Empirical Removal of Tides and Inverse Barometer Effect on DInSAR From Double DInSAR and a Regional Climate Model

Ice shelves-the floating extensions of the Antarctic ice sheet-regulate the Antarctic contribution to sea-level rise by restraining the grounded ice flowing from upstream. Therefore, ice-shelf change (e.g., ice-shelf thinning) results in accelerated ice discharge into the ocean, which has a direct effect on sea level. Studying ice-shelf velocity allows the monitoring of the ice shelves' stability and evolution. Differential synthetic aperture radar interferometry (DInSAR) is a common technique from which highly accurate velocity maps can be inferred at high resolution. Because ice shelves are afloat, small sea-level changes-i.e., ocean tides and varying atmospheric pressure (aka inverse barometer effect) lead to vertical displacements. If not accounted for in the interferometric process, these effects will induce a strong bias in the horizontal velocity estimation. In this article, we present an empirical DInSAR correction technique from geophysical models and double DInSAR, with a study on its variance propagation. The method is developed to be used at large coverage on short timescales, essential for the near-continuous monitoring of rapidly changing areas on polar ice sheets. We used Sentinel-1 SAR acquisitions in interferometric wide and extra -wide swath modes. The vertical interferometric bias is estimated using a regional climate model (MAR) and a tide model (CATS2008). The study area is located on the Roi Baudouin Ice Shelf in Dronning Maud Land, East Antarctica. Results show a major decrease (67 m·a -1 ) in the vertical-induced displacement bias.Fil: Glaude, Quentin. Université Libre de Bruxelles; Bélgica. Université de Liège; BélgicaFil: Amory, Charles. Universite de Liege. Faculty Of Applied Sciences.; BélgicaFil: Berger, Sophie. Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung; Alemania. Université Libre de Bruxelles; BélgicaFil: Derauw, Dominique Maurice. Universidad Nacional de Río Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiología y Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pattyn, Frank. Vrije Unviversiteit Brussel; Bélgica. Université Libre de Bruxelles; BélgicaFil: Barbier, Christian. Université de Liège; BélgicaFil: Orban, Anne. Université Catholique de Louvain; Bélgic

Added value of the regional climate model MAR for simulating the surface mass balance of the Antarctic ice sheet compared to a global climate model (ACCESS1.3)

Due to their ability to produce climate projections, General circulation models (GCM) are often used to provide estimates of the surface mass balance (SMB) of the Antarctic ice sheet that can be used to constrain ice sheet models. However, GCM still benefit from a poor representation of polar climate specificities such as stable boundary layers, polar clouds or interactions between snow-covered surfaces and the atmosphere. In this study, we highlight the importance of downscaling GCM outputs from the Fifth Climate Model Intercomparison Project (CMIP5) with a regional climate model to provide accurate estimates of the Antarctic SMB. For that purpose, the regional climate model MAR is forced by 6-hourly outputs from ACCESS1.3 that is currently considered as one of the best GCM from CMIP5 over the Antarctic ice sheet. Estimates of the SMB computed by MAR and ACCESS1.3 are evaluated against SMB observations. Even if the temporal variability of the SMB is forced by the driving GCM, the comparison shows that MAR improves the spatial variability of the Antarctic SMB, emphasizing the added value of using a polar RCM for downscaling GCM outputs at high latitudes

Comparison Between Surface Melt Estimation From Sentinel-1 Synthetic Aperture Radar and a Regional Climate Model. Case Study Over the Roi Baudouin Ice Shelf, East Antarctica

peer reviewedAntarctica is the largest potential contributor to sea-level rise and needs to be monitored. It is also one of the first victims of global warming. However, it is often difficult to obtain high-resolution data on this vast and distant continent. Thanks to the Copernicus space program providing free and open access to high-quality data, this paper aims to show the complementarity between Sentinel-1 images and Modèle Atmosphérique régional (MAR) data over Antarctica. This study is conducted over Roi Baudouin Ice Shelf. The complementarity between the two datasets is established by a quantitative, temporal, and spatial comparison of the amplitude information of the radar signal and several variables modelled by MAR. Comparisons show strong spatial correlations between MAR variables representing melt and the backscatter coefficient recorded by the satellite. While temporal and quantitative analyses also give impressive results, further investigations are required to explain contrasting behaviors in other different areas of the ice shelf

Greater Greenland Ice Sheet contribution to global sea level rise in CMIP6

Future climate projections show a marked increase in Greenland Ice Sheet (GrIS) runoff during the 21st century, a direct consequence of the Polar Amplification signal. Regional climate models (RCMs) are a widely used tool to downscale ensembles of projections from global climate models (GCMs) to assess the impact of global warming on GrIS melt and sea level rise contribution. Initial results of the CMIP6 GCM model intercomparison project have revealed a greater 21st century temperature rise than in CMIP5 models. However, so far very little is known about the subsequent impacts on the future GrIS surface melt and therefore sea level rise contribution. Here, we show that the total GrIS sea level rise contribution from surface mass loss in our high-resolution (15 km) regional climate projections is 17.8 ± 7.8 cm in SSP585, 7.9 cm more than in our RCP8.5 simulations using CMIP5 input. We identify a +1.3 °C greater Arctic Amplification and associated cloud and sea ice feedbacks in the CMIP6 SSP585 scenario as the main drivers. Additionally, an assessment of the GrIS sea level contribution across all emission scenarios highlights, that the GrIS mass loss in CMIP6 is equivalent to a CMIP5 scenario with twice the global radiative forcing.Peer reviewe

Reconstructions of the 1900–2015 Greenland ice sheet surface mass balance using the regional climate MAR model

With the aim of studying the recent Greenland ice sheet (GrIS) surface mass balance (SMB) decrease relative to the last century, we have forced the regional climate MAR (Modèle Atmosphérique Régional; version 3.5.2) model with the ERA-Interim (ECMWF Interim Re-Analysis; 1979–2015), ERA-40 (1958–2001), NCEP–NCARv1 (National Centers for Environmental Prediction–National Center for Atmospheric Research Reanalysis version 1; 1948–2015), NCEP–NCARv2 (1979–2015), JRA-55 (Japanese 55-year Reanalysis; 1958–2014), 20CRv2(c) (Twentieth Century Reanalysis version 2; 1900–2014) and ERA-20C (1900–2010) reanalyses. While all these forcing products are reanalyses that are assumed to represent the same climate, they produce significant differences in the MAR-simulated SMB over their common period. A temperature adjustment of +1 °C (respectively −1 °C) was, for example, needed at the MAR boundaries with ERA-20C (20CRv2) reanalysis, given that ERA-20C (20CRv2) is ∼ 1 °C colder (warmer) than ERA-Interim over Greenland during the period 1980–2010. Comparisons with daily PROMICE (Programme for Monitoring of the Greenland Ice Sheet) near-surface observations support these adjustments. Comparisons with SMB measurements, ice cores and satellite-derived melt extent reveal the most accurate forcing datasets for the simulation of the GrIS SMB to be ERA-Interim and NCEP– NCARv1. However, some biases remain in MAR, suggesting that some improvements are still needed in its cloudiness and radiative schemes as well as in the representation of the bare ice albedo.Results from all MAR simulations indicate that (i) the period 1961–1990, commonly chosen as a stable reference period for Greenland SMB and ice dynamics, is actually a period of anomalously positive SMB (∼ +40 Gt yr−1) compared to 1900–2010; (ii) SMB has decreased significantly after this reference period due to increasing and unprecedented melt reaching the highest rates in the 120- year common period; (iii) before 1960, both ERA-20C and 20CRv2-forced MAR simulations suggest a significant precipitation increase over 1900–1950, but this increase could be the result of an artefact in the reanalyses that are not well-enough constrained by observations during this period and (iv) since the 1980s, snowfall is quite stable after having reached a maximum in the 1970s. These MAR-based SMB and accumulation reconstructions are, however, quite similar to those from Box (2013) after 1930 and confirm that SMB was quite stable from the 1940s to the 1990s. Finally, only the ERA-20C-forced simulation suggests that SMB during the 1920–1930 warm period over Greenland was comparable to the SMB of the 2000s, due to both higher melt and lower precipitation than normal

VECU QUOTIDIEN DES FEMMES CESARISEES SUR LES INFECTIONS POST OPERATOIRE

L'Organisation Mondiale de la Santé précise que l'infection post césarienne constitue un problème de santé publique partout au monde, dans les pays industrialisés aussi bien que dans les Pays en développement. L'auteur estime que sur l'ensemble des cas de chirurgie abdominale dans le monde, 2 milliards des opérés présentent l'infection post-opératoire dont 29,7% concernent les infections post-césariennes. Objectif de cette étude est de comprendre le vécu quotidien des femmes césarisées ayant eu une infection du site opératoire afin d'améliorer leur prise en charge. Une étude qualitative d'inspiration phénoménologique dont  la population est constituée des femmes qui ont subi la césarienne dont leurs plaies opératoires sont infectées en post-opératoire dans le service de gyneco-obstetrique de l'Hôpital Général de Référence d’Isiro. La taille de l'Echantillon a été constituée progressivement sur terrain jusqu'à la saturation. Les enquêtées interrogées à ce sujet ont présenté leurs vécus différemment. Les unes ont déclarées que l'infection est la présence des secrétions purulentes du site opératoire qui s'accompagnent de douleurs atroces, les autres disent que l'infection est une situation stressante et dégoutante qui engendre des conséquences néfastes telles que le prolongement supplémentaire du séjour hospitalier des césarisées, l'hémorragie financière et une charge supplémentaire pour l'entourage. Une autre catégorie a argumenté sur la relation soignant-soignée et la prise en charge personnelle par les mesures d'hygiène corporelle et environnementale.L'Organisation Mondiale de la Santé précise que l'infection post césarienne constitue un problème de santé publique partout au monde, dans les pays industrialisés aussi bien que dans les Pays en développement. L'auteur estime que sur l'ensemble des cas de chirurgie abdominale dans le monde, 2 milliards des opérés présentent l'infection post-opératoire dont 29,7% concernent les infections post-césariennes. Objectif de cette étude est de comprendre le vécu quotidien des femmes césarisées ayant eu une infection du site opératoire afin d'améliorer leur prise en charge. Une étude qualitative d'inspiration phénoménologique dont  la population est constituée des femmes qui ont subi la césarienne dont leurs plaies opératoires sont infectées en post-opératoire dans le service de gyneco-obstetrique de l'Hôpital Général de Référence d’Isiro. La taille de l'Echantillon a été constituée progressivement sur terrain jusqu'à la saturation. Les enquêtées interrogées à ce sujet ont présenté leurs vécus différemment. Les unes ont déclarées que l'infection est la présence des secrétions purulentes du site opératoire qui s'accompagnent de douleurs atroces, les autres disent que l'infection est une situation stressante et dégoutante qui engendre des conséquences néfastes telles que le prolongement supplémentaire du séjour hospitalier des césarisées, l'hémorragie financière et une charge supplémentaire pour l'entourage. Une autre catégorie a argumenté sur la relation soignant-soignée et la prise en charge personnelle par les mesures d'hygiène corporelle et environnementale

Estimation of the Antarctic surface mass balance using the regional climate model MAR (1979-2015) and identification of dominant processes

The Antarctic ice sheet mass balance is a major component of the sea level budget and results from the difference of two fluxes of a similar magnitude: ice flow discharging in the ocean and net snow accumulation on the ice sheet surface, i.e. the surface mass balance (SMB). Separately modelling ice dynamics and SMB is the only way to project future trends. In addition, mass balance studies frequently use regional climate models (RCMs) outputs as an alternative to observed fields because SMB observations are particularly scarce on the ice sheet. Here we evaluate new simulations of the polar RCM MAR forced by three reanalyses, ERA-Interim, JRA-55, and MERRA-2, for the period 1979&ndash;2015, and we compare MAR results to the last outputs of the RCM RACMO2 forced by ERA-Interim. We show that MAR and RACMO2 perform similarly well in simulating coast-to-plateau SMB gradients, and we find no significant differences in their simulated SMB when integrated over the ice sheet or its major basins. More importantly, we outline and quantify missing or underestimated processes in both RCMs. Along stake transects, we show that both models accumulate too much snow on crests, and not enough snow in valleys, as a result of drifting snow transport fluxes not included in MAR and probably underestimated in RACMO2 by a factor of 3. Our results tend to confirm that drifting snow transport and sublimation fluxes are much larger than previous model-based estimates and need to be better resolved and constrained in climate models. Sublimation of precipitating particles in low-level atmospheric layers is responsible for the significantly lower snowfall rates in MAR than in RACMO2 in katabatic channels at the ice sheet margins. Atmospheric sublimation in MAR represents 363&thinsp; Gt &thinsp; yr&minus;1 over the grounded ice sheet for the year 2015, which is 16&thinsp;% of the simulated snowfall loaded at the ground. This estimate is consistent with a recent study based on precipitation radar observations and is more than twice as much as simulated in RACMO2 because of different time residence of precipitating particles in the atmosphere. The remaining spatial differences in snowfall between MAR and RACMO2 are attributed to differences in advection of precipitation with snowfall particles being likely advected too far inland in MAR.</p

The extraordinary March 2022 East Antarctica "heat" wave. Part I: observations and meteorological drivers

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The extraordinary March 2022 East Antarctica "heat" wave. Part II: impacts on the Antarctic ice sheet

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