Session 20 ( Paleoclimate) Flashcards
Paleoclimate
Measuring the earths climate prior to human existence
Climate Proxies
indirect forms of evidence to infer climate.
Commonly used proxies
- Sediments (fossils)
- Ice cores
- Tree rings
- lake varves
- coral bed rings
- Speleothems
Dendrochronology (tree rings) (1000 years)
Wider rings = more growth. Vise Versa.
Anoxic Lakes ( Varves) (Century- Millenium)
Runoff sediment composition.
Light = Mineral rich
Dark = Organic rich
Speleothens (cave dripstones) (seasonal to millennium)
formed as a part of the meteoric water cycle
Corals (100+ years)
Lighter shade show fast growth (summer) dark layers show slow growth (winter)
Ice Cores (Poles) 800,000 years
Lighter layers in summer vs darker in winter
When do Ice ages happen?
when CO2 concentrations are low
Slow Carbon Cycle
Plates shift forcing CO2 from plankton to go under volcanos making them erupt and add more CO2 back into the atmosphere
What can cause the sediments to have different colors?
Oceans became acidic from the PETM causing the color change
Paleocene–Eocene Thermal Maximum (PETM)
a period of rapid global warming caused by a massive injection of carbon into the ocean and atmosphere
What did PETM Cause
Caused rainforest to flourish but marine life struggled with intense ocean acidification causing loss in calcium.
Methane Hydrates
Crystal like cages that enclose a methane molecules thriving at low temperature and high pressure.
How did PETM affect Methane release
The intense heating of the ocean released methane into the atmosphere
Milankovitch Cylces
Cycles of the sun and earth that cause warming and cooling in intervals over time
Precision of Equinoxes
When the northern hemesphere is tilted away or towards the sun (19 and 23 KY)
Aphelion
When the earth is furthest from the sun
Perihelion
When the earth is closest to the sun
Obliquity Cycle
Changes in tilt. More tilt will create more severe seasons and less tilt will create moderate seasons.
What is the Atlantic Meridional Overturning Circulation (AMOC)
A system of ocean currents that form a vertical loop that extends the whole length of the atlantic moving warm water to the poles and cold water to the equator
Why is AMOC reaching its tipping point
With ocean water becoming warmer, the AMOC weakens creating extreme weather
How the AMOC effects europe
Causes very severe cold temperatures in the north and very hot in the south.
What happens to the Antarctic ice sheet and southern polar jet stream because of AMOC
Causes warm water to stop going north and accumulates in the south causing western ice sheets to melt. Intense jet streams are caused due to the increase in temperture change between the poles and equator.
Feedback loop for loss of ice in western Antarctica
Ice melts causing colder and less dense waters weakening the AMOC
Upwelling
Cold, Deep, nutrient-rich water moving to the surface.
Downwelling
Pushing water downwards
Ekman Transport
Wind causes surface water to move, however, because of coriolis effect, it moves at a 40 degree angle.
Net Transport in the NH
90 degrees to the right
Net Transport in the SH
90 degrees to the left
Winds heading north along the west coast cause it?
Downwelling because Ekman transport pushes currents toward the shore
Winds heading south along the west coast cause what?
Upwelling because ekman transport pushes water away from the coast pushing currents away from the shore
Atlantic Ocean Bifurcation
The Amoc shutting down due to icemelting and putting less dense freshwater at the surface
Sterodynamic sea-
level variability
Changes in ocean circulation due to changes in temperature and salinity
If the North of the North Atlantic
cools, why does that not
stimulate deepwater formation?
The water also needs to be dense enough to sink.
What does a warming of the
Southern Atlantic Ocean imply
for the global meridional
overturning circulation?
altered weather patterns, regional cooling or warming effects, and changes in oceanic carbon storage.
Which oxygen is lifted more with evaporation
O16
Does a colder climate mean more O16 in ice or ocean?
In ICE because the O16 comes from the ocean through evaporation and builds up in the ice
Does a Warmer climate mean more O16 in ice or ocean?
In the ocean because the Ice is melting
