Coasts 4 - Sea level changes Flashcards
(48 cards)
What scale are the affects of eustatic change on
Global
What is eustatic sea level change caused by?
A change in the volume of water in the sea or by a change in the shape of ocean basins (worldwide level change)
What causes these global affects?
Changes in climate and tectonic movement of crust
How does an increase in temperature change sea levels
Causes ice sheets to melt increasing sea level. Also causes water to expand increasing sea levels
How does a decrease in temperature change sea levels
Causes more precipitation to fall as snow, increasing the volume of water stored in glaciers and reduces the volume of sea decreasing sea levels
What does tectonic movements of crust do
After the shape and volume of ocean basins eg - sea floor spreads increases the volume of the basin and decreases sea level
What is isostatic sea level change caused by
Vertical movements of the land relative to the sea
What does downward and upward land cause
Downward - Sea level to rise locally
Upward - Sea level to fall locally
What are the 3 causes of isostatic sea level change
1) Tectonic processes - eg - 1 plate is forced beneath another at a plate margin
2) Subsidence of land due to shrinkage after abstraction of ground water like drainage or marshland
3) Uplift or depression of the earths crust due to accumulation or melting. If its slow it continues for 1000s of years after the retreating glacier has gone
Where and what does accumulation of sediment cause?
The mouths of major rivers causing depression
What does sea level vary with
The tidal cycle
What else causes the sea surface to rise temporarily
Onshore winds and low atmospheric pressure systems
Give 4 ways global sea level has changed
1) Last glacial period, water was ice sheets, so sea level was lower. At the last glacial maximum sea level was 130m lower than now
2) As temp increases, ice sheets ,melt and sea level rose rapidly. It reached its present level around 4000 years ago
3) Over the last 4000 years sea level has fluctuated above and below current level
4) Since 1930, sea levels have been rising
What is global warming?
Temperatures increasing rapidly over the last century
Whyat do scientists think is the cause of climate change
Human activity - deforestation and burning fossil fuels
What do these activities do
Increase the concentration of greenhouse gases in the atmosphere
What do greenhouse gases do
Absorb outgoing long-wave radiation, so less is lost in space. As their concentration increases more energy is trapped and the planet warms up
Why is an increase in temp likely to cause an increase in sea levels
Through melting of ice sheets and thermal and expansion of water in oceans
How is global sea levels currently rising
2mm a year
What will happen if greenhouse gas emissions remain high?
It’s predicted to increase 8 to 16mm a year by 2100
Why are storms likely to9 become more frequent and intense
Changes in ocean circulation and wind pattens
What would this do
Damage ecosystems and settlements
What are 4 major impacts will sea level rise have on coastal areas
1) More frequent and severe flooding
2) Submergence of low-lying islands
3) Changes in coastline
4) Contamination if water sources and farmland
How does more frequent and serve coastal flooding happen
Flooding of low lying areas has increased with sea level rise and it will increase more with further rises
