Initial studies of samples collected during China's 22nd Antarctic expedition show that a part of the continent was warmer than it is today, holding important clues to understanding global warming.
Six weeks after a 144-strong Chinese research team anchored at the port of Shanghai on March 28, team members are still unraveling what they collected during their 131-day scientific expedition in Antarctica.
This was China's 22nd Antarctic expedition, which left on November 18 last year on the icebreaker Xuelong (Snow Dragon).
One such item is the first lunar aerolite Chinese scientists discovered during the expedition.
Initial studies of other samples show that at least part of the Antarctica at one time was warmer than it is today. Some 3-5 million years ago, the coldest continent on earth might have nurtured some plants.
Samples of penguin and seal excrement as well as seal furs offer insights into the relationship between global climate change and wildlife in the area.
Meanwhile, some 30 scientists from the 22nd expedition are continuing research at the Zhongshan and Changcheng (Great Wall) stations, the two Chinese stations on Antarctica, during its long winter.
Ice sheet retreat
Having been to Antarctica twice, Yang Huigen, deputy director of the Shanghai-based Polar Research Institute of China, called the latest expedition the most significant and fruitful since China landed on the old continent in 1980.
The team went into the Grove Mountains, the inland area of Antarctica, for the fourth time in China's Antarctic exploration history and collected much scientific evidence.
Among the most exciting discoveries are glacial scratches on cliffs of some nunataks of Grove Mountains, which imply a large-scale relocation of icebergs in history.
Dr Fang Aimin, a scientist who is working on evidence of glacial evolution in this area, said the scratches stretched from southeast to northwest at a certain angle (ranging from 285 to 292 degrees), indicating the direction of the icebergs' shift.
"Also, they are 50 to 100 meters higher than ice-capped surfaces, suggesting there was a sudden increase in temperature in that area hundreds of thousand years ago," said Fang, an assistant researcher with the Beijing-based Institute of Geology and Geophysics at the Chinese Academy of Sciences.
One of his colleagues, Dr Huang Feixin, is now trying to define the exact time of formation of the scratches by analyzing the exposure age of engraved rocks.
Under the same cliffs where scratches were found, explorers also discovered several moraine banks containing Cenozoic sedimentary clasts, a significant evidence of the warm climate in this region.
Sedimentary rocks are formed from pre-existing rocks with pieces of once-living organisms. And they take shape from deposits that have been washed downstream under the effect of glacier, water and wind, layer after layer.
"The place where the sedimentary debris was uncovered is 400 kilometers away from today's ice edge, signifying a considerable iceberg retreat, about one-third of the ice, in ancient times," Fang added.
And in the same area, researchers spotted some frozen pools suggesting a process of ice melting over the years.
Since all the major discoveries were made in the same place, Fang believes they indicate the same climate change event. "The temperature at that time could be 10 to 15 degrees higher than today. But all these need further proof," he added.
As the continent with the oldest Cenozoic ice sheet, Antarctica has the longest record of climate changes on earth. Thus, its climate history is a significant index of global climate.
There are wide disputes among international scientists over the icecap formation of Antarctica and global warming today.
Some scientists hold to the belief that the icecap of Antarctica has remained stable since taking shape; some argue against it. "Our study has shown that there was once a big ice melting in that area, which vindicates the opinion of an unstable icecap," Fang explained.
Also, as a number of scientists have said that current global warming may simply be elementary climate change, in which human activities are not as much to blame as extreme environmentalists advocate, Fang said his study will also contribute to further investigation into global climate change.
"It is indisputable that our earth is getting feverish. But is it a natural phenomenon or is it going to get worse? If we know what happened in the past, we may be able to predict the future," Fang added.
Although it is not the first time that the expedition team has brought back sedimentary boulder samples, the new exploration outshines previous ones with respect to both the number of samples and their variety.
Among the 100-odd pieces of sedimentary rock samples, Fang's team has for the first time discovered records of ancient plants. "We ran pollen analyses on some of these samples and discovered the trace of some plants that lived 3 to 5 million years ago," he said.
Since the Grove Mountains has no signs of plants today, this finding shows that the area used to have an environment suited to wildlife.
Fang said further analyses of these samples, especially more data on their geochemical and mineral compositions and biological evidence, could "unveil the environment back then."
Chinese scientists were the first to put forward the idea of studying glacial movement from a perspective of ecological geology.
During the latest expedition, they continued this research and cooperated with their Australian peers in collecting excrement sediments of both penguins and seals around Zhongshan Station and Davis Station.
The samples were sent back to Professor Sun Liguang, a leading scientist in this area.
Sun, who is with the University of Science and Technology of China, discovered the relationship between Antarctic climate change and the changing number of penguins by analyzing their excrement, about eight years ago.
"We are trying to probe into the variation of penguins' diet through their excrement, hoping to establish a connection between climate change and the oceanic food chain," Sun said.
For instance, he added, the penguins feed on krill, a small shrimp-like crustacean that is plentiful in the southern oceans. "We know that if the weather gets colder, the ice shelf will rise, which will in return result in a drop in the krill population," the professor said.
Thus, evidence of a smaller intake of krill from the penguins' excrement, may be indicative of colder weather.
The team is also conducting a preliminary study into seal fur samples collected for the first time during the expedition. Scientists will examine the influence of heavy metals such as mercury and lead, on seals in the past 200 years through an isotopic element analysis.
Sun is also eager to fix the migratory pattern of penguins by collecting more information about their habitats as "it must have something to do with climate change."
Penguins, which stay close to ice, will relocate themselves to wherever icebergs stand, he explained.
Out of the 5,354 meteorites gathered from the 22nd expedition, one is especially precious as it comes from the moon.
Weighing just 0.8 grams, the lunar aerolite looks burnt black with some white exposures. "The white part is plagioclase, a kind of unique rock on the moon, " said Lin Yangting, one of China's most famed meteorite experts.
Spotted in the Grove Mountains, the lunar aerolite is among the 80-odd ones collected around the world and is probably the smallest.
But despite the size, it is no less important as "the country is planning a lunar exploration," said Lin, a scientist with the Institute of Geology and Geophysics.
He explained that like other lunar aerolites, this one will "surely also provide some important information about the moon."
"The more we know about where we are going, the better we can design our spaceship and research plan," Lin added.
The more than 80 lunar meteorites found so far represent 28 to 32 different locations on the moon, because some of them are actually scattered parts of the same meteorite. Previous lunar expeditions from the United States and the former Soviet Union focused on a small area, comprising just 5 to 8 percent of the moon's surface.
"In this sense, every discovery of lunar aerolite is significant," Lin said.
The treasure lies preserved in sub-zero temperatures at the Polar Research Institute of China, awaiting further study.
Lin revealed that the Meteorite Commission of China plans to select 600 meteorites from Antarctic collections for more research starting next month. "Our institute will work on the lunar aerolite," he said.
China has altogether gathered more than 10,000 meteorites from the Grove Mountains during four expeditions, ranking among the first three countries with most pieces of meteorites.
Apart from the lunar aerolite, scientists also found some meteorites that will help research into the origins of life and some big planets in the solar system.
Thanks to more data from the latest expedition, geologists are completing two detailed geological maps of the Pridz Bay area and the Grove Mountains, which will help promote future South Pole exploration, according to Hu Jianmin, also a scientist with the Institute of Geology and Geophysics.
Drawn to a scale of 1:500,000, the maps will be released to the world next September at an international Antarctic geology conference in the United States, both in Chinese and English.
Hu said the maps will highlight some first-hand geological discoveries by Chinese scientists and are the first of their kind in that area of the world.
(China Daily May 10, 2006)