Great Salt Lake (GSL), Utah, USA, is a large hypersaline lake, but during short-lived (~10 – 20 kyr) pluvials, it was an expansive freshwater lake. We update the age model of GLAD1-GSL00-4, a 120-m sediment core recovered by the Global Lakes Drilling (GLAD) project, with new U-series measurements, seeking to date evaporites representing the driest times in lake history and provide a new basal age of 236.3 ka (2σ uncertainty = 6.7 kyr) during the penultimate interglacial. We measure abundances of microbial membrane lipids (glycerol dialkyl glycerol tetraethers; GDGTs) to reconstruct salinity over the last two glacial cycles. High and variable salinity precludes use of GDGTs as a proxy for temperature. We detect freshening during the “Bonneville” and “Little Valley” deep lake phases, here dated to 30.3 – 16.1 ka (2σ = 1.0 – 1.4 kyr) and 140.4 – 134.6 ka (2σ = 5.5 – 5.7 kyr) respectively. The salinity rise following the last glacial termination pluvial agrees with water balance reconstructions from well-dated lacustrine carbonates. However, the evaporite (thenardite) deposition dates to 12.2 – 16.1 (2σ = 0.8 – 1.0 kyr), and contrasts with reports of Holocene deposition elsewhere in the basin. The same sequence of salinity increase and evaporite deposition (halite) occurs in the penultimate glacial termination. Despite four disparate halite dates spanning 90 – 160 ka, age model assignment of the preceding Little Valley freshening agrees with U-series dating of shoreline tufa, highlighting cyclical lake expansion/contraction followed by evaporite deposition during glacial terminations, consistent with regional pluvials.

Paleorecords of the Southeast Asian autumn monsoon indicate that global sea-level change drove abrupt shifts in rainfall, yet the magnitude of these changes remains unquantified. Using delta Ca-44 and Mg/Ca measurements from a speleothem from central Vietnam, we generate semi-quantitative rainfall records spanning 45-4 ka. When compared to modern rainfall, our results reveal a similar to 50-60 % reduction in rainfall during the Last Glacial Maximum (LGM), associated with the sea-level lowstand. While climate models and a data assimilation product (PMIP4-CMIP6, iTRACE, DAMP-21ka) also show LGM drying (annual model mean = 8.5 % drier), the coarse spatial resolution of the models does not resolve the north-south trending Truong Son Mountains, an orographic barrier that blocks summer rainfall from reaching central Vietnam and enhances autumn rainfall. This causes a causes a summer rainfall wet bias in the models leading to an underestimation of annual rainfall change. However, simulations of autumn rainfall show better agreement with speleothem proxies (autumn model mean = 29 % drier), demonstrating that the models broadly capture changes in autumn monsoon rainfall amount. These findings underscore the sensitivity of the Southeast Asian autumn monsoon to sea-level change and highlight the value of using speleothem delta Ca-44 and Mg/Ca to validate climate model simulations of rainfall amount.

Abstract Great Salt Lake (GSL), Utah, USA, is a large hypersaline lake, but during short‐lived (∼10–20 kyr) pluvials, it was an expansive freshwater lake. We update the age model of GLAD1‐GSL00‐4, a 120‐m sediment core recovered by the Global Lakes Drilling (GLAD) project, with new U‐series measurements dating evaporites representing the driest times in lake history and providing a new basal age of 236.3 ka (2 σ uncertainty = 6.7 kyr) during the penultimate interglacial. We measure microbial membrane lipid abundances, dialkyl glycerol diethers and glycerol dialkyl glycerol tetraethers (GDGT), to reconstruct salinity over the last two glacial cycles. High and variable salinity precludes use of GDGTs as a proxy for temperature. The freshwater, deep, expanded lake phases “Bonneville” and “Little Valley,” here dated to 30.3–16.1 ka (2 σ = 1.0–1.4 kyr) and 140.4–134.6 ka (2 σ = 5.5–5.7 kyr) respectively, occur during deglacial pluvials and briefly interrupt the hypersaline conditions which dominate the record. The salinity rise following the last pluvial agrees with water balance reconstructions from well‐dated lacustrine carbonates. However, evaporite (thenardite) deposition dated to 16.1–12.2 ka (2 σ = 0.8–1.0 kyr) contrasts with Holocene timing elsewhere in the basin. After the Little Valley highstand, a salinity increase culminates in halite precipitation. Despite four disparate halite dates spanning 90–160 ka, age model assignment agrees with U‐series dating of Little Valley shoreline tufa. This continuous salinity record provides context for lake expansion/contraction followed by evaporite deposition across two glacial terminations, consistent with regional pluvials.

Abstract Modern lake triple oxygen isotopes (17O-excess [Δ′17O], δ18O) can be used to distinguish flow-through from closed-basin systems and to quantitatively model precipitation composition and evaporative loss. Extending this framework to paleolake carbonates enables new hydrologic and climate reconstructions. For example, regional hydrologic models suggest that cold temperatures and reduced evaporation, not increased precipitation, sustained large Last Glacial Maximum (LGM) lakes. But this has not been tested with proxies sensitive to lake hydrology. We quantitatively assessed changing evaporation and temperature conditions at Pleistocene Lake Bonneville (Utah, USA), the LGM counterpart of the Great Salt Lake, using Δ′17O and clumped isotope (Δ47) analyses of modern lake water and lacustrine carbonates. We measured the Δʹ17O, δ18O, and Δ47 of 26–18 ka Lake Bonneville gastropods, tufa, and deep-lake carbonate. Δ47 values consistently indicate paleolake waters 6–12 °C below modern. Δ′17O–δ18O data place Lake Bonneville with modern flow-through lakes and clearly separate it from evaporative systems like the Great Salt Lake. Combined Δ′17O and Δ47 analyses robustly characterize paleolake hydrology and provide new proxy-based support for the lower-temperature, lower-evaporation hypothesis. We find via Δ′17O–based reconstruction of meteoric δ18O that LGM precipitation had higher Δ′17O values than modern. One explanation is that regional LGM moisture was sourced from higher latitudes, as a southward westerlies shift would drive ice-adjacent air masses toward the lake.

The cultural history of the Caribbean and Mesoamerica unfolded against a backdrop of climate variability, but despite scattered climate records from across the region, a coherent picture of its magnitude, frequency, and underlying drivers, especially in Cuba and the northern Caribbean, remains elusive. Here we present a 3400-year oxygen and carbon isotope record from a stalagmite (CL), collected in Garibaldi Cave, northern Cuba. This new record reveals multi-decadal to centennial hydroclimate variability that aligns with Atlantic Multidecadal Variability, the North Atlantic Oscillation, and Northern Hemisphere sea-surface temperature anomalies. A significant drying trend in delta 18O and delta 13C between -800 and 1700 CE culminates during the Little Ice Age (-1500-1650 CE), consistent with widespread aridity across the Caribbean. Comparison with Cuban, Mexican, and Central American speleothems and sediments indicates that the CL record captures recurrent dry intervals during the Maya Terminal Classic Period (-750-950 CE) and earlier Preclassic transitions, overlapping with droughts identified in high-resolution Yucatan precipitation records and suggesting broader northern Caribbean hydroclimate stress, while showing regional differences in timing and magnitude. These intervals of recurrent hydroclimate variability coincided with episodes of societal disruption in the Maya Lowlands and may have also affected populations in Cuba. Additionally, charcoal fragments directly beneath the stalagmite base provides evidence of prehistoric cave use, linking this climate archive to human activity. Our findings suggest that lateHolocene hydroclimate variability included periods of widespread drying across parts of the Caribbean, reflecting large-scale reorganizations of the tropical hydroclimate system. By integrating paleoclimate and cultural evidence, our results indicate that recurrent episodes of regional drying likely constituted a persistent environmental stressor for rainfall-dependent societies, highlighting climate-culture linkages across the Caribbean while acknowledging regionally variable responses.

We present the oldest speleothem isotope record from Central America and the Caribbean, a high-resolution stalagmite ("Katun") spanning discontinuously similar to 198-322 ka BP, that documents hydroclimate variability across glacial-interglacial and millennial timescales. Katun delta O-18 covaries significantly with atmospheric CO2 and CH4, and multivariate analyses show that CO2 + CH4 together explain more variance in delta O-18 than either gas alone. Consistent with a CO2-mediated SST mechanism, Katun delta O-18 correlates with tropical Atlantic and eastern Pacific SST reconstructions, indicating that radiative forcing influenced Caribbean precipitation primarily through tropical surface warming. At millennial scales, Katun delta O-18 tracks North Atlantic variability: it aligns with CH4 peaks associated with Greenland D-O cycles and with detrital proxies of Heinrich-type ice-rafting, implicating AMOC-paced ITCZ shifts and SST-driven convection as key controls. A weak Katun-Cariaco Mo relationship highlights proxy sensitivities and argues against ITCZ migration as the sole driver. In contrast to Asian monsoon archives, Katun shows little precessional insolation imprint, emphasizing the dominance of internal ocean-atmosphere dynamics (AMOC, SSTs) in regulating Caribbean hydroclimate and modulating tropical wetland methane emissions during MIS 7-9.

Understanding past climate trends is crucial for projecting future hydroclimate changes, especially in the context of rapid anthropogenic climate change. Here, we focus on reconstructing hydroclimate variability during periods of past climate change from the tropics , which remain underrepresented in climate variability studies despite their heightened vulnerability to ongoing climatic shifts. Here, we investigate ẟ18O, ẟ13C, and trace elements (Mg/Ca, Ba/Ca, Sr/Ca) in multiple speleothem samples across the Philippines. Speleothem sample, BH-1, was collected from Hinagdanan Cave (9.6253° N, 123.8009° E) and grew between 26-51 kyrs B.P. with an average growth rate of 8.12 μm/yr. Another speleothem sample PPUR-GP-3 collected from the Puerto Princesa Subterranean River National Park (10.1926° N, 118.9266° E) grew between 4-48 kyrs B.P. with a hiatus between 16,243 ± 146 years B.P. to 35,300 ± 538 years (±2𝜎). Collectively, speleothem growth encompasses critical periods of past climate change such as Heinrich Events 1 through 5, the Younger Dryas, and the last deglaciation. Modern climatology data and ongoing cave monitoring data suggests that Hinagdanan Cave and Princesa Subterranean River National Park recharges from summer precipitation. Initial geochemical findings indicate fluctuating trace element data suggesting drying trends over time, characterized by an increase in Mg/Ca and a decrease in Sr/Ca in PPUR-GP3. Change-point analysis conducted on the ẟ18O record in BH-1 reveals that Heinrich Event 3 in the Philippines experienced drying conditions. The drying is in alignment with ẟ18O trends reflected in Borneo stacked speleothem records. Further investigation of BH-1 and PPUR-GP3 trace elements and stable isotopes will disentangle regional (ẟ18O amount effect, moisture source) versus local (prior calcite precipitation) hydroclimate variability. Finally, we will compare our new geochemical results with existing isotope-enabled climate model simulations (iTRACE) to discern potential climate drivers that modulate IPWP hydroclimate during key climate events.

The growth and decay of the Laurentide ice sheet altered the hydrological cycle over southwestern North America. While it is well-documented that the last glacial was wetter and had isotopically lighter precipitation, much less information is available for prior glacials. Increased proxy coverage is needed to test climate models' ability to reconstruct these changes and to assess their predictive power for water availability in response to future climate change. Here, we present parallel precipitation isotope records spanning the last two glacial cycles from two large, proximal lakes in Utah, USA: Great Salt Lake and Bear Lake. We use plant wax n-alkane delta D as a proxy for precipitation delta D (delta Dprecip) and find coherent glacial-interglacial fluctuations in delta Dprecip, with a similar to 30 parts per thousand D-depletion during glacial maxima relative to interglacials. We find similar delta Dprecip values between the Holocene and Eemian, but at the lower-pCO2 MIS 7 interglacial, D-enrichment is only weakly recorded at Great Salt Lake and absent at higher elevation Bear Lake. Comparison to regional proxy archives finds large-scale coherence in regional hydroclimate change over the last two glacial cycles is best explained by thermodynamic processes, with increased rainout efficiency, isotopic fractionation, and snow in a colder atmosphere. Comparison of proxies to climate model experiments showed models considerably underestimate glacial lowering of precipitation isotopic values, but overestimate inland Rayleigh distillation. New and assembled proxy reconstructions provide greater temporal and spatial coverage as targets for model skill in capturing hydroclimate variations across the past two glacial cycles.

Mountain permafrost is a climatically sensitive but poorly constrained component of the terrestrial cryosphere. We use 108 U-Th dates from speleothems in two limestone caves in the Uinta Mountains of northern Utah, USA, to reconstruct a 600,000 year history of permafrost presence and absence in this alpine setting. Speleothem growth in both caves is confined almost entirely to discrete intervals that align with interglacial conditions of Marine Isotope Stages (MIS) 5e, 7e, 9e, 11c, and 13. In contrast, growth hiatuses correspond to glacial periods, when permafrost apparently inhibited infiltration of liquid water. Regional lapse rates indicate that cooling of similar to 3 degrees C to 5 degrees C relative to present would be sufficient to generate permafrost above the caves. The persistence of age clustering across multiple speleothems in two independent cave systems suggests that mountain permafrost repeatedly formed and degraded in concert with orbitally paced climate cycles. Comparison with nearby paleoclimate records confirms that these changes reflect regional-scale climate forcing. Our results provide rare empirical evidence for the extent of alpine permafrost over Quaternary timescales. As mountain permafrost degrades under modern warming, such records are essential for refining climate models, assessing geomorphic and hydrologic risks, and placing recent changes within the context of natural variability.

Marking the transition between the last glacial and Holocene, the last deglaciation featured rapid climate shifts including Heinrich event 1 and the Bolling-Allerod. This study presents the highest-resolution, continuous hydroclimate proxy records of this interval from the tropical Americas based on a precisely dated Cuban stalagmite. The records span 17.6-14.3 thousand years before present, revealing persistent interannual to multidecadal rainfall variability, attributed to El Nino-Southern Oscillation and Atlantic Multidecadal Variability. Broader centennial to millennial-scale trends are linked to major climate events. We observe peak aridity in western Cuba during Heinrich event 1.1 and 1.2 (similar to 16.2 and similar to 15.1 thousand years before present), with preceding dry periods within chronological uncertainty, suggesting synchronicity. Wetter conditions and increased growth rates follow during the Bolling-Allerod. Model-based rainfall estimates support these results. Our proxy data highlight the dynamic nature of tropical hydroclimate, demonstrating wet and dry conditions fluctuate across timescales, despite climate state.

The study of glacial to interglacial climate transitions is extremely important for understanding the full scale of climate variability from global to local scale. Unfortunately, there are large areas where multimillennial paleoclimate timeseries are unavailable. Southern Caucasus, is such a region as currently only a few continental climate time series extend beyond the short instrumental records. Importantly, temperature-related proxies are virtually absent here, thus impeding to evaluate how global-scale rapid climate instabilities propagate and impact this area. This work provides the first paleoclimate reconstruction from Georgia (Southern Caucasus) spanning approximately the last 13500 years. Four stalagmites named Zak-1, Zak-3, Zak-4 and Zak-6, measuring 46, 50, 55 and 102 cm respectively, were collected from the Zakariasklde Cave (42°10′ N; 43°20′ E). Dated by the U-Th method, Zak-1 was deposited between 3.1+0.04/-0.03 to 0.32+0.46/-0.44 ka (ka = kiloyears before 1950 AD); Zak-3 between 13.48+0.07/-0.08 to 10.11+0.05/-0.09 ka; Zak-4 between 12.01+0.08/-0.09 to 9.73+0.53/-0.61 ka; and Zak-6 between 8.77+0.07/-0.08 to 0.71+0.16/-0.13 ka, with a possible hiatus between 4.45+0.19/-1.49 and 3.27+1.35/- 0.34 ka. Timeseries of δ18O-δ13C from calcite show the main patterns of temperature variations during the last glacial-interglacial shift as well as throughout the Holocene, which mostly agree in pace and tempo with global records (i.e., Greenland ice and Atlantic/Mediterranean sediment cores). Then, δ18O-δ2H from speleothem fluid inclusions (FI) are preliminarily applied to quantitatively calculate temperatures. Conveniently, FI resulted well aligned with the modern meteoric water line in Georgia, thus indicating that isotopic fractionation occurred during the karst flow-path and calcite precipitation was negligible. FI-derived temperatures document the effects of climate warming in Southern Caucasus related to the last deglaciation, with a ca. 4.5ºC increase of average temperatures from ~12 to ~10 ka. Paleotemperatures during the Holocene instead presents a gradual decrease of around 2ºC from ~10 ka to ~3 ka. This potentially supports the existence of a Holocene thermal maximum during the Early Holocene, which is still a matter of debate. However, calculation uncertainties make this finding debatable. The interpretation of the record is refined by considering changes of rainfall (e.g., amount, provenance/source and seasonality) as well as soils (e.g., vegetation bioactivity). To comprehend the climate mechanisms of South Caucasus climate during rapid global instabilities, the Zak-timeseries is compared to the others from different climate regimes to advance the current characterization of regional climate shifts. Therefore, the results of this study certainly help to further investigate possible climatic teleconnections on a regional to global scale.

Modern Lake Chad has shrunk in area by around 90 % since the 1960s under the twin pressures of climate change and increasing water demand. During the early to mid Holocene, the Chad basin featured a megalake with an area approximately 100 times larger than its modern remnant. In the mid/late Holocene (approximately 5000 years ago), this megalake dried out leaving behind vast deposits of readily deflated fine-grained sediments that are suggested to contribute similar to 25 % of the annual total global atmospheric mineral dust load. Erosion has obliterated much of the evidence of earlier North African humid periods within the Lake Chad basin, limiting our understanding of the relationship between global/regional climatology, local hydrology and dust export. Here, we present new records of thorium-normalized flux estimates of mineral dust and its radiogenic isotope composition deposited at Ocean Drilling Program Site 662, situated downwind of Megalake Chad underneath the North African winter dust plume, in the equatorial Atlantic Ocean. Our records show that sediments of the Megalake Chad basin have a distinct neodymium isotopic signature that can be traced thousands of kilometers downwind from their source when the megalake basin was dry and dust-active, whereas the fingerprint of its input was strongly suppressed at times of high lake levels. Our results show that marine sedimentary archives can preserve uninterrupted proxy records of climate-driven hydrological change on the continents, in this case, a bellwether region of Africa that features the world's most active dust source, the Bodele Depression.

Across all future IPCC Shared Socioeconomic Pathways, the strength of the Atlantic Meridional Overturning Circulation (AMOC) is projected to decline. However, there is much less certainty about the impacts of AMOC decline further afield. Evidence from paleoclimate archives and simulations suggests eastern African monsoons weakened under periods of high meltwater forcing in the North Atlantic, particularly during the most recent deglaciation. To explore the dynamics of this high- to low-latitude teleconnection, we use a compilation of ~30 sea surface temperature (SST) records from the tropical Indian Ocean spanning the last 30 ka. The zonal Indian Ocean SST gradient calculated from this compilation shows a remarkable similarity with North Atlantic 231Pa/230Th records of AMOC strength, particularly during intervals of variable meltwater forcing such as the Younger Dryas, Bølling-Allerød, and Heinrich stadials. A weaker AMOC is associated with cooler western Indian Ocean and a warmer eastern Indian Ocean, suggesting a tight linkage between AMOC strength and zonal Indian Ocean variability. To better understand this teleconnection, we analyzed a meltwater single-forcing scenario from a transient simulation of the Last Glacial Maximum to present (TraCE, 22ka-0ka). Under simulated meltwater forcing events, the tropical zonal Indian Ocean SST gradient intensifies (i.e., relative cooling in the west and warming in the east), in agreement with SST paleorecords. This response stems from an intensification of the subtropical high over Southern Europe which drives northerly surface wind anomalies across Arabia and the Horn of Africa, with cooler Northern Hemisphere anomalies extending as far south as Madagascar. This cools the surface western Indian Ocean, particularly in the Arabian Sea, enhancing the Bjerknes feedback and strengthening the Walker circulation across the basin. This effect is strongest in austral summer (DJF) when the Somali Jet reverses and northerly winds advect cool northern air into the deep tropics. Anomalous northerly winds and western Indian Ocean cooling were also found to be common feature of eight hosing experiments under preindustrial boundary conditions from the North Atlantic Hosing Model Intercomparison Project (NAHosMIP). Overall, we hypothesize an atmospheric mechanism connecting the high-latitude North Atlantic and tropical Indian Ocean under meltwater forcing, with the western Indian Ocean playing an outsized role in steepening the zonal SST gradient across the basin which weakens monsoon systems in eastern Africa.

The Colombian Andes has a hydroclimate with multiple proposed drivers of interannual, sub-decadal and multidecadal variability, including the meridional movement of the Inter Tropical Convergence Zone, El Ni & ntilde;o Southern Oscillation (ENSO), and Pacific Decadal/Atlantic Multidecadal Oscillation. Globally, the late Holocene (3-4 k yrs B.P.) is of interest as multiple proxy studies suggest modern multidecadal rainfall variability developed during this period. Limited high-resolution proxy studies assess changes in rainfall during the late Holocene from the Tropical Andes. We present a record of stable isotopes (delta 18O and delta 13C) from two speleothems, C2A-1 and C8A, that grew during the late Holocene in the Eastern Cordillera of the Colombian Andes from Cueva de la F & aacute;brica. Hendy Tests on both stalagmites were consistent with isotopic equilibrium at the time of calcite deposition, suggesting delta 18O values reflect climate variability. Frequency analyses revealed statistically significant oscillations at the sub-decadal and multidecadal scale in the faster-growing portion of C2A-1. We isolated the sub-decadal delta 18O variability through a band-pass filter, calculated the amount of rainfall for C2A-1, and compared the distribution against modern (1979-2016 C.E.) rainfall. The unimodal distribution of band-pass filtered speleothem delta 18O data suggests a response to an internal mode of climate variability, such as ENSO. A regional speleothem proxy comparison over 3-4 k yrs B.P. suggest a bimodal expression of rainfall at the multidecadal timescale with drier central Amazonia and wetter coastal and high-Andes mean rainfall states. This complex regional picture of multidecadal hydroclimate is likely attributed to internal climate forcings between the Pacific and Atlantic Oceans.