This study presents the first nationwide assessment of vanished glaciers in Switzerland. By comparing the Swiss Glacier Inventories SGI1973 and SGI2016, we identify 1019 vanished glaciers, representing more than 40% of all glaciers inventoried in 1973 and accounting for 13% (47±3 km²) of total glacier area loss. Glacier disappearance was most widespread along the main Alpine divide, in regions with relatively low peak elevations. Most vanished glaciers were very small (<0.10 km2) and steep, south- or east-facing glaciers more often vanished with respect to the initial glacier distribution. In the 2300–2550 m elevation band, vanished glaciers contributed over 30% of total area loss. Regionally, the Rhine basin hosts the largest number of vanished glaciers (423), while the Po (39%) and Danube (55%) basins have the highest share of glaciers disappearing with respect to the initial number. These findings underscore the relevance of systematically including vanished glaciers in change assessments. With a new inventory underway and two extreme melt years in 2022 and 2023, this study provides a benchmark for tracking continued glacier extinction in the Swiss Alps.

The Lunana region in Bhutan, which hosts four large glacial lakes with significant hazard potential, has undergone rapid changes over the past decade. Using PlanetScope satellite scenes, we mapped ice velocities at monthly intervals from 2017 to 2023. We reveal that the disintegration of Thorthormi Glacier’s terminus in 2022 coincided with year-on-year acceleration with mean surface velocities as high as 448 ± 10.0 m a−1 by 2021, and seasonal variability in surface velocity magnitude >144.6 ± 10.0 m a−1. This acceleration is attributed to a reduction in basal drag as the terminus reached flotation, evidenced by the calving of tabular icebergs. While Bechung, Raphstreng and Lugge exhibited a similar interannual velocity trend, the upper regions of Bechung and Raphstreng showed a higher seasonal range (31% and 19.9% from their mean) compared to Lugge (4.2%). In the upper regions, we also find a decelerating velocity trend (3.5–20.6% over the 6 years), which is attributed to surface thinning and reducing driving stresses. We show that accelerating trends in velocity can be a precursor to higher rates of retreat and rapid lake expansion, demonstrating the importance of continuous monitoring of lake-terminating glacier ice velocities in the Himalaya.

Ophiuroids have been major components of marine seafloor communities since the early Paleozoic. Past paleontological studies, especially those dealing with Paleozoic specimens, have based taxonomic descriptions on whole-skeleton morphology while mostly overlooking disarticulated ossicles, causing a large gap in our knowledge of Paleozoic ophiuroids. Recent studies of Mesozoic and Cenozoic ophiuroids, however, have examined the fine-scale morphological details of ophiuroid arm plates and have documented useful characters for taxonomic assignment. Here, we use similar methods for examining disarticulated ophiuroids to describe a Late Mississippian (Serpukhovian) ophiuroid fauna based solely on dissociated ossicles, preserved as microfossils and sieved from shale samples collected from the Indian Springs Shale Member of the Big Clifty Formation in Sulphur, Indiana, USA. We describe 11 species in total, 10 of which are new to science: Umerophiura daki n. sp., Strataster lisae n. sp., Schoenaster limbeckae n. sp., Vandelooaster douglasi n. sp., Furcaster wardi n. sp., Furcaster mccantae n. sp., Furcaster coulombeae n. sp., Sulphaster odellettorum n. gen. n. sp., Covidaster medicus n. gen. n. sp., and Suchaster granulosus n. gen. n. sp. Also present are ossicles of Cholaster sp. indet. The assemblage described in this paper significantly increases the known ophiuroid diversity in the Mississippian, yielding more species than all previous reports on Mississippian ophiuroids combined. Furthermore, our study shows that the evolution of the modern ophiuroid clade began much earlier than expected. Our results imply that the microfossil record of ophiuroids is paramount to unveiling the true paleobiodiversity of this evolutionarily important echinoderm clade.

UUID: http://zoobank.org/21fc0302-5a9f-41de-b1e3-6972de4b57bc

The basal thermal state of the Antarctic ice sheet (AIS)—whether the base is frozen or thawed—fundamentally underpins its flow and is an important factor in understanding its large-scale response to external forcings. Here, we present a first synthesis of the AIS basal thermal state combining two indirect and independent methods: (1) a compilation of nine three-dimensional thermomechanical simulations that calculate AIS basal temperature as part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) and (2) an estimate of the basal slip ratio, defined as the ratio of observed surface speed to deformational speed. This synthesis is evaluated against direct observations from deep boreholes and predicted flowpaths for water originating from subglacial lakes detected by altimetry and radar sounding. The synthesis predicts a thawed bed across most of West Antarctica and localized regions in East Antarctica. Most of the Antarctic Peninsula, the Transantarctic Mountains and several regions of East Antarctica are likely frozen at the bed. Overall, our synthesis suggests 46% of the AIS bed is likely thawed, 18% likely frozen and the remaining 36% is uncertain. Additional observations, particularly at the continental scale, are required to improve our understanding of Antarctica’s basal thermal state.

In 1988, meteorological measurements started at the Spanish research station Juan Carlos I (JCI) on Livingston Island. A second station - Gabriel de Castilla (GdC) - was installed in 2005 on Deception Island. These long-term measurements improved our climatological understanding of the western region of the South Shetland Islands (SSI), a region that has received less attention than the more station-populated King George Island in the central SSI. Here, we present a complete climatological analysis of these stations after undertaking a full quality control process of the data. This analysis covers temperature, wind, precipitation, radiation, relative humidity and pressure, as well as trends and variability. The results show: 1) the stations along the western SSI coastline, particularly JCI, are warmer than those on the central SSI, especially in summer, 2) at GdC, winters are colder due to stagnant cold air pooling within the Deception Island caldera, 3) the importance of island orography in shaping local climatology, especially regarding wind patterns, and 4) the critical need to correct precipitation measurements for undercatchment of solid precipitation by common pluviometers. This study provides a climatological framework to support further research conducted in the region.

Glaciers provide critical ecosystem services, including water resources, biodiversity, cultural value and climate signals. But what makes a glacier a glacier? And when is a glacier no longer a glacier? Different glacier definitions can conflict. While a common definition emphasizes ‘past or present flow’, practical applications involve criteria like observable ice flow, crevassing, minimum thickness, minimum area, surficial features related to hydrology and/or debris cover and/or relative size. Increasingly, glacier inventories apply multiple criteria, acknowledging the nuanced, continuous nature of glacier retreat rather than a binary status. In the context of increasingly melting, shrinking and vanishing glaciers, as glaciologists consider when to declare a glacier lost, disappeared or dead, it is important to explore glacier definitions and their application. Ultimately, the glacier definition applied depends on the specific context, purpose and audience. This also highlights the need for careful language choice, clear communication and localized expertise in considering glacier loss.