Delayed build-up of Arctic ice sheets during 400,000-year minima in insolation variability

• Published in: Nature (London) 2012-10, Vol.490 (7420), p.393-396
• Main Authors: Hao, Qingzhen, Wang, Luo, Oldfield, Frank, Peng, Shuzhen, Qin, Li, Song, Yang, Xu, Bing, Qiao, Yansong, Bloemendal, Jan, Guo, Zhengtang
• Format: Article
• Language: English
• Subjects: 704/106; 704/106/125; Archives & records; Arctic Regions; China; Climate change; Climate variability; Earth sciences; Earth, ocean, space; Edible Grain - anatomy & histology; Edible Grain - growth & development; Environmental aspects; Eolian dust; Exact sciences and technology; Global temperature changes; Global Warming - history; Global Warming - statistics & numerical data; Grain size; History, Ancient; Humanities and Social Sciences; Ice; Ice Cover; Ice sheets; Latitude; letter; Loess; Marine and continental quaternary; Monsoons; multidisciplinary; Oxygen - analysis; Oxygen - metabolism; Oxygen Isotopes; Particle Size; Polar environments; Proxies; Rain; Science; Seasons; Siberia; Snow accumulation; Summer; Sunlight; Surficial geology; Time series; Wind
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature11493

An East Asian winter monsoon proxy record using grain size variations in Chinese loess over the past 900,000 years shows that for up to 20,000 years after the interglacials at 400,000-year intervals, the weak monsoon winds maintain a mild, non-glacial climate at high northern latitudes. Expect 'non-glacial' Arctic climate to persist Qingzhen Hao and colleagues present a record of grain-size variations in the Chinese Loess Plateau — a proxy of variations in the strength of the East Asian winter monsoon — and show that relatively high insolation at 400,000-year intervals held off the inception of the subsequent ice age for about 20,000 years relative to other glacial inceptions. Mechanistically, the extension of warm conditions was probably linked to a weak Siberian high-pressure system associated with a delayed build up of northern ice and snow. The authors speculate that these observations imply that Arctic climate may remain in non-glacial mode for more than 40,000 years, even in the absence of anthropogenic greenhouse gases. Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial 1 may help to inform our understanding of future climate change. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic 18 O content represent an integrated signal of changes in ice volume in both polar regions 2 . However, variations in Northern Hemisphere ice sheets influence the Siberian High 3 (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)—as recorded in the aeolian dust deposits on the Chinese Loess Plateau—can serve as a useful proxy of Arctic climate variability before the ice-core record begins. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections representative of sequences across the whole of the Chinese Loess Plateau over the past 900,000 years. The results show that during periods of low eccentricity and precessional variability at approximately 400,000-year intervals, the grain-size-inferred intensity of the EAWM remains weak for up to 20,000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for both the 400,000-year interglacials, the weak EAWM winds maintain a mil