Part 1

Background Information

Locations

A map of the area will greatly help students to appreciate the location and scale of the places referred to.

The Antarctic Peninsula extends northwards towards the southern tip of South America. It reaches beyond the Antarctic Circle into sub-antarctic conditions. James Ross Island and the Larson Ice Shelf are part of the peninsular region. Antarctica proper lies mostly south of 70°S. It contains the Central or Trans-Antarctic Mountains and the Ronne and Ross Ice Shelves.

Types of ice cover

Antarctic ice exists in several different forms, and each behaves differently.

Glaciers, in mountainous regions, feed the huge ice sheet which covers virtually the whole continent of Antarctica.

This land-based ice moves slowly towards the sea and extends out over coastal waters as solid sheets or ice shelves. These generally float, but sometimes they are grounded on the sea bed in shallow areas.

Pack ice is frozen sea water which, in winter, forms a border around ice shelves or the coast itself. In summer it tends to break up into horizontal slabs called ice floes.

Evidence of climate change

The Larson Ice Shelf

The Larson Ice Shelf is cracking apart. Rifts (fault lines in the ice) run for 30km. An icy land almost the length of Britain is collapsing into the sea - the most dramatic sign yet, say scientists, of the power of climate change.

The temperature on the Antarctic Peninsula is rising at more than twice the average rate for the planet. The face of Antarctica is changing. Under the summer sun, melt-water forms lakes on the surface, which seep into crevices, melting or 'rotting' the ice.

In this fragile place, a degree's variation in temperature either way can make the difference over the years between an ice shelf and an ocean. This is the first-ever film of the rifts - until now they've been seen only in blurred images from satellites.

The Larson is the third largest of the massive floating ice shelves that surround Antarctica. In 1996, the entire northern section (Larson A) disintegrated. Weeks later, scientists saw an iceberg the size of Jamaica break off from the much larger central section (Larson B).

Circumnavigation of James Ross Island

These were uncharted waters. For at least 10,000 years the seas around James Ross Island at the north-eastern tip of the peninsula have been ice-bound. The first seal hunters crossed from the mainland on a permanent ice bridge 200m wide. When the Larson Shelf collapsed, the bridge disintegrated. James Ross Island emerged from the ice.

A Greenpeace team sailing on the icebreaker Arctic Sunrise to gather evidence of these changes completed the first circumnavigation of the island in 1996.

Disappearance of glaciers on James Ross Island

The glaciers on James Ross Island have disappeared. The bare rock is warming up. The white ice which once covered the island used to reflect sunlight back into space, but the brown rock now absorbs the heat and so accelerates the melting.

The glaciers 'feed' the ice shelf. This means that as the glaciers disappear the ice shelf is destroyed. The destruction of the ice shelf is thus a result of the increase in temperature.

Rainfall

Antarctica is getting much wetter. Research workers have basically changed the way they dress. For as long as anyone can remember they have had to protect themselves from snow and wind, but now their main concern is not to get wet. It rains a lot, as the film crew found during their interviewing and filming.

Causes of change

Global warming is an umbrella term for global rises in temperature.

Temperatures seem to have been rising since the nineteenth century, but awareness of the problem only emerged in the latter part of the twentieth century.

Rates of warming

Scientists can only make an educated guess about how long the ice will last, because they do not yet understand the complex feedback mechanisms between ice and climate.

The Antarctic Peninsula has warmed by 2.5°C over the past 50 years, compared with a global average rise of 1°C. The sea ice is retreating, and this is setting off a series of changes in the ecosysytem.

Factors

The greenhouse effect

The greenhouse effect is a major cause of global warming, and therefore a key factor in the destruction of the ice shelves. For several decades from 1945 onwards the ice shelf was receding at a rate of about 1km per year. But suddenly the rate has increased to 15km per year.

The carbon dioxide level in the atmosphere has increased by a third since the Industrial Revolution, and levels of several other important greenhouse gases have also increased. These gases allow high-frequency sunlight into the atmosphere without allowing it to escape back as infra-red; this causes an accumulation of heat in the atmosphere.

Theozone layer

Thinning of the the ozone layer, especially the creation of a hole in it over Antarctica, also contributes to global warming.

The destruction of the ozone layer by gases such as CFCs allows more ultraviolet solar radiation to penetrate the atmosphere - especially where the layer is very thin or non-existent. This raises temperatures, as well as increasing the risks of skin cancer for humans and major damage to creatures like plankton at the bottom of the food chain.