GES 3A — Climate history + glacial cycles
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21 Terms
Hot-house climate
A climate state with no year-round ice at the poles.
Cold-house climate
A climate state where ice is present at the poles year-round.
Current climate state
Earth is currently in a cold-house climate state.
Snowball Earth
An extreme cold-house state where nearly the whole planet is covered in ice.
Glacial period
A colder time when glaciers advance and cover more of Earth.
Interglacial period
A warmer time between glacial periods when glaciers retreat and sea level rises.
Current glacial-cycle period
Earth is currently in the Holocene interglacial period.
Holocene
The current interglacial period that began about 11,700 years ago.
Glacial cycle
The natural advance and retreat of glaciers over time, including both glacial and interglacial periods.
What drives glacial cycles
Milankovitch cycles plus Earth feedback loops.
Oxygen isotopes and climate
The ratio of O-18 to O-16 in shells and ice cores helps scientists infer past temperature and ice volume.
O-18 in seashells
A larger positive O-18 departure in seashell sediment usually means colder conditions.
O-18 in ice cores
Colder climates leave less heavy oxygen in ice cores because O-18 condenses and falls out sooner.
Why O-18 changes with climate
In cold climates, heavy oxygen precipitates more easily, enriching oceans and shells while leaving less in polar ice.
Laurentide Ice Sheet
A huge ice sheet that covered much of North America during the last ice age.
Evidence of the last ice age
Great Lakes, smoothed landforms, erratics, fertile plains soils, and cold-adapted fossils.
Erratics
Rocks dropped by glaciers as the ice melts.
Volcanism and deglaciation
As ice retreats, reduced ice mass can contribute to isostatic rebound and may influence volcanism.
Younger Dryas
A sudden return to near-glacial conditions during the warming out of the last ice age.
Why Younger Dryas matters
It is a famous example of abrupt climate change.
Cause of Younger Dryas
It is believed to be linked to weakening of the Atlantic Meridional Overturning Circulation (AMOC).