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
What was an initial problem for carrying out research in to peatland in New Zealand?
Much research had been carried out in the northern hemisphere that was dominated by a different flora to that which dominated the peatlands in the southern hemisphere
What was the name of the flora that dominated northern hemisphere and New Zealand peatlands?
Sphagnum Moss in Northern Hemisphere and then Epodisma in New Zealand.
What needed to happen after researchers found that the peatlands were dominated by a different flora?
They needed a different approach
What work was done before real research began in to peatlands in new Zealand?
A preliminary investigation to determine the potential of using Epodisma cellulose as a proxy for isotopic composition of carbon and oxygen. The result was that it was successful.
What isotopes were analyses in the new Zealand peatland record?
Oxygen 18 and Carbon 13
Why was New Zealand chosen as a site for research in to climate changes in the southern hemisphere?
Located at boundary of lower pressure zones and higher pressure zones between latitudes meaning its subject to influences from tropics and poles.
Climate is dominated by SWWB which is under investigation
What is the ongoing conclusion of the work in new Zealand?
Confidence that there is a relationship between plants and atmospheric moisture
What was the study infrastructure like in New Zealand?
Network of sites established over 2 years
What work was carried out in Patagonia to establish understanding of climate in the southern hemisphere?
Studied testate amoebae taxa within peat bogs
How small are testae amoebae?
20-300 microns
Where are testate amoebae commonly found and how many taxa are there for species that live in that environment?
Peat bogs - usually 60 taxa
What is the benefit of 60 taxa of testate amoebae?
This is relatively few and so makes the research a bit easier as there are fewer to identify
What are testate amoebae normally an indication of?
Water table depth, pH, water conductivity
Why is it important that testate amoebae are a proxy for water table depth?
because this is an indication of water balance (balance between precipitation and evaporation)
What happened to knowledge about testate amoebae as research in Patagonia started?
It was thrown out the window because the process was completely different to the knowledge generated in the northern hemisphere
What was the hoped conclusion of the research in to testate amoebae in Patagonia?
Increased abundance of a testate amoebae taxa that was associated with drier conditions
What undermined the hoped conclusion of the research in Patagonia?
The taxa are more resilient to increases in UVB that took place as a result of the hole in the ozone layer from the 1970s. There increased abundance of this taxa was therefore blamed on this environmental condition rather than on drier conditions because it demonstrated a stronger correlation
What site was chosen for research in to climate of the southern hemisphere in the Antarctic Peninsula? Why?
The frozen peatlands because they were prevented from decomposing over time.
What statistic demonstrates that the Antarctic Peninsula is one of the fastest warming areas on earth?
It has warmed 3 degrees Celsius since the 1950s
What are the frozen peatlands in the Antarcitc peninsula known as?
moss banks
How deep can the frozen peatlands/moss banks in the Antarctic peninsula be? and how long can they extend to?
3m deep and over 5,000 years old
What technique is used to analyse the peatlands in the Antarctic peninsula?
coring
What did the research in the Antarctic peninsula frozen peatlands/moss banks find? What does it suggest about the future?
There was a dramatic response of the peatlands to warming events from the 1950s onwards. It suggests that they will respond dramatically also to the anthropogenic global warming with increases in microbial activity and growth rate.
What statistic demonstrates the importance of the findings in the Antarctic peninsula?
It was one of the top 100 scientific papers of 2017 and the 5th most discussed climate paper
When did Antarctic ice cores begin?
1950s
What is the current oldest Antarctic ice core and where is it found?
Dome C it is 800,000 years old
What important debunked myth is there about depth and age of ice core?
Depth does not always correlate with age
What ice core was found in 2013 and how old was it thought to be?
2.5km thick and extended back 1.5m years
What ice core was found in 2017 and how old was it thought to be but what was the problem?
2.7m years old but it had a fragmented record
What becomes more difficult to determine about ice cores as you reach the deeper layers? why?
Their age because the layers become blurred
What is tephra?
Volcanic ash
What can tephra be preserved in? and how?
Ice cores - it may get caught in the SWWB of which this then gets preserved in the terrestrial record and used as evidence of that eruption
What thing, similar to tephra, can also be stored within ice cores? what can they indicate?
dust - it serves as a proxy for atmospheric circulation changes as it may be preserved in areas unexpected
What liquid thing can also be preserved in the ice cores and what does it serve to proxy?
sea spray - proxy for storminess or sea ice extent
What are the oldest archaeological remains of people dated back to South America?
14.5 - 14.25 kya
Where are the oldest archaeological remains of people dated back to in South America?
Monte Verde, Southern Chile
What leads to thoughts that the remains of the first people found in South America moved there quickly?
because they were found and dated to around the same time as those remains found in Northern America. they travelled a long distance south in a short period.
What is an alternative idea for how the first people ended up in South America?
they travelled across the pacific ocean
What is thought to have allowed people in Australia to emerge?
lower sea level during LGM
When are the estimates for when the first Australians emerged?
40-80kya
What evidence predicts that Australian people emerged earlier and when is this estimation?
Radiocarbon evidence: 60kya
Fire Evidence: 70-100kya
Human Genome: 60kya
Mass Megafauna: 46kya
What mass megafauna in Australia were discovered and dated back to 46kya?
Giant Kangaroos and Koalas
What place surprisingly took a long time for humans to emigrate to despite the emergence of them in Australia?
New Zealand
What happened to the humans that emerged in Australia later?
They emigrated to places in the Pacific Ocean
