Test 2 Flashcards
What are the 2 fundamental motions that affect us?
- Rotation on its axis
- Revolution around the sun
What does the Earth’s rotation control?
= controls our day / night
What does the Earth’s Revolution around the sun influence?
= controls the summer/winter
Summer:
=closer to sun
- longer sunlight
Winter:
= farther from sun
- sunlight is diffused
MIDTERM: What are the 3 Properties that fluctuate?
- Tilt
- Eccentricity
- Axel Precession (“Wobble”)
Definition: Tilt
“a metronome”
- oscillates between 22.2 and 24.5 degrees
1 cycle takes 41 000 years
= in phase between hemispheres
MIDTERM: how long is 1 cycle of Tilt
= 41, 000 years
What is our current tilt? is it increasing or decreasing?
23.5 degrees
= decreasing (tilt is getting more vertical)
Definition: Eccentricity
“more circular / elliptical”
= sometimes closer and farther to sun
=how elliptical is the earth’s orbit around the sun
- may be due to the Gravitational pull of Saturn and Jupiter
Controlled by 2 dominent periodcites:
- 100,000 and 413,000
MIDTERM: How long is 1 cycle of eccentricity?
100,000 years
Definition: Axel Precession
= wobble on the axis
Period: 23, 000 years
= out of phase between hemispheres
MIDTERM: How long is 1 period of Precession?
23, 000years
MAX Tilt + Precession coincide with Perihelion or Aphelion?
Perihelion = closest to the sun
Where can you find MAX Warming?
- in the N hemisphere
= when the summer solstice coincides with perihelion - MAX Tilt + precession
What do the 3 fluctuating properties result in?
= these result in a shift in position of the equinoxes (and solstices) around the Earth’s orbit every 23,000 years
What happens every 23,000 years?
= the shift in the position of the equinoxes (and solstices) around the Earth’s orbit
results in a differing amount of sun in the summer
= precession
Definition: Aphelian
= when the Earth is in the farthest position from the Sun
Definition: Perihelion
= when the Earth is in the closest position towards the sun
What is the importance of orbital properties?
= these determine how much radiation is received
Definition: Insolation
= Radiation received at the top of the Earth’s atmosphere
Units: Watts per square metre (W/m2)
T/F: The N/S Hemisphere gets more sunlight all year round and the Equator gets more short term
FALSE
The Equator gets more sunlight all year round
The N/S Hemisphere gets more short term sunlight
____ has a stronger affect at higher latitudes than ____
a) Tilt
b) Precession
Tilt has a stronger affect at higher latitudes than Precession
Out of tilt, precession, and eccentricity, which is the least important?
Eccentricity = least important
- approximately 0.2% incoming solar radiation
- small difference in sunlight
Tilt + Precession:
- approximately 10% difference in long-term mean
Tilt is in phase / out of phase between hemispheres?
In phase
T/F: Tilt affects the N/S hemispheres differently.
FALSE: It affects both hemispheres equally
Both hemispheres get hotter when they face the sun
T/F: Pression affects the N/S hemispheres differently
TRUE:
When the S hemisphere is warm, the N hemisphere is cold
When 1 hemisphere is in aphelion, the other is perihelion.
If summer occurs at perihelion it will be dimmer/brighter, but longer/shorter
If summer occurs at perihelion, it will be brighter but shorter
What is the caloric isolation seasons
= divide year into halves based on total isolation
182 brightest days vs 182 dimmest days
T/F: Tilt is more important at high latitudes
TRUE
T/F: Pression is more important at high latitudes
FALSE: Pression is more important at low latitudes
Definition: Time Series Analysis
= a set of tools and techniques for analyzing time series data
eg. data from tree rings, climate data
eg. Spectral Analysis:
= used to identify dominent frequences of variability
“how strong is the variability”
Definition: Spectral Analysis
- a ,method for time series analysis
= used to identify dominant frequences of variability
“how strong is the variability
Why does the real-world spectra never look like the model?
- because the 41,000 and 23,000 have changed over time
- hard to tell with oceans because of mixing
- we tend to under sample (aka aliasing)
- a problem with most climate records. eg ice sediments / oceans
- results in missing data - the paleorecord = imperfect,
- cliamte differs in different locations
Definiton: Aliasing
=mis-identification of signal frequency during sampling
- aka undersampling
- results in missing data
What data is not under sampled?
Data from tree rings
Over the years, how has our tectonic scale changed the earth’s orbit?
- rotation on the axis is slower
- precession = slightly slower
- tilt cycle = longer
How are Monsoon Circulations caused?
= when there is a really high heat difference from the ocean and land
Oceans have a higher heat capacity than continents
= drived large-scale advection of moisture
Continents are hotter in the summer and colder in the winter (creating summer and winter monsoons)
T/F: Oceans have a lower heat capacity than continents
FALSE: Oceans have a HIGHER heat capacity than continents
How are Summer Monsoons formed?
In the summer,
- continents = warmer
-oceans = colder
- air on continents warm up from the evaporation over oceans, resulting in rain –> monsoon
How are Winter Monsoons formed?
In the winter,
- continents = colder
- oceans = warmer
Where are Monsoons strongest? and Why?
= in the N Hemisphere
- B/c there are more continental land masses than in the S hemisphere
- creates a stronger affect - B/c there are more mountains
- mountains amplify rising air
Describe the Coriolis Effect
In the N Hemisphere:
- Objects moving N will deflect to the right
- Objects moving S will deflect to the left
The opposite will occur in the S Hemisphere.
- this increases towards the poles
What happens do the the motion of a rotating surface?
= objectes in motion will be deflected due to differences in linear velocity
- causes the coriolis effect
With the coriolis effect, in the N hemisphere, objects moving N will deflect to the ____
a) left
b) right
a) right
With the coriolis effect, in the N hemisphere, objects moving S will deflect to the ____
a) left
b) right
b) left
Definition: Orbital Monsoon Hyp
= orbital changes in solar radiation should influence the intensity of monsoon rains
In the N hemisphere,
hotter summers + more tilt = stronger monsoons
What creates the strongest monsoons?
In the N hemisphere with hottest summer + MAX Tilt
What evidence from N. Africa can help explain monsoons?
A more intense monsoon = higher lake levels
- water pushed up into N Africa (goes up North)
Less Intense = lower / no lakes
- weak monsoon = pushes up less strong
What are the 3 underlying assumptions for evidence in N. Africa?
- threshold response
= when solar radiation goes up, it does not go past a threshold - monsoon strength “a” isolation > threshold (alpha = a)
- lake levels “a” strength of monsoon
= are proportional
Definition: stinky mud
= when fresh water with high organic content dumps into less dense salt water resulting in a cap of organic debris
- fresh H2O (less dense) = from nile river
- mediterranean (more dense)= salt water
= this results in “a cap” = prevents oxygen going down into the deep water –> results in anaeobic decomposition (aka stinky mud)
low salinity lid separates from Oxygen-rich deep water
What happens to the fresh H2O diatoms in the Summer?
Summer = high evaporation
Fresh H2O diatoms (from continental lakes)
- Diatoms = single-celled algae (a common marine phytoplankton) is exposed to wind erosion
- These diatoms end up in the N. Atlantic from fresh water lakes that dry up.
Definition: Diatoms
= single-celled algae
- a common marine phytoplankton
- deliver 23,000 years
MIDTERM: Definition: CLIMAP
= when different people come together to map 1 point in time
MIDTERM: What are the 3 lines of evidence for the Orbital Monsoon Hyp
- stinky mud in the Mediterranean
- anaerobic when fresh H2O comes up - pond filling in N. Africa
- Fresh water diatoms
- strong monsoons = winds blow into N. Africa
–> deliver water from atlantic to ponds
–> weak winds / monsoons - lakes dry out
When looking at the N African Paleorecord, Sediment cores fro the Atlantic ocean south of the Equator shows a _________ year cycle
23,000 year cycle
What evidence is there to support a 23,000 year cycle of the N African Paleorecord?
- Monsoon Phasing
- the last monsoon maximum lagged isolation peak by approximately 2K years.
= expect to be out of sync between hemispheres. B/c - a delay because of ice sheets
- misalignment betewen monsoons and equinox
- sun comes up but it takes time for the system to warm up - Regional Evidence
= there are different monsoons across the world
- Asian monsoon = the most powerful
- Brazillian monsoon = most important in S hemispheres.
(big delivery of water from ocean to terrestrial regions)
How does Monoon Phasing support how the N. African Paleorecord has a 23,000 year cycle
- Monsoon Phasing
- the last monsoon maximum lagged isolation peak by approximately 2K years.
= expect to be out of sync between hemispheres.
B/c
1. a delay because of ice sheets
- misalignment betewen monsoons and equinox
- sun comes up but it takes time for the system to warm up
How does regional evidence support how the N. African Paleorecord has a 23,000 year cycle.
Regional Evidence
= there are different monsoons across the world
- Asian monsoon = the most powerful
- Brazillian monsoon = most important in S hemispheres.
(big delivery of water from ocean to terrestrial regions)
Precession is expected to be out of phase between the hemispheres. What does this mean for teh N and S hemispheres?
When the N Hemisphere is in Perihelion, the S Hemisphere is in Aphelion
What can give a record of monsoons?
Speleothems
= are also out of phase
(18O is enriched in brazil, and it is depleted in china
-dry in N hemisphere + wet in S hemisphere
= driven by precession
When there is more energy in the system,
= more 18O is evaporated and ending up in the terrestrial
- 18O evaporates and ends up in ice cores/speleothems/tree rings
Cold Climates:
- have more 18O in the ocean
What happens when tilt coincides with Perihelion?
=summers will be hotter
=winters will be colder
What happens when summers coincide with perihelion?
= it points towards the sun and the S. hemisphere has warmer summers
What is the conclusion of the orbital monsoon hyp?
= it has passed so many tests that it merits the higher status of a theory
- every prediction has been proven true for orbital monsoons and orbital fluctuations
“almost considered fact”
Why does the orbital monsoon hyp matter?
= relates to rising CO2
T/F: In the summer, the land heats up faster than the ocean
TRUE:
= mountains + large continental bases help
(= stronger at low latitudes)
What can we assume about Monsoons on Pangaea (200My ago)
-large continents at low latitudes were driven by monsoons
- low latitudes = assume driven by precession
How can you interpret deep lake sediments?
= use varves: layers in rock
- normalluy annual
- abundant in carbon
How can you interpret shallow sediments?
= use fish remains
- get fish scales, located on shallow sediments
How can you interpret dried out sediments?
= using oxidized cracked footprints
What are 3 ways to look at sediments?
- deep lake sediments: varves
- shallow lake sediments: fish remains
- dried out sediments: oxidized cracked footprints
T/F: tectonic scale processes are shorter than orbital scale processes
FALSE: tectonic scale processes are LONGER than orbital scale processes
How do plate tectonics affects monsoons?
- lots of uplifting from mountains result in cooling –> dampen monsoons
Now, monsoon systems is weaker (b/c of plate tectonics)
+ the threshold for monsoons is surpassed more often in the past. Less in the present
Describe how ice accumulation occurs?
Glaciers develop wherever
(polar position hyp = glaciers occur at high latitudes)
- accumulation exceeds ablation
- accumulation occurs up to the Mean Annual Temperature (below 10 deg C)
- High Temp = limits accumlation
- due to increased rain (rain helps melt ice) - Low Temp = limits accumulation
- due to low moisture (cool air doesn’t warm water = low moisture)
MAX accumulation: a rate of 0.5m per year
How does High T limit accumulation
= increased rain
- rain helps melt ice
How does Low T limit accumulation
= low moisture
(cold air doesn’t warm the water = low moisture)
MIDTERM: What are the 3 main mechanisms of Ice accumulation?
- Solar warming
- Advection
- wind from polar - Calving
Defintion: Ice Mass balance
= the difference between accumulation and ablation
aka “mass balance”
accumulation - typically in winter
ablation - typically in summer
Net positive mass balance:
- alpine at high elevation
Net negative mass balance:
- low elevations
Ice extent = ice balance over time
Defintion: Ice extent
ice balance over time
What does it mean for glaciers if our climate is static
Climate = static
- meaning glaciers will continue to gain mass and deliver across a slope
Do glaciers grow in the winter or summer? Why not the other?
= winter
Winter:
- high latitude winters ae always cold
- insolation is always low in winter
Summer:
- hot summers will melt snow, no matter how much falls
-hot summers drive interglacial cycles more than winter
-low insolation results in less ice ablation
MIDTERM: Milankovitch Theory
= hypothesized that the 65 deg N is the most critical latitude
- has large land masses
-latitude where ice develop first and melts lask
conclusion: ice sheets grow when summer insolation at 65 deg N = minimal (grow at N hemisphere)
- low tilt
- in N hemispere: Summer solstice at aphelion
-orbit = more eccentric (more elliptical)
overall hypothesis: the earth-sun geometry drove what is happening with glaciation
In what conditions can ice sheets grow (Milankovitch theory)
= when summer insolation at 65 deg N is minimal
- grow in the N hemisphere ( when summer solstice is at aphelion)
- low tilt
-orbit is more eccentric = elliptical
What happens when solar insolation is high?
= more melting
What do Ice Sheet Models display?
= consider a 2D model of ice growth at high latitudes
Definition: Phase lags?
= the delay in 1 cycle relative to another
What is the phase lag between 65 deg N and ice volume?
= about 10K years
What are the bedrock responses to ice sheets?
- ice builds up on continental terrain
- will depress the surface underneath (aka the underlying bedrock)
= this will lower the ice sheet
- when the sun melts the ice sheet, the land will spring back, resulting in a cycle.
1 cycle is 30, 000 years
= a positive feedback loop
How long is 1 cycle of the bedrock response to ice sheets?
30, 000 years
What did Milankovitch not hypothesize?
- glaciers can self maintain at a certain height (when glaciers get big enough)
- if below, they melt - insolation lags: lag between insolation and ice volume
- phase lags
- didn’t anticipate that the phase lags are different between tilt and precession
Definition: Insolation Lags
= lag between insolation and ice volume
Are bedrock responses to ice sheets a positive / negative feedback loop?
= 2 positive feedback
-more ice building at a certain height = more growth
-more ice melting = below the standard ground level = more ice melting
When was the start of the Pleistocene?
= 2.75MYA
How long is the lag between glaciation and non-glaciation, and then what has it shifted to?
41K years and then it shifted to 100K years
What are 3 hypotheses of the shift in period between glaciation and non-glaciation?
- there are two 41K cycles, not one 100K
- b/c they were wet based glaciers that transitioned into dry-based
-sediments don’t exist anymore because of many wet-based glaciers - didn’t predict that CO2 drops
(ice sheets grow with lower insolation, then CO2 grops making ice sheets grow = colder - positive feedback loop)
Explain how wet-based glaciers can transition into dry-based glaciers?
Wet based glaciers:
- easy to slip over mud / sediments
-lots of wet based glaciers = less sediments + mud
= leads glaciers to grind over bedrock (= dry based glaciers)
Are CO2 levels and ice growth a positive or negative feedback loop?
= positive
- ice sheets grow with lower insolation
- CO2 drops = ice sheets grow
= colder –> ice sheets grow
What are ice flow models based on?
=based on esitmated rates of accumulation physics of ice flow
MIDTERM: Ice bubbles are trapped (or not entrained/ exchange with the surface below ____m?
35m
What 2 areas could explain the missing CO2 from the atmosphere? What is the most proabbly answer?
- Vegetation
- Deep Ocean
Best Guess Deep Ocean
Why do we NOT think that CO2 went into vegetation?
- terrestrial vegetation reduced by 25% (probably less vegetation during glaciation
- during warmer climates, soils don’t store as much carbon
-all carbon from vegetation is also missing
(so there is missing CO2 from biosphere and atmophere)
Why DO we think that the missing CO2 from the atmosphere went into the Deep ocean?
= looked at the benthicforaminifera
- live at the bottom of the ocean + absorb CO2 from the atmosphere
= showed a signal between 13C and temp have a feedback where temp amplifies 13C. Temp tracks carbon
T/F: 13C tracks temp
FALSE: Temp tracks carbon
What is the global mean 13C from benthic foraminifera?
= -0.35% to -0.4%
What is the difference between Carbon 12, Carbon 13 and Carabon 14?
12C = stable and common (98.9%)
13C = stable but rare (1.1%)
14C = unstable (reerts to 14N)
What are 3 ways Carbon could get into Oceans?
- Increased CO2 Solubility
- Biological transfer from surface waters
- Changes in feep water circulation
- increased CO2 solubility
=oceans absorb CO2 when it gets colder
- colder fluids exchange gas more readily than warmer
- colder water dissolves CO2 more readily
- salty water = less readily than fresh water
= net effect: 14PPM is removed
- ice core reconstructions suggest approximately 90PPM
- Biological transfer from surface waters
- surface waters = more productive (more plants that photosynthesize) –> more photosynthesis = more pumped into the deep ocean
= increased transport of carbon
- may be less evaporation + less clouds = more photosynthesis?
- most photosynthesis in shallow waters against continental margins (nutrients are from rivers in the form of dust in colder regions)
-most productivity at poles
Iron fertilization Hyp:
= stronger glacial winds + increased aridity = more iron-rich dust into the oceans
- dust from continents are fertilizing plants in ocean
= limited by iron, the dust storms fertilize the oceans = more productivity = moving carbon out of the atmopshere
- Changes in deep water circulation
=the LGM led the oceans heat transport to sped up –> increased CO2 into deep ocean
- associated with glacial periods
- no mechanisms (if there is enough chnage in terrestrial env during, you don’t need ocean fertilization, you existing Carbon and pump it down faster = reduced level of CO2
- less N atlandtic deep water formation + more antarctic deep water formation
= more deep water formation coincides with glacial (less with interglacial)
-stronger antarctice overturning = more production _ downward C pumping
-Polar Alkalinity Hyp:
= Antarctic deep water is more corrosive = more carbonates (and then they will react with CO2 = less CO2 in atmosphere)
How can we estimate the age of ice and age of air bubbles?
= how ever long it takes for 35+ m of ice to form
- approx 200 - 2000 years
What is the Iron Fertilization Hyp
= stronger glacial winds and increased aridity –> mnore iron-rich dust entering oceans
=dust from continents are fertilizing plants in the ocean
- productivity is limited by iron (dust storms fertilize the oceans = more productivity = moving more carbon out of the atmosphre)
Where is Methane = produced?
= anoxic environments
(w/out oxygen)
- wetlands
- Wetland hyp = stronger monsoons = more wetlands - permafrost
What are the orbital scale climate roles of CO2 and CH4?
- 23K year cycle
-mostly in phase with isolation (monsoons + methane) - 41K year cycle lags isolation
- no signal at 100K
Are GHGs a forcing or feedback?
AKA is temp a driver or is methane a driver?
= Probably both
- GHGs amplify the effect of isolation on glaciation at 23,000 year scale
(not as much at 100K scale - glaciation afffect GHG abundance at 41,000 year scale
-reason = unknown (zeev thinks it is tilt)
T/F: Once you change the ice sheet, you can change the climate
= TRUE:
Ice sheets are an internal forcing
How are Ice sheets internal forcing agents?
- high elevation
- ice sheets have high elevation
-thin air above - high albedo (positive feedback: ice = high albedo –> reflects heat = colder –> more ice growth )
- Low temp (takes a lot of energy to turn water into ice)
- low moisture
- takes a lot of energy to sublimate and melt ice
During glacial periods, are deep oceans high/low in 18O and 13C
- high 18O
-low 13C
During interglacial periods, are deep oceans high/low in 18O and 13C?
- low 18O
-high 13C
12C gets back into atmosphere and into plants
Describe the Polar Alkalinity Hyp
=antarctic deep water is more corrosive = more carbonates
(and then they will reactice with CO2 = less CO2 in the atmosphere)
What is the Wetland Hyp?
stronger monsoons = more wetlands
What are the 2 Milankovitch theories?
- Milankovitch cycles change both ice and GHGs
= changes in solar forcing = change decay and growth of ice and the composition of GHGs - Milankovitch cycles change growth and decay of ice sheets. The change of ice sheets then cause GHGs
What cycle is driving Summer isolation?
= 23K year
What cycle is driving ice volume in the Early Pleistocene?
= 41K year - probably driven by something at high latitudes
What cycles is driving ice volume in the Late Pleistocene?
= huge strength at the 100K scale
- could be some lags of the 41year cycle
What are the 3 possibilities for the 41K year glacial world (in the Early Pleistocene)?
- insolation variability weak at 23K year
-summer insolation increases at 23K year are cancelled by shorter summers
- high tilt = hotter summers - interhemispheric cancellation of 23K year signal
- N and S hemisphere glaciers have a 23K year signal
= signals cancel out
- but if it is a 23K, it should be out of phase (eg. S has huge ice sheets and N has none) == but this is wrong
- N Hem ice did vary at the 41K year preiod based on the Benthic Foraminifera (strong variation at the 41K year) - CO2 feedback at 41K year
- b/c of a positie feedback from CO2
- GHGs amplify the effect of insolation on glaciation at the 23K year scale
- glaciation affects the GHG abundance at the 41K year scale
prediction
- a 41K year cycle at high latitudes where there is a lot of permafrost – canada
Definition: Glacial Flour
= glaciers grind fown sediment
How has the climate signal tranferred south?
= evidence of 100K year cycles in pollen records
-led to the South pacific mystery
T/F: high ice volume has less grasses
FALSE: high ice volume has lots of grasses
Define the South Pacific Mystery
= why/how is the N hemisphere ice signal transferred south?
What are the 3 predictions of how the N ice signal transferred south?
- Changes in sea level
- sea level drops
= atmospheric cooling
= oceans get further away –> the ocean affect is diminished - Changes in deep water circulation
-thermohaline circulation
-changes in 13C
-may have less heat transfer = S gets colder - Changes in GHGs
- ice ages = less methane /CO2 = colder cliamte
- more cooling at polar regions
Why do N icew sheets vary at the 100K year?
= ice interations with bedrock
- could take 100K years for the ice to push bedrock down
- ice sheet sliding
- Early Pleistocene: water under ice sheet = good for sliding
- Milankovitch driven
- all mud is gone = no sliding = no small glaciers form = the ice will get bigger/taller = restricted to N and do not melt becuse they are above the equilibrium line
What is the supporting evidence to why N ice sheets vary at the 100K year?
= Moraines
What is the most probable of the least likely reasons of why N ice sheets varied at the 100K year?
= interactions with GHGs
- b/c ice does not completely melt between 41K year cycles, CO2 effect is amplified
this should have resulted in a 82,000 year cycle
Glacial cycles at 41K year (and especially the 100K year) are proabbly controlled by _______
timing of ablation
