Ice Cores And Ocean Cores Flashcards
Name 2 ice cores.
Antarctica - EPICA. Extends 800,000 years. Longest record. Extends 8 full interglacial/glacial cycles.
Greenland - GRIP (ice core project). Extends 100,000 years.
Name 3 techniques for dating cores.
Tephrachronology
Numerical modelling
Radiometric dating with oxygen isotopes
Ice cores
Provides actual atmosphere from when snow was laid.
Gas trapped in snow and compressed.
During glacial ice caps isotopically light and oceans isotopically heavy.
Interglacial = ocean isotopically light.
Ocean cores
Can look at sediment layers.
- forams found in sediment give indication to past climate.
- oxygen isotopes can also be used.
Potential influence of Milankovitch cycles on the mass balance of ice sheets.
Periodicity of eccentricity matches up with glacial/interglacial cycles.
Elliptical orbital means 30% more solar radiation received.
Therefore more solar radiation, warmer, more melt, less ice.
During less elliptical = less solar radiation = cooler = ice masses grow.
Other causes
Broeker and Denton (1989) said milankovitch can’t be sole cause of ice mass change.
Isostatic depression - earths crust depresses under weight of ice
Isostatic uplift - relief of crust. Takes longer.
Sub Milankovitch Cycles
- Name both
Dansgaard-Oeschger events
Heinrich events.
What is a Dansgaard-Oeschger event?
It is a warm stadial period.
Evidence of 10 degrees warming in Greenland in 100 years.
Timescale of Dansgaard-Oeschger?
Occur around every 1500 years.
24 events in last glacial.
What is a Heinrich event?
Periods of cooling, cold stadials.
Timescale of Heinrich?
Around every 7,200 years.
7 during last glacial.
Causes of Dansgaard-Oeschger events?
Opening and shutting off of ocean circulation.
Warm, Atlantic water from Mexico circulate Britain and parts of Europe during interglacial.
During glacial polar front shuts off this warm water.
