The cumulative numbers of particles obtained from seven waters in the depth range of 0-100m in coastal seas and in the North Pacific Ocean followed a hyperbolic distribution with two segments on log-log plots (132 sets of data). An alteration of the segment-slope in the fine size classes (1.59-10.08μm in the coastal region, 1.59-6.35μm in the open sea) was assumed to show a loss or a supply of fine particles due to aggregation or disaggregation.We studied relationships between segment slopes, static stabilities of water above the pycnocline which concern the dynamics of particles, and C/N ratios as an indicator of freshness of particles. A negative correlation between the segment-slope of particle size distribution and static stability was obtained, though the slope P of the regression line varied from 0.059 to 0.316. The average C/N ratio in the waters were in the range of 7.5 to 16.3. The slope P negatively correlated to the C/N ratio (r=-0.97). The present results suggested that aggregations of fine-sized particles in the sea are activated in the water with fresh organic matter and with high static stability.

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Results are described from a limited area barotropic model of the North Pacific with 1/3°×1/3° resolution and bounded by latitudes 10°N and 50°N and longitudes 120°E and 160°E. The model employs dynamics linearised about a state of rest and incorporates realistic bottom topography. It is driven by the seasonally varying part of the Hellerman and Rosenstein wind stress field and by inflow along the northern and eastern boundaries specified from a 1°×1° version of the model applied to the whole North Pacific. The model-calculated transport variations through the Tokara Strait are similar to those of the observed seasonal sea level differences across the Strait, although the model appears to underestimate the amplitude of the signal by a factor of at least 2. The inclusion of realistic bottom topography is shown to be crucial in determining the model response.

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The generation mechanism of internal waves by a relatively strong tidal flow over a sill is clarified analytically. Special attention is directed to the role of the tidal advection effect, which is examined by use of characteristics.
An internal wave which propagates upstream is gradually formed through interference of infinitesimal amplitude internal waves (elementary waves) emanating from the sill at each instant of time. In the accelerating (or decelerating) stage of the tidal flow, the effective amplification of the internal wave takes place as the internal Froude number exceeds (or falls below) unity because during this period the internal wave slowly travels downstream (or upstream) while crossing over the sill where elementary wayes are efficiently superimposed. In fact, the variability in the internal wave field actually observed in a realistic situation (Stellwagen Bank in Massachusetts Bay) is shown to be satisfactorily interpreted in terms of this mechanism. Furthermore, by using this analytical model, the relation between the strength of the tidal advection effect and the resulting internal waveform is clarified.
This theory is easily extended to include a vertically sheared steady flow. In this case, although the fundamental generation mechanism is the same as above, the amplitude of the elementary wave varies with time depending on the relative direction of the tidal flow and steady shear flow, so that the internal wave field over the sill differs markedly between the ebb and flood tidal phases. As an example, the internal wave generation process over the sill in the Strait of Gibraltar is qualitatively discussed on the basis of this analytical model.
The effect of vertical mixing caused by breaking of these large-amplitude internal waves on the coastal environment is also pointed out. In particular, a brief discussion is made on the control of water exchange by the fortnightly modulation of tidal mixing processes at the sills and constrictions in channels connecting freshwater sources with the ocean.

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