+Extreme Climate

geologic indicators in sedimentary rocks

• presence of liquid water: ripples, conglomerates, channels, etc

• ice: striations, dropstones, till

• evaporites

Oxygen isotope 18 in the Water Cycle

16O is preferentially evaporated from sea water →18O is preferentially precipitated back into oceans b/c its heavier→16O gets to higher latitudes and is locked away in ice →18O concentration is higher in sea water which is recorded in shells of formanifera — forams use it to grow their shells

Describe climate regulation by CO2

increased CO2 → increased surface temp → increased weathering → more calcium carbonate washed into oceans → more carbon deposited on sea floor by dying organisms with calcium carbonate chells → recycled into mantle → outgassed by volcanism

• volcanic outgassing releases CO2

• sediment weathering takes up CO2

Foraminifera as a proxy for

ice level, temperature

The big 5 mass extinctions

1. End ordivician

2. late devonian

3. permian trassic

4. triassic-jurrasic

5. cretaceous-paleogene

what defines a mass extinction

when the rate of extinction is greater then rate of speciation (Rate of evolving)

Large Igneous Provinces

superseries of volcanic eruptions — releasing co2, sulfur dioxide, methane

• ex. Deccan traps in India that caused Cretaceous-Paleogene extinction

all mass extinctions occured at same time as LIP eruption

Process of Ocean Acidification

pH falls → decrease carbonate ions → no way to build shells

oxygen minimum zones

increased nutrients in surface level → more phytoplankton → more zooplankton at depth → too many to survive and takes up all oxygen -→ anoxia

Permian-Triassic Mass Extinction

• 96% marine species

• 70% terrestrial species

• coincided with eruption of Siberian Traps

• cause: siberian traps

• consequences: warming and ocean acidification, anoxia

Cretaceous-Paleocene Boundary (kPg)

• 75% of marine + terrestrial species lost

• Deccan traps cause destabilisation of environment

• Asteroid struck in Mexico

• effect: global darkness b/c of aerosols in atmopshere

• collapse of base of food chain

• deep ocean unaffected

Magnetoostratigraphy

sediment records flips in Earth’s magnetic field

Melankovitch Cycles

eccentricity (shape), obliquity (angle), and precession (tilt) all control insolation and its latitudinal distribution

Early Cenozoic Greenhouse

temps 6-16 C warmer than today

• analogue for anthropogenic climate change

• Antarctica was vegetated

• Alligators in Arctic

Paleocene-Eocene Thermal Maximum

• temp increase of 5-8 C in ~5,000 years

• severe increase in ocean acidity

• geologically rapid - BUT we will release this much in a shorter time

Eocene/Oligocene transition

into coolhouse

• increased silicate weathering, reduced outgassing

• other cause: orbital cyclicity and the 41kyr cycle of obliquity changes

• northern hemisphere glaciation

100kyr cycle

eccentricity - glacial and interglacial cycles

stadials

cold periods

interstadials

warm periods

Atlantic Meridional Overturning Circulation (AMOC)

changes in AMOC influenced by Greenland temp, N. Atlantic temp and deep ocean circulation

• gulf stream keeps Scotland warm

• controls: density

  • guld brings warm saline surface water that cools and sinks as it meets Arctic

Stadial Events and AMOC

• ice sheets melt and introduce fresh water, so water doesn’t sink, and it stops the Gulf Stream — cooling of N. Europe

Mid-Pliocene warm period

global mean surface temperature was 2.5-4 C higher, high precipitation, stronger monsoons, biomes moved poleward