- Eustatic sea level change – caused by a change in the volume of water in the sea, or by a change in the shape of the ocean basins.
- Causes:
- Climate change.
- Tectonic movements.
- Isostatic sea level change – caused by vertical movements of the land relative to the sea.
- Causes:
- Uplift or depression of the Earth’s crust due to accumulation or melting of ice sheets.
- Subsidence of land due to shrinkage after abstraction of groundwater.
- Tectonic processes.
- Sea level has risen in the last 10,000 years:
- Sea level varies daily with the tidal cycle. Onshore winds and low atmospheric pressure systems cause the sea surface to rise temporarily.
- During the last glacial period, water was stored in ice sheets, so sea level was lower than present. At the last glacial maximum, sea level was about 130m lower than present.
- As temperatures started to rise, ice sheets melted, and sea level rose rapidly.
- Over the last 4,000 years, sea level has fluctuated around its present value.
- Since about 1930, sea level has been rising.
