Glacial Characteristics Flashcards
What is glacial budget?
The balance between a glacial input and output
What is positive glacial budget?
When there is more accumulation than ablation
- the glacier advances
What is negative glacial budget?
When there is more ablation than accumulation
- the glacier retreats
How will the seasons affect glacial mass balance?
Summer = hotter,more ablation. Negative glacial budget.
Winter= colder, more accumulation. Positive glacial budget.
What influences the short term change in glacial budget?
Seasons
What influences the long term change in glacial budget?
Climate Change (driven by humans)
Stadials and interstadials
Glacials and interglacials
How does human-driven climate change influence the long term glacial budget?
- increased fossil fuel consumption causes the enhanced greenhouse effect
- increased GG in atmosphere insulates the Earth more
- more solar energy is absorbed = the Earth warms
= GLOBAL WARMING - as the avergae temperature is higher, outputs from the glacier increase. NEGATIVE GLACIAL BUDGET, the glacier will retreat
- positive feedback loops ensures this continues to happen even more
What is a positive feedback?
a process within a system where an initial change triggers a series of events that enhances/amplifies the change
-pushes the system further away from the equilibrium state (snowball effect)
What is negative feedback?
a process within a system to counteract the initial change and bring the system back to an equilibrium state
Give an example of positive feedback influenced by climate change
The albedo effect
What is the albedo effect?
Albedo = reflectivity of the Earth’s surface
Climate change warms temperatures - leads to increased melting of the glaciers
- Increased melting means there are more darker surfaces
- Increased darker surfaces mean less solar radiation is reflected/more is absorbed
- this leads to warming temperatures
- which leads to more melting … (etc)
What is a glacial?
When was the last one?
A period of time where the temperatures of the Earth are low enough for the Earth’s surface to be covered in ice due to the advance of glaciers
- part of an ice age: can last for thousands of years. Last one was the Pleistocene - 100,000YA-10,000YA
What is an interglacial?
When was the most recent one?
A period of time within an ice age where the temperature of the Earth increases and glaciers retreat
- currently in an interglacial = Holocene. 10,000YA - present
What are stadials and interstadials?
Phases that divide the Quaternary period
What is a stadial?
- a substage of a glacial stage marked by ice advancing again
- a period of colder climate withing a glacial
What is an interstadial?
- a substage of a glacial stage marked by ice retreating again
- a period of warmer climate within a glacial
What is a cause of long term climate change? (Not human caused)
Milankovitch theories
What are the Milankovitch theories?
Eccentricity
Obliquity
Precession
What is eccentricity?
The degree of variation of the Earth’s orbit around the sun from circular to more elliptical
- over 2 periods - one shorter at around 100,000 years, and one longer around 413,000 years
How does a circular orbit affect climate change?
- lower temp difference between seasons
= GLACIAL - ice can be sustained because steady temperatures allow accumulation
How does elliptical orbit affect climate change?
- higher temp difference between seasons
= INTERGLACIAL - ice cannot be sustained because fluctuating temperatures donot allow steady accumulation and compaction
What is obliquity?
The angle that the Earth’s axis is tilted as it orbits the sun
- the reason the Earth has seasons
- angle of tilt has varied between 22.1 and 24.5 degrees over the past million years
- tilt varies over 41,000 years
How does obliquity affect glacial and interracial periods?
INCREASED TILT
- tropics will get wider
- summers will be hotter
- winters will be colder
- the increased temperature difference = more extreme
so it favours INTERGLACIAL because ice cannot be maintained in the landscape, therefore glaciers cannot advance
DECREASED TILT
- tropics will get narrower
- summers will be colder
- winters will be warmer
- the decreased temperature difference = less extreme
so it favours GLACIAL because snowfall can persist in the landscape. feedback loops will kick in, the ice will compact, and we will enter a glacial period
What is precession?
The slow, gradual wobble or shift in the orientation of the Earth’s rotational axis over a time span of around 26,000 years
- Earth is closest to sun (perihelion) currently during Northern Hemisphere winter, but this will shift so it occurs during summer
How does precession affect climate change?
- it alters the intensity and distribution of solar insolation reaching different parts of the planet throughout the year
- as it changes, it changes the patterns of seasons and advance and retreat of ice ages
How can volcanos have a short term effect on climate change?
AEROSOLS IN ATMOSPHERE = increased absorption of sunlight which caused global dimming and the temperatures drop
PYROCLASTIC FLOWS AND TEPHRA FALL - cover crops/plants, which means less photosynthesis, so it will get warmer
CHANGES IN GAS COMPOSITION: more H2S03 affects UV absorption, temps cool up to 3 degrees
