Causes of Sea level Change

Sea level change is relative change in level of the sea surface that rise or fall with respect to the land surface.

The sea level changes have been caused by several possible causes, these are-

A.)Long Term Causes of Sea Level Changes:

i.)Changes in Ocean water volume: Changes in volume occurs due to melting & freezing of ice sheets. When ice sheet melts, volume of ocean water increases & sea level also rises. This sea level changes is called Eustatic change. If all of the in Antarctica were to melt, world sea level would rise between about 60 to 75m, & the Greenland in cap would add add about 5m. it glaciations develops then ocean water changes into ice & sea level subsides.

ii.)Changes in Ocean Basin Volume: Changes in the volume of ocean basins have been the most important factor in the influencing the broad trend of global sea level. Such changes can arise from a variety of causes. These causes are-

a)     Sediment causes,

b)    Trench formation,

c)     Subsidence of ocean crust,

d)    Uplift of mid oceanic crust,

e)     An increase or decrease in the length of the ridge system,

f)     Effect of orogenesis,

g)    Desiccation of small ocean basins, 

iii.)Geoidal Effects: The changes in the volume of water in the sea adjustment by adjusting the bottom of the ocean.

Characteristics of Lithosphere, Hydrosphere, Atmosphere & Biosphere.		Sea Level Condition
		Green House State	Oxigeneted State
1.	Sea level	High	Low
2.	Ocean Basin	Wide & Shallow	Narrow & Steep
3.	Latitudinal Temperature Gradient	High	Low
4.	Plate Tectonics	Rapid Mental Convection	Slow Convection
5.	Volcanism	High	Low
6.	Continental Relief	Low	High
7.	Erosion & Weathering	Slow	High
8.	Biomass	Low	High
9.	CO2	High	Low
10.	Temperature	Warm	Cool
11.	Atmospheric & Ocean Circulation	High	Low
12.	Dissolve O2	Low	High

B.)Short Term Causes of Sea Level Changes:

The short term changes, which are effective during a year are mainly due to change in volume of water. The short term causes of sea level changes as follow-

i.)Sea Density: This is controlled mainly by temperature & to a much lesser extent by salinity, the lower the temperature & the greater salinity the higher the density & the lower is sea level.

ii.)Atmospheric Pressure: High atmospheric pressure give lower local sea level.

iii.)Speed of Ocean Currents: These speeds vary with total global energy budget & there may be as much as 18 cm difference in sea levels on opposite sides of curving, fast-flowing current.

iv.)Water Locked Up in Winter Snow: water locked up in winter snow in the Northern Hemisphere leads to the lowering of the level.

v.)Seasonal Pilling Up of Water: Seasonal pilling up of water along windward coast increase the sea level, e.g. South & East Asia during the summer monsoon.