Editor's Summary
16 July 2009
All glacials are not alike
Several lines of evidence, including the varying extent of Northern Hemisphere ice sheets, point to fluctuating severity of glacial periods, despite the fact that ice cores extracted from the Antarctic ice sheet suggest that glacial conditions and the relationship between temperatures and atmospheric carbon dioxide concentrations have been constant for the past 800,000 years. A new 800,000-year record of sea surface temperature and ocean productivity, from an ocean sediment core obtained from the south-west Indian Ocean, reveals that during the coldest glacial periods, the subtropical front off the coast of South Africa migrated northwards, altering the strength of the Agulhas Current that carries heat and salt to the Atlantic meridional overturning circulation. This work suggests that the degree of northwards migration of the subtropical front can act to partially decouple global climate from atmospheric carbon dioxide concentrations.
News and Views: Climate change: Beyond the CO2 connection
At times in the past, mobile ocean fronts in the subtropics have exercised an influence on the magnitude of climate change by decoupling temperature from levels of carbon dioxide in the atmosphere.
Rainer Zahn
doi:10.1038/460335a
Letter: Migration of the subtropical front as a modulator of glacial climate
Edouard Bard & Rosalind E. M. Rickaby
doi:10.1038/nature08189
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