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.
- what you expect weather - what you
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 centered on
the South Pole, the climates are cold, but there are distinct
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 centimeters a year
e.g. Vostok, 78°27'S, 106°52'E,
average temperature -55.1°C, range 36°C
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
- 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
- Coasts often have fast-ice through the year which keeps
e.g. McMurdo, 77°50'S, 166°30'E,
average temperature -16.9°C, range 23.8°C
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
e.g. Mawson, 67°36'S, 62°55E,
average temperature -11.9°C, range 18.9°C
- Fairly typical maritime climate, cold winter and warmer
- The western side of the Peninsula is warmer than the
- 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
- Maritime climate similar to the Antarctic Peninsula
- 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
- 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
2/ What sorts of weather does Antarctica experience?
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
and 60°S the Westerly winds are driven by the pole/equator
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.
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
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
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
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
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
A combination of high winds and blowing
snow, the snow may or may not be falling from the sky
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
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
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.
4/ what is the circumpolar vortex?
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.
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.
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.
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
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.
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.