What Advantages does studying Glacial-scale bring about
- We can reconstruct climate in more detail
- We can cover a larger area (Regionalization)
- We have better date records (14C dates)
When was the Last Glacial Maximum (LGM)
21,000 yrs ago
Describe some geographic characteristics of the LGM (animals and land)
- Large mammals, Cave men
- More ice sheets (Canada, north US, Europe, Eurasia)
- Sea Level c. 110m lower than today
- sparsely vegetated
What are some differences and similarities between now and LGM
- differences, Colder, drier, windier, less vegetated,
- similarities
similiar tectonic scale configuration of continents
What was the CLIMAP project and what did it accomplish?
A panel of interdisciplinary experts on ice sheets + Windblown deposits + marine sediments + climate modeling,
-Reconstructed the first LGM
List the location of ice sheets and their names. (3)
- North America = laurentide and Cordilleran ice sheets
- North europe = Scandinavian ice sheets
- Northern Eurasia = Barents ice sheet
- Greenland and Antartica
How can one be sure that the LGM occured
- Observing the relative heights of coral reefs and performing U dating
- Observing the leoss deposits that are present,
- Dust transport by winds was also important
what is COHMAP
Coorperative Holocene Mapping Project
Disscuss correlation between LGM proxy data and climate models.
- We must test models against known paleoclimate records.
- typically a good correlation if one applies low CO2 and moisture levels
What proxy data is a good test of the LGM Holocene
- Pollen and lake sediments are known to have a good resolution for this time period.
- Dry weather favours grass vs tree
- coldness favours Spruce vs Oak
- pollens outlayer is resistant to weathering
what affet did the ice sheet have on polar jetstream
Split into two
Dry cold weather
Difference in eurasia’s climate from today to the LGM
Today - Azore high and islandic low
LGM - high pressure cell on Scandinavian ice sheet.
Difference in asia’s climate from today to the LGM
LGM - Total absence of trees
- permafrost (10m)
Today - Summer monsoons
Cause of climate changes?
CO2
Difference in Australia and south america’s climate from today to the LGM
LGM
- more arid , drier for the most part,
- higher winds were observed at the time
- Drier because there was colder oceans therefore less precipitation
What drove the cooling of the tropics?
Not driven by ice volume,
- Caused by drops in GHG
- CO2 levels were 30% lower
- CH4 levels were 50% lower
What is the difference in sea ice in the NH and SH
Sea ice in the NH grew much more than that of sea ice found in SH was not as great.
Why is the LGM o interesting to climate researchers
It provides a great analog for icehouse earth, with extremely low levels of CO2
What happend after the LGM
- Melting of Ice sheets, (raised sea levels (110m))
- Lakes formed, massive floods, pulses of meltwater released
- Vegetation migrations
- monsoons strengthened until about 10 Krs
What caused the end of the ice age
- Large Axis tilt + Precessional movement reulted in the max summer insolation at high latitudes.
- Lead to an increase of CO2 from 190-270ppm
How did insolation max melt the ice so quickly (deglaciation)?
Positive feedback loops,
- CO2 feedback
- Albedo feedback
Why do SH Temp. stickly follow CO2 levels, why does the NH Temp. (5)
- Cold water holds more CO2
- Deglaciation, low CO2 solubility
- High CO2 in ATM
+ sea ice cover limits release of CO2 in atm. - During deglaciation, melt water brought about CO2 resvoirs from southern ocean
- Evidence of strong upwelling in southern ocean (wind based process)
-Resulted in release of CO2 (physical carbon pump).
What is Younger Dryas
Cold ‘Short’ episode when ice sheets stopped retreating. In some regions, the re-advanced
What did the Deglaciation result in
Monsoon arrival
