Late Holocene Asian summer monsoon variability reflected byδ¹⁸O in tree-rings from Tibetan junipers

Abstract

Recent warming in High Asia might have a strong impact on Asian summer monsoon variability with consequences for the hydrological cycle. Based on correlations between climate data, the tree‐ring δ18O of high‐elevation junipers is an indicator of August precipitation. Thus, our 800‐year long annually resolved oxygen isotope series reflects long‐term variations in summer monsoon activity on the southern Tibetan plateau. Summer precipitation was reduced during 13th–15th centuries and since the 19th century, whereas the Little Ice Age period (15th–19th century) was rather moist. The late 20th century was among the driest periods during the past 800 years, showing a tendency to slightly wetter conditions after AD 1990.

Variability of summer humidity during the past 800 years on the eastern Tibetan Plateau inferred from δ<sup>18</sup>O of tree-ring cellulose

“…Thus, the MWP is characterized by the highest humidity values within the past 800 years. Similar conditions were observed for inner Asia and the northern TP (Pederson et al, 2014;Yang et al, 2013) but were not corroborated for the central TP (Grießinger et al, 2011). The moderate oscillation of our humidity reconstruction during the LIA contrasts results of increasing and decreasing moisture trends at different parts of the TP (Grießinger et al, 2011;Shao et al, 2005;Yao et al, 2008).…”

“…Similar conditions were observed for inner Asia and the northern TP (Pederson et al, 2014;Yang et al, 2013) but were not corroborated for the central TP (Grießinger et al, 2011). The moderate oscillation of our humidity reconstruction during the LIA contrasts results of increasing and decreasing moisture trends at different parts of the TP (Grießinger et al, 2011;Shao et al, 2005;Yao et al, 2008). We identified extreme interannual humidity variations by calculating the third standard deviation of the first differences.…”

“…The period is characterized by the driest summer in AD 1943 (RH = 68.4 %). The remarkable moisture reduction since the end of the LIA has been validated for the southern and south-eastern part of the TP (Liu (Grießinger et al, 2011;Liu et al, 2013;Shi et al, 2012) and might be caused by uneven warming trends of the northern and equatorial Indian Ocean sea surface temperatures (Chung and Ramanathan, 2006). More humid periods were detected during AD 1193-1300, AD 1345-1390, AD 1455-1475, and AD 1740-1750, with the highest relative humidity in AD 1272 (RH = 83.5 %).…”

“…Recently published tree-ring δ 18 O chronologies from the TP show a common strong response to regional moisture changes. Grießinger et al, 2011 successfully reconstructed August precipitation over the past 800 years. They demonstrated reduced precipitation during the Medieval Warm Period (MWP), stronger rainfalls during the Little Ice Age (LIA), decreasing precipitation rates since the 1810s, and slightly wetter conditions since the 1990s.…”

Tree-ring derived millennial precipitation record for the south-central Tibetan Plateau and its possible driving mechanism

“…Many researchers have recently reconstructed the climate history for the area (Fang et al, 2010;Gou et al, 2007;Li et al, 2011Li et al, , 2012Liang et al, 2009;Yang et al, 2010aYang et al, , 2010bYang et al, , 2010cZhang et al, 2003Zhang et al, , 2011Zhu et al, 2008); however, very few studies have focused on the southern TP (Bräuning, 2001;Bräuning and Mantwill, 2004;Fan et al, 2008;Grießinger et al, 2011) because of its remote location. Therefore, an improved tree-ring data set with a dense spatial coverage and long time span is needed for the southern and south-central TP region.…”