A three-dimensional full Stokes model of the grounding line dynamics: effect of a pinning point beneath the ice shelf

The West Antarctic ice sheet is confined by a large area of ice shelves, fed by inland ice through fast flowing ice streams. The dynamics of the grounding line, which is the line-boundary between grounded ice and the downstream ice shelf, has a major influence on the dynamics of the whole ice sheet. However, most ice sheet models use simplifications of the flow equations, as they do not include all the stress components, and are known to fail in their representation of the grounding line dynamics. Here, we present a 3-D full Stokes model of a marine ice sheet, in which the flow problem is coupled with the evolution of the upper and lower free surfaces, and the position of the grounding line is determined by solving a contact problem between the shelf/sheet lower surface and the bedrock. Simulations are performed using the open-source finite-element code Elmer/Ice within a parallel environment. The model's ability to cope with a curved grounding line and the effect of a pinning point beneath the ice shelf are investigated through prognostic simulations. Starting from a steady state, the sea level is slightly decreased to create a contact point between a seamount and the ice shelf. The model predicts a dramatic decrease of the shelf velocities, leading to an advance of the grounding line until both grounded zones merge together, during which an ice rumple forms above the contact area at the pinning point. Finally, we show that once the contact is created, increasing the sea level to its initial value does not release the pinning point and has no effect on the ice dynamics, indicating a stabilising effect of pinning points

Resurrecting the alien director: Jean-Pierre Jeunet in Hollywood

This essay examines the critical reception of Jean-Pierre Jeunet's Alien Resurrection in the popular Anglo-American press, where the film was often discussed in terms that highlighted the director's status as an 'outsider'. The anxiety that the film elicits among critics, it is argued, is a function of the very abjection that is depicted graphically within the film: a fear of the unclassifiable and of the crossing of boundaries

Enhanced basal lubrication and the contribution of the Greenland ice sheet to future sea-level rise

We assess the effect of enhanced basal sliding on the flow and mass budget of the Greenland ice sheet, using a newly developed parameterization of the relation between meltwater runoff and ice flow. A wide range of observations suggest that water generated by melt at the surface of the ice sheet reaches its bed by both fracture and drainage through moulins. Once at the bed, this water is likely to affect lubrication, although current observations are insufficient to determine whether changes in subglacial hydraulics will limit the potential for the speedup of flow. An uncertainty analysis based on our best-fit parameterization admits both possibilities: continuously increasing or bounded lubrication. We apply the parameterization to four higher-order ice-sheet models in a series of experiments forced by changes in both lubrication and surface mass budget and determine the additional mass loss brought about by lubrication in comparison with experiments forced only by changes in surface mass balance. We use forcing from a regional climate model, itself forced by output from the European Centre Hamburg Model (ECHAM5) global climate model run under scenario A1B. Although changes in lubrication generate widespread effects on the flow and form of the ice sheet, they do not affect substantial net mass loss; increase in the ice sheet’s contribution to sea-level rise from basal lubrication is projected by all models to be no more than 5% of the contribution from surface mass budget forcing alone

Dynamically coupling full Stokes and shallow shelf approximation for marine ice sheet flow using Elmer/Ice (v8.3)

Ice flow forced by gravity is governed by the full Stokes (FS) equations, which are computationally expensive to solve due to the nonlinearity introduced by the rheology. Therefore, approximations to the FS equations are commonly used, especially when modeling a marine ice sheet (ice sheet, ice shelf, and/or ice stream) for 103 years or longer. The shallow ice approximation (SIA) and shallow shelf approximation (SSA) are commonly used but are accurate only for certain parts of an ice sheet. Here, we report a novel way of iteratively coupling FS and SSA that has been implemented in Elmer/Ice and applied to conceptual marine ice sheets. The FS–SSA coupling appears to be very accurate; the relative error in velocity compared to FS is below 0.5&thinsp;% for diagnostic runs and below 5&thinsp;% for prognostic runs. Results for grounding line dynamics obtained with the FS–SSA coupling are similar to those obtained from an FS model in an experiment with a periodical temperature forcing over 3000 years that induces grounding line advance and retreat. The rapid convergence of the FS–SSA coupling shows a large potential for reducing computation time, such that modeling a marine ice sheet for thousands of years should become feasible in the near future. Despite inefficient matrix assembly in the current implementation, computation time is reduced by 32&thinsp;%, when the coupling is applied to a 3-D ice shelf.</p

Future Sea Level Change Under Coupled Model Intercomparison Project Phase 5 and Phase 6 Scenarios From the Greenland and Antarctic Ice Sheets

Projections of the sea level contribution from the Greenland and Antarctic ice sheets (GrIS and AIS) rely on atmospheric and oceanic drivers obtained from climate models. The Earth System Models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6) generally project greater future warming compared with the previous Coupled Model Intercomparison Project phase 5 (CMIP5) effort. Here we use four CMIP6 models and a selection of CMIP5 models to force multiple ice sheet models as part of the Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6). We find that the projected sea level contribution at 2100 from the ice sheet model ensemble under the CMIP6 scenarios falls within the CMIP5 range for the Antarctic ice sheet but is significantly increased for Greenland. Warmer atmosphere in CMIP6 models results in higher Greenland mass loss due to surface melt. For Antarctica, CMIP6 forcing is similar to CMIP5 and mass gain from increased snowfall counteracts increased loss due to ocean warming

Результаты открытого многоцентрового неинтервенционного исследования клинической эффективности и переносимости эторикоксиба при остеоартрите и неспецифической боли в спине с дополнительной оценкой влияния препарата на «центральные» проявления боли

The formation of chronic musculoskeletal pain (MSP) is a multifactorial process, in its pathogenesis mechanism of central sensitization (CS) plays an important role.Objective: to evaluate the effectiveness of etoricoxib at a dose of 60 mg per day in diseases accompanied by moderate/severe chronic MPS, with an additional analysis of the effect of this drug on the manifestations of CS.Patients and methods. An open observational study, 790 patients (71.6% women, mean age 54.5±13.0 years) with osteoarthritis and chronic nonspecific back pain received etoricoxib 60 mg/day for 2 weeks. The dynamics of pain, dysfunction, fatigue, sleep disturbances, general health assessment (GHA) on a numerical rating scale (NRS 0–10), as well as signs of CS according to part A of the CSI questionnaire were assessed.Results and discussion. After 2 weeks, the intensity of pain during movement, at rest and at night decreased on average by 58.8±24.1, 69.7±32.6 and 70.1±32.8% respectively; functional insufficiency by 58.2±22.5%, fatigue by 52.2±25.8%, GHA by 50.0±22.6%, sleep improvement by 54.3±25.8% was observed (p&lt;0.001 for all parameters). There was a decrease in the CSI value by an average of 33.1±14.5% (p&lt;0.001), as well as a decrease in the number of patients with highly probable CS (CSI ≥40) from 35.3 to 10.3% (p&lt;0.001). No serious drug-related complications were recorded. The overall frequency of adverse reactions was 5.9%, with dyspepsia and hypertension being the most common.Conclusion. Etoricoxib is an effective and relatively safe treatment for chronic MSP. It reduces the severity of CS, one of the central mechanisms of the pathogenesis of chronic MSP.Формирование хронической скелетно-мышечной боли (СМБ) – многофакторный процесс, в патогенезе которого существенную роль играет механизм центральной сенситизации (ЦС).Цель исследования – оценка эффективности эторикоксиба в дозе 60 мг/сут при заболеваниях, сопровождающихся умеренно выраженной/выраженной хронической СМБ, с дополнительным анализом влияния этого препарата на проявления ЦС.Пациенты и методы. Было проведено открытое наблюдательное исследование, в котором 790 пациентов (71,6% женщин, средний возраст 54,5±13,0 лет) с остеоартритом и хронической неспецифической болью в спине в течение 2 нед получали эторикоксиб по 60 мг/сут. Оценивалась динамика боли, нарушения функции, усталости, расстройств сна, общей оценки состояния здоровья (ООСЗ) по числовой рейтинговой шкале (ЧРШ, 0–10), а также признаков ЦС по части А опросника CSI.Результаты и обсуждение. Через 2 нед интенсивность боли при движении, в покое и ночью снизилась в среднем соответственно на 58,8±24,1; 69,7±32,6 и 70,1±32,8%, функциональная недостаточность – на 58,2±22,5%, усталость – на 52,2±25,8%, ООСЗ – на 50,0±22,6%, наблюдалось улучшение сна на 54,3±25,8% (р&lt;0,001 для всех параметров). Было отмечено снижение значения CSI в среднем на 33,1±14,5% (р&lt;0,001), а также числа пациентов с высоковероятной ЦС (CSI≥40) с 35,3 до 10,3% (р&lt;0,001). Не было зафиксировано серьезных лекарственных осложнений. Общая частота нежелательных реакций составила 5,9%, наиболее часто встречались диспепсия и артериальная гипертензия.Заключение. Эторикоксиб является эффективным и относительно безопасным средством для контроля хронической СМБ. Он снижает выраженность ЦС – одного из центральных механизмов патогенеза хронической СМБ

A full Stokes ice flow model for the vicinity of Dome Fuji, Antarctica, with induced anisotropy and fabric evolution

A three-dimensional, thermo-mechanically coupled ice flow model with induced anisotropy has been applied to a ～200 x 200 km domain around the Dome Fuji drill site, Antarctica. The model ("Elmer/Ice") is based on the open-source multi-physics package Elmer (http://www.csc.fi/elmer/) and solves the full Stokes equations. Flow-induced anisotropy in ice is accounted for by an implementation of the Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor ("CAFFE model"). Steady-state simulations for present-day climate conditions are conducted. The main findings are: (i) the flow regime at Dome Fuji is a complex superposition of vertical compression, horizontal extension and bed-parallel shear; (ii) for an assumed geothermal heat flux of 60 mW m^[-2] the basal temperature at Dome Fuji reaches the pressure melting point and the basal melting rate is ～0.35 mma^[-1]; (iii) in agreement with observational data, the fabric shows a strong single maximum at Dome Fuji, and the age of the ice is decreased compared to an isotropic scenario; (iv) as a consequence of spatially variable basal melting conditions, the basal age tends to be smaller where the ice is thicker and larger where the ice is thinner. The latter result is of great relevance for the consideration of a future drill site in the area