Top Zafer

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  • Technical Report
    A trans-Indian Ocean hydrographic section at latitude 32°South : data report of RRS Charles Darwin cruise #29
    (Woods Hole Oceanographic Institution, 1992-01) Cook, Margaret F. ; Toole, John M. ; Knapp, George P. ; Fine, Rana A. ; Top, Zafer ; Jennings, Joe C.
    A trans-Indian Ocean hydrographic section employing CTD/O2 profilers was conducted between Africa and Australia during austral spring 1987. The cruise track ranged between 29°S and 34°S; the average latitude of the crossing was 32°S. The purpose of the cruise was to explore various aspects of the South Indian Ocean including the characteristics of the core water masses of this ocean, the strength of the subtropical gyre, the structure and transport of deep western-boundary currents, and the net meridional heat flux. A total of 109 CTD/O2 profiles with associated rosette water sample measurements and 347 XBT profiles were collected, supplemented by underway upper ocean velocity, bathymetric and sea surface temperature and salinity data. This report detals the data collection, calibration, and reduction methods, and summarizes the hydrographic observations.
  • Article
    Mantle 3He distribution and deep circulation in the Indian Ocean
    (American Geophysical Union, 2004-06-10) Srinivasan, Ashwanth ; Top, Zafer ; Schlosser, Peter ; Hohmann, Roland ; Iskandarani, Mohamed ; Olson, Donald B. ; Lupton, John E. ; Jenkins, William J.
    The World Ocean Circulation Experiment Indian Ocean helium isotope data are mapped and features of intermediate and deep circulation are inferred and discussed. The 3He added to the deep Indian Ocean originates from (1) a strong source on the mid-ocean ridge at about 19°S/65°E, (2) a source located in the Gulf of Aden in the northwestern Indian Ocean, (3) sources located in the convergent margins in the northeastern Indian Ocean, and (4) water imported from the Indonesian Seas. The main circulation features inferred from the 3He distribution include (1) deep (2000–3000 m) eastward flow in the central Indian Ocean, which overflows into the West Australian Basin through saddles in the Ninetyeast Ridge, (2) a deep (2000–3000 m) southwestward flow in the western Indian Ocean, and (3) influx of Banda Sea Intermediate Waters associated with the deep core (1000–1500 m) of the through flow from the Pacific Ocean. The large-scale 3He distribution is consonant with the known pathways of deep and bottom water circulation in the Indian Ocean.
  • Preprint
    Isotopic, geophysical and biogeochemical investigation of submarine groundwater discharge : IAEA-UNESCO intercomparison exercise at Mauritius Island
    ( 2011-09) Povinec, Pavel P. ; Burnett, William C. ; Beck, A. ; Bokuniewicz, Henry J. ; Charette, Matthew A. ; Gonneea, Meagan E. ; Groening, M. ; Ishitobi, T. ; Kontar, E. ; Kwong, L. Liong Wee ; Marie, D. E. P. ; Moore, Willard S. ; Oberdorfer, J. A. ; Peterson, R. ; Ramessur, R. ; Rapaglia, J. ; Stieglitz, T. ; Top, Zafer
    Submarine groundwater discharge (SGD) into a shallow lagoon on the west coast of Mauritius Island (Flic-en-Flac) was investigated using radioactive (3H, 222Rn, 223Ra, 224Ra, 226Ra, 228Ra) and stable (2H, 18O) isotopes and nutrients. SGD intercomparison exercises were carried out to validate the various approaches used to measure SGD including radium and radon measurements, seepage-rate measurements using manual and automated meters, sediment bulk conductivity and salinity surveys. SGD measurements using benthic chambers placed on the floor of the Flic-en-Flac Lagoon showed discharge rates up to 500 cm/day. Large variability in SGD was observed over distances of a few meters, which were attributed to different geomorphological features. Deployments of automated seepage meters captured the spatial and temporal variability of SGD with a mean seepage rate of 10 cm/day. The stable isotopic composition of submarine waters was characterized by significant variability and heavy isotope enrichment and was used to predict the contribution of fresh terrestrially derived groundwater to SGD (range from a few % to almost 100 %). The integrated SGD flux, estimated from seepage meters placed parallel to the shoreline, was 35 m3/m day, which was in a reasonable agreement with results obtained from hydrologic water balance calculation (26 m3/m day). SGD calculated from the radon inventory method using in situ radon measurements were between 5 and 56 m3/m per day. Low concentrations of radium isotopes observed in the lagoon water reflected the low abundance of U and Th in the basalt that makes up the island. High SGD rates contribute to high nutrients loading to the lagoon, potentially leading to eutrophication. Each of the applied methods yielded unique information about the character and magnitude of SGD. The results of the intercomparison studies have resulted a better understanding of groundwater-seawater interactions in coastal regions. Such information is an important pre-requisite for the protection management of coastal freshwater resources.