No abstract available

No abstract available

[en] Research Progress is reported for the period February 1980 through January 1981. 129 coral samples have been collected from the Atlantic, Pacific, and Indian Oceans. Three Strontium 90 records, one each from Bermuda, Oahu and Tarawa, have been generated. Models have been constructed and tested which are used to reproduce the essential features of the coral ⁹⁰Sr and ¹⁴C time histories

[en] The relative importance of lateral and vertical mixing in the interior of the oceans cannot be reliably determined from conventional oceanographic measurements, nor from observations of fallout radionuclides. It is suggested that the problem could be most effectively studied by an experiment in which a large quantity of a suitable tracer was deliberately released in deep water, and its subsequent dispersion was followed for at least one year. The feasibility of such an experiment is examined. It is concluded that it is indeed feasible, and that helium-3 would be the most suitable tracer, with tritium as a possible alternative. About 30 g f Helium-3 would be needed for each release. Such a quantity may be dissoled in about 1 m³ of water at pressures greater than 500 dbar, is easily available, and would cost about $100K. Concentrations would have fallen to unmeasurable levels by the time the patch had spread sufficiently to interfere with measurements of natural or radiogenic helium-3. The patch would need to be marked with dusters of neutrally buoyant floats in order that its movement may be followed. It is estimated that it would be around 1000 km across after one year, and anything from a few meters to a few hundred meters thick. Vertically integrating samples would probably be most suitable, used in conjunction with ship-board helium-3 mass spectrometer. Methods of dissolving the helium in situ, and making the release with minimum disturbance are also proposed. The cost would be several million dollars, spread over several years

No abstract available

[en] In addition to sampling the 13 Pacific sites, we have analyzed one coral sample from Bermuda for ¹⁴C and ⁹⁰Sr for the period 1950 to 1973 at 2-year intervals. The high precision ⁹⁰Sr record from our Bermuda coral shows excellent agreement with historical measurements of ⁹⁰Sr in surface seawater between 30 to 40⁰N lat. Therefore, with a high degree of confidence, we can proceed to reconstruct the temporal history of ⁹⁰Sr in other regions of the world's ocean where we have few or no historical measurements of ⁹⁰Sr in surface water

[en] Direct knowledge of the rates of gas exchange in lakes and the ocean is based almost entirely on measurements of the isotopes ¹⁴C, ²²²Rn and ³He. The distribution of natural radiocarbon has yielded the average rate of CO₂ exchange for the ocean and for several closed basin lakes. That of bomb produced radiocarbon has been used in the same systems. The ²²²Rn to ²²⁶Ra ratio in open ocean surface water has been used to give local short term gas exchange rates. The radon method generally cannot be used in lakes, rivers, estuaries or shelf areas because of the input of radon from sediments. A few attempts have been made to use the excess ³He produced by decay of bomb produced tritium in lakes to give gas transfer rates. The uncertainty in the molecular diffusivity of helium and in the diffusivity dependence of the rate of gas transfer holds back the application of this method. A few attempts have been made to enrich the surface waters of small lakes with ²²⁶Ra and ³H in order to allow the use of the ²²²Rn and ³He methods. While these studies give broadly concordant results, many questions remain unanswered. The wind velocity dependence of gas exchange rate has yet to be established in field studies. The dependence of gas exchange rate on molecular diffusivity also remains in limbo. Finally, the degree of enhancement of CO₂ exchange through chemical reactions has been only partially explored. 49 references, 2 figures, 2 tables

[en] The report is to the Energy Research and Development Administration on accomplishments of the Lamont-Doherty Geological Observatory geochemistry and physical oceanography groups during the 1975-1976 funding period on grant E(11-1)2185. Goals are to obtain detailed, quantitative knowledge of the rates of mixing within coastal waters of the New York Bight and across the continental slope and the exchange of water masses and species transported within them between shelf and Atlantic Ocean waters. The research is aimed at understanding the chemical, physical, and biological processes which control the origin, dispersal, and fate of particulate matter and trace metals, and to ultimately model the impact of energy related pollutants on the continental shelf

[en] The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF₆, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF₆, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF₆ and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer

[en] This report summarizes the history and scientific results of the Lamont-Doherty Geological Observatory coral radioisotope project. The report includes abstracts of works in the literature or in preparation resulting from the coral project and a complete listing of the radiocarbon and ⁹⁰Sr data measured in the course of the project. Also, some possible future research directions for the coral project are suggested