New climate data from old ice
In all cold periods of the last 740,000 years, the sea ice coverage around Antarctica was much more extensive than in interglacial periods. At the same time, the south of South America was significantly drier and windier than today, which led to a sharp increase in the amount of dust entering the Antarctic. This was shown by the investigation of aerosol particles in a three-kilometer-long ice core by a European team of scientists with the participation of the Alfred Wegener Institute for Polar and Marine Research.
For their studies, the scientists determined the concentrations of the smallest aerosol particles in the ice, which were produced far away on the ocean surface or on the continents and transported to Antarctica by the wind. The concentration of sea s alt aerosols, which are formed when seawater freezes, indicates a large-scale expansion of the sea ice cover around Antarctica in all cold periods.
Increased concentrations of small mineral dust particles during the cold periods indicate a drier climate in the adjacent continents, particularly South America. The dust transported by the wind into the Southern Ocean also provides increased nutrients for the plankton in the ocean. However, analyzes of ice core sulfate aerosol produced during algal blooms do not indicate increased biological production in the Southern Ocean.
The results put the previous understanding of how biology in the Southern Ocean could have reacted to climate change in a new light, says Hubertus Fischer, head of chemical investigations at the Alfred Wegener Institute. At least for the southern part of the Southern Ocean, ideas about an increase in biological productivity during ice ages have to be reconsidered.
In addition to the temperature profile already analyzed, this data is essential for understanding future climate development. Because a similar sequence of the same change processes has been observed whenever warm climate conditions have alternated with cold ones over the past 740,000 years, researchers led by Eric Wolff of the British Antarctic Survey conclude that the Earth follows rules as climate changes. If you understand these rules, you can improve climate models and thus forecasts for the future.
The EPICA project (European Project for Ice Coring in Antarctica) is carried out by a consortium of ten European countries (Belgium, Denmark, Germany, Great Britain, France, Italy, Netherlands, Norway, Sweden, Switzerland). EPICA is coordinated by the European Science Foundation (ESF) and funded by the participating countries and the European Union. The aim of EPICA was to drill two ice cores in the Antarctic ice cap that reach down to the bedrock. The Dome C team worked in temperatures as low as minus 40 degrees Celsius until drilling was completed in December 2004. Only the upper 3000 meters of the 3260 meters of ice core have been analyzed so far. Glaciologists estimate that the undisturbed climate history is stored in the even older ice up to an age of about 900,000 years. It is thus the longest continuous ice core archive ever recovered.
In addition to the Dome C well, an EPICA well was drilled at Kohnen Station in Dronning Maud Land and was successfully completed during the past 2005/06 field season. The chemical and physical investigations on the ice core obtained are in full swing. © Alfred Wegener Institute
The Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research (AWI) in Bremerhaven is part of the Helmholtz Association. It is dedicated to researching the polar regions and also takes a look at topics such as marine biology and climate change.