The Migration Patterns and Identity of the Okun-Yoruba People of Central Nigeria

Migration is a global phenomenon. From time immemorial, man has been moving from one place to another for temporary or permanent settlements. This is largely facilitated by natural or artificial factors. The former include nat­ural disasters such as ecological change and draught, while the latter can be in­stigated by wars and search for better fortunes. This study examines the nature of the movements of the Okun-Yoruba people from the western region of Ni­geria to the confluence of the Niger and Benue rivers in the Central Geograph­ical Zone of Nigeria. It reveals how their long years of interactions with peoples of the confluence region were aided by the European delimitation of the area as part of the North, which has been the basis of sociopolltical agitation. The study reveals that Okun-Yoruba people, despite their geographical delimitation as northerners, see themselves more as southerners.

Do Winds Control the Confluence of Subtropical and Subantarctic Surface Waters East of New Zealand?

<p>The confluence region east of New Zealand is one of only a few places in the world where the Antarctic Circumpolar Current meets the strong southwardflowing boundary current of a subtropical gyre. The convergence of subtropical and subantarctic water creates strong fronts. The fronts have clear signatures in height and temperature that make them appropriate places to investigate ocean/climate variability. The location and extent of the New Zealand confluence should respond to changes in large-scale wind patterns, as changes in South Pacific currents have been linked to wind shifts. However, recent studies have shown that highly energetic eddies, local winds, and the bathymetry may be significant controls of currents and associated fronts. This thesis investigates the temporal and spatial variability of the confluence and evaluates its response to variability in South Pacific winds. Analysis of the 18-year time series, from January 1993 to December 2010, of sea surface height mapped from satellite altimetry was used to investigate the location and extent of fronts and the eddy activity and relate these to the wind forcing. Wind stress data were used with the Island Rule to estimate the winddriven transport of the western boundary currents that feed the confluence. In addition, the climate modes Southern Annular Mode (SAM) and Southern Oscillation Index (SOI) were used to examine the influence of the principal modes of atmospheric variability. Time series of the local wind stress curl and local climate indices were calculated and compared to the intensity of the confluence to test any influence of local forcing. In addition, bathymetric effects were investigated by evaluating evidence for preferred front locations near topographic features. Sea level anomalies in the confluence region are increasing at 3.4 cm decade⁻¹. The sea surface height gradients and the eddy kinetic energy are also increasing at a rate of 0.01 cm km⁻¹ and 23 cm² s⁻² per decade respectively, indicating an intensification of the fronts and eddy activity in the confluence. There is a high and significant correlation (r = 0.84) between the front and eddy signals reflecting baroclinic instabilities inherent in the fronts. Difference in transport anomalies across the confluence derived from the Island Rule are also increasing at 8.8 Sv decade⁻¹. SAM and SOI indices showed little or no correspondence with variability in the confluence intensity and eddy kinetic energy, and the same lack of correspondence was observed in local winds and local indices. While these results suggest a connection between the variability in the confluence and South Pacific winds, there is a preferential location of the strongest fronts and eddy activity northeast of Bounty Plateau and Bollons Seamount, indicating some bathymetric control. The correspondence between basin-scale winds and sea surface height gradients in the confluence region indicates that if wind stress continues to increase, as current trends predict, front intensity and eddy activity will also increase, enhancing the transfer of heat and nutrients that, respectively, influence energy transfer and biological productivity.</p>

Do Winds Control the Confluence of Subtropical and Subantarctic Surface Waters East of New Zealand?

<p>The confluence region east of New Zealand is one of only a few places in the world where the Antarctic Circumpolar Current meets the strong southwardflowing boundary current of a subtropical gyre. The convergence of subtropical and subantarctic water creates strong fronts. The fronts have clear signatures in height and temperature that make them appropriate places to investigate ocean/climate variability. The location and extent of the New Zealand confluence should respond to changes in large-scale wind patterns, as changes in South Pacific currents have been linked to wind shifts. However, recent studies have shown that highly energetic eddies, local winds, and the bathymetry may be significant controls of currents and associated fronts. This thesis investigates the temporal and spatial variability of the confluence and evaluates its response to variability in South Pacific winds. Analysis of the 18-year time series, from January 1993 to December 2010, of sea surface height mapped from satellite altimetry was used to investigate the location and extent of fronts and the eddy activity and relate these to the wind forcing. Wind stress data were used with the Island Rule to estimate the winddriven transport of the western boundary currents that feed the confluence. In addition, the climate modes Southern Annular Mode (SAM) and Southern Oscillation Index (SOI) were used to examine the influence of the principal modes of atmospheric variability. Time series of the local wind stress curl and local climate indices were calculated and compared to the intensity of the confluence to test any influence of local forcing. In addition, bathymetric effects were investigated by evaluating evidence for preferred front locations near topographic features. Sea level anomalies in the confluence region are increasing at 3.4 cm decade⁻¹. The sea surface height gradients and the eddy kinetic energy are also increasing at a rate of 0.01 cm km⁻¹ and 23 cm² s⁻² per decade respectively, indicating an intensification of the fronts and eddy activity in the confluence. There is a high and significant correlation (r = 0.84) between the front and eddy signals reflecting baroclinic instabilities inherent in the fronts. Difference in transport anomalies across the confluence derived from the Island Rule are also increasing at 8.8 Sv decade⁻¹. SAM and SOI indices showed little or no correspondence with variability in the confluence intensity and eddy kinetic energy, and the same lack of correspondence was observed in local winds and local indices. While these results suggest a connection between the variability in the confluence and South Pacific winds, there is a preferential location of the strongest fronts and eddy activity northeast of Bounty Plateau and Bollons Seamount, indicating some bathymetric control. The correspondence between basin-scale winds and sea surface height gradients in the confluence region indicates that if wind stress continues to increase, as current trends predict, front intensity and eddy activity will also increase, enhancing the transfer of heat and nutrients that, respectively, influence energy transfer and biological productivity.</p>

Broadband Characteristics of Zooplankton Sound Scattering Layer in the Kuroshio–Oyashio Confluence Region of the Northwest Pacific Ocean in Summer of 2019

Acoustic technology, as an important investigation method for fishery resources, has been widely used in zooplankton surveys. Since the Kuroshio–Oyashio confluence region has an extensive distribution of zooplankton, describing and analyzing the characteristic of the zooplankton sound scattering layer (SSL) in this area is essential for marine ecology research. To understand its spatial–temporal distribution, acoustic data of the Kuroshio–Oyashio confluence region at the Northwest Pacific Ocean, obtained by a Simrad EK80 broadband scientific echosounder in 2019, were used on board the research vessel (RV) Songhang. After noise removal, the volume backscattering strength (SV) was measured to plot the broadband scattering spectrogram of each water layer and to exhibit zooplankton distribution. The results show that the main sound scattering within 0–200 m originate from the zooplankton, and the SV of each layer increases with the rise of the transducer frequency. The magnitude of SV was closely synchronized with the solar altitude angle, which gets smaller when the angle is positive, then larger when the angle is negative. It means that the SSL has a diel vertical migration (DVM) behavior with the variation of solar height. Meanwhile, scattering strength was positively correlated with temperature in the vertical direction and showed a maximum of −54.31 dB at 20–40 m under the influence of the thermocline. The Kuroshio and Oyashio currents had an obvious influence on the scattering strengths in this study, indicating a low value when next to the Oyashio side and a high value on the Kuroshio side. The scattering strength near the warm vortex center was higher than that at the vortex edge. The results of this study could provide references for a long-term study on ecological environment variation and its impacts on zooplankton distribution.

Organic Matter Characterization from sediments of the Tietê and Piracicaba rivers dam (Brazil).

&lt;p&gt;&lt;span&gt;The sediments are complex and heterogeneous environments, thus, besides determining the concentration of potentially toxic metals present in sediments, it is necessary to understand the sediment's ability to accumulate or release contaminants, because many biogeochemical processes are involved, influencing the fate of these metals. The main modes of dispersion, which can lead to remobilization of contaminants are (i) early diagenesis, (ii) natural or anthropogenic resuspension of the sediment and (iii) the diffusive flow at the water-sediment interface&lt;/span&gt;&lt;span&gt;. In this context, it is important to understand in how sedimentary organic matter (SedOM) acts in the retention and remobilization of metals, what environmental risks and how climate change influences the flow of rivers and causes remobilization of sedimentation, resulting in the release of these metals. As a result, it will be possible to evaluate if SedOM is a danger or protection against contaminants. In this work were used 69 samples collected at different depths at 3 points on the Tiet&amp;#234; river, at 3 points on the Piracicaba river and at one point in the confluence region. The samples were freeze-dried, crushed, and sieved through a 100 mesh sieve. Two SedOM extraction methods were conducted in this work: NaOH extraction and deionized water extraction. Approximately 1.0 g of each sediment was placed in polypropylene flasks with 45.0 mL of 0.1 mol L&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-1&lt;/span&gt;&lt;/sup&gt;&lt;span&gt; NaOH and 45.0 mL of deionized water, and then shaken for 24 h in an overhead shakerat 10 rpm. Then the samples were centrifuged at 3,000 g for 10 min and filtered over a 0.45 &lt;/span&gt;&amp;#956;&lt;span&gt;m syringe filters. To study the fluorescence mode in EEM, 1.0 mL of each diluted with same absorbance sample was placed in quartz cells with 1.0 mL of 0.3 mol L&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-1&lt;/span&gt;&lt;/sup&gt;&lt;span&gt; HEPES and 1.5 mL of 0.1 mol L&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-1&lt;/span&gt;&lt;/sup&gt;&lt;span&gt; NaClO&lt;/span&gt;&lt;sub&gt;&lt;span&gt;4&lt;/span&gt;&lt;/sub&gt;&lt;span&gt;. The fluorescence spectra were acquired in scan speed of 2,400 nm min&lt;/span&gt;&lt;sup&gt;&lt;span&gt;-1&lt;/span&gt;&lt;/sup&gt;&lt;span&gt; from 250 to 700 nm in emission and from 200 to 500 nm in excitation. The steps and slits of emission and excitation were fixed at 5 nm, and the detector voltage was 700 V. EEM data were processed using the method of Parallel Factor Analysis to determine the contribution of each component using homemade PROGMEEF software. SedOM samples extracted with NaOH and deionized water from Tiet&amp;#234; and Piracicaba rivers presented COre CONsistency DIAgnostic of 83.3% with the contribution of four components or fluorophores. According the components obtained by PARAFAC, the component 2 is noise and it was excluded. The emission wavelength of fluorophore 1 is approximately 450 nm, fluorophore 3 is 550 nm and fluorophore 4 is 400 nm. Therefore, the fluorophore 4 refers to OM fresher, simpler and less humidified. Whereas fluorophore 3 refers to OM older, more complex and more humidified, that is, it is from the terrestrial environments. According to data obtained by EEM and treated with PARAFAC was possible to determine the presence of three fluorophores and the complexity of their structure.&lt;/span&gt;&lt;/p&gt;