Mean sea level (MSL) is the average (mean) height of the sea, with reference to a suitable reference surface.
Defining the reference level, however, involves complex measurement, and accurately determining MSL can prove difficult.
Sea level has changed over geologic time.
During the most recent ice age (at its maximum about 20,000 years ago) the world's sea level was about 130 m lower than today, due to the large amount of sea water that had evaporated and been deposited as snow and ice in northern hemisphere glaciers.
For more information about the topic Sea level, read the full article at Wikipedia.org, or see the following related articles:
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