Global Warming in Antarctica - summary
of this page
New research is being carried out, new things found and
understanding is improving. Global warming in Antarctica
is going to be a popular topic in the future.
these pages after reading an awful lot of articles, scientific
explanations and news reports*. These statements summarize
the situation as I understand at the moment:
*ALWAYS take news reports in the papers,
offline or online with a pinch of salt, the real purpose
of many newspaper stories is very often to sell newspapers
and/or gain some fame or career progression for the journalist.
warming is real. It
is happening more quickly in some parts of the world
Peninsula is particularly sensitive to small rises in
the annual average temperature. This has increased about 2.5°C
in the region in the last 50 years. This is 2 or 3 times
faster than the average in other parts of the world.
This makes it an excellent study area.
The temperature of the rest
of Antarctica - the other 96% - shows no current indications
There is no unusual significant
loss of ice of any kind from the larger 96% of Antarctica
that is not the Peninsula.
temperatures cause ice shelves to break up
- as they are floating this will not affect sea levels.
It may cause the glaciers behind them to speed up their
flow-rate considerably. These glaciers will add to sea-level
rise if they melt.
of Antarctica as a whole is predicted to rise by a small
amount over the next 50 years. Any increase in the rate of
ice melting is expected to be at least partly balanced
by increased snowfall as a result of the warming.
in Antarctica is not always changing, but because scientists
are regularly assessing the problem they are just making
new discoveries. These
discoveries are things the decline of krill populations
1/ What evidence
is there from ice shelves?
Larsen B ice shelf, 17th Feb 2002
Larsen B ice shelf, 5th March 2002 (16 days later)
dimensions of photograph area approx.
130 x 160 km (80 x 100 miles)
of the Larsen B ice shelf in early 2002.
Global warming has been blamed for this event. That it occurred
is beyond dispute. It is a result of the warming of the
Antarctic Peninsula where it is situated. What scientists
are not sure of is whether this is something which will
affect the whole of Antarctic or whether it is only affecting
the Antarctic Peninsula.
An ice shelf is a thick
layer of ice that is floating on the sea. They are fed from
the land by glaciers. Where the ice leaves the land and
starts to float on the sea is a region known as the "hinge
zone". This region is particularly chaotic, broken-up and
a nightmare to try and travel over. Ice shelves surround
much of Antarctica.
The Larsen B ice shelf was about
220m thick (720 feet) and during a 35 day period in early
2002 lost about 3,250 km2 of ice into the ocean. It is thought
to have been in existence for at least 400 years prior to
this and probably as long as 12,000 years since the end
of the last ice age.
It is an important even because
it is a big disintegration of ice in a short time period.
What now remains of the Larsen B is about 40% of what was
there in 1995. It had been breaking up at what was considered
to be a rapid rate anyway before this major event. The break-up
is thought to be a result of higher temperatures and large
amounts of summer melt-water running down crevasses in the
ice shelf. This speeds up the disintegration process.
Overall in the Antarctic Peninsula, there
are seven ice shelves which have altogether declined in
area by about 13,500 km2 since 1974.
A more recent
problem which followed this ice shelf collapse is that the
glaciers that fed the ice shelf now seem to be flowing down
to the sea more quickly than before. This will certainly
put more water in the oceans because this ice was previously
on the land. It will add to an increase in sea-level. The
Antarctic peninsula doesn't have enough ice to make much
of a difference to sea level in itself even if it were all
to melt, but it helps scientists understand what is happening
in other parts of the world.
An ice shelf which had
previously blocked the Prince Gustav Channel on the Antarctic
Peninsula collapsed and evidence from seabed sediments have
shown that it had disappeared at least once before in the
last 10,000 years.
"Thus, the present loss of
ice shelves cannot be assumed to be a consequence of
Man-made climate change, unless and until a cause can
British Antarctic Survey
A photograph that
may not be able to be taken again for a few
hundred or even thousand years. In 1985, HMS
Endurance is moored up to the ice barrier that
blocked the Prince Gustav channel between James
Ross Island and the Antarctic Peninsula. Standing
by the ship and looking to the left in the picture,
the ice slope could be seen to rise to well
over 100 feet (30m) altitude into the distance
(and 9 to 10 times that thickness under the
level of the sea). Today, the whole lot has
2/ Is the whole
of Antarctica warming?
The short answer is - no
The Antarctic Peninsula, particularly
the West coast of the Peninsula is warming at a rate 2 or
3 times faster than the global average. This has received a lot of publicity
in recent years. This is where the Larsen B ice shelf (see
above) is situated. The average annual temperature of this
region has increased about 2.5°C in the last 50 years.
However, data on temperatures in Antarctica only really
go back about 50 years. Anything before that is estimated
from ice cores or other sources. So we don't really know
how the temperatures vary over even the medium term in Antarctica.
The Antarctic Peninsula also makes up only about 4%
of the whole continent. The other 96% appears to have had
a stable temperature over the last 40 years. This stability
is very interesting especially when you compare it with
the quick changes happening in other parts of the world.
One reason that the Peninsula region appears to be so
dramatically warming is that it has a large amount of snow
and ice, glaciers, ice shelves and other features but has
an annual average temperature very close to the freezing
point of water. This means that a small increase in the
average annual temperature can mean more time during the
year when melting can occur. It becomes easier to see ice
features reducing or disappearing.
The vast majority
of Antarctica is so cold that even if the temperature was
to rise by the same amount as the Peninsula, there still
wouldn't be any melting going on at all. The average surface
temperature of continental Antarctica is about -37°C. It
is -5°C in the warmest places on the peninsula.
A warm day in much of Antarctica still gives a temperature
well below freezing, the result = nothing much to see.
A warm day in the Peninsula could take temperatures
above the freezing point at which the ice begins to melt.
The result = lots of melting and potential ice break up.
This is no reason to become unworried because part of
the reason that the Antarctic ice sheet is so cold is that
it's so high, due to the thickness of the ice. The melting
and flow of the glaciers removing ice from the continent
is also slowed down by the ice shelves around the continent's
Small rises in temperature that start to break
ice away a little faster at the edges could eventually speed
up the loss of ice and cause greater temperature rises to
take place further inland. Ice shelves seem to act as "corks"
in the Antarctic "ice-bottle". Remove the ice shelf and
a huge amount of ice from the interior could start to flow
towards the sea where it will melt even though the temperature
in the interior may be stable.
The problem with
trying to predict the future in these matters is that firstly
there is not enough data available to base predictions on.
Secondly, the way things work is not fully understood.
Most models from different researchers and teams tend
to agree however that there will be some small changes in
temperature over the next 50 years. It is also expected
that the rise in global temperature will put more moisture
into the atmosphere and more of this will reach Antarctica.
This will give a greater snowfall to balance the melting
ice. Despite all the snow and ice Antarctica is actually
classed as a desert as there is so little snow-fall. It's
just that what does fall - stays there.
3/ Are there any biological
effects of global warming
only two flowering plant species that grow only on the Peninsula
have spread significantly in the last few decades.
They are now more abundant
and they have spread to other parts of Antarctica. In some
areas they are becoming the dominant species.
Adelie penguins (Pygoscelis adeliae) have also been steadily
declining in parts of the Antarctic Peninsula region for
the last 20 years. Adelies are reducing in number and abandoning
certain nesting sites while Chinstrap penguins (Pygoscelis
antarctica) are taking their place. Adlies need pack
ice for most of the year and feed almost exclusively on
Krill, Chinstrap penguins will eat a wider variety of foods
and prefer open water. The sea ice has declined over the
last 20 years with the rise in temperature in the Peninsula
region. Gentoo penguins (Pygoscelis papua) have also started
to nest on the Peninsula in recent years, for the first
time in living memory ( and it needs to be noted that any
memory of Antarctica doesn't stretch much beyond a hundred
Studies of the bones and remains found in
abandoned colonies show that prior to 1950, no Gentoo penguins
nested in these sites at all.
Studies (November 2004) have shown that stocks of krill
in Antarctica have declined significantly in recent years.
The reason for this is likely to be a fall in the amount
of sea ice in the winter months particularly in the Antarctic
Krill numbers may have dropped
by as much as 80% since the 1970's - so today's stocks are
about one fifth of what they were only 30 years ago.
The decline in krill may be the reason why some penguin
species are also declining.
Dr Angus Atkinson from British
Antarctic Survey, says:
"This is the first time that we
have understood the full scale of this decline. Krill feed
on the algae found under the surface of the sea-ice, which
acts as a kind of 'nursery'.
Antarctic Peninsula, a key breeding ground for the
krill, is one of the places in the world where there has
been the greatest rise in temperatures due to global
warming. This region has warmed by 2.5°C
in the last 50 years (much more than the mean global rate),
with a striking consequential decrease in winter sea-ice
"We don't fully understand how the loss of
sea-ice here is connected to the warming, but we believe
that it could be behind the decline in krill."
This could also be a problem for
businesses. The Southern Ocean is a valuable fisheries resource.
Many of the fish species caught feed on krill. Thousands
of tourists are also attracted to Antarctica to enjoy the
spectacular wildlife, most of which feed on krill.
There has been previous speculation that krill stocks
might have decreased, based on smaller more localized surveys
over shorter time periods. This new finding comes from data
from nine countries working in Antarctica. They all got
together and evaluated their separate data covering 40 Antarctic
summers, in the period between 1926 and 2003. This is
the first time such a large-scale view of change across
the Southern Ocean has been seen.
There is another
animal that feeds on the same phytoplankton food as krill.
This is a jelly-like colonial animal called salp that drifts
in the ocean currents. Their numbers have increased in the
same time the krill numbers have decreased.
decline in krill will also make it more difficult for the
great baleen whales to return to pre-exploitation levels
following their significant decline in numbers during the
years from approximately 1925-1975. This was before whaling