The claim is audacious because the region today is synonymous with aridity. The Dasht-e Kavir, or Great Salt Desert, and the Dasht-e Lut rank among the most inhospitable landscapes on Earth. Yet the study assembles an unusually broad range of evidence, from Zoroastrian scripture and Sassanid administrative records to satellite-derived elevation models and sediment cores, to argue that this desert was once a shoreline. If confirmed by future fieldwork, PAMELA would join the ranks of the world’s great reconstructed pluvial lakes, such as Lake Bonneville in North America, Mega-Lake Chad in Africa, and the giant Altiplano lakes of South America.

The methodological heart of the study is a systematic sweep of more than 350 historical sources, including Islamic-era chronicles, geographical compendia, travel narratives, and Persian epic literature. Using qualitative analysis software, the team extracted environmental keywords such as lakes, navigation, coasts, and fish, then mapped each reference in time and space using dynastic periods, place names, and climatological metaphors as anchors. Ambiguous or anachronistic entries were deliberately excluded, a filtering step the authors say was essential to keep the reconstruction testable rather than speculative.

Those textual signals were then cross-checked against the landscape itself. The researchers used high-resolution digital elevation models from the ALOS PALSAR satellite, with a vertical accuracy of 12.5 meters, alongside multispectral Landsat-8 imagery acquired between 2013 and 2023. Paleo-shorelines were traced through slope-break detection along topographic transects, and the resulting features were validated in a geographic information system against historical attestations of boat transport, fish populations, and coastal settlements. Strikingly, the positions of ancient mill hills near the reconstructed shore correspond closely to what would have been ports and shallow coastlines.

The historical record itself is remarkably rich. Ancient Zoroastrian texts, including the Avesta and the Bundahishn, describe a vast, life-sustaining body of water called Vourukasha or Farakhkurt, located near the mythical Alborz range and regarded as the origin of all terrestrial waters. Scholars have long debated whether such descriptions were purely cosmological, but recent philological work identifies linguistic and geographic correspondences between these sacred accounts and the hypothesized boundaries of PAMELA along the southern flanks of the Alborz Mountains. The study suggests these texts may preserve echoes of a real geographic feature rather than pure myth.

Later sources become increasingly concrete. The medieval chronicle Tarikh-e-Qom reports that during the reign of the Arsacid king Goudarz, around 91 BCE, a sizable body of water extended between Rey and Saveh. A fifth-century account describes the Sassanid king Yazdgird II ordering the founding of three cities served by a port named Bargīn on the shores of Lake Saveh, roughly 66 kilometers from Yazd. Cities such as Meybod and Bideh, situated near the 1000-meter elevation contour, are interpreted as shoreline settlements. By the sixth century CE, the geographer Zakariya Qazvini reported in his Athar al-Bilad that the lake had dried up and turned into arable land, an event he placed around the birth of the Prophet Muhammad, circa 570 CE.

European explorers added their own observations. The Swedish geographer Sven Hedin, traveling through the Iranian deserts in the early twentieth century, documented pronounced paleo-shoreline features between the towns of Jandagh and Torud and recorded a striking detail: the city gate of Jandagh had been rebuilt using timber salvaged from a ship that had run aground nearby, implying that vessels had once navigated what locals called the Desert Sea. Other travelers and scholars reported lacustrine sediments east of Saveh, marine fossils on the Saveh Plain, and the ruins of abandoned port towns bearing names such as Barajin, Barjin, and Parchin. A Qajar-era official even recorded that the lake bed briefly refilled with water in 1886.

The study places these observations within the framework of Holocene climate variability. Global paleoclimate records identify a humid Early Holocene period and a Mid-Holocene Climatic Optimum, roughly between 11,700 and 5,500 years ago, when increased effective moisture promoted lake expansion across the arid belt of the Northern Hemisphere. The integrated analysis points to a high probability of sustained water in the PAMELA basin from around 10,000 BCE until the sixth century CE, with peak lake levels during the Early Holocene. Abrupt downturns, including the Younger Dryas, the 8.2-kiloyear cooling event, and the 4.2-kiloyear aridification, would have repeatedly stressed the lake and the communities dependent on it.

The final desiccation may have been part of a larger crisis. The lake’s disappearance around 570 CE coincides with the Late Antique Little Ice Age, a period between roughly 536 and 660 CE marked by volcanic forcing, reduced solar output, and documented famines across Eurasia, including a great famine in 570 CE. The authors caution that causality cannot be directly confirmed, but they note that the synchronicity between the lake’s regression and the memory preserved in Islamic historiography suggests the drying of Saveh Lake may have been one facet of a broader regional environmental breakdown. Geological studies add that tectonic activity and falling groundwater levels likely contributed alongside the climatic shift.

For the researchers, the scattered sediment records already documented from Iranian basins such as Jazmurian and Hamoun may in fact be fragments of a single, larger paleolacustrine puzzle. They argue that Iran occupies a critical climatic crossroads between the Mediterranean Westerlies and the Indian Summer Monsoon, making its closed basins sensitive recorders of moisture anomalies comparable to those that filled the Great Basin, the Sahara, and the Altiplano. The team calls for stratigraphic coring, radiometric dating, and high-resolution terrain modeling to deliver a definitive reconstruction. Until then, PAMELA remains a compelling hypothesis: the idea that the cradle of some of Iran’s oldest settlements, its sacred geography, and even its legends of ships crossing the desert was shaped by a lake that modern science is only now learning to see.

Subject of Research: Reconstruction of the Paleo Mega Lake of Rey, a vast Holocene paleolake in central Iran, using historical texts, satellite data, and paleoclimate records

Article Title: Historical background of Paleo Mega Lake of Rey

Article References: Historical background of Paleo Mega Lake of Rey. (n.d.). https://doi.org/10.5194/hgss-16-41-2025

Image Credits: AI Generated

DOI: 10.5194/hgss-16-41-2025

Keywords: paleolake, PAMELA, Iran, Holocene, paleoclimatology, Saveh Lake, Zoroastrian texts, remote sensing, geomorphology, Late Antique Little Ice Age, Rey, desert

The stakes of the project extend far beyond the lake itself. The Tibetan Plateau and its surrounding ranges, including the Hindu Kush, Karakoram, and Himalayas, store the largest volume of ice outside the polar regions, earning the region its nickname as an Asian Water Tower. Meltwater and precipitation feeding the Brahmaputra, Mekong, Yangtze, Yellow, Indus, and Ganges river systems supply freshwater to nearly two billion people downstream. Understanding how this water tower has responded to natural climate cycles in the past is therefore essential for predicting how it will behave under future warming, and Nam Co’s sediments offer a way to read that history directly.

The lake sits in a closed basin whose water balance is governed almost entirely by precipitation and evaporation, with smaller contributions from permafrost thaw, glacial meltwater, and groundwater. Its climate is modulated by the interplay of the Indian Summer Monsoon, the East Asian Monsoon, and the mid-latitude Westerly Jet, and one of NamCore’s central goals is to pin down the timing and magnitude of monsoon variability and its interaction with the Westerlies across multiple glacial-interglacial cycles. A long-standing scientific debate concerns whether precession, eccentricity, or obliquity dominates the orbital forcing of Asian monsoon strength, and a terrestrial record of this length from the plateau itself should help settle the question.

Getting the core was an operational feat. Drilling ran from 6 June to 17 July 2024 as ICDP Expedition 5073, using a barge positioned over the deepest part of the lake at a water depth of about 93 meters. In total, 1,415.45 meters were drilled and 1,175.99 meters cored across seven holes at a single site, with an overall sediment recovery of 80.8 percent. Site selection drew on roughly 1,500 kilometers of seismic profiles acquired during four Sino-German hydro-acoustic surveys between 2005 and 2016, which revealed several hundred meters of well-stratified sediment infill and helped the team steer clear of steep faults that slice through the basin.

The drilling itself proved harder than anticipated. Pre-site surveys had suggested predominantly fine-grained sediments, but the recovered sequence turned out to be interrupted by sand beds up to a meter thick that repeatedly collapsed into the borehole, demanding large volumes of bentonite- and polymer-conditioned drilling fluids and continuous use of rotary coring tools. The Hydraulic Piston Corer worked only in the upper 12 meters of soft mud; below that, only the Alien Coring Tool could advance through the increasingly consolidated sediments. The team abandoned plans for additional shallower sites along the original transect when seismic data hinted at even more extensive coarse-grained strata near shore, and instead concentrated all effort on the single deep site.

Initial analysis of core catcher material has already revealed a strikingly dynamic lake. The sediment sequence divides into five major lithological units built from four recurring lithologies: calcareous mud, non-calcareous mud, calcareous mud with ferric staining, and sand. The deepest unit, between 510.12 and 435.58 meters below the lake floor, shows highly consolidated silty to sandy calcareous mud with shear strengths exceeding 600 kilonewtons per square meter, carbonate contents peaking at 61 percent, and organic geochemical signals suggesting strong terrigenous input, possibly tied to a very low lake level in an early stage of the basin’s evolution.

Higher in the core, between roughly 321 and 242 meters depth, the sediments change character dramatically, with sand contents reaching up to 77 percent. The team interprets this as evidence of a significant environmental shift, potentially reflecting lower lake levels, increased glacier melt, or enhanced fluvial input, though the researchers caution that these partly competing explanations require a fuller dataset to resolve. Above this sandy interval, the record settles into alternating calcareous and non-calcareous muds, and in the uppermost unit carbonate content climbs steadily toward the top of the sequence, tracing the lake’s gradual chemical evolution toward its present slightly alkaline, saline, oligotrophic state.

The biological signals in the core are equally revealing, if unusual. Diatoms, the workhorse algae of most lake-based paleoclimate studies, are almost entirely absent, found only as fragments in 12 of 84 examined samples, likely because growing or preservation conditions were unsuitable. Ostracods, tiny bivalved crustaceans, step into the gap: six taxa were identified, including Leucocytherella sinensis and species of Leucocythere and Ilyocypris, with abundances swinging from complete absence to more than 1,000 valves per sample. Shifts in the ostracod assemblage, including a transition toward a fauna broadly comparable to the modern one in the upper section, appear to track changing environmental conditions, while intervals with a very poor record may indicate sedimentation in deep, cold, poorly oxygenated waters.

Organic geochemistry adds another layer of environmental detail. Analyses of n-alkanes, waxy molecules produced by plant cuticles and aquatic organisms, show systematic shifts in chain length through the core. The ratio favoring aquatic macrophyte input ranges from 0.10 to 0.73 and varies in ways that may reflect lake-level fluctuations and glacial-interglacial cycles, while the average chain length of long-chain n-alkanes, which tends to lengthen under drier conditions as plants synthesize longer waxes to conserve water, oscillates between 28.7 and 30.9. The terrestrial-to-aquatic ratio peaks above 30 in the lower part of the record, pointing to episodes of strong terrestrial input, possibly from lake shrinkage or intensified runoff.

The work has only begun. Samples collected during successive core-opening and sampling parties in Beijing will feed a chronology built from radiocarbon, cosmogenic beryllium-10, magnetostratigraphy, luminescence dating, and amino acid racemization, alongside biomarker, palynological, and sedimentary ancient DNA analyses. The project also targets the deep biosphere, probing how microbial communities in these mostly carbonate-rich sediments exploit tectonically derived fluids, and will use microfluidic laboratory experiments to mimic redox processes in the sediment’s pore spaces. Paleomagnetic U-channels, extracted down to about 12 meters before the sediments became too consolidated, will chart secular variation of Earth’s magnetic field. Together, these analyses promise to transform a frozen lake on the roof of the world into one of the most detailed terrestrial chronicles of climate change ever assembled, with direct implications for the billions of people who depend on the water it stores.

Subject of Research: A 510.2-meter lake sediment core from Nam Co, Tibet, recording monsoon variability, glacial-interglacial cycles, and high-altitude ecosystem evolution over the late Quaternary

Article Title: The ICDP Nam Co Drilling Project (NamCore), Tibet: a 510.2 m sedimentary record from the Third Pole

Article References: Adolph, M.-L., Wang, J., Zhu, L., Clarke, L. J., Henderson, A. C. G., Vogel, H., Daut, G., Frenzel, P., Ju, J., Kou, Q., Michaelis, D., Schmitz, O., Schwarz, A., Spiess, V., Ulfers, A., Zhaxi, C., Ariztegui, D., Barbolini, N., Bauersachs, T., … Haberzettl, T. (2026). The ICDP Nam Co Drilling Project (NamCore), Tibet: a 510.2 m sedimentary record from the Third Pole. Scientific Drilling, 35(1), 99-117. https://doi.org/10.5194/sd-35-99-2026

Image Credits: AI Generated

DOI: 10.5194/sd-35-99-2026

Keywords: NamCore, Tibetan Plateau, Nam Co, ICDP, scientific drilling, paleoclimatology, Indian Summer Monsoon, Westerlies, ostracods, n-alkanes, glacial-interglacial cycles, Third Pole

The research team, led by Laura Lipfert of the Institute of Geography and the Oeschger Centre for Climate Change Research at the University of Bern, together with Ralf Hand, Angela-Maria Burgdorf, Christian Pfister, Heinz Wanner and Stefan Brönnimann, set out to quantify a relationship that climate scientists have long suspected but rarely been able to test over long timescales. Most observational studies of the spring precipitation to summer heat link have been confined to the instrumental era, generally extending no further back than the mid-twentieth century. By combining documentary archives, a 600-year paleoclimate reanalysis and thousands of years of model simulations, the Bern group has now pushed the record back to 1421, and with documentary evidence alone, to the early 1300s.

The physical mechanism at the heart of the study is the land-atmosphere feedback. When spring rainfall is scarce, soils enter the summer with depleted moisture reserves. Evapotranspiration, the process by which plants and soil release water vapor that carries away latent heat, becomes restricted. Energy that would otherwise be consumed evaporating water instead directly heats the air, amplifying temperature anomalies. This feedback is most powerful in regions where evaporation is moisture-limited, meaning that water, not energy, is the constraining resource. Southern and southeastern Europe sit squarely in this regime, which is precisely where the new analysis finds the signal to be strongest.

The study’s centerpiece case study is the summer of 1473, arguably the most extreme heat event of the past six centuries in terms of duration and geographical extent. Documentary sources describe an almost unimaginable year: rivers from France to western Russia shrank to trickles that could be forded on horseback or on foot, wells dried up across the Po Valley, forests burned uncontrollably in Poland and Belarus, and trees shed their leaves as if it were midwinter. In Basel, not a drop of rain fell from late June to mid-September. The drought persisted into the following winter, and in 1474 and 1475 swarms of migratory locusts invaded Central Europe. The year belongs to what researchers have described as a European megadrought period spanning roughly 1400 to 1480.

The reanalysis maps of 1473 reveal the atmospheric machinery behind the disaster. The preceding spring showed a pronounced precipitation deficit over Central and Eastern Europe, accompanied by a distinct positive East Atlantic pattern in sea-level pressure, a signature found in 19 of 20 ensemble members. The summer itself featured a large anomaly in 500-hectopascal geopotential height centered over Germany, along with a jet stream over the Atlantic-European sector that was stronger, more zonal and shifted poleward. Crucially, when the team examined the full statistical record, these same circulation fingerprints, a positive East Atlantic pattern and increased atmospheric blocking over north-central Europe in spring, emerged as recurring precursors of hot summers, not quirks of one exceptional year.

To conduct the statistical analysis, the researchers used the ModE-RA paleo-reanalysis, a 20-member global gridded monthly reconstruction spanning 1421 to 2008 at a resolution of roughly 1.8 degrees. ModE-RA blends an ensemble of transient simulations from the ECHAM6 atmospheric general circulation model with natural proxies, documentary records and instrumental measurements through an offline data assimilation scheme. The team supplemented this with ModE-RAclim, a variant in which the model prior is time-invariant so that any variability stems purely from the assimilated observations, and with the raw model ensemble ModE-Sim, which supplied a staggering 11,760 simulated years for the analysis. Anomalies were computed against a moving 31-year climatology using LOESS locally weighted regression, allowing fair comparison across centuries that include both the Little Ice Age and the modern warming era.

The results were consistent across all three datasets. Grid-point correlations between January-to-May precipitation and June-to-August temperature were significantly negative in a band between roughly 36 and 48 degrees north, with the strongest signal over southeastern Europe and near-zero values in northern Europe, where abundant moisture means evaporation is not water-limited. Composite analysis, drawing on the full ensemble to isolate one-in-ten-year events, showed that hot summers are typically preceded by dry springs over southeastern Europe with deficits reaching 1.4 millimeters per day, and that dry springs are followed by summer warming approaching one degree Celsius centered over the same region. Notably, for the Mediterranean region, 23 percent of the hottest summers were also dry-spring years, the highest overlap of any region examined.

Perhaps the most important result concerns causation. A skeptic could argue that atmospheric circulation simply drives both the dry spring and the hot summer, making precipitation a bystander rather than an agent. To test this, the team ran a regression analysis for the northern Mediterranean land area, predicting summer temperature from monthly precipitation, six circulation indices including the North Atlantic Oscillation, the East Atlantic and Scandinavian patterns, and three jet stream indices, plus Atlantic sea-surface temperatures, the NINO3.4 index and volcanic aerosol loading. Even after accounting for circulation in winter, spring and summer, April and particularly May precipitation remained significant predictors. The moisture deficit itself, not merely the circulation that produced it, exerts a direct influence on summer heat. Dry springs were also followed by more frequent and intense summer heatwaves in the model simulations, defined as spells of at least three consecutive days exceeding the 90th percentile.

The documentary record adds rich texture to the statistics. Of 22 historically documented hot summers, 16 were preceded by dry springs, including 1304, when the Rhine could reportedly be crossed on horseback between Strasbourg and Basel and ripe grapes appeared in Alsace by early July, and 1540, the legendary year when Lake Constance fell so low that its lake floor became visible and annual precipitation on the Swiss Plateau reached only about a quarter of the twentieth-century average. Yet the record also contains instructive exceptions: 1590 and 2024 saw hot summers after wet or variable springs, and several dry springs, such as those of 1420, 1559 and 1686, were not followed by drought summers. The link is real but probabilistic, not deterministic.

The authors caution that their setup was not designed to measure seasonal forecast skill, and the weak grid-point correlations, around minus 0.2, underline that a dry spring raises the odds of a hot summer without guaranteeing one. Even so, the implications are sobering. Under EURO-CORDEX projections, summer precipitation is expected to decline across Europe south of about 50 degrees north, while southeastern Europe, the study’s identified hotspot of land-atmosphere coupling, faces its own shifting rainfall regime. As 2022 and 2026 have demonstrated, when a spring precipitation deficit covers the continent, summer heat arrives with a depleted water balance already in place, producing compound heat and drought events that stress agriculture, rivers and power grids simultaneously. Six hundred years of history suggest that the atmosphere remembers a dry April and May, and that the price is often paid in July and August.

Subject of Research: The historical relationship between spring precipitation deficits and summer heat extremes in Europe over the past 600 years

Article Title: Historical climate extremes in Europe and the connection between spring precipitation and summer heat

Article References: Lipfert, L., Hand, R., Burgdorf, A.-M., Pfister, C., Wanner, H., & Brönnimann, S. (2026). Historical climate extremes in Europe and the connection between spring precipitation and summer heat. Climate of the Past, 22(10), 1863-1879. https://doi.org/10.5194/cp-22-1863-2026

Image Credits: AI Generated

DOI: 10.5194/cp-22-1863-2026

Keywords: paleoclimatology, heatwaves, drought, soil moisture, land-atmosphere feedback, Europe, ModE-RA, East Atlantic pattern, atmospheric blocking, 1473 summer, Climate of the Past, compound extremes

Lead author Julia Cole, professor and chair of the University of Michigan Department of Earth and Environmental Sciences, emphasized that the comparison between past and present is strikingly unambiguous. According to Cole, there is no period in the reconstructed record where El Niños were as strong as they are today, and the strength of El Niño appears to change in parallel with the warming of global temperatures. The findings, she noted, demonstrate that the large El Niño events of the last 40 years are not normal within the context of the last thousand years. This conclusion carries significant weight because El Niño is one of the most influential sources of year-to-year climate variability on the planet, capable of reshaping weather patterns across entire continents and driving droughts, floods, wildfires, and disease outbreaks far from its tropical Pacific origins.

Understanding why the researchers turned to corals requires an appreciation of both the phenomenon itself and the remarkable natural recorders that grow in the waters surrounding the Galápagos. El Niño is a natural climate oscillation that, every few years, causes the tropical Pacific to become warmer than usual. Under normal conditions, trade winds blow steadily along the equator from east to west, pushing sun-warmed surface water from the coast of South America toward Australia and Indonesia. When these trade winds weaken, the warm water sloshes back eastward toward South America, setting an El Niño event in motion. The atmosphere responds in turn: strong rainfall shifts from the Indonesian region into the central Pacific, leaving the western Pacific in drought, which further weakens the trade winds and locks in El Niño conditions that can persist for one to two years.

Although these temperature and precipitation fluctuations originate in the tropical Pacific, their consequences ripple across the entire globe. Storm tracks over the United States shift southward, bringing more rain to the desert Southwest and less to the Pacific Northwest. Similar circulation changes around the world produce droughts and flooding that contribute to crop failure, wildfires, waterborne disease, and other crises affecting human health and well-being. The Galápagos Islands sit at a geographic sweet spot for recording these shifts, a location where El Niño exerts its largest influence. The archipelago is famous for its astounding biodiversity, a product of high nutrient availability and the mixing of cool and warm waters, and its corals grow in an environment that faithfully registers every swing of the eastern Pacific climate system.

To reconstruct the history of El Niño intensity, Cole and her colleagues sampled cores from 13 corals, drawing on both living colonies and boulders of ancient coral collected from the Galápagos. Corals grow by secreting layers of calcium carbonate at a rate of roughly one to two centimeters per year, and the chemistry of each layer preserves a record of the seawater temperature in which the coral grew. Because El Niño extremes occur every few years, the team focused on core samples spanning at least 20 years, ensuring that each record captured multiple events. Sampling the cores a millimeter at a time, the researchers measured two independent aspects of the skeleton’s chemistry, building a robust proxy archive of past ocean conditions.

The first measurement targeted the ratio of strontium to calcium in the coral skeleton, a geochemical parameter that depends directly on the temperature at which the coral formed its skeleton. The team supplemented these results with an analysis of oxygen isotope ratios, which at this particular site also serve as a reliable measure of temperature. Together, these two proxies yielded a detailed history of temperature variability in the Galápagos region. The pattern that emerged was remarkably consistent: strong El Niños appeared throughout the last 40 to 50 years, whereas the El Niños recorded prior to that period displayed a steady pattern of lower intensity. Cole described the experience of adding record after record and expecting the story to grow more complicated, only to find that it did not—the signal was that clear.

A critical next step was to rule out the possibility that natural processes alone could have produced a strengthening of this magnitude. The researchers turned to climate models that simulate the last thousand years using reconstructions of volcanic eruptions and solar variability, the two dominant natural forcings of pre-industrial climate. When the models were run with these natural drivers, they produced no large shifts in El Niño behavior that could account for the magnitude of change documented in the coral records. This absence of a natural explanation, combined with the timing of the intensification after about 1850, points toward human-driven global warming as the most plausible cause of the observed strengthening, a conclusion consistent with the finding that El Niño intensity tracks rising global temperatures.

The timing of the study’s release gives its conclusions particular urgency. As a powerful El Niño develops atop an already warmed climate system, Cole noted that the relevant question is not whether the event will happen but how severe it will become and how damaging its impacts will be. Because the event is superimposed on global warming, it is likely to supercharge the temperature increase that would normally be expected from greenhouse gases alone. Forecasts cited in connection with the study suggest global temperatures could reach as much as 1.7 or 1.8 degrees Celsius above pre-industrial levels during this period, which would be considerably higher than the current record. The research was supported by the U.S. National Science Foundation and the United Kingdom Natural Environmental Research Council, with additional support from the Galápagos National Park and the Charles Darwin Research Station.

The implications extend well beyond the immediate forecast. El Niño is a major source of climate extremes, and if the phenomenon is intensifying, then its impacts intensify with it: droughts, floods, wildfire, and food insecurity. Changes in the hydrologic cycle also translate into damage to infrastructure, including floods that destroy homes, highways, and railroads, as well as public health consequences such as outbreaks of diseases like cholera. Cole and her colleagues argue that global warming is supercharging El Niño, and if that is correct, stronger climate extremes should be expected to amplify ecological, infrastructural, and human losses. No country, she cautioned, has the resources to be fully protected from these impacts, a reality that makes the strengthening of El Niño a global concern rather than a regional one.

For the research team, the ultimate takeaway is a call for mitigation. The coral archives of the Galápagos have delivered one of the clearest long-term pictures yet of how a major climate oscillation is responding to human influence, and the message is that the recent strengthening of El Niño represents one more reason to move away from fossil fuels, which the researchers identify as the root cause of the problem. The study’s co-authors include University of Michigan researchers Kelsey Dyez, Cameron Tripp, Jonathan Overpeck, and alumnus Jake Okun; University of Arizona researchers Diane Thompson and Marcus Lofverstrom; Samantha Stevenson-Karl of the University of California, Santa Barbara; Sandy Tudhope of the University of Edinburgh; Allison Lawman of Colorado College; Jessica Conroy of the University of Illinois; Gloria Jimenez of Moody’s Risk Management Services; and R. Lawrence Edwards of the University of Minnesota. Together, their work transforms a string of tropical islands into a millennium-scale warning system, one that indicates the powerful El Niños of recent decades stand alone in a thousand years of climate history.

Subject of Research: Unprecedented strengthening of El Niño events over the last four decades reconstructed from Galápagos coral paleoclimate records

Article Title: El Niños more intense over last 40 years than previous 1,000, according to U-M study

Article References: El Niños more intense over last 40 years than previous 1,000, according to U-M study. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: El Niño, ENSO, coral proxies, paleoclimatology, Galápagos Islands, climate change, global warming, tropical Pacific, strontium-to-calcium ratio, oxygen isotopes, climate models, University of Michigan

The research, led by scientists at the USC Dornsife College of Letters, Arts and Sciences and published in the journal Paleoceanography and Paleoclimatology, reconstructs nearly 240,000 years of lake history from a sediment core drilled from the lakebed. The team found that the enormous lakes of the past were brief departures from the basin’s usual hypersaline state, an extremely salty condition that has dominated the record for the vast majority of the time. Both giant lakes appear to have followed the same pattern: as the regional climate warmed and dried, the water receded, salinity climbed and salt deposits formed on the lakebed. The scientists note that the timing of the older of the two transitions is less precise than the younger one, but the overall trajectory of shrinkage and salinification is consistent across both events.

Corresponding author Rachel So, a recent PhD graduate in Earth sciences at USC Dornsife, compares the long-term record to watching a puddle that remains nearly the same size for an hour, briefly swells into a pond and then shrinks again. Scaled up to the size of the present Great Salt Lake, she explains, that is essentially what the basin looked like across nearly a quarter of a million years. For most of the past 240,000 years the lake stayed roughly the same size, but on two separate occasions it briefly grew to ten times its modern extent. The comparison captures the central finding of the study: the freshwater phases that produced the region’s most spectacular lakes were geologically fleeting interruptions in an otherwise salty story.

Scientists have long known that Lake Bonneville once covered much of western Utah during the last ice age, and its ancient shorelines remain etched into the landscape today, visible as terraces on hillsides far above the modern waterline. But those shorelines provide snapshots rather than a continuous account of how the lake’s size and salinity changed through time. To build a continuous record, the researchers turned to a nearly 400-foot sediment core drilled from the bed of Great Salt Lake in 2000. Its layered sediments preserve an archive stretching back about 236,000 years, spanning multiple glacial cycles and capturing both of the great freshwater episodes in a single, uninterrupted sequence.

The team dated the sediment layers by measuring radioactive decay in minerals, a technique that functions as a kind of geological clock and anchors the record in time. They also analyzed molecules left behind by microorganisms that once lived in the lake. Because the relative abundance of those molecules changes with salinity, their signatures allowed the researchers to broadly gauge whether the water at any given moment was fresh, brackish or extremely salty. Together, the dating and the biomarker analysis turned the core into a chronicle of the lake’s alternating states, revealing two major interruptions in its long hypersaline history.

The first and most recent interruption came between roughly 30,000 and 16,000 years ago, when the lake expanded into Lake Bonneville. The second, an earlier deep lake known from the Little Valley interval, existed roughly 140,000 to 135,000 years ago. Shoreline evidence suggests both lakes approached 1,000 feet in depth, but they were not identical twins. The Little Valley lake may have remained somewhat brackish rather than truly fresh, and it lasted less than half as long as Lake Bonneville. The most recent freshwater phase was therefore both longer and fresher than its older counterpart, a difference that offers clues about how variable the region’s wet episodes can be.

Senior author Sarah Feakins, professor of Earth sciences at USC Dornsife, emphasizes that the core’s span of two and a half glacial cycles is what makes the comparison possible. Because the record captures two complete fresh-to-salty transitions, the researchers can compare the two freshwater events directly, evaluating their durations and their degrees of freshness, and seeing how fragile and fleeting those moments were in the basin’s history. The record also aligns with evidence from elsewhere in the American West: various records from Nevada, California and Arizona show similar wet-to-dry shifts during the same periods, suggesting that Great Salt Lake was responding to climate changes felt across the entire region rather than to purely local conditions.

The mechanism behind the lake’s dramatic swings comes down to a balance between water arriving and water leaving. Feakins explains that during the cooler periods, lower temperatures slowed evaporation while more frequent storms delivered additional water into the basin, allowing Lake Bonneville to fill, as she puts it, one storm at a time. As temperatures rose, the balance reversed: evaporation increased, storms became less frequent, and the lakes dwindled. Their remaining water grew progressively saltier until minerals began to form crystals and settle onto the lakebed, leaving salt deposits that the core still preserves today. Great Salt Lake’s lack of an outlet makes it especially sensitive to this balance, since water leaves the basin mainly through evaporation, so any shift in temperature, precipitation or river flow is registered directly in the lake’s level and salinity.

Modern Great Salt Lake faces pressures its ancient predecessors never encountered. Human water use, mostly for agriculture, reduces the amount of water reaching the lake, while human-caused climate change increases evaporation across the region. Feakins notes that today the climate is warming at an unprecedented rate, and that warming makes the atmosphere thirstier, accelerating evaporative drying from soils and lakes throughout the West. Both researchers caution against misreading the ancient record as reassurance. So warns that people should not use the argument that climate changed naturally in the past, and so the lake shrank, to justify treating shrinking lakes today as normal or purely natural phenomena. The geological record shows what a warming and drying climate can do to a closed basin; it does not excuse the additional human pressures now compounding that vulnerability.

The study is not without limitations, and the researchers are candid about them. Dating precision decreases in the core’s older layers, where margins of error span several thousand years, and dating some of the ancient salt deposits proved especially difficult. Attempts to reconstruct past temperatures were also hampered, because the lake’s high salinity made those results unreliable. Despite these challenges, the sediment core delivers a nearly continuous account of a lake responding to major shifts in the West’s water balance, and it demonstrates with unusual clarity how a vast freshwater lake covering thousands of square miles can give way to salt when the climate warms and dries. As the modern West grapples with a shrinking Great Salt Lake, the basin’s own sediments provide a 240,000-year perspective on just how quickly fresh water can disappear.

Subject of Research: Reconstruction of 240,000 years of salinity and lake-level change at Great Salt Lake, Utah, from sediment core evidence

Article Title: Great Salt Lake’s ancient past reveals how quickly fresh water can disappear

Article References: Great Salt Lake’s ancient past reveals how quickly fresh water can disappear. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Great Salt Lake, Lake Bonneville, paleoclimatology, sediment core, salinity, climate change, USC Dornsife, hypersaline lakes, American West, evaporation, glacial cycles, water resources

The snail at the center of the study, Figuladra bayensis, is a banded land snail native to the forests of Queensland. Like trees, snails add material to their shells incrementally, producing growth bands that can be sampled and analyzed one by one. A project led by researchers in the University of Queensland’s School of the Environment took tiny samples of the shell at millimetre intervals, a resolution fine enough to resolve individual growth episodes within the animal’s lifespan. Each band, the team realized, potentially encoded both a timestamp and a weather report: the chemistry of the carbonate laid down at any moment reflects the environmental conditions the snail was experiencing as it secreted new shell material.

Dating those bands precisely was the first challenge, and the researchers turned to one of the most distinctive chronological tools of the modern era: the radiocarbon signature left by atmospheric nuclear testing. During the 1950s and 1960s, nuclear weapons tests, including tests conducted in Australia, injected large quantities of artificial radiocarbon into the atmosphere. This so-called bomb pulse was absorbed by plants, incorporated into the food chain, and ultimately recorded in the tissues and shells of animals alive at the time. Dr Nicholas Patton, who led the project, explained that the shell contained elevated levels of radiocarbon from the nuclear tests of the 1960s. Using high-resolution radiocarbon dating, the team was able to anchor the growth bands in time and determine that the snail had lived for approximately four and a half years.

With the chronology established, the researchers analyzed the stable isotopes of oxygen and carbon preserved in each band. Oxygen isotope ratios in shell carbonate are governed largely by the isotopic composition of the water the animal ingests, which in turn is strongly influenced by the source and amount of rainfall in the local environment. Carbon isotopes reflect the animal’s diet and the photosynthetic pathways of the plants it consumed. Together, these two proxies provide a complementary picture of the climate and ecology surrounding the snail as it grew. By reading the isotope values band by band, the team could reconstruct a timeline of the rainfall conditions the snail experienced across the roughly four and a half years of its life.

What the team expected to find was a straightforward relationship between shell growth and annual climate. Honorary Professor Jamie Shulmeister, a co-author of the study, said the researchers initially anticipated that the rapid growth phases would correspond to years with heavier rainfall, which would have made more food available for the snail and fueled faster shell deposition. The logic seemed sound: wetter years should mean lusher vegetation, better nutrition, and more vigorous growth. But when the team compared the growth record against the meteorological history of the region, the expected pattern failed to appear. The shell’s growth was not tracking the overall wetness of each year at all.

Instead, the data revealed something far more striking. The shell had not grown continuously during the snail’s life; rather, there were periods of rapid growth separated by periods of little or no growth. When the researchers mapped these growth spurts against the dates established by radiocarbon dating, they found that the spurts aligned with periods immediately following two major tropical cyclones: Severe Tropical Cyclone Marcia in 2015 and Tropical Cyclone Debbie in 2017. Both storms caused extreme rainfall within Coalstoun Lakes National Park, dumping extraordinary volumes of water on the landscape in short periods. The snail, it turned out, was responding not to the gentle accumulation of seasonal rain but to the deluges that follow catastrophic storms.

The implications of this finding extend well beyond the biography of one snail. Because the growth spurts in the shell could be linked so clearly to specific, dated cyclones, the researchers recognized that snail shells could serve as proxies for extreme weather events extending back into periods before modern meteorological records began. Shulmeister described the realization as surprising and quite exciting, noting that the humble snail could become a tool for reconstructing the paths of past cyclones, potentially even in prehistoric times. For a region like the Queensland coast, where tropical cyclones pose a recurrent hazard, a new archive of pre-instrumental storm activity would be scientifically and socially invaluable.

The value of such an archive is difficult to overstate. Instrumental records of cyclone activity in Australia span little more than a century, and reliable satellite-based monitoring only a few decades. Beyond that window, scientists depend on sparse historical documents, geological storm deposits, and natural proxies such as coral cores and tree rings, each with its own limitations. Land snail shells, by contrast, are abundant, widely distributed, and durable enough to survive in sediment layers for thousands of years. If each shell preserves a chemical fingerprint of the extreme rainfall events during its lifetime, then a stratified sequence of shells could yield a decade-by-decade, or even finer, chronology of past storminess.

The research team’s next step is to test exactly that proposition. Dr Patton explained that if shells can be found within different layers of sediment deposits, the individual shell records can be combined to extend the information further back in time. Stacking multiple shell chronologies from successive sediment layers would, in principle, allow researchers to build a continuous reconstruction of extreme rainfall and cyclone activity across centuries or millennia. Such a reconstruction would help answer pressing questions about the natural variability of cyclone frequency in the Southwest Pacific, providing a baseline against which the influence of modern climate change on storm behavior can be assessed.

The study was completed in collaboration with Professor Melanie Leng of the British Geological Survey and the University of Nottingham, and Dr Quan Hua of the Australian Nuclear Science and Technology Organisation, institutions whose expertise in stable isotope analysis and radiocarbon dating underpinned the technical achievement of the work. The research, published in The Holocene under the title evaluating the Biggenden Banded Snail as a climate archive for South East Queensland using stable isotopes and radiocarbon dating, was conducted as an experimental study, and the authors declared no potential conflicts of interest. For now, the finding stands as a reminder that some of the most valuable scientific archives are not locked in ice cores or deep-sea sediments, but carried quietly on the backs of creatures small enough to fit in a palm, patiently recording the fury of the skies above them one growth band at a time.

Subject of Research: Land snail shells as climate archives for reconstructing historical and prehistoric cyclone activity in Queensland, Australia

Article Title: Snail shells are surprise weather time capsules

Article References: Snail shells are surprise weather time capsules. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: snail shells, paleoclimatology, cyclones, radiocarbon dating, stable isotopes, Queensland, extreme rainfall, The Holocene, University of Queensland, climate proxies, Figuladra bayensis, bomb pulse

The research centered on a careful comparison of two sets of ice cores drilled from the Guliya ice cap, one recovered in 1992 and the other in 2015. When the team analyzed the oxygen isotope patterns preserved in both samples, they found strikingly similar signatures, indicating that the environmental signals locked within the ice are consistent and reproducible across a gap of more than two decades. This kind of internal agreement is a cornerstone of paleoclimate science, because it demonstrates that the record has not been distorted by melting, refreezing, or other processes that can scramble the layered history of a glacier. Lonnie Thompson, lead author of the study, professor of earth sciences and senior research scientist at the Byrd Polar Research Center at The Ohio State University, emphasized the significance of this match, noting that reproducibility of records within a given ice cap is extremely important and that obtaining an identical record a quarter of a century later reveals a great deal about the behavior of the ice over time.

Determining the true age of ancient ice is one of the most technically demanding challenges in glaciology. Ice cores serve as vital climate archives of the locations and time periods they represent, but deciphering these flash-frozen treasure troves requires an accurate knowledge of the core’s timescale. Without reliable dating, the chemical and physical signals within the ice cannot be confidently matched to specific climatic events. To overcome this obstacle, the research team deployed advanced dating techniques capable of detecting two radioactive isotopes, beryllium and chlorine, whose half-lives make them reliable tools for capturing large-scale environmental changes across deep time. These cosmogenic isotopes are produced when cosmic rays interact with the atmosphere and are then deposited onto the ice surface, where their concentrations can serve as chronological markers for extraordinary events in Earth’s history.

The pivotal marker used in this study was the Laschamp Geomagnetic Excursion, a dramatic reversal of Earth’s magnetic field that occurred more than 41,000 years ago. During this event, the planet’s protective magnetic shield weakened substantially, allowing greater fluxes of cosmic radiation to reach the atmosphere. That surge in cosmic ray intensity produced elevated concentrations of cosmogenic isotopes such as beryllium-10 and chlorine-36, which were subsequently deposited and preserved in the accumulating snow of the Guliya ice cap. By identifying this distinctive isotopic spike within the cores and anchoring it to the well-established timing of the Laschamp event, the team was able to construct a robust chronological framework for the ice, effectively pinning a known date onto the deep layers of the glacier and allowing the ages of overlying and underlying ice to be constrained with far greater confidence.

To further validate and extend this timescale, the researchers compared their isotope-based results with oxygen-isotope records obtained from cave deposits in nearby regions of the Tibetan Plateau. Speleothems, the mineral formations that grow in caves, carry their own independent records of past climate and can be dated with high precision using uranium-series methods. The alignment between the Guliya ice core signals and these cave records led the team to estimate that the age of the Guliya record may stretch back well over 128,000 years, a span that reaches into or beyond the last interglacial period. This cross-verification between two entirely independent paleoclimate archives represents a powerful convergence of evidence, strengthening the case that the deepest ice at Guliya predates the Holocene by a wide margin.

The significance of this finding becomes especially clear when placed in a global context. Thompson pointed out that outside of the polar regions, this is the only ice core from the mountaintops that reaches back that far. He contrasted the Guliya record with that of Huascarán in the Peruvian Andes, another celebrated high-altitude drilling site where the ice record extends back only over 30,000 years rather than over 100,000. That comparison makes Guliya a very unique record, preserving a continuous or near-continuous account of climate variability across a stretch of time that no other mountain glacier on Earth has been shown to retain. For scientists seeking to reconstruct how monsoons, temperature regimes, and atmospheric circulation patterns behaved across multiple glacial cycles in Asia, the Guliya cores now stand as an irreplaceable resource.

The new evidence also settles a persistent scientific controversy. Previous work had suggested that the Guliya record stopped at the Mid-Holocene, an era that began nearly 12,000 years ago, implying that the ice cap contained only relatively young ice. If that interpretation had been correct, it would have meant that the large ice sheets of the last ice age did not persist through the early Holocene on the Tibetan Plateau. The evidence from this work lays those doubts to rest, confirming that some of the ice is in fact much older than the Holocene. As Thompson explained, if only Holocene-era ice existed in Tibet, it would indicate that the great ice masses of the last glacial period failed to survive into the current warm epoch, but the data demonstrate that they did. This confirmation reshapes scientific understanding of glacial persistence in one of the most climatically sensitive regions on the planet, often described as the water tower of Asia because its glaciers feed major river systems serving billions of people.

Guliya’s distinctive topography likely plays an important role in its extraordinary ability to preserve such ancient paleoclimate records. The ice cap sits at extreme altitude, where frigid temperatures limit surface melting, and its geometry may shield deeper layers from the deformation and basal processes that typically destroy old ice. Yet the value of constructing a more accurate timescale for the ice cap extends beyond validating its antiquity. A precise chronology opens the door to answering bigger environmental questions, such as when Earth’s intense periods of glaciation began and ended. Thompson framed the challenge in stark terms, asking when ice started forming on the planet and what the natural processes of ice loss looked like, and observing that the only way to truly demonstrate these dynamics is with accurate timescales on these records. In an era when scientists are working to distinguish natural climate variability from human-driven change, benchmarks of past glacial behavior drawn directly from ice are indispensable.

Because these results open new pathways for detailed scientific investigations of the Guliya ice cores, the team plans to use future samples to determine how other key climate and environmental indicators may change in light of this revised understanding of Earth’s geologic history. Dust concentrations, trapped atmospheric gases, microbial communities, and a host of geochemical tracers preserved in the ice can now be interpreted against a trustworthy timeline, potentially yielding insights into past atmospheric composition and ecosystem responses at altitudes above six kilometers. The international collaboration behind the study included Ohio State co-authors Mary Davis and Ellen Mosley-Thompson, along with Juerg Beer from the Swiss Federal Institute of Aquatic Science and Technology, Christof Vockenhuber and Marcus Christl from ETH Zurich in Switzerland, Tandong Yao from the Chinese Academy of Sciences, and Ninglian Wang and Ling Fang from Northwest University in China, with support from the U.S. National Science Foundation. Reflecting on the work, Thompson observed that the results tell a very consistent story, and that if the science is done right, it is consistent, adding that it is human understanding of what the ice is trying to tell us that has to catch up.

Subject of Research: Dating of ancient ice cores from the Guliya ice cap on the Tibetan Plateau

Article Title: Digging deep, researchers find high-altitude glacier endured last ice age

Article References: Digging deep, researchers find high-altitude glacier endured last ice age. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Guliya ice cap, Tibetan Plateau, ice cores, paleoclimatology, Laschamp Geomagnetic Excursion, cosmogenic isotopes, beryllium-10, chlorine-36, oxygen isotopes, last ice age, glaciology, Science Advances