Millennial minimum temperature variations in the Qilian Mountains, China: evidence from tree rings

Abstract

Abstract.A 1343-year tree-ring chronology was developed from Qilian junipers in the central Qilian Mountains of the northeastern Tibetan Plateau (TP), China. The climatic implications of this chronology were investigated using simple correlation, partial correlation and response function analyses. The chronology was significantly positively correlated with temperature variables prior to and during the growing season, especially with monthly minimum temperature. Minimum temperature anomalies from January to August since AD 670 were then reconstructed based on the treering chronology. The reconstruction explained 58 % of the variance in the instrumental temperature records during the calibration period and captured the variation patterns in minimum temperature at the annual to centennial timescales over the past millennium. The most recent 50 years were the warmest period, while 1690-1880 was the coldest period since AD 670. Comparisons with other temperature series from neighbouring regions and for the Northern Hemisphere as a whole supported the validity of our reconstruction and suggested that it provided a good regional representation of temperature change in the northeastern Tibetan Plateau. The results of wavelet analysis showed the occurrence of significant quasi-periodic patterns at a number of recurring periods (2-4, 40-50, and 90-170 years), which were consistent with those associated with El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO) and solar activity. The comparison between the reconstructed temperature and the index of tropical volcanic radiative forcing indicated that some cold events recorded by tree rings may be due to the impact of tropical volcanic eruptions.

The response of annual minimum temperature on the eastern central Tibetan Plateau to large volcanic eruptions over the period 1380–2014 CE

“…On the southeastern TP, the cold period from 1816 to 1822 may have also been related to the Tambora eruption (Liang et al, 2008). Other research in the northeastern TP has shown that cold years can be matched with known tropical volcanic events in 15 of 21 cases (Zhang et al, 2014). We compared the years of cooling we identified in this study with those identified by Zhang et al (2014) and found that the cooling years are either the same or within a year of each other.…”

“…Qilian juniper samples were taken from a natural woodland 35 km west of Ningmute town, Henan County, Qinghai Province, China (100.96 • E, 34.62 • N, 3806 m a.s.l.). This area is located in the sub-frigid zone and has a semi-humid climate (Zheng et al, 2013). According to climate data of the Henan meteorological station ; Table 1), mean annual temperature is 0.31 • and mean annual precipitation is 582 mm.…”

“…The reconstructed T min 87 was further compared with minimum temperature reconstructions from other regions of the TP, including HY (northeastern TP; Zhang et al, 2014), QML(ZHD) (central TP; He et al, 2014), HBL (eastern TP; Gou et al, 2007), YS (southern central TP; Liang et al, 2008), and LIT(TAN) (southeastern TP; Li and Li, 2017). As a result of differences in reconstruction factors, study regions, and methods of chronology establishment, there are some differences between the chronologies.…”

“…Comparison of our reconstructed T min 87 with other T min reconstructions from the TP for the period 1380-2014 CE. (a) HY, January-August T min on the northeastern TP (Zhang et al, 2014); (b) QML(ZHD), January-December T min on the central TP (He et al, 2014); (c) our study; (d) HBL, October-April T min on the eastern TP (Gou et al, 2007); (e) YS, June-August T min on the southern central TP (Liang et al, 2008); (f) LIT(TAN), April-March T min on the southeastern TP (Li and Li, 2017). Columns with slash marks indicate warm periods in our reconstruction; solid gray columns indicate cold periods.…”

“…Tree rings from the TP can potentially be used to study the regional response of climate to volcanic activities. Previous tree-ring-based studies have shown that some cold years are closely correlated with large volcanic events (Liang et al, 2008(Liang et al, , 2016Zhang et al, 2014). Li et al (2017a) quantitatively assessed the correlation between temperature changes on the southeastern TP and volcanic eruptions and showed that most of the years of extreme cold in the past 304 years occurred 1-2 years after major volcanic eruptions.…”