<p> The isotopic composition and concentration of dissolved helium have been measured in over 250 samples of Atlantic and Pacific seawater. The helium isotope ratios were measured using a double collection "static" mass spectrometer specifically designed and constructed for this purpose. The helium and neon contents of 118 of these samples were determined using the isotope dilution technique, and the helium contents of the remaining samples were determined by peak-height comparison with standard air aliquots. Krypton and xenon concentrations were measured by isotope dilution for the Pacific samples. </p> <p> Two sources of excess nonatmospheric ³He are discerned in the Atlantic Ocean: a primordial component and a component produced by in situ decay of bomb-produced tritium. The former component occurs in three distinct features; two emanating from the south at 1000 m and greater than 4000 m depths, and one emanating from the north at about 3000 m depth. The spatial properties of these features are studied in the framework of simple models. The latter, or "tritiugenic" component is coupled with tritium concentrations measured by others to obtain Tritium-helium Ages, the characteristics of which are compared with hydrographic features. For example, the spreading velocity of the Mediterranean Water is determined to be ⪝ 1.5cm sec⁻¹ in the North-Western Atlantic. </p> <p> The helium and neon concentrations measured in Atlantic Waters indicate that significant variations occur for helium contents, both as a function of depth and latitude. The Antarctic Bottom Water appears to be a source of excess helium. </p> <p> In the Pacific, the distribution of excess ³He is shown to be consistent with injection of primordial ³He into the Deep and Bottom Waters from the East Pacific Rise. The characteristic mid-depth maximum seen in the helium isotope ratio anomaly profiles is shown to be a circulational feature. Upper and lower limits on the amount of excess nonatmospheric ⁴He are set at 5.5 and 2.6% respectively. Application of the simple one-dimensional diffusive-advective model indicate an upward flux of 6±2 and 1.1 ± 0.5 × 10⁶ atoms/cm²/sec for ³He and ⁴He respectively. </p> Pacific seawater is, on the average, 16 and 31% supersaturated in krypton and xenon respectively. Although there is no known process that is capable of such enrichments, the spatial distribution of the krypton and xenon concentrations indicate that a significant amount of the enrichment occurs in situ in Pacific Deep Waters. </p> / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/18542 |
| Date | 05 1900 |
| Creators | Jenkins, William John |
| Contributors | Clarke, W. B., Physics |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
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