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Sample records for ice cores reveal

  1. Lomonosovfonna and Holtedahlfonna ice cores reveal eastwest disparities of the Spitsbergen environment since AD 1700

    E-print Network

    Moore, John

    Centre, Tromsø, Norway ABSTRACT. An ice core extracted from Holtedahlfonna ice cap, western Spitsbergen developed for these low-altitude ice caps. For instance, Iizuka and others (2002) and Grinsted and others (2006) found good summer melting indices based on ion concentrations of snow and ice from Austfonna

  2. Dust deposition events in Caucasus Mountains as revealed by shallow ice cores from Mt Elbrus

    NASA Astrophysics Data System (ADS)

    Kutuzov, Stanislav; Shahgedanova, Maria; Kemp, Sarah; Lavrentiev, Ivan; Mikhalenko, Vladimir; Popov, Gregory

    2013-04-01

    Dust aerosol transported to the high mountains and is deposited and stored in snow pack and glacier ice. Present and past records of dust stored in glaciers provide valuable information on frequency of deposition events, source regions and atmospheric pathways of mineral dust. The Caucasus Mountains, located between the Black and the Caspian seas is a glacierized region affected by deposition of desert dust from the Middle East and Sahara. In this study, a combination of ice core analysis, remote sensing and air mass trajectory modelling was used to identify the source regions of dust deposited on the glaciers of Mt Elbrus in the central Greater Caucasus and to characterize atmospheric pathways of dust with high temporal and spatial resolution. Shallow ice cores were extracted at Mt Elbrus in 2009 and 2012. Dust deposition events, recorded as brown layers in the snow, firn and ice were dated to the precision on months using oxygen and deuterium isotopic analyses. Examination of the local meteorological and NCEP/NCAR reanalysis data and application of HYSPLIT atmospheric trajectory model enabled dating dust deposition events with a precision of days, identification of potential source regions of desert dust and its pathways in the atmosphere. Examination of red-blue green infrared composite imagery from Spinning Enhanced Visible and Infra-Red Imager (SEVIRI) on board the Meteosat Second Generation (MSG) satellite enabled further provenancing of desert dust with high temporal (hours) and spatial (c. 100 km) resolution. Seventeen dust layers deposited between May 2009 and July 2012 were detected in the shallow cores. The source regions of the desert dust transported to Mt Elbrus were primarily located in the Middle East, in particular in eastern Syria and in the Syrian Desert at the border between Saudi Arabia, Iraq and Jordan. Northern Sahara, the foothills of the Djebel Akhdar Mountains in eastern Libya and the border region between Libya and Algeria were other important sources of desert dust. Fifteen dust deposition events occurred between March and June and two events occurred in October. The relatively high frequency of dust deposition events on Mt Elbrus may be due to the prolonged 2007-2010 drought in the Middle East resulting in more frequent activation of dust sources. Particle size and shape distributions were analysed for each dust sample using scanning electron microscope (SEM). The volume median diameter of dust particles from dust samples ranged from 3 to 13 microns. Particles with diameter of 1-10 microns accounted for 90±3% of the analysed samples. Detailed characterization of desert dust pathways from the Middle East and Sahara to the Caucasus leads to better understanding of pathways of desert dust in the atmosphere and highlights the importance of the Elbrus deep ice cores for the reconstruction of past environmental conditions in the south-eastern Europe and the Middle East in the future. This study is supported by the Marie Curie FP7-PEOPLE-2010-IIF project DIOGENES; Royal Soc JP100-235; RFBR N 1105-00304-a.

  3. Making an Ice Core.

    ERIC Educational Resources Information Center

    Kopaska-Merkel, David C.

    1995-01-01

    Explains an activity in which students construct a simulated ice core. Materials required include only a freezer, food coloring, a bottle, and water. This hands-on exercise demonstrates how a glacier is formed, how ice cores are studied, and the nature of precision and accuracy in measurement. Suitable for grades three through eight. (Author/PVD)

  4. Ice Core Investigations

    ERIC Educational Resources Information Center

    Krim, Jessica; Brody, Michael

    2008-01-01

    What can glaciers tell us about volcanoes and atmospheric conditions? How does this information relate to our understanding of climate change? Ice Core Investigations is an original and innovative activity that explores these types of questions. It brings together popular science issues such as research, climate change, ice core drilling, and air…

  5. Lattice distortion in ice crystals from the Vostok core (Antarctica) revealed by hard X-ray diffraction; implication in the deformation of ice at low stresses

    NASA Astrophysics Data System (ADS)

    Montagnat, Maurine; Duval, Paul; Bastie, Pierre; Hamelin, Bernard; Lipenkov, Volodya Ya.

    2003-09-01

    Hard X-ray diffraction experiments have been carried out on ice monocrystals taken from the 3623 m long Vostok core (Antarctica). Strain gradients associated with the storage of geometrically necessary dislocations appear to be a general feature of the deformation microstructure of ice. The observed lattice distortion is related to the bending of the basal plane and the torsion of the lattice around the c-axis. The lattice distortion is shown to be compatible with the basal dislocations generally observed in ice crystals, supporting the assumption of deformation modes governed by basal slip and accommodated by recrystallization processes. The dependence of the ice viscosity on grain size in ice sheets appears to be compatible with these accommodation modes.

  6. Ices in Starless and Starforming Cores

    NASA Astrophysics Data System (ADS)

    Öberg, Karin I.; Boogert, A. C. Adwin; Pontoppidan, Klaus M.; van den Broek, Saskia; van Dishoeck, Ewine F.; Bottinelli, Sandrine; Blake, Geoffrey A.; Evans, Neal J.

    2011-12-01

    Icy grain mantles are commonly observed through infrared spectroscopy toward dense clouds, cloud cores, protostellar envelopes and protoplanetary disks. Up to 80% of the available oxygen, carbon and nitrogen are found in such ices; the most common ice constituents - H2O, CO2 and CO - are second in abundance only to H2 in many star forming regions. In addition to being a molecular reservoir, ice chemistry is responsible for much of the chemical evolution from H2O to complex, prebiotic molecules. Combining the exisiting ISO, Spitzer, VLT and Keck ice data results in a large sample of ice sources (~80) that span all stages of star formation and a large range of protostellar luminosities (<0.1-105 L?). Here we summarize the different techniques that have been applied to mine this ice data set on information on typical ice compositions in different environments and what this implies about how ices form and evolve during star and planet formation. The focus is on how to maximize the use of empirical constraints from ice observations, followed by the application of information from experiments and models. This strategy is used to identify ice bands and to constrain which ices form early during cloud formation, which form later in the prestellar core and which require protostellar heat and/or UV radiation to form. The utility of statistical tests, survival analysis and ice maps is highlighted; the latter directly reveals that the prestellar ice formation takes place in two phases, associated with H2O and CO ice formation, respectively, and that most protostellar ice variation can be explained by differences in the prestellar CO ice formation stage. Finally, special attention is paid to the difficulty of observing complex ices directly and how gas observations, experiments and models help in constraining this ice chemistry stage.

  7. Ice Core Dating Software for Interactive Dating of Ice Cores

    NASA Astrophysics Data System (ADS)

    Kurbatov, A. V.; Mayewski, P. A.; Abdul Jawad, B. S.

    2005-12-01

    Scientists involved in ice core dating are well familiar with the problem of identification and recording the depth of annual signals using stable isotopes, glaciochemistry, ECM (electrical conductivity), DEP (dielectric properties) and particle counter data. Traditionally all parameters used for ice core dating were plotted as a function of depth, printed and after years were marked on the paper, converted to depth vs. age time scale. To expedite this tedious and manual process we developed interactive computer software, Ice core Dating (ICD) program. ICD is written in Java programming language, and uses GPL and GPL site licensed graphic libraries. The same 3.5 Mb in size pre-compiled single jar file, that includes all libraries and application code, was successfully tested on WinOS, Mac OSX, Linux, and Solaris operating systems running Java VM version 1.4. We have followed the modular design philosophy in our source code so potential integration with other software modules, data bases and server side distributed computer environments can be easily implemented. We expect to continue development of new suites of tools for easy integration of ice core data with other available time proxies. ICD is thoroughly documented and comes with a technical reference and cookbook that explains the purpose of the software and its many features, and provides examples to help new users quickly become familiar with the operation and philosophy of the software. ICD is available as a free download from the Climate Change Institute web site ( under the terms of GNU GPL public license.

  8. Siple Dome ice reveals two modes of millennial CO2 change during the last ice age

    PubMed Central

    Ahn, Jinho; Brook, Edward J.

    2014-01-01

    Reconstruction of atmospheric CO2 during times of past abrupt climate change may help us better understand climate-carbon cycle feedbacks. Previous ice core studies reveal simultaneous increases in atmospheric CO2 and Antarctic temperature during times when Greenland and the northern hemisphere experienced very long, cold stadial conditions during the last ice age. Whether this relationship extends to all of the numerous stadial events in the Greenland ice core record has not been clear. Here we present a high-resolution record of atmospheric CO2 from the Siple Dome ice core, Antarctica for part of the last ice age. We find that CO2 does not significantly change during the short Greenlandic stadial events, implying that the climate system perturbation that produced the short stadials was not strong enough to substantially alter the carbon cycle. PMID:24781344

  9. THE SPITZER ICE LEGACY: ICE EVOLUTION FROM CORES TO PROTOSTARS

    SciTech Connect

    Oeberg, Karin I.; Boogert, A. C. Adwin; Pontoppidan, Klaus M.; Van den Broek, Saskia; Van Dishoeck, Ewine F.; Bottinelli, Sandrine; Blake, Geoffrey A.; Evans, Neal J.

    2011-10-20

    Ices regulate much of the chemistry during star formation and account for up to 80% of the available oxygen and carbon. In this paper, we use the Spitzer c2d Legacy ice survey, complimented with data sets on ices in cloud cores and high-mass protostars, to determine standard ice abundances and to present a coherent picture of the evolution of ices during low- and high-mass star formation. The median ice composition H{sub 2}O:CO:CO{sub 2}:CH{sub 3}OH:NH{sub 3}:CH{sub 4}:XCN is 100:29:29:3:5:5:0.3 and 100:13:13:4:5:2:0.6 toward low- and high-mass protostars, respectively, and 100:31:38:4:-:-:- in cloud cores. In the low-mass sample, the ice abundances with respect to H{sub 2}O of CH{sub 4}, NH{sub 3}, and the component of CO{sub 2} mixed with H{sub 2}O typically vary by <25%, indicative of co-formation with H{sub 2}O. In contrast, some CO and CO{sub 2} ice components, XCN, and CH{sub 3}OH vary by factors 2-10 between the lower and upper quartile. The XCN band correlates with CO, consistent with its OCN{sup -} identification. The origin(s) of the different levels of ice abundance variations are constrained by comparing ice inventories toward different types of protostars and background stars, through ice mapping, analysis of cloud-to-cloud variations, and ice (anti-)correlations. Based on the analysis, the first ice formation phase is driven by hydrogenation of atoms, which results in an H{sub 2}O-dominated ice. At later prestellar times, CO freezes out and variations in CO freezeout levels and the subsequent CO-based chemistry can explain most of the observed ice abundance variations. The last important ice evolution stage is thermal and UV processing around protostars, resulting in CO desorption, ice segregation, and the formation of complex organic molecules. The distribution of cometary ice abundances is consistent with the idea that most cometary ices have a protostellar origin.

  10. Biological Ice Core Analysis in Russian Altai

    NASA Astrophysics Data System (ADS)

    Uetake, J.; Nakazawa, F.; Kohshima, S.; Miyake, T.; Narita, H.; Fujita, K.; Takeuchi, N.; Nakawo, M.

    2007-12-01

    In July 2003, a 171m long ice core was excavated from top of Belukha glacier (4,200m a. s. l.) in the Russian Altai Mountains. We examined vertical distributions of microorganisms (unicellular green algae, fungal spore, yeast) and pollens for potential use of ice core dating and reconstruction of past climate. Microorganisms have no seasonal variation in pit samples, however 5 genus of pollen (Fir, Spruce, Pine, Birch tree and Mugwort) have seasonality of each dispersed season. Therefore, this ice core can be identified past seasonal layers by pollen distribution. Pollen dating analysis of ice core estimate upper 48m ice core contain 86 years snow and ice, and this dating method well correspond to the 1963 peak in Tritium. This dating analysis is more accurate than other markers (oxygen isotope, dust, chemical concentration and melt percentage). Oxygen isotope trend from 1917 and temperature record of meteorological station near the glacier slightly increased and melt percentage have some anomalies from 1950s show recent temperature rising in this region. Otherwise, microorganisms and pollen have no trend except yeast. Vertical distribution of yeast peaks are well correspond to peaks of melt percentage show that yeast cell can grow in surface snow only in the warm period when liquid water available. In 1970s and 1980s, Nitrate increased and peaked because of anthropogenic emissions. Nitrate is major nutrient of photosynthetic microorganism, however, no clear relationship nitrate between unicellular green algae.

  11. Ice Chemistry in Starless Molecular Cores

    NASA Astrophysics Data System (ADS)

    Kalv?ns, J.

    2015-06-01

    Starless molecular cores are natural laboratories for interstellar molecular chemistry research. The chemistry of ices in such objects was investigated with a three-phase (gas, surface, and mantle) model. We considered the center part of five starless cores, with their physical conditions derived from observations. The ice chemistry of oxygen, nitrogen, sulfur, and complex organic molecules (COMs) was analyzed. We found that an ice-depth dimension, measured, e.g., in monolayers, is essential for modeling of chemistry in interstellar ices. Particularly, the H2O:CO:CO2:N2:NH3 ice abundance ratio regulates the production and destruction of minor species. It is suggested that photodesorption during the core-collapse period is responsible for the high abundance of interstellar H2O2 and O2H and other species synthesized on the surface. The calculated abundances of COMs in ice were compared to observed gas-phase values. Smaller activation barriers for CO and H2CO hydrogenation may help explain the production of a number of COMs. The observed abundance of methyl formate HCOOCH3 could be reproduced with a 1 kyr, 20 K temperature spike. Possible desorption mechanisms, relevant for COMs, are gas turbulence (ice exposure to interstellar photons) or a weak shock within the cloud core (grain collisions). To reproduce the observed COM abundances with the present 0D model, 1%-10% of ice mass needs to be sublimated. We estimate that the lifetime for starless cores likely does not exceed 1 Myr. Taurus cores are likely to be younger than their counterparts in most other clouds.

  12. Seasonal precipitation timing and ice core records

    SciTech Connect

    Steig, E.J.; Grootes, P.M.; Stuiver, M. )

    1994-12-16

    This is a commentary on global circulation model experiments of moisture source changes in Greenland, urging caution in how they are applied because they have important implications for paleoclimate reconstruction from ice cores. The work comes from preliminary find is of a ice core (GISP2) of the authors. The authors conclude that at present anomalies in Greenland ice core records should not be interpreted solely in terms of source region variations. The combined use of oxygen 18, D and ionic species in the new Summit, Greenland cores should make it possible to answer empirically some of the questions raised by the GCM experiments as to the interpretation of oxygen 18 records in terms of temperature. 4 refs., 1 fig.

  13. A New Paradigm for Ice Core Drilling

    NASA Astrophysics Data System (ADS)

    Albert, Mary; Bentley, Charles; Twickler, Mark

    2010-09-01

    The search for answers to questions about the changing climate has created an urgent need to discover past climate signatures archived in glaciers and ice sheets, and to understand current ice sheet behavior. Recognizing that U.S. scientific productivity in this area depends upon a mechanism for ensuring continuity and international cooperation in ice coring and drilling efforts, along with the availability of appropriate drills, drilling expertise, and innovations in drilling technology, the U.S. National Science Foundation (NSF) has established the Ice Drilling Program Office (IDPO) and its partner, the Ice Drilling Design and Operations group (IDDO), together known as IDPO/IDDO (Figure 1). This approach to integrated research and technology planning and delivery replaces the prior approach to drilling, which involved a series of NSF contracts with the Polar Ice Coring Office (PICO) and Ice Coring and Drilling Services (ICDS). This contracting approach lacked integrated planning. Previously, NSF had no way to forecast what science the community would propose—it would get compelling climate proposals that needed ice cores for data, but in many cases no existing drill could retrieve the core needed in the proposal. Constructing the needed drill—a process that takes years—forced science objectives to be put on hold. Now the science community is able to give feedback on its needs to IDPO/IDDO continually, allowing those who develop drilling technology to begin designing and constructing drills that scientists will need for the science proposals that they will submit years in the future. As such, IDPO/IDDO represents a new paradigm for integrated science and science support.

  14. Interpreting insolation signals in ice core records

    NASA Astrophysics Data System (ADS)

    Hutterli, M. A.; Sime, L. C.

    2009-04-01

    High resolution East Antarctica stable water isotope ice core records are inversely related to Southern Hemisphere summer insolation intensity at the precession and obliquity timescales. Because Southern Hemisphere summer insolation varies directly out of phase with that in the Northern Hemisphere, this has lead to the suggestion that global climate is controlled by some measure of Northern Hemisphere summer insolation intensity. Here we present results from a snow metamorphism model and an isotope enabled GCM suggesting that the East Antarctic isotope ice core variations in the precession and obliquity bands may instead be caused by post-depositional processes that are modulated by changes in local insolation. This likely also applies to other ice core records and has implications for the interpretation of global climate change at these orbital periods.

  15. Antarctic-Wide Array of High-Resolution Ice Core Records Reveals Pervasive Lead Pollution Began in 1889 and Persists Today

    NASA Technical Reports Server (NTRS)

    McConnell, J. R.; Maselli, O. J.; Sigl, M.; Vallelonga, P.; Neumann, Thomas Allen; Anschutz, H.; Bales, R. C.; Curran, M. A. J.; Das, S. B.; Edwards, R.; Kipfstuhl, S.; Layman, L.; Thomas, E. R.

    2014-01-01

    Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead pollution at South Pole and throughout Antarctica by 1889 - beating polar explorers by more than 22 years. Unlike the Arctic where lead pollution peaked in the 1970s, lead pollution in Antarctica was as high in the early 20th century as at any time since industrialization. The similar timing and magnitude of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19th century and remains a significant source today. An estimated 660 t of industrial lead have been deposited over Antarctica during the past 130 years as a result of mid-latitude industrial emissions, with regional-to-global scale circulation likely modulating aerosol concentrations. Despite abatement efforts, significant lead pollution in Antarctica persists into the 21st century.

  16. Antarctic-wide array of high-resolution ice core records reveals pervasive lead pollution began in 1889 and persists today

    NASA Astrophysics Data System (ADS)

    McConnell, J. R.; Maselli, O. J.; Sigl, M.; Vallelonga, P.; Neumann, T.; Anschütz, H.; Bales, R. C.; Curran, M. A. J.; Das, S. B.; Edwards, R.; Kipfstuhl, S.; Layman, L.; Thomas, E. R.

    2014-07-01

    Interior Antarctica is among the most remote places on Earth and was thought to be beyond the reach of human impacts when Amundsen and Scott raced to the South Pole in 1911. Here we show detailed measurements from an extensive array of 16 ice cores quantifying substantial toxic heavy metal lead pollution at South Pole and throughout Antarctica by 1889 - beating polar explorers by more than 22 years. Unlike the Arctic where lead pollution peaked in the 1970s, lead pollution in Antarctica was as high in the early 20th century as at any time since industrialization. The similar timing and magnitude of changes in lead deposition across Antarctica, as well as the characteristic isotopic signature of Broken Hill lead found throughout the continent, suggest that this single emission source in southern Australia was responsible for the introduction of lead pollution into Antarctica at the end of the 19th century and remains a significant source today. An estimated 660 t of industrial lead have been deposited over Antarctica during the past 130 years as a result of mid-latitude industrial emissions, with regional-to-global scale circulation likely modulating aerosol concentrations. Despite abatement efforts, significant lead pollution in Antarctica persists into the 21st century.

  17. Ice chemistry in starless molecular cores

    E-print Network

    Kalvans, Juris

    2015-01-01

    Starless molecular cores are natural laboratories for interstellar molecular chemistry research. The chemistry of ices in such objects was investigated with a three-phase (gas, surface, and mantle) model. We considered the center part of five starless cores, with their physical conditions derived from observations. The ice chemistry of oxygen, nitrogen, sulfur, and complex organic molecules (COMs) was analyzed. We found that an ice-depth dimension, measured, e.g., in monolayers, is essential for modeling of chemistry in interstellar ices. Particularly, the H2O:CO:CO2:N2:NH3 ice abundance ratio regulates the production and destruction of minor species. It is suggested that photodesorption during core collapse period is responsible for high abundance of interstellar H2O2 and O2H, and other species synthesized on the surface. The calculated abundances of COMs in ice were compared to observed gas-phase values. Smaller activation barriers for CO and H2CO hydrogenation may help explain the production of a number of...

  18. Extended East Antarctic ice-core tephrostratigraphy

    NASA Astrophysics Data System (ADS)

    Narcisi, Biancamaria; Petit, Jean Robert; Delmonte, Barbara

    2010-01-01

    Three new tephra layers have been identified and analysed in the deeper sections of the EPICA Dome C (EDC) and Vostok ice record (East Antarctic plateau): one from EDC (358 ka old), originated from an Antarctic volcano, and two from Vostok (406 and 414 ka old, respectively), which are related to Antarctic volcanoes and to southern Andes and/or Antarctic Peninsula centres, respectively. These layers represent the oldest tephra-bearing events so far detected in deep polar ice cores and extend the regional tephrostratigraphic framework back to the fourth climatic cycle. Although differences between the drill sites are observed, new and previously published tephra data from deep ice cores broadly confirm that the clockwise circum-Antarctic atmospheric circulation played a major role in the dispersal of volcanic dust onto the plateau. While the last 220-ka core sections contain about a dozen visible tephra fall layers, the ice representing the time interval from 220 ka back to 800 ka (i.e. the EDC core bottom) is almost devoid of observed tephras. Although it is possible that the reduced frequency is an observational artefact, the observed pattern could alternatively reflect late Quaternary activity fluctuations of sources for tephra in the East Antarctic plateau, particularly South Sandwich Islands, with enhanced explosive activity in the last two glacial cycles with respect to previous periods.

  19. Ice-core evidence of abrupt climate changes.

    PubMed

    Alley, R B

    2000-02-15

    Ice-core records show that climate changes in the past have been large, rapid, and synchronous over broad areas extending into low latitudes, with less variability over historical times. These ice-core records come from high mountain glaciers and the polar regions, including small ice caps and the large ice sheets of Greenland and Antarctica. PMID:10677460

  20. Biological proxies recorded in a Belukha ice core, Russian Altai

    NASA Astrophysics Data System (ADS)

    Papina, T.; Blyacharchyuk, T.; Eichler, A.; Malygina, N.; Mitrofanova, E.; Schwikowski, M.

    2013-05-01

    Different biological proxies such as pollen, cysts, and diatoms were identified and quantified in the upper part of a Belukha ice core from the Russian Altai. The ice core from the Belukha glacier collected in 2001 (4062 m a.s.l., 49°48' N, 86° 34' E) was analyzed with annual resolution in the period 1964-2000. We used daily data of the frequency of synoptic patterns observed in the Northern Hemisphere along with daily data of precipitation to identify the main modern sources of biological proxies deposited at the Belukha glacier. Our analyses revealed that main sources of diatoms in the Belukha ice core are water bodies of the Aral, Caspian, and North Kazakhstan basins. Coniferous trees pollen originated from the taiga forest of the boreal zone of West Siberia and pollen of hardwoods and herbs from steppe and forest steppe vegetation in the Northern Altai and East Kazakhstan. Cysts of algae and spores of inferior plants were transported from local water bodies and forests. The identified source regions of the biological species are supported by back trajectory analyses and are in good agreement with emission source regions of the trace species in the ice core.

  1. ACEX Grain Size Analyses, Revealing Arctic Paleo-Ice Environments

    NASA Astrophysics Data System (ADS)

    Ashmankas, C. E.; Moran, K.; O'Regan, M.; Sugisaki, S.

    2006-12-01

    Summer 2004 hosted an unprecedented event in Arctic research; the successful coring of Arctic sediments to obtain a paleo-climate record that extends through the Cenozoic Era. Low resolution grain size analyses of samples taken during the Arctic Coring Expedition (ACEX) reveal five ice rafted debris (IRD) relationships, which we hypothesize to correspond to five distinct Arctic paleo-ice environments. This study defines IRD as the percentage of terrigenous grains > 63 ?m. IRD is comprised of both sea-ice rafted debris (SIRD) and iceberg rafted debris (IBRD). IBRD is defined as the percentage of terrigenous grains > 250 ?m (modified from Bischof, 2000). Grain size analyses were completed using a Malvern Mastersizer 2000. The five relationships and their corresponding environments are: 1) high IRD percentage and high iceberg rafted debris (IBRD) percentage, reflecting a vastly glaciated environment, 2) low IRD percentage and low IBRD percentage, indicating a possibly seasonally cold environment with little permanent ice, 3) high IRD percentage and low IBRD percentage, an indication of a sea-ice dominated environment, 4) low IRD percentage and high IBRD percentage, indicative of conditions of considerable iceberg expulsion and low sea-ice production, and 5) No IRD present, corresponding to a warm ice-free Arctic climate. The earliest indication of IRD in the ACEX record occurs in the Eocene, a time much older than the intensification of Northern Hemisphere glaciation of ~ 3 Ma. Throughout the Neogene, IRD remains an important component of the sedimentary record. Differentiating modes of IRD in terms of SIRD and IBRD is an important step in reconstructing Arctic paleo- environment.

  2. white paper, 9 March 2009 An ice core to reconstruct Greenland ice sheet mass balance

    E-print Network

    Box, Jason E.

    through the Pleistocene ice age and even reaching the end of the Eemian warmthwhite paper, 9 March 2009 1 An ice core to reconstruct Greenland ice sheet mass balance Recent satellite and GPS observations spanning

  3. Millennial climate variability: GCM-simulation and Greenland ice cores

    NASA Astrophysics Data System (ADS)

    Blender, Richard; Fraedrich, Klaus; Hunt, Barrie

    2006-02-01

    The low frequency variability of the near surface temperature in a climate simulation is compared with Greenland ice core ?18O time series during the holocene. The simulation is performed with the coupled CSIRO atmosphere-ocean model under present-day conditions. The variability, analyzed by the detrended fluctuation analysis, reveals power-law scaling of the power-spectrum for frequency f, S(f) ~ f-?, and long term memory (LTM) given by ? > 0. The near surface temperature shows intense LTM in the North Atlantic south of Greenland, weak LTM in parts of the Antarctic ocean and the tropical Atlantic, and no LTM in the Pacific ocean. The power-law exponent ? ~ 0.5 near Greenland agrees with ice core temperature proxies up to time scales of 1000 years. The LTM of the surface temperature is explained by the high low frequency variability of the zonally averaged stream-function in the Atlantic with maxima in the Arctic ocean.

  4. Ice core evidence for Antarctic sea ice decline since the 1950s.

    PubMed

    Curran, Mark A J; van Ommen, Tas D; Morgan, Vin I; Phillips, Katrina L; Palmer, Anne S

    2003-11-14

    The instrumental record of Antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal Antarctica. Here we report a significant correlation (P < 0.002) between methanesulphonic acid (MSA) concentrations from a Law Dome ice core and 22 years of satellite-derived sea ice extent (SIE) for the 80 degrees E to 140 degrees E sector. Applying this instrumental calibration to longer term MSA data (1841 to 1995 A.D.) suggests that there has been a 20% decline in SIE since about 1950. The decline is not uniform, showing large cyclical variations, with periods of about 11 years, that confuse trend detection over the relatively short satellite era. PMID:14615537

  5. Antarctic ice core samples: culturable bacterial diversity.

    PubMed

    Shivaji, Sisinthy; Begum, Zareena; Shiva Nageswara Rao, Singireesu Soma; Vishnu Vardhan Reddy, Puram V; Manasa, Poorna; Sailaja, Buddi; Prathiba, Mambatta S; Thamban, Meloth; Krishnan, Kottekkatu P; Singh, Shiv M; Srinivas, Tanuku N R

    2013-01-01

    Culturable bacterial abundance at 11 different depths of a 50.26 m ice core from the Tallaksenvarden Nunatak, Antarctica, varied from 0.02 to 5.8 × 10(3) CFU ml(-1) of the melt water. A total of 138 bacterial strains were recovered from the 11 different depths of the ice core. Based on 16S rRNA gene sequence analyses, the 138 isolates could be categorized into 25 phylotypes belonging to phyla Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. All isolates had 16S rRNA sequences similar to previously determined sequences (97.2-100%). No correlation was observed in the distribution of the isolates at the various depths either at the phylum, genus or species level. The 25 phylotypes varied in growth temperature range, tolerance to NaCl, growth pH range and ability to produce eight different extracellular enzymes at either 4 or 18 °C. Iso-, anteiso-, unsaturated and saturated fatty acids together constituted a significant proportion of the total fatty acid composition. PMID:23041141

  6. Seasonal precipitation timing and ice core records

    SciTech Connect

    Charles, C.D.; Rind, D.; Jouzel, J.

    1995-07-14

    Commenting on our work with isotope tracers and the origin of moisture in general circulation model simulations suggest that changes in the seasonal distribution of precipitation may provide strong control on isotopic variability in Greenland ice cores. In principle, we agree with the thrust of their comment. In a broad sense, without consideration of specific processes, the seasonality effects discussed and the moisture source effects described in our report are two classes of the same general phenomenon: evaporation, distillation, and transport of isotopes over different temperature regimes. Although the analysis for Greenland precipitation over the last century suggests that seasonal effects are a significant component of interannual isotopic variability, general circulation model (GCMs) represent one of the few means of assessing the importance of this phenomenon for interpreting the isotopic record over glacial cycles. The GCM approach is important for understanding the relationship between {delta}{sup 18}O and temperature because (1) thermodynamic principles and analysis of modern isotopic data suggest that present-day spatial {delta}{sup 18}O-temperature correlations cannot be considered an exact surrogate for the temporal relationship between these variables (2) geographic isotopic variability-for example, the differences in isotopic values among ice cores-can best be examined with a three-dimensional mode. This short article goes on to explain the researchers` results and reasoning. 5 refs., 1 fig.

  7. Mineralogical composition of EPICA Dome C aeolian ice core dust

    NASA Astrophysics Data System (ADS)

    Sala, M.; Dapiaggi, M.; Delmonte, B.; Marino, F.; Artioli, G.; Maggi, V.; Revel-Rolland, M.; Petit, J. R.

    2009-04-01

    Optimization of analytical procedures for mineralogical characterization of aeolian ice core dust trapped in Antarctic ice has been developed in this work. The analytical protocol includes X-Ray Powder Diffraction (XRPD) and High Resolution-Transmission Electron Microscopy (HR-TEM) coupled to Energy Dispersive-X-Ray Fluorescence (ED-XRF) techniques. This procedure has been applied on small East Antarctic ice core samples; in particular, samples from the EPICA-Dome C (EDC, 75°06'S; 123°21'E) ice core have been selected from the last two climatic cycles. In parallel, similar mineralogical characterization was performed on dust and sediment samples from potential source areas (onwards PSA) as South America (SSA), South Africa (SSAf), Australia (AUS), New Zealand (NZ), and Antarctica (ANT). These PSA samples are the same used for Sr and Nd isotope geochemistry (Delmonte et al., 2004; Revel-Rolland et al., 2006). Implicit in this approach is to consider the Sr and Nd isotopic composition of dust as tracer for dust provenance, and the mineralogical composition of dust from PSAs and from ice cores as indicator for dust source weathering and environment. Therefore dust mineralogy provides important complementary information which cannot be detected from isotope geochemistry alone, and ideally these two methods must be used in combination. Results from the present work on the EDC ice core, obtained by coupling powder and single crystal investigations, confirm and improve the pioneer results obtained on the "old" Dome C and on the Vostok ice cores using electron microscopy (Gaudichet et al., 1986 and 1988). XRPD and HR-TEM results revealed that the mineral dust reaching inland East Antarctica during glacial periods is composed mainly by chlorite, mica, illite-smectite, quartz and feldspar, while during interglacials a significant decrease in the concentration of illite-smectite and chlorite can be observed along with an increase of mica and presence of kaolinite. The mineralogical characterization of the fine size fraction (below 5 micron) of selected Southern Hemisphere aeolian sediments highlights that smectite and feldspar are characteristic for SSA and ANT sediments, chlorite for SSA, ANT and NZ sediments, and kaolinite for AUS and SSAf sediments. Overall, illite and quartz represent the most common minerals in the Southern Hemisphere dust source areas. Comparison of EDC ice core dust with PSAs collected in the Southern Hemisphere continental lands confirm that SSA can be considered the most probable dust source for dust over the East Antarctic interior during the glacial periods, while the mineralogical evidence observed for interglacials indicates a mixed provenance from SSA and likely AUS during warm periods. This work highlights the utility of XRPD coupled with HR-TEM to help in the interpretation of dust transport and deposition from the continental source regions the Antarctic continent, and the potential to understand the environmental conditions at the source regions themselves.

  8. Devon island ice cap: core stratigraphy and paleoclimate.

    PubMed

    Koerner, R M

    1977-04-01

    Valuable paleoclimatic information can be gained by studying the distribution of melt layers in deep ice cores. A profile representing the percentage of ice in melt layers in a core drilled from the Devon Island ice cap plotted against both time and depth shows that the ice cap has experienced a period of very warm summers since 1925, following a period of colder summers between about 1600 and 1925. The earlier period was coldest between 1680 and 1730. There is a high correlation between the melt-layer ice percentage and the mass balance of the ice cap. The relation between them suggests that the ice cap mass balance was zero (accumulation equaled ablation) during the colder period but is negative in the present warmer one. There is no firm evidence of a present cooling trend in the summer conditions on the ice cap. A comparison with the melt-layer ice percentage in cores from the other major Canadian Arctic ice caps shows that the variation of summer conditions found for the Devon Island ice cap is representative for all the large ice caps for about 90 percent of the time. There is also a good correlation between melt-layer percentage and summer sea-ice conditions in the archipelago. This suggests that the search for the northwest passage was influenced by changing climate, with the 19th-century peak of the often tragic exploration coinciding with a period of very cold summers. PMID:17733504

  9. Implementation of counted layers for coherent ice core chronology

    NASA Astrophysics Data System (ADS)

    Lemieux-Dudon, B.; Bazin, L.; Landais, A.; Toyé Mahamadou Kele, H.; Guillevic, M.; Kindler, P.; Parrenin, F.; Martinerie, P.

    2015-06-01

    A recent coherent chronology has been built for four Antarctic ice cores and the NorthGRIP (NGRIP) Greenland ice core (Antarctic Ice Core Chronology 2012, AICC2012) using a Bayesian approach for ice core dating (Datice). When building the AICC2012 chronology, and in order to prevent any confusion with official ice core chronology, the AICC2012 chronology for NGRIP was forced to fit exactly the GICC05 chronology based on layer counting. However, such a strong tuning did not satisfy the hypothesis of independence of background parameters and observations for the NGRIP core, as required by Datice. We present here the implementation in Datice of a new type of markers that is better suited for constraints deduced from layer counting: the duration constraints. Estimating the global error on chronology due to such markers is not straightforward and implies some assumption on the correlation between individual counting errors for each interval of duration. We validate this new methodological implementation by conducting twin experiments and a posteriori diagnostics on the NGRIP ice core. Several sensitivity tests on marker sampling and correlation between counting errors were performed to provide some guidelines when using such a method for future dating experiments. Finally, using these markers for NGRIP in a five-core dating exercise with Datice leads to new chronologies that do not differ by more than 410 years from AICC2012 for Antarctic ice cores and 150 years from GICC05 for NGRIP over the last 60 000 years.

  10. Snow algae in an ice core drilled on Grigoriev Ice cap in the Kyrgyz Tien Shen Mountains

    NASA Astrophysics Data System (ADS)

    Honda, M.; Takeuchi, N.; Sera, S.; Fujita, K.; Okamoto, S.; Naoki, K.; Aizen, V. B.

    2012-12-01

    Snow algae are photosynthetic microorganisms and are living on the surfase of glaciers. They grow on melting surface from spring to summer and their biomass and community structure are changed with physical and chemical conditions on glaciers. Ice cores drilled from glaciers also contain snow algae that grew in the past. Studying biomass and community structure of snow algae in ice cores could reveal the temporal variation in snow algae in the past, and also environmental conditions relating propagation of snow algae. In this study, we anlalyzed snow algae preserved in an ice core of Grigoriev Ice cap located in eastern Kyrgyzstan of the central Asia, and to describe their temporal variations for the last 200 years. The ice core drilling was carried out on September in 2007 on the Grigoriev Ice cap in the Kyrgyz Tien Shen Mountains. A 87 m long ice core from the surface to the bedrock was recovered at the top of the ice cap. The core was horizontally cut every 5 cm (total 1212 samples). The samples were melted and preserved as a 3% formalin solution. After the sample water was filtered through a hydrophilized PTFE membrane filter, observed by microscope. Snow algae in the sample water were counting. The algal biomass was represented by the cell number per unit water volume. Here, we showed the results between the surface to the 64 m in depth. We also analyzed the snow algal communities on the surface of the ice cap collected from five different sites from the top down to the terminus. Microscopy revealed that the ice core contained three taxa of filamentous cyanobacteria, an unicellular cyanobacterium, and two green algae. They were also found on the ice or snow surface of the i Ice cap. The quantitative analyses of the algae in the part of upper 64 m deep of the ice core samples revealed that the algal biomass varied significantly and showed many peaks. Furthermore, the biomass profile differed among the taxa. The filamentous cyanobacterium varied from 0.0 to 4.6 x 103?m3 mL-1 (mean: 56?m3 mL-1 ), the unicellular cyanobacterium varied from 0.0 to 3.0 x 104?m3 mL-1 (mean: 1.2 x 103?m3 mL-1 ), and Green algae varied from 0.0 to 2.3 x 104?m3 mL-1 (mean: 2.2 x 103?m3 mL-1 ). Based on the dating by pollen grains, the 64 m core covers 237 years. The results suggest that the snow algae did not grow every year on the top of the ice cap, and their biomass and community structure varied greatly from year to year. The total biomass after the 1960s was significantly higher than those before the 1950s. This suggested suggests that the surface conditions changed more favorable to the growth of algae in the 1960s. Annal variation of the algal biomass was found to be significantly correlated with air temperature at the nearest observing station from Grigoriev the iIce cap and hydrogen stable isotope (?D) in the ice core. The results suggest that the algal growth is more preferable in warmer year.

  11. Ice core evidence for extensive melting of the greenland ice sheet in the last interglacial.

    PubMed

    Koerner, R M

    1989-05-26

    Evidence from ice at the bottom of ice cores from the Canadian Arctic Islands and Camp Century and Dye-3 in Greenland suggests that the Greenland ice sheet melted extensively or completely during the last interglacial period more than 100 ka (thousand years ago), in contrast to earlier interpretations. The presence of dirt particles in the basal ice has previously been thought to indicate that the base of the ice sheets had melted and that the evidence for the time of original growth of these ice masses had been destroyed. However, the particles most likely blew onto the ice when the dimensions of the ice caps and ice sheets were much smaller. Ice texture, gas content, and other evidence also suggest that the basal ice at each drill site is superimposed ice, a type of ice typical of the early growth stages of an ice cap or ice sheet. If the present-day ice masses began their growth during the last interglacial, the ice sheet from the earlier (Illinoian) glacial period must have competely or largely melted during the early part of the same interglacial period. If such melting did occur, the 6-meter higher-than-present sea level during the Sangamon cannot be attributed to disintegration of the West Antarctic ice sheet, as has been suggested. PMID:17731883

  12. On the occurrence of annual layers in Dome Fuji ice core early Holocene ice

    NASA Astrophysics Data System (ADS)

    Svensson, A.; Fujita, S.; Bigler, M.; Braun, M.; Dallmayr, R.; Gkinis, V.; Goto-Azuma, K.; Hirabayashi, M.; Kawamura, K.; Kipfstuhl, S.; Kjær, H. A.; Popp, T.; Simonsen, M.; Steffensen, J. P.; Vallelonga, P.; Vinther, B. M.

    2015-03-01

    Whereas ice cores from high accumulation sites in coastal Antarctica clearly demonstrate annual layering, it is debated whether a seasonal signal is also preserved in ice cores from lower accumulation sites further inland and particularly on the East Antarctic Plateau. In this study, we examine five metres of early Holocene ice from the Dome Fuji (DF) ice core in high temporal resolution by continuous flow analysis. The ice was continuously analyzed for concentrations of dust, sodium, ammonium, liquid conductivity, and water isotopic composition. Furthermore, a dielectric profiling was performed on the solid ice. In most of the analyzed ice, the multi-parameter impurity dataset appears to resolve the seasonal variability although the identification of annual layers is not always unambiguous. A layer counting based on the same principles as those previously applied to the Greenland NGRIP and the Antarctic EPICA Dronning Maud Land (EDML) ice cores leads to a mean annual layer thickness for the DF ice of 3.0 ± 0.3 cm that compares well to existing estimates. The measured DF section is linked to the EDML ice core through a characteristic pattern of three significant acidity peaks that are present in both cores. The corresponding section of the EDML ice core has recently been dated by annual layer counting and the number of years identified independently in the two cores agree within error estimates. We therefore conclude that, to first order, the annual signal is preserved in this section of the DF core. This case study demonstrates the feasibility of determining annually deposited strata on the central Eastern Antarctic Plateau. It also opens the possibility of resolving annual layers in the Eemian section of the DF ice core where the accumulation is estimated to have been greater than in the Holocene.

  13. AVHRR imagery reveals Antarctic ice dynamics

    SciTech Connect

    Bindschadler, R.A.; Vornberger, P.L. STX Corp., Lanham, MD )

    1990-06-01

    A portion of AVHRR data taken on December 5, 1987 at 06:15 GMT over a part of Antarctica is used here to show that many of the most significant dynamic features of ice sheets can be identified by a careful examination of AVHRR imagery. The relatively low resolution of this instrument makes it ideal for obtaining a broad view of the ice sheets, while its wide swath allows coverage of areas beyond the reach of high-resolution imagers either currently in orbit or planned. An interpretation is given of the present data, which cover the area of ice streams that drain the interior of the West Antarctic ice sheet into the Ross Ice Shelf. 21 refs.

  14. Tributaries of West Antarctic Ice Streams Revealed by RADARSAT Interferometry.

    PubMed

    Joughin; Gray; Bindschadler; Price; Morse; Hulbe; Mattar; Werner

    1999-10-01

    Interferometric RADARSAT data are used to map ice motion in the source areas of four West Antarctic ice streams. The data reveal that tributaries, coincident with subglacial valleys, provide a spatially extensive transition between slow inland flow and rapid ice stream flow and that adjacent ice streams draw from shared source regions. Two tributaries flow into the stagnant ice stream C, creating an extensive region that is thickening at an average rate of 0.49 meters per year. This is one of the largest rates of thickening ever reported in Antarctica. PMID:10514370

  15. WD2014: A new reference chronology for ice cores from Antarctica?

    NASA Astrophysics Data System (ADS)

    Sigl, Michael; McConnell, Joseph R.; Winstrup, Mai; Fudge, Taylor J.; Cole-Dai, Jihong; Ferris, David; Taylor, Kendrick; Buizert, Christo; Rhodes, Rachael; McGwire, Ken; Welten, Kees C.; Woodruff, Thomas E.; Dunbar, Nelia; Iverson, Nels; Maselli, Olivia J.; Pasteris, Daniel R.; Muscheler, Raimund

    2015-04-01

    Here we present a chronology (WD2014) for the upper part (0-2850 m, 31.2 ka BP) of the West Antarctic Ice Sheet (WAIS)-Divide ice core which is based on layer counting of distinctive annual cycles preserved in the elemental, chemical and electrical conductivity records. These cycles are caused by the seasonally varying impurity concentrations in snowfall reflecting source strength of emissions, transport and deposition efficiency. A new ice core chronology has been developed using manual interpretation as well as by using a layer detection algorithm based on Hidden Markov Models taking advantage of the large suite of sub-annually resolved and co-registered aerosol records from high-resolution continuous measurements. The age model is validated against the absolute dated radiocarbon calibration curve IntCal13 using ice-core Be-10 measurements for proxy synchronization. These records reveal an unprecedented accuracy of the new ice core chronology since the Last Glacial Maximum. The new chronology can become a reference chronology for ice cores with synchronization to other ice cores achievable through the unique high-resolution sulfur record indicating hundreds of volcanic signals common to many other deep ice cores in Antarctica. A developing tephra framework for ice cores from West Antarctica will allow to better integrating Antarctic ice cores and the marine and terrestrial records from the southern hemisphere in the future, thus gaining a detailed chronologic picture of climatic changes and environmental consequences for the region over the past 31,000 years. This southern hemisphere perspective is a fundamental step in developing a detailed global understanding of the effects of past climate changes, and its implications for the future. Due to a small ice-age gas-age difference (delta-age) at WAIS Divide - because of high annual snowfall rates at this site - and a new high-resolution WAIS CH4 record, this new ice core chronology provides also independent, precise ages for abrupt climate transitions in the northern hemisphere (e.g., GS1-GI1 warming; 14,580 ± 50 years) during the last deglaciation. Thus, WD2014 provides a new perspective on the variability of global sea-level, climate and ice-sheet histories.

  16. Ice Core Records of Recent Northwest Greenland Climate

    NASA Astrophysics Data System (ADS)

    Osterberg, E. C.; Wong, G. J.; Ferris, D.; Lutz, E.; Howley, J. A.; Kelly, M. A.; Axford, Y.; Hawley, R. L.

    2014-12-01

    Meteorological station data from NW Greenland indicate a 3oC temperature rise since 1990, with most of the warming occurring in fall and winter. According to remote sensing data, the NW Greenland ice sheet (GIS) and coastal ice caps are responding with ice mass loss and margin retreat, but the cryosphere's response to previous climate variability is poorly constrained in this region. We are developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate change and cryospheric response in NW Greenland to improve projections of future ice loss and sea level rise in a warming climate. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 21 m) from the coastal region of the GIS (2Barrel site; 76.9317o N, 63.1467o W, 1685 m el.) and the summit of North Ice Cap (76.938o N, 67.671o W, 1273 m el.) in 2011, 2012 and 2014. The 2Barrel ice core record has statistically significant relationships with regional spring and fall Baffin Bay sea ice extent, summertime temperature, and annual precipitation. Here we evaluate relationships between the 2014 North Ice Cap firn core glaciochemical record and climate variability from regional instrumental stations and reanalysis datasets. We compare the coastal North Ice Cap record to more inland records from 2Barrel, Camp Century and NEEM to evaluate spatial and elevational gradients in recent NW Greenland climate change.

  17. West Antarctic Ice-core Records of Sea-Ice Variability: A Neural Network Perspective

    NASA Astrophysics Data System (ADS)

    Reusch, D. B.

    2009-12-01

    Full understanding of Antarctic sea-ice variability is hindered by limited detailed records beyond the satellite era. Ice-core records from the adjacent continental ice sheet offer a possible solution to this problem. Here we apply new tools from the field of artificial neural networks (ANNs) to reconstruct centennial-scale records of West Antarctic sea-ice variability using a suite of recent ice-core datasets and the satellite-based record of sea ice. Antarctic ice cores are known to record aspects of sea-ice variability (e.g., sea ice-edge and sulfate content). However, the field has yet to fully exploit all of the available ice-core data, and the nonlinear properties therein, to develop robust ice core-sea ice calibrations that can be used to build detailed spatial histories of sea ice. Self-organizing maps (SOMs) and ANNs offer a solution to this problem. With SOMs, we develop sets of representative patterns from our multivariate datasets that, for example, simplify the representation of chemistry data from multiple ice core sites. These patterns let us replace a multidimensional coordinate in data space (e.g., chemistry at all sites at time t) with a 2-d coordinate in “SOM space”. Patterns also classify the input dataset and identify times where particular conditions exist in the data. ANNs allow us to nonlinearly relate a set of predictors to a set of targets, e.g., ice-core chemistry to sea-ice extent. With a well-trained ANN, sea ice conditions outside the satellite era may be developed from extended ice-core datasets. A significant challenge to this approach (as well as any other calibration) is the limited overlap between the ice-core and satellite-based sea ice records. SOM analysis of monthly sea-ice-edge data produces a set of generalized patterns concisely capturing both spatial and temporal variability in this climate variable, e.g., identifying the multiple spatial patterns that correspond to “greatest extent conditions”. By tracking the most common patterns for each month, the annual cycling of expansion and contraction is readily visualized, including variability in the rate of change in extent at different times of the year, e.g., retreat in January is faster than November. Eighteen West Antarctic sites (e.g., Siple Dome, CWA, USITASE) provide extensive glaciochemical data for this work. Preliminary SOM analyses of these data (for the period 1870-1994) readily show the spatial variability of this region. For example, the patterns of high Na+ values focus on sites in the region ~77-79 °S, 115-125 °W (~250 km north of Byrd). Additional analyses will help to identify the best ice-core predictors of sea-ice variability. Further analysis of these sea-ice and ice-core datasets will bring additional insights and the development of long-term West Antarctic sea-ice reconstructions.

  18. Black carbon concentration in a Greenland Dye-3 ice core

    NASA Astrophysics Data System (ADS)

    Chylek, Petr; Johnson, Bruce; Wu, Hong

    1992-10-01

    We have determined the black carbon concentration in Greenland Dye-3 ice core samples covering the time period from about 3380 to 100 years before present. The average concentration found is 1.53 microg of black carbon per 1 kg of ice. We have found significantly lower black carbon concentrations during the time period from 750 to 100 years before present connected possibly with the Little Ice Age and corresponding changes in atmospheric general circulation patterns and black carbon sources.

  19. Black carbon concentration in a Greenland Dye-3 ice core

    SciTech Connect

    Chylek, P.; Johnson, B.; Wu, Hong )

    1992-10-01

    We have determined the black carbon concentration in Greenland Dye-3 ice core samples covering the time period from about 3380 to 100 years before present. The average concentration found is 1.53 microg of black carbon per 1 kg of ice. We have found significantly lower black carbon concentrations during the time period from 750 to 100 years before present connected possibly with the Little Ice Age and corresponding changes in atmospheric general circulation patterns and black carbon sources. 18 refs.

  20. Greenland ice core evidence of the 79 AD Vesuvius eruption

    NASA Astrophysics Data System (ADS)

    Barbante, C.; Kehrwald, N. M.; Marianelli, P.; Vinther, B. M.; Steffensen, J. P.; Cozzi, G.; Hammer, C. U.; Clausen, H. B.; Siggaard-Andersen, M.-L.

    2013-06-01

    Volcanic tephra are independent age horizons and can synchronize strata of various paleoclimate records including ice and sediment cores. The Holocene section of the Greenland Ice Core Project (GRIP) ice core is dated by multi-parameter annual layer counting, and contains peaks in acidity, SO42- and microparticle concentrations at a depth of 429.1 to 429.3 m, which have not previously been definitively ascribed to a volcanic eruption. Here, we identify tephra particles and determine that volcanic shards extracted from a depth of 429.3 m in the GRIP ice core are likely due to the 79 AD Vesuvius eruption. The chemical composition of the tephra particles is consistent with the K-phonolitic composition of the Vesuvius juvenile ejecta and differs from the chemical composition of other major eruptions (? VEI 4) between 50-100 AD.

  1. North Atlantic Deep Water Formation: Information from Ice Cores

    NASA Technical Reports Server (NTRS)

    Oeschger, H.

    1984-01-01

    The main results of measurements of the CO2 concentration of air occluded in natural ice during periods of climatic change are presented, as well as other measured ice core parameters. Elements of an interpretation of the data in terms of mechanisms of changing environmental systems are briefly discussed.

  2. Correlating Ice Cores from Quelccaya Ice Cap with Chronology from Little Ice Age Glacial Extents

    NASA Astrophysics Data System (ADS)

    Stroup, J. S.; Kelly, M. A.; Lowell, T. V.

    2010-12-01

    Proxy records indicate Southern Hemisphere climatic changes during the Little Ice Age (LIA; ~1300-1850 AD). In particular, records of change in and around the tropical latitudes require attention because these areas are sensitive to climatic change and record the dynamic interplay between hemispheres (Oerlemans, 2005). Despite this significance, relatively few records exist for the southern tropics. Here we present a reconstruction of glacial fluctuations of Quelccaya Ice Cap (QIC), Peruvian Andes, from pre-LIA up to the present day. In the Qori Kalis valley, extensive sets of moraines exist beginning with the 1963 AD ice margin (Thompson et al., 2006) and getting progressively older down valley. Several of these older moraines can be traced and are continuous with moraines in the Challpa Cocha valley. These moraines have been dated at <1050-1350-AD (Mercer and Palacios, 1977) and interpreted to have been deposited during the Little Ice Age. We present a new suite of surface exposure and radiocarbon dates collected in 2008 and 2009 that constrain the ages of these moraines. Preliminary 10Be ages of boulder surfaces atop the moraines range from ~350-1370 AD. Maximum and minimum-limiting radiocarbon ages bracketing the moraines are ~0-1800 AD. The chronology of past ice cap extents are correlated with ice core records from QIC which show an accumulation increase during ~1500-1700 AD and an accumulation decrease during ~1720-1860 AD (Thompson et al., 1985; 1986; 2006). In addition, other proxy records from Peru and the tropics are correlated with the records at QIC as a means to understand climate conditions during the LIA. This work forms the basis for future modeling of the glacial system during the LIA at QIC and for modeling of past temperature and precipitation regimes at high altitude in the tropics.

  3. Chemical signals of past climate and environment from polar ice cores and firn air.

    PubMed

    Wolff, Eric W

    2012-10-01

    Chemical and isotopic records obtained from polar ice cores have provided some of the most iconic datasets in Earth system science. Here, I discuss how the different records are formed in the ice sheets, emphasising in particular the contrast between chemistry held in the snow/ice phase, and that which is trapped in air bubbles. Air diffusing slowly through the upper firn layers of the ice sheet can also be sampled in large volumes to give more recent historical information on atmospheric composition. The chemical and geophysical issues that have to be solved to interpret ice core data in terms of atmospheric composition and emission changes are also highlighted. Ice cores and firn air have provided particularly strong evidence about recent changes (last few decades to centuries), including otherwise inaccessible data on increases in compounds that are active as greenhouse gases or as agents of stratospheric depletion. On longer timescales (up to 800,000 years in Antarctica), ice cores reveal major changes in biogeochemical cycling, which acted as feedbacks on the very major changes in climate between glacial and interglacial periods. PMID:22930179

  4. Eemian interglacial reconstructed from a Greenland folded ice core.

    PubMed

    2013-01-24

    Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling ('NEEM') ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8?±?4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400?±?250 metres, reaching surface elevations 122,000 years ago of 130?±?300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future. PMID:23344358

  5. Measurements of sea ice proxies from Antarctic coastal shallow cores

    NASA Astrophysics Data System (ADS)

    Maffezzoli, Niccolò; Vallelonga, Paul; Spolaor, Andrea; Barbante, Carlo; Frezzotti, Massimo

    2015-04-01

    Despite its close relationship with climate, the climatic impact of sea ice remains only partially understood: an indication of this is the Arctic sea ice which is declining at a faster rate than models predict. Thus, the need for reliable sea ice proxies is of crucial importance. Among the sea ice proxies that can be extracted from ice cores, interest has recently been shown in the halogens Iodine (I) and Bromine (Br) (Spolaor, A., et al., 2013a, 2013b). The production of sea ice is a source of Sodium and Bromine aerosols through frost flower crystal formation and sublimation of salty blowing snow, while Iodine is emitted by the algae living underneath sea ice. We present here the results of Na, Br and I measurements in Antarctic shallow cores, drilled during a traverse made in late 2013 - early 2014 from Talos Dome (72° 00'S, 159°12'E) to GV7 (70° 41'S, 158° 51'E) seeking for sea ice signature. The samples were kept frozen until the analyses, that were carried out by Sector Field Mass Spectroscopy Inductive Coupled Plasma (SFMS-ICP): special precautions and experimental steps were adopted for the detection of such elements. The coastal location of the cores allows a clear signal from the nearby sea ice masses. The multiple cores are located about 50 km from each other and can help us to infer the provenance of the sea ice that contributed to the proxy signature. Moreover, by simultaneously determining other chemical elements and compounds in the snow, it is possible to determine the relative timing of their deposition, thus helping us to understand their processes of emission and deposition.

  6. The isotopic composition of methane in polar ice cores

    NASA Technical Reports Server (NTRS)

    Craig, H.; Chou, C. C.; Welhan, J. A.; Stevens, C. M.; Engelkemeir, A.

    1988-01-01

    Air bubbles in polar ice cores indicate that about 300 years ago the atmospheric mixing ratio of methane began to increase rapidly. Today the mixing ratio is about 1.7 parts per million by volume, and, having doubled once in the past several hundred years, it will double again in the next 60 years if current rates continue. Carbon isotope ratios in methane up to 350 years in age have been measured with as little as 25 kilograms of polar ice recovered in 4-meter-long ice-core segments. The data show that: (1) in situ microbiology or chemistry has not altered the ice-core methane concentrations, and (2) that the carbon-13 to carbon-12 ratio of atmospheric CH4 in ice from 100 years and 300 years ago was about 2 per mil lower than at present. Atmospheric methane has a rich spectrum of isotopic sources: the ice-core data indicate that anthropogenic burning of the earth's biomass is the principal cause of the recent C-13H4 enrichment, although other factors may also contribute.

  7. Evolution of the texture along the EPICA Dome C ice core Gael Durand

    E-print Network

    Gagliardini, Olivier

    records in ice cores back to 800 kyr [2]. Besides this increase in the age of ice core records, alsoEvolution of the texture along the EPICA Dome C ice core Ga¨el Durand , Anders Svensson , Asbjørn Dahl-Jensen Niels Bohr institute, Ice and Climate Group, University of Copenhagen, Denmark. Contact

  8. Ice deformation in the vicinity of the ice-core site at Taylor Dome, Antarctica, and a derived accumulation rate history

    E-print Network

    Rasmussen, L.A.

    Ice deformation in the vicinity of the ice-core site at Taylor Dome, Antarctica, and a derived@ess.washington.edu ABSTRACT. Knowledge of ice flow and strain rate in the vicinity of the Taylor Dome (East Antarctica) ice-core site enhances interpretation of the paleoclimate information from the ice core. We measured surface ice

  9. Apollo Rock Reveals Moon Had Molten Core | Universe Additional Resources

    E-print Network

    Weiss, Benjamin P.

    Apollo Rock Reveals Moon Had Molten Core | Universe Today Subscribe Podcast Home Additional Apollo Rock Reveals Moon Had Molten Core Written by Nancy Atkinson If you're new here, you may want to subscribe to my RSS feed. Thanks for visiting! Apollo Rock Reveals Moon Had Molten Core | Universe Today

  10. Seismic anisotropy in ice: numerical modelling, ice core measurements and in-situ observations

    NASA Astrophysics Data System (ADS)

    Kendall, J. M.; Baird, A. F.; Walker, A.; Wookey, J. M.; Lloyd, G. E.; Stuart, G. W.; Harland, S.; Obbard, R. W.; Smith, A.; Brisbourne, A.

    2013-12-01

    The stress distribution and style of flow in ice produces elastic and rheological anisotropy, which informs ice flow modelling as to how ice masses respond to external changes such as global warming. Here observations of shear wave splitting from three-component icequake seismograms are used to characterise ice anisotropy in the Rutford ice stream, West Antarctica. Over 110 high quality measurements are made on 41 events recorded at five stations temporarily deployed near the ice stream grounding line. The magnitude of the splitting ranges from 2ms to 80ms and suggest a maximum of 6% shear wave splitting. The fast shear wave polarisation direction is roughly perpendicular to the ice flow direction. Motivated by these observations, we consider mechanisms for seismic anisotropy in ice using numerical modelling of the development of crystal preferred orientation of ice and measurement of crystal alignment in an ice core using electron back-scattered diffraction (EBSD). These results suggest transitions in the style of anisotropy both with depth and laterally within an ice stream. Seismic anisotropy is developed with increasing hydrostatic pressure producing a VTI fabric with a vertical alignment of c-axes (so-called cluster fabric). However, convergence in the ice flow and along-flow extension leads to girdles of c-axes (and an HTI fabric). Based on the Rutford shear-wave splitting observations we can rule out a cluster fabric as the sole cause of anisotropy - an HTI component is needed, which may be due extension in the direction of flow forming a girdle fabric or the alignment of cracks or ice-films in the plane perpendicular to the flow direction. Cumulatively, our observations suggest a combination of anisotropy mechanisms are at play in deforming ice sheets. We discuss seismic measurements that can be made to better discriminate between plausible mechanisms for our shear-wave splitting observations and how these different mechanisms may in turn alter ice flow and glacial response to external changes.

  11. Pre-cometary ice composition from hot core chemistry.

    PubMed

    Tornow, Carmen; Kührt, Ekkehard; Motschmann, Uwe

    2005-10-01

    Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same prebiotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere. PMID:16225436

  12. Evidence for warmer interglacials in East Antarctic ice cores.

    PubMed

    Sime, L C; Wolff, E W; Oliver, K I C; Tindall, J C

    2009-11-19

    Stable isotope ratios of oxygen and hydrogen in the Antarctic ice core record have revolutionized our understanding of Pleistocene climate variations and have allowed reconstructions of Antarctic temperature over the past 800,000 years (800 kyr; refs 1, 2). The relationship between the D/H ratio of mean annual precipitation and mean annual surface air temperature is said to be uniform +/-10% over East Antarctica and constant with time +/-20% (refs 3-5). In the absence of strong independent temperature proxy evidence allowing us to calibrate individual ice cores, prior general circulation model (GCM) studies have supported the assumption of constant uniform conversion for climates cooler than that of the present day. Here we analyse the three available 340 kyr East Antarctic ice core records alongside input from GCM modelling. We show that for warmer interglacial periods the relationship between temperature and the isotopic signature varies among ice core sites, and that therefore the conversions must be nonlinear for at least some sites. Model results indicate that the isotopic composition of East Antarctic ice is less sensitive to temperature changes during warmer climates. We conclude that previous temperature estimates from interglacial climates are likely to be too low. The available evidence is consistent with a peak Antarctic interglacial temperature that was at least 6 K higher than that of the present day -approximately double the widely quoted 3 +/- 1.5 K (refs 5, 6). PMID:19924212

  13. Holocene climate variability from ice core records in the Ross Sea area (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Braida, Martina; Stenni, Barbara; Masson-Delmotte, Valerie; Pol, Katy; Selmo, Enricomaria; Mezgec, Karin

    2014-05-01

    Past polar climate variability can be documented at high resolution thanks to ice core records, which have revealed significant Holocene variations in Antarctica. Paleotemperature reconstructions from Antarctic ice cores are mainly based on ?18O (?D) records, a proxy for local, precipitation-weighted atmospheric temperatures. Here, we present a new climate record spanning the past 12,000 years resulting from high resolution (10 cm) stable isotope analyses of the ice core drilled at Talos Dome (TD) in East Antarctica from 2003 to 2007 in the framework of the TALDICE (TALos Dome Ice CorE) project. Talos Dome (72°49'S, 159°11'E; 2315 m; -41°C) is an ice dome on the edge of the East Antarctic plateau, where moisture is mainly advected from the Indian and western Pacific sectors of the Southern Ocean. Pacific moisture arriving at TD has been transported above the Ross Sea, where extensive presence of sea ice also occurs during summer. High-resolution ?18O data have been measured using both IRMS and CRDS techniques on 10 cm samples, leading to a mean time resolution of two years. The long-term trend of the TALDICE ?18O profile shows characteristic features already observed in other ice cores from the East Antarctic plateau. Following the approach of Pol et al. (2011), high frequency climate variability has been investigated using a 3000-year running standard deviation on the de-trended record. The results are compared to the same analysis performed on the nearby Taylor Dome ice core ?18O data, which is the single East Antarctic ice core showing a strong Holocene decreasing trend. Despite these trend differences, both sites share common features regarding changes in variance. We also investigate changes in deuterium excess, a proxy reflecting changes in moisture source conditions. Both deuterium excess records show a two-step increasing trend in the first part of the Holocene. Taylor Dome deuterium excess however depicts an enhanced variability since about 7000 years BP. A wavelet analysis shows a change in isotopic variability patterns at 6-7000 years BP at both sites, suggesting changes in regional climate variability attributed to the opening of the Ross Sea area after the deglaciation. Pol K. et al. (2011). Links between MIS 11 millennial to sub-millennial climate variability and long term trends as revealed by new high resolution EPICA Dome C deuterium data - A comparison with the Holocene. Clim. Past, 7, 437-450.

  14. High Resolution Continuous Flow Analysis System for Polar Ice Cores

    NASA Astrophysics Data System (ADS)

    Dallmayr, Remi; Azuma, Kumiko; Yamada, Hironobu; Kjær, Helle Astrid; Vallelonga, Paul; Azuma, Nobuhiko; Takata, Morimasa

    2014-05-01

    In the last decades, Continuous Flow Analysis (CFA) technology for ice core analyses has been developed to reconstruct the past changes of the climate system 1), 2). Compared with traditional analyses of discrete samples, a CFA system offers much faster and higher depth resolution analyses. It also generates a decontaminated sample stream without time-consuming sample processing procedure by using the inner area of an ice-core sample.. The CFA system that we have been developing is currently able to continuously measure stable water isotopes 3) and electrolytic conductivity, as well as to collect discrete samples for the both inner and outer areas with variable depth resolutions. Chemistry analyses4) and methane-gas analysis 5) are planned to be added using the continuous water stream system 5). In order to optimize the resolution of the current system with minimal sample volumes necessary for different analyses, our CFA system typically melts an ice core at 1.6 cm/min. Instead of using a wire position encoder with typical 1mm positioning resolution 6), we decided to use a high-accuracy CCD Laser displacement sensor (LKG-G505, Keyence). At the 1.6 cm/min melt rate, the positioning resolution was increased to 0.27mm. Also, the mixing volume that occurs in our open split debubbler is regulated using its weight. The overflow pumping rate is smoothly PID controlled to maintain the weight as low as possible, while keeping a safety buffer of water to avoid air bubbles downstream. To evaluate the system's depth-resolution, we will present the preliminary data of electrolytic conductivity obtained by melting 12 bags of the North Greenland Eemian Ice Drilling (NEEM) ice core. The samples correspond to different climate intervals (Greenland Stadial 21, 22, Greenland Stadial 5, Greenland Interstadial 5, Greenland Interstadial 7, Greenland Stadial 8). We will present results for the Greenland Stadial -8, whose depths and ages are between 1723.7 and 1724.8 meters, and 35.520 to 35.636 kyr b2k 7), respectively. The results show the conductivity measured upstream and downstream of the debubbler. We will calculate the depth resolution of our system and compare it with earlier studies. 1) Bigler at al, "Optimization of High-Resolution Continuous Flow Analysis For Transient Climate Signals in Ice Cores". Environ. Sci. Technol. 2011, 45, 4483-4489 2) Kaufmann et al, "An Improved Continuous Flow Analysis System for High Resolution Field Measurements on Ice Cores". Environmental Environ. Sci. Technol. 2008, 42, 8044-8050 3) Gkinis, V., T. J. Popp, S. J. Johnsen and T, Blunier, 2010: A continuous stream flash evaporator for the calibration of an IR cavity ring down spectrometer for the isotopic analysis of water. Isotopes in Environmental and Health Studies, 46(4), 463-475. 4) McConnell et al, "Continuous ice-core chemical analyses using inductively coupled plasma mass spectrometry. Environ. Sci. Technol. 2002, 36, 7-11 5) Rhodes et al, "Continuous methane measurements from a late Holocene Greenland ice core : Atmospheric and in-situ signals" Earth and Planetary Science Letters. 2013, 368, 9-19 6) Breton et al, "Quantifying Signal Dispersion in a Hybrid Ice Core Melting System". Environ. Sci. Technol. 2012, 46, 11922-11928 7) Rasmussen et al, " A first chronology for the NEEM ice core". Climate of the Past. 2013, 9, 2967--3013

  15. A TEM analysis of nanoparticulates in a Polar ice core

    SciTech Connect

    Esquivel, E.V.; Murr, L.E

    2004-03-15

    This paper explores the prospect for analyzing nanoparticulates in age-dated ice cores representing times in antiquity to establish a historical reference for atmospheric particulate regimes. Analytical transmission electron microscope (TEM) techniques were utilized to observe representative ice-melt water drops dried down on carbon/formvar or similar coated grids. A 10,000-year-old Greenland ice core was melted, and representative water drops were transferred to coated grids in a clean room environment. Essentially, all particulates observed were aggregates and either crystalline or complex mixtures of nanocrystals. Especially notable was the observation of carbon nanotubes and related fullerene-like nanocrystal forms. These observations are similar with some aspects of contemporary airborne particulates including carbon nanotubes and complex nanocrystal aggregates.

  16. Ice Cube Observed PeV Neutrinos from AGN Cores

    E-print Network

    Floyd W. Stecker

    2013-08-05

    I show that the high energy neutrino flux predicted to arise from AGN cores can explain the PeV neutrinos detected by Ice Cube without conflicting with the constraints from the observed extragalactic cosmic ray and gamma-ray backgrounds.

  17. Glacial-interglacial variability change: a view beyond ice cores

    NASA Astrophysics Data System (ADS)

    Rehfeld, Kira; Münch, Thomas; Ho, Sze Ling; Laepple, Thomas

    2015-04-01

    The last Glacial was characterized by a highly variable climate, including abrupt changes such as Heinrich- and Dansgaard-Oeschger events. By contrast, the warm Holocene time period appears as relatively stable. This variability change is often discussed based on data from polar ice cores, particularly from Greenland. Here, we contrast the polar ice-core based variability change with the variability change as recorded by a global compilation of marine and terrestrial proxy records. Accounting for uneven sampling in time and space, we develop an understanding of proxy signal-to-noise ratios which allows insight into proxy-specific biases concerning the recording of climate variability. Globally, we find climate around the Last Glacial Maximum five times more variable than during the Holocene. This variability is expressed in particular by the polar ice cores: We find a stronger polar amplification of climate variability during the Glacial than during the warm Holocene. Our results indicate that the view of an extremely variable Glacial contrasting with a quiet Holocene, given by central Greenland ice core isotope ratios, may underestimate the actual variability of the present warm Interglacial on the global scale.

  18. Holocene-Late pleistocene climatic ice core records for Qinghai-Tibetan plateau

    SciTech Connect

    Thompson, L.G.; Mosley-Thompson, E.; Davis, M.E.; Bolzan, J.F.; Dai, J.; Klien, L. ); Yao, T.; Wu, X.; Xie, Z. ); Gundestrup, N. )

    1989-10-27

    Three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau of China provide a detailed record of Holocene and Wisconsin-Wuerm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative {delta}{sup 18}O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly {approximately} 10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago.

  19. Earth's Climate History from Glaciers and Ice Cores

    NASA Astrophysics Data System (ADS)

    Thompson, Lonnie

    2013-03-01

    Glaciers serve both as recorders and early indicators of climate change. Over the past 35 years our research team has recovered climatic and environmental histories from ice cores drilled in both Polar Regions and from low to mid-latitude, high-elevation ice fields. Those ice core -derived proxy records extending back 25,000 years have made it possible to compare glacial stage conditions in the Tropics with those in the Polar Regions. High-resolution records of ?18O (in part a temperature proxy) demonstrate that the current warming at high elevations in the mid- to lower latitudes is unprecedented for the last two millennia, although at many sites the early Holocene was warmer than today. Remarkable similarities between changes in the highland and coastal cultures of Peru and regional climate variability, especially precipitation, imply a strong connection between prehistoric human activities and regional climate. Ice cores retrieved from shrinking glaciers around the world confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions today are different from those under which these ice fields originated and have been sustained. The ongoing widespread melting of high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth's climate system is underway. Observations of glacier shrinkage during the 20th and 21st century girdle the globe from the South American Andes, the Himalayas, Kilimanjaro (Tanzania, Africa) and glaciers near Puncak Jaya, Indonesia (New Guinea). The history and fate of these ice caps, told through the adventure, beauty and the scientific evidence from some of world's most remote mountain tops, provide a global perspective for contemporary climate. NSF Paleoclimate Program

  20. An Automated Method for Annual Layer Counting in Ice Cores

    NASA Astrophysics Data System (ADS)

    Winstrup, M.; Svensson, A.

    2010-12-01

    The Greenland ice cores provide a wealth of data on past changes in climate, and have - compared to most other paleoclimatic archives - the potential to be dated very accurately by annual layer counting. An effort of manually doing annual layer counting using multiple chemical components has resulted in the Greenland Ice Core Chronology (GICC05), common to several Greenland deep ice cores. The oldest part of the chronology is based on data from the NGRIP ice core, which has a particularly fine yearly data resolution with depth. However, due to the increased thinning of annual layers with depth, the annual layers in most components are no longer recognizable in the ice core for depths below 2430m, corresponding to an age of 60 ka. At this depth, only the annual layering in the visual stratigraphy is still intact, but due to a high noise-level in these data, it is difficult manually to do annual layer counting only using this data record. In this study, an automated method has been developed, which takes into account the underlying statistical properties of the visual stratigraphy data sequence, and hereby is able to detect layers otherwise unrecovered. The data sequence is modeled using a Hidden Markov Model (HMM), with algorithms otherwise mainly applied to speech recognition. Preliminary studies are promising, and even crude implementations of the method agree to within 90% of the GICC05 counting. Due to more noise in the visual stratigraphy data during warm periods, the method is likely to give better results in cold periods than during warm. However, as the annual layers are thicker during warm periods, it seems to be possible to use other parameters than the visual stratigraphy for counting annual layers during these. Using the combined data, it should therefore be possible to develop a high-resolution timescale for the NGRIP ice core extending back to at least 90 ka. In the future, a similar approach might be used for a general multi-parameter annual layer counting of ice cores and other paleoclimatic records which display annual layering.

  1. Effect of periodic melting on geochemical and isotopic signals in an ice core from Lomonosovfonna, Svalbard

    E-print Network

    Moore, John

    Effect of periodic melting on geochemical and isotopic signals in an ice core from Lomonosovfonna in an ice core taken from a periodically melting ice field, Lomonosovfonna in central Spitsbergen, Svalbard. The aim is to determine the degree to which the signals are altered by periodic melting of the ice. We use

  2. Glaciological and climatic significance of Hercules Dome, Antarctica: An optimal site for deep ice core drilling

    E-print Network

    Jacobel, Robert W.

    traverse indicate accumulation rates of 0.16­0.20 m/yr ice equivalent over the last 300 years. Age controlGlaciological and climatic significance of Hercules Dome, Antarctica: An optimal site for deep ice as a deep ice core site. Annual layering in dD ratios from a 72 m ice core collected by the US-ITASE 2002

  3. Timescale Calculations for Ice Core Drilling Sites on the Temperate Ice Caps in Iceland

    NASA Astrophysics Data System (ADS)

    Thorsteinsson, T.; Einarsson, B.

    2005-12-01

    Modelling of age vs. depth profiles and annual-layer thickness changes with depth in ice sheets forms part of the investigations carried out prior to the selection of ice core drilling sites. The well known Nye model, which assumes a constant vertical strain rate with depth in an ice sheet of thickness H is generally applicable in the upper half of polar and temperate ice caps, but the assumption of a constant vertical strain rate is unrealistic near the bed in an ice sheet frozen to bedrock. Dansgaard-Johnsen (D-J) type models assume that the vertical strain rate is constant down to height h above bedrock and then decreases linearly with depth towards zero at the bed. The parameter h can be calibrated according to the way in which the horizontal velocity varies with depth. Here we introduce a new derivation of the D-J model that accounts for bottom melting due to the geothermal heat flux, which averages 200 mW/m2 in Iceland. The model is then applied to five different locations on the temperate ice caps in Iceland, with ice thicknesses varying between 220 m and 850 m and accumulation rates ranging between 2.0 and 3.6 m ice/year. Data from ice cores drilled at three of these sites are used to calibrate the model. For the summit location on the Hofsjokull ice cap (H = 300 m), we find that a D-J model with a relatively high h/H ratio reproduces the timescale from a 100 m ice core better than the Nye model. Results indicate that a continuous precipitation record covering the last 400-500 years could be retrieved at the Hofsjokull summit (1790 m a.s.l.), and the assumption of bottom melting has a large effect on the modelled timescale at this site, yielding 50% lower ages at 90% of the ice depth than model runs that neglect bottom melting. For deeper drillings in Iceland, the ice-filled caldera at Bardarbunga, NW-Vatnajokull (H = 850 m), where a 415 m core was drilled in 1972, is among the most promising sites. Selection of the h/H ratio in the D-J model for timescale calculation within the caldera rims is complicated by an unusual ice-flow pattern but results strongly indicate that a 700-800 m ice core could yield a record covering historical time in Iceland (870 AD - present). Model results predict that by 90% of ice depth, the annual layers have thinned to 17 cm at the Hofsjokull summit and 8 cm within the Bardarbunga caldera. Annual layers of this thickness are detectable with the methods used in pilot ice core drilling and processing efforts in Iceland in recent years.

  4. Biological proxies recorded in a Belukha ice core, Russian Altai

    NASA Astrophysics Data System (ADS)

    Papina, T.; Blyakharchuk, T.; Eichler, A.; Malygina, N.; Mitrofanova, E.; Schwikowski, M.

    2013-10-01

    Different biological proxies such as pollen, cysts, and diatoms were identified and quantified in the upper part of a Belukha ice core from the Russian Altai. The ice core from the Belukha glacier collected in 2001 (4062 m a.s.l., 49°48' N, 86°34' E) was analyzed with annual resolution in the period 1964-2000. Daily data of the frequency of synoptic patterns observed in the Northern Hemisphere along with daily data of precipitation have been used to identify the predominant atmospheric circulations (elementary circulating mechanisms, or ECMs) generating the entry of biological proxies on the glacier surface. It was shown that the high-resolution records of diatoms, cysts, spores, and plant pollen in the Belukha ice core are the biological proxies for the changes in the structure of precipitation in the Altai region since these records can reflect changes in the contribution of different atmospheric circulation to annual or seasonal precipitation. The joint consideration of the transport ability of the biological species and the data of precipitation allowed us to determine the main modern sources of biological proxies deposited at the Belukha glacier. The main sources of diatoms in the Belukha ice core are water bodies of the Aral, Caspian, and northern Kazakhstan basins; coniferous tree pollen originated from the taiga forest of the boreal zone of western Siberia; pollen of deciduous trees and herbs from steppe and forest-steppe vegetation in the northern Altai and eastern Kazakhstan; and cysts and spores of plants were transported from local water bodies and forests. The identified source regions of the biological species are supported by back trajectory analyses and are in good agreement with emission source regions of the trace elements in the ice core.

  5. IceChrono v1: a probabilistic model to compute a common and optimal chronology for several ice cores

    NASA Astrophysics Data System (ADS)

    Parrenin, F.

    2014-10-01

    Polar ice cores provides exceptional archives of past environmental conditions. Dating ice and air bubbles/hydrates in ice cores is complicated since it involves different dating methods: modeling of the sedimentation process (accumulation of snow at surface, densification of snow into ice with air trapping and ice flow), use of dated horizons by comparison to other well dated targets (other dated paleo-archives or calculated variations of Earth's orbital parameters), use of dated depth intervals, use of ?depth information (depth shift between synchronous events in the ice matrix and its air/hydrate content), use of stratigraphic links in between ice cores (ice-ice, air-air or mix ice-air links). Here I propose IceChrono v1, a new probabilistic model to combine these different kinds of chronological information to obtain a common and optimized chronology for several ice cores, as well as its confidence interval. It is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the vertical thinning function. IceChrono is similar in scope to the Datice model, but has differences on the mathematical, numerical and programming point of views. I apply IceChrono on two dating experiments. The first one is similar to the AICC2012 experiment and I find similar results than Datice within a few centuries, which is a confirmation of both IceChrono and Datice codes. The second experiment involves only the Berkner ice core in Antarctica and I produce the first dating of this ice core. IceChrono v1 is freely available under the GPL v3 open source license.

  6. Ice Core Evidence to support a Paleo Global Moonsoon

    NASA Astrophysics Data System (ADS)

    Sowers, T. A.

    2013-05-01

    The notion that many of the monsoon regions are teleconnected over long timescales has gained traction recently. Numerous high resolution climate records from speleothem coral sites, high accumulation rate deep sea sediments, and ice cores tend to support the general notion of a global paleo-monsoon system that appears to be driven by changes in the latitudinal distribution of incident radiation. In particular, the atmospheric CH4 record from ice cores has been shown to follow tropical insolation variations with a strong precession index. High CH4 levels occur during periods of elevated summer insolation presumably related to enhanced tropical emissions from a growth in the areal extent of wetlands and elevated summer temperatures. Here we present a new ultra-high resolution atmospheric CH4 record from the recently completed WAIS divide Antarctic ice core (79S, 112W). Using a new automated CH4 analytical system, we have measured 2632 discrete samples throughout the entire core. The vast majority of the samples were taken from the glacial portion of the core (N=1706) with gas ages between 20 and 68ka, corresponding to roughly one sample every 30 years. Comparisons between our new CH4 record, the isotopic temperature record from the NGRIP ice core in Greenland, and various speleothem d18O records illustrates rather convincingly that all three proxies are responding to the same forcing. The phasing between the abrupt climatic events in all three records is not easily deciphered due to uncertainties in the independent timescales. However, the amazing covariation between these three proxy records is most easily explained by invoking strong teleconnections within the global hydrologic cycle that are paced by changes in incident radiation.

  7. Gas ageice age differences and the chronology of the Vostok ice core, M. L. Bender,1

    E-print Network

    Chappellaz, Jérôme

    Gas age­ice age differences and the chronology of the Vostok ice core, 0­100 ka M. L. Bender,1 G the ice in which it is embedded. The age difference is not well constrained for slowly accumulating ice chronologies that use different assumptions to calculate gas age­ice age differences. We then evaluate

  8. Marine sediments in Disko Trough reveal meltwater-influenced sedimentation during ice-stream retreat

    NASA Astrophysics Data System (ADS)

    Hogan, Kelly A.; Cofaigh, Colm Ó.; Jennings, Anne E.; Dowdeswell, Julian A.

    2015-04-01

    Marine geophysical data from middle and outer Disko Trough, West Greenland reveal thick (more than ten metres) acoustically-laminated, fine-grained sediments between subglacial tills at their base and post-glacial marine sediments at the seafloor. These sediments are interpreted as a transitional facies deposited as ice retreated from the trough during deglaciation. New sediment-core records indicate that these units were likely deposited by meltwater plumes emanating from a nearby grounded-ice margin, probably during stillstands in ice retreat. The retreat of ice in the trough may have been stabilised at a narrowing in DiskoTrough on the mid-shelf, as well as at the basalt escarpment south of Disko Island. Such thicknesses of deglacial or "transitional" glacimarine sediments are relatively unusual on high-latitude continental shelves and indicate a significant meltwater production in central West Greenland during deglaciation. This is consistent with the seafloor landforms in the inner and middle parts of the trough that include channels and moats around bedrock protrusions that look to have been eroded by water. IRD counts from the cores indicate that iceberg rafting also occurred during this transitional phase but that this signal was diluted by the fine-grained transitional sediments. Once ice had withdrawn from the area and sedimentation was hemipelagic in nature the IRD signal was less diluted.

  9. Bipolar ice core records of millennial scale climate variability : an overview of recent findings (Invited)

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Landais, A.

    2013-12-01

    Greenland and Antarctic ice cores offer high resolution records of the imprints of millennial scale climate variability on polar climate, aerosol deposition, and atmospheric composition (Wolff et al, QSR, 2010). Improved chronologies and spatial coverage provide new data against which the mechanisms involved in millennial variability and simulated by climate models can be tested. We will first discuss the bipolar sequence of events based on the new AICC2012 chronology, during the last climatic cycle (Veres et al, Clim. Past, 2013; Bazin et al, Clim. Past, 2013). The matrix of ice cores allows to investigate regional differences in the cross-Greenland fingerprints of Dansgaard-Oeschger events (Guillevic et al, Clim. Past, 2013) and the circum-Antarctic signature of their Antarctic Isotopic Maxima counterpart (Buiron et al, QSR, 2012). While Heinrich events have long remained difficult to identify in ice core records, a step change in atmospheric CO2 concentrations has been identified during Heinrich 4 (Ahn et al, GRL, 2012), challenging the gradual CO2 emissions expected from the classical bipolar see-saw explanation. High resolution Antarctic data also reveal centennial to millennial variability during interglacial periods and glacial inceptions which bears similarities with glacial Antarctic Isotopic Maxima, questioning the source and amplifiers of glacial millennial variability. New investigations of the magnitude and recurrence of millennial variability based on multiple long Antarctic ice core records are expected to provide further hints on the interplay between mean climatic states and this millennial variability.

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

    SciTech Connect

    Steig, E.J.

    1996-12-31

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

  11. Could a new ice core offer an insight into the stability of the West Antarctic Ice Sheet during the last interglacial?

    NASA Astrophysics Data System (ADS)

    Mulvaney, R.; Hindmarsh, R. C.

    2013-12-01

    Vaughan et al., in their 2011 paper 'Potential Seaways across West Antarctica' (Geochem. Geophys. Geosyst., 12, Q10004, doi:10.1029/2011GC003688), offer the intriguing prospect that substantial ice loss from the West Antarctic Ice Sheet during the previous interglacial period might have resulted in the opening of a seaway between the Weddell Sea and the Amundsen Sea. One of their potential seaways passes between the south western corner of the present Ronne Ice Shelf and the Pine Island Bay, through what is currently the course of the Rutford Ice Stream, between the Ellsworth Mountains and the Fletcher Promontory. To investigate whether this seaway could have existed (and to recover a paleoclimate and ice sheet history from the Weddell Sea), a team from the British Antarctic Survey and the Laboratoire de Glaciologie et Géophysique de l'Environnement drilled an ice core from a close to a topographic dome in the ice surface on the Fletcher Promontory in January 2012, reaching the bedrock at 654.3m depth from the surface. The site was selected to penetrate directly through the centre of a Raymond cupola observed in internal radar reflections from the ice sheet, with the intention that this would ensure we obtained the oldest ice available from the Fletcher Promontory. The basal ice sheet temperature measured was -18°C, implying the oldest ice would not have melted away from the base, while the configuration of the Raymond cupola in the radar horizons suggested stability in the ice dome topography during the majority of the Holocene. Our hypothesis is that chemical analysis of the ice core will reveal whether the site was ever relatively close to open sea water or ice shelf in the Rutford channel 20 km distant, rather than the current 700 km distance to sea ice/open water in either the Weddell Sea or the Amundsen Sea. While we do not yet have the chemistry data to test this hypothesis, in this poster we will discuss whether there is in reality any potential local meteoric ice remaining from the previous interglacial that could provide the evidence we need. We show likely age-depth models in an ice dome with a pronounced Raymond cupola and flat bedrock. The evidence from the stable water isotope temperature history from the site shows the Last Glacial Maximum/Holocene boundary substantially above the bedrock, implying the possibility of much older ice in the lowest ice layers.

  12. Critical Fracture Toughness Measurements of an Antarctic Ice Core

    NASA Astrophysics Data System (ADS)

    Christmann, Julia; Müller, Ralf; Webber, Kyle; Isaia, Daniel; Schader, Florian; Kippstuhl, Sepp; Freitag, Johannes; Humbert, Angelika

    2014-05-01

    Fracture toughness is a material parameter describing the resistance of a pre-existing defect in a body to further crack extension. The fracture toughness of glacial ice as a function of density is important for modeling efforts aspire to predict calving behavior. In the presented experiments this fracture toughness is measured using an ice core from Kohnen Station, Dronning Maud Land, Antarctica. The samples were sawed in an ice lab at the Alfred Wegener Institute in Bremerhaven at -20°C and had the dimensions of standard test samples with thickness 14 mm, width 28 mm and length 126 mm. The samples originate from a depth of 94.6 m to 96 m. The grain size of the samples was also identified. The grain size was found to be rather uniform. The critical fracture toughness is determined in a four-point bending approach using single edge V-notch beam samples. The initial notch length was around 2.5 mm and was prepared using a drilling machine. The experimental setup was designed at the Institute of Materials Science at Darmstadt. In this setup the force increases linearly, until the maximum force is reached, where the specific sample fractures. This procedure was done in an ice lab with a temperature of -15°C. The equations to calculate the fracture toughness for pure bending are derived from an elastic stress analysis and are given as a standard test method to detect the fracture toughness. An X-ray computer tomography (CT scanner) was used to determine the ice core densities. The tests cover densities from 843 kg m-3 to 871 kg m-3. Thereby the influence of the fracture toughness on the density was analyzed and compared to previous investigations of this material parameter. Finally the dependence of the measured toughness on thickness, width, and position in the core cross-section was investigated.

  13. IceChrono v1: a probabilistic model to compute a common and optimal chronology for several ice cores

    NASA Astrophysics Data System (ADS)

    Parrenin, Frédéric

    2015-04-01

    Polar ice cores provide exceptional archives of past environmental conditions. The dating of ice cores is essential to interpret the paleo records that they contain, but it is a complicated problem since it involves different dating methods. Here I present IceChrono v1, a new probabilistic model to combine different kinds of chronological information to obtain a common and optimized chronology for several ice cores, as well as its uncertainty. It is based on the inversion of three quantities: the surface accumulation rate, the Lock-In Depth (LID) of air bubbles and the vertical thinning function. The chronological information used are: models of the sedimentation process (accumulation of snow, densification of snow into ice and air trapping, ice flow), ice and gas dated horizons, ice and gas dated depth intervals, ?depth observations (depth shift between synchronous events recorded in the ice and in the air), stratigraphic links in between ice cores (ice-ice, air-air or mix ice-air and air-ice links). The optimization problem is formulated as a least squares problems, that is, all densities of probabilities are assumed gaussian. It is numerically solved using the Levenberg-Marquardt algorithm and a numerical evaluation of the model's Jacobian. IceChrono is similar in scope to the Datice model, but has differences from the mathematical, numerical and programming point of views. I apply IceChrono on an AICC2012-like experiment and I find similar results than Datice within a few centuries, which is a confirmation of both IceChrono and Datice codes. IceChrono v1 is freely available under the GPL v3 open source license.

  14. An automated approach for annual layer counting in ice cores

    NASA Astrophysics Data System (ADS)

    Winstrup, M.; Svensson, A. M.; Rasmussen, S. O.; Winther, O.; Steig, E. J.; Axelrod, A. E.

    2012-07-01

    A novel method for automated annual layer counting in seasonally-resolved paleoclimate records has been developed. It relies on algorithms from the statistical framework of Hidden Markov Models (HMMs), which originally was developed for use in machine speech-recognition. The strength of the layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on statistical criteria for annual layer identification. The most likely positions of multiple layer boundaries in a section of ice core data are determined simultaneously, and a probabilistic uncertainty estimate of the resulting layer count is provided, ensuring an objective treatment of ambiguous layers in the data. Furthermore, multiple data series can be incorporated and used simultaneously. In this study, the automated layer counting algorithm has been applied to an ice core record from Greenland. The algorithm shows high skill in reproducing the results from manual layer counts.

  15. Low-latitude ice cores and freshwater availability

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie Marie

    2009-12-01

    Recent retreat of Tibetan Plateau glaciers affects at least half a billion people. Himalayan glaciers seasonally release meltwater into tributaries of the Indus, Ganges, and Brahmaputra Rivers and supply freshwater necessary to support agricultural and economic practices. Tibetan Plateau glaciers are retreating more rapidly than mountain glaciers elsewhere in the world, and this retreat is accelerating. The Naimona'nyi (30°27'N; 81°91'E, 6050 m a.s.l), Guliya (35°17'N; 81°29'E, 6710 m a.s.l.) and Dasuopu (28°23'N; 85°43'E, 7200 m a.s.l.) ice cores place this recent retreat into a longer time perspective through quantifying climate parameters such as past temperature, aridity, and atmospheric chemistry. Naimona'nyi has not accumulated mass since at least 1950, as evidenced by the virtual lack of radiogenic isotopes (36Cl, 3 H, and beta radioactivity) present in the ice core. These isotopes were produced by U.S. and Soviet atmospheric thermonuclear bomb tests conducted in the 1950s and 1960s and provide independent dating horizons for the ice cores. Lead-210 dates imply that the uppermost preserved glacial ice on Naimona'nyi formed during the 1940s. While this is the highest documented glacial thinning in the world other glaciers at elevations similar to that of Naimona'nyi, such as Kilimanjaro (3°4'S; 37°21'E, 5893 m a.s.l.), are also losing mass at their summits. The global scope of high-elevation glacial thinning suggests that ablation on the Earth's highest ice fields may be more prevalent as global mean temperatures continue to increase. Glacial thinning has not been taken into account in future projections of regional freshwater availability, and the net mass loss indicates that Himalayan glaciers currently store less freshwater than assumed in models. The acceleration of Tibetan Plateau glacial retreat has been hypothesized to be due in part to deposition of black carbon (BC) from biomass burning on to ice fields, thereby lowering the reflectivity of the glacier surface and melting the upper ice. The application of a novel technique of measuring and radiocarbon-dating ultra-small samples (< 100mug) of the BC and total organic carbon (TOC) fractions of Naimona'nyi demonstrates a decrease (˜12 to 14 ka versus ˜7 ka) in the composite age of BC in the upper 40 m and lowest 20 m of the 137 m ice core, suggesting the incorporation of radiocarbon-dead BC. Precambrian black shale in the Lesser Himalaya provide a natural source material which may be operationally defined as black carbon and which may incorporate radiocarbon-dead sediments into the bulk 14C measurements, yet as the mean 14C age is ˜10 ka, modern BC from biomass burning must also be incorporated into the ice core record. While the uppermost sample (5 m) contains 38% BC, 210 Pb dates show that this depth corresponds to an age before 1850 AD, or before the regional Industrial Revolution. As BC is a hydrophobic substance, the BC is unlikely to have migrated through the firn and glacial ice. Therefore, the high-elevation thinning on Naimona'nyi appears to be a response to increased temperatures rather than primarily driven by changes in surface albedo. This technique was applied to the annually-dated ice core from the accumulating summit of the Quleccaya ice cap, Peru (13'56'S; 70°50'W; 5670 m a.s.l.). A marked increase in modern BC and TOC was measured since 1880 AD. No increase in radiocarbon-dead (> 60,000 ka) BC or TOC was noted, suggesting that the source of the carbon was from biomass burning, with a possible contribution of Amazon slash and burn clearing, rather than the input of fossil fuel combustion. The age of the BC and TOC is thousands of years older than the age of the surrounding ice, and should not be used to date the ice core. Although Naimona'nyi provides challenges for constructing an ice core chronology due to its lack of independent horizons such as volcanic activity, methane gas measurements, 14C dates, 3H, 36Cl, or beta radioactivity, the oxygen isotopic record can be correlated with the neighboring Dasuopu and Guliya ice

  16. Paleo Environmental Records from Mid-Latitude Ice Cores

    NASA Astrophysics Data System (ADS)

    Schwikowski, M.

    2004-12-01

    Ice core records from mid-latitude glaciers give insight into the atmospheric composition history. One example is the reconstruction of air pollution levels in Europe from Alpine ice cores, showing dramatic increases of anthropogenic emissions starting with the onset of industrialisation in the middle of the 19th century and the reduction in emissions of certain pollutants since regulatory measures were put into effect in the 1970ies. Anthropogenic emissions had a strong impact particularly on the concentrations of various aerosol-related species such as sulphate, nitrate, ammonium, copper, lead, and zinc as well as of carbonaceous particles and radionuclides. Thus, ice core records from mid-latitude glaciers contribute to our understanding of anthropogenic perturbations upon the composition of the atmosphere. This is particularly important in context of aerosol particles with significant climate-forcing potential e.g. sulphate, mineral dust, and carbonaceous particles (including black carbon and organic matter). Because aerosol lifetimes are typically only several days, the global distribution is very inhomogeneous, thus requiring data from many locations to assess the effect on climate.

  17. Where might we find evidence of a Last Interglacial West Antarctic Ice Sheet collapse in Antarctic ice core records?

    E-print Network

    Siddall, Mark

    increased melting from valley glaciers and small ice caps (estimated ~0.6±0.1 m, Radi and Hock, 2010), oceanWhere might we find evidence of a Last Interglacial West Antarctic Ice Sheet collapse in Antarctic ice core records? S.L. Bradley a, , M. Siddall a , G.A. Milne b , V. Masson-Delmotte c , E. Wolff d

  18. Historical and future black carbon deposition on the three ice caps: Ice core measurements and model simulations from 1850 to 2100

    E-print Network

    Historical and future black carbon deposition on the three ice caps: Ice core measurements black carbon deposition on the three ice caps: Ice core measurements and model simulations from 1850 tends to enhance snow and ice melting due to the absorption caused by the increased BC deposition

  19. An ice core record of net snow accumulation and seasonal snow chemistry at Mt. Waddington, southwest British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Neff, P. D.; Steig, E. J.; Clark, D. H.; McConnell, J. R.; Pettit, E. C.; Menounos, B.

    2011-12-01

    We recovered a 141 m ice core from Combatant Col (51.39°N, 125.22°W, 3000 m asl) on the flank of Mt. Waddington, southern Coast Mountains, British Columbia, Canada. Aerosols and other impurities in the ice show unambiguous seasonal variations, allowing for annual dating of the core. Clustered melt layers, originating from summer surface heating, also aid in the dating of the core. Seasonality in water stable isotopes is preserved throughout the record, showing little evidence of diffusion at depth, and serves as an independent verification of the timescale. The annual signal of deuterium excess is especially well preserved. The record of lead deposition in the core agrees with those of ice cores from Mt. Logan and from Greenland, with a sharp drop-off in concentration in the 1970s and early 1980s, further validating the timescales. Despite significant summertime melt at this mid-latitude site, these data collectively reveal a continuous and annually resolved 36-year record of snow accumulation. We derived an accumulation time series from the Mt. Waddington ice core, after correcting for ice flow. Years of anomalously high or low snow accumulation in the core correspond with extremes in precipitation data and geopotential height anomalies from reanalysis data that make physical sense. Specifically, anomalously high accumulation years at Mt. Waddington correlate with years where "Pineapple Express" atmospheric river events bring large amounts of moisture from the tropical Pacific to western North America. The Mt. Waddington accumulation record thus reflects regional-scale climate. These results demonstrate the potential of ice core records from temperate glaciers to provide meaningful paleoclimate information. A longer core to bedrock (250-300 m) at the Mt. Waddington site could yield ice with an age of several hundred to 1000 years.

  20. Spatial and temporal characteristics of the Little Ice Age: The Antarctic ice-core record

    SciTech Connect

    Mosley-Thompson, E.; Thompson, L.G.

    1992-03-01

    Recently, ice core records from both hemispheres, in conjunction with other proxy records (e.g., tree rings, speleothems and corals), have shown that the Little Ice Age (LIA) was spatially extensive, extending to the Antarctic. This paper examines the temporal and spatial characteristics of the dust and delta 18O information from Antarctic ice cores. Substantial differences exist in the records. For example, a 550-year record of delta 18O and dust concentrations from Siple Station, Antarctica suggests that, less dusty conditions prevailed from A.D. 1600 to 1830. Alternately, dust and delta 18O data from South Pole Station indicate that opposite conditions (e.g., cooler and more dusty) were prevalent during the LIA. Three additional Antarctic delta 18O records are integrated with the Siple and South Pole histories for a more comprehensive picture of LIA conditions. The records provide additional support for the LIA temperature opposition between the Antarctic Peninsula region and East Antarctica. In addition, periods of strongest LIA cooling are not temporally synchronous over East Antarctica. These strong regional differences demonstrate that a suite of spatially distributed, high resolution ice core records will be necessary to characterize the LIA in Antarctica.

  1. Magnetic properties of aerosol dust in peripheral and inner Antarctic ice cores as a proxy for dust provenance

    NASA Astrophysics Data System (ADS)

    Lanci, L.; Delmonte, B.

    2013-11-01

    We use laboratory-induced remanent magnetization of polar ice to measure the rock-magnetic properties of the aerosol dust directly in ice samples. Former studies on Vostok and EPICA-Dome C ice core, recovered on the inner East Antarctic ice sheet, revealed that glacial and interglacial periods of the latter are characterized by distinct magnetic mineralogies at Dome C, which might reflect different dust source areas. In this work we present the first results on glacial and Holocene samples from the TALDICE ice core, collected at the peripheral site of Talos Dome located at high-elevation on the ice sheet close to some ice-free areas of the Transantarctic mountains. Magnetic properties of interglacial samples from both Dome-C and Talos Dome ice cores turned out to have peculiar characteristics that suggest an enhanced concentration of Fe-rich minerals in the aerosol dust, compared to Vostok. The most likely explanation for the extremely high dust magnetization measured in interglacial samples is the presence of volcanic material, although occasional occurrence of meteoritic material (micrometeorites) cannot be ruled out. The volcanic nature of the Holocene aerosol dust and its variability between sites provides further constrains on dust geographic provenance that are complementary to geochemical and physical evidences. Moreover, the calculations of the flux of the highly magnetic dust provide information on wind transport toward the continent interior during the Holocene.

  2. Multi-proxy fingerprint of Heinrich event 4 in Greenland ice core records

    NASA Astrophysics Data System (ADS)

    Guillevic, M.; Bazin, L.; Landais, A.; Stowasser, C.; Masson-Delmotte, V.; Blunier, T.; Eynaud, F.; Falourd, S.; Michel, E.; Minster, B.; Popp, T.; Prié, F.; Vinther, B. M.

    2014-03-01

    Glacial climate was characterised by two types of abrupt events. Greenland ice cores record Dansgaard-Oeschger events, marked by abrupt warming in-between cold, stadial phases. Six of these stadials coincide with major Heinrich events (HE), identified from ice-rafted debris (IRD) and large excursions in carbon and oxygen stable isotopic ratios in North Atlantic deep sea sediments, documenting major ice sheet collapse events. This finding has led to the paradigm that glacial cold events are induced by the response of the Atlantic Meridional Overturning Circulation to such massive freshwater inputs, supported by sensitivity studies conducted with climate models of various complexities. This mechanism could however never be confirmed or infirmed because the exact timing of Heinrich events and associated low latitude hydrological cycle changes with respect to Greenland stadials has so far remained elusive. Here, we provide the first multi-proxy fingerprint of H4 within Stadial 9 in Greenland ice cores through ice and air proxies of low latitude climate and water cycle changes. Our new dataset demonstrates that Stadial 9 consists of three phases, characterised first by Greenland cooling during 550 ± 60 years (as shown by markers of Greenland temperature ?18O and ?15N), followed by the fingerprint of Heinrich Event 4 as identified from several proxy records (abrupt decrease in 17O excess and Greenland methane sulfonic acid (MSA), increase in CO2 and methane mixing ratio, heavier ? D-CH4 and ?18Oatm), lasting 740 ± 60 years, itself ending approximately 390 ± 50 years prior to abrupt Greenland warming. Preliminary investigations on GS-13 encompassing H5, based on the ice core proxies ?18O, MSA, ?18Oatm, CH4 and CO2 data also reveal a 3 phase structure, as well as the same sequence of events. The decoupling between stable cold Greenland temperature and low latitude HE imprints provides new targets for benchmarking climate model simulations and testing mechanisms associated with millennial variability.

  3. Chemical compositions of soluble aerosols around the last termination in the NEEM (Greenland) ice core

    NASA Astrophysics Data System (ADS)

    Oyabu, Ikumi; Iizuka, Yoshinori; Karlin, Torbjorn; Fukui, Manabu; Hondoh, Takeo; Hansson, Margareta

    2013-04-01

    The polar ice cores provide us with reconstruction of past atmospheric aerosols. Atmospheric aerosols such as dust and sea salt in both Arctic and Antarctic ice cores are well discussed by using the proxy of ion concentration/flux. Recently, studies on the chemical compositions of soluble aerosols in the ice cores have been carried out. The chemical compositions and transition of soluble aerosols in the Dome Fuji (Antarctica) has been revealed, however, there are few studies on those of soluble aerosols in Greenland ice cores. Using ice sublimation method #1, we analyzed the chemical compositions of soluble aerosols around the last termination in the NEEM (Greenland) ice core. A total of 43 samples were distributed from NEEM ice core section from 1280 to 1580 m. Soluble aerosols were extracted from the samples by sublimation system. Constituent elements and diameter of each non-volatile particle were measured by scanning electron micro scope (SEM) and energy dispersive X-ray spectroscopy (EDS). By using a method in our recent paper #2, we assumed that particles containing Ca and S are calcium sulfate and particles containing Na and S are sodium sulfate. We divided around the last termination into 4 stages by focusing on the temperature; Holocene, Younger Dryas (YD), Bølling-Allerød (B-A) and Last Glacial Period (LGP), and compared the mass ratio of sulfate and chloride aerosols in each stage. During the cold stage in YD and LGP, calcium sulfate accounted large percentage of soluble aerosols. On the other hand, during the warm stage in Holocene and B-A, sodium sulfate accounted large percentage of soluble aerosols. These relationships between chemical composition and temperature are probably related to non sea salt (nss)-calcium ion concentration. We will discuss the relationship between nss-calcium ion concentration and chemical compositions of soluble aerosols in the presentation. References #1 Iizuka et al., J. Glaciol., 55(191), 58-64, 2009. #2 Iizuka, Y. et al. J. Geophys. Res. 117, D04308, 2012.

  4. Ion fractionation and percolation in ice cores with seasonal melting John C. Moore*, Aslak Grinsted **

    E-print Network

    Moore, John

    and with the type of data that was expected to come from ice caps with seasonal melt. The objective of this paperIon fractionation and percolation in ice cores with seasonal melting John C. Moore*, Aslak Grinsted that suffer limited seasonal melting. We show that the impact in the case of at least one Svalbard ice core

  5. Peatland Constraints on the Deglacial CO2 Rise from Ice Cores

    E-print Network

    Keel, Markus

    · Brook, E. "The Ice Age Carbon Puzzle." Science: 336 pg. 682-683. · Gorham, EPeatland Constraints on the Deglacial CO2 Rise from Ice Cores Alice Nadeau on the Deglacial CO2 Rise from Ice Cores." Science: 336 pg. 711-713. #12;

  6. The Mount Logan (Yukon) Ice Cores: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Fisher, D. A.

    2004-05-01

    Three ice cores were taken at different elevations on or near My Logan in the years 2001 and 2002. The summit core (PRCol) comes from the summit plateau ( 5340 masl, length 187 m to bedrock, mean temperature -29 C ) and was done by the Geological Survey of Canada. The NIPR group cored 210m on the flanks of the mountain at King Col (4200 masl mean temperature -16C) and the UNH group cored 20 km from the mountain at Eclipse "Dome" (3015 masl,length 345 m mean temperature -5C) . The three cores were done cooperatively by GSC, NIPR and UNH and cover nominally 30 ka, 1 ka and 2ka respectively . Located very close to the Gulf of Alaska these core records are thought to reflect the climate history of the Pacific Ocean and having three widely spaced elevations, the sites "see" different distances to different sources. The lowest site (Eclipse) has excellent seasonals but a very muted ? 18O history with no obvious little ice age, whereas the most recent 1ka of the PRCol summit sites contains two very large and sudden ? 18O and d (deuterium excess) shifts at 1850 AD and ~ 800 AD. The ? 18O shifts which happen from one year to the next are about 4 o/oo . The summit site (PRCol) ? 18O response is "backwards", ie the Little Ice Age ? 18O values are 4 o/oo more positive than recent ones. The PRCol ? 18O and d suggest that the source water can either be ëlocalí (Gulf of Alaska) or very distant (tropics) . The Eclipse site seems only to get the local water . A massive dust storm originating in central Asia (Gobi) in April 2001 dumped a visible layer all over the St Elias Mountains and this layer was sampled, to provide a calibration "Asian dust event". The satellite and isotoic signatures both agreed that Gobi was the source. The PRCol record covers the Holocene and well back into the ice age. The transition is defined by a sudden ECM shift on the flanks of a more gradual O18 shift. Acknowledgements. Logan consortium consists of : Geological Survey of Canada : Jocelyne Bourgeois, Mike Demuth, David Fisher, Roy Koerner,Chris Zdanowicz, James Zheng. University of Ottawa: Ian Clarke,Raphaelle Cardyn. National Institute of Polar Research (Japan): Kumiko Goto-Azuma University of New Hampshire: Cam Wake, Kaplan Yalcin. University of Maine: Karl Kreutz, Paul Mayewski, Erich Osterberg. Arctic Institute of North America: Gerald Holdsworth. University of Washington: Eric J. Steig, Summer B. Rupper. University of Copenhagen: Dorthe Dahl-Jensen. David Fisher is the presenter but many contributed to what is a joint preliminary offering.

  7. Reconstruction of interannual Antarctic climate variability from ice cores

    NASA Astrophysics Data System (ADS)

    Steig, E. J.; Schneider, D. P.

    2004-05-01

    Antarctica represents a significant gap in efforts to achieve reliable reconstructions of interannual to century-scale climate variability. A reliable reconstruction of Antarctic climate on these timescales requires obtaining precisely dated ice cores at high temporal resolution, and with sufficient spatial coverage to adequately capture large-scale climate variability. Ice cores retrieved by the International TransAntarctic Scientific Expedition (ITASE) program are a major step towards this goal. As part of US ITASE, ice cores were obtained from twenty-three sites that are widely distributed across the West Antarctic Ice Sheet, providing continuous records of snow chemistry covering at least 200 years. These cores have been dated at better-than-annual resolution, primarily though the identification of summer peaks in non-sea-salt sulfate (nss-SO{4}). Validation of the timescales was achieved through independent identification of other seasonal variations and marker horizons. Dating precision to within 1-2 months is demonstrated by the occurrence of spring-time nitrate peaks ~3 months before the nss-SO{4} maxima, by the identification of distinct mid-winter warming in some years in both instrumental temperature records and stable isotope ratios, and by the timing of hydrogen peroxide maxima. Dating accuracy to within ±1 one year is demonstrated by volcanic marker horizons, Tambora (1815-1816) being the most prominent. Additional validation of the ±1 year accuracy is provided by the tracing of isochronal layers from site to site using high-frequency ice penetrating radar observations. Reconstruction of climate variability from the ice core data is achieved in three stages. First, satellite-derived anomalies are used to define characteristic patterns of Antarctic temperature variability by conventional EOF analysis; this provides approximately 20 years of monthly data. Using instrumental weather station data (largely from the Antarctic coastline)] as predictor variables, we obtain a reconstruction of the principal components of Antarctic temperatures, with coverage over the entire continent back to 1961. Finally, the resulting 40+ years of spatiotemporal variations in Antarctic temperatures are used as a calibration target for the ice core data. Our current reconstruction uses five stable isotope records from West Antarctica, plus data from Talos Dome and Law Dome. The results show an overall warming of Antarctica since at least the early 1960s, but with cooling in the summer months. Preliminary results also suggest overall warming since the mid 1800s, with significant multi-decadal scale variations. These results, if further validated, will have important implications for the interpretation of recent observed trends in the Southern Annular Mode/Antarctic Oscillation. Major contributors to this work, in addition to this listed authors, include D. Dixon, G. Hamilton, S. Kaspari, A. Kurbatov, P. Mayewski, B. Spikes (University of Maine), M. Albert, S. Arcone, A. Gow, D. Meese (CRREL), C. Shuman (NASA/Goddard), M. Frey (University of Arizona), M. Wumkes (Glacier Data) and T. van Ommen (Antarctic CRC).

  8. THE TROPICAL CONNECTION BETWEEN THE ATLANTIC SECTOR ICE CORES AND THE NORTH PACIFIC MT LOGAN ICE CORE

    NASA Astrophysics Data System (ADS)

    Fisher, D. A.

    2009-12-01

    The stable isotope record from the Mt Logan, Yukon, Canada ice core spans the late Glacial to present and shows very large and sudden variations in O18 during the Holocene . It is hypothesized that they are driven by changes in the water sources ,which in turn, are determined by the state of ENSO. There seems to be no correlations between the Logan ice core isotope record and those from the North Atlantic (Greenland and Eastern Canadian Arctic). Using the stacked and co-dated Greenland and Eastern Canadian Arctic ice core records from the Holocene, it is possible to reproduce the Logan isotope record by subtracting the stacked Atlantic record from itself with an 1100 year lag. The correlations obtainable are -0.43 for 50 year average series. This correlation is significant at the 99.8 % level . The 1100 lag has also been found in previous studies comparing the Greenland to Antarctic ice cores (Stocker and Johnsen,2003). It is argued that such a lagged difference series is a proxy for the difference between the ocean water surface and deep temperatures in the tropical Pacific . ENSO’s amplitude is driven by this temperature difference, (Sun 2000). When the deep water is too warm, then the difference is too small to produce ENSO oscillations and strong tropical easterly winds persist (ie strong and constant La Nina). The ice core records from Mt Logan , Greenland and Eastern Arctic Canada all point to a similar history of ENSO oscillation strength. Prior to ~ 4200 BP the strong and constant La Nina tended to drive the tropical Pacific winds and moisture across to produce strong and reliable monsoons. Since 4200 BP the “modern” and variable pattern has been in place. There was a smaller scale shift about 1840 AD . For about a couple of centuries prior to 1840 AD , La Nina was in charge and after there were the oscillations that are thought of as normal. If the 1100 year lag between surface and bottom temperatures is true and if the bottom temperatures are echoes those from the N Atlantic 1100 years ago, there are implications for what we could expect from the tropical Pacific oscillations (ENSO) in the future. Sun D. 2000. Global climate change and El Nino: a theoretical framework. in "El Nino and The Southern Oscillation", editors H. F. Diaz and V. Markgraf. Cambridge UP. Stocker T.F. and S.J. Johnsen. 2003. A minimum thermodynamic model for the bipolar seesaw.. Paleoceanography vol 18, No 4 , pp11-19.

  9. Measurement of fracture toughness of an ice core from Antarctica

    NASA Astrophysics Data System (ADS)

    Christmann, J.; Müller, R.; Webber, K. G.; Isaia, D.; Schader, F. H.; Kipfstuhl, S.; Freitag, J.; Humbert, A.

    2014-09-01

    The critical fracture toughness is a material parameter describing the resistance of a cracked body to further crack extension. It is an important parameter to simulate and predict the break-up behaviour of ice shelves from calving of single icebergs to the disintegration of entire ice shelves over a wide range of length scales. The fracture toughness values are calculated with equations that are derived from an elastic stress analysis. Additionally, an X-ray computer tomography (CT scanner) was used to identify the density as a function of depth. The critical fracture toughness of 91 Antarctic inland ice samples with densities between 840 to 870 kg m-3 has been determined by applying a four-point-bending technique on single edge v-notched beam samples. The examined ice core was drilled 70 m north of Kohnen Station, Dronnning Maud Land (75°00' S, 00°04' E, 2882 m). Supplementary data are available at doi:10.1594/PANGAEA.835321.

  10. Halogen-based reconstruction of Russian Arctic sea ice area from the Akademii Nauk ice core (Severnaya Zemlya)

    NASA Astrophysics Data System (ADS)

    Spolaor, A.; Opel, T.; McConnell, J. R.; Maselli, O. J.; Spreen, G.; Varin, C.; Kirchgeorg, T.; Fritzsche, D.; Vallelonga, P.

    2015-08-01

    The role of sea ice in the Earth climate system is still under debate, although it is known to influence albedo, ocean circulation, and atmosphere-ocean heat and gas exchange. Here we present a reconstruction of AD 1950 to 1998 sea ice in the Laptev Sea based on the Akademii Nauk ice core (Severnaya Zemlya, Russian Arctic). The halogens bromine (Br) and iodine (I) are strongly influenced by sea ice processes. Bromine reacts with the sea ice surface in auto-catalyzing "Bromine explosion" events causing an enrichment of the Br / Na ratio and the bromine excess (Brexc) in snow compared to that in seawater. Iodine is emitted from algal communities growing under sea ice. The results suggest a connection between Brexc and spring sea ice area, as well as a connection between iodine concentration and summer sea ice area. These two halogens are therefore good candidates for extended reconstructions of past sea ice changes in the Arctic.

  11. Shallow seafloor glacial features reveal ice streaming and re-advance of the last British Ice Sheet, offshore eastern Scotland and north-eastern England, UK

    NASA Astrophysics Data System (ADS)

    Stewart, H. A.; Bradwell, T.

    2013-12-01

    Multibeam echosounder datasets have been combined with high-resolution topographic digital surface models (NEXTMap), 2D seismic reflection profiles and shallow cores to reveal strong evidence for onshore-offshore palaeo-ice streaming in eastern Scotland and north-eastern England, UK. The study area includes the catchments of the previously proposed, but only partly mapped, Strathmore, Forth-Tay, and Tweed palaeo-ice streams. Long suspected to terminate offshore, the full flow path and dimensions of this palaeo-ice stream system can now be reconstructed with some certainty using these new data. The ice sheet glacial landsystem is extremely well preserved on the seabed with four main types of subglacial and ice marginal morphology present: 1) highly elongate flow-parallel ridges and grooves strongly suggestive of ice streaming; 2) shorter-elongation flow aligned drumlins and crag and tails indicative of fast-flowing and persistent ice-sheet flow configurations; 3) large arcuate moraine ridges marking frontal stillstands or readvances of the ice sheet margin; and 4) tunnel valleys and deeply incised meltwater channels probably associated with retreat phases of the British Ice Sheet (BIS) following Last Glacial Maximum. The mapped bedforms indicate that fast-flowing corridors (palaeo-ice streams) existed within the last BIS emanating from the central belt of Scotland and northeast England. This new geomorphological evidence shows that these ice streams extended at least 60km offshore and probably accelerated across the transition from bedrock-dominated onshore terrain to till- dominated North Sea Basin. Of particular note is the observation that the Forth-Tay ice stream diverged, forming two glaciologically separate streams running parallel to the present-day coastline. Evidence shows that the southerly arm of this palaeo-ice stream overprinted the Tweed palaeo-ice stream which is contrary to the previously proposed trajectory. Spatial and morphological relationships between the landforms within this glacial landsystem allow inferences about ice sheet history and behaviour to be reconstructed. Most notably, elongate streamlined bedforms superimposed on conspicuous moraine ridges indicate that an extensive advance of palaeo-ice streams took place into the North Sea Basin during overall ice sheet retreat.

  12. Caldicellulosiruptor Core and Pangenomes Reveal Determinants for

    SciTech Connect

    Blumer-Schuette, Sara E.; Giannone, Richard J; Zurawski, Jeffrey V; Ozdemir, Inci; Ma, Qin; Yin, Yanbin; Xu, Ying; Kataeva, Irena; Poole, Farris; Adams, Michael W. W.; Hamilton-Brehm, Scott; Elkins, James G; Larimer, Frank W; Land, Miriam L; Hauser, Loren John; Cottingham, Robert W; Hettich, Robert {Bob} L; Kelly, Robert M

    2012-01-01

    Extremely thermophilic bacteria of the genus Caldicellulosiruptor utilize carbohydrate components of plant cell walls, including cellulose and hemicellulose, facilitated by a diverse set of glycoside hydrolases (GHs). From a biofuel perspective, this capability is crucial for deconstruction of plant biomass into fermentable sugars. While all species from the genus grow on xylan and acidpretreated switchgrass, growth on crystalline cellulose is variable. The basis for this variability was examined using microbiological, genomic, and proteomic analyses of eight globally diverse Caldicellulosiruptor species. The open Caldicellulosiruptor pangenome (4,009 open reading frames [ORFs]) encodes 106 GHs, representing 43 GH families, but only 26 GHs from 17 families are included in the core (noncellulosic) genome (1,543 ORFs). Differentiating the strongly cellulolytic Caldicellulosiruptor species from the others is a specific genomic locus that encodes multidomain cellulases from GH families 9 and 48, which are associated with cellulose-binding modules. This locus also encodes a novel adhesin associated with type IV pili, which was identified in the exoproteome bound to crystalline cellulose. Taking into account the core genomes, pangenomes, and individual genomes, the ancestral Caldicellulosiruptor was likely cellulolytic and evolved, in some cases, into species that lost the ability to degrade crystalline cellulose while maintaining the capacity to hydrolyze amorphous cellulose and hemicellulose.

  13. Optimisation of glaciological parameters for ice core chronology by implementing counted layers between identified depth levels

    NASA Astrophysics Data System (ADS)

    Bazin, L.; Lemieux-Dudon, B.; Landais, A.; Guillevic, M.; Kindler, P.; Parrenin, F.; Martinerie, P.

    2014-08-01

    A~recent coherent chronology has been built for 4 Antarctic ice cores and the NorthGRIP (NGRIP) Greenland ice core (Antarctic Ice Core Chronology 2012, AICC2012) using a bayesian approach for ice core dating (Datice). When building the AICC2012 chronology, and in order to prevent any confusion with official ice cores chronology, it has been imposed that the AICC2012 chronology for NGRIP should respect exactly the GICC05 chronology based on layer counting. However, such a strong tuning did not satisfy the hypothesis of independence of background parameters and observations for the NGRIP core as required by Datice. We present here the implementation in Datice of a new type of markers that is better suited to constraints deduced from layer counting: the markers of age-difference. Using this type of markers for NGRIP in a 5 cores dating exercise with Datice, we have performed several sensitivity tests and show that the new ice core chronologies obtained with these new markers do not differ by more than 400 years from AICC2012 for Antarctic ice cores and by more than 130 years from GICC05 for NGRIP over the last 60 000 years. With this new parameterization, the accumulation rate and lock-in depth associated with NGRIP are more coherent with independent estimates than those obtained in AICC2012. While these new chronologies should not be used yet as new ice core chronologies, the improved methodology presented here should be considered in the next coherent ice core dating exercise.

  14. Trace elements in a dated ice core from Antarctica

    SciTech Connect

    Keshin, S.S.; Xudong Huang; Olmez, I. ); Langway, C.C. Jr. )

    1992-01-01

    Aerosol particles from both natural and anthropogenic sources are emitted into the atmosphere and transported by wind systems by various mechanisms. Once airborne, the particles, which contain various trace elements, accumulate on the earth's surface as either condensation nuclei or by dry fallout processes. In the polar regions, these particles are incorporated and deposited in snow layers in sequential time-unit increments. The trace analysis of elements contained in dated annual snow layers provides a measure of the elemental chemistry content of the atmosphere for the same time interval. A 164-m-deep, 10-cm-diam ice core was obtained at Byrd Station, Antarctica, in November 1989. Other physical and chemistry studies on this ice core have identified its detailed chronology in annual increments for the past 1360 yr. This study presents the results of the instrumental neutron activation analysis (INAA) measurements made on 26 individually dated samples of this core, selected between the 6.43- and 118.15-m depths.

  15. 10Be in ice - four decades, two ice sheets, 15 deep coring sites

    NASA Astrophysics Data System (ADS)

    Berggren, Ann-Marie; Aldahan, Ala; Possnert, Göran

    2010-05-01

    Over the last few decades, numerous studies of 10Be in ice cores from Antarctica and Greenland have comprised a significant source of information on climate, solar activity and geomagnetic field intensity over the past 800 000 years. There is, however, a large variability in the available 10Be records in terms of resolution and time coverage. We here present a comprehensive summary of results that have been put forward since the 1960s. Marine sediment was the first type of natural archive in which 10Be was detected (Arnold, 1956), and a decade later McCorkell et al. (1967) pioneered the ice archive field by counting 10Be beta activity in samples from Camp Century, Greenland. The method demands a large amount of material; in this case 1.2×106 litres of water were used. Using accelerator mass spectrometry, AMS, Raisbeck et al. (1978) undertook the second study of 10Be in polar ice, measuring 10Be concentrations in ice from Dome C, Antarctica. The AMS technique is exclusively used today for measurements of 10Be in small ice volumes (

  16. Svalbard summer melting, continentality, and sea ice extent from the Lomonosovfonna ice core

    NASA Astrophysics Data System (ADS)

    Grinsted, Aslak; Moore, John C.; Pohjola, Veijo; Martma, Tõnu; Isaksson, Elisabeth

    2006-04-01

    We develop a continentality proxy (1600-1930) based on amplitudes of the annual signal in oxygen isotopes in an ice core. We show via modeling that by using 5 and 15 year average amplitudes the effects of diffusion and varying layer thickness can be minimized, such that amplitudes then reflect real seasonal changes in ?18O under the influence of melt. A model of chemical fractionation in ice based on differing elution rates for pairs of ions is developed as a proxy for summer melt (1130-1990). The best pairs are sodium with magnesium and potassium with chloride. The continentality and melt proxies are validated against twentieth-century instrumental records and longer historical climate proxies. In addition to summer temperature, the melt proxy also appears to reflect sea ice extent, likely as a result of sodium chloride fractionation in the oceanic sea ice margin source area that is dependent on winter temperatures. We show that the climate history they depict is consistent with what we see from isotopic paleothermometry. Continentality was greatest during the Little Ice Age but decreased around 1870, 20-30 years before the rise in temperatures indicated by the ?18O profile. The degree of summer melt was significantly larger during the period 1130-1300 than in the 1990s.

  17. Adsorption and dissociation of acidic trace gases on ice surfaces - caught in the act with core level spectroscopy

    NASA Astrophysics Data System (ADS)

    Waldner, Astrid; Orlando, Fabrizio; Ammann, Markus; Kleibert, Armin; Huthwelker, Thomas; Peter, Thomas; Bartels-Rausch, Thorsten

    2015-04-01

    Chemistry and physical processes in Earth's ice and snow cover can change the composition of the atmosphere and the contaminant content of the cryosphere. They have thus direct impacts on geochemical cycles and the climate system. Our ability to predict the fate of chemicals in snow or air masses in exchange with the cryosphere on a regional scale or to model those in snow chemistry models is currently hampered by our limited understanding of the underlying mechanisms on a molecular level. So far, direct experimental observations under environmentally relevant conditions of the ice surface and of the adsorption of trace gases to it are very limited. The unique approach of this study is to combine two surface sensitive spectroscopic methods to directly probe the hydrogen-bonding network at the ice surface ( ~1 nm depth) and the concentration, depth profile (~1 to 10 nm), and dissociation degree of the dopant. We present first core-electron photoemission (XPS) and partial electron yield X-ray absorption (NEXAFS) measurements of formic acid adsorbed to ice at 240 K. The analysis of oxygen NEXAFS spectra reveals information on changes in the hydrogen-bonding network of the ice surface upon adsorption of formic acid. Depth profiles based on XPS measurements indicate that the adsorbed acid stays at the ice surface. Furthermore we obtained a preliminary estimation of the degree of formic acid dissociation at the ice surface. Results are compared to earlier core-electron studies of several trace gases adsorbed to ice at 240 K and compared to results from more traditional method to and snow to reveal fundamental aspects of the ice surface and how it interacts with dopants. Even with the focus on adsorption of acidic trace gases to ice, results of this study will thus be of high relevance also for other chemical processes in ice and snow. This is of interest not only in environmental science but also in material science, cryobiology, and astrophysics.

  18. Glacial-interglacial sea ice proxies from the Antarctic Peninsula using the James Ross Island ice core.

    NASA Astrophysics Data System (ADS)

    Benton, A. K.; Mulvaney, R.; Triest, J.; Abram, N.

    2014-12-01

    Ice core records from Antarctica have shown promise as highly-resolved indicators of regional sea ice change, but to date semi-quantified reconstructions do not extend back more than ~150 years. In this study the chemical composition of the James Ross Island ice core is presented as a potential sea ice proxy record spanning the full Holocene and into the last glacial interval. A CFA-TE method was used to analyse the chemical composition of the entire 363.9m core including final 5m which contains evidence of glacial age ice. MSA- and major anions were measured at 4cm effective resolution, along with trace elements Na, Ca, K, Mg, Mn, H2O2, NO3, total conductivity and dust at <0.5cm effective resolution. Seasonal signals from H2O2 in the upper 50m of the core support the use of non sea salt-SO42- for determining seasonality in deeper sections. This multi-proxy analysis of the oldest ice core to date from the Antarctic Peninsula region allows the concurrent interpretation of sea ice changes and their environmental drivers. The potential dual influence of previous winter sea ice extent and air pathway source region on MSA concentrations in the core are interpreted with use of Na as a winter maximum indicator and Ca and dust signal strength showing changes in dust flux indicating potential source region variation.

  19. The Late Holocene Atmospheric Methane Budget Reconstructed from Ice Cores

    NASA Astrophysics Data System (ADS)

    Mitchell, Logan E.

    In this thesis I used a newly developed methane measurement line to make high-resolution, high-precision measurements of methane during the late Holocene (2800 years BP to present). This new measurement line is capable of an analytical precision of < 3 ppb using ˜120 g samples. The reduced sample size requirements as well as automation of a significant portion of the analysis process have enabled me to make >1500 discrete ice core methane measurements and construct the highest resolution records of methane available over the late Holocene. I first used a shallow ice core from WAIS Divide (WDC05A) to produce a 1000 year long methane record with a ˜9 year temporal resolution. This record confirmed the existence of multidecadal scale variations that were first observed in the Law Dome, Antarctica ice core. I then explored a range of paleoclimate archives for possible mechanistic connections with methane concentrations on multidecadal timescales. In addition, I present a detailed description of the analytical methods used to obtain high-precision measurements of methane including the effects of solubility and a new chronology for the WDC05A ice core. I found that, in general, the correlations with paleoclimate proxies for temperature and precipitation were low over a range of geographic regions. Of these, the highest correlations were found from 1400-1600 C.E. during the onset of the Little Ice Age and with a drought index in the headwater region of the major East Asian rivers. Large population losses in Asia and the Americas are also coincident with methane concentration decreases indicating that anthropogenic activities may have been impacting multidecadal scale methane variability. In the second component I extended the WAIS Divide record back to 2800 years B.P. and also measured methane from GISP2D over this time interval. These records allowed me to examine the methane Inter-Polar Difference (IPD) which is created by greater northern hemispheric sources. The IPD provides an important constraint on changes in the latitudinal distribution of sources. We used this constraint and an 8-box global methane chemical transport model to examine the Early Anthropogenic Hypothesis which posits that humans began influencing climate thousands of years ago by increasing greenhouse gas emissions and preventing the onset of the next ice age. I found that most of the increase in methane sources over this time came from tropical regions with a smaller contribution coming from the extratropical northern hemisphere. Based on previous modeling estimates of natural methane source changes, I found that the increase in the southern hemisphere tropical methane emissions was likely natural and that the northern hemispheric increase in methane emissions was likely due to anthropogenic activities. These results also provide new constraints on the total magnitude of pre-industrial anthropogenic methane emissions, which I found to be between the high and low estimates that have been previously published in the literature. For the final component of my thesis I assembled a coalition of scientists to investigate the effects of layering on the process of air enclosure in ice at WAIS Divide. Air bubbles are trapped in ice 60-100m below the surface of an ice sheet as snow compacts into solid ice in a region that is known as the Lock-In Zone (LIZ). The details of this process are not known and in the absence of direct measurements previous researchers have assumed it to be a smooth process. This project utilized high-resolution methane and air content measurements as well as density of ice, delta15N of N2, and bubble number density measurements to show that air entrapment is affected by high frequency (mm scale) layering in the density of ice within the LIZ. I show that previous parameterizations of the bubble closure process in firn models have not accounted for this variability and present a new parameterization which does. This has implications for interpreting rapid changes in trace gases measured in ice cores since variable bubble closure wi

  20. Element composition of dust from a shallow Dunde ice core, Northern China

    NASA Astrophysics Data System (ADS)

    Wu, Guangjian; Zhang, Chenglong; Gao, Shaopeng; Yao, Tandong; Tian, Lide; Xia, Dunsheng

    2009-06-01

    The Dunde ice cap (38°06'N, 96°24'E, with a summit of 5325 m) is situated at the centre of the northern Chinese deserts and receives dust from these regions. Here, we present the trace and rare earth element (REE) compositions of dust extracted from a shallow ice core from the Dunde ice cap, which provide a framework to trace the source of Dunde dust. Trace and REE parameters of Dunde dust show characteristics of a typical eolian deposit, with an average La/Th ratio of 2.6, a Th/U ratio of 3.7, and a strong negative Eu anomaly (0.61). The dirty layers in the ice core section have the same element characteristics as in the clear layers, indicating that the dust in Dunde is well-mixed and has a stable composition. Trace element and REE ratio plots show that Dunde dust has a similar composition to the finer fraction materials in the Taklimakan desert, suggesting that the Tarim Basin might be an important source for Dunde dust under the present circulation, but not favoring a material contribution from Badain Jaran. Our results reveal distinct differences in composition between Dunde dust and Chinese loess materials, which suggests that they have different sources.

  1. Fire in Ice: Glacial-Interglacial biomass burning in the NEEM ice core

    NASA Astrophysics Data System (ADS)

    Zennaro, Piero; Kehrwald, Natalie; Zangrando, Roberta; Gambaro, Andrea; Barbante, Carlo

    2014-05-01

    Earth is an intrinsically flammable planet. Fire is a key Earth system process with a crucial role in biogeochemical cycles, affecting carbon cycle mechanisms, land-surface properties, atmospheric chemistry, aerosols and human activities. However, human activities may have also altered biomass burning for thousands of years, thus influencing the climate system. We analyse the specific marker levoglucosan to reconstruct past fire events in ice cores. Levoglucosan (1,6-anhydro-?-D-glucopyranose) is an organic compound that can be only released during the pyrolysis of cellulose at temperatures > 300°C. Levoglucosan is a major fire product in the fine fraction of woody vegetation combustion, can be transported over regional to global distances, and is deposited on the Greenland ice sheet. The NEEM, Greenland ice core (77 27'N, 51 3'W, 2454 masl) documents past fire activity changes from the present back to the penultimate interglacial, the Eemian. Here we present a fire activity reconstruction from both North American and Eurasian sources over the last 120,000 yrs based on levoglucosan signatures in the NEEM ice core. Biomass burning significantly increased over the boreal Northern Hemisphere since the last glacial, resulting in a maximum between 1.5 and 3.5 kyr BP yet decreasing from ~2 kyr BP until the present. Major climate parameters alone cannot explain the observed trend and thus it is not possible to rule out the hypothesis of early anthropogenic influences on fire activity. Over millennial timescales, temperature influences Arctic ice sheet extension and vegetation distribution at Northern Hemisphere high latitudes and may have altered the distance between NEEM and available fuel loads. During the last Glacial, the combination of dry and cold climate conditions, together with low boreal insolation and decreased atmospheric carbon dioxide levels may have also limited the production of available biomass. Diminished boreal forest extension and the southward shift of taiga may have reduced the levoglucosan flux over Greenland during the Glacial, thus limiting the biomass burning signatures in the glacial NEEM section. Eemian biomass burning would be expected to be greater than that of the last Glacial due to incresed temperatures and the lack of continental ice sheets. However, NEEM Eemian levoglucosan concentrations are unexpectedly low, and are lower than any other climate period including the last Glacial. We propose that microbial activity in melting ice layers is a potential explanation for the low observed Eemian levoglucosan values.

  2. Recent Increases in Snow Accumulation and Decreases in Sea-Ice Concentration Recorded in a Coastal NW Greenland Ice Core

    NASA Astrophysics Data System (ADS)

    Osterberg, E. C.; Thompson, J. T.; Wong, G. J.; Hawley, R. L.; Kelly, M. A.; Lutz, E.; Howley, J.; Ferris, D. G.

    2013-12-01

    A significant rise in summer temperatures over the past several decades has led to widespread retreat of the Greenland Ice Sheet (GIS) margin and surrounding sea ice. Recent observations from geodetic stations and GRACE show that ice mass loss progressed from South Greenland up to Northwest Greenland by 2005 (Khan et al., 2010). Observations from meteorological stations at the U.S. Thule Air Force Base, remote sensing platforms, and climate reanalyses indicate a 3.5C mean annual warming in the Thule region and a 44% decrease in summer (JJAS) sea-ice concentrations in Baffin Bay from 1980-2010. Mean annual precipitation near Thule increased by 12% over this interval, with the majority of the increase occurring in fall (SON). To improve projections of future ice loss and sea-level rise in a warming climate, we are currently developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate variability and cryospheric response in NW Greenland, with a focus on past warm periods. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 20 m) from the coastal region of the GIS (2Barrel site; 76.9317 N, 63.1467 W) and the summit of North Ice Cap (76.938 N, 67.671 W) in 2011 and 2012, respectively. The 2Barrel ice core was sampled using a continuous ice core melting system at Dartmouth, and subsequently analyzed for major anion and trace element concentrations and stable water isotope ratios. Here we show that the 2Barrel ice core spanning 1990-2010 records a 25% increase in mean annual snow accumulation, and is positively correlated (r = 0.52, p<0.01) with ERA-Interim precipitation. The 2Barrel annual sea-salt Na concentration is strongly correlated (r = 0.5-0.8, p<0.05) with summer and fall sea-ice concentrations in northern Baffin Bay near Thule (Figure 1). We hypothesize that the positive correlation represents a significant Na contribution from frost flowers growing on fall frazil ice. Ongoing analyses will evaluate the relationship between MSA concentrations and sea ice extent. Our results show that a deep ice core collected from this dynamic and climate-sensitive region of NW Greenland would produce a valuable record of late Holocene climate and sea ice extent.

  3. Climatic and insolation control on the high-resolution total air content in the NGRIP ice core

    NASA Astrophysics Data System (ADS)

    Eicher, O.; Baumgartner, M.; Schilt, A.; Schmitt, J.; Schwander, J.; Stocker, T. F.; Fischer, H.

    2015-11-01

    Because the total air content (TAC) of polar ice is directly affected by the atmospheric pressure, its record in polar ice cores was considered as a proxy for past ice sheet elevation changes. However the Antarctic ice core TAC record is known to also contain an insolation signature, although the underlying physical mechanisms are still a matter of debate. Here we present a high-resolution TAC record over the whole North Greenland Ice Core Project ice core, covering the last 120 000 years, which independently supports an insolation signature in Greenland. Wavelet analysis reveals a clear precession and obliquity signal similar to previous findings on Antarctic TAC, with different insolation history. In our high-resolution record we also find a decrease of 3-5 % (3-4.2 mL kg-1) in TAC as a response to Dansgaard-Oeschger-Events (DO-events). TAC starts to decrease in parallel to increasing Greenland surface temperature and slightly before CH4 reacts to the warming, but also shows a two-step decline that lasts for several centuries into the warm phase/interstadial. The TAC response is larger than expected considering only local temperature and atmospheric pressure as a driver, pointing to transient firnification response caused by the accumulation-induced increase in the load on the firn at bubble close-off, while temperature changes deeper in the firn are still small.

  4. Variability of sulfate signal in ice-core records based on five replicate cores

    NASA Astrophysics Data System (ADS)

    Gautier, E.; Savarino, J.; Erbland, J.; Lanciki, A.; Possenti, P.

    2015-08-01

    Current volcanic reconstructions based on ice core analysis have significantly improved over the last decades. Relying on limited and disparate sulfate profiles at first, they have progressively incorporated multi cores analysis with high temporal resolution from different parts of the Polar Regions. Regional patterns of volcanic deposition flux are now based on composite records, built from several cores taken at both poles. However, it is worth mentioning that most of the time only a single record at a given site is used for such reconstructions. This implicitly assumes that transport and regional meteorological patterns are the only source of the dispersion of the volcanic-products. In the present work, we evaluate the local scale variability of a sulfate profile in a low accumulation site (Dome C, Antarctica), in order to assess the representativeness of one core for such reconstruction. We evaluate the depth variability, statistical occurrence, and sulfate flux deposition variability of volcanic eruptions detected on 5 ice cores, drilled 1 m away from each other. Local scale variability, essentially attributed to snow drift and surface roughness at Dome C, can lead to a non-exhaustive record of volcanic events when a single core is used as the site reference with a bulk probability of 30 % of missing volcanic events and 60 % uncertainty on the volcanic flux estimation. Averaging multiple records almost erases the probability of missing volcanic events and can reduce by half the uncertainty pertaining to the deposition flux.

  5. Ice cores and SeaRISE: What we do (and don't) know

    NASA Technical Reports Server (NTRS)

    Alley, Richard B.

    1991-01-01

    Ice core analyses are needed in SeaRISE to learn what the West Antarctic ice sheet and other marine ice sheets were like in the past, what climate changes led to their present states, and how they behave. The major results of interest to SeaRISE from previous ice core analyses in West Antarctic are that the end of the last ice age caused temperature and accumulation rate increases in inland regions, leading to ice sheet thickening followed by thinning to the present.

  6. Characterizing black carbon in rain and ice cores using coupled tangential flow filtration and transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Ellis, A.; Edwards, R.; Saunders, M.; Chakrabarty, R. K.; Subramanian, R.; van Riessen, A.; Smith, A. M.; Lambrinidis, D.; Nunes, L. J.; Vallelonga, P.; Goodwin, I. D.; Moy, A. D.; Curran, M. A. J.; van Ommen, T. D.

    2015-09-01

    Antarctic ice cores have been used to study the history of black carbon (BC), but little is known with regards to the physical and chemical characteristics of these particles in the remote atmosphere. Characterization remains limited by ultra-trace concentrations in ice core samples and the lack of adequate methods to isolate the particles unaltered from the melt water. To investigate the physical and chemical characteristics of these particles, we have developed a tangential flow filtration (TFF) method combined with transmission electron microscopy (TEM). Tests using ultrapure water and polystyrene latex particle standards resulted in excellent blanks and significant particle recovery. This approach has been applied to melt water from Antarctic ice cores as well as tropical rain from Darwin, Australia with successful results: TEM analysis revealed a variety of BC particle morphologies, insoluble coatings, and the attachment of BC to mineral dust particles. The TFF-based concentration of these particles has proven to give excellent results for TEM studies of BC particles in Antarctic ice cores and can be used for future studies of insoluble aerosols in rainwater and ice core samples.

  7. Characterizing black carbon in rain and ice cores using coupled tangential flow filtration and transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Ellis, A.; Edwards, R.; Saunders, M.; Chakrabarty, R. K.; Subramanian, R.; van Riessen, A.; Smith, A. M.; Lambrinidis, D.; Nunes, L. J.; Vallelonga, P.; Goodwin, I. D.; Moy, A. D.; Curran, M. A. J.; van Ommen, T. D.

    2015-06-01

    Antarctic ice cores have been used to study the history of black carbon (BC), but little is known with regards to the physical and chemical characteristics of these particles in the remote atmosphere. Characterization remains limited by ultra-trace concentrations in ice core samples and the lack of adequate methods to isolate the particles unaltered from the melt water. To investigate the physical and chemical characteristics of these particles, we have developed a tangential flow filtration (TFF) method combined with transmission electron microscopy (TEM). Tests using ultrapure water and polystyrene latex particle standards resulted in excellent blanks and significant particle recovery. This approach has been applied to melt water from Antarctic ice cores as well as tropical rain from Darwin, Australia with successful results: TEM analysis revealed a variety of BC particle morphologies, insoluble coatings, and the attachment of BC to mineral dust particles. The TFF-based concentration of these particles has proven to give excellent results for TEM studies of BC particles in Antarctic ice cores and can be used for future studies of insoluble aerosols in rainwater and ice core samples.

  8. Tree ring and ice core time scales around the Santorini eruption

    NASA Astrophysics Data System (ADS)

    Löfroth, Elin; Muscheler, Raimund; Aldahan, Ala; Possnert, Göran; Berggren, Ann-Marie

    2010-05-01

    When studying cosmogenic radionuclides in ice core and tree ring archives around the Santorini eruption a ~20 year discrepancy was found between the records (Muscheler 2009). In this study a new 10Be dataset from the NGRIP ice core is presented. It has a resolution of 7 years and spans the period 3752-3244 BP (1803-1295 BC). The NGRIP 10Be record and the previously published 10Be GRIP record were compared to the IntCal datasets to further investigate the discrepancy between the ice core and tree ring chronologies. By modelling the 14C production rate based on atmospheric 14C records a comparison could be made to the 10Be flux which is assumed to represent the 10Be production rate. This showed a time shift of ~23 years between the records. The sensitivity of the results to changes in important model parameters was evaluated. Uncertainties in the carbon cycle model cannot explain a substantial part of the timing differences. Potential influences of climate and atmospheric processes on the 10Be deposition were studied using ?18O from the respective cores and GISP2 ice core ion data. The comparison to ?18O revealed a small but significant correlation between 10Be flux and ?18O when the 14C-derived production signal was removed from the 10Be curves. The ion data, as proxies for atmospheric circulation changes, did not show any correlations to the 10Be record or the 10Be/14C difference. When including possible data uncertainties there is still a minimum discrepancy of ~10 years between the 10Be ice core and the 14C tree ring record. Due to lack of alternative explanations it is concluded that the ice core and/or the tree ring chronologies contains unaccounted errors in this range. This also reconciles the radiocarbon 1627-1600 BC (Friedrich et al., 2006) and ice core 1642±5 BC (Vinther et al., 2006) datings of the Santorini eruption. Friedrich, W.L., Kromer, B., Friedrich, M., Heinemeier, J., Pfeiffer, T., & Talamo, S., 2006: Santorini eruption radiocarbon dated to 1627-1600 BC. Science 312, 548-548. Muscheler, 2009: 14C and 10Be around 1650 cal BC. In Warburton, D.A., (ed.): Time's Up! Dating the Minoan Eruption of Santorini: acts of the Minoan Eruption Chronology Workshop, Sandbjerg November 2007: Monographs of the Danish Institute at Athens. Aarhus University Press, Aarhus. 298 pp. Vinther, B.M., Clausen, H.B., Johnsen, S.J., Rasmussen, S.O., Andersen, K.K., Buchardt, S.L., Dahl-Jensen, D., Seierstad, I.K., Siggaard-Andersen, M.L., Steffensen, J.P., Svensson, A., Olsen, J., & Heinemeier, J., 2006: A synchronized dating of three Greenland ice cores throughout the Holocene. Journal of Geophysical Research-Atmospheres 111, 11.

  9. Carbonyl sulfide during the late Holocene from measurements in Antarctic ice cores (Invited)

    NASA Astrophysics Data System (ADS)

    Aydin, M.; Fudge, T. J.; Verhulst, K. R.; Waddington, E. D.; Saltzman, E. S.

    2013-12-01

    Carbonyl sulfide (COS) is the most abundant sulfur gas in the troposphere with a global average mixing ratio of about 500 parts per trillion (ppt) and a lifetime of 3 years. It is produced by a variety of natural and anthropogenic sources. Oceans are the largest source, emitting COS and precursors carbon disulfide and dimethyl sulfide. The most important removal process of COS is uptake by terrestrial plants during photosynthesis. Interest in the atmospheric variability of COS is primarily due to its potential value as a proxy for changes in gross primary productivity of the land biosphere. Ice core COS records may provide the long term observational basis needed to explore climate driven changes in terrestrial productivity and the resulting impacts, for example, on atmospheric CO2 levels. Previous measurements in a South Pole ice core established the preindustrial COS levels at ~30% of the modern atmosphere and revealed that atmospheric COS increased at an average rate of 1.8 ppt per 100 years over the last 2,000 years [Aydin et al., 2008]. We have since measured COS in 5 additional ice cores from 4 different sites in Antarctica. These measurements display a site-dependent downcore decline in COS, apparently driven by in situ hydrolysis. The reaction is strongly temperature dependent, with the hydrolysis lifetimes (e-folding) ranging from thousands to hundreds of thousands of years. We implement a novel technique that uses ice and heat flow models to predict temperature histories for the ice core samples from different sites and correct for the COS lost to in situ hydrolysis assuming first order kinetics. The 'corrected' COS records confirm the trend observed previously in the COS record from the South Pole ice core. The new, longer record suggests the slow increase in atmospheric COS may have started about 5,000 years ago and continued for 4,500 years until levels stabilized about 500 years ago. Atmospheric CO2 was also rising during this time period, suggesting the atmospheric levels of both trace gases might have changed as a response to a long-term decline in terrestrial productivity during the late Holocene.

  10. Assessing Stationarity in Ice Core Record-Sea Level Pressure Relationships for Yukon Territory Ice Core Records

    NASA Astrophysics Data System (ADS)

    Kelsey, E. P.; Wake, C. P.; Osterberg, E. C.

    2014-12-01

    We assess the stationarity of the relationship between Northern Hemisphere winter (Dec-Feb) sea-level pressure (SLP) and proxy time series (major ions, accumulation, and stable isotopes) from the Eclipse (3017 m asl) and the Mt. Logan Prospector-Russell Col (PRCol; 5340 m asl) ice cores from Yukon, Canada. We develop a novel spatial calibration procedure to identify ranges of ice core values that are associated with consistent winter SLP anomaly patterns. Each ice core variable time series was ranked and divided into groups of 13 years each. We assess stationarity by splitting the 1872-2001 analysis period in half (1872-1936 and 1937-2001) and comparing the locations and magnitudes of SLP anomaly patterns during the two periods for each group of ice core values. Northern Hemisphere monthly mean SLP from the 20th Century Reanalysis dataset are used. The high accumulation rate (1.38 m a-1) at Eclipse allows us to analyze 6-month seasonal mean values (Oct-Mar and Apr-Sep), whereas annual mean values are used from PRCol where the accumulation rate is lower (0.40 m a-1). The Eclipse cold season accumulation and PRCol annual mean sodium concentrations (Na+) exhibit the strongest correlations with winter SLP anomaly patterns. In particular, the lowest and highest 20% annual Na+ values at PRCol and lowest 10% cold season accumulation values at Eclipse exhibit stationarity with consistent SLP anomaly patterns in the North Pacific for all three time periods. A weaker Aleutian Low consistently occurred in the central to eastern North Pacific for the lowest Na+ years at PRCol and lowest accumulation cold seasons at Eclipse, although these groups of years are mostly independent. A stronger Aleutian Low occurs in the North Pacific for the highest Na+ years at PRCol. A stationary SLP anomaly pattern is not observed through all three time periods for high cold season accumulation at Eclipse. Application of this calibration procedure with other traditional calibration and reconstruction methods can help identify the proxy values that are most likely to produce an accurate climate reconstruction. This study highlights an application where incorporating more SLP observations into the pre-1930 period of the 20th Century Reanalysis can improve the fidelity of climate proxy calibrations and paleoclimate reconstructions.

  11. Eight glacial cycles from an Antarctic ice core.

    PubMed

    Augustin, Laurent; Barbante, Carlo; Barnes, Piers R F; Barnola, Jean Marc; Bigler, Matthias; Castellano, Emiliano; Cattani, Olivier; Chappellaz, Jerome; Dahl-Jensen, Dorthe; Delmonte, Barbara; Dreyfus, Gabrielle; Durand, Gael; Falourd, Sonia; Fischer, Hubertus; Flückiger, Jacqueline; Hansson, Margareta E; Huybrechts, Philippe; Jugie, Gérard; Johnsen, Sigfus J; Jouzel, Jean; Kaufmann, Patrik; Kipfstuhl, Josef; Lambert, Fabrice; Lipenkov, Vladimir Y; Littot, Geneviève C; Longinelli, Antonio; Lorrain, Reginald; Maggi, Valter; Masson-Delmotte, Valerie; Miller, Heinz; Mulvaney, Robert; Oerlemans, Johannes; Oerter, Hans; Orombelli, Giuseppe; Parrenin, Frederic; Peel, David A; Petit, Jean-Robert; Raynaud, Dominique; Ritz, Catherine; Ruth, Urs; Schwander, Jakob; Siegenthaler, Urs; Souchez, Roland; Stauffer, Bernhard; Steffensen, Jorgen Peder; Stenni, Barbara; Stocker, Thomas F; Tabacco, Ignazio E; Udisti, Roberto; Van De Wal, Roderik S W; Van Den Broeke, Michiel; Weiss, Jerome; Wilhelms, Frank; Winther, Jan-Gunnar; Wolff, Eric W; Zucchelli, Mario

    2004-06-10

    The Antarctic Vostok ice core provided compelling evidence of the nature of climate, and of climate feedbacks, over the past 420,000 years. Marine records suggest that the amplitude of climate variability was smaller before that time, but such records are often poorly resolved. Moreover, it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records. Here we report the recovery of a deep ice core from Dome C, Antarctica, that provides a climate record for the past 740,000 years. For the four most recent glacial cycles, the data agree well with the record from Vostok. The earlier period, between 740,000 and 430,000 years ago, was characterized by less pronounced warmth in interglacial periods in Antarctica, but a higher proportion of each cycle was spent in the warm mode. The transition from glacial to interglacial conditions about 430,000 years ago (Termination V) resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases, but there are significant differences in the patterns of change. The interglacial stage following Termination V was exceptionally long--28,000 years compared to, for example, the 12,000 years recorded so far in the present interglacial period. Given the similarities between this earlier warm period and today, our results may imply that without human intervention, a climate similar to the present one would extend well into the future. PMID:15190344

  12. An automated approach for annual layer counting in ice cores

    NASA Astrophysics Data System (ADS)

    Winstrup, M.; Svensson, A. M.; Rasmussen, S. O.; Winther, O.; Steig, E. J.; Axelrod, A. E.

    2012-11-01

    A novel method for automated annual layer counting in seasonally-resolved paleoclimate records has been developed. It relies on algorithms from the statistical framework of hidden Markov models (HMMs), which originally was developed for use in machine speech recognition. The strength of the layer detection algorithm lies in the way it is able to imitate the manual procedures for annual layer counting, while being based on statistical criteria for annual layer identification. The most likely positions of multiple layer boundaries in a section of ice core data are determined simultaneously, and a probabilistic uncertainty estimate of the resulting layer count is provided, ensuring an objective treatment of ambiguous layers in the data. Furthermore, multiple data series can be incorporated and used simultaneously. In this study, the automated layer counting algorithm has been applied to two ice core records from Greenland: one displaying a distinct annual signal and one which is more challenging. The algorithm shows high skill in reproducing the results from manual layer counts, and the resulting timescale compares well to absolute-dated volcanic marker horizons where these exist.

  13. Ice core evidence for a 20th century decline of sea ice in the Bellingshausen Sea, Antarctica

    NASA Astrophysics Data System (ADS)

    Abram, Nerilie J.; Thomas, Elizabeth R.; McConnell, Joseph R.; Mulvaney, Robert; Bracegirdle, Thomas J.; Sime, Louise C.; Aristarain, Alberto J.

    2010-12-01

    This study uses ice core methanesulphonic acid (MSA) records from the Antarctic Peninsula, where temperatures have been warming faster than anywhere else in the Southern Hemisphere, to reconstruct the 20th century history of sea ice change in the adjacent Bellingshausen Sea. Using satellite-derived sea ice and meteorological data, we show that ice core MSA records from this region are a reliable proxy for regional sea ice change, with years of increased winter sea ice extent recorded by increased ice core MSA concentrations. Our reconstruction suggests that the satellite-observed sea ice decline in the Bellingshausen Sea during recent decades is part of a long-term regional trend that has occurred throughout the 20th century. The long-term perspective on sea ice in the Bellingshausen Sea is consistent with evidence of 20th century warming on the Antarctic Peninsula and may reflect a progressive deepening of the Amundsen Sea Low due to increasing greenhouse gas concentrations and, more recently, stratospheric ozone depletion. As a first-order estimate, our MSA-based reconstruction suggests that sea ice in the Bellingshausen Sea has retreated southward by ˜0.7° during the 20th century. Comparison with other 20th century sea ice observations, reconstructions, and model simulations provides a coherent picture of Antarctic sea ice decline during the 20th century, although with regional-scale differences evident in the timing and magnitude of this sea ice decline. This longer-term perspective contrasts with the small overall increase in Antarctic sea ice that is observed in post-1979 satellite data.

  14. Insight of dust provenance in Antarctic ice cores from ice magnetization

    NASA Astrophysics Data System (ADS)

    Lanci, Luca; Delmonte, Barbara

    2015-04-01

    Unlike isotopic analysis, magnetic properties of airborne dust measured in ice samples cannot univocally identify their source area, however they are very sensitive, non destructive and can be thus applied to small samples from old interglacials. They show that mineral dust aerosol underwent significant variability in magnetic properties with time and climate stages. This variability reflects a different magnetic mineralogy and concentration, and very likely it represents variation of dust source area and/or transport. Magnetic investigation of old climate periods from Vostok and EPICA Dome C suggest for the first time that no major variability in the interglacial stages occurred in the last 800 kyr. Conversely, some interesting changes are found among glacial stages, especially from EPICA Dome C ice core. Isotopic (Sr-Nd) analyses also showed tiny differences between "dusty" glacials and "less dusty" glacials. Work is now in progress to understand the origin of these differences.

  15. Expression and Characterization of an Ice Binding Protein from a Bacterium Isolated at a Depth of 3,519 Meters in the Vostok Ice Core, Antarctica

    NASA Astrophysics Data System (ADS)

    Christner, B. C.; Achberger, A.; Brox, T. I.; Skidmore, M. L.

    2011-12-01

    The cryopreservation of microorganisms in ancient glacial ice is possible if lethal levels of macromolecular damage are not incurred and cellular integrity is not compromised via intracellular ice formation or recrystallization. There are numerous examples of cold-adapted species that prevent or limit ice crystal growth by producing ice-binding proteins (IBP). Previously, a bacterium (isolate 3519-10; Flavobacteriaceae family) recovered from a depth of 3,519 meters below the surface in the Vostok ice core was shown to produce and secrete an IBP that inhibits the recrystallization of ice. To explore the phenotypic advantage that IBPs confer to ice-entrapped cells, experiments were designed to examine the expression of 3519-10's IBP gene and protein at different temperatures, assess the effect of the IBP on bacterial viability in ice, and determine how the IBP influences the physical structure of the ice. Total RNA isolated from aerobic cultures grown at temperatures between 4C to 25C and analyzed by reverse transcription-PCR indicated constitutive expression of the IBP gene. Additionally, SDS-PAGE analysis of 3519-10's extracellular proteins revealed a polypeptide corresponding to the predicted size of the 54 kDa IBP at all temperatures tested. The total extracellular protein fraction was subsequently used in assays with Escherichia coli to examine the effect of the IBP on bacterial survival in warm ice (-5C) and after freeze-thaw cycling. In the presence of 100 ?g mL-1 of extracellular protein from 3519-10, the survival of E. coli was increased by greater than 100-fold; however, the survival of E. coli suspensions containing the same concentration of bovine serum albumin was not significantly different than controls (p<0.05). Microscopic analysis of ice formed in the presence of the IBP indicated that in a mm^2 field of view, there were 5 times as many crystals as in ice formed in the presence of washed 3519-10 cells and non-IBP producing bacteria, and 10 times as many crystals as in particle-free deionized water. Presumably, the effect that the IBP has on bacterial viability and ice crystal structure is due to its activity as an inhibitor of ice recrystallization. Although a myriad of molecular adaptations are likely to play a role in bacterial persistence under frozen conditions, the ability of 3519-10's IBP to control ice crystal structure may provide one explanation for its successful survival deep within the Antarctic ice sheet for thousands of years.

  16. Glacial/interglacial changes in the isotopes of nitrate from the Greenland Ice Sheet Project 2 (GISP2) ice core

    E-print Network

    Sigman, Daniel M.

    (GISP2) ice core Meredith G. Hastings1 and Daniel M. Sigman Department of Geosciences, Princeton [Freyer, 1978; Heaton, 1986; Freyer et al., 1993; Russell et al., 1998; Xiao and Liu, 2002; Hastings et al

  17. Spatially-resolved chemical analysis of frozen ice cores by cryo-cell-UV-laser-ablation-ICPMS

    NASA Astrophysics Data System (ADS)

    Müller, Wolfgang; Della Lunga, Damiano; Rasmussen, Sune O.; Svensson, Anders

    2015-04-01

    High-latitude ice cores have become the master records of late Pleistocene climate variability. Especially the high-resolution data from Greenland of the past ~125 ka reveal a remarkably changeable glacial climate, and these rapid climate oscillations have been shown to take place within a few years only [1, 2]. The requirement for an improvement in spatial resolution in ice core analysis arises from 1) the continuous thinning of annual layers in deep parts of ice cores to below what is routinely resolvable by continuous flow analysis and 2) the concomitant recrystallization of ice that potentially affects the location of impurities and thus the identification of annual layers. We developed a new technique to analyze elemental concentrations at ppb-levels in frozen ice cores at ~100 um (0.1 mm) resolution, which focuses on seasalt and dust tracers (e.g. Na, Mg, Ca, Al, Fe). It utilizes a custom-built, peltier-cooled cryo-sample holder fully compatible with the two-volume Laurin LA-cell of our RESOlution M-50 excimer (193 nm ArF) LA system, which is coupled to an Agilent 7500cs ICPMS, operated in reaction cell gas mode with H2 to eliminate 40Ar and 40Ar16O to access 40Ca and 56Fe [3]. Using 3 x 5 cm strips of ice cores per sample holder, this setup allows elemental concentrations to be acquired using both depth-profiling along (chains of) spots and/or as continuous lateral profiles, following surface cleaning with a major-element-free ceramic blade. Ice crystal boundaries can be observed with transmitted or reflected light illumination. We focus on NGRIP samples from Greenland Stadial 22 (GS22; ~84-88 ka; ~2695-2720 m) with its corresponding transitions. Owing to analysis in frozen ice, we can easily identify - relative to ice crystal boundaries - the location of cation impurities in both clear ice and so-called cloudy bands that are enriched in impurities. We find a remarkable difference in the location of impurities between these different ice domains [4]. Lower concentration clear ice shows strong impurity-enrichment along grain boundaries and junctions (similar to S concentrations in [5]), whereas cloudy bands do not display significant differences in elemental concentrations between grain interiors and boundaries, at overall higher concentrations. These results together with those of 2D and even 3D mapping of impurities as well as profiles across the two warm/cold transitions will be presented.

  18. Melting and refreezing beneath Roi Baudouin Ice Shelf (East Antarctica) inferred from radar, GPS, and ice core data

    NASA Astrophysics Data System (ADS)

    Pattyn, F.; Matsuoka, K.; Callens, D.; Conway, H.; Depoorter, M.; Docquier, D.; Hubbard, B.; Samyn, D.; Tison, J. L.

    2012-12-01

    Ice-penetrating radar profiles across the grounding line of a small ice-rise promontory located within the Roi Baudouin Ice Shelf in the Dronning Maud Land sector of East Antarctica show downward dipping englacial radar-detected reflectors. Model results indicate that this reflector pattern is best fit by including basal melting of at least 15 cm a-1. This rate of melting is low compared with rates observed on larger ice shelves in both West and East Antarctica. Ice cores extracted from a rift system close to the ice-rise promontory show several meters of marine ice accreted beneath the shelf. These observations of low rates of basal melting, and limited distribution of accreted marine ice suggest that either Antarctic surface water may reach the ice shelf base or that circulation beneath the shelf is likely dominated by the production of high salinity shelf water rather than the incursion of circumpolar deep water, implying a weak sub-shelf circulation system here. Many of the ice shelves located along the coast of Dronning Maud Land are, like Roi Baudouin Ice Shelf, characterized by frequent ice rises and promontories. Therefore, it is highly likely that these are also of shallow bathymetry and are subject to similarly weak side-shelf basal melting and refreezing.

  19. A search in north Greenland for a new ice-core drill site

    E-print Network

    Dahl-Jensen, D.; Gundestrup, N. S.; Keller, K.; Johnsen, S. J.; Gogineni, Sivaprasad; Allen, Christopher Thomas; Chuah, T. S.; Miller, H.; Kipfstuhl, S.; Waddington, E. D.

    1997-01-01

    A new deep ice-core drilling site has been identified in north Greenland at 75.12 ° N, 42 .30 ° W, 316 km north-northwest (NNW) of the GRIP drill site on the summit of the ice sheet. The ice thickness here is 3085 m; the ...

  20. Expression and Partial Characterization of an Ice-Binding Protein from a Bacterium Isolated at a Depth of 3,519?m in the Vostok Ice Core, Antarctica

    PubMed Central

    Achberger, Amanda Marie; Brox, Timothy Ian; Skidmore, Mark Leslie; Christner, Brent Craig

    2011-01-01

    Cryopreservation of microorganisms in ancient glacial ice is possible if lethal levels of macromolecular damage are not incurred and cellular integrity is not compromised via intracellular ice formation or recrystallization. Previously, a bacterium (isolate 3519-10) recovered from a depth of 3,519?m below the surface in the Vostok ice core was shown to secrete an ice-binding protein (IBP) that inhibits the recrystallization of ice. To explore the advantage that IBPs confer to ice-entrapped cells, experiments were designed to examine the expression of 3519-10’s IBP gene and protein at different temperatures, assess the effect of the IBP on bacterial viability in ice, and determine how the IBP influences the physical structure of the ice. Total RNA isolated from cultures grown between 4 and 25°C and analyzed by reverse transcription-PCR indicated constitutive expression of the IBP gene. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of 3519-10’s extracellular proteins revealed a polypeptide of the predicted size of the 54-kDa IBP at all temperatures tested. In the presence of 100??g?mL?1 of extracellular protein from 3519-10, the survival of Escherichia coli was increased by greater than 100-fold after 5 freeze-thaw cycles. Microscopic analysis of ice formed in the presence of the IBP indicated that per square millimeter field of view, there were ~5 times as many crystals as in ice formed in the presence of washed 3519-10 cells and non-IBP producing bacteria, and ~10 times as many crystals as in filtered deionized water. Presumably, the effect that the IBP has on bacterial viability and ice crystal structure is due to its activity as an inhibitor of ice recrystallization. A myriad of molecular adaptations are likely to play a role in bacterial persistence under frozen conditions, but the ability of 3519-10’s IBP to control ice crystal structure, and thus the liquid vein network within the ice, may provide one explanation for its successful survival deep within the Antarctic ice sheet for thousands of years. PMID:22207866

  1. Isotopic Studies of Ice Core Nitrate and Atmospheric Nitrogen Oxides in Polar Regions

    E-print Network

    Winglee, Robert M.

    Isotopic Studies of Ice Core Nitrate and Atmospheric Nitrogen Oxides in Polar Regions Julia C ____________________________ #12;University of Washington Abstract Isotopic Studies of Ice Core Nitrate and Atmospheric Nitrogen and present changes in atmospheric NOx (NO + NO2) is possible through measurements of nitrate (NO3 - or nitric

  2. Ice core paleovolcanic records from the St. Elias Mountains, Yukon, Canada

    E-print Network

    Kurapov, Alexander

    and dynamical climate forcing capability [e.g., Robock, 2000; Zielinski, 2000]. Volcanic sulfate aerosols a record of regionally significant volcanic eruptions in the North Pacific using an ice core from Eclipse to extend our record of North Pacific volcanism to 550 years before present using a suite of four ice cores

  3. Modeling Climate and Production-related Impacts on Ice-core Beryllium-10

    E-print Network

    Modeling Climate and Production-related Impacts on Ice-core Beryllium-10 Christy Veeder Submitted Modeling Climate and Production-related Impacts on Ice-core Beryllium-10 Christy Veeder I use the Goddard Institute for Space Studies ModelE general circulation model to ex- amine the how beryllium-10, a cosmogenic

  4. Bacterial study of Vostok drilling fluid: the tool to make ice core finding confident

    NASA Astrophysics Data System (ADS)

    Alekhina, I. A.; Petit, J. R.; Lukin, V. V.; Bulat, S. A.

    2003-04-01

    Decontamination of Vostok ice core is a critical issue in molecular biology studies. Core surface contains a film of hardly removable 'dirty' drilling fluid representing a mixture of polyhydrocarbons (PHC) including polyaromatic hydrocarbons (PAH) and freon. To make ice microbial finding more confident the original Vostok drilling fluid sampled from different depths (110m - 3600m) was analyzed for bacterial content by ribosomal DNA sequencing. Total, 33 clones of 16S ribosomal DNA were recovered from four samples of drilling fluid at 110, 2750, 3400, and 3600m leading to identification of 8 bacterial species. No overlapping was observed even for neighboring samples (3400m and 3600m). At present four major bacteria with the titer more than 103-104 cells per ml (as estimated from PCR results) are identified. Among them we found: unknown representative of Desulfobacteraceae which are able to oxidize sulphates and degrade benzenes (110m); PAH-degrading alpha-proteobacterium Sphingomonas natatoria (3400m); alpha-proteobacterium representing closely-related group of Sphingomonas sp. (e.g., S. aurantiaca) which are able to degrade PAH as well, and human pathogen closely related to Haloanella gallinarum of CFB group (3600m). Four additional species were revealed as single clones and showed relatedness to human pathogens and saprophytes as well as soil bacteria. These bacteria may represent drilling fluid contaminants introduced during its sampling or DNA extraction procedure. Of four major bacteria revealed, one species, Sphingomonas natatoria, has been met by us in the Vostok core from 3607 m depth (AF532054) whereas another Sphingomonas sp. which we refer to as S. aurantiaca was found in Antarctic microbial endolithic community (AF548567), hydrocarbon-containing soil near Scott Base in Antarctica (AF184221) and even isolated from 3593m Vostok accretion ice (AF324199) and Taylor Dome core (AF395031). The source for major human pathogen-related bacteria is rather uncertain indicating that very unusual microbes can be contained in a drilling fluid. All this testifies that kerosene film is indeed hard to remove and everyone should be aware on bacteria introduced with any drilling fluid. Our results demonstrate the necessity to have a drilling fluid data base when studying the microbial contents of ice cores.

  5. Water isotopic ratios from a continuously melted ice core sample

    E-print Network

    Gkinis, V; Blunier, T; Bigler, M; Schüpbach, S; Kettner, E; Johnsen, S J

    2014-01-01

    A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We built an interface between a Wavelength Scanned Cavity Ring Down Spectrometer (WS-CRDS) purchased from Picarro Inc. and a Continuous Flow Analysis (CFA) system. The system offers the possibility to perform simultaneous water isotopic analysis of $\\delta^{18}$O and $\\delta$D on a continuous stream of liquid water as generated from a continuously melted ice rod. Injection of sub ${\\mu}$l amounts of liquid water is achieved by pumping sample through a fused silica capillary and instantaneously vaporizing it with 100% efficiency in a home made oven. A calibration procedure allows for proper reporting of the data on the VSMOW--SLAP scale. Application of spectral methods yields the combined uncertainty of the system at below 0.1 permil and 0.5 permil for $\\delta^{18}$O and $\\delta$D, respectively. This performance is comparable to that achieved with mass spectrometry. Dispersion of the sampl...

  6. Recent increase in Ba concentrations as recorded in a South Pole ice core

    NASA Astrophysics Data System (ADS)

    Korotkikh, Elena V.; Mayewski, Paul A.; Dixon, Daniel; Kurbatov, Andrei V.; Handley, Michael J.

    2014-06-01

    Here we present high-resolution (?9.4 samples/year) records of Ba concentrations for the period from 1541 to 1999 A.D. obtained from an ice core recovered at the South Pole (US ITASE-02-6) site. We note a significant increase in Ba concentration (by a factor of ?23) since 1980 A.D. The Ba crustal enrichment factor (EFc) values rise from ?3 before 1980 A.D. to ?32 after 1980 A.D. None of the other measured major and trace elements reveal such significant increases in concentrations and EFc values. Comparison with previously reported Antarctic Ba records suggests that significant increases in Ba concentrations at South Pole since 1980 A.D. are most likely caused by local source pollution. The core was collected in close proximity to Amundsen-Scott South Pole Station; therefore activities at the station, such as diesel fuel burning and intense aircraft activity, most likely caused the observed increase in Ba concentrations and its EFc values in the South Pole ice core record.

  7. Proxies and measurement techniques for mineral dust in Antarctic ice cores.

    PubMed

    Ruth, Urs; Barbante, Carlo; Bigler, Matthias; Delmonte, Barbara; Fischer, Hubertus; Gabrielli, Paolo; Gaspari, Vania; Kaufmann, Patrik; Lambert, Fabrice; Maggi, Valter; Marino, Federica; Petit, Jean-Robert; Udisti, Roberto; Wagenbach, Dietmar; Wegner, Anna; Wolff, Eric W

    2008-08-01

    To improve quantitative interpretation of ice core aeolian dust records, a systematic methodological comparison was made. This involved methods for water-insoluble particle counting (Coulter counter and laser-sensing particle detector), soluble ion analysis (ion chromatography and continuous flow analysis), elemental analysis (inductively coupled plasma mass spectroscopy at pH 1 and after full acid digestion), and water-insoluble elemental analysis (proton induced X-ray emission). Antarctic ice core samples covering the last deglaciation from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land (EDML) cores were used. All methods correlate very well among each other, but the ratios of glacial age to Holocene concentrations, which are typically a factor approximately 100, differ between the methods by up to a factor of 2 with insoluble particles showing the largest variability. The recovery of ICP-MS measurements depends on the digestion method and is differentfor different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analyzed samples further reveal a change of dust composition during the last deglaciation. PMID:18754492

  8. Variations of air content in Dasuopu ice core from AD 1570e1927 and implications fore climate change

    E-print Network

    Chappellaz, Jérôme

    (represented by volume) in ice was mainly dominated by the atmospheric pressure and temperature in the dry iceVariations of air content in Dasuopu ice core from AD 1570e1927 and implications fore climate June 2010 a b s t r a c t An ice core air content record that was recovered from the refrozen

  9. Climate variability during the last 1000 years inferred from Andean ice cores: A review of methodology and recent results

    E-print Network

    Vuille, Mathias

    Andean Isotopic Index Little Ice Age ENSO Andean ice core investigations began approximately 30 years ago tropical climate dynamics. Finally we discuss records of ENSO, the Little Ice Age and the 20th centuryClimate variability during the last 1000 years inferred from Andean ice cores: A review

  10. Little Ice Age evidence from a south-central North American ice core, U.S.A.

    USGS Publications Warehouse

    Naftz, D.L.; Klusman, R.W.; Michel, R.L.; Schuster, P.F.; Ready, M.M.; Taylor, H.E.; Yanosky, T.M.; McConnaughey, E.A.

    1996-01-01

    In the past, ice-core records from mid-latitude glaciers in alpine areas of the continental United States were considered to be poor candidates for paleoclimate records because of the influence of meltwater on isotopic stratigraphy. To evaluate the existence of reliable paleoclimatic records, a 160-m ice core, containing about 250 yr of record was obtained from Upper Fremont Glacier, at an altitude of 4000 m in the Wind River Range of south-central North America. The ??18O (SMOW) profile from the core shows a -0.95??? shift to lighter values in the interval from 101.8 to 150 m below the surface, corresponding to the latter part of the Little Ice Age (LIA). Numerous high-amplitude oscillations in the section of the core from 101.8 to 150 m cannot be explained by site-specific lateral variability and probably reflect increased seasonality or better preservation of annual signals as a result of prolonged cooler temperatures that existed in this alpine setting. An abrupt decrease in these large amplitude oscillations at the 101.8-m depth suggests a sudden termination of this period of lower temperatures which generally coincides with the termination of the LIA. Three common features in the ??18O profiles between Upper Fremont Glacier and the better dated Quelccaya Ice Cap cores indicate a global paleoclimate linkage, further supporting the first documented occurrence of the LIA in an ice-core record from a temperate glacier in south-central North America.

  11. Technique for continuous high-resolution analysis of trace substances in firn and ice cores

    SciTech Connect

    Roethlisberger, R.; Bigler, M.; Hutterli, M.; Sommer, S.; Stauffer, B.; Junghans, H.G.; Wagenbach, D.

    2000-01-15

    The very successful application of a CFA (Continuous flow analysis) system in the GRIP project (Greenland Ice Core Project) for high-resolution ammonium, calcium, hydrogen peroxide, and formaldehyde measurements along a deep ice core led to further development of this analysis technique. The authors included methods for continuous analysis technique. The authors included methods for continuous analysis of sodium, nitrate, sulfate, and electrolytical conductivity, while the existing methods have been improved. The melting device has been optimized to allow the simultaneous analysis of eight components. Furthermore, a new melter was developed for analyzing firn cores. The system has been used in the frame of the European Project for Ice Coring in Antarctica (EPICA) for in-situ analysis of several firn cores from Dronning Maud Land, Antarctica, and for the new ice core drilled at Dome C, Antarctica.

  12. The 1500m South Pole Ice Core: Recovering a 40 Ka Environmental Record

    NASA Technical Reports Server (NTRS)

    Casey, Kimberly Ann; Neumann, Thomas Allen; Fudge, T. J.; Neumann, T. A.; Steig, E. J.; Cavitte, M. G. P.; Blankenship, D. D.

    2014-01-01

    Supported by the US National Science Foundation, a new 1500 m, approximately 40 ka old ice core will be recovered from South Pole during the 2014/15 and 2015/16 austral summer seasons using the new US Intermediate Depth Drill. The combination of low temperatures, relatively high accumulation rates and low impurity concentrations at South Pole will yield detailed records of ice chemistry and trace atmospheric gases. The South Pole ice core will provide a climate history record of a unique area of the East Antarctic plateau that is partly influenced by weather systems that cross the West Antarctic ice sheet. The ice at South Pole flows at approximately 10m a(exp-1) and the South Pole ice-core site is a significant distance from an ice divide. Therefore, ice recovered at depth originated progressively farther upstream of the coring site. New ground-penetrating radar collected over the drill site location shows no anthropogenic influence over the past approximately 50 years or upper 15 m. Depth-age scale modeling results show consistent and plausible annual-layer thicknesses and accumulation rate histories, indicating that no significant stratigraphic disturbances exist in the upper 1500m near the ice-core drill site.

  13. Combining ice core records and ice sheet models to explore the evolution of the East Antarctic Ice sheet during the Last Interglacial period

    NASA Astrophysics Data System (ADS)

    Bradley, S. L.; Siddall, M.; Milne, G. A.; Masson-Delmotte, V.; Wolff, E.

    2013-01-01

    This study evaluates the influence of plausible changes in East Antarctic Ice sheet (EAIS) thickness and the subsequent glacio-isostatic response as a contributor to the Antarctic warming indicated by ice core records during the Last Interglacial period (LIG). These higher temperatures have been estimated primarily using the difference in the ?D peak (on average ~ 15‰) in these LIG records relative to records for the Present Interglacial (PIG). Using a preliminary exploratory modelling study, it is shown that introducing a relatively moderate reduction in the amount of thickening of the EAIS over the LIG period introduces a significant increase (up to 8‰) in the predicted elevation-driven only ?D signal at the central Antarctic Ice sheet (AIS) ice core sites compared to the PIG. A sensitivity test in response to a large prescribed retreat of marine-based ice in the Wilkes and Aurora subglacial basins (equivalent to ~ 7 m of global mean sea-level rise) results in a distinct elevation signal that is resolvable within the ice core stable isotope records at three sites (Taylor Dome, TALDICE and EPICA Dome C). These findings have two main implications. First, EAIS elevation's only effects could account for a significant fraction of the LIG warming interpreted from ice core records. This result highlights the need for an improved estimate to be made of the uncertainty and size of this elevation-driven ?D signal which contributes to this LIG warming and that these effects need to be deconvolved prior to attempting to extract a climatic-only signal from the stable isotope data. Second, a fingerprint of significant retreat of ice in the Wilkes and Aurora basins should be detectable from ice core ?D records proximal to these basins and therefore used to constrain their contribution to elevated LIG sea levels, after accounting for ice sheet-climate interactions not considered in our approach.

  14. High-resolution variations in size, number and arrangement of air bubbles in the EPICA DML (Antarctica) ice core

    E-print Network

    Garbe, Christoph S.

    (Antarctica) ice core Verena BENDEL,1Ã Kai J. UELTZHO¨ FFER,2 Johannes FREITAG,3 Sepp KIPFSTUHL,3 Werner F bubbles in the EPICA Dronning Maud Land (EDML) (Antarctica) ice core, down to the end of the bubble. Lipenkov (2000) observed that bubbles formed in cold periods in the Vostok (East Antarctica) ice core

  15. Feasibility of reconstructing paleoatmospheric records of selected alkanes, methyl halides, and sulfur gases from Greenland ice cores

    E-print Network

    Saltzman, Eric

    from contemporaneous sections of fluid- and dry-drilled ice cores to examine what effects using n of reconstructing paleoatmospheric levels of short-lived trace gases from dry- and fluid-drilled Greenland ice cores, and sulfur gases from Greenland ice cores M. Aydin,1 M. B. Williams,1 and E. S. Saltzman1 Received 7

  16. Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over the last millennium

    E-print Network

    Gilli, Adrian

    Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier 2009. [1] Black carbon (BC) and mineral dust aerosols were analyzed in an ice core from the Colle), Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over

  17. The design and performance of IceCube DeepCore

    NASA Astrophysics Data System (ADS)

    Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Allen, M. M.; Altmann, D.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; BenZvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Brown, A. M.; Buitink, S.; Caballero-Mora, K. S.; Carson, M.; Chirkin, D.; Christy, B.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; Cruz Silva, A. H.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; De Clercq, C.; Degner, T.; Demirörs, L.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Dunkman, M.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Góra, D.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, B.; Homeier, A.; Hoshina, K.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kroll, G.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lünemann, J.; Madsen, J.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Miarecki, S.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Panknin, S.; Paul, L.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Richman, M.; Rodrigues, J. P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schönwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Stüer, M.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, C.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Zoll, M.

    2012-05-01

    The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking physics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

  18. The Design and Performance of IceCube DeepCore

    NASA Technical Reports Server (NTRS)

    Stamatikos, M.

    2012-01-01

    The IceCube neutrino observatory in operation at the South Pole, Antarctica, comprises three distinct components: a large buried array for ultrahigh energy neutrino detection, a surface air shower array, and a new buried component called DeepCore. DeepCore was designed to lower the IceCube neutrino energy threshold by over an order of magnitude, to energies as low as about 10 GeV. DeepCore is situated primarily 2100 m below the surface of the icecap at the South Pole, at the bottom center of the existing IceCube array, and began taking pbysics data in May 2010. Its location takes advantage of the exceptionally clear ice at those depths and allows it to use the surrounding IceCube detector as a highly efficient active veto against the principal background of downward-going muons produced in cosmic-ray air showers. DeepCore has a module density roughly five times higher than that of the standard IceCube array, and uses photomultiplier tubes with a new photocathode featuring a quantum efficiency about 35% higher than standard IceCube PMTs. Taken together, these features of DeepCore will increase IceCube's sensitivity to neutrinos from WIMP dark matter annihilations, atmospheric neutrino oscillations, galactic supernova neutrinos, and point sources of neutrinos in the northern and southern skies. In this paper we describe the design and initial performance of DeepCore.

  19. Sensitivity of interglacial Greenland temperature and ?18O: ice core data, orbital and increased CO2 climate simulations

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Braconnot, P.; Hoffmann, G.; Jouzel, J.; Kageyama, M.; Landais, A.; Lejeune, Q.; Risi, C.; Sime, L.; Sjolte, J.; Swingedouw, D.; Vinther, B.

    2011-09-01

    The sensitivity of interglacial Greenland temperature to orbital and CO2 forcing is investigated using the NorthGRIP ice core data and coupled ocean-atmosphere IPSL-CM4 model simulations. These simulations were conducted in response to different interglacial orbital configurations, and to increased CO2 concentrations. These different forcings cause very distinct simulated seasonal and latitudinal temperature and water cycle changes, limiting the analogies between the last interglacial and future climate. However, the IPSL-CM4 model shows similar magnitudes of Arctic summer warming and climate feedbacks in response to 2 × CO2 and orbital forcing of the last interglacial period (126 000 years ago). The IPSL-CM4 model produces a remarkably linear relationship between TOA incoming summer solar radiation and simulated changes in summer and annual mean central Greenland temperature. This contrasts with the stable isotope record from the Greenland ice cores, showing a multi-millennial lagged response to summer insolation. During the early part of interglacials, the observed lags may be explained by ice sheet-ocean feedbacks linked with changes in ice sheet elevation and the impact of meltwater on ocean circulation, as investigated with sensitivity studies. A quantitative comparison between ice core data and climate simulations requires stability of the stable isotope - temperature relationship to be explored. Atmospheric simulations including water stable isotopes have been conducted with the LMDZiso model under different boundary conditions. This set of simulations allows calculation of a temporal Greenland isotope-temperature slope (0.3-0.4‰ per °C) during warmer-than-present Arctic climates, in response to increased CO2, increased ocean temperature and orbital forcing. This temporal slope appears half as large as the modern spatial gradient and is consistent with other ice core estimates. It may, however, be model-dependent, as indicated by preliminary comparison with other models. This suggests that further simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL-CM4/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8-10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300-400 m.

  20. Sensitivity of interglacial Greenland temperature and ?18O to orbital and CO2 forcing: climate simulations and ice core data

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Braconnot, P.; Hoffmann, G.; Jouzel, J.; Kageyama, M.; Landais, A.; Lejeune, Q.; Risi, C.; Sime, L.; Sjolte, J.; Swingedouw, D.; Vinther, B.

    2011-05-01

    The sensitivity of interglacial Greenland temperature to orbital and CO2 forcing is investigated using the NorthGRIP ice core data and coupled ocean-atmosphere IPSL-CM4 model simulations. These simulations were conducted in response to different interglacial orbital configurations, and to increased CO2 concentrations. These different forcings cause very distinct simulated seasonal and latitudinal temperature and water cycle changes, limiting the analogies between the last interglacial and future climate. However, the IPSL-CM4 model shows similar magnitudes of Arctic summer warming and climate feedbacks in response to 2 × CO2 and orbital forcing of the last interglacial period (126 000 yr ago). The IPSL model produces a remarkably linear relationship between top of atmosphere incoming summer solar radiation and simulated changes in summer and annual mean central Greenland temperature. This contrasts with the stable isotope record from the Greenland ice cores, showing a multi-millennial lagged response to summer insolation. During the early part of interglacials, the observed lags may be explained by ice sheet-ocean feedbacks linked with changes in ice sheet elevation and the impact of meltwater on ocean circulation, as investigated with sensitivity studies. A quantitative comparison between ice core data and climate simulations requires to explore the stability of the stable isotope - temperature relationship. Atmospheric simulations including water stable isotopes have been conducted with the LMDZiso model under different boundary conditions. This set of simulations allows to calculate a temporal Greenland isotope-temperature slope (0.3-0.4 ‰ per °C) during warmer than present Arctic climates, in response to increased CO2, increased ocean temperature and orbital forcing. This temporal slope appears twice as small as the modern spatial gradient and is consistent with other ice core estimates. A preliminary comparison with other model results implies that other mechanisms could also play a role. This suggests that further simulations and detailed inter-model comparisons are also likely to be of benefit. Comparisons with Greenland ice core stable isotope data reveals that IPSL/LMDZiso simulations strongly underestimate the amplitude of the ice core signal during the last interglacial, which could reach +8-10 °C at fixed-elevation. While the model-data mismatch may result from missing positive feedbacks (e.g. vegetation), it could also be explained by a reduced elevation of the central Greenland ice sheet surface by 300-400 m.

  1. Coherent composition of glacial dust on opposite sides of the East Antarctic Plateau inferred from the deep EPICA ice cores

    NASA Astrophysics Data System (ADS)

    Marino, F.; Castellano, E.; Nava, S.; Chiari, M.; Ruth, U.; Wegner, A.; Lucarelli, F.; Udisti, R.; Delmonte, B.; Maggi, V.

    2009-12-01

    The dust provenance identification through isotopic and geochemical tracers focused mostly on ice cores drilled in the Pacific-Indian sector of Antarctica, where a common provenance of dust from Southern South America during glacial ages was demonstrated. Conversely, in other areas of the East Antarctic Plateau as Dronning Maud Land provenance was deduced indirectly from back trajectory analyses and soluble chemistry records. In this work, we present the first comparison of major elemental composition of dust archived in two ice cores from opposite sides of Antarctica, in the framework of the EPICA Project. Mineral particles extracted from the EDC and EDML cores date back to glacial MIS 2, 4 and 6, over the last 200 kyr. Results reveal a coherent geochemical dust composition at both locations, providing experimental evidence of a common provenance over the wide area of East Antarctica during glacials, and key analytical constrains for atmospheric general circulation models.

  2. Twentieth century sea-ice trends in the Ross Sea from a high-resolution, coastal ice-core record

    NASA Astrophysics Data System (ADS)

    Sinclair, Kate E.; Bertler, Nancy A. N.; Bowen, Melissa M.; Arrigo, Kevin R.

    2014-05-01

    We present the first proxy record of sea-ice area (SIA) in the Ross Sea, Antarctica, from a 130 year coastal ice-core record. High-resolution deuterium excess data show prevailing stable SIA from the 1880s until the 1950s, a 2-5% reduction from the mid-1950s to the early-1990s, and a 5% increase after 1993. Additional support for this reconstruction is derived from ice-core methanesulphonic acid concentrations and whaling records. While SIA has continued to decline around much of the West Antarctic coastline since the 1950s, concurrent with increasing air and ocean temperatures, the underlying trend is masked in the Ross Sea by a switch to positive SIA anomalies since the early-1990s. This increase is associated with a strengthening of southerly winds and the enhanced northward advection of sea ice.

  3. 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.

  4. Arcticibacter eurypsychrophilus sp. nov., isolated from ice core.

    PubMed

    Shen, Liang; Liu, Yongqin; Gu, Zhengquan; Yao, Tandong; Xu, Baiqing; Wang, Ninglian; Jiao, Nianzhi; Liu, Hongcan; Zhou, Yuguang

    2015-02-01

    A Gram-stain-negative, rod-shaped, non-flagellated bacterium, strain MJ9-5(T), was isolated from ice core of Muji Glacier. Colonies of strain MJ9-5(T) were pink, convex and round on R2A agar. Strain MJ9-5(T) grew between -1 to 25 °C with an optimum growth temperature of 10-15 °C. The strain tolerated 0-1.2 % (w/v) NaCl with an optimum of 1 %. The major cellular fatty acids of strain MJ9-5(T) were iso-C15 : 0, summed feature 3 (C16 : 1?6c and/or C1 6 : 1?7c). The G+C content of the genomic DNA was 38.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain MJ9-5(T) was related to members of the genus Arcticibacter. On the basis of the phenotypic characteristics and phylogenetic analysis, a novel species of this genus, Arcticibacter eurypsychrophilus sp. nov., is proposed. The type strain is MJ9-5(T) (?= KCTC 42008(T)?= JCM 19862(T)). PMID:25410942

  5. Past fire reconstructions in the EPICA ice core through the determination of specific molecular markers

    NASA Astrophysics Data System (ADS)

    Barbante, C.; Gabrielli, P.; Kehrwald, N. M.; Gambaro, A.; Zangrando, R.

    2010-12-01

    The chemical composition of aerosol is important for understanding the organic component contribution of biomass burning emissions to the atmosphere and complements existing data on the signatures of direct organic emissions from biomass sources. Compounds from biomass burning include monosaccharide anhydrides (MAs), and the most important tracer compound among them is levoglucosan. This is a specific molecular tracer utilized for the assessment of particulate matter composition from biomass burning in the atmosphere because it cannot be generated by non-combustive processes or by non-wood combustion. Molecular markers such as levoglucosan are important tools in tracking the transport of particles produced by biomass burning. In order to the current concentrations of levoglucosan in the atmosphere in prespective, it is important to quantify the fluxes of this compound during the past by examining environmental archives such as snow and ice cores. Polar ice core studies have extensively documented large changes in the content of aerosol constituents such as ionic species, dust, trace elements, and organic compounds during the late Quaternary period. In the current work we reconstructed past biomass burning activity through the determination of levoglucosan in a series of samples collected at Dome C, East Antarctica. The analyses of about 75 samples that cover the last 750 kyr, reveals changes in the glacial/interglacial fluxes of levoglucosan, demonstrating different fire regimes during different climatic periods.

  6. Polychlorinated biphenyls in glaciers. 1. Deposition history from an Alpine ice core.

    PubMed

    Pavlova, Pavlina Aneva; Schmid, Peter; Bogdal, Christian; Steinlin, Christine; Jenk, Theo M; Schwikowski, Margit

    2014-07-15

    We present a highly time-resolved historical record of polychlorinated biphenyls (PCBs) from an Alpine ice core (Fiescherhorn glacier, Switzerland). Introduced in the 1940s, PCBs were widely used industrial chemicals. Because of their persistence they are still found in the environment, long after their production phase-out. The Fiescherhorn ice core record covers the entire time period of industrial use of PCBs, that is, 1940-2002. The total concentration of six PCBs varies from 0.5 to 5 ng L(-1) and reveals a temporal trend, with an 8-fold increase from the early 1940s to the peak value in the 1970s. The level in 2002 is comparable to the concentration in the 1940s, when PCBs were introduced into the market. The time trend of PCBs associated with the particulate fraction closely follows the trend found in the dissolved fraction, but the absolute values are a factor of 10 lower. In addition to changing emissions, fluctuations in the PCB record were explained by variabilty in convective transport and postdepositional processes such as surface melting. Concentrations of PCBs are in agreement with data from seasonal snow samples in the Alps, but are a factor of 100 higher than concentrations measured in the Arctic. Contrasting time trends and congener patterns between the Alpine and Arctic region indicate the importance of atmospheric transport and postdepositional effects. PMID:24968761

  7. A new method for geochemical characterization of atmospheric mineral dust from polar ice cores: preliminary results from Talos Dome ice core (East Antarctica, Pacific-Ross Sea sector)

    NASA Astrophysics Data System (ADS)

    Baccolo, Giovanni; Delmonte, Barbara; Clemenza, Massimiliano; Previtali, Ezio; Maggi, Valter

    2015-04-01

    Assessing the elemental composition of atmospheric dust entrapped in polar ice cores is important for the identification of the potential dust sources and thus for the reconstruction of past atmospheric circulation, at local, regional and global scale. Accurate determination of major and trace elements in the insoluble fraction of dust extracted from ice cores is also useful to better understand some geochemical and biogeochemical mechanisms which are linked with the climate system. The extremely reduced concentration of dust in polar ice (typical Antarctic concentrations during interglacials are in the range of 10 ppb), the limited availability of such samples and the high risk of contamination make these analyses a challenge. A new method based on low background Instrumental Neutron Activation Analysis (INAA) was specifically developed for this kind of samples. The method allows the determination of the concentration of up to 35 elements in extremely reduced dust samples (20-30 ?g). These elements span from major to trace and ultra-trace elements. Preliminary results from TALDICE (TALos Dome Ice CorE, East Antarctica, Pacific-Ross Sea Sector) ice core are presented along with results from potential source areas in Victoria Land. A set of 5 samples from Talos Dome, corresponding to the last termination, MIS3, MIS4 and MIS6 were prepared and analyzed by INAA.

  8. On high-resolution sampling of short ice cores: Dating and temperature information recovery from Antarctic Peninsula virtual cores

    NASA Astrophysics Data System (ADS)

    Sime, Louise C.; Lang, Nicola; Thomas, Elizabeth R.; Benton, Ailsa K.; Mulvaney, Robert

    2011-10-01

    Recent developments in ice melter systems and continuous flow analysis (CFA) techniques now allow higher-resolution ice core analysis. Here, we present a new method to aid interpretation of high-resolution ice core stable water isotope records. Using a set of simple isotopic recording and postdepositional assumptions, the European Centre for Medium-Range Weather Forecasts' 40 year reanalysis time series of temperature and precipitation are converted to "virtual core" depth series across the Antarctic Peninsula, helping us to understand what information can be gleaned from the CFA high-resolution observations. Virtual core temperatures are transferred onto time using three different depth-age transfer assumptions: (1) a perfect depth-age model, (2) a depth-age model constructed from single or dual annual photochemical tie points, and (3) a cross-dated depth-age model. Comparing the sampled temperatures on the various depth-age models with the original time series allows quantification of the effect of ice core sample resolution and dating. We show that accurate annual layer count depth-age models should allow some subseasonal temperature anomalies to be recovered using a sample resolution of around 40 mm, or 10-20 samples per year. Seasonal temperature anomalies may be recovered using sample lengths closer to 60 mm, or about 7-14 samples per year. These results tend to confirm the value of current CFA ice core sampling strategies and indicate that it should be possible to recover about a third of subannual (but not synoptic) temperature anomaly information from annually "layer-counted" peninsula ice cores.

  9. Continuous acidity measurements of the Roosevelt Island (coastal Antarctica) ice core

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Vallelonga, Paul; Simonsen, Marius; Bertler, Nancy; Neff, Peter; Svensson, Anders

    2015-04-01

    A novel dye-based continuous flow analysis method for the determination of acidity has been developed and applied to the Roosevelt Island ice core. The Roosevelt Island ice core (79.36° S, 161.71° W) was drilled in 2011-13 at the top of the Roosevelt Island ice dome, a location surrounded by the Ross ice shelf. The site has high accumulation; 0.26 m of ice equivalent is deposited annually allowing sub-annual determination of conductivity, calcium and acidity. The proximity to the ocean combined with the low altitude makes the RICE ice core loaded with sea salts, which dominate the conductivity signal. Similarly Ca2+, which was measured by Continuous Flow Analysis, is primarily of oceanic origin. The proximity of the ocean also leads to high background levels of acidity (primarily sulphate) which mask volcanic peaks and thus complicate the identification of tropical volcanic eruptions. Using a combined approach of high resolution acidity, melt water conductivity and calcium measurements we have succeeded in identifying more than 450 volcanic eruptions in the top 500 metres of the RICE ice core. The combination of high-resolution acidity and calcium records allow for speculation into the inverse relationship between the two, which may be related to sea ice extent in the nearby Ross and Amundsen seas. Please fill in your abstract text.

  10. Visual-Stratigraphic Dating of the GISP2 Ice Core: Basis, Reproducibility, and Application

    NASA Technical Reports Server (NTRS)

    Alley, R. B.; Shuman, C. A.; Meese, D. A.; Gow, A. J.; Taylor, K. C.; Cuffey, K. M.; Fitzpatrick, J. J.; Grootes, P. M.; Zielinski, G. A.; Ram, M.; Spinelli, G.; Elder, B.

    1997-01-01

    Annual layers are visible in the Greenland Ice Sheet Project 2 ice core from central Greenland, allowing rapid dating of the core. Changes in bubble and grain structure caused by near-surface, primarily summertime formation of hoar complexes provide the main visible annual marker in the Holocene, and changes in "cloudiness" of the ice correlated with dustiness mark Wisconsinan annual cycles; both markers are evident and have been intercalibrated in early Holocene ice. Layer counts are reproducible between different workers and for one worker at different times, with 1% error over century-length times in the Holocene. Reproducibility is typically 5% in Wisconsinan ice-age ice and decreases with increasing age and depth. Cumulative ages from visible stratigraphy are not significantly different from independent ages of prominent events for ice older than the historical record and younger than approximately 50,000 years. Visible observations are not greatly degraded by "brittle ice" or many other core-quality problems, allowing construction of long, consistently sampled time series. High accuracy requires careful study of the core by dedicated observers.

  11. SOLUBILITY OF WATER ICE IN METALLIC HYDROGEN: CONSEQUENCES FOR CORE EROSION IN GAS GIANT PLANETS

    SciTech Connect

    Wilson, H. F.; Militzer, B.

    2012-01-20

    Using ab initio simulations we investigate whether water ice is stable in the cores of giant planets, or whether it dissolves into the layer of metallic hydrogen above. By Gibbs free energy calculations we find that for pressures between 10 and 40 Mbar the ice-hydrogen interface is thermodynamically unstable at temperatures above approximately 3000 K, far below the temperature of the core-mantle boundaries in Jupiter and Saturn. This implies that the dissolution of core material into the fluid layers of giant planets is thermodynamically favored, and that further modeling of the extent of core erosion is warranted.

  12. Simulating the temperature and precipitation signal in an Alpine ice core

    NASA Astrophysics Data System (ADS)

    Brönnimann, S.; Mariani, I.; Schwikowski, M.; Auchmann, R.; Eichler, A.

    2012-12-01

    Accumulation and ?18O data from Alpine ice cores provide information on past temperature and precipitation. However, their correlation with seasonal or annual mean temperature and precipitation at nearby sites is often low. Based on an example we argue that, to some extent, this is due to the irregular sampling of the atmosphere by the ice core (i.e. ice cores only record precipitation events and not dry periods) and the possible incongruity between annual layers and calendar year due to dating uncertainty. Using daily meteorological data from nearby stations and reanalyses we replicate the ice core from the Grenzgletscher (Switzerland, 4200 m a.s.l.) on a sample-by-sample basis. Over the last 15 yr of the ice core record, accumulation and ?18O variations can be well reproduced on a sub-seasonal scale. This allows a wiggle-matching approach for defining quasi-annual layers. For this period, correlations between measured and replicated quasi-annual ?18O values approach 0.8. Further back in time, the quality of the agreement deteriorates rapidly. Nevertheless, we find significant correlations for accumulation and precipitation over the entire length of the record (1938-1993), which is not the case when comparing ice core ?18O with annual mean temperature. A Monte Carlo resampling approach of long meteorological time series is used to further explore the relation, in a replicated ice core, between ?18O and annual mean temperature. Results show that meteorologically very different years can lead to quasi-identical values for ?18O. This poses limitations to the use of ?18O from Alpine ice cores for temperature reconstructions in regions with a variable seasonality in precipitation.

  13. Simulating the temperature and precipitation signal in an Alpine ice core

    NASA Astrophysics Data System (ADS)

    Brönnimann, S.; Mariani, I.; Schwikowski, M.; Auchmann, R.; Eichler, A.

    2013-08-01

    Accumulation and ?18O data from Alpine ice cores provide information on past temperature and precipitation. However, their correlation with seasonal or annual mean temperature and precipitation at nearby sites is often low. This is partly due to the irregular sampling of the atmosphere by the ice core (i.e. ice cores almost only record precipitation events and not dry periods) and the possible incongruity between annual layers and calendar years. Using daily meteorological data from a nearby station and reanalyses, we replicate the ice core from the Grenzgletscher (Switzerland, 4200 m a.s.l.) on a sample-by-sample basis by calculating precipitation-weighted temperature (PWT) over short intervals. Over the last 15 yr of the ice core record, accumulation and ?18O variations can be well reproduced on a sub-seasonal scale. This allows a wiggle-matching approach for defining quasi-annual layers, resulting in high correlations between measured quasi-annual ?18O and PWT. Further back in time, the agreement deteriorates. Nevertheless, we find significant correlations over the entire length of the record (1938-1993) of ice core ?18O with PWT, but not with annual mean temperature. This is due to the low correlations between PWT and annual mean temperature, a characteristic which in ERA-Interim reanalysis is also found for many other continental mid-to-high-latitude regions. The fact that meteorologically very different years can lead to similar combinations of PWT and accumulation poses limitations to the use of ?18O from Alpine ice cores for temperature reconstructions. Rather than for reconstructing annual mean temperature, ?18O from Alpine ice cores should be used to reconstruct PWT over quasi-annual periods. This variable is reproducible in reanalysis or climate model data and could thus be assimilated into conventional climate models.

  14. Bipolar volcanic events in ice cores and the Toba eruption at 74 ka BP (Invited)

    NASA Astrophysics Data System (ADS)

    Svensson, A.

    2013-12-01

    Acidity spikes in Greenland and Antarctic ice cores are applied as tracers of past volcanic activity. Besides providing information on the timing and magnitude of past eruptions, the acidity spikes are also widely used for synchronization of ice cores. All of the deep Greenland ice cores are thus synchronized throughout the last glacial cycle based on volcanic markers. Volcanic matching of ice cores from the two Hemispheres is much more challenging but it is feasible in periods of favourable conditions. Over the last two millennia, where ice cores are precisely dated, some 50 bipolar volcanic events have thus been identified. In order for an eruption to express a bipolar fingerprint it generally needs to be a low latitude eruption with stratospheric injection. Sometimes tephra is associated with the ice-core acidity spikes, but most often there is no tephra present in the ice. As yet, an unknown eruption occurring in 1259 AD is the only event reported to have deposited tephra in both Greenland and Antarctica. During the last glacial period bipolar volcanic matching is very challenging and very little work has been done, but recent high-resolution ice core records have the potential to provide bipolar ice core matching for some periods. Recently, Greenland and Antarctic ice cores have been linked by acidity spikes in the time window of the most recent eruption (the YTT eruption) of the Indonesian Toba volcano that is situated close to equator in Sumatra. Ash from this Toba event is widespread over large areas in Asia and has been identified as far west as Africa, but no corresponding tephra has been found in polar ice cores despite several attempts. The age of the YTT eruption is well constrained by recent Ar-Ar dating to have occurred some 74 ka ago close to the Marine Isotope Stage 4/5 boundary and close to the onset of the cold Greenland Stadial 20 and the corresponding mild Antarctic Isotopic Maxima 19 and 20. Surprisingly, no single outstanding acidity spike can be associated with the YTT Toba eruption in Greenland or Antarctica. Instead, several large bipolar ice cores acidity spikes are occurring within a couple of centuries at the time of the YTT eruption. To complicate matters, the intensity of those acidity spikes varies greatly from ice core to ice core. At this point, it is therefore impossible to relate the Toba eruption to a single event in the ice cores. Probably there have been several large low-latitude eruptions occurring close to the time of the YTT or the Toba volcano itself had multiple large eruptions within centuries. Bipolar volcanic matching allows for an estimation of the climatic impact of eruptions on a global scale. In the case of Toba, there must have been a global cooling following the enormous eruption, but unfortunately at this depth the resolution of the ice core temperature proxies does not allow for an identification of short term events (<100 yr). A significant warming event in Antarctica following the period associated with the YTT shows, however, that Toba did not initiate a long-term global cooling (>100 yr). At the time of YTT it appears that the inter-hemispheric climate variability is governed by the bipolar seesaw pattern that is active throughout most of the last glacial period. Still, it is intriguing that Toba occurs right at the time when Greenland and much of the northern Hemisphere enters its most extreme cold stadial of the last glacial period.

  15. Supplementing ice core time series at a small scale Alpine glacier with a 3D full stokes ice flow model using Elmer/Ice

    NASA Astrophysics Data System (ADS)

    Licciulli, Carlo; Bohleber, Pascal; Wagenbach, Dietmar; Eisen, Olaf; Gagliardini, Olivier; Hoelzle, Martin

    2015-04-01

    The cold glacier saddle Colle Gnifetti (CG) is the unique drilling site in the European Alps offering ice core records substantially exceeding the instrumental period. In spite of an ice thickness not much exceeding 100 m, CG provides long-term ice core records due to its low net accumulation and rapid layer thinning. However, net accumulation at CG is characterised by strong spatio-temporal variability causing depositional noise and, combined with a complex flow regime, upstream-effects. These intricate glaciological settings hamper the full exploitation of the unique potential for long-term ice core records of this site. Here we present first results from developing a new model attempt, i.e. full stokes with consideration of firn rheology, specifically tailored to the complex CG settings, and utilizing the 3D finite element model Elmer/Ice in combination with existing CG ice core as well as geophysical data. A major objective is to map source trajectories of existing ice core sites in order to evaluate potential upstream effects. Since dating the CG ice cores becomes a challenge already after the last 100 years or so, an additional focus is to assist in finding a reliable age scale, especially targeting depths where annual layers can no more be counted. This includes the calculation of isochronous surfaces for intercomparison of different drilling sites within the CG multi core array. As already known from previous model attempts at CG, a main limitation arises from insufficient knowledge of the bedrock topography. The currently known bedrock topography for CG is based on recent GPR measurements and ice core drillings, but is still not precise enough. Here we present first results concerning the reconstruction of the bedrock topography by inverse modelling, using an iterative sequence of diagnostic runs. Relying on empirical evidence from direct measurements, bedrock topography used as model input is adjusted to achieve best possible agreement among other calculated and measured quantities, e.g. surface accumulation. Next steps in refining the model are concerned with obtaining better constrained model parameters and boundary conditions, e.g. basal heat flux, using an iterative sequence of prognostic runs, similar to the adjustments for bedrock topography.

  16. Little ice age evidence from a south-central North American ice core, U.S.A.

    SciTech Connect

    Naftz, D.L.; Klusman, R.W.; Michel, R.L.

    1996-02-01

    In the past, ice-core records from mid-latitude glaciers in alpine areas of the continental United States were considered to be poor candidates for paleoclimate records because of the influence of meltwater on isotopic stratigraphy. To evaluate the existence of reliable paleoclimatic records, a 160-m ice core, containing about 250 yr of record was obtained from Upper Fremont Glacier, at an altitude of 4000 m in the Wind River Range of south-central North America. The {gamma}{sup 18}O (SMOW) profile from the core shows a -0.95{per_thousand} shift to lighter values in the interval from 101.8 to 150 m below the surface, corresponding to the latter part of the Little Ice Age (LIA). Numerous high-amplitude oscillations in the section of the core from 101.8 to 150 m cannot be explained by site-specific lateral variability and probably reflect increased seasonality or better preservation of annual signals as a result of prolonged cooler temperatures that existed in this alpine setting. An abrupt decrease in these large amplitude oscillations at the 101.8-m depth suggests a sudden termination of this period of lower temperatures which generally coincides with the termination of the LIA. Three common features in the {gamma}{sup 18}O profiles between Upper Fremont Glacier and the better dated Quelccaya Ice Cap cores indicate a global paleoclimate linkage, further supporting the first documented occurrence of the LIA in an ice-core record from a temperate glacier in south-central North America.

  17. Spatial and temporal variability of snow accumulation using ground-penetrating radar and ice cores on a Svalbard glacier

    E-print Network

    Moore, John

    Spatial and temporal variability of snow accumulation using ground-penetrating radar and ice cores.The profile passed two shallow and one deep ice-core sites.Two internal radar reflection layers were dated layering in snow or ice. Layering in radar images of glacier snow or firn can be attributed to differences

  18. Volatility of unevenly sampled fractional Brownian motion: an application to ice core records

    NASA Astrophysics Data System (ADS)

    Davidsen, J.; Griffin, J.

    2009-05-01

    The analysis of many natural time series and especially those related to ice core records often suffers from uneven sampling intervals. Here, we introduce a method that allows one to reliably estimate the volatility properties of fractional Brownian motion despite uneven sampling. It is based on the linear correlations of the process which are used to rescale the volatility series. For high-resolution temperature proxy records from Antarctica, we confirm that its volatility properties reveal a strong nonlinear component in the time series for time scales of 5 - 200 kyr. The results suggest that temperature increments appear in clusters of big and small increments --- a big (positive or negative) climate change is most likely followed by a big (positive or negative) climate change and a small climate change is most likely followed by a small climate change.

  19. Volatility of unevenly sampled fractional Brownian motion: an application to ice core records

    NASA Astrophysics Data System (ADS)

    Davidsen, J.; Griffin, J.

    2008-12-01

    The analysis of many natural time series and especially those related to ice core records often suffers from uneven sampling intervals. Here, we introduce a method that allows one to reliably estimate the volatility properties of fractional Brownian motion despite uneven sampling. It is based on the linear correlations of the process which are used to rescale the volatility series. For high-resolution temperature proxy records from Antarctica, we confirm that its volatility properties reveal a strong nonlinear component in the time series for time scales of 1 - 100 kyr. The results suggest that temperature increments appear in clusters of big and small increments --- a big (positive or negative) climate change is most likely followed by a big (positive or negative) climate change and a small climate change is most likely followed by a small climate change.

  20. Effects of postdepositional processing on nitrogen isotopes of nitrate in the Greenland Ice Sheet Project 2 ice core

    NASA Astrophysics Data System (ADS)

    Geng, Lei; Zatko, Maria C.; Alexander, Becky; Fudge, T. J.; Schauer, Andrew J.; Murray, Lee T.; Mickley, Loretta J.

    2015-07-01

    Records of ice core nitrate and its isotopes hold the potential to assess past atmospheric conditions regarding NOx and oxidant levels. However, relating such records to past atmospheric conditions requires a site-specific understanding of the postdepositional processing of snow nitrate. We report ?15N(NO3-) records from the Greenland Ice Sheet Project 2 (GISP2) ice core over major climate transitions. Model calculations and comparison with records of parameters influencing UV-driven postdepositional processing of snow nitrate suggest that the observed variability in GISP2 ?15N(NO3-) over major climate transitions is primarily driven by changes in the degree of postdepositional loss of snow nitrate. Estimates of the fractional loss of snow nitrate is (16-23)% in the Holocene and (45-53)% in the glacial period, suggesting a (41 ± 32)% lower nitrate depositional flux to Greenland during the glacial period relative to the Holocene.

  1. Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 ka BP)

    NASA Astrophysics Data System (ADS)

    Svensson, A.; Bigler, M.; Fischer, H.; Johnsen, S. J.; Kipfstuhl, S.; Parrenin, F.; Rasmussen, S. O.; Steffensen, J. P.; Vinther, B. M.; Wegner, A.

    2012-04-01

    The Toba eruption that occurred some 74 ka ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia where it constitutes a major reference horizon close to the Marine Isotope Stage 3/4 (MIS 3/4) boundary. Up to now, no tephra has been associated with Toba neither in Greenland nor in Antarctic ice cores, but based on Toba tephra identified in marine records from the Arabian Sea it is very likely that Greenland ice core acidity spikes related to Toba occur towards the end of Greenland Interstadial 20 (GI-20). Furthermore, the linking of Greenland and Antarctic ice cores by gas records suggests that the Antarctica counterpart should be situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores based on matching of a pattern of bi-polar volcanic spikes and annual layer counting in both cores around 74 ka BP. The synchronization pattern covers some 2000 years in GI-20 and AIM 19/20 and includes 5 major and several minor acidity peaks that are recognized in both ice cores. The most prominent acidity spikes in this time interval that occur towards the end of GI-20, are those thought to originate from Toba, but the proposed linking is independent of the source of the volcanic spikes. Although the linking of Greenland and Antarctic ice cores around Toba is already quite well constrained by matching of gas records, the relative phasing between ice cores from the two hemispheres still has some uncertainty related to the offset in the age of ice and air bubbles in the ice cores (delta-gas age). The identification of a direct Toba synchronization may help to determine the exact phasing of inter-hemispheric climate during this period and to constrain delta-gas ages. It also provides a way to place paleo-environmental records other than ice cores into a precise climatic context.

  2. Fire in ice: two millennia of Northern Hemisphere fire history from the Greenland NEEM ice core

    NASA Astrophysics Data System (ADS)

    Zennaro, P.; Kehrwald, N.; McConnell, J. R.; Schüpbach, S.; Maselli, O.; Marlon, J.; Vallelonga, P.; Leuenberger, D.; Zangrando, R.; Spolaor, A.; Borrotti, M.; Barbaro, E.; Gambaro, A.; Barbante, C.

    2014-02-01

    Biomass burning is a major source of greenhouse gases and influences regional to global climate. Pre-industrial fire-history records from black carbon, charcoal and other proxies provide baseline estimates of biomass burning at local to global scales, but there remains a need for broad-scale fire proxies that span millennia in order to understand the role of fire in the carbon cycle and climate system. We use the specific biomarker levoglucosan, and multi-source black carbon and ammonium concentrations to reconstruct fire activity from the North Greenland Eemian (NEEM) ice cores (77.49° N; 51.2° W, 2480 m a.s.l.) over the past 2000 years. Increases in boreal fire activity (1000-1300 CE and 1500-1700 CE) over multi-decadal timescales coincide with the most extensive central and northern Asian droughts of the past two millennia. The NEEM biomass burning tracers coincide with temperature changes throughout much of the past 2000 years except for during the extreme droughts, when precipitation changes are the dominant factor. Many of these multi-annual droughts are caused by monsoon failures, thus suggesting a connection between low and high latitude climate processes. North America is a primary source of biomass burning aerosols due to its relative proximity to the NEEM camp. During major fire events, however, isotopic analyses of dust, back-trajectories and links with levoglucosan peaks and regional drought reconstructions suggest that Siberia is also an important source of pyrogenic aerosols to Greenland.

  3. Reassessing Lake Vostok's behaviour from existing and new ice core data

    NASA Astrophysics Data System (ADS)

    Souchez, R.; Petit, J.-R.; Jouzel, J.; de Angelis, M.; Tison, J.-L.

    2004-01-01

    Interpretation of new ice core data and reappraisal of existing data, both from the basal part of the Vostok ice core, give strong support to a kind of thermohaline circulation in Lake Vostok. Although the salinity of the lake is considered as weak (less than 1‰), the prominent influence of salinity at high pressure and low temperature on water density makes such a circulation possible. As a consequence, subglacial melting along the northern shores of the lake is balanced, further south, by frazil ice production in the upper water column, its accretion and consolidation at the ice-water interface followed by accreted ice export out of the system together with the southeasterly glacier flow. The dynamics of the system is documented by a stable water isotope budget estimate, by inferences concerning accreted ice formation and by an investigation of ice properties at the transition between meteoric ice and accreted ice. This complex behaviour is the controlling factor on water, biota and sediment fluxes in the lake environment.

  4. Aerial photographs reveal late-20th-century dynamic ice loss in northwestern Greenland.

    PubMed

    Kjær, Kurt H; Khan, Shfaqat A; Korsgaard, Niels J; Wahr, John; Bamber, Jonathan L; Hurkmans, Ruud; van den Broeke, Michiel; Timm, Lars H; Kjeldsen, Kristian K; Bjørk, Anders A; Larsen, Nicolaj K; Jørgensen, Lars Tyge; Færch-Jensen, Anders; Willerslev, Eske

    2012-08-01

    Global warming is predicted to have a profound impact on the Greenland Ice Sheet and its contribution to global sea-level rise. Recent mass loss in the northwest of Greenland has been substantial. Using aerial photographs, we produced digital elevation models and extended the time record of recent observed marginal dynamic thinning back to the mid-1980s. We reveal two independent dynamic ice loss events on the northwestern Greenland Ice Sheet margin: from 1985 to 1993 and 2005 to 2010, which were separated by limited mass changes. Our results suggest that the ice mass changes in this sector were primarily caused by short-lived dynamic ice loss events rather than changes in the surface mass balance. This finding challenges predictions about the future response of the Greenland Ice Sheet to increasing global temperatures. PMID:22859486

  5. Orbital tuning of deep ice cores using O2/N2 of trapped air

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Aoki, S.; Nakazawa, T.

    2014-12-01

    The chronology of the first Dome Fuji deep ice core (80,000-340,000 yr BP) was established by orbital tuning of measured O2/N2 ratios in trapped air to the past local summer insolation at the drill site (Kawamura et al., 2007). The O2/N2 ratios found in ice cores are generally lower than atmospheric ratio because of size-dependent molecular fractionation during bubble close-off. The magnitude of this gas fractionation appears to be influenced by snow metamorphism when the layer was originally at the surface, which in turn is controlled by local summer insolation (Fujita et al., 2009). The O2/N2 record has little 100,000-yr periodicity (strongest in climatic records), suggesting insignificant climatic influence in the orbital tuning. Agreement of the O2/N2 chronology with U-Th radiometric chronology of speleothems (within ~2000 yr) suggests that O2/N2 and summer insolation are indeed in phase. However, it may not be common to all ice cores that O2/N2 signal only records local summer insolation. For example, the GISP2 ice core (Greenland) has clear imprint of abrupt climate changes in the O2/N2 record, indicating climatic (non-insolation) signal in the record and the possibility of phase variability of O2/N2 relative to the past insolation (Suwa and Bender, 2008). Here we present new O2/N2 record from the second Dome Fuji ice core with significant improvements in ice core storage practice and mass spectrometry. In particular, the ice core had been stored at about -50 ?C until the air extraction except during transportations, which prevent fractionation due to gas loss during the core storage. The precision of the new O2/N2 data set is improved by a factor of 3 over the previous data, and we do not observe outliers (there were 15% outliers in the previous data). Clear imprint of local insolation is recognizable in the new O2/N2, which would enable us to generate a chronology with accuracy of ~2000 yr towards older periods. Samples from the first core after long storage (>10 yr) at -25 ?C and -50 ?C were measured as well, and the data show clear dependence of O2/N2 depletion on the storage temperature. We also plan to measure the NEEM ice core (Greenland) for the Eemian and the last glacial period in order to investigate the feasibility of O2/N2 tuning for the Greenland ice cores.

  6. 27 m of lake ice on an Antarctic lake reveals past hydrologic variability

    NASA Astrophysics Data System (ADS)

    Dugan, H. A.; Doran, P. T.; Wagner, B.; Kenig, F.; Fritsen, C. H.; Arcone, S.; Kuhn, E.; Ostrom, N. E.; Warnock, J.; Murray, A. E.

    2014-07-01

    Lake Vida, located in Victoria Valley, is one of the largest lakes in the McMurdo Dry Valleys. Unlike other lakes in the region, the surface ice extends at least 27 m, which has created an extreme and unique habitat by isolating a liquid-brine with salinity of 195 g L-1. Below 21 m, the ice is marked by well-sorted sand layers up to 20 cm thick, within a matrix of salty ice. From ice chemistry, isotopic abundances of 18O and 2H, ground penetrating radar profiles, and mineralogy, we conclude that the entire 27 m of ice formed from surface runoff, and the sediment layers represent the accumulation of fluvial and aeolian deposits. Radiocarbon and optically stimulated luminescence dating limit the maximum age of the lower ice to 6300 14C yr BP. As the ice cover ablated downwards during periods of low surface inflow, progressive accumulation of sediment layers insulated and preserved the ice and brine beneath; analogous to the processes that preserve shallow ground ice. The repetition of these sediment layers reveals climatic variability in Victoria Valley during the mid- to late Holocene. Lake Vida is an excellent Mars analog for understanding the preservation of subsurface brine, ice and sediment in a cold desert environment.

  7. A novel method for the detection of acidity in ice cores

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Vallelonga, Paul; Svensson, Anders

    2014-05-01

    The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on the absorption spectroscopy of two common pH-indicator dyes, bromophenol blue and chlorophenol red. The method does not require calibration with CO2 and is simpler than existing continuous flow analysis (CFA) methods for pH determination in ice cores, offering a 10-90% peak response time of 45s and a combined uncertainty of 9%. The method has been applied to sections of Greenland firn and Antarctic ice and compared to standard techniques such as Electrical Conductivity Measurements (ECM), conducted on the solid ice, and electrolytic conductivity of melted ice samples. The acidity as detected in the Greenland NEGIS firn core (75.38N, 35.56W), show an increasing trend up to the 1970's that can be explained by deposition of anthropogenic SO42- and NOX. The seasonal variability show highest acidity in winter (1900-1950 AD), but shifts towards spring for the period 1950-2000 AD. Conductivity and pH are found to be highly correlated in the Greenland NEGIS firn core with all signals greater than 3? variability being related to either volcanic eruptions or forest fire activity. The method is ideal for finding the volcanic spikes in the firn than conventional ECM and DEP, which require density corrections in firn. In contrast to the NEGIS site, the Antarctic Roosevelt Island ice core (79.36S, 161.71W) features an anti-correlation between conductivity and pH, most likely due to the influence of marine salts.

  8. Optimal site selection for a high resolution ice core record in East Antarctica

    NASA Astrophysics Data System (ADS)

    Vance, T.; Roberts, J.; Moy, A.; Curran, M.; Tozer, C.; Gallant, A.; Abram, N.; van Ommen, T.; Young, D.; Grima, C.; Blankenship, D.; Siegert, M.

    2015-11-01

    Ice cores provide some of the best dated and most comprehensive proxy records, as they yield a vast and growing array of proxy indicators. Selecting a site for ice core drilling is nonetheless challenging, as the assessment of potential new sites needs to consider a variety of factors. Here, we demonstrate a systematic approach to site selection for a new East Antarctic high resolution ice core record. Specifically, seven criteria are considered: (1) 2000 year old ice at 300 m depth, (2) above 1000 m elevation, (3) a minimum accumulation rate of 250 mm yr-1 IE, (4) minimal surface re-working to preserve the deposited climate signal, (5) a site with minimal displacement or elevation change of ice at 300 m depth, (6) a strong teleconnection to mid-latitude climate and (7) an appropriately complementary relationship to the existing Law Dome record (a high resolution record in East Antarctica). Once assessment of these physical characteristics identified promising regions, logistical considerations (for site access and ice core retrieval) were briefly considered. We use Antarctic surface mass balance syntheses, along with ground-truthing of satellite data by airborne radar surveys to produce all-of-Antarctica maps of surface roughness, age at specified depth, elevation and displacement change and surface air temperature correlations to pinpoint promising locations. We also use the European Centre for Medium-Range Weather Forecast ERA 20th Century reanalysis (ERA-20C) to ensure a site complementary to the Law Dome record is selected. We find three promising sites in the Indian Ocean sector of East Antarctica in the coastal zone from Enderby Land to the Ingrid Christensen Coast (50-100° E). Although we focus on East Antarctica for a new ice core site, the methodology is more generally applicable and we include key parameters for all of Antarctica which may be useful for ice core site selection elsewhere and/or for other purposes.

  9. THE SEARCH FOR SUPERNOVA GRAINS IN AN ICE CORE A. L. Cole1

    E-print Network

    Floss, Christine

    THE SEARCH FOR SUPERNOVA GRAINS IN AN ICE CORE A. L. Cole1 National Superconducting Cyclotron, Washington University, St. Louis, MO 63130 Received 2005 December 20; accepted 2006 January 27 ABSTRACT A search was conducted for grains of the potential core-collapse supernova (SN) condensate minerals

  10. Separation of melting and environmental signals in an ice core with seasonal melt

    E-print Network

    Moore, John

    for these periods all differ significantly, reflecting complex changes in environmental conditions. Thus the core N, 17° 250 3000 E, 1255 m a.s.l.). Total ice depth from radar sounding was 123 m, and the site et al., 2002]. Extensive shallow coring and snow pits indicate that any summer melt water is refrozen

  11. Sensitivity of IceCube-DeepCore to neutralino dark matter in the MSSM-25

    SciTech Connect

    Silverwood, Hamish; Adams, Jenni; Brown, Anthony M; Scott, Pat; Danninger, Matthias; Savage, Christopher; Edsjö, Joakim; Hultqvist, Klas E-mail: patscott@physics.mcgill.ca E-mail: savage@physics.utah.edu E-mail: jenni.adams@canterbury.ac.nz E-mail: klas.hultqvist@fysik.su.se

    2013-03-01

    We analyse the sensitivity of IceCube-DeepCore to annihilation of neutralino dark matter in the solar core, generated within a 25 parameter version of the minimally supersymmetric standard model (MSSM-25). We explore the 25-dimensional parameter space using scanning methods based on importance sampling and using DarkSUSY 5.0.6 to calculate observables. Our scans produced a database of 6.02 million parameter space points with neutralino dark matter consistent with the relic density implied by WMAP 7-year data, as well as with accelerator searches. We performed a model exclusion analysis upon these points using the expected capabilities of the IceCube-DeepCore Neutrino Telescope. We show that IceCube-DeepCore will be sensitive to a number of models that are not accessible to direct detection experiments such as SIMPLE, COUPP and XENON100, indirect detection using Fermi-LAT observations of dwarf spheroidal galaxies, nor to current LHC searches.

  12. A comparison of the present and last interglacial periods in six Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Buiron, D.; Ekaykin, A.; Frezzotti, M.; Gallée, H.; Jouzel, J.; Krinner, G.; Landais, A.; Motoyama, H.; Oerter, H.; Pol, K.; Pollard, D.; Ritz, C.; Schlosser, E.; Sime, L. C.; Sodemann, H.; Stenni, B.; Uemura, R.; Vimeux, F.

    2010-10-01

    We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories which are compared to ice sheet model results. Our results suggest that, for coastal sites, elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.

  13. A comparison of the present and last interglacial periods in six Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Buiron, D.; Ekaykin, A.; Frezzotti, M.; Gallée, H.; Jouzel, J.; Krinner, G.; Landais, A.; Motoyama, H.; Oerter, H.; Pol, K.; Pollard, D.; Ritz, C.; Schlosser, E.; Sime, L. C.; Sodemann, H.; Stenni, B.; Uemura, R.; Vimeux, F.

    2011-04-01

    We compare the present and last interglacial periods as recorded in Antarctic water stable isotope records now available at various temporal resolutions from six East Antarctic ice cores: Vostok, Taylor Dome, EPICA Dome C (EDC), EPICA Dronning Maud Land (EDML), Dome Fuji and the recent TALDICE ice core from Talos Dome. We first review the different modern site characteristics in terms of ice flow, meteorological conditions, precipitation intermittency and moisture origin, as depicted by meteorological data, atmospheric reanalyses and Lagrangian moisture source diagnostics. These different factors can indeed alter the relationships between temperature and water stable isotopes. Using five records with sufficient resolution on the EDC3 age scale, common features are quantified through principal component analyses. Consistent with instrumental records and atmospheric model results, the ice core data depict rather coherent and homogenous patterns in East Antarctica during the last two interglacials. Across the East Antarctic plateau, regional differences, with respect to the common East Antarctic signal, appear to have similar patterns during the current and last interglacials. We identify two abrupt shifts in isotopic records during the glacial inception at TALDICE and EDML, likely caused by regional sea ice expansion. These regional differences are discussed in terms of moisture origin and in terms of past changes in local elevation histories, which are compared to ice sheet model results. Our results suggest that elevation changes may contribute significantly to inter-site differences. These elevation changes may be underestimated by current ice sheet models.

  14. Glacial records of global climate: A 1500-year tropical ice core record of climate

    SciTech Connect

    Thompson, L.G.; Davis, M.E.; Mosley-Thompson, E. )

    1994-03-01

    A general discussion is given of climate variability over the last 1500 years as interpreted from two ice cores from the Quelccaya ice cap, Peru. The possible role of climatic variability in prehistory over this period is discussed with emphases on (1) relationships between climate and the rise and decline of coastal and highland cultures; (2) the possible causes of two major dust events recorded in the quelccaya ice cores around AD 920 and AD 600; (3) implications of climatic variation for the occupation and abandonment of the Gran Pajaten area. The remarkable similarity between changes in highland and coastal cultures and changes in accumulation as determined from the Quelccaya ice cores implies a strong connection between human activities and climate in this region of the globe. Two ice cores drilled to bedrock from the 6047 masl col of Huascaran in the Cordillera Blanca, Peru in 1993 offer the potential of an annual to decadal climatic and environmental record which should allow the study of human-climate and human-environmental relationships over 10,000+ years. The 1991 and 1993 evidence from the Quelccaya ice cap indicates that recent and rapid warming is currently underway in the tropical Andes. Thus, many of the unique glacier archives are in imminent danger of being lost forever.

  15. Microbial Analyses of Ancient Ice Core Sections from Greenland and Antarctica

    PubMed Central

    Knowlton, Caitlin; Veerapaneni, Ram; D’Elia, Tom; Rogers, Scott O.

    2013-01-01

    Ice deposited in Greenland and Antarctica entraps viable and nonviable microbes, as well as biomolecules, that become temporal atmospheric records. Five sections (estimated to be 500, 10,500, 57,000, 105,000 and 157,000 years before present, ybp) from the GISP2D (Greenland) ice core, three sections (500, 30,000 and 70,000 ybp) from the Byrd ice core, and four sections from the Vostok 5G (Antarctica) ice core (10,500, 57,000, 105,000 and 105,000 ybp) were studied by scanning electron microscopy, cultivation and rRNA gene sequencing. Bacterial and fungal isolates were recovered from 10 of the 12 sections. The highest numbers of isolates were found in ice core sections that were deposited during times of low atmospheric CO2, low global temperatures and low levels of atmospheric dust. Two of the sections (GISP2D at 10,500 and 157,000 ybp) also were examined using metagenomic/metatranscriptomic methods. These results indicated that sequences from microbes common to arid and saline soils were deposited in the ice during a time of low temperature, low atmospheric CO2 and high dust levels. Members of Firmicutes and Cyanobacteria were the most prevalent bacteria, while Rhodotorula species were the most common eukaryotic representatives. Isolates of Bacillus, Rhodotorula, Alternaria and members of the Davidiellaceae were isolated from both Greenland and Antarctica sections of the same age, although the sequences differed between the two polar regions. PMID:24832659

  16. Basal Melt Under the Interior of the Greenland Ice Sheet: Comparison of Models, Deep Ice Cores, and Radar Observations

    NASA Astrophysics Data System (ADS)

    Rezvanbehbahani, S.; Stearns, L. A.; van der Veen, C. J.

    2014-12-01

    Basal ice temperature is a critical boundary condition for ice sheet models. It modulates the basal melt rate and sliding conditions, and also affects the ice hardness which alters the deformational velocity. Therefore, in order to obtain reliable estimates on the future mass loss of the ice sheets using numerical models, basal ice temperature is of paramount importance. In this study, the basal temperature and basal melt rate under the Greenland Ice Sheet are estimated using the Robin temperature solution. The analytical Robin solution is obtained by solving the heat conservation equation for steady state conditions, assuming that advection and diffusion are significant only in the vertical direction. In this study, the sensitivity of the basal temperature obtained from the Robin solution to changes in input parameters, including changes in atmospheric conditions, ice thickness, and geothermal heat flux is tested. Although the Robin solution is frequently used in glaciology, there has been no quantitative study to estimate the effect of neglecting the horizontal advection on basal temperatures in regions of higher velocity. Here, a two-dimensional model is applied to quantify the effect of horizontal heat advection on basal temperatures. Overall, horizontal heat advection lowers the basal temperature except in regions where surface mass balance gradients are negative along the flow. Comparing the results from the 2D temperature model to the Robin solution along multiple flowlines of the Greenland Ice Sheet suggest that the horizontal heat advection alters the basal temperatures by less than 3°C up to 30-45% of the flow distance away from the ice divide; at greater distances this difference increases rapidly. All simulations using the Robin solution predict substantial basal melting under the northeast drainage basin of the ice sheet. Our 2D model results also show that because of the negative surface mass balance gradient, horizontal heat advection increases the basal temperatures in the northeast basin. Our obtained map of basal melting area matches well with the radar detected basal water under the north and northeast drainage basins. However, low basal temperatures estimated at the Camp Century ice core location in the northwest of the ice sheet is in contrast with the radar observations.

  17. Post-coring entrapment of modern air in polar ice: Evidence from CFC-12 measurements in Antarctic firn air and shallow ice cores

    NASA Astrophysics Data System (ADS)

    Aydin, K. M.; Montzka, S. A.; Battle, M. O.; Williams, M. B.; de Bruyn, W. J.; Butler, J. H.; Verhulst, K. R.; Tatum, C.; Gun, B. K.; Plotkin, D. A.; Hall, B. D.; Saltzman, E. S.

    2009-12-01

    This study is a comparison of CFC-12 (CCl2F2) measurements in firn air and ice core samples from three Antarctic sites: South Pole, West Antarctic Ice Sheet Divide (79.46°S, 112.13°W), and Siple Dome (81.65°S, 148.81°W). CFC-12 is a synthetic chlorofluorocarbon manufactured during the mid-late 20th century for use as a refrigerant and an aerosol spray propellant. Its atmospheric history is well established with agreement among instrumental time series measurements and industry-reported production data [Walker et al., 2000], the distribution of dissolved CFC-12 in the oceans [e.g. Weiss et al., 1985], and firn air measurements [Butler et al., 1999]. The atmospheric history indicates that there was no measureable CFC-12 in the atmosphere prior to the 1940’s. The firn air CFC-12 profiles are consistent with the known atmospheric history of this gas. In contrast, the air in ice core samples collected near the close-off depth exhibit anomalously high CFC-12 levels. We propose that this is due to entrapment of modern air in open pores that close after drilling, resulting in elevated CFC-12 mixing ratios. These results demonstrate how the composition of air trapped in shallow ice cores can be altered during the post-drilling period through purely physical processes. Comparison of firn air and ice core bubble composition is one of the commonly used tools for studying the bubble close-off process. The post-drilling entrapment process detected in this study represents a potential complication for such investigations.

  18. The Antarctic Ice.

    ERIC Educational Resources Information Center

    Radok, Uwe

    1985-01-01

    The International Antarctic Glaciological Project has collected information on the East Antarctic ice sheet since 1969. Analysis of ice cores revealed climatic history, and radar soundings helped map bedrock of the continent. Computer models of the ice sheet and its changes over time will aid in predicting the future. (DH)

  19. Complex Antarctic Ice-Shelf Height Changes Revealed By Eighteen Years of Satellite Radar Altimetry

    NASA Astrophysics Data System (ADS)

    Paolo, F. S.; Fricker, H. A.; Padman, L.

    2014-12-01

    Recent mass losses from the grounded Antarctic Ice Sheet have been associated with changes in its floating ice shelves, but the duration and variability of these changes is so far undocumented. Using data from three overlapping satellite radar altimetry missions (ERS-1, ERS-2 and Envisat) we construct a record, at high spatial and temporal resolution, of ice-shelf height changes for the 18-year period 1994-2012. The record reveals a complex pattern of ice-shelf height change resulting from the varying impacts of the Antarctic oceans and atmosphere on the ice sheet. We show that Antarctica-wide average ice-shelf height increased moderately up until ~2003 and then declined rapidly after ~2006. The Amundsen Sea ice shelves have experienced persistent surface lowering since the beginning of the record, with mean values ranging from ~-10 cm/year (Pine Island) to ~-30 cm/year (Dotson). Lowering is more rapid at the deep grounding lines than at the shallower ice shelf fronts, consistent with thermal erosion driven by warm Circumpolar Deep Water flowing under the ice shelves. On the eastern Antarctic Peninsula, surface lowering starts at the northernmost portion and develops southwards, consistent with a response to the observed trend of atmospheric warming. Contrary to previous ICESat-based estimates from 2003-2009, the Wilkes Land ice shelves show a positive rate of height change with a regional mean value over +3 cm/year. Although relatively stable with average rates of +0.5-2 cm/year, the three largest ice shelves (Ross, Filchner-Ronne and Amery) show large interannual and spatial variability. Our 18-year-long dataset demonstrates that results from single satellite missions, with typical duration of a few years, are insufficient to draw conclusions about long-term response of ice shelves to changes in oceanic and atmospheric conditions.

  20. Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics

    PubMed Central

    Csatho, Beata M.; Schenk, Anton F.; van der Veen, Cornelis J.; Babonis, Gregory; Duncan, Kyle; Rezvanbehbahani, Soroush; van den Broeke, Michiel R.; Simonsen, Sebastian B.; Nagarajan, Sudhagar; van Angelen, Jan H.

    2014-01-01

    We present a new record of ice thickness change, reconstructed at nearly 100,000 sites on the Greenland Ice Sheet (GrIS) from laser altimetry measurements spanning the period 1993–2012, partitioned into changes due to surface mass balance (SMB) and ice dynamics. We estimate a mean annual GrIS mass loss of 243 ± 18 Gt?y?1, equivalent to 0.68 mm?y?1 sea level rise (SLR) for 2003–2009. Dynamic thinning contributed 48%, with the largest rates occurring in 2004–2006, followed by a gradual decrease balanced by accelerating SMB loss. The spatial pattern of dynamic mass loss changed over this time as dynamic thinning rapidly decreased in southeast Greenland but slowly increased in the southwest, north, and northeast regions. Most outlet glaciers have been thinning during the last two decades, interrupted by episodes of decreasing thinning or even thickening. Dynamics of the major outlet glaciers dominated the mass loss from larger drainage basins, and simultaneous changes over distances up to 500 km are detected, indicating climate control. However, the intricate spatiotemporal pattern of dynamic thickness change suggests that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions. Recent projections of dynamic contributions from the entire GrIS to SLR have been based on the extrapolation of four major outlet glaciers. Considering the observed complexity, we question how well these four glaciers represent all of Greenland’s outlet glaciers. PMID:25512537

  1. A chemical pacemaker to refine chronology for the deep East Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Petit, J. R.; Parrenin, F.; Delmonte, B.

    2012-04-01

    Dating of the deep East Antarctic ice core spanning more than 100,000 years of climate records is challenging but benefited recently from iterative and complementary approaches. As a principle, ice core dating relies on ice flow modelling (thinning function of ice layer) as well as on the (modelled) estimate of the past snow accumulation rate. The inverse method allows integration of various dated horizons from other records assuming the physical properties of the ice (its deformation) remain within realistic boundaries. The modelled ice chronology is generally constrained by few dated horizons (volcanic, 10Be peaks from solar or from magnetic inversion related events…) and/or by orbital tuning process (temperature proxy, 18O of air bubbles…). Due to the scarcity of absolute dating, the use of orbital tuning from ice proxies may serve as a test of the modelled ice age. As a prerequisite, the proxy should not already be used to constrain the modelled chronology. Also, to prevent gas-age/ice age uncertainties, a preference should be given to a proxy associated to the ice instead to the air bubbles. Also, the physical link with the insolation should be rather direct, and a preference given to proxies sensitive to precession band (20kyr) instead obliquity band (41kyr). The continental dust and marine sodium records were so far not used to constrain the modelled chronology of EPICA and Vostok ice core. The dust and marine sodium appear firstly correlated to patterns of temperature and therefore to the hydrological cycle which influences at the same time the source emissions (for dust), the atmospheric cleansing and the deposition onto the ice sheet. Once the overall temperature effects is compensated, the residual signal for dust and sodium concentrations over the last 400 ky from EPICA Dome C and Vostok records display strong precession oscillations for both sites. Interestingly, the sodium residuals appear to increase with austral summer insolation while the dust residuals decrease, and remaining out of phase. Such behaviour could be understood by a positive effect of insolation on sodium emission (strengthening of spring cyclonic activity…) and negative effect on dust sources (reduction of Patagonian dust emission by strengthening of Southern American monsoon…). This dual behaviour which needs to be determined, allows combination of sodium and dust residuals providing a "chemical pacemaker" dominated by precession which could be used to refine the modelled chronology. A test was done on the EDC3 modelled age of the Epica Dome C deep ice core which covers the last 800ky.

  2. Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 kyr BP)

    NASA Astrophysics Data System (ADS)

    Svensson, A.; Bigler, M.; Blunier, T.; Clausen, H. B.; Dahl-Jensen, D.; Fischer, H.; Fujita, S.; Goto-Azuma, K.; Johnsen, S. J.; Kawamura, K.; Kipfstuhl, S.; Kohno, M.; Parrenin, F.; Popp, T.; Rasmussen, S. O.; Schwander, J.; Seierstad, I.; Severi, M.; Steffensen, J. P.; Udisti, R.; Uemura, R.; Vallelonga, P.; Vinther, B. M.; Wegner, A.; Wilhelms, F.; Winstrup, M.

    2012-11-01

    The Toba eruption that occurred some 74 kyr ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia where it constitutes a major time marker close to the Marine Isotope Stage 4/5 boundary. As yet, no tephra associated with Toba has been identified in Greenland or Antarctic ice cores. Based on new accurate dating of Toba tephra from Malaysia and on accurately dated European stalagmites the Toba event is known to occur between the onsets of Greenland Interstadials (GI) 19 and 20. Furthermore, the existing linking of Greenland and Antarctic ice cores by gas records and by the bipolar seesaw hypothesis suggests that the Antarctic counterpart is situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption based on matching of a pattern of bipolar volcanic spikes. Annual layer counting between volcanic spikes in both cores allows for a unique match. We first demonstrate this bipolar matching technique at the already synchronized Laschamp geomagnetic excursion (41 kyr BP) before we apply it to the suggested Toba interval. The Toba synchronization pattern covers some 2000 yr in GI-20 and AIM 19/20 and includes nine acidity peaks that are recognized in both ice cores. The suggested bipolar Toba synchronization has decadal precision. It thus allows a determination of the exact phasing of inter-hemispheric climate in a time interval of poorly constrained ice core records, and it allows for a discussion of the climatic impact of the Toba eruption in a global perspective. Furthermore, our bipolar match provides a way to place paleo-environmental records other than ice cores into a precise climatic context.

  3. Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 ka BP)

    NASA Astrophysics Data System (ADS)

    Svensson, A.; Bigler, M.; Blunier, T.; Clausen, H. B.; Dahl-Jensen, D.; Fischer, H.; Fujita, S.; Goto-Azuma, K.; Johnsen, S. J.; Kawamura, K.; Kipfstuhl, S.; Kohno, M.; Parrenin, F.; Popp, T.; Rasmussen, S. O.; Schwander, J.; Seierstad, I.; Severi, M.; Steffensen, J. P.; Udisti, R.; Uemura, R.; Vallelonga, P.; Vinther, B. M.; Wegner, A.; Wilhelms, F.; Winstrup, M.

    2013-03-01

    The Toba eruption that occurred some 74 ka ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia, where it constitutes a major time marker close to the Marine Isotope Stage 4/5 boundary. As yet, no tephra associated with Toba has been identified in Greenland or Antarctic ice cores. Based on new accurate dating of Toba tephra and on accurately dated European stalagmites, the Toba event is known to occur between the onsets of Greenland interstadials (GI) 19 and 20. Furthermore, the existing linking of Greenland and Antarctic ice cores by gas records and by the bipolar seesaw hypothesis suggests that the Antarctic counterpart is situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption based on matching of a pattern of bipolar volcanic spikes. Annual layer counting between volcanic spikes in both cores allows for a unique match. We first demonstrate this bipolar matching technique at the already synchronized Laschamp geomagnetic excursion (41 ka BP) before we apply it to the suggested Toba interval. The Toba synchronization pattern covers some 2000 yr in GI-20 and AIM-19/20 and includes nine acidity peaks that are recognized in both ice cores. The suggested bipolar Toba synchronization has decadal precision. It thus allows a determination of the exact phasing of inter-hemispheric climate in a time interval of poorly constrained ice core records, and it allows for a discussion of the climatic impact of the Toba eruption in a global perspective. The bipolar linking gives no support for a long-term global cooling caused by the Toba eruption as Antarctica experiences a major warming shortly after the event. Furthermore, our bipolar match provides a way to place palaeo-environmental records other than ice cores into a precise climatic context.

  4. Ice magnetization in the EPICA-Dome C ice core: Implication for dust sources during glacial and interglacial periods

    NASA Astrophysics Data System (ADS)

    Lanci, L.; Delmonte, B.; Maggi, V.; Petit, J. R.; Kent, D. V.

    2008-07-01

    Isothermal remanent magnetization and insoluble dust content of ice samples from EPICA-Dome C ice core were measured to characterize the magnetic properties of atmospheric dust. Despite the larger concentration of dust aerosol during glacial stages, the magnetization of the dust fraction was found to be higher during interglacials and exhibits a larger variability. Changes in magnetic mineralogy of aerosol dust in ice from different climatic stages were also characterized using coercivity of remanence. Variations of magnetic properties of dust from glacial to interglacial stages indicate changes in dust provenance, in agreement with previous results based on geochemical analysis. However, the extremely large magnetizations of some interglacial samples also suggest that episodical eolian deposition from highly magnetic deposits occurred during interglacial periods.

  5. Mineral Dust Elemental Composition Over the Last 220 Kyr from the EPICA-Dome C ice core (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Marino, F.; Maggi, V.; Delmonte, B.; Ghermandi, G.; Petit, J.; Hinkley, T. K.

    2004-12-01

    Mineral windblown aerosol (dust) represents a small fraction of the total mass of atmospheric aerosols. However, it may play an important role in climate and, in turn, it is itself sensitive to climatic changes. The investigation of the temporal variability of dust flux as well as the changes of its mineralogical composition within different climatic periods offers a unique way of assessing the source-related environmental changes, the variation in atmospheric circulation, and the potential influence of dust on biogeochemical cycles, for several key elements (such as Si and Fe). The mineral composition of dust found in ice cores is still poorly known, because few techniques are able to provide information on the chemical composition of the insoluble aerosol fraction, because of the very low mass of dust usually present in polar ice samples. Total volume of mineral content is provided by Coulter Counter measurements, and the dust record shows higher dust input during glacial periods than during interglacials (Delmonte et al., 2004). Sr and Nd isotopic tracers for identification of dust provenance to East Antarctica suggest southern South America as the dominant common source for dust in glacial periods of the late Pleistocene (Delmonte et al., 2004), whereas dust provenance during interglacials periods is still highly uncertain. Elemental composition of mineral dust from the Dome C ice core (75° 06' S, 123° 21' E) drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA) is presented, showing measurements obtained by the Proton Induced X-ray Emission (PIXE) technique applied on insoluble atmospheric dust in ice cores. Within this work, substantial improvements to the experimental set-up and data processing have been made, compared to previously presented works on the first 2200 m of the EDC ice core, corresponding to about 220 kyr of climatic history (Marino et al., 2004; Ghermandi et al., 2003). The PIXE technique, based on X-ray spectrometry, allows direct measurements on filters of the insoluble dust fraction without sample pre-treatment, with analytical detection limits less than 1 ppb. The minimum required mass density of sample material on the filter is about 0.1 microg cm-2. Improvements made here allowed us to obtain accurate records of 8 major and minor crustal elements (Si, Al, Fe, Ti, K, Ca, Mg, Na). The data for these 8 elements, as well as their proportions as oxides, are shown for different climatic periods. Because O, Si, Al, Fe, Ti, K, Ca, Mg, Na are the principal constituents (99.90 %) of the Earth's Continental Crust, a comparison with literature data can reveal changes in relative elemental abundances, and hence variable composition of dust under different climatic conditions.

  6. Greenland ice cores tell tales on past climate changes (Louis Agassiz Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, Dorthe

    2014-05-01

    Greenland ice cores contain very highly resolved climate records reaching 128.000 years back in time. When dated and matched they tell tales on very abrupt climate changes especially during the glacial period demonstrating that internal energy exchange in the climate system can cause dramatic and fast changes with no external forcing. When the water stable isotope records from the six deep ice cores are compared they inform on both temperature changes and elevation changes of the Greenland ice sheet during glacial and interglacial periods. The temperature and elevation changes during the last 128.000 years are presented and the knowledge gained is used to discuss how this knowledge can be used to predict the future volume change of the Greenland ice sheet. This knowledge can improve estimates of future sea level rise predictions and is a demonstration of how knowledge from the past can be used to predict the future.

  7. Low time resolution analysis of polar ice cores cannot detect impulsive nitrate events

    E-print Network

    Smart, D F; Melott, A L; Laird, C M

    2015-01-01

    Ice cores are archives of climate change and possibly large solar proton events (SPEs). Wolff et al. (2012) used a single event, a nitrate peak in the GISP2-H core, which McCracken et al. (2001a) time associated with the poorly quantified 1859 Carrington event, to discredit SPE-produced, impulsive nitrate deposition in polar ice. This is not the ideal test case. We critique the Wolff et al. analysis and demonstrate that the data they used cannot detect impulsive nitrate events because of resolution limitations. We suggest re-examination of the top of the Greenland ice sheet at key intervals over the last two millennia with attention to fine resolution and replicate sampling of multiple species. This will allow further insight into polar depositional processes on a sub-seasonal scale, including atmospheric sources, transport mechanisms to the ice sheet, post-depositional interactions, and a potential SPE association.

  8. Atmospheric volcanic loading derived from bipolar ice cores: Accounting for the spatial distribution of volcanic deposition

    NASA Astrophysics Data System (ADS)

    Gao, Chaochao; Oman, Luke; Robock, Alan; Stenchikov, Georgiy L.

    2007-05-01

    Previous studies have used small numbers of ice core records of past volcanism to represent hemispheric or global radiative forcing from volcanic stratospheric aerosols. With the largest-ever assembly of volcanic ice core records and state-of-the-art climate model simulations of volcanic deposition, we now have a unique opportunity to investigate the effects of spatial variations on sulfate deposition and on estimates of atmospheric loading. We have combined 44 ice core records, 25 from the Arctic and 19 from Antarctica, and Goddard Institute for Space Studies ModelE simulations to study the spatial distribution of volcanic sulfate aerosols in the polar ice sheets. We extracted volcanic deposition signals by applying a high-pass loess filter to the time series and examining peaks that exceed twice the 31-year running median absolute deviation. Our results suggest that the distribution of volcanic sulfate aerosol follows the general precipitation pattern in both regions, indicating the important role precipitation has played in affecting the deposition pattern of volcanic aerosols. We found a similar distribution pattern for sulfate aerosols from the 1783-1784 Laki and 1815 Tambora eruptions, as well as for the total ? activity after the 1952-1954 low-latitude Northern Hemisphere and 1961-1962 high-latitude Northern Hemisphere atmospheric nuclear weapon tests. This confirms the previous assumption that the transport and deposition of nuclear bomb test debris resemble those of volcanic aerosols. We compare three techniques for estimating stratospheric aerosol loading from ice core data: radioactive deposition from nuclear bomb tests, Pinatubo sulfate deposition in eight Antarctic ice cores, and climate model simulations of volcanic sulfate transport and deposition following the 1783 Laki, 1815 Tambora, 1912 Katmai, and 1991 Pinatubo eruptions. By applying the above calibration factors to the 44 ice core records, we have estimated the stratospheric sulfate aerosol loadings for the largest volcanic eruptions during the last millennium. These loadings agree fairly well with estimates based on radiation, petrology, and model simulations. We also estimate the relative magnitude of sulfate deposition compared with the mean for Greenland and Antarctica for each ice core record, which provides a guideline to evaluate the stratospheric volcanic sulfate aerosol loading calculated from a single or a few ice core records.

  9. Insight of dust provenance in Antarctic ice cores prior to M.I.S. 6 from ice magnetization

    NASA Astrophysics Data System (ADS)

    Lanci, L.; Delmonte, B.

    2014-12-01

    The identification of dust provenance and its characteristics is a key issue to understand climate, atmospheric and environmental changes, and provides key constraints to dust transport processes. Many traditional geochemical methods for dust source tracking are not relevant in Antarctic ice cores because of their extremely low dust content, spanning from a few ppb during warm interglacial periods to a few hundreds of ppb, in the case of relatively dustier glacial periods. For the same reason, the Sr-Nd-Pb radiogenic isotope composition of mineral dust in ice cores, that is the most widely-used technique for dust source fingerprint has intrinsic limitations related to dust abundance that drastically limit the temporal information one can achieve. Rock-magnetic properties of aerosol dust, instead, can be measured directly in small ice samples despite its very low concentration. Intensity of isothermal remanent magnetization and coercivity of magnetic minerals are directly related to that of insoluble dust and these magnetic properties are informative of the dust provenance areas. We investigated rock-magnetic properties of aerosol dust in Antartic ice older than M.I.S. 6 in EPiCA Dome-C and Vostok ice core to gather information on dust provenance prior to the last interglacial times. New and previously published results from rock-magnetism suggests that aerosol dust provenance has changed in time during subsequent glacial-interglacial climatic stages. Moreover parallel changes in Dome-C and Vostok sites suggest that such changes result from long-distance dust transportation implying that transportation paths and/or dust sources did not remained the same during the last few glacial-interglacial cycles.

  10. 30-Year Satellite Record Reveals Accelerated Arctic Sea Ice Loss, Antarctic Sea Ice Trend Reversal

    NASA Technical Reports Server (NTRS)

    Cavalieri, Donald J.; Parkinson, C. L.; Vinnikov, K. Y.

    2003-01-01

    Arctic sea ice extent decreased by 0.30 plus or minus 0.03 x 10(exp 6) square kilometers per decade from 1972 through 2002, but decreased by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per decade from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast to the Arctic, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased, with an overall 30-year trend of -0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent observed in the early 1970's.

  11. Temperature and precipitation signal in two Alpine ice cores over the period 1961-2001

    NASA Astrophysics Data System (ADS)

    Mariani, I.; Eichler, A.; Jenk, T. M.; Brönnimann, S.; Auchmann, R.; Leuenberger, M. C.; Schwikowski, M.

    2014-06-01

    Water stable isotope ratios and net snow accumulation in ice cores are commonly interpreted as temperature or precipitation proxies. However, only in a few cases has a direct calibration with instrumental data been attempted. In this study we took advantage of the dense network of observations in the European Alpine region to rigorously test the relationship of the annual and seasonal resolved proxy data from two highly resolved ice cores with local temperature and precipitation. We focused on the time period 1961-2001 with the highest amount and quality of meteorological data and the minimal uncertainty in ice core dating (±1 year). The two ice cores were retrieved from the Fiescherhorn glacier (northern Alps, 3900 m a.s.l.), and Grenzgletscher (southern Alps, 4200 m a.s.l.). A parallel core from the Fiescherhorn glacier allowed assessing the reproducibility of the ice core proxy data. Due to the orographic barrier, the two flanks of the Alpine chain are affected by distinct patterns of precipitation. The different location of the two glaciers therefore offers a unique opportunity to test whether such a specific setting is reflected in the proxy data. On a seasonal scale a high fraction of ?18O variability was explained by the seasonal cycle of temperature (~60% for the ice cores, ~70% for the nearby stations of the Global Network of Isotopes in Precipitation - GNIP). When the seasonality is removed, the correlations decrease for all sites, indicating that factors other than temperature such as changing moisture sources and/or precipitation regimes affect the isotopic signal on this timescale. Post-depositional phenomena may additionally modify the ice core data. On an annual scale, the ?18O/temperature relationship was significant at the Fiescherhorn, whereas for Grenzgletscher this was the case only when weighting the temperature with precipitation. In both cases the fraction of interannual temperature variability explained was ~20%, comparable to the values obtained from the GNIP stations data. Consistently with previous studies, we found an altitude effect for the ?18O of -0.17‰/100 m for an extended elevation range combining data of the two ice core sites and four GNIP stations. Significant correlations between net accumulation and precipitation were observed for Grenzgletscher during the entire period of investigation, whereas for Fiescherhorn this was the case only for the less recent period (1961-1977). Local phenomena, probably related to wind, seem to partly disturb the Fiescherhorn accumulation record. Spatial correlation analysis shows the two glaciers to be influenced by different precipitation regimes, with the Grenzgletscher reflecting the characteristic precipitation regime south of the Alps and the Fiescherhorn accumulation showing a pattern more closely linked to northern Alpine stations.

  12. A method for analysis of vanillic acid in polar ice cores

    NASA Astrophysics Data System (ADS)

    Grieman, M. M.; Greaves, J.; Saltzman, E. S.

    2015-02-01

    Biomass burning generates a wide range of organic compounds that are transported via aerosols to the polar ice sheets. Vanillic acid is a product of conifer lignin combustion, which has previously been observed in laboratory and ambient biomass burning aerosols. In this study a method was developed for analysis of vanillic acid in melted polar ice core samples. Vanillic acid was chromatographically separated using reversed-phase liquid chromatography (HPLC) and detected using electrospray ionization-triple quadrupole mass spectrometry (ESI-MS/MS). Using a 100 ?L injection loop and analysis time of 4 min, we obtained a detection limit of 77 ppt (parts per trillion by mass) and an analytical precision of ±10%. Measurements of vanillic acid in Arctic ice core samples from the Siberian Akademii Nauk core are shown as an example application of the method.

  13. Nitrate ions spikes in ice cores are not suitable proxies for solar proton events

    E-print Network

    Duderstadt, Katharine A; Jackman, Charles H; Randall, Cora E; Schwadron, Nathan A; Solomon, Stanley C; Spence, Harlan E; Yudin, Valery A

    2015-01-01

    Nitrate ion spikes in polar ice cores are contentiously used to estimate the intensity, frequency, and probability of historical solar proton events, quantities that are needed to prepare for potentially society-crippling space weather events. We use the Whole Atmosphere Community Climate Model to calculate how large an event would have to be to produce enough odd nitrogen throughout the atmosphere to be discernible as nitrate peaks at the Earth's surface. These hypothetically large events are compared with probability of occurrence estimates derived from measured events, sunspot records, and cosmogenic radionuclides archives. We conclude that the fluence and spectrum of solar proton events necessary to produce odd nitrogen enhancements equivalent to the spikes of nitrate ions in Greenland ice cores are unlikely to have occurred throughout the Holocene, confirming that nitrate ions in ice cores are not suitable proxies for historical individual solar proton events.

  14. Evidence for warmer interglacials in East Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Sime, L.; Wolff, E.; Oliver, K.; Tindall, J.

    2009-04-01

    Stable isotope ratios of oxygen and hydrogen in the Antarctic ice record provide invaluable proxy temperature information. Conversions from these isotope ratios to temperature are generally based on geographical observations of the spatial relationship. The relationship is said to be uniform

  15. Magnetic properties of aerosol dust in Antarctic ice cores as a proxy for dust provenance

    NASA Astrophysics Data System (ADS)

    Lanci, L.; Delmonte, B.

    2012-04-01

    Laboratory-induced remanent magnetization of polar ice is a measurement of the magnetization carried by the ferromagnetic dust particles in the ice. Ferromagnetic minerals in the aerosol dust have variable rock-magnetic properties and concentration that are directly related to the source material and transport dynamics. Magnetic methods, which are particularly effective in recognizing volcanic material and highly oxidized soils, can be used as a tool to discriminate among aerosol dust sources. In Antarctic ice the rock-magnetism of aerosol dust showed, in fact, distinct properties in ice from glacial and interglacial periods that may reflect different dust source areas. The comparison of magnetic properties of ice samples with that from Possible Source Area (PSA) samples shows a general good agreement between South American PSA and glacial ice dust. However, many questions are risen when considering the magnetic properties of interglacial samples from both Dome-C and Talos Dome ice cores. No good agreement has been found between interglacial samples and any of the measured PSA samples from the most common areas, suggesting that these cores have a significant contribution of dust from a source that has not been yet taken into consideration. In particular, the extremely high IRM measured in some interglacial samples is likely to be explained only with a large concentration of Fe-rich rocks such as volcanic or meteoritic material.

  16. Carbonaceous aerosol tracers in ice-cores record multi-decadal climate oscillations

    PubMed Central

    Seki, Osamu; Kawamura, Kimitaka; Bendle, James A. P.; Izawa, Yusuke; Suzuki, Ikuko; Shiraiwa, Takayuki; Fujii, Yoshiyuki

    2015-01-01

    Carbonaceous aerosols influence the climate via direct and indirect effects on radiative balance. However, the factors controlling the emissions, transport and role of carbonaceous aerosols in the climate system are highly uncertain. Here we investigate organic tracers in ice cores from Greenland and Kamchatka and find that, throughout the period covered by the records (1550 to 2000 CE), the concentrations and composition of biomass burning-, soil bacterial- and plant wax- tracers correspond to Arctic and regional temperatures as well as the warm season Arctic Oscillation (AO) over multi-decadal time-scales. Specifically, order of magnitude decreases (increases) in abundances of ice-core organic tracers, likely representing significant decreases (increases) in the atmospheric loading of carbonaceous aerosols, occur during colder (warmer) phases in the high latitudinal Northern Hemisphere. This raises questions about causality and possible carbonaceous aerosol feedback mechanisms. Our work opens new avenues for ice core research. Translating concentrations of organic tracers (?g/kg-ice or TOC) from ice-cores, into estimates of the atmospheric loading of carbonaceous aerosols (?g/m3) combined with new model constraints on the strength and sign of climate forcing by carbonaceous aerosols should be a priority for future research. PMID:26411576

  17. Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

    NASA Astrophysics Data System (ADS)

    Tison, J.-L.; de Angelis, M.; Littot, G.; Wolff, E.; Fischer, H.; Hansson, M.; Bigler, M.; Udisti, R.; Wegner, A.; Jouzel, J.; Stenni, B.; Johnsen, S.; Masson-Delmotte, V.; Landais, A.; Lipenkov, V.; Loulergue, L.; Barnola, J.-M.; Petit, J.-R.; Delmonte, B.; Dreyfus, G.; Dahl-Jensen, D.; Durand, G.; Bereiter, B.; Schilt, A.; Spahni, R.; Pol, K.; Lorrain, R.; Souchez, R.; Samyn, D.

    2015-08-01

    An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (?D-?18Oice, ?18Oatm, total air content, CO2, CH4, N2O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice-bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future "oldest ice" drilling location in Antarctica.

  18. Global ice-core research: Understanding and applying environmental records of the past

    USGS Publications Warehouse

    Cecil, L. DeWayne; Green, Jaromy R.; Naftz, David L.

    2000-01-01

    Environmental changes are of major concern at low- or mid-latitude regions of our Earth simply because this is where 80 to 90 percent of the world’s human population live. Ice cores collected from isolated polar regions are, at best, proxy indicators of low- and mid-latitude environmental changes. Because polar icecore research is limiting in this sense, ice cores from low- and mid-latitude glaciers are being used to study past environmental changes in order to better understand and predict future environmental changes that may affect the populated regions of the world.

  19. Interlaboratory comparison of 10Be concentrations in two ice cores from Central West Antarctica

    NASA Astrophysics Data System (ADS)

    Woodruff, Thomas E.; Welten, Kees C.; Caffee, Marc W.; Nishiizumi, Kunihiko

    2013-01-01

    To improve sample processing efficiency for cosmogenic radionuclide measurements in samples from the West Antarctic Ice Sheet Divide core, two chemical lines, one at Purdue University and one at the University of California, Berkeley, are being used. Sections from two shallow ice cores from West Antarctica were processed at each lab, while all 10Be accelerator mass spectrometry measurements were performed at PRIME Lab, Purdue University. Duplicate samples gave 10Be results that are identical to within the AMS measurement uncertainties of 2-3%.

  20. Neutrino oscillations with IceCube DeepCore and PINGU

    SciTech Connect

    DeYoung, T.; Collaboration: IceCube-PINGU Collaboration

    2014-11-18

    The IceCube neutrino telescope was augmented with the DeepCore infill array, completed in the 2010/11 austral summer, to enhance its response to neutrinos below 100 GeV. At these energies, neutrino oscillation effects are visible in the flux of atmospheric neutrinos traversing path lengths comparable to the Earth's diameter. Initial measurements of muon neutrino disappearance parameters using data from DeepCore are presented, as well as an estimate of potential future precision. In addition, plans for a Precision IceCube Next Generation Upgrade (PINGU), which could permit determination of the neutrino mass hierarchy within the coming decade, are discussed.

  1. Detailed history of atmospheric trace elements from the Quelccaya ice core (Southern Peru) during the last 1200 years

    NASA Astrophysics Data System (ADS)

    Uglietti, C.; Gabrielli, P.; Thompson, L. G.

    2013-12-01

    The recent increase in trace element concentrations, for example Cr, Cu, Zn, Ag, Pb, Bi, and U, in polar snow and ice has provided compelling evidence of a hemispheric change in atmospheric composition since the nineteenth century. This change has been concomitant with the expansion of the Industrial Revolution and points towards an anthropogenic source of trace elements in the atmosphere. There are very few low latitude trace element ice core records and these are believed to be sensitive to perturbations of regional significance. To date, these records have not been used to document a preindustrial anthropogenic impact on atmospheric composition at low latitudes. Ice cores retrieved from the tropical Andes are particularly interesting because they have the potential to reveal detailed information about the evolution and environmental consequences of mineral exploitation related to the Pre Inca Civilizations, the Inca Empire (1438-1533 AD) and the subsequent Spanish invasion and dominance (1532-1833 AD). The chemical record preserved in the ice of the Quelccaya ice cap (southern Peruvian Andes) offers the exceptional opportunity to geochemically constrain the composition of the tropical atmosphere at high resolution over the last ~1200 years. Quantification of twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V, and Zn) was performed by ICP-SFMS over 105 m of the Quelccaya North Dome core (5600 m asl, 128.57 m) by analyzing 2450 samples. This provides the first atmospheric trace element record in South America spanning continuously and at high resolution for the time period between 1990 and 790 AD. Ag, As, Bi, Cd, Cr, Co, Cu, Mn, Mo, Sb, Sn, Pb and Zn show increases in concentration and crustal enrichment factor starting at different times between 1450 and 1550 AD, in concomitance with the expansions of the Inca Empire and, subsequently, the Spanish Empire well before the inception of the Industrial Revolution. This indicates that there have been additional anthropogenic sources that have impacted the South American atmosphere during the past ~550 years. Furthermore, As, Bi and Pb record shows, the two most significant increases have occurred in the 20th century, one beginning in ~1905 AD and peaking in the 1920s and the second beginning in ~1955 AD and peaking in the 1970s. Comparison with other trace element records from Greenland and Antarctica reveals concomitant peaks of different amplitude in Pb concentration and crustal enrichment factor, possibly pointing to an unexpected larger than regional scale significance for the Quelccaya ice core record during the last century. In conclusion, the Quelccaya ice core indicates that societal and industrial development influenced the atmospheric composition in South America, from different large scale sources, during the last ~550 years. This is the first time that a low latitude ice core record has been used to reconstruct pre-industrial anthropogenic forcing on the atmosphere.

  2. cm-scale variations of crystal orientation fabric in cold Alpine ice core from Colle Gnifetti

    NASA Astrophysics Data System (ADS)

    Kerch, Johanna; Weikusat, Ilka; Eisen, Olaf; Wagenbach, Dietmar; Erhardt, Tobias

    2015-04-01

    Analysis of the microstructural parameters of ice has been an important part of ice core analyses so far mainly in polar cores in order to obtain information about physical processes (e.g. deformation, recrystallisation) on the micro- and macro-scale within an ice body. More recently the influence of impurities and climatic conditions during snow accumulation on these processes has come into focus. A deeper understanding of how palaeoclimate proxies interact with physical properties of the ice matrix bears relevance for palaeoclimatic interpretations, improved geophysical measurement techniques and the furthering of ice dynamical modeling. Variations in microstructural parameters e.g. crystal orientation fabric or grain size can be observed on a scale of hundreds and tens of metres but also on a centimetre scale. The underlying processes are not necessarily the same on all scales. Especially for the short-scale variations many questions remain unanswered. We present results from a study that aims to investigate following hypotheses: 1. Variations in grain size and fabric, i.e. strong changes of the orientation of ice crystals with respect to the vertical, occur on a centimetre scale and can be observed in all depths of an ice core. 2. Palaeoclimate proxies like dust and impurities have an impact on the microstructural processes and thus are inducing the observed short-scale variations in grain size and fabric. 3. The interaction of proxies with the ice matrix leads to depth intervals that show correlating behaviour as well as ranges with anticorrelation between microstructural parameters and palaeoclimatic proxies. The respective processes need to be identified. Fabric Analyser measurements were conducted on more than 80 samples (total of 8 m) from different depth ranges of a cold Alpine ice core (72 m length) drilled in 2013 at Colle Gnifetti, Switzerland/Italy. Results were obtained by automatic image processing, providing estimates for grain size distributions and crystal orientation fabric, and comparison with data from continuous flow analysis of chemical impurities. A microstructural characterisation of the analysed core is presented with emphasis on the observed variations in crystal orientation fabric. The relevance of these results for palaeoclimate reconstruction and geophysical applications in ice are discussed.

  3. Simple procedure for ion chromatographic determination of anions and cations at trace levels in ice core samples

    E-print Network

    Moore, John

    Simple procedure for ion chromatographic determination of anions and cations at trace levels in ice for the determination of ng mlÀ1 levels of major cations and anions, including formate and methyl sulphonate, in ice. Keywords: Ice core; Ion chromatography; Anions; Cations 1. Introduction Low detection limits and high

  4. Greenland ice reveals imprint of the Early Cenozoic passage of the Iceland mantle plume

    NASA Astrophysics Data System (ADS)

    Rogozhina, I.; Petrunin, A. G.; Vaughan, A. P.; Kaban, M. K.; Mulvaney, R.; Steinberger, B. M.; Koulakov, I.; Thomas, M.; Johnson, J. V.

    2013-12-01

    Modelling and observation of ice sheet basal conditions suggests that elevated values of geothermal heat flow (GHF) result in enhanced basal melting. For the Greenland Ice Sheet (GIS), radar soundings and deep ice core measurements indicate unexpectedly high local values of GHF in areas where thick and stable Early Proterozoic lithosphere suggests they should be low. Rapid basal ice melt and accelerated ice flow, linked to abnormal GHF, indicate that regional heat flow patterns strongly influence the present-day thermodynamic state of the GIS and may affect its evolution in the future. Using a coupled model of climate-driven GIS and lithosphere, constrained by a wide range of interdisciplinary data, we detect a laterally continuous west-to-east area of high GHF in central-northern Greenland. The area of elevated heat flow closely coincides with a west-to-east negative anomaly in seismic velocity, which recent high-resolution tomography models tie to the present-day location of the Iceland mantle plume. Plate paleoreconstructions and analysis of magmatism in eastern and western Greenland suggest passage of the Greenland lithosphere over a mantle plume between around 80 and 35 Ma. Independent evidence under the GIS for magmatism along the putative mantle plume track comes from local gravity anomalies, igneous rock fragments recovered from the bedrock beneath the deep ice core GISP2, and radar sounding evidence of a caldera-like bedrock structure under the central GIS. We argue that long-lived, non-stationary effects of the mantle plume still affect the thermal state of the present-day Greenland lithosphere and are the origin of rapid basal ice melting over vast areas of central and northern Greenland.

  5. A 2000 year atmospheric history of methyl chloride from a South Pole ice core: Evidence for climate-controlled variability

    E-print Network

    Saltzman, Eric

    A 2000 year atmospheric history of methyl chloride from a South Pole ice core: Evidence for climate 2007; revised 17 February 2007; accepted 7 March 2007; published 13 April 2007. [1] Methyl chloride (CH history of methyl chloride from a South Pole ice core: Evidence for climate- controlled variability

  6. A 100-year record of North Pacific volcanism in an ice core from Eclipse Icefield, Yukon Territory, Canada

    E-print Network

    Kurapov, Alexander

    A 100-year record of North Pacific volcanism in an ice core from Eclipse Icefield, Yukon Territory Pacific over the last century has been developed using a glaciochemical record from Eclipse Icefield, Yukon Territory, Canada. Tephrochronology of the Eclipse ice core provides positive identification

  7. Advances in reconstructing past atmospheric oxidation chemistry using the oxygen isotope composition of nitrate and sulfate in ice cores

    E-print Network

    Winglee, Robert M.

    composition of nitrate and sulfate in ice cores Shelley A. Kunasek A dissertation submitted in partial composition of nitrate and sulfate in ice cores Shelley A. Kunasek Chair of the Supervisory Committee of nitrate and sulfate (!17 O(NO3 - ) and !17 O(SO4 2- )(!17 O " !17 O ­ 0.52" (!18 O)) provide a means

  8. Volcanic Forcing of Climate over the Past 1500 Years: An Improved Ice-Core-Based Index for Climate Models

    E-print Network

    Robock, Alan

    Volcanic Forcing of Climate over the Past 1500 Years: An Improved Ice-Core-Based Index for Climate: Volcanic forcing of climate over the past 1500 years: An improved ice-core-based index for climate models stratospheric volcanic sulfate aerosol injections for the period from 501 to 2000 AD. Units are Tg sulfate

  9. Recent History of the NW Corner of the Ross Ice Shelf, Antarctica, from Sediment Cores

    NASA Astrophysics Data System (ADS)

    Barrett, P.; Dunbar, G.; Carter, L.; Giorgetti, G.; Niessen, F.; Nixdorf, U.; Pyne, A.; Riesselman, C.; Robinson, N.

    2003-12-01

    Cores of sea floor sediments beneath the Ross Ice Shelf behind Ross Island contain a record of sub-ice shelf sedimentation over the last 20,000 years. The sediments have been accumulating in a 900-m-deep depression resulting from the loading of Erebus volcano, and are being deposited from relatively slow (5-10 cm/sec) currents whose average flow direction is eastward (from McMurdo Sound toward the central Ross Sea). Cores from the two sites were both 60 cm long, but significantly different in character. The core from site 1 was taken about 5 km east of the shelf edge where the ice is 70 m thick. It is an unconsolidated pebbly sandy mud from 62 to 34 cm below the sea floor, where it changes over a cm to a soft fine sandy mud that dominates the rest of the core. Samples yielded uncorrected AMS bulk organic carbon ages of 24,550 years at 34 cm, 18,080 years at 21 cm and 4343 years at 1 cm, indicating an average sedimentation rate of 0.03 mm/year. The changes in sedimentary facies are taken to record a shift of the grounding line landward followed by establishment of the present open circulation that continued to the present day. The low shear strength throughout the core shows that the ice shelf was not grounded, even at the height of the Last Glacial Maximum. The core from site 2, which lies 12 km east of the shelf edge beneath 140 m of ice, is entirely a soft terrigenous sandy mud with a higher diatom content than the upper part of site 1, but similar in other respects. It yielded ages from 12,797 years at 59 cm, 6562 years at 29 cm and 2701 years at 2 cm, indicating a higher sedimentation rate (0.06 mm/year), and records relatively constant conditions throughout that time. The facies and chronology suggest that the Ross Ice Shelf front has not retreated significantly from its present position during the Holocene. The cores also indicate the potential value for recovering a history for the Ross Ice Shelf back to Pliocene times through the proposed coring of Windless Bight by the ANDRILL consortium to 1000 m below the sea floor.

  10. A 420 Year Annual 10Be Record from the WAIS Divide Ice Core

    NASA Astrophysics Data System (ADS)

    Woodruff, T. E.; Welten, K. C.; Caffee, M. W.; Nishiizumi, K.

    2011-12-01

    Annual ice layers archive the cosmogenic radionuclide 10Be, which is in turn an important proxy for solar activity, complementary to the 14C tree ring archive. Although production is primarily determined by the strength of the solar magnetic field 10Be deposition is also determined by local weather phenomena and snow accumulation rates, especially within shorter timescales. Accordingly, multiple ice core records of varying locations and accumulation rates are necessary to build a representative 10Be archive. We are presently engaged in a study to obtain continuous 10Be and 36Cl records in the West Antarctic Ice Sheet (WAIS) Divide ice core, a high snow accumulation site analogous to the GISP2 core from Greenland (Finkel and Nishiizumi1997). Here we present an annual resolution record of 10Be in the WAIS Divide core spanning the last 420 years including the Maunder (1645-1715 AD) and Dalton (1790-1830 AD) solar minima. Preliminary results for the periods of 1580-1740 and 1945-2006 AD show that the10Be flux during the Maunder Minimum was ~60% higher than in the last 60 years (4.8 vs. 3.0 x 105 atoms yr-1 cm-2). Although the low sunspot numbers during the Maunder Minimum suggest little change in solar activity, the 10Be data show that the heliomagnetic field strength continued to vary in a 11-year cycle, as observed in other annual 10Be records (e.g., Beer et al. 1990; Berggren et al. 2009). The 10Be record for the WAIS Divide core will be compared to 10Be records of Greenland ice cores as well as the 14C tree ring record. Acknowledgment. This work was supported by NSF grants ANT-0839042 and 0839137. Beer J. et al. 1990.Nature 347, 164. Finkel R. C. and Nishiizumi K. 1997.J. Geophys. Res. 102, 26,699. Berggren A.- M., et al. 2009. Geophys. Res. Lett. 36, L11801.

  11. Phylogenetic analysis of anaerobic psychrophilic enrichment cultures obtained from a greenland glacier ice core

    NASA Technical Reports Server (NTRS)

    Sheridan, Peter P.; Miteva, Vanya I.; Brenchley, Jean E.

    2003-01-01

    The examination of microorganisms in glacial ice cores allows the phylogenetic relationships of organisms frozen for thousands of years to be compared with those of current isolates. We developed a method for aseptically sampling a sediment-containing portion of a Greenland ice core that had remained at -9 degrees C for over 100,000 years. Epifluorescence microscopy and flow cytometry results showed that the ice sample contained over 6 x 10(7) cells/ml. Anaerobic enrichment cultures inoculated with melted ice were grown and maintained at -2 degrees C. Genomic DNA extracted from these enrichments was used for the PCR amplification of 16S rRNA genes with bacterial and archaeal primers and the preparation of clone libraries. Approximately 60 bacterial inserts were screened by restriction endonuclease analysis and grouped into 27 unique restriction fragment length polymorphism types, and 24 representative sequences were compared phylogenetically. Diverse sequences representing major phylogenetic groups including alpha, beta, and gamma Proteobacteria as well as relatives of the Thermus, Bacteroides, Eubacterium, and Clostridium groups were found. Sixteen clone sequences were closely related to those from known organisms, with four possibly representing new species. Seven sequences may reflect new genera and were most closely related to sequences obtained only by PCR amplification. One sequence was over 12% distant from its closest relative and may represent a novel order or family. These results show that phylogenetically diverse microorganisms have remained viable within the Greenland ice core for at least 100,000 years.

  12. Climate Variability in West Antarctica Derived from Marine Aerosol Species from ITASE Firn/Ice Cores

    NASA Astrophysics Data System (ADS)

    Kaspari, S. D.; Mayewski, P. A.; Dixon, D. A.; Sneed, S. B.

    2003-12-01

    Marine aerosol species (sodium, chloride, magnesium, sulfate) from 13 high-resolution ice cores covering the last approximately 200 years from the Pine Island-Thwaites and Ross drainage systems and the South Pole are used to examine climate variability in West Antarctica. The large-scale spatial distribution of the ice cores improves characterization of the source regions and pathways of marine aerosols into West Antarctica. The Ross Sea is the dominant source region for marine aerosols in the study area, and the dominant pathway is across the Ross Ice Shelf. Factors contributing to the amount of marine aerosols transported inland are strength and positioning of low pressure systems, sea-ice extent, and wind strength. Associations of the sodium time-series with sea level pressure are investigated using the National Centers for Environmental Prediction (NCEP) data reanalysis, the Southern Oscillation Index (SOI), and Trans-Polar Index (TPI). Sea-ice associations are explored by correlating sea-ice extent with the marine aerosol time-series, and wind strength is investigated using a circumpolar vortex index and the NCEP meridional and zonal wind fields. The associations demonstrate that West Antarctic climate is extremely dynamic, with regional differences in the mechanisms driving marine aerosol variability.

  13. Investigating the preservation of nitrate isotopic composition in a tropical ice core from the Quelccaya Ice Cap, Peru

    NASA Astrophysics Data System (ADS)

    Buffen, Aron M.; Hastings, Meredith G.; Thompson, Lonnie G.; Mosley-Thompson, Ellen

    2014-03-01

    The nitrogen and oxygen isotopic composition of nitrate in ice cores offers unique potential for examining reactive nitrogen oxide (NOx) budgets and oxidation chemistry of past atmospheres. A low-latitude record is of particular interest given that the dominant natural sources of NOx and production of hydroxyl radical are most prevalent in the tropics. Any interpretation of nitrate in ice cores, however, must first consider that nitrate in snow is vulnerable to postdepositional loss and isotopic alteration. We report and assess the integrity of nitrate-?15N, -?18O, and -?17O in a 30 m ice core from a high-elevation site in the central Andes. Clear seasonality in ?15N, ?18O, and nitrate concentration exists throughout most of the record and cannot be explained by photolysis or evaporation based on our current understanding of these processes. In contrast, nitrate in the upper ~12 m of the core and in a snowpit shows very different behavior. This may reflect alteration facilitated by recent melting at the surface. The relationships between ?15N, ?18O, ?17O, and concentration in the unaltered sections can be interpreted in terms of mixing of nitrate from discrete sources. Transport effects and an englacial contribution from nitrification cannot be ruled out at this time, but the observed isotopic compositions are consistent with expected signatures of known NOx sources and atmospheric oxidation pathways. Specifically, nitrate deposited during the wet season reflects biogenic soil emissions and hydroxyl/peroxy radical chemistry in the Amazon, while dry season deposition reflects a lightning source and ozone chemistry at higher levels in the troposphere.

  14. An 80-year summer temperature history from the Xiao Dongkemadi ice core in the central Tibetan Plateau and its association with atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Li, Xiangying; Ding, Yongjian; Yu, Zhongbo; Mika, Sillanpää; Liu, Shiyin; Shangguan, Donghui; Lu, Chengyang

    2015-02-01

    The climate significance of oxygen isotopes from the central Tibetan Plateau (cTP) ice cores is a debated issue because of large scale atmospheric circulation. A high-resolution ?18O record was recovered from the Xiao Dongkemadi (XD) ice core, which expanded the spatial coverage of ?18O data in this region. Annual average ?18O correlated significantly with nearby MJJAS air temperatures, suggesting the ?18O can be used as a proxy to reconstruct regional climate change. The reconstructed temperature anomaly is related to the regional and global warming trends, and the greater warming amplitude since 1970s is related to the elevation dependency of the warming signal. The close relationship of the warming to variations in glacier mass balances and discharge reveal that recent warming has led to obvious glacier shrinkage and runoff increase. Correlation analysis suggests that monsoon and westerly moisture substantially influence the cTP ice core records, along with an increase in their level of contribution to the XD core accumulation in recent decades, and confirms a teleconnection of regional climate of the cTP ice cores with climate parameters in the Indian and North Atlantic Oceans.

  15. Warm climate isotopic simulations: what do we learn about interglacial signals in Greenland ice cores?

    NASA Astrophysics Data System (ADS)

    Sime, Louise C.; Risi, Camille; Tindall, Julia C.; Sjolte, Jesper; Wolff, Eric W.; Masson-Delmotte, Valérie; Capron, Emilie

    2013-05-01

    Measurements of Last Interglacial stable water isotopes in ice cores show that central Greenland ?18O increased by at least 3‰ compared to present day. Attempting to quantify the Greenland interglacial temperature change from these ice core measurements rests on our ability to interpret the stable water isotope content of Greenland snow. Current orbitally driven interglacial simulations do not show ?18O or temperature rises of the correct magnitude, leading to difficulty in using only these experiments to inform our understanding of higher interglacial ?18O. Here, analysis of greenhouse gas warmed simulations from two isotope-enabled general circulation models, in conjunction with a set of Last Interglacial sea surface observations, indicates a possible explanation for the interglacial ?18O rise. A reduction in the winter time sea ice concentration around the northern half of Greenland, together with an increase in sea surface temperatures over the same region, is found to be sufficient to drive a >3‰ interglacial enrichment in central Greenland snow. Warm climate ?18O and ?D in precipitation falling on Greenland are shown to be strongly influenced by local sea surface condition changes: local sea surface warming and a shrunken sea ice extent increase the proportion of water vapour from local (isotopically enriched) sources, compared to that from distal (isotopically depleted) sources. Precipitation intermittency changes, under warmer conditions, leads to geographical variability in the ?18O against temperature gradients across Greenland. Little sea surface warming around the northern areas of Greenland leads to low ?18O against temperature gradients (0.1-0.3‰ per °C), whilst large sea surface warmings in these regions leads to higher gradients (0.3-0.7‰ per °C). These gradients imply a wide possible range of present day to interglacial temperature increases (4 to >10 °C). Thus, we find that uncertainty about local interglacial sea surface conditions, rather than precipitation intermittency changes, may lead to the largest uncertainties in interpreting temperature from Greenland ice cores. We find that interglacial sea surface change observational records are currently insufficient to enable discrimination between these different ?18O against temperature gradients. In conclusion, further information on interglacial sea surface temperatures and sea ice changes around northern Greenland should indicate whether +5 °C during the Last Interglacial is sufficient to drive the observed ice core ?18O increase, or whether a larger temperature increases or ice sheet changes are also required to explain the ice core observations.

  16. Retrieving a Common Accumulation Record From Greenland Ice Cores for the Past 1800 Years

    NASA Astrophysics Data System (ADS)

    Andersen, K. K.; Ditlevsen, P. D.; Rasmussen, S. O.; Clausen, H. B.; Johnsen, S. J.

    2005-12-01

    In the accumulation zone of the Greenland ice sheet the annual accumulation rate may be identified through identification of the annual cycle in the isotopic climate signal and other seasonally varying parameters. On an annual basis the accumulation rate in different Greenland ice cores is highly variable, and the degree of correlation between the accumulation series from different ice cores is low. When using multiyear averages of the different accumulation records the correlation however increases significantly. A statistical model has been developed estimating the common climate signal in the different records through optimization of the signal to noise variance ratio. A common Greenland accumulation record with five years resolution for the past 1800 years has been extracted. The record establishes a climatic record which points to a possible cause for the disappearance of the Norse settlements in Greenland.

  17. Statistical distributions of ice core sulfate from climatically relevant volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Naveau, P.; Ammann, C. M.

    2005-03-01

    Quantitative knowledge of external climate forcing is required for accurately attributing past climatic changes. Information on volcanic activity over the past millennium has primarily been drawn from high-latitude ice cores. A few large events with distinct signatures in the ice are well known and they are commonly used as marker events to synchronize time scales in individual ice cores. Over the past decade different efforts have been undertaken to systematically identify lesser known eruptions and to develop time series of past volcanic forcing. Here we mathematically quantify the distribution of the magnitude of volcanic events that have a climatic relevance during the past millennium. Volcanic sulfate magnitudes of such events clearly exhibit a ``heavy tailed'' extreme value distribution. Indeed, the climatically relevant eruptions are only the extremes of global volcanic activity. This characterization of volcanic amplitude is a fundamental step in detection and attribution studies of past natural forcing and of its effects on climate.

  18. Cosmogenic production and climate contributions to nitrate record in the TALDICE Antarctic ice core

    E-print Network

    Usoskin, Ilya G.

    the TALDICE drilling project (Talos Dome, Antarctica), which covers the age range 12,000­700 BP (years before the Earth. Galactic cosmic ray flux is modulated by solar activity in the heliosphere and is roughly that the nitrate record from the TALDICE ice core depicts significant coherence with the cosmogenic radiocarbon 14

  19. 10Be climate fingerprints during the Eemian in the NEEM ice core, Greenland

    PubMed Central

    Sturevik-Storm, Anna; Aldahan, Ala; Possnert, Göran; Berggren, Ann-Marie; Muscheler, Raimund; Dahl-Jensen, Dorthe; Vinther, Bo M.; Usoskin, Ilya

    2014-01-01

    Several deep Greenland ice cores have been retrieved, however, capturing the Eemian period has been problematic due to stratigraphic disturbances in the ice. The new Greenland deep ice core from the NEEM site (77.45°N, 51.06°W, 2450?m.a.s.l) recovered a relatively complete Eemian record. Here we discuss the cosmogenic 10Be isotope record from this core. The results show Eemian average 10Be concentrations about 0.7 times lower than in the Holocene which suggests a warmer climate and approximately 65–90% higher precipitation in Northern Greenland compared to today. Effects of shorter solar variations on 10Be concentration are smoothed out due to coarse time resolution, but occurrence of a solar maximum at 115.26–115.36?kyr BP is proposed. Relatively high 10Be concentrations are found in the basal ice sections of the core which may originate from the glacial-interglacial transition and relate to a geomagnetic excursion about 200?kyr BP. PMID:25266953

  20. Inferring paleo-accumulation records from ice-core data by an adjoint method

    NASA Astrophysics Data System (ADS)

    Martin, Carlos; Hilmar Gudmundsson, G.; Mulvaney, Robert; Corr, Hugh

    2014-05-01

    Ice cores contain a record of Earth's climate, and are used to understand how recently observed changes in climate fit within a long history of natural climatic variability. For a complete climatic record, a dated history of snow-accumulation needs to be derived as this gives information about past atmospheric circulation and a history of mass imbalance for the polar regions. We present here a novel adjoint method to construct a complete climatic record by both optimally dating an ice-core and deriving from it a detailed accumulation history. Our modelling approach uses all the available data extracted from the ice-core of the distribution with depth of age and thickness of an annual layer and present temperature. We discuss the applicability of our method to different ice-core characteristics and time-scales, and compare our method results with more commonly employed Bayesian techniques. We conclude that our methodology is more efficient and deals better with noise in the observed variables.

  1. Atmospheric volcanic loading derived from bipolar ice cores: Accounting for the spatial distribution of volcanic deposition

    E-print Network

    Robock, Alan

    records and state-of-the-art climate model simulations of volcanic deposition, we now have a unique sulfate deposition in eight Antarctic ice cores, and climate model simulations of volcanic sulfate pollution and land surface modification on climate. Of all the natural causes, volcanic eruptions and solar

  2. PeV neutrinos observed by IceCube from cores of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Stecker, Floyd W.

    2013-08-01

    I show that the high energy neutrino flux predicted to arise from active galactic nuclei cores can explain the PeV neutrinos detected by IceCube without conflicting with the constraints from the observed extragalactic cosmic-ray and ?-ray backgrounds.

  3. PeV Neutrinos Observed by IceCube from Cores of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.

    2013-01-01

    I show that the high energy neutrino flux predicted to arise from active galactic nuclei cores can explain the PeV neutrinos detected by IceCube without conflicting with the constraints from the observed extragalactic cosmic-ray and gamma-ray backgrounds.

  4. The GISP ice core record of volcanism since 7000 B.C.

    SciTech Connect

    Fiedel, S.J.

    1995-01-13

    Two technical comments are presented on an article by Zielinski concerning the GISP ice core record of volcanic activity in 7000 BC, including a detailed record of the volcanic contribution to sulfate concentrations. The authors describe concerns about (1) correct C14 dating for known eruptions correlated to calendar years and (2) the need for unambiguous volcanic source identifications. 24 refs., 1 tab.

  5. Time-series analysis of chemical trends in a dated ice core from Antarctica

    SciTech Connect

    Keskin, S.S.; Olmez, I.; Langway, C.C. Jr.

    1994-12-31

    Polar ice sheets contain valuable information about past atmospheric conditions. Atmospherically produced or transported substances from natural and anthropogenic sources are preserved stratigraphically within the ice layers as a result of both wet and dry deposition mechanisms. Substances deposited include aerosols and gaseous compounds. The analysis of trace elements contained in dated annual snow layers provides a measure of the elemental chemistry content of the atmosphere during the same time interval. The aerosol content of the atmosphere and ice sheets is one of the most important parameters for cloud/radiation interaction processes. Ice cores were obtained from the Byrd Station, West Antarctica, in November, 1989. This study presents results obtained from instrumental neutron activation analysis and ion chromatography on 30 samples over a 20 year period.

  6. High-precision measurements of 14C in ice cores: results and future prospects

    NASA Astrophysics Data System (ADS)

    Petrenko, V. V.; Severinghaus, J. P.; Smith, A. M.; Schaefer, H.; Riedel, K.; Brook, E.; Buizert, C.; Baggenstos, D.; Harth, C. M.; Hua, Q.; Orsi, A. J.; Bauska, T. K.; Schilt, A.; Mitchell, L.; Fain, X.; Takeshita, Y.; Lee, J. E.; Brailsford, G.; Franz, P.; Weiss, R. F.; Dickson, A. G.

    2012-12-01

    Measurements of 14C in carbon dioxide (CO2), methane (CH4) and carbon monoxide (CO) from glacial ice are potentially useful for absolute dating of ice cores, studies of the past atmospheric CH4 budget and for reconstructing the past cosmic ray flux and solar activity. Interpretation of 14C signals in ice is complicated by the fact that there is a poorly-understood in situ cosmogenic component in addition to the trapped atmospheric component. A new analytical system allowed 14C of CH4 in glacial ice to be measured for the first time and improved measurement precision for 14C of CO in ice by an order of magnitude over prior work. Measurements of 14C of CH4 in ablating Greenland ice suggested that wetlands were the likely main driver of the Younger Dryas - Preboreal rapid atmospheric CH4 rise ? 11,600 yr ago, but interpretation was complicated by what appeared to be an unexpected significant in situ cosmogenic 14CH4 component. Subsequent measurements in shallow firn at Greenland Summit and in 50-kyr-old ablating ice at Taylor Glacier, Antarctica ice definitively confirmed in situ cosmogenic 14CH4 production in glacial ice. The Taylor Glacier measurements also precisely quantified the in situ 14CH4 / 14CO ratio for muogenic 14C production (0.0078 ± 0.0001). The observed constancy of this ratio demonstrated that 14C of CO can be used to quantify the cosmogenic 14CH4 content, allowing for accurate reconstructions of the absolute paleo-atmospheric 14C of CH4 from glacial ice. Measurements in Greenland shallow firn clearly demonstrated that almost all in situ cosmogenic 14C is rapidly lost from the shallow firn to the atmosphere. This implies that 14C of CO2 at most ice core sites is dominated by the atmospheric component and, with a 14CO-based correction for the cosmogenic component, can likely be used for absolute dating of ice. Even given the rapid in-situ cosmogenic 14C loss in the firn, 14C of CO is still expected to be dominated by the cosmogenic component and is a promising tracer for past cosmic ray flux.

  7. Metagenomics Reveals Microbial Community Composition And Function With Depth In Arctic Permafrost Cores

    NASA Astrophysics Data System (ADS)

    Jansson, J.; Tas, N.; Wu, Y.; Ulrich, C.; Kneafsey, T. J.; Torn, M. S.; Hubbard, S. S.; Chakraborty, R.; Graham, D. E.; Wullschleger, S. D.

    2013-12-01

    The Arctic is one of the most climatically sensitive regions on Earth and current surveys show that permafrost degradation is widespread in arctic soils. Biogeochemical feedbacks of permafrost thaw are expected to be dominated by the release of currently stored carbon back into the atmosphere as CO2 and CH4. Understanding the dynamics of C release from permafrost requires assessment of microbial functions from different soil compartments. To this end, as part of the Next Generation Ecosystem Experiment in the Arctic, we collected two replicate permafrost cores (1m and 3m deep) from a transitional polygon near Barrow, AK. At this location, permafrost starts from 0.5m in depth and is characterized by variable ice content and higher pH than surface soils. Prior to sectioning, the cores were CT-scanned to determine the physical heterogeneity throughout the cores. In addition to detailed geochemical characterization, we used Illumina MiSeq technology to sequence 16SrRNA genes throughout the depths of the cores at 1 cm intervals. Selected depths were also chosen for metagenome sequencing of total DNA (including phylogenetic and functional genes) using the Illumina HiSeq platform. The 16S rRNA gene sequence data revealed that the microbial community composition and diversity changed dramatically with depth. The microbial diversity decreased sharply below the first few centimeters of the permafrost and then gradually increased in deeper layers. Based on the metagenome sequence data, the permafrost microbial communities were found to contain members with a large metabolic potential for carbon processing, including pathways for fermentation and methanogenesis. The surface active layers had more representatives of Verrucomicrobia (potential methane oxidizers) whereas the deep permafrost layers were dominated by several different species of Actinobacteria. The latter are known to have a diverse metabolic capability and are able to adapt to stress by entering a dormant yet viable state. In addition, several isolates were obtained from different depths throughout the cores, including methanogens from some of the deeper layers. Together these data present a new view of potential geochemical cycles carried out by microorganisms in permafrost and reveal how community members and functions are distributed with depth.

  8. 115 year ice-core data from Akademii Nauk ice cap, Severnaya Zemlya: high-resolution record of Eurasian Arctic climate change

    E-print Network

    Fischer, Hubertus

    , as reflected by sodium and chloride, whereas sulphate and nitrate are strongly affected by anthropogenic percolation, this ice core provides valuable information on the regional climate and environmental history. We

  9. Reconstruction of recent climate change in Alaska from the Aurora Peak ice core, central Alaska

    NASA Astrophysics Data System (ADS)

    Tsushima, A.; Matoba, S.; Shiraiwa, T.; Okamoto, S.; Sasaki, H.; Solie, D. J.; Yoshikawa, K.

    2015-02-01

    A 180.17 m ice core was drilled at Aurora Peak in the central part of the Alaska Range, Alaska, in 2008 to allow reconstruction of centennial-scale climate change in the northern North Pacific. The 10 m depth temperature in the borehole was -2.2 °C, which corresponded to the annual mean air temperature at the drilling site. In this ice core, there were many melt-refreeze layers due to high temperature and/or strong insolation during summer seasons. We analyzed stable hydrogen isotopes (?D) and chemical species in the ice core. The ice core age was determined by annual counts of ?D and seasonal cycles of Na+, and we used reference horizons of tritium peaks in 1963 and 1964, major volcanic eruptions of Mount Spurr in 1992 and Mount Katmai in 1912, and a large forest fire in 2004 as age controls. Here, we show that the chronology of the Aurora Peak ice core from 95.61 m to the top corresponds to the period from 1900 to the summer season of 2008, with a dating error of ± 3 years. We estimated that the mean accumulation rate from 1997 to 2007 (except for 2004) was 2.04 m w.eq. yr-1. Our results suggest that temporal variations in ?D and annual accumulation rates are strongly related to shifts in the Pacific Decadal Oscillation index (PDOI). The remarkable increase in annual precipitation since the 1970s has likely been the result of enhanced storm activity associated with shifts in the PDOI during winter in the Gulf of Alaska.

  10. ``Pre-Vostok'' Greenhouse Gas Concentrations Reconstructed From the EPICA Dome C Ice Core

    NASA Astrophysics Data System (ADS)

    Stocker, T. F.; Siegenthaler, U.; Spahni, R.; Chappellaz, J.; Fischer, H.

    2004-12-01

    The new deep ice core recovered from Dome Concordia in the framework of EPICA, the European Project of Ice Coring in Antarctica, contains a continuous climate history of the past 740,000 years [EPICA Community Members, 2004]. We present the current status of measurements of CO2, CH4 and N2O on air trapped in the bubbles of the Dome C ice core. CO2 is measured using laser absorption spectroscopy on samples of less than 10 g of ice which are mechanically crushed or milled. CH4 and N2O are extracted using a melt-refreeze technique and then measured by gas chromatography. The ice core contains an uncontaminated climate record down to Marine Isotope Stage 14 (MIS 14) as verified by a consistent gas age/ice age difference determined at terminations V and VI. CO2 and CH4 results from MIS 11 show that the normal levels of greenhouse gases prevailed during this exceptionally long interglacial. This demonstrates that the length of the interglacial was not due to exceptionally high greenhouse gas levels. MIS 13 and earlier interglacials, however, show significantly colder interglacials. In addition, the glacials are shorter which results in a more balanced sequence of cold and warm phases. Measurements of the greenhouse gas concentrations are central in understanding the mechanisms in the climate system which cause the significant change of character of the ice age cycles at around 400 kyr BP. We will present greenhouse gas measurements covering the first of the "pre-Vostok" interglacials from MIS 11 to MIS 14 (410 to 550 kyr BP) for CO2, and from MIS 11 to MIS 16 (410 to 620 kyr BP) for CH4. These measurements will resolve the "EPICA Challenge" [Wolff et al., 2004] put out to modelers to predict the expected greenhouse gas levels prior to 400 kyr BP based on the knowledge of the orbital parameters, and known paleoclimatic proxies (sea level from marine sediment records, dust load and isotopic concentration of precipitation in Antarctica from the EPICA Dome C ice core). \\scriptsize EPICA Community Members, Nature, 429, 623-628, 2004. Wolff, E.W., et al., EOS; Trans. Am. Geophys. Un., in press, 2004.

  11. Air bubble migration rates as a proxy for bubble pressure distribution in ice cores

    NASA Astrophysics Data System (ADS)

    Dadic, Ruzica; Schneebeli, Martin; Bertler, Nancy

    2015-04-01

    Air bubble migration can be used as a proxy to measure the pressure of individual bubbles and can help constrain the gradual close-off of gas bubbles and the resulting age distribution of gases in ice cores. The close-off depth of single bubbles can vary by tens of meters, which leads to a distribution of pressures for bubbles at a given depth. The age distribution of gases (along with gas-age-ice-age differences) decreases the resolution of the gas level reconstructions from ice cores and limits our ability to determine the phase relationship between gas and ice, and thus, the impact of rapid changes of greenhouse gases on surface temperatures. For times of rapid climate change, including the last 150 years, and abrupt climate changes further back in the past, knowledge of the age distribution of the gases trapped in air bubbles will enable us to refine estimates of atmospheric changes. When a temperature gradient is applied to gas bubbles in an ice sample, the bubbles migrate toward warmer ice. This motion is caused by sublimation from the warm wall and subsequent frost deposition on the cold wall. The migration rate depends on ice temperature and bubble pressure and is proportional to the temperature gradient. The spread in migration rates for bubbles in the same samples at given temperatures should therefore reflect the variations in bubble pressures within a sample. Air bubbles with higher pressures would have been closed off higher in the firn column and thus have had time to equilibrate with the surrounding ice pressure, while air bubbles that have been closed off recently would have pressures that are similar to todays atmospheric pressure above the firn column. For ice under pressures up to ~13-16 bar, the pressure distribution of bubbles from a single depth provides a record of the trapping function of air bubbles in the firn column for a certain time in the past. We will present laboratory experiments on air bubble migration, using Antarctic ice core samples from a range of depths, to show that air bubble migration is a valid proxy for bubble pressure and can thus be used to determine the trapping function of air bubbles and gas age distribution for past conditions.

  12. A chemical pacemaker to refine chronology for the deep East Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    Petit, J. R.; Delmonte, B.; Lemieux-Dudon, B.; Parrenin, F.

    2009-04-01

    A current dating approach of ice core records of the deep East Antarctic ice cores relies on ice flow modelling (thinning function of ice layer) as well as on the estimate of the snow accumulation rate. By the use of inverse method, the modelled ice chronology is generally constrained by few dated horizons (volcanic, 10Be peaks from solar or from magnetic inversion related events…) and/or by orbital tuning process (temperature proxy, 18O of air bubbles…). In absence of absolute dating the orbital tuning from new data or proxies is attractive and may serve as a test of the modelled ice age. In this respect a proxy showing orbital frequencies is adequate if: i) it was not already used to constrain the modelled chronology, ii) it reflects properties of the ice rather than properties of the gas (to prevent gas-age/ice age uncertainties), iii) its physical link with insolation must be rather direct, iv) the precession band (20kyr) which supplies more tie points than the obliquity band (41kyr) should dominate. The continental dust and marine sodium records were so far not used to constrain the modelled chronology. The dust and marine sodium appear firstly correlated to patterns of temperature and therefore to the hydrologic cycle which influences at the same time the source emissions (for dust), the atmospheric cleansing and the deposition onto the ice sheet. Once the overall temperature effects is compensate by best fit functions, the residual signal for dust and sodium concentrations over the last 400 ky from Epica Dome C and Vostok records display strong precession oscillations for both sites. Interestingly, the sodium residuals appear to increase with austral summer insolation while the dust residuals decrease remaining out of phase. Such behaviour could be understood by a positive effect of insolation on sodium emission (strengthening of spring cyclonic activity…) and negative effect on dust sources (reduction of Patagonian dust emission by strengthening of Southern American monsoon…). This dual behaviour which need to be determined, allows combination of sodium and dust residuals providing a "chemical pacemaker" dominated by precession which could be used to refine the modelled chronology. A test was done on the EDC3 modelled age of the Epica Dome C deep ice core which covers the last 800ky.

  13. Recent climate tendencies on an East Antarctic ice shelf inferred from a shallow firn core network

    PubMed Central

    Schlosser, E; Anschütz, H; Divine, D; Martma, T; Sinisalo, A; Altnau, S; Isaksson, E

    2014-01-01

    Nearly three decades of stable isotope ratios and surface mass balance (SMB) data from eight shallow firn cores retrieved at Fimbul Ice Shelf, East Antarctica, in the Austral summers 2009–2011 have been investigated. An additional longer core drilled in 2000/2001 extends the series back to the early eighteenth century. Isotope ratios and SMB from the stacked record of all cores were also related to instrumental temperature data from Neumayer Station on Ekström Ice Shelf. Since the second half of the twentieth century, the SMB shows a statistically significant negative trend, whereas the ?18O of the cores shows a significant positive trend. No trend is found in air temperature at the nearest suitable weather station, Neumayer (available since 1981). This does not correspond to the statistically significant positive trend in Southern Annular Mode (SAM) index, which is usually associated with a cooling of East Antarctica. SAM index and SMB are negatively correlated, which might be explained by a decrease in meridional exchange of energy and moisture leading to lower precipitation amounts. Future monitoring of climate change on the sensitive Antarctic ice shelves is necessary to assess its consequences for sea level change. Key Points Mass balance and stable oxygen isotope ratios from shallow firn cores Decreasing trend in surface mass balance, no trend in stable isotopes Negative correlation between SAM and SMB PMID:25821663

  14. Joint inference of misaligned irregular time series with application to Greenland ice core data

    NASA Astrophysics Data System (ADS)

    Doan, T. K.; Haslett, J.; Parnell, A. C.

    2015-03-01

    Ice cores provide insight into the past climate over many millennia. Due to ice compaction, the raw data for any single core are irregular in time. Multiple cores have different irregularities; and when considered together, they are misaligned in time. After processing, such data are made available to researchers as regular time series: a data product. Typically, these cores are independently processed. This paper considers a fast Bayesian method for the joint processing of multiple irregular series. This is shown to be more efficient than the independent alternative. Furthermore, our explicit framework permits a reliable modelling of the impact of the multiple sources of uncertainty. The methodology is illustrated with the analysis of a pair of ice cores. Our data products, in the form of posterior marginals or joint distributions on an arbitrary temporal grid, are finite Gaussian mixtures. We can also produce process histories to study non-linear functionals of interest. More generally, the concept of joint analysis via hierarchical Gaussian process models can be widely extended, as the models used can be viewed within the larger context of continuous space-time processes.

  15. Radioactive fallouts as temporal makers for glacier ice cores dating

    NASA Astrophysics Data System (ADS)

    Clemenza, M.; Cucciati, G.; Maggi, V.; Pattavina, L.; Previtali, E.

    2012-06-01

    In this paper, we intend to show how analytical methods used in nuclear physics, as gamma spectroscopy, are powerful tools for the dating of environmental archives. Specifically, we will show how events related to the release in the environment of great amount of radioactive isotopes ( e.g., atmospheric nuclear test explosions) can be used as temporal markers in alpine glaciers. The radio-isotope selected for the dating of ice carrots is 137Cs , because of its chemical and nuclear properties. The radioactive measurements have been conducted using a low-background high-purity germanium detector. The sensitivity for the prepared samples is 10mBq/kg. We will illustrate how dating curves (date versus depth of the sample) can be considered as an absolute calibrator for all the other chemical dating methods used on glacier samples analyses.

  16. Chronological refinement of an ice core record at Upper Fremont Glacier in south central North America

    USGS Publications Warehouse

    Schuster, P.F.; White, D.E.; Naftz, D.L.; Cecil, L.D.

    2000-01-01

    The potential to use ice cores from alpine glaciers in the midlatitudes to reconstruct paleoclimatic records has not been widely recognized. Although excellent paleoclimatic records exist for the polar regions, paleoclimatic ice core records are not common from midlatitude locations. An ice core removed from the Upper Fremont Glacier in Wyoming provides evidence for abrupt climate change during the mid-1800s. Volcanic events (Krakatau and Tambora) identified from electrical conductivity measurements (ECM) and isotopic and chemical data from the Upper Fremont Glacier were reexamined to confirm and refine previous chronological estimates of the ice core. At a depth of 152 m the refined age-depth profile shows good agreement (1736 ?? 10 A.D.) with the 14C age date (1729 ?? 95 A.D.). The ??18O profile of the Upper Fremont Glacier (UFG) ice core indicates a change in climate known as the Little Ice Age (LIA). However, the sampling interval for ??18O is sufficiently large (20 cm) such that it is difficult to pinpoint the LIA termination on the basis of ??18O data alone. Other research has shown that changes in the ??18O variance are generally coincident with changes in ECM variance. The ECM data set contains over 125,000 data points at a resolution of 1 data point per millimeter of ice core. A 999-point running average of the ECM data set and results from f tests indicates that the variance of the ECM data decreases significantly at about 108 m. At this depth, the age-depth profile predicts an age of 1845 A.D. Results indicate the termination of the LIA was abrupt with a major climatic shift to warmer temperatures around 1845 A.D. and continuing to present day. Prediction limits (error bars) calculated for the profile ages are ??10 years (90% confidence level). Thus a conservative estimate for the time taken to complete the LIA climatic shift to present-day climate is about 10 years, suggesting the LIA termination in alpine regions of central North America may have occurred on a relatively short (decadal) timescale. Copyright 2000 by the American Geophysical Union.

  17. Investigation of a deep ice core from the Elbrus Western Plateau, the Caucasus, Russia

    NASA Astrophysics Data System (ADS)

    Mikhalenko, V.; Sokratov, S.; Kutuzov, S.; Ginot, P.; Legrand, M.; Preunkert, S.; Lavrentiev, I.; Kozachek, A.; Ekaykin, A.; Faïn, X.; Lim, S.; Schotterer, U.; Lipenkov, V.; Toropov, P.

    2015-07-01

    A 182 m ice core has been recovered from a borehole drilled through the glacier to the bedrock at the Western Plateau of Mt Elbrus (43°20'53.9'' N, 42°25'36.0'' E; 5115 m a.s.l.), the Caucasus, Russia, in 2009. This is the first ice core in the region which represents a paleoclimate record practically undisturbed by seasonal melting. Relatively high snow accumulation rate at the drilling site enabled analysis of the intra-seasonal climate proxies' variability. Borehole temperatures ranged from -17 °C at 10 m depth and -2.4 °C at 182 m. A detailed radio-echo sounding survey showed that the glacier thickness ranged from 45 m near marginal zone of the plateau up to 255 m at the central part. The ice core has been analyzed for stable isotopes (?18O and ? D), major ions (K+, Na+, Ca2+, Mg2+, NH4+, SO42-, NO3-, Cl-, F-), succinic acid (HOOCCH2COOH), and tritium content. The mean annual net accumulation rate was estimated from distinct annual oscillations of ?18O, ? D, succinic acid, and NH4+ and is 1455 mm w.e. for the last 140 years. Using annual layer counting also for the dating of the ice core, a good agreement with the absolute markers of the tritium 1963 bomb test time horizon located at the core depth of 50.7 m w.e. and the sulfate peak of the Katmai eruption (1912) at 87.7 m w.e. was obtained. According to mathematical modeling results, the bottom ice age at the maximal glacier depth is predicted to be about 660 years BP. As the 2009 borehole was situated downstream of this point, the estimated bottom ice age of the drilling site does not exceed 350-400 years BP. Taking into account the information that we have acquired on the Western Plateau Elbrus glacier and first results of the ice core analysis, these data can be used to reconstruct the atmospheric history of the European region.

  18. Chronological refinement of an ice core record at Upper Fremont Glacier in south central North America

    SciTech Connect

    Schuster, Paul F.; White, David E.; Naftz, David L.; Cecil, L. DeWayne

    2000-02-27

    The potential to use ice cores from alpine glaciers in the midlatitudes to reconstruct paleoclimatic records has not been widely recognized. Although excellent paleoclimatic records exist for the polar regions, paleoclimatic ice core records are not common from midlatitude locations. An ice core removed from the Upper Fremont Glacier in Wyoming provides evidence for abrupt climate change during the mid-1800s. Volcanic events (Krakatau and Tambora) identified from electrical conductivity measurements (ECM) and isotopic and chemical data from the Upper Fremont Glacier were reexamined to confirm and refine previous chronological estimates of the ice core. At a depth of 152 m the refined age-depth profile shows good agreement (1736{+-}10 A.D.) with the {sup 14}C age date (1729{+-}95 A.D.). The {delta}{sup 18}O profile of the Upper Fremont Glacier (UFG) ice core indicates a change in climate known as the Little Ice Age (LIA). However, the sampling interval for {delta}{sup 18}O is sufficiently large (20 cm) such that it is difficult to pinpoint the LIA termination on the basis of {delta}{sup 18}O data alone. Other research has shown that changes in the {delta}{sup 18}O variance are generally coincident with changes in ECM variance. The ECM data set contains over 125,000 data points at a resolution of 1 data point per millimeter of ice core. A 999-point running average of the ECM data set and results from f tests indicates that the variance of the ECM data decreases significantly at about 108 m. At this depth, the age-depth profile predicts an age of 1845 A.D. Results indicate the termination of the LIA was abrupt with a major climatic shift to warmer temperatures around 1845 A.D. and continuing to present day. Prediction limits (error bars) calculated for the profile ages are {+-}10 years (90% confidence level). Thus a conservative estimate for the time taken to complete the LIA climatic shift to present-day climate is about 10 years, suggesting the LIA termination in alpine regions of central North America may have occurred on a relatively short (decadal) timescale. (c) 2000 American Geophysical Union.

  19. Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over the last millennium

    NASA Astrophysics Data System (ADS)

    Thevenon, Florian; Anselmetti, Flavio S.; Bernasconi, Stefano M.; Schwikowski, Margit

    2009-09-01

    Black carbon (BC) and mineral dust aerosols were analyzed in an ice core from the Colle Gnifetti glacier (Monte Rosa, Swiss-Italian Alps, 45°55'N, 7°52'E, 4455 m above sea level) using chemical and optical methods. The resulting time series obtained from this summer ice record indicate that BC transport was primarily constrained by regional anthropogenic activities, i.e., biomass and fossil fuel combustion. More precisely, the ?13C composition of BC suggests that wood combustion was the main source of preindustrial atmospheric BC emissions (C3:C4 ratio of burnt biomass of 75:25). Despite relatively high BC emissions prior to 1570, biomass burning activity and especially C4 grassland burning abruptly dropped between 1570 and 1750 (C3:C4 ratio of burnt biomass of 90:10), suggesting that agricultural practices strongly decreased in Europe during this cold period of the "Little Ice Age" (LIA). On the other hand, optical analysis revealed that the main source for atmospheric dust transport to the southern parts of the Alps during summer months was driven by large-scale atmospheric circulation control on the dust export from the northern Saharan desert. This southern aerosol source was probably associated with global-scale hydrologic changes, at least partially forced by variability in solar irradiance. In fact, periods of enhanced Saharan dust deposition in the ice core (around 1200-1300, 1430-1520, 1570-1690, 1780-1800, and after 1870) likely reflect drier winters in North Africa, stronger North Atlantic southwesterlies, and increased spring/summer precipitation in west-central Europe. These results, therefore, suggest that the climatic pejorations and the resulting socioeconomic crises, which occurred in Europe during periods of the LIA, could have been indirectly triggered by large-scale meridional advection of air masses and wetter summer climatic conditions.

  20. Anomalously-dense firn in an ice-shelf channel revealed by wide-angle radar

    NASA Astrophysics Data System (ADS)

    Drews, R.; Brown, J.; Matsuoka, K.; Witrant, E.; Philippe, M.; Hubbard, B.; Pattyn, F.

    2015-10-01

    The thickness of ice shelves, a basic parameter for mass balance estimates, is typically inferred using hydrostatic equilibrium for which knowledge of the depth-averaged density is essential. The densification from snow to ice depends on a number of local factors (e.g. temperature and surface mass balance) causing spatial and temporal variations in density-depth profiles. However, direct measurements of firn density are sparse, requiring substantial logistical effort. Here, we infer density from radio-wave propagation speed using ground-based wide-angle radar datasets (10 MHz) collected at five sites on Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, Antarctica. Using a novel algorithm including traveltime inversion and raytracing with a prescribed shape of the depth-density relationship, we show that the depth to internal reflectors, the local ice thickness and depth-averaged densities can reliably be reconstructed. For the particular case of an ice-shelf channel, where ice thickness and surface slope change substantially over a few kilometers, the radar data suggests that firn inside the channel is about 5 % denser than outside the channel. Although this density difference is at the detection limit of the radar, it is consistent with a similar density anomaly reconstructed from optical televiewing, which reveals 10 % denser firn inside compared to outside the channel. The denser firn in the ice-shelf channel should be accounted for when using the hydrostatic ice thickness for determining basal melt rates. The radar method presented here is robust and can easily be adapted to different radar frequencies and data-acquisition geometries.

  1. Sulfur Isotope Composition of Volcanic Sulfate in Polar Ice Cores (Invited)

    NASA Astrophysics Data System (ADS)

    Cole-Dai, J.; Savarino, J.; Thiemens, M. H.

    2011-12-01

    Explosive volcanic eruptions often emit copious amounts of sulfur gases into the atmosphere. Similar to that of anthropogenic aerosols, volcanic aerosols can influence climate by altering the atmosphere's radiative properties. Traces of sulfate aerosols from past explosive eruptions are preserved in the snow strata of polar ice sheets and can be retrieved with ice cores. We have been measuring sulfur isotope composition of volcanic sulfate in Antarctica and Greenland ice cores to investigate the kinetics of atmospheric oxidation chemistry and to determine the climatic impact of the eruptions. We have found that the chemical conversion process of volcanic sulfur dioxide into sulfuric acid and sulfate aerosols in the stratosphere proceeds through oxidation reaction pathways different from those for sulfur dioxide in the troposphere. Recent laboratory experiments and modeling efforts by other investigators support the hypothesis that short wavelength ultra-violet radiation above the stratospheric ozone layer plays a key role in the chemical conversion or oxidation and can cause mass independent fractionation (MIF) of sulfur isotopes (33S, 34S, 36S). The discovery of the sulfur MIF isotope signatures in the volcanic sulfate offers a unique and dependable way to distinguish the signals of large, stratospheric eruptions in the ice core volcanic records from those of eruptions with little or no climate impact. Identification of the climate-impacting eruptions helps to improve our understanding of the volcano-climate connection.

  2. Sulfur Isotope Composition of Volcanic Sulfate in Polar Ice Cores (Invited)

    NASA Astrophysics Data System (ADS)

    Cole-Dai, J.; Savarino, J.; Thiemens, M. H.

    2013-12-01

    Explosive volcanic eruptions often emit copious amounts of sulfur gases into the atmosphere. Similar to that of anthropogenic aerosols, volcanic aerosols can influence climate by altering the atmosphere's radiative properties. Traces of sulfate aerosols from past explosive eruptions are preserved in the snow strata of polar ice sheets and can be retrieved with ice cores. We have been measuring sulfur isotope composition of volcanic sulfate in Antarctica and Greenland ice cores to investigate the kinetics of atmospheric oxidation chemistry and to determine the climatic impact of the eruptions. We have found that the chemical conversion process of volcanic sulfur dioxide into sulfuric acid and sulfate aerosols in the stratosphere proceeds through oxidation reaction pathways different from those for sulfur dioxide in the troposphere. Recent laboratory experiments and modeling efforts by other investigators support the hypothesis that short wavelength ultra-violet radiation above the stratospheric ozone layer plays a key role in the chemical conversion or oxidation and can cause mass independent fractionation (MIF) of sulfur isotopes (33S, 34S, 36S). The discovery of the sulfur MIF isotope signatures in the volcanic sulfate offers a unique and dependable way to distinguish the signals of large, stratospheric eruptions in the ice core volcanic records from those of eruptions with little or no climate impact. Identification of the climate-impacting eruptions helps to improve our understanding of the volcano-climate connection.

  3. Reassessment of Crete (Greenland) ice core acidity/volcanism link to climate change

    SciTech Connect

    Crowley, T.J.; Criste, T.A.; Smith, N.R. )

    1993-02-05

    Previous comparisons of the Crete (Greenland) ice core acidity record with climate variations of the last 1,400 years suggested that changes in volcanism may have significantly influenced climate on this time scale. However, the ice core acidity record consists of volcanically-induced spikes superimposed on a background acidity of nonvolcanic origin that varied significantly in amplitude. Herein the authors produce a record of Crete volcanism based solely on an objective definition of individual volcanic events in the ice core record. There are 92 acidity peaks in the 1,420-year record. Since at least 26% of the post-1,600 eruptions are of local (Icelandic) origin, they estimate a mean recurrence interval of 20.8 years for hemispheric-scale eruptions rich in sulphate. On decadal time scales, volcanism has varied by a factor of three-four over the last 1,400 years. However, the climate-volcanism correlation is considerably less impressive (r = [minus]0.23) than previously concluded (r = [minus]0.52). The good correspondence between volcanism and climate previously reported are due to background acidity levels that show a significant Little Ice Age increase. The background increase may reflect changes in ocean productivity. 24 refs., 5 figs., 1 tab.

  4. Multi-decadal variability in the Greenland ice core records obtained using intrinsic timescale decomposition

    NASA Astrophysics Data System (ADS)

    Zhou, Jiansong; Tung, Ka-Kit; Li, King-Fai

    2015-10-01

    By performing a new adaptive time series decomposition on the composite average of multiple ice core records obtained from the Arctic and Greenland, we extracted a robust quasi-oscillatory signal with a period of ~70 years throughout the preceding millennium, and showed that it is strongly connected to the Atlantic Multidecadal Oscillation (AMO). In the same decomposition there exists the Greenland signature of the Little Ice Age and Medieval Warm Period. Throughout the warm and cold periods the AMO properties remained robust. It implies that the evolution of the AMO has its own coherent mechanism and was little affected by these large climatic excursions.

  5. Cryogenic EBSD reveals structure of directionally solidified ice–polymer composite

    SciTech Connect

    Donius, Amalie E.; Obbard, Rachel W.; Burger, Joan N.; Hunger, Philipp M.; Baker, Ian; Doherty, Roger D.; Wegst, Ulrike G.K.

    2014-07-01

    Despite considerable research efforts on directionally solidified or freeze-cast materials in recent years, little fundamental knowledge has been gained that links model with experiment. In this contribution, the cryogenic characterization of directionally solidified polymer solutions illustrates, how powerful cryo-scanning electron microscopy combined with electron backscatter diffraction is for the structural characterization of ice–polymer composite materials. Under controlled sublimation, the freeze-cast polymer scaffold structure is revealed and imaged with secondary electrons. Electron backscatter diffraction fabric analysis shows that the ice crystals, which template the polymer scaffold and create the lamellar structure, have a-axes oriented parallel to the direction of solidification and the c-axes perpendicular to it. These results indicate the great potential of both cryo-scanning electron microscopy and cryo-electron backscatter diffraction in gaining fundamental knowledge of structure–property–processing correlations. - Highlights: • Cryo-SEM of freeze-cast polymer solution reveals an ice-templated structure. • Cryo-EBSD reveals the ice crystal a-axis to parallel the solidification direction. • The honeycomb-like polymer phase favors columnar ridges only on one side. • Combining cryo-SEM with EBSD links solidification theory with experiment.

  6. Interpreting ice core records of inter-annual temperature change across the Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Sime, L.; Marshall, G.

    2009-04-01

    The Antarctica Peninsula has a rapidly changing climate, however there is a paucity of long term meterological observations of temperature across the region. Decadal to centennial ice cores records can potentially help to fill this gap. Interpretation of the ice cores requires an understanding of the relationship between temperature change and the accumulation record recovered from each Peninsula core site. To facilitate this interpretation, we present an analysis of 22 years (1980-2002) of ECMWF ERA40 surface temperature, precipitation, and accumulation data. Inter-annual variability in temperature is quite is similar across the Peninsula. However, changes in the covariance between accumulation and temperature over the Peninsula region at the seasonal and synoptic time periods strongly affect the potential ice core recording of temperature change: with a clear trend in the fraction of inter-annual temperature change recorded along the Peninsula. It is likely that only about 25% of the actual inter-annual temperature change will be visible in the accumulation record at the northern end of the Peninsula near James Ross Island, 70% at Dyer in the central regions, and 120% at the southern end in the Gomez region. This study is likely to facilitate understand of decadal to centennial temperature change obtained from stable water isotopes in this sensitive polar region.

  7. Recent Increase in Elemental Carbon Concentration and Deposition in a Svalbard Ice Core

    NASA Astrophysics Data System (ADS)

    Ruppel, M.; Isaksson, E. D.; Ström, J.; Svensson, J.; Beaudon, E.; Korhola, A.

    2013-12-01

    Black carbon (BC) is an aerosol produced by incomplete combustion of biomass and fossil fuels. Due to its strong light absorption it warms the atmosphere. Climate effects of BC are intensified in the Arctic where its deposition on snow and ice decreases surface albedo, causing earlier spring melt and associated feedbacks. Despite the significant role of BC in Arctic climate warming, there is little information on its concentrations and climate effects in the Arctic in time periods preceding direct observational data. Here we present first results on BC (here operationally defined as elemental carbon (EC)) concentrations and deposition on a Svalbard (European Arctic) glacier (Holtedahlfonna) from 1700 to 2004. The inner part of a 125 m deep ice core was melted, filtered and analyzed for apparent elemental carbon using a thermal optical method. EC concentrations (?g L-1) and the deposition (mg m-2 yr-1) were generally low in the pre-industrial era. Concentrations peaked around 1910 and again around 1950, whereas only the 1910 peak was recorded in the EC deposition, followed by decreasing deposition values. Strikingly, both EC concentration and deposition started to increase rapidly from the 1970s until 2004. This rise is not seen in any thus far published European or Arctic ice core, and it seems to contradict atmospheric BC measurements from the Arctic which indicate decreasing atmospheric BC concentrations since the beginning of the observations at the end of 1980s. However, the magnitude of the measured concentrations is in accordance with previous ice core EC measurements from the European Alps and a BC concentration and deposition peak around 1910 has also been recorded in Greenland ice cores. Work is continuing to disentangle the cause of the increasing EC values in the recent decades suggested by the present ice core. Contribution from any local sources has been ruled out. Back trajectory modeling is carried out to establish the EC source areas. The present results might indicate some long-range transport of EC to Svalbard, since BC emissions have decreased or stayed constant in Europe and North America for the last decades, whereas the emissions from China, India and parts of the former USSR have increased at the same time. Regardless of the cause of the increasing EC values, these results have significant implications to the past radiative transfer at the coring site. This project will continue with modeling of the past EC surface radiative forcing in the Holtedahlfonna area based on the present results.

  8. Applications of a rapid endospore viability assay for monitoring UV inactivation and characterizing arctic ice cores.

    PubMed

    Shafaat, Hannah S; Ponce, Adrian

    2006-10-01

    We have developed a rapid endospore viability assay (EVA) in which endospore germination serves as an indicator for viability and applied it to (i) monitor UV inactivation of endospores as a function of dose and (ii) determine the proportion of viable endospores in arctic ice cores (Greenland Ice Sheet Project 2 [GISP2] cores; 94 m). EVA is based on the detection of dipicolinic acid (DPA), which is released from endospores during germination. DPA concentrations were determined using the terbium ion (Tb3+)-DPA luminescence assay, and germination was induced by L-alanine addition. The concentrations of germinable endospores were determined by comparison to a standard curve. Parallel EVA and phase-contrast microscopy experiments to determine the percentage of germinable spores yielded comparable results (54.3% +/- 3.8% and 48.9% +/- 4.5%, respectively), while only 27.8% +/- 7.6% of spores produced CFU. EVA was applied to monitor the inactivation of spore suspensions as a function of UV dose, yielding reproducible correlations between EVA and CFU inactivation data. The 90% inactivation doses were 2,773 J/m2, 3,947 J/m2, and 1,322 J/m2 for EVA, phase-contrast microscopy, and CFU reduction, respectively. Finally, EVA was applied to quantify germinable and total endospore concentrations in two GISP2 ice cores. The first ice core contained 295 +/- 19 germinable spores/ml and 369 +/- 36 total spores/ml (i.e., the percentage of germinable endospores was 79.9% +/- 9.3%), and the second core contained 131 +/- 4 germinable spores/ml and 162 +/- 17 total spores/ml (i.e., the percentage of germinable endospores was 80.9% +/- 8.8%), whereas only 2 CFU/ml were detected by culturing. PMID:17021233

  9. Investigating age and origin of ice-cored moraines in Jotunheimen and Breheimen/Southern Norway

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan; Matthews, John; Wilson, Peter

    2015-04-01

    Ice-cored moraines characteristic for the high-alpine zones in the Jotunheimen and Breheimen mountain regions of southern Norway have been recognised, described, and studied as early as during the 1950s and 1960s. These complex multiple-ridged, ramp-like moraines of up to 50 m in height occurring at comparatively small but high-lying glaciers differ considerably from those typical for the other glaciers at lower altitudes. The existence of their ice-core beneath rather thin debris cover and a spatial concentration in the north-eastern part of the regions with a higher snow line and stronger climatic continentality points towards their link with alpine permafrost. Until today, there is no consensus about either the mechanisms of their formation or their age constraints. Based on few (possibly less reliable) radiocarbon ages retrieved from dust within the ice cores the innermost (proximal) ridges were, for example, interpreted as rather old and the outermost ridges as youngest. Consequently, the innermost ridges need to have survived successive overriding during more extensive glacier advances. Alternatively, these ice-cored moraines have also been interpreted as initial rock glaciers and the younger ages of the outer ridges explained by 'pressing-out' of material from the base of the moraine by its own weight and gravity. Other theories developed include also a mixture of traditional push moraine processes and deformation structures caused by the glacier advancing in a permafrost environment ('push-deformation moraine'). Because reliable age constraints for individual ridges of those complex ice-cored moraine complexes are crucial for any interpretation of their mode of formation, this study aims to provide insights into their age and origin by applying high-precision Schmidt-hammer exposure-age dating (SHD). Local SHD calibration curves using moraine ridges dating from the last 50 years to the Preboreal (c. 9700 years ago) have been used to give age estimates for individual ridges of three selected ice-core moraine complexes in Jotunheimen and Breheimen. The results ranged from c. 3900 years to modern age at Gråsubreen, c. 400 to 250 years at Vesle Juvbreen and 2250 to 1600 years at Østre Tundradalskyrkjabre. The R-value distributions were often negatively skewed and interpreted as related to weathered boulders from reworked surfaces, hence all moraine ages obtained need to be seen as maximum age estimates. The abovementioned theory that the inner proximal moraine ridges are the oldest and overridden several times can, however, be rejected on basis of the SHD results alongside the theory of these moraines being rock glaciers. Instead, the ice-cored moraine complexes are considered to be glaciotectonic structures produced by the interaction of polythermal glaciers and permafrost during the late Holocene. All the individual ridges were essentially formed over the 'Little Ice Age' glacier advance from material deposited earlier during multiple Neoglacial events. The considerable size of the moraine complexes is attributed to the accumulation of material from these different events over a long period of time and their survival during periods of glacier retreat when the ice cores did not melt and paraglacial activity remained ineffective in the periglacial environment.

  10. Ice-volcano interactions during the 2010 Eyjafjallajökull eruption, as revealed by airborne imaging radar

    NASA Astrophysics Data System (ADS)

    Magnússon, E.; Gudmundsson, M. T.; Roberts, M. J.; Sigurã°Sson, G.; HöSkuldsson, F.; Oddsson, B.

    2012-07-01

    During the eruption of the ice-covered Eyjafjallajökull volcano, a series of images from an airborne Synthetic Aperture Radar (SAR) were obtained by the Icelandic Coast Guard. Cloud obscured the summit from view during the first three days of the eruption, making the weather-independent SAR a valuable monitoring resource. Radar images revealed the development of ice cauldrons in a 200 m thick ice cover within the summit caldera, as well as the formation of cauldrons to the immediate south of the caldera. Additionally, radar images were used to document the subglacial and supraglacial passage of floodwater to the north and south of the eruption site. The eruption breached the ice surface about four hours after its onset at about 01:30 UTC on 14 April 2010. The first SAR images, obtained between 08:55 and 10:42 UTC, show signs of limited supraglacial drainage from the eruption site. Floodwater began to drain from the ice cap almost 5.5 h after the beginning of the eruption, implying storage of meltwater at the eruption site due to initially constricted subglacial drainage from the caldera. Heat transfer rates from magma to ice during early stages of cauldron formation were about 1 MW m-2 in the radial direction and about 4 MW m-2 vertically. Meltwater release was characterized by accumulation and drainage with most of the volcanic material in the ice cauldrons being drained in hyperconcentrated floods. After the third day of the eruption, meltwater generation at the eruption site diminished due to an insulating lag of tephra.

  11. Tephra studies on the deep Talos Dome ice core, East Antarctic Plateau

    NASA Astrophysics Data System (ADS)

    Narcisi, B.; Petit, J.; Delmonte, B.; Stenni, B.

    2011-12-01

    In the context of the TALDICE (TALos Dome Ice CorE) project conducted by a consortium of five European nations led by Italy, a 1620-m long ice core has been drilled at Talos Dome (72°49'S, 159°11'E; 2315 m; www.taldice.org), on the eastern edge of the East Antarctic plateau during the field seasons 2004-2008. Owing to its relatively high accumulation rate, this near-coastal core preserves a detailed undisturbed paleoclimate record covering the past 250,000 years, back to Marine Isotope Stage (MIS) 7.5. The Talos Dome ice is a significant volcanic ash archive. During core inspection of the TALDICE core, more than 100 macroscopic tephra layers were located and inventoried, with an average tephra frequency one order of magnitude greater than the tephra frequency in deep cores from inland East Antarctic plateau over the last two glacial cycles. TALDICE prominent tephra layers, studied by scanning electron microscopy, Coulter Counter and electron microprobe analysis, display an alkaline geochemical character indicating an origin in nearby volcanoes of the Melbourne Volcanic Province (McMurdo Volcanic Group). Our tephra record helps reconstruct an improved history of explosive eruptions in northern Victoria Land, supplementing the stratigraphic record obtained by outcrop studies and documenting previously unknown temporal trends and specific episodes. Investigations on less prominent tephra horizons are in progress with the aim of complementing the Holocene volcanic record of local visible beds and establishing the detailed tephrostratigraphy for the region. To date about ten discrete ice sections showing anomalously coarse grain size has proved to contain significant concentrations of unreworked volcanic glass. Single shard major element analyses of some invisible volcanic horizons indicate subalkaline compositions, which are incompatible with Antarctic volcanism and suggesting long-distance tephra transport from either South American and/or New Zealand volcanoes. Ongoing comparison between geochemical results and literature data on Holocene tephrostratigraphies of potential source volcanoes will likely suggest correlation of TALDICE invisible tephras with known radiometrically-dated eruptions, with potential implications for ice core timescale and stratigraphic correlations over wide areas.

  12. 30-Year Satellite Record Reveals Contrasting Arctic and Antarctic Decadal Sea Ice Variability

    NASA Technical Reports Server (NTRS)

    Cavalieri, D. J.; Parkinson, C. L.; Vinnikov, K. Y.

    2003-01-01

    A 30-year satellite record of sea ice extents derived mostly from satellite microwave radiometer observations reveals that the Arctic sea ice extent decreased by 0.30+0.03 x 10(exp 6) square kilometers per 10 yr from 1972 through 2002, but by 0.36 plus or minus 0.05 x 10(exp 6) square kilometers per 10yr from 1979 through 2002, indicating an acceleration of 20% in the rate of decrease. In contrast, the Antarctic sea ice extent decreased dramatically over the period 1973-1977, then gradually increased. Over the full 30-year period, the Antarctic ice extent decreased by 0.15 plus or minus 0.08 x 10(exp 6) square kilometers per 10 yr. The trend reversal is attributed to a large positive anomaly in Antarctic sea ice extent in the early 1970's, an anomaly that apparently began in the late 1960's, as observed in early visible and infrared satellite images.

  13. The Southern Hemisphere at glacial terminations: insights from the Dome C ice core

    NASA Astrophysics Data System (ADS)

    Röthlisberger, R.; Mudelsee, M.; Bigler, M.; de Angelis, M.; Fischer, H.; Hansson, M.; Lambert, F.; Masson-Delmotte, V.; Sime, L.; Udisti, R.; Wolff, E. W.

    2008-12-01

    The many different proxy records from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core allow for the first time a comparison of nine glacial terminations in great detail. Despite the fact that all terminations cover the transition from a glacial maximum into an interglacial, there are large differences between single terminations. For some terminations, Antarctic temperature increased only moderately, while for others, the amplitude of change at the termination was much larger. For the different terminations, the rate of change in temperature is more similar than the magnitude or duration of change. These temperature changes were accompanied by vast changes in dust and sea salt deposition all over Antarctica. Here we investigate the phasing between a South American dust proxy (non-sea-salt calcium flux, nssCa2+), a sea ice proxy (sea salt sodium flux, ssNa+) and a proxy for Antarctic temperature (deuterium, ?D). In particular, we look into whether a similar sequence of events applies to all terminations, despite their different characteristics. All proxies are derived from the EPICA Dome C ice core, resulting in a relative dating uncertainty between the proxies of less than 20 years. At the start of the terminations, the temperature (?D) increase and dust (nssCa2+ flux) decrease start synchronously. The sea ice proxy (ssNa+ flux), however, only changes once the temperature has reached a particular threshold, approximately 5°C below present day temperatures (corresponding to a ?D value of -420‰). This reflects to a large extent the limited sensitivity of the sea ice proxy during very cold periods with large sea ice extent. At terminations where this threshold is not reached (TVI, TVIII), ssNa+ flux shows no changes. Above this threshold, the sea ice proxy is closely coupled to the Antarctic temperature, and interglacial levels are reached at the same time for both ssNa+ and ?D. On the other hand, once another threshold at approximately 2°C below present day temperature is passed (corresponding to a ?D value of -402‰), nssCa2+ flux has reached interglacial levels and does not change any more, despite further warming. This threshold behaviour most likely results from a combination of changes to the threshold friction velocity for dust entrainment and to the distribution of surface wind speeds in the dust source region.

  14. The southern hemisphere at glacial terminations: insights from the Dome C ice core

    NASA Astrophysics Data System (ADS)

    Röthlisberger, R.; Mudelsee, M.; Bigler, M.; de Angelis, M.; Fischer, H.; Hansson, M.; Lambert, F.; Masson-Delmotte, V.; Sime, L.; Udisti, R.; Wolff, E. W.

    2008-06-01

    The many different proxy records from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core allow for the first time a comparison of nine glacial terminations in great detail. Despite the fact that all terminations cover the transition from a glacial maximum into an interglacial, there are large differences between single terminations. For some terminations, Antarctic temperature increased only moderately, while for others, the amplitude of change at the termination was much larger. For the different terminations, the rate of change in temperature is more similar than the magnitude or duration of change. These temperature changes were accompanied by vast changes in dust and sea salt deposition all over Antarctica. Here we investigate the phasing between a South American dust proxy (non-sea-salt calcium flux, nssCa), a sea ice proxy (sea salt sodium flux, ssNa) and a proxy for Antarctic temperature (deuterium, ?D). In particular, we look into whether a similar sequence of events applies to all terminations, despite their different characteristics. All proxies are derived from the EPICA Dome C ice core, resulting in a relative dating uncertainty between the proxies of less than 20 years. At the start of the terminations, the temperature (?D) increase and dust (nssCa flux) decrease start synchronously. The sea ice proxy (ssNa flux), however, only changes once the temperature has reached a particular threshold, approximately 5°C below present day temperatures (corresponding to a ?D value of 420‰). This reflects to a large extent the limited sensitivity of the sea ice proxy during very cold periods with large sea ice extent. At terminations where this threshold is not reached (TVI, TVIII), ssNa flux shows no changes. Above this threshold, the sea ice proxy is closely coupled to the Antarctic temperature, and interglacial levels are reached at the same time for both ssNa and ?D. On the other hand, once another threshold at approximately 2°C below present day temperature is passed (corresponding to a ?D value of 402‰), nssCa flux has reached interglacial levels and does not change any more, despite further warming. This threshold behaviour most likely results from a combination of changes to the threshold friction velocity for dust entrainment and to the distribution of surface wind speeds in the dust source region.

  15. Cosmic ray event of A.D. 774-775 shown in quasi-annual 10Be data from the Antarctic Dome Fuji ice core

    NASA Astrophysics Data System (ADS)

    Miyake, Fusa; Suzuki, Asami; Masuda, Kimiaki; Horiuchi, Kazuho; Motoyama, Hideaki; Matsuzaki, Hiroyuki; Motizuki, Yuko; Takahashi, Kazuya; Nakai, Yoichi

    2015-01-01

    content in tree rings and 10Be concentration records in polar ice core provide information about past cosmic ray intensities. The A.D. 774-775 cosmic ray event has been identified by 14C measurement in several tree rings from all over the world. Although the quasi-decadal 10Be Dome Fuji data in the Antarctic ice core also shows a sharp peak around A.D. 775, annual 10Be variations in the Dome Fuji core or in other cores have not been revealed. We have measured quasi-annual 10Be concentrations from approximately A.D. 763-794 in the Dome Fuji ice core, and detected a clear increase (~80% above the baseline) in 10Be concentration around A.D. 775. However, an accurate height of this increase is not straightforwardly estimated due to the background variation in 10Be concentration. The 10Be increase can be due to the same cosmic ray event as shown in the 14C content in A.D. 774-775.

  16. Defining the geochemical composition of the EPICA Dome C ice core dust during the last glacial-interglacial cycle

    NASA Astrophysics Data System (ADS)

    Marino, F.; Castellano, E.; Ceccato, D.; de Deckker, P.; Delmonte, B.; Ghermandi, G.; Maggi, V.; Petit, J. R.; Revel-Rolland, M.; Udisti, R.

    2008-10-01

    The major element composition of the insoluble, windborne long-range dust archived in the European Project for Ice Coring in Antarctica Dome C ice core has been determined by Particle Induced X-ray Emission analyses. The geochemistry of dust from the last glacial maximum (LGM) and from the Holocene is discussed in terms of past environmental changes, throughout the last climatic cycle. Antarctic dust from glacial and interglacial climate clearly reveals different geochemical compositions. The weathered crustal-like signature of LGM dust is characterized by a low compositional variability, suggesting a dominant source under the glacial regime. The close correspondence between the major element composition of Antarctic glacial dust and the composition of southern South American sediments supports the hypothesis of a dominant role of this area as major dust supplier during cold conditions. Conversely, the major element composition of Holocene dust displays high variability and high Al content on average. This implies that an additional source could also play some role. Comparison with size-selected sediments suggests that a contribution from Australia is likely during warm times, when a reduced glacial erosion decreases the primary dust production and a more intense hydrological cycle and larger vegetation cover inactivates dust mobility in a large part of southern South America, weakening its contribution as a massive dust supplier to Antarctica.

  17. Multilayer Formation and Evaporation of Deuterated Ices in Prestellar and Protostellar Cores

    NASA Technical Reports Server (NTRS)

    Taquet, Vianney; Charnley, Steven B.; Sipila, Olli

    2014-01-01

    Extremely large deuteration of several molecules has been observed toward prestellar cores and low-mass protostars for a decade. New observations performed toward low-mass protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimensional model of a collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial and temporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of ices with a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin states of H2 and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous and show an increase of their deuterium fractionation toward the surface. The differentiation of the deuteration in ices induces an evolution of the deuteration within protostellar envelopes. The warm inner region is poorly deuterated because it includes the whole molecular content of ices, while the deuteration predicted in the cold external envelope scales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuteration within protostellar envelopes, but we are still unable to predict the superhigh deuteration observed for formaldehyde and methanol. Finally, the extension of this study to the deuteration of complex organics, important for the prebiotic chemistry, shows good agreement with the observations, suggesting that we can use the deuteration to retrace their mechanisms and their moments of formation.

  18. Multilayer formation and evaporation of deuterated ices in prestellar and protostellar cores

    SciTech Connect

    Taquet, Vianney; Charnley, Steven B.; Sipilä, Olli

    2014-08-10

    Extremely large deuteration of several molecules has been observed toward prestellar cores and low-mass protostars for a decade. New observations performed toward low-mass protostars suggest that water presents a lower deuteration in the warm inner gas than in the cold external envelope. We coupled a gas-grain astrochemical model with a one-dimensional model of a collapsing core to properly follow the formation and the deuteration of interstellar ices as well as their subsequent evaporation in the low-mass protostellar envelopes with the aim of interpreting the spatial and temporal evolutions of their deuteration. The astrochemical model follows the formation and the evaporation of ices with a multilayer approach and also includes a state-of-the-art deuterated chemical network by taking the spin states of H{sub 2} and light ions into account. Because of their slow formation, interstellar ices are chemically heterogeneous and show an increase of their deuterium fractionation toward the surface. The differentiation of the deuteration in ices induces an evolution of the deuteration within protostellar envelopes. The warm inner region is poorly deuterated because it includes the whole molecular content of ices, while the deuteration predicted in the cold external envelope scales with the highly deuterated surface of ices. We are able to reproduce the observed evolution of water deuteration within protostellar envelopes, but we are still unable to predict the super-high deuteration observed for formaldehyde and methanol. Finally, the extension of this study to the deuteration of complex organics, important for the prebiotic chemistry, shows good agreement with the observations, suggesting that we can use the deuteration to retrace their mechanisms and their moments of formation.

  19. Assessment of the Relationship between Andean Ice Core Precipitation Indicators and Amazon River Discharge

    NASA Astrophysics Data System (ADS)

    Johnson, N.; Alsdorf, D.; Thompson, L.; Mosley-Thompson, E.; Melack, J.

    2006-12-01

    Prior to the last 100 years, there is a significant lack of hydrologic knowledge for the Amazon Basin. A 100- year record of discharge from the city of Manaus, located at the confluence of the Solimoes and Negro rivers, is the most complete record for the basin. Inundated wetlands play a key role in carbon out-gassing to the atmosphere whereas discharge from the Amazon River contributes about 20% of the total freshwater flux delivered to the world's oceans. As discharge (Q) and inundation are directly related to precipitation, we are developing a method to extend our understanding of Q and inundation into the 19^{th} century. Using proxy data preserved in Andean glaciers and ice caps and recovered from ice cores, annually resolved histories of ?^{18)O and mass accumulation are available. The latter is a proxy for local precipitation amount whereas ?18O is influenced by continental scale processes (i.e., evaporation, convection) as well as by temperature and hence, by varying climate regimes. We have correlated the accumulation and ?18O records from Core 1 drilled on the Quelccaya ice-cap in the southern Andes of Peru with the Manaus discharge data. As ice core annual layers correspond to the thermal year (in Peru, July to June of the following year) and the discharge records are kept daily (January to December), we averaged 365 days of Q data seeking the optimal correlation for each start and end date. The best statistical relationship between ?18O and Q (r = -0.41, p = < 0.001) is attained when Q is averaged from March 16 to March 15 of the following year. We also correlated 23 years of ENSO events, which are linked to both Amazon River discharge and ice core ?18O (r = -0.60, p = < 0.001). These linear relationships are used to create Amazon discharge for the 20^{th} century and to extrapolate Q into the 19^{th} century. Previously developed relationships between Q and mainstem inundated area are then used to estimate inundated area along the main Amazon channel for the past 200 years. The ice core-derived estimate of inundated area for the past 100 years compares well with the previous and more straightforward estimates based on discharge and remote sensing data.

  20. Depletion of chlorine into HCl ice in a protostellar core

    E-print Network

    Kama, M; Lopez-Sepulcre, A; Wakelam, V; Dominik, C; Ceccarelli, C; Lanza, M; Lique, F; Ochsendorf, B B; Lis, D C; Caballero, R N; Tielens, A G G M

    2014-01-01

    The freezeout of gas-phase species onto cold dust grains can drastically alter the chemistry and the heating-cooling balance of protostellar material. In contrast to well-known species such as carbon monoxide (CO), the freezeout of various carriers of elements with abundances $chlorine in the protostellar core, OMC-2 FIR 4. We observed transitions of HCl and H2Cl+ towards OMC-2 FIR 4 using the Herschel Space Observatory and Caltech Submillimeter Observatory facilities. Our analysis makes use of state of the art chlorine gas-grain chemical models and newly calculated HCl-H$_{2}$ hyperfine collisional excitation rate coefficients. A narrow emission component in the HCl lines traces the extended envelope, and a broad one traces a more compact central region. The gas-phase HCl abundance in FIR 4 is 9e-11, a factor of only 0.001 that of volatile elemental chlorine. The H2Cl+ lines are detected in absorption and trace a tenuous fo...

  1. Retrieving a common accumulation record from Greenland ice cores for the past 1800 years

    NASA Astrophysics Data System (ADS)

    Andersen, K. K.; Ditlevsen, P. D.; Rasmussen, S. O.; Clausen, H. B.; Vinther, B. M.; Johnsen, S. J.; Steffensen, J. P.

    2006-08-01

    In the accumulation zone of the Greenland ice sheet the annual accumulation rate may be determined through identification of the annual cycle in the isotopic climate signal and other parameters that exhibit seasonal variations. On an annual basis the accumulation rate in different Greenland ice cores is highly variable, and the degree of correlation between accumulation series from different ice cores is low. However, when using multiyear averages of the different accumulation records, the correlation increases significantly. A statistical model has been developed to estimate the common climate signal in the different accumulation records through optimization of the ratio between the variance of the common signal and of the residual. Using this model, a common Greenland accumulation record for the past 1800 years has been extracted. The record shows significant 11.9 years periodicity. A sharp transition to very dry conditions is found just before A.D. 1200, and very dry conditions during the 13th century together with dry and cold spells during the 14th century may have put extra strain on the Norse population in Greenland and may have contributed to their extinction. Accumulation rates gradually decrease from a distinct maximum in A.D. 1394 to very dry conditions in the late 17th century and thus reflect the Little Ice Age.

  2. Effects of sudden mixing in the solar core on solar neutrinos and ice ages.

    NASA Technical Reports Server (NTRS)

    Ezer, D.; Cameron, A. G. W.

    1972-01-01

    Some numerical experiments with a solar model have been conducted in connection with the hypothesis regarding the effects of mixing in the solar core. Questions concerning a plausible mechanism by which such a mixing could be produced are explored. The variation of solar luminosity throughout the numerical experiments is shown. In connection with a great change in luminosity after a second mixing, it is suggested that the earth is presently undergoing an ice age.

  3. Recent and past dust concentrations and fluxes from a developing array of Antarctic ice cores

    NASA Astrophysics Data System (ADS)

    McConnell, J. R.; Anschütz, H.; Baggenstos, D.; Das, S. B.; Isaksson, E. D.; Lawrence, R.; Layman, L.; Maselli, O.; Severinghaus, J. P.; Sigl, M.; Petit, J. R.; Grente, B.

    2012-12-01

    Continental dust is an important component of climate forcing, both because of its interaction with incoming solar and outgoing long wave radiation and because of its impact on albedo when deposited on bright surfaces such as fresh snow. Continental dust may also play an important role in ocean fertilization and carbon sequestration. Because the lifetime of dust aerosol in the atmosphere is only on the order of days to weeks, spatial and temporal variability in concentrations and fluxes is high and understanding of recent and long term changes is limited. Here we present and discuss detailed continuous, high depth resolution measurements of a range of dust proxies in a developing array of Antarctic ice cores. Included are traditional proxies such as non-sea-salt (nss) calcium and insoluble particle number and size distribution as well as less traditional proxies such as aluminum, vanadium, manganese, rare earth elements, and nss uranium which together provide important insights into how dust sources and transport may have changed in the past. The array includes a number of new shallow ice core records from East and West Antarctica spanning recent centuries to millennia, as well as Last Glacial Maximum to early Holocene records from the deep WAIS Divide and Taylor Glacier Horizontal ice cores.

  4. Significant recent warming over the northern Tibetan Plateau from ice core ?18O records

    NASA Astrophysics Data System (ADS)

    An, W.; Hou, S.; Zhang, W.; Wang, Y.; Liu, Y.; Wu, S.; Pang, H.

    2015-07-01

    Stable oxygen isotopic records in ice cores provide valuable information about past temperature, especially for regions with scarce instrumental measurements. This paper presents the ?18O result of an ice core drilled to bedrock from Mt. Zangser Kangri (ZK), a remote area on the northern Tibetan Plateau (TP). Combining the ZK ?18O records with those from three other ice cores in the region (Muztagata, Puruogangri and Geladaindong), we reconstructed the regional temperature history covering 1951-2008 for the northern TP. The reconstruction showed significant warming at 1.12 ± 0.08 to 1.31 ± 0.10 °C(10 yr)-1 since 1970, a much higher rate than the trend of instrumental records of the northern TP (0.45 ± 0.06 °C(10 yr)-1) and the global temperature trend (0.28 ± 0.02 °C(10 yr)-1) at the same time. Moreover, the rapid warming remained for this region during the last decade, when the mean global temperature showed very little change. Our study suggests that the temperature variations at high elevations could behave differently due to specific topographic and circulation mechanisms.

  5. 9,400 years of cosmic radiation and solar activity from ice cores and tree rings.

    PubMed

    Steinhilber, Friedhelm; Abreu, Jose A; Beer, Jürg; Brunner, Irene; Christl, Marcus; Fischer, Hubertus; Heikkilä, Ulla; Kubik, Peter W; Mann, Mathias; McCracken, Ken G; Miller, Heinrich; Miyahara, Hiroko; Oerter, Hans; Wilhelms, Frank

    2012-04-17

    Understanding the temporal variation of cosmic radiation and solar activity during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such as (10)Be and (14)C which are stored in polar ice cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar activity over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different (10)Be ice core records from Greenland and Antarctica with the global (14)C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution (10)Be record from Dronning Maud Land obtained within the European Project for Ice Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar activity to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate. PMID:22474348

  6. 9,400 years of cosmic radiation and solar activity from ice cores and tree rings

    PubMed Central

    Steinhilber, Friedhelm; Beer, Jürg; Brunner, Irene; Christl, Marcus; Fischer, Hubertus; Heikkilä, Ulla; Kubik, Peter W.; Mann, Mathias; McCracken, Ken G.; Miller, Heinrich; Miyahara, Hiroko; Oerter, Hans

    2012-01-01

    Understanding the temporal variation of cosmic radiation and solar activity during the Holocene is essential for studies of the solar-terrestrial relationship. Cosmic-ray produced radionuclides, such as 10Be and 14C which are stored in polar ice cores and tree rings, offer the unique opportunity to reconstruct the history of cosmic radiation and solar activity over many millennia. Although records from different archives basically agree, they also show some deviations during certain periods. So far most reconstructions were based on only one single radionuclide record, which makes detection and correction of these deviations impossible. Here we combine different 10Be ice core records from Greenland and Antarctica with the global 14C tree ring record using principal component analysis. This approach is only possible due to a new high-resolution 10Be record from Dronning Maud Land obtained within the European Project for Ice Coring in Antarctica in Antarctica. The new cosmic radiation record enables us to derive total solar irradiance, which is then used as a proxy of solar activity to identify the solar imprint in an Asian climate record. Though generally the agreement between solar forcing and Asian climate is good, there are also periods without any coherence, pointing to other forcings like volcanoes and greenhouse gases and their corresponding feedbacks. The newly derived records have the potential to improve our understanding of the solar dynamics and to quantify the solar influence on climate. PMID:22474348

  7. New mineral dust record from the TALDICE ice core (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Maggi, V.; Delmonte, B.; Albani, S.; Mazzola, C.

    2010-12-01

    Aeolian mineral dust is an active component of the climate system, interacting both directly and indirectly with radiation and biogeochemistry. Its deposition and stratigraphical preservation in appropriate environmental setting leaves deposits that once dated can be used as paleoclimate proxies. In particular dust records from ice cores can provide insights into past variations of environmental conditions at the dust source areas, atmospheric circulation, the hydrological cycle at source and deposition sites and dust deposition mechanisms. Here we present the new dust record from the 1620 m deep TALDICE ice core, drilled at Talos Dome (159°11' E, 72°49' S, 2315 m A.S.L.), on the edge of the East Antarctic plateau, about 290 km from the Southern Ocean and 250 km from the Ross Sea. We analysed variations in dust concentration, depositional flux, size distributions and geochemical fingerprint. The TALDICE dust records confirms the major findings from previous ice core studies in terms of the big glacial/interglacial variations in dust deposition, thanks to the relatively high accumulation rate and good dating. We also show new peculiar aspects emerging for this record, such as the importance of Antarctic sources for dust for this peripheral sites and the relation between variations in dust deposition during the deglaciation and the Holocene to variations in the atmospheric circulation in the Ross Sea.

  8. Evidence for an early Holocene climate optimum in the Antarctic deep ice-core record

    SciTech Connect

    Ciais, P.; Lipenkov, V.; Nicolaiev, V.

    1992-01-01

    In the interpretation of the Antarctic deep ice-core data, little attention has been given to the Holocene part of the records. As far as translation of the stable isotope content in terms of temperature is concerned, this can be understood because expected temperature changes may be obscured by isotopic noise of various origins and because no {sup 14}C dating has yet been available for this type of sequence. In this article, we focus on the Dome C and Vostok cores and on a new 850-m long ice core drilled out at Komsomolskaia by the Soviet Antarctic Expeditions. These three sites are located in East Antarctica, on the Antarctic plateau, in a region essentially undisturbed by ice-flow conditions, so that their detailed intercomparison may allow us to identify the climatically significant isotopic signal. Our results compare well with the proximal records of Southern Hemisphere high latitudes and support the existence of a warmer {open_quotes}climatic optimum{close_quotes} between 10 and 6 ka y BP. Maximum temperatures are reached just at the end of the last deglaciation, which confirms previous observations at high latitudes, in contrast with later dates for the Atlantic and hypsithermal optima in Europe and North America. 60 refs., 6 figs.

  9. Influence of large-scale teleconnection patterns on methane sulfonate ice core records in Dronning Maud Land

    E-print Network

    Fischer, Hubertus

    -salt record), which vanishes in the deeper part of the ice core as a consequence of diffusion processes. From is dime- thylsulfoniopropionate (DMSP), which is used by phyto- plankton as organic osmosis regulator

  10. Atmospheric variability of methyl chloride during the last 300 years from an Antarctic ice core and firn air

    E-print Network

    Saltzman, Eric

    Atmospheric variability of methyl chloride during the last 300 years from an Antarctic ice core] Measurements of methyl chloride (CH3Cl) in Antarctic polar ice and firn air are used to describe, and M. Battle (2004), Atmospheric variability of methyl chloride during the last 300 years from

  11. Comparative evaluation of the indigenous microbial diversity vs. drilling fluid contaminants in the NEEM Greenland ice core.

    PubMed

    Miteva, Vanya; Burlingame, Caroline; Sowers, Todd; Brenchley, Jean

    2014-08-01

    Demonstrating that the detected microbial diversity in nonaseptically drilled deep ice cores is truly indigenous is challenging because of potential contamination with exogenous microbial cells. The NEEM Greenland ice core project provided a first-time opportunity to determine the origin and extent of contamination throughout drilling. We performed multiple parallel cultivation and culture-independent analyses of five decontaminated ice core samples from different depths (100-2051 m), the drilling fluid and its components Estisol and Coasol, and the drilling chips collected during drilling. We created a collection of diverse bacterial and fungal isolates (84 from the drilling fluid and its components, 45 from decontaminated ice, and 66 from drilling chips). Their categorization as contaminants or intrinsic glacial ice microorganisms was based on several criteria, including phylogenetic analyses, genomic fingerprinting, phenotypic characteristics, and presence in drilling fluid, chips, and/or ice. Firmicutes and fungi comprised the dominant group of contaminants among isolates and cloned rRNA genes. Conversely, most Proteobacteria and Actinobacteria originating from the ice were identified as intrinsic. This study provides a database of potential contaminants useful for future studies of NEEM cores and can contribute toward developing standardized protocols for contamination detection and ensuring the authenticity of the microbial diversity in deep glacial ice. PMID:24450335

  12. Kinetics of Heterogeneous Ice Nucleation on the Surfaces of Mineral Dust Cores Inserted into Aqueous Ammonium Sulfate Particles

    E-print Network

    -235 K) surface tensions of ice against aqueous ammonium sulfate solutions. The slope of the temperatureKinetics of Heterogeneous Ice Nucleation on the Surfaces of Mineral Dust Cores Inserted dependence is positive for pure water but is progressively negative as the ammonium sulfate content increases

  13. Mount Logan ice core record of tropical and solar influences on Aleutian Low variability: 500-1998 A.D.

    NASA Astrophysics Data System (ADS)

    Osterberg, Erich C.; Mayewski, Paul A.; Fisher, David A.; Kreutz, Karl J.; Maasch, Kirk A.; Sneed, Sharon B.; Kelsey, Eric

    2014-10-01

    Continuous, high-resolution paleoclimate records from the North Pacific region spanning the past 1500 years are rare; and the behavior of the Aleutian Low (ALow) pressure center, the dominant climatological feature in the Gulf of Alaska, remains poorly constrained. Here we present a continuous, 1500 year long, calibrated proxy record for the strength of the wintertime (December-March) ALow from the Mount Logan summit (PR Col; 5200 m asl) ice core soluble sodium time series. We show that ice core sodium concentrations are statistically correlated with North Pacific sea level pressure and zonal wind speed. Our ALow proxy record reveals a weak ALow from circa 900-1300 A.D. and 1575-1675 A.D., and a comparatively stronger ALow from circa 500-900 A.D., 1300-1575 A.D., and 1675 A.D. to present. The Mount Logan ALow proxy record shows strong similarities with tropical paleoclimate proxy records sensitive to the El Niño-Southern Oscillation and is consistent with the hypothesis that the Medieval Climate Anomaly was characterized by more persistent La Niña-like conditions while the Little Ice Age was characterized by at least two intervals of more persistent El Niño-like conditions. The Mount Logan ALow proxy record is significantly (p < 0.05) correlated and coherent with solar irradiance proxy records over various time scales, with stronger solar irradiance generally associated with a weaker ALow and La Niña-like tropical conditions. However, a step-like increase in ALow strength during the Dalton solar minimum circa 1820 is associated with enhanced Walker circulation. Furthermore, rising CO2 forcing or internal variability may be masking the twentieth century rise in solar irradiance.

  14. Mineralogical and Crystal Chemical Characterization of Dust Particles From Antarctica Ice Cores

    NASA Astrophysics Data System (ADS)

    Sala, M.; Dapiaggi, M.; Artioli, G.; Marino, F.; Delmonte, B.; Maggi, V.; Frezzotti, M.

    2006-12-01

    Antarctic ice cores are actively studied to understand and reconstruct past climatic changes. Valuable data to this aim are the physical and chemical characteristics of the very cold ice, that in several places in Antarctica laid undisturbed since the time of deposition, carrying information on depostion rates and trapped chemical components, and especially the aeolian mineral particles, which is mainly transported by the wind, its mineralogical and chemical composition being influenced by a complex interplay of atmospheric, hydrological, geographical and geological parameters. Besides a few pioneering studies in the eighties there are no recent detailed investigations on the mineralogical composition of the dust particulate enclosed in the Antarctic ice cores, so that its compostion is commonly evaluated indirectly, by means of recalculations from chemical analyses. A recent project was started to set up an analytical protocol to define the mineralogical and crystal chemical composition of ice dust material. The main challenge is the very small amount of solid particles, which is generally below the ppm range (1-100 mg of dust per kg of melted ice), which makes sample preparation for the different analytical techniques very difficult and prone to external contamination. The developed protocol encompasses X-ray powder diffraction (XRPD), high-resolution transmission electron microscopy (HR-TEM) coupled to energy dispersive X-ray fluorescence analysis (ED-XRF), and proton induced X-ray emission analysis (PIXE) on the same sample, so to combine single-particle and bulk analysis of the material. The results from the different techniques provide for robust procedures for mineral phases identification, as the XRPD informations are cross-checked with single particle TEM results. At the same time XRPD provides for the statistics intrinsically lacking in single particle TEM evaluation. Moreover, the TEM-associated ED-XRF analysis yields an approximate crystal chemistry of each mineral phase, which combined to the quantitative phase analysis obtained by XRPD allows for proper assessment of the PIXE data. Successful identification and analysis has been performed on smectite, illite, kaolinite, talc, K-feldspar, albite, quartz and calcite of a few samples from the EPICA (EPICA - Dome C; 75°06' S, 123°24' E, 3233 m a.s.l., mean annual accumulation rate 2.5 g cm-2 yr-1 and Talos Dome (TDC, 159°04'E, 72°46'S, 2316 m a.s.l., mean annual accumulation rate 8 g cm-2 yr-1 ice cores. The procedure is now being applied systematically to the investigation of all dust components from the ice of these drillings.

  15. A new direction for Antarctic ice cores: reconstructing Pacific decadal variability and Australian drought history from the Law Dome ice core.

    NASA Astrophysics Data System (ADS)

    Vance, Tessa; Roberts, Jason; Plummer, Chris; Kiem, Anthony; van Ommen, Tas

    2015-04-01

    Decadal scale SST oscillations in the Pacific significantly influence rainfall variability and drought risk across and beyond the Pacific region. Understanding long-term decadal SST behavior in the Pacific is necessary to assess past and future climate, particularly drought risk. However, short instrumental records through much of the Pacific region, in particular the South Pacific, make such assessments difficult. A new reconstruction of Pacific decadal variability covering the last millennium has been produced from the Law Dome ice core, a high snow accumulation site in East Antarctica. The Law Dome ice core samples (at sub-annual resolution) a broad mid-latitude swathe of the Indian and South West Pacific region. This region exhibits wind speed and direction anomalies that are coherent with the phase of the Interdecadal Pacific Oscillation (IPO), an index measuring the decadal-scale Pacific SST state. This is the first millennial length IPO reconstruction and is based on the annual accumulation (snowfall) and sub-annual sea salt (wind proxy) records from Law Dome. To demonstrate the versatility of this new IPO reconstruction, we used it to explore drought history in eastern Australia, a region where drought risk is elevated during IPO positive phases. To do this, we super-imposed the 1000 year IPO reconstruction on a Law Dome proxy for eastern Australian rainfall (previously shown to represent rainfall with high significance during IPO positive phases (r =0.406-0.677, p <0.0001-0.01). Eight 'mega-droughts' (dry periods >5 years duration) were identified over the last millennium. Six mega-droughts occurred between AD 1000-1320 including one 39 y drought (AD 1174-1212). Water resources and infrastructure planning in Australia has been based on very limited statistical certainty around drought risk due to the short (~100 year) instrumental record and lack of rainfall proxies. This study shows that, similar to SW North America, Australia also experienced mega-droughts during the medieval period. Knowledge of the occurrence, duration and frequency of such mega-droughts will greatly improve drought risk assessment in Australia. Importantly, this new IPO reconstruction will help with assessing climate risk over the longer term in the wider Pacific Basin, particularly in the data-sparse Southern Hemisphere. In addition, the hydrological application of producing an annually dated drought record to calculate long-term drought risk represents a new use of Antarctic ice core records.

  16. High permafrost ice contents in Holocene slope deposits as observed from shallow geophysics and a coring program in Pangnirtung, Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Carbonneau, A.; Allard, M.; L'Hérault, E.; LeBlanc, A.

    2011-12-01

    A study of permafrost conditions was undertaken in the Hamlet of Pangnirtung, Nunavut, by the Geological Survey of Canada (GSC) and Université Laval's Centre d'études nordiques (CEN) to support decision makers in their community planning work. The methods used for this project were based on geophysical and geomorphological approaches, including permafrost cores drilled in surficial deposits and ground penetrating radar surveys using a GPR Pulse EKKO 100 extending to the complete community area and to its projected expansion sector. Laboratory analysis allowed a detailed characterization of permafrost in terms of water contents, salinity and grain size. Cryostratigraphic analysis was done via CT-Scan imagery of frozen cores using medical imaging softwares such as Osiris. This non destructive method allows a 3D imaging of the entire core in order to locate the amount of the excess ice, determine the volumetric ice content and also interpret the ice-formation processes that took place during freezing of the permafrost. Our new map of the permafrost conditions in Pangnirtung illustrates that the dominant mapping unit consist of ice-rich colluvial deposits. Aggradationnal ice formed syngenitically with slope sedimentation. Buried soils were found imbedded in this colluvial layer and demonstrates that colluviation associated with overland-flow during snowmelt occurred almost continuously since 7080 cal. BP. In the eastern sector of town, the 1 to 4 meters thick colluviums cover till and a network of ice wedges that were revealed as spaced hyperbolic reflectors on GPR profiles. The colluviums also cover ice-rich marine silt and bedrock in the western sector of the hamlet; marine shells found in a permafrost core yielded a radiocarbon date of 9553 cal. BP which provides a revised age for the local deglaciation and also a revised marine submergence limit. Among the applied methods, shallow drilling in coarse grained permafrost, core recovery and CT-Scan allowed the discovery of the importance of Holocene slope processes on shaping the surface of the terrain and leading to the observed cryostructures and ice contents in the near surface permafrost.

  17. Atmospheric CO2 and d13C-CO2 reconstruction of the Little Ice Age from Antarctic ice cores.

    NASA Astrophysics Data System (ADS)

    Rubino, Mauro; David, Etheridge; Trudinger, Cathy; Allison, Colin; Rayner, Peter; Mulvaney, Robert; Steele, Paul; Langenfeld, Ray; Sturges, William; Curran, Mark; Smith, Andrew

    2015-04-01

    The decrease of atmospheric CO2 concentration recorded in Antarctic ice around 1600 AD is one of the most significant atmospheric changes to have occurred during the last millennia, before the onset of the industrial period. Together with the temperature decrease, the CO2 drop has been used to derive the sensitivity of carbon stores to climate. However, the cause of it is still under debate because models are not yet able to reproduce either its magnitude, or its timing. Here we present new measurements of the CO2 concentration decrease recorded in an ice core from a medium accumulation rate site in Antarctica (DML). We show that the new record is compatible (differences <2 ppm) with the CO2 record from the high accumulation rate DSS site on Law Dome (East Antarctica), when the different age distributions are taken into account. We have also measured the d13C-CO2 change in DML ice, filling a gap around 1600 AD in the DSS d13C record. We use a double deconvolution of the CO2 and d13C records together to provide quantitative evidence that the CO2 decrease was caused by a change in the net flux to the terrestrial biosphere. Finally, we provide a new interpretation of a published record showing increasing atmospheric carbonyl sulphide during the CO2 decrease, suggesting that cooler LIA climate affected terrestrial biospheric fluxes. Altogether our findings support the hypothesis that reduced soil heterotrophic respiration is likely to have given the most significant contribution to the LIA CO2 decrease implying a positive CO2-climate feedback.

  18. A 2800-year Siberian ice core record of vanillic acid and p-hydroxybenzoic acid

    NASA Astrophysics Data System (ADS)

    Grieman, M. M.; Saltzman, E. S.; McConnell, J. R.; Fritzsche, D.; Opel, T.

    2014-12-01

    Biomass burning plays an important role in atmospheric chemistry, the global carbon cycle, and climate. The relationship between burning and climate, and the factors that influence burning emissions over long timescales are not well understood. Therefore, well-dated records are needed to establish a history of biomass burning. In this study we examine the distribution of vanillic (VA) and p-hydroxybenzoic (p-HBA) acids in a Siberian Arctic ice core (Akademii Nauk) covering the past 2800 years. These molecules are produced by the incomplete combustion of lignin, incorporated into atmospheric aerosols, and transported/deposited on ice sheets. VA and p-HBA are generated from the combustion of conifers and grasses, respectively, but are not uniquely derived from these sources. These records should be considered qualitative because a wide range of aerosols is generated from various plant materials under different combustion conditions. The records may also reflect changes in source region locations, transport efficiency, and atmospheric removal prior to deposition. Ice core samples were analyzed using ion chromatography with electrospray MS/MS detection. VA and p-HBA levels were markedly elevated during three time periods. The most recent of these periods occurred from AD 1450-1720 (140-220 m). The timing of two earlier peaks is less well constrained. They are estimated to be from 300-700 AD (400-500 m) and from 800-400 BC (610-670 m). The similarity between VA and p-HBA suggests that the two compounds are derived from a common source. These three periods of elevated VA and p-HBA are not evident in nitrate, ammonium, or black carbon measurements from the same ice core or with high latitude sedimentary charcoal records from North America, Europe, or eastern Siberia.

  19. Functional gene pyrosequencing reveals core proteobacterial denitrifiers in boreal lakes

    PubMed Central

    Saarenheimo, Jatta; Tiirola, Marja Annika; Rissanen, Antti J.

    2015-01-01

    Denitrification is an important microbial process in aquatic ecosystems that can reduce the effects of eutrophication. Here, quantification and pyrosequencing of nirS, nirK, and nosZ genes encoding for nitrite and nitrous oxide reductases was performed in sediment samples from four boreal lakes to determine the structure and seasonal stability of denitrifying microbial populations. Sediment quality and nitrate concentrations were linked to the quantity and diversity of denitrification genes, the abundance of denitrifying populations (nirS and nosZ genes) correlated with coupled nitrification-denitrification (Dn), and the denitrification of the overlying water NO3- (Dw) correlated with the nirS/nirK ratio. The number of core nirS, nirK, and nosZ operational taxonomical units (OTUs) was low (6, 7, and 3, respectively), and most of these core OTUs were shared among the lakes. Dominant nirK sequences matched best with those of the order Rhizobiales, which was one of the main bacterial orders present in the sediment microbiomes, whereas the dominant nirS sequences were affiliated with the order Burkholderiales. Over half of the nosZ sequences belonged to a single OTU of the order Burkholderiales, but coupled nitrification–denitrification rate correlated with another dominant nosZ OTU assigned to the order Rhodospirillales. The study indicates that a few core proteobacterial clusters may drive denitrification in boreal lake sediments, as the same Alpha- and Betaproteobacteria denitrifier clusters were present in different lakes and seasons. PMID:26191058

  20. Physical and chemical characteristics of the Subglacial Lake Whillans sediment cores, Whillans Ice Stream, West Antarctica

    NASA Astrophysics Data System (ADS)

    Hodson, T. O.; Powell, R. D.

    2013-12-01

    Sediment recovered from Subglacial Lake Whillans (SLW) is well-homogenized, structureless diamict; typical subglacial till. Based on theoretical estimates, the basal ice above SLW should be below the pressure melting point preventing melt-out of debris from basal ice. Therefore, the lake floor diamict likely formed through deformation while the ice stream was grounded at the drill site. Using satellite altimetry, Fricker, et al. (2007) inferred that SLW experiences short (~7 month) discharge events, lowering the ice surface and lake water level by between 1 and 4 m. The lake 'lowstands' are separated by longer periods of gradual recharge, but over the period of a lowstand the ice stream is suspected to touch down and couple with the lake floor, potentially shearing new till into the lake. The lack of sorted sediment or erosional lags indicates water flow during discharge/recharge events has had a low current velocity with quiescent conditions in the lake. The most notable variability in the cores is a uniformly weak, critical porosity horizon extending to ~50 cm depth above more consolidated till. We interpret the weak upper horizon as the product of shear deformation and decreasing effective pressure experienced during the final stages of grounding prior to a lake recharge event (see generally, the undrained plastic bed model of Tulaczyk et al. (2000)). The presence of this weak layer illustrates the importance of hydrology in modulating till rheology and is an example of how subglacial sediments can preserve archives of hydrologic conditions at the glacial bed. Fricker, H.A., T. Scambos, R. Bindschadler and L. Padman. 2007. An active subglacial water system in West Antarctica mapped from space. Science, 315(5818), 1544-1548. Tulaczyk S, Kamb WB, Engelhardt HF. 2000. Basal mechanics of Ice Stream B, West Antarctica. 2. Undrained plastic bed model. J. Geophys. Res. 105:483-94.

  1. Globally synchronous ice core volcanic tracers and abrupt cooling during the last glacial period

    USGS Publications Warehouse

    Bay, R.C.; Bramall, N.E.; Price, P.B.; Clow, G.D.; Hawley, R.L.; Udisti, R.; Castellano, E.

    2006-01-01

    We perform a Monte Carlo pattern recognition analysis of the coincidence between three regional volcanic histories from ice coring of Greenland and Antarctica over the period 2 to 45 ka, using SO4 anomalies in Greenland and East Antarctica determined by continuous core chemistry, together with West Antarctic volcanic ash layers determined by remote optical borehole logging and core assays. We find that the Antarctic record of volcanism correlates with Glacial abrupt climate change at a 95% to >99.8% (???3??) significance level and that volcanic depositions at the three locations match at levels exceeding 3??, likely indicating that many common horizons represent single eruptive events which dispersed material world wide. These globally coincident volcanics were associated with abrupt cooling, often simultaneous with onsets or sudden intensifications of millennial cold periods. The striking agreement between sites implies that the consistency of current timescales obtained by isotopic and glaciological dating methods is better than estimated. Copyright 2006 by the American Geogphysical Union.

  2. THE FAINTEST SEYFERT RADIO CORES REVEALED BY VLBI

    SciTech Connect

    Giroletti, Marcello; Panessa, Francesca E-mail: francesca.panessa@iasf-roma.inaf.i

    2009-12-01

    In this Letter, we report on dual-frequency European VLBI Network observations of the faintest and least luminous radio cores in Seyfert nuclei, going to sub-millijansky flux densities and radio luminosities around 10{sup 19} W Hz{sup -1}. We detect radio emission from the nuclear region of four galaxies (NGC 4051, NGC 4388, NGC 4501, and NGC 5033), while one (NGC 5273) is undetected at the level of approx100 muJy. The detected compact nuclei have rather different radio properties: spectral indices range from steep (alpha>0.7) to slightly inverted (alpha = -0.1), brightness temperatures vary from T{sub B} = 10{sup 5} K to larger than 10{sup 7} K, and cores are either extended or unresolved, in one case accompanied by lobe-like features (NGC 4051). In this sense, diverse underlying physical mechanisms can be at work in these objects: jet-base or outflow solutions are the most natural explanations in several cases; in the case of the undetected NGC 5273 nucleus, the presence of an advection-dominated accretion flow is consistent with the radio luminosity upper limit.

  3. Zeroing tests of luminescence sediment dating in the Arctic Ocean: Review and new results from Alaska-margin core tops and central-ocean dirty sea ice

    NASA Astrophysics Data System (ADS)

    Berger, Glenn W.

    2009-07-01

    Additional numeric dating techniques are needed for sediments in the Arctic Ocean that span at least the last half million years. Almost all presently suitable geochronometers are relative-dating methods, requiring significant assumptions about sedimentation rates (such as continuous deposition and preservation). An alternative 'absolute' geochronometer, luminescence sediment dating, assumes daylight exposure of siliciclastic grains before burial. Early tests and applications of thermoluminescence (TL) techniques in the western Arctic Ocean showed some promise, but trans-ocean application to core tops of more sensitive photon-stimulated-luminescence (PSL) multi-aliquot procedures revealed large regional variations in accuracy. Recent applications of single-aliquot PSL procedures to core tops and dirty sea ice refine our understanding of the limitations and capabilities of PSL dating in this ocean. Dirty sea ice is the source of most of the bottom sediment. Particular procedures for multi-aliquot and single-aliquot PSL dating produce near-zero ages for silt grains from 4 available dirty sea-ice samples. This suggests that TL and PSL age overestimates obtained previously from core-top samples were due mainly to bottom-current reworking (mixing or stripping) of silt grains in abyssal darkness, rather than due to sedimentation of relict-age grains from sea ice. Single-aliquot PSL dating of silt grains from core tops at two different-depth sites at the Alaskan margin reveals large variations in accuracy. This re-emphasizes the critical sensitivity of fine-silt PSL dating accuracy to the effects of bottom-current processes. These recent applications are beginning to provide a more precise knowledge of just where and how PSL methods are likely to be accurate in the Arctic Ocean.

  4. Non-Target Analyses of organic compounds in ice cores using HPLC-ESI-UHRMS

    NASA Astrophysics Data System (ADS)

    Zuth, Christoph; Müller-Tautges, Christina; Eichler, Anja; Schwikowski, Margit; Hoffmann, Thorsten

    2015-04-01

    To study the global climatic and environmental changes it is necessary to know the environmental and especially atmospheric conditions of the past. By analysing climate archives, such as for example ice cores, unique environmental information can be obtained. In contrast to the well-established analysis of inorganic species in ice cores, organic compounds have been analysed in ice cores to a much smaller extent. Because of current analytical limitations it has become commonplace to focus on 'total organic carbon' measurements or specific classes of organic molecules, as no analytical methods exist that can provide a broad characterization of the organic material present[1]. On the one hand, it is important to focus on already known atmospheric markers in ice cores and to quantify, where possible, in order to compare them to current conditions. On the other hand, unfortunately a wealth of information is lost when only a small fraction of the organic material is examined. However, recent developments in mass spectrometry in respect to higher mass resolution and mass accuracy enable a new approach to the analysis of complex environmental samples. The qualitative characterization of the complex mixture of water soluble organic carbon (WSOC) in the ice using high-resolution mass spectrometry allows for novel insights concerning the composition and possible sources of aerosol derived WSOC deposited at glacier sites. By performing a non-target analysis of an ice core from the Swiss Alps using previous enrichment by solid-phase extraction (SPE) and high performance liquid chromatography coupled to electrospray ionization and ultra-high resolution mass spectrometry (HPLC-ESI-UHRMS) 475 elemental formulas distributed onto 659 different peaks were detected. The elemental formulas were classified according to their elemental composition into CHO-, CHON-, CHOS-, CHONS-containing compounds and 'others'. Several methods for the analysis of complex data sets of high resolution mass spectrometry were applied to the results of the non-target analysis. By various classifications in Van Krevelen plots[2], amino acids and degradation products of proteins as well as degradation products of lignins have been determined as the main components of the ice core. Furthermore, the majority of WSOC molecular formulas identified in this non-target analysis had molar H/C and O/C ratios similar to mono- and di-carboxylic acids and SOAs[3]. Studies of the carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol showed that a majority of the elemental formulas can be associated with the combustion of biomass as a major source of the WSOC[4]. References: [1] Grannas et al., J. Geophys Res.,2006, 111 [2] Sleighter, RL, Hatcher, PG, J. Mass Spectrom., 2007, 42, 559-574 [3] Wozniak et al., Atmos. Chem. Phys., 2008, 8, 5099-5111 [4] Kroll et al., Nature Chemistry, 2011, 3, 133-139

  5. Factors affecting the reproducibility of trace element analyses of ice core samples

    NASA Astrophysics Data System (ADS)

    Rhodes, R. H.; Baker, J.; Millet, M.; Bertler, N.

    2010-12-01

    Ice cores provide high-resolution records of past atmospheric and environmental conditions. Increasingly, conventional stable isotope and major ion analyses of ice cores are being complimented by determination of ultra-trace levels of trace elements by inductively coupled plasma mass spectrometry (ICP-MS). Typically, these analyses are performed on acidified, melted, ice without removal of particulates by centrifugation or filtration. We have carried out a systematic investigation of the factors influencing the reproducibility of trace element determinations in ice core samples, which can be considered to contain three inorganic chemical components: marine salt, aerosol and mineral dust. The prevalent method of ICP-MS analysis of ice core samples involves analysing acidified samples (typically to 1% HNO3). To mimic these conditions, we undertook systematic leaching experiments on geochemically well-characterised, powdered, rock standards to examine how trace element measurements varied depending on the length of the acidification time, whether samples were frozen after acidification or not, dust lithology and the dust concentration. Four certified standards were leached at a dust concentration of 10 ppm in 1% HNO3 and leachates were sampled at regular time intervals up to a period of several months. The standards encompass a range of lithologies and textures, including basalt (BHVO-2), dolerite (W-2), granite (JG-2) and Fe-Mn oxyhydroxide (Nod P-1) materials. The basalt, dolerite and granite all have silicate mineralogies and showed some similar trace element trends during leaching. For example, the concentration of Al in the leachates increased by between 125% and 280% during the first 12 hr and did not stop rising after 8 weeks of leaching. In contrast, rare earth element and Y concentrations in the leachates became constant after just 2 hr. However, total element recovery differed between lithologies. After 12 hr of acidification the recovery of elements from Na to Mn was less than 10% for basalt and dolerite but was significantly higher for the granite, reaching up to 57% for Mg. For the Nod P-1 standard, nearly all elements reached a constant leachate concentration after 12 hr, but recovery of different elements varied from 3.5% to 80%. These patterns of trace element leaching were similar at different dust concentrations, however, freezing of acidified samples promotes leaching of elements such as Zr and Ti. These results reflect variable and time-dependent leaching of different elements from different mineral constituents in the rock standards which has important implications for ultra-trace element analysis of ice core material: (1) trace element concentrations and ratios will generally not reflect that of the source dust material; (2) trace element concentrations and ratios will vary considerably (more than an order of magnitude) depending on the acidification time; (3) trace element concentrations determined on ice core material containing mineral dust will not be reproducible unless dust is removed prior to acidification and ICP-MS analysis.

  6. Low-energy neutrino search for dark matter in the Galactic Center with IceCube-DeepCore

    SciTech Connect

    Flis, Samuel; Collaboration: IceCube Collaboration

    2014-11-18

    The cubic-kilometer sized IceCube neutrino observatory, constructed in the glacial ice at the South Pole, offers new opportunities for neutrino physics to reach lower neutrino energies with its in-fill array 'DeepCore'. A set of analysis techniques where the outer layers of IceCube are used as a veto makes it possible to reject atmospheric muons and thereby allows low-energy neutrino searches to be performed above the horizon. With these techniques the Galactic Center, an important target in searches for self-annihilating dark matter, becomes accessible for IceCube. In this contribution, we present the status of the Galactic Center dark matter analysis, using more than 10 months of data taken with the 79-string configuration of IceCube-DeepCore, as well as the new veto techniques used in the analysis.

  7. The IceCube data acquisition system for galactic core collapse supernova searches

    SciTech Connect

    Baum, Volker; Collaboration: IceCube Collaboration

    2014-11-18

    The IceCube Neutrino Observatory was designed to detect highly energetic neutrinos. The detector was built as a lattice of 5160 photomultiplier tubes monitoring one cubic kilometer of clear Antarctic ice. Due to low photomultiplier dark noise rates in the cold and radio-pure ice, IceCube is also able to detect bursts of O(10MeV) neutrinos expected to be emitted from core collapse supernovae. The detector will provide the world’s highest statistical precision for the lightcurves of galactic supernovae by observing an induced collective rise in all photomultiplier rates [1]. This paper presents the supernova data acquisition system, the search algorithms for galactic supernovae, as well as the recently implemented HitSpooling DAQ extension. HitSpooling will overcome the current limitation of transmitting photomultiplier rates in intervals of 1.6384 ms by storing all recorded time-stamped hits for supernova candidate triggers. From the corresponding event-based information, the average neutrino energy can be estimated and the background induced by detector noise and atmospheric muons can be reduced.

  8. Stability and evolution of ice cored glacial deposits on the flanks of volcanoes

    NASA Astrophysics Data System (ADS)

    Helbert, J.; Reiss, D.; Breuer, D.

    2005-12-01

    There are several units on Mars which have been interpreted as glacial deposits based on morphological evidences. Many of these units are found on the flanks of volcanic edifices. Especially the recent imaging by the HRSC camera on Mars Express has provided us with a wealth of new examples and with much more morphological details. These include deposits as young as 5-14 Ma for example on the flanks of Hecates Tholus. We have recently studied this deposit and found a high likelihood that it is still ice cored. Based on our cautious estimates this ice would be protected by an only 10-50m thick sublimation till. We will report more detailed on these findings and compare it with comparable deposits at the flanks of other volcanoes. This deposit is especially interesting because there are indications for very recent activity of Hecates Tholus, including lava flows potentially as young as 2Ma. Assuming that we are today in a quieter but still active phase of the volcano we will discuss the implications for the internal structure and especially the redistribution of ice in such a deposit assuming episodic changes in the internal heat flow. There are indications for the formation of ice lenses potentially sealing environments at the base of this and similar deposits on other volcanic edifices. There is a wide variety of implications ranging from storage and delayed release of volcanic gases (incl. methane) up to potentially forming niches for biological activities.

  9. Lead isotopic compositions in the EPICA Dome C ice core and Southern Hemisphere Potential Source Areas

    NASA Astrophysics Data System (ADS)

    Vallelonga, P.; Gabrielli, P.; Balliana, E.; Wegner, A.; Delmonte, B.; Turetta, C.; Burton, G.; Vanhaecke, F.; Rosman, K. J. R.; Hong, S.; Boutron, C. F.; Cescon, P.; Barbante, C.

    2010-01-01

    A record of Pb isotopic compositions and Pb and Ba concentrations are presented for the EPICA Dome C ice core covering the past 220 ky, indicating the characteristics of dust and volcanic Pb deposition in central East Antarctica. Lead isotopic compositions are also reported in a suite of soil and loess samples from the Southern Hemisphere (Australia, Southern Africa, Southern South America, New Zealand, Antarctica) in order to evaluate the provenance of dust present in Antarctic ice. Lead isotopic compositions in Dome C ice support the contention that Southern South America was an important source of dust in Antarctica during the last two glacial maxima, and furthermore suggest occasional dust contributions from local Antarctic sources. The isotopic signature of Pb in Antarctic ice is altered by the presence of volcanic Pb, inhibiting the evaluation of glacial-interglacial changes in dust sources and the evaluation of Australia as a source of dust to Antarctica. Consequently, an accurate evaluation of the predominant source(s) of Antarctic dust can only be obtained from glacial maxima, when dust-Pb concentrations were greatest. These data confirm that volcanic Pb is present throughout Antarctica and is emitted in a physical phase that is free from Ba, while dust Pb is transported within a matrix containing Ba and other crustal elements.

  10. High speed, high resolution, and continuous chemical analysis of ice cores using a melter and ion chromatography.

    PubMed

    Cole-Dai, Jihong; Budner, Drew M; Ferris, Dave G

    2006-11-01

    Measurement of trace chemical impurities in ice cores contributes to the reconstruction of records of the atmospheric environment and of the climate system. Ion chromatography (IC) is an effective analytical technique for ionic species in ice cores but has been used on discretely prepared ice samples, resulting in extensive and slow sample preparation and potential for contamination. A new technique has been developed that utilizes IC as the online detection technique in a melter-based continuous flow system for quantitative determination of major ionic chemical impurities. The system, called CFA-IC for continuous flow analysis with ion chromatography detection, consists of an ice core melter, several ion chromatographs, and an interface that distributes meltwater to the IC instruments. The CFA-IC technique combines the accuracy, precision, and ease of use of IC measurement with the enhanced speed and depth resolution of continuous melting systems and is capable of virtually continuous, high-speed and high-resolution chemical analysis of long ice cores. The new technique and operating procedures have been tested and validated with the analysis of over 100 m of ice cores from Antarctica. The current CFA-IC system provides an all-major-ion analysis speed of up to 8 m a day at a depth resolution of approximately 2 cm. PMID:17144308

  11. Changes in Black Carbon Deposition to Antarctica from Two Ice Core Records, A.D. 1850-2000

    NASA Technical Reports Server (NTRS)

    Bisiaux, Marion M.; Edward, Ross; McConnell, Joseph R.; Curran, Mark A. J.; VanOmmen, Tas D.; Smith, Andrew M.; Neumann, Thomas A.; Pasteris, Daniel R.; Penner, Joyce E.; Taylor, Kendrick

    2012-01-01

    Continuous flow analysis was based on a steady sample flow and in-line detection of BC and other chemical substances as described in McConnell et al. (2007). In the cold room, previously cut one meter ice core sticks of 3x3cm, are melted continuously on a heated melter head specifically designed to eliminate contamination from the atmosphere or by the external parts of the ice. The melted ice from the most inner part of the ice stick is continuously pumped by a peristaltic pump and carried to a clean lab by Teflon lines. The recorded signal is continuous, integrating a sample volume of about 0.05 mL, for which the temporal resolution depends on the speed of melting, ice density and snow accumulation rate at the ice core drilling site. For annual accumulation derived from the WAIS and Law Dome ice cores, we assumed 3.1 cm water equivalent uncertainty in each year's accumulation from short scale spatial variability (glaciological noise) which was determined from several measurements of annual accumulation in multiple parallel ice cores notably from the WAIS Divide ice core site (Banta et al., 2008) and from South Pole site (McConnell et al., 1997; McConnell et al., 2000). Refractory black carbon (rBC) concentrations were determined using the same method as in (Bisiaux et al., 2011) and adapted to continuous flow measurements as described by (McConnell et al., 2007). The technique uses a single particle intracavity laser induced incandescence photometer (SP2, Droplet Measurement Technologies, Boulder, Colorado) coupled to an ultrasonic nebulizer/desolvation (CETAC UT5000) Flow Injection Analysis (FIA). All analyses, sample preparation etc, were performed in a class 100 cleanroom using anti contamination "clean techniques". The samples were not acidified.

  12. Isotopic composition of ice cores and meltwater from upper fremont glacier and Galena Creek rock glacier, Wyoming

    USGS Publications Warehouse

    DeWayne, Cecil L.; Green, J.R.; Vogt, S.; Michel, R.; Cottrell, G.

    1998-01-01

    Meltwater runoff from glaciers can result from various sources, including recent precipitation and melted glacial ice. Determining the origin of the meltwater from glaciers through isotopic analysis can provide information about such things as the character and distribution of ablation on glaciers. A 9.4 m ice core and meltwater were collected in 1995 and 1996 at the glacigenic Galena Creek rock glacier in Wyoming's Absaroka Mountains. Measurements of chlorine-36 (36Cl), tritium (3H), sulphur-35 (35S), and delta oxygen-18 (??18O) were compared to similar measurements from an ice core taken from the Upper Fremont Glacier in the Wind River Range of Wyoming collected in 1991-95. Meltwater samples from three sites on the rock glacier yielded 36Cl concentrations that ranged from 2.1 ?? 1.0 X 106 to 5.8??0.3 X 106 atoms/l. The ice-core 36Cl concentrations from Galena Creek ranged from 3.4??0.3 X 105 to 1.0??0.1 X 106 atoms/l. Analysis of an ice core from the Upper Fremont Glacier yielded 36Cl concentrations of 1.2??0.2 X 106 and 5.2??0.2 X 106 atoms/l for pre- 1940 ice and between 2 X 106 and 3 X 106 atoms/l for post-1980 ice. Purdue's PRIME Lab analyzed the ice from the Upper Fremont Glacier. The highest concentration of 36Cl in the ice was 77 ?? 2 X 106 atoms/l and was deposited during the peak of atmospheric nuclear weapons testing in the late 1950s. This is an order of magnitude greater than the largest measured concentration from both the Upper Fremont Glacier ice core that was not affected by weapons testing fallout and the ice core collected from the Galena Creek rock glacier. Tritium concentrations from the rock glacier ranged from 9.2??0.6 to 13.2??0.8 tritium units (TU) in the meltwater to -1.3??1.3 TU in the ice core. Concentrations of 3H in the Upper Fremont Glacier ice core ranged from 0 TU in the ice older than 50 years to 6-12 TU in the ice deposited in the last 10 years. The maximum 3H concentration in ice from the Upper Fremont Glacier deposited in the early 1960s during peak weapons testing fallout for this isotope was 360 TU. One meltwater sample from the rock glacier was analyzed for 35S with a measured concentration of 5.4??1.0 millibecquerel per liter (mBeq/l). Modern precipitation in the Rocky Mountains contains 35S from 10 to 40 mBeq/L. The ??18O results in meltwater from the Galena Creek rock glacier (-17.40??0.1 to -17.98??0.1 per mil) are similar to results for modern precipitation in the Rocky Mountains. Comparison of these isotopic concentrations from the two glaciers suggest that the meltwater at the Galena Creek site is composed mostly of melted snow and rain that percolates through the rock debris that covers the glacier. Additionally, this water from the rock debris is much younger (less than two years) than the reported age of about 2000 years for the subsurface ice at the mid-glacier coring site. Thus the meltwater from the Galena Creek rock glacier is composed primarily of melted surface snow and rain water rather than melted glacier ice, supporting previous estimates of slow ablation rates beneath the surface debris of the rock glacier.

  13. Melting and metallization of silica in the cores of gas giants, ice giants, and super Earths

    NASA Astrophysics Data System (ADS)

    Mazevet, S.; Tsuchiya, T.; Taniuchi, T.; Benuzzi-Mounaix, A.; Guyot, F.

    2015-07-01

    The physical state and properties of silicates at conditions encountered in the cores of gas giants, ice giants, and of Earth-like exoplanets now discovered with masses up to several times the mass of the Earth remain mostly unknown. Here, we report on theoretical predictions of the properties of silica, SiO2, up to 4 TPa and about 20 000 K by using first principles molecular dynamics simulations based on density functional theory. For conditions found in the super Earths and in ice giants, we show that silica remains a poor electrical conductor up to 10 Mbar due to an increase in the Si-O coordination with pressure. For Jupiter and Saturn cores, we find that MgSiO3 silicate has not only dissociated into MgO and SiO2, as shown in previous studies, but that these two phases have likely differentiated to lead to a core made of liquid SiO2 and solid (Mg,Fe)O.

  14. Melting and metallization of silica in the cores of gas giants, ice giants and super Earths

    E-print Network

    Mazevet, S; Taniuchi, T; Benuzzi-Mounaix, A; Guyot, F

    2014-01-01

    The physical state and properties of silicates at conditions encountered in the cores of gas giants, ice giants and of Earth like exoplanets now discovered with masses up to several times the mass of the Earth remains mostly unknown. Here, we report on theoretical predictions of the properties of silica, SiO$_2$, up to 4 TPa and about 20,000K using first principle molecular dynamics simulations based on density functional theory. For conditions found in the Super-Earths and in ice giants, we show that silica remains a poor electrical conductor up to 10 Mbar due to an increase in the Si-O coordination with pressure. For Jupiter and Saturn cores, we find that MgSiO$_3$ silicate has not only dissociated into MgO and SiO$_2$, as shown in previous studies, but that these two phases have likely differentiated to lead to a core made of liquid SiO$_2$ and solid (Mg,Fe)O.

  15. Phylogenetic and physiological diversity of microorganisms isolated from a deep greenland glacier ice core

    NASA Technical Reports Server (NTRS)

    Miteva, V. I.; Sheridan, P. P.; Brenchley, J. E.

    2004-01-01

    We studied a sample from the GISP 2 (Greenland Ice Sheet Project) ice core to determine the diversity and survival of microorganisms trapped in the ice at least 120,000 years ago. Previously, we examined the phylogenetic relationships among 16S ribosomal DNA (rDNA) sequences in a clone library obtained by PCR amplification from genomic DNA extracted from anaerobic enrichments. Here we report the isolation of nearly 800 aerobic organisms that were grouped by morphology and amplified rDNA restriction analysis patterns to select isolates for further study. The phylogenetic analyses of 56 representative rDNA sequences showed that the isolates belonged to four major phylogenetic groups: the high-G+C gram-positives, low-G+C gram-positives, Proteobacteria, and the Cytophaga-Flavobacterium-Bacteroides group. The most abundant and diverse isolates were within the high-G+C gram-positive cluster that had not been represented in the clone library. The Jukes-Cantor evolutionary distance matrix results suggested that at least 7 isolates represent new species within characterized genera and that 49 are different strains of known species. The isolates were further categorized based on the isolation conditions, temperature range for growth, enzyme activity, antibiotic resistance, presence of plasmids, and strain-specific genomic variations. A significant observation with implications for the development of novel and more effective cultivation methods was that preliminary incubation in anaerobic and aerobic liquid prior to plating on agar media greatly increased the recovery of CFU from the ice core sample.

  16. Increase in elemental carbon values between 1970 and 2004 observed in a 300-year ice core from Holtedahlfonna (Svalbard)

    NASA Astrophysics Data System (ADS)

    Ruppel, M. M.; Isaksson, I.; Ström, J.; Beaudon, E.; Svensson, J.; Pedersen, C. A.; Korhola, A.

    2014-10-01

    Black carbon (BC) is a light-absorbing particle that warms the atmosphere-Earth system. The climate effects of BC are amplified in the Arctic, where its deposition on light surfaces decreases the albedo and causes earlier melt of snow and ice. Despite its suggested significant role in Arctic climate warming, there is little information on BC concentrations and deposition in the past. Here we present results on BC (here operationally defined as elemental carbon (EC)) concentrations and deposition on a Svalbard glacier between 1700 and 2004. The inner part of a 125 m deep ice core from Holtedahlfonna glacier (79°8' N, 13°16' E, 1150 m a.s.l.) was melted, filtered through a quartz fibre filter and analysed for EC using a thermal-optical method. The EC values started to increase after 1850 and peaked around 1910, similar to ice core records from Greenland. Strikingly, the EC values again increase rapidly between 1970 and 2004 after a temporary low point around 1970, reaching unprecedented values in the 1990s. This rise is not seen in Greenland ice cores, and it seems to contradict atmospheric BC measurements indicating generally decreasing atmospheric BC concentrations since 1989 in the Arctic. For example, changes in scavenging efficiencies, post-depositional processes and differences in the vertical distribution of BC in the atmosphere are discussed for the differences between the Svalbard and Greenland ice core records, as well as the ice core and atmospheric measurements in Svalbard. In addition, the divergent BC trends between Greenland and Svalbard ice cores may be caused by differences in the analytical methods used, including the operational definitions of quantified particles, and detection efficiencies of different-sized BC particles. Regardless of the cause of the increasing EC values between 1970 and 2004, the results have significant implications for the past radiative energy balance at the coring site.

  17. Unexpected increase in elemental carbon values over the last 30 years observed in a Svalbard ice core

    NASA Astrophysics Data System (ADS)

    Ruppel, M. M.; Isaksson, E.; Ström, J.; Beaudon, E.; Svensson, J.; Pedersen, C. A.; Korhola, A.

    2014-05-01

    Black carbon (BC) is a light-absorbing particle that warms the atmosphere-Earth system. The climate effects of BC are amplified in the Arctic where its deposition on light surfaces decreases the albedo and causes earlier melt of snow and ice. Despite its suggested significant role in Arctic climate warming there is little information on BC concentrations and deposition in the past. Here we present results on BC (here operationally defined as elemental carbon (EC)) concentrations and deposition on a Svalbard glacier between 1700 and 2004. The inner part of a 125 m deep ice core from Holtedahlfonna glacier (79°8' N, 13°16' E, 1150 m a.s.l.) was melted, filtered through a quartz fibre filter and analysed for EC using a thermal optical method. The EC values started to increase after 1850 and peaked around 1910, similar to ice core records from Greenland. Strikingly, the EC values again increase rapidly between 1970 and 2004. This rise is not seen in Greenland ice cores and it seems to contradict atmospheric BC measurements indicating generally decreasing atmospheric BC concentrations since 1989 in the Arctic. Several hypotheses, such as changes in scavenging efficiencies, post-depositional processes and differences in the vertical distribution of BC in the atmosphere, are discussed for the differences between the Svalbard and Greenland ice core records, and the ice core and atmospheric measurements in Svalbard. In addition, the divergent BC trends between Greenland and Svalbard ice cores may be caused by differences in the analytical methods used, including the operational definitions of quantified particles, and detection efficiencies of different-sized BC particles. Regardless of the cause of the increasing EC values in the recent decades, the results have significant implications for the past radiative energy balance at the coring site.

  18. Oxygen isotopic composition of micrometer-sized quartz grains in EPICA-Dome C ice core

    NASA Astrophysics Data System (ADS)

    Delmonte, B.; Hoppe, P.; Hellebrand, E.; Huth, J.; Petit, J.; Maggi, V.

    2006-12-01

    Depicting the geographic provenance of aeolian dust reaching the interior of the East Antarctic plateau is of primary importance for a thorough underst94anding of paleo-atmospheric circulation patterns. A geochemical approach based on the 87Sr/86Sr versus 143Nd/144Nd isotopic signature of mineral particles extracted from Antarctic ice cores and comparison with samples from the Potential Source Areas (PSA) of the Southern Hemisphere has been classically used. This allowed pointing out a dominant Southern South American provenance for dust in the EPICA-Dome C and Vostok ice cores during late Quaternary glacial stages. However, the Sr-Nd isotopic fields from other potential source regions did show a partial overlap with the South American and glacial dust fields, and complementary arguments had to be invoked to infer that their possible contribution is negligible. In this study, we propose a new approach for dust fingerprinting based on the 18O/16O ratios of micrometer- sized quartz grains (1 to 2 ?m in size) entrapped in Antarctic ice. Micrometric quartz grains were first identified through SEM/EDX in a sample from the EPICA-Dome C ice core dating back the last glacial maximum. O-isotopic measurements on 25 single grains were performed with the NanoSIMS ion microprobe at the Max-Plank-Institute for Chemistry in Mainz. 18OSMOW values are between 2 and 43 per mil; however most 18OSMOW values fall within a gaussian distribution with a mean 18OSMOW of 25.5 per mil and standard deviation of 2.6 per mil (1^3). These results suggest that a significant contribution from Australian and New Zealand sources seems very unlikely during glacial stage 2, but unfortunately 18OSMOW values for small quartz grains from the Southern Hemisphere PSAs are very scarce. NanoSIMS O-isotopic measurements on Aeolian quartz grains entrapped in Antarctic ice by is a promising tool for investigating the geographic provenance of mineral dust in Quaternary times.

  19. Aromatic acids from biomass burning in the WAIS Divide ice core

    NASA Astrophysics Data System (ADS)

    Saltzman, E. S.; Grieman, M. M.; McConnell, J.; Cole-Dai, J.

    2014-12-01

    Biomass burning plays an important role in atmospheric chemistry, carbon cycling, and climate. The global long-term history of biomass burning is not well established, making it difficult to study the relationship between burning, climate change, and atmospheric chemistry. Here we present the Antarctic ice core records of vanillic acid and p-hydroxybenzoic from the WAIS Divide ice core covering the past 2.4-30 kyrs BP. These molecules are derived from incomplete combustion of plant lignin and transported/deposited as aerosols onto the ice sheet. Vanillic and p-hydroxybenzoic acids are associated with combustion of conifers and grasses, respectively, but are not uniquely derived from these plant types. Analyses were done using ion chromatography with electrospray MS/MS detection in negative ion SRM mode. Vanillic p-hydroxybenzoic acid exhibited a range from baseline levels near 0.01 ppb (detection limit) to >0.5 ppb. Vanillic acid exhibited striking millennial scale variability during late glacial period, with 6 major peaks between 25 and 13.5 kyrs BP, with a spacing of 1.5-3 kyrs and durations of up to 1 kyr. There are no comparable peaks during the early-mid Holocene. A late Holocene vanillic acid peak starts at 3 kyrs BP. p-Hydroxybenzoic acid shares the same major peaks as vanillic acid from 25-13.5 kyrs BP, but exhibits additional variability of comparable magnitude throughout the WAIS Divide 2.4-30 kyr record. These paleo records should be viewed as qualitative burning proxies because 1) a wide range of aerosol composition and sizes can be generated from combustion of various plant materials under different conditions, and 2) the ice core levels of aromatic acids may reflect changes in source regions, transport and atmospheric removal efficiency, and postdepositional mobilization. The major peaks in the WAIS Divide aromatic acid records most likely do not represent changes in global biomass burning emissions, because they are not highly correlated with variations in atmospheric methane. Such caveats notwithstanding, these records provide a surprising new picture of the long-term variability in the deposition of burning-derived aerosols to the Antarctic ice sheet.

  20. The ice-core record - Climate sensitivity and future greenhouse warming

    NASA Technical Reports Server (NTRS)

    Lorius, C.; Raynaud, D.; Jouzel, J.; Hansen, J.; Le Treut, H.

    1990-01-01

    The prediction of future greenhouse-gas-warming depends critically on the sensitivity of earth's climate to increasing atmospheric concentrations of these gases. Data from cores drilled in polar ice sheets show a remarkable correlation between past glacial-interglacial temperature changes and the inferred atmospheric concentration of gases such as carbon dioxide and methane. These and other palaeoclimate data are used to assess the role of greenhouse gases in explaining past global climate change, and the validity of models predicting the effect of increasing concentrations of such gases in the atmosphere.

  1. Ice core based Pb pollution from gasoline in South America in the context of a 2000 year metallurgical history

    NASA Astrophysics Data System (ADS)

    Eichler, Anja; Gramlich, Gabriela; Kellerhals, Thomas; Tobler, Leonhard; Schwikowski, Margit

    2015-04-01

    Lead (Pb) is highly neurotoxic and, in contrast to many other heavy metals including cobalt, copper, and zinc, it has no beneficial effects to humans even at low concentrations. The introduction of leaded gasoline in the 1920s initiated a period of unabated growth in the global emissions of Pb. Prior to the onset of leaded gasoline phase-out in the 1970s, atmospheric Pb levels increased dramatically. Long-term histories of Pb pollution in Eastern and Western Europe, Asia, and North America suggest that emissions from leaded gasoline within the Northern Hemisphere are dominant compared to that from metallurgy and coal combustion during the second half of the 20th century. However, there is no equivalent data for Southern America. Although exploitation of the extensive polymetallic deposits of the Andean Altiplano in South America since pre-colonial times has caused substantial emissions of neurotoxic Pb into the atmosphere, its historical significance compared to recent Pb pollution from leaded gasoline is not yet resolved. Here we present the first comprehensive, high-resolution two millennia Pb emission history for South America, based on ice core records of Pb concentrations, Pb enrichment factors (EFs), and Pb isotope ratios from Illimani glacier in Bolivia. Complementary to local air pollution recorded in lake sediments, ice cores from mid latitude glaciers provide information about more extended source areas. Illimani is the highest mountain of the eastern Bolivian Andes and is located at the northeastern margin of the Bolivian Altiplano. The ice core Pb deposition history revealed enhanced Pb EFs due to metallurgical processing for silver production during periods of the Tiwanaku/Wari culture (AD 450-950), the Inca empires (AD 1450-1532), colonial times (AD 1532-1900), and tin production at the beginning of the 20th century. After the 1960s 208Pb/207Pb ratios decreased significantly, whereas Pb EFs increased by a factor of three compared to the emission level from metal production, which we attribute to gasoline related Pb emissions. Our results show that anthropogenic Pb pollution levels from road traffic in South America exceed those of any historical metallurgy in the last two millennia, even in regions with exceptional high local metallurgical activity.

  2. Probing non-standard interaction of neutrinos with IceCube and DeepCore

    NASA Astrophysics Data System (ADS)

    Esmaili, Arman; Smirnov, Alexei Yu.

    2013-06-01

    We consider effects of the Non-Standard Interactions (NSI) on oscillations of the high energy atmospheric neutrinos. The ? ? -oscillograms are constructed and their dependence on the NSI strength parameters ? ?? studied. We computed the zenith angle distributions of the ? ? -events in the presence of NSI in different energy regions. The distributions are confronted with the IceCube-79 (high energy sample) and the DeepCore (low energy sample) data and constraints on the strength parameters | ? ?? |? 6 × 10-3 and | ? ?? - ? ?? | ? 3 × 10-2 (90% C.L.) have been obtained. Future measurements of the zenith angle distributions by DeepCore in several energy bins will allow to improve the bounds by factor 2-3. We discuss the signatures of NSI in the zenith angle and energy distributions of events which allow to discriminate them from the effects of sterile neutrinos.

  3. Two Millennia of Pb Pollution Related to Altiplano Metallurgical Activities and Leaded Gasoline in South America from Illimani Ice Core

    NASA Astrophysics Data System (ADS)

    Eichler, A.; Gramlich, G.; Kellerhals, T.; Tobler, L.; Schwikowski, M.

    2014-12-01

    The exploitation of the extended polymetallic deposits of the Altiplano in South America led to significant emissions of the neurotoxic Pb into the atmosphere already since pre-Colonial times. Long-term histories of Pb pollution in Eastern and Western Europe, Asia, and North America suggest that within the Northern Hemisphere emissions from metallurgy and coal combustion are minor compared to that from leaded gasoline during the second half of the 20th century. However, there is no equivalent data for Southern America. Here we present the first comprehensive, high-resolution two millennia Pb emission history for South America, based on an ice core record from Illimani glacier in Bolivia. Illimani is the highest mountain of the eastern Bolivian Andes and is located at the northeastern margin of the Bolivian Altiplano. The 2000 year ice-core based decadal Pb deposition history revealed highest Pb Enrichment Factors (EFs) during the period 1965-85. Metallurgical processing for silver production during periods of the Tiwanaku culture (400-900 AD), the Inca empire (1450-1532 AD), colonial times (1532-1900 AD), and the tin production at the beginning of the 20th century were identified as major sources for enhanced Pb EFs before the 1960s. Gasoline related Pb emissions in 1965-85, however, led to a threefold increase of the Pb EFs compared to the emission level from metal production, considerably preceding those of the past 2000 years. This finding is complementary to the local air pollution signal preserved in lake sediments and in good agreement with various studies from the Northern Hemisphere.

  4. EPICA-Dome C Ice Core FIC Analysis: the Longest Chloride, Nitrate and Sulfate High Resolution Record From an Ice Core (900 kyr).

    NASA Astrophysics Data System (ADS)

    Udisti, R.; Becagli, S.; Benassai, S.; Castellano, E.; Severi, M.; Traversi, R.; Deangelis, M.; Delmonte, B.; Hansson, M.; Jouzel, J.; Lambert, F.; Littot, G.; Petit, J.; Ruth, U.; Steffensen, J.

    2004-12-01

    In the framework of the EPICA project, Fast Ion Chromatographic (FIC) analysis of the 3200 m of the ice core drilled at Dome C yielded a continuous high resolution record of Cl-, NO3- and SO42-, spanning the last 900 kyr and covering the last nine glacial/interglacial cycles. About 140 kdata for each component, with resolutions ranging from 2.0 to 4.0 cm (covering from 1.5 to 50 years), were performed in the field and in the cold laboratory of AWI on continuously melted firn and ice core sections. Cl-, NO3- and SO42- profiles were compared together with the dust and isotopic (dD) smoothed profiles in order to enlighten leads and lags between environmental and climatic changes. Particular attention was devoted to the chemical trend interpretation of the fast climatic variations occurring during the glacial onsets and terminations and the interstadial periods. Since Cl- and NO3- are not irreversibly fixed in the snow layers and can be re-emitted into the atmosphere as gaseous acidic species, their preservation in the snow is affected by accumulation rate and acidity. In particular, the NO3-profile shows a close positive relationship with dust content demonstrating that the acidity neutralization drives the preservation of NO3- in low accumulation periods. Cl-, which are stable for relatively low accumulation rate (higher than 80 kg m-2 yr-1) shows a higher sensitivity to accumulation rate changes. Indeed, high Cl- levels are recorded both in glacial period characterized by high dust content and in high accumulation rate periods such as interglacial climatic optima and interstadials. The SO42- profile is marked by volcanic signatures superimposed to the biogenic background contribution (mainly biogenic). Preliminary evidences showed biogenic SO42- depositional fluxes in the snow was not significantly different in the different climatic stages. In this, way, the SO42- background profile is only tuned by changes in snow accumulation rate constituting a potential proxy-marker for accumulation rate.

  5. Meteoric smoke fallout over the Holocene epoch revealed by iridium and platinum in Greenland ice.

    PubMed

    Gabrielli, Paolo; Barbante, Carlo; Plane, John M C; Varga, Anita; Hong, Sungmin; Cozzi, Giulio; Gaspari, Vania; Planchon, Frédéric A M; Cairns, Warren; Ferrari, Christophe; Crutzen, Paul; Cescon, Paolo; Boutron, Claude F

    2004-12-23

    An iridium anomaly at the Cretaceous/Tertiary boundary layer has been attributed to an extraterrestrial body that struck the Earth some 65 million years ago. It has been suggested that, during this event, the carrier of iridium was probably a micrometre-sized silicate-enclosed aggregate or the nanophase material of the vaporized impactor. But the fate of platinum-group elements (such as iridium) that regularly enter the atmosphere via ablating meteoroids remains largely unknown. Here we report a record of iridium and platinum fluxes on a climatic-cycle timescale, back to 128,000 years ago, from a Greenland ice core. We find that unexpectedly constant fallout of extraterrestrial matter to Greenland occurred during the Holocene, whereas a greatly enhanced input of terrestrial iridium and platinum masked the cosmic flux in the dust-laden atmosphere of the last glacial age. We suggest that nanometre-sized meteoric smoke particles, formed from the recondensation of ablated meteoroids in the atmosphere at altitudes >70 kilometres, are transported into the winter polar vortices by the mesospheric meridional circulation and are preferentially deposited in the polar ice caps. This implies an average global fallout of 14 +/- 5 kilotons per year of meteoric smoke during the Holocene. PMID:15616558

  6. Ice Core Perspective on Mercury Pollution during the Past 600 Years.

    PubMed

    Beal, Samuel A; Osterberg, Erich C; Zdanowicz, Christian M; Fisher, David A

    2015-07-01

    Past emissions of the toxic metal mercury (Hg) persist in the global environment, yet these emissions remain poorly constrained by existing data. Ice cores are high-resolution archives of atmospheric deposition that may provide crucial insight into past atmospheric Hg levels during recent and historical time. Here we present a record of total Hg (HgT) in an ice core from the pristine summit plateau (5340 m asl) of Mount Logan, Yukon, Canada, representing atmospheric deposition from AD 1410 to 1998. The Colonial Period (?1603-1850) and North American "Gold Rush" (1850-1900) represent minor fractions (8% and 14%, respectively) of total anthropogenic Hg deposition in the record, with the majority (78%) occurring during the 20th Century. A period of maximum HgT fluxes from 1940 to 1975 coincides with estimates of enhanced anthropogenic Hg emissions from commercial sources, as well as with industrial emissions of other toxic metals. Rapid declines in HgT fluxes following peaks during the Gold Rush and the mid-20th Century indicate that atmospheric Hg deposition responds quickly to reductions in emissions. Increasing HgT fluxes from 1993 until the youngest samples in 1998 may reflect the resurgence of Hg emissions from unregulated coal burning and small-scale gold mining. PMID:26011603

  7. Human and climate impacts on Holocene fire activity recorded in polar and mountain ice cores

    NASA Astrophysics Data System (ADS)

    Kehrwald, Natalie; Zennaro, Piero; Kirchgeorg, Torben; Li, Quanlian; Wang, Ninglian; Power, Mitchell; Zangrando, Roberta; Gabrielli, Paolo; Thompson, Lonnie; Gambaro, Andrea; Barbante, Carlo

    2014-05-01

    Fire is one of the major influences of biogeochemical change on local to hemispheric scales through emitting greenhouse gases, altering atmospheric chemistry, and changing primary productivity. Levoglucosan (1,6-anhydro-?-D-glucopyranose) is a specific molecular that can only be produced by cellulose burning at temperatures > 300°C, comprises a major component of smoke plumes, and can be transported across > 1000 km distances. Levoglucosan is deposited on and archived in glaciers over glacial interglacial cycles resulting in pyrochemical evidence for exploring interactions between fire, climate and human activity. Ice core records provide records of past biomass burning from regions of the world with limited paleofire data including polar and low-latitude, high-altitude regions. Here, we present Holocene fire activity records from the NEEM, Greenland (77° 27'N; 51° 3'W; 2454 masl), EPICA Dome C, Antarctica (75° 06'S; 123° 21'E; 3233 masl), Kilimanjaro, Tanzania (3° 05'S, 21.2° E, 5893 masl) and the Muztagh, China (87.17° E; 36.35° N; 5780 masl ice cores. The NEEM ice core reflects boreal fire activity from both North American and Eurasian sources. Temperature is the dominant control of NEEM levoglucosan flux over decadal to millennial time scales, while droughts influence fire activity over sub-decadal timescales. Our results demonstrate the prominence of Siberian fire sources during intense multiannual droughts. Unlike the NEEM core, which incorporates the largest land masses in the world as potential fire sources, EPICA Dome C is located far from any possible fire source. However, EPICA Dome C levoglucosan concentrations are consistently above detection limits and demonstrate a substantial 1000-fold increase in fire activity beginning approximately 800 years ago. This significant and sustained increase coincides with Maori arrival and dispersal in New Zealand augmented by later European arrival in Australia. The EPICA Dome C levoglucosan profile is similar to regional charcoal compilations from New Zealand and southeastern Australia. Evidence from Kilimanjaro demonstrates a major increase in fire activity centered around 800-1000 years ago, corresponding to both increased temperatures and aridity as recorded in regional lake cores. This peak in fire activity is an order of magnitude higher than at any other time in the record including the most recent period. Environmental and anthropological studies suggest that upslope human migrations have occurred in response to the warmer, drier conditions. Kilimanjaro is surrounded by flammable savanna vegetation, yet the Muztagh core is located in an especially arid section of the Tibetan Plateau and consistently contains levoglucosan concentrations that are 100 to 1000 times greater than the mean Kilimanjaro flux. These high concentrations and the lack of available fuel suggest that regional rather than local biomass burning may be the source of the fire products. Biomass burning aerosols are a major component of the South Asian Brown Cloud and may influence the composition and concentration of pyrogenic aerosols across the Tibetan Plateau. The relative impact of human activity versus climate change on Holocene biomass burning varies regionally. Combining ice and sediment core data with model output can help place these regional differences into a global context with implications for a warming climate.

  8. A pervasive link between Antarctic ice core and subarctic Pacific sediment records over the past 800 kyrs

    E-print Network

    Gilli, Adrian

    Dome C (EDC) ice-core record. Ba/Al and biogenic opal show a strong resemblance to the EDC dD and CO2 by a deepening of the calcite lysocline, presumably due to reduced storage of respired CO2 in the deep North concentrations (pCO2) varied cyclically from low values (w160­180 ppmv) during ice ages to higher values (w280

  9. A two century record of strontium isotopes from an ice core drilled at Mt Blanc, France

    NASA Astrophysics Data System (ADS)

    Burton, G. R.; Rosman, K. J. R.; Van de Velde, K. P.; Boutron, C. F.

    2006-08-01

    New techniques which allow small amounts of Sr to be reliably analysed [G.R. Burton, V.I. Morgan, C.F. Boutron, K.J.R. Rosman, High-sensitivity measurements of strontium isotopes in polar ice, Anal. Chim. Acta 469 (2002) 225-233] by TIMS (Thermal Ionisation Mass Spectrometry) have been used to measure the isotopic composition of Sr and the concentration of Rb and Sr at sub-nanogram per gram levels in a Mt Blanc snow and ice core. This two century time series of Sr isotopes is the first to be reported in an Alpine glacier. The Sr and Rb concentrations range from 3 ng/g to 20 pg/g and 1 ng/g to 10 pg/g, respectively, with higher concentrations evident in more recent times. This trend is consistent with that reported previously for other metals such as Cd, Cu and Zn [K. Van de Velde, C. Barbante, G. Cozzi, I. Moret, T. Bellomi, C. Ferrari, C. Boutron, Changes in the occurrence of silver, gold, platinum, palladium and rhodium in Mont Blanc ice and snow since the 18th century, Atmos. Environ. 34 (2000) 3117-3127; K. Van de Velde, C. Boutron, C. Ferrari, T. Bellomi, C. Barbante, S. Rudnev, M. Bolshov, Seasonal variations of heavy metals in the 1960s Alpine ice: sources versus meteorological factors, Earth Planet. Sci. Lett. 164 (1998) 521-533; K.J.R. Rosman, C. Ly, K. Van de Velde, C.F. Boutron, A two century record of lead isotopes in high altitude Alpine snow and ice, Earth Planet. Sci. Lett. 176 (2000) 413-424]. The 87Sr/ 86Sr ratios vary between 0.7020 and 0.7176 and display relatively larger variations in recent times which have been attributed to seasonal variations made evident by the increased sampling resolution available at shallower depths. No change with time is evident in this ratio which has a mean value of ˜ 0.712 and is similar to Glacial ice at Summit Greenland, suggesting that aerosols reaching Mt Blanc represent the same mixture of sources. Also, anthropogenic sources would appear to have the same isotopic ratio. The presence of Saharan dust in some samples is confirmed here by their strontium isotopic ratios.

  10. Core to Atmosphere Exploration of Ice Giants: A Uranus Mission Concept Study

    NASA Astrophysics Data System (ADS)

    Jensema, R. J.; Arias-Young, T. M.; Wilkins, A. N.; Ermakov, A.; Bennett, C.; Dietrich, A.; Hemingway, D.; Klein, V.; Mane, P.; Marr, K. D.; Masterson, J.; Siegel, V.; Stober, K. J.; Talpe, M.; Vines, S. K.; Wetteland, C. J.

    2014-12-01

    Ice giants remain largely unexplored, as their large distance from the Sun limits both Earth-based observations and spacecraft visits. The significant occurrence of ice giant-sized planets among detected exoplanets presents an impetus to study Uranus to understand planetary formation, dynamics, and evolution. In addition, Uranus is also uniquely interesting, given the large inclination of its rotation axis and magnetospheric configuration. In this work, we design a mission concept that aims to maximize scientific return by measuring Uranus' chemical composition, internal structure, and magnetosphere, the first two being primary indicators of ice giant formation mechanisms. For this study, we analyze the trade space for a Uranus mission constrained by a cost cap of $1B. We discuss the decision making processes behind our choices of the science priorities, instrument suite and orbital configuration. Trade space decisions include a strong onboard instrument suite in lieu of a descent probe, an orbiter instead of a flyby mission, and design constraints on the power and propulsion systems. The mission, CAELUS (Core and Atmospheric Evolution Laboratory for Uranus Science), is designed for an August 2023 launch. Following a 14-year cruise with multiple planetary gravity assists, the spacecraft would begin its science mission, which consists of a series of ten 30-day near-polar orbits around Uranus. The instrument suite would consist of a microwave radiometer, Doppler seismometer, magnetometer, and UV spectrometer. These four instruments, along with a high-gain antenna capable of gravity science, would provide a comprehensive science return that meets the bulk of the scientific objectives of the 2013 NRC Planetary Science Decadal Survey for ice giants, most notably those regarding the chemical composition, interior structure, and dynamo of Uranus. This mission concept was created as part of an educational exercise for the 2014 Planetary Science Summer School at the Jet Propulsion Laboratory.

  11. Detection prospects for GeV neutrinos from collisionally heated gamma-ray bursts with IceCube/DeepCore.

    PubMed

    Bartos, I; Beloborodov, A M; Hurley, K; Márka, S

    2013-06-14

    Jet reheating via nuclear collisions has recently been proposed as the main mechanism for gamma-ray burst (GRB) emission. In addition to producing the observed gamma rays, collisional heating must generate 10-100 GeV neutrinos, implying a close relation between the neutrino and gamma-ray luminosities. We exploit this theoretical relation to make predictions for possible GRB detections by IceCube + DeepCore. To estimate the expected neutrino signal, we use the largest sample of bursts observed by the Burst and Transient Source Experiment in 1991-2000. GRB neutrinos could have been detected if IceCube + DeepCore operated at that time. Detection of 10-100 GeV neutrinos would have significant implications, shedding light on the composition of GRB jets and their Lorentz factors. This could be an important target in designing future upgrades of the IceCube + DeepCore observatory. PMID:25165903

  12. Chlorine-36 and cesium-137 in ice-core samples from mid-latitude glacial sites in the Northern Hemisphere

    USGS Publications Warehouse

    Green, J.R.; Cecil, L.D.; Synal, H.-A.; Kreutz, K.J.; Wake, C.P.; Naftz, D.L.; Frape, S.K.

    2000-01-01

    Chlorine-36 (36Cl) concentrations, 36Cl/Cl ratios, and 36Cl fluxes in ice-core samples collected from the Upper Fremont Glacier (UFG) in the Wind River Mountain Range, Wyoming, United States and the Nangpai Gosum Glacier (NGG) in the Himalayan Mountains, Nepal, were determined and compared with published results from the Dye-3 ice-core drilling site on the Greenland Ice Sheet. Cesium-137 (137Cs) concentrations in the NGG also were determined. The background fluxes for 36Cl for each glacial site were similar: (1.6??0.3)??10-2 atoms/cm2 s for the UFG samples, (0.7??0.1)??10-2 atoms/cm2 s for the NGG samples, and (0.4??0.1)??10-2 atoms/cm2 s for the Dye-3 samples. The 36Cl fluxes in ice that was deposited as snow during peak atmospheric nuclear weapon test (1957-1958) were (33??1)??10-2 atoms/cm2 s for the UFG site, (291??3)??10-2 atoms/cm2 s for the NGG site, and (124??5)??10-2 atoms/ cm2 s for the Dye-3 site. A weapon test period 137Cs concentration of 0.79??0.05 Bq/kg in the NGG ice core also was detected in the same section of ice that contained the largest 36Cl concentration. ?? 2000 Elsevier Science B.V. All rights reserved.

  13. Laurentide Ice Sheet dynamics in the Bay of Fundy, Canada, revealed through multibeam sonar mapping of glacial landsystems

    NASA Astrophysics Data System (ADS)

    Todd, Brian J.; Shaw, John

    2012-12-01

    Recent multibeam sonar data collected in the Bay of Fundy, Canada, interpreted in conjunction with geophysical profiling and sediment sampling, reveal in unprecedented detail a suite of glacial landforms associated with the southwest margin of the Laurentide Ice Sheet. These landforms constitute four glacial landsystems. 1) Subglacial landsystem I: In southwestern Bay of Fundy, the elongated Grand Manan Basin contains ice-contact sediments of possible mid-Wisconsinan age overlain by late-Wisconsinan ice-contact sediments strongly imprinted by iceberg furrows and pits. In places, possible mid-Wisconsinan glaciomarine sediments have been eroded by late-Wisconsinan ice, creating streamlined landforms. Eroded bedrock and megafluted ice-contact sediment on the flanks of Grand Manan Basin indicate the southwest direction of topographically-steered ice. 2) Subglacial landsystem II: Along the southern margin of the Bay of Fundy, an array of drumlins, with superimposed esker complexes, was formed by glacial ice that emanated northwest from the interior of Nova Scotia and was deflected to the southwest by the ice flowing out of the Bay of Fundy to the Gulf of Maine. The esker complexes formed later when the Nova Scotia ice sheet stagnated and meltwater escaped northwest via topographic gaps. 3) Ice-marginal landsystem I: In northern Bay of Fundy, both small De Geer moraines and larger, basin-bounding moraines were created when retreating late-Wisconsinan ice became grounded in relatively shallow water. New radiocarbon ages show that the Owen Basin Moraine in this landsystem was abandoned prior to c. 14,600 14C yr BP (cal BP 17,015-17,270 [0.7], 17,286-17,405 [0.3]). 4) Ice-marginal landsystem II: This distinctive landsystem consists of numerous arcuate moraines, commonly superimposed on one another. This landsystem was formed by thin (170 m), lightly grounded ice that retreated northeast into the Bay of Fundy. The splayed pattern of the ice margin was a response to a large accommodation space and velocity variations within the ice. The Isle Haute Moraine is a large lobate moraine; its age is poorly constrained by shells from glaciomarine sediments (13,750 ± 60 14C yr BP (cal BP 15,970-15,996 [0.03], 16,047-16,665 [0.97])) but the moraine may be coeval with the onset of a terrestrial ice margin established at the head of the Bay of Fundy by c. 14,300 14C yr BP (cal BP 16,824-17,013).

  14. Linking high resolution 14C records to ice core time scales by means of Bayesian wiggle-matching

    NASA Astrophysics Data System (ADS)

    Adolphi, F.; Muscheler, R.; Friedrich, M.; Güttler, D.; Wacker, L.; Kromer, B.

    2014-12-01

    Radiocarbon dating is the key method for obtaining chronological information of paleoclimate records covering the last ~45,000 years. The wealth of paleoclimatic information reconstructed from Greenland and Antarctic ice cores are often used as blue-prints to place these radiocarbon dated records into a wider context. However, while layer counted ice core time scales from Greenland provide high precision on the duration of events, the absolute age uncertainty increases back in time. This poses limitations on the possible detail and robustness of comparisons between radiocarbon dated, and ice core records. Cosmogenic radionuclide records, i.e. based on 14C and 10Be, provide a unique tool for synchronizing different time scales from various archives. They carry the common production rate signal which is modulated by variations in the strength of the helio- and geo- magnetic fields, which are climate-independent processes and global. We will present a method for synchronizing radiocarbon and Greenland ice core time scales back to 16,000 years ago based on Bayesian wiggle matching of cosmogenic radionuclide records. The method utilizes the strength of the high relative precision of ice core time scales as well as the small absolute age uncertainty from tree-ring chronologies and U/Th dated speleothems. The method provides combined error estimates and allows testing i) the accuracy of ice core time scales, ii) the quality of 14C records underlying the radiocarbon calibration curve as well as iii) assumptions of synchronicity of rapid climate changes. Furthermore, we will illustrate how this method can be used for high-precision radiocarbon wiggle-match dating of floating tree ring chronologies beyond 14,000 years ago, and potentially improve the radiocarbon calibration curve.

  15. A 16,000-yr tephra framework for the Antarctic ice sheet: a contribution from the new Talos Dome core

    NASA Astrophysics Data System (ADS)

    Narcisi, Biancamaria; Petit, Jean Robert; Delmonte, Barbara; Scarchilli, Claudio; Stenni, Barbara

    2012-08-01

    A detailed tephra record for the last 16,000 years of the TALDICE ice core drilled at Talos Dome (East Antarctica, Pacific/Ross Sea sector) is documented. Traces of 26 different explosive volcanic eruptions, dated by ice core chronology and framed within the climate (?18O) record for the core, have been identified. Glass major element composition and grain size data indicate that all prominent tephra layers derive from Antarctic volcanic activity and likely originated in proximal volcanoes of the Melbourne Volcanic Province (Northern Victoria Land). Two other Antarctic horizons may have originated from the more distant volcanoes of Mount Berlin (Marie Byrd Land, West Antarctica) and Mount Erebus (Ross Island, Southern Victoria Land). Moreover, based on glass-shard geochemistry and a 20-year analysis of atmospheric back trajectories suggesting ash transport from South America to the drilling site by the circumpolar westerly circulation, a few faint microtephra horizons are attributed to Andean volcanic activity. Two of these tephras are interpreted to be related to known Holocene explosive eruptions from the volcanoes of Mount Hudson and Mount Burney. Finally, by comparing compositional features in conjunction with age data, three TALDICE tephras have been successfully correlated with volcanic layers in other ice records of the Antarctic ice sheet. Altogether, our results expand the Antarctic tephrostratigraphic framework and add value to the prospects for continental-scale correlations between ice cores and Southern Hemisphere sediment archives.

  16. Roosevelt Island Climate Evolution Project (RICE): A 65 Kyr ice core record of black carbon aerosol deposition to the Ross Ice Shelf, West Antarctica.

    NASA Astrophysics Data System (ADS)

    Edwards, Ross; Bertler, Nancy; Tuohy, Andrea; Neff, Peter; Proemse, Bernedette; Feiteng, Wang; Goodwin, Ian; Hogan, Chad

    2015-04-01

    Emitted by fires, black carbon aerosols (rBC) perturb the atmosphere's physical and chemical properties and are climatically active. Sedimentary charcoal and other paleo-fire records suggest that rBC emissions have varied significantly in the past due to human activity and climate variability. However, few paleo rBC records exist to constrain reconstructions of the past rBC atmospheric distribution and its climate interaction. As part of the international Roosevelt Island Climate Evolution (RICE) project, we have developed an Antarctic rBC ice core record spanning the past ~65 Kyr. The RICE deep ice core was drilled from the Roosevelt Island ice dome in West Antarctica from 2011 to 2013. The high depth resolution (~ 1 cm) record was developed using a single particle intracavity laser-induced incandescence soot photometer (SP2) coupled to an ice core melter system. The rBC record displays sub-annual variability consistent with both austral dry-season and summer biomass burning. The record exhibits significant decadal to millennial-scale variability consistent with known changes in climate. Glacial rBC concentrations were much lower than Holocene concentrations with the exception of several periods of abrupt increases in rBC. The transition from glacial to interglacial rBC concentrations occurred over a much longer time relative to other ice core climate proxies such as water isotopes and suggests . The protracted increase in rBC during the transition may reflected Southern hemisphere ecosystem / fire regime changes in response to hydroclimate and human activity.

  17. Central Asian Water Cycle Variability over the past Century from Ice-core Isotope Records (Altai, Tien Shan)

    NASA Astrophysics Data System (ADS)

    Aizen, V.; Aizen, E.; Mayewski, P.; Kreutz, K.; Joswiak, D.; Takeuchi, N.; Fujita, K.

    2004-12-01

    The Altai and Tien Shan ice cores records are expanding our understanding of the inter-Hemispheric water cycle and climate dynamics: the moisture advection from Atlantic and Pacific Oceans, and from Aral-Caspian closed drainage basin to the Arctic Ocean defining the interaction over time between the westerly jet stream, and the Asian monsoon, Siberian and Tibetan Highs and deciphering local verses regional change over the temperate and high latitudes. The multi-parameter high-resolution (i.e., sub-seasonal) glacio-climatic and environmental records from the upper fifty meter of the 175 m surface to bottom ice core recovered in 2003 from the Belukha snow-firn plateau at 4115 m (Altai Mts.) and the upper 20 m of the 160 m deep ice-core recovered in 2000 from the head of Inylchek Glacier at 5200 m (Tien Shan Mts.) were developed and evaluated. The long-term meteorological, synoptic, dust storm and forest fire records and physical stratigraphy data were the basis for calibration, validation and interpretation. The mean annual snow accumulation on the Inylchek glacier for the period from 1992 to 1998 was found to be 116 g cm-2/yr. Validation of the Altai ice core records through the marker horizon of volcanic eruptions showed monthly accordance in the dating century accumulation ice core records with the mean accumulation rate of 650 g cm-2/yr. The ? 18O, ? D and d excess records showed well-preserved seasonal variation, which is significantly controlled by air temperature, by share of cold/or warm season precipitation amount and origin, transport and recycling of moisture. The ? 18O-? D relationship in the upper 50 m of the Altai ice core records has the same slope to the co-variance as that of the global meteoric water line (i.e., 8), while the Tien Shan ice-core records has lower slope (i.e., 7). The snow accumulation of central Asian glaciers was formed from oceanic precipitation and the moisture originated over Aral-Caspian sources. The Northern Atlantic contributed 15% of moisture, while Black and Eastern Mediterranean Seas 32% to the 20 m Inylchek accumulation. The rest precipitation on the Tien Shan glacier has inter-continental origin. The d-excess show means maximum in winter and minimum in summer in both ice-cores records. About 70% of the Altai snow firn core d-excess records vary within 6% and 15% with maximum of more than 40% within the range from 8% to 13% with the shift to higher values in the upper part of ice core pointing on increased share of moisture recycled over intercontinental Asia. More than half of accumulation on the Altai records had Atlantic Ocean origin. Precipitation from the Arctic and Pacific Oceans had the smallest deuterium excess and their share in total accumulation is increasing. Ice core analysis of the composition of ? 18O reflected different synoptic situations, which will be reconstructed along with air temperature for about the century of ice core records.

  18. New high-resolution aerosol proxy data from the Greenland NEEM ice core covering the last 128,000 years

    NASA Astrophysics Data System (ADS)

    Schüpbach, Simon; Bigler, Matthias; Gfeller, Gideon; Fischer, Hubertus

    2014-05-01

    High-resolution multicomponent continuous flow analysis (CFA) measurements have been performed over the entire depth of the NEEM ice core in three field seasons 2009-2011. Only in the brittle ice section, covering an age of approx. 4,000-8,000 years, continuous measurements could not be performed due to the bad ice quality which hampered such analyses. On all the other ice, continuous records of tracers for sea salt aerosol (sodium), mineral dust aerosol (calcium), inorganic and biogenic nitrogen compounds (nitrate and ammonium), hydrogen peroxide, and electrolytic conductivity were recorded. Data evaluation and quality control of the raw data of the 2.5 km long ice core have recently been finalised, resulting in the final multi-proxy CFA dataset of the NEEM ice core presented here. It covers the last 128,000 years including the entire (stratigraphically folded) Eemian warm period in Greenland. Our chemical CFA measurements are performed in a nominal resolution of 0.5 mm, allowing for the resolution of seasonal cycles over the top 1500 m of the ice core. Thus, seasonality of aerosol tracers can be studied as far back as the early Holocene, and to a certain extent even further back in time. The lower part of the ice core, however, including the last glacial period as well as the Eemian ice section, is subject to such strong thinning of the ice that no unambiguous seasonal cycles can be resolved any more. Nevertheless, long-term glacial-interglacial and stadial-interstadial changes on the one side and the peculiarities of the first Greenland Eemian aerosol record in comparison to the Holocene on the other can be investigated in highest resolution. Here, the new NEEM aerosol proxy records are presented and compared to NGRIP and GRIP CFA records focussed on the early Holocene and last glacial period. Thanks to the particularly high resolution we can furthermore closely investigate the timing and phasing of fast climate transitions such as Termination I and Dansgaard-Oeschger events during the last glacial period.

  19. Changes in environment over the last 800,000 years from chemical analysis of the EPICA Dome C ice core

    NASA Astrophysics Data System (ADS)

    Wolff, E. W.; Barbante, C.; Becagli, S.; Bigler, M.; Boutron, C. F.; Castellano, E.; de Angelis, M.; Federer, U.; Fischer, H.; Fundel, F.; Hansson, M.; Hutterli, M.; Jonsell, U.; Karlin, T.; Kaufmann, P.; Lambert, F.; Littot, G. C.; Mulvaney, R.; Röthlisberger, R.; Ruth, U.; Severi, M.; Siggaard-Andersen, M. L.; Sime, L. C.; Steffensen, J. P.; Stocker, T. F.; Traversi, R.; Twarloh, B.; Udisti, R.; Wagenbach, D.; Wegner, A.

    2010-01-01

    The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and sequential ice. Numerous chemical species have been measured along the length of the cores. Here we concentrate on interpreting the main low-resolution patterns of major ions. We extend the published record for non-sea-salt calcium, sea-salt sodium and non-sea-salt sulfate flux to 800 ka. The non-sea-salt calcium record confirms that terrestrial dust originating from South America closely mirrored Antarctic climate, both at orbital and millennial timescales. A major cause of the main trends is most likely climate in southern South America, which could be sensitive to subtle changes in atmospheric circulation. Sea-salt sodium also follows temperature, but with a threshold at low temperature. We re-examine the use of sodium as a sea ice proxy, concluding that it is probably reflecting extent, with high salt concentrations reflecting larger ice extents. With this interpretation, the sodium flux record indicates low ice extent operating as an amplifier in warm interglacials. Non-sea-salt sulfate flux is almost constant along the core, confirming the lack of change in marine productivity (for sulfur-producing organisms) in the areas of the Southern Ocean contributing to the flux at Dome C. For the first time we also present long records of reversible species such as nitrate and chloride, and show that the pattern of post-depositional losses described for shallower ice is maintained in older ice. It appears possible to use these concentrations to constrain snow accumulation rates in interglacial ice at this site, and the results suggest a possible correction to accumulation rates in one early interglacial. Taken together the chemistry records offer a number of constraints on the way the Earth system combined to give the major climate fluctuations of the late Quaternary period.

  20. Ammonium and non-sea salt sulfate in the EPICA ice cores as indicator of biological activity in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Kaufmann, Patrik; Fundel, Felix; Fischer, Hubertus; Bigler, Matthias; Ruth, Urs; Udisti, Roberto; Hansson, Margareta; de Angelis, Martine; Barbante, Carlo; Wolff, Eric W.; Hutterli, Manuel; Wagenbach, Dietmar

    2010-01-01

    Sulfate (SO 42-) and ammonium (NH 4+) flux records over the last 150,000 years from both Antarctic EPICA ice cores (European Project for Ice Coring in Antarctica) are presented. The ice core record from Dome C is influenced by the Indian sector of the Southern Ocean (SO), whereas Dronning Maud Land is facing the Atlantic sector. Generally, they reflect the past atmospheric aerosol load and, thus, potentially reveal the fingerprint of marine biogenic sources from the SO. The most important feature of both, the nssSO 42- as well as NH 4+ flux records, is the absence of any significant glacial cycles, in contrary to the distinct transitions for mineral dust and sea salt aerosol over the last 150,000 years. This finding challenges the iron fertilization hypothesis on long time scales, as the significant changes in dust, e.g. from the last glacial maximum toward the Holocene have neither an impact on nssSO 42- nor on NH 4+ fluxes found in interior Antarctica. The inter-site correlation of both species is weak, r2 = 0.42 for the nssSO 42- flux and r2 = 0.12 for the NH 4+ flux respectively, emphasizing the local source characteristics of biogenic aerosol from the SO. Millennial variability in NH 4+ and nssSO 42- is within the uncertainty of our flux estimates. Correlation with mineral dust and sea ice derived sodium shows only a very weak influence of dust deposition on those insignificant changes in nssSO 42- flux for the Atlantic sector of the Southern Ocean, but also small transport changes or terrigeneous sulfate contributions may contribute to those variations at EDML.

  1. Geophysical imaging reveals brine system beneath an ice-sealed Antarctic lake

    NASA Astrophysics Data System (ADS)

    Dugan, H.; Doran, P. T.; Tulaczyk, S. M.; Mikucki, J.; Arcone, S. A.; Auken, E.; Schamper, C.; Virginia, R. A.

    2014-12-01

    The habitability of polar desert environments on Earth, and other neighboring planets, is dependent on the availability of liquid water. In areas where the surface is frozen, lenses of water present in the subsurface may act as microbial refugia. In the McMurdo Dry Valleys of Antarctica, the presence of highly saline brine in valley lakes raises the potential for the existence of a deep groundwater network. We report on a geophysical study that shows Lake Vida, in Victoria Valley, is nearly frozen, and the remaining brine is confined beneath thick ice. Near surface, bathymetric mapping of grounded lake ice was accomplished from a series of ground penetrating radar surveys. Radar penetration was limited to 20 m. An airborne transient electromagnetic survey (AEM) revealed a low resistivity zone at 30-100 m depth beneath the surface of the lake. Based on previous knowledge of brine chemistry and local geology, this zone is interpreted as brine saturated unconsolidated sediments with a porosity of 23-42%. Brine volume is calculated at 15 to 32 million cubic meters, which is of similar magnitude to the brine volume in nearby saline lakes. The AEM survey provided a means of quantifying the spatial extent of deep subsurface brine in this remote environment, and has provided a new perspective on the potential for subsurface habitats in areas often considered devoid of life.

  2. Characterizing atmospheric circulation signals in Greenland ice cores: insights from a weather regime approach

    NASA Astrophysics Data System (ADS)

    Ortega, Pablo; Swingedouw, Didier; Masson-Delmotte, Valérie; Risi, Camille; Vinther, Bo; Yiou, Pascal; Vautard, Robert; Yoshimura, Kei

    2014-11-01

    Greenland ice cores offer seasonal to annual records of ?18O, a proxy for precipitation-weighted temperature, over the last few centuries to millennia. Here, we investigate the regional footprints of the North Atlantic weather regimes on Greenland isotope and climate variability, using a compilation of 22 different shallow ice-cores and the atmospheric pressure conditions from the twentieth century reanalysis (20CR). As a first step we have verified that the leading modes of winter and annual ?18O are well correlated with oceanic (Atlantic multidecadal oscillation) and atmospheric [North Atlantic oscillation (NAO)] indices respectively, and also marginally with external forcings, thus confirming earlier studies. The link between weather regimes and Greenland precipitation, precipitation-weighted temperature and ?18O is further explored by using an isotope simulation from the LMDZ-iso model, where the 3-dimensional wind fields are nudged to those of 20CR. In winter, the NAO+ and NAO- regimes in LMDZ-iso produce the largest isotopic changes over the entire Greenland region, with maximum anomalies in the South. Likewise, the Scandinavian blocking and the Atlantic ridge also show remarkable imprints on isotopic composition over the region. To assess the robustness and model dependency of our findings, a second isotope simulation from the isotopic model is also explored. The percentage of Greenland ?18O variance explained by the ensemble of weather regimes is increased by a factor near two in both LMDZ-iso and IsoGSM when compared to the contribution of the NAO index only. Similarly, weather regimes provide a net gain in the ?18O variance explained of similar magnitude for the whole set of ice core records. Greenland ?18O also appears to be locally affected by the low-frequency variations in the centres of action of the weather regimes, with clearer imprints in the LMDZ-iso simulation. This study opens the possibility for reconstructing past changes in the frequencies of occurrence of the weather regimes, which would rely on the sensitive regions identified here, and the use of additional proxies over the North Atlantic region.

  3. A synthetic ice core approach to estimate ion relocation in an ice field site experiencing periodical melt; a case study on Lomonosovfonna, Svalbard

    NASA Astrophysics Data System (ADS)

    Vega, C. P.; Pohjola, V. A.; Beaudon, E.; Claremar, B.; van Pelt, W. J. J.; Pettersson, R.; Isaksson, E.; Martma, T.; Schwikowski, M.; Bøggild, C. E.

    2015-09-01

    Physical and chemical properties of four different ice cores (LF-97, LF-08, LF-09 and LF-11) drilled at Lomonosovfonna, Svalbard, were compared to investigate the effects of meltwater percolation on the chemical and physical stratigraphy of these records. A synthetic ice core approach was employed as reference record to estimate the ionic relocation and meltwater percolation length at this site during the period 2007-2010. Using this method, the ion elution sequence obtained for Lomonosovfonna was SO42- > NO3- > NH4+ > Mg2+ > Cl-, K+ > Na+ > Ca2+, with acidic ions being the most mobile within the snowpack. The relocation length of most of the ions was in the order of 1 m, with the exception of SO42- showing relocation lengths > 2 m during this period. In addition, by using both a positive degree day (PDD) and a snow-energy model approaches to estimate the percentage of melt at Lomonosovfonna, we have calculated a melt percentage (MP) of the total annual accumulation within the range between 48 and 70 %, for the period between 2007 and 2010 which is above the MP range suggested by the ion relocation evidenced in the LF-syn core (i.e. MP = 30 %). Using a firn-densification model to constrain the melt range, a MP of 30 % was found over the same period which is consistent with the results of the synthetic ice core approach, and a 45 % of melt for the last 60 years. Considering the ionic relocation lengths and annual melt percentages, we estimate that the atmospheric ionic signal remains preserved in recently drilled Lomonosovfonna ice cores at an annual or bi-annual resolution.

  4. Subsurface imaging reveals a confined aquifer beneath an ice-sealed Antarctic lake

    NASA Astrophysics Data System (ADS)

    Dugan, H. A.; Doran, P. T.; Tulaczyk, S.; Mikucki, J. A.; Arcone, S. A.; Auken, E.; Schamper, C.; Virginia, R. A.

    2015-01-01

    water oases are rare under extreme cold desert conditions found in the Antarctic McMurdo Dry Valleys. Here we report geophysical results that indicate that Lake Vida, one of the largest lakes in the region, is nearly frozen and underlain by widespread cryoconcentrated brine. A ground penetrating radar survey profiled 20 m into lake ice and facilitated bathymetric mapping of the upper lake basin. An airborne transient electromagnetic survey revealed a low-resistivity zone 30-100 m beneath the lake surface. Based on previous knowledge of brine chemistry and local geology, we interpret this zone to be a confined aquifer situated in sediments with a porosity of 23-42%. Discovery of this aquifer suggests that subsurface liquid water may be more pervasive in regions of continuous permafrost than previously thought and may represent an extensive habitat for microbial populations.

  5. Getting to the 'Core' of Environmental Change: Analytical Advances for the Analysis and Characterization of Dissolved Organic Matter in Ice Cores Using High Resolution FTICR-MS

    NASA Astrophysics Data System (ADS)

    Boschi, V.; Grannas, A. M.

    2010-12-01

    As the importance of understanding contemporary environmental issues heightens, many researchers look to the science of ice cores to provide information surrounding past climatic and environmental events extending over hundreds of thousands of years of Earth’s history. Atmospheric composition and temperature data as well as the identification of individual elements and lower molecular weight compounds deposited on the ice surface are examples of the valuable information already obtained from the analysis of ice cores. However the characterization of larger, more complex molecular species, such as dissolved organic matter (DOM), has yet to be performed. The analysis of DOM in ice cores holds much potential and can provide additional evidence regarding past atmospheric and environmental conditions. For example the presence of anthropogenic compounds can provide an understanding of the effects of industrial development just as remnants of biological species may be indicative of glacial and interglacial periods. However studies of this nature are challenging due to the low concentrations of organic material and the need to consume minimal amounts of such a limited sample. In this study, high resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is utilized to analyze the low concentration of DOM in ice cores from Antarctica and Greenland. Considering this analytical technique has not been extensively utilized in past studies of ice cores, method development is the most crucial portion of this research. Various minimally invasive sample concentration and/or desalination techniques (including solid phase C18 extraction, PPL extraction, separation using RP-HPLC, and rotovapory concentration) have allowed us to greatly reduce the volume of sample required for analysis. In addition, various ionization sources are being explored (including positive and negative ESI, nanospray ESI, and APPI) to determine the analytical method capable of producing the most informative mass spectra. Once this is accomplished, a comparative analysis can be conducted relating the composition of DOM in ice core samples geographically (within and between either polar region) and chronologically (depth profile of a single region) providing unique and valuable information in an effort to construct a ‘picture’ of past environments on Earth.

  6. Can we retrieve a clear paleoclimatic signal from the deeper part of the EPICA Dome C ice core?

    NASA Astrophysics Data System (ADS)

    Tison, J.-L.; de Angelis, M.; Littot, G.; Wolff, E.; Fischer, H.; Hansson, M.; Bigler, M.; Udisti, R.; Wegner, A.; Jouzel, J.; Stenni, B.; Johnsen, S.; Masson-Delmotte, V.; Landais, A.; Lipenkov, V.; Loulergue, L.; Barnola, J.-M.; Petit, J.-R.; Delmonte, B.; Dreyfus, G.; Dahl-Jensen, D.; Durand, G.; Bereiter, B.; Schilt, A.; Spahni, R.; Pol, K.; Lorrain, R.; Souchez, R.; Samyn, D.

    2015-01-01

    An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (?D-?18Oice, ?18Oatm, total air content, CO2, CH4, N2O, dust, high resolution chemistry, ice texture) of the bottom 60 m of the EPICA Dome C ice core from central Antarctica. These bottom layers have been subdivided in two sections: the lower 12 m showing visible solid inclusions (basal ice) and the 48 m above which we refer to as "deep ice". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end-term from a previous/initial ice sheet configuration) can explain the observed bottom ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of allochtone material at the ice-bedrock interface. We also discuss how the proposed mechanism is compatible with the other variables described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the time scale has been considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice.

  7. Measurement of Atmospheric Neutrino Oscillations with IceCube/DeepCore in its 79-string Configuration

    NASA Astrophysics Data System (ADS)

    Euler, Sebastian

    With its low-energy extension DeepCore, the IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station is able to detect neutrino events with energies as low as 10 GeV. This permits the investigation of flavor oscillations of atmospheric muon neutrinos in an energy range not covered by other experiments, opening a new window on the physics of atmospheric neutrino oscillations. The oscillation probability depends on the observed neutrino zenith angle and energy. Maximum disappearance is expected for vertically upward moving muon neutrinos at around 25 GeV. A recent analysis has rejected the non-oscillation hypothesis with a significance of about 5 ? based on data obtained with IceCube while it was operating in its 79-string configuration [1]. The analysis presented here uses data from the same detector configuration, but implements a more powerful approach for the event selection, which yields a dataset with an order of magnitude higher statistics (more than 8 000 events). We present new results based on a likelihood analysis of the two observables zenith angle and energy. The non-oscillation hypothesis is rejected with a significance32 of about 5.7 ?. In the 2-flavor approximation, our best-fit oscillation parameters are ?m2 = (2.2 ± 0.5) · 10-3eV2 and0.14 sin2 (2?23) = 1.0+0-0.14, in good agreement with measurements at lower energy.

  8. Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change

    PubMed Central

    Geng, Lei; Alexander, Becky; Cole-Dai, Jihong; Steig, Eric J.; Savarino, Joël; Sofen, Eric D.; Schauer, Andrew J.

    2014-01-01

    Nitrogen stable isotope ratio (?15N) in Greenland snow nitrate and in North American remote lake sediments has decreased gradually beginning as early as ?1850 Christian Era. This decrease was attributed to increasing atmospheric deposition of anthropogenic nitrate, reflecting an anthropogenic impact on the global nitrogen cycle, and the impact was thought to be amplified ?1970. However, our subannually resolved ice core records of ?15N and major ions (e.g., , ) over the last ?200 y show that the decrease in ?15N is not always associated with increasing concentrations, and the decreasing trend actually leveled off ?1970. Correlation of ?15N with H+, , and HNO3 concentrations, combined with nitrogen isotope fractionation models, suggests that the ?15N decrease from ?1850–1970 was mainly caused by an anthropogenic-driven increase in atmospheric acidity through alteration of the gas?particle partitioning of atmospheric nitrate. The concentrations of and also leveled off ?1970, reflecting the effect of air pollution mitigation strategies in North America on anthropogenic NOx and SO2 emissions. The consequent atmospheric acidity change, as reflected in the ice core record of H+ concentrations, is likely responsible for the leveling off of ?15N ?1970, which, together with the leveling off of concentrations, suggests a regional mitigation of anthropogenic impact on the nitrogen cycle. Our results highlight the importance of atmospheric processes in controlling ?15N of nitrate and should be considered when using ?15N as a source indicator to study atmospheric flux of nitrate to land surface/ecosystems. PMID:24711383

  9. Nitrogen isotopes in ice core nitrate linked to anthropogenic atmospheric acidity change.

    PubMed

    Geng, Lei; Alexander, Becky; Cole-Dai, Jihong; Steig, Eric J; Savarino, Joël; Sofen, Eric D; Schauer, Andrew J

    2014-04-22

    Nitrogen stable isotope ratio (?(15)N) in Greenland snow nitrate and in North American remote lake sediments has decreased gradually beginning as early as ?1850 Christian Era. This decrease was attributed to increasing atmospheric deposition of anthropogenic nitrate, reflecting an anthropogenic impact on the global nitrogen cycle, and the impact was thought to be amplified ?1970. However, our subannually resolved ice core records of ?(15)N and major ions (e.g., NO3(-), SO4(2-)) over the last ?200 y show that the decrease in ?(15)N is not always associated with increasing NO3(-) concentrations, and the decreasing trend actually leveled off ?1970. Correlation of ?(15)N with H(+), NO3(-), and HNO3 concentrations, combined with nitrogen isotope fractionation models, suggests that the ?(15)N decrease from ?1850-1970 was mainly caused by an anthropogenic-driven increase in atmospheric acidity through alteration of the gas-particle partitioning of atmospheric nitrate. The concentrations of NO3(-) and SO4(2-) also leveled off ?1970, reflecting the effect of air pollution mitigation strategies in North America on anthropogenic NO(x) and SO2 emissions. The consequent atmospheric acidity change, as reflected in the ice core record of H(+) concentrations, is likely responsible for the leveling off of ?(15)N ?1970, which, together with the leveling off of NO3(-) concentrations, suggests a regional mitigation of anthropogenic impact on the nitrogen cycle. Our results highlight the importance of atmospheric processes in controlling ?(15)N of nitrate and should be considered when using ?(15)N as a source indicator to study atmospheric flux of nitrate to land surface/ecosystems. PMID:24711383

  10. Dating the Vostok ice core record by importing the Devils Hole chronology

    USGS Publications Warehouse

    Landwehr, J.M.; Winograd, I.J.

    2001-01-01

    The development of an accurate chronology for the Vostok record continues to be an open research question because these invaluable ice cores cannot be dated directly. Depth-to-age relationships have been developed using many different approaches, but published age estimates are inconsistent, even for major paleoclimatic events. We have developed a chronology for the Vostok deuterium paleotemperature record using a simple and objective algorithm to transfer ages of major paleoclimatic events from the radiometrically dated 500,000-year ??18O-paleotemperature record from Devils Hole, Nevada. The method is based only on a strong inference that major shifts in paleotemperature recorded at both locations occurred synchronously, consistent with an atmospheric teleconnection. The derived depth-to-age relationship conforms with the physics of ice compaction, and internally produces ages for climatic events 5.4 and 11.24 which are consistent with the externally assigned ages that the Vostok team needed to assume in order to derive their most recent chronology, GT4. Indeed, the resulting V-DH chronology is highly correlated with GT4 because of the unexpected correspondence even in the timing of second-order climatic events that were not constrained by the algorithm. Furthermore, the algorithm developed herein is not specific to this problem; rather, the procedure can be used whenever two paleoclimate records are proxies for the same physical phenomenon, and paleoclimatic conditions forcing the two records can be considered to have occurred contemporaneously. The ability of the algorithm to date the East Antarctic Dome Fuji core is also demonstrated.

  11. Validity of the Temperature Reconstruction from Water Isotopes in Ice Cores

    NASA Technical Reports Server (NTRS)

    Jouzel, J.; Alley, R. B.; Cuffey, K. M.; Dansgaard, W.; Grootes, P.; Hoffmann, G.; Johnsen, S. J.; Koster, R. D.; Peel, D.; Shuman, C. A.; Stievenard, M.; Stuiver, M.; White, J.

    1997-01-01

    Well-documented present-day distributions of stable water isotopes (HDO and others) show the existence, in middle and high latitudes, of a linear relationship between the mean annual isotope content of precipitation (SD and 51"0) and the mean annual temperature at the precipitation site. Paleoclimatologists have used this relationship, which is particularly well obeyed over Greenland and Antarctica, to infer paleotemperatures from ice core data. There is, however, growing evidence that spatial and temporal isotope/ surface temperature slopes differ, thus complicating the use of stable water isotopes as paleothermometers. In this paper we review empirical estimates of temporal slopes in polar regions and relevant information that can be inferred from isotope models: simple, Rayleigh-type distillation models and (particularly over Greenland) general circulation models (GCMS) fitted with isotope tracer diagnostics. Empirical estimates of temporal slopes appear consistently lower than present-day spatial slopes and are dependent on the timescale considered. This difference is most probably due to changes in the evaporative origins of moisture, changes in the seasonality of the precipitation, changes in the strength of the inversion layer, or some combination of these changes. Isotope models have not yet been used to evaluate the relative influences of these different factors. The apparent disagreement in the temporal and spatial slopes clearly makes calibrating the isotope paleothermometer difficult. Nevertheless, the use of a (calibrated) isotope paleothermometer appears justified; empirical estimates and most (though not all) GCM results support the practice of interpreting ice core isotope records in terms of local temperature changes.

  12. Estimation and calibration of the water isotope differential diffusion length in ice core records

    NASA Astrophysics Data System (ADS)

    van der Wel, G.; Fischer, H.; Oerter, H.; Meyer, H.; Meijer, H. A. J.

    2015-08-01

    Palaeoclimatic information can be retrieved from the diffusion of the stable water isotope signal during firnification of snow. The diffusion length, a measure for the amount of diffusion a layer has experienced, depends on the firn temperature and the accumulation rate. We show that the estimation of the diffusion length using power spectral densities (PSDs) of the record of a single isotope species can be biased by uncertainties in spectral properties of the isotope signal prior to diffusion. By using a second water isotope and calculating the difference in diffusion lengths between the two isotopes, this problem is circumvented. We study the PSD method applied to two isotopes in detail and additionally present a new forward diffusion method for retrieving the differential diffusion length based on the Pearson correlation between the two isotope signals. The two methods are discussed and extensively tested on synthetic data which are generated in a Monte Carlo manner. We show that calibration of the PSD method with this synthetic data is necessary to be able to objectively determine the differential diffusion length. The correlation-based method proves to be a good alternative for the PSD method as it yields precision equal to or somewhat higher than the PSD method. The use of synthetic data also allows us to estimate the accuracy and precision of the two methods and to choose the best sampling strategy to obtain past temperatures with the required precision. In addition to application to synthetic data the two methods are tested on stable-isotope records from the EPICA (European Project for Ice Coring in Antarctica) ice core drilled in Dronning Maud Land, Antarctica, showing that reliable firn temperatures can be reconstructed with a typical uncertainty of 1.5 and 2 °C for the Holocene period and 2 and 2.5 °C for the last glacial period for the correlation and PSD method, respectively.

  13. Characteristics and sources of tephra layers in the EPICA-Dome C ice record (East Antarctica): Implications for past atmospheric circulation and ice core stratigraphic correlations [rapid communication

    NASA Astrophysics Data System (ADS)

    Narcisi, B.; Petit, J. R.; Delmonte, B.; Basile-Doelsch, I.; Maggi, V.

    2005-11-01

    Thirteen discrete air-fall tephra layers were identified in the last 200,000-yr section of the EPICA-Dome C ice record drilled in the East Antarctic plateau (75°06'S, 123°21'E). Quantitative grain size, glass particle morphology, and the grain-discrete major element composition of the glass fraction of these layers were investigated. Through comparison with literature data on the rock composition of Quaternary volcanic centres located within and around Antarctica, five tephra layers were attributed to South Sandwich volcanoes in the South Atlantic Ocean, two to South Shetland volcanoes (northern Antarctic Peninsula), two to Andean volcanoes, and four to Antarctic (Marie Byrd Land and Melbourne) provinces. The abundance of layers originating in the southern part of the Atlantic confirms that westerly atmospheric circulation spiralling towards East Antarctica prevailed over the last 200 ka. Moreover, the record of events from Antarctic centres suggests that atmospheric trajectories from West to East Antarctica can also be significant. A few ash layers are geochemically distinct and appear equivalent to levels from Vostok and Dome Fuji deep ice records, located ca. 600 km and ca. 2000 km, respectively, from Dome C on the Antarctic plateau. These layers provide unambiguous markers for future correlation with other Antarctic ice cores and circumpolar marine climatic records. They also provide reliable constraints to get a common timescale by glaciological modelling, and represent a first step towards absolute ice core dating.

  14. Seasonal deuterium excess in a Tien Shan ice core: Influence of moisture transport and recycling in Central Asia

    USGS Publications Warehouse

    Kreutz, K.J.; Wake, C.P.; Aizen, V.B.; DeWayne, Cecil L.; Synal, H.-A.

    2003-01-01

    Stable water isotope (??18O, ??D) data from a high elevation (5100 masl) ice core recovered from the Tien Shan Mountains, Kyrgyzstan, display a seasonal cycle in deuterium excess (d = ??D - 8*??18O) related to changes in the regional hydrologic cycle during 1994-2000. While there is a strong correlation (r2 = 0.98) between ??18O and ??D in the ice core samples, the regression slope (6.9) and mean d value (23.0) are significantly different than the global meteoric water line values. The resulting time-series ice core d profile contains distinct winter maxima and summer minima, with a yearly d amplitude of ???15-20???. Local-scale processes that may affect d values preserved in the ice core are not consistent with the observed seasonal variability. Data from Central Asian monitoring sites in the Global Network of Isotopes in Precipitation (GNIP) have similar seasonal d changes. We suggest that regional-scale hydrological conditions, including seasonal changes in moisture source, transport, and recycling in the Caspian/Aral Sea region, are responsible for the observed spatial and temporal d variability.

  15. Changes in black carbon deposition to Antarctica from two ice core records, A.D. 1850-2000

    E-print Network

    Meskhidze, Nicholas

    Changes in black carbon deposition to Antarctica from two ice core records, A.D. 1850-2000 - Supporting information - Marion M. Bisiaux1* , Ross Edwards2 , Joseph R. McConnell1 , Mark A. J. Curran3 (marion.ma.bisiaux@gmail.com) Black carbon measurements Continuous flow analysis was based on a steady

  16. A 12,000 year record of explosive volcanism in the Siple Dome Ice Core, West Antarctica

    E-print Network

    Dunbar, Nelia W.

    regions provide the best means to evaluate the impact of volcanism on global climate [Robock, 2000 a high priority for attain- ing a complete understanding of the volcanism-climate system. SpatialA 12,000 year record of explosive volcanism in the Siple Dome Ice Core, West Antarctica A. V

  17. Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models

    E-print Network

    Robock, Alan

    Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate have investigated one of the most important natural causes of climate change, volcanic eruptions climate model with this new volcanic forcing data set, together with solar and anthropogenic forcing

  18. A potential pollen proxy for ENSO derived from the Sajama ice core Kam-Biu Liu,1

    E-print Network

    Liu, Kam-biu

    A potential pollen proxy for ENSO derived from the Sajama ice core Kam-Biu Liu,1 Carl A. Reese,2 May 2007. [1] An annually resolved pollen record spanning a 39-year period (1958­1996) from the Sajama pollen concentration and composition. The pollen assemblages within the annual layers are dominated

  19. Crystal Structure of the Oligomerization Domain of NSP4 from Rotavirus Reveals a Core

    E-print Network

    Crystal Structure of the Oligomerization Domain of NSP4 from Rotavirus Reveals a Core Metal: rotavirus; nsp4; ns28; fusion; parallel coiled-coil*Corresponding author Introduction Rotavirus,000 deaths annually in the third world (Glass et al., 1994). A member of the Reoviri- dae family, rotavirus

  20. Generated using version 3.2 of the official AMS LATEX template Reemergence Mechanisms for North Pacific Sea Ice Revealed1

    E-print Network

    Majda, Andrew J.

    dynamics are the36 Bering Sea and the Sea of Okhotsk in the North Pacific Ocean. Empirical orthogonal ice dipole between the Okhotsk and Bering seas, and a second mode with spatially39 uniform ice changes Pacific Sea Ice Revealed1 through Nonlinear Laplacian Spectral Analysis2 Mitchell Bushuk, Dimitrios

  1. A new 10Be record recovered from an Antarctic ice core: validity and limitations to record the solar activity

    NASA Astrophysics Data System (ADS)

    Baroni, Mélanie; Bard, Edouard; Aster Team

    2015-04-01

    Cosmogenic nuclides provide the only possibility to document solar activity over millennia. Carbon-14 (14C) and beryllium-10 (10Be) records are retrieved from tree rings and ice cores, respectively. Recently, 14C records have also proven to be reliable to detect two large Solar Proton Events (SPE) (Miyake et al., Nature, 2012, Miyake et al., Nat. Commun., 2013) that occurred in 774-775 A.D. and in 993-994 A.D.. The origin of these events is still under debate but it opens new perspectives for the interpretation of 10Be ice core records. We present a new 10Be record from an ice core from Dome C (Antarctica) covering the last millennium. The chronology of this new ice core has been established by matching volcanic events on the WAIS Divide ice core (WDC06A) that is the best dated record in Antarctica over the Holocene (Sigl et al., JGR, 2013, Sigl et al., Nat. Clim. Change, 2014). The five minima of solar activity (Oort, Wolf, Spörer, Maunder and Dalton) are detected and characterized by a 10Be concentration increase of ca. 20% above average in agreement with previous studies of ice cores drilled at South Pole and Dome Fuji in Antarctica (Bard et al., EPSL, 1997; Horiuchi et al., Quat. Geochrono., 2008) and at NGRIP and Dye3 in Greenland (Berggren et al., GRL, 2009). The high resolution, on the order of a year, allows the detection of the 11-year solar cycle. Sulfate concentration, a proxy for volcanic eruptions, has also been measured in the very same samples, allowing a precise comparison of both 10Be and sulfate profiles. We confirm the systematic relationship between stratospheric eruptions and 10Be concentration increases, first evidenced by observations of the stratospheric volcanic eruptions of Agung in 1963 and Pinatubo in 1991 (Baroni et al., GCA, 2011). This relationship is due to an increase in 10Be deposition linked to the role played by the sedimentation of volcanic aerosols. In the light of these new elements, we will discuss the limitations and possibilities of using a 10Be ice core record to detect SPE and the variations of past solar activity.

  2. A Centrifuge-Based Technique for Dry Extraction of Air for Ice Core Studies of Carbon Dioxide.

    NASA Astrophysics Data System (ADS)

    Grachev, A. M.; Brook, E. J.

    2008-12-01

    High resolution CO2 data from the Law Dome ice core document an abrupt ~10 ppm drop in CO2 at about 1600 AD (MacFarling Meure et al., Geophys. Res Lett., v. 33, L14810), which has been attributed to changes in human activities. CO2 measurements in ice cores are difficult, however, making verification of this feature an important task. We are undertaking a high-resolution study of CO2 between 1400 and 1800 AD in the WAIS Divide (Antarctica) ice core with a new dry extraction technique. The need for a dry extraction technique as opposed to a melt-refreeze technique in studies of CO2 from ice cores arises because of the well-documented artifacts in CO2 imposed by the presence of liquid water. Three dry-extraction methods have been employed by previous workers to measure CO2: needle-crushing method, ball-bearings method, and cheese-grater method (B. Stauffer, in: Encyclopedia of Quaternary Science, p. 1181, Elsevier 2007). Each has limitations, and we propose a simpler dry extraction technique, based on a large-capacity refrigerated centrifuge (the "centrifuge technique"), which eliminates the need to employ cryogenic temperatures to collect extracted gas and is more compatible with high sample throughput. The technique is now being tested on ~25-gram WAIS Divide samples in conjunction with CO2 measurements with a gas chromatograph. The technique employs a Beckman J- 6B centrifuge, in which evacuated stainless steel flask is placed: the flask has a weight inside positioned directly over a tall-standing piece of ice whose cross-section is small compared to that of the flask. Upon acceleration to 3000 rpm the weight moves down and presses the ice sample into a thin tablet covering flask's bottom, yielding the air extraction efficiency of ~80%. Preliminary tests suggest that precision and accuracy can be achieved at the level of ~1 ppm once the system is fine-tuned.

  3. Analysis of vanillic acid in polar ice cores as a biomass burning proxy - preliminary results from the Akademii Nauk Ice Cap in Siberia

    NASA Astrophysics Data System (ADS)

    Grieman, M. M.; Jimenez, R.; McConnell, J. R.; Fritzsche, D.; Saltzman, E. S.

    2013-12-01

    Biomass burning influences global climate change and the composition of the atmosphere. The drivers, effects, and climate feedbacks related to fire are poorly understood. Many different proxies have been used to reconstruct past fire frequency from lake sediments and polar ice cores. Reconstruction of historical trends in biomass burning is challenging because of regional variability and the qualitative nature of various proxies. Vanillic acid (4-hydroxy-3-methoxybenzoic acid) is a product of the combustion of conifer lignin that is known to occur in biomass burning aerosols. Biomass burning is likely the only significant source of vanillic acid in polar ice. In this study we describe an analytical method for quantifying vanillic acid in polar ice using HPLC with electrospray ionization and tandem mass spectrometric detection. The method has a detection limit of 100 pM and a precision of × 10% at the 100 pM level for analysis of 100 ?l of ice melt water. The method was used to analyze more than 1000 discrete samples from the Akademii Nauk ice cap on Severnaya Zemlya in the high Russia Arctic (79°30'N, 97°45'E) (Fritzsche et al., 2002; Fritzsche et al., 2005; Weiler et al., 2005). The samples range in age over the past 2,000 years. The results show a mean vanillic acid concentration of 440 × 710 pM (1?), with elevated levels during the periods from 300-600 and 1450-1550 C.E.

  4. Evolution of a highly vulnerable ice-cored moraine: Col des Gentianes, Swiss Alps

    NASA Astrophysics Data System (ADS)

    Ravanel, L.; Lambiel, C.; Oppikofer, T.; Mazotti, B.; Jaboyedoff, M.

    2012-04-01

    Rock mass movements are dominant in the morphodynamics of high mountain rock slopes and are at the origin of significant risks for people who attend these areas and for infrastructures that are built on (mountain huts, cable cars, etc.). These risks are becoming greater because of permafrost degradation and glacier retreat, two consequences of the global warming. These two commonly associated factors may affect slope stability by changing mechanical properties of the interstitial ice and modifying the mechanical constraints in these rock slopes. Between 1977 and 1979, significant works were carried out on the Little Ice Age moraine of the Tortin glacier at the Col des Gentianes (2894 m), in the Mont Fort area (Verbier, Switzerland), for the construction of a cable car station and a restaurant. Since the early 1980s, the glacier drastically retreated and the moraine became unstable: its inner slope has retreated for several meters. Various observations and geoelectric measurements indicate that significant volume of massive ice mass is still present within the moraine (ice-cored moraine). Its melting could therefore increase the instability of the moraine. Since 2007, the moraine is surveyed by terrestrial laser scanning (TLS) in order to characterize its evolution: 8 campaigns were conducted between July 2007 and October 2011. The comparison of the high resolution 3D models so obtained allowed the detection and quantification of mass movements that have affected the moraine over this period, essentially by calculating difference maps (shortest oblique distances between two models). Between July 2007 and October 2011, 7 landslides were measured, involving volumes between 87 and 1138 m3. The most important of these occurred during the summers 2009 and 2011. TLS data also allowed identifying: (i) two main areas affected by slower but sometimes substantial movements (displacements of blocks on more than 2 m during a summer period); (ii) significant deposits of anthropogenic materials and their mechanical readjustments; and (iii) a loss of thickness of the glacier approaching 10 m at the foot of the moraine. Except for the morphological changes related to the landscaping of ski-runs, mass movements identified by TLS since 2007 are mainly resulting from glacier retreat and, to a lesser extent, to permafrost creep and degradation.

  5. Microscopic simulation of methanol and formaldehyde ice formation in cold dense cores

    NASA Astrophysics Data System (ADS)

    Cuppen, H. M.; van Dishoeck, E. F.; Herbst, E.; Tielens, A. G. G. M.

    2009-12-01

    Context: Methanol and its precursor formaldehyde are among the most studied organic molecules in the interstellar medium and are abundant in the gaseous and solid phases. We recently developed a model to simulate CO hydrogenation via H atoms on interstellar ice surfaces, the most important interstellar route to H2CO and CH3OH, under laboratory conditions. Aims: We extend this model to simulate the formation of both organic species under interstellar conditions, including freeze-out from the gas and hydrogenation on surfaces. Our aim is to compare calculated abundance ratios with observed values and with the results of prior models. Methods: Our model utilises the continuous-time, random-walk Monte Carlo method, which - unlike other approaches - is able to simulate microscopic grain-surface chemistry over the long timescales in interstellar space, including the layering of ices during freeze-out. Results: Simulations under different conditions, including density and temperature, have been performed. We find that H2CO and CH3OH form efficiently in cold dense cores or the cold outer envelopes of young stellar objects. The grain mantle is found to have a layered structure with CH3OH on top. The species CO and H2CO are found to exist predominantly in the lower layers of ice mantles where they are not available for hydrogenation at late times. This finding is in contrast with previous gas-grain models, which do not take into account the layering of the ice. Some of our results can be reproduced by a simple quasi-steady-state analytical model that focuses on the outer layer. Conclusions: Observational solid H2CO/CH3OH and CO/CH3OH abundance ratios in the outer envelopes of an assortment of young stellar objects agree reasonably well with our model results, which also suggest that the large range in CH3OH/H2O observed abundance ratios is due to variations in the evolutionary stages. Finally, we conclude that the limited chemical network used here for surface reactions apparently does not alter the overall conclusions.

  6. 115 year ice-core data from Akademii Nauk ice cap, Severnaya Zemlya: high-resolution record of Eurasian Arctic climate change

    NASA Astrophysics Data System (ADS)

    Opel, Thomas; Fritzsche, Diedrich; Meyer, Hanno; Schütt, Rainer; Weiler, Karin; Ruth, Urs; Wilhelms, Frank; Fischer, Hubertus

    From 1999 to 2001 a 724 m deep ice core was drilled on Akademii Nauk ice cap, Severnaya Zemlya, to gain high-resolution proxy data from the central Russian Arctic. Despite strong summertime meltwater percolation, this ice core provides valuable information on the regional climate and environmental history. We present data of stable water isotopes, melt-layer content and major ions from the uppermost 57 m of this core, covering the period 1883-1998. Dating was achieved by counting seasonal isotopic cycles and using reference horizons. Multi-annual ?18O values reflect Eurasian sub-Arctic and Arctic surface air-temperature variations. We found strong correlations to instrumental temperature data from some stations (e.g. r = 0.62 for Vardø, northern Norway). The ?18O values show pronounced 20th-century temperature changes, with a strong rise about 1920 and the absolute temperature maximum in the 1930s. A recent decrease in the deuterium-excess time series indicates an increasing role of the Kara Sea as a regional moisture source. From the multi-annual ion variations we deduced decreasing sea-salt aerosol trends in the 20th century, as reflected by sodium and chloride, whereas sulphate and nitrate are strongly affected by anthropogenic pollution.

  7. Evidence for Past Melting at the Base of the GISP2 Ice Core from Uranium-Thorium Disequilibrium Measurements

    NASA Astrophysics Data System (ADS)

    Goldstein, S. J.; Lee, V. E.; Nishiizumi, K.; Murrell, M. T.; Amato, R. S.; Nunn, A. J.

    2011-12-01

    We measured 238U-234U-230Th disequilibria by mass spectrometric methods for silty ice samples from the base of the GISP2 Greenland ice core, at a depth of 3040-3052 m. The expected age of these samples is >150 kyr based on counting ice layers. We separated the samples into several fractions by filtration and analyzed the <50 nm (truly dissolved + particulate) and >200 nm (particulate) filtered fractions. In the <50 nm fractions, low Th/U mass ratios of 0.51-0.65 indicate that a large portion (86-89%) of U is truly dissolved and not associated with particles. In addition, 230Th/234U activity ratios are quite low (0.18-0.24), suggesting either recent 230Th loss and/or 234U addition to the samples. This Th/U fractionation is not consistent with an age >150 kyr. Since liquid water is characterized by 230Th/234U activity ratios <<1, these results suggest that recent melting/freezing event(s) have occurred at the base of the GISP2 core. The particulate (>200 nm) fraction is characterized by Th/U ratios of ~4.4-4.9, 234U/238U activity ratios of 1.049-1.056, and 230Th/234U activity ratios of 1.12-1.23. The U-Th disequilibrium in the particles is consistent with recent (<350 kyr) fractionation of U-Th in these ice samples. We have modeled these results using a two component mass balance calculation, with dissolved and particulate pools for each radionuclide. The main assumption is that all of the 232Th in the <50 nm fraction is due to particles, due to the low aqueous solubility of 232Th. By mass balance, 230Th/234U activity ratios for the truly dissolved fraction are 0.031-0.062, and dates for when the samples were last frozen are 3.5-6.9 kyr. These results are consistent with the notion of ice melting at the base of large continental ice sheets, with recent evidence of large sub-glacial lakes in Antarctica and active melting at the base of the nearby N-GRIP Greenland ice core. There also appears to be a significant difference in age for the deepest ice sample (3.5 kyr; 3052 m) and the other samples (5.2-6.9 kyr; 3040-3048 m), suggesting that the deepest part of the ice core adjacent to bedrock at 3053.3 m depth may have existed as liquid water for at least several hundred - few thousand years.

  8. Alaskan Ice Core Shows Relationship Between Asian Dust Storm And The Stratosphere Troposphere Exchange

    NASA Astrophysics Data System (ADS)

    Yasunari, T. J.; Shiraiwa, T.; Kanamori, S.; Fujii, Y.; Igarashi, M.; Yamazaki, K.; Benson, C. S.; Hondoh, T.

    2005-12-01

    Atmospheric dust absorbs and scatters solar radiation, and affects global radiative balance. Dust storm in arid and semi-arid regions in East Asia is main dust source in the northern hemisphere. Asian dust has large effect on radiative balance in the northern hemisphere and its long range transport to Alaskan region frequently occurs in springtime. On the other hand, the stratosphere-troposphere exchange (STE) is a important phenomenon for material exchange among the spheres. Some parameters such as tritium, ozone and beryllium can be transferred from the stratosphere into the troposphere under some conditions such as tropopause folding outbreaks, cut-off low developing and cyclonic activities. STE has a seasonal exchange with maximum in springtime. In June 2003, a 50m ice core was drilled at the summit of Mount Wrangell volcano (60N, 144W, 4100 m), Alaska. Dust particle concentration, tritium content and ratio of stable hydrogen isotope were analyzed. Tritium is the stratospheric tracer recently because the effect of nuclear tests in 1960s has faded these days, and its concentration is highest north of 30th parallel. Therefore, the ice core drilled here is ideal to assess both the Asian dust transport and STE. The core covers 1992-2002 with divided four seasons (winter, spring, late-spring and summer). Fine dust less than one micro meter generally represents long range transport increased in springtime every year. The drastic fine and coarse dust flux increases after 2000 correspond to recent increase of Asian Dust outbreaks. These indicate that Asian dust storm largely affects Mount Wrangell every year. Here we show the fact that highest positive correlation between tritium and fine dust fluxes was seen in the term from late-spring to summer (also high correlation between tritium and coarse dust fluxes in this term), suggesting that the stratosphere-troposphere exchange was most intensified by Asian dust storms in this transient season from spring to summer. Asian dust and STE are dominant in springtime. However, our results showed that these activities related each other the most from late-spring to summer. Asian dust storm and STE are not active in summer. Hence, our results are assumed to mainly reflect late-spring relationship between Asian dust storm and STE. Asian dust outbreaks with severe weather would impact on vertical and horizontal material circulation from the stratosphere to the troposphere. Further studies for Asian dust and STE especially focused on late-spring may lead to elucidate the mechanism of material circulation and assess the radiative forcing of Asian dust in springtime.

  9. Cosmogenic 36Cl and 10Be in the WAIS Divide ice core from 6-21 kyr BP

    NASA Astrophysics Data System (ADS)

    Woodruff, T. E.; Welten, K. C.; Caffee, M. W.; Nishiizumi, K.

    2013-12-01

    Cosmogenic nuclides such as 10Be and 36Cl, produced in the atmosphere by spallation reactions of primary and secondary cosmic ray particles with atoms in the atmosphere, are deposited to the surface with precipitation and stored in glacial ice sheet archives. The final concentration of these nuclides in the ice is dependent upon a number of factors including variations in solar activity, strength of the geomagnetic field, atmospheric transport patterns and snow accumulation rates. Although 10Be is the most commonly measured cosmogenic isotope in ice cores, the measurement of a single isotope may not be sufficient to disentangle these factors. Here we present measurements of 10Be and 36Cl from the West Antarctic Ice Sheet (WAIS) Divide ice core from approximately 6-21 kyr BP. Owing to the differing production rates of 10Be and 36Cl as a function of cosmic ray energy, changes in their ratio may provide information about changes in solar activity in the past. We will also compare this ratio to the accumulation rate at WAIS Divide in order to investigate differences in deposition between the two isotopes. This work was supported by NSF grants ANT-0839042 and 0839137.

  10. A sequential Bayesian approach for the estimation of the age-depth relationship of Dome Fuji ice core

    NASA Astrophysics Data System (ADS)

    Nakano, S.; Suzuki, K.; Kawamura, K.; Parrenin, F.; Higuchi, T.

    2015-06-01

    A technique for estimating the age-depth relationship in an ice core and evaluating its uncertainty is presented. The age-depth relationship is mainly determined by the accumulation of snow at the site of the ice core and the thinning process due to the horizontal stretching and vertical compression of ice layers. However, since neither the accumulation process nor the thinning process are fully understood, it is essential to incorporate observational information into a model that describes the accumulation and thinning processes. In the proposed technique, the age as a function of depth is estimated from age markers and ?18O data. The estimation is achieved using the particle Markov chain Monte Carlo (PMCMC) method, in which the sequential Monte Carlo (SMC) method is combined with the Markov chain Monte Carlo method. In this hybrid method, the posterior distributions for the parameters in the models for the accumulation and thinning processes are computed using the Metropolis method, in which the likelihood is obtained with the SMC method. Meanwhile, the posterior distribution for the age as a function of depth is obtained by collecting the samples generated by the SMC method with Metropolis iterations. The use of this PMCMC method enables us to estimate the age-depth relationship without assuming either linearity or Gaussianity. The performance of the proposed technique is demonstrated by applying it to ice core data from Dome Fuji in Antarctica.

  11. Chemical compositions of sulfate and chloride salts over the last termination reconstructed from the Dome Fuji ice core, inland Antarctica

    NASA Astrophysics Data System (ADS)

    Oyabu, Ikumi; Iizuka, Yoshinori; Uemura, Ryu; Miyake, Takayuki; Hirabayashi, Motohiro; Motoyama, Hideaki; Sakurai, Toshimitsu; Suzuki, Toshitaka; Hondoh, Takeo

    2014-12-01

    The flux and chemical composition of aerosols impact the climate. Antarctic ice cores preserve the record of past atmospheric aerosols, providing useful information about past atmospheric environments. However, few studies have directly measured the chemical composition of aerosol particles preserved in ice cores. Here we present the chemical compositions of sulfate and chloride salts from aerosol particles in the Dome Fuji ice core. The analysis method involves ice sublimation, and the period covers the last termination, 25.0-11.0 thousand years before present (kyr B.P.), with a 350 year resolution. The major components of the soluble particles are CaSO4, Na2SO4, and NaCl. The dominant sulfate salt changes at 16.8 kyr B.P. from CaSO4, a glacial type, to Na2SO4, an interglacial type. The sulfate salt flux (CaSO4 plus Na2SO4) inversely correlates with ?18O in Dome Fuji over millennial timescales. This correlation is consistent with the idea that sulfate salt aerosols contributed to the last deglacial warming of inland Antarctica by reducing the aerosol indirect effect. Between 16.3 and 11.0 kyr B.P., the presence of NaCl suggests that winter atmospheric aerosols are preserved. A high NaCl/Na2SO4 fraction between 12.3 and 11.0 kyr B.P. indicates that the contribution from the transport of winter atmospheric aerosols increased during this period.

  12. Geomagnetic fluctuations reveal stable stratification at the top of the Earth's core.

    PubMed

    Buffett, Bruce

    2014-03-27

    Modern observations of the geomagnetic field reveal fluctuations with a dominant period of about 60?years. These fluctuations are probably a result of waves in the liquid core, although the precise nature of the waves is uncertain. Common suggestions include a type of magnetic wave, known as a torsional oscillation, but recent studies favour periods that are too short to account for a 60-year fluctuation. Another possibility involves MAC waves, which arise from the interplay between magnetic, Archimedes and Coriolis forces. Waves with a suitable period can emerge when the top of the core is stably stratified. Here I show that MAC waves provide a good description of time-dependent zonal flow at the top of the core, as inferred from geomagnetic secular variation. The same wave motion can also account for unexplained fluctuations in the dipole field. Both of these independent predictions require a 140-kilometre-thick stratified layer with a buoyancy frequency comparable to the Earth's rotation rate. Such a stratified layer could have a thermal origin, implying a core heat flow of about 13?terawatts. Alternatively, the layer could result from chemical stratification. In either case, the existence of a stratified layer at the top of the core obscures the nature of flow deeper in the core, where the magnetic field is continually regenerated. PMID:24670768

  13. Surface elevation change artifact at the NEEM ice core drilling site, North Greenland.

    NASA Astrophysics Data System (ADS)

    Berg Larsen, Lars; Schøtt Hvidberg, Christine; Dahl-Jensen, Dorthe; Lilja Buchardt, Susanne

    2014-05-01

    The NEEM deep drilling site (77.45°N 51.06°W) is located at the main ice divide in North Greenland. For the ice core drilling project, a number of buildings was erected and left on the snow surface during the five-year project period. The structures created snowdrifts that formed accordingly to the predominant wind direction on the lee side on the buildings and the overwintering cargo. To get access to the buildings, the snowdrifts and the accumulated snow were removed and the surface in the camp was leveled with heavy machinery each summer. In the camp a GPS reference pole was placed as a part of the NEEM strain net, 12 poles placed in three diamonds at distances of 2,5 km, 7,5 km and 25 km they were all measured with high precision GPS every year. Around the reference pole, a 1 km x 1 km grid with a spacing of 100 m was measured with differential GPS each year. In this work, we present results from the GPS surface topography measurements in and around the campsite. The mapping of the topography in and around the campsite shows how the snowdrifts evolve and are the reason for the lift of the camp site area. The accumulated snowdrifts are compared to the dominant wind directions from year to year. The annual snow accumulation at the NEEM site is 0.60 m. The reference pole in the camp indicates an additional snow accumulation of 0.50 m per year caused by collected drifting snow. The surface topography mapping shows that this artificially elevated surface extends up to several kilometers out in the terrain. This could have possible implications on other glaciological and geophysical measurements in the area i.e. pit and snow accumulation studies.

  14. Glacial-interglacial changes in moisture sources for Greenland: Influences on the ice core record of climate

    SciTech Connect

    Charles, C.D. ); Rind, D. ); Jouzel, J. ); Koster, R.D. ); Fairbanks, R.G. )

    1994-01-28

    Large, abrupt shifts in the [sup 18]O/[sup 16]O ratio found in Greenland ice must reflect real features of the climate system variability. These isotopic shifts can be viewed as a result of air temperature fluctuations, but determination of the cause of the changes - the most crucial issue for future climate concerns - requires a detailed understanding of the controls on isotopes in precipitation. Results from general circulation model experiments suggest that the sources of Greenland precipitation varied with different climate states, allowing dynamic atmospheric mechanisms for influencing the ice core isotope shifts.

  15. Evidence from an Ice Core of a Large Impact Circa 1443 A.D.

    NASA Astrophysics Data System (ADS)

    Abbott, D.; Biscaye, P.; Cole-Dai, J.; Breger, D.

    2005-12-01

    Published data on melt water from the Siple Dome ice core show distinct anomalies at 1443.16 A.D. The Ca value is 111 ppb, over 9 times the next highest Ca value between 850-1760 A.D. The K value is 20 ppb, about 1.4 times the next highest K value. The Ca anomaly may be due to partial dissolution of CaCO3 microfossils from the 24 km Mahuika bolide impact crater on the southern New Zealand shelf. Deep-sea samples of the Mahuika ejecta layer contain >98% carbonate microfossils. The Mahuika impact may have produced tsunami runups of 130 meters in Jervis Bay, Australia. The Australian megatsunami deposits date to 1450±50 A.D. We analyzed the melt water from 8 ice-core samples from the West Antarctic Siple Dome ice core that date from 1440-1448 A.D. The 1443 A.D. level contained a peak in K of 53 ppb as compared to a background of ~6-7 ppb. Ca was high at 26 ppb but this is not as pronounced as reported earlier. We extracted solid material from the melt water. Except for the 1443 A.D. horizon and one fractured grain at the 1442 A.D. level, most samples were barren except for typical dust. At the 1443 A.D. level, we found 5 carbonate microfossils (coccoliths?) from 5 to 20 microns across. Two were round and solid. One microfossil appeared either caught during mitosis or broken during deformation and elongation. Another carbonate microfossil was unbroken, but appeared deformed into a square. We found a Cu grain with a small amount of oxygen. It is most likely a grain of native copper with an oxidized surface. Deformed microfossils and native minerals are both characteristic of bolide impacts. We also found many microcrystalline magnetite cubes, with an average crystal size of 0.3 microns or less. The high magnetic susceptibility of impact ejacta layers is caused by microcrystalline magnetite. We found a grain of conchoidally fractured feldspar ~15 microns long. A semi-quantitive EDAX analysis found 21% Si, 55% O, 9% Al, 5% Na, 3% K, 2% Fe, and 1% Ca (atomic %), well within the range of K-feldspar compositions. Because Fe does not fit into the feldspar structure, its occurrence implies either that the Fe-bearing feldspar is a glass, or that the Fe is in microcracks within the grain. As ice is not Fe-rich, the former is more likely. Because conchoidal fracture is characteristic of glass, this suggests that the feldspar is a glass (maskelynite) derived from an impact onto continental crust. We also found Al Fe oxide, Ti Al oxide, and amphibole. A semi-quantitative EDAX analysis of the latter found 53% O, 20% Si, 5% Na, 4% Al, Mg, and Fe, 3% Ca, and 0.5% K (atomic %) with trace Ti, S and Cl, close to the composition of the alkali amphibole richterite, which forms in contact metamorphosed limestones (skarns). The Al Fe oxide is most likely hercynite, a spinel that forms in contact metamorphic aureoles in silica-poor environments. All mineral grains had distinct edges. We also found radiating, fibrous crystals of a Ca Na silicate. An EDAX analysis of the mineral found 59% O, 13% Ca, 8% Si, 3% Na, and 1% Mg (atomic %). The Ca Na silicate is most likely pectolite (NaCa2Si3O8), which has radiating, fibrous crystals and forms in skarns. The presence of minerals characteristic of contact metamorphism is important as we have found abundant skarn facies minerals in the Mahuika ejecta layer within deep sea sediment. Thus, our data taken together are most consistent with an impact ejecta layer within the Siple Dome ice core that comes from the Mahuika impact event about 4044 kilometers away; providing a well-constrained date for the event around 1443 A.D.

  16. Aerosol data over the last 3000 years in seasonal resolution from the Greenland NEEM ice core

    NASA Astrophysics Data System (ADS)

    Leuenberger, Daiana; Gfeller, Gideon; Schüpbach, Simon; Bigler, Matthias; Fischer, Hubertus

    2013-04-01

    During the field season in summer 2009, the first 600 m (corresponding to 3 kyr b2k (3000 years before A.D. 2000) on the GICC05 timescale) of the Greenland NEEM ice core have been analysed for a variety of aerosol constituents using Continuous Flow Analysis (CFA). Here, the records of electric conductivity, sodium (Na+), calcium (Ca2+), particle numbers of insoluble dust, ammonium (NH4+), nitrate (NO3-) and hydrogen peroxide (H2O2) are presented with an average effective resolution of 1-2 cm, depending on the component. Since the annual layer thickness ? amounts to 15cm at minimum sub-annual signals are resolved in all components over the Holocene period. We achieved to extend the aerosol record over the early Holocene period except for a large gap over the brittle zone from 5-9 kyr b2k. Seasonal variations and extreme events are preserved in great detail and all components. H2O2 is a reliable proxy for the strength of photochemical processes in the lower atmosphere and thus shows its minima and maxima at the summer and winter solstice, respectively. Dust-derived species (insoluble dust, Ca2+) show peak concentrations in early spring and minima in mid-summer. The marine-derived Na+peaks in mid-winter and is lowest during early summer. The mean annual variability in concentrations is about 20 ppbw for both Ca2+andNa+. Moreover, it is of the same order of magnitude in NH4+, butconsiderably larger in NO3- (100 ppbw), both representing continental biogenic sources peaking in spring and showing minima in autumn. The interpretation itsclimatic signal is restricted by NO3- undergoing post-depositional redistribution processes. Not only is the analysis of impurities in sub-annual resolution crucial for the accurate dating of the ice core, but also for establishing a detailed chronology of the occurrence of extreme events such as volcanic eruptions and wildfires. Furthermore, possible changes in the seasonal variability of aerosol concentrations can be investigated. First results are presented here.

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

    NASA Astrophysics Data System (ADS)

    Calzas, M.; Rousseau, D. D.

    2014-12-01

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

  18. Long-distance relationship between large-scale tropical SSTs and ice core-derived oxygen isotopic records in the Third Pole Region

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Yao, T.; Mosley-Thompson, E. S.; Lin, P.

    2012-12-01

    The tropical hydrological cycle is a key factor coupling isotopic records from ice core, speleothem and lake records with tropical SSTs and the vertical amplification of temperature in the Tropics. Stable isotopic ratios, particularly of oxygen, preserved in glacier ice provide high resolution records of climate changes over long time periods. In polar ice sheets the isotopic signal is driven primarily by temperature while in low-latitudes it depends on a variety of hydrologic and thermal influences in the broad geographic region that supplies moisture to the mountain glaciers. The strong correlation between ice core-derived isotopic records throughout the low- and mid-latitudes and tropical SSTs likely reflects the dominance of tropical evaporation in the flux of water vapor to the atmosphere and provides a possible explanation for the large-scale isotopic links among low- and mid-latitude paleoclimate records. Many low- to mid-latitude ice fields provide continuous, annually-resolved proxy records of climatic and environmental variability recorded by many preserved and measurable parameters including oxygen and hydrogen isotopic ratios and net mass balance (accumulation). These records present an opportunity to examine the nature of climate variability in these regions in greater detail and to extract new information about long-distance relationships in the climate system. Understanding these relationships is essential for proper interpretation of the isotopic records archived in glaciers, lakes, speleothems and other paleo-archives in the Third Pole (TP) Region. Here we compare high resolution records from Dasuopu Glacier in the Himalaya, a speleothem record from Wanxiang Cave in Gansu Province on the TP and the annually resolved ice core records from the Quelccaya Ice Cap in the tropical Andes of South America. The purpose is to explore the role of long-distance processes in determining the isotopic composition of paleo archives on the TP. Running correlations between the Quelccaya and Dasuopu records over the last 500 years reveal that through time isotopes and net balance are both positively and negatively correlated over multi-decades scales while correlation of the annual values over the entire period is quite low. The annual isotopic records are strongly correlated with tropical Pacific SSTs (R2 = 0.55) reflecting the strong linkage between tropical Pacific SSTs associated with ENSO and tropospheric temperatures in the low latitudes. The well-documented contemporaneous loss of ice cover on Quelccaya, Naimona'nyi, Kilimanjaro in eastern Africa and the ice fields near Puncak Jaya in Papua, Indonesia likely reflects the dominance of large-scale processes. Moreover, such widespread melting is consistent with model predictions for a vertical amplification of temperature in the tropics and with increasing isotopic enrichment with elevation across the Third Pole Region over the last 100 years.

  19. Southern Ocean frontal structure and sea-ice formation rates revealed by elephant seals

    PubMed Central

    Charrassin, J.-B.; Hindell, M.; Rintoul, S. R.; Roquet, F.; Sokolov, S.; Biuw, M.; Costa, D.; Boehme, L.; Lovell, P.; Coleman, R.; Timmermann, R.; Meijers, A.; Meredith, M.; Park, Y.-H.; Bailleul, F.; Goebel, M.; Tremblay, Y.; Bost, C.-A.; McMahon, C. R.; Field, I. C.; Fedak, M. A.; Guinet, C.

    2008-01-01

    Polar regions are particularly sensitive to climate change, with the potential for significant feedbacks between ocean circulation, sea ice, and the ocean carbon cycle. However, the difficulty in obtaining in situ data means that our ability to detect and interpret change is very limited, especially in the Southern Ocean, where the ocean beneath the sea ice remains almost entirely unobserved and the rate of sea-ice formation is poorly known. Here, we show that southern elephant seals (Mirounga leonina) equipped with oceanographic sensors can measure ocean structure and water mass changes in regions and seasons rarely observed with traditional oceanographic platforms. In particular, seals provided a 30-fold increase in hydrographic profiles from the sea-ice zone, allowing the major fronts to be mapped south of 60°S and sea-ice formation rates to be inferred from changes in upper ocean salinity. Sea-ice production rates peaked in early winter (April–May) during the rapid northward expansion of the pack ice and declined by a factor of 2 to 3 between May and August, in agreement with a three-dimensional coupled ocean–sea-ice model. By measuring the high-latitude ocean during winter, elephant seals fill a “blind spot” in our sampling coverage, enabling the establishment of a truly global ocean-observing system. PMID:18695241

  20. Sustained High Basal Motion of the Greenland Ice Sheet Revealed by Borehole Deformation

    NASA Technical Reports Server (NTRS)

    Ryser, Claudia; Luthi, Martin P.; Andrews, Lauren C.; Hoffman, Matthew, J.; Catania, Ginny A.; Hawley, Robert L.; Neumann, Thomas A.; Kristensen, Steen S.

    2014-01-01

    Ice deformation and basal motion characterize the dynamical behavior of the Greenland ice sheet (GrIS). We evaluate the contribution of basal motion from ice deformation measurements in boreholes drilled to the bed at two sites in the western marginal zone of the GrIS. We find a sustained high amount of basal motion contribution to surface velocity of 44-73 percent in winter, and up to 90 percent in summer. Measured ice deformation rates show an unexpected variation with depth that can be explained with the help of an ice-flow model as a consequence of stress transfer from slippery to sticky areas. This effect necessitates the use of high-order ice-flow models, not only in regions of fast-flowing ice streams but in all temperate-based areas of the GrIS. The agreement between modeled and measured deformation rates confirms that the recommended values of the temperature-dependent flow rate factor A are a good choice for ice-sheet models.

  1. Pink marine sediments reveal rapid ice melt and Arctic meltwater discharge during Dansgaard-Oeschger warmings.

    PubMed

    Rasmussen, Tine L; Thomsen, Erik

    2013-01-01

    The climate of the last glaciation was interrupted by numerous abrupt temperature fluctuations, referred to as Greenland interstadials and stadials. During warm interstadials the meridional overturning circulation was active transferring heat to the north, whereas during cold stadials the Nordic Seas were ice-covered and the overturning circulation was disrupted. Meltwater discharge, from ice sheets surrounding the Nordic Seas, is implicated as a cause of this ocean instability, yet very little is known regarding this proposed discharge during warmings. Here we show that, during warmings, pink clay from Devonian Red Beds is transported in suspension by meltwater from the surrounding ice sheet and replaces the greenish silt that is normally deposited on the north-western slope of Svalbard during interstadials. The magnitude of the outpourings is comparable to the size of the outbursts during the deglaciation. Decreasing concentrations of ice-rafted debris during the interstadials signify that the ice sheet retreats as the meltwater production increases. PMID:24264767

  2. Massilia eurypsychrophila sp. nov. a facultatively psychrophilic bacteria isolated from ice core.

    PubMed

    Shen, Liang; Liu, Yongqin; Gu, Zhengquan; Xu, Baiqing; Wang, Ninglian; Jiao, Nianzhi; Liu, Hongcan; Zhou, Yuguang

    2015-07-01

    Strain B528-3(T), a Gram-stain-negative, rod-shaped, aerobic, facultatively psychrophilic bacterium with polar flagella, was isolated from an ice core drilled from Muztagh Glacier, Xinjiang, China. The novel isolate was classified into the genus Massilia. The 16S rRNA gene sequence of the novel isolate shares a pairwise similarity of less than 97% with those of all the type strains of the genus Massilia. The major fatty acids of strain B528-3(T) were summed feature 3 (C16:1?7c and/or iso-C15:0 2-OH) (57.31%), C16:0 (11.46%) and C18:1?7c (14.72%). The predominant isoprenoid quinone was Q-8. The DNA G + C content was 62.2 mol% (Tm). The major polar lipids of this bacterium were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. From the genotypic and phenotypic data, it is evident that strain B528-3(T) represents a novel species of the genus Massilia, for which the name Massilia eurypsychrophila sp. nov. is proposed. The type strain is B528-3(T) (?= JCM 30074(T) = CGMCC 1.12828(T)). PMID:25851590

  3. First ice core records of NO3- stable isotopes from Lomonosovfonna, Svalbard

    NASA Astrophysics Data System (ADS)

    Vega, C. P.; Pohjola, V. A.; Samyn, D.; Pettersson, R.; Isaksson, E.; Björkman, M. P.; Martma, T.; Marca, A.; Kaiser, J.

    2015-01-01

    from two ice cores drilled at Lomonosovfonna, Svalbard, covering the period 1957-2009, and 1650-1995, respectively, were analyzed for NO3-concentrations, and NO3- stable isotopes (?15N and ?18O). Post-1950 ?15N has an average of (-6.9 ± 1.9)‰, which is lower than the isotopic signal known for Summit, Greenland but agrees with values observed in recent Svalbard snow and aerosol. Pre-1900 ?15N has an average of (4.2 ± 1.6)‰ suggesting that natural sources, enriched in the 15 N isotope, dominated before industrialization. The post-1950 ?18O average of (75.1 ± 4.1)‰ agrees with data from low and polar latitudes, suggesting similar atmospheric NOy (NOy = NO + NO2 + HNO3) processing pathways. The combination of anthropogenic source ?15N and transport isotope effect was estimated as -29.1‰ for the last 60 years. This value is below the usual range of NOx (NOx = NO + NO2) anthropogenic sources which is likely the result of a transport isotope effect of -32‰. We suggest that the ?15N recorded at Lomonosovfonna is influenced mainly by fossil fuel combustion, soil emissions, and forest fires; the first and second being responsible for the marked decrease in ?15N observed in the post-1950s record with soil emissions being associated to the decreasing trend in ?15N observed up to present time, and the third being responsible for the sharp increase of ?15N around 2000.

  4. Preliminary Black Carbon Record (1805 - 1943 AD) from the High Altitude Dasuopu Ice Core (7200 m) in the Central Himalaya

    NASA Astrophysics Data System (ADS)

    Barker, J. D.; Kaspari, S.; Wegner, A.; Thompson, L. G.; Gabrielli, P.

    2013-12-01

    Black carbon (BC) produced by the incomplete combustion of fossil and biofuels both amplifies mid-tropospheric atmospheric warming and decreases glacier surface albedo, and thus may influence regional climatic trends and water resource availability. The rapidly developing economies in Asia have been identified as significant sources of BC to the atmosphere on a continental scale in recent decades, but records available from this region to reconstruct BC concentrations spatially and temporally are limited. The analysis of BC preserved in glacier ice can provide a record of atmospheric BC content over time. We analyzed the Dasuopu Glacier ice core (Central Himalaya) for BC concentration at ~5 cm resolution using a Single Particle Soot Photometer (Droplet Measurement Technologies), and use the resultant record to describe trends in atmospheric BC from 1805 - 1943 AD. The Dasuopu ice core is unique because it was obtained at an exceptionally high elevation (7200 m a.s.l.) which may insolate it from local BC sources and reflect BC trends in a more mixed upper troposphere. Preliminary analysis of discrete sections shows that the Dasuopu ice core captures the seasonal BC deposition signal exceptionally well, with higher BC concentrations during winter-spring and lower concentrations during the summer monsoon season. Peak winter-spring concentrations pre-1890 are 10 ng g-1, increasing to as high as 30 ng g-1 during the 1890s - 1943. Additionally, background BC concentrations prior to 1890 are less than 0.5 ng g-1, and are consistently higher than 0.5 ng g-1 during the 1890s - 1943. The early 20th century BC increases are coincident with post-colonial industrialization of the Indian subcontinent. Preliminary results from the Dasuopu ice core highlight the utility of the BC record to detect perturbations in the carbon cycle at a regional scale, and the importance of an exceptionally high altitude location for detecting and preserving an atmospheric BC record. Future analyses will measure BC concentrations through the entire Dasuopu ice core and provide a continuous record of BC deposition in the region spanning 1442 - 1997.

  5. A comparison of age-depth scales derived from shallow ice cores and an FMCW radar in West Antarctica

    NASA Astrophysics Data System (ADS)

    Koenig, L.; Onana, V.; Forster, R. R.; Miege, C.; Rupper, S.; Burgener, L. K.; Patel, A. E.; MacGregor, J. A.

    2012-12-01

    The Satellite Era Accumulation Traverse (SEAT) collected near-surface firn cores and Ultra High Frequency (UHF) Frequency Modulated Continuous Wave (FMCW) radar data across the West Antarctic Ice Sheet (WAIS) divide in 2010. Five firn cores were collected with average accumulation rates ranging from approximately 200 to 275 mm of water equivalent per year. Age-depth scales for each core were developed using the seasonal signals of the ?18O and ?D records. ECM and density profiles were used to refine sections of the age-depth scale where the isotopic seasonal cycles were noisy or unclear. Age-depth scales were determined from the radar data by picking spatially continuous (approximately 1 km) layers in the radar echograms at the core sites. The continuous radar layers were assumed annual and dated. This study used data from the Ku-band Radar developed by the University of Kansas' Center for Remote Sensing of Ice Sheets operating between the frequencies of 12.5 GHz to 15.132 GHz, giving a vertical resolution of approximately 4.5 cm in the firn. Radar travel time was converted to depth using 2 cm density data from the ice core. A comparison of the core and radar derived age-depth scales shows that at higher accumulation sites the independent age-depth scales agree relatively well with maximum errors of up to +/-3 years in a given year. At lower accumulation sites dating errors from the radar age-depth scale are larger which is attributed to the difficulty in distinguishing annual layers from sub-annual peaks in density in the radar echogram.

  6. Accurate age scale of the Dome Fuji ice core, Antarctica from O2/N2 ratio of trapped air

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Aoki, S.; Nakazawa, T.; Suzuki, K.; Parrenin, F.

    2012-04-01

    Chronology of the first Dome Fuji deep ice core (core length: 2,500 m, ice thickness: 3,035 m) for the age range from 80 kyr to 340 kyr ago was established by orbital tuning of measured O2/N2 ratios in trapped air to local summer insolation, with precision better than about 2,000 years (Kawamura et al., 2007). The O2/N2 ratios found in polar ice cores are slightly lower than the atmospheric ratio because of size-dependent molecular fractionation during bubble close-off. The magnitude of this gas fractionation is believed to be governed by the magnitude of snow metamorphism when the layer was originally at the surface, which in turn is controlled by local summer insolation (Fujita et al., 2009). A strong advantage of the O2/N2 chronology is that there is no need to assume a lag between climatic records in the ice core and orbital forcings, becacuse O2/N2 ratios record local insolation through physical processes. Accuracy of the chronology was validated by comparing the O2/N2 chronology with U-Th radiometric chronology of speleothem records (Cheng et al., 2009) for the ends of Terminations II, III and IV, as well as several large climatic events, for which both ice-core CH4 and speleothem ?18O (a proxy for precipitation) show abrupt shifts as seen in the last glacial period. All ages from O2/N2 and U-Th chronology agreed with each other within ~2,000 yr. The O2/N2 chronology permits comparisons between Antarctic climate, greenhouse gases, astronomically calculated orbital parameters, and radiometrically-dated sea level and monsoon records. Here, we completed the measurements of O2/N2 ratios of the second Dome Fuji ice core, which reached bedrock, for the range from 2,400 to 3,028 m (320 - 700 kyr ago) at approximately 2,000-year time resolution. We made significant improvements in ice core storage practices and mass spectrometry. In particular, the ice core samples were stored at about -50 ° C until the air extraction, except during short periods of transportation, in order to prevent size-dependent fractionation due to gas loss during storage. The precision of the new O2/N2 data set is improved by a factor of 3 over the previous data. Clear imprint of local insolation is recognizable in the O2/N2 data towards the deepest depths, even around 400 kyr ago when summer insolation wiggles are small due to small orbital eccentricity. A new chronology using this O2/N2 data set will be established by applying the inverse method for EDC3 age scale (Parrenin et al., 2007) for the entire 700 kyr, and climatic implications will also be discussed especially on Terminations and interglacial periods.

  7. A 100-year Reconstruction of Regional Sea Ice Extent in the Ross and Amundsen-Bellingshausen Seas as Derived from the RICE Ice Core, Coastal West Antarctica

    NASA Astrophysics Data System (ADS)

    Emanuelsson, D. B.; Bertler, N. A. N.; Baisden, W. T.; Keller, E. D.

    2014-12-01

    Antarctic sea ice increased over the past decades. This increase is the result of an increase in the Ross Sea (RS) and along the coast of East Antarctica, whereas the Amundsen-Bellingshausen Seas (ABS) and the Antarctic Peninsula has seen a general decline. Several mechanisms have been suggested as drivers for the regional, complex sea ice pattern, which include changes in ocean currents, wind pattern, as well as ocean and atmospheric temperature. As part of the Roosevelt Island Climate Evolution (RICE) project, a 763 m deep ice core was retrieved from Roosevelt Island (RI; W161° 21', S79°41', 560 m a.s.l.), West Antarctica. The new record provides a unique opportunity to investigate mechanism driving sea ice variability in the RS and ABS sectors. Here we present the water stable isotope record (?D) from the upper part of the RICE core 0-40 m, spanning the time period from 1894 to 2011 (Fig. 1a). Annual ?D are correlated with Sea Ice Concentration (SIC). A significant negative (r= -0.45, p? 0.05) correlation was found between annual ?D and SIC in the eastern RS sector (boxed region in Fig. 1b) for the following months NDJFMA (austral summer and fall). During NDJFMA, RI receives local moisture input from the RS, while during the rest of the year a large extent of this local moisture source area will be covered with sea ice with the exception of the RS Polynya. Concurrently, we observe positive ?D and SIC correlations in the ABS, showing a dipole pattern with the eastern RS. For this reason, we suggest that the RICE ?D might be used as a proxy for past SIC for the RS and ABS region. There is no overall trend in ?D over 100 years (r= -0.08 ‰ dec-1, p= 0.81, 1894-2011). However, we observe a strong increase from 2000-2011 of 17.7 ‰ dec-1(p? 0.1), yet the recent ?D values and trend of the last decade are not unprecedented (Fig. 1a). We investigate changes in sea surface temperature, atmospheric temperature, inferred surface ocean currents and atmospheric wind fields to determine the driving mechanisms over the observational period (1979-2011). Figure 1. a) Annual ?D RI record 1894-2011 (black dots) and ?D decadal running mean (blue line). b) Correlation plot between ?D and six-months (NDJFMA) seasonal SIC means between 1980- 2011. Red star indicates location of RI and white contours shows areas where the correlation is significant to ?95% confidence level.

  8. North Atlantic Simulations in Coordinated Ocean-Ice Reference Experiments Phase II (CORE-II). Part I: Mean States

    NASA Technical Reports Server (NTRS)

    Danabasoglu, Gokhan; Yeager, Steve G.; Bailey, David; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Boning, Claus; Bozec, Alexandra; Canuto, Vittorio M.; Cassou, Christophe; Chassignet, Eric; Coward, Andrew C.; Danilov, Sergey; Diansky, Nikolay; Drange, Helge; Farneti, Riccardo; Fernandez, Elodie; Fogli, Pier Giuseppe; Forget, Gael; Fujii, Yosuke; Griffies, Stephen M.; Gusev, Anatoly; Heimbach, Patrick; Howard, Armando M

    2013-01-01

    Simulation characteristics from eighteen global ocean-sea-ice coupled models are presented with a focus on the mean Atlantic meridional overturning circulation (AMOC) and other related fields in the North Atlantic. These experiments use inter-annually varying atmospheric forcing data sets for the 60-year period from 1948 to 2007 and are performed as contributions to the second phase of the Coordinated Oceanice Reference Experiments (CORE-II). The protocol for conducting such CORE-II experiments is summarized. Despite using the same atmospheric forcing, the solutions show significant differences. As most models also differ from available observations, biases in the Labrador Sea region in upper-ocean potential temperature and salinity distributions, mixed layer depths, and sea-ice cover are identified as contributors to differences in AMOC. These differences in the solutions do not suggest an obvious grouping of the models based on their ocean model lineage, their vertical coordinate representations, or surface salinity restoring strengths. Thus, the solution differences among the models are attributed primarily to use of different subgrid scale parameterizations and parameter choices as well as to differences in vertical and horizontal grid resolutions in the ocean models. Use of a wide variety of sea-ice models with diverse snow and sea-ice albedo treatments also contributes to these differences. Based on the diagnostics considered, the majority of the models appear suitable for use in studies involving the North Atlantic, but some models require dedicated development effort. atmospheric forcing atmospheric temperatures

  9. 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

  10. 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

    2013-08-01

    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

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

    NASA Astrophysics Data System (ADS)

    Adolphi, F.; Muscheler, R.

    2015-07-01

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

  12. Testing the integrity of stable isotope records of two Spitsbergen ice cores by using high-resolution tritium data.

    NASA Astrophysics Data System (ADS)

    van der Wel, L. G.; Meijer, H. A. J.; Isaksson, E.; Helsen, M. M.; van de Wal, R. S. W.; Martma, T.; Pohjola, V. A.; Moore, J. C.

    2009-04-01

    The ratios of 1H16O2H and 1H18O1H in precipitation water vary with temperature and can therefore be used as a proxy for past climate. Ever since the 1960-s, retrieving these isotope signals has been the main motivation for the drilling of deep ice cores. Most of the ice core records originate from selected sites in Greenland and Antarctica. Other Arctic locations are much less used. However, since the late 1990-s ice cores have been drilled on the Lomonosovfonna and Holtedahlfonna ice caps in Spitsbergen. The advantages of drilling at these sites lies in the high accumulation rate present in Spitsbergen, as well as the very location of the Spitsbergen archipelago. However, due to relatively high temperatures in this region, the isotope record is affected by melt and subsequent percolation, thereby potentially losing its value for climatic studies. In an attempt to test the integrity of the Spitsbergen cores, we measured the concentration of the radioactive isotope of hydrogen (tritium) at high spatial (and thus temporal) resolution. Due to above-ground nuclear bomb tests in the 1950-s and 1960-s, the tritium signal in the atmosphere has been highly variable in that period, with distinct peaks. Moreover, due to the high load of tritium in the stratosphere at that time, spring and early summer mixing between stratosphere and troposphere induced a clear seasonal pattern in precipitation records for two decades. The tritium concentration in precipitation has been measured (monthly average) since the 1950-s. After precipitation the tritium record is altered due to decay, diffusion and melt. Incorporating information of these three processes into a numerical model, we produce a quantitative estimate how much the isotope record is influenced by melt and percolation. This gives us a tool to determine whether the stable isotope record is a valid proxy for past temperatures.

  13. The agricultural history of human-nitrogen interactions as recorded in ice core ?15N-NO3-

    NASA Astrophysics Data System (ADS)

    Felix, J. David; Elliott, Emily M.

    2013-04-01

    The advent and industrialization of the Haber Bosch process in the early twentieth century ushered in a new era of reactive nitrogen distributions on Earth. Since the appearance of the first commercial scale Haber Bosch fertilizer plants, fertilizer application rates have greatly increased in the U.S. While the contributions of fertilizer runoff to eutrophication and anoxic dead zones in coastal regions have been well-documented, the potential influences of increased fertilizer applications on air quality and precipitation chemistry are poorly constrained. Here we combine a 255-year record of precipitation nitrate isotopes preserved in a Greenland ice core, historical reconstructions of fertilizer application rates, and field characterization of the isotopic composition of nitrogen oxides produced biogenically in soils, to provide new constraints on the contributions of biogenic emissions to North American NOx inventories. Our results indicate that increases in twentieth century commercial fertilizer use led to large increases in soil NO, a byproduct released during nitrification and denitrification reactions. These large shifts in soil NO production are evidenced by sharp declines in ice core ?15N-NO3- values. Further, these results suggest that biogenic NOx emissions are underestimated by two to four fold in the U.S. NOx emission inventories used to construct global reactive nitrogen budgets. These results demonstrate that nitrate isotopes in ice cores, coupled with newly constrained ?15N-NOx values for NOx emission sources, provide a novel means for estimating contemporary and historic contributions from individual NOx emission sources to deposition.

  14. Unexpected increase in elemental carbon concentrations and deposition in a Svalbard ice core since 1970 and its implications for Arctic warming

    NASA Astrophysics Data System (ADS)

    Ruppel, Meri; Isaksson, Elisabeth; Ström, Johan; Beaudon, Emilie; Svensson, Jonas; Pedersen, Christina A.; Korhola, Atte

    2014-05-01

    Changes in albedo and related feedbacks in the Arctic have been suggested to be one of the driving mechanisms for the observed amplified Arctic warming. Black carbon (BC) is an aerosol produced by incomplete combustion of biomass and fossil fuels. Due to its strong light absorption it warms the atmosphere. Its climate effects are intensified in the Arctic where its deposition on snow and ice decreases surface albedo. BC has been suggested to have caused 20% of the Arctic melting hitherto. Despite the significant role of BC in Arctic warming, there is little information on its concentrations and climate effects in the area in the past. Here we present results on elemental carbon (EC, proxy for BC) concentrations and deposition on a Svalbard glacier (Holtedahlfonna) from 1700 to 2004. The inner part of a 125 m deep ice core was melted, filtered through a quartz fiber filter and analyzed for EC using a thermal optical method. The EC values increased after 1850 and peaked around 1910, similar to previous ice core records from Greenland. Strikingly, EC values increase abruptly since 1970. Such a rise is not seen in Greenland ice cores, and it seems to contradict atmospheric measurements indicating decreasing atmospheric BC concentrations since 1989 in the Arctic. However, the trend gains additional credence from a melt index derived from the same ice core indicating increased summer melt since 1970. The rise in EC values since 1970 is possibly explained by increased washout ratio of BC especially due to increased temperatures. In addition, post-depositional processes, such as increased melt, may enrich EC in most recent ice layers. These processes enable rising EC values in the ice core while atmospheric concentrations have decreased. Possible explanations for the differences in the recorded ice core BC trends from Greenland and Svalbard in the recent decades are partly different sources and the vertical distribution of emissions in the atmosphere. Specifically, the Svalbard ice core may record flaring emissions from northern Russia that do not reach the Greenland ice core sites. The results indicate that BC deposition may not necessarily be straightforwardly connected to atmospheric BC concentrations and that BC trends recorded from different ice cores may be dissimilar due to several factors independent of atmospheric concentrations. Regardless of the cause for the increasing EC values, the present results have significant implications for the past radiative transfer at the coring site. It remains to be determined how broad the signal and its albedo implications are. The results may give rise for further investigations on the significance of BC deposition to the Arctic sea ice retreat.

  15. Revealing potential past collapses of the West Antarctic Ice Sheet - Upcoming drilling in the Amundsen Sea Embayment

    NASA Astrophysics Data System (ADS)

    Kuhn, Gerhard; Gohl, Karsten; Uenzelmann-Neben, Gabriele; Bickert, Torsten; Schulz, Michael; Larter, Robert D.; Hillenbrand, Claus-Dieter

    2014-05-01

    The West Antarctic Ice-Sheet (WAIS) is likely to have been subject to very dynamic changes during its history as most of its base is grounded below modern sea-level, making it particularly sensitive to climate changes. Its collapse would result in global sea-level rise of 3-5 m. The reconstruction and quantification of possible partial or full collapses of the WAIS in the past can provide important constraints for ice-sheet models, used for projecting its future behaviour and resulting sea-level rise. Large uncertainties exist regarding the chronology, extent, rates as well as spatial and temporal variability of past advances and retreats of the WAIS across the continental shelves. By using the seafloor drilling device MeBo during an RV Polarstern cruise scheduled for early 2015, a series of sediment cores will be drilled on the Amundsen Sea Embayment (ASE) shelf, where seismic data show glacially-derived sequences covered by only a thin veneer of postglacial deposits in some areas. From analyses of seismic data, we infer that interglacial sediments can be sampled which may have been deposited under seasonally open water conditions and thus contain datable microfossil-bearing material. A shallow basin near the Pine Island Glacier front will be one of the prime targets for the drilling. The near-horizontal seismic reflection horizons may represent a sequence of continuously deposited, mainly terrigenous material, including ice-rafted debris, meltwater deposits and hemipelagic sediments deposited rapidly during the Holocene or a series of unconformities caused by erosion resulting from grounding line oscillations through many glacial cycles. Subglacial bedforms imaged in multibeam bathymetric data indicate fast glacial flow over some shelf areas of the ASE, where seismic profiles show acoustic basement near the seafloor. It is unknown, whether fast ice-flow in these areas was facilitated by water-lubricated sliding over bedrock or presence of a thin layer of deformable till (perhaps less than a metre in thickness). The nature of this layer holds important clues for understanding the processes that operated beneath the margin of the ice-sheet, beneath ice-flows and on ridges between ice-streams during the Last Glacial Maximum. Grounding zone wedges (GZWs) are widely thought to be important in stabilising grounding line positions during ice-sheet retreat, but hypotheses about the processes and duration of their formation and their composition, are mainly based on conceptual models. Drill sites on and near GZWs are aimed to establish the nature of their sediments, their formation processes, their rates of growth and the palaeo-environmental conditions in their surroundings.

  16. Innovative optical spectrometers for ice core sciences and atmospheric monitoring at polar regions

    NASA Astrophysics Data System (ADS)

    Grilli, Roberto; Alemany, Olivier; Chappellaz, Jérôme; Desbois, Thibault; Faïn, Xavier; Kassi, Samir; Kerstel, Erik; Legrand, Michel; Marrocco, Nicola; Méjean, Guillaume; Preunkert, Suzanne; Romanini, Daniele; Triest, Jack; Ventrillard, Irene

    2015-04-01

    In this talk recent developments accomplished from a collaboration between the Laboratoire Interdisciplinaire de Physique (LIPhy) and the Laboratoire de Glaciologie et Géophysique de l'Environnement (LGGE) both in Grenoble (France), are discussed, covering atmospheric chemistry of high reactive species in polar regions and employing optical spectrometers for both in situ and laboratory measurements of glacial archives. In the framework of an ANR project, a transportable spectrometer based on the injection of a broadband frequency comb laser into a high-finesse optical cavity for the detection of IO, BrO, NO2 and H2CO has been realized.[1] The robust spectrometer provides shot-noise limited measurements for as long as 10 minutes, reaching detection limits of 0.04, 2, 10 and 200 ppt (2?) for the four species, respectively. During the austral summer of 2011/12 the instrument has been used for monitoring, for the first time, NO2, IO and BrO at Dumont d'Urville Station at East of Antarctica. The measurements highlighted a different chemistry between East and West coast, with the halogen chemistry being promoted to the West and the OH and NOx chemistry on the East.[2] In the framework of a SUBGLACIOR project, an innovative drilling probe has been realized. The instrument is capable of retrieving in situ real-time vertical profiles of CH4 and ?D of H2O trapped inside the ice sheet down to more than 3 km of depth within a single Antarctic season. The drilling probe containing an embedded OFCEAS (optical-feedback cavity-enhanced absorption spectroscopy) spectrometer will be extremely useful for (i) identify potential sites for investigating the oldest ice (aiming 1.5 Myrs BP records for resolving a major climate reorganization called the Mid-Pleistocene transition occurred around 1 Myrs ago) and (ii) providing direct access to past temperatures and climate cycles thanks to the vertical distribution of two key climatic signatures.[3] The spectrometer provides detection limit of 0.2 ppbv for CH4 and a precision of 0.2o on the ?D of H2O within ~1 min of integration time. The spectrometer and the home-made gas sampling has been tested during an oceanographic campaign last summer in the Mediterranean Sea, measuring the vertical distribution of CH4 dissolved in seawater. The project is now moving forward its final goal which consists of employing the probe for a first test season at Concordia station during the Austral summer of 2016/17, and then for the 'oldest ice challenge' drilling season scheduled in the Austral summer of 2017/18. Finally, preliminary results on the isotope ratio measurements of CO18O,13CO2 and 13CO18O will be presented. A novel spectrometer, based on OFCAES technique employing a Quantum Cascade Laser around 4.4 ?m wavelength, offers a precision below 0.05 o for the three isotopic anomalies, for 200 ppmv of CO2 samples. The optical device will be employed for laboratory experiments coupling it with a continuous ice-crushing extraction system for analyzing trapped bubbles of gas in Antarctica ice cores. [1] R. Grilli, G. Méjean, S. Kassi, I. Ventrillard, C. Abd-Alrahman, and D. Romanini, 'Frequency Comb Based Spectrometer for in Situ and Real Time Measurements of IO, BrO, NO2, and H2CO at pptv and ppqv Levels.,' Environ. Sci. Technol., vol. 46, no. 19, pp. 10704-10, Oct. 2012. [2] R. Grilli, M. Legrand, A. Kukui, G. Méjean, S. Preunkert, and D. Romanini, 'First investigations of IO, BrO, and NO2 summer atmospheric levels at a coastal East Antarctic site using mode-locked cavity enhanced absorption spectroscopy,' Geophys. Res. Lett., vol. 40, pp. 1-6, Feb. 2013. [3] R. Grilli, N. Marrocco, T. Desbois, C. Guillerm, J. Triest, E. Kerstel, and D. Romanini, 'Invited Article: SUBGLACIOR: An optical analyzer embedded in an Antarctic ice probe for exploring the past climate,' Rev. Sci. Instrum., vol. 85, no. 111301, pp. 1-7, 2014.

  17. Comparative Genomics Reveals the Core and Accessory Genomes of Streptomyces Species.

    PubMed

    Kim, Ji-Nu; Kim, Yeonbum; Jeong, Yujin; Roe, Jung-Hye; Kim, Byung-Gee; Cho, Byung-Kwan

    2015-10-28

    The development of rapid and efficient genome sequencing methods has enabled us to study the evolutionary background of bacterial genetic information. Here, we present comparative genomic analysis of 17 Streptomyces species, for which the genome has been completely sequenced, using the pan-genome approach. The analysis revealed that 34,592 ortholog clusters constituted the pan-genome of these Streptomyces species, including 2,018 in the core genome, 11,743 in the dispensable genome, and 20,831 in the unique genome. The core genome was converged to a smaller number of genes than reported previously, with 3,096 gene families. Functional enrichment analysis showed that genes involved in transcription were most abundant in the Streptomyces pan-genome. Finally, we investigated core genes for the sigma factors, mycothiol biosynthesis pathway, and secondary metabolism pathways; our data showed that many genes involved in stress response and morphological differentiation were commonly expressed in Streptomyces species. Elucidation of the core genome offers a basis for understanding the functional evolution of Streptomyces species and provides insights into target selection for the construction of industrial strains. PMID:26032364

  18. Spores of many common airborne fungi reveal no ice nucleation activity in oil immersion freezing experiments

    NASA Astrophysics Data System (ADS)

    Pummer, B. G.; Atanasova, L.; Bauer, H.; Bernardi, J.; Druzhinina, I. S.; Fröhlich-Nowoisky, J.; Grothe, H.

    2013-12-01

    Fungal spores are ubiquitous biological aerosols, which are considered to act as ice nuclei. In this study the ice nucleation (IN) activity of spores harvested from 29 fungal strains belonging to 21 different species was tested in the immersion freezing mode by microscopic observation of water-in-oil emulsions. Spores of 8 of these strains were also investigated in a microdroplet freezing array instrument. The focus was laid on species of economical, ecological or sanitary significance. Besides common molds (Ascomycota), some representatives of the widespread group of mushrooms (Basidiomycota) were also investigated. Fusarium avenaceum was the only sample showing IN activity at relatively high temperatures (about 264 K), while the other investigated fungal spores showed no freezing above 248 K. Many of the samples indeed froze at homogeneous ice nucleation temperatures (about 237 K). In combination with other studies, this suggests that only a limited number of species may act as atmospheric ice nuclei. This would be analogous to what is already known for the bacterial ice nuclei. Apart from that, we selected a set of fungal strains from different sites and exposed them to occasional freezing stress during their cultivation. This was in order to test if the exposure to a cold environment encourages the expression of ice nuclei during growth as a way of adaptation. Although the total protein expression was altered by this treatment, it had no significant impact on the IN activity.

  19. Historical whaling records reveal major regional retreat of Antarctic sea ice

    NASA Astrophysics Data System (ADS)

    Cotté, Cédric; Guinet, Christophe

    2007-02-01

    Several studies have provided evidence of a reduction of the Antarctic sea ice extent. However, these studies were conducted either at a global scale or at a regional scale, and possible inter-regional differences were not analysed. Using the long-term whaling database we investigated circum-Antarctic changes in summer sea ice extent from 1931 to 1987. Accounting for bias inherent in the whaling method, this analysis provides new insight into the historical ice edge reconstruction and inter-regional differences. We highlight a reduction of the sea ice extent occurring in the 1960s, mainly in the Weddell sector where the change ranged from 3° to 7.9° latitude through summer. Although the whaling method may not be appropriate for detecting fine-scale change, these results provide evidence for a heterogeneous circumpolar change of the sea ice extent. The shift is temporally and spatially consistent with other environmental changes detected in the Weddell sector and also with a shift in the Southern Hemisphere annular mode. The large reduction of the sea ice extent has probably influenced the ecosystem of the Weddell Sea, particularly the krill biomass.

  20. Paleo-Climate and Glaciological Reconstruction in Central Asia through the Collection and Analysis of Ice Cores and Instrumental Data from the Tien Shan

    SciTech Connect

    Vladimir Aizen; Donald Bren; Karl Kreutz; Cameron Wake

    2001-05-30

    While the majority of ice core investigations have been undertaken in the polar regions, a few ice cores recovered from carefully selected high altitude/mid-to-low latitude glaciers have also provided valuable records of climate variability in these regions. A regional array of high resolution, multi-parameter ice core records developed from temperate and tropical regions of the globe can be used to document regional climate and environmental change in the latitudes which are home to the vase majority of the Earth's human population. In addition, these records can be directly compared with ice core records available from the polar regions and can therefore expand our understanding of inter-hemispheric dynamics of past climate changes. The main objectives of our paleoclimate research in the Tien Shan mountains of middle Asia combine the development of detailed paleoenvironmental records via the physical and chemical analysis of ice cores with the analysis of modern meteorological and hydrological data. The first step in this research was the collection of ice cores from the accumulation zone of the Inylchek Glacier and the collection of meteorological data from a variety of stations throughout the Tien Shan. The research effort described in this report was part of a collaborative effort with the United State Geological Survey's (USGS) Global Environmental Research Program which began studying radionuclide deposition in mid-latitude glaciers in 1995.

  1. Estimation and calibration of the water isotope differential diffusion length in ice core records

    NASA Astrophysics Data System (ADS)

    van der Wel, G.; Fischer, H.; Oerter, H.; Meyer, H.; Meijer, H. A. J.

    2015-02-01

    Paleoclimatic information can be retrieved from the diffusion of the stable water isotope signal during firnification of snow. The diffusion length, a measure for the amount of diffusion a layer has experienced, depends on the firn temperature and the accumulation rate. We show that the estimation of the diffusion length using Power Spectral Densities (PSD) of the record of a single isotope species can be biased and is therefore not a reliable proxy for past temperature reconstruction. Using a second water isotope and calculating the difference in diffusion lengths between the two isotopes this problem is circumvented. We study the PSD method applied to two isotopes in detail and additionally present a new forward diffusion method for retrieving the differential diffusion length based on the Pearson correlation between the two isotope signals. The two methods are discussed and extensively tested on synthetic data which are generated in a Monte Carlo manner. We show that calibration of the PSD method with this synthetic data is necessary to be able to objectively determine the differential diffusion length. The correlation based method proofs to be a good alternative for the PSD method as it yields equal or somewhat higher precision than the PSD method. The use of synthetic data also allows us to estimate the accuracy and precision of the two methods and to choose the best sampling strategy to obtain past temperatures with the required precision. Additional to application to synthetic data the two methods are tested on stable isotope records from the EPICA ice core drilled in Dronning Maud Land, Antarctica, showing that reliable firn temperatures can be reconstructed with a typical uncertainty of 1.5 and 2 °C for the Holocene period and 2 and 2.5 °C for the last glacial period for the correlation and PSD method, respectively.

  2. A method for estimating the age-depth relationship of Dome Fuji Ice Core using a sequential Monte Carlo method

    NASA Astrophysics Data System (ADS)

    Nakano, Shinya; Suzuki, Kazue; Kawamura, Kenji; Parrenin, Frederic; Higuchi, Tomoyuki

    2015-04-01

    A technique for estimating the age-depth relationship and its uncertainty in ice cores has been developed. The age-depth relationship is mainly determined by the accumulation of snow at the site of the ice core and the thinning process due to the horizontal stretching and vertical compression of an ice layer. However, both the accumulation process and the thinning process are not fully known. In order to appropriately estimate the age as a function of depth, it is crucial to incorporate observational information into a model describing the accumulation and thinning processes. In the proposed technique, the age as a function of depth is estimated from age markers and time series of ?18O data. The estimation is achieved using a method combining a sequential Monte Carlo method and the Markov chain Monte Carlo method as proposed by Andrieu et al. (2010). In this hybrid method, the posterior distributions for the parameters in the models for the accumulation and thinning processes are basically computed using a way of the standard Metropolis-Hastings method. Meanwhile, sampling from the posterior distribution for the age-depth relationship is achieved by using a sequential Monte Carlo approach at each iteration of the Metropolis-Hastings method. A sequential Monte Carlo method normally suffers from the degeneracy problem, especially in cases that the number of steps is large. However, when it is combined with the Metropolis-Hastings method, the degeneracy problem can be overcome by collecting a large number of samples obtained by many iterations of the Metropolis-Hastings method. We will demonstrate the result obtained by applying the proposed technique to the ice core data from Dome Fuji in Antarctica.

  3. Northeast Siberian ice wedges reveal Arctic long-term winter warming over the past two millennia

    NASA Astrophysics Data System (ADS)

    Opel, Thomas; Meyer, Hanno; Laepple, Thomas; Wetterich, Sebastian; Werner, Martin; Dereviagin, Alexander; Schirrmeister, Lutz

    2015-04-01

    The Arctic currently experiences a pronounced and unprecedented warming. This highly dynamic response on changes in climate forcing and the global impact of the Arctic water, carbon and energy balance make the Arctic a key region to study past and future climate changes on different spatial, temporal and seasonal scales. Recent proxy-based Arctic and Northern Hemisphere temperature reconstructions show a long-term cooling trend over the past millennia that has been reversed by the ongoing Arctic warming. This cooling is mainly related to the decrease in summer insolation. Climate models on the other hand show no significant change or even a slight warming. This model-proxy mismatch might be caused by a summer bias of most records. Hence, there is strong need for past winter climate information. Moreover, the Russian Arctic is largely underrepresented in recent Arctic-wide proxy compilations. Ice wedges may help to fill these seasonal and spatial gaps. Polygonal ice wedges are a widespread permafrost feature in the Arctic coastal lowlands. They are formed by the periodic repetition of wintertime frost cracking and subsequent crack filling in spring mostly by melt water of winter snow. Hence, the isotopic composition of wedge ice is indicative of past climate conditions during this extended winter season. ?18O of ice is interpreted as proxy for local air temperatures. Radiocarbon dating of organic remains in ice-wedge samples enables one to generate chronologies for single ice wedges as well as stacked records with an up to centennial resolution. Here we present ice-wedge records from the Oyogos Yar coast in the Northeast Siberian Arctic (72.7°N, 143.5°E) that cover the past two millennia. We discuss the chronological approaches as well as the paleoclimatic findings. The co-isotopic relationship of wedge ice is close to the Global Meteoric Water Line pointing to no significant isotopic changes during ice-wedge formation and, therefore, to a good suitability for paleoclimate studies. Our ice wedge data show a clear long-term warming trend over the past two millennia detectable in single ice wedge profiles as well as in a stacked record. This trend culminates in an unprecedented rise over the last decades reflecting the ongoing Arctic warming and reaching the absolutely highest ?18O values found in Late Quaternary ice wedges in the study region. These findings are related to the increases in winter insolation as well as in greenhouse gas forcing over the past two millennia. However, this temperature pattern is in contradiction to most other Arctic temperature records that, in turn, are likely summer-biased. This underlines the seasonally different orbital forcing trends. Our ice-wedge record adds therefore unique and substantial climate information for understanding the seasonal patterns of Late Holocene paleoclimate. It supports recent findings from Holocene ice wedges in the Lena River Delta and might help bridging the gap between proxy records and climate models in the Arctic.

  4. TRACEing Last Glacial Period (25-80 ka b2k) Tephra Horizons between North Atlantic marine-cores and the Greenland ice-cores

    NASA Astrophysics Data System (ADS)

    Abbott, Peter; Davies, Siwan; Griggs, Adam; Bourne, Anna; Cook, Eliza; Austin, William; Chapman, Mark; Hall, Ian; Purcell, Catriona; Rasmussen, Tine; Scourse, James

    2014-05-01

    Tephrochronological investigations are currently being undertaken on a network of marine cores from a range of locations and depositional settings within the North Atlantic. This work forms a component of the ERC-funded project Tephra constraints on Rapid Climate Events (TRACE). The main aim of this project is to utilise isochronous tephra horizons as direct tie-lines to correlate North Atlantic marine sequences and the Greenland ice-cores to determine the relative timing of oceanic and atmospheric changes associated with the rapid climate events that dominated the last glacial period. Early comparisons of six North Atlantic marine records (MD99-2251, MD04-2820CQ, MD04-2829CQ, MD04-2822, MD01-2461 and JM11-19PC) and the Greenland ice-cores highlight six tephra horizons common to the ice record and one or more marine sequences. These horizons are within GS-3 (26,740 ± 390 a b2k and 29,130 ± 456 a b2k), GS-9 (38,300 ± 703 a b2k), GS-10 (40,220 ± 792 a b2k) and GS-12 (43,680 ± 877 a b2k) and the widespread North Atlantic Ash Zone II (55,380 ± 1184 a b2k). New high-resolution proxy information from MD04-2820CQ allows us to explore the relative timing of climatic changes between the Goban Spur, North Atlantic and Greenland over GI-12 to GI-8 using two tephra correlations that link the records. Tephra horizons have been identified in the marine records through the successful use of cryptotephra extraction techniques more commonly applied to the study of terrestrial sequences. All horizons have an Icelandic source with horizons of both rhyolitic and basaltic composition isolated. The acquisition of high-resolution profiles of shard concentration and comprehensive geochemical characterisations for horizons is vital to this work. This allows us to disentangle the processes that transported material to core sites, which can include primary airfall, sea-ice rafting and iceberg rafting, and the potential impact of secondary reworking processes such as bottom current reworking and bioturbation on the stratigraphic integrity of horizons. We are also applying the innovative techniques of micromorphology and X-ray tomography to the study of these processes.

  5. West Antarctica snow accumulation trend study (1979-2011) from Snow Radar and ice core profiles

    E-print Network

    Feng, Boyu

    2014-12-31

    periods to be determined. The focus is on one particular ice penetrating radar system: Snow Radar from the Center for Remote Sensing of Ice Sheet (CReSIS). The Snow Radar is a 2-8 GHz ultra-wideband (UWB), frequency-modulated, continuous-wave (FMCW) radar...

  6. Molecular Probe Dynamics Reveals Suppression of Ice-Like Regions in Strongly Confined Supercooled Water

    PubMed Central

    Banerjee, Debamalya; Bhat, Shrivalli N.; Bhat, Subray V.; Leporini, Dino

    2012-01-01

    The structure of the hydrogen bond network is a key element for understanding water's thermodynamic and kinetic anomalies. While ambient water is strongly believed to be a uniform, continuous hydrogen-bonded liquid, there is growing consensus that supercooled water is better described in terms of distinct domains with either a low-density ice-like structure or a high-density disordered one. We evidenced two distinct rotational mobilities of probe molecules in interstitial supercooled water of polycrystalline ice [Banerjee D, et al. (2009) ESR evidence for 2 coexisting liquid phases in deeply supercooled bulk water. Proc Natl Acad Sci USA 106: 11448–11453]. Here we show that, by increasing the confinement of interstitial water, the mobility of probe molecules, surprisingly, increases. We argue that loose confinement allows the presence of ice-like regions in supercooled water, whereas a tighter confinement yields the suppression of this ordered fraction and leads to higher fluidity. Compelling evidence of the presence of ice-like regions is provided by the probe orientational entropy barrier which is set, through hydrogen bonding, by the configuration of the surrounding water molecules and yields a direct measure of the configurational entropy of the same. We find that, under loose confinement of supercooled water, the entropy barrier surmounted by the slower probe fraction exceeds that of equilibrium water by the melting entropy of ice, whereas no increase of the barrier is observed under stronger confinement. The lower limit of metastability of supercooled water is discussed. PMID:23049747

  7. Isotopic variability in the deepest Vostok (East Antarctica) ice core suggests not perfect mixing of Lake Vostok water

    NASA Astrophysics Data System (ADS)

    Ekaykin, A. A.; Lipenkov, V. Ya.

    2009-04-01

    One of the key questions about subglacial Antarctic Lake Vostok (LV) hydrological system is whether the water of the lake is well mixed or not. Not complete mixing of water from the sources feeding the lake (glacier melt and hydrothermal water) with the water of main lake body would have several important consequences: 1) lake ice retrieved from 5G-1 borehole at Vostok Station is likely formed from a water layer which is not fully representative for the entire lake; 2) effective residence time of water in the main lake body is likely significantly longer than that deduced from simple mass balance estimations; 3) and, likely most important, not perfect mixing of lake water would suggest the existence of ecological niches where micro-biota can hide from lethal influence of high oxygen concentration likely typical for the lake. A powerful and promising tool for studying hydrological regime of LV is analyses of lake ice isotope content variability. Up to now, isotopic data from the lake ice have been only used to roughly estimate the components of the lake's mass balance. However, closer view to the lake ice isotopic signal may provide with a range of valuable information about processes taking place just beneath the glacier sole. Here we present new isotopic data from the deepest part of Vostok ice core (3611-3650 m), as well as revisit the previously published data from the 3538-3611 m interval. It is shown that the lake ice isotope content experiences small-scale variability which is related to the changes of the isotopic composition of the freezing water. Since the time-scale of these oscillations is much less than the expected LV residence time, it suggests that lake water is not perfectly mixed. Most likely it is due to not complete mixing of melt water and/or hydrothermal water with lake resident water on their way to the freezing site. The work is carried out in frames of Project 4 of Russian Federal Targeted Program "Antarctica". We thank Russian Antarctic Expedition for logistical operations, St. Petersburg Mining Institute for providing with the high-quality ice core, Laboratoire des Sciences du Climat et l'Environnement (Saclay, France), Niels Bohr Institute (Copenhagen, Denmark) and St. Petersburg Geological Institute (VSEGEI, Russia) for the mass-spectrometric analyses.

  8. The Role of the Tropics in Last Glacial Abrupt Climate Change from a West Antarctic Ice Core

    NASA Astrophysics Data System (ADS)

    Jones, T. R.; White, J. W. C.; Steig, E. J.; Cuffey, K. M.; Vaughn, B. H.; Morris, V. A.; Vasileios, G.; Markle, B. R.; Schoenemann, S. W.

    2014-12-01

    Debate exists as to whether last glacial abrupt climate changes in Greenland, and associated changes in Antarctica, had a high-latitude or tropical trigger. An ultra high-resolution water isotope record from the West Antarctic Ice Sheet Divide (WAIS Divide) Ice Core Project has been developed with three key water isotope parameters that offer insight into this debate: ?D, ?18O, and deuterium excess (dxs). ?D and ?18O are a proxy for local temperature and regional atmospheric circulation, while dxs is primarily a proxy for sea surface temperature at the ice core's moisture source(s) (relative humidity and wind speed also play a role). We build on past studies that show West Antarctic climate is modulated by El Niño Southern Oscillation (ENSO) teleconnection mechanisms, which originate in the equatorial Pacific Ocean, to infer how past ENSO changes may have influenced abrupt climate change. Using frequency analysis of the water isotope data, we can reconstruct the amplitude of ENSO-scale climate oscillations in the 2-15 year range within temporal windows as low as 100 years. Our analysis uses a back diffusion model that estimates initial amplitudes before decay in the firn column. We combine ?D, ?18O, and dxs frequency analysis to evaluate how climate variability at WAIS Divide is influenced by tropical climate forcing. Our results should ultimately offer insight into the role of the tropics in abrupt climate change.

  9. Net accumulation rates derived from ice core stable isotope records of Pío XI glacier, Southern Patagonia Icefield

    NASA Astrophysics Data System (ADS)

    Schwikowski, M.; Schläppi, M.; Santibañez, P.; Rivera, A.; Casassa, G.

    2012-12-01

    Pío XI, the largest glacier of the Southern Patagonia Icefield, reached its neoglacial maximum extent in 1994 and is one of the few glaciers in that area which is not retreating. In view of the recent warming it is important to understand glacier responses to climate changes. Due to its remoteness and the harsh conditions in Patagonia, no systematic mass balance studies have been performed. In this study we derived net accumulation rates for the period 2000 to 2006 from a 50 m (33.2 4 m weq) ice core collected in the accumulation area of Pío XI (2600 m a.s.l., 49°16´40´´ S, 73°21´14´´ W). Borehole temperatures indicate near temperate ice, but the average melt percent is only 16% ± 14%. Records of stable isotopes are well preserved and were used for identification of annual layers. Net accumulation rates range from 3.4 to 7.1 water equivalent (m weq) with an average of 5.8 m weq, comparable to precipitation amounts at the Chilean coast, but not as high as expected for the Icefield. Ice core stable isotope data correlate well with upper air temperatures and may be used as temperature proxy.

  10. Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Anderson, T.; Arguelles, C.; Arlen, T. C.; Auffenberg, J.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Brayeur, L.; Bretz, H.-P.; Brown, A. M.; Brunner, J.; Buzinsky, N.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Christy, B.; Clark, K.; Classen, L.; Clevermann, F.; Coenders, S.; Cowen, D. F.; Cruz Silva, A. H.; Daughhetee, J.; Davis, J. C.; Day, M.; de André, J. P. A. M.; De Clercq, C.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; Dunkman, M.; Eagan, R.; Eberhardt, B.; Eichmann, B.; Eisch, J.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feintzeig, J.; Felde, J.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Flis, S.; Franckowiak, A.; Frantzen, K.; Fuchs, T.; Gaisser, T. K.; Gaior, R.; Gallagher, J.; Gerhardt, L.; Gier, D.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Goodman, J. A.; Góra, D.; Grant, D.; Gretskov, P.; Groh, J. C.; Groß, A.; Ha, C.; Haack, C.; Haj Ismail, A.; Hallen, P.; Hallgren, A.; Halzen, F.; Hanson, K.; Hebecker, D.; Heereman, D.; Heinen, D.; Helbing, K.; Hellauer, R.; Hellwig, D.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Homeier, A.; Hoshina, K.; Huang, F.; Huelsnitz, W.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobi, E.; Jacobsen, J.; Jagielski, K.; Japaridze, G. S.; Jero, K.; Jlelati, O.; Jurkovic, M.; Kaminsky, B.; Kappes, A.; Karg, T.; Karle, A.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kiryluk, J.; Kläs, J.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Koob, A.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Kriesten, A.; Krings, K.; Kroll, G.; Kroll, M.; Kunnen, J.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lanfranchi, J. L.; Larsen, D. T.; Larson, M. J.; Lesiak-Bzdak, M.; Leuermann, M.; Lünemann, J.; Madsen, J.; Maggi, G.; Maruyama, R.; Mase, K.; Matis, H. S.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meli, A.; Meures, T.; Miarecki, S.; Middell, E.; Middlemas, E.; Milke, N.; Miller, J.; Mohrmann, L.; Montaruli, T.; Morse, R.; Nahnhauer, R.; Naumann, U.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke, A.; Odrowski, S.; Olivas, A.; Omairat, A.; O'Murchadha, A.; Palczewski, T.; Paul, L.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pfendner, C.; Pieloth, D.; Pinat, E.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Pütz, J.; Quinnan, M.; Rädel, L.; Rameez, M.; Rawlins, K.; Redl, P.; Rees, I.; Reimann, R.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rodrigues, J. P.; Rongen, M.; Rott, C.; Ruhe, T.; Ruzybayev, B.; Ryckbosch, D.; Saba, S. M.; Sander, H.-G.; Sandroos, J.; Santander, M.; Sarkar, S.; Schatto, K.; Scheriau, F.; Schmidt, T.; Schmitz, M.; Schoenen, S.; Schöneberg, S.; Schönwald, A.; Schukraft, A.; Schulte, L.; Schulz, O.; Seckel, D.; Sestayo, Y.; Seunarine, S.; Shanidze, R.; Smith, M. W. E.; Soldin, D.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stanisha, N. A.; Stasik, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Strahler, E. A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Taavola, H.; Taboada, I.; Tamburro, A.; Tepe, A.; Ter-Antonyan, S.; Terliuk, A.; Teši?, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Tosi, D.; Tselengidou, M.; Unger, E.; Usner, M.; Vallecorsa, S.; van Eijndhoven, N.; Vandenbroucke, J.; van Santen, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Wallraff, M.; Weaver, Ch.; Wellons, M.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Whitehorn, N.; Wichary, C.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wissing, H.; Wolf, M.; Wood, T. R.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.; Ziemann, J.; Zierke, S.; Zoll, M.; IceCube Collaboration

    2015-04-01

    We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser IceCube instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 and 100 GeV, where a strong disappearance signal is expected. The IceCube detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by ? m322=2.72-0.20+0.19×10-3 eV2 and sin2?23=0.53-0.12+0.09 (normal mass ordering assumed). The results are compatible, and comparable in precision, to those of dedicated oscillation experiments.

  11. 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.

  12. Taxonomic characterization, adaptation strategies and biotechnological potential of cryophilic yeasts from ice cores of Midre Lovénbreen glacier, Svalbard, Arctic.

    PubMed

    Singh, Purnima; Tsuji, Masaharu; Singh, Shiv Mohan; Roy, Utpal; Hoshino, Tamotsu

    2013-04-01

    Ten strains of cryophilic yeast were studied from glacier ice cores of Svalbard, Arctic. The ice melt samples contained about 3×10(3) - 1×10(4) colony forming unit (CFUs) per ml. Sequence analysis of the isolates, using D1/D2 domain identified five species of yeasts: Cryptococcus adeliensis (MLB-18 JX192655), Cryptococcus albidosimilis (MLB-19 JX192656), Cryptococcus saitoi (MLB-22 JX192659), Rhodosporidium lusitaniae (MLB-20 JX192657), and Rhodotorula mucilaginosa (MLB-27 JX192664). Effect of temperature on growth of these isolates was studied. The strains are able to grow at temperatures ranging between 1 and 20°C. Screening of the cultures for amylase, cellulase, protease, lipase, urease and catalase activity were carried out indicating varying amounts of enzyme production at different temperatures. Characterization of lipase in strain Cryptococcus sp. MLB-24 was performed. Fatty acid methyl ester (FAME) analysis of the cultures grown at four different temperatures (1, 4, 15, and 20°C) was also done. Decrease in temperature was reported to cause increase in concentration of unsaturated fatty acids. High amount of oleic acid accumulated with increase in temperature. These fatty acids possibly help the strains to survive in glacial ice core cold environment. The extracellular and intracellular filtrate of the cultures showed negative antifreeze protein (AFP) activity. The observations indicate that probably the isolates in the present undertaking adapt to low temperatures, by enzyme and PUFA secretion rather than by antifreeze protein secretion. PMID:23353800

  13. Systematic Localization of the Arabidopsis Core Cell Cycle Proteins Reveals Novel Cell Division Complexes1[W][OA

    E-print Network

    Gent, Universiteit

    Systematic Localization of the Arabidopsis Core Cell Cycle Proteins Reveals Novel Cell Division proteolysis, and protein-protein interactions. Although immunological assays can define cell cycle protein of 60 Arabidopsis (Arabidopsis thaliana) core cell cycle proteins fused to green fluorescent proteins

  14. Global analysis of the core cell cycle regulators of Arabidopsis identifies novel genes, reveals multiple and highly specific

    E-print Network

    Murray, J.A.H.

    Global analysis of the core cell cycle regulators of Arabidopsis identifies novel genes, reveals multiple and highly specific profiles of expression and provides a coherent model for plant cell cycle conserved and plant-specific core cell cycle regulators, but in most cases neither their timing

  15. Characteristics of correlation between climate and environmental elements from past 700,000 years in Dome Fuji ice core, Antarctica

    NASA Astrophysics Data System (ADS)

    Motoyama, H.; Fuji Ice Core Project members, Dome

    2012-04-01

    Two deep ice cores (DF1: 2503m and DF2: 3035m) at Dome Fuji, Antarctica have the in-depth information of global environmental change from present to the past 700,000 years. We made the data set of major ion concentration, dust concentration and stable isotope ratio which were analyzed 10cm sample every 50cm from 2400m to 3035m using the DF2 core. The age of this depth was covered from 300,000 to 700,000 years before. Using the DF1 core, major chemical species were carried out using 7-10cm ice samples cut out of the 50 cm-long spaced from 0.5 to 2.5m. All data was averaged by every 5 m or every 1,000 years. The correlations between climate and environmental elements were calculated. The indexes of climate and environment are the following elements; MSA-, Cl-, NO3-, SO42-, H+ (calculated from pH), Na+, NH4+, K+, Mg2+, Ca2+, ss-Na+, nss-Cl-, nss-SO42-, nss-K+, nss-Mg2+, nss-Ca2+, ?D, ?18O, d-excess, dust, pH and electrical conductivity. There is a feature in correlation respectively by the climatic stage. ?D or ?18O which becomes the index of the temperature and the environmental elements (for example, Na+ and Mg2+) indicate the strong negative correlation, but its degree is different depending on the climatic stages. In particular, environmental changes around Mid-Brunhes event (i.e. 430kyrBP) were examined. Ice core drilling reached just near the bedrock in ice sheet. Liquid water which existed around the basal ice was soaked into the borehole. Its water was frozen and was picked up with drill machine. Characteristics of ion concentrations near the bedrock (i.e, from 3000m to 3035m) were reported. There was no big change in ?18O , ?D and d-excess profiles in deeper part. Dust and nssCa2+ concentrations did not show the conspicuous change between 3000m to 3034m. They became high concentrations under 3034m. The concentration of Na+, SO42-, NO3- became small but Cl- became large from 3020m to 3033.5m. The concentrations of all ion components were suddenly decreased from 30033.5m. The borehole measurement was carried out in January 2011. The items of borehole measurements were; borehole diameter, ice temperature and liquid temperature, liquid pressure, inclination of vertical borehole. The interesting vertical profiles of ice temperature and borehole diameter were observed. We discuss the characteristics of basal ice and subglacial water.

  16. Temporal changes in methane stable isotopes in polar ice cores: big picture and implications for ecosystem changes

    NASA Astrophysics Data System (ADS)

    Bock, Michael; Schmitt, Jochen; Seth, Barbara; Beck, Jonas; Fischer, Hubertus

    2014-05-01

    Methane (CH4) is the third most important greenhouse gas after water vapour and carbon dioxide (CO2). Since the industrial revolution the mixing ratio of CH4 in the atmosphere rose to ~1800 ppb, a value never reached within the last 800 000 years. Nowadays, CH4 contributes ~20% to the total radiative forcing from all of the long-lived greenhouse gases. This CH4 increase can only be assessed in relation to natural methane changes in the past. Firn air and air enclosures in polar ice cores represent the only direct paleoatmospheric archive. The latter show that atmospheric CH4 concentrations changed in concert with northern hemisphere temperature during both glacial/interglacial transitions as well as rapid climate changes (Dansgaard-Oeschger events), however, the sources of the methane concentration changes are still a matter of debate. Stable isotopes of methane (?13CH4 and ?D(CH4)) may help to distinguish differences in the magnitude of source type emissions (e.g. Bock et al. 2010). However, recently we could show that it is difficult to interpret the atmospheric loading of methane by relative source mix changes alone (Möller et al. 2013). In fact it appears, that the carbon isotopic signature (?13CH4) of e.g. tropical wetlands undergoes drastic shifts connected to climate, CO2, sea level or potentially other unknown processes. Here we present the big picture derived from the EDML (European Project for Ice Coring in Antarctica, Dronning Maud Land) and Vostok ice cores (Möller et al. 2013) and additional new dual isotope data from 4 ice cores from both poles that cover three interglacials: the Holocene, MIS 5 and MIS 11. The contribution sheds light on our current understanding of methane biogeochemistry and discusses open questions. References: Bock, M., J. Schmitt, L. Möller, R. Spahni, T. Blunier, H. Fischer (2010). 'Hydrogen Isotopes Preclude Marine Hydrate CH4 Emissions at the Onset of Dansgaard-Oeschger Events', Science, 328, 1686-1689 Möller, L., T. Sowers, M. Bock, R. Spahni, M. Behrens, J. Schmitt, H. Miller and H. Fischer (2013). "Independent variations of CH4 emissions and isotopic composition over the past 160,000 years" Nature Geoscience, 10.1038/ngeo1922. Bock, M., J. Schmitt, J. Beck, R. Schneider, H. Fischer (2013). "Improving accuracy and precision of ice core ?D(CH4) analyses using methane pre- and hydrogen post-pyrolysis trapping and subsequent chromatographic separation', Atmos. Meas. Tech. Discuss., 6, 11279-11307, doi:10.5194/amtd-6-11279-2013, 2013. Schmitt J., B. Seth, M. Bock and H. Fischer (2014). "Online technique for isotope and mixing ratios of CH4, N2O, Xe and mixing ratios of organic trace gases on a single ice core sample', submitted to Atmos. Meas. Tech. Discuss.

  17. Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core

    E-print Network

    Tison, J. L.; de Angelis, M.; Littot, G.; Wolff, E.; Hansson, M.; Bigler, M.; Udisti, R.; Wegner, A.; Jouzel, J.; Stenni, B.; Johnsen, S.; Masson-Delmotte, V.; Landis, A.; Lipenkov, V.; Loulergue, L.; Barnola, J. M.; Petit, J. R.; Delmonte, B.; Dreyfus, G.; Dahl-Jensen, D.; Durand, G.; Bereiter, B.; Schilt, A.; Spahni, R.; Pol, K.; Lorrain, R.; Souchez, R.; Samyn, D.

    2015-08-20

    sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved...

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

    PubMed

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

    2015-11-17

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

  19. Rapid measurement of perchlorate in polar ice cores down to sub-ng L(-1) levels without pre-concentration.

    PubMed

    Peterson, Kari; Cole-Dai, Jihong; Brandis, Derek; Cox, Thomas; Splett, Scott

    2015-10-01

    An ion chromatography-electrospray ionization-tandem mass spectrometry (IC-ESI-MS/MS) method has been developed for rapid and accurate measurement of perchlorate in polar snow and ice core samples in which perchlorate concentrations are expected to be as low as 0.1 ng L(-1). Separation of perchlorate from major inorganic species in snow is achieved with an ion chromatography system interfaced to an AB SCIEX triple quadrupole mass spectrometer operating in multiple reaction monitoring mode. Under optimized conditions, the limit of detection and lower limit of quantification without pre-concentration have been determined to be 0.1 and 0.3 ng L(-1), respectively, with a linear dynamic range of 0.3-10.0 ng L(-1) in routine measurement. These represent improvements over previously reported methods using similar analytical techniques. The improved method allows fast, accurate, and reproducible perchlorate quantification down to the sub-ng L(-1) level and will facilitate perchlorate measurement in the study of natural perchlorate production with polar ice cores in which perchlorate concentrations are anticipated to vary in the low and sub-ng L(-1) range. Initial measurements of perchlorate in ice core samples from central Greenland show that typical perchlorate concentrations in snow dated prior to the Industrial Revolution are about 0.8 ng L(-1), while perchlorate concentrations are significantly higher in recent (post-1980) snow, suggesting that anthropogenic sources are a significant contributor to perchlorate in the current environment. PMID:26297465

  20. Dust optical properties in antarctic ice cores: application of the Single Particle Extinction and Scattering (SPES) method

    NASA Astrophysics Data System (ADS)

    Potenza, Marco; Villa, Stefano; Sanvito, Tiziano; Albani, Samuel; Delmonte, Barbara; Maggi, Valter

    2015-04-01

    From the point of view of light scattering each particle is characterized by several parameters, the size being by far the most important in determining the amount of radiated power. Nevertheless, composition, internal structure, shape do slightly affect the way light is scattered, and in turn also prevent the possibility to extract the correct size. Recovering the whole information is of paramount difficulty, if not impossibile for single particles. A trade off can be obtained by introducing the optical thickness, i.e. the product of the size and the refractive index, which determines the optical properties. Here we focus at studying the optical thickness of dust particles from the EPICA Dome C ice core. We provide for the first time a direct measurement of dust optical parameters that is the most direct information needed by climate models, and highlight important differences among samples. The SPES method is named after its capability to access both the extinction cross section and the forward scattered field amplitude for each particle. This method is well working with extremely dilute suspensions, such as Antarctic ice core samples. The SPES method is based upon combined and simultaneous measurements of the power reduction of a laser beam in presence of the particle (extinction by definition) and the interference between the intense transmitted beam and the much fainter forward scattered wave (scattering). In such a way it is possible to access both the amplitude and phase of the scattered wave, which means both the real and imaginary parts of the complex field amplitude. This makes the difference with traditional approaches. We show some preliminary results from glacial and interglacial samples from the EPICA ice core and suggest a method to extract information which is important for the light scattering properties of the ensemble of dust particles contained in each sample.

  1. Changes in atmospheric chemical composition determined from ice core records in southwestern Siberia during the twentieth century

    NASA Astrophysics Data System (ADS)

    Joswiak, Daniel R.

    The presented research includes analysis and interpretation of the upper 50 m of a deep ice core which was drilled at 49°48'22"N, 86°33'52" (4115 m.a.s.l.) on the Belukha Plateau, Altai, in southwestern Siberia. The main goal was to examine variability of geochemical records preserved in the ice in relation to climatic and environmental changes; and to determine the main aerosol sources using ground- and upper-level meteorological data. Ion chromatography was used to determine concentrations of anions (SO4, NO3, NO2, Cl), cations (NH4, Ca, K, Mg, Na), the carboxylic (organic) acids acetate (CH3COOH), formate (HCOOH), oxalate (C2O4), and methanesulfonic acid (CH3SO 3H). Major ion concentrations were dominated by sulfate (30.3%), nitrate (18.1%), formate (15.0%), and ammonium (12.4%). Highest concentrations were observed for sulfate; over 1460 ppb. Laser particle counting was used to determine size resolved number concentrations of particles ranging from 0.5 to 16.0 mum. Logarithmic distribution of particles was observed, with over 90% of the particle number concentration coming from particles less than 1.4 mum. Particle mass, calculated from the number concentration, revealed the greatest contribution (59%) to mass arrived with medium size particles (4.0-8.0 microm). Back-trajectories were modeled using NOAA's Hyplit model were modeled for the four days of maximum annual precipitation during a year of increased (1991) and decreased (1990) ion and particle concentrations. Principle components factor analysis was used to determine the main aerosol sources. The upper 50 m covers the time period from 1917 to 2002. Glacier flow models indicated the full depth of 170 m should provide over 1000 years of records. Insoluble particle concentrations preserved in the ice core were affected mainly by climatic conditions including precipitation regimes and wind speed variability. The small size particles (0.5-1.0 mm) are transported inter-continentally and associated with background atmospheric concentrations in the middle-troposphere. The large size particles (4.0-16.0 mum) are deposited from the atmosphere rapidly compared to small particles and were transported to high elevations from the central Asian desert sources. All size particles were found to be negatively correlated with average monthly temperatures indicating low temperatures during the dry particle deposition. During the first half of the 20th Century, soluble ions were dominated by organic acids; indicating mainly natural sources from vegetation and biomass burning. Ion profiles associated with human activities such as fuel combustion (SO4, NO3) significantly increased in concentration from the mid-1950s; coinciding with population growth in large industrialized cities upwind from the study location. Highest correlations between major ions and the ground and upper level wind speed were observed for SO4, indicating long-range transport of pollution to the Altai Mountains. Ion profiles associated with central Asian dust (Ca, Mg) and with sea salt aerosols (Na, Cl) were mainly influenced by climatic factors, and average concentrations did not significantly change during the 20th Century. Factor analysis revealed that ions typically associated with biomass burning (NH4, K) were not resolvable as indicators of separate aerosol source. The organic acid components better preserve forest fire signatures at this study location. The back-trajectories exhibited several notable differences in transport paths of air masses. The trajectories modeled for 1991 show a farther transport distance with significant time of transfer over heavily populated regions of Europe and Russia. The modeled back-trajectories over the Middle-East on two heaviest precipitation days in 1991 provided evidence of the large oil fires in Kuwait, appeared as increased concentrations in sulfate, nitrate, and organic acids. The modeled back-trajectories for 1990 show more localized transport paths or transport over sparsely populated Arctic and Polar Regions. Correlations were not found between the ic

  2. Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

    NASA Astrophysics Data System (ADS)

    Graham, Alastair G. C.; Larter, Robert D.; Gohl, Karsten; Hillenbrand, Claus-Dieter; Smith, James A.; Kuhn, Gerhard

    2009-12-01

    The presence of a complex bedform arrangement on the sea floor of the continental shelf in the western Amundsen Sea Embayment, West Antarctica, indicates a multi-temporal record of flow related to the activity of one or more ice streams in the past. Mapping and division of the bedforms into distinct landform assemblages reveals their time-transgressive history, which implies that bedforms can neither be considered part of a single downflow continuum nor a direct proxy for palaeo-ice velocity, as suggested previously. A main control on the bedform imprint is the geology of the shelf, which is divided broadly between rough bedrock on the inner shelf, and smooth, dipping sedimentary strata on the middle to outer shelf. Inner shelf bedform variability is well preserved, revealing information about local, complex basal ice conditions, meltwater flow, and ice dynamics over time. These details, which are not apparent at the scale of regional morphological studies, indicate that past ice streams flowed across the entire shelf at times, and often had onset zones that lay within the interior of the Antarctic Ice Sheet today. In contrast, highly elongated subglacial bedforms on sedimentary strata of the middle to outer shelf represent a timeslice snapshot of the last activity of ice stream flow, and may be a truer representation of fast palaeo-ice flow in these locations. A revised model for ice streams on the shelf captures complicated multi-temporal bedform patterns associated with an Antarctic palaeo-ice stream for the first time, and confirms a strong substrate control on a major ice stream system that drained the West Antarctic Ice Sheet during the Late Quaternary.

  3. High-Resolution Dust record of last glacial period (MIS 4 to MIS 2) from Talos Dome Ice Core

    NASA Astrophysics Data System (ADS)

    Mazzola, Claudia; Maggi, Valter; Delmonte, Barbara; Marino, Federica; Albani, Samuel

    2010-05-01

    Mineral dust trapped in Antarctic ice cores plays an important role in the study of past climate and atmospheric circulation variability in the Southern Hemisphere. In this work we investigate the Talos Dome (Northern Victoria Land, East Antarctica) ice core dust concentration record through a Laser Sensor (LS) technique. Analyses were performed in continuous as a part of the Continuous Flow Analysis (CFA) system, and discontinuously with Beckman Coulter©Counter for comparison and LS calibration. The LS device provided two basic outputs: (1) "bag" (1 m long sections) mean values and (2) high resolution (1 cm resolution) data. Both signals were processed in the contest of this work and two dust records, respectively at low and high resolution, were produced. Here we report the bag mean dust record from the end of the last deglaciation (about 12,000 years B.P.) to Marine Isotopic Stage 4 (MIS 4, 70,000 years BP). The comparison of the TALDICE LS and EPICA-Dome C dust record provides interesting information about climatic conditions of South Pacific-Ross Sea sector of Antarctica, and atmospheric circulation patterns during last glacial period, with a good agreement between MIS 3 and Last Glacial Maximum (LGM), where several millennial and plurimillennial scale climatic oscillation are observed. For these reasons it is possible suppose that dust transport mechanisms towards TD and DC were the same during the last glacial period. However, MIS 4 in TD ice core was lower, both in concentration and flux, compared to EDC. Likely, during LGM, very cool air masses extended above the Antarctic plateau, even in TD area, have created a subsidence condition which haven't allowed the cyclonic perturbation to penetrate the interior of Antarctica continent. In fact, the Polar Front has moved towards lower latitude in that period, maintaining far away the disturbances. These preliminary observations suggest that the coupling between inner sites such as EDC and the Talos Dome peripheral site becomes progressively stronger from early pleniglacial conditions (MIS 4) to late pleniglacial conditions (late MIS 3, MIS 2). The work was carried out in Alfred Wegner Institute for Polar and Marine Research (AWI - Bremerhaven, Germany) in the contest of a collaboration between Germany, Switzerland and Italian groups. This work is part of the TALDICE (TALos Dome ICE core) project, leaded by Italy, that involved also Germany, France, Switzerland and UK.

  4. Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

    NASA Astrophysics Data System (ADS)

    Fujita, S.; Parrenin, F.; Severi, M.; Motoyama, H.; Wolff, E. W.

    2015-10-01

    Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d-6. Therefore, we hypothesize that the causes of the DFO2006-AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d-6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, ?Dice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, -230 years (minimum) at MIS 7a and +60 to +126 years on average.

  5. GeV neutrinos from collisional heating in GRBs: Detection prospects with IceCube-DeepCore

    SciTech Connect

    Bartos, Imre

    2014-11-18

    The observed gamma-ray burst (GRB) emission may be due to jet reheating via nuclear collisions. The role of this collisional heating can be probed through the observation of 10–100 GeV neutrinos, which are generated in nuclear collisions along with gamma rays. Neutrino and gamma-ray luminosities are closely related, which further aids observations. If the main mechanism behind the production of GRBs is collisional heating then IceCube-DeepCore could detect the GeV-neutrino emission of GRBs with a few years of observation.

  6. An assessment of Southern Ocean water masses and sea ice during 1988-2007 in a suite of interannual CORE-II simulations

    NASA Astrophysics Data System (ADS)

    Downes, Stephanie M.; Farneti, Riccardo; Uotila, Petteri; Griffies, Stephen M.; Marsland, Simon J.; Bailey, David; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Böning, Claus; Bozec, Alexandra; Canuto, Vittorio M.; Chassignet, Eric; Danabasoglu, Gokhan; Danilov, Sergey; Diansky, Nikolay; Drange, Helge; Fogli, Pier Giuseppe; Gusev, Anatoly; Howard, Armando; Ilicak, Mehmet; Jung, Thomas; Kelley, Maxwell; Large, William G.; Leboissetier, Anthony; Long, Matthew; Lu, Jianhua; Masina, Simona; Mishra, Akhilesh; Navarra, Antonio; George Nurser, A. J.; Patara, Lavinia; Samuels, Bonita L.; Sidorenko, Dmitry; Spence, Paul; Tsujino, Hiroyuki; Wang, Qiang; Yeager, Stephen G.

    2015-10-01

    We characterise the representation of the Southern Ocean water mass structure and sea ice within a suite of 15 global ocean-ice models run with the Coordinated Ocean-ice Reference Experiment Phase II (CORE-II) protocol. The main focus is the representation of the present (1988-2007) mode and intermediate waters, thus framing an analysis of winter and summer mixed layer depths; temperature, salinity, and potential vorticity structure; and temporal variability of sea ice distributions. We also consider the interannual variability over the same 20 year period. Comparisons are made between models as well as to observation-based analyses where available. The CORE-II models exhibit several biases relative to Southern Ocean observations, including an underestimation of the model mean mixed layer depths of mode and intermediate water masses in March (associated with greater ocean surface heat gain), and an overestimation in September (associated with greater high latitude ocean heat loss and a more northward winter sea-ice extent). In addition, the models have cold and fresh/warm and salty water column biases centred near 50°S. Over the 1988-2007 period, the CORE-II models consistently simulate spatially variable trends in sea-ice concentration, surface freshwater fluxes, mixed layer depths, and 200-700 m ocean heat content. In particular, sea-ice coverage around most of the Antarctic continental shelf is reduced, leading to a cooling and freshening of the near surface waters. The shoaling of the mixed layer is associated with increased surface buoyancy gain, except in the Pacific where sea ice is also influential. The models are in disagreement, despite the common CORE-II atmospheric state, in their spatial pattern of the 20-year trends in the mixed layer depth and sea-ice.

  7. An Assessment of Southern Ocean Water Masses and Sea Ice During 1988-2007 in a Suite of Interannual CORE-II Simulations

    NASA Technical Reports Server (NTRS)

    Downes, Stephanie M.; Farneti, Riccardo; Uotila, Petteri; Griffies, Stephen M.; Marsland, Simon J.; Bailey, David; Behrens, Erik; Bentsen, Mats; Bi, Daohua; Biastoch, Arne; Canuto, Vittorio M.; Howard, Armando; Kelley, Maxwell; Leboissetier, Anthony

    2015-01-01

    We characterise the representation of the Southern Ocean water mass structure and sea ice within a suite of 15 global ocean-ice models run with the Coordinated Ocean-ice Reference Experiment Phase II (CORE-II) protocol. The main focus is the representation of the present (1988-2007) mode and intermediate waters, thus framing an analysis of winter and summer mixed layer depths; temperature, salinity, and potential vorticity structure; and temporal variability of sea ice distributions. We also consider the interannual variability over the same 20 year period. Comparisons are made between models as well as to observation-based analyses where available. The CORE-II models exhibit several biases relative to Southern Ocean observations, including an underestimation of the model mean mixed layer depths of mode and intermediate water masses in March (associated with greater ocean surface heat gain), and an overestimation in September (associated with greater high latitude ocean heat loss and a more northward winter sea-ice extent). In addition, the models have cold and fresh/warm and salty water column biases centred near 50 deg S. Over the 1988-2007 period, the CORE-II models consistently simulate spatially variable trends in sea-ice concentration, surface freshwater fluxes, mixed layer depths, and 200-700 m ocean heat content. In particular, sea-ice coverage around most of the Antarctic continental shelf is reduced, leading to a cooling and freshening of the near surface waters. The shoaling of the mixed layer is associated with increased surface buoyancy gain, except in the Pacific where sea ice is also influential. The models are in disagreement, despite the common CORE-II atmospheric state, in their spatial pattern of the 20-year trends in the mixed layer depth and sea-ice.

  8. Ice core sulfur and methanesulfonic acid (MSA) records from southern Greenland document North American and European air pollution and suggest a decline in regional biogenic sulfur emissions.

    NASA Astrophysics Data System (ADS)

    Pasteris, D. R.; McConnell, J. R.; Burkhart, J. F.; Saltzman, E. S.

    2014-12-01

    Sulfate aerosols have an important cooling effect on the Earth because they scatter sunlight back to space and form cloud condensation nuclei. However, understanding of the atmospheric sulfur cycle is incomplete, leading to uncertainty in the assessment of past, present and future climate forcing. Here we use annually resolved observations of sulfur and methanesulfonic acid (MSA) concentration in an array of precisely dated Southern Greenland ice cores to assess the history of sulfur pollution emitted from North America and Europe and the history of biogenic sulfate aerosol derived from the North Atlantic Ocean over the last 250 years. The ice core sulfur time series is found to closely track sulfur concentrations in North American and European precipitation since records began in 1965, and also closely tracks estimated sulfur emissions since 1850 within the air mass source region as determined by back trajectory analysis. However, a decline to near-preindustrial sulfur concentrations in the ice cores after 1995 that is not so extensive in the source region emissions indicates that there has been a change in sulfur cycling over the last 150 years. The ice core MSA time series shows a decline of 60% since the 1860s, and is well correlated with declining sea ice concentrations around Greenland, suggesting that the phytoplankton source of biogenic sulfur has declined due to a loss of marginal sea ice zone habitat. Incorporating the implied decrease in biogenic sulfur in our analysis improves the match between the ice core sulfur record and the source region emissions throughout the last 150 years, and solves the problem of the recent return to near-preindustrial levels in the Greenland ice. These findings indicate that the transport efficiency of sulfur air pollution has been relatively stable through the industrial era and that biogenic sulfur emissions in the region have declined.

  9. The multiproxy analysis of a lacustrine-palustrine sediment core from Lebanon reveals four climate cycles

    NASA Astrophysics Data System (ADS)

    Gasse, F. A.; van Campo, E.; Demory, F.; Develle, A.; Tachikawa, K.; Buchet, N.; Sonzogni, C.; Thouveny, N.; Bard, E. G.; Vidal, L.

    2013-12-01

    The study of a sediment core retrieved from the small Yammouneh basin (34.06°N-34.09°N, 36.0°E-36.03°E, 1360 m a.s.l.), Lebanon, provides for the first time a nearly continuous record spanning approximately 360 ka in northern Levant. The basin, located on the eastern flank of Mount Lebanon, is mainly supplied by karstic springs which discharge snowmelt water infiltrated through the western highlands. Part of its water inputs is lost by seepage through its faulted bottom. The core, 73 m long, consists of four whitish carbonated intervals rich in lacustrine organism remains, interrupting a thick accumulation of colored silty clays almost devoid of shells but for ostracods. We analyzed sediment features (mineralogical and elemental composition, light microscopy and SEM observations, grain size), magnetic properties, pollen and calcite oxygen isotopes (?c) derived from ostracod shell composition. The chronological framework is based on 14C ages of wood fragments, U/Th dating, and a high resolution reconstruction of relative paleointensity variations correlated with regional (Portuguese margin) and global (Sint-800) master curves down to about 360 ka. Although the chronology still needs improvement, the 3 upper carbonated intervals undoubtedly fit Interglacials MIS 1, MIS 5.5 and MIS 7, respectively. The deepest one (49-60 m) is assigned to MIS 9 by its proxy analogies with dated Interglacials. The sequence covers a large part of MIS 10. Relationships between individual indicators are explored, in addition to visual comparisons of individual records, from the multiproxy matrix after resampling at a common depth scale of 25 cm. We compute simple linear coefficients between 20 variables, perform Principal Component Analyses based on all variables, on terrestrial pollen biomes, on all sedimentological proxies, and cross-correlations between them and ?c. During Interglacial maxima, high local and regional efficient moisture is evidenced by dense arboreal vegetation of varied types, lacustrine organism rests, and in situ carbonate sedimentation. During glacial phases, variable aridity conditions (MIS 6 was relatively humid) are inferred from open steppic landscapes favoring physical erosion, and sedimentation of eolian and local detrital material. Water was possibly stored as ice on Mount Lebanon and in frozen soils during the coldest periods. The ?c signal is complex but is reconciled with other proxies when corrected for the 'temperature effect' and the 'source effect' (isotopic composition of the eastern Mediterranean Sea), and when considering interglacial enhanced seasonality. Our record appears in line with paleoclimate records from the northeastern Mediterranean area, while the Dead Sea basin, in the rain shadow of the Judean mountains, behaved the opposite way. Variable influence of air masses from western, northern and tropical origin is discussed.

  10. A model for large glacial-interglacial climate-induced changes in dust and sea salt concentrations in deep ice cores (central Antarctica): palaeoclimatic implications and prospects for refining ice core chronologies

    NASA Astrophysics Data System (ADS)

    Petit, J. R.; Delmonte, B.

    2009-11-01

    A semi-empirical model has been developed to reproduce glacial-interglacial changes of continental dust and marine sodium concentrations (factor of ~50 and ~5, respectively) observed in inland Antarctic ice cores. The model uses conceptual pathways of aerosols within the high troposphere; assumes the dry deposition of impurities on the Antarctic surface; uses estimates of aerosol transit times taken independent of climate; assumes a temperature-dependent removal process during aerosol pathways from the mid-latitudes. The model is fitted to the data over the last four climate cycles from Vostok and EPICA Dome C Antarctic sites. As temperature is cooling, the aerosol response suggests different modes of climate couplings between latitudes, which can be continuous or below temperature thresholds for sodium and dust, respectively. The model estimates a southern South America dust source activity two to three times higher for glacial periods than for the Holocene and a glacial temperature over the Southern Ocean 3-5 °C cooler. Both estimates appear consistent with independent observations. After removal of temperature effects, dust and sodium residuals for both sites show orbital frequencies in opposite phase at the precession timescale. Such long-term insolation-related modulation of terrestrial and marine aerosol input, could provide a chemical pacemaker useful for refining ice core chronologies.

  11. Period spacings in red giants. I. Disentangling rotation and revealing core structure discontinuities

    NASA Astrophysics Data System (ADS)

    Mosser, B.; Vrard, M.; Belkacem, K.; Deheuvels, S.; Goupil, M. J.

    2015-12-01

    Context. Asteroseismology allows us to probe the physical conditions inside the core of red giant stars. This process relies on the properties of the global oscillations with a mixed character that are highly sensitive to the physical properties of the core. However, overlapping rotational splittings and mixed-mode spacings result in complex structures in the mixed-mode pattern, which severely complicates its identification and the measurement of the asymptotic period spacing. Aims: This work aims at disentangling the rotational splittings from the mixed-mode spacings in order to open the way to a fully automated analysis of large data sets. Methods: An analytical development of the mixed-mode asymptotic expansion is used to derive the period spacing between two consecutive mixed modes. The échelle diagrams constructed with the appropriately stretched periods are used to exhibit the structure of the gravity modes and of the rotational splittings. Results: We propose a new view of the mixed-mode oscillation pattern based on corrected periods, called stretched periods, that mimic the evenly spaced gravity-mode pattern. This provides a direct understanding of all oscillation components, even in the case of rapid rotation. In this way, the measurement of the asymptotic period spacing and the signature of the structural glitches on mixed modes can be performed easily. Conclusions: This work makes it possible to derive all seismic global parameters in an automated way, including the identification of the different rotational multiplets and the measurement of the rotational splitting, even when this splitting is significantly larger than the period spacing. Revealing buoyancy glitches provides a detailed view of the radiative core.

  12. HST Images Reveal Dramatic Changes in the Core of IRC+10216

    NASA Astrophysics Data System (ADS)

    Kim, Hyosun; Lee, Ho-Gyu; Mauron, Nicolas; Chu, You-Hua

    2015-05-01

    IRC+10216 is the nearest carbon star with a very high mass-loss rate. The existence of a binary companion has been hinted at by indirect observational evidence, such as the bipolar morphology of its nebula and a spiral-like pattern in its circumstellar material; however, to date, no companion has been identified. We have examined archival Hubble Space Telescope images of IRC+10216, and find that the images taken in 2011 exhibit dramatic changes in its innermost region from those taken at earlier epochs. The scattered light is more spread out in 2011. After proper motion correction, the brightest peak in 2011 is close to, but not coincident with, the dominant peak in previous epochs. A fainter point-like object was revealed at ?0.?5 from this brightest peak. We suggest that these changes at the core of IRC+10216 are caused by dissipation of intervening circumstellar dust, as indicated by the brightening trend in the light curve extracted from the Catalina photometric survey. We tentatively identify the brightest peak in 2011 as the primary star of IRC+10216 and the fainter point-like source as a companion. The cause of non-detections of the companion candidate in earlier epochs is uncertain. These identifications need to be verified by monitoring the core of IRC+10216 at high resolution in the future.

  13. Rich club analysis in the Alzheimer's disease connectome reveals a relatively undisturbed structural core network.

    PubMed

    Daianu, Madelaine; Jahanshad, Neda; Nir, Talia M; Jack, Clifford R; Weiner, Michael W; Bernstein, Matt A; Thompson, Paul M

    2015-08-01

    Diffusion imaging can assess the white matter connections within the brain, revealing how neural pathways break down in Alzheimer's disease (AD). We analyzed 3-Tesla whole-brain diffusion-weighted images from 202 participants scanned by the Alzheimer's Disease Neuroimaging Initiative-50 healthy controls, 110 with mild cognitive impairment (MCI) and 42 AD patients. From whole-brain tractography, we reconstructed structural brain connectivity networks to map connections between cortical regions. We tested whether AD disrupts the "rich club" - a network property where high-degree network nodes are more interconnected than expected by chance. We calculated the rich club properties at a range of degree thresholds, as well as other network topology measures including global degree, clustering coefficient, path length, and efficiency. Network disruptions predominated in the low-degree regions of the connectome in patients, relative to controls. The other metrics also showed alterations, suggesting a distinctive pattern of disruption in AD, less pronounced in MCI, targeting global brain connectivity, and focusing on more remotely connected nodes rather than the central core of the network. AD involves severely reduced structural connectivity; our step-wise rich club coefficients analyze points to disruptions predominantly in the peripheral network components; other modalities of data are needed to know if this indicates impaired communication among non rich club regions. The highly connected core was relatively preserved, offering new evidence on the neural basis of progressive risk for cognitive decline. PMID:26037224

  14. Sgr B2(N): A Bipolar Outflow and Rotating Hot Core Revealed by ALMA

    NASA Astrophysics Data System (ADS)

    Higuchi, Aya E.; Hasegawa, Tetsuo; Saigo, Kazuya; Sanhueza, Patricio; Chibueze, James O.

    2015-12-01

    We present the results of SiO (2 ? 1) and SO2 ({12}{4,8}{--}{13}{3,11}) line observations of Sgr B2(N) made with the Atacama Large Millimeter/submillimeter Array at an angular resolution of ?2?. Our analysis of the SiO and SO2 line emission reveals a bipolar molecular outflow in an east–west direction whose driving source is located at K2. In addition, the SO2 line core shows a north–south velocity gradient most probably indicating a hot core of molecular gas rotating around K2. Fractional abundances of SO2 and SiO (X(SO2) and X(SiO), respectively) in the outflowing molecular gas are derived from comparisons with the C18O emission. Assuming an excitation temperature of 100 ± 50 K, we calculate X(SO2) = {2.3}-0.4+2.6 × 10?8 and X(SiO) = {1.2}-0.1+0.1 × 10?9. The outflow from Sgr B2(N) K2 is characterized as a young (5 × 103 yr) and massive (?2000 {M}? ) but moderately collimated (?60°) outflow. We also report a possible detection of the SiO (v=2,J=2{--}1) maser emission from the position of K2. If confirmed, it would make Sgr B2(N) the fourth star-forming region associated with SiO masers.

  15. Modeling historical long-term trends of sulfate, ammonium, and elemental carbon over Europe: A comparison with ice core records in the Alps

    NASA Astrophysics Data System (ADS)

    Fagerli, Hilde; Legrand, Michel; Preunkert, Susanne; Vestreng, Vigdis; Simpson, David; Cerqueira, Mario

    2007-12-01

    The regional EMEP chemical transport model has been run for the 1920-2003 period and the simulations compared to the long-term seasonally resolved trends of major inorganic aerosols (sulfate and ammonium) derived from ice cores extracted at Col du Dôme (CDD, 4250 m above sea level, French Alps). Source-receptor calculations have been performed in order to allocate the sources of air pollution arriving over the Alps. Spain, Italy, France, and Germany are found to be the main contributors at CDD in summer, accounting for 50% of sulfate and 75% of ammonium. In winter more European wide and trans-Atlantic contributions are found. The relative impact of these sources remains similar over the whole Alpine massif although transport from US and emissions from Spain contribute less as we move eastward from CDD, toward other alpine ice core drill sites like Colle Gnifetti (CG) in the Swiss Alps. For sulfate, the CDD ice core records and the simulated trends match very well. For ammonium, the trend simulated by the model and the summer ice core record are in reasonable agreement, both showing greater changes in ammonium concentrations than would be suggested by historical ammonia emissions. Motivated by a such good agreement between simulations of past atmospheric concentrations and ice core records for inorganic aerosol species, we also use the model to simulate trends in elemental carbon for which less information on past emission inventories are available.

  16. Two Extreme Climate Events of the Last 1000 Years Recorded in Himalayan and Andean Ice Cores: Impacts on Humans

    NASA Astrophysics Data System (ADS)

    Thompson, L. G.; Mosley-Thompson, E. S.; Davis, M. E.; Kenny, D. V.; Lin, P.

    2013-12-01

    In the last few decades numerous studies have linked pandemic influenza, cholera, malaria, and viral pneumonia, as well as droughts, famines and global crises, to the El Niño-Southern Oscillation (ENSO). Two annually resolved ice core records, one from Dasuopu Glacier in the Himalaya and one from the Quelccaya Ice Cap in the tropical Peruvian Andes provide an opportunity to investigate these relationships on opposite sides of the Pacific Basin for the last 1000 years. The Dasuopu record provides an annual history from 1440 to 1997 CE and a decadally resolved record from 1000 to 1440 CE while the Quelccaya ice core provides annual resolution over the last 1000 years. Major ENSO events are often recorded in the oxygen isotope, insoluble dust, and chemical records from these cores. Here we investigate outbreaks of diseases, famines and global crises during two of the largest events recorded in the chemistry of these cores, particularly large peaks in the concentrations of chloride (Cl-) and fluoride (Fl-). One event is centered on 1789 to 1800 CE and the second begins abruptly in 1345 and tapers off after 1360 CE. These Cl- and F- peaks represent major droughts and reflect the abundance of continental atmospheric dust, derived in part from dried lake beds in drought stricken regions upwind of the core sites. For Dasuopu the likely sources are in India while for Quelccaya the sources would be the Andean Altiplano. Both regions are subject to drought conditions during the El Niño phase of the ENSO cycle. These two events persist longer (10 to 15 years) than today's typical ENSO events in the Pacific Ocean Basin. The 1789 to 1800 CE event was associated with a very strong El Niño event and was coincidental with the Boji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive droughts are documented in Central and South America. Likewise, the 1345 to 1360 CE event, although poorly documented historically in South America, is concomitant with major droughts in India, the collapse of the Yang Dynasty and the Black Death that eliminated roughly one third of the global population. Understanding the characteristics and drivers of these 'natural' events is critical to design adaptive measures for a world with over seven billion people and a climate system now influenced by human activities.

  17. Deformation and folds of the basal ice under the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, D.; Gogineni, P.; Paden, J.; Leuschen, C.; Kipfstuhl, S.; Montagnat, M.; Waddington, E.

    2012-04-01

    Improvement of the depth sounding radio echo sounding over Greenland Ice Sheet has made it possible to map the near basal layers that have not been 'seen' earlier due to the very high demand of attenuation needed to reach through more than 3000m of ice. The basal 10% of the ice thickness reveals very disturbed layering in the central and north parts of the Greenland ice sheet. The onset of the disturbances very often seem to coincide with the ice from the climatic inception from the Eemian period to the Last Glacial period around 115.000 years before present. Studies of the ice rheology reveals big changes of ice crystal size and orientation at this boundary caused by big contrast of impurity concentrations in the ice from the warm and cold climatic periods. The warm ice from the Eemian (130.000 years - 115.000 years b2k) seems to behave as a big rather hard layer in the ice with the easier deformable glacial ice above and below. Examples of the ice folds from CReSIS radio echo images especially from the NASA ICEBRIDGE spring 2011 campaign over Greenland is shown together with ice rheology studies from the GRIP, NGRIP and NEEM ice cores.

  18. Geochemical characteristics of insoluble dust as a tracer in an ice core from Miaoergou Glacier, east Tien Shan

    NASA Astrophysics Data System (ADS)

    Du, Zhiheng; Xiao, Cunde; Liu, Yaping; Wu, Guoju

    2015-04-01

    An ice core was extracted from Miaoergou Glacier, east Tien Shan, China. Concentrations of the rare earth elements (REEs) and Sr-Nd isotopic ratios were measured in insoluble dust sampled from the core. The ratios of REEs in insoluble dust were found to have characteristics typical of aeolian deposition, similar to those of sand and loess from Taklamakan. This suggests that the Taklamakan Desert might be an important source of dust reaching the Miaoergou Glacier. Sr (87Sr/86Sr average 0.718014 and range 0.717025 to 0.718958) and Nd (?Nd(0) average - 9.1 and range - 9.5 to - 8.5) isotopic compositions in insoluble dust are similar to those of desert sand from Taklamakan and Gobi, suggesting that the Gobi Desert may be another major aeolian source for Miaoergou Glacier. Our results can be compared with Sr-Nd isotopic ratios from Greenland snow and ice, further demonstrating how the dust from Asian deserts contributes a high proportion of aeolian dust in the Greenland region.

  19. Century-long Record of Black Carbon in an Ice Core from the Eastern Pamirs: Estimated Contributions from Biomass Burning

    SciTech Connect

    Wang, Mo; Xu, B.; Kaspari, Susan D.; Gleixner, Gerd; Schwab, Valerie; Zhao, Huabiao; Wang, Hailong; Yao, Ping

    2015-08-01

    We analyzed refractory black carbon (rBC) in an ice core spanning 1875-2000 AD from Mt. Muztagh Ata, the Eastern Pamirs, using a Single Particle Soot Photometer (SP2). Additionally a pre-existing levoglucosan record from the same ice core was used to differentiate rBC that originated from open fires, energy-related combustion of biomass, and fossil fuel combustion. Mean rBC concentrations increased four-fold since the mid-1970s and reached maximum values at the end of 1980s. The observed decrease of the rBC concentrations during the 1990s was likely driven by the economic recession of former USSR countries in Central Asia. Levoglucosan concentrations showed a similar temporal trend to rBC concentrations, exhibiting a large increase around 1980 AD followed by a decrease in the 1990s that was likely due to a decrease in energy-related biomass combustion. The time evolution of levoglucosan/rBC ratios indicated stronger emissions from open fires during the 1940s-1950s, while the increase in rBC during the 1980s-1990s was caused from an increase in energy-related combustion of biomass and fossil fuels.