Test 1: Flashcards
What is the difference between weather and climate
Weather
- daily
Climate
-over a period of time
Why can we not rely on climate records?
- They are short
- measure up to 250 years max - They are sparse
- biased around the N. atmosphere - measurement systems change consistently
- new advancing technology
what is equilibrium
-inputs = outputs
Definition: Response Time:
- how is it measured?
= time it takes the climate system to respond to some imposed change in forcing
measured:
- by the time it gets to 50%
what if the forcing is slower?
=climate system tracks the forcing
what if the forcing is faster?
= little response
eg. volcanoes
the length of “on” time is (directly or indirectly) related to the magnitue of response
Directly related
Definition: Flux Response
= the flux intensity of a forcing
- there can be a lag (eg. heat and H2O)
T/F: system components have DIFFERENT reaction time to the same forcing
TRUE
Climate forcing in cycles can result in cyclic responses from the climate system. What is this known as:
Feedbacks: response of a system to a change in itself
T/F: Responses will only track/closely follow the force(s), not lag behind
FALSE: Some responses will track/closely follow and some will lag behind.
What feedback amplifies?
a) Positive
b) Negative
a) Positive
What feedback reduces or dampens?
a) Positive
b) Negative
b) Negative
The Earth’s system is known as a:
a) Positive
b) Negative
b) Negative
Definition: Threshold
= the system can persist to a certain point (the threshold)
Definition: Weather
= the state of atmosphere at a point in time
Definition: Climate
= Statistics of weather over long-term
-mean
-variability/trends
“What’s expected”
What measures climate + a main component? Where should you not put this device?
Weather stations
- use electronic thermometers (more sensitive than mercury thermometers)
Not good beside a tree
-absorbs radiation
(For rain gauges, the tree can block certain areas)
How has measuring atmospheric climate advanced over time
- kites
- balloons
- satellites
- radiotelescopes
How old is the Earth?
a) 4.45B years
b) 4.55B years
c) 4.58B years
d) 4.75B years
b) 4.55B years
What are the climate system’s components?
- air
- H2O / ice
- land
-vegetation
What are the 2 fundamental climate forces?
- Tectonic forces
- Orbital forces
What are the 2 tectonic climate forces?
Are these slow/fast processes
- earth’s internal heat
- change topography
= slowest process
What are orbital forces?
= variations in earth-sun geometry
If the force source is the Sun, what changes/responses can you expect?
Changes in:
- plate tectonics
- earth’s orbit
sun’s strength
If the force source is the Sun, what climate variation can you expect?
Changes to:
- glaciers: –> H2O levels
- vegetation
- ocean
- land surface
Why is there more solar reflection at the south poles?
Because of Antarctica (a large continental landmass)
the greater angle of incidence, the more reflection (ie. at the n/s latitudes)
T/F: the N hemisphere gets more sunlight than the equator for a short amount of time.
FALSE: the SOUTH hemisphere gets more sunlight than the equator for a short amount of time.
Why is land more variable than water?
Soil has a higher thermal conductivity than water (therefore water gets colder with little sunlight)
Water mixes from prevailing winds + gravity
T/F: Warm air condenses into clouds and will go polewards
TRUE: heat transfers polewards
Definition: Proxy Records
+ give an example
= give insight into climate of that time period
- existed long before weather stations
Eg. ice cores, pollen, glaciers, tree rings, 18O, etc
What are the 2 stable isotopes of Oxygen?
Oxygen 16 and Oxygen 18
T/F: O18 is heavier than O16
TRUE: b/c it has more neutrons
T/F: 16O is more rare in the atmosphere
FALSE: 18O is more rare b/c it is harder to evaporate
If there is more 18O, what does this imply about the climate?
= warmer climate
What is the best available record for over 99% of geological time? Why?
Sediments - b/c it is composed of chemical, physical, and biological material that is usually deposited in water
Pros and Cons to using deep-sea sediments for interpreting climate?
Pros:
- deep ocean waters = stable with continuous deposition
Cons:
- record = only to 100M years due to plate tectonics
(takes 100M years for subduction to occur)
Definition: Loess
= silt-sized grains transported by wind to specific regions of the earth
- contain some clay and sand
MIDTERM: How would you interpret climate from Loess deposits?
Deposits will give data for the last 3M years
- deposits coincide when climates are cold and dry
- oldest deposits = bottom
Why were there no Loess deposits in Canada?
b/c there were ice sheets
What ways can you interpret climate using glacial ice?
- air bubbles - determine composition of atmosphere
- dust
- see 18O water - determine temperature
- pollen / organic matter - see wind direction
What are 2 limitations to using glacial ice to interpret climate?
- the big time scale are only in Greenland and Antarctica
- currently disappearing
How can we use tree rings to measure climate?
= measure the amount fo 18O
18O = enriched (lots) = warm climate
How can we use Geoducks to interpret climate?
- long lived (up to 168 years)
- growth rings are produced in the winter
- abundant along the west coast
- shell growth = sensitive to climate (sea ocean temperature)
MIDTERM: What are the 3 Dating Climate Records?
- Radiometric
- Counting
- Correlative
What components are looked at with Radiometric dating?
= based on radioactive decay of unstable isotopes
Older: Uranium, Lead
Recent: Carbon to Nitrogen
Explain how Carbon can get converted to Nitrogen
- 14C (unstable isotope) is formed when 14N is hit by a neutron (cosmic radiation
- 14N loses 1 proton
- 14C wants to revert back to 14N - 14C bonds with O = CO2
- CO2 - taken up by plants + animals
- Look at the rate of decay from 14C to 14N
- measure how much 14C is left when transitioning - 14C decays back into 14N by either
- finding another proton = 14N
- when an organism dies
What is the half life of 14C?
a) 5580
b) 5560
c) 5780
d) 5790
c) 5780 years (5000-6000 years)
What happens to the 14C that was once 14N?
= it disappears into the atmosphere
What happens to the lead that was once Uranium?
= the lead stays as a solid (stable), which can be measured
How do you perform counting dating?
- can count annual (or sub-annual) layering
(1 band = 1 year)
Eg. trees, coral, speleothems, lake sediments
How do you perform correlative dating?
+ give an example
= relating an unknown proxy series to a known chronology
“happen at the same time as other things”
-find the same species in 1 sediment that was dated and compare to 1 unknown
Eg. Index fossils
- we can associate samples with others we beleive are in the same time scale
Eg. earth’s magnetic polarity
Pros and Cons of using Index fossils:
Pros:
Widespread - can compare fossils from other continents / locations
Cons:
Need to be short lived fossils
- Need fossils that pop up in sediment for a short amount of time and then disappeared.
- can associate that fossil / species with a specific time frame
-better to know it was their 100 years vs if it was 100-10 000 years.
How would you use Earth’s magnetic polarity to describe climate?
- Give an example
- orbital variations have a known periodicity + have a measureable impact on climate
- earth’s polarity has reduced over time + reverses episodically
- match magnetic polarity with rock and time, then with the climate
Eg. Magma with Iron comes up and redirects N/S
What are the problems with using weather stations?
- only data btwn 50-200 years
- changed instrumentation
- difference between ground-based and satellite-based
How much data can be interpreted by tree rings?
= can get data from the last 1K years
How are speleothems used to interpret climate?
= from stalagmites from the ground
- data from the last 700K years
(long record but mixing could occur = unreliable) - not certian if rings in sediment are annual or not
Definition: Half-life
= time it takes for 50% of parent isotope to decay into the daugther isotope
What are the 2 categories of Climate Models
- Physical: ocean/atmosphere, ice, land surface
- Geochemical: biochemical components of the earth’s system
Definition: Physical Climate Models
= models that create a simulation of the Earth’s climate (based on our best understanding on the physics and our best computing power)
- tracks change of energy (energy into system - energy out of system)
MIDTERM: What are the 2 reasons why we use Physical Climate Models?
- Can test hyps in models that we can’t do in real life
- test hyps about observed climate change in the past - Make predictions about the future
- can do predictions in the present (instead of waiting for it to happen naturally)
Eg. predictions about climate change
For any system, we can say the Change of Energy is equal to
= Energy into the system - energy out of system
What are the 4 steps to the “Simplest Equilibrium Model of the Earth”
Step 1: 1-D climate model: Add layers to the atmosphere
- no land-masses / oceans
Step 2: Add latitudinal differences (equator = more solar radiation)
- exchange energy / mass horizontally
- head from equator moves to the poles
Step 3: 2-D energy balance model
- = temperature distribution
Step 4: 3D climate model: add seasonal cycle - increasing levels of complexity
- make the system cover the whole earth
- add more vertical levels
- add an ocean, plants, ice, clouds
Definition: Geochemical Models
= Models used to track Earth’s chemicals as they flow through the climate system.
Eg. sediments, ions, C, O, N, etc
- often coupled to vegetation models
- driven by physical models
-tracks fluxes:
input flux –> reservoir size –> output flux
In the “Simplest Equilibrium Model”, what is Step 2?
Step 2: Add latitudinal differences
- equator gets more solar radiation
- exchange energy / mass horizontally
- heat from equator moves to the poles
In the “Simplest Equilibrium Model”, what is Step 1?
Step 1: 1-D climate model: Add layers to the atmosphere
- no land-masses / oceans
In the “Simplest Equilibrium Model”, what is Step 3?
Step 3: 2-D energy balance model
- = temperature distribution
In the “Simplest Equilibrium Model”, what is Step 4?
Step 4: 3D Climate Models: add seasonal cycle - increasing levels of complexity
- make system cover the whole earth
- add more vertical levels
- add an ocean, plants, ice, clouds
T/F: Geochemical Models track fluxes
input flux –> reservoir size –> output flux
TRUE
MIDTERM: Definition: Residence Time
= amount of time it takes for an element to move from 1 reservoir to another
“avg time it takes for a chemical to pass through a reservoir”
What are 2 problems supporting why the Earth wasn’t always habitable?
- Early sun was 25% less bright than the present
= runaway ice house: freezing of all surface water
- Faint Young Sun Paradox - Venus receives about half the surface sunlight but is way hotter.
“less sun, but is hotter”
- water helps reglate surface temp
Where can you find Carbon on Earth?
- rocks
- coal
- gas + oil
- vegetation
- atmosphere («1%)
(vs Venus: has 96% CO2 = hotter)
How much Carbon is in the atmosphere?
«1%
Definition: The Greenhouse Effect
= CO2 absorbs longwave radiation
Definition: Faint Sun Paradox
= assumes the Early Sun was 25-30% less bright
- should’ve resulted in freezing of all surface water –> runaway ice house”
- high albedo
- no clouds + liquid water b/c water is all frozen
What is the theory of why the Earth wasn’t frozen for 3B years?
+ what is the assumption?
Assumption: something happened that made the earth warm back then, that isn’t happening now
= Thermostat Hypthesis
- some process heats the earth when it’s cold (and vise versa)
What is the theory of why the Earth wasn’t frozen for 3B years?
+ what is the assumption?
Assumption: something happened that made the earth warm back then, that isn’t happening now
= Thermostat Hypthesis
- some process heats the earth when it’s cold (and vise versa)
- assume it’s the GHG Effect
Explain how Volcanic Activity could be the Earth’s Thermostat.
Early in Earth’s History - Lots of Volcanic Activity
–> High CO2 in atmosphere = warming temperature
As the sun got brighter = slower warming
–> High rates of weathering –> less CO2 in atmosphere = relative cooling
How many years woudl it take to absorb all carbon in volcanoes if all volcanic activity stopped?
a) 0.5 years
b) 1.0 years
c) 1.5 years
d) 2.0 years
c) 1.5 years
What is believed to be the balance between carbon in the atmosphere and in the reservoirs?
= Chemical Weathering
Warmer:
= CO2 rise –> more organic acids form (more erosion / weathering)
Colder:
= more CO2 kept in the atmosphere
What are the 3 important factors for chemical weathering?
- Temperature (cold = less weathering)
- Precipitation (More water = more weathering)
- Vegetation (more organic acids = more chemical weathering)
What environment would be optimal for lots of chemical weathering
- Warm Temperature
- More Precipitation / Water
- More Vegetation ( More organic acids = more chemical weathering)
What would happen to chemical weathering if there were no plants?
No plants = no organic acids = Chemical weathering = 1000x slower than today
Why would chemical weathering NOT be earth’s thermostat?
Initial change would be colder, not warmer
-w/ less sun: cold environment, slower hydrologic cycle + less vegetation = less chemcial weathering
What are 3 Alternative Hypotheses with not much evidence?
- Early Sun = bigger
- Solar Wind = stronger
- Decreased Surface Albedo (darker surface)
- less continental area
- no vegetation
What is the most potent GHG?
a) CH4
b) NH3 - ammonia
c) Water Vapour
c) Water Vapour
What are the issue of why the Water Vapour Feedback is NOT the Thermostat?
It is a Positive Feedback
- the others would be negative
(more evaporation = more heat trapped = more heating = more evaporation = …)
Definition: Gaia Hypothesis
: Life = Earth’s Thermostat
- life regulates the climate of the earth in order to maintain a life-supporting cliamte
(insects, plants, people, etc) - Vegetation: critical role in the Carbon Cycle
What are 3 problems with the Gaia Hypothesis?
- There was probably no life present during the early Faint Sun period
- There is no selection pressure
- US (people) - people do not regulate the climate
What was the results of the thermostat” malfunction
= signs of near global glaciation (850-550M years before present) = glaciers
What happened to the carbon after glaciation?
= carbon was left in the atmosphere = frozen
Out of all the options, what is most likely to be the Earth’s Thermostat (and responsible for warming of the earth’s atmosphere)?
= Carbon in Plate Tectonics
Definition: Continental Drift Hypothesis
= Continents started as a supercontinent, Pangaea, and drifted into their current positions
What is the evidence for Continental Drift?
- Continents fit together
- SA + Africa - Rock Type and Structural Similarities
- fossil evidence in different continents - Paleoclimatic Evidence:
Mountains:
- appalachian mountians has the same rock type found in africa
-common age mountains
Glaciation
- glaciation: in areas that are now tropical (eg. africa - could’ve been further south to explain glaciation)
- common glaciation evidence: spread out from antarctica into other continents
What is Wegner’s Dilemma? + who solved this?
= good evidence on continental drift, but no mechanism
- solved by: Hess (Marine Geologist)
What was Hess’ findings?
- saw sea floor spreading when making a detailed map of the sea floor
- saw areas of magma getting out of earth’s core
-Earth’s upper mantle has convection = sea-floor spreading
Evidence:
- see episodic reversals in volcanoes (iron would point north)
How would the climate during Pangaea differ from today?
- continents were in different climate zones in the past
- ocean circulation was different
- 1 big water mass: oceans were not divided - CO2 outgassing may have been different
- Past Glaciation
What is the Polar Position Hypothesis?
= past glaciation occured when the continents were near the poles (for episodic glaciation)
Why is the Polar Position Hypothesis inconsistent?
+ what new hypothesis can we make?
= there were no ice sheets in continents that were in the polar region
New hyp: High latitude is probably necessary “but not a sufficient condition” for glaciation
- need GHGs
What is the Missing Component for Polar Position Hypothesis? How?
=GHGs
What are the 2 hypotheses of why GHGs were so abundant?
- Sea floor spreading hyp (BLAG)
- Uplift weathering hyp - Control of CO2 by Chemcial Weathering
What is the BLAG Hyp?
= rapid seafloor spreading caused more CO2 emissions
-rates of speading = highly variable
In the BLAG hypothesis, what will happen if there is FAST sea floor spreading?
= more precipitation
–> more vegetation
–> more chemical weathering
= take CO2 from atmosphere (reduces)
In the BLAG hypothesis, what will happen if there is SLOW sea floor spreading?
= colder climate
–> less vegetation + less precipitation
= CO2 is added to the atmosphere (warmer)
What is the Uplift-Weathering Hypothesis?
= Control of CO2 by Chemcial Weathering
“Chemical Weathering is the INITIAL DRIVER of climate change, not consequence”
- rate of chem weathering: determined by availability of fresh rock
- young sediments weather more quickly
Why do young sediments weather more quickly?
= becuase they are highly prone to rapid weathering
- steep slopes
- mass weathering
- high precipitation
- glaciers ( turn rock into silt = highly weatherable)
At what 2 main plate boundaries do mountains form? + what are mountains impact on CO2
- Subduction zones
- Continental collisions
Mountains forming take CO2 out of the atmosphere
How can you interpret climate using Wind River Basins?
- Morains = 200-130K years BP
- Basins are the same identical in rock composition
- but rock is varibale in age
Why don’t periods of rapid uplift lead to runaway ice house conditions?
becuase there is continuous mountain building
What was the Earth’s climate 100M years ago
- Seal level: 100m higher
- Central SA, N Africa + Australia = flooded
- Polar regions = warmer climate
- found tropical fossils at poles - Dinosaurs
Why is the S pole warmer than the N pole?
- Antarctica is on land, arctic = on water
- Antarctica = higher elevation
What are the 2 ways of how Paleoclimate is estimated? + examples
- Temp sensitive plants + animals
- Geo-chemcial markers (18O in plankton shells)
Definition: Foraminifera
- bottom dwelling
- shells made of CaCO3
MIDTERM: What are the 3 categories of error?
- Model Physics
-model = wrong
-computers = inaccurate (not refined) - Boundary Conditions
- continent positions + atmosphere components change
- sun position = wrong
-changes in prognostic variables: variables that were once static (height of mountains, sea level depth, glaciers etc) - Reference Climate
- wrong target
What is the Ocean Heat Transport Hypothesis?
: 2/3 heat = transported by atmosphere + 1/3 = by oceans
What did looking at pristine shells imply about the climate
= it reconstructed the Cretaceous climate as it suggests tropical climate was approximately 5 deg C warmer than previously realized
- shells decrease quicker in warmer water
What is Climate sensitivity important for?
- Ice sheets
- Polar bears
- Sea level change
- Global mean sea level = fluctuates by 100m or more over long time scale
Definition: LMSL (Local Mean Sea Level)
= mean sea level (compared to a local benchmark)
-affected by ocean currents, height of land, amount of water
What sea level is affected by ocean currents, heigh of land, and amount of sea level?
a) LMSL
b) Eustatic Sea Level
a) LMSL
What sea level is affected by total amount of water and volume of ocean basins
b) Eustatic Sea Level
Define: Eustatic Sea Level
= mean global sea level
- across the globe
-affected by the total amount of water and volume of ocean basins
What would happen if there is low Eustatic Sea level?
= erosion from continents deposited at the margin
What would happen if there were high Eustatic sea levels?
= erosion inland deposits in the continental shelf
The Cretaceous sea level is estimated to range from 100-300m above modern levels.
What are the 5 reasons that cause this uncertainty?
- decreased volume of ocean basins
1a) decreased mid ocean ridge forming = slow spreading –> larger basin = deeper ocean = lower sea level
1b) fast sea floor spreading –> magma spreads faster + faster subduction = fat profile = higher sea level
- collision of continent effects
- eustatic sea level drops when the basin is bigger (collision = uplift in a plateau and a downfall (aka the root) - transfer of continental sediments
= fan: river dumping sediments - water stored in ice sheets:
- hard to find the exact amount
-antarctic ice can result in a 66m sea level rise (but can decrease as ice has a higher volume than H2O) - thermal expansion of sea water
- water expands when warmed
But, water has cooled to 5-15 deg C in the last 100M years = 7m drop in sea level
What would a decreased mid ocean ridge forming change sea level?
decreased mid ocean ridge forming = slow spreading –> larger basin = deeper ocean = lower sea level
How would fast sea floor spreading change sea level?
fast sea floor spreading –> magma spreads faster + faster subduction = fat profile = higher sea level
If these ice objects melted, how much sea level rise can we expect?
- Antarctica Ice
- Greenland Ice sheet
- Alpine Glaciers
- Antarctica Ice = 66m
- Greenland Ice sheet = 6m
- Alpine Glaciers = 1m
What are the 5 Uncertainties of sea level change complicated by?
- Weight of water depresses ocean floor
- Continentental margins rise and fall
- Shape of Earth (Geoid)
- has changed - Gravitational Variations
What ended the Cretaceous period?
= a meterorite landing in the Upperton Peninsula
What did the meterorite landing in the Upperton Peninsula result in? (Hint: 3 stages)
- Immediate warming
- shockwaves flattened everything around it
- seismic wave = 10^11 - Cooling
- soot blocked light = global cooling effect - Warming
- Increase CO2 from wildfires –> warming
What is the Paleocene-eocene thermal maximum (PETM)?
=55Mya the cliamte suddenly warmed even more
-lasted 150K years
-see depletion of 18O in oceans from sediments (= 18O is evaporated)
What are 3 evidences of cooling?
- Growing Glaciers
- Southern beech trees growing in antarctica (found fossil wood)
- Change in fossil record of leaf shape
- jagged edge leaves / finely toothed= colder climate
- smooth = warmer climate
What are jagged edge leaves / finely toothed leaves associated with?
= colder climate
What are the 2 main processes that affect 18O?
- Ocean temperature
- Size of continental ice sheets
- ice sheets forming = depleted in 18O (ocean = enriched)
b/c ocean loses 16O, as 18O is stays behind (dense)
MIDTERM: Definition: Fractionation
= a change in the relative abundance of a stable isotope during a chemical / physical process
Fractionation points: freezing, evap, melting, condensation, infiltration, runoff, taken up by trees (carbon - by leaf stomata)
-water fractionation = driven by temperature
-tropics = less depleted in 18O than in Arctic
because of precipitation recycling / fractionation
T/F: Tropics are more depleted in 18O than in the Arctic
True: tropics = more depleted in 18O than in Arctic
because of precipitation recycling / fractionation
T/F: In colder climates, there will be more 18O in oceans
TRUE
When ice sheets formed 40My BP, ocean 18O increased from +0.75% to ___%.
a) 2.5%
b) 3.5%
c) 4.5%
d) 5.5%
b) 3.5%
For shells made of CaCO3, what may happen in warm water?
= shells may uptake Mg to make shells instead
MIDTERM: What are 3 reasons why the earth is getting colder?
- Geography (do not believe)
- continental plates move around
-disproven by the Polar position hyp - Ocean Gateway Hyp (do not believe)
=opening and closing of ocean gates changed poleward transport of heat and silt
–> give opposite predictions
a) Pacific ocean (fresh, high precip) does not mix with Atlantic (large evap –> more salty / dense)
- at Drake’s passage (S. America + Antarctica)
- may resulted in cooling of S. Pole
(but does not significantly change the cliamte outside of antarctica)
-reduce poleward fluxes
b) Closing of Panama
= should’ve resulted in warming
- enhanced poleward fluxes
- GHGs
a) BLAG
b) Uplift Weathering
Explain the Ocean Gateway Hypothesis and why it is disproven.
=opening and closing of ocean gates changed poleward transport of heat and silt
a) Pacific ocean (fresh, high precip) does not mix with Atlantic (large evap –> more salty / dense)
- at Drake’s passage (S. America + Antarctica)
- may result in cooling S. Pole
-glaciation coincides with opening of Drake’s passage
(but does not significantly change the cliamte outside of antarctica)
-reduce poleward fluxes
b) Closing of Panama
= should’ve resulted in warming
- enhanced poleward fluxes
Disproven:
= give opposite predictions
Antarctica –> reduce poleward fluxes
Panama –> enhanced poleward fluxes
- neither = cause for glaciation (but important for ocean circulation)
Could decreased GHGs by BLAG cause the observed cooling?
= can result in early cooling, but predicts recent warming that hasn’t happened
- slow sea floor spreading does not explain cooling
What are the 3 Key Assumptions associated with Uplift Weatering as the cause for cooling
Assumes: it takes out CO2 from atmosphere and stored into permanent reservoir in ocean as sediments
- More high elevation terrain
- uplift of Tibetan plateau: think CO2 gets stored in ocean basins
- no evidence of collisions in previous 250Mya - Unusual rates of fragmentation
a) Physical: transfer of CO2 from dissolved and back into atmosphere
b) Chemical: 2nd transfer of CO2 = turned into a solute and stored - Fresh sediments weathering quickly
- than older sediments
What cliamte can you expect if Oceans are depleted in 18O
= warmer climate (taken out onto land)
Why is unusual chemical weathering difficult to measure?
- dissolved ions come from hydrolysis or dissolution
- too many rivers to measure
- human land-use complicates modern signal
Why is Palea signal more difficult to measure?
= exposing fresh sediment –> high chemical weathering
(although there may be no fresh(new) mountains in the headwaters)
