Salt and dust help unravel past climate change
Tiny amounts of salt and dust trapped in the Antarctic ice sheet for the last 740,000 years shed new light on changes to the Earth’s climate.
The results, published this week in the journal Nature, come from the team who extracted a 3 km long ice core from Dome C, high on East Antarctica’s plateau – the oldest continuous climate record obtained from ice cores so far.
Since reporting in 2004 that the Earth experienced eight climate cycles (each consisting of an ice age and warm period) the team have been analysing the chemical impurities in the cores to unravel how different parts of Earth’s climate varied over the last 740,000 years. This work is vital for understanding future climate change.
By measuring the varying amount of salt in the cores the team can estimate how far the sea ice around Antarctica extended every time Antarctica got colder. The salt appears to come from brine expelled to the top of newly formed sea ice (frozen sea water). The white sea ice replaces the dark ocean, making the Earth reflect more sunlight.
Small dust particles are blown by the wind from surrounding continents. Many more of them are found in ice from cold times, and the team conclude that the nearest continent, southern South America, was much drier or windier. The extra dust may have provided nutrients to the ocean, helping microbes to take up CO2 from the atmosphere. From the different responses of salt and dust, the authors propose that each time the Earth warmed, emerging from an ice age, there was an order of events, with South America responding early, and sea ice extent responding late.
Lead author Dr Eric Wolff from British Antarctic Survey said,
“Our research shows that, throughout the last 740,000 years, every time cold conditions gave way to mild ones, similar changes occurred in the same sequence. We conclude that the Earth follows rules when climate changes and if we can understand those rules we can improve climate models and make better predictions for the future.“
The Dome C drilling is part of the ‘European Project for Ice Coring in Antarctica’ (EPICA). The team at Dome C endured summer temperatures as low as minus 40ºC at the remote drilling site over a thousand kilometres from the nearest research station. The consortium completed the drilling in December 2004 after penetrating 3260 m of ice.
Issued by the British Antarctic Survey on behalf of the EPICA chemistry consortium
The paper ‘Southern Ocean sea-ice extent, productivity and iron flux over the past eight glacial cycles’, is published in Nature on 23 March.
For more information, contact:
Eric Wolff +44 1223 221491, ewwo@bas.ac.uk, or British Antarctic Survey Press Office: Linda Capper – tel: (01223) 221448, mob: 07714 233744, email:
Becky Allen – tel: (01223) 221414, mob: 07736 921693, email: b.allen@bas.ac.uk
For more information in other countries of co-authors on the paper, contact:
Denmark : Jorgen Peder Steffensen : + 45 35 32 05 57, jps@gfy.ku.dk
France: Martine de Angelis: +33 (0)4 76 82 42 33, ange@lgge.obs.ujf-grenoble.fr
Germany: Hubertus Fischer: +49 471 48311174, hufischer@awi-bremerhaven.de
Italy: Roberto Udisti +39 055 4573252, udisti@unifi.it; Carlo Barbante +39 041 2348942, barbante@unive.it
Sweden: Margareta Hansson: +46 86747865, margareta.hansson@natgeo.su.se
Switzerland: Thomas Stocker: +41 31 631 44 64, stocker@climate.unibe.ch
NOTES TO EDITORS:
EPICA (European Ice Core Project in Antarctica) is a consortium of 10 European countries (Belgium, Denmark, France, Germany, Italy, Netherlands, Norway, Sweden, Switzerland, UK). EPICA is coordinated by the European Science Foundation (ESF), and funded by the participating countries and by the European Union.
The EPICA research team is using the unique climate record from ice cores to investigate the relationship between the chemistry of the atmosphere and climate changes over the past 800,000 years, especially the effects of carbon dioxide, methane and other components of the atmosphere. The results will be used to test and enhance computer models used to predict future climate. EPICA’s aim was to drill two ice cores to the base of the Antarctic ice sheet, one at Dome C, the other in Dronning Maud Land. Both drillings have now reached the base of the ice sheet, and further analyses are underway.
The ice cores are cylinders of ice 10 cm in diameter that are brought to the surface in lengths of about 3 metres at a time. Snowflakes collect particles from the atmosphere, and pockets of air become trapped between snow crystals as ice is formed. Analysis of the chemical composition and physical properties of the snow and the trapped air, including atmospheric gases such as CO2 and methane, shows how the Earth’s climate has changed over time.
The Antarctic fieldwork is challenging both scientifically and environmentally. Dome C (75° 06’S, 123° 21’E) is one of the most hostile places on the planet, and average annual temperatures are below –54 degrees Celsius. Researchers and their equipment have to be transported 1000 km from coastal stations.
British Antarctic Survey is a world leader in research into global issues in an Antarctic context. It is the UK’s national operator and is a component of the Natural Environment Research Council. It has an annual budget of around £40 million, runs nine research programmes and operates five research stations, two Royal Research Ships and five aircraft in and around Antarctica. More information about the work of the Survey can be found on our website: www.antarctica.ac.uk.