The observational study documents these linked changes but does not isolate a single cause or demonstrate that the ice shelf is approaching large-scale collapse. The Pine Island Ice Shelf regulates ice discharge from the Pine Island Glacier basin and is commonly divided into northern, central and southern sectors that differ in flow speed, basal melt rate and buttressing strength. Compared with the rapidly thinning and fast-flowing central and southern sectors, the northern ice shelf, designated N-PIIS, has received less attention.

It is primarily fed by the Larter, Lucchitta and Velasco glaciers. Earlier mapping showed that its area had fallen by 13.3% relative to 1966 by 1992, by 16.7% by 1996 and by 27.2% by 2000. A major calving event in 2015 disconnected it from the central ice shelf, although grounding lines at the Lucchitta and Larter glaciers have remained comparatively stable over mountainous, prograde bed topography.

The new analysis combines Landsat optical images, Sentinel-1 synthetic aperture radar, Sentinel-2 imagery, annual ice-velocity products, ICESat-2 laser-altimetry data, sea-ice observations and double-differential interferometry. Ice-front positions were mapped from 1973 through 2026, with extraction uncertainties ranging from about 10 metres for recent Sentinel-1 observations to 60 metres for early Landsat-1 imagery. Annual velocities from 2014 to 2026 were extracted at nine sites, including the grounded Larter and Lucchitta glaciers, floating parts of the northern shelf and several locations on the Velasco Glacier.

Pinning-point evolution was assessed from optical imagery acquired in 1997, 2003, 2007 and 2026, while interferograms generated from Sentinel-1 acquisitions tracked grounding-zone changes from 2017 through 2025. Surface elevation along one repeating ICESat-2 track was analysed from 2019 to 2025. Three mapped subregions experienced marked area loss.

N-PIIS1 lost about 600 square kilometres between 1973 and 2026, including roughly 200 square kilometres during 2014–2015 when it separated from the central shelf. N-PIIS2 decreased by about 120 square kilometres over the same period, with pronounced retreat after 1986. N-PIIS3 lost around 40 square kilometres, with most of that loss occurring after 2007.

An ice front previously connected to pinning point P7 retreated to P8 after calving between 23 January and 27 December 2011. More calving followed in the N-PIIS2 and N-PIIS3 regions during periods when SMOS thin-sea-ice measurements approached zero, indicating little or no landfast ice immediately offshore. By contrast, the N-PIIS1 front, where several pinning points remain and Pine Island Bay provides shelter, did not undergo comparable calving during open-water periods.

The most closely documented sequence unfolded at the Velasco Glacier. A rift was first observed on 14 September 2021, coinciding with the formation of a polynya. The polynya expanded, new fractures formed within the fast ice on 10 November, breakup progressed toward the ice tongue by 28 November, and complete disintegration was observed by 20 December as the polynya continued to expand.

The event ultimately detached an iceberg of approximately 3.50 square kilometres. Another sequence began after landfast sea ice near N-PIIS2 and N-PIIS3 almost completely broke up following 28 November 2025. Several calving events occurred between December 2025 and March 2026, producing further ice-shelf area loss and additional calving at the Velasco Glacier.

The area near pinning point P8 changed less, suggesting that local pinning continued to restrain part of the ice front. Annual velocity records show that ice movement generally accelerated between 2014 and 2026. Sites N1 and N2, on the grounded Larter and Lucchitta glaciers, and sites N3 and N4 on the floating N-PIIS1 shelf increased by approximately 50–100 metres per year.

Velocities at N5 and N6 remained relatively stable at about 50–70 metres per year. At the grounded Velasco Glacier, velocity rose from 2014 to 2022, declined from 2022 to 2024 and increased again after 2024. Floating sites N8 and N9 followed a similar pattern, accelerating through 2021, decelerating through 2024 and accelerating again afterward.

The loss of contact between the Velasco Glacier and N-PIIS3 after 2024 coincided with faster glacier flow. This temporal correspondence suggests that reduced buttressing may have contributed to the velocity increase, although the authors stress that other factors may also have affected the glacier’s response. Interferometric observations reveal a parallel decline in the ice shelf’s attachment to bedrock.

Pinning points P1, P2 and P3 remained visible in optical imagery from 1997 to 2026, although P4 was no longer detectable by 2026 after nearby calving, and P5 disappeared after 2007. Between 2017 and 2025, P1 persisted throughout the record. P2 showed the greatest variability: it was clearly detectable from 2017 to November 2020, appeared intermittently from January 2021 onward, and its centre gradually migrated southward.

P3 was no longer detectable after October 2022, while P5 began disappearing in December 2023 following calving that removed its contact with the ice shelf. Interferograms also showed deformation associated with basal channels. Together with lower surface elevations and the appearance of polynyas, the redistribution of pinning points indicates continued thinning and episodic loss of grounding.

Measurements of the two rifts document continued fracture growth and a change in the propagation rate of the older feature. The rift that developed in 2022 grew from 4.5 kilometres on 14 December 2022 to 8.5 kilometres on 21 December 2023 and 11.3 kilometres on 27 December 2024, an average rate of about 4 kilometres per year. From 27 December 2024 to 28 December 2025, it lengthened from 11.3 to 19.5 kilometres, corresponding to about 8 kilometres per year, nearly twice the earlier rate.

A second rift initiated north of pinning point P2 between June and August 2025. It expanded from approximately 4.1 kilometres on 26 June 2025 to 12.5 kilometres on 29 March 2026, an elongation of 8.4 kilometres in less than one year. Both rifts were close to areas where pinning points were changing, consistent with thinning-driven ephemeral grounding and altered internal stresses influencing fracture propagation.

The observations point to several interacting processes rather than a single demonstrated mechanism. Loss of pinning points can reduce local buttressing and redistribute stresses within the shelf. Breakup of landfast sea ice can also expose the ice front to ocean swell and associated flexural stresses.

ICESat-2 measurements indicated surface elevations near 50 metres in N-PIIS1 but below 15 metres in N-PIIS2 and N-PIIS3. After allowing for approximately 20 metres of firn air content, the researchers estimated ice thickness at about 300 metres in N-PIIS1 and less than 150 metres in the two thinner regions. They note that ocean swell may produce stronger flexural effects in ice shelves below 150 metres thick, although the observations do not quantify its contribution to individual calving events.

Overall, the analysis documents a northern ice shelf that is smaller, thinner and less securely pinned than it was decades ago, with faster ice flow, repeated frontal retreat and rifts that continue to propagate. Polynyas were not detected in the Landsat scenes examined for 1986, 1989 or 1997, although those images showed surface changes, including supraglacial lakes in 1997. Polynyas were clearly visible in imagery from 2003, 2005, 2007, 2019, 2020, 2021, 2022 and 2026, with marked expansion in 2021 and 2026.

Satellite radar also recorded areas of reduced backscatter during the austral winter of 2024, while ICESat-2 data showed a continuous elevation decrease in those areas. The study did not report a large-scale collapse of the N-PIIS and cannot determine the relative influence of basal melting, ocean swell, sea-ice loss, pinning-point change and other factors. The authors instead call for sustained satellite observations, in situ measurements and numerical modelling to quantify those contributions and assess the potential for further rift propagation and structural change.

Subject of Research: Satellite analysis of retreat, thinning, calving and rift propagation in West Antarctica’s northern Pine Island Ice Shelf

Article Title: Progressive changes in geometry and dynamics of the Northern Pine Island Ice Shelf, West Antarctica

Article References: Chien, Y., Zhou, C., & Zhang, B. (2026). Progressive changes in geometry and dynamics of the Northern Pine Island Ice Shelf, West Antarctica. The Cryosphere, 20(10), 6071-6086. https://doi.org/10.5194/tc-20-6071-2026

Image Credits: AI Generated

DOI: 10.5194/tc-20-6071-2026

Keywords: Pine Island Ice Shelf, West Antarctica, ice-shelf retreat, ice-shelf thinning, pinning points, rift propagation, polynyas, sea-ice breakup, satellite observations, glacier dynamics, Progressive, changes

Sub-ice-shelf bathymetry is a major boundary condition for models of Antarctic ice sheets and the ocean cavities beneath them. The shape of the seabed helps determine where relatively warm, salty ocean water can enter a cavity, how currents are steered across the basin, and where deep troughs may permit dense water to penetrate toward grounded ice. Bathymetric roughness also influences turbulence in the cavity and the transfer of heat to the ice. Direct observations remain rare because the cavities are difficult for ships and other platforms to access, leaving gravity inversion as an important tool for estimating hidden terrain between scattered measurements.

The approach works because the large density contrast between rock and seawater leaves a measurable imprint on Earth’s gravitational field. Airborne surveys can recover broad features of a sub-ice-shelf basin, typically at wavelengths of about 5 kilometres and above. Geological complications make the calculation less straightforward. Lateral variations in crustal thickness, rocks with different densities, and other subsurface structures can distort the measured anomaly. Earlier inversions addressed some of these issues by tying reconstructed topography to known elevations, but the new analysis indicates that this can be insufficient when a large, deep basin lacks centrally positioned tie points.

New observations collected beneath the Dotson and Crosson ice shelves revealed the scale of the problem. Autonomous underwater vehicles Ran and Autosub Long Range surveyed the ocean-facing margin during the RV Nathaniel B. Palmer expedition in January and March 2022. Ran collected multibeam profiles with a Kongsberg EM2040 system, supported by Doppler velocity log and inertial navigation; comparisons with shipborne swaths indicated an absolute horizontal positional error below 40 metres and a relative error below 10 metres. Autosub Long Range followed three routes extending 2, 16 and 39 kilometres inboard from the ice-shelf margin with a single-beam depth sounder whose local depth accuracy was below 1 metre. Three profiling floats and seismic measurements from 27 active shot points added observations farther across the cavity.

Comparison of these observations with the earlier gravity-derived model showed that parts of the Dotson basin had been estimated as too shallow by at least 400 metres. The discrepancies were most systematic at wavelengths longer than 30 kilometres, whereas the previous inversion reproduced much of the observed variation at intermediate scales of 10 to 30 kilometres. Differences below 10 kilometres were also expected because the airborne gravity data had been filtered at a 5-kilometre wavelength and collected with line spacing of 7.5 to 10 kilometres. The long-wavelength mismatch pointed to a systematic regional bias rather than merely unresolved small-scale terrain or scattered measurement errors.

The study’s explanation is that glacial excavation removes mass from the crust and prompts an upward adjustment of the Mohorovičić discontinuity, the boundary between less-dense crust and denser mantle. This isostatic compensation brings dense mantle material closer to the surface beneath a deep basin. Its positive gravitational contribution can offset part of the negative anomaly produced when excavated rock is replaced by water, causing the basin to appear shallower than it is. The method therefore calculates a model of the compensating gravity field and subtracts it from the original free-air anomaly before the bathymetric inversion. The researchers describe it as a pseudo-isostatic correction because its initial topography is inferred from gravity rather than directly observed.

For the calculation, the team used an Airy isostatic model, which assumes that the crust has no lateral strength. They adopted a reference Mohorovičić depth of 30 kilometres, crustal density of 2,670 kilograms per cubic metre, and mantle density of 3,330 kilograms per cubic metre. The chosen reference depth was deeper than some local seismic estimates, but the authors considered it a reasonable global average given uncertainty in the crustal and upper-mantle density structure. The Airy model generates the maximum local Moho deflection and therefore the largest correction among models with different crustal strengths. The researchers also calculated the compensation while treating excavated material as having displaced air rather than water, amplifying the modelled Moho topography by 1.6 times. This selected treatment produced a good fit with the direct observations beneath the ice shelf.

After subtracting the modelled isostatic gravity effect, the adjusted anomaly was converted into an initial topographic surface using a rearranged Bouguer-slab equation. The researchers then modelled the gravity field of that surface using prisms, calculated the residual against the adjusted observations, and iteratively updated the topography. Two further iterations brought the residual below about 1 milligal across most of the survey area. Where direct observations were available, the difference between the reconstructed surface and measured elevation was interpolated into a correction field. Subtracting that field from the gravity-derived estimate produced a model that followed the observations while retaining the regional shape supplied by gravity. The inversion was also run without the sub-ice-shelf observations as an independent test of the isostatic correction.

Against the longest Autosub Long Range profile, the isostatically corrected inversion reduced the mean error from 195 to 3.2 metres and the standard deviation from 105 to 70 metres. Comparison with float observations produced a smaller improvement in the mean error, from 313 to 135 metres, while the standard deviation remained 187 metres. The researchers attributed the difference partly to the floats following the steep coast of Bear Island, where an approximately one-kilometre topographic step falls from coastal terrain of about 300 metres to adjacent depths near 700 metres below sea level. That feature is not recoverable using gravity data filtered at wavelengths above 5 kilometres. Float navigation also had horizontal uncertainty of about 1 kilometre or more, which could make measured depths appear displaced from the model. The vehicle profile lay closer to the centre of the basin and away from the steep fjord wall, making it a more favourable test of the method.

The revised method changed the regional picture most strongly beneath Dotson and Crosson, where the basin is deep and direct constraints are sparse. The final model combined the corrected inversion with the new observations and was slightly deeper in places than the unconstrained, isostatically corrected result. The authors said this version should provide the best bathymetric estimate currently available for the area given the available data. They also cautioned that the 70-metre standard deviation along the main vehicle profile is location-specific: it incorporates unresolved short-wavelength topography, errors of about 1.67 milligals in the gravity observations, local geological variability, and navigation uncertainty. Unknown geology remains difficult to quantify, while thick sediment layers could create a different, negative gravity effect that the model does not explicitly resolve.

Beyond the study area, the results show that gravity-derived bathymetry can contain regional errors of several hundred metres when isostatic compensation is ignored. Such errors may affect simulations of ocean circulation beneath ice shelves and assessments of grounded-ice vulnerability to warming oceans, because a modelled seabed raised above a sill can artificially restrict the entry of warm water. The correction is likely to matter most for small or poorly explored ice shelves containing broad erosional basins and few direct measurements, rather than the much larger Ross or Ronne-Filchner ice shelves. Its influence was smaller near Thwaites Glacier, where the predicted compensation field had a low-amplitude, approximately uniform gradient, so interpolation between observations on either side of the data gap could provide a reasonable result. The study therefore indicates that direct observations remain essential, while a physically informed isostatic correction can make gravity inversion substantially more reliable for recovering regional bathymetry beneath Antarctic ice shelves.

Subject of Research: Gravity-based recovery of bathymetry beneath the Dotson and Crosson ice shelves using an isostatic correction

Article Title: Improved recovery of sub-ice shelf bathymetry from gravity data using an isostatic correction: a case study from the Dotson and Crosson ice shelves, West Antarctica

Article References: Jordan, T. A., Heywood, K. J., Wåhlin, A., Hall, R. A., Muto, A., Dutrieux, P., Hogan, K., Girton, J., Alley, K. E., & Pettit, E. (2026). Improved recovery of sub-ice shelf bathymetry from gravity data using an isostatic correction: a case study from the Dotson and Crosson ice shelves, West Antarctica. Solid Earth, 17(10), 1187-1199. https://doi.org/10.5194/se-17-1187-2026

Image Credits: AI Generated

DOI: 10.5194/se-17-1187-2026

Keywords: Antarctica, ice-shelf bathymetry, gravity inversion, isostatic compensation, Dotson Ice Shelf, Crosson Ice Shelf, glacial erosion, seabed mapping, autonomous underwater vehicles, West Antarctica, Improved, recovery

The research, led by Jonathan Adams of Imperial College London and the British Antarctic Survey with colleagues including Dylan Rood, Klaus Wilcken, Stephen Roberts, and Joanne Johnson, hinges on a technique called cosmogenic nuclide surface exposure dating. The principle is elegantly simple. When cosmic rays strike rock at the Earth’s surface, they shatter atoms in the mineral quartz and forge rare isotopes such as beryllium-10 and carbon-14. The longer a rock sits exposed to the sky, the more of these cosmogenic nuclides accumulate. Measure their concentrations, and you can calculate how long ago the ice melted away and the rock first saw daylight. For ice sheet scientists, these ages are the ground truth against which computer models of past and future retreat are validated.

But the two isotopes behave very differently, and that difference is the heart of the study. Beryllium-10 has a half-life of 1.387 million years, so it accumulates essentially forever and lingers through multiple cycles of burial and re-exposure. In Antarctica, where cold-based ice often freezes to the bed without eroding it, rocks can carry inherited beryllium-10 from exposures that happened tens or even hundreds of thousands of years ago, long before the last glacial maximum. That inherited signal can make a freshly deglaciated surface look deceptively old. In situ produced carbon-14, by contrast, has a half-life of just 5,700 years. Any carbon-14 built up before the last glacial maximum largely decays away while the rock sits under deep ice, so a surface re-exposed at the end of the ice age carries almost none of this legacy. A rock that was saturated with carbon-14 before the last glacial maximum, buried at 25,000 years ago, and re-exposed at 10,000 years ago would retain a pre-ice-age inventory amounting to only about six percent of what is measured today. That makes carbon-14 uniquely suited to dating the most recent chapter of ice retreat.

Adams and his team collected nine rounded erratic cobbles from three sites on Mount Murphy: the Notebook Cliffs at around 850 to 900 meters above sea level, Turtle Rock between roughly 440 and 700 meters, and a scoria cone near Kay Peak sitting just 180 to 240 meters above the ice, less than a kilometer from the grounding line of Pope Glacier. All nine had previously been dated with beryllium-10, and those ages told a coherent story: the ice surface at Mount Murphy thinned dramatically during the early to mid-Holocene, reaching low elevations by roughly 9,000 to 6,000 years ago. The new carbon-14 measurements, however, told a different tale. Six of the nine samples yielded carbon-14 ages of only 5,000 to 3,000 years, implying the ice lingered thousands of years longer than the beryllium-10 record suggested.

When the two isotopes from the same sample are compared on a paired nuclide diagram, where the beryllium-10 concentration is plotted against the carbon-14 to beryllium-10 ratio, the samples split into two camps. Concordant pairs, in which the two ages agree within uncertainty, indicate a simple exposure history since the ice age. Discordant pairs, where the ages do not overlap, hint at burial, shielding, or shifting production rates. At Mount Murphy, some samples were concordant while others, often at the same elevation, were discordant, and the discordant carbon-14 ages were systematically the younger ones. Stranger still, some high-elevation samples yielded younger ages than low-elevation ones, the exact inverse of the pattern expected as an ice sheet thins upward through time.

The team systematically hunted for a geological explanation. They examined aerial photographs from 1966 showing that the lower scoria cone outcrop was once buried by ice, confirming that at least some samples experienced late Holocene shielding. They tested whether thin layers of till or snow could explain the discrepancies, and whether erratics might have been exposed at higher elevations before being transported downslope, a mechanism invoked at Shark Fin Nunatak near Tucker Glacier. They even modeled scenarios in which subsurface production of carbon-14 by muons, which contributes roughly twenty percent of total carbon-14 production at the surface compared with under two percent for beryllium-10, could inflate the carbon-14 to beryllium-10 ratio in buried samples, producing seemingly impossible nuclide ratios like those seen at Sjögren Glacier on the Antarctic Peninsula. None of these geological scenarios could account for the Mount Murphy pattern.

The breakthrough came from the laboratory rather than the landscape. The researchers had run repeat carbon-14 measurements on four of their samples, and three of those four failed to reproduce within their stated uncertainties. The initial measurements produced ages 5,000 to 3,000 years younger than the replicates, with some replicate ages more than 150 percent older than their first-pass counterparts. Crucially, the older, reproducible ages agreed with the beryllium-10 chronology, while the young, irreproducible ages did not. Sensitivity analyses using different blank corrections and different calibration values for the CRONUS-A reference material could not rescue the young ages, no matter how the numbers were shuffled. The problem, it appeared, lay in the measurements themselves, not in the ice history.

To find out whether this was an isolated glitch, the team turned to the informal cosmogenic-nuclide exposure-age database, ICE-D, and compiled every sample worldwide with replicate carbon-14 measurements, thirty-one in total, spanning the Antarctic Peninsula, the Weddell Sea Embayment, Lake Bonneville in Utah, and the Northwest Highlands of Scotland. The result was sobering: in eighteen of the thirty-one samples, at least one carbon-14 measurement failed to reproduce within the nominal six percent uncertainty conventionally assigned to such data, and fifteen still failed at the more forgiving two-sigma level. Interlaboratory comparisons of CRONUS-A tell a similar story, with long-term average carbon-14 concentrations varying by roughly fifteen percent between extraction facilities, from about 6.12 times ten to the fifth atoms per gram at Tulane University to 7.28 times ten to the fifth at ETH Zurich. The inescapable conclusion is that the analytical uncertainty quoted for in situ carbon-14 is currently underestimated, particularly for the moderate concentrations typical of Holocene-aged samples, where contamination from background carbon in processing blanks becomes dominant.

The good news for Antarctic science is that the accepted deglaciation history of Mount Murphy, and by extension the Amundsen Sea Embayment, survives this scrutiny intact. The concordant, reproducible carbon-14 ages align with the beryllium-10 record, confirming that ice there thinned substantially between about 9,000 and 6,000 years ago, and the team credits access to the Tulane laboratory’s quality control data with preventing them from publishing a badly wrong chronology. The broader lesson is a call to arms for the geochronology community: routinely publish replicate measurements, quantify and minimize scatter in process blanks, and pursue interlaboratory comparison studies with additional reference materials to establish consensus calibration values. As automation of carbon-14 extraction lines increases throughput, these checks become practical. The stakes could hardly be higher. Thwaites Glacier is one of the largest contributors to sea-level rise from Antarctica, and projections of its future depend on models calibrated against the past. If the isotopic clocks that record that past are even slightly miscalibrated, the sub-millennial precision needed to capture phases of retreat and readvance slips out of reach. This study shows both the fragility and the resilience of the method: the clocks can go wrong, but with enough cross-checks, science can catch them before the story gets rewritten.

Subject of Research: Cosmogenic carbon-14 and beryllium-10 exposure dating of Holocene ice sheet thinning at Mount Murphy, West Antarctica

Article Title: Paired 14C–10Be exposure ages from Mount Murphy, West Antarctica: Implications for accurate and precise deglacial chronologies

Article References: Adams, J. R., Rood, D. H., Wilcken, K., Roberts, S. J., & Johnson, J. S. (2026). Paired 14 C– 10 Be exposure ages from Mount Murphy, West Antarctica: Implications for accurate and precise deglacial chronologies. Geochronology, 8(2), 255-277. https://doi.org/10.5194/gchron-8-255-2026

Image Credits: AI Generated

DOI: 10.5194/gchron-8-255-2026

Keywords: cosmogenic nuclides, in situ carbon-14, beryllium-10, Mount Murphy, Thwaites Glacier, West Antarctica, exposure dating, deglaciation, Holocene, ice sheet thinning, sea-level rise, analytical uncertainty

The story begins with a sediment core recovered from the Amundsen Sea during an expedition of the research icebreaker Polarstern. In 2020, the same international team, led by marine geologist Dr Johann Klages of the Alfred Wegener Institute, stunned the scientific community when they announced in the journal Nature that the core contained an extraordinarily well-preserved forest soil dating back roughly 90 million years, complete with abundant pollen, spores and a dense network of fossil roots. During the Cretaceous, tectonic conditions placed this temperate rainforest even farther south than the drill site itself, a mere 900 kilometres from the geographic South Pole. Today, average annual temperatures at that location hover around minus 30 degrees Celsius, and the entire region lies beneath an ice sheet several kilometres thick.

The climate that supported such a forest was shaped by greenhouse conditions unlike anything in the recent geological past. Atmospheric carbon dioxide concentrations during the warmest interval of the Cretaceous were four to six times higher than preindustrial modern levels, and the average annual temperature in the West Antarctic rainforest reached around 12 degrees Celsius, roughly two degrees warmer than present-day Germany. Rainfall was plentiful but strongly seasonal: dry periods regularly gave way to monsoon-like rainy seasons. For about four months of each year, the forest endured the continuous darkness of the polar night, yet conifers and tree ferns thrived, and dinosaurs roamed through the misty swamplands. It was this combination of warmth, abundant moisture and pronounced seasonality that set the stage for the fires the team has now documented.

In the new study, the researchers re-examined the same core using a broader suite of analytical methods, and the evidence of fire proved unmistakable. Throughout the Late Cretaceous section of the sediment sequence, the team identified microscopic charcoal particles, the diagnostic residue of vegetation burned in situ or transported short distances by water and wind. Critically, the abundance of these charcoal particles increased steadily in the younger sediments, indicating that fires became more frequent as the ecosystem evolved. The particles themselves carried chemical and structural signatures showing that the fuel was mainly soft conifer wood burned at relatively low temperatures, a pattern typical of surface fires that creep through undergrowth and ground litter without climbing into the forest canopy.

Fire left its mark in more than charcoal. The sediments also yielded amber, the fossilised form of tree resin, appearing in a configuration that suggests the resin flowed over fire-damaged areas of tree trunks and hardened into a protective seal, much as living conifers today exude resin to wall off wounds. Together, the charcoal and amber record a forest that was burned and healed, burned and healed again, over an extended stretch of Late Cretaceous time. Because volcanically active areas lay at least 400 kilometres away from the site during that period, the researchers conclude that the most plausible ignition source was not lava or volcanic ash flows but lightning strikes from thunderstorms, a conclusion consistent with the strongly seasonal, storm-prone climate inferred from the broader sedimentological and palaeontological evidence.

Perhaps the most consequential discovery in the core concerns what grew back after the fires. The sediments contain countless spores of peat moss of the genus Sphagnum, the same group of plants that dominates raised bogs across the modern Northern Hemisphere. These spores provide evidence of some of the earliest raised bogs known, and their rise was closely intertwined with the recurrence of fire. According to the scenario the researchers developed from their data, the temperate and very swampy Antarctic rainforest, with its alternating dry and monsoon seasons, gradually silted up and transitioned into a peatland dominated by peat mosses. Wildfires, growing ever more frequent, played a decisive role in that transition by keeping the vegetation open, preventing the re-establishment of dense forest, and creating the conditions under which waterlogged, moss-dominated ground could persist and expand.

Once the peat bog had formed, fire did not disappear from the system. Instead, it changed character. Ground-level smouldering fires occurred repeatedly within the peat itself, burning slowly through damp, carbon-rich material rather than racing through standing forest. Co-first author Prof. Dr Ulrich Salzmann of Northumbria University draws a direct line from that ancient process to the present day, noting that such smouldering ground fires resemble those that have become increasingly common in German peatlands in recent years, where prolonged drought has lowered water tables and left once-saturated peat vulnerable to slow, persistent combustion. The Antarctic core thus preserves a complete natural experiment in how fire, hydrology and vegetation interact during the birth and maturation of a peatland, conducted under greenhouse conditions far warmer than today’s.

The climate significance of that experiment is difficult to overstate. Peatlands are among the most effective long-term carbon stores on Earth, accumulating partially decomposed plant material over thousands to millions of years because waterlogged conditions slow decay to a crawl. Co-first author Prof. Dr Thorsten Bauersachs of RWTH Aachen University emphasises that peatlands played a key role in the climate system then as now, precisely because of this capacity to lock away carbon over long periods. Paradoxically, the Cretaceous record suggests that in a warm climate, where wetlands dry out more quickly and fires that suppress forest development occur more frequently, conditions can actually favour the formation of new peatlands, allowing carbon-rich plant matter to accumulate even as the world warms. Fire, in other words, was not merely a destructive force in this ancient ecosystem but an architect of one of the planet’s most durable carbon sinks.

For the research team, the parallels between the Cretaceous Antarctic and today’s high latitudes were among the most surprising findings of the study. Dr Johann Klages, co-first author of the paper, describes the team’s astonishment at finding evidence in the core of an early Antarctic ecosystem that, in many respects, resembled today’s Arctic raised bogs and also experienced regular fires. Modern raised bogs in Arctic and boreal regions face acute threats from climate change and increasing drought, and the fate of the carbon they store is a major uncertainty in projections of future warming. The West Antarctic record demonstrates that peat formation and fire can coexist and even reinforce one another under greenhouse conditions, but it also shows how sensitive these systems are to the balance between moisture and burning, a balance that human-driven warming is now shifting across the northern peatlands.

The study also underscores how much remains hidden beneath the Antarctic ice. A single sediment core, drilled through the seafloor of the Amengen Sea region, has now yielded a rainforest soil, a fire history and the trace of the earliest polar peatlands, all from a time when the South Pole itself was green. As analytical methods grow more sensitive, existing cores continue to surrender new secrets, and each one refines the picture of how Earth’s most extreme greenhouse intervals functioned. Ninety million years ago, lightning-lit fires crackled through swampy conifer forests under a polar night, and from those ashes rose the bogs that would bury carbon for geological time. Understanding that ancient dance between flame and moss may prove essential to anticipating what a warming world will do to the peatlands that still guard vast reservoirs of carbon today.

Subject of Research: Cretaceous wildfires and early Sphagnum peatland formation near the South Pole

Article Title: Evidence of ancient wildfires near the South Pole

Article References: Evidence of ancient wildfires near the South Pole. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Antarctica, wildfires, Cretaceous, peatlands, Sphagnum, paleoclimate, charcoal, amber, carbon storage, West Antarctica, sediment core, climate change