| dc.contributor.author | Azetsu-Scott, Kumiko. | en_US |
| dc.date.accessioned | 2014-10-21T12:38:53Z | |
| dc.date.available | 1992 | |
| dc.date.issued | 1992 | en_US |
| dc.identifier.other | AAINN80080 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55309 | |
| dc.description | Marine particles play a key role in biogeochemical cycles in the ocean as primary sites of chemical transport, as microcosms for biological communities and as a food source for larger animals. Fundamental questions that need to be answered include: what does the particle distribution in the ocean look like and what causes that distribution? In this work the hypothesis that the density structure of the water column affects the vertical distribution of marine particles was tested in various marine environments, in the laboratory and by modelling. | en_US |
| dc.description | The particle distribution profile was measured using a recording backward light-scattering meter that enables the collection of a continuous, real time data set, that also included measurements of salinity and temperature. A time series study of the particle distribution was conducted during a six month period, including the spring phytoplankton bloom, in a coastal basin, Bedford Basin, Nova Scotia, Canada. A high particle load at the pycnocline, particle patchiness in mid-depth and the formation of bottom nepheloid layers (BNL) were observed. The BNL is not a steady state but rather is a dynamic phenomenon. In Emerald Basin on the Scotian Shelf, there was also a high particle load on the pycnocline. In contrast, strong intermittent intermediate nepheloid layers (INL) were recorded in mid-depth. Depths of INLs coincided with the critical depth for possible generation, amplification and breaking of internal waves with semi-diurnal (M$\sb2$) internal tide frequency. Intermittent particle resuspension at the "critical" depth on the Basin slope, together with temporal variability of the currents, appear to be the likely cause of the observed intermittency of the INLs. | en_US |
| dc.description | Particle distributions were significantly different for the two environments investigated in the field (a coastal and a shelf basin) as were the respective controlling factors. However, the two areas had a common feature--a high particle load always on the surface pycnocline. The distribution of particles below the pycnocline, in mid- and deep water, was not related to water density structure. Instead the particle distribution below the mixed layer was characterized by biological (in the coastal basin) or local physical factors (in the shelf basin). | en_US |
| dc.description | The hypothesis of control of the distribution of particles by density structure was also approached from the perspective of particle characteristics. A new method was developed to measure physical properties of aggregates. The method measures aggregate size, settling velocity and density of constituent matter simultaneously and independently for each aggregate. This last property, density of constituent matter, is presented for the first time for marine aggregates. A high density of constituent matter of aggregates ($>$1.095 g/cm$\sp3$) relative to sea water, considered with measured settling velocities, suggests that aggregates have high porosity ($>$94%). | en_US |
| dc.description | A simple model, using measurements obtained both in the field and in the laboratory, demonstrates that constituent matter density, porosity and exchange rate of interstitial water of aggregates are important parameters for particle settling behaviour and consequently for explaining the distribution of particles at the density discontinuity layer in the ocean. Of the three parameters, two of them (constituent density and porosity) were obtained in this study. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1992. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Physical Oceanography. | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.subject | Biogeochemistry. | en_US |
| dc.title | Vertical distribution and transport processes of marine particles. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
