The First Loess-Based Paleoclimatic Reconstruction over the Last Interglacial-Glacial Cycle in the Hunshandake Sandy Land

Objective Although extensive lakes and eolian sands within and surrounding the Hunshandake Sandy Land(HSL)are sensitive to paleoenvironmental variations in arid and semi-arid eastern Inner Mongolia(e.g.,Yang et al.,2013),these records are commonly confined to the last deglaciation,hampering a complete understanding of

Ice sheet expansion in the Cretaceous greenhouse world

Globally elevated temperatures during the Cretaceous extreme greenhouse climate interval were punctuated by the Valanginian cooling event,which was characterized by a positive carbon isotope excursion,global cooling,and a glacial event approximately at 135 Ma.Disentangling ocean temperature and continental ice volume trends enables us to better understand climate fluctuations over deep time.We investigated the ocean temperature-ice sheet dynamics of glaciation events that occurred in the Cretaceous greenhouse world.New clumped isotope andδ^(18) O data from sites in the Tethyan Ocean show that seawater temperatures decreased by 5-6°C,consistent with the development of glacial periods,and maximum ice volumes about half the size of present-day Antarctica.This cooling event provides a counter-example to other Mesozoic climate transitions driven by changes in atmospheric greenhouse gas contents.Our results emphasize the importance of quantitatively reconstructing continental ice volume,providing further support for exploring deep-time Earth climate dynamics.

Recent advances on reconstruction of climate and extreme events in China for the past 2000 years

China is distinguished by a prominent monsoonal climate in the east of the country, a continental arid climate in the northwest and a highland cold climate on the Qinghai-Tibet Plateau. Because of the long history of Chinese civilization, there are abundant and well-dated documentary records for climate variation over the whole of the country as well as many natural archives（e.g., tree-rings, ice cores, stalagmites, varved lake sediments and corals） that enable high-resolution paleoclimatic reconstruction. In this paper, we review recent advances in the reconstruction of climate and extreme events over the last 2000 years in China. In the last 10 years, many new reconstructions, based on multi-proxies with wide spatial coverage, have been published in China. These reconstructions enable us to understand the characteristics of climate change across the country as well as the uncertainties of regional reconstructions. Synthesized reconstructed temperature results show that warm intervals over the last 2000 years occurred in AD 1–200, AD 551–760, AD 951–1320, and after AD 1921, and also show that cold intervals were in AD 201–350, AD 441–530, AD 781–950, and AD 1321–1920. Extreme cold winters, seen between 1500 and 1900, were more frequent than those after 1950. The intensity of regional heat waves, in the context of recent global warming, may not in fact exceed natural climate variability seen over the last 2000 years. In the eastern monsoonal region of China, decadal, multi-decadal and centennial oscillations are seen in rainfall variability. While the ensemble mean for drought/flood spatial patterns across all cold periods shows a meridional distribution, there is a tri-pole pattern with respect to droughts south of 25°N, floods between 25° and 30°N, and droughts north of 30°N for all warm periods. Data show that extreme drought events were most frequent in the periods AD 301–400, AD 751–800, AD 1051–1150, AD 1501–1550, and AD 1601–1650, while extreme flood events were frequent in the periods AD 101–150, AD 251–300, AD 951–1000, AD 1701–1750, AD 1801–1850, and AD 1901–1950. Between AD 1551–1600, extreme droughts and flood events occurred frequently. In arid northwest China, climate was characterized by dry conditions in AD 1000–1350, wet conditions in AD 1500–1850, and has tended to be wet over recent decades. On the northeastern Qinghai-Tibet Plateau, centennial-scale oscillations in precipitation have occurred over the last 1000 years, interrupted by several multidecadal-scale severe drought events. Of these, the most severe were in the 1480 s and 1710 s. In southwest China, extreme droughts as severe as those seen in Sichuan and Chongqing in 2006 are known to have occurred during historical times.

Climatic significance of δD time series in tree rings from Tianmu Mountain

Based on cross-dating tree ring age from Tianmu Mountain, Zhejiang Province, theδD of each tree ring nitrocellulose was measured and then theδ D annual time series was established. Using meteorological data from Tianmu Mountain Observatory, the responds ofδ D of tree ring to climatic factors were analyzed. The results suggest that theδ D time series of the tree ring correlates well with climatic conditions, primarily with precipitation of the second half of each year, average annual air temperature and average annual maximum air temperature. The reconstructed maximum winter air temperature by theδ D of tree ring is in good correlation with local instrumental data. The low-frequency variations of reconstructed mean maximum air temperature of the winter in Tianmu Mountain corroborate with the temperature change in a large special scale. Tianmu Mountain is located in winter monsoon sensitive zone, thus the influence of winter temperature on tree growth is quite obvious. The results in this paper suggest thatδ D of tree ring is an effective proxy for winter temperature in non-limited regions.