Term
|
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
|
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
|
Definition
|
|
Term
Changes In Global Climate
Over The Last 60 Million Years |
|
Definition
|
|
Term
| Cooling occurred on land and in the oceans: |
|
Definition
| Extinction of warm-water plankton |
|
|
Term
|
Definition
Dense vegetation turned to mixture of forests
and grasslands
– Extinction of many forest-dwelling mammals |
|
|
Term
|
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
|
Definition
|
|
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
|
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
|
|
Term
|
Definition
Positive feedback renders cold climates
colder and warm climates warmer |
|
|
Term
|
Definition
More snow increases global snow cover
– Higher albedo reflects more sunlight back into
space
– As a result, it gets colder |
|
|
Term
|
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
|
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
|
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
|
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
|
|
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
|
|
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
|
|
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
|
|
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
|
|
