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Ch 13B
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68
Geology
Undergraduate 1
04/22/2014

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Term
Temperature
Definition
changes over the last
1.6 my must be obtained indirectly in
what are known as proxy recorders:
Term
Temperature changes over the last
1.6 my must be obtained indirectly in
what are known as proxy recorders:
Definition
Oxygen isotope changes in ice cores
– Trapped atmospheric gases in ice cores
– Oxygen isotope and other changes in
fossils in oceans and lakes
Term
Lighter H2
16O
preferentially
evaporated
Definition
increasing
H2
18O concentrations in
oceans
Term
Carbon dioxide, methane, and
nitrous oxide concentrations in
the atmosphere have
Definition
increased
over the last two centuries;
This increase has dramatically
accelerated since 1950.
Term
Global Temperature Cycles in
Definition
Past
Determined From Deep-sea Cores
Term
Deep sea sedimentary record more
Definition
complete than glacial deposits on land
Term
Reversal of coiling direction and oxygen
isotopes of foraminifera shells can
Definition
determine seawater temperatures at the
time shells formed:
Term
Reversal of coiling direction and oxygen
isotopes of foraminifera shells can
determine seawater temperatures at the
time shells formed:
Definition
Shells formed over the last 80,000 years can
be dated by carbon 14
– Protactinium 231 - thorium 230 can date
associated deep-sea clays back to 300,000
years
– Other methods used to date older fossils
Term
Changes in oxygen isotopes in ice cores
compliment that measured in marine
fossils:
Definition
When ice cores have lower H2
18O, the
oceans have higher H2
18O
Term
Marine life record this change as they
grow their shells
Definition
When they die, their shells leave a
continuous record of oxygen isotopes in
ocean sediments
Term
Support for Global Temperature
Changes
Definition
Ice core records of gases and oxygen
isotopes similar in Greenland and
Antarctica
Term
Causes of Climate Change
Definition
Long-term climatic changes (millions of years):
Shorter-term climatic changes (tens of thousands of
years):
Short-term climatic changes (tens to hundreds of
years):

Near-instantaneous to long-term changes
Term
Long-term climatic changes (millions of years):
Definition
Plate tectonics and positions of continents
Term
Shorter-term climatic changes (tens of thousands of
years):
Definition
Milankovitch cycles
– Feedback mechanisms
Term
Short-term climatic changes (tens to hundreds of
years):
Definition
Solar variability (sunspots)
– Changes in ocean circulation
– Anthropogenic greenhouse gases
Term
Near-instantaneous to long-term changes
Definition
Volcanic eruptions
– Extraterrestrial impacts
Term
Major glaciations may be related to
migration of landmasses to higher, cooler
latitudes
Definition
Evidence from ancient glacial deposits and
other features found today in areas like NW
Africa and India that are far removed from cold
climates
Term
Mountain building can also cause
glaciation
Definition
Force mountain summits above the snow line
– Influence weather patterns and jet-stream
circulation
Term
Decline of >10o C in global temperature from
~57 million to 30 million years ago
Definition
Antarctic glaciation initiated ~30 m.y. ago
Term
Eocene
Definition
Oligocene Cooling
Term
Changes In Global Climate
Over The Last 60 Million Years
Definition
(Cenozoic Era)
Term
Cooling occurred on land and in the oceans:
Definition
Extinction of warm-water plankton
Term
Dryer climates on land
Definition
Dense vegetation turned to mixture of forests
and grasslands
– Extinction of many forest-dwelling mammals
Term
Late Cenozoic Glaciation
Definition
Arctic ice caps formed ~3 m.y. ago
Term
Over last 2 million years, ice advanced and
retreated at ~100,000 year cycles
Definition
Glaciation episode lasted ~90,000 years
– Deglaciation occurred over ~10,000 years
Term
We are presently within
Definition
interglacial cycle
Term
Plate Tectonics and Climate
Definition
The positions of continents affect global
circulation of oceans (thus climate)
Term
Cenozoic positions of continents
prevented warm equatorial waters from
reaching the poles:
Definition
Arctic ocean almost completely surrounded by
land masses
– Separation of Antarctica from the other land
masses allowed establishment of circum-
Antarctic current that prevented warm waters
from reaching continent
Term
After continents collide and assemble
Definition
Less volcanic activity from island arcs, hence
less CO2 in atmosphere
– Elevated continents produce stronger rivers that
carry more Ca to oceans
– Increased formation of carbonate rocks removes
atmospheric CO2, causing cooling
– Also, mountains accumulate more glaciers,
resulting in higher albedo and cooler climate
Term
Continental break-up reverses trend
Definition
Increased volcanic activity releases CO2
– Fewer mountains
Term
Shorter-term Climatic Cycles
(Tens Of Thousands Of Years
Definition
Milankovitch Cycles and
Feedback Mechanisms
Term
Milankovich Cycles
Definition
Changes In Earth’s Orbital
Parameters As It Revolves
Around The Sun
Term
Do Milankovich Cycles Explain
Global Temperature Changes
Definition
Milankovitch cycles can initiate
warming or cooling, but alone can’t
explain large climate shifts
Term
Do the periods of lower
solar radiation in the
purple column match
periods of cooling based
on marine oxygen
isotopic ratios (green
column)?
Definition
no
Term
Climatic Positive Fe
Definition
Positive feedback renders cold climates
colder and warm climates warmer
Term
For climatic cooling
Definition
More snow increases global snow cover
– Higher albedo reflects more sunlight back into
space
– As a result, it gets colder
Term
For climatic warming
Definition
– Retreating ice exposes rocks, reducing albedo
– More solar heat absorbed by Earth
– Increased warmth accelerates melting of ice
Term
Climatic Negative Feedback
Definition
Term
For climatic cooling
Definition
Greater snow cover reduces activity of CO2 sinks
like photosynthesis and formation of carbonate
rocks that remove carbon dioxide from the
atmosphere
– Carbon dioxide increases in atmosphere
– Resulting greenhouse effect warms climate
Term
For climatic warming
Definition
– More evaporation and clouds
– More sunlight reflected back into space
– Climate cools
Term
Calcium (Ca) as a positive feedback
Definition
– Milankovitch cycles initiate cooling
– Evaporating water is removed from oceans and
stored in growing ice caps, causing sea level to
drop
– Lower sea level lowers the base level of rivers,
causing greater erosion of rocks
– More Ca is carried by rivers to oceans
– Higher Ca concentrations in oceans cause more
carbonate rocks to form, resulting in decrease of
atmospheric CO2
– It gets colder
Term
Sunspot activity varies over 11 year cycles:
Definition
11 years between peaks in sunspot abundance
– Corresponds to 22-year cycles of magnetic
reversals on the Sun
Term
Large-scale sunspot activity has changed
over the last 360 years
Definition
– From 1645 to 1715, overall sunspot activity
diminished and the earth was cooler
– Peaks in sunspot activity around 1950, 1960 and
1990 higher than peaks in first half of 20th Century:
Term
Comparison Between Number of
Sunspots and Little Ice Age
Definition
Upper atmosphere cooled during periods of reduced
sunspot activity because of diminished solar wind
Term
Larger numbers of sunspots increase the
solar wind and thus the temperature of
Earth’s uppermost atmosphere
Definition
BUT we have no mechanism to explain how
this causes heating in the lower atmosphere!
– Also, solar radiation only changes by 0.1%
between minimum and maximum sunspot
activity:
Term
Dansgaard-Oeschger Cycles
Definition
Changes in ocean salinity may cause climatic
changes of thousand-year duration or less
Term
Influx of fresh water into North Atlantic
lowers salinity and shuts down thermohaline
conveyor belt
Definition
The more buoyant fresh water in North Atlantic
does not effectively sink to form NABW
– This prevents warm equatorial waters from flowing
north, thus causing climate cooling
Term
Eventually conveyor belt is reestablished
after freshwater stops entering N. Atlantic
Definition
Term
Arctic Ocean today covered by two kinds of
ice:
Definition
Floating sea ice (frozen seawater)
– Glacier ice (frozen freshwater
Term
Ice pack thins in summer and sometimes
breaks up
Definition
2005 -2007: Loss exceeded area of California
– Northwest Passage ice free in September 2007
– Northeast Passage ice-free for several years
– Will freshening of Arctic Ocean again shut down
the thermohaline conveyor belt
Term
Less ice cover lowers the
albedo
Definition
causing
temperatures to further
increase
Term
Petermann Glacier on northern coast of
Greenland began breaking up in 2008:
Definition
– A 29 km2 ice island broke away that year
Term
In August, 2010, a giant 250 km2 ice island
four times the size of Manhattan Island
broken away from the Petermann Glacier:
Definition
Ice Island has since broken into two parts
– Will eventually track south towards Canadian
shipping lanes
Term
Antarctica and Global Warming
Definition
Since 1993, six ice shelves have
disintegrated:
Term
Larsen Ice Shelf has been retreating for
years
Definition
Larsen A disintegrated in 1995
– Collapse of Larsen B in 2002 occurred further
south of any previous event
– Larsen C is presently losing mass on its
underside
Term
The Chicxulub Impact
Definition
Asteroid impact near Yucatan Peninsula ~65
million years ago may have been responsible
for the Late Cretaceous mass extinctions:
– Impact generated huge wildfires, earthquakes, and
tsunamis that instantly killed many life forms
– Sulfuric acid rain followed
Term
Stratified drift is most likely deposited by ___________
Definition
.
Glacial meltwater
Term
Sea ice and ice shelves in the Arctic and Antarctica have increased in area over the past two decades in spite of recent global warming.
Definition
Correct False
Term
which of the following would LEAST LIKELY characterize a periglacial landscape?
Definition
Areas in subarctic and polar climates where the ground is cold but never freezes.
Term
how did global climate overall change throughout the last 60 million years of the Cenozoic Era?
Definition
Cenozoic climate was warmest 60 million years ago and has gradually cooled since then, culminating in the Pleistocene Ice Age beginning 2 million years ago
Term
Changes in the angle of tilt of Earth's rotational axis occurs approximately in _________ year cycles
Definition
41,000
Term
Which of the following statements best describes an esker?
Definition
Sinuous, narrow ridge of coarse sand and gravel formed by a meltwater stream that flowed beneath a glacier
Term
Which of the following events MOST-LIKELY occurred during the last ice age when glaciers reached maximum extent ~18,000 years ago?
Definition
Plants and animals characteristic of colder climates migrated southward to lower latitudes
Term
Which of the following features of an Alpine glacier is (are) formed by deposition rather than erosion?
Definition
d.
Lateral moraine
Term
How can sunspot activity possibly affect Earth's climate?
Definition
Higher sunspot activity increases the solar wind, which in turn warms Earth's upper atmosphere
Term
Ice cores recovered in Greenland and Antarctica provide a record of changes in atmospheric temperature and compositon dating back to over 100,000 years ago. Based on ice core data, which of the following statements is TRUE?
Definition
Atmospheric temperature has been steadily increasing over the last 12 thousand years and we are presently in an interglacial cycle
Term
Which of the following examples will result in positive feedback?
Definition
Climate cooling increases the snow cover on land, thus increasing global albedo and causing more solar radiation to be reflected back into space
Term
For an alpine glacier, which of the following features or processes occurs within the zone of accumulation?
Definition
Cirque
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