Lecture 18: Ice Age Earth II Southern Hemisphere Flashcards
Why are we interested in the southern hemisphere during the quaternary?
- Very different to northern hemisphere - no continental-sized ice sheets
- Glaciers in strange places today
What are some places that glaciers were found in the southern hemisphere?
Tasmania, East Africa, Papua New Guinea
Which hemisphere has the research in to quaternary science tended to focus on?
Northern hemisphere
Why has quaternary research been focused in the northern hemisphere?
Historical academic bias
Greater pool of archives to infer different changes
Why are there typically more archives of paleorecords in the northern hemisphere?
Because there is a greater area of land compared to the south so more places for records to emerge
Why has there been a growing effort to establish understanding of the ice age changes in the southern hemisphere during the quaternary?
To gain a global understanding of the changes as for all it does operate between both hemispheres
What are some global climate components that are located in the southern hemisphere?
ENSO, SAM, ACC
How is the southern ocean defined spatially?
Any ocean that is located further south than 60 degrees south
What are 5 reasons why the southern ocean is so important for global climate?
- place where cold water from poles meets warmer water from mid-latitudes
- highly productive biosphere
- longest and strongest ocean current (ACC)
- Inter-basin exchange between earth’s most important oceans (Atlantic, Pacific, Indian)
- Place where a lot of the global ocean deep water resurfaces.
What % of the global ocean deep water flow resurfaces in the southern ocean?
80%
What also adds to the resurfacing of the deep ocean water in the southern ocean and why?
Southern Westerlies that create a strong surface flow which promotes upwelling more
How does the Southern Westerly wind belt differ from its northern hemisphere counterpart?
North is interrupted by continental land masses all year round.
South is uninterrupted and year round in strength
What demonstrates the strength difference between the southern and northern hemispheres?
Southern hemispheres winter westerlies are as strong as northern hemisphere’s summer westerlies.
What latitude are southern westerlies particularly strong over during summer?
40-60 degrees south
What sort of names have been given to the westerlies in the southern hemisphere due to their strength and latitude?
Roaring forties
furious fifties
screaming sixties
What determines whether the southern ocean acts as a source or sink of atmospheric CO2?
the strength and position of the south westerly wind belt
What will happen when the SWWB is strong?
It will promote upwelling which brings deep water containing CO2 to the surface which will result in its loss to the atmosphere. If they are weak the opposite happens.
Why is it important to study the variation in the SWWB over time to understand climate?
To construct a better picture of the long-term carbon cycle
Which atmospheric system is the SWWB heavily influenced by?
Southern Annular Mode (SAM)
What is the SAM?
The pressure gradient between southern polar regions and the higher latitudes
What is the SAM similar to in how it operates?
NAO
What does it mean if the SAM is positive?
Strong lows over Antarctica and stronger highs over areas further north will create poleward winds
What will happen to the ocean when the SAM is positive?
The stronger poleward winds will increase upwelling leading to increase likelihood of CO2 release to the atmosphere
What has the SAM displayed in recent years and why?
Increasingly positive in strength for an unknown reason so far
What easily attainable climate proxy record can tell us about wind strength and how?
Precipitation record is helpful because generally if precipitation increases then winds are stronger.
What are some of the places in which projects are taking place to determine wind strength in the southern ocean?
Antarctic Peninsula, New Zealand and Patagonia
What is a limitation to carrying out more proxy analysis in the southern hemisphere?
There is a limited supply of land from which to core from
What site is proxied in new Zealand and what records for?
Peatlands - assessed for oxygen and carbon isotopes