A 249 kyr stack of eight loess grain size records from northern China documenting millennial‐scale climate variability

Abstract

In order to construct a stacked climatic record of millennial-scale variability for northern China, grain size was measured for 12,330 samples from eight thick loess sections. Between section correlation of these grain size records shows that, although small depositional hiatuses may be present within a single section, most parts of the sections display continuous dust deposition. By correlating the eight records with the precisely dated Chinese stalagmite d 18 O record, a stacked 249 kyr-long grain size time series was constructed, termed the ''CHILOMOS'' record, which is the first high-resolution stack documenting millennialscale variability in northern China. This stack shows millennial-scale climatic events superimposed on a prominent cooling trend during the last and penultimate glaciations, consistent with the pattern of increasing global ice volume. However, this cooling trend is dampened in the stalagmite record and totally suppressed in the low-latitude ocean record. It follows that the Loess Plateau, far from the low-latitude ocean, is largely influenced by the northern high-latitude ice sheets, while the proximal stalagmites of southern China primarily document signals from the low-latitude ocean. Cross correlations of climatic records from high and low latitudes demonstrate that the millennial-scale abrupt changes originated in the northern polar area and were propagated into East Asia largely through the East Asian winter monsoon. The CHILO-MOS record also confirms that the driest and coldest interval of the last 249 kyr occurred in the late MIS 6, and that MIS 7d was extremely cold and dry, similar to the stadial conditions of MIS 6.

Warming-induced northwestward migration of the East Asian monsoon rain belt from the Last Glacial Maximum to the mid-Holocene

“…The radiocarbon ages of S 0 and L 1-1 overlap with or are slightly younger than the dates of HTM (∼11-5 ka) and LGM (∼26.5-19 ka), respectively. Because measured 14 C ages of soil organic matter are always younger than the true age of deposition, due to addition of younger organic matter through rootlet penetration, bioturbation, and percolation of soluble organic substances (32,35), our radiocarbon dates are compatible with the widely accepted assumption that the coarsest interval of L 1-1 represents the coldest interval of the LGM, whereas the finest interval of S 0 represents the warmest interval in the Holocene (22,24). At each site, the samples dated were selected from the finest-grained part of the Holocene soil (S 0 ) and the coarsest part of the LGM loess unit (L 1-1 ).…”

“…These results strongly support the idea that the Earth's thermal equator will move northward in a warmer world, and that the observed southward migration of the monsoon rain belt over the last few decades is transient and northern China will eventually become wet as global warming advances. studies (19,20,22,25) demonstrate that (i) L 1-1 was deposited in marine isotope stage (MIS) 2 (∼27-11 ka), which includes the LGM (∼26.5-19 ka) (26); (ii) S 0 was deposited in the early-midHolocene (∼11-3 ka), which includes the Holocene Thermal Maximum (HTM) (∼11-5 ka) (27); and (iii) L 1-2 was deposited in late MIS 3 (∼38-27 ka). To ensure that we used a complete cold-warm cycle for C 3 /C 4 vegetation reconstruction, almost all of the sections were sampled down to loess unit L 1-2 .…”

“…Loess unit L 1 , yellowish in color and massive in structure, was deposited during the last glacial period. L 1 can generally be divided into five subunits termed L 1-1 , L 1-2 , L 1-3 , L [1][2][3][4] , and L [1][2][3][4][5] (22,24). L 1-2 and L 1-4 are weakly developed soils, and the other subunits are typical loess horizons.…”

Eolian dust dispersal patterns since the last glacial period in eastern Central Asia: insights from a loess-paleosol sequence in the Ili Basin

“…Many studies have speculated that millennial-scale oscillations represent a teleconnection between the North Atlantic and East Asia (e.g., Porter and An, 1995;Yang and Ding, 2014), although the dynamics involved are poorly understood. Porter and An (1995) and Sun et al (2012) suggested, based on CLP loess physical characteristics, that a strong influence from the westerlies resulted in transport of the North Atlantic signal to East Asia.…”

“…Porter and An (1995) and Sun et al (2012) suggested, based on CLP loess physical characteristics, that a strong influence from the westerlies resulted in transport of the North Atlantic signal to East Asia. Conversely, Yang and Ding (2014) proposed that millennial-scale North Atlantic climate signals might have been transmitted to the Siberian High via the Barents and Kara Sea ice sheets, and were propagated eastwards to the CLP via the winter monsoon system. In the western CLP (Chen et al, 1997), for example, evidence of millennial-scale (likely Heinrich) events are preserved within the loess stratigraphy during phases of strong winter monsoon in China; however, not all of the strong winter monsoon events in China correlate with Heinrich events in the North Atlantic, so challenging the Yang and Ding (2014) hypothesis.…”