The ice was bored up by scientists and technicians from ten European countries, including Sweden, in a collaborative project that has been underway for eight years. Analyses of ice bore cores from inland ice shows how the temperature varied over the ages, but they also reveal how the concentration of gases and particles has varied in the atmosphere.
The first results of the analysis establish that the earth has undergone eight ice ages in the last 740,000 years, when the climate was much colder than it is today. These ice ages were interrupted by eight warmer interglacial periods. During the last 400,000 years, these warm periods have had a climate similar to that of today. Before that, the warm periods were cooler but lasted longer.
Scientists can now draw parallels with earlier climatic changes. Without the interference of humans, the warm period we are now experiencing, which has already been going on for 12,000 years, should continue at least another 15,000 years.
Carbon dioxide content never before as high as today
The next step is to analyze the air in the tiny air bubbles in the ice and see how the mixture of various gases in the atmosphere has varied. Preliminary analyses indicate that in the last 440,000 years the carbon dioxide content has never been as high as it is today. By enhancing our knowledge of what has driven the climate earlier, scientists will be in a better position to predict future climate changes.
The core sampling at Dome C is part of the European collaborative project EPICA (European Project for Ice Coring in Antarctica). The research team has lived for a couple of summer months each year at the remote boring site Dome C, more than a thousand kilometers (600 miles) from the closest research station, with temperatures dropping to 40o C. In December 2004 the coring will continue at Dome C, and the objective is to reach bedrock. A mere 100 meters remains to be drilled. If all goes well, the researchers will find ice that is more than 900,000 years old at the base of the inland ice.
Working in the Antarctic is challenging in many ways. Dome C (75 o 06’ S, 123 o 21’ E) is one of the least hospitable places on earth, with an annual mean temperature of -54o C. To reach Dome C, scientists travel thousands of kilometers over endless white expanses, where blizzards are a daily occurrence.
In this coring work, Sweden has been represented by scientists from the Department of Physical Geography and Quaternary Geology, Stockholm University, under the leadership of Associate Professor Margareta Hansson. The department is now busy analyzing the unique ice core. In Stockholm, the focus is on examining particles that were once part of the atmosphere. These particles affect the climate, and the particle content, like greenhouse gases, has varied with time.