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Signs of ancient sea ice

Fossils of certain marine algae suggest floating ice debuted in the Arctic at least 47.5 million years ago

1:09pm, July 15, 2009

Fossils of ice-dependent algae reveal that Arctic sea ice, which is today very much an endangered species, formed at least 47.5 million years ago, about 1.5 million years earlier than previously recognized.

Sediments on the bottom of the Arctic Ocean often contain pebbles and mineral grains carried to sea by icebergs or by ice that formed in shallow water along the coast. Previous analyses of such ice-rafted debris, such as physical studies of the shape and surface texture of those bits of rock, suggest that sea ice first graced the Arctic Ocean, at least seasonally, about 46 millio

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