Terms in this set (42)
Climate Parameters such as temperature are averaged over how many years?
What is a positive feedback mechanism and what is a negative feedback mechanism? Example of either one of these.
Positive mechanism: Initial climate forcing -> Initial climate response -> Response AMPLIFIED by climate system.
Negative mechanism: Initial climate forcing -> Initial climate response -> Response REDUCED by climate system.
Re-distribution of heat on the planet can come in the form of these 2 types of heat transfer.
Sensible heat exchange, Latent heat exchange.
Name 2 gases that are considered greenhouse gases.
Write the chemical equation for photosynthesis
H2O + CO2 -> CH2O + O2
Name two areas of significant ocean upwelling
Equator + Near Shoreline
True or False: Cold, salty water is denser than warm fresher water.
True or False: The presence of sea ice increases air temperature.
True or False: Melting of sea ice contributes to sea level rise.
Which likely represents more time: 1 meter of fluvial sandstone or 1 meter of abyssal shales?
1 meter abyssal shale
If you are interested in studying season changes in precipitation...which archive would be better to study and why? A) deep marine sed rocks or B) speleothem records?
B) speleothem records, because their resolution includes seasonal changes to thousands of years, while deep marine sed rocks have worse resolution.
Name one climate archive.
Because of plate tectonics and subduction, rocks with climate records older than 170 million years old can only be found where?
Describe one paleotemperature proxy. How / why does it work, what are advantages, disadvantages / problems with this proxy?
Pros - Sense of paleoelevation, Idea of rock/sediment types from glacial range.
Cons - Glaciers were not everywhere, Sediments and till are all jumbled up, no sense of deposition timing. Not quantitative.
Describe one paleoprecipitation proxy. How / why does it work, what are advantages, disadvantages / problems with this proxy?
Coal beds: Coal beds are formed from swamps and bog-like ecosystems, so coal beds = wet environments.
Pros - Location of coal in strat colums give good idea of timing, Can find really well preserved organic material.
Cons - Not everywhere, Bed thickness may not be a good indicator of time, Not quantitative.
Describe one paleo-CO2 proxy. How / why does it work, what are advantages, disadvantages / problems with this proxy?
Leaf Stomates: More leaf stomates in a leaf means less CO2 present.
Pros - Same pattern is found today so easily comparable, Pretty good resolution.
Cons - Finding nicely preserved leaves, Due to fragility of leaf stomates may not be well preserved may lead to miscount, Inaccurate @ high CO2 concentrations.
Name one mineral or rock type that has specific implications for climate and explain the climate implication:
Precipitates at temperatures <4°C, sea ice.
Sketch a graph of the relationship between D18O calcite and temperature. Given this relationship and assuming constant D18O of water, which was formed at higher temp a calcite formed at o%%PDB or 2%%PDB?
Indirect relationship, high Temp = low D18O. O%% PDB.
Remember T(C) = 113.3-4.38(D18Ophosp-D18Ow)
T(C) = 113.3-4.38(D18Ophosp-D18Ow)
Aside from your instructor giving you incorrect information, describe some concerns with using the leaf margin and leaf size proxies for climate parameters that you experienced. Despite this, Royer suggest that for temp, standard error for leaf margin analysis are about what?
1) May be difficult to determine a damaged leaf from a toothed leaf. 2) May not find all types of leaves, may only see lucky ones that got preserved and may not be representative of all leaves. 3) Royer suggests +-2 to +-5 C.
Why model climates of the past?
To better predict what may happen in the future, also to better understand feedbacks of certain events so if they happen again we can predict.
Name and describe one reason why general circulation climate models might give an incorrect "answer"
Very difficult to include all boundary conditions, for example cloud cover can't be modeled but plays a large role in climate. The resolution is too large and smaller, latitude range conditions are not included.
Ture/False: Ocean Circulation models adequately model flows such as the gulf stream:
False: not within the 2-3 latitude meaning gulf stream is too small.
In the figure above from Berner 1999, the loop characterized by L->G->B is a positive or negative feedback loop?
Negative, only passes through a circle once, if zero or even times through a circle it is positive.
What do geochemical models do differently than physical climate models?
Incorporate burial and reserves of C. Much longer time frame and include equations for increase and decrease of CO2 depending on the weathering / uplift etc.
In modeling a greenhouse climate such as the Cretaceous, does paleogeography alone account for global warmth? If not, what climate factor seems to be needed to reproduce global warmth?
No, also need to include uplift and orbital factors which help us understand overall presence of ice sheets. Greenhouse gasses is generally needed to approach greenhouse conditions.
Greenhouse gases keep Earth
~33 degrees warmer then it would be without greenhouse gasses.
Of all the carbon reservoirs, the largest is?
Sediments and rocks
In modeling a greenhouse climate such as the Cretaceous, what has been a major problem to model-proxy mis-match? Provide one possible resolution to this mis-match.
Presence of ice sheets. In order to increase temperature enough to have no ice sheets on poles, the equator becomes too hot. One possible resolution would be to include seafloor spreading and changing paleogeography. In general improve climate models.
Water combines with CO2 to produce what?
Describe how the chemical weathering of silicates reduce CO2 in the atmosphere? Feel free to use sketches, chemical equations.
CaSiO3 + CO2 -> SiO2 + CaCO3. By weathering silicates, Calcium is free to bond with CO32- to create carbonate and also silicate shells, effectively removing CO2 from the atmosphere.
An increase in chemical weathering occurs with
All of these (an increase in temperature, an increase vegetation, an increase in precipitation)
Describe the sea floor spreading hypothesis (something called the BLAG hypothesis) for controls of long-term (tectonic scale) CO2 changes through time.
Once seafloor is spreading, we get an increase in CO2 in the atmosphere as deep carbon reserves are "returned" to the lithosphere surface.
Describe the uplift and weathering hypothesis
During the uplift we get more silicate weathering, primarily in C-C collision as silicates weather we remove a lot of CO2 from the atmosphere.
Name one line of evidence of overall Cenozoic cooling
Smaller leaves on average smaller leaves indicate lower MAI.
Name 3 orbital patterns. Which of these affect the high latitudes the most?
1) Wobble (23,000) - how much the earth wobbles as it tilts, 2) Tilt (41,000) The range from 23 tilt to 28 tilt, 3) Eccentricity (100,000) - the distance from the sun at aphelion and parihelion. The tilt is what affects high latitude the most.
Describe summer and winter monsoons. Which has more of an average annual climatic impact, a strong summer or strong winter monsoon? How do orbital variations affect the monsoon?
Summer has the larger climate impact while a strong summer = a strong winter, the summer is more important as it rains over land. Along with the wobble of the earth, strong summer monsoons occur every 23,000 years.
Which is most important for growth of ice sheets: weak summer insolation or weak winter insolation?
Weak summer insolation.
From Zachos et al., 2001, describe Trend, Rhythems, and Aberrations.
Trend: The overall trend seen is a global cooling seen as an increase in D18O %% since ~70 Ma to now.
Rhythm: While the trend is cooling oscillating patterns of D18O indicate the fluctuations over short periods of time. (@ orbital scale pacing)
Aberrations: Three main aberrations or unique occurrences are seen at ~55 ma, 33 ma, and 24 ma. These are unusual occurrences which mark unique events caused by something unusual.
True / False: Very cold conditions result in faster ice sheet growth:
False, Too cold = no precipitation.
Are greenhouse gases a trigger, a feedback or both in their relationship to ice sheet growth?
Both, as a trigger to lesser the greenhouse gasses in the atmosphere, the colder (on average) the Earth making the ice sheet line on land. But if ice sheets melt, more methane is released as a feedback to temperature increase. @ 23 kyr scale is on pace w/ orbital variation @ 100 ky there is a lag. So likely a trigger @23 ky scale + feedback @100ky.
What is CO2 sensitivity? Is it always the same?
CO2 sensitivity is the effect of a doubling of CO2 on MAT and is not always the same depending on the cause of the increase or decrease.