WorldWideScience

Sample records for upwelling altered radiocarbon

  1. Estimates of upwelling rates in the Arabian Sea and the equatorial Indian Ocean based on bomb radiocarbon.

    Science.gov (United States)

    Bhushan, R; Dutta, K; Somayajulu, B L K

    2008-10-01

    Radiocarbon measurements were made in the water column of the Arabian Sea and the equatorial Indian Ocean during 1994, 1995 and 1997 to assess the temporal variations in bomb 14C distribution and its inventory in the region with respect to GEOSECS measurements made during 1977-1978. Four GEOSECS stations were reoccupied (three in the Arabian Sea and one in the equatorial Indian Ocean) during this study, with all of them showing increased penetration of bomb 14C along with decrease in its surface water activity. The upwelling rates derived by model simulation of bomb 14C depth profile using the calculated exchange rates ranged from 3 to 9 m a(-1). The western region of the Arabian Sea experiencing high wind-induced upwelling has higher estimated upwelling rates. However, lower upwelling rates obtained for the stations occupied during this study could be due to reduced 14C gradient compared to that during GEOSECS.

  2. Borderline radiocarbon

    NARCIS (Netherlands)

    van der Plicht, J.

    Radiocarbon dating of peat has its intrinsic problems. This is often caused by mobile organic fractions. For the Weichselian Pleniglacial, another methodological problem arises: the limit of the C-14 dating method. This is discussed in terms of bulk (i.e. non-selected material, generally dated

  3. Radiocarbon dating

    International Nuclear Information System (INIS)

    Lazos R, L.

    2005-01-01

    The application of the radiocarbon dating in archaeology has not served only to solve problems related with the establishment of chronologies, but also in the development of archaeological methods of excavation and interpretation. This has been possible because the dating method by radiocarbon provides a common temporary scale that transcends the cultural and regional frontiers. It is even spoken of the revolution that has meant the fact that the application of this method has allowed to the archaeologist to pass from the construction of chronologies until the evaluation and dynamic interpretation of the archaeological data to build theories. This work explains and compares methods for the detection of 14 C, as the gas counting, the liquid scintillation counting and the mass spectrometry with accelerators. (Author)

  4. Transcriptomics reveal transgenerational effects in purple sea urchin embryos: Adult acclimation to upwelling conditions alters the response of their progeny to differential pCO2 levels.

    Science.gov (United States)

    Wong, Juliet M; Johnson, Kevin M; Kelly, Morgan W; Hofmann, Gretchen E

    2018-03-01

    Understanding the mechanisms with which organisms can respond to a rapidly changing ocean is an important research priority in marine sciences, especially in the light of recent predictions regarding the pace of ocean change in the coming decades. Transgenerational effects, in which the experience of the parental generation can shape the phenotype of their offspring, may serve as such a mechanism. In this study, adult purple sea urchins, Strongylocentrotus purpuratus, were conditioned to regionally and ecologically relevant pCO 2 levels and temperatures representative of upwelling (colder temperature and high pCO 2 ) and nonupwelling (average temperature and low pCO 2 ) conditions typical of coastal upwelling regions in the California Current System. Following 4.5 months of conditioning, adults were spawned and offspring were raised under either high or low pCO 2 levels, to examine the role of maternal effects. Using RNA-seq and comparative transcriptomics, our results indicate that differential conditioning of the adults had an effect on the gene expression patterns of the progeny during the gastrula stage of early development. For example, maternal conditioning under upwelling conditions intensified the transcriptomic response of the progeny when they were raised under high versus low pCO 2 conditions. Additionally, mothers that experienced upwelling conditions produced larger progeny. The overall findings of this study are complex, but do suggest that transgenerational plasticity in situ could act as an important mechanism by which populations might keep pace with rapid environmental change. © 2018 John Wiley & Sons Ltd.

  5. Progress in radiocarbon dating

    International Nuclear Information System (INIS)

    Hedges, R.E.M.

    1985-01-01

    The article concerns radiocarbon dating, the most important method for dating in archaeology. The principles and practice of the dating method are described. Recent developments in radiocarbon dating due to technical advances, are discussed, and include radiometric counting of small samples and accelerator mass spectrometry. Carbon isotopes and the environment are also discussed. (U.K.)

  6. History of radiocarbon dating

    Energy Technology Data Exchange (ETDEWEB)

    Libby, W F [Department of Chemistry and Institute of Geophysics, University of California, Los Angeles, CA (United States)

    1967-08-15

    The development is traced of radiocarbon dating from its birth in curiosity regarding the effects of cosmic radiation on Earth. Discussed in historical perspective are: the significance of the initial measurements in determining the course of developments; the advent of the low-level counting technique; attempts to avoid low-level counting by the use of isotopic enrichment; the gradual appearance of the environmental effect due to the combustion of fossil fuel (Suess effect); recognition of the atmosphere ocean barrier for carbon dioxide exchange; detailed understanding of the mixing mechanism from the study of fallout radiocarbon; determination of the new half-life; indexing and the assimilation problem for the massive accumulation of dates; and the proliferation of measurement techniques and the impact of archaeological insight on the validity of radiocarbon dates. (author)

  7. Radiocarbon dates XXI

    International Nuclear Information System (INIS)

    Lowdon, J.A.; Blake, W. Jr.

    1981-01-01

    This list includes 105 radiocarbon age determinations on 104 geological samples made by the Radiocarbon Dating Laboratory. They are on samples from various areas as follows: Labrador Shelf (2); Newfoundland (12); Nova Scotia (2); New Brunswick (1); Quebec (3); Ontario (1); Manitoba (1); Alberta (2); British Columbia (15); Yukon Territory (35); Northwest Territories, Mainland (10); Northwest Territories, Arctic Archipelago (21). Details of background and standard for the 2 L and 5 L counters during the period from November 4, 1980 to October 31, 1981 are summarized in Tables 1 and 2; Table 3 gives the number of counts used to determine the average background and standard counting rates; and Table 4 lists the number of different background and standard gas preparations used for counting

  8. Radiocarbon dating for contributors

    International Nuclear Information System (INIS)

    Jansen, H.S.

    1984-06-01

    This report describes the radiocarbon facility at the Institute of Nuclear Sciences, and is written for potential contributors, current users, and for those who advise others. The report briefly outlines the principles and practices of C-14 dating; with emphasis on factors that enable contributors to judge whether C-14 work is appropriate, and to assist them with the procedures to be followed in order to get the best results. Age determinations, being the main requirements by contributors, have been discussed in detail

  9. Radiocarbon dating of lake sediments

    OpenAIRE

    Pocevičius, Matas

    2016-01-01

    Matas Pocevičius, Radiocarbon dating of lake sediments, bachelor thesis, Vilnius University, Faculty of Physics, Department of General Physics and Spectroscopy, physics, Vilnius, 45 p., 2016. The aim of this study is to evaluate the possibility of radiocarbon dating application for Tapeliai lake bottom sediments. The literature review discusses topics related to accelerator mass spectrometry, principles of radiocarbon formation, importance of nuclear fallout for 14C, possible applications of ...

  10. Bomb pulse radiocarbon dating

    International Nuclear Information System (INIS)

    Tuniz, C.; Zoppi, U.; Hotchkis, M.A.C.

    2004-01-01

    Modern forensic science has to deal not only with homicides and other traditional crimes but also with more global threats such as the smuggling of nuclear materials, clandestine production of weapons of mass destruction, stockpiling of illicit drugs by state controlled groups and war crimes. Forensic applications have always benefited from the use of advanced analytical tools that can characterize materials found at crime scenes. In this paper we will discuss the use of accelerator mass spectrometry (AMS) as an ultrasensitive tool for the crime laboratories of the third millennium. An important objective in forensic science is to order past events chronologically by analysing materials associated with criminal actions. Radiocarbon dating is known to the general public for its application to historical and prehistorical investigations. Examples of forensic significance include the assassination of the Inca Atahualpa by Francisco Pizarro in the early 1530s, the possible murder of the Tyrolean Ice Man (Oetzi) 5300 years ago and the analysis of the burial cloths allegedly associated with the crucifixion of Jesus Christ . Recent murders, including those associated with war crimes in the Balkans during the 1990s, can be studied using 14 C bomb pulse dating. This method has other forensic applications, including investigation of frauds related to food and wine counterfeiting, dating of opium crops and dating of substances used in biological warfare. AMS extends the applicability of the radiocarbon method, allowing the analysis of 14 C in submilligram organic samples. Specific molecular compounds extracted from bones, hair, skin and other carbon bearing substances of forensic significance can now be dated, enhancing the sensitivity and reliability of chronological determinations. AMS can also be used to analyse rare actinide isotopes released into the environment during the clandestine production of nuclear weapons or associated with the smuggling of nuclear materials. In

  11. Under pressure: Climate change, upwelling and eastern boundary upwelling ecosystems

    Directory of Open Access Journals (Sweden)

    Marisol eGarcía-Reyes

    2015-12-01

    Full Text Available The IPCC AR5 provided an overview of the likely effects of climate change on Eastern Boundary Upwelling Systems (EBUS, stimulating increased interest in research examining the issue. We use these recent studies to develop a new synthesis describing climate change impacts on EBUS. We find that model and observational data suggest coastal upwelling-favorable winds in poleward portions of EBUS have intensified and will continue to do so in the future. Although evidence is weak in data that are presently available, future projections show that this pattern might be driven by changes in the positioning of the oceanic high-pressure systems rather than by deepening of the continental low-pressure systems, as previously proposed. There is low confidence regarding the future effects of climate change on coastal temperatures and biogeochemistry due to uncertainty in the countervailing responses to increasing upwelling and coastal warming, the latter of which could increase thermal stratification and render upwelling less effective in lifting nutrient-rich deep waters into the photic zone. Although predictions of ecosystem responses are uncertain, EBUS experience considerable natural variability and may be inherently resilient. However, multi-trophic level, end-to-end (i.e., winds to whales studies are needed to resolve the resilience of EBUS to climate change, especially their response to long-term trends or extremes that exceed pre-industrial ranges.

  12. New biomedical applications of radiocarbon

    International Nuclear Information System (INIS)

    Davis, J.C.

    1990-12-01

    The potential of accelerator mass spectrometry (AMS) and radiocarbon in biomedical applications is being investigated by Lawrence Livermore National Laboratory (LLNL). A measurement of the dose-response curve for DNA damage caused by a carcinogen in mouse liver cells was an initial experiment. This demonstrated the sensitivity and utility of AMS for detecting radiocarbon tags and led to numerous follow-on experiments. The initial experiment and follow-on experiments are discussed in this report. 12 refs., 4 figs. (SM)

  13. How marine upwelling influences the distribution of Artemesia longinaris (Decapoda: Penaeoidea?

    Directory of Open Access Journals (Sweden)

    Gustavo S Sancinetti

    2014-05-01

    Full Text Available Upwelling events can occur in most of the oceans altering the water physical, chemical and sediment conditions and consequently the species communities dwelling the areas. For better understanding the behavior of populations inhabiting upwelling regions, the spatial and temporal distribution of a Penaeoidea shrimp was studied correlating it with the abiotic factors that vary during upwelling and non-upwelling periods in an area under influence of Cabo Frio upwelling. Bottom salinity and temperature, organic matter and sediment type from each station were sampled from March 2008 to February 2010, in six stations located between 5 and 45 m depth. The lowest temperatures were recorded during spring and summer for both years with temperature values lower than 19ºC. A total of 26,466 Artemesia longinaris shrimps were captured mainly in 10-35 m depth. Upwelling periods showed significant differences in abundance in relation to non-upwelling periods. The spatial distribution among stations varied according to the temperature with higher abundance in stations with values between 19 and 21ºC. The highest abundance of A. longinaris was recorded in spring and summer when intrusions of the cold waters of South Atlantic Central Waters (SACW were frequent. Thus, the effect of cold water of SACW boosted by the upwelling was a determinant factor in the spatial and temporal distribution of A. longinaris in the studied region.

  14. Nutrients, Recycling, and Biological Populations in Upwelling Ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T. E.

    1980-01-01

    Nutrient recycling has been studied in the upwelling areas of Baja California, Northwest Africa, and Peru. Regeneration by biological populations in these areas contributes significant quantities of recycled nitrogen which is utilized in productivity processes. Each area has a different combination of organisms which leads to differences in the relative contributions of zooplankton, nekton, or benthos to the nutrient cycles. Comparisons of ammonium regeneration rates of zooplankton and nekton-micronekton populations in the three upwelling areas show that zooplankton recycle relatively less nitrogen in the Baja California and Peru systems than nekton. In the Northwest Africa upwelling region, however, zooplankton, fish, and benthic inputs are all substantial. In recent years the Peruvian upwelling system has been altered with the decline of the anchoveta population and an increase in the importance of zooplankton in nutrient recycling. The distribution of recycled nitrogen (ammonium and urea) in transects across the shelf at 10°S and 15°S indicates that regeneration is relatively more important at 10°S in the region of the wide shelf. In both areas the distribution of ammonium and urea are not entirely coincident thereby indicating differences in their production and/or utilization.

  15. Warm water upwelling in the Cenozoic Era

    Science.gov (United States)

    Zhang, Y.

    2017-12-01

    Modern observations show that the occurrence of wind-driven upwelling is often tied to cold sea surface temperatures (SSTs). However, SST reconstructions indicate that globally, the upwelling regions were much warmer in the Miocene and Pliocene. This questions the overall strength of deep-water upwelling in the geological past, with important implications for the associated atmospheric, climatic and biogeochemical processes, and the fate of upwelling regions in a high-CO2 world. We recently showed that the eastern equatorial Pacific (EEP) was characterized by strong air-sea disequilibrium of CO2 during the late Miocene - Pliocene. Combined with export productivity proxies, we interpreted these as signs of vigorous upwelling. The upwelled waters were nutrient- and CO2-rich, but warm. The cause of the "excess" warming in the upwelling regions is linked to the source waters which originated from the higher latitudes. In other words, the reduced east (upwelling) to west (non-upwelling) temperature gradients along the equator in major ocean basins are rooted in the reduced meridional temperature gradients. To further test this hypothesis, we examine the history of the EEP and temperature gradients during the even-warmer Eocene - middle Miocene.

  16. Radiocarbon dating of iron artefacts

    Energy Technology Data Exchange (ETDEWEB)

    Cresswell, R. [Australian National Univ., Canberra, ACT (Australia). Dept. of Nuclear Physics

    1997-12-31

    Iron artefacts are generally dated by association or on stylistic grounds. This may not give a true indication of the date of manufacture, or may not be possible if the piece is out of context, ambiguous in style, or a copy. Obtaining a direct date on the artefact would be preferable. During the processes of manufacture, carbon is incorporated into the iron from the fuel source. If the fuel is of a material containing contemporaneous carbon, i.e. has an ambient radiocarbon signature, e.g. charcoal, then we may reliably radiocarbon date the artefact by extracting this carbon. Care must be taken, however, to ensure that re-working has not introduced multiple sources of carbon that would give an erroneous date. Detailed chemical analysis must precede radiocarbon analysis. Sample size is determined by carbon content, and before the advent of accelerator mass spectrometry, several tens of grams of carbon were required for radiocarbon dating (van der Merwe, 1969), prohibiting this method except for high-carbon cast-irons and bulk samples, e.g. caches of nails. AMS permits the analysis of sub-gram pieces of iron (Cresswell, 1991), thereby permitting the analysis of museum pieces with only minimal loss of material, and small fragments of iron recovered from archaeological sites. A few examples are given to illustrate these points. Paper no. 41; Extended abstract. 6 refs.

  17. Radiocarbon dating of iron artefacts

    International Nuclear Information System (INIS)

    Cresswell, R.

    1997-01-01

    Iron artefacts are generally dated by association or on stylistic grounds. This may not give a true indication of the date of manufacture, or may not be possible if the piece is out of context, ambiguous in style, or a copy. Obtaining a direct date on the artefact would be preferable. During the processes of manufacture, carbon is incorporated into the iron from the fuel source. If the fuel is of a material containing contemporaneous carbon, i.e. has an ambient radiocarbon signature, e.g. charcoal, then we may reliably radiocarbon date the artefact by extracting this carbon. Care must be taken, however, to ensure that re-working has not introduced multiple sources of carbon that would give an erroneous date. Detailed chemical analysis must precede radiocarbon analysis. Sample size is determined by carbon content, and before the advent of accelerator mass spectrometry, several tens of grams of carbon were required for radiocarbon dating (van der Merwe, 1969), prohibiting this method except for high-carbon cast-irons and bulk samples, e.g. caches of nails. AMS permits the analysis of sub-gram pieces of iron (Cresswell, 1991), thereby permitting the analysis of museum pieces with only minimal loss of material, and small fragments of iron recovered from archaeological sites. A few examples are given to illustrate these points

  18. Radiocarbon dating of lowbog peat

    International Nuclear Information System (INIS)

    Trettin, R.; Hiller, A.; Mundel, G.

    1982-01-01

    Owing to complex formation conditions, the age determination of lowbog peat is generally considered difficult. Within the framework of peat profile investigations of the Havellaendisches Luch, factors that may exercise an influence on the radiocarbon concentration and disturb an ordered age sequence are discussed. With regard to lowbog peat, the interpretation of the sample material to be measured is of particular importance. (author)

  19. Dating the humans by radiocarbon

    International Nuclear Information System (INIS)

    Fedi, M.E.

    2011-01-01

    Radiocarbon has become a very powerful tool used for dating. This paper deals with a specific application of 1 4C i.e. dating of humans. Attention is focused on those aspects that, if neglected, might lead to a misinterpretation of the results or to an unsatisfying accuracy of the measurement. After a brief description of the main principles on which the radiocarbon method is based and of Accelerator Mass Spectrometry, examples taken from the research activity of INFN-LABEC (Laboratorio di Tecniche Nucleari per I Beni Culturali) in Florence are presented. The case of the relic of St. Francis represents an example of dating not directly human remains but other objects that can be associated to them. The case of two burials from the archaeological area of Baratti-Populonia, in Tuscany, gives the possibility to show the importance of estimating the human palaeodiet when dating bone samples.

  20. Radiocarbon dating of ancient Japanese documents

    International Nuclear Information System (INIS)

    Oda, H.

    2001-01-01

    History is a reconstruction of past human activity, evidence of which is remained in the form of documents or relics. For the reconstruction of historic period, the radiocarbon dating of ancient documents provides important information. Although radiocarbon age is converted into calendar age with the calibration curve, the calibrated radiocarbon age is still different from the historical age when the document was written. The difference is known as 'old wood effect' for wooden cultural property. The discrepancy becomes more serious problem for recent sample which requires more accurate age determination. Using Tandetron accelerator mass spectrometer at Nagoya University, we have measured radiocarbon ages of Japanese ancient documents, sutras and printed books written dates of which are clarified from the paleographic standpoint. The purpose is to clarify the relation between calibrated radiocarbon age and historical age of ancient Japanese document by AMS radiocarbon dating. This paper reports 23 radiocarbon ages of ancient Japanese documents, sutras and printed books. The calibrated radiocarbon ages are in good agreement with the corresponding historical ages. It was shown by radiocarbon dating of the ancient documents that Japanese paper has little gap by 'old wood effect'; accordingly, ancient Japanese paper is a suitable sample for radiocarbon dating of recent historic period. (author)

  1. Predicted net efflux of radiocarbon from the ocean and increase in atmospheric radiocarbon content

    Science.gov (United States)

    Caldeira, Ken; Rau, Greg H.; Duffy, Philip B.

    Prior to changes introduced by man, production of radiocarbon (14C) in the stratosphere nearly balanced the flux of 14C from the atmosphere to the ocean and land biosphere, which in turn nearly balanced radioactive decay in these 14C reservoirs. This balance has been altered by land-use changes, fossil-fuel burning, and atmospheric nuclear detonations. Here, we use a model of the global carbon cycle to quantify these radiocarbon fluxes and make predictions about their magnitude in the future. Atmospheric nuclear detonations increased atmospheric 14C content by about 80% by the mid-1960's. Since that time, the 14C content of the atmosphere has been diminishing as this bomb radiocarbon has been entering the oceans and terrestrial biosphere. However, we predict that atmospheric 14C content will reach a minimum and start to increase within the next few years if fossil-fuel burning continues according to a “business-as-usual” scenario, even though fossil fuels are devoid of 14C. This will happen because fossil-fuel carbon diminishes the net flux of 14C from the atmosphere to the oceans and land biosphere, forcing 14C to accumulate in the atmosphere. Furthermore, the net flux of both bomb and natural 14C into the ocean are predicted to continue to slow and then, in the middle of the next century, to reverse, so that there will be a net flux of 14C from the ocean to the atmosphere. The predicted reversal of net 14C fluxes into the ocean is a further example of human impacts on the global carbon cycle.

  2. Role of nutrient recycling in upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T E

    1979-01-01

    The regeneration of nitrogen is an important process that increases the efficiency of the upwelling ecosystem by enlarging their spatial scales. Ammonium regeneration was considered to contribute 42 to 72 percent of phytoplankton nitrogen requirements in the northwest Africa, Peru, and Baja California upwelling systems. Zooplankton are responsible for the largest portion of regenerated nitrogen; however, fish and benthic sediments may be nearly as large. Comparisons of the importance of ammonium regeneration in upwelling areas with coastal and open ocean regions indicate that the percentage contributions are similar. Future nutrient regeneration studies are needed to assess the recycling of benthic sediments, microzooplankton, gelatinous zooplankton, demersal fish, bacterioplankton, and mollusks.

  3. ZAGRADA - A New Radiocarbon Database

    International Nuclear Information System (INIS)

    Portner, A.; Obelic, B.; Krajcar Bornic, I.

    2008-01-01

    In the Radiocarbon and Tritium Laboratory at the Rudjer Boskovic Institute three different techniques for 14C dating have been used: Gas Proportional Counting (GPC), Liquid Scintillation Counting (LSC) and preparation of milligram-sized samples for AMS dating (Accelerator Mass Spectrometry). The use of several measurement techniques has initiated a need for development of a new relational database ZAGRADA (Zagreb Radiocarbon Database) since the existing software package CARBO could not satisfy the requirements for parallel processing/using of several techniques. Using the SQL procedures, and constraints defined by primary and foreign keys, ZAGRADA enforces high data integrity and provides better performances in data filtering and sorting. Additionally, the new database for 14C samples is a multi-user oriented application that can be accessed from remote computers in the work group providing thus better efficiency of laboratory activities. In order to facilitate data handling and processing in ZAGRADA, the graphical user interface is designed to be user-friendly and to perform various actions on data like input, corrections, searching, sorting and output to printer. All invalid actions performed in user interface are registered with short textual description of an error occurred and appearing on screen in message boxes. Unauthorized access is also prevented by login control and each application window has implemented support to track last changes made by the user. The implementation of a new database for 14C samples has significant contribution to scientific research performed in the Radiocarbon and Tritium Laboratory and will provide better and easier communication with customers.(author)

  4. Upwelling along the east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Murty, C.S.; Varadachari, V.V.R.

    the premonsoon and monsoon periods. Waters from deeper layers of the shelf appear to reach the surface causing considerable fall of surface temperature near the coast. The probable causes for these differences in upwelling along the coast are discussed...

  5. Microscale radiocarbon dating of paintings

    International Nuclear Information System (INIS)

    Hendriks, Laura; Hajdas, Irka; McIntyre, Cameron; Kueffner, Markus; Ferreira, Ester S.B.; Scherrer, Nadim C.

    2016-01-01

    In this paper, radiocarbon dating of paintings using minimal sample sizes has been investigated, in an effort to address the problem of limited access to sample material in paintings. 14 C analyses were conducted on signed and dated paintings from two Swiss artists of the twentieth century. The selected paintings dated from the 1930s and 1960s, provided the opportunity to evaluate the dating accuracy on paintings realized before and after 1950 AD when the 14 C bomb peak was created, as a result of the nuclear tests conducted in the 1950/1960s. The work focused on the one hand on minimizing the size of the canvas sample required for accelerator mass spectrometer radiocarbon measurement on the gas ion source of the MICADAS and, on the other hand, on testing the possibility of dating the organic binder of the paint. Following careful characterization of the paint composition by X-ray fluorescence spectroscopy, Fourier transformed infrared spectroscopy, and Raman spectroscopy, paints containing no other carbon source than the natural organic binder were identified and dated. (orig.)

  6. Microscale radiocarbon dating of paintings

    Energy Technology Data Exchange (ETDEWEB)

    Hendriks, Laura; Hajdas, Irka; McIntyre, Cameron [ETH Zurich, Ion Beam Physics, Zurich (Switzerland); Kueffner, Markus; Ferreira, Ester S.B. [SIK-ISEA, Zurich, Zurich (Switzerland); Scherrer, Nadim C. [Bern University of Applied Sciences, HKB, Bern (Switzerland)

    2016-03-15

    In this paper, radiocarbon dating of paintings using minimal sample sizes has been investigated, in an effort to address the problem of limited access to sample material in paintings. {sup 14}C analyses were conducted on signed and dated paintings from two Swiss artists of the twentieth century. The selected paintings dated from the 1930s and 1960s, provided the opportunity to evaluate the dating accuracy on paintings realized before and after 1950 AD when the {sup 14}C bomb peak was created, as a result of the nuclear tests conducted in the 1950/1960s. The work focused on the one hand on minimizing the size of the canvas sample required for accelerator mass spectrometer radiocarbon measurement on the gas ion source of the MICADAS and, on the other hand, on testing the possibility of dating the organic binder of the paint. Following careful characterization of the paint composition by X-ray fluorescence spectroscopy, Fourier transformed infrared spectroscopy, and Raman spectroscopy, paints containing no other carbon source than the natural organic binder were identified and dated. (orig.)

  7. (abstract) Seasonal Variability in Coastal Upwelling: A Comparison of Four Coastal Upwelling Sites from Space

    Science.gov (United States)

    Carr, Mary-Elena

    1996-01-01

    Coastal upwelling of subsurface nutrient-rich water occurs along the eastern boundary of the ocean basins and leads to high primary production and fish catches. In this study satellite observations are used to compare the seasonal cycle in wind forcing and in the oceanic and biological response of the major coastal upwelling regions associated with the Canary, Benguela, California, and Humboldt Currents.

  8. Making a date with radiocarbon

    International Nuclear Information System (INIS)

    Gribbin, J.

    1979-01-01

    The use of 14 C dating techniques for samples of organic materials up to 50,000 years old is discussed with especial reference to adjustment necessary to take account of both the most recent figure for the 14 C half-life and also the natural fluctuations in the production of 14 C over 50,000 years. Methods of detection and the accuracy of the measurements are considered. It is hoped that future developments including both the possibility of counting 14 C ions directly using an accelerator as a mass spectrometer, and also the use of laser enrichment techniques will not only push back the radiocarbon calendar to 100,000 years but will also allow the use of much smaller samples than before. (U.K.)

  9. Cosmogonic radiocarbon in the Earth atmosphere

    International Nuclear Information System (INIS)

    Dergachev, V.A.

    1981-01-01

    The state and prospects of studying some processes in nature (cosmic ray intensity variations on a long time scale, mainly) using radiocarbon methods are discussed. The problem of radiocarbon preparation in exchange geochemical tanks is considered. It is noted that a set of dendrochronological and nuclear methods for analyzing tree rings is a powerful instrument for studying different processes in nature. The measurement results of radiocarbon concentration in dated wood samples for the last approximately 8000 years are presented. The relation between different indices of solar activity and the rate of radiocarbon production for separate solar cycles is investigated. The production rate variation both for separate cycles and long periods is estimated. The results of investigations lead to the conclusion that 11-year, secular, more durable peculiarities in the run of radiocarbon activity variations in the atmospheric reservoir can be explained by solar origin. The analysis of the experimental data on radiocarbon permit to compare the radiocarbon concentration variations with magnetic or solar activity [ru

  10. Atmospheric radiocarbon as a Southern Ocean wind proxy over the last 1000 years

    Science.gov (United States)

    Rodgers, K. B.; Mikaloff Fletcher, S.; Galbraith, E.; Sarmiento, J. L.; Gnanadesikan, A.; Slater, R. D.; Naegler, T.

    2009-04-01

    Measurements of radiocarbon in tree rings over the last 1000 years indicate that there was a pre-industrial latitudinal gradient of atmospheric radiocarbon of 3.9-4.5 per mail and that this gradient had temporal variability of order 6 per mil. Here we test the idea that the mean gradient as well as variability in he gradient is dominated by the strength of the winds over the Southern Ocean. This is done using an ocean model and an atmospheric transport model. The ocean model is used to derive fluxes of 12CO2 and 14CO2 at the sea surface, and these fluxes are used as a lower boundary condition for the transport model. For the mean state, strong winds in the Southern Ocean drive significant upwelling of radiocarbon-depleted Circumpolar Deep Water (CDW), leading to a net flux of 14CO2 relative to 12CO2 into the ocean. This serves to maintain a hemispheric gradient in pre-anthropogenic atmospheric delta-c14. For perturbations, increased/decreased Southern Ocean winds drive increased/decreased uptake of 14CO2 relative to 12CO2, thus increasing/decreasing the hemispheric gradient in atmospheric delta-c14. The tree ring data is interpreted to reveal a decrease in the strength of the Southern Ocean winds at the transition between the Little Ice Age and the Medieval Warm Period.

  11. NERC radiocarbon dating: 1975-1985

    International Nuclear Information System (INIS)

    Bowen, D.Q.; Harkness, D.D.

    1986-06-01

    The paper reviews the work of the Natural Environment Research Council Radiocarbon Dating Laboratory in connection with Quaternary research, over the last decade. A description is given of the development of the dating service and in-house research. Quaternary research investigations aided by radiocarbon dating are described under the topic headings: The late Devensian glacial maximum, late glacial, middle Devensian, palaeomagnetic secular variation in lake sediments, vegetational history, faunal history, palaeolimnology, ground water, volcanology, periglacial research, palaoeohydrology, geomorphology, quaternary events in low-latitudes, environmental archaeology, archaeology, deep sea sediments, continental shelf, coastal geomorphology, and radiocarbon dating in Antarctica. (U.K.)

  12. AMS radiocarbon dating of ancient Japanese sutras

    CERN Document Server

    Oda, H; Nakamura, T; Fujita, K

    2000-01-01

    Radiocarbon ages of ancient Japanese sutras whose historical ages were known paleographically were measured by means of accelerator mass spectrometry (AMS). Calibrated radiocarbon ages of five samples were consistent with the corresponding historical ages; the 'old wood effect' is negligible for ancient Japanese sutras. Japanese paper has been made from fresh branches grown within a few years and the interval from trimming off the branches to writing sutra on the paper is within one year. The good agreement between the calibrated radiocarbon ages and the historical ages is supported by such characteristics of Japanese paper. It is indicated in this study that Japanese sutra is a suitable sample for radiocarbon dating in the historic period because of little gap by 'old wood effect'.

  13. AMS radiocarbon dating of ancient Japanese sutras

    International Nuclear Information System (INIS)

    Oda, Hirotaka; Yoshizawa, Yasukazu; Nakamura, Toshio; Fujita, Keiko

    2000-01-01

    Radiocarbon ages of ancient Japanese sutras whose historical ages were known paleographically were measured by means of accelerator mass spectrometry (AMS). Calibrated radiocarbon ages of five samples were consistent with the corresponding historical ages; the 'old wood effect' is negligible for ancient Japanese sutras. Japanese paper has been made from fresh branches grown within a few years and the interval from trimming off the branches to writing sutra on the paper is within one year. The good agreement between the calibrated radiocarbon ages and the historical ages is supported by such characteristics of Japanese paper. It is indicated in this study that Japanese sutra is a suitable sample for radiocarbon dating in the historic period because of little gap by 'old wood effect'

  14. Radiocarbon Values From Otoliths of Regional Bottomfishes

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data set contains bomb radiocarbon dating of opakapaka (Pristipomoides filamentosus) otoliths from recent and archival collections (1978-2008). Specimens were...

  15. Bomb radiocarbon: imbalance in the budget

    International Nuclear Information System (INIS)

    Joos, Fortunat

    1994-01-01

    An improved understanding of the global carbon cycle is crucial to global climate change research. The uncertainties surrounding the level of oceanic carbon uptake are discussed. A revision downwards of 25% in the currently accepted figure is suggested by authors who base their estimates on a new analysis of the oceanic uptake of radiocarbon released in the atomic bomb tests of the late 1950s and early 1960s. The reduction in uptake level is required to take account of a global imbalance in the bomb-radiocarbon budget in the post test-ban period which emerges from recent carbon-cycle models. Large uncertainties exist in the estimate of the imbalance, however, and bomb-radiocarbon and anthropogenic CO 2 do not behave identically. Any revision of CO 2 uptake estimates may be substantially smaller than the 25% put forward for the bomb-radiocarbon inventory. (UK)

  16. Accuracy of radiocarbon analyses at ANTARES

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, E M; Fink, D; Hotchkis, M; Hua, Q; Jacobsen, G; Smith, A M; Tuniz, C [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1997-12-31

    Accuracy in Accelerator Mass Spectroscopy (AMS) measurements, as distinct from precision, requires the application of a number of corrections. Most of these are well known except in extreme circumstances and AMS can deliver radiocarbon results which are both precise and accurate in the 0.5 to 1.0% range. The corrections involved in obtaining final radiocarbon ages are discussed. 3 refs., 1 tab.

  17. Accuracy of radiocarbon analyses at ANTARES

    Energy Technology Data Exchange (ETDEWEB)

    Lawson, E.M.; Fink, D.; Hotchkis, M.; Hua, Q.; Jacobsen, G.; Smith, A.M.; Tuniz, C. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1996-12-31

    Accuracy in Accelerator Mass Spectroscopy (AMS) measurements, as distinct from precision, requires the application of a number of corrections. Most of these are well known except in extreme circumstances and AMS can deliver radiocarbon results which are both precise and accurate in the 0.5 to 1.0% range. The corrections involved in obtaining final radiocarbon ages are discussed. 3 refs., 1 tab.

  18. Sample processing procedures and radiocarbon dating

    International Nuclear Information System (INIS)

    Svetlik, Ivo; Tomaskova, Lenka; Dreslerova, Dagmar

    2010-01-01

    The article outlines radiocarbon dating routines and highlights the potential and limitations of this method. The author's institutions have been jointly running a conventional radiocarbon dating laboratory using the international CRL code. A procedure based on the synthesis of benzene is used. Small samples are sent abroad for dating because no AMS instrumentation is available in the Czech Republic so far. Our laboratory plans to introduce routines for the processing of milligram samples and preparation of graphitized targets for AMS

  19. Radiocarbon dating for the Quaternary scientist

    International Nuclear Information System (INIS)

    Pilcher, J.R.

    1991-01-01

    The accuracy of many conventional and accelerator mass spectrometry (AMS) radiocarbon dates is not adequate for the sort of questions now being asked in Quaternary studies. The need for, and effects of, radiocarbon calibration are discussed and guide-lines offered for the selection of a laboratory. High precision laboratories and the use of wiggle matching will go a long way to answering the critical questions of rates of change and durations of events in the Holocene. (Author)

  20. AMS Radiocarbon Dating at Notre Dame

    Science.gov (United States)

    Howard, Sean

    2014-09-01

    Current development of a local radiocarbon dating method using Accelerator Mass Spectrometry (AMS) at the University of Notre Dame seeks to provide sensitive, reproducible, and accurate measurements for future interdisciplinary projects. While AMS has been the premier radiocarbon dating method for a few decades, repurposing Notre Dame's FN Tandem accelerator for radiocarbon dating has provided many unique challenges. Experiments have shown radiocarbon dating possible and reproducible using the FN Tandem accelerator, found optimal settings for said accelerator, and established sensitivity limits comparable to dedicated radiocarbon dating facilities. In addition, there is ongoing work to create a local chemistry lab to convert organic artifacts into graphite samples to be dated locally. Once the chemistry side has been completed, several artifacts from the IAEA's radiocarbon intercomparison have been procured. Dating these previously studied artifacts will provide an additional measure on the accuracy and repeatability of both the accelerator and chemical treatment. Provided that these IAEA artifacts are dated successfully, exciting projects will ensue, such as the authentication of artwork and dating of anthropological samples.

  1. Interactions between trophic levels in upwelling and non-upwelling regions during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Malik, A; Fernandes, C.E.G.; Gonsalves, M.J.B.D.; Subina, N.S.; Mamatha, S.S.; Krishna, K.S.; Varik, S.; RituKumari; Gauns, M.; Cejoice, R.P.; Pandey, S.S.; Jineesh, V.K.; Kamaleson, A; Vijayan, V.; Mukherjee, I.; Subramanyan, S.; Nair, S.; Ingole, B.S.; LokaBharathi, P.A

    Coastal upwelling is a regular phenomenon occurring along the southwest coast of India during summer monsoon (May–September). We hypothesize that there could be a shift in environmental parameters along with changes in the network of interactions...

  2. Coastal upwelling south of Madagascar: Temporal and spatial variability

    Science.gov (United States)

    Ramanantsoa, Juliano D.; Krug, M.; Penven, P.; Rouault, M.; Gula, J.

    2018-02-01

    Madagascar's southern coastal marine zone is a region of high biological productivity which supports a wide range of marine ecosystems, including fisheries. This high biological productivity is attributed to coastal upwelling. This paper provides new insights on the structure, variability and drivers of the coastal upwelling south of Madagascar. Satellite remote sensing is used to characterize the spatial extent and strength of the coastal upwelling. A front detection algorithm is applied to thirteen years of Multi-scale Ultra-high Resolution (MUR) Sea Surface Temperatures (SST) and an upwelling index is calculated. The influence of winds and ocean currents as drivers of the upwelling is investigated using satellite, in-situ observations, and a numerical model. Results reveal the presence of two well-defined upwelling cells. The first cell (Core 1) is located in the southeastern corner of Madagascar, and the second cell (Core 2) is west of the southern tip of Madagascar. These two cores are characterized by different seasonal variability, different intensities, different upwelled water mass origins, and distinct forcing mechanisms. Core 1 is associated with a dynamical upwelling forced by the detachment of the East Madagascar Current (EMC), which is reinforced by upwelling favourable winds. Core 2 appears to be primarily forced by upwelling favourable winds, but is also influenced by a poleward eastern boundary flow coming from the Mozambique Channel. The intrusion of Mozambique Channel warm waters could result in an asynchronicity in seasonality between upwelling surface signature and upwelling favourables winds.

  3. Radiocarbon and stable isotopes in Palmyra corals during the past century

    Science.gov (United States)

    Druffel-Rodriguez, Kevin C.; Vetter, Desiree; Griffin, Sheila; Druffel, Ellen R. M.; Dunbar, Robert B.; Mucciarone, David A.; Ziolkowski, Lori A.; Sanchez-Cabeza, Joan-Albert

    2012-04-01

    Annual samples from two Palmyra Atoll corals (Porites lutea) that lived during the past 110 years were analyzed for radiocarbon (Δ14C) and δ18O. The Δ14C values decreased 7.6‰ from 1896 to 1953, similar to other coral records from the tropical and subtropical Pacific. Δ14C values rose from ˜-60‰ to ˜+110‰ by 1980 due to the input of bomb radiocarbon from the atmosphere. Elevated Δ14C values were observed for the mid- to late-1950s, suggesting early input of bomb radiocarbon, possibly from the largest Marshall Islands bomb tests in 1954. Secondary aragonite precipitation was identified in a portion of one core using scanning electron microscopy and X-radiography, and was responsible for high δ18O and δ13C values and a correlation between them. The Δ14C results were more resistant to alteration, except when contamination was from the bomb era (>1956).

  4. Reservoir effects in radiocarbon dating

    International Nuclear Information System (INIS)

    Head, M.J.

    1997-01-01

    Full text: The radiocarbon dating technique depends essentially on the assumption that atmospheric carbon dioxide containing the cosmogenic radioisotope 14 C enters into a state of equilibrium with all living material (plants and animals) as part of the terrestrial carbon cycle. Terrestrial reservoir effects occur when the atmospheric 14 C signal is diluted by local effects where systems depleted in 14 C mix with systems that are in equilibrium with the atmosphere. Naturally, this can occur with plant material growing close to an active volcano adding very old CO 2 to the atmosphere (the original 14 C has completely decayed). It can also occur in highly industrialised areas where fossil fuel derived CO 2 dilutes the atmospheric signal. A terrestrial reservoir effect can occur in the case of fresh water shells living in rivers or lakes where there is an input of ground water from springs or a raising of the water table. Soluble bicarbonate derived from the dissolution of very old limestone produces a 14 C dilution effect. Land snail shells and stream carbonate depositions (tufas and travertines) can be affected by a similar mechanism. Alternatively, in specific cases, these reservoir effects may not occur. This means that general interpretations assuming quantitative values for these terrestrial effects are not possible. Each microenvironment associated with samples being analysed needs to be evaluated independently. Similarly, the marine environment produces reservoir effects. With respect to marine shells and corals, the water depth at which carbonate growth occurs can significantly affect quantitative 14 C dilution, especially in areas where very old water is uplifted, mixing with top layers of water that undergo significant exchange with atmospheric CO 2 . Hence, generalisations with respect to the marine reservoir effect also pose problems. These can be exacerbated by the mixing of sea water with either terrestrial water in estuaries, or ground water where

  5. Tree rings and radiocarbon calibration

    International Nuclear Information System (INIS)

    Barbetti, M.

    1999-01-01

    Only a few kinds of trees in Australia and Southeast Asia are known to have growth rings that are both distinct and annual. Those that do are therefore extremely important to climatic and isotope studies. In western Tasmania, extensive work with Huon pine (Lagarostrobos franklinii) has shown that many living trees are more than 1,000 years old, and that their ring widths are sensitive to temperature, rainfall and cloud cover (Buckley et al. 1997). At the Stanley River there is a forest of living (and recently felled) trees which we have sampled and measured. There are also thousands of subfossil Huon pine logs, buried at depths less than 5 metres in an area of floodplain extending over a distance of more than a kilometre with a width of tens of metres. Some of these logs have been buried for 50,000 years or more, but most of them belong to the period between 15,000 years and the present. In previous expeditions in the 1980s and 1990s, we excavated and sampled about 350 logs (Barbetti et al. 1995; Nanson et al. 1995). By measuring the ring-width patterns, and matching them between logs and living trees, we have constructed a tree-ring dated chronology from 571 BC to AD 1992. We have also built a 4254-ring floating chronology (placed by radiocarbon at ca. 3580 to 7830 years ago), and an earlier 1268-ring chronology (ca. 7,580 to 8,850 years ago). There are many individuals, or pairs of logs which match and together span several centuries, at 9,000 years ago and beyond

  6. The freshwater reservoir effect in radiocarbon dating

    DEFF Research Database (Denmark)

    Philippsen, Bente

    case studies will show the degree of variability of the freshwater reservoir effect over short and long timescales. Radiocarbon dating of recent water samples, aquatic plants and animals, shows that age differences of up to 2000 years can occur within one river. In the Limfjord, freshwater influence......The freshwater reservoir effect can result in too high radiocarbon ages of samples from lakes and rivers, including the bones of people whose subsistence was based on freshwater fish, and pottery in which fish was cooked. In my talk, I will explain the causes and consequences of this effect. Two...... caused reservoir ages to vary between 250 and 700 years during the period 5400 BC - AD 700. Finally, I will discuss the implications of the freshwater reservoir effect for radiocarbon dating of Mesolithic pottery from inland sites of the Ertebølle culture in Northern Germany....

  7. Development of BASIC program for radiocarbon dating

    International Nuclear Information System (INIS)

    Omoto, Kunio

    1982-01-01

    The continuous improvement of the system and the needs have produced the successful radiocarbon dating system of today to detect very low energy β-radioactivity. However, it still takes longer than 1,000 minutes for a sample counting. In a gas counting system, it is very difficult to keep the drift of impressed high voltage for a proportional counter less than 5 volts throughout the counting time. The temperature and the characteristics of gas itself also change during experiment. The accumulation of the above drift and errors are closely concerned with the accuracy and reliability of the radiocarbon date. The detection and reduction of the errors are only possible by using a ''fully automatic radiocarbon dating system'' linked to a personal computer system. In this paper, the author presents the BASIC (Beginners All-purpose Symbolic Instruction Code) program for a fully automatic radiocarbon dating system. In this paper, the outline of the system and software development are described. The details of the program include the description for gas-collection, gas-enclosing, plateau counting, β-ray counting, age calculation and data file maintenance. The author wrote numerous remark statements into the program so that it can be understood by users without detailed knowledge of the operation of a personal computer system or of the radiocarbon dating. Using this system, the author found that the radiocarbon dating has greatly progressed in speed and labour-saving, and that the accuracy and reliability of the date itself has also improved much than former manual systems. (Wakatsuki, Y.)

  8. Rarotonga Radiocarbon (delta 14C) for 1950 to 1997

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Rarotonga coral radiocarbon (14C) timeseries. Coral radiocarbon (Delta-14C) on untreated, low-speed drilled samples. Precision is +/- 4 per mil as documented by an...

  9. Handlist of radiocarbon laboratories. Appendix III

    International Nuclear Information System (INIS)

    Watkins, T.; Harkness, D.D.

    1975-01-01

    A list is given of radiocarbon laboratories known to be active, and open to archaeologists, at least in some circumstances. It is not claimed to have produced an exhaustive list, which can be found in the journal Radiocarbon. The present list gives (a) some indication to would-be users, of the ability of willingness of laboratories to undertake archaeological dating; (b) a statement from each laboratory concerning the special services it may offer; (c) the likely time taken to obtain a C-14 date; and (d) a scale of charges. (U.K.)

  10. Impact of Equatorial Waves on the Variability of Upwelling Process Along West Coast of India

    Science.gov (United States)

    Prakash, K. R.; Nigam, T.; Pant, V.

    2017-12-01

    Coastal upwelling is a seasonal phenomenon along the south eastern Arabian Sea (SEAS) due to favourable wind setup during Indian Summer Monsoon Season (June-September). This upwelling brings subsurface cold and nutrient rich water to the surface layers. The cold water transported northward by the altered along shore current of west coast of India in the post-monsoon season. The different climatological forcing of positive Indian Ocean Dipole (IOD) and normal years were utilised to simulate the upwelling off the west coast of India using a three dimensional Regional Ocean Modelling System (ROMS). Strength of upwelling and the northward transport were found to be weaken for positive IOD simulations as compared to normal years. Analysis suggests that the meridional wind stress weakening resulted into a decrease in strength of West India Coastal Current (WICC) and, therefore, reduced magnitude of offshore Ekman transport. The mixed layer heat budget calculation also supports the findings by showing dominated vertical process in comparison to net heat flux effect. The post-monsoon northward transport of cold water was found to be correlated with the coastally trapped downwelling Kelvin waves. These waves are the only remote forcing from the Bay of Bengal that reaches to the south-eastern Arabian Sea during the months of October-December. The composite of sea surface height anomalies for the positive IOD and normal years shows that the downwelling Kelwin wave was absent during October-December.

  11. Microbial and biogeochemical responses to projected future nitrate enrichment in the California upwelling system

    Directory of Open Access Journals (Sweden)

    Katherine Rose Marie Mackey

    2014-11-01

    Full Text Available Coastal California is a dynamic upwelling region where nitrogen (N and iron (Fe can both limit productivity and influence biogeochemistry over different spatial and temporal scales. With global change, the flux of nitrate from upwelling is expected to increase over the next century, potentially driving additional oceanic regions toward Fe limitation. In this study we explored the effect of changes in Fe/N ratio on native phytoplankton from five currently Fe-replete sites near the major California upwelling centers at Bodega Bay and Monterey Bay using nutrient addition incubation experiments. Despite the high nitrate levels (13-30 M in the upwelled water, phytoplankton at three of the five sites showed increased growth when 10 M nitrate was added. None of the sites showed enhanced growth following addition of 10 nM Fe. Nitrate additions favored slow sinking single-celled diatoms over faster sinking chain-forming diatoms, suggesting that future increases in nitrate flux could affect carbon and silicate export and alter grazer populations. In particular, solitary cells of Cylindrotheca were more abundant than the toxin-producing genus Pseudonitzschia following nitrate addition. These responses suggest the biogeochemistry of coastal California could change in response to future increases in nitrate, and multiple stressors like ocean acidification and hypoxia may further result in ecosystem shifts.

  12. Marine radiocarbon reservoir age variation in Donax obesulus shells from northern Peru: late Holocene evidence for extended El Niño

    Science.gov (United States)

    Etayo-Cadavid, Miguel F.; Andrus, C. Fred T.; Jones, Kevin B.; Hodgins, Gregory W. L.; Sandweiss, Daniel H.; Uceda-Castillo, Sandiago; Quilter, Jeffrey

    2013-01-01

    For at least 6 m.y., El Niño events have posed the greatest environmental risk on the Peruvian coast. A better understanding of El Niño is essential for predicting future risk and growth in this tropical desert. To achieve this we analyzed archaeological and modern pre-bomb shells from the surf clam Donax for the radiocarbon reservoir effect (ΔR) to characterize late Holocene coastal upwelling conditions in northern Peru (8°14′S). Mean ΔR values from these shells suggest that modern upwelling conditions in this region were likely established between A.D. 539 and A.D. 1578. Our radiocarbon data suggest that upwelling conditions ca. A.D. 539 were less intense than those in modern times. The observed coastal water enrichment in 14C may be consequence of frequent strong El Niño events or extended El Niño–like conditions. These ΔR-inferred marine conditions are in agreement with proposed extended El Niño activity in proxy and archaeological records of ca. A.D. 475–530. Extended El Niño conditions have been linked to political destabilization, societal transformation, and collapse of the Moche civilization in northern Peru. A return to such conditions would have significant impacts on the dense population of this region today and in the near future.

  13. Use of radiocarbon technique for archaelogic dating

    International Nuclear Information System (INIS)

    Chausson, Y.

    1986-01-01

    The nuclear technique based on the beta radiation measurements emitted by the radiocarbon is applied an the geochronologycal dating of organic samples of prehistoric fires and sambaqui shells. This paper describes the origin of the method, the technique used and its applications, the analysis method, the equipments and the experiences performed. (Author) [pt

  14. Radiocarbon dating of interlaboratory check samples

    International Nuclear Information System (INIS)

    Blake, W.

    1983-01-01

    This note presents the results of a series of interlaboratory age determinations in which the Geological Survey of Canada's Radiocarbon Dating Laboratory has been involved. There is good agreement between laboratories, although there may be other problems related to the interpretation of individual samples

  15. Spatio-Temporal Variation in Effects of Upwelling on the Fatty Acid Composition of Benthic Filter Feeders in the Southern Benguela Ecosystem: Not All Upwelling Is Equal.

    Directory of Open Access Journals (Sweden)

    Eleonora Puccinelli

    Full Text Available Variability in mesoscale nearshore oceanographic conditions plays an important role in the distribution of primary production and food availability for intertidal consumers. Advection of nutrient rich waters by upwelling usually allows the proliferation of diatoms, later replaced by dinoflagellates. We examined upwelling effects on the fatty acid (FA signature of a benthic intertidal filter feeder to identify its response to pulsed variability in food availability. The study took place in two contrasting seasons and at two upwelling and two non-upwelling sites interspersed within the southern Benguela upwelling system of South Africa. We investigated the FA composition of the adductor muscles and gonads of the mussel Mytilus galloprovincialis to assess how FA are apportioned to the different tissues and whether this changes between upwelling and non-upwelling conditions. In situ temperature loggers used to identify upwelling conditions at the four sites indicated that such events occurred only at the upwelling centres and only in summer. Tissues differed strongly, with gonads presenting a higher proportion of essential FAs. This could reflect the faster turnover rate of gonad tissue or preferential retention of specific FA for reproductive purposes. FA composition did not vary as a direct function of upwelling, but there were strong dissimilarities among sites. Upwelling influenced mussel diets at one upwelling site while at the other, the expected signature of upwelling was displaced downstream of the core of upwelling. Condition Index (CI and Gonad Index (GI differed among sites and were not influenced by upwelling, with GI being comparable among sites. In addition, FA proportions were consistent among sites, indicating similar food quality and quantity over time and under upwelling and non-upwelling conditions. This suggests that the influence of upwelling on the west coast of South Africa is pervasive and diffuse, rather than discrete; while

  16. Radiocarbon dating development and practices at MINT

    International Nuclear Information System (INIS)

    Kamisah Alias; Bashillah Baharuddin; Juhari Mohd Yusof; Ahmad Raduan Ujang

    2002-01-01

    The MINT radiocarbon dating technique was introduced and a very well-designed vacuum line was developed to generate benzene from samples containing carbon. A liquid scintillation counter provides a very good prerequisite for precise measurement of the C-14 activity in the benzene. From time to time, assessment on the status of the analytical capabilities of the system and advice on improvement and upgrading required was made. For routine analysis, standard sampling, pretreatment, carbon dioxide conversion and measurement procedures were adopted. Radiocarbon dating is now, one of the most important developments of the twenties century in the comprehension of the history of human development, a quick, easy, reliable and scientifically acceptable method to determine the age of historical artefacts and archaeological samples. (Author)

  17. Geological Survey of Canada radiocarbon dates XXIX

    International Nuclear Information System (INIS)

    McNeely, R.; McCuaig, S.

    1991-01-01

    This list presents 622 radiocarbon age determinations made by the Radiocarbon Dating Laboratory. All samples dated more than two years ago have now been reported in date lists. The total number (609) of samples from various areas are as follows: Offshore (43); Newfoundland (42); Labrador (11); Nova Scotia (39); New Brunswick (7); Champlain Sea (38); Quebec (54); Ontario (23); Manitoba (3); Saskatchewan (9); Alberta (6); British Columbia (92); Yukon Territory (71); Northwest Territories, mainland (33); Northwest Territories, Arctic Archipelago (126); U.S.A. - New York (6); Washington (1); Denmark Greenland (3). Tables 1 and 2 summarize the details of background and standard counts for the 2 L and 5 L counters during the period from December 6, 1988 to January 9, 1990. (author). Refs

  18. The freshwater reservoir effect in radiocarbon dating

    DEFF Research Database (Denmark)

    Philippsen, Bente

    2013-01-01

    of magnitude and degree of variability of the freshwater reservoir effect over short and long timescales. Radiocarbon dating of recent water samples, aquatic plants, and animals, shows that age differences of up to 2000 14C years can occur within one river. The freshwater reservoir effect has also implications......The freshwater reservoir effect can result in anomalously old radiocarbon ages of samples from lakes and rivers. This includes the bones of people whose subsistence was based on freshwater fish, and pottery in which fish was cooked. Water rich in dissolved ancient calcium carbonates, commonly known...... as hard water, is the most common reason for the freshwater reservoir effect. It is therefore also called hardwater effect. Although it has been known for more than 60 years, it is still less well-recognized by archaeologists than the marine reservoir effect. The aim of this study is to examine the order...

  19. Geological Survey of Canada radiocarbon dates XXIX

    Energy Technology Data Exchange (ETDEWEB)

    McNeely, R; McCuaig, S

    1992-12-31

    This list presents 622 radiocarbon age determinations made by the Radiocarbon Dating Laboratory. All samples dated more than two years ago have now been reported in date lists. The total number (609) of samples from various areas are as follows: Offshore (43); Newfoundland (42); Labrador (11); Nova Scotia (39); New Brunswick (7); Champlain Sea (38); Quebec (54); Ontario (23); Manitoba (3); Saskatchewan (9); Alberta (6); British Columbia (92); Yukon Territory (71); Northwest Territories, mainland (33); Northwest Territories, Arctic Archipelago (126); U.S.A. - New York (6); Washington (1); Denmark Greenland (3). Tables 1 and 2 summarize the details of background and standard counts for the 2 L and 5 L counters during the period from December 6, 1988 to January 9, 1990. (author). Refs.

  20. Ekman estimates of upwelling at cape columbine based on ...

    African Journals Online (AJOL)

    Ekman estimates of upwelling at cape columbine based on measurements of longshore wind from a 35-year time-series. AS Johnson, G Nelson. Abstract. Cape Columbine is a prominent headland on the south-west coast of Africa at approximately 32°50´S, where there is a substantial upwelling tongue, enhancing the ...

  1. Coastal Upwelling Drives Intertidal Assemblage Structure and Trophic Ecology.

    Science.gov (United States)

    Reddin, Carl J; Docmac, Felipe; O'Connor, Nessa E; Bothwell, John H; Harrod, Chris

    2015-01-01

    Similar environmental driving forces can produce similarity among geographically distant ecosystems. Coastal oceanic upwelling, for example, has been associated with elevated biomass and abundance patterns of certain functional groups, e.g., corticated macroalgae. In the upwelling system of Northern Chile, we examined measures of intertidal macrobenthic composition, structure and trophic ecology across eighteen shores varying in their proximity to two coastal upwelling centres, in a hierarchical sampling design (spatial scales of >1 and >10 km). The influence of coastal upwelling on intertidal communities was confirmed by the stable isotope values (δ13C and δ15N) of consumers, including a dominant suspension feeder, grazers, and their putative resources of POM, epilithic biofilm, and macroalgae. We highlight the utility of muscle δ15N from the suspension feeding mussel, Perumytilus purpuratus, as a proxy for upwelling, supported by satellite data and previous studies. Where possible, we used corrections for broader-scale trends, spatial autocorrelation, ontogenetic dietary shifts and spatial baseline isotopic variation prior to analysis. Our results showed macroalgal assemblage composition, and benthic consumer assemblage structure, varied significantly with the intertidal influence of coastal upwelling, especially contrasting bays and coastal headlands. Coastal topography also separated differences in consumer resource use. This suggested that coastal upwelling, itself driven by coastline topography, influences intertidal communities by advecting nearshore phytoplankton populations offshore and cooling coastal water temperatures. We recommend the isotopic values of benthic organisms, specifically long-lived suspension feeders, as in situ alternatives to offshore measurements of upwelling influence.

  2. Upwelling features near Sri Lanka in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    ShreeRam, P.; Rao, L.V.G.

    , the southwest monsoon in summer and the northeast monsoon in winter. The wind stress associated with these winds cause mass drift of oceanic waters leading to upwelling and downwelling. The upwelling features in the Bay of Bengal with a special mention about...

  3. Ecological features of harmful algal blooms in coastal upwelling ...

    African Journals Online (AJOL)

    The mass mortalities that accompany anoxia, common to the Benguela and Peru upwelling systems, may be a trophic control mechanism to maintain biogeochemical balance and regional homeostasis, which are vital to upwelling ecosystem dynamics. Some traditional concepts of phytoplankton ecology may not completely

  4. Radiocarbon calibration - past, present and future

    Energy Technology Data Exchange (ETDEWEB)

    Plicht, J. van der E-mail: plicht@phys.rug.nl

    2004-08-01

    Calibration of the Radiocarbon timescale is traditionally based on tree-rings dated by dendrochronology. At present, the tree-ring curve dates back to about 9900 BC. Beyond this limit, marine datasets extend the present calibration curve INTCAL98 to about 15 600 years ago. Since 1998, a wealth of AMS measurements became available, covering the complete {sup 14}C dating range. No calibration curve can presently be recommended for the older part of the dating range until discrepancies are resolved.

  5. Radiocarbon measurements on submerged forest floating chronologies

    International Nuclear Information System (INIS)

    Campbell, J.A.; Baxter, M.S.

    1979-01-01

    It is stated that the submerged forests along the west coast of England and Wales provide a unique source of wood for radiocarbon/ dendrochronological studies. 14 C age determinations are reported on sequential growth increments from three 'gloating' chronologies. A sampling frequency of approximately 10 samples per century was used. Fluctuations in atmospheric 14 C levels of 2 to 3% over several decades can occur, these variations being superimposed on a smoothly changing trend. (author)

  6. Radiocarbon calibration - past, present and future

    International Nuclear Information System (INIS)

    Plicht, J. van der

    2004-01-01

    Calibration of the Radiocarbon timescale is traditionally based on tree-rings dated by dendrochronology. At present, the tree-ring curve dates back to about 9900 BC. Beyond this limit, marine datasets extend the present calibration curve INTCAL98 to about 15 600 years ago. Since 1998, a wealth of AMS measurements became available, covering the complete 14 C dating range. No calibration curve can presently be recommended for the older part of the dating range until discrepancies are resolved

  7. Radiocarbon accelerator mass spectrometry: background and contamination

    International Nuclear Information System (INIS)

    Beukens, R.P.

    1993-01-01

    Since the advent of radiocarbon accelerator mass spectrometry (AMS) many studies have been conducted to understand the background from mass spectrometric processes and the origins of contamination associated with the ion source and sample preparation. By studying the individual contributions a better understanding of these processes has been obtained and it has been demonstrated that it is possible to date samples reliably up to 60 000 BP. (orig.)

  8. Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene

    Science.gov (United States)

    Toth, Lauren T.; Cheng, Hai; Edwards, R. Lawrence; Ashe, Erica; Richey, Julie N.

    2017-01-01

    A growing body of research suggests that the marine environments of south Florida provide a critical link between the tropical and high-latitude Atlantic. Changes in the characteristics of water masses off south Florida may therefore have important implications for our understanding of climatic and oceanographic variability over a broad spatial scale; however, the sources of variability within this oceanic corridor remain poorly understood. Measurements of ΔR, the local offset of the radiocarbon reservoir age, from shallow-water marine environments can serve as a powerful tracer of water-mass sources that can be used to reconstruct variability in local-to regional-scale oceanography and hydrology. We combined radiocarbon and U-series measurements of Holocene-aged corals from the shallow-water environments of the Florida Keys reef tract (FKRT) with robust statistical modeling to quantify the millennial-scale variability in ΔR at locations with (“nearshore”) and without (“open ocean”) substantial terrestrial influence. Our reconstructions demonstrate that there was significant spatial and temporal variability in ΔR on the FKRT during the Holocene. Whereas ΔR was similar throughout the region after ∼4000 years ago, nearshore ΔR was significantly higher than in the open ocean during the middle Holocene. We suggest that the elevated nearshore ΔR from ∼8000 to 5000 years ago was most likely the result of greater groundwater influence associated with lower sea level at this time. In the open ocean, which would have been isolated from the influence of groundwater, ΔR was lowest ∼7000 years ago, and was highest ∼3000 years ago. We evaluated our open-ocean model of ΔR variability against records of local-to regional-scale oceanography and conclude that local upwelling was not a significant driver of open-ocean radiocarbon variability in this region. Instead, the millennial-scale trends in open-ocean ΔR were more likely a result of broader

  9. Radiocarbon mass spectrometry for drug development

    International Nuclear Information System (INIS)

    Ulrich, Schulze-Konig Tim

    2011-01-01

    Full text: Radiocarbon has a huge potential as a tracer for metabolism studies in humans. By using Accelerator Mass Spectrometry (AMS) for its detection, a unique sensitivity is reached reducing required radiation doses to a negligible level. Until recently, a widespread use of AMS in biomedical research was impeded by the high complexity of the instrument, time-consuming sample preparation, and a limited availability of measurement capacity. Over the last few years, tremendous progress has been achieved in the reduction of size and complexity of AMS instruments. It allowed designing a compact AMS system, dubbed BioMICADAS to address the needs of biomedical users. For more than two years, this system is in successful operation at a commercial service provider for the pharmaceutical industry. A further drastic simplification of radiocarbon mass spectrometers seems possible and could establish a regular usage of this technology in drug development. However, to reach this goal a better integration of AMS into the workflow of bioanalytical laboratories will be necessary. For this purpose, CO 2 accepting ion sources may be a key, since they enable an almost automated sample preparation. The status of radiocarbon AMS in biomedical research and its perspective will be discussed

  10. Accelerator mass spectrometry for radiocarbon dating

    International Nuclear Information System (INIS)

    Bronk, C.R.

    1987-01-01

    Accelerator mass spectrometry (AMS) has been used routinely for radiocarbon measurements for several years. This thesis describes theoretical work to understand the reasons for low accuracy and range and offers practical solutions. The production and transport of the ions used in the measurements are found to be the most crucial stages in the process. The theories behind ion production by sputtering are discussed and applied to the specific case of carbon sputtered by caesium. Experimental evidence is also examined in relation to the theories. The phenomena of space charge and lens aberrations are discussed along with the interaction between ion beams and gas molecules in the vacuum. Computer programs for calculating phase space transformations are then described; these are designed to help investigations of the effects of space charge and aberrations on AMS measurements. Calculations using these programs are discussed in relation both to measured ion beam profiles in phase space and to the current dependent transmission of ions through the Oxford radiocarbon accelerator. Improvements have been made to this accelerator and these are discussed in the context of the calculations. C - ions are produced directly from carbon dioxide at the Middleton High Intensity Sputter Source. Experiments to evaluate the performance of such a source are described and detailed design criteria established. An ion source designed and built specifically for radiocarbon measurements using carbon dioxide is described. Experiments to evaluate its performance and investigate the underlying physical processes are discussed. (author)

  11. Radiocarbon C-14 dating - MINT experience

    International Nuclear Information System (INIS)

    Kamisah Alias

    2002-01-01

    The measurement of a radiocarbon date is a complex process which involved all the stages from advice given prior to submission of samples right through to reporting of results. The aim of our radiocarbon dating is to determine the residual 14 C content of a sample, the value of which is translated into an age that is an estimate of the time elapsed since the given sample was removed from the environment in which it had formed in equilibrium with respect to 14-C radioactive decay and metabolic assimilation. Carbon is obtained from carbon containing samples in the form of carbon dioxide, which is then reacted with lithium forming lithium carbide. The carbide is then hydrolysed to acetylene before it was polymerised to benzene using a high-efficiency vanadium-alumina-silica catalyst to produce benzene with up to 96% yield. Sample, background and modem standard activities are measured with a coincidence scintillation counter using in glass vials of 21 ml capacity. An improved chemical procedure was used to obtain and purify the benzene from the samples for measurement using a liquid scintillation counter. Radiocarbon dating measurements of samples collected reveal some results. The validity of the data have yet to be confirmed by the results of the measurements on two international control samples. (Author)

  12. Detection of radiocarbon in the cyclotrino

    International Nuclear Information System (INIS)

    Bertsche, K.J.; Karadi, C.A.; Muller, R.A.; Paulson, G.C.

    1990-04-01

    A small low energy cyclotron (the ''cyclotrino''), which was proposed for direct detection of radiocarbon in 1980, has now detected radiocarbon at natural abundance. This device combines the suppression of background through the use of negative ions with the high intrinsic mass resolution of a cyclotron. A high current cesium sputter negative ion source generates a beam of carbon ions which is pre-separated with Wien filter and is transported to the cyclotron via a series of electrostatic lenses. Beam is injected radially into the cyclotron using electrostatic deflectors and an electrostatic mirror. Axial focusing is entirely electrostatic. A microchannel plate detector is used with a phase-gated output. Data is presented showing resolution of radiocarbon at natural abundance. In its present form the system is capable of improving the sensitivity of detecting 14 C in some biomedical experiments by a factor of 10 4 . Modifications are discussed which could bring about an additional factor of 100 in sensitivity, which is important for archaeological and geological applications. Possibilities for measurements of other isotopes are discussed. 16 refs., 7 figs

  13. Low energy cyclotron for radiocarbon dating

    International Nuclear Information System (INIS)

    Welch, J.J.

    1984-12-01

    The measurement of naturally occurring radioisotopes whose half lives are less than a few hundred million years but more than a few years provides information about the temporal behavior of geologic and climatic processes, the temporal history of meteoritic bodies as well as the production mechanisms of these radioisotopes. A new extremely sensitive technique for measuring these radioisotopes at tandem Van de Graaff and cyclotron facilities has been very successful though the high cost and limited availability have been discouraging. We have built and tested a low energy cyclotron for radiocarbon dating similar in size to a conventional mass spectrometer. These tests clearly show that with the addition of a conventional ion source, the low energy cyclotron can perform the extremely high sensitivity 14 C measurements that are now done at accelerator facilities. We found that no significant background is present when the cyclotron is tuned to accelerate 14 C negative ions and the transmission efficiency is adequate to perform radiocarbon dating on milligram samples of carbon. The internal ion source used did not produce sufficient current to detect 14 C directly at modern concentrations. We show how a conventional carbon negative ion source, located outside the cyclotron magnet, would produce sufficient beam and provide for quick sampling to make radiocarbon dating milligram samples with a modest laboratory instrument feasible

  14. The Triassic upwelling system of Arctic Alaska

    Science.gov (United States)

    Yurchenko, I.; Graham, S. A.

    2017-12-01

    The Middle to Upper Triassic Shublik Formation of Arctic Alaska is a laterally and vertically heterogeneous rock unit that has been analyzed both in outcrop and in the subsurface. The Shublik Formation sediments are distinguished by a characteristic set of lithologies that include glauconitic, phosphatic, organic-rich, and cherty facies consistent with a coastal upwelling zone deposition interpretation. It is often recognized by abundance of impressions and shells of distinctive Triassic bivalves. To understand main controls on lithofacies distributions, this study reviews and refines lithologic and paleoenvironmental interpretations of the Shublik Formation, and incorporates the newly acquired detailed geochemical analyses of two complete Shublik cores. This work focuses on organic geochemistry (analyses of biomarkers and diamondoids), chemostratigraphy (hand-held XRF), and iron speciation analysis to reconstruct paleoproductivity and redox conditions. Based on the available evidence, during Shublik deposition, an upwelling-influenced open shelf resulted in high nutrient supply that stimulated algal blooms leading to high net organic productivity, reduced water transparency, oxygen deficiency, and water column stratification. Evidence of such eutrophic conditions is indicated by the lack of photic benthic organisms, bioturbation and trace fossils, and dominance of the monospecific light-independent epibenthic bivalves. The flat, subcircular, thin shells of these carbonate-secreting organisms allowed them to adapt to dysoxic conditions, and float on soft, soupy, muddy substrate. The distinctive clay- and organic-rich facies with abundant bivalves occurred on the mid to outer stable broad shelf, and were deposited when organic productivity at times overlapped with periods of increased siliciclastic input controlled by sea level and changes in local sediment dispersal systems, and therefore are more spatially and temporally localized than the widespread clay

  15. AMS radiocarbon dating of ancient Japanese documents of known age

    International Nuclear Information System (INIS)

    Oda, H.; Niu, E.; Nakamura, T.

    2003-01-01

    Radiocarbon ages of 17 ancient Japanese documents of known age and 3 unknown samples were measured by AMS. Radiocarbon dating on the known documents concluded that the Japanese paper is a suitable sample for radiocarbon dating because of small discrepancy between the calibrated radiocarbon age and the historical age due to the characteristics of Japanese paper. From the dating of the paper samples of unknown age, the wood-block prints, it was clarified that they had been produced between the 11th century and the first half of the 12th century as the historical information suggested. (author)

  16. Life cycle strategies of copepods in coastal upwelling zones

    Science.gov (United States)

    Peterson, W.

    1998-06-01

    Life cycles of copepods of coastal upwelling zones are of the multigenerational type—as many as 10 or more generations may be produced each year, depending upon water temperature, food concentration and length of the upwelling season. Abundant food resources and moderate temperature convey advantages to those copepods living in coastal upwelling zones, however, there is a clear disadvantage in that coastal upwelling zones are highly advective environments. Typically, water circulation patterns are such that surface waters are carried offshore, deeper waters carried onshore and most of the water column over the continental shelf is moving equatorward. The challenge to copepod species that inhabit upwelling systems is life cycle closure—how do eggs, nauplii, juveniles and adults avoid being swept out of these ecosystems in the face of persistent transport out of the system? In this review, I first list the species which dominate coastal upwelling ecosystems then discuss three variations on the multigenerational life cycle scheme that are observed in upwelling systems. The latter part of the review is devoted to discussion of how individuals are retained in the productive continental shelf waters within coastal upwelling ecosystems. The suggestion is made that the only copepod species that successfully achieve life cycle closure in such systems are those that are preadapted to upwelling circulation patterns. Our quantitative understanding of the relative importance of physical factors (such as advection) and biological factors (birth, growth, and mortality) on life cycle strategies and population dynamics is quite rudimentary. It would help our understanding if there were more field studies and more computer modeling studies that focused on seasonal cycles of abundance, development times and vertical distribution of life cycle stages, and measurements of water circulation patterns.

  17. Spatiotemporal variation of vertical particle fluxes and modelled chlorophyll a standing stocks in the Benguela Upwelling System

    Science.gov (United States)

    Vorrath, Maria-Elena; Lahajnar, Niko; Fischer, Gerhard; Libuku, Viktor Miti; Schmidt, Martin; Emeis, Kay-Christian

    2018-04-01

    Marine particle fluxes from high productive coastal upwelling systems return upwelled CO2 and nutrients to the deep ocean and sediments and have a substantial impact on the global carbon cycle. This study examines relations between production regimes on the shelf and over the continental margin of the Benguela Upwelling System (BUS) in the SE Atlantic Ocean. Data of composition and timing of vertical particle flux come from sediment trap time series (deployed intermittently between 1988 and 2014) in the regions Walvis Ridge, Walvis Bay, Luederitz and Orange River. We compare their seasonal variability to modelled patterns of chlorophyll concentrations in a 3-D ecosystem model. Both modelled seasonal chlorophyll a standing stocks and sampled particle flux patterns are highly correspondent with a bimodal seasonal cycle offshore the BUS. The material in the particle flux in offshore traps is dominantly carbonate (40-70%), and flux peaks in offshore particle flux originate from two independent events: in austral autumn thermocline shoaling and vertical mixing are decoupled from coastal upwelling, while fluxes in spring coincide with the upwelling season, indicated by slightly elevated biogenic opal values at some locations. Coastal particle fluxes are characterized by a trimodal pattern and are dominated by biogenic opal (22-35%) and organic matter (30-60%). The distinct seasonality in observed fluxes on the shelf is caused by high variability in production, sinking behaviour, wind stress, and hydrodynamic processes. We speculate that global warming will increase ocean stratification and alter coastal upwelling, so that consequences for primary production and particle flux in the BUS are inevitable.

  18. Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century.

    Science.gov (United States)

    Graven, Heather D

    2015-08-04

    Radiocarbon analyses are commonly used in a broad range of fields, including earth science, archaeology, forgery detection, isotope forensics, and physiology. Many applications are sensitive to the radiocarbon ((14)C) content of atmospheric CO2, which has varied since 1890 as a result of nuclear weapons testing, fossil fuel emissions, and CO2 cycling between atmospheric, oceanic, and terrestrial carbon reservoirs. Over this century, the ratio (14)C/C in atmospheric CO2 (Δ(14)CO2) will be determined by the amount of fossil fuel combustion, which decreases Δ(14)CO2 because fossil fuels have lost all (14)C from radioactive decay. Simulations of Δ(14)CO2 using the emission scenarios from the Intergovernmental Panel on Climate Change Fifth Assessment Report, the Representative Concentration Pathways, indicate that ambitious emission reductions could sustain Δ(14)CO2 near the preindustrial level of 0‰ through 2100, whereas "business-as-usual" emissions will reduce Δ(14)CO2 to -250‰, equivalent to the depletion expected from over 2,000 y of radioactive decay. Given current emissions trends, fossil fuel emission-driven artificial "aging" of the atmosphere is likely to occur much faster and with a larger magnitude than previously expected. This finding has strong and as yet unrecognized implications for many applications of radiocarbon in various fields, and it implies that radiocarbon dating may no longer provide definitive ages for samples up to 2,000 y old.

  19. Radiocarbon dating prehistoric pottery from Northern Europe

    DEFF Research Database (Denmark)

    Philippsen, Bente; Craig, Oliver; Heron, Carl

    2012-01-01

    , such as when aquatic products have been prepared in the pottery. Soot can derive from old wood that was used for the hearth fire, or from (potentially aquatic) food that boiled over. Plant remains may have been present in the clay for a long time before manufacture of the pottery. Post......-depositional contamination with organic carbon, such as humic acids, may also be problematic. We present these data with radiocarbon datings of contemporaneous terrestrial and aquatic samples to find out the true age of the pottery and estimate the reservoir age. Lipid analysis and bulk carbon and nitrogen stable isotope...

  20. An assessment of variability in radiocarbon dating

    International Nuclear Information System (INIS)

    Scott, E.M.; Baxter, M.S.; Aitchison, T.C.

    1981-01-01

    A series of replicate experiments, involving analysis of homogenized wood and identical tree-ring sections, suggests that the 14 C counting error in radiocarbon dating quantifies only part of the total variability of measurement. Statistical modelling implies that a more realistic assessment of error is provided by a value approximately three times the counting error. The incorporation of this more realistic measure of variability into an appropriate procedure for calibrating a single date and for matching a floating chronology to a master chronology is described. (author)

  1. Radiocarbon clock strikes the glacial period pulse

    International Nuclear Information System (INIS)

    Serebryannyj, L.R.

    1976-01-01

    Discussed are some aspects of the theory of radiocarbon dating in application to the study of the history of the Earth. The accumulation and the decay of C 14 and methods for its recording are desribed. Presented is a block diagram of a scintillation counter for recording C 14 . The chronology of the last glaciation of Europe has been determined: the Interglacial period (between 50 and 40 thousand years) a prolonged preglacil period (between 40 and 25 thousand years), the last glaciation (between 25 and 10 thousand years ago)

  2. Upwelling systems in eastern boundary currents have been ...

    African Journals Online (AJOL)

    spamer

    Differences are found in the location of return, onshore flow. .... eastern boundary currents, downstream of the west wind drift ... show maximum upwelling conditions (equatorward winds) in ..... The work of PTS and CJ was supported by Grant.

  3. Upwelling filaments are cold, typically narrow features in surface ...

    African Journals Online (AJOL)

    spamer

    They are defined by strong ... transporting coastally upwelled water to the deep ... surface temperature anomaly up to 2°C. The cool temperature signal was restricted to a shallow surface ... towards the important process of exchanges between.

  4. Abyssal Upwelling and Downwelling and the role of boundary layers

    Science.gov (United States)

    McDougall, T. J.; Ferrari, R. M.

    2016-02-01

    The bottom-intensified mixing activity arising from the interaction of internal tides with bottom topography implies that the dianeutral advection in the ocean interior is downwards, rather than upwards as is required by continuity. The upwelling of Bottom Water through density surfaces in the deep ocean is however possible because of the sloping nature of the sea floor. A budget study of the abyss (deeper than 2000m) will be described that shows that while the upwelling of Bottom Water might be 25 Sv, this is achieved by very strong upwelling in the bottom turbulent boundary layer (of thickness 50m) of 100 Sv and strong downwelling in the ocean interior of 75 Sv. This downwelling occurs within 10 degrees of longitude of the continental boundaries. This near-boundary confined strong upwelling and downwelling clearly has implications for the Stommel-Arons circulation.

  5. The Benguela upwelling system lying off southern Africa's west ...

    African Journals Online (AJOL)

    spamer

    Africa's west coast is one of the world's four main upwelling ..... Regions of current shear, convergence and divergence, as well ..... between Cape Point and Danger Point in 1975. .... processes in relation to eastern boundary current pelagic.

  6. Radiocarbon and other radionuclide studies using accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Jull, A.J.T.; Donahue, D.J.; Burr, G.S.; Beck, J.W.; McHargue, L.R.; Hatheway, A.L.; Lange, T.E.; O'Malley, J.M.; Biddulph, D.L.

    2002-01-01

    The research program at our laboratory encompasses a wide range of applications of AMS radiocarbon dating. We highlight some of our methods as well as some of these radiocarbon applications in this paper. We also discuss results of 10 Be and 129 I measurements made on the new 3MV AMS machine in Tucson. (author)

  7. Gaseous radiocarbon measurements of small samples

    International Nuclear Information System (INIS)

    Ruff, M.; Szidat, S.; Gaeggeler, H.W.; Suter, M.; Synal, H.-A.; Wacker, L.

    2010-01-01

    Radiocarbon dating by means of accelerator mass spectrometry (AMS) is a well-established method for samples containing carbon in the milligram range. However, the measurement of small samples containing less than 50 μg carbon often fails. It is difficult to graphitise these samples and the preparation is prone to contamination. To avoid graphitisation, a solution can be the direct measurement of carbon dioxide. The MICADAS, the smallest accelerator for radiocarbon dating in Zurich, is equipped with a hybrid Cs sputter ion source. It allows the measurement of both, graphite targets and gaseous CO 2 samples, without any rebuilding. This work presents experiences dealing with small samples containing 1-40 μg carbon. 500 unknown samples of different environmental research fields have been measured yet. Most of the samples were measured with the gas ion source. These data are compared with earlier measurements of small graphite samples. The performance of the two different techniques is discussed and main contributions to the blank determined. An analysis of blank and standard data measured within years allowed a quantification of the contamination, which was found to be of the order of 55 ng and 750 ng carbon (50 pMC) for the gaseous and the graphite samples, respectively. For quality control, a number of certified standards were measured using the gas ion source to demonstrate reliability of the data.

  8. Radiocarbon intercomparison program for Chauvet Cave

    International Nuclear Information System (INIS)

    Cuzange, M.T.; Delque-Kolic, E.; Oberlin, C.; Goslar, T.; Grootes, P.M.; Nadeau, M.J.; Higham, T.; Ramsey, C.B.; Kaltnecker, E.; Paterne, M.; Valladas, H.; Van der Plicht, J.; Van der Plicht, J.; Clottes, J.; Geneste, J.M.

    2007-01-01

    We present the first results of an accelerator mass spectrometry (AMS) radiocarbon intercomparison program on 3 different charcoal samples collected in one of the hearths of the Megaceros gallery of Chauvet Cave (Ardeche, France). This cave, rich in parietal decoration, is important for the study of the appearance and evolution of prehistoric art because certain drawings have been 14 C dated to the Aurignacian period at the beginning of the Upper Paleolithic. The new dates indicate an age of about 32,000 BP, which is consistent with this attribution and in agreement with the results from the same sector of the cave measured previously at the Laboratoire des Sciences du Climat et de l'Environnement (LSCE). Six laboratories were involved in the intercomparison. Samples were measured in 4 AMS facilities: Center for Isotope Research, Groningen University, the Netherlands; the Oxford Radiocarbon Accelerator Unit, UK; the Centre de datation par le carbone 14, Univ. Claude Bernard Lyon 1, France (measured by AMS facilities of Poznan University, Poland); and the LSCE, UMR CEA-CNRS-UVSQ, France (measured by the Leibniz-Labor of Christian-Albrechts-Universitat Kiel, Germany). (authors)

  9. The Benguela upwelling ecosystem lies adjacent to the south ...

    African Journals Online (AJOL)

    denise

    The Benguela upwelling ecosystem lies adjacent to the south-western coast of Africa, from southern Angola. (15°S) to Cape Agulhas (35°S; Fig. 1). Ecologically, it is split into separate northern and southern sub- systems by a zone of intense perennial upwelling near. Lüderitz (26–27.5°S; Shannon 1985). As is charac-.

  10. Pliocene Warm Period Upwelling in the Southern Benguela Region

    Science.gov (United States)

    Petrick, B. F.; McClymont, E.; Felder, S.; Leng, M. J.; Rosell Mele, A.; Rueda, G.

    2014-12-01

    The mid-Pliocene has been proposed as a possible analogue for understanding future climate change and testing climate models. Previous work has shown that during the Pliocene the major upwelling systems were relatively warm, and thus either inactive, contracted, or upwelling warmer waters than present. Here we examine evidence from a core site located on the margins of the modern Benguela upwelling system, to test whether the upwelling cells had migrated or contracted relative to present during the Pliocene. We applied several organic geochemistry proxies and foraminiferal analyses to reconstruct the Pliocene history of ODP site 1087 (31º28'S, 15º19'E, 1374m water depth), including the UK37' index and TEX86 index (for reconstructing sea surface temperatures), chlorins (for estimating primary productivity) and planktonic foraminifera assemblages (for inferring water mass changes). These proxies show that between 3.5 and 3.0 Ma the southern Benguela region was significantly cooler than the northern Benguela region, the latter where the main upwelling cells are found today. Coupled with higher primary production, a shift in planktonic foraminifera assemblage, and an offset between the UK37' index and TEX86 index, we infer that more extensive upwelling was present in the southern Benguela region during the Pliocene. We infer that the main Benguela upwelling cells had shifted southward relative to today, as a result of changes in the local wind field. We find evidence for pronounced cooling and a shift in the planktonic foraminifera assemblage during the M2 and KM2 glacial stages, showing a sensitivity of Benguela upwelling to these short-lived climate events.

  11. Trends in the number of extreme hot SST days along the Canary Upwelling System due to the influence of upwelling

    Directory of Open Access Journals (Sweden)

    Xurxo Costoya

    2014-07-01

    Full Text Available Trends in the number of extreme hot days (days with SST anomalies higher than the 95% percentile were analyzed along the Canary Upwelling Ecosystem (CUE over the period 1982- 2012 by means of SST data retrieved from NOAA OI1/4 Degree. The analysis will focus on the Atlantic Iberian sector and the Moroccan sub- region where upwelling is seasonal (spring and summer are permanent, respectively. Trends were analyzed both near coast and at the adjacent ocean where the increase in the number of extreme hot days is higher. Changes are clear at annual scale with an increment of 9.8±0.3 (9.7±0.1 days dec-1 near coast and 11.6±0.2 (13.5±0.1 days dec-1 at the ocean in the Atlantic Iberian sector (Moroccan sub-region. The differences between near shore and ocean trends are especially patent for the months under intense upwelling conditions. During that upwelling season the highest differences in the excess of extreme hot days between coastal and ocean locations (Δn(#days dec-1 occur at those regions where coastal upwelling increase is high. Actually, Δn and upwelling trends have shown to be significantly correlated in both areas, R=0.88 (p<0.01 at the Atlantic Iberian sector and R=0.67 (p<0.01 at the Moroccan sub-region.

  12. Collagen Fingerprinting: A New Screening Technique for Radiocarbon Dating Ancient Bone.

    Directory of Open Access Journals (Sweden)

    Virginia L Harvey

    Full Text Available Collagen is the dominant organic component of bone and is intimately locked within the hydroxyapatite structure of this ubiquitous biomaterial that dominates archaeological and palaeontological assemblages. Radiocarbon analysis of extracted collagen is one of the most common approaches to dating bone from late Pleistocene or Holocene deposits, but dating is relatively expensive compared to other biochemical techniques. Numerous analytical methods have previously been investigated for the purpose of screening out samples that are unlikely to yield reliable dates including histological analysis, UV-stimulated fluorescence and, most commonly, the measurement of percentage nitrogen (%N and ratio of carbon to nitrogen (C:N. Here we propose the use of collagen fingerprinting (also known as Zooarchaeology by Mass Spectrometry, or ZooMS, when applied to species identification as an alternative screening method for radiocarbon dating, due to its ability to provide information on collagen presence and quality, alongside species identification. The method was tested on a series of sub-fossil bone specimens from cave systems on Cayman Brac (Cayman Islands, chosen due to the observable range in diagenetic alteration, and in particular, the extent of mineralisation. Six (14C dates, of 18 initial attempts, were obtained from remains of extinct hutia, Capromys sp. (Rodentia; Capromyidae, recovered from five distinct caves on Cayman Brac, and ranging from 393 ± 25 to 1588 ± 26 radiocarbon years before present (yr BP. All of the bone samples that yielded radiocarbon dates generated excellent collagen fingerprints, and conversely those that gave poor fingerprints also failed dating. Additionally, two successfully fingerprinted bone samples were screened out from a set of 81. Both subsequently generated (14C dates, demonstrating successful utilisation of ZooMS as an alternative screening mechanism to identify bone samples that are suitable for 1(4C analysis.

  13. Collagen Fingerprinting: A New Screening Technique for Radiocarbon Dating Ancient Bone.

    Science.gov (United States)

    Harvey, Virginia L; Egerton, Victoria M; Chamberlain, Andrew T; Manning, Phillip L; Buckley, Michael

    2016-01-01

    Collagen is the dominant organic component of bone and is intimately locked within the hydroxyapatite structure of this ubiquitous biomaterial that dominates archaeological and palaeontological assemblages. Radiocarbon analysis of extracted collagen is one of the most common approaches to dating bone from late Pleistocene or Holocene deposits, but dating is relatively expensive compared to other biochemical techniques. Numerous analytical methods have previously been investigated for the purpose of screening out samples that are unlikely to yield reliable dates including histological analysis, UV-stimulated fluorescence and, most commonly, the measurement of percentage nitrogen (%N) and ratio of carbon to nitrogen (C:N). Here we propose the use of collagen fingerprinting (also known as Zooarchaeology by Mass Spectrometry, or ZooMS, when applied to species identification) as an alternative screening method for radiocarbon dating, due to its ability to provide information on collagen presence and quality, alongside species identification. The method was tested on a series of sub-fossil bone specimens from cave systems on Cayman Brac (Cayman Islands), chosen due to the observable range in diagenetic alteration, and in particular, the extent of mineralisation. Six (14)C dates, of 18 initial attempts, were obtained from remains of extinct hutia, Capromys sp. (Rodentia; Capromyidae), recovered from five distinct caves on Cayman Brac, and ranging from 393 ± 25 to 1588 ± 26 radiocarbon years before present (yr BP). All of the bone samples that yielded radiocarbon dates generated excellent collagen fingerprints, and conversely those that gave poor fingerprints also failed dating. Additionally, two successfully fingerprinted bone samples were screened out from a set of 81. Both subsequently generated (14)C dates, demonstrating successful utilisation of ZooMS as an alternative screening mechanism to identify bone samples that are suitable for 1(4)C analysis.

  14. Perspectives in radiocarbon dating by radiometry

    International Nuclear Information System (INIS)

    Polach, H.A.

    1987-01-01

    Opportunities for individual contributions to the technology of radiocarbon dating over the past 40 years have been large. Meaningful developments are traced in this review of C-14 dating by gas proportional (GP) and liquid scintillation (LS) spectrometry. The performance of characteristic as well as state of the art GP and LS systems is tabulated and their merit for low-level counting of C-14 is evaluated. Future developments in radiometry will lie in the updating of existing systems to incorporate new technologies and the refinement of resolution and identification of extreme low-level signals. Parallel development with AMS, sharing on merit the ever widening applied C-14 research field, and enhanced interdisciplinary collaboration are foreseen as the scenario leading to the year 2000

  15. Perspectives in radiocarbon dating by radiometry

    International Nuclear Information System (INIS)

    Polach, H.A.

    1987-01-01

    Opportunities for individual contributions to the technology of radiocarbon dating over the past 40 years have been large. Meaningful developments are traced in this review of C-14 dating by gas proportional (GP) and liquid scintillation (LS) spectrometry. The performance of characteristic as well as state of the art GP and LS systems is tabulated and their merit for low-level counting of C-14 is evaluated. Future developments in radiometry will lie in the updating of existing systems to incorporate new technologies and the refinement of resolution and identification of extreme low-level signals. Parallel development with AMS, sharing on merit the ever widening applied C-14 research field, and enhanced interdisciplinary collaboration are foreseen as the scenario leading to the year 2000. (orig.)

  16. Radiocarbon positive-ion mass spectrometry

    International Nuclear Information System (INIS)

    Freeman, Stewart P.H.T.; Shanks, Richard P.; Donzel, Xavier; Gaubert, Gabriel

    2015-01-01

    Proof-of-principle of a new mass spectrometric technique for radiocarbon measurement is demonstrated. Interfering nitrogen and hydrocarbon molecules are largely eliminated in a charge-exchange cell operating on non-metallic gas. The positive-to-negative ion conversion is the reverse of that conventionally used in accelerator mass spectrometry (AMS) and is compatible with plasma ion sources that may be significantly more efficient and capable of greater output than are AMS sputter ion sources. The Nanogan electron cyclotron resonance (ECR) ion source employed exhibited no sample memory and the >50 kyrs age range of AMS was reproduced. A bespoke prototype new instrument is now required to optimise the plasma and cell physics and to realise hypothetical performance gains over AMS.

  17. Radiocarbon dating of Irish Sea sediments

    Science.gov (United States)

    Kershaw, P. J.

    1986-09-01

    Radiocarbon dating has been carried out on three cores from areas of muddy sediments in the N. Irish Sea to estimate rates of sediment accumulation. 14C age profiles of the two eastern basin cores revealed a near-constant age from the sediment surface to the base of the core (12 500±1000 years bp). The 14C age profile of the western basin core revealed a zone of apparent mixing to a depth of 55 cm, underlain by a zone of constant sedimentation rate (0·018 cm y -1) to 160 cm. These data are discussed in relation both to previously reported sedimentological studies of the area and to the authorised discharges of low-level radioactive waste from the Sellafield nuclear fuel reprocessing plant.

  18. Radiocarbon positive-ion mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, Stewart P.H.T.; Shanks, Richard P. [Scottish Universities Environmental Research Centre (SUERC), Scottish Enterprise Technology Park, East Kilbride G75 0QF (United Kingdom); Donzel, Xavier; Gaubert, Gabriel [Pantechnik S.A., 13 Rue de la Résistance, 14400 Bayeux (France)

    2015-10-15

    Proof-of-principle of a new mass spectrometric technique for radiocarbon measurement is demonstrated. Interfering nitrogen and hydrocarbon molecules are largely eliminated in a charge-exchange cell operating on non-metallic gas. The positive-to-negative ion conversion is the reverse of that conventionally used in accelerator mass spectrometry (AMS) and is compatible with plasma ion sources that may be significantly more efficient and capable of greater output than are AMS sputter ion sources. The Nanogan electron cyclotron resonance (ECR) ion source employed exhibited no sample memory and the >50 kyrs age range of AMS was reproduced. A bespoke prototype new instrument is now required to optimise the plasma and cell physics and to realise hypothetical performance gains over AMS.

  19. Radiocarbon dating with accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Blake, W. Jr.

    1985-01-01

    Radiocarbon dating by means of accelerator mass spectrometry (AMS) has two great advantages over conventional dating: 1) much smaller samples can be handled and 2) counting time is significantly shorter. Three examples are given for Holocene-age material from east-central Ellesmere Island. The results demonstrate the potential use of this technique as a powerful research tool in studies of Quaternary chronology. Individual fragments of marine shells as small as 0.1 g have been dated successfully at the IsoTrace Laboratory, University of Toronto. In the case of an aquatic moss from a lake sediment core, an increment 0.5 cm thick could be used instead of a 5 cm-thick slice, thus allowing a much more precise estimate of the onset of organic sedimentation

  20. Radiocarbon dating of soils, a review

    International Nuclear Information System (INIS)

    Scharpenseel, H.W.; Schiffmann, H.

    1977-01-01

    The application of radiocarbon dating techniques for pedological purposes is reviewed in chronological sequence of its phases of introduction. Initially dating of charcoal and buried paleosols was dominating and accompanied by few soil dating attempts of recent soil formations on the basis of extracted humic acid-C. The following controversy regarding the potentialities and limitations of recent soil dating, still being involved in the intact turnover processes of modern biodynamics, led to intensive search for the relatively oldest, most favorable C-fraction, particularly a biologically inert C-fraction of the organic C-pool. Inclusion of C-14 dating in pedogenetic working concepts required soil profile date-scanning in order to reveal the age versus depth interdependence. (orig./HK) [de

  1. Radiocarbon dating methods using benzene liquid scintillation

    International Nuclear Information System (INIS)

    Togashi, Shigeko; Matsumoto, Eiji

    1983-01-01

    The radiocarbon dating method using benzene liquid scintillation is reported in detail. The results of measurement of NBS oxalic acid agree with the recommended value, indicating that isotopic fractionation during benzene synthesis can be negligible. Ten samples which have been already measured by gas counter are dated by benzene liquid scintillation. There is no significant difference in age for the same sample between benzene liquid scintillation and gas counters. It is shown that quenching has to be corrected for the young sample. Memory effect in stainless steel reaction vessel can be removed by using an exchangeable inner vessel and by baking it in the air. Using this method, the oldest age that can be measured with 2.3 g carbon is 40,000 years B.P. (author)

  2. Radiocarbon dating in the quarternary geology and archaeology of Estonia

    International Nuclear Information System (INIS)

    Ilves, Eh.; Liiva, A.; Punning, Ya.M.

    1974-01-01

    Work of the Tartusk radiocarbon laboratory for the last 15 years is presented. Methodological problems of the radiocarbon method are discussed. The geochemistry of carbon isotopes, principles of radiocarbon dating, and areas of its application are considered. Methods of recording natural radiocarbon and materials used for radiocarbon dating are discussed. Preliminary treatment of the samples and synthesis of the radioactive carbon carrier are presented. The preparation of the counter compound in the form of a liquid scintillator from the synthesized natural radiocarbon carrier is described. The scintillator efficiencies of different scintillators are compared. Data are given on the development of criteria for selecting the photoelectron multiplier. Construction of alumina cuvettes used for scintillation counting is described. It is noted that, in the counter apparatus system, amplitude analyzers with two differential discriminators are used, which allows directing the recording of activity to two 14 C regions. The results of using the radiocarbon method for different aspects of natural science and archeology are considered. Problems of geology of the late Pleistocene and the Pre-Baltic Holocene are considered: base of the mid-Valdaisk Karukyulask interglacier, history of deterioration of the final glacial mantle, development of a drainage system and late glacier, development and paleography of the Holocene, and others. New material on the chronology of primeval cultures in the Estonia region and on growth of meteoric craters are presented

  3. Radiocarbon measurements of tree-ring samples from Japanese woods

    International Nuclear Information System (INIS)

    Ozaki, Hiromasa; Sakamoto, Minoru; Imamura, Mineo; Mitsutani, Takumi

    2008-01-01

    Since radiocarbon age is a model age based on constancy of atmospheric radiocarbon concentration and a provisional value of 5568 years for the 14 C half-life, calibration to calendar age is required for practical dating. The dataset, called IntCal, used for the calibration has been constructed by international consortium. Most parts of the IntCal have been based on the measurement of radiocarbon in dendrochronologically dated tree-ring samples from woods in Europe and North America. Regional offsets, which are designed as differences of local atmospheric radiocarbon from IntCal, have been pointed out based on recent radiocarbon measurements for tree-ring samples from a few regions. We have also measured radiocarbon of tree-ring samples from Japanese woods in order to investigate regional offsets in Japan. In this study, radiocarbon measurements for tree-ring samples from three different Japanese woods at around AD500 were carried out. Consequently, differences from IntCal04 at around AD500 were confirmed, although no systematic offset are found. However, the results obtained in this study agree with the raw data used for construction of IntCal04. This could pose a question to calculation method of IntCal04. (author)

  4. Optimization of simultaneous tritium–radiocarbon internal gas proportional counting

    Energy Technology Data Exchange (ETDEWEB)

    Bonicalzi, R.M. [Seattle Central College, 1701 Broadway, Seattle, WA 98122 (United States); Aalseth, C.E.; Day, A.R.; Hoppe, E.W. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA 99352 (United States); Mace, E.K., E-mail: Emily.Mace@pnl.gov [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA 99352 (United States); Moran, J.J.; Overman, C.T.; Panisko, M.E.; Seifert, A. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, WA 99352 (United States)

    2016-03-21

    Specific environmental applications can benefit from dual tritium and radiocarbon measurements in a single compound. Assuming typical environmental levels, it is often the low tritium activity relative to the higher radiocarbon activity that limits the dual measurement. In this paper, we explore the parameter space for a combined tritium and radiocarbon measurement using a natural methane sample mixed with an argon fill gas in low-background proportional counters of a specific design. We present an optimized methane percentage, detector fill pressure, and analysis energy windows to maximize measurement sensitivity while minimizing count time. The final optimized method uses a 9-atm fill of P35 (35% methane, 65% argon), and a tritium analysis window from 1.5 to 10.3 keV, which stops short of the tritium beta decay endpoint energy of 18.6 keV. This method optimizes tritium-counting efficiency while minimizing radiocarbon beta-decay interference. - Highlights: • Use of a single compound (methane) for dual tritium and radiocarbon measurements. • Optimized analysis window for simultaneous tritium and radiocarbon measurement. • Allows for optimization of tritium counting in the presence of radiocarbon.

  5. Optimal model of radiocarbon residence time in exchange reservoir

    International Nuclear Information System (INIS)

    Dergachev, V.A.

    1977-01-01

    Radiocarbon content variations in the earth atmosphere were studied using a mathematical model. The so-called exchange reservoir was considered consisting of layers, and the radiocarbon exchange rate at the interfaces between these layers was supposed to be constant. The process of 14 C mixing and exchange in a dynamic system is described by a system of nonhomogeneous 1st order differential equations. The model also accounts for the change in rate of radiocarbon formation in the earth atmosphere due to cosmic and geophysical effects (solar activity, solar cycle, etc.). (J.P.)

  6. Determination of the Prebomb Southern (Antarctic) Ocean Radiocarbon in Organic Matter

    International Nuclear Information System (INIS)

    Guilderson, T P

    2001-01-01

    The Southern Hemisphere is an important and unique region of the world's oceans for water-mass formation and mixing, upwelling, nutrient utilization, and carbon export. In fact, one of the primary interests of the oceanographic community is to decipher the climatic record of these processes in the source or sink terms for Southern Ocean surface waters in the CO 2 balance of the atmosphere. Current coupled ocean-atmosphere modeling efforts to trace the input of CO 2 into the ocean imply a strong sink of anthropogenic CO 2 in the southern ocean. However, because of its relative inaccessibility and the difficulty in directly measuring CO 2 fluxes in the Southern Ocean, these results are controversial at best. An accepted diagnostic of the exchange of CO 2 between the atmosphere and ocean is the prebomb distribution of radiocarbon in the ocean and its time-history since atmospheric nuclear testing. Such histories of 14 C in the surface waters of the Southern Ocean do not currently exist, primarily because there are few continuous biological archives (e.g., in corals) such as those that have been used to monitor the 14 C history of the tropics and subtropics. One of the possible long-term archives is the scallop Adamussium collbecki. Although not independently confirmed, relatively crude growth rate estimates of A. collbecki indicate that it has the potential to provide continuous 100 year time-series. We are exploring the suitability of this potential archive

  7. Research on radiocarbon calibration records, focussing on new measurements from Lake Suigetsu, Japan

    OpenAIRE

    2011-01-01

    Radiocarbon calibration is a fundamental stage of the radiocarbon dating process if meaningful calendar ages are to be derived from samples’ radiocarbon determinations. However, the present limit of direct, non-reservoir-corrected, atmospheric radiocarbon calibration is 12,550 calibrated years before present (Reimer et al. 2009), leaving approximately three quarters of the radiocarbon timescale to be necessarily calibrated via less secure marine records.The sediment profile of Lake Suigetsu, ...

  8. Assessing screening criteria for the radiocarbon dating of bone mineral

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Ricardo, E-mail: ldv1452@gmail.com [Leibniz Labor for Isotopic and Radiometric Dating, Max-Eyth-Str. 11-13, 24118 Kiel (Germany); Graduate School Human Development in Landscapes, Christian Albrecht University, Kiel (Germany); Huels, Matthias [Leibniz Labor for Isotopic and Radiometric Dating, Max-Eyth-Str. 11-13, 24118 Kiel (Germany); Nadeau, Marie-Josee; Grootes, Pieter M. [Leibniz Labor for Isotopic and Radiometric Dating, Max-Eyth-Str. 11-13, 24118 Kiel (Germany); Graduate School Human Development in Landscapes, Christian Albrecht University, Kiel (Germany); Garbe-Schoenberg, C.-Dieter [Institute of Geosciences, Marine Climate Research and ICPMS Lab, Kiel University, Ludewig-Meyn-Str. 10, D-24118 Kiel (Germany); Graduate School Human Development in Landscapes, Christian Albrecht University, Kiel (Germany); Hollund, Hege I. [Institute for Geo- and Bioarchaeology, The VU University, De Boelelaan 1085, 1081 HV Amsterdam (Netherlands); Lotnyk, Andriy [Faculty of Engineering, Institute for Material Science, Synthesis and Real Structure, Kiel University, Kaiserstr. 2, D-24143 Kiel (Germany); Leibniz Institute of Surface Modification (IOM), Permoserstr. 15, D-04318 Leipzig (Germany); Kienle, Lorenz [Faculty of Engineering, Institute for Material Science, Synthesis and Real Structure, Kiel University, Kaiserstr. 2, D-24143 Kiel (Germany); Graduate School Human Development in Landscapes, Christian Albrecht University, Kiel (Germany)

    2013-01-15

    Radiocarbon dating of bone mineral (carbonate in the apatite lattice) has been the target of sporadic research for the last 40 years. Results obtained by different decontamination protocols have, however, failed to provide a consistent agreement with reference ages. In particular, quality criteria to assess bone mineral radiocarbon dating reliability are still lacking. Systematic research was undertaken to identify optimal preservation criteria for bone mineral in archeological bones. Six human long bones, originating from a single site, were radiocarbon-dated both for collagen and apatite, with the level of agreement between the dates providing an indication of exogenous carbon contamination. Several techniques (Histology, FTIR, TEM, LA-ICP-MS) were employed to determine the preservation status of each sample. Research results highlight the importance of a micro-scale approach in establishing bone preservation, in particular the use of trace element concentration profiles demonstrated its potential use as a viable sample selection criterion for bone carbonate radiocarbon dating.

  9. Radiocarbon dating of a very large African baobab.

    Science.gov (United States)

    Patrut, Adrian; von Reden, Karl F; Lowy, Daniel A; Alberts, Andries H; Pohlman, John W; Wittmann, Rudolf; Gerlach, Dana; Xu, Li; Mitchell, Clark S

    2007-11-01

    In late 2004, Grootboom, probably the largest known African baobab (Adansonia digitata L.), collapsed unexpectedly in northeastern Namibia. Ten wood samples collected from different areas of the trunk were processed and investigated by accelerator mass spectrometry radiocarbon dating. The radiocarbon dates of three samples were greater than 1000 years BP (radiocarbon years before present, i.e., before AD 1950). The corresponding calibrated calendar age of the oldest sample was 1275 +/- 50 years, making Grootboom the oldest known angiosperm tree with reliable dating results. Variations in radiocarbon dates among the wood samples indicated that, morphologically, Grootboom was a quintuple tree, whereas genetically, it was a single individual. Ages of extreme lateral samples revealed that, over the past 500-600 years, Grootbooom had almost ceased growing, providing information about climate changes in central southern Africa. The sudden demise of Grootboom coincided with the spread of the poorly studied baobab disease, which has become epidemic in Namibia.

  10. The measure of radiocarbon in the drating of environmental samples

    International Nuclear Information System (INIS)

    Ruiz Pessenda, L.C.; Camargo, P.B. de

    1990-01-01

    An analytical system for radiocarbon dating of environmental samples (charcoal, shell, wood, etc.) using low level liquid scintillation spectrometry has been developed and optimized at Center for Nuclear Energy in Agriculture of the University of Sao Paulo. Physical and chemical pretreatment of samples to remove oils, resins, carbonates and fulvic and humic acids; the benzene synthesis of NBS oxalic acid standard, calcium carbonate P.A. and marble and the results of benzene yield; the optimization of radiocarbon counting window; the effect of scintillators PPO-POPOP and butyl PBD on the efficiency of detection and background of radiocarbon, are described. Samples of charcoal, shell and wood, previously dated at the radiocarbon laboratories of Centre des Faibles Radioactives, France, and Instituto de Geociencias of USP, are analysed for preliminary laboratory intercomparison. (author) [pt

  11. Optimization of simultaneous tritium–radiocarbon internal gas proportional counting

    Energy Technology Data Exchange (ETDEWEB)

    Bonicalzi, R. M.; Aalseth, C. E.; Day, A. R.; Hoppe, E. W.; Mace, E. K.; Moran, J. J.; Overman, C. T.; Panisko, M. E.; Seifert, A.

    2016-03-01

    Specific environmental applications can benefit from dual tritium and radiocarbon measurements in a single compound. Assuming typical environmental levels, it is often the low tritium activity relative to the higher radiocarbon activity that limits the dual measurement. In this paper, we explore the parameter space for a combined tritium and radiocarbon measurement using a methane sample mixed with an argon fill gas in low-background proportional counters of a specific design. We present an optimized methane percentage, detector fill pressure, and analysis energy windows to maximize measurement sensitivity while minimizing count time. The final optimized method uses a 9-atm fill of P35 (35% methane, 65% argon), and a tritium analysis window from 1.5 to 10.3 keV, which stops short of the tritium beta decay endpoint energy of 18.6 keV. This method optimizes tritium counting efficiency while minimizing radiocarbon beta decay interference.

  12. Radiative transfer modeling of upwelling light field in coastal waters

    International Nuclear Information System (INIS)

    Sundarabalan, Balasubramanian; Shanmugam, Palanisamy; Manjusha, Sadasivan

    2013-01-01

    Numerical simulations of the radiance distribution in coastal waters are a complex problem, but playing a growingly important role in optical oceanography and remote sensing applications. The present study attempts to modify the Inherent Optical Properties (IOPs) to allow the phase function to vary with depth, and the bottom boundary to take into account a sloping/irregular surface and the effective reflectance of the bottom material. It then uses the Hydrolight numerical model to compute Apparent Optical Properties (AOPs) for modified IOPs and bottom boundary conditions compared to the default values available in the standard Hydrolight model. The comparison of the profiles of upwelling radiance simulated with depth-dependent IOPs as well as modified bottom boundary conditions for realistic cases of coastal waters off Point Calimere of southern India shows a good match between the simulated and measured upwelling radiance profile data, whereas there is a significant drift between the upwelling radiances simulated from the standard Hydrolight model (with default values) and measured data. Further comparison for different solar zenith conditions at a coastal station indicates that the upwelling radiances simulated with the depth-dependent IOPs and modified bottom boundary conditions are in good agreement with the measured radiance profile data. This simulation captures significant changes in the upwelling radiance field influenced by the bottom boundary layer as well. These results clearly emphasize the importance of using realistic depth-dependent IOPs as well as bottom boundary conditions as input to Hydrolight in order to obtain more accurate AOPs in coastal waters. -- Highlights: ► RT model with depth-dependent IOPs and modified bottom boundary conditions provides accurate L u profiles in coastal waters. ► The modified phase function model will be useful for coastal waters. ► An inter-comparison with measured upwelling radiance gives merits of the

  13. Mass spectrometric detection of radiocarbon for dating applications

    OpenAIRE

    Synal Hans-Arno

    2013-01-01

    Radiocarbon is still the most important nuclide measured by accelerator mass spectrometry (AMS). The related capabilities for dating and tracer studies are eminent not only in archaeology but also drive important applications in the earth and environmental sciences as well as in biomedical research. So far standard mass spectrometric systems have not been capable of radiocarbon dating because of interfering molecular isobars which however can be completely eliminated in charge changing proces...

  14. Constructing deposition chronologies for peat deposits using radiocarbon dating

    Directory of Open Access Journals (Sweden)

    N. Piotrowska

    2011-06-01

    Full Text Available Radiocarbon dating is one of the main methods used to establish peat chronologies. This article reviews the basis of the method and its application to dating of peat deposits. Important steps in the radiocarbon dating procedure are described, including selection and extraction of material (and fractions for dating, chemical and physical preparation of media suitable for measurements, measurements of 14C activity or concentration, calculations, calibration of results and age-depth modelling.

  15. Mass spectrometric detection of radiocarbon for dating applications

    Energy Technology Data Exchange (ETDEWEB)

    Synal, H.-A., E-mail: synal@phys.ethz.ch [ETH Zurich, Laboratory of Ion Beam Physics, Building HPK, 8093 Zurich (Switzerland); Schulze-Koenig, T.; Seiler, M.; Suter, M.; Wacker, L. [ETH Zurich, Laboratory of Ion Beam Physics, Building HPK, 8093 Zurich (Switzerland)

    2013-01-15

    Radiocarbon is still the most important nuclide measured by accelerator mass spectrometry (AMS). The related capabilities for dating and tracer studies are eminent not only in archaeology but also drive important applications in the earth and environmental sciences as well as in biomedical research. So far, standard mass spectrometric systems have not been capable of radiocarbon dating because of interfering molecular isobars which, however, can be completely eliminated in charge changing processes at high ion beam energies (MeV) [1,2]. Here, we present a novel type mass spectrometry system for radiocarbon analyses. Radiocarbon dating was performed using 45 keV {sup 14}C ions from the ion source and a molecule dissociation unit kept at ground potential. This proof-of-principle experiment demonstrates for the first time the feasibility of mass spectrometric radiocarbon dating without an accelerator. The results obtained will be the basis of an optimized design for a radiocarbon dating instrument comparable in size, complexity and cost to standard mass spectrometers.

  16. Mass spectrometric detection of radiocarbon for dating applications

    International Nuclear Information System (INIS)

    Synal, H.-A.; Schulze-König, T.; Seiler, M.; Suter, M.; Wacker, L.

    2013-01-01

    Radiocarbon is still the most important nuclide measured by accelerator mass spectrometry (AMS). The related capabilities for dating and tracer studies are eminent not only in archaeology but also drive important applications in the earth and environmental sciences as well as in biomedical research. So far, standard mass spectrometric systems have not been capable of radiocarbon dating because of interfering molecular isobars which, however, can be completely eliminated in charge changing processes at high ion beam energies (MeV) [1,2]. Here, we present a novel type mass spectrometry system for radiocarbon analyses. Radiocarbon dating was performed using 45 keV 14 C ions from the ion source and a molecule dissociation unit kept at ground potential. This proof-of-principle experiment demonstrates for the first time the feasibility of mass spectrometric radiocarbon dating without an accelerator. The results obtained will be the basis of an optimized design for a radiocarbon dating instrument comparable in size, complexity and cost to standard mass spectrometers.

  17. Mass spectrometric detection of radiocarbon for dating applications

    Science.gov (United States)

    Synal, H.-A.; Schulze-König, T.; Seiler, M.; Suter, M.; Wacker, L.

    2013-01-01

    Radiocarbon is still the most important nuclide measured by accelerator mass spectrometry (AMS). The related capabilities for dating and tracer studies are eminent not only in archaeology but also drive important applications in the earth and environmental sciences as well as in biomedical research. So far, standard mass spectrometric systems have not been capable of radiocarbon dating because of interfering molecular isobars which, however, can be completely eliminated in charge changing processes at high ion beam energies (MeV) [1,2]. Here, we present a novel type mass spectrometry system for radiocarbon analyses. Radiocarbon dating was performed using 45 keV 14C ions from the ion source and a molecule dissociation unit kept at ground potential. This proof-of-principle experiment demonstrates for the first time the feasibility of mass spectrometric radiocarbon dating without an accelerator. The results obtained will be the basis of an optimized design for a radiocarbon dating instrument comparable in size, complexity and cost to standard mass spectrometers.

  18. Investigating bomb radiocarbon transport in the southern Pacific Ocean with otolith radiocarbon

    Science.gov (United States)

    Grammer, G. L.; Fallon, S. J.; Izzo, C.; Wood, R.; Gillanders, B. M.

    2015-08-01

    To explore the transport of carbon into water masses from the surface ocean to depths of ∼ 1000 m in the southwest Pacific Ocean, we generated time series of radiocarbon (Δ14C) from fish otoliths. Otoliths (carbonate earstones) from long-lived fish provide an indirect method to examine the "bomb pulse" of radiocarbon that originated in the 1950s and 1960s, allowing identification of changes to distributions of 14C that has entered and mixed within the ocean. We micro-sampled ocean perch (Helicolenus barathri) otoliths, collected at ∼ 400- 500 m in the Tasman Sea, to obtain measurements of Δ14C for those depths. We compared our ocean perch Δ14C series to published otolith-based marine surface water Δ14C values (Australasian snapper (Chrysophrys auratus) and nannygai (Centroberyx affinis)) and to published deep-water values (800-1000 m; orange roughy (Hoplostethus atlanticus)) from the southwest Pacific to establish a mid-water Δ14C series. The otolith bomb 14C results from these different depths were consistent with previous water mass results in the upper 1500 m of the southwest Pacific Ocean (e.g. World Ocean Circulation Experiment and Geochemical Ocean Sections Study). A comparison between the initial Δ14C bomb pulse rise at 400-500 m suggested a ventilation lag of 5 to 10 yr, whereas a comparison of the surface and depths of 800-1000 m detailed a 10 to 20 yr lag in the time history of radiocarbon invasion at this depth. Pre-bomb reservoir ages derived from otolith 14C located in Tasman Sea thermocline waters were ∼ 530 yr, while reservoir ages estimated for Tasman Antarctic intermediate water were ∼ 730 yr.

  19. Radiocarbon dispersion around Canadian nuclear facilities

    International Nuclear Information System (INIS)

    Milton, G.M.; Kramer, S.J.; Brown, R.M.; Repta, C.J.W.; King, K.J.; Rao, R.R.

    1995-01-01

    Canadian deuterium uranium (CANDU) pressurized heavy-water reactors produce 14 C by neutron activation of trace quantities of nitrogen in annular gas and reactor components ( 14 N(n,p) 14 C), and from 17 O in the heavy water moderator by ( 17 O(n,α) 14 C). The radiocarbon produced in the moderator is removed on ion exchange resins incorporated in the water purification systems; however, a much smaller gaseous portion is vented from reactor stacks at activity levels considerably below 1% of permissible derived emission limits. Early measurements of the carbon speciation indicated that >90% of the 14 C emitted was in the form of CO 2 .We conducted surveys of the atmospheric dispersion of 14 CO 2 at the Chalk River Laboratories and at the Pickering Nuclear Generating Station. We analyzed air, vegetation, soils and tree rings to add to the historical record of 14 C emissions at these sites, and to gain an understanding of the relative importance of the various carbon pools that act as sources/sinks within the total 14 C budget. Better model parameters than those currently available for calculating the dose to the critical group can be obtained in this manner. Global dose estimates may require the development of techniques for estimating emissions occurring outside the growing season. (author)

  20. Air pollutants targeted by radiocarbon dating

    International Nuclear Information System (INIS)

    Anon.

    1987-01-01

    Chemists at the Commerce Department's National Bureau of Standards (NBS) are answering questions about where certain atmospheric contaminants originate by refining a method best known for determining the age of archeological objects. Called radiocarbon dating, the method allows NBS scientists to examine air samples and determine whether contaminants come from naturally occurring or manmade sources-or a combination of the two. Making these distinctions is important to federal and state environmental agencies, which identify industrial sources of pollution for regulatory action. An overbalance of atmospheric carbon can cause a number of environmental problems. In methane's case, high levels are of concern to environmental agencies because of greenhouse properties. Methane also has been implicated as a possible contributor to changes in the ozone layer that protects the Earth from excessive ultraviolet light. Levels of methane have been increasing at an annual rate of about one percent over the last decade. This has caused concern in the environmental community, which hopes to determine just where the elevated levels are coming from. The NBS research is aimed at definitively pinpointing sources of methane and other atmospheric contaminants

  1. Radiocarbon: nature's tracer for carbonaceous pollutants

    International Nuclear Information System (INIS)

    Currie, L.A.; Klouda, G.A.; Gerlach, R.W.

    1982-01-01

    Recent developments in radiocarbon dating techniques have made it feasible to determine 14 C/ 12 C ratios in samples containing milligram or even microgram quantities of carbon. As a result, it has become practicable to apply these techniques to the study of trace gases and particles in the atmosphere, as a means of resolving anthropogenic from natural source components. Interpretation of 14 C data is straightforward: biospheric carbon (such as vegetation) is alive with a 14 C/ 12 C ratio of about 1.5 x 10 -12 , whereas fossil carbon is dead. Beyond this dichotomous classification it becomes very interesting to combine the isotopic data with concurrent chemical data, as well as spatial and temporal distributions, in order to infer the strengths of specific sources of carbonaceous pollutants. A brief review will be presented of our program on atmospheric gases and carbonaceous particles. For the latter, we have assayed individual chemical and size fractions, and samples collected in urban, rural, and remote locales. The biogenic carbon fraction - presumably from wood-burning - ranged from 10% to 100% for the urban samples analyzed

  2. Considerations on the modelling of environmental radiocarbon

    International Nuclear Information System (INIS)

    Scott, E.M.; McCartney, M.

    1991-01-01

    Modelling radionuclide transfer within the natural environment involves three general steps: model formulation, its fitting using appropriate experimental data and model validation. The last process typically involves a sensitivity analysis and is used to modify model formulation and to direct future experimental effort. A wide variety of models exists appropriate to a number of different applications. Recently, attention has been directed to the development of principles for establishing local, regional and global upper bounds to doses. Here important considerations in model choice are the spatial detail required within the model, the links between models of differing resolution and the availability of suitable experimental data. We illustrate the model-building stages and discuss the above considerations in transfer modelling using radiocarbon which is produced and released as part of the nuclear fuel cycle. Its long half life of 5730 years, its mobility in the environment and its incorporation into man via the food chain make it of some considerable radiological significance. We consider local modelling of 14 C transfer using a Gaussian plume model, while its global dispersal is modelled using a large globally-averaged compartmental model. The global analysis is used to make short term predictions of 14 C specific activities to 2050 and longer-term predictions over a period of 10,000 years. We discuss the validation of these models and attempt to quantify the sources and magnitudes of the uncertainties in the model predictions. (26 refs., 2 figs.)

  3. Upwelling regions, the most fertile of the seas' habitats, are also ...

    African Journals Online (AJOL)

    spamer

    apply to dinoflagellate bloom events in coastal upwelling systems. * Graduate School of ..... exclusive of coccolithophorids (Smayda 1997b). Group. Daily growth rates ..... route taken partly dependent on the duration of the upwelling relaxation ...

  4. Influence of monsoon upwelling on the planktonic foraminifera off Oman during Late Quaternary

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    Planktonic foraminifer abundances, fluxes, test sizes, and coiling properties are influenced in various ways by the southwest monsoon winds and associated upwelling in the western Arabian Sea. The influence of monsoon driven upwelling...

  5. Si-Traceable Scale for Measurements of Radiocarbon Concentration

    Science.gov (United States)

    Hodges, Joseph T.; Fleisher, Adam J.; Liu, Qingnan; Long, David A.

    2017-06-01

    Radiocarbon (^{14}C) dating of organic materials is based on measuring the ^{14}C/^{12}C atomic fraction relative to the nascent value that existed when the material was formed by photosynthetic conversion of carbon dioxide present in the atmosphere. This field of measurement has numerous applications including source apportionment of anthropogenic and biogenic fuels and combustion emissions, carbon cycle dynamics, archaeology, and forensics. Accelerator mass spectrometry (AMS) is the most widely used method for radiocarbon detection because it can measure extremely small amounts of radiocarbon (background of nominally 1.2 parts-per-trillion) with high relative precision (0.4 %). AMS measurements of radiocarbon are typically calibrated by reference to standard oxalic-acid (C_2H_2O_4) samples of known radiocativity that are derived from plant matter. Specifically, the internationally accepted absolute dating reference for so-called "modern-equivalent" radiocarbon is 95 % of the specific radioactivity in AD 1950 of the National Bureau of Standards (NBS) oxalic acid standard reference material and normalized to δ^{13}C_{VPDB} = 19 per mil. With this definition, a "modern-equivalent" corresponds to 1.176(70) parts-per-trillion of ^{14}C relative to total carbon content. As an alternative radiocarbon scale, we propose an SI-traceable method to determine ^{14}C absolute concentration which is based on linear Beer-Lambert-law absorption measurements of selected ^{14}C^{16}O_2 ν_3-band line areas. This approach is attractive because line intensities of chosen radiocarbon dioxide transitions can be determined by ab initio calculations with relative uncertainties below 0.5 %. This assumption is justified by the excellent agreement between theoretical values of line intensities and measurements for stable isotopologues of CO_2. In the case of cavity ring-down spectroscopy (CRDS) measurements of ^{14}C^{16}O_2 peak areas, we show that absolute, SI-traceable concentrations of

  6. Upwelling Index, 30N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  7. Upwelling Index, 42N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  8. Upwelling Index, 54N 134W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  9. Upwelling Index, 60N 149W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  10. Upwelling Index, 39N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  11. Upwelling Index, 36N 122W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  12. Upwelling Index, 24N 113W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  13. Upwelling Index, 21N 107W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  14. Upwelling Index, 48N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  15. Upwelling Index, 45N 125W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  16. Upwelling Index, 27N 116W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  17. Upwelling Index, 57N 137W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  18. Upwelling Index, 60N 146W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  19. Upwelling Index, 33N 119W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  20. Upwelling Index, 51N 131W, 6-hourly

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Upwelling index computed from 1-degree FNMOC sea level pressure for 15 locations off the North American West Coast at each 3 degrees of latitude from 21N to 60N. The...

  1. Although most of the phytoplankton of the Benguela upwelling ...

    African Journals Online (AJOL)

    spamer

    The Benguela upwelling system is subjected to blooms of harmful and toxic algae, the incidence and consequences of which are ... the coupling between this physical environment and ... Gordons Bay) and the 24 stations at which Fisheries Control Officers are located ... Oil Pollution vessels and aircraft, the Air Force.

  2. Nitrate reducing activity pervades surface waters during upwelling.

    Digital Repository Service at National Institute of Oceanography (India)

    Fernandes, S.O.; Halarnekar, R.; Malik, A.; Vijayan, V.; Varik, S.; RituKumari; Jineesh V.K.; Gauns, M.U.; Nair, S.; LokaBharathi, P.A.

    .A., Roson, G., Perez, F.F., Figueiras, F.G., Pazos, Y., 1996. Nitrogen cycling in an estuarine upwelling system, the Ria de Arousa (NW Spain). Short-time-scale patterns of hydrodynamic and biogeochemical circulation. Mar. Ecol. Prog. Ser. 135, 259...

  3. Joint effect of freshwater plume and coastal upwelling on phytoplankton growth off the Changjiang River

    Science.gov (United States)

    Tseng, Y.-F.; Lin, J.; Dai, M.; Kao, S.-J.

    2014-01-01

    The Changjiang (Yangtze) River discharges vast amount of unbalanced nutrients (dissolved inorganic nitrogen and phosphorus with N / P ratio > 80 in general) into the East China Sea in summer. To study nutrient dynamics and P-stress potential for phytoplankton, a cruise was conducted in the Changjiang plume during summer 2011. With 3-D observations of nutrients, chlorophyll a (Chl a), and bulk alkaline phosphatase activity (APA), we concluded that the Changjiang Diluted Water and coastal upwelling significantly influenced the horizontal and vertical heterogeneities of phytoplankton P deficiency in the Changjiang plume. Allochthonous APA was detected at nutrient-enriched freshwater end. Excessive N (~ 10 to 112 μM) was observed throughout the entire plume surface. In the plume fringe featuring stratification and excess N, diapycnal phosphate supply was blocked and phytoplankton APA was stimulated for growth. We observed an upwelling just attaching to the turbidity front at seaward side where Chl a peaked yet much less APA was detected. An external phosphate supply from subsurface, which promoted phytoplankton growth but inhibited APA, was suggested to be sourced from the Nearshore Kuroshio Branch Current. In the so hydrographically complicated Changjiang plume, phosphate supply instead of its concentration may be more important in determining the expression of APA. Meanwhile, allochthonous APA may also alter the usefulness of APA as a P-stress indicator.

  4. Linking the Modern and Recent Record of Cabo Frio Upwelling with Local Climate and Biogeochemical Processes in Hypersaline Coastal Lagoons, Região dos Lagos, Rio de Janeiro, Brazil

    Science.gov (United States)

    McKenzie, J. A.; Nascimento, G. S.; Albuquerque, A. L.; Belem, A. L.; Carreira, R.; Eglinton, T. I.; Vasconcelos, C.

    2015-12-01

    A unique marine and lagoonal system along the coast east of Rio de Janeiro is being investigated to understand the impact of climatic variability on the South Atlantic carbon cycle and biomineralisation processes involved in carbonate precipitation in the hypersaline coastal lagoons. The region is dominated by a semi-arid microclimate attributed to the local coastal upwelling phenomenon near Cabo Frio. The intensity of the upwelling affects the hydrology of the annual water and biogeochemical cycles in the lagoons, as well as biogeochemical signals of environmental change recorded in both onshore and offshore sediments. Preliminary results of δ18O and δD values of water samples collected monthly in Lagoa Vermelha and Brejo do Espinho from 2011 to 2014 show lower values for waters corresponding to the wet season, reflecting increased input of meteoric water. The higher values for waters collected during the dry season reflect the greater amount of evaporation with increased seasonal aridity. Radiocarbon dating of Holocene marine and lagoonal cores indicates that Mg-carbonate precipitation in the lagoons is associated with high evaporation. Modern field observations for the last 3 years suggest that the amount of carbonate precipitation is correlated with evaporitic conditions associated with the upwelling phenomenon. A calibration study of hydrogen isotopic fractionation in the modern lagoons is underway to define a relationship between δDlipid of suspended particles and δDwater of associated water. This isotopic relationship will be applied to material obtained in cores from the lagoons. Offshore cores will be studied using well-tested paleotemperature proxies to evaluate the intensity of the upwelling during the Holocene. In summary, linking the coastal upwelling with the lagoonal hydrology has the potential to furnish important insights about the relationship between the local climate and paleoceanographic circulation associated with the regional carbon cycle.

  5. On an upwelling front, propagation of upwelling and vertical velocity in the eastern Arabian sea during monsoon, 1987

    Digital Repository Service at National Institute of Oceanography (India)

    Antony, M.K.; Unnikrishnan, A.S.

    A coastal upwelling front parallel to the coast and identifiable upto a depth of 75 m was observed between 12.5 and 16 degrees N along the eastern Arabian Sea in September, 1987 from closely spaced digital BT data. With a north-south slope...

  6. Studies on the radiocarbon sample from the shroud of turin

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Raymond N. [Los Alamos National Laboratory, University of California, 1961 Cumbres Patio, Los Alamos, NM 87544 (United States)]. E-mail: rnrogers@att.net

    2005-01-20

    In 1988, radiocarbon laboratories at Arizona, Cambridge, and Zurich determined the age of a sample from the Shroud of Turin. They reported that the date of the cloth's production lay between A.D. 1260 and 1390 with 95% confidence. This came as a surprise in view of the technology used to produce the cloth, its chemical composition, and the lack of vanillin in its lignin. The results prompted questions about the validity of the sample. Preliminary estimates of the kinetics constants for the loss of vanillin from lignin indicate a much older age for the cloth than the radiocarbon analyses. The radiocarbon sampling area is uniquely coated with a yellow-brown plant gum containing dye lakes. Pyrolysis-mass-spectrometry results from the sample area coupled with microscopic and microchemical observations prove that the radiocarbon sample was not part of the original cloth of the Shroud of Turin. The radiocarbon date was thus not valid for determining the true age of the shroud.

  7. Gas chromatographic isolation technique for compound-specific radiocarbon analysis

    International Nuclear Information System (INIS)

    Uchida, M.; Kumamoto, Y.; Shibata, Y.; Yoneda, M.; Morita, M.; Kawamura, K.

    2002-01-01

    Full text: We present here a gas chromatographic isolation technique for the compound-specific radiocarbon analysis of biomarkers from the marine sediments. The biomarkers of fatty acids, hydrocarbon and sterols were isolated with enough amount for radiocarbon analysis using a preparative capillary gas chromatograph (PCGC) system. The PCGC systems used here is composed of an HP 6890 GC with FID, a cooled injection system (CIS, Gerstel, Germany), a zero-dead-volume effluent splitter, and a cryogenic preparative collection device (PFC, Gerstel). For AMS analysis, we need to separate and recover sufficient quantity of target individual compounds (>50 μgC). Yields of target compounds from C 14 n-alkanes to C 40 to C 30 n-alkanes and approximately that of 80% for higher molecular weights compounds more than C 30 n-alkanes. Compound specific radiocarbon analysis of organic compounds, as well as compound-specific stable isotope analysis, provide valuable information on the origins and carbon cycling in marine system. Above PCGC conditions, we applied compound-specific radiocarbon analysis to the marine sediments from western north Pacific, which showed the possibility of a useful chronology tool for estimating the age of sediment using organic matter in paleoceanographic study, in the area where enough amounts of planktonic foraminifera for radiocarbon analysis by accelerator mass spectrometry (AMS) are difficult to obtain due to dissolution of calcium carbonate. (author)

  8. Studies on the radiocarbon sample from the shroud of turin

    International Nuclear Information System (INIS)

    Rogers, Raymond N.

    2005-01-01

    In 1988, radiocarbon laboratories at Arizona, Cambridge, and Zurich determined the age of a sample from the Shroud of Turin. They reported that the date of the cloth's production lay between A.D. 1260 and 1390 with 95% confidence. This came as a surprise in view of the technology used to produce the cloth, its chemical composition, and the lack of vanillin in its lignin. The results prompted questions about the validity of the sample. Preliminary estimates of the kinetics constants for the loss of vanillin from lignin indicate a much older age for the cloth than the radiocarbon analyses. The radiocarbon sampling area is uniquely coated with a yellow-brown plant gum containing dye lakes. Pyrolysis-mass-spectrometry results from the sample area coupled with microscopic and microchemical observations prove that the radiocarbon sample was not part of the original cloth of the Shroud of Turin. The radiocarbon date was thus not valid for determining the true age of the shroud

  9. The Worldwide Marine Radiocarbon Reservoir Effect: Definitions, Mechanisms, and Prospects

    Science.gov (United States)

    Alves, Eduardo Q.; Macario, Kita; Ascough, Philippa; Bronk Ramsey, Christopher

    2018-03-01

    When a carbon reservoir has a lower radiocarbon content than the atmosphere, this is referred to as a reservoir effect. This is expressed as an offset between the radiocarbon ages of samples from the two reservoirs at a single point in time. The marine reservoir effect (MRE) has been a major concern in the radiocarbon community, as it introduces an additional source of error that is often difficult to accurately quantify. For this reason, researchers are often reluctant to date marine material where they have another option. The influence of this phenomenon makes the study of the MRE important for a broad range of applications. The advent of Accelerator Mass Spectrometry (AMS) has reduced sample size requirements and increased measurement precision, in turn increasing the number of studies seeking to measure marine samples. These studies rely on overcoming the influence of the MRE on marine radiocarbon dates through the worldwide quantification of the local parameter ΔR, that is, the local variation from the global average MRE. Furthermore, the strong dependence on ocean dynamics makes the MRE a useful indicator for changes in oceanic circulation, carbon exchange between reservoirs, and the fate of atmospheric CO2, all of which impact Earth's climate. This article explores data from the Marine Reservoir Database and reviews the place of natural radiocarbon in oceanic records, focusing on key questions (e.g., changes in ocean dynamics) that have been answered by MRE studies and on their application to different subjects.

  10. Rate of radiocarbon retention onto calcite by isotope exchange

    Energy Technology Data Exchange (ETDEWEB)

    Lempinen, Janne; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry

    2016-11-01

    Radiocarbon ({sup 14}C) is a top priority class radionuclide associated with the long-term safety of spent nuclear fuel disposal. Dissolved inorganic radiocarbon can be retained in bedrock via isotope exchange with calcite (CaCO{sub 3}) at solubility equilibrium with groundwater. In the present study, the rate of the isotope exchange process was investigated on synthetic calcite using batch experiments. Experiments were performed in solutions with a calcium concentration of 0.0002-0.1 M, including two synthetic reference groundwaters. The radiocarbon activity in the solutions decreased exponentially as a function of time, thus following first-order kinetics. The rate of isotope exchange was quantified from an exponential fit to the activity data over time. The rate of radiocarbon retention increased as a function of the calcium activity. The isotope exchange half-life was only 4.3 days at calcium ion activities over 0.01. This half-life is very much shorter than the half-life of {sup 14}C or the time scale of groundwater movements; consequently calcite can effectively retain radiocarbon from brackish and saline groundwaters.

  11. Rate of radiocarbon retention onto calcite by isotope exchange

    International Nuclear Information System (INIS)

    Lempinen, Janne; Lehto, Jukka

    2016-01-01

    Radiocarbon ( 14 C) is a top priority class radionuclide associated with the long-term safety of spent nuclear fuel disposal. Dissolved inorganic radiocarbon can be retained in bedrock via isotope exchange with calcite (CaCO 3 ) at solubility equilibrium with groundwater. In the present study, the rate of the isotope exchange process was investigated on synthetic calcite using batch experiments. Experiments were performed in solutions with a calcium concentration of 0.0002-0.1 M, including two synthetic reference groundwaters. The radiocarbon activity in the solutions decreased exponentially as a function of time, thus following first-order kinetics. The rate of isotope exchange was quantified from an exponential fit to the activity data over time. The rate of radiocarbon retention increased as a function of the calcium activity. The isotope exchange half-life was only 4.3 days at calcium ion activities over 0.01. This half-life is very much shorter than the half-life of 14 C or the time scale of groundwater movements; consequently calcite can effectively retain radiocarbon from brackish and saline groundwaters.

  12. Variability of 14C reservoir age and air-sea flux of CO2 in the Peru-Chile upwelling region during the past 12,000 years

    Science.gov (United States)

    Carré, Matthieu; Jackson, Donald; Maldonado, Antonio; Chase, Brian M.; Sachs, Julian P.

    2016-01-01

    The variability of radiocarbon marine reservoir age through time and space limits the accuracy of chronologies in marine paleo-environmental archives. We report here new radiocarbon reservoir ages (ΔR) from the central coast of Chile ( 32°S) for the Holocene period and compare these values to existing reservoir age reconstructions from southern Peru and northern Chile. Late Holocene ΔR values show little variability from central Chile to Peru. Prior to 6000 cal yr BP, however, ΔR values were markedly increased in southern Peru and northern Chile, while similar or slightly lower-than-modern ΔR values were observed in central Chile. This extended dataset suggests that the early Holocene was characterized by a substantial increase in the latitudinal gradient of marine reservoir age between central and northern Chile. This change in the marine reservoir ages indicates that the early Holocene air-sea flux of CO2 could have been up to five times more intense than in the late Holocene in the Peruvian upwelling, while slightly reduced in central Chile. Our results show that oceanic circulation changes in the Humboldt system during the Holocene have substantially modified the air-sea carbon flux in this region.

  13. Dinoflagellate blooms in upwelling systems: Seeding, variability, and contrasts with diatom bloom behaviour

    Science.gov (United States)

    Smayda, T. J.; Trainer, V. L.

    2010-04-01

    The influence of diatom bloom behaviour, dinoflagellate life cycles, propagule type and upwelling bloom cycles on the seeding of dinoflagellate blooms in eastern boundary current upwelling systems is evaluated. Winter-spring diatom bloom behaviour is contrasted with upwelling bloom behaviour because their phenology impacts dinoflagellate blooms. The winter-spring diatom bloom is usually sustained, whereas the classical upwelling diatom bloom occurs as a series of separate, recurrent mini-blooms intercalated by upwelling-relaxation periods, during which dinoflagellates often bloom. Four sequential wind-regulated phases characterize upwelling cycles, with each phase having different effects on diatom and dinoflagellate bloom behaviour: bloom “spin up”, bloom maximum, bloom “spin down”, and upwelling relaxation. The spin up - bloom maximum is the period of heightened diatom growth; the spin down - upwelling-relaxation phases are the periods when dinoflagellates often bloom. The duration, intensity and ratio of the upwelling and relaxation periods making up upwelling cycles determine the potential for dinoflagellate blooms to develop within a given upwelling cycle and prior to the subsequent “spin up” of upwelling that favours diatom blooms. Upwelling diatoms and meroplanktonic dinoflagellates have three types of propagules available to seed blooms: vegetative cells, resting cells and resting cysts. However, most upwelling dinoflagellates are holoplanktonic, which indicates that the capacity to form resting cysts is not an absolute requirement for growth and survival in upwelling systems. The long-term (decadal) gaps in bloom behaviour of Gymnodinium catenatum and Lingulodinium polyedrum, and the unpredictable bloom behaviour of dinoflagellates generally, are examined from the perspective of seeding strategies. Mismatches between observed and expected in situ bloom behaviour and resting cyst dynamics are common among upwelling dinoflagellates. This

  14. Fire and Fish: Using Radiocarbon And Stratigraphy To Discern The Impact Of Wildfire On Fish Metapopulations

    Science.gov (United States)

    Schaffrath, K. R.; Finch, C.; Belmont, P.; Budy, P.

    2015-12-01

    Wildfires have profound and variable impacts on erosion, channel morphology, and aquatic habitat. Previous research has quantified post-fire geomorphic response on event and millennial timescales. While these studies have informed our understanding of post-fire geomorphic response during the Holocene, we have yet to fully understand the variability of post-wildfire geomorphic response and how it might change in response to changing climate. Response of aquatic biota is just as variable as post-wildfire response yet we know very little about effects on metapopulations and how management decisions affect aquatic populations. Barriers to movement are installed to isolate native fish populations and prescribed fire and thinning are used to try to reduce future wildfire severity and extent. In order to improve understanding of the implications of management decisions, we evaluated geomorphic response and synchronicity of wildfires over the Holocene relative to the impact to the metapopulation of Bonneville cutthroat trout from a recent wildfire. The Twitchell Canyon fire burned 45,000 acres near Beaver, UT in July 2010. Over 30% of the area burned at high severity, which included two major headwater streams that sustained a trout population. In summer 2011, monsoonal thunderstorms caused massive debris flows and sheetflow erosion that altered channel morphology and aquatic habitat in the burned area. A previously robust, non-native trout fishery was nearly extirpated as a result of the geomorphic response to the wildfire. We used radiocarbon dating of burned material to determine how often headwater streams burned synchronously over the Holocene. Radiocarbon dates are associated with field observations of stratigraphy in order to infer geomorphic response to historic wildfires. Thirty samples were collected from sediment layers in 10 alluvial fans distributed among three watersheds (two burned and one unburned in the 2010 fire). Preliminary results suggest that we

  15. a Numerical Study of Basic Coastal Upwelling Processes.

    Science.gov (United States)

    Li, Zhihong

    Available from UMI in association with The British Library. Two-dimensional (2-D) and three-dimensional (3 -D) numerical models with a second order turbulence closure are developed for the study of coastal upwelling processes. A logarithmic coordinate system is introduced to obtain increased resolution in the regions near the surface and bottom where high velocity shear occurs and in the upwelling zone where its width is confined to the coast. In the experiments performed in the 2-D model an ocean initially at rest is driven by a spatially uniform alongshore wind-stress. There is a development of an offshore flow in the surface layer and an onshore flow below the surface layer. In the wind-stress direction there is a development of a coastal surface jet. The neglect of the alongshore pressure gradient leads to the intensification of the jet, and the concentration of the onshore flow in an over-developed Ekman layer yielding an unrealistic deepening of a bottom mixed layer. When bathymetric variations are introduced, some modifications in the dynamics of upwelling are observed. On the shelf region there is another upwelling zone and isotherms are interested with the bottom topography. When an alongshore pressure gradient is added externally into the model, the strength of the coastal jet decreases and a coastal undercurrent exists at greater depth. In addition the return onshore flow is largely independent of depth and the deepening of the bottom mixed layer disappears. In the experiments performed in the 3-D model a wind-stress with limited domain is used. Coastally trapped waves are generated and propagate along the coastline leading to a development of an alongshore pressure gradient, which has a significant effect on upwelling. The evolution of the alongshore flow, vertical velocity and the temperature is determined by both remote and local wind due to the propagation of waves. As the integration proceeds, the flow pattern becomes remarkably 3-dimensional

  16. Radiocarbon dates from the Oxford AMS system: Archaeometry datelist 17

    International Nuclear Information System (INIS)

    Hedges, R.E.M.; Housley, R.A.; Ramsey, C.B.; Van Klinken, G.J.

    1993-01-01

    This seventeenth list of accelerator dates consists mainly of material dated since the beginning of 1991, but includes a number of measurements made earlier in the dating programme. In accordance with international radiocarbon convention all dates are expressed in radiocarbon years before AD 1950 (years BP) using the half-life of 5568 years, this convention having been reaffirmed at the Trondheim Radiocarbon Conference 1985. Errors are quoted as one standard deviation and are based on an assessment of all the contributions to the error in the laboratory isotope ratio measurement. Natural fractionation of carbon isotopes is accounted for by estimating δ 13 C values except for more recent dates where δ 13 C have been measured relative to PDB (only to within ± 0.5-1.0%). All combining procedures and significance tests are based on Ward and Wilson (1978). Comments composed by the Laboratory on the basis of information supplied by submitters are given without attribution. (author)

  17. Precision radiocarbon dating of a Late Holocene vegetation history

    International Nuclear Information System (INIS)

    Prior, C.A.; Chester, P.I.

    2001-01-01

    The purpose of this research is to precisely date vegetation changes associated with early human presence in the Hawkes Bay region. A sequence of AMS radiocarbon ages was obtained using a new technique developed at Rafter Radiocarbon Laboratory. A density separation method was used to concentrate pollen and spores extracted from unconsolidated lake sediments from a small-enclosed lake in coastal foothills of southern Hawkes Bay. Radiocarbon measurements were made on fractions of concentrated pollen, separated from associated organic debris. These ages directly date vegetation communities used to reconstruct the vegetation history of the region. This technique results in more accurate dating of Late Holocene vegetation changes interpreted from palynological analyses than techniques formerly used. Precision dating of palynological studies of New Zealand prehistory and history is necessary for correlation of vegetation changes to cultural changes because of the short time span of human occupation of New Zealand. (author). 35 refs., 3 figs., 1 tab

  18. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-02-28

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from jets characteristic of pulse jet mixers (PJMs) has been analyzed, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell break through? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored.

  19. Coastal upwelling in the Gelendzhik area of the Black Sea: Effect of wind and dynamics

    Science.gov (United States)

    Silvestrova, K. P.; Zatsepin, A. G.; Myslenkov, S. A.

    2017-07-01

    Long series data of a thermistor chain in the Black Sea coastal zone near Gelendzhik were analyzed. A thermistor chain installed 1 km offshore and at a depth of 22 m. There are full and incomplete upwelling events observed. The study of upwelling genesis based on: wind speed data from the NCEP/CFSR reanalysis and Gelendzhik weather station, velocity and direction of coastal currents measured by ADCP profiler moored on the bottom near the thermistor chain. Over the whole observation period (warm seasons of 2013-2015), more than 40 events of upwelling were registered four of them were full upwellings, when presence of under-thermocline water was observed near the sea surface. For every upwelling event, conditions prior to the changes in thermic structure, were analyzed. It is found that full upwelling generally occur under synergistic wind and current forcing. Fairly strong forcing of one of these factors is sufficient for partial upwelling to occur.

  20. Precision and reproducibility in AMS radiocarbon measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Hotchkis, M A; Fink, D; Hua, Q; Jacobsen, G E; Lawson, E M; Smith, A M; Tuniz, C [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1997-12-31

    Accelerator Mass Spectrometry (AMS) is a technique by which rare radioisotopes such as {sup 14}C can be measured at environmental levels with high efficiency. Instead of detecting radioactivity, which is very weak for long-lived environmental radioisotopes, atoms are counted directly. The sample is placed in an ion source, from which a negative ion beam of the atoms of interest is extracted, mass analysed, and injected into a tandem accelerator. After stripping to positive charge states in the accelerator HV terminal, the ions are further accelerated, analysed with magnetic and electrostatic devices and counted in a detector. An isotopic ratio is derived from the number of radioisotope atoms counted in a given time and the beam current of a stable isotope of the same element, measured after the accelerator. For radiocarbon, {sup 14}C/{sup 13}C ratios are usually measured, and the ratio of an unknown sample is compared to that of a standard. The achievable precision for such ratio measurements is limited primarily by {sup 14}C counting statistics and also by a variety of factors related to accelerator and ion source stability. At the ANTARES AMS facility at Lucas Heights Research Laboratories we are currently able to measure {sup 14}C with 0.5% precision. In the two years since becoming operational, more than 1000 {sup 14}C samples have been measured. Recent improvements in precision for {sup 14}C have been achieved with the commissioning of a 59 sample ion source. The measurement system, from sample changing to data acquisition, is under common computer control. These developments have allowed a new regime of automated multi-sample processing which has impacted both on the system throughput and the measurement precision. We have developed data evaluation methods at ANTARES which cross-check the self-consistency of the statistical analysis of our data. Rigorous data evaluation is invaluable in assessing the true reproducibility of the measurement system and aids in

  1. Precision and reproducibility in AMS radiocarbon measurements.

    Energy Technology Data Exchange (ETDEWEB)

    Hotchkis, M.A.; Fink, D.; Hua, Q.; Jacobsen, G.E.; Lawson, E. M.; Smith, A.M.; Tuniz, C. [Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW (Australia)

    1996-12-31

    Accelerator Mass Spectrometry (AMS) is a technique by which rare radioisotopes such as {sup 14}C can be measured at environmental levels with high efficiency. Instead of detecting radioactivity, which is very weak for long-lived environmental radioisotopes, atoms are counted directly. The sample is placed in an ion source, from which a negative ion beam of the atoms of interest is extracted, mass analysed, and injected into a tandem accelerator. After stripping to positive charge states in the accelerator HV terminal, the ions are further accelerated, analysed with magnetic and electrostatic devices and counted in a detector. An isotopic ratio is derived from the number of radioisotope atoms counted in a given time and the beam current of a stable isotope of the same element, measured after the accelerator. For radiocarbon, {sup 14}C/{sup 13}C ratios are usually measured, and the ratio of an unknown sample is compared to that of a standard. The achievable precision for such ratio measurements is limited primarily by {sup 14}C counting statistics and also by a variety of factors related to accelerator and ion source stability. At the ANTARES AMS facility at Lucas Heights Research Laboratories we are currently able to measure {sup 14}C with 0.5% precision. In the two years since becoming operational, more than 1000 {sup 14}C samples have been measured. Recent improvements in precision for {sup 14}C have been achieved with the commissioning of a 59 sample ion source. The measurement system, from sample changing to data acquisition, is under common computer control. These developments have allowed a new regime of automated multi-sample processing which has impacted both on the system throughput and the measurement precision. We have developed data evaluation methods at ANTARES which cross-check the self-consistency of the statistical analysis of our data. Rigorous data evaluation is invaluable in assessing the true reproducibility of the measurement system and aids in

  2. Microgram level radiocarbon (14C) determination on carbonaceous particles in ice

    DEFF Research Database (Denmark)

    Jenk, Theo Manuel; Szidat, S.; Schwikowski, M.

    2007-01-01

    Accelerator mass spectrometry; Organic carbon; Elemental carbon; Radiocarbon dating; Ice cores; Paleo-record Udgivelsesdato: June......Accelerator mass spectrometry; Organic carbon; Elemental carbon; Radiocarbon dating; Ice cores; Paleo-record Udgivelsesdato: June...

  3. High-precision radiocarbon chronometry of ancient Egypt, and comparisons with Nubia, Palestine and Mesopotamia

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, F A; Robinson, S W

    1987-03-01

    The use of radiocarbon age measurements in historical chronology is examined for ancient Egypt and neighbouring regions. A methodology is presented aimed at improving the reliability and precision of radiocarbon age determinations.

  4. Urvina Bay, Galapagos Coral Radiocarbon (delta 14C) Data for 1956 to 1982

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Urvina Bay coral radiocarbon (14C) timeseries. (90 deg W, 0.5 deg S) Coral radiocarbon (Delta-14C) on untreated, low-speed drilled samples. Precision is +/- 4 per...

  5. Radiocarbon-dates of snow petrel regurgitations can reveal exposure periods for nunataks in Antarctica

    CSIR Research Space (South Africa)

    Ryan, PG

    1992-11-01

    Full Text Available There are several problems associated with determining radiocarbon dates, particularly for organic material from Antarctica. However, this study attempts to find accurate measure of the length of time these radiocarbon dates have been established...

  6. Radiocarbon dates to access the origin of the ice man

    Energy Technology Data Exchange (ETDEWEB)

    Niklaus, R. [Institute of Particle Physics, ETH Zurich, Hongerberg (Switzerland)]|[Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience; Bonani, G. [Institute of Particle Physics, ETH Zurich, Hongerberg (Switzerland); Prinoth-Fornwagner, R. [Innsbruck Univ. (Austria)

    1996-12-31

    Different samples from the Late and Final Neolithic in Northern Italy were radiocarbon dated at the AMS Facility in Zurich, Switzerland in order to determine the origin of the Ice Man from the Hauslabjoch. The cultural classification was obtained on the basis of topological studies of the cooper axe and of the flint dagger as well as studies of artefact materials (the flint or the wood of a composite arrow), while the chronological classification of the Ice Man was obtained with the help of new and old radiocarbon dates. 9 refs., 1 tab., 2 figs.

  7. Radiocarbon dates to access the origin of the ice man

    Energy Technology Data Exchange (ETDEWEB)

    Niklaus, R [Institute of Particle Physics, ETH Zurich, Hongerberg (Switzerland); [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience; Bonani, G [Institute of Particle Physics, ETH Zurich, Hongerberg (Switzerland); Prinoth-Fornwagner, R [Innsbruck Univ. (Austria)

    1997-12-31

    Different samples from the Late and Final Neolithic in Northern Italy were radiocarbon dated at the AMS Facility in Zurich, Switzerland in order to determine the origin of the Ice Man from the Hauslabjoch. The cultural classification was obtained on the basis of topological studies of the cooper axe and of the flint dagger as well as studies of artefact materials (the flint or the wood of a composite arrow), while the chronological classification of the Ice Man was obtained with the help of new and old radiocarbon dates. 9 refs., 1 tab., 2 figs.

  8. Late-Glacial radiocarbon- and palynostratigraphy in the Swiss Plateau

    International Nuclear Information System (INIS)

    Ammann, B.; Lotter, A.F.

    1989-01-01

    A detailed Late-Glacial radiocarbon stratigraphy for the Swiss Plateau has been established on the basis of over 90 accelerator 14 C dates on terrestrial plant macrofossils. A comparison of the radiocarbon ages derived from terrestrial, telmatic and limnic material at different sites on the Swiss Plateau yields a proposal for modifying the zonation system of Welten for the Late-Glacial. By retaining the limits of chronozones and by refining the palynostratigraphic criteria for the limits of biozones, a separation between chrono- and biozonation at the beginning of the Boelling and the Younger Dryas becomes obvious. 54 refs

  9. Standard reference materials analysis for MINT Radiocarbon Laboratory

    International Nuclear Information System (INIS)

    Noraishah Othman; Kamisah Alias; Nasasni Nasrul

    2004-01-01

    As a follow-up to the setting up of the MINT Radiocarbon Dating facility. an exercise on the IAEA standard reference materials was carried out. Radiocarbon laboratories frequently used these 8 natural samples to verify their systems. The materials were either pretreated or analysed directly to determine the activity of 14 C isotopes of the five samples expressed in % Modern (pMC) terms and to make recommendations on further use of these materials. We present the results of the five materials and discuss the analyses that were undertaken. (Author)

  10. Radiocarbon dating of mortars from ancient Greek palaces

    International Nuclear Information System (INIS)

    Zouridakis, N.; Saliege, J.F.; Person, A.; Filippakis, S.E.

    1987-01-01

    The study deals with radiocarbon dating of lime mortars which were used as supports for Mycenaean and Minoan paintings. The 14 C dates are, on the whole, compatible with the historical data, and thus show that a large proportion of the Mycenaean surficial coatings can be dated by the radiocarbon method. However, in order to determine the age of the mortars accurately, it is necessary to evaluate the amount of sedimentary carbonate which may have been added to them. It is shown here that the oxygen and carbon isotope compositions of lime mortars are significant indicators that such a mixing actually took place. (author)

  11. Radiocarbon dating of mortars from ancient Greek palaces

    Energy Technology Data Exchange (ETDEWEB)

    Zouridakis, N.; Saliege, J.F.; Person, A.; Filippakis, S.E.

    1987-02-01

    The study deals with radiocarbon dating of lime mortars which were used as supports for Mycenaean and Minoan paintings. The /sup 14/C dates are, on the whole, compatible with the historical data, and thus show that a large proportion of the Mycenaean surficial coatings can be dated by the radiocarbon method. However, in order to determine the age of the mortars accurately, it is necessary to evaluate the amount of sedimentary carbonate which may have been added to them. It is shown here that the oxygen and carbon isotope compositions of lime mortars are significant indicators that such a mixing actually took place.

  12. Bomb radiocarbon in metabolically inert tissues from terrestrial and marine mammals

    International Nuclear Information System (INIS)

    Bada, J.L.; Vrolijk, C.D.; Brown, S.; Druffel, E.R.M.; Hedges, R.E.M.

    1987-01-01

    We report here radiocarbon measurements of monkey eye lens nucleus proteins and a narwhal tusk, biological tissues which have sampled the bomb radiocarbon signal in different ways. The results confirm the metabolic inertness of eye lens nucleus proteins and demonstrate the feasibility of measuring radiocarbon in small samples of biological tissue using accelerator mass spectrometry (AMS). The narwhal tusk provides a unique record of the radiocarbon activity in Arctic Ocean waters over most of the 20th century

  13. Nutrient pumping by submesoscale circulations in the mauritanian upwelling system

    Science.gov (United States)

    Hosegood, P. J.; Nightingale, P. D.; Rees, A. P.; Widdicombe, C. E.; Woodward, E. M. S.; Clark, D. R.; Torres, R. J.

    2017-12-01

    Observations made within a cold filament in the Mauritanian upwelling system demonstrate that intense submesoscale circulations at the peripheral edges of the filament are likely responsible for anomalously high levels of observed primary productivity by resupplying nutrients to the euphotic zone. Measurements made on the shelf within the recently upwelled water reveal that primary production (PP) of 8.2 gC/m-2 day-1 was supported by nitrate concentrations (NC) of 8 mmol m-3. Towards the front that defined the edge of the filament containing the upwelled water as it was transported offshore, PP dropped to 1.6 gC m-2 day-1 whilst NC dropped to 5.5 mmol m-3. Thus, whilst the observed nutrients on the shelf accounted for 90% of new production, this value dropped to ∼60% near the filament's front after accounting for vertical turbulent fluxes and Ekman pumping. We demonstrate that the N15 was likely to have been supplied at the front by submesoscale circulations that were directly measured as intense vertical velocities ⩾100 m day-1 by a drifting acoustic Doppler current profiler that crossed a submesoscale surface temperature front. At the same time, a recently released tracer was subducted out of the mixed layer within 24 h of release, providing direct evidence that the frontal circulations were capable of accessing the reservoir of nutrients beneath the pycnocline. The susceptibility of the filament edge to submesoscale instabilities was demonstrated by O(1) Rossby numbers at horizontal scales of 1-10 km. The frontal circulations are consistent with instabilities arising from a wind-driven nonlinear Ekman buoyancy flux generated by the persistent northerly wind stress that has a down-front component at the northern edge of the inshore section of the filament. The prevalence of submesoscale instabilities and their associated vertical circulations are proposed to be a key mechanism operating at sub-grid scales and sustaining new production throughout the upwelling

  14. Meteorological constraints on oceanic halocarbons above the Peruvian Upwelling

    OpenAIRE

    S. Fuhlbrügge; B. Quack; E. Atlas; A. Fiehn; H. Hepach; K. Krüger

    2015-01-01

    Halogenated very short lived substances (VSLS) are naturally produced in the ocean and emitted to the atmosphere. Recently, oceanic upwelling regions in the tropical East Atlantic were identified as strong sources of brominated halocarbons to the atmosphere. During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (M...

  15. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    OpenAIRE

    Fuhlbrügge, Steffen; Quack, Birgit; Atlas, Elliot; Fiehn, Alina; Hepach, Helmke; Krüger, Kirstin

    2016-01-01

    During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs) – bromoform, dibromomethane and methyl iodide – together with high-resolution meteorological measurements, Lagrangian transport and source–loss calculations. ...

  16. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    Directory of Open Access Journals (Sweden)

    S. Fuhlbrügge

    2016-09-01

    Full Text Available During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs – bromoform, dibromomethane and methyl iodide – together with high-resolution meteorological measurements, Lagrangian transport and source–loss calculations. Oceanic emissions of bromoform and dibromomethane were relatively low compared to other upwelling regions, while those for methyl iodide were very high. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting as strong barriers for convection and vertical transport of trace gases in this region. Observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height correlated well during the cruise. We used a simple source–loss estimate to quantify the contribution of oceanic emissions along the cruise track to the observed atmospheric concentrations. This analysis showed that averaged, instantaneous emissions could not support the observed atmospheric mixing ratios of VSLSs and that the marine background abundances below the trade inversion were significantly influenced by advection of regional sources. Adding to this background, the observed maximum emissions of halocarbons in the coastal upwelling could explain the high atmospheric VSLS concentrations in combination with their accumulation under the distinct MABL and trade inversions. Stronger emissions along the nearshore coastline likely added to the elevated abundances under the steady atmospheric conditions. This study underscores the importance of oceanic upwelling and trade wind systems on the atmospheric distribution of marine VSLS emissions.

  17. Meteorological constraints on oceanic halocarbons above the Peruvian upwelling

    Science.gov (United States)

    Fuhlbrügge, Steffen; Quack, Birgit; Atlas, Elliot; Fiehn, Alina; Hepach, Helmke; Krüger, Kirstin

    2016-09-01

    During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian upwelling. This study presents novel observations of the three very short lived substances (VSLSs) - bromoform, dibromomethane and methyl iodide - together with high-resolution meteorological measurements, Lagrangian transport and source-loss calculations. Oceanic emissions of bromoform and dibromomethane were relatively low compared to other upwelling regions, while those for methyl iodide were very high. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting as strong barriers for convection and vertical transport of trace gases in this region. Observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height correlated well during the cruise. We used a simple source-loss estimate to quantify the contribution of oceanic emissions along the cruise track to the observed atmospheric concentrations. This analysis showed that averaged, instantaneous emissions could not support the observed atmospheric mixing ratios of VSLSs and that the marine background abundances below the trade inversion were significantly influenced by advection of regional sources. Adding to this background, the observed maximum emissions of halocarbons in the coastal upwelling could explain the high atmospheric VSLS concentrations in combination with their accumulation under the distinct MABL and trade inversions. Stronger emissions along the nearshore coastline likely added to the elevated abundances under the steady atmospheric conditions. This study underscores the importance of oceanic upwelling and trade wind systems on the atmospheric distribution of marine VSLS emissions.

  18. Isotopic evidences of past upwelling intensity in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Naidu, P.D.

    and understand the history of upwelling as it is recorded in deep-sea sediments. The southwest (SW) monsoon strongly influences the climatic conditions in South and Southeast Asia and biological productivity in the Arabian Sea. ability at the ODP Site 728... climatic change and ocean history (McCrea, 1950; Epstein et al., 1953; Emiliani, 1955). The isotopic role of planktic forami- nifera expanded, it was recognized that foraminifera did not secret their shells in isotopic equilibrium with ambient water (Be...

  19. Decadal- to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon

    Energy Technology Data Exchange (ETDEWEB)

    Kilbourne, K H; Quinn, T M; Guilderson, T P; Webb, R S; Taylor, F W

    2006-12-05

    Water that forms the Florida Current, and eventually the Gulf Stream, coalesces in the Caribbean from both subtropical and equatorial sources. The equatorial sources are made up of, in part, South Atlantic water moving northward and compensating for southward flow at depth related to meridional overturning circulation. Subtropical surface water contains relatively high amounts of radiocarbon ({sup 14}C), whereas equatorial waters are influenced by the upwelling of low {sup 14}C water and have relatively low concentrations of {sup 14}C. We use a 250-year record of {Delta}{sup 14}C in a coral from southwestern Puerto Rico along with previously published coral {Delta}{sup 14}C records as tracers of subtropical and equatorial water mixing in the northern Caribbean. Data generated in this study and from other studies indicate that the influence of either of the two water masses can change considerably on interannual to interdecadal time scales. Variability due to ocean dynamics in this region is large relative to variability caused by atmospheric {sup 14}C changes, thus masking the Suess effect at this site. A mixing model produced using coral {Delta}{sup 14}C illustrates the time varying proportion of equatorial versus subtropical waters in the northern Caribbean between 1963 and 1983. The results of the model are consistent with linkages between multidecadal thermal variability in the North Atlantic and meridional overturning circulation. Ekman transport changes related to tradewind variability are proposed as a possible mechanism to explain the observed switches between relatively low and relatively high {Delta}{sup 14}C values in the coral radiocarbon records.

  20. Large Topographic Rises on Venus: Implications for Mantle Upwelling

    Science.gov (United States)

    Stofan, Ellen R.; Smrekar, Suzanne E.; Bindschandler, Duane L.; Senske, David A.

    1995-01-01

    Topographic rises on Venus have been identified that are interpreted to be the surface manifestation of mantle upwellings. These features are classified into groups based on their dominant morphology. Atla and Beta Regiones are classified as rift-dominated, Dione, western Eistla, Bell, and Imdr Regiones as volcano-dominated, and Themis, eastern Eistla, and central Eistla Regiones as corona-dominated. At several topographic rises, geologic indicators were identified that may provide evidence of uplifted topography (e.g., volcanic flow features trending upslope). We assessed the minimum contribution of volcanic construction to the topography of each rise, which in general represents less than 5% of the volume of the rise, similar to the volumes of edifices at terrestrial hotspot swells. The total melt volume at each rise is approximated to be 10(exp 4) - 10(exp 6) cu km. The variations in morphology, topography, and gravity signatures at topographic rises are not interpreted to indicate variations in stage of evolution of a mantle upwelling. Instead, the morphologic variations between the three classes of topographic rises are interpreted to indicate the varying influences of lithospheric structure, plume characteristics, and regional tectonic environment. Within each class, variations in topography, gravity, and amount of volcanism may be indicative of differing stages of evolution. The similarity between swell and volcanic volumes for terrestrial and Venusian hotspots implies comparable time-integrated plume strengths for individual upwellings on the two planets.

  1. Oceanic upwelling and productivity in the eastern tropical Pacific

    International Nuclear Information System (INIS)

    Fiedler, P.C.; Philbrick, V.; Chavez, F.P.

    1991-01-01

    An oceanographic survey of the eastern tropical Pacific Ocean in August-November 1990 found a productive, nutrient-rich, moderately high-chlorophyll surface layer in two oceanic upwelling regions: the equatorial divergence, especially east of the Galapagos, and the countercurrent divergence out to 105 degree W, > 1,000 km west of the Costa Rica Dome. Although NO 3 is not depleted in upwelling regions, relationships among nutrient concentrations and temperature in 1986-1988 data from the same area show that NO 3 is the first macronutrient to be depleted in adjacent, less-productive regions. A three-dimensional, two-layer box model of NO 3 flux within and into the euphotic zone gives estimated rates of new production that are ∼29% of measured rates of 14 C phytoplankton production. Persistence of excess NO 3 in the euphotic zone exceeds 1 yr under high-nutrient, low-chlorophyll conditions off the equator where weak upwelling, or downwelling, occurs. These results indicate substantial control or limitation of NO 3 utilization and productivity in nutrient-rich oceanic regions of the eastern tropical Pacific

  2. Patterns of copepod diversity in the Chilean coastal upwelling system

    Science.gov (United States)

    Hidalgo, Pamela; Escribano, Ruben; Vergara, Odette; Jorquera, Erika; Donoso, Katty; Mendoza, Paula

    2010-12-01

    The copepod community structure from the Northern and Central/southern upwelling regions off Chile was studied and compared. The derived community descriptors were species abundance (N), species richness (R) and the Shannon-Wiener diversity index (H'). These descriptors were related to distinct habitats and conditions, sea surface temperature (SST) and depth of the upper boundary of the oxygen minimum zone (OMZ). From 159 samples, obtained between 2002 and 2008, a total number of 118 species were found of which the calanoids Paracalanus indicus, Acartia tonsa and Eucalanus inermis, along with the cyclopoid Oithona similis, and the poecilostomatoids Triconia conifera and Oncaea media were the dominant species. H' was higher in the northern region, but no differences in N and R were detected between regions. N was higher in the epipelagic vs the deep habitat, but R and H' did not differ. N, R and H' correlated positively to SST and negatively to OMZ depth. The ascent of the OMZ to the upper layer forced by upwelling was proposed as a mechanism that aggregates and increases copepod diversity in the food-rich photic zone. All these findings suggest a fundamental role of upwelling variation for modulating copepod dynamics and community structure in this highly productive but strongly variable marine ecosystem.

  3. Study of a metallurgical site in Tuscany (Italy) by radiocarbon dating

    International Nuclear Information System (INIS)

    Cartocci, A.; Fedi, M.E.; Taccetti, F.; Benvenuti, M.; Chiarantini, L.; Guideri, S.

    2007-01-01

    Tuscany represents one of the most important ancient mining districts of Italy. Metalworking activities have been present in the area since ancient times and several mining centres have been active in the region since the Etruscan period. Two of the more notable mining locations are the island of Elba and the towns of Populonia and Massa Marittima. In order to reconstruct the development of metallurgical techniques in the past, a multi-disciplinary approach is required, involving both archaeological study and archaeometric analysis of the sites of interest. One of the most complex problems is establishing the chronological history of metallurgical exploitation in ancient sites: archaeological remains are sometimes incomplete and the stratigraphy of archaeological horizons might have been deeply altered. Thus, direct dating of metallurgical slags and other remains of mining and metalworking activities using radiocarbon measurements is particularly useful for developing site chronologies. Charcoal samples from a recent excavation in Populonia were dated by AMS radiocarbon in order to reconstruct the chronological evolution of ancient metallurgical production; results reported here are consistent with archaeological observations

  4. Study of a metallurgical site in Tuscany (Italy) by radiocarbon dating

    Energy Technology Data Exchange (ETDEWEB)

    Cartocci, A. [Dipartimento di Fisica dell' Universita e I.N.F.N. Sezione di Firenze, via Sansone 1, 50019 Sesto Fiorentino, Florence (Italy); Fedi, M.E. [Dipartimento di Fisica dell' Universita e I.N.F.N. Sezione di Firenze, via Sansone 1, 50019 Sesto Fiorentino, Florence (Italy)]. E-mail: fedi@fi.infn.it; Taccetti, F. [Dipartimento di Fisica dell' Universita e I.N.F.N. Sezione di Firenze, via Sansone 1, 50019 Sesto Fiorentino, Florence (Italy); Benvenuti, M. [Dipartimento di Scienze della Terra dell' Universita di Firenze, via La Pira 4, 50121 Florence (Italy); Chiarantini, L. [Dipartimento di Scienze della Terra dell' Universita di Firenze, via La Pira 4, 50121 Florence (Italy); Guideri, S. [Societa Parchi Val di Cornia S.p.a., via G. Lerario, Piombino, Livorno (Italy)

    2007-06-15

    Tuscany represents one of the most important ancient mining districts of Italy. Metalworking activities have been present in the area since ancient times and several mining centres have been active in the region since the Etruscan period. Two of the more notable mining locations are the island of Elba and the towns of Populonia and Massa Marittima. In order to reconstruct the development of metallurgical techniques in the past, a multi-disciplinary approach is required, involving both archaeological study and archaeometric analysis of the sites of interest. One of the most complex problems is establishing the chronological history of metallurgical exploitation in ancient sites: archaeological remains are sometimes incomplete and the stratigraphy of archaeological horizons might have been deeply altered. Thus, direct dating of metallurgical slags and other remains of mining and metalworking activities using radiocarbon measurements is particularly useful for developing site chronologies. Charcoal samples from a recent excavation in Populonia were dated by AMS radiocarbon in order to reconstruct the chronological evolution of ancient metallurgical production; results reported here are consistent with archaeological observations.

  5. Radiocarbon dating and compositional analysis of pre-Columbian human bones

    International Nuclear Information System (INIS)

    Andrade, E.; Solís, C.; Canto, C.E.; Lucio, O.G. de; Chavez, E.; Rocha, M.F.; Villanueva, O.; Torreblanca, C.A.

    2014-01-01

    Analysis of ancient human bones found in “El Cóporo”, an archaeological site in Guanajuato, Mexico; were performed using a multi techniques scheme: 14 C radiocarbon dating, IBA (Ion Beam Analysis), SEM-EDS (Scanning Electron Microscope Energy Dispersive X-ray Spectroscopy). We measured the elemental composition of the bones, especially some with a superficial black pigmentation. Soil samples collected from the burial place were also analyzed. The 14 C dating was performed with a new High Voltage Europe 1 MV Tandentron Accelerator Mass Spectrometer (AMS) recently installed in the IFUNAM (Instituto de Física, Universidad Nacional Autónoma de México). The radiocarbon dating allowed us to determine the date of death of the individual in a period between the year 890 and 975 AD, which is consistent with the late period of the Cóporo civilization. The element sample analysis of bones with the surface black pigmentation show higher levels of Fe, Mn and Ba compared when bone’s black surface was mechanically removed. These three elements were found in soil samples from the skeleton burial place. These results indicate more likely that the bone black coloration is due to a postmortem alteration occurring in the burial environment

  6. Radiocarbon dating and compositional analysis of pre-Columbian human bones

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, E., E-mail: andrade@fisica.unam.mx [Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México D.F. (Mexico); Solís, C.; Canto, C.E.; Lucio, O.G. de [Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 México D.F. (Mexico); Chavez, E. [ESIME-Z, Instituto Politécnico Nacional, ALM Zacatenco, 07738 México D.F. (Mexico); Rocha, M.F.; Villanueva, O.; Torreblanca, C.A. [Centro INAH Zacatecas, Miguel Auza No. 205, Col. Centro, Zacatecas/Zacatecas CP 98000 (Mexico)

    2014-08-01

    Analysis of ancient human bones found in “El Cóporo”, an archaeological site in Guanajuato, Mexico; were performed using a multi techniques scheme: {sup 14}C radiocarbon dating, IBA (Ion Beam Analysis), SEM-EDS (Scanning Electron Microscope Energy Dispersive X-ray Spectroscopy). We measured the elemental composition of the bones, especially some with a superficial black pigmentation. Soil samples collected from the burial place were also analyzed. The {sup 14}C dating was performed with a new High Voltage Europe 1 MV Tandentron Accelerator Mass Spectrometer (AMS) recently installed in the IFUNAM (Instituto de Física, Universidad Nacional Autónoma de México). The radiocarbon dating allowed us to determine the date of death of the individual in a period between the year 890 and 975 AD, which is consistent with the late period of the Cóporo civilization. The element sample analysis of bones with the surface black pigmentation show higher levels of Fe, Mn and Ba compared when bone’s black surface was mechanically removed. These three elements were found in soil samples from the skeleton burial place. These results indicate more likely that the bone black coloration is due to a postmortem alteration occurring in the burial environment.

  7. Radiocarbon dating and compositional analysis of pre-Columbian human bones

    Science.gov (United States)

    Andrade, E.; Solís, C.; Canto, C. E.; de Lucio, O. G.; Chavez, E.; Rocha, M. F.; Villanueva, O.; Torreblanca, C. A.

    2014-08-01

    Analysis of ancient human bones found in "El Cóporo", an archaeological site in Guanajuato, Mexico; were performed using a multi techniques scheme: 14C radiocarbon dating, IBA (Ion Beam Analysis), SEM-EDS (Scanning Electron Microscope Energy Dispersive X-ray Spectroscopy). We measured the elemental composition of the bones, especially some with a superficial black pigmentation. Soil samples collected from the burial place were also analyzed. The 14C dating was performed with a new High Voltage Europe 1 MV Tandentron Accelerator Mass Spectrometer (AMS) recently installed in the IFUNAM (Instituto de Física, Universidad Nacional Autónoma de México). The radiocarbon dating allowed us to determine the date of death of the individual in a period between the year 890 and 975 AD, which is consistent with the late period of the Cóporo civilization. The element sample analysis of bones with the surface black pigmentation show higher levels of Fe, Mn and Ba compared when bone's black surface was mechanically removed. These three elements were found in soil samples from the skeleton burial place. These results indicate more likely that the bone black coloration is due to a postmortem alteration occurring in the burial environment.

  8. Surface circulation and upwelling patterns around Sri Lanka

    Science.gov (United States)

    de Vos, A.; Pattiaratchi, C. B.; Wijeratne, E. M. S.

    2013-09-01

    Sri Lanka occupies a unique location within the equatorial belt in the northern Indian Ocean with the Arabian Sea on its western side and the Bay of Bengal on its eastern side. The region is characterised by bi-annually reversing monsoon winds resulting from seasonal differential heating and cooling of the continental land mass and the ocean. This study explored elements of the dynamics of the surface circulation and coastal upwelling in the waters around Sri Lanka using satellite imagery and the Regional Ocean Modelling System (ROMS) configured to the study region and forced with ECMWF interim data. The model was run for 2 yr to examine the seasonal and shorter term (∼10 days) variability. The results confirmed the presence of the reversing current system in response to the changing wind field: the eastward flowing Southwest Monsoon Current (SMC) during the Southwest (SW) monsoon transporting 11.5 Sv and the westward flowing Northeast Monsoon Current (NMC) transporting 9.5 Sv during the Northeast (NE) monsoon, respectively. A recirculation feature located to the east of Sri Lanka during the SW monsoon, the Sri Lanka Dome, is shown to result from the interaction between the SMC and the Island of Sri Lanka. Along the eastern and western coasts, during both monsoon periods, flow is southward converging along the south coast. During the SW monsoon the Island deflects the eastward flowing SMC southward whilst along the east coast the southward flow results from the Sri Lanka Dome recirculation. The major upwelling region, during both monsoon periods, is located along the south coast and is shown to be due to flow convergence and divergence associated with offshore transport of water. Higher surface chlorophyll concentrations were observed during the SW monsoon. The location of the flow convergence and hence the upwelling centre was dependent on the relative strengths of wind driven flow along the east and west coasts: during the SW (NE) monsoon the flow along the

  9. Accurate dating with radiocarbon from the atom bomb tests

    CSIR Research Space (South Africa)

    Vogel

    2002-09-01

    Full Text Available The artificial radiocarbon produced by the thermonuclear bomb tests in the 1950s and 1960s significantly increased the level of C-14 in the environment. A detailed record of the subsequent changes in the C-14 concentration of the atmosphere can...

  10. Radiocarbon dating of Mesolithic pottery from Northern Germany

    DEFF Research Database (Denmark)

    Philippsen, Bente

    2013-01-01

    The earliest pottery in Schleswig-Holstein, Northern Germany, was produced by the Final Mesolithic Ertebølle culture. Radiocarbon dating of food crusts on Ertebølle pottery indicated that ceramics from inland sites were substantially older than those from the coast. Therefore, a freshwater...

  11. Annually resolved atmospheric radiocarbon records reconstructed from tree-rings

    Science.gov (United States)

    Wacker, Lukas; Bleicher, Niels; Büntgen, Ulf; Friedrich, Michael; Friedrich, Ronny; Diego Galván, Juan; Hajdas, Irka; Jull, Anthony John; Kromer, Bernd; Miyake, Fusa; Nievergelt, Daniel; Reinig, Frederick; Sookdeo, Adam; Synal, Hans-Arno; Tegel, Willy; Wesphal, Torsten

    2017-04-01

    The IntCal13 calibration curve is mainly based on data measured by decay counting with a resolution of 10 years. Thus high frequency changes like the 11-year solar cycles or cosmic ray events [1] are not visible, or at least not to their full extent. New accelerator mass spectrometry (AMS) systems today are capable of measuring at least as precisely as decay counters [2], with the advantage of using 1000 times less material. The low amount of material required enables more efficient sample preparation. Thus, an annually resolved re-measurement of the tree-ring based calibration curve can now be envisioned. We will demonstrate with several examples the multitude of benefits resulting from annually resolved radiocarbon records from tree-rings. They will not only allow for more precise radiocarbon dating but also contain valuable new astrophysical information. The examples shown will additionally indicate that it can be critical to compare AMS measurements with a calibration curve that is mainly based on decay counting. We often see small offsets between the two measurement techniques, while the reason is yet unknown. [1] Miyake F, Nagaya K, Masuda K, Nakamura T. 2012. A signature of cosmic-ray increase in AD 774-775 from tree rings in Japan. Nature 486(7402):240-2. [2] Wacker L, Bonani G, Friedrich M, Hajdas I, Kromer B, Nemec M, Ruff M, Suter M, Synal H-A, Vockenhuber C. 2010. MICADAS: Routine and high-precision radiocarbon dating. Radiocarbon 52(2):252-62.

  12. Status of mass spectrometric radiocarbon detection at ETHZ

    Energy Technology Data Exchange (ETDEWEB)

    Seiler, Martin; Maxeiner, Sascha; Wacker, Lukas; Synal, Hans-Arno

    2015-10-15

    A prototype of a mass spectrometric radiocarbon detection instrument without accelerator stage was built for the first time and set into operation at ETH Zurich. The system is designed as an experimental platform to optimize performance of {sup 14}C detection at low ion energies and to study the most relevant processes that may limit system performance. The optimized stripper unit incorporates differential pumping to maintain a low gas outflow and a revised tube design to better match the phase space volume of the ion beam at low energies. The system is fully operational and has demonstrated true radiocarbon dating capabilities. The overall beam transmission through the stripper tube is about 40% for the 1{sup +} charge state. Radiocarbon analyses with an overall precision of 0.6% were obtained on a single sample under regular measurement conditions. By analyzing multiple targets of the same sample material an uncertainty level of 0.3% has been reached. The background level corresponds to a radiocarbon age of 40,000 years.

  13. Short-term variations of radiocarbon during the last century

    International Nuclear Information System (INIS)

    Burchuladze, A.A.; Pagava, S.V.; Jurina, V.; Povinec, P.; Usacev, S.

    1982-01-01

    Radiocarbon variations related to the 11-year solar cycle during the last century are discussed. Previous investigations on short term 14 C variations in tree rings are compared with 14 C measurements in Georgian wine samples. The amplitude of 14 C variations as obtained by various authors ranges from 0.2 to about 1%. (author)

  14. Radiocarbon dating in archaeology: Interdisciplinary aspects and consequences (an overview)

    Science.gov (United States)

    Palincaş, Nona

    2017-06-01

    This paper is an overview of recent developments in the radiocarbon dating of the most frequently analyzed archaeological materials - wood, short-lived plants, and human and animal bones - and draws attention to two sets of consequences. Firstly, while radiocarbon dating has become more accessible to archaeologists thanks to an increase in the number of laboratories, a lowering of prices, and a reduction in sample sizes, it has also grown far more dependent on fields of research, other than the traditional chemical pretreatment of samples and the physics involved in their measurement, such as wood anatomy and other fields of botany, stable isotope-based diet studies, geochemistry, micromorphology, statistics, etc., most of which are not easily accessible by the vast majority of users of radiocarbon dating (and sometimes not familiar to practicing archaeologists). Secondly, given that, on the one hand, there is still much scope for research in radiocarbon dating and, on the other, archaeological sites are a limited resource, there is need to create archives containing the detailed documentation of samples and, whenever possible, sample residues.

  15. Radiocarbon application in environmental science and archaeology in Croatia

    Energy Technology Data Exchange (ETDEWEB)

    Krajcar Bronic, I., E-mail: krajcar@irb.h [Radiocarbon Laboratory, Department of Experimental Physics, Ruder Boskovic Institute, Bijenicka 54, 10000 Zagreb (Croatia); Obelic, B.; Horvatincic, N.; Baresic, J.; Sironic, A. [Radiocarbon Laboratory, Department of Experimental Physics, Ruder Boskovic Institute, Bijenicka 54, 10000 Zagreb (Croatia); Minichreiter, K. [Institute of Archaeology, Ulica grada Vukovara 68, 10000 Zagreb (Croatia)

    2010-07-21

    Radiocarbon is a cosmogenic radioisotope equally distributed throughout the troposphere and biosphere. This fact enables its most common application-radiocarbon dating. Natural equilibrium of radiocarbon has been disturbed by diverse anthropogenic activities during the last {approx}150 years, enabling also the use of {sup 14}C in various environmental applications. Here we present three types of studies by using {sup 14}C that were performed in the Zagreb Radiocarbon Laboratory. {sup 14}C in atmospheric CO{sub 2} has been monitored at several sites with various anthropogenic influences and the difference between the clean-air sites, the industrial city and the vicinity of a nuclear power plant has been established. {sup 14}C has been applied in geochronology of karst areas, especially in dating of tufa, speleothems and lake sediments, as well as in studies of geochemical carbon cycle. {sup 14}C has been used in various archaeological studies, among which the dating of the early Neolithic settlements in Croatia is presented. In these studies {sup 14}C was measured by radiometric techniques, i.e., by gas proportional counting and more recently by liquid scintillation counting (LSC). Two sample preparation techniques for LSC measurement were used: benzene synthesis for archaeological dating and other applications that require better precision, and direct absorption of CO{sub 2} for monitoring purposes. The presented results show that various studies by using {sup 14}C can be successfully performed by the LSC technique, providing a large enough sample (>1 g of carbon).

  16. Radiocarbon adjustments to the dendrochronology of a yellowwood tree

    CSIR Research Space (South Africa)

    Vogel, JC

    2001-03-01

    Full Text Available High-precision radiocarbon dating of a millennium-old yellowwood tree from the Midlands of Natal shows that the tree-rings do, in general, record annual growth, but that both missing and false rings occur. At two places along the transect...

  17. Laboratory Intercomparison of Pleistocene Bone Radiocarbon Dating Protocols

    NARCIS (Netherlands)

    Huels, Matthias; van der Plicht, Johannes; Brock, Fiona; Matzerath, Simon; Chivall, David

    2017-01-01

    Since its invention in the late 1940s, radiocarbon (14C) dating has become an important tool for absolute dating. A prerequisite for the acceptance of this method is consistency between, and compatibility of, 14C dates from different laboratories. To meet these requirements, international laboratory

  18. Iberian and California-Oregon Upwelling Systems: trends and status of two upwelling systems at the same latitude over the last four decades.

    Science.gov (United States)

    Barreiro, B.; Barton, E. D.

    2012-04-01

    The study of Eastern Boundary Upwelling Systems is of vital importance, given the interest in rational management of the fisheries resources. The high level of biogeochemical activity associated with the physical process of upwelling increases primary production and enriches the living resources of these areas. This presentation focuses on the variability of these physical processes on daily to interdecadal scales, in an investigation of the effects of climate change in the Iberian and California-Oregon Upwelling Systems. The Upwelling Index (UI) was analysed for the period 1967-2010 at 35.5-44.5°N in both areas. The two systems differ in that the magnitudes of upwelling intensity off California-Oregon are 3.3 higher than off Iberia but they show a similar latitudinal behaviour. The annual/interannual scale variability of upwelling can be represented by the recently introduced Cumulative Upwelling Index (CUI) based on summing the mean daily UI. The seasonal cycle results show the length of upwelling season increases southwards from 180 to 300 days and a net upwelling occurs only for latitudes lower than 43°N. On the interannual scales, the CUI showed a roughly linear change at high and low latitudes (R>0.9), with slopes between 250 and -130 m3 s-1 km-1 day-1 in Iberian and 620 and -290 m3 s-1 km-1 day-1 in California-Oregon. The central areas (40.5-42.5°N) are less stable and shifted between net upwelling and downwelling over extended periods. This information helps us contextualize the present state of the study area and interpreted ongoing intensive process-oriented studies within the longer term variability.

  19. Compound-specific radiocarbon analysis - Analytical challenges and applications

    Science.gov (United States)

    Mollenhauer, G.; Rethemeyer, J.

    2009-01-01

    Within the last decades, techniques have become available that allow measurement of isotopic compositions of individual organic compounds (compound-specific isotope measurements). Most often the carbon isotopic composition of these compounds is studied, including stable carbon (δ13C) and radiocarbon (Δ14C) measurements. While compound-specific stable carbon isotope measurements are fairly simple, and well-established techniques are widely available, radiocarbon analysis of specific organic compounds is a more challenging method. Analytical challenges include difficulty obtaining adequate quantities of sample, tedious and complicated laboratory separations, the lack of authentic standards for measuring realistic processing blanks, and large uncertainties in values of Δ14C at small sample sizes. The challenges associated with sample preparation for compound-specific Δ14C measurements will be discussed in this contribution. Several years of compound-specific radiocarbon analysis have revealed that in most natural samples, purified organic compounds consist of heterogeneous mixtures of the same compound. These mixtures could derive from multiple sources, each having a different initial reservoir age but mixed in the same terminal reservoir, from a single source but mixed after deposition, or from a prokaryotic organism using variable carbon sources including mobilization of ancient carbon. These processes not only represent challenges to the interpretation of compound-specific radiocarbon data, but provide unique tools for the understanding of biogeochemical and sedimentological processes influencing the preserved organic geochemical records in marine sediments. We will discuss some examples where compound-specific radiocarbon analysis has provided new insights for the understanding of carbon source utilization and carbon cycling.

  20. Secular variation of cosmic ray intensity recorded in the radiocarbon concentration of tree rings

    International Nuclear Information System (INIS)

    Kigoshi, K.

    1978-01-01

    Study of the secular variations of cosmic ray intensity on the basis of the secular variations of atmospheric radiocarbon concentration in 8000 years is considered. The data on the radiocarbon concentration is received by three laboratories using the dendrochronologically dated tree ring samples. In order to use the data the variations due to geochemical process must be eliminated. From this point of view the climatic effect on the atmospheric radiocarbon concenttration is estimated using the data on sunspot number and global surface temperature during 1650-1800 y. The barge influence of climate on the atmospheric radiocarbon concentration syggests the small contribution of change of radiocarbon production rate to the short-period fluctuations in the atmospheric radiocarbon concentration. Elimination of variations caused by climate and sunspot activities from the variations in atmospheric radiocarbon concentration gives a long-term scale of its concentration which agrees well to the observed paleo-geomagnetic data

  1. Are large macroalgal blooms necessarily bad? Nutrient impacts on seagrass in upwelling-influenced estuaries.

    Science.gov (United States)

    Hessing-Lewis, Margot L; Hacker, Sally D; Menge, Bruce A; McConville, Sea-oh; Henderson, Jeremy

    2015-07-01

    Knowledge of nutrient pathways and their resulting ecological interactions can alleviate numerous environmental problems associated with nutrient increases in both natural and managed systems. Although not unique, coastal systems are particularly prone to complex ecological interactions resulting from nutrient inputs from both the land and sea. Nutrient inputs to coastal systems often spur ulvoid macroalgal blooms, with negative consequences for seagrasses, primarily through shading, as well as through changes in local biogeochemistry. We conducted complementary field and mesocosm experiments in an upwelling-influenced estuary, where marine-derived nutrients dominate, to understand the direct and indirect effects of nutrients on the macroalgal-eelgrass (Zostera marina L.) interaction. In the field experiment, we found weak evidence that nutrients and/or macroalgal treatments had a negative effect on eelgrass. However, in the mesocosm experiment, we found that a combination of nutrient and macroalgal treatments led to strongly negative eelgrass responses, primarily via indirect effects associated with macroalgal additions. Together, increased total light attenuation and decreased sediment oxygen levels were associated with larger effects on eelgrass than shading alone, which was evaluated using mimic algae treatments that did not alter sediment redox potential. Nutrient addition in the mesocosms directly affected seagrass density; biomass, and morphology, but not as strongly as macroalgae. We hypothesize that the contrary results from these parallel experiments are a consequence of differences in the hydrodynamics between field and mesocosm settings. We suggest that the high rates of water movement and tidal submersion of our intertidal field experiments alleviated the light reduction and negative biogeochemical changes in the sediment associated with macroalgal canopies, as well as the nutrient effects observed in the mesocosm experiments. Furthermore, adaptation

  2. Coastal upwelling seasonality and variability of temperature and chlorophyll in a small coastal embayment

    Science.gov (United States)

    Walter, Ryan K.; Armenta, Kevin J.; Shearer, Brandon; Robbins, Ian; Steinbeck, John

    2018-02-01

    While the seasonality of wind-driven coastal upwelling in eastern boundary upwelling systems has long been established, many studies describe two distinct seasons (upwelling and non-upwelling), a generalized framework that does not capture details relevant to marine ecosystems. In this contribution, we present a more detailed description of the annual cycle and upwelling seasonality for an understudied location along the central California coast. Using both the mean monthly upwelling favorable wind stress and the monthly standard deviation, we define the following seasons (contiguous months) and a transitional period (non-contiguous months): "Winter Storms" season (Dec-Jan-Feb), "Upwelling Transition" period (Mar and Jun), "Peak Upwelling" season (Apr-May), "Upwelling Relaxation" season (Jul-Aug-Sep), and "Winter Transition" season (Oct-Nov). In order to describe the oceanic response to this upwelling wind seasonality, we take advantage of nearly a decade of full water-column measurements of temperature and chlorophyll made using an automated profiling system at the end of the California Polytechnic State University Pier in San Luis Obispo Bay, a small ( 2 km wide near study site) and shallow ( 10 m average bay depth) coastal embayment. Variability and average-year patterns are described inside the bay during the various upwelling seasons. Moreover, the role of the local coastline orientation and topography on bay dynamics is also assessed using long-term measurements collected outside of the bay. The formation of a seasonally variable upwelling shadow system and potential nearshore retention zone is discussed. The observations presented provide a framework on which to study interannual changes to the average-year seasonal cycle, assess the contribution of higher-frequency features to nearshore variability, and better predict dynamically and ecologically important events.

  3. Lipid biomarker patterns of phosphogenic sediments from upwelling regions

    DEFF Research Database (Denmark)

    Arning, Esther T.; Birgel, Daniel; Schultz-Vogt, Heide N.

    2008-01-01

    Sediments of upwelling regions off Namibia, Peru, and Chile contain dense populations of large nitrate-storing sulfide-oxidizing bacteria, Thiomargarita, Beggiatoa, and Thioploca. Increased contents of monounsaturated C16 and C18 fatty acids have been found at all stations studied, especially when...... these bacteria. As a consequence, the distributions of sulfate reducers in sediments of Namibia, Peru, and Chile are closely related to differences in the motility of the various sulfide oxidizers at the three study sites. Depth profiles of mono-O-alkyl glycerol ethers have been found to correlate best...

  4. Atmosphere-ocean feedbacks in a coastal upwelling system

    Science.gov (United States)

    Alves, J. M. R.; Peliz, A.; Caldeira, R. M. A.; Miranda, P. M. A.

    2018-03-01

    The COAWST (Coupled Ocean-Atmosphere-Wave-Sediment Transport) modelling system is used in different configurations to simulate the Iberian upwelling during the 2012 summer, aiming to assess the atmosphere-ocean feedbacks in the upwelling dynamics. When model results are compared with satellite measurements and in-situ data, two-way coupling is found to have a moderate impact in data-model statistics. A significant reinforcement of atmosphere-ocean coupling coefficients is, however, observed in the two-way coupled run, and in the WRF and ROMS runs forced by previously simulated SST and wind fields, respectively. The increasing in the coupling coefficient is associated with slight, but potentially important changes in the low-level coastal jet in the atmospheric marine boundary layer. While these results do not imply the need for fully coupled simulations in many applications, they show that in seasonal numerical studies such simulations do not degrade the overall model performance, and contribute to produce better dynamical fields.

  5. Towards a management perspective for coastal upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Howe, S.O.; Walsh, J.J.

    1976-01-01

    Data are reviewed from studies on the general distribution of upwelling of coastal waters, associated current patterns, and first order biological effects. Field observations and theory are discussed. Recent research has shown that variability and dynamism are the predominant characteristic features of these regions. Populations related by nonlinear interactions occur in constantly moving patches and swirls subjected to variability in the winds, currents, water chemistry, and solar insolation. Gross stationary features of upwelling communities have been described, but the responses of critical components and their relationships to human or natural perturbations remain poorly defined in this and other types of coastal ecosystems. Large scale research programs recognize that the continental shelf ecosystems are complex event-oriented phenomena. It is postulated that assessment of living resources in an environmental vacuum may lead to mismanagement and hindcasting rather than prescient management. A growing data base encourages the development of computer simulation models of ecosystem relationships and responses will lead to better understanding and management of these and other marine ecosystems in the future. 80 references.

  6. Submesoscale CO2 variability across an upwelling front off Peru

    Science.gov (United States)

    Köhn, Eike E.; Thomsen, Sören; Arévalo-Martínez, Damian L.; Kanzow, Torsten

    2017-12-01

    As a major source for atmospheric CO2, the Peruvian upwelling region exhibits strong variability in surface fCO2 on short spatial and temporal scales. Understanding the physical processes driving the strong variability is of fundamental importance for constraining the effect of marine emissions from upwelling regions on the global CO2 budget. In this study, a frontal decay on length scales of 𝒪(10 km) was observed off the Peruvian coast following a pronounced decrease in down-frontal (equatorward) wind speed with a time lag of 9 h. Simultaneously, the sea-to-air flux of CO2 on the inshore (cold) side of the front dropped from up to 80 to 10 mmol m-2 day-1, while the offshore (warm) side of the front was constantly outgassing at a rate of 10-20 mmol m-2 day-1. Based on repeated ship transects the decay of the front was observed to occur in two phases. The first phase was characterized by a development of coherent surface temperature anomalies which gained in amplitude over 6-9 h. The second phase was characterized by a disappearance of the surface temperature front within 6 h. Submesoscale mixed-layer instabilities were present but seem too slow to completely remove the temperature gradient in this short time period. Dynamics such as a pressure-driven gravity current appear to be a likely mechanism behind the evolution of the front.

  7. Effects of structural factors on upwelling fouling community, Southeast Brazil

    Directory of Open Access Journals (Sweden)

    Bruno Pereira Masi

    Full Text Available Abstract To assess the successional pattern of fouling organisms three hypotheses were tested: 1 a thermocline is caused by seasonal upwelling events, and therefore, depth influences the successional trajectory of the fouling community; 2 a reduction in the intensity of natural light of the substrate influences the fouling composition and the successional trajectory; 3 fish predation influences the community composition and its successional trajectory. During one year, up-facing and down-facing PVC panels on open, partially caged or fully caged, and placed at depths of 1.5 and 3.5 meters were monthly sampled by digital photograph to determine the community composition and by contact point to estimate the percent coverage of organisms. The upwelling impact provided different water masses, and light intensity was also a determining factor of the overall successional trajectory of the fouling community. After the installation of full and partial cages, differences were identified in the respective successional trajectories. The results of this study suggest that each physical factor or biological process can change the successional trajectory of the community, and the successional model (e.g., convergent, divergent, parallel, or cyclic depends on the magnitudes of the determinants that act on the community at each stage of its trajectory.

  8. The utilisation of thermal analysis to optimise radiocarbon dating procedures

    International Nuclear Information System (INIS)

    Brandova, D.; Keller, W.A.; Maciejewski, M.

    1999-01-01

    Thermal analysis combined with mass spectrometry was applied to radiocarbon dating procedures (age determination of carbon-containing samples). Experiments carried out under an oxygen atmosphere were used to determine carbon content and combustion range of soil and wood samples. Composition of the shell sample and its decomposition were investigated. The quantification of CO 2 formed by the oxidation of carbon was done by the application of pulse thermal analysis. Experiments carried out under an inert atmosphere determined the combustion range of coal with CuO as an oxygen source. To eliminate a possible source of contamination in the radiocarbon dating procedures the adsorption of CO 2 by CuO was investigated. (author)

  9. Radiocarbon ages of Sorori ancient rice of Korea

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyeong Ja, E-mail: kjkim@kigam.re.kr [Korea Institute of Geoscience and Mineral Resources, Daejeon (Korea, Republic of); Lee, Yung-Jo; Woo, Jong-Yoon [Institute of Korean Prehistory, Cheongju (Korea, Republic of); Jull, A.J. Timothy [NSF Arizona AMS Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

    2013-01-15

    Samples of Sorori ancient rice were excavated in 1998 from the Sorori Paleolithic site located at Sorori, Oksan-myeon, Cheong-won County in Chungcheongbuk-do, Korea. We have made new radiocarbon measurements for Sorori samples in 2009 at the NSF Arizona AMS Laboratory. Both ancient rice samples and surrounded peat from the Sorori site were dated. The AMS results confirmed that the ages of the rice and peat soil were 12,520 {+-} 150 and 12,552 {+-} 90 BP, respectively. These radiocarbon ages are consistent with the previously published data of quasi rice measured at Seoul National University and confirm that the Sorori rice is the oldest ancient rice currently reported.

  10. The PSI/ETH small radiocarbon dating system

    International Nuclear Information System (INIS)

    Synal, H.-A.; Jacob, S.; Suter, M.

    2000-01-01

    A small and compact radiocarbon dating system has been built at PSI/ETH. The system is based on a National Electrostatics Corporation (NEC) pelletron accelerator with a maximum terminal voltage of 550 kV. It is the first accelerator mass spectrometry (AMS) system that uses 1 + ions at the high-energy end of the accelerator. Interfering isobaric molecules are destroyed by collisions in the gas stripper inside the accelerator. The system has been designed to fulfill two primary goals. First, it can be used as an experimental platform to study the relevant charge exchange and molecular break up processes at low energies. Second, it is able to perform high quality radiocarbon dating measurements. A detailed system description is given and results of performance tests are discussed

  11. Techniques of biomolecular quantification through AMS detection of radiocarbon

    International Nuclear Information System (INIS)

    Vogel, S.J.; Turteltaub, K.W.; Frantz, C.; Felton, J.S.; Gledhill, B.L.

    1992-01-01

    Accelerator mass spectrometry offers a large gain over scintillation counting in sensitivity for detecting radiocarbon in biomolecular tracing. Application of this sensitivity requires new considerations of procedures to extract or isolate the carbon fraction to be quantified, to inventory all carbon in the sample, to prepare graphite from the sample for use in the spectrometer, and to derive a meaningful quantification from the measured isotope ratio. These procedures need to be accomplished without contaminating the sample with radiocarbon, which may be ubiquitous in laboratories and on equipment previously used for higher dose, scintillation experiments. Disposable equipment, materials and surfaces are used to control these contaminations. Quantification of attomole amounts of labeled substances are possible through these techniques

  12. Lichens as indicators of tritium and radiocarbon contamination

    International Nuclear Information System (INIS)

    Daillant, Olivier; Kirchner, Gerald; Pigree, Gilbert; Porstendorfer, Justin

    2004-01-01

    Lichens were collected in France in the surroundings of a military nuclear facility in Burgundy, near the la Hague reprocessing plant and in an area away from any direct source of contamination. Organically bound tritium (OBT) has been analysed on 18 samples and radiocarbon on 11. It appeared that on the most contaminated spots, the OBT activity in lichens was higher than the background by a factor of 1000 and was still a factor 10-100 at a distance of 20 km from the source. Radiocarbon from la Hague could be traced by lichens. The slow metabolism of lichens makes them suitable for the follow-up of 3 H and 14 C, which have been incorporated by photosynthesis

  13. New radiocarbon dates on the cereals from Wadi Kubbaniya

    International Nuclear Information System (INIS)

    Wendorf, F.; Schild, R.; Close, A.E.

    1984-01-01

    In 1978, three carbonized grains of barley and a carbonized grain of einkorn wheat were found in a buried hearth at a Late Paleolithic site at Wadi Kubbaniya in Egypt. In 1981, two large clusters of barley seeds, which were identified as six-row barley and thus domestic, were found at a nearby site of comparable age. Numerous grinding stones, presumed to have been used for processing the cereals, were found in these and other sites, often deeply buried, and 30 radiocarbon dates placed the occupations between 18,500 and 17,000 radiocarbon years ago. These finds led us to suggest an early origin of food production, with implications for the initial development of complex societies. Several barley seeds were analyzed by electron spin resonance spectroscopy to determine the maximal temperature to which they had been subjected before burial. Six barley seeds and three small pieces of wood charcoal were dated directly by using a tandem accelerator mass spectrometer

  14. Radiocarbon concentration in modern tree rings from Valladolid, Spain

    International Nuclear Information System (INIS)

    Rakowski, Andrzej Z.; Nakamura, Toshio; Pazdur, Anna; Charro, Elena; Villanueva, Jose Luis Gutierrez; Piotrowska, Natalia

    2010-01-01

    New results of radiocarbon concentration in tree rings from the City of Valladolid (Spain) covering a growth period of 22 year have been measured using an AMS. Samples were taken using a hollow drill from a living tree, and α-cellulose was extracted from each of annual rings (early and late wood separately). The set of data shows lower radiocarbon concentration than that reported for 'clean air' at the reference station, indicating a remarkable input of 'dead' CO 2 of fossil fuel origin. Using data of carbon dioxide and 14 C concentrations from Schauinsland, the corresponding summer and winter values of the fossil component (c f ) in carbon dioxide were calculated for the City of Valladolid. By fitting exponential and linear functions to the experimental data, the exchange time was calculated, and the expected future 14 C concentration in the atmosphere was estimated.

  15. Atmospheric radiocarbon variations 11,000 years ago

    Energy Technology Data Exchange (ETDEWEB)

    Hajdas, I.; Bonani, G. [Eidgenoessische Technische Hochschule, Zurich (Switzerland); Peteet, D. [LDEO of Columbia Univ. (United States); Boden, P. [Stockholm Univ. (Sweden)

    1997-09-01

    Records of climate changes were {sup 14}C dated using AMS method. High resolution dating allowed reconstruction of the atmospheric {sup 14}C variations at the time of deglaciation. An abrupt rise of up to 100%o in the atmospheric {sup 14}C/{sup 12}C ratio was found at 11`000 BP (radiocarbon age) which coincides with the limit of an abrupt cooling and a decrease in ocean ventilation. (author) 1 fig., 6 refs.

  16. AMS radiocarbon dating of cemetery of Jin Marquises in China

    CERN Document Server

    Wu, X; Wang, J; Guo, Z; Liu, K; Lü, X; Ma, H; Li, K; Yuan, J; Cai, L

    2000-01-01

    Bones are very important samples to determine the hosts of the cemetery of Jin Marquises which were excavated at Tianma-Qucun site in Shanxi Province in China. In order to obtain accurate AMS radiocarbon dates, bones were pretreated by two kinds of methods, the gelatin-extraction method and the amino-acid method. Charcoals collected from the same sites were also used. The measured dates agree with historical record.

  17. Radiocarbon dating of sediment cores from Hachinohe, the Kamikita Plain

    International Nuclear Information System (INIS)

    Hitoki, Eri; Nakamura, Toshio; Matsumoto, Yui; Tsuji, Sei-ichiro; Fujine, Hisashi

    2013-01-01

    We investigated stratigraphy and chronology by analyses of Holocene sediments and radiocarbon dating of sediment cores from the Kamikita Plain. On the Kamikita Plain, which faces the Pacific coast of Northeast Japan, marine and fluvial terraces covered with tephras derived from Towada and Hakkoda volcanoes are well developed. We clarified that Towada Chuseri tephra and fluvial deposits consisted of volcanic sediments influenced an alluvial depositional system in the Kamikita Plain after a maximum of the Jomon Transgression. (author)

  18. Radiocarbon dating of archaeological geological and groundwater samples

    International Nuclear Information System (INIS)

    Chinh, N.K.; Dung, H.H.; Quan, H.M.; Thuy, T.K.

    1989-01-01

    In the context of the project VIE/8/003 sponsored by the IAEA, a regular and complete C 1 4 laboratory was installed at the Centre of the Nuclear Techniques in 1986. In this paper the authors present the procedure of sample treatment and saple activity measurement of the radiocarbon method and some preliminary results obtained after more than one year of operation of the laboratory

  19. Radiocarbon dating at sub MeV energies

    International Nuclear Information System (INIS)

    Synal, H.A.; Jacob, S.; Suter, M.

    1999-01-01

    Accelerator Mass Spectrometry (AMS) is currently the leading technique for the detection of long-lived radionuclides, such as 10 Be, 14 C, 26 Al, 36 Cl, 41 Ca, 53 Mn, 59 Ni, 60 Fe and 129 I at natural isotopic concentrations. However, radiocarbon plays the primary role and 14 C AMS systems, which are able to provide high precision measurements, are nowadays commercially available

  20. AMS radiocarbon dating of 'Grotta Cappuccini' in Southern Italy

    International Nuclear Information System (INIS)

    Quarta, G.; Calcagnile, L.; D'Elia, M.; Rizzo, A.; Ingravallo, E.

    2004-01-01

    We present the results of AMS radiocarbon dating of human bones recovered in 'Grotta Cappuccini', a prehistoric cave in Galatone, Lecce (Southern Italy). The AMS analysis has confirmed the archaeological dating of the cave to the period between the end of the Copper Age and the early Bronze Age, and has given a fundamental contribution to the chronological definition of an important cultural aspect of the prehistory of Southern Italy

  1. Year of birth determination using radiocarbon dating of dental enamel.

    Science.gov (United States)

    Buchholz, B A; Spalding, K L

    2010-05-01

    Radiocarbon dating is typically an archaeological tool rather than a forensic one. Recently however, we have shown that the amount of radiocarbon present in tooth enamel, as a result of nuclear bomb testing during the cold war, is a remarkably accurate indicator of when a person is born. Enamel isolated from human teeth is processed to form graphite and carbon-14 ((14)C) levels are measured using accelerator mass spectrometry. Since there is no turnover of enamel after it is formed, (14)C levels in the enamel represent (14)C levels in the atmosphere at the time of its formation. In this paper we describe the strategy used to determine the date of birth of an individual based on radiocarbon levels in tooth enamel, focusing on the methodology of this strategy. Year of birth information can significantly assist police investigators when the identity of a deceased individual is unknown. In such cases police will try to match particulars of the unidentified individual (which is often only gender and/or an estimate of age), with particulars from missing persons lists.

  2. Year of Birth Determination Using Radiocarbon Dating of Dental Enamel

    Energy Technology Data Exchange (ETDEWEB)

    Buchholz, B A; Spalding, K L

    2009-03-10

    Radiocarbon dating is typically an archaeological tool rather than a forensic one. Recently however, we have shown that the amount of radiocarbon present in tooth enamel, as a result of nuclear bomb testing during the cold war, is a remarkably accurate indicator of when a person is born. Enamel isolated from human teeth is processed to form graphite and carbon-14 ({sup 14}C) levels are measured using accelerator mass spectrometry. Since there is no turnover of enamel after it is formed, {sup 14}C levels in the enamel represent {sup 14}C levels in the atmosphere at the time of its formation. In this paper we describe the strategy used to determine the date of birth of an individual based on radiocarbon levels in tooth enamel, focusing on the methodology of this strategy. Year of birth information can significantly assist police investigators when the identity of a deceased individual is unknown. In such cases police will try to match particulars of the unidentified individual (which is often only gender and/or an estimate of age), with particulars from missing persons lists.

  3. Late Holocene Radiocarbon Variability in Northwest Atlantic Slope Waters

    Energy Technology Data Exchange (ETDEWEB)

    Sherwood, O; Edinger, E; Guilderson, T P; Ghaleb, B; Risk, M J; Scott, D B

    2008-08-15

    Deep-sea gorgonian corals secrete a 2-part skeleton of calcite, derived from dissolved inorganic carbon at depth, and gorgonin, derived from recently fixed and exported particulate organic matter. Radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters, respectively. Using specimens collected from Northwest Atlantic slope waters, we generated radiocarbon records for surface and upper intermediate water layers spanning the pre- and post bomb-{sup 14}C eras. In Labrador Slope Water (LSW), convective mixing homogenizes the pre-bomb {Delta}{sup 14}C signature (-67 {+-} 4{per_thousand}) to at least 1000 m depth. Surface water bomb-{sup 14}C signals were lagged and damped (peaking at {approx} +45{per_thousand} in the early 1980s) relative to other regions of the northwest Atlantic, and intermediate water signals were damped further. Off southwest Nova Scotia, the vertical gradient in {Delta}{sup 14}C is much stronger. In surface water, pre-bomb {Delta}{sup 14}C averaged -75 {+-} 5{per_thousand}. At 250-475 m depth, prebomb {Delta}{sup 14}C oscillated quasi-decadally between -80 and -100{per_thousand}, likely reflecting interannual variability in the presence of Labrador Slope Water vs. Warm Slope Water (WSW). Finally, subfossil corals reveal no systematic changes in vertical {Delta}{sup 14}C gradients over the last 1200 years.

  4. Metabolic kinetics and biological effects of radiocarbon (14C)

    International Nuclear Information System (INIS)

    Vasilenko, I.Ya.; Osipov, V.A.; Lyaginskaya, A.M.; Bugryshev, P.F.; Istomina, A.G.; Turova, V.I.; Dement'ev, S.I.; Zhorova, E.S.; Mart'yanov, B.M.; Shal'nova, G.A.; Kuz'mina, T.D.; Shebenko, V.A.; Pomerantseva, M.D.; Ramajya, L.K.

    1988-01-01

    Radiocarbon 14 C is one of the most widespread radionuclides. Increased concentration of anthropogenic 14 C in the biosphere is a problem of considerable hygienic and ecological significance. The paper presents the results of comprehensive studies for years on biokinetics of the main 14 C compounds, inorganic (Na H 14 CO 3 , Na 2 14 CO 3 , K 2 14 CO 3 , Ca 14 CO 3 ) as well as organic ( 14 C-glucose, 14 C-succinic acid, 14 C-glucosamine, 14 C-glycine, 14 C-tryptophane, 14 C-valine, 14 C-palmitic acid, 14 C-stearic acid, 14 C-ethyl alcohol, 14 C-methyl alcohol, 14 C-urea), of 14 C as food constituent and of elementary radiocarbon. The 14 C toxicity is investigated for both acute and chronic small doses received by animals. The nuclide's genetic efficiency is assessed. Based on research evidence, the accumulation multiple and equilibrium time are estimated for long-term 14 C intake by humans. The data may be used for setting genetic standards and estimating an anthropogenic increase of 14 C concentration in the environment. The hazard of anthropogenic radiocarbon is assessed with allowance for further development of nuclear power industry. (author)

  5. Radiocarbon dating of planktonic foraminifer shells: A cautionary tale

    Science.gov (United States)

    Mekik, Figen

    2014-01-01

    rate, bioturbation, winnowing, and calcite dissolution produce significant radiocarbon age offsets among multiple species of coexisting planktonic foraminifers and pteropod fragments. We compare the radiocarbon age of foraminifer species and pteropod fragments with estimates of percent calcite dissolved made with a sedimentary proxy (Globorotalia menardii fragmentation index—MFI) to delineate the effect of dissolution on radiocarbon age of foraminifers. Data from two core top transects on the Rio Grande Rise (RIO) and Ontong Java Plateau (OJP) and from down core sediments of varying sedimentation rates in the tropical Pacific (ME-27, MD98 2177, and MW91-9 56GGC) reveal that sediments with the greatest accumulation rates produce the least age offsets among coexisting species. Age offsets among coexisting foraminifers are about 3500 years on RIO, and 1000 years on OJP. Two core tops from RIO yield an age of the Last Glacial Maximum possibly due to mass displacement of younger sediments downslope. Foraminifer age increases with increasing dissolution and there is a consistent pattern of older foraminifer fragments coexisting with younger whole shells of the same species. The only exception is sediments which have experienced high dissolution where fragments are younger than whole shells. The age offset between fragments of G. menardii and its coexisting whole shells does not exceed the age offset among other coexisting foraminifer species in the same core tops.

  6. An upwelling-induced retention area off Senegal: A mechanism to ...

    African Journals Online (AJOL)

    Chlorophyll distribution peaks nearshore. This unique surface structure is interpreted as the result of a “double cell” structure in the upwelling vertical circulation: a first cell located at the shelf break, the main upwelling cell that brings cold and nutrient-rich subsurface water to the surface, and a second cell located inshore of ...

  7. Response of Mytilus edulis to enhanced phytoplankton availibility by controlled upwelling in an oligographic fjord

    NARCIS (Netherlands)

    Strohmeier, T.; Strand, Ø.; Alunno-Bruscia, M.; Duinker, A.; Rosland, R.; Jansen, H.M.

    2015-01-01

    The controlled upwelling of nutrient-rich deep water in oligotrophic coastal regions has been proposed as a means of increasing phytoplankton and, subsequently, bivalve aquaculture production. This was tested as part of a large-scale upwelling experiment in an oligotrophic environment (Lysefjord,

  8. Spatio-temporal variability of upwelling along the southwest coast of India based on satellite observations

    Science.gov (United States)

    Jayaram, Chiranjivi; Kumar, P. K. Dinesh

    2018-03-01

    Upwelling phenomenon along the eastern boundaries of global ocean has received greater attention in the recent times due to its environmental and economic significance in the global warming and the scenario of changing climate as opined by IPCC AR5. In this context, the availabile satellite data on sea surface winds, sea surface temperature (SST), sea level anomaly (SLA) and chlorophyll-a concentration (Chl-a), for the period 1981-2016 were analyzed to identify the coastal upwelling pattern in the Southeastern Arabian Sea (SEAS). Synergistic approach, using winds, SST, SLA and Chl-a revealed that strong upwelling was prevailing between 8°N and 12°N. During the study period, geographical differences existed in the peak values of upwelling favorable conditions considered for study. Analysis of the alongshore winds which are conducive for upwelling were observed to be curtailed towards the northern part of the study region between 2005 and 2010. Also, the strength of upwelling reduced during the strong ENSO years of 1997 and 2015. Linear regression based trend analysis of upwelling indices like Ekman transport, SST and chlorophyll along the coast, during the upwelling period, revealed slight increase in the strength towards the southern region while it decreased to the north during the study period.

  9. The future of coastal upwelling in the Humboldt current from model projections

    Science.gov (United States)

    Oyarzún, Damián; Brierley, Chris M.

    2018-03-01

    The Humboldt coastal upwelling system in the eastern South Pacific ocean is one of the most productive marine ecosystems in the world. A weakening of the upwelling activity could lead to severe ecological impacts. As coastal upwelling in eastern boundary systems is mainly driven by wind stress, most studies so far have analysed wind patterns change through the 20th and 21st Centuries in order to understand and project the phenomenon under specific forcing scenarios. Mixed results have been reported, and analyses from General Circulation Models have suggested even contradictory trends of wind stress for the Humboldt system. In this study, we analyse the ocean upwelling directly in 13 models contributing to phase 5 of the Coupled Model Intercomparison Project (CMIP5) in both the historical simulations and an extreme climate change scenario (RCP8.5). The upwelling is represented by the upward ocean mass flux, a newly-included variable that represents the vertical water transport. Additionally, wind stress, ocean stratification, Ekman layer depth and thermocline depth were also analysed to explore their interactions with coastal upwelling throughout the period studied. The seasonal cycle of coastal upwelling differs between the Northern and Southern Humboldt areas. At lower latitudes, the upwelling season spans most of the autumn, winter and spring. However, in the Southern Humboldt area the upwelling season takes place in spring and the summertime with downwelling activity in winter. This persists throughout the Historical and RCP8.5 simulations. For both the Northern and Southern Humboldt areas an increasing wind stress is projected. However, different trends of upwelling intensity are observed away from the sea surface. Whereas wind stress will continue controlling the decadal variability of coastal upwelling on the whole ocean column analysed (surface to 300 m depth), an increasing disconnect with upwelling intensity is projected below 100 m depth throughout the 21

  10. Regeneration of nitrogen by zooplankton and fish in the Northwest Africa and Peru upwelling ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Whitledge, T E

    1976-01-01

    The availability of nutrients and light are the dominant controlling factors of the levels of primary production in the ocean. In the lower latitudes where most coastal upwelling areas are located, the amount of light is seldom below the critical level to inhibit productivity so nutrients are often the limiting factor in phytoplankton growth. Nutrients utilized in primary productivity are derived from two sources in upwelling areas. Nutrients are introduced to the euphotic zone from depth by the physical processes that create upwelling and nutrients are recycled by biological organisms that inhabit the area. Nitrate introduced into the euphotic zone by upwelling supports new productivity while ammonium and other excretory products regenerated by zooplankton and nekton supports regenerated productivity. Results are reported from studies off the coast of Northwest Africa and Peru using /sup 15/N as a tracer that showed that recycled ammonium may fulfill nearly half of the daily nitrogen requirement of phytoplankton and upwelled nitrate may provide the other half.

  11. Variability of Iberian upwelling implied by ERA-40 and ERA-Interim reanalyses

    Directory of Open Access Journals (Sweden)

    José M. R. Alves

    2013-05-01

    Full Text Available The Regional Ocean Modeling System ocean model is used to simulate the decadal evolution of the regional waters in offshore Iberia in response to atmospheric fields given by ECMWF ERA-40 (1961–2001 and ERA-Interim (1989–2008 reanalyses. The simulated sea surface temperature (SST fields are verified against satellite AVHRR SST, and they are analysed to characterise the variability and trends of coastal upwelling in the region. Opposing trends in upwelling frequency are found at the northern limit, where upwelling has been decreasing in recent decades, and at its southern edge, where there is some evidence of increased upwelling. These results confirm previous observational studies and, more importantly, indicate that observed SST trends are not only due to changes in radiative or atmospheric heat fluxes alone but also due to changes in upwelling dynamics, suggesting that such a process may be relevant in climate change scenarios.

  12. Nutrient supply, surface currents, and plankton dynamics predict zooplankton hotspots in coastal upwelling systems

    Science.gov (United States)

    Messié, Monique; Chavez, Francisco P.

    2017-09-01

    A simple combination of wind-driven nutrient upwelling, surface currents, and plankton growth/grazing equations generates zooplankton patchiness and hotspots in coastal upwelling regions. Starting with an initial input of nitrate from coastal upwelling, growth and grazing equations evolve phytoplankton and zooplankton over time and space following surface currents. The model simulates the transition from coastal (large phytoplankton, e.g., diatoms) to offshore (picophytoplankton and microzooplankton) communities, and in between generates a large zooplankton maximum. The method was applied to four major upwelling systems (California, Peru, Northwest Africa, and Benguela) using latitudinal estimates of wind-driven nitrate supply and satellite-based surface currents. The resulting zooplankton simulations are patchy in nature; areas of high concentrations coincide with previously documented copepod and krill hotspots. The exercise highlights the importance of the upwelling process and surface currents in shaping plankton communities.

  13. Dynamics of a "low-enrichment high-retention" upwelling center over the southern Senegal shelf

    Science.gov (United States)

    Ndoye, Siny; Capet, Xavier; Estrade, Philippe; Sow, Bamol; Machu, Eric; Brochier, Timothée.; Döring, Julian; Brehmer, Patrice

    2017-05-01

    Senegal is the southern tip of the Canary upwelling system. Its coastal ocean hosts an upwelling center which shapes sea surface temperatures between latitudes 12° and 15°N. Near this latter latitude, the Cape Verde headland and a sudden change in shelf cross-shore profile are major sources of heterogeneity in the southern Senegal upwelling sector (SSUS). SSUS dynamics is investigated by means of Regional Ocean Modeling System simulations. Configuration realism and resolution (Δx≈ 2 km) are sufficient to reproduce the SSUS frontal system. Our main focus is on the 3-D upwelling circulation which turns out to be profoundly different from 2-D theory: cold water injection onto the shelf and upwelling are strongly concentrated within a few tens of kilometers south of Cape Verde and largely arise from flow divergence in the alongshore direction; a significant fraction of the upwelled waters are retained nearshore over long distances while travelling southward under the influence of northerly winds. Another source of complexity, regional-scale alongshore pressure gradients, also contributes to the overall retention of upwelled waters over the shelf. Varying the degree of realism of atmospheric and oceanic forcings does not appreciably change these conclusions. This study sheds light on the dynamics and circulation underlying the recurrent sea surface temperature pattern observed during the upwelling season and offers new perspectives on the connections between the SSUS physical environment and its ecosystems. It also casts doubt on the validity of upwelling intensity estimations based on simple Ekman upwelling indices at such local scales.

  14. Long-time observation of annual variation of Taiwan Strait upwelling in summer season

    Science.gov (United States)

    Tang, D. L.; Kawamura, H.; Guan, L.

    The Taiwan Strait is between Taiwan Island and Mainland China, where several upwelling zones are well known for good fishing grounds. Earlier studies in the strait have been conducted on detecting upwelling by ship measurements with short-term cruises, but long-term variations of upwelling in this region are not understood. The present paper examines satellite images for a long-time observation of two major upwelling zones in the Taiwan Strait: Taiwan Bank Upwelling (TBU) and Dongshan Upwelling (DSU). Sea surface temperature (SST) and chlorophyll a (Chl-a) images have been analyzed for summer months (June, July, and August) from 1980 to 2002. Results reveal annual variation of two upwelling zones. These two upwelling zones occur every year characterized with distinct low water temperature and high Chl-a concentrations. During the period from 1989 to 1998, SST is found to be 1.15 °C lower in TBU, and 1.42 °C lower in the DSU than the Taiwan Strait. The size of DSU has been found to be larger during summer of 1989, 1990, 1993 and 1995; TBU has been found to be weak during summer of 1994 and 1997. Ocean color images obtained from CZCS, OCI, and SeaWiFS also show high Chl-a concentrations (0.8-2.5 mg m-3) in two upwelling zones, which coincide with low SST in terms of location, shape, and time. These high Chl-a concentrations in TBU and DSU may be related to upwelling waters that bring nutrients from bottom to surface. The present results also show the potential of using satellite data for monitoring of ocean environment for long time period.

  15. Hot upwelling conduit beneath the Atlas Mountains, Morocco

    Science.gov (United States)

    Sun, Daoyuan; Miller, Meghan S.; Holt, Adam F.; Becker, Thorsten W.

    2014-11-01

    The Atlas Mountains of Morocco display high topography, no deep crustal root, and regions of localized Cenozoic alkaline volcanism. Previous seismic imaging and geophysical studies have implied a hot mantle upwelling as the source of the volcanism and high elevation. However, the existence, shape, and physical properties of an associated mantle anomaly are debated. Here we use seismic waveform analysis from a broadband deployment and geodynamic modeling to define the physical properties and morphology of the anomaly. The imaged low-velocity structure extends to ~200 km beneath the Atlas and appears ~350 K hotter than the ambient mantle with possible partial melting. It includes a lateral conduit, which suggests that the Quaternary volcanism arises from the upper mantle. Moreover, the shape and temperature of the imaged anomaly indicate that the unusually high topography of the Atlas Mountains is due to active mantle support.

  16. Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

    Energy Technology Data Exchange (ETDEWEB)

    Kjeldsen, Henrik, E-mail: kjeldsen@phys.au.d [AMS 14C Dating Centre, Department of Physics and Astronomy, University of Aarhus, Aarhus (Denmark); Heinemeier, Jan [AMS 14C Dating Centre, Department of Physics and Astronomy, University of Aarhus, Aarhus (Denmark); Heegaard, Steffen [Eye Pathology Section, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen (Denmark); Jacobsen, Christina; Lynnerup, Niels [Department of Forensic Medicine, University of Copenhagen, Copenhagen (Denmark)

    2010-04-15

    Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy of a few years by radiocarbon dating.

  17. Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

    International Nuclear Information System (INIS)

    Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen; Jacobsen, Christina; Lynnerup, Niels

    2010-01-01

    Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth, in accordance with expectations. Moreover, it has been possible to develop an age model for the formation of the eye-lens crystallines. From this model a radiocarbon calibration curve for lens crystallines has been calculated. As a consequence, the time of birth of humans can be determined with an accuracy of a few years by radiocarbon dating.

  18. Relative contributions of local wind and topography to the coastal upwelling intensity in the northern South China Sea

    Science.gov (United States)

    Wang, Dongxiao; Shu, Yeqiang; Xue, Huijie; Hu, Jianyu; Chen, Ju; Zhuang, Wei; Zu, TingTing; Xu, Jindian

    2014-04-01

    Topographically induced upwelling caused by the interaction between large-scale currents and topography was observed during four cruises in the northern South China Sea (NSCS) when the upwelling favorable wind retreated. Using a high-resolution version of the Princeton Ocean Model, we investigate relative contributions of local wind and topography to the upwelling intensity in the NSCS. The results show that the topographically induced upwelling is sensitive to alongshore large-scale currents, which have an important contribution to the upwelling intensity. The topographically induced upwelling is comparable with the wind-driven upwelling at surface and has a stronger contribution to the upwelling intensity than the local wind does at bottom in the near-shore shelf region. The widened shelf to the southwest of Shanwei and west of the Taiwan Banks intensifies the bottom friction, especially off Shantou, which is a key factor for topographically induced upwelling in terms of bottom Ekman transport and Ekman pumping. The local upwelling favorable wind enhances the bottom friction as well as net onshore transport along the 50 m isobath, whereas it has less influence along the 30 m isobath. This implies the local wind is more important in upwelling intensity in the offshore region than in the nearshore region. The contribution of local upwelling favorable wind on upwelling intensity is comparable with that of topography along the 50 m isobath. The effects of local upwelling favorable wind on upwelling intensity are twofold: on one hand, the wind transports surface warm water offshore, and as a compensation of mass the bottom current transports cold water onshore; on the other hand, the wind enhances the coastal current, and the bottom friction in turn increases the topographically induced upwelling intensity.

  19. Artificial upwelling using offshore wind energy for mariculture applications

    Directory of Open Access Journals (Sweden)

    Álvaro Viúdez

    2016-09-01

    Full Text Available Offshore wind is proposed as an energy source to upwell nutrient-rich deep water to the ocean photic layers. A spar-buoy wind turbine with a rigid tube about 300 m long is proposed as a pipe to drive deep water up to the surface. The minimum energy required to uplift the water is the potential energy difference between surface waters inside and outside the pipe, which depends on the background density profile. The corresponding surface jump or hydraulic head, h, calculated for several analytical and experimental density profiles, is of the order of 10 cm. If the complete turbine power (of the order of several MW is used for raising the water (assuming a 100% pump efficiency, in a frictionless flow, very large water volumes, of the order of thousands of m3 s-1, will be transported to the photic layers. In a more realistic case, taking into account pipe friction in wide pipes, of the order of 10 m radius, and a power delivered to the fluid of 1 MW, the volume transport is still very large, about 500 m3 s-1. However, such a large amount of dense water could sink fast to aphotic layers due to vertical static instability (the fountain effect, ruining the enhancement of primary production. Hence, some ways to increase the turbulent entrainment and avoid the fountain effect are proposed. From the energetic viewpoint, artificial upwelling using offshore wind energy is a promising way to fertilize large open sea regions. This mariculture application is, however, severely subjected to atmosphere and ocean climatology, as well as to ecological dynamics. The general problem is multidisciplinary, and some important physical, engineering and ecological questions need to be seriously addressed to improve our confidence in the approach presented here.

  20. Community response of zooplankton to oceanographic changes (2002-2012) in the central/southern upwelling system of Chile

    Science.gov (United States)

    Medellín-Mora, Johanna; Escribano, Ruben; Schneider, Wolfgang

    2016-03-01

    A 10-year time series (2002-2012) at Station 18 off central/southern Chile allowed us to study variations in zooplankton along with interannual variability and trends in oceanographic conditions. We used an automated analysis program (ZooImage) to assess changes in the mesozooplankton size structure and the composition of the taxa throughout the entire community. Oceanographic conditions changed over the decade: the water column became less stratified, more saline, and colder; the mixed layer deepened; and the oxygen minimum zone became shallower during the second half of the time series (2008-2012) in comparison with the first period (2002-2007). Both the size structure and composition of the zooplankton were significantly associated with oceanographic changes. Taxonomic and size diversity of the zooplankton community increased to the more recent period. For the second period, small sized copepods (1.5 mm) and medium size copepods (1-1.5 mm), whereas euphausiids, decapod larvae, appendicularian and ostracods increased their abundance during the second period. These findings indicated that the zooplankton community structure in this eastern boundary ecosystem was strongly influenced by variability of the upwelling process. Thus, climate-induced forcing of upwelling trends can alter the zooplankton community in this highly productive region with potential consequences for the ecosystem food web.

  1. Application of AMS radiocarbon in earth system science studies

    International Nuclear Information System (INIS)

    Kang, Dong Jin; Park, Mi Kyung; Kim, Kyung Ryul

    2001-01-01

    Radiocarbon, a cosmic ray-produced isotope, is one of the most important tracers in Earth system sciences. The strong involvement of carbon in the biosphere and its half life of 5720 years are reflected in appropriate applications in archeology, as well as in the Earth system sciences. Radiocarbon dating had an important turning point in 1977 with the discovery that mass spectrometry with tandem acceleration could be used to measure C-14. This new technique, known as AMS or accelerator mass spectrometry reduced the required sample size to the order of mg, three orders of magnitude smaller than for conventional techniques, thus opening the range of applicability of C-14 studies to a much wider range of samples. However, the application has been complicated by two major activities of human beings on a global scale: the extensive usage of fossil fuel since the industrial revolution and nuclear testing in the atmosphere, which have influenced the natural balance of radiocarbon in the atmosphere. However, the separation of bomb-produced carbon from natural background carbon has produced a very fruitful understanding of the global carbon cycle and the conveyor belt system in the ocean, which will be essential for understanding global environmental problems, such as global warming, in the coming century. Carbon cycle studies in Korea have been made since the early 1990s. The studies include monitoring of CO 2 concentrations in the atmosphere, stable isotope studies, and carbon cycle studies in the sea around Korea. The opening of ths AMS facility at Seoul National University (SNU) will enhance carbon studies in Earth system sciences greatly in the future

  2. Radiocarbon accelerator mass spectrometry (AMS) sample preparation laboratory in Brazil

    International Nuclear Information System (INIS)

    Macario, Kita D.; Gomes, Paulo R. S.; Anjos, Roberto M. dos; Linares, Roberto; Queiroz, Eduardo; Oliveira, Fabiana M. de; Cardozo, Laio; Carvalho, Carla R.A.

    2011-01-01

    Full text: For decades Accelerator Mass Spectrometry has been widely used for radiocarbon measurements all over the world with application in several fields of science from archaeology to geosciences. This technique provides ultrasensitive analysis of reduced size samples or even specific compounds since sample atoms are accelerated to high energies and measured using nuclear particle detectors. Sample preparation is extremely important for accurate radiocarbon measurement and includes chemical pre-treatment to remove all possible contaminants. For beam extraction in the accelerator ion source, samples are usually converted to graphite. In this work we report a new radiocarbon sample preparation facility installed at the Physics Institute of Universidade Federal Fluminense (UFF), in Brazil. At the Nuclear Chronology Laboratory (LACRON) samples are chemically treated and converted to carbon dioxide by hydrolysis or combustion. A stainless steel based vacuum line was constructed for carbon dioxide separation and graphitization is performed in sealed quartz tubes in a muffle oven. Successful graphite production is important to provide stable beam currents and to minimize isotopic fractionation. Performance tests for graphite production are currently under way and isotopic analysis will soon be possible with the acquisition of a Single Stage AMS System by our group. The Single Stage Accelerator produced by National Electrostatic Corporation is a 250 kV air insulated accelerator especially constructed to measure the amount of 14 C in small modern graphite samples to a precision of 0.3 % or better. With the installation of such equipment in the first half of 2012, UFF will be ready to perform the 14C -AMS technique. (author)

  3. Physical structure and algae community of summer upwelling off eastern Hainan

    Science.gov (United States)

    Xu, H.; Liu, S.; Xie, Q.; Hong, B.; Long, T.

    2017-12-01

    The upwelling system is the most productive ecosystem along the continental shelf of the northern South China Sea Shelf. It brings nutrient from bottom to surface and blooms biotic community driven by summer monsoon. In this study, we present observed results of physical and biotic community structures during August, 2015 in the upwelling system along Hainan eastern coast, which is one the strongest upwelling systems in the northern South China Sea. By using hydrological data collected by CTD, we found a significant cold water tongue with high salinity which extended from offshore to 100 m isobaths. However, dissolved oxygen (DO) showed a sandwich structure in which high core of DO concentration appeared at the layer from 5 m to 30 m. It possibly was caused by the advection transport of high DO from adjacent area. Basically, this upwelling system was constrained at northern area of 18.8ºN in horizontal due to the weakening summer monsoon in August. In addition, we collected water sample at the upwelling area and measured algae categories and concentration by high performance liquid chromatography (HPLC). Results show the biotic community was dominated by five types of algae mainly, they were diatoms, dinoflagellates, green algae, prokaryotes and prochlorococcus. And different patterns of different algae were demonstrated. In the upwelling area, diatoms and prokaryotes show opposite structures, and more complex pattern for the rest three algae indicating an active biotic community in the upwelling system.

  4. Upwelling events, coastal offshore exchange, links to biogeochemical processes - Highlights from the Baltic Sea Science Congress

    Directory of Open Access Journals (Sweden)

    Bogdan Ołdakowski

    2008-03-01

    Full Text Available The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled"Upwelling events, coastal offshore exchange, links to biogeochemical processes" 20 presentations were given,including 7 talks and 13 posters related to the theme of the session.This paper summarises new findings of the upwelling-related studies reported in the session. It deals with investigationsbased on the use of in situ and remote sensing measurements as well as numerical modelling tools. The biogeochemicalimplications of upwelling are also discussed.Our knowledge of the fine structure and dynamic considerations of upwelling has increased in recent decades with the advent ofhigh-resolution modern measurement techniques and modelling studies. The forcing and the overall structure, duration and intensity ofupwelling events are understood quite well. However, the quantification of related transports and the contribution to the overall mixingof upwelling requires further research. Furthermore, our knowledge of the links between upwelling and biogeochemical processes is stillincomplete. Numerical modelling has advanced to the extent that horizontal resolutions of c. 0.5 nautical miles can now be applied,which allows the complete spectrum of meso-scale features to be described. Even the development of filaments can be describedrealistically in comparison with high-resolution satellite data.But the effect of upwelling at a basin scale and possible changes under changing climatic conditions remain open questions.

  5. Radiocarbon dating of bottom sediments of the Red Sea

    International Nuclear Information System (INIS)

    Kuptsov, V.M.; Palkina, A.M.

    1986-01-01

    Results of radiocarbon dating of 23 cores (81 definitions) sampled in the Red Sea rifton at 18 deg N are presented. Dating encompasses all major tectonic structures: the upper and the lower tectonic steps, saline scarp, axial zone. For sediments of the upper tectonic step the normal course of sedimentogenesis is detected, in all other structures with a strongly dissected topography redeposition and nonaccumulation of sediments are widely developed. In Holocene the rate of sediment accumulation is 1.5-2 times lower than that in the late Wurm

  6. Utilization of minicomputer in the radiocarbon analysis measurements

    International Nuclear Information System (INIS)

    Szarka, J.; Krnac, S.

    1984-01-01

    Possibilities of minicomputer applications for radiocarbon analysis with multielement proportional counters are considered. Off-line on-line measuring system operation is possible. TPA-70 minicomputer and CAMAC electronics are used in on-line operation. Block-diagrams of data acquisition and data processing as well as the block-diagram of data evaluation program, which permits not only to increase the precision of the measurements, but also reduces the measuring time by 1/3, as compared with conventional methods, are given

  7. Radiocarbon dates on bones of extinct birds from Hawaii.

    OpenAIRE

    James, H F; Stafford, T W; Steadman, D W; Olson, S L; Martin, P S; Jull, A J; McCoy, P C

    1987-01-01

    Bones from a stratified sedimentary deposit in the Puu Naio Cave site on Maui, Hawaiian Islands, reveal the late Holocene extinction of 19 species of birds. The age of the sediment and associated fauna was determined by direct radiocarbon dating (tandem particle accelerator-mass spectrometer; TAMS) of amino acids extracted from bones weighing as little as 450 mg. The 14C dates indicate that sediment has been accumulating in the lava tube for at least the last 7750 years, a suitable time frame...

  8. A Holocene record of ocean productivity and upwelling from the northern California continental slope

    Science.gov (United States)

    Addison, Jason A.; Barron, John A.; Finney, Bruce P.; Kusler, Jennifer E.; Bukry, David; Heusser, Linda E.; Alexander, Clark R.

    2018-01-01

    The Holocene upwelling history of the northern California continental slope is examined using the high-resolution record of TN062-O550 (40.9°N, 124.6°W, 550 m water depth). This 7-m-long marine sediment core spans the last ∼7500 years, and we use it to test the hypothesis that marine productivity in the California Current System (CCS) driven by coastal upwelling has co-varied with Holocene millennial-scale warm intervals. A combination of biogenic sediment concentrations (opal, total organic C, and total N), stable isotopes (organic matter δ13C and bulk sedimentary δ15N), and key microfossil indicators of upwelling were used to test this hypothesis. The record of biogenic accumulation in TN062-O550 shows considerable Holocene variability despite being located within 50 km of the mouth of the Eel River, which is one of the largest sources of terrigenous sediment to the Northeast Pacific Ocean margin. A key time interval beginning at ∼2900 calibrated years before present (cal yr BP) indicates the onset of modern upwelling in the CCS, and this period also corresponds to the most intense period of upwelling in the last 7500 years. When these results are placed into a regional CCS context during the Holocene, it was found that the timing of upwelling intensification at TN062-O550 corresponds closely to that seen at nearby ODP Site 1019, as well as in the Santa Barbara Basin of southern California. Other CCS records with less refined age control show similar results, which suggest late Holocene upwelling intensification may be synchronous throughout the CCS. Based on the strong correspondence between the alkenone sea surface temperature record at ODP Site 1019 and the onset of late Holocene upwelling in northern California, we suggest that CCS warming may be conducive to upwelling intensification, though future changes are unclear as the mechanisms forcing SST variability may differ.

  9. Biological and oceanographic upwelling indicators at Cabo Frio (RJ

    Directory of Open Access Journals (Sweden)

    Gleyci A. O. Moser

    1997-01-01

    Full Text Available Phytoplankton biomass, chemical parameters and hydrology were studied in a transect 101.6 km long off Cabo Frio (RJ, Southeast Brazil, during summer (December 29 to 31, 1991 and winter (June 27 to 30, 1992. Wind induced upwelling events are frequently observed in the area during summer, becoming rare during winter. By the summer cruise a bloom of phytoplankton was observed in surface, close to the coast, with chlorophyll concentrations reaching 25.55 mg Chl-a m-3, uncoupled from the cold, nutrient rich waters of South Atlantic Central Water (SACW, found below 40 m depth. During the winter cruise, the SACW raised at the surface waters in front of Cabo Frio depicting an upwelling event. However, in spite of high surface nitrate concentrations (up to 7.7 f.1M chlorophyll-a were lower than 2 mg Chl-a m-3. The phytoplankton biomass, meteorological and hydrological data suggest a probable upwelling event immediately before the summer cruise, and an ongoing one during winter time. Cluster analyses and principal component analyses (PCA were applied to summer and winter data, pointing out multidimensional fronts in the area during both seasons.A biomassa fitoplanctônica, parâmetros químicos e hidrologia foram estudadas em um transecto de 101,6 Km ao largo de Cabo Frio, (RJ Brasil, durante o verão (Dezembro 29 a 31, 1991 e inverno (Junho 27 a 30, 1992. Nesta área, eventos de ressurgência induzidos pelo vento são comuns durante o verão, tornando-se mais raros durante o inverno. Durante o período de verão uma floração de fitoplâncton foi observada na superfície próximo ao continente, apresentando um máximo de clorofila-a igual a 25,55 mg Cl-a m'3 desacoplado das águas frias e ricas em nutrientes da Água Central do Atlântico Sul (ACAS, presente abaixo de 40 m. Durante o inverno, a ACAS alcançou a superflcie em frente a Cabo Frio, caracterizando um evento de ressurgência. Entretanto, apesar das altas concentrações de nitrato na superf

  10. Change of the radiocarbon natural level in the Earth atmosphere and geomagnetic field

    International Nuclear Information System (INIS)

    Vasil'ev, S.S.; Dergachev, V.A.

    1995-01-01

    Harmonic spectral analysis of change of radiocarbon concentration on the Earth atmosphere during the last 7000 years, including time intervals of both high and low intensity of the Earth magnetic field, was conducted. The effect of geomagnetic field on a harmonic amplitudes and frequencies in variations of radiocarbon concentration, conditioned by solar activity, was shown

  11. Dating the time of birth: A radiocarbon calibration curve for human eye-lens crystallines

    DEFF Research Database (Denmark)

    Kjeldsen, Henrik; Heinemeier, Jan; Heegaard, Steffen

    2010-01-01

    Radiocarbon bomb-pulse dating has been used to measure the formation age of human eye-lens crystallines. Lens crystallines are special proteins in the eye-lens that consist of virtually inert tissue. The experimental data show that the radiocarbon ages to a large extent reflect the time of birth...

  12. Intracavity OptoGalvanic Spectroscopy Not Suitable for Ambient Level Radiocarbon Detection

    NARCIS (Netherlands)

    Paul, Dipayan; Meijer, Harro

    2015-01-01

    IntraCavity OptoGalvanic Spectroscopy as a radiocarbon detection technique was first reported by the Murnick group at Rutgers University, Newark, NJ, in 2008. This technique for radiocarbon detection was presented with tremendous potentials for applications in various fields of research.

  13. Very little in situ produced radiocarbon retained in accumulating Antarctic ice

    NARCIS (Netherlands)

    Kemp, W.J.M. van der; Alderliesten, C.; Borg, K. van der; Holmlund, P.; Jong, A.F.M. de; Karlöf, L.; Lamers, R.A.N.; Oerlemans, J.; Thomassen, M.; Wal, R.S.W. van de

    2000-01-01

    Ice samples from Dronning Maud Land, Antarctica, were analyzed for 14CO2 and 14CO by accelerator mass spectrometry. Only a small amount (~2%) of in situ produced radiocarbon was detected. The calibrated radiocarbon ages, corrected for in situ produced 14C, are in fair agreement with age estimates

  14. New observations on the stratigraphy and radiocarbon dates at the Cross Creek site, Opito, Coromandel Peninsula

    International Nuclear Information System (INIS)

    Furey, L.; Petchey, F.; Sewell, B.; Green, R.

    2008-01-01

    This paper re-examines stratigraphy and radiocarbon dates at Cross Creek in Sarah's Gully. Three new radiocarbon dates are presented for Layer 9, the earliest, and previously undated, occupation. This investigation is part of a programme of archaeological work being carried out on the Coromandel Peninsula. (author). 51 refs., 4 figs., 3 tabs

  15. Bomb conversion of CO2 to graphite for radiocarbon measurement by tandem accelerator mass spectrometry (TAMS)

    International Nuclear Information System (INIS)

    Lowe, D.C.; Judd, W.J.

    1985-01-01

    TAMS has extended the scope of radiocarbon dating but improved sample target preparation techniques are still required. In this paper a quick and reliable method for the conversion of CO 2 into graphite targets suitable for radiocarbon dating is presented. In the outlined procedure a single operator can produce 20 graphite targets a day. (author)

  16. Atmospheric radiocarbon calibration beyond 11,900 cal BP from Lake Suigetsu laminated sediments

    NARCIS (Netherlands)

    Kitagawa, H; van der Plicht, J

    2000-01-01

    This paper presents an updated atmospheric radiocarbon calibration from annually laminated (varved) sediments from Lake Suigetsu (LS). central Japan. As presented earlier, the LS varved sediments can be used to extend the radiocarbon time scale beyond the tree ring calibration range that reaches

  17. Aquifer recharging in South Carolina: radiocarbon in environmental hydrogeology

    International Nuclear Information System (INIS)

    Stone, P.A.; Knox, R.L.; Mathews, T.D.

    1985-01-01

    Radiocarbon activities of dissolved inorganic carbon (and tritium activities where infiltration rates are rapid and aquifers shallow) provide relatively unambiguous and inexpensive evidence for identification of significant recharge areas. Such evidence is for the actual occurrence of modern recharge in the aquifer and thus is less inferential than stratigraphic or potentiometric evidence. These underutilized isotopic techniques are neither arcane nor complex and have been more-or-less standardized by earlier researchers. In South Carolina, isotopic evidence has been used from both calcareous and siliceous sedimentary aquifers and fractured crystalline rock aquifers. The Tertiary limestone aquifer is shown not to be principally recharged in its subcrop area, unlike conditions assumed for many other sedimentary aquifers in southeastern United States, and instead receives considerable lateral recharge from interfingering updip Tertiary sand aquifers in the middle coastal plain. Induced recharging at Hilton Head Island is mixing ancient relict water and modern recharge water. Recharging to deeper portions of the Cretaceous Middendorf basal sand aquifer occurs at least as far coastward as the middle coastal plain, near sampling sites that stratigraphically appear to be confined. Pronounced mineralization of water in fractured rocks cannot be considered as evidence of ancient or relict ground water that is isolated from modern contaminants, some of these waters contain considerable radiocarbon and hydrogen-bomb tritium

  18. Influence of thermal treatments on radiocarbon dating of groundwater samples

    Science.gov (United States)

    Stanciu, Iuliana Madalina; Sava, Tiberiu Bogdan; Pacesila, Doru Gheorghe; Gaza, Oana; Simion, Corina Anca; Stefan, Bianca Maria; Sava, Gabriela Odilia; Ghita, Dan Gabriel; Mosu, Vasile

    2017-06-01

    Radiocarbon measurements of dissolved inorganic carbon (DIC) in water provides information about the formation of oceanic circulation of the water volumes, the hydrogeological systems, and also valuable information can be gained about the aquifer storage and the degree of containment relative to the surface waters. Radiocarbon dating refers to the determination of small quantities of the naturally occurring carbon 14 in the water, which can be integrated in the groundwater mass through the gaseous CO2, carbonaceous deposits dissolved by water and organic remains. The aim of this study is to investigate the influence of the temperature and pressure over the amount of each isotope of carbon during the sample preparation stage. The first step was to evaporate several underground water samples at 65°C under different conditions until the carbonates were obtained, then the CO2 was extracted with orto-phosphoric acid and transformed to graphite. The second step was to obtain graphite from an untreated water sample. Finally, the samples were measured with the 1MV Cockcroft-Walton Tandetron Accelerator by Accelerator Mass Spectrometry.

  19. Carbon extraction methods for radiocarbon dating of pottery

    International Nuclear Information System (INIS)

    Delque-Kolic, E.

    1995-01-01

    Pottery is a direct witness of human activity and gives, through its macroscopic and microscopic studies, lots of information about its manufacturers. Nevertheless, radiocarbon dating, currently applied in archaeology to charcoals, wood and bones has only been rarely employed with ceramic. The problem is that many different carbon sources, of different radiocarbon age, may contribute to the potsherd carbon content. So, the aim of all dating projects is to separate carbon related to the period when the potsherd was manufactured and used. In a first time, we have made our own samples with raw materials (clay and temper) known in nature and age. We have fired them with wood of known age under reducing atmosphere. Under these conditions, soot produced by wood burning forms a more or less important deposit on the surface of the pots. It is this source of carbon, present in many archaeological sherds, that we first tried to select. Burning these potsherds at low temperature under an O 2 flow, we have noticed that carbon from kiln wood was preferentially extracted. This treatment applied to a thin lamella cut in a smoked part of the potsherd provides, almost exclusively, carbon from smoke. These techniques, applied to known archaeological sherds, have given encouraging results. We have also explored a new method which consists in oxidizing carbon with a laser beam at the surface of the sample. The use of this process for extracting carbon from smoke seems promising if serious experimental precautions are taken when working with so low carbon content. (author)

  20. Application of Bomb Radiocarbon Chronologies to Shortfin Mako (Isurus oxyrinchus)

    Energy Technology Data Exchange (ETDEWEB)

    Ardizzone, D; Cailliet, G M; Natanson, L J; Andrews, A H; Kerr, L A; Brown, T A

    2007-07-16

    and the number of samples for MIA analysis was insufficient for some months. Hence, unequivocal validation of shortfin mako age estimates has yet to be accomplished. Atmospheric testing of thermonuclear devices in the 1950s and 1960s effectively doubled the natural atmospheric radiocarbon ({sup 14}C). The elevated {sup 14}C levels were first recorded in 1957-58, with a peak around 1963. As a consequence, {sup 14}C entered the ocean through gas exchange with the atmosphere at the ocean surface and in terrestrial runoff. Despite variable oceanographic conditions, a worldwide rise of the bomb {sup 14}C signal entered the ocean mixed layer as dissolved inorganic carbon (DIC) in 1957-58. The large amounts of {sup 14}C released from the bomb tests produced a signature that can be followed through time, throughout the marine food web, and into deeper waters. The marked increase of radiocarbon levels was first measured in the DIC of seawater and in biogenic marine carbonates of hermatypic corals in Florida. Subsequently, this record was documented in corals from other regions and in the thallus of rhodoliths. The accumulation of radiocarbon in the hard parts of most marine organisms in the mixed layer (such as fish otoliths and bivalves) was synchronous with the coral time-series. This technique has been used to validate age estimates and longevity of numerous bony fishes to date, as well as to establish bomb radiocarbon chronologies from different oceans. In the first application of this technique to lamnoid sharks, validated annual band-pair deposition in vertebral growth bands for the porbeagle (Lamna nasus) aged up to 26 years. Radiocarbon values from samples obtained from 15 porbeagle caught in the western North Atlantic Ocean (some of which were known-age) produced a chronology similar in magnitude to the reference carbonate chronology for that region. The observed phase shift of about 3 years was attributed to different sources of carbon between vertebrae and those for

  1. Vertebral bomb radiocarbon suggests extreme longevity in white sharks.

    Science.gov (United States)

    Hamady, Li Ling; Natanson, Lisa J; Skomal, Gregory B; Thorrold, Simon R

    2014-01-01

    Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ(14)C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of (14)C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought.

  2. Millennium scale radiocarbon variations in Eastern North Atlantic thermocline waters: 0-7000 years

    Energy Technology Data Exchange (ETDEWEB)

    Frank, N.; Tisnerat-Laborde, N.; Hatte, C. [LSCE, F-91190 Gif Sur Yvette, (France); Colin, C. [Univ Paris 11, IDES, Orsay, (France); Dottori, M.; Reverdin, G. [Univ Paris 06, LOCEAN, F-75252 Paris, (France)

    2009-07-01

    Complete text of publication follows: Deep water corals are exceptional archives of modern and past ocean circulation as combined U-series and radiocarbon dating allows to reconstruct seawater radiocarbon. Here we present thermocline water radiocarbon concentrations that have been reconstructed for the past {approx} 7000 years for the eastern north Atlantic, based on deep-water corals from Rockall Bank and Porcupine Seabight. We find that thermocline water radiocarbon values follow overall the mean atmospheric long term trend with an average offset of {Delta}{sup 14}C between intermediate water and atmosphere of -55{+-}5 per thousand until 1960 AD. Residual variations are strong ({+-}25 per thousand) over the past 7000 years and there is first evidence that those are synchronous to millennium scale climate variability. Over the past 60 years thermocline water radiocarbon values increase due to the penetration of bomb-radiocarbon into the upper intermediate ocean. Radiocarbon increases by {Delta}{sup 14}C of +95 per thousand compared to +210 per thousand for eastern North Atlantic surface waters. Moreover, bomb-radiocarbon penetration to thermocline depth occurs with a delay of {approx} 10-15 years. Based on high resolution ocean circulation models we suggest that radiocarbon changes at upper intermediate depth are today barely affected by vertical mixing and represent more likely variable advection and mixing of water masses from the Labrador Sea and the temperate Atlantic (including Mediterranean outflow water). Consequently, we assume that residual radiocarbon variations over the past 7000 years reflect millennium scale variability of the Atlantic sub-polar and sub-tropical gyres

  3. Near-surface temperature gradient in a coastal upwelling regime

    Science.gov (United States)

    Maske, H.; Ochoa, J.; Almeda-Jauregui, C. O.; Ruiz-de la Torre, M. C.; Cruz-López, R.; Villegas-Mendoza, J. R.

    2014-08-01

    In oceanography, a near homogeneous mixed layer extending from the surface to a seasonal thermocline is a common conceptual basis in physics, chemistry, and biology. In a coastal upwelling region 3 km off the coast in the Mexican Pacific, we measured vertical density gradients with a free-rising CTD and temperature gradients with thermographs at 1, 3, and 5 m depths logging every 5 min during more than a year. No significant salinity gradient was observed down to 10 m depth, and the CTD temperature and density gradients showed no pronounced discontinuity that would suggest a near-surface mixed layer. Thermographs generally logged decreasing temperature with depth with gradients higher than 0.2 K m-1 more than half of the time in the summer between 1 and 3 m, 3 and 5 m and in the winter between 1 and 3 m. Some negative temperature gradients were present and gradients were generally highly variable in time with high peaks lasting fractions of hours to hours. These temporal changes were too rapid to be explained by local heating or cooling. The pattern of positive and negative peaks might be explained by vertical stacks of water layers of different temperatures and different horizontal drift vectors. The observed near-surface gradient has implications for turbulent wind energy transfer, vertical exchange of dissolved and particulate water constituents, the interpretation of remotely sensed SST, and horizontal wind-induced transport.

  4. Lagrangian pathways of upwelling in the Southern Ocean

    Science.gov (United States)

    Viglione, Giuliana A.; Thompson, Andrew F.

    2016-08-01

    The spatial and temporal variability of upwelling into the mixed layer in the Southern Ocean is studied using a 1/10° ocean general circulation model. Virtual drifters are released in a regularly spaced pattern across the Southern Ocean at depths of 250, 500, and 1000 m during both summer and winter months. The drifters are advected along isopycnals for a period of 4 years, unless they outcrop into the mixed layer, where lateral advection and a parameterization of vertical mixing are applied. The focus of this study is on the discrete exchange between the model mixed layer and the interior. Localization of interior-mixed layer exchange occurs downstream of major topographic features across the Indian and Pacific basins, creating "hotspots" of outcropping. Minimal outcropping occurs in the Atlantic basin, while 59% of drifters outcrop in the Pacific sector and in Drake Passage (the region from 140° W to 40° W), a disproportionately large amount even when considering the relative basin sizes. Due to spatial and temporal variations in mixed layer depth, the Lagrangian trajectories provide a statistical measure of mixed layer residence times. For each exchange into the mixed layer, the residence time has a Rayleigh distribution with a mean of 30 days; the cumulative residence time of the drifters is 261 ± 194 days, over a period of 4 years. These results suggest that certain oceanic gas concentrations, such as CO2 and 14C, will likely not reach equilibrium with the atmosphere before being resubducted.

  5. Ekman Upwelling, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  6. Observed anomalous upwelling in the Lakshadweep Sea during the summer monsoon season of 2005

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishna, V.V.; Rao, R.R.; Nisha, K.; GirishKumar, M.S.; Pankajakshan, T.; Ravichandran, M.; Johnson, Z.; Girish, K.; Aneeshkumar, N.; Srinath, M.; Rajesh, S.; Rajan, C.K.

    of local and remote forcings are examined to explain the observed anomalous upwelling during SMS of 2005. The equatorward alongshore wind stress (WS) along the KK XBT transect persisted in a transient manner beyond September only during SMS of 2005...

  7. Upwelling along the western Indian continental margin and its geological record - a summary

    Digital Repository Service at National Institute of Oceanography (India)

    Setty, M.G

    sediment components can be correlated to the characteristics of the water masses and, thereby, to the intensity and magnitude of upwelling. Benthic and planktonic foraminifers are particularly useful indicators; e.g., the invasion of immigrant populations...

  8. Ekman Upwelling, METOP ASCAT, 0.25 degrees, Global, Near Real Time

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  9. Upwelling and associated hydrography along the west coast of india during southwest monsoon, 1999

    Digital Repository Service at National Institute of Oceanography (India)

    Maheswaran, P.A.; Rajesh, G.; Revichandran, C.; Nair, K.K.C.

    ) and 1.2 degrees C (off Mangalore) from the farthest stations, indicating the presence of upwelled water near the coast. Well defined thermal, saline and density fronts were visible. Relatively high offshore transport was observed off Kanyakumari...

  10. On an upwelling front along the west coast of India during later part of southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Unnikrishnan, A.S.; Antony, M.K.

    A coastal front, associated with upwelling, is identified from the observed thermal field along the west coast of India during September, 1987. The front, which is seen very clearly upto a depth of about 75 m, has a horizontal gradient...

  11. Observational evidence of upwelling off the southwest coast of India during June-July 2006

    Digital Repository Service at National Institute of Oceanography (India)

    Lekshmi, S.; Smitha, B.R.; Revichandran, C.

    transects off Thiruvananthapuram (8.5 degrees N) and off Koilam (9 degrees N), during June 25th-6th July 2006. Observed upwelling parameters (local temperature anomalies, salinity, isothermal layer depth (ILD), Mixed Layer Depth (MLD), isotherm slope...

  12. Discriminating the biophysical impacts of coastal upwelling and mud banks along the southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Karnan, C.; Jyothibabu, R.; Arunpandi, N.; Jagadeesan, L.; Muraleedharan, K.R.; Pratihary, A.K.; Balachandran, K.K.; Naqvi, S.W.A.

    Coastal upwelling and mud banks are two oceanographic processes concurrently operating along certain stretches of the southwest (Kerala) coast of India during the Southwest Monsoon period (June-September), facilitating significant enhancement...

  13. Intensive aggregate formation with low vertical flux during an upwelling-induced diatom bloom

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Tiselius, P.; Mitchell-Innes, B.

    1998-01-01

    of turbulent shear in the ocean such stickiness coefficients predict very high specific coagulation rates (0.3 d(-1)). In situ video observation demonstrated the occurrence of abundant diatom aggregates with surface water concentrations between 1,000 and 3,000 ppm. Despite the very high concentration......The surfaces of most pelagic diatoms are sticky at times and may therefore form rapidly settling aggregates by physical coagulation. Stickiness and aggregate formation may be particularly adaptive in upwelling systems by allowing the retention of diatom populations in the vicinity of the upwelling...... center. We therefore hypothesized that upwelling diatom blooms are terminated by aggregate formation and rapid sedimentation. We monitored the development of a maturing diatom (mainly Chaetoceros spp.) bloom in the Benguela upwelling current during 7 d in February. Chlorophyll concentrations remained...

  14. A long history of equatorial deep-water upwelling in the Pacific Ocean

    Science.gov (United States)

    Zhang, Yi Ge; Pagani, Mark; Henderiks, Jorijntje; Ren, Haojia

    2017-06-01

    Cold, nutrient- and CO2-rich waters upwelling in the eastern equatorial Pacific (EEP) give rise to the Pacific cold tongue. Quasi-periodic subsidence of the thermocline and attenuation in wind strength expressed by El Niño conditions decrease upwelling rates, increase surface-water temperatures in the EEP, and lead to changes in regional climates both near and far from the equatorial Pacific. EEP surface waters have elevated CO2 concentrations during neutral (upwelling) or La Niña (strong upwelling) conditions. In contrast, approximate air-sea CO2 equilibrium characterizes El Niño events. One hypothesis proposes that changes in physical oceanography led to the establishment of a deep tropical thermocline and expanded mixed-layer prior to 3 million years ago. These effects are argued to have substantially reduced deep-water upwelling rates in the EEP and promoted a "permanent El Niño-like" climate state. For this study, we test this supposition by reconstructing EEP "excess CO2" and upwelling history for the past 6.5 million years using the alkenone-pCO2 methodology. Contrary to previous assertions, our results indicate that average temporal conditions in the EEP over the past ∼6.5 million years were characterized by substantial CO2 disequilibrium and high nutrient delivery to surface waters - characteristics that imply strong upwelling of deep waters. Upwelling appears most vigorous between ∼6.5 to 4.5 million years ago coinciding with high accumulation rates of biogenic material during the late Miocene - early Pliocene "biogenic bloom".

  15. Upwelling and Other Environmental Influences on Growth of a Nearshore Benthic Fish

    Science.gov (United States)

    von Biela, V. R.; Zimmerman, C. E.; Kruse, G. H.; Mueter, F. J.; Black, B.; Douglas, D. C.; Bodkin, J. L.

    2016-02-01

    The role of upwelling in nearshore benthic systems is more uncertain compared to the relatively strong positive associations with pelagic production. To understand how upwelling and other environmental conditions influence nearshore benthic production, we developed an annual index of production from growth increments recorded in otoliths of kelp greenling (Hexagrammos decagrammus) at nine sites in the seasonally-upwelling California Current and downwelling Alaska Coastal currents. Kelp greenling are a benthic-feeding fish common in kelp forests with food webs sustained by both kelp and phytoplankton primary production. We explored the influence of basin- and local-scale conditions, including upwelling, across all seasons at lags up to two years taken to represent changes in the quantity and quality of prey. Upwelling strength was positively related to fish growth in both current systems, although relationships in the Alaska Coastal Current were indicative of faster growth with relaxed downwelling, rather than upwelling. Looking across a suite of basin- and local-scale environmental indicators, complex relationships emerged in the California Current, with faster growth related to within-year warm conditions and lagged-year cool conditions. In contrast, fish in the downwelling system grew faster both during and subsequent to warm conditions. The complex lag-dependent dynamics in the upwelling system may reflect differences in conditions that promote quantity versus quality of benthic invertebrate prey. Thus, we hypothesize that benthic production is maximized when cool and warm years alternate during periods of high frequency climate variability in the California Current. Such a pattern is consistent with previous findings suggesting that benthic invertebrate abundance (e.g., recruitment) is food-limited during warm years with reduced upwelling, while quality (e.g., energy content) is temperature-limited during cool years.

  16. Upwelling Dynamic Based on Satellite and INDESO Data in the Flores Sea

    Science.gov (United States)

    Kurniawan, Reski; Suriamihardja, D. A.; Hamzah Assegaf, Alimuddin

    2018-03-01

    Upwelling phenomenon is crucial to be forecasted, mainly concerning the information of potential fishery areas. Utilization of calibrated model for recorded upwelling such as INDESO gives benefit for historical result up to the present time. The aim of this study is to estimate areas and seasons of upwelling occurrences in the Flores Sea using data assimilation of satellite and modeling result. This study uses sea surface temperature, chlorophyll-a data from level 3 of MODIS image and sea surface height from satellite Jason-2 monthly for three years (2014-2016) and INDESO model data for sea surface temperature, sea surface height, and chlorophyll-a daily for three years (2014-2016). The upwelling is indicated by declining of sea surface temperature, sea surface height and increasing of chlorophyll-a. Verification is conducted by comparing the model result with recorded MODIS satellite image. The result shows that the area of southern Makassar Strait having occurrences of upwelling phenomenon every year starting in June, extended to July and August. The strongest upwelling occurred in 2015 covering more or less the area of 23,000 km2. The relation of monthly data of satellite has significantly correlated with daily data of INDESO model

  17. Pathways of upwelling deep waters to the surface of the Southern Ocean

    Science.gov (United States)

    Tamsitt, Veronica; Drake, Henri; Morrison, Adele; Talley, Lynne; Dufour, Carolina; Gray, Alison; Griffies, Stephen; Mazloff, Matthew; Sarmiento, Jorge; Wang, Jinbo; Weijer, Wilbert

    2017-04-01

    Upwelling of Atlantic, Indian and Pacific deep waters to the sea surface in the Southern Ocean closes the global overturning circulation and is fundamentally important for oceanic uptake of anthropogenic carbon and heat, nutrient resupply for sustaining oceanic biological production, and the melt rate of ice shelves. Here we go beyond the two-dimensional view of Southern Ocean upwelling, to show detailed Southern Ocean upwelling pathways in three dimensions, using hydrographic observations and particle tracking in high-resolution ocean and climate models. The northern deep waters enter the Antarctic Circumpolar Current (ACC) via narrow southward currents along the boundaries of the three ocean basins, before spiraling southeastward and upward through the ACC. Upwelling is greatly enhanced at five major topographic features, associated with vigorous mesoscale eddy activity. Deep water reaches the upper ocean predominantly south of the southern ACC boundary, with a spatially nonuniform distribution, regionalizing warm water supply to Antarctic ice shelves and the delivery of nutrient and carbon-rich water to the sea surface. The timescale for half of the deep water to upwell from 30°S to the mixed layer is on the order of 60-90 years, which has important implications for the timescale for signals to propagate through the deep ocean. In addition, we quantify the diabatic transformation along particle trajectories, to identify where diabatic processes are important along the upwelling pathways.

  18. Plants as Indicators of Past and Present Zones of Upwelling Soil CO2 at the ZERT Facility

    Science.gov (United States)

    Apple, M. E.; Sharma, B.; Zhou, X.; Shaw, J. A.; Dobeck, L.; Cunnningham, A.; Spangler, L.; ZERT Team

    2011-12-01

    By their very nature, photosynthetic plants are sensitive and responsive to CO2, which they fix during the Calvin-Benson cycle. Responses of plants to CO2 are valuable tools in the surface detection of upwelling and leaking CO2 from carbon sequestration fields. Plants exposed to upwelling CO2 rapidly exhibit signs of stress such as changes in stomatal conductance, hyperspectral signatures, pigmentation, and viability (Lakkaraju et al. 2010; Male et al. 2010). The Zero Emission Research and Technology (ZERT) site in Bozeman, MT is an experimental facility for surface detection of CO2 where 0.15 ton/day of CO2 was released (7/19- 8/15/2010, and 7/18 - 8/15/2011) from a 100m horizontal injection well, (HIW), 1.5 m underground with deliberate leaks of CO2 at intervals, and from a vertical injector, (VIW), (6/3-6/24/2010). Soil CO2 concentrations reached 16%. Plants at ZERT include Taraxacum officinale (Dandelion), Dactylis glomerata (Orchard Grass), Poa pratensis, (Kentucky Bluegrass), Phleum pratense (Timothy), Bromus japonicus (Japanese Brome), Medicago sativa (Alfalfa) and Cirsium arvense (Canadian Thistle). Dandelion leaves above the zones of upwelling CO2 at the HIW and the VIW changed color from green to reddish-purple (indicative of an increase in anthocyanins) to brown as they senesced within two weeks of CO2 injection. Their increased stomatal conductance along with their extensive surface area combined to make water loss occur quickly following injection of CO2. Xeromorphic grass leaves were not as profoundly affected, although they did exhibit changes in stomatal conductance, accelerated loss of chlorophyll beyond what would normally occur with seasonal senescence, and altered hyperspectral signatures. Within two weeks of CO2 injection at the HIW and the VIW, hot spots formed, which are circular zones of visible leaf senescence that appear at zones of upwelling CO2. The hot spots became more pronounced as the CO2 injection continued, and were detectable

  19. Radiocarbon dating of VIRI bone samples using ultrafiltration

    Energy Technology Data Exchange (ETDEWEB)

    Minami, Masayo, E-mail: minami@nendai.nagoya-u.ac.jp [Center for Chronological Research, Nagoya University, Nagoya 464-8602 (Japan); Yamazaki, Kana [Faculty of Science, Nagoya University, Nagoya 464-8602 (Japan); Omori, Takayuki [University Museum, University of Tokyo, Tokyo 113-0033 (Japan); Nakamura, Toshio [Center for Chronological Research, Nagoya University, Nagoya 464-8602 (Japan)

    2013-01-15

    Ultrafiltration can effectively remove low-molecular-weight (LMW) contaminants from bone gelatin to extract high-molecular-weight (HMW) proteins that are derived from original bone collagen, though it cannot remove HMW collagen crosslinked with humic acids. Therefore, ultrafiltration is often used to obtain more accurate {sup 14}C dates of bones. However, ultrafiltration may introduce new contaminants to bone gelatins, mainly from ultrafilters used. To study the effects of ultrafiltration on {sup 14}C age, we analyzed the C/N ratio, {delta}{sup 13}C{sub PDB} and {delta}{sup 15}N{sub AIR} values, and {sup 14}C ages of acid-soluble bone collagen obtained by decalcification, gelatin extracted from acid-insoluble bone collagen, and the HMW gelatin and LMW fractions produced during ultrafiltration of the extracted gelatin. Bone samples from the Fifth International Radiocarbon Intercomparison (VIRI) were used: VIRI-E (mammoth), -F (horse), -G (human), and -I (whale). In this study, carbon and nitrogen content and gelatin yields were used to evaluate collagen preservation in the VIRI bone samples. Radiocarbon ages, {delta}{sup 13}C{sub PDB} and {delta}{sup 15}N{sub AIR} values of unfiltered and HMW gelatins were obtained and compared with the published consensus values. The LMW fraction was found to exhibit different values from those of the other fractions, indicating the possible presence of extraneous contamination. The Vivaspin Trade-Mark-Sign 6 ultrafilters used in this study were analyzed and radiocarbon dated both before and after cleaning. We present evidence to suggest that LMW fraction contaminants could be derived from the ultrafilters rather than humic substances. Excessively long ultrafiltration time was suspected to have contaminated the bone samples with material from the ultrafilter, because those samples exhibited older {sup 14}C ages than did those filtered for shorter durations. The results in this study indicate that {sup 14}C ages of unfiltered

  20. Implications of Upwells as Hydrodynamic Jets in a Pulse Jet Mixed System

    Energy Technology Data Exchange (ETDEWEB)

    Pease, Leonard F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Bamberger, Judith A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Minette, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-08-01

    This report evaluates the physics of the upwell flow in pulse jet mixed systems in the Hanford Tank Waste Treatment and Immobilization Plant (WTP). Although the initial downward flow and radial flow from pulse jet mixers (PJMs) has been analyzed in some detail, the upwells have received considerably less attention despite having significant implications for vessel mixing. Do the upwells behave like jets? How do the upwells scale? When will the central upwell breakthrough? What proportion of the vessel is blended by the upwells themselves? Indeed, how the physics of the central upwell is affected by multiple PJMs (e.g., six in the proposed mixing vessels), non-Newtonian rheology, and significant multicomponent solids loadings remain unexplored. The central upwell must satisfy several criteria to be considered a free jet. First, it must travel for several diameters in a nearly constant direction. Second, its velocity must decay with the inverse of elevation. Third, it should have an approximately Gaussian profile. Fourth, the influence of surface or body forces must be negligible. A combination of historical data in a 12.75 ft test vessel, newly analyzed data from the 8 ft test vessel, and conservation of momentum arguments derived specifically for PJM operating conditions demonstrate that the central upwell satisfies these criteria where vigorous breakthrough is achieved. An essential feature of scaling from one vessel to the next is the requirement that the underlying physics does not change adversely. One may have confidence in scaling if (1) correlations and formulas capture the relevant physics; (2) the underlying physics does not change from the conditions under which it was developed to the conditions of interest; (3) all factors relevant to scaling have been incorporated, including flow, material, and geometric considerations; and (4) the uncertainty in the relationships is sufficiently narrow to meet required specifications. Although the central upwell

  1. Atmospherically dispersed radiocarbon at the Chalk River Laboratories

    International Nuclear Information System (INIS)

    Milton, G.M.; Brown, R.M.; Repta, C.J.W.; Selkirk, C.J.

    1996-01-01

    A small percentage of the total radiocarbon produced by the NRX and NRU experimental reactors at the Chalk River Laboratories has been vented from the main reactor stack and atmospherically dispersed across the site. Surveys conducted in 1982-83 and 1993-94 have shown that atmospheric levels more than 50 m from the stack are never greater than 600 Bq.kg -1 carbon above the natural background level, falling to near-global atmospheric levels at the site boundaries roughly 7 km away. A dispersion factor > 1.2 x 10 6 m 3 .s -1 at ∼ 0.75 km distance from the point of emission is calculated on the basis of recent in-stack monitoring. Analysis of growth rings in on-site trees has provided an opportunity to search for correlations of 14 C output summer power production and/or moderator losses. (author). 16 refs., 14 tabs., 11 figs

  2. Accelerator radiocarbon dating of evidence for prehistoric horticulture in Illinois

    Science.gov (United States)

    Conard, N.; Asch, D.L.; Asch, N.B.; Elmore, D.; Gove, H.; Rubin, M.; Brown, J.A.; Wiant, M.D.; Farnsworth, K.B.; Cook, T.G.

    1984-01-01

    With the development of direct detection radiocarbon dating, which uses an accelerator as part of a highly selective mass spectrometer, it is now possible to determine the age of milligram samples of organic materials1-5. One application of accelerator dating is in evaluating scanty, sometimes controversial evidence for early horticulture throughout the world. We have now used the technique to date small samples of carbonized, cultivated plant remains from archaeological sites in Illinois. The results, reported here, establish (1) that squash was introduced by 7,000 yr ago, 2,500 yr before eastern North American records previously reported; (2) that horticulture involving indigenous plants had begun by 4,000 BP in eastern North America with domestication of Iva annua, a small-seeded annual; (3) that anomalous discoveries of Archaic period maize represent contaminants; and (4) that introduction of maize by initial Middle Woodland times (~2,000 BP) is questionable.

  3. Accelerator radiocarbon dating of evidence for prehistoric horticulture in Illinois

    Energy Technology Data Exchange (ETDEWEB)

    Conrad, N [Rochester Univ., NY (USA). Dept. of Anthropology; Rochester Univ., NY (USA). Dept. of Chemistry); Asch, D L; Asch, N B [Center for American Archeology, Kampsville, ILL (USA). Archeobotanical Lab.

    1984-03-29

    The authors have now used direct detection radiocarbon dating (which uses an accelerator as part of a highly selective mass spectrometer) to date small samples of carbonized, cultivated plant remains from archaeological sites in Illinois. The results, reported here, establish (1) that squash was introduced by 7,000 yr ago, 2,500 yr before eastern North American records previously reported; (2) that horticulture involving indigenous plants had begun by 4,000 BP in eastern North American with domestication of Iva annua, a small-seeded annual; (3) that anomalous discoveries of Archaic period maize represent contaminants; and (4) that introduction of maize by initial Middle Woodland times (approx. 2,000 BP) is questionable.

  4. Small-mass AMS radiocarbon analysis at Nagoya University

    Energy Technology Data Exchange (ETDEWEB)

    Minami, Masayo, E-mail: minami@nendai.nagoya-u.ac.jp [Center for Chronological Research, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Kato, Tomomi [Faculty of Science, Nagoya University, Nagoya 464-8602 (Japan); Miyata, Yoshiki; Nakamura, Toshio [Center for Chronological Research, Nagoya University, Chikusa, Nagoya 464-8602 (Japan); Hua Quan [Australian Nuclear Science and Technology Organization, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia)

    2013-01-15

    As part of the ongoing development at the AMS facility of the Center for Chronological Research at Nagoya University to radiocarbon ({sup 14}C) analyze samples smaller than 0.5 mg carbon (mgC), a compact graphitization manifold has been built. Tests with various reference materials show it performs well for samples as small as 0.1 mgC. Preparation with this new system is compared with the performance of the older protocol for regular-sized samples. Furthermore, it is shown that the addition of Cu and Ag before and stepwise heating during sealed-tube combustion of samples with high S content improve the degree of conversion to CO{sub 2} without having to resort to special purification measures such as the use of Co{sub 3}O{sub 4} + Ag reagent and an n-pentane/LN{sub 2} trap before graphitization.

  5. Radiocarbon dating of bone samples by liquid scintillation spectroscopy

    International Nuclear Information System (INIS)

    Lisi, C.S.; Pessenda, L.C.R.; Cruz, M.V.; Pessin, G.; Pazdur, M.F.

    1995-01-01

    It is developed and adapted methodology for radiocarbon dating of bone samples. The collagen, the most representative fraction of age of bone samples, was extracted by Login method. To eliminate/minimize the contamination of gaseous compounds (nitrogen oxides) produced during the collagen combustion, two methods were used: CO 2 precipitation as Ba CO 3 and Sr CO 3 with subsequent acid hydrolysis. It was determined the efficiency of combustion of collagen sample, the performance of methods in the CO 2 purification and the effect of atmospheric 14 CO 2 contamination and radioactivity of reagents in the determination of 14 C activity. To verify the accuracy of the method, it was realized a laboratory intercomparison, analysing bone and collagen samples also dated by 14 C laboratories of Gliwice, Poland and Groningen, the Netherlands. (author). 4 refs, 2 figs, 1 tab

  6. Radiocarbon dating with the Chalk River MP Tandem accelerator

    International Nuclear Information System (INIS)

    Ball, G.C.; Andrews, H.R.; Brown, R.M.; Burn, N.; Davies, W.G.; Imahori, Y.; Milton, J.C.D.

    1981-01-01

    During the past three years an automated radiocarbon dating system based on the MP Tandem accelerator has been developed for the analysis of 14 C in groundwater samples from the nuclear waste disposal research program and other small samples of scientific interest. At the present time 14 C/ 12 C ratio measurements can be determined with an accuracy of about 5% and the system background levels (approx. 35000 to 45000 years) are totally determined by sample and/or ion source contamination. Our goal has been to develop a dedicated reliable system for routine analysis that will produce accurate results with a minimum expenditure of human resources and accelerator beam time. Improvements required to operate the tandem accelerator as a quantitative tool have also benefited the rest of the experimental nuclear physics program. The early evolution of the dating facility was described previously. This paper is a brief report of the current status at Chalk River

  7. Radiocarbon chronology of Manot Cave, Israel and Upper Paleolithic dispersals

    Science.gov (United States)

    Alex, Bridget; Barzilai, Omry; Hershkovitz, Israel; Marder, Ofer; Berna, Francesco; Caracuta, Valentina; Abulafia, Talia; Davis, Lauren; Goder-Goldberger, Mae; Lavi, Ron; Mintz, Eugenia; Regev, Lior; Bar-Yosef Mayer, Daniella; Tejero, José-Miguel; Yeshurun, Reuven; Ayalon, Avner; Bar-Matthews, Mira; Yasur, Gal; Frumkin, Amos; Latimer, Bruce; Hans, Mark G.; Boaretto, Elisabetta

    2017-01-01

    The timing of archeological industries in the Levant is central for understanding the spread of modern humans with Upper Paleolithic traditions. We report a high-resolution radiocarbon chronology for Early Upper Paleolithic industries (Early Ahmarian and Levantine Aurignacian) from the newly excavated site of Manot Cave, Israel. The dates confirm that the Early Ahmarian industry was present by 46,000 calibrated years before the present (cal BP), and the Levantine Aurignacian occurred at least between 38,000 and 34,000 cal BP. This timing is consistent with proposed migrations or technological diffusions between the Near East and Europe. Specifically, the Ahmarian could have led to the development of the Protoaurignacian in Europe, and the Aurignacian in Europe could have spread back to the Near East as the Levantine Aurignacian. PMID:29152566

  8. Using accelerator mass spectrometry for radiocarbon dating of textiles

    Energy Technology Data Exchange (ETDEWEB)

    Jull, A.J.T.

    1997-12-01

    Since 1981 we have operated an NSF Accelerator Mass Spectrometry (AMS) Facility at the University of Arizona. The AMS method allows us to use very small samples of carbon, <1 mg for radiocarbon dating in contrast to earlier counting techniques. This has opened a vast array of applications of radiocarbon dating that was difficult to do before AMS because of sample size limitations of decay counting. Some of the many applications of AMS include paleoclimatic studies, archaeological research and the age of first settlement of North America by man, dating of art works and artifacts, fall times and terrestrial residence ages of meteorites, production of {sup 14}C in lunar samples by galactic and solar cosmic rays, studies of in situ {sup 14}C produced by cosmic ray spallation in rocks and ice, and studies of {sup 14}C in groundwater dissolved inorganic carbon and dissolved organic carbon. At our laboratory, we have also successfully applied AMS {sup 14}C to dating of many types of textiles, including silks and linens, art works, documents and artifacts fabricated from wood, parchment, ivory, and bone. The results for many of these samples are often important in questions of the authenticity of these works of art and artifacts. Our studies have encompassed a wide range of art works ranging from the Dead Sea Scrolls, the Shroud of Turin, and the Chinese silk trade to the works of Raphael, Rembrandt, and Picasso. Recently, we also dated the Vinland Map, a controversial document that shows the eastern coast of North America apparently using information from Viking voyages.

  9. Continuous-flow accelerator mass spectrometry for radiocarbon analysis

    International Nuclear Information System (INIS)

    Wills, J.S.C.; Han, B.X.; Von Reden, K.F.; Schneider, R.J.; Roberts, M.L.

    2006-01-01

    Accelerator Mass Spectrometry (AMS) is a widely used technique for radiocarbon dating of archaeological or environmental samples that are very small or very old (up to 50,000 years before present). Because of the method's extreme sensitivity, AMS can also serve as an environmental tracer and supplements conventional nuclear counting techniques for monitoring 14 C emissions from operating nuclear power plants and waste repositories. The utility of present AMS systems is limited by the complex sample preparation process required. Carbon from combusted artefacts must be incorporated into a solid metallic target from which a negative ion beam is produced and accelerated to MeV energies by an accelerator for subsequent analysis. This paper will describe a novel technique being developed by the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Laboratory at the Woods Hole Oceanographic Institution for the production of negative carbon ion beams directly from a continuously flowing sample gas stream, eliminating the requirement for a solid target. A key component of the new technique is a microwave-driven, gaseous-feed ion source originally developed at Chalk River Laboratories for the very different requirements of a high current proton linear accelerator. A version of this ion source is now being adapted to serve as an injector for a dedicated AMS accelerator facility at NOSAMS. The paper begins with a review of the fundamentals of radiocarbon dating. Experiments carried out at NOSAMS with a prototype of the microwave ion source are described, including measurements of sample utilization efficiency and sample 'memory' effect. A new version of the microwave ion source, optimized for AMS, is also described. The report concludes with some predictions of new research opportunities that will become accessible to the technique of continuous-flow AMS. (author)

  10. Radiocarbon detection by ion charge exchange mass spectrometry

    International Nuclear Information System (INIS)

    Hotchkis, Michael; Wei, Tao

    2007-01-01

    A method for detection of radiocarbon at low levels is described and the results of tests are presented. We refer to this method as ion charge exchange mass spectrometry (ICE-MS). The ICE-MS instrument is a two stage mass spectrometer. In the first stage, molecular interferences which would otherwise affect radiocarbon detection at mass 14 are eliminated by producing high charge state ions directly in the ion source (charge state ≥2). 14 N interference is eliminated in the second stage by converting the beam to negative ions in a charge exchange cell. The beam is mass-analysed at each stage. We have built a test apparatus consisting of an electron cyclotron resonance ion source and a pair of analysing magnets with a charge exchange cell in between, followed by an electrostatic analyser to improve the signal to background ratio. With this apparatus we have measured charge exchange probabilities for (C n+ → C - ) from 4.5 to 40.5 keV (n = 1-3). We have studied the sources of background including assessment of limits for nitrogen interference by searching for negative ions from charge exchange of 14 N ions. Our system has been used to detect 14 C in enriched samples of CO 2 gas with 14 C/ 12 C isotopic ratio down to the 10 -9 level. Combined with a measured sample consumption rate of 4 ng/s, this corresponds to a capability to detect transient signals containing only a few μBq of 14 C activity, such as may be obtained from chromatographic separation. The method will require further development to match the sensitivity of AMS with a gas ion source; however, even in its present state its sensitivity is well suited to tracer studies in biomedical research and drug development

  11. Radiocarbon mass balance for a Magnox nuclear power station

    International Nuclear Information System (INIS)

    Metcalfe, M.P.; Mills, R.W.

    2015-01-01

    Highlights: • First comprehensive assessment of C-14 arisings in a Magnox nuclear power station. • C-14 production in graphite and coolant gas quantified by activation modelling. • Principal C-14 production pathway is via C-13 with a small contribution from N-14. • C-14 mass balance model provides a basis for analyses on other reactors. - Abstract: Nuclear power generation in the United Kingdom is based principally on graphite-moderated gas-cooled reactors. The mass of irradiated graphite associated with these reactors, including material from associated experimental, prototype and plutonium production reactors, exceeds 96,000 tonnes. One of the principal long-lived radionuclides produced during graphite irradiation is radiocarbon (C-14). Its potential as a hazard must be taken into account in decommissioning and graphite waste management strategies. While C-14 production processes are well-understood, radionuclide distributions and concentrations need to be characterised. A common misconception is that generic statements can be made about C-14 precursors and their location. In fact, the composition of the original manufactured material, the chemical environment of the graphite during service and its irradiation history will all influence C-14 levels. The analysis presented here provides the first assessment of the principal C-14 activation pathways for a UK Magnox reactor. Activation modelling has been used to predict C-14 production rates in both the graphite core and the carbon dioxide coolant over a selected period of operation and the results compared with monitored site C-14 discharges. Principal activation routes have been identified, which should inform future graphite waste management strategies relating to radiocarbon

  12. Continuous-flow accelerator mass spectrometry for radiocarbon analysis

    International Nuclear Information System (INIS)

    Wills, J.S.C.; Han, B.X.; Von Reden, K.F.; Schneider, R.J.; Roberts, M.L.

    2006-05-01

    Accelerator Mass Spectrometry (AMS) is a widely used technique for radiocarbon dating of archaeological or environmental samples that are very small or very old (up to 50,000 years before present). Because of the method's extreme sensitivity, AMS can also serve as an environmental tracer and supplements conventional nuclear counting techniques for monitoring 14 C emissions from operating nuclear power plants and waste repositories. The utility of present AMS systems is limited by the complex sample preparation process required. Carbon from combusted artefacts must be incorporated into a solid metallic target from which a negative ion beam is produced and accelerated to MeV energies by an accelerator for subsequent analysis. This paper will describe a novel technique being developed by the National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Laboratory at the Woods Hole Oceanographic Institution for the production of negative carbon ion beams directly from a continuously flowing sample gas stream, eliminating the requirement for a solid target. A key component of the new technique is a microwave-driven, gaseous-feed ion source originally developed at Chalk River Laboratories for the very different requirements of a high current proton linear accelerator. A version of this ion source is now being adapted to serve as an injector for a dedicated AMS accelerator facility at NOSAMS. The paper begins with a review of the fundamentals of radiocarbon dating. Experiments carried out at NOSAMS with a prototype of the microwave ion source are described, including measurements of sample utilization efficiency and sample 'memory' effect. A new version of the microwave ion source, optimized for AMS, is also described. The report concludes with some predictions of new research opportunities that will become accessible to the technique of continuous-flow AMS. (author)

  13. On the presence of coastal upwelling along the northeastern Tyrrhenian coast

    Science.gov (United States)

    Martellucci, Riccardo; Melchiorri, Cristiano; Costanzo, Lorenzo; Marcelli, Marco

    2017-04-01

    The Mediterranean region shows a high climate variability due to the interactions between mid-latitude and tropical processes. This variability makes the Mediterranean a potentially vulnerable region to climatic changes. The present research aims to investigate the hydrographical response to Northerly wind in the northeastern Tyrrhenian coast, to identify the relations between upwelling events and teleconnection patterns. In the Tyrrhenian basin northerly winds flow between North-East and North-West and could be considered upwelling favorable winds. This atmospheric circulation can causes a divergent flow near the coast that generates a subsurface water flows inshore toward the coast up to the surface layer that is upwelling. This phenomenon strongly influence the marine ecosystems, contributing to the supply of nutrients and affecting the primary producers. In this context multi-platform observing system is an important tool to follow the evolution of these phenomena. Sea temperature and wind field acquired by the C-CEMS Observing system were used to identify upwelling phenomena between 2012 and 2016, in the coastal area of Civitavecchia, Northern Tyrrhenian sea, Italy. Moreover a thirty years' wind-driven upwelling conditions have been studied in the area. ERA-Interim (ECMWF) wind data for the period 1982-2012 have been used to compute the distribution of upwelling favorable wind events. These have been compared to "Copernicus Marine Environment Monitoring Service" Sea Surface Temperature (SST) to compute upwelling events. Upwelling favorable wind has been defined in the sector between Northwest and Northeast (Wd >330°N & Wd analysis. An increase of upwelling events in the Tyrrhenian coast is observed in the last thirty years; the occurrence of upwelling events has a seasonal oscillation, with a maximum frequency during winter and spring seasons. In the last decade an increase of these events in winter and a decrease in spring is observed; also a recurrence of

  14. Intracavity OptoGalvanic Spectroscopy not suitable for ambient level radiocarbon detection.

    Science.gov (United States)

    Paul, Dipayan; Meijer, Harro A J

    2015-09-01

    IntraCavity OptoGalvanic Spectroscopy as a radiocarbon detection technique was first reported by the Murnick group at Rutgers University, Newark, NJ, in 2008. This technique for radiocarbon detection was presented with tremendous potentials for applications in various fields of research. Significantly cheaper, this technique was portrayed as a possible complementary technique to the more expensive and complex accelerator mass spectrometry. Several groups around the world started developing this technique for various radiocarbon related applications. The IntraCavity OptoGalvanic Spectroscopy setup at the University of Groningen was constructed in 2012 in close collaboration with the Murnick group for exploring possible applications in the fields of radiocarbon dating and atmospheric monitoring. In this paper we describe a systematic evaluation of the IntraCavity OptoGalvanic Spectroscopy setup at Groningen for radiocarbon detection. Since the IntraCavity OptoGalvanic Spectroscopy setup was strictly planned for dating and atmospheric monitoring purposes, all the initial experiments were performed with CO2 samples containing contemporary levels and highly depleted levels of radiocarbon. Because of recurring failures in differentiating the two CO2 samples, with the radiocarbon concentration 3 orders of magnitude apart, CO2 samples containing elevated levels of radiocarbon were prepared in-house and experimented with. All results obtained thus far at Groningen are in sharp contrast to the results published by the Murnick group and rather support the results put forward by the Salehpour group at Uppsala University. From our extensive test work, we must conclude that the method is unsuited for ambient level radiocarbon measurements, and even highly enriched CO2 samples yield insignificant signal.

  15. The radiocarbon dating of the neolithic flint mines at Krzemionki in central Poland

    International Nuclear Information System (INIS)

    Babel, J.; Braziewicz, J.; JaskoIa, M.; Kretschmer, W.; Pajek, M.; Semaniak, J.; Scharf, A.; Uhl, T.

    2005-01-01

    Ten samples taken from wooden torches and small fireplaces discovered at the Krzemionki neolithic flint mine localized in central Poland were dated using the AMS facility at Erlangen University. The radiocarbon results points two main periods of exploitation of studied mines, i.e. approximately to 3500-3100 BC and to 3100-2900 BC. The results are discussed in the aspect of the mine chronology. The new radiocarbon dates confirm the previous radiocarbon data obtained from other mine units in this part of the Krzemionki mine complex

  16. Does mesoscale matters in decadal changes observed in the northern Canary upwelling system?

    Science.gov (United States)

    Relvas, P.; Luís, J.; Santos, A. M. P.

    2009-04-01

    The Western Iberia constitutes the northern limb of the Canary Current Upwelling System, one of the four Eastern Boundary Upwelling Systems of the world ocean. The strong dynamic link between the atmosphere and the ocean makes these systems highly sensitive to global change, ideal to monitor and investigate its effects. In order to investigate decadal changes of the mesoscale patterns in the Northern Canary upwelling system (off Western Iberia), the field of the satellite-derived sea surface temperature (SST) trends was built at the pixel scale (4x4 km) for the period 1985-2007, based on the monthly mean data from the Advanced Very High Resolution Radiometer (AVHRR) on board NOAA series satellites, provided by the NASA Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory. The time series were limited to the nighttime passes to avoid the solar heating effect and a suite of procedures were followed to guarantee that the temperature trends were not biased towards the seasonally more abundant summer data, when the sky is considerably clear. A robust linear fit was applied to each individual pixel, crossing along the time the same pixel in all the processed monthly mean AVHRR SST images from 1985 until 2007. The field of the SST trends was created upon the slopes of the linear fits applied to each pixel. Monthly mean SST time series from the one degree enhanced International Comprehensive Ocean-Atmosphere Data Set (ICOADS) and from near-shore measurements collected on a daily basis by the Portuguese Meteorological Office (IM) are also used to compare the results and extend the analysis back until 1960. A generalized warming trend is detected in the coastal waters off Western Iberia during the last decades, no matter which data set we analyse. However, significant spatial differences in the warming rates are observed in the satellite-derived SST trends. Remarkably, off the southern part of the Western Iberia the known

  17. The NAO Influence on the Early to Mid-Holocene North Atlantic Coastal Upwelling

    Science.gov (United States)

    Hernandez, A.; Cachão, M.; Sousa, P.; Trigo, R. M.; Freitas, M. C.

    2017-12-01

    Coastal upwelling regions yield some of the oceanic most productive ecosystems, being crucial for the worldwide social and economic development. Most upwelling systems, emerging cold nutrient-rich deep waters, are located in the eastern boundaries of the Atlantic and Pacific basins, and are driven by meridional wind fields parallel to the coastal shore. These winds are associated with the subsiding branch of the large-scale Anticyclonic high pressure systems that dominate the subtropical ocean basins, and therefore can be displaced or intensified within the context of past and future climate changes. However, the role of the current global warming influencing the coastal upwelling is, as yet, unclear. Therefore it is essential to derive a long-term perspective, beyond the era of instrumental measurements, to detect similar warm periods in the past that have triggered changes in the upwelling patterns. In this work, the upwelling dynamics in the Iberian North Atlantic margin during the early and mid-Holocene is reconstructed, using calcareous nannofossils from a decadally resolved estuarine sediment core located in southwestern Portugal. Results suggest that the coastal dynamics reflects changes in winds direction likely related to shifts in the NAO-like conditions. Furthermore, the reconstructed centennial-scale variations in the upwelling are synchronous with changes in solar irradiance, a major external forcing factor of the climate system that is known to exert influence in atmospheric circulation patterns. In addition, these proxy-based data interpretations are in agreement with wind field and solar irradiance simulation modelling for the mid-Holocene. Therefore, the conclusion that the solar activity via the NAO modulation controlled the North Atlantic upwelling of western Iberia during the early and mid-Holocene at decadal to centennial timescales can be derived. The financial support for attending this meeting was possible through FCT project UID/GEO/50019

  18. A Lagrangian study tracing water parcel origins in the Canary Upwelling System

    Directory of Open Access Journals (Sweden)

    Evan Mason

    2012-08-01

    Full Text Available The regional ocean circulation within the Canary Upwelling System between 31°N and 35°N is studied using numerical tools. Seasonal mean and near-instantaneous velocity fields from a previously-generated climatological Regional Ocean Modelling System (ROMS solution of the Canary Basin are used to force a series of offline Lagrangian particle-tracking experiments. The primary objective is to identify the pathways through which water parcels arrive at the upwelling region north of Cape Ghir. Examining year-long pathways, the Azores Current contributes over 80% of particles annually, of which a large proportion arrive directly from offshore (from the northwest, while others travel along the shelf and slope from the Gulf of Cadiz. The remaining ~20% originate within the Gulf of Cadiz or come from the south, although the southern contribution is only significant in autumn and winter. When season-long pathways are considered, the alongshore contributions become increasingly important: northern contributions reach 40% in spring and summer, while southern values exceed 35% in winter. This study also shows that coastal upwelling changes both spatially and temporally. Upwelling becomes intensified near Cape Beddouza, with most upwelling occurring within ~40 km from shore although significant values may reach as far as 120 km offshore north of Cape Beddouza; at these locations the offshore integrated upwelling reaches as much as 4 times the offshore Ekman transport. In the Cape Beddouza area (32°N to 33°N, upwelling is negligible in February but intensifies in autumn, reaching as much as 3 times the offshore Ekman transport.

  19. Natural ocean acidification at Papagayo upwelling system (north Pacific Costa Rica: implications for reef development

    Directory of Open Access Journals (Sweden)

    C. Sánchez-Noguera

    2018-04-01

    Full Text Available Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May–June 2013, with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2. These results were compared with published data from the 2009 upwelling season. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive intra- and interseasonal changes. Lowest pH (7.8 and highest pCO2 (658.3 µatm values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH  =  7.8, pCO2  =  643.5 µatm, unveiling that natural acidification also occurs sporadically in the non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During the non-upwelling season, the aragonite saturation state (Ωa rises to values of  >  3.3 and during the upwelling season falls below 2.5. The Ωa threshold values for coral growth were derived from the correlation between measured Ωa and coral linear extension rates which were obtained from the literature and suggest that future ocean acidification will threaten the continued growth of reefs in Bahía Culebra. These data contribute to building a better understanding of the carbonate system dynamics and coral reefs' key response (e.g., coral growth to natural low-pH conditions, in upwelling areas in the eastern tropical

  20. Natural ocean acidification at Papagayo upwelling system (north Pacific Costa Rica): implications for reef development

    Science.gov (United States)

    Sánchez-Noguera, Celeste; Stuhldreier, Ines; Cortés, Jorge; Jiménez, Carlos; Morales, Álvaro; Wild, Christian; Rixen, Tim

    2018-04-01

    Numerous experiments have shown that ocean acidification impedes coral calcification, but knowledge about in situ reef ecosystem response to ocean acidification is still scarce. Bahía Culebra, situated at the northern Pacific coast of Costa Rica, is a location naturally exposed to acidic conditions due to the Papagayo seasonal upwelling. We measured pH and pCO2 in situ during two non-upwelling seasons (June 2012, May-June 2013), with a high temporal resolution of every 15 and 30 min, respectively, using two Submersible Autonomous Moored Instruments (SAMI-pH, SAMI-CO2). These results were compared with published data from the 2009 upwelling season. Findings revealed that the carbonate system in Bahía Culebra shows a high temporal variability. Incoming offshore waters drive intra- and interseasonal changes. Lowest pH (7.8) and highest pCO2 (658.3 µatm) values measured during a cold-water intrusion event in the non-upwelling season were similar to those minimum values reported from upwelling season (pH = 7.8, pCO2 = 643.5 µatm), unveiling that natural acidification also occurs sporadically in the non-upwelling season. This affects the interaction of photosynthesis, respiration, calcification and carbonate dissolution and the resulting diel cycle of pH and pCO2 in the reefs of Bahía Culebra. During the non-upwelling season, the aragonite saturation state (Ωa) rises to values of > 3.3 and during the upwelling season falls below 2.5. The Ωa threshold values for coral growth were derived from the correlation between measured Ωa and coral linear extension rates which were obtained from the literature and suggest that future ocean acidification will threaten the continued growth of reefs in Bahía Culebra. These data contribute to building a better understanding of the carbonate system dynamics and coral reefs' key response (e.g., coral growth) to natural low-pH conditions, in upwelling areas in the eastern tropical Pacific and beyond.

  1. Summertime sea surface temperature fronts associated with upwelling around the Taiwan Bank

    Science.gov (United States)

    Lan, Kuo-Wei; Kawamura, Hiroshi; Lee, Ming-An; Chang, Yi; Chan, Jui-Wen; Liao, Cheng-Hsin

    2009-04-01

    It is well known that upwelling of subsurface water is dominant around the Taiwan Bank (TB) and the Penghu (PH) Islands in the southern Taiwan Strait in summertime. Sea surface temperature (SST) frontal features and related phenomena around the TB upwelling and the PH upwelling were investigated using long-term AVHRR (1996-2005) and SeaWiFS (1998-2005) data received at the station of National Taiwan Ocean University. SST and chlorophyll-a (Chl-a) images with a spatial resolution of 0.01° were generated and used for the monthly SST and Chl-a maps. SST fronts were extracted from each SST images and gradient magnitudes (GMs); the orientations were derived for the SST fronts. Monthly maps of cold fronts where the cooler SSTs were over a shallower bottom were produced from the orientation. Areas with high GMs (0.1-0.2 °C/km) with characteristic shapes appeared at geographically fixed positions around the TB/PH upwelling region where SSTs were lower than the surrounding waters. The well-shaped high GMs corresponded to cold fronts. Two areas with high Chl-a were found around the TB and PH Islands. The southern border of the high-Chl-a area in the TB upwelling area was outlined by the high-GM area. Shipboard measurements of snapshot vertical sections of temperature (T) and salinity (S) along the PH Channel showed a dome structure east of PH Islands, over which low SST and high GM in the maps of the corresponding month were present. Clear evidence of upwelling (vertically uniform distributions of T and S) was indicated at the TB edge in the T and S sections close to TB upwelling. This case of upwelling may be caused by bottom currents ascending the TB slope as pointed out by previous studies. The position of low SSTs in the monthly maps matched the upwelling area, and the high GMs corresponded to the area of eastern surface fronts in the T/S sections.

  2. Radiocarbon ages of pedogenic calcic nodules formed within vertisols, Coimbatore region, Tamil Nadu, India

    International Nuclear Information System (INIS)

    Achyuthan, H.; Flora, O.; Braida, M.; Stenni, B.; Shankar, N.

    2009-05-01

    In this paper we discuss the limitation of radiocarbon dates on the pedogenic calcic nodules formed in situ within the vertisols in the upland region of Coimbatore, Tamil Nadu. The radiocarbon ages were obtained using low level scintillation counters and the ages range from ∼24 Ka to ∼31 Ka. The ages correlate well with the marine isotope stage of Late MIS3. Since the calcic nodules are pedogenised and formed in a terrestrial open system we express caution in the interpretation of the radiocarbon ages obtained on pedogenic carbonate nodules. The radiocarbon dates represent maximum ages and hence the ages measured should only be considered as age estimates and not absolute geologic ages. Multiple sub-mm size subsamples could provide more reliable estimates of soil chronology. (author)

  3. Experiments to determine the efficiency of two standard decontamination procedures for radiocarbon samples

    International Nuclear Information System (INIS)

    Currie, D.R.

    1980-02-01

    Laboratory tests were made to decontaminate radiocarbon samples containing known amounts of contamination. Results for both acid-alkali treatment and acid hydrolysis indicate that decontamination is not 100% efficient

  4. Report on Radiocarbon Analysis of Surface Sediments from the Fore-Arc Basin of Nankai Trough

    National Research Council Canada - National Science Library

    Pohlman, John

    2004-01-01

    .... Radiocarbon analysis of the total organic carbon (TOC) and total inorganic carbon (TIC) on 30 sediment samples from two multicores and six piston cores was performed to investigate the fate of methane carbon in sediment of the Nankal Trough...

  5. LBA-ECO CD-08 Radiocarbon Dates for Large Trees from a Forest near Manaus, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set reports the ages and growth rates of trees as determined by radiocarbon dating (14C), selected from a logging operation near the city of Itacoatiara,...

  6. LBA-ECO CD-08 Radiocarbon Dates for Large Trees from a Forest near Manaus, Brazil

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: This data set reports the ages and growth rates of trees as determined by radiocarbon dating (14C), selected from a logging operation near the city of...

  7. Radiocarbon age and diagenesis of oolitic sediments from the Persian Gulf

    International Nuclear Information System (INIS)

    Silar, J.

    1980-01-01

    Radiocarbon measurements of different parts of ooids of Pleistocene and Holocene oolitic sediments from the Persian Gulf on the coast of Kuwait indicated that atmospheric carbon dioxide had been involved in the recrystallization of aragonite and in the diagenesis of the oolitic sediments. The radiocarbon activity of different layers of sediments generally corresponds to their stratigraphic sequence. The radiocarbon ages of several earlier layers, however, seem to be reduced due to recrystallization and diagenesis. The radiocarbon ages of well-preserved shells of mollusks of the fossiliferous horizon are lower than their alleged Pleistocene geological age. The rate of emergence of the shore between one and several mm.yr -1 was established which corresponds to that recorded in the mouth of the Persian Gulf and in Qatar. (author)

  8. Examining sources of bias in radiocarbon ages of New Zealand Kiore

    Energy Technology Data Exchange (ETDEWEB)

    Beavan, N.R.; Sparks, R.J. [Institute of Geological and Nuclear Sciences, (New Zealand). Rafter Radiocarbon Laboratory

    1997-12-31

    Recent AMS dates for the Pacific rat (Rattus exulans / Kiore) from natural and archaeological sites are significantly older than the generally accepted time for human arrival in New Zealand. Because Rattus exulans is recognized as a human commensal for Polynesian colonization in Oceania, radiocarbon ages for Kiore could be used as an indicator of earliest human contact with New Zealand. A strictly chronological interpretation of the radiocarbon ages assembled, though, raises serious questions about this arrival time. Therefore, factors that could affect the age determinations were also examined. A research programme in progress at the Rafter Radiocarbon Laboratory aims to identify the range and influence of natural bias and variance in radiocarbon ages in kiore bone samples. It was found that the main factors that could bias these ages were the incomplete removal of contaminants by the current bone preparation methods, and dietary carbon reservoir effects. Preliminary results of the various analytical techniques employed are presented.

  9. Octopus vulgaris paralarvae vertical distribution in a fluctuating upwelling-downwelling system

    Directory of Open Access Journals (Sweden)

    Lorena Olmos Pérez

    2014-06-01

    - Upwelling situation: superficial waters (0-20m enter through the northern mouth of the Ría and are washed through the southern mouth. This water movement promotes the entrance of cold, bottom upwelled water through the southern mouth of the Ría. Under this scenario, Octopus paralarvae are concentrated at the surface (10-0m, thus leaving the Ría. This difference is bigger after strong upwelling during the previous days. Abundances inside the Ría are the highest, maybe because it acts as a temporal retention area, or because cold upwelled waters might stimulate hatching inside the Ría. Day/night changes under strong upwelling conditions: paralarvae abundance in both mouths was quite similar, except that during the day they were in sub-surficial waters (10-5 m, while at night paralarvae were mainly found close to the surface (0-5 m. This vertical distribution during the day is remarkable because paralarvae may select offward surface waters.

  10. Radiocarbon dating of an ancient Japanese document 'Minamoto no Yoritomo Sodehan Migyosho' by accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Oda, H.; Nakamura, T.; Masuda, T.

    2007-01-01

    We measured radiocarbon age of an ancient document 'Minamoto no Yoritomo Sodehan Migyosho'. The content tells that it was issued in 1189 by 'Minamoto no Yoritomo' known as the virtually first shogun in Japan to grant 'Matsugi' family the privilege of controlling craftsmen of foundry industry. Paleographical views, however, suggested that it can be a counterfeit. The radiocarbon dating clarified that the document was written not in the 12 th but after the 16 th century. (author)

  11. Predicting decadal trends and transient responses of radiocarbon storage and fluxes in a temperate forest soil

    OpenAIRE

    Sierra, C. A.; Trumbore, S. E.; Davidson, E. A.; Frey, S. D.; Savage, K. E.; Hopkins, F. M.

    2012-01-01

    Representing the response of soil carbon dynamics to global environmental change requires the incorporation of multiple tools in the development of predictive models. An important tool to construct and test models is the incorporation of bomb radiocarbon in soil organic matter during the past decades. In this manuscript, we combined radiocarbon data and a previously developed empirical model to explore decade-scale soil carbon dyn...

  12. Very little in situ produced radiocarbon retained in accumulating Antarctic ice

    International Nuclear Information System (INIS)

    Kemp, W.J.M. van der; Alderliesten, C.; Borg, K. van der; Holmlund, P.; Jong, A.F.M. de; Karloef, L.; Lamers, R.A.N.; Oerlemans, J.; Thomassen, M.; Wal, R.S.W. van de

    2000-01-01

    Ice samples from Dronning Maud Land, Antarctica, were analyzed for 14 CO 2 and 14 CO by accelerator mass spectrometry. Only a small amount (∼2%) of in situ produced radiocarbon was detected. The calibrated radiocarbon ages, corrected for in situ produced 14 C, are in fair agreement with age estimates obtained from stratigraphical methods added to a gas inclusion model. The ages of the entrapped air range from recent to ca. 1200 AD

  13. New radiocarbon measurement methods in the Hertelendi Laboratory, Hungary

    Science.gov (United States)

    Janovics, Róbert; Major, István; Rinyu, László; Veres, Mihály; Molnár, Mihály

    2013-04-01

    In this paper we present two very different and novel methods for C-14 measurement from dissolved inorganic carbonate (DIC) of water samples. A new LSC sample preparation method for liquid scintillation C-14 measurements was implemented in the ATOMKI. The first method uses direct absorption into a special absorbent (Carbosorb E®) and a following liquid scintillation measurement. Typical sample size is 20-40 litre of water. The developed CO2 absorption method is fast, and simple. The C-14 activities is measured by an ultra low background LSC (TRI-CARB 3170 TR/SL, Perkin Elmer) including quenching parameter (tSIE).The corresponding limit of C-14 dating is 31200 year. Several tests were executed with old borehole CO2 gas without significant content of C-14 and also performed on samples of known C-14 activities between 29 and 7000 pMC, previously measured by GPC. The combined uncertainty of the described determination is about 2 % in the case of recent carbon. It is a very cost-effective and easy to use method based on a novel and simple static absorption process for the CO2 extracted from groundwater. The other very sensitive method is based on accelerator mass spectrometry (AMS) using gas ion source. This method does not require graphite generation and a small volume of water sample (1-20mL) is enough for the radiocarbon measurement. The procedure is very similar to pre-treatment of carbonate contained sample preparation for stable isotope measurement with gasbench technique. We applied a MICADAS type accelerator mass spectrometry (AMS) with gas ion source for C-14 analysis. The radiocarbon content of water was sat free with phosphoric acid and then the headspace gas was rinsed vials. The whole measurement needs only 20 min of each sample. The precision of measurement is better than 1% for modern samples. The preparation is vastly reduced compared to the other AMS methods and principally allows fully automated measurements of groundwater samples with an auto

  14. Radiocarbon Mass Balance for a Magnox Nuclear Power Station

    International Nuclear Information System (INIS)

    Metcalfe, M.P.; Mills, R.W.

    2016-01-01

    Nuclear power generation in the United Kingdom is based principally on graphite-moderated gas-cooled reactors. The mass of irradiated graphite associated with these reactors, including material from associated experimental, prototype and production reactors, exceeds 96,000 tonnes. One of the principal long-lived radionuclides produced during graphite irradiation is radiocarbon (C-14), which has a half-life of 5730 ± 40 years. Decommissioning and graphite waste management strategies must take account of this radionuclide. In order to identify appropriate options for addressing the potential hazard of C-14, it is important that the production processes are understood and the distributions and concentrations of C-14 are characterised. In fact, C-14 precursors and their activation processes are well-known. However, there is ongoing debate over the relative importance of different C-14 precursors, which will determine the location of C-14 within graphite components and hence its mobility/response to treatment. A generally held misconception concerning C-14 in irradiated graphite is that generic statements can be made about its precursors and their location. C-14 location and activities will depend upon the composition of the original manufactured graphite (raw materials, impurities), the chemical environment of the graphite during service and the irradiation history of the graphite. So, while there may be some similarities across, for example, carbon dioxide cooled graphite moderated designs (Magnox, AGR, UNGG), any informed assessment of a core’s C-14 inventory would require more-precise characterisation. The analysis presented here focuses on a UK Magnox reactor core, Reactor 1 at Wylfa Nuclear Power Station. The objective of the analysis is to present a full C-14 mass balance over a selected period of operation for which there are accurate C-14 discharge records. The analysis presented here provides the first assessment of the principal C-14 activation pathways

  15. Relevance of medieval, Egyptian and American dates to the study of climatic and radiocarbon variability

    International Nuclear Information System (INIS)

    Berger, R.

    1990-01-01

    Basic radiocarbon dating and dendrochronology have been combined to yield calibrated dates that are more accurate than conventional radiocarbon dates. This has been shown to be true for medieval and Egyptian dynastic dating. Because radiocarbon is a cosmogenically produced radioisotope, heliomagnetic and geomagnetic fields play a major role in its synthesis in the Earth's upper atmosphere. Inasmuch as a calibrated radiocarbon record exists for nearly 10 000 years, we now seem to possess in the short-time variations of the production rate a history of solar activity expressed via heliomagnetic fields carried by the solar wind. In turn, solar activity has a controlling effect on climate on Earth within modifications provided by the complex interactions of the atmosphere-Earth-ocean system. Both radiocarbon measurements and other empirical research methods agree on variations of climate during historically more recent periods on Earth. This leads to the suggestion that the radiocarbon calibration curve may be also a significant indicator or tracer for climatic changes for the Holocene or the Neolithic-Mesolithic. (author)

  16. Relevance of medieval, Egyptian and American dates to the study of climatic and radiocarbon variability

    Energy Technology Data Exchange (ETDEWEB)

    Berger, R [California Univ., Los Angeles, CA (USA). Inst. of Geophysics and Planetary Physics

    1990-04-24

    Basic radiocarbon dating and dendrochronology have been combined to yield calibrated dates that are more accurate than conventional radiocarbon dates. This has been shown to be true for medieval and Egyptian dynastic dating. Because radiocarbon is a cosmogenically produced radioisotope, heliomagnetic and geomagnetic fields play a major role in its synthesis in the Earth's upper atmosphere. Inasmuch as a calibrated radiocarbon record exists for nearly 10 000 years, we now seem to possess in the short-time variations of the production rate a history of solar activity expressed via heliomagnetic fields carried by the solar wind. In turn, solar activity has a controlling effect on climate on Earth within modifications provided by the complex interactions of the atmosphere-Earth-ocean system. Both radiocarbon measurements and other empirical research methods agree on variations of climate during historically more recent periods on Earth. This leads to the suggestion that the radiocarbon calibration curve may be also a significant indicator or tracer for climatic changes for the Holocene or the Neolithic-Mesolithic. (author).

  17. Lagrangian Timescales of Southern Ocean Upwelling in a Hierarchy of Model Resolutions

    Science.gov (United States)

    Drake, Henri F.; Morrison, Adele K.; Griffies, Stephen M.; Sarmiento, Jorge L.; Weijer, Wilbert; Gray, Alison R.

    2018-01-01

    In this paper we study upwelling pathways and timescales of Circumpolar Deep Water (CDW) in a hierarchy of models using a Lagrangian particle tracking method. Lagrangian timescales of CDW upwelling decrease from 87 years to 31 years to 17 years as the ocean resolution is refined from 1° to 0.25° to 0.1°. We attribute some of the differences in timescale to the strength of the eddy fields, as demonstrated by temporally degrading high-resolution model velocity fields. Consistent with the timescale dependence, we find that an average Lagrangian particle completes 3.2 circumpolar loops in the 1° model in comparison to 0.9 loops in the 0.1° model. These differences suggest that advective timescales and thus interbasin merging of upwelling CDW may be overestimated by coarse-resolution models, potentially affecting the skill of centennial scale climate change projections.

  18. Upwelling regime off the Cabo Frio region in Brazil and impact on acoustic propagation.

    Science.gov (United States)

    Calado, Leandro; Camargo Rodríguez, Orlando; Codato, Gabriel; Contrera Xavier, Fabio

    2018-03-01

    This work introduces a description of the complex upwelling regime off the Cabo Frio region in Brazil and shows that ocean modeling, based on the feature-oriented regional modeling system (FORMS) technique, can produce reliable predictions of sound speed fields for the corresponding shallow water environment. This work also shows, through the development of simulations, that the upwelling regime can be responsible for the creation of shadow coastal zones, in which the detection probability is too low for an acoustic source to be detected. The development of the FORMS technique and its validation with real data, for the particular region of coastal upwelling off Cabo Frio, reveals the possibility of a sustainable and reliable forecast system for the corresponding (variable in space and time) underwater acoustic environment.

  19. Gradients in microbial methanol uptake: productive coastal upwelling waters to oligotrophic gyres in the Atlantic Ocean

    Science.gov (United States)

    Dixon, Joanna L; Sargeant, Stephanie; Nightingale, Philip D; Colin Murrell, J

    2013-01-01

    Methanol biogeochemistry and its importance as a carbon source in seawater is relatively unexplored. We report the first microbial methanol carbon assimilation rates (k) in productive coastal upwelling waters of up to 0.117±0.002 d−1 (∼10 nmol l−1 d−1). On average, coastal upwelling waters were 11 times greater than open ocean northern temperate (NT) waters, eight times greater than gyre waters and four times greater than equatorial upwelling (EU) waters; suggesting that all upwelling waters upon reaching the surface (⩽20 m), contain a microbial population that uses a relatively high amount of carbon (0.3–10 nmol l−1 d−1), derived from methanol, to support their growth. In open ocean Atlantic regions, microbial uptake of methanol into biomass was significantly lower, ranging between 0.04–0.68 nmol l−1 d−1. Microbes in the Mauritanian coastal upwelling used up to 57% of the total methanol for assimilation of the carbon into cells, compared with an average of 12% in the EU, and 1% in NT and gyre waters. Several methylotrophic bacterial species were identified from open ocean Atlantic waters using PCR amplification of mxaF encoding methanol dehydrogenase, the key enzyme in bacterial methanol oxidation. These included Methylophaga sp., Burkholderiales sp., Methylococcaceae sp., Ancylobacter aquaticus, Paracoccus denitrificans, Methylophilus methylotrophus, Methylobacterium oryzae, Hyphomicrobium sp. and Methylosulfonomonas methylovora. Statistically significant correlations for upwelling waters between methanol uptake into cells and both chlorophyll a concentrations and methanol oxidation rates suggest that remotely sensed chlorophyll a images, in these productive areas, could be used to derive total methanol biological loss rates, a useful tool for atmospheric and marine climatically active gas modellers, and air–sea exchange scientists. PMID:23178665

  20. The development and decline of phytoplankton blooms in the southern Benguela upwelling region

    International Nuclear Information System (INIS)

    Brown, P.C.

    1986-10-01

    Productivity/chlorophyll a relationship are investigated with a view to estimating phytoplankton productivity from extensive chlorophyll a measurements in the southern Benguela region. Phytoplankton bloom dynamics in newly upwelled water off the Cape Peninsula are investigated on five different occasions during the upwelling season. A drogue was used to tag a 'parcel' of upwelled water which was monitored for between 4 and 8 days. In upwelling source water, mean chlorophyll a concentrations were typically low (0.7 mg.m -3 ) and nutrient concentrations were high (nitrates, silicates and phosphates were 20.8, 16.6 and 1.88 mmol.m -3 respectively). Along the drogue tracks nutrients decreased rapidly in the euphotic zone as chlorophyll increased to peak at concentrations of up to 26 mg.m -3 . Elemental changes in nitrates, silicates, phosphates and oxygen were used to estimate primary productivity. These 'Redfield productivity estimates' were similar to 14 C-uptake productivity but lower than estimates obtained from changes in particle volume. Daily rates of 14 C-uptake water column productivity ranged between 0.94 and 14.01 g C.m -2 .d -1 (mean 3.80 g C.m -2 .d -1 ) and were similar to or higher than productivity estimates reported for other upwelling areas. Phytoplankton biomass in the upper 50 metres ranged between 8 and 506 mg chll a. m -2 (mean 208 mg chll a.m -2 ). The temporal scale of phytoplankton bloom development was investigated in terms of changes in chlorophyll a concentrations in the euphotic zone. The build up and decline of the primary phytoplankton (diatom) bloom in newly upwelled water occurred within 6-8 days. The initiation of blooming was controlled by the stability of the water body. The decline of the bloom was associated with reduced nutrient levels and is considered to result mainly from phytoplankton cells sinking out of the surface layers

  1. The role of Southern Ocean mixing and upwelling in glacial-interglacial atmospheric CO2 change

    International Nuclear Information System (INIS)

    Watson, Andrew J.; Naveira Garabato, Alberto C.

    2006-01-01

    Decreased ventilation of the Southern Ocean in glacial time is implicated in most explanations of lower glacial atmospheric CO 2 . Today, the deep (>2000 m) ocean south of the Polar Front is rapidly ventilated from below, with the interaction of deep currents with topography driving high mixing rates well up into the water column. We show from a buoyancy budget that mixing rates are high in all the deep waters of the Southern Ocean. Between the surface and 2000 m depth, water is upwelled by a residual meridional overturning that is directly linked to buoyancy fluxes through the ocean surface. Combined with the rapid deep mixing, this upwelling serves to return deep water to the surface on a short time scale. We propose two new mechanisms by which, in glacial time, the deep Southern Ocean may have been more isolated from the surface. Firstly, the deep ocean appears to have been more stratified because of denser bottom water resulting from intense sea ice formation near Antarctica. The greater stratification would have slowed the deep mixing. Secondly, subzero atmospheric temperatures may have meant that the present-day buoyancy flux from the atmosphere to the ocean surface was reduced or reversed. This in turn would have reduced or eliminated the upwelling (contrary to a common assumption, upwelling is not solely a function of the wind stress but is coupled to the air/sea buoyancy flux too). The observed very close link between Antarctic temperatures and atmospheric CO 2 could then be explained as a natural consequence of the connection between the air/sea buoyancy flux and upwelling in the Southern Ocean, if slower ventilation of the Southern Ocean led to lower atmospheric CO 2 . Here we use a box model, similar to those of previous authors, to show that weaker mixing and reduced upwelling in the Southern Ocean can explain the low glacial atmospheric CO 2 in such a formulation

  2. Factors structuring the phytoplankton community in the upwelling site off El Loa River in northern Chile

    Science.gov (United States)

    Herrera, Liliana; Escribano, Ruben

    2006-06-01

    Understanding processes affecting the structure of the autotrophic community in marine ecosystems is relevant because species-dependent characters may affect productivity and carbon fluxes of the ocean. In this work, we studied the influence of oceanographic variability on phytoplankton species composition at a coastal upwelling site off northern Chile. Four seasonal cruises carried out during 2003 off El Loa River (21°S) showed that upwelling occurs year-round supporting a large number of diatoms, dinoflagellates, naked nanoflagellates, and silicoflagellates. The analysis of species composition showed that changes in the structure of the autotrophic community are expressed both in abundance and in differences in species assemblages. These changes occurred not only over the seasonal scale but also over the spatial pattern of distribution, and they correlated well to temporal variability of upwelling and spatial variation of upwelling conditions over the cross-shelf axis. A K-means clustering and principal component analyses showed that species assemblages can be represented by few dominant species strongly coupled to alternate upwelling vs. non-upwelling conditions. Both conditions are well defined, and mostly explained by changes in depth of the upper boundary of the oxygen minimum zone (OMZ) (a prominent feature in northern Chile), surface temperature and water column stratification. Abundance of dominant phytoplankton species were strongly correlated to both OMZ depth and water column stratification. Processes through which OMZ depth might influence species abundance and composition are unknown, although they may relate to changes in redox conditions which affect the nutrient field. Another explanation may relate to changes in grazing pressure derived from the effect of low oxygen water on zooplankton vertical distribution.

  3. The use of circulation weather types to predict upwelling activity along the Western Iberian Peninsula coast

    Science.gov (United States)

    Ramos, Alexandre M.; Cordeiro Pires, Ana; Sousa, Pedro M.; Trigo, Ricardo M.

    2013-04-01

    Coastal upwelling is a phenomenon that occurs in most western oceanic coasts due to the presence of mid-latitude high-pressure systems that generate equatorward winds along the coast and consequent offshore displacement of surface waters that in turn cause deeper, colder, nutrient-rich waters to arise. In western Iberian Peninsula (IP) the high-pressure system associated to northerly winds occurs mainly during spring and summer. Upwelling systems are economically relevant, being the most productive regions of the world ocean and crucial for fisheries. In this work, we evaluate the intra- and inter-annual variability of the Upwelling Index (UI) off the western coast of the IP considering four locations at various latitudes: Rias Baixas, Aveiro, Figueira da Foz and Cabo da Roca. In addition, the relationship between the variability of the occurrence of several circulation weather types (Ramos et al., 2011) and the UI variability along this coast was assessed in detail, allowing to discriminate which types are frequently associated with strong and weak upwelling activity. It is shown that upwelling activity is mostly driven by wind flow from the northern quadrant, for which the obtained correlation coefficients (for the N and NE types) are higher than 0.5 for the four considered test locations. Taking into account these significant relationships, we then developed statistical multi-linear regression models to hindcast upwelling series (April to September) at the four referred locations, using monthly frequencies of circulation weather types as predictors. Modelled monthly series reproduce quite accurately observational data, with correlation coefficients above 0.7 for all locations, and relatively small absolute errors. Ramos AM, Ramos R, Sousa P, Trigo RM, Janeira M, Prior V (2011) Cloud to ground lightning activity over Portugal and its association with Circulation Weather Types. Atmospheric Research 101:84-101. doi: 10.1016/j.atmosres.2011.01

  4. Anomalous elevated radiocarbon measurements of PM2.5

    International Nuclear Information System (INIS)

    Buchholz, Bruce A.; Fallon, Stewart J.; Zermeño, Paula; Bench, Graham; Schichtel, Bret A.

    2013-01-01

    Two-component models are often used to determine the contributions made by fossil fuel and natural sources of carbon in airborne particulate matter (PM). The models reduce thousands of actual sources to two end members based on isotopic signature. Combustion of fossil fuels produces PM free of carbon-14 ( 14 C). Wood or charcoal smoke, restaurant fryer emissions, and natural emissions from plants produce PM with the contemporary concentration of 14 C approximately 1.2 × 10 −1214 C/C. Such data can be used to estimate the relative contributions of fossil fuels and biogenic aerosols to the total aerosol loading and radiocarbon analysis is becoming a popular source apportionment method. Emissions from incinerators combusting medical or biological wastes containing tracer 14 C can skew the 14 C/C ratio of PM, however, so critical analysis of sampling sites for possible sources of elevated PM needs to be completed prior to embarking on sampling campaigns. Results are presented for two ambient monitoring sites in different areas of the United States where 14 C contamination is apparent. Our experience suggests that such contamination is uncommon but is also not rare (∼10%) for PM sampling sites.

  5. Titan's Radioactive Haze : Production and Fate of Radiocarbon On Titan

    Science.gov (United States)

    Lorenz, R. D.; Jull, A. J. T.; Swindle, T. D.; Lunine, J. I.

    Just as cosmic rays interact with nitrogen atoms in the atmosphere of Earth to gener- ate radiocarbon (14C), the same process should occur in Titan`s nitrogen-rich atmo- sphere. Titan`s atmosphere is thick enough that cosmic ray flux, rather than nitrogen column depth, limits the production of 14 C. Absence of a strong magnetic field and the increased distance from the sun suggest production rates of 9 atom/cm2/s, approx- imately 4 times higher than Earth. On Earth the carbon is rapidly oxidised into CO2. The fate and detectability of 14C on Titan depends on the chemical species into which it is incorporated in Titan's reducing atmosphere : as methane it would be hopelessly diluted even in only the atmosphere (ignoring the other, much more massive carbon reservoirs likely to be present on Titan, like hydrocarbon lakes.) However, in the more likely case that the 14C attaches to the haze that rains out onto the surface (as tholin, HCN or acetylene and their polymers - a much smaller carbon reservoir) , haze in the atmosphere or recently deposited on the surface would therefore be quite intrinsically radioactive. Such activity may modify the haze electrical charging and hence its coag- ulation. Measurements with compact instrumentation on future in-situ missions could place useful constraints on the mass deposition rates of photochemical material on the surface and identify locations where surface deposits of such material are `freshest`.

  6. Single amino acid radiocarbon dating of Upper Paleolithic modern humans

    Science.gov (United States)

    Marom, Anat; McCullagh, James S. O.; Higham, Thomas F. G.; Sinitsyn, Andrey A.; Hedges, Robert E. M.

    2012-01-01

    Archaeological bones are usually dated by radiocarbon measurement of extracted collagen. However, low collagen content, contamination from the burial environment, or museum conservation work, such as addition of glues, preservatives, and fumigants to “protect” archaeological materials, have previously led to inaccurate dates. These inaccuracies in turn frustrate the development of archaeological chronologies and, in the Paleolithic, blur the dating of such key events as the dispersal of anatomically modern humans. Here we describe a method to date hydroxyproline found in collagen (∼10% of collagen carbon) as a bone-specific biomarker that removes impurities, thereby improving dating accuracy and confidence. This method is applied to two important sites in Russia and allows us to report the earliest direct ages for the presence of anatomically modern humans on the Russian Plain. These dates contribute considerably to our understanding of the emergence of the Mid-Upper Paleolithic and the complex suite of burial behaviors that begin to appear during this period. PMID:22517758

  7. The Remarkable Metrological History of Radiocarbon Dating [II].

    Science.gov (United States)

    Currie, Lloyd A

    2004-01-01

    This article traces the metrological history of radiocarbon, from the initial breakthrough devised by Libby, to minor (evolutionary) and major (revolutionary) advances that have brought (14)C measurement from a crude, bulk [8 g carbon] dating tool, to a refined probe for dating tiny amounts of precious artifacts, and for "molecular dating" at the 10 µg to 100 µg level. The metrological advances led to opportunities and surprises, such as the non-monotonic dendrochronological calibration curve and the "bomb effect," that gave rise to new multidisciplinary areas of application, ranging from archaeology and anthropology to cosmic ray physics to oceanography to apportionment of anthropogenic pollutants to the reconstruction of environmental history. Beyond the specific topic of natural (14)C, it is hoped that this account may serve as a metaphor for young scientists, illustrating that just when a scientific discipline may appear to be approaching maturity, unanticipated metrological advances in their own chosen fields, and unanticipated anthropogenic or natural chemical events in the environment, can spawn new areas of research having exciting theoretical and practical implications.

  8. The Geological Survey of Canada Radiocarbon Dating Laboratory

    International Nuclear Information System (INIS)

    Lowdon, J.A.

    1985-01-01

    The Radiocarbon Dating Laboratory of the Geological Survey of Canada began routine 14 C age determinations in 1961 using a 2 litre copper, proportional counter and CO 2 as the counting gas. This counter is operated routinely at a pressure of 2 atmospheres where the maximum dating limit is approximately 40 000 years using the 4σ criterion. In 1964 a 5 litre counter was put into operation. Routinely this counter is operated at a pressure of 1 atmosphere where its dating limit is approximately 40 000 years. When operated at 4 atmospheres its age limit increases to about 54 000 years. Organic samples are burned in a stream of oxygen and the CO 2 released is purified on passage through a series of chemicals and traps. Inorganic samples are dissolved in phosphoric acid. Up to the end of 1983 more than 3700 age determinations have been carried out on various types of sample material. Since 1963 twenty-three Geological Survey of Canada Date Lists have been published. The Laboratory also carries out a program of 14 C determinations of samples of known age for the purpose of assessing the accuracy of the method and learning more about the natural and man-made 14 C distribution and circulation in nature

  9. Physical Research Laboratory radiocarbon 14C dates : CS-I

    International Nuclear Information System (INIS)

    Agrawal, D.P.; Krishnamurthy, R.V.; Kusumgar, Sheela; Pant, R.K.

    1978-01-01

    The 14 C dates of archaeological samples measured at the Radiocarbon Laboratory of the Physical Research Laboratory, Ahmedabad are presented. Samples were converted into methane and measured in gas proportional counters. Ninety-five percent activity of NBS oxalic acid was used as modern standard. The dates in years B.P. are given for each sample based on the half-life values of 5568 +- 30 years and 5730 +- 40 years, the latter within parenthesis. The dates are not calibrated for 14 C/ 12 C variations. To convert the dates into AD/BC scale, 1950 AD should be used as reference year. A number of 14 C dates (PRL-81, -83, -67, -68) now confirm that the Painted Grey Ware culture extended upto the 3rd century BC. Some of the dates from Barkhera (PRL-113), Bateshwar (PRL-200), Bhimbetka (PRL-17) and Koldihawa (PRL-100, 101) are older than normally expected, probably indicative of some hitherto unknown basal cultures in these regions. 14 C dates on in situ Megalithic materials do not seem to go beyond 200 BC. (author)

  10. Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

    Directory of Open Access Journals (Sweden)

    B. Ausín

    2018-01-01

    Full Text Available A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions. However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past

  11. Spatial and temporal variability in coccolithophore abundance and distribution in the NW Iberian coastal upwelling system

    Science.gov (United States)

    Ausín, Blanca; Zúñiga, Diana; Flores, Jose A.; Cavaleiro, Catarina; Froján, María; Villacieros-Robineau, Nicolás; Alonso-Pérez, Fernando; Arbones, Belén; Santos, Celia; de la Granda, Francisco; Castro, Carmen G.; Abrantes, Fátima; Eglinton, Timothy I.; Salgueiro, Emilia

    2018-01-01

    A systematic investigation of the spatial and temporal variability in coccolithophore abundance and distribution through the water column of the NW Iberian coastal upwelling system was performed. From July 2011 to June 2012, monthly sampling at various water depths was conducted at two parallel stations located at 42° N. Total coccosphere abundance was higher at the outer-shelf station, where warmer, nutrient-depleted waters favoured coccolithophore rather than phytoplanktonic diatom blooms, which are known to dominate the inner-shelf location. In seasonal terms, higher coccosphere and coccolith abundances were registered at both stations during upwelling seasons, coinciding with high irradiance levels. This was typically in conjunction with stratified, nutrient-poor conditions (i.e. relaxing upwelling conditions). However, it also occurred during some upwelling events of colder, nutrient-rich subsurface waters onto the continental shelf. Minimum abundances were generally found during downwelling periods, with unexpectedly high coccolith abundance registered in subsurface waters at the inner-shelf station. This finding can only be explained if strong storms during these downwelling periods favoured resuspension processes, thus remobilizing deposited coccoliths from surface sediments, and hence hampering the identification of autochthonous coccolithophore community structure. At both locations, the major coccolithophore assemblages were dominated by Emiliania huxleyi, small Gephyrocapsa group, Gephyrocapsa oceanica, Florisphaera profunda, Syracosphaera spp., Coronosphaera mediterranea, and Calcidiscus leptoporus. Ecological preferences of the different taxa were assessed by exploring the relationships between environmental conditions and temporal and vertical variability in coccosphere abundance. These findings provide relevant information for the use of fossil coccolith assemblages in marine sediment records, in order to infer past environmental conditions, of

  12. A Fortran-77 program for Monte Carlo simulation of upwelling light from the sea

    Digital Repository Service at National Institute of Oceanography (India)

    Sathe, P.V.; Sathyendranath, S.

    for Monte Carlo simulation of spectral and angular composition of upwelling light emerging from a wind-roughened sea under given physical conditions and for a given water quality. The program also simulates the light field prevailing immediately below... constituents of the sea which influence the quality of upwelling light. Because the program is a direct simulation of radiative transfer from the atmosphere to the sea and vice versa, it may be put to a variety of uses in studies in marine optics. Simulated...

  13. Evaluation of ERTS data for certain oceanographic uses. [upwelling, water circulation, and pollution in Great Lakes

    Science.gov (United States)

    Strong, A. E. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Upwelling along the eastern shore of Lake Michigan was occurring during the 3 and 21 August 1973 visits by ERTS-1. The NOAA-2 VHRR thermal-IR data are being digitized for comparison. Early indications are that these upwellings induced a calcium carbonate precipitate to form in the surface waters. It is most pronounced in the MSS-4 channel. On the lake bottom this jell-like sediment is known as marl and adds to the eutrophication of the lake. This phenomenon may help to explain the varve-like nature of bottom cores that have been observed in the Great Lakes.

  14. What Can Radiocarbon Depth Profiles Tell Us About The LGM Circulation?

    Science.gov (United States)

    Burke, A.; Stewart, A.; Adkins, J. F.; Ferrari, R. M.; Thompson, A. F.; Jansen, M. F.

    2014-12-01

    Published reconstructions of radiocarbon in the Atlantic sector of the Southern Ocean indicate that there is a mid-depth maximum in radiocarbon age during the last glacial maximum (LGM). This is in contrast to the modern ocean where intense mixing between water masses along shared density surfaces (isopycnals) results in a relatively homogenous radiocarbon profile. A recent study (Ferrari et al. 2014) suggested that the extended Antarctic sea ice cover during the LGM necessitated a shallower boundary between the upper and lower branches of the meridional overturning circulation (MOC). This shoaled boundary lay above major topographic features and their associated strong diapycnal mixing, which isolated dense southern-sourced water in the lower branch of the overturning circulation. This isolation would have allowed radiocarbon to decay, and thus provides a possible explanation for the mid-depth radiocarbon age bulge. We test this hypothesis using an idealized, 2D, residual-mean dynamical model of the global overturning circulation. Concentration distributions of a decaying tracer that is advected by the simulated overturning are compared to published radiocarbon data. We test the sensitivity of the mid-depth radiocarbon age to changes in sea ice extent, wind strength, and isopycnal and diapycnal diffusion. The mid-depth radiocarbon age bulge is most likely caused by the different circulation geometry, associated with increased sea ice extent. In particular, with an LGM-like sea ice extent the upper and lower branches of the MOC no longer share isopycnals, so radiocarbon-rich northern-sourced water is no longer mixed rapidly into the southern-sourced water. However, this process alone cannot explain the magnitude of the glacial radiocarbon anomalies; additional isolation (e.g. from reduced air-sea gas exchange associated with the increased sea ice) is required. Ferrari, R., M. F. Jansen, J. F. Adkins, A. Burke, A. L. Stewart, and A. F. Thompson (2014), Antarctic sea

  15. Coastal upwelling fluxes of O2, N2O, and CO2 assessed from continuous atmospheric observations at Trinidad, California

    Directory of Open Access Journals (Sweden)

    T. J. Lueker

    2004-01-01

    Full Text Available Continuous atmospheric records of O2/N2, CO2 and N2O obtained at Trinidad, California document the effects of air-sea exchange during coastal upwelling and plankton bloom events. The atmospheric records provide continuous observations of air-sea fluxes related to synoptic scale upwelling events over several upwelling seasons. Combined with satellite, buoy and local meteorology data, calculated anomalies in O2/N2 and N2O were utilized in a simple atmospheric transport model to compute air-sea fluxes during coastal upwelling. CO2 fluxes were linked to the oceanic component of the O2 fluxes through local hydrographic data and estimated as a function of upwelling intensity (surface ocean temperature and wind speed. Regional air-sea fluxes of O2/N2, N2O, and CO2 during coastal upwelling were estimated with the aid of satellite wind and SST data. Upwelling CO2 fluxes were found to represent ~10% of export production along the northwest coast of North America. Synoptic scale upwelling events impact the net exchange of atmospheric CO2 along the coastal margin, and will vary in response to the frequency and duration of alongshore winds that are subject to climate change.

  16. Development of upwelling on pathway and freshwater transport of Pearl River plume in northeastern South China Sea

    Science.gov (United States)

    Chen, Zhaoyun; Jiang, Yuwu; Liu, James T.; Gong, Wenping

    2017-08-01

    In situ observations, satellite images, and numerical modeling results have shown that the Pearl River plume axis extends alongshore and passes through two separate upwelling regions—one off the Guangdong and Fujian coasts (the Yuedong upwelling) and the other in the Taiwan Bank during the initial and medium stages of the Yuedong upwelling, while it is directed offshore when the Yuedong upwelling is strong. Model experiments are conducted to examine the effects of wind strength and baroclinicity on the upwelling and the corresponding pathway and freshwater transport of the Pearl River plume. The baroclinic effect is important to intensifying the horizontal velocity at the upwelling front and freshwater transport in the northeastern South China Sea. The freshwater transport flux is further decomposed into advection, vertical shear, and tidal pumping components, and advection is the dominant contributor. As the Yuedong upwelling develops, the zone with a relatively high-pressure gradient moves offshore due to offshore Ekman transport and the shift in the upwelling front, which is responsible for the offshore transport of the river plume. When the river plume is transported to the outer-shelf, sometimes it can be further entrained into eddies, allowing its export to the open sea.

  17. Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology

    OpenAIRE

    Uno, Kevin T.; Quade, Jay; Fisher, Daniel C.; Wittemyer, George; Douglas-Hamilton, Iain; Andanje, Samuel; Omondi, Patrick; Litoroh, Moses; Cerling, Thure E.

    2013-01-01

    Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon (14C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric 14C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa...

  18. Thermal history of the Acoculco geothermal system, eastern Mexico: Insights from numerical modeling and radiocarbon dating

    Science.gov (United States)

    Canet, Carles; Trillaud, Frederic; Prol-Ledesma, Rosa María; González-Hernández, Galia; Peláez, Berenice; Hernández-Cruz, Berenice; Sánchez-Córdova, María M.

    2015-10-01

    Acoculco is a geothermal prospective area hosted by a volcanic caldera complex in the eastern Trans-Mexican Volcanic Belt. Surface manifestations are scarce and consist of gas discharges (CO2-rich) and acid-sulfate springs of low temperature, whereas hydrothermal explosive activity is profusely manifested by meter-scale craters and mounds of hydrothermal debris and breccias. Silicic alteration extends for several square kilometers around the zone with gas manifestations and explosive features, affecting surficial volcanic rocks, primarily tuffs and breccias. In the subsurface, an argillic alteration zone (ammonium illite) extends down to a depth of ∼ 600 m, and underneath it a propylitic zone (epidote-calcite-chlorite) occurs down to ∼ 1000 m. Thermal logs from an exploratory borehole (EAC-1, drilled in 1995 down to 1810 m) showed a conductive heat transfer regime under high geothermal gradient (∼ 140 °C/1000 m). In contrast, the thermal profile established from temperatures of homogenization of fluid inclusions-measured on core samples from the same drill hole-suggests that convection occurred in the past through the upper ~ 1400 m of the geothermal system. A drop in permeability due to the precipitation of alteration minerals would have triggered the cessation of the convective heat transfer regime to give place to a conductive one. With the purpose of determining when the transition of heat transfer regime occurred, we developed a 1D model that simulates the time-depth distribution of temperature. According to our numerical simulations, this transition happened ca. 7000 years ago; this date is very recent compared to the lifespan of the geothermal system. In addition, radiocarbon chronology indicates that the hydrothermal explosive activity postdates the end of the convective heat transfer regime, having dated at least three explosive events, at 4867-5295, 1049-1417 and 543-709 y cal. BP. Therefore, hydrothermal explosions arise from the self-sealing of

  19. Constraint on radiocarbon age correction in Lake Biwa environment from the middle to late Holocene

    Energy Technology Data Exchange (ETDEWEB)

    Miyata, Y., E-mail: miyata@nendai.nagoya-u.ac.jp [Center for Chronological Research, Nagoya University, Nagoya 464-8602 (Japan); National Museum of Japanese History, Sakura 285-8502 (Japan); Minami, M. [Center for Chronological Research, Nagoya University, Nagoya 464-8602 (Japan); Onbe, S. [National Museum of Japanese History, Sakura 285-8502 (Japan); Archaeological Heritage Management Office, Tokushima University, Tokushima 770-8503 (Japan); Sakamoto, M. [National Museum of Japanese History, Sakura 285-8502 (Japan); Nakamura, T. [Center for Chronological Research, Nagoya University, Nagoya 464-8602 (Japan); Imamura, M. [National Museum of Japanese History, Sakura 285-8502 (Japan)

    2013-01-15

    Using data from previous studies and newly collected data, we compared the measured radiocarbon ages of molluscan shells, common reed (Phragmites australis) and pine needles (Pinus thunbergii) collected in 1966, 1970, 1990 and 2008 at Lake Biwa in Japan, and of archaeological samples, to examine radiocarbon reservoir effects at Lake Biwa. We also tested for differences in the radiocarbon reservoir effect between species and locations in the lake. The effects of nuclear bomb tests conducted in the 1950s and 1960s are clear, the offset between atmospheric {sup 14}C and the Lake Biwa freshwater {sup 14}C is larger for this period because the atmospheric {sup 14}C is so high. The semiclosed Lake Biwa system is in dynamic equilibrium with the atmosphere, resulting in the {sup 14}C content of the water following the changes in atmospheric {sup 14}C caused by nuclear testing. The shells collected after 1990 had radiocarbon ages that were 330-450 {sup 14}C years older than those of the coeval atmosphere. The apparent differences in radiocarbon age (about 300 {sup 14}C years) between shell fossils and wood samples excavated from the same layer of the submerged Awazu shell midden at Lake Biwa suggest that the radiocarbon reservoir effect also existed in the middle Holocene (the Middle Jomon period, about 5000 years ago). Because the present-day average residence time of Lake Biwa water is 3-6 years, its direct influence on the radiocarbon reservoir effect is small, which suggests that old carbon has been supplied into Lake Biwa.

  20. Intracavity optogalvanic spectroscopy: Is there any evidence of a radiocarbon signal?

    International Nuclear Information System (INIS)

    Persson, Anders; Salehpour, Mehran

    2015-01-01

    In 2008, the first report of an ultrasensitive method for ro-vibrational spectrometry of radiocarbon dioxide was published. The method, called intracavity optogalvanic spectroscopy (ICOGS), claimed a sensitivity and limit-of-detection comparable to accelerator mass spectroscopy. ICOGS was claimed to utilize the isotope-dependent ro-vibrational absorption lines of carbon dioxide in the infrared spectrum. In order to facilitate unambiguous detection of radiocarbon, the sample was placed inside the cavity of a radiocarbon dioxide laser. This intracavity approach was claimed to increase the sensitivity by seven orders of magnitude compared with traditional optogalvanic methods. However, despite the methodical and thorough efforts of several research groups worldwide, these claims have not been possible to reproduce. Instead, we have previously reported serious deviations from the original results, where we found that ICOGS suffers from considerable problems with the stability and reproducibility of the optogalvanic signal, and that misinterpretations of these uncertainties likely are the explanation for the claimed sensitivity in the first reports. Having identified the stability and reproducibility of the detection as major concerns, we decided to improve the setup by with state-of-the-art plasma source technology. Deploying a custom-made stripline split-ring resonator optogalvanic detector, we have now investigated the applicability of ICOGS to radiocarbon detection even further. Measurements have been made with a wide range of parameters including different gas mixtures at various pressures and wavelengths. We have also conducted measurements with gas flowing through the sample cell to investigate the effect of plasma induced decomposition of the sample. Still, we have seen no indications of a significant radiocarbon signal in a concentration range between 0.29 Modern and 9.7 Modern, i.e., the range of interest to the radiocarbon community. Hence, our conclusions

  1. Radiocarbon measurements at LAC-UFF: Recent performance

    Energy Technology Data Exchange (ETDEWEB)

    Linares, Roberto, E-mail: rlinares@if.uff.br [Laboratório de Radiocarbono, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza, s/n, Niterói 24230-346 (Brazil); Macario, Kita D. [Laboratório de Radiocarbono, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza, s/n, Niterói 24230-346 (Brazil); Santos, Guaciara M. [Earth System Science, University of California, Irvine, B321 Croul Hall, Irvine, CA 92697-3100 (United States); Carvalho, Carla [Laboratório de Radiocarbono, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza, s/n, Niterói 24230-346 (Brazil); Departamento de Geoquímica, Universidade Federal Fluminense, Outeiro São João Batista, s/n, Niterói 24020-141 (Brazil); Santos, Hellen C. dos; Gomes, Paulo R.S.; Castro, Maikel D.; Oliveira, Fabiana M.; Alves, Eduardo Q. [Laboratório de Radiocarbono, Universidade Federal Fluminense, Av. Gal. Milton Tavares de Souza, s/n, Niterói 24230-346 (Brazil)

    2015-10-15

    In 2012 a single stage accelerator mass spectrometer from NEC was installed at the Radiocarbon Laboratory of Universidade Federal Fluminense (LAC-UFF), Niterói, Brazil. Here, we present a status report of our facility. We discuss some modifications applied to our combustion protocol in an attempt to reduce our procedural blank, mostly to processed organic samples. Measurements of reference materials indicate low precision and accuracy that are partially related to beam optics through the acceleration tube. We observed that once the beam current intensity increases the measured {sup 13}C{sup +}/{sup 12}C{sup +} becomes erratic. Therefore, in order to maintain the AMS-δ{sup 13}C values within reasonable values, so that fractionation corrections using the spectrometer {sup 13}C{sup +}/{sup 12}C{sup +} values does not affect the final {sup 14}C results, we are forced to limit the {sup 12}C{sup −} beam intensity to ⩽30 μA. This requirement was confirmed during our accuracy tests, when measuring selected annual tree-rings wood samples from a Parana pine (Araucaria angustifolia) between 1927 and 1997 previously measured at the Keck Carbon Cycle AMS Facility (KCCAMS), at the University of California, Irvine (UCI). At the LAC-UFF tree-ring wood samples were processed and measured in 4 different batches during a period of about 5 months. The {sup 14}C results were later compared to the high-precision data obtained at KCCAMS/UCI and reached a good agreement. Recently a problem associated with graphitization yield were finally identified and new measurements with secondary standards are promising.

  2. Radiocarbon Based Ages and Growth Rates: Hawaiian Deep Sea Corals

    Energy Technology Data Exchange (ETDEWEB)

    Roark, E B; Guilderson, T P; Dunbar, R B; Ingram, B L

    2006-01-13

    The radial growth rates and ages of three different groups of Hawaiian deep-sea 'corals' were determined using radiocarbon measurements. Specimens of Corallium secundum, Gerardia sp., and Leiopathes glaberrima, were collected from 450 {+-} 40 m at the Makapuu deep-sea coral bed using a submersible (PISCES V). Specimens of Antipathes dichotoma were collected at 50 m off Lahaina, Maui. The primary source of carbon to the calcitic C. secundum skeleton is in situ dissolved inorganic carbon (DIC). Using bomb {sup 14}C time markers we calculate radial growth rates of {approx} 170 {micro}m y{sup -1} and ages of 68-75 years on specimens as tall as 28 cm of C. secundum. Gerardia sp., A. dichotoma, and L. glaberrima have proteinaceous skeletons and labile particulate organic carbon (POC) is their primary source of architectural carbon. Using {sup 14}C we calculate a radial growth rate of 15 {micro}m y{sup -1} and an age of 807 {+-} 30 years for a live collected Gerardia sp., showing that these organisms are extremely long lived. Inner and outer {sup 14}C measurements on four sub-fossil Gerardia spp. samples produce similar growth rate estimates (range 14-45 {micro}m y{sup -1}) and ages (range 450-2742 years) as observed for the live collected sample. Similarly, with a growth rate of < 10 {micro}m y{sup -1} and an age of {approx}2377 years, L. glaberrima at the Makapuu coral bed, is also extremely long lived. In contrast, the shallow-collected A. dichotoma samples yield growth rates ranging from 130 to 1,140 {micro}m y{sup -1}. These results show that Hawaiian deep-sea corals grow more slowly and are older than previously thought.

  3. An upwelling filament North-West of Cape Town, South Africa ...

    African Journals Online (AJOL)

    One is the sporadic advection of warm water from the Agulhas Bank onto the southern shelf. The cruise took place following such an event. The anticipated shelf-edge jet was greatly diminished and forced inshore. The possible effect of barotropic shelf waves on the configuration of the upwelling tongue and the formation of ...

  4. Coastal upwelling along the southwest coast of India – ENSO modulation

    Directory of Open Access Journals (Sweden)

    K. Muni Krishna

    2008-06-01

    Full Text Available An index of El Niño Southern Oscillation (ENSO in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold ENSO events being associated with relaxation (intensification of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

  5. Riverine influence on nitrogen fixation in the upwelling region off Vietnam, South China Sea

    DEFF Research Database (Denmark)

    Voss, Maren; Bombar, Deniz; Loick, Natalie

    2006-01-01

    with the intermonsoon season and find that nitrogen fixation rates are app. 10 times higher during the monsoon season. However, this was not the case in the actual upwelling region - a 40-50 km wide strip along the coast - but further offshore, where the Mekong plume was noticeable. Therefore, we hypothesize...

  6. On the warm nearshore bias in Pathfinder monthly SST products over Eastern Boundary upwelling systems

    CSIR Research Space (South Africa)

    Dufois, F

    2012-01-01

    Full Text Available Using in situ sea surface temperature (SST) data and MODIS/TERRA SST, the monthly AVHRR Pathfinder (version 5.0 and 5.2) SST product was evaluated within the four main Eastern Boundary Upwelling Systems. A warm bias in the monthly Pathfinder data...

  7. Environmental changes associated with monsoon induced upwelling, off central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    DeSousa, S.N.; Sawkar, K.; Rao, P.V.S.S.D.P.

    in response to prevailing equatorward winds. High salinity ocean waters of rich nutrient contents were observed at the coast in some locations. However, the effect of upwelling on the surface distribution of properties was reduced to some extent due to coastal...

  8. Why coastal upwelling is expected to increase along the western Iberian Peninsula over the next century?

    Science.gov (United States)

    Sousa, Magda Catarina; deCastro, Maite; Alvarez, Ines; Gomez-Gesteira, Moncho; Dias, João Miguel

    2017-08-15

    Former studies about coastal upwelling along the Western Iberian Peninsula (WIP) using historical data indicated contradictory results, showing either its strengthening or reduction, while previous studies using Global Climate Models (GCMs) indicated that global warming is likely to intensify this phenomenon although predicting different rates and not justifying the patterns found. Taking advantage of the recent high spatial resolution Regional Climate Models (RCMs) projections from EURO-CORDEX project (Representative Concentration Pathway, RCP 8.5), detailed higher accuracy estimations of the spatio-temporal trends of Upwelling Index (UI) along the WIP coast were performed in this study, integrating the coastal mesoscale effects within the framework of climate change. Additionally, this research brings new insights about the origin of the WIP coastal upwelling intensification over the next century. These new projections clarified the upwelling strengthening rates predicted along the coast of the WIP from 2006 to 2099 revealing more prominent changes in the northern limit of the region (25-30m 3 s -1 km -1 per decade between 41.5 and 42.5°N). Trends observed at high latitudes of the region were found to be induced by the displacement of the Azores High, which will intensify (0.03hPa per decade) and drift northeastward (10km per decade) during the 21st century. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Spatial distribution of upwelling off the central east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, T.V.N.

    of the data collected along the five sections. At all the sections, a decrease in water temperature and an increase in salinity from the offshore stations to the stations closest to the shore indicated coastal upwelling. The Rossby radii of deformation...

  10. Insights into the Microbial and Viral Dynamics of a Coastal Downwelling-Upwelling Transition.

    Directory of Open Access Journals (Sweden)

    Gustavo Bueno Gregoracci

    Full Text Available Although previous studies have described opposing states in upwelling regions, i.e., the rise of cold nutrient-rich waters and prevalence of surface warm nutrient-poor waters, few have addressed the transition from one state to the other. This study aimed to describe the microbial and viral structure during this transition and was able to obtain the taxonomic and metabolic compositions as well as physical-chemical data. This integrated approach allowed for a better understanding of the dynamics of the downwelling upwelling transition, suggesting that a wealth of metabolic processes and ecological interactions are occurring in the minute fractions of the plankton (femto, pico, nano. These processes and interactions included evidence of microbial predominance during downwelling (with nitrogen recycling and aerobic anoxygenic photosynthesis, different viral predation pressures over primary production in different states (cyanobacteria vs eukaryotes, and a predominance of diatoms and selected bacterial and archaeal groups during upwelling (with the occurrence of a wealth of nitrogen metabolism involving ammonia. Thus, the results provided insights into which microbes, viruses and microbial-mediated processes are probably important in the functioning of upwelling systems.

  11. Internal structure of the upwelling events at Punta Gallinas (Colombian Caribbean) from modis-sst imagery

    Science.gov (United States)

    Alonso, J.; Blázquez, E.; Isaza-Toro, E.; Vidal, J.

    2015-10-01

    The upwelling at Punta Gallinas in the Guajira Peninsula (Colombian Caribbean) was studied from the point of view of the Mathematical Morphology using 10 years of monthly composite MODIS-SST imagery. Among all the morphological operators, the skeleton is widely used to compute the axis of the of the SST fields for the observed upwelling events. The skeleton is characterized by means of the Geometrical Theory of Measurement using the fractal dimension. The upwelling in the area is driven by the dynamic of the ITCZ (InterTropical Convergence Zone) and the relationship between the area and the East-West component of the trade winds has a lag of about 4 months. It has been found that the fractal dimension of the skeleton and the area of the upwelling are related. Some relationship was found between the fractal dimension of the skeleton (its complexity) and the Southern Oscillation Index by means of linear regression and cross-spectral analysis finding coherent energy at 1 year, 6 months and in the low frequency band. Finally, a sensitivity analysis between fractal dimension and threshold SST points out to take an extreme care at the time of fixing the last one.

  12. The physical structure of an upwelling filament off the North-west ...

    African Journals Online (AJOL)

    ... in dispersal of material originating in the region of active coastal upwelling. The location of the filament studied appears repeatable from year to year, suggestive of a strong relation with the topographically trapped eddy, which was situated downstream of a lateral ridge between the. Canary Islands and the African coast.

  13. Arabian Sea upwelling - A comparison between coastal and open ocean regions

    Digital Repository Service at National Institute of Oceanography (India)

    Muraleedharan, P.M.; PrasannaKumar, S.

    The response of the eastern Arabian Sea to prevailing winds during an upwelling event, in the peak of southwest monsoon, was studied at both coastal and open ocean environment based on the data collected as a part of the Indian Joint Global Ocean...

  14. Sources of new nitrogen in the Vietnamese upwelling region of the South China Sea

    DEFF Research Database (Denmark)

    Bombar, Deniz; Dippner, Joachim W.; Doan, Hai Nhu

    2010-01-01

    In the South China Sea, the southwest monsoon between June and September induces upwelling off the southern central Vietnamese coast. During field campaigns in July 2003 and 2004 we evaluated the importance of nitrate and nitrogen fixation as sources of new nitrogen for phytoplankton primary...

  15. Climate change and ocean deoxygenation within intensified surface-driven upwelling circulations.

    Science.gov (United States)

    Bakun, Andrew

    2017-09-13

    Ocean deoxygenation often takes place in proximity to zones of intense upwelling. Associated concerns about amplified ocean deoxygenation arise from an arguable likelihood that coastal upwelling systems in the world's oceans may further intensify as anthropogenic climate change proceeds. Comparative examples discussed include the uniquely intense seasonal Somali Current upwelling, the massive upwelling that occurs quasi-continuously off Namibia and the recently appearing and now annually recurring 'dead zone' off the US State of Oregon. The evident 'transience' in causal dynamics off Oregon is somewhat mirrored in an interannual-scale intermittence in eruptions of anaerobically formed noxious gases off Namibia. A mechanistic scheme draws the three examples towards a common context in which, in addition to the obvious but politically problematic remedy of actually reducing 'greenhouse' gas emissions, the potentially manageable abundance of strongly swimming, finely gill raker-meshed small pelagic fish emerges as a plausible regulating factor.This article is part of the themed issue 'Ocean ventilation and deoxygenation in a warming world'. © 2017 The Author(s).

  16. Nearshore currents on the southern Namaqua shelf of the Benguela upwelling system

    Science.gov (United States)

    Fawcett, A. L.; Pitcher, G. C.; Shillington, F. A.

    2008-05-01

    Nearshore currents of the southern Namaqua shelf were investigated using data from a mooring situated three and a half kilometres offshore of Lambert's Bay, downstream of the Cape Columbine upwelling cell, on the west coast of South Africa. This area is susceptible to harmful algal blooms (HABs) and wind-forced variations in currents and water column structure are critical in determining the development, transport and dissipation of blooms. Time series of local wind data, and current and temperature profile data are described for three periods, considered to be representative of the latter part of the upwelling season (27 January-22 February), winter conditions (5-29 May) and the early part of the upwelling season (10 November-12 December) in 2005. Differences observed in mean wind strength and direction between data sets are indicative of seasonal changes in synoptic meteorological conditions. These quasi-seasonal variations in wind forcing affect nearshore current flow, leading to mean northward flow in surface waters early in the upwelling season when equatorward, upwelling-favourable winds are persistent. Mean near-surface currents are southward during the latter part of the upwelling season, consistent with more prolonged periods of relaxation from equatorward winds, and under winter conditions when winds were predominantly poleward. Within these seasonal variations in mean near-surface current direction, two scales of current variability were evident within all data sets: strong inertial oscillations were driven by diurnal winds and introduced vertical shear into the water column enhancing mixing across the thermocline, while sub-inertial current variability was driven by north-south wind reversals at periods of 2-5 days. Sub-inertial currents were found to lag wind reversals by approximately 12 h, with a tendency for near-surface currents to flow poleward in the absence of wind forcing. Consistent with similar sites along the Californian and Iberian coasts

  17. Solar flares and radiocarbon abundance in the atmosphere of the Earth

    International Nuclear Information System (INIS)

    Metskhvarishvili, R.Ya.; Imedadze, T.Sh.; Tleugaliev, S.Kh.; Tsinamdzgvrishvili, T.Sh.; Tsereteli, S.L.

    1978-01-01

    The correlation between the radiocarbon ( 14 C) content in the atmosphere of the Earth and the solar activity is studied. Annual measurements of the 14 C content in the tree rings for the last 120 years have been made. Relations of the radiocarbon content in dendrochronologically dated tree rings and the Wolf numbers for the period from 1850 to 1940 are presented. The spectroscopic and Borg methods have been used to ascertain the periodicities in the radiocarbon series. It is shown that well-defined periods of approximately 11 and approximately 65 years are observed in the radiocarbon series. The former is associated with an 11-year and the latter with a secular cycle of the 14 C content in the earth atmosphere. To study the relation of the solar activity to the level of radiocarbon in the earth atmosphere a mutual correlation function was calculated for various values of the time lags of 14 C with respect to the processes on the Sun. It follows from the data obtained that a positive correlation takes place for time lags smaller than three years. The detected positive correlation has revealed that the effect of solar flares in the 11-year cycle is prevalent

  18. A re-analysis of the Lake Suigetsu terrestrial radiocarbon calibration dataset

    International Nuclear Information System (INIS)

    Staff, R.A.; Bronk Ramsey, C.; Nakagawa, T.

    2010-01-01

    Lake Suigetsu, Honshu Island, Japan provides an ideal sedimentary sequence from which to derive a wholly terrestrial radiocarbon calibration curve back to the limits of radiocarbon detection (circa 60 ka bp). The presence of well-defined, annually-deposited laminae (varves) throughout the entirety of this period provides an independent, high resolution chronometer against which radiocarbon measurements of plant macrofossils from the sediment column can be directly related. However, data from the initial Lake Suigetsu project were found to diverge significantly from alternative, marine-based calibration datasets released around the same time (e.g. ). The main source of this divergence is thought to be the result of inaccuracies in the absolute age profile of the Suigetsu project, caused by both varve counting uncertainties and gaps in the sediment column of unknown duration between successively-drilled core sections. Here, a re-analysis of the previously-published Lake Suigetsu data is conducted. The most recent developments in Bayesian statistical modelling techniques (OxCal v4.1; ) are implemented to fit the Suigetsu data to the latest radiocarbon calibration datasets and thereby estimate the duration of the inter-core section gaps in the Suigetsu data. In this way, the absolute age of the Lake Suigetsu sediment profile is more accurately defined, providing significant information for both radiocarbon calibration and palaeoenvironmental reconstruction purposes.

  19. A combined method for DNA analysis and radiocarbon dating from a single sample.

    Science.gov (United States)

    Korlević, Petra; Talamo, Sahra; Meyer, Matthias

    2018-03-07

    Current protocols for ancient DNA and radiocarbon analysis of ancient bones and teeth call for multiple destructive samplings of a given specimen, thereby increasing the extent of undesirable damage to precious archaeological material. Here we present a method that makes it possible to obtain both ancient DNA sequences and radiocarbon dates from the same sample material. This is achieved by releasing DNA from the bone matrix through incubation with either EDTA or phosphate buffer prior to complete demineralization and collagen extraction utilizing the acid-base-acid-gelatinization and ultrafiltration procedure established in most radiocarbon dating laboratories. Using a set of 12 bones of different ages and preservation conditions we demonstrate that on average 89% of the DNA can be released from sample powder with minimal, or 38% without any, detectable collagen loss. We also detect no skews in radiocarbon dates compared to untreated samples. Given the different material demands for radiocarbon dating (500 mg of bone/dentine) and DNA analysis (10-100 mg), combined DNA and collagen extraction not only streamlines the sampling process but also drastically increases the amount of DNA that can be recovered from limited sample material.

  20. Towards radiocarbon dating of single foraminifera with a gas ion source

    Science.gov (United States)

    Wacker, L.; Lippold, J.; Molnár, M.; Schulz, H.

    2013-01-01

    Carbonate shells from foraminifera are often analysed for radiocarbon to determine the age of deep-sea sediments or to assess radiocarbon reservoir ages. However, a single foraminiferal test typically contains only a few micrograms of carbon, while most laboratories require more than 100 μg for radiocarbon dating with an accelerator mass spectrometry (AMS) system. The collection of the required amount of foraminifera for a single analyses is therefore time consuming and not always possible. Here, we present a convenient method to measure the radiocarbon content of foraminifera using an AMS system fitted with a gas ion source. CO2 is liberated from 150 to 1150 μg of carbonate in septum sealed vials by acid decomposition of the carbonate. The CO2 is collected on a zeolite trap and subsequently transferred to a syringe from where it is delivered to the ion source. A sample of 400 μg (50 μg C) typically gives a 12C- ion source current of 10-15 μA over 20 min, yielding a measurement precision of less than 7 per mil for a modern sample. Using this method, we were able to date a single 560 μg Cibicides pseudoungerianus test at 14,030 ± 160 radiocarbon years. Only a minor modification to our existing gas handling system was required and the system is fully automatable to further reduce the effort involved for sample preparation.

  1. Towards radiocarbon dating of single foraminifera with a gas ion source

    International Nuclear Information System (INIS)

    Wacker, L.; Lippold, J.; Molnár, M.; Schulz, H.

    2013-01-01

    Carbonate shells from foraminifera are often analysed for radiocarbon to determine the age of deep-sea sediments or to assess radiocarbon reservoir ages. However, a single foraminiferal test typically contains only a few micrograms of carbon, while most laboratories require more than 100 μg for radiocarbon dating with an accelerator mass spectrometry (AMS) system. The collection of the required amount of foraminifera for a single analyses is therefore time consuming and not always possible. Here, we present a convenient method to measure the radiocarbon content of foraminifera using an AMS system fitted with a gas ion source. CO 2 is liberated from 150 to 1150 μg of carbonate in septum sealed vials by acid decomposition of the carbonate. The CO 2 is collected on a zeolite trap and subsequently transferred to a syringe from where it is delivered to the ion source. A sample of 400 μg (50 μg C) typically gives a 12 C − ion source current of 10–15 μA over 20 min, yielding a measurement precision of less than 7 per mil for a modern sample. Using this method, we were able to date a single 560 μg Cibicides pseudoungerianus test at 14,030 ± 160 radiocarbon years. Only a minor modification to our existing gas handling system was required and the system is fully automatable to further reduce the effort involved for sample preparation.

  2. Towards radiocarbon dating of single foraminifera with a gas ion source

    Energy Technology Data Exchange (ETDEWEB)

    Wacker, L., E-mail: wacker@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Lippold, J. [Heidelberg Academy of Sciences, 69120 Heidelberg (Germany); Molnar, M. [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Institute of Nuclear Research, Hungarian Academy of Sciences, 4026 Debrecen (Hungary); Schulz, H. [Institute for Geosciencies, University of Tuebingen, 72076 Tuebingen (Germany)

    2013-01-15

    Carbonate shells from foraminifera are often analysed for radiocarbon to determine the age of deep-sea sediments or to assess radiocarbon reservoir ages. However, a single foraminiferal test typically contains only a few micrograms of carbon, while most laboratories require more than 100 {mu}g for radiocarbon dating with an accelerator mass spectrometry (AMS) system. The collection of the required amount of foraminifera for a single analyses is therefore time consuming and not always possible. Here, we present a convenient method to measure the radiocarbon content of foraminifera using an AMS system fitted with a gas ion source. CO{sub 2} is liberated from 150 to 1150 {mu}g of carbonate in septum sealed vials by acid decomposition of the carbonate. The CO{sub 2} is collected on a zeolite trap and subsequently transferred to a syringe from where it is delivered to the ion source. A sample of 400 {mu}g (50 {mu}g C) typically gives a {sup 12}C{sup -} ion source current of 10-15 {mu}A over 20 min, yielding a measurement precision of less than 7 per mil for a modern sample. Using this method, we were able to date a single 560 {mu}g Cibicides pseudoungerianus test at 14,030 {+-} 160 radiocarbon years. Only a minor modification to our existing gas handling system was required and the system is fully automatable to further reduce the effort involved for sample preparation.

  3. Predicting decadal trends and transient responses of radiocarbon storage and fluxes in a temperate forest soil

    Directory of Open Access Journals (Sweden)

    C. A. Sierra

    2012-08-01

    Full Text Available Representing the response of soil carbon dynamics to global environmental change requires the incorporation of multiple tools in the development of predictive models. An important tool to construct and test models is the incorporation of bomb radiocarbon in soil organic matter during the past decades. In this manuscript, we combined radiocarbon data and a previously developed empirical model to explore decade-scale soil carbon dynamics in a temperate forest ecosystem at the Harvard Forest, Massachusetts, USA. We evaluated the contribution of different soil C fractions to both total soil CO2 efflux and microbially respired C. We tested the performance of the model based on measurable soil organic matter fractions against a decade of radiocarbon measurements. The model was then challenged with radiocarbon measurements from a warming and N addition experiment to test multiple hypotheses about the different response of soil C fractions to the experimental manipulations. Our results showed that the empirical model satisfactorily predicts the trends of radiocarbon in litter, density fractions, and respired CO2 observed over a decade in the soils not subjected to manipulation. However, the model, modified with prescribed relationships for temperature and decomposition rates, predicted most but not all the observations from the field experiment where soil temperatures and nitrogen levels were increased, suggesting that a larger degree of complexity and mechanistic relations need to be added to the model to predict short-term responses and transient dynamics.

  4. Improved precision radiocarbon measurements and natural 14C variations around 10.000 cal BP

    International Nuclear Information System (INIS)

    Goslar, T.

    1990-01-01

    The subject of present work, natural radiocarbon variations in the past, is one of the most significant methodological questions of radiocarbon chronology. In the first three chapters, the author discusses problems connected with calibration of conventional radiocarbon dates, and consequences of monitoring the 14 C variations for the research of the changes of geomagnetic field, solar activity and global carbon cycle. Dendrochronological dating, which, in connection with 14 C measurements enables us to reconstruct the radiocarbon variations in the past, is also widely described. Fourth chapter concerns the technical problems of detection 14 C β-activity, especially accounting for proportional counters technique. In the next chapter the author describes results of his own dendrochonological research. Sixth chapter comprises frame discussion of the system for improved precision radiocarbon dating, together with short presentation of equipment, its calibration and analysis of errors. The last chapter gives the reconstruction of the pattern of atmospheric 14 C variations in 300-year period around 10.000 cal BP. It was found that in the last 10.000 years similar pattern repeats periodically. In the end, the author discusses the meaning of negative correlation between 14 C variations and changes of annual tree-ring widths in the oak trunk from Lublinek, for searching the connection between solar activity and climate. (author)

  5. Biogenic halocarbons from coastal oceanic upwelling regions as tropospheric halogen source

    Science.gov (United States)

    Krüger, Kirstin; Fuhlbrügge, Steffen; Hepach, Helmke; Fiehn, Alina; Atlas, Elliot; Quack, Birgit

    2016-04-01

    Halogenated very short lived substances (VSLS) are naturally produced in the ocean and emitted to the atmosphere. Recently, oceanic upwelling regions in the tropical East Atlantic were identified as strong sources of brominated halocarbons to the troposphere. During a cruise of R/V METEOR in December 2012 the oceanic sources and emissions of various halogenated trace gases and their mixing ratios in the marine atmospheric boundary layer (MABL) were investigated above the Peruvian Upwelling for the first time. This study presents novel observations of the three VSLS bromoform, dibromomethane and methyl iodide together with high resolution meteorological measurements and Lagrangian transport modelling. Although relatively low oceanic emissions were observed, except for methyl iodide, surface atmospheric abundances were elevated. Radiosonde launches during the cruise revealed a low, stable MABL and a distinct trade inversion above acting both as strong barriers for convection and trace gas transport in this region. Significant correlations between observed atmospheric VSLS abundances, sea surface temperature, relative humidity and MABL height were found. We used a simple source-loss estimate to identify the contribution of oceanic emissions to observed atmospheric concentrations which revealed that the observed marine VSLS abundances were dominated by horizontal advection below the trade inversion. The observed VSLS variations can be explained by the low emissions and their accumulation under different MABL and trade inversion conditions. Finally, observations from a second Peruvian Upwelling cruise with R/V SONNE during El Nino in October 2015 will be compared to highlight the role of different El Nino Southern Oscillation conditions. This study confirms the importance of coastal oceanic upwelling and trade wind systems on creating effective transport barriers in the lowermost atmosphere controlling the distribution of VSLS abundances above coastal ocean upwelling

  6. The circulation dynamics associated with a northern Benguela upwelling filament during October 2010

    Science.gov (United States)

    Muller, Annethea A.; Mohrholz, Volker; Schmidt, Martin

    2013-07-01

    Upwelling filaments, a common feature in all the major upwelling systems, are also regularly observed in the Benguela upwelling system and are thought to provide an effective mechanism for the exchange of matter between the shelf and the open ocean. The mesoscale dynamics of a northern Benguela upwelling filament located at approximately 18.5°S were examined and the associated transport was quantified. The development of the filament was tracked using optimal interpolated SST satellite data and two transects were consequently sampled across the feature using a towed undulating CTD (ScanFish). Additional hydrographic, nutrient and biological parameters were investigated at several stations along each transect. Following 7 days of strong upwelling favorable winds, sampling coincided with a period of relative wind relaxation and the filament was presumably in a decaying state. The basic mesoscale structure of the investigated filament corresponded well to what had previously been described for filaments from other eastern boundary current systems. The cross-shore transport associated with the filament was found to be significantly greater than the integrated Ekman transport in the region. With the combination of the high resolution dataset and a MOM-4 ecosystem model the complex mesoscale flow field associated with the feature could be observed and the counterbalancing onshore transport, associated with subsurface dipole eddies, was revealed within the filament. The results further suggest that an interaction between the offshore bending of flow at the Angola-Benguela Front (ABF), the detachment of the strong poleward flow from the coast as the thermal front meanders and the observed dipole eddies may be driving filament occurrence in the region off Cape Frio.

  7. Hot-spots of primary productivity: An Alternative interpretation to Conventional upwelling models

    Science.gov (United States)

    van Ruth, Paul D.; Ganf, George G.; Ward, Tim M.

    2010-12-01

    The eastern Great Australian Bight (EGAB) forms part of the Southern and Indian Oceans and is an area of high ecological and economic importance. Although it supports a commercial fishery, quantitative estimates of the primary productivity underlying this industry are open to debate. Estimates range from 500 mg C m -2 day -1. Part of this variation may be due to the unique upwelling circulation of shelf waters in summer/autumn (November-April), which shares some similarities with highly productive eastern boundary current upwelling systems, but differs due to the influence of a northern boundary current, the Flinders current, and a wide continental shelf. This study examines spatial variations in primary productivity in the EGAB during the upwelling seasons of 2005 and 2006. Daily integral productivity calculated using the vertically generalised production model (VGPM) showed a high degree of spatial variation. Productivity was low (modelled with the VGPM, which uses surface measures of phytoplankton biomass to calculate productivity. Macro-nutrient concentrations could not be used to explain the difference in the low and high productivities (silica > 1 μmol L -1, nitrate/nitrite > 0.4 μmol L -1, phosphate > 0.1 μmol L -1). Mixing patterns or micro-nutrient concentrations are possible explanations for spatial variations in primary productivity in the EGAB. On a global scale, daily rates of primary productivity of the EGAB lie between the highly productive eastern boundary current upwelling systems, and less productive coastal regions of western and south eastern Australia, and the oligotrophic ocean. However, daily productivity rates in the upwelling hotspots of the EGAB rival productivities in Benguela and Humboldt currents.

  8. Combined dendrochronological and radiocarbon dating of six Russian icons from the 15th-17th centuries

    Science.gov (United States)

    Dolgikh, A. V.; Matskovsky, V. V.; Voronin, K. V.; Solomina, O. N.

    2017-06-01

    The results of dendrochronological and radiocarbon dating by means of accelerator mass spectrometry (AMS) of six medieval icons, originating from northern European Russia and painted on wooden panels made from Scots pine, dated to the 15th to 17th centuries are presented. The panels of each icon were studied using dendrochronology. Five to six AMS dates were obtained for four icons. Although five icons were dendro-dated successfully, one failed to be reliably cross-dated with the existing master tree-ring chronologies and it was dated by radiocarbon wiggle-matching. Dendrochronological dating and wiggle-matching of radiocarbon dates allowed us to determine the narrow chronological intervals of icon creation.

  9. Simulation of influence of some climatic factors on radiocarbon concentration in the Earth atmosphere

    International Nuclear Information System (INIS)

    Akhmetkereev, S.Kh.; Dergachev, V.A.

    1981-01-01

    The effect of different climatic factors on radiocarbon concentration in the Earth atmosphere is analyzed by modelling the exchange radiocarbon system. It is supposed that the exchange system consists of four reservoirs: long-lived surface vegetation and its remnants, the atmosphere, surface layer of the World ocean. It is shown that the variations of the ocean temperature and the variations in CO 2 amount in the atmosphere connected with it do not affect the atmosphere radiocarbon concentration. Variations in the square of sea ice on the time scale of >=1000 years could bring about variations in the 14 C concentration with the amplitude up to 1%. 14 C concentration in the atmosphere in the icing maximum 18 thousands of years ago was 7% higher than present concentration [ru

  10. Radiocarbon-dating of earthenware of the Earliest Jomon period from Obihiro city, in Hokkaido prefecture

    International Nuclear Information System (INIS)

    Kobayashi, Kenichi

    2013-01-01

    This paper investigated radiocarbon dating of earthenware of the Earliest Jomon period from Obihiro City, in Hokkaido Prefecture. The authors investigated radiocarbon age differences among charred woods and charred residues on the surface of potteries. Results of radiocarbon dates of URAHORO-type pottery adhesions showed ca. 7560-7987 14 C BP, and that of charcoals were ca. 7180 14 C BP and 7285 14 C BP. The age of charred residues on the inside surface of potteries show 300-800 yrs older than the 14 C age of the charred woods, which corresponded to the actual age of the archaeological site, respectively. It becomes a cause to have cooked the salmon by earthenware and I think that the marine reservoir effect occurred. (author)

  11. Radiocarbon dating of a sutra container excavated at the Minagi Daibutsuyama site, Fukuoka Prefecture, Japan

    International Nuclear Information System (INIS)

    Oda, Hirotaka; Nakamura, Toshio; Tsukamoto, Toshio

    2004-01-01

    The historical age of a sutra container (Kyozutsu) excavated at the Minagi Daibutsuyama site was estimated by the AMS method. Radiocarbon ages for samples of the charred sutra kept in the container range from 950 to 1000 BP, corresponding to the first half of the 11th or the middle of the 12th century in the calibrated ages. The radiocarbon ages of wood charcoal blocks excavated around the container range from 1000 to 1100 BP, corresponding to calibrated ages from the 10th to the early 11th century. Since the radiocarbon age of wood charcoal can be decades older than the age of production as a result of the old wood effect, the historical age of the sutra container formation is estimated at the first half of the 11th century

  12. Radiocarbon dating and 13 C/12 C ratio of soils under tropical and subtropical climates

    International Nuclear Information System (INIS)

    Valencia, Edwin P.E.

    1993-01-01

    It was used an association radiocarbon dates with the carbon isotopic composition of soil organic matter, where 14 C dating gives elements of chronology, and δ 13 C is used as indicator of the vegetation types in the environment. The total soil organic matter was dried, floated and sieved. The humin fraction was extracted from the 0,250 mm fraction. Radiocarbon datings were performed by a liquid scintillation method. The carbon of the soil organic matter and humin fraction are transformed into benzene, that was analyzed in low level liquid scintillation spectrometer. Based on results of carbon isotope analysis and Radiocarbon dating of soil samples of Londrina, Piracicaba and Altamira, it is concluded that probable changes of vegetation and climate occurred in the South and Southeast regions of Brazil in the mid-Holocene. (author). 81 refs., 16 figs., 7 tabs

  13. The early Lateglacial re-colonization of Britain: new radiocarbon evidence from Gough's Cave, southwest England

    Science.gov (United States)

    Jacobi, R. M.; Higham, T. F. G.

    2009-09-01

    Gough's Cave is still Britain's most significant Later Upper Palaeolithic site. New ultrafiltered radiocarbon determinations on bone change our understanding of its occupation, by demonstrating that this lasted for only a very short span of time, at the beginning of the Lateglacial Interstadial (Greenland Interstadial 1 (GI-1: Bølling and Allerød)). The application of Bayesian modelling to the radiocarbon dates from this, and other sites from the period in southwest England, suggests that re-colonization after the Last Glacial Maximum took place only after 14,700 cal BP, and is, therefore, more recent than that of the Paris Basin and the Belgian Ardennes. On their own, the radiocarbon determinations cannot tell us whether re-colonization was synchronous with, just prior to, or after, Lateglacial warming. Isotopic studies of humanly-modified mammalian tooth enamel may be one way forward.

  14. Upwelling characteristics in the Gulf of Finland (Baltic Sea) as revealed by Ferrybox measurements in 2007-2013

    Science.gov (United States)

    Kikas, Villu; Lips, Urmas

    2016-07-01

    Ferrybox measurements have been carried out between Tallinn and Helsinki in the Gulf of Finland (Baltic Sea) on a regular basis since 1997. The system measures autonomously water temperature, salinity, chlorophyll a fluorescence and turbidity and takes water samples for further analyses at a predefined time interval. We aimed to show how the Ferrybox technology could be used to study the coastal upwelling events in the Gulf of Finland. Based on the introduced upwelling index and related criteria, 33 coastal upwelling events were identified in May-September 2007-2013. The number of events, as well as the frequency of their occurrence and intensity expressed as a sum of daily average temperature deviations in the 20 km wide coastal area, were almost equal near the northern and southern coasts. Nevertheless, the wind impulse, which was needed to generate upwelling events of similar intensity, differed between the northern and southern coastal areas. It is suggested that the general thermohaline structure adapted to the prevailing forcing and the estuarine character of the basin weaken the upwelling created by the westerly to southwesterly (up-estuary) winds and strengthen the upwelling created by the easterly to northeasterly (down-estuary) winds. Two types of upwelling events were identified - one characterized by a strong temperature front and the other revealing gradual decrease in temperature from the open sea to the coastal area, with maximum temperature deviation close to the shore.

  15. Age estimation in forensic sciences: Application of combined aspartic acid racemization and radiocarbon analysis

    Energy Technology Data Exchange (ETDEWEB)

    Alkass, K; Buchholz, B A; Ohtani, S; Yamamoto, T; Druid, H; Spalding, S L

    2009-11-02

    Age determination of unknown human bodies is important in the setting of a crime investigation or a mass disaster, since the age at death, birth date and year of death, as well as gender, can guide investigators to the correct identity among a large number of possible matches. Traditional morphological methods used by anthropologists to determine age are often imprecise, whereas chemical analysis of tooth dentin, such as aspartic acid racemization has shown reproducible and more precise results. In this paper we analyze teeth from Swedish individuals using both aspartic acid racemization and radiocarbon methodologies. The rationale behind using radiocarbon analysis is that above-ground testing of nuclear weapons during the cold war (1955-1963) caused an extreme increase in global levels of carbon-14 ({sup 14}C) which have been carefully recorded over time. Forty-four teeth from 41 individuals were analyzed using aspartic acid racemization analysis of tooth crown dentin or radiocarbon analysis of enamel and ten of these were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods correlated well (R2=0.66, p < 0.05). Radiocarbon analysis showed an excellent precision with an overall absolute error of 0.6 {+-} 04 years. Aspartic acid racemization also showed a good precision with an overall absolute error of 5.4 {+-} 4.2 years. Whereas radiocarbon analysis gives an estimated year of birth, racemization analysis indicates the chronological age of the individual at the time of death. We show how these methods in combination can also assist in the estimation of date of death of an unidentified victim. This strategy can be of significant assistance in forensic casework involving dead victim identification.

  16. New hydroxyproline radiocarbon dates from Sungir, Russia, confirm early Mid Upper Palaeolithic burials in Eurasia.

    Directory of Open Access Journals (Sweden)

    Shweta Nalawade-Chavan

    Full Text Available Sungir (Russia is a key Mid-Upper Palaeolithic site in Eurasia, containing several spectacular burials that disclose early evidence for complex burial rites in the form of a range of grave goods deposited along with the dead. Dating has been particularly challenging, with multiple radiocarbon dates ranging from 19,160±270 to 28,800±240 BP for burials that are believed to be closely similar in age. There are disparities in the radiocarbon dates of human bones, faunal remains and charcoal found on the floor of burials. Our approach has been to develop compound-specific methods using High Performance Liquid Chromatography (HPLC to separate single amino acids, such as hydroxyproline, and thereby avoid the known human contamination on the bones themselves. Previously, we applied this technique to obtain radiocarbon dates of ∼30,000 BP for Sungir 2, Sungir 3 and a mammoth bone from the occupation levels of the site. The single amino acid radiocarbon dates were in good agreement with each other compared to all the dates previously reported, supporting their reliability. Here we report new hydroxyproline dates for two more human burials from the same site, Sungir 1 and Sungir 4. All five hydroxyproline dates reported are statistically indistinguishable and support an identical age for the group. The results suggest that compound-specific radiocarbon analysis should be considered seriously as the method of choice when precious archaeological remains are to be dated because they give a demonstrably contaminant-free radiocarbon age. The new ages are, together with the previously dated 'Red Lady of Paviland' human in the British Isles, the earliest for Mid Upper Palaeolithic burial behaviour in Eurasia, and point to the precocious appearance of this form of rite in Europe Russia.

  17. An Improved Method for Estimating Water-Mass Ventilation Age from Radiocarbon Measurements

    Science.gov (United States)

    Devries, T. J.; Primeau, F. W.

    2009-12-01

    Paleoceanographic data can help to constrain the state of the past ocean circulation. One critical quantity that can be constrained by paleoceanographic data is the ventilation age, which measures the vigor of the ocean circulation. Paleoceanographers often use radiocarbon data to estimate paleo-ventilation ages by calculating either the benthic-planktonic (B-P) age difference, or the so-called “projection” age. However, recent studies have shown that neither of these calculations yield correct estimates of ventilation age, due to fluctuations in atmospheric radiocarbon content and mixing processes in the ocean. Here we propose a new method for more accurately inferring paleo-ventilation ages based on radiocarbon data. Our method makes use of a model that uses parameterized transfer functions to simulate the effects of circulation and mixing in the ocean. We show how this model can be used in a Bayesian framework to infer a ventilation age from a paired radiocarbon- and calendar-age measurement. The Bayesian framework allows us to quantify the uncertainty in the inferred ventilation age due to uncertainty in the data, as well as uncertainty in the assumptions made in the model itself. We applied this framework to previously published radiocarbon data from the deep North Pacific spanning 10 000 to 20 000 years before present. Ventilation ages inferred using our method are significantly different from the B-P ages or projection ages calculated from the same data. Furthermore, our analysis suggests that the uncertainty of the ventilation ages is on the order of 400-500 years, and that the main sources of uncertainty are uncertainty in the age of surface source waters and in the true calendar age of the radiocarbon data. Our results do not show a clear change in the ventilation age of deep North Pacific waters during the last deglaciation.

  18. New hydroxyproline radiocarbon dates from Sungir, Russia, confirm early Mid Upper Palaeolithic burials in Eurasia.

    Science.gov (United States)

    Nalawade-Chavan, Shweta; McCullagh, James; Hedges, Robert

    2014-01-01

    Sungir (Russia) is a key Mid-Upper Palaeolithic site in Eurasia, containing several spectacular burials that disclose early evidence for complex burial rites in the form of a range of grave goods deposited along with the dead. Dating has been particularly challenging, with multiple radiocarbon dates ranging from 19,160±270 to 28,800±240 BP for burials that are believed to be closely similar in age. There are disparities in the radiocarbon dates of human bones, faunal remains and charcoal found on the floor of burials. Our approach has been to develop compound-specific methods using High Performance Liquid Chromatography (HPLC) to separate single amino acids, such as hydroxyproline, and thereby avoid the known human contamination on the bones themselves. Previously, we applied this technique to obtain radiocarbon dates of ∼30,000 BP for Sungir 2, Sungir 3 and a mammoth bone from the occupation levels of the site. The single amino acid radiocarbon dates were in good agreement with each other compared to all the dates previously reported, supporting their reliability. Here we report new hydroxyproline dates for two more human burials from the same site, Sungir 1 and Sungir 4. All five hydroxyproline dates reported are statistically indistinguishable and support an identical age for the group. The results suggest that compound-specific radiocarbon analysis should be considered seriously as the method of choice when precious archaeological remains are to be dated because they give a demonstrably contaminant-free radiocarbon age. The new ages are, together with the previously dated 'Red Lady of Paviland' human in the British Isles, the earliest for Mid Upper Palaeolithic burial behaviour in Eurasia, and point to the precocious appearance of this form of rite in Europe Russia.

  19. Phytoplankton community and environmental correlates in a coastal upwelling zone along western Taiwan Strait

    Science.gov (United States)

    Wang, Yu; Kang, Jian-hua; Ye, You-yin; Lin, Geng-ming; Yang, Qing-liang; Lin, Mao

    2016-02-01

    Upwelling system in western Taiwan Strait is important for facilitating the fishery production. This study investigated hydro-chemical properties, phytoplankton biomass, phytoplankton species composition, three-dimensional (horizontal, vertical and transect) distribution of phytoplankton abundance, as well as phytoplankton annual variation and the correlation of phytoplankton community with the upwelling of underlying current and nutrients according to samples of Fujian-Guangdong coastal upwelling zone in western Taiwan Strait from August 27 to September 8, 2009. The results manifest that the nutrient-rich cold and high salinity current on the continental shelf of South China Sea upwells to the Fujian-Guangdong coastal waters through Taiwan Bank and the surging strength to surface is weak while strong at 30-m layer. The thermohaline center of coastal upwelling shifts to the east of Dongshan Island and expanded to offshore waters in comparison with previous records. A total of 137 phytoplankton species belonging to 59 genera in 4 phyla are identified excluding the unidentified species. Diatom is the first major group and followed by dinoflagellate. Cyanobacteria mainly composed by three Trichodesmium species account for a certain proportions, while Chrysophyta are only found in offshore waters. The dominant species include Thalassionema nitzschioides, Pseudo-nitzschia pungens, Thalassionema frauenfeldii, Pseudo-nitzschia delicatissima, Rhizosolenia styliformis, Chaetoceros curvisetus, Diplopsalis lenticula and Trichodesmium thiebautii. Phytoplankton community mainly consists of eurythermal and eurytopic species, followed by warm-water species, tropic high-salinity species and oceanic eurythermic species in order. Phytoplankton abundance ranges from 1.00 × 102 ind./L ~ 437.22 × 102 ind./L with an average of 47.36 × 102 ind./L. For vertical distribution, maximum abundance is found at 30 m-depth and the surface comes second. Besides, the abundance below 30 m

  20. Heterotrophic bacterial production, respiration, and growth efficiency associated with upwelling intensity in the Ulleung Basin, East Sea

    Science.gov (United States)

    Kim, Bomina; Kim, Sung-Han; Kwak, Jung Hyun; Kang, Chang-Keun; Lee, Sang Heon; Hyun, Jung-Ho

    2017-09-01

    We investigated bacterial production (BP) and respiration (BR), as well as the physico-chemical properties of the water column, to elucidate the effect of upwelling on heterotrophic bacterial metabolic activities and growth efficiency (BGE) in July 2012 and May 2013 in the Ulleung Basin (UB), East/Japan Sea. The upwelled conditions were characterized by higher chlorophyll-a (Chl-a) concentrations resulting from the upward shift of the nitracline compared to that of the non-upwelled condition. Analyses of the size fractions of Chl-a and pigment composition revealed that large size phytoplankton (> 20 μm), mainly consisting of diatoms, appeared to be the major phytoplankton component. BP and BR were significantly correlated with Chl-a (P 0.05). These results suggest that bacterial metabolic activities are stimulated by the availability of organic resources enhanced by upwelling in the UB. Further statistical analysis showed that the difference in BP and BGE with variations in upwelling intensity were significant (P = 0.018 for BP, P = 0.035 for BGE), but the difference in BR was not significant (P = 0.321). These results suggest that metabolic energy is partitioned more for BP under a strong upwelling condition, i.e. high nutrient and Chl-a conditions. In contrast, the energy generated via respiration was partitioned more for maintaining metabolism rather than for biomass production under weakly or non-upwelled conditions, i.e. stratified and low Chl-a conditions. Overall, our results suggest that any changes in upwelling intensity would significantly affect the carbon cycle associated with the fate of primary production, and the role of the microbial loop in the UB where changes in the intensity and frequency of upwelling associated with climatic changes are in progress.

  1. Radiocarbon age of the recent deposits of the Indian Ocean western part (Seychelles)

    International Nuclear Information System (INIS)

    Svitoch, A.A.; Parunin, O.B.

    1988-01-01

    Mass radiocarbon dating according to Pleistocene precipitations of the islands of the Western Part of the Indian ocean is carried out. Time of formation of black-rock precipitations, low benches and island sandstones of low islands - middle-late Holocene - is established. Rocks of a reef complex are late Pleistocene. Relative concentration of dates according to various types of deposits points to the trustworthness and testifies about usefulness of radiocarbon analysis for stratigraphic and chronological separation of carbonate precipitations of islands of the equatorial zone of the ocean

  2. The use of AMS radiocarbon dating for Xia-Shang-Zhou chronology

    CERN Document Server

    Guo, Z Y; LiuKeXin; Lu Xiang Yang; Ma Hong Ji; Wu Xiao Hon; Yuan Si Xun

    2000-01-01

    The possibility and problems of using radiocarbon dating to historical chronology are discussed. The current situation of ancient Chinese chronology and the project of Xia-Shang-Zhou chronology are introduced. A chronological study requires the AMS radiocarbon dating with high precision, high reliability and high efficiency. The Peking University AMS facility (PKUAMS) has been upgraded and a series of quality control steps were adopted. To reduce the error of calendar age, wiggle matching with serial samples should be used. Some preliminary results of Xia-Shang-Zhou chronology are presented.

  3. Simultaneous measurement of tritium and radiocarbon by ultra-low-background proportional counting.

    Science.gov (United States)

    Mace, Emily; Aalseth, Craig; Alexander, Tom; Back, Henning; Day, Anthony; Hoppe, Eric; Keillor, Martin; Moran, Jim; Overman, Cory; Panisko, Mark; Seifert, Allen

    2017-08-01

    Use of ultra-low-background capabilities at Pacific Northwest National Laboratory provide enhanced sensitivity for measurement of low-activity sources of tritium and radiocarbon using proportional counters. Tritium levels are nearly back to pre-nuclear test backgrounds (~2-8 TU in rainwater), which can complicate their dual measurement with radiocarbon due to overlap in the beta decay spectra. We present results of single-isotope proportional counter measurements used to analyze a dual-isotope methane sample synthesized from ~120mg of H 2 O and present sensitivity results. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. [Radiocarbon dating of pollen and spores in wedge ice from Iamal and Kolyma].

    Science.gov (United States)

    Vasil'chuk, A K

    2004-01-01

    Radiocarbon dating of pollen concentrate from late Pleistocene syngenetic wedge ice was carried out using acceleration mass spectrometry (AMS) in Seyakha and Bizon sections. Comparison of the obtained dating with palynological analysis and AMS radiocarbon dating previously obtained for other organic fractions of the same samples allowed us to evaluate accuracy of dating of different fractions. Quantitative tests for data evaluation were considered in terms of possible autochthonous or allochthonous accumulation of the material on the basis of pre-Pleistocene pollen content in these samples. Paleoecological information content of pollen spectra from late Pleistocene syngenetic wedge ice was evaluated.

  5. Optical Measurement of Radiocarbon below Unity Fraction Modern by Linear Absorption Spectroscopy.

    Science.gov (United States)

    Fleisher, Adam J; Long, David A; Liu, Qingnan; Gameson, Lyn; Hodges, Joseph T

    2017-09-21

    High-precision measurements of radiocarbon ( 14 C) near or below a fraction modern 14 C of 1 (F 14 C ≤ 1) are challenging and costly. An accurate, ultrasensitive linear absorption approach to detecting 14 C would provide a simple and robust benchtop alternative to off-site accelerator mass spectrometry facilities. Here we report the quantitative measurement of 14 C in gas-phase samples of CO 2 with F 14 C radiocarbon measurement science including the study of biofuels and bioplastics, illicitly traded specimens, bomb dating, and atmospheric transport.

  6. Radiocarbon analysis of the Torah scrolls from the National Museum of Brazil collection

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Fabiana M. [Instituto de Física – Universidade Federal Fluminense (IF-UFF), Campus da Praia Vermelha, Av. Gal. Milton Tavares de Souza, s/n°, CEP 24210-346 Niterói, RJ (Brazil); Araujo, Carlos A.R. [Departamento de História (Programa de História Comparada), Universidade Federal do Rio de Janeiro (UFRJ), Largo de São Francisco 1/sala 311, CEP 20051-070 Centro Rio de Janeiro, RJ (Brazil); Macario, Kita D., E-mail: kitamacario@gmail.com [Instituto de Física – Universidade Federal Fluminense (IF-UFF), Campus da Praia Vermelha, Av. Gal. Milton Tavares de Souza, s/n°, CEP 24210-346 Niterói, RJ (Brazil); Cid, Alberto S. [Instituto de Física – Universidade Federal Fluminense (IF-UFF), Campus da Praia Vermelha, Av. Gal. Milton Tavares de Souza, s/n°, CEP 24210-346 Niterói, RJ (Brazil)

    2015-10-15

    This radiocarbon study aims to physically verify the critical analysis of the Torah scrolls from the National Museum of Brazil collection. Although the manuscript was formerly believed to be as old as the 10th century, the paleographic and stylistic study of the books of Genesis and Deuteronomy revealed features that could be associated to the year 1560 AD. Radiocarbon analysis was performed and a phase model limited by a Historical boundary was applied. The results are in agreement with the critical analysis of the manuscript that it is not older than the 16th century.

  7. Radiocarbon dating of extinct fauna in the Americas recovered from tar pits

    International Nuclear Information System (INIS)

    Jull, A.J.T.; Iturralde-Vinent, M.; O'Malley, J.M.; MacPhee, R.D.E.; McDonald, H.G.; Martin, P.S.; Moody, J.; Rincon, A.

    2004-01-01

    We have obtained radiocarbon dates by accelerator mass spectrometry on bones of extinct large mammals from tar pits. Results on some samples of Glyptodon and Holmesina (extinct large mammals similar to armadillos) yielded ages of >25 and >21 ka, respectively. We also studied the radiocarbon ages of three different samples of bones from the extinct Cuban ground sloth, Parocnus bownii, which yielded dates ranging from 4960 ± 280 to 11 880 ± 420 yr BP. In order to remove the tar component pretreat the samples sufficiently to obtain reliable dates, we cleaned the samples by Soxhlet extraction in benzene. Resulting samples of collagenous material were often small

  8. Changes in optical characteristics of surface microlayers hint to photochemically and microbially-mediated DOM turnover in the upwelling region off Peru

    Science.gov (United States)

    Galgani, L.; Engel, A.

    2015-12-01

    The coastal upwelling system off Peru is characterized by high biological activity and a pronounced subsurface oxygen minimum zone, as well as associated emissions of atmospheric trace gases such as N2O, CH4 and CO2. During the Meteor (M91) cruise to the Peruvian upwelling system in 2012, we investigated the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples at 38 stations determining DOC concentration, amino acid composition, marine gels, CDOM and bacterial and phytoplankton abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slope (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources and sinks. We identified five fluorescent components of the CDOM pool, of which two had excitation/emission characteristics of protein-like fluorophores and were highly enriched in the SML. CDOM composition and changes in spectral slope properties suggested a local microbial release of HMW DOM directly in the SML as a response to light exposure in this extreme environment. Our results suggest that microbial and photochemical processes play an important role for the production, alteration and loss of optically active substances in the SML.

  9. Modelling shelf-ocean exchange and its biogeochemical consequences in coastal upwelling systems

    DEFF Research Database (Denmark)

    Muchamad, Al Azhar

    margin bathymetry, and 3) what processes determine the observed variability of total organic carbon (TOC) content in shelf sediments underlying the upwelling system, with implications for the formation of petroleum source rocks. Here, a numerical ocean modeling approach is used in this thesis to explore...... processes and the development of anoxia/euxinia under the present day or past geological conditions. Thirdly and last, processes controlling distribution of total organic carbon (TOC) content in sediments across the continental margin is evaluated by application of the model to the Benguela upwelling system....... In the model, biological primary production and shelf bottom-water anoxia result in enhanced sedimentary TOC concentrations on the mid shelf and upper slope. The simulated TOCs implicate that bottom lateral transport only has a significant effect on increasing the deposition of the organic carbon on the mid...

  10. Fish species composition, density-distribution patterns, and impingement during upwelling

    International Nuclear Information System (INIS)

    Spigarelli, S.A.; Sharma, R.K.

    1975-01-01

    The effects of cooling system intakes and discharges on Lake Michigan fishes are highly dependent on inshore species composition and spatial distribution which, in turn, are affected by natural hydrological conditions. Significant (5 to 10 C) short-term decreases in water temperature (due to upwelling) could cause cold shock in fish equilibrated to either ambient or plume temperatures; substantial changes in distribution due to avoidance or attraction responses; and resultant changes in susceptibility to impingement. The objectives of this study are to characterize the changes in fish species composition, density, and thermal distribution as a result of natural upwellings, and to relate these factors to intake and discharge effects. Day and night sampling was conducted in ambient (reference) and thermal plume waters near the Zion Nuclear Plant on four occasions between 17 July and 11 September 1975. Density-distribution patterns and species composition of fish were determined by means of gill nets, bottom trawls, seines, and a sonic fish locater

  11. Does deep ocean mixing drive upwelling or downwelling of abyssal waters?

    Science.gov (United States)

    Ferrari, R. M.; McDougall, T. J.; Mashayek, A.; Nikurashin, M.; Campin, J. M.

    2016-02-01

    It is generally understood that small-scale mixing, such as is caused by breaking internal waves, drives upwelling of the densest ocean waters that sink to the ocean bottom at high latitudes. However the observational evidence that the turbulent fluxes generated by small-scale mixing in the stratified ocean interior are more vigorous close to the ocean bottom than above implies that small-scale mixing converts light waters into denser ones, thus driving a net sinking of abyssal water. Using a combination of numerical models and observations, it will be shown that abyssal waters return to the surface along weakly stratified boundary layers, where the small-scale mixing of density decays to zero. The net ocean meridional overturning circulation is thus the small residual of a large sinking of waters, driven by small-scale mixing in the stratified interior, and a comparably large upwelling, driven by the reduced small-scale mixing along the ocean boundaries.

  12. Episodic Upwelling of Zooplankton within a Bowhead Whale Feeding Area Near Barrow, AK

    Science.gov (United States)

    2013-09-30

    recorders. 4. Determine the correlations between exchange events and wind speed and direction , wind duration, ice cover, shelf water column...sample over longer time periods in that region in order to better describe the impact of the strength and magnitude of the wind on upwelling along the...oceanography of the shelf is complex, dynamic, and highly variable and that advection is closely coupled to the direction and magnitude of the winds . In

  13. Interspecific differences in depth preference: Regulation of larval transport in an upwelling system

    OpenAIRE

    Miller, SH; Morgan, SG

    2013-01-01

    Dispersal is fundamental to understanding the ecology and evolution of species and effectively managing resources, but information on dispersal is rare for the vast majority of marine life that develops as miniscule larvae in the plankton. Until recent evidence to the contrary, it was widely suspected that larvae developing in productive upwelling regimes along eastern ocean margins are susceptible to cross-shelf transport by strong, dynamic currents and often are unable to replenish populati...

  14. Contrasting biogeochemical responses of ENSO induced upwelling variability in the Humboldt Current System

    Science.gov (United States)

    Franco, Ana C.; Gruber, Nicolas; Münnich, Matthias

    2017-04-01

    The Humboldt Current System (HCS) is one of the most productive ecosystems in the world. This high productivity is supported by a large input of nutrients from the subsurface layers to the surface due to year-round upwelling. However, upwelling also supplies waters with low pH and low aragonite saturation state potentially affecting many organisms, especially those that calcify. The influence, extent and source of upwelled water vary substantially on interannual timescales in association with the El Niño/Southern Oscillation (ENSO) phenomenon, generating natural contrasting responses on the biogeochemistry of this system. Here we analyze these responses using an eddy resolving, basin-scale ocean model that covers the whole Pacific Ocean with high resolution (4 km) on the west coast of South America. We performed a simulation of the last 30 years (hindcast simulation) that allows us to investigate the influence of at least eight El Niño episodes and eight La Niña episodes on productivity variations and changes in oxygen concentration and aragonite saturation state. An absolute change in surface omega aragonite of almost 2 units, as well as an absolute change of the aragonite saturation depth of 200 m result from the change of an El Niño phase to a La Niña phase. This variability is on the same order of magnitude as the projected change in the aragonite saturation state in a centennial timescale. During La Niña events, a lower aragonite saturation state values and reduced oxygen concentration in the surface layer are a direct consequence of enhanced upwelling and increased net primary productivity. The opposite is true during El Niño events, where high values of omega aragonite occur in concordance with extraordinarily low net primary productivity values.

  15. Convergent tectonics and coastal upwelling: a history of the Peru continental margin ( Pacific).

    Science.gov (United States)

    von Huene, Roland E.; Suess, E.; Emeis, K.C.

    1987-01-01

    Late in 1986, scientists on the ODP drillship JOIDES Resolution confirmed that the upper slope of the Peruvian margin consists of continental crust whereas the lower slope comprises an accretionary complex. An intricate history of horizontal and vertical movements can be detected, and the locations of ancient centers of upwelling appear to have varied, partly due to tectonic movements of the margin. In this review of Leg 112, the 3 scientific leaders on this cruise discuss their results. -from Journal Editor

  16. Shifts between gelatinous and crustacean plankton in a coastal upwelling region

    OpenAIRE

    Bode, Antonio; Álvarez-Ossorio, Maria Teresa; Miranda, Ana; Ruiz-Villarreal, Manuel

    2013-01-01

    proyectos RADIALES (IEO) y EURO-BASIN (Ref. 264933, 7FP) Variability in the dominance of copepods vs. gelatinous plankton was analysed using monthly time-series covering the last 55 years and related to changes in climatic, oceanographic, and fishery conditions in the upwelling region of Galicia (NW Spain). Seasonality was generally the main component of variability in all groups, both along the coast and in the nearby ocean, but no common long-term trend was found. Coastal copepo...

  17. Biogenic halocarbons from the Peruvian upwelling region as tropospheric halogen source

    Directory of Open Access Journals (Sweden)

    H. Hepach

    2016-09-01

    Full Text Available Halocarbons are produced naturally in the oceans by biological and chemical processes. They are emitted from surface seawater into the atmosphere, where they take part in numerous chemical processes such as ozone destruction and the oxidation of mercury and dimethyl sulfide. Here we present oceanic and atmospheric halocarbon data for the Peruvian upwelling zone obtained during the M91 cruise onboard the research vessel METEOR in December 2012. Surface waters during the cruise were characterized by moderate concentrations of bromoform (CHBr3 and dibromomethane (CH2Br2 correlating with diatom biomass derived from marker pigment concentrations, which suggests this phytoplankton group is a likely source. Concentrations measured for the iodinated compounds methyl iodide (CH3I of up to 35.4 pmol L−1, chloroiodomethane (CH2ClI of up to 58.1 pmol L−1 and diiodomethane (CH2I2 of up to 32.4 pmol L−1 in water samples were much higher than previously reported for the tropical Atlantic upwelling systems. Iodocarbons also correlated with the diatom biomass and even more significantly with dissolved organic matter (DOM components measured in the surface water. Our results suggest a biological source of these compounds as a significant driving factor for the observed large iodocarbon concentrations. Elevated atmospheric mixing ratios of CH3I (up to 3.2 ppt, CH2ClI (up to 2.5 ppt and CH2I2 (3.3 ppt above the upwelling were correlated with seawater concentrations and high sea-to-air fluxes. During the first part of the cruise, the enhanced iodocarbon production in the Peruvian upwelling contributed significantly to tropospheric iodine levels, while this contribution was considerably smaller during the second part.

  18. Changes in upwelling and surface productivity in the Eastern Pacific during Terminations I and II

    Science.gov (United States)

    Erdem, Z.; De Bar, M.; Stolwijk, D.; Schneider, R. R.; S Sinninghe Damsté, J.; Schouten, S.

    2017-12-01

    The Eastern Pacific coastal system is characterized by intense upwelling and consequently by an enhanced surface primary productivity. Combination of this high organic matter flux with sluggish bottom water ventilation results in one of the most pronounced oxygen minimum zones reaching from offshore California in the North to offshore Chile in the South. As a result of this process, the region is particularly interesting in view of nutrient and carbon cycling as well as ecosystem dynamics. The dynamics of the upwelling and oxygen concentrations are closely related to climatic conditions. Therefore, paleo-reconstructions of different settings are crucial in order to improve our understanding of the response of these nutrient-rich, oxygen-deficient, environments in relation to the recent global ocean warming, acidification and deoxygenation. In this study, we present downcore results from three different sites in the Eastern Pacific: offshore California (IODP site 1012), Peru (M77/2-52-2) and Chile (IODP site 1234). We applied different biomarkers as proxies to decipher changes in phytoplankton community composition, including the upwelling index based on long chain diols, and other common productivity indicators such as bulk organic carbon, carbonate and biogenic opal. In addition, application of carbon and nitrogen isotope ratios of total organic carbon and benthic foraminifera complement our multiproxy approach. Herewith we aim to compare at least two glacial-interglacial transitions with different magnitudes of deglacial warming along the Eastern Pacific upwelling systems at different latitudes. The data presented will cover the last 160 ka BP offshore California and Chile, and 30 ka BP offshore Peru enabling comparison between glacial Terminations I and II.

  19. REGIONAL AIR-SEA INTERACTION (RASI) GAP WIND AND COASTAL UPWELLING EVENTS CLIMATOLOGY GULF OF PAPAGAYO, COSTA RICA V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The Regional Air-Sea Interactions (RASI) Gap Wind and Coastal Upwelling Events Climatology Gulf of Papagayo, Costa Rica dataset was created using an automated...

  20. Influence of upwelling induced near shore hypoxia on the Alappuzha mud banks, South West Coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    GireeshKumar, T.R.; Mathew, D.; Pratihary, A.K.; Naik, H.; Narvekar, K.U.; Araujo, J.; Balachandran, K.K.; Muraleedharan, K.R.; Thorat, B.R.; Nair, M.; Naqvi, S.W.A.

    The results of the first time-series measurements spanning 18-weeks (22 April to 20 September 2014) from a coastal environment (Alappuzha, southwest India), where two process of upwelling and mud banks are concurrent during summer monsoon...

  1. Resource partitioning within major bottom fish species in a highly productive upwelling ecosystem

    Science.gov (United States)

    Abdellaoui, Souad; El Halouani, Hassan; Tai, Imane; Masski, Hicham

    2017-09-01

    The Saharan Bank (21-26°N) is a wide subtropical continental shelf and a highly productive upwelling ecosystem. The bottom communities are dominated by octopus and sparid fish, which are the main targets of bottom-trawl fishing fleets. To investigate resource partitioning within the bottom fish community, adult fish from 14 of the most abundant species were investigated for stomach content analysis. Samples were collected during two periods: October 2003 and May 2007. The diet of the analysed species showed more variation between periods than between size classes, suggesting that temporal or spatial variability in prey availability appears to play a significant role in their diet. Multivariate analysis and subsequent clustering led to a grouping of the species within five trophic guilds. Two species were fish feeders, and the others mainly fed on benthic invertebrates, where epibenthic crustaceans, lamellibranchs and fish were the most important groups in defining trophic guilds. We found that the studied species had a high rate of overlapping spatial distributions and overlapping trophic niches. In this highly productive upwelling ecosystem, where food resources may not be a limiting factor, inter-specific competition did not appear to be an important factor in structuring bottom fish communities. For the species that showed differences in the proportions of prey categories in comparison with other ecosystems, the rise of the proportion of epibenthic crustaceans in their diet was a common feature; a possible consequence of the benthic productivity of this highly productive upwelling ecosystem.

  2. Macro-Scale Patterns in Upwelling/Downwelling Activity at North American West Coast.

    Directory of Open Access Journals (Sweden)

    Romeo Saldívar-Lucio

    Full Text Available The seasonal and interannual variability of vertical transport (upwelling/downwelling has been relatively well studied, mainly for the California Current System, including low-frequency changes and latitudinal heterogeneity. The aim of this work was to identify potentially predictable patterns in upwelling/downwelling activity along the North American west coast and discuss their plausible mechanisms. To this purpose we applied the min/max Autocorrelation Factor technique and time series analysis. We found that spatial co-variation of seawater vertical movements present three dominant low-frequency signals in the range of 33, 19 and 11 years, resembling periodicities of: atmospheric circulation, nodal moon tides and solar activity. Those periodicities might be related to the variability of vertical transport through their influence on dominant wind patterns, the position/intensity of pressure centers and the strength of atmospheric circulation cells (wind stress. The low-frequency signals identified in upwelling/downwelling are coherent with temporal patterns previously reported at the study region: sea surface temperature along the Pacific coast of North America, catch fluctuations of anchovy Engraulis mordax and sardine Sardinops sagax, the Pacific Decadal Oscillation, changes in abundance and distribution of salmon populations, and variations in the position and intensity of the Aleutian low. Since the vertical transport is an oceanographic process with strong biological relevance, the recognition of their spatio-temporal patterns might allow for some reasonable forecasting capacity, potentially useful for marine resources management of the region.

  3. Mantle upwellings and convective instabilities revealed by seismic tomography and helium isotope geochemistry beneath eastern Africa

    Science.gov (United States)

    Montagner, Jean-Paul; Marty, Bernard; Stutzmann, Eléonore; Sicilia, Déborah; Cara, Michel; Pik, Raphael; Lévêque, Jean-Jacques; Roult, Geneviève; Beucler, Eric; Debayle, Eric

    2007-11-01

    The relationship between intraplate volcanism and continental tectonics has been investigated for North and East Africa using a high resolution three-dimensional anisotropic tomographic model derived from seismic data of a French experiment ``Horn of Africa'' and existing broadband data. The joint inversion for seismic velocity and anisotropy of the upper 400 km of the mantle, and geochemical data reveals a complex interaction between mantle upwellings, and lithosphere. Two kinds of mantle upwellings can be distinguished: The first one, the Afar ``plume'' originates from deeper than 400 km and is characterized by enrichment in primordial 3He and 3He/4He ratios higher than those along mid-ocean ridges (MOR). The second one, associated with other Cenozoic volcanic provinces (Darfur, Tibesti, Hoggar, Cameroon), with 3He/4He ratios similar to, or lower than MOR, is a consequence of shallower upwelling. The presumed asthenospheric convective instabilities are oriented in an east-west direction, resulting from interaction between south-north asthenospheric mantle flow, main plume head and topography on the base of lithosphere.

  4. Response of the Benguela upwelling systems to spatial variations in the wind stress

    Science.gov (United States)

    Fennel, Wolfgang; Junker, Tim; Schmidt, Martin; Mohrholz, Volker

    2012-08-01

    In this paper we combine field observations, numerical modeling and an idealized analytical theory to study some features of the Benguela upwelling system. The current system can be established through a combination of observations and realistic simulations with an advanced numerical model. The poleward undercurrent below the equator-ward coastal jet is often found as a countercurrent that reaches the sea surface seaward of the coastal jet. The coastal band of cold upwelled water appears to broaden from south to north and at the northern edge of the wind band an offshore flow is often detected, which deflects the coastal Angola current to the west. These features can be explained and understood with an idealized analytical model forced by a spatially variable wind. A crucial role is played by the wind stress curl, which shapes the oceanic response through Ekman-pumping. The interplay of the curl driven effects and the coastal Ekman upwelling together with the coastal jet, Kelvin waves, and the undercurrent is the key to understand the formation of the three-dimensional circulation patterns in the Benguela system. While the numerical model is based on the full set of primitive equations, realistic topography and forcing, the analytic model uses a linear, flat-bottomed f-plane ocean, where the coast is a straight wall and the forcing is represented by an alongshore band of dome-shaped wind stress. Although the analytical model is highly idealized it is very useful to grasp the basic mechanisms leading to the response patterns.

  5. Future changes in coastal upwelling ecosystems with global warming: The case of the California Current System.

    Science.gov (United States)

    Xiu, Peng; Chai, Fei; Curchitser, Enrique N; Castruccio, Frederic S

    2018-02-12

    Coastal upwelling ecosystems are among the most productive ecosystems in the world, meaning that their response to climate change is of critical importance. Our understanding of climate change impacts on marine ecosystems is largely limited to the open ocean, mainly because coastal upwelling is poorly reproduced by current earth system models. Here, a high-resolution model is used to examine the response of nutrients and plankton dynamics to future climate change in the California Current System (CCS). The results show increased upwelling intensity associated with stronger alongshore winds in the coastal region, and enhanced upper-ocean stratification in both the CCS and open ocean. Warming of the open ocean forces isotherms downwards, where they make contact with water masses with higher nutrient concentrations, thereby enhancing the nutrient flux to the deep source waters of the CCS. Increased winds and eddy activity further facilitate upward nutrient transport to the euphotic zone. However, the plankton community exhibits a complex and nonlinear response to increased nutrient input, as the food web dynamics tend to interact differently. This analysis highlights the difficulty in understanding how the marine ecosystem responds to a future warming climate, given to range of relevant processes operating at different scales.

  6. Results of radiocarbon dating of Holocene fluvial sediments from Northeastern Bohemia

    International Nuclear Information System (INIS)

    Silar, J.; Zeman, A.

    1989-01-01

    Samples of wood and charcoal from the latest Holocene fluvial sediments under the lowest surface of alluvial plains were dated by radiocarbon in order to check paleomagnetic data at four sites in northeastern Bohemia. The results are presented as funcorrected 14 C ages and dendrochronologically corrected ages. Two samples were recent. 4 figs., 1 tab., 3 refs

  7. Radiocarbon as a Novel Tracer of Extra-Antarctic Feeding in Southern Hemisphere Humpback Whales.

    Science.gov (United States)

    Eisenmann, Pascale; Fry, Brian; Mazumder, Debashish; Jacobsen, Geraldine; Holyoake, Carlysle Sian; Coughran, Douglas; Bengtson Nash, Susan

    2017-06-29

    Bulk stable isotope analysis provides information regarding food web interactions, and has been applied to several cetacean species for the study of migration ecology. One limitation in bulk stable isotope analysis arises when a species, such as Southern hemisphere humpback whales, utilises geographically distinct food webs with differing isotopic baselines. Migrations to areas with different baselines can result in isotopic changes that mimic changes in feeding relations, leading to ambiguous food web interpretations. Here, we demonstrate the novel application of radiocarbon measurement for the resolution of such ambiguities. Radiocarbon was measured in baleen plates from humpback whales stranded in Australia between 2007 and 2013, and in skin samples collected in Australia and Antarctica from stranded and free-ranging animals. Radiocarbon measurements showed lower values for Southern Ocean feeding than for extra-Antarctic feeding in Australian waters. While the whales mostly relied on Antarctic-derived energy stores during their annual migration, there was some evidence of feeding within temperate zone waters in some individuals. This work, to our knowledge, provides the first definitive biochemical evidence for supplementary feeding by southern hemisphere humpback whales within temperate waters during migration. Further, the work contributes a powerful new tool (radiocarbon) for tracing source regions and geographical feeding.

  8. Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life

    DEFF Research Database (Denmark)

    Lynnerup, Niels; Kjeldsen, Henrik; Heegaard, Steffen

    2008-01-01

    , there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its (14)C content from the atmospheric carbon dioxide. The (14)C content of the lens proteins thus reflects the atmospheric content of (14)C when the lens crystallines were formed. Precise radiocarbon...

  9. Application of the bomb radiocarbon chronometer to the validation of redfish Centroberyx affinis age

    International Nuclear Information System (INIS)

    Kalish, J.M.

    1995-01-01

    Validation of methods used to estimate fish age is a critical element of the fish stock assessment process. Despite the importance of validation, few procedures are available that provide unbiased estimates of true fish age and those methods that are available are seldom used. The majority of these methods are unlikely to provide an indication of the true age of individual fish, data that are best suited to the validation process. Accelerator mass spectrometry analyses of radiocarbon in selected regions of Centroberyx affinis otoliths were used to validate the age estimation method for this species. Radiocarbon data from the otoliths of C. affinis with presumed birth dates between 1955 and 1985 described the increase in ocean radiocarbon attributable to the atmospheric detonation of nuclear weapons in the 1950s and 1960s. The results confirm the longevity of C. affinis and demonstrate the effectiveness of the bomb radiocarbon chronometer for the validation of age-estimation methods. (author). 31 refs., 2 tabs., 1 fig

  10. Radiocarbon dating of fluvial organic matter reveals land-use impacts in boreal peatlands

    DEFF Research Database (Denmark)

    Hulatt, Chris J.; Kaartokallio, Hermanni; Oinonen, Markku

    2014-01-01

    This study measured the effects of land use on organic matter released to surface waters in a boreal peat catchment using radiocarbon dating of particulate and dissolved organic carbon (POC and DOC), DOC concentration, stable carbon and nitrogen isotope composition, and optical measurements. Undi...

  11. Radiocarbon in the air of central Europe: long-term investigations

    Czech Academy of Sciences Publication Activity Database

    Světlík, Ivo; Povinec, P. P.; Molnár, M.; Váňa, M.; Šivo, A.; Bujtás, T.

    2010-01-01

    Roč. 52, č. 2 (2010), s. 823-834 ISSN 0033-8222. [International Radiocarbon Conference /20./. Big Island, Hawai, 31.05.2009-05.06.2009] Institutional research plan: CEZ:AV0Z10480505 Keywords : 14CO2 * troposphere * Suess effect * fossil fuel combustion Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.703, year: 2010

  12. Radiocarbon dating uncertainties and their effects on studies of the past

    International Nuclear Information System (INIS)

    Chappell, J.

    1982-01-01

    The handling of sets of age results and their errors for hypothesis testing is discussed. The paper focusses on radiocarbon dating but most of the principles apply to other dating methods, although some formulae will be different. One conclusion is that the conventional age error should be enlarged to allow for past variations of 14 C level in the atmosphere

  13. Revised age of deglaciation of Lake Emma based on new radiocarbon and macrofossil analyses

    Science.gov (United States)

    Elias, S.A.; Carrara, P.E.; Toolin, L.J.; Jull, A.J.T.

    1991-01-01

    Previous radiocarbon ages of detrital moss fragments in basal organic sediments of Lake Emma indicated that extensive deglaciation of the San Juan Mountains occurred prior to 14,900 yr B.P. (Carrara et al., 1984). Paleoecological analyses of insect and plant macrofossils from these basal sediments cast doubt on the reliability of the radiocarbon ages. Subsequent accelerator radiocarbon dates of insect fossils and wood fragments indicate an early Holocene age, rather than a late Pleistocene age, for the basal sediments of Lake Emma. These new radiocarbon ages suggest that by at least 10,000 yr B.P. deglaciation of the San Juan Mountains was complete. The insect and plant macrofossils from the basal organic sediments indicate a higher-than-present treeline during the early Holocene. The insect assemblages consisted of about 30% bark beetles, which contrasts markedly with the composition of insects from modern lake sediments and modern specimens collected in the Lake Emma cirque, in which bark beetles comprise only about 3% of the assemblages. In addition, in the fossil assemblages there were a number of flightless insect species (not subject to upslope transport by wind) indicative of coniferous forest environments. These insects were likewise absent in the modern assemblage. ?? 1991.

  14. Radiocarbon evidence for a smaller oceanic carbon dioxide sink than previously believed

    Science.gov (United States)

    Hesshaimer, Vago; Heimann, Martin; Levin, Ingeborg

    1994-07-01

    RADIOCARBON produced naturally in the upper atmosphere or arti-ficially during nuclear weapons testing is the main tracer used to validate models of oceanic carbon cycling, in particular the exchange of carbon dioxide with the atmosphere1-3 and the mixing parameters within the ocean itself4-7. Here we test the overall consistency of exchange fluxes between all relevant compartments in a simple model of the global carbon cycle, using measurements of the long-term tropospheric CO2 concentration8 and radiocarbon composition9-12, the bomb 14C inventory in the stratosphere13,14 and a compilation of bomb detonation dates and strengths15. We find that to balance the budget, we must invoke an extra source to account for 25% of the generally accepted uptake of bomb 14C by the oceans3. The strength of this source decreases from 1970 onwards, with a characteristic timescale similar to that of the ocean uptake. Significant radiocarbon transport from the remote high stratosphere and significantly reduced uptake of bomb 14C by the biosphere can both be ruled out by observational constraints. We therefore conclude that the global oceanic bomb 14C inventory should be revised downwards. A smaller oceanic bomb 14C inventory also implies a smaller oceanic radiocarbon penetration depth16, which in turn implies that the oceans take up 25% less anthropogenic CO2 than had previously been believed.

  15. MESOLITHIC HUMAN BONES FROM THE UPPER VOLGA BASIN : RADIOCARBON AND TRACE ELEMENTS

    NARCIS (Netherlands)

    Alexandrovskiy, A. L.; Alexandrovskaya, E. I.; Zhilin, M. I.; van der Plicht, J.

    2009-01-01

    Human bones from 3 Mesolithic sites in the Upper Volga basin were analyzed for trace elements, and dated by accelerator mass spectrometry (AMS). The radiocarbon dates of the bones correspond to the Mesolithic era. However, some dates differ from those obtained for the enclosing deposits and for the

  16. Býčí skála Cave, Czech Republic: Radiocarbon dates of rock paintings

    Czech Academy of Sciences Publication Activity Database

    Svoboda, Jiří; van der Plicht, H.; Balák, I.

    2005-01-01

    Roč. 43, - (2005), s. 7-9 ISSN 1022-3282 Institutional research plan: CEZ:AV0Z80010507 Keywords : Býčí skála Czech Republic * rock art * radiocarbon dating Subject RIV: AC - Archeology, Anthropology, Ethnology

  17. Holocene environmental changes disclosed from anoxic fjord sediments by biomarkers and their radiocarbon content

    NARCIS (Netherlands)

    Smittenberg, R.H.

    2003-01-01

    The power and validity of compound-specific radiocarbon dating was evaluated using sediments from Saanich Inlet, Canada, in age ranging from recent to 5000 yr BP. Compounds characteristic of higher plants, phytoplankton and archaea, were isolated by preparative GC and

  18. The most direct and precise radiocarbon date for the Minoan eruption of Santorini

    DEFF Research Database (Denmark)

    Friedrich, Walter L.; Heinemeier, Jan

    for the Minoan eruption. Together with a second olive tree, excavated only 9 meters from the first one, it enables us to repeat the earlier measurements of the first tree 2006 (Friedrich, W.L . Kromer, B Friedrich, M. Heinemeier, J. Pfeiffer, T. Talamo, S. Santorini Eruption Radiocarbon Dated to 1627-1600 BC...

  19. IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP

    NARCIS (Netherlands)

    Reimer, Paula J.; Baillie, Mike G.L.; Bard, Edouard; Bayliss, Alex; Beck, J. Warren; Bertrand, Chanda J.H.; Blackwell, Paul G.; Buck, Caitlin E.; Burr, George S.; Cutler, Kirsten B.; Damon, Paul E.; Edwards, R. Lawrence; Fairbanks, Richard G.; Friedrich, Michael; Guilderson, Thomas P.; Hogg, Alan G.; Hughen, Konrad A.; Kromer, Bernd; McCormac, Gerry; Manning, Sturt; Bronk Ramsey, Christopher; Reimer, Ron W.; Remmele, Sabine; Southon, John R.; Stuiver, Minze; Talamo, Sahra; Taylor, F.W.; Plicht, Johannes van der; Weyhenmeyer, Constanze E.

    2004-01-01

    A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0–24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from

  20. Marine04 marine radiocarbon age calibration, 0-26 cal kyr BP

    NARCIS (Netherlands)

    Hughen, Konrad A.; Baillie, Mike G.L.; Bard, Edouard; Beck, J. Warren; Bertrand, Chanda J.H.; Blackwell, Paul G.; Buck, Caitlin E.; Burr, George S.; Cutler, Kirsten B.; Damon, Paul E.; Edwards, Richard L.; Fairbanks, Richard G.; Friedrich, Michael; Guilderson, Thomas P.; Kromer, Bernd; McCormac, Gerry; Manning, Sturt; Bronk Ramsey, Christopher; Reimer, Paula J.; Reimer, Ron W.; Remmele, Sabine; Southon, John R.; Stuiver, Minze; Talamo, Sahra; Taylor, F.W.; Plicht, Johannes van der; Weyhenmeyer, Constanze E.

    2004-01-01

    New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration data sets extend an additional 2000 yr, from 0–26 cal kyr BP (Before Present, 0 cal BP = AD 1950), and

  1. INTCAL09 AND MARINE09 RADIOCARBON AGE CALIBRATION CURVES, 0-50,000 YEARS CAL BP

    NARCIS (Netherlands)

    Reimer, P. J.; Baillie, M. G. L.; Bard, E.; Bayliss, A.; Beck, J. W.; Blackwell, P. G.; Ramsey, C. Bronk; Buck, C. E.; Burr, G. S.; Edwards, R. L.; Friedrich, M.; Grootes, P. M.; Guilderson, T. P.; Hajdas, I.; Heaton, T. J.; Hogg, A. G.; Hughen, K. A.; Kaiser, K. F.; Kromer, B.; McCormac, F. G.; Manning, S. W.; Reimer, R. W.; Richards, D. A.; Southon, J. R.; Talamo, S.; Turney, C. S. M.; van der Plicht, J.; Weyhenmeye, C. E.; Weyhenmeyer, C.E.

    2009-01-01

    The IntCal04 and Marine04 radiocarbon calibration curves have been updated from 12 cal kBP (cal kBP is here defined as thousands of calibrated years before AD 1950), and extended to 50 cal kBP, utilizing newly available data sets that meet the IntCal Working Group criteria for pristine corals and

  2. Summary findings of the fourth international radiocarbon intercomparison (FIRI) (1998–2001)

    NARCIS (Netherlands)

    Boaretto, Elisabetta; Bryant, Charlotte; Carmi, Israel; Cook, Gordon; Gulliksen, Steinar; Harkness, Doug; Heinemeier, Jan; McClure, John; McGee, Edward; Naysmith, Philip; Possnert, Goran; Scott, Marian; Plicht, Hans van der; Strydonck, Mark van

    2002-01-01

    Interlaboratory comparisons have been widely used in applied radiocarbon science. These are an important part of ongoing quality assurance (QA) programmes, which are vital to the appropriate interpretation of the evidence provided by the 14C record in Quaternary applications (including climate

  3. Radiocarbon dating in near-Eastern contexts : Confusion and quality control

    NARCIS (Netherlands)

    van der Plicht, J; Bruins, HJ; Bruins, Hendrik J.; Boaretto, E.; Carmi, I.

    2001-01-01

    Near-Eastern archaeology has long remained oblivious to radiocarbon dating as unique historical calendars brought about a perception that C-14 dating is superfluous. Circular chronological reasoning may occur as a result. There is now strong C-14 evidence that the early part of Egyptian history

  4. Accelerator mass spectrometry radiocarbon ages of amino acid extracts from Californian palaeoindian skeletons

    International Nuclear Information System (INIS)

    Bada, J.L.; Gillespie, R.; Gowlett, J.A.J.; Hedges, R.E.M.

    1984-01-01

    The authors have used accelerator mass spectrometry to determine the radiocarbon ages of the amino acid extracts used in the original racemization studies of skeletal remains found in California. The studies indicate that some of the controversial Californian skeletons, which had been assigned to the Upper Pleistocene, are in fact Holocene. (author)

  5. Atmospheric radiocarbon calibration to 45,000 yr BP: Late glacial fluctuations and cosmogenic isotope production

    NARCIS (Netherlands)

    Kitagawa, H.; van der Plicht, J.

    1998-01-01

    More than 250 carbon-14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from Lake Suigetsu (Japan) provide a first atmospheric calibration for almost the total range of the radiocarbon method (45,000 years before the present), The results confirm the

  6. Radiocarbon dating of American pika fecal pellets provides insights into population extirpations and climate refugia

    Science.gov (United States)

    Constance I. Millar; Katherine Heckman; Christopher Swanston; Karena Schmidt; Robert D. Westfall; Diane L. Delany

    2014-01-01

    The American pika (Ochotona princeps) has become a species of concern for its sensitivity to warm temperatures and potential vulnerability to global warming. We explored the value of radiocarbon dating of fecal pellets to address questions of population persistence and timing of site extirpation. Carbon was extracted from pellets collected at 43...

  7. Luminescence and radiocarbon dating of raised beach sediments, Bunger Hills, East Antarctica

    International Nuclear Information System (INIS)

    Augustinus, P.C.; Duller, G.A.T.

    2002-01-01

    Luminescence and radiocarbon dating of raised marine sediments from the Bunger Hills, East Antarctica, demonstrates that luminescence methods can be applied to such poorly bleached sediments as long as the luminescence behaviour of the sediments is understood. This is essential as the complete zeroing of the luminescence signal due to light exposure is required to allow an accurate age for the sediment accumulation. Unfortunately, independent checks on the luminescence ages are rare. In the present study, some independent age control is provided by AMS radiocarbon ages from shell obtained from and adjacent to the luminescence dated horizons, although the radiocarbon ages may suffer to some degree from variability in the marine reservoir effect. Application of the single aliquot luminescence technique to feldspar grains from the marine sediments demonstrated that the luminescence behaviour of the sediments was complex. For each sample, 18 replicate paleodose estimates were used to demonstrate whether the sediments were well bleached before deposition. Optically, well-bleached samples give younger luminescence ages, whilst poorly bleached samples often give excessively old ages compared to the associated radiocarbon-dated material. (author)

  8. SELECTION AND TREATMENT OF DATA FOR RADIOCARBON CALIBRATION : AN UPDATE TO THE INTERNATIONAL CALIBRATION (INTCAL) CRITERIA

    NARCIS (Netherlands)

    Reimer, Paula J.; Bard, Edouard; Bayliss, Alex; Beck, J. Warren; Blackwell, Paul G.; Ramsey, Christopher Bronk; Brown, David M.; Buck, Caitlin E.; Edwards, R. Lawrence; Friedrich, Michael; Grootes, Pieter M.; Guilderson, Thomas P.; Haflidason, Haflidi; Hajdas, Irka; Hatte, Christine; Heaton, Timothy J.; Hogg, Alan G.; Hughen, Konrad A.; Kaiser, K. Felix; Kromer, Bernd; Manning, Sturt W.; Reimer, Ron W.; Richards, David A.; Scott, E. Marian; Southon, John R.; Turney, Christian S. M.; van der Plicht, Johannes

    2013-01-01

    High-quality data from appropriate archives are needed for the continuing improvement of radiocarbon calibration curves. We discuss here the basic assumptions behind C-14 dating that necessitate calibration and the relative strengths and weaknesses of archives from which calibration data are

  9. Youngest radiocarbon age for Jefferson's ground sloth, Megalonyx jeffersonii (Xenarthra, Megalonychidae)

    DEFF Research Database (Denmark)

    Gregory McDonald, H.; Stafford, Thomas W.; Gnidovec, Dale M.

    2015-01-01

    A partial skeleton of the extinct ground sloth, Megalonyx jeffersonii, recovered from a farm near Millersburg, Ohio in 1890, was radiocarbon dated for the first time. The ungual dated is part of a skeleton mounted for exhibit at the Orton Geological Museum at Ohio State University and was the fir...

  10. Radiocarbon determination of particulate organic carbon in glacier ice from the Grenzgletscher (Monte Rosa)

    International Nuclear Information System (INIS)

    Steier, P.; Drosg, R.; Kutschera, W.; Wild, E.M.; Fedi, M.; Schock, M.; Wagenbach, D.

    2005-01-01

    Full text: Dating ice cores from cold glaciers via radiocarbon is still an unsolved problem. This work describes our approach towards extraction and AMS radiocarbon dating of the particulate organic carbon (POC) fraction in ice samples at VERA (Vienna Environmental Research Accelerator). First measurements were performed on 1 snow and 11 ice samples from Gorner Glacier and Colle Gnifetti in the Monte Rosa Mountain region (Swiss Alps). The sample masses used were between 0.3 kg and 1.4 kg ice yielding between 18 μg and 307 μg carbon as POC. The carbon contamination introduced during the sample processing varied between 9 μg and 33 μg C and originates mainly from the quartz filters and the rinsing liquids used. Minimum sample sizes for successful graphitization of carbon dioxide in our laboratory have been reduced to less than 10 μg carbon. The background in the graphitization process is approximately 0.5 μg carbon of 40 pMC. Scatter and outliers in the radiocarbon data suggest that presently a single radiocarbon date of glacial POC has limited significance. For the set of 11 ice samples, a calibrated age of 2100 BC to 900 AD (95% confidence level) is obtained. (author)

  11. The marine radiocarbon bomb pulse across the temperate North Atlantic: a compilation of Delta

    NARCIS (Netherlands)

    Scourse, J.D.; Wanamaker jr., A.D.; Weidman, C.; Heinemeier, J.; Reimer, P.J.; Butler, P.G.; Witbaard, R.; Richardson, C.A.

    2012-01-01

    Marine radiocarbon bomb-pulse time histories of annually resolved archives from temperate regions have been underexploited. We present here series of Delta C-14 excess from known-age annual increments of the long-lived bivalve mollusk Arctica islandica from 4 sites across the coastal North Atlantic

  12. THE IRON AGE AROUND THE MEDITERRANEAN : A HIGH CHRONOLOGY PERSPECTIVE FROM THE GRONINGEN RADIOCARBON DATABASE

    NARCIS (Netherlands)

    van der Plicht, J.; Bruins, H.J.; Nijboer, A.J.

    2009-01-01

    In this paper, we present an overview of radiocarbon dating contributions from Groningen, concerning 9 sites from around the Mediterranean region: Israel, Sinai (Egypt), Jordan, Spain, Tunisia, and Italy. Full date lists of the 9 sites are presented. Our (14)C dates are discussed in terms of present

  13. Comparative study of potential transfer of natural and anthropogenic cadmium to plankton communities in the North-West African upwelling

    International Nuclear Information System (INIS)

    Auger, P.A.; Machu, E.; Gorgues, T.; Grima, N.; Waeles, M.

    2015-01-01

    A Lagrangian approach based on a physical–biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the North-West African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates. - Highlights: • We model the physical–biogeochemical dynamics in the North-West African upwelling. • We model the transport of cadmium from natural and anthropogenic sources. • We derive proxies of potential cadmium absorption and bioaccumulation in the plankton food chain. • The anthropogenic signal off Morocco at least equals the natural upwelling signal off Mauritania. • We compare our results with observed cadmium levels in mollusks and fishes

  14. Far-reaching transport of Pearl River plume water by upwelling jet in the northeastern South China Sea

    Science.gov (United States)

    Chen, Zhaoyun; Pan, Jiayi; Jiang, Yuwu; Lin, Hui

    2017-09-01

    Satellite images from the Moderate Resolution Imaging Spectroradiometer (MODIS) show that there was a belt of turbid water appearing along an upwelling front near the Chinese coast of Guangdong, and indicate that the turbid water of the Pearl River plume water could be transported to a far-reaching area east of the Taiwan Bank. Numerical modeling results are consistent with the satellite observations, and reveal that a strong jet exists at the upwelling front with a speed as high as 0.8 m s- 1, which acts as a pathway for transporting the high-turbidity plume water. The dynamical analysis suggests that geostrophic equilibrium dominates in the upwelling front and plume areas, and the baroclinicity of the upwelling front resulting from the horizontal density gradient is responsible for the generation of the strong jet, which enhances the far-reaching transport of the terrigenous nutrient-rich water of the Pearl River plume. Model sensitivity analyses also confirm that this jet persists as long as the upwelling front exists, even when the wind subsides and becomes insignificant. Further idealized numerical model experiments indicate that the formation and persistence of the upwelling front jet depend on the forcing strength of the upwelling-favorable wind. The formation time of the jet varies from 15 to 158 h as the stress of the upwelling-favorable wind changes from 0.2 to 0.01 N m- 2. With the persistent transport of the nutrient-rich plume water, biophysical activities can be promoted significantly in the far-reaching destination area of the oligotrophic water.

  15. Comparative study of potential transfer of natural and anthropogenic cadmium to plankton communities in the North-West African upwelling

    Energy Technology Data Exchange (ETDEWEB)

    Auger, P.A., E-mail: pierreamael.auger@gmail.com [Laboratoire de Physique des Océans (LPO), UMR-CNRS 6523/IFREMER/IRD/UBO, BP70, 29280 Plouzané (France); Machu, E.; Gorgues, T.; Grima, N. [Laboratoire de Physique des Océans (LPO), UMR-CNRS 6523/IFREMER/IRD/UBO, BP70, 29280 Plouzané (France); Waeles, M. [Université de Bretagne Occidentale (UBO), Laboratoire de l' Environnement Marin (LEMAR), UMR-CNRS 6539/IRD/UBO, place N. Copernic, 29280 Plouzané (France)

    2015-02-01

    A Lagrangian approach based on a physical–biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the North-West African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates. - Highlights: • We model the physical–biogeochemical dynamics in the North-West African upwelling. • We model the transport of cadmium from natural and anthropogenic sources. • We derive proxies of potential cadmium absorption and bioaccumulation in the plankton food chain. • The anthropogenic signal off Morocco at least equals the natural upwelling signal off Mauritania. • We compare our results with observed cadmium levels in mollusks and fishes.

  16. Changes in the partial pressure of carbon dioxide in the Mauritanian–Cap Vert upwelling region between 2005 and 2012

    Directory of Open Access Journals (Sweden)

    M. González-Dávila

    2017-08-01

    Full Text Available Coastal upwellings along the eastern margins of major ocean basins represent regions of large ecological and economic importance due to the high biological productivity. The role of these regions for the global carbon cycle makes them essential in addressing climate change. The physical forcing of upwelling processes that favor production in these areas are already being affected by global warming, which will modify the intensity of upwelling and, consequently, the carbon dioxide cycle. Here, we present monthly high-resolution surface experimental data for temperature and partial pressure of carbon dioxide in one of the four most important upwelling regions of the planet, the Mauritanian–Cap Vert upwelling region, from 2005 to 2012. This data set provides direct evidence of seasonal and interannual changes in the physical and biochemical processes. Specifically, we show an upwelling intensification and an increase of 0.6 Tg yr−1 in CO2 outgassing due to increased wind speed, despite increased primary productivity. This increase in CO2 outgassing together with the observed decrease in sea surface temperature at the location of the Mauritanian Cap Blanc, 21° N, produced a pH rate decrease of −0.003 ± 0.001 yr−1.

  17. Age estimation in forensic sciences: application of combined aspartic acid racemization and radiocarbon analysis.

    Science.gov (United States)

    Alkass, Kanar; Buchholz, Bruce A; Ohtani, Susumu; Yamamoto, Toshiharu; Druid, Henrik; Spalding, Kirsty L

    2010-05-01

    Age determination of unknown human bodies is important in the setting of a crime investigation or a mass disaster because the age at death, birth date, and year of death as well as gender can guide investigators to the correct identity among a large number of possible matches. Traditional morphological methods used by anthropologists to determine age are often imprecise, whereas chemical analysis of tooth dentin, such as aspartic acid racemization, has shown reproducible and more precise results. In this study, we analyzed teeth from Swedish individuals using both aspartic acid racemization and radiocarbon methodologies. The rationale behind using radiocarbon analysis is that aboveground testing of nuclear weapons during the cold war (1955-1963) caused an extreme increase in global levels of carbon-14 ((14)C), which has been carefully recorded over time. Forty-four teeth from 41 individuals were analyzed using aspartic acid racemization analysis of tooth crown dentin or radiocarbon analysis of enamel, and 10 of these were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods correlated well (R(2) = 0.66, p Aspartic acid racemization also showed a good precision with an overall absolute error of 5.4 +/- 4.2 years. Whereas radiocarbon analysis gives an estimated year of birth, racemization analysis indicates the chronological age of the individual at the time of death. We show how these methods in combination can also assist in the estimation of date of death of an unidentified victim. This strategy can be of significant assistance in forensic casework involving dead victim identification.

  18. New protocol for compound-specific radiocarbon analysis of archaeological bones.

    Science.gov (United States)

    Deviese, Thibaut; Comeskey, Daniel; McCullagh, James; Bronk Ramsey, Christopher; Higham, Thomas

    2018-03-15

    For radiocarbon results to be accurate, samples must be free of contaminating carbon. Sample pre-treatment using a high-performance liquid chromatography (HPLC) approach has been developed at the Oxford Radiocarbon Accelerator Unit (ORAU) as an alternative to conventional methods for dating heavily contaminated bones. This approach isolates hydroxyproline from bone collagen, enabling a purified bone-specific fraction to then be radiocarbon dated by accelerator mass spectrometry (AMS). Using semi-preparative chromatography and non-carbon-based eluents, this technique enables the separation of underivatised amino acids liberated by hydrolysis of extracted bone collagen. A particular focus has been the isolation of hydroxyproline for single-compound AMS dating since this amino acid is one of the main contributors to the total amount of carbon in mammalian collagen. Our previous approach, involving a carbon-free aqueous mobile phase, required a two-step separation using two different chromatographic columns. This paper reports significant improvements that have been recently made to the method to enable faster semi-preparative separation of hydroxyproline from bone collagen, making the method more suitable for routine radiocarbon dating of contaminated and/or poorly preserved bone samples by AMS. All steps of the procedure, from the collagen extraction to the correction of the AMS data, are described. The modifications to the hardware and to the method itself have reduced significantly the time required for the preparation of each sample. This makes it easier for other radiocarbon facilities to implement and use this approach as a routine method for preparing contaminated bone samples. Copyright © 2017 John Wiley & Sons, Ltd.

  19. Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

    Science.gov (United States)

    Ohde, Thomas; Dadou, Isabelle

    2018-01-01

    We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass

  20. Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

    Directory of Open Access Journals (Sweden)

    Thomas Ohde

    Full Text Available We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area. The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone

  1. Global Peak in Atmospheric Radiocarbon Provides a Potential Definition for the Onset of the Anthropocene Epoch in 1965.

    Science.gov (United States)

    Turney, Chris S M; Palmer, Jonathan; Maslin, Mark A; Hogg, Alan; Fogwill, Christopher J; Southon, John; Fenwick, Pavla; Helle, Gerhard; Wilmshurst, Janet M; McGlone, Matt; Bronk Ramsey, Christopher; Thomas, Zoë; Lipson, Mathew; Beaven, Brent; Jones, Richard T; Andrews, Oliver; Hua, Quan

    2018-02-19

    Anthropogenic activity is now recognised as having profoundly and permanently altered the Earth system, suggesting we have entered a human-dominated geological epoch, the 'Anthropocene'. To formally define the onset of the Anthropocene, a synchronous global signature within geological-forming materials is required. Here we report a series of precisely-dated tree-ring records from Campbell Island (Southern Ocean) that capture peak atmospheric radiocarbon ( 14 C) resulting from Northern Hemisphere-dominated thermonuclear bomb tests during the 1950s and 1960s. The only alien tree on the island, a Sitka spruce (Picea sitchensis), allows us to seasonally-resolve Southern Hemisphere atmospheric 14 C, demonstrating the 'bomb peak' in this remote and pristine location occurred in the last-quarter of 1965 (October-December), coincident with the broader changes associated with the post-World War II 'Great Acceleration' in industrial capacity and consumption. Our findings provide a precisely-resolved potential Global Stratotype Section and Point (GSSP) or 'golden spike', marking the onset of the Anthropocene Epoch.

  2. Comparison of accelerator and radiometric radiocarbon measurements obtained from Late Devensian Lateglacial lake sediments from Llyn Gwernan, North Wales, UK

    International Nuclear Information System (INIS)

    Lowe, J.J.; Lowe, S.; Fowler, A.J.

    1988-01-01

    Accelerator mass spectrometry measurements of the radiocarbon activity of various chemical fractions prepared from Late Devensian Lateglacial lake sediments from the site of Llyn Gwernan, near Cader Idris. North Wales are presented and assessed. These are compared with radiocarbon measurements obtained by radiometric (decay) counting which were reported earlier from the same site and are considered in the light of pollen-stratigraphic information. The potensial advantages of accelerator radiocarbon measurements to the assessment of the chronology and correlation of Lateglacial lake sediments are evaluated

  3. Applications of radiocarbon measurements in environmental studies at INFN-LABEC, Florence

    Directory of Open Access Journals (Sweden)

    Chiari M.

    2012-04-01

    Full Text Available Radiocarbon is one of the most widespread radionuclides in nature. Although it is probably best known for dating in archaeology, in the case of the general public, it represents a useful tracer to study our environment, both in the past and nowadays. For instance, carbonaceous particles, which are in many cases the most abundant among aerosols constituents, are believed to play a major role in both health and climatic effects of aerosols. In particular, measurement of radiocarbon concentration in particulate matter samples can give information on the contributions of the fossil fuels combustion and of natural sources to the carbonaceous fraction in aerosols. These measurements are especially effective when separately performed on different carbonaceous fractions, like elemental and organic carbon (EC and OC, respectively. Past climate is also studied thanks to old archives, as e.g. marine sediments can be. In this case, instead of radiocarbon dating the bulk sediment, a reliable method to fix chronological markers is represented by dating foraminifera tests of CaCO3 picked from different layers in the sediment. Both the aforementioned applications are characterized by the fact that the samples that can be collected for 14C measurements are typically very small, i.e. few mg or less (before any treatment. Accelerator Mass Spectrometry (AMS is thus the only technique that can be applied to measure radiocarbon in such samples. Anyway, measurements cannot be so straightforward. In the case of the measurement of radiocarbon concentration in aerosol samples, a preparation line especially dedicated to the extraction of only the carbonaceous fraction of interest is mandatory. Actually, this line should include a combustion oven, from which either total carbon or EC and OC can separately evolve, and a system of traps to purify and collect the CO2. In the case of foraminifera tests (inorganic carbon, special care must be taken in the pre-treatment phase

  4. Insights into soil carbon dynamics across climatic and geologic gradients from temporally-resolved radiocarbon measurements

    Science.gov (United States)

    van der Voort, T. S.; Hagedorn, F.; Mannu, U.; Walthert, L.; McIntyre, C.; Eglinton, T. I.

    2016-12-01

    Soil carbon constitutes the largest terrestrial reservoir of organic carbon, and therefore quantifying soil organic matter dynamics (carbon turnover, stocks and fluxes) across spatial gradients is essential for an understanding of the carbon cycle and the impacts of global change. In particular, links between soil carbon dynamics and different climatic and compositional factors remains poorly understood. Radiocarbon constitutes a powerful tool for unraveling soil carbon dynamics. Temporally-resolved radiocarbon measurements, which take advantage of "bomb-radiocarbon"-driven changes in atmospheric 14C, enable further constraints to be placed on C turnover times. These in turn can yield more precise flux estimates for both upper and deeper soil horizons. This project combines bulk radiocarbon measurements on a suite of soil profiles spanning strong climatic (MAT 1.3-9.2°C, MAP 600 to 2100 mm m-2y-1) and geologic gradients with a more in-depth approach for a subset of locations. For this subset, temporal and carbon-fraction specific radiocarbon data has been acquired for both topsoil and deeper soils. These well-studied sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). Resulting temporally-resolved turnover estimates are coupled to carbon stocks, fluxes across this wide range of forest ecosystems and are examined in the context of environmental drivers (temperature, precipitation, primary production and soil moisture) as well as composition (sand, silt and clay content). Statistical analysis on the region-scale - correlating radiocarbon signature with climatic variables such as temperature, precipitation, primary production and elevation - indicates that composition rather than climate is a key driver of ­­Δ14C signatures. Estimates of carbon turnover, stocks and fluxes derived from temporally-resolved measurements highlight the pivotal role of soil moisture as a

  5. Changes in optical characteristics of surface microlayers in the Peruvian upwelling region hint to photochemically and microbially-mediated DOM turnover

    Science.gov (United States)

    Engel, A.; Galgani, L.

    2016-02-01

    The coastal upwelling system off Peru is characterized by high biological activity and associated subsurface oxygen minimum zone, leading to an enhanced emission of atmospheric trace gases. High biological productivity in the water column may promote the establishment of enriched organic surface films, key environments for processes regulating gas fluxes across the water-air interface. During M91 cruise to the Peruvian upwelling, we focused our attention on the composition of the sea-surface microlayer (SML), the oceanic uppermost boundary directly subject to high solar radiation, often enriched in specific organic compounds of biological origin like Chromophoric Dissolved Organic Matter (CDOM) and marine gels. In the SML, the continuous photochemical and microbial recycling of organic matter may strongly influence gas exchange between marine systems and the atmosphere. In order to understand organic matter cycling in surface films, we analyzed SML and underlying water samples in 38 stations determining DOC concentrations, amino acids composition, marine gels, CDOM and bacterial abundance as indicators of photochemical and microbial alteration processes. CDOM composition was characterized by spectral slopes (S) values and Excitation-Emission Matrix fluorescence (EEMs), which allow to track changes in molecular weight (MW) of DOM, and to determine potential DOM sources. Profound changes in spectral slope properties were observed suggesting smaller MW CDOM in the SML compared to underlying water. Microbial and photochemical degradation are likely the main drivers for organic matter cycling in the top layer of the ocean. Consequences on the formation of inorganic and organic species highly relevant for air-sea gas exchange and for climate dynamics will be discussed.

  6. Discriminating the biophysical impacts of coastal upwelling and mud banks along the southwest coast of India

    Science.gov (United States)

    Karnan, C.; Jyothibabu, R.; Arunpandi, N.; Jagadeesan, L.; Muraleedharan, K. R.; Pratihari, A. K.; Balachandran, K. K.; Naqvi, S. W. A.

    2017-08-01

    Coastal upwelling and mud banks are two oceanographic processes concurrently operating along certain stretches of the southwest (Kerala) coast of India during the Southwest Monsoon period (June-September), facilitating significant enhancement in plankton biomass. Mud banks have scientific and societal attention from time immemorial, predominantly due to the large fisheries associated with them. In this paper, for the first time, the specific biophysical roles of these oceanographic processes have been discriminated, based on a focused 18 weekly/fortnightly time-series study (April to September 2014) in a mud bank-upwelling area (off Alappuzha, southwest coast of India). In conjunction with standard hydrographical and satellite remote sensing data, we utilised a FlowCAM to track the biophysical linkage in terms of plankton composition abundance and size structure at three locations (M1, M2 and M3) in the study area. During the Pre-Southwest Monsoon (April-May), the entire study area was warmer with low nitrate concentration in the surface waters, which caused lower biomass of autotrophs compared to the Southwest Monsoon (June-September). By the onset of the Southwest Monsoon (June), drastic hydrographical transformations took place in the study domain due to the Coastal upwelling, reflected as the surfacing of significantly cool, high nutrient and hypoxic waters. Concurrently, mud bank formed at location M2 due to the presence of relatively high-suspended sediments in the region, creating a localised calm environment conducive for fishing activities. In response to the hydrographical transformations in the entire study area during the Southwest Monsoon, the autotrophic plankton biomass and size structure experienced significant change. The micro-autotrophs biomass that was low during the Pre-Southwest Monsoon (av. 0.33 ± 0.2 mgC L- 1 at surface and av. 0.07 ± 0.04 mgC L- 1 at subsurface) noticeably increased during the Southwest Monsoon (av. 1.6 ± 0.4 mgC L- 1 at

  7. Seasonal climatology of hydrographic conditions in the upwelling region off northern Chile

    Science.gov (United States)

    Blanco, J. L.; Thomas, A. C.; Carr, M.-E.; Strub, P. T.

    2001-06-01

    Over 30 years of hydrographic data from the northern Chile (18°S-24°S) upwelling region are used to calculate the surface and subsurface seasonal climatology extending 400 km offshore. The data are interpolated to a grid with sufficient spatial resolution to preserve cross-shelf gradients and then presented as means within four seasons: austral winter (July-September), spring (October-December), summer (January-March), and fall (April-June). Climatological monthly wind forcing, surface temperature, and sea level from three coastal stations indicate equatorward (upwelling favorable) winds throughout the year, weakest in the north. Seasonal maximum alongshore wind stress is in late spring and summer (December-March). Major water masses of the region are identified in climatological T-S plots and their sources and implied circulation discussed. Surface fields and vertical transects of temperature and salinity confirm that upwelling occurs year-round, strongest in summer and weakest in winter, bringing relatively fresh water to the surface nearshore. Surface geostrophic flow nearshore is equatorward throughout the year. During summer, an anticyclonic circulation feature in the north which extends to at least 200 m depth is evident in geopotential anomaly and in both temperature and geopotential variance fields. Subsurface fields indicate generally poleward flow throughout the year, strongest in an undercurrent near the coast. This undercurrent is strongest in summer and most persistent and organized in the south (south of 21°S). A subsurface oxygen minimum, centered at ˜250 m, is strongest at lower latitudes. Low-salinity subsurface water intrudes into the study area near 100 m, predominantly in offshore regions, strongest during summer and fall and in the southernmost portion of the region. The climatological fields are compared to features off Baja within the somewhat analogous California Current and to measurements from higher latitudes within the Chile

  8. Radiolarian Indices of Paleoproductivity Variation in the late Pleistocene Benguela Upwelling System, ODP Site 1084

    Science.gov (United States)

    Bittniok, B. B.; Lazarus, D. B.; Diester-Haass, L.; Billups, K.; Meyers, P.

    2006-12-01

    Changes in export productivity play a significant role in ocean carbon budgets and global climate change. Proxies for export productivity can be difficult to interpret: benthic foraminifera accumulation rates (BFAR) can be affected by carbonate dissolution in organic-carbon rich sediments; bulk opal can be affected by silica limitation of source waters. Recent work (Lazarus et al. 2006; Mar. Micropal.) has shown that a new index based on radiolarian faunal changes (WADE ratio) correlates well to total organic carbon (TOC) values from the same samples over the long term (latest Miocene-Recent) history of productivity in the Benguela Upwelling System (BUS). We present new data on variation in export productivity proxies (WADE, TOC, carbonate, radiolarian opal, BFAR) for the last glacial-interglacial cycle from ODP Site 1084, located just offshore from the main coastal upwelling cells of the BUS. Our age model, from mean Quaternary sedimentation rates (Leg 175 Scientific Results), is in accordance with cyclic variation in other climate sensitive parameters (carbonate and color reflectance). Although opal content and radiolarian preservation is only moderate in our samples, WADE values vary significantly and suggest higher productivity during the last glacial, in accordance with current interpretations of BUS history. Radiolarian opal accumulation is also higher during the last glacial, suggesting that silica limitation (opal paradox) conditions did not dominate over this time period. Similar results for bulk opal have been reported from late Quaternary piston cores from the more northerly Congo upwelling region (Schneider et al, 1997; Paleoc.). We conclude that WADE ratios are a useful proxy for late Pleistocene productivity in the BUS at glacial- interglacial time scales.

  9. Phytoplankton stimulation in frontal regions of Benguela upwelling filaments by internal factors

    Directory of Open Access Journals (Sweden)

    Norbert Wasmund

    2016-11-01

    Full Text Available Filaments are intrusions of upwelling water into the sea, separated from the surrounding water by fronts. Current knowledge explains the enhanced primary production and phytoplankton growth found in frontal areas by external factors like nutrient input. The question is whether this enhancement is also caused by intrinsic factors, i.e. simple mixing without external forcing. In order to study the direct effect of frontal mixing on organisms, disturbing external influx has to be excluded. Therefore mixing was simulated by joining waters originating from inside and outside the filament in mesocosms (tanks. These experiments were conducted during two cruises in the northern Benguela upwelling system in September 2013 and January 2014. The mixed waters reached a much higher net primary production and chlorophyll a (chla concentration than the original waters already 2-3 days after their merging. The peak in phytoplankton biomass stays longer than the chla peak. After their maxima, primary production rates decreased quickly due to depletion of the nutrients. The increase in colored dissolved organic matter (CDOM may indicate excretion and degradation. Zooplankton is not quickly reacting on the changed conditions. We conclude that already simple mixing of two water bodies, which occurs generally at fronts between upwelled and ambient water, leads to a short-term stimulation of the phytoplankton growth. However, after the exhaustion of the nutrient stock, external nutrient supply is necessary to maintain the enhanced phytoplankton growth in the frontal area. Based on these data, some generally important ecological factors are discussed as for example nutrient ratios and limitations, silicate requirements and growth rates.

  10. Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

    Directory of Open Access Journals (Sweden)

    A. Randelhoff

    2018-04-01

    Full Text Available The future of Arctic marine ecosystems has received increasing attention in recent years as the extent of the sea ice cover is dwindling. Although the Pacific and Atlantic inflows both import huge quantities of nutrients and plankton, they feed into the Arctic Ocean in quite diverse regions. The strongly stratified Pacific sector has a historically heavy ice cover, a shallow shelf and dominant upwelling-favourable winds, while the Atlantic sector is weakly stratified, with a dynamic ice edge and a complex bathymetry. We argue that shelf break upwelling is likely not a universal but rather a regional, albeit recurring, feature of the new Arctic. It is the regional oceanography that decides its importance through a range of diverse factors such as stratification, bathymetry and wind forcing. Teasing apart their individual contributions in different regions can only be achieved by spatially resolved time series and dedicated modelling efforts. The Northern Barents Sea shelf is an example of a region where shelf break upwelling likely does not play a dominant role, in contrast to the shallower shelves north of Alaska where ample evidence for its importance has already accumulated. Still, other factors can contribute to marked future increases in biological productivity along the Arctic shelf break. A warming inflow of nutrient-rich Atlantic Water feeds plankton at the same time as it melts the sea ice, permitting increased photosynthesis. Concurrent changes in sea ice cover and zooplankton communities advected with the boundary currents make for a complex mosaic of regulating factors that do not allow for Arctic-wide generalizations.

  11. Short commentary on marine productivity at Arctic shelf breaks: upwelling, advection and vertical mixing

    Science.gov (United States)

    Randelhoff, Achim; Sundfjord, Arild

    2018-04-01

    The future of Arctic marine ecosystems has received increasing attention in recent years as the extent of the sea ice cover is dwindling. Although the Pacific and Atlantic inflows both import huge quantities of nutrients and plankton, they feed into the Arctic Ocean in quite diverse regions. The strongly stratified Pacific sector has a historically heavy ice cover, a shallow shelf and dominant upwelling-favourable winds, while the Atlantic sector is weakly stratified, with a dynamic ice edge and a complex bathymetry. We argue that shelf break upwelling is likely not a universal but rather a regional, albeit recurring, feature of the new Arctic. It is the regional oceanography that decides its importance through a range of diverse factors such as stratification, bathymetry and wind forcing. Teasing apart their individual contributions in different regions can only be achieved by spatially resolved time series and dedicated modelling efforts. The Northern Barents Sea shelf is an example of a region where shelf break upwelling likely does not play a dominant role, in contrast to the shallower shelves north of Alaska where ample evidence for its importance has already accumulated. Still, other factors can contribute to marked future increases in biological productivity along the Arctic shelf break. A warming inflow of nutrient-rich Atlantic Water feeds plankton at the same time as it melts the sea ice, permitting increased photosynthesis. Concurrent changes in sea ice cover and zooplankton communities advected with the boundary currents make for a complex mosaic of regulating factors that do not allow for Arctic-wide generalizations.

  12. Radiocarbon dating of samples for archaeologic and geologic interesting by liquid scintillation spectrometry with low background radiation

    International Nuclear Information System (INIS)

    Pessenda, L.C.R.; Camargo, P.B. de

    1991-01-01

    An analytical system for radiocarbon dating of environmental samples using low level liquid scintillation counting spectrometry was developed at the Center for Nuclear Energy in Agriculture, University of Sao Paulo. Physical and chemical pretreatment and benzene synthesis of samples, counting procedure, optimization of analytical parameters and laboratory intercomparison with radiocarbon laboratories of Center for Applied Isotope Studies, University of Georgia, USA and University of Waterloo, Canada, are described. (author)

  13. Towards constraining the stratosphere-troposphere exchange of radiocarbon: strategies of stratospheric 14CO2 measurements using AirCore

    Science.gov (United States)

    Chen, Huilin; Paul, Dipayan; Meijer, Harro; Miller, John; Kivi, Rigel; Krol, Maarten

    2016-04-01

    Radiocarbon (14C) plays an important role in the carbon cycle studies to understand both natural and anthropogenic carbon fluxes, but also in atmospheric chemistry to constrain hydroxyl radical (OH) concentrations in the atmosphere. Apart from the enormous 14C emissions from nuclear bomb testing in the 1950s and 1960s, radiocarbon is primarily produced in the stratosphere due to the cosmogenic production. To this end, better understanding the stratospheric radiocarbon source is very useful to advance the use of radiocarbon for these applications. However, stratospheric 14C observations have been very limited so that there are large uncertainties on the magnitude and the location of the 14C production as well as the transport of radiocarbon from the stratosphere to the troposphere. Recently we have successfully made stratospheric 14C measurements using AirCore samples from Sodankylä, Northern Finland. AirCore is an innovative atmospheric sampling system, which passively collects atmospheric air samples into a long piece of coiled stainless steel tubing during the descent of a balloon flight. Due to the relatively low cost of the consumables, there is a potential to make such AirCore profiling in other parts of the world on a regular basis. In this study, we simulate the 14C in the atmosphere and assess the stratosphere-troposphere exchange of radiocarbon using the TM5 model. The Sodankylä radiocarbon measurements will be used to verify the performance of the model at high latitude. Besides this, we will also evaluate the influence of different cosmogenic 14C production scenarios and the uncertainties in the OH field on the seasonal cycles of radiocarbon and on the stratosphere-troposphere exchange, and based on the results design a strategy to set up a 14C measurement program using AirCore.

  14. Biological response to coastal upwelling and dust deposition in the area off Northwest Africa

    Science.gov (United States)

    Ohde, T.; Siegel, H.

    2010-05-01

    Nutrient supply in the area off Northwest Africa is mainly regulated by two processes, coastal upwelling and deposition of Saharan dust. In the present study, both processes were analyzed and evaluated by different methods, including cross-correlation, multiple correlation, and event statistics, using remotely sensed proxies of the period from 2000 to 2008 to investigate their influence on the marine environment. The remotely sensed chlorophyll- a concentration was used as a proxy for the phytoplankton biomass stimulated by nutrient supply into the euphotic zone from deeper water layers and from the atmosphere. Satellite-derived alongshore wind stress and sea-surface temperature were applied as proxies for the strength and reflection of coastal upwelling processes. The westward wind and the dust component of the aerosol optical depth describe the transport direction of atmospheric dust and the atmospheric dust column load. Alongshore wind stress and induced upwelling processes were most significantly responsible for the surface chlorophyll- a variability, accounting for about 24% of the total variance, mainly in the winter and spring due to the strong north-easterly trade winds. The remotely sensed proxies allowed determination of time lags between biological response and its forcing processes. A delay of up to 16 days in the surface chlorophyll- a concentration due to the alongshore wind stress was determined in the northern winter and spring. Although input of atmospheric iron by dust storms can stimulate new phytoplankton production in the study area, only 5% of the surface chlorophyll- a variability could be ascribed to the dust component in the aerosol optical depth. All strong desert storms were identified by an event statistics in the time period from 2000 to 2008. The 57 strong storms were studied in relation to their biological response. Six events were clearly detected in which an increase of chlorophyll- a was caused by Saharan dust input and not by

  15. Biological consequences of environmental changes related to coastal upwelling: a simulation study

    Energy Technology Data Exchange (ETDEWEB)

    Howe, S.O.

    1979-05-01

    Two simulation models of marine ecosystem dynamics are formulated and applied to field data. The first is a time-dependent model of phytoplankton growth in nutrient-enriched batch cultures where spatial gradients of dependent variables and the effects of higher tropic level processes are not included. Rates of photosynthesis, nutrient uptake, chlorophyll synthesis and cell division for a single phytoplankton functional group are simulated as functions of photosynthetically active solar radiation, dissolved nutrient concentrations and cell quotas of carbon, nitrogen and silica. The second model combines the phytoplankton growth model with a time dependent, two-dimensional model of coastal upwelling off northwest Africa.

  16. L' upwelling de la côte atlantique du Maroc entre 1994 et 1998

    Science.gov (United States)

    Makaoui, Ahmed; Orbi, Abdelattif; Hilmi, Karim; Zizah, Soukaina; Larissi, Jamila; Talbi, Mohammed

    2005-12-01

    The pelagic ecosystem of the Moroccan Atlantic coast is influenced by the spatiotemporal variability of upwelling. The changes in the physicochemical and biological parameters as well as their interrelationship and regrouping by the principal components analysis allowed us to subdivide the Atlantic coast in four active areas: two areas located at the north of Cape Juby (28°N), characterised by a summery activity and two areas located at the south, active permanently, with a variable intensity. To cite this article: A. Makaoui et al., C. R. Geoscience 337 (2005).

  17. Bowhead whale body condition and links to summer sea ice and upwelling in the Beaufort Sea

    Science.gov (United States)

    George, John C.; Druckenmiller, Matthew L.; Laidre, Kristin L.; Suydam, Robert; Person, Brian

    2015-08-01

    We examined the response of bowhead whale (Balaena mysticetus) body condition to summer sea ice conditions and upwelling-favorable winds. We used a long-term dataset collected from whales of the Bering-Chukchi-Beaufort Seas (BCB) stock to estimate various body condition indices (BCI's) for individual whales that were harvested by Alaskan Eskimos. A series of offshore regions frequented by bowhead whales in summer were delineated and used to quantify interannual summertime environmental conditions including: (a) mean open water fraction, (b) duration of melt season, (c) date of continuous freeze-up, and (d) mean upwelling-favorable wind stress. Body condition was analyzed relative to these metrics for both the preceding summer feeding season and the previous three seasons combined. Our analysis indicates a significant increase in the long-term trend in an axillary girth-based body condition index (BCIG) over the study period (1989-2011). The increase in BCIG is likely associated with the trend in overall reduction of sea ice, including increased duration of open water, changes in upwelling potential (wind stress), and possibly higher primary production in the Pacific Arctic marine ecosystem favoring water-column invertebrates. We found strong significant positive correlations between BCIG and late summer open water fraction in the Beaufort Sea and smaller nearshore areas off the Mackenzie Delta and west of Banks Island. Additionally, BCIG was positively and significantly correlated with duration of melt season, later date of freeze-up in the Beaufort Sea, and upwelling-favorable winds on the Mackenzie shelf and west of Banks Island. A strong seasonal difference in BCI's was noted for subadult bowheads, presumably associated with summer feeding; however, yearlings were found to drop in BCI over at least the first summer after weaning. Our results indicate an overall increase in bowhead whale body condition and a positive correlation with summer sea ice loss over the

  18. Regulation of bacterial sulfate reduction and hydrogen sulfide fluxes in the central Namibian coastal upwelling zone

    DEFF Research Database (Denmark)

    Bruchert, V.; Jørgensen, BB; Neumann, K.

    2003-01-01

    The coastal upwelling system off central Namibia is one of the most productive regions of the oceans and is characterized by frequently occurring shelf anoxia with severe effects for the benthic life and fisheries. We present data on water column dissolved oxygen, sulfide, nitrate and nitrite, pore......-depleted bottom waters, the oxygen minimum zone on the continental slope, and the lower continental slope below the oxygen minimum zone. High concentrations of dissolved sulfide, up to 22 mM, in the near-surface sediments of the inner shelf result from extremely high rates of bacterial sulfate reduction...

  19. Radiocarbon signal of a low and intermediate level radioactive waste disposal facility in nearby trees.

    Science.gov (United States)

    Janovics, R; Kelemen, D I; Kern, Z; Kapitány, S; Veres, M; Jull, A J T; Molnár, M

    2016-03-01

    Tree ring series were collected from the vicinity of a Hungarian radioactive waste treatment and disposal facility and from a distant control background site, which is not influenced by the radiocarbon discharge of the disposal facility but it represents the natural regional (14)C level. The (14)C concentration of the cellulose content of tree rings was measured by AMS. Data of the tree ring series from the disposal facility was compared to the control site for each year. The results were also compared to the (14)C data of the atmospheric (14)C monitoring stations at the disposal facility and to international background measurements. On the basis of the results, the excess radiocarbon of the disposal facility can unambiguously be detected in the tree from the repository site. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Old ages of two historical Romanian trees assessed by AMS radiocarbon dating

    International Nuclear Information System (INIS)

    Patrut, Adrian; Reden, Karl F. von; Lowy, Daniel A.; Patrut, Roxana T.; Lucian Vaida, D.; Margineanu, Dragos

    2013-01-01

    Two large Romanian poplars are considered to be associated with significant historical events of the past. In order to verify these claims, wood samples collected from the broken trunks of the two poplars were radiocarbon dated by AMS. The oldest radiocarbon dates were found to be 275 ± 20 bp for the black poplar of Mocod and 316 ± 22 bp for the gray poplar of Rafaila. These values correspond to calibrated ages of 365 ± 10 and 465 ± 25 years, respectively. The dating results indicate old ages for the two trees, i.e., 455 years for the Mocod poplar and 560 years for the Rafaila poplar. Such age values validate historical information on the two large Romanian trees.

  1. Radiocarbon dating of ancient bronze statues: Preliminary results from the Riace statues

    International Nuclear Information System (INIS)

    Calcagnile, L.; D'Elia, M.; Quarta, G.; Vidale, M.

    2010-01-01

    The low amount of material needed for the measurements makes AMS radiocarbon a technique suitable for the dating of ancient bronze artefacts through the analysis of the organic residues contained into the casting cores. We present the results of the AMS radiocarbon dating analyses carried out on the organic remains extracted from the casting cores of the Riace bronzes, among the most famous and well preserved sculptures of the Greek-Classical period. Although different dating hypotheses have been suggested on the base of stylistic considerations, no conclusive answers are, so far, available. The sample selection and preparation protocols of the different kind of organic materials (charred wood, vegetal remains and animal hairs) are described as well as the interpretation of the results in the frame of the current dating hypotheses and available analytical information about the casting technology.

  2. Inversions of radiocarbon age of humus in the profile of modern soils

    International Nuclear Information System (INIS)

    Chichagova, O.A.; Cherkinskij, A.E.; Tolchel'nikov, Yu.S.

    1984-01-01

    Exogenous and endogenous inversions of humus radiocarbon age in the orofile of modern soils are studied. The reasons for exogenous and endogenous invesrsions are enumerated and examples are given. Thus, the exogenous inversion of the chernozem by the underbush (Kursk region) is explained by a high activity of soricids. The age determination of the disturbed profile in the depth of 49-59 cm turns out to be rejuvanated - 1820+-70 years and that of the non-disturbed one - 4050+-60 years. A conclusion is made on the necessity of a detailed analysis of each soil profile, specific features of its genesis as well as a possibility of postgenetic transformations, especially Anthropogenic ones. In this case an interpretation of the radiocarbon data will be more accurate

  3. New radiocarbon dates for terminal Pleistocene and early Holocene settlements in West Turkana, northern Kenya

    Science.gov (United States)

    Beyin, Amanuel; Prendergast, Mary E.; Grillo, Katherine M.; Wang, Hong

    2017-07-01

    The Turkana Basin in northern Kenya is located in an environmentally sensitive region along the eastern African Rift system. Lake Turkana's sensitivity to fluctuations in precipitation makes this an ideal place to study prehistoric human adaptations during key climatic transitions. Here we present eleven radiocarbon dates from two recently excavated sites in West Turkana, Kokito 01 and Kokito 02. The sites span the Pleistocene-Holocene transition, a time of fluctuating lake levels and novel cultural responses within the region. Several scenarios are laid out for the interpretation of site chronologies, and these are discussed with reference to the terminal Pleistocene and early Holocene chronological record for the region. Given the paucity of well-dated sites from this timespan in the Turkana Basin, the new radiocarbon dates are an important step toward establishing human settlement history and associated cultural developments in the region.

  4. AMS radiocarbon investigation of the African baobab: Searching for the oldest tree

    Energy Technology Data Exchange (ETDEWEB)

    Patrut, Adrian, E-mail: apatrut@gmail.com [Babes-Bolyai University, Department of Chemistry, Arany Janos 11, 400028 Cluj-Napoca (Romania); Reden, Karl F. von [Woods Hole Oceanographic Institution, Department of Geology and Geophysics, NOSAMS Facility, 360 Woods Hole Rd., Mailstop 8, Woods Hole, MA 02543 (United States); Mayne, Diana H. [Baobab Trust, P.O. Box 1566, Parklands 2121, Johannesburg (South Africa); Lowy, Daniel A. [FlexEl, LLC, 387 Technology Drive, College Park, MD 20742 (United States); Patrut, Roxana T. [Babes-Bolyai University, Department of Biology and Geology, Gh. Bilascu 44, 400015 Cluj-Napoca (Romania)

    2013-01-15

    The Glencoe baobab, a very large specimen from South Africa, split twice in 2009. Several wood samples were collected from the eastern cavity, from the outer part of the main section and also from the largest broken segment which was connected to this section. These wood samples were processed and investigated by AMS radiocarbon dating. The radiocarbon date of the oldest sample was found to be 1838 {+-} 21 BP, which corresponds to a calibrated age of 1835 {+-} 40 years. Thus, the Glencoe baobab becomes the oldest dated baobab and also the oldest angiosperm tree with accurate dating results. The distribution of dating results revealed that the Glencoe baobab is a multi-generation tree, with several standing or collapsed and partially fused stems, showing different ages.

  5. Old ages of two historical Romanian trees assessed by AMS radiocarbon dating

    Energy Technology Data Exchange (ETDEWEB)

    Patrut, Adrian, E-mail: apatrut@gmail.com [Babes-Bolyai University, Department of Chemistry, Arany Janos 11, 400028 Cluj-Napoca (Romania); Reden, Karl F. von [Woods Hole Oceanographic Institution, Department of Geology and Geophysics, NOSAMS Facility, 360 Woods Hole Rd., Mailstop 8, Woods Hole, MA 02543 (United States); Lowy, Daniel A. [FlexEl, LLC, 387 Technology Drive, College Park, MD 20742 (United States); Patrut, Roxana T. [Babes-Bolyai University, Department of Biology and Geology, Gh. Bilascu 44, 400015 Cluj-Napoca (Romania); Lucian Vaida, D. [Museum of Border Regiment Nasaud, Granicerilor 19, 425200 Nasaud (Romania); Margineanu, Dragos [Babes-Bolyai University, Department of Chemistry, Arany Janos 11, 400028 Cluj-Napoca (Romania)

    2013-01-15

    Two large Romanian poplars are considered to be associated with significant historical events of the past. In order to verify these claims, wood samples collected from the broken trunks of the two poplars were radiocarbon dated by AMS. The oldest radiocarbon dates were found to be 275 {+-} 20 bp for the black poplar of Mocod and 316 {+-} 22 bp for the gray poplar of Rafaila. These values correspond to calibrated ages of 365 {+-} 10 and 465 {+-} 25 years, respectively. The dating results indicate old ages for the two trees, i.e., 455 years for the Mocod poplar and 560 years for the Rafaila poplar. Such age values validate historical information on the two large Romanian trees.

  6. Inclusions in bone material as a source of error in radiocarbon dating

    International Nuclear Information System (INIS)

    Hassan, A.A.; Ortner, D.J.

    1977-01-01

    Electron probe microanalysis, X-ray diffraction and microscopic examination were conducted on bone material from several archaeological sites in order to identify post-burial inclusions which, if present, may affect radiocarbon dating of bone. Two types of inclusions were identified: (1) precipitates from ground water solutions, and (2) solid intrusion. The first type consists of calcite, pyrite, humates and an unknown material. The second type includes quartz grains, hyphae, rootlets, wood and charcoal. Precipitation of calcite in a macro-molecular level in bone may lead to erroneaous dating of bone apatite if such calcite was not removed completely. A special technique, therefore, must be employed to remove calcite comletely. Hyphae and rootlets also are likely to induce errors in radiocarbon dating of bone collagen. These very fine inclusions require more than hand picking. (author)

  7. Enhancing sample preparation capabilities for accelerator mass spectrometry radiocarbon and radiocalcium studies

    International Nuclear Information System (INIS)

    Taylor, R.E.

    1991-01-01

    With support provided by the LLNL Accelerator Mass Spectrometry Laboratory, the UCR Radiocarbon Laboratory continued its studies involving sample pretreatment and target preparation for both AMS radiocarbon ( 14 C) and radiocalcium ( 41 Ca) involving applications to archaeologically -- and paleoanthropologically- related samples. With regard to AMS 14 C-related studies, we have extended the development of a series of procedures which have, as their initial goal, the capability to combust several hundred microgram amounts of a chemically-pretreated organic sample and convert the resultant CO 2 to graphitic carbon which will consistently yield relatively high 13 C - ion currents and blanks which will yield, on a consistent basis, 14 C count rates at or below 0.20% modern, giving an 2 sigma age limit of >50,000 yr BP

  8. Radiocarbon dating the end of moa-hunting in New Zealand prehistory

    International Nuclear Information System (INIS)

    Schmidt, M.

    2000-01-01

    For over 150 years, New Zealand scientists and prehistorians have investigated and debated when the last moa (Aves : Dinornithiformes) was hunted and killed by humans (see Anderson 1989). Prior to the introduction of radiocarbon dating into New Zealand archaeology in the mid-1950s, theories on when moa predation ended were based on Maori oral tradition, dubious eye witness accounts, moa bones found on the surface of the ground and arbitrary archaeological excavations of large culling sites. Radiocarbon dating provided an absolute chronological tool for determining when the remains of moa found in prehistoric context were deposited, meaning the activity of moa-hunting could be more easily attributed to a particular period in New Zealand prehistory. (author)

  9. Simultaneous measurement of tritium and radiocarbon by ultra-low-background proportional counting

    Energy Technology Data Exchange (ETDEWEB)

    Mace, Emily; Aalseth, Craig; Alexander, Tom; Back, Henning; Day, Anthony; Hoppe, Eric; Keillor, Martin; Moran, Jim; Overman, Cory; Panisko, Mark; Seifert, Allen

    2017-08-01

    Use of ultra-low-background capabilities at Pacific Northwest National Laboratory provide enhanced sensitivity for measurement of low-activity sources of tritium and radiocarbon using proportional counters. Tritium levels are nearly back to pre-nuclear test backgrounds (~2-8 TU in rainwater), which can complicate their dual measurement with radiocarbon due to overlap in the isotope’s respective energy spectra. This activity makes direct dual-isotope measurements challenging without additional chemistry to concentrate the tritium in a sample. We present results of single-isotope proportional counter measurements used to analyze a dual-isotope methane sample synthesized from ~120 mg of H2O and present sensitivity results.

  10. Radiocarbon dating of floodplain and young terraces alluvial sediments of Latvia rivers

    International Nuclear Information System (INIS)

    Eberhards, G.; Saltupe, B.

    2000-01-01

    This paper include new information about alluvial sediments structure and radiocarbon data of some Latvia free-meandering rivers (Gauja, Ogre, Liela and Maza Jugla, Daugava) floodplains and first terraces. In this present study we examined Gauja river floodplains in the different geomorphological and geological areas. Radiocarbon dating add the fact that the high level floodplain (4-5 m) formation and sediment accumulation take place 3000-5000 years before present (BP) middle level floodplains formed 1500-2100 years BP. Investigations show that one river terraces and floodplains with same relative height have a several absolute age. The rivers crossed same hypsometrical regions (highlands, lowlands) downstream in lowlands alluvial terraces performed as floodplains or from from floodplains to terraces with same height. On the highest, middle and in the lower parts of the rivers with free - meandering channel to - day the dynamic balance of the channel processes exits 4000-5000 years. (author)

  11. Initial observation of upwelling along east coast of Peninsular Malaysia musica-gratis.softonic.it/ >musica gratis

    Science.gov (United States)

    Akhir, M.; Tanggang, F.

    2013-12-01

    There is no published evidence of upwelling in coastal area along the east coast of Peninsular Malaysia. However numbers of recent cruise data collected during the southwest monsoon found features of thermocline lifting and isolated cooler temperature water along the coast, These sign was observed along the 104°E from numbers of parallel transects. To confirm the presence of upwelling, satellite remote sensing data was used, and numerical model experiments were conducted. Cooler sea-surface temperature along the coast was observed from both in-situ and satellite data, while upward movement in the vertical profiles agreed with the location of upwelling from both in-situ and satellite data. Moreover, these data also show that the upwelled water band along the 104°E longitude stretch approximately 650 km long. Initially, southwesterly wind during this season is believed to be the important mechanism that contributed to this wind-induced Ekman upwelling. musica-gratis.softonic.it/ >musica gratis

  12. Coastal upwelling by wind-driven forcing in Jervis Bay, New South Wales: A numerical study for 2011

    Science.gov (United States)

    Sun, Youn-Jong; Jalón-Rojas, Isabel; Wang, Xiao Hua; Jiang, Donghui

    2018-06-01

    The Princeton Ocean Model (POM) was used to investigate an upwelling event in Jervis Bay, New South Wales (SE Australia), with varying wind directions and strengths. The POM was adopted with a downscaling approach for the regional ocean model one-way nested to a global ocean model. The upwelling event was detected from the observed wind data and satellite sea surface temperature images. The validated model reproduced the upwelling event showing the input of bottom cold water driven by wind to the bay, its subsequent deflection to the south, and its outcropping to the surface along the west and south coasts. Nevertheless, the behavior of the bottom water that intruded into the bay varied with different wind directions and strengths. Upwelling-favorable wind directions for flushing efficiency within the bay were ranked in the following order: N (0°; northerly) > NNE (30°; northeasterly) > NW (315°; northwesterly) > NE (45°; northeasterly) > ENE (60°; northeasterly). Increasing wind strengths also enhance cold water penetration and water exchange. It was determined that wind-driven downwelling within the bay, which occurred with NNE, NE and ENE winds, played a key role in blocking the intrusion of the cold water upwelled through the bay entrance. A northerly wind stress higher than 0.3 N m-2 was required for the cold water to reach the northern innermost bay.

  13. Radiocarbon dating of a Japanese ancient document 'Minamoto no Yoritomo Sodehan Migyosho' by AMS

    International Nuclear Information System (INIS)

    Oda, H.; Nakaura, T.; Akiyama, M.

    2005-01-01

    In this study, radiocarbon age of a Japanese ancient document 'Minamoto no Yoritomo Sodehan Migyosho' was measured by AMS. The purpose of this study is to judge whether the document is genuine or not. The document descended to the Matsugi family which had controlled the craftsmen of metal casting. The document has a description of the written age, AD1189. The content of the document is about the formal recognition of their authority over the craftsmen by Minamoto no Yoritomo who established the first military government in AD1192. This document is written on a slightly-blackish-paper sheet called Shukushi. Shukushi paper sheets had been commonly used for the official documents of the Emperor. Therefore, if the document was really issued by Minamoto no Yoritomo, it can be a sole example as the document of warrior class among the extant Shukushi paper. The paleographical views, however, suggested that the document may be a counterfeit written in several centuries later. Japanese paper fragment is a suitable sample for radiocarbon dating because there is little discrepancy between the calibrated radiocarbon age and the written age. The calibrated radiocarbon age of 'Minamoto no Yoritomo Sodehan Migyosho' indicated the 16th century or the first half of the 17th century. This age corresponds to the period when the ancestor of Matsugi family appeared in Japanese history. This result shows that the document was forged in the Warring State Period for the legitimacy of their control over the craftsmen. The Shukusi used for the counterfeit document of warrior class is the outcome of the forger's misunderstanding that Shukushi paper should be used for the important documents.

  14. New radiocarbon dates for the transition from middle to upper palaeolithic at El Castillo (Cantabria)

    International Nuclear Information System (INIS)

    Valladas, H.; Cabrera-Valdes, V.; De Quiros, F.B.

    1996-01-01

    The stratigraphic sequence at the El Castillo cave in Cantabria, Spain, extends from Lower to Upper Palaeolithic. The transition from Middle to Upper Palaeolithic is represented by levels assigned to Quina Mousterian and Early Aurignacian. Accelerator Mass Spectrometry Radiocarbon dates put the archaic Aurignacian industries at ca. 40,000 years ago and indicate that in northern Spain the Upper Palaeolithic began several millennia earlier than in other parts of western Europe. (authors). 16 refs., 1 tab

  15. From 14C/12C measurements towards radiocarbon dating of ice

    NARCIS (Netherlands)

    Oerlemans, J.; Wal, R.S.W. van de; Roijen, J.J. van; Raynaud, D.; Borg, K. van der; Jong, A.F.M. de; Lipenkov, V.; Huybrechts, P.

    1994-01-01

    A dry extraction method of CO2 included in glacier ice adds a contamination equivalent to 1.8 μg modern carbon for a 35 μg C sample. This enables radiocarbon dating by accelerator mass spectrometry of 35 μg C samples to about 25 000 BP. Measured 14C/12C ratios are presented for a part of the Vostok

  16. Preparation of graphite targets for radiocarbon dating by tandem accelerator mass spectrometer (TAMS)

    International Nuclear Information System (INIS)

    Lowe, D.C.

    1984-01-01

    The introduction of TAMS has exciting implications for radiocarbon dating but improved sample preparation methods are needed. This paper describes a promising method for the conversion of a few milligrams of wood or charcoal into graphite targets for use in a caesium sputter ion source. Targets containing a large proportion of G-type graphite produced large C - currents, but those containing a high proportion of turbostatic Tn graphite were unsatisfactory; the type of graphite in the target is clearly of significance. (author)

  17. Radiocarbon facility at the Research Laboratory for Archaeology in Oxford - a review

    International Nuclear Information System (INIS)

    White, N.R.; Hedges, R.E.M.; Wand, J.O.; Hall, E.T.

    1981-01-01

    The Oxford accelerator mass spectrometry facility is primarily intended for radiocarbon work. It has been designed and built within the department, except for the 3 MV tandem, which is being purchased from General Ionex and is still awaited. This system has been described many times before, so this paper will not give a comprehensive description of the facility, but only cover in detail areas of recent progress, or areas where our approach differs from other labs

  18. Radiocarbon dates from Wairau Bar and their implications for the prehistoric colonisation of New Zealand

    International Nuclear Information System (INIS)

    Higham, T.F.G.; Anderson, A.J.

    1997-01-01

    A set of thirteen moa eggshell samples from burial features at the Wairau Bar site were used for dating. The samples were obtained from the Canterbury Museum in Christchurch where they have been displayed as part of a permanent exhibition.Three marine shell samples were also analysed. Radiocarbon dating of the samples was carried out using conventional and AMS techniques. The results will be presented and the archaeological implications for the prehistoric colonization of New Zealand will be discussed

  19. Radiocarbon constraints on the glacial ocean circulation and its impact on atmospheric CO2

    Science.gov (United States)

    Skinner, L. C.; Primeau, F.; Freeman, E.; de la Fuente, M.; Goodwin, P. A.; Gottschalk, J.; Huang, E.; McCave, I. N.; Noble, T. L.; Scrivner, A. E.

    2017-01-01

    While the ocean’s large-scale overturning circulation is thought to have been significantly different under the climatic conditions of the Last Glacial Maximum (LGM), the exact nature of the glacial circulation and its implications for global carbon cycling continue to be debated. Here we use a global array of ocean–atmosphere radiocarbon disequilibrium estimates to demonstrate a ∼689±53 14C-yr increase in the average residence time of carbon in the deep ocean at the LGM. A predominantly southern-sourced abyssal overturning limb that was more isolated from its shallower northern counterparts is interpreted to have extended from the Southern Ocean, producing a widespread radiocarbon age maximum at mid-depths and depriving the deep ocean of a fast escape route for accumulating respired carbon. While the exact magnitude of the resulting carbon cycle impacts remains to be confirmed, the radiocarbon data suggest an increase in the efficiency of the biological carbon pump that could have accounted for as much as half of the glacial–interglacial CO2 change. PMID:28703126

  20. Radiocarbon AMS determination of the biogenic component in CO2 emitted from waste incineration

    International Nuclear Information System (INIS)

    Calcagnile, L.; Quarta, G.; D’Elia, M.; Ciceri, G.; Martinotti, V.

    2011-01-01

    The thermal utilization of waste for energy production is gaining importance in European countries. Nevertheless, the combustion of waste leads to significant CO 2 emissions in the atmosphere which, depending on the fraction of biogenic and fossil materials, have to be only partially accounted for the national greenhouse gas inventory. For this reason the development of proper methodologies for the measurement of the biogenic fraction in the combusted waste is an active research field. In fact the determination of the radiocarbon concentration in the carbon dioxide stack emissions allows to have a direct indication of the biogenic component in the burned fuel. We present the results of the AMS radiocarbon analyses carried out on carbon dioxide sampled at the stack of three power plants located in Northern Italy burning natural gas, landfill biogas and SRF (Solid Recovered Fuel) derived from MSW (Municipal Solid Waste). The sampling apparatus and the applied processing protocols are described together with the calculation procedures used to determine, from the measured radiocarbon concentrations, the proportion of biogenic and fossil component in the flue gas and in the combusted fuel. The results confirm the high potentialities of this approach in the analysis of industrial CO 2 emissions.

  1. The comparison of absolute dating (Radiocarbon dating) and relative dating of Pringapus and Gondosuli temples

    International Nuclear Information System (INIS)

    Faisal, W; Arumbinang, H; Taftazani, A; Widayati, S; Sumiyatno; Suhardi

    1996-01-01

    The absolute dating (radiocarbon, 14 C dating) and relative dating of Pringapus and Gondosuli temples in Temanggung regency (district) of Central Java Province have been carried out. The field sampling was done especially with the purpose to obtain vertical data, so that excavation method was adopted in the case. The main data were the ecofacts of organic habitation such as bones, woods, charcoals, shells, and paper artefacts. The artefacts data were used as a comparison. The comparative data analysis were conducted at Yogyakarta archaeological Department Laboratory, thus included dating of artefacts which were performed according to archaeological analysis procedures, generally based on the attributes attached to the artefacts, whereas the absolute dating of charcoal samples were performed in the Radiocarbon Dating Laboratory at Yogyakarta Nuclear Research Centre. Based on the relative dating of epigraphy content on the andesit rock from Gondosuli Temple which showed the year of 754 Saka or 832 AD, the Pringapus Temple was estimated to be built in the 850 AD. According to the absolute dating (Radiocarbon Dating with delta 13 C and tree ring corrections) the age for Gondosuli temple based on GDS/LU-2/Spit-7 samples is (384 -602) AD and from GDS/LU-2/Spit-8 = (452 - 652) AD. With these significant differences in the results obtained, it can be concluded that culture environment where the sample were collected already existed before the temple was built. Further investigation is still required

  2. Radiocarbon in dissolved organic matter in the central North Pacific Ocean

    International Nuclear Information System (INIS)

    Williams, P.M.; Druffel, E.R.M.

    1987-01-01

    The authors present the first detailed profile of radiocarbon measured in dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in the oligotrophic gyre of the central North Pacific. Δ 14 C of DOC ranged from -150 per mille (1,310 yr BP) in surface waters to -540 per mille (6,240 yr BP) at 5,710 m, 40 m off the bottom. The surprising similarity in the shapes of the profiles of Δ 14 C in the DOC and DIC pools suggest that similar processes are controlling the radiocarbon distribution in each of the two reservoirs and that bomb-produced radiocarbon has penetrated the DOC + DIC pools to a depth of ∼ 900 m. The depletion of the Δ 14 Csub(DOC) values by 300 per mille with respect to the Δ 14 Csub(DIC) values suggests that a certain fraction of the DOC is recycled within the ocean on longer time-scales than DIC. (author)

  3. Radiocarbon dating of a pine tree (Pinus densiflora) from Yeongwol, Korea

    International Nuclear Information System (INIS)

    Kim, C.H.; Lee, J.H.; Kang, J.; Song, S.; Yun, M.H.; Kim, J.C.

    2015-01-01

    We report the results of the dating of a pine tree (Pinus densiflora) from Yeongwol, Korea. The age of the tree was estimated to be in the range of hundreds of years, however, the tree had been broken by a strong wind in March 2010 and now only the stump of the tree is left. At the time of sampling in 2014, there were several decayed parts in the stump, so using the usual dendrochronological method (i.e. ring counting) for dating was difficult. However, we found a small wood sample with tree rings near the center of the stump that could be used for radiocarbon wiggle-match dating. Radiocarbon dates were determined using Accelerator mass spectrometry (AMS). The IntCal13 curve was used to calibrate the radiocarbon dates, and the wiggle matching technique was used to reduce the error of the calibrated ages. Based on the dating results, we suggest that the pine tree is approximately 300 years or older.

  4. Radiocarbon dating of lake sediments and peats by accelerator mass spectrometry

    International Nuclear Information System (INIS)

    Fowler, A.J.

    1985-01-01

    The small sample size requirement of accelerator mass spectrometry has allowed the measurement of the 14C/12C ratio for components of various lake sediment and peat samples, with a view to gaining greater understanding of sedimentary processes and to overcome some of the problems associated with conventional radiocarbon dating of sediments, where the 14C/12C ratio of the whole sample, less carbonate, is measured. Some of the fractions of sedimentary organic matter are amenable to analysis. Different molecules are specific to higher plants, algae and bacteria, so estimates of the major sources of input to the sediment can be made. The lipid fraction, though a small component (1%) of the total organic matter, yields most source information. Analyses of n-fatty acids and n-alkanes by capillary gas chromatography are used to interpret the radiocarbon result for the total crude lipid samples in the light of the environmental information so gained. Comparison of the various radiocarbon results for different components of the sediment has provided evidence for the importance of the amount of organic carbon in the samples, microbial attack during storage, the presence of mineral carbon, mixing, hard-water effects and the influence of terrestrial material on lake sediments. A regime has been proposed for the routine preparation of samples at an accelerator mass spectrometry facility in order to provide maximum useful information on a sediment sample. (author)

  5. Radiocarbon dating of Sphagnum cellulose from Mohos peat bog, East Carpathians

    Science.gov (United States)

    Hubay, Katalin; Braun, Mihály; Harangi, Sándor; Palcsu, László; Túri, Marianna; Rinyu, László; Molnár, Mihály

    2015-04-01

    This work focuses on building a high-resolution age-depth model for quantitative paleoclimate study from the Mohos peat bog, East Carpathians. Peats are important archives for Quaternary science, because they preserve environmental changes. To study the chronology of peat profiles the key is in the precise coring and reliable dating. However, many studies dealing with coring and radiocarbon dating of peat deposits they often shown problems with the proper methods and material. With our novel coring technique we reached undisturbed and uncompressed peat cores from the Mohos bog. A 10 meter deep peat profile was drilled in 2012 using a modified technique of a piston corer. The core presents a continuous peat profile from the last 11.500 cal. yr BP. The chronology was based on AMS radiocarbon analyses of the separated Sphagnum samples from different depths of the profile. The peat samples were wet sieved (40-280 μm) to avoid contamination by rootlets. Dry Sphagnum samples for AMS dating were prepared using the classical acid-base-acid (ABA) method completed with an oxidative bleaching step to get clean cellulose. Sphagnum cellulose samples were converted to CO2 and later graphite and measured by EnvironMICADAS accelerator mass spectrometry (AMS) in Hertelendi Laboratory (Debrecen, Hungary). Fine peat accumulation rate changes (sections with lowest accumulation values) were observed along the profile. Based on the chronology in further studies we want to focus special intervals to investigate environmental changes in the Holocene. Key words: peat, radiocarbon, cellulose

  6. AMS Radiocarbon Dating of Large Za Baobabs (Adansonia za) of Madagascar.

    Science.gov (United States)

    Patrut, Adrian; Patrut, Roxana T; Danthu, Pascal; Leong Pock-Tsy, Jean-Michel; Rakosy, Laszlo; Lowy, Daniel A; von Reden, Karl F

    2016-01-01

    The article reports the radiocarbon investigation of Anzapalivoro, the largest za baobab (Adansonia za) specimen of Madagascar and of another za, namely the Big cistern baobab. Several wood samples collected from the large inner cavity and from the outer part/exterior of the tree were investigated by AMS (accelerator mass spectrometry) radiocarbon dating. For samples collected from the cavity walls, the age values increase with the distance into the wood up to a point of maximum age, after which the values decrease toward the outer part. This anomaly of age sequences indicates that the inner cavity of Anzapalivoro is a false cavity, practically an empty space between several fused stems disposed in a ring-shaped structure. The radiocarbon date of the oldest sample was 780 ± 30 bp, which corresponds to a calibrated age of around 735 yr. Dating results indicate that Anzapalivoro has a closed ring-shaped structure, which consists of 5 fused stems that close a false cavity. The oldest part of the biggest za baobab has a calculated age of 900 years. We also disclose results of the investigation of a second za baobab, the Big cistern baobab, which was hollowed out for water storage. This specimen, which consists of 4 fused stems, was found to be around 260 years old.

  7. Radiocarbon data collection, filtering and analysis at the NRL TEAMS facility

    International Nuclear Information System (INIS)

    Tumey, S.J.; Grabowski, K.S.; Knies, D.L.; Mignerey, A.C.

    2004-01-01

    This report describes a novel approach to collection and analysis of radiocarbon data due to the unique design of the Naval Research Laboratory Trace Element Accelerator Mass Spectrometry system. In this approach, targets are loaded on the cathode wheel such that samples are clustered in groups of five between standards. Each target is measured until the external error asymptotically reaches a constant value and the internal error dominates, or until a predefined time limit is reached. These measurements are repeated until the desired level of counting statistics is attained. Cycle control software saves the measured beam currents and count rate, as well as all system parameters to disc at fixed intervals throughout each measurement. Data visualization software has aided in system diagnosis by exposing relationships between the measured isotope ratios and system parameters. A filtering algorithm is employed to the data set of each target measurement in an attempt to achieve a Gaussian distribution. Final results are generated by a radiocarbon calculator that allows a user to select which target measurements to treat as samples, standards and blanks, and calculates the desired values (i.e. conventional radiocarbon age, percent modern carbon, etc.) with full error propagation. Currently, a Microsoft Access [reg] relational database is being developed which will be integrated into the existing LabVIEW [reg] control, filtering and calculation programs in order to streamline the process from sample submission to report generation, as well as improve quality control

  8. Radiocarbon dating of a pine tree (Pinus densiflora) from Yeongwol, Korea

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.H.; Lee, J.H.; Kang, J.; Song, S.; Yun, M.H. [AMS Lab., NCIRF, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, J.C. [Dept. of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2015-10-15

    We report the results of the dating of a pine tree (Pinus densiflora) from Yeongwol, Korea. The age of the tree was estimated to be in the range of hundreds of years, however, the tree had been broken by a strong wind in March 2010 and now only the stump of the tree is left. At the time of sampling in 2014, there were several decayed parts in the stump, so using the usual dendrochronological method (i.e. ring counting) for dating was difficult. However, we found a small wood sample with tree rings near the center of the stump that could be used for radiocarbon wiggle-match dating. Radiocarbon dates were determined using Accelerator mass spectrometry (AMS). The IntCal13 curve was used to calibrate the radiocarbon dates, and the wiggle matching technique was used to reduce the error of the calibrated ages. Based on the dating results, we suggest that the pine tree is approximately 300 years or older.

  9. Radiocarbon dating of a pine tree (Pinus densiflora) from Yeongwol, Korea

    Science.gov (United States)

    Kim, C. H.; Lee, J. H.; Kang, J.; Song, S.; Yun, M. H.; Kim, J. C.

    2015-10-01

    We report the results of the dating of a pine tree (Pinus densiflora) from Yeongwol, Korea. The age of the tree was estimated to be in the range of hundreds of years, however, the tree had been broken by a strong wind in March 2010 and now only the stump of the tree is left. At the time of sampling in 2014, there were several decayed parts in the stump, so using the usual dendrochronological method (i.e. ring counting) for dating was difficult. However, we found a small wood sample with tree rings near the center of the stump that could be used for radiocarbon wiggle-match dating. Radiocarbon dates were determined using Accelerator mass spectrometry (AMS). The IntCal13 curve was used to calibrate the radiocarbon dates, and the wiggle matching technique was used to reduce the error of the calibrated ages. Based on the dating results, we suggest that the pine tree is approximately 300 years or older.

  10. Gas chromatographic isolation of individual compounds from complex matrices for radiocarbon dating.

    Science.gov (United States)

    Eglinton, T I; Aluwihare, L I; Bauer, J E; Druffel, E R; McNichol, A P

    1996-03-01

    This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for (14)C analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the (14)C time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons). Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous samples studied revealed that Δ(14)C values generally agreed well (±10%). Background contamination was assessed at each stage of the isolation procedure, and incomplete solvent removal prior to combustion was the only significant source of additional carbon. Isotope fractionation was addressed through compound-specific stable carbon isotopic analyses. Fractionation of isotopes during isolation of individual compounds was minimal (radiocarbon measurements. The addition of carbon accompanying derivatization of functionalized compounds (e.g., fatty acids and sterols) prior to chromatographic separation represents a further source of potential error. This contribution can be removed using a simple isotopic mass balance approach. Based on these preliminary results, the PCGC-based approach holds promise for accurately determining (14)C ages on compounds specific to a given source within complex, heterogeneous samples.

  11. AMS Radiocarbon Dating of Large Za Baobabs (Adansonia za of Madagascar.

    Directory of Open Access Journals (Sweden)

    Adrian Patrut

    Full Text Available The article reports the radiocarbon investigation of Anzapalivoro, the largest za baobab (Adansonia za specimen of Madagascar and of another za, namely the Big cistern baobab. Several wood samples collected from the large inner cavity and from the outer part/exterior of the tree were investigated by AMS (accelerator mass spectrometry radiocarbon dating. For samples collected from the cavity walls, the age values increase with the distance into the wood up to a point of maximum age, after which the values decrease toward the outer part. This anomaly of age sequences indicates that the inner cavity of Anzapalivoro is a false cavity, practically an empty space between several fused stems disposed in a ring-shaped structure. The radiocarbon date of the oldest sample was 780 ± 30 bp, which corresponds to a calibrated age of around 735 yr. Dating results indicate that Anzapalivoro has a closed ring-shaped structure, which consists of 5 fused stems that close a false cavity. The oldest part of the biggest za baobab has a calculated age of 900 years. We also disclose results of the investigation of a second za baobab, the Big cistern baobab, which was hollowed out for water storage. This specimen, which consists of 4 fused stems, was found to be around 260 years old.

  12. Direct radiocarbon dating and DNA analysis of the Darra-i-Kur (Afghanistan) human temporal bone.

    Science.gov (United States)

    Douka, Katerina; Slon, Viviane; Stringer, Chris; Potts, Richard; Hübner, Alexander; Meyer, Matthias; Spoor, Fred; Pääbo, Svante; Higham, Tom

    2017-06-01

    The temporal bone discovered in the 1960s from the Darra-i-Kur cave in Afghanistan is often cited as one of the very few Pleistocene human fossils from Central Asia. Here we report the first direct radiocarbon date for the specimen and the genetic analyses of DNA extracted and sequenced from two areas of the bone. The new radiocarbon determination places the find to ∼4500 cal BP (∼2500 BCE) contradicting an assumed Palaeolithic age of ∼30,000 years, as originally suggested. The DNA retrieved from the specimen originates from a male individual who carried mitochondrial DNA of the modern human type. The petrous part yielded more endogenous ancient DNA molecules than the squamous part of the same bone. Molecular dating of the Darra-i-Kur mitochondrial DNA sequence corroborates the radiocarbon date and suggests that the specimen is younger than previously thought. Taken together, the results consolidate the fact that the human bone is not associated with the Pleistocene-age deposits of Darra-i-Kur; instead it is intrusive, possibly re-deposited from upper levels dating to much later periods (Neolithic). Despite its Holocene age, the Darra-i-Kur specimen is, so far, the first and only ancient human from Afghanistan whose DNA has been sequenced. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Performance report for the low energy compact radiocarbon accelerator mass spectrometer at Uppsala University

    Energy Technology Data Exchange (ETDEWEB)

    Salehpour, M., E-mail: mehran.salehpour@physics.uu.se [Department of Physics and Astronomy, Ion Physics, Applied Nuclear Physics Division, P.O. Box 516, SE-751 20 Uppsala (Sweden); Håkansson, K.; Possnert, G. [Department of Physics and Astronomy, Ion Physics, Applied Nuclear Physics Division, P.O. Box 516, SE-751 20 Uppsala (Sweden); Wacker, L.; Synal, H.-A. [Ion Physics, ETH Zurich, Otto-Stern-Weg 5, 8093 (Switzerland)

    2016-03-15

    A range of ion beam analysis activities are ongoing at Uppsala University, including Accelerator Mass Spectrometry (AMS). Various isotopes are used for AMS but the isotope with the widest variety of applications is radiocarbon. Up until recently, only the 5 MV Pelletron tandem accelerator had been used at our site for radiocarbon AMS, ordinarily using 12 MeV {sup 14,13,12}C{sup 3+} ions. Recently a new radiocarbon AMS system, the Green-MICADAS, developed at the ion physics group at ETH Zurich, was installed. The system has a number of outstanding features which will be described. The system operates at a terminal voltage of 175 kV and uses helium stripper gas, extracting singly charged carbon ions. The low- and high energy mass spectrometers in the system are stigmatic dipole permanent magnets (0.42 and 0.97 T) requiring no electrical power nor cooling water. The system measures both the {sup 14}C/{sup 12}C and the {sup 13}C/{sup 12}C ratios on-line. Performance of the system is presented for both standard mg samples as well as μg-sized samples.

  14. Performance report for the low energy compact radiocarbon accelerator mass spectrometer at Uppsala University

    Science.gov (United States)

    Salehpour, M.; Håkansson, K.; Possnert, G.; Wacker, L.; Synal, H.-A.

    2016-03-01

    A range of ion beam analysis activities are ongoing at Uppsala University, including Accelerator Mass Spectrometry (AMS). Various isotopes are used for AMS but the isotope with the widest variety of applications is radiocarbon. Up until recently, only the 5 MV Pelletron tandem accelerator had been used at our site for radiocarbon AMS, ordinarily using 12 MeV 14,13,12C3+ ions. Recently a new radiocarbon AMS system, the Green-MICADAS, developed at the ion physics group at ETH Zurich, was installed. The system has a number of outstanding features which will be described. The system operates at a terminal voltage of 175 kV and uses helium stripper gas, extracting singly charged carbon ions. The low- and high energy mass spectrometers in the system are stigmatic dipole permanent magnets (0.42 and 0.97 T) requiring no electrical power nor cooling water. The system measures both the 14C/12C and the 13C/12C ratios on-line. Performance of the system is presented for both standard mg samples as well as μg-sized samples.

  15. Recharge quantification with radiocarbon: Independent corroboration in three Karoo aquifer studies in Botswana

    International Nuclear Information System (INIS)

    Verhagen, B.Th.; Bredenkamp, D.B.; Janse van Rensburg, H.; Farr, J.L.

    1999-01-01

    Environmental isotope data from a 'snapshot' sampling hold out the promise of producing acceptable estimates of ground water recharge for resource management purposes. In three major ground water developments in Botswana, estimates of recharge to the Karoo aquifers in the Kalahari, were based on residence times derived from radiocarbon data. In the assessment, three factors needed to be considered: 1) the model leading to acceptable values of residence times 2) the initial, or recharge, radiocarbon value and 3) appropriate values of aquifer porosity. In the three studies, porosity had been measured on numerous drill cores obtained from the principal fractured sandstone aquifers. The resulting isotope-based recharge values correspond reasonably with independent recharge assessments using the equal volume method to analyse long-term rest level observations in two cases; in the third, recharge was independently assessed on the basis of chloride balance in both unsaturated and saturated zones. It is concluded that a) the isotope snapshot approach can give acceptable values for recharge in the development of ground water resources, providing rational management information early in the life of a ground water supply scheme; b) the exponential model and an initial radiocarbon values of 85% atmospheric are realistic in this environment and c) the total porosity appears to be the appropriate parameter in the calculation of recharge. This also provides an insight into the behaviour of the aquifers. (author)

  16. Opening of the South China Sea and Upwelling of the Hainan Plume

    Science.gov (United States)

    Yu, Mengming; Yan, Yi; Huang, Chi-Yue; Zhang, Xinchang; Tian, Zhixian; Chen, Wen-Huang; Santosh, M.

    2018-03-01

    Opening of the South China Sea and upwelling of the Hainan Plume are among the most challenging issues related to the tectonic evolution of East Asia. However, when and how the Hainan Plume affected the opening of the South China Sea remains unclear. Here we investigate the geochemical and isotopic features of the 25 Ma mid-ocean ridge basalt (MORB) in the Kenting Mélange, southern Taiwan, 16 Ma MORB drilled by the IODP Expedition 349, and 9 Ma ocean island basalt-type dredged seamount basalt. The 25 Ma MORBs reveal a less metasomatic depleted MORB mantle-like source. In contrast, the Miocene samples record progressive mantle enrichment and possibly signal the contribution of the Hainan Plume. We speculate that MORBs of the South China Sea which could have recorded plume-ridge source mixing perhaps appear since 23.8 Ma. On the contrary, the Paleocene-Eocene ocean island basalt-type intraplate volcanism of the South China continental margin is correlated to decompression melting of a passively upwelling fertile asthenosphere due to continental rifting.

  17. Currents and upwelling along the Latium coasts in the Central Tyrrhenian Sea (western Mediterranean

    Directory of Open Access Journals (Sweden)

    V. Rossi

    1995-04-01

    Full Text Available In this study, springtime coastal currents along the Latium coast and their relation to external forcings, mainly wind stress curl and atmospheric pressure, are analysed. As a main result, we find that hydrographical measurements reveal currents parallel to the bottom isobaths, but with isopycnal sloping upwards towards the coast, suggesting the importance of upwellings in determining the coastal currents. This is confirmed by thermal satellite data showing the presence of a ~10-km-wide patch of cold water east of Mount Argentario, i.e. a cyclonic vortex. The current meter data give rather small values of the time-averaged alongshore velocities (~2 cm s–1 for most current meters and ~3 cm s–1 for the current meter placed immediately off the Argentario and also smaller values for the offshore velocities. The correlation between these two types of currents is rather poor; this is also due to the variability characteristic of a wind-induced upwelling. Finally, we obtain a value of 0.74 for the correlation between the alongshore current (first mode of Empirical Orthogonal Functions decomposition and the wind stress if a 23-h time lag is assumed.

  18. Isotopic and enzymatic analyses of planktonic nitrogen utilisation in the vicinity of Cape Sines (Portugal) during weak upwelling activity

    Science.gov (United States)

    Slawyk, Gerd; Coste, Bernard; Collos, Yves; Rodier, Martine

    1997-01-01

    Using measurements of 15N uptake and activities of nitrate reductase and glutamine synthetase, the utilization of nitrogenous nutrients by microplankton in the Portuguese upwelling area was investigated. During this cruise the euphotic zone of coastal waters was in most cases bisected by a nitracline forming two layers. Total inorganic nitrogen uptake rates (NH 4+ + NO 3-) in the upper mixed and nitrate-impoverished layer ranged from 0.1 to 0.8 nM h -1 and were primarily supported by regenerated (ammonium) nitrogen (62-97%), whereas they varied between 0.9 and 10.4 nM h -1 in the deep nitrate-rich layer and were mainly driven by new (nitrate) nitrogen (52-82%). Depth profiles of Chl a-specific uptake rates for ammonium and nitrate paralleled those of absolute uptake rates, i.e. values of VNH 4+Chl were highest (up to 16.1 nmol μg -1 h -1) in nitrate-poor surface waters while values of VNO 3-Chl were maximum (up to 8.4 nmol μg -1 h -1)within the nitracline. This latter vertical ordering of planktonic nitrogen nutrition was consistent with an aged upwelling situation. However, applying several indices of cell metabolism and nutritional status, such as 15N uptake/enzyme activity, surge uptake internally controlled uptake, and V maxChl/K t ratios, we were able to demonstrate that the phytoplankton assemblages inhabiting the nutrient-impoverished upper layer still bore the signature of physically mediated nitrogen (nitrate) supply generated by active upwelling that had occurred during the week before our visit to the area. This signature was the most evident in samples from the station furthest inshore and faded with distance from shore as a result of the deepening of the nitrate isopleths (weakening of upwelling activity), which showed the same offshore trend. The appearance of nitrate-rich waters at the surface, after a strong pulse of upwelling favourable winds just before the end of the cruise, led to a five-fold increase in average (over the euphotic zone

  19. Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event

    DEFF Research Database (Denmark)

    Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu

    2017-01-01

    to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event...... (10–20 µm) prevailed ubiquitously during reduced upwelling. During normal upwelling, the diatom Rhizosolenia sp. dominated the cell-carbon biomass in the silicate poor upwelling waters. Trichodesmium erythraeum dominated in the Mekong-influenced and nutrient depleted offshore waters, where it co......Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam...

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

    Science.gov (United States)

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

    2015-12-01

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