Explaining Rapid Climate Fluctuations

摘要

Dansgaard-Oeschger (DO) cycles-rapid warming events with durations of approximately 1000 years, followed by a more gradual return to cold conditions-are some of the most dramatic examples of rapid climate change that occurred in the North Atlantic region over the last glacial period. Although there has been no lack of suggestions about their possible origins, all of the causal mechanisms proposed thus far have run into difficulty explaining one part of the cycle or another. Petersen et al. step into the fray, suggesting that DO events resulted from a combination of the effects of sea ice and ice shelves-structures that help define the margins of ice sheets-to account for both the rapid and the slower parts of the cycle. Their model relies on the ability of thin sea ice to respond quickly to changing environmental conditions and on the more gradual behavior of thick ice shelves to cause cooling. Although more work needs to be done to support this model, it is consistent with existing proxy records, model results, and modern observations.