ANTARTICA-AS PERCEIVED IN THE 21ST
CENTURY
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A
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A little over
a century ago, men of the ilk of Scott, Shackleton and Mawson battled
against Antarctica’s blizzards, cold and deprivation. In the name of Empire
and in an age of heroic deeds they created an image of Antarctica that was
to last well into the 20th century—an image of remoteness, hardship,
bleakness and isolation that was the province of only the most courageous
of men. The image was one of a place removed from everyday reality, of a
place with no apparent value to anyone.
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B
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As we enter the 21st century,
our perception of Antarctica has changed. Although physically Antarctica is
no closer and probably no warmer, and to spend time there still demands a dedication
not seen in ordinary life, the continent and its surrounding ocean are
increasingly seen to be an integral part of Planet Earth, and a key component
in the Earth System. Is this because the world seems a little smaller these
days, shrunk by TV and tourism, or is it because Antarctica really does
occupy a central spot on Earth’s mantle? Scientific research during the past
half century has revealed—and continues to reveal—that Antarctica's great
mass and low temperature exert a major influence on climate and ocean circulation,
factors which influence the lives of millions of people all over the globe.
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C
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Antarctica
was not always cold. The slow break-up of the super-continent Gondwana with
the northward movements of Africa, South America, India and Australia
eventually created enough space around Antarctica for the development of an
Antarctic Circumpolar Current (ACC), that flowed from west to east under
the influence of the prevailing westerly winds. Antarctica cooled, its
vegetation perished, glaciation began and the continent took on its present-day
appearance. Today the ice that overlies the bedrock is up to 4km thick, and
surface temperatures as low as -89.2deg C have been recorded. The icy blast
that howls over the ice cap and out to sea—the so-called katabatic wind—can
reach 300 km/hr, creating fearsome wind-chill effects,
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D
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Out of this extreme
environment come some powerful forces that reverberate around the world.
The Earth’s rotation, coupled to the generation of cells of low pressure
off the Antarctic coast, would allow Astronauts a view of Antarctica that
is as beautiful as it is awesome. Spinning away to the northeast, the cells
grow and deepen, whipping up the Southern Ocean into the mountainous seas
so respected by mariners. Recent work is showing that the temperature of
the ocean may be a better predictor of rainfall in Australia than is the
pressure difference between Darwin and Tahiti—the Southern Oscillation
Index. By receiving more accurate predictions, graziers in northern
Queensland are able to avoid overstocking in years when rainfall will be
poor. Not only does this limit their losses but it prevents serious pasture
degradation that may take decades to repair. CSIRO is developing this as a
prototype forecasting system, but we can confidently predict that as we
know more about the Antarctic and Southern Ocean we will be able to enhance
and extend our predictive ability.
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E
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The ocean’s
surface temperature results from the interplay between deep-water
temperature, air temperature and ice. Each winter between 4 and 19 million
square km of sea ice form, locking up huge quantities of heat close to the
continent. Only now can we start to unravel the influence of sea ice on the
weather that is experienced in southern Australia. But in another way the
extent of sea ice extends its influence far beyond Antarctica. Antarctic
krill—the small shrimp-like crustaceans that are the staple diet for baleen
whales, penguins, some seals, flighted sea birds and many fish—breed well
in years when sea ice is extensive and poorly when it is not. Many species
of baleen whales and flighted sea birds migrate between the hemispheres and
when the krill are less abundant they do not thrive.
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F
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The circulatory system of the
world’s oceans is like a huge conveyor belt, moving water and dis-solved
minerals and nutrients from one hemisphere to the other, and from the
ocean's abyssal depths to the surface. The ACC is the longest current in
the world, and has the largest flow. Through it, the deep flows of the
Atlantic, Indian and Pacific Oceans are joined to form part of a single
global thermohaline circulation, During winter, the howling katabatics sometimes
scour the ice off patches of the sea's surface leaving large ice-locked
lagoons, or ’polynyas'. Recent research has shown that as fresh sea ice forms,
it is continuously stripped away by the wind and may be blown up to 90km in
a single day. Since only fresh water freezes into ice, the water that
remains becomes increasingly salty and dense, sinking until it spills over the
continental shelf. Cold water carries more oxygen than warm water, so when
it rises, well into the northern hemi-sphere, it reoxygenates and revitalises
the ocean. The state of the northern oceans, and their biological
productivity, owe much to what happens in the Antarctic.
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Questions 14-18
Reading Passage 2 has six paragraphs, A-F.
Which paragraph contains the following information?
Write the correct letter, A-F, in boxes 14-18 on your answer sheet:
14
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The example of a research on building weather prediction for agriculture
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15
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An explanation of how Antarctic sea ice brings back oceans’ vitality
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16
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The
description of a food chain that influences animals’ living pattern
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17
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The reference of an extreme temperature and a cold wind in Antarctica
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18
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The
reference of how Antarctica was once thought to be a forgotten and insignificant
continent
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Questions 19-21
Match the natural phenomenon with the
correct determined factor. Write the correct letter, A-F, in boxes 19-21 on your answer sheet.
19
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Globally, Antarctica’s massive size and _____________ would
influence our climate
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20
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_____________ circulated under contributory force from wind blowing
from the west.
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21
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The ocean
temperature and index based on air pressure can help predict _____________ in
Australia.
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A
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Antarctic Circumpolar Current (ACC)
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B
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katabalic winds
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C
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rainfall
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D
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temperature
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E
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glaciers
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F
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pressure
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Questions 22-26
Choose the correct letter, A, B, C or D.
Write the correct letter in boxes 22-26
on your answer sheet.
22
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In paragraph B, the author intends to
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A
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show
Antarctica has been a central topic of global warming discussion in Mass
media.
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B
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illustrate how its huge sea
ice brings food to millions of lives in the world.
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C
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emphasise the
significance of Antarctica to the global climate and ocean currents.
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D
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illustrate the geographical
location of Antarctica as the central spot on Earth.
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23
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Why should
Australian farmers keep an eye on the Antarctic ocean temperature?
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A
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It can help farmers reduce
their economic loss.
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B
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It allows for
recovery of grassland lost to overgrazing.
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C
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It can help to prevent animals
from dying.
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D
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It enables
astronauts to have a clear view of the Antarctic continent.
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24
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The decrease in the number of
whales and seabirds is due to
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A
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killer
whales’ activity around Antarctica.
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B
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the correlation between sea
birds’ migration and the salinity level of the ocean.
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C
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the lower
productivity of food source resulting from less sea ice.
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D
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the failure of seals to
produce babies.
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25
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What is the
final effect of the katabatic winds?
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A
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Increasing the moving speed of
ocean current.
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B
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Increasing
the salt level near ocean surface.
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C
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Bringing fresh ice into the
oceans.
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D
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Piling up the
mountainous ice cap respected by mariners.
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26
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What factor drives Antarctic
water to move beyond the continental shelf?
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A
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A The
increase of salt and density of the water
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B
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The decrease of salt and
density of the water
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C
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The rising
temperature due to global warming
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D
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The melting of fresh ice into
the ocean
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