About 14,700 years ago (14.7 kyr BP), towards the end of the last ice age, the climate warmed dramatically and abruptly around the North Atlantic—by as much as the difference between full glacial and interglacial conditions—in no more than a decade or two. This is all the more remarkable because it occurred in the presence of massive ice sheets and continuation of the albedo forcing that presumably had been helping maintain glacial conditions up to that point. But it was not to last. Sometime just after 13 kyr BP this Bølling-Allerød warm period ended as climate first cooled, and then abruptly cooled, into the so-called Younger Dryas. As near-glacial conditions returned, glaciers advanced in Europe, and the forests that had established themselves in the preceding warm epoch died. The Younger Dryas ended with a second abrupt warming that occurred over only a decade or so and that shifted temperatures back to those of the Holocene and of today. The idea that the climate system goes through such abrupt shifts did not take the climate research community by storm but dribbled into acceptance in the 1980s and the early 1990s. Only when duplicate ice cores said the same thing and the evidence was found in multiple indicators within the ice—oxygen isotopes, dust concentrations, snow accumulation, and so on—and could be correlated with terrestrial and marine records did acceptance that abrupt climate change was a reality sink in. This gradual acceptance is telling. When Hays et al. (1976) showed just how well climate records from deep-sea cores could be matched to orbital cycles, it was deeply satisfying: the gradual waxing and waning of the great ice sheets could be explained by equally gradual changes in the distribution of delivery of solar radiation to the Earth's surface. Insolation over high northern latitudes was deemed to be particularly important, with reduction in summer leading to retention of winter snow and ice sheet growth. All that remained was to show exactly how the climate system accomplished the necessary links.
Challenges to Our Understanding of the General Circulation:
Published 2021 in The Global Circulation of the Atmosphere
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- Publication year
2021
- Venue
The Global Circulation of the Atmosphere
- Publication date
2021-09-14
- Fields of study
Geology, Environmental Science
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- External record
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Semantic Scholar
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