• 14C Profiles in the Norwegian and Greenland Seas by Conventional and AMS Measurements

      Nydal, Reidar; Gislefoss, Jorunn; Skjelvan, Ingunn; Skogseth, Fred; Jull, A. J. T. (Department of Geosciences, The University of Arizona, 1992-01-01)
      CO2 in the atmosphere is an important climate gas because of its absorption of infrared radiation. More knowledge about CO2 uptake in the ocean is of critical significance in predicting future climate development. For a period of approximately 30 years, radioactive carbon from nuclear tests has been a very useful tracer in CO2 exchange studies. Up to now, the measurements have been based mainly on the conventional counting technique with large CO2 samples (ca. 5 liters). Accelerator mass spectrometry (AMS) with small CO2 samples (1-2 ml) has made sampling much easier, and has especially stimulated the use of 14C as a tracer in the ocean. At higher latitudes, the ocean acts as a sink for CO2. In addition to Delta-14C measurements, we are concerned here with dissolved inorganic carbon (DIC) and delta-13C in the Norwegian and Greenland Seas. During cruises in 1989 and 1990, we obtained several Delta-14C profiles, and also repeated a few GEOSECS profiles taken in 1972. The shape of these profiles changes with time, and provides information about the mixing rate and the age of the deep water. From changes in the profiles, it appears that the deep water in the Greenland Sea has obtained about 25% of the 14C concentration in the ocean surface over a period of 25 years. The Norwegian Sea deepwater is estimated to be 50-100 years older than that of the Greenland Sea.
    • A Critical Review of Radiocarbon Dating of a Norse Settlement at L'Anse Aux Meadows, Newfoundland, Canada

      Nydal, Reidar (Department of Geosciences, The University of Arizona, 1989-01-01)
      Recent progress in high-precision calibrations of radiocarbon dates has led to evaluations of earlier research. This has been the case with dates from the Norse settlement at L'Anse aux Meadows which was discovered by Helge Ingstad in 1960. The most problematic feature of this series up to now was the use of sample material which partly derived from driftwood. The present paper concludes that charcoalfrom this site demonstrated no greater errors than normal from other settlement sites. With an assumed total systematic error of 30 +/- 20 years, as a mean for various tree rings, the calibrated age range of L'Anse aux Meadows is AD 975 -1020. This agrees well with the assumed historical age of ca AD 1000, a result which has also been recently corroborated by high-precision accelerator dating at the University of Toronto.
    • A Time History of Pre- and Post-Bomb Radiocarbon in the Barents Sea Derived from Arcto-Norwegian Cod Otoliths

      Kalish, John M.; Nydal, Reidar; Nedreaas, Kjell H.; Burr, George S.; Eine, Gro L. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collectedfor fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, wepresent the first preand post-bomb time series (1919-1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.
    • A Tribute to Minze Stuiver Upon His Retirement

      Long, Austin; Mook, Wim; van der Plicht, Hans; Willis, E. H.; Damon, Paul; Nydal, Reidar; Broecker, Wally; Reimer, Paula; Grootes, Pieter (Department of Geosciences, The University of Arizona, 1998-01-01)
    • An Analysis of Shielding Efficiency for 14C Counters

      Nydal, Reidar; Gulliksen, Steinar; Lövseth, Knut (American Journal of Science, 1980-01-01)
      The "shielding" efficiency of the guard counters has been a main scope of the present investigation. Our special guard counters consist of closed shells (ca 3cm thick) filled with propane at 1.2 atmospheres pressure. These guard counters are nearly 100 percent efficient against charged particles, and 1 to 2 percent against gamma and neutrons. The efficiency has now been studied more in detail in an arrangement with four guard shells around a 14C counter. For each extra guard shell, the cosmic fraction of the counter background was reduced by ca 13 percent. The reduction does not involve penetrating high energy charged particles, but is related to ray showers penetrating the guards. A thicker old lead shield between 14C counter and the guard counters also reduces the background and serves the same purpose. In order to approach underground conditions for the 1.5 liter counter background (0.32 +/- 0.01 c/min), most of the shielding material has to be put inside guard shells. An ordinary guard counter combined with an extra guard on top of the iron shield is very efficient. A background of 0.48 +/- 0.01 c/min has already been obtained.
    • Atmospheric CO2 Exchange with the Biosphere and the Ocean

      Bergh, Roger; Nydal, Reidar (Department of Geosciences, The University of Arizona, 1989-01-01)
      We model the exchange of carbon between the different reservoirs (atmosphere, ocean mixed layer, deep ocean and biosphere). The influence of the biosphere is investigated using two extreme assumptions: 1) no net biospheric effect and 2) biospheric uptake of CO2 proportional to the atmospheric content of CO2 and time-dependent deforestation. Observations of atmospheric CO2 at Mauna Loa and the South Pole may be fit by both these assumptions.
    • Bomb 14C in the Ocean Surface, 1966-1981

      Nydal, Reidar; Gulliksen, Steinar; Lövseth, Knut; Skogseth, Fred H. (American Journal of Science, 1984-01-01)
      Bomb 14C has been used as a tracer for COin ocean surface water to study CO2 exchange between atmosphere and ocean. Using ordinary cargo ships for sampling, we have been able to cover some parts of the Atlantic, Pacific, and Indian Oceans for certain periods. A total number of 520 samples from 89 locations were measured during the last 15 years. The data are presented both in tables and graphs. A maximum 14C concentration (Delta-14C) of ca 20% was observed in temperate northern latitudes, and a few per cent lower at southern latitudes. A seasonal trend in the 14C variation, with summer maximum and winter minimum, was observed both in downwelling and upwelling areas.
    • Comparing Long-Term Atmospheric 14C and 3H Records near Groningen, the Netherlands with Fruholmen, Norway and Izaña, Canary Islands 14C Stations

      Meijer, Harro J. A.; van der Plicht, Johannes; Gislefoss, Jorunn S.; Nydal, Reidar (Department of Geosciences, The University of Arizona, 1995-01-01)
      We present the results of the 14CO2 atmospheric monitoring station at the Smilde observation station, near Groningen, the Netherlands, a typical continental station. We compared these data, for absolute values and annual variation, with data from Fruholmen, Nordkapp, Norway and Izaña, Tenerife, Canary Islands, which are situated in areas less influenced by fossil-fuel CO2. The 20-yr Smilde record shows much seasonal variation (peak-to-trough variation is approximately 30 per mil in contrast to approximately 12 per mil for Fruholmen, and approximately 5 per mil for Izaña) and a lower overall value due to fossil-fuel consumption, in accordance with findings from similar stations in continental Western Europe. The Fruholmen and Izaña data show fairly equal mean Delta-14C levels, but differ in seasonal amplitude. This difference could be due partly to the elevation difference between the stations. The Izaña station also has a slow exchange with the ground-level air because of an inversion layer. It is speculative whether annual injection of 14C from the stratosphere also plays a role. We give the Groningen long record of tritium in precipitation, showing profound seasonality.
    • delta-13C and Diet: Analysis of Norwegian Human Skeletons

      Johansen, Olav Sverre; Gulliksen, Steinar; Nydal, Reidar (American Journal of Science, 1986-01-01)
      The relationship between 13C content of human bone and the marine fraction in the individual diet is well established. In the present investigation human skeletons from inland and coastal areas in Norway were analyzed. Both regional and chronologic differences are revealed, and larger variability than expected at specific sites indicate more complex cultural adaptations than earlier recognized. Extremely high delta-13C values, comparable with those obtained from Eskimo sites, are found for material from Early Stone Age fishing/hunting communities.
    • Radiocarbon in the Ocean

      Nydal, Reidar (Department of Geosciences, The University of Arizona, 2000-01-01)
      In addition to dating, radiocarbon has heen widely used as a tracer in the study of the global carbon cycle. And particularly the exchange of CO2 between the atmosphere and the ocean. The anthropogenic input of 14C from nuclear weapons tests in the atmosphere stimulated this research. Developing from frequent measurements made in the atmosphere and ocean's surface, the measuremens later became more focused towards understanding the circulation in the deep ocean. From a few attempts at the end of 1950 to measure the 14C increase in the ocean surface (Rafter and Fergusson 1957), the measurement program developed to include such programs as GEOSECS, TTO, JGOFS, SAVE, and WOCE, which obtain comprehensive ocean data, including 14C for the study of ocean circulation. Only in the ocean surface has it been possible to obtain timeseries of 14C measurements as in the atmosphere. For the deep ocean, repeat measurements arc generally several years apart. This sampling frequency is probably sufficient for the majority of the deep ocean. With its long time scale of change.
    • The Radon Problem in 14C Dating

      Nydal, Reidar (American Journal of Science, 1983-01-01)
      Due to traces of radium and uranium in most 14C samples, radon appears as a radioactive contamination in the CO2 prepared by combustion. This contamination must be removed by an active purification prodecure or by storing the CO2 prior to measurement. No effective electronic discrimination against radon and its daughter elements can be performed. The necessary storage time until radon has decayed varies widely, especially for marine shells. The latter material, collected from Norway and Svalbard, has been a main object for the present investigation. In a few cases, a measureable amount of radon may be left even after eight weeks. The behavior of radon and its daughter elements in a CO2 proportional counter has been studied.
    • Transfer of Bomb 14C to the Ocean Surface

      Nydal, Reidar; Lövseth, Knut; Skogseth, Fred H. (American Journal of Science, 1980-01-01)
      Additional 14C data from the atmosphere and ocean have been provided since the ninth 14C conference in 1976. At the moment, one sampling station in the troposphere in each hemisphere seems to give sufficient accuracy for exchange studies. The 14C concentration in the troposphere in December 1978 constituted a mean value of 30 +/- 1 percent (∆14C) above normal level, a concentration that has been reduced to about one half during 12 years, 14C measurements have been performed with intervals of 1 to 4 months in the surface water of the Atlantic, Pacific, and Indian Oceans. In addition to the 14C data observed, the salinity and temperature are also measured. Because of earlier objections against storing sea water in steel drums on board ships for months before treatment, the CO2 has now been flushed out immediately after collection. The reliability of previous measurements has been confirmed with 10 parallel samples. 14C concentration in ocean surface on each location shows some seasonal variation due to variable exchange of water with deeper layers.
    • Trondheim Natural Radiocarbon Measurements III

      Nydal, Reidar (American Journal of Science, 1962-01-01)
    • Trondheim Natural Radiocarbon Measurements IV

      Nydal, Reidar; Holm, Marianne; Lövseth, Knut; Skullerud, Kari E. (American Journal of Science, 1964-01-01)
    • Trondheim Natural Radiocarbon Measurements IX

      Nydal, Reidar; Gulliksen, Steinar; Lövseth, Knut; Skogseth, Fred (American Journal of Science, 1985-01-01)
    • Trondheim Natural Radiocarbon Measurements VI

      Nydal, Reidar; Gulliksen, Steinar; Lövseth, Knut (American Journal of Science, 1972-01-01)
    • Trondheim Natural Radiocarbon Measurements VII

      Gulliksen, Steinar; Nydal, Reidar; Lövseth, Knut (American Journal of Science, 1975-01-01)
    • Trondheim Natural Radiocarbon Measurements VIII

      Gulliksen, Steinar; Nydal, Reidar; Skogseth, Fred (American Journal of Science, 1978-01-01)