Simulated Greenland Surface Mass Balance in the GISS ModelE2 GCM: Role of the Ice Sheet Surface

The rate of growth or retreat of the Greenland and Antarctic ice sheets remains a highly uncertain component of future sea level change. Here we examine the simulation of Greenland ice sheet surface mass balance (GrIS SMB) in the NASA Goddard Institute for Space Studies (GISS) ModelE2 General Circulation Model (GCM). GCMs are often limited in their ability to represent SMB compared with polarregion Regional Climate Models (RCMs). We compare ModelE2 simulated GrIS SMB for presentday (19962005) simulations with fixed ocean conditions, at a spatial resolution of 2 latitude by 2.5 longitude (~200 km), with SMB simulated by the Modle Atmosphrique Rgionale (MAR) RCM (19962005 at a 25 km resolution). ModelE2 SMB agrees well with MAR SMB on the whole, but there are distinct spatial patterns of differences and large differences in some SMB components. The impact of changes to the ModelE2 surface are tested, including a subgridscale representation of SMB with surface elevation classes. This has a minimal effect on ice sheetwide SMB, but corrects local biases. Replacing fixed surface albedo with satellitederived values and an agedependent scheme has a larger impact, increasing simulated melt by 60100%. We also find that lower surface albedo can enhance the effects of elevation classes. Reducing ModelE2 surface roughness length to values closer to MAR reduces sublimation by ~50%. Further work is required to account for meltwater refreezing in ModelE2, and to understand how differences in atmospheric processes and model resolution influence simulated SMB

Efficient communication protection of many-core systems against active attackers

Many-core system-on-chips, together with their established communication infrastructures, Networks-on-Chip (NoC), are growing in complexity, which encourages the integration of third-party components to simplify and accelerate production processes. However, this also adversely exposes the surface for attacks through the injection of hardware Trojans. This work addresses active attacks on NoCs and focuses on the integrity and availability of transmitted data. In particular, we consider the modification and/or dropping of data during transmission as active attacks that might be performed by malicious routers. To mitigate the impact of such active attacks, we propose two lightweight solutions that respect the performance constraints of NoCs. Assuming the presence of symmetric keys, these approaches combine lightweight authentication codes for integrity protection with network coding for increased efficiency and robustness. The proposed solutions prevent undetected modifications and significantly increase availability through a reliable detection of attacks. The efficiency of these solutions is investigated in different scenarios using cycle-accurate simulations and the area overhead is analyzed relative to state-of-the-art many-core system. The results demonstrate that one authentication scheme with network coding protects the integrity of data to a low residual error of 1.36% at 0.2 attack probability with an area overhead of 2.68%. For faster and more flexible evaluation, an analytical approach is developed which is validated against the cycle-accurate simulations. The analytical approach is more than 1000× faster while having a maximum estimation error of 5%. Moreover, the analytical model provides a deeper insight into the system’s behavior. For example, it reveals which factors influence the performance parameters

Assimilation of satellite-derived melt extent increases melt simulated by MAR over the Amundsen sector (West Antarctica)

Surface melt over the Antarctic ice shelves is one of the largest uncertainties related to sea level rise over the 21st century. However, current climate models still struggle to accurately represent it, limiting our comprehension of processes driving melt spatial and temporal variability and its consequences on the stability of the Antarctic ice sheet. Recent advances in Earth monitoring thanks to satellites have enabled new estimations of Antarctic melt extent. They can detect if and where melt occurs, while the amount of meltwater produced can only be deduced from model simulations. In order to combine advantages of both tools, we present new melt estimates based on a regional climate model assimilating the satellite-derived melt extent. This improves the comparison between model and satellite estimates paving the way for a re-estimation of the amount of melt produced each year on the surface of the entire Antarctic ice sheet.La fonte de surface sur les plateformes de glace en Antarctique est l'une des plus grandes incertitudes liées à l'augmentation du niveau de la mer pendant le 21e siècle. Cependant, les modèles climatiques actuels peinent encore à la représenter avec précision, ce qui limite la compréhension des processus expliquant sa variabilité spatiale et temporelle et ses conséquences sur la stabilité de l’inlandsis de l’Antarctique. Les progrès récents de surveillance de la Terre grâce aux satellites ont permis de créer de nouvelles estimations de l'étendue de la fonte en Antarctique. Ceux-ci peuvent détecter si et où la fonte se produit, tandis que la quantité d'eau de fonte produite ne peut par contre être déduite que de simulations climatiques. Afin de combiner les avantages des deux outils, nous présentons de nouvelles estimations de la fonte basées sur un modèle climatique régional assimilant l'étendue de la fonte dérivée des satellites. Cela améliore la comparaison entre les estimations du modèle et du satellite, ouvrant ainsi la voie à une ré-estimation de la quantité de fonte produite chaque année à la surface de l'ensemble de l'inlandsis de l’Antarctique

Investigation of the natural sand transport on the Belgian Continental shelf: BUDGET (<u>B</u>eneficial <u>u</u>sage of <u>d</u>ata and <u>g</u>eo-<u>e</u>nvironmental <u>t</u>echniques)

On the Belgian continental shelf (BCS), a variety of sediment dynamical studies have been performed both by governmental organisations and research institutions. Each study proposed to achieve a better insight in the sediment dynamical processes taking place on a specific spatial scale and during a particular time period. However, all these studies contain a piece of information, which contribute to the global sediment dynamical behaviour of the sediments of the BCS.In the course of the project, an overview has been produced of all these studies. Most of the data has been re-evaluated and the results were compiled in a synthesis map to characterise the natural sand transport on the Belgian continental shelf. The map indicates the general nature of the surficial sediments superimposed with the occurrence of larger bedforms. Additionally, areas are indicated where the thickness of the quaternary deposits is less than 2.5 mas these sediments might take part in the sediment transport process. To illustrate the hydrodynamics of the BCS, current ellipses have been selected based on modelling results on a 750 mgrid resolution and locations were indicated where current meter or other hydrodynamic data has been collected. Towards the directions of sediment transport, a variety of arrows are drawn whereby a distinction is made between transport vectors based on geo-environmental methods and those based on in-situ sediment transport measurements and on modelling results. If available, quantities are added uniformised in tonnes/m/day.The study also included a critical analysis of the data and methods used. The deduction of residual transport directions was evaluated on the basis of the asymmetry of bedforms, tracer experiments, sediment differentiation, current and suspended sediment concentration measurements and based on numerical sediment transport modelling. Evaluation criteria were set-up regarding the different space and time scales involved. The influence of hydro-meteorological conditions on the sediment dynamics was discussed.The results allowed defining gaps in the present knowledge and including recommendations for future research and propositions for an integrated research programme on the Belgian continental shelf. Main emphasis is put on an efficient mapping of the seafloor including the set-up of an automated characterisation of seabed sediments albeit combined with a suitable sampling strategy. Regarding hydrodynamical and sand transport measurements, the development of a multi-sensor bottom frame is recommended including a realistic quantification of sediment fluxes through the water column.To enhance the efficiency and practical use of seabed data, the set-up of an overall Geographical Information System (GIS) is highly recommended including guidelines and protocols on the prerequisites of mapping and sampling projects since this would largely facilitate the set-up and evaluation of environmental impact assessments. The project largely benefited from contributions from foreign researchers from France, England and the Netherlands

Sensitivity of a Greenland ice sheet model to atmospheric forcing fields

International audiencePredicting the climate for the future and how it will impact ice sheet evolution requires coupling ice sheet models with climate models. However, before we attempt to develop a realistic coupled setup, we propose, in this study, to first analyse the impact of a model simulated climate on an ice sheet. We undertake this exercise for a set of regional and global climate models. Modelled near surface air temperature and precipitation are provided as upper boundary conditions to the GRISLI (GRenoble Ice Shelf and Land Ice model) hybrid ice sheet model (ISM) in its Greenland configuration. After 20 kyrs of simulation, the resulting ice sheets highlight the differences between the climate models. While modelled ice sheet sizes are generally comparable to the observed one, there are considerable deviations among the ice sheets on regional scales. These deviations can be explained by biases in temperature and precipitation near the coast. This is especially true in the case of global models. But the deviations between the climate models are also due to the differences in the atmospheric general circulation. To account for these differences in the context of coupling ice sheet models with climate models, we conclude that appropriate downscaling methods will be needed. In some cases, systematic corrections of the climatic variables at the interface may be required to obtain realistic results for the Greenland ice sheet (GIS)

Genomic sequence analysis and characterization of Sneathia amnii sp. nov

Background Bacteria of the genus Sneathia are emerging as potential pathogens of the female reproductive tract. Species of Sneathia, which were formerly grouped with Leptotrichia, can be part of the normal microbiota of the genitourinary tracts of men and women, but they are also associated with a variety of clinical conditions including bacterial vaginosis, preeclampsia, preterm labor, spontaneous abortion, post-partum bacteremia and other invasive infections. Sneathia species also exhibit a significant correlation with sexually transmitted diseases and cervical cancer. BecauseSneathia species are fastidious and rarely cultured successfully in vitro; and the genomes of members of the genus had until now not been characterized, very little is known about the physiology or the virulence of these organisms. Results Here, we describe a novel species, Sneathia amnii sp. nov, which closely resembles bacteria previously designated Leptotrichia amnionii . As part of the Vaginal Human Microbiome Project at VCU, a vaginal isolate of S. amnii sp. nov. was identified, successfully cultured and bacteriologically cloned. The biochemical characteristics and virulence properties of the organism were examined in vitro, and the genome of the organism was sequenced, annotated and analyzed. The analysis revealed a reduced circular genome of ~1.34 Mbp, containing ~1,282 protein-coding genes. Metabolic reconstruction of the bacterium reflected its biochemical phenotype, and several genes potentially associated with pathogenicity were identified. Conclusions Bacteria with complex growth requirements frequently remain poorly characterized and, as a consequence, their roles in health and disease are unclear. Elucidation of the physiology and identification of genes putatively involved in the metabolism and virulence of S. amnii may lead to a better understanding of the role of this potential pathogen in bacterial vaginosis, preterm birth, and other issues associated with vaginal and reproductive health