Distinct ice sheets formed sometimes coming into contact with one another
Britain: 3 distinct glacial advances
Youngest: Devensian (12-71 ka)
How do we know this?
Chronology of ice-look at oxygen isotopes in ice cores or deep sea sediments to see where 16O was at the time.
If more 16O (lighter oxygen) in ice cores- less melting after snowfall- locked up in ice. So sea has more 18O. - cooler periods= Higher 18O:16O ratio
If less 16O in ice cores- know moved back to sea via meltwater- climate likely to have been warmer. Sea will have a lower 18O: 16O ratio- enriched with 18O.
Ice ages cause rise and falls in sea level.
During ice ages- water is stored on land as ice and snow- sea level falls
Deglaciation- increase in meltwater- water returns to the oceans- sea level rises
Sea level processes:
1000s years- ice sheet melts/grow; land motions
10s years: ocean processes, glacial melt/growth.