Biosci 100 - Lecutre 4

Why is Antarctica so cold? Give at least FIVE factors.

Any five of:

• Low solar radiation — sunlight is spread over a large area, so heating is less intense.

• Albedo — snow and ice reflect about 80% of sunlight, so little is absorbed.

• Sea ice — winter sea ice doubles, increasing reflection and reducing heating.

• Altitude — Antarctica has a high average elevation (~2500 m), which contributes to colder temperatures.

• Thermal isolation — the ACC prevents warm ocean currents from reaching Antarctica.

• Dryness — dry air allows heat to escape easily.

• Light–dark cycle — Earth's tilt means Antarctica gets little or no sunlight during part of the year.

Thermal isolation

Antarctic Circumpolar Current (ACC)

The ACC surrounds Antarctica and helps prevent warm ocean currents from reaching the continent.

Why is Antarctica so dry?

• Temperature: Cold air holds less water vapour.

• Pressure: High pressure causes sinking air, producing dry conditions.

• Continentality: The large interior is far from the ocean, so there is little moisture available.

Westerlies → ______ → ______ → thermal isolation

Westerlies → West Wind Drift → Antarctic Circumpolar Current (ACC) → thermal isolation

An air mass is moving southward in the Southern Hemisphere. Which direction will the Coriolis effect deflect it?

East

What is the Coriolis effect, and why does it occur?

It arises because of Earth's rotation. In the Southern Hemisphere, moving air and water are deflected to the left.

Why does Antarctica's high altitude contribute to its cold temperatures?

Air pressure drops as elevation increases. Thinner air holds less heat.

Which factor causes Antarctica to receive little or no sunlight during part of the year?

Earths tilt

What percentage of sunlight do snow and ice reflect in Antarctica?

~80%

Which process is most directly responsible for katabatic winds?

Cold, dense air flowing downslope

What are the two types of winds mentioned in your notes as contributing to Antarctic wind patterns?

• Katabatic winds — on the continent

• Oceanic winds — associated with the Antarctic Circumpolar Trough

Why does cold air contribute to Antarctica being dry?

Cold air holds less water vapour, so there is less moisture in the atmosphere.

What does high pressure over Antarctica cause?

Sinking dry air

Explain how the westerlies eventually lead to thermal isolation.

Westerlies → West Wind Drift → ACC → thermal isolation

What was the name of the ancient supercontinent that Antarctica was part of?

Gondwana

What plant genus is particularly important as evidence that Antarctica was once part of Gondwana?

Glossopteris

What major geological event occurred around 180 Ma?

Gondwana broke apart, associated with the formation/emplacement of Ferrar dolerite.

How did plate tectonics influence the development of Antarctica's ice sheet?

Plate tectonic movements changed Antarctica's position and eventually isolated it from other continents. Around 34 Ma, Antarctica became isolated and major ice-sheet formation began. Later, around 23 Ma, the Drake Passage opened and the ACC became established, providing thermal isolation that helped maintain Antarctica's cold conditions.