Relative sea level (abbreviated as RSL) is defined as the sea level that is observed with respect to a land-based reference frame.
It is often contrasted with
eustatic sea level
The eustatic sea level is the distance from the center of the earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, increasing spreading rates of the mid-ocean ridges or more mid-oceanic ridges. ...
, which is a measure of the total mass or volume of the oceans. Relative sea level can change by the processes changing eustatic sea level (e.g. ice melt and thermal expansion), but also by changes on land such as subsidence and
isostatic rebound
Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound a ...
.
In
sequence stratigraphy
Sequence stratigraphy is a branch of geology, specifically a branch of stratigraphy, that attempts to discern and understand historic geology through time by subdividing and linking sedimentary deposits into unconformity bounded units on a variety ...
it is similarly defined as the distance from the ocean surface to the bottom of the sediment on the ocean floor.
Therefore, relative sea level is independent of the thickness of the sediment layer at the bottom of the ocean, which makes it a different concept than
water depth
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...
.
References
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