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No. 98: Mar-Apr 1995

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Six Immense Armadas Of Icebergs Invaded The North Atlantic

"Observations of large and abrupt climate changes recorded in Greenland ice cores have spurred a search for clues to their cause. The search has revealed that at six times during the last glaciation, huge armadas of icebergs launched from Canada spread across the northern Atlantic Ocean, each triggering a climate response of global extent."

The foregoing abstract does not mention the interesting Heinrich layers that fostered the above scenario. In 1988, H. Heinrich published a paper describing a curious set of sedimentary layers found in cores drilled in the tops of the Dreizack seamounts in the eastern North Atlantic. Heinrich concluded that each of the six layers he found represented the melting of "six great armadas of icebergs." These icebergs carried debris picked up in Canada and, as they melted, deposited it on the seamounts and ocean floor. Each layer could be correlated with the major climate boundaries revealed by the Greenland ice cores.

Very fittingly, these iceberg incursions are now termed "Heinrich Events."

(Broecker, Wallace S.; "Massive Iceberg Discharges as Triggers for Global Climate Changes," Nature, 372:421, 1994.)

From Science Frontiers #98, MAR-APR 1995. � 1995-2000 William R. Corliss