ENVIRSC 3CC3 Study Guide - Final Guide: Hydrolysis, Ource, Foraminifera

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ES 3CC3 Final Prep.
Q1. What is a Faint-Young Sun paradox, and how can it be explained?
Answer:
Recreated over 4.55 Byr extenence of our solar system
Models indicated that sun shone 25% to 30% more faintly than today, which meant
colder environment for the Earth making it freeze.
But evidence left in Earth’s sedimentary deposits shows that Earth was not frozen
for first half-billion years of its existence.
The question is “why wasn’t the Earth frozen for the first two thirds of its history
despite the weak sun?”
This mystery has been named the “Faint-Young Sun Paradox.”
Explanation:
In order to explain it requires some sort of thermostat acting to moderate the swings
in temperature
Possible thermostat are the greenhouse gases
Chemical weathering acting as thermostat to generate increase in greenhouse
gases
Hydrolysis: weathering of CaSiO3 by rain and CO2 is a viable explanation
since it there is no CO2 being produced in this case, therefore, CO2 can be
removed from the atmosphere over millions of years
CaSiO3 + H2CO3 CaCO3 + H2O + SiO2 (Dissolution)
Chemical weathering would result in negative feedback by reducing both the
intensity of a) climate warming and b) climate cooling.
3 things effecting rate of chemical weathering:
Temperature: higher temperature result in higher rate of weathering,
thus, more chemical weathering would occur near the equator than the
poles
Precipitation: higher precipitation result in higher chemical
weathering, since the rate of physical weathering also increase thus,
increasing the available surface
Total amount of vegetation: plants extract CO2 from the atmosphere
and deliver it to soil and form carbonic acid, which contributes in
chemical weathering
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Q2. Describe the Younger Dryas Event
The mid-deglacial pause in ice melting, which was accompanied by a brief
climatic oscillation is the Younger Dryas Event
The pause in the deglaciation and the reversal resulted in the decrease in
the global temperature
This occurred 14 12 000 years ago, and it was described as a slow process
13 000 years ago, arctic vegetation returned to northern Europe
11 700 years go was the start of
final advance of forest
The trigger of the Younger Dryas Event is still unknown
May have provided a pause in the feedback:
Increase in temperature will result in increased thinning and ice flow to the
margins (releasing melt water). This will lead to an increase in the global
sea level and bedrock rebounding as a result
Evidences:
1) Pollen records in Europe: reversal towards arctic vegetation
2) North Atlantic polar foraminifera found in depth of ice cores
Relative abundance of the polar foraminifera
3) Polar front: re-advance of the polar fronts
The southern margin of the cold water a zone of rapid transition to the more
temperate waters to south
Ex. Zone of rapid transition from icy polar water to more temperate waters
It represents major reversal in circulation patterns, it is estimated that the sea
surface temperature in the Atlantic Ocean was cooled by at least 7 degrees C
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Q3. What is the difference between Dansgaard-Oeschger oscillation and Heinrich events?
DO oscillation:
Short oscillations between positive and negative delta O18 values between full-
glacial and full-interglacial periods
They were spaced at intervals that ranged form as little as 1000 years to
almost 9000 years in length
Rapid oscillation between extremely cold intervals (stadial) and relatively mild
intervals
Fluctuation in delta O18 value of 4 to 6%
The best evidence of the DO events remains in the Greenland Ice cores, which
goes back to end of the last interglacial
25 observed DO events that occurred in matter of decades, it consisted of an
abrupt warming to near-interglacial conditions that occurred and was followed by
a gradual cooling
Repeated every several thousand years on average
Heinrich events:
Also short term interval between stadial and interstadial intervals
Based on the sediment deposition at some sites in North Atlantic: 10 20 cm per
1000 years
Events: unusual episodes of rapid flow of ice bergs in North Atlantic, with
sediment deposition
Separated by intervals of 5000 to 15 000 years
6 distinctive events that recorded in North Atlantic marine sediments as layers
with a large amount of coarse-grained sediments derived from land
Iceberg carries sand-sized grains eroded by ice sheets, when it encounters
warmer ocean water; they melt and drop their sediment load onto the sea
floor.
A southward extension of cold, polar waters allowed for icebergs to travel
farther before melting
Occurred less frequently than DO events
Approximately 10 000 years elapsed between each events, neither of the two
events are periodic.
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