deposits associated with the Provo shoreline, Pleistocene Lake Bonneville, Utah

    USGS Publications Warehouse

    Godsey, H.S.; Oviatt, Charles G.; Miller, D.M.; Chan, M.A.

    2011-01-01

    Stratigraphic descriptions and radiocarbon data from eleven field locations are presented in this paper to establish a chronostratigraphic framework for offshore to nearshore deposits of Lake Bonneville. Based on key marker beds and geomorphic position, the deposits are interpreted to have accumulated during the period from the late transgressive phase, through the overflowing phase, into the regressive phase of the lake. Radiocarbon ages of sediments associated with the Provo shoreline indicate that Lake Bonneville dropped rapidly from the Provo shoreline at about 12,600 14C yr BP (15,000 cal yr B.P.). The presence of one or more sand beds in the upper part of the Provo-aged marl indicates rapid lowering of lake level or storm events at the end of the Provo episode. An accurate understanding of the timing and nature of Lake Bonneville's climate-driven regression from the Provo shoreline is critical to correlations with records of regional and hemispheric climate change. The rapid descent of the lake from the Provo shoreline correlates with the decline of Lakes Lahontan and Estancia, and with the onset of the B??lling-Aller??d warming event. ?? 2011 Elsevier B.V.

  5. Subtsve A~é­ An In-situ Remediation Method For The Saturated and Unsaturated Zone

    NASA Astrophysics Data System (ADS)

    Koschitzky, H.-P.; Troetschler, O.; Weber, K.

    two different industrial sites, the ratio is about 1 until the steam hits the unsaturated zone. The remediation efficiency for a site-specific multi-component contamination in the groundwater fluctuation zone was investigated in 2-D experiments comparing the 1 steam injection into the groundwater with the steam injection into the capillary fringe. A slightly higher effectiveness with a recovery rate of more than 97% was measured for the steam injection into the groundwater. A significant difference between both methods was obtained in the kind of removal of the contaminants. SubTSVE yields to a higher mass removal by phase extraction from the groundwater table as a free organic phase. To reduce the risk of mobilisation as a free product the injection of a steam-air mixture into the groundwater is proposed in order to evaporate the contaminants. The effects of steam-air injection will be investigated in VEGAS large container (l = 6 m, w = 3 m, h = 4.5 m) filled with soil from an industrial site and compared with those of steam injection within the same container. References ITAMURA &UDELL (1993): Experimental Cleanup of a Dense Non-Aqueous Phase Liqid in the Unsaturated Zone of a Porous Medium Using Steam Injection, Multiphase Transport in Porous Media, ASME, HTD-Vol. 265, 57-62 FÄRBER, A. (1997): Wärmetransport in der ungesättigten Bodenzone: Entwicklung einer thermischen In-situ-Sanierungstechnologie, Mitteilungen Institut für Wasserbau, Universität Stuttgart, Heft 96 UDELL et al. (1994): NAS Lemoore JP-5 cleanup demonstration, Berkeley Environ- mental Restoration Center, University of California, Berkeley NEWMARK &AINES (1995): Summary of the LLNL Gasoline Spill Demonstration Dynamic Underground Stripping Project, Lawrence Livermore Natl. Lab., UCRL-ID- 120416 SCHMIDT et al. (1999): Pilothafte Sanierung eines BTEX Schadens an einem ehema- ligen Gaswerksstandort mit der thermisch unterstützten Bodenluftabsaugung (TUBA) durch Dampfinjektion, Wiss. Bericht WB 99

  6. Deglacial variability in Okhotsk Sea Intermediate Water ventilation and biogeochemistry: Implications for North Pacific nutrient supply and productivity

    NASA Astrophysics Data System (ADS)

    Lembke-Jene, Lester; Tiedemann, Ralf; Nürnberg, Dirk; Kokfelt, Ulla; Kozdon, Reinhard; Max, Lars; Röhl, Ursula; Gorbarenko, Sergey A.

    2017-03-01

    The modern North Pacific plays a critical role in marine biogeochemical cycles, as an oceanic sink of CO2 and by bearing some of the most productive and least oxygenated waters of the World Ocean. The capacity to sequester CO2 is limited by efficient nutrient supply to the mixed layer, particularly from deeper water masses in the Pacific's subarctic and marginal seas. The region is in addition only weakly ventilated by North Pacific Intermediate Water (NPIW), which receives its characteristics from Okhotsk Sea Intermediate Water (OSIW). Here, we present reconstructions of intermediate water ventilation and productivity variations in the Okhotsk Sea that cover the last glacial termination between eight and 18 ka, based on a set of high-resolution sediment cores from sites directly downstream of OSIW formation. In a multi-proxy approach, we use total organic carbon (TOC), chlorin, biogenic opal, and CaCO3 concentrations as indicators for biological productivity. C/N ratios and XRF scanning-derived elemental ratios (Si/K and Fe/K), as well as chlorophycean algae counts document changes in Amur freshwater and sediment discharge that condition the OSIW. Stable carbon isotopes of epi- and shallow endobenthic foraminifera, in combination with 14C analyses of benthic and planktic foraminifera imply decreases in OSIW oxygenation during deglacial warm phases from c. 14.7 to 13 ka (Bølling-Allerød) and c. 11.4 to 9 ka (Preboreal). No concomitant decreases in Okhotsk Sea benthic-planktic ventilation ages are observed, in contrast to nearby, but southerly locations on the Japan continental margin. We attribute Okhotsk Sea mid-depth oxygenation decreases in times of enhanced organic matter supply to maxima in remineralization within OSIW, in line with multi-proxy evidence for maxima in primary productivity and supply of organic matter. Sedimentary C/N and Fe/K ratios indicate more effective entrainment of nutrients into OSIW and thus an increased nutrient load of OSIW during

  7. Evaluating an ecosystem management approach for improving water quality in two contrasting study catchments in south-west England.

    NASA Astrophysics Data System (ADS)

    Glendell, Miriam; Brazier, Richard

    2014-05-01

    The European Water Framework Directive (WFD) 2000 established a new emphasis for the management of freshwaters by establishing ecologically-based water quality targets that are to be achieved through holistic, catchment-scale, ecosystem management approaches. However, significant knowledge gaps still exist in the understanding of the cumulative effectiveness of multiple mitigation measures on a number of pollutants at a catchment scale. This research furthers the understanding of the effectiveness of an ecosystem management approach to deliver catchment-scale water quality improvements in two contrasting study catchments in south-west England: the lowland agricultural Aller and the upland semi-natural Horner Water. Characterisation of the spatial variability of soil properties (bulk density, total carbon, nitrogen, C:N ratio, stable isotope δ15N, total, organic and inorganic phosphorus) in the two study catchments demonstrated extensive alteration of soil properties in the agricultural catchment, with likely long-term implications for the restoration of ecosystem functioning and water quality management (Glendell et al., 2014b). Further, the agricultural catchment supported a proportionally greater total fluvial carbon (dissolved and particulate) export than the semi-natural catchment. During an eight month period for which a comparable continuous turbidity record was available, the estimated SS yields from the agricultural catchment (25.5-116.2 t km-2) were higher than from the semi-natural catchment (21.7-57.8 t km-2). In addition, the agricultural catchment exported proportionally more TPC (0.51-2.59 kg mm-1) than the semi-natural catchment (0.36-0.97 kg mm-1) and a similar amount of DOC (0.26-0.52 kg mm-1 in the Aller and 0.24-0.32 kg mm-1 in Horner Water), when normalised by catchment area and total discharge, despite the lower total soil carbon pool, thus indicating an enhanced fluvial loss of sediment and carbon (Glendell and Brazier, in review). Whilst

  8. Holywell Coombe, Folkestone: A 13,000 year history of an English Chalkland Valley

    NASA Astrophysics Data System (ADS)

    Preece, R. C.; Bridgland, D. R.

    1999-07-01

    Holywell Coombe is a valley cut into the scarp-face of the North Downs Chalk cuesta, near Folkestone, Kent. Its geological importance stems from a highly fossiliferous sequence of Lateglacial and Holocene deposits that line the valley floor. These have yielded a molluscan succession of particular importance, providing a record of environmental change throughout the past 13,000 radiocarbon years. Waterlogging of the basal deposits has prevented oxidation, leading to the preservation of a range of organic fossils, such as plant and insect remains, that normally do not survive in calcareous environments. This enables linkage between faunal and vegetational records, allowing the differential rates of response of particular groups to be critically compared. The importance of the site was revealed in 1968 in trial pits connected with an aborted Channel Tunnel project. Resurrection of plans to build a tunnel led in 1987 to major 'rescue' excavations and multidisciplinary investigations, the results of which are reviewed here. A three-dimensional picture of the valley infill was established from a network of 180 boreholes. Critical parts of the sequence were investigated in specially excavated trenches and sections exposed during construction of the tunnel. Systematic sampling at a number of locations within the valley provided a palaeontological record from the full stratigraphical succession. A number of Lateglacial and Holocene soils were found to be represented in the sequence, including that formed during the Allerød phase of the Lateglacial interstadial. The molluscan zonation scheme previously defined at Holywell Coombe, and applicable over large areas of southern Britain and possibly further afield, has been refined and dated with greater precision. The Lateglacial sequence has been extended back to the early part of the Lateglacial interstadial by this study and the site chronology is now underpinned by over 35 new radiocarbon dates. Quantitative palaeoclimatic

  9. Carbon Inputs to Arctic Streams and Lakes during Climate Warming: Lessons from Prehistory

    NASA Astrophysics Data System (ADS)

    Mann, D. H.; Gaglioti, B.; Pohlmann, J. W.; Rasic, J. T.; Jones, B. M.; Wooller, M. J.

    2013-12-01

    Warming of the Arctic will cause perennially frozen ground (permafrost) to thaw and release ancient carbon into streams and lakes. How sensitive is permafrost-carbon release to warming? One way to answer this question is to quantify how permafrost C responded to prehistoric warming events. Here we use lake sediments as a long-term record of permafrost-C release from an arctic watershed. The radiocarbon-age offset is the age difference between the true age of deposition (the 14C age of delicate, terrestrial plant remains) and the apparent age of the sedimentary stratum where these plant remains were laid down (the 14C age of the surrounding bulk sediment). In many arctic lakes, true age is younger than apparent age because bulk organic sediment contains particulate and dissolved C originating from soils, peat, and permafrost. Shifts in the magnitude of the 14C-age offset over time provide a proxy for changes in the relative amount of permafrost C released from the watershed. Our age-offset record comes from the Lake of the Pleistocene (LOP), a partially-drained lake basin on the northern flank of the Brooks Range whose macrofossil-rich deposits were laid down continuously after 14,500 calendar years BP (cal yr BP). The LOP watershed is underlain by continuous permafrost and contains extensive, frozen peatlands. We excavated a wide swath of the former lake bed and collected paired samples of twigs and their enclosing sediment to construct a high-resolution age-offset chronology. Today, the radiocarbon age of dissolved and particulate organic matter being deposited in the LOP basin is 2,500 yr. During the warmer-than-present, Bølling-Allerød period (14,700-12,800 cal yr BP), and during Holocene Thermal Maximum (11,700-8500 cal yr BP), the age offset doubled to around 4,000 yr. This enhanced input of old C was interrupted during a reversion to cold conditions during the Younger Dryas (12,800-11,700 cal yr BP). Interesting, 14C-age offsets during the YD were similar

  10. Climate and sea-level controls on turbidity current activity on the Tanzanian upper slope during the last deglaciation and the Holocene

    NASA Astrophysics Data System (ADS)

    Liu, Xiting; Rendle-Bühring, Rebecca; Henrich, Rüdiger

    2016-02-01

    Turbidity current is one of the most important mechanisms for rapid transportation of terrigenous sediments from the continental margin to the deep sea. Although extensive work on turbidite systems has been carried out globally, the Tanzanian margin, off East Africa, is poorly understood. This paper will therefore use a well-dated high-resolution marine core (GeoB12624-1), obtained during RV Meteor Cruise M75/2, from the upper Tanzanian continental slope, offshore the Rufiji River delta, to demonstrate which environmental parameters, e.g., climate versus sea level, control the temporal distribution of the turbidite deposits during the last deglaciation and the Holocene. Results show that the turbidite deposits are composed of coarser-grained sediments with normally graded bedding. The thickness, mean grain size and frequency of the turbidite beds were estimated to detect turbidity current activity since the Last Glacial Maximum (LGM). A total of 12 turbidite beds (TI-T12) was recognized and divided into three intervals, based on the presence and intensity of the turbidite deposits. (I) a glacial sea-level lowstand (LGM and Heinrich Stadial 1; 19.3-14.6 ka): suppressed turbidity current activity due to arid conditions in the hinterland and sea-level lowstand. (II) A deglacial sea-level rise period (Bølling-Allerød interval to the early Holocene; 14.6-8 ka): turbidity current activity started to be strengthened during the Bølling-Allerød warming interval (T1), followed by a first increase in turbidite frequency, thickness and mean grain-size during the Younger Dryas (T2-T4) and a second increase during the early Holocene (T5-T10). (III) An interglacial sea-level highstand period (mid-to late Holocene; 8-2.5 ka): turbidity current activity diminished from the mid- (T11, T12) to late Holocene. This temporal distribution of turbidite deposits indicates that turbidity currents were most active during the last sea-level rise, synchronous with more humid climate in the

  11. The magnetism of speleothems: a novel tool for paleoclimatic studies

    NASA Astrophysics Data System (ADS)

    Lascu, I.; Feinberg, J. M.

    2011-12-01

    The magnetism of speleothems is an untapped resource of paleoclimatic, hydrogeologic, and geomagnetic information. Similar to other deposits containing magnetic minerals, speleothems chronicle the evolution of local environmental parameters via the concentration, composition and grain size of their magnetic mineral assemblages. Environmental magnetic studies on speleothems represent a new frontier in paleoclimate research because the low concentration of magnetic minerals in speleothems was often at or below the limit of detection of older magnetometers. Recent improvements in instrument sensitivity and resolution enable speleothems to reveal high quality data comparable to that of the most complete enviromagnetic records from traditional sedimentary deposits. The advantage of obtaining such records from speleothems is that they can be directly compared to temperature and precipitation reconstructions based on geochemical proxies from the same specimens. Well-dated environmental magnetic records from speleothems can yield high resolution reconstructions of regional and local climatic, erosional, or pedogenic histories, and may also contain information about the local hydrogeological conditions and aquifer architecture. In addition, speleothem records of the Earth's magnetic field intensity can provide information about the amplitude of shielding from cosmic rays, which determines the cosmogenic isotope production rate in the atmosphere, a key aspect of dating and paleoclimate reconstructions. Here we present two case studies of stalagmites whose magnetic properties can help decipher the local and regional environmental conditions at the time of speleothem formation. The first is a stalagmite from a cave in central China that grew continuously in the period 13,600-12,000 years BP, spanning the Late Glacial Allerød-Younger Dryas transition. The specimen is a fast-growing, annually-laminated speleothem. Continuous measurements using a pull-through cryogenic

  12. The temperature and precipitation reconstructions on Swiss stalagmites with a special emphasis on altitude gradient using noble-gases, δO-18 and δD of fluid inclusions

    NASA Astrophysics Data System (ADS)

    Ghadiri, Elaheh; Brennwald, Matthias; Kipfer, Rolf

    2017-04-01

    We present the results of an application of 'Combined Vacuum Crushing and Sieving (CVCS)' system (e.g., allowing to crush samples to defined grain size in vacuum) for the first time to stalagmites grown in cold climates during the last glacial-interglacial transition, but at different altitudes. Recently, concentrations of dissolved atmospheric noble gases in fluid inclusions of stalagmites were used to reconstruct past ambient cave temperatures, the annual mean temperature and hydrological conditions when the water was trapped. To reconstruct temperatures from noble gases (noble gas temperature: NGT) in water-filled inclusions, we processed samples from Swiss stalagmites M6 from Milandre cave (400 m.a.s.l) and GEF1 from Grotte aux Fées cave (895 m.a.s.l) covering the climatic transitions Allerød-Younger Dryas-Holocene. Water content. The amount of water extracted per unit mass of calcite fabric (e.g., 'water yield': WT) was shown to be a measure of the total water content. The data shows that the WT systematically changes with δ18Ocalcite of the calcite. We therefore conclude that WT records can be linked on changes in drip rates and thus can be used to track changes of past precipitation even in cold regions. Noble gases. Noble gas analysis shows that the annual mean temperatures in Milandre cave were 2.2±2.0°C during the late Allerød and dropped to 0±2°C at the Younger Dryas. Such temperatures close 0°C indicate that drip water supply stopped in response to the formation of permafrost conditions around the cave preventing further stalagmite growth. However, one late Holocene sample gave a cave temperature of 8.7±1.4°C agreeing generally with present day annual mean temperature. The annual mean temperature of 5.7±1.3°C from GEF1 was determined for the early Holocene. The observed data show systematic variations with sample elevation, e.g., higher temperature from lower altitude and vice versa. Combining the isotopic composition of water in fluid

  13. Remote Correlation of Paleoceanographic Events in the Northern Parts of Bering and Barents Seas during the Termination I and Early Holocene

    NASA Astrophysics Data System (ADS)

    Ivanova, E. V.; Ovsepyan, E.; Murdmaa, I.; de Vernal, A.; Risebrobakken, B.; Seitkalieva, E.; Radionova, E.; Alekhina, G.

    2014-12-01

    The Barents and Bering seas are closely linked to the High Arctic and to the THC by marine gateways as well as by land-sea and ocean-atmosphere interactions. Our multi-proxy time series demonstrate that these remote seas exhibited dramatic changes during the deglaciation through a succession of global and regional paleoceanographic events including the beginning of Termination I (BT1), Heinrich-1 or Oldest Dryas (OD), Bølling-Allerød (B/A), Younger Dryas (YD) and early Holocene (EH). In the NW Barents Sea, the increased subsurface-to-bottom Atlantic water inflow via the Kvitøya-Erik Eriksen trough (cores S 2519 and S 2528) is inferred at the late OD, late B/A and late YD/EH transition. These events are generally coupled with the strengthened AMOC. A remarkable sea surface warming and sea ice retreat are documented at ~ 13 ka BP. Surface warming and strong Atlantic water inflow were followed by intense iceberg calving in the Erik Eriksen Trough as indicated by the high IRD content of Core S-2519. The rock fragments are unsorted and mainly angular suggesting their ice-rafted (likely iceberg-rafted) origin. Svalbard glaciers apparently derived the material dominated by black schistous mudstones, hard limestones with coral remains, fine-grained sandstones from nearby islands, and icebergs spread it in the Kvitøya-Erik Eriksen Trough during the early deglaciation. The ice rafted coarse terrigenous material supply during the BT1 is also suggested for the NW Bering Sea. In the NW Pacific, NW Bering Sea and Sea of Okhotsk, surface bioproductivity peaked at B/A and EH mainly due to the global warming, enhanced nutrient supply by surface currents from the flooded northeastern shelf, intensified vertical mixing and water exchange through the opened straits. Oxygen-depleted bottom water at intermediate depths characterized several locations including the NW Bering Sea (Core SO201-2-85KL).

  14. Sackung in the highest mountains of Carpathians: response to retreat of Quaternary glaciers and regional climate changes?

    NASA Astrophysics Data System (ADS)

    Pánek, T.; Mentlík, P.; Engel, Z.; Braucher, R.; Zondervan, A.; Team, A.

    2016-12-01

    Sackung represents a common mode of deep-seated rock-slope failures in alpine landscapes, but proof of its temporal and causal relationship to glacier retreat and other extrinsic factors such as climatic changes or seismic activity remains elusive. Based on the terrestrial cosmogenic nuclide dating of 18 sackung scarps supported by one radiocarbon-dated scarp, we reconstructed the post-glacial chronology of sackungen in the Tatra Mts (central Europe, Slovakia), the highest part of the Carpathians. Recently designed glacial chronology suggests the regional Last Glacial Maximum (LGM) 26-20 k.y. ago and several glacial phases in the Late Glacial. All detected sackungen ages between 17 and 4 k.y. post-date the regional LGM. Systematic decrease of scarp ages with their increasing altitude suggests direct link between sackung origin and post-LGM glacier thinning. Substantial lag (more than 3-3.5 k.y.) of sackung origin relative to dated glacier retreat suggests that glaciers withdrawal acted as preparatory (not triggering) factor during sackung origin. Resulting slope deformations originated either as a consequence of stress relaxation within the rock mass lasting several k.y. or alternatively could be triggered by hydroclimatic processes. Indeed, majority of sackung scarps emerged during predominantly warmer and more humid periods with the majority of dates coinciding with Bølling-Allerød chronozone, early Holocene and especially the termination of Holocene Climatic Optimum. Earthquake trigger is less probable, as the Tatra Mts. lack significant modern and historic seismic activity and there is not geomorphic evidence of fault offsets on the Late Quaternary landforms. In concert with other contemporary studies, we propose that large rock slope failures in high mountains seldom react immediately to glacier withdrawal, but rather display temporal delay lasting up to several millennia.

  15. Probing the Relativistic Jets of Active Galactic Nuclei with Multiwavelength Monitoring

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Jorstad, Svetlana G.; Aller, Margo

    2005-01-01

    The work completed includes the analysis of observations obtained during Cycle 7 (March 2002-February 2003) of the Rossi X-ray Timing Explorer (RXTE). The project was part of a longer-term, continuing program to study the X-ray emission process in blazars and radio galaxies in collaboration with Dr. Ian McHardy (U. of Southampton, UK) and Prof. Thomas Balonek (Colgate U.). The goals of the program are to study the X-ray emission mechanism in blazars and radio galaxies and the relation of the X-ray emission to changes in the relativistic jet. The program includes contemporaneous brightness and linear polarization monitoring at radio and optical wavelengths, total and polarized intensity imaging at at 43 GHz with a resolution of 0.1 milliarcseconds with the VLBA, and well-sampled X-ray light curves obtained from a series of approved RXTE programs. The objects studied in the time period covered by the grant were 3C 120, 3C 279, PKS 1510-089, and 3C 273, all with radio jets containing bright knots that appear to move at superluminal speeds. During RXTE Cycle 7, the project was awarded RXTE time to monitor PKS 1510-089 two times per week, 3C 273 and 3C 279 three times per week, and 3C 120 four times per week. In addition, 3C273 and 3C 279 were observed several times per day during a ten-day period in April 2002. The X-ray data, including those from earlier cycles, were compared with radio measurements obtained in the centimeter-wave band by the monitoring program of Drs. Margo and Hugh Aller at the University of Michigan Radio Astronomy Observatory, monthly imaging observations with the VLBA at 43 GHz, and optical observations obtained at several telescopes around the world.

  16. Dynamique moléculaire et canaux ioniques

    NASA Astrophysics Data System (ADS)

    Crouzy, S.

    2005-11-01

    Diffusion de neutrons et Dynamique Moléculaire (DM) sont deux techniques intimement liées car elles portent sur les mêmes échelles de temps: la première apporte des informations structurales ou dynamiques sur le système physique ou biologique, la seconde permet de décoder ces informations à travers un modèle facilitant l'interprétation des résultats. Au delà de l'intérêt que la technique de DM peut avoir en relation directe avec les neutrons, il est intéressant de comprendre comment les modèles sont construits et comment les techniques de simulation peuvent aller beaucoup plus loin que de simples modélisations. Nous décrirons brièvement, dans la suite de cet exposé, la technique de DM et les méthodes plus sophistiquées de calculs d'énergie libre et de potentiels de force moyenne à partir des simulations de DM. Puis nous verrons avec deux exemples tirés de nos travaux théoriques sur les canaux ioniques comment ces calculs peuvent nous donner accès à des vitesses de réaction ou des constantes d'affinité ou de liaison. La première étude porte sur un analogue de la gramicidine A qui forme un canal conducteur d'ions interrompus par le basculement d'un cycle dioxolane [1]. La seconde concerne le canal potassique KcsA dont nous avons étudié le blocage du coté extracellulaire par l'ion Tetra Ethyl Ammonium [2].

  17. Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change

    USGS Publications Warehouse

    Gaglioti, Benjamin V.; Mann, Daniel H.; Jones, Benjamin M.; Pohlman, John W.; Kunz, Michael L.; Wooller, Matthew J.

    2014-01-01

    Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets (14C) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2 ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9–11.7 ka). In contrast, age-offsets were higher (3.0–5.0 ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7–9.0 ka) and Bølling-Allerød periods (14.5–12.9 ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were ~10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events.

  18. Effective reprocessing of reusable dispensers for surface disinfection tissues - the devil is in the details.

    PubMed

    Kampf, Günter; Degenhardt, Stina; Lackner, Sibylle; Ostermeyer, Christiane

    2014-01-01

    Hintergrund: Kürzlich wurde berichtet, dass wiederverwendbare Tuchspender für Flächendesinfektionsmittel kontaminiert sein können, besonders mit adaptiertem Achromobacter species 3, wenn Produkte auf Basis oberflächenaktiver Wirkstoffe verwendet werden. Frisch angesetzte Lösung kann schnell rekontaminiert werden, wenn die Tuchspender nicht sachgerecht aufbereitet werden.Methode: Wir untersuchten die Wirksamkeit von sechs manuellen und drei maschinellen Aufbereitungsverfahren für kontaminierte Tuchspender mit dem Ziel, die Rekontamination der frisch angesetzten Desinfektionsmittellösung (Mikrobac forte 0,5%) zu vermeiden. Die Tuchspender wurden bei Raumtemperatur über 28 d stehen gelassen. Proben der Desinfektionsmittellösung wurden alle 7 d quantitativ auf bakterielle Kontamination untersucht.Ergebnisse: Alle maschinellen Verfahren verhinderten die Rekontamination der Desinfektionsmittellösung, wenn eine Temperatur zwischen 60–70°C über mindestens 5 min sichergestellt wurde, sowohl mit als auch ohne Zusatz chemischer Reinigungsmittel. Manuelle Aufbereitungsverfahren verhinderten die Rekontamination der Desinfektionsmittellösung, wenn heißes Wasser oder ein gründlicher Reinigungsschritt vor der Desinfektion aller Flächen mit einem alkoholischen oder sauerstoffabspaltenden Flächendesinfektionsmittel erfolgte. Andere Reinigungs- bzw. Desinfektionsverfahren einschließlich der Anwendung eines alkoholischen Flächendesinfektionsmittels verhinderte nicht die Rekontamination.Schlussfolgerungen: Die Ergebnisse zeigen, dass nicht alle Verfahren zur Aufbereitung wiederverwendbarer Tuchspender für Flächendesinfektionsmittel wirksam sind. Eine hohe Temperatur in der Reinigungsphase bzw. die Anwendung eines biofilmwirksamen Reinigers sind essentiell.

  19. Interaction between climate, volcanism, and isostatic rebound in Southeast Alaska during the last deglaciation

    USGS Publications Warehouse

    Praetorius, Summer; Mix, Alan; Jensen, Britta; Froese, Duane; Milne, Glenn A.; Wolhowe, Matthew; Addison, Jason A.; Prahl, Fred

    2016-01-01

    Observations of enhanced volcanic frequency during the last deglaciation have led to the hypothesis that ice unloading in glaciated volcanic terrains can promote volcanism through decompression melting in the shallow mantle or a reduction in crustal magma storage time. However, a direct link between regional climate change, isostatic adjustment, and the initiation of volcanism remains to be demonstrated due to the difficulty of obtaining high-resolution well-dated records that capture short-term climate and volcanic variability traced to a particular source region. Here we present an exceptionally resolved record of 19 tephra layers paired with foraminiferal oxygen isotopes and alkenone paleotemperatures from marine sediment cores along the Southeast Alaska margin spanning the last deglacial transition. Major element compositions of the tephras indicate a predominant source from the nearby Mt. Edgecumbe Volcanic Field (MEVF). We constrain the timing of this regional eruptive sequence to 14.6–13.1 ka. The sudden increase in volcanic activity from the MEVF coincides with the onset of Bølling–Allerød interstadial warmth, the disappearance of ice-rafted detritus, and rapid vertical land motion associated with modeled regional isostatic rebound in response to glacier retreat. These data support the hypothesis that regional deglaciation can rapidly trigger volcanic activity. Rapid sea surface temperature fluctuations and an increase in local salinity (i.e., δ18Osw) variability are associated with the interval of intense volcanic activity, consistent with a two-way interaction between climate and volcanism in which rapid volcanic response to ice unloading may in turn enhance short-term melting of the glaciers, plausibly via albedo effects on glacier ablation zones.

  20. The Late Quaternary tephrostratigraphy of annually laminated sediments from Meerfelder Maar, Germany

    NASA Astrophysics Data System (ADS)

    Lane, Christine S.; Brauer, Achim; Martín-Puertas, Celia; Blockley, Simon P. E.; Smith, Victoria C.; Tomlinson, Emma L.

    2015-08-01

    The record of Late Quaternary environmental change within the sediments of Meerfelder Maar in the Eifel region of Germany is renowned for its high precision chronology, which is annually laminated throughout the Last Glacial to Interglacial transition (LGIT) and most of the Holocene. Two visible tephra layers are prominent within the floating varve chronology of Meerfelder Maar. An Early Holocene tephra layer, the Ulmener Maar Tephra (∼11,000 varve years BP), provides a tie-line of the Meerfelder Maar record to the varved Holocene record of nearby Lake Holzmaar. The Laacher See Tephra provides another prominent time marker for the late Allerød, ∼200 varve years before the transition into the Younger Dryas at 12,680 varve years BP. Further investigation has now shown that there are also 15 cryptotephra layers within the Meerfelder Maar LGIT-Holocene stratigraphy and these layers hold the potential to make direct comparisons between the Meerfelder Maar record and other palaeoenvironmental archives from across Europe and the North Atlantic. Most notable is the presence of the Vedde Ash, the most widespread Icelandic eruption known from the Late Quaternary, which occurred midway through the Younger Dryas. The Vedde Ash has also been found in the Greenland ice cores and can be used as an isochron around which the GICC05 and Meerfelder Maar annual chronologies can be compared. Near the base of the annual laminations in Meerfelder Maar a cryptotephra is found that correlates to the Neapolitan Yellow Tuff, erupted from Campi Flegrei in southern Italy, 1200 km away. This is the furthest north that the Neapolitan Yellow Tuff has been found, highlighting its importance in the construction of a European-wide tephrostratigraphic framework. The co-location of cryptotephra layers from Italian, Icelandic and Eifel volcanic sources, within such a precise chronological record, makes Meerfelder Maar one of the most important tephrostratotype records for continental Europe during

  1. Millennial-Scale Subsurface Temperature Change in the Niger Delta Linked to Atlantic Meridional Overturning Circulation Variability During the Last Deglacial

    NASA Astrophysics Data System (ADS)

    Schmidt, M. W.; Parker, A. O.; Chang, P.

    2015-12-01

    Understanding how Atlantic Meridional Overturning Circulation (AMOC) variability influenced the abrupt climatic changes that characterized the last deglacial has become a fundamental topic in Paleoceanography. Both modern observations and modeling simulations suggest that subsurface temperatures between 300-600 m across the Tropical North Atlantic warm when AMOC weakens, providing a possible fingerprint for reconstructing past AMOC variability (Schmidt et al., 2012). Furthermore, this AMOC-induced subsurface warming has the potential to impact the West African Monsoon, possibly providing an important high-latitude / tropical climate teleconnection (Chang et al., 2008). Here, we present a new high-resolution Mg/Ca record of subsurface (~300 m water depth) temperature variability across the last deglacial from sediment core Fan 17 (4.81oN, 4.41oE, 1178 m depth) recovered from the Niger Delta based on the deep-dwelling planktonic foraminifera Globorotalia crassaformis. Our G. crassaformis Mg/Ca record suggests an increase in subsurface temperatures up to 4oC from 17.2 to 14.8 kyr, consistent with previously published proxy data suggesting AMOC was in a reduced state during Heinrich Event 1 and the subsequent Mystery Interval (McManus et al., 2004). The G. crassaformis Mg/Ca record then shows a cooling associated with the onset of the Bølling Allerød interstadial, followed by a second warming at the start of the Younger Dryas. These millennial-scale warming events are nearly synchronous with a similar record of subsurface temperature change from the Bonaire Basin in the Southern Caribbean (Schmidt et al., 2012) and may provide important evidence for the rapid adjustment of tropical Atlantic subsurface temperatures in response to a weakened AMOC state.

  2. Evaluating the Effects of Sediment Reworking on the Sulfur Isotopic Composition of Aqueous and Mineral Sulfides

    NASA Astrophysics Data System (ADS)

    Johnson, D.; Rose, C.; Fike, D. A.

    2014-12-01

    The sulfur isotopic compositions of sulfide minerals preserved in the rock record are widely used in reconstructions of past ocean and atmospheric chemistry, but little is known about how syn- and post-depositional processes may affect these compositions. Furthermore, recent discoveries of pyrite more enriched in 34S than coeval sulfate in the rock record (e.g., Ries et al., 2009) and in modern deltaic sediments (e.g., Aller et al., 2010) have indicated a need to develop a better understanding of the controls on isotopic fractionation during sulfur cycling in natural environments. Here, we report the results of a controlled laboratory experiment designed to simulate the repeated oxidative reworking of sediments using a series of sediment columns constructed with bulk carbonate mud from Florida Bay, Florida. A rapid decline in [H2S] was observed in reworked sediments during the first 12 weeks of the experiment. Decreases in the δ34S of sulfide phases and increases in Δ34SSO4-H2S (i.e., the difference between the δ34S of sulfate, δ34SSO4, and that of hydrogen sulfide, δ34SH2S, at a given depth) were also documented across all columns. These results indicate a decline in labile organic matter concentrations within the sediments and a corresponding decrease in MSR rates with time. Complete reoxidation did not generate superheavy pyrite in this study, but did stimulate biological activity through the generation of sharp redox boundaries. Partial oxidation of aqueous sulfide and an associated increase in residual δ34SH2S must thus be key if oxidation itself is important to superheavy pyrite formation. These findings further suggest that organic matter lability may have played a more fundamental role than [SO42-] in regulating MSR fractionation throughout Earth history and provide motivation for future research.

  3. Surface exposure dates of cirque basin deglaciation along a western Ireland transect

    NASA Astrophysics Data System (ADS)

    Barth, A. M.; Clark, J.; Clark, P. U.; McCabe, A.

    2013-12-01

    During the last deglaciation (20ka -11ka), variations in the Atlantic Meridional Overturning Circulation (AMOC), accompanied by changes in North Atlantic Deep Water production, caused centennial-to-millennial abrupt climate change. Because of Ireland's proximity to North Atlantic deep-water convection sites, changes in climate associated with variations in the AMOC would be particularly pronounced there, and are recorded by fluctuations of the Irish Ice Sheet. Many of Ireland's mountains also hosted cirque glaciers during the last glaciation, which would have been particularly sensitive to abrupt climate changes of the last deglaciation. Dating of cirque glacier moraines with cosmogenic nuclides can provide a millennial-scale reconstruction of variability in these highly sensitive cirque glaciers. We report 11 new 10Be ages from two cirques basins in County Mayo, western Ireland. A moraine adjacent to Lougaharry Lough near Killary Harbour suggests deglaciation at 13.81 × 0.14 ka during the Bølling-Allerød interval. Two moraines, one inner and one outer, at Lough Accorymore on Achill Island returned ages of 17.04 × 0.31 ka and 18.43 × 0.79 ka, respectively. Both Accorymore dates are Oldest Dryas in age and suggest variability during the millennial-scale Clogher Head Stadial in Ireland. To develop a more regional reconstruction of glacier-climate variability during the last deglaciation, we have also sampled moraines from cirque basins spanning western Ireland from County Kerry in the south to County Donegal in the north. Boulders were sampled from a total of 23 moraines from seven additional cirques to provide this more expansive coverage.

  4. Late Quaternary sackungen in the highest mountains of the Carpathians

    NASA Astrophysics Data System (ADS)

    Pánek, Tomáš; Mentlík, Pavel; Engel, Zbyněk; Braucher, Règis; Zondervan, Albert

    2017-03-01

    Sackungen represents a common mode of deep-seated rock-slope failures in alpine landscapes, but proof of their temporal and causal relationship to extrinsic factors such as climatic changes, glacier retreat or seismic activity remains elusive. Based on the terrestrial cosmogenic nuclide (TCN) dating of 18 sackung scarps supported by one radiocarbon-dated scarp, we reconstructed the post-glacial chronology of sackungen in the Tatra Mts. (central Europe, Slovakia and Poland), the highest part of the Carpathians. The obtained ages (∼15.7-4.3 ka) indicate that sackungen post-date the regional LGM and some of them originated soon after the glacier withdrawal from adjacent valleys. Furthermore, systematic decrease of scarp ages with their increasing altitude suggests a direct link between sackung origin and post-LGM glacier thinning. However, substantial lag (>5 ka) of some sackungen in respect to glacier retreat implies complex relationships between sackung onset and deglaciation where retreat of glaciers acted predominantly as a preparatory, not a triggering factor during the genesis of these slope deformations. They originated either as a consequence of stress relaxation within the rock mass lasting several ka or alternatively could be triggered by climatic processes or seismicity. Indeed, a significant part of sackung activity took place during predominantly warmer and more humid periods, with some dates coinciding with the Bølling-Allerød chronozone, but especially with the onset of the Holocene and the Holocene Climatic Optimum. Earthquake triggering is less probable, as the Tatra Mts. lack significant modern and historic seismic activity and there is no geomorphic evidence of fault offsets on the Late Quaternary landforms. In concert with other recent studies, we propose that large rock slope failures in high mountains seldom react immediately to glacier withdrawal, but could display temporal delay lasting up to several millennia.

  5. Wisconsinan and early Holocene glacial dynamics of Cumberland Peninsula, Baffin Island, Arctic Canada

    NASA Astrophysics Data System (ADS)

    Margreth, Annina; Gosse, John C.; Dyke, Arthur S.

    2017-07-01

    Three glacier systems-an ice sheet with a large marine-based ice stream, an ice cap, and an alpine glacier complex-coalesced on Cumberland Peninsula during the Late Wisconsinan. We combine high-resolution mapping of glacial deposits with new cosmogenic nuclide and radiocarbon age determinations to constrain the history and dynamics of each system. During the Middle Wisconsinan (Oxygen Isotope Stage 3, OIS-3) the Cumberland Sound Ice Stream of the Laurentide Ice Sheet retreated well back into Cumberland Sound and the alpine ice retreated at least to fiord-head positions, a more significant recession than previously documented. The advance to maximal OIS-2 ice positions beyond the mouth of Cumberland Sound and beyond most stretches of coastline remains undated. Partial preservation of an over-ridden OIS-3 glaciomarine delta in a fiord-side position suggests that even fiord ice was weakly erosive in places. Moraines formed during deglaciation represent stillstands and re-advances during three major cold events: H-1 (14.6 ka), Younger Dryas (12.9-11.7 ka), and Cockburn (9.5 ka). Distinctly different responses of the three glacial systems are evident, with the alpine system responding most sensitively to Bølling-Allerød warming whereas the larger systems retreated mainly during Pre-Boreal warming. While the larger ice masses were mainly influenced by internal dynamics, the smaller alpine glacier system responded sensitively to local climate effects. Asymmetrical recession of the alpine glacier complex indicates topoclimatic control on deglaciation and perhaps migration of the accumulation area toward moisture source.

  6. Evidence from the northwestern Venezuelan Andes for extraterrestrial impact: The black mat enigma

    NASA Astrophysics Data System (ADS)

    Mahaney, W. C.; Kalm, V.; Krinsley, D. H.; Tricart, P.; Schwartz, S.; Dohm, J.; Kim, K. J.; Kapran, B.; Milner, M. W.; Beukens, R.; Boccia, S.; Hancock, R. G. V.; Hart, K. M.; Kelleher, B.

    2010-03-01

    A carbon-rich black layer encrusted on a sandy pebbly bed of outwash in the northern Venezuelan Andes, previously considered the result of an alpine grass fire, is now recognized as a 'black mat' candidate correlative with Clovis Age sites in North America, falling within the range of 'black mat' dated sites (~ 12.9 ka cal BP). As such, the bed at site MUM7B, which dates to < 11.8 ka 14C years BP (raw dates) and appears to be contemporaneous with the Younger Dryas (YD) cooling event, marks a possibly much more extensive occurrence than previously identified. No fossils (megafauna) or tool assemblages were observed at this newly identified candidate site (3800 a.m.s.l.), as in the case of the North American sites. Here, evidence is presented for an extraterrestrial impact event at ~ 12.9 ka. The impact-related Andean bed, located ~ 20 cm above 13.7-13.3 ka cal BP alluvial and glaciolacustrine deposits, falls within the sediment characteristics and age range of 'black mat' dated sites (~ 12.9 ka cal BP) in North America. Site sediment characteristics include: carbon, glassy spherules, magnetic microspherules, carbon mat 'welded' onto coarse granular material, occasional presence of platinum group metals (Rh and Ru), planar deformation features (pdfs) in fine silt-size fragmental grains of quartz, as well as orthoclase, and monazite (with an abundance of Rare Earth Elements—REEs). If the candidate site is 'black mat', correlative with the 'black mat' sites of North America, such an extensive occurrence may support the hypothesized airburst/impact over the Laurentide Glacier, which led to a reversal of Allerød warming and the onset of YD cooling and readvance of glaciers. While this finding does not confirm such, it merits further investigation, which includes the reconnaissance for additional sites in South America. Furthermore, if confirmed, such an extensive occurrence may corroborate an impact origin.

  7. Deutsches "Nationales Krebshilfe-Monitoring" 2015-2019 - Studienprotokoll und erste Ergebnisse.

    PubMed

    Schneider, Sven; Görig, Tatiana; Schilling, Laura; Breitbart, Eckhard W; Greinert, Rüdiger; Diehl, Katharina

    2017-09-01

    Das Projekt "Nationales Krebshilfe-Monitoring zur Solariennutzung" (National Cancer Aid Monitoring of Tanning Bed Use, NCAM) ist eine deutsche Großstudie mit dem Ziel, die wichtigsten Risikofaktoren für Hautkrebs zu beobachten: natürliches Sonnenlicht und künstliche UV-Strahlung. NCAM ist eine bundesweite Querschnittstudie mit zunächst vier Runden der Datenerfassung (sogenannten Wellen) zwischen 2015 und 2018. Jedes Jahr wird eine bundesweit repräsentative Stichprobe aus 3.000 Personen im Alter von 14 bis 45 Jahren befragt. Die Querschnittsbefragung wird durch eine Kohorte von n = 450 aktuellen Solariennutzern ergänzt. Die erste Welle im Jahr 2015 ergab eine Gesamtprävalenz der Solariennutzung von 29,5 %. Elf Prozent aller Teilnehmer hatten in den vergangenen zwölf Monaten ein Solarium genutzt. Zu den Determinanten der aktuellen Solariennutzung gehörten jüngeres Alter, weibliches Geschlecht und Vollzeit-/Teilzeitbeschäftigung. Die hauptsächlichen Beweggründe, die für die Nutzung eines Solariums genannt wurden, waren Entspannung und Attraktivitätssteigerung. NCAM ist weltweit die erste Studie zur Überwachung der Risikofaktoren für Hautkrebs in jährlichen Intervallen anhand einer großen, landesweit repräsentativen Stichprobe. Erste Ergebnisse deuten darauf hin, dass Millionen Deutsche trotz Warnungen der WHO Solarien nutzen, und dass viele dieser Nutzer Jugendliche sind - trotz gesetzlicher Beschränkungen, die das Ziel haben, die Nutzung von Solarien durch Minderjährige zu verhindern. © 2017 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.

  8. Postglacial climate-change record in biomarker lipid compositions of the Hani peat sequence, Northeastern China

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Zheng, Yanhong; Meyers, Philip A.; Jull, A. J. Timothy; Xie, Shucheng

    2010-05-01

    The peat sequence at Hani in northeastern China accumulated over the past 16 cal kyr in a percolation mire in which rain water and ground water seeped through the peat system. The molecular compositions of n-alkanes, n-alkanols, and n-alkanoic acids extracted from the Hani peat sequence reveal different responses to the progressive evolution of climate and changes in the nature of the peat-forming vegetation. Long chain length components that originate from the waxy coatings of subaerial vascular plants dominate the n-alkane distributions throughout the Hani peat sequence. The paleoclimate integrity of these biomarker molecules appears to be well preserved. Most of the n-alkanol distributions are similarly dominated by long chain components that indicate their origins from subaerial plants. In contrast, n-alkanoic acid distributions are dominated by secondary components that record the importance of post-depositional microbial activity in this peat sequence, which evidently can be extensive in a percolation mire. Elevated n-alkane Paq values and C 23/C 29 ratios, which are both molecular proxies for water-loving plants, record an especially moist local climate in the Bølling-Allerød (14.5 to 12.9 ka), Younger Dryas (12.9 to 11.5 ka), and Pre-Boreal (11.5 to 10.5 ka) portions of the Hani peat sequence. Depressed Paq values and C 23/C 29 ratios and larger n-alkane average chain length values indicate that the Holocene Climatic Optimum (10.5 to 6 ka) was a period of warmer climate with lower effective precipitation, which contrasts with evidence of wetter climates in most of East Asia.

  9. Human-induced changes in the distribution of rainfall

    PubMed Central

    Putnam, Aaron E.; Broecker, Wallace S.

    2017-01-01

    A likely consequence of global warming will be the redistribution of Earth’s rain belts, affecting water availability for many of Earth’s inhabitants. We consider three ways in which planetary warming might influence the global distribution of precipitation. The first possibility is that rainfall in the tropics will increase and that the subtropics and mid-latitudes will become more arid. A second possibility is that Earth’s thermal equator, around which the planet’s rain belts and dry zones are organized, will migrate northward. This northward shift will be a consequence of the Northern Hemisphere, with its large continental area, warming faster than the Southern Hemisphere, with its large oceanic area. A third possibility is that both of these scenarios will play out simultaneously. We review paleoclimate evidence suggesting that (i) the middle latitudes were wetter during the last glacial maximum, (ii) a northward shift of the thermal equator attended the abrupt Bølling-Allerød climatic transition ~14.6 thousand years ago, and (iii) a southward shift occurred during the more recent Little Ice Age. We also inspect trends in seasonal surface heating between the hemispheres over the past several decades. From these clues, we predict that there will be a seasonally dependent response in rainfall patterns to global warming. During boreal summer, in which the rate of recent warming has been relatively uniform between the hemispheres, wet areas will get wetter and dry regions will become drier. During boreal winter, rain belts and drylands will expand northward in response to differential heating between the hemispheres. PMID:28580418

  10. Zeitlicher Verlauf der avaskulären Nekrose des Hüftkopfes bei Patienten mit Pemphigus vulgaris.

    PubMed

    Balighi, Kamran; Daneshpazhooh, Maryam; Aghazadeh, Nessa; Saeidi, Vahide; Shahpouri, Farzam; Hejazi, Pardis; Chams-Davatchi, Cheyda

    2016-10-01

    Pemphigus vulgaris (PV) wird in der Regel mit systemischen Corticosteroiden und Immunsuppressiva behandelt. Avaskuläre Nekrose (AVN) des Hüftkopfes ist eine gut bekannte schwerere Komplikation einer Corticosteroid-Therapie. Die Charakteristika dieser schweren Komplikation bei PV sind nach wie vor unbekannt. Nicht kontrollierte, retrospektive Untersuchung aller PV-bedingten AVN-Fälle, die in einer iranischen Klinik für bullöse Autoimmunerkrankungen zwischen 1985 und 2013 diagnostiziert wurden. Anhand der Krankenakten von 2321 untersuchten PV-Patienten wurden 45 Fälle (1,93 %) von femoraler AVN identifiziert. Dreißig davon waren Männer. Das mittlere Alter bei der Diagnose der AVN betrug 47,4 ± 14,2 Jahre. Der mittlere Zeitraum zwischen der Diagnose des PV und dem Einsetzen der AVN lag bei 25,3 ± 18,3 Monaten. Mit Ausnahme von acht Fällen (17,8 %) setzte die AVN bei der Mehrheit der Patienten innerhalb von drei Jahren nach Diagnose des PV ein. Die mittlere kumulative Dosis von Prednisolon bei Patienten mit AVN betrug 13.115,8 ± 7041,1 mg. Zwischen der Prednisolon-Gesamtdosis und dem Zeitraum bis zum Einsetzen der AVN bestand eine starke Korrelation (p = 0,001). Bei Patienten mit Alendronateinnahme in der Vorgeschichte war dieser Zeitraum signifikant kürzer (p = 0,01). Die AVN ist eine schwere Komplikation einer Corticosteroid-Behandlung bei Patienten mit PV. Sie wird bei 2 % der Patienten beobachtet und tritt vor allem in den ersten drei Behandlungsjahren auf. Bei Patienten, die höhere Dosen von Prednisolon erhalten, setzt die AVN tendenziell früher ein. © 2016 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.

  11. Kombinierte Hoch-/Niedrig-Dosis-Therapie mit systemischen Glukokor-tikoiden bei schweren Verlaufsformen der Alopecia areata im Kindesalter.

    PubMed

    Jahn-Bassler, Karin; Bauer, Wolfgang Michael; Karlhofer, Franz; Vossen, Matthias G; Stingl, Georg

    2017-01-01

    Schwere Verlaufsformen der Alopecia areata (AA) im Kindesalter sind aufgrund limitierter Optionen therapeutisch herausfordernd. Systemische, hochdosierte Glukokortikoide weisen die schnellste Ansprechrate auf, nach dem Absetzen kommt es allerdings zu Rezidiven. Eine längerfristige Hochdosis-Anwendung ist aufgrund der zu erwartenden Nebenwirkungen nicht empfehlenswert. Eine dauerhafte Steroiderhaltungstherapie unterhalb der Cushing-Schwellen-Dosis nach Bolustherapie könnte die Krankheitsaktivität ohne Nebenwirkungen längerfristig unterdrücken. Im Rahmen einer offenen Anwendungsbeobachtung wurden 13 Kinder mit schweren Formen der AA in diese Studie eingeschlossen. Bei sieben Kindern lag eine AA totalis/universalis vor, bei sechs eine multifokale AA mit Befall von mehr als 50 % der Kopfhaut. Das Therapieregime sah eine initiale Prednisolon-Dosierung von 2 mg/kg Körpergeweicht (KG) vor und wurde innerhalb von neun Wochen auf eine Erhaltungsdosierung unter der individuellen Cushing-Schwelle reduziert. Der Nachbeobachtungszeitraum betrug ein bis drei Jahre. Wir beobachteten in 62 % aller Fälle ein komplettes Nachwachsen der Haare. Die mittlere Dauer bis zum Ansprechen lag bei 6,6 Wochen und konnte mit der Erhaltungstherapie über den gesamten Beobachtungszeitraum aufrechterhalten werden. An Nebenwirkungen wurden ausschließlich eine Gewichtszunahme (1-3 kg) bei allen Behandelten sowie eine milde Steroidakne in 23 % der Fälle beobachtet. Die kombinierte Hoch-/Niedrig-Dosis-Therapie mit systemischen Glukokortikoiden mittels Prednisolon zeigte eine hohe, dauerhafte Ansprechrate ohne signifikante Nebenwirkungen. © 2017 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.

  12. Intraläsionale Therapie niedrig maligner primär kutaner B-Zell-Lymphome mit Anti-CD20-Antikörper: Nebenwirkungen korrelieren mit gutem klinischen Ansprechen.

    PubMed

    Eberle, Franziska C; Holstein, Julia; Scheu, Alexander; Fend, Falko; Yazdi, Amir S

    2017-03-01

    Die intraläsionale Gabe von Anti-CD20-Antikörpern (Rituximab) wurde als effektive Therapieoption für Patienten mit niedrig malignen primär kutanen B-Zell-Lymphomen beschrieben. Bis heute wurden allerdings keine Parameter identifiziert, welche reproduzierbar ein gutes klinisches Ansprechen dieser Therapie vorhersagen. Ziel dieser Studie ist, sowohl das klinische Ansprechen und die unerwünschten Nebenwirkungen als auch die Patientenwahrnehmung hinsichtlich intraläsionaler Injektionen von anti-CD20-Antikörpern zur Behandlung indolenter primär kutaner B-Zell-Lymphome im Vergleich mit anderen Therapien zu evaluieren. Elf Patienten mit einem primär kutanen B-Zell-Lymphom, namentlich primär kutanes Keimzentrumslymphom (n = 9) und primär kutanes Marginalzonenlymphom (n = 2), welche mittels intraläsionalem Anti-CD20-Antikörper behandelt wurden, wurden retrospektiv evaluiert hinsichtlich der Ansprechrate und unerwünschter Nebenwirkungen sowie in Bezug auf deren Selbsteinschätzung dieser und anderer Therapien des primär kutanen B-Zell-Lymphoms. Patienten, deren primär kutanes B-Zell-Lymphom mittels intraläsionaler Gabe von Anti-CD20-Antikörper behandelt wurde, zeigten ein komplettes oder partielles Ansprechen in 45 % beziehungsweise 27 % aller Patienten. Speziell Patienten mit grippeähnlichen Symptomen nach erfolgter Injektion zeigten ein gutes Ansprechen. Die Mehrheit der Patienten empfand die Therapie mit Rituximab als die beste Therapie im Vergleich zu anderen Therapien wie beispielsweise chirurgische Exzision oder Radiotherapie. Intraläsionales Rituximab ist eine effektive Therapie mit hoher Patientenzufriedenheit. Starke therapiebedingte Nebenwirkungen wie Fieber, Schüttelfrost und Kopfschmerzen nach Gabe von Rituximab könnten als Indikator für gute Wirksamkeit dienen. © 2017 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.

  13. Gebrauch von Komplementärmedizin bei Patienten mit metastasierendem Melanom unter Therapie mit Ipilimumab innerhalb einer klinischen Studie.

    PubMed

    Huebner, Jutta; Mohr, Peter; Simon, Jan-Christoph; Fluck, Michael; Berking, Carola; Zimmer, Lisa; Loquai, Carmen

    2016-05-01

    In Deutschland wenden 40-90 % aller Krebspatienten Methoden der komplementären and alternativen Medizin (KAM) an. Bis dato gibt es kein Datenmaterial zum Einsatz der KAM bei Melanompatienten. Das Ziel unserer Studie war es, Daten über den Gebrauch, die Informationsquellen und Ziele von Patienten mit metastasierendem Melanom zu erfassen. Einhundertsechsundfünfzig Patienten aus 25 Studienzentren nahmen an der DecOG-MM-PAL Multibasket Studie teil. Die beteiligten Personen wurden auch gebeten, an einer Nebenstudie teilzunehmen, die ihren Gebrauch von KAM erfassen sollte. Dazu wurde während der Behandlung ein standardisierter Fragebogen zu genau festgelegten Zeitpunkten ausgeteilt. Insgesamt gingen 55 Fragebögen von 32 (21 %) Melanompatienten ein. Von diesen gaben 17 (53 %) ein Interesse an KAM an, und sieben (22 %) machten von KAM Gebrauch. Die Hauptinformationsquellen (31 %) waren Familienmitglieder und Freunde, gefolgt von Ärzten (19 %). Die Hauptgründe für die Anwendung von KAM waren die Stärkung des Immunsystems (41 %) und des Körpers (34 %). Nahrungsergänzungsmittel (Vitamine und Spurenelemente) wurden am häufigsten angewendet (28 %). Eine relativ hohe Anzahl an Patienten mit metastasierendem Melanom machte trotz Teilnahme an einer klinischen Studie von KAM Gebrauch. Wechselwirkungen könnten durch biologisch basierte KAM auftreten, und hier besonders bei immunmodulierenden KAM- Strategien. Um Risiken zu vermeiden, sollte die Kommunikation zwischen den Ärzten und den Patienten verbessert werden. © 2016 Deutsche Dermatologische Gesellschaft (DDG). Published by John Wiley & Sons Ltd.

  14. A deglacial and Holocene record of climate variability in south-central Alaska from stable oxygen isotopes and plant macrofossils in peat

    USGS Publications Warehouse

    Jones, Miriam C.; Wooller, Matthew J.; Peteet, Dorothy M.

    2014-01-01

    We used stable oxygen isotopes derived from bulk peat (δ18OTOM), in conjunction with plant macrofossils and previously published carbon accumulation records, in a ∼14,500 cal yr BP peat core (HT Fen) from the Kenai lowlands in south-central Alaska to reconstruct the climate history of the area. We find that patterns are broadly consistent with those from lacustrine records across the region, and agree with the interpretation that major shifts in δ18OTOM values indicate changes in strength and position of the Aleutian Low (AL), a semi-permanent low-pressure cell that delivers winter moisture to the region. We find decreased strength or a more westerly position of the AL (relatively higher δ18OTOM values) during the Bølling-Allerød, Holocene Thermal Maximum (HTM), and late Holocene, which also correspond to warmer climate regimes. These intervals coincide with greater peat preservation and enhanced carbon (C) accumulation rates at the HT Fen and with peatland expansion across Alaska. The HTM in particular may have experienced greater summer precipitation as a result of an enhanced Pacific subtropical high, a pattern consistent with modern δ18O values for summer precipitation. The combined warm summer temperatures and greater summer precipitation helped promote the observed rapid peat accumulation. A strengthened AL (relatively lower δ18OTOM values) is most evident during the Younger Dryas, Neoglaciation, and the Little Ice Age, consistent with lower peat preservation and C accumulation at the HT Fen, suggesting less precipitation reaches the leeward side of the Kenai Mountains during periods of enhanced AL strength. The peatlands on the Kenai Peninsula thrive when the AL is weak and the contribution of summer precipitation is higher, highlighting the importance of precipitation seasonality in promoting peat accumulation. This study demonstrates that δ18OTOM values in peat can be applied toward understand large-scale shifts in atmospheric circulation

  15. WISEP J004701.06+680352.1: AN INTERMEDIATE SURFACE GRAVITY, DUSTY BROWN DWARF IN THE AB DOR MOVING GROUP

    SciTech Connect

    Gizis, John E.; Allers, Katelyn N.; Liu, Michael C.; Harris, Hugh C.; Faherty, Jacqueline K.; Burgasser, Adam J.; Kirkpatrick, J. Davy

    2015-02-01

    We present spectroscopy, astrometry, and photometry of the brown dwarf WISEP J004701.06+680352.1 (W0047+68), an unusually red field L dwarf at a distance of 12.2 ± 0.4 pc. The three-dimensional space motion identifies it as a member of the AB Dor Moving Group, an identification supported by our classification of W0047+68 as intermediate surface gravity (INT-G) using the Allers and Liu near-infrared classification system. This moving group membership implies near-solar metallicity, age ∼100-125 Myr, M ≈ 0.018 M {sub ☉}, and log g ≈ 4.5; the thick condensate clouds needed to explain the infrared spectrum are, therefore, a result of surface gravity that is lower than that of ordinary field brown dwarfs. From the observed luminosity and evolutionary model radius, we find T {sub eff} ≈ 1300 K, a temperature normally associated with early T dwarfs. Thick clouds are also used to explain the spectral properties of directly imaged giant planets, and we discuss the successes and challenges for such substellar models in matching the observed optical and infrared spectra. W0047+68 shows that cloud thickness is more sensitive to intermediate surface gravity than in most models. We also present a trigonometric parallax of the dusty L6 dwarf 2MASS J21481628+4003593. It lies at 8.060 ± 0.036 parsecs; its astrometry is consistent with the view that it is older and metal-rich.

  16. Linking glacier and oceanic variability in northern Spitsbergen during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Bartels, Martin; Hillaire-Marcel, Claude; Fahl, Kirsten; Titschack, Jürgen; Stein, Rüdiger; Hebbeln, Dierk

    2016-04-01

    Paleoceanographic records from the Svalbard area provide important information for the documentation of heat transfer from the North Atlantic into the Arctic Ocean. The archipelago stands at the northernmost surface occurrence of warm Atlantic Water (AW). Here, we pay specific attention to the Holocene variability of AW advection as far as northern Svalbard. The study is based on sediment core GeoB10817-4 from the mouth of Woodfjorden, northern Spitsbergen. Assemblages and isotopic compositions of benthic foraminifera as well as sedimentological features (e.g. ice rafted debris) are used to document the interplay between oceanographic conditions and glacier variability. Data from the highly resolved early deglacial interval from the lower part of the core illustrate the penetration of chilled AW into the fjord during the Bølling-Allerød. However, the disintegration of the Svalbard-Barents Sea Ice Sheet in the vicinity of the site maintained turbulent and cold bottom waters until the end of the Younger Dryas, i.e. when the glacier front finally retreated to an inner fjord position. During the early Holocene, the Arctic Front moved towards the site, bringing a high amount of nutrients enhancing productivity and foraminifera production. These improved conditions were shortly interrupted, at ca. 11,000 calibrated years BP, during a "Preboreal Oscillation". At the same time sedimentological parameters as well as the faunal composition signify an increasing (seasonal) sea ice cover as far as the fjord outlet. Data so far indicate intricate influences of large scale changes in ocean surface currents, local glacier margin fluctuations, primary productivity, and tipping point sea-ice spreading occurrences, thus requiring the use of a large array of proxies to decipher the specific role of each of these boundary conditions.

  17. A comparison of benthic foraminiferal Mn / Ca and sedimentary Mn / Al as proxies of relative bottom-water oxygenation in the low-latitude NE Atlantic upwelling system

    NASA Astrophysics Data System (ADS)

    McKay, C. L.; Groeneveld, J.; Filipsson, H. L.; Gallego-Torres, D.; Whitehouse, M. J.; Toyofuku, T.; Romero, O. E.

    2015-09-01

    Trace element incorporation into foraminiferal shells (tests) is governed by physical and chemical conditions of the surrounding marine environment, and therefore foraminiferal geochemistry provides a means of palaeo-oceanographic reconstructions. With the availability of high-spatial-resolution instrumentation with high precision, foraminiferal geochemistry has become a major research topic over recent years. However, reconstructions of past bottom-water oxygenation using foraminiferal tests remain in their infancy. In this study we explore the potential of using Mn / Ca determined by secondary ion mass spectrometry (SIMS) as well as by flow-through inductively coupled plasma optical emission spectroscopy (FT-ICP-OES) in the benthic foraminiferal species Eubuliminella exilis as a proxy for recording changes in bottom-water oxygen conditions in the low-latitude NE Atlantic upwelling system. Furthermore, we compare the SIMS and FT-ICP-OES results with published Mn sediment bulk measurements from the same sediment core. This is the first time that benthic foraminiferal Mn / Ca is directly compared with Mn bulk measurements, which largely agree on the former oxygen conditions. Samples were selected to include different productivity regimes related to Marine Isotope Stage 3 (35-28 ka), the Last Glacial Maximum (28-19 ka), Heinrich Event 1 (18-15.5 ka), Bølling Allerød (15.5-13.5 ka) and the Younger Dryas (13.5-11.5 ka). Foraminiferal Mn / Ca determined by SIMS and FT-ICP-OES is comparable. Mn / Ca was higher during periods with high primary productivity, such as during the Younger Dryas, which indicates low-oxygen conditions. This is further supported by the benthic foraminiferal faunal composition. Our results highlight the proxy potential of Mn / Ca in benthic foraminifera from upwelling systems for reconstructing past variations in oxygen conditions of the sea floor environment as well as the need to use it in combination with other proxy records such as faunal

  18. Pelagic-benthic coupling within an upwelling system of the subtropical northeast Atlantic over the last 35 ka BP

    NASA Astrophysics Data System (ADS)

    McKay, C. L.; Filipsson, H. L.; Romero, O. E.; Stuut, J.-B. W.; Donner, B.

    2014-12-01

    We present a high resolution, multiproxy study of the relationship between pelagic and benthic environments of a coastal upwelling system in the subtropical NE Atlantic Ocean. Marine sediments corresponding to late MIS3 to the Holocene in the radiocarbon dated core GeoB7926, retrieved off Mauritania (21°N) were analysed to reconstruct productivity in surface waters and its linkage to deep waters during the last 35 ka BP. High latitude cold events and changes in atmospheric and oceanographic dynamics influenced upwelling intensity over this time period. Subsequently, this caused changes in primary productivity off this low-latitude coastal upwelling locality. The benthic foraminiferal fauna displays four main community shifts corresponding to fundamental climatic events, first of all during late MIS3 (35-28 ka BP), secondly from 28 to 19 ka BP (including Heinrich event 2 and the LGM), thirdly within Heinrich event 1, the Bølling Allerød and the Younger Dryas (18-11.5 ka BP) and finally during the Holocene (11.5-0 ka BP). In particular, strong pelagic-benthic coupling is apparent in MIS 3, as demonstrated by increased primary productivity, indicated by moderate DAR and the dominance of benthic foraminiferal species which prefer fresh phytodetritus. A decline in upwelling intensity and nutrient availability follows, which resulted in a proportionately larger amount of older, degraded matter, provoking a shift in the benthic foraminifera fauna composition. This rapid response of the benthic environment continues with a progressive increase in upwelling intensity due to sea level and oceanographic changes and according high surface production during the LGM. During Heinrich event 1 and the Younger Dryas, extreme levels of primary production actually hindered benthic environment through the development of low oxygen conditions. After this period, a final change in benthic foraminiferal community composition occurs which indicates a return to more oxygenated conditions

  19. Final deglaciation of the Scandinavian Ice Sheet and implications for the Holocene global sea-level budget

    NASA Astrophysics Data System (ADS)

    Cuzzone, Joshua K.; Clark, Peter U.; Carlson, Anders E.; Ullman, David J.; Rinterknecht, Vincent R.; Milne, Glenn A.; Lunkka, Juha-Pekka; Wohlfarth, Barbara; Marcott, Shaun A.; Caffee, Marc

    2016-08-01

    The last deglaciation of the Scandinavian Ice Sheet (SIS) from ∼ 21, 000 to 13,000 yr ago is well-constrained by several hundred 10Be and 14C ages. The subsequent retreat history, however, is established primarily from minimum-limiting 14C ages and incomplete Baltic-Sea varve records, leaving a substantial fraction of final SIS retreat history poorly constrained. Here we develop a high-resolution chronology for the final deglaciation of the SIS based on 79 10Be cosmogenic exposure dates sampled along three transects spanning southern to northern Sweden and Finland. Combining this new chronology with existing 10Be ages on deglaciation since the Last Glacial Maximum shows that rates of SIS margin retreat were strongly influenced by deglacial millennial-scale climate variability and its effect on surface mass balance, with regional modulation of retreat associated with dynamical controls. Ice-volume estimates constrained by our new chronology suggest that the SIS contributed ∼ 8 m sea-level equivalent to global sea-level rise between ∼14.5 ka and 10 ka. Final deglaciation was largely complete by ∼10.5 ka, with highest rates of sea-level rise occurring during the Bølling-Allerød, a 50% decrease during the Younger Dryas, and a rapid increase during the early Holocene. Combining our SIS volume estimates with estimated contributions from other remaining Northern Hemisphere ice sheets suggests that the Antarctic Ice Sheet (AIS) contributed 14.4 ± 5.9 m to global sea-level rise since ∼13 ka. This new constraint supports those studies that indicate that an ice volume of 15 m or more of equivalent sea-level rise was lost from the AIS during the last deglaciation.

  20. A 22,000 year record of changing redox conditions from the Peruvian Oxygen Minimum Zone (OMZ): benthic foraminifera approach

    NASA Astrophysics Data System (ADS)

    Erdem, Z.; Schönfeld, J.; Glock, N.

    2015-12-01

    Benthic foraminifera have been used as proxies for the prevailing conditions at the sediment-water interface. Their distribution patterns are thought to facilitate reconstruction of past environmental conditions. Variations of bottom water oxygenation can be traced by the downcore distribution of benthic foraminifera and some of their morphological characters. Being one of the strongest and most pronounced OMZs in today's world oceans, the Peruvian OMZ is a key area to study such variations in relation with changing climate. Spatial changes or an extension of the OMZ through time and space are investigated using sediment cores from the lower OMZ boundary. We focus on time intervals Late Holocene, Early Holocene, Bølling Allerød, Heinrich-Stadial 1 and Last Glacial Maximum (LGM) to investigate changes in bottom-water oxygen and redox conditions. The recent distributions of benthic foraminiferal assemblages provide background data for an interpretation of the past conditions. Living benthic foraminiferal faunas from the Peruvian margin are structured with the prevailing bottom-water oxygen concentrations today (Mallon et al., 2012). Downcore distribution of benthic foraminiferal assemblages showed fluctuations in the abundance of the indicator species depicting variations and a decreasing trend in bottom water oxygen conditions since the LGM. In addition, changes in bottom-water oxygen and nitrate concentrations are reconstructed for the same time intervals by the pore density in tests of Planulina limbata and Bolivina spissa (Glock et al., 2011), respectively. The pore densities also indicate a trend of higher oxygen and nitrate concentrations in the LGM compared to the Holocene. Combination of both proxies provide information on past bottom-water conditions and changes of oxygen concentrations for the Peruvian margin. Glock et al., 2011: Environmental influences on the pore density of Bolivina spissa (Cushman), Journal of Foraminiferal Research, v. 41, no. 1, p

  1. An improved chronology for the Lateglacial palaeoenvironmental record of Lake Haemelsee, Germany: challenges for independent site comparisons

    NASA Astrophysics Data System (ADS)

    Lane, Christine; Brauer, Achim; Ramsey Christopher, Bronk; Engels, Stefan; Haliuc, Aritina; Hoek, Wim; Hubay, Katalin; Jones, Gwydion; Sachse, Dirk; Staff, Richard; Turner, Falko; Wagner-Cremer, Frederike

    2016-04-01

    Exploring temporal and spatial variability of environmental response to climatic changes requires the comparison of widespread palaeoenvironmental sequences on their own, independently-derived, age models. High precision age-models can be constructed using statistical methods to combine absolute and relative age estimates measured using a range of techniques. Such an approach may help to highlight otherwise unrecognised uncertainties, where a single dating method has been applied in isolation. Radiocarbon dating, tephrochronology and varve counting have been combined within a Bayesian depositional model to build a chronology for a sediment sequence from Lake Haemelsee (Northern Germany) that continuously covers the entire Lateglacial and early Holocene. Each of the dating techniques used brought its own challenges. Radiocarbon dates provide the only absolute ages measured directly in the record, however a low macrofossil content led to small sample sizes and a limited number of low precision dates. A floating varved interval provided restricted but very precise relative dating for sediments covering the Allerød to Younger Dryas transition. Well-spaced, visible and crypto- tephra layers, including the widespread Laacher See , Vedde Ash, Askja-S and Saksunarvatn tephra layers, allow absolute ages for the tephra layers established in other locations to be imported into the Haemelsee sequence. These layers also provide multiple tie-lines that allow the Haemelsee sequences to be directly compared at particular moments in time, and within particular intervals, to other important Lateglacial archives. However, selecting the "best" published tephra ages to use in the Haemelsee age model is not simple and risks biasing comparison of the palaeoenvironmental record to fit one or another comparative archive. Here we investigate the use of multiple age models for the Haemelsee record, in order to retain an independent approach to investigating the environmental transitions of

  2. Sea surface temperature variation during the last deglaciation in the southern Okinawa Trough: Modulation of high latitude teleconnections and the Kuroshio Current

    NASA Astrophysics Data System (ADS)

    Zhao, Jingtao; Li, Jun; Cai, Feng; Wei, Helong; Hu, Bangqi; Dou, Yanguang; Wang, Libo; Xiang, Rong; Cheng, Hongwei; Dong, Liang; Zhang, Chuanlun L.

    2015-11-01

    Three paleotemperature records (foraminiferal Mg/Ca, TEX86 and UK‧37) were generated for the past 17.3 ka in the southern Okinawa Trough (OT) using a sediment core (OKT-3) taken at a water depth of 1792 m. Temperature estimates based on the inorganic and organic indices for the OKT-3 core top sample approximated modern sea surface temperature (SST) and extended to the mixed layer (<50 m) in warmer seasons. Reconstructed SSTs from OKT-3 gradually increased towards the top of the core with lower values occurring during Heinrich Stadial 1 (HS1) and the Younger Dryas (YD). These values coincided with the glacial-interglacial cycles established by the Globigerinoides ruber δ18O curve. Notably, SSTs decreased during the BØlling-AllerØd (B-A) but warming occurred before and after the B-A, from approximately 16 to 14 ka and 12.5 to 10 ka. The SST cooling during the B-A corresponded to the timing of the Antarctic Cold Reversal (ACR), which is thought to be connected with melt water pulse 1a (MWP1a). The cooling was also concurrent with the spread of millennial-scale cold signals to the OT during the HS1 and YD periods, when widespread melt and collapse of Northern Hemisphere ice sheets occurred along with reduced Atlantic Meridional Overturning Circulation (AMOC) and a southward shift of the Intertropical Convergence Zone (ITCZ). The last deglaciation, which began approximately 16-15 ka BP in the OT, might mark the time when the Kuroshio Current (KC) began to strengthen.

  3. Solar-, monsoon- and Kuroshio-influenced thermocline depth and sea surface salinity in the southern Okinawa Trough during the past 17,300 years

    NASA Astrophysics Data System (ADS)

    Wang, Libo; Li, Jun; Zhao, Jingtao; Wei, Helong; Hu, Bangqi; Dou, Yanguang; Sun, Zhilei; Zou, Liang; Bai, Fenglong

    2016-08-01

    Factors influencing millennial-scale variability in the thermocline depth (vertical mixing) and sea surface salinity (SSS) of the southern Okinawa Trough (OT) during the past 17,300 years were investigated based on foraminifer oxygen isotope records of the surface dweller Globigerinoides ruber sensu stricto and the thermocline dweller Pulleniatina obliquiloculata in the AMS 14C dated OKT-3 core. The thermocline depth is influenced by surface thermal buoyancy (heat) flux, in turn controlled by the annual mean insolation at 30°N and the strength of the East Asian winter monsoon (EAWM). Strong insolation and weak EAWM tend to increase buoyancy gain (decrease buoyancy loss), corresponding to shallow thermocline depths, and vice versa. Regional SSS is influenced by the global ice volume, the Kuroshio Current (KC), and vertical mixing. A deep thermocline coincides with a high SSS because strong vertical mixing brings more, saltier subsurface KC water to the surface, and vice versa. Local SSS (excluding the global ice volume effect) became lower in the northern OT than in the southern OT after ~9.2 ka, implying that Changjiang diluted water had stronger influence in the northern sector. SSS show no major changes during the Bølling/Allerød and Younger Dryas events, probably because the KC disturbed the North Atlantic signals. This argues against earlier interpretations of sea surface temperature records of this core. Wavelet and spectral analyses of the Δδ18OP-G (δ18O of P. obliquiloculata minus G. ruber s.s.) and δ18Olocal records display 1,540-, 1,480-, 1,050-, 860-, 640-, and 630-year periods. These are consistent with published evidence of a pervasive periodicity of 1,500 years in global climate as well as EAWM and KC signatures, and a fundamental solar periodicity of 1,000 years and intermediary derived periodicity of 700 years.

  4. A Crystallographic Study of the Role of Sequence Context in Thymine Glycol Bypass by a Replicative DNA Polymerase Serendipitously Sheds Light on the Exonuclease Complex

    SciTech Connect

    Aller, Pierre; Duclos, Stéphanie; Wallace, Susan S.; Doublié, Sylvie

    2012-06-27

    Thymine glycol (Tg) is the most common oxidation product of thymine and is known to be a strong block to replicative DNA polymerases. A previously solved structure of the bacteriophage RB69 DNA polymerase (RB69 gp43) in complex with Tg in the sequence context 5'-G-Tg-G shed light on how Tg blocks primer elongation: The protruding methyl group of the oxidized thymine displaces the adjacent 5'-G, which can no longer serve as a template for primer elongation [Aller, P., Rould, M. A., Hogg, M, Wallace, S. S. and Doublie S. (2007). A structural rationale for stalling of a replicative DNA polymerase at the most common oxidative thymine lesion, thymine glycol. Proc. Natl. Acad. Sci. USA, 104, 814-818.]. Several studies showed that in the sequence context 5'-C-Tg-purine, Tg is more likely to be bypassed by Klenow fragment, an A-family DNA polymerase. We set out to investigate the role of sequence context in Tg bypass in a B-family polymerase and to solve the crystal structures of the bacteriophage RB69 DNA polymerase in complex with Tg-containing DNA in the three remaining sequence contexts: 5'-A-Tg-G, 5'-T-Tg-G, and 5'-C-Tg-G. A combination of several factors - including the associated exonuclease activity, the nature of the 3' and 5' bases surrounding Tg, and the cis-trans interconversion of Tg - influences Tg bypass. We also visualized for the first time the structure of a well-ordered exonuclease complex, allowing us to identify and confirm the role of key residues (Phe123, Met256, and Tyr257) in strand separation and in the stabilization of the primer strand in the exonuclease site.

  5. A History of Correlations Between Optical and Radio Outbursts in the Blazar AO 0235+164

    NASA Astrophysics Data System (ADS)

    McGrath, E. J.; Balonek, T. J.; Brandt, T. J.

    2000-05-01

    We present a ten year optical light curve for the blazar AO 0235+164 from 1989 through mid-1999. Observations were conducted at the Foggy Bottom Observatory at Colgate University using a sixteen inch Cassegrain telescope and CCD camera. Herein we note the correlations between optical and radio variations (radio observations obtained at the University of Michigan Radio Astronomy Observatory, UMRAO). MacLeod, Andrew, and Harvey (1976); Ledden, Aller, and Dent (1976); and Rieke et al. (1976) first noted a correlation between the optical and radio variations in a 1975 outburst of AO 0235+164. Balonek and Dent (1980) showed a second correlation in a 1979 outburst. Subsequent optical outbursts and further optical-radio correlations have been studied by several authors. We study the long and short time scale variations in four additional optical outbursts in 1990, 1991, 1992, and 1998. We find that some of the bursts appear to be strongly correlated with radio bursts, while others do not exhibit simple correlations. Different physical phenomena may be needed in order to explain the differences in these outbursts. In the correlated cases, the optical burst appears to either nearly coincide with a radio burst, or precede a subsequent radio burst by a few months. The time scales of the outbursts agree with the generally accepted model of Blandford and Konigl (1979) of a relativistic shock propagating down a jet. In addition, intra-night variability is seen during these outbursts on much shorter time scales and is most likely caused by another phenomenon.

  6. Vegetation and climate history in arid western China during MIS2: New insights from pollen and grain-size data of the Balikun Lake, eastern Tien Shan

    NASA Astrophysics Data System (ADS)

    Zhao, Yongtao; An, Cheng-Bang; Mao, Limi; Zhao, Jiaju; Tang, Lingyu; Zhou, Aifeng; Li, Hu; Dong, Weimiao; Duan, Futao; Chen, Fahu

    2015-10-01

    Marine Isotope Stage (MIS) 2 is mostly a cold period encompassing the Last Glacial Maximum (LGM), but the regional expression of MIS2 in arid areas of China is not well known. In this paper, we use high-resolution lacustrine pollen and grain-size records from Balikun Lake to infer vegetation, lake evolution, and climate in arid western China during MIS2. Our results suggest that: 1) the regional vegetation around Balikun was mainly dominated by desert and/or desert-steppe, and Balikun Lake was relatively shallow and experienced high aeolian input during MIS2; 2) distinctive runoff from mountain glacial meltwater in the eastern parts of the Balikun basin caused a high relative abundance of Artemisia pollen during the LGM (26.5-19.2 cal kyr BP), while simultaneously the desert areas expanded as indicated by the high abundance of desert shrubs (e.g., Elaeagnaceae, Rhamnaceae, Hippophae). This cold and dry LGM climate triggered a substantial lowering of lake level; 3) an extremely cold and dry climate prevailing from 17.0 to 15.2 cal kyr BP, correlated with Heinrich event 1 (H1), would explain the low vegetation cover found then; and 4) the warm and humid Bølling/Allerød interstadial (BA: ca. 15-ca. 13 cal kyr BP) is clearly recorded in the Balikun region by the development of wetland herb communities (e.g., Poaceae, Cyperaceae, Typha), and the lake level rose due to increased runoff. Our results challenge the traditional view of cold and wet climatic conditions and high lake levels in arid western China during the LGM, and we propose that changes in local temperature modulated by July insolation was an indispensable factor in triggering vegetation evolution in the Balikun region during MIS2.

  7. Millennial-scale Asian summer monsoon variations in South China since the last deglaciation

    NASA Astrophysics Data System (ADS)

    Wang, Xisheng; Chu, Guoqiang; Sheng, Mei; Zhang, Shuqin; Li, Jinhua; Chen, Yun; Tang, Ling; Su, Youliang; Pei, Junling; Yang, Zhenyu

    2016-10-01

    Characterizing spatiotemporal variability of the Asian summer monsoon (ASM) is critical for full understanding of its behavior, dynamics, and future impacts. The present knowledge about ASM variations since the last glaciation in South China largely relies on several precisely-dated speleothem stable oxygen isotope (δ18 O) records. Although these speleothem δ18 O signals provide useful evidence for regional past environmental changes, their validity for denoting ASM intensity remains a great controversy. The Huguangyan Maar Lake (HML) provides one of the most complete archives of environmental and climatic changes in the tropical-subtropical South and East Asia since the last glaciation. Here we document a continuous centennial- to millennial-scale ASM record over the past 16 ky BP from the high-sedimentation-rate HML sediments. In contrast with the low-amplitude variations of Chinese speleothem-derived δ18 O signals and the Chinese loess-based monsoon precipitation proxy indexes, our multi-proxy records reveal a pattern of high-amplitude regional climatic fluctuations, including fine-scale oscillations during the Bølling-Allerød warming, the 8.2 ka cooling event, and an abrupt climate shift from 6.5-5.9 ka. The existence of Bond-like cold/dry events indicates a distinct influence of the North Atlantic circulation on low-latitude monsoon changes. The broad comparability between the HML paleo-proxies, Chinese speleothem δ18 O records, and the northern hemisphere summer insolation throughout the Holocene, suggests that solar insolation exerts a profound influence on ASM changes. These findings reinforce a model of combined insolation and glacial forcing of the ASM.

  8. NASA Astrophysics Data System (ADS)

    2017-06-01

    Biogeochemical reactions implemented in the model and their corresponding rate laws are given in Tables 2 and 3, respectively. Corresponding reaction parameters were taken from literature. Where parameters were not available or no fit to the data could be obtained with existing parameter ranges they were constrained using the model (Table 4). Both Fe oxides and organic matter are divided into highly reactive (α), less reactive (β) and inert (γ) phases. The β phase of the Fe oxides is assumed to be less reactive towards dissolved sulfide than the α phase and, in contrast to the α phase, cannot be used by organoclastic Fe reduction (Egger et al., 2016a; Rooze et al., 2016). The latter assumption was made to test whether Fe-AOM alone could explain the apparent Fe reduction at depth and to allow an assessment of the potential impact of Fe-AOM on sedimentary CH4 cycling. Note that the modeled Fe oxide phases do not directly relate to the operationally defined pools of Fe oxides. The model includes authigenic formation of Fe sulfides, Fe carbonates (siderite; FeCO3) and vivianite (Fe3(PO4)2) to account for sinks of pore water Fe2+, assuming second-order kinetics (Egger et al., 2016a; Rooze et al., 2016) as well as apatite (Ca5(PO4)3OH) formation and linear adsorption of NH4+ (Mackin and Aller, 1984; Soetaert and Herman, 2009). A model sensitivity analysis for key parameters is provided in the Supplementary Information (Supplementary Figs. S2-S4).

  9. Asteroids to Quasars

    NASA Astrophysics Data System (ADS)

    Lugger, Phyllis M.

    2004-12-01

    Asteroid dedication; William Liller: Biographical Sketch; William Liller: Autobiographical Meanderings; Preface; List of Participants; Conference Photo; Part I. 1. Solar System Astronomy: Asteroids Joseph Veverka; 2. Sixteen years of stellar occultations James Elliott; 3. Comets to Quasars: Surface photometry from standard stars and the morphology of the galaxy-quasar interface Peter Usher; 4. Observing Solar Eclipses Jay Pasachoff; Part II. 5. Planetary Nebulae: new insights and opportunities Lawrence Aller; 6. Studies of planetary nebulae at radio wavelengths Yervant Terzian; 7. Optical identifications of compact galactic X-ray sources: Liller Lore Jonathan Grindlay; 8. Ages of globular clusters derived from BVRI CCD photometry Gonzalo Alcaino; 9. Stellar spectrum synthesis Jun Jugaku; 10. Mass exchange and stellar abundance anomalies Benjamin Peery; Part III. Extragalactic Astronomy: 11. The M31 globular cluster system John Huchra; 12. Spiral structure and star formation in galaxies Debra Elmegreen; 13. The discovery of hot coronae around early type galaxies William Forman and Christine Jones; 14. The morphology of clusters of galaxies, the formation efficiency of galaxies and the origin of the intracluster medium Christine Jones and William Forman; 15. Testing models for the dynamical evolution of clusters of galaxies Phyllis Lugger; 16. What is in the X-ray sky? Rudolph Schild; 17. Einstein deep surveys Stephen Murray, Christine Jones and William Forman; Part IV. History, Lore and Archaeoastronomy: 18. Robert Wheeler Willson: His Life and Legacy Barbara Welther; 19. The great mnemonics contest Owen Gingerich; 20. Hetu'u Rapanui: The archaeoastronomy of Easter Island William Liller; Indexes; Names; Objects; Subjects.

  10. U-series vs 14C ages of deep-sea corals from the southern Labrador Sea: Sporadic development of corals and geochemical processes hampering estimation of ambient water ventilation ages

    NASA Astrophysics Data System (ADS)

    Hillaire-Marcel, Claude; Maccali, Jenny; Ménabréaz, Lucie; Ghaleb, Bassam; Blénet, Aurélien; Edinger, Evan

    2017-04-01

    Deep-sea scleractinian corals were collected with the remotely operated ROPOS vehicle off Newfounland. Fossil specimens of Desmophyllum dianthus were raised from coral graveyards at Orphan Knoll (˜1700m depth) and Flemish cap (˜2200 m depth), while live specimens were collected directly in overlying steep rock slopes. D. dianthus has an aragonitic skeleton and is thus particularly suited for U-Th dating. We obtained > 70 U-series ages along with > 20 14C measurements. Results display a discrete age distribution with two age clusters: a Bølling-Allerød and Holocene cluster with > 20 samples, and a Marine Isotope Stage (MIS) 5c cluster with ˜50 samples. Only two samples lay outside these clusters, at ˜ 64 ka and at ˜181 ka. Contrary to the New England seamounts where coral presence seems to have been continue through the last 70 ka, Orphan Knoll and Flemish Cap graveyards are marked by the absence of preserved specimens from MIS 2 to MIS 4 and throughout MIS 6. For filter-feeding deep-sea corals, access to food-rich waters is essential. Hence the Holocene and MIS 5 clusters observed in the Labrador basin might represent intervals linked to high food availability, either through production in the overlying water column, more effectively in relation to particulate and dissolved organic carbon transport via an active Western Boundary Undercurrent. Comparison of 230Th-ages vs 14C-ages in order to document changes in ventilation ages of the ambient water masses is equivocal due to the presence of some diagenetic and/or initial 230Th-excess. In addition, discrete diagenetic U-fluxes can be documented from 234U/238U vs 230Th/238U data. They point to a recent winnowing of sediment overlying the fossil corals that we link to the Holocene intensification of the Western Boundary Undercurrent, which resulted in driving Fe-Mn coatings.

  11. Geomorphological evolution of Mediterranean enclosed depressions in the Late glacial and Holocene: The example of Canohès (Roussillon, SE France)

    NASA Astrophysics Data System (ADS)

    Carozza, Jean-Michel; Llubes, Muriel; Danu, Mihaela; Faure, Elodie; Carozza, Laurent; David, Mélodie; Manen, Claire

    2016-11-01

    The origin and evolution of the enclosed depressions (pans) of southern France during the period from the Late Glacial to the Holocene are discussed on the basis of new stratigraphical, geophysical and chronological (14C) data from the Canohès depression (Roussillon, Southern of France) and its nearby environment. The Canohès depression is non-karstic, excavated from Pliocene arkosic sands that were shaped by eolian erosion during cold stages of the Middle and Upper Pleistocene. The timing and controlling factors of eolian carving of the depression are discussed on the basis of geomorphological data, surrounding alluvial terrace chronology, preserved ledge within the depression and alluvial infill of the depression. Formation of the depression was controlled, locally, by climate variability and its consequences on vegetation and water table position and, regionally, by the sea base level. The enclosed depression probably started to form during MIS 6, reaching its maximum depth during MIS 2. Climate variability in the region is recorded in the depression's infill. The basal deposits are of fluvial origin and record the increase of moisture and temperature during the Early Late-Glacial. The first lacustrine deposits are observed during the Bölling/GI-1e stage, while continental sedimentation and drying occurred during the Alleröd and Younger Dryas stages. During the Early and Middle Holocene, lacustrine conditions prevailed, except during short periods of drying. The specific evolution of the Canohès depression as regards other such formations is discussed in light of regional deglaciation and climate chronology. A regional synthesis of eolian erosion is proposed.

  12. WISEP J004701.06+680352.1: An Intermediate Surface Gravity, Dusty Brown Dwarf in the AB Dor Moving Group

    NASA Astrophysics Data System (ADS)

    Gizis, John E.; Allers, Katelyn N.; Liu, Michael C.; Harris, Hugh C.; Faherty, Jacqueline K.; Burgasser, Adam J.; Kirkpatrick, J. Davy

    2015-02-01

    We present spectroscopy, astrometry, and photometry of the brown dwarf WISEP J004701.06+680352.1 (W0047+68), an unusually red field L dwarf at a distance of 12.2 ± 0.4 pc. The three-dimensional space motion identifies it as a member of the AB Dor Moving Group, an identification supported by our classification of W0047+68 as intermediate surface gravity (INT-G) using the Allers & Liu near-infrared classification system. This moving group membership implies near-solar metallicity, age ~100-125 Myr, M ≈ 0.018 M ⊙, and log g ≈ 4.5; the thick condensate clouds needed to explain the infrared spectrum are, therefore, a result of surface gravity that is lower than that of ordinary field brown dwarfs. From the observed luminosity and evolutionary model radius, we find T eff ≈ 1300 K, a temperature normally associated with early T dwarfs. Thick clouds are also used to explain the spectral properties of directly imaged giant planets, and we discuss the successes and challenges for such substellar models in matching the observed optical and infrared spectra. W0047+68 shows that cloud thickness is more sensitive to intermediate surface gravity than in most models. We also present a trigonometric parallax of the dusty L6 dwarf 2MASS J21481628+4003593. It lies at 8.060 ± 0.036 parsecs; its astrometry is consistent with the view that it is older and metal-rich.

  13. Millennial-scale changes of surface and bottom water conditions in the northwestern Pacific during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Kim, Sunghan; Khim, Boo-Keun; Ikehara, Ken; Itaki, Takuya; Shibahara, Akihiko; Yamamoto, Masanobu

    2017-07-01

    Changes in water column conditions in the northwestern Pacific during the last 23 ka were reconstructed using geochemical and isotope proxies and redox elemental compositions along with published data (alkenone sea surface temperature (SST) and benthic foraminiferal fauna) at core GH02-1030. Surface water primary productivity in terms of biogenic opal and TOC contents, which mainly represented export production of diatom, was closely related to alkenone (spring-summer) SST and the development of spring-summer mixed layer depth. The different variation patterns of nitrate and silicic acid utilization, estimated by bulk δ15N and δ30Sidiatom values, respectively, are most likely due to the water column denitrification influence on bulk δ15N. Dysoxic bottom water conditions occurred during the Bølling-Allerød (BA) and the Pre-Boreal (PB), which was evident by laminated sediments, abundant dysoxic benthic foraminifers, and increased redox elemental compositions. Although surface water productivity increased during the BA and PB, dysoxic bottom water conditions were caused by a combination of enhanced surface water productivity and reduced ventilation of North Pacific Intermediate Water (NPIW) in response to meltwater input from the high latitude areas. Based on records of core GH02-1030 and other cores in the northwestern Pacific, the Okhotsk Sea, and the Bering Sea, which are all proximal to the modern NPIW source region, dissolved oxygen concentrations of bottom water were more depleted during the BA than PB. Such difference was attributed to more sluggish NPIW ventilation due to more meltwater input during the BA than the PB. The opening or closure of the Bering Strait is critical to the direction of meltwater transport to the northwestern Pacific.

  14. Grossesse ovarienne: à propos de 3 cas et une revue de la literature

    PubMed Central

    Ranaivoson, Haingo Voahangy Rabetafika; Ranaivomanana, Volahasina Françine; Nomenjanahary, Lalaina; Andriamampionona, Tsitohery Francine; Randrianjafisamindrakotroka, Nantenaina Soa

    2016-01-01

    La grossesse ovarienne représente une entité rare parmi les grossesses ectopiques où l'ovaire est le siège de la nidation. Son diagnostic nécessite une démarche bien codifiée. Les particularités des facteurs déterminant, des caractéristiques histopathologiques et évolutives des grossesses ovariennes nous a conduit à porter un intérêt pour cette forme de grossesse ectopique. Nous rapportons 3 cas de grossesse ovarienne diagnostiqués dans notre service. Les trois femmes ont entre 30 à 42 ans et un terme de 13 à 37 semaines d'aménorrhée. Elles sont toutes révélées par des douleurs abdominales d'intensité variable avec un état de choc. L'examen anatomopathologique de l'annexe droite, siège caractéristique des grossesses ovariennes, a permis de confirmer le diagnostic. Elles sont toutes des grossesses ovariennes primitives juxta-corticales. La grossesse ovarienne est une entité très rare de la grossesse extra-utérine qui présente certaines particularités. Son diagnostic est difficile et se base sur des constations per-opératoires. La présence de la zone de nidation ovarienne à l'examen histopathologique est optimale pour confirmer le diagnostic. Actuellement, on admet que la grossesse ovarienne est la forme de grossesse ectopique qui peut aller à terme ou même jusqu'à une naissance vivante. PMID:28292090

  15. Improvements to the DRASTIC ground-water vulnerability mapping method

    USGS Publications Warehouse

    Rupert, Michael G.

    1999-01-01

    Ground-water vulnerability maps are designed to show areas of greatest potential for ground-water contamination on the basis of hydrogeologic and anthropogenic (human) factors. The maps are developed by using computer mapping hardware and software called a geographic information system (GIS) to combine data layers such as land use, soils, and depth to water. Usually, ground-water vulnerability is determined by assigning point ratings to the individual data layers and then adding the point ratings together when those layers are combined into a vulnerability map. Probably the most widely used ground-water vulnerability mapping method is DRASTIC, named for the seven factors considered in the method: Depth to water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone media, and hydraulic Conductivity of the aquifer (Aller and others, 1985, p. iv). The DRASTIC method has been used to develop ground-water vulnerability maps in many parts of the Nation; however, the effectiveness of the method has met with mixed success (Koterba and others, 1993, p. 513; U.S. Environmental Protection Agency, 1993; Barbash and Resek, 1996; Rupert, 1997). DRASTIC maps usually are not calibrated to measured contaminant concentrations. The DRASTIC ground-water vulnerability mapping method was improved by calibrating the point rating scheme to measured nitrite plus nitrate as nitrogen (NO2+NO3–N) concentrations in ground water on the basis of statistical correlations between NO2+NO3–N concentrations and land use, soils, and depth to water (Rupert, 1997). This report describes the calibration method developed by Rupert and summarizes the improvements in results of this method over those of the uncalibrated DRASTIC method applied by Rupert and others (1991) in the eastern Snake River Plain, Idaho.

  16. [German translation and adaptation of the uncertainty stress scale high risk pregnancy version III (USS-HRPV) for hospitalised women with high-risk pregnancy].

    PubMed

    Amsler, Marlen; König, Claudia; Ikhilor, Paola Origlia; Cignacco, Eva Lucia

    2014-06-01

    Hintergrund: Medizinisch und gesellschaftlich bedingte Faktoren führen zu einer Zunahme hospitalisierter Frauen mit Risikoschwangerschaft. Die Unvorhersehbarkeit des weiteren Schwangerschaftsverlaufs kann zu Ungewissheit und je nach Bewältigungsstrategie auch zu Stress führen. Ziele: Ziele dieser Studie waren die deutsche Übersetzung und Adaptation der USS-HRPV. Methode: Die Übersetzung in die deutsche Sprache erfolgte mittels Vor- und Rückwärtsübersetzung. Die zwei Phasen umfassende Adaptation wurde mit hospitalisierten Frauen mit Risikoschwangerschaft (n = 24) sowie diplomierten Hebammen (n = 10) durchgeführt und beruht sowohl auf kognitiven Interviews wie auch auf einer Testung der Inhaltsvalidität mittels «Content Validity Index» (CVI). Nach jeder Erhebungsphase wurde das Messinstrument mithilfe von Fachexpertinnen (n = 3) modifiziert. Ergebnisse: Der für jedes Item berechnete CVI (I-CVI) ergab in der ersten Phase für beide Teilstichproben Werte zwischen 0,10 und 1,0, der über das gesamte Messinstrument berechnete CVI (S-CVI/Ave) einen Wert von 0,62 respektive 0,70. Die I-CVI-Werte der hospitalisierten Frauen mit Risikoschwangerschaft der zweiten Phase lagen zwischen 0,17 und 1,0, der S-CVI/Ave betrug 0,73. Insgesamt wurden unter Berücksichtigung aller Daten 44 der ursprünglich 86 Items entfernt und 28 sprachlich verändert. Schlussfolgerungen: Aufgrund der methodischen Vorgehensweise konnte eine solide Ausgangslage für die weiteren Validierungsschritte zur Weiterentwicklung des Messinstrumentes für den deutschsprachigen Raum erarbeitet werden.

  17. Regional hydroclimate response to freshwater fluxes from the Fennoscandian Ice Sheet during the Last Termination

    NASA Astrophysics Data System (ADS)

    Macdonald, F. A.; Schmitz, M. D.; Condon, D. J.; Zhu, M.; Rooney, A. D.; Brandon, A. D.

    2014-12-01

    Resolving the effects of freshwater forcing during the last glacial-interglacial transition, the Last Termination, is critical to our comprehension of rapid climate change. In particular, the role of Fennoscandian Ice Sheet (FIS) and freshwater from the eastern seaboard of the North Atlantic has been entirely disregarded in the context of the abrupt regional hydroclimate shifts that characterized this period. Here we infer freshwater input variations from the FIS to the Nordic Seas based on two accurately dated hydroclimate reconstructions from lake sediment records from Southern Sweden and one SST reconstruction from the Nordic Seas. The records indicate a number of abrupt freshwater discharges into the Nordic Seas at the start of the Bølling interstadial and during the Allerød interstadial. We observe that these intervals of enhanced FIS freshwater outflow correspond to different modalities of hydroclimate regime shifts in Greenland. Using a set of climate model simulations, we show that the dominant Greenland hydroclimate state can be influenced by the degree of FIS freshwater recirculation in the Nordic Seas, which redirects the excess of sea ice partitioned into the Barents Sea towards the eastern Greenland Current. The tradeoff between buildup and recirculation of sea ice in the Nordic Seas generate large-scale sea-level pressure anomalies that may explain the sign and magnitude of the isotopic and temperature changes inferred from Greenland and North European reconstructions. We conclude that air-sea interactions in the North Atlantic are more sensitive to Fennoscandian freshwater forcing than previously thought. These results could help to solve the problematic relationship between origin, timing and magnitude of freshwater perturbations and abrupt deglacial changes in North Atlantic Ocean circulation in numerical simulations.

  18. Regional hydroclimate response to freshwater fluxes from the Fennoscandian Ice Sheet during the Last Termination

    NASA Astrophysics Data System (ADS)

    Muschitiello, F.; Dokken, T. M.; Pausata, F. S. R.; Smittenberg, R.; Wohlfarth, B.

    2015-12-01

    Resolving the effects of freshwater forcing during the last glacial-interglacial transition, the Last Termination, is critical to our comprehension of rapid climate change. In particular, the role of Fennoscandian Ice Sheet (FIS) and freshwater from the eastern seaboard of the North Atlantic has been entirely disregarded in the context of the abrupt regional hydroclimate shifts that characterized this period. Here we infer freshwater input variations from the FIS to the Nordic Seas based on two accurately dated hydroclimate reconstructions from lake sediment records from Southern Sweden and one SST reconstruction from the Nordic Seas. The records indicate a number of abrupt freshwater discharges into the Nordic Seas at the start of the Bølling interstadial and during the Allerød interstadial. We observe that these intervals of enhanced FIS freshwater outflow correspond to different modalities of hydroclimate regime shifts in Greenland. Using a set of climate model simulations, we show that the dominant Greenland hydroclimate state can be influenced by the degree of FIS freshwater recirculation in the Nordic Seas, which redirects the excess of sea ice partitioned into the Barents Sea towards the eastern Greenland Current. The tradeoff between buildup and recirculation of sea ice in the Nordic Seas generate large-scale sea-level pressure anomalies that may explain the sign and magnitude of the isotopic and temperature changes inferred from Greenland and North European reconstructions. We conclude that air-sea interactions in the North Atlantic are more sensitive to Fennoscandian freshwater forcing than previously thought. These results could help to solve the problematic relationship between origin, timing and magnitude of freshwater perturbations and abrupt deglacial changes in North Atlantic Ocean circulation in numerical simulations.

  19. Assessing oxygen depletion in the Northeastern Pacific Ocean during the last deglaciation using I/Ca ratios from multiple benthic foraminiferal species

    NASA Astrophysics Data System (ADS)

    Taylor, M. A.; Hendy, I. L.; Chappaz, A.

    2017-08-01

    Paleo-redox proxies are crucial for reconstructing past bottom water oxygen concentration changes brought about by ocean circulation and marine productivity shifts in response to climate forcing. Carbonate I/Ca ratios of multiple benthic foraminifera species from Ocean Drilling Program Hole 1017E—a core drilled within the Californian oxygen minimum zone (OMZ), on the continental slope—are employed to reexamine the transition from the well-oxygenated last glacial into poorly oxygenated modern conditions. The redox and export productivity history of this site is constrained by numerous proxies used to assess sensitivity of I/Ca ratios of benthic foraminifera to changes in bottom and pore water O2 concentrations. Reconstructed iodate (IO3-) availability is from the I/Ca ratio of epifaunal (Cibicidoides sp.), shallow infaunal (Uvigerina peregrina), and deep infaunal (Bolivina spissa) foraminifera. The reconstructed IO3- availability profile is used to determine the contribution of bottom water O2 relative to oxidant demand on pore water O2 concentrations. These results suggest that high export productivity on the California Margin drove low pore water O2 concentrations during the Bølling. In contrast, low bottom water O2 concentrations at 950 m water depth only contributed to reduced sediments during the Allerød. Increased contribution of modified North Pacific Intermediate Water to the California Current System ventilated the California OMZ during the late glacial and the Younger Dryas such that water overlying the site was oxygenated. These results highlight the promising potential of this new proxy for understanding the relative influence of bottom water O2 concentration and pore water oxidant demand on OMZs.

  20. Vegetation history since the last glacial maximum in the Ozark highlands (USA): A new record from Cupola Pond, Missouri

    NASA Astrophysics Data System (ADS)

    Jones, Rachel A.; Williams, John W.; Jackson, Stephen T.

    2017-08-01

    The timing and drivers of vegetation dynamics and formation of no-analog plant communities during the last deglaciation in the unglaciated southeastern US are poorly understood. We present a multi-proxy record spanning the past 19,800 years from Cupola Pond in the Ozarks Mountains, consisting of replicate high-resolution pollen records, 25 AMS radiocarbon dates, and macrofossil, charcoal, and coprophilous spore analyses. Full-glacial Pinus and Picea forests gave way to no-analog vegetation after 17,400 yr BP, followed by development of Quercus-dominated Holocene forests, with late Holocene rises in Pinus and Nyssa. Vegetation transitions, replicated in different cores, are closely linked to hemispheric climate events. Rising Quercus abundances coincide with increasing Northern Hemisphere temperatures and CO2 at 17,500 yr BP, declining Pinus and Picea at 14,500 yr BP are near the Bølling-Allerød onset, and rapid decline of Fraxinus and rise of Ostrya/Carpinus occur 12,700 yr BP during the Younger Dryas. The Cupola no-analog vegetation record is unusual for its early initiation (17,000 yr BP) and for its three vegetation zones, representing distinct rises of Fraxinus and Ostrya/Carpinus. Sporormiella was absent and sedimentary charcoal abundances were low throughout, suggesting that fire and megaherbivores were not locally important agents of disturbance and turnover. The Cupola record thus highlights the complexity of the late-glacial no-analog communities and suggests direct climatic regulation of their formation and disassembly.

  1. Magnetic record of deglaciation using FORC-PCA, sortable-silt grain size, and magnetic excursion at 26 ka, from the Rockall Trough (NE Atlantic)

    NASA Astrophysics Data System (ADS)

    Channell, J. E. T.; Harrison, R. J.; Lascu, I.; McCave, I. N.; Hibbert, F. D.; Austin, W. E. N.

    2016-05-01

    Core MD04-2822 from the Rockall Trough has apparent sedimentation rates of ˜ 1 m/kyr during the last deglaciation (Termination I). Component magnetization directions indicate a magnetic excursion at 16.3 m depth in the core, corresponding to an age of 26.5 ka, implying an excursion duration of ˜350 years. Across Termination I, the mean grain size of sortable silt implies reduced bottom-current velocity in the Younger Dryas and Heinrich Stadial (HS)-1A, and increased velocities during the Bølling-Allerød warm period. Standard bulk magnetic parameters imply fining of magnetic grain size from the mid-Younger Dryas (˜12 ka) until ˜ 8 ka. First-order reversal curves (FORCs) were analyzed using ridge extraction to differentiate single domain (SD) from background (detrital) components. Principal component analysis (FORC-PCA) was then used to discriminate three end members corresponding to SD, pseudo-single domain (PSD), and multidomain (MD) magnetite. The fining of bulk magnetic grain size from 12 to 8 ka is due to reduction in concentration of detrital (PSD + MD) magnetite, superimposed on a relatively uniform concentration of SD magnetite produced by magnetotactic bacteria. The decrease in PSD+MD magnetite concentration from 12 to 8 ka is synchronized with increase in benthic δ13C, and with major (˜70 m) regional sea-level rise, and may therefore be related to detrital sources on the shelf that had reduced influence as sea level rose, and to bottom-water reorganization as Northern Source Water (NSW) replaced Southern Source Water (SSW).

  2. Millennial-scale sea surface temperature changes in the eastern Mediterranean (Nile River Delta region) over the last 27,000 years

    NASA Astrophysics Data System (ADS)

    Castañeda, Isla S.; Schefuß, Enno; Pätzold, Jürgen; Sinninghe Damsté, Jaap S.; Weldeab, Syee; Schouten, Stefan

    2010-03-01

    In this study we utilize two organic geochemical proxies, the U37k‧ index and TEX86, to examine past sea surface temperatures (SST) from a site located near the Nile River Delta in the eastern Mediterranean (EM) Sea. The U37k‧ and TEX86 records generally are in agreement and indicate SST ranges of 14°C-26°C and 14°C-28°C, respectively, during the last 27 cal ka. During the Holocene, TEX86-based SST estimates are usually higher than U37k‧-based SST estimates, which is likely due to seasonal differences between the timing of the haptophyte and crenarchaeota blooms in the EM and is related to the onset of the modern flow regime of the Nile River. Both records show that SST varied on centennial to millennial timescales in response to global climate events, i.e., cooling during the Last Glacial Maximum (LGM), Heinrich event 1 (H1), and the Younger Dryas (YD) and warming during the Bølling-Allerød and in the early Holocene during deposition of sapropel S1. The H1 cooling was particularly severe and is marked by a drop in SST of ˜4.5°C in comparison to pre-H1 SST, with temperatures >1°C cooler than during the LGM. In contrast to high-latitude and western Mediterranean records, which indicate both an abrupt onset and termination of the YD event, the transition from the YD to the Holocene was much more gradual in the EM.

  3. Offset timing of climate oscillations during the last two glacial-interglacial transitions connected with large-scale freshwater perturbation

    NASA Astrophysics Data System (ADS)

    Jiménez-Amat, Patricia; Zahn, Rainer

    2015-06-01

    Multidecadal to centennial planktic δ18O and Mg/Ca records were generated at Ocean Drilling Program Site 976 (ODP976) in the Alboran Sea. The site is in the flow path of Atlantic inflow waters entering the Mediterranean and captured North Atlantic signals through the surface inflow and the atmosphere. The records reveal similar climatic oscillations during the last two glacial-to-interglacial transitions, albeit with a different temporal pacing. Glacial termination 1 (T1) was marked by Heinrich event 1 (H1), post-H1 Bølling/Allerød warming, and Younger Dryas (YD) cooling. During T2 the H11 δ18O anomaly was twice as high and lasted 30% longer than during H1. The post-H11 warming marked the start of MIS5e while the subsequent YD-style cooling occurred during early MIS5e. The post-H11 temperature increase at ODP976 matched the sudden Asian Monsoon Termination II at 129 ka B.P. Extending the 230Th-dated speleothem timescale to ODP976 suggests glacial conditions in the Northeast Atlantic region were terminated abruptly and interglacial warmth was reached in less than a millennium. The early-MIS5e cooling and freshening at ODP976 coincided with similar changes at North Atlantic sites suggesting this was a basin-wide event. By analogy with T1, we argue that this was a YD-type event that was shifted into the early stages of the last interglacial period. This scenario is consistent with evidence from northern North Atlantic and Nordic Sea sites that the continuing disintegration of the large Saalian Stage (MIS6) ice sheet in Eurasia delayed the advection of warm North Atlantic waters and full-strength convective overturn until later stages of MIS5e.

  4. Terrestrial climate variability and seasonality changes in the Mediterranean region between 15 000 and 4000 years BP deduced from marine pollen records

    NASA Astrophysics Data System (ADS)

    Dormoy, I.; Peyron, O.; Combourieu Nebout, N.; Goring, S.; Kotthoff, U.; Magny, M.; Pross, J.

    2009-10-01

    Pollen-based climate reconstructions were performed on two high-resolution pollen marines cores from the Alboran and Aegean Seas in order to unravel the climatic variability in the coastal settings of the Mediterranean region between 15 000 and 4000 years BP (the Lateglacial, and early to mid-Holocene). The quantitative climate reconstructions for the Alboran and Aegean Sea records focus mainly on the reconstruction of the seasonality changes (temperatures and precipitation), a crucial parameter in the Mediterranean region. This study is based on a multi-method approach comprising 3 methods: the Modern Analogues Technique (MAT), the recent Non-Metric Multidimensional Scaling/Generalized Additive Model method (NMDS/GAM) and Partial Least Squares regression (PLS). The climate signal inferred from this comparative approach confirms that cold and dry conditions prevailed in the Mediterranean region during the Oldest and Younger Dryas periods, while temperate conditions prevailed during the Bølling/Allerød and the Holocene. Our records suggest a West/East gradient of decreasing precipitation across the Mediterranean region during the cooler Late-glacial and early Holocene periods, similar to present-day conditions. Winter precipitation was highest during warm intervals and lowest during cooling phases. Several short-lived cool intervals (i.e. Older Dryas, another oscillation after this one (GI-1c2), Gerzensee/Preboreal Oscillations, 8.2 ka event, Bond events) connected to the North Atlantic climate system are documented in the Alboran and Aegean Sea records indicating that the climate oscillations associated with the successive steps of the deglaciation in the North Atlantic area occurred in both the western and eastern Mediterranean regions. This observation confirms the presence of strong climatic linkages between the North Atlantic and Mediterranean regions.

  5. Terrestrial climate variability and seasonality changes in the Mediterranean region between 15000 and 4000 years BP deduced from marine pollen records

    NASA Astrophysics Data System (ADS)

    Dormoy, I.; Peyron, O.; Combourieu-Neboutb, N.; Goring, S.; Kotthoff, U.; Magny, M.; Pross, J.

    2009-02-01

    Pollen-based climate reconstructions were performed on two high-resolution pollen - marines cores from the Alboran and Aegean Seas in order to unravel the climatic variability in the coastal settings of the Mediterranean region between 15 000 and 4000 cal yrs BP (the Lateglacial, and early to mid-Holocene). The quantitative climate reconstructions for the Alboran and Aegean Sea records focus mainly on the reconstruction of the seasonality changes (temperatures and precipitation), a crucial parameter in the Mediterranean region. This study is based on a multi-method approach comprising 3 methods: the Modern Analogues Technique (MAT), the recent Non-Metric Multidimensional Scaling/Generalized Additive Model method (NMDS/GAM) and Partial Least Squares regression (PLS). The climate signal inferred from this comparative approach confirms that cold and dry conditions prevailed in the Mediterranean region during the Heinrich event 1 and Younger Dryas periods, while temperate conditions prevailed during the Bølling/Allerød and the Holocene. Our records suggest a West/East gradient of decreasing precipitation across the Mediterranean region during the cooler Late-glacial and early Holocene periods, similar to present-day conditions. Winter precipitation was highest during warm intervals and lowest during cooling phases. Several short-lived cool intervals (i.e., Older Dryas, another oscillation after this one (GI-1c2), Gerzensee/Preboreal Oscillations, 8.2 ka event, Bond events) connected to the North Atlantic climate system are documented in the Alboran and Aegean Sea records indicating that the climate oscillations associated with the successive steps of the deglaciation in the North Atlantic area occurred in both the western and eastern Mediterranean regions. This observation confirms the presence of strong climatic linkages between the North Atlantic and Mediterranean regions.

  6. Human-induced changes in the distribution of rainfall.

    PubMed

    Putnam, Aaron E; Broecker, Wallace S

    2017-05-01

    A likely consequence of global warming will be the redistribution of Earth's rain belts, affecting water availability for many of Earth's inhabitants. We consider three ways in which planetary warming might influence the global distribution of precipitation. The first possibility is that rainfall in the tropics will increase and that the subtropics and mid-latitudes will become more arid. A second possibility is that Earth's thermal equator, around which the planet's rain belts and dry zones are organized, will migrate northward. This northward shift will be a consequence of the Northern Hemisphere, with its large continental area, warming faster than the Southern Hemisphere, with its large oceanic area. A third possibility is that both of these scenarios will play out simultaneously. We review paleoclimate evidence suggesting that (i) the middle latitudes were wetter during the last glacial maximum, (ii) a northward shift of the thermal equator attended the abrupt Bølling-Allerød climatic transition ~14.6 thousand years ago, and (iii) a southward shift occurred during the more recent Little Ice Age. We also inspect trends in seasonal surface heating between the hemispheres over the past several decades. From these clues, we predict that there will be a seasonally dependent response in rainfall patterns to global warming. During boreal summer, in which the rate of recent warming has been relatively uniform between the hemispheres, wet areas will get wetter and dry regions will become drier. During boreal winter, rain belts and drylands will expand northward in response to differential heating between the hemispheres.

  7. Postglacial paleoceanographic environments in the Barents and Baltic seas

    NASA Astrophysics Data System (ADS)

    Ivanova, E. V.; Murdmaa, I. O.; Emelyanov, E. M.; Seitkalieva, E. A.; Radionova, E. P.; Alekhina, G. N.; Sloistov, S. M.

    2016-01-01

    This paper presents reconstructions of ice sheet boundaries, lacustrine and marine paleobasins, as well as the connections of the Barents and Baltic seas with the North Atlantic from the Last Glacial Maximum to the Holocene. The reconstructions are based on original and published data obtained from the northern and western parts of the Barents Sea and Baltic depressions with account for the available regional schematic maps of deglaciation. The early deglaciation of the Scandinavian-Barents ice sheet culminated with the Bølling-Allerød interstadial (14.5-12.9 cal ka BP), which was characterized by a more vigorous Atlantic meridional overturning circulation (AMOC) and a corresponding increase in surface Atlantic water inflow into the Barents Sea through deep troughs. The Baltic Ice Lake (BIL) remained a dammed-up isolated basin during deglaciation from 16.0 to 11.7 cal ka BP. In the Younger Dryas (YD), the lake drained into the North Sea and was replaced by a brackish Yoldia Sea (YS) at the beginning of the Holocene (Preboreal, 11.7-10.7 cal ka BP), due to a limited connection between two basins through the Närke Strait. In the Barents Sea, the next increase in the Atlantic water influx into the deep basins corresponded to terminal YD and Preboreal events with a culmination in the Early Holocene. The Yoldia Sea became a lake again during the next stage, the Ancylus (~10.7-8.8 cal ka BP). Atlantic water inflow both into the Barents and Baltic seas varied during the Holocene, with a maximum contribution in the Early Holocene, when the Littorina Sea (LS, 8-4 cal ka BP) connection with the North Sea via the Danish Straits was formed to replace the Ancylus Lake. The recent, post-Littorina stage (PS, the last 4 cal ka) of the Baltic Sea evolution began in the Late Holocene.

  8. Agreement between allergen-specific IgE assays and ensuing immunotherapy recommendations from four commercial laboratories in the USA

    PubMed Central

    Plant, Jon D; Neradelik, Moni B; Polissar, Nayak L; Fadok, Valerie A; Scott, Brian A

    2014-01-01

    Background Canine allergen-specific IgE assays in the USA are not subjected to an independent laboratory reliability monitoring programme. Hypothesis/Objectives The aim of this study was to evaluate the agreement of diagnostic results and treatment recommendations of four serum IgE assays commercially available in the USA. Methods Replicate serum samples from 10 atopic dogs were submitted to each of four laboratories for allergen-specific IgE assays (ACTT®, VARL Liquid Gold, ALLERCEPT® and Greer® Aller-g-complete®). The interlaboratory agreement of standard, regional panels and ensuing treatment recommendations were analysed with the kappa statistic (κ) to account for agreement that might occur merely by chance. Six comparisons of pairs of laboratories and overall agreement among laboratories were analysed for ungrouped allergens (as tested) and also with allergens grouped according to reported cross-reactivity and taxonomy. Results The overall chance-corrected agreement of the positive/negative test results for ungrouped and grouped allergens was slight (κ = 0.14 and 0.13, respectively). Subset analysis of the laboratory pair with the highest level of diagnostic agreement (κ = 0.36) found slight agreement (κ = 0.13) for ungrouped plants and fungi, but substantial agreement (κ = 0.71) for ungrouped mites. The overall agreement of the treatment recommendations was slight (κ = 0.11). Altogether, 85.1% of ungrouped allergen treatment recommendations were unique to one laboratory or another. Conclusions and clinical importance Our study indicated that the choice of IgE assay may have a major influence on the positive/negative results and ensuing treatment recommendations. PMID:24461034

  9. From valley to marginal glaciation in alpine-type relief: Lateglacial glacier advances in the Pięć Stawów Polskich/Roztoka Valley, High Tatra Mountains, Poland

    NASA Astrophysics Data System (ADS)

    Zasadni, Jerzy; Kłapyta, Piotr

    2016-01-01

    The Pięć Stawów Polskich-Roztoka Valley in the High Tatras (Western Carpathians) features typical alpine-type relief with a deeply incised glacial trough and large, compound trough head cirque. The prominent hypsographic maximum in the valley (1680-2000 m) along with a broad cirque bottom had provided a vast space for recording glacial and periglacial landforms, specifically the most recent Lateglacial advances. The valley has been intensively studied before in the context of glacial chronology. In this paper, we re-establish the post-Last Glacial Maximum (LGM) glacial chronology of the valley via detailed geomorphologic mapping, equilibrium line altitude (ELA) reconstruction, and Schmidt hammer (SH) dating, along with a critical review of previously published cosmogenic exposure age data (36Cl) and lacustrine sediment chronology. Our results indicate that the first four of the five distinguished Lateglacial stages (Roztoka I-III, Pusta I) occurred before the Bølling/Allerød (B/A) interstadial; thus, virtually the entire valley became deglaciated in course of the Oldest Dryas cold phase. A distinct reorganization of deglacial patterns from valley-type to marginal-type occurred before B/A warming when the ELA increased above the valley hypsographic maximum concentrated at the cirque bottom elevation. It shows that noticeable deglaciation step can be caused due to topographic reason with a minimal climate forcing. This points also to an important role of glaciated valley hypsography in regulating the distribution of moraines which is rarely taken into account in paleoglaciological reconstructions. We infer that glaciers vanished in the Tatra Mountains during the B/A interstadial. Later, a renewed advance during the Younger Dryas (Pusta II) formed a nearly continuous, festoon shaped pattern of moraines and rock glaciers in close distance to cirque backwalls. Furthermore, we discus some paleoenvironmental significance of the geomorphological record in the valley

  10. Paleotemperature reconstructions from speleothem fluid inclusions between 14 - 10 ka BP in Milandre cave (NW Switzerland)

    NASA Astrophysics Data System (ADS)

    Affolter, Stéphane; Häuselmann, Anamaria; Fleitmann, Dominik; Leuenberger, Markus

    2016-04-01

    In cave environments, speleothems constitute a well preserved and precisely dated continental climate archive that record past environmental changes such as paleotemperature or moisture source, namely through oxygen and hydrogen isotopes variations. Fluid inclusions are common in speleothems and they correspond to micrometric voids that often contain fossil liquid water representing past precipitation falling above the cave nearly at the time the inclusions were sealed. To measure the δD and δ18O isotopic composition of speleothem fluid inclusions, we extracted submicrolitre amounts of water from stalagmites (old and recent) coming from Milandre cave (Switzerland) using a new online method developed at the University of Bern (Affolter et al., 2014). The released water is then flushed directly to a Picarro L1102-i or L2140-i laser based instrument that allows to simultaneously monitor hydrogen and oxygen isotopes. At Milandre cave site, a two year isotope monitoring campaign has confirmed that isotopes in precipitation for northwestern Switzerland are principally controlled by air temperature (Affolter et al., 2015). Therefore, when combined with calcite δ18O, the fluid inclusion water isotopes can be used to calculate paleotemperatures. We reconstructed a cold season biased (roughly autumn - winter - spring) paleotemperature trend for the time interval covering the Allerød, the Younger Dryas cold interval and the early Holocene (13'900 - 9'900 BP). References: Affolter S., Fleitmann D., and Leuenberger M.: New online method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS), Clim. Past, 10, 1291-1304, doi:10.5194/cp-10-1291-2014, 2014. Affolter S., Häuselmann A.D., Fleitmann D., Häuselmann P., Leuenberger M.: Triple isotope (δD, δ17O, δ18O) study on precipitation, drip water and speleothem fluid inclusions for a Western Central European cave (NW Switzerland), Quat. Sci. Rev., 127, pp. 73-89, 2015.

  11. a Continuous Record of Trace Element and Stable Isotope Variations in a West Virginia Speleothem: Pre-Lgm to Early Holocene

    NASA Astrophysics Data System (ADS)

    Buckles, J. A.; Rowe, H. D.; Gao, Y.; Cheng, H.; Edwards, R.; Springer, G. S.

    2011-12-01

    A stalagmite (CCC-003) from Culverson Creek Cave, West Virginia, grew uninterrupted for approximately 15,000 years across the Last Glacial Maximum (LGM) to the early Holocene. Stable isotope carbon and oxygen and high resolution trace element (Sr/Ca) chronologies are supported by 37 Th-230 age dates. The timing of Heinrich events 1 and 2, LGM, Bølling/Allerød and Younger Dryas are well-constrained by abrupt shifts in both stable isotope and trace element records, and provide a detailed account of paleohydrological and paleoclimate change for the southern Appalachian region. Fluctuations in stalagmite δ18O are largely synchronous with well-documented changes observed in the GRIP and GISP2 records. The stable isotope chronology, however, is markedly different from speleothem chronologies from other regions, possibly due to local/regional effects. We present a comparison of the southern Appalachian record with those of other regions, as well as an interpretation of the various climatic mechanisms controlling speleothem deposition. In addition, we also present a novel non-destructive method for trace element analysis (Sr/Ca) through μ-X Ray Fluorescence (μ-XRF). Trace element ratios in speleothems (Sr/Ca, Mg/Ca, Ba/Ca) have been used to interpret the hydrogeochemical processes in the epikarst zone as well as partitioning that occurs at the calcite-water interface. The Sr/Ca results from CCC-003 reflect changes observed in δ13C, which further supports the interpretation of trace element variation. During periods of low rainfall, trace element ratios generally increase as a result of the longer residence time of water in the soil and epikarst zones. High-resolution time series analyses of these elements in speleothems provide evidence for changing paleohydrological and geochemical conditions over time. CCC-003 has produced a high resolution record of the LGM and YD utilizing conventional stable isotopes and μ-XRF.

  12. Radiocarbon chronology of woolly mammoth (Mammuthus primigenius) from Poland

    NASA Astrophysics Data System (ADS)

    Nadachowski, Adam; Lipecki, Grzegorz; Wojtal, Piotr

    2010-05-01

    Many fossil mammoth remains from more than 300 localities have been discovered over last 170 years in Poland. First radiocarbon dates of woolly mammoth from Poland were published in the 1960s and the 1970s. These dates must be regarded with caution due to absence of details of the used methods. Recently, about 40 fossil mammoth remains were radiocarbon dated by accelerator mass spectrometry (AMS) method in the Poznań Radiocarbon Laboratory. Dates are given as an uncalibrated radiocarbon dates (BP) and as calendar dates (cal. BP). The dates range from ca. 52 ka BP to ca. 13,2 ka BP (> 50,0 - ca. 16,1 cal. ka BP) and can be correlated with Oxygen Isotope Stage (OIS) 3 and OIS 2. A new radiocarbon evidence fits into the well known colonization pattern of Mammuthus primigenius in Central Europe and confirms a continuous distribution in the Grudziądz Interstadial (middle Weichselian, OIS 3) and the onset of the Last Glacial Maximum (LGM). On the other hand, the severe climatic circumstances lasting in conventional radiocarbon dates from ca. 22 ka BP to ca. 17 ka BP probably reduced the number of animals or even cased the withdrawal of woolly mammoth from the area north from the Sudetes and the Carpathian Mountains for 4-5 millennia. Only one date ca. 20,3 ka BP (ca. 24,2 cal, ka BP) is available from this time-span. Mammuthus primigenius reappeared in southern Poland ca. 14,6 ka BP (ca. 17,9 cal. BP) but soon had disappeared from this region because of marked reduction in open habitats at the beginning of Late Glacial Interglacial warming (Greenland Interstadial I or Bølling and Allerød) The latest available record from Poland is from Dzierżysław: 13,180±60 BP (ca. 15,600±400 cal. BP).

  13. Early deglaciation (18.1 ka BP) of the southwest Scandinavian Ice Sheet and Late Glacial sea-level change reconstructed from isolation basins on Karmøy

    NASA Astrophysics Data System (ADS)

    Vasskog, Kristian; Svendsen, John-Inge; Mangerud, Jan; Svean, Arve; Lunnan, Eva Marie; Briner, Jason

    2016-04-01

    A series of cosmogenic exposure dates (10Be) suggest that the island Utsira off the SW coast of Norway became ice free as early as 20 ka years ago. Here we present a preliminary sea level curve that has been constructed for the island of Karmøy, which is situated at the mouth of Boknafjorden just a few km inside Utsira, based on coring and analyses of sediment sequences from isolation basins. A deglaciation age of 18.1±0.1 ka BP has been established for southern Karmøy based on radiocarbon dating of foraminifera from basal marine sediments in two basins; lake Grødheimsvatnet (15.5 m above present sea level) and the bog Kringlemyr (12.0 m above present sea level). Lithostratigraphic and microfossil analyses show that Grødheimsvatnet became isolated from the sea at 17.8±0.1 ka BP, while Kringlemyr emerged at 17.0±0.2 ka BP. The results from these basins give a mean rate of emergence of about 4.4 mm/yr during the first millennium after the area became ice-free. Relative sea level on Karmøy then fell more rapidly at the transition to the Bølling interstadial before levelling out some 3-4 m below present day sea level around 14 ka BP. Following this period of stillstand the sea level started to rise during the Allerød culminating at 6-7 m above present towards the end of Younger Dryas, after which another, more rapid regression phase started. We have combined the curve from Karmøy with far-field sea-level data in order to quantify the contributing factors (i.e. glacial isostatic adjustment and geoid changes) in the reconstructed shoreline displacement.

  14. A 75 ka Stalagmite Paleoclimate Record from Northern Venezuela

    NASA Astrophysics Data System (ADS)

    Retrum, J. B.; Gonzalez, L. A.; Edwards, R.; Tincher, S. M.; Cheng, H.; Urbani, F.

    2011-12-01

    A stalagmite collected from Cueva Zarraga in the northern Venezuelan Andes was analyzed to determine local paleoclimatic history and help examine climate change in the Caribbean. Ages were determined by U/Th disequilibrium and the stalagmite shows a nearly complete record for ~ 75 ka. Two significant periods of non-deposition have been identified. The first period ranges between the Last Glacial Maximum at 19,820 ± 149 cal yr BP and a brief resumption of stalagmite growth at 15,409 ± 747 cal yr BP, likely representing the Bølling-Allerød interstadial. After the brief period of deposition, growth does not resume unil the Holocene at 10,408 ± 78 cal yr BP. Carbon and oxygen isotopes show a major depletion shift from the last glacial period to the Holocene, suggesting warmer and wetter conditions during the Holocene. The oxygen isotope depletion shift is also seen in the Cariaco Basin foraminifera record off the northern coast of Venezuela. While tempting to attribute δ13C depletion to decrease of the C4 plant contribution, there is no evidence that the area experience major vegetation changes. We attribute the δ13C depletion to enhanced recycling of soil CO2 resulting from canopy effects. Today, Cueva Zarraga is at the northern extent of the Inter-Tropical Convergence Zone (ITCZ). The cooler and drier conditions of the last glacial period suggest a southern displacement of the ITCZ. The close proximity of Cueva Zarraga to Cariaco Basin may allow for a high resolution tropical terrestrial and oceanic climatic response comparison.

  15. Late Pleistocene and Holocene palaeogeography of the Lower Tagus Valley (Portugal): effects of relative sea level, valley morphology and sediment supply

    NASA Astrophysics Data System (ADS)

    Vis, Geert-Jan; Kasse, Cornelis; Vandenberghe, Jef

    2008-09-01

    Because of the deep glacial incision, the Lower Tagus Valley hosts a sedimentary record since ˜20 000 cal BP, making this a unique site along the European Atlantic margin with respect to palaeogeographic and sea level changes. Based on nine cross-sections and 55 radiocarbon dates together with a newly created relative sea level curve, we constructed five palaeogeographic maps of the infill of the Lower Tagus Valley since ˜20 000 cal BP. We illustrate that relative sea level rise and fluvial sediment supply were the prime forcing factors determining the depositional history and palaeogeographic changes. Around 20 000 cal BP a deeply incised braided river existed, which was directly connected to the ocean across the narrow continental shelf. After that (˜12 000 cal BP) the gradually moister and warmer climate caused a change to a single-channel river. During the following period (12 000-7000 cal BP) relative sea level rise resulted in a transgression in the Lower Tagus Valley and the establishment of extensive tidal environments. After relative sea level rise had ended (˜7000 cal BP) the valley was progressively filled by a fluvial wedge and tidally influenced bayhead delta. Since ˜1000 cal BP the valley-fill history was dominated by increased sediment input due to human-induced degradation of catchment slopes. Generally, climate was of subordinate importance during the entire studied period, merely causing a single-channel river resulting from the change from the cold Heinrich event 1 to the temperate Bölling-Allerød interstadial. Despite the tectonic activity in the region, neotectonic uplift or subsidence was limited, as supported by the horizontal relative sea level curve since ˜7000 cal BP. Neotectonics played a minor role due to the large distance from the Fennoscandian ice sheet and the narrow continental shelf, which prohibited strong glacio- and hydro-isostatic movements.

  16. Deglacial subarctic Pacific surface water hydrography and nutrient dynamics and links to North Atlantic climate variability and atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Maier, E.; Méheust, M.; Abelmann, A.; Gersonde, R.; Chapligin, B.; Ren, J.; Stein, R.; Meyer, H.; Tiedemann, R.

    2015-07-01

    The glacial-to-Holocene evolution of subarctic Pacific surface water stratification and silicic acid (Si) dynamics is investigated based on new combined diatom oxygen (δ18Odiat) and silicon (δ30Sidiat) isotope records, along with new biogenic opal, subsurface foraminiferal δ18O, alkenone-based sea surface temperature, sea ice, diatom, and core logging data from the NE Pacific. Our results suggest that δ18Odiat values are primarily influenced by changes in freshwater discharge from the Cordilleran Ice Sheet (CIS), while corresponding δ30Sidiat are primarily influenced by changes in Si supply to surface waters. Our data indicate enhanced glacial to mid Heinrich Stadial 1 (HS1) NE Pacific surface water stratification, generally limiting the Si supply to surface waters. However, we suggest that an increase in Si supply during early HS1, when surface waters were still stratified, is linked to increased North Pacific Intermediate Water formation. The coincidence between fresh surface waters during HS1 and enhanced ice-rafted debris sedimentation in the North Atlantic indicates a close link between CIS and Laurentide Ice Sheet dynamics and a dominant atmospheric control on CIS deglaciation. The Bølling/Allerød (B/A) is characterized by destratification in the subarctic Pacific and an increased supply of saline, Si-rich waters to surface waters. This change toward increased convection occurred prior to the Bølling warming and is likely triggered by a switch to sea ice-free conditions during late HS1. Our results furthermore indicate a decreased efficiency of the biological pump during late HS1 and the B/A (possibly also the Younger Dryas), suggesting that the subarctic Pacific has then been a source region of atmospheric CO2.

  17. Strong middepth warming and weak radiocarbon imprints in the equatorial Atlantic during Heinrich 1 and Younger Dryas

    NASA Astrophysics Data System (ADS)

    Weldeab, Syee; Friedrich, Tobias; Timmermann, Axel; Schneider, Ralph R.

    2016-08-01

    We present a benthic foraminiferal multiproxy record of eastern equatorial Atlantic (EEA) middepth water (1295 m) covering the last deglacial. We show that EEA middepth water temperatures were elevated by 3.9 ± 0.5°C and 5.2 ± 1.2°C during Heinrich event 1 (H1) and Younger Dryas (YD), respectively. The radiocarbon content of the EEA middepth during H1 and YD is relatively low and comparable to the values of the pre-H1 episode and Bølling-Allerød, respectively. A transient Earth system model simulation, which mimics the observed deglacial Atlantic Meridional Overturning Circulation (AMOC) history, qualitatively reproduces the major features of the EEA proxy records. The simulation results suggest that fresh water-induced weakening of the AMOC leads to a vertical shift of the horizon of Southern Ocean-sourced water and a stronger influence of EEA sea surface temperatures via mixing. Our findings reaffirm the lack of a distinctive signature of radiocarbon depletion and therefore do not support the notion of interhemispheric exchanges of strongly radiocarbon-depleted middepth water across the tropical Atlantic during H1 and YD. Our temperature reconstruction presents a critical zonal and water depth extension of existing tropical Atlantic data and documents a large-scale and basin-wide warming across the thermocline and middepth of the tropical Atlantic during H1 and YD. Significant difference in the timing and pace of H1 middepth warming between tropical Atlantic and North Atlantic likely points to a limited role of the tropical Atlantic middepth warming in the rapid heat buildup in the North Atlantic middepth.

  18. To what extent did changes in July temperature influence Lateglacial vegetation patterns in NW Europe?

    NASA Astrophysics Data System (ADS)

    Birks, Hilary H.; Birks, H. John B.

    2014-12-01

    What was the impact of July temperature changes on vegetation patterns during the Lateglacial period in north-west Europe? Chironomid-inferred mean July air temperature estimates (C-Tjul) are proxy temperature records independent of terrestrial vegetation. The relationships between Lateglacial vegetation inferred from pollen percentages and these temperature estimates are explored using data synthesised geographically from 15 sites where both pollen percentages and C-Tjul are published to assess the influence of temperature and of temperature changes on regional vegetation. Direct impacts of temperature on a species involve passing the range limits or realised niche of that species. The Bølling warming allowed vegetation to develop. The Younger Dryas cooling had direct impacts on species and vegetation types that were at a critical ecotone and thus sensitive to change. Precipitation is extremely important and its interaction with temperature controlled most of the vegetation patterns inferred from these NW European pollen data. High precipitation was important in W Norway, whereas aridity in the YD was a controlling factor in N Norway, the Netherlands, and NE Germany. Under constant climate, ecological processes occurred such as immigration, succession, and soil development that resulted in vegetation changes. Biotic interactions were also important, such as the impact of grazing by mega-herbivores during Allerød time in Ireland that may have restricted the development of birch woodland. At the coarse scale of this synthesis, July temperature alone is seen not to be a good predictor of the patterns of pollen percentages and hence of vegetation through the Lateglacial. Rather, it is the interactions of temperature and precipitation, combined with ecological processes that appear to be the major factors influencing Lateglacial palynological and vegetation patterns in NW Europe.

  19. Paleoceanographic insights on oxygen minimum zone expansion: Lessons from the most recent deglaciation

    NASA Astrophysics Data System (ADS)

    Moffitt, S. E.; Moffitt, R.; Sauthoff, W.; Davis, C. V.; Hewett, K.; Hill, T. M.

    2013-12-01

    The expansion of low oxygen hydrographic zones in the modern ocean, known as Oxygen Minimum Zones (OMZ), has the potential to deteriorate ecosystems, alter ocean nutrient cycling and inflict mass mortality events upon benthic and pelagic communities. During the last deglaciation (18-10 ka), large, climate-driven changes in the oxygen content of the upper ocean occurred. We propose that previous climate-driven OMZ expansions are data-rich events with which to characterize the spatial scales of OMZ hydrographic perturbation, and the temporal scales of natural OMZ variability. Here we synthesize a global compilation of marine sediment records from modern OMZ regions to investigate deglacial changes in the vertical extent, intensity, and surface area impingements of hypoxic waters upon continental margins. We surveyed sediment core records within water depths of 183-3,296 meters below sea level (mbsl) and took advantage of cores with geochemical, sedimentary or microfossil oxygenation proxies to reconstruct the timing, depth and intensity of seafloor hypoxia. OMZ maximum vertical extent during the deglaciation was variable by region: Subarctic Pacific (~600-2,900 mbsl), California Current (~330-1,500 mbsl), Baja and Mexico (~330-830 mbsl), and Equatorial Pacific and Humboldt Current (~110-3,100 mbsl). Expansion timing is regionally coherent but not globally synchronous, such that Subarctic Pacific and California Current marginal areas exhibit tight correlation and oxygenation reversals with Northern Hemisphere deglacial events (Termination 1A, Bølling-Allerød, Younger Dryas and Termination 1B). Southern regions (Baja and Mexico, and the Equatorial Pacific and Humboldt Current) exhibit hypoxia expansion prior to Termination 1A (~16 ka), and no oxygenation reversals. Our analysis provides new evidence for the geospatially coherent and temporally rapid expansion of OMZs during the last deglaciation, and reveals the extreme shallowness of the upper hypoxic boundary in

  20. Tree-Ring Proxies of Hydroclimate Variability in the Great Lakes Region during Cold Excursions Back to 15ka

    NASA Astrophysics Data System (ADS)

    Panyushkina, I. P.; Leavitt, S. W.

    2014-12-01

    A decade-long investigation of subfossil wood buried in glacio-fluvial, fluvial and lacustrine deposits from the U.S. Great Lakes region has resulted in a Great Lakes tree-ring network (GLTRN) comprising 47 sites dated from ca. 15 ka to 3ka. The GLTRN provides high-resolution proxies for exploration of local and regional responses to hydroclimate change at inter-annual scales during the transition from the Late Pleistocene to the Holocene. Classification of radiometric ages of GLTRN wood with relative cumulative-probability function delineates intervals and importance of hydrological changes in time and space. The overwhelming majority of wood burial events correlate with generally cold climate excursions. Forest-stand deterioration and tree mortality events at the studied sites are demonstrated to result from flooding, via river aggradation (identifying occurrence of extreme hydrologic events), rise of water table, or lake inundation. To better evaluate the special patterns of hydrological change back to 15ka, we developed four floating d13C chronologies from spruce tree rings. The length of these tree-ring proxy series that capture high-frequency moisture variability of the Great Lakes area ranges from 120 to 250 years. Our data indicate progressive wet intervals during the cold excursions precisely dated with 14C tree-ring wiggles at 13.7ka, 12.1ka, and 11.3ka that fall in the Bølling-Allerød and Pre-Boreal Interstadials, and Younger Dryas Stadial. The inter-annual and decadal variability of tree-ring moisture proxies are similar across the studied locations and time intervals. Such coherence of respective proxies may result from both local ecological stability of spruce communities or regional response to a common source of moisture at the studied time intervals and locations. This study demonstrates a potential of GLTRN proxies for modeling hydroclimatic changes at the North American continent back 15 ka.

  1. Chemical compositions of solid particles present in the Greenland NEEM ice core over the last 110,000 years

    NASA Astrophysics Data System (ADS)

    Oyabu, Ikumi; Iizuka, Yoshinori; Fischer, Hubertus; Schüpbach, Simon; Gfeller, Gideon; Svensson, Anders; Fukui, Manabu; Steffensen, Jørgen Peder; Hansson, Margareta

    2015-09-01

    This study reports the chemical composition of particles present along Greenland's North Greenland Eemian Ice Drilling (NEEM) ice core, back to 110,000 years before present. Insoluble and soluble particles larger than 0.45 µm were extracted from the ice core by ice sublimation, and their chemical composition was analyzed using scanning electron microscope and energy dispersive X-ray spectroscopy and micro-Raman spectroscopy. We show that the dominant insoluble components are silicates, whereas NaCl, Na2SO4, CaSO4, and CaCO3 represent major soluble salts. For the first time, particles of CaMg(CO3)2 and Ca(NO3)2•4H2O are identified in a Greenland ice core. The chemical speciation of salts varies with past climatic conditions. Whereas the fraction of Na salts (NaCl + Na2SO4) exceeds that of Ca salts (CaSO4 + CaCO3) during the Holocene (0.6-11.7 kyr B.P.), the two fractions are similar during the Bølling-Allerød period (12.9-14.6 kyr B.P.). During cold climate such as over the Younger Dryas (12.0-12.6 kyr B.P.) and the Last Glacial Maximum (15.0-26.9 kyr B.P.), the fraction of Ca salts exceeds that of Na salts, showing that the most abundant ion generally controls the salt budget in each period. High-resolution analyses reveal changing particle compositions: those in Holocene ice show seasonal changes, and those in LGM ice show a difference between cloudy bands and clear layers, which again can be largely explained by the availability of ionic components in the atmospheric aerosol body of air masses reaching Greenland.

  2. Anesthesiology residents' perspective about good teaching--a qualitative needs assessment.

    PubMed

    Ortwein, Heiderose; Blaum, Wolf E; Spies, Claudia D

    2014-01-01

    Hintergrund: In Deutschland wird es, wie in vielen Ländern, in absehbarer Zukunft einen Mangel an qualifizierten Ärzten geben. Einer der Gründe für Unzufriedenheit unter den Weiterbildungsassistenten sind die relativ unstrukturierten Weiterbildungsprogramme trotz der zunehmenden Wichtigkeit von Ergebnis-orientierter Weiterbildung. Ziel dieser Studie ist es, Charakteristika von und Anforderungen an gute Lehre während der anästhesiologischen Facharztweiterbildung aus Sicht der Weiterzubildenden zu identifizieren. Methoden: Es wurde eine Konsensus-Konferenz mit Weiterzubildenden von allen 39 anästhesiologischen Universitätskliniken Deutschlands durchgeführt. Die Teilnehmer wurden Gruppen zu einem von drei Themen zugeordnet, die anhand der nationalen Evaluation der Weiterbildung 2009 identifiziert wurden. Diese Themen waren (A) Charakteristika hilfreicher/guter Weiterbildner, (B) Charakteristika hilfreicher/guter Bedingungen und (C) Charakteristika hilfreicher/guter Curriculumsstruktur. Jede Gruppe folgte dem Nominal-Group-Technik-Konsensprozess, um Charakteristika guter Weiterbildung zu definieren und zu priorisieren. Ergebnisse: 31 (79,5%) Assistentensprecher waren anwesend. Die Ergebnisse betonen die Bedeutung strukturierter Curricula inklusive transparenter Ziele und Inhalte, formativer Zwischenprüfungen und Qualitätssicherungsmaßnahmen der Programme. Weiterbildungsassistenten wünschen sich zudem ausgebildete Weiterbildende mit formaler Lehrqualifikation und geschützte Zeit zum Lehren.Schlussfolgerung: Gute Facharztweiterbildung setzt eine sorgfältige Berücksichtigung der Bedürfnisse aller Beteiligten voraus. Die Ergebnisse bestätigen und erweitern bisherige Publikationen und können zum Teil einfach umgesetzt werden. Die Ergebnisse sind ein wichtiger Schritt hin zu einem breiteren Konsens innerhalb einer Fachdisziplin.

  3. Lake level changes in Hala Lake(NW China) based on ostracodassemblages during the LGM and Post-LGM

    NASA Astrophysics Data System (ADS)

    Yan, D.; Wuennemann, B.

    2012-12-01

    The Hala Lake, located in the Qilian Mountains, Qinghai Province, China, at 4078 m a.s.l. may archive in its sediments hydrological and climate changes during the Late Quaternary time, as it is close to the area impacted by the East-Asian Summer monsoon and westerly-driven air masses. Based on the sediment core H7, which was taken in the center of the lake at 65m water depth,ostracod assemblages and stable isotopes from ostracode shells were investigated in details. Three main species were found, which are common species in high altitude saline lakes of the Tibetan Plateau: Leucocythere sp.,Limnocythereinopinata and Eucypris sp.They started to occur in deeper part of H7,indicating an early onset of favorable living conditions during the LGM and post-LGM periods. Besides, algae occurred between 25 and 32m water depth. According to the unevenly distributed amount of ostracods and oxygen isotope data, our results indicate important lake level changes during the global LGM and Lateglacial. The lake experienced lowest levels of 25-50 m below the present water line. Ostracods disappeared with the onset of the early Holocene.A stepwise refilling started already at ca. 16 kyr BP and reached -25 m level during the Bølling/Allerød warm phase at ca. 13.5 kyr BP.Latest at ca.7.6 kyr BP, the lake reached a stable highstand similar to the present level until ca.6 kyr BPas . The subsequent lake development remains unclear due to strong mismatches of the data but may indicate a general trend to deteriorating conditions and lake level lowstands at ca. 5.0-4.2, 2.0 and at around 0.5 kyr BP.; Ostracods Distribution in H2 ; Ostracods plate in Hala lake

  4. Early Results from VLT SPHERE: Long-slit Spectroscopy of 2MASS 0122-2439 B, a Young Companion Near the Deuterium Burning Limit

    NASA Astrophysics Data System (ADS)

    Hinkley, Sasha; Bowler, Brendan P.; Vigan, Arthur; Aller, Kimberly M.; Liu, Michael C.; Mawet, Dimitri; Matthews, Elisabeth; Wahhaj, Zahed; Kraus, Stefan; Baraffe, Isabelle; Chabrier, Gilles

    2015-05-01

    We present 0.95-1.80 μm spectroscopy of the ˜12-27 MJup companion orbiting the faint (R ˜ 13.6), young (˜120 Myr) M-dwarf 2MASS J01225093-2439505 (“2M0122-2439 B”) at 1.″ 5 separation (50 AU). Our coronagraphic long-slit spectroscopy was obtained with the new high contrast imaging platform Very Large Telescope Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) during Science Verification. The unique long-slit capability of SPHERE enables spectral resolution an order of magnitude higher than other extreme AO exoplanet imaging instruments. With a low mass, cool temperature, and very red colors, 2M0122-2439 B occupies a particularly important region of the substellar color-magnitude diagram by bridging the warm directly imaged hot planets with late-M/early-L spectral types (e.g., β Pic b and ROXs 42Bb) and the cooler, dusty objects near the L/T transition (HR 8799bcde and 2MASS 1207b). We fit BT-Settl atmospheric models to our R ≈ 350 spectrum and find {{T}eff} = 1600 ± 100 K and log (g) = 4.5 ± 0.5 dex. Visual analysis of our 2M0122-2439 B spectrum suggests a spectral type L3-L4, and we resolve shallow J-band alkali lines, confirming its low gravity and youth. Specifically, we use the Allers & Liu spectral indices to quantitatively measure the strength of the FeH, VO, KI, spectral features, as well as the overall H-band shape. Using these indices, along with the visual spectral type analysis, we classify 2M0122-2439 B as an intermediate gravity object with spectral type L3.7 ± 1.0. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory Under Program ID 060.A-9381.

  5. Neotectonic faulting and the Late Weichselian shoreline gradients in SW Norway

    NASA Astrophysics Data System (ADS)

    Helle, Stein Kjetil; Rye, Noralf; Stabell, Bjørg; Prösch-Danielsen, Lisbeth; Hoel, Christer

    2007-10-01

    The Younger Dryas (YD) maximum highstand shoreline in SW Norway has traditionally been considered as being slightly concave, gradually steepening in the direction of uplift. This phenomenon is attributed to geoidal and isostatic effects near the former ice-sheet margin. On the basis of isolation basin data from the region, we have reconstructed this shoreline, and a Bølling-Allerød (B-A) lowstand shoreline, along three profiles in SW Norway. Along all profiles there are shore levels which, within the error limits estimated, cannot be captured by a single straight (or curved) shoreline. The anomalous shore levels occur near major fault zones and are interpreted to reflect differential uplift rates on opposite sides of faults, superimposed on the general glacio-isostatic tilting of the region. The inferred faulting is consistent with observations previously reported as neotectonic 'claims' in the region and shed new light on the deformational structures observed in seismic profiles of the fjord sediments. Excluding the anomalous shore levels, a straight shoreline with gradient ca. 1.1 m/km provides the best and most consistent representation of the YD shore levels along the three profiles. The B-A lowstand shoreline is constrained by fewer data points, but is approximately parallel-dipping the highstand shoreline. Our reconstructions imply a less steep YD maximum highstand shoreline compared to previous reconstructions, where gradients up to 1.4 m/km have been inferred. This may imply that the ice load effect on the lithosphere in SW Norway during the YD is less than previously assumed.

  6. Precise chronology of Heinrich-1 meltwater pulses in the Nordic Seas (Invited)

    NASA Astrophysics Data System (ADS)

    Sarnthein, M.; Grootes, P. M.; Kuehn, H.; Voelker, A.

    2009-12-01

    Various ocean mechanisms have been proposed to explain the abrupt warming of DO event 1 forming the onset of the Bølling/Allerød (BA) period near 14.7 cal. ka BP, for example invoking multiple equilibria of Atlantic meridional overturning circulation (AMOC) and southern hemisphere climate forcing. A transient state-of-the-art model simulation of the deglacial ocean and climate evolution by Liu et al. recently reproduced the abrupt BA warming, provided a sudden termination of meltwater fluxes (MWF) to the North Atlantic occurred a few centuries prior to the BA. Thus an accurate history of MWF before the BA is crucial. Up to now, however, a precise timing of Heinrich-1 MWF prior to the BA warming has not been established for deep-sea sediment records from the northern North Atlantic because great changes in planktic 14C reservoir ages of a few hundred to 2500 years form a major obst¬acle for precise age control. The 14C plateau-tuning technique now paves the way for closely constraining the age of Heinrich-1 MWF signals which are recorded by abrupt negative planktic δ18O excursions reaching 1.5-2.0 per mil. In the East Greenland Current we find intensive MWF from 17.25 to ~15.0 ka ago. Likewise in the Norwegian Sea we date vast meltwater fluxes associated with the deglacial break-up of the Barents ice sheet at ~73°N. This plume terminated no more than a few hundred years prior to the onset of the BA. In summary our records support the simulations of Liu et al. by showing that MWF to the North Atlantic did suddenly stop shortly after 15 ka BP, which could drive a quick restoration and overshoot of the AMOC and in turn, the abrupt warming at the onset of the BA. Liu, Z. et al., 2009, Science 325, 310-314.

  7. Lateglacial/early Holocene fluvial reactions of the Jeetzel river (Elbe valley, northern Germany) to abrupt climatic and environmental changes

    NASA Astrophysics Data System (ADS)

    Turner, Falko; Tolksdorf, Johann Friedrich; Viehberg, Finn; Schwalb, Antje; Kaiser, Knut; Bittmann, Felix; von Bramann, Ullrich; Pott, Richard; Staesche, Ulrich; Breest, Klaus; Veil, Stephan

    2013-01-01

    Mechanisms of climatic control on river system development are still only partially known. Palaeohydrological investigations from river valleys often lack a precise chronological control of climatic processes and fluvial dynamics, which is why their specific forces remain unclear. In this multidisciplinary case study from the middle Elbe river valley (northern Germany) multiple dating of sites (palynostratigraphy, radiocarbon- and OSL-dating) and high-resolution analyses of environmental and climatological proxies (pollen, plant macro-remains and ostracods) reveal a continuous record of the environmental and fluvial history from the Lateglacial to the early Holocene. Biostratigraphical correlation to northwest European key sites shows that river system development was partially out of phase with the main climatic shifts. The transition from a braided to an incised channel system predated the main phase of Lateglacial warming (˜14.6 ka BP), and the meandering river did not change its drainage pattern during the cooling of the Younger-Dryas period. Environmental reconstructions suggest that river dynamics were largely affected by vegetation cover, as a vegetation cover consisting of herbs, dwarf-shrubs and a few larger shrubs seems to have developed before the onset of the main Lateglacial warming, and pine forests appear to have persisted in the river valley during the Younger Dryas. In addition, two phases of high fluvial activity and new channel incision during the middle part of the Younger Dryas and during the Boreal were correlated with changes from dry towards wet climatic conditions, as indicated by evident lake level rises. Lateglacial human occupation in the river valley, which is shown by numerous Palaeolithic sites, forming one of the largest settlement areas of that period known in the European Plain, is assigned to the specific fluvial and environmental conditions of the early Allerød.

  8. Sea-surface bioproductivity changes in the Northwest Pacific over the last 25 kyr

    NASA Astrophysics Data System (ADS)

    Ovsepyan, E. A.; Ivanova, E. V.; Murdmaa, L. O.; Alekhina, G. N.

    2014-07-01

    The sea-surface bioproductivity changes over the last 25 kyr were inferred from published data on 30 sediment cores from the open Northwest Pacific (NWP), Sea of Okhotsk, Bering Sea and Sea of Japan accounting for the glacioeustatic sea-level changes. A novel method was developed to compare the variations of several independent productivity proxies relative to the present-day values. During the Last Glacial Maximum, the bioproductivity in the Sea of Okhotsk and the western Bering Sea (BS) was lower than at present, whereas the southern and southeastern Bering Sea and the open NWP are characterized by enhanced bioproductivity. During the early deglacial stage, an increase in bioproductivity was estimated only for the southeastern Bering Sea. High and fairly high bioproductivity was estimated for Heinrich 1 in the open NWP, above the Umnak Plateau and on the Shirshov and Bowers Ridges in the Bering Sea. The high productivity in the Bering Sea, Sea of Okhotsk and NWP during the Bølling/Allerød was caused by the global warming and enhanced nutrient supply by meltwater from the continent. During the Early Holocene, high productivity was estimated for almost the entire NWP. The Late Holocene sea-surface bioproductivity was generally lower than that of the Early Holocene. Proposed factors that have controlled the sea-surface bioproductivity during the last 25 kyr include: the location of the sea ice margin, the river runoff, gradual flooding of the Bering Sea and the Sea of Okhotsk shelf areas, the water mass exchange between the marginal seas and the open NWP, the eolian supply and the deep vertical mixing of the water column.

  9. Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species-specific benthic foraminiferal 14C dates

    NASA Astrophysics Data System (ADS)

    Ezat, Mohamed M.; Rasmussen, Tine L.; Thornalley, David J. R.; Olsen, Jesper; Skinner, Luke C.; Hönisch, Bärbel; Groeneveld, Jeroen

    2017-02-01

    Formation of deep water in the high-latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water-column radiocarbon age reconstructions in the Faroe-Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to 26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were 1500 and 1100 14C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation ( 20-18 ka), Nordic Seas overflow was weak but active. During the early deglaciation ( 17.5-14.5 ka), our data reveal large differences between 14C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 14C years, while all other species reveal ventilation ages <2000 14C years. These data either suggest subcentennial, regional, circulation changes or that miliolid-based 14C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this "enigma," the onset of the Bølling-Allerød interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.

  10. Ansätze zur Ordnungsreduktion von nichtlinearen Oszillatormodellen zur Anwendung im Schaltungsentwurf

    NASA Astrophysics Data System (ADS)

    Reit, M.; Bremer, J.-K.; Mathis, W.; Stoop, R.

    2010-10-01

    Im Rahmen dieser Arbeit wird ein Konzept zur Ordnungsreduktion von höherdimensionalen nichtlinearen Oszillatormodellen vorgestellt. Hierbei werden zwei wesentliche Ziele verfolgt. Zum einen wird eine höherdimensionale Modellierung der Oszillatorschaltung verwendet. Hierdurch lassen sich die Einflüsse parasitärer Effekte sowie struktureller Erweiterungen auf das dynamische Verhalten des Systems berücksichtigen. Zum anderen wird durch eine anschließende Ordnungsreduktion über die Methode der Zentrumsmannigfaltigkeit eine zweidimensionale Systembeschreibung erzeugt, deren wesentliche Dynamik derjenigen des höherdimensionalen Systems entspricht. Durch diese, in der Ordnung reduzierte, nichtlineare und parameterabhängige Systembeschreibung wird die Anwendbarkeit nichtlinearer Analysemethoden ermöglicht bzw. vereinfacht. Mit der Anwendung der Andronov-Hopf-Bifurkationsanalyse auf das reduzierte System lässt sich eine Stabilitätsuntersuchung durchführen sowie die Amplitude und Frequenz aller Zustandsgrößen approximieren. Das vorgestellte Konzept wird anhand des Beispielsystems eines LC-Tank-VCOs durchgeführt. In this paper, an order reduction technique for higher-dimensional nonlinear oscillator models, based on a center manifold approach, is presented. By modeling the oscillator circuit in the higher-dimensional state space, influences of parasitic elements and of structural extensions of the oscillator architecture on the dynamical system behavior can be examined. Using the proposed order reduction technique, a generalized second order model will be derived, which includes selected design parameters of the higher order model. By using an Andronov-Hopf bifurcation analysis, the reduced system can be studied with respect to stability as well as the amplitude and frequency of the individual state variables. The concept is applied to the design of LC-tank VCOs.

  11. Paleoceanographic Insights on Recent Oxygen Minimum Zone Expansion: Lessons for Modern Oceanography

    PubMed Central

    Moffitt, Sarah E.; Moffitt, Russell A.; Sauthoff, Wilson; Davis, Catherine V.; Hewett, Kathryn; Hill, Tessa M.

    2015-01-01

    Climate-driven Oxygen Minimum Zone (OMZ) expansions in the geologic record provide an opportunity to characterize the spatial and temporal scales of OMZ change. Here we investigate OMZ expansion through the global-scale warming event of the most recent deglaciation (18-11 ka), an event with clear relevance to understanding modern anthropogenic climate change. Deglacial marine sediment records were compiled to quantify the vertical extent, intensity, surface area and volume impingements of hypoxic waters upon continental margins. By integrating sediment records (183-2,309 meters below sea level; mbsl) containing one or more geochemical, sedimentary or microfossil oxygenation proxies integrated with analyses of eustatic sea level rise, we reconstruct the timing, depth and intensity of seafloor hypoxia. The maximum vertical OMZ extent during the deglaciation was variable by region: Subarctic Pacific (~600-2,900 mbsl), California Current (~330-1,500 mbsl), Mexico Margin (~330-830 mbsl), and the Humboldt Current and Equatorial Pacific (~110-3,100 mbsl). The timing of OMZ expansion is regionally coherent but not globally synchronous. Subarctic Pacific and California Current continental margins exhibit tight correlation to the oscillations of Northern Hemisphere deglacial events (Termination IA, Bølling-Allerød, Younger Dryas and Termination IB). Southern regions (Mexico Margin and the Equatorial Pacific and Humboldt Current) exhibit hypoxia expansion prior to Termination IA (~14.7 ka), and no regional oxygenation oscillations. Our analyses provide new evidence for the geographically and vertically extensive expansion of OMZs, and the extreme compression of upper-ocean oxygenated ecosystems during the geologically recent deglaciation. PMID:25629508

  12. Prevalence of osseous fragments in distal and proximal interphalangeal, metacarpo- and metatarsophalangeal and tarsocrural joints of Hanoverian Warmblood horses.

    PubMed

    Stock, K F; Hamann, H; Distl, O

    2005-10-01

    The prevalence of osseous fragments in different limb joints was analysed in 3749 young Warmblood riding horses, which were pre-selected for sale at auction from 1991 to 1998 by the Association of Hanoverian Warmblood Breeders (Verband hannoverscher Warmblutzüchter e.V.) in Verden (Aller), Germany. The evaluation of these horses was based on a standardized radiological examination, including the distal interphalangeal (DIJ), the proximal interphalangeal (PIJ), the metacarpo- and metatarsophalangeal (MC/MTJ) and the tarsocrural joints (TCJ). In 32% of all horses at least one osseous fragment was found on these radiographs. TCJ were affected in 9.6% of the horses and MC/MTJ in 20.7%. The percentage of horses affected in the MTJ was significantly higher (13.7%) than that of horses affected in the MCJ (9.5%). The prevalences of osseous fragments were considerably lower in DIJ (4.5%) and PIJ (0.9%). Osseous fragments only occurred either in DIJ or PIJ or MC/MTJ or TCJ in 87% of the affected horses. Depending on the joint type, osseous fragments were found in analogous joints in the front and the hind limbs in up to 26% of the affected horses, whilst bilateral affection occurred in between 10% and 46% of the horses. Distribution of osseous fragments in the limb joints investigated here did not differ significantly between male and female horses. There was a significant increase in the percentage of horses with osseous fragments in MC/MTJ during the study period. The results of this study indicate the need to act against the high prevalences of osseous fragments in the limb joints of young Warmblood riding horses.

  13. Interaction between climate, volcanism, and isostatic rebound in Southeast Alaska during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Praetorius, Summer; Mix, Alan; Jensen, Britta; Froese, Duane; Milne, Glenn; Wolhowe, Matthew; Addison, Jason; Prahl, Fredrick

    2016-10-01

    Observations of enhanced volcanic frequency during the last deglaciation have led to the hypothesis that ice unloading in glaciated volcanic terrains can promote volcanism through decompression melting in the shallow mantle or a reduction in crustal magma storage time. However, a direct link between regional climate change, isostatic adjustment, and the initiation of volcanism remains to be demonstrated due to the difficulty of obtaining high-resolution well-dated records that capture short-term climate and volcanic variability traced to a particular source region. Here we present an exceptionally resolved record of 19 tephra layers paired with foraminiferal oxygen isotopes and alkenone paleotemperatures from marine sediment cores along the Southeast Alaska margin spanning the last deglacial transition. Major element compositions of the tephras indicate a predominant source from the nearby Mt. Edgecumbe Volcanic Field (MEVF). We constrain the timing of this regional eruptive sequence to 14.6-13.1 ka. The sudden increase in volcanic activity from the MEVF coincides with the onset of Bølling-Allerød interstadial warmth, the disappearance of ice-rafted detritus, and rapid vertical land motion associated with modeled regional isostatic rebound in response to glacier retreat. These data support the hypothesis that regional deglaciation can rapidly trigger volcanic activity. Rapid sea surface temperature fluctuations and an increase in local salinity (i.e., δ18Osw) variability are associated with the interval of intense volcanic activity, consistent with a two-way interaction between climate and volcanism in which rapid volcanic response to ice unloading may in turn enhance short-term melting of the glaciers, plausibly via albedo effects on glacier ablation zones.

  14. Glacial-to-interglacial changes in nitrate supply and consumption in the subarctic North Pacific from microfossil-bound N isotopes at two trophic levels

    NASA Astrophysics Data System (ADS)

    Ren, Haojia; Studer, Anja S.; Serno, Sascha; Sigman, Daniel M.; Winckler, Gisela; Anderson, Robert F.; Oleynik, Sergey; Gersonde, Rainer; Haug, Gerald H.

    2015-09-01

    Reduced nitrate supply to the subarctic North Pacific (SNP) surface during the last ice age has been inferred from coupled changes in diatom-bound δ15N (DB-δ15N), bulk sedimentary δ15N, and biogenic fluxes. However, the reliability of bulk sedimentary and DB-δ15N has been questioned, and a previously reported δ15N minimum during Heinrich Stadial 1 (HS1) has proven difficult to explain. In a core from the western SNP, we report the foraminifera-bound δ15N (FB-δ15N) in Neogloboquadrina pachyderma and Globigerina bulloides, comparing them with DB-δ15N in the same core over the past 25 kyr. The δ15N of all recorders is higher during the Last Glacial Maximum (LGM) than in the Holocene, indicating more complete nitrate consumption. N. pachyderma FB-δ15N is similar to DB-δ15N in the Holocene but 2.2‰ higher during the LGM. This difference suggests a greater sensitivity of FB-δ15N to changes in summertime nitrate drawdown and δ15N rise, consistent with a lag of the foraminifera relative to diatoms in reaching their summertime production peak in this highly seasonal environment. Unlike DB-δ15N, FB-δ15N does not decrease from the LGM into HS1, which supports a previous suggestion that the HS1 DB-δ15N minimum is due to contamination by sponge spicules. FB-δ15N drops in the latter half of the Bølling/Allerød warm period and rises briefly in the Younger Dryas cold period, followed by a decline into the mid-Holocene. The FB-δ15N records suggest that the coupling among cold climate, reduced nitrate supply, and more complete nitrate consumption that characterized the LGM also applied to the deglacial cold events.

  15. Calcium signalling mediated by the 9 acetylcholine receptor in a cochlear cell line from the immortomouse.

    PubMed

    Jagger, D J; Griesinger, C B; Rivolta, M N; Holley, M C; Ashmore, J F

    2000-08-15

    1. We have investigated the characteristics of the alpha9 acetylcholine receptor (alpha9AChR) expressed in hair cell precursors in an immortalized cell line UB/OC-2 developed from the organ of Corti of the transgenic H-2Kb-tsA58 mouse (the Immortomouse) using both calcium imaging and whole-cell recording. 2. Ratiometric measurements of fura-2 fluorescence revealed an increase of intracellular calcium concentration in cells when challenged with 10 microM ACh. The calcium increase was seen in 66 % of the cells grown at 39 degrees C in differentiated conditions. A sm aller fraction (34%) of cells grown at 33 degrees C in proliferative con ditions responded. 3. Caffeine (10mM) elevated cell calcium. In the ab sence of caffeine, the majority of imaged cells responded only once to A Ch presentations. Pretreatment with caffeine ingibited all calcium respo nses to ACh. 4. In whole-cell tight-seal recordings 10 microM ACh activa ted inward current was dependent on the extracellular calcium concentrat ion with an estimated PCa/PNa of 80 for the alpha9 receptor at physiological calcium levels. 5 . The data indicate that ACh activates a calcium-permeable channel alpha 9AChR in UB/OC-2 cells and that the channel has a significantly higher c alcium permeability than other AChRs. The results indicate that the alp ha9AChR may be able to elevate intracellular calcium levels in hair cell s both directly and via store release.

  16. Distribution of dissolved silver in marine waters

    NASA Astrophysics Data System (ADS)

    Barriada, J. L.; Achterberg, E. P.; Tappin, A.; Truscott, J.

    2003-04-01

    Silver is one of the most toxic heavy metals, surpassed only by mercury [1-3]. Monitoring of dissolved silver concentrations in natural waters is therefore of great importance. The determination of dissolved silver in waters is not without challenges, because of its low (picomolar) concentrations. Consequently, there are only a few reported studies in marine waters, which have been performed in USA [4-6] and Japan [7]. The analytical techniques used in the reported studies for the determination of silver in seawater were Graphite Furnace Atomic Absorption Spectroscopy (GFAAS) after solvent extraction [2,4,5], and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) after solvent extraction or solid phase extraction [7,8]. In this contribution, we will present an optimised Magnetic Sector (MS) ICP-MS technique for the determination of dissolved silver in marine waters. The MS-ICP-MS method used anion exchange column to preconcentrate silver from saline waters, and to remove the saline matrix. The ICP-MS method has been used successfully to determine total dissolved silver in estuarine and oceanic samples. Bibliography 1. H. T. Ratte, Environ. Toxicol. Chem. 1999, 18: p. 89-108. 2. R. T. Herrin, A. W. Andren and D. E. Armstrong, Environ. Sci. Technol. 2001, 35: 1953-1958. 3. D. E. Schildkraut, P. T. Dao, J. P. Twist, A. T. Davis and K. A. Robillard, Environ. Toxicol. Chem. 1998, 17: 642-649. 4. E. Breuer, S. A. Sanudo-Wilhelmy and R. C. Aller, Estuaries. 1999, 22:603-615. 5. A. R. Flegal, S. A. Sanudowilhelmy and G. M. Scelfo, Mar. Chem. 1995, 49: 315-320. 6. S. N. Luoma, Y. B. Ho and G. W. Bryan, Mar. Pollut. Bull. 1995, 31: 44-54. 7. Y. Zhang, H. Amakawa and Y. Nozaki, Mar. Chem. 2001, 75: 151-163. 8. L. Yang and R. E. Sturgeon, J. Anal. At. Spectrom. 2002, 17: 88-93.

  17. A Record of Tropical Vegetation Change from Terrestrial Biomarkers Preserved in Cariaco Basin Sediments

    NASA Astrophysics Data System (ADS)

    Makowski, M.; Eglinton, T.; Hughen, K.

    2001-05-01

    A record of tropical vegetation change since the last glacial maximum was established using terrestrial biomarkers preserved in Cariaco Basin sediments. Vascular plant biomarkers derived from proximal terrestrial sources preserved in these anoxic sediments can be compared to previously established records of North Atlantic climate change from the same location. The terrestrial biomarkers used consisted of C24-C32 n-alkanoic acids, which are derived from plant leaf waxes. Average carbon chain length and δ 13C of n-alkanoic acids were used to construct the vegetation record. For C30 and C32 n-alkanoic acids, δ 13C variations of more than 3‰ between the last glacial maximum and the present interglacial period suggest changes in the character of terrestrial biota that parallel changes in climate, as inferred from North Atlantic sediment and Greenland ice core records. Terrestrial biomarker δ 13C data indicates that C3 plants predominated in this area of the tropics during warm periods, such as the B\\o{}lling-Aller\\o{}d and the Holocene, and C4 plants proliferated during cold periods, such as the last glacial maximum and the Younger Dryas. The tradeoff between C3 and C4 plants represents a switch from arid grasslands to more humid forest vegetation as the climate warmed. Average carbon chain length data also show variations synchronous with climate changes during the last deglaciation. The biomarker record agrees with pollen data previously developed from Cariaco Basin sediments, confirming that leaf wax compounds preserved in marine sediments can accurately record terrestrial vegetation changes. This study shows that terrestrial biomarkers are a useful paleoclimate proxy and could be used to compare marine and terrestrial climate changes in the same marine sediment core. With the aid of automated analytical techniques, these compounds can be analyzed much more quickly than pollen, and can therefore be used for construction of long, high-resolution records.

  18. Past and future evolution of Abies alba forests in Europe - comparison of a dynamic vegetation model with palaeo data and observations.

    PubMed

    Ruosch, Melanie; Spahni, Renato; Joos, Fortunat; Henne, Paul D; van der Knaap, Willem O; Tinner, Willy

    2016-02-01

    Information on how species distributions and ecosystem services are impacted by anthropogenic climate change is important for adaptation planning. Palaeo data suggest that Abies alba formed forests under significantly warmer-than-present conditions in Europe and might be a native substitute for widespread drought-sensitive temperate and boreal tree species such as beech (Fagus sylvatica) and spruce (Picea abies) under future global warming conditions. Here, we combine pollen and macrofossil data, modern observations, and results from transient simulations with the LPX-Bern dynamic global vegetation model to assess past and future distributions of A. alba in Europe. LPX-Bern is forced with climate anomalies from a run over the past 21 000 years with the Community Earth System Model, modern climatology, and with 21st-century multimodel ensemble results for the high-emission RCP8.5 and the stringent mitigation RCP2.6 pathway. The simulated distribution for present climate encompasses the modern range of A. alba, with the model exceeding the present distribution in north-western and southern Europe. Mid-Holocene pollen data and model results agree for southern Europe, suggesting that at present, human impacts suppress the distribution in southern Europe. Pollen and model results both show range expansion starting during the Bølling-Allerød warm period, interrupted by the Younger Dryas cold, and resuming during the Holocene. The distribution of A. alba expands to the north-east in all future scenarios, whereas the potential (currently unrealized) range would be substantially reduced in southern Europe under RCP8.5. A. alba maintains its current range in central Europe despite competition by other thermophilous tree species. Our combined palaeoecological and model evidence suggest that A. alba may ensure important ecosystem services including stand and slope stability, infrastructure protection, and carbon sequestration under significantly warmer

  19. An ultra-high resolution continuous record of methane variations during the last glacial-interglacial transition from the WAIS Divide ice core

    NASA Astrophysics Data System (ADS)

    Rhodes, R. H.; Brook, E.; McConnell, J. R.; Blunier, T.; Lee, J. E.; Edwards, J. S.; Rosen, J. L.; Stowasser, C.

    2012-12-01

    Records of past atmospheric methane mixing ratios developed from ancient air trapped in polar ice cores are integral to our understanding of the global carbon cycle and its interaction with climate. Previously, temporal resolution of these records has been limited by time-, labour- and sample- intensive analytical methods. Here we present an ultra-high resolution, continuous record of the methane mixing ratio across the last deglaciation, obtained using a continuous system in which air extracted from the ice core was analysed on-line by a specially adapted laser spectrometer. 800 m of ice core from the West Antarctic Ice Sheet (WAIS) Divide project, spanning the time period from 10.1 to 22.8 ka, were analysed at a minimum spatial resolution of 4.5 cm depth, which equates to a temporal resolution of better than 2 yr. The variability of our record closely matches that of discrete measurements conducted on the WAIS Divide core. For example, the 130 ppbv increase in the methane mixing ratio over ~250 yr that marks the onset of the Bølling period is extremely well reproduced, as are all other variations in atmospheric methane known from previously published ice core data. Furthermore, we document in great detail variability not previously observed, for example, a methane concentration increase of 45 ppbv occurs within 90 yr at 16.55 ka. The Bølling-Allerød interstadial is characterized by 10-40 ppbv amplitude methane concentration oscillations with periods of 100-200 yr, whilst in the Early Holocene (10,100 to 11,400 yr) the methane signal is dominated by sub-centennial oscillations of 15-20 ppbv amplitude. Spectral analysis of this dataset is ongoing and will explore possible drivers of these high frequency features.

  20. Warm summers during Younger Dryas cold reversal over Eurasia

    NASA Astrophysics Data System (ADS)

    Schenk, Frederik; Muschitiello, Francesco; Heikkilä, Miaja; Väliranta, Minna; Tarasov, Lev; Brandefelt, Jenny; Johansson, Arne; Näslund, Jens-Ove; Wohlfarth, Barbara

    2016-04-01

    The Younger Dryas cold reversal (GS-1) sticks out as a major stadial interrupting the mid to late deglaciation with a sharp temperature drop of several degrees around the North Atlantic with global teleconnections. The abrupt return to a very cold glacial-like ocean state introduces a strong temperature anomaly to the climate system contrasting the high solar radiation received by northern summers. Here we show that, in contrast to earlier coarse resolution climate simulations of the Younger Dryas, these competing factors result in rather warm summer conditions over Eurasia comparable to the preceding warm period of the late Allerød (GI-1a). Despite up to 10 K colder sea-surface-temperatures in summer, our high resolution simulation with the Community Earth System Model 1 (CESM1.0.5) suggests that the presence of large ice sheets over Scandinavia, Spitsbergen and the Kara Sea significantly modifies atmospheric flow in summer preventing cold westerly winds from the Atlantic to impact the continent. Instead, fluid dynamics around ice sheets deflect winds to the north or south along the coasts supported by divergent flow from ice domes, stratification and increased tendency to high pressure and atmospheric blocking. Consistent with our model simulation, we show that temperature reconstructions derived from an extended compilation of multi-proxy lake records (chironomids, aquatic pollen, macrofossils) suggest warm July conditions of 13-17° C for continental Europe with exception of coastal and high elevation sites. The analysis of simulated growing degree days, season length and first results from paleo lake modelling driven by climate model output suggests that severe winter to spring conditions significantly delay and shorten the vegetation season but do not produce cold summers as previously simulated.

  1. Influence of climate warming on arctic mammals? New insights from ancient DNA studies of the collared lemming Dicrostonyx torquatus.

    PubMed

    Prost, Stefan; Smirnov, Nickolay; Fedorov, Vadim B; Sommer, Robert S; Stiller, Mathias; Nagel, Doris; Knapp, Michael; Hofreiter, Michael

    2010-05-27

    Global temperature increased by approximately half a degree (Celsius) within the last 150 years. Even this moderate warming had major impacts on Earth's ecological and biological systems, especially in the Arctic where the magnitude of abiotic changes even exceeds those in temperate and tropical biomes. Therefore, understanding the biological consequences of climate change on high latitudes is of critical importance for future conservation of the species living in this habitat. The past 25,000 years can be used as a model for such changes, as they were marked by prominent climatic changes that influenced geographical distribution, demographic history and pattern of genetic variation of many extant species. We sequenced ancient and modern DNA of the collared lemming (Dicrostonyx torquatus), which is a key species of the arctic biota, from a single site (Pymva Shor, Northern Pre Urals, Russia) to see if climate warming events after the Last Glacial Maximum had detectable effects on the genetic variation of this arctic rodent species, which is strongly associated with a cold and dry climate. Using three dimensional network reconstructions we found a dramatic decline in genetic diversity following the LGM. Model-based approaches such as Approximate Bayesian Computation and Markov Chain Monte Carlo based Bayesian inference show that there is evidence for a population decline in the collared lemming following the LGM, with the population size dropping to a minimum during the Greenland Interstadial 1 (Bølling/Allerød) warming phase at 14.5 kyrs BP. Our results show that previous climate warming events had a strong influence on genetic diversity and population size of collared lemmings. Due to its already severely compromised genetic diversity a similar population reduction as a result of the predicted future climate change could completely abolish the remaining genetic diversity in this population. Local population extinctions of collared lemmings would have severe

  2. Environmental magnetic records of the Dali Lake borehole sequence in Inner Mongolia and implications for paleoclimatic variations in the semi-arid East Asia since the last deglaciation

    NASA Astrophysics Data System (ADS)

    Liu, S.; Deng, C.; Xiao, J.; LI, J.; Paterson, G. A.; Chang, L.; Yi, L.; Qin, H.; Pan, Y.; Zhu, R.

    2016-12-01

    High-resolution paleoclimate research is essential in the semi-arid East Asian interior due to its sensitivity to climate variability and importance for human inhabitance. A high-resolution environmental magnetic investigation is performed on the Dali Lake core, which covers the past 16 ka. Different magnetic mineral sources were identified based on mag­netic measurements, electron telescope observation, and X-ray diffraction of both core and catchment sediments. The Holocene Warm Period (HWP, 9.8-5.9 ka) is magnetically dominated by biogenic magnetite, which is highly magnetic, fine grain-sized and with little SP contribution. The abundance of magnetofossils reflects conditions during the HWP when the warm and wet climate and associated improved nutrient supply enhanced biomineralization. The pro­nounced increase of magnetofossil concentrations at 9.8 ka reflects a gradual warming into the HWP, while the abrupt decrease at 5.9 ka coincides with the sudden termination of the HWP, and can be linked to drying at 6 ka in the Asian interior. The two-stage transition at 7.7 ka corresponds to the inferred turning point at which water input into Dali Lake transfers from colder snow/ice melt to warmer monsoonal precipitation at 7.6 ka. Our magnetofossil record represents the response of biotic systems in semi-arid lakes, through nutrient availability, to climate changes during the HWP. Magnetic minerals from the deglaciation are from erosion of the lake catchment. The titano-magnetite from the surrounding basalt in the catchment reflects erosion of bedrock under cold and dry conditions after the Last Glacial Maximum. Magnetic minerals likely from erosion of surface soils are linked to ameliorating climates since the Bølling-Allerød warming. Overall, our magnetic record during the last deglaciation documents paleoclimatically controlled erosion and transportation mechanisms in the lake catchments.

  3. Ages for the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz: Implications for deglaciation chronology

    NASA Astrophysics Data System (ADS)

    Lepper, Kenneth; Fisher, Timothy G.; Hajdas, Irka; Lowell, Thomas V.

    2007-07-01

    Glacial Lake Agassiz has been implicated as the trigger for numerous episodes of abrupt climate change at the close of the last ice age, yet the beginning age of the lake has never been determined. Here we report the first numerical age data on the Big Stone Moraine and the oldest beaches of glacial Lake Agassiz. Organic remains from lakes, bogs, and channels distal to, and inset to, the Big Stone Moraine require that glacial activity at this moraine ceased prior to 12,000 14C yr B.P. (13,950 cal [calendar] yr). A site near New Effington, South Dakota (United States), implies full glacial recession north of the topographic divide prior to 11,810 14C yr B.P. (13,670 cal yr), synchronous with the beginning of glacial Lake Agassiz. Lake Agassiz shorelines inset to the moraine yield optically stimulated luminescence (OSL) ages from 14,200-12,600 yr cal. Lower strandlines are younger, but the similarity of ages suggests that initial lake lowering was faster than OSL ages can currently resolve. Nevertheless, the OSL ages represent the first numerical age assignments for the Herman, Norcross, and Upham beach ridges, setting the stage for future numerical age assignments within the Lake Agassiz basin. These two dating methods yield strongly consistent results within stated uncertainties. The age of the Big Stone Moraine implies an interval of rapid retreat for the Des Moines lobe of the Laurentide Ice Sheet during the Bölling-Alleröd warm interval. The overlapping ages for the uppermost beach levels and abandonment of the highest Lake Agassiz spillway indicate a rapidly evolving lake until at least 13,500 yr cal.

  4. Aspects of vulnerable patients and informed consent in clinical trials.

    PubMed

    Kuthning, Maria; Hundt, Ferdinand

    2013-01-01

    Ziel: Diskussion der Aspekte der Einwilligung schutzbedürftiger Patienten nach Aufklärung zur Teilnahme an klinischen Prüfungen aus europäischem und deutschem Blick.Methoden: Wissenschaftliche Literaturrecherche via PubMed, Medline und Google. Ergebnis: Das freiwillige Einverständnis ist ein Eckpfeiler aller Regularien von klinischen Prüfungen. Einen Patienten in eine klinische Prüfung aufzunehmen, ohne zuvor die mit seiner Unterschrift versehene schriftliche Einverständnis eingeholt zu haben, ist als schwerwiegendes Fehlverhalten anzusehen. Die Entstehung ethischer Leitlinien begann bereits vor christlicher Zeitrechnung mit dem Hippokratischen Eid. In allen danach für die klinische Forschung entwickelten Leitlinien wird verdeutlicht, dass eine Hauptfunktion der Einwilligung nach Aufklärung die Sicherstellung der Willensfreiheit ist, um auch so das Wohl der Teilnehmer in klinischen Prüfungen sicherzustellen. Minderjährigen ist es nicht möglich ein diesbezüglich bindendes Einverständnis zu geben, dieses Problem wird durch eine Kombination von elterlicher Zustimmung sowie soweit möglich der Einwilligung des Minderjährigen adressiert. Analphabetismus ist betreffs der informierten Einwilligung ein kritischer Aspekt, der die ganze Welt betrifft. Er existiert in allen Gesellschaften, allen Bevölkerungsschichten und in jeder Altersgruppe. Um die Kommunikation mit diesen Patienten zu verbessern, können neue Strategien mittels Verwendung von Videotapes oder animierten Illustrationen und Trickfilmen gelehrt werden. Letztlich scheint die mit dem potentiellen Teilnehmer verbrachte Zeit der beste Weg zu sein, um die Verständigung zu verbessern.Schlussfolgerung: Die Erforschung lebensrettender und lebensverbessernder neuer Behandlungen erfordert eine Partnerschaft, die auf guter Kommunikation und Vertrauen zwischen Patienten und Forschern, Sponsoren, Ethikkommissionen, Behörden, Juristen und Politikern basiert, damit auch schutzbedürftige Patienten ohne

  5. Constraining past behavior of The Antarctic Peninsula Ice Sheet: An important source of meltwater during deglaciation?

    NASA Astrophysics Data System (ADS)

    Rixon, R. N.; Fogwill, C. J.; Hunter, M. A.

    2009-04-01

    Although smaller than it neighbors The Antarctic Peninsula Ice Sheet (APIS) is poorly constrained in terms its behavior during since the Last Glacial Maximum (LGM). To the west of the APIS geophysical and oceanographic studies have demonstrated clear evidence of APIS expansion at the LGM, but to the east there are few constraints due to the presence of fringing Larson Ice Shelf. Recent modeling studies have suggested that this region could be an important source of melt water during deglaciation, possibly contributing to meltwater pulse 1A (mwp-1A). This event is responsible for 20-25% of the eustatic sea-level rise observed from the LGM to present. Such a rapid, large-magnitude event would have had a significant effect on global climate and could have produced dramatically different influences on the climate system depending on the distribution of melt water sources for this event. Recent research suggests that a significant southern hemisphere source for mwp-1A may explain the onset of the Bølling-Allerød warm interval. However, this result remains controversial given the current debate on whether the mwp-IA event was sourced primarily from the northern or southern hemispheres. Here we report the results of field investigations during 2008/9, from a transect from the central Eternity Range down to Frances Island a small island out on the Larson Ice Shelf off the Foyn Bowman Coast. Through detailed geomorphological mapping and cosmogenic isotope sampling this work aims to constrain past thickening inland and resultant grounding of the APIS in the Weddell Sea.

  6. Linking the Holocene glacial and oceanographic variability in northern Spitsbergen

    NASA Astrophysics Data System (ADS)

    Bartels, Martin; Hebbeln, Dierk

    2015-04-01

    The Svalbard area can be considered as a key region for Arctic heat transfer. The archipelago is located where relatively warm Atlantic Water is reaching further north than at any other Arctic location at similar latitudes. The Holocene variability of Atlantic Water advection is well documented for the western coasts of Spitsbergen whereas records from northern Svalbard are still rare. Here we present a sedimentary record from Woodfjorden in northern Spitsbergen where the influence of Atlantic Water is fading out and glaciers are responding much more sensitive to oceanographic variations than at the western coasts of Spitsbergen. We analyzed the foraminiferal fauna and the distribution of Ice Rafted Debris (IRD) to trace the interplay between the oceanographic and glacial variability, respectively. The appearance of Nonionellina labradorica, a species which is adapted to warm Atlantic Water, shows that the advection of Atlantic-derived water correlates positively with summer insolation. The amount of IRD - increasing during the Allerød interstadial - diminished subsequently with intensifying inflow of Atlantic Water. During the Mid-Holocene, the strong influence of these relative warm water masses concurs with very low IRD values, possibly reflecting the retreat of tidewater glaciers from the coast to a further inland position disconnecting glacier dynamics from the respective marine archives at that time. With declining inflow of Atlantic Water during the late Holocene sea ice expanded, indicated by increased percentages of Islandiella norcrossi. The appearance of this species shows a similar trend as reported for sea-ice biomarkers in the eastern Fram Strait. Thus, variations of Atlantic Water inflow directly affected glacial activity as well as sea-ice coverage. Combining marine and terrestrial proxies enabled us to reconstruct regional (sea-ice) as well as local (glacial expansion) changes over time.

  7. The deglaciation over Laurentian Fan: History of diatoms, IRD, ice and fresh water

    NASA Astrophysics Data System (ADS)

    Gil, Isabelle M.; Keigwin, Lloyd D.; Abrantes, Fatima

    2015-12-01

    A high-resolution diatom census coupled with other proxy data from Laurentian Fan (LF) provides a detailed description of the last deglaciation, bringing new insight to that period by revealing directly the timing of sea-ice formation and melting. Cold events Heinrich Event 1 (H1) and the Younger Dryas (YD) were multiphase events. H1 (∼16.8-15.7 cal kyr BP) was defined by a two-pulse release of icebergs promoting sea-ice formation. Melting of sea-ice after H1 corresponds to a cold and fresh anomaly that may have kept the Bølling colder than the Allerød. At ∼13.6 cal kyr BP, a cooling trend culminated with sea-ice formation, marking the YD onset (∼12.8 cal kyr BP). The decrease in sea-ice (∼12.2 cal kyr BP) led to a YD second phase characterized by very cold winters. However, the contribution of warm water diatoms tends to increase at the same time and the YD gradual end (∼11.6 cal kyr BP) contrasts with its abrupt end in Greenland ice cores. The YD cannot be regarded as an event triggered by a fresh water input through the Laurentian Channel since only one weak brief input nearly 1000 yrs after its onset is recorded. Very cold and cool conditions without ice mark the following Preboreal. A northward heat flux between 10.8 and 10.2 cal kyr BP was interrupted by the increased influence of coastal waters likely fed by inland melting. There was no further development of sea-ice or ice-drift then.

  8. Changes in CO2 concentration and carbon cycle during the last glacial termination

    NASA Astrophysics Data System (ADS)

    Ahn, J.; Lee, H. G.; Shin, J.; Brook, E.

    2015-12-01

    Ice cores from Antarctica have revealed that atmospheric CO2 concentration is strongly linked with climate over the past hundreds of thousands years. During the last glacial termination CO2 concentration increased by ~80 ppm and the increase rate changed with abrupt climate events such as Bølling-Allerød and Younger Dryas. Precise and high-resolution CO2 records during the events may help us better understand climate-carbon cycle feedbacks. However, most of the existing ice core records are severely smoothed by gradual bubble close-off and gas diffusion in the firn layer. Recently, a CO2 record with an unprecedented temporal resolution was obtained from West Antarctic Ice Sheet (WAIS) Divide ice core, where glaciological conditions permit a relatively small gas smoothing effect. The WAIS Divide record shows three abrupt CO2 increases of 10-15 ppm in less than 200 years during the last glacial termination. The ancient air extracted from the WAIS Divide ice core was in a form of air hydrates and the results must yet be confirmed with other ice cores. Here we present a new high-resolution atmospheric CO2 record from the Siple Dome ice core, in which air is preserved only in bubbles. Our data cover 11.0-21.0 ka with an average time resolution of 65 yrs. The Siple Dome records show that abrupt CO2 increases of ~ 10 ppm within 100-200 years at 11.7, 14.7, and 16.3 ka, confirming the rapid CO2 increases observed in the WAIS Divide record. We are analyzing the common and uncommon features during the three rapid CO2 increases in order to decipher the control mechanisms. The updated results will be presented at the meeting.

  9. Developing and piloting a multifactorial intervention to address participation and quality of life in nursing home residents with joint contractures (JointConImprove): study protocol.

    PubMed

    Müller, Martin; Bartoszek, Gabriele; Beutner, Katrin; Klingshirn, Hanna; Saal, Susanne; Stephan, Anna-Janina; Strobl, Ralf; Grill, Eva; Meyer, Gabriele

    2015-01-01

    Hintergrund: Gelenkkontrakturen sind häufige Probleme gebrechlicher älterer Menschen in Pflegeheimen. Unabhängig von der genauen Anzahl an älteren Menschen, die an Gelenkkontrakturen leiden, scheint dieses Syndrom ein relevantes Problem im Setting Pflegeheim dazustellen. Durch einen zunehmenden Fokus auf Gelenkkontrakturen, z.B. durch die Pflegeversicherung, kam es zu einem Anstieg im Dokumentations- und Assessmentaufwand und in der Einführung von Präventionsmaßnahmen. Viel mehr Aufmerksamkeit sollte aber auf die tatsächliche Situation der älteren Menschen mit Gelenkkontrakturen in Pflegeheimen gelegt werden, vor allem deren tatsächlichen Einschränkungen in Aktivitäten und Teilhabe. Das Ziel dieser Studie ist daher, 1) die Entwicklung einer maßgeschneiderten Intervention zur Verbesserung der Funktionsfähigkeit, sozialen Teilhabe und Lebensqualität von Menschen mit Gelenkkontrakturen in Pflegeheimen und 2) die Überprüfung der Machbarkeit der Intervention, begleitet von einer Prozessevaluation.Methoden: Die Entwicklung der komplexen Intervention folgt dem UK Medical Research Council (MRC) Framework und integriert die Perspektiven aller potenziell relevanten Benutzergruppen von den betroffenen Personen über Kliniker und Forscher. Der Entwicklungsprozess beinhaltet einen systematischen Literaturreview, die Re-Analyse vorhandener Daten, Fokusgruppeninterviews mit Betroffenen, eine Expertentagung und eine Delphi-Studie mit klinischen Experten sowie eine Cluster-randomisierte Pilotstudie mit umfassender Prozessevaluation. Diskussion: Die geplante Studie wird eine maßgeschneiderte Intervention zur Verbesserung von Funktionsfähigkeit, sozialer Teilhabe und Lebensqualität von Menschen mit Gelenkkontrakturen in Pflegeheimen bereitstellen. Die Pilotstudie inklusive der Prozessevaluation stellt einen ersten Schritt zur Schätzung der Stärke des Interventionseffektes dar und wird weitere Studien vorbereiten.

  10. Penultimate and last glacial oceanographic variations in the Bering Sea on millennial timescales: Links to North Atlantic climate

    NASA Astrophysics Data System (ADS)

    Ovsepyan, E. A.; Ivanova, E. V.; Lembke-Jene, L.; Max, L.; Tiedemann, R.; Nürnberg, D.

    2017-05-01

    We present high-resolution multi-proxy records from a marine sediment core (SO201-2-85KL) from the western Bering Sea to assess orbital- and millennial-scale paleoceanographic conditions during two last glacial intervals, including both terminations. Based on changes in foraminiferal assemblages, grain-size content and previously published TOC and δ13C records, we reconstruct variations in sea-surface biological productivity, intermediate-water oxygenation and sea-ice conditions during the last 180 kyr. Our data demonstrate remarkable differences between the penultimate (MIS 6) and last (MIS 4-2) glacial. Relatively high sea surface bioproductivity and reduced sea-ice cover are reconstructed for the penultimate glacial interval, whereas low bioproductivity and expanded sea-ice cover appear to be typical for the last glacial. Millennial-scale changes in intermediate water ventilation are inferred from faunal records for the middle part of the penultimate glacial. High-amplitude environmental variability during the penultimate glacial time in the Bering Sea resembles the well-known Dansgaard-Oeschger oscillations, and roughly corresponds to similar rapid climatic fluctuations found in North Atlantic records. The Termination II and I intervals display a similar succession of high-bioproductivity events, being more pronounced during the penultimate glacial-interglacial transition, probably due to the different orbital configuration. During the late phase of Termination II, two short intervals, characterized by high sea surface bioproductivity and low oxygen content of bottom waters, resemble the Bølling and Allerød warmings, whereas an episode with low bioproductivity occurs in between, similar to the Older Dryas. Our results provide support for a close circumpolar coupling between high-latitude environments on millennial timescales at least since the penultimate glacial.

  11. Thermal evolution of the western South Atlantic and the adjacent continent during Termination 1

    NASA Astrophysics Data System (ADS)

    Chiessi, C. M.; Mulitza, S.; Mollenhauer, G.; Silva, J. B.; Groeneveld, J.; Prange, M.

    2014-12-01

    During Termination 1, millennial-scale weakening events of the Atlantic meridional overturning circulation (AMOC) supposedly produced major changes in sea surface temperatures (SST) of the western South Atlantic, and in mean air temperatures (MAT) over southeastern South America. It was suggested, for instance, that the Brazil Current (BC) would strengthen (weaken) and the North Brazil Current (NBC) would weaken (strengthen) during slowdown (speed-up) events of the AMOC. This anti-phase pattern was claimed to be a necessary response to the decreased North Atlantic heat piracy during periods of weak AMOC. However, the thermal evolution of the western South Atlantic and the adjacent continent is largely unknown and a compelling record of the BC-NBC anti-phase behavior remains elusive. Here we address this issue, presenting high temporal resolution SST and MAT records from the BC and southeastern South America, respectively. We identify a warming in the western South Atlantic during Heinrich Stadial 1 (HS1), which is followed first by a drop and then by increasing temperatures during the Bølling-Allerød, in-phase with an existing NBC record. Additionally, a similar SST evolution is shown by a southernmost eastern South Atlantic record, suggesting a South Atlantic-wide pattern in SST evolution during most of Termination 1. Over southeastern South America, our MAT record shows a two-step increase during Termination 1, synchronous with atmospheric CO2 rise (i.e., during the second half of HS1 and during the Younger Dryas), and lagging abrupt SST changes by several thousand years. This delay corroborates the notion that the long duration of HS1 was fundamental to drive the Earth out of the last glacial.

  12. Thermal evolution of the western South Atlantic and the adjacent continent during Termination 1

    NASA Astrophysics Data System (ADS)

    Chiessi, C. M.; Mulitza, S.; Mollenhauer, G.; Silva, J. B.; Groeneveld, J.; Prange, M.

    2015-06-01

    During Termination 1, millennial-scale weakening events of the Atlantic meridional overturning circulation (AMOC) supposedly produced major changes in sea surface temperatures (SSTs) of the western South Atlantic, and in mean air temperatures (MATs) over southeastern South America. It has been suggested, for instance, that the Brazil Current (BC) would strengthen (weaken) and the North Brazil Current (NBC) would weaken (strengthen) during slowdown (speed-up) events of the AMOC. This anti-phase pattern was claimed to be a necessary response to the decreased North Atlantic heat piracy during periods of weak AMOC. However, the thermal evolution of the western South Atlantic and the adjacent continent is so far largely unknown. Here we address this issue, presenting high-temporal-resolution SST and MAT records from the BC and southeastern South America, respectively. We identify a warming in the western South Atlantic during Heinrich Stadial 1 (HS1), which is followed first by a drop and then by increasing temperatures during the Bølling-Allerød, in phase with an existing SST record from the NBC. Additionally, a similar SST evolution is shown by a southernmost eastern South Atlantic record, suggesting a South Atlantic-wide pattern in SST evolution during most of Termination 1. Over southeastern South America, our MAT record shows a two-step increase during Termination 1, synchronous with atmospheric CO2 rise (i.e., during the second half of HS1 and during the Younger Dryas), and lagging abrupt SST changes by several thousand years. This delay corroborates the notion that the long duration of HS1 was fundamental in driving the Earth out of the last glacial.

  13. Paleoceanographic insights on recent oxygen minimum zone expansion: lessons for modern oceanography.

    PubMed

    Moffitt, Sarah E; Moffitt, Russell A; Sauthoff, Wilson; Davis, Catherine V; Hewett, Kathryn; Hill, Tessa M

    2015-01-01

    Climate-driven Oxygen Minimum Zone (OMZ) expansions in the geologic record provide an opportunity to characterize the spatial and temporal scales of OMZ change. Here we investigate OMZ expansion through the global-scale warming event of the most recent deglaciation (18-11 ka), an event with clear relevance to understanding modern anthropogenic climate change. Deglacial marine sediment records were compiled to quantify the vertical extent, intensity, surface area and volume impingements of hypoxic waters upon continental margins. By integrating sediment records (183-2,309 meters below sea level; mbsl) containing one or more geochemical, sedimentary or microfossil oxygenation proxies integrated with analyses of eustatic sea level rise, we reconstruct the timing, depth and intensity of seafloor hypoxia. The maximum vertical OMZ extent during the deglaciation was variable by region: Subarctic Pacific (~600-2,900 mbsl), California Current (~330-1,500 mbsl), Mexico Margin (~330-830 mbsl), and the Humboldt Current and Equatorial Pacific (~110-3,100 mbsl). The timing of OMZ expansion is regionally coherent but not globally synchronous. Subarctic Pacific and California Current continental margins exhibit tight correlation to the oscillations of Northern Hemisphere deglacial events (Termination IA, Bølling-Allerød, Younger Dryas and Termination IB). Southern regions (Mexico Margin and the Equatorial Pacific and Humboldt Current) exhibit hypoxia expansion prior to Termination IA (~14.7 ka), and no regional oxygenation oscillations. Our analyses provide new evidence for the geographically and vertically extensive expansion of OMZs, and the extreme compression of upper-ocean oxygenated ecosystems during the geologically recent deglaciation.

  14. Biomineral formation as a biosignature for microbial activities Precambrian cherts

    NASA Astrophysics Data System (ADS)

    Rincón Tomás, Blanca; Mühlen, Dominik; Hoppert, Michael; Reitner, Joachim

    2015-04-01

    In recent anoxic sediments manganese(II)carbonate minerals (e.g., rhodochrosite, kutnohorite) derive mainly from the reduction of manganese(IV) compounds by microbial anaerobic respiration. Small particles of rhodochrosite in stromatolite-like features in the Dresser chert Fm (Pilbara supergroup, W-Australia), associated with small flakes of kerogen, account for biogenic formation of the mineral in this early Archaean setting. Contrastingly, the formation of huge manganese-rich (carbonate) deposits requires effective manganese redox cycling, also conducted by various microbial processes, mainly requiring conditions of the early and late Proterozoic (Kirschvink et al., 2000; Nealson and Saffrani 1994). However, putative anaerobic pathways like microbial nitrate-dependent manganese oxidation (Hulth et al., 1999), anoxygenic photosynthesis (Johnson et al., 2013) and oxidation in UV light may facilitate manganese cycling even in a reducing atmosphere. Thus manganese redox cycling might have been possible even before the onset of oxygenic photosynthesis. Hence, there are several ways how manganese carbonates could have been formed biogenically and deposited in Precambrian sediments. Thus, the minerals may be suitable biosignatures for microbial redox processes in many respects. The hyperthermophilic archaeon Pyrobaculum islandicum produces rhodochrosite during growth on hydrogen and organic compounds and may be a putative model organism for the reduction of Mn(IV). References Hulth S, Aller RC, Gilbert F. (1999) Geochim Cosmochim Acta, 63, 49-66. Johnson JE, Webb SM, Thomas K, Ono S, Kirschvink JL, Fischer WW. (2013) Proc Natl Acad Sci USA, 110, 11238-11243. Kirschvink JL, Gaidos EJ, Bertani LE, Beukes NJ, Gutzmer J, Maepa LN, Steinberger LE. (2000) Proc Natl Acad Sci USA, 97, 1400-1405. Nealson KH, Saffarini D. (1994). Annu Rev Microbiol, 48, 311-343.

  15. Late Glacial and Holocene Record of Hydroclimate in the San Luis Valley, Southern Colorado, USA

    NASA Astrophysics Data System (ADS)

    Yuan, F.; Koran, M.

    2012-12-01

    Lake sediments from the San Luis Valley, south-central Colorado, archive a detailed record of Late Glacial and Holocene climatic fluctuations in the southern Rocky Mountains. Together with radiometric dating analysis, measurements of grain size, magnetic susceptibility, total inorganic carbon (TIC), oxygen and carbon isotopic composition of the TIC fraction on sediment samples from San Luis Lake (at an average resolution of 60 years per sample) allow us to generate a sediment record of climatic change in the region spanning the last 16ka (1 ka=1000 cal yrs). This record documents the timing and duration of major climate episodes and trends, comparable to the existing paleoclimate records from the American Southwest. The Late Glacial record of San Luis Lake contains a big wet episode in the late part of the Mystery Interval (MI), a relatively dry climate during Bølling-Allerød (B/A) warm interval, and a relatively wet episode during the Younger Dryas (YD) interval, similar to the lake-level record found in the Estancia basin in central New Mexico. The early to middle Holocene record of d18O in the San Luis Lake parallels the calcite d18O record of Bison Lake in northern Colorado, documenting a history of significant change in precipitation seasonality across the northern boundary of the North American monsoon (NAM). The middle Holocene epoch is characterized by greater variations in magnetic susceptibility, d18O and d13C, suggesting the prevalence of wet, variable or transitional climate conditions. In contrast, the late Holocene climate is relatively dry, as indicated by more positive values of d18O in San Luis Lake. The results of this study reveal a complex history of climate evolution due to the interactions of two seasonally distinct precipitation regimes with mountainous landforms in the region.

  16. Response of the Indo-Australian Monsoon System to Heinrich Events: Evidence from Marine and Terrestrial Sediments

    NASA Astrophysics Data System (ADS)

    Muller, J.; McManus, J. F.; Oppo, D.; Francois, R. H.

    2012-12-01

    The biannual Asian monsoon dominates the climate of tropical and subtropical regions, bringing a strong seasonal rainfall contrast in these areas. In recent years computer models and paleoclimate records from various tropical locations have demonstrated the sensitivity of the tropical monsoon system to Northern Hemisphere abrupt climate change events. This study presents data from a somewhat underrepresented region, the Australian and southern Indonesian region. Here we compare a new deep-sea sediment record for the Flores Sea, with a terrestrial peat core record from Lynch's Crater, NE Queensland Australia. In the Flores Sea we use the long-lived nuclide 232Th as a novel proxy for detrital riverine input and 230Th normalization to estimate the history of preserved fluxes reaching the seafloor in the Flores Sea. The 230Th normalized burial fluxes of lithogenic and biogenic matter demonstrate that both detrital and biogenic fluxes in the Flores Sea were higher during Heinrich Stadial 1 (HS1) than any other period in the past 22 kyr. High detrital fluxes indicate enhanced precipitation runoff from surrounding landmasses during a period of maximum southward shift of the Intertropical Convergence Zone (ITCZ). The enhanced precipitation associated with HS1 over the Flores Sea is in good timing with a previously interpreted wet event over Lynch's Crater, NE Australia. Our results provide strong evidence for a southward migration of the ITCZ during HS1 and a return northward during the Bølling-Allerød interstadial. This work highlights the sensitivity of Australasian rainfall patterns to high latitude climate change in the Northern Hemisphere. In addition, our work constrains both the northern and southern limits of enhanced rainfall associated with a southward shift of the monsoon belt at the time of HS1 and highlights the value of 232Th as a proxy for continental input to deep-sea sediment records.

  17. Centennial to millennial climate variability in the far northwestern Pacific (off Kamchatka) and its linkage to the East Asian monsoon and North Atlantic from the Last Glacial Maximum to the early Holocene

    NASA Astrophysics Data System (ADS)

    Gorbarenko, Sergey A.; Shi, Xuefa; Malakhova, Galina Yu.; Bosin, Aleksandr A.; Zou, Jianjun; Liu, Yanguang; Chen, Min-Te

    2017-08-01

    High-resolution reconstructions based on productivity proxies and magnetic properties of core LV63-41-2 (off Kamchatka) reveal prevailing centennial productivity/climate variability in the northwestern (NW) Pacific from the Last Glacial Maximum (LGM) to the early Holocene (EH). The age model of the core is established by AMS 14C dating and by projections of AMS 14C data of the nearby core SO-201-12KL through correlation of the productivity proxies and relative paleomagnetic intensity. The resulting sequence of centennial productivity increases/climate warming events in the NW Pacific occurred synchronously with the East Asian summer monsoon (EASM) sub-interstadials during the LGM (four events), Heinrich Event 1 (HE1) (four events), Bølling-Allerød (B/A) warming (four events), and over the EH (four events). Remarkable similarity of the sequence of the NW Pacific increased-productivity events with the EASM sub-interstadials over the LGM-HE1 implies that the Siberian High is a strong and common driver. The comparison with the δ18O record from Antarctica suggests that another mechanism associated with the temperature gradient in the Southern Hemisphere may also be responsible for the EASM/NW Pacific centennial events over the LGM-HE1. During the B/A warming and resumption of the Atlantic Meridional Overturning Circulation (AMOC), clear synchronicity between the NW Pacific, EASM and Greenland sub-interstadials was mainly controlled by changes in the atmospheric circulation. During the EH the linkages between solar forcing, ocean circulation, and climate changes likely control the synchronicity of abrupt climate changes in the NW Pacific and North Atlantic. The sequence of centennial events recorded in this study is a persistent regional feature during the LGM-EH, which may serve as a template in high-resolution paleoceanography and sediment stratigraphy in the NW Pacific.

  18. A catastrophic meltwater flood event and the formation of the Hudson Shelf Valley

    USGS Publications Warehouse

    Thieler, E. Robert; Butman, Bradford; Schwab, William C.; Allison, Mead A.; Driscoll, Neal W.; Donnelly, John P.; Uchupi, Elazar

    2007-01-01

    The Hudson Shelf Valley (HSV) is the largest physiographic feature on the U.S. mid-Atlantic continental shelf. The 150-km long valley is the submerged extension of the ancestral Hudson River Valley that connects to the Hudson Canyon. Unlike other incised valleys on the mid-Atlantic shelf, it has not been infilled with sediment during the Holocene. Analyses of multibeam bathymetry, acoustic backscatter intensity, and high-resolution seismic reflection profiles reveal morphologic and stratigraphic evidence for a catastrophic meltwater flood event that formed the modern HSV. The valley and its distal deposits record a discrete flood event that carved 15-m high banks, formed a 120-km2 field of 3- to 6-m high bedforms, and deposited a subaqueous delta on the outer shelf. The HSV is inferred to have been carved initially by precipitation and meltwater runoff during the advance of the Laurentide Ice Sheet, and later by the drainage of early proglacial lakes through stable spillways. A flood resulting from the failure of the terminal moraine dam at the Narrows between Staten Island and Long Island, New York, allowed glacial lakes in the Hudson and Ontario basins to drain across the continental shelf. Water level changes in the Hudson River basin associated with the catastrophic drainage of glacial lakes Iroquois, Vermont, and Albany around 11,450 14C year BP (∼ 13,350 cal BP) may have precipitated dam failure at the Narrows. This 3200 km3 discharge of freshwater entered the North Atlantic proximal to the Gulf Stream and may have affected thermohaline circulation at the onset of the Intra-Allerød Cold Period. Based on bedform characteristics and fluvial morphology in the HSV, the maximum freshwater flux during the flood event is estimated to be ∼ 0.46 Sv for a duration of ∼ 80 days.

  19. Lateglacial-Holocene abrupt vegetation changes at Lago Trifoglietti in Calabria, Southern Italy: The setting of ecosystems in a refugial zone

    NASA Astrophysics Data System (ADS)

    Beaulieu, Jacques-Louis de; Brugiapaglia, Elisabetta; Joannin, Sébastien; Guiter, Frédéric; Zanchetta, Giovanni; Wulf, Sabine; Peyron, Odile; Bernardo, Liliana; Didier, Julien; Stock, Agnès; Rius, Damien; Magny, Michel

    2017-02-01

    Retrospective science such as palaeoecology deeply depends on the preservation of archives in sensitive places. As an example, mountains of medium altitude from Mediterranean peninsulas have long been identified by biogeographers as refuges zones allowing the survival of European temperate taxa during the ice ages, but archives to validate this hypothesis are scarce, especially in Southern Italy. Here we present a new sequence from Lago Trifoglietti (1048 m a.s.l.) in the Calabrian Mountains, which covers the Late Glacial Interstadial (LGI, corresponding to the Bölling-Alleröd period in northern-central Europe) and the transition to the Holocene. The independent chronology based on seven radiocarbon dates is supported by the evidence of three tephra layers already identified in other regional sequences. During the LGI, besides the high diversity of non arboreal pollen grains, a great number of pollens of temperate forest trees are present or abundant (mostly deciduous oaks and fir). These assemblages suggest that the site was above but not far from the upper limit of diversified woodland stands. They confirm a local survival during the last glacial. The Younger Dryas is not marked by major changes, and oak percentages are even higher, suggesting a resilient expansion at lower altitude. Surprisingly the site remains above the timberline until an aridity crisis centered at 11,100 cal 14C yr PB, which is correlated with the Preboreal Oscillation (PBO). This event is immediately followed by the local settlement of a dense fir and beech forest around the lake. A comparison with other Italian key sequences aims at explaining the climate forcing factors that governed this original vegetation dynamic. Further investigations using additional proxies are needed for a more robust climate reconstruction.

  20. North Atlantic forcing of millennial-scale Indo-Australian monsoon dynamics during the Last Glacial period

    NASA Astrophysics Data System (ADS)

    Denniston, Rhawn F.; Wyrwoll, Karl-Heinz; Asmerom, Yemane; Polyak, Victor J.; Humphreys, William F.; Cugley, John; Woods, David; LaPointe, Zachary; Peota, Julian; Greaves, Elizabeth

    2013-07-01

    Recent studies of the Last Glacial period Indo-Australian summer monsoon (IASM) have revealed links to both northern and southern hemisphere high latitude climate as well as to regional ocean conditions. Particular interest has been paid to the monsoon response to Heinrich events, with variability explained by meridional shifts in positioning of the intertropical convergence zone (ITCZ), but this model has not been adequately tested. In addition, the shorter-lived Dansgaard/Oeschger (D/O) events have not been detected (beyond D/O-1, the Bølling/Allerød) in land-based records from the Indo-Pacific, despite their prominent expression in stalagmites from southern Asia, raising questions about the sensitivity of the IASM to these events. Here we present a Southern Hemisphere stalagmite oxygen isotopic time series from Ball Gown Cave (BGC), tropical northern Australia, located on the margins of the modern austral summer ITCZ, that spans 40-31 and 27-8 ka. Elevated IASM rainfall coincides with Heinrich stadials and the Younger Dryas, while decreased rainfall characterizes D/O interstadials, a response that is anti-phased with sites spanning the Indo-Pacific Warm Pool and with Chinese records of the East Asian summer monsoon. The BGC time series thus reveals a precipitation dipole consistent with a southward (northward) migration of the ITCZ during periods of high northern latitude cooling (warming) as the primary driver of millennial-scale IASM variability during the Last Glacial period. Our record indicates a strengthening of the IASM after the Younger Dryas period, likely as a result of rising sea level and sea surface temperatures, breaking the link with the high latitudes.

  1. Younger Dryas sea level and meltwater pulse 1B recorded in Barbados reef crest coral Acropora palmata

    NASA Astrophysics Data System (ADS)

    Abdul, N. A.; Mortlock, R. A.; Wright, J. D.; Fairbanks, R. G.

    2016-02-01

    The Younger Dryas climate event occurred during the middle of the last deglacial cycle and is marked by an abrupt shift in the North Atlantic polar front almost to its former glacial position, trending east to west. Using high-precision and high-accuracy U-Th-dated Barbados reef crest coral, Acropora palmata, we generate a detailed sea level record from 13.9 to 9000 years before present (kyr B.P.) and reconstruct the ice volume response to the Younger Dryas cooling. From the mid-Allerød (13.9 kyr B.P.) to the end of the Younger Dryas (11.65 kyr B.P.), rates of sea level rise decreased smoothly from 20 mm yr-1 to 4 mm yr-1, culminating in a 400 year "slow stand" before accelerating into meltwater pulse 1B (MWP-1B). The MWP-1B event at Barbados is better constrained as beginning by 11.45 kyr B.P. and ending at 11.1 kyr B.P. during which time sea level rose 14 ± 2 m and rates of sea level rise reached 40 mm yr-1. We propose that MWP-1B is the direct albeit lagged response of the Northern Hemisphere ice sheets to the rapid warming marking the end of the Younger Dryas coinciding with rapid warming in the circum-North Atlantic region and the polar front shift from its zonal to meridional position 11.65 kyr B.P. As predicted by glaciological models, the ice sheet response to rapid North Atlantic warming was lagged by 400 years due to the thermal inertia of large ice sheets. The regional circum-North Atlantic Younger Dryas climate event is elevated to a global response through sea level changes, starting with the global slowdown in sea level rise during the Younger Dryas and culminating with MWP-1B. No meltwater pulses are evident at the initiation of the Younger Dryas climate event as is often speculated.

  2. Morphological and lithological transformation records of the Lake Czechowskie basin on the basis of paleogeography and GIS techniques analysis

    NASA Astrophysics Data System (ADS)

    Kramkowski, M. A.; Błaszkiewicz, M.; Tyszkowski, S.; Kordowski, J.

    2014-12-01

    The analyses of the annually laminated lacustrine sediments are particularly important in the studies of global climate change. They provide information about the ecosystem response to environmental and climate changes. The condition for the laminated sedimentation with the annual resolution is a calm sedimentation environment where there is no mixing and thus there are anaerobic conditions in the benthic zone. Below a certain depth there is no wave induced mixing and temperature is constant, which causes water stagnation. In shallower areas such conditions are favoured by the morphology of the lake basin and the long presence of ice cover (bradymictic). The combination of these environmental features predispose to the deposition of laminated sediments. Lake Czechowskie is located within the limit of the Scandinavian Ice Sheet during the Last Glaciation in the Central European Lowland (northern Poland - 53°52"N 18°14"E) in a deep kettle-hole type. Taking into account the thickness of the lacustrine sediments, the maximum depth of the basin exceeds 70 m. Detailed surveying as well as geological drilling using the GIS techniques made it possible to reconstruct the morphology of the basin of Lake Czechowskie and its adjacent areas before the biogenic sedimentation started in Allerød. At that time water level was 2 m higher than in the modern times. Following climate changes initiated the natural processes of the lake basin transformation. The analysis of the morphology of the lake basin is the basis for modelling the sedimentation conditions considering, inter alia, the wind direction and wind velocity, fluctuations of the water levels and the degree of filling the basin with the deposits in different periods of the Late Glacial and Holocene. It allows specifying the variability and sedimentation rate within the basin. The analysis shows the spatial variation of the erosion and accumulation zones, and enables to determine the zones of calm sedimentation revealing

  3. The role of atmosphere and ocean mechanisms in coupling millennial-scale climate variability between the hemispheres

    NASA Astrophysics Data System (ADS)

    Pedro, J. B.; Steig, E. J.; Ding, Q.; Bitz, C. M.

    2013-12-01

    Recent improvements in the dating of Antarctic and Greenland ice cores confirm an essentially synchronous onset of the Antarctic Cold Reversal (ACR) and Bølling-Allerød interstadial (DO1). Latest results also indicate zero phase lag through this period between Antarctic temperature and atmospheric CO2. Here we use these constraints and output from the first full transient general circulation model simulation of the last deglaciation (Community Climate System Model version 3; He et al, [2013]) to test existing hypotheses on the mechanisms of north-south climate coupling and CO2 ventilation from the deep Southern Ocean. The ocean bipolar seesaw hypothesis proposes that north-south coupling is explained by changes in the strength of northward heat transport in the Atlantic Ocean. An alternative (potentially complementary) mechanism suggests that the coupling results from atmospheric teleconnections in which temperature and sea ice changes in the North Atlantic force a shift in the position of the ITCZ, and in turn in the position and intensity of the southern hemisphere mid-latitude westerly winds. Both mechanisms can be linked to changes in atmospheric CO2 through their impacts on physical mixing and biogeochemical conditions in the Southern Ocean. The model run shows a two-stage response in southern high latitudes to the simulated DO1 warming. The first stage, lasting 200--300 years, sees an immediate northward shift in the ITCZ and a weakening of the westerlies. There is also an immediate increase in northward ocean heat transport, though this is confined to latitudes north of the Antarctic Circumpolar Current (ACC). The weaker westerlies would be expected to decrease wind-driven upwelling of warm circum-polar deep-waters, driving regional cooling. However strong cooling and expansion of Antarctic sea ice only begin in the second stage, which spans the next 300--400 years. During this interval the atmospheric fields return to their prior values. The increase in

  4. The last deglacial and Holocene temperature changes revealed by GDGTs of loess-paleosol sequence in northeastern Tibetan Pleteau

    NASA Astrophysics Data System (ADS)

    Duan, Y.

    2016-12-01

    Paleohydrology reconstructions based on various proxies since last deglacial and Holocene in Tibetan Plateau (TP) has been widely reported. However, less attention was paid to paleotemperature reconstructions in this region due to lack of reliable proxies. Moreover, the temperature changes trend during Holocene inferred from proxy index reconstructions are contradicted with those from climate model stimulation. In this study, a loess-paleosol section (YWY14) which is located in the northeastern TP and well dated based on charcoals were used to reconstruct annual temperature change spanning the last deglaciation and the whole Holocene. The proxy indexes of GDGTs of 37 samples using newly proposed analytical approach were used for climate reconstruction based on credible research on modern processes. The results show that temperature inferred from MBT'5ME during last deglaciation was warmer than that during the Holocene, but decreased from 11.5 to 8 kyr BP, and then gradually increased after 8 kyr BP. The reconstructed temperature during the last decades can be well compared with modern meteorological record. In addition, the Bølling/Allerød warm period (BA), the Younger Dryas cold event (YD) and cold events at 8 kyr BP are well documented in this record. Ri/b, which is used as an aridity proxy, indicates precipitation gradually increased from 16 to 11.5 kyr BP, and then generally decreased after 11.5 kyr BP. When compared with paleohydrology proxy from the same section, it is suggested that the studied area was warm and wet during the period from 16-8 kyr BP, and became warm and dry after 8 kyr BP. Therefore, variations of temperature and hydrology changes were not always coupled since last deglaciation on the northeastern Tibetan Plateau, which provide reference to predict precipitation changes under the condition of global warming. The increasing trend from the mid to the late Holocene in our record is consistent with climatic modelling results. We hypothesis

  5. A single standardized practical training for surgical scrubbing according to EN1500: effect quantification, value of the standardized method and comparison with clinical reference groups.

    PubMed

    Fichtner, Andreas; Haupt, Elke; Karwath, Tobias; Wullenk, Katharina; Pöhlmann, Christoph; Jatzwauk, Lutz

    2013-01-01

    Die standardisierte Schulung klinisch-praktischer Fertigkeiten in sog. Skills Labs ist erst seit wenigen Jahren an deutschen Universitäten verbreitet. Den zumeist umfangreichen und sehr guten Evaluationsergebnissen stehen kaum Untersuchungen zur Effektquantifizierung und Kosten-Nutzen-Analyse gegenüber. In der vorliegenden Studie soll eine Methode zur digitalen Quantifizierung der Güte der chirurgischen Händedesinfektion vorgestellt werden sowie das Skills-Lab-Training der standardisierten Einreibemethode nach EN1500 auf seinen Effekt hin untersucht und mit OP-Pflegepersonal und Operateuren als klinische Referenzgruppen verglichen werden.Methode: 161 Studierende der Medizin eines 8. Semesters wurden in Kontroll- und Interventionsgruppe randomisiert. Die Interventionsgruppe erhielt ein 45-minütiges standardisiertes Training durch geschulte Mitstudierende zum Verhalten im OP mit dem Teilaspekt der chirurgischen Händedesinfektion nach EN1500. Dem Desinfektionsmittel wurde Fluoreszenzfarbstoff beigemischt. Nach der Desinfektion wurden die 4 Handflächen eines jeden Probanden digital fotografiert und teilautomatisiert die nicht ausreichend benetzte Handfläche bestimmt. Die Ergebnisse aller studentischer Probanden wurden verglichen, sowie das Kompetenzniveau anhand zweier klinischer Referenzgruppen eingeordnet.Ergebnisse: Die Interventionsgruppe erreichte nach dem studentisch angeleiteten Training eine zu durchschnittlich 4,99% (SD 2,34) der gesamten vier Handflächen nicht sicher ausreichende Benetzung und war damit hoch signifikant (p<0,01) besser als die Kontrollgruppe mit 7,33% (SD 3,91). Im Vergleich zu den Referenzgruppen konnte in der Kontrollgruppe kein signifikanter Unterschied gezeigt werden, die Interventionsgruppe zeigte aber im Vergleich zu beiden Referenzgruppen hoch signifikant bessere Ergebnisse: Operateure 9,32% (SD 4,97), OP-Pflege 8,46% (SD 4,66). Der Methodenfehler ist vernachlässigbar gering. In der Subgruppenanalyse hinsichtlich der

  6. Reconstructing the Vertical 14C Gradient of the Baja Margin during the Last Deglaciation

    NASA Astrophysics Data System (ADS)

    Lindsay, C. M.; Lehman, S. J.; Marchitto, T. M.; Ortiz, J. D.; van Geen, A.

    2011-12-01

    The radiocarbon activity (Δ14C) of the atmosphere decreased in two steps during the last deglaciation, coinciding with the well-known Heinrich 1 (H1) and Younger Dryas (YD) stadials. A leading explanation for these periods of decline involves the release of 14C-depleted carbon from a deep, isolated ocean reservoir- a mechanism that may also help to explain the deglacial rise in atmospheric CO2. Reconstructions of intermediate water Δ14C near Baja California, Mexico (Marchitto et al., 2007 Science) and in the Arabian Sea (Bryan et al., 2010 Earth Planet. Sci. Lett.) document two intervals of extreme depletion relative to the coeval atmosphere during H1 and the YD that are interpreted as evidence of the return of this aged carbon from the deep reservoir to the upper ocean and atmosphere. Here we report on 14C measurements in additional cores from the Baja margin that expand the depth range of our observations and enable reconstruction of the vertical Δ14C gradient. Calendar ages were determined by (1) correlation of diffuse spectral reflectance (DSR, a proxy related to local productivity) with the layer-counted age model in the GISP2 ice core and (2) correlation of raw planktic G. ruber 14C ages to new measurements in core PC08 previously studied by Marchitto et al. (2007). Together these provide a common and consistent calendar age model for margin core PCO8 (depth 705 m), core PC13 from Soledad Basin (sill depth 290 m) and margin core GC38 (depth 1270 m). In preliminary results, G. ruber Δ14C data from PC08 exhibit a record of deglacial depletion events that is consistent with partial upward mixing of the intermediate-depth signal to the surface. Δ14C at 1270 meters showed relatively little change during H1 and YD, indicating that anomalously depleted water did not penetrate to this depth. The vertical gradient collapsed to within observational uncertainties at the start of the Bølling-Allerød/Antarctic Climate Reversal. Taken together the results support

  7. Quantitative reconstruction of temperature at a Jōmon site in the Incipient Jōmon Period in northern Japan and its implications for the production of early pottery and stone arrowheads

    NASA Astrophysics Data System (ADS)

    Kawahata, Hodaka; Ishizaki, Yui; Kuroyanagi, Azumi; Suzuki, Atsushi; Ohkushi, Ken-ichi

    2017-02-01

    The first emergence and development of pottery is an important archeological research topic. Climate change and associated ecological changes likely promoted the development of pottery. However, little is known about these environmental factors at the regional scale. Sedimentary Core MD01-2409 was collected off the coast of northern Honshu, Japan, and provided an excellent opportunity to quantitatively estimate temperature using an alkenone proxy. This estimation is based upon the positive correlation between the sea surface temperature (SST) and the atmospheric temperature (AT) near the core collection site. The Jōmon began to produce the earliest pottery found in Japan during this period. This corresponds to a climatic anomaly that could be attributed to one of the global effects of the Heinrich Event I. The event's origin in the northern North Atlantic consequently weakened the Asian Monsoon because the two are linked via atmospheric circulation. Japan experienced its coldest summer (SST of 8.7 °C; AT of 5.2 °C) around 15.68 cal kyr BP; these summer temperatures were approximately 7-11 °C lower than they are currently (∼15.7 °C and ∼16.7 °C), respectively. The summer environment was a little colder than those experienced in the present-day cities of Nemuro and/or Nosappu in Hokkaido. Subsistence in a terrestrial environment would have been difficult for the Jōmon people; however, marine products such as fish and shellfish would have been plentiful. These conditions are consistent with the evidence that the earliest pottery was predominantly used for cooking marine and freshwater resources and increased diversification in the range of aquatic products used. The Bølling-Allerød and pre-Boreal warm Episodes during deglaciation warmed climatic environments and enhanced marine biogenic production. The maximum SST during this period is comparable to the modern SST despite its short duration (of approximately a century or less). Even though the

  8. The complex behavior of the Cordilleran Ice Sheet and mountain glaciers to abrupt climate change during the latest Pleistocene

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Goehring, Brent; Osborn, Gerald; Clarke, Garry K. C.; Ward, Brent; Margold, Martin; Bond, Jeff; Clague, John J.; Lakeman, Tom; Schaefer, Joerg; Koch, Joe; Gosse, John; Stroeven, Arjen P.; Seguinot, Julien; Heyman, Jakob; Fulton, Robert

    2014-05-01

    Surficial mapping and more than 70 radiometric ages 10Be, 14C] constrain the evolution of the Cordilleran Ice Sheet (CIS) and associated mountain glaciers in western Canada during the latest Pleistocene. Our data suggest that: i) there is widespread evidence for the Younger Dryas (YD) throughout the mountains of western Canada; ii) late Pleistocene climate reconstructions based solely on alpine moraines may be misleading in regions with decaying ice sheets; iii) extensive interfluves in some mountain regions were ice-free between 16 ka and 13 ka (kilo calibrated yrs BP). Initial decay of the CIS from its maximum extent around 16 ka was likely due to a combination of climatic (surface melting) and dynamical factors. Climate amelioration during the Bølling-Allerød Warm Period [14.7-12.9 ka], likely the cause for the major phase of CIS decay, resulted in ice sheet equilibrium line altitudes (ELAs) ranging from 2500 m asl in southern BC to around 2000 m asl along the BC-Yukon border. Hence, before the onset of the Younger Dryas (YD) Cold Period [12.9-11.7 ka], the ice sheet shrank and became a labyrinth of individual and coalescing valley glaciers fed by major accumulation zones centered on the Coast Mountains and other high ranges of NW Canada. The response of remnant ice and cirque glaciers to the YD climate deterioration was highly variable. In some cases, small glaciers (0.5-2 km2) built YD moraines that were only hundreds of meters beyond those constructed during the Little Ice Age (LIA) [0.30-0.15 ka]. Our dating also reveals that much larger glaciers persisted in nearby valleys that lie hundreds of meters below the cirques. Hence, we infer that many cirques were completely deglaciated prior the YD, in contrast to low-lying valleys where ice sheet remnants persisted. Glaciers also advanced in north-central British Columbia during the YD, but here glaciers constructed large terminal and lateral moraines. In the Cassiar and northern Coast mountains, for example

  9. Lake Level Changes in the Mono Basin During the Last Deglacial Period

    NASA Astrophysics Data System (ADS)

    Wang, X.; Ali, G.; Hemming, S. R.; Zimmerman, S. R. H.; Stine, S. W.; Hemming, G.

    2014-12-01

    much weakened. When the climate shifted from cold to warm, the lake dropped significantly, during the transition between Heinrich Stadial 1 and the Bølling time interval, and then during the Allerød period. The U/Th ages on the tufa samples therefore not only establish a highly resolved chronology of hydroclimate history in the Mono Basin, but also put the lake level oscillations in a global context.

  10. Leads and lags between the Antarctic temperature and carbon dioxide during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Gest, Léa; Parrenin, Frédéric; Raynaud, Dominique; Fudge, Tyler J.

    2017-04-01

    To understand causal relationships in past climate variations, it is essential to have accurate chronologies of paleoclimate records. Ice cores in Antarctica provide important paleoclimate variables, such as local temperature and global atmospheric CO2. Unfortunately, temperature is recorded in the ice while CO2 is recorded in the enclosed air bubbles. The ages of the former and of the latter are different since air is trapped at 50-120 m below the surface. For the last deglacial warming, 18,000 to 11,000 years ago, Parrenin et al. (Science, 2013) inferred that CO2 and Antarctic temperature started to increase in phase while CO2 lagged temperature at the beginning of the Holocene period. However, this study suffers from various uncertainties that we tried to address in the current study. First, Antarctic temperature was inferred from a stack of 5 Antarctic ice cores that were not always accurately synchronized. Here we use a stack of 4 Antarctic ice cores which are all accurately synchronized thanks to volcanic peak matching. Second, Parrenin et al. (Science, 2013) used a relatively low-resolution CO2 record from the EPICA Dome C ice core. Here, we use the more recent and higher resolution CO2 record from the West Antarctic Ice Sheet Divide ice core. Third, the air trapping depth was deduced on the low accumulation EPICA Dome C ice core using the gravitational enrichment of the δ15N isotopes and assuming a zero convective depth, a hypothesis that was not proved. Here, we use the higher accumulation WAIS Divide ice core, where the ice-air age shift is one order of magnitude smaller, and therefore better constrained. Finally, we use an improved mathematical method to infer break points in the Antarctic temperature and atmospheric CO2 records. We find that, at the onset of the last deglaciation and the onset of the Bølling-Allerød period, the phasing between CO2 and Antarctic temperature is negligible within a range of 130 years. Then CO2 slightly leads by 200

  11. Peat Insulation Moderates the Sensitivity of Permafrost Carbon to Climate Warming in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Gaglioti, B.; Mann, D. H.; Farquharson, L. M.; Jones, B. M.; Wooller, M. J.; Baughman, C. A.; Groves, P.; Kunz, M.; Pohlman, J.; Wiles, G. C.; Reanier, R.

    2016-12-01

    Continued warming in the Arctic may cause permafrost to thaw and release large amounts of soil carbon (C) both downstream and into the atmosphere. Understanding how permafrost C responded to prehistoric warming events can tell us how sensitive this process is. We investigated how soil and permafrost C budgets responded to paleo-warming events over the last 40,000 years in Arctic Alaska. In this presentation we first describe paleoclimatic changes using oxygen isotope ratios in ancient willow wood, which is a proxy for air temperature and sea-ice-extent. We then quantify how much permafrost C was released from watersheds using radiocarbon (14C) age-offsets in lake sediment. Stepped-temperature 14C analysis constrains both the age and quality of discreet organic matter sources that were vulnerable to thaw. Results showed that during the relatively warm Bølling-Allerød period (B-A; 14,700-12,800 cal years ago) and Holocene Thermal Maximum (HTM; 11,700-8500 cal years ago), 14C age-offsets were 2-3x their modern levels, and up to 10x more ancient C was being released, indicating significant permafrost thaw in the surrounding watershed. Deep, Yedoma C from ice age deposits was vulnerable to thaw during the BA period, but not during the HTM warming. This enhanced release of ancient C during the BA and HTM was interrupted during the cold and dry Younger Dryas interval (YD; 12,800-11,700 cal years ago) when age-offsets were reduced. Even though recent air temperatures are comparable to those estimated for the warm HTM, age-offsets today are relatively low, and similar to the cold YD. This pattern suggests that the insulating peat layer that has accumulated in the region since the early Holocene is stabilizing permafrost C in the face of recent warming. To estimate the capacity of this peat-buffering feedback to protect permafrost from thaw, we compare these paleo-results with permafrost modeling simulations involving peat covers varying in thickness and moisture content.

  12. Dueling Deglacial Depth Transects: A Synthesis of Isotope Records from the South Atlantic and Pacific Oceans Provides Insight into Deglacial Ocean Circulation

    NASA Astrophysics Data System (ADS)

    Sikes, E. L.; Allen, K. A.; Lund, D. C.

    2016-12-01

    , early shallow to intermediate ventilation differed between the two basins and simultaneous deep ventilation occurred later in the deglaciation, coincident with the reinitiation of deep overturning circulation during the Bølling-Allerød.

  13. The influence of extreme seasonality on lake temperatures during Younger Dryas

    NASA Astrophysics Data System (ADS)

    Schenk, F.; Stranne, C.; Wohlfarth, B.

    2016-12-01

    The Younger Dryas cold reversal ( 12.9 to 11.7 kyr BP) is the last abrupt climate change event interrupting the warming of the late deglaciation right before the onset of the Holocene. The spatial pattern of the cooling event seen in proxy data is largely consistent with those of climate simulations and suggests that the Younger Dryas is linked to a significant slowdown of the Atlantic Meridional Overturning Circulation (AMOC). However, despite the strong ocean cooling of up to 6 K along the European coasts and a significant southward extension of sea-ice during the Younger Dryas, different climate simulations do not reproduce summer cooling over Europe as seen in July lake temperature reconstructions based on chironomids. Aquatic plants used as climate indicator species do in contrast not show such a strong cooling and are more in line with climate simulations. To investigate this discrepancy, we use two numerical lake models driven by high resolution climate model output for the Younger Dryas and the preceding warm period of the late Alleröd ( 13 kyr BP). First, we investigate to which extent simulated lake temperatures in summer still reflect atmospheric summer temperatures despite a strong increase in seasonality during Younger Dryas. Because the (paleo-)lake depths are usually not well known, we use the lake models to test their sensitivity to changes in seasonality as a function of depth. Second, we artificially change the temperatures used as forcing for the lake models to investigate how cold air temperatures would need to be to match the up to 5 K July cooling suggested by chironomids. The results show that more care needs to be taken about the location and (paleo-)lake depths when comparing lake temperatures with simulated air temperatures. The simulated atmospheric circulation patterns during summer appears to be rather insensitive to the Younger Dryas cooling owing to the dominance of high atmospheric pressure over the Euro-Atlantic region. This would

  14. Latest Pleistocene to Holocene hydroclimates from Lake Elsinore, California

    NASA Astrophysics Data System (ADS)

    Kirby, Matthew E.; Feakins, Sarah J.; Bonuso, Nicole; Fantozzi, Joanna M.; Hiner, Christine A.

    2013-09-01

    The hydroclimate of the southwestern United States (US) region changed abruptly during the latest Pleistocene as the continental ice sheets over North America retreated from their most southerly extent. To investigate the nature of this change, we present a new record from Lake Elsinore, located 36 km inland from the Pacific Ocean in Southern California and evaluate it in the context of records across the coastal and interior southwest United States, including northwest Mexico. The sediment core recovered from Lake Elsinore provides a continuous sequence with multi-decadal resolution spanning 19-9 ka BP. Sedimentological and geochemical analyses reveal hydrologic variability. In particular, sand and carbonate components indicate abrupt changes at the Oldest Dryas (OD), Bølling-Allerød (BA), and Younger Dryas (YD) transitions, consistent with the timing in Greenland. Hydrogen isotope analyses of the C28n-alkanoic acids from plant leaf waxes (δDwax) reveal a long term trend toward less negative values across 19-9 ka BP. δDwax values during the OD suggest a North Pacific moisture source for precipitation, consistent with the dipping westerlies hypothesis. We find no isotopic evidence for the North American Monsoon reaching as far west as Lake Elsinore; therefore, we infer that wet/dry changes in the coastal southwest were expressed through winter-season precipitation, consistent with modern climatology. Comparing Lake Elsinore to other southwest records (notably Cave of Bells and Fort Stanton) we find coincident timing of the major transitions (OD to BA, BA to YD) and hydrologic responses during the OD and BA. The hydrologic response, however, varied during the YD consistent with a dipole between the coastal and interior southwest. The coherent pattern of hydrologic responses across the interior southwest US and northwest Mexico during the OD (wet), the BA (drier), and YD (wet) follows changes in the Atlantic Meridional Overturning Circulation, presumably via its

  15. Pleistocene - Holocene Rainfall and Productivity Records in Alfonso Basin Baja California Sur

    NASA Astrophysics Data System (ADS)

    Martinez-Perez, V. D. R.; Gonzalez-Yajimovich, O.; Mejia-Pina, K. G.

    2014-12-01

    Northwesterly winds dominate the southern Gulf of California during most of the year and are associated with high primary productivity due to upwelling. The North American Monsoon causes the wind direction to reverse during the summer months and this brings humid and warms conditions to the region. This climatic temporal-variation generates alternate sedimentation and as a consequence laminated deposits of biogenic and terrigenous composition, preserved by the presence of an oxygen minimum zone. A 5.4 m long piston core (36N) was recovered from Cuenca Alfonso during the DIPAL IV cruise on May 2011. The core was sampled at 1 cm intervals to produce high-resolution proxy records of primary productivity (biogenic opal, total organic carbon and carbonate content) and rainfall (terrigenous content). The core spans from late Pleistocene to the present and it's the longest analyzed record for the basin for the above-mentioned proxies. In general, the proxies show a negative trend towards the present, suggesting a more productive basin and wetter climate in the past. During climatic events like the Bølling-Allerød and the Holocene climatic optimum (HCO) CaCO3 content decreased and opal content increased; suggesting the presence of stronger NW winds and nutrient-richer waters. In contrast, during the Younger Dryas and 8.2 Kyr events the opal content decrease and the CaCO3 increase. At 5.5 KyBP the negative trends in all components intensify, especially during the Medieval Warm Period (MWP). An exception to this occurs during the little ice Age (LIA) where the opal and CaCO3 increase. The organic carbon content increases at the end of the HCO and during the MWP, and decreases during the BA, YD, 8.2 Kyr and LIA. The terrigenous content follows the 24°N summer insolation trend, but shows an increase during warm events (BA, HCO and MWP), and can be attributed to migration of the average position of the Intertropical Convergence Zone driven by variations in solar insolation.

  16. What Happens when Sea Ice Retreats, Peatlands Form, and a Landbridge Drowns? A Molecular View of the Last Deglacial from the Pacific-Arctic Gateway

    NASA Astrophysics Data System (ADS)

    Kocis, J. J.; Petsch, S.; Castañeda, I. S.; Brigham-Grette, J.

    2014-12-01

    Arctic peatlands and thermokarst lakes (TK) are thought to play a significant role in changing atmospheric methane concentration (AMC) during the last deglacial. However, there is debate concerning timing of their initiation and extent they drove variations in AMC. Models show sea ice cover (SIC) and sea surface temperatures (SSTs) can also play a significant role. Yet, changes in peatland/TK lake areal extent in response to those dynamics as continental shelves were submerged are often not considered. To examine such connections, we report on molecular proxies in marine records that reveal change in terrestrial organic matter (TOM) export, SIC, and SSTs as sea levels rose during the last 18 ka in the Pacific-Arctic Gateway. Here, TOM input to the ocean was tracked by measuring the flux of branched glycerol dialkyl glycerol tetraethers, n-alkyl lipids, and pentacyclic triterpenoids. SIC and SSTs were reconstructed using modern calibrations of highly branched isoprenoid alkene abundances in surface sediments from the Bering and Chukchi Seas. SSTs were also reconstructed based on the relative abundance of isoprenoid glycerol dialkyl glycerol tetraethers. Our sediment records reveal increased flux of TOM coincides with peatland/TK lake initiation, reduced SIC (~20%), and warmer SSTs (~4°C) as AMC increased during the Bølling-Allerød (BA). Terrestrial flux dramatically reduced as SIC increased (~50%) and SSTs cooled as AMC fell during the Younger Dryas. Most notably, TOM export rapidly rebounds as AMC abruptly rose throughout the Holocene Thermal Maximum (HTM), when SSTs warmed by ~3°C and SIC diminished and peatland areal extent increased. Using multi-proxy evidence in combination with a simple model that accounts for submergence of peatland/TK lake area, we estimate that the exposed Beringian shelf emitted an amount of CH4 comparable to previously reported peatland emissions in Alaska during the BA and HTM. The GDGT-based methane index (MI) was <0.3 throughout

  17. Paleoclimate and paleoceanographic reconstruction in the southern Iberian Mediterranean and Atlantic margins across the Younger Dryas event

    NASA Astrophysics Data System (ADS)

    Rodrigo-Gámiz, Marta; Martínez-Ruiz, Francisca

    2017-04-01

    The Alboran Sea basin in the Mediterranean and the Gulf of Cadiz in the Atlantic have provided excellent paleoarchives for reconstructing past climate variability in southern Iberian regions. Particularly interesting has been the study of the paleoclimate evolution of abrupt climate events from the Last Glacial Maximum (LGM) to the onset of the Holocene such as the Younger Dryas (YD). A diverse range of geochemical proxies, integrating inorganic and organic, has been used for paleoclimate reconstructions in these regions. Elemental concentrations and elemental ratios have been used for determining detrital inputs and bottom water oxygen conditions while organic molecular biomarkers as algal and archaea derived lipids have been used for estimating sea surface temperature (SST). Al-ratios mirroring eolian input, such as Zr/Al and Si/Al ratios, record enhanced dust input at the end of the LGM, during the last Heinrich event (H1) and at the onset of the YD in the Alboran Sea. For this latest interval, these ratios suggest an initial dry phase followed by a progressive aridity decrease throughout the YD. In the Gulf of Cadiz, these variations are not similarly recorded, probably due to less sensitive open ocean records in comparison to the restricted nature of the Alboran Sea basin. Selected redox proxies, Fe/Al and Mn/Al ratios, show peaks of oxidation fronts during the LGM and the H1 in the Alboran Sea and during the Bölling-Alleröd and the onset of the Holocene in the Gulf of Cadiz, derived from variations in ventilation and oxygen conditions that differ in the Mediterranean and Atlantic regions. SST records have also showed remarkable differences between both basins with minima temperature estimated values during the YD of ca. 12°C in the Alboran Sea and ca. 18°C in the Gulf of Cadiz, according to the freshening of the Atlantic jet along the Alboran basin. In general, a different paleoclimate and oceanographic evolution with a different YD response is recorded

  18. Paleoceanography of the Gulf of Alaska during the past 15,000 years: results from diatoms, silicoflagellates, and geochemistry

    USGS Publications Warehouse

    Barron, John A.; Bukry, David; Dean, Walter E.; Addison, Jason A.; Finney, Bruce

    2009-01-01

    High-resolution records of diatoms, silicoflagellates, and geochemistry covering the past 15,000 years were studied in three cores from the Gulf of Alaska (GOA). Core EW0408-85JC in an oceanic setting on the Kayak Slope displays a paleoceanographic record similar to that at several locations on the California margin during deglaciation. Biologic productivity as reconstructed using geochemical and microfossil proxies increased abruptly during the Bølling–Alleröd (Bø–Al) warm interval (14.7–12.9 cal ka), declined during the Younger Dryas (YD) cold interval (12.9 to 11.7 cal kyr BP), and rose again during the earliest Holocene. At this site, the record after ~ 11 cal kyr BP is dominated by oceanic diatoms and silicoflagellates, with geochemical proxies displaying more subtle variation. Cores EW0408-66JC in the Yakobi Sea Valley near Cross Sound and EW0408-11JC in the Gulf of Esquibel contain an expanded, composite record along the southeast Alaskan margin. Core 66JC contains a detailed record of the Bø–Al and YD. Diatoms and silicoflagellates indicate that coastal upwelling and biosiliceous productivity were strong during the Bø–Al but declined during the YD. Sea ice-related diatoms increased in abundance during the YD, indicating cooler, but less productive waters. The glacial to biogenic marine sediment transition in core 11JC occurs at 1280 cmbsf (centimeters below sea floor), probably representing rising sea level and deglaciation early in the Bø–Al. Freshwater and sea-ice related diatoms are common in the lower part of the core (Bø–Al and YD), but upwelling-related diatoms and silicoflagellates quickly increased in relative abundance up-core, dominating the record of the past 11,000 years. Low oxygen conditions in the bottom water as reconstructed using geochemical proxies (U and Mo concentration) were most intense between ~ 6.5 and 2.8 cal kyr BP, the beginning of which is coincident with increases in abundance of upwelling-related diatoms

  19. Timing of last deglaciation in the Cantabrian Mountains (Iberian Peninsula; North Atlantic Region) based on in situ-produced 10Be exposure dating

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; Domínguez-Cuesta, María José; Rinterknecht, Vincent; Pallàs, Raimon; Aumaître, Georges; Bourlès, Didier L.; Keddadouche, Karim; Aster Team

    2017-09-01

    The Last Glacial Termination led to major changes in ice sheet coverage that disrupted global patterns of atmosphere and ocean circulation. Paleoclimate records from Iberia suggest that westerly episodes played a key role in driving heterogeneous climate in the North Atlantic Region. We used 10Be Cosmic Ray Exposure (CRE) dating to explore the glacier response of small mountain glaciers (ca. 5 km2) that developed on the northern slope of the Cantabrian Mountains (Iberian Peninsula), an area directly under the influence of the Atlantic westerly winds. We analyzed twenty boulders from three moraines and one rock glacier arranged as a recessional sequence preserved between 1150 and 1540 m above sea level (a.s.l.) in the Monasterio valley (Redes Natural Park). Results complement previous chronologic data based on radiocarbon and optically stimulated luminescence from the Monasterio valley, which suggest a local Glacial Maximum (local GM) prior to 33 ka BP and a long-standing glacier advance at 24 ka coeval to the global Last Glacial Maximum (LGM). Resultant 10Be CRE ages suggest a progressive retreat and thinning of the Monasterio glacier over the time interval 18.1-16.7 ka. This response is coeval with the Heinrich Stadial 1, an extremely cold and dry climate episode initiated by a weakening of the Atlantic Meridional Overturning Circulation (AMOC). Glacier recession continued through the Bølling/Allerød period as indicate the minimum exposure ages obtained from a cirque moraine and a rock glacier nested within this moraine, which yielded ages of 14.0 and 13.0 ka, respectively. Together, they suggest that the Monasterio glacier experienced a gradual transition from glacier to rock glacier activity as the AMOC started to strengthen again. Glacial evidence ascribable to the Younger Dryas cooling was not dated in the Monasterio valley, but might have occurred at higher elevations than evidence dated in this work. The evolution of former glaciers documented in the

  20. Record of methane emissions from the Arctic during the last Deglaciation

    NASA Astrophysics Data System (ADS)

    Panieri, Giuliana; Consolaro, Chiara; James, Rachael; Westbrook, Graham; Rasmussen, Tine; Mienert, Jürgen

    2014-05-01

    The methane hydrates of the Arctic represent potentially significant carbon resources that are sensitive to climate change. Methane hydrate provinces are widespread in the Arctic, but their stability and longevity through time, and the significance of their contribution to the global carbon budget, is still poorly understood. It is, therefore, critical to resolve the frequency of methane (CH4) seafloor emissions through time, in relation to past climate change with a special focus on periods of climate warming. The values of δ13C in benthic foraminifera have been measured in two cores, one collected from an area of active methane venting and one from an inactive area on the Vestnesa Ridge (NW Svalbard continental margin), in order to reconstruct the local history of methane emissions over the past 16,000 years BP. The chronostratigraphic framework of the cores has been derived from biostratigraphic analysis and AMS 14C dates. While foraminifera from some intervals have δ13C within the normal marine range (0 to -1), several intervals are characterized by much lower δ13C, as low as -17.4o in the active core and as low as -4.37o in the inactive core. These intervals are interpreted to record the incorporation of 13C-depleted carbon in the presence of methane emissions at the seafloor during biomineralization of the carbonate foraminiferal tests and subsequent secondary mineralization. The longest of these 'methane emission events' (MEE) coincides with the start of the warm Bølling-Allerød Interstadial (GI-1 in the Greenland ice core record). The lack of correlation between the values of δ13C and δ18O, however, appears to preclude warming of bottom waters as the principal control on methane release. Rather, it seems likely that methane release is related to changes in gas migration pathways, or other geological processes still under debate. Details on the CAGE research plan and organization can be found on www.cage.uit.no to foster opportunities for cross

  1. Prevention and control of catheter-associated urinary tract infections - implementation of the recommendations of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) in nursing homes for the elderly in Frankfurt am Main, Germany.

    PubMed

    Heudorf, Ursel; Gasteyer, Stefanie; Müller, Maria; Samoiski, Yvonne; Serra, Nicole; Westphal, Tim

    2016-01-01

    Ziel: Nicht nur in Krankenhäusern, auch in Altenpflegeheimen zählen Harnwegsinfektionen zu den häufigsten nosokomialen Infektionen der Bewohner. Das größte Risiko für eine Harnwegsinfektion sind Harnwegskatheter. In den Empfehlungen „Infektionsprävention in Heimen“ (2005) und „Prävention und Kontrolle Katheter-assoziierter Harnwegsinfektionen“ (2015) hat die Kommission für Krankenhaushygiene und Infektionsprävention (KRINKO) geeignete Präventionsmaßnahmen empfohlen. Im Jahr 2015 wurde in allen Frankfurter Altenpflegeheimen die Umsetzung dieser KRINKO-Empfehlungen untersucht.Methode: Alle 40 Altenpflegeheime wurden anhand einer auf Grundlage dieser Empfehlungen erstellten Checkliste überprüft. Neben allgemeinen Arbeitsanweisungen, Indikationen etc. wurden bei allen Bewohnern mit Katheter Alter, Geschlecht, die Liegedauer des Katheters und Harnwegsinfekte aktuell und in den letzten 6 Monaten erfragt.Ergebnisse: In 35 (87,5%) der Altenpflegeheime lagen Arbeitsanweisungen zum Umgang mit Harnwegskathetern vor. Die Indikation für einen Harnwegskatheter wird von Ärzten gestellt, das Legen des Katheters wird häufig an den Pflegedienst delegiert; in aller Regel werden Silikonkatheter gelegt. In drei Viertel der Heime wurden feste Intervalle zum Katheterwechsel von 4–6 Wochen angegeben. Am jeweiligen Erhebungstag waren 7,3% der Bewohner mit einem Katheter versorgt. 3,6% (4,2%) von ihnen hatten am Erhebungstag, insgesamt 28% (28,9%) von ihnen in den vorangegangenen 6 Monaten eine Harnwegsinfektion (Prävalenz der Antibiotikatherapie in Klammern). Ciprofloxacin wurde am häufigsten eingesetzt, gefolgt von Cefuroxim und Cotrimoxazol.Diskussion: Bei der aktuellen Erhebung waren weniger Altenpflegeheimbewohner in Frankfurt mit Harnwegskathetern versorgt als in früheren Jahren und die Rate der Harnwegsinfektionen war niedrig. Dies spricht für einen zunehmend zurückhaltenderen und offenbar weitgehend sachgerechten Umgang mit Harnwegskathetern. Auch die

  2. Cosmogenic 10Be Chronologies of Moraines and Glacially Scoured Bedrock in the Teton Range, with Implications for Paleoclimatic Events and Tectonic Activity

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Pierce, K. L.; Thackray, G. D.; Finkel, R. C.; Zimmerman, S. R. H.

    2015-12-01

    Last Glacial Maximum, but well before the start of the Bølling-Allerød warm interval. This expanded chronology provides a refined understanding of the timing of late Pleistocene glacier events in the central Rocky Mountains, and allows a more critical examination of climatic influences on glacier fluctuations in this region.

  3. A new Greenland ice core chronology for the last glacial termination

    NASA Astrophysics Data System (ADS)

    Rasmussen, S. O.; Andersen, K. K.; Svensson, A. M.; Steffensen, J. P.; Vinther, B. M.; Clausen, H. B.; Siggaard-Andersen, M.-L.; Johnsen, S. J.; Larsen, L. B.; Dahl-Jensen, D.; Bigler, M.; RöThlisberger, R.; Fischer, H.; Goto-Azuma, K.; Hansson, M. E.; Ruth, U.

    2006-03-01

    We present a new common stratigraphic timescale for the North Greenland Ice Core Project (NGRIP) and GRIP ice cores. The timescale covers the period 7.9-14.8 kyr before present and includes the Bølling, Allerød, Younger Dryas, and early Holocene periods. We use a combination of new and previously published data, the most prominent being new high-resolution Continuous Flow Analysis (CFA) impurity records from the NGRIP ice core. Several investigators have identified and counted annual layers using a multiparameter approach, and the maximum counting error is estimated to be up to 2% in the Holocene part and about 3% for the older parts. These counting error estimates reflect the number of annual layers that were hard to interpret, but not a possible bias in the set of rules used for annual layer identification. As the GRIP and NGRIP ice cores are not optimal for annual layer counting in the middle and late Holocene, the timescale is tied to a prominent volcanic event inside the 8.2 kyr cold event, recently dated in the DYE-3 ice core to 8236 years before A. D. 2000 (b2k) with a maximum counting error of 47 years. The new timescale dates the Younger Dryas-Preboreal transition to 11,703 b2k, which is 100-150 years older than according to the present GRIP and NGRIP timescales. The age of the transition matches the GISP2 timescale within a few years, but viewed over the entire 7.9-14.8 kyr section, there are significant differences between the new timescale and the GISP2 timescale. The transition from the glacial into the Bølling interstadial is dated to 14,692 b2k. The presented timescale is a part of a new Greenland ice core chronology common to the DYE-3, GRIP, and NGRIP ice cores, named the Greenland Ice Core Chronology 2005 (GICC05). The annual layer thicknesses are observed to be log-normally distributed with good approximation, and compared to the early Holocene, the mean accumulation rates in the Younger Dryas and Bølling periods are found to be 47 ± 2% and

  4. Deglacial and Holocene sea-ice variability north of Iceland and response to ocean circulation changes

    NASA Astrophysics Data System (ADS)

    Xiao, Xiaotong; Zhao, Meixun; Knudsen, Karen Luise; Sha, Longbin; Eiríksson, Jón; Gudmundsdóttir, Esther; Jiang, Hui; Guo, Zhigang

    2017-08-01

    Sea-ice conditions on the North Icelandic shelf constitute a key component for the study of the climatic gradients between the Arctic and the North Atlantic Oceans at the Polar Front between the cold East Icelandic Current delivering Polar surface water and the relatively warm Irminger Current derived from the North Atlantic Current. The variability of sea ice contributes to heat reduction (albedo) and gas exchange between the ocean and the atmosphere, and further affects the deep-water formation. However, lack of long-term and high-resolution sea-ice records in the region hinders the understanding of palaeoceanographic change mechanisms during the last glacial-interglacial cycle. Here, we present a sea-ice record back to 15 ka (cal. ka BP) based on the sea-ice biomarker IP25, phytoplankton biomarker brassicasterol and terrestrial biomarker long-chain n-alkanols in piston core MD99-2272 from the North Icelandic shelf. During the Bølling/Allerød (14.7-12.9 ka), the North Icelandic shelf was characterized by extensive spring sea-ice cover linked to reduced flow of warm Atlantic Water and dominant Polar water influence, as well as strong meltwater input in the area. This pattern showed an anti-phase relationship with the ice-free/less ice conditions in marginal areas of the eastern Nordic Seas, where the Atlantic Water inflow was strong, and contributed to an enhanced deep-water formation. Prolonged sea-ice cover with occasional occurrence of seasonal sea ice prevailed during the Younger Dryas (12.9-11.7 ka) interrupted by a brief interval of enhanced Irminger Current and deposition of the Vedde Ash, as opposed to abruptly increased sea-ice conditions in the eastern Nordic Seas. The seasonal sea ice decreased gradually from the Younger Dryas to the onset of the Holocene corresponding to increasing insolation. Ice-free conditions and sea surface warming were observed for the Early Holocene, followed by expansion of sea ice during the Mid-Holocene.

  5. El Niño, Climate and Societies

    NASA Astrophysics Data System (ADS)

    Haug, G. H.; Peterson, L. C.; Yancheva, G.

    2010-03-01

    One tropical climate archive with an appropriate memory for the societal most relevant sub-centennial to sub-decadal scale climate swings is the anoxic Cariaco Basin off northern Venezuela. Millimeter to micrometer-scale geochemical data in the laminated sediments of the Cariaco Basin have been interpreted to reflect variations in the hydrological cycle and the mean annual position of the Intertropical Convergence Zone (ITCZ) over tropical South America during the past millennia. These data with decadal to (sub)annual resolution show that the Terminal Collapse of the Classic Maya civilization occurred during an extended dry period. In detail, the Cariaco record reveals evidence for three separate droughts during the period of Maya downfall, each lasting a decade or less. These data suggest that climate change was potentially one immediate cause of the demise of Mayan civilization, with a century-scale decline in rainfall putting a general strain on resources and several multi-year events of more intense drought pushing Mayan society over the edge. An archive of comparable quality and resolution are sediments of lake Huguang Maar in coastal southeast China. The titanium content and redox-sensitive magnetic properties record the strength of winter monsoon winds at subdecadal resolution over the last 16 thousand years. The record indicates a stronger winter monsoon prior to the Bølling Allerød warming, during the Younger Dryas, and during the middle and late Holocene, when cave stalagmite oxygen isotope data indicate a weaker summer monsoon. The anti-correlation between winter and summer monsoon strength is best explained by migrations in the ITCZ that occurred simultaneously in central America and Africa. Drought associated with southward ITCZ migration may have played a role in the termination of several Chinese dynasties. A remarkable similarity of ITCZ migration in east Asia and the Americas from 700 to 900 AD raises the possibility that the coincident declines

  6. Unexpected spontaneous ignition of Late Glacial sediments from the palaeolake Wukenfurche (NE Germany)

    NASA Astrophysics Data System (ADS)

    Dräger, Nadine; Brademann, Brian; Theuerkauf, Martin; Wulf, Sabine; Tjallingii, Rik; Słowiński, Michał; Schlaak, Norbert; Błaszkiewicz, Mirosław; Brauer, Achim

    2015-04-01

    A new finely laminated sediment archive has been recovered from the palaeolake Wukenfurche, NE Germany, comprising the last Glacial to Interglacial transition. The site is located within the Eberswalde ice-marginal valley and south of the terminal moraine that was formed during the Pomeranian phase of the Weichselian glaciation. Two sediment cores were obtained from the presently swampy area in July 2014. From these individual profiles a 14.7 m long continuous composite profile has been compiled by correlation of distinct marker layers. Glacial sand deposits covered by basal peat are found at the base of the cores. A visible volcanic ash layer 6 cm above the transition from basal peat into the overlaying finely laminated lake sediments corresponds most likely to the late Allerød Laacher See Tephra (LST). Preliminary counting on core photographs of the 3.5 m thick package of reddish and black alternating laminae above the LST yields a total of ca. 2500 layer couplets. Further micro-facies analyses on large-scale thin sections will be applied to test if these couplets are of annual origin (i.e. varves). Standard preparation for large-scale thin sections involves freeze-drying (for 48 hours) of 10 cm-long sediment slabs stored in aluminum boxes. Immediately after releasing the vacuum of the freeze-dryer chamber we observed an unexpected spontaneous combustion of the sediment from a particular interval of the profile. The exothermic combustion process lasted for approximately 10 to 20 minutes during which temperatures of up to 350°C have been measured with an infrared camera. Preliminary results suggest that oxidation of iron sulfides contributes to the observed reaction. To our knowledge this is the first time that such spontaneous combustion of lake sediments after freeze-drying has been observed. Details of the combustion process and sediment characteristics will be provided. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape

  7. Deglacial 14C plateau suites recalibrated by Suigetsu atmospheric 14C record - Revised 14C reservoir ages from three ocean basins corroborate extreme surface water variations

    NASA Astrophysics Data System (ADS)

    Sarnthein, M.; Balmer, S.; Grootes, P. M.

    2013-12-01

    Radiocarbon (14C) reservoir/ventilation ages (Δ14C) provide unique insights into the dynamics of ocean water masses over LGM and deglacial times. The 14C plateau-tuning technique enables us to derive both an absolute chronology for marine sediment records and a high-resolution record of changing Δ14C values for deglacial surface and deep waters (Sarnthein et al., 2007; AGU Monogr. 173, 175). We designate as 14C plateau a sediment section in the age-depth profile with several almost constant planktic 14C ages - variation less than ×100 to ×300 yr - which form a plateau-shaped scatter band that extends over ~5 to 50 and up to 200 cm in sediment cores with sedimentation rates of >10 cm/ky. Previously, a suite of >15 plateau boundary ages were calibrated to a joint reference record of U/Th-dated 14C time series measured on coral samples, the Cariaco sediment record, and speleothems (Fairbanks et al., 2005, QSR 24; Hughen et al., 2006, QSR 25; Beck et al., 2001, Science 292). We now used the varve-counted atmospheric 14C record of Lake Suigetsu (Ramsey et al., 2012, Science 338, 370) to recalibrate the boundary ages and average ages of 14C plateaus and apply the amended plateau-tuning technique to a dozen Δ14C records from the Atlantic and Indo-Pacific. Main results are: (1) The Suigetsu atmospheric 14C record reflects all 14C plateaus, their internal structures and relative length previously identified, but implies a rise in the average plateau age by <200 14C yr during the LGM, >700 yr at its end, and <200 yr in the Bølling-Allerød. (2) Based on different 14C ages of coeval atmospheric and planktic 14C plateaus surface water Δ14C may have temporarily dropped to an equivalent of 200 yr in low-latitude stratified waters, such as off northwestern South America, and in turn reached values corresponding to an age difference of >2500 14C yr in stratified subpolar regions and upwelled waters such as in the South China Sea, values that differ significantly from a

  8. Tectonics of the baikal rift deduced from volcanism and sedimentation: a review oriented to the Baikal and Hovsgol lake systems.

    PubMed

    Ivanov, Alexei V; Demonterova, Elena I

    2009-01-01

    Asia. All these tectonic and climatic events could (and actually did) influence the biota of Lake Baikal. The Hovsgol rift basin was shaped to its recent form between 5.5 and 0.4 Ma. However, freshwater Lake Hovsgol appeared only in the latest pre-Holocene time as a result of meltwater inflow and increase of atmospheric precipitations during the Bølling-Allerød warming. Prior to this, a significantly smaller, saline outflow-free precursor of Lake Hovsgol existed. It explains why two, now connected, lakes of similar water chemistry within similar climatic and tectonic conditions differ so much in their biodiversity.

  9. Renouvellement des eaux du fjord du Saguenay

    NASA Astrophysics Data System (ADS)

    Belzile, Melany

    variabilite saisonniere dans les profondeurs des evenements de renouvellement peuvent etre expliques par le cycle saisonnier de salinite des eaux presentes au seuil, qui est lui-meme influence par la saisonnalite de la circulation estuarienne du Saint-Laurent. Nous avons estime un temps typique de renouvellement du bassin interne de 2 mois, mais pouvant aller jusqu' a 6 mois maximum.

  10. Navigating the maze of requirements for obtaining approval of non-interventional studies (NIS) in the European Union.

    PubMed

    Ramirez, Isabelle

    2015-01-01

    Ziel: Dieser Artikel soll über die Komplexität und unerwartete regulatorische Anforderungen bei multinationalen und multizentrischen, nicht-interventionellen Studien (NIS) in der Europäischen Union aufklären.Methoden: Die Internetseiten der zuständigen nationalen Behörden, Ethikkommissionen (EK) und Datenschutzbehörden wurden konsultiert, um Vorschriften und Richtlinien zum Genehmigungsverfahren von NIS in den verschiedenen Mitgliedstaaten der EU zu finden.Ergebnis: Viele zusätzliche Hürden wurden identifiziert, die weder offengelegt noch deutlich in den jeweiligen Verordnungen/Richtlinien für NIS beschrieben waren. Obwohl die Genehmigung durch die nationale Behörde für NIS grundsätzlich nicht erforderlich ist, wird in vielen Ländern dennoch empfohlen die geplante NIS – vor dem EK-Antrag – der nationalen Behörde anzuzeigen, um die Bestätigung zu erhalten, dass die geplante NIS nicht in die Kategorie „interventionelle Studie“ fällt. Zudem ist in einigen Ländern eine Probandenversicherung erforderlich. In vielen Ländern, in denen multizentrische NIS geplant sind, bedarf es zusätzlich zur Zustimmung der zentralen Ethikkommission auch noch die zustimmende Bewertung aller lokalen Ethikkommissionen, denn ein zentrales EK-Gutachten wird nicht als ausreichend betrachtet. Die Anforderungen an EK-Dokumente und an Gebühren für die Einreichung variieren stark unter allen Mitgliedsstaaten. Zusätzliche Genehmigungen von den Datenschutzbehörden und Versicherungsgesellschaften sind in einigen Ländern einzuholen.Schlussfolgerung: Das Genehmigungsverfahren für multizentrische und multinationale NIS ist zeitaufwendig, vor allem wegen des Mangels an Transparenz und den unterschiedlichen regulatorischen Anforderungen der Mitgliedsstaaten. Die EU-Rechtsvorschriften zur Pharmakovigilanz und die neue EU-Verordnung Nr. 536/2014 über klinische Studien sind zwar ein Schritt nach vorn bei der Schaffung eines Rechtsrahmens für PASS (post-authorisation safety

  11. Productivity and sedimentary δ15N variability for the last 17,000 years along the northern Gulf of Alaska continental slope

    NASA Astrophysics Data System (ADS)

    Addison, Jason A.; Finney, Bruce P.; Dean, Walter E.; Davies, Maureen H.; Mix, Alan C.; Stoner, Joseph S.; Jaeger, John M.

    2012-03-01

    Biogenic opal, organic carbon, organic matter stable isotope, and trace metal data from a well-dated, high-resolution jumbo piston core (EW0408-85JC; 59° 33.3'N, 144° 9.21'W, 682 m water depth) recovered from the northern Gulf of Alaska continental slope reveal changes in productivity and nutrient utilization over the last 17,000 years. Maximum values of opal concentration (˜10%) occur during the deglacial Bølling-Allerød (B-A) interval and earliest Holocene (11.2 to 10.8 cal ka BP), moderate values (˜6%) occur during the Younger Dryas (13.0 to 11.2 cal ka BP) and Holocene, and minimum values (˜3.5%) occur during the Late Glacial Interval (LGI). When converted to opal mass accumulation rates, the highest values (˜5000 g cm-2 kyr-1) occur during the LGI prior to 16.7 cal ka BP, which points to a strong influence by LGI glacimarine sedimentation regimes. Similar patterns are also observed in total organic carbon and cadmium paleoproductivity proxies. Mid-Holocene peaks in the terrestrial organic matter fraction at 5.5, 4.7, 3.5, and 1.2 cal ka BP indicate periods of enhanced delivery of glaciomarine sediments by the Alaska Coastal Current. The B-A and earliest Holocene intervals are laminated, and enrichments of redox-sensitive elements suggest dysoxic-to-anoxic conditions in the water column. The laminations are also associated with mildly enriched sedimentary δ15N ratios, indicating a link between productivity, nitrogen cycle dynamics, and sedimentary anoxia. After applying a correction for terrestrial δ15N contributions based on end-member mixing models of terrestrial and marine organic matter, the resulting B-A marine δ15N (6.3 ± 0.4 ‰) ratios are consistent with either mild denitrification, or increased nitrate utilization. These findings can be explained by increased micronutrient (Fe) availability during episodes of rapid rising sea level that released iron from the previously subaerial coastal plain; iron input from enhanced terrestrial runoff

  12. High vs low latitude sequence of events over the last deglaciation using ice core isotopic proxies and an isotope-enabled climate model

    NASA Astrophysics Data System (ADS)

    Landais, Amaelle; Roche, Didier; Prié, Frédéric; Minster, Bénédicte; Masson-Delmotte, Valérie; Vinther, Bo; Capron, Emilie; Popp, Trevor; Rhodes, Rachael

    2017-04-01

    The last deglaciation is recorded with annual resolution in the ice d18O records from Greenland ice cores. In addition to long term change associated with orbital variations, the last deglaciation is associated with abrupt changes in the northern hemisphere with the sequence of Heinrich 1, Bølling-Allerød and Younger Dryas. The combination of orbital and millennial scale variability during deglaciations has also been recorded in many other continental and marine records. Still, the underlying mechanism linking orbital and millennial changes over deglaciation is not fully understood. Limitations come from the exact description of the sequence of events between external forcing, high and low latitudes climate and environmental changes. In order to progress on this issue, our study combines low and high latitudes climate proxies measured in ice cores as well as transient modeling simulations of the last deglaciation run with an intermediate complexity model equipped with water isotopes (iLOVECLIM). New high resolution measurements of 17O-excess and d-excess from the NorthGRIP ice core covering the last deglaciation are used to decipher the local from the distant effect on the water isotopic records measured in Greenland ice cores. These second order parameters are indeed sensitive to climatic conditions at the oceanic evaporative regions and to the trajectories of the water mass toward the polar precipitation sites. These new measurements clearly highlight a decoupling between Greenland and lower latitudes over the time period corresponding to Heinrich event 1. This time period is recorded as a two phase sequence in the 17O-excess and d-excess records. This two phase sequence is confirmed by atmospheric d18O (d18Oatm) data from ice cores covering the same time period. d18O atm is a global atmospheric signal measured on the air trapped in ice cores interpreted as a proxy for low latitude water cycle that can be compared to calcite d18O records from East Asian caves

  13. Profil clinique et bactériologique des infections néonatales bactériennes à l'Hôpital Laquintinie de Douala, Cameroun

    PubMed Central

    Kemeze, Sandrine; Moudze, Béatrice; Chiabi, Andreas; Eposse, Charlotte; Kaya, Alexis; Mbangue, Madeleine; Guifo, Odette; Kago, Innocent

    2016-01-01

    Introduction L'Organisation Mondiale de la Santé a estimé la survenue globale de décès néonatal à 2,8 millions en 2015, dont 47,6% étaient dues aux infections. Ces infections peuvent survenir chez un nouveau-né de 0 à un mois de vie, pouvant aller jusqu’à 3 mois. Méthodes C'est une étude prospective allant du 1er mars au 30 juin 2015 au Service de néonatologie de l'Hôpital Laquintinie de Douala. Etaient inclus tout nouveau-né symptomatique avec ou sans critère anamnestique et tout nouveau-né asymptomatique, présentant au moins un risque infectieux et ayant au moins une culture positive ou une anomalie de la numération formule sanguine ou une protéine C réactive positive. Résultats Des 310 nouveau-nés admis, 300 ont été retenus pour infection néonatale, soit une incidence de 96,8%. Nous avons réalisé 104 cultures dont 25 positives, soit une incidence de l'infection néonatale confirmée de 24%. Les facteurs associés à l'infection étaient la prématurité inexpliquée <35 semaines d'aménorrhée(45,1%) et la réanimation néonatale (34,8%). La fièvre (56%) et les troubles neurologiques (48,8%) étaient les manifestations cliniques les plus fréquentes. Les Gram négatifs étaient les germes les plus fréquents (56%). L'imipenème (95%) et l'amikacine (66,7%) étaient les antibiotiques les plusefficaces. L’évolution était favorable dans 66,4% des cas et le taux de décès était de 33,6%. Conclusion Cette étude révèle une forte prévalence de l'infection dans cet hôpital. L’écologie bactérienne est dominée par les Gram négatifs, on note une importante résistance aux antibiotiques usuels et une mortalité assez élevée. PMID:27222688

  14. Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Jones, Benjamin M.; Wiles, Gregory C.; Groves, Pamela; Kunz, Michael L.; Baughman, Carson A.; Reanier, Richard E.

    2017-08-01

    Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500-7500 calibrated 14C years before present; 13.5-7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owc values from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9-11.7 ka), and the Holocene Thermal Maximum (11.7-9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by sea ice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are similar

  15. Reconstructing lake evaporation history and the isotopic composition of precipitation by a coupled δ18O-δ2H biomarker approach

    NASA Astrophysics Data System (ADS)

    Hepp, Johannes; Tuthorn, Mario; Zech, Roland; Mügler, Ines; Schlütz, Frank; Zech, Wolfgang; Zech, Michael

    2015-10-01

    Over the past decades, δ18O and δ2H analyses of lacustrine sediments became an invaluable tool in paleohydrology and paleolimnology for reconstructing the isotopic composition of past lake water and precipitation. However, based on δ18O or δ2H records alone, it can be challenging to distinguish between changes of the precipitation signal and changes caused by evaporation. Here we propose a coupled δ18O-δ2H biomarker approach that provides the possibility to disentangle between these two factors. The isotopic composition of long chain n-alkanes (n-C25, n-C27, n-C29, n-C31) were analyzed in order to establish a 16 ka Late Glacial and Holocene δ2H record for the sediment archive of Lake Panch Pokhari in High Himalaya, Nepal. The δ2Hn-alkane record generally corroborates a previously established δ18Osugar record reporting on high values characterizing the deglaciation and the Older and the Younger Dryas, and low values characterizing the Bølling and the Allerød periods. Since the investigated n-alkane and sugar biomarkers are considered to be primarily of aquatic origin, they were used to reconstruct the isotopic composition of lake water. The reconstructed deuterium excess of lake water ranges from +57‰ to -85‰ and is shown to serve as proxy for the evaporation history of Lake Panch Pokhari. Lake desiccation during the deglaciation, the Older Dryas and the Younger Dryas is affirmed by a multi-proxy approach using the Hydrogen Index (HI) and the carbon to nitrogen ratio (C/N) as additional proxies for lake sediment organic matter mineralization. Furthermore, the coupled δ18O and δ2H approach allows disentangling the lake water isotopic enrichment from variations of the isotopic composition of precipitation. The reconstructed 16 ka δ18Oprecipitation record of Lake Panch Pokhari is well in agreement with the δ18O records of Chinese speleothems and presumably reflects the Indian Summer Monsoon variability.

  16. Productivity and sedimentary δ15N variability for the last 17,000 years along the northern Gulf of Alaska continental slope

    USGS Publications Warehouse

    Addison, Jason A.; Finney, Bruce P.; Dean, Walter E.; Davies, Maureen H.; Mix, Alan C.; Stoner, Joseph S.; Jaeger, John M.

    2012-01-01

    Biogenic opal, organic carbon, organic matter stable isotope, and trace metal data from a well-dated, high-resolution jumbo piston core (EW0408–85JC; 59° 33.3′N, 144° 9.21′W, 682 m water depth) recovered from the northern Gulf of Alaska continental slope reveal changes in productivity and nutrient utilization over the last 17,000 years. Maximum values of opal concentration (∼10%) occur during the deglacial Bølling-Allerød (B-A) interval and earliest Holocene (11.2 to 10.8 cal ka BP), moderate values (∼6%) occur during the Younger Dryas (13.0 to 11.2 cal ka BP) and Holocene, and minimum values (∼3.5%) occur during the Late Glacial Interval (LGI). When converted to opal mass accumulation rates, the highest values (∼5000 g cm−2 kyr−1) occur during the LGI prior to 16.7 cal ka BP, which points to a strong influence by LGI glacimarine sedimentation regimes. Similar patterns are also observed in total organic carbon and cadmium paleoproductivity proxies. Mid-Holocene peaks in the terrestrial organic matter fraction at 5.5, 4.7, 3.5, and 1.2 cal ka BP indicate periods of enhanced delivery of glaciomarine sediments by the Alaska Coastal Current. The B-A and earliest Holocene intervals are laminated, and enrichments of redox-sensitive elements suggest dysoxic-to-anoxic conditions in the water column. The laminations are also associated with mildly enriched sedimentary δ15N ratios, indicating a link between productivity, nitrogen cycle dynamics, and sedimentary anoxia. After applying a correction for terrestrial δ15N contributions based on end-member mixing models of terrestrial and marine organic matter, the resulting B-A marine δ15N (6.3 ± 0.4 ‰) ratios are consistent with either mild denitrification, or increased nitrate utilization. These findings can be explained by increased micronutrient (Fe) availability during episodes of rapid rising sea level that released iron from the previously subaerial coastal plain; iron input from enhanced

  17. A 26,600 yr record of climate and vegetation from Rice Lake in the Eel River drainage of the northern California Coast Range

    NASA Astrophysics Data System (ADS)

    Heusser, L. E.

    2014-12-01

    Rice Lake, (40'41" N; 123'30" W, 1109 m elev.) lies in the transition zone of the precipitation dipole in the western United States, which is reflected by the present vegetation - a mosaic of mesic northern mixed hardwood-evergreen forests (Quercus spp., Pinus spp., Calocedrus/Juniperus) and more arid southern oak foothill woodlands (Quercus spp.) that borders the westernmost edge of coastal redwoods (Sequoia sempervirens) forest. The site, which lies on the active Lake Mountain fault zone, is now a large (~15 ha) sagpond that dries in summer. Between ~26,600 yr - ~15,000 yr, a permanent lake with aquatic vegetation (Isoetes) occupied the core site. Montane conifer forests, with pine (Pinus, spp.), mountain hemlock (Tsuga mertensiana), spruce (Picea spp), and western hemlock (T. heterophylla) covered the region. Climatic parameters of modern montane coniferous forest and the continued presence of aquatic vegetation (Isoetes) suggest higher precipitation and lower temperatures during the last glacial. Charcoal (fire event frequency) was minimal. Rapid oscillations of oak, the riparian alder (Alnus), pine, Cupressaceae (Juniperus, Calocedrus), Douglas fir (Pseudotsuga menzeii), and fir (Abies) characterize the deglacial, and reflect rapid changes in precipitation and temperatures, e.g, Bølling-Allerød warming and Younger Dryas cooling. Between ~15,000 yr and ~13,000 yr, aquatic vegetation of the lake abruptly decreased. Expansion of oak, tanoak (Lithocarpus), shrubs (cf. Ceanothus) and decline of pine and montane conifers, along with the development of marshes with Typha and Cyperaceae on the former lakebed, imply early Holocene warming and decreasing precipitation. This is supported by an increase in charcoal, which is attributed to forest fires. Between ~5,000 yr - ~6,000 yr, a short interval of increased precipitation (inferred from a peak in alder and decrease in Cupressaceae) initiates the development of modern mixed hardwood-evergreen forest. Correlative data

  18. Sequence and chronology of the Cuerpo de Hombre paleoglacier (Iberian Central System) during the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Carrasco, Rosa M.; Pedraza, Javier; Domínguez-Villar, David; Willenbring, Jane K.; Villa, Javier

    2015-12-01

    marked by the indicators and its chronology confirm that the whole of the Late Glacial sequence identified in Cuerpo de Hombre can be correlated with the traditionally established in northern Europe (climatic periods or stadials and interstadials): Oldest Dryas-Bølling-Older Dryas-Allerød-Younger Dryas. The minimum ages obtained for the cold periods (stadials) in this sequence in the Cuerpo de Hombre paleoglacier are (respectively): ∼17.5 ka, ∼13.9 ka and ∼11.1 ka. This complete sequence of the Late Glacial Period, including the stadials Older and Younger Dryas, had not been previously identified in any of the paleoglaciers in the Iberian Central System.

  19. Two Late Pleistocene climate-driven incision/aggradation rhythms in the middle Dnieper River basin, west-central Russian Plain

    NASA Astrophysics Data System (ADS)

    Panin, Andrei; Adamiec, Grzegorz; Buylaert, Jan-Pieter; Matlakhova, Ekaterina; Moska, Piotr; Novenko, Elena

    2017-06-01

    warm climate phases - late MIS 3, post-LGM warming including the Bølling-Allerød interstadial. Anomalously large size of the preserved river palaeochannels prove that the post-LGM incision phase was induced by a climatically forced large increase of water runoff. Considerable increase of water discharges is considered the most probably cause for the late MIS 4 incision phase also. Therefore river incision seems to have been governed rather by changing water runoff that oscillated in phase shift with the thermal regime.

  20. Late Quaternary vegetation and climate dynamics at the northern limit of the East Asian summer monsoon and its regional and global-scale controls

    NASA Astrophysics Data System (ADS)

    Leipe, Christian; Nakagawa, Takeshi; Gotanda, Katsuya; Müller, Stefanie; Tarasov, Pavel E.

    2015-05-01

    A late Quaternary pollen record from northern Sakhalin Island (51.34°N, 142.14°E, 15 m a.s.l.) spanning the last 43.7 ka was used to reconstruct regional climate dynamics and vegetation distribution by using the modern analogue technique (MAT). The long-term trends of the reconstructed mean annual temperature (TANN) and precipitation (PANN), and total tree cover are generally in line with key palaeoclimate records from the North Atlantic region and the Asian monsoon domain. TANN largely follows the fluctuations in solar summer insolation at 55°N. During Marine Isotope Stage (MIS) 3, TANN and PANN were on average 0.2 °C and 700 mm, respectively, thus very similar to late Holocene/modern conditions. Full glacial climate deterioration (TANN = -3.3 °C, PANN = 550 mm) was relatively weak as suggested by the MAT-inferred average climate parameters and tree cover densities. However, error ranges of the climate reconstructions during this interval are relatively large and the last glacial environments in northern Sakhalin could be much colder and drier than suggested by the weighted average values. An anti-phase relationship between mean temperature of the coldest (MTCO) and warmest (MTWA) month is documented during the last glacial period, i.e. MIS 2 and 3, suggesting more continental climate due to sea levels that were lower than present. Warmest and wettest climate conditions have prevailed since the end of the last glaciation with an optimum (TANN = 1.5 °C, PANN = 800 mm) in the middle Holocene interval (ca 8.7-5.2 cal. ka BP). This lags behind the solar insolation peak during the early Holocene. We propose that this is due to continuous Holocene sea level transgression and regional influence of the Tsushima Warm Current, which reached maximum intensity during the middle Holocene. Several short-term climate oscillations are suggested by our reconstruction results and correspond to Northern Hemisphere Heinrich and Dansgaard-Oeschger events, the Bølling-Aller

  1. Annually resolved lake and shallow marine sediment records of global climate change of the past 16,000 years

    NASA Astrophysics Data System (ADS)

    Haug, G. H.; Brauer, A.; Yancheva, G.; Dulski, P.; Negendank, J. F.; Peterson, L. C.; Sigman, D. M.

    2007-12-01

    In the sediments of lake Huguang Maar in coastal southeast China, the titanium content and redox-sensitive magnetic properties record the strength of winter monsoon winds at subdecadal to annual resolution over the last 16 thousand years. The record indicates a stronger winter monsoon prior to the Bølling-Allerød warming, during the Younger Dryas, and during the middle and late Holocene, when cave stalagmite oxygen isotope data indicate a weaker summer monsoon. The anti-correlation between winter and summer monsoon strength is best explained by migrations in the ITCZ that occurred simultaneously in central America and Africa. Drought associated with southward ITCZ migration may have played a role in the termination of several Chinese dynasties. A remarkable similarity of ITCZ migration in east Asia and the Americas from 700 to 900 AD raises the possibility that the coincident declines of the important Tang Dynasty in China and the Classic Maya in Central America were catalyzed by the same ITCZ migrations. The mechanisms behind these decadal-scale ITCZ-monsoon swings can be further exoplored at major climate transitions such as the onset of Younger Dryas cooling at ~12.7 ka, one of the most abrupt climate changes observed in ice core, lake and marine records in the North Atlantic realm and much of the Northern Hemisphere. Annually laminated lake sediments ideally record the dynamics of abrupt climate changes since seasonal deposition immediately responds to climate and varve counts accurately estimate the time of change. We report new sub-annual geochemical and varve microfacies data from a lake in Western Germany, which provides one of the best-dated records currently available for this climate transition, which we compare to the Cariaco Basin and Lake Huguang Maar records. The Lake Meerfelder Maar record indicates an abrupt increase in storminess, occurring from one year to the next at 12,678 ka BP, coincident with other observed climate changes in the region

  2. A pollen-based environmental reconstruction in Lake Hazar (Eastern Turkey) during the Late Pleistocene-Holocene: Example for the Eastern Mediterranean Realm

    NASA Astrophysics Data System (ADS)

    Biltekin, Demet; Kadir Eris, Kürsad; Namik Cagatay, Memet; Nagihan Arslan, Tugce; Akcer On, Sena; Acar, Dursun

    2016-04-01

    Eastern Mediterranean realm historically is a melting area for ancient civilisations. This region has been therefore anthropogenically influenced since the Late Pleistocene. The understanding the processes between vegetation and climate, pollen analysis is a significant proxy in the investigation of past climate, vegetation records and the human influence on the environment. In this research, we carried out the environmental changes during the Late Pleistocene-Holocene using multi-proxy analysis (palynology, XRF core scanner, magnetic susceptibility and TOC) in the sediment core obtained from 54.39 m depth on the northern shelf of Lake Hazar using a percussion piston corer. Lake Hazar (38° 31' N-39° 25' E) is located at ca. 1255 m above sea level, 22 km south-east of Elazıǧ city in eastern Turkey in the south-east Taurus Mountains. It is an oligotrophic, alkaline soda and a tectonic lake being situated on East Anatolian Fault Zone (EAFZ). The chronology of the sediment core has been determined using AMS radiocarbon method. We present the first pollen record from the core sediments in Lake Hazar, providing insight into multi-millennial scale climatic changes over the last ~15 14C ka BP. In the piston core, the Bølling/Allerød period is associated by the presence of Pistacia reflecting milder winter conditions with high biological productivity. Onset of the Younger Dryas (YD) period is marked by increase in herbaceous plants and lake level lowering that can also be documented by high magnetic susceptibility and Ca/Ti ratio. The spread of deciduous Quercus at the beginning of Holocene can be attributed to significant forestation due to a high humidity that was presumably sufficient for the establishment of oak forest. An increase in Quercus continued in most of the early and middle Holocene. The 3rd millenium crisis is strongly characterized by an increase in herbal elements, and a decline in Quercus, pointing to dry climatic conditions. The most striking

  3. Millennial-scale Changes of Surface and Bottom Water Conditions in the Northwest Pacific during the Last Deglacial Period

    NASA Astrophysics Data System (ADS)

    Khim, B. K.; Kim, S.; Ikehara, K.; Itaki, T.; Shibahara, A.; Yamamoto, M.

    2015-12-01

    The last deglacial changes of the water column conditions in the Northwest Pacific were reconstructed using geochemical and isotope proxies (biogenic opal, CaCO3, total organic carbon (TOC), redox sensitive elements, bulk nitrogen isotopes (δ15N), and silicon isotopes (δ30Sidiatom) of diatom frustules) along with the published data (alkenone temperatures and benthic foraminiferal faunas) at core GH02-1030 recovered from the slope off Tokachi. Age model for core GH02-1030 was determined using both planktonic and benthic foraminiferal AMC 14C dates (Ikehara et al., 2006). Alkenone sea surface temperature (SST) shows that biogenic opal productivity was related to the degree of spring-summer mixed layer depth (MLD). Biogenic opal and TOC contents change almost in parallel. δ30Sidiatom values are high (~+1‰) during the Holocene and low (~-0.4‰) during the last glacial maximum. During the Bølling-Allerød (BA) and the Pre-Boreal (PB), silicic acid utilization represented by δ30Sidiatom increased when the biogenic opal productivity and export TOC productivity are high under shoaling of spring-summer MLD. The BA and the PB intervals contain laminated sediment layers, which are characterized by increases of CaCO3 contents, bulk δ15N values, and redox element concentrations (Mo/Al, Cd/Al, and U/Al). All these indicate low dissolved oxygen content of the bottom water during the BA and PB periods, which is supported by the good preservation of dysoxic benthic foraminifera. In addition, compared to the Holocene biogenic opal productivity and related silicic acid utilization, the high δ15N values during the BA and the PB seemed to be attributed more to denitrification through the water column rather than complete utilization of nitrate. Another distinct feature based on benthic foraminiferal assemblage, CaCO3 contents and redox element concentrations is that the dissolved oxygen content in bottom water was lower during the BA than the PB. Because biogenic opal

  4. The response of the Okhotsk Sea environment to the orbital-millennium global climate changes during the Last Glacial Maximum, deglaciation and Holocene

    NASA Astrophysics Data System (ADS)

    Gorbarenko, Sergey A.; Artemova, Antonina V.; Goldberg, Evgeniy L.; Vasilenko, Yuriy P.

    2014-05-01

    Reconstruction of regional climate and the Okhotsk Sea (OS) environment for the Last Glacial Maximum (LGM), deglaciation and Holocene was performed on the basis of high-resolution records of ice rafted debris (IRD), СаСО3, opal, total organic carbon (TOС), biogenic Ba (Ba_bio) and redox sensitive element (Mn, Mo) content, and diatom and pollen results of four cores that form a north-southern transect. Age models of the studied cores were earlier established by AMS 14C data, oxygen-isotope chronostratigraphy and tephrochronology. According to received results, since 25 ka the regional climate and OS environmental conditions have changed synchronously with LGM condition, cold Heinrich event 1, Bølling-Allerød (BA) warming, Younger Dryas (YD) cooling and Pre-Boreal (PB) warming recorded in the Greenland ice core, North Atlantic sediment, and China cave stalagmites. Calculation of IRD MAR in sediment of north-south transect cores indicates an increase of sea ice formation several times in the glacial OS as compared to the Late Holocene. Accompanying ice formation, increased brine rejection and the larger potential density of surface water at the north shelf due to a drop of glacial East Asia summer monsoon precipitation and Amur River run off, led to strong enhancement of the role of the OS in glacial North Pacific Intermediate Water (NPIW) formation. The remarkable increase in OS productivity during BA and PB warming was probably related with significant reorganisation of the North Pacific deep water ventilation and nutrient input into the NPIW and OS Intermediate Water (OSIW). Seven Holocene OS millennial cold events based on the elevated values of the detrended IRD stack record over the IRD broad trend in the sediments of the studied cores have occurred synchronously with cold events recorded in the North Atlantic, Greenland ice cores and China cave stalagmites after 9 ka. Diatom production in the OS was mostly controlled by sea ice cover changes and surface

  5. Late Quaternary Sea-Ice Variability at the North Icelandic Shelf (Sub-Arctic): Reconstruction from Biomarkers

    NASA Astrophysics Data System (ADS)

    Xiao, X.; Zhao, M.; Jiang, H.; Eiriksson, J.; Guo, Z.

    2015-12-01

    Sea ice, prevailing in the polar region and characterized by distinct seasonal and interannual variability, plays a pivotal role in Earth's climate system (Thomas and Dieckmann, 2010). In order to understand processes controlling the recent dramatic reduction in Arctic sea-ice cover, it is essential to determine temporal changes in sea-ice occurrence and its natural variability in the past. The North Icelandic shelf, bordering a marginal area of the Arctic Ocean, is located at the present-day boundary between the cold polar currents and warm Atlantic water masses, very sensitive to the changes in sea-ice cover, ice sheet and oceanic circulation patterns (Knudsen and Eiriksson, 2002). All these processes have been recorded in the marine shelf-sediment cores. We determined the concentrations of sea-ice diatom-derived biomarker "IP25" (monoene highly-branched isoprenoid with 25 carbon atom; Belt et al., 2007), phytoplankton-derived biomarkers (brassicasterol and dinosterol) and terrigenous biomarkers (campesterol and ß-sitosterol) in a sediment core from the North Icelandic shelf to reconstruct the Late Quaternary sea-ice conditions and related surface-water processes. The sea-ice cover reached its maximum during the cold period (i.e., Last Glacial Maximum and Younger dryas), while an open ocean environment existed during less severe periods (e.g. Bølling-Allerød and 8.2 ka event) in the study area. The biomarker records from this sediment core give insights into the variability in sea ice and circulation patterns as well as primary productivity in the Arctic marginal area during the Late Quaternary. References Belt, S.T., Massé, G., Rowland, S.J., Poulin, M., Michel, C., LeBlanc, B., 2007. A novel chemical fossil of palaeo sea ice: IP25. Org. Geochem. 38, 16-27. Knudsen, K.L. and Eiriksson, J., 2002. Application of tephrochronology to the timing and correlation of palaeoceanographic events recorded in Holocene and Late Glacial shelf sediments off North Iceland

  6. Paleoceanographic Synthesis of Abrupt Sea Ice and Temperature Changes in the Subarctic Pacific and Marginal Seas through the Past 20,000 Years

    NASA Astrophysics Data System (ADS)

    Davis, C. V.; Myhre, S. E.; Borreggine, M. J.; Caissie, B.; Praetorius, S. K.; Katsuki, K.; Moffitt, R.; Deutsch, C.

    2016-12-01

    Substantial efforts have been concentrated over the last half-century on the paleoceaongraphy of the North Pacific. Here we synthesize existing paleoceanographic records of temperature and sea ice extent across the Subarctic Pacific and marginal seas, including the Bering Sea, Alaskan Gyre, and Sea of Okhotsk. We focus on 26 cores collected between 1988-2009 and from 36-60°N with well-developed chronologies to reconstruct the abrupt climate transitions of the last 20,000 years, including the abrupt warming events of the Northern Hemisphere glacial terminations (Termination IA, IB). Specifically, we utilize foraminiferal (δ18O & Mg/Ca) and coccolithophore (Uk'37) derived proxies for near-surface temperature reconstructions, and diatom assemblages and indicator species to reconstruct sea ice extent and marginal sea ice environments. Sea-ice associated diatom species peaked in compositional dominance mid-way through the deglaciation from the mid-Bølling ( 14.5 ka) to the early Allerød ( 13.8 ka). Even at the lowest latitude site (36°01.4'N, core MD01-2421), sea-ice affiliated diatoms peak in the Last Glacial Maximum ( 18 ka) and the early Bølling ( 13.8 ka). Biogeochemical proxies for late-spring to late-summer temperatures across the Subarctic Pacific indicate surface ocean warming between the Last Glacial Maximum ( 6°) and the Holocene (12-18°C) at all sites. However, region-specific, latitudinal differences in the timing and magnitude of warming and millennial scale deglacial oscillations are evident. For example, in the Western Subarctic Pacific the higher-latitude sites show lower amplitude warming through the deglaciation, but greater expression of ephemeral mid-Bølling cooling than lower latitude sites. Sea ice and temperature are important primary metrics for understanding the rate and magnitude of surface ocean response to abrupt warming events, including the response of subpolar environments to warming in the modern ocean.

  7. Electronic acquisition of OSCE performance using tablets.

    PubMed

    Hochlehnert, Achim; Schultz, Jobst-Hendrik; Möltner, Andreas; Tımbıl, Sevgi; Brass, Konstantin; Jünger, Jana

    2015-01-01

    Hintergrund: OSCE-Prüfungen sind oft mit einem erheblichen Material- und Organisationsaufwand verbunden, da die Leistungserfassung üblicherweise auf Papier durchgeführt wird. Eine elektronisch unterstützte Durchführung stellt hierzu eine Alternative dar, mit der der Verbrauch materieller Ressourcen reduziert werden kann. Insbesondere erscheint hier der Einsatz von Tablets sinnvoll, da diese zudem leicht zu transportieren sind und damit flexibel eingesetzt werden können. Zielsetzung: Die Nutzerakzeptanz der Verwendung von Tablets bei OSCE-Prüfungen wurde bislang allerdings nur wenig untersucht. Ziel dieser Studie war daher eine Evaluation Tablet-basierter OSCE-Prüfungen aus Sicht der Benutzer (Prüfer) und der geprüften Studierenden.Methodik: Bei zwei OSCE-Prüfungen des Faches Innere Medizin der Universität Heidelberg wurde die Nutzerakzeptanz einer Tablet-basierten Durchführung (Zufriedenheit mit der Funktionalität) und die subjektive Anstrengung aus Sicht der Prüfer untersucht. Hierzu wurden standardisierte Fragebögen und halbstandardisierte Interviews eingesetzt (Vollerfassung aller teilnehmenden Prüfer). Zudem wurde bei einer der Prüfungen die subjektive Bewertung dieser Prüfungsvariante an einer Stichprobe teilnehmender Studierender mittels halbstandardisierter Interviews erhoben.Ergebnisse: Die Prüfer waren mit der Tablet-Prüfungsvariante insgesamt sehr zufrieden. Die subjektive Anstrengung der Bedienung der Tablets wurde im Mittel als „kaum anstrengend“ empfunden. In den Interviews wurden insbesondere die einfache Handhabung und die geringe Fehleranfälligkeit von den Prüfern als Vorteile dieser Prüfungsvariante genannt. In der Befragung der geprüften Studierenden zeigte sich ebenfalls eine Akzeptanz der Tablet-Prüfungsvariante. Diskussion: Insgesamt hat sich gezeigt, dass der Einsatz von Tablets in OSCE-Prüfungen sowohl von Prüfern als auch Studierenden gut angenommen wird. Es wird erwartet, dass diese Prüfungsvariante auch

  8. Spatial Pattern of Rapid Climatic Oscillations and Vegetation Response During the Last Deglaciation in Northeastern North America

    NASA Astrophysics Data System (ADS)

    Yu, Z.

    2003-12-01

    Large and abrupt climatic oscillations occurred during the last deglaciation evident from ice, lacustrine and marine records in different regions. Stable isotopes retrieved from these records could provide a common proxy in correlating the records and detecting temporal and spatial patterns. The emerging pattern is critical in understanding the nature and forcing mechanisms of climate changes. Here I provide new isotopic and pollen results from the Mid-Atlantic region of USA to expand the existing late-glacial records from the Great Lakes region to the Atlantic Seaboard. White Lake, a marl lake in NW New Jersey, provides high-resolution sedimentary records since ca. 15,000 cal yr BP (15 ka). The chronology of late-glacial and early Holocene period was controlled by 6 AMS 14C dates on terrestrial macrofossils. Oxygen isotopes of marl samples (contain >90% carbonates) from this period vary between -8 and -4 permil (VPDB) and show multiple oscillations at millennial and centennial scales, including the Younger Dryas (YD) with ca. 3 permil shifts in δ 18O at 12.6-11.3 ka and three cold events of 1-2 permil shifts during the Bølling-Allerød (B-A) period at 14.3-12.6 ka. Pollen diagram from this site shows strong similarity with previously published pollen records from this region, with the YD event having high boreal taxa (Alnus, Abies, Betula) after establishment of a mixed deciduous-coniferous forest containing Quercus, Fraxinus and Ostrya/Carpinus. A plateau-like B-A period is similar to some (Ammersee, Germany; Cariaco Basin, Caribbean) but not other records (ice cores form Greenland Summit; Crawford Lake, Ontario) around the Atlantic Ocean, suggesting that a strong climate gradient might have existed then. Vegetation shows different sensitivity in responding to the YD at sites along a transect from New Jersey, through western New York, to southern Ontario, which was probably caused by a combination of species migration/availability, location of then ecotones

  9. Millennial-Scale Climate Variability during the Last 28 cal. ka BP in the Tyrrhenian Sea (central Sector of Mediterranean Sea)

    NASA Astrophysics Data System (ADS)

    Amore, F. Ornella; Palumbo, Eliana; Elderfield, Henry; Perugia, Carmen; Emanuele, Dario; Petrillo, Zaccaria

    2014-05-01

    High resolution reconstructions of coccolithophore assemblages and plankton carbon and oxygen stable isotope data from Ocean Drilling Project (ODP) Hole 974D have been studied to investigate climate variability in the Tyrrhenian Sea (Western Mediterranean) during the last 28 cal. ka BP. The main climatic signal is showed by coccolithophore assemblages and isotopic records at glacial/interglacial timescale. Through the application of statistical analyses, a possible role of half and fourth precession cycles was hypothesised, more likely linked to the influence of the Equator insolation on central sector of Western Mediterranean circulation. The occurrence of abrupt coolings, more likely connected to Northern Hemisphere global climatic changes, was hypothesised also in the Tyrrhenian Sea during the Last Glacial (LG) and the Holocene, highlighted by the occurrence of the subpolar species Coccolithus pelagicus pelagicus. The events of the LG occurred in correspondence of the Dansgaard/Oeschger (D/O) stadial at 28 cal. ka BP and Heinrich event 2. The Holocene events were quite synchronous with several Bond Cycles and Rapid Climate Changes. In addition, marine warm phases, coincident with the D/O interstadial 2 and the Bølling-Allerød interval, were recognised at ODP Hole 974D by increases of warm species. Furthermore, during the Younger Dryas, oxygen stable isotope record indicates the occurrence of a cooling while coccolithophore assemblages testify increased nutrient conditions, highlighted by the group of small Gephyrocapsa. During the transition to the Holocene a latitudinal warming was observed, through the comparison of available data from coccolithophore assemblages of other sites of the Tyrrhenian Sea (Sbaffi et al., 2001; Buccheri et al., 2002; Amore et al., 2004). The latitudinal warming moved northward versus the central part of the basin, reaching the maximum amplitude in correspondence of Tyrrhenian Holocene Climatic Optimum (Buccheri et al., 2002). Other

  10. Constraining the vertical movement of OMZ waters in Santa Barbara Basin for the past 15 ky

    NASA Astrophysics Data System (ADS)

    Myhre, S.; Hill, T. M.; Kennett, J.; Behl, R. J.; Ohkushi, K.

    2010-12-01

    Here we constrain the upper vertical boundary of the California Margin Oxygen Minimum Zone (OMZ) through the past 15ky, with focus on the Bölling-Alleröd (B/A) warm interval. The depth range of the OMZ along the California Margin is responsive to events of rapid warming, however the spatial extent and underlying mechanism for the synchrony is not clear. We construct a depth transect within Santa Barbara Basin (34° 15’N, 119° 45’W) using a core from 418m water depth (MV0811-15JC), and previously investigated cores from 481m (MD02-2504) and 570m (MD02-2503) water depths. Isotope stratigraphy and radiocarbon dating (planktonic calcite) were used to generate a working age model. Foraminiferal and micro-invertebrate assemblages and preserved sediment laminations constrain the movement of low-oxygen water. Oxygen isotopic values at all three sites record similar surface water δ18O shifts over the deglaciation (1.5‰ magnitude; based upon planktonic foraminifera G. bulloides) and a smaller but analogous δ18O shift is seen in benthic records (0.5‰ magnitude; based on benthic foraminifera U. peregrina). All three cores exhibit a ~1‰ decrease in G. bulloides (planktonic) δ13C values across the deglaciation, and then a return to more stable values of ~-0.75‰ during the Holocene. All three cores show an increase in δ13C values of benthic foraminfera U. peregrina at the onset of the Holocene (~1‰ positive shift); in the future, these records may be coupled with total organic carbon analyses to understand the role of productivity and terrestrial carbon export in influencing OMZ strength. During the B/A lamination records indicate strong hypoxia below 480m; however laminations are not preserved at 418m. In contrast, benthic foraminiferal assemblages show similar responses (albeit more muted the in shallowest site) to low-oxygen concentrations during the B/A, with species N. stella, B. tumida, and B. tenuata dominating at all three sites. At the 418m site, the

  11. Insights from a synthesis of old and new climate-proxy data from the Pyramid and Winnemucca lake basins for the period 48 to 11.5 cal ka

    USGS Publications Warehouse

    Benson, Larry; Smoot, J.P.; Lund, S.P.; Mensing, S.A.; Foit, F.F.; Rye, R.O.

    2013-01-01

    A synthesis of old and new paleoclimatic data from the Pyramid and Winnemucca lake basins indicates that, between 48.0 and 11.5·103 calibrated years BP (hereafter ka), the climate of the western Great Basin was, to a degree, linked with the climate of the North Atlantic. Paleomagnetic secular variation (PSV) records from Pyramid Lake core PLC08-1 were tied to the GISP2 ice-core record via PSV matches to North Atlantic sediment cores whose isotopic and(or) carbonate records could be linked to the GISP2 δ18O record. Relatively dry intervals in the western Great Basin were associated with cold Heinrich events and relatively wet intervals were associated with warm Dansgaard-Oeschger (DO) oscillations. The association of western Great Basin dry events with North Atlantic cold events (and vice versa) switched sometime after the Laurentide Ice Sheet (LIS) reached its maximum extent. For example, the Lahontan highstand, which culminated at 15.5 ka, and a period of elevated lake level between 13.1 and 11.7 ka were associated with cold North Atlantic conditions, the latter period with the Youngest Dryas event. Relatively dry periods were associated with the Bølling and Allerød warm events. A large percentage of the LIS may have been lost to the North Atlantic during Heinrich events 1 and 2 and may have resulted in the repositioning of the Polar Jet Stream over North America. The Trego Hot Springs, Wono, Carson Sink, and Marble Bluff tephras found in core PLC08-1 have been assigned GISP2 calendar ages of respectively, 29.9, 33.7, 34.1, and 43.2 ka. Given its unique trace-element chemistry, the Carson Sink Bed is the same as Wilson Creek Ash 15 in the Mono Lake Basin. This implies that the Mono Lake magnetic excursion occurred at approximately 34 ka and it is not the Laschamp magnetic excursion. The entrance of the First Americans into the northern Great Basin is dated to approximately 14.4 ka, a time when the climate was relatively dry. Evidence for human occupation of

  12. Millennial environmental variability on Shirshov Ridge, Bering Sea, during the penultimate and last glacial cycles

    NASA Astrophysics Data System (ADS)

    Ivanova, E.; Ovsepyan, E.; Murdmaa, I.; Max, L.; Riethdorf, J.; Nuernberg, D.; Tiedemann, R.; Alekseeva, T.

    2011-12-01

    planktic and benthic foraminiferal abundances early in the deglaciation, Bølling/Allerød and early Holocene. A few intervals with high content of G. bulloides are also found within both glaciations. The earliest maximum in the total planktic foraminiferal abundance, just after the last glacial maximum, was not previously known in the region, and is likely associated with early reorganization of the Bering Sea circulation and a corresponding increase in the surface bioproductivity. Our new data on coarse fraction distribution point to millennial variations in the IRD supply mainly occurring in cold stages and with a few short-term events during warm stages. Interestingly, IRD gravel grains are very scarce over the LGM whereas they are common during MIS 3 and MIS 6. The diverse petrology and shape of the gravel grains suggest both icebergs and sea ice as the transporting agents.

  13. Paleolimnological reconstruction of environmental variability during the Late Pleistocene and Holocene in the south-east Baltic region

    NASA Astrophysics Data System (ADS)

    Kublitskiy, Iurii; Subetto, Dmitriy; Druzhinina, Olga; Kulkova, Marianna; Arslanov, Khikmatula

    2016-04-01

    The main goal of our research is the high-resolution reconstruction of environmental and climatic changes in SE Baltic region since the Last Glacial Maximum by palaeolimnological data. The 6 objects - lakes and peat-bogs, were studied since 2009 in the Kaliningrad region, Russian Federation. According to palaeolimnological studies of bottom sediments of the Kamyshovoe Lake (N 54°22,6`; E22°42,8`, 189 m a.s.l.), located in the Vishtynets Highland, the south-east part of Kaliningrad district, the environmental and climatic changes after the late glacial have been reconstructed. At that moment the radiocarbon and loss-on-ignition (LOI) data, geochemistry and diatom analysis for the whole sediment core, and pollen analyze for the bottom part of the core have been completed. According to the pollen data the Alleröd interstadial starts at 13 200 cal. yrs BP and is marked by the rising of birch and pine pollen. The transition to the Younger Dryas around 12 700 cal. yrs BP corresponds with the development of patches of shrublands in which light-demanding species, such as juniper, flourished and communities of steppe herbs. The late Preboreal is marked by the appearance of Populus and an increase of the role of grasses in the vegetation cover 11 300-11 100 cal. yrs BP (Druzinina et al., 2015). The Holocene climatic zones have been identified by LOI and geochemistry analyses. The Boreal period started about 10 200 cal. yrs BP, Atlantic around 9100 cal. yrs BP, Subboreal 5800 cal. yrs BP, and Subatlantic 3200 cal. yrs BP (Kublitskiy et al., 2015). During the conference the new palaeolimnological data of environmental variability during the late Pleistocene and Holocene in SE Baltic region will be presented. Acknowledgements The investigations have been granted by the Russian Fund for Basic Research (12-05-33013, 13-05-41457, 15-35-50721). References Druzhinina, O., Subetto, D., Stančikaitė, M., Vaikutienė, G., Kublitsky, J., Arslanov, Kh., 2015. Sediment record from the

  14. Evolution of Chaka Salt Lake in NW China in response to climatic change during the Latest Pleistocene Holocene

    NASA Astrophysics Data System (ADS)

    Xingqi, Liu; Dong, Hailiang; Rech, Jason A.; Matsumoto, Ryo; Bo, Yang; Yongbo, Wang

    2008-04-01

    The Late Pleistocene and Holocene hydrologic balance of Chaka Salt Lake in the eastern Qaidam Basin of NW China was studied based on the analysis of lithostratigraphy, mineralogy, total organic carbon, and total nitrogen from a 9.0-m long sediment core. An age-depth model for the lake sediments is based on eight accelerator mass spectrometry (AMS) 14C measurements of organic matter and a 1700-year radiocarbon reservoir correction. The Pitzer model was used to calculate the sequence of minerals precipitated as a function of salinity assuming that the initial lake water was recharged from adjacent rivers and springs. Lake salinity values were derived from a good match between the calculated and observed mineral sequences. Our multi-proxy based hydrologic reconstruction of Chaka Lake indicates that it was a clastic-dominated, freshwater lake between 17.2 and 11.4 cal ka BP, which may have resulted from the input of glacial water into the lake at that time. During the Lateglacial and Holocene, a warm climatic regime predominated between 13.9 and 12.7 cal ka BP and then a cold climatic regime prevailed between 12.7 and 11.4 cal ka BP. These warm and cold periods correlate with the Bølling-Allerød and Younger Dryas events in the region. Beginning at 11.4 cal ka BP, a saline or hypersaline lake developed, which may have resulted from increased summer insolation and temperatures. These conditions persisted throughout the Holocene. Modeling indicates that lake salinity fluctuated between 66 and 223 ppt from 11.4 to 7.2 cal ka BP and then increased to 223-322 ppt between 7.2 and 6.0 cal ka BP, when most regions of China recorded high moisture availability (i.e. the so-called "mid-Holocene Climatic Optimum"). Lake salinity decreased to 66-223 ppt during a short time period between 6.0 and 5.3 cal ka BP, possibly caused by reduced evaporation. Subsequently, salinity values rapidly increased to 223-322 ppt between 5.3 and 5.2 cal ka BP and a hypersaline lake with a salinity

  15. Sensitivity of permafrost carbon release to past climate change in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Gaglioti, B.; Mann, D. H.; Wooller, M. J.; Jones, B. M.; Farquharson, L. M.; Pohlman, J.

    2015-12-01

    Warming may cause arctic permafrost to thaw and release large stores of carbon (C) downstream and into the atmosphere. Documenting how permafrost-C release responded to prehistoric warming events can help determine its sensitivity to future climate change. We did this by first quantifying past climate change in Arctic Alaska over the last 15,000 years using oxygen isotope ratios in ancient wood cellulose, which is a proxy for summer temperatures and moisture sources. We then used radiocarbon (14C) age-offsets in lake sediment to determine how much permafrost C was being released over this same time period. A 14C age-offset is the difference between the true age of deposition determined by the 14C ages of delicate, terrestrial plant remains and the age of bulk sediment from the same stratigraphic layer. This bulk sediment contains ancient C derived from permafrost in the lake's watershed. Shifts in the magnitude of the age-offset over time provide a proxy for changes in the relative amount of permafrost C being released. Today, the age-offset in our study lake is 2,000 calibrated years before present (cal yr BP), which is the lowest it has been over the last 15,000 years. During the warmer-than-present, Bølling-Allerød period (BA; 14,700-12,900 cal yr BP), and the Holocene Thermal Maximum (HTM; 11,700-8,500 cal yr BP), the age offset reached 4,000-6,000 cal yr, indicating large inputs of ancient C to the lake via permafrost thaw. This enhanced input of ancient C was interrupted during the cold and dry Younger Dryas interval (YD; 12,900-11,700 cal yr BP). Interestingly, age-offsets during the YD were similar to today's, suggesting that the insulating peat layer now covering much of the LOP watershed is stabilizing permafrost C in the face of recent warming. However, this buffering capacity has a limit, and judging by the heightened influx of permafrost C during the HTM, this limit may be reached if summer temperatures warm a further 2-3°C. Temperature and

  16. Post-glacial variability of sea ice cover, river run-off and biological production in the western Laptev Sea (Arctic Ocean) - A high-resolution biomarker study

    NASA Astrophysics Data System (ADS)

    Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.

    2016-07-01

    Multi-proxy biomarker measurements were applied on two sediment cores (PS51/154, PS51/159) to reconstruct sea ice cover (IP25), biological production (brassicasterol, dinosterol) and river run-off (campesterol, β-sitosterol) in the western Laptev Sea over the last ∼17 ka with unprecedented temporal resolution. The absence of IP25 from 17.2 to 15.5 ka, in combination with minimum concentration of phytoplankton biomarkers, suggests that the western Laptev Sea shelf was mostly covered with permanent sea ice. Very minor river run-off and restricted biological production occurred during this cold interval. From ∼16 ka until 7.5 ka, a long-term decrease of terrigenous (riverine) organic matter and a coeval increase of marine organic matter reflect the gradual establishment of fully marine conditions in the western Laptev Sea, caused by the onset of the post-glacial transgression. Intensified river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7-12.9 ka). Prominent peaks of the DIP25 Index coinciding with maximum abundances of subpolar foraminifers, are interpreted as pulses of Atlantic water inflow on the western Laptev Sea shelf. After the warm period, a sudden return to severe sea ice conditions with strongest ice-coverage between 11.9 and 11 ka coincided with the Younger Dryas (12.9-11.6 ka). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (reflected in a distinct drop in terrigenous and phytoplankton biomarkers) was detected. During the last 7 ka, the sea ice proxies reflect a cooling of the Laptev Sea spring/summer season. This cooling trend was superimposed by a short-term variability in sea ice coverage, probably representing Bond cycles (1500 ± 500 ka) that are related to solar activity changes. Hence, atmospheric circulation changes were apparently able to affect the sea ice conditions on the Laptev Sea shelf under modern sea level

  17. Spatio-temporal evolution of the Choisille River (southern Parisian Basin, France) during the Weichselian and the Holocene as a record of climate trend and human activity in north-western Europe

    NASA Astrophysics Data System (ADS)

    Morin, Eymeric; Macaire, Jean-Jacques; Hinschberger, Florent; Gay-Ovéjéro, Isabelle; Rodrigues, Stéphane; Bakyono, Jean-Paul; Visset, Lionel

    2011-02-01

    The morpho-sedimentary evolution of the Choisille floodplain (lowland river, catchment: 288 km 2), a tributary of the River Loire in the south-western Parisian Basin, was studied through 61 core drillings along eight transects and a geophysical survey located in four stretches of the river: stretches A and B correspond to two sub-catchments, and stretches C and D are in the main valley. Sixty 14C and four OSL datings were obtained, and sediments were analysed on seven reference cores. Eight phases of evolution differing markedly from the evolution of more northern areas in the Parisian Basin and north-western Europe were identified from spatio-temporal distribution of nine lithological facies. The deepest incision phase (1) occurred during the first part of the Weichselian, followed by the deposition of a gravelly-sandy unit (phase 2) during the Middle Pleniglacial, which was deeply incised (phase 3), probably during the Bölling. From the Allerød up to the last third of the Boreal (phase 4), sedimentation was continuously dominated by peaty deposits, with no evidence of either increased hydraulic energy during the Younger Dryas, or of incision during the LateGlacial-Holocene transition. This trend seems to reflect the specificity of the south-western Parisian Basin climate from the Late Weichselian up to the end of the Boreal, due to the influence of the Atlantic Ocean, compared to more northern areas where the climate was more continental. The downstream incision trend during the last third of the Boreal up to the Subatlantic (phases 5 and 6) indicates a sharp increase in precipitation and vegetation cover; the lack of peaty sediments, widespread in north-western Europe, and also of precipitated carbonates frequent in the Parisian Basin, seems to be due to local physiographic characteristics. The main part of the sediment filling, which is principally silty and retrograde, began during the Subatlantic (phase 7 and 8) as a result of deforestation of the plateaux

  18. Sea ice cover variability and river run-off in the western Laptev Sea (Arctic Ocean) since the last 18 ka

    NASA Astrophysics Data System (ADS)

    Hörner, T.; Stein, R.; Fahl, K.; Birgel, D.

    2015-12-01

    Multi-proxy biomarker measurements were performed on two sediment cores (PS51/154, PS51/159) with the objective reconstructing sea ice cover (IP25, brassicasterol, dinosterol) and river-runoff (campesterol, β-sitosterol) in the western Laptev Sea over the last 18 ka with unprecedented temporal resolution. The sea ice cover varies distinctly during the whole time period. The absence of IP25 during 18 and 16 ka indicate that the western Laptev Sea was mostly covered with permanent sea ice (pack ice). However, a period of temporary break-up of the permanent ice coverage occurred at c. 17.2 ka (presence of IP25). Very little river-runoff occurred during this interval. Decreasing terrigenous (riverine) input and synchronous increase of marine produced organic matter around 16 ka until 7.5 ka indicate the gradual establishment of a marine environment in the western Laptev Sea related to the onset of the post-glacial transgression of the shelf. Strong river run-off and reduced sea ice cover characterized the time interval between 15.2 and 12.9 ka, including the Bølling/Allerød warm period (14.7 - 12.9 ka). Moreover, the DIP25 Index (ratio of HBI-dienes and IP25) might document the presence of Atlantic derived water at the western Laptev Sea shelf area. A sudden return to severe sea ice conditions occurred during the Younger Dryas (12.9 - 11.6 ka). This abrupt climate change was observed in the whole circum-Arctic realm (Chukchi Sea, Bering Sea, Fram Strait and Laptev Sea). At the onset of the Younger Dryas, a distinct alteration of the ecosystem (deep drop in terrigenous and phytoplankton biomarkers) may document the entry of a giant freshwater plume, possibly relating to the Lake Agassiz outburst at 13 ka. IP25 concentrations increase and higher values of the PIP25 Index during the last 7 ka reflect a cooling of the Laptev Sea spring season. Moreover, a short-term variability of c. 1.5 thousand years occurred during the last 12 ka, most probably following Bond Cycles.

  19. Bottom-water oxygenation and environmental change in Santa Monica Basin, southern California during the last 22 kyr

    DOE PAGES

    Balestra, Barbara; Krupinksi, Nadine Quintana; Erhoina, Tzvetina; ...

    2017-09-29

    The Southern California Borderland (SCB) is a region that experiences strong natural variations in bottom water oxygen and pH. Here, we use marine sediments from the Santa Monica Basin (SMB) to reconstruct environmental conditions and changes in the basin's bottom water oxygenation from the Last Glacial Maximum (LGM) to present, and compare the records to the adjacent Santa Barbara Basin (SBB) and Santa Lucia Slope (SLS). High-resolution records of benthic foraminiferal oxygen and carbon isotopes (δ18O and δ13C), benthic foraminiferal assemblages, and bulk sedimentary organic matter geochemistry records exhibit major changes associated with late Quaternary millennial-scale global climate oscillations. Ourmore » data show the dominance of low-oxygen benthic foraminifera assemblages during warm intervals, and assemblages representing higher dissolved oxygen during cooler intervals, as also seen in SBB and SLS. But, our record shows a stronger and longer-lasting oxygen minimum zone (OMZ) between the end of the Bølling-Allerød (B-A) and the Early Holocene (including the Younger Dryas) than at neighboring sites, indicated by dominance of Bolivina tumida (characteristic of major hypoxia) in the assemblage. The middle to late Holocene (from ~ 8.8 to 0 ka) had weaker hypoxia than the early Holocene, with assemblages mainly composed of Bolivina argentea and Uvigerina peregrina. The SMB remains mostly slightly low in oxygen throughout the studied interval, with differences in the degree of hypoxia relative to SBB and SLS (especially from the B-A to the Early Holocene) likely due to its greater depth and its more southern geographic position and therefore decreased exposure to North Pacific Intermediate Water current. Regional effects, such as changing intermediate water source and/or changing ventilation (oxygenation) of the intermediate water source, also affect SMB deep water. Our analysis utilizing parallel geochemical and micropaleontological records brings new

  20. The Surface Expression of Radiocarbon Anomalies near Baja California during Deglaciation

    NASA Astrophysics Data System (ADS)

    Lindsay, C. M.; Lehman, S.; Marchitto, T. M.; Ortiz, J. D.; van Geen, A.

    2013-12-01

    In 2007, Marchitto et al. noted that periods of declining atmospheric radiocarbon activity (Δ14C) during the Heinrich 1 and Younger Dryas stadials coincided with intervals of rising atmospheric CO2, as well as extremely 14C-depleted carbon at intermediate depths near Baja California, Mexico. They interpreted this as evidence of aged carbon emerging through the intermediate ocean to the atmosphere from an isolated deep marine reservoir, and proposed that the signal was transported to Baja from the Southern Ocean via Antarctic Intermediate Water. Here we report on measurements from the same core used by Marchitto et al. (2007) that enable us to reconstruct the Δ14C of surface waters. 14C was measured in mono-specific samples of G. ruber, G. sacculifer and G. bulloides planktonic foraminifera. Independent calendar ages were provided by the published age model, which tied diffuse spectral reflectance to the layer-counted GISP2 oxygen isotope record. Preliminary results reveal that surface ocean Δ14C relative to the coeval atmosphere was lower during periods of low benthic Δ14C, consistent with upwelling and subsequent mixing and/or partial atmospheric equilibration of the intermediate-depth signal. Planktic Δ14C was higher during the Bølling-Allerød/Antarctic Climate Reversal (BA/ACR), reflecting upwelling of better-ventilated waters at a time when benthic Δ14C had a modern-like offset from the atmosphere. G. ruber Δ14C is lower than in other planktonic species during deglaciation. We propose that this offset arises from a late summer G. ruber calcification habitat and a spring G. bulloides and G. sacculifer habitat, combined with a seasonal change in the source of coastal upwelling waters from northern in the spring to southern in late summer, as the shelf-trapped poleward California Undercurrent strengthens. This interpretation invokes a southern hemisphere source for depleted carbon at the Baja surface, via northward, coastal advection of southern

  1. Younger-Dryas cooling and sea-ice feedbacks were prominent features of the Pleistocene-Holocene transition in Arctic Alaska

    USGS Publications Warehouse

    Gaglioti, Benjamin V.; Mann, Daniel H.; Wooller, Matthew J.; Jones, Benjamin M.; Wiles, Gregory C.; Groves, Pamela; Kunz, Michael L.; Baughman, Carson; Reanier, Richard E.

    2017-01-01

    Declining sea-ice extent is currently amplifying climate warming in the Arctic. Instrumental records at high latitudes are too short-term to provide sufficient historical context for these trends, so paleoclimate archives are needed to better understand the functioning of the sea ice-albedo feedback. Here we use the oxygen isotope values of wood cellulose in living and sub-fossil willow shrubs (δ18Owc) (Salix spp.) that have been radiocarbon-dated (14C) to produce a multi-millennial record of climatic change on Alaska's North Slope during the Pleistocene-Holocene transition (13,500–7500 calibrated 14C years before present; 13.5–7.5 ka). We first analyzed the spatial and temporal patterns of δ18Owc in living willows growing at upland sites and found that over the last 30 years δ18Owc values in individual growth rings correlate with local summer temperature and inter-annual variations in summer sea-ice extent. Deglacial δ18Owcvalues from 145 samples of subfossil willows clearly record the Allerød warm period (∼13.2 ka), the Younger Dryas cold period (12.9–11.7 ka), and the Holocene Thermal Maximum (11.7–9.0 ka). The magnitudes of isotopic changes over these rapid climate oscillations were ∼4.5‰, which is about 60% of the differences in δ18Owc between those willows growing during the last glacial period and today. Modeling of isotope-precipitation relationships based on Rayleigh distillation processes suggests that during the Younger Dryas these large shifts in δ18Owc values were caused by interactions between local temperature and changes in evaporative moisture sources, the latter controlled by seaice extent in the Arctic Ocean and Bering Sea. Based on these results and on the effects that sea-ice have on climate today, we infer that ocean-derived feedbacks amplified temperature changes and enhanced precipitation in coastal regions of Arctic Alaska during warm times in the past. Today, isotope values in willows on the North Slope of Alaska are

  2. Deep water formation in the North Pacific and deglacial CO2 rise

    NASA Astrophysics Data System (ADS)

    Rae, James W. B.; Sarnthein, Michael; Foster, Gavin L.; Ridgwell, Andy; Grootes, Pieter M.; Elliott, Tim

    2014-06-01

    Deep water formation in the North Atlantic and Southern Ocean is widely thought to influence deglacial CO2 rise and climate change; here we suggest that deep water formation in the North Pacific may also play an important role. We present paired radiocarbon and boron isotope data from foraminifera from sediment core MD02-2489 at 3640 m in the North East Pacific. These show a pronounced excursion during Heinrich Stadial 1, with benthic-planktic radiocarbon offsets dropping to ~350 years, accompanied by a decrease in benthic δ11B. We suggest that this is driven by the onset of deep convection in the North Pacific, which mixes young shallow waters to depth, old deep waters to the surface, and low-pH water from intermediate depths into the deep ocean. This deep water formation event was likely driven by an increase in surface salinity, due to subdued atmospheric/monsoonal freshwater flux during Heinrich Stadial 1. The ability of North Pacific Deep Water (NPDW) formation to explain the excursions seen in our data is demonstrated in a series of experiments with an intermediate complexity Earth system model. These experiments also show that breakdown of stratification in the North Pacific leads to a rapid ~30 ppm increase in atmospheric CO2, along with decreases in atmospheric δ13C and Δ14C, consistent with observations of the early deglaciation. Our inference of deep water formation is based mainly on results from a single sediment core, and our boron isotope data are unavoidably sparse in the key HS1 interval, so this hypothesis merits further testing. However, we note that there is independent support for breakdown of stratification in shallower waters during this period, including a minimum in δ15N, younging in intermediate water 14C, and regional warming. We also re-evaluate deglacial changes in North Pacific productivity and carbonate preservation in light of our new data and suggest that the regional pulse of export production observed during the Bølling-Aller

  3. Quantitative woody cover reconstructions from eastern continental Asia of the last 22 kyr reveal strong regional peculiarities

    NASA Astrophysics Data System (ADS)

    Tian, Fang; Cao, Xianyong; Dallmeyer, Anne; Ni, Jian; Zhao, Yan; Wang, Yongbo; Herzschuh, Ulrike

    2016-04-01

    We present a calibration-set based on modern pollen and satellite-based Advanced Very High Resolution Radiometer (AVHRR) observations of woody cover (including needleleaved, broadleaved and total tree cover) in eastern continental Asia, which shows good performance under cross-validation with the modern analogue technique (all the coefficients of determination between observed and predicted values are greater than 0.65). The calibration-set is used to reconstruct woody cover from a taxonomically harmonized and temporally standardized fossil pollen dataset (including 274 cores) with 500-year resolution over the last 22 kyr. The spatial range of forest has not noticeably changed in eastern continental Asia during the last 22 kyr, although woody cover has, especially at the margin of the eastern Tibetan Plateau and in the forest-steppe transition area of north-central China. Vegetation was sparse during the LGM in the present forested regions, but woody cover increased markedly at the beginning of the Bølling/Allerød period (B/A; ca. 14.5 ka BP) and again at the beginning of the Holocene (ca. 11.5 ka BP), and is related to the enhanced strength of the East Asian Summer Monsoon. Forest flourished in the mid-Holocene (ca. 8 ka BP) possibly due to favourable climatic conditions. In contrast, cover was stable in southern China (high cover) and arid central Asia (very low cover) throughout the investigated period. Forest cover increased in the north-eastern part of China during the Holocene. Comparisons of these regional pollen-based results with simulated forest cover from runs of a global climate model (for 9, 6 and 0 ka BP (ECHAM5/JSBACH ∼1.125° spatial resolution)) reveal many similarities in temporal change. The Holocene woody cover history of eastern continental Asia is different from that of other regions, likely controlled by different climatic variables, i.e. moisture in eastern continental Asia; temperature in northern Eurasia and North America.

  4. Antarctic link with East Asian summer monsoon variability during the Heinrich Stadial-Bølling interstadial transition

    NASA Astrophysics Data System (ADS)

    Zhang, Hongbin; Griffiths, Michael L.; Huang, Junhua; Cai, Yanjun; Wang, Canfa; Zhang, Fan; Cheng, Hai; Ning, Youfeng; Hu, Chaoyong; Xie, Shucheng

    2016-11-01

    Previous research has shown a strong persistence for direct teleconnections between the East Asian summer monsoon (EASM) and high northern latitude climate variability during the last glacial and deglaciation, in particular between monsoon weakening and a reduced Atlantic meridional overturning circulation (AMOC). However, less attention has been paid to EASM strengthening as the AMOC was reinvigorated following peak Northern Hemisphere (NH) cooling. Moreover, climate model simulations have suggested a strong role for Antarctic meltwater discharge in modulating northward heat transport and hence NH warming, yet the degree to which Southern Hemisphere (SH) climate anomalies impacted the Asian monsoon region is still unclear. Here we present a new stalagmite oxygen-isotope record from the EASM affected region of central China, which documents two prominent stages of increased 18O-depleted moisture delivery to the region through the transition from Heinrich Stadial 1 (HS1) to the Bølling-Allerød (B-A) interstadial; this is in general agreement with the other monsoonal records from both NH and SH mid to low latitudes. Through novel comparisons with a recent iceberg-rafted debris (IRD) record from the Southern Ocean, we propose that the two-stage EASM intensification observed in our speleothem records were linked with two massive Antarctic icesheet discharge (AID) events at ∼16.0 ka and ∼14.7 ka, immediately following the peak HS1 stadial event. Notably, the large increase in EASM intensity at the beginning of the HS1/B-A transition (∼16 ka) is relatively muted in the NH higher latitudes, and better aligns with the changes observed in the SH, indicating the Antarctic and Southern Ocean perturbations could have an active role in driving the initial EASM strengthening at this time. Indeed, Antarctic freshwater input to the Southern Ocean during these AID events would have cooled the surrounding surface waters and caused an expansion of sea ice, restricting the

  5. OSL age and stratigraphy of the Strauss sand sheet in New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Hall, Stephen A.; Goble, Ronald J.

    2015-07-01

    The Strauss sand sheet occurs in south-central New Mexico, USA, and northern Chihuahua, Mexico, covering an area of about 4740 km2. Its chronology is determined by 19 OSL ages. The sand sheet formed primarily during three phases of eolian deflation and deposition, each phase with a separate sand source and under different climatic and environmental circumstances. The first phase of eolian sedimentation occurred 45 to 15 ka with the deposition of unit 1. The sand source for the first phase was beach-related features along the eastern shoreline of pluvial Lake Palomas in Mexico. The glacial-age climate was cool, wet, and windy because of the southern path of the jet stream at that time. After 15 ka, with the onset of warmer conditions of the Bølling-Allerød, the shutting down of the Palomas sand source, and wet conditions of the Younger Dryas, the sand sheet stabilized with weak soil development in unit 1. By 11 ka, the climate shifted to Holocene drying conditions and the second phase of sand accumulation began, forming unit 2; the sand source was the local deflation of the previously deposited unit 1 sand. The sand sheet stabilized again by 1.9 ka with slightly wetter late Holocene climate; a weak soil formed in unit 2 sand. About A.D. 1500 and extending to about A.D. 1850 or later, an A horizon formed on the sand sheet, probably in response to a desert grassland vegetation during the period of wet climate of the Little Ice Age. In an anthropogenic third phase of eolian activity, after A.D. 1850, the vegetation was likely disturbed by overgrazing; and the unit 2 and A horizon (unit 3) sands were deflated, resulting in the deposition of a thin layer of massive eolian sand (unit 4) across the sand sheet. By about A.D. 1900 mesquite shrubs had increased in abundance; and deflated sand, largely from unit 2, began to accumulate around the shrubs, forming coppice dunes (unit 5). Mesquite coppice dunes continued to increase in number and volume during the twentieth

  6. Progress and challenges in deciphering the glacial chronology of the Alpine Lateglacial of the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Reitner, Juergen

    2015-04-01

    For more than a hundred years efforts have been undertaken to decipher the Alpine Lateglacial (appr. 20 -12 ka), i.e., the period beginning with the withdrawal of the LGM glaciers from their tongue basins until the onset of the Holocene. Since the pioneering work of Penck & Brückner many modifications and improvements of the original subdivision into glacial stadials have been put forward. Especially the application of equilibrium line altitude depressions (ΔELAs) resulted in the definition of new glacial stadials since the 1960's. In addition, previously defined stadials were re-defined using morphological criteria as well as ΔELAs but without any reference to the original type localities. Finally, modern geochronology, especially surface exposure dating with cosmogenic nuclides, helped to establish a chronological framework and enabled correlation with high-resolution marine and ice-core records and elaborated paleoclimatic consideration. However, the results of comprehensive geological mapping in combination with surface exposure dating and radiocarbon dating indicate a bias in the commonly used subdivision of the Alpine Lateglacial. This seems to be, on the one hand, the result of a rigorous application of differences in ΔELA for chronological correlations, which led to the underestimation of regional differences within one climatic phase. On the other hand, only one type-locality has been dated so far. Moreover, as no "type-valley" exists where all moraines of the proposed glacial stadials are evident, we run into the danger of using a sub-division of the Alpine Lateglacial, which contains unjustified chronostratigraphic artefacts. In other words, based on recent work an overclassification may have been established. Beyond the well-known Younger Dryas glaciation only a floating or at least poorly referenced stratigraphy prior to the Bølling/Allerød interstadial (> 14.7 ka) is in use. Examples will be presented which show the current problems and how

  7. Termination-II interstadial/stadial climate change recorded in two stalagmites from the north European Alps

    NASA Astrophysics Data System (ADS)

    Moseley, Gina E.; Spötl, Christoph; Cheng, Hai; Boch, Ronny; Min, Angela; Edwards, R. Lawrence

    2015-11-01

    Understanding the sequence of events that take place during glacial-interglacial climate transitions is important for improving our knowledge of abrupt climate change. Here, we present a new stacked, high-resolution, precisely-dated speleothem stable isotope record from the northern Alps, which provides an important record of temperature and moisture-source changes between 134 and 111 ka for Europe and the wider North Atlantic realm. The record encompasses the penultimate deglaciation (Termination II (TII)), which lies beyond the limit of radiocarbon dating, thus providing an important new archive for a crucial period of rapid paleoclimate change. Warmer and wetter ice-free conditions were achieved by 134.1 ± 0.7 ka (modelled ages) as indicated by the presence of liquid water at the site. Temperatures warmed further at 133.7 ± 0.5 ka and led into an interstadial, synchronous with slightly elevated monsoon strength during the week monsoon interval. The interstadial experienced an unstable climate with a trough in temperature associated with a slowdown in Atlantic Meridional Overturning Circulation (AMOC) and a reduction in North Atlantic Deep Water (NADW) formation. The interstadial ended with a more extreme cold reversal lasting 500 years in which NADW formation remained active but the subpolar gyre weakened allowing cool polar waters to penetrate southwards. The main warming associated with TII was very rapid, taking place between 130.9 ± 0.9 and 130.7 ± 0.9 ka coeval with initial monsoon strengthening. Temperatures then plateaued before being interrupted by a 600-year cold event at 129.1 ± 0.6 ka, associated once again with penetration of polar waters southwards into the North Atlantic and a slowdown in monsoon strengthening. Sub-orbital climate oscillations were thus a feature of TII in the north Atlantic realm, which broadly resemble the Bølling/Allerød-Younger Dryas-8.2 ka event pattern of change observed in Termination I despite monsoon records

  8. Temperature, vegetation and precipitation variability in the Nile River drainage during the past 27,000 years: Insights from molecular and isotopic proxies

    NASA Astrophysics Data System (ADS)

    Castañeda, Isla; Schouten, Stefan; Pätzold, Jürgen; Schefuß, Enno

    2013-04-01

    The paleoclimate history of the Eastern Mediterranean (EM) region is of much interest due to its long history of human occupation. To date, much of our knowledge of past climate in the EM region comes from marine sedimentary records. These indicate that since the Last Glacial Maximum, major and sometimes abrupt sea surface temperature (SST) fluctuations occurred in response to global climate events including the Younger Dryas (YD), the Bølling-Allerød, and Heinrich Event 1 (H1). In comparison, less is known regarding continental paleoclimate conditions in this region due to a scarcity of well-dated continuous climate archives, particularly from Saharan North Africa. Here, we present new reconstructions of continental precipitation (plant leaf wax δD), C3 vs. C4 vegetation (plant leaf wax δ13C) and soil temperature (MBT/CBT paleothermometer) in the Nile River catchment in conjunction with previously published U37k' and TEX86SST reconstructions from the EM Sea. Our multiproxy records indicate that relative to the present, the LGM was characterized by arid conditions with cooler SST and soil temperatures in the catchment. The H1 event stands out as a major excursion in nearly all proxies and is characterized by an abrupt decrease in SST and the most arid conditions of the past 27,000 years. The African Humid Period (AHP) of the early Holocene is the wettest interval of the entire record and is observed from ~10,000 to 5,500 cal BP, with maximum wet conditions noted at ~8,000 cal BP. Interestingly, a rather abrupt cooling is noted in the MBT/CBT record at ~5.5 cal kyr, coinciding with the end of the AHP off west Africa; however, the transition out of the AHP is more gradual in the δD record. Overall both the continental and marine climate records indicate millennial scale climate variability. Our records also shed light on shifting sources of organic matter in response to the sequential cessation and re-initiation of different tributaries to the main flow of the

  9. Climatic and morphological controls on post-glacial lake and river valley evolution in the Weichselian belt - an example from the Wda valley, Northern Poland

    NASA Astrophysics Data System (ADS)

    Kramkowski, M. A.; Błaszkiewicz, M.; Piotrowski, J. A.; Brauer, A.; Gierszewski, P.; Kordowski, J.; Lamparski, P.; Lorenz, S.; Noryśkiewicz, A. M.; Ott, F.; Slowinski, M. M.; Tyszkowski, S.

    2014-12-01

    The River Wda valley is a classical example of a polygenetic valley, consisting of former lake basins joined by erosive gap sections. In its middle section, which was the subject of our research, a fragment of an abandoned Lateglacial river valley is preserved, which is unique for the Weichselian moraine belt in the Central European Lowlands. The analysis of the relationship between the lacustrine and fluvial sediments and landforms enabled the authors to report many evolutionary connections between the initial period of the river system formation and the emergence of lakes during the Weichselian Lateglacial. The surface drainage essentially determined the progress of melting of dead ice blocks buried in the glacial depressions, which finally led to lake formation there. Most of the lake basins in the study area were formed during the Bølling-Allerød period. However, one section of the subglacial channel was not exposed to the thermokarst conditions and was therefore preserved with dead ice blocks throughout the entire Lateglacial. The dead ice decay at the beginning of the Holocene, as well as the emergence of another lake, created a lower base level of erosion in the close vicinity of the abandoned valley and induced a change of the river's course. Both fluvial and lacustrine deposits and landforms distributed in the central section of the River Wda valley indicate two processes, which proceeded simultaneously: (1) emergence of fluvially joined lake basins within a glacial channel, (2) degradation of the river bed in the gap sections interfering between the lakes. The processes described for the central section of the River Wda channel indicate a very dynamic river valley development during the Weichselian Lateglacial and the early Holocene. The valley formation was tightly interwoven with the morphogenesis of the primary basins within the valley, mainly with the melting of the buried blocks of dead ice and the development of lakes. This study is a contribution

  10. Abrupt Climate Change & Paleoindian Environments in western Colorado from 17-9 ka yr BP

    NASA Astrophysics Data System (ADS)

    Whitlock, C. L.; Briles, C.; Meltzer, D. J.

    2010-12-01

    The late-glacial period was characterized by rapid climate changes that resulted in significant ecosystem reorganizations worldwide. In western Colorado, one of the coldest locations in North American today, mountain environments during the late-glacial period are poorly known. Yet, archeological evidence indicates that Folsom-age Paleoindians were present in the region, perhaps even occasionally over-wintering in the Gunnison Basin during the Younger Dryas Chronozone (YDC; 12.9 to 11.5ka yr BP). To determine the climate, vegetation, and fire history during the late-glacial/early-Holocene transition, a 17-kyr-old sediment core from Lily Pond (38°56’06” N, 106°38’37”W, 3208m elevation) was analyzed for pollen and charcoal and compared with other high-resolution records from the region. The data suggest that, following deglaciation, the region supported an alpine parkland dominated by Artemisia and scattered Picea. Conditions warmed and became wetter than before during the Bølling-Allerød period (B/A; 14.7 to 12.9ka yr BP), when the region was covered by open Picea, Pinus, and Abies forest. Cooling during the YDC is inferred from abundant Picea, slightly more Artemisia and decreased Pinus, which indicate the presence of subalpine parkland. With the onset of the Holocene at ~11.5 ka yr BP, Pinus, Quercus, Artemisia, and Chenopodiaceae increased, suggesting an upslope expansion of xerophytic taxa in response to warmer and effectively drier summers than before or at present. Fire activity was absent prior to 14.7 ka yr BP, increased substantially during the B/A, decreased during the YDC, increased at the beginning of the Holocene, and declined in the early Holocene. The vegetation changes that occurred at Lily Pond are generally consistent with other high-resolution records in the Colorado Rockies in showing cooler-than-present YDC followed by rapid warming. The Lily Lake data provide new information that indicates substantial warming and establishment of

  11. Reconstruction of hydrologic responses to late-Glacial (9-33ka) abrupt climate transitions in the coastal southwest United States

    NASA Astrophysics Data System (ADS)

    Wu, M.; Feakins, S. J.; Kirby, M. E.

    2013-12-01

    A sediment core retrieved from Lake Elsinore, the largest natural freshwater lake in southern California, spans an age of 9 to 33ka BP. The period includes several late-Glacial abrupt climate transitions such as the Heinrich events (HEs) 1-3, the Bølling-Allerød (B-A), and the Younger Dryas (YD). This terrestrial site provides a unique opportunity to evaluate changes in hydrology in coastal southwest United States across these key abrupt climate transition events. Hydrogen isotopic ratios (δDwax) of the long-chain C28 alkanoic acid, a biomarker for terrestrial leaf wax, extracted from the sediments, were analyzed to reveal the δD of precipitation water in the past (δDprecip). In the modern climate, higher δDprecip values are associated with moisture sourced from the tropical Pacific, which brings a drier and warmer climate, whereas lower δDprecip values are associated with moisture sourced from north Pacific brought by polar jet stream, causing a wetter and colder climate. δDwax ranges from about -210‰ to -100‰ between late-Glacial HEs and the beginning of Holocene. The pattern generally correlates with Greenland ice core and regional speleothem records, with lower δDwax values corresponding to colder periods (HEs), and higher δDwax values corresponding to warmer periods (B-A and early Holocene). We infer cold and wet climate with north Pacific sourced moisture during the glacial, followed by gradual warming and drying into the B-A and Holocene, when the moisture sources shifted to the tropical Pacific. There is no substantive response to the YD. The fluctuations of δDwax into and out of the HEs can be as large as about 60‰, suggesting greatly variable hydrology across these late-Glacial abrupt climate transition events. The large shifts in δDwax signal during deglaciation and HEs indicate that hydrology in the coastal southwest US has responded sensitively to climate change, and therefore has important implications for water resources in this

  12. Spatial scaling of deglacial hypoxia in the Santa Barbara Basin: Using rank-abundance curves and kurtosis to understand paleoecological community stress

    NASA Astrophysics Data System (ADS)

    Myhre, S.; Hill, T. M.; Okushi, K.; Kennett, J.; Behl, R. J.

    2011-12-01

    Deglacial sediment from Santa Barbara Basin (SBB) reveals the complex spatial and temporal variability of intermediate water oxygenation. We use formainiferal community end-member indices and the kurtosis of rank-abundance curves to articulate the variability of oxygen by depth through the deglaciation (4-17ky). We construct a vertical and geographic transect across SBB (34° 15'N, 119° 45'W) using a core from 418m water depth (MV0811-15JC), and previously investigated cores from 440m (MD02-2504) and 570m (MD02-2503) water depths. All three cores show the classical deglaciation δ18O structure at terminations 1A and 1B, previously published for the two deepest cores. Foraminifera are well adapted to a broad environmental range of oxygen concentrations, and thus are well suited for fine-scale oxygenation reconstructions. Indices of end-member species proportional abundance oscillate with the deglacial trends of Bølling-Allerød warming and Younger Dryas cooling. These data illustrate that deglacial changes in the environmental extremes in oxygenation, but not necessarily the average state, occurred simultaneously across these distinct depths and locations with the SBB. Interestingly, the two deeper cores are laminated across the deglaciation, while the shallowest and most northwestern of the cores is not laminated. We evaluate these data with using rank-abundance curves (RAC) as a diagnostic of foraminiferal community stress across the deglaciation; kurtosis of these community curves is used as a measure of RAC peakedness or flatness. Kurtosis value excursions were associated with communities dominated by the species Bolivina tumida, a foraminifera associated with low-oxygen, methane-rich environments. Importantly, communities in the deepest core had extremely low abundances at horizons of environmental deoxygenation, indicating that these events correspond to prohibitively-low deoxygenation events, and potentially the coarse sampling interval at these horizons

  13. The Paleoceanography of Cariaco Basin and its Relationship to Deglacial and Abrupt Climate Change

    NASA Astrophysics Data System (ADS)

    Peterson, L. C.; Yurco, L. N.; Gibson, K.; Haug, G. H.; Deplazes, G.; Black, D. E.; Thunell, R.

    2011-12-01

    wet interval in the northern tropics of South America that falls within the enigmatic Late Glacial period known as the "Mystery Interval". Spanning the Bølling/Allerød and Younger Dryas, an abrupt pulse of biogenic opal accumulation is observed that may reflect advection of silica-rich deep waters to the surface as a result of deep water reorganization. Though Cariaco sea surface temperatures appear to mimic changes in Greenland, oxygen isotopes in planktic foraminifers closely resemble Antarctic air temperature records during the deglaciation, suggesting that a complex mixture of hemispheric signals is preserved in the southern Caribbean.

  14. High resolution paleoceanography of the Guaymas Basin, Gulf of California, during the past 15 000 years

    USGS Publications Warehouse

    Barron, J.A.; Bukry, D.; Bischoff, J.L.

    2004-01-01

    Deep Sea Drilling Project Site 480 (27??54.10???N, 111??39.34???W; 655 m water depth) contains a high resolution record of paleoceanographic change of the past 15 000 years for the Guaymas Basin, a region of very high diatom productivity within the central Gulf of California. Analyses of diatoms and silicoflagellates were completed on samples spaced every 40-50 yr, whereas ICP-AES geochemical analyses were completed on alternate samples (sample spacing 80-100 yr). The B??lling-Aller??d interval (14.6-12.9 ka) (note, ka refers to 1000 calendar years BP throughout this report) is characterized by an increase in biogenic silica and a decline in calcium carbonate relative to surrounding intervals, suggesting conditions somewhat similar to those of today. The Younger Dryas event (12.9-11.6 ka) is marked by a major drop in biogenic silica and an increase in calcium carbonate. Increasing relative percentage contributions of Azpeitia nodulifera and Dictyocha perlaevis (a tropical diatom and silicoflagellate, respectively) and reduced numbers of the silicoflagellate Octactis pulchra are supportive of reduced upwelling of nutrient-rich waters. Between 10.6 and 10.0 ka, calcium carbonate and A. nodulifera abruptly decline at DSDP 480, while Roperia tesselata, a diatom indicative of winter upwelling in the modern-day Gulf, increases sharply in numbers. A nearly coincident increase in the silicoflagellate Dictyocha stapedia suggests that waters above DSDP 480 were more similar to the cooler and slightly more saline waters of the northern Gulf during much of the early and middle parts of the Holocene (???10 to 3.2 ka). At about 6.2 ka a stepwise increase in biogenic silica and the reappearance of the tropical diatom A. nodulifera marks a major change in oceanographic conditions in the Gulf. A winter shift to more northwesterly winds may have occurred at this time along with the onset of periodic northward excursions (El Nin??o-driven?) of the North Equatorial Countercurrent

  15. Paleoceanographic development in the SW Barents Sea during the Late Weichselian-Early Holocene transition

    NASA Astrophysics Data System (ADS)

    Aagaard-Sørensen, S.; Husum, K.; Hald, M.; Knies, J.

    2010-12-01

    The Late Weichselian-Early Holocene variability of the North Atlantic Current has been studied with focus on the zonal component of this meridional transport during the transition from glacial to interglacial conditions. The investigated sediment core is from 409 m water depth in the SW Barents Sea. Eight Accelerator mass spectrometry (AMS) 14C dates show that the core covers the last 20,000 cal yr B.P. with a centennial scale resolution during Late Weichselian-Early Holocene. Planktic foraminiferal assemblages were analyzed using the >100 μm size fraction and foraminiferal planktic and benthic δ 13C and δ 18O isotopes were measured. Furthermore, a range of physical and chemical analyses has been carried out on the bulk sediment samples. Four time periods have been identified which represent the varying oceanographic conditions in Ingøydjupet, a glacial trough located off the north coast of Norway in the SW Barents Sea. 1) The late glacial (before ca 15,000 cal yr B.P.) influenced by the nearby ice sheets with high amounts of sea ice- or iceberg-transported detritus. 2) The late Oldest Dryas stadial and the Bølling-Allerød interstadial (ca 15,000-12,700 cal yr B.P.) with cold surface water conditions influenced by the collapse of the nearby ice sheets, high amounts of sea ice- or iceberg-transported detritus and melt water and weak subsurface inflow of Atlantic Water. 3) The Younger Dryas cold stadial (12,700-11,650 cal yr B.P.) with low primary productivity and extensive sea ice cover and 4) The Preboreal and Early Holocene (11,650-6800 cal yr B.P. cal yr B.P.) with strong influx of Atlantic Water into the area, near absence of ice rafted debris and generally ameliorated conditions in both surface and bottom water masses as seen from a high flux of foraminifera and increased marine primary production.

  16. Deposition rates, mixing intensity and organic content in two contrasting submarine canyons

    NASA Astrophysics Data System (ADS)

    García, R.; van Oevelen, D.; Soetaert, K.; Thomsen, L.; De Stigter, H. C.; Epping, E.

    2008-02-01

    The hydrographically different conditions characterising the Western Iberian Margin (NE Atlantic) and the Gulf of Lions (Mediterranean) may play an important role in determining the biogeochemical characteristics of the sediments. To investigate this, we compared the Nazaré and Cap de Creus canyons, and their respective adjacent open slopes in terms of the organic carbon (C org) contents, chlorophyll- a (chl- a) concentrations, C:N and chl- a:phaeopigment ratios, and also in terms of modelled mixing intensities, chl- a and 210Pb deposition and background concentrations in sediments. Chlorophyll- a and 210Pb profiles were fitted simultaneously with a reactive transport model to estimate mixing intensity, deposition and background concentrations. Further, to account for the possibility that the decay of chl- a may be lower in the deep sea than in shallow areas, we estimated the model parameters with two models. In one approach (model 1), the temperature dependent decay rate of chl- a as given by Sun et al. [Sun, M.Y., Lee, C., Aller, R.C. (1993) Laboratory Studies of Oxic and Anoxic Degradation of chlorophyll- a in Long-Island sound sediments. Geochimica et Cosmochimica Acta, 57, 147-157] for estuaries was used. In the other approach (model 2), an extra parameter was estimated to derive the chlorophyll- a degradation rate. An F-test, taking into account the different number of parameters in the models, was used to single out the model that significantly fitted the data best. In most cases, the model parameters were best-explained with model 1, indicating the empirical relationship by Sun et al. (1993) is a valid means to estimate the chlorophyll- a degradation rate in deep sea sediments. To assess the robustness with which the model parameters were estimated we provide a first application of Bayesian analysis in the modelling of tracers in sediments. Bayesian analysis allows calculating the mean and standard deviation for each model parameter and correlations among

  17. Oxygen and carbon isotopic systematics of aragonite speleothems and water in Furong Cave, Chongqing, China

    NASA Astrophysics Data System (ADS)

    Li, Ting-Yong; Shen, Chuan-Chou; Li, Hong-Chun; Li, Jun-Yun; Chiang, Hong-Wei; Song, Sheng-Rong; Yuan, Dao-Xian; Lin, Chris D.-J.; Gao, Pan; Zhou, Liping; Wang, Jian-Li; Ye, Ming-Yang; Tang, Liang-Liang; Xie, Shi-You

    2011-08-01

    To understand oxygen and carbon stable isotopic characteristics of aragonite stalagmites and evaluate their applicability to paleoclimate, the isotopic compositions of active and fossil aragonite speleothems and water samples from an in situ multi-year (October 2005-July 2010) monitoring program in Furong Cave located in Chongqing of China have been examined. The observations during October 2005-June 2007 show that the meteoric water is well mixed in the overlying 300-500-m bedrock aquifer, reflected by relatively constant δ 18O, ±0.11-0.14‰ (1 σ), of drip waters in the cave, which represents the annual status of rainfall water. Active cave aragonite speleothems are at oxygen isotopic equilibrium with drip water and their δ 18O values capture the surface-water oxygen isotopic signal. Aragonite-to-calcite transformation since the last glaciation is not noticeable in Furong stalagmites. Our multi-year field experiment approves that aragonite stalagmite δ 18O records in this cave are suitable for paleoclimate reconstruction. With high U, 0.5-7.2 ppm, and low Th, 20-1270 ppt, the Furong aragonite stalagmites provide very precise chronology (as good as ±20s yrs (2 σ)) of the climatic variations since the last deglaciation. The synchroneity of Chinese stalagmite δ 18O records at the transition into the Bølling-Allerød (t-BA) and the Younger Dryas from Furong, Hulu and Dongge Caves supports the fidelity of the reconstructed East Asian monsoon evolution. However, the Furong record shows that the cold Older Dryas (OD) occurred at 14.0 thousand years ago, agreeing with Greenland ice core δ 18O records but ˜200 yrs younger than that in the Hulu record. The OD age discrepancy between Chinese caves can be attributable to different regionally climatic/environmental conditions or chronological uncertainty of stalagmite proxy records, which is limited by changes in growth rate and subsampling intervals in absolute dating. Seasonal dissolved inorganic carbon δ 13C

  18. Influence of Climate Warming on Arctic Mammals? New Insights from Ancient DNA Studies of the Collared Lemming Dicrostonyx torquatus

    PubMed Central

    Prost, Stefan; Smirnov, Nickolay; Fedorov, Vadim B.; Sommer, Robert S.; Stiller, Mathias; Nagel, Doris; Knapp, Michael; Hofreiter, Michael

    2010-01-01

    Background Global temperature increased by approximately half a degree (Celsius) within the last 150 years. Even this moderate warming had major impacts on Earth's ecological and biological systems, especially in the Arctic where the magnitude of abiotic changes even exceeds those in temperate and tropical biomes. Therefore, understanding the biological consequences of climate change on high latitudes is of critical importance for future conservation of the species living in this habitat. The past 25,000 years can be used as a model for such changes, as they were marked by prominent climatic changes that influenced geographical distribution, demographic history and pattern of genetic variation of many extant species. We sequenced ancient and modern DNA of the collared lemming (Dicrostonyx torquatus), which is a key species of the arctic biota, from a single site (Pymva Shor, Northern Pre Urals, Russia) to see if climate warming events after the Last Glacial Maximum had detectable effects on the genetic variation of this arctic rodent species, which is strongly associated with a cold and dry climate. Results Using three dimensional network reconstructions we found a dramatic decline in genetic diversity following the LGM. Model-based approaches such as Approximate Bayesian Computation and Markov Chain Monte Carlo based Bayesian inference show that there is evidence for a population decline in the collared lemming following the LGM, with the population size dropping to a minimum during the Greenland Interstadial 1 (Bølling/Allerød) warming phase at 14.5 kyrs BP. Conclusion Our results show that previous climate warming events had a strong influence on genetic diversity and population size of collared lemmings. Due to its already severely compromised genetic diversity a similar population reduction as a result of the predicted future climate change could completely abolish the remaining genetic diversity in this population. Local population extinctions of collared

  19. Paleoenvironmental changes in the northern South China Sea over the past 28,000 years: A study of TEX 86-derived sea surface temperatures and terrestrial biomarkers

    NASA Astrophysics Data System (ADS)

    Shintani, Tomoya; Yamamoto, Masanobu; Chen, Min-Te

    2011-04-01

    We have generated a record of TEX 86 ( TEX86H)-derived sea surface temperatures (SSTs) over the last 28 ka for core MD97-2146 from the northern South China Sea (SCS). The TEX86H-derived temperature of a core-top sample corresponds to the SSTs in warmer seasons. The SST record shows a drop during the Oldest Dryas period, an abrupt rise at the onset of the Bølling-Allerød period, a plateau across the Younger Dryas period, and an abrupt rise at the beginning of the Holocene. The glacial-interglacial contrast in TEX86H-derived temperature is almost the same as that in foraminiferal Mg/Ca ratio-derived temperature, but it is larger than those in U37K and transfer function-derived temperatures. Possible interpretations are: (1) the seasonal shift of glycerol dialkyl glycerol tetraether (GDGT) production, (2) the overestimation of temperature change by TEX86H, and (3) the underestimation of temperature change by U37K and transfer function approaches. The similar variation in TEX86H-derived temperature at the study site and Chinese stalagmite δ 18O during the last deglaciation suggests that changes in TEX86H-derived temperature in this period reflected atmospheric and oceanic reorganization on a millennial timescale. The long-chain n-alkanes are mainly of higher plant origin before ˜14 ka and a mixture of higher plant and lithic origins after ˜14 ka; the abundance ratio of long-chain to short-chain n-fatty acids decreases at ˜15 ka, suggesting a drastic change in sediment sources at ˜14-15 ka. We attribute the higher content of fresh higher plant n-alkanes and long-chain n-fatty acids before ˜14-15 ka to enhanced aeolian transportation and/or arid environments. Increased precipitation likely due to intensified summer monsoon after ˜14-15 ka enhanced the erosion of sedimentary rocks and increased the contribution of lithic n-alkanes.

  20. Detrital cave sediments record Late Quaternary hydrologic and climatic variability in northwestern Florida, USA

    NASA Astrophysics Data System (ADS)

    Winkler, Tyler S.; van Hengstum, Peter J.; Horgan, Meghan C.; Donnelly, Jeffrey P.; Reibenspies, Joseph H.

    2016-04-01

    Detrital sediment in Florida's (USA) submerged cave systems may preserve records of regional climate and hydrologic variability. However, the basic sedimentology, mineralogy, stratigraphic variability, and emplacement history of the successions in Florida's submerged caves remains poorly understood. Here we present stratigraphic, mineralogical, and elemental data on sediment cores from two phreatic cave systems in northwestern Florida (USA), on the Dougherty Karst Plain: Hole in the Wall Cave (HITW) and Twin Cave. Water flowing through these caves is subsurface flow in the Apalachicola River drainage basin, and the caves are located just downstream from Jackson Blue (1st magnitude spring, > 2.8 m3 s- 1 discharge). Sedimentation in these caves is dominated by three primary sedimentary styles: (i) ferromanganese deposits dominate the basal recovered stratigraphy, which pass upsection into (ii) poorly sorted carbonate sediment, and finally into (iii) fine-grained organic matter (gyttja) deposits. Resolving the emplacement history of the lower stratigraphic units was hampered by a lack of suitable material for radiocarbon dating, but the upper organic-rich deposits have a punctuated depositional history beginning in the earliest Holocene. For example, gyttja primarily accumulated in HITW and Twin Caves from ~ 5500 to 3500 cal yr. BP, which coincides with regional evidence for water-table rise of the Upper Floridian Aquifer associated with relative sea-level rise in the Gulf of Mexico, and evidence for invigorated drainage through the Apalachicola River drainage basin. Gyttja sediments were also deposited in one of the caves during the Bølling/Allerød climate oscillation. Biologically, these results indicate that some Floridian aquatic cave (stygobitic) ecosystems presently receive minimal organic matter supply in comparison to prehistoric intervals. The pre-Holocene poorly sorted carbonate sediment contains abundant invertebrate fossils, and likely documents a period

  1. A high-resolution, absolute-dated deglacial speleothem record of Indian Ocean climate from Socotra Island, Yemen

    NASA Astrophysics Data System (ADS)

    Shakun, Jeremy D.; Burns, Stephen J.; Fleitmann, Dominik; Kramers, Jan; Matter, Albert; Al-Subary, Abdulkarim

    2007-07-01

    Stalagmite M1-5 from Socotra Island, Yemen in the northwest Indian Ocean provides a robust, high-resolution paleoclimate record from ˜ 27.4-11.1 ka based on 717 stable isotope and 28 230Th measurements. Variations in M1-5 oxygen isotope ratios ( δ18O) are interpreted to be primarily driven by an amount effect related to changes in the mean position and/or intensity of convection of the intertropical convergence zone, the island's only source of precipitation. The M1-5 δ18O time series is strongly correlated to the Greenland ice cores, similar to an older Socotra speleothem deposited from 53-40 ka [S.J. Burns, D. Fleitmann, A. Matter, J. Kramers, A. Al-Subbary, Indian Ocean climate and an absolute chronology over Dansgaard/Oeschger events 9 to 13, Science 301 (2003) 1365-1367], indicating that a North Atlantic-Indian Ocean cold-dry/warm-wet teleconnection persisted through the end of the last glacial period. Peak aridification occurred at ˜ 23 ka and a gradual increase in moisture thereafter was interrupted by an abrupt drying event at ˜ 16.4 ka, perhaps related to Heinrich event 1. Indian Ocean rainfall increased dramatically during the Bølling period and then decreased continuously and gradually through the Allerød and Younger Dryas. The Holocene began abruptly with increased precipitation at 11.4 ka and was followed by a major but short-lived drying during the Preboreal Oscillation at ˜ 11.2 ka. M1-5 is highly correlated to the Dongge Cave record from 15.5-11 ka, suggesting much of the Indian Ocean monsoon region responded similarly to the major climate changes of the last deglaciation. The transitions into the Younger Dryas and to a lesser extent the Bølling are remarkably gradual in M1-5, as they are in all other Asian speleothem records, occurring over several centuries. These gradual transitions are in striking contrast to high-resolution records from around the North Atlantic basin where the transitions are extremely abrupt and generally occur in

  2. Late Pleistocene to Holocene paleoceanographic and paleo-climatic changes in Gulf of Gemlik, Sea of Marmara, Turkey

    NASA Astrophysics Data System (ADS)

    Filikci, Betül; Kadir Eriş, K.; Namık Çaǧatay, M.; Gasperini, Luca; Sabuncu, Asen; Acar, Dursun; Yalamaz, Burak

    2016-04-01

    Gulf of Gemlik is an east-west oriented marine inlet with a maximum depth of 113 m in the south-eastern part of the Sea of Marmara. It is located on the middle branch of the North Anatolian Fault Zone. While the Gulf of Gemlik is separated from the SoM by a bedrock sill at -50 m, there were presumably several disconnections during the Late Pleistocene to Holocene, but the timing of the youngest connection around the onset of the Holocene is still controversial. Here, we attempt to elucidate the paleoceanographic and paleoenvironmental changes during the late glacial-Holocene using the multi-proxy analysis of a core extending back to 13 ka BP. The multi-proxy data include physical and geochemical properties together with AMS 14C ages. The core sediments covering the time period of the last 13 ka BP consists of two main lithostratigraphic units. The lower Unit L2 represents the lacustrine phase of the gulf prior to 10.6 ka BP, while the upper Unit L1 is an overlying transgressive mud drape deposited during the main part of the Holocene. Unit L2 deposited prior 10.6 ka BP represents Bølling-Allerød and Younger Dryas climatic periods, when prograding shelf edge sediments were deposited in the form of well sorted medium sands with brackish water bivalve shells (Dreissenapolymorpha). At the beginning of the Holocene, the rising sea level in the Sea of Marmara breached the -50 m sill at 10.6 ka BP, and therefore the Gulf of Gemlik was converted into a marine realm. Soon after, the water stratifications allowed to the formation of the previously studied two sapropels in the gulf, as shown by increased TOC contents. μ-XRF Ca/Ti and Sr/Ca profiles of Unit L1 provide evidence of rapid climatic changes at 8.2 ka BP and 4.2 ka BP, representing cold and dry short climatic periods which are well correlated with previous marine and lake studies in İznik Lake south of the Sea of Marmara. Keywords: Gemlik Gulf, core, paleoclimate, Late Pleistocene to Holocene

  3. Deglacial Record in the Illinois River Valley Explains Asynchronous Phases of Meltwater Pulses and Clay Mineral Excursions in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Wang, H.

    2014-12-01

    One prominent event of the Bølling/Allerød (B/A) interstadial was the large meltwater release to global oceans. The Laurentide Ice Sheet (LIS) is usually considered the main source. But, the large LIS meltwater discharge conflicts with the marine record showing an active North Atlantic meridional overturning circulation (AMOC) during the B/A interval. Continuous dune-lacustrine successions in the Illinois River Valley (IRV) have shown complete records of the last deglacial chronozones. Their grain-size distributions and accurate B/A age 14C dates of plant fossils from 15 m deep lacustrine sediment in the IRV suggest that most of the IRV and parts of the adjacent upland were inundated by water. The inundation was caused by a sediment dam interpreted to have been constructed and followed by a breach at the confluence of the Mississippi and Illinois Rivers during the B/A interval due to sediment mobilization by the large meltwater release. The grain size distributions correlate with meltwater pulses and mineralogical excursions in sediments from the Gulf of Mexico (GOM) very well. The blockage and release of illite and chlorite rich fine-grained sediments from the Lake Michigan basin changed the relative abundance of clay minerals and thus the ratio of smectite/(illite + chlorite) in the sediment of the GOM. This finding explains why the meltwater episodes from the LIS and the associated detrital discharges are not synchronous in the sediments in the GOM. The finding also ties meltwater pulses and associated detrital discharges in the GOM closely to the LIS discharges via the Mississippi River Valley on chronozonal scales. Three arguments can be made from this result: 1) unaffected AMOC during B/A interval resulted potentially from the hyperpycnal inflow into the GOM floor; 2) limited volume of the meltwater discharge did not significantly influence the AMOC; and 3) the freshwater input into the GOM from the LIS at this particular location did not significantly

  4. Lacustrine Basal Ages Constrain the Last Deglaciation in the Uinta Mountains, Utah, USA

    NASA Astrophysics Data System (ADS)

    Munroe, Jeffrey; Laabs, Benjamin

    2013-04-01

    Basal radiocarbon ages from 21 high-elevation lakes limit the timing of final Pleistocene deglaciation in the Uinta Mountains of northeastern Utah, USA. The lakes are located in glacial valleys and cirques 5 to 20 km upstream from LGM terminal moraines at elevations from 2830 to 3475 m. Many are impounded behind recessional moraines. Cores were retrieved from a floating platform with a percussion corer driven to the point of refusal. All penetrated inorganic silty clay beneath gyttja. AMS radiocarbon analyses were made on terrestrial macrofossils, daphnia ephippia, pollen concentrates, and bulk sediment retrieved from the base of each core. No radiocarbon reservoir effect was observed when bulk dates were checked against terrestrial material. Radiocarbon results were converted to calendar years using the IntCal09 calibration curve in OxCal 4.1. Given the stratigraphy observed in the cores, these calibrated basal ages are considered close limits on the timing of the local deglaciation and lake formation. The oldest three lakes have basal radiocarbon ages that calibrate to a few centuries after the Bölling/Alleröd warming, indicating that the landscape was becoming ice free at this time. These are followed by an overlapping group of five lakes with basal ages between 13.5 and 13.0 ka BP. Five more cores, from four separate lakes, have basal ages tightly clustered between 13.0 and 12.5 ka BP. Three of these lakes are dammed by moraines, suggesting glacial activity during the early part of the Younger Dryas interval. The lone kettle lake in the study yielded a basal age of 12.3 ka BP, considerably younger than the basal age of 13.9 ka BP from a nearby lake filling a bedrock basin, indicating that buried ice may have been locally stable for more than a millennium after deglaciation. The remaining seven lakes have basal ages between 12.0 and 11.0 ka BP. Four of these lakes are also dammed by moraines. These two non-overlapping clusters of basal ages for moraine

  5. Origin and fate of sedimentary organic matter in the northern Bay of Bengal during the last 18 ka

    NASA Astrophysics Data System (ADS)

    Contreras-Rosales, L. A.; Schefuß, E.; Meyer, V.; Palamenghi, L.; Lückge, A.; Jennerjahn, T. C.

    2016-11-01

    The Northern Bay of Bengal (NBoB) is a globally important region for deep-sea organic matter (OM) deposition due to massive fluvial discharge from the Ganges-Brahmaputra-Meghna (G-B-M) rivers and moderate to high surface productivity. Previous studies have focused on carbon burial in turbiditic sediments of the Bengal Fan. However, little is known about the storage of carbon in pelagic and hemipelagic sediments of the Bay of Bengal over millennial time scales. This study presents a comprehensive history of OM origin and fate as well as a quantification of carbon sediment storage in the Eastern Bengal Slope (EBS) during the last 18 ka. Bulk organic proxies (TOC, TIC, TN, δ13CTOC, δ15NTN) and content and composition of total hydrolysable amino acids (THAA) in a sediment core (SO188-342KL) from the EBS were analyzed. Three periods of high OM accumulation were identified: the Late Glacial (LG), the Bölling/Alleröd (B/A), and the Early Holocene Climatic Optimum (EHCO). Lower eustatic sea level before 15 ka BP allowed a closer connection between the EBS and the fluvial debouch, favoring high terrestrial OM input to the core site. This connection was progressively lost between 15 and 7 ka BP as sea level rose to its present height and terrestrial OM input decreased considerably. Export and preservation of marine OM was stimulated during periods of summer monsoon intensification (B/A and EHCO) as a consequence of higher surface productivity enhanced by cyclonic-eddy nutrient pumping and fluvial nutrient delivery into the photic zone. Changes in the THAA composition indicate that the marine plankton community structure shifted from calcareous-dominated before 13 ka BP to siliceous-dominated afterwards. They also indicate that the relative proportion of marine versus terrestrial OM deposited at site 342KL was primarily driven by relative sea level and enlarged during the Holocene. The ballasting effect of lithogenic particles during periods of high coastal proximity and

  6. Pleistocene Megafaunal Collapse in North America Preceded the Younger Dryas: Evidence from the Midwest

    NASA Astrophysics Data System (ADS)

    Gill, J. L.; Donnelly, J.; Jackson, S. T.; Lininger, K. B.; Marsicek, J. P.; Robinson, G.; Simonson, B. M.; Williams, J. W.

    2009-12-01

    The recent Younger Dryas (YD) impact theory suggests that an extraterrestrial impact event at 12,900 calendar years BP was responsible for rapid and widespread environmental change, including the extinction of the Pleistocene megafauna. Evidence for such an event is expected to be preserved in lake sediments; lakes are robust archives of environmental change, including abrupt events such as the YD. Sporormiella, a dung fungal proxy for megafaunal presence, has recently been added to classic lake sediment proxies such as pollen and charcoal. Sporormiella spores have been found to be abundant in Pleistocene deposits and mostly absent during the Holocene until the historic introduction of domestic grazers, and are therefore a suitable proxy for Pleistocene herbivory regimes. At Appleman Lake, IN, fossil pollen, charcoal, and Sporormiella were analyzed to reconstruct changes in vegetation, fire regime, and megafaunal presence. The Sporormiella record indicates that Pleistocene megaherbivores declined from 14.6 to 13.7 ka calendar BP, well before the onset of Younger Dryas cooling and the proposed impact event. However, these data are consistent with the oldest well-dated evidence of pre-Clovis human presence from butchered mammoth remains in the Midwest. Immediately following the Sporormiella decline, pollen and charcoal data indicate shifts in plant community composition and an increase in fire frequency, possibly due to the release of palatable hardwood taxa and a build-up of landscape biomass following the local extirpation of herbivores. While the onset of the decline does correspond with Bølling-Allerød warming, the mechanism for the decline does not appear to be vegetation-induced habitat loss. Additionally, sediment cores from Appleman and Spicer Lakes, IN, and Silver Lake in Ohio have been analyzed for evidence of an extra-terrestrial impact, including mineral spherules, charcoal peaks, ET-associated elements, magnetic grains, and loss-on-ignition. Our sites

  7. Organic geochemical investigations of the Dali Lake sediments in northern China: Implications for environment and climate changes of the last deglaciation in the East Asian summer monsoon margin

    NASA Astrophysics Data System (ADS)

    Fan, Jiawei; Xiao, Jule; Wen, Ruilin; Zhang, Shengrui; Wang, Xu; Cui, Linlin; Yamagata, Hideki

    2017-06-01

    Millennial-scale environment and climate changes in the East Asian summer monsoon margin during the last deglaciation are reconstructed by systematic studies on the characteristic of sedimentary organic matter from Dali Lake in northern China. Concurrent increases in the TOC and TN concentrations indicate increases in terrestrial organic matter and nutrient inputs to the lake and a development of terrestrial vegetation and phytoplankton productivity related to increases in regional temperature and precipitation. C/N ratios reflect changes in the proportions of terrestrial and aquatic organic matter. Decreases in both δ13Corg and δ15N values indicate increases in the isotopically lighter, terrestrial carbon and nitrogen inputs to the lake, due to increases in surface runoffs; while a sharp decrease in the δ15N value implies a significant weakening in the biological activities of nitrifying and amonifying bacteria, due to abrupt decrease in the water temperature. The geochemical data indicate that regional temperature and precipitation exhibited increasing trends from 15,000 to 12,350 cal yr BP; temperature decreased abruptly at 12,350 cal yr BP and then maintained a low level from 12,350 to 11,400 cal yr BP, precipitation decreased to a relatively low level from 12,350 to 11,400 cal yr BP; and both temperature and precipitation returned to increase after 11,400 cal yr BP. The climate change in the Dali Lake region during the last deglaciation corresponds, within age uncertainties, to the Bølling-Allerød (BA) warm phase and Younger Dryas (YD) cold reversal occurring over northern high latitudes. However, the gradual and mild increasing trends of regional temperature and precipitation during the BA warm period contrasts with the general cooling trend in northern high latitude temperature, implying a dominant influence from increases in the Northern Hemisphere summer insolation; while the slight decreases in regional precipitation relative to the rapid and

  8. Noble gas paleotemperatures and humidity during the last Glacial - Interglacial transition in Switzerland - first application of the CVCS system to a stalagmite grown under cool climatic conditions

    NASA Astrophysics Data System (ADS)

    Vogel, Nadia; Figura, Simon; Fleitmann, Dominik; Maden, Colin; Wieler, Rainer; Kipfer, Rolf

    2014-05-01

    Stalagmites represent excellent multi-proxy paleoclimate archives as they cover long timescales and can be dated with high precision [1]. We determine noble gas temperatures (NGTs) using the CVCS (Combined Vacuum Crushing and Sieving) technique, which enables to preferentially reduce the air content of stalagmite samples, such that temperature information can be deduced from the noble gases dissolved in the stalagmite's water inclusions [2]. The system allows accurate temperature determination from Ne, Ar, Kr, and Xe, as shown in a cross-calibration study on a stalagmite from Borneo [3,4]. We have now applied the CVCS technique to samples of stalagmite M2 from Milandre Cave (Swiss Jura Mountains), covering the transitions Bølling-Allerød - Younger Dryas (YD) - Preboreal [5]. So far, we have determined three preliminary NGTs, indicating cave temperatures before the onset of the YD of ~3°C, and dropping to ~1°C at the onset of the YD. These temperatures compare well with theoretical mean annual Milandre cave temperatures inferred from summer temperatures deduced from sediments of Gerzensee [6], located south of Milandre. We also determined in 12 M2 samples water contents, which, for samples grown under hot and rather dry climatic conditions provide information about drip water availability [7]: higher water contents point to irregular, low drip rates and vice versa. In M2, water contents increase strongly at the onset of the YD, suggesting a progressively dryer climate. Towards the end of the YD water contents drop again and are very low at the onset of the Preboreal, indicating a return to more humid conditions. The same conclusion was drawn from a M2 carbon isotope record, reflecting reduced discharge and vegetation density due to dryer conditions during the cold period [8]. Our data emphasize the applicability of the water content as a drip rate proxy also for stalagmites grown under cool climatic conditions. [1] Henderson G.M. (2006) Science, 313, 620-622. [2

  9. Benthic foraminiferal faunal and geochemical proxies as tracers for paleoenvironmental and paleoceanographic changes in the western Mediterranean over the last 24 ka

    NASA Astrophysics Data System (ADS)

    Pérez-Asensio, José N.; Cacho, Isabel; Frigola, Jaime; Pena, Leopoldo D.; Sierro, Francisco J.; Asioli, Alessandra; Kuhlmann, Jannis; Huhn, Katrin

    2017-04-01

    Paleoenvironmental and paleoceanographic changes in the western Mediterranean are reconstructed for the last 24 ka using a combination of benthic foraminiferal assemblages and geochemical proxies measured on benthic foraminiferal shells (Mg/Ca-deep water temperatures and stable isotopes). The studied materials are sediment cores HER-GC-UB06 and MD95-2043recovered at 946 m and 1841 m, respectively, from the Alboran Sea. At present, both core sites are bathed by the Western Mediterranean Deep Water (WMDW), although UB06 core is close to the boundary with the overlying Levantine Intermediate Water (LIW). Therefore, past variability of both water masses can potentially be recorded by the benthic foraminiferal proxies from the studied sites. Benthic foraminiferal assemblages and geochemical data show fluctuations in bottom-water ventilation, organic matter accumulation and deep-water temperatures related to WMDW and LIW circulation. During the glacial interval, an alternation of events showing better ventilation (higher abundance of Cibicides pachyderma) with lower temperatures and events of warmer deep water temperatures with poorer ventilation (Nonionella iridea assemblage, lower abundance of C. pachyderma) are observed. This variability might reflect stronger WMDW formation during the Last Glacial Maximum (LGM) and Heinrich Stadial 1. During the Bølling-Allerød and Younger Dryas (YD) periods, cold temperatures and the lowest oxygenation rates are recorded coinciding with the highest abundance of deep infaunal taxa on both UB06 and MD95-2043 cores. This interval was coetaneous to the deposition of an Organic Rich Layer in the Alboran Sea. However, a re-ventilation trend started at the end of the YD in the shallower site (UB06 core) whereas low-oxygen conditions prevailed until the end of the early Holocene in the deep site (MD95-2043 core). During the early Holocene a significant deep water temperature increase occurred at the shallower site suggesting the

  10. Regional benthic δ18O stacks with radiocarbon age models show Termination I onset differences of up to 4,000 years

    NASA Astrophysics Data System (ADS)

    Stern, J.; Lisiecki, L. E.

    2013-12-01

    The assumption of globally synchronous benthic foraminiferal δ18O changes is central to the development of global stacks (averages) and many other types of paleoclimate studies. However, a few well-dated individual benthic δ18O records have suggested the possibility of regional differences in the timing of Termination I (e.g., Skinner and Shackleton, 2005; Waelbroeck et al., 2011). These previous studies often used single core locations to describe vast areas of the ocean, so it has remained unclear whether the observed diachroneities are truly regional in scale or merely local. Here, we bridge the gap between global benthic δ18O stacks and individual records by presenting eight regional benthic δ18O stacks from 252 cores with age models based on a total of 776 planktonic foraminiferal radiocarbon dates from 61 of those cores. The earliest termination onset (beginning of deglacial benthic δ18O decrease) occurs in the intermediate South Atlantic stack at 18.5 kyr BP, shortly after the initial deglacial melting of Northern Hemisphere ice sheets. The latest termination onset occurs in the deep Indian stack at 14.5 kyr BP, coeval with the Bølling-Allerød warming. We find synchronous termination onsets at 17.5 kyr BP in the intermediate North Atlantic, deep North Atlantic, and deep South Atlantic, contrary to Waelbroeck et al. (2011). The deglacial benthic δ18O decrease in the deep Pacific lagged that of the deep Atlantic by an average of 1000 yr, with a maximum lag of ~1700 yr during the middle of the termination. The intermediate Pacific termination onset at 16.5 kyr BP happens 1000 yr after the deep Pacific termination onset at 17.5 kyr BP. The stacks extend beyond Termination I to ~40 kyr BP, allowing us to clarify and update certain aspects of millennial-scale benthic δ18O chronostratigraphy surrounding Heinrich events 2-3 and the transition into the Last Glacial Maximum. Our radiocarbon-dated regional benthic δ18O stacks demonstrate some of the

  11. Late Pleistocene deglaciation and paleo-environment in the Retezat Mountains, Southern Carpathians

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Madarász, Balázs; Kern, Zoltán; Urdea, Petru; Braucher, Régis; Aster Team

    2017-04-01

    This study aims to use in situ produced 10Be based Cosmic Ray Exposure (CRE) ages to reconstruct glacier evolution in the Retezat Mts, the Southern Carpathians most glaciated area with peak elevations up to 2509 m asl. In the study area currently devoid of glaciers, the calculated theoretical ELA is at ˜2860 m asl. The paleo-Equilibrium Line Altitudes (ELAs) were calculated over the ˜21 to ˜13 ka time period based on the reconstructed glacial stillstands or re-advances geometries using the ssAAR method [1, 2]. Regarding the Northern side of the Retezat Mts, new and re-evaluated 10Be CRE ages (n=34) [3] were used while regarding the Southern side, they all result from a new sampling (n=25). According to the data, the most extended glaciation occurred during the LGM, down to ˜1050 m asl. on both sides of the Retezat Mts with most probable 10Be CRE ages of 21.0 -1.5+0.8 ka and 20.7 -1.0+0.9 ka. The reconstructed ELA depression in the North was ˜1010 m while it was ˜1190 m, in the South where the valleys glacial system (Lăpuşnicu - Judele) was significantly larger with longer glacier tongues. At the beginning of the Lateglacial (˜17-18 ka) the glaciers withdrew and the North-South difference between the ELA depression was decreased (˜885 m and ˜945 m, respectively). The ELA differences further reduced and vanished for the ˜15.3 ka glacial event - the last cold stage before the abrupt Bölling/Alleröd warming - with ELA depressions of ˜728 m and ˜712 m, respectively. The last glacial phase in the area characterized by small cirque glaciers occurred at 13.5 -0.6+0.6 ka in the North and 13.9 -0.4+0.9 ka in the South. By this time, the ELA depression was reduced to ˜660-680 m. Due to the small glacier size this value may have been influenced by local topoclimatic factors. So far, no data support Younger Dryas or Holocene glaciation of the Retezat Mts. The elevation difference of the ELAs suggests more precipitation on the Southern side of the Retezat Mts

  12. High Resolution deglacial monsoon δ18O record from a new stalagmite from the Kailash Cave, Central India

    NASA Astrophysics Data System (ADS)

    Allu C, Narayana; Pawan K, Gautam; Shraddha, Band; Madhusudan G, Yadava; Rengaswamy, Ramesh; Shen, Chuan-Chou

    2016-04-01

    corresponding to Bølling-Allerød Interstadial appear to be cyclic in nature. We performed time-series analyses on the δ18O record to investigate the periodicities to understand the influence of both solar and non-solar frequencies during last deglacial. REDFIT (Schulz & Mudelsee, 2002) with Monte Carlo simulation was used to calculate the red noises. Spectral analysis of the δ18O time series show statistically most significant periodicity (>95%) centered at 592 years. The other significant periodicities found are 42, 37, 19, 18, 16, and14.5 years.

  13. Deglaciation of the Eurasian ice sheet complex

    NASA Astrophysics Data System (ADS)

    Patton, Henry; Hubbard, Alun; Andreassen, Karin; Auriac, Amandine; Whitehouse, Pippa L.; Stroeven, Arjen P.; Shackleton, Calvin; Winsborrow, Monica; Heyman, Jakob; Hall, Adrian M.

    2017-08-01

    2.5 × 106 km2 and drained the present day Vistula, Elbe, Rhine and Thames rivers through the Seine Estuary. During the Bølling/Allerød oscillation after c. 14.6 ka BP, two major proglacial lakes formed in the Baltic and White seas, buffering meltwater pulses from eastern Fennoscandia through to the Younger Dryas when these massive proglacial freshwater lakes flooded into the North Atlantic Ocean. Deglaciation temporarily abated during the Younger Dryas stadial at 12.9 ka BP, when remnant ice across Svalbard, Franz Josef Land, Novaya Zemlya, Fennoscandia and Scotland experienced a short-lived but dynamic re-advance. The final stage of deglaciation converged on present day ice cover around the Scandes mountains and the Barents Sea by 8.7 ka BP, although the phase-lagged isostatic recovery still continues today.

  14. How do German veterinarians use social networks? A study, using the example of the 'NOVICE' veterinary medicine network.

    PubMed

    Schaper, Elisabeth; Forrest, Neil D; Tipold, Andrea; Ehlers, Jan P

    2013-01-01

    Zielsetzung: NOVICE (Network Of Veterinary ICt in Education, http://www.noviceproject.eu) ist ein soziales professionelles online-Netzwerk für Tiermediziner, Dozierende und Studierende der Tiermedizin sowie für E-Learning-Berater bzw. Didaktiker der veterinärmedizinischen Bildungsstätten. In dieser Arbeit sollte untersucht werden, wie die Akzeptanz bei deutschen Tierärzten, Dozierenden und Studierenden der Veterinärmedizin sowie E-Learning-Beauftragten für ein fachspezifisches Netzwerk ist, welche Anforderungen durch die Nutzer an soziale online-Netzwerke gestellt werden, wie der Umgang mit Web 2.0-Werkzeugen [21], [30] erfolgt und welches Potential ein berufsspezifisches Netzwerk bieten könnte. Methodik: Die Untersuchung erfolgte mittels Datenanalyse durch die Datenbank der Elgg-Plattform sowie zusätzlich mit google analytics. Jährliche Fokusgruppenbefragungen und Einzelinterviews wurden durchgeführt, um eine Akzeptanzanalyse der Netzwerk-Nutzer vorzunehmen.Ergebnisse: In NOVICE haben sich zwischen dem 01. September 2010 und 21. März 2012 1961 Mitglieder aus 73 Ländern registriert, dabei hat Deutschland mit 565 Nutzern (28,81%) den größten Anteil. In diesem Zeitraum kamen auch die meisten Einzelbesuche der Webseite aus Deutschland. Insgesamt sind im Netzwerk 24,83% aller Mitglieder und 19,22% der deutschen Mitglieder aktiv. In Bezug auf das Geschlecht befinden sich sowohl in Hinblick auf alle Mitglieder als auch auf die deutschen Mitglieder deutlich mehr Frauen als Männer in NOVICE. Die am häufigsten verwendeten Web 2.0-Werkzeuge sind das Versenden von Chat- und Email-Nachrichten sowie das Schreiben von Wiki- und Diskussionsbeiträgen. Aus den Fokusgruppenbefragungen ging hervor, dass von den Befragten in der Regel auch andere online-communities in Anspruch genommen werden, die aktiven Mitglieder mehr Web 2.0-Werkzeuge nutzen als in anderen Netzwerken, während die passiven Mitglieder in allen Netzwerken eher zurückhaltend sind. Über ein eigenes

  15. Controls on suspended sediment, particulate and dissolved organic carbon export from two adjacent catchments with contrasting land-uses, Exmoor UK.

    NASA Astrophysics Data System (ADS)

    Glendell, M.; Brazier, R. E.

    2012-04-01

    The fluvial export of total organic carbon (particulate and dissolved) plays an important role in the transportation of organic carbon from terrestrial to aquatic ecosystems, with implications for the understanding of the global carbon cycle and calculations of regional carbon budgets. The terrestrial biosphere contains large amounts of stored carbon in the soil and vegetation, thus a small change in the terrestrial carbon pool may have significant implications for atmospheric CO2 concentrations. Since the onset of agriculture, human activities have accelerated soil erosion rates 10- to 100- fold above all estimated natural background levels, especially in the uplands and at lower latitudes, whilst increasing DOC concentrations over the past decades have been reported in rivers across Western Europe and North America, raising concerns about potential destabilisation of the terrestrial soil carbon pool. The increased input of fine sediment and organic carbon into aquatic environments is also an important factor in stream water quality, being responsible for direct ecological effects as well as transport of a range of contaminants. Many factors, such as topography, hydrological regime and vegetation are known to influence the fluvial export of carbon from catchments. However, most work to date has focused on DOC losses from either forested or peaty catchments, with only limited studies examining the controls and rates of TOC (dissolved and particulate) fluxes from agricultural catchments, particularly during flood events. This research aims to: • Quantify the fluxes of total suspended sediment, total dissolved and total particulate carbon in two adjacent catchments with contrasting land-uses and • Examine the controlling factors of total fluvial carbon fluxes in a semi-natural and agricultural catchment in order to assess the impact of agricultural land-use on fluvial carbon export. The two contrasting study catchments (the Aller and Horner), in south

  16. Impact processes, permafrost dynamics, and climate and environmental variability in the terrestrial Arctic as inferred from the unique 3.6 Myr record of Lake El'gygytgyn, Far East Russia - A review

    NASA Astrophysics Data System (ADS)

    Wennrich, Volker; Andreev, Andrei A.; Tarasov, Pavel E.; Fedorov, Grigory; Zhao, Wenwei; Gebhardt, Catalina A.; Meyer-Jacob, Carsten; Snyder, Jeffrey A.; Nowaczyk, Norbert R.; Schwamborn, Georg; Chapligin, Bernhard; Anderson, Patricia M.; Lozhkin, Anatoly V.; Minyuk, Pavel S.; Koeberl, Christian; Melles, Martin

    2016-09-01

    Lake El'gygytgyn in Far East Russia is a 3.6 Myr old impact crater lake. Located in an area that has never been affected by Cenozoic glaciations nor desiccation, the unique sediment record of the lake represents the longest continuous sediment archive of the terrestrial Arctic. The surrounding crater is the only impact structure on Earth developed in mostly acid volcanic rocks. Recent studies on the impactite, permafrost, and sediment sequences recovered within the framework of the ICDP "El'gygytgyn Drilling Project" and multiple pre-site surveys yielded new insight into the bedrock origin and cratering processes as well as permafrost dynamics and the climate and environmental history of the terrestrial Arctic back to the mid-Pliocene. Results from the impact rock section recovered during the deep drilling clearly confirm the impact genesis of the El'gygytgyn crater, but indicate an only very reduced fallback impactite sequence without larger coherent melt bodies. Isotope and element data of impact melt samples indicate a F-type asteroid of mixed composition or an ordinary chondrite as the likely impactor. The impact event caused a long-lasting hydrothermal activity in the crater that is assumed to have persisted for c. 300 kyr. Geochemical and microbial analyses of the permafrost core indicate a subaquatic formation of the lower part during lake-level highstand, but a subaerial genesis of the upper part after a lake-level drop after the Allerød. The isotope signal and ion compositions of ground ice is overprinted by several thaw-freeze cycles due to variations in the talik underneath the lake. Modeling results suggest a modern permafrost thickness in the crater of c. 340 m, and further confirm a pervasive character of the talik below Lake El'gygytgyn. The lake sediment sequences shed new leight into the Pliocene and Pleistocene climate and environmental evolution of the Arctic. During the mid-Pliocene, significantly warmer and wetter climatic conditions in

  17. Late Pleistocene to early Holocene aeolian and flash-flood sedimentation and soil formation in a small hilly catchment in SW-Germany (Palatinate forest)

    NASA Astrophysics Data System (ADS)

    Dotterweich, M.; Kühn, P.; Tolksdorf, J. F.; Müller, S.; Nelle, O.

    2012-04-01

    This paper focuses on the dynamics of sedimentation processes and soil development in a steep slope 0-order catchment in the sandy Lower Bunter of the south-western mid-range mountains in Germany during the transition period from the late Glacial to the early Holocene. Italso discusses how late Palaeolithic gatherers and hunters may have influenced these processes by sedentary land occupation. The investigated dry valley covers an area of around 16.6 ha and is characterized by short and steep slopes of 30° to 60°. A significant amount of the sediments from the adjacent slopes had been captured along the wide and rather flat valley bottom and at the small outlet. Several exposures, pits, and percussion liner drillings revealed a weak to highly weathered reddish sandy material at the base and eight subsequent layers of incoherent sandy and charcoal (from pines) enriched sediments with different colours ranging from olive-brown to dull reddish brown. By stratigraphical means, the lowermost sediment can be ascribed to the early Lateglacial when the deposition of aeolian sands under cold conditions with scarce vegetation cover was a widespread phenomenon. The subsequent layer contains a higher amount of silt and dates into the Allerød as suggested by radiocarbon dating. This is corroborated by the occurrence of LST that indicate that these sediments have been near to the surface around 12,900 yr BP. It shows characteristics of a palaeosol with Bwb and BwAhb horizons (Brunic Arenosols dystric) and with greyish Ahb and Eb horizons (Albic Arenosols dystric) similar to the Usselo/Finow soils in north-eastern Germany. In the material above, many remnants of roots and organic particles and rounded bone fragments were revealed by micromorphological analyses. Then, an alternation of reddish brown coarse to fine sands and small, partly rounded stones with some small intercalate aggregations of humic material rich in charcoal which dates to around 10,000 yr BP were deposited

  18. Impact of a modified Broviac maintenance care bundle on bloodstream infections in paediatric cancer patients.

    PubMed

    Furtwängler, Rhoikos; Laux, Carolin; Graf, Norbert; Simon, Arne

    2015-01-01

    Hintergrund: Während der intensiven Chemotherapie sind bei Kindern mit Krebserkrankungen Blutstrominfektionen (BSI) eine potentiell lebensbedrohliche Komplikation. Die meisten Patienten haben einen dauerhaft implantierten oder getunnelten zentralen Venenkatheter (CVAD, z.B. Broviac). Ein verbessertes Protokoll der Erhaltungspflege kann möglicherweise die Rate von BSI senken. Methode: Interventionsstudie zum Nutzen eines modifizierten Präventionsbündels in zwei prospektiven Beobachtungszeiträumen (P1: bis 05-2011; P2: 09-2011 bis 05-2013); prospektive Surveillance aller mikrobiologisch gesicherten BSI. In P2 wurden fertig konfektionierte NaCl 0.9% Spritzen (10 ml) zum Spülen des Broviacs verwendet. Außerdem wurden alle Konnektions- und Zuspritzstellen (Dreiwegehähne) mit Octenidin/Propanol desinfiziert.Ergebnisse: Während P1 wurden 84 Patienten und während P2 81 eingeschlossen. Die beiden Patientenpopulationen zeigten keine signifikanten Unterschiede in Bezug auf das Alter, die Grunderkrankung oder ihren Status (Anteil mit Rezidiv). Praktisch alle CVAD waren Broviac-Katheter. Die mediane Nutzungsdauer lag in P1 bei 192 d (Interquartile-Range (IQR); 110–288 Tage) und in P2 bei 191 d (IQR; 103–270 Tage). In P1 wurden insgesamt 28 BSI bei 22 Patienten diagnostiziert (Inzidenz für mind. 1 BSI 26%), in P2 waren es nur 15 BSI bei 12 Patienten in P2 (Inzidenz 15%). Die entsprechenden Ergebnisse für die Inzidenzdichte lagen bei 0.44 (CI95 0.29–0.62) BSI pro 100 stationäre Patiententage für P1 vs. 0.34 (0.19–0.53) für P2. Die Inzidenzrate (IR) pro 1.000 stationäre Anwendungstage lag bei 7.76 (5.16–10.86) für P1 vs. 4.75 (2.66–7.43) für P2. Während in P1 9 BSI durch CoNS detektiert wurden, waren es in P2 nur 2 (IR 2.49; CI95 0.17–4.17 vs. 0.63; CI95 0.08–1.72). Fazit: Das modifizierte Präventionsbündel führte zu einer Reduktion von BSI bei pädiatrisch onkologischen Patenten mit Broviac Katheter. Wie in einigen Studien U

  19. Correlation of the Late Pleistocene Usselo Horizon (Europe) and the Clovis Layer (North America)

    NASA Astrophysics Data System (ADS)

    Kloosterman, J. B.

    2007-05-01

    In 1940, a dark charcoal-rich layer, 10 to 15cm thick, was found within the Late Pleistocene Coversands of the Netherlands, and named the Usselo Layer (de Laag van Usselo) by its discoverer, archaeologist CCJW Hijszeler (1902-1982). Usselo is a village near Enschedé, a few kilometres from the Dutch-German border. Research started after the war, and publications, both scientific and popular, came forth in the 1950s. By pollen content, the layer was dated to the Alleröd, the last interstadial of the Würm (Wisconsin) glaciation; radiocarbon dating indicated (pre-AMS) dates of about 11,200 14C BP. Identification of the layer at other localities was visual, and it was found in Belgium, France, Germany, Poland, and Belarus; it was also found in the UK and in Denmark, in which countries, however, no correlation was made with the other occurrences. Hijszeler had found the layer all over the Netherlands and abroad from Ostende to Hamburg, and he hypothesized the cause as a general wildfire provoked by the eruption of an Eiffel volcano. The European geologists and archaeologists, however, did not adopt his views and interpreted the layer as a paleosol, vitiating the chronology by representing the layer as the result of a long development, instead of as an eolian sediment laid down perhaps in a day or even less that provides us with a sharp marker horizon. The prehistoric Clovis culture of North America was found in the 1930s and dated to the Twocreekan, the last interstadial of the Wisconsin glaciation. The Clovis layer was especially investigated by archaeologist C.Vance Haynes Jr. Visually, the layer is easily identifiable with the Usselo Horizon of Europe. Its stratigraphic position is coincident with the end of the Clovis culture and with the disappearance of the Pleistocene megafauna. In Europe, there is a clear correlation with the sudden demise of the Magdalenian culture, best known for the Franco-Cantabrian cave paintings, and with megafaunal extinctions such as

  20. Timing and duration of the Melt-Water Pulse 1A

    NASA Astrophysics Data System (ADS)

    Deschamps, P.; Durand, N.; Bard, E. G.; Hamelin, B.; Camoin, G.; Thomas, A. L.; Henderson, G. M.; Okuno, J.; Yokoyama, Y.

    2011-12-01

    Studying past sea levels provides invualuable information to further our understanding of ice-sheets' response to climate forcing. So far, the most complete and accurate sea-level record that encompassed the period between the Last Glacial Maximum and the present day is based on cores drilled offshore the Barbados coral reef. This record suggests a non-monotonous sea-level rise punctuated by dramatic accelerations, the so-called Melt Water Pulse events, that correspond to massive inputs of continental ice. The most extreme of these events, the MWP1-A, initially identified in the coral-based sea level record from the Barbados island, suggests a sea-level rise of ~20 meters between 14.1 and 13.6 ka. However, this event remains enigmatic and controversial. The temporal relationship between the MWP1-A and the abrupt climatic events that punctuated the last deglaciation is a subject of controversial debates. Several records are consistent with its occurrence, but no broad agreement emerges about its timing. Finally, large uncertainties surrounding the amplitude and timing of this Melt-Water Pulse 1A have raised doubts about the ice source responsible for such a step in sea-level rise and have questioned its temporal and causal relationships with the Bølling - Older Dryas - Allerød alternance, a major climatic oscillation during the last deglaciation. Consequently, it remains a key issue to fully confirm the existence, timing and amplitude of the MWP-1A by a precise coral reef record. The recent IODP Expedition 310 Tahiti Sea Level offers a unique opportunity to fully confirm the existence, timing and amplitude of the MWP-1A by a precise coral reef record. U-Th ages obtained on shallow to deeper corals collected during the IODP Expedition 310 offshore Tahiti Island extend the previous Tahiti sea-level and allow to document the sea-level rise during the key period of the MWP-1A. Our results confirm the occurrence of an acceleration of the sea-level rise during that