Science / Tides and Currents Glossary

Upwelling: An upward flow of subsurface water due to such causes as surface divergence, offshore wind, and wind drift transport away from shore.

Vanishing Tide: In a predominantly mixed tide with a very large diurnal inequality, the lower high water and higher low water become indistinct (or vanish) at times of extreme declinations.

Variation (Of Compass): Difference between true north as determined by the Earth's axis of rotation and magnetic north as determined by the Earth's magnetism. Variation is designated as east or positive when the ma . . . View Full Definition

Variational Inequality: An inequality in the Moon's motion due mainly to the tangential component of the Sun's attraction.

West Australian Current: An Indian Ocean current setting northward along the west coast of Australia.

West Greenland Current: A North Atlantic Ocean current setting northward along the west coast of Greenland.

Wind Drift: An ocean current in which only the Coriolis and frictional forces are significant. The wind drift embodies an Ekman spiral.

ZO: Symbol recommended by the International Hydrographic Organization to represent the elevation of mean sea level above chart datum.

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