COASTS: Sea Level Changes Flashcards
Eustatic changes
Global 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.
Isostatic changes
Local sea level changes caused by vertical movements of the land relative to the sea.
What are the 2 main causes of eustatic change?
Changes in climate
Tectonic movements
How can climate change lead to eustatic sea level change?
- Increase in temp causes ice sheets to melt.
- Also causes water to expand.
- Increases sea level further.
What are the main causes of isostatic change?
- Uplift or depression of Earth’s crust due to accumulation or melting of ice sheets.
- Subsidence of land due to shrinkage after abstraction of ground water.
- Tectonic processes.
What can cause variation in sea level?
Tidal change.
Onshore winds.
Low atmospheric pressure systems.
When was the last glacial period?
Approx. 110,000 to 12,000 years ago.
When was the last glacial maximum?
Approx. 21,000 years ago.
At the last glacial maximum, how much lowere was the sea level?
About 130m lower than present.
When did the sea level reach its present level?
Approx. 4000 years ago
What has happened to sea level over the past 4000 years?
It has fluctuated around its present value.
What has happened to sea level since about 1930?
It has been rising.
At what rate is global sea level rising each year?
Almost 2mm each year.
If greenhouse gas emissions remain high during the 21st century, what is predicted to happen?
Sea levels will rise 8-16mm a year by 2100.
What is likely to increase due to climate change?
Storm frequency and intensity due to changes in ocean circulations and wind patterns.
