Holocene moisture changes in western China, Central Asia, inferred from stalagmites

Abstract

Central Asia lies at the convergence between the Mediterranean and Asian monsoon climates, and there is a complex interaction between the westerlies with the monsoon to form the climate of that region and its variability. The region is highly vulnerable to changes in rainfall, highlighting the need to understand the underlying controls. We present a stalagmite-based δ 18 O record from Kesang Cave in western China, using MC-ICP-MS U-series dating and stable isotope analysis. Stalagmite calcite δ 18 O largely documents changes in the δ 18 O of precipitation. δ 18 O in stalagmites was low during the early and middle Holocene (10.0-3.0 ka BP), and shifted to higher values between 3.0 and 2.0 ka BP. After 2.0 ka BP, δ 18 O fluctuates with distinct centennial-scale variations. Drawing from results of state-of-the-art atmospheric general circulation model simulations for the preindustrial period and 9 ka BP, we propose that changes in moisture source regions and the wetter climate both contributed to the isotopic depletion of precipitation during the early and middle Holocene. Multiple records from surrounding regions indicate a generally wetter climate during the early and mid-Holocene, supporting our © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ interpretation on the speleothem δ 18 O. Changes in precipitation seasonality do not appear to be a viable explanation for the observed changes, nor increased penetration of monsoonal moisture tothe study site. We speculate that the climatic regime shifted around 3.0-2.0 ka BP towards a drier climate, resulting in temperature having dominant control on precipitation δ 18 O. The demise of three settlements around 500AD at the margin of Tarim Basin coincided with a period of decreased precipitation and increased temperature that likely affected local water resources, underscoring the potential impact of climate on human habitation in this region.

Holocene Solar Activity Imprint on Centennial‐ to Multidecadal‐Scale Hydroclimatic Oscillations in Arid Central Asia

“…(b) Kesang cave (Cheng et al, ). (c) Kesang cave (Cai et al, ); the black and gray lines represent stalagmites CNKS‐9 and CNKS‐7, respectively. (d) Ton cave (Cheng et al, ); the gray and red lines represent stalagmites TON‐1 and TON‐2, respectively.…”

“…To verify the representativeness of the Baluk cave δ 18 O record for the study of centennial‐ to multidecadal‐scale hydroclimatic oscillations, we compared it with several other speleothem records from ACA: nearby Kesang cave in Xinjiang (Cai et al, ; Cheng et al, ) and Tonnel'naya (Ton) cave in Uzbekistan (Cheng et al, ). A similar long‐term trend of gradually increasing δ 18 O values is evident in all the records (Figure ).…”

“…(a) Location of Baluk cave (red star) in Northwest China, arid central Asia. Yellow dots indicate the localities of Kesang cave in Northwest China (Cai et al, ; Cheng et al, 2016, ) and Tonnel'naya (Ton) cave in Uzbekistan, central Asia (Cheng et al, ). Blue arrows show the vertically integrated moisture flux during April to July (1981–2010) based on National Centers for Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) reanalysis data (Kalnay et al, ).…”

Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes

“…It has been termed the “Holocene Turnover” (Paasche et al ., ) that subsequently resulted in the establishment of a new climatic regime or mode (Paasche and Bakke, ), or the “4.07 ka BP climatic anomaly” in southern Africa (Railsback et al, ). The event appears to be global in nature, occurring in proxy records across seven continents from North America and northern Europe, through the Mediterranean, Middle East (Weiss, , 2017a) and India (Berkelhammer et al ., ; Kathayat et al ., ) to China (Cai et al ., ; Zhang et al ., ) and Australia (Denniston et al ., ); and across Africa (Chase et al ., ; Ruan et al ., ), Andean–Patagonian South America (Schimpf et al ., ), and Antarctica (Peck et al ., ). In the North Atlantic and western Canada, the event is reflected in atmospheric and oceanic cooling (Gkinis et al ., ; Orme et al ., ; Zhang et al ., ) and so‐called “neoglaciation” with glacier readvances (Balascio et al ., ; Geirsdóttir et al ., ; Menounos et al ., ), while in the mid‐ and low latitudes across both hemispheres it is marked by aridification (Booth et al ., ; Wanner et al ., ).…”

Comparing proxy and model estimates of hydroclimate variability and change over the Common Era

“…In addition to whether speleothem δ 18 O records rainfall amount, source, or other large-scale processes, there are other challenges that arise when interpreting them (e.g., Cheng et al, 2012;Denniston et al, 2015;Cai et al, 2017). A recent paper by Hu et al (2017) pointed out several challenges that especially apply over the CE, including serial autocorrelation, the test multiplicity problem in connection with a climate field, and the presence of age uncertainties.…”