The research, published in The Cryosphere, was carried out by Dorothea Elisabeth Baur of the British Antarctic Survey and University of Cambridge, together with Andrea Spolaor and Federico Scoto of Italy’s Institute of Polar Sciences and Elizabeth R. Thomas of the British Antarctic Survey. Over eleven days in March 2023, the team conducted seventeen tracer percolation experiments in nine snow pits on the Gruvebadet slope, roughly a kilometre south of Ny-Ålesund. Their goal was deceptively simple: to simulate a small winter rain event, watch the water move, and then compare the chemical fingerprints of the snow before and after. What they found reshapes how scientists can read melt-affected ice cores, and it offers a measure of hope for archives that many feared were already lost.

The stakes are high because Svalbard is warming faster than almost anywhere on Earth. Mean temperatures on the archipelago rose by three to five degrees Celsius between 1971 and 2017, with winters warming at roughly 1.35 degrees per decade. Glaciers that were once cold throughout are turning temperate, and perennial meltwater aquifers have now been documented on the Holtedahlfonna, Lomonosovfonna and Austfonna ice caps, in some cases at elevations and times of year that would have been unthinkable a generation ago. During a drilling project on Holtedahlfonna in March 2023, researchers encountered liquid water in the firn before spring had even begun. Melt generally enriches snow in the heavy isotope oxygen-18, mixes neighbouring layers and smooths the seasonal cycles that ice-core scientists rely on, a deterioration already documented in nearby Austre Brøggerbreen and Holtedahlfonna and, more dramatically, in the alpine Corbassière glacier in Switzerland.

To catch melt in the act, the team designed an experiment that could work within the strict environmental protections of Brøggerhalvøya, using only harmless natural substances. They prepared a tracer of ultrapure water enriched with deuterium oxide, heavy hydrogen that is chemically identical to water but detectable in isotope measurements, and coloured it with blue food dye. Each experiment poured a known volume, between 250 and 2000 millilitres, equivalent to about 6.25 millimetres of water on the 40 by 20 centimetre test plot, onto a carefully characterised patch of snow. Before each pour, the researchers measured snow temperature profiles at five-centimetre resolution, mapped the full stratigraphy of grain size, shape and hardness, and took density measurements. After the water had drained and refrozen, they cut fresh faces into the pit wall and photographed, measured and sampled the blue-stained structures.

The structural results were strikingly diverse. In colder snow, the meltwater froze into a distinct, bubble-free surface crust, with sharply defined vertical preferential flow paths, fingers of dyed water up to 5.5 centimetres wide, connecting the surface to isolated melt lenses deeper down. In warmer snow, near the end of the campaign, the behaviour changed completely: there was no refrozen surface layer, and instead the water spread in a broad, partly undersaturated wetting front that compacted the snow and lowered the surface by four to eight centimetres. Most remarkably, the team documented internal layering within melt lenses on a millimetre scale, with white remnants of the original snow structure surviving between saturated blue segments. Such fine-scale heterogeneity had been seen in laboratory experiments and computer models before, but never observed forming in the field within a single melt event.

Statistical analysis of the experiments revealed what controlled this behaviour. A multiple linear regression of percolation depth against snow and water properties explained about 63 percent of the variance, and three factors stood out as significant: warmer surface snow allowed deeper infiltration, transitions from fine-grained to coarse-grained layers retarded vertical flow, and larger water volumes pushed the wetting front deeper. Stratigraphy could even override temperature entirely. In one experiment on 29 March, when the snowpack was comparatively warm, the tracer was trapped within the top 1.5 centimetres of fine-grained snow and spread sideways instead of sinking, ponding above the first hard layer. Capillary forces at fine-to-coarse grain transitions, not just dense ice layers, act as barriers to downward flow.

The chemical story, however, is where the study delivers its most consequential message. By sampling stable water isotope ratios, the oxygen-18 to oxygen-16 ratio expressed as δ18O and the deuterium-to-hydrogen ratio expressed as δD, before and after each experiment, the researchers could quantify exactly how much the meltwater had rewritten the snow’s climate record. Melt-affected samples were clearly enriched, with δ18O shifted by about plus 3 per mil and δD by about plus 39 per mil on average. But samples taken just outside the visible blue structures were essentially unchanged, with mean differences of plus 1 per mil for δ18O and plus 7 per mil for δD, within the range of measurement noise. In one vivid example, a dyed flow path carried an enriched δ18O value of minus 15.8 per mil, while samples taken a mere 1.5 centimetres to either side retained their original value of minus 19.5 per mil.

This localisation matters enormously for ice-core interpretation. It means that melt does not homogenise the entire annual layer; it carves enriched channels and lenses through it, leaving the surrounding snow intact. Where enough snow accumulates each year, sub-annual isotope information can still be recovered from the unaffected parts of the profile. The study also suggests a counterintuitive protective effect: refrozen melt layers can act as lids that prevent wind from scouring and mixing the surface, preserving the stratification, and the isotope record, beneath them. Previous work has described melt layers as diffusion-limiting in this way, and the new field observations support that picture. At the same time, the fine-scale heterogeneity that melt introduces is a warning: a single core profile may not capture the true variability of a melt-affected layer, and the number of ice layers in a core will not necessarily equal the number of rain events that occurred.

The experiments also carry a caution about scale. The simulated events, at around 6.25 millimetres of water equivalent, represent small winter rain episodes typical of coastal Svalbard, not the extreme storms the region has seen, such as the 98-millimetre rainfall event of January 2012. The tracer liquid had to be warmed, averaging 11.7 degrees Celsius, to keep it from freezing in the sprinkler during fieldwork at temperatures as low as minus 25 degrees, and the team acknowledges that repeating the experiments through spring and under warmer conditions would broaden the picture. Still, the approach is deliberately simple and cheap, requiring no electricity or wireless equipment, which makes it reproducible at other melt-threatened drilling sites across the polar regions.

For the growing community of scientists racing to extract climate records from warming glaciers, the message is twofold. Melt is not a uniform eraser; it is a sculptor whose work depends on the temperature, texture and layering of the snow it passes through, and whose fingerprints can be read, and partly corrected for, if researchers sample carefully enough. But the study is also a reminder of urgency. Svalbard’s glaciers are among the key Arctic ice-core archives, and the conditions that allow seasonal signals to survive are themselves disappearing. As the authors note, the invaluable firn and ice-core records of melt-prone regions need to be retrieved before the local climate no longer permits their preservation.

Subject of Research: In-situ tracer percolation experiments quantifying how rain-on-snow melt affects snow structure and stable water isotope records in the Svalbard snowpack

Article Title: In-situ tracer percolation experiments to quantify the influence of near-surface melting on Svalbard snow signatures

Article References: Baur, D. E., Spolaor, A., Scoto, F., & Thomas, E. R. (2026). In-situ tracer percolation experiments to quantify the influence of near-surface melting on Svalbard snow signatures. The Cryosphere, 20(9), 5533-5558. https://doi.org/10.5194/tc-20-5533-2026

Image Credits: AI Generated

DOI: 10.5194/tc-20-5533-2026

Keywords: Svalbard, rain-on-snow, meltwater percolation, stable water isotopes, ice cores, snow stratigraphy, Ny-Ålesund, Arctic warming, preferential flow, climate proxies, firn, The Cryosphere

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