Climate change in the Quaternary period Flashcards
How long have we been the Quaternary Ice Age for?
The last 2.6 million years.
Which lasts longer, glacials or interglacials?
Glacials.
What does the saw-tooth structure refer to?
Gradual cooling into glacials followed by much more rapid warming into interglacials. It takes much longer to cool down than it does to warm up.
What is Milankovitch forcing and what does it influence?
Variations in how the earth orbits the sun which influences seasonality and glacial-interglacial cycles.
What are the three main aspects to Milankovitch forcing?
Eccentricity, obliquity and precision.
What is eccentricity?
How circular the earth’s orbit is around the sun. Some years the orbit is more oval and distorted meaning at times we receive more of the suns energy than on average and other times we receive less.
What is obliquity and what does it cause?
The tilt of the earth on it axis which varies over time (usually has a 41ka/41,000 year cycle). It produces seasons; it is summer in the southern hemisphere when it is winter in the northern hemisphere and vice versa. When there is more tilt seasons are more extreme (hotter summers and colder winters).
What is precission and what does it cause?
Precision refers to the wobble of the earth, meaning sometimes we point towards the North star and other times we point towards other stars. It determines during which season we are closest to the sun, e.g. at the moment precision means earth is particularly close to the sun during northern hemisphere winter and southern hemisphere summer (winter less extreme, summer more extreme).
What is the Quaternary period also known as?
The Pleistocene.
What is the Middle Pleistocene transition (MPT)? Why was it unusual?
The emergence of low-frequency, high amplitude glacial variability during the middle Pleistocene. Previously glacial-interglacial cycles occurred line with obliquity changes (Clark et al., 2006). More recently they have occurred in line with eccentricity changes.
Why do glacials that last longer require less energy to cross the threshold into an interglacial?
The longer a glacial lasts the larger and more unstable the ice sheets will become, meaning they are easier to collapse.
What are D-O (Dansgaard-Oeschger) events?
Rapid warming followed by more gradual cooling.
What is a stadial?
A cooler period in a glacial.
What is an interstadial?
A warmer period in a glacial.
What are Heinrich events?
Very cold periods with iceberg discharges into the Atlantic.
