Modern stalagmite oxygen isotopic composition and its implications of climatic change from a high-elevation cave in the eastern Qinghai-Tibet Plateau over the past 50 years

Abstract

An oxygen isotope record of a stalagmite from Huanglong Cave in the eastern Qinghai-TibetPlateau dated with 230 Th and 210 Pb methods provides variations of the Asian monsoon with an average resolution of 1 year over the past 50 years. This study shows that the δ 18 O of dripwater in the cave represents the annual mean δ 18 O of local meteoric precipitation and the stalagmites were deposited in isotopic equilibrium. A comparison of the stalagmite δ 18 O record with instrumentally meteorological data indicates that shifts of the δ 18 O are largely controlled by the amount effect of meteoric precipitation conveyed through the southwest monsoon (the Indian monsoon) and less affected by temperature. Therefore, the variations of δ 18 O record reflect the changes in monsoon precipitation on inter-annual time scales under the influence of the southwest monsoon. Like many other stalagmite δ 18 O records in the Asian monsoon regions, the δ 18 O record of the stalagmite from Huanglong Cave also reveals a gradually enriched trend during the past 50 years, i.e. relatively enriched in 18 O. This trend may indicate the decline of the Asian monsoon intensity which is consistent with the decrease of monsoon indices. The weakening of the modern Asian monsoon well matched with the temperature changes in stratosphere, which may illustrate that the weakening of the monsoon mainly results from the lowering of solar radiation. stalagmite, oxygen isotopic composition, Asian monsoon, high-resolution, Qinghai-Tibet PlateauStalagmite record has a much longer time span and reserves integrated information [1] , so it is a valuable supplement archive to records of ice core, loess, lake sediment and peat core, etc [2] . Furthermore, stalagmite is an ideal material for precise U-series dating and yields independent time scales [3] . Therefore, stalagmite has become a major data source for continent paleo-climate reconstruction. Among multi-proxy records in stalagmite including stable carbon/oxygen isotope, trace element and laminae, the stalagmite δ 18 O is the most widely used proxies at present [4] . There are multi-answers in explaining oxygen isotopic compositions of stalagmites from different regions because the shifts of the stalag-

Implications of stalagmite density for past climate change: An example from stalagmite growth during the last deglaciation from Wanxiang Cave, western Loess Plateau

“…High-resolution subsampling was conducted using the dental drill and graver [25]. First, two 10-mm parallel lines along the growth axis were drawn on the polished stalagmite section.…”

Asian summer monsoon precipitation recorded by stalagmite oxygen isotopic composition in the western Loess Plateau during AD1875–2003 and its linkage with ocean-atmosphere system

“…Many significant results have been obtained on the variation and strength of AM [7][8][9][10][11]13,14] and the relationship between the AM and solar insolation on glacial/interglacial, millennial and centennial timescales using stalagmites [7][8][9]11,[13][14][15][16] . In particular, it was recently found that the stalagmite oxygen isotopic composition (δ 18 O) of stalagmite calcite could record interannual variation of the AM [17] and some historical severe famine events in tropics and subtropics [18] that corresponded to a weakening of the AM. Moreover, that the monsoonal precipitation was strongly linked to ocean-atmosphere systems in the Pacific Ocean and the North Atlantic Ocean, e.g., PDO, El Niño/Southern Oscillation (ENSO) [15] and North Atlantic Oscillation [19] .…”

Changes in extreme wet events in Southwestern China in 1960–2011

“…However, the trends of extreme wet events among the stations over the SC are unremarkable in the 2000s compared with the other decades (Fig. 4), which can likewise be attributed to the weak southwest monsoon (Fleitmann et al, 2004;He et al, 2005;Yang et al, 2007). During the summer and winter monsoon period (Fig.…”

“…These changes are abnormal, and can be attributed to the weakening of the Asian monsoon circulation (Li et al, 2012) and climate change (Trenberth et al, 2003;Groisman et al, 2005). In addition, many studies have demonstrated that the strength of the southwest monsoon has gradually weakened for nearly half a century in China (Fleitmann et al, 2004;He et al, 2005;Yang et al, 2007), which can further explain the results.…”