Midterm 1 Ice Ages Flashcards
Ocean _____ proxy for the amount of ice on the planet through time
18O/16O
Because 16O is easier to evaporate, more gets
stored as ice on land during an ice age. So, the
concentration of 18O in the ____ increases.
ocean
Ocean 18O/16O record dominated by 20, 40, 100 thousand year cycles for past million years same
length as Milankovitch orbital cycles, indicating orbital changes trigger _____
ice ages
Key point:
orbital cycles DO NOT change total ____ striking earth, just redistributes between different
latitudes and seasons, so insolation changes in some place and time of year must matter more than others
for driving ice sheets.
sunlight
Milankovitch theory says that Arctic summer insolation is the key latitude/season for driving ice sheets
since it controls how much ___ survives one winter to the next
snow
Whole world goes in and out of Ice Ages together, despite the fact that global sunlight does not change –
indicating that while Arctic summer insolation may have driven Arctic ice sheets, something else must
have caused whole world to ______
warm up and cool down
- Milankovitch
triggers Northern
Hemisphere ice
sheet melt - Ocean conveyor
belt shutdown
links hemispheres - Warming around
Antarctica draws
CO2 out of the
deep ocean - Rising CO2 warms
the whole world
out of the ice age
Ancient _______ preserved far above present sea level show that the ocean was much higher during some
past warm periods between ice ages
coral reefs
There were dozens of abrupt (years to decades) climate changes during the last ______, with opposite
temperature changes in the Northern versus Southern Hemisphere (i.e., South warmed when North
cooled, and vice versa)
And Antarctic
temperature changed in
the opposite way,
warming when Greenland
was cold and cooling
when Greenland was
warm. What caused it?
caused by the deep ocean conveyor belt tipping on and off.
ice age
What could cause this??
The ocean conveyor belt
tipping point. When it is on,
it pulls heat to the north and
cools the south. When it is
off, the north gets cold and
heat builds up in the south
Ice Ages recap
Ice ages were triggered by slow
variations in Earth’s orbit that
redistribute sunlight, but don’t change the global energy balance. Resulting changes in CO2 levels were the main driver of global ice ages. CO2 is currently far higher than anytime in the past million years.
Sea level varied by 100 meters over ice ages and reached several meters higher than today during past warm times.
There were lots of abrupt climate
changes during ice ages when the _____ tipped on and off.
deep ocean circulation
