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Height above mean sea level (AMSL) is the elevation (on the ground) or altitude (in the air) of an object, relative to a reference datum for mean sea level (MSL). It is also used in aviation, where some heights are recorded and reported with respect to mean sea level (contrast with flight level ), and in the atmospheric sciences , and in land ...
Sea surface height change from 1992 to 2019: Blue regions are where sea level has gone down, and orange/red regions are where sea level has risen (the visualization is based on satellite data). [ 2 ] Between 1901 and 2018, the average sea level rose by 15–25 cm (6–10 in), with an increase of 2.3 mm (0.091 in) per year since the 1970s.
There are two competing arguments for second-order sea-level changes. The first states the sea level can be affected by the number of and the volume of the magma being produced at mid-ocean ridges. [6] During times of increased sea floor spreading, more magma is being produced and the volume of the ocean basins are displaced by this. This would ...
Over geologic time sea level has fluctuated by more than 300 metres, possibly more than 400 metres. The main reasons for sea level fluctuations in the last 15 million years are the Antarctic ice sheet and Antarctic post-glacial rebound during warm periods. The current sea level is about 130 metres higher than the historical minimum.
The Bruun rule gives a linear relationship between sea level rise and shoreline recession based on equilibrium profile theory, which asserts that shore face profile maintains an equilibrium shape, and as sea level rises the increasing accommodation space forces this equilibrium profile landward and upward to preserve its shape relative to the new sea level. [4]
The precise measurements of TOPEX/Poseidon's and Jason-1 have brought knowledge of ocean tides to an unprecedented level. The change of water level due to tidal motion in the deep ocean is known everywhere on the globe to within 2.5 centimetres (one inch). This new knowledge has revised notions about how tides dissipate.
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Oceanic lithosphere moves into trenches at a global rate of about a tenth of a square meter per second. Trenches are generally parallel to a volcanic island arc, and about 200 km from a volcanic arc. Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor.