N hemisphere Flashcards
what are the continental ice sheets in the N hemisphere?
- Laurentide & Cordilleran (N America)
- British, Scandinavian (Europe)
- Barents, Kara (Russia)
- Greenland
when was the European continent created?
at the end of the post glacial period
what was the British Quaternary Stratigraphy?
- E Anglian coast
- river terrace, glacial till and raised beach deposits framework for glacial-interglacial cycle
- 4 phases of glaciation along the coast
when did the British ice sheet form?
- devensian glacial
- lgm ~21,000 y/a
- covered Scotland, Ireland, Wales and N England
- 800,000km3
- up to 1.5km thick
sea level change in the quaternary
- global av. sea level fluctuates with global ice vol.
- sl correlated with glacial-interglacial cycle
- sl at lgm ~120m lower than present
what can cause isostatic sl rise after deglaciation?
crustal rebound
type of landforms in the quaternary
- wave cut platform
- raised beach
- marine fossils
examples of landforms due to sl change in the quaternary
- Hope’s Nose Peninsula, S Devon
- Huon Peninsula, Papua New Guinea
when was the LGM?
20-25k y/a
landscape change in the quaternary
- permafrost
- periglacial landscape processes
- veg, animals, humans
2 causes of the last ice age
1- increased summer insolation at higher N latitudes
obliquity reached maximum
precession (wobble) brought earth closer to the sun
2- increase in atmospheric CO2 from 190-280ppm
ocean degassing
biomass feedbacks
example of deglaciation
beginning of Holocene, just a small ice cap on Scotland’s Trossarchs and Highland Range then glacial re-advance during the Loch Lomond stadial
common name for Loch Lomond
Younger Dryas
what happened at the end of the last ice age?
biome shifts
- temp biomes expand N
- glacial refugia
- tundra contracts
- implications for fauna
when did Britain submerge by at the end of the last glacial?
~8200 y/a
a late glacial type site
- lake windermere, Cumbria
what indicates a change in geomorphological processes in catchment?
changing sedimentology
what was the last interglacial in the UK?
Ipswichian
last interglacial in Europe
Eemian
last interglacial in N America
Sangamon
which ice sheets are either side of the continental divide of the Rocky Mountains?
Laurentide- 3km thick, 33mil km3
Cordilleran merged with Laurentide during LGM
what is the North Atlantic Ocean pressure gradient between?
- subpolar Icelandic low
- subtropical Azores high
what does the NAO do?
- influences strength and position of NA jet stream, northern westerlies
- modulates patterns of zonal and meridional (lat and long) heat and moisture transport
- affects changes in temp and ppt across region
what happens in a +ve NAO pressure gradient?
strong gradient so jet stream is forced N
what happens if NAO pressure gradient is -ve?
weaker gradient so enhanced trough-peak-trough in jet stream
what is AMOC?
Atlantic Meridional Oceanic Circulation
what happens in AMOC?
- N flow of warm salty surface water
- S flow of colder, deep water
what is the thermohaline circulation system?
transport of heat energy from tropics and S hemisphere to NA where heat is lost to atm
the impacts of AMOC on the global climate system
- sea surface temps
- arctic sea ice
- moisture supply
could AMOC be disrupted during glaciation?
yes
when are Dansgaard-Oeschger events common?
in glacials and weak in interglacials
in the N hemisphere, what are DO events characterised by?
rapid warming to interglacial temps, then slower cooling
in S hemisphere what are DO events characterised by?
slow warming and smaller temp fluctuations
what are Heinrich events?
- occur in cold spells preceding some DO events
- icebergs break off from ice sheets
- transport terrestrial, minerogenic ice rafted debris into NA, deposited on the ocean floor
is there external forcing in Heinrich events?
- changes in NA circulation freshwater pulses, thermohaline
- ice sheet dynamics: binge-purge cycle
types of external forcing
solar activity and orbital cycles
what happened to Laurentide and Cordilleran ice sheets during LGM?
- they fused resulting in coast-to-coast ice
- ice-free corridor route, people migrated into central N America as Cordilleran ice sheet melted
