sea level

sea level

the level of the surface of the sea with respect to the land, taken to be the mean level between high and low tide, and used as a standard base for measuring heights and depths

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

sea level

[′sē ‚lev·əl]

(geology)

The level of the surface of the ocean; especially, the mean level halfway between high and low tide, used as a standard in reckoning land elevation or sea depths.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

sea level

The level of the sea, which serves as the datum used for measurement of land elevations and ocean depths. Sea levels vary greatly from one location to another. Locally, the levels of the surface of the world's oceans are disturbed by wind-driven waves and tides. The mean sea level is used as a reference height to determine a standard condition for the atmosphere and for the altitude measurement. It is measured over a nineteen-year period. It does not remain constant over the surface of the entire earth; the mean sea level at the Pacific end of the Panama Canal stands 7.8 in (20 cm) higher than at the Atlantic end.

An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Sea Level

 

the position that the surface of seas and oceans would assume if uninfluenced by tides, waves, or swells, measured as the vertical distance between the water surface and a reference point on land. Sea level is classified as instantaneous, tidal, daily mean, monthly mean, annual mean, and long-term mean.

Sea level is constantly changing under the influence of wind disturbances, tides, the heating and cooling of the ocean surface, atmospheric pressure fluctuations, precipitation and evaporation, and river and glacial runoff. Long-term mean sea level, however, is not affected by these factors; it is determined by the distribution of gravity and by the uneven spatial distribution of such hydrometeorological characteristics as water density and atmospheric pressure. Long-term mean sea level, which is constant at any given point, is used as a reference level from which land elevations are measured. In order to determine the depths of seas with minimal tidal variation, long-term mean sea level is taken as zero depth, from which depths are calculated in accordance with navigational requirements.

In the USSR, absolute elevations on the earth’s surface are measured from the long-term mean sea level of the Baltic Sea, which is read off from the zero point of the tide gage at Kronstadt.

REFERENCES

Duvanin, A. I. Uroven’ moria. Leningrad, 1956.
Duvanin, A. I., G. P. Kalinin, and R. K. Klige. “O mnogoletnikh kolebaniiakh urovnia okeanov, nekotorykh morei i ozer.” Vestnik MGU, Seriia 5: Geografiia, 1975, no. 6.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.