Lijuan Sha

Paleosol carbonate nodules may preserve environmental information despite later burial alteration, yet disentangling original signals from diagenetic overprints remains a central challenge. Here we apply paired clumped and triple oxygen isotope analyses (Δ₄₇–Δ’¹⁷O) to microsampled Eocene paleosol carbonates from the Gonjo Basin, southeastern Tibet. Intra-nodule TΔ₄₇ values of 9–58 °C define a spectrum of microscale thermal heterogeneity, spanning lower-temperature to more strongly burial-modified domains. In contrast, carbonate Δ’¹⁷O does not vary systematically with TΔ₄₇ (R² < 0.6), whereas reconstructed diagenetic-water compositions (δ¹⁸O_w and Δ’¹⁷O_w) covary with TΔ₄₇, suggesting progressive fluid–rock exchange during burial. Together with petrographic and geochemical observations, these data are most consistent with fluid-limited, rock-buffered recrystallization at low-water–rock ratios, with modeled solutions for most micritic domains falling at W/R < 0.05. Reconstructed Δ’¹⁷O_w values of diagenetic fluids range from −77 to −27 per meg, consistent with interaction with isotopically evolved meteoric waters and plausibly reflecting prior evaporative modification, although alternative fluid histories cannot be fully excluded. Rather than fully erasing environmental information, burial recrystallization in these carbonates appears to preserve a quantifiable record of fluid–rock interaction and hydroclimatic conditions. Our results show that paired Δ₄₇–Δ’¹⁷O approach can help distinguish lower-temperature domains from more strongly burial-modified domains and trace diagenetic fluid evolution in ancient terrestrial carbonates.

Orbital-scale variations in insolation are widely considered to drive tropical and monsoonal rainfall, with higher summer insolation linked to stronger precipitation. Here, we present a precisely dated speleothem record from Cuba that reconstructs Atlantic Warm Pool (AWP) hydroclimate over the past 129,000 years and challenges this paradigm. Instead, we identify a previously unrecognized link between AWP hydroclimate and the North Atlantic Subtropical High (NASH) operating on millennial to orbital timescales. During intervals of high summer insolation coupled with cooler tropical North Atlantic sea surface temperatures (SSTs), NASH strengthens and expands westward, reducing rainfall across the AWP. This SST-NASH coupling amplified precessional-scale hydroclimate variability between 130 and 60 ka, when insolation amplitude was nearly twice that of the 60- to 12-ka interval. Our data further show that particularly strong insolation peaks at 105 and 126 ka caused pronounced westward NASH expansion, triggering two extreme dry events, similar to the process observed during modern midsummer dry spells.

Speleothem multiproxy records are important for understanding the differences between the dynamic and thermodynamic aspects of the Asian summer monsoon. In this study, we simultaneously provide the seasonally resolved oxygen isotope (δ ¹⁸ O _s ) and trace element ratio (Mg/Ca, Sr/Ca, and Ba/Ca) records from an actively growing stalagmite from Zhangjia Cave, Sichuan Basin, southwestern China, covering the past ∼130 years. The overall increasing trend in δ ¹⁸ O _s indicates a weakening of Asian summer monsoon circulation over the last century, while the trace element ratios suggest a relatively stable precipitation trend. Notably, the correlation between δ ¹⁸ O _s and trace element ratios has experienced a significant transition since the acceleration of global warming from the 1970s. Our findings reinforce the notion that the forcing of greenhouse gases weakened monsoon dynamics (circulation) over the past century, whereas the monsoon thermodynamic (precipitation) was essentially unchanged, thus highlighting the different influences of the greenhouse gases on the monsoon dynamics and thermodynamics, respectively.

Tropical oceans are the main global water vapor and latent heat sources, but their responses to radiative forcing remain unclear. Here, we investigate oceanic moisture dynamics of the western tropical Pacific (WTP) over the past 210,000 years through an approach of planktonic foraminiferal triple oxygen isotope (Δ′ ¹⁷ O). The Δ′ ¹⁷ O record is dominated by the precession cycles (~23,000 years), with lower values reflecting higher humidity in concert with higher Northern Hemisphere summer insolation. Our empirical and modeling results, combined with other geological archives, suggest that the enhanced moisture convergence over the WTP largely intensifies changes in the meridional and zonal hydrological cycles, affecting rainfall patterns in East Asia and northern South America. We propose that the insolation-driven WTP moisture dynamics play a pivotal role in regulating tropical hydroclimate.

Precipitation δ¹⁸O has offered valuable insights into the evolution of the Asian monsoon. Recent researches focusing on precipitation Δ′¹⁷O has enhanced our understanding by offering new perspectives beyond those of δ¹⁸O, revealing insights into vapor sources and continental recycling. Nevertheless, there remains a lack of interannual triple oxygen isotope data, particularly in the Asian monsoon region. In this study, we analyzed the triple oxygen isotopes and hydrogen isotopes in monthly precipitation samples collected from Chongqing in Southwest China between 2019 and 2022 A.D. Seasonal variations in δD, δ¹⁸O, δ¹⁷O, and d‐excess values were observed, with lower values during the rainy season and higher values during the dry season, highlighting the impact of changes in moisture sources and local meteorological conditions on seasonal shifts in δD, δ¹⁸O, and δ¹⁷O. While, mean Δ′¹⁷O values were higher in rainy season and lower in dry season. Notably, during rainy season, there is a negative correlation between monthly Δ′¹⁷O values and the RH of the vapor source area, as well as a positive correlation with d‐excess. Recalculated Δ′¹⁷O values based on RH of oceanic moisture source, are higher than the measured values for this period, indicating the contribution of terrigenous moisture to precipitation in SW China. Precipitation Δ′¹⁷O values provide a more precise reflection of changes in moisture source, continental recycling, and evapotranspiration processes that drive water cycling compared Integrating modeling works in future will facilitate the use of precipitation Δ′¹⁷O values to quantify the impact of different moisture source on precipitation.

The Indo-Pacific, a vast biogeographic of Earth, is influenced by both the Indian and East Asian monsoons. Despite its geographical importance, this region has been less studied compared to East Asia and India. Here, we present speleothem records from southern Thailand that cover the last 1500 years, including a hiatus during the Little Ice Age, providing insights into the interactions among climate dynamics, human influences, and ecological responses to climate change. Notably, our records lack the characteristic cold and warm periods observed in other regions, such as the Dark Ages Cold Period and Medieval Warm Period, which may reflect the complexity of the tropical climate system or the region’s unique topography. The analysis reveals a link between ENSO multi-decadal variability and hydroclimate conditions in southern Thailand, as evidenced by speleothem δ¹⁸O. Furthermore, a comparison between speleothem δ¹³C and the Normalized Difference Vegetation Index (NDVI) indicates significant vegetation changes in the last three decades, corresponding with increased atmospheric CO₂ levels and expansion of agricultural land due to human activities during the Current Warm Period. Additionally, our study suggests that an abrupt increase in sea surface temperatures may enhance vegetation growth in the Indo-Pacific by influencing atmospheric circulation and increasing precipitation.

Characterization of moisture origins is crucial to understanding hydroclimatic processes. Nevertheless, documenting past atmospheric moisture contents and their sources remains challenging partially due to insufficient moisture-tracing proxies. Here, we present triple oxygen isotope compositions in 21 cave speleothems from monsoonal Asia to examine spatial moisture origin differences in eastern Asia over the past 300 years. Our data suggest an isotopic equilibrium fractionation during speleothem formation, and thus parent water ¹⁷O anomalies (Δ′¹⁷O) values reconstructed from speleothems preserve information on moisture origins and recycling across space. Notably, speleothem Δ′¹⁷O records exhibit a distinct geographical distribution, with low values in central-eastern and southern China, high values in northwestern and northern China, and relatively high values in the Yangtze River region. This spatial pattern underscores the diverse influence of different moisture sources regulated by regional hydrological circulation, and demonstrates the potential use of speleothem Δ′¹⁷O in reconstructing the moisture cycle at spatial scales.

Significant multi‐centennial climate oscillations have been documented in a number of well‐dated climate records across the Holocene epoch and left various imprints in human cultural history. In this study, we developed speleothem δ¹³C, δ¹⁸O, trace elements, and lamina thickness records from the Yunnan‐Guizhou Plateau (YGP). Our high‐resolution and precisely dated records show a significant ∼550‐yr cycle as the dominant pattern of regional temperature and vegetation variations between ∼5,870 and ∼3,670 years ago. The phase analyses of the 550‐yr cycles among our speleothem records, other Northern Hemisphere climate records, solar activity index, and Atlantic meridional overturning circulation (AMOC) variations suggest that this climate cycle has a large spatial extent, and may be causally linked to the AMOC changes through coupled oceanic‐atmospheric processes. Additionally, the first cold phase of the ∼550‐yr cycle in our records coincides with the major cultural development on the YGP at ∼5,500–5,000 years ago, suggesting a critical relationship between climate and prehistorical cultural changes in the region.

We present absolutely dated speleothem δ¹⁸O records spanning the past ∼1.5 kyr, which provide new evidence of the transmission of an anthropogenic signal to natural climatic archives in NW Africa. Combined with three other speleothem δ¹⁸O records from SW Morocco, the results indicate unprecedentedly dry conditions during the 20th century, which developed more rapidly than those during the Medieval Climate Anomaly (900–1350 CE), likely due to rising atmospheric CO₂ levels. The 20th century drying evident in the speleothem records is consistent with the “Hockey Stick” pattern of increasing temperatures due to global warming. We demonstrate that this rapid drying is linked to warmer sea surface temperatures (SSTs) over the Azores High region, and cooler local SSTs off the coast of NW Africa. These changes intensified the Canary Current Upwelling, which promoted increased biological productivity in the surface water and enhanced the coastal fishing industry in Morocco.