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Antarctica Climate
and Weather
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Climate - the average atmospheric conditions over long time periods,
weeks, months, years.
Weather - what is happening in a particular place at a particular
time, usually over short periods, hours or days, e.g, rain, blizzard, sunny and
calm.
| 1/ What
is the climate like in Antarctica? |
Antarctica is a
continent, bigger than either Europe, North America or Australia, and as
such it doesn't just have one climate zone, but several. As it is
centred on the South Pole, the climates are cold, but there are distinct
zones:
 | Continental High Plateau
 | Around the centre of the continent, high altitude
with an average height of around 3,000m (10,000ft) |
| Extreme cold year-round, approx. -20°C
to -60°C monthly averages, large temperature range |
| Clear skies common, constant
light winds from the South |
| Snowfall is rare,
precipitation in the form of fine ice crystals, no more than a
few centimetres a year |
| e.g. Vostok, 78°27'S,
106°52'E, average temperature -55.1°C,
range 36°C
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|
| Continental Low Plateau
| Lower altitude West
Antarctica and closer to the coast in East Antarctica, approx.
1000-1,500m (3500-5000ft) |
| Very cold year-round, approx. -12°C
to -35°C monthly averages, smaller temperature range than higher
altitude |
| Clear skies, calm air, little
precipitation common |
| Weather more variable as
depressions can bring blizzards with heavy snowfall and strong
winds |
| e.g. Byrd,
80°01'S,
120°00'W, average temperature -27.9°C,
range 22.3°C
|
|
| Continental High Latitude
Coast
| Coastal areas in the deep
south 70°S + |
| Cold winters and short cold
summers, approx. -2°C
to -30°C monthly averages |
| Frequently changing weather,
cloud and year-round snow is common |
| Coasts often have fast-ice
through the year which keeps temperatures low |
| e.g. McMurdo,
77°50'S,
166°30'E, average temperature -16.9°C,
range 23.8°C
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|
| Continental Low Latitude
Coast
| Coastal areas approx. 65°S
- 70°S |
| Cold winters and short cold
summers, approx. +2°C
to -20°C monthly averages |
| Temperatures are higher than
many non-Antarctic continental areas even in winter, summer
temperatures kept low due to ice and snow cover |
| Precipitation can be heavy,
winds often very strong - katabatic |
| e.g. Mawson,
67°36'S,
62°55E, average temperature -11.9°C,
range 18.9°C
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| Antarctic Peninsula
| Fairly typical maritime
climate, cold winter and warmer summers. The western side of the
Peninsula is warmer than the eastern side. |
| Cold winters and short cold
summers, approx. +1°C
to -15°C monthly averages |
| Depressions come in from the
west bringing cloud precipitation and winds, rain frequently
falls in summer |
| e.g. Rothera,
67°34'S,
68°08'W, average temperature -5.3°C,
range 13.6°C
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|
| Antarctic Islands
| Maritime climate similar to
the Antarctic Peninsula but milder |
| Cold winters and short cold
summers, approx. +1°C
to -10°C monthly averages |
| Winter temperatures brought
down by sea-ice |
| Low cloud common in summer
with rain and sleet, heavy snow in winter |
| e.g. Orcadas,
60°44'S,
44°44'W, average temperature -4.3°C,
range 11°C
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| Sub-Antarctic Islands
| Southern ocean islands above
the northern limit of sea-ice |
| Oceanic climate with cool
summers and similar but cooler winters,
approx. +4°C
to -1.5°C monthly averages |
| Depressions bring rain in
summer, snow in winter and strong winds year-round |
| e.g. South Georgia,
54°18'S,
36°30'W, average temperature 1.8°C,
range 6.9°C |
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Temperature Data
°C |
|
Jan |
Feb |
Mar |
Apr |
May |
Jun |
Jul |
Aug |
Sep |
Oct |
Nov |
Dec |
Average |
Range |
|
Continental High Plateau |
Vostok |
-32.1 |
-44.3 |
-57.9 |
-64.7 |
-65.6 |
-65.2 |
-66.9 |
-67.6 |
-66.0 |
-57.1 |
-43.3 |
-32.1 |
-55.1 |
36.0 |
|
Continental Low Plateau |
Byrd |
-14.7 |
-19.8 |
-27.7 |
-29.7 |
-33.0 |
-34.1 |
-35.6 |
-36.7 |
-36.6 |
-30.2 |
-21.4 |
.14.4 |
-27.9 |
22.3 |
|
Continental High Latitude
Coast |
McMurdo |
-2.9 |
-9.5 |
-18.2 |
-20.7 |
-21.7 |
-23.0 |
-25.7 |
-26.1 |
-24.6 |
-18.9 |
-9.7 |
-3.4 |
-16.9 |
23.8 |
|
Continental Low Latitude
Coast` |
Mawson |
-0.7 |
-5.4 |
-11.2 |
-15.0 |
-16.8 |
-16.7 |
-18.0 |
-18.8 |
-18.2 |
-13.9 |
-6.2 |
-0.9 |
-11.9 |
18.9 |
|
Antarctic Peninsula |
Rothera |
1.0 |
0.1 |
-1.6 |
-3.7 |
-6.8 |
-8.8 |
-12.6 |
-11.8 |
-9.4 |
-7.2 |
-3.3 |
0.2 |
-5.3 |
13.6 |
|
Antarctic Islands |
Orcadas |
0.3 |
0.5 |
-0.6 |
-3.0 |
-6.7 |
-9.8 |
-10.5 |
-9.8 |
-6.4 |
-3.4 |
-2.1 |
-0.5 |
-4.3 |
11.0 |
|
Sub-Antarctic Islands |
South Georgia |
4.7 |
5.4 |
4.6 |
2.5 |
0.2 |
-1.5 |
-1.5 |
-1.5 |
0.1 |
1.7 |
3.0 |
3.8 |
1.8 |
6.9 |
|
| 2/ What
sort of weather does Antarctica experience? |
|
Wind
|
Antarctica is the windiest
continent on earth, the relative intensities is told by the old
sailors descriptions of:
Roaring Forties, Furious Fifties and Screaming Sixties (degrees
of latitude) |
|
Storms are common in Antarctica
and are frequently very energetic and dramatic |
|
Between 50°S
and 60°S the Westerly winds are driven by the pole/equator
temperature gradient |
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Below
60°S winds are
largely katabatic, this is a result of cold air forming
over the pole and falling (as cold air is heavier). The pole is
on a high plateau 3,000m (10,000ft), so the cold air falls down
the slope getting faster as it goes. By the time it gets to the
coast, the earth's rotation (Coriolis force) makes the wind
westerly.
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Cloud
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Estimations of
cloud cover has been problematic in Antarctica as the whole
landscape is difficult to estimate and features that may seem a
few km distant can actually be 50km or more, this makes cloud
height estimations particularly difficult |
|
Cloud cover
averages may be 6/8 or 4/8, but the reality is that often cloud
is either 0/8 or 8/8 i.e. no cloud or total cloud |
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Coastal areas are
cloudier than continental areas and continental clouds are often
made up entirely of ice crystals rather than the mix of ice and
water vapour at the coast
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Precipitation
|
Most
precipitation falls as snow in Antarctica. Constant strong winds
make measurement of snow fall very difficult as once it's fallen
it then blows around an awful lot without any extra being added
to any one position |
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Precipitation is
often measured as "water equivalent" the amount of water that
would be obtained if the snow was melted |
|
The high plateau
of East Antarctica is a desert with less than 50mm of water
equivalent falling per year, this does not fall as snow but as
tiny ice crystals in the air known as "diamond dust" from a
perfectly clear sky and causes many optical phenomena such as
solar pillars and haloes |
|
The heaviest snow
falls are on the western coast of the Antarctic Peninsula |
|
Rain commonly
falls in coastal regions in the summer
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Blizzards
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A combination of high winds and blowing snow,
the snow may or may not be falling from the sky |
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When snow falls
in low temperatures, or when ice crystals in the air settle,
they are only very loosely bound together and so may be blown
around for a long time, the result is that there is often
blowing snow in Antarctica without there being very much
precipitation |
|
A blizzard may
easily lead to white-out conditions when it is impossible to see
surface features, the whole world is just a big white blur, this
can be very dangerous as it is possible to walk over a cliff
edge without even being aware it is there |
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| 3/ How
does Antarctica influence the climate and weather in the rest of the
world? |
| The contribution to global
weather is actually very small, Antarctic weather keeps itself to
itself most of the time, there is a much greater influence from ocean
currents than from atmospheric effects. This contributes to Antarctica
being so cold, as the weather goes round and round rather than spilling
over to lower latitudes as the arctic weather systems do.
A greater influence is from the Thermohaline
circulation. Thermo - heat, Haline - salt/salinity. Very salty water
is denser than less salty water and will sink beneath it, colder water
likewise is denser than warmer water and sinks beneath it. Around
Antarctica very low air temperatures cause surface waters to cool,
become denser and sink beneath the rest of the ocean, this falls to the
bottom of the sea and then starts to flow northwards (similar thing
happens in the Arctic). It is important as means that there are deep
currents moving sea water around the oceans that are independent of
winds and moves huge amounts of heat around the planet largely
independent of surface weather (although surface weather initiates it)
these currents can takes 100's of years to reach their destination.
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Related Questions |
| 4/ what
is the circumpolar vortex? |
| The "circumpolar vortex"
is a strong Westerly circulation of winds that builds up during the
winter months in the upper layers of the atmosphere (stratosphere) over
Antarctica.
 This
cuts off the central Antarctic weather causing temperatures to fall and
stay low. It also adds to the breakdown of the ozone layer by trapping
clouds called "Polar Stratospheric Clouds" that cause ozone depletion by
(also trapped) Chlorine containing compounds (such as
chlorofluorocarbons - CFC's). These clouds may be called "Nacreous" as
they look like the nacre of shells or mother-of-pearl.
The circumpolar vortex breaks up in the spring and
summer months, it maintains very low and stable temperatures in the
winter. |
| 5/ What
is Infrared cooling? |
| A way of saying that hot
things cool down! At night the warm earth gives out infrared rays
that cool it down, it also happens during the day, but we don't notice
it amongst the warmth from the sun, it only really causes a temperature
drop at night. It's this that balances the heat coming in from the sun,
so the planet doesn't just keep getting hotter and hotter. |
| 6/ What
is Specific heat? |
| It's a measure of the
energy needed to raise a standard amount of a substance by 1°C,
usually given in Joules, could be calories. e.g. the specific heat of
water is 4.2 J/g °C,
it takes 4.2J to raise 1g of water by 1°C,
ice is 2.1J, air 1J, iron 0.45J. Also gives an indication of how much
heat energy something can store and how slowly it cools down. |
| 7/ Some
statistics say ice sheets melting, but others say more ice is
accumulating (increased precipitation leads to a fall in pressure
therefore more storms and increased precipitation and ice cover) Aren't
they contradicting each other? |
| Yes and no - remember
Antarctica is a continent, larger than Europe. Ice is being lost from
the Peninsula region, but there is build up of ice from precipitation
over the much larger land mass of Eastern Antarctica. Many models of
climate change show Eastern and Western Antarctica (especially the
Peninsula) as behaving quite differently. |
| 8/ Where
is the continental shelf? |
| Offshore from continental
landmasses, a "shelf" around the continent. The Earth is made of
land and sea tectonic plates. Land plates are less dense and float
higher than the sea plates. Erosion around the edges of land plates
causes shallow seas so some of the land plate is under water, when you
reach the edge of the land plate, it drops off quite steeply to the
depths of the sea-plate. This drop-off is called the continental shelf.
Continental shelves have shallow seas and so respond more quickly to
weather changes, they are also usually much more biologically productive
than the deep sea abyssal-plains. |
| 9/ What
are the characteristics of Pack ice? |
| Pack ice is floating ice
that is frozen sea-water, it may have formed in situ, or may have
floated from many hundreds or thousands of miles away. It can be
open-pack or closed-pack, depending on how pushed together the pieces
are. It can last a year or less, or may be old ice that has survived 2
or 3 years before being broken up and drifting off. It forms each year
from the sea, does not contribute to sea-level changes, but has a major
impact in reflecting light and heat from the sun. More pack ice makes it
colder, less makes it warmer. |
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