Browsing by Author "Waldron, Howard Neil"

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    Influences on the hydrology of the Cape Columbine/St. Helena region
    (1985) Waldron, Howard Neil; Brundrit, Geoff
    The overall objective of the thesis is to investigate and interpret hydrological events occurring at the Cape Columbine upwelling site and the adjacent coastal waters, with special reference to St. Helena Bay. The first step in the study involves monitoring the meteorological occurrences which resulted in the prevailing hydrology and thus give a general background to the observed structure. It became necessary to establish two sub-systems in the area which can be distinguished on the basis of the time scales within which they operate. Generally speaking, outside St. Helena Bay the waters have a 3-5 day synoptic variability governed by meteorological conditions, but within the semi-closed system of the Bay itself a longer time span of around 25 days governs the processes in this separate but inextricably linked water body.
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    Regional estimates of potential new production in the southern Benguela upwelling system
    (1996) Waldron, Howard Neil; Brundrit, Geoff; Probyn, Trevor A
    The estimation of annual potential new production at a regional scale for the decade of the 1980s provides the main focus of this thesis. New production is the proportion of total primary production which relies on the uptake of NO₃-N by the phytoplankton while potential new production assumes that all the NO₃-N available to primary producers is assimilated. The Redfield ratio between carbon and nitrogen in the marine environment was used to express rates of potential new production in terms of carbon. In order to arrive at annual estimates of potential new production it was necessary to progress from the event-scale to the annual scale. This was achieved by the adoption of two novel methods of approach. Event-scale estimates of potential new production were made by assessing the amount of NO₃-N present in the nominal euphotic zone as a result of upwelling. Remotely-sensed images of sea surface temperature (SST) coincident with or shortly after upwelling events were used in combination with a derived relationship between SST and NO₃-N concentrations integrated over the depth range of the productive surface layer in the southern Benguela region. In this way it was possible to overcome the main shortcoming of passive satellite imagery by quantifying a sub-surface variable. The event-scale estimates of potential new production were extrapolated to the annual-scale by taking into account the dynamics of the system. Sea level fluctuation at the coast preceding upwelling events was found to be related to the event-scale estimates of introduced NO₃-N and hence used as a proxy for upwelling. Using a ten year record of sea level, estimates of annual potential new production, spanning the period June to May inclusive, were made for the period 1980/81 to 1989/90. Bibliography: pages 92-108.