2A.1 Key Words Flashcards
Greenhouse Earth
Little or no ice cover
Icehouse earth
High average glacier ice cover
Albedo
The reflective coefficient of a surface i.e., the proportion of incident radiation reflected by a surface (very high in the case of snow or ice).
Glacial
Cold, icehouse periods
Interglacial
Warner periods similar to present.
Pleistocene Epoch
A geological period from around 2.58 MYA to 11,700 YA, the early part of the Quaternary which includes the most recent ice age.
Stadial
Short-lived colder periods within a major glacial, associated with ice advance.
Interstadial
Short-lived warmer periods within a major glacial, associated with ice retreat.
Thermohaline Circulation (THC)
Global system of ocean currents. Driven by differences in temperature (thermo) and salinity (haline).
What has the dominant tyep of Earth been?
Greenhouse Earth.
Icehouse ages in geological time.
Huronian = 2.3-2.2 billion ya
Cryogenia = 720-635 mya
Late Ordovician = 445.6 -443.7 mya
LAte Devonian to early Carboniferous = 361-349 mya
Permo-Carboniferous = 326-267 mya
Pleistocene = 34 mya - present
Pleistocene epoch
2.58 mya to 11,700 ya (start of Holocene).
Within quaternary period
Most recent ice house
Last glacial maximum
Devensian - 20,000 ya
Loch Lomond Stadial (Younger Dryas)
Drainage of huge pro-glacial lake disrupted THC, cutting off poleward heat transport from the Gulf Stream.
temperatures fluctuated, at least 3 pulses of ice advance and retreat between 26,000 and 10,000 ya.
Ice sheets retreating around 18,000 ya, rapid deglaciation by 15,000 ya.
Evidence of Loch Lomond Stadial
Scotland - plateau ice fields
Wales - cirque glaciation (Snowdonia)
England - ice fields and valley glaciers (Lake District)
Ice dammed lakes - parallel roads of Glen Roy.
Little Ice Age
Period of cooling particularly pronounce in North Atlantic region.
1550-1850.
Cooler conditions by 1-2 degrees, caused colder winters (frozen Thames).
Crop failure across Europe.
Varying causes: volcanic activity, decreased levels of solar radiation (sunspot activity).
Milankovitch Cycles
Eccentricity (100,000 yrs)
Obliquity (41,000 yrs)
Precession (23,000 yrs)
Eccentricity
100,000 yrs
Shape of the Earth’s orbit around the sun.
Alters distance travelled by short-wave radiation.
Obliquity
Axial tilt
41,000 yrs
21.5 to 24.5 degrees
Responsible for seasonal differences.
Precession
Wobble of the Earth on its axis.
23,000 yrs
Makes seasonal contrasts more extreme in one hemisphere and less extreme in the other.
Variations in solar output
Sunspots - flares on suns surface.
High level of sunspots = increased radiation and average temperature.
Temperature change between +0.5 and -0.5 degrees globally.
Volcanic eruptions
Need to be large and explosive to change Earth’s climate. Ash and gas will reflect solar energy back into space cooling the planet.
1815 - Tambora volcano in Indonesia erupted (largest in history) and cooling temperatures caused no summer and 20,000 deaths from crop failure. Effects lasted 4-5 years.
Positive feedback loop
Starts one way and ends the same way.
Negative feedback loop
Starts one way but ends the other way.
Positive feedback loop - climate change
Snow and ice cover, Albedo effect reflects energy back into space causing cooling and more ice cover.
Melting snow and ice due to CO2 causes decrease in Albedo effect, permafrost melts releasing methane causing more calving of ice sheets. Less ice cover = less albedo effect accelerating warming.
Negative feedback loop - climate change
Increased warming - more evaporation - cloudier skies reflects more solar energy cooing the Earth, ‘global dimming’.
Warmer Arctic waters disrupts THC, less warm water in Gulf Stream drawn north leading to cooling in Europe.
