Antarctica Global Warming - Easy

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. For the latest news try here

I wrote 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.

The break-up 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 be identified". British Antarctic Survey

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 edge.

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.

Antarctica's 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.

Adélie penguins (Pygoscelis adeliae) have also been steadily declining in parts of the Antarctic Peninsula region for the last 20 years. Adélies are reducing in number and abandoning certain nesting sites while Chinstrap penguins (Pygoscelis antarctica) are taking their place. Adélies 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 years).

Studies of the bones and remains found in abandoned colonies show that prior to 1950, no Gentoo penguins nested in these sites at all.

Krill shortages

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 Peninsula region.

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'.

The 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 cover.

"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.

This 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 was stopped.

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