Early initiation of Arctic sea-ice...(f a million years later by the onset of ...)

The findings have potentially important implications for climate. Spring sea ice and summer cloud formation would have reduced oceanic heat loss to the atmosphere and increased the amount of solar radiation reflected back out into space. "A stable sea-ice regime also suggests the possibility of concomitant glacial ice," say the researchers, and indeed they find some evidence for the presence of small isolated glaciers at the time.

Furthermore, their data indicate that sea ice formed in the Arctic before it did in Antarctica. Atmospheric levels of the greenhouse gas carbon dioxide were declining in the middle Eocene, one of the reasons postulated in causing the Earth to cool. However, the new findings imply that the threshold for sea-ice formation was first crossed in the Arctic, which, say the authors, is "a hypothesis opposite to that modelled for glacial ice, whereby Antarctica is shown to glaciate much earlier (that is, at higher levels of carbon dioxide) than circum-Arctic continents."

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