Mountain permafrost, constituting 30% of the global permafrost area, is sensitive to climate change and strongly impacts mountain ecosystems and communities. This study examines 21st century permafrost warming in European mountains using decadal ground temperature data from sixty-four boreholes in the Alps, Scandinavia, Iceland, Sierra Nevada and Svalbard. During 2013–2022, warming rates at 10 metres depth exceed 1 °C dec⁻¹ in cases, generally surpassing previous estimates because of accelerated warming and the use of a comprehensive data set. Substantial permafrost warming occurred at cold and ice-poor bedrock sites at high elevations and latitudes, at rates comparable to surface air temperature increase. In contrast, latent heat effects in ice-rich ground near 0 °C reduce warming rates and mask important changes of mountain permafrost substrates. The warming patterns observed are consistent across all sites, depths and time periods. For the coming decades, the propagation of permafrost warming to greater depths is largely predetermined already.

Mass loss at the Greenland Ice Sheet is influenced by atmospheric processes controlling its surface mass balance, and by submarine melt and calving where glaciers terminate in fjords. There, an ice mélange – a composite matrix of calved ice bergs and sea ice – may provide a buttressing force on a glacier terminus and control terminus dynamics. Kangerlussuaq Glacier is a major outlet of the Greenland Ice Sheet, for which recent major retreat events in 2004/2005 and 2016–2018 coincided with the absence of an ice mélange in Kangerlussuaq Fjord. To better understand the response of Kangerlussuaq Glacier to climatic and oceanic drivers, a 2D flowline model is employed. Results indicate that an ice mélange buttressing force exerts a major control on calving frequency and rapid retreat. When an ice mélange forms in Kangerlussuaq Fjord, it provides stabilising forces and conditions favourable for winter terminus re-advance. When it fails to form during consecutive years, model results indicate that Kangerlussuaq Glacier is primed to retreat into the large overdeepenings in Kangerlussuaq Fjord, and to terminus positions more than 30 km farther inland, implying that excessive mass loss from Kangerlussuaq Glacier by the year 2065 cannot be excluded.

Irregular climate events frequently occur in Southeast Asia due to the numerous climate patterns combining. Thailand sits at the confluence of these interactions, and consequently experiences major hydrological events, such as droughts. Proxy data, speleothem records, lake sediment sequences and tree ring chronologies were used to reconstruct paleo drought conditions. These trends were compared with modelled and historic El Niño Southern Oscillation (ENSO) data to assess if the ENSO climate phenomena is causing droughts in Thailand. Drought periods were found to occur both during El Niño events and ENSO neutral conditions. This indicates droughts are not a product of one climate pattern, but likely the result of numerous patterns interacting. There is uncertainty regarding how climate patterns will evolve under climate change, but changes in amplitude and variability could potentially lead to more frequent and wider reaching hydrological disasters. It is vital that policies are implemented to cope with the resulting social and economic repercussions, including diversification of crops and reorganisation of water consumption behaviour in Thailand.

The northern sector of the Greenland Ice Sheet contains some of the ice sheet's last remaining glaciers with floating ice tongues. One of these glaciers is Ryder Glacier, which has been relatively stable in recent decades, in contrast to the neighbouring Petermann and C.H. Ostenfeld glaciers. Understanding Ryder Glacier's future behaviour is important as ice-tongue loss could lead to acceleration and increased ice discharge. Meanwhile, it is unclear whether Greenland-wide modelling attempts are able to accurately resolve the influence of fjord and bedrock topography and small-scale variations in ice dynamics for a glacier like Ryder. To fill these gaps, here we conduct targeted high-resolution modelling of Ryder Glacier until the year 2300. We find that mass loss is dominated by discharge under a low-emissions scenario all the way to 2300, leading to a sea level contribution of between 0.8 and 2 mm depending on the amount of ocean warming. Discharge also plays a key role under a high-emissions scenario up until 2100, after which a strongly negative surface mass balance becomes the dominant driver of mass loss. This negative surface mass balance leads to a much higher sea level rise contribution by 2300 of between 44 and 52 mm, with little sensitivity to the range of ocean warming scenarios used in this study.

Ice–ocean interactions at Greenland Ice Sheet outlet glaciers exert critical control on ice-sheet mass loss and, consequently, global sea-level rise. The GEOEO North of Greenland 2024 icebreaker expedition acquired a breadth of data in the unsurveyed Victoria Fjord, north-western Greenland, to assess the causes of the rapid break-up of the C.H. Ostenfeld ice tongue in 2002, and the environmental changes since. The observations reveal inflows of warm (>0 °C) Atlantic water reaching the grounded ice margin. We propose that Atlantic warm water pulses entering the Arctic Ocean reach north-western Greenland, where they interact with glacier fronts, enhance ice discharge, and amplify the climate-driven retreat of marine-terminating glaciers. The collapse of C.H. Ostenfeld’s ice tongue, unlike the slower retreats of the ice tongues of neighbouring Petermann and Ryder glaciers, reflects unimpeded Atlantic water inflow due to the absence of a shielding bathymetric sill, a function of the region’s bedrock geology.

Sweden currently hosts 270 glaciers, four of which belong to the 61 reference glaciers monitored worldwide. Eight Swedish glaciers disappeared during the warm summer of 2024, and under the global warming scenario associated with current climate policies, all four Swedish reference glaciers (Mårmaglaciären, Storglaciären, Rabots glaciär, and Riukojietna) are projected to vanish within this century. Such change will have implications for people, ecosystems, infrastructure, and local meteorological processes, highlighting the need to better constrain the resultant emerging post-glacial landscapes. During 2024–2025, we conducted radio-echo sounding (RES) surveys on the four Swedish reference glaciers and obtained a total of 40470 ice thickness point measurements. The mean and maximum measured ice thicknesses are 97 and 242 m for Mårmaglaciären, 88 and 225 m for Storglaciären, 85 and 158 m for Rabots glaciär, and 32 and 87 m for Riukojietna. The corresponding mean ice-thickness uncertainties are 12.0, 12.4, 11.4, and 7.5 m, respectively. The RES-measured ice thicknesses were used to produce high-resolution (10 m × 10 m) maps of ice thickness distribution and subglacial topography for each reference glacier, and to calculate their ice volumes as 0.32 (Mårmaglaciären), 0.25 (Storglaciären), 0.23 (Rabots glaciär), and 0.10 km³ (Riukojietna). The RES data for the four reference glaciers are available at https://doi.org/10.17043/tarfala-marma-res-survey-1, https://doi.org/10.17043/tarfala-storglaciaren-res-survey-1, https://doi.org/10.17043/tarfala-rabot-res-survey-1, and https://doi.org/10.17043/tarfala-rivgojiehkki-res-survey-1 (Wang et al., 2026b, d, a, c). The ice thickness and subglacial topography for the four reference glaciers are available at https://doi.org/10.17043/tarfala-marma-res-2, https://doi.org/10.17043/tarfala-storglaciaren-res-2, https://doi.org/10.17043/tarfala-rabot-res-2, and https://doi.org/10.17043/tarfala-rivgojiehkki-res-2 (Wang et al., 2025a, d, b, c).