scholarly journals Impact of radiation penetration on Antarctic surface melt and subsurface snow temperatures in RACMO2.3p3

2021 ◽  
Author(s):  
Christiaan Timo van Dalum ◽  
Willem Jan van de Berg ◽  
Michiel Roland van den Broeke
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
Surface Mass ◽  
Surface Melt ◽  
The Antarctic ◽  
The Impact ◽  
Snow Temperature

Abstract. This study investigates the sensitivity of modeled surface melt and subsurface heating on the Antarctic ice sheet to a new spectral snow albedo and radiative transfer scheme in the Regional Atmospheric Climate Model (RACMO2), version 2.3p3 (Rp3). We tune Rp3 to observations by performing several sensitivity experiments and assess the impact on temperature and melt by changing one parameter at a time. When fully tuned, Rp3 compares well with in situ and remote sensing observations of surface mass and energy balance, melt, temperature, albedo and snow grain specific surface area. Furthermore, the introduction of subsurface heating in Rp3 significantly improves the snow temperature profile. Near surface snow temperature is especially sensitive to the prescribed fresh snow specific surface area and fresh dry snow metamorphism. These processes, together with the refreezing grain size and subsurface heating, are important for melt around the margins of the Antarctic ice sheet. Moreover, small changes in the albedo and the aforementioned processes can lead to an order of magnitude overestimation of melt, locally leading to runoff and a reduced surface mass balance.

scholarly journals Effect of Secondary Carbon Nanofillers on the Electrical, Thermal, and Mechanical Properties of Conductive Hybrid Composites Based on Epoxy Resin and Graphite

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4169
Author(s):  
Marcel Zambrzycki ◽  
Krystian Sokolowski ◽  
Maciej Gubernat ◽  
Aneta Fraczek-Szczypta
Keyword(s):  
Mechanical Properties ◽  
Specific Surface ◽  
Epoxy Resin ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hybrid Composites ◽  
Department Of Energy ◽  
Carbon Nanofillers ◽  
The Impact ◽  
Secondary Carbon

In this work, we present a comparative study of the impact of secondary carbon nanofillers on the electrical and thermal conductivity, thermal stability, and mechanical properties of hybrid conductive polymer composites (CPC) based on high loadings of synthetic graphite and epoxy resin. Two different carbon nanofillers were chosen for the investigation—low-cost multi-layered graphene nanoplatelets (GN) and carbon black (CB), which were aimed at improving the overall performance of composites. The samples were obtained by a simple, inexpensive, and effective compression molding technique, and were investigated by the means of, i.a., scanning electron microscopy, Raman spectroscopy, electrical conductivity measurements, laser flash analysis, and thermogravimetry. The tests performed revealed that, due to the exceptional electronic transport properties of GN, its relatively low specific surface area, good aspect ratio, and nanometric sizes of particles, a notable improvement in the overall characteristics of the composites (best results for 4 wt % of GN; σ = 266.7 S cm−1; λ = 40.6 W mK−1; fl. strength = 40.1 MPa). In turn, the addition of CB resulted in a limited improvement in mechanical properties, and a deterioration in electrical and thermal properties, mainly due to the too high specific surface area of this nanofiller. The results obtained were compared with US Department of Energy recommendations regarding properties of materials for bipolar plates in fuel cells. As shown, the materials developed significantly exceed the recommended values of the majority of the most important parameters, indicating high potential application of the composites obtained.

Chemical EOR in Low Permeability Sandstone Reservoirs: Impact of Clay Content on the Transport of Polymer and Surfactant

2021 ◽  
Author(s):  
Imane Guetni ◽  
Claire Marlière ◽  
David Rousseau
Keyword(s):  
Porous Media ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Clay Content ◽  
Low Permeability ◽  
Depth Propagation ◽  
The Impact ◽  
Polymer Retention ◽  
Injection Strategies

Abstract Application of chemical enhanced oil recovery (C-EOR) processes to low-permeability sandstone reservoirs (in the 10-100 mD range) can be very challenging as strong retention and difficult in-depth propagation of polymer and surfactant can occur. Transport properties of C-EOR chemicals are particularly related to porous media mineralogy (clay content). The present experimental study aimed at identifying base mechanisms and providing general recommendations to design economically viable C-EOR injection strategies in low permeability clayey reservoirs. Polymer and surfactant injection corefloods were conducted using granular packs (quartz and clay mixtures) with similar petrophysical characteristics (permeability 70-130 mD) but having various mineralogical compositions (pure quartz sand, sand with 8 wt-% kaolinite and sand with 8 wt-% smectite). The granular packs were carefully characterized in terms of structure (SEM) and specific surface area (BET). The main observables from the coreflood tests were the resistance and residual resistance factors generated during the chemical injections, the irreversible polymer retention and the surfactant retention in various injection scenarios (polymer alone, surfactant alone, polymer and surfactant). A first, the impact of the clay contents on the retention of polymer and surfactant considered independently was examined. Coreflood results have shown that retention per unit mass of rock strongly increased in presence of both kaolinite and smectite, but not in the same way for both chemicals. For polymer, retention was about twice higher with kaolinite than with smectite, despite the fact that the measured specific surface area of the kaolinite was about 5 times less than that of the smectite. Conversely, for surfactant, retention was much higher with smectite than with kaolinite. Secondly, the impact of the presence of surfactant on the polymer in-depth propagation and retention was investigated in pure quartz and kaolinite-bearing porous media. In both mineralogies, the resistance factor quickly stabilized when polymer was injected alone whereas injection of larger solution volumes was required to reach stabilization when surfactant was present. In pure quartz, polymer retention was shown, surprisingly, to be one order of magnitude higher in presence of surfactant whereas with kaolinite, surfactant did not impact polymer retention. The results can be interpreted by considering adsorption-governed retention. The mechanistic pictures being that (a) large polymer macromolecules are not able to penetrate the porosity of smectite aggregates, whereas surfactant molecules can, and (b) that surfactant and polymer mixed adsorbed layers can be formed on surfaces with limited affinity for polymer. Overall, this study shows that C-EOR can be applied in low permeability reservoirs but that successful injection strategies will strongly depend on mineralogy.

Subglacial hydrology modulates basal sliding response to climate forcing of the Antarctic ice sheet

2021 ◽  
Author(s):  
Elise Kazmierczak ◽  
Sainan Sun ◽  
Frank Pattyn
Keyword(s):  
Water Pressure ◽  
Ice Sheet ◽  
Effective Pressure ◽  
Rcp Scenarios ◽  
Overburden Pressure ◽  
Antarctic Ice Sheet ◽  
Surface Mass ◽  
Wide Range ◽  
Basal Sliding ◽  
The Antarctic

<p>Sliding laws determine to a large extent the sensitivity of the Antarctic ice sheet on centennial time scales (Pattyn, 2017, Bulthuis et al, 2019, Sun et al, 2020). Especially the contrast between linear and plastic sliding laws makes the latter far more responsive to changes at the grounding line. However, most studies neglect subglacial processes linked to those sliding laws. Subglacial hydrology may also play a role in modulating the amplitude of the reaction of marine ice sheets to forcing. Subglacial processes influence the effective pressure at the base. For a hard bed system, the latter can be defined by the ice overburden pressure minus the subglacial water pressure determined by routing of subglacial meltwater through a thin film. For soft-bed systems, the effective pressure is determined from till properties and physics. Here we investigate a wide range of subglacial processes and hydrology used in ice sheet models and implemented them in one ice sheet model (f.ETISh).</p><p> </p><p>The subglacial hydrology models and till deformation models are coupled to different sliding and friction laws (linear, power law, Coulomb), leading to 24 different representations. The Antarctic ice sheet model was then forced by the ISMIP6 forcing in surface mass balance and ocean temperature until 2100 for different RCP scenarios (Seroussi et al., 2020). Furthermore, to sample the intrinsic sensitivity we performed the ABUMIP experiments (Sun et al., 2020) for the full set of subglacial characteristics.  Results demonstrate that the type of sliding law is the most determining factor in the sensitivity of the ice sheet, modulated by the subglacial hydrology.</p>

scholarly journals The Effects of Silica-Based Fillers on the Properties of Epoxy Molding Compounds

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1811 ◽  
Author(s):  
Mitja Linec ◽  
Branka Mušič
Keyword(s):  
Mechanical Properties ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Fused Silica ◽  
Spiral Flow ◽  
Scanning Calorimetry ◽  
Molding Compounds ◽  
Material Development ◽  
The Impact

Global design and manufacturing of the materials with superb properties remain one of the greatest challenges on the market. The future progress is orientated towards researches into the material development for the production of composites of better mechanical properties to the existing materials. In the field of advanced composites, epoxy molding compounds (EMCs) have attained dominance among the common materials due to their excellent properties that can be altered by adding different fillers. One of the main fillers is often based on silicon dioxide (SiO2). The concept of this study was to evaluate the effects of the selected silica-based fillers on the thermal, rheological, and mechanical properties of EMCs. Various types of fillers with SiO2, including crystalline silica and fused silica, were experimentally studied to clarify the impact of filler on final product. Fillers with different shape (scanning electron microscope, SEM), along with different specific surface area (specific surface area analyzer, BET method) and different chemical structure, were tested to explore their modifications on the EMCs. The influence of the fillers on the compound materials was determined with the spiral flow length (spiral flow test, EMMI), glass transition temperature (differential scanning calorimetry, DSC), and the viscosity (Torque Rheometer) of the composites.

scholarly journals Retrieval of Snow Properties from the Sentinel-3 Ocean and Land Colour Instrument

2019 ◽  
Vol 11 (19) ◽  
pp. 2280 ◽  
Author(s):  
Alexander Kokhanovsky ◽  
Maxim Lamare ◽  
Olaf Danne ◽  
Carsten Brockmann ◽  
Marie Dumont ◽  
...  
Keyword(s):  
Grain Size ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Environmental Changes ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
The Arctic ◽  
Observation Data ◽  
Snow Properties

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing. In this work, we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400–1020 nm, we derived important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on a spatial grid of 300 m. The algorithm also incorporated cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long-term snow property records essential for climate monitoring and data assimilation studies—especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.

scholarly journals Seasonal variations of the backscattering coefficient measured by radar altimeters over the Antarctic Ice Sheet

2018 ◽  
Vol 12 (5) ◽  
pp. 1767-1778 ◽  
Author(s):  
Fifi Ibrahime Adodo ◽  
Frédérique Remy ◽  
Ghislain Picard
Keyword(s):  
Seasonal Variations ◽  
Seasonal Cycle ◽  
Ice Sheet ◽  
Surface Elevation ◽  
Backscattering Coefficient ◽  
Antarctic Ice Sheet ◽  
Radar Wave ◽  
The Antarctic ◽  
Snow Temperature ◽  
Ku Band

Abstract. Spaceborne radar altimeters are a valuable tool for observing the Antarctic Ice Sheet. The radar wave interaction with the snow provides information on both the surface and the subsurface of the snowpack due to its dependence on the snow properties. However, the penetration of the radar wave within the snowpack also induces a negative bias on the estimated surface elevation. Empirical corrections of this space- and time-varying bias are usually based on the backscattering coefficient variability. We investigate the spatial and seasonal variations of the backscattering coefficient at the S (3.2 GHz ∼ 9.4 cm), Ku (13.6 GHz ∼ 2.3 cm) and Ka (37 GHz ∼ 0.8 cm) bands. We identified that the backscattering coefficient at Ku band reaches a maximum in winter in part of the continent (Region 1) and in the summer in the remaining (Region 2), while the evolution at other frequencies is relatively uniform over the whole continent. To explain this contrasting behavior between frequencies and between regions, we studied the sensitivity of the backscattering coefficient at three frequencies to several parameters (surface snow density, snow temperature and snow grain size) using an electromagnetic model. The results show that the seasonal cycle of the backscattering coefficient at Ka frequency is dominated by the volume echo and is mainly driven by snow temperature evolution everywhere. In contrast, at S band, the cycle is dominated by the surface echo. At Ku band, the seasonal cycle is dominated by the volume echo in Region 1 and by the surface echo in Region 2. This investigation provides new information on the seasonal dynamics of the Antarctic Ice Sheet surface and provides new clues to build more accurate corrections of the radar altimeter surface elevation signal in the future.

scholarly journals An Evaluation of Surface Climatology in State-of-the-Art Reanalyses over the Antarctic Ice Sheet

2019 ◽  
Vol 32 (20) ◽  
pp. 6899-6915 ◽  
Author(s):  
A. Gossart ◽  
S. Helsen ◽  
J. T. M. Lenaerts ◽  
S. Vanden Broucke ◽  
N. P. M. van Lipzig ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Surface Temperature ◽  
Mass Balance ◽  
Ice Sheet ◽  
Surface Mass Balance ◽  
Antarctic Ice Sheet ◽  
Near Surface ◽  
Surface Mass ◽  
Atmospheric Rivers ◽  
The Antarctic

Abstract In this study, we evaluate output of near-surface atmospheric variables over the Antarctic Ice Sheet from four reanalyses: the new European Centre for Medium-Range Weather Forecasts ERA-5 and its predecessor ERA-Interim, the Climate Forecast System Reanalysis (CFSR), and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). The near-surface temperature, wind speed, and relative humidity are compared with datasets of in situ observations, together with an assessment of the simulated surface mass balance (approximated by precipitation minus evaporation). No reanalysis clearly stands out as the best performing for all areas, seasons, and variables, and each of the reanalyses displays different biases. CFSR strongly overestimates the relative humidity during all seasons whereas ERA-5 and MERRA-2 (and, to a lesser extent, ERA-Interim) strongly underestimate relative humidity during winter. ERA-5 captures the seasonal cycle of near-surface temperature best and shows the smallest bias relative to the observations. The other reanalyses show a general temperature underestimation during the winter months in the Antarctic interior and overestimation in the coastal areas. All reanalyses underestimate the mean near-surface winds in the interior (except MERRA-2) and along the coast during the entire year. The winds at the Antarctic Peninsula are overestimated by all reanalyses except MERRA-2. All models are able to capture snowfall patterns related to atmospheric rivers, with varying accuracy. Accumulation is best represented by ERA-5, although it underestimates observed surface mass balance and there is some variability in the accumulation over the different elevation classes, for all reanalyses.

scholarly journals Retrieval of snow properties from the Sentinel-3 Ocean and Land Colour Instrument

2019 ◽  
Author(s):  
Alexander Kokhanovsky ◽  
Maxim Lamare ◽  
Olaf Danne ◽  
Marie Dumont ◽  
Carsten Brockmann ◽  
...  
Keyword(s):  
Grain Size ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Environmental Changes ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
The Arctic ◽  
Observation Data ◽  
Snow Properties

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing (http://step.esa.int/main/toolboxes/snap/). In this work we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400-1020nm, we derive important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on the spatial grid of 300m. The algorithm also incorporates cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long – term snow property records essential for climate monitoring and data assimilation studies - especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.

scholarly journals A new approach to estimate ice dynamic rates using satellite observations in East Antarctica

2016 ◽  
Author(s):  
Bianca Kallenberg ◽  
Paul Tregoning ◽  
Janosch F. Hoffmann ◽  
Rhys Hawkins ◽  
Anthony Purcell ◽  
...  
Keyword(s):  
Mass Balance ◽  
Satellite Altimetry ◽  
Ice Sheet ◽  
East Antarctica ◽  
Surface Mass Balance ◽  
Antarctic Ice Sheet ◽  
Surface Mass ◽  
Elevation Changes ◽  
Ice Sheet Mass Balance ◽  
The Antarctic

Abstract. Mass balance changes of the Antarctic ice sheet are of significant interest due to its sensitivity to climatic changes and its contribution to changes in global sea level. While regional climate models successfully estimate mass input due to snowfall, it remains difficult to estimate the amount of mass loss due to ice dynamic processes. It's often been assumed that changes in ice dynamic rates only need to be considered when assessing long term ice sheet mass balance; however, two decades of satellite altimetry observations reveal that the Antarctic ice sheet changes unexpectedly and much more dynamically than previously expected. Despite available estimates on ice dynamic rates obtained from radar altimetry, information about changes in ice dynamic rates are still limited, especially in East Antarctica. Without understanding ice dynamic rates it is not possible to properly assess changes in ice sheet mass balance, surface elevation or to develop ice sheet models. In this study we investigate the possibility of estimating ice dynamic rates by removing modelled rates of surface mass balance, firn compaction and bedrock uplift from satellite altimetry and gravity observations. With similar rates of ice discharge acquired from two different satellite missions we show that it is possible to obtain an approximation of ice dynamic rates by combining altimetry and gravity observations. Thus, surface elevation changes due to surface mass balance, firn compaction and ice dynamic rates can be modelled and correlate with observed elevation changes from satellite altimetry.

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