Climate variations of Central Asia on orbital to millennial timescales

Abstract

The extent to which climate variability in Central Asia is causally linked to large-scale changes in the Asian monsoon on varying timescales remains a longstanding question. Here we present precisely dated high-resolution speleothem oxygen-carbon isotope and trace element records of Central Asia’s hydroclimate variability from Tonnel’naya cave, Uzbekistan, and Kesang cave, western China. On orbital timescales, the supra-regional climate variance, inferred from our oxygen isotope records, exhibits a precessional rhythm, punctuated by millennial-scale abrupt climate events, suggesting a close coupling with the Asian monsoon. However, the local hydroclimatic variability at both cave sites, inferred from carbon isotope and trace element records, shows climate variations that are distinctly different from their supra-regional modes. Particularly, hydroclimatic changes in both Tonnel’naya and Kesang areas during the Holocene lag behind the supra-regional climate variability by several thousand years. These observations may reconcile the apparent out-of-phase hydroclimatic variability, inferred from the Holocene lake proxy records, between Westerly Central Asia and Monsoon Asia.

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

“…First, the 15 U‐Th dates of stalagmite BLK12B are relatively dense and evenly distributed, while those of the Kesang and Ton cave records are sparse (five to six dates during the study period; Figure ). Second, the mean temporal resolution of the Baluk δ 18 O record (~22.8 years) is higher than those of Kesang (~34.4 years) and Ton (~37.0 years) caves (Cheng et al, , ). This relatively high temporal resolution is important for studying hydroclimatic changes on the centennial to multidecadal timescales.…”

“…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 ).…”

“…For instance, in the Baluk cave record there are substantial increases in δ 18 O centered at 8.2, 5.1, and 2.9 ka; however, a shift of similarly high amplitude is only evident in stalagmite KS06‐A‐H‐A from Kesang cave, which is centered at 2.9 ka (Cheng et al, ; Figure ). The mismatch of the record of abrupt events between stalagmites CNKS‐7 and CNKS‐9 records from Kesang cave is likely caused mainly by their large dating errors (Cai et al, ), whereas in the case of Ton cave it is likely due to the low stalagmite growth rate and hence the inherently low temporal resolution (Cheng et al, ). Third, stalagmite BLK12B is 125 mm long and clearly exhibits continuous growth cycles (Figure d), whereas the Holocene intervals of the stalagmites from Kesang and Ton caves are no more than ~50 mm.…”

“…The growth rate of stalagmite BLK12B ranges from 15.0 to 46.7 mm/kyr, with a mean of 22.9 mm/kyr. There are, however, substantial variations in growth rates in the Kesang and Ton cave stalagmites: from ~0.2 to ~6 mm/kyr (with a mean of 3.2 mm/kyr; Cheng et al, ), from 1.8 to 37.8 mm/kyr (with a mean of 18.3 mm/kyr; Cai et al, ), and from 1.2 to 10 mm/kyr (with a mean of 3.9 mm/kyr; Cheng et al, ). Thus, stalagmite BLK12B grew at a faster rate and has the potential to provide a higher‐resolution paleoclimatic record than the stalagmites from the other caves.…”

“…(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, ).…”