Atmospheric and Oceanic Sciences

The graphitization of diamond is of significant interest for nanodiamond synthesis from laser-shocked hydrocarbons, for its use as a detector material, and for the application in diamond anvil cells. The transition can be triggered either locally through sufficiently rapid energy deposition, or thermally at temperatures above 1800 K. We report on an experiment in which a heavy-ion beam was used to volumetrically heat monocrystalline diamond, investigating the intermediate regime between these two competing mechanisms. Our sample is probed using x-ray radiation generated from a laser-driven titanium plasma. The ratio of elastic to inelastic scattering in backward direction allows for measuring the samples' bulk temperature. We observe good agreement between the x-ray based technique and stopping power simulations up to ∼ 2000 K. When increasing the heating further by fully stopping the ions in the target, we reach conditions where graphitization is predicted to occur. In this regime, elastic x-ray scattering is notably stronger than expected for pristine, heated diamond. Simultaneous x-ray diffraction measurements show a modification of the previously sharp diamond peaks in this range, which is also accompanied by changes in the optical properties of the sample. A thermally induced transition to graphite provides the most plausible explanation of the observations.

Hyperodapedontine rhynchosaurs, a group of specialized herbivorous archosauromorphs, are restricted to the Late Triassic Lower Maleri Formation of the Pranhita-Godavari (P-G) basin, India and their remains are found mostly within the thick red mudstone unit, calcirudite and mixed mud-sand lithologies. A good number of specimens (~ 210) of these rhynchosaurs, belonging to a minimum of 30 individuals, had been collected historically since 1960s, dominantly from six key accumulation sites near Kothapalle, Bheemini, Narlapuram, Venkatapur, Achlapur and Rampur, Telangana, India. Classical taphonomic studies on these specimens indicated highly fragmentary, transported, weathered and altered bones. This implied significant effects of high energy fluvial transportation on the bones, punctuated by episodes of long subaerial exposures in floodplains. Here, multivariate and spatial statistics have been employed to objectively infer a compact taphonomic framework, conduct a robust taphofacies analysis and precisely reconstruct the palaeoenvironment for the entire rhynchosaur assemblage of the Lower Maleri Formation, P-G basin. Five taphofacies and three taphofacies-lithofacies association (TL1, TL2, TL3) are derived from the combined analyses. TL1 is the dominant association, with a mix of articulated and weathered remains preserved within intercalated parallel-laminated and massive sandstone, indicating considerable transport followed by rapid burial, accompanying the waning of high-energy pulses. TL2 is characterized by fragmented and abraded bones preserved in a finely laminated and stratified mudstone, with occasionally articulated elements, indicating deposition from waning floodwaters in abandoned channel settings. TL3 represents the inter-flood stability phase, where prolonged subaqueous exposure and low sedimentation rates facilitated biological encrustation and early cementation.

Subterranean ecosystems host highly specialized and often cryptic biodiversity, yet even intensively studied landscapes may conceal deeply divergent vertebrate lineages. Here we describe Demogorgonichthys arcanus gen. et sp. nov., a new genus and species of cave-obligate fish discovered in Bobcat Cave, a long-monitored karst system on Redstone Arsenal in northern Alabama, USA. Phylogenetic analyses based on mitochondrial nd2, complete mitochondrial genomes, and the nuclear gene rhodopsin place D. arcanus within Amblyopsidae but reveal deep divergence from all described genera, including extensive lineage-specific degeneration of a vision-related gene. Notably, D. arcanus occurs in syntopy with the Southern Cavefish (Typhlichthys subterraneus) despite lacking a close phylogenetic relationship, providing evidence for multiple independent evolutionary origins of cave adaptation within a single groundwater system. This discovery highlights persistent detection bias in groundwater ecosystems and demonstrates that cryptic vertebrate diversity can persist even in well-characterized environments. Extreme endemism and restriction to a single cave-aquifer system further underscore the vulnerability of subterranean biodiversity and the importance of integrating evolutionary and conservation perspectives.

This study investigates sea level trends in the North Indian Ocean (NIO) from 2003 to 2024, quantifying the contributions of thermosteric, halosteric, and ocean mass components using satellite altimetry, observation-based gridded products, and GRACE gravimetry datasets. The NIO Sea level is rising at 4.83 ± 0.22 mm/yr, driven primarily by thermosteric sea level (2.21 ± 0.16 mm/yr) followed by ocean mass component (1.69 ± 0.09 mm/yr). Sub-basinal analysis reveals strong spatial heterogeneity, with the highest rates of sea level rise in the Western Bay of Bengal (5.19 ± 0.41 mm/yr) and the lowest in the Western Arabian Sea (4.29 ± 0.27 mm/yr). A distinct halosteric contrast exists, where freshening accelerates rise in the Bay of Bengal (up to 0.65 ± 0.08 mm/yr in the Eastern Bay), and increasing salinity suppresses it in the Arabian Sea (down to -1.12 ± 0.12 mm/yr in the western Arabian Sea). Furthermore, while western sub-basins are predominantly steric-driven, eastern sub-basins of Bay of Bengal and Equatorial Indian Ocean exhibit anomalously high GRACE-derived mass contributions (> 3 mm/yr), likely influenced by post-seismic crustal adjustments from the 2004 Sumatra-Andaman earthquake. Interannual variability closely tracks steric changes modulated by ENSO and the Indian Ocean Dipole (IOD), triggering basin-specific responses via wind anomalies and long-period waves. Further analysis of tropical SST indices reveals that the Western Tropical Indian Ocean SST index closely mirrors the spatial correlation structures of the Dipole Mode Index, and may serve as a useful indicator of regional sea level variability, particularly over the Equatorial Indian Ocean and Bay of Bengal. Ultimately, unlike the predominantly mass-driven global trends where both mass and steric contributions are of comparable magnitude, the NIO remains uniquely steric-dominated and the sea level budget leaves a residual of 0.98 mm/yr (~ 20% of the total trend), which, while comparable to uncertainties in individual components, highlights remaining challenges in fully closing the regional sea level budget.