EAR 111 TEST 2

Archives

Fossils, sediments, ice cores, speleothems, tree rings, coral, historic records

climate archives

are deposits or settings in which scientists
can find information about past climates

climate proxies

are materials and/or properties contained in archives that we use to infer past climate

Fossils

proxies: leaf shape, species assembeleges

sediment

biological (what lived there, who fast did it grow, time deposited?) and geochemical (texture, rate of accumulation, chemical characteristics of organic and inorganic)

Ocean - 10s of millions year old bc of ocean crust is recycled through subduction, before 170

Lake - many from last glaceriation

foraminifera

calcite shell

diatoms

silica shell bearing organism

ice core

gases, particules, physical charateristics, isotope

speleothems (cave depo)

chemistry, isotopes

trees

density, width, Carbon and oxygen

coral

chemistry

history records

phenology (timing of leaf out and flowering), logs, photos

fractionation

light isotope move faster than heavy

Heavy isotopes prefer liquid/solid to vapor

light evaporates

heavy condense

ice volume effect

Light water isotopes preferentially taken upfrom ocean and
deposited on ice
• Ocean water gets heavier as ice sheet grows

EVAPORATION - light isotopes

ONDESATION - HEAVY

direct temperature effect

positive correlation between local air temperature and the ratio of heavy to light stable isotope

As ocean temperatures get warmer:

more fractionation, lighter = lower δ18O, More of the lighter 16O preferentially incorporated into CaCO3

colder: higher δ18O,

Radiocarbon

Radiocarbon half life : 5730 years

aka carbon 14 - 6 protons and 8 neutrons

half lives — 1/2, 1/4, 1/8 etc

carbon cycle

cycle of carbon is exchanged between Earth
system components: biosphere, atmosphere,
hydrosphere, and lithosphere

regulates CO2

organic carbon cycle

the biological process by which carbon moves between the atmosphere, living organisms, soil, and aquatic ecosystems through photosynthesis, consumption, respiration, and decomposition

starts with primary producers and consumers

Primary Producers

Organisms that directly create
organic matter from inorganic
components (sunlight, nutrients)

photosythisis

Consumers

Organisms that get energy and accumulate biomass from
eating other organisms

respriation

respiration uses oxygen to break down carbohydrates to get energy
carbonhydrate + oxygen = water + energy + co2

plant/plankton , consumers, microbial decobial decomp, fire

methanogenesis

In some special cases (ie, without oxygen), decomposition of
organic matter occurs

carbohydrate = methane + CO2

cow poop

ocean reservior

CO2 from biomass gets carried via erosion/runoff to oceans,
where it dissolves and gets converted to bicarbonate

dissolved CO2 + water -> bicarbonate

Bicarbonate in ocean is used to biosynthesize tissues and shells
of photosynthesizing marine organisms

biological pump

Transfers CO2 from surface to the deep ocean reservoir

ocean reservior = bio pump

Upwelling branch of the thermohaline circulation brings carbon from deep ocean back to surface

ocean reservoirs/fluxes

ground of oil and natural gas

Surface ocean biomass – primary productivity
• Respiration → C to atmosphere
• Organic matter settles → C to deep ocean
•Deep Ocean - Decomposition
• Biological Pump (respiration) → C to surface

reservoirs/fluxes with rock

shales and coal
Terrestrial sedimentary rock –
Organic matter → burial → shales and coal

Seafloor to Oceanic Sedimentary Rock
Organic matter→ burial→ shales & petroleum

Inorganic carbon cycle

Cycle of carbon that does not involve organic carbon

Three main reservoirs:
• Atmosphere
• Ocean
• Sedimentary Rocks (mostly limestone)

air sea exchange

the continuous transfer of momentum (wind stress), energy (heat flux), moisture, and gases (CO2 and Methane) across the boundary layer where the Earth's atmosphere meets the ocean

driven by the concentration gradient of CO2
CO2 diffuses from areas of high concentration to areas
of low concentration

Partial pressure

sea air exchange

portion of the pressure due to a specific component

pN2 pO2 pCO2

Total pressure

sum of all the partial pressures of gases in the atmosphere or ocean

pN2, pO2, and pCO2

There are spatial variations

Red = oceans losing CO2 to atmosphere

Bllue= oceans taking CO2 from the atmosphere

happens bc CO2 is more soluble in
cold than warm water

ocean acidification

Increase in CO2 concentrations in the atmosphere increase the
concentration of H+ in the ocean

CO2 + H20 —> carbonic acid —> H+ —> Bicarbonate

carbonate effects

latches onto the excess H+ instead of Ca+ = less
carbonate shells formation

excess carbonic acid dissolves existing shells

chemical weathering

CO2 dissolves in rainfall, forming carbonic acid (H2CO3)

Reacts with silicate and carbonate minerals

• Solutes (Ca, Si) are carried to ocean

volcanos

Volcanoes link the carbon stored in the lithosphere to atmosphere

emit gases

Carbon returned to atmosphere via
• Volcanic activity (natural)

plate techtonics

the idea that plates move rock that shape planets surface

wegner

proposing the hypothesis of continental drift looked at fossils and rock formations

form of plate tectonic theory

Paleomagentism

Earth’s magnetic field generated by the molten iron in the earth’s
outer core

iron-rich mineralsorient like a compass needle towards the magnetic poles

Volcanic rocks from different continents suggested that either the poles had wandered thru time

paleomagnetism debate

the continents themselves moved in relation to the magnetic poles

Volcanic rocks from different continents suggested that either
the poles had wandered thru time

Seafloor spreading

Ocean crust - magnetic mineral orientation show that seafloor forms at spreading ridge

pangea

200 million years ago, the continents were connected

High atmospheric CO2 concentration (1650 ppm)

widespread aridity in low latitude pangea

• Hadley circulation (lots of land with descending, dry air

• Trade winds (easterlies) losing moisture before reaching interiors

Geologic evidence: Evaporates = salts precipitated
out of water in lakes and coastal settings

moist by water , dry inside

Extreme seasonality

Large temperature changes on land compared to ocean

Moderating effect of ocean did not reach the interiors

Geologic Evidence: Summers too warm for glaciers to expand

supermonsoons

• Large seasonal changes in land temperatures
• Pressure gradients drive winds! (and moisture flow)

Geologic Evidence: Red beds = iron oxide minerals that form
in areas with large season moisture contrasts

polar position hypothesis

• Ice sheets exist in polar regions today
• Cold temperatures from low sun angle Ice-albedo feedbacks

Ice sheets form when continents move into a
position where they exist near one of the poles

some periods there is ice

some periods theres no ice bc of Atmospheric CO2 and greenhouse forcing

BLAG hypothesis

sea-floor spreading has changed thru time — rise in chem weather

Over millions of years, CO2 production (volcanism) is balanced by CO2 removal (weathering)

delays = climate change

chemical weathering BLAG

C and Si buried in
deep ocean =
carbon sink
• Carbon returned to
lithosphere

uplifting weathering hypothesis

mountain building accerated the chemical weathering process

Weathering is mainly affected by availability of rock and mineral surfaces

May be more important to weathering on a global scale than climate/precipitation/vegetation

This means more surfaces for chemical
weathering
More chemical weathering = more
draw-down of CO2 from the atmospher

uplifting weathering hypothesis in SA

Mountain areas 80% of dissolved
chemical load in the Amazon
• High temp/precip/veg areas of the
lowlands = 20%
• Mountain-building = a fresh supply
of minerals to be weathered
Tectonic controls on CO2 – Uplift + Weathering

Continental plate collision

Happens less frequently than
subduction-driven mountain
building
• May help explain cooler,
glaciated intervals in the past

cretaceous period

hot greenhouse climate, high sea levels , warm global temp, ice free

BYE BYE DINOSAUR

CO2 during cretatoes pd

intense volcanic activity and seafloor spreading

= more co2

Sea level cretaceous

Geologic evidence: Lower foram δ18O in oceans (lighter
isotopes) = no glacial ice = larger ocean
water mass + thermal expansion

More seafloor spreading 100 Ma = wider
mid-ocean ridges = smaller ocean basin
volume

ocean spreading - cretaceous

Changes in volume of ocean basins
• More seafloor spreading 100 Ma =
wider ridges at MORs
• Less collision of continents

PETM

Paleocene-Eocene Thermal Maximum - LASTING 200K YRS , TEMP INCREASE, 5 IN TROPIC 9 IN POLES

ocean acidification, “rapid” change due to CO2 and methane

caused oceans to be acidic - bye bye forams

methane clathrates

crystalline form of methane found in the oceans
Warming oceans = methane released to atmosphere

extreme warming

cezonic cooling

from warm to cold

cezonic cooling antaritica

last tree in antartica - beech 40k Ma

first local ice

botanical evidence

smoothness of leaf edge
correlates with mean annual temperature
• Suggest progressive cooling over last 50 Ma

plant - middle

Andes mountain glaciers

7-3 MA

ice rafted debris

dropstones found in ocean sediments

geochemical evidence

Lower foram δ18O = less ice on land, warmer ocean temperature
• Higher foram δ18O = more ice on land, colder ocean temperature

table O isotopes in foraminifera, Deep ocean cooled by ~14°C

gateway hypothesis

Separation of South America from Antarctica 37-33 Ma

opens drake passage

drake passage

allows circumpolar current to develop around Antarctica

Prevents the poleward transport of energy

ice development = further cooling of Antarctic climate

NOT SUPPORTED

ISTHMUS OF PANAMA

Redirected flow of warm salty water in Pacific towards the Poles

This means increased precipitation in North Atlantic = ice sheets

models show this actually warmed the region = warm summers

NOT SUPPORTED

CO2 DRAWDOWN

Models show that ice sheets form in Antarctica when CO2 falls below 750 ppm

Ice forms in Greenland when CO2 reaches 280 ppm Or lower

CO2 DRAWDOWN evidence

Major decrease in CO2
30-25 Ma – ice on
Antarctica by 34 Ma
• 250 ppm 25-20 Ma – ice
on Greenland 7-3 Ma

uncertain, may be decreasing

BLAG Hypothesis icehouse climate

explains overall trends in atmospheric CO2, except after 15 ma

uplift weathering hypothesis reason 1

plate coliding making really high mountains

No major continental collisions 100-65 Ma (warm Cretaceous)

Uplift-weathering hypothesis reason 2

unusual physical weathering

Sediment influx to ocean from Himalayas increased through time
• Rapid increase after 10 Ma

bc As mountains get taller and taller = more mass wasting
(steep slopes, glaciers)

uplift weathering hypothesis 3

unusall chemical weathering

Much more difficult to
measure and compare
between time periods

Chemical
weathering is what draws
CO2 out of the atmosphere