CHLOROFLUOROCARBON EVIDENCE FOR RECENT VENTILATION OF THE DEEP BERINGSEA

The pattern of the global thermohaline circulation of today's oceans i s controlled by deep-water formation at the northern and southern limi ts of the Atlantic. The apparent lack of deep-water formation in the N orth Pacific, on the other hand, suggests that this ocean plays only a minor role in the global circulation, but it is unclear whether this was also the case during periods of glaciation-there is conflicting ev idence in the sedimentary record for the existence of a deep-water sou rce in the North Pacific during the Last Glacial Maximum(1-4). Here we report the detection of anthropogenic chlorofluorocarbons in the bott om waters of the Aleutian basin in the eastern Bering Sea, which sugge sts that a small amount of bottom water has formed in this region duri ng the past 40 years. Although the small volumes of water involved are unlikely to play a significant role in determining present-day global circulation patterns, the results lend credence to the possibility th at this sea was an important source of deep water for the northwestern Pacific Ocean during the Last Glacial Maximum.