Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica.

Enhanced submarine ice-shelf melting strongly controls ice loss in the Amundsen Sea embayment (ASE) of West Antarctica, but its magnitude is not well known in the critical grounding zones of the ASE's major glaciers. Here we directly quantify bottom ice losses along tens of kilometres with airborne radar sounding of the Dotson and Crosson ice shelves, which buttress the rapidly changing Smith, Pope and Kohler glaciers. Melting in the grounding zones is found to be much higher than steady-state levels, removing 300-490 m of solid ice between 2002 and 2009 beneath the retreating Smith Glacier. The vigorous, unbalanced melting supports the hypothesis that a significant increase in ocean heat influx into ASE sub-ice-shelf cavities took place in the mid-2000s. The synchronous but diverse evolutions of these glaciers illustrate how combinations of oceanography and topography modulate rapid submarine melting to hasten mass loss and glacier retreat from West Antarctica

Ефективність і конкурентоспроможність підприємств

Стаття присвячена пошуку зв'язку між поняттями ефективність і конкурентоспроможність та вивченню основних чинників, що впливають на отримання і утримання конкурентоспроможності протягом тривалого часу.Статья посвящена отысканию связи между понятиями "эффективность" и "конкурентоспособность" и изучению основных факторов, влияющих на достижение и удержание конкурентоспособности в долгосрочной перспективе.The article is devoted to searching a tie between the notions of "effectiveness" and "competitiveness"; and scrutinizing main factors, which effect reaching and keeping competitiveness in a long-term perspective

Mechanisms driving variability in the ocean forcing of Pine Island Glacier

Pine Island Glacier (PIG) terminates in a rapidly melting ice shelf, and ocean circulation and temperature are implicated in the retreat and growing contribution to sea level rise of PIG and nearby glaciers. However, the variability of the ocean forcing of PIG has been poorly constrained due to a lack of multi-year observations. Here we show, using a unique record close to the Pine Island Ice Shelf (PIIS), that there is considerable oceanic variability at seasonal and interannual timescales, including a pronounced cold period from October 2011 to May 2013. This variability can be largely explained by two processes: cumulative ocean surface heat fluxes and sea ice formation close to PIIS; and interannual reversals in ocean currents and associated heat transport within Pine Island Bay, driven by a combination of local and remote forcing. Local atmospheric forcing therefore plays an important role in driving oceanic variability close to PIIS

Recent progress in understanding and projecting regional and global mean sea-level change

Considerable progress has been made in understanding the present and future regional and global sea level in the 2 years since the publication of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Here, we evaluate how the new results affect the AR5’s assessment of (i) historical sea level rise, including attribution of that rise and implications for the sea level budget, (ii) projections of the components and of total global mean sea level (GMSL), and (iii) projections of regional variability and emergence of the anthropogenic signal. In each of these cases, new work largely provides additional evidence in support of the AR5 assessment, providing greater confidence in those findings. Recent analyses confirm the twentieth century sea level rise, with some analyses showing a slightly smaller rate before 1990 and some a slightly larger value than reported in the AR5. There is now more evidence of an acceleration in the rate of rise. Ongoing ocean heat uptake and associated thermal expansion have continued since 2000, and are consistent with ocean thermal expansion reported in the AR5. A significant amount of heat is being stored deeper in the water column, with a larger rate of heat uptake since 2000 compared to the previous decades and with the largest storage in the Southern Ocean. The first formal detection studies for ocean thermal expansion and glacier mass loss since the AR5 have confirmed the AR5 finding of a significant anthropogenic contribution to sea level rise over the last 50 years. New projections of glacier loss from two regions suggest smaller contributions to GMSL rise from these regions than in studies assessed by the AR5; additional regional studies are required to further assess whether there are broader implications of these results. Mass loss from the Greenland Ice Sheet, primarily as a result of increased surface melting, and from the Antarctic Ice Sheet, primarily as a result of increased ice discharge, has accelerated. The largest estimates of acceleration in mass loss from the two ice sheets for 2003–2013 equal or exceed the acceleration of GMSL rise calculated from the satellite altimeter sea level record over the longer period of 1993–2014. However, when increased mass gain in land water storage and parts of East Antarctica, and decreased mass loss from glaciers in Alaska and some other regions are taken into account, the net acceleration in the ocean mass gain is consistent with the satellite altimeter record. New studies suggest that a marine ice sheet instability (MISI) may have been initiated in parts of the West Antarctic Ice Sheet (WAIS), but that it will affect only a limited number of ice streams in the twenty-first century. New projections of mass loss from the Greenland and Antarctic Ice Sheets by 2100, including a contribution from parts of WAIS undergoing unstable retreat, suggest a contribution that falls largely within the likely range (i.e., two thirds probability) of the AR5. These new results increase confidence in the AR5 likely range, indicating that there is a greater probability that sea level rise by 2100 will lie in this range with a corresponding decrease in the likelihood of an additional contribution of several tens of centimeters above the likely range. In view of the comparatively limited state of knowledge and understanding of rapid ice sheet dynamics, we continue to think that it is not yet possible to make reliable quantitative estimates of future GMSL rise outside the likely range. Projections of twenty-first century GMSL rise published since the AR5 depend on results from expert elicitation, but we have low confidence in conclusions based on these approaches. New work on regional projections and emergence of the anthropogenic signal suggests that the two commonly predicted features of future regional sea level change (the increasing tilt across the Antarctic Circumpolar Current and the dipole in the North Atlantic) are related to regional changes in wind stress and surface heat flux. Moreover, it is expected that sea level change in response to anthropogenic forcing, particularly in regions of relatively low unforced variability such as the low-latitude Atlantic, will be detectable over most of the ocean by 2040. The east-west contrast of sea level trends in the Pacific observed since the early 1990s cannot be satisfactorily accounted for by climate models, nor yet definitively attributed either to unforced variability or forced climate change

Understanding biases in ICESat-2 data due to subsurface scattering using Airborne Topographic Mapper waveform data

The process of laser light reflecting from surfaces made of scattering materials that do not strongly absorb at the wavelength of the laser can involve reflections from hundreds or thousands of individual grains, which can introduce delays in the time between light entering and leaving the surface. These time-of-flight biases depend on the grain size and density of the medium, and thus they can result in spatially and temporally varying surface height biases estimated from laser altimeters, such as NASA's ICESat-2 (Ice Cloud, and land Elevation Satellite-2) mission. Modeling suggests that ICESat-2 might experience a bias difference as large as 0.1–0.2 m between coarse-grained melting snow and fine-grained wintertime snow (Smith et al., 2018), which exceeds the mission's requirement to measure seasonal height differences to an accuracy better than 0.1 m (Markus et al., 2017). In this study, we investigate these biases using a model of subsurface scattering, laser altimetry measurements from NASA's ATM (Airborne Topographic Mapper) system, and grain size estimates based on optical imagery of the ice sheet. We demonstrate that distortions in the shapes of waveforms measured using ATM are related to the optical grain size of the surface estimated using optical reflectance measurements and show that they can be used to estimate an effective grain radius for the surface. Using this effective grain radius as a proxy for the severity of subsurface scattering, we use our model with grain size estimates from optical imagery to simulate corrections for biases in ICESat-2 data due to subsurface scattering and demonstrate that, on the basis of large-scale averages, the corrections calculated based on the satellite optical imagery match the biases in the data. This work demonstrates that waveform-based altimetry data can measure the optical properties of granular surfaces and that corrections based on optical grain size estimates can correct for subsurface-scattering biases in ICESat-2 data.</p

A case study of mesospheric planetary waves observed over a three-radar network using empirical mode decomposition

In this paper an attempt is made to study equatorial Kelvin waves using a network of three radars: Kototabang (0.204° S, 100.320° E) meteor radar, Pameungpeuk (7.646° S, 107.688° E) medium-frequency radar, and Pontianak (0.003° S, 109.367° E) medium-frequency radar. We have used the continuous data gathered from the three radars during April–May 2010. Empirical mode decomposition (EMD), Lomb–Scargle periodogram (LSP) analysis, and wavelet techniques are used to study the temporal and altitude structures of planetary waves. Here, we used a novel technique called EMD to extract the planetary waves from wind data. The planetary waves of  ∼  6.5 and  ∼  3.6 days periodicity are observed in all three radar stations with peak amplitudes of about 12 and 11 m s−1, respectively. The 3.6-day wave has an average vertical wavelength from the three radars of about 42 km. The 3.6- and 6.5-day planetary waves are particularly strong in the zonal wind component. We find that the two waves are present at the 84–94 km height region. The observed features of the 3.6- and 6.5-day waves at the three tropical-latitude stations show some correspondence with the results reported for the equatorial-latitude stations

Community estimate of global glacier mass changes from 2000 to 2023

\ua9 The Author(s) 2025. Glaciers are indicators of ongoing anthropogenic climate change1. Their melting leads to increased local geohazards2, and impacts marine3 and terrestrial4,5 ecosystems, regional freshwater resources6, and both global water and energy cycles7,8. Together with the Greenland and Antarctic ice sheets, glaciers are essential drivers of present9,10 and future11, 12–13 sea-level rise. Previous assessments of global glacier mass changes have been hampered by spatial and temporal limitations and the heterogeneity of existing data series14, 15–16. Here we show in an intercomparison exercise that glaciers worldwide lost 273 \ub1 16 gigatonnes in mass annually from 2000 to 2023, with an increase of 36 \ub1 10% from the first (2000–2011) to the second (2012–2023) half of the period. Since 2000, glaciers have lost between 2% and 39% of their ice regionally and about 5% globally. Glacier mass loss is about 18% larger than the loss from the Greenland Ice Sheet and more than twice that from the Antarctic Ice Sheet17. Our results arise from a scientific community effort to collect, homogenize, combine and analyse glacier mass changes from in situ and remote-sensing observations. Although our estimates are in agreement with findings from previous assessments14, 15–16 at a global scale, we found some large regional deviations owing to systematic differences among observation methods. Our results provide a refined baseline for better understanding observational differences and for calibrating model ensembles12,16,18, which will help to narrow projection uncertainty for the twenty-first century11,12,18

Two decades of dynamic change and progressive destabilization on the Thwaites Eastern Ice Shelf

The Thwaites Eastern Ice Shelf (TEIS) buttresses the eastern grounded portion of Thwaites Glacier through contact with a pinning point at its seaward limit. Loss of this ice shelf will promote further acceleration of Thwaites Glacier. Understanding the dynamic controls and structural integrity of the TEIS is therefore important to estimating Thwaites' future sea-level contribution. We present a &sim;&thinsp;20-year record of change on the TEIS that reveals the dynamic controls governing the ice shelf's past behaviour and ongoing evolution. We derived ice velocities from MODIS and Sentinel-1 image data using feature tracking and speckle tracking, respectively, and we combined these records with ITS_LIVE and GOLIVE velocity products from Landsat-7 and Landsat-8. In addition, we estimated surface lowering and basal melt rates using the Reference Elevation Model of Antarctica (REMA) DEM in comparison to ICESat and ICESat-2 altimetry. Early in the record, TEIS flow dynamics were strongly controlled by the neighbouring Thwaites Western Ice Tongue (TWIT). Flow patterns on the TEIS changed following the disintegration of the TWIT around 2008, with a new divergence in ice flow developing around the pinning point at its seaward limit. Simultaneously, the TEIS developed new rifting that extends from the shear zone upstream of the ice rise and increased strain concentration within this shear zone. As these horizontal changes occurred, sustained thinning driven by basal melt reduced ice thickness, particularly near the grounding line and in the shear zone area upstream of the pinning point. This evidence of weakening at a rapid pace suggests that the TEIS is likely to fully destabilize in the next few decades, leading to further acceleration of Thwaites Glacier. &nbsp;</p