CLIMATOLOGY

Seesawing on Seesawing

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Science  24 Aug 2001:
Vol. 293, Issue 5534, pp. 1403
DOI: 10.1126/science.293.5534.1403b

During the last deglaciation, ocean warming was interrupted in both the Northern and Southern Hemispheres, although apparently not synchronously. The apparent delay of the northern cooling event with respect to that of the south, inferred first from ice cores, has been interpreted as evidence of a “bipolar seesaw” in ocean circulation patterns. Results from the Taylor Dome, Antarctic ice core [Steig et al., Science 282, 92 (1998)] showed that warming there seemed to be in phase with the warming shown in Greenland ice cores, and provided an exception to the concept of bipolar antiphasing widely accepted at the time.

Now, Jouzel et al. present results from the high-accumulation-rate Dome Concordia, Antarctic ice core that strengthen the suspicion that the concept of a bipolar seesaw may be too simple. Their results support the idea that the gradual warming that occurred between 18,000 and 14,000 years ago in the south preceded the more abrupt warming at about 15,000 years ago in the north, but also indicate that both hemispheres cooled concurrently after 14,000 years ago. This finding suggests that the transfer of heat between high northern and southern latitudes is not strictly a zero-sum game. — HJS

Geophys. Res. Lett. 28, 3199 (2001).

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