When was the Pleistocene Epoch?
2.6 Ma to 10,000 years ago
When was the Holocene Epoch?
10,000 years ago to present
When was the last major glaciation?
Wisconsin ice age
When was the Wisconsin ice age?
100,000 to 10,000 years ago
What is the Wisconsin ice age preceded by?
Sangamon interglacial
When was the Sangamon interglacial?
125,000 to 100,000 years ago
What is the Sangamon interglacial preceded by?
Illinoian ice age
When was the Illinoian ice age?
191,000 to 125,000 years ago
When was the maximum extent of ice?
21,000 years ago
How was the the sea level during Wisonsin ice age?
120 m lower than present day
How much atmospheric CO2 was there in the Wisconsin ice age?
190 pm
How was the summer insolation during the Wisconsin ice age?
Comparable to today
What is the lag time for insolation?
Reflects a lag time of 4,000 years
When did minimum insolation occur?
25,000 years ago
What does maximum extent of ice reflect?
Low atmospheric CO2 and higher albedo from ice sheets
What is the Laurentide Ice Sheet?
Primary continental glacier of North America
How thick is the Laurentide Ice Sheet?
2-3 km maximum thickness
What is the Cordilleran Ice Sheet?
Ice sheet primarily over the Canadian Rocky Mountains and western North America
What does glacial comminution produce?
Sediment ranging from boulders to clay (till)
What are moraines?
Unsorted sediment deposited along the edges of moving glaciers
What is glacial outwash?
Glacial material transported by running water
What is loess?
Fine-grained sediment transported by wind
What does loess reflect?
Arid and vegetationless landscape
What is loess termed in Nebraska?
Peoria Loess
When was Peoria Loess deposited?
14,000 to 25,000 years ago
Which direction did the wind deposit the Peoria Loess?
Wind form the west-northwest
What source of rocks is Peoria Loess?
Rock from South Dakota, western Nebraska, and northeastern Colorado
How was the Peoria Loess initially?
In outwash from Laurentide Ice Sheet
How was the rocks from the Laurentide Ice Sheet transported to Nebraska?
Missouri River
What is pollen widely dispersed by?
Wind
What does spruce pollen reflect?
Cold and wet climate
What is an example of spruce pollen?
Picea
What did Picea become?
Dominant pollen shortly after last glacial maximum in midwestern United States
When was the last glacial maximum?
21,000 years ago
When was the Holocene?
10,000 years ago
What is the Pleistocene-Holocene transisiton?
Last glacial maximum to Holocene
What happened to atmospheric CO2 in the Pleistocene-Holocene transition?
Atmospheric CO2 rises from 190 ppm to 280 ppm between 17,000 years ago and 10,000 years ago
What happened in regards to summer insolation during the Pleistocene-Holocene transition?
Summer insolation was increasing until 10,000 years ago
What happened by 10,000 years?
Tilt of Earth's axis reached a maximum and precession resulted in Earth closest to the Sun on June 21st
What happened to albedo during the Pleistocene-Holocene transition?
Reduction in albedo as ice sheets retreated
What happened to temperatures and precipitation during the Pleistocene-Holocene transition?
Large and rapid fluctuations in temperature and precipitation
Where are environmental changes during the Pleistocene-Holocene recorded?
Sediments in lakes and bogs that formed after retreat of Laurentide Ice Sheet
When did the majority of glacial melting occur?
17,000 years ago and 13,000 years ago
Where is there evidence of the majority of glacial melting during 17,000 and 13,000 years ago?
Gulf of Mexico
When was the Younger Dryas Stadial?
13,000 years ago to 11,500 years ago
What was the Younger Dryas Stadial?
Abrupt temperature cooling to near glacial conditions in Northern Hemisphere
What happened to glaciers during the Younger Dryas Stadial?
Some glaciers readvanced
What happened temperature wise to the Southern Hemisphere during the Younger Dryas Stadial?
Warming in Southern Hemisphere
What happens to cold, more dense and more saline water at the Poles?
It sinks
What happens to warm, less dense and less saline water at the equator?
Move to Poles to replace sinking water
What does the warm, less dense and less saline water at the equator that moves to the Poles to replace sinking water result in?
Ocean circulation patterns that constantly transfer heat from equator to poles
What is the Atlantic meridional overturning circulation?
System of currents that transports warm equatorial water to the North Atlantic via the Gulf Stream
What does AMOC stand for?
Atlantic meridional overturning circulation
Where did Lake Agassiz form?
Along the margin of retreating Laurentide sheet
Where was drainage where Lake Agassiz formed of retreating Laurentide sheet initially?
Down the Mississippi River
When the ice retreated what happened with Lake Agassiz?
It could drain to the Mackenzie River (not St. Lawrence River)
What did the draining of Lake Agassiz into the Mackenzie River do?
Added fresh water to North Atlantic and slowed AMOC
What did the addition of fresh water to the North Atlantic and slowing of the AMOC do?
Reduced heat being transferred from equator
How is the present-day Gulf stream?
Slowest it has been in the last 1,600 years
How much slower is the Gulf Stream?
15% slower than in mid 20th century
Why is the Gulf Stream slower?
Result of melting Arctic and Greenland ice
How does the slowing of the Gulf Stream modify Global climate?
Colder winters in Northern Europe and warmer U.S. east coast
What does a warmer U.S. east coast result in?
Higher sea levels for U.S. east coast
What do colder winters in northern Europe do?
Possibly reduce hurricane activity
What happened after the Younger Dryas Stadial?
Steady warming
When was onset of Holocene?
10,000 years ago
What was the onset of the Holocene characterized by?
Relative warm temperatures and stable climate
What is El Nino?
southern oscillation (ENSO) cycles
What is southern oscillation?
High barometric pressure over Australia and low barometric pressure in south-central Pacific from August to December to produce El Nino events
How many years do the alternating changes in pressure between Australia and south-central Pacific occur?
Every 2 to 7 years
How does El Nino blow wind?
Winds blow warm equatorial water westward towards Indonesia
What does the winds blowing warm equatorial water westward towards Indonesia cause?
Cooler, deeper water to rise to surface near South America
During ENSO, what do weaker winds cause?
Warm surface water at the equator to move east towards Central and South America
What do the weaker winds that cause warm surface water at the equator to move east towards Central and South America force?
Warm surface water against Central and South America that then moves northward towards California and southward
What do the weaker winds that cause warm surface water at the equator to move east towards Central and South America increase?
Rain in South and Central America and United states, but other parts of the world may experience drought
What is El Nina?
Strong reversal of El Nino
Presently how should Earth be?
Cooling
Presently how is Earth?
Very rapidly warming
What is the likely response of Earth rapidly warming?
Very likely in response to anthropogenic increases in atmospheric CO2
When did warming of the Earth start?
1880
When was the warmest years in the past 1,000?
2016 and 2019
How much temperature increase has there been since 1880?
2 Celsius degrees increase globally
How have global temperatures varied?
Global temperatures have not varied more than 2 Celsius degrees in the past 10,000 years
How has atmospheric CO2 levels changes since the industrial revolution?
They are steadily increasing
What has cause the steady increase in atmospheric CO2 levels since the industrial revolution?
Petroleum, coal, natural gas combustion, and cement production
Since when have we measured atmospheric CO2 levels?
Measured directly since 1958
Where do we get atmospheric CO2 measurements prior to 1958?
Bubbles in ice cores
How much atmospheric CO2 is there now?
415 ppm since November 2020 which is the highest in the last 800,000
In Nebraska, what part of the state is warming the fastest?
Over the past 100 years, the panhandle is warming faster than the rest of the state
How do computer models predict global warming?
They do not predict uniform global warming
Where is the greatest warming predicted to be?
Arctic
What do models predict in regards to precipitation?
The amount of precipitation across North America will be different in 100 years.
How will summers be in 100 years?
Summers will be dryer
How will winters be in 100 year?
Winters will be wetter
If current rates of warming continue how will summer temperatures in Lincoln be by 2100?
By 2100 summer temperatures in Lincoln, Nebraska will be comparable to those of current Pharr, Texas
What is global warming predicted to cause?
Cause a rise in sea level due to water added form melting glaciers, ice shelves, an ice caps
What do tide gauges document?
A steady rise in sea level over the last 140 years
Between 2002 and 2014 how has the rate of CO2 changed?
The rate at which CO2 increased in the atmosphere was relatively constant
Why was the rate of CO2 between 2002-2014 relatively constant?
Result of vegetation consuming more carbon from the air than in previous decades
What happens as CO2 levels rise in the atmosphere?
Photosynthetic activity increases, plants take in more carbon, and stimulating more plant growth