Bay Coastline Research Articles

An analogue model study of electromagnetic induction for cape and bay coastlines

The electric and magnetic field variations across bay and cape coastlines are determined from scaled laboratory analogue models. The effect on the field response of such features along an otherwise straight coastline is limited to a distance approximately equal to the dimensions (diameter of the bay or cape) of the irregularity. For the E-polarization of the source field the perturbations in H z and H y are more confined, mainly to the immediate region of the bay or cape. The coast effect H z / H y for this polarization, and variations with a 4.2 min. period, is approximately a factor of two larger for the cape than for the bay, while the straight coastline H z / H y is roughly mid-way between the cape and bay values. For H-polarization the coast effect is again approximately a factor of two larger for the cape than for the bay, but both values are larger than the value for a straight coastline. The response of the various field components to the bay and cape features is decreased at longer periods, and as a measure, the coast effect is approximately a factor of 1.2 greater for the cape than for the bay for a 42 min. period as compared with the factor of 2 for a 4.2 min. period. The bay and cape deflect the induced currents flowing in the ocean and modify the currents diffusing into the land. This study demonstrates that data from coastal sites may be unreliable for correcting magnetic surveys or for analyses of short period geomagnetic source-field variations.

Studies on lichen-dominated systems. VI. Interrelations of vegetation and soil moisture in the Hudson Bay Lowlands

Soil moisture measurements are presented for the summer period of 1971 for nine sites spaced inland from the Hudson Bay coastline adjacent to East Pen Island. The sites show a great variation in natural vegetation from a sparsely vegetated young raised-beach to older beach ridges dominated by thick mats of lichen. The sites include a non-vegetated blowout in a sand dune and areas which have been damaged by caterpillar tractors and by burning.Differences in soil moisture between sites are very pronounced and are closely related to the organic content of the soils. There are also substantial variations in the rate of soil moisture withdrawal during the summer period and this is reflected in differences in the seasonal evapotranspiration rates. The soil moisture characteristics are widely variable in the surface soils at the different sites but virtually the same at soil depths below 30 cm.