M2: Glaciation Cycles

What was the Quaternary Period?

A period of dramatic biogeographic upheaval caused by repeated glacial-interglacial cycles

What were the two epochs that made up the Quaternary Period?

Pleistocene and Holocene

When did the Pleistocene begin?

Began 2.58 millions of years ago

When did the Holocene begin?

Began 11.7 thousands of years ago

What is considered the most recent extension of the Pleistocene?

Holocene

What does plio- mean?

More

What does -cene mean?

Recent

What was the time frame for Pliocene Cooling?

5.33 - 2.58 millions of years ago

What occurred from pliocene cooling?

1. A downward trend in temp

2. Drier conditions (from cooler temps not holding moisture)

3. Climate oscillations

What are climate oscillations?

natural, cyclical shifts in ocean temperatures, air pressure, and wind patterns that redistribute heat around the globe. Cause temporary weather anomalies

Where the glacial periods of the Pleistocene Glacial-Interglacial cycles long or short?

Glacial periods were long

Where the inter-glacial periods of the Pleistocene Glacial-Interglacial cycles long or short?

Interglacial periods were relatively short. Warm periods lasting 10K years

What can be inferred from Pleistocene Glacial - Interglacial cycles

Majority of organisms were evolving in much cooler conditions compared to today.

What great fluxes were there in this quaternary period?

1. Temperature

2. Precipitation

3. Atmospheric and ocean currents

4. Ice distribution (Large walls of ice)

5. Sea levels (dropped)

Who was the first to recognize glacial periods and coined the term “The Ice Age”?

Louis Agassiz

What year was Louis Agassiz active in?

1836

What did Louis Agassiz study?

Glaciation in the Alps

What did Louis Agassiz postulate?

Polar ice masses were highly dynamic

What did Louis Agassiz say about the impacts from glaciation?

There was great impact on the distributions of plants and animals

What are the major factors influencing climate? (8)

Variations in:

1. Earths orbit

2. Absorption and reflectivity in the atmosphere

3. Absorption and reflectivity of surfaces (albedo)

4. Solar radiation output

5. Positions of land masses

6. Areas of ice accumulation

7. Atmospheric gasses

8. Feedback interactions

What was the Glacial-Interglacial cycle described as?

High amplitude swings in global temp

What was the Glacial-Interglacial cycle driven by?

Changes in Earth’s orbit which is, in turn, driven by the changes in other planets positions and their gravitational pull on Earth

What does the glacial-interglacial cycle predominately affect?

Where and when solar radiation strikes Earth

Who was the Milankovitch Cycles named after?

Milutin Milankovitch

What are the three main patterns that drive the Earth’s climate?

1. Eccentricity

2. Obliquity

3. Precession

What is eccentricity?

The shape of the Earth’s orbit - elongated elliptical orbit that lengths and shortens in a 96K year cycle

What is obliquity?

The title of the earth’s axis

When the tilt is greater, more solar radiation is intercepted by polar regions during summer

What is precession?

The orientation of Earth’s axis in relation to the sun

What do these changes in Earth’s orbit affect?

1. Total energy (heat) budget of Earth

2. Temporary and spatial variation

What does precession affect?

Affects whether the periods of most direct solar radiation (during summer solstice in the Northern Hemisphere) occurs when Earth is at the perihelion (ice melting) or aphelion (ice accumulation), or some intermediate position

Warmer summers in NH melt snow faster than it can accumulate during winter

Colder summers in NH allow accumulation of snow

Before roughly 1 million years ago, how long were cold periods?

25-30 K years long

Before roughly 1 million years ago, how long were warm periods?

10-15 K years long

After roughly 1 million years ago, how long are cold periods now?

80-90 K years long

After roughly 1 million years ago, how long are warm periods now?

10-15 K years long

When was the Last Glacial Maximum (LGM) when 1/3 of the land was covered in ice?

26.5 - 19 thousands of years ago

What was the largest impact of the Pleistocene Glaciation and its LGM?

80% of ice accumulation in the Northern Hemisphere

What was the size of glaciers and what was the impact of their weight?

2-3 Km thick, the weight warped the Earth’s crust underneath and lowered sea levels

What were the effects of the Pleistocene Glaciation on non-glaciated areas?

1. Cooler air temps

2. Generally drier conditions

3. Cooler oceans

4. Climate zones shifted downward in elevation

What were the colder periods of climates during glacial periods called?

Stadials

What were the warmer periods of climates during glacial periods called?

Interstadials

How was the climate described as during glacial periods?

Unstable

What was the full name of DO events?

Dansgaard - Oeschger Events

What were DO events?

Abrupt shifts in climate during the last glacial period

Within what length of time did the Northern Hemisphere plunge back in and the bout of glacial conditions due to DO events?

Shift may have occurred within decades