Week 8 - Neogene and Quaternary Flashcards
What is the albedo effect?
The albedo effect refers to the ability of a surface to reflect sunlight. Ice has a high albedo, which helps regulate global temperatures by reflecting solar energy.
How does ice sheet expansion affect global temperatures?
Ice sheet expansion increases albedo, reflecting more sunlight and reinforcing cooling effects.
What happens when ice sheets melt in terms of albedo?
When ice sheets melt, the albedo decreases, leading to more solar absorption and accelerating warming.
How do ice sheets influence ocean circulation?
Ice sheets affect thermohaline circulation, which distributes heat, salt, and nutrients globally. Melting ice can disrupt this circulation by adding freshwater to oceans.
What effect does ice sheet melting have on sea levels?
Melting ice sheets raise global sea levels. Since 1880, sea levels have risen by about 25 cm due to thermal expansion and melting land ice.
How much could sea levels rise by 2100, according to IPCC reports?
Sea levels could rise by up to 1 meter by 2100.
When did the first major Antarctic glaciation occur?
The first major Antarctic glaciation occurred around 34 million years ago at the Eocene-Oligocene boundary.
When did the Northern Hemisphere begin to experience significant glaciation?
The Northern Hemisphere began significant glaciation around 2.5 million years ago during the late Pliocene.
What role did declining CO₂ levels play in Cenozoic glaciation?
Declining CO₂ levels were a primary trigger for ice growth, with specific CO₂ thresholds required for glaciation in different hemispheres.
What is the significance of the opening of the Southern Ocean Gateways?
The opening of gateways like the Drake and Tasmanian Passages isolated Antarctica, preventing warm tropical waters from reaching it, leading to cooling and glaciation.
What are Milankovitch cycles?
Milankovitch cycles refer to changes in Earth’s orbit (eccentricity, obliquity, precession) that influence climate cycles, but they were not enough to trigger glaciation on their own.
How did the closure of the Panamanian Seaway affect glaciation?
The closure of the Panamanian Seaway redirected the Gulf Stream, increasing moisture transport to high latitudes, possibly helping initiate Northern Hemisphere glaciation.
What is Ice-Rafted Debris (IRD)?
IRD consists of sand-sized grains transported by icebergs, providing evidence of past glaciation.
What do oxygen isotopes (δ18O) in benthic foraminifera indicate?
δ18O values track ice volume and ocean temperature. Higher δ18O values indicate cooler climates with more ice.
What is the significance of glacial tills in North America?
Early Pleistocene glacial tills (~2.4 million years ago) coincide with the major intensification of Northern Hemisphere glaciation.
Why is the Antarctic Ice Sheet vulnerable to climate change?
Much of the Antarctic Ice Sheet lies below sea level, making it susceptible to ocean warming. The collapse of the West Antarctic Ice Sheet may already be irreversible.
How much sea-level rise could result from Greenland’s ice sheet melting?
If fully melted, Greenland’s ice sheet could raise global sea levels by approximately 7 meters.
What are the predictions for future sea-level rise?
Simulations predict the collapse of the West Antarctic Ice Sheet during warm interglacials, leading to sea-level rise by several meters over the coming centuries.
What do current CO₂ levels suggest for ice sheets in the future?
Current CO₂ levels exceed 420 ppm, which is within the range of past warm periods when ice sheets collapsed, leading to predictions of unstoppable ice-sheet loss if warming reaches 2-3°C.
How are high evaporation and oxygen isotopes linked?
High evaporation leaves oxygen-18 behind in the ocean, and oxygen-16 is more abundant in land ice, as recorded by benthic foraminifera.
What major climatic trend occurred during the Neogene period?
The Neogene period was marked by increasing land ice volume and cooling climates, particularly in the Northern and Southern Hemispheres.
When did Antarctica begin to experience glaciation?
Antarctica began to experience glaciation around 34 million years ago during the Eocene-Oligocene boundary.
What was the significance of the Quaternary period in terms of ice volume?
The Quaternary period saw the intensification of ice-sheet growth, particularly in the Northern Hemisphere, and was characterized by repeated glacial and interglacial cycles.
How did CO₂ levels influence glaciation during the Neogene and Quaternary periods?
CO₂ levels played a crucial role in controlling glaciation timing. Lower CO₂ levels, especially below ~280 ppm, allowed for ice-sheet formation, while higher levels hindered glaciation.
How did glaciation in the Neogene and Quaternary affect global ocean and atmospheric circulation?
The growth of ice sheets during these periods dramatically altered ocean and atmospheric circulation patterns, especially by redistributing heat, salt, and moisture globally.
What evidence supports the idea of cooling climates during the Neogene and Quaternary?
Evidence includes the expansion of land ice, lower CO₂ levels, and isotopic data (e.g., δ18O values in benthic foraminifera), indicating cooler temperatures and increased ice volume.
What event marks the beginning of the Pleistocene glaciation?
The beginning of the Pleistocene is marked by the intensification of Northern Hemisphere glaciation, around 2.4 million years ago.
