Week 8 LGM Flashcards
(24 cards)
When did the LGM occur?
23,000 – 19,000 BP, centred on ~21,000 ka BP
What is the LGM?
defined as ‘peak’ glacial conditions when ice sheets were largest and global temperatures were at a minimum.
When did the last glacial period occur?
115,000 – 11,500 years BP.
What does the LGM mrak?
the culmination of a nearly 100 kyr long glacial
period, during which ice-sheets had continued to build up.
What were the conditions during the LGM
icy, dry, cold, windy and sparsely vegetated
What was the insolation at mx ice sheets?
summer insolation had risen closer
to modern levels
what helped force LGM
Lower CO2
insolation
presence of ice sheets
What where global sea level during LGM?
110-125 m lower than today
How much of the world was covered by ice sheets today and in the LGM?
10% today
25% LGM
Which ice sheet was the largest in NH?
The North American ice sheet (Laurentide and Cordilleran) was the largest accounting for 55%
of the extra ice volume.
What did the presence of large ice sheets impact?
sea level, atmospheric circulation and
vegetation
What are loess fields?
large amounts of dust deposited from a glacier
What did the presence of ice sheets do?
generated large
amounts of dust leading to the formation of loess fields
Why do ice sheets cause more dust?
Ice sheets grind across the landscape, scraping and
dislodging soils, producing large amounts of debris
(boulders to fine clay).
Where did dust in Antarctica come from?
predominantly from Patagonia.
Where did dust in Antarctica come from?
eastern Asia
How much dust is in glacials what causes these dust levels?
10 x more dust
result of a more turbulent atmosphere
greater production of debris
a drier climate.
What was the global temperature in the LGM?
Global temperatures were 3-8 °C cooler than today
Where was cooling greatest in the LGM?
polar regions
Greenland was 21-25 °C cooler than the present.
•Antarctica was 7-10 °C cooler than the present.
How was Sea surface temperature affected?
North Atlantic was at least 8°C cooler
Other regions may actually have been warmer
How did atmospheric circulation change during LGM?
meaning sites in the north had reduced precipitation,
and those further south had enhanced precipitation
How can we tell what happened with vegetation in the LGM?
using pollen preserved in lake sediments
reflect the average composition of vegetation
What was the total biomass in the LGM?
Total biomass on Earth was 25% less than
today
How much cooler where tropic oceans during LGM?
4-6°C cooler than present
mountain regions were 4-6°C cooler than present
