Old cold: Climatologists in pursuit of 1 million-year-old ice in Antarctica
Climate scientists want to drill down to a layer of ice in Antarctica. It could give information about the past and future of Earth’s atmosphere. Recently, scientists met in Tasmania, an Australian island south of the main continent. They were at the International Partnerships in Ice Core Sciences conference, trying to figure out where to find the ice layer. It froze 1.5 million years ago, and captured tiny bubbles of air. Finding the layer would bring a sample of the ancient atmosphere through time to the present day.
Scientists drill out a tube of ice, called an ice core, from the ice sheet. An ice sheet is a mass of glacier ice. Also called continental glaciers, they cover most of Greenland and Antarctica. An ice core can be a couple of miles long. It provides a timeline of what the atmosphere was like over hundreds of thousands of years. There are already dozens of ice cores from Antarctica and Greenland.
Ice Captures How Temperature And Gas Relate
Together the cores show the relationship between carbon dioxide and temperature. Carbon dioxide is a gas produced when people and animals breathe out, or when certain fuels are burned. It is used by plants for energy. The ice cores also show that there are high levels of carbon dioxide in the atmosphere now.
Ice cores can provide samples up to about 800,000 years old. The samples are from several ice ages, times when a large part of the world was covered with ice. The samples show much about carbon dioxide and temperature, but the record stops at an important moment.
Data Needed To Explain Changes In Ice Ages
Scientists already know what temperatures were like on Earth going back millions of years. Air temperature leaves a mark in the stone and sand at the bottom of the ocean. It also leaves marks in ice and in tree rings, layers of wood produced during a single growing season.
When they examined those marks, scientists found that the cycle of ice ages sped up about 1 million years ago. At first, ice ages occurred every 100,000 years. Then, they started happening every 40,000 years. “The fact that we can’t fully explain why that change occurred tells us that we still don’t know all that we’d like to know about the climate system,” Tas van Ommen says. He works at the University of Tasmania.
800,000 Years Just Isn't Old Enough
Van Ommen says carbon dioxide could be the reason for the change. However, because the ice core record stops at 800,000 years, there is no way to tell. So, scientists are looking for something older. “We’re pretty sure that there exists ice that is 1 million years or older towards the bottom of the Antarctic ice sheet, but knowing exactly where is a big exercise,” says van Ommen.
Teams of scientists around the world have been studying the ice on Antarctica. They want to find a place where ice is likely to have sat undisturbed for a million years. Other teams have been flying planes with radar over Antarctica. They map the bottom of the ice. Teams have also been studying the past climates of Antarctica.
Meanwhile, Back At The Ice Sheet
Van Ommen says, “In the past year or two it’s become apparent there are three or four sites that are promising.” Each site is on a peak of ice that has remained high above land. He says it could take a few more years for the international group of scientists to start drilling.
Some teams are already drilling in Antarctica. The Polar Research Institute of China is one of them. Van Ommen says it is not certain that the Chinese project will find million-year-old ice, but that does not mean it has failed. Each ice core carries information, which adds to the knowledge that scientists have about the past. Small differences in things such as salt in the ice, for example, can show how windy it was many years ago. Scientists learn from this what the weather was like.
The information is helping another project, which is gathering as many ice cores as possible from the last 2,000 years. Scientists want to compare them to ice cores now, to see how humans are affecting the climate. They have about 100 ice cores from Antarctica, but most go back less than 100 years.