1
Q
What were the features defining the (most recent) glacial world?
A
=more ice, less gas
1. Continents in ucrrent configurations
2. mountains and plateaus where they are today
3. !!ginormous ice sheets!! (defining feature)
4. less GHGs (CO2 in atmosphere)
- not sure why less CO2 +CH4
2
Q
Definition: Cold based glacier
A
= on ice (therefore it moves slowly forward)
- ablation occurs by calving
3
Q
CLIMAP: how big were the ice sheets?
What are the 3 main points of contentions?
A
- Did ice sheets reach their max extents at the same time?
- “did the 3 big ice sheets grow at the same time”
- Evidence (benthic foraminifera)= yes - How extensive were marine ice sheets?
- “how big”
- Not sure - How thick were the ice sheets?
“ how much CO2 came out of the atmosphere”
- CLIMAP - predicts ice was thick
: dry glaciers - less slip, stqay above ablation line = grow taller
- Current thinking - thinner: looking at how fast it retreated
: look at isostatic rebound but more extensive
4
Q
What are “prolific produces of rock debris”?
A
=Glaciers
- this gives good evidence on the previous glaciers, but looking at the glacier soils and dirt.
5
Q
What happened with the ice sheets 9K years ago?
A
= they did not grow, even though solar insolation decreases
- This is because of tilt and precession (the solar forcing doesn’t decrease as fast to cause another galciation)
6
Q
Why are there no sand loess deposits in Canada?
A
= because it was covered in ice
7
Q
What are white sands associated with?
A
= glaciation
8
Q
What can be trapped in ice cores?
A
- ice bubbles
- pollen
- dust
- Na ions
- NaCl ions
9
Q
What are 2 characteristics of Pine plants?
A
- prolific produces of pollen
- can’t self pollinate: can only with those that are wind borne
10
Q
T/F: The climate ouside of the ice affected regions were also affected in the N and S hemisphere
A
TRUE
11
Q
In the southern hemisphere, the cliamte changed NORTH/SOUTH of ice affected regions?
A
SOUTH
12
Q
How much colder were the tropics? + why does this matter?
A
CLIMAP: says it was 1-2 deg C colder
Why it matters:
- tropics are not directly affected by ice, therefore it must be responding to GHGs
= the change in temperature shows how sensitive is the earth
- If it was a lot colder,
= we would be highly sensitive to rise in CO2.
13
Q
T/F: Terrestrial environments experience small amounts of cooling.
A
FALSE, Large amounts of cooling
14
Q
LOW LATITUDES in Terrestrial environments experience __ - __ deg C of adiabatic cooling?
+ what type of adiabatic cooling is this?
A
3-4 deg C
assume wet adiabatic lapse rate (if it was dry, it would be 6-10 deg C)
15
Q
What is the problem with CLIMAP’s estimate of the climate in the tropics?
A
= estimate is too small
- tropical plankton is less sensitive to temperature than to food availability
- small changes in community structure were due to increased food availability
16
Q
What is the problem of Glacial data’s estimate of the cliamte in the tropics?
A
= estimate is too big
- glaical seas were lower back then
- mountains were higher
17
Q
What is today’s world climate compared to the cliamte in the tropics?
A
= in the middle
- not as sensitive as terrestrial suggests but more than CLIMAP suggests
18
Q
What is the Climate sensitivity to GHGs?
A
= approx 1 deg C / 30 ppm
Reasoning:
- tropical cooling was approx 30 deg C
- Atmosphere CO2 was 90ppm lower
19
Q
Modern CO2 is ___ ppm higher than pre-industrial
A
140ppm
20
Q
How can you tell when ice sheets melt?
A
= use carbon dating
- Deglacial processes ended 10K years ago
(10K years ago: Max tilt, summer coincided with perihelion)
Radio carbon dating in corals
- come from atmosphere + into the mixing layer in the ocean
- deep ocean had older carbon compared to atmosphere
21
Q
When did max tilt occure at the same time when summer coincided with perihelion?
A
10K years ago
22
Q
Describe the Deglacial two-step.
A
= suggests complex ice dynamics
- shows the amount of H2O added as a function of time (glaciation)
- fast part of glaciation
- slow part of clatiation (Younger dryas)
23
Q
What provides evidence of local melting?
A
=planktic foraminifera in meltwater regions
foraminifera will be 18O depleted when glacial ice melts into the ocean
(b/c glacial ice is highly depleted in 18O)
24
Q
What are the 5 lines of evidence for younger dryas?
A
- pollen archives
- atlantic foraminifera
= pollen from the oceans - temperature proxies (chironomids)
- shed outside skin
-sensitive to temp - moraines (glacial readvances)
- ice cores
25
T/F: there was less ice accumulation in the interglacial period and rapid ice accumulation during the younger dryas
FALSE,
- rapid ice accumulation in interglacial
- less ice accumulation during younger dryas
26
What caused the Younger Dryas
= the Younger Dryas cooling remains an enigma
Possibility: changes in flow of meltwater
Fresh + Salt water have diff densities = cap --> prevents N atlantic water
Cons:
- still a lot of water coming from the Gulf of Mexico
- no evidence in Arctic, no mass of fresh water coming in at once
27
Why is the change in flow of meltwater not a plausible explanation for causing the Younger Dryas?
- still a lot of water coming from the Gulf of Mexico
- no evidence in Arctic, no mass of fresh water coming in at once
28
Define: Deglacial Climate Feedbacks + give 2 examples
- deglacial climate initated by rising insolation
- needs positive feedbacks to amplify the signal
2 examples
= ice dynamics could have caused rapid thinning
1. lifting
= sea level will rise, ocean will life up tongue of glacier and glacier may lift and slip into the ocean (as well as calf)
2. glacier grinds bedrock
29
How are deglacial lakes and floods formed?
= ice accumulates mass > depresses underlying bedrock = lakes form at the front of glacier
floods can form after a dam (1 major floor of many small floods)
30
What are the 4 channeled scablands?
1. V-shape valleys - from rivers
2. U - shaped valleys - from glaciers
3. square shaped valleys
3. ripples
31
T/F: stronger monsoons are associated with increased solar forcing
TRUE
32
If the wind blows in one way, in what direction is is the mass transport?
= the mass transport is 90 deg in the direction of the prevailing winds
--> wind blows in one way, the ocean transport is 90 deg
- brings up deep water and monsoon associated species
33
Geological evidence suggest even stronger monsoons than the theory predicts. Why is this so?
1. stength of monsoons are based on the strength of the winds
Why? more feedbacks happen in the monsoon system
2. precipitation recycling by vegetation enhances moisture transport.
- see max precipitation at 10-15 deg N (with vegetation, there will be more precipitation higher north)
34
At the LGM, what regulated high latitude cliamtes?
=ice sheets
- as ice sheets melt, isolation dominates
35
What changes occured after ice sheets melted after the LGM in high latitudes
1. vegetation migrated N following glacial retreat
2. diff species migrated at diff rates in diff directions
36
Define the "No Analog Problem"
1. postglacial vegetation assemblages exist nowhere today:
eg. midwestern forests (spruce, ash, etc)
2. unique climate
there is no similar cliamte regime that exists today
3. unique vegetation history
= vegetation responding individualistically to HUGE changes in climate
37
Describe the Hypsithermal Era
+ provide 2 potential causes
=mid holocene temperatures were the highest in the last 100K years
- no ice, 5% brighter
Causes:
1. sea ice feedbacks
= high latitude warming amplified by albedo changes
2. role of vegetation - vegetation feedbacks
= high latitudes amplied by albedo changes
- vegetation responds to warmer temperatures
38
Why does vegetation matter for monsoons?
=plants transpire and then wind blows it more inland = monsoons occur further inland
39
T/F: After the Hypsithermal era, there was a period of renewed warming
FALSE, renewed cooling
40
Describe the renewed cooling period, following the hypsithermal era
= isolation has decreased 5%
- ice cores from arctic
- marine sediment cores in N. Atlantic
- glacial advances in high arctic
- treeline retreat: further north / further upslope
41
Definition: Millenial Oscillations
= range from 1-9K years
- strongest / mainly during glacial periods
- is quasi-cyclical
-out of phase between hemispheres
-decreases in 18O are matched by increases in dust
- no obvious cause
2 parts:
1. Stadials: the cold part of the cycles
2. the warm(er) phases in between the stadials
42
With millenial oscillations, decreases in 18O are matched by increases in dust. Why is this important
There is more -ve oxygen in oceans when its colder, and less when its warmer
43
How can we get information on the N atlantic oscillations?
= look at sedmient drift
- have high resolution
- accumulation rates are 10x higher than most ocean records
44
Why are most ocean records not sufficiently resolved?
- accumulation rates 1-2cm / K years
- bioturbulation in top 5-10 cm
45
Why is detecting and dating elsewhere hard?
= not easy to do
- climate resolution too slow
- dating inaccuracies are approx 1K years
46
T/F: there is little to no evidence for interglacial oscillations
TRUE
47
What are the 5 potential causes of Millenial Oscillations?
1. Stochastic resonance
= red noise w/ a weak preference for millenial variability
2. Solar variability
- stronger sun = less production of radiocarbon
- cycles: 420 years or 2100 year
3. Ice Sheet Instability
= ice dynamics along ocean margins impact a- 1K year signal
- ice sheets vary on diff continents
3a. Build up ice
= glacier stalls out, geothermal heat will melt glacial ice = calving + ice retreat
3b. sea level rise: positive feedback loop
- sea level will rise when ice melts from being calved off in the ocean
- short / long scale sea level change
4. GHG forcing
- insufficient data
5. Ocean Heat Transport
- only affects coastal regions
48
Why are millenial oscillations important to understand?
= because they are much faster than orbital changes
49
Is the current warming natural?
= probably not
- unpredictable
- only occured during ice ages
50
EXAM: Describe the Savannah hyp
= African forests dried out to form patchy savannas. This influenced humans to evolve and stand to look around
51
EXAM: Describe the variability Selection Hyp
= rapid evolution occured in response to a changing environment
- early pleistocene: 41K time scale glaciers
- late pleistocene: 100K time scale glaciers
(alternate from dry to wet conditions)
therefore, needed to adapt under those variable conditions
52
What conclusion can be drawn from the Savannah Hyp and Variability Selection Hyp? What is a challenge of this?
= evidence supports a transition from forested to savanna conditions at the point of rapid evolution
Challenge:
- can't tell if there is a slow evolution and then a rapid selection (not enought evidence)
53
What are the 2 suggestions of why farming started at the end of the last glaciation?
1. Warmer wetter climate made it possible
2. The younger dryas made it necessary
- agriculture is a solution (when it got cold and dry)
54
What can we look at to discover how humans had a profound impact on land cover
= pollen records
55
Describe the OverKill Hyp
= humans had the tools and experience to kill more animals to the point of extinction
= humans changed the climate so much to drive large mammals to extinction
"early agriculture had an impact on GHGs and climate"
56
Why is the last glaciation event unlike every other glaciation event?
= CO2 and CH4 started to rise after the last glaciation event, whereas the other glaciation events saw that they went lower
57
Describe the Early Anthropogenic Hyp.
=deforestation associated with early farming efforts released CO2
+ rice paddies and livestock released CH4
(half life of CH4 is short)
58
T/F: the Half life of CH4 is short
TRUE, it is 25 years
59
How can humnas raise CO2 by a significant amount?
= they can't. They need unknown feedbacks to amplify
60
Describe the Medieval Warming Period
= climate warmed from 1000-1300 CE
- mostly focused in N Atlantic
(europe got warmer)
- globally asyncronous (suggests some warming in certain places)
61
T/F: THe Medival Warming period was globally synchronous
FALSE, globally asynchronous
62
What happened 100 years after the Medieval Warming Period?
The Little Ice Age
63
Describe the Little Ice Age
= climate cooled from 1400-1900 CE
- widespread evidence in the N Hemisphere
areas covered in ice now have vegetation in the present day
64
How can we use Map Lichen to understand if an area is glaciated?
- grows radially - can date using their diameter
= bigger diameter = suggests its not glaciated
- get scraped off by ice / killed from snow
65
What are the 3 lines of evidence that the recent climate warming was unprecidented and there was a medieval warming period
1. Quelccaya ice cap peru
in 1975: 1500 years of annually recovered data
1991: unprecedented ice melt (only melt water)
- the melting lost the annual signal
2. Tree Rings
3. Corals
after 1850, it gets warmer
66
What are the 5 Causes of Preindustrial Climate Changes? + what is the best answer
Best answer: All contribute (except orbital forcing)
1. Orbital forcing
- too slow
- could cause about half of observed cooling before the Medieval Warming Period
- could also contributed to anomalous warming during the Medieval Warming Period
2. Bipolar seesaw
- Dansgaard-Oeschger oscillations could enhance orbital forcing (only in glacial periods)
- could also contributed to anomalous warming during the Medieval Warming Period
3. solar variability
- sunspot variability could affect the climate
Direct Measurement: satellites measure 0.11% variability in solar output
Indirect Measreuments: look at # of sunspots
- max height of ice extent ( in ice age) = lowerest number of sunspots
- end of ice age = lots of sun spots
4. Volcanoes
- volcanic emissions exert a strong cooling affect
EXAM: if it is the extratropics, it only affects the hemisphere, what is the volcano affect in different positions on earth?
- Eruptions > 25 deg N/S, hemispheric impact is only in THAT hemsiphere
- tropical eruptions = global impact
5. GHGs
- natural (solar + volcanic)
- people (land cover change)
- black death = small pop density = less need for land cover = less need for trees to take up CO2
67
EXAM: At what location do volcanos have a hemispheric impact (only in that hemispehre)
When Eruptions are > than 25 deg N/S
68
EXAM: At what location do volcanos have a global impact
= in the tropics
69
Describe El Nino (southern Oscillation)
= wind blows from east to west, warms up
- every now and then, the circulation cell breaks down (eg. water sloshes back)
- specific to the pacific - because of the size of the pacific ENSO
70
T/F: Pacific decadal oscillations spatially look at el nina
FALSE, El nino
71
Global T has risen __ deg C since 1850
1 deg C
72
The Global T has risen 1 deg C since 1850. How much of that is natural? GIve potential sources
Biggest impact:
1. Rising CO2
- fron land clearing
- from burning fossil fuels (smoking gun)
2. Rising Methane
- cows
- rice patties
3. Halo-carbon
- CFCs: deplete ozone
73
Definiton: The Smoking Gun
= we know burning fossil fuels are really old because it has no C14 (transitioned back into 14N)
- all carbon in fossil fuels are depleted in C13 (high C12:C13 ratio)
74
Definition: Climate Sensitivity
+ what aare the 2 ways to estimate cliamte sensitivity
= a measure of how responsive the surface temp of the earth is to a chnage radiative forcing deg C/ (W/m2)
2 methods:
1. GCMs: Climate Model Estimates
- run models of potential scenarios
2. Paleoclimate estimates
- look at time where CO2 was high + low
- don't know a lot (only 4 data points: LGM, cretaceous, paleocene-eocene thermal maximum (PETM)
75
Why isn't the earth warmer if the temp rose to 1 deg C +GHG are now 60%?
= ignores 2 factors:
1. Ocean Heat Capacity
Total warming commitment approx 2 deg C
= aka if we stopped emitting today, it would still increase by 2 deg C because of the amounts we already emitted.
- b/c it takes time for the oceans to absorb extra heat and the next location for absorption is the atmosphere
2. Aerosol Cooling
- sulphate aerosols have a net cooling affect
= will offset
76
If the temp rises fast, what does it say about the climate in response to GHGs
= that the climate is sensitive to GHGs
77
If the temp rise is natural / gradual, what does it say about the climate?
= it is insensitive to GHGs
78
What is the current disequilibrium? What are some fast and slow respondings?
= current emission rates are much faster than tectonic/orbital/glacial changes
Fast responding:
- atmosphere
- land surface / vegetation
- upper ocean
Slow responding:
- ice sheets
- deep ocean
79
Why can we not look at the past to run models for climate disequilibrium?
= because there is
GEOG 2210
flashcards
Decks in class (3)
# Cards
