Lec6: Antarctic climate and winter

Question 1

Are these in order from coldest to warmest or vice versa?

Antartic Peninsuala, Coast, Inland.

Answer 1

Warmest to coldest.

Question 2

What is the average temperature throughout all of Antarctica?

Answer 2

Below Freezing.

Question 3

What is the coldest region in the South Pole and why?

Answer 3

Higher parts of polar plateau, due to:

1. Elevation
2. Distance from ocean

Question 4

In most parts of Antartica, why does temperature increase (not decrease) for a little while when moving up from the surface?

Answer 4

Because the surface radiates energy, cooling the areas nearer to it more efficiently.

Question 5

What is the coreless winter and what is the cause of it?

Answer 5

There is no “core” month of minimum mean temperatures in Antarctica during winter, they simply remain -60 to -65 degrees celsius from April to September.
Most heat comes from surface radiation (not sunlight) which rapidly establishes equillibrium.

Question 6

How can interglacial and glacial periods be distinguished in Sediment Cores?

Answer 6

1. Glacial = ice sheets rise = sediments fall

2. Interglacial = ice sheets fall = sediments rise

Question 7

What are the two possible lengths of interglacial and glacial cycles and how often do these change?

Answer 7

Every 41000 to 100000 years, and change every 1 million years (for reasons unknown).

Question 8

What did the Snowball Earth enable?

Answer 8

Cambrian explosion of life.

Question 9

How many major ice ages have there been in the past 2.5 billion years?

Answer 9

5.

Question 10

When was the earliest ice age?

Answer 10

Pretorozoic era (Precambrian).

Question 11

What happens to the ratio of oxygen-18 and oxygen-16 during glacial periods compared to interglacial periods and why?

Answer 11

1. Glacial = sea levels fall = O-16 evaporates = ratio rises

2. Interglacial = O-16 returns = ratio is roughly 0

Question 12

As well as using oxygen isotopes in water, what other molecules are in water that scientists can use?

Answer 12

Hydrogen.

Question 13

What is the purpose of measuring oxygen isotopes in water?

Answer 13

As a record of the extent of changing sea levels over glacial-interglacial cycles.

Question 14

Why is the earth’s orbit so critical to long-term climate variability?

Answer 14

Influences the
1. Timing
2. Location
3. Amount
of solar energy reaching the Earth's surface.

Question 15

What are the four orbital parameters, and include the length of the cycle for each?

Answer 15

1. Precession - wobble
2. Obliquity - tilt (41000 yrs)
3. Eccentricity - shape of orbit around sun (100000 years)

Question 16

Marine oxygen isotope ratio and ice core records show a relationship between changing sea-levels and climate, with what factor?

Answer 16

Milankovic cycles.

Question 17

List the 7 reasons that Antarctica is so cold.

Answer 17

LALA has STD:

1. Low Solar Angle
2. Albedo
3. Light-Dark cycle
4. Altitude
5. Sea Ice
6. Thermal Isolation
7. Dryness

Question 18

Describe the low solar angle making Antarctica cold.

Answer 18

Summer sunlight is distributed over more of Earth’s surface at S.pole compared to equator, which means sun energy reaching the pole is comparatively less intense.

Question 19

Describe albedo making Antarctica so cold.

Answer 19

Snow+ice covers 99%, reflecting 80% of sun’s energy.

Question 20

Describe light-dark cycle making Antarctica so cold.

Answer 20

Earth’s tilt is such that areas above Antarctic circle only receive sunlight for part of the year.

Question 21

Describe altitude making Antartica so cold.

Answer 21

Adiabatic expansion cooling. Air expands at higher altitudes (due to less pressure) but heat energy remains constant, so temperature decreases.

Question 22

Describe sea ice making Antarctica so cold.

Answer 22

1. Reflects solar radiation

2. Blocks heat transfer

Question 23

Describe thermal isolation making Antarctica so cold.

Answer 23

Circumpolar currents prevent warm subtropical currents from reaching continent.

Question 24

Describe dryness making Antarctica so cold.

Answer 24

Heat radiated back is lost instead of absorbed by water vapour.

Question 25

What are the two reasons that Antarctica is so windy?

Answer 25

1. Antarctic circumpolar trough

2. Katabatic winds

Question 26

Describe the antarctic circumpolar trough (ACT).

Answer 26

Zone of low pressure at 65 degrees South. Subtropical air fills low pressure zone, and is deflected east by Coriolis force, creating west wind drift.

Question 27

What are katabatic winds?

Answer 27

Cold dense air flowing downhill under the force of gravity.

Question 28

Where are katabatic winds strongest and why?

Answer 28

Near coast, where they converge.

Question 29

Through what process do katabatic winds bring about warming, and how so?

Answer 29

Adiabatic compression heating = Winds flowing downhill are compressed by increasing pressure. becoming warmer.

Question 30

What devices can detect oncoming katabatic storm and why?

Answer 30

Thermometers and Barometers detect adiabatic compression heating.

Question 31

Are katabatic winds slow onset?

Answer 31

No, rapid onset.

Question 32

Why is Antarctica so dry?

Answer 32

1. Most precipation falls as snow.

2. CD air at S.pole creates permenant high pressure zone.

Question 33

Is the S.pole the most cloudless place on earth?

Answer 33

Yes.