Hydroclimatic changes on multiple timescales since 7800 y BP in the winter precipitation–dominated Central Asia

Significance While numerous studies show a moistening trend in ECA over the Holocene, the hydroclimate changes in WCA have remained elusive. In this study, we used various stalagmite-based geochemical proxies from Kyrgyzstan to reconstruct a precise history of hydroclimatic changes from the winter precipitation–dominated WCA over the last 7,800 y. Our data unveil a prolonged drying trend in WCA, superimposed by a series of droughts and pluvials. We attribute divergent precipitation trends in WCA and ECA to disparate responses of winter and summer westerly jets to seasonal solar insolation. Our findings not only deepen our understanding of regional hydroclimate dynamics but also hold the potential to refine future climate change projections in this environmentally fragile region.


Figures and Tables
Figure S1.Annual mean temperature (~13 °C) and precipitation (~300 mm) in the area of Talisman Cave.The highest temperature occurs in July (25 °C), and lowest in January (-1.4°C) (data from meteorological station at Osh, 40 km east of Talisman Cave).Observed data from the Bishkek station (300 km northeast of Osh) show lower precipitation δ 18 O during winter and spring than that in summer and autumn.

Figure S2 .
Figure S2.Polished section of stalagmite F11 and F2.The total lengths of F11 and F2 are 20 and 15 cm, respectively.Red boxes mark the locations of XRD analyses.

Figure S4 .
Figure S4.Age-depth models of (A) F11 and (B) F2.Age models were established using 5000 Monte-Carlo simulations in the COPRA routine (ref.66).Gray lines represent the 95% confidence intervals and black lines represent the median ages, respectively.Error bars are 2σ error (red).Dash line in panel B denotes a hiatus of 114.5 mm from the top of the F2.

Figure S5 .
Figure S5.Comparisons of the (A) δ 18 O and (B) δ 13 C records between F11 (blue line) and F2 (purple line).Dots with error bars represent 230 Th dates of F11 and F2, respectively.Both the δ 18 O and δ 13 C records replicate well within the dating errors of the two stalagmites, indicating their deposition at or near isotopic equilibrium fractionation conditions (ref.21).

Figure S6 .
Figure S6."Hendy test" on four layers of F11, with Panel A for carbon isotopes, and panel B for oxygen isotopes (ref.20).

Figure S8 .
Figure S8.Summer (A) and winter (B) westerly jet differences between the late Holocene (LH) and early Holocene (EH) from the Community Earth System Model (CESM) simulation.The westerly jet variations are represented by the differences of 200 hPa wind field (m/s).Red vectors and shading denote the differences significant at the 95% confidence level (ref.51).

Figure S10 .
Figure S10.Comparisons of precipitation changes in WCA and climate changes in the North Atlantic since 7800 yr BP. (A) Detrended drought index record from WCA (this study); (B) hematite-stained grains record of Ice-Rafted Debris (IRD) in the North Atlantic (ref.57); (C) storminess activities in the North Atlantic recorded by detrended coarse sand (>125 μm) percentage (ref.58).The grey bars mark notable dry periods in WCA, which corresponded to increased storminess and IRD in the North Atlantic, suggesting northward shifts of the westerly jet.

Figure S11 .
Figure S11.Continuous transform wavelet spectra for the drought index record of F11 from WCA. Spectral power is shown by colors ranging from deep blue (weak) to yellow (strong).Irregular black curves represent 95% confidence time-frequency regions in which the spectral strength is above that expected for an AR(1) red noise signal (ref.S2).

Table S1 .
Locations of sites referred in Figure1

Table S3 .
The Pearson correlation matrix of the δ 18 O, δ 13 C, and Sr/Ca data of F11.Asterisks (*) mean significance at 99% confidence level (two-tailed, t-test; after accounting for autocorrelation).All records are linearly interpolated to 4-yr resolution age-depth scale where appropriate before analysis.

Table S4 .
Component Matrix of the Principal Component Analysis for the δ 18 O, δ 13 C, and Sr/Ca records of F11.All records are linearly interpolated to 4-yr resolution prior to analysis.